Tuning spontaneous emission through waveguide cavity effects in semiconductor nanowires

The ability to tailor waveguide cavities and couple them with quantum emitters has developed a realm of nanophotonics encompassing, for example, highly efficient single photon generation or the control of giant photon nonlinearities. Opening new grounds by pushing the interaction of the waveguide cavity and integrated emitters further into the deep subwavelength regime, however, has been complicated by nonradiative losses due to the increasing importance of surface defects when decreasing cavity dimensions. Here, we show efficient suppression of nonradiative recombination for thin waveguide cavities using core-shell semiconductor nanowires. We experimentally reveal the advantages of such nanowires, which host mobile emitters, that is, free excitons, in a one-dimensional (1D) waveguide, highlighting the resulting potential for tunable, active, nanophotonic devices. In our experiment, controlling the nanowire waveguide diameter tunes the luminescence lifetime of excitons in the nanowires across 2 orders of magnitude up to 80 ns. At the smallest wire diameters, we show that this luminescence lifetime can be manipulated by engineering the dielectric environment of the nanowires. Exploiting this unique handle on the spontaneous emission of mobile emitters, we demonstrate an all-dielectric spatial control of the mobile emitters along the axis of the 1D nanowire waveguide

Formative Assessment of ARM-U: A Modular Intervention for Decreasing Risk Behaviors Among HIV-Positive and HIV-Negative Methamphetamine-Using MSM

BACKGROUND: Methamphetamine is a major contributor to HIV transmission among men who have sex with men (MSM). Recent studies show that up to one-third of methamphetamine-using MSM (MUMSM) inject the drug. We developed a behavioral intervention for MUMSM to decrease unprotected anal intercourse and increase awareness of parenteral HIV transmission risk. This 6-session (3 in-person, 3 by telephone) modular intervention was designed to be tailored to participants' HIV (+/-) and injection drug user ([IDU] yes/no) status. We present results of formative research used to evaluate the content and to assess feasibility and acceptability of this individual-level HIV risk-reduction intervention. SETTING: HIV research clinic in a high MSM and methamphetamine prevalence neighborhood. PROJECT: Avoiding Risks from Methamphetamine-Use (ARM-U) is a brief toolbox intervention that allows counselors to select modules that suit a client's individual risk profile and intervention needs employing motivational interviewing and cognitive behavioral theory. We evaluated the format and content of the intervention through focus groups and pre-testing of the entire intervention using volunteers from the target population stratified into four groups (HIV+/IDU, HIV-/IDU, HIV+/non-IDU, HIV-/non-IDU). Four individuals in each stratum were recruited to undergo the intervention and complete a satisfaction survey at the end of each in-person session. RESULTS: In total, 25 MUMSM attended one of five focus groups. Participants thought all proposed intervention topics were important and could aid in reducing sexual risk behaviors among MUMSM. However, the neurocognitive effects of methamphetamine were reported to be a barrier to practicing safer sex, condom use negotiation or HIV status disclosure. Fifteen (94%) of 16 participants completed all 6 sessions and the satisfaction survey. On average, participants felt the intervention was useful for MUMSM, made them contemplate and move toward behavior change, and would recommend the program to their peers. LESSONS LEARNED: Based on our formative research, we revised the ARM-U intervention to emphasize pre-planning to avoid combining methamphetamine use and sex or develop strategies to avoid sex risk following methamphetamine use. We also increased emphasis on referrals for care and other requested services. Future efficacy trials are needed to evaluate the intervention's ability to reduce HIV-associated risk behaviors

Computational analysis of cardiac structure and function in congenital heart disease:Translating discoveries to clinical strategies

Increased availability and access to medical image data has enabled more quantitative approaches to clinical diagnosis, prognosis, and treatment planning for congenital heart disease. Here we present an overview of long-term clinical management of tetralogy of Fallot (TOF) and its intersection with novel computational and data science approaches to discovering biomarkers of functional and prognostic importance. Efforts in translational medicine that seek to address the clinical challenges associated with cardiovascular diseases using personalized and precision-based approaches are then discussed. The considerations and challenges of translational cardiovascular medicine are reviewed, and examples of digital platforms with collaborative, cloud-based, and scalable design are provided

