Hanle effect in coherent backscattering

We study the shape of the coherent backscattering (CBS) cone obtained when resonant light illuminates a thick cloud of laser-cooled rubidium atoms in presence of a homogenous magnetic field. We observe new magnetic field-dependent anisotropies in the CBS signal. We show that the observed behavior is due to the modification of the atomic radiation pattern by the magnetic field (Hanle effect in the excited state).Comment: 4 pages, 3 figure

Surface Analysis of Tarnished Dental Alloys

Six crown and bridge alloys ranging in nobility between 25-63 wt % (18-45 at %) were analyzed by optical microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and secondary ion mass spectroscopy (SIMS), as well as by L*a*b* colorimetry before and after in vitro tarnishing in artificial saliva with and without additions of 0.00016, 0.016, and 1.6 % Na2S with a rotating wheel apparatus. All alloys except the lowest of 18 at % changed colors to about the same degree after 72 h of tarnishing. All alloys decreased in L*, while increased in both a* and b*, thus appearing darker and with increased redness and yellowness. This was due to localized darkening and to other products. For all alloys except one, saliva without sulfide promoted color changes more severe than for saliva with 0.016% Na2S. For the most part, analysis by EDS was unable to detect differences between the tarnished films and the as-polished surfaces. SIMS analysis, however, showed changes in the substrate ion (Cu, Ag, Pd, and In) peak intensities. In most cases the intensities decreased and with the decrease greater with the sulfide-free saliva than with sulfide-containing. This indicated that sulfide promoted insoluble deposition of products. Changes in the Ag, Pd, and In peak intensities followed much the same pattern as with Cu. The as-polished surfaces, even though carefully prepared, showed much contamination in the form of organics, namely C, CH, N, NH, 0, CHN, CN, as well as from Na, K, Ca, Si, S, Cl, and others. Most tarnished surfaces showed large increases in Na, K, and Ca, and with the sulfide-free saliva being more severe in this regard. The mass spectrum also showed peaks with atomic mass units in the ranqe 55-58 related to only some of the tarnished surfaces

Modern mining and mining and processing productions in Mongolia: economic aspect

Актуальность и практическая необходимость данного исследования обусловлены необходимостью повышения эффективности международного сотрудничества совместных предприятий с участием иностранного капитала в горнорудной и горно- обогатительной промышленности Монголии. Цель работы: на основе анализа современного развития горнодобывающей промышленности Монголии, преимуществ и недостатков использования различных форм международной кооперации разработать предложения и наметить перспективы по повышению эффективности взаимодействия монгольских и иностранных компа- ний. Методы исследования: статистический, сравнительный, исторический, абстрактно-логический. Результаты: выявлены сильные и слабые стороны расширения межгосударственного сотрудничества в горнорудной и горно-обогатительной промышленности Монголии, на основе которых предполагается разработка рекомендаций по совершенствованию государственной политики на макро- и микроуровнях в целях повышения эффективности функционирования экономической системы.The relevance and practical necessity of the research tend to improve the effectiveness of international cooperation of foreign invested joint factories in the mining industry of Mongolia. The aims of the study are to develop proposals and outline the prospects for improving the efficiency of interaction among Mongolian and foreign companies through researching current development of the Mongolian mining industry and analysing pros and cons of the international cooperation. Methods of the research: statistical, comparative, historical, abstractlogical method. Results. The authors have identified the strengths and weaknesses of the international cooperation expansion in the mining industry of Mongolia. It is expected that they will be the base for development of recommendations for improving public policy at the macro and micro levels in order to perfect the functioning of the economic system

Психологическая готовность инвалидов к получению профессионального образования

Представленные результаты пилотажного исследования психологической готовности абитуриентов-инвалидов к получению профессионального образования получены на основе психолого-педагогического общения исследователей с группой молодых инвалидов-слушателей курса довузовской подготовки. Итоги исследования убеждают, что профессиональное образование является для инвалидов ведущей целью, с ним они связывают достижение наиболее важных жизненных целей, возможность самореализации в будущем

Evaluation of patients treated with natalizumab for progressive multifocal leukoencephalopathy

Background: Progressive multifocal leukoencephalopathy (PML) was reported to have developed in three patients treated with natalizumab. We conducted an evaluation to determine whether PML had developed in any other treated patients. Methods: We invited patients who had participated in clinical trials in which they received recent or long-term treatment with natalizumab for multiple sclerosis, Crohn's disease, or rheumatoid arthritis to participate. The clinical history, physical examination, brain magnetic resonance imaging (MRI), and testing of cerebrospinal fluid for JC virus DNA were used by an expert panel to evaluate patients for PML. We estimated the risk of PML in patients who completed at least a clinical examination for PML or had an MRI. Results: Of 3417 patients who had recently received natalizumab while participating in clinical trials, 3116 (91 percent) who were exposed to a mean of 17.9 monthly doses underwent evaluation for PML. Of these, 44 patients were referred to the expert panel because of clinical findings of possible PML, abnormalities on MRI, or a high plasma viral load of JC virus. No patient had detectable JC virus DNA in the cerebrospinal fluid. PML was ruled out in 43 of the 44 patients, but it could not be ruled out in one patient who had multiple sclerosis and progression of neurologic disease because data on cerebrospinal fluid testing and follow-up MRI were not available. Only the three previously reported cases of PML were confirmed (1.0 per 1000 treated patients; 95 percent confidence interval, 0.2 to 2.8 per 1000). Conclusions: A detailed review of possible cases of PML in patients exposed to natalizumab found no new cases and suggested a risk of PML of roughly 1 in 1000 patients treated with natalizumab for a mean of 17.9 months. The risk associated with longer treatment is not known

