Performance Evaluation of Packet Mobile Communications through Level Crossing Analysis

In this paper the performance of a packet mobile radio network is studied inthe presence of shadow fading outage intervals.Under quite general assumptions for the medium access protocol,the probability mass function of the sequence of packets that may be lostdue to an outage interval is derived. It is seen that long sequences of lostpackets are likely to occur for typical values of the mobile speed andshadowing correlation parameters.For delay constrained sources, e.g., voice, the analysis is mainly focused atderiving the probability function of the sequence of dropped packetsand the probability of dropping. For data sources, the delay statistic isalso derived. In the latter case, the effect of finite buffer length isaddressed. Simulation is used to verify the accuracy of approximations introduced in the analysis.     

Primary lymphoma of the breast. Three cases of non-Hodgkin lymphoma

Primary and sole breast lymphoma is a very rare disease. With the review of our series of 616 cases operated on for breast cancer, only 3 cases (0.48%) of primary breast non-Hodgkin lymphoma (LNH) have been observed. The authors outline the problems concerning diagnosis and therapy of this rare disease: pathological and immunohistochemical aspects are discussed. They stress the importance of staging in order to plan a correct multidisciplinary approach.     

Spinal reflex pattern to foot nociceptive stimulation in standing humans

We describe here the results of a screening program conducted to discover inhibitors of the type-I interleukin-1 receptor (IL-1RI) from samples of microbial origin. An innovative approach, based on automated, nonradioactive receptor binding assays has been employed. Specially prepared cell-free systems have allowed the use of high concentrations of microbial metabolites in the reaction mixtures with a low percentage of false positives. More than 30,000 microbial samples from different species of soil isolates have been tested and two interesting activities have been purified and characterized. One of these, isolated from Streptomyces sp. GE48009, was identified as niphimycin, an antifungal agent also known as scopafungin. Preliminary evidence suggests that this molecule and azalomycin F, a structural analogue, inhibit IL-IRI by virtue of their long-chain guanidinium moiety. The other activity, isolated from Aspergillus sp. GE49752, was identified as flavipin, a substituted o-phthalaldehyde.     

A multivariate classification of individual household census data for Italy

Never before have regional scientists had access to individual census data for an entire country. The paper describes the application of a taxonomic procedure to classify the 15.6 million households identified by the 1971 Italian census. The results are important both for what they reveal about Italian social structure and because they provide a basis for a constructing aggregate census data so that within area variations are retained.     

A new experimental approach to the investigation of contact forces at an interface

The piezoelectric films recently developed permit the design of very efficient thin sensors which are suited to interesting applications in contact problems, not only in industrial robotics but also in experimental research. After a brief introduction exemplifying the electrical principles, the primary aspects of the technique are presented and discussed with reference to possible structural engineering applications. A rather simple example regarding the interaction between a steel bar and a block of concrete is also presented. The bar is excited by dynamic cyclic loads having variable frequency. The reliability of forces detected via a PVDF sensor is evaluated by comparing the results with those obtained in parallel by means of a dynamometer strain-gauge. The comparison is promising, even if some technological problems must be resolved before this experimental technique may be applied extensively.

