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We report on hyperfine-resolved laser spectroscopy of the A2Π ← X2Σ+ transition of magnesium monofluoride (MgF), relevant for laser cooling. We recorded 25 rotational transitions with an absolute accuracy of better than 20 MHz, assigned 56 hyperfine lines, and determined precise rotational, fine, and hyperfine structure parameters for the A2Π state. The radiative lifetime of the A2Π state was determined to be 7.2(3) ns, in good agreement with ab initio calculations. The transition isotope shift between bosonic isotopologues of the molecule is recorded and compared to predicted values within the Born–Oppenheimer approximation. We measured the Stark effect of selected rotational lines of the A2Π ← X2Σ+ transition by applying electric fields of up to 10.6 kV cm−1 and determined the permanent electric dipole moments of 24MgF in its ground X2Σ+ and first excited A2Π states to be μX = 2.88(20) D and μA = 3.20(22) D, respectively. Based on these measurements, we caution for potential losses from the optical cycling transition due to electric field induced parity mixing in the excited state. In order to scatter 104 photons, the electric field must be controlled to below 1 V cm−1. [ABSTRACT FROM AUTHOR]

Understanding the mechanisms that promote the coexistence of hundreds of species over small areas in tropical forest remains a challenge. Many tropical tree species are presumed to be functionally equivalent shade tolerant species but exist on a continuum of performance trade‐offs between survival in shade and the ability to quickly grow in sunlight. These trade‐offs can promote coexistence by reducing fitness differences.Variation in plant functional traits related to resource acquisition is thought to predict variation in performance among species, perhaps explaining community assembly across habitats with gradients in resource availability. Many studies have found low predictive power, however, when linking trait measurements to species demographic rates.Seedlings face different challenges recruiting on the forest floor and may exhibit different traits and/or performance trade‐offs than older individuals face in the eventual adult niche. Seed mass is the typical proxy for seedling success, but species also differ in cotyledon strategy (reserve vs. photosynthetic) or other leaf, stem and root traits. These can cause species with the same average seed mass to have divergent performance in the same habitat.We combined long‐term studies of seedling dynamics with functional trait data collected at a standard life‐history stage in three diverse neotropical forests to ask whether variation in coordinated suites of traits predicts variation among species in demographic performance.Across hundreds of species in Ecuador, Panama and Puerto Rico, we found seedlings displayed correlated suites of leaf, stem, and root traits, which strongly correlated with seed mass and cotyledon strategy. Variation among species in seedling functional traits, seed mass, and cotyledon strategy were strong predictors of trade‐offs in seedling growth and survival. These results underscore the importance of matching the ontogenetic stage of the trait measurement to the stage of demographic dynamics.Our findings highlight the importance of cotyledon strategy in addition to seed mass as a key component of seed and seedling biology in tropical forests because of the contribution of carbon reserves in storage cotyledons to reducing mortality rates and explaining the growth‐survival trade‐off among species.Synthesis: With strikingly consistent patterns across three tropical forests, we find strong evidence for the promise of functional traits to provide mechanistic links between seedling form and demographic performance. [ABSTRACT FROM AUTHOR]

Summary: Among tropical forests, lianas are predicted to have a growth advantage over trees during seasonal drought, with substantial implications for tree and forest dynamics. We tested the hypotheses that lianas maintain higher water status than trees during seasonal drought and that lianas maximize leaf cover to match high, dry‐season light conditions, while trees are more limited by moisture availability during the dry season.We monitored the seasonal dynamics of predawn and midday leaf water potentials and leaf phenology for branches of 16 liana and 16 tree species in the canopies of two lowland tropical forests with contrasting rainfall regimes in Panama.In a wet, weakly seasonal forest, lianas maintained higher water balance than trees and maximized their leaf cover during dry‐season conditions, when light availability was high, while trees experienced drought stress. In a drier, strongly seasonal forest, lianas and trees displayed similar dry season reductions in leaf cover following strong decreases in soil water availability.Greater soil moisture availability and a higher capacity to maintain water status allow lianas to maintain the turgor potentials that are critical for plant growth in a wet and weakly seasonal forest but not in a dry and strongly seasonal forest. [ABSTRACT FROM AUTHOR]

Pre‐dispersal seed mortality caused by premature fruit drop is a potentially important source of plant mortality, but one which has rarely been studied in the context of tropical forest plants. Of particular interest is premature fruit drop triggered by enemies, which—if density dependent—could contribute to species coexistence in tropical forest plant communities.We used a long‐term (31 year) dataset on seed and fruit fall obtained through weekly collections from a network of seed traps in a lowland tropical forest (Barro Colorado Island, Panama) to estimate the proportion of seeds prematurely abscised for 201 woody plant species. To determine whether enemy attack might contribute to premature fruit drop, we tested whether plant species abscise more of their fruit prematurely if they (a) have attributes hypothesised to be associated with high levels of enemy attack and (b) are known to be attacked by one enemy group (insect seed predators). We also tested (c) whether mean rates of premature fruit drop for plant species are phylogenetically conserved.Overall rates of premature fruit drop were high in the plant community. Across all species, 39% of seeds were abscised before completing their development. Rates of premature seed abscission varied considerably among species and could not be explained by phylogeny. Premature seed abscission rates were higher in species which are known to host pre‐dispersal insect seed predators and species with attributes that were hypothesised to make them more susceptible to attack by pre‐dispersal enemies, namely species which (a) have larger seeds, (b) have a greater average height, (c) have temporally predictable fruiting patterns and (d) are more abundant at the study site.Synthesis. Premature fruit drop is likely to be a major source of seed mortality for many plant species on Barro Colorado Island. It is plausible that pre‐dispersal seed enemies, such as insect seed predators, contribute to community‐level patterns of premature fruit drop and have the potential to mediate species coexistence through stabilising negative density dependence. Our study suggests that the role of pre‐dispersal enemies in structuring tropical plant communities should be considered alongside the more commonly studied post‐dispersal seed and seedling enemies. [ABSTRACT FROM AUTHOR]

Nutrient addition experiments indicate that nitrogen and phosphorus limit plant processes in many tropical forests. However, the long‐term consequences for forest structure and species composition remain unexplored. We are positioned to evaluate potential long‐term consequences of nutrient addition in central Panama where we have maintained a factorial nitrogen–phosphorus–potassium fertilization experiment for 21 yr and an independent study quantified the species‐specific nutrient requirements of 550 local tree species. Here, we ask whether nutrients limit reproduction at the species and community levels. We also ask whether species‐specific reproductive responses to nutrient addition are stronger among species associated with naturally fertile soils, which could contribute to a shift in species composition. We quantified species‐level reproductive responses for 38 focal species in the 21st year of the experiment and community‐level reproductive litter production for the first 20 yr. Species‐level reproductive responses to nitrogen and potassium addition were weak, inconsistent across species, and insignificant across the 38 focal species. In contrast, species‐level responses to phosphorus addition were consistently and significantly positive across the 38 focal species but were unrelated to species‐specific phosphorus requirements documented independently for the same species. Community‐level reproductive litter production was unaffected by nutrient addition, possibly because spatial and temporal variation is large. We conclude that phosphorus limits reproduction by trees in our experiment but find no evidence that reproductive responses to phosphorus addition favor species associated with naturally phosphorus‐rich soils. [ABSTRACT FROM AUTHOR]

