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Every year, an estimated 15 million babies are born preterm (37 weeks' gestational age [GA]) globally. These preterm infants are exposed to repeated stressful and often painful procedures as part of routine life-saving care within the neonatal intensive care unit (NICU). Preterm birth continues to be a major health issue associated with increased risk of neurodevelopmental and behavioral disorders such as cerebral palsy, cognitive impairment, autism spectrum disorders and psychiatric disease.This paper identifies epigenetic alterations and incidence of telomere erosion that have been studied in preterm infants while in the NICU and as a long-term outcome measure. Better understanding of epigenetic alterations and telomere erosion might aid in early detection and prevention/alleviation of the negative effects of cumulative painful/stressful experiences in this population.The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) standards were used to guide this review. Systematic searches of databases included PubMed, CINAHL, SCOPUS and PsychInfo.Twenty-one studies were included, appraised and then synthesized into a narrative summary.Several putative epigenetic markers were identified although there was a paucity of studies related to telomere length. The interaction of disease entity combined with therapeutic interventions intended to treat may inadvertently increase infant allostatic load or ability to adapt to stress. Future research should include not only human studies but leverage newly available large data sets to conduct additional analysis.

Combining population genetic studies with demographic surveys in long-lived clonal herbs can yield insight into the population dynamics of clonal plant populations. In this study, we assayed clonal diversity and spatial genetic structure in a population of a long-lived understory herb, Trillium recurvatum, that has been the focus of a demographic study spanning 26 years at the Meeman Biological Station in Memphis, Tennessee, USA. Using a set of five newly developed simple sequence repeat markers first reported here, we assessed 1) the extent of clonal diversity within the Meeman site, 2) the degree to which genetic diversity varies with stage class (juvenile, non-flowering, and flowering adults) at this site, 3) whether there is spatial genetic structure at the Meeman site, and 4) how measures of genetic diversity and inbreeding at the Meeman site compare to two additional nearby populations. Along with these analyses, we calculated and compared traditional population genetic metrics with information theory-based diversity indices. Although clonal propagation was present, the focal population displayed moderate levels of clonal diversity comprising 81 genets from the 174 individuals sampled. In the focal site, we also found that genetic diversity was highest in the flowering stage class when compared to the non-flowering and juvenile classes. We report that genets exhibited spatial genetic structure in the focal site exhibiting values for the Sp statistic of 0.00199 for linear distance and 0.0271 for log distance. Measures of unbiased gene diversity and the inbreeding coefficient were comparable across the sampled populations. Our results provide complementary genetic data to previous demographic studies in T. recurvatum, and these findings provide data for future studies aimed at integrating the degree of clonality, genetic variation, and population dynamics in this species. Our findings suggest that T. recurvatum at the focal Meeman site displays higher levels of sexual reproduction than were previously suggested, and spatial genetic structure estimates were comparable to other plant species with mixed and outcrossing mating strategies.

Near-infrared spectroscopy (NIRS)-based monitoring of regional tissue oxygenation (rSO2) is becoming more commonplace in the neonatal intensive care unit (NICU). While increasing evidence supports rSO2 monitoring, actual standards for applying this noninvasive bedside technique continue to evolve. This review highlights the current strengths and pitfalls surrounding practical NIRS-based monitoring in the neonatal population. The physiologic background of rSO2 monitoring is discussed, with attention to understanding oxygen delivery/consumption mismatch and its effects on tissue oxygen extraction. The bedside utility of both cerebral and peripheral rSO2 monitoring in the NICU is then explored from two perspectives: (1) disease/event-specific "responsive" monitoring and (2) "routine," continuous monitoring. Recent evidence incorporating both monitoring approaches is summarized with emphasis on practical applicability in the NICU. Finally, a future paradigm for a broad-based NIRS monitoring strategy is presented, with attention towards improving personalization of neonatal care and ultimately enhancing long-term outcomes.

The observed properties of valves in collecting lymphatic vessels include transmural pressure-dependent bias to the open state and hysteresis. The bias may reduce resistance to flow when the vessel is functioning as a conduit. However, lymphatic pumping implies a streamwise increase in mean pressure across each valve, suggesting that the bias is then potentially unhelpful. Lymph pumping by a model of several collecting lymphatic vessel segments (lymphangions) in series, which incorporated these properties, was investigated under conditions of adverse pressure difference while varying the refractory period between active muscular contractions and the inter-lymphangion contraction delay. It was found that many combinations of the timing parameters and the adverse pressure difference led to one or more intermediate valves remaining open instead of switching between open and closed states during repetitive contraction cycles. Cyclic valve switching was reliably indicated if the mean pressure in a lymphangion over a cycle was higher than that in the lymphangion upstream, but either lack of or very brief valve closure could cause mean pressure to be lower downstream. Widely separated combinations of refractory period and delay time were found to produce the greatest flow-rate for a given pressure difference. The efficiency of pumping was always maximized by a long refractory period and lymphangion contraction starting when the contraction of the lymphangion immediately upstream was peaking. By means of an ex vivo experiment, it was verified that intermediate valves in a chain of pumping lymphangions can remain open, while the lymphangions on either side of the open valve continue to execute contractions.

