Sollicitations des murs en cas de dégradation locale du sol modélisée par la variation de la raideur du sol et de son volume

Résumé On présente birévement les effets de la dégradation du sol sur les structures murales. L'étude de cette dégradation est faite par modélisation de la variation de la raideur et du volume du sol. Les murs sont modélisés par un système de poutres ou paros fléchies, croisées dans le plan et posées sur semelles, pieux ou puits. Les modèles de l'interaction sol-murs présentés sont construits d'une manière récurrente et permettent d'analyser toutes les phases de la construction et de l'exploitation et tous les changements causés par les destructions, reconstructions ou reprises des murs. Ils doivent faciliter l'analyse et le choix de l'intervention de sauvegarde appropriée. Ils peuvent être aussi appliqués dans le cas de structures murales nouvelles, soumises aux effets de l'hétérogénéité du sol dans le plan et en fonction du temps.

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Summary This report presents the relationship between the local degradation of soil and the state of walls, together with possible preventative measures. The degradation is modelled by the spontaneous inplane and time-dependent variation of the stiffness and volume of soil. It should be defined at the instant when destruction is observed. The walls are modelled by a generally hyperstatic system of beams or walls under bending, crossed in plane and placed on continuous footings, piles or shafts. The real flexibility of this system which is variable over time is modelled by a particular combination of two limit states of wall behaviour, accompanied by a distribution of loads in two parts, according to the type of loads, walls and soil. One of these parts is attributed to the system mentioned, but assumed perfectly flexible. It has no effect on the system loads and acts on the soil-like pressure transferred directly. The other is attributed to the same system but assumed perfectly rigid. This part causes the bending and torsion of the system and acts on the soil indirectly following the intervention of the system. The same can be carefully calculated by keeping plane soil sections in this case to apply the idea of equivalence of stiffness and of the homogenized section of the foundation. Once the soil reactions and settlement are calculated, the system becomes isolated and externally isostatic and the loads, stresses, deformations and displacements can be calculated by applying one of the known structural design methods. The models of soil-structure interaction are set up in a recurrent way and it is possible to use them to analyse all the phases of construction and service and all the changes caused by destruction, reconstruction or underpinning. They should make analysis and the appropriate choice of the prevention measures easier. They can also be applied in the case of new walls, subjected to the effects of the heterogeneous nature of soil and as a function of time.

     

Bivalent peptides as models for multimeric targets of PDZ domains

PDZ domains are among the most common modules in eukaryotic, including human, genomes. They are found exclusively in large, multidomain cytosolic proteins--often with other domains that belong to a variety of families--and are involved in a plethora of physiological and pathophysiological events. PDZ domains mediate protein-protein interactions by binding to solvent-exposed and extended C-terminal short fragments of membrane-associated proteins, such as receptors and ion channels. Most of what is known about the mechanisms of target binding by PDZ domains is inferred from studies that involve isolated recombinant PDZ domains and short synthetic peptides that represent the targets. These binary systems constitute an obvious oversimplification and disregard factors such as noncanonical modes of binding and enhanced affinity due to multimeric interactions mediated by clusters and oligomers of PDZ-domain-containing proteins. We have tested whether the interaction between a dimeric form of PDZ domain that mimics a functional dimeric guanine nucleotide exchange factor, PDZ-RhoGEF (PDZ-containing RhoA-specific guanine nucleotide exchange factor) or LARG (leukemia-associated RhoA specific guanine nucleotide exchange factor), and a bivalent peptide that mimics the dimer of the plexin B receptor, could enhance the interaction between the two moieties. Peptide dimerization was achieved by cross-linking the N-terminal ends of peptides attached to Wang resin with poly(ethylene glycol) spacers (30-45 Angstroms in length). The interaction of dimeric PDZ domains with dimeric peptides resulted in an up to 20-fold increase in affinity compared to the simple binary system. This is consistent with the notion that multimerization of both receptors and PDZ-containing proteins might constitute an important regulatory mechanism.     

Agriculture Grade Ammonium Nitrate as the Basic Ingredient of Massive Explosive Charges

Prilled ammonium nitrate (AN) is manufactured globally in millions of tons and is mainly used as fertilizer or as the main ingredient of modern mining blasting explosives. The availability of AN poses a serious threat to public security as it enables preparation of massive explosive charges using a simple technology in order to carry out terrorist attacks. This paper examines the option of using agriculture AN manufactured in several Polish plants as the basic ingredient of explosive mixtures with liquid fuels or powdered aluminum. Fuel oil (FO), 2‐EHN and nitromethane were used as liquid fuels. Additionally, the effect of an inorganic additive (dolomite) in AN on the detonation velocity of mixtures of granulated and milled AN with various fuels was examined.     

Suitability of the milk of native breeds of cows from low‐input farms for cheese production,including rennet curd texture

The cheesemaking suitability of the milk of native cow breeds [Polish Red (RP) and White‐Backed (BG)] raised on low‐input farms was assessed. The milk of Polish Holstein‐Friesian cows raised in an intensive system constituted the reference group. Chemical composition, pH, rennet coagulation time, fat dispersion and curd texture were determined. The cows on the low‐input farms produced over 40% less milk, but with higher (P ≤ 0.01) fat content, shorter coagulation time by over 2 min and lower (P ≤ 0.05) fat dispersion. The curds from this milk were significantly springier, more cohesive and harder. The best milk indices were obtained for the RP cows.     

The Detonation Properties of Explosive-Water Mixtures

Mixtures of crystalline explosive and water have as a rule detonation properties different from the dry material. It has been shown that the character of those changes is closely related to the structure of the particles (crystals, granules) of the explosives. The critical diameters and detonation velocities have been measured for a range of explosive-water mixtures, and the results are interpreted in terms of the hotspot theory.