Applicability of stable isotope fractionation analysis for the characterization of benzene biodegradation in a BTEX-contaminated aquifer

In recent years the analysis of stable isotope fractionation has increasingly been used for characterizing and quantifying biodegradation of contaminants in aquifers. The correlation of carbon and hydrogen isotope signatures of benzene in a BTEX-contaminated aquifer located in the area of a former hydrogenation plant gave indications that biodegradation mainly occurred under anoxic conditions. This finding was consistent with the investigation of hydrogeochemical conditions within the aquifer. Furthermore, the biodegradation of benzene was calculated by changes in carbon isotope signatures using the Rayleigh-equation-streamline approach. Since contaminant concentrations can be also affected by nonisotope-fractionating abiotic processes such as dilution, volatilization, or irreversible sorption to the aquifer matrix, the Rayleigh-equation-streamline approach was adjusted for scenarios assuming that biodegradation and abiotic processes occur either consecutively or simultaneously along a groundwater flow path between contaminant source and sampling well. The results of the scenarios differed significantly, indicating that an abiotic process (typically dilution) causes a decrease in benzene concentration within the investigated aquifer transect. This comparison of results derived from the different scenarios can help to identify whether biodegradation is the predominant process for decrease in contaminant concentration. However, for a proper quantification of biodegradation, the temporal sequence between biodegradation and dilution needs to be known. The uncertainty associated with the quantification of pollutant biodegradation by the Rayleigh-equation-streamline approach increases when nonisotope-fractionating abiotic processes cause a significant decrease in contaminant concentrations.     

Sensitive detection of anaerobic monochlorobenzene degradation using stable isotope tracers

Microbial degradation of monochlorobenzene (MCB) under anaerobic conditions was investigated using a stable isotope tracer under in and ex situ conditions. In situ microcosms were incubated directly in an anoxic aquifer and carbon derived from [13C6]-MCB was found to be incorporated into the microbial biomass. In laboratory microcosms, amended with [13C6]-MCB, anaerobic mineralization of MCB was indicated by the production of 13CO2. Further, recovery of the 13C-label in the fatty acids confirmed the assimilation of MCB-derived carbon into microbial biomass. The described approach may be applied to various other organic groundwater contaminants of concern using carbon (13C) as well as other stable isotope tracers, such as nitrogen (15N), allowing direct and sensitive detection of biodegradation.     

Microevolution in genomic short sequence repeats of Candida albicans in non-neutropenic patients

The genome of the yeast Candida albicans harbours many genomic short sequence repeats (SSRs). These are stable upon transition of colonization to infection in immune-compromised patients. We show here that in non-neutropenic patients this transition may coincide with variation in several of the SSRs. This may have implications for stage-specific expression of C. albicans pathogenicity factors.     

Hinged nanorods made using a chemical approach to flexible nanostructures

The fabrication of multifunctional nanomaterials and their subsequent use for novel applications in various branches of nanotechnology has been under intense scrutiny. Particularly in the area of nanomechanics, the design of multicomponent nanostructures with an integrated multifunctionality would enable the construction of building blocks for nanoscale analogues of macroscopic objects. Here, we introduce a new class of flexible nanostructures: metallic nanorods with polyelectrolyte hinges, synthesized using layer-by-layer electrostatic self-assembly of oppositely charged polyelectrolytes on barcode metal nanorods followed by segment-selective chemical etching. Nanorods with hinges that consist of one polyelectrolyte bilayer display considerable flexibility, but with a greater number of bilayers the flexibility of the hinge is significantly reduced. Magnetically induced bending about the polymer hinge is illustrated through the incorporation of nickel segments into the barcodes and the application of an external fluctuating magnetic field.     

Targeted delivery of magnetic aerosol droplets to the lung

The inhalation of medical aerosols is widely used for the treatment of lung disorders such as asthma, chronic obstructive pulmonary disease, cystic fibrosis, respiratory infection and, more recently, lung cancer. Targeted aerosol delivery to the affected lung tissue may improve therapeutic efficiency and minimize unwanted side effects. Despite enormous progress in optimizing aerosol delivery to the lung, targeted aerosol delivery to specific lung regions other than the airways or the lung periphery has not been adequately achieved to date. Here, we show theoretically by computer-aided simulation, and for the first time experimentally in mice, that targeted aerosol delivery to the lung can be achieved with aerosol droplets comprising superparamagnetic iron oxide nanoparticles--so-called nanomagnetosols--in combination with a target-directed magnetic gradient field. We suggest that nanomagnetosols may be useful for treating localized lung disease, by targeting foci of bacterial infection or tumour nodules.     

