Spreading and power allocation for multiple antenna transmission using decorrelating receivers

We propose a new scheme for multiple antenna transmission in the context of spread-spectrum signaling. The new scheme consists of using shifted Gold sequences to modulate independent information on the multiple antennas. We show that this strategy of using multiphase spreading (MPS) on different antennas greatly improves the throughput over currently known spread-spectrum multiple-antenna methods. We also find the optimal power allocation strategy among multiple transmit antennas for a fixed rate of channel state information, which might be provided via a feedback link, at the transmitter. We demonstrate the differences in optimal power distribution for maximizing capacity and minimizing probability of outage. When the transmission from the two antennas uses orthogonal spreading, we find that optimizing the power does not give much gain over the equal power transmission. However, when the transmissions are not orthogonal as in the case of MPS, then allocating power to maximize throughput gives considerable gain over equal power transmission. We also consider the effect of imperfections in the feedback channel on the optimal power allocation and show that our power allocation scheme is robust to feedback errors.     

Delay-bounded packet scheduling of bursty traffic over wireless channels

In this paper, we study minimal power transmission of bursty sources over wireless channels with constraints on mean queuing delay. The power minimizing schedulers adapt power and rate of transmission based on the queue and channel state. We show that packet scheduling based on queue state can be used to trade queuing delay with transmission power, even on additive white Gaussian noise (AWGN) channels. Our extensive simulations show that small increases in average delay can lead to substantial savings in transmission power, thereby providing another avenue for mobile devices to save on battery power. We propose a low-complexity scheduler that has near-optimal performance. We also construct a variable-rate quadrature amplitude modulation (QAM)-based transmission scheme to show the benefits of the proposed formulation in a practical communication system. Power optimal schedulers with absolute packet delay constraints are also studied and their performance is evaluated via simulations.     

Severe defects in immunity and hematopoiesis caused by SHP-1 protein-tyrosine-phosphatase deficiency

Spontaneous mouse mutations that cause severe immunodeficiency or autoimmunity are invaluable tools with which to investigate the mammalian immune system. Mutations at the 'motheaten' locus result in severe immunological dysfunction due to disruption of the structural gene encoding Src-homology 2-domain phosphatase-1 (SHP-1). This natural model for a specific protein-tyrosine-phosphatase deficiency is being widely utilized to determine the role of SHP-1 in the negative regulation of multiple signaling pathways in a number of hematopoietic lineages.     

Unexceptional spatial memory in an exceptional memorist.

Rajan Mahadevan evidences an exceptional memory for arrays of digits. The authors tested whether Rajan's spatial memory was likewise exceptional. Eight control Ss and Rajan were instructed to remember the position and orientation of 48 images of common objects shown either to the left or the right of fixation and facing either left or right. Rajan's accuracy for judging whether the position and orientation of these pictures had changed when they were shown in a different sequence was lower than that of control Ss for both judgments. Rajan's exceptional memory capacity apparently does not extend to spatial relations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comprehensive study of two-variable Hurwitz polynomials

As a result of the varied applications of Hurwitz polynomials in the analysis and design of two-dimensional circuits and systems, several different classes of two-variable Hurwitz polynomials have been defined. The authors provide a comprehensive presentation of the definitions of different classes, the interrelationships among them, and their applications. The place and role of the newly defined principal Hurwitz polynomials among the various Hurwitz polynomials are also brought to light. Using a continuity property of the zeros of two-variable polynomials, new proofs for the test procedures of the different Hurwitz polynomials are presented. Applications of the Hurwitz polynomials in the study of the stability of two-dimensional systems and the properties of two-variable passive networks are summarized     

A generalization of some existence results on orthogonal designs for STBCs

It is shown that two theorems regarding the existence of generalized linear processing orthogonal designs (GLPOD) are valid under more general conditions than those for which they have been stated and proved (for original paper see V. Tarokh et al., "Space-time block codes from orthogonal designs", ibid., vol. 45, p. 1456-1467 (1999)).     

