Statistical dynamics of spatial-order formation by communicating cells

Communicating cells can coordinate their gene expressions to form spatial patterns. 'Secrete-and-sense cells' secrete and sense the same molecule to do so and are ubiquitous. Here we address why and how these cells, from disordered beginnings, can form spatial order through a statistical mechanics-type framework for cellular communication. Classifying cellular lattices by 'macrostate' variables - 'spatial order paramete' and average gene-expression level - reveals a conceptual picture: cellular lattices act as particles rolling down on 'pseudo-energy landscapes' shaped by a 'Hamiltonian' for cellular communication. Particles rolling down represent cells' spatial order increasing. Particles trapped on the landscapes represent metastable spatial configurations. The gradient of the Hamiltonian and a 'trapping probability' determine the particle's equation of motion. This framework is extendable to more complex forms of cellular communication

Topological defects in flat nanomagnets: the magnetostatic limit

We discuss elementary topological defects in soft magnetic nanoparticles in the thin-film geometry. In the limit dominated by magnetostatic forces the low-energy defects are vortices (winding number n = +1), cross ties (n = -1), and edge defects with n = -1/2. We obtain topological constraints on the possible composition of domain walls. The simplest domain wall in this regime is composed of two -1/2 edge defects and a vortex, in accordance with observations and numerics.Comment: 3 pages, eps figures. Proceedings of MMM 0

Mechanisms Driving the Effect of Weight Loss on Arterial Stiffness

Aims Arterial stiffness decreases with weight loss in overweight and obese adults, but the mechanisms by which this occurs are poorly understood. We aimed to elucidate these mechanisms. Methods We evaluated carotid-femoral pulse wave velocity (cfPWV), a measure of aortic stiffness, and brachial-ankle pulse wave velocity (baPWV), a mixed measure of central and peripheral arterial stiffness, in 344 young adults (mean age 38 yrs, mean body mass index (BMI) 32.9 kg/m2, 23% male) at baseline, 6 and 12 months in a behavioral weight loss intervention. Linear mixed effects models were used to evaluate associations between weight loss and arterial stiffness and to examine the degree to which improvements in obesity-related factors explained these associations. Pattern-mixture models using indicator variables for dropout pattern and Markov Chain Monte Carlo multiple imputation were used to evaluate the influence of different missing data assumptions. Results At 6 months (7% mean weight loss from baseline), there was a statistically significant median decrease of 47.5 cm/s (interquartile range (IQR) -44.5, 148) in cfPWV (p<0.0001) and a mean decrease of 11.7 cm/s (standard deviation (SD) 91.4) in baPWV (p=0.049). At 12 months (6% mean weight loss from baseline) only cfPWV remained statistically significantly reduced from baseline (p=0.02). Change in BMI (p=0.01) was statistically significantly positively associated with change in cfPWV after adjustment for changes in mean arterial pressure (MAP) or any other measured obesity-related factor. Common carotid artery diameter (p=0.003) was associated and heart rate (p=0.08) and MAP (p=0.07) marginally associated longitudinally with cfPWV. Reductions in heart rate (p<0.0001) and C-reactive protein (p=0.02) were associated with reduced baPWV, and each removed the statistical significance of the effect of weight loss on baPWV. Pattern-mixture modeling revealed several differences between completers and non-completers in the models for cfPWV, but marginal parameter estimates changed little from the original models for either PWV measure. Conclusions The public health importance of this thesis is that firstly, weight loss improves arterial stiffness in overweight and obese young adults. Secondly, its effect on baPWV may be explained by concurrent reductions in heart rate and inflammation. Missing data did not appear to bias these results

Condensation of magnons and spinons in a frustrated ladder

Motivated by the ever-increasing experimental effort devoted to the properties of frustrated quantum magnets in a magnetic field, we present a careful and detailed theoretical analysis of a one-dimensional version of this problem, a frustrated ladder with a magnetization plateau at m=1/2. We show that even for purely isotropic Heisenberg interactions, the magnetization curve exhibits a rather complex behavior that can be fully accounted for in terms of simple elementary excitations. The introduction of anisotropic interactions (e.g., Dzyaloshinskii-Moriya interactions) modifies significantly the picture and reveals an essential difference between integer and fractional plateaux. In particular, anisotropic interactions generically open a gap in the region between the plateaux, but we show that this gap closes upon entering fractional plateaux. All of these conclusions, based on analytical arguments, are supported by extensive Density Matrix Renormalization Group calculations.Comment: 15 pages, 15 figures. minor changes in tex

