Effect of Cryogrinding on Physico-Chemical Properties of Drugs. II. Cortisone Acetate: Particles Sizes and Polymorphic Transition

The low temperature grinding (at 78 K) of cortisone acetate was carried out. From electron microscopy data, there were determined a form, mean linear sizes of particles and then specific surface was calculated. From X-ray data, a part of microcrystalline fraction in cryogrinded samples was calculated. As was indicated by X-ray data, the mechano-induced phase transition from “monoclinic” phase (form F_I) to “orthorhombic” one (form F_II) takes place as a result of I0-min grinding. The transition is confirmed by IR-spectroscopy results too. The local pressures induced by the mechanical stress seems to be the main cause of the phase transition observed.     

Elastoplastic analysis of layered materials under thermal loading: Edge cracks parallel to the interface

The present study is a fracture mechanics analysis of a layered bimaterial with sharp interface having a stationary edge crack parallel to the interface and subjected to monotonic variation in temperature. Elastic and incremental elastoplastic analyses are carried out to evaluate the energy release rate. Closed-form solutions are derived, as functions of the thermomechanical properties and the geometry of the layers, for different critical temperatures at which distinct transitions occur in the deformation due to thermal loading. Finite-element simulations are used to examine the influence of variation in thermo- mechanical properties of the layers with temperature, as well as the effects of finite geometry. The evolution and path dependency of the J-integral with variation in temperature is examined. Detailed finite-element results are presented for the technologically important Ni-Al₂O₃ bimaterial system. The effect of crack propagation is considered. This revised version was published online in August 2006 with corrections to the Cover Date.     

An efficient chemical systems modelling approach

Systems of stiff chemical reactions are often associated with atmospheric chemistry modelling, which plays a very important role in the studies of stratospheric ozone depletion, tropospheric air pollution problems, and future chemistry-climate feedbacks and interactions. This paper revisits an open-source stiff system solver SVODE and presents its efficient use in modelling different levels of complexity of a range of chemical systems. The chemical systems discussed here are the Lotka–Volterra (predator–prey) model, the Brusselator model, the Oregonator model, and the Lorenz model. The first two models consist of two variables, while the remaining two models consist of three variables. Finally, an application of this modelling approach to a generalised organic/NOx mechanism for characterising air pollution development is presented. Since the SVODE is an open-source code, and the simulations were run on a Linux PC (with g77 compiler), all results discussed in this paper can be easily reproduced. Most importantly, the approach shown here can be readily extended to other larger scale applications such as the three-dimensional air pollution modelling.     

Crack propagation in monolithic ceramics under mixed mode loading

Finite element calculations are presented for a semi-infinite crack in a brittle solid undergoing microcracking normal to the maximum tensile direction. Microcracks are presumed stable and a saturation stage is postulated wherein the effective elastic moduli attain steady state values. Mode I, mode II and mixed mode loading conditions are investigated. In these two latter cases, the method of analysis employed allows for cracks to grow out of their initial planes. The mixed mode loading case investigated corresponds to taking equal values of the remote mode I and II stress intensity factors. Contrary to what is observed in the mode I case, no appreciable R-curve behavior is found under mode II or mixed mode conditions.

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Résumé On présente des calculs par éléments finis pour une fissure semi-infinie dans un corps fragile comportant une micro-fissuration normale par rapport à la direction des tensions principales. On suppose que les microfissures sont stables et on postule un stade de saturation au cours duquel les modules d'élasticité atteignent des valeurs constantes. Les conditions de sollicitation en Mode I, et Mode II et en mode mixte sont étudiées et, dans les deux derniers cas, la méthode d'analyse utilisée autorise les fissures à croître hors de leur plant initial.Le mode mixte de mise en charge étudiée revient à prendre des valeurs égales pour les facteurs d'intensité des contraintes agissant à distance selon les Modes I et II.A l'inverse de ce que l'on observe dans le cas du Mode I, on ne trouve pas de comportement significatif selon une courbe R pour les conditions en Mode II et en mode mixte.

     

Mechanical behaviour of Zn–Fe alloy coated mild steel

Zinc alloy coatings containing various amounts of Fe were deposited by electrodeposition technique on a mild steel substrate. The concentration of Fe in the produced alloy coatings ranged from 0 to 14 wt.%, whereas the thickness of the coatings was about 50 μm. Structural and metallurgical characterization of the produced coatings was performed with the aid of X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) techniques. This study aims in investigating the mechanical behaviour of Zn–Fe coated mild steel specimens, as no research investigation concerning the tensile behaviour of Zn alloy coated ferrous alloys has been reported in the past. The experimental results indicated that the ultimate tensile strength of the Zn–Fe coated mild steel was lower than the bare mild steel. In addition, the ductility of the Zn–Fe coated mild steel was found to decrease significantly with increasing Fe content in the coating.     

An Autonomous System Supplied Only by a Pitch-Controlled Variable-Speed Wind Turbine

This paper presents a control strategy for a variable-speed pitch-controlled wind turbine (WT) generation scheme for the supply of an autonomous system with no energy storage units. The synchronous generator includes two three-phase stator windings displaced by 30deg that are connected to the transformer load through two dc links with voltage source inverters (VSI). Following priority rules, the load is divided into steps. Each load step can be supplied by the WT when the wind speed varies between two predefined speed levels. The first goal of the WT control system is to supply the load with constant real power under constant voltage as the wind speed varies between two levels and the second is to operate smoothly interchanging the load steps when the wind speed breaks through a speed level. There are two controllers: the inverter controller that keeps the load voltage constant and the pitch controller acting on the blade's angle. Using simulation techniques, the operation of the WT system and the efficiency of the proposed control strategy are demonstrated for a wide range of wind speeds.     

High strain sensitivity controlled by the surface density of platinum nanoparticles

We report a controllable strain gauge factor obtained using a two-dimensional nanoparticle layer formed from platinum nanoparticles. A vacuum technique is used for room temperature nanoparticle deposition that allows control of the electrical resistance of the film, exhibiting semiconducting-like behavior when nanoparticle arrays cover the surface below a threshold value while above it a metallic behavior is prevalent. The highest sensitivity is obtained for intermediate density values of the nanoparticle assemblies, which could be explained using a tunneling and hopping current expression. The device, which exhibits more than one order of magnitude higher strain sensitivity than continuous metallic films, is fabricated at room temperature through standard lithographic processing allowing for miniaturization and easy integration in silicon technology or flexible substrates.     

Neuroanatomic correlates of visual agnosia in Alzheimer's disease: a clinicopathologic study

Adeno-associated virus 2 (AAV)-based vectors have gained attention as a potentially useful alternative to the more commonly used retroviral and adenoviral vectors for human gene therapy. Although AAV uses the ubiquitously expressed cell surface heparan sulfate proteoglycan (HSPG) as a receptor, the transduction efficiency of AAV vectors varies greatly in different cells and tissues in vitro and in vivo. We demonstrate here that cell surface expression of HSPG alone is insufficient for AAV infection, and that AAV also requires human fibroblast growth factor receptor 1 (FGFR1) as a co-receptor for successful viral entry into the host cell. We document that cells that do not express either HSPG or FGFR1 fail to bind AAV and, consequently, are resistant to infection by AAV. These non-permissive cells are successfully transduced by AAV vectors after stable transfections with cDNAs encoding the murine HSPG and the human FGFR1. Furthermore, AAV infection of permissive cells, known to express both FGFR1 and the epidermal growth factor receptor, is abrogated by treatment of cells with basic fibroblast growth factor, but not with epidermal growth factor. The identification of FGFR1 as a co-receptor for AAV should provide new insights not only into its role in the life cycle of AAV, but also in the optimal use of AAV vectors in human gene therapy.     

Revisiting the effect of history on learning performance: the problem of the demanding lord

In a variety of settings ranging from recommendation systems to information filtering, approaches which take into account feedback have been introduced to improve services and user experience. However, as also indicated in the machine learning literature, there exist several settings where the requirements and target concept of a learning system changes over time, which consists a case of “concept drift”. In several systems, a sliding window over the training instances has been used to follow drifting concepts. However, no general analytic study has been performed on the relation between the size of the sliding window and the average performance of a learning system, since previous works have focused on instantaneous performance and specific underlying learners and data characteristics. This work proposes an analytic model that describes the effect of memory window size on the prediction performance of a learning system that is based on iterative feedback. The analysis considers target concepts changing over time, either periodically or randomly, using a formulation termed “the problem of the demanding lord”. Using a signal-to-noise approach to sketch learning ability of underlying machine learning algorithms, we estimate the average performance of a learning system regardless of its underlying algorithm and, as a corollary, propose a stepping stone toward finding the memory window that maximizes the average performance for a given drift setting and a specific modeling system. We experimentally support the proposed methodology with very promising results on three synthetic and four real datasets, using a variety of learning algorithms including Support Vector Machines, Naive Bayes, Nearest Neighbor and Decision Trees on classification and regression tasks. The results validate the analysis and indicate very good estimation performance in different settings.     

Infertility and multiple urogenital abnormalities in a male with mosaic 46,XY/45,XO/47,XXY karyotype and mixed phenotype

The effect of infusing the neuroactive steroids pregnanolone and iso-pregnanolone on somatosensory evoked potentials (SEP) and electrocortical (ECoG) activity was studied in unanaesthetised fetal sheep, 130-135 days gestation. Intravenous infusion of pregnanolone (6 mg/kg per h) significantly increased the proportion of high voltage ECoG (56.1+/-4.8% vs. control 43.5+/-3.2%, P < 0.05), and decreased low voltage ECoG (43.9+/-4.8% vs. control 56.6+/-3.2%, P < 0.05). Pregnanolone treatment decreased the amplitude of the N25 peak of the SEP (89.9+/-2.8% of control, P < 0.05) evoked following stimulation of the skin of the upper lip. In contrast, iso-pregnanolone treatment had no effect on ECoG activities, or on the amplitude and latency of peaks in the SEP. We conclude that 3alpha-hydroxy pregnane steroids are active at GABA(A) receptors in fetal sheep and can modulate sleep/wake activity before birth.