Prevention of acute adenolymphangitis in brugian filariasis: comparison of the efficacy of ivermectin and diethylcarbamazine, each combined with local treatment of the affected limb

Staphylococcal enterotoxins A and C1 (SEA or SEC1) bound to major histocompatibility-I (MHCI) molecules with high affinity (binding constants ranging from 1.1 microM to 79 nM). SEA and SEC1 directly bound MHCI molecules that had been captured by monoclonal antibodies specific for H-2Kk, H-2Dk, or both. In addition, MHCI-specific antibodies inhibited the binding of SEC1 to LM929 cells and SEA competitively inhibited SEC1 binding; indicating that the superantigens bound to MHCI on the cell surface. The affinity and number of superantigen binding sites differed depending on whether MHCI was expressed in the membrane of LM929 cells or whether it was captured. These data support the hypothesis that MHCI molecules can serve as superantigen receptors.     

Transport phenomena under unsteady conditions in an agitated vessel

An experimental study of transport phenomena at the wall of an agitated vessel with a propeller impeller under unsteady conditions is reported. The transient in heat transfer at the wall is caused by a step change in the speed of agitation from an initial static condition. The results are expressed in terms of a rise in modified “j-factor” above the initial free convection value and the number of revolutions taken by the impeller from the start of agitation. Also, an attempt has been made to find an analogy beween heat and momentum transfer. Results are given for the power in terms of Euler number plotted against the impeller Reynolds number. An empirical expression is also given for the transient heat transfer considering the system as a pure first order one with time delay. A “time-factor” constant which gives the number of impeller revolutions for 63.2% of the change from the initial to a final steady state is expressed as a function of impeller Reynolds number (10² to 10⁶) and fluid Prandtl number (6 to 10⁶).     

The measurement of thermal diffusivity in poly(methyl acrylate) by photoacoustic technique

It is suggested that when a polymer is synthesized from a monomer and an added initiator in the presence of ultrasound, the process may produce polymers with predetermined structures and physical properties. An attempt is made to measure thermal diffusivity. Poly(methyl acrylate) (PMA) is synthesized using monomer methyl acrylate and an added initiator peroxodisulfate in the presence of ultrasound of frequency 35 kHz and power 100 W/cm² at 50°C for various known sonication periods. PMA is obtained as a colorless, semitransparent solid. The solid PMA is cut into thin wafers in a highly symmetric direction to have uniform sizes. PMA samples are synthesized for 11 different sonication periods. These PMA samples are use to study their thermal diffusivity (α) by photoacoustic (PA) technique. Thermal diffusivity is calculated by measuring the amplitude and phase of the PA signal separately. A plot of the sonication period versus thermal diffusivity obtained from amplitude measurements of PMA indicates that there is an increase in thermal diffusivity from 2 × 10^?6 to 4.7 × 10^?6 m²/s when sonication period is increased from 30 to 330 min in steps of 30 min. The same trend is seen in a plot between sonication period and thermal diffusivity when the thermal diffusivity is calculated by PA phase measurements. There is a small difference in the experimental values obtained by the two measurements. Dependence of thermal diffusivity of PMA on ultrasonic sonication is discussed in detail. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 3756–3760, 2006     

Crystallographic evolution of microstructure in thin film processing: Part I. grain size distribution

Processing parameters and the resulting properties of a material are linked by the relationship between processing and microstructure. Characterizing the effect of processing variations on microstructure and determining its origin are essential to advanced material development. In this and a companion article, some readily applied techniques for producing quantitative data on grain size and shape, as well as grain and boundary crystallography, are described. The method described in Part I utilizes transmission electron microscopy and image analysis to measure grain size in large quantities (2000 to 3000 grains per sample), differentiated into orientation class subpopulation distributions. On application to Ni thin films produced by ion assisted deposition, the results have identified an orientation subpopulation that is predominantly responsible for the larger grain sizes observed in films grown under high ion flux. Larger grain size and the development of a preferred orientation have both been associated with increasing ion flux during growth, however, these results give the first experimental evidence connecting grain size and texture in these films.