Maternal hypertension after a low-birth-weight delivery differs by race/ethnicity: Evidence from the National Health and Nutrition Examination Survey (NHANES) 1999-2006

Studies have suggested an increase in maternal morbidity and mortality due to cardiovascular diseases in women with a prior low-birth-weight (LBW, <2,500 grams) delivery. This study evaluated blood pressure and hypertension in women who reported a prior preterm or small-for-gestational-age (SGA) LBW delivery in the National Health and Nutrition Examination Survey 1999-2006 (n = 6,307). This study also aimed to explore if race/ethnicity, menopause status, and years since last pregnancy modified the above associations. A total of 3,239 white, 1,350 black, and 1,718 Hispanics were assessed. Linear regression models were used to evaluate blood pressure by birth characteristics (preterm-LBW, SGA-LBW, and birthweight ≥2,500). Logistic regression models estimated the odds ratios (OR) of hypertension among women who reported a preterm-LBW or SGA-LBW delivery compared with women who reported an infant with birthweight ≥2,500 at delivery. Overall, there was a positive association between a preterm-LBW delivery and hypertension (adjusted OR = 1.39, 95% confidence interval (CI) 1.02-1.90). Prior SGA-LBW also increased the odds of hypertension, but the estimate did not reach statistical significance (adjusted OR = 1.21, 95% CI 0.76-1.92). Race/ethnicity modified the above associations. Only black women had increased risk of hypertension following SGA-LBW delivery (adjusted OR = 2.09, 95% CI 1.12-3.90). Black women were at marginally increased risk of hypertension after delivery of a preterm-LBW (adjusted OR = 1.49, 95% CI 0.93-2.38). Whites and Hispanics had increased, but not statistically significant, risk of hypertension after a preterm-LBW (whites: adjusted OR = 1.39, 95% CI 0.92-2.10; Hispanics: adjusted OR = 1.22, 95% CI 0.62-2.38). Stratified analysis indicated that the associations were stronger among women who were premenopausal and whose last pregnancy were more recent. The current study suggests that in a representative United States population, women with a history of preterm- or SGA-LBW deliveries have increased odds of hypertension and this risk appears to be higher for black women and younger women. © 2014 Xu et al

Spatial distributions and temporal changes of coastal bivalve populations

Bivalves are common animals in coastal ecosystems that alter energy flows and the characteristics of their surroundings, which contributes to ecosystem functions and services. Most bivalve species are suspension-feeders, clearing the water from organic particles and phytoplankton and thereby lowering water turbidity and exert top-down control on phytoplankton communities. Faeces are deposited on the sea floor, coupling the pelagic and benthic ecosystem components and enhancing the long-term storage and remineralization of nutrients which is important for mitigating negative effects of eutrophication. The infaunal species’ burrowing behaviour reworks the sediment which increases the flux of oxygen and other solutes between sediments and water, while epifaunal species create complex reef structures that can be utilized by other species promoting biodiversity. Globally, much of the epifaunal bivalve reefs have been greatly diminished, resulting in a loss of function and services, while invasive species have been introduced in many areas causing shifts in ecosystems. The aim of this thesis was to describe the coastal bivalve communities on the Skagerrak coast in terms of species composition, distribution, abundances and biomass. This was done in order to identify key species, functional groups and habitat types that contribute to ecosystem functions and services. Recently collected data was contrasted against older records to access temporal changes in the structure of the bivalve populations. The possible underlying mechanisms to these changed and the potential consequences for ecosystem functioning was also explored. The results showed that populations are shaped by a combination of environmental factors, species habitat preference and the availability of those habitats. While epifaunal species are overall more ecologically relevant than infaunal species, the later can be locally more impactful. Since the invasive Pacific oyster arrived it has become the dominant species in terms of biomass which has, together with a general decline of infaunal bivalves, likely caused shifts in bivalve ecosystem functions and services. The methods and analyses described provide an important current baseline for the bivalve populations in this area and to compare further changes to in the future

