Polarization fluctuations in vertical cavity surface emitting lasers: a key to the mechanism behind polarization stability

We investigate the effects of the electron-hole spin dynamics on the polarization fluctuations in the light emitted from a vertical cavity surface emitting laser (VCSEL). The Langevin equations are derived based on a rate equation model including birefringence, dichroism, and two carrier density pools seperately coupled to right and left circular polarization. The results show that the carrier dynamics phase lock the polarization fluctuations to the laser mode. This is clearly seen in the difference between fluctuations in ellipticity and fluctuations in polarization direction. Seperate measurements of the polarization fluctuations in ellipticity and in polarization direction can therefore provide quantitative information on the non-linear contribution of the carrier dynamics to polarization stability in VCSELs.Comment: 6 pages RevTex and 3 figures, to be published in Quantum and Semiclassical Optics, minor changes to the discussion of timescale

A Promising Young Man: André Jolles Portrayed by Jan Veth and Jan Toorop

André Jolles, author of Einfache Formen, enjoys some fame in the Netherlands as the close friend of the Dutch cultural historian Johan Huizinga (1872–1945). They became friends in 1896, but their friendship came to an end when Jolles joined the National Socialist Party in Germany in 1933. In the correspondence of Huizinga of about half a century, dozens of letters are written by Jolles. Huizinga’s own letters to Jolles are supposed to be destroyed by the latter. When Jolles was fourteen, he lost his father. His mother, when André was in his early twenties, had him portrayed by two well known Dutch artists: Jan Veth and Jan Toorop. In my essay I present for the first time all the portraits in their context. As is to be concluded from the correspondence between Jolles’ mother and Jan Veth, the main problem was to get André Jolles so far to “sit” for Jan Veth as a model, what he reluctantly did.André Jolles, auteur des Formes simples, connaît une certaine renommée aux Pays-Bas en tant qu’ami de l’historien de la culture Johan Huizinga (1872-1945). Ils se lièrent d’amitié à partir de 1896, mais leurs rapports prirent fin lorsque, en 1933, Jolles adhéra au Parti national-socialiste en Allemagne. Leur correspondance, qui dura plus de trente ans, consiste en des dizaines de lettres de Jolles, alors que l’on suppose que celles de Huizinga aient été détruites par le destinataire. Jolles perdit son père à l’âge de quatorze ans. Lorsqu’il eut vingt ans, sa mère demanda à deux importants artistes néerlandais, Jan Veth et Jan Toorop, de faire le portrait de son fils. Dans cette contribution je présente pour la première fois tous les portraits qui ont été peints de Jolles dans leur contexte historico-biographique. Comme l’on apprend de la correspondance entre la mère de Jolles et Jan Veth, le principal obstacle à la réalisation de son portrait était constitué par la réluctance de Jolles à poser pour l’artiste.André Jolles, autore di Forme semplici, gode di una certa fama in Olanda come amico dello storico della cultura Johan Huizinga (1872-1945). La loro amicizia ebbe inzio nel 1896, ma si interruppe quando Jolles aderì nel 1933 in Germania al Partito Nazionalsocialista. La corrispondenza tra i due, che copre quasi mezzo secolo, consta di decine di lettere di Jolles, mentre si suppone che quelle di Huizinga siano state distrutte dall’amico. Jolles perse il padre a quattordici anni. Quando compì vent’anni la madre lo fece ritrarre da due importanti artisti olandesi: Jan Veth e Jan Toorop. In questo articolo presento per la prima volta tutti i ritratti di Jolles nel loro contesto storico-biografico. Come si desume dalla corrispondenza tra la madre di Jolles e Jan Veth, il principale ostacolo fu costituito dalla riluttanza di Jolles a fare da modello all’artista

Are depression trials generalizable to clinical practice? Something clinicians always wanted to know about RCTs, but were afraid to ask.....

In this project we investigated the difference between efficacy (treatment outcome investigated in randomized clinical trials, RCTs) and effectiveness (treatment outcome when these treatments are applied in daily psychiatric practice) for major depressive disorder. Treatment outcome and patient features in daily practice were assessed with routine outcome monitoring. We found that effectiveness is significantly lower than efficacy. In RCTs, a stringent patient selection is applied bij inclusion/exclusion criteria. We found that patients in daily practice do differ significantly from participants in RCTs with respect to baseline severity, comorbid disorders, suicidality and employment status. However, we found that these differences have very little influence on treatment outcome. In other words, if, hypothetically, only patients who are eligible for participation in RCTs for major depressive disorder would be tre ated, treatment success would not improve dramatically.UBL - phd migration 201

Spatial holeburning effects in the amplified spontaneous emission spectra of the non-lasing supermode in semiconductor laser arrays

The amplified spontaneous emission spectrum of the light field in the non-lasing supermode of two coupled semiconductor lasers is analyzed using linearized Langevin equations. It is shown that the interference betweeen the laser mode and the fluctuating light field in the non-lasing mode causes spatial holeburning. This effect introduces a phase sensitive coupling between the laser field and the fluctuations in the non-lasing mode. For high laser fields, this coupling splits the spectrum of the non-lasing mode into a triplet consisting of two relaxation oscillation sidebands which are in phase with the laser light and a center line at the lasing frequency with a phase shift of pi half relative to the laser light. As the laser intensity is increased close to threshold, the spectrum shows a continuous transition from the single amplified spontaneous emission line at the frequency of the laser mode to the triplet structure. An analytical expression for this transition is derived and typical features are discussed.Comment: 16 pages RevTex and 12 figures, discussion of carrier diffusion added, to be published in JOSA