Mechanically stacked tandem solar cells are a potential near-term solution for increasing the efficiency of photovoltaic modules. Practical implementation requires an interconnection approach that maximizes efficiency and minimizes complexity and cost. Connecting the top and bottom cells in a voltage-matched configuration allows two-terminal modules to be fabricated without altering the cell design or processing methods. Here, we experimentally demonstrate two-terminal voltage-matched GaInP2 / Si minimodules. The two-terminal minimodules performed just as well as four terminal configurations when voltage-matching requirements were met. The magnitude of the efficiency loss experienced by the voltage-matched minimodule when voltage-matched conditions were not met depends on whether the voltage was constrained by the GaInP2 or Si cells. Monte Carlo simulations also indicate that the two-terminal voltage-matched tandems respond to small cell-to-cell parameter variations in a similar manner as four terminal tandems.

In this paper we simulate a nanodisc reflector array that can enhance light trapping to overcome the limitations of low absorption in thin crystalline Si (c-Si). We performed a numerical simulation for a cell design with a thin c-Si absorber layer less than 20$\mu$m thick. Our results show that a potential short circuit current increase of up to 22.9% is achievable, effectively doubling the optical path length compared to a planar metallic reflector.

Betavoltaic converters are attractive power sources due to their long duration, continuous discharge and highenergy densities in comparison with other modes of energy harvesting. The main obstacle to widen the application of betavoltaics is their low power output. 2D Monte Carlo numerical simulations coupled with drift-diffusionmodeling were conducted to evaluate commercially available and emerging wideband gap semiconductors as potential absorbers with widely available tritium (H-3) isotope. Results show that power enhancement can be achieved by using emerging ultra wide bandgap material such as diamond. Using those materials, >40% increase in the power density in comparison with current 4H-SiC technology can be achieved.

A dose-response relationship between proportions of donor human milk (DHM) intake and in-neonatal intensive care unit (in-NICU) growth rates, if any, remains poorly defined. Objective was to evaluate interrelationships between percentages of DHM, mother's own milk (MOM), and preterm formula (PF) intake and neonatal growth parameters at 36 weeks postmenstrual age or NICU discharge.Infants eligible for this single-center retrospective study were inborn at ≤32 weeks gestation or ≤1800 g, stayed in the NICU for ≥7 days, and received enteral nutrition consisting of human milk fortified with Enfamil human milk fortifier acidified liquid. Study exposures were defined as 10% increments in the total volumetric proportions of infant diet provided as MOM, DHM, or PF. Outcomes were growth parameters at 36 weeks postmenstrual age or NICU discharge. Multivariable linear regression modeled the adjusted additive effect of infant diet on individual growth parameters.A total of 314 infants records were eligible for analysis. Using MOM as reference, the adjusted mean growth velocity for weight significantly decreased by 0.17 g · kg · day for every 10% increase in DHM intake, but did not vary with PF intake. The adjusted mean change in weight z score significantly decreased with increasing proportion of DHM intake but significantly improved with increasing PF intake. The adjusted mean head circumference velocity was significantly decreased by 0.01 cm/wk for every 10% increase in DHM intake, in reference to MOM, but did not vary with PF intake. Neither proportion of DHM nor PF intake was associated with length velocity.When DHM and MOM are fortified interchangeably, preterm infants receiving incremental amounts of DHM are at increased risk of postnatal growth restriction. The dose-response relationship between DHM, MOM, and PF and long-term growth and neurodevelopmental outcomes warrants further research.

Background The multifactorial pathology and broad clinical presentation of necrotizing enterocolitis (NEC) development in premature infants make prediction of disease onset extremely challenging. Over the past decade, packed red blood cell (PRBC) transfusions have been temporally linked to the development of NEC in severely anemic preterm infants, although this issue is highly controversial. Purpose In this case study, we describe events of an extremely low birth-weight infant who developed NEC complicated by pneumoperitoneum after receiving multiple PRBC transfusions. Specifically, we describe mesenteric tissue oxygenation trend changes as measured by continuous near-infrared spectroscopy (NIRS) technology. Methods As part of a larger prospective, observational investigation, this infant was monitored with NIRS (INVOS 5100C; Medtronic, Boulder, Colorado) before, during, and 48 hours following PRBC transfusions. Results The infant demonstrated severe, prolonged, and persistent reductions in mesenteric tissue oxygenation following blood transfusions, yet routine physiologic monitoring did not indicate intestinal hypoperfusion or impending NEC onset. Implications for practice This report demonstrates the ability of NIRS to capture possible tissue ischemia during early stages of NEC that may help guide bedside therapeutic interventions. Implications for research Larger cohort studies to evaluate the ability of NIRS to capture early tissue ischemia are essential to validate the feasibility of adding this technology as a routine clinical bedside tool.Video Abstract available at https://journals.lww.com/advancesinneonatalcare/Pages/videogallery.aspx.