Molecular design of heteroatom-doped nanoporous carbons with controlled porosity and surface polarity for gas physisorption and energy storage

The world energy consumption has constantly increased every year due to economic development and population growth. This inevitably caused vast amount of CO2 emission, and the CO2 concentration in the atmosphere keeps increasing with economic growth. To reduce CO2 emission, various methods have been developed but there are still many bottlenecks to be solved. Solvents easily absorbing CO2 such as monoethanol-amine (MEA) and diethanolamine, for example, have limitations of solvent loss, amine degradation, vulnerability to heat and toxicity, and the high cost of regeneration which is especially caused due to chemisorption process. Though some of these drawbacks can be compensated through physisorption with zeolites and metal-organic frameworks (MOFs) by displaying significant adsorption selectivity and capacity even in ambient conditions, limitations for these materials still exist. Zeolites demand relatively high regeneration energy and have limited adsorption kinetics due to the exceptionally narrow pore structure. MOFs have low stability against heat and moisture and high manufacturing cost. Nanoporous carbons have recently received attention as an attractive functional porous material due to their unique properties. These materials are crucial in many applications of modern science and industry such as water and air purification, catalysis, gas separation, and energy storage/conversion due to their high chemical and thermal stability, and in particular electronic conductivity in combination with high specific surface areas. Nanoporous carbons can be used to adsorb environmental pollutants or small gas molecules such as CO2 and to power electrochemical energy storage devices such as batteries and fuel cells. In all fields, their pore structure or electrical properties can be modified depending on their purposes. This thesis provides an in-depth look at novel nanoporous carbons from the synthetic and the application point of view. The interplay between pore structure, atomic construction, and the adsorption properties of nanoporous carbon materials are investigated. Novel nanoporous carbon materials are synthesized by using simple precursor molecules containing heteroatoms through a facile templating method. The affinity, and in turn the adsorption capacity, of carbon materials toward polar gas molecules (CO2 and H2O) is enhanced by the modification of their chemical construction. It is also shown that these properties are important in electrochemical energy storage, here especially for supercapacitors with aqueous electrolytes which are basically based on the physisorption of ions on carbon surfaces. This shows that nanoporous carbons can be a “functional” material with specific physical or chemical interactions with guest species just like zeolites and MOFs. The synthesis of sp2-conjugated materials with high heteroatom content from a mixture of citrazinic acid and melamine in which heteroatoms are already bonded in specific motives is illustrated. By controlling the removal procedure of the salt-template and the condensation temperature, the role of salts in the formation of porosity and as coordination sites for the stabilization of heteroatoms is proven. A high amount of nitrogen of up to 20 wt. %, oxygen contents of up to 19 wt.%, and a high CO2/N2 selectivity with maximum CO2 uptake at 273 K of 5.31 mmol g–1 are achieved. Besides, the further controlled thermal condensation of precursor molecules and advanced functional properties on applications of the synthesized porous carbons are described. The materials have different porosity and atomic construction exhibiting a high nitrogen content up to 25 wt. % as well as a high porosity with a specific surface area of more than 1800 m2 g−1, and a high performance in selective CO2 gas adsorption of 62.7. These pore structure as well as properties of surface affect to water adsorption with a remarkably high Qst of over 100 kJ mol−1 even higher than that of zeolites or CaCl2 well known as adsorbents. In addition to that, the pore structure of HAT-CN-derived carbon materials during condensation in vacuum is fundamentally understood which is essential to maximize the utilization of porous system in materials showing significant difference in their pore volume of 0.5 cm3 g−1 and 0.25 cm3 g−1 without and with vacuum, respectively. The molecular designs of heteroatom containing porous carbon derived from abundant and simple molecules are introduced in the presented thesis. Abundant precursors that already containing high amount of nitrogen or oxygen are beneficial to achieve enhanced interaction with adsorptives. The physical and chemical properties of these heteroatom-doped porous carbons are affected by mainly two parameters, that is, the porosity from the pore structure and the polarity from the atomic composition on the surface. In other words, controlling the porosity as well as the polarity of the carbon materials is studied to understand interactions with different guest species which is a fundamental knowledge for the utilization on various applications.Nanoporöse Kohlenstoffe haben in letzter Zeit aufgrund ihrer einzigartigen Eigenschaften als ein attraktives funktionelles poröses Material Aufmerksamkeit erregt. Diese Materialien sind aufgrund ihrer hohen chemischen und thermischen Stabilität und insbesondere aufgrund ihrer elektronischen Leitfähigkeit in Kombination mit hohen spezifischen Oberflächen von entscheidender Bedeutung für viele Anwendungen der modernen Wissenschaft und Industrie wie Wasser- und Luftreinigung, Katalyse, Gastrennung und Energiespeicherung/-umwandlung. Nanoporöse Kohlenstoffe können verwendet werden, um Umweltschadstoffe oder kleine Gasmoleküle wie CO2 zu adsorbieren und elektrochemische Energiespeicher wie Batterien und Brennstoffzellen anzutreiben. Ihre Porenstruktur oder ihre elektrischen Eigenschaften je nach Einsatzzweck modifiziert werden. Diese Arbeit bietet einen eingehenden Blick auf neuartige nanoporöse Kohlenstoffe aus synthetischer und anwendungstechnischer Sicht. Das Zusammenspiel zwischen Porenstruktur, atomarem Aufbau und den Adsorptionseigenschaften von nanoporösen Kohlenstoffmaterialien wird untersucht. Neuartige nanoporöse Kohlenstoffmaterialien werden unter Verwendung einfacher Vorläufermoleküle, die Heteroatome enthalten, durch ein einfaches Templatverfahren synthetisiert. Die Affinität und damit die Adsorptionskapazität von Kohlenstoffmaterialien gegenüber polaren Gasmolekülen (CO2 und H2O) wird durch die Modifikation ihres chemischen Aufbaus erhöht. Es wird auch gezeigt, dass diese Eigenschaften bei der elektrochemischen Energiespeicherung wichtig sind. Hier insbesondere für Superkondensatoren mit wässrigen Elektrolyten, die grundsätzlich auf der Physisorption von Ionen an Kohlenstoffoberflächen beruhen. Dies zeigt, dass nanoporöse Kohlenstoffe, genauso wie Zeolithen und MOFs, ein „funktionelles“ Material mit spezifischen physikalischen oder chemischen Wechselwirkungen mit Gastspezien sein können. Mit den Vorteilen einer hohen elektrischen Leitfähigkeit, einer gut entwickelten Porenstruktur und einer stark hydrophilen Oberflächenstruktur sind nanoporöse Kohlenstoffe vielversprechende Materialien, die weitreichende Auswirkungen auf verschiedene Bereiche des zukünftigen Energiebedarfs haben

