A toolbox for parameter-free predictions of solid-state properties of monodisperse glassy polymers with frozen-in molecular orientation

A toolbox that allows designers to predict the properties of oriented glassy polymers using only existing material constants is constructed from a constitutive model applicable to both polymer solids and polymer melts. Two solid-state properties of practical engineering interest are considered: optical birefringence, and craze initiation stress. Predictions from the toolbox are compared to new experimental measurements on well characterized grades of monodisperse polystyrene, and confirm that the toolbox can account for the effect of polymer molecular weight

Large deformations in oriented polymer glasses: experimental study and a new glass-melt constitutive model

An experimental study was made of the effects of prior molecular orientation on large tensile deformations of polystyrene in the glassy state. A new hybrid glass-melt constitutive model is proposed for describing and understanding the results, achieved by parallel coupling of the ROLIEPOLY molecularly-based melt model with a model previously proposed for polymer glasses. Monodisperse and polydisperse grades of polystyrene are considered. Comparisons between experimental results and simulations illustrate that the model captures characteristic features of both the melt and glassy states. Polystyrene was stretched in the melt state and quenched to below Tg, and then tensile tested parallel to the orientation direction near the glass transition. The degree of strain-hardening was observed to increase with increasing prior stretch of molecules within their entanglement tubes, as predicted by the constitutive model. This was explored for varying temperature of stretching, degree of stretching, and dwell time before quenching. The model in its current form, however, lacks awareness of processes of subentanglement chain orientation. Therefore, it under-predicts the orientation-direction strain hardening and yield stress increase, when stretching occurs at the lowest temperatures and shortest times, where it is dominated by subentanglement orientation

Machine learning to expedite concept monopile design

Offshore wind turbine generators (WTG)s are typically supported by monopile foundations in shallow water (<50m). The design of monopile foundations is usually conducted using rule-based soil reaction curves (SRC)s in a 1D or 0D model. For the derivation of SRCs, WTG location-specific 3D finite element analysis (FEA) is now typically adopted in industry to ensure optimised foundation design. However, this approach is time consuming to calibrate to new sites and hence not well suited for early-stage structural design and load simulations where thousands of calculations are performed to finalise the offshore wind farm layout. This paper presents a novel approach for early stage monopile design (i.e. concept or pre-FEED), in which a concept design surrogate model was trained on a database of 2000 3D FEA simulations using a machine learning algorithm. The surrogate model provides rapid estimations of monopile design for Natural Frequency Analysis (NFA) and Fatigue Limit State (FLS) conditions, while also intrinsically incorporating the fidelity of the 3D FEA simulations. The surrogate model predicts results close to that of 3D FEA, over 10000 times faster, for layered soil profiles and a wide range of monopile dimensions inside the training space. Published monopile lateral response results from field testing were used to further validate the model. Use of such a tool in practice will speed up the process of preliminary monopile design and load simulations, reducing risks and time for developers, whilst improving site feasibility studies and cost estimates

Θ\Theta vacua states in heavy ion collisions in presence of dissipation and noise

We have studied possible formation of $\Theta$ vacua states in heavy ion collisions. Random phases of the chiral fields were evolved in a finite temperature potential, incorporating the breaking of $U_A(1)$ symmetry. Initial random phases very quickly settle into oscillation around the values dictated by the potential. The simulation study indicate that an initial $\Theta$=0 state do not evolve into a $\Theta$ $\neq$ 0 state. However, an initial $\Theta$ $\neq$ 0 state, if formed in heavy ion collision, can survive, as a coherent superposition of a number of modes.Comment: 6 pages, 6 figure

Quantum field dynamics of the slow rollover in the linear delta expansion

We show how the linear delta expansion, as applied to the slow-roll transition in quantum mechanics, can be recast in the closed time-path formalism. This results in simpler, explicit expressions than were obtained in the Schr\"odinger formulation and allows for a straightforward generalization to higher dimensions. Motivated by the success of the method in the quantum-mechanical problem, where it has been shown to give more accurate results for longer than existing alternatives, we apply the linear delta expansion to four-dimensional field theory. At small times all methods agree. At later times, the first-order linear delta expansion is consistently higher that Hartree-Fock, but does not show any sign of a turnover. A turnover emerges in second-order of the method, but the value of $$at the turnover is larger that that given by the Hartree-Fock approximation. Based on this calculation, and our experience in the corresponding quantum-mechanical problem, we believe that the Hartree-Fock approximation does indeed underestimate the value of$$ at the turnover. In subsequent applications of the method we hope to implement the calculation in the context of an expanding universe, following the line of earlier calculations by Boyanovsky {\sl et al.}, who used the Hartree-Fock and large-N methods. It seems clear, however, that the method will become unreliable as the system enters the reheating stage.Comment: 17 pages, 9 figures, revised version with extra section 4.2 including second order calculatio

