Isolating quantum coherence with pathway-selective coherent multi-dimensional spectroscopy

Coherent coupling between spatially separated systems has long been explored as a necessary requirement for quantum information and cryptography. Recent discoveries suggest such phenomena appear in a much wider range of processes, including light-harvesting in photosynthesis. These discoveries have been facilitated by developments in coherent multi-dimensional spectroscopy (CMDS) that allow interactions between different electronic states to be identified in crowded spectra. For complex systems, however, spectral broadening and multiple overlapping peaks limit the ability to separate, identify and properly analyse all contributions. Here we demonstrate how pathway-selective CMDS can overcome these limitations to reveal, isolate and allow detailed analysis of weak coherent coupling between spatially separated excitons localised to different semiconductor quantum wells. Selective excitation of the coherence pathways, by spectrally shaping the laser pulses, provides access to previously hidden details and enables quantitative analysis that can facilitate precise and detailed understanding of interactions in this and other complex systems

Estimating marginal cohort working life expectancies from sequential cross-sectional survey data

This article applies recently developed health expectancy methodologies to estimate the average duration of future work life in different states of work ability. Data on working capacity obtained from sequential cross-sectional samples of the cohort population were available from Finnish surveys conducted among active municipal employees. We used these data to estimate cohort marginal probabilities and expected occupancy times in the work ability states. One finding is that the proportion of workers with excellent or good work ability decreased monotonically with advancing age for both genders, but men were prone to have worse work ability and a shorter work career than women. Transition from poor to good or excellent work ability state was estimated to increase working life expectancy of a 45-year-old person by four years for both genders. This study indicates that the work ability of aging Finnish workers deteriorates prematurely, leading to serious socio-economic consequences. Thus it is important to examine the development of work ability already at an early age when it is still possible to intervene in the process

Noncognitive Predictors of Academic Performance and Persistence in Horizontal and Vertical Transfer Students By Academic Level

College students increasingly are transferring among institutions of higher education in pursuit of their educational goals. The existing research on transfer students, however, does not adequately explore the unique characteristics of this heterogeneous population. The literature on transfer students suggests that transfer students are at-risk for experiencing academic difficulty and attrition. Research indicates that degree attainment is associated with the success of the student and their parents. Furthermore, attrition negatively impacts higher education finances, so colleges and universities that focus on helping students be successful and persist to graduation maintain revenue streams. Many studies have focused on cognitive measures of academic performance and persistence; however, research has shown that cognitive measures alone are not the best predictors of academic performance and persistence (Duggan & Pickering, 2008; Pickering, Calliotte, & McAuliffe, 1992). Researchers have explored various noncognitive and cognitive measures of academic performance and persistence, but the literature has not controlled for the unique characteristics of the transfer student population. Research needs to focus on examining transfer students as subpopulations with common characteristics. The purpose of this research was to analyze noncognitive, cognitive, and demographic variables to determine if incorporating the transfer history of students would result in better predictions of academic performance and persistence. The population examined in this study included first-time transfer students who most resemble the traditional college student characteristics which excluded distance learners, international students, military students, and students over the age of 29. Transfer students were divided into six subpopulations: first-year vertical transfers (n = 143), sophomore vertical transfers (n = 469), upper-division vertical transfer ( n = 554), first-year horizontal transfers (n = 166), sophomore horizontal transfers (n = 306), and upper-division horizontal transfers (n = 77). Logistical regressions were used to answer four research questions. Results of the analysis revealed that a noncognitive index (TSS Index) based on student attitudes, behaviors, and experiences, was a significant predictor of academic difficulty for each of the subpopulations of transfer students. First semester cumulative GPA at the target institution was predictive of attrition for each subpopulation of transfer students. The findings also revealed that the other predictors vary in significance among the subpopulations which supports the need for additional research on the uniqueness of transfer students. Findings from this study justify the need for additional research on transfer students that further examine the characteristics of unique subpopulations of these students. College administrators in areas of student services and enrollment management can use the results to gain a better understanding of the transfer student population and identify and develop resources to assist these students with their academic endeavors

Insights into the Nature of Synergistic Effects in Proton-Conducting 4,4−1H,1H-Bitriazole-Poly(ethylene oxide) Composites

A nitrogen-containing heterocycle (NCH), 4,4-1H-1H-bi-1,2,3-triazole (bitriazole), capable of mimicking the hydrogen bonding of water in the solid state is synthesized and its ability to conduct protons in the presence of poly(ethylene oxides) under anhydrous conditions is investigated. Bitriazole is shown to have sufficient thermal and electrochemical stability for fuel cell applications. The composites formed between bitriazole and poly(ethylene oxides) give proton conductivities that can be described by the Vogel−Tamman−Fulcher (VTF) equation. These characteristics suggest coupling between polymer segmental motion and ion transport. The bitriazole N-H proton is shown to be the source of conductivity, and bitriazole and poly(ethylene oxides) function synergistically through specific intermolecular interactions and polymer-induced segmental motion to create a pathway for proton transport via structural diffusion

