Precursor-mediated crystallization process in suspensions of hard spheres

We report on a large scale computer simulation study of crystal nucleation in hard spheres. Through a combined analysis of real and reciprocal space data, a picture of a two-step crystallization process is supported: First dense, amorphous clusters form which then act as precursors for the nucleation of well-ordered crystallites. This kind of crystallization process has been previously observed in systems that interact via potentials that have an attractive as well as a repulsive part, most prominently in protein solutions. In this context the effect has been attributed to the presence of metastable fluid-fluid demixing. Our simulations, however, show that a purely repulsive system (that has no metastable fluid-fluid coexistence) crystallizes via the same mechanism.Comment: 4 figure

Ergonomic Models of Anthropometry, Human Biomechanics and Operator-Equipment Interfaces

The Committee on Human Factors was established in October 1980 by the Commission on Behavioral and Social Sciences and Education of the National Research Council. The committee is sponsored by the Office of Naval Research, the Air Force Office of Scientific Research, the Army Research Institute for the Behavioral and Social Sciences, the National Aeronautics and Space Administration, and the National Science Foundation. The workshop discussed the following: anthropometric models; biomechanical models; human-machine interface models; and research recommendations. A 17-page bibliography is included

Elephant Grass

Elephant Grass, sometimes known as Napier\u27s Fodder, is a hardy, palatable and nutritious plant which under good conditions will give heavy yields. When once established it will remain as a permanent stand so long as it receives good treatment. It grows well in many parts of Western Australia and up to date appears to be free from attack by pests and diseases. * (Revised from Leaflet No. 600, by H. G. Elliott

Sperm morphology and the evolution of intracellular sperm-egg interactions

This is the final version of the article. Available from Wiley via the DOI in this record.Sperm morphology is incredibly diverse, even among closely related species, yet the coevolution between males and females of fertilization recognition systems is necessary for successful karyogamy (male and female pronuclear fusion). In most species, the entire sperm enters the egg during fertilization so sperm morphological diversity may impact the intracellular sperm–egg interactions necessary for karyogamy. We quantified morphological variation of sperm inside eggs prior to and following karyogamy in several species of Drosophila to understand whether evolution of sperm morphology could influence intracellular sperm–egg interactions (ISEIs). We measured seven parameters that describe ISEIs among species to determine whether these parameters varied both within a species across development and across species at the same developmental stage. We used heterospecific crosses to test the relative role of male origin, female origin, and interaction between the male and female in determining ISEIs. We found that sperm shape changed within a species as development proceeded and, at particular development stages, species varied in some ISEIs. Parental origin had an effect on some ISEIs, with a general trend for a stronger female effect. Overall, our findings identify conserved and variable ISEIs among species and demonstrate the potential to contribute understanding to gamete evolution and development.Leverhulme Trus

Genetic structure and genetic diversity of Swietenia macrophylla (Meliaceae): implications for sustainable forest management in Mexico

The genetic structure and genetic diversity of Mexican populations of Swietenia macrophylla were evaluated. In Mexico, this neotropical tree reaches its northernmost distribution limit. The relationship between genetic diversity and geographic position (longitude, latitude) of four populations was described. The mean genetic and pairwise genetic differentiations were estimated to study the geographic pattern in the genetic structure. The mean overall values for observed heterozygosis (Ho), expected heterozygosis (He) and fixation coefficient (Fis) were 0.41, 0.71 and 0.449 respectively. The mean values per population of Ho, He and Fis correlated with latitude only. The genetic differentiation between populations revealed by the coefficient of differentiation (Fst= 0.047) was statistically significant (p=0.0001). Unweighted pair group method analysis showed that the extent of pairwise genetic differentiation increased with latitudinal position of populations, although no isolation by distance was observed (r=0.76, p=0.15). Results were discussed in the context of the marginal distribution of Mexican populations. Implications of the results on the conservation of S. macrophylla , particularly for populations located in the Mayan zone were discussed

Asymptotic analysis for the generalized langevin equation

Various qualitative properties of solutions to the generalized Langevin equation (GLE) in a periodic or a confining potential are studied in this paper. We consider a class of quasi-Markovian GLEs, similar to the model that was introduced in \cite{EPR99}. Geometric ergodicity, a homogenization theorem (invariance principle), short time asymptotics and the white noise limit are studied. Our proofs are based on a careful analysis of a hypoelliptic operator which is the generator of an auxiliary Markov process. Systematic use of the recently developed theory of hypocoercivity \cite{Vil04HPI} is made.Comment: 27 pages, no figures. Submitted to Nonlinearity

Local influence of boundary conditions on a confined supercooled colloidal liquid

