Adaptive nonuniform phase-shift-key modulation for multimediatraffic in wireless networks

The characteristics of mobile wireless communication channels fluctuate for many reasons, including movement of the radios, changes in path attenuation, and variations in interference. Several adaptive signaling techniques have been proposed for use in wideband code-division multiple-access (CDMA) systems including adaptive data rates, adaptive spreading code rates, discontinuous transmission, and multicode CDMA. We introduce adaptive signaling techniques that use nonuniform phase-shift-key (PSK) modulation. These techniques have several advantages for use in CDMA communications, and they support multimedia transmission by simultaneously delivering different types of traffic, each with its own required quality of service. The signaling methods that we propose deliver a basic message at a specified error rate and simultaneously deliver an additional message by exploiting any extra capability that is available. We show that by adapting the location of the points in a PSK constellation, the throughput can be maximized for the additional message while maintaining an acceptable error rate for the basic message. Responses to larger changes in channel quality are accomplished by adapting the PSK constellation size, signaling rate, and error-correcting code. Examples of adaptive signaling schemes that employ nonuniform PSK constellations are presented, including an application to a cellular CDMA system     

The Effect of Cook‐Off on the Bulk Permeability of a Plastic Bonded Explosive

Plastic bonded explosives when exposed to prolonged heating environments undergo a variety of changes that affect their bulk chemical, thermophysical, and mechanical properties. During slow heating conditions, referred to as cook‐off, the thermal behavior of the polymeric binder plays an important role in the transformations of these composite energetic materials. The recently introduced Darcian flow hypothesis for PBX‐9501 implies that, during preignition, temperature gradients will lead to pressure gradients which in turn will drive convection of decomposition gases throughout the explosive, thus affecting ignition time and location. Here, we focus on the cook‐off behavior of PBX‐9501 and investigate its effects on bulk permeability to gases produced as a result of thermal decomposition. The concept of Darcian convection through porous media is defined and illustrated in detail by the derivation of the governing equations for a permeameter. Based on a systematic analysis involving: 1) our current understanding about binder behavior as a function of temperature, 2) the physics of the gas permeameter apparatus, 3) the concept of liquid drainage by gas, and 4) the experimental record of four permeameter experiments with cooked PBX‐9501, we conclude that samples heated up to 186 °C were not permeable in the Darcy‐flow sense.     

Concatenated parity and turbo codes

Turbo codes have an error floor that is caused by low-weight error events. Here, it is shown that a concatenated code with a simple rectangular parity-check outer code and a turbo inner code can significantly reduce the error floor. It is also shown that in several situations, the concatenated parity-check and turbo code performs significantly better than a turbo code alone     

The Representation of Four Personality Disorders by the Schedule for Nonadaptive and Adaptive Personality Dimensional Model of Personality.

This study examined the relationships of the Schedule for Nonadaptive and Adaptive Personality (SNAP) model of personality to 4 targeted personality disorders (PDs) in a large multisite sample of patients. Data were examined from 529 patients, who were assigned 1 of 5 primary diagnoses: borderline, schizotypal, avoidant, and obsessive-compulsive PDs and major depression without PD. Patients were administered the SNAP questionnaire and results were compared among diagnostic groups and between patient groups and nonclinical norms. Results indicated that the dimensions of the model appear to have considerable promise in differentiating normal from abnormal personality, particularly in the propensity of individuals with PDs to manifest negative affects and interpersonal detachment. Furthermore, the model appeared to successfully distinguish specific PDs, a property that represents a particular challenge for dimensional models of personality. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Generalizability of treatment studies utilizing solicited patients.

States that although clinical researchers have turned increasingly to media advertisements in recent years to obtain sufficiently large and homogeneous samples for psychotherapy and psychopharmacological treatment outcome studies, it has not been clear to what extent it is possible to generalize from solicited to traditionally referred patient populations. A review of 14 studies that compared solicited and nonsolicited patient groups treated or studied in clinical settings suggests that it may be possible to generate relatively comparable samples of solicited and nonsolicited patients, in terms of pretreatment symptomatology, provided there is adequate screening. Although the existing data suggest that treatment response may also be similar across these groups, these data are too limited to permit conclusions regarding generalizability of treatment efficacy findings based in solicited patient samples. Possible implications for treatment outcome of differences found on 2 variables (presence of precipitants and duration of illness) are discussed. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Voltage Control of the Resonance Frequency of Dielectric Electroactive Polymer (DEAP) Membranes

We report on the characterization, active tuning, and modeling of the first mode resonance frequency of dielectric electroactive polymer (DEAP) membranes. Unlike other resonance frequency tuning techniques, the tuning procedure presented here requires no external actuators or variable elements. Compliant electrodes were sputtered or implanted on both sides of 20-35-mum-thick and 2-4-mm-diameter polydimethylsiloxane membranes. The electrostatic force from an applied voltage adds compressive stress to the membrane, effectively softening the device and reducing its resonance frequency, in principle to zero at the buckling threshold. A reduction in resonance frequency up to 77% (limited by dielectric breakdown) from the initial value of 1620 Hz was observed at 1800 V for ion-implanted membranes. Excellent agreement was found between our measurements and an analytical model we developed based on the Rayleigh-Ritz theory. This model is more accurate in the tensile domain than the existing model for thick plates applied to DEAPs. By varying the resonance frequency of the membranes (and, hence, their compliance), they can be used as frequency-tunable attenuators. The same technology could also allow the fine-tuning of the resonance frequencies in the megahertz range of devices made from much stiffer polymers.     

