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排序方式: 共有290条查询结果,搜索用时 15 毫秒
51.
Alexander Leube Imre Kovats Siegfried Wahl Wolfgang Sickenberger 《Contact lens & anterior eye》2017,40(6):394-400
Purpose
Pilot study to investigate the feasibility of an axis-free correction approach of regular astigmatism using soft, bifocal contact lenses (CL).Methods
The investigation covers an optical simulation and a pilot study for the assessment of visual performance (over refraction OR, monocular visual acuity VA). The power of the two zones was adjusted according to the power of the astigmatic meridians, individually. Subjective performance was assessed in 30 participants with a mean horizontal cylindrical component of J0 = ? 0.65 ± 1.29 D (cylinder from ?0.75 to ?4.00 DC). OR and VA were measured directly after fitting the CL, after one hour and after 5 days (3FUP).Results
Evaluating the modulation transfer function, CL increased the Strehl ratio by 10% and the transferred spatial frequency was improved from 6.6 cpd to 21.3 cpd. Analysis of Sturm’s interval revealed a residual astigmatism of DAst = 0.73 D. OR revealed a statistically significant reduction of spherical error between baseline and all follow up (ΔM = ?2.14 D, p < 0.001) and between the J0 from baseline to 3FUP (ΔJ0 = ?0.46 D, p = 0.04). Wearing the CL for 5 days did not result in a significant difference of VA (ΔVA3FUP = +0.01 logMAR, p = 0.99).Conclusion
Axis-free correction of astigmatism using bifocal CL resulted in reasonable performance based on computer simulation. Participants showed no clinically reduced visual acuity or contrast sensitivity. Further clinical studies are needed to show if this approach provides a good alternative to conventional astigmatic correction. 相似文献52.
53.
The Differential Mobility Analyzer (DMA) is designed to measure particle mobility diameter, which for spherical particles is equal to particle volume equivalent diameter. In contrast, the mobility diameter of aspherical particles is a function of the particle shape and orientation. The magnitude of the DMA electric fields is such that it can cause aspherical particles to align preferentially in a specific orientation. The same electric field and the sheath flow rate ( q sh ) define the particle mobility diameter. But, the fact that particle orientation depends on the electric field makes the dynamic shape factor and hence the mobility diameter depend on q sh . Here, we describe an operating procedure that relies on a tandem DMA system, in which the second DMA is operated at a number of q sh , to obtain information about particle shape by measuring the effect of particle alignment on the particle mobility diameter. We show how the relationship between the mobility diameter and q sh can even be used to physically separate particles according to their shapes. In addition we explore the use of simultaneous measurements of particle alignment and particle vacuum aerodynamic diameters to gain further information on particle shape and account for particle alignment in the calculations of dynamic shape factor. We first test this approach on doublets and compact triplets of PSL spheres, for which the orientation dependent dynamic shape factors are known. We then investigate applications on a number of polydisperse particle systems of various shapes. 相似文献
54.
Magda Pl Kamirn ron Hamow Altafur Rahman Imre Majlth Judit Tajti Orsolya Kinga Gondor Mohamed Ahres Fatemeh Gholizadeh Gabriella Szalai Tibor Janda 《International journal of molecular sciences》2022,23(15)
Although light-emitting diode (LED) technology has extended the research on targeted photomorphogenic, physiological, and biochemical responses in plants, there is not enough direct information about how light affects polyamine metabolism. In this study, the effect of three spectral compositions (referred to by their most typical characteristic: blue, red, and the combination of blue and red [pink] lights) on polyamine metabolism was compared to those obtained under white light conditions at the same light intensity. Although light quality induced pronounced differences in plant morphology, pigment contents, and the expression of polyamine metabolism-related genes, endogenous polyamine levels did not differ substantially. When exogenous polyamines were applied, their roborative effect were detected under all light conditions, but these beneficial changes were correlated with an increase in polyamine content and polyamine metabolism-related gene expression only under blue light. The effect of the polyamines on leaf gene expression under red light was the opposite, with a decreasing tendency. Results suggest that light quality may optimize plant growth through the adjustment of polyamine metabolism at the gene expression level. Polyamine treatments induced different strategies in fine-tuning of polyamine metabolism, which were induced for optimal plant growth and development under different spectral compositions. 相似文献
55.
Dina Kata Ilona Grf Zsfia Hoyk Eszter Ducza Mria A. Deli Istvn Zupk Imre Fldesi 《International journal of molecular sciences》2022,23(16)
Estrogens regulate a variety of neuroendocrine, reproductive and also non-reproductive brain functions. Estradiol biosynthesis in the central nervous system (CNS) is catalyzed by the enzyme aromatase, which is expressed in several brain regions by neurons, astrocytes and microglia. In this study, we performed a complex fluorescent immunocytochemical analysis which revealed that aromatase is colocalized with the nuclear stain in glial fibrillary acidic protein (GFAP) positive astrocytes in cell cultures. Confocal immunofluorescent Z-stack scanning analysis confirmed the colocalization of aromatase with the nuclear DAPI signal. Nuclear aromatase was also detectable in the S100β positive astrocyte subpopulation. When the nuclear aromatase signal was present, estrogen receptor alpha was also abundant in the nucleus. Immunostaining of frozen brain tissue sections showed that the nuclear colocalization of the enzyme in GFAP-positive astrocytes is also detectable in the adult rat brain. CD11b/c labelled microglial cells express aromatase, but the immunopositive signal was distributed only in the cytoplasm both in the ramified and amoeboid microglial forms. Immunostaining of rat ovarian tissue sections and human granulosa cells revealed that aromatase was present only in the cytoplasm. This novel observation suggests a new unique mechanism in astrocytes that may regulate certain CNS functions via estradiol production. 相似文献
56.