The secondary lymphatic valve is a bi-leaflet structure frequent throughout collecting vessels that serves to prevent retrograde flow of lymph. Despite its vital function in lymph flow and apparent importance in disease development, the lymphatic valve and its associated fluid dynamics have been largely understudied. The goal of this work was to construct a physiologically relevant computational model of an idealized rat mesenteric lymphatic valve using fully coupled fluid-structure interactions to investigate the relationship between three-dimensional flow patterns and stress/deformation within the valve leaflets. The minimum valve resistance to flow, which has been shown to be an important parameter in effective lymphatic pumping, was computed as 268 g/mm4-s. Hysteretic behavior of the lymphatic valve was confirmed by comparing resistance values for a given transvalvular pressure drop during opening and closing. Furthermore, eddy structures were present within the sinus adjacent to the valve leaflets in what appear to be areas of vortical flow; the eddy structures were characterized by non-zero velocity values (up to ∼4 mm/s) in response to an applied unsteady transvalvular pressure. These modeling capabilities present a useful platform for investigating the complex interplay between soft tissue motion and fluid dynamics of lymphatic valves and contribute to the breadth of knowledge regarding the importance of biomechanics in lymphatic system function.

The lymphatic system is vital to a proper maintenance of fluid and solute homeostasis. Collecting lymphatics are composed of actively contracting tubular vessels segmented by bulbous sinus regions that encapsulate bi-leaflet check valves. Valve resistance to forward flow strongly influences pumping performance. However, because of the sub-millimeter size of the vessels with flow rates typically < 1 ml/hour and pressures of a few cmH2O, resistance is difficult to measure experimentally. Using a newly defined idealized geometry, we employed an uncoupled approach where the solid leaflet deflections of the open valve were computed and lymph flow calculations were subsequently performed. We sought to understand: 1) the effect of sinus and leaflet size on the resulting deflections experienced by the valve leaflets and 2) the effects on valve resistance to forward flow of the fully open valve. For geometries with sinus-to-root diameter ratios > 1.39, the average resistance to forward flow was 0.95 × 106 [g/(cm4 s)]. Compared to the viscous pressure drop that would occur in a straight tube the same diameter as the upstream lymphangion, valve leaflets alone increase the pressure drop up to 35%. However, the presence of the sinus reduces viscous losses, with the net effect that when combined with leaflets the overall resistance is less than that of the equivalent continuing straight tube. Accurately quantifying resistance to forward flow will add to the knowledge used to develop therapeutics for treating lymphatic disorders and may eventually lead to understanding some forms of primary lymphedema.

The principle of superposition is commonly utilized in the analysis of current transport under dark and light conditions for several different types of solar cells. However, this principle assumes that the photocurrent is voltage independent and that the diode injection current is generation independent, which restricts its validity. Indeed, the superposition principle cannot be applied to most thin-film solar cells because the above mentioned assumptions are not generally valid. In order to address this issue, a novel numerical modeling approach is described that allows independent computation of the photocurrent and of the diode injection current as components of the total current under illumination. Then, using several test cases, where the principle of superposition breaks down, the usefulness of this modeling approach is demonstrated.

The shear stress applied to lymphatic endothelial cells (LEC) by lymph flow changes dramatically under normal conditions as well as in response to disease conditions and immune reactions. In general, LEC are known to regulate the contraction frequency and strength of lymphatic pumping in response to shear stress. Intracellular calcium concentration ([Ca2+]i) is an important factor that regulates lymphatic contraction characteristics. In this study, we measured changes in the [Ca2+]iunder different shear stress levels and determined the source of this calcium signal. Briefly, human dermal LEC were cultured in custom-made microchannels for 3 days before loading with 2 µM fura-2 AM, a ratiometric calcium dye to measure [Ca2+]i. Step changes in shear stress resulted in a rapid increase in [Ca2+]ifollowed by a gradual return to the basal level and sometimes below the initial baseline (45.2 ± 2.2 nM). The [Ca2+]ireached a peak at 126.2 ± 5.6 nM for 10 dyn/cm2stimulus, whereas the peak was only 71.8 ± 5.4 nM for 1 dyn/cm2stimulus, indicating that the calcium signal depends on the magnitude of shear stress. Removal of the extracellular calcium from the buffer or pharmocological blockade of calcium release-activated calcium (CRAC) channels significantly reduced the peak [Ca2+]i, demonstrating a role of extracellular calcium entry. Inhibition of endoplasmic reticulum (ER) calcium pumps showed the importance of intracellular calcium stores in the initiation of this signal. In conclusion, we demonstrated that the shear-mediated calcium signal is dependent on the magnitude of the shear and involves ER store calcium release and extracellular calcium entry.

In this study, we develop an approach to characterize the surface and bulk properties for thin films of photovoltaic materials by combining two experimental photoluminescence (PL) techniques with one multiphysics simulation. This contactless, in-line characterization technique allows reliable extraction of key lifetime parameters. In this study, we first discuss the strengths and weaknesses of both steady-state and transient PL techniques (specifically, steady-state PL excitation spectroscopy and time-resolved PL) and show that combining them with numerical simulation can be used to extract surface and bulk lifetimes self consistently. The method is applied to InP thin films grown with a novel vapor-liquid-solid method. The InP thin film tested is found to have a bulk Shockley-Read-Hall (SRH) lifetime of 12 ns and a front surface recombination velocity of 5×10 4 cm/s.

