Monolith formation and ring-stain suppression in low-pressure evaporation of poly(ethylene oxide) droplets

When droplets of dilute suspensions are left to evaporate the final dry residue is typically the familiar coffee-ring stain, with nearly all material deposited at the initial triple line (Deegan et al, Nature, vol. 389, 1997, pp. 827-829). However, aqueous poly(ethylene oxide) (PEO) droplets only form coffee-ring stains for a very narrow range of the experimental parameters molecular weight, concentration and drying rate. Instead, over a wide range of values they form either a flat disk or a very distinctive tall central monolith via a four-stage deposition process which includes a remarkable bootstrap-building step. To predict which deposit will form, we present a quantitative model comparing the effects of advective build-up at the triple line to diffusive flux and use this to calculate a dimensionless number χ. By experimentally varying concentration and flux (using a low-pressure drying chamber), the prediction is tested over nearly two orders of magnitude in both variables and shown to be in good agreement with the boundary between disks and monoliths at χ ≈ 1.6

The Rotational Spectrum of the β-Cyanovinyl Radical: A Possible Astrophysical N-Heterocycle Precursor

International audienceA fundamental question in the field of astro-chemistry is whether the molecules essential to life originated in the interstellar medium (ISM) and, if so, how they were formed. Nitrogen-containing heterocycles are of particular interest because of their role in biology, but to date no N-heterocycle has been detected in the ISM and it is unclear how and where such species might form. Recently, the β-cyanovinyl radical (HCCHCN) was implicated in the low temperature gas-phase formation of pyridine. While neutral vinyl cyanide (H 2 CCHCN) has been rotationally characterized and detected in the ISM, HCCHCN has not. Here we present the first theoretical study of all three cyanovinyl isomers at the CCSD(T)/ANO1 level of theory and the experimental rotational spectra of cis-and trans-HCCHCN, as well as those of their 15 N isotopologues, from 5 to 75 GHz. The observed spectra are in good agreement with calculations , and provide a basis for further laboratory and astronomical investigations of these radicals

Taco Tuesday Anyone? Understanding student demand and knowledge of local seafood.

The Gulf of Maine fishing industry continues to be a major economic driver throughout the region, integrating culture, history, and development across working waterfronts spanning thousands of miles from Cape Cod Massachusetts in the south to Nova Scotia Canada in the north. Local seafood harvesting and consumption attract visitors from around the world to enjoy the abundance of lobster, clams, mussels and oysters from the Gulf of Maine. What tourists and residents alike may not understand is the opportunity of other species that are plentiful, economical and delicious. Coupled with the local food movement, underutilized seafood presents additional potential especially within the environmental-conscious consumer groups. Thus, the purpose of this study was to evaluate seafood consumption, species preferences, and eco-label knowledge within one such consumer setting (higher education, college campus setting). College students from the University of Southern Maine were surveyed in the fall of 2017 (N=227) and spring of 2018 (N=320). Most consume seafood regularly, with more than half of participants eating fish or shellfish weekly or monthly. Top species preferences were salmon, shrimp and tuna, followed by local New England fare, ending with underutilized fish species being the least popular. Recognition of seafood eco-labeling trended positively, yet reading of educational outreach was poor despite strong desire for sustainable, local, healthy food. Study participants viewed cost as the top barrier for consuming local seafood. When offered at a price equivalent, lack of visibility was the top impediment for purchasing the underutilized fish entrée. To summarize, this study demonstrates strong demand for regionally and responsibly harvested seafood while highlighting the need for improved communication to market such seafood

