211 research outputs found
The Effect of Surface Roughness on the Universal Thermal Conductance
We explain the reduction of the thermal conductance below the predicted
universal value observed by Schwab et al. in terms of the scattering of thermal
phonons off surface roughness using a scalar model for the elastic waves. Our
analysis shows that the thermal conductance depends on two roughness
parameters: the roughness amplitude and the correlation length .
At sufficiently low temperatures the conductance decrease from the universal
value quadratically with temperature at a rate proportional to .
Values of equal to 0.22 and equal to about 0.75 of the width of
the conduction pathway give a good fit to the data.Comment: 10 pages, 5 figures. Ref. added, typo correcte
Trichinella nativa in a black bear from Plymouth, New Hampshire
A suspected case of trichinellosis was identified in a single patient by the New Hampshire Public Health Laboratories in Concord, NH. The patient was thought to have become infected by consumption of muscle larvae (ML) in undercooked meat from a black bear killed in Plymouth, NH in October 2003 and stored frozen at 20 8C fro 4 months. In January 2004, a 600 g sample of the meat was thawed at 4 8C, digested in hydrochloric acid and pepsin, and larvae were collected by sedimentation. Intact, coiled, and motile ML were recovered (366 larvae per gram (lpg) of tissue), which were passed into mice and pigs. Multiplex PCR revealed a single 127 bp amplicon, indicative of Trichinella nativa. The Reproductive Capacity Index (RCI) for the T. nativa-Plymouth isolate in mice was 24.3. Worm burdens in the diaphragms of two 3-month-old pigs given 2500 ML were 0.05 and 0.2 lpg by 35 days post-inoculation, while 2.2 and 0.75 lpg were recovered from two 3-month-old pigs given 10,000 ML; no larvae were recovered from four 1-year-old pigs given 2500 ML (n = 2) or 10,000 ML (n = 2). Viable larvae were also recovered from frozen black bear meat harvested at two additional locations, one in southern Ontario, Canada, and one in upstate New York, USA. Multiplex PCR using genomic DNA from these parasite samples demonstrated that both isolates were T. nativa. This is the first report of the freeze-resistant species, T. nativa, within the continental United States
Herbs, thyme essential oil and condensed tannin extracts as dietary supplements for broilers, and their effects on performance, digestibility, volatile fatty acids and organoleptic properties
International audienceABSTRACT 1. Herbs, thyme essential oil (EO) and condensed tannin (CT) extracts were compared for their effects as dietary supplements, on broiler growth performance, nutrient digestibility and volatile fatty acid (VFA) profiles in the gut. Cooked meat from the birds fed diets with 4 herbs and an EO extract was compared by a taste panel against those fed the control treatment, for organoleptic properties in the meat. 2. Female broiler chicks were fed wheat-soybean meal diets from 0-42 days of age. These chicks were fed either the basal ration (control), or the basal ration with one of rosemary, garlic or yarrow herbs, mimosa, cranberry or grapeseed CT's, or thyme EO supplements (8 treatments in total). Body mass (BM) and feed consumption (AFC) were measured (7, 21 and 42 days of age). 3. The garlic supplement tended (P>0.05) to improve growth rate over the first 7 days, while mimosa CT and thyme EO supplements reduced weight gains. The mimosa supplement in diets lowered (P<0.05) AFC up to study day 21. Meanwhile, the addition of a cranberry supplement reduced the digestibility of DM, OM and N, compared to the controls. Dietary thyme EO, yarrow, rosemary and garlic supplements modified caecal isovaleric and isobutyric acid proportions (Other VFA; P<0.05). Dietary herb supplements affected the intensity of meat flavour (P<0.001), and the potential of observing both garlic (P<0.001) and abnormal (P<0.001) flavours. There were large differences between the consumption of red and white meat samples, while meat temperature affected several flavour attributes. 4. Dietary garlic and grapeseed CT supplements maintained broiler performance and digestibility similarly to those birds fed the control diet, and these supplements appear suitable for dietary inclusion. Careful choices are necessary when selecting dietary plant extract supplements for broilers, but beneficial effects can be observed
Dynamic transitions between metastable states in a superconducting ring
Applying the time-dependent Ginzburg-Landau equations, transitions between
metastable states of a superconducting ring are investigated in the presence of
an external magnetic field. It is shown that if the ring exhibits several
metastable states at a particular magnetic field, the transition from one
metastable state to another one is governed by both the relaxation time of the
absolute value of the order parameter tau_{|psi|} and the relaxation time of
the phase of the order parameter tau_{phi}. We found that the larger the ratio
tau_{|psi|}tau_{phi} the closer the final state will be to the absolute minimum
of the free energy, i.e. the thermodynamic equilibrium. The transition to the
final state occurs through a subsequent set of single phase slips at a
particular point along the ring.Comment: 7 pages, 6 figures, Revtex 4.0 styl
Theory of periodic swarming of bacteria: application to Proteus mirabilis
The periodic swarming of bacteria is one of the simplest examples for pattern
formation produced by the self-organized collective behavior of a large number
of organisms. In the spectacular colonies of Proteus mirabilis (the most common
species exhibiting this type of growth) a series of concentric rings are
developed as the bacteria multiply and swarm following a scenario periodically
repeating itself. We have developed a theoretical description for this process
in order to get a deeper insight into some of the typical processes governing
the phenomena in systems of many interacting living units. All of our
theoretical results are in excellent quantitative agreement with the complete
set of available observations.Comment: 11 pages, 8 figure
In search of disorders: internalizing symptom networks in a large clinical sample.
Background
The coâoccurrence of internalizing disorders is a common form of psychiatric comorbidity, raising questions about the boundaries between these diagnostic categories. We employ network psychometrics in order to: (a) determine whether internalizing symptoms cluster in a manner reflecting DSM diagnostic criteria, (b) gauge how distinct these diagnostic clusters are and (c) examine whether this network structure changes from childhood to early and then late adolescence.
Method
Symptomâlevel data were obtained for service users in publicly funded mental health services in England between 2011 and 2015 (N = 37,162). A symptom network (i.e. Gaussian graphical model) was estimated, and a community detection algorithm was used to explore the clustering of symptoms.
Results
The estimated network was densely connected and characterized by a multitude of weak associations between symptoms. Six communities of symptoms were identified; however, they were weakly demarcated. Two of these communities corresponded to social phobia and panic disorder, and four did not clearly correspond with DSM diagnostic categories. The network structure was largely consistent by sex and across three age groups (8â11, 12â14 and 15â18 years). Symptom connectivity in the two older age groups was significantly greater compared to the youngest group and there were differences in centrality across the age groups, highlighting the ageâspecific relevance of certain symptoms.
Conclusions
These findings clearly demonstrate the interconnected nature of internalizing symptoms, challenging the view that such pathology takes the form of distinct disorders
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