One important feature of the mammalian immune system is the highly specific binding of antigens to antibodies. Antibodies generated in response to one infection may also provide some level of cross immunity to other infections. One model to describe this cross immunity is the notion of antigenic space, which assigns each antibody and each virus a point in ℝ(n). Past studies using hemagglutination data have suggested the dimensionality of antigenic space, n, is low. We propose that influenza evolution may be modeled as a Gaussian random walk. We then show that hemagluttination data would be consistent with a walk in very high dimensions. The discrepancy between our result and prior studies is due to the fact that random walks can appear low dimensional according to a variety of analyses including principal component analysis (PCA) and multidimensional scaling (MDS). A high dimensionality of antigenic space is of importance to modelers, as it suggests a smaller role for pre-existing immunity within the host population.

We examine the potential to enhance cell performance using wide bandgap metal oxide films as full-area rear contacts to p-type crystalline Si (c-Si) solar cells. We aim to introduce a band offset through wide bandgap nickel oxide rather than introducing a band bending through transition metal oxides (e.g. MoO x , V 2 Ox, WO x ). Our numerical simulation shows it is possible to achieve one-sun efficiency of 21.6% with the open-circuit voltage (V oc ) of 652 mV, the short-circuit current density (J sc ) of 39.9 mA/cm2 and the fill factor (FF) of 82.5% when the back surface recombination velocities is 100 cm/s at p-Si/NiO x .

In this study, we investigate the effectiveness of MoOx, and TiO2layers as minority carrier selective contacts in crystalline silicon solar cells. We use numerical simulation to show that it is possible to achieve an improvement in open circuit voltage by up to 70 mV for TiO2and 100 mV for MoOxwith one-sun efficiencies exceeding 20%. We further determine the material parameters of primary importance to each of the materials in determining their effectiveness at surface passivation, finding that the density of surface defects is most important for TiO2, while the electron affinity predominates for MoOx.

Tunnel junctions with low differential resistance and high transparency have been grown by molecular beam epitaxy on GaSb substrates. The resulting devices have been characterized and analyzed using a combination of electrical measurements and modeling. These devices have importance to multi-junction solar cells grown on GaSb substrates. The structures contain an n-type InAs quantum well embedded in a GaSb p/n junction, exploiting the high tunnel probability at the broken gap interface between p-type GaSb and n-type InAs, whilst having a minimal impact on the transparency of the device.

Simulations were performed with LT-SPICE™ to evaluate the limiting effects of cell size, perimeter recombination, and sheet resistance on the performance of a solar cell under 500 sun light concentration. A circuit model was generated using parameters extracted from a 3 junction InGaP/GaAs/InGaAsN device and simulated with various contact configurations. The results of the simulation were then used to determine the optimal cell size for a gridless cell and the conditions under which a gridless cell is more efficient than a cell with grid fingers.

Mechanically-stacked tandem solar cells combining existing photovoltaic technologies present a straightforward path toward higher conversion efficiencies. Voltage-matched configurations have been proposed as a simplified approach for fabricating two terminal modules, but they are subject to performance losses compared to four terminal configurations if voltage-matching conditions are not met. Here, we demonstrate a two terminal voltage-matched GalnP 2 /Si tandem with 23 % efficiency. Through a combination of experimental measurement and simulation, we explore the impact of voltage and fill factor mismatches between the top and bottom sub-cell strings. Our results show that efficiency losses are minimized when voltage-mismatches are accommodated by designing the bottom strings to have a higher voltage. Fill factor mismatches due to differences in series resistance also lead to changes in the optimal ratio of the number of cells in the top and bottom sub-cell strings.

Radiation tolerance is a critical concern for space power applications. In this paper we demonstrate intrinsic radiation tolerance in ultra-thin (

Many tissues exhibit subatmospheric interstitial pressures under normal physiologic conditions. The mechanisms by which the lymphatic system extracts fluid from these tissues against the overall pressure gradient are unknown. We address this important physiologic issue by combining experimental measurements of contractile function and pressure generation with a previously validated mathematical model. We provide definitive evidence for the existence of ‘suction pressure’ in collecting lymphatic vessels, which manifests as a transient drop in pressure downstream of the inlet valve following contraction. This suction opens the inlet valve and is required for filling in the presence of low upstream pressure. Positive transmural pressure is required for this suction, providing the energy required to reopen the vessel. Alternatively, external vessel tethering can serve the same purpose when the transmural pressure is negative. Suction is transmitted upstream, allowing fluid to be drawn in through initial lymphatics. Because suction plays a major role in fluid entry to the lymphatics and is affected by interstitial pressure, our results introduce the phenomenon as another important factor to consider in the study of lymphoedema and its treatment.

