Experimental studies on shear failure of freeze-bonds in saline ice: Part I. Set-up, failure mode and freeze-bond strength

The strength of freeze-bonds in thin saline ice has been investigated through two series (in 2008 and 2009) of experiments in the Hamburg Ship Model Basin (HSVA) as a function of the normal confinement (σ), the submersion time (Δt) and the initial ice temperature (T_i). The freeze-bonds were mostly formed in a submerged state, but some were also formed in air. The experimental set-up was improved in the 2009 experiments. In 2008 a ductile-like failure mode dominated (78%), whereas in 2009 the brittle-like dominated (93%). We suggest that this is a combined ice and test set-up effect. The 2009 experimental procedures allowed for careful sample handling giving higher strength and it was softer. Both these things should provoke a more brittle-like force-time response. The average freeze-bond strength in brittle-like samples was around 9 kPa while in ductile-like samples was around 2 kPa. The maximum freeze-bonds strength were measured for short submersion times, from 1 to 20 min, and reached a maximum value of 30 kPa.A Mohr-Coulomb like failure model was found appropriate to represent the freeze-bond shear strength as function of the normal confinement. Saline freeze-bonds in saline water had cohesion/friction angle around 4 and 1.4 kPa/25° for the brittle- and ductile-like samples respectively, which fitted well with previously published data.A bell-shape dependence for τ_c vs. Δt was found, which agreed with the predictions by Shafrova and Høyland (2007). We suggest that this is essentially a freeze-bond porosity effect and propose three phases in time with subsequent cooling, heating and equilibrium to account for this trend. Qualitative experiments showed that the submersion time and the initial ice temperature were strongly coupled.To account for the connection between contact time, block dimensions and ice properties and the freeze-bond strength, dimensionless number were used. Fourier scaling was more appropriate than Froude scaling to scale freeze-bonds.The freeze-bonding made in air developed fast (in less than 30 s) when the ice was cold and dry, but no freeze-bonding occurred for the same contact times when the ice was warm and wet.     

A direct link between gaze perception and social attention.

How information is exchanged between the cognitive mechanisms responsible for gaze perception and social attention is unclear. These systems could be independent; the “gaze cueing” effect could emerge from the activation of a general-purpose attentional mechanism that is ignorant of the social nature of the gaze cue. Alternatively, orienting to social gaze direction might be directly determined by the operation of cognitive mechanisms specifically dedicated to gaze perception. This second notion is the dominant assumption in the literature, but there is little direct support for this account. Here, we systematically manipulated observers' perception of gaze direction by implementing a gaze adaptation paradigm. Gaze cueing was reduced only in conditions where perception of specific averted gaze stimuli was impaired (Experiment 1). Adaptation to a pointing stimulus failed to impact gaze cueing (Experiment 2). Overall, these data suggest a direct link between the specific operation of gaze perception mechanisms and the consequential orienting of attention. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

The Combination of the M2 Muscarinic Receptor Agonist and Chemotherapy Affects Drug Resistance in Neuroblastoma Cells

One of the major limits of chemotherapy is depending on the ability of the cancer cells to elude and adapt to different drugs. Recently, we demonstrated how the activation of the M2 muscarinic receptor could impair neuroblastoma cell proliferation. In the present paper, we investigate the possible effects mediated by the preferential M2 receptor agonist arecaidine propargyl ester (APE) on drug resistance in two neuroblastoma cell lines, SK-N-BE and SK-N-BE(2C), a sub-clone presenting drug resistance. In both cell lines, we compare the expression of the M2 receptor and the effects mediated by the M2 agonist APE on cell cycle, demonstrating a decreased percentage of cells in S phase and an accumulation of SK-N-BE cells in G1 phase, while the APE treatment of SK-N-BE(2C) cells induced a block in G2/M phase. The withdrawal of the M2 agonist from the medium shows that only the SK-N-BE(2C) cells are able to rescue cell proliferation. Further, we demonstrate that the co-treatment of low doses of APE with doxorubicin or cisplatin significantly counteracts cell proliferation when compared with the single treatment. Analysis of the expression of ATP-binding cassette (ABC) efflux pumps demonstrates the ability of the M2 agonist to downregulate their expression and that this negative modulation may be dependent on N-MYC decreased expression induced by the M2 agonist. Our data demonstrate that the combined effect of low doses of conventional drugs and the M2 agonist may represent a new promising therapeutic approach in neuroblastoma treatment, in light of its significant impact on drug resistance and the possible reduction in the side effects caused by high doses of chemotherapy drugs.     

