Search

Active matter, which includes crowds of organisms, is composed of constituents that independently consume and dissipate energy. Some active matter systems have been shown to sustain the propagation of various types of waves, resulting from the interplay between density and alignment. Here, we examine a type of solitary wave in dense two-dimensional columns of Solenopsis invicta , fire ants, in which the local activity, density and alignment all play a key role. We demonstrate that these waves are nonlinear and that they are composed of aligned ants that are constrained at the top by the time it takes disordered ants to activate and align and at the bottom by a density minimum enforced by gravity. Our results suggest that intrinsically switchable activity can be a productive framework to understand and trigger a broad range of wave-like behaviors, including stampedes in crowds and herds.

Carotenoid pigments have myriad functions in fish, including coloration and immunity. The “carotenoid trade-off hypothesis” posits that dietary limitation of carotenoids imposes constraints on animals to allocate to one function at the expense of another. This hypothesis rarely has been tested in fish. We quantified tissue carotenoids in breeding and non-breeding female convict cichlids in Lake Xiloa, Nicaragua. This species is reverse sexually dichromatic such that females possess carotenoid-based coloration that males lack. We also collected algae samples near nest sites to assess carotenoid availability, recorded water depth, and examined cichlids’ behavioral interactions with pair mates, conspecifics, heterospecific competitors, and predators. Each of these, we predicted, would mediate potential carotenoid trade-offs. We found that non-breeding females had significantly higher levels of carotenoids in their integument, liver, and gonads compared to breeding fish. We found that algae and total carotenoids declined with depth across our study transects at 9, 11, 13, and 15 m, but the concentration of carotenoids (ng carotenoid g−1 algae, or algal quality) did not vary with depth. Furthermore, relationships among carotenoid concentrations of the three tissue types did not vary with depth, and female color status (orange or not) was not affected by behavioral interactions with other community members, reproductive status, or water depth. Our results support previous studies showing that carotenoid pigmentation may serve a signal function that facilitates the establishment of non-breeding females within the breeding population. Our study also uncovered no evidence indicating that carotenoids are limiting in the diet of breeding female convict cichlids.

Alternative metrics are unique bibliometrics comprising social, news, and other sources of media outside of traditional academic citations. Some have suggested that these metrics can complement traditional metrics of research impact, including public engagement with research. The COVID-19 pandemic provides a unique opportunity to study alternative metrics and the dissemination of scientific research given the heightened academic and public interest. This study analyzed Altmetric Attention Scores for the top 25 publications on COVID-19 and the top 25 non–COVID-19 publications in 2020. There were significantly higher levels of social attention scores across multiple metrics for COVID-19 articles than for non–COVID-19 articles for that year. There was a slightly higher goodness of fit between Altmetric Attention Scores and academic citations for COVID-19 publications than for non–COVID-19 publications, although trendline differences were not significant. These results suggest that researchers should be aware that their studies can become highly visible on publicly available social and news media platforms, especially during events of high interest (such as a global pandemic).

Significance Several antibiotics targeting the large ribosomal subunit interfere with translation in a context-specific manner, preventing ribosomes from polymerizing specific amino acid sequences. Here, we reveal kasugamycin as a small ribosomal subunit-targeting antibiotic whose action depends on the sequence context of the untranslated messenger RNA (mRNA) segments. We show that kasugamycin-induced ribosomal arrest at the start codons of the genes and the resulting inhibition of gene expression depend on the nature of the mRNA nucleotide immediately preceding the start codon and on the proximity of the stop codon of the upstream cistron. Our findings underlie the importance of mRNA context for the action of protein synthesis inhibitors and might help to guide the development of better antibiotics., Kasugamycin (KSG) is an aminoglycoside antibiotic widely used in agriculture and exhibits considerable medical potential. Previous studies suggested that KSG interferes with translation by blocking binding of canonical messenger RNA (mRNA) and initiator transfer tRNA (tRNA) to the small ribosomal subunit, thereby preventing initiation of protein synthesis. Here, by using genome-wide approaches, we show that KSG can interfere with translation even after the formation of the 70S initiation complex on mRNA, as the extent of KSG-mediated translation inhibition correlates with increased occupancy of start codons by 70S ribosomes. Even at saturating concentrations, KSG does not completely abolish translation, allowing for continuing expression of some Escherichia coli proteins. Differential action of KSG significantly depends on the nature of the mRNA residue immediately preceding the start codon, with guanine in this position being the most conducive to inhibition by the drug. In addition, the activity of KSG is attenuated by translational coupling as genes whose start codons overlap with the coding regions or the stop codons of the upstream cistrons tend to be less susceptible to drug-mediated inhibition. Altogether, our findings reveal KSG as an example of a small ribosomal subunit-targeting antibiotic with a well-pronounced context specificity of action.

