Use of skew rays in multimode fibers to generate speckle field with nonzero vorticity

Beams at the output of an axially symmetric multimode fiber were produced with mostly positive or negative values of angular index m through skew illumination of the input end of the fiber. In this way rays with predominantly positive or negative helicity were excited inside the fiber. The output cw speckle field at the wavelength lambda = 632.8 nm contained large densities N(+) and N(-) of wave-front dislocations, or optical vortices, of both positive and negative sign. Vorticity was defined as V = N(+) - N(-) , was expressed analytically through the Wigner function of the field, and was found experimentally to be in good agreement with theory.     

高能质子源靶用氢化铒薄膜制备过程影响因素

采用两步法制备了高能质子源靶用氢化铒薄膜。并研究了氢化时间、氢化速度等因素对氢化铒薄膜质量的影响。XRD结果显示,只有氢化时间超过24 h才能获得较纯净的氢化铒薄膜。将氢化反应温度和氢气压力控制在适当范围内,使得铒薄膜缓慢被氢化并使得氢化过程所产生的应力缓慢释放,可获得较完整的氢化铒薄膜。所获得的5~15 μm氢化铒薄膜已经应用于高能质子束的产生实验,取得了良好的实验结果。     

高能质子源靶用氢化铒薄膜制备过程影响因素

 采用两步法制备了高能质子源靶用氢化铒薄膜。并研究了氢化时间、氢化速度等因素对氢化铒薄膜质量的影响。XRD结果显示,只有氢化时间超过24 h才能获得较纯净的氢化铒薄膜。将氢化反应温度和氢气压力控制在适当范围内,使得铒薄膜缓慢被氢化并使得氢化过程所产生的应力缓慢释放,可获得较完整的氢化铒薄膜。所获得的5~15 μm氢化铒薄膜已经应用于高能质子束的产生实验,取得了良好的实验结果。     

太阳能电池板在剪草机上应用的研究

利用太阳能电池板作为能源装置,电机为剪草的动力装置的太阳能剪草机工作时安静无污染更适合未来社会对绿色生活的要求。     

Recovery of accurate T2 from historical 1.5 tesla proton density and T2-weighted images: Application to 7-year T2 changes in multiple sclerosis brain

ObjectiveTo determine accurate quantitative transverse relaxation times (T₂) using retrospective clinical images and apply it to examine 7-year changes in multiple sclerosis (MS) brain.MethodsA method for T₂ mapping from retrospective proton density (PD) and T₂-weighted fast spin echo images was recently introduced, but requires measurement of flip angles. We examined whether 1.5 T flip angle variation in brain can be predicted, thus enabling T₂ analysis of historical PD and T₂-weighted images without a concurrent flip angle map. After method validation in healthy volunteers, retrospective longitudinal T₂ analysis was performed in 14 MS subjects over seven years. Changes in patient T₂ values were compared with brain atrophy, T₂ lesion load and disability score in MS.ResultsSimilar flip angle maps across volunteers enabled retrospective T₂ from PD and T₂-weighted images even when different refocusing angles were used. Over seven years, significant T₂ changes of 2–4% were observed when using T₂ modelling and the 7-year effect size for globus pallidus T₂ was 0.56, which was more significant than brain atrophy. No significant T₂ results were found when using exponential fit, which cannot account for refocusing angle variation. Moreover, change is T₂ in globus pallidus and internal capsule correlated with MS disability score over time when using T₂ modelling.ConclusionsAccurate quantitative T₂ can be extracted from standard clinical 1.5 T MRI exams that include PD and T₂-weighted imaging even when no flip angle map is available. This method was applied retrospectively to examine seven year changes in MS.     

