Nonparametric confidence bounds, using censored data, on the meanresidual life

An approach to inverting confidence bounds on the failure rate to obtain conservative nonparametric confidence statements about the mean residual life (MRL) for type I and II censoring and random right (left) censoring is described. A mild nonparametric condition of increasing (or decreasing) MRL is used. The condition of increasing (or decreasing) MRL is not required for the whole time axis. All example which uses type II censored data is included     

Interface Corner Failure Analysis of Joint Strength: Effect of Adherend Stiffness

The strength of cylindrical butt joints, fabricated by bonding either aluminum or steel adherends together with an epoxy adhesive, has been determined for a wide range of bond thicknesses. Joint strength varied significantly with bond thickness. The measured strength of joints with steel adherends varied as the inverse cube root of bond thickness, while the strength of joints with aluminum adherends varied as the inverse fourth root of bond thickness. This bond thickness dependence is accurately predicted by an analysis that assumes failure occurs at a critical value of the interface corner stress intensity factor. The difference in the measured joint strength-bond thickness relation for joints with aluminum and steel adherends is a consequence of the difference in the order of the interface corner stress singularity.     

Additional Interface Corner Toughness Data for an Adhesively-bonded Butt Joint

Over a period of 15 months, five sets of adhesively-bonded butt joints were fabricated and tested. This previously unreported data is used to assess the variability of measured interface corner toughness values, K_ac, as well as the dependence of K_ac on surface preparation. A correlation between K_ac and the size of the adhesive failure zone is also noted. This revised version was published online in July 2006 with corrections to the Cover Date.     

An information-theoretic framework for deriving canonical decision-feedback receivers in Gaussian channels

A framework is presented that allows a number of known results relating feedback equalization, linear prediction, and mutual information to be easily understood. A lossless, additive decomposition of mutual information in a general class of Gaussian channels is introduced and shown to produce an information-preserving canonical decision-feedback receiver. The approach is applied to intersymbol interference (ISI) channels to derive the well-known minimum mean-square error (MMSE) decision-feedback equalizer (DFE). When applied to the synchronous code-division multiple-access (CDMA) channel, the result is the MMSE (or signal-to-interference ratio (SIR) maximizing) decision-feedback detector, which is shown to achieve the channel sum-capacity at the vertices of the capacity region. Finally, in the case of the asynchronous CDMA channel we are able to give new connections between information theory, decision-feedback receivers, and structured factorizations of multivariate spectra.     

A nonlinear least-squares method for determining cerebrospinal fluid formation and absorption kinetics in pseudotumor cerebri

Data from 14 patients with benign intracranial hypertension (pseudotumor cerebri) have been analyzed using a nonlinear least-squares regression model which was developed and programmed from in-hospital microcomputer use. The method of analysis permits rapid estimation of cerebrospinal fluid (CSF) formation and absorption rates as functions of pressure in individual patients using data from constant-rate infusion manometrics. The analysis predicts that prednisone therapy in pseudotumor cerebri reduces resting CSF pressure by increasing CSF absorption at all intracranial pressures studied, and decreasing CSF formation at high pressures. This result is in accordance with evidence suggesting that impaired CSF absorption plays a major role in the pathogenesis of increased intracranial pressure in pseudotumor cerebri.     

Bandwidth-efficient multiple access (BEMA): a new strategy based onsignal design under quality-of-service constraints forsuccessive-decoding-type multiuser receivers

This paper considers the design of signature waveforms for successive-decoding-type multiuser receivers (including the optimum successive decoder (OSD)) in a correlated-waveform multiple-access channel. The problem is to obtain signature waveforms that require as little bandwidth as possible while allowing the receiver to meet a given set of quality-of-service (QoS) objectives. The QoS objectives are specified for each user in terms of capacity, or equivalently, the signal-to-interference ratio. A (generally unachievable) lower bound is obtained on the minimum bandwidth required to achieve these QoS constraints. Moreover, a simple algorithm is proposed for obtaining signal sets that meet the QoS constraints when used with the OSD, and which, while not optimal, require a bandwidth that can be very close to the minimum required bandwidth. It is also shown that such signal sets allow for a significantly more efficient use of bandwidth than do orthogonal signals used in time- or frequency-division multiple access (TDMA/FDMA). Based on our signal design approach, we propose a new multiple-access strategy that we refer to as bandwidth-efficient multiple access (BEMA). While BEMA is more bandwidth efficient than TDMA or FDMA, it retains their desirable feature of needing only single-user coding (and decoding) for each user     

