Mathematical Analysis of Throughput Bounds in Random Access with Z<Emphasis Type="SmallCaps">ig</Emphasis>Z<Emphasis Type="SmallCaps">ag</Emphasis> Decoding

We investigate the throughput improvement that ZigZag decoding (Gollakota and Katabi 2008) can achieve in multi-user random access systems. ZigZag is a recently proposed 802.11 receiver design that allows successful reception of packets despite collision. Thus, the maximum achievable throughput of a wireless LAN can be significantly improved by using ZigZag decoding. We analyze the throughput bounds in four different idealized multi-access system models for the case when ZigZag decoding is used. We also provide results for the Aloha and CSMA models where exact closed form solutions are infeasible to calculate. Our analysis and simulation results show that ZigZag decoding can significantly improve the maximum throughput of the random access system.     

How to assess the limits of ion-selective electrodes: method for the determination of the ultimate span, response range, and selectivity coefficients of neutral carrier-based cation selective electrodes

The span and range of an ion-selective electrode (ISE) has been identified by IUPAC as a potential or activity difference between the upper and lower detection limits of the electrode. Once the span is known, the ultimately attainable detection limit of the ISE can be calculated using its theoretical response slope. In this paper, we propose an original method for the determination of the ultimate span and response range of ISEs. The simple measurement of span is recommended to aid the fast screening of novel ionophores and help to focus optimization processes to the most promising candidates. The measurement of span is combined with a generally applicable procedure for the determination of the three seminal parameters of ISEs: the response slope, the ultimate selectivity coefficients, and detection limit. In the proposed procedure, following the span measurement, two subsequent exponential dilution experiments are completed in which the responses of the electrode for the primary and the interfering ions are tested using a solution of a discriminated ion and deionized water as diluting electrolytes in consecution. The advantages and the practical usefulness of the proposed methods and procedures are demonstrated through the evaluation of the performance characteristics of novel and well-characterized ionophore-based potassium and calcium sensors.     

A broad-spectrum microbicide with virucidal activity against sexually transmitted viruses

Sodium dodecyl sulfate (SDS), an alkyl sulfate surfactant derived from an organic alcohol, possesses surfactant properties but also denatures and unfolds both monomeric and subunit proteins. In preliminary experiments, we demonstrated that SDS is a potent inactivator of herpes simplex virus type 2 and human immunodeficiency virus type 1 at concentrations comparable to those used for the surfactant nonoxynol-9. We hypothesized that SDS might be capable of denaturing the capsid proteins of nonenveloped viruses. In this report, we demonstrate inactivation of rabbit, bovine, and human papillomaviruses after brief treatment with dilute solutions of SDS. Effective concentrations were nontoxic to rabbit skin and to split-thickness grafts of human foreskin epithelium. This is the first report of a microbicidal surfactant that will inactivate papillomaviruses. We propose that SDS is now a candidate microbicide for formulation and testing with humans.     

"Semantic priming from letter-searched primes occurs for low- but not high-frequency targets: Automatic semantic access may not be a myth": Correction to Tse and Neely (2007).

Reports an error in "Semantic priming from letter-searched primes occurs for low- but not high-frequency targets: Automatic semantic access may not be a myth" by Chi-Shing Tse and James H. Neely (Journal of Experimental Psychology: Learning, Memory, and Cognition, 2007[Nov], Vol 33[6], 1143-1161). In the article, the URL for the supplemental materials was incomplete. The complete URL is http://dx.doi.org/10.1037/0278-7393.33.6.1143.supp (The following abstract of the original article appeared in record 2007-15531-012.) Letter-search (LS) within a prime often eliminates semantic priming. In 2 lexical decision experiments, the authors found that priming from LS primes occurred for low-frequency (LF) but not high-frequency (HF) targets whether the target's word frequency was manipulated between or within participants and whether the prime-target pairs were associated symmetrically or forward asymmetrically. For the LF targets, LS priming was (a) equivalent for forward asymmetric and symmetric pairs and (b) equal to silent-read (SR) priming for forward asymmetric pairs but less than SR priming for symmetric pairs. The typical finding of greater SR priming for response times for LF than for HF targets occurred for symmetric priming but not for forward asymmetric priming, which showed the interaction for errors. The authors consider their findings' implications for various accounts of how LS affects priming and explain the findings within J. H. Neely and D. E. Keefe's (1989) 3-process model as follows: (a) LS eliminates expectancy and semantic matching but does not reduce semantic activation and (b) expectancy contributes to SR priming for HF targets but not for LF targets, whereas the opposite is so for semantic matching. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An emotional exposure-based treatment of traumatic stress for people with chronic pain: Preliminary results for fibromyalgia syndrome.

Emotional trauma occurs in many patients with chronic pain, particularly fibromyalgia syndrome (FMS). Current cognitive-behavioral treatments for chronic pain have limited effects, perhaps because the trauma is not addressed, whereas emotional exposure-based treatments improve post-traumatic stress, but have not been tested on chronic pain. The authors present a novel, brief treatment protocol for people with chronic pain and unresolved trauma (Multi- Stimulus, Multi-Technique Emotional Exposure Therapy), which involves detecting avoidance of a range of emotion-related stimuli, implementing exposure techniques tailored to the patient's avoidances, and negotiating the process and therapeutic alliance. This treatment was pilot tested on 10 women with intractable FMS and trauma histories. Three months post-treatment, the sample showed moderate to large effects on stress symptoms, FMS impact, and emotional distress; and small-to-moderate improvements on pain and disability. Two patients showed substantial improvement, four made moderate gains, two showed modest improvement, and two did not benefit. This pilot study suggests that emotional exposure treatment for unresolved trauma may benefit some patients with FMS. Controlled testing of the treatment for FMS and other chronic pain populations is indicated. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Human, but not bovine, oxidized cerebral spinal fluid lipoproteins disrupt neuronal microtubules