Bereitstellung konstruktionsgerechter Lastannahmen durch anwenderorientierte Simulationstechnik

Das vorliegende Programmsystem SIMOFFICE stellt ein modernes, graphisch orientiertes Werkzeug zur Modellbildung und Schwingungssimulation elektromechanischer Systeme dar. Dabei wird es dem Anspruch an ein anwenderfreundliches Hilfsmittel gerecht. Die offene Programmstruktur erlaubt eine einfache Erweiterung um zusaetzliche Objekte in allen Programmteilen. Entwicklungsbedarf besteht in der Programmierung einer Schnittstelle zu vorhandenen CAD-Systemen. Entsprechende Filter sind fuer die verschiedenen CAD-Systeme zu entwickeln. Durch die Uebernahme von Baugruppen aus CAD-Systemen laesst sich die Neugenerierung des physikalischen Modells auf ein Minimum reduzieren. Zur Zeit stellt sich die Diskretisierung in MOBIL als halbautomatischer Vorgang dar. Da die Diskretisierung in der beschriebenen Form jedoch nicht vollautomatisch ablaufen kann, sondern auf den Eingriff des Anwenders angewiesen ist, koennte hier ein Diskretisierungs-Assistent zum Einsatz kommen. Ueberall dort, wo der Eingriff des Anwenders erforderlich wird, werden in zahlreichen Anwendungen Assistenten oder auch sog. Wizards eingesetzt. Die Unterstuetzung des Anwenders durch einen Assistenten wuerde die Anwenderfreundlichkeit erheblich im Bereich der Diskretisierung unterstreichen. Erster Einblick in die Dynamik des Schwingungsmodells kann der Anwender mit Hilfe der Eigenfrequenzen erlangen. Daher ist der Programmteil SIM um ein entsprechendes Modul zu erweitern. Die gedaempften Eigenfrequenzen in Verbindung mit den Eigenschwingformen dienen darueber hinaus der Daempfungsabstimmung des Modells. Damit steht schlussendlich ein Werkzeug zur Verfuegung, mit dem die gesamtheitliche Modellbildung und Simulation elektromechanischer Systeme moeglich wird.SIGLEAvailable from TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Tuning Spontaneous Emission through Waveguide Cavity Effects in Semiconductor Nanowires

6 pags., 4 figs.The ability to tailor waveguide cavities and couple them with quantum emitters has developed a realm of nanophotonics encompassing, for example, highly efficient single photon generation or the control of giant photon nonlinearities. Opening new grounds by pushing the interaction of the waveguide cavity and integrated emitters further into the deep subwavelength regime, however, has been complicated by nonradiative losses due to the increasing importance of surface defects when decreasing cavity dimensions. Here, we show efficient suppression of nonradiative recombination for thin waveguide cavities using core-shell semiconductor nanowires. We experimentally reveal the advantages of such nanowires, which host mobile emitters, that is, free excitons, in a one-dimensional (1D) waveguide, highlighting the resulting potential for tunable, active, nanophotonic devices. In our experiment, controlling the nanowire waveguide diameter tunes the luminescence lifetime of excitons in the nanowires across 2 orders of magnitude up to 80 ns. At the smallest wire diameters, we show that this luminescence lifetime can be manipulated by engineering the dielectric environment of the nanowires. Exploiting this unique handle on the spontaneous emission of mobile emitters, we demonstrate an all-dielectric spatial control of the mobile emitters along the axis of the 1D nanowire waveguide.We gratefully acknowledge financial support by the German Research Foundation (DFG) via SFB 689 and 1277 Project A01. J.A.S.-G. and D.R.A. acknowledge partial financial support from the Spanish Ministerio de Ciencia, Innovación y Universidades through Grants NANOTOPO (FIS201791413-EXP) and MELODIA (PGC2018-095777-B-C21, MCIU/AEI/FEDER, UE), and through the FPU Ph.D.Fellowship FPU15/03566