Time to abandon small-sample cohort research in health psychology?

Comments on the original article, "Avoidant coping as a predictor of mortality in veterans with end-stage renal disease" by E. J. Wolf and D. L. Mori (see record 2009-06704-009), in which the authors report that among 61 patients with endstage renal disease (ESRD), avoidant coping more than doubled the odds of mortality in multivariable analysis. The authors concluded that evaluating coping style in patients with ESRD would be clinically useful and that interventions targeting avoidant coping should be investigated. In this commentary, the current authors note that Wolf and Mori’s (2009) finding was based on a sample where only 23 patients died over 9 years, and results were evaluated using a Cox regression model with six covariates, a ratio of only 3.8 outcome events per variable—well below recommended thresholds (e.g., Babyak, 2004; Peduzzi et al., 1995). Beyond this, the model did not assess key variables typically included in studies of ESRD outcomes (e.g., transplant status, cardiovascular problems). Wolf and Mori chose to focus on the relationship between avoidant coping and mortality. However, bivariable correlations and confidence intervals reported or generated from data in the article showed that the association between avoidant coping and mortality (r=.28, 95% CI [.03 to .50]) was not significantly stronger than two other correlations that were in the opposite direction of what would have been expected: hypertension with mortality (r=?.39, 95% CI [?.15 to ?.59]) and medication compliance with mortality (r=.16, 95% CI [?.10 to .40]). Oddities of this sort are often encountered in very small datasets and, as a result, stronger evidence must be accrued from larger, more robust samples. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Characterization of nanostructured hydroxyapatite prepared by Nd:YAG laser deposition

Pulsed laser deposition, under dry and water vapor conditions, was employed to synthesize nanostructured hydroxyapatite films by pulsed laser deposition (PLD) of chlorapatite target for the purpose of coating metallic bone implants by this material. A pulsed Nd:YAG laser operating at a wavelength of 1064 nm and emitting 9 ns pulses was used for deposition. AFM microscopy, FTIR spectroscopy, optical microscopy, adhesion and microhardness measurements were conducted to characterize the films. The in vitro test for the synthesized hydroxyapatite was performed using simulated body fluid (SBF). The results showed a successful transformation of the chlorapatite to hydroxyapatite films characterized by all the HAp peaks with 60 nm root mean square roughness, (80–327) nm grain size, and a microhardness of 512 HV.     

Ductile necking behavior of nanoscale metallic glasses under uniaxial tension at room temperature

Glasses are normally brittle materials with no tensile ductility at room temperature. Using in situ, quantitative nanomechanical tests inside a transmission electron microscope, we demonstrate that certain nanoscale metallic glass samples are exceptions to this general rule. Such metallic glasses can be intrinsically ductile, capable of elongation and necking under uniaxial tension, in lieu of catastrophic fracture caused by severe shear banding. Beam-off tests confirm that the ductile behaviors are not artifacts due to electron-beam effects during the in situ tests. Additional experiments indicate that ductile necking gives way to fast shear banding failure at increased samples sizes and elevated strain rates. The observed spread-out shear transformations delaying strain localization and severe shear banding are explained in terms of the propensity for participation in deformation, while the tendency towards necking is attributed to the lack of strain hardening mechanism and inadequate strain rate hardening.     

Environmental controls of cadmium desorption during CO₂ leakage

Geologic carbon sequestration represents a promising option for carbon mitigation. Injected CO(2), however, can potentially leak into water systems, increase water acidity, and mobilize metals. This study used column experiments to quantify the effects of environmental controls on cadmium desorption during CO(2) leakage in subsurface systems without ambient flow. Results show that fast leakage rates are responsible for earlier and larger amounts of Cd desorption. Long weathering time of Cd laden clay leads to low Cd desorption. Calcite content as low as 10% can mitigate the effect of pH reduction and result in zero Cd desorption. Increasing the salinity of the leaking fluid has a relatively minor effect, primarily due to the offsetting impacts of an increased extent of ion exchange and the decrease in CO(2) solubility (and therefore acidity). This work systematically quantifies, for the first time, the effects of environmental controls on Cd desorption and points to key parameters for risk assessment associated with metal mobilization during CO(2) leakage.     

Projecting water withdrawal and supply for future decades in the U.S. under climate change scenarios

The sustainability of water resources in future decades is likely to be affected by increases in water demand due to population growth, increases in power generation, and climate change. This study presents water withdrawal projections in the United States (U.S.) in 2050 as a result of projected population increases and power generation at the county level as well as the availability of local renewable water supplies. The growth scenario assumes the per capita water use rate for municipal withdrawals to remain at 2005 levels and the water use rates for new thermoelectric plants at levels in modern closed-loop cooling systems. In projecting renewable water supply in future years, median projected monthly precipitation and temperature by sixteen climate models were used to derive available precipitation in 2050 (averaged over 2040-2059). Withdrawals and available precipitation were compared to identify regions that use a large fraction of their renewable local water supply. A water supply sustainability risk index that takes into account additional attributes such as susceptibility to drought, growth in water withdrawal, increased need for storage, and groundwater use was developed to evaluate areas at greater risk. Based on the ranking by the index, high risk areas can be assessed in more mechanistic detail in future work.     