Use of non-aqueous electrochemical cells to investigate air- and water-sensitive hydrogen storage materials

Electrochemical methods have been used to study hydrogen in vanadium, titanium and three binary magnesium alloy systems. These materials are all sensitive to air and/or water, which prohibits the use of aqueous electrolytes. The measurements have involved the use of alkali halide and lower temperature organic-anion molten salts saturated with an alkali hydride so that they conduct charge by the transport of hydride ions, rather than protons. Alkali metals, or their alloys, can be used as indirect reference electrodes for hydrogen in these electrolytes.     

遥测振动信号EMD-WVD分布应用研究

飞行器飞行试验采集的遥测振动信号频段丰富、成分构成复杂,合理有效地解读其包括的时频信息在分析飞行器结构和环境特性方面至关重要。依托经验模态分解(EMD)方法将复杂信号分解成准单分量信号,借助相关系数法将伪分量信号剔除,保证分解信号的有效性。通过EMD和 WVD方法的结合,将保留的准单分量信号进行WVD变换并做平滑伪处理,从而获得复杂信号的时频分布。EMD-WVD组合模型经在仿真信号上的应用检验,能够检测信号自身的时频特性,进一步应用其在遥测振动信号上,同平滑伪WVD抑制交叉项方法进行了比较,结果表明EMD-WVD组合模型更加有效,能够反映复杂工程信号的时频分布特性。     

以活动单为“桥梁”,强化课堂有效反馈

通过设计活动单导学的模式,探索加强课堂反馈的思路,从本质上、实效上提高学生的发展能力．     

MR spectroscopic imaging of glutathione in the white and gray matter at 7 T with an application to multiple sclerosis

Detection of glutathione (GSH) is technically challenging at clinical field strengths of 1.5 or 3 T due to its low concentration in the human brain coupled with the fact that conventional single-echo acquisitions, typically used for magnetic resonance (MR) spectroscopy acquisitions, cannot be used to resolve GSH given its overlap with other resonances. In this study, an MR spectral editing scheme was used to generate an unobstructed detection of GSH at 7 T. This technique was used to obtain normative white (WM) and gray matter (GM) GSH concentrations over a two-dimensional region. Results indicated that GSH was significantly higher (P<.001) in GM relative to WM in normal subjects. This finding is consistent with previous radionuclide experiments and histochemical staining and validates this 7 T MR spectroscopy technique. To our knowledge, this is the first study to report normative differences in WM and GM glutathione concentrations in the human brain. Glutathione is a biomarker for oxidative status and this non-invasive in vivo measurement of GSH was used to explore its sensitivity to oxidative state in multiple sclerosis (MS) patients. There was a significant reduction (P<.001) of GSH between the GM in MS patients and normal controls. No statistically significant GSH differences were found between the WM in controls and MS patients. Reduced GSH was also observed in a MS WM lesion. This preliminary investigation demonstrates the potential of this marker to probe oxidative state in MS.     

Use of smoke samples in diamond-anvil cells to measure pressure dependence of optical spectra: Application to the ZnO exciton

We present measurements of ZnO exciton peak energies, E₀, at pressures up to 107.3 kbar. Smoke samples consisting of randomly oriented single crystal particles were prepared by oxidizing metallic zinc in air and were collected on one diamond face of a Merrill-Bassett pressure cell. Pressures were measured by the ruby fluorescence technique. In the pressure range between 5 and 90 kbar, our results indicate a consistent linear dependence with dE₀/dP = 2.33 × 10^?3 eV kbar^?1 for both increasing and decreasing pressures. A mixed phase structure is suggested by the observed irregular peak shapes and measured pressure dependence for the sample that had been taken beyond ? 90 kbar where the transformation to the NaCl structure has been reported.     

