High Resolution Waveguide Terahertz Time-Domain Spectroscopy

Terahertz time-domain spectroscopy accesses the frequency range between 100 GHz and 5 THz by using the coherent generation and detection based on femtosecond laser sources. On the way to obtain fingerprint absorption spectra of molecular solids, terahertz waveguides have proven to be a valuable tool to extend the results to narrow and high resolution linewidths of crystalline solids. We will discuss the development, properties and applications of terahertz waveguide geometries for spectroscopic applications, in particular high-resolution measurements using parallel-plate waveguides.     

Electrochemically Tuned Properties for Electrolyte‐Free Carbon Nanotube Sheets

Injecting high electronic charge densities can profoundly change the optical, electrical, and magnetic properties of materials. Such charge injection in bulk materials has traditionally involved either dopant intercalation or the maintained use of a contacting electrolyte. Tunable electrochemical charge injection and charge retention, in which neither volumetric intercalation of ions nor maintained electrolyte contact is needed, are demonstrated for carbon nanotube sheets in the absence of an applied field. The tunability of electrical conductivity and electron field emission in the subsequent material is presented. Application of this material to supercapacitors may extend their charge‐storage times because they can retain charge after the removal of the electrolyte.     

Municipalities as a Driver for Wireless Broadband Access

Municipalities can form a driving force behind the deployment of new telecom infrastructure. While a telecom operator focuses on direct (financial) profits, a municipality is mainly interested in the social benefits for its inhabitants. In this paper, we evaluate a wireless municipality network from both a technical and an economic point of view. WiFi and WiMAX are considered as the most suited technologies for this purpose. A detailed techno-economic study has been performed including forecasting of the user adoption, dimensioning of the wireless network and modelling the related costs and revenues. The trade-off between installing a high number of relatively cheap WiFi access points, and a smaller number of more expensive WiMAX base stations for delivering full coverage is investigated in several scenarios.

Throughput of unslotted direct-sequence spread-spectrummultiple-access channels with block FEC coding

An analysis of unslotted random-access direct-sequence spread-spectrum multiple-access (DS/SSMA) channels with block forward error correction (FEC) coding is presented. Extending a methodology that was introduced in an earlier paper on unslotted packet code-division multiple access (CDMA) without coding, a procedure for calculating the error probability of an L-bit packet in the variable message length, FEC-coded, DS/SSMA environment is described. This procedure is then used in conjunction with appropriate flow equilibrium traffic models to compute channel throughput. Using BCH block coding as an example, the analytical model is exercised to obtain throughput versus channel traffic curves over a range of code rates, leading to an assessment of maximum achievable throughput and the associated optimum FEC code rate. The results show that the use of block FEC coding provides a significant improvement in the bandwidth-normalized channel throughput (utilization), approaching values competitive with those for comparable narrowband ALOHA channels     

Device fabrication on epitaxial Si-Ge alloys

PMOS transistors, p-n junctions and diffused resistors have been fabricated in Si-Ge alloy having a range of Ge content from 0 to 38%. The p-n junctions showed lower forward voltage drops than one would expect from simple band-gap lowering information. A Ge build-up at the surface may be causing this. MOS transistors exhibited low mobilities in the range of 20–50 cm²/V-s. The mobility value was affected by the surface condition and smoother surface areas resulted in the higher values of mobility. Diffused resistors had very high resistor values compared to control samples fabricated on silicon. Contact resistance problems were suspected but not proved to be the cause.     

An Integrated Circuit-Based Optical Sensor for In Vivo Measurement of Blood Oxygenation

The theory, design, and initial evaluation of an optkal sensor for the measurement of blood oxygen saturation (SO2) and hematocrit (Hct) are presented. A model based on the diffusion of light in an anisotropically scattering medium is developed and used to predict the effects of physiological parameters and the source/detector configuration on the diffuse reflectance of blood measured by the sensor. From model results, a ratiometric method is developed by which SO2 and Hct can be determined using a sensor comprised of three light sources and a detector. An implantable integrated circuit-based sensor was built to perform the blood reflectance measurements. The design of the monolithic signal processor is discussed, along with techniques for combining the chip with hybrid optoelectronics on the same glasscapped silicon substrate. Finally, preliminary results of an in vitro evaluation of prototype sensors are presented.     

Fade rates at 13 GHz on Earth-space paths

Fade rate distributions for 13 GHz signals on Earth-space paths have been compiled from the equivalent of 15 station-years of radiometer data that were recorded in Canada. Fade rates of up to 0.42 dB per second were found with the high fade rates tending to occur when the attenuation was also high. As with attenuation statistics, fade rate statistics for Earth-space paths are determined mainly by the climate that is local to the ground station.     

AN ANALYSIS OF THE OXYGEN BALANCE IN AN ANOXIC TIDAL RIVER

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Inhibition by adenosine triphosphate of heart microsomal neutral lipase activity

Triacylglycerol lipolysis was inhibited by palmitate, in the isolated perfused normal rat heart. Acetate or acetylcarnitine could reproduce the inhibitory effects of palmitate. Since heart neutral lipase plays an important role in the lipolysis of heart triacylglycerols, the effects of acetylcarnitine, acetyl CoA and related metabolites on the microsomal neutral lipase activity were studied. ATP inhibited the enzyme activity in a concentration-dependent manner without a lag phase. AMP and adenylyl imidodiphosphate, two compounds structurally related to ATP but whose phosphate groups cannot be transferred, did not inhibit the microsomal lipase activity. These results suggested that ATP inhibited the lipase activity through the transfer of its phosphate group. It is proposed that cellular ATP concentration is a determinant of tricylglycerol lipolysis in the heart.     

Experiences of depression in normal young adults.

Investigated depression as a normal affect state that could have continuity with types of clinical depression. A 66-item Depressive Experiences Questionnaire (DEQ) was constructed to assess a wide range of experiences that, though not direct symptoms of depression, are frequently associated with it. The DEQ, the Wessman-Ricks Mood Scale, a version of the semantic differential, and the Death-Concern Questionnaire were administered to 500 female and 160 male college students. In another sample, 128 college students were given the DEQ and the Zung Self-Rating Depression Scale. Three highly stable factors emerged from the DEQ: Dependency, Self-Criticism, and Efficacy. These factors had significant differential correlations with other measures, which support the interpretation of the factors derived from the items. These data indicate the need to consider dependency and self-criticism as 2 primary dimensions of depression and the value of investigating the continuity between normal mood states and the clinical phenomena of depressions. (38 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)