Realtime stable isotope monitoring of natural waters by parallel-flow laser spectroscopy

A parallel-flow H(2)O(liquid)-H(2)O(vapor) equilibration and laser spectroscopy method provides a new way to monitor the hydrogen and oxygen stable isotopic composition of water from rivers or lakes or in hydrologic tracer tests in real time. Two custom-built equilibrator devices and one commercial membrane device were tested to determine if they could be used to convert natural water samples (lakes, rivers, groundwater) to a H(2)O gas phase for continuous online δ(18)O and δD isotopic analysis by laser spectroscopy. Both the commercial minimodule device and the marble-filled equilibrator produced water vapor in isotopic equilibrium with the flowing liquid water, suggesting that unattended field measurement using these devices is possible. Oxygen isotope disequilibrium was indicated using the minimodule device at low temperatures.     

Radiative Properties of Blackbody Calibration Sources:Recent Advances in Computer Modeling

The radiative characteristics (spectral effective emissivity, spectral radiance, and radiance temperature) of blackbody calibration sources widely used in radiation thermometry are an important subject for advanced computer modeling by the Monte Carlo method. An algorithm and code for stochastic modeling of the radiant heat transfer inside cavities has been developed on the basis of the reciprocity principle and backward ray tracing. The importance sampling technique has been applied to generate the reflected rays according to the surface reflection model that can be a linear combination of the following primary models: Lambertian, Specular, and TETRA (a microfacet model of random tetrahedral pits that mimics reflections from a rough surface). A wide range of axisymmetrical cavities, cylindrical cavities with an inclined flat bottom, and a rectilinear grooved radiator of polygonal profile have been implemented. Various conditions of observation can be modeled to compute appropriate radiation characteristics. A number of different temperature distributions can be assigned to the same node set on the cavity surface, so several related tasks can be modeled in a single run. The results obtained for the radiative properties of isothermal and non-isothermal non-diffuse blackbodies used for the calibration of infrared radiation thermometers are presented and discussed.     

Estimating the cell density and invasive radius of three-dimensional glioblastoma tumor spheroids grown in vitro

To gain insight into brain tumor invasion, experiments are conducted on multicellular tumor spheroids grown in collagen gel. Typically, a radius of invasion is reported, which is obtained by human measurement. We present a simple, heuristic algorithm for automated invasive radii estimation (AIRE) that uses local fluctuations of the image intensity. We then derive an analytical expression relating the image graininess to the cell density for a model imaging system. The result agrees with the experiment up to a multiplicative constant and thus describes a novel method for estimating the cell density from bright-field images.     

Elemental analysis of organic species with electron ionization high-resolution mass spectrometry

We present a new elemental analysis (EA) technique for organic species (CHNO) that allows fast on-line analysis (10 s) and reduces the required sample size to approximately 1 ng, approximately 6 orders of magnitude less than standard techniques. The composition of the analyzed samples is approximated by the average elemental composition of the ions from high-resolution electron ionization (EI) mass spectra. EA of organic species can be performed on organic/inorganic mixtures. Elemental ratios for the total organic mass, such as oxygen/carbon (O/C), hydrogen/carbon (H/C), and nitrogen/carbon (N/C), in addition to the organic mass to organic carbon ratio (OM/OC), can be determined. As deviations between the molecular and the ionic composition can appear due to chemical influences on the ion fragmentation processes, the method was evaluated and calibrated using spectra from 20 compounds from the NIST database and from 35 laboratory standards sampled with the high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). The analysis of AMS (NIST) spectra indicates that quantification of O/C is possible with an error (average absolute value of the relative error) of 30% (17%) for individual species. Precision is much better than accuracy at +/-5% in the absence of air for AMS data. AMS OM/OC has an average error of 5%. Additional calibration is recommended for types of species very different from those analyzed here. EA was applied to organic mixtures and ambient aerosols (sampled at 20 s from aircraft). The technique is also applicable to other EI-HRMS measurements such as direct injection MS.     

Adaptation and readaptation to different shift work schedules measured with sleep diary and actigraphy.