The lymphatic system has a major significance in the metastatic pathways in women's cancers. Lymphatic pumping depends on both extrinsic and intrinsic mechanisms, and the mechanical behavior of lymphatic vessels regulates the function of the system. However, data on the mechanical properties and function of human lymphatics are lacking. Our aim is to characterize, for the first time, the passive biomechanical behavior of human collecting lymphatic vessels removed at pelvic lymph node dissection during primary debulking surgeries for epithelial ovarian cancer. Isolated vessels were cannulated and then pressurized at varying levels of applied axial stretch in a calcium-free Krebs buffer. Pressurized vessels were then imaged using multi-photon microscopy for collagen-elastin structural composition and fiber orientation. Both pressure-diameter and force-elongation responses were highly nonlinear, and axial stretching of the vessel served to decrease diameter at constant pressure. Pressure-diameter behavior for the human vessels is very similar to data from rat mesenteric vessels, though the human vessels were approximately 10× larger than those from rats. Multiphoton microscopy revealed the vessels to be composed of an inner layer of elastin with an outer layer of aligned collagen fibers. This is the first study that successfully described the passive biomechanical response and composition of human lymphatic vessels in patients with ovarian cancer. Future work should expand on this knowledge base with investigations of vessels from other anatomical locations, contractile behavior, and the implications on metastatic cell transport.

Fluid homeostasis in vertebrates critically relies on the lymphatic system forming a hierarchical network of lymphatic capillaries and collecting lymphatics, for the efficient drainage and transport of extravasated fluid back to the cardiovascular system. Blind-ended lymphatic capillaries employ specialized junctions and anchoring filaments to encourage a unidirectional flow of the interstitial fluid into the initial lymphatic vessels, whereas collecting lymphatics are responsible for the active propulsion of the lymph to the venous circulation via the combined action of lymphatic muscle cells and intraluminal valves. Here we describe recent findings on molecular and physical factors regulating the development and maturation of these two types of valves and examine their role in tissue-fluid homeostasis.

Relatively little attention has been paid to the relationship between commute time variances and city size. In this paper, we utilize 2009 Nationwide Highway Travel Survey data and test the relationship between area commute-time means as well as variances in metropolitan-area size. We include tests for metropolitan areas as a whole and for residents from urban, suburban, second city, and town-and-county areas. The regression analysis shows that all estimated slopes are statistically significant but not much greater than zero. Commute time means and variances are highly correlated. These relationships are also invariant with respect to the place of residence. An extensive collection of literature provides evidence for the co-location of workers and jobs hypothesis: average commute times do not rise appreciably as metropolitan population increases. We conclude that these results are additional, although indirect, evidence for the co-location hypothesis.

Thin-film solar cells often show a crossover between the illuminated and dark I–V characteristics. Several device specific reasons for crossover exist and have been discussed extensively. In this paper, we show that a low contact-to-contact built-in potential can produce a voltage-dependent photocurrent that leads to I–V crossover at a voltage that is almost exactly the device built-in potential. This mechanism can produce crossover in the absence of carrier trapping or recombination. It can be a contributing factor to crossover, but when an anomalously low contact-to-contact built-in potential exists, it can be the dominant factor. Using numerical simulations, we examine a variety of model solar cell structures with low contact-to-contact built-in potential and show a strong correlation of the crossover and built-in potential voltages. These simulations also suggest that a plot of the illuminated minus dark current may help identify when a low $V_{bi}$ is limiting device performance.

In order to assess the effects of age on flooding tolerance, we conducted a mesocosm flooding experiment that examined biomass accumulation of two age cohorts of Xanthium strumarium L. We also examined repeated measures of stem height and diameter of each cohort for the duration of the experiment. We hypothesized that change in biomass measures (root and shoot biomass, increase in total biomass, and root shoot ratio) of older individuals would be greater than younger individuals under simulated flooded conditions. We further hypothesized that older individuals would be impacted more than younger individuals regarding stress; i.e., the younger cohort would acclimate and thus flooding effects would be masked. Results indicate that older individuals were more impacted by flooding than younger individuals for all biomass parameters. Height repeated measures indicated that older individuals differentially responded to flooding stress, compared to younger individuals; which was also the case for diamet...

One advantage of microconcentrator photovoltaics (μ-CPV) is the range of possible circuit connection arrangements. Large numbers of cells can be connected in combinations of series and parallel strings, which can provide a means to protect the module against performance loss due to cell failure, cell shading, and other variations in cell parameters that may arise during the fabrication and wiring processes. We introduce a model to evaluate the best strategy for optimizing module reliability through circuit layout using a combination of series and parallel connected cell strings. The model uses realistic solar cell device parameters in an electrical network simulation, coupled with a Monte Carlo method to introduce defects into the array with different probabilities. We use the model to optimize the layout of a μ-CPV panel designed to be integrated with the conventional 60-cell crystalline silicon panels for diffuse light capture to produce a hybrid direct/diffuse CPV product.

In the past two decades, California’s share of the national cut flower market has decreased from 64 percent to 20 percent. California growers’ largest competitors are South American growers; Colombia controls 75 percent of the US market. South American growers have several competitive advantages, including the favorable trucking rates they enjoy by consolidating all shipments in Miami, Florida, prior to US distribution. This paper evaluates the California cut flower industry’s current transportation practices and investigates the feasibility and cost of establishing a shipping consolidation center in Oxnard, California. Applying a simple inventory management policy, we estimate a 35 percent system-wide transportation cost decrease of $20 million per year if all California cut flower growers participate in the consolidation center. The California Cut Flower Commission incorporated our findings into an application for federal funds from the US Department of Transportation to construct a new flower transportation and logistics center in California. The state’s flower growers are also searching for alternative ways to cooperatively fund a consolidation center.

