On the importance of direct resistance heating in thermo-mechanical fatigue

A computationally efficient method of determining the temperature distribution and stress intensity factor induced by the resistance heating method of cycling temperature in thermo-mechanical fatigue is presented. It is further used to evaluate the importance of the singularity of the heat source caused by the electric current. Results indicate the thermally induced stress intensity factor of cracked components cycled by the direct resistance method of heating increases with the frequency of the thermal loading and may become quite large at higher frequencies.     

DNA barcoding to confirm morphological traits and determine relative abundance of burrowing mayfly species in western Lake Erie

Burrowing mayfly species of the genus Hexagenia are well known indicators of environmental health in lakes and rivers. Two species, H. limbata and H. rigida, are indistinguishable as nymphs and as adult females. Our objectives were to develop a genetic technique to distinguish between the two species and identify morphological features that separate cryptic nymphs and adult females. Fifty nymphs were collected before emergence from 10 sites throughout the western basin of Lake Erie in 2004 and 2005. Using known specimens of adult aerial male H. limbata and H. rigida, we used the mitochondrial cytochrome c oxidase subunit 1 (COI) gene to identify a 16 base pair (bp) difference between species. DNA sequencing confirmed correct species identification based on differences in abdominal pigmentation patterns on adult female imagos in 19 of 20 cases; the lone exception was a female with very faint pigmentation. Pigmentation patterns between species were consistent on nymphs, subimagos and imagos of both sexes. Populations of both species are panmictic across the western basin of Lake Erie, but H. limbata is the numerically dominant species, representing 70 to 100% of nymphs at sites in both years. A separate lineage of H limbata was discovered in the samples. The ability to distinguish nymphs of the two species will aid in developing more sensitive ecosystem indicators.     

Aflatoxin and PAH exposure biomarkers in a U.S. population with a high incidence of hepatocellular carcinoma

The incidence of hepatocellular carcinoma (HCC) is significantly elevated in a Hispanic community in Bexar County, Texas. Chronic exposure to dietary aflatoxins (AFs) is a major risk factor for HCC; increased risk has been linked to polycyclic aromatic hydrocarbon (PAH) co-exposure and hepatitis virus infection. The aims of this study were to assess AF and PAH exposures, investigate dietary factors that may contribute to increased AF exposure, and determine the prevalence of hepatitis virus infection in Bexar Co. Blood and urine samples were collected from 184 volunteers for biomarker analyses and hepatitis screening. Serum AFB₁-lysine adduct, urinary AFM₁ and 1-hydroxypyrene (1-OHP) levels were measured using high-performance liquid chromatography. The average AFB₁-lysine adduct level detected in 20.6% of serums was 3.84 ± 3.11 pg/mg albumin (range 1.01-16.57 pg/mg). AFM₁ was detected in 11.7% of urines, averaging 223.85 ± 250.56 pg/mg creatinine (range 1.89-935.49 pg/mg). AFM₁ detection was associated with increased consumption of corn tortillas (p = 0.009), nuts (p = 0.033) and rice (p = 0.037). A significant difference was observed between mean 1-OHP values of non-smokers (0.07 ± 0.13) and smokers (0.80 ± 0.68) μmol/mol creatinine (p < 0.01). A high hepatitis C virus positivity rate (7.1%) was observed. Findings suggest that the incidence and level of AF and PAH exposure were less than those observed in a high-risk population; however, participants consuming higher amounts of foods prone to AF contamination may be more vulnerable to exposure and interactions with other environmental/biological factors (i.e., HCV).     

Strengthening the case for pair programming

The software industry has practiced pair programming (two programmers working side by side at one computer on the same problem) with great success for years, but people who haven't tried it often reject the idea as a waste of resources. The authors demonstrate that using pair programming in the software development process yields better products in less time-and happier, more confident programmers     

Sonographic findings in testicular sarcoidosis simulating malignant nodule

Testicular involvement by sarcoidosis is rare. We report a case of a patient with known sarcoid who had a unilateral testicular nodule with apparent capsular invasion on sonography. The epididymis was normal on both sides. Despite these atypical features, pathology showed the nodule to be a sarcoid granuloma. In patients with sarcoidosis, the differential diagnosis of an intratesticular mass should include testicular involvement by sarcoid.     

Suppressor effects in coping research with African American adolescents from low-income communities.

Objective: The purpose of the current study was to demonstrate the replicable nature of statistical suppressor effects in coping research through 2 examples with African American adolescents from low-income communities. Method: Participants in the 1st example included 497 African American adolescents (mean age = 12.61 years, SD = 0.99; 57% female) reporting on dispositional coping, and participants in the 2nd example included 268 African American adolescents (mean age = 12.90 years, SD = 1.27; 56% female) reporting on situation-based coping. Participants in both samples completed self-report measures of coping strategies (Children's Coping Strategies Checklist and How I Coped Under Pressure Scale) and internalizing symptoms (Youth Self-Report, Children's Depression Inventory, and Revised Children's Manifest Anxiety Scale). Results: The results of structural equation modeling revealed significant suppressor effects, with active coping and support-seeking coping enhancing the association between avoidant coping and internalizing symptoms. Conclusions: The demonstration of replicable suppressor effects helps to advance coping research and intervention by providing evidence of the interdependence of coping strategies, thus increasing understanding of how coping strategies work together to predict outcomes. The current study offers recommendations for understanding associations among coping strategies within the context of suppression effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Shannon capacity calculation on multimode fibres

As the ultimate transmission performance of installed multimode fibres is uncertain, there is a need to understand the practical maximum capacity limit that a multimode fibre can support. The authors therefore present a new model to determine the worst-case Shannon capacity limit for multimode fibres. Detailed calculations are reported for fibre-distributed-data-interface (FDDI)-grade and OM1 fibres for operation using serial transmission with a single wavelength near 1310 nm. The method is also applicable to FDDI-grade, OM1, OM2 and OM3 fibres at all wavelengths of operation. The Shannon capacity limit of a multimode fibre is calculated for 220 m link lengths, assuming a link power budget consistent with the IEEE 10GBASE-LRM Gigabit Ethernet standard. It is shown that the Shannon capacity for non-optimised and optimised transmission spectra are at least 42 and 52 Gb/s, respectively.     

DNA repair: caretakers of the genome?

Recent results show that the 8-oxoguanine DNA repair system is functionally conserved in bacteria and mammals. The bacterial system protects the genome from the mutagenic effects of oxidative stress; the role of the mammalian system is expected to be similar and defects in it may increase susceptibility to cancer.