1,011 research outputs found
Some effects of the anisotropy in a simple lattice gauge model at finite temperature
Monte Carlo simulations are carried out on the (3+1)-dimensional Z(2)
anisotropic lattice model, and a new method to simulate extremely anisotropic
lattice systems with discrete symmetries is proposed. Dependence of the
temporal and spatial average plaquette, Wilson loops on the anisotropy
parameter is presented.Comment: talk given by L.A.Averchenkova at LATTICE'99 (Finite Temperature and
Density), Pisa, Italy, 3 pages, Latex, 3 pictures as a ps-fil
Comparison of micronuclei frequency in bone marrow cells of three rat lines
The aim of this paper is to compare the spontaneous and induced with cyclophosphamide micronucleus indexes in bone marrow cells of the Sprague Dawley, Lewis and Wistar rat lines. Five experimental groups were formed (10 animals of each sex and of each line, in every group). The first group was used as the negative control (intact animals), the second one was exposed to oral administration of drugs; other conditions were the same as for the other groups. The third group was treated with 2 % Tween 65 and the fourth group was treated with 0.9 % NaCl. Both substances were administered by oral way to 2 ml/kg during 14 days. The fifth group was treated intraperitoneally with strong mutagen cyclophosphamide in the dose of 50 mg/kg (10 ml/kg in solution), on 48th and 24th hours before euthanasia. The Sprague Dawley line (both sexes) was significantly different from the other lines. Rats of this line had lower index of spontaneous formation of micronuclei, higher index of cyclophosphamideinduced micronucle formation, percent of micronucleated erythrocytes in bone marrow and the index of cytotoxicity. The results obtained make it possible to identify the most appropriate line of rats as model animals for studies of genotoxicity. It will allow also to obtain more accurate estimates of genotoxicity of various substances.Сравнивали спонтанные и индуцированные циклофосфамидом микроядерные индексы в клетках костного мозга трех линий крыс – Sprague Dawley, Льюис и Вистар. Сформировали пять экспериментальных групп (по 10 животных каждого пола и линии в каждой группе). Первую группу использовали в качестве негативного контроля (интактные животные), вторая служила контролем влияния перорального приема препаратов. Все условия содержания были одинаковыми для всех групп животных. Крыс третьей группы обрабатывали 2 % Tween 65, а четвертой группы – 0,9 % NaCl. Оба вещества вводили перорально в дозе 2 мл/кг в течение 14 дней. Животных пятой группы обрабатывали внутрибрюшинно циклофосфамидом в дозе 50 мг/кг (10 мл/кг раствора), за 48 и 24 ч до эвтаназии. Линия Sprague Dawley (оба пола) существенно отличается от других. Крысы этой линии имели низкие показатели спонтанного образования микроядер и высокий индекс при индукции циклофосфамидом, а также процент эритроцитов с микроядрами в костном мозге и индекс цитотоксичности. Полученные результаты позволяют определить наиболее подходящие линии крыс в качестве модельных животных для изучения генотоксичности. Это также позволит получать более точные оценки генотоксичности различных веществ. Порівнювали спонтанні та індуковані циклофосфамідом мікроядерні індекси в клітинах кісткового мозку трьох ліній щурів – Sprague Dawley, Люіс і Вистар.Сформували п’ять експериментальних груп (по 10 тварин кожної статі і лінії в кожній групі). Першу групу використали як негативний контроль (інтактні тварини), друга слугувала контролем впливу перорального прийому препаратів. Всі умови утримання були однаковими для всіх груп тварин. Щурів третьої групи обробляли 2 % Тween 65, а четвертої групи – 0,9 % NaCl. Обидві речовини вводили перорально в дозі 2 мл/кг впродовж 14 днів. Тварин п’ятої групи обробляли внутрішньочеревно циклофосфамідом в дозі 50 мг/кг (10 мл/кг розчину), за 48 і 24 год до евтаназії. Лінія Sprague Dawley (обидві статі) істотно відрізнялась від інших. Щури цієї лінії мали низькі показники спонтанного утворення мікроядер і високий індекс при індукції циклофосфамідом, а також відсоток еритроцитів з мікроядрами в кістковому мозку та індекс цитотоксичності. Отримані результати дозволяють визначити найбільш відповідні лінії щурів як модельних тварин для вивчення генотоксичності. Це також дозволить отримувати точніші оцінки генотоксичності різних речовин
Social vulnerabilities as determinants of overweight in 2-, 4-and 6-year-old Spanish children
Background: Differences in obesity prevalence among vulnerable groups exist in childhood but it remains unclear whether these differences may be partly determined by socioeconomic status (SES), parental body mass index (BMI) and early life risk factors. We aimed to explore (i) longitudinal associations between belonging to a minority group and being overweight/obese at age 2, 4 and 6 and (ii) associations between accumulation of social vulnerabilities and being overweight/obese at age 6. Methods: In total, 1031 children (53.8% boys) were evaluated at birth and re-examined during a 6-year follow-up in a representative cohort of Aragon (Spain). Children from minority (vulnerable) groups included Spanish Roma/gypsies, Eastern Europeans, Latin Americans and Africans. Two more vulnerable groups were defined at baseline as children whose parents reported low occupation and