Requirements for modeling of a snowdrift

In an experiment of a model snowdrift formed behind each of two model snow fences, which are the same in shape but different in size, the independence of the wind speed ratio between them from their length ratio was observed. This phenomenon can be explained not by the Froude number, but by the effect of wakes behind an obstruction and movement characteristics of snow particles. The wind speed ratio and the duration of a storm in which the model snowdrifts of glass beads and activated clay particles become similar to each other, were examined. It follows from the result that the friction speed ratio is equal to the ratio of the threshold friction speed of both model snow particles, and the ratio of storm duration can be calculated by comparing the volume of both model snowdrifts. This result suggests strongly that the same relationships hold between the model and the prototype snowdrift.     

Formaldehyde Release From Urea-Formaldehyde Bonded Wood Products

During the past decade significant progress has been made in reducing formaldehyde release from UF-bonded wood products. The purpose of this work was to test formaldehyde release from medium density fibreboard (MDF) manufactured in a commercial pilot plant using seven different UF resins with molar ratios between 1.85 and 1.05 that were available in spring 1983. Formaldehyde release measured with the 2 hr. U.S. desiccator test ranged from 8.6 mg/l to 0.3 mg/l after 6 weeks. European perforator standard values ranged from 80 mg/100 g to 9 mg/100 g. Low molar ratio resin produced MDF with good mechanical properties while yielding formaldehyde release rates that were sufficiently low to meet the requirement of the German wood product class E-1 and the 0.1 ppm requirement of ASHRAE 62-1981 or similar standards for minimum acceptable indoor air quality at reasonable product loading ratios.     

Optimal state-space lumping in Markov chains

We prove that the optimal lumping quotient of a finite Markov chain can be constructed in O(mlgn) time, where n is the number of states and m is the number of transitions. Our proof relies on the use of splay trees (designed by Sleator and Tarjan [J. ACM 32 (3) (1985) 652-686]) to sort transition weights.     

Probabilistic Logical Characterization

Probabilistic automata exhibit both probabilistic and non-deterministic choice. They are therefore a powerful semantic foundation for modeling concurrent systems with random phenomena arising in many applications ranging from artificial intelligence, security, systems biology to performance modeling. Several variations of bisimulation and simulation relations have proved to be useful as means to abstract and compare different automata. This paper develops a taxonomy of logical characterizations of these relations on image-finite and image-infinite probabilistic automata.     

Comparative studies on cytotoxic effects of dental amalgams and alternative alloys according to ISO standards in vitro

Deleterious effects of dental alloys, especially those of dental amalgams, have become an important issue in current discussions on biomaterials. Cytotoxicity and further related risks of amalgams are discussed in a controversial way in the literature without leading to a final conclusion. There is still a need for basic clinical and pre-clinical research, especially with respect to the wide distribution of dental amalgams. Standardized methods of cytotoxicity testing have been established by the ISO. It was the aim of the present study to detect and compare possible cytotoxic effects of dental amalgams and alternative non-amalgam alloys in vitro. According to the ISO standards, direct contact tests and extract dilution tests were performed using the cell lines HeLa and L-929 as well as primary isolated human fibroblasts, a relevant cell type of the human gingiva. For direct contact tests the samples were fixed on thermanox discs. Zn and Ni-chloride in defined molar concentrations were used as positive controls in the extract dilution tests, while copper was the positive control in the direct contact tests. The tested amalgam was a Non-Gamma-2 amalgam. For extract dilution tests sixteen extraction dilutions were performed. The different cell types were incubated with the extracts in 96-well microtitre plates. MTT-testing was performed to evaluate the effects on cellular metabolism. The BrdU labelling index was determined with the help of EIA methods to analyse the effects of the extracts on the cellular proliferation at DNA synthesis level. The morphological status of the cells seeded on the materials (direct contact test) were studied with the help of light microscopy. No cytotoxic effects of formerly extracted dental amalgam was found, although fresh amalgam elicited a significant cytotoxic effect, in general the non-amalgams have to be regarded as non cytotoxic. The negative control and the non-amalgams elicited no measurable cytotoxicity in the indirect contact assays, independent of the number of extraction dilutions. This applied to all cell types studied. The tested amalgam also gave a significant cytotoxic effect in the MTT-assays, while in addition a significant reduction of BrdU incorporation after incubation with the extracts of the first dilution series, compared to the silicone control was found. The effects were reduced after an incubation with the extracts of the higher dilution series. It is suggested by the presented results that amalgams might have cytotoxic effects, especially when being freshly applied. The cytotoxic effects were no longer detectable after extraction procedures. Nevertheless, a negative effect around such amalgams must be considered. The insights provided by the present studies might be helpful for a rational choice of dental materials.     