Background Recent evidence suggests that antecedent packed red blood cell (PRBC) transfusions increase the risk for necrotizing enterocolitis (NEC), the most common gastrointestinal emergency encountered by very low birth weight (VLBW) infants. The underlying mechanism for this association is unknown. Altered oxygenation of the mesenteric vasculature during PRBC transfusion has been hypothesized to contribute to NEC development and was investigated in this study.

Lymph flow depends on both the rate of lymph production by tissues and the extent of passive and active pumping. Here we aim to characterize the passive mechanical properties of a lymphangion in both mid-lymphangion and valve segments to assess regional differences along a lymphangion, as well as evaluating its structural composition.Mesenteric lymphatic vessels were isolated and cannulated in a microchamber for pressure-diameter (P-D) testing. Vessels were inflated from 0 to 20 cmH(2)O at a rate of 4 cmH(2)O/min, and vessel diameter was continuously tracked, using an inverted microscope, video camera, and custom LabVIEW program, at both mid-lymphangion and valve segments. Isolated lymphatic vessels were also pressure-fixed at 2 and 7 cmH(2)O and imaged using a nonlinear optical microscope (NLOM) to obtain collagen and elastin structural information. We observed a highly nonlinear P-D response at low pressures (3-5 cmH(2)O), which was modeled using a three-parameter constitutive equation. No significant difference in the passive P-D response was observed between mid-lymphangion and valve regions. NLOM imaging revealed an inner elastin layer and outer collagen layer at all locations. Lymphatic valve leaflets were predominantly elastin with thick axially oriented collagen bands at the insertion points.We observed a highly nonlinear P-D response at low pressures (3-5 cmH(2)O) and developed the first constitutive equation to describe the passive P-D response for a lymphangion. The passive P-D response did not vary among regions, in agreement with the composition of elastin and collagen in the lymphatic wall.

Lake Ontario water levels are regulated under the International Joint Commission's Order of Approval. We assessed the availability of spawning habitat for eight fish guilds (grouped by vegetation and spawning temperature preferences) that use nearshore habitat in the Bay of Quinte, Lake Ontario, under regulated and pre-project water level scenarios. Our model used habitat characteristics of depth, substrate, vegetation cover and temperature across 14,876 habitat units and guild-based habitat suitabilities to assess the weighted suitable area (WSA) available for spawning. During the modelled 1951–2000 period, regulated water levels were on average 0.25 m lower than pre-project levels and varied about half as much. Overall, the large and shallow upper bay within the Bay of Quinte benefited from pre-project flows whereas the smaller and deeper lower bay benefited from regulated flows. Higher variance in water levels increased highly suitable wetland area and higher mean water levels increased the availability of shallow flooded area in the upper and middle bays, where the bathymetry is gradually sloping. The number of days over which WSA was available was generally greater for high temperature guilds, and appeared to decrease when temperature mismatches occurred in a season. Results emphasize the complexity of the relationship between fish habitat supply and water level regime.

The use of steady-state photoluminescence spectroscopy as a contactless characterization tool, suitable for inline optical characterization, has been previously demonstrated for high efficiency solar cells such as GaAs. In this paper, we demonstrate the use of PLE characterization on a thin film CdS/CdTe np heterojunction solar cell, and compare the results to measured EQE and I-V data. In contrast to previous work on high-quality GaAs, the PLE and EQE spectra do not match closely here. We still find, however, that reliable material parameters can be extracted from the PLE measurements. We also provide a physical explanation of the limits defining the cases when the PLE and EQE spectra may be expected to match.

Photoluminescence excitation spectroscopy is a contactless characterization technique that can provide valuable information about the surface and bulk recombination parameters of a semiconductor device, distinct from other sorts of photoluminescent measurements. For this technique, a temperature-tuned light emitting diode (LED) has several advantages over other light sources. The large radiation density offered by LEDs from near-infrared to ultraviolet region at a low cost enables efficient and fast photoluminescence measurements. A simple and inexpensive LED-based setup facilitates measurement of surface recombination velocity and bulk Shockley-Read-Hall lifetime, which are key parameters to assess device performance. Under the right conditions, this technique can also provide a contactless way to measure the external quantum efficiency of a solar cell.

The lymphatic system is an open-ended network of vessels that run in parallel to the blood circulation system. These vessels are present in almost all of the tissues of the body to remove excess fluid. Similar to blood vessels, lymphatic vessels are found in branched arrangements. Due to the complexity of experiments on lymphatic networks and the difficulty to control the important functional parameters in these setups, computational modeling becomes an effective and essential means of understanding lymphatic network pumping dynamics. Here we aimed to determine the effect of pumping coordination in branched network structures on the regulation of lymph flow. Lymphatic vessel networks were created by building upon our previous lumped-parameter model of lymphangions in series. In our network model, each vessel is itself divided into multiple lymphangions by lymphatic valves that help maintain forward flow. Vessel junctions are modeled by equating the pressures and balancing mass flows. Our results demonstrated that a 1.5 s rest-period between contractions optimizes the flow rate. A time delay between contractions of lymphangions at the junction of branches provided an advantage over synchronous pumping, but additional time delays within individual vessels only increased the flow rate for adverse pressure differences greater than 10.5 cmH2O. Additionally, we quantified the pumping capability of the system under increasing levels of steady transmural pressure and outflow pressure for different network sizes. We observed that peak flow rates normally occurred under transmural pressures between 2 to 4 cmH2O (for multiple pressure differences and network sizes). Networks with 10 lymphangions per vessel had the highest pumping capability under a wide range of adverse pressure differences. For favorable pressure differences, pumping was more efficient with fewer lymphangions. These findings are valuable for translating experimental measurements from the single lymphangion level to tissue and organ scales.

