789 research outputs found
Deciding first-order properties of nowhere dense graphs
Nowhere dense graph classes, introduced by Nesetril and Ossona de Mendez,
form a large variety of classes of "sparse graphs" including the class of
planar graphs, actually all classes with excluded minors, and also bounded
degree graphs and graph classes of bounded expansion.
We show that deciding properties of graphs definable in first-order logic is
fixed-parameter tractable on nowhere dense graph classes. At least for graph
classes closed under taking subgraphs, this result is optimal: it was known
before that for all classes C of graphs closed under taking subgraphs, if
deciding first-order properties of graphs in C is fixed-parameter tractable,
then C must be nowhere dense (under a reasonable complexity theoretic
assumption).
As a by-product, we give an algorithmic construction of sparse neighbourhood
covers for nowhere dense graphs. This extends and improves previous
constructions of neighbourhood covers for graph classes with excluded minors.
At the same time, our construction is considerably simpler than those. Our
proofs are based on a new game-theoretic characterisation of nowhere dense
graphs that allows for a recursive version of locality-based algorithms on
these classes. On the logical side, we prove a "rank-preserving" version of
Gaifman's locality theorem.Comment: 30 page
Technical note:On the reliability of laboratory beta-source calibration for luminescence dating
The dose rate of the 90Srâ/â90Y beta source used in most
luminescence readers is a laboratory key parameter. There is a
well-established body of knowledge about parameters controlling accuracy and
precision of the calibration value but some hard-to-explain inconsistencies
still exist. Here, we have investigated the impact of grain size, aliquot
size and irradiation geometry on the resulting calibration value through
experiments and simulations. The resulting data indicate that the dose rate
of an individual beta source results from the interplay of a number of
parameters, most of which are well established by previous studies. Our
study provides evidence for the impact of aliquot size on the absorbed dose
in particular for grain sizes of 50â200â”m. For this grain-size
fraction, the absorbed dose is enhanced by âŒâ10â%â20â% as
aliquot size decreases due to the radial increase of dose rate towards
the centre of the aliquot. The enhancement is most variable for 50â100â”m
grains mounted as aliquots of <â8âmm size. The enhancement is
reversed when large grains are mounted as small aliquots due to the edge
effect by which the dose induced by backscattered electrons is reduced.
While the build-up of charge dictates the increase of absorbed dose with the
increase of grain size, this principle becomes more variable with changing
irradiation geometry. We conclude that future calibration samples should
consist of subsamples composed of small, medium, large and very large quartz
grains, each obtaining several gamma doses. The calibration value measured
with small, medium and large aliquots is then obtained from the inverse
slope of the fitted line, not from a single data point. In this way, all
possible irradiation geometries of an individual beta source are covered,
and the precision of the calibration is improved.</p
The Learning Curve for a Fetal Cardiac Intervention Team
Objectives. Multiple technical difficulties are encountered when a multidisciplinary team of subspecialists begins a minimally-invasive fetal cardiac interventional program. We describe the learning curve. Study Design. Ten pregnant sheep underwent ultrasound-guided balloon valvuloplasty of the aortic valve. Team members and their roles remained constant through the trial. The time between needle insertion and entrance of the left ventricle at the aortic root was recorded. F-test was used to assess significance (P †.05). Results. The time required to accurately position the needle tip at the aortic root decreased significantly over the course of the trial, from 12 minutes with the first attempt to one minute with the last (P = .003). Conclusion. A significant learning curve is encountered when a multidisciplinary team begins a minimally-invasive fetal cardiac intervention program. However, technical proficiency can be achieved with practice. Institutions interested in developing such a program should consider practice in an animal model before proceeding to the human fetus
Compact Labelings For Efficient First-Order Model-Checking
We consider graph properties that can be checked from labels, i.e., bit
sequences, of logarithmic length attached to vertices. We prove that there
exists such a labeling for checking a first-order formula with free set
variables in the graphs of every class that is \emph{nicely locally
cwd-decomposable}. This notion generalizes that of a \emph{nicely locally
tree-decomposable} class. The graphs of such classes can be covered by graphs
of bounded \emph{clique-width} with limited overlaps. We also consider such
labelings for \emph{bounded} first-order formulas on graph classes of
\emph{bounded expansion}. Some of these results are extended to counting
queries
Cytogenetically distinguishable sympatric and allopatric populations of the mosquito Anopheles albitarsis