Crystallographic, thermoelectric, and mechanical properties of polycrystalline type-I Ba8Al16Si30-based clathrates

Crystallographic, thermoelectric, and mechanical properties of polycrystalline Ba₈Al₁₆Si₃₀-based samples with type-I clathrate structure prepared by combining arc melting and spark plasma sintering methods were investigated. The major phase of the samples was a type-I clathrate with an actual Al/Si ratio of ~15/31, strongly suggesting that framework deficiency was absent or was present in very low concentration in the samples. The Hall carrier concentration n of the samples was approximately 1 × 10²¹ cm^?3, which is lower than the values reported so far for the Ba₈Al₁₆Si₃₀ system. Other important material parameters of the samples were as follows: the density-of-states effective mass m* = 2.3m ₀, Hall mobility μ = 7.4 cm² V^?1 s^?1, and the lattice thermal conductivity κ _L = 1.2 W m^?1 K^?1. The thermoelectric figure of merit ZT reached approximately 0.4 (900 K) for a sample with n = 9.7 × 10²⁰ cm^?3. Simulation using the experimentally determined values of material parameters showed that ZT reached values >0.5 if the carrier concentration is optimized at about 3 × 10²⁰ cm^?3. Young’s, shear, and bulk moduli were estimated to be approximately 98, 39, and 117 GPa, respectively, and Poisson’s ratio was found to be 0.25 from the longitudinal and transverse velocities of sound, v _L = 6038 m/s and v _T = 3503 m/s, respectively, for a sample with ZT = 0.4. The coefficient of thermal expansion (CTE) ranged from approximately 8 × 10^?6 K^?1 to 10 × 10^?6 K^?1 (330–690 K), which is smaller than the values reported for Ba₈Ga₁₆Ge₃₀ and Sr₈Ga₁₆Ge₃₀ clathrates.     

Certainty equivalent citation: generalized classes of citation indexes

Drawing from the existing literature on risk and inequality measurement, we implement the notion of “certainty equivalent citation” in order (i) to generalize most of the h-type citation indexes (h-, g-, $\tilde{g},$ t-, f-, w-index), and (ii) to highlight the centrality of the decision-maker’s preferences on distributive aspects (concentration aversion) for the ranking of citation profiles. In order to highlight the sensitivity of citation orderings with respect to concentration aversion, an application to both simulated and real citation profiles is presented.     

A single STAT recruitment module in a chimeric cytokine receptor complex is sufficient for STAT activation

We established a system of receptor chimeras that enabled us to induce heterodimerization of different cytoplasmic tails. Fusion constructs were created that are composed of the extracellular parts of the interleukin-5 receptor alpha and beta chains, respectively, and the transmembrane and intracellular parts of gp130, the signal transducing chain of the interleukin-6 receptor complex. In COS-7 transfectants we observed a dose-dependent interleukin-5-inducible STAT1 activation for which the presence of both the alpha and the beta chain chimera was needed. No STAT activity was detected if one of the cytoplasmic tails of the receptor complex was deleted, indicating that STAT activity resulted from a receptor dimer rather than from higher receptor aggregates. We further investigated whether dimerization of STAT1 depends on the juxtaposition of two STAT recruitment modules in a receptor complex. We show that a receptor dimer with only a single STAT1 docking site was still able to lead to STAT1 activation. This indicates that the formation of a paired set of STAT binding sites in a receptor complex is not the prerequisite for STAT factor dimerization. Our findings are discussed in view of alternative STAT dimerization models.     

A case of adult intussusception due to the inverted Meckel''s diverticulum with ectopic pancreas which showed characteristic findings of MRI

Power spectrum analysis of heart-rate variability was made in seven men [mean age 22 (SEM 1) years] in head-out water immersion (W) and in air (A, control) at rest and during steady-state cycling to maximal intensity (maximum oxygen uptake, VO2max). At rest W resulted in a trebled increase in the total power (P < 0.05), coupled with minimal changes in the power (as a percentage of the total) of the high frequency peak (HF, centred at 0.26 Hz; 18% vs 28%) and of the low frequency peak (LF, 0.1 Hz; 24% vs 32%). A third peak at about 0.03 Hz (very low frequency, VLF) represented the remaining power both in W and A. These changes as a whole indicated that immersion caused a vagal dominance in cardiac autonomic interaction, due to the central pooling of blood and/or the pressure of water on the trunk. Exercise caused a decrease in the total power in W and A. The LF% did not change up to about 50% V02max, thereafter decreasing towards nil in both conditions. The HF% decreased in similar ways in W and A to about half at 55%-60% VO2max and then increased to reach 1.5 times the resting values at VO2max. The central frequency of HF increased linearly with oxygen uptake, showing a tendency to be higher in W than in A at medium to high intensities. The VLF% remained unchanged. The lack of differences in the LF peak between W and A during exercise would suggest that blood distribution had no effect on the readjustments in control mechanisms of arterial pressure. On the other hand, the findings of similar HF powers and the very similar values for ventilation in W and A confirmed the direct effect of the respiratory activity in heart rate modulation during exercise.