Microchannel flow boiling has shown great cooling potential with steady-state studies demonstrating the capability to dissipate heat fluxes over 1 kW cm−2. However, most microelectronic devices undergo transient heat loads involving cold startups or pulse-like power operation. Transient heating events in low thermal resistance, low thermal capacity cold plates may exacerbate boiling instabilities and result in device damage or failure due to local dryout conditions. Currently, limited studies are investigating these effects and potential mitigation strategies. In this study, step function, or pulsed, and ramped heat loads are investigated on a multimicrochannel silicon evaporator using R134a under a range of heat fluxes and ramping rates. The transient temperature response of the base heater is recorded using a calibrated infrared (IR) camera, while fluid flow visualization is captured using a video camera microscope. Pulsed heat loads resulted in a large temperature overshoot in the test section until the fluid reached the onset of nucleate boiling (ONB), while significant vapor backflow is observed despite the presence of channel inlet restrictions. Steady boiling is eventually reached and vapor backflow is suppressed. The magnitude of the temperature overshoot is observed to be strongly dependent on peak heat flux. In contrast, ramped heat loads resulted in lower peak temperature rises before ONB as well as significantly reduced vapor backflow compared to the pulsed heat loads.

Collections of fire ants are a form of active matter, as the ants use their internal metabolism to self-propel. In the absence of aligning interactions, theory and simulations predict that active matter with spatially dependent motility can undergo motility-induced phase separation. However, so far in experiments, the motility effects that drive this process have come from either crowding or an external parameter. Though fire ants are social insects that communicate and cooperate in nontrivial ways, we show that the effect of their interactions can also be understood within the framework of motility-induced phase separation. In this context, the slowing down of ants when they approach each other results in an effective attraction that can lead to space-filling clusters and an eventual formation of dynamical heterogeneities. These results illustrate that motility-induced phase separation can provide a unifying framework to rationalize the behavior of a wide variety of active matter systems.

We perform small angle neutron scattering on ultralow-crosslinked microgels and find that while in certain conditions both the particle size and the characteristic internal length scale change in unison, in other instances this is not the case. We show that nonuniform deswelling depends not only on particle size, but also on the particular way the various contributions to the free energy combine to result in a given size. Only when polymer-solvent demixing strongly competes with ionic or electrostatic effects do we observe nonuniform behavior, reflecting internal microphase separation. The results do not appreciably depend on particle number density; even in concentrated suspensions, we find that at relatively low temperature, where demixing is not very strong, the deswelling behavior is uniform, and that only at sufficiently high temperature, where demixing is very strong, does the microgel structure change akin to internal microphase separation.

When grains are added to a cylinder, the weight at the bottom is smaller than the total weight of the column, which is partially supported by the lateral walls through wall/grain frictional forces. This is known as the Janssen effect. Via a combined experimental and numerical investigation, here we demonstrate a reverse Jansen effect whereby the fraction of the weight supported by the base overcomes one. We characterize the dependence of this phenomenon on the various control parameters involved, rationalize the physical process responsible for the emergence of the compressional frictional forces responsible for the anomaly, and introduce a model to reproduce our findings. Contrary to prior assumptions, our results demonstrate that the constitutive relation on a material element can depend on the applied stress., Supplementary material included; Editor suggestion; Featured in Physics

We present evidence suggesting that some male convict cichlids (Amatitlania siquia) in Lake Xiloa, Nicaragua engage in alternative reproductive tactics (ARTs). These putative ART males were smaller than typical parental males, displayed coloration similar to breeding females, and possessed enlarged gonads. Gonadosomatic indices in these males were 16-fold higher than parental males and three-fold higher than females. This phenotype is consistent with the ‘sneaker’ or ‘satellite’ phenotype reported in other species. A survey of 282 fish in 2014 found three males (1% of all fish, 2% of males) with these characteristics. This finding is significant because convict cichlids are frequently studied in laboratory and field in the context of monogamy and biparental care.