Monitoring biodegradation of ethene and bioremediation of chlorinated ethenes at a contaminated site using compound-specific isotope analysis (CSIA)

Chlorinated ethenes are commonly found in contaminated groundwater. Remediation strategies focus on transformation processes that will ultimately lead to nontoxic products. A major concern with these strategies is the possibility of incomplete dechlorination and accumulation of toxic daughter products (cis-1,2-dichloroethene (cDCE), vinyl chloride (VC)). Ethene mass balance can be used as a direct indicator to assess the effectiveness of dechlorination. However, the microbial processes that affect ethene are not well characterized and poor mass balance may reflect biotransformation of ethene rather than incomplete dechlorination. Microbial degradation of ethene is commonly observed in aerobic systems but fewer cases have been reported in anaerobic systems. Limited information is available on the isotope enrichment factors associated with these processes. Using compound-specific isotope analysis (CSIA) we determined the enrichment factors associated with microbial degradation of ethene in anaerobic microcosms (ε = -6.7‰ ± 0.4‰, and -4.0‰ ± 0.8‰) from cultures collected from the Twin Lakes wetland area at the Savannah River site in Georgia (United States), and in aerobic microcosms (ε = -3.0‰ ± 0.3‰) from Mycobacterium sp. strain JS60. Under anaerobic and aerobic conditions, CSIA can be used to determine whether biotransformation of ethene is occurring in addition to biodegradation of the chlorinated ethenes. Using δ(13)C values determined for ethene and for chlorinated ethenes at a contaminated field site undergoing bioremediation, this study demonstrates how CSIA of ethene can be used to reduce uncertainty and risk at a site by distinguishing between actual mass balance deficits during reductive dechlorination and apparent lack of mass balance that is related to biotransformation of ethene.     

Work function tuning for flexible transparent electrodes based on functionalized metallic single walled carbon nanotubes

We present a method to control the work function of metallic carbon nanotube transparent electrodes by functionalization of the random network with metallic nanoparticles. Flexible functionalized electrodes with high transparency (～90%) can be obtained with work function values ranging from ～4.6 up to ～5.1 eV, depending on the nature of the nanoparticles. The work function values were obtained by comparative in situ Kelvin probe force microscopy under ultra high vacuum and ultraviolet photoelectron spectroscopy measurements. Interestingly, by appropriate choice of the metal source for functionalization, work function engineering can lead to work function values higher or lower than that for pristine metallic nanotubes. This could be of great interest for adjusting the work function of transparent electrodes to active layers in many optoelectronics devices.     

Opportunities and risks of the proposed FCTC protocol on illicit trade

Illicit trade in tobacco products presents a threat to public health because it undermines the use of tax and price policies, which are among the most effective mechanisms for reducing tobacco consumption. Parties to the WHO Framework Convention on Tobacco Control (FCTC) are in the final stages of negotiating a protocol aimed at strengthening international cooperation in the fight against illicit tobacco trade. While an effective multilateral response to illicit tobacco trade would make a significant contribution to global tobacco control, achieving this through the FCTC forum is challenging. First, while illicit tobacco trade is a health problem, the expertise, experience and capacity needed to combat illicit trade are not traditionally found in health agencies. The development of links with other agencies, both domestic and international, is critical to ensure both an effective response and an efficient use of limited governmental and non-governmental resources. Second, in many parts of the world, the tobacco industry cooperates closely with governments in the combating of illicit trade. This cooperation poses risks for tobacco control, particularly if relationships and norms of cooperation spill over into other areas of FCTC implementation. An examination of the industry's positioning suggests that it sees an opportunity to portray itself as 'legitimate' and 'responsible', a friend of governments, and a way to integrate itself into FCTC processes. This paper makes suggestions for moving forward in this challenging area towards ensuring that the approach taken actually reduces illicit tobacco trade, strengthens tobacco tax policies and does not operate to undermine the FCTC.     

Inactivation of barotolerant Listeria monocytogenes in sausage by combination of high-pressure processing and food-grade additives

Food-grade additives were used to enhance the efficacy of high-pressure processing (HPP) against barotolerant Listeria monocytogenes. Three strains of L. monocytogenes (Scott A, OSY-8578, and OSY-328) were compared for their sensitivity to HPP, nisin, tert-butylhydroquinone (TBHQ), and their combination. Inactivation of these strains was evaluated in 0.2 M sodium phosphate buffer (pH 7.0) and commercially sterile sausage. A cell suspension of L. monocytogenes in buffer (10(9) CFU/ml) was treated with TBHQ at 100 ppm, nisin at 100 IU/ml, HPP at 400 MPa for 5 min, and combinations of these treatments. Populations of strains Scott A, OSY-8578, and OSY-328 decreased 3.9, 2.7, and 1.3 log with HPP alone and 6.4, 5.2, and 1.9 log with the HPP-TBHQ combination, respectively. Commercially sterile sausage was inoculated with the three L. monocytogenes strains (10(6) to 10(7) CFU/g) and treated with selected combinations of TBHQ (100 to 300 ppm), nisin (100 and 200 ppm), and HPP (600 MPa, 28 degrees C, 5 min). Samples were enriched to detect the viability of the pathogen after the treatments. Most of the samples treated with nisin, TBHQ, or their combination were positive for L. monocytogenes. HPP alone resulted in a modest decrease in the number of positive samples. L. monocytogenes was not detected in any of the inoculated commercial sausage samples after treatment with HPP-TBHQ or HPP-TBHQ-nisin combinations. These results suggest that addition of TBHQ or TBHQ plus nisin to sausage followed by in-package pressurization is a promising method for producing Listeria-free ready-to-eat products.     

Shape-independent lateral force calibration

Current methods for lateral force calibration are often time-consuming, expensive, or cause significant wear of the tip. A quick and simple alternative is presented in which the linear relationship between force and voltage is exploited. The technique is independent of the shapes of the sample and cantilever and eliminates common problems, while maintaining better than 10% precision. This advance will facilitate quantitative comparisons between experiments.