---

Resume L'étude expérimentale des forces qui se manifestent à une interface équivaut souvent à un problème technique insoluble car chaque appareillage influe de manière significative sur le comportement mécanique. En outre, si l'interface se situe dans un continuum, l'utilisation de transducteurs ou d'extensomètres devient aussi plus complexe. Dans tous les cas, les mesures peuvent se faire éventuellement à proximité de l'interface, mais non à l'interface. Des améliorations techniques récentes dans le domaine de la robotique permettent d'utiliser des films de polymères piézoélectriques (fluoride de polyvinylidène, PVDF). En raison de l'épaisseur de ce capteur qui ne dépasse pas quelques micromètres, le comportement mécanique n'est pas perturbé. Le principle électrique est typique du transducteur piézoélectrique: les charges crées par le film piézoélectrique sollicité sont concentrées sur les surfaces métallisées qui le recouvrent. Cette technique permet d'étudier de nombreux problèmes structurels. S'il s'agit de béton armé, par exemple, il est intéressant d'examiner la répartition de la pression sur un appui de poutre ou bien à la surface d'un boulon d'ancrage, les contraintes interfaciales aussi bien d'une barre d'armature chargée axialement et transversalement, que de goujons dans des structures composites. Un exemple simple montre la fiabilité de la nouvelle technique: une haute barre d'adhérence enrobée dans un bloc de béton est mise sous charge dynamique. On compare la force détectée par le capteur PVDF placé à l'interface barre d'acier-barre d'enrobage avec celle qui est mesurée au moyen du dynamomètre traditionnel placé parallèlement au support. La comparaison, établie à différentes fréquences, est satisfaisante. Cependant, pour utiliser cette nouvelle technique sur une grande échelle, il convient de résoudre quelques problèmes techniques: l'améioration de la conductivité électrique des connexions entre les surfaces métallisées de la couche sensible et les fils d'entrée et de sortie la prévention d'une éventuelle perforation du film par des particules de granulats siliceux qui sont un des constituants de base des mortiers et bétons; l'évaluation de la sensibilité d'un capteur multicouches à l'écrasement inévitable du matériau à proximité d'une barre d'acier, avec une microfissuration locale et un glissement limité. La recherche se poursuit tant au niveau technologique qu'électronique.

     

The structure of serine hydroxymethyltransferase as modeled by homology and validated by site-directed mutagenesis

We describe a model for the three-dimensional structure of E. coli serine hydroxymethyltransferase based on its sequence homology with other PLP enzymes of the alpha-family and whose tertiary structures are known. The model suggests that certain amino acid residues at the putative active site of the enzyme can adopt specific roles in the catalytic mechanism. These proposals were supported by analysis of the properties of a number of site-directed mutants. New active site features are also proposed for further experimental testing.     

Enhancement Effects in the Percutaneous Absorption of Alprazolam Through Human Skin in vitro

The enhancement effects of some chemicals on the percutaneous absorption of alprazolam through human skin was investigated in vitro. Linoleic acid, oleic acid, Comperlan F® (linoleic acid diethanolamide), Comperlan KD® (coconut fatty acid diethanolamide) and Ethomeen C12® (bis-(2-hydroxyethyl)cocamine) were evaluated for their enhancing effect either as neat solvents or combined with propylene glycol. The effects of skin pretreatment with the enhancers on the percutaneous absorption of alprazolam from a drug suspension in an aqueous gel were also investigated: skin pretreatment with some enhancers has shown potentially interesting aspects. The determination of alprazolam partitioning into untreated and pretreated horny layer supported the idea that, with oleic and linoleic acid, a contribution to the modification of the diffusional resistance of the skin was given by an increase of the drug solubility in the stratum coraeum.     

Magnetic resonance features of supravalvular aortic stenosis in William''s syndrome. Report of 2 cases

A wandering spleen and splenic cysts are uncommon conditions in children. A combination of both entities has only rarely been reported in the literature. Another case of this complex pathology in 12-year-old girl is presented. She was initially referred for evaluation of a large abdominal mass. Diagnostic studies raised the suspicion of a hematoma in an abnormally located spleen, but the definitive diagnosis was established at laparotomy. Successful surgical management consisted of total cystectomy and splenopexy.     

New accurate two-noded shear-flexible curved beam elements

 There are two purposes of this work. One is to present two accurate two-noded finite elements which are derived from the potential energy principle and the Hellinger–Reissner functional principle respectively. The second is to show the successful application of the internal displacement parameters in developing a high-order related displacement-rotation interpolation field. Because the derived interpolation field is capable of accurately modeling deformation modes in extreme thin curved beams and nearly straight beams, both shear locking and membrane shocking are avoided. Several standard numerical tests display superior behaviors of the present elements. Received: 5 February 2002 / Accepted: 16 September 2002     

热轧带钢连续冷却过程中相变体积分数的计算

基于相变动力学原理 ,在充分考虑变形对相变影响的情况下研究了奥氏体向铁素体、珠光体和贝氏体相变的动力学。探索了热轧带钢连续冷却过程中相变体积分数的计算方法。用此方法进行的计算机模拟与实验结果相当吻合。