Correlation between airborne particle concentrations in seven industrial plants and estimated respiratory tract deposition by number,mass and elemental composition

The number and mass distribution of airborne particles were recorded in several industrial plants. From the data obtained, particle deposition was estimated in three regions of the respiratory tract using the ICRP grand average deposition model based on Hinds' (1999) parameterization. The median diameter was 30–70 nm (number distributions), and >4 μm (mass distributions) near most work activities, resulting in linear relationships between the deposited number/mass concentrations and the number/mass concentrations in the air. Welding and laser cutting produced particles in the 200–500-nm range; total deposition was small, not in accordance with the linear relationship observed for the other work activities. The elemental content varied between particle sizes in some workplaces, causing different elements to deposit in different respiratory regions. Iron was the most abundant element in the particles in many of the workplaces; in an iron foundry, however, Fe was most abundant only in the micron-sized particles whereas the nanoparticles mainly comprised Pb and Sb.     

Application of Acoustic Emission Measurements to Investigate Adhesion in Filled Polymeric Composites

Adhesion in filled polymeric composites is characterized by an acoustic technique in which specimens of the composites are subjected to a ramped uni-axial tensile stress while particle-matrix debonding events are detected acoustically. The maximum in a fitted distribution of debonding events as a function of applied stress is related to the interfacial strength using elasticity theory. Results are reported for different silanetreated and untreated glass and aluminum spheres embedded in a poly(vinyl butyral) matrix. Silane treatment profoundly affects the adhesive strength, with the strongest bonds being formed when acid-base interactions between the particle surface and the matrix polymer are promoted. Significant differences are also found between the aluminum-particle and glass-particle cases, attributable in part to differences in mechanical interlocking.     

Mucoadhesive films inside the colonic tube: performance in a three-dimensional world

A self-propelling colonoscopic device moving inside the colonic tube should be able to periodically grip safely to the colonic wall as well as to manipulate the generated friction. The feasibility of achieving high grip and friction manipulation by covering the device with mucoadhesive films is experimentally tested. More precisely, the frictional behaviour of mucoadhesive films inside the colonic tube is tested in vitro in porcine colon. It appears that mucoadhesive films generate significantly higher friction than conventional materials (ANOVA p=0, 95% CIs=−3.04, −2.14). The geometry of the film plays a role as well. When holes are, for instance, present in the film geometry and are large enough so that the colonic tissue can wrap their borders, friction can be significantly increased (ANOVA p=0, 95% CIs=−2.53, −1.26). By altering the contact area or the film geometry, friction manipulation can be achieved. Moreover, a simple theoretical model is developed and experimentally verified (R=0.92). The model can be used to estimate the level of the friction generated by three-dimensional configurations of mucoadhesive films as a function of their geometric characteristics and the material properties of the colon.     

Bulk Sediment and Diatom Silica Carbon Isotope Composition from Coastal Marine Sediments off East Antarctica

Organic carbon occluded in diatom silica is assumed to be protected from degradation in the sediment. δ¹³C from diatom carbon (δ¹³C_(diatom)) therefore potentially provides a signal of conditions during diatom growth. However, there have been few studies based on δ¹³C_(diatom). Numerous variables can influence δ¹³C of organic matter in the marine environment (e.g., salinity, light, nutrient and CO₂ availability). Here we compare δ¹³C_(diatom) and δ¹³C_(TOC) from three sediment records from individual marine inlets (Rauer Group, East Antarctica) to (i) investigate deviations between δ¹³C_(diatom) and δ¹³C_(TOC), to (ii) identify biological and environmental controls on δ¹³C_(diatom) and δ¹³C_(TOC), and to (iii) discuss δ¹³C_(diatom) as a proxy for environmental and climate reconstructions. The records show individual δ¹³C_(diatom) and δ¹³C_(TOC) characteristics, which indicates that δ¹³C is not primarily controlled by regional climate or atmospheric CO₂ concentration. Since the inlets vary in water depths offsets in δ¹³C are probably related to differences in water column stratification and mixing, which influences redistribution of nutrients and carbon within each inlet. In our dataset changes in δ¹³C_(diatom) and δ¹³C_(TOC) could not unequivocally be ascribed to changes in diatom species composition, either because the variation in δ¹³C_(diatom) between the observed species is too small or because other environmental controls are more dominant. Records from the Southern Ocean show depleted δ¹³C_(diatom) values (1–4 ‰) during glacial times compared to the Holocene. Although climate variability throughout the Holocene is low compared to glacial/interglacial variability, we find variability in δ¹³C_(diatom), which is in the same order of magnitude. δ¹³C of organic matter produced in the costal marine environment seems to be much more sensitive to environmental changes than open ocean sites and δ¹³C is of strongly local nature.     