This article explores how formerly sighted Deaf individuals confront vision loss and grapple with adopting new identities as Deaf-Blind individuals. Co-researchers in this study analyze sighted Deaf culture and the resulting power dynamics that have relegated the Deaf-Blind body as inferior, revoking membership from sighted Deaf culture. From the perspective of 6 Deaf-Blind individuals, the balance of power within sighted Deaf culture is explored and solidified to reveal a hierarchy which categorizes the Deaf Disabled body in comparison to the sighted, Deaf normate. Members of the Deaf-Blind communities are beginning to develop their own culture which is separate from sighted Deaf culture and operates under different norms. Deaf-Blind communities reject the label of Deaf with a disability and have begun to take ownership of not only the definition of culture, but the modality in which they communicate. A majority of Deaf-Blind individuals lose vision in early adulthood, which means at some point, they were members of sighted Deaf culture and then become outcasts as a "disabled" body. The research indicates that Deaf culture actually has an unspoken hierarchy where power is concerned, an analysis that is not yet part of the academic discourse, particularly where Deaf Critical Theory is concerned. [ABSTRACT FROM AUTHOR]

Summary: Background: A temporal relationship between hidradenitis suppurativa (HS) and obesity has not been established. Objectives: To compare baseline body mass index (BMI) and change in BMI for patients with HS and controls before and after diagnosis. Methods: We performed a retrospective case–control analysis of 1284 patients with HS and controls matched for age, sex, race and calendar year between 1 January 1999 and 9 September 2019. BMI 7 years prior to first HS diagnosis, and rate of BMI change, were compared for patients with HS and controls using linear mixed effects models. Results: Baseline BMI was higher among patients with HS than controls [mean difference 3·03 kg m−2, 95% confidence interval (CI) 2·44–3·62; P < 0·001)]. This difference was larger for women [mean difference 3·37 kg m−2 (95% CI 2·73–4·01)] than men [mean difference 1·27 kg m−2 (95% CI − 0·20–2·73; interaction P = 0·01)], and for patients with HS diagnosed before age 40 years [mean difference 4·10 kg m−2 (95% CI 3·15–5·06)] than those diagnosed after age 40 years [mean difference 2·38 kg m−2 (95% CI 1·63–3·12; interaction P < 0·001)]. Prior to diagnosis, average annual increase in BMI among patients with HS was slightly higher than controls. There was no statistically significant change in annual BMI among patients with HS following diagnosis. Conclusions: Baseline BMI and, to a lesser extent, rate of BMI change appear to be risk factors for developing HS. The influence of BMI may play a larger role among female patients and younger patients. What is already known about this topic? The association between hidradenitis suppurativa (HS) and obesity is well established.However, whether obesity influences the development of HS or is a consequence of having HS is unknown. What does this study add? We have observed that obesity and, to a lesser extent, rate of change in body mass index appear to be risk factors for developing HS. Linked Comment: L.A.V. Orenstein. Br J Dermatol 2021; 185:6–7. [ABSTRACT FROM AUTHOR]

Tropical forest productivity represents an important global carbon sink, but many tropical forests grow on infertile soils. Efficient nutrient cycling by litterfall has long been assumed to maintain tropical tree growth, but there is no direct evidence that the nutrients cycled in litterfall are essential for tropical forest productivity.To test whether nutrient cycling by litterfall maintains tropical forest above‐ground productivity, we established large‐scale long‐term litter removal (L−) and litter addition (L+) treatments in a mature lowland tropical forest. We hypothesised that the removal of nutrients in litter would reduce tree growth, survival and litter production in L− plots. By contrast, the addition of nutrients in litter would enhance tree growth, survival and litter production in L+ plots. To test our hypotheses, we recorded tree growth and survival every 2 years, and measured litterfall monthly during 17 years of treatments.Tree growth and litterfall declined over time in L− plots, with consistently lower growth rates compared to controls after 8 years, and lower litter production after 4 years of treatments. By contrast, although litterfall was higher in the L+ plots relative to the controls, there was only a minor transient increase in tree growth immediately after the start of treatments. Tree survival declined over time in all treatments but was not affected by litter manipulation.The long‐term decline in tree growth and litterfall in the L− plots provides the first empirical evidence that nutrient cycling by litterfall plays a key role in maintaining above‐ground productivity in this tropical forest. By contrast, the transient increase in growth in the L+ plots can be attributed to the large inputs of nutrients with the addition of the entire litter standing crop at the start of treatments. The addition of nutrients in litter over the long term was nonetheless sufficient to enhance litter production, possibly by accelerating leaf turnover.Synthesis: Efficient nutrient cycling by litterfall makes an important contribution to the annual nutrient requirements of mature tropical forest trees, compensating for infertile soils. Disturbances that disrupt this finely balanced cycle could therefore reduce biomass carbon sequestration in tropical forests. [ABSTRACT FROM AUTHOR]

A Thomson Web of Science search for the topic "leaf age" AND potassium AND tropic* identified just one similar study, which reported a similar strong decline in foliar K with leaf age ([16]). This scientific commentary refers to 'Changes in leaf functional traits with leaf age: When do leaves decrease their photosynthetic capacity in Amazonian forests? Google Scholar Crossref Search ADS WorldCat 6 Kitajima K, Mulkey SS, Wright SJ (1997 a) Decline of photosynthetic capacity with leaf age in relation to leaf longevities for five tropical canopy tree species. The LDO model integrates seasonality in the timing of leaf production and abscission, total leaf area present and the contribution of expanding, mature and old leaves to successfully explain seasonality in gross ecosystem production. [Extracted from the article]

Dating between Deaf gay men who are American Sign Language (ASL) users and hearing gay men who use spoken language has historically been a challenge, creating a binary in Deaf-hearing relationships. The dating game has been revolutionized by the creation of geo-social networking (GSN) apps, where people communicate through the medium of written English and digital photographs. Furthermore, GSN apps have created a network for meeting other men who identify as Deaf and gay, as well as revealing the existence of a sexual fetish for Deaf partners. The main research question driving this investigation is: What are the impacts of gay GSN apps upon the dating and mating rituals of Deaf gay men in the United States? Using Grounded Theory Methodology, findings indicate that GSN apps have lifted previously-encountered communication barriers between Deaf and hearing men, creating a causeway for communication that gives rise to increased comfort, but leads to an increase in rejection based on being Deaf. [ABSTRACT FROM AUTHOR]

Shock-free ion transmission from atmospheric pressure to a microelectromechanical system (MEMS)-based mass spectrometer has been achieved using micro-engineered nickel skimmers. The signal level has increased 70-fold compared with a previous configuration in which the skimmer did not sample the supersonic flow. The skimmers are formed by electroplating internal surfaces of anisotropically etched, pyramidal holes in (100) silicon. Etching from the reverse of the wafer exposes free-standing, open-ended skimmers supported by remaining silicon. High-resolution schlieren imaging has been used to visualise gas flow within the interface. Signal enhancement and increased gas throughput are observed when the skimmer attaches to the supersonic gas expansion via oblique shocks. The silicon back wall interacts with the flow field, causing the free jet Mach disc to evolve into a bowl-shaped surface shock whose position asymptotically approaches a stand-off separation as the interface pressure decreases. Ideally, the skimmer entrance should be located approximately midway between the inlet and the back wall. This development should allow a sensitivity increase in MEMS mass spectrometers using pumps of moderate capacity. [ABSTRACT FROM AUTHOR]

