The role of thermal shock in cyclic oxidation

The effect of thermal shock on the spalling of oxides from the surfaces of several commercial alloys was determined. The average cooling rate was varied from approximately 240°C/sec to less than 1.0°C/sec during cyclic oxidation tests in air. The tests consisted of 100 cycles of 1 hr at the maximimum temperature (1100 or 1200°C). The alloys were HOS-875, TD-Ni, TD-NiCrAl, In-601, In-702, and B-1900 plus Hf. All of these alloys exhibited partial spalling within the oxide rather than total oxide loss down to bare metal. Thermal shock resulted in deformation of the metal, which in turn resulted, in most cases, in change of the oxide failure mode from compressive to tensile. Tensile failures were characterized by cracking of the oxide and little loss, while compressive failures were characterized by explosive loss of platelets of oxide. This behavior was confirmed by examination of mechanically stressed oxide scales. The thermally shocked oxides spalled less than the slow-cooled samples with the exception of TD-NiCrAl. This material failed in a brittle manner rather than by plastic deformation. The HOS-875 and the TD-Ni did not spall during either type of cooling. Thus, the effect of thermal shock on spalling is determined, in large part, by the mechanical properties of the metal.     

TBT causes regime shift in shallow lakes

Tributyltin (TBT) is an organotin compound used since the early 1960s as a biocide in boat antifouling paints. Its use has been linked to a host of negative effects in marine ecosystems including malformations and imposex in Mollusca and acute toxicity in many other aquatic animals. Yet, the consequences of TBT use in freshwaters are largely unknown. Here, for the first time we reveal that TBT may have caused hitherto unsuspected damage to freshwater ecosystems. Through an analysis of dated sediment cores collected from a system of recreationally boated, shallow lakes, we show that first evidence of TBT is associated with a dramatic loss of submerged vegetation and associated diverse animal communities. Cause and effect are difficult to unravel in our study. However, we hypothesize that TBT, through reducing populations of grazing organisms in lakes already affected by eutrophication, promoted the replacement of macrophytes by phytoplankton, ultimately leading to a regime shift in the ecosystem. Our findings may have parallels in freshwater ecosystems all over the world.     

Genetic evaluation of mastitis in dairy cattle using linear models, threshold models, and survival analysis: a simulation study

The objective was to study, by simulation, whether survival analysis results in a more precise genetic evaluation for mastitis in dairy cattle than cross-sectional linear models and threshold models by using observation periods for mastitis of 2 lengths (the first 150 d of lactation, and the full lactation, respectively). True breeding values for mastitis liability on the underlying scale were simulated for daughters of 400 sires (average daughter group size, 60 or 150), and the possible event of a mastitis case within lactation for each cow was created. For the linear models and the threshold models, mastitis was defined as a binary trait within either the first 150 d of lactation or the full lactation. For the survival analysis, mastitis was defined as the number of days from calving to either the first case of mastitis (uncensored record) or to the day of censoring (i.e., day of culling, lactation d 150 or day of next calving; censored record). Cows could be culled early in lactation (within 10 d after calving) for calving-related reasons or later on because of infertility. The correlation between sire true breeding values for mastitis liability and sire predicted breeding values was greater when using the full lactation data (0.76) than when using data from the first 150 d (0.70) with an average of 150 daughters per sire. The corresponding results were 0.60 and 0.53, respectively, with an average of 60 daughters per sire. Under these simulated conditions, the method used had no effect on accuracy. The higher accuracy of sire breeding values can be translated into a greater genetic gain, unless counteracted by a longer generation interval.     

Molecular weight distribution of polyphenylene sulfide by high temperature gel permeation chromatography

Poly(phenylene sulfide) (PPS) has been characterized using a novel high temperature gel permeation chromatograph (GPC). Samples were injected in slurry form at ambient temperature, and redissolved by an in-line precolumn heater at 250°C. A viscometer consisting of a capillary tube with inlet and outlet taps connected to a sensitive differential pressure transducer was used as sole detector, with deflections converted to concentration using the column calibration. Columns and viscometer were operated at 210°C. Universal calibration was carried out using intrinsic viscosity/molecular weight relations for polystyrene and PPS, determined by light scattering. Satisfactory operation was confirmed by agreement between intrinsic viscosity calculated from GPC with independently measured values, and comparisons with melt flow data. Samples of PPS tested were found to be of relatively narrow distribution, with M_w/M_n typically less than two.     