Macroscopic constitutive model for ergodic and non-ergodic lead-free relaxors

A fully electromechanically coupled, three dimensional phenomenological constitutive model for relaxor ferroelectric materials was developed for the use in a finite-element-method (FEM) solution procedure. This macroscopic model was used to simulate the macroscopic electromechanical response of lead-free ergodic 0.94Na1/2Bi1/2TiO3−0.06BaTiO3 and non-ergodic 0.90Na1/2Bi1/2TiO3−0.06BaTiO3−0.04K0.5Na0.5NbO3 relaxor materials. The presented constitutive model is capable of accounting for the observed pinched hysteretic response as well as non-deviatoric polarization induced strain and internal order transitions. Time integration of the history dependent internal variables is done with a predictor-corrector integration scheme. The adaptability of the constitutive model regarding the pinching of the hystereses is shown. Simulations are compared to experimental observations

The Effect of Age-At-Release on Survival of Adoptive Parent-Reared Bobwhite Chicks

Translocation of wild northern bobwhites (Colinus virginianus) to restore local populations is a viable conservation tool under some scenarios; however, the supply of wild bobwhites is limited. Bobwhites can be artificially propagated, as an alternative to translocation, using methods that mimic natural brood-rearing. The parent-rearing adoptive process (PRAP) uses wild-strain bobwhite adults to brood and foster newly hatched wild-strain chicks in outdoor aviaries that emulate a natural environment. Adoptive parent-reared bobwhites have higher survival rates than artificially-reared bobwhites but only a single age-of-release (i.e., 6-weeks) has been tested. We tested the effect of age-at-release (3, 6, and 9-weeks) on adoptive parent-reared chicks released on the same date in Hanna Hammock of Tall Timbers Research Station. All chicks were marked with patagial wing tags and a subset of the group received radio transmitters. The 3-week-olds (n = 25) received suture-style transmitters and 6-week-olds (n = 30) and 9-week-olds (n = 30) received necklace-style transmitters. Our adoptive parent-reared chicks had low survival rates over 3 months post-release, the 9-week age group had the highest overall survival rates which could portend that increased physiological development may aid in increasing the survivability of adoptive parent-reared bobwhites. The low survival rates across all 3 age classes calls into question the efficacy of the PRAP as a bobwhite restoration method. Our results do suggest that additional modifications to release age (\u3e 9-weeks) should be explored along with further modifications to the PRAP. Additional modifications include incorporating predator avoidance training, altering release dates, and changing nutritional regimes. These results should caution the bobwhite community to remain suspect when deriving conclusions about the PRAP until all process modifications have been fully evaluated by scientific research

Hotshots, hot spots, and female preference: exploring lek formation models with a bower-building cichlid fish

In many animals, males congregate in leks that females visit for the sole purpose of mating. We observed male and female behavior on 3 different-sized leks of the bower-building cichlid fish Nyassachromis cf. microcephalus to test predictions of 3 prominent lek models: the "hotshot,” "hot spot,” and "female preference” models. In this system, we were able to refine these predictions by distinguishing between indirect mate choice, by which females restrict their set of potential mates in the absence of individual male assessment, and direct mate choice, by which females assess males and their territories through dyadic behavioral interactions. On no lek were males holding central territories favored by indirect or direct mate choice, contrary to the prediction of the hotshot model that leks form because inferior males establish territories surrounding hotshot males preferred by females. Average female encounter rate of males increased with lek size, a pattern typically interpreted as evidence that leks form through female preference for lekking males, rather than because males congregate in hot spots of high female density. Female propensity to engage in premating behavior once courted did not increase with lek size, suggesting female preference for males on larger leks operated through indirect choice rather than direct choice based on individual assessment. The frequency of male-male competitive interactions increased with lek size, whereas their foraging rate decreased, implying a cost to males maintaining territories on larger leks. Together these data most strongly support the female preference model, where females may benefit through indirect mate choice for males able to meet the competitive cost of occupying larger lek

Necrotic tumor growth: an analytic approach

The present paper deals with a free boundary problem modeling the growth process of necrotic multi-layer tumors. We prove the existence of flat stationary solutions and determine the linearization of our model at such an equilibrium. Finally, we compute the solutions of the stationary linearized problem and comment on bifurcation.Comment: 14 pages, 3 figure