With each heartbeat, the right ventricle (RV) inputs blood into the pulmonary vascular (PV) compartment, which conducts blood through the lungs at low pressure and concurrently fills the left atrium (LA) for output to the systemic circulation. This overall hemodynamic function of the integrated RV-PV-LA unit is determined by complex interactions between the components that vary over the cardiac cycle but are often assessed in terms of mean pressure and flow. Exercise challenges these hemodynamic interactions as cardiac filling increases, stroke volume augments, and cycle length decreases, with PV pressures ultimately increasing in association with cardiac output. Recent cardiopulmonary exercise hemodynamic studies have enriched the available data from healthy adults, yielded insight into the underlying mechanisms that modify the PV pressure-flow relationship, and better delineated the normal limits of healthy responses to exercise. This review will examine hemodynamic function of the RV-PV-LA unit using the two-element Windkessel model for the pulmonary circulation. It will focus on acute PV and LA responses that accommodate increased RV output during exercise, including PV recruitment and distension and LA reservoir expansion, and the integrated mean pressure-flow response to exercise in healthy adults. Finally, it will consider how these responses may be impacted by age-related remodeling and modified by sex-related cardiopulmonary differences. Studying the determinants and recognizing the normal limits of PV pressure-flow relations during exercise will improve our understanding of cardiopulmonary mechanisms that facilitate or limit exercise. [ABSTRACT FROM AUTHOR]

With each heartbeat, the right ventricle (RV) inputs blood into the pulmonary vascular (PV) compartment, which conducts blood through the lungs at low pressure and concurrently fills the left atrium (LA) for output to the systemic circulation. This overall hemodynamic function of the integrated RV-PV-LA unit is determined by complex interactions between the components that vary over the cardiac cycle but are often assessed in terms of mean pressure and flow. Exercise challenges these hemodynamic interactions as cardiac filling increases, stroke volume augments, and cycle length decreases, with PV pressures ultimately increasing in association with cardiac output. Recent cardiopulmonary exercise hemodynamic studies have enriched the available data from healthy adults, yielded insight into the underlying mechanisms that modify the PV pressure-flow relationship, and better delineated the normal limits of healthy responses to exercise. This review will examine hemodynamic function of the RV-PV-LA unit using the two-element Windkessel model for the pulmonary circulation. It will focus on acute PV and LA responses that accommodate increased RV output during exercise, including PV recruitment and distension and LA reservoir expansion, and the integrated mean pressure-flow response to exercise in healthy adults. Finally, it will consider how these responses may be impacted by age-related remodeling and modified by sex-related cardiopulmonary differences. Studying the determinants and recognizing the normal limits of PV pressureflow relations during exercise will improve our understanding of cardiopulmonary mechanisms that facilitate or limit exercise. [ABSTRACT FROM AUTHOR]

With each heartbeat, the right ventricle (RV) inputs blood into the pulmonary vascular (PV) compartment, which conducts blood through the lungs at low pressure and concurrently fills the left atrium (LA) for output to the systemic circulation. This overall hemodynamic function of the integrated RV-PV-LA unit is determined by complex interactions between the components that vary over the cardiac cycle but are often assessed in terms of mean pressure and flow. Exercise challenges these hemodynamic interactions as cardiac filling increases, stroke volume augments, and cycle length decreases, with PV pressures ultimately increasing in association with cardiac output. Recent cardiopulmonary exercise hemodynamic studies have enriched the available data from healthy adults, yielded insight into the underlying mechanisms that modify the PV pressure-flow relationship, and better delineated the normal limits of healthy responses to exercise. This review will examine hemodynamic function of the RV-PV-LA unit using the two-element Windkessel model for the pulmonary circulation. It will focus on acute PV and LA responses that accommodate increased RV output during exercise, including PV recruitment and distension and LA reservoir expansion, and the integrated mean pressure-flow response to exercise in healthy adults. Finally, it will consider how these responses may be impacted by age-related remodeling and modified by sex-related cardiopulmonary differences. Studying the determinants and recognizing the normal limits of PV pressure-flow relations during exercise will improve our understanding of cardiopulmonary mechanisms that facilitate or limit exercise. [ABSTRACT FROM AUTHOR]

Antisense oligonucleotide exon skipping therapy in Duchenne Muscular Dystrophy (DMD) works to change the splicing pattern to increase the amount of functional dystrophin protein produced. Clinical studies have demonstrated modest increases in dystrophin levels as well as milder declines in scores on the North Star Ambulatory Assessment (NSAA) as compared to controls. All currently approved exon skipping therapies require a once weekly intravenous injection; patients with intravenous (IV) access issues therefore may receive a port-a-catheter for frequent central venous access. Indwelling port-a-catheters pose certain risks, including early (i.e., malpositioning of catheter, hemothorax) and delayed (i.e., infection, catheter thrombosis, catheter fracture with extravasation, or fracture with extravasation) complications. Patients with DMD on chronic high-dose steroids may also be at increased risk of poor wound healing following central catheter placement. We sought to determine if we could identify reliable markers in DMD patients who ultimately required insertion port-a-catheter; this data would help guide initial conversations about potential risks and benefits of exon skipping therapy. From January 2015 to present we had 15 patients at our center with mutations in the DMD gene amendable to exon-skipping therapy (exon skipping 45, 51, and 53). At the time of enrollment, 8 boys were ambulatory and at the time of last visit 7 of them were still able to complete the NSAA. During this period 6 of 15 boys required port-a-catheter placement for their weekly IV infusions. The indication for all boys receiving central venous access was difficulty obtaining peripheral IV access during home infusions. Patients who were older (≥10 years-of-age), non-ambulatory, and with higher body mass index (BMI; ≥25) at the time of exon skipping therapy were more likely to require insertion of a port-a-catheter. Length-of-time on exon skipping therapy did not appear to predict need for central venous access. Additional studies in larger cohorts are required to determine if statistically significant predictors can be identified. However, this limited data may help guide the DMD clinician during conversations surrounding initiating exon skipping therapies with their older, non-ambulatory patients. [ABSTRACT FROM AUTHOR]

With rising atmospheric CO2 concentrations, strategies for greater carbon sequestration and long‐term storage are urgently needed. Current reforestation schemes typically use fast‐growing tree species with low wood density, limiting the amount of carbon stored. In most tropical forests, there are native species with relatively fast growth rates, high wood density and low mortality rates that also achieve large adult size—'exceptional species'.We present a simulated assessment of the carbon sequestration potential using these exceptional species in assisted secondary succession in the Neotropics.In our example, the selected exceptional species could add up to 16.2 Mg C/ha of sequestered carbon in secondary wet forests at maturity.Synthesis and applications. By increasing the representation of exceptional species in reforestation efforts, we could potentially boost long‐term carbon storage in reforestation projects focussed on carbon sequestration. However, our approach is not a substitute for protecting existing old primary forests and reforested lands plus reducing deforestation and emissions. [ABSTRACT FROM AUTHOR]