Cerebral spinal fluid (CSF) lipoproteins have become a focus of research since the observation that inheritance of particular alleles of the apolipoprotein E gene affects the risk of Alzheimer's disease (AD). There is evidence of increased lipid peroxidation in CSF lipoproteins from patients with AD, but the biological significance of this observation is not known. A characteristic of the AD brain is a disturbance of the neuronal microtubule organization. We have shown previously that 4-hydroxy-2(E)-nonenal, a major product of lipid peroxidation, causes disruption of neuronal microtubules and therefore tested whether oxidized CSF lipoproteins had the same effect. We exposed Neuro 2A cells to human CSF lipoproteins and analyzed the microtubule organization by immunofluorescence. In vitro oxidized human CSF lipoproteins caused disruption of the microtubule network, while their native (nonoxidized) counterparts did not. Microtubule disruption was observed after short exposures (1 h) and lipoprotein concentrations were present in CSF (20 μg/mL), conditions that did not result in loss of cell viability. Importantly, adult bovine CSF lipoproteins, oxidized under identical conditions, had no effect on the microtubule organization of Neuro 2A cells. Comparison of human and bovine CSF lipoproteins revealed similar oxidation-induced modifications of apolipoproteins E and A-I as analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting. Fatty acid analysis revealed substantially lower amounts of unsaturated fatty acids in bovine CSF lipoproteins, when compared to their human counterparts. Our data therefore indicate that oxidized human CSF lipoproteins are detrimental to neuronal microtubules. This effect is species-specific, since equally oxidized bovine CSF lipoproteins left the neuronal microtubule organization unchanged.     

Utilization of a piezoelectric polymer to sense harmonics of electromagnetic torque

In this paper, the use of a piezoelectric polymer material to measure the harmonics of electromagnetic torque produced by a permanent magnet synchronous machine is described. The advantages of the polymer include low cost, durability, and flexibility. In addition, wide-bandwidth sensors are relatively easy to design and couple to drive system hardware for harmonic evaluation or to use in feedback-based control. To illustrate the use of the polymer, the electrical and mechanical properties of three sensors are described. The results of time-domain simulation and hardware experiments are used to validate that the voltage obtained from the sensors is linearly related to the torque ripple produced by the machine.     

Investigating risks of outcome-based service contracts from a provider’s perspective

Outcome-based contracts (OBC) refer to agreements between providers and customers where providers are paid based on the outcomes they deliver to customers. OBCs have become common for manufacturing firms that are servitising, especially those firms providing advanced services focusing on availability and capability. Whilst many authors acknowledge the importance of understanding risks in OBCs from a provider’s perspective, there are relatively few in depth extant studies. To address this gap in the literature, we conducted 24 interviews with 11 companies to explore risks and risk factors in OBCs from the provider’s perspective. The case studies reveal that the two major risk categories in OBCs are commercial risk regarding the contract negotiations and contract decisions at the contracting stage, and operational risk regarding the implementation and the delivery of OBCs. Our study identifies 23 risk factors that can lead to commercial risk and operational risk in five dimensions: (i) complexity and (ii) dynamism regarding the context of OBCs, (iii) capability, (iv) alignment and (v) dependency regarding the stakeholders of OBCs. The paper explores the links between these risk factors and commercial and operational risk. In doing so, the paper provides a framework for understanding risk in OBCs.     

Negative thermal expansion in a zirconium tungstate/epoxy composite at low temperatures

We have investigated a composite of cubic α-ZrW₂O₈ and epoxy with a high ceramic loading for its thermal expansion properties at cryogenic temperatures. The composite was fabricated by allowing the ceramic to sediment in the epoxy resin before curing, using only the dense bottom fraction of the composite for further measurements. Density measurements and thermogravimetric analysis showed that the samples repeatably consisted of approximately 60 vol% tungstate without significant voids. The coefficient of thermal expansion was measured by dilatometry at temperatures from 25 to 300 K, and we found negative thermal expansion occurring at temperatures below about 100 K. The observed behavior is consistent with predictions produced by a variational model, which shows that the high ceramic loading is necessary to reliably achieve negative thermal expansion in the composite. The composite has potential applications as compensators for unwanted thermal expansion at low temperatures and for fiber-optic cryogenic temperature sensors.     

Rethinking information theory for mobile ad hoc networks

The subject of this article is the long standing open problem of developing a general capacity theory for wireless networks, particularly a theory capable of describing the fundamental performance limits of mobile ad hoc networks. A MANET is a peer-to-peer network with no preexisting infrastructure. MANETs are the most general wireless networks, with single-hop, relay, interference, mesh, and star networks comprising special cases. The lack of a MANET capacity theory has stunted the development and commercialization of many types of wireless networks, including emergency, military, sensor, and community mesh networks. Information theory, which has been vital for links and centralized networks, has not been successfully applied to decentralized wireless networks. Even if this was accomplished, for such a theory to truly characterize the limits of deployed MANETs it must overcome three key roadblocks. First, most current capacity results rely on the allowance of unbounded delay and reliability. Second, spatial and timescale decompositions have not yet been developed for optimally modeling the spatial and temporal dynamics of wireless networks. Third, a useful network capacity theory must integrate rather than ignore the important role of overhead messaging and feedback. This article describes some of the shifts in thinking that may be needed to overcome these roadblocks and develop a more general theory.