Female convict cichlids (Amatitlania siquia) exhibit bright orange ventral coloration that males lack. The behavioral implications of this color are poorly understood, particularly in naturally occurring populations where female coloration could play a role in the expression of territorial nest-guarding behaviors. In this field experiment, monogamous breeding pairs of convict cichlids were presented with 3D printed model conspecific intruders of three body sizes (small, medium, and large) exhibiting three orange patch sizes (large, small, or none) to observe how territorial aggression varied as a function of intruder size and female coloration. Individuals occupying breeding pairs that were defending hatched offspring were significantly more aggressive toward intruders with small and large amounts of orange than toward models lacking orange, indicating that color is an important context-dependent elicitor of aggression in this species. Males were significantly more aggressive toward the intruder than females, and male aggression was strongly influenced by their size relative to the intruder. When males were smaller than the intruder, they performed significantly more aggressive acts than when they were the same size or larger than the intruder; this trend persisted across three putative populations in Lake Xiloa, Nicaragua. A potential explanation for these findings is that the orange color functions as a signal of individual quality or breeding readiness and that breeding pairs increase aggression to repel intruders that pose the greatest threat to pair bond and nest maintenance. One or both sexes of many animal species possess brightly colored features that might communicate information about overall heath or reproductive status. In convict cichlid fish, males and females establish pair bonds and jointly defend their nest and offspring. Single females exhibit striking orange coloration that males and breeding females lack. Our field-based experiment provided evidence that more colorful females, which likely pose a threat to pair bond stability and nest maintenance, incite more aggression from breeding pairs than drab females. Our study suggests that color provides salient information about, perhaps, female quality or readiness to breed in natural populations, and adds to a growing body of research that seeks to understand the varied roles that colorful ornaments play in animal communication.

White-tailed deer are one of the most sought after game species in Kentucky. While much of the Commonwealth boasts high deer populations, those in southeast Kentucky are viewed as relatively low compared to other regions, even after a decade of restrictive doe harvest and multiple years of population supplementation via translocation. We studied survival and cause specific mortality of a local population of deer near the Redbird District of the Daniel Boone National Forest in Clay and Leslie County, Kentucky from January 2014 - January 2017. We estimated female annual survival at 0.89 (CI: 0.88-0.87), with an overall 3-year survival of 0.69 (CI: 0.56-0.84). Deer vehicle collisions and poaching were the most frequent mortality causes and represented 13 of 18 (72%) of mortalities. Managers should consider all forms of mortality and their relative importance in wildlife population dynamics when making harvest decisions. We recommend longer-term studies similar to ours to better understand population trends and inform regional management of this species in Kentucky.

The signaling function of carotenoid-based orange ventral coloration expressed by female convict cichlids (A. siquia) is still largely unknown. This field study examined the relationship between breeding female A. siquia orange coloration and predation stress, territorial competition, and offspring developmental stage. Female orange coloration decreased significantly with increased behavioral interactions with predators and heterospecific competitors, and the presence of wrigglers, fry, or juveniles was significantly associated with a lack of orange coloration. Multiple alternative explanations for these observations are discussed, including body carotenoid re-allocation and variation in environmental characteristics.

A method is presented for calibrating the higher eigenmodes (resonance modes) of atomic force microscopy cantilevers that can be performed prior to any tip-sample interaction. The method leverages recent efforts in accurately calibrating the first eigenmode by providing the higher-mode stiffness as a ratio to the first mode stiffness. A one-time calibration routine must be performed for every cantilever type to determine the power-law relationship between stiffness and frequency, which is then stored for future use on similar cantilevers. Then, future calibrations only require a measurement of the ratio of resonance frequencies and the stiffness of the first mode. This method is verified through stiffness measurements using three independent approaches: interferometric measurement, AC approach-curve calibration, and finite element analysis simulation. Power-law values for calibrating higher-mode stiffnesses are reported for three popular multifrequency cantilevers. Once the higher-mode stiffnesses are known, the amplitude of each mode can also be calibrated from the thermal spectrum by application of the equipartition theorem., 14 pages, 10 figures

Triatoma (kissing bugs), a predatory genus of blood-sucking insects which belongs to the family Reduviidae, subfamily Triatominae, is a well-known vector in the transmission of Trypanosoma cruzi, the causative agent in Chagas disease. However, it is less well appreciated that bites from these insects can cause a range of symptoms varying from localized cutaneous symptoms to a generalized anaphylactic reaction. While anaphylactic reactions following bites have been reported with five of the eleven species endemic to the United States, the majority are associated with Triatoma protracta, and Triatoma rubida. There have been very few reported cases of anaphylactic reaction to the bite Triatoma rubrofasciata, which is endemic to Florida and Hawai‘i. We report a case of a 50 year old previously healthy female from a rural area in Honolulu County who suffered three separate bites from Triatoma rubrofasciata and experienced a generalized anaphylactic reaction on each occasion. There is currently no commercially available skin test to determine allergy to Triatoma bites, and there is likewise no immunotherapy. Avoidance is the best strategy and allergic patients should always have an epinephrine auto injector readily available.