397 research outputs found
Nonequilibrium Approach to Bloch-Peierls-Berry Dynamics
We examine the Bloch-Peierls-Berry dynamics under a classical nonequilibrium
dynamical formulation. In this formulation all coordinates in phase space
formed by the position and crystal momentum space are treated on equal footing.
Explicitly demonstrations of the no (naive) Liouville theorem and of the
validity of Darboux theorem are given. The explicit equilibrium distribution
function is obtained. The similarities and differences to previous approaches
are discussed. Our results confirm the richness of the Bloch-Peierls-Berry
dynamics
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Aerotaxis in the closest relatives of animals
As the closest unicellular relatives of animals, choanoflagellates serve as useful model organisms for understanding the evolution of animal multicellularity. An important factor in animal evolution was the increasing ocean oxygen levels in the Precambrian, which are thought to have influenced the emergence of complex multicellular life. As a first step in addressing these conditions, we study here the response of the colony-forming choanoflagellate to oxygen gradients. Using a microfluidic device that allows spatio-temporal variations in oxygen concentrations, we report the discovery that displays positive aerotaxis. Analysis of the spatial population distributions provides evidence for logarithmic sensing of oxygen, which enhances sensing in low oxygen neighborhoods. Analysis of search strategy models on the experimental colony trajectories finds that choanoflagellate aerotaxis is consistent with stochastic navigation, the statistics of which are captured using an effective continuous version based on classical run-and-tumble chemotaxis.Engineering and Physical Sciences Research Council, St John’s College, European Research Council (Advanced Investigator Grant ID: 247333), Wellcome Trust (Senior Investigator Award
Binary Bose-Einstein Condensate Mixtures in Weakly and Strongly Segregated Phases
We perform a mean-field study of the binary Bose-Einstein condensate mixtures
as a function of the mutual repulsive interaction strength. In the phase
segregated regime, we find that there are two distinct phases: the weakly
segregated phase characterized by a `penetration depth' and the strongly
segregated phase characterized by a healing length. In the weakly segregated
phase the symmetry of the shape of each condensate will not take that of the
trap because of the finite surface tension, but its total density profile still
does. In the strongly segregated phase even the total density profile takes a
different symmetry from that of the trap because of the mutual exclusion of the
condensates. The lower critical condensate-atom number to observe the complete
phase segregation is discussed. A comparison to recent experimental data
suggests that the weakly segregated phase has been observed.Comment: minor change
Variational and Potential Formulation for Stochastic Partial Differential Equations
There is recent interest in finding a potential formulation for Stochastic
Partial Differential Equations (SPDEs). The rationale behind this idea lies in
obtaining all the dynamical information of the system under study from one
single expression. In this Letter we formally provide a general Lagrangian
formalism for SPDEs using the Hojman et al. method. We show that it is possible
to write the corresponding effective potential starting from an s-equivalent
Lagrangean, and that this potential is able to reproduce all the dynamics of
the system, once a special differential operator has been applied. This
procedure can be used to study the complete time evolution and spatial
inhomogeneities of the system under consideration, and is also suitable for the
statistical mechanics description of the problem. Keywords: stochastic partial
differential equations, variational formulation, effective potential. PACS:
45.20.Jj; 02.50.-r; 02.50.Ey.Comment: Letter, 4 pages, no figures; v2: references added, minor change
Patterns of dominant flows in the world trade web
The large-scale organization of the world economies is exhibiting
increasingly levels of local heterogeneity and global interdependency.
Understanding the relation between local and global features calls for
analytical tools able to uncover the global emerging organization of the
international trade network. Here we analyze the world network of bilateral
trade imbalances and characterize its overall flux organization, unraveling
local and global high-flux pathways that define the backbone of the trade
system. We develop a general procedure capable to progressively filter out in a
consistent and quantitative way the dominant trade channels. This procedure is
completely general and can be applied to any weighted network to detect the
underlying structure of transport flows. The trade fluxes properties of the
world trade web determines a ranking of trade partnerships that highlights
global interdependencies, providing information not accessible by simple local
analysis. The present work provides new quantitative tools for a dynamical
approach to the propagation of economic crises
Macroscopic quantum tunneling of two-component Bose-Einstein condensates
We show theoretically the existence of a metastable state and the possibility
of decay to the ground state through macroscopic quantum tunneling in
two-component Bose-Einstein condensates with repulsive interactions. Numerical
analysis of the coupled Gross-Pitaevskii equations clarifies the metastable
states whose configuration preserves or breaks the symmetry of the trapping
potential, depending on the interspecies interaction and the particle number.