Observation of coherent backscattering of light by cold atoms

Coherent backscattering (CBS) of light waves by a random medium is a signature of interference effects in multiple scattering. This effect has been studied in many systems ranging from white paint to biological tissues. Recently, we have observed CBS from a sample of laser-cooled atoms, a scattering medium with interesting new properties. In this paper we discuss various effects, which have to be taken into account for a quantitative study of coherent backscattering of light by cold atoms.Comment: 25 pages LaTex2e, 17 figures, submitted to J. Opt. B: Quant. Semicl. Op

Large Faraday rotation of resonant light in a cold atomic cloud

We experimentally studied the Faraday rotation of resonant light in an optically-thick cloud of laser-cooled rubidium atoms. Measurements yield a large Verdet constant in the range of 200 000 degrees/T/mm and a maximal polarization rotation of 150 degrees. A complete analysis of the polarization state of the transmitted light was necessary to account for the role of the probe laser's spectrum

Predictability of the spontaneous lumbar curve correction after selective thoracic fusion in idiopathic scoliosis

In this study we tried to achieve a better understanding of the biodynamic mechanism of balance in the scoliotic spine. Therefore we focused on the pre- and postoperative spine of patients with idiopathic scoliosis with a primary thoracic curve and a secondary lumbar curve. Several studies showed that the lumbar curve spontaneously corrects and improves after selective thoracic fusion. We try to understand and describe this spontaneous compensatory lumbar curve correction after selective thoracic correction and fusion. We performed a retrospective examination of pre- and postoperative radiographs of the spine of 38 patients with idiopathic scoliosis King type II and III. Frontal Cobb angles of the thoracic and lumbar curves were assessed on pre- and postoperative antero-posterior and side bending radiographs. We determined the postoperative corrections of the thoracic and lumbar curves. Relative (%) corrections and correlations of the postoperative corrections were calculated. The group was divided in three subgroups, depending on lumbar curve modifier, according to Lenkes classification system. The calculations were done for the whole group as for each subgroup. As expected, significant correlations were present between the relative correction of the main thoracic and the lumbar curve (mean R = 0.590; P = 0.001). The relation between relative thoracic and lumbar correction decreased with the lumbar modifier type. This study shows a highly significant correlation between the relative corrections of the main thoracic curve and the lumbar curve after selective thoracic fusion in idiopathic scoliosis. This correlation depends on lumbar curve modifier type. This new classification system seems to be of great predictable value for the spontaneous correction of the lumbar curve. Depending on the curve-type, a different technique for predicting the outcome should be used. The lumbar curve correction does not occur throughout the whole lumbar curve. Most correction is achieved in the upper part of the curve. The distal lumbar curve seems to be more rigid and less important in the spontaneous curve correction

The effect of starting point placement technique on thoracic transverse process strength: an ex vivo biomechanical study

<p>Abstract</p> <p>Background</p> <p>The use of thoracic pedicle screws in spinal deformity, trauma, and tumor reconstruction is becoming more common. Unsuccessful screw placement may require salvage techniques utilizing transverse process hooks. The effect of different starting point placement techniques on the strength of the transverse process has not previously been reported. The purpose of this paper is to determine the biomechanical properties of the thoracic transverse process following various pedicle screw starting point placement techniques.</p> <p>Methods</p> <p>Forty-seven fresh-frozen human cadaveric thoracic vertebrae from T2 to T9 were disarticulated and matched by bone mineral density (BMD) and transverse process (TP) cross-sectional area. Specimens were randomized to one of four groups: A, control, and three others based on thoracic pedicle screw placement technique; B, straightforward; C, funnel; and D, in-out-in. Initial cortical bone removal for pedicle screw placement was made using a burr at the location on the transverse process or transverse process-laminar junction as published in the original description of each technique. The transverse process was tested measuring load-to-failure simulating a hook in compression mode. Analysis of covariance and Pearson correlation coefficients were used to examine the data.</p> <p>Results</p> <p>Technique was a significant predictor of load-to-failure (<it>P </it>= 0.0007). The least squares mean (LS mean) load-to-failure of group A (control) was 377 N, group B (straightforward) 355 N, group C (funnel) 229 N, and group D (in-out-in) 301 N. Significant differences were noted between groups A and C, A and D, B and C, and C and D. BMD (0.925 g/cm²[range, 0.624-1.301 g/cm²]) was also a significant predictor of load-to-failure, for all specimens grouped together (<it>P </it>< 0.0001) and for each technique (<it>P <</it>0.05). Level and side tested were not found to significantly correlate with load-to-failure.</p> <p>Conclusions</p> <p>The residual coronal plane compressive strength of the thoracic transverse process is dependent upon the screw starting point placement technique. The funnel technique significantly weakens transverse processes as compared to the straightforward technique, which does not significantly weaken the transverse process. It is also dependent upon bone mineral density, and low failure loads even in some control specimens suggest limited usefulness of the transverse process for axial compression loading in the osteoporotic thoracic spine.</p