Current California agricultural practices strive to comanage food safety and habitat conservation on farmland. However, the ecology of foodborne pathogens in wild bird populations, especially those avian species residing in proximity to fresh produce production fields, is not fully understood. In this repeated crosssectional study, avifauna within agricultural lands in California were sampled over 1 year. Feces, oral swabs, and foot/feather swabs were cultured for zoonotic Salmonella spp., Escherichia coli O157:H7, and non-O157 Shiga toxin-producing E. coli (STEC) and characterized by serotyping and pulsed-field gel electrophoresis. Of 60 avian species sampled, 8 species (13.3%, bird groups of sparrows, icterids, geese, wrens, and kinglets) were positive for at least one of these foodborne pathogens. At the individual bird level, the detection of foodborne pathogens was infrequent in feces (n=583; 0.5% Salmonella, 0.34% E. coli O157:H7, and 0.5% non-O157 STEC) and in feet/feathers (n=401; 0.5% non-O157 STEC), and it was absent from oral swabs (n=353). Several subtypes of public health importance were identified, including Salmonella enterica serotype Newport, E. coli O157:H7, and STEC serogroups O103 and O26. In late summer and autumn, the same STEC subtype was episodically found in several individuals of the same and different avian species, suggesting a common source of contamination in the environment. Sympatric free-range cattle shared subtypes of STEC O26 and O163 with wild geese. A limited rate of positive detection in wild birds provides insights into broad risk profile for contamination considerations but cannot preclude or predict risk on an individual farm. [ABSTRACT FROM AUTHOR]

Current California agricultural practices strive to co-manage food safety and habitat conservation on farmland. However, the ecology of foodborne pathogens in wild bird populations, especially those avian species residing in proximity to fresh produce production fields, is not fully understood. In this repeated cross-sectional study, avifauna within agricultural lands in California were sampled over one year. Feces, oral swabs and feet/feather swabs were cultured for zoonotic Salmonella, Escherichia coli O157:H7 and non- O157 Shiga toxin-producing E. coli (STEC) and characterized by serotyping and pulsed-field gel electrophoresis. Of 60 avian species sampled, 8 species (13.3%, bird groups sparrows, icterids, geese, wrens and kinglets) were positive for at least one of these foodborne pathogens. At the individual bird level, the detection of foodborne pathogens was infrequent in feces (n=583, 0.5% Salmonella, 0.34% E. coli O157:H7 and 0.5% non-O157 STEC) and in feet/feathers (n=401, 0.5% non-O157 STEC), and absent from oral swabs (n=353). Several subtypes of public health importance were identified including Salmonella Newport, E. coli O157:H7, and STEC serogroups O103 and O26. In late summer and autumn, the same STEC subtype was episodically found in several individuals of the same and different avian species, suggesting a common source of contamination in the environment. Sympatric free-range cattle shared subtypes of STEC O26 and O163 with wild geese. A limited rate of positive detection in wild birds provides insights to broad risk profile considerations, but cannot preclude or predict risk on an individual farm. The shedding dynamics of foodborne pathogens by wild birds on farmland is not well- characterized. This year-long study sampled wild birds for foodborne pathogens within agricultural lands in Northern California. There was a low prevalence of Salmonella, Escherichia coli O157:H7 and non-O157 Shiga-toxin producing E. coli (prevalence 0.34% to 0.50%) identified in bird populations in this study. However, pathogens of public health importance were identified in fecal samples, such as Salmonella Newport, E. coli O157:H7, STEC O103 and O26, and two birds carried STEC on their feet or feathers. Identical pathogen strains were shared episodically among birds, and between wild geese and free- range cattle. This result suggests a common source of contamination in the environment, and potential transmission between species. These findings can be used to assess the risk posed by bird intrusions in produce fields and enhance policy decisions towards the co-management of food safety and farmland habitat conservation. [ABSTRACT FROM AUTHOR]

We present experimental studies of the current pumped through a dynamic quantum dot over a wide range of magnetic fields. At low fields we observe a repeatable structure indicating increased confinement of the electrons in the dynamic dot. At higher fields (B>5T), we observe a structure which changes markedly from device to device suggesting that in this regime the transport is sensitive to local disorder. The results are significant for the development of dynamic quantum dot pumps as quantum standards of electrical current. [ABSTRACT FROM AUTHOR]

In this work, we explore the role of chemical reactions on the properties of buffer gas cooled molecular beams. In particular, we focus on scenarios relevant to the formation of AlF and CaF via chemical reactions between the Ca and Al atoms ablated from a solid target in an atmosphere of a fluorine-containing gas, in this case, SF6 and NF3. Reactions are studied following an ab initio molecular dynamics approach, and the results are rationalized following a tree-shaped reaction model based on Bayesian inference. We find that NF3 reacts more efficiently with hot metal atoms to form monofluoride molecules than SF6. In addition, when using NF3, the reaction products have lower kinetic energy, requiring fewer collisions to thermalize with the cryogenic helium. Furthermore, we find that the reaction probability for AlF formation is much higher than for CaF across a broad range of kinetic temperatures. [ABSTRACT FROM AUTHOR]

These results suggested that HS diet provoked more severe mucosa lesions in the glandular region of the stomach and a higher inflammation both in the jejunum and pelvic flexure. I An epidemic of equine influenza (EI) occurred in Europe in 2019. Gut health in horses I The conventional feeding management of horses is still characterised by high-starch and low-fibre diets, which can negatively affect gastrointestinal health. [Extracted from the article]

Across three experiments, we examined the cuing properties of metric (distance and direction) and nonmetric (lighting) cues in different tasks. In Experiment 1, rats were trained on a response problem in a T-maze, followed by four reversals. Rats that experienced a change in maze orientation (Direction group) or a change in the length of the start arm (Distance group) across reversals showed facilitation of reversal learning relative to a group that experienced changes in room lighting across reversals. In Experiment 2, rats learned a discrimination task more readily when distance or direction cues were used than when light cues were used as the discriminative stimuli. In Experiment 3, performance on a go/no-go task was equivalent using both direction and lighting cues. The successful use of both metric and nonmetric cues in the go/no-go task indicates that rats are sensitive to both types of cues and that the usefulness of different cues is dependent on the nature of the task. [ABSTRACT FROM AUTHOR]

Humans are increasing nutrient deposition across the globe, and we know little about how these changes influence consumer populations in tropical rainforests. We used a long-term fertilization experiment conducted in a Panamanian forest to explore how nutrient availability and tree traits affect abundance of a higher-level consumer. We added nitrogen, phosphorus and potassium in a factorial design for 18 years. Given that phosphorus often limits ecosystem processes in lowland tropical forests, and added nitrogen reduces insect abundance in our experiment, we first hypothesized that phosphorus addition would increase nest density and nest size of Azteca chartifex ants while nitrogen addition would have the opposite effects. We found 48% lower nest density in the canopy of nitrogen addition plots relative to plots that did not receive nitrogen. Phosphorus addition did not affect nest density or size. These nutrient effects were not diminished by the selectivity of host trees. In general, larger trees held more nests, despite their low frequencies across the forest, while some abundant species (e.g., palms) were rarely used. We further predicted higher nest frequency on trees with extrafloral nectaries, because this ant fuels its large colonies with extrafloral nectar. Despite the non-random distribution of A. chartifex nests, across tree species and nutrient treatments, trees with extrafloral nectaries did not host more nests. Our study suggests that areas of a tropical lowland forest which are not oversaturated with nitrogen, and contain large trees, have higher nest density. This could enable A. chartifex in similar areas to outcompete other ants due to high abundance. [ABSTRACT FROM AUTHOR]

