Complete single mode wavelength coverage over 40 nm with a superstructure grating DBR laser

The spectral characteristics of a widely tunable super structure grating distributed Bragg reflector (SSG-DBR) laser are investigated and the design considerations of the grating reflectors are given. By systematically adjusting the control currents of the two reflector sections and the phase section it is experimentally shown that every wavelength in an interval of 40 nm can be reached with a side-mode suppression usually better than 30 dB     

An algorithm for generalizing topography to grids while preserving subscale morphologic characteristics—creating a glacier bed DEM for Jakobshavn trough as low-resolution input for dynamic ice-sheet models

The objective of this paper is to derive an algorithm for preserving important subscale morphologic characteristics at grids of lower-resolution, in particular for linear features such as canyons and ridge lines. The development of such an algorithm is necessitated by applications that require reduced spatial resolution, as is common in cartographic generalization, GIS applications, and geophysical modeling. Since any algorithm that results in weighted averages, including optimum interpolation and ordinary kriging, cannot reproduce correct depths, a new algorithm is designed based on principles of mathematical morphology. The algorithm described here is applied to derive a subglacial bed of the Greenland Ice Sheet that includes the trough of Jakobshavn Isbræ as a continuous canyon at correct depth in a low-resolution (5-km) digital elevation model (DEM). Data from recent airborne radar measurements of the elevation of the subglacial bed as part of the CReSIS project are utilized. The morphologic algorithm is designed with geophysical ice-sheet modeling in mind, in the following context. Currently occurring changes in the Earth's climate and the cryosphere cause changes in sea level, and the societal relevance of these natural processes motivates estimation of maximal sea-level rise in the medium-term future. The fast-moving outlet glaciers are more sensitive to climatic change than other parts of the Greenland ice sheet. Jakobshavn Isbrae, the fastest-moving ice stream in Greenland, follows a subglacial geologic trough. Since the existence of the trough causes the acceleration of the slow-moving inland ice in the Jakobshavn region and the formation of the ice stream, correct representation of the trough in a DEM is essential to model changes in the dynamics of the ice sheet and resultant sea-level predictions, even if current ice-sheet models can typically be run only at 5-km resolution. The DEM resultant from this study helps to bridge the conceptual gap between data analysis and geophysical modeling approaches. It is available as SeaRISE Greenland bed data set dev1.2 at http://websrv.cs.umt.edu/isis/index.php/SeaRISE_Assessment.     

Plasma noradrenaline correlates to sympathetic muscle nerve activity in normotensive man

Recordings of multiunit sympathetic activity were made in muscle branches of the peroneal nerve in 22 healthy subjects at rest in recumbent position. Nerve activity was quantitated in terms of burst incidence (number of pulse synchronous sympathetic bursts per 100 heart beats or per min). In a separate session, 4-45 months later, blood was drawn from an antecubital vein for noradrenaline analysis. Both sympathetic activity and plasma concentrations of noradrenaline varied widely between subjects and both parameters increased with age. There was a significant positive correlation between a subject's level of sympathetic activity and his plasma concentration of noradrenaline. It is suggested that overflow of transmitter from sympathetic terminals in muscles contributes significantly to plasma levels of noradrenaline at rest.     

Critical aspects of sinter-hardening of prealloyed Cr–Mo steel

In recent years, growing demand for greater mechanical properties of PM steel components with competitive fabrication cost has led to significant innovations in different fields of powder metallurgy. Recent research has been focused on reaching higher performance with lower cost. To this end, the possibility of combining the conventional sintering and post-sintering processes for a particular powder composition has been introduced. Sinter-hardening is a result of the research conducted along this line. Elimination of any secondary operation such as quench-hardening by incorporating it in the sintering process (i.e. sinter-hardening) is of great interest, as it will lead to lower processing costs and equal, if not higher mechanical performance. However, to ensure the desired mechanical properties of the final component and robustness of the performance, critical aspects of the sinter-hardening process should be rigorously studied.Hence with specific attention to a Cr–Mo steel powder (FL-5305), this study deals with the influence of density on cooling rate, the effect of different sintering temperatures (e.g. 1120 °C and 1250 °C) on austenite grain size and consequently, hardenability. The microstructure development in sinter-hardened FL-5305 material has been analyzed and predicted by means of the available literature for solid steel and also using the commercial software (JMatPro 5.0) for materials assessment based on thermodynamic and kinetics modeling. Finally, inaccurate carbon control and its adverse impact on excessive formation of cementite have been addressed.     