Polarized neutron reflectivity and X-ray scattering measurements as tools to study properties of Pt/Co/Pt ultrathin layers irradiated by femtosecond laser pulses

ABSTRACT

We have used polarized neutron reflectivity, X-ray diffraction, X-ray reflectivity and magneto-optical Kerr effect in polar configuration to study the properties of ultrathin Pt/Co/Pt films. Structures consisting of a 5-nm thick Pt buffer, 3-nm thick Co layer and 5-nm thick Pt cover layer were deposited onto (0001)-oriented Al₂O₃ substrate by the molecular beam epitaxy (MBE) method. Irreversible modifications of film properties, resulting from its illumination by single femtosecond laser pulses, of duration of 40 fs and wavelength of 800 nm, were observed and analyzed. As prepared films exhibited magnetization in-plane, but after laser irradiation, the direction of magnetization was rotated to out-of-plane state. Formation of Co–Pt alloy phase caused by quasi-uniform film irradiation was demonstrated by the results of X-ray and neutron scattering measurements. Moreover, polarized neutron and X-ray reflectivity data showed that after illumination Co was distributed mostly in the area of nominal Co layer and Pt cover layer and its diffusion into the Pt buffer was less significant.     

Selection of the Optimal Smart Meter to Act as a Data Concentrator with the Use of Graph Theory

Changing the construction of mart Meter (SM) devices, more specifically equipping them with more than one communication module, facilitates the elimination of a Transformer Station Data Concentrator (TSC) module, moving its function to one of the SMs. The opportunity to equip a chosen device in an additional communication module makes it possible to use it as an acquisition node. The introduction of this solution creates a problem with the optimum selection of the above-mentioned node out of all the nodes of the analyzed network. This paper suggests the criterion of its location and, as per the criterion, the way of conduct using the elements of the graph theory. The discussion is illustrated with the examples of the possibility to use the method for the optimization of the architecture of the network. The described method makes it possible to choose the location of a backup acquisition node as well as locate intermediary nodes (signal repeaters) in case of a failure (removal) of some SM devices. In the era of the common introduction of dispersed telemetric systems requiring an adequate level of performance and reliability of information transmission, the offered method can be used for the optimization of the structures of Smart Grids.     

YOYO as a Dye to Track Penetration of LK15 DNA Complexes in Spheroids: Use and Limits

To elucidate the reasons underlying the poor penetration of non-viral vectors in tissues, relating transport properties to physico-chemical parameters of vectors may be crucial. These properties can be influenced by the presence of multiples labels that are used. Therefore utilizing a vector with minimum of labels preferably not more than one is important to studying penetration in tissues. The cell impermeant bisintercalating dye YOYO-1 was found suitable to both monitor the formation of complexes between DNA and an amphipathic peptide LK15 and, to track their penetration in HCT116 spheroids by confocal microscopy. The results revealed a limited decrease of fluorescence ascribed to the high affinity of YOYO-1 to bind DNA. The residual fluorescence of complexes can be exploited to monitor penetration into spheroids, after correction for YOYO-1 attenuation, and to revealing hyaluronidase-induced reduced binding. Hence high affinity dyes such as YOYO-1 with inefficiently quenched fluorescence may be important to establish a relation between novel medicines characteristics and penetration in tissues.     

Use of state of polarization transparent scheme for polarization shift keying signal as optical phase conjugator to improve the transmission performance

Transmission characteristics of polarization shift keying (PolSK) signal is experimentally demonstrated in this work. Performance degradation due to transmission is improved using optical phase conjugation (OPC) technique. The wavelength converter based on the proposed state of polarization (SOP) transparent scheme for PolSK signal is effective to use it as mid-link optical phase conjugator and which is difficult to achieve using conventional wavelength conversion scheme. It is found that for fiber transmission, the performance of both of the orthogonal SOPs of the PolSK signal is different for their respective chirping characteristics which can be optimized to be similar using proposed OPC technique.     