Phenology models developed for temperate and boreal plants predict a single, population‐level first flowering date for each year. These models cannot accommodate species that flower multiple times each year in humid tropical forests nor flowering data with census‐interval rather than daily temporal resolution. Here, we present a new model framework able to predict the timing of multiple annual flowering events from census data. We extend a recent model, which predicted tropical flowering probabilities as discrete events occurring on census dates, by integrating predicted flowering probabilities over all dates between censuses. We evaluate our model against 29 years of daily climate and weekly flowering records for Hybanthus prunifolius (Violaceae) and Handroanthus guayacan (Bignoniaceae) from Barro Colorado Island, Panama. Previous experiments demonstrate that both species flower shortly after a heavy, dry‐season rain interrupts an extended dry period. Our model captures this sequence of rainfall events. Best‐fit model parameters are consistent with previous experimental results. This match suggests the new model framework will provide novel insights for other humid tropical forest species. We present a new model framework to evaluate hypotheses concerning environmental cues for phenology using observational records. We validate the approach using 29 years of daily climate records and weekly flowering observations for two tropical tree species whose flowering cues are known from prior experiments. The new model framework successfully identified the experimentally determined flowering cues promising new insights for the vast majority of species whose phenology has not been manipulated experimentally. [ABSTRACT FROM AUTHOR]

Numerous Neotropical rainforest species are distributed in both Amazonia and Central America, reflecting a rich history of biotic interchange between regions. However, some plant lineages are endemic to one region, due in part to the dispersal barrier posed by the Northern Andean Cordilleras and adjacent savannas. To investigate the role of biogeographic filtering across the northern Andes in regional community assembly, we examined environmental tolerances, functional traits, and biogeographic distributions of >1000 woody plant species (trees, shrubs, lianas) locally co‐occurring in forest plots in lowland Panama (542 species) and Amazonian Ecuador (667 species). High regional abundance was strongly predictive of the probability of being geographically widespread (i.e. present on both sides of the Andes). However, we also found that species with broad environmental tolerances (those that are able to inhabit high elevations and areas of low mean annual precipitation) were more likely to have a cross‐Andean distribution even after accounting for regional abundance, suggesting that biogeographic filtering for these traits has mediated cross‐Andean dispersal. Regional abundance and environmental tolerances were additionally associated with a suite of life‐history traits related to high dispersal–colonization ability, but most traits reflecting dispersal–colonization ability were not predictive of biogeographic distribution. Our results highlight how the process of biogeographic filtering, based primarily on environmental tolerances, has mediated regional‐scale floristic assembly of Neotropical rainforests. The impacts of this process, which we term filter‐dispersal assembly, are likely to be especially important to forests in Central America, where biotic interchange with Amazonia has heavily influenced regional community composition. [ABSTRACT FROM AUTHOR]

Presents a study which examined the band alignment in gallium arsenide:(aluminum, gallium)arsenic heterostructures over a full range of alloy composition. Experiment; Measurement technique; Discussion.

Presents a study that described the measurement of the energy band discontinuities in gallium arsenide:(Al,Ga)arsenic heterostructures. Parameter that influences the electrical and optical properties of a heterojunction; Description of the structure used in the study; Illustration of a typical n-type structure.

Report that the Reagan administration revived chemical weapons development programs dormant for decades. Change of policy under Reagan; Challenge for new administration under President-elect George Bush; Research and development.

Abstract: We present a meta‐analysis of plant responses to fertilization experiments conducted in lowland, species‐rich, tropical forests. We also update a key result and present the first species‐level analyses of tree growth rates for a 15‐yr factorial nitrogen (N), phosphorus (P), and potassium (K) experiment conducted in central Panama. The update concerns community‐level tree growth rates, which responded significantly to the addition of N and K together after 10 yr of fertilization but not after 15 yr. Our experimental soils are infertile for the region, and species whose regional distributions are strongly associated with low soil P availability dominate the local tree flora. Under these circumstances, we expect muted responses to fertilization, and we predicted species associated with low‐P soils would respond most slowly. The data did not support this prediction, species‐level tree growth responses to P addition were unrelated to species‐level soil P associations. The meta‐analysis demonstrated that nutrient limitation is widespread in lowland tropical forests and evaluated two directional hypotheses concerning plant responses to N addition and to P addition. The meta‐analysis supported the hypothesis that tree (or biomass) growth rate responses to fertilization are weaker in old growth forests and stronger in secondary forests, where rapid biomass accumulation provides a nutrient sink. The meta‐analysis found no support for the long‐standing hypothesis that plant responses are stronger for P addition and weaker for N addition. We do not advocate discarding the latter hypothesis. There are only 14 fertilization experiments from lowland, species‐rich, tropical forests, 13 of the 14 experiments added nutrients for five or fewer years, and responses vary widely among experiments. Potential fertilization responses should be muted when the species present are well adapted to nutrient‐poor soils, as is the case in our experiment, and when pest pressure increases with fertilization, as it does in our experiment. The statistical power and especially the duration of fertilization experiments conducted in old growth, tropical forests might be insufficient to detect the slow, modest growth responses that are to be expected. [ABSTRACT FROM AUTHOR]

The article offers information on a conference, organized on behalf of the Royal College of Pathologists, which was attended by experts from various clinical disciplines, along with leaders of transfusion science. Topics include a lecture by Connie Westhoff, of New York Blood Center, on the development of genomic techniques and its relevance to transfusion science; a session by Andrew Klein, of Papworth Hospital, on evidence-based transfusion practice; and challenges in transplantation.

Producing and retaining leaves underlie the performance and survivorship of seedlings in deeply shaded tropical forests. These habitats are characterized by conditions ideal for foliar bacteria, which can be potent plant pathogens. Leaf production, retention and susceptibility to enemies may ultimately depend upon interactions among soil nutrients and foliar microbes, yet this has never been tested., We experimentally evaluated the degree that foliar bacteria and soil resource supply mediate leaf dynamics for five common tree species (five different families) in a Panamanian forest. We reduced foliar bacteria with antibiotics for 29 months and measured leaf production, retention and damage for seedlings nested within a replicated 15-yr factorial nutrient enrichment experiment (nitrogen, N; phosphorus, P; potassium, K)., Our results demonstrate that when we applied antibiotics, soil nutrients - particularly N - always regulated seedling leaf production (and to a lesser extent herbivore damage) for all five tree species. In addition, it was common for two macronutrients together to negate or completely reverse the impact of applying either one alone., Our findings of frequent plant-microbe-nutrient interactions are novel and suggest that these interactions may reinforce plant species-environment associations, thereby creating a fairly cryptic and fine-scale dimension of niche differentiation for coexisting tree species. [ABSTRACT FROM AUTHOR]