Loosening the reins or tightening them?:Complex relationships between parenting, effortful control, and adolescent psychopathology

Background Adolescents face major developmental tasks such as increasing individuation and establishing autonomy. These developmental tasks increase demands on adolescent self-control, hereby putting youth with poor effortful control at risk for psychopathology. Specific parenting behaviors might be warranted to buffer against this risk. Objective This study was designed to examine parenting-related risk and protective factors in the associations between effortful control and adolescent psychopathology. We hypothesized that youth with poor effortful control require more parental involvement (i.e., lower autonomy granting) to help complete these developmental tasks and subsequently avoid psychopathology. Methods Via adolescent self-reports (N = 809), associations between effortful control, perceived parenting (i.e., psychological control and autonomy support), and externalizing (i.e., interpersonal aggression and rule-breaking) and internalizing problems (i.e., depressive and anxiety problems) were examined. Results Regression analyses supported our hypothesis in boys: higher levels of autonomy support exacerbated the negative association between effortful control and rule-breaking. In contrast, in girls this was the case for lower levels of autonomy support. For both genders, low autonomy support and psychological control exacerbated negative associations between effortful control and internalizing problems. No buffering effects of parenting were found. Conclusions Low effortful control is associated with psychopathology in adolescents, but parenting can affect this association in several ways, depending on the type of psychopathology and the adolescent’s gender. Future research should focus on finding ‘optimal’ levels of parental control that can help avoid psychopathological problems in youth with poor effortful control

Band structure of absorptive two-dimensional photonic crystals

The band structure for an absorptive two-dimensional photonic crystal made from cylinders consisting of a Drude material is calculated. Absorption causes the spectrum to become complex and form islands in the negative complex half-plane. The boundaries of these islands are not always formed by the eigenvalues calculated for Bloch vectors on the characteristic path, and we find a hole in the spectrum. For realistic parameter values, the real part of the spectrum is hardly influenced by absorption, typically less than 0.25%. The employed method uses a Korringa-Kohn-Rostoker procedure together with analytical continuation. This results in an efficient approach that allows these band-structure calculations to be done on a Pentium III personal computer

Elevated extracellular matrix production and degradation upon bone morphogenetic protein-2 (BMP-2) stimulation point toward a role for BMP-2 in cartilage repair and remodeling

Bone morphogenetic protein-2 (BMP-2) has been proposed as a tool for cartilage repair and as a stimulant of chondrogenesis. In healthy cartilage, BMP-2 is hardly present, whereas it is highly expressed during osteoarthritis. To assess its function in cartilage, BMP-2 was overexpressed in healthy murine knee joints and the effects on proteoglycan (PG) synthesis and degradation were evaluated. Moreover, the contribution of BMP in repairing damage induced by interleukin-1 (IL-1) was investigated. Ad-BMP-2 was injected intra-articularly into murine knee joints, which were isolated 3, 7, and 21 days after injection for histology, immunohistochemistry, and autoradiography. In addition, patellar and tibial cartilage was isolated for RNA isolation or measurement of PG synthesis by means of 35SO4 2- incorporation. To investigate the role for BMP-2 in cartilage repair, cartilage damage was induced by intra-articular injection of IL-1. After 2 days, Ad-BMP-2, Ad-BMP-2 + Ad-gremlin, Ad-gremlin, or a control virus was injected. Whole knee joints were isolated for histology at day 4 or patellae were isolated to measure 35SO42- incorporation. BMP-2 stimulated PG synthesis in patellar cartilage on all days and in tibial cartilage on day 21. Aggrecan mRNA expression had increased on all days in patellar cartilage, with the highest increase on day 7. Collagen type II expression showed a similar expression pattern. In tibial cartilage, collagen type II and aggrecan mRNA expression had increased on days 7 and 21. BMP-2 overexpression also induced increased aggrecan degradation in cartilage. VDIPEN staining (indicating matrix metalloproteinase activity) was elevated on day 3 in tibial cartilage and on days 3 and 7 in patellar cartilage, but no longer was by day 21. Increased NITEGE staining (indicating aggrecanase activity) was found on days 7 and 21. In IL-1-damaged patellar cartilage, BMP-2 boosted PG synthesis. Blocking of BMP activity resulted in a decreased PG synthesis compared with IL-1 alone. This decreased PG synthesis was associated with PG depletion in the cartilage. These data show that BMP-2 boosts matrix turnover in intact and IL-damaged cartilage. Moreover, BMP contributes to the intrinsic repair capacity of damaged cartilage. Increased matrix turnover might be functional in replacing matrix molecules in the repair of a damaged cartilage matrix

Photonic crystals of coated metallic spheres

It is shown that simple face-centered-cubic (fcc) structures of both metallic and coated metallic spheres are ideal candidates to achieve a tunable complete photonic bandgap (CPBG) for optical wavelengths using currently available experimental techniques. For coated microspheres with the coating width to plasma wavelength ratio $l_c/\lambda_p \leq 10$ and the coating and host refractive indices $n_c$ and $n_h$, respectively, between 1 and 1.47, one can always find a sphere radius $r_s$ such that the relative gap width $g_w$ (gap width to the midgap frequency ratio) is larger than 5% and, in some cases, $g_w$ can exceed 9%. Using different coatings and supporting liquids, the width and midgap frequency of a CPBG can be tuned considerably.Comment: 14 pages, plain latex, 3 ps figures, to appear in Europhys. Lett. For more info on this subject see http://www.amolf.nl/research/photonic_materials_theory/moroz/moroz.htm