Approximating the risk for time-to-failure models through using statistics of extremes

This paper studies the approximation of the partitioned multiobjective risk method's (PMRM) extreme event risk function for time-to-failure models. The analytic expression of the approximation for the extreme event risk function is derived through the use of the statistics of extremes for the case where the underlying distribution is of an extreme-value type III for minima. This analytic expression provides an effective theoretical tool for understanding the behavior of conditional expected values for time-to-failure models for a large class of distribution functions used in reliability. The results are confirmed for example problems of exponential and uniform distributions.     

Securing the global,remote, mobile user

Electronic commerce is inevitable and will reshape our lives, but before true electronic commerce environments can be realized, it will be necessary to secure your enterprise against outside attacks on its electronic information and provide controls for authorized access to that information. Copyright © 1999 John Wiley & Sons, Ltd.     

Use of an alteplase algorithm for the management of hemodialysis catheter dysfunction

Hemodialysis (HD) catheter dysfunction compromises HD adequacy and increases the cost of patient care. Repeated administration of alteplase in HD catheters typically produces only short-term benefits. The purpose of this study was to design, implement, and evaluate the efficacy of an experimental alteplase algorithm to manage HD catheter dysfunction. This was a two-part prospective nonrandomized study. Baseline data of alteplase use and catheter exchange were collected during part 1 of the study. Part 2 consisted of the alteplase algorithm implementation and repeat collection of catheter data. Rates of alteplase use and catheter exchange per 1000 catheter-days were the primary and secondary outcomes of the study. One hundred and seventy-two catheters in 131 patients were followed prospectively during the course of the study. The adjusted relative rate (RR) of alteplase use showed no significant difference between both parts of the study, adjusted RR: 1.10, 95% confidence interval (CI) (0.73-1.65). Similarly, catheter exchange rates were not significantly different over the duration of the study (1.12 vs. 1.03 per 1000 catheter-days). However, waiting time for catheter exchange increased from 20.36 ± 14 days in part 1 to 38.42 ± 28 days in part 2 (P < 0.05). The alteplase algorithm did not significantly reduce alteplase use. This may be partially explained by repeated use of alteplase in part 2, due to longer waiting times for catheter exchange procedures.     

La1−xSrxMyFe1−yO3−δ perovskites as oxygen-carrier materials for chemical-looping reforming

The use of perovskites with the general formula La_1−xSr_xM_yFe_1−yO₃ (M = Ni, Co, Cr, Cu) as oxygen carriers for syngas generation from methane by Chemical Looping Reforming is investigated in the present work. The experimental study concerns the oxidation of a fuel, using the oxygen from a solid oxygen carrier, instead of oxygen from air. Subsequent oxidation of the reduced solid is performed either with gaseous oxygen or with water. In the latter case additional hydrogen is produced, which is very pure and therefore appropriate to be used in fuel cell applications. The performance of the candidate materials is ranked by taking into account the hydrogen and carbon monoxide yields during the fuel oxidation step as well as the amount of oxygen per mole solid (δ) that can be delivered reversibly to the fuel. The effect of the materials composition and of NiO addition is examined. The best performance was obtained with the La_0.7Sr_0.3Cr_0.1Fe_0.9O₃ sample mixed with 5% NiO. The H₂ yield was up to 90%.     

Cuticular Hydrocarbons and Soldier Defense Secretions of <Emphasis Type="Italic">Reticulitermes</Emphasis> in Southern California: A Critical Analysis of the Taxonomy of the Genus in North America

Cuticular hydrocarbons (CHC) and soldier defense secretions (SDS) were characterized for collections of Reticulitermes from six counties (Los Angeles, Orange, Riverside, San Bernardino, San Diego, and Santa Barbara) in southern California. Collection sites included the type locality for R. hesperus, Lake Arrowhead (formerly known as Little Bear Lake) in the San Bernardino Mountains. In southern California, there are two CHC phenotypes, SC-A and SC-B, which are easily distinguished by the presence or absence of 5-methyl pentacosane, 5-methyl heptacosane, 5,17-dimethyl pentacosane, and 5,17-dimethyl heptacosane. These phenotypes are similar, but not identical, to previously designated phenotypes of Reticulitermes from northern California. The SDS of termites collected from southern California were characterized; (—)-germacrene A was abundant in all but the four samples from Lake Arrowhead. Soldiers of phenotype SC-A produced >79% germacrene A. The four samples from Lake Arrowhead produced no germacrene A, but contained >78% γ-cadinene. The SDS from the Lake Arrowhead samples were more similar to those of CA-A/CA-A′ from northern California than to any of the CHC phenotypes from southern California. Soldiers of CHC phenotype SC-B produced germacrene A, with the proportion varying from 16.2 to 98.7%. The SDS of SC-B were more similar to those of SC-A than to any of the phenotypes from northern California. The CHC phenotype SC-A found in southern California likely represents R. hesperus and SC-B appears to be a new, as yet undescribed species. We discuss the state of current taxonomic research on Reticulitermes.

Exposures to transit and other sources of noise among New York City residents

To evaluate the contributions of common noise sources to total annual noise exposures among urban residents and workers, we estimated exposures associated with five common sources (use of mass transit, occupational and nonoccupational activities, MP3 player and stereo use, and time at home and doing other miscellaneous activities) among a sample of over 4500 individuals in New York City (NYC). We then evaluated the contributions of each source to total noise exposure and also compared our estimated exposures to the recommended 70 dBA annual exposure limit. We found that one in ten transit users had noise exposures in excess of the recommended exposure limit from their transit use alone. When we estimated total annual exposures, 90% of NYC transit users and 87% of nonusers exceeded the recommended limit. MP3 player and stereo use, which represented a small fraction of the total annual hours for each subject on average, was the primary source of exposure among the majority of urban dwellers we evaluated. Our results suggest that the vast majority of urban mass transit riders may be at risk of permanent, irreversible noise-induced hearing loss and that, for many individuals, this risk is driven primarily by exposures other than occupational noise.     

