Effects of internal luminescence and internal optics on V-oc and J(sc) of III-V solar cells

For solar cells dominated by radiative recombination, the performance can be significantly enhanced by improving the internal optics. Internally radiated photons can be directly emitted from the cell, but if confined by good internal reflectors at the front and back of the cell they can also be re-absorbed with a significant probability. This so-called photon recycling leads to an increase in the equilibrium minority carrier concentration and therefore the open-circuit voltage, Voc. In multijunction cells, the internal luminescence from a particular junction can also be coupled into a lower bandgap junction where it generates photocurrent in addition to the externally generated photocurrent, and affects the overall performance of the tandem. We demonstrate and discuss the implications of a detailed model that we have developed for real, non-idealized solar cells that calculates the external luminescent efficiency, accounting for wavelength-dependent optical properties in each layer, parasitic optical and electrical losses, multiple reflections within the cell and isotropic internal emission. The calculation leads to Voc, and we show data on high quality GaAs cells that agree with the trends in the model as the optics are systematically varied. For multijunction cells the calculation also leads to the luminescent coupling efficiency, and we show data on GaInP/GaAs tandems where the trends also agree as the coupling is systematically varied. In both cases, the effects of the optics are most prominent in cells with good material quality. The model is applicable to any solar cell for which the optical properties of each layer are well-characterized, and can be used to explore a wide phase space of design for single junction and multijunction solar cells

Mechanically stacked four-junction concentrator solar cells

Multijunction solar cells can be fabricated by bonding together component cells that are grown separately. Because the component cells are each grown lattice-matched to suitable substrates, this technique allows alloys of different lattice constants to be combined without the structural defects introduced when using metamorphic buffers. Here we present results on the fabrication and performance of four-junction mechanical stacks composed of GaInP/GaAs and GaInAsP/GaInAs tandems, grown on GaAs and InP substrates, respectively. The two tandems were bonded together with a lowindex, transparent epoxy that acts as an omni-directional reflector to the GaAs bandedge luminescence, while simultaneously transmitting nearly all of the sub-bandgap light. As determined by electroluminescence measurements and optical modeling, the GaAs subcell demonstrates a higher internal radiative limit and thus higher subcell voltage, compared with GaAs subcells without enhanced internal optics; all four subcells exhibit excellent material quality. The device was fabricated with four contact terminals so that each tandem can be operated at its maximum power point, which raises the cumulative efficiency and decreases spectral sensitivity. Efficiencies exceeding 38% at one-sun have been demonstrated. Eliminating the series resistance is the key challenge for the concentrator cells. We will discuss the performance of one-sun and concentrator versions of the device, and compare the results to recently fabricated monolithic four-junction cells

Bostonia: The Boston University Alumni Magazine. Volume 9

Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs

Vasa previa in singleton pregnancies: Diagnosis and clinical management based on an international expert consensus

There are limited data to guide the diagnosis and management of vasa previa. Currently, what is known is largely based on case reports or series and cohort studies. (s): To systematically collect and classify expert opinions and achieve consensus on the diagnosis and clinical management of vasa previa using focus group discussions (FGD) and a Delphi technique. A four-round FGD and a three-round Delphi survey of an international panel of experts on vasa previa were conducted. Experts were selected based on their publication record on vasa previa. First, we convened an FGD panel of 20 experts and agreed on which issues were unresolved in the diagnosis and management of vasa previa. A three-round anonymous electronic survey was then sent to the full expert panel. Survey questions were presented on the diagnosis and management of vasa previa that the experts were asked to rate on a 5-point Likert scale (from strongly disagree = 1 to strongly agree = 5). Consensus was defined as a median score of 5. Following responses to each round, any statements that had median scores of 3 or less were deemed to have had no consensus and excluded. Statements with a median score of 4 were revised and re-presented to the experts in the next round. Consensus and non-consensus statements were then aggregated. Sixty-eight international experts were invited to participate in the study, of which 57 participated. Experts were from 13 countries on five continents and have contributed to over 80% of published cohort studies on vasa previa, as well as national and international society guidelines. Completion rates were 84%, 93%, 91% for the first, second, and third rounds, respectively, and 71% completed all three rounds. The panel reached a consensus on 26 statements regarding the diagnosis and key points of management of vasa previa, including: 1) While there is no agreement on a distance between the fetal vessels and the cervical internal os to define vasa previa, the definition should not be limited to a 2 cm distance; 2) All pregnancies should be screened for vasa previa with routine examination for placental cord insertion and a color Doppler sweep of the region over the cervix at the second-trimester anatomy scan; 3) When a low-lying placenta or placenta previa is found in the second trimester, a transvaginal ultrasound with Doppler should be performed at around 32 weeks to rule out vasa previa; 4) Outpatient management of asymptomatic patients without risk factors for preterm birth is reasonable; 5)Asymptomatic patients with vasa previa should be delivered by scheduled cesarean between 35- and 37-weeks of gestation; and 6) There was no agreement on routine hospitalization, avoidance of intercourse, or use of 3-dimensional ultrasound for diagnosis of vasa previa. Through FGD and a Delphi process, an international expert panel reached consensus on the definition, screening, clinical management, and timing of delivery in vasa previa, which could inform the development of new clinical guidelines. [Abstract copyright: Copyright © 2024. Published by Elsevier Inc.