Proton-Conducting Solid Electrolyte via Ozonolysis of Cationic Ammonium Organoalkoxysilane Surfactant-Templated MCM-41

A functional polymerizable surfactant has been synthesized and used as a template to prepare MCM-41. Ozonolysis of the olefin functional group in the composite material generates a nonporous proton-conducting solid acid that has a conductivity of ca. 6 mS cm^(-1) at 95 °C and an activation energy of 14.2 kJ/mol

Transfer having a coupling coefficient higher than its active material

A coupling coefficient is a measure of the effectiveness with which a shape-changing material (or a device employing such a material) converts the energy in an imposed signal to useful mechanical energy. Device coupling coefficients are properties of the device and, although related to the material coupling coefficients, are generally different from them. This invention describes a class of devices wherein the apparent coupling coefficient can, in principle, approach 1.0, corresponding to perfect electromechanical energy conversion. The key feature of this class of devices is the use of destabilizing mechanical pre-loads to counter inherent stiffness. The approach is illustrated for piezoelectric and thermoelectrically actuated devices. The invention provides a way to simultaneously increase both displacement and force, distinguishing it from alternatives such as motion amplification, and allows transducer designers to achieve substantial performance gains for actuator and sensor devices

Estimating cohort health expectancies from cross-sectional surveys of disability

A life history can be regarded as a random process that evolves with age through various states of health before terminating with absorption into the state of death. Health expectancies are the occupation times of the non-absorbing states and their estimation is of interest. A continuing major problem has been the lack of satisfactory longitudinal data on which to base estimates and as a result standard inferential techniques may not be relevant. Supposing only cross-sectional data available, we propose a method that is generally applicable and first estimates a logistic parametrization of the probabilities of the various states. A large sample approximation is obtained for the distribution of age specific log (odds). Parameters are estimated by weighted least squares, and this in turn leads to estimates of cohort health expectancies. A result of Liang and Zeger is used to find standard errors. The method is illustrated by application to Australian data from the health surveys of 1981, 1988 and 1993

Polarization restricts hepatitis C virus entry into HepG2 hepatoma cells

The primary reservoir for hepatitis C virus (HCV) replication is believed to be hepatocytes, which are highly polarized with tight junctions (TJ) separating their basolateral and apical domains. HepG2 cells develop polarity over time, resulting in the formation and remodeling of bile canalicular (BC) structures. HepG2 cells expressing CD81 provide a model system to study the effects of hepatic polarity on HCV infection. We found an inverse association between HepG2-CD81 polarization and HCV pseudoparticle entry. As HepG2 cells polarize, discrete pools of claudin-1 (CLDN1) at the TJ and basal/lateral membranes develop, consistent with the pattern of receptor staining observed in liver tissue. The TJ and nonjunctional pools of CLDN1 show an altered association with CD81 and localization in response to the PKA antagonist Rp-8-Br-cyclic AMPs (cAMPs). Rp-8-Br-cAMPs reduced CLDN1 expression at the basal membrane and inhibited HCV infection, supporting a model where the nonjunctional pools of CLDN1 have a role in HCV entry. Treatment of HepG2 cells with proinflammatory cytokines, tumor necrosis factor alpha and gamma interferon, perturbed TJ integrity but had minimal effect(s) on cellular polarity and HCV infection, suggesting that TJ integrity does not limit HCV entry into polarized HepG2 cells. In contrast, activation of PKC with phorbol ester reduced TJ integrity, ablated HepG2 polarity, and stimulated HCV entry. Overall, these data show that complex hepatocyte-like polarity alters CLDN1 localization and limits HCV entry, suggesting that agents which disrupt hepatocyte polarity may promote HCV infection and transmission within the liver

Influence of classical resonances on chaotic tunnelling

Dynamical tunnelling between symmetry-related stable modes is studied in the periodically driven pendulum. We present strong evidence that the tunnelling process is governed by nonlinear resonances that manifest within the regular phase-space islands on which the stable modes are localized. By means of a quantitative numerical study of the corresponding Floquet problem, we identify the trace of such resonances not only in the level splittings between near-degenerate quantum states, where they lead to prominent plateau structures, but also in overlap matrix elements of the Floquet eigenstates, which reveal characteristic sequences of avoided crossings in the Floquet spectrum. The semiclassical theory of resonance-assisted tunnelling yields good overall agreement with the quantum-tunnelling rates, and indicates that partial barriers within the chaos might play a prominent role