Adverse effects of medications on urinary symptoms and flow rate: a community-based study

The relationship between urinary symptoms and medication use was investigated in a community-based cross-sectional study involving a random sample of 2115 men 40-79 years of age in Olmsted County, Minnesota. The American Urological Association Symptom Index (AUASI) was generated from a validated self-administered questionnaire. Medication use was assessed by in-person interviews. While 1087 men reported daily medication use, only 136 reported daily use of medications known to affect urinary function adversely, including antidepressants (42), antihistamines (23), and bronchodilators (43). Age-adjusted AUASI scores were higher in men reporting daily use of antidepressants, and the association persisted after additionally adjusting for the Depression and Anxiety subscales of the General Psychological Well-Being Scale (adjusted mean difference, 2.1; 95% confidence interval (CI), 0.5-3.6; p = 0.008). The adjusted AUASI was also higher among men who took antihistamines daily (adjusted mean difference, 2.3; 95% CI, 0.3-4.3; p = 0.03). Lower age-adjusted urinary flow rates occurred with antidepressants, but not with antihistamines or bronchodilators. Clinicians evaluating men for causes of voiding dysfunction in accordance with the Agency for Health Care Policy and Research practice guideline for the diagnosis and management of benign prostatic hyperplasia should be aware that daily use of antidepressants or antihistamines may be associated with AUASI scores that are two to three points higher than in men not taking these medications.     

Multiscale modeling in computational biomechanics

Biomechanics is broadly defined as the scientific discipline that investigates the effects of forces acting on and within biological structures. The realm of biomechanics includes the circulatory and respiratory systems, tissue mechanics and mechanotransduction, and the musculoskeletal system and motor control. As in many other biological phenomena, many spatial scales are crossed by biomechanics research: intracellular, multicellular, and extracellular matrices; and tissue, organ, and multiorgan systems. It is well established that the effect of forces at higher scales influence behavior at lower scales and that lower-scale properties influence higher-scale response. However, computational methods that incorporate these interactions in biomechanics are relatively rare. In general, computational models that include representation of multiple spatial or temporal scales are loosely defined as multiscale. The fact that multiscale modeling is not well defined lends the term to a variety of scenarios within the computational physiology community. In biomechanics, multiscale modeling may mean establishing a hierarchical link between the spatial and temporal scales, while the output of a larger-scale system is passed through a finely detailed representation at a lower scale (e.g., body-level movement simulations that provide net joint loading for tissue-level stress analysis). In reality, multiscale modeling may require more intricate representation of interactions among scales. A concurrent simulation strategy is inevitable to adequately represent nonlinear associations that have been known for decades [1].     

Signal design for bandwidth-efficient multiple-accesscommunications based on eigenvalue optimization

Bandwidth-efficient multiple access (BEMA) is a strategy where transmitter pulses are continually designed at the base station and are dynamically allocated to the transmitters via a feedback channel. Such pulses (or “signature waveforms”) are designed to conserve bandwidth while simultaneously enabling the receiver at the base station to meet a quality-of-service (QoS) specification for each transmitter. The key technical problem in BEMA communication is therefore the design of the transmitter pulses for the base station receiver. In an earlier paper, we presented solutions to this problem that were shown to be superior (in terms of strict bandwidth) to common signaling schemes such as time-, frequency-, and code-division multiple access (TDMA, FDMA, and CDMA). This paper uses the framework developed earlier, but considers strictly time-limited transmitter pulses and the root-mean squared (RMS) bandwidth measure. As in the earlier paper, significant bandwidth savings over the traditional multiple-access strategies are obtained. However, in contrast to the rank-conserving approach, the bandwidth gains of this paper are realized by tailoring the signature waveform design to conserve RMS bandwidth via eigenvalue optimization problems