128 research outputs found
A cloudy model for the Circumnuclear Disk in the Galactic Centre
We present a first attempt to construct an analytic model for a clumped gas
and dust disk and apply it to the Galactic Centre. The clumps are described as
isothermal spheres partially ionized by the external UV radiation field. The
disk structure formed by the clouds is described as a quasi standard continuous
accretion disk using adequately averaged parameters of the discrete cloud
model. The viscosity in the Circumnuclear Disk is due to partially inelastic
cloud-cloud collisions. We find two different solutions for the set of
equations corresponding to two stable cloud regimes: (i) the observed molecular
clouds and (ii) much lighter and smaller clouds which correspond to the
stripped cores of the observed clouds. It is shown that the resulting physical
characteristics of the heavy clouds and the disk are in very good agreement
with all comparable observations at multiple wavelengths. A mass accretion rate
of approx. 10^-4 M_solar/yr for the isolated Circumnuclear Disk is inferred. We
propose that the Circumnuclear Disk has a much longer lifetime (approx. 10^7
yr) than previously assumed.Comment: 12 pages with 13 figures, A&A, in pres
Behavioral Assessment of Acute Inhibition of System x\u3csub\u3ec\u3c/sub\u3e\u3csup\u3e -\u3c/sup\u3e in rats
Rationale
Gaps in our understanding of glutamatergic signaling may be key obstacles in accurately modeling complex CNS diseases. System xc - is an example of a poorly understood component of glutamate homeostasis that has the potential to contribute to CNS diseases. Objectives
This study aims to determine whether system xc - contributes to behaviors used to model features of CNS disease states. Methods
In situ hybridization was used to map mRNA expression of xCT throughout the brain. Microdialysis in the prefrontal cortex was used to sample extracellular glutamate levels; HPLC was used to measure extracellular glutamate and tissue glutathione concentrations. Acute administration of sulfasalazine (8–16 mg/kg, IP) was used to decrease system xc - activity. Behavior was measured using attentional set shifting, elevated plus maze, open-field maze, Porsolt swim test, and social interaction paradigm. Results
The expression of xCT mRNA was detected throughout the brain, with high expression in several structures including the basolateral amygdala and prefrontal cortex. Doses of sulfasalazine that produced a reduction in extracellular glutamate levels were identified and subsequently used in the behavioral experiments. Sulfasalazine impaired performance in attentional set shifting and reduced the amount of time spent in an open arm of an elevated plus maze and the center of an open-field maze without altering behavior in a Porsolt swim test, total distance moved in an open-field maze, or social interaction. Conclusions
The widespread distribution of system xc - and involvement in a growing list of behaviors suggests that this form of nonvesicular glutamate release is a key component of excitatory signaling
Vertical-external-cavity surface-emitting lasers and quantum dot lasers
The use of cavity to manipulate photon emission of quantum dots (QDs) has
been opening unprecedented opportunities for realizing quantum functional
nanophotonic devices and also quantum information devices. In particular, in
the field of semiconductor lasers, QDs were introduced as a superior
alternative to quantum wells to suppress the temperature dependence of the
threshold current in vertical-external-cavity surface-emitting lasers
(VECSELs). In this work, a review of properties and development of
semiconductor VECSEL devices and QD laser devices is given. Based on the
features of VECSEL devices, the main emphasis is put on the recent development
of technological approach on semiconductor QD VECSELs. Then, from the viewpoint
of both single QD nanolaser and cavity quantum electrodynamics (QED), a
single-QD-cavity system resulting from the strong coupling of QD cavity is
presented. A difference of this review from the other existing works on
semiconductor VECSEL devices is that we will cover both the fundamental aspects
and technological approaches of QD VECSEL devices. And lastly, the presented
review here has provided a deep insight into useful guideline for the
development of QD VECSEL technology and future quantum functional nanophotonic
devices and monolithic photonic integrated circuits (MPhICs).Comment: 21 pages, 4 figures. arXiv admin note: text overlap with
arXiv:0904.369
Reduction in Phencyclidine Induced Sensorimotor Gating Deficits in the Rat Following Increased System Xc − Activity in the Medial Prefrontal Cortex
Rationale: Aspects of schizophrenia, including deficits in sensorimotor gating, have been linked to glutamate dysfunction and/or oxidative stress in the prefrontal cortex. System xc −, a cystine–glutamate antiporter, is a poorly understood mechanism that contributes to both cellular antioxidant capacity and glutamate homeostasis.
Objectives: Our goal was to determine whether increased system xc − activity within the prefrontal cortex would normalize a rodent measure of sensorimotor gating.
Methods: In situ hybridization was used to map messenger RNA (mRNA) expression of xCT, the active subunit of system xc −, in the prefrontal cortex. Prepulse inhibition was used to measure sensorimotor gating; deficits in prepulse inhibition were produced using phencyclidine (0.3–3 mg/kg, sc). N-Acetylcysteine (10–100 μM) and the system xc − inhibitor (S)-4-carboxyphenylglycine (CPG, 0.5 μM) were used to increase and decrease system xc − activity, respectively. The uptake of 14C-cystine into tissue punches obtained from the prefrontal cortex was used to assay system xc − activity.
Results: The expression of xCT mRNA in the prefrontal cortex was most prominent in a lateral band spanning primarily the prelimbic cortex. Although phencyclidine did not alter the uptake of 14C-cystine in prefrontal cortical tissue punches, intraprefrontal cortical infusion of N-acetylcysteine (10–100 μM) significantly reduced phencyclidine- (1.5 mg/kg, sc) induced deficits in prepulse inhibition. N-Acetylcysteine was without effect when coinfused with CPG (0.5 μM), indicating an involvement of system xc −.
Conclusions: These results indicate that phencyclidine disrupts sensorimotor gating through system xc − independent mechanisms, but that increasing cystine–glutamate exchange in the prefrontal cortex is sufficient to reduce behavioral deficits produced by phencyclidine
Take This Job and … : Quitting and Other Forms of Resistance to Workplace Bullying
Dominant culture and bullying : personal accounts of workers in Malaysia
Workplace bullying has been termed the cancer of the workplace; it is a widespread and often intractable problem. Internationally, a wealth of research has examined the prevalence of workplace bullying and its negative effects. This research base and the scientific definition of workplace bullying are, however, based on Western perspectives and supported by theories, models, and research studies conducted in Western cultures. The differences in cultural perspectives of Western and Eastern countries mean that workplace bullying may not be understood in the same way across different cultural groups, particularly when cultures differ along the Individualism-Collectivism dimension. Given that Malaysia is an Eastern country with a number of ethnic groups, a more comprehensive understanding of workplace bullying in the Malaysian context is important. Through a case study comprising in-depth qualitative interviews with 20 employees from different organisations in Malaysia, this chapter reveals six lay beliefs of workplace bullying and 19 lay beliefs about bullying behaviors. The study also found that the 12 bullying behaviors are work related while the other seven are personal-nature bullying behaviors. These results emphasize the influence of culture on how bullying is perceived within the Malaysian context, and the importance of understanding lay representations of workplace bullying from the Eastern context that apparent across nation. Based on the interviews, a general definition of workplace bullying from Malaysian employees' perspectives is presented and developed. The chapter concludes with implications for understanding bullying as an important psychosocial hazard at work and recommendations for future research and practice across the Asia Pacific region
Workplace bullying and post-traumatic stress symptoms among family physicians in Lithuania: An occupation and region specific approach
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