Numerical solution for shape optimization of an impactor penetrating into a semi-infinite target

The shape of the impactor with the maximum depth of penetration (DOP) for a given impact velocity is found using a numerical procedure for solving a corresponding non-classical variational problem. It is shown that the optimum shape in a general case is close to a blunt cone. The variation of the optimal shape of the impactor and the dependence of the DOP vs. the initial (impact) velocity and friction coefficient is studied. The analysis is performed also for optimal conical impactors.     

NADPH diaphorase activity in mammalian retinas is modulated by the state of visual adaptation

NADPH diaphorase histochemistry is commonly used to identify cells containing nitric oxide synthase (NOS), the enzyme catalyzing the production of nitric oxide from L-arginine. NADPH diaphorase activity and NOS immunostaining was demonstrated in different cells of the vertebrate retina; photoreceptors, horizontal cells, amacrine cells, ganglion cells, and Müller cells. However, the physiological role of nitric oxide (NO) in the retina has yet to be elucidated. In this study, we tested the assumption that NADPH diaphorase activity in the retinas of rabbits and rats depended on the state of visual adaptation. In the rabbit, light adaptation enhanced NADPH diaphorase activity in amacrine cells and practically eliminated it in horizontal cells. Dark adaptation induced the opposite effects; the NADPH diaphorase activity was reduced in amacrine cells and enhanced in horizontal cells. Retinas from eyes that were injected intravitreally with L-glutamate exhibited a pattern of NADPH diaphorase activity that was similar to that seen in dark-adapted retinas. In rats, the NADPH diaphorase activity of amacrine and horizontal cells exhibited adaptation dependency similar to that of the rabbit retina. But, the most pronounced effect of dark adaptation in the rat's retina was an enhancement of NADPH diaphorase activity in Müller cells, especially of the endfoot region. Assuming that NADPH diaphorase activity is a marker for NOS, these findings suggest that NO production in the mammalian retina is modulated by the level of ambient illumination and support the notion that NO plays a physiological role in the retina.     

Kappa calculus and evidential strength: A note on Åqvist's logical theory of legal evidence

Lennart Åqvist (1992) proposed a logical theory of legal evidence, based on the Bolding-Ekelöf of degrees of evidential strength. This paper reformulates Åqvist's model in terms of the probabilistic version of the kappa calculus. Proving its acceptability in the legal context is beyond the present scope, but the epistemological debate about Bayesian Law isclearly relevant. While the present model is a possible link to that lineof inquiry, we offer some considerations about the broader picture of thepotential of AI & Law in the evidentiary context. Whereas probabilisticreasoning is well-researched in AI, calculations about the threshold ofpersuasion in litigation, whatever their value, are just the tip of theiceberg. The bulk of the modeling desiderata is arguably elsewhere, if one isto ideally make the most of AI's distinctive contribution as envisaged forlegal evidence research.     

Cryptographic Hash Functions from Expander Graphs

We propose constructing provable collision resistant hash functions from expander graphs in which finding cycles is hard. As examples, we investigate two specific families of optimal expander graphs for provable collision resistant hash function constructions: the families of Ramanujan graphs constructed by Lubotzky-Phillips-Sarnak and Pizer respectively. When the hash function is constructed from one of Pizer’s Ramanujan graphs, (the set of supersingular elliptic curves over with ℓ-isogenies, ℓ a prime different from p), then collision resistance follows from hardness of computing isogenies between supersingular elliptic curves. For the LPS graphs, the underlying hard problem is a representation problem in group theory. Constructing our hash functions from optimal expander graphs implies that the outputs closely approximate the uniform distribution. This property is useful for arguing that the output is indistinguishable from random sequences of bits. We estimate the cost per bit to compute these hash functions, and we implement our hash function for several members of the Pizer and LPS graph families and give actual timings.     

The use of RO to remove emerging micropollutants following CAS/UF or MBR treatment of municipal wastewater

The removal of various organic micropollutants (OMPs), including six antibiotics (ERY, ROX, CLA, SMX, SMZ, and TMP), three pharmaceuticals (ibuprofen, salicylic acid, and diclofenac), one industrial product (BPA), and one hormone (cholesterol), was investigated in two pilot plants treating the same raw sewage of the Tel-Aviv WWTP. The effluent production by CAS-UF was 45 m³/h while that of MBR was 40 L/h. Each system's effluent constituted the feed for its RO, which comprised three RO steps after the CAS/UF and a semi-batch RO system after the MBR. Despite significant molecular differences between the selected OMPs, high removal rates were achieved after the RO stage (> 99% for macrolides, pharmaceuticals, cholesterol, and BPA, 95% for diclofenac, and > 93% removal of sulfonamides). However, low antibiotics concentrations and 28–223 ng/L residuals of ibuprofen, diclofenac, salicylic acid, cholesterol, and BPA in the MBR/RO and CAS-UF/RO permeates showed that although RO is an efficient removal solution, it cannot serve as an absolute barrier to OMPs. Therefore, additional treatment techniques should be considered to be incorporated aside the RO to ensure complete removal of such substances.     

A solar still augmented with a flat-plate collector

A single-stage, basin-type solar still and a conventional flat-plate collector were connected together in order to studythe effect of augmentation on the still under local conditions. The still inlet was connected to a locally made, fin-tube collector such that its outlet was fed to the still basin instead of the common storage tank. Measurements of various temperatures, solar intensities and distilled water productions were taken for several days at various operating conditions. Several modes of operation were studied: still connected to collector for a 24-h period; still connected only during sunlight hours from 8 am to 5 pm, and still operating alone for a 24-h period. These tests were performed using tap water and saline water as a feed. It was found that the mass of distilled water production using augmentation was increased by 231% in the case of tap water as a feed and by 52% in the case of salt water as a feed.     

A nondimensional analysis of dusty shock waves in steady flows

The governing equations describing the flow field which results when a dust-gas suspension passes through a normal shock wave were nondimensionalized. The nondimensionalization resulted in a set of nondimensional groups of parameters which, if kept constant, lead to a self-similar solution. An investigation of these nondimensional groups of parameters revealed, for example, that the relaxation length depends linearily on the material density of the solid particles. Dependence of the relaxation length on the other parameters of thd dust is discussed.     

The influence of P2O5 on clinker reactions

Synthetic clinkers, similar to high-silica Portland Cement clinkers, were prepared from raw material containing at times more than 50% oil shale from Har-Tuv area (central Israel) to which phosphate rock and laboratory grade CaCO₃ and SiO₂ were added. Although some clinkers contained more than 3% P₂O₅, their mineralogical composition was satisfactory (50 to 60% C₃S). This result was obtained by taking into account in the SM formula the P₂O₅ concentrations. The resultant relatively high silica concentrations raise the melting point of the raw meal, causing a non-equilibrium state which allows the formation of C₃S and its preservation.     

The microstructure and infra-red spectra of hydrated tricalcium silicate containing phosphate

The influence of phosphate, in the concentration range 0.7 to 4.5%, on the hydration reaction of tricalcium silicate was examined with a scanning electron microscope and an infra-red spectrometer. Correlation between the morphology and infra-red vibrations, on the one hand, and the free lime content dependence on the phosphate concentration, on the other, is discussed.This paper is in partial fulfilment of the MSc degree of Y. Rubinsztain, at the Hebrew University.