We study confined colloidal suspensions as a model system which approximates the behavior of confined small molecule glass-formers. Dense colloidal suspensions become glassier when confined between parallel glass plates. We use confocal microscopy to study the motion of confined colloidal particles. In particular, we examine the influence particles stuck to the glass plates have on nearby free particles. Confinement appears to be the primary influence slowing free particle motion, and proximity to stuck particles causes a secondary reduction in the mobility of free particles. Overall, particle mobility is fairly constant across the width of the sample chamber, but a strong asymmetry in boundary conditions results in a slight gradient of particle mobility.Comment: For conference proceedings, "Dynamics in Confinement", Grenoble, March 201

Contribution of forest foods to dietary intake and their association with household food insecurity: a cross-sectional study in women from rural Cameroon

To determine the contribution of forest foods to dietary intake and estimate their association with household food insecurity. Cross-sectional survey conducted among 279 households. Using a 7 d recall questionnaire, information on household food consumption was collected from women and used to determine the household dietary diversity score, food variety score and forest food consumption score (FFCS). Household Food Insecurity Access Scale (HFIAS) score was determined and Spearman rank correlation was used to establish the relationship between consumption of forest foods and HFIAS score. Women’s dietary intake was estimated from two 24 h recalls. The contribution of forest foods to women’s nutrient intakes was calculated and women’s nutrient intakes were compared with estimated average nutrient requirements. Rural forest-dependent households in twelve villages in eastern and southern Cameroon. Household heads and their non-pregnant, non-lactating spouses. Forty-seven unique forest foods were identified; of these, seventeen were consumed by 98 % of respondents over the course of one week and by 17 % of women during the two 24 h recall periods. Although forest foods contributed approximately half of women’s total daily energy intake, considerably greater contributions were made to vitamin A (93 %), Na (100 %), Fe (85 %), Zn (88 %) and Ca (89 %) intakes. Despite a highly biodiverse pool of foods, most households (83 %) suffered from high food insecurity based on the HFIAS. A significant inverse correlation was observed between the HFIAS score and the FFCS (r2=−0·169, P=0·0006), demonstrating that forest foods play an important role in ensuring food security in these forest-dependent communities. Forest foods are widely consumed by forest-dependent communities. Given their rich nutrient content, they have potential to contribute to food and nutrition security

Examination of the effect of tool mass and work postures on perceived exertion for a screw driving task

Eighteen subjects with industrial work experience drove screws into perforated sheet metal at three vertical (64, 114 and 165 cm) locations with a pistol-shaped tool, and at two horizontal (13 and 63 cm) work locations using an in-line tool. Both air-powered tools were varied in mass (1, 2 and 3 kg). Subjects drove screws using each tool mass at all work locations. After driving 25 screws at a particular work location/tool mass combination, subjects assessed their perceived exertion for that condition using the Borg ten-point ratio rating scale and completed a body part discomfort survey. Both tool mass and work location were significant factors in determining the ratings. As tool mass increased, so did the ratings of perceived exertion (18% to 100%). The lowest ratings of perceived exertion were at 114 cm on the vertical surface and at 13 cm on the horizontal surface. For the vertical surface, the body part discomfort data revealed that the low back and the right arm were often cited as uncomfortable at 64 cm, the right arm was identified as uncomfortable at 114 cm, and the right arm and the chest were cited as uncomfortable at 165 cm. For the horizontal surface, at both 13 cm and 63 cm, the neck and the right arm were identified as uncomfortable.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30647/1/0000289.pd

Delayed gastric emptying and reduced postprandial small bowel water content of equicaloric whole meal bread versus rice meals in healthy subjects: novel MRI insights

BACKGROUND/OBJECTIVES: Postprandial bloating is a common symptom in patients with functional gastrointestinal (GI) diseases. Whole meal bread (WMB) often aggravates such symptoms though the mechanisms are unclear. We used magnetic resonance imaging (MRI) to monitor the intragastric fate of a WMB meal (11% bran) compared to a rice pudding (RP) meal. SUBJECTS/METHODS: 12 healthy volunteers completed this randomised crossover study. They fasted overnight and after an initial MRI scan consumed a glass of orange juice with a 2267 kJ WMB or an equicaloric RP meal. Subjects underwent serial MRI scans every 45 min up to 270 min to assess gastric volumes and small bowel water content and completed a GI symptom questionnaire. RESULTS: The MRI intragastric appearance of the two meals was markedly different. The WMB meal formed a homogeneous dark bolus with brighter liquid signal surrounding it. The RP meal separated into an upper, liquid layer and a lower particulate layer allowing more rapid emptying of the liquid compared to solid phase (sieving). The WMB meal had longer gastric half emptying times (132±8 min) compared to the RP meal (104±7 min), P<0.008. The WMB meal was associated with markedly reduced MRI-visible small bowel free mobile water content compared to the RP meal, P<0.0001. CONCLUSIONS: WMB bread forms a homogeneous bolus in the stomach which inhibits gastric sieving and hence empties slower than the equicaloric rice meal. These properties may explain why wheat causes postprandial bloating and could be exploited to design foods which prolong satiation