Field-theoretical approach to a dense polymer with an ideal binary mixture of clustering centers

We propose a field-theoretical approach to a polymer system immersed in an ideal mixture of clustering centers. The system contains several species of these clustering centers with different functionality, each of which connects a fixed number segments of the chain to each other. The field-theory is solved using the saddle point approximation and evaluated for dense polymer melts using the Random Phase Approximation. We find a short-ranged effective inter-segment interaction with strength dependent on the average segment density and discuss the structure factor within this approximation. We also determine the fractions of linkers of the different functionalities.Comment: 27 pages, 9 figures, accepted on Phys. Rev.

Single-cycle THz pulses with amplitudes exceeding 1 MV/cm generated by optical rectification in LiNbO3

Using the tilted-pulse-intensity-front scheme, we generate single-cycle terahertz (THz) pulses by optical rectification of femtosecond laser pulses in LiNbO3. In the THz generation setup, the condition that the image of the grating coincides with the tilted-optical-pulse front is fulfilled to obtain optimal THz beam characteristics and pump-to-THz conversion efficiency. The designed focusing geometry enables tight focus of the collimated THz beam with a spot size close to the diffraction limit, and the maximum THz electric field of 1.2 MV/cm is obtained

Discovery of a wandering radio jet base after a large X-ray flare in the blazar Markarian 421

We investigate the location of the radio jet bases ("radio cores") of blazars in radio images, and their stationarity by means of dense very long baseline interferometry (VLBI) observations. In order to measure the position of a radio core, we conducted 12 epoch astrometric observation of the blazar Markarian 421 with the VLBI Exploration of Radio Astrometry at 22 GHz immediately after a large X-ray flare, which occurred in the middle of 2011 September. For the first time, we find that the radio core is not stationary but rather changes its location toward 0.5 mas downstream. This angular scale corresponds to the de-projected length of a scale of $10^5$ Schwarzschild radii (Rs) at the distance of Markarian~421. This radio-core wandering may be a new type of manifestation associated with the phenomena of large X-ray flares.Comment: 6 pages, 4 figures, 1 table, has been published in ApJ Letter

Majorana Neutrino Masses from Neutrinoless Double Beta Decay and Cosmology

When three Majorana neutrinos describe the solar and atmospheric neutrino data via oscillations, a nonzero measurement of neutrinoless double beta ($0\nu\beta\beta$) decay can determine the sum of neutrino masses $\sum m_\nu$ if the solar solution has small-angle mixing, and place a lower bound on $\sum m_\nu$ for large-angle solar mixing. If in addition a nonzero $\sum m_\nu$ is deduced from cosmology, the neutrino mass spectrum may be uniquely specified for some ranges of neutrino parameters. For $\sum m_\nu > 0.75$ eV, the small-angle solar solution is excluded by the current upper limit on neutrinoless double beta decay. In models with maximal solar mixing the $CP$ phases of the neutrinos may be strongly constrained by stringent upper bounds on $0\nu\beta\beta$ decay.Comment: 13 pages, Latex2.09, uses epsf.sty, 4 postscript figure

Survival of charmonia above Tc in anisotropic lattice QCD

We find a strong evidence for the survival of $J/\Psi$ and $\eta_c$ as spatially-localized $c\bar c$ (quasi-)bound states above the QCD critical temperature $T_c$, by investigating the boundary-condition dependence of their energies and spectral functions. In a finite-volume box, there arises a boundary-condition dependence for spatially spread states, while no such dependence appears for spatially compact states. In lattice QCD, we find almost {\it no} spatial boundary-condition dependence for the energy of the $c\bar c$ system in $J/\Psi$ and $\eta_c$ channels for $T\simeq(1.11-2.07)T_c$. We also investigate the spectral function of charmonia above $T_c$ in lattice QCD using the maximum entropy method (MEM) in terms of the boundary-condition dependence. There is {\it no} spatial boundary-condition dependence for the low-lying peaks corresponding to $J/\Psi$ and $\eta_c$ around 3GeV at $1.62T_c$. These facts indicate the survival of $J/\Psi$ and $\eta_c$ as compact $c\bar c$ (quasi-)bound states for $T_c < T < 2T_c$.Comment: 4 pages, 1 figur

