Optimization of Brownian ratchets for the manipulation of charged components within supported lipid bilayers

In probability theory, there is a counter-intuitive result that it is possible to construct a winning strategy from two individually losing (or at most breaking-even) "games" by alternating between them. The work presented here demonstrates the application of this principle to supported lipid bilayers (SLBs) in order to create directed motion of charged lipid components in the membrane, which was achieved through the use of "Brownian ratchets" in patterned SLBs. Both a finite element analysis model and an experimental setup have been used to investigate the role of key parameters for the operation of these ratchets: (1) the asymmetry of the ratchet teeth and (2) the relation of the ratchet height to the period of the applied electric field. Importantly, we find that the efficiency of the ratchet for a given charged species is dependent on the diffusion coefficient. This opens the possibility for separation of membrane species according to their size or viscous drag coefficient within the membrane

Effect of Systematically Tuning Conjugated Donor Polymer Lowest Unoccupied Molecular Orbital Levels via Cyano Substitution on Organic Photovoltaic Device Performance

We report a systematic study into the effects of cyano substitution on the electron accepting ability of the common acceptor 4,7-bis(thiophen-2-yl)-2,1,3-benzothiadiazole (DTBT). We describe the synthesis of DTBT monomers with either 0, 1, or 2 cyano groups on the BT unit and their corresponding copolymers with the electron rich donor dithienogermole (DTG). The presence of the cyano group is found to have a strong influence on the optoelectronic properties of the resulting donor–acceptor polymers, with the optical band gap red-shifting by approximately 0.15 eV per cyano substituent. We find that the polymer electron affinity is significantly increased by ∼0.25 eV upon addition of each cyano group, while the ionization potential is less strongly affected, increasing by less than 0.1 eV per cyano substituent. In organic photovoltaic (OPV) devices power conversion efficiencies (PCE) are almost doubled from around 3.5% for the unsubstituted BT polymer to over 6.5% for the monocyano substituted BT polymer. However, the PCE drops to less than 1% for the dicyano substituted BT polymer. These differences are mainly related to differences in the photocurrent, which varies by 1 order of magnitude between the best (1CN) and worst devices (2CN). The origin of this variation in the photocurrent was investigated by studying the charge generation properties of the photoactive polymer–fullerene blends using fluorescence and transient absorption spectroscopic techniques. These measurements revealed that the improved photocurrent of 1CN in comparison to 0CN was due to improved light harvesting properties while maintaining a high exciton dissociation yield. The addition of one cyano group to the BT unit optimized the position of the polymer LUMO level closer to that of the electron acceptor PC71BM, such that the polymer’s light harvesting properties were improved without sacrificing either the exciton dissociation yield or device VOC. We also identify that the drop in performance for the 2CN polymer is caused by very limited yields of electron transfer from the polymer to the fullerene, likely caused by poor orbital energy level alignment with the fullerene acceptor (PC71BM). This work highlights the impact that small changes in chemical structure can have on the optoelectronic and device properties of semiconducting polymer. In particular this work highlights the effect of LUMO–LUMO offset on the excited state dynamics of polymer–fullerene blends

Pure Samples of Quark and Gluon Jets at the LHC

Having pure samples of quark and gluon jets would greatly facilitate the study of jet properties and substructure, with many potential standard model and new physics applications. To this end, we consider multijet and jets+X samples, to determine the purity that can be achieved by simple kinematic cuts leaving reasonable production cross sections. We find, for example, that at the 7 TeV LHC, the pp {\to} {\gamma}+2jets sample can provide 98% pure quark jets with 200 GeV of transverse momentum and a cross section of 5 pb. To get 10 pb of 200 GeV jets with 90% gluon purity, the pp {\to} 3jets sample can be used. b+2jets is also useful for gluons, but only if the b-tagging is very efficient.Comment: 19 pages, 16 figures; v2 section on formally defining quark and gluon jets has been adde

Valley spin polarization by using the extraordinary Rashba effect on silicon

The addition of the valley degree of freedom to a two-dimensional spin-polarized electronic system provides the opportunity to multiply the functionality of next-generation devices. So far, however, such devices have not been realized due to the difficulty to polarize the valleys, which is an indispensable step to activate this degree of freedom. Here we show the formation of 100% spin-polarized valleys by a simple and easy way using the Rashba effect on a system with C-3 symmetry. This polarization, which is much higher than those in ordinary Rashba systems, results in the valleys acting as filters that can suppress the backscattering of spin-charge. The present system is formed on a silicon substrate, and therefore opens a new avenue towards the realization of silicon spintronic devices with high efficiency.X114334Nsciescopu

