Requirement for multiple lymphocyte subsets in protection by a live attenuated vaccine against retroviral infection

STUDY DESIGN: A case report and literature review of thoracic hyperkyphosis deformity secondary to glucocorticoid-induced osteoporosis in Cushing's disease. OBJECTIVES: To identify the pathophysiology of glucocorticoid-induced osteoporosis and to outline the diagnosis and treatment options for a patient with severe spinal deformity secondary to unrecognized excess glucocorticoid activity. SUMMARY OF BACKGROUND DATA: Glucocorticoid-induced osteoporosis is seen in patients exposed to supraphysiologic levels of endogenous or exogenously administered glucocorticoids. In these patients, glucocorticoids act to suppress bone formation and increase bone resorption by indirect and direct effects. These patients have a high prevalence of trabecular bone loss, resulting in much higher rates of vertebral body collapse and pathologic fracture and thus causing an increased propensity toward kyphotic spinal malalignment. METHODS: The literature was reviewed and case reports studied. This case report highlights the pathophysiology of the disease process that caused the spinal deformity and the surgical intervention used to correct the kyphotic deformity after the metabolic problem was resolved. RESULTS: This patient has responded well to treatment and surgical intervention to correct a thoracic hyperkyphotic deformity without complication. CONCLUSIONS: Unrecognized endogenous production of glucocorticoids in Cushing's disease should be considered in young adult patients with progressive osteoporotic spinal deformities.     

The crystal structure of human procathepsin K

Cathepsin K is a cysteine protease present in human osteoclasts that plays an important role in bone resorption. Cathepsin K is synthesized as an inactive proenzyme and activated under conditions of low pH. Autoproteolytic processing of the N-terminal 99 amino acid propeptide produces the active, mature form of cathepsin K. It is presumed that the activation of procathepsin K in vivo occurs in the bone resorption pit, which has a low-pH environment. We have determined the structure of human procathepsin K at 2.8 A resolution. The structure of the mature enzyme domain within procathepsin K is virtually identical to that of mature cathepsin K. The fold of the propeptide of procathepsin K is similar to that observed in procathepsins B and L despite differences in length and sequence. A portion of the propeptide occupies the active site cleft of cathepsin K. Hydrophobic interactions, salt bridges, and hydrogen-bonding interactions are observed in the structure of the propeptide and between the propeptide and the mature enzyme of procathepsin K. These interactions suggest an explanation for the stability of the proenzyme. The structure of procathepsin K contributes to an understanding of the molecular basis of inhibition by the propeptide portion of the molecule and activation of this important member of the cysteine protease family.     

An inverse problem analysis for the determination of probalistic parameters of concrete behavior modeled by a statistical approach

When the Monte Carlo method is used to simulate the heterogeneous behavior of concrete in the framework of a finite element probabilistic analysis, N samples of the vector of random variables (tensile strength, Young's modulus, etc.) are generated from a specific probability density function. If the uncertainties of these material parameters are assumed to vary spatially following a normal distribution, the N samples corresponding to a simulation are function of the mean and the standard deviation that define the Gauss density function. The problem is that these statistical moments are not known,a priori, for the characteristic volume of the finite elements for which the problem has been discretized. In this paper an algorithm is proposed to evaluate the parameters characterizing the statistical distribution (e. g. for a normal distribution: the mean and the standard deviation) for a given response of the structure (for instance, a mean load-displacement curve) following an inverse analysis procedure. A very simple mechanical system is used to verify the feasibility of the procedure. By way of example, it is shown that this kind of inverse problem for the identification of statistical parameters is suitable for concrete.