PREMISE OF THE STUDY: Wood density is the top predictor of growth and mortality rates (vital rates) but with modest explanatory power at best. Stronger links to vital rates are expected if wood density is decomposed into its anatomical properties at sapling and adult stages, since saplings and adults differ in wood traits and vital rates. We examined whether anatomical determinants of wood density and strength of the relationship between wood traits and vital rates shift between saplings and adults. METHODS: Using wood segments from near pith (sapling) and near bark (adult) for 20 tree species (three adults each) from Barro Colorado Island, Panama, we quantified wood traits. Vital rates for saplings and adults were obtained from an earlier study. KEY RESULTS: Anatomical predictors of wood density were similar for sapling and adult wood, with wood density variation largely explained by fiber lumen area and fiber wall fraction. In sapling wood only, growth rates decreased with fiber wall fraction and increased with fiber lumen area, while mortality rates increased with vessel area but decreased with fiber wall fraction and vessel density. CONCLUSIONS: Wood traits of sapling trees provide functional insight into the growth-mortality tradeoff. Sapling wood with relatively large fiber lumen area and wide vessels, enabling faster hydraulic transport but less mechanical strength, is associated with fast growth and high mortality. Sapling wood with relatively more fiber wall and many narrow vessels, enabling greater mechanical strength but slower hydraulic transport, is associated with slow growth and low mortality. [ABSTRACT FROM AUTHOR]

Multiple anthropogenic drivers affect every natural community, and there is broad interest in using functional traits to understand and predict the consequences for future biodiversity. There is, however, no consensus regarding the choice of analytical methods. We contrast species- and community-level analyses of change in the functional composition for four traits related to drought tolerance using three decades of repeat censuses of trees in the 50-ha Forest Dynamics Plot on Barro Colorado Island, Panama. Community trait distributions shifted significantly through time, which may indicate a shift toward more drought tolerant species. However, at the species level, changes in abundance were unrelated to trait values. To reconcile these seemingly contrasting results, we evaluated species-specific contributions to the directional shifts observed at the community level. Abundance changes of just one to six of 312 species were responsible for the community-level shifts observed for each trait. Our results demonstrate that directional changes in community-level functional composition can result from idiosyncratic change in a few species rather than widespread community-wide changes associated with functional traits. Future analyses of directional change in natural communities should combine community-, species-, and possibly individual-level analyses to uncover relationships with function that can improve understanding and enable prediction. [ABSTRACT FROM AUTHOR]

As children living with HIV (CLHIV) grow into adolescence and adulthood, caregivers and healthcare providers are faced with the sensitive challenge of when to disclose to a CLHIV his or her HIV status. Despite WHO recommendations for CLHIV to know their status, in countries most affected by HIV, effective resources are often limited, and national guidance on disclosure is often lacking. To address the need for effective resources, gray and scientific literature was searched to identify existing tools and resources that can aid in the disclosure process. From peer-reviewed literature, seven disclosure models from six different countries were identified. From the gray literature, 23 resources were identified including children’s books (15), job aides to assist healthcare providers (5), and videos (3). While these existing resources can be tailored to reflect local norms and used to aid in the disclosure process, careful consideration must be taken in order to avoid damaging disclosure practices. [ABSTRACT FROM AUTHOR]

For species to coexist, performance must decline as the density of conspecific individuals increases. Although evidence for such conspecific negative density dependence (CNDD) exists in forests, the within-species spatial repulsion it should produce has rarely been demonstrated in adults. In this study, we show that in comparison to a null model of stochastic birth, death, and limited dispersal, the adults of dozens of tropical forest tree species show strong spatial repulsion, some to surprising distances of approximately 100 meters. We used simulations to show that such strong repulsion can only occur if CNDD considerably exceeds heterospecific negative density dependence—an even stronger condition required for coexistence—and that large-scale repulsion can indeed result from small-scale CNDD. These results demonstrate substantial niche differences between species that may stabilize species diversity. [ABSTRACT FROM AUTHOR]

Background: Tropical rainforests are frequently limited by soil nutrient availability. However, the response of the metabolic phenotypic plasticity of trees to an increase of soil nutrient availabilities is poorly understood. We expected that increases in the ability of a nutrient that limits some plant processes should be detected by corresponding changes in plant metabolome profile related to such processes. Methodology/Principal findings: We studied the foliar metabolome of saplings of three abundant tree species in a 15 year field NPK fertilization experiment in a Panamanian rainforest. The largest differences were among species and explained 75% of overall metabolome variation. The saplings of the large canopy species, Tetragastris panamensis, had the lowest concentrations of all identified amino acids and the highest concentrations of most identified secondary compounds. The saplings of the “mid canopy” species, Alseis blackiana, had the highest concentrations of amino acids coming from the biosynthesis pathways of glycerate-3P, oxaloacetate and α-ketoglutarate, and the saplings of the low canopy species, Heisteria concinna, had the highest concentrations of amino acids coming from the pyruvate synthesis pathways. Conclusions/Significance: The changes in metabolome provided strong evidence that different nutrients limit different species in different ways. With increasing P availability, the two canopy species shifted their metabolome towards larger investment in protection mechanisms, whereas with increasing N availability, the sub-canopy species increased its primary metabolism. The results highlighted the proportional distinct use of different nutrients by different species and the resulting different metabolome profiles in this high diversity community are consistent with the ecological niche theory. [ABSTRACT FROM AUTHOR]

Rare plant species often suffer stronger conspecific negative density dependence (CNDD) in studies that assess the impact of local conspecific density on individual survival. All else equal, this causes a relative disadvantage among rare species that appears inconsistent with the role of CNDD in coexistence. The resolution to this apparent paradox is for lower species abundance to decrease the frequency of conspecific interactions sufficiently to outweigh the disadvantage of stronger CNDD. Whether this occurs in natural systems is untested because existing metrics do not isolate demographic impacts of CNDD, and it is also uncertain for tropical forest trees because the greater spatial aggregation observed in rare species could cause higher frequency of conspecific interactions despite lower abundance on the landscape. We develop a new metric, effective density-dependent mortality (EDDM), to quantify the proportion of individuals that are killed by density-dependent effects. We apply EDDM to a long-term study of seed fall and recruitment at Barro Colorado Island, Panama. Rare species had stronger CNDD but lower conspecific densities, and EDDM increased with abundance. Lower abundance, thus, reduces the frequency of conspecific interaction and, consequently, mortality associated with CNDD. This mechanism allows rare species to avoid a disadvantage-when-rare that would, all else equal, result from stronger CNDD in rare species. Our work provides empirical support for a resolution to the apparently paradoxical findings that rare species experience stronger CNDD and may help reconcile contrasting findings for the relationship between the CNDD strength and abundance. [ABSTRACT FROM AUTHOR]