Salivary gland chromosome slides of Anopheles albitarsis from Brasil, Colombia and Venezuela indicate that at least three chromosomally differentiated populations of this species exist in this area. The B1 population from Brasil contains one heterozygous inversion in the X and two in the autosomes. Population B2, sympatric with B1 in Brasil, differs from it by two inversions in the X and ten in the autosomes. Population C in Colombia and Venezuela is closer to B1, from which it differs by three inversions in chromosome 2 and three in chromosome 3. Each population, B1, B2 and C may be distinguished with about 98% certainty using the banding patterns of the X chromosomes. Most of the remaining individuals may be identified using a combination of the X and autosomal paracentric inversions. The scarcity of shared inversions argues for little if any natural hybridization among these populations. A standard salivary gland chromosome map, based on the B1 populations, is presented.Estudos citolĂłgicos utilizando cromossomos politĂȘnicos das glĂąndulas salivares de Anopheles albitarsis, coletados no Brasil, ColĂŽmbia e Venezuela indicam que existem pelo menos 3 populaçÔes, que sĂŁo diferentes cromossomicamente. Todas as trĂȘs podem ser diferenciadas usando somente o cromossomo X. A população B1 do Brasil tem uma inversĂŁo heterozigota no cromossomo X e duas nos autossomos. A população B2, simpĂĄtrica com a B1, no Brasil, varia daquela por duas inversĂ”es no X e dez nos autossomos. A terceira população C, a qual se encontra na ColĂŽmbia e Venezuela, mostra mais proximidade a B1, da qual ela varia por trĂȘs inversĂ”es no cromossomo 2 e trĂȘs inversĂ”es no cromossomo 3. Cada população, B1, B2 e C pode ser identificada com 98 por cento de certeza usando a seqĂŒĂȘncia das bandas do cromossomo X. A escassez das inversĂ”es comuns indica uma baixa taxa de hibridismo na natureza entre estas populaçÔes. Ă apresentado um mapa dos cromossomos de glĂąndulas salivares de larvas da população B1 para ser considerado como padrĂŁo para esta espĂ©cie
Dilution of the magnetic lattice in the Kitaev candidate -RuCl by Rh doping
Magnetic dilution of a well-established Kitaev candidate system is realized
in the substitutional RuRhCl series (). Optimized
syntheses protocols yield uniformly-doped single crystals and polycrystalline
powders that are isostructural to the parental -RuCl as per X-ray
diffraction. The Rh content is accurately determined by the quantitative
energy-dispersive X-ray spectroscopy technique with standards. We determine the
magnetic phase diagram of RuRhCl for in-plane magnetic fields
from magnetization and specific-heat measurements as a function of and
stacking periodicity, and identify the suppression of the magnetic order at towards a disordered phase, which does not show any clear
signature of freezing into a spin glass. Comparing with previous studies on the
substitution series RuIrCl, we propose that chemical pressure
would contribute to the suppression of magnetic order especially in
RuIrCl and that the zigzag magnetic ground state appears to be
relatively robust with respect to the dilution of the
Kitaev----Heisenberg magnetic lattice. We also discovered a slight
dependence of the magnetic properties on thermal cycling, which would be due to
an incomplete structural transition
Dilution of the magnetic lattice in the Kitaev candidate α-RuCl<sub>3</sub> by Rh<sup>3+</sup> doping
A Comparison of Temperatures Inside Protective Headgear With Indicators of Physiological Strain and Core Temperatures During Exercise in a Hot Environment
Introduction: Non-invasive temperature monitoring with a sensor mounted inside protective headgear such as a football or military helmet or a construction hardhat may be an effective method of detecting temperatures that are indicative of increased risk of heat illness. Hothead Technologies has developed a system for providing temperature information to medical personnel responsible for the health of the individual. Purpose: The purposes of this study were to establish the relationship between in-hardhat temperature (Tih) readings, markers of physiological strain and perceptual responses, and to determine the differences between the in-helmet temperature readings and core temperature (Tc) as measured by rectal (Tre) and esophageal (Tes) probes. Methods: Thirty males (age, 24.57 ± 4.32 years; height 180.51 ±7.06 cm; body mass, 81.06 ±9.35 kg; percent body fat, 13.76 ±5.11; VO2max, 46.84 ± 7.10 mL/Kg/min) completed two experimental trials separated by a minimum of one week: a continuous submaximal exercise (CSE) condition and a series of high intensity 30-second sprints (HIE) with a one-minute rest period between each sprint. Exercise in both conditions was carried out in a 36o C environment with a relative humidity of 40% while wearing a standard construction hardhat with a sensor mounted in the forehead area of the head strap, and continued until one of the following two criteria was met: the subject voluntarily terminated the session, or the subjectâs Tc reached 39.5oC. Temperatures, heart rate, cardiorespiratory, and perceptual responses were monitored throughout, and balance error scoring system (BESS) and mental function tests were conducted before and after exercise. A physiological strain index (PSI) was calculated from Tc and HR.
Results:
CV- Calculated from final temp.