Robustness of quantitative compressive sensing MRI: the effect of random undersampling patterns on derived parameters for DCE- and DSC-MRI

Compressive sensing (CS) in Cartesian magnetic resonance imaging (MRI) involves random partial Fourier acquisitions. The random nature of these acquisitions can lead to variance in reconstruction errors. In quantitative MRI, variance in the reconstructed images translates to an uncertainty in the derived quantitative maps. We show that for a spatially regularized 2 ×-accelerated human breast CS DCE-MRI acquisition with a 192 (2) matrix size, the coefficients of variation (CoVs) in voxel-level parameters due to the random acquisition are 1.1%, 0.96%, and 1.5% for the tissue parameters K(trans), v(e), and v(p), with an average error in the mean of -2.5%, -2.0%, and -3.7%, respectively. Only 5% of the acquisition schemes had a systematic underestimation larger than than 4.2%, 3.7%, and 6.1%, respectively. For a 2 × -accelerated rat brain CS DSC-MRI study with a 64(2) matrix size, the CoVs due to the random acquisition were 19%, 9.5%, and 15% for the cerebral blood flow and blood volume and mean transit time, respectively, and the average errors in the tumor mean were 9.2%, 0.49%, and -7.0%, respectively. Across 11 000 different CS reconstructions, we saw no outliers in the distribution of parameters, suggesting that, despite the random undersampling schemes, CS accelerated quantitative MRI may have a predictable level of performance.     

Comparison of methods for detection and isolation of cold- and freeze-stressed Escherichia coli O157:H7 in raw ground beef

A comparison was made of the relative efficiencies of three enrichment media, RapidChek Escherichia coli O157:H7 enrichment broth (REB), R&F broth (RFB), and modified E. coli broth containing novobiocin (mEC+n), and four selective plating media for detection of cold- and freeze-stressed E. coli O157:H7 in raw ground beef. Ground beef (25 g) was inoculated with E. coli O157:H7 at < or =0.5 and < or =2 CFU/g, and samples were then enriched immediately or were stored at 4 degrees C for 72 h or at -20 degrees C for 2 weeks and then enriched. After 8 or 20 h of enrichment, the cultures were plated onto R&F E. coli O157: H7 chromogenic plating medium, cefixime-tellurite sorbitol MacConkey agar, CHROMagar O157, and Rainbow agar O157 and tested using the RapidChek E. coli O157 lateral flow immunoassay and a multiplex PCR assay targeting the E. coli O157: H7 eae, stx1, and stx2 genes. Recovery of E. coli O157:H7 on the four agar media was 4.0 to 7.9 log CFU/ml with the REB enrichment, 1.4 to 7.4 log CFU/ml with RFB, 1.7 to 6.7 log CFU/ml with mEC+n incubated at 42 degrees C, and 1.3 to 3.3 log CFU/ml from mEC+n incubated at 35 degrees C. The percentages of positive ground beef samples containing nonstressed, cold-stressed, and freeze-stressed E. coli O157:H7 as obtained by plating, the immunoassay, and the PCR assay were 97, 88, and 97%, respectively, with REB, 92, 81, and 78%, respectively, with RFB, 97, 58, and 53%, respectively, with mEC+n incubated at 42 degrees C, and 22, 31, and 25%, respectively, with mEC+n incubated at 35 degrees C. Logistic regression analyses of the data indicated significant main effects of treatment, type of medium, enrichment time, inoculum concentration, and detection method. In particular, a positive result was 1.1 times more likely to occur after 20 h of enrichment than after 8 h, 25 times more likely with RFB and REB than with mEC+n at 35 degrees C, 3.7 times more likely with an initial inoculum of < or = 2.0 CFU/g than with < or = 0.5 CFU/g, 2.5 to 3 times more likely using freeze-stressed or nonstressed bacteria than with cold-stressed bacteria, and 2.5 times more likely by plating than by the immunoassay or the PCR assay. REB had better overall performance for enrichment of cold- and freeze-stressed E. coli O157:H7 present in ground beef than did the other media examined.     

Mental state decoding abilities in young adults with borderline personality disorder traits.

Previous studies have demonstrated that patients with borderline personality disorder (BPD) tend to misattribute malevolence to benign social stimuli, including facial expressions. Yet, facial emotion recognition studies examining those with BPD have yielded mixed results, with some studies showing impaired accuracy and others demonstrating enhanced accuracy in the recognition of emotions or mental states. The current study examined the ability to decode mental states from photographs of just the eye region of faces in a nonclinical sample of young adults who exhibited BPD traits (high BPD) compared with those who did not (low BPD). Group differences in mental state decoding ability depended on the valence of the stimuli. The high-BPD group performed better for negative stimuli compared with the low-BPD group, but did not perform significantly different from the low-BPD group for stimuli of neutral or positive valence. The high-BPD group also demonstrated a response bias for attributing negative mental states to facial stimuli. In addition, findings suggested that the group difference in accuracy for negative stimuli could not be explained by response bias, because the group difference in response bias for negative stimuli did not reach significance. These findings suggest that BPD traits may be associated with enhanced ability to detect negative emotions and a bias for attributing negative emotions to nonnegative social stimuli. (PsycINFO Database Record (c) 2011 APA, all rights reserved)