Contagious seed dispersal refers to the tendency for some sites to receive many dispersed seeds while other sites receive few dispersed seeds. Contagious dispersal can lead to interspecific associations in seed arrival, and this in turn might lead to interspecific associations in seedling recruitment. We evaluate the extent of spatially contagious seed arrival, the frequency of positive interspecific associations in seed arrival, and their consequences for seedling recruitment at the community level in a tropical moist forest. We quantified seed arrival to 200 passive seed traps for 28 yr of weekly censuses and seedling recruitment to 600 1-m2 quadrats for 21 yr of annual censuses on Barro Colorado Island, Panama. We assessed whether spatially contagious seed dispersal was more important among zoochorous species than among anemochorous species, increased in importance with similarity in fruiting times, and led to interspecific associations in seed arrival and seedling recruitment. We controlled adult seed source associations statistically to evaluate predicted relationships. We found that spatially contagious seed arrival was widespread among zoochorous species, but also occurred among anemochorous species when the strong, consistent trade winds were present. Significant interspecific associations in seed arrival were more likely for pairs of species with zoochorous seeds and similar fruiting times and persisted through seedling recruitment. Thus, interspecifically contagious seed dispersal affects local species composition and alters the mixture of interspecific interactions through the seed, germination, and early seedling stages in this forest. Future investigations should consider the implications of interspecific association at the regeneration stages documented here for later life stages and species coexistence. [ABSTRACT FROM AUTHOR]

Seed size and toughness affect seed predators, and size-dependent investment in mechanical defence could affect relationships between seed size and predation. We tested how seed toughness and mechanical defence traits (tissue density and protective tissue content) are related to seed size among tropical forest species. Absolute toughness increased with seed size. However, smaller seeds had higher specific toughness both within and among species, with the smallest seeds requiring over 2000 times more energy per gram to break than the largest seeds. Investment in mechanical defence traits varied widely but independently of the toughness-mass allometry. Instead, a physical scaling relationship confers a toughness advantage on small seeds independent of selection on defence traits and without a direct cost. This scaling relationship may contribute to seed size diversity by decreasing fitness differences among large and small seeds. Allometric scaling of toughness reconciles predictions and conflicting empirical relationships between seed size and predation. [ABSTRACT FROM AUTHOR]

We consider minimization of functions that are compositions of convex or prox-regular functions (possibly extended-valued) with smooth vector functions. A wide variety of important optimization problems fall into this framework. We describe an algorithmic framework based on a subproblem constructed from a linearized approximation to the objective and a regularization term. Properties of local solutions of this subproblem underlie both a global convergence result and an identification property of the active manifold containing the solution of the original problem. Preliminary computational results on both convex and nonconvex examples are promising. [ABSTRACT FROM AUTHOR]

In Neotropical forests, lianas are increasing in abundance relative to trees. This increased species richness may reflect a positive response to global change factors including increased temperature, atmospheric CO, habitat fragmentation, and drought severity; however, questions remain as to the specific mechanisms facilitating the response. Previous work suggests that lianas may gain an ecological advantage over trees through leaf functional traits that offer a quick return on investment of resources, although it is unknown whether this pattern extends to root traits and relationships with fungal or bacterial symbionts belowground. We sampled confamilial pairs of liana and tree species and quantified morphological and chemical traits of leaves and fine roots, as well as root symbiont abundance, to determine whether functional traits associated with resource acquisition differed between the two. Compared to trees, lianas possessed higher specific leaf area, specific root length, root branching intensity, and root nitrogen (N) and phosphorus (P) concentrations, and lower leaf and root tissue density, leaf and root carbon (C), root diameter, root C:P and N:P, and mycorrhizal colonization. Our study provides new evidence that liana leaf and root traits are characterized by a rapid resource acquisition strategy relative to trees. These liana functional traits may facilitate their response to global change, raising questions about how increased liana dominance might affect ecosystem processes of Neotropical forests. [ABSTRACT FROM AUTHOR]

Numerous grassland experiments have found evidence for a complementarity effect, an increase in productivity with higher plant species richness due to niche partitioning. However, empirical tests of complementarity in natural forests are rare. We conducted a spatially explicit analysis of 518 433 growth records for 274 species from a 50-ha tropical forest plot to test neighborhood complementarity, the idea that a tree grows faster when it is surrounded by more dissimilar neighbors. We found evidence for complementarity: focal tree growth rates increased by 39.8% and 34.2% with a doubling of neighborhood multi-trait dissimilarity and phylogenetic dissimilarity, respectively. Dissimilarity from neighbors in maximum height had the most important effect on tree growth among the six traits examined, and indeed, its effect trended much larger than that of the multi-trait dissimilarity index. Neighborhood complementarity effects were strongest for light-demanding species, and decreased in importance with increasing shade tolerance of the focal individuals. Simulations demonstrated that the observed neighborhood complementarities were sufficient to produce positive stand-level biodiversity-productivity relationships. We conclude that neighborhood complementarity is important for productivity in this tropical forest, and that scaling down to individual-level processes can advance our understanding of the mechanisms underlying stand-level biodiversity-productivity relationships. [ABSTRACT FROM AUTHOR]

Metabolic rate is a critical factor in animal biology and ecology, providing an objective measure that can be used in attributing a cost to different activities and to assessing what animals do against some optimal behaviour. Ideally, metabolic rate would be estimated directly by measuring heat output but, until recently, this has not been easily tractable with fishes so instead metabolic rate is usually estimated using indirect methods. In the laboratory, oxygen consumption rate is the indirect method most frequently used for estimating metabolic rate, but technical requirements preclude the measurement of either heat output or oxygen consumption rate in free-ranging fishes. There are other field methods for estimating metabolic rate that can be used with mammals and birds but, again, these cannot be used with fishes. Here, the use of electronic devices that record body acceleration in three dimensions (accelerometry) is considered. Accelerometry is a comparatively new telemetric method for assessing energy metabolism in animals. Correlations between dynamic body acceleration ( DBA) and oxygen consumption rate demonstrate that this will be a useful proxy for estimating activity-specific energy expenditure from fishes in mesocosm or field studies over extended periods where other methods ( e.g. oxygen consumption rate) are not feasible. DBA therefore has potential as a valuable tool for attributing cost to different activities. This could help in gaining a full picture of how fishes make energy-based trade-offs between different levels of activity when faced with conflicting or competing demands arising from increased and combined environmental stressors. [ABSTRACT FROM AUTHOR]

The importance of lianas through time and their effect on tree reproduction are evaluated for the first time in a Southeast Asian Dipterocarp forest. We quantified flower and seed production by lianas and trees for 13 years, assessed liana loads in the crowns of all trees larger than 30 cm in diameter at breast height (1.3 m) in 2002 and 2014, and assessed levels of reproduction for the same trees during a strong general flowering event in 2014 for the 50-ha forest dynamics plot at the Pasoh Forest Reserve, Malaysia. General flowering refers to synchronous reproduction by hundreds of plant species at irregular, multiyear intervals and only occurs in Southeast Asian Dipterocarp forests. Overall, lianas were present in 50% of tree crowns and comprised 31% of flower production and 46% of seed production. Lianas reduced growth, survival, and reproduction by their host trees. Lianas were less frequent in canopyemergent trees, Dipterocarps comprised a disproportionately large proportion of canopy emergents, and, as a consequence, lianas were less frequent in Dipterocarps than in trees from other plant families. Lianas infested the crowns of significantly fewer trees in 2014 (47.9%) than in 2002 (52.3%); however, the decrease was restricted to trees with the lightest liana loads and sample sizes and statistical power were enormous. Lianas comprised a stable proportion of flower production and a highly variable proportion of seed production from 2002 through 2013. We conclude lianas have a huge impact on trees in this forest and were a stable component of the forest between 2002 and 2014. The emergent habit and associated ability to avoid lianas might contribute to the success of the Dipterocarpaceae. [ABSTRACT FROM AUTHOR]