Isoprene emission from terrestrial ecosystems in response to global change: minding the gap between models and observations

Coupled surface-atmosphere models are being used with increased frequency to make predictions of tropospheric chemistry on a 'future' earth characterized by a warmer climate and elevated atmospheric CO2 concentration. One of the key inputs to these models is the emission of isoprene from forest ecosystems. Most models in current use rely on a scheme by which global change is coupled to changes in terrestrial net primary productivity (NPP) which, in turn, is coupled to changes in the magnitude of isoprene emissions. In this study, we conducted measurements of isoprene emissions at three prominent global change experiments in the United States. Our results showed that growth in an atmosphere of elevated CO2 inhibited the emission of isoprene at levels that completely compensate for possible increases in emission due to increases in aboveground NPP. Exposure to a prolonged drought caused leaves to increase their isoprene emissions despite reductions in photosynthesis, and presumably NPP. Thus, the current generation of models intended to predict the response of isoprene emission to future global change probably contain large errors. A framework is offered as a foundation for constructing new isoprene emission models based on the responses of leaf biochemistry to future climate change and elevated atmospheric CO2 concentrations.     

The relationship between human resource investments and organizational performance: A firm-level examination of equilibrium theory.

It is commonly believed that human resource investments can yield positive performance-related outcomes for organizations. Utilizing the theory of organizational equilibrium (H. A. Simon, D. W. Smithburg, & V. A. Thompson, 1950; J. G. March & H. A. Simon, 1958), the authors proposed that organizational inducements in the form of competitive pay will lead to 2 firm-level performance outcomes--labor productivity and customer satisfaction--and that financially successful organizations would be more likely to provide these inducements to their employees. To test their hypotheses, the authors gathered employee-survey and objective performance data from a sample of 126 large publicly traded U.S. organizations over a period of 3 years. Results indicated that (a) firm-level financial performance (net income) predicted employees' shared perceptions of competitive pay, (b) shared pay perceptions predicted future labor productivity, and (c) the relationship between shared pay perceptions and customer satisfaction was fully mediated by employee morale. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recollection- and familiarity-based memory in healthy aging and amnestic mild cognitive impairment.

Little is known about the cognitive mechanisms of the memory impairment associated with amnestic mild cognitive impairment (aMCI). We explored recollection and familiarity in 27 healthy young adults, 45 healthy older adults, and 17 individuals with aMCI. Relative to the younger adults, recollection was reduced in the older adults, especially among those with aMCI. Familiarity did not differ among groups. In the healthy younger and older adults, better performance on a set of clinical memory measures that are sensitive to medial temporal lobe functioning was associated with greater recollection. In addition, among the healthy older adults better executive functioning was also associated with greater recollection. These results are consistent with the notion that recollection is a product of strategic processes mediated by the prefrontal cortex that suppport the retrieval of context-dependent memories from the hippocampus. Hippocampal atrophy associated with aMCI may disrupt this brain network, and thereby interfere with recollection. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Mothers and Toddlers Program: Preliminary findings from an attachment-based parenting intervention for substance-abusing mothers.

The authors examined pilot data from an attachment-based parenting intervention for substance-abusing mothers of toddlers (ages 12-36 months). The Mothers and Toddlers Program (MTP) is a 20-week individual therapy intervention that aims to help mothers develop more balanced representations of their children and improve their capacity for reflective functioning (i.e., recognition of the intentional nature of children's behavior). The authors hypothesized that improvement in maternal representational balance and maternal capacity for reflective functioning would correspond with improvements in maternal behavior with toddlers (e.g., sensitivity to cues, responsiveness to distress, and social-emotional growth fostering) and reduction in maternal psychiatric distress and substance abuse. Eight mothers who completed MTP showed moderate improvements in representational balance and reflective functioning, and these changes corresponded with significant improvements in maternal behaviors with toddlers. The authors also compared MTP completers and noncompleters on sociodemographic and psychosocial indexes and examined the validity of the intervention's proposed mechanisms of change. Preliminary findings support the importance of attachment mechanisms and indicate that attachment-based interventions may strengthen substance-abusing mothers' capacities to foster their toddlers' socioemotional development. (PsycINFO Database Record (c) 2010 APA, all rights reserved)