Social threat hurts! : the influence of social threat on pain

status: publishe

Polarized emission from hexagonal-silicon-germanium nanowires

We present polarized emission from single hexagonal silicon-germanium (hex-SiGe) nanowires. To understand the nature of the band-to-band emission of hex-SiGe, we have performed photoluminescence spectroscopy to investigate the polarization properties of hex-SiGe core-shell nanowires. We observe a degree of polarization of 0.2 to 0.32 perpendicular to the nanowire c-axis. Finite-difference time-domain simulations were performed to investigate the influence of the dielectric contrast of nanowire structures. We find that the dielectric contrast significantly reduces the observable degree of polarization. Taking into account this reduction, the experimental data are in good agreement with polarized dipole emission perpendicular to the c-axis, as expected for the fundamental band-to-band transition, the lowest energy direct band-to-band transition in the hex-SiGe band structure.</p

Low Surface Recombination in Hexagonal SiGe Alloy Nanowires:Implications for SiGe-Based Nanolasers

Monolithic integration of silicon-based electronics and photonics could open the door toward many opportunities including on-chip optical data communication and large-scale application of light-based sensing devices in healthcare and automotive; by some, it is considered the Holy Grail of silicon photonics. The monolithic integration is, however, severely hampered by the inability of Si to efficiently emit light. Recently, important progress has been made by the demonstration of efficient light emission from direct-bandgap hexagonal SiGe (hex-SiGe) alloy nanowires. For this promising material, realized by employing a nanowire structure, many challenges and open questions remain before a large-scale application can be realized. Considering that for other direct-bandgap materials like GaAs, surface recombination can be a true bottleneck, one of the open questions is the importance of surface recombination for the photoluminescence efficiency of this new material. In this work, temperature-dependent photoluminescence measurements were performed on both hex-Ge and hex-SiGe nanowires with and without surface passivation schemes that have been well documented and proven effective on cubic silicon and germanium to elucidate whether and to what extent the internal quantum efficiency (IQE) of the wires can be improved. Additionally, time-resolved photoluminescence (TRPL) measurements were performed on unpassivated hex-SiGe nanowires as a function of their diameter. The dependence of the surface recombination on the SiGe composition could, however, not be yet addressed given the sample-to-sample variations of the state-of-the-art hex-SiGe nanowires. With the aforementioned experiments, we demonstrate that at room temperature, under high excitation conditions (a few kW cm–2), the hex-(Si)Ge surface is most likely not a bottleneck for efficient radiative emission under relatively high excitation conditions. This is an important asset for future hex(Si)Ge optoelectronic devices, specifically for nanolasers

Direct bandgap quantum wells in hexagonal Silicon Germanium

Silicon is indisputably the most advanced material for scalable electronics, but it is a poor choice as a light source for photonic applications, due to its indirect band gap. The recently developed hexagonal Si1−xGex semiconductor features a direct bandgap at least for x &gt; 0.65, and the realization of quantum heterostructures would unlock new opportunities for advanced optoelectronic devices based on the SiGe system. Here, we demonstrate the synthesis and characterization of direct bandgap quantum wells realized in the hexagonal Si1−xGex system. Photoluminescence experiments on hex-Ge/Si0.2Ge0.8 quantum wells demonstrate quantum confinement in the hex-Ge segment with type-I band alignment, showing light emission up to room temperature. Moreover, the tuning range of the quantum well emission energy can be extended using hexagonal Si1−xGex/Si1−yGey quantum wells with additional Si in the well. These experimental findings are supported with ab initio bandstructure calculations. A direct bandgap with type-I band alignment is pivotal for the development of novel low-dimensional light emitting devices based on hexagonal Si1−xGex alloys, which have been out of reach for this material system until now.</p

Feeling More Pain, Yet Showing Less: The Influence of Social Threat on Pain

The present study investigated the effects of social threat to physical integrity on reported pain and facial pain expression. Predictions of a cognitive appraisal model and a communicative perspective on pain expression were compared. Participants (N = 67) received 5 electric pain stimuli administered by a confederate. They were led to believe that 5 pain stimuli were the minimum, a fixed amount, or the maximum number of pain stimuli allowed, thereby varying the social threat posed by the confederate. Reported pain and facial pain expression were recorded during the delivery of pain stimuli. Increased perceived social threat led to an increase of reported pain, specifically for high pain catastrophizing participants, while it led to a reduction of facial pain expression. This is the first study to demonstrate that a social threat manipulation has opposite effects on reported pain and facial expression, suggesting differences in adaptive function for both forms of pain expression. Perspective: This is the first demonstration showing an increase in verbal pain report and a decrease in nonverbal pain expression at the same time during social threat. This knowledge may contribute to improving pain assessment in different contexts. (C) 2011 by the American Pain Societ

Excretion and metabolism of desogestrel in healthy postmenopausal women

The metabolism of desogestrel (13-ethyl-11-methylene-18,19-dinor-17 alpha -pregn-4-en-20-yn-17-ol), a progestagen used in oral contraceptives and hormone replacement therapy, was studied in vivo after a single oral administration of 150 mug [C-14]-labeled desogestrel and 30 mug ethinylestradiol under steady state conditions to healthy postmenopausal women. After this oral administration, desogestrel was extensively metabolized. The dosed radioactivity was predominantly (similar to 60%) excreted via urine, while about 35% was excreted via the feces. Desogestrel was metabolized mainly at the C3-, C5-, C6- and C13-CH2CH3 positions. At the C3-position, the 3-keto moiety was found and in addition, 3 beta -hydroxy and 3 alpha -hydroxy groups were observed in combination with a reduced Delta (4)-double bond (5 alpha -H). Hydroxy groups were introduced at the C6- (6 beta -OH), the C13-ethyl (C13-CH2CH2OH) and possibly the C15- (15 alpha -OH) position of desogestrel. Conjugation of the 3 alpha -hydroxy moiety with sulfonic acid and conjugation with glucuronic acid were also major metabolic routes found for desogestrel in postmenopausal women. The 3-keto metabolite of desogestrel (the biologically active metabolite) was the major compound present in plasma at least up to 24 h after administration of the radioactive dose. Species comparison of the metabolic routes of desogestrel after oral administration indicates that in rats and dogs desogestrel is also mainly metabolized at the C3-position, similar to what is now found for post menopausal women. Most other metabolic routes of desogestrel were found to differ between species. Finally, major metabolic routes found in the present study in postmenopausal women are in line with outcome of previous in vitro metabolism studies with human liver tissue (microsomes and postmitochondrial liver fractions) and intestinal mucosa. (C) 2001 Elsevier Science Ltd. All rights reserved