education. Ethnicity, SES and parental BMI were collected via interviews. We used logistic mixed-effects models and adjusted for parental BMI, SES, mother''s tobacco use, maternal weight gain, birth weight, infant weight gain and breastfeeding practices. Results: Regardless of confounders, Roma/gypsy children (OR = 4.63;[1.69-12.70]95% CI) and with Latin American background (OR = 3.04;[1.59-5.82]95% CI) were more likely to be overweight/obese at age 6 compared with non-gypsy Spanish group. Children with three vulnerabilities (OR = 2.18;[1.31-3.64]95% CI) were more likely to be overweight/obese at age 6 compared with children with no vulnerabilities. No associations were found between belonging to a minority group and overweight/obesity in children under 6. Conclusion: Interventions should target Roma/gypsy children, Latin American children and those who accumulate more vulnerabilities as they are at higher risk of being overweight/obese at age 6
Tethered Monte Carlo: computing the effective potential without critical slowing down
We present Tethered Monte Carlo, a simple, general purpose method of
computing the effective potential of the order parameter (Helmholtz free
energy). This formalism is based on a new statistical ensemble, closely related
to the micromagnetic one, but with an extended configuration space (through
Creutz-like demons). Canonical averages for arbitrary values of the external
magnetic field are computed without additional simulations. The method is put
to work in the two dimensional Ising model, where the existence of exact
results enables us to perform high precision checks. A rather peculiar feature
of our implementation, which employs a local Metropolis algorithm, is the total
absence, within errors, of critical slowing down for magnetic observables.
Indeed, high accuracy results are presented for lattices as large as L=1024.Comment: 32 pages, 8 eps figures. Corrected Eq. (36), which is wrong in the
published pape
Nature of the spin-glass phase at experimental length scales
We present a massive equilibrium simulation of the three-dimensional Ising
spin glass at low temperatures. The Janus special-purpose computer has allowed
us to equilibrate, using parallel tempering, L=32 lattices down to T=0.64 Tc.
We demonstrate the relevance of equilibrium finite-size simulations to
understand experimental non-equilibrium spin glasses in the thermodynamical
limit by establishing a time-length dictionary. We conclude that
non-equilibrium experiments performed on a time scale of one hour can be
matched with equilibrium results on L=110 lattices. A detailed investigation of
the probability distribution functions of the spin and link overlap, as well as
of their correlation functions, shows that Replica Symmetry Breaking is the
appropriate theoretical framework for the physically relevant length scales.
Besides, we improve over existing methodologies to ensure equilibration in
parallel tempering simulations.Comment: 48 pages, 19 postscript figures, 9 tables. Version accepted for
publication in the Journal of Statistical Mechanic
Modeling electrolytically top gated graphene
We investigate doping of a single-layer graphene in the presence of
electrolytic top gating. The interfacial phenomena is modeled using a modified
Poisson-Boltzmann equation for an aqueous solution of simple salt. We
demonstrate both the sensitivity of graphene's doping levels to the salt
concentration and the importance of quantum capacitance that arises due to the
smallness of the Debye screening length in the electrolyte.Comment: 7 pages, including 4 figures, submitted to Nanoscale Research Letters
for a special issue related to the NGC 2009 conference
(http://asdn.net/ngc2009/index.shtml
Natural variation in stress response gene activity in the allopolyploid Arabidopsis suecica
Background
Allopolyploids contain genomes composed of more than two complete sets of chromosomes that originate from at least two species. Allopolyploidy has been suggested as an important evolutionary mechanism that can lead to instant speciation. Arabidopsis suecica is a relatively recent allopolyploid species, suggesting that its natural accessions might be genetically very similar to each other. Nonetheless, subtle phenotypic differences have been described between different geographic accessions of A. suecica grown in a common garden.
Results
To determine the degree of genomic similarity between different populations of A. suecica, we obtained transcriptomic sequence, quantified SNP variation within the gene space, and analyzed gene expression levels genome-wide from leaf material grown in controlled lab conditions. Despite their origin from the same progenitor species, the two accessions of A. suecica used in our study show genomic and transcriptomic variation. We report significant gene expression differences between the accessions, mostly in genes with stress-related functions. Among the differentially expressed genes, there are a surprising number of homoeologs coordinately regulated between sister accessions.
Conclusions
Many of these homoeologous genes and other differentially expressed genes affect transpiration and stomatal regulation, suggesting that they might be involved in the establishment of the phenotypic differences between the two accessions
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