Shape-based optimal estimation and design of curve evolutionprocesses with application to plasma etching

Considers the problem of determining a finite number of discrete parameters appearing in a nonlinear partial differential equation describing a curve evolution process. The method is applied to the plasma etching of thin films for semiconductor manufacturing. Results are obtained within the mathematical framework of level set methods. Here, the evolution of the curve under study is captured through the evolution of a level set function. The underlying physics of the process are completely contained in a scalar function called the speed function. The degree of difficulty of treating the evolution equation depends on the functional dependencies of the speed function. The paper presents optimal estimation and design techniques based on analytical gradient computations for a class of position and orientation dependent speed functions. The technique is demonstrated on a plasma etching model taken from the literature. Only simulation results are presented, but the model under study has been shown to reproduce experimental data with reasonable accuracy. In the estimation problem, parameters in the model are fit to best match the feature shape measured in experiments. In the optimal design problem, parameter values are selected to most closely attain a desired feature shape     

Failure mechanisms of pressurized microchannels: model andexperiments

MicrochanneIs were created by fusion bonding of a Pyrex cover to a thermally oxidized silicon wafer, which contained anisotropically etched grooves. Such channels are frequently used in microfluidic handling systems, for example, in chemical analysis. Since in some of these labs-on-a-chip, in particular those used in liquid chromatography, the channels are subjected to high pressures of up to a few hundred bar, it is important to have information about the mechanical stability of the channel chip, in particular of the wafer bond involved in it. The latter is the subject of this paper. The maximum pressure that can be applied to several different channel chips was investigated experimentally. In order to find the relation among this maximum pressure, channel geometry, materials elasticity, and bond energy, an energy model was developed that is generally applicable to all types of wafer bonds. It was shown that the model is substantiated by the experimental pressure data, from which it could be calculated that the effective bond energy increased from 0.018 to 0.19 J/m² for an annealing temperature ranging from 310 to 470°C     

Symmetric approximation arguments for monotone lower bounds without sunflowers

We propose a symmetric version of Razborov's method of approximation to prove lower bounds for monotone circuit complexity. Traditionally, only DNF formulas have been used as approximators, whereas we use both CNF and DNF formulas. As a consequence we no longer need the Sun ower Lemma that has been essential for the method of approximation. The new approximation argument corresponds to Haken's recent method for proving lower bounds for monotone circuit complexity (counting bottlenecks) in a natural way.?We provide lower bounds for the BMS problem introduced by Haken, Andreev's polynomial problem, and for Clique. The exponential bounds obtained are the same as those previously best known for the respective problems. Received: July 16, 1996.     

"Psychotherapy with HIV-infected clients: Factors influencing notification of third parties": Comment.

Comments on the article by N. F. Kozlowski et al (see record 1998-10341-011) about HIV infected clients and whether or not there ought to be notification. Kozlowski et al cite the California case of Tarasoff v. Regents of University of California (1976) 9 times, however, they never officially cite it, nor do they put it in their reference section. Without going into a refresher course about the meaning of Tarasoff, when employing this case law in a study it is important to (1) carefully read the case, (2) become familiar with the case law in your state or states, (3) shepardize all relevant cases to make sure that they are still good law (there has been a lot of movement with Tarasoff over the years), and (4) have at least a consultation with an attorney who is familiar with this area of law. Legal accuracy is extremely important and without it, our studies cannot withstand interdisciplinary scrutiny. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The avian egg as a test system for endocrine disrupters: effects of diethylstilbestrol and ethynylestradiol on sex organ development.

Many environmental contaminants are known or suspected to interfere with hormonal function in animals. In vivo test methods to detect and characterize chemicals that disrupt the endocrine system are therefore urgently needed. In this study, we assessed the usefulness of abnormalities of the reproductive organs as test endpoints for estrogenic activity of xenobiotics in Japanese quail embryos. Two synthetic estrogens, diethylstilbestrol (DES) and ethynylestradiol (EE2), were injected into the yolks of embryonated eggs. At a dose as low as 2 ng EE2/g egg, all male embryos became feminized, containing ovary-like tissue in the left testis. The extent of feminization of the testes was determined by measuring the relative area of the ovary-like component. Persistent Müllerian ducts (oviducts) in male embryos, and malformations of the Müllerian ducts in females occurred at 2 ng EE2/g egg and higher doses. DES was approximately one-third to one-tenth as potent as EE2. The morphological changes studied were dose-dependent, indicating that they are useful as test endpoints for estrogenic activity. Feminization of the left testis in males proved to be the most sensitive endpoint. We propose the quail egg as a simple in vivo test system for estrogenic compounds.     

Direct recording of nicotinic responses in presynaptic nerve terminals

Nicotinic acetylcholine receptors are widely expressed in the nervous system, but their functions remain poorly understood. One attractive hypothesis is that the receptors act presynaptically to modulate synaptic transmission. We provide a direct demonstration of presynaptic nicotinic receptors in situ by using whole-cell patch-clamp techniques to record currents in large presynaptic calyces that midbrain neurons form on ciliary neurons. Bath application of nicotine induced inward currents in the calyces capable of generating action potentials that overrode the limited space clamp achievable. The inward currents reversed near 0 mV and showed inward rectification common for neuronal nicotinic receptors. Tetrodotoxin (TTX) blocked the action potentials but not the inward currents. alpha-Bungarotoxin blocked both, consistent with the presynaptic receptors containing alpha7 subunits. Recording from the postsynaptic ciliary neurons during nicotine exposure revealed EPSCs that TTX blocked, presumably by blocking presynaptic action potentials. The postsynaptic cells also displayed bimodal inward currents caused by their own nicotinic receptors; the bimodal currents were not blocked by TTX but were blocked partially by alpha-bungarotoxin and completely by D-tubocurarine. Dye-filling with Lucifer yellow from the recording pipette confirmed the identity of patched structures and showed no dye transfer between calyx and ciliary neuron. When calyces or ciliary neurons were labeled en mass with neurobiotin and biocytin through nerve roots, dye transfer was rarely observed. Thus, electrical synapses were infrequent and unlikely to influence calyx responses. Immunochemical analysis of preganglionic nerve extracts identified receptors that bind alpha-bungarotoxin and contain alpha7 subunits. The results unambiguously document the existence of functional presynaptic nicotinic receptors.