In this study we examine sleep during adaptation and readaptation to different shift work schedules in the offshore oil industry. The sleep of 19 offshore workers was assessed daily for 1 week before, during the work period, and for 1 week after 3 different work schedules: (1) day (14 consecutive days of work), (2) night (14 consecutive nights of work), and (3) swing shift work (first 7 nights with night work then 7 days of day work). The workers' sleep was assessed for 84 days. Actigraphy and sleep diary estimates of sleep was applied assessing: (1) adaptation to offshore shift work, (2) sleep across the 2 offshore work weeks, and (3) readaptation after the work period. Regarding adaptation, sleep efficiency was higher when working day than night and swing shift the first week of work. Sleep quality was better during swing than regular day/night shifts the first week of work. Total sleep time was longer during day and night shift than swing shift across the 2 work weeks. Sleep efficiency, based on sleep diaries, was higher during day than night and swing shift during the 2 work weeks. There were no significant differences between the shifts in readaptation in terms of sleep. To conclude, adaptation to swing shift was more difficult than adaptation to regular day and night shifts in terms of sleep. Readaptation to day work after 1 week of night work affected sleep negatively. There were no differences between the shift schedules the week after the work period. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Visual acuity and macular hole size after unsuccessful macular hole closure

We have identified and characterized a novel protein from adult zebrafish retina, which we named ES1. Database search revealed that the ES1 gene has significant similarity to two genes with unknown functions: the Escherichia coli sigma cross-reacting protein 27a (scrp27a) and the human KNP-I/GT335. In situ hybridization and immunohistochemistry experiments showed that both ES1 mRNA and protein are expressed specifically in adult photoreceptor cells. ES1 seems to be a cytoplasmic protein. An ES1-like antigen was also detected in photoreceptor cells of goldfish with anti-ES1 antibodies. The retina specific expression and the evolutionary conservation suggest that ES1 protein may be important for maintaining normal retina structure and function.     

Towards a generalized model for the primary and secondary contamination of lakes by Chernobyl-derived radiocesium

As part of the UK Ministry of Agriculture Fisheries and Food Directorate of Fisheries Research (MAFF/DFR) post-Chernobyl monitoring program, a detailed study was carried out of the change over time in dissolved-phase 137Cs concentrations in a number of lakes in Cumbria, UK. These measurements have been combined with published data on 137Cs in Cumbrian and other European lakes in order to develop and test a "double exponential" model for changes in lakewater concentrations: A exp(-k1t) + B exp(-k2t) where the exponential terms correspond, respectively, to the initial fast flush of activity through the system followed by longer-term transfers (timescale, years) from the catchment. Parameter values have been determined for this model by curve-fitting to the set of measurements of post-Chernobyl 137Cs activities in lakes. Values of fitted parameters are shown to be related, in a simple manner, to the physical characteristics of the system, in particular water residence time and mean lake depth. These parameters are generalized to give a simple empirical model for the full set of study lakes. The model is shown to give estimates of 137Cs activity to within a factor of 5 of field data for a period of several years after the fallout. Initial fractional losses of activity from catchment to lake were determined to be within the range 0.44-8.7% per year, declining exponentially with a mean rate constant 0.98 x 10(-3) d(-1).     

Phase-stress partition during uniaxial tensile loading of a TiC-particulate-reinforced Al composite

Using neutron diffraction, we measured during in situ loading the lattice elastic mean phase (LEMP) strains in the matrix and reinforcement of a 15 vol pct TiC-particulate-reinforced 2219 Al composite. From the strain components longitudinal to and transverse to loading, the in situ normal phase stresses (average normal stresses in the constituent phases) were obtained through Hooke’s law. The internal stress partition between the matrix and reinforcement, i.e., load sharing, can then be inferred. Internal stress development was also modeled using the finite-element method (FEM), showing good agreement with the experimental results. Both indicate that the relationship between the LEMP strains/phase stresses and the applied load noticeably deviates from linearity during composite microyielding, long before the nominal 0.2 pct proof stress is reached. The nonlinearity arises (despite the linear elastic relationship between phase stresses and LEMP strains) because the applied traction is not synonymous with the phase stresses, and the ratio of phase stresses may vary during loading. Notably, the morphology of the LEMP strain development with applied load differs in the directions parallel to or perpendicular to the load. The differences are explained by considering the evolution of local matrix plasticity. Thermal residual stresses and inelastic stress relaxation, driven by interfacial diffusion, are also discussed.     

The responsible psychotherapist.

Contends that psychologists in general, and psychotherapists in particular, have been concerned with both ethical and legal liability. Contracts, informed consent, and participatory decision making have been recommended as requisites for an ethical psychotherapy. However, when the various types of responsibility (role, causal, capacity, and liability) are differentiated, it becomes clear that the recommendations entail an inconsistent set of assumptions. These recommendations ignore difficulties in establishing liability. It is suggested that since there may be inherent conflicts between effective psychotherapy and the ethical recommendations that have been made, future recommendations should be relative to a particular theory of psychotherapy. (97 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)