Conclusion: The general agreement between the Tih and other temperature measures along with the consistency as indicated by the low coefficient of variation in the recordings of the Tih sensors at the point of termination suggest that this device may have application as a warning system for impending heat-related problems
Exercise-Induced Th17 Lymphocyte Response and Their Relationship to Cardiovascular Disease Risk Factors in Obese, Post-Menopausal Women
Obesity-induced inflammation promotes type 2 diabetes and cardiovascular disease (CVD). A causative link between adaptive immunity and pathogenesis of obesity-associated diseases has been established. PURPOSE: To examine the effects of exercise on circulating T-helper (Th) 17 lymphocytes in overweight/obese post-menopausal women. METHODS: Twenty-seven overweight/obese women (BMI 32.7 ± 5.1 kgĂm-2, 55-75 yr) were randomly assigned to the exercise (EX, n=14) or education (ED, n=13) groups. EX performed a 25-min walk (75-80% HRR) and 2 sets of 8 resistance exercises (70-80% 1RM) with blood samples obtained at: pre-exercise, post-exercise, one-hour and two-hour post-exercise. Blood samples were obtained at the same time points in resting ED. Whole blood was stained using the extracellular markers CD4, CD196, CD194, CD26, and CD161 to identify Th17 lymphocytes via flow cytometry. RESULTS: Acute exercise increased lymphocyte number (p = 0.0001), but decreased percent of CD4+ cells (p = 0.019) at PO. We observed a diurnal response (main effect) where CD26 expression was significantly lower by 2H compared to PRE (PR: 10631 ± 208; 2H: 9961 ± 271 MFI). There was a main effect (p=0.024) of group for CD26 expression (EX: 10745 ± 251; ED 9880 ± 260 MFI). The difference may have been driven by the apparent exercise-induced plateau of CD26 expression at 2H, which minimized the diurnal reduction observed in ED (p \u3e 0.05). There was a tendency (p = 0.09) for a group x time interaction in Th17 cell number at 1HR (EX = 25.3 ± 4.8; ED =37.2 ± 5.2 x 103 cellsĂml-1). BMI was significantly correlated with Th17% (r = 0.5, p = 0.008). HbA1c was positively correlated with Th17 number and percentage (r = 0.598, p = 0.003; r = 0.614, p = 0.001, respectively), as well as CCR4+ Th17 cells (r = 0.421, p = 0.036). Multiple regression analysis revealed that BMI, fat percentage, and HbA1c were significant predictors (69%, r2 = 0.685) of Th17 cell %. CONCLUSION: Exercise reduced CD26 expression, the receptor responsible for Th17 cell migration, but did not significantly alter Th17 concentration (p = 0.09). CD26 upregulation may indicate that Th17 cells, via chemokine release, promote the stress-dependent migratory response of T-helper cells (CD4+). Obese individuals may experience a preferential differentiation of Th17 cells, based on their association with adiposity (BMI and %fat) and HbA1c
Acute Exercise-Induced Response of Platelet-Monocyte Complexes in Obese, Postmenopausal Women
Inactivity-related diseases such as cardiovascular disease (CVD) are linked to chronic low-grade, systemic inflammation. Platelet-monocyte complexes (PMCs) are markers of in vivo platelet activation and atherosclerosis, and may be early indicators of subclinical inflammation. PURPOSE: To examine the effects of an exercise bout on PMCs in those at risk for CVD. METHODS: Twenty-five overweight-obese (BMI 32.7 ± 5.2 kgĂm-2, 55-75 yr) women were randomly assigned to either the exercise (EX, n=13) or non-exercise control (CON, n=12) group. EX performed 2 sets of 8 resistance exercises and a 25-min treadmill walk at 70-80% HRR. Blood was obtained pre-exercise (PR), post- (PO), 1-hour and 2 hours post-exercise (1HR and 2HR). Blood was obtained at the same time points in CON. PMCs were identified via flow cytometry and analyzed in each monocyte phenotype. Monocyte phenotypes were defined as: Mon1 (CD14+CD16âCCR2+), Mon2 (CD14+CD16+CCR2+), and Mon3 (CD14+CD16+CCR2â). All events positive for both CD14 and CD42a (marker for platelets) were considered PMCs. RESULTS: A main effect for time revealed an increase in PMC number at PO (p=0.036) which appears to have been driven by EX (EX = 61.5%; CON = 33.8% increase). PMCs formed with Mon1 and Mon2 followed a similar response. A significant group x time interaction for Mon3 PMC number (p=0.002) indicated an increase from PR to PO (PR = 5218±1170, PO = 8195±1152 cells·ml-1), and a decrease from PO to 1HR and 2HR (1HR = 3767±820 cells·ml-1 2HR = 3818±814 cells·ml-1) in EX. PMC number remained constant for CON at all timepoints. Estimated VO2max was negatively correlated with CD42a MFI (a marker of platelet density per monocyte) (r = -0.583, p = 0.003). Systolic blood pressure (SBP) positively correlated with percent PMC (% CD42a positive monocytes; r = 0.458, p = 0.042). CONCLUSION: Aerobic fitness appears to reduce platelet activation indicated by the negative relationship between VO2max and CD42a MFI. Chronic elevations in resting SBP are linked to PMC percentage, possibly due to sheer stress-induced platelet activation. It is possible that PMC elevation at PO is at least partially driven by exercise-induced increases in BP. These results support previous literature, indicating that PMCs are a CVD risk marker and may elucidate one mechanism by which physical fitness reduces risk for CVD
- âŠ