NOR expression increases in interphase lymphocytes of Down syndrome babies/children as AgNORs surface, according to the mitogen concentration in the culture medium

The extra chromosome 21 of Down syndrome (DS) or trisomy 21 patients contains an average of 40 extra copies of rRNA genes and the in vivo/in vitro regulation of the activity of these genes is not fully understood. The objective of this work was to compare the NORs expression pattern in interphase lymphocytes of DS patients with regular trisomy 21 and control individuals according to phytohemagglutinin (PHA) concentration (0.37, 0.75, 1.48 and 2.21 ml) per 100 ml of medium. Because the AgNOR staining is an indicator of the active rRNA genes, comparison of the image analysis values of the AgNOR area in 72 h cultivated lymphocytes for each concentration of PHA between DS patients (N=30) and controls (N=24) provided a plausible conclusion on the regulation of the extra rRNA genes in DS lymphocytes. The nucleolus organizer regions area/total nuclear area (NORa/TNa) was calculated using an in-house computer program. Fifty consecutive interphases per PHA concentration were analysed for each individual, for determination of the NORa/TNa. In contrast to healthy controls, NORa/TNa of lymphocytes from DS patient babies/children (0-8 years old) increased gradually in parallel with the PHA concentration in the culture medium: 10.44+/-1.72% for 0.37 ml of PHA, 11.74+/-1.93% for 0.75 ml of PHA, 13.25+/-2.03% for 1.48 ml of PHA and 13.43+/-2.08% for 2.21 ml of PHA per 100 ml of medium. Contrary to control cells (in which the NORa/TNa ratio according to PHA concentration in the culture medium remains constant), DS interphase lymphocytes in culture do not down-regulate their NOR expression. These results obtained from interphase NORs are consistent with the previous results obtained by evaluating the mean of AgNOR+ chromosome number in metaphase cells, also in relation to the mitogen concentration in the culture medium.     

Using environmental scanning electron microscopy (ESEM) as a quantitative method to analyse the attachment of Giardia duodenalis to epithelial cells

Giardia duodenalis is a human parasite that colonises the small intestine. In some studies, it may be necessary to estimate the parasite-host adhesion index. When working in vitro, it is very difficult to determine the relative number of parasites adhered to intestinal cells because parasites might be removed from enterocytes during specimen preparation. We have encountered such difficulties with sample analyses when using light and conventional scanning electron microscopy, including the loss of adherent cells during the processing steps. In this study, we showed that environmental scanning electron microscopy (ESEM), which allows the examination of specimens at normal atmospheric pressure or in very low vacuum without any previous treatment, can be used effectively in quantitative studies of the parasite-host relationship.     

Use of thermal imaging to characterize laser light reflection from thermoplastics as a function of thickness,laser incidence angle and surface roughness

Laser light reflection during the laser transmission welding (LTW) of thermoplastics has the potential to overheat and/or cause unintentional welding of adjacent features of the part being welded. For this reason, and in order to assess how much light is being absorbed by the transparent part (after measurement of the light transmitted through the transparent part), it is important to be able to quantify the magnitude and distribution of reflected light. The magnitude and distribution of the reflected light depends on the total laser input power as well as its distribution, the laser incidence angle (angle between the normal to the transparent part surface and the laser beam), the laser light polarization as well as the surface and optical properties of the transparent part. A novel technique based on thermal imaging of the reflected light was previously developed by the authors. It is used in this study to characterize the magnitude and distribution of reflected light from thermoplastics as a function of thickness (1–3.1 mm), laser incidence angle (20–40°) and surface roughness (0.04–1.04 μm). Results from reflection tests on nearly polished nylon 6 (surface roughness between 0.04 and 0.05 μm) have shown that, for the various thicknesses tested (1–3.1 mm), the total reflection was larger than the specular top surface reflection predicted via the Fresnel relation. From these observations, it is conjectured that, in addition to top surface reflection, the bulk and/or bottom surface also contribute to the total reflection. The results also showed that reflection decreased slightly with increasing thickness. As expected, for the p-polarized light used in this study, the reflection decreased with increasing angle of incidence for the range of angles studied. It was also found that when the surface roughness was close to zero and when it was close to the wavelength of the input laser beam (i.e. 940 nm), the reflectance values were close and reached a minimum between these two roughness values.