Does shear wave ultrasound independently predict axillary lymph node metastasis in women with invasive breast cancer?

Shear wave elastography (SWE) shows promise as an adjunct to greyscale ultrasound examination in assessing breast masses. In breast cancer, higher lesion stiffness on SWE has been shown to be associated with features of poor prognosis. The purpose of this study was to assess whether lesion stiffness at SWE is an independent predictor of lymph node involvement. Patients with invasive breast cancer treated by primary surgery, who had undergone SWE examination were eligible. Data were retrospectively analysed from 396 consecutive patients. The mean stiffness values were obtained using the Aixplorer(®) ultrasound machine from SuperSonic Imagine Ltd. Measurements were taken from a region of interest positioned over the stiffest part of the abnormality. The average of the mean stiffness value obtained from each of two orthogonal image planes was used for analysis. Associations between lymph node involvement and mean lesion stiffness, invasive cancer size, histologic grade, tumour type, ER expression, HER-2 status and vascular invasion were assessed using univariate and multivariate logistic regression. At univariate analysis, invasive size, histologic grade, HER-2 status, vascular invasion, tumour type and mean stiffness were significantly associated with nodal involvement. Nodal involvement rates ranged from 7 % for tumours with mean stiffness <50 kPa to 41 % for tumours with a mean stiffness of >150 kPa. At multivariate analysis, invasive size, tumour type, vascular invasion, and mean stiffness maintained independent significance. Mean stiffness at SWE is an independent predictor of lymph node metastasis and thus can confer prognostic information additional to that provided by conventional preoperative tumour assessment and staging