Renal impairment in a rural African antiretroviral programme

Background: There is little knowledge regarding the prevalence and nature of renal impairment in African populations initiating antiretroviral treatment, nor evidence to inform the most cost effective methods of screening for renal impairment. With the increasing availability of the potentially nephrotixic drug, tenofovir, such information is important for the planning of antiretroviral programmes Methods: (i) Retrospective review of the prevalence and risk factors for impaired renal function in 2189 individuals initiating antiretroviral treatment in a rural African setting between 2004 and 2007 (ii) A prospective study of 149 consecutive patients initiating antiretrovirals to assess the utility of urine analysis for the detection of impaired renal function. Severe renal and moderately impaired renal function were defined as an estimated GFR of ≤ 30 mls/min/1.73 m2 and 30–60 mls/min/1.73 m2 respectively. Logistic regression was used to determine odds ratio (OR) of significantly impaired renal function (combining severe and moderate impairment). Co-variates for analysis were age, sex and CD4 count at initiation. Results: (i) There was a low prevalence of severe renal impairment (29/2189, 1.3% 95% C.I. 0.8–1.8) whereas moderate renal impairment was more frequent (287/2189, 13.1% 95% C.I. 11.6–14.5) with many patients having advanced immunosuppression at treatment initiation (median CD4 120 cells/μl). In multivariable logistic regression age over 40 (aOR 4.65, 95% C.I. 3.54–6.1), male gender (aOR 1.89, 95% C.I. 1.39–2.56) and CD4<100 cells/ul (aOR 1.4, 95% C.I. 1.07–1.82) were associated with risk of significant renal impairment (ii) In 149 consecutive patients, urine analysis had poor sensitivity and specificity for detecting impaired renal function. Conclusion: In this rural African setting, significant renal impairment is uncommon in patients initiating antiretrovirals. Urine analysis alone may be inadequate for identification of those with impaired renal function where resources for biochemistry are limited

Anonymous Single-Sign-On for n designated services with traceability

Anonymous Single-Sign-On authentication schemes have been proposed to allow users to access a service protected by a verifier without revealing their identity which has become more important due to the introduction of strong privacy regulations. In this paper we describe a new approach whereby anonymous authentication to different verifiers is achieved via authorisation tags and pseudonyms. The particular innovation of our scheme is authentication can only occur between a user and its designated verifier for a service, and the verification cannot be performed by any other verifier. The benefit of this authentication approach is that it prevents information leakage of a user's service access information, even if the verifiers for these services collude which each other. Our scheme also supports a trusted third party who is authorised to de-anonymise the user and reveal her whole services access information if required. Furthermore, our scheme is lightweight because it does not rely on attribute or policy-based signature schemes to enable access to multiple services. The scheme's security model is given together with a security proof, an implementation and a performance evaluation.Comment: 3

Novel and simple patterning process of quantum dots via transfer printing for active matrix qd-led

© 2020 SID. The next generation of a self-emitting display requires precise and stable patterning techniques to shape Red, Green, and Blue pixels using quantum dots. In this study, we propose the novel and simple transfer printing process for the active matrix QD-LEDs

Heavy Squarks at the LHC

The LHC, with its seven-fold increase in energy over the Tevatron, is capable of probing regions of SUSY parameter space exhibiting qualitatively new collider phenomenology. Here we investigate one such region in which first generation squarks are very heavy compared to the other superpartners. We find that the production of these squarks, which is dominantly associative, only becomes rate-limited at mSquark > 4(5) TeV for L~10(100) fb-1. However, discovery of this scenario is complicated because heavy squarks decay primarily into a jet and boosted gluino, yielding a dijet-like topology with missing energy (MET) pointing along the direction of the second hardest jet. The result is that many signal events are removed by standard jet/MET anti-alignment cuts designed to guard against jet mismeasurement errors. We suggest replacing these anti-alignment cuts with a measurement of jet substructure that can significantly extend the reach of this channel while still removing much of the background. We study a selection of benchmark points in detail, demonstrating that mSquark= 4(5) TeV first generation squarks can be discovered at the LHC with L~10(100)fb-1

Validation of the CogDrisk Instrument as Predictive of Dementia in Four General Community-Dwelling Populations

Background: Lack of external validation of dementia risk tools is a major limitation for generalizability and translatability of prediction scores in clinical practice and research. Objectives: We aimed to validate a new dementia prediction risk tool called CogDrisk and a version, CogDrisk-AD for predicting Alzheimer’s disease (AD) using cohort studies. Design, Setting, Participants and Measurements: Four cohort studies were identified that included majority of the dementia risk factors from the CogDrisk tool. Participants who were free of dementia at baseline were included. The predictors were component variables in the CogDrisk tool that include self-reported demographics, medical risk factors and lifestyle habits. Risk scores for Any Dementia and AD were computed and Area Under the Curve (AUC) was assessed. To examine modifiable risk factors for dementia, the CogDrisk tool was tested by excluding age and sex estimates from the model. Results: The performance of the tool varied between studies. The overall AUC and 95% CI for predicting dementia was 0.77 (0.57, 0.97) for the Swedish National study on Aging and Care in Kungsholmen, 0.76 (0.70, 0.83) for the Health and Retirement Study - Aging, Demographics and Memory Study, 0.70 (0.67,0.72) for the Cardiovascular Health Study Cognition Study, and 0.66 (0.62,0.70) for the Rush Memory and Aging Project. Conclusions: The CogDrisk and CogDrisk-AD performed well in the four studies. Overall, this tool can be used to assess individualized risk factors of dementia and AD in various population settings