Questions remain as to which soil nutrients limit primary production in tropical forests. Phosphorus (P) has long been considered the primary limiting element in lowland forests, but recent evidence demonstrates substantial heterogeneity in response to nutrient addition, highlighting a need to understand and diagnose nutrient limitation across diverse forests. Fine-root characteristics including their abundance, functional traits, and mycorrhizal symbionts can be highly responsive to changes in soil nutrients and may help to diagnose nutrient limitation. Here, we document the response of fine roots to long-term nitrogen (N), P, and potassium (K) fertilization in a lowland forest in Panama. Because this experiment has demonstrated that N and K together limit tree growth and P limits fine litter production, we hypothesized that fine roots would also respond to nutrient addition. Specifically we hypothesized that N, P, and K addition would reduce the biomass, diameter, tissue density, and mycorrhizal colonization of fine roots, and increase nutrient concentration in root tissue. Most morphological root traits responded to the single addition of K and the paired addition of N and P, with the greatest response to all three nutrients combined. The addition of N, P, and K together reduced fine-root biomass, length, and tissue density, and increased specific root length, whereas root diameter remained unchanged. Nitrogen addition did not alter root N concentration, but P and K addition increased root P and K concentration, respectively. Mycorrhizal colonization of fine roots declined with N, increased with P, and was unresponsive to K addition. Although plant species composition remains unchanged after 14 years of fertilization, fine-root characteristics responded to N, P, and K addition, providing some of the strongest stand-level responses in this experiment. Multiple soil nutrients regulate fine-root abundance, morphological and chemical traits, and their association with mycorrhizal fungi in a species-rich lowland tropical forest. [ABSTRACT FROM AUTHOR]

Defaunation alters trophic interactions between plants and vertebrates, which may disrupt trophic cascades, thereby favoring a subset of plant species and reducing diversity. If particular functional traits characterize the favored plant species, then defaunation may alter community-wide patterns of functional trait composition. Changes in plant functional traits occurring with defaunation may help identify the species interactions affected by defaunation and the potential for other cascading effects of defaunation. We tested the hypotheses that defaunation would (1) disrupt seed dispersal, thereby favoring species whose dispersal agents are not affected (e.g., small birds, bats, and abiotic agents), (2) reduce seed predation, thereby favoring larger-seeded species, and (3) reduce herbivory, thereby favoring species with lower leaf mass per area (LMA), leaf toughness, and wood density. We examined how these six traits responded to vertebrate defaunation caused by hunters or by experimental exclosures among more than 30 000 woody seedlings in a lowland tropical moist forest. Exclosures reduced terrestrial frugivores, granivores, and herbivores, while hunters also reduced volant and arboreal frugivores and granivores. The comparison of exclosures and hunting allowed us to parse the impacts of arboreal and volant species (reduced by hunters only) and terrestrial species (reduced by both hunters and exclosures). The loss of terrestrial vertebrates alone had limited effects on plant trait composition. The additional loss of volant and arboreal vertebrates caused significant shifts in plant species composition towards communities with more species dispersed abiotically, including lianas and low wood-density tree species, and fewer species dispersed by large vertebrates. In contrast to previous studies, community seed mass did not decline significantly in hunted sites. Our exclosure results suggest this is because reducing seed predators disproportionately benefits large-seeded species, partially compensating for the reduction of seed dispersers at hunted sites. Our results demonstrate that decreased seed dispersal and seed predation are important determinants of seedling community compositional change as a consequence of defaunation. Defaunation may also negatively impact carbon storage in tropical forests, by favoring lianas and low wood density tree species. [ABSTRACT FROM AUTHOR]

Lianas are a prominent growth form in tropical forests, and there is compelling evidence that they are increasing in abundance throughout the Neotropics. While recent evidence shows that soil resources limit tree growth even in deep shade, the degree to which soil resources limit lianas in forest understories, where they coexist with trees for decades, remains unknown. Regardless, the physiological underpinnings of soil resource limitation in deeply shaded tropical habitats remain largely unexplored for either trees or lianas. Theory predicts that lianas should be more limited by soil resources than trees because they occupy the quick-return end of the ''leaf economic spectrum,'' characterized by high rates of photosynthesis, high specific leaf area, short leaf life span, affinity to high-nutrient sites, and greater foliar nutrient concentrations. To address these issues, we asked whether soil resources (nitrogen, phosphorus, and potassium), alone or in combination, applied experimentally for more than a decade would cause significant changes in the morphology or physiology of tree and liana seedlings in a lowland tropical forest. We found evidence for the first time that phosphorus limits the photosynthetic performance of both trees and lianas in deeply shaded understory habitats. More importantly, lianas always showed significantly greater photosynthetic capacity, quenching, and saturating light levels compared to trees across all treatments. We found little evidence for nutrient 3 growth form interactions, indicating that lianas were not disproportionately favored in nutrient-rich habitats. Tree and liana seedlings differed markedly for six key morphological traits, demonstrating that architectural differences occurred very early in ontogeny prior to lianas finding a trellis (all seedlings were self-supporting). Overall, our results do not support nutrient loading as a mechanism of increasing liana abundance in the Neotropics. Rather, our finding that lianas always outperform trees, in terms of photosynthetic processes and under contrasting rates of resource supply of macronutrients, will allow lianas to increase in abundance if disturbance and tree turnover rates are increasing in Neotropical forests as has been suggested. [ABSTRACT FROM AUTHOR]

Leaf defences vary widely among tree species, affecting rates of herbivory, survival and reproduction., Two contrasting hypotheses account for variation in leaf defences among species. The first predicts that a slow life history, which is characteristic of larger seeded species adapted to resource-limited environments, is associated with well-defended leaves. The second, apparency theory, predicts that elevated leaf defences are necessitated for species that are more detectable to herbivores., Here we use comparative methods and a global data set to test (i) the relationship between seed size and leaf defences and (ii) the relationship between clumping (spatial apparency) and leaf defences., We found that seed size was positively related to leaf fracture toughness, but not phenolics or tannin concentration and that spatial aggregation was unrelated to leaf defences., Synthesis. Our results suggest that larger seed size and increased leaf toughness are correlated as part of a trait syndrome associated with a slow, resource-limited life history, not clumped dispersion and increased spatial apparency. [ABSTRACT FROM AUTHOR]

I This study by Sabine i Mann and co-workers I in the USA aimed to evaluate the role of oxidative stress, cholestasis, liver injury and infection with equine hepacivirus (EqHV) or equine parvovirus-hepatitis (EqPV-H) infection in racehorses with increased serum gamma-glutamyl i transferase (GGT) activity. Osteoarthritis prevention using MSCs I In this study i Lélia Bertoni and co-workers I in France evaluated allogeneic bone-marrow-derived and umbilical cord blood- derived mesenchymal stem cells (MSCs) to prevent the development of osteoarthritis (OA) in an equine model i . This study evaluated the ability of a single blinded intra- articular injection of allogeneic bone-marrow (BM) derived MSCs and umbilical cord blood (UCB) derived MSC to limit the development of OA-associated pathological changes compared to placebo in a post-traumatic OA model applied to all four fetlock joints of eight horses. [Extracted from the article]