Battlemind debriefing and battlemind training as early interventions with soldiers returning from iraq: Randomization by platoon.

Researchers have found that there is an increase in mental heath problems as a result of military-related traumatic events, and such problems increase in the months following return from combat. Nevertheless, researchers have not assessed the impact of early intervention efforts with this at-risk population. In the present study, the authors compared different early interventions with 2,297 U.S. soldiers following a year-long deployment to Iraq. Platoons were randomly assigned to standard postdeployment stress education, Battlemind debriefing, and small and large group Battlemind training. Results from a 4-month follow-up with 1,060 participants showed those with high levels of combat exposure who received Battlemind debriefing reported fewer posttraumatic stress symptoms, depression symptoms, and sleep problems than those in stress education. Small group Battlemind training participants with high combat exposure reported fewer posttraumatic stress symptoms and sleep problems than stress education participants. Compared to stress education participants, large group Battlemind training participants with high combat exposure reported fewer posttraumatic stress symptoms and lower levels of stigma and, regardless of combat exposure, reported fewer depression symptoms. Findings demonstrate that brief early interventions have the potential to be effective with at-risk occupational groups. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mass Transport in Shallow Turbulent Wake Flow by Planar Concentration Analysis Technique

A planar concentration analysis (PCA) system is used for observing the transport and mixing of a tracer mass in a shallow turbulent free-surface wake flow of a large cylindrical obstacle. The nonintrusive, fieldwise PCA measuring technique is applied to evaluate depth-averaged mass concentrations by making use of light attenuation due to absorption and scattering processes related to a dissolved tracer mass. The scalar fields are decomposed into a low-frequency quasiperiodic part, the coherent flow, and a randomly fluctuating part. From accompanying near-surface velocity measurements, large-scale coherent structures are identified and related to the coherent mass fields. This allows one to assess the role of the large-scale vortices for advection and diffusion in shallow wake flows. The time–mean wake flow displays a self-similar spanwise distribution both for mass and velocity. The longitudinal development of shallow wakes initially shows the growth of unbounded wakes; in the wake far field an attenuated behavior applies.     

Stigma and barriers to care in soldiers postcombat.

The present study examined the effects of leadership and unit cohesion on mental health stigma and perceived barriers to care. A sample of 680 soldiers from combat support units were surveyed 3 months after their return from combat operations in Iraq. The survey included scales on psychological symptoms and perceptions of leader behaviors and unit cohesion, as well as items assessing stigma and barriers to care. The sample was used to test the independent and interactive effects of leadership and unit cohesion on soldiers’ perceptions of stigma and barriers to care. Analyses yielded significant interaction effects between leadership and cohesion in predicting stigma and barriers to care, while controlling for the effects of mental health symptoms. Soldiers who rated their leaders more highly and who reported higher unit cohesion also reported lower scores on both stigma and perceived barriers to care. Thus, positive leadership and unit cohesion can reduce perceptions of stigma and barriers to care, even after accounting for the relationship between mental health symptoms and these outcomes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of the damage in sapphire due to implantation of boron, nitrogen, and iron

The damage microstructure and optical properties of sapphire implanted with boron, nitrogen and iron were examined by RBS-C, TEM, and optical absorption. Implantations were conducted at RT and 1000 °C at 150 keV and fluences of 3 × 10¹⁶-1 × 10¹⁷ ions/cm². Optical absorption measurements indicate that the boron-implanted samples contained the highest number of F-type centers and the nitrogen-implanted samples the fewest. The microstructure of the boron-implanted samples shows only ‘black-spot’ defect clusters, as did the iron-implanted samples at the lower fluences. At higher fluences, the iron implanted samples revealed the presence of nanometer-sized precipitates of single crystal bcc iron that contributed to additional optical scattering. Bubbles formed in samples implanted with low fluences of nitrogen. A second damage region is apparent in the RBS-C patterns for higher fluences of nitrogen.     

Reversing the Bipolar Drift–Introducing the IAB

The IAB's mission is to help the Computer Society critically examine the organization's business plans and practices and to offer advice and assistance to make the Society a relevant professional association.