Decreased lumbar cerebrospinal fluid levels of monoamine metabolites in vascular dementia

The levels of the monoamine metabolites 5-hydroxy-indoleacetic acid (5-HIAA), homovanillic acid (HVA), and 4-hydroxy-3-methoxy-phenylglycol (HMPG) were determined in lumbar cerebrospinal fluid (CSF) of 56 patients with vascular dementia (VAD) and 57 healthy controls. Despite CSF sampling under standardized conditions, the variability in values was wide among both patients and controls. This suggests that yet unknown factors affect the lumbar CSF concentrations of monoamine metabolites. The VAD group showed significantly lower mean concentrations of 5-HIAA (p < .001) and HVA (p < .001) than the control group. These low concentrations appear to be no disease-specific phenomenon, but may be attributable to subcortical white-matter changes or a decreased production of monoamines, which are dependent on oxygen for their synthesis.     

Optimal growth interrupts for very high quality InGaAs(P)/InP superlattices grown by MOVPE

The effects of different growth interrupt schemes at the compositional interfaces in 30 period InGaAs(P)/InP superlattices grown by metal-organic vapor phase epitaxy have been studied for quarternary compositions λ = 1.35 and 1.52 μm as well as for the ternary case λ = 1.67 μm. The best full width at half maximum of the photoluminescence peaks at 4 K are 7–8 meV for the InGaAsP/InP and 4.6 meV for the InGaAs/InP superlattices indicating extremely high optical quality and vertical homogenity of the samples. However, strong memory effects relating to both the presence and the absence of arsenic are evident from x-ray diffraction measurements. Reactor purging as a remedy is limited by the surface roughening and defect formation induced by a non-equilibrium vapor phase composition. Optimal growth interrupts must therefore be determined considering both the interface smoothness and abruptness and will in general be composition dependent.     

Enhancement of the anti-tumor immune response using a combination of interferon-gamma and B7 expression in an experimental mammary carcinoma

BACKGROUND: An extensive literature describes structural lesions in apraxia, but few studies have used functional neuroimaging. We used positron emission tomography (PET) to characterize relative cerebral glucose metabolism in a 65-year-old, right-handed woman with progressive decline in ability to manipulate objects, write, and articulate speech. OBJECTIVE: To characterize functional brain organization in apraxia. DESIGN AND METHODS: The patient underwent a neurological examination, neuropsychological testing, magnetic resonance imaging, and fludeoxyglucose F 18 PET. The patient's magnetic resonance image was coregistered to her PET image, which was compared with the PET images of 7 right-handed, healthy controls. Hemispheric regions of interest were normalized by calcrine cortex. RESULTS: Except for apraxia and mild grip weakness, results of the neurological examination were normal. There was ideomotor apraxia of both hands (command, imitation, and object) and buccofacial apraxia. The patient could recognize meaningful gestures performed by the examiner and discriminate between his accurate and awkward pantomime. The magnetic resonance image showed moderate generalized atrophy and mild ischemic changes. Positron emission tomographic scans showed abnormal fludeoxyglucose F 18 uptake in the posterior frontal, supplementary motor, and parietal regions, the left affected more than the right. Focal metabolic deficit was present in the angular gyrus, an area hypothesized to store conceptual knowledge of skilled movement. CONCLUSIONS: Greater parietal than frontal physiological dysfunction and preserved gesture recognition are not consistent with the theory that knowledge of limb praxis is stored in the dominant parietal cortex. Gesture comprehension may be more diffusely distributed.