We calculate the tunneling decay rate of the metastable state by using the
collective coordinate method under the WKB approximation. Then the height of
the energy barrier is estimated by the saddle point solution. It is found that
macroscopic quantum tunneling is observable in a wide range of particle
numbers. Macroscopic quantum coherence between two distinct states is
discussed; this might give an additional coherent property of two-component
Bose condensed systems. Thermal effects on the decay rate are estimated.Comment: 11 pages, 10 figures, revtex
Observation of metastable states in spinor Bose-Einstein condensates
Bose-Einstein condensates have been prepared in long-lived metastable excited
states. Two complementary types of metastable states were observed. The first
is due to the immiscibility of multiple components in the condensate, and the
second to local suppression of spin-relaxation collisions. Relaxation via
re-condensation of non-condensed atoms, spin relaxation, and quantum tunneling
was observed. These experiments were done with F=1 spinor Bose-Einstein
condensates of sodium confined in an optical dipole trap.Comment: 3 figures included in paper, fourth figure separat
Alcohol imagery on New Zealand television
BACKGROUND: To examine the extent and nature of alcohol imagery on New Zealand (NZ) television, a content analysis of 98 hours of prime-time television programs and advertising was carried out over 7 consecutive days' viewing in June/July 2004. The main outcome measures were number of scenes in programs, trailers and advertisements depicting alcohol imagery; the extent of critical versus neutral and promotional imagery; and the mean number of scenes with alcohol per hour, and characteristics of scenes in which alcohol featured. RESULTS: There were 648 separate depictions of alcohol imagery across the week, with an average of one scene every nine minutes. Scenes depicting uncritical imagery outnumbered scenes showing possible adverse health consequences of drinking by 12 to 1. CONCLUSION: The evidence points to a large amount of alcohol imagery incidental to storylines in programming on NZ television. Alcohol is also used in many advertisements to market non-alcohol goods and services. More attention needs to be paid to the extent of alcohol imagery on television from the industry, the government and public health practitioners. Health education with young people could raise critical awareness of the way alcohol imagery is presented on television
Diagnostic utility of p63/P501S double sequential immunohistochemical staining in differentiating urothelial carcinoma from prostate carcinoma
<p>Abstract</p> <p>Background</p> <p>Distinguishing urothelial carcinoma (UC) from prostate carcinoma (PC) is important due to potential therapeutic and prognostic implications. However, this can be a diagnostic challenge when there is limited tissue and in poorly differentiated tumors. We evaluated the diagnostic utility of a dual immunohistochemical stain comprising p63 and P501S (prostein), applied sequentially on a single slide and visualized by double chromogen reaction, in differentiating these two cancers. Thus far, there have been no previous studies assessing the diagnostic utility of p63 and P501S combined together as a dual immunostain in distinguishing between these two cancers.</p> <p>Methods</p> <p>p63/P501S dual-color sequential immunohistochemical staining was performed on archival material from 132 patients with high-grade UC and 23 patients with PC, and evaluated for p63 (brown nuclear) and P501S (red cytoplasmic) expression. Both the staining intensity and percentage of positive tumor cells were assessed.</p> <p>Results</p> <p>p63 was positive in 119/132 of UC and negative in PC. P501S was positive in 22/23 of PC and negative in UC. The p63+/P501S- immunoprofile had 90% sensitivity and 100% specificity for UC. The p63-/P501S+ immunoprofile had 96% sensitivity and 100% specificity for PC.</p> <p>Conclusion</p> <p>Our results indicate that double sequential immunohistochemical staining with p63 and P501S is highly specific and can be a useful tool in distinguishing UC from PC especially when there is limited diagnostic tissue as it can be performed on a single slide.</p
Self-medication with antibiotics for the treatment of menstrual symptoms in southwest Nigeria: a cross-sectional study
Background: Self-medication with antibiotics is an important factor contributing to the development of bacterial
antibiotic resistance. The purpose of this study was to evaluate the prevalence of self-medication with antibiotics
for the treatment of menstrual symptoms among university women in Southwest Nigeria.
Methods: A cross-sectional survey was administered to female undergraduate and graduate students (n = 706) at
four universities in Southwest Nigeria in 2008. The universities were selected by convenience and the study
samples within each university were randomly selected cluster samples. The survey was self-administered and
included questions pertaining to menstrual symptoms, analgesic and antibiotic use patterns, and demographics.
Data were analyzed using descriptive statistics and logistic regression.
Results: The response rate was 95.4%. Eighty-six percent (95% CI: 83-88%) of participants experienced menstrual
symptoms, and 39% (95% CI: 36-43%) reported using analgesics to treat them. Overall, 24% (95% CI: 21-27%) of
participants reported self-medicated use of antibiotics to treat the following menstrual symptoms: cramps, bloating,
heavy bleeding, headaches, pimples/acne, moodiness, tender breasts, backache, joint and muscle pain. Factors
associated with this usage were: lower levels of education (Odds Ratio (OR): 2.8, 95% CI: 1.1-7.1, p-value: 0.03); nonscience
major (OR: 1.58, 95% CI: 1.03-2.50, p-value: 0.04); usage of analgesics (OR: 3.17, 95% CI: 2.07-4.86, p-value:
<0.001); and mild to extreme heavy bleeding (OR: 1.64, 95% CI: 1.01-2.67, p-value: 0.05) and pimples/acne (OR: 1.57,
95% CI: 0.98-2.54, p-value: 0.06). Ampicillin, tetracycline, ciprofloxacin and metronidazole were used to treat the
most symptoms. Doctors or nurses (6%, 95% CI: 4-7%), friends (6%, 95% CI: 4-7%) and family members (7%, 95% CI:
5-8%) were most likely to recommend the use of antibiotics for menstrual symptoms, while these drugs were most
often obtained from local chemists or pharmacists (10.2%, 95% CI: 8-12%).
Conclusions: This is the first formal study to report that approximately 1 out of 4 university women surveyed in
Southwest Nigeria self-medicate with antibiotics to treat menstrual symptoms. This practice could provide monthly,
low-dose exposures to antibiotics among users. Further studies are necessary to evaluate the impacts of selfmedication
on student health
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