Precise spatio-temporal control of rapid optogenetic cell ablation with mem-KillerRed in Zebrafish

The ability to kill individual or groups of cells in vivo is important for studying cellular processes and their physiological function. Cell-specific genetically encoded photosensitizing proteins, such as KillerRed, permit spatiotemporal optogenetic ablation with low-power laser light. We report dramatically improved resolution and speed of cell targeting in the zebrafish kidney through the use of a selective plane illumination microscope (SPIM). Furthermore, through the novel incorporation of a Bessel beam into the SPIM imaging arm, we were able to improve on targeting speed and precision. The low diffraction of the Bessel beam coupled with the ability to tightly focus it through a high NA lens allowed precise, rapid targeting of subsets of cells at anatomical depth in live, developing zebrafish kidneys. We demonstrate that these specific targeting strategies significantly increase the speed of optoablation as well as fish survival

Choosing wisely? Quantifying the extent of three low value psychotropic prescribing practices in Australia

BACKGROUND:The global Choosing Wisely campaign has identified the following psychotropic prescribing as low-value (harmful or wasteful): (1) benzodiazepine use in the elderly, (2) antipsychotic use in dementia and (3) prescribing two or more antipsychotics concurrently. We aimed to quantify the extent of these prescribing practices in the Australian population. METHODS:We applied indicators to dispensing claims of a 10% random sample of Australian Pharmaceutical Benefits Scheme beneficiaries to quantify annual rates of each low-value practice from 2013 to 2016. We also assessed patient factors and direct medicine costs (extrapolated to the entire Australian population) associated with each practice in 2016. RESULTS:We observed little change in the rates of the three practices between 2013 and 2016. In 2016, 15.3% of people aged ≥65 years were prescribed a benzodiazepine, 0.5% were prescribed antipsychotics in the context of dementia and 0.2% of people aged ≥18 years received two or more antipsychotics concurrently. The likelihood of elderly people receiving benzodiazepines or antipsychotics in the context of dementia increased with age and the likelihood of receiving all three practices increased with comorbidity burden. In 2016, direct medicine costs to the government of all three practices combined, extrapolated to national figures, were > $21 million AUD. CONCLUSIONS:Our indicators suggest that the frequency of these three practices has not changed appreciably in recent years and that they incur significant costs. Worryingly, people with the greatest risk of harm from these prescribing practices are often the most likely to receive them.Jonathan Brett, Helga Zoega, Nicholas A. Buckley, Benjamin J. Daniels, Adam G. Elshaug and Sallie-Anne Pearso

The ZZ' kinetic mixing in the light of the recent direct and indirect dark matter searches

Several constructions, of stringy origins or not, generate abelian gauge extensions of the Standard Model (SM). Even if the particles of the SM are not charged under this extra $U'(1)$, one cannot avoid the presence of a kinetic mixing between $U'(1)$ and the hypercharge $U_Y(1)$. In this work, we constraint drastically this kinetic mixing, taking into account the recent experimental data from accelerator physics, direct detection and indirect detection of dark matter. We show that the region respecting WMAP and experimental constraints is now very narrowed along the pole line where $M_{Z_D}\simeq 2 m_{DM}$, $Z_D$ being the gauge boson associated to the extra $U'(1)$.Comment: 9 pages, 3 figures, final version to appear in JCA

CP asymmetries in the supersymmetric trilepton signal at the LHC

In the CP-violating Minimal Supersymmetric Standard Model, we study the production of a neutralino-chargino pair at the LHC. For their decays into three leptons, we analyze CP asymmetries which are sensitive to the CP phases of the neutralino and chargino sector. We present analytical formulas for the entire production and decay process, and identify the CP-violating contributions in the spin correlation terms. This allows us to define the optimal CP asymmetries. We present a detailed numerical analysis of the cross sections, branching ratios, and the CP observables. For light neutralinos, charginos, and squarks, the asymmetries can reach several 10%. We estimate the discovery potential for the LHC to observe CP violation in the trilepton channel.Comment: 39 pages, 8 figures, version to appear in EPJC, discussion(s) added, typo in (D.79), (D.118) corrected, new Fig. 7; The European Physical Journal C, Volume 72, Issue 3, 201

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results