Imre Zólomy 《Solid-state electronics》1985,28(6):537-547
A basic concept of bipolar amplifying devices as well as of negative-resistance devices is formulated. With the aid of this scheme a systematic survey is given for already reported and for possible new amplifying and negative-resistance devices, starting from five basic effects: the pn junction, the metal-(tunnel oxide)-semiconductor diode, the Schottky barrier, the bulk-barrier and the avalanche multiplication. Selecting two of these mechanisms and combining them into a feedback loop, a wide variety of negative-resistance devices can be constructed. Structures with more than two amplifying mechanisms are also briefly considered. 相似文献
57.
Imre A. Varga E. Ji L. Ilic B. Metlushko V. Csaba G. Orlov A. Bernstein G.H. Porod W. 《IEEE transactions on magnetics》2006,42(11):3641-3644
Ferromagnetic ring elements on the micrometer and submicrometer scale exhibit flux-closure magnetic vortex states in an intermediate step of their magnetization reversal. These clockwise or counterclockwise flux-closure states are of interest for applications that encode binary information in magnetic elements. Here, we study the magnetization reversal process of triangular cobalt rings made by e-beam lithography and lift-off. We demonstrate that full control over the direction of flux-closure magnetic states can be achieved solely by homogeneous external magnetic fields applied in particular directions. We have extracted statistical experimental data pertaining to the range of critical field values that trigger magnetization reversal from magnetic force microscopy images, and we explain the results on the basis of micromagnetic simulations 相似文献
58.
Possibilities of means of dilatometry in connection with production of multiphase (DP- and TRIP-) steels were examined in detail. These steels are characterized by an excellent combination of high strength and good press formability,which are essentially important in the automotive industry. Transformation processes, cooling rates, holding temperatures,composition and technological parameters play a very important role in formation of applicable microstructure of multiphase steels. Dilatometrical experiments were carried out to study the processes of intercritical annealing and hot rolling of several DP- and TRIP-steels. 相似文献
59.
We prove the secret key rate formulas and derive security threshold parameters of multicarrier continuous‐variable quantum key distribution CVQKD. In a multicarrier CVQKD scenario, the Gaussian input quantum states of the legal parties are granulated into Gaussian subcarrier continuous variables (CVs). The multicarrier communication formulates Gaussian subchannels from the physical quantum channel, each dedicated to the transmission of a subcarrier CV. The Gaussian subcarriers are decoded by a unitary CV operation, which results in the recovered single‐carrier Gaussian CVs. We derive the formulas through the adaptive multicarrier quadrature division (AMQD) scheme, the singular value decomposition (SVD)–assisted AMQD, and the multiuser AMQD multiuser quadrature allocation (MQA). We prove that the multicarrier CVQKD leads to improved secret key rates and higher tolerable excess noise in comparison with single‐carrier CVQKD. We derive the private classical capacity of a Gaussian subchannel and the security parameters of an optimal Gaussian collective attack in the multicarrier setting. We reveal the secret key rate formulas for one‐way and two‐way multicarrier CVQKD protocols, assuming homodyne and heterodyne measurements and direct and reverse reconciliation. The results reveal the physical boundaries of physically allowed Gaussian attacks in a multicarrier CVQKD scenario and confirm that the improved transmission rates lead to enhanced secret key rates and security thresholds. 相似文献
60.
Farhad Faraji Imre Safarik Otto P. Strausz Erdal Yildirim Manuel E. Torres 《加拿大化工杂志》1999,77(1):78-84
The pyrolysis of COS has been studied over the temperature range 300 to 750°C using a variety of catalysts. The observed product distribution confirmed that two parallel reaction paths: 2 COS → 2 CO S2 (2) and 2 COS → CO2 + CS2 (4) are involved in the decomposition. The decomposition yield increased with rising temperature, accompanied with a shift in selectivity. At temperatures lower than ~700°C the disproportionation reaction 4 was predominant, whereas at temperatures higher than 700°C, reaction 2 was favoured. In the high-temperature region (700 to 750°C) it was possible to achieve full suppression of reaction 4 with added CS2. The pyrolysis of COS was also studied in a reactor packed with quartz chips without catalysts at high temperatures. Between 800 and 900°C, up to 99% conversion (with respect to the thermodynamic limit) could be achieved, with the almost complete absence of the disproportionation reaction 4. The results point to the commercial potential in the two-step reaction sequence: for the economic conversion of hydrogen sulfide to hydrogen and sulfur. 相似文献