Small Molecule Receptor Binding Inhibitors with In Vivo Efficacy against Botulinum Neurotoxin Serotypes A and E

Botulinum neurotoxins (BoNTs) are the most poisonous substances in nature. Currently, the only therapy for botulism is antitoxin. This therapy suffers from several limitations and hence new therapeutic strategies are desired. One of the limitations in discovering BoNT inhibitors is the absence of an in vitro assay that correlates with toxin neutralization in vivo. In this work, a high-throughput screening assay for receptor-binding inhibitors against BoNT/A was developed. The assay is composed of two chimeric proteins: a receptor-simulating protein, consisting of the fourth luminal loop of synaptic vesicle protein 2C fused to glutathione-S-transferase, and a toxin-simulating protein, consisting of the receptor-binding domain of BoNT/A fused to beta-galactosidase. The assay was applied to screen the LOPAC1280 compound library. Seven selected compounds were evaluated in mice exposed to a lethal dose of BoNT/A. The compound aurintricarboxylic acid (ATA) conferred 92% protection, whereas significant delayed time to death (p < 0.005) was observed for three additional compounds. Remarkably, ATA was also fully protective in mice challenged with a lethal dose of BoNT/E, which also uses the SV2 receptor. This study demonstrates that receptor-binding inhibitors have the potential to serve as next generation therapeutics for botulism, and therefore the assay developed may facilitate discovery of new anti-BoNT countermeasures.     

Nantucket pine tip moth,Rhyacionia frustrana: Identification of two sex pheromone components

Two compounds identified as components of the sex pheromone system ofRhyacionia frustrana are (E)-9-dodecen-1-yl acetate (I) and (E)-9,11-dodecadien-1-yl acetate (II), which were found in female gland extracts in the ratio of 964, respectively. The identifications were based on chemical and instrumental analyses, electroantennogram studies, and field trapping tests. The optimum ratio for trapping maleR. frustrana is the range of 955 to 97.52.5 (III), when dispensed from rubber septa at a loading of ca. 1000/g/lure. In addition to these two compounds, evidence was obtained for the presence of dodecan-1-ol and (E)-9-dodecen-1-ol in female tip extracts and in female effluvium, and for dodecan-1-yl acetate in female tip extracts.Lepidoptera: Tortricidae: Olethreutinae.Supported in part by the Rockefeller Foundation and by National Science Foundation grants GB-38020 and PCM 78-13241.     

Magnetic Resonance Imaging of Strawberry (Fragaria vesca) Slices During Osmotic Dehydration and Air Drying

The aim of this study was to develop experience in acquiring water mobility and moisture data that could be used to develop improved models for predicting water loss during osmotic dehydration and/or air-drying. One-dimensional magnetic resonance imaging protocols were used to follow temporal and spatial changes in water mobility via T₂ profiles, water content via M₀ profiles, and structural shrinkage of strawberry slices during osmotic dehydration with 600 g/kg aqueous sucrose over 2 h. Those measurements were also made for 1 h during air-drying of normal and osmotically dried slices at 20, 30, 45 and 60 °C. Air-drying above 20 °C resulted in changes in the strawberry matrix, which suggests the need for a model that incorporates the interaction between the strawberry tissue and the water that diffuses during drying. Modelling of the air-drying of osmotically pretreated slices would be complicated by the variable amounts of sucrose solution remaining after osmotic dehydration.     

Integration and efficient lookup of compressed XML accessibility maps

XML is emerging as a useful platform-independent data representation language. As more and more XML data is shared across data sources, it becomes important to consider the issue of XML access control. One promising approach to store the accessibility information is based on the CAM (compressed accessibility map). We make two advancements in this direction: 1) Previous work suggests that for each user group and each operation type, a different CAM is built. We observe that the performance and storage requirements can be further improved by combining multiple CAMs into an ICAM (integrated CAM). We explore this possibility and propose an integration mechanism. 2) If the change in structure of the XML data is not frequent, we suggest an efficient lookup method, which can be applied to CAMs or ICAMs, with a much lower time complexity compared to the previous approach. We show by experiments the effectiveness of our approach.     

An efficient implementation of PRNGs based on the digital sawtooth map

In this paper, the sawtooth map digitally implemented is analysed to evaluate its suitability for pseudo‐random binary numbers generation. Period and statistical properties of the sequences generated by the digital map are evaluated versus arithmetic precision, approximation strategy and characteristic parameter of the map. In general, the digital implementation of the sawtooth map requires the use of a multiplier, which is quite expensive in terms of gate count. However, results show that values of design parameters that lead to adequate statistical features and to a relatively high period also allow for significantly reducing the complexity required in the implementation. To better evaluate performance of the digital sawtooth map as a pseudo‐random number generator, it is compared to a linear feedback shift register with the same number of flip‐flops, which is well known for its output sequences with a long period, appealing statistical quality, and for a reduced gate count. Performance comparison and implementation on a programmable logic device show that the digital sawtooth map is suitable for pseudo‐random number generation, also requiring a relatively small amount of hardware. Copyright © 2004 John Wiley & Sons, Ltd.