Longitudinal Response of Confined Semiflexible Polymers

The longitudinal response of single semiflexible polymers to sudden changes in externally applied forces is known to be controlled by the propagation and relaxation of backbone tension. Under many experimental circumstances, realized, e.g., in nano-fluidic devices or in polymeric networks or solutions, these polymers are effectively confined in a channel- or tube-like geometry. By means of heuristic scaling laws and rigorous analytical theory, we analyze the tension dynamics of confined semiflexible polymers for various generic experimental setups. It turns out that in contrast to the well-known linear response, the influence of confinement on the non-linear dynamics can largely be described as that of an effective prestress. We also study the free relaxation of an initially confined chain, finding a surprising superlinear t^(9/8) growth law for the change in end-to-end distance at short times.Comment: 18 pages, 1 figur

Screening and alcohol brief interventions in antenatal care: a realistic evaluation

Background: Prenatal alcohol consumption is one of the leading preventable causes of birth defects, including fetal alcohol syndrome and learning disabilities. Although there is strong evidence of the benefits of screening and alcohol brief interventions (ABIs) in reducing hazardous and harmful drinking among the primary care population, evidence of its effectiveness with the antenatal care population is limited. Nevertheless, the Scottish Government is incorporating an alcohol screening and ABI programme as part of the routine antenatal care provided to women in a bid to protect the health and safety of the unborn child and improve subsequent health and developmental outcomes. This research therefore seeks to increase understanding of the factors that are likely to influence the effectiveness of this recently implemented programme. It also aims to explore the extent to which contemporary issues such as change in guidelines regarding alcohol consumption during pregnancy influences perceptions and attitudes, and the possible implications of these on the screening and ABI delivery. Methods: The study described in this thesis employed a realistic evaluation methodology. Realistic evaluation is a theory-driven approach to investigating social programmes. It is concerned with hypothesising, testing and refining programme theories by exploring the interaction of contexts, mechanisms and outcomes. To identify the relevant screening and ABI programme theories, two separate systematic reviews, a critical review and four face-to-face interviews were undertaken with health policy implementers. The findings were used to construct context, mechanism and outcomes propositions. The propositions were then tested by conducting individual interviews with seventeen pregnant women and fifteen midwives, a further six midwifery team leaders were involved in a focus group discussion. A thematic approach using a hybrid of inductive and deductive coding and theme development informed the qualitative analysis. Results: In the context of uncertainties regarding the threshold of drinking that causes fetal harm, pregnant women reported that screening assessment helped them to reflect on their drinking behaviour and facilitate behaviour change. For women who drank at hazardous and harmful levels before attending the booking appointment, screening and ABI may be helpful in terms of eliciting behaviour change. However, they may not be very beneficial in terms of reducing harm to the fetus as it has been found that drinking during the first trimester poses the most risk to the fetus. Training and resources provided to midwives as part of the screening and ABI programme were found to be facilitating mechanisms that midwives indicated improved their skills and confidence. However, most of the midwives had not subsequently employed the motivational interviewing skills required for the ABI delivery, as many of the pregnant women reported that they reduced or abstained from alcohol consumption once pregnancy was confirmed. The outcome noted was that midwives confidence decreased leading to missed opportunities to appropriately deliver the ABI to eligible women. The small numbers of women being identified for ABI meant midwives rarely delivered the ABI. This negatively influenced midwives attitudes as they then accorded ABI low priority in their workload. Other disenabling mechanisms noted to be hampering the implementation of the screening and ABI initiative included midwives contending with competing priorities at the booking appointments, and the lack of adequate rapport between midwives and pregnant women at the booking appointment to discuss alcohol issues appropriately, leading to women providing socially desirable responses to screening questions. Conclusions: The findings of this study has generated greater explanations of the working of the screening and ABI programme in antenatal care setting and has provided transferable lessons that can be used by others intending to implement similar programmes in other settings

The topological glass in ring polymers

We study the dynamics of concentrated, long, semi-flexible, unknotted and unlinked ring polymers embedded in a gel by Monte Carlo simulation of a coarse-grained model. This involves the ansatz that the rings compactify into a duplex structure where they can be modelled as linear polymers. The classical polymer glass transition involves a rapid loss of microscopic freedom within the polymer molecule as the temperature is reduced toward Tg. Here we are interested in temperatures well above Tg where the polymers retain high microscopic mobility. We analyse the slowing of stress relaxation originating from inter-ring penetrations (threadings). For long polymers an extended network of quasi-topological penetrations forms. The longest relaxation time appears to depend exponentially on the ring polymer contour length, reminiscent of the usual exponential slowing (e.g., with temperature) in classical glasses. Finally, we discuss how this represents a universality class for glassy dynamics