Jimmy Swaggart's Secular Confession

This is the author's accepted manuscript. The published version is available from http://dx.doi.org/10.1080/02773940902766748 .Following the exposure of televangelist Jimmy Swaggart’s illicit rendezvous with a New Orleans prostitute, the Assemblies of God simultaneously orchestrated a massive attempt to silence those who would discuss the tryst and arranged the most widely publicized confession in American history theretofore. The coincidence of a “silence campaign” with the vast distribution of a public confession invites us to reconsider the nature of the public confession. For what place has a public confession, the discourse of disclosure par excellence, in a silence campaign? This question is best answered, I argue, if we understand public confession not as a stable a-historical form, but as a practice that is informed by multiple, competing traditions. I argue that by situating Swaggart’s performance in a philosophically modern and secular tradition of public confession we can understand both its complicity in a silence campaign and, more generally, the political logic of the modern public confession

The EpsE Flagellar Clutch Is Bifunctional and Synergizes with EPS Biosynthesis to Promote Bacillus subtilis Biofilm Formation

Many bacteria inhibit motility concomitant with the synthesis of an extracellular polysaccharide matrix and the formation of biofilm aggregates. In Bacillus subtilis biofilms, motility is inhibited by EpsE, which acts as a clutch on the flagella rotor to inhibit motility, and which is encoded within the 15 gene eps operon required for EPS production. EpsE shows sequence similarity to the glycosyltransferase family of enzymes, and we demonstrate that the conserved active site motif is required for EPS biosynthesis. We also screen for residues specifically required for either clutch or enzymatic activity and demonstrate that the two functions are genetically separable. Finally, we show that, whereas EPS synthesis activity is dominant for biofilm formation, both functions of EpsE synergize to stabilize cell aggregates and relieve selective pressure to abolish motility by genetic mutation. Thus, the transition from motility to biofilm formation may be governed by a single bifunctional enzyme

Envejecimiento de la población

•Actividades básicas de la vida diaria en personas mayores y factores asociados •Asociación entre depresión y posesión de mascotas en personas mayores •Calidad de vida en adultos mayores de Santiago aplicando el instrumento WHOQOL-BREF •Calidad de vida en usuarios con enfermedad de Parkinson, demencia y sus cuidadores, comuna de Vitacura •Caracterización de egresos hospitalarios de adultos mayores en Puerto Natales (2007-2009) •Comportamiento de las patologías incluidas como GES para el adulto mayor atendido en un Cesfam •Contribución de vitaminas y minerales a las ingestas recomendadas diarias en ancianos institucionalizados de Madrid •Estado de salud oral del paciente inscrito en el Programa de Visita Domiciliaria •Evaluación del programa de discapacidad severa en Casablanca con la matriz de marco lógico •Factores asociados a satisfacción vital en una cohorte de adultos mayores de Santiago, Chile •Pauta instrumental para la identificación de riesgos para el adulto mayor autovalente, en su vivienda •Perfil farmacológico del paciente geriátrico institucionalizado y posibles consecuencias en el deterioro cognitivo •Programa de cuidados paliativos y alivio del dolor en Puerto Natales •Rehabilitación mandibular implantoprotésica: efecto en calidad de vida relacionada con salud bucal en adultos mayores •Salud bucodental en adultos mayores autovalentes de la Región de Valparaíso •Transición epidemiológica y el estudio de carga de enfermedad en Brasi

Genome-wide analyses reveal a potential role for the MAPT, MOBP, and APOE loci in sporadic frontotemporal dementia

Frontotemporal dementia (FTD) is the second most common cause of early-onset dementia after Alzheimer disease (AD). Efforts in the field mainly focus on familial forms of disease (fFTDs), while studies of the genetic etiology of sporadic FTD (sFTD) have been less common. In the current work, we analyzed 4,685 sFTD cases and 15,308 controls looking for common genetic determinants for sFTD. We found a cluster of variants at the MAPT (rs199443; p = 2.5 × 10−12, OR = 1.27) and APOE (rs6857; p = 1.31 × 10−12, OR = 1.27) loci and a candidate locus on chromosome 3 (rs1009966; p = 2.41 × 10−8, OR = 1.16) in the intergenic region between RPSA and MOBP, contributing to increased risk for sFTD through effects on expression and/or splicing in brain cortex of functionally relevant in-cis genes at the MAPT and RPSA-MOBP loci. The association with the MAPT (H1c clade) and RPSA-MOBP loci may suggest common genetic pleiotropy across FTD and progressive supranuclear palsy (PSP) (MAPT and RPSA-MOBP loci) and across FTD, AD, Parkinson disease (PD), and cortico-basal degeneration (CBD) (MAPT locus). Our data also suggest population specificity of the risk signals, with MAPT and APOE loci associations mainly driven by Central/Nordic and Mediterranean Europeans, respectively. This study lays the foundations for future work aimed at further characterizing population-specific features of potential FTD-discriminant APOE haplotype(s) and the functional involvement and contribution of the MAPT H1c haplotype and RPSA-MOBP loci to pathogenesis of sporadic forms of FTD in brain cortex

Bostonia: The Boston University Alumni Magazine. Volume 5

Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs