Chalcogenide Glasses Based on Germanium Disulfide for Second Harmonic Generation

High second‐order susceptibilities are created by thermal poling in bulk germanium disulfide based chalcogenide glasses. Experimental conditions of the poling treatment (temperature, voltage, time) were optimized for each glass composition. The second‐order nonlinear signals were recorded by using the Maker fringes experiment and a second‐order coefficient χ⁽²⁾ up to 8 pm V^–1 was measured in the Ge₂₅Sb₁₀S₆₅ glass. This value is obtained using a simulation based on accurate knowledge of the thickness of the nonlinear layer. Two mechanisms are proposed to explain the creation of a nonlinear layer under the anode: the formation and the migration of charged defects towards the anode may mainly occur in Ge₂₀Ga₅Sb₁₀S₆₅ and Ge₂₅Ga₅S₇₀ glasses, whereas the migration of Na⁺ ions towards the cathode may be responsible for the accumulation of negative charges under the anode in Ge₃₃S₆₇ and Ge₂₅Sb₁₀S₆₅ glasses. Different electronic conductivity behaviors seem to be at the origin of the phenomenon. In parallel, the potential effect of the poling treatment on the structural and electronic properties is studied using Raman spectroscopy and secondary ion mass spectroscopy measurements.     

Hypersensitivity to airborne allergens common in the central region of Coahuila

A retrospective review of 247 clinical files of patient that have responded to the office allergy and immunology since 1990 to 1993 in Monclova, Coah., for allergy illness. This study was to determine the frequency of Aeroalergens and foods sensitization in Monclova, Coahuila, mediated Allergy Test Skin (intradermo reactions, and Prick) and MAST immuno Systems (Multiple Allergy System Test). The patients were highly sensitive to house dust (13.5%) others aeroalergen pollen grains, were; rusian thistle (7.1%), Pigweed (5.4%), Cynodon Dactylon (4.9%), Pecan (4.8%), Ragweed Mix (4.8%), Rye grass (4.8%) other polen (32.4%). The molds: Candida (3.2%), Alternaria (2.7%), Rhizopus (3.6%), Penicillium (2.1%), Fusarium (2.1%), other molds (8.7%). The foods more important were: Wheat (21.3%), Cheese (10.0%), Shellfish Mix (10.0%), Pork (8.8%), Egg Yolk (7.5%).     

The action of local anesthetics on myelin structure and nerve conduction in toad sciatic nerve

X-ray scattering and electrophysiological experiments were performed on toad sciatic nerves in the presence of local anesthetics. In vitro experiments were performed on dissected nerves superfused with Ringer's solutions containing procaine, lidocaine, tetracaine, or dibucaine. In vivo experiments were performed on nerves dissected from animals anesthesized by targeted injections of tetracaine-containing solutions. In all cases the anesthetics were found to have the same effects on the x-ray scattering spectra: the intensity ratio of the even-order to the odd-order reflections increases and the lattice parameter increases. These changes are reversible upon removal of the anesthetic. The magnitude of the structural changes varies with the duration of the superfusion and with the nature and concentration of the anesthetic molecule. A striking quantitative correlation was observed between the structural effects and the potency of the anesthetic. Electron density profiles, which hardly showed any structural alteration of the unit membrane, clearly indicated that the anesthetics have the effect of moving the pairs of membranes apart by increasing the thickness of the cytoplasmic space. Electrophysiological measurements performed on the very samples used in the x-ray scattering experiments showed that the amplitude of the compound action potential is affected earlier than the structure of myelin (as revealed by the x-ray scattering experiments), whereas conduction velocity closely follows the structural alterations.     

Low-resolution structures of proteins in solution retrieved from X-ray scattering with a genetic algorithm

Small-angle x-ray solution scattering (SAXS) is analyzed with a new method to retrieve convergent model structures that fit the scattering profiles. An arbitrary hexagonal packing of several hundred beads containing the problem object is defined. Instead of attempting to compute the Debye formula for all of the possible mass distributions, a genetic algorithm is employed that efficiently searches the configurational space and evolves best-fit bead models. Models from different runs of the algorithm have similar or identical structures. The modeling resolution is increased by reducing the bead radius together with the search space in successive cycles of refinement. The method has been tested with protein SAXS (0.001 < S < 0.06 A(-1)) calculated from x-ray crystal structures, adding noise to the profiles. The models obtained closely approach the volumes and radii of gyration of the known structures, and faithfully reproduce the dimensions and shape of each of them. This includes finding the active site cavity of lysozyme, the bilobed structure of gamma-crystallin, two domains connected by a stalk in betab2-crystallin, and the horseshoe shape of pancreatic ribonuclease inhibitor. The low-resolution solution structure of lysozyme has been directly modeled from its experimental SAXS profile (0.003 < S < 0.03 A(-1)). The model describes lysozyme size and shape to the resolution of the measurement. The method may be applied to other proteins, to the analysis of domain movements, to the comparison of solution and crystal structures, as well as to large macromolecular assemblies.     

Metastatic brain involvement in Ewing family of tumors in children

OBJECTIVE: To evaluate the incidence and clinical characteristics of CNS involvement in Ewing family of tumors (EF) in children. METHODS: Chart reviews of children with EF treated in our center from 1972 to 1997. Clinical and imaging data regarding possible CNS involvement were collected. RESULTS: During this 25-year period, 80 children with EF were treated. Intracranial involvement was found in eight (10%) children: the brain was involved in seven children (8.8%) and a retro-orbital metastasis without parenchymal brain involvement was noted in one child. Metastases were localized intrahemispherically, or in the cerebellum or the basal ganglia. Intracranial spread was hematogenous in five children and by contiguous spread from the skull in three children. Intracranial involvement was diagnosed 1.3 to 11 years from initial presentation. Seizures and hemiparesis were the main neurologic complications. CONCLUSIONS: The rate of parenchymal brain involvement in our patients with EF was 8.8%. Spread was mainly hematogenous. Substantial morbidity was associated with CNS disease, which appeared in most patients late in the course of disease.     

Bimanual mirror letter writing: a post-traumatic case

Mirror writing is inverse writing that can only be read with the help of a mirror. It is generally associated with dominant hemisphere lesions and affects only one hand. We describe the case of a patient who, after cranial injury, developed bimanual mirror writing for letters but no other focal neurological symptom. The only abnormal complementary finding was a zone of left parieto-occipital hypoperfusion visibly by SPECT. No signs of psychological disorder were present to which the dysgraphia could be attributed. Symptoms disappeared after three months. We conclude that isolated bimanual mirror letter writing may be an expression of reversible parieto-occipital dysfunction of the dominant hemisphere.     

An approximate nonlinear design procedure for partially prestressed concrete beams

The theoretical basis and the main results of an approximate nonlinear design procedure which attempts to predict the behavior at ultimate of prestressed and partially prestressed concrete members is presented. Difficulties encountered in simulating the actual behavior of concrete and steel are discussed; particular emphasis is put on comparing the various available stress-strain relationships for prestressing steels, and observed variability in their actual properties. Recommended equations and corresponding coefficients are given. Typical results showing the influence on ultimate behavior of major variables such as the type and amount of prestressing steel, the amount of nonprestressed tensile and compressive reinforcement, and the ultimate concrete compressive strain are presented and compared with code derived results. They help point out where the code recommendations, if used, may lead to an unsafe design and what modifications may be needed to make them more representative of observed trends.     

Examination of Aluminum Corrosion Products in Marine or Industrial Marine Atmosphere

A method has been developed to characterize the passivation film formed on aluminum in marine atmosphere, whether polluted or not by sulphur oxides and fluorides The information thus obtained was integrated by X-ray diffractometric analyses. The following corrosion products were found in the marine atmosphere: Al₂O₃· 3H₂O + Al (oxychoride) + Al (hydroxide) (The latter two compounds had not been revealed by X-ray analysis). The corrosion products found in the polluted atmosphere were: AlF₃; Al₂(SO₄)₃ · H₂SO₄; Al₁₁(OH)₃₀Cl₃; AlF_1.96(OH)_1.4; 16Al(OH,F)₃ · 6H₂O; AlF_1.65(OH)_1.35 · H₂O. Since the developed method provides useful quantitative information on the aluminum distribution between the various anions, it is deemed to be a useful tool to study the corrosion kineties and mechanism.     

Ureteropelvic junction obstruction: relation of etiology and age at surgical repair to clinical outcome

Ureteropelvic junction (UPJ) obstruction is a congenital anomaly either caused by intrinsic narrowing of the upper ureter or by extrinsic pressure on the ureter caused by aberrant vessels or fibrous bands. We reviewed 121 cases of pyeloplasties performed in our department for UPJ obstruction. The cases were grouped by age and by the underlying pathology. Postoperative urographic evaluation showed that dismembered pyeloplasty was successful in 98.4% of the patients, with no significant difference between age groups. Persistence or recurrence of preoperative symptoms occurred in some patients (16.6%). Extrinsic obstruction of the ureter was associated with better postoperative clinical results and less recurrence of symptoms.