Questions: Do species arriving early (priority effect) to a site have a competitive advantage over species arriving later? Does early arrival aid in species ability to tolerate water stress? Is intra- and interspecific competition different for early and late arrivers? Location: Greenhouse, University of Northern Colorado, Greeley, Colorado, USA. Methods: A 1-mo ‘head start’ in the greenhouse was used to simulate early arrival of Panicum capillare and Polygonum persicaria. We used a completely randomized design to examine the effects of water stress (drained, drought, flood) and priority competition (interspecific and intraspecific) in relation to species’ cohort [older (established) and younger (novel) individuals planted in different combinations]. We calculated increases in root and shoot weights, total biomass, root/shoot ratios, height, leaf number and length of longest leaf. All dependent variables were analysed using MANOVA and individual GLM ANOVAs. Results: Increases in shoot and root biomass were significantly affected by water stress but the effects were species- and priority level-specific. Root biomass for established individuals was significantly reduced after flooding and drought. Shoot biomass was least for drought and flood treatments of both older and younger P. persicaria ,b ut older and youngerP. capillare were unaffected. There were species-specific priority differences (i.e. greater for older individuals) for shoot height and increases in leaf number; however, the opposite was seen for increases in leaf length. Conclusions: In terms of community assembly, neither species appears to have an advantage in relation to competition or water stress, as both seem plastic and are negatively affected by flood and drought stress. The greater impact of older P. persicaria onP. capillare is the only advantage P. persicariaseems to have in the greenhouse. Correlating this to natural conditions, it appears that chance in reaching a site first plays a major role in P. persicaria’s colonization success. This study provides evidence of the impacts of arrival time on subsequent physiological and competitive abilities of plants.

Two tick-borne diseases with expanding case and vector distributions are ehrlichiosis (transmitted by Amblyomma americanum) and rickettiosis (transmitted by A. maculatum and Dermacentor variabilis). There is a critical need to identify the specific habitats where each of these species is likely to be encountered to classify and pinpoint risk areas. Consequently, an in-depth tick prevalence study was conducted on the dominant ticks in the southeast. Vegetation, soil, and remote sensing data were used to test the hypothesis that habitat and vegetation variables can predict tick abundances. No variables were significant predictors of A. americanum adult and nymph tick abundance, and no clustering was evident because this species was found throughout the study area. For A. maculatum adult tick abundance was predicted by NDVI and by the interaction between habitat type and plant diversity; two significant population clusters were identified in a heterogeneous area suitable for quail habitat. For D. variabilis no environmental variables were significant predictors of adult abundance; however, D. variabilis collections clustered in three significant areas best described as agriculture areas with defined edges. This study identified few landscape and vegetation variables associated with tick presence. While some variables were significantly associated with tick populations, the amount of explained variation was not useful for predicting reliably where ticks occur; consequently, additional research that includes multiple sampling seasons and locations throughout the southeast are warranted. This low amount of explained variation may also be due to the use of hosts for dispersal, and potentially to other abiotic and biotic variables. Host species play a large role in the establishment, maintenance, and dispersal of a tick species, as well as the maintenance of disease cycles, dispersal to new areas, and identification of risk areas.

The state of the nation’s infrastructure is the subject of widespread discussion and comment because it is thought to include many deteriorating and unsafe bridges. Ever since the terrorist attacks of 9/11, there has been increasing concern over the extent to which an attack on infrastructure could result in serious economic disruption. This research develops a model to analyze the economic consequences of an attack on a major element of the highway network. We add a freight network to a national multiregional economic impact model and make freight traffic flows endogenous. The use of a sub-national interstate model recognizes that most infrastructure planning is at the state level and most political leaders’ interest is local. We base our approach on the National Interstate Economic Model (NIEMO) and refer to an elaboration that we name Transportation network and the National Interstate Economic Model (TransNIEMO). The new model enables us to study the state-specific and industry-specific economic impacts of some significant changes in the nature of highway freight movements. We tested the model for selected freight movements in and out of California. The results are entirely plausible and encourage us to elaborate and test the model for hypothetical disruptions of freight traffic throughout the US.

To examine short-term morphological changes and variables controlling this change, we conducted a study on five lower Mississippi River islands in 2007 and 2008. The southernmost island was located 25 km north of Memphis, TN, and the northernmost island was located 105 km north of Memphis. We surveyed elevations along six transects for each of the five islands to examine morphological changes between years and measured river velocity and backscatter intensity (sediment load) at the head, middle, toe, zee, and fore sides of the islands. We predicted the impacts of flooding on island geomorphology would be greatest at the head (upstream edge) and fore (thalweg) side. In addition, we predicted the morphology of islands present in the main channel in the 1890s would differ in morphology from contemporary islands. Results indicated morphological change during the study period but only in width. Islands showed general lateral migration, with one side aggrading while the other side eroded. Changes in mo...