Pilot-Assisted and Blind Joint Data Detection and Channel Estimation in Partial-Time Jamming

We consider a communication scenario in which a message is received in the presence of partial-time Gaussian jamming and additive white Gaussian noise. We consider a quasi-static channel, in which the amplitude and phase are constant over each packet transmission. The receiver does not know the amplitude and phase of the incoming signal, which symbols are jammed, or even the statistics of the jammer, such as the jamming power and jamming probability. In this scenario, the receiver must accurately estimate the parameters of the channel and the jamming to achieve good performance. We apply the expectation-maximization (EM) algorithm to iteratively approximate the maximum-likelihood (ML) estimator for all of the parameters. We find that the overall performance of the EM algorithm is very sensitive to the initial estimates, so we propose a new initial estimator that offers good performance. The EM algorithm approach requires pilot symbols to resolve a phase ambiguity. Thus, we also present a blind estimation algorithm to avoid the reduction in overall code rate from the use of pilot symbols     

False-positive hepatitis B surface antigen screening test results in patients receiving granulocyte-colony-stimulating factor

BACKGROUND: Granulocyte-colony-stimulating factor (G-CSF) is used for the mobilization of progenitor cells and granulocytes. False-positive hepatitis B surface antigen (HBsAg) enzyme-linked immunosorbent assays (ELISAs) (NML) from one manufacturer in individuals receiving G-CSF have been observed. STUDY DESIGN AND METHODS: Sixty-six autologous peripheral blood progenitor cell donors from 1994 were retrospectively reviewed. Donors typically received 5 to 10 micrograms of G-CSF per kg subcutaneously for 5 days before collection. Additional ELISA dilutional studies (1-in-10, 1-in-100, 1-in-1000) with known HBsAg-negative serum were made with G-CSF. Testing was performed by the University of North Carolina, the American Red Cross in Charlotte, NC, or the National American Red Cross, Washington, DC. RESULTS: Of the 66 patients, none reacted for antibody to hepatitis B core antigen, and 30 (45%) had a positive reaction in the ELISA. Surface antigen positivity was "confirmed" on 6 of the 30 patients by neutralizing ELISA reactivity with an antibody to HBsAg test from the same manufacturer. In all cases, the clinical presentation was not suggestive of hepatitis, and these individuals were not at high risk for hepatitis B. Twenty-seven of the 30 cases were tested with a monoclonal HBsAg ELISA (AUSZYME) from another manufacturer in the peridonation period and did not react. In 1994, 256 autologous whole-blood donors not receiving G-CSF were similarly tested and only 1 (0.4%) had a positive reaction with the second manufacturer's HBsAg ELISA (p < 0.001). Of this group, 41 patients with histories of malignancy were identified, which is comparable to the history of the peripheral blood progenitor cell donors in this study, and none of these blood donors tested positive for HBsAg (p < 0.001). Dilutional studies with G-CSF produced no reactions. CONCLUSION: The NML HBsAg ELISA studied has an unacceptably high false-positive rate in patients or donors receiving G-CSF. The false reactivity of this assay appears to be an indirect consequence of G-CSF administration, which can also lead to spurious confirmation by the HBsAg neutralization assay from the same manufacturer.     

Wearable Soft Technologies for Haptic Sensing and Feedback

Virtual reality (VR) and augmented reality (AR) systems have garnered recent widespread attention due to increased accessibility, functionality, and affordability. These systems sense user inputs and typically provide haptic, audio, and visual feedback to blend interactive virtual environments with the real world for an enhanced or simulated reality experience. With applications ranging from immersive entertainment, to teleoperation, to physical therapy, further development of this technology has the potential for impact across multiple disciplines. However, VR/AR devices still face critical challenges that hinder integration into everyday life and additional applications; namely, the rigid and cumbersome form factor of current technology that is incompatible with the dynamic movements and pliable limbs of the human body. Recent advancements in the field of soft materials are uniquely suited to provide solutions to this challenge. Devices fabricated from flexible and elastic bio-compatible materials have significantly greater compatibility with the human body and could lead to a more natural VR/AR experience. This review reports state-of-the-art experimental studies in soft materials for wearable sensing and haptic feedback in VR/AR applications, explores emerging soft technologies for on-body devices, and identifies current challenges and future opportunities toward seamless integration of the virtual and physical world.