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Résumé Si la méthode de Monte-Carlo est utilisée pour simuler l'hétérogénéité du béton dans le cadre d'une analyse probabiliste par éléments finis, N échantillons du vecteur des variables aléatoires (résistance à la traction, module d'Young, etc.) sont générés à partir d'une fonction de densité de probabilité donnée. Si la dispersion de ce matériau peut être représentée par une distribution normale, les N échantillons correspondant à une simulation, sont fonction de la moyenne et de l'écart type qui définissent la fonction de densité de Gauss. Le problème c'est que ces moments statistiques ne sont pas connus,a priori, pour le volume caractéristique des éléments finis selon lesquels le problème a été discrétisé. Dans cet article, on propose un algorithme pour l'évaluation des paramètres qui caractérisent la distribution statistique (comme exemple, pour une distribution normale: la moyenne et l'écart type) correspondant à la réponse donnée d'une structure (par exemple: une courbe force-déplacement) suivant un processus d'analyse inverse. Un système mécanique très simple est utilisé pour vérifier la faisabilité du processus. Il est montré, à partir d'un exemple, que ce type d'analyse inverse peut être utilisé pour le béton.

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Editorial note COPPE/UFRJ and LCPC are RILEM Titular Members.     

Numerical simulation of dam construction using low-CO<Subscript>2</Subscript>-emission concrete

Cement production gives rise to CO₂ emissions generated by the calcination of CaCO₃ and by the combustion of fossil fuels, being responsible for about 5% of the global CO₂ emissions. These emissions can be substantially reduced if cement replacement materials are used. In this paper two residual ashes that can be used as mineral additions are considered: sugar cane bagasse ash and rice husk ash. A case study of the construction of a dam with a blended material composed by cement and these two ashes is presented, indicating the potentiality of its use for civil engineering applications. The analyses were performed using experimental and numerical tools developed on the basis of a thermo-chemo-mechanical model. This model considers the coupling, within the theory of thermodynamics, of the several phenomena that intervene in the hydration process, namely, exothermicity, thermo-activation, chemo-plasticity, evolution of thermal and mechanical properties with the hydration reaction, which includes creep and relaxation.     

Tinnitus: etiology and management

Tinnitus is the perceived sensation of sound in the absence of acoustic stimulation. Individuals who suffer from it are commonly between the ages of 40 and 80 years. Tinnitus is often classified as objective or subjective, yet the pathophysiologic cause is still unknown. Subjective tinnitus is largely identified with hearing loss. Management of tinnitus is based on an individual approach; there is no single treatment or regimen for it.     

Performance evaluation of cement mortars modified with metakaolin or ground brick

The work analyzes the performance of mortars prepared with two metakaolin samples and ground calcined-clay brick. Complete stress–strain deformation response under compression, porosity, sorptivity, pore size distribution and resistance to penetration of chloride ions have been determined for mortars with up to 40% cement replacement. Continuum damage mechanics analyzes using a scalar model allowed to extract information on the mode of deformation leading to failure of the mortars during compressive loading. It is shown that not only the ultimate strength, but also the pre-peak deformation response is influenced by calcined-clay addition. The ultimate strength of the mortar mixture depended on the type of calcined-clay added, but in all cases mortars with addition were marginally more compliant during the elastic deformation stage and more brittle as fracture approached.     

Use of computed radiography in the study of an historic painting

The authors demonstrate the use of radiography in the investigation of an historic painting and describe the potential benefits of computed radiography compared with conventional screen-film radiography. The subject for the comparison was a 16 x 19-foot oil-on-canvas painting, Scipio Africanus Freeing Massiva, by Giovanni Battista Tiepolo. Radiographs of the painting were obtained by using a portable, industrial radiographic unit and both conventional screen-film and photostimulable phosphor plate cassettes. For this investigation, computed radiography had a number of advantages over screen-film radiography, largely due to its wider dynamic range and its capabilities for enhancing the digital images with image processing tools such as magnification, edge enhancement, colorization, and airbrushing. The ability to electronically combine images from the large painting into a single composite image file was extremely valuable, as this technique was much less cumbersome and resulted in much higher quality composite images than could be achieved with conventional radiography. An additional advantage of computed radiography includes the capability to easily archive and transmit these images in a digital format for subsequent review.