Spectral statistics of the quenched normal modes of a network-forming molecular liquid

We evaluate the density of states of the quenched normal modes of ST2 water, and their statistical fluctuations, for a range of densities spanning three regimes of behavior of a hydrogen bonded liquid: a lower-density regime of random tetrahedral network formation; in the vicinity of a liquid-liquid critical point; and in a higher-density regime of fragile glass-forming behavior. For all cases we find that the fluctuations around the mean spectral densities obey the predictions of the Gaussian orthogonal ensemble of random matrix theory. We also measure the participation ratio of the normal modes across the entire frequency range, and find behavior consistent with the majority of modes being of an extended nature, rather than localized.Comment: Accepted for publication in The Journal of Chemical Physic

Reducing Polarization Mode Dispersion With Controlled Polarization Rotations

One of the fundamental limitations to high bit rate, long distance, telecommunication in optical fibers is Polarization Mode Dispersion (PMD). Here we introduce a conceptually new method to reduce PMD in optical fibers by carrying out controlled rotations of polarization at predetermined locations along the fiber. The distance between these controlled polarization rotations must be less than both the beat length and the mode coupling length of the fiber. This method can also be combined with the method in which the fiber is spun while it drawn. The incidence of imperfections on the efficiency of the method is analysed.Comment: 4 page

Nonlinear c-axis transport in Bi_2Sr_2CaCu_2O_(8+d) from two-barrier tunneling

Motivated by the peculiar features observed through intrinsic tunneling spectroscopy of Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ mesas in the normal state, we have extended the normal state two-barrier model for the c-axis transport [M. Giura et al., Phys. Rev. B {\bf 68}, 134505 (2003)] to the analysis of $dI/dV$ curves. We have found that the purely normal-state model reproduces all the following experimental features: (a) the parabolic $V$-dependence of $dI/dV$ in the high-$T$ region (above the conventional pseudogap temperature), (b) the emergence and the nearly voltage-independent position of the "humps" from this parabolic behavior lowering the temperature, and (c) the crossing of the absolute $dI/dV$ curves at a characteristic voltage $V^\times$. Our findings indicate that conventional tunneling can be at the origin of most of the uncommon features of the c axis transport in Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$. We have compared our calculations to experimental data taken in severely underdoped and slightly underdoped Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ small mesas. We have found good agreement between the data and the calculations, without any shift of the calculated dI/dV on the vertical scale. In particular, in the normal state (above $T^\ast$) simple tunneling reproduces the experimental dI/dV quantitatively. Below $T^\ast$ quantitative discrepancies are limited to a simple rescaling of the voltage in the theoretical curves by a factor $\sim$2. The need for such modifications remains an open question, that might be connected to a change of the charge of a fraction of the carriers across the pseudogap opening.Comment: 7 pages, 5 figure

Study of the local field distribution on a single-molecule magnet-by a single paramagnetic crystal; a DPPH crystal on the surface of an Mn12-acetate crystal

The local magnetic field distribution on the subsurface of a single-molecule magnet crystal, SMM, above blocking temperature (T >> Tb) detected for a very short time interval (~ 10-10 s), has been investigated. Electron Paramagnetic Resonance (EPR) spectroscopy using a local paramagnetic probe was employed as a simple alternative detection method. An SMM crystal of [Mn12O12(CH3COO)16(H2O)4].2CH3COOH.4H2O (Mn12-acetate) and a crystal of 2,2- diphenyl-1-picrylhydrazyl (DPPH) as the paramagnetic probe were chosen for this study. The EPR spectra of DPPH deposited on Mn12-acetate show additional broadening and shifting in the magnetic field in comparison to the spectra of the DPPH in the absence of the SMM crystal. The additional broadening of the DPPH linewidth was considered in terms of the two dominant electron spin interactions (dipolar and exchange) and the local magnetic field distribution on the crystal surface. The temperature dependence of the linewidth of the Gaussian distribution of local fields at the SMM surface was extrapolated for the low temperature interval (70-5 K)

Next-Generation Sequencing-Based Approaches for Mutation Mapping and Identification in Caenorhabditis elegans

The use of next-generation sequencing (NGS) has revolutionized the way phenotypic traits are assigned to genes. In this review, we describe NGS-based methods for mapping a mutation and identifying its molecular identity, with an emphasis on applications in Caenorhabditis elegans. In addition to an overview of the general principles and concepts, we discuss the main methods, provide practical and conceptual pointers, and guide the reader in the types of bioinformatics analyses that are required. Owing to the speed and the plummeting costs of NGS-based methods, mapping and cloning a mutation of interest has become straightforward, quick, and relatively easy. Removing this bottleneck previously associated with forward genetic screens has significantly advanced the use of genetics to probe fundamental biological processes in an unbiased manner

Who are Non-Resident Fathers?: A British Socio-Demographic Profile

Despite international growth of, and policy interest in, divorce and separation since the 1970s, there is still surprisingly little known about non-residential fatherhood. This paper presents a 'father-centric' analysis and provides one of the first profiles of non-residential fatherhood in early millennium UK. Using data from Understanding Society Wave 1, a nationally representative survey of over 30,000 households in the UK, we found 1,070 men self-identifying as having a non-resident child under 16 years old (https://www.understandingsociety.ac.uk). We estimate a prevalence of 5 per cent of British men having a non-resident dependent child. Through latent class analysis, four distinct groups of non-resident fathers are identified: 'Engaged' fathers, 'Less Engaged' fathers, 'Disengaged' fathers and 'Distance' fathers. Our analysis finds that non-resident fathers form a heterogeneous group in terms of their socio-demographic profile and family behaviour. It is recommended that legislation and policy concerning fathers in post-separation families are sensitive to variation as well as commonality in socio-economic conditions and family lives and situations

Tunnel and thermal c-axis transport in BSCCO in the normal and pseudogap state

We consider the problem of c-axis transport in double-layered cuprates, in particular with reference to Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ compounds. We exploit the effect of the two barriers on the thermal and tunnel transport. The resulting model is able to describe accurately the normal state c-axis resistivity in Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$, from the underdoped side up to the strongly overdoped. We extend the model, without introducing additional parameters, in order to allow for the decrease of the barrier when an external voltage bias is applied. The extended model is found to describe properly the c-axis resistivity for small voltage bias above the pseudogap temperature $T^{*}$, the c-axis resistivity for large voltage bias even below $T_c$, and the differential $dI/dV$ curves taken in mesa structures.Comment: 12 pages, 6 figures. Submitted to Superconductor Science and Technolog

Britain's slow movement to a Gender Egalitarian Equilibrium: Parents and Employment in the UK 2001 - 2013

This paper examines the working lives of British couple families across the first decade of the millennium using EU Labour Force Survey data (2001-2013) taking a multiple equilibria approach (Esping-Andersen and Billari, 2015). We identify a growth in dual full-time earners, increased working hours of mothers in part-time employment and a growing proportion of households with ‘non-standard’ working patterns, suggesting both a convergence and greater diversity in economic provisioning within parent couple households. We find that household employment patterns remain strongly associated with maternal education and family size but are becoming less sensitive to the age of youngest child. The dual full-time earner model is growing in significance for British parents of young children but a new gender egalitarian equilibrium has not yet been reached