Secondary lymphatic valves are essential for minimizing backflow of lymph and are presumed to gate passively according to the instantaneous trans-valve pressure gradient. We hypothesized that valve gating is also modulated by vessel distention, which could alter leaflet stiffness and coaptation. To test this hypothesis, we devised protocols to measure the small pressure gradients required to open or close lymphatic valves and determine if the gradients varied as a function of vessel diameter. Lymphatic vessels were isolated from rat mesentery, cannulated, and pressurized using a servo-control system. Detection of valve leaflet position simultaneously with diameter and intraluminal pressure changes in two-valve segments revealed the detailed temporal relationships between these parameters during the lymphatic contraction cycle. The timing of valve movements was similar to that of cardiac valves, but only when lymphatic vessel afterload was elevated. The pressure gradients required to open or close a valve were determined in one-valve segments during slow, ramp-wise pressure elevation, either from the input or output side of the valve. Tests were conducted over a wide range of baseline pressures (and thus diameters) in passive vessels as well as in vessels with two levels of imposed tone. Surprisingly, the pressure gradient required for valve closure varied >20-fold (0.1–2.2 cmH2O) as a passive vessel progressively distended. Similarly, the pressure gradient required for valve opening varied sixfold with vessel distention. Finally, our functional evidence supports the concept that lymphatic muscle tone exerts an indirect effect on valve gating.

In order to better understand the factors governing community assembly on riverine islands, we conducted a greenhouse experiment that examined the effects of species interactions in combination with flooding that mimicked hydrologic gradients found on Mississippi River islands. Specifically, we examined the effects of inter and intra-specific competition and three disturbance treatments (drained, drought, and flood) on the growth performance of three island-ubiquitous herbaceous plant species (Amaranthus palmeri, Cyperus strigosus. and Xanthium strumarium). We predicted a decrease in interspecific competitive effects in disturbance treatments. Specifically, we expected A palmeri to be most affected by flooding treatment based on its facultative upland status suggesting that it should be a poor tolerator of flooded conditions. X. strumarium and C. strigosus both facultative wetland species in their status, should tolerate flooding, but we predict that C. strigosus should have greater stress tolerance due to its perennial life history. Because we find these species coexisting at the same elevation zones on riverine islands, we also predicted stronger intraspecific competition effects. Our results indicate that disturbance indeed affected competitive interactions, but the effects were species-specific. X. strumarium showed stronger competitive effects when grown with conspecifics while C. strigosus experienced greater competition with heterospecifics under drought treatments. Based on its wetland indicator status and life history characteristics, we expected A palmeri to exhibit a facilitative effect, as it is typically an upland species, but instead it was impacted most by interspecific competition. Our study indicates that factors other than competition, facilitation, and flood tolerance (e.g., priority effects) may be controlling island plant community dynamics, further studies are required.

To understand how plant communities respond to fluctuations in hydrology, we conducted a natural study on five riverine islands located within the lower Mississippi River. Specifically, we addressed whether species richness and diversity peak at intermediate elevations of flooding and whether plant assembly on these islands follow a niche-derived continuum pattern or develop due to chance processes. Elevations of islands were standardized into 1 m zones providing replicate island gradients of flood frequency and intensity. We examined effects of changing frequency and duration along the gradient and between years, and changes in intensity due to flow based on island side (main channel sides had greater intensity floods). We analyzed diversity data using nonparametric general linear models and compositional dissimilarity using Sorenson's index. Less frequent, more intense disturbances decreased both landscape level and local diversity with the frequency and intensity (alone) of floods affecting co...

The lymphatic system is an extensive vascular network featuring valves and contractile walls that pump interstitial fluid and plasma proteins back to the main circulation. Immune function also relies on the lymphatic system’s ability to transport white blood cells. Failure to drain and pump this excess fluid results in edema characterized by fluid retention and swelling of limbs. It is, therefore, important to understand the mechanisms of fluid transport and pumping of lymphatic vessels. Unfortunately, there are very few studies in this area, most of which assume Poiseuille flow conditions. In vivo observations reveal that these vessels contract strongly, with diameter changes of the order of magnitude of the diameter itself over a cycle that lasts typically 2–3 seconds. The radial velocity of the contracting vessel is on the order of the axial fluid velocity, suggesting that modeling flow in these vessels with a Poiseuille model is inappropriate. In this paper, we describe a model of a radially expanding and contracting lymphatic vessel and investigate the validity of assuming Poiseuille flow to estimate wall shear stress, which is presumably important for lymphatic endothelial cell mechanotransduction. Three different wall motions; periodic sinusoidal, skewed sinusoidal and physiologic wall motions, were investigated with steady and unsteady parabolic inlet velocities. Despite high radial velocities resulting from the wall motion, wall shear stress values were within 4% of quasi-static Poiseuille values. Therefore, Poiseuille flow is valid for the estimation of wall shear stress for the majority of the lymphangion contractile cycle.