A Model for the Elasticity of Compressed Emulsions

We present a new model to describe the unusual elastic properties of compressed emulsions. The response of a single droplet under compression is investigated numerically for different Wigner-Seitz cells. The response is softer than harmonic, and depends on the coordination number of the droplet. Using these results, we propose a new effective inter-droplet potential which is used to determine the elastic response of a monodisperse collection of disordered droplets as a function of volume fraction. Our results are in excellent agreement with recent experiments. This suggests that anharmonicity, together with disorder, are responsible for the quasi-linear increase of $G$ and $\Pi$ observed at $\varphi_c$.Comment: RevTeX with psfig-included figures and a galley macr

Quantum superconductor-metal transition

We consider a system of superconducting grains embedded in a normal metal. At zero temperature this system exhibits a quantum superconductor-normal metal phase transition. This transition can take place at arbitrarily large conductance of the normal metal.Comment: 13 pages, 1 figure include

Speleothems Reveal 500,000-year History of Siberian Permafrost

Soils in permafrost regions contain twice as much carbon as the atmosphere, and permafrost has an important influence on the natural and built environment at high northern latitudes. The response of permafrost to warming climate is uncertain and occurs on time scales longer than those assessed by direct observation. We dated periods of speleothem growth in a north-south transect of caves in Siberia to reconstruct the history of permafrost in past climate states. Speleothem growth is restricted to full interglacial conditions in all studied caves. In the northernmost cave (at 60°N), no growth has occurred since Marine Isotopic Stage (MIS) 11. Growth at that time indicates that global climates only slightly warmer than today are sufficient to thaw extensive regions of permafrost

Saccade dysmetria indicates attenuated visual exploration in autism spectrum disorder

Background: Visual exploration in autism spectrum disorder (ASD) is characterized by attenuated social attention. The underlying oculomotor function during visual exploration is understudied, whereas oculomotor function during restricted viewing suggested saccade dysmetria in ASD by altered pontocerebellar motor modulation. Methods: Oculomotor function was recorded using remote eye tracking in 142 ASD participants and 142 matched neurotypical controls during free viewing of naturalistic videos with and without human content. The sample was heterogenous concerning age (6–30 years), cognitive ability (60–140 IQ), and male/female ratio (3:1). Oculomotor function was defined as saccade, fixation, and pupil‐dilation features that were compared between groups in linear mixed models. Oculomotor function was investigated as ASD classifier and features were correlated with clinical measures. Results: We observed decreased saccade duration (∆M = −0.50, CI [−0.21, −0.78]) and amplitude (∆M = −0.42, CI [−0.12, −0.72]), which was independent of human video content. We observed null findings concerning fixation and pupil‐dilation features (POWER = .81). Oculomotor function is a valid ASD classifier comparable to social attention concerning discriminative power. Within ASD, saccade features correlated with measures of restricted and repetitive behavior. Conclusions: We conclude saccade dysmetria as ASD oculomotor phenotype relevant to visual exploration. Decreased saccade amplitude and duration indicate spatially clustered fixations that attenuate visual exploration and emphasize endogenous over exogenous attention. We propose altered pontocerebellar motor modulation as underlying mechanism that contributes to atypical (oculo‐)motor coordination and attention function in ASD

Superconducting zero temperature phase transition in two dimensions and in the magnetic field

We derive the Ginzburg-Landau-Wilson theory for the superconducting phase transition in two dimensions and in the magnetic field. Without disorder the theory describes a fluctuation induced first-order quantum phase transition into the Abrikosov lattice. We propose a phenomenological criterion for determining the transition field and discuss the qualitative effects of disorder. Comparison with recent experiments on MoGe films is discussed.Comment: 7 pages, 2 figure

Enzymatic Regulation of Protein-Protein Interactions in Artificial Cells

Membraneless organelles are important for spatial organization of proteins and regulation of intracellular processes. Proteins can be recruited to these condensates by specific protein–protein or protein–nucleic acid interactions, which are often regulated by post-translational modifications. However, the mechanisms behind these dynamic, affinity-based protein recruitment events are not well understood. Here, a coacervate system that incorporates the 14-3-3 scaffold protein to study enzymatically regulated recruitment of 14-3-3-binding proteins is presented, which mostly bind in a phosphorylation-dependent manner. Synthetic coacervates are efficiently loaded with 14-3-3, and phosphorylated binding partners, such as the c-Raf pS233/pS259 peptide (c-Raf), show 14-3-3-dependent sequestration with up to 161-fold increase in local concentration. The c-Raf domain is fused to green fluorescent protein (GFP-c-Raf) to demonstrate recruitment of proteins. In situ phosphorylation of GFP-c-Raf by a kinase leads to enzymatically regulated uptake. The introduction of a phosphatase into coacervates preloaded with the phosphorylated 14-3-3-GFP-c-Raf complex results in a significant cargo efflux mediated by dephosphorylation. Finally, the general applicability of this platform to study protein–protein interactions is demonstrated by the phosphorylation-dependent and 14-3-3-mediated active reconstitution of a split-luciferase inside artificial cells. This work presents an approach to study dynamically regulated protein recruitment in condensates, using native interaction domains.</p

How does fusion hindrance show up in medium-light systems? The case of 48Ca + 48Ca

The fusion excitation function of 48Ca + 48Ca has been measured above and well below the Coulomb barrier, thereby largely extending the energy range of a previous experiment down to very low cross sections. This system has a negative Q-value for compound nucleus formation. The fusion cross section decreases steadily below the barrier with no conspicuous change of slope below 300 μb. Coupled-channels calculations using a Woods–Saxon potential indicate that a large diffuseness parameter is needed to reproduce the sub-barrier cross sections. A close analogy with the case of 36S + 48Ca, with Q>0, is pointed out. The sign of the Q-value does not influence fusion cross sections down to the 300–600 nb leve

Born too soon: care before and between pregnancy to prevent preterm births: from evidence to action

This article is part of the supplement: Born too soonProviding care to adolescent girls and women before and between pregnancies improves their own health and wellbeing, as well as pregnancy and newborn outcomes, and can also reduce the rates of preterm birth. This paper has reviewed the evidence based interventions and services for preventing preterm births; reported the findings from research priority exercise; and prescribed actions for taking this call further. Certain factors in the preconception period have been shown to increase the risk for prematurity and, therefore, preconception care services for all women of reproductive age should address these risk factors through preventing adolescent pregnancy, preventing unintended pregnancies, promoting optimal birth spacing, optimizing pre-pregnancy weight and nutritional status (including a folic acid containing multivitamin supplement, and ensuring that all adolescent girls have received complete vaccination. Preconception care must also address risk factors that may be applicable to only some women. These include screening for and management of chronic diseases, especially diabetes; sexually-transmitted infections; tobacco and smoke exposure; mental health disorders, notably depression; and intimate partner violence. The approach to research in preconception care to prevent preterm births should include a cycle of development and delivery research that evaluates how best to scale up coverage of existing, evidence-based interventions, epidemiologic research that assesses the impact of implementing these interventions, and discovery science that better elucidates the complex causal pathway of preterm birth and helps to develop new screening and intervention tools. In addition to research, policy and financial investment is crucial to increasing opportunities to implement preconception care, and rates of prematurity should be included as a tracking indicator in global and national maternal child health assessments.Sohni V Dean, Elizabeth Mary Mason, Christopher P Howson, Zohra S Lassi, Ayesha M Imam, and Zulfiqar A Bhutt