Tropospheric effects on design of line-of-sight space-diversity system

The successful application of space diversity to achieve a high propagation reliability over line-of-sight microwave links requires proper separation between diversity antennas, whereby the signals received at the antennas are sufficiently decorrelated. The multipath-propagation model is examined, and en expression is derived for the envelope correlation coefficient which is a function of antenna spacing and is dependent on the parameters of the troposphere.     

Spectral-domain analysis of circular patch frequency selective surfaces

A computationally efficient method is presented for analyzing the scattering from frequency selective surfaces (FSS) comprised of circular metal patches. The formulation is carried out in the spectral domain where the convolution form of the integral equation for the induced current reduces to an algebraic one and the spectral-Galerkin technique is used to solve the resulting equation. Entire-domain basis functions that satisfy the edge condition are introduced to expand the unknown induced current on the metal patches. Calculated results using this procedure show good agreement with data reported by other authors.     

Biosynthesis of phospholipids in subcellular particles from cultured cells of human tissue

A time study of the incorporation of³²P_i into the phospholipids of HeLa, KB, human heart, and liver tissue-culture cell lines has been carried out. The incorporation of³²P_i at various time-intervals into the phospholipids of nuclei, mitochondria, and microsomes of HeLa and KB cells was investigated. The labeling of the isotope into the phospholipids was divided into three groups. The first had two components: phosphatidyl inositol and polyglycerol phosphatides, which showed the greatest incorporation of the isotope as demonstrated in the specific activity values and the percentage of total radioactivity after 15 to 30 minutes of incubation. A second group was composed of the major phospholipids of all tissue-culture cell lines studied, phosphatidyl choline, and phosphatidyl ethanolamine. At first, there was a delayed labeling of these phospholipids; however, after one hour of incubation, a rapid increase was shown in the incorporation of³²P_i. A third group of lipids containing sphingomyelin and phosphatidyl serine demonstrated low specific activity values. The phospholipids of the subcellular fractions, nuclei, mitochondria, and microsomes, had a high degree of incorporation of the isotope into the individual phospholipids and probably represented an active process in the membranes of these cellular units or a renewal of the biological membrane structures. Part of a thesis submitted to the Graduate School of the University of North Dakota in partial fulfillment for the degree of Doctor of Philosophy.     

Radiation resistance of antennas in lossy media

Using the concept of modified power density, expressions are derived for the radiation resistance and efficiency of antennas in a dissipative medium.     

Comparison of Vibrio cholerae O1 isolates by polymerase chain reaction fingerprinting and ribotyping

AIM: To determine reproducibility and accuracy of the Nikon Retinomax autorefractor when used with children who were made cycloplegic. METHODS: Autorefraction and retinoscopy or subjectively refined retinoscopy (where, under the patient's direction, the refraction was varied until the best visual acuity was achieved) were performed on the right eye of 47 children, age 11-93 months. Autorefraction was performed using the Nikon Retinomax, which provides up to eight measured values of refractive error and one representative measurement of refractive error. RESULTS: Autorefractor measurements were successfully obtained from 7/9 children age 3 years or younger, and from all older children. Vector methods were used to calculate differences. Retinomax reproducibility averaged 0.43 D. Unbiased Retinomax and retinoscopy measurements differed by an average of 0.82 D. Unbiased Retinomax and subjectively refined retinoscopy differed by an average of 1.03 D. CONCLUSIONS: Reproducibility of Retinomax measured values in children is comparable with reproducibility of retinoscopy, subjective refraction, and autorefraction measurements in adults. Agreement between Retinomax and retinoscopy and agreement between Retinomax and subjective refinement in children is comparable with agreement between autorefraction and subjective refraction in adults. The study indicates that the Retinomax is a useful instrument for measuring refractive errors in young children.     

Compositional nonuniformities and strain relaxation at misoriented InxGa(1−x)As/GaAs interfaces

Compositional nonuniforimities and misfit dislocations are observed near misoriented In_0.2Ga_0.8As/GaAs interfaces. The compositional nonuniformities results from In interdiffusion at the interface over a distance of 3 nm and formation of InAs platelet precipitates. The misfit dislocations are of pure edge and 60° types. The core of pure edge misfit dislocations generally consists of two 60° dislocations separated by approximately 2.5 nm. One of these 60° dislocations is usually split into partials and decorated by platelets of InAs. The interface and surface morphologies are strongly influenced by the substrate tilt away from exact [001] crystallographic orientation.     

关于狭义相对论的修正以及新引力理论的方案

相对论存在一定的局限性.狭义相对论适用于电磁的相互作用.没有强有力的证据显示狭义相对论也适用于其它3种基本相互作用.至少在弱相互作用中,中微子可能是超光速粒子.物理学需采取多种时间的定义,一种推广伽利略变换的时间值得进一步研究.广义相对论很大程度上是一种数学理论.作为物理学的引力理论,它存在很多基本缺陷.检验广义相对论一些天文实验,误差很大,需要重新分析.笔者将讨论一种新引力理论的方案.它的引力场方程与电磁理论的麦克斯韦方程十分相似.     

Versatile,Benzimidazole/Amine‐Based Ambipolar Compounds for Electroluminescent Applications: Single‐Layer,Blue, Fluorescent OLEDs,Hosts for Single‐Layer,Phosphorescent OLEDs

A series of compounds containing arylamine and 1,2‐diphenyl‐1H‐benz[d]imidazole moieties are developed as ambipolar, blue‐emitting materials with tunable blue‐emitting wavelengths, tunable ambipolar carrier‐transport properties and tunable triplet energy gaps. These compounds possess several novel properties: (1) they emit in the blue region with high quantum yields; (2) they have high morphological stability and thermal stability; (3) they are capable of ambipolar carrier transport; (4) they possess tunable triplet energy gaps, suitable as hosts for yellow‐orange to green phosphors. The electron and hole mobilities of these compounds lie in the range of 0.68–144 × 10^?6 and 0.34–147 × 10^?6 cm² V^?1 s^?1, respectively. High‐performance, single‐layer, blue‐emitting, fluorescent organic light‐emitting diodes (OLEDs) are achieved with these ambipolar materials. High‐performance, single‐layer, phosphorescent OLEDs with yellow‐orange to green emission are also been demonstrated using these ambipolar materials, which have different triplet energy gaps as the host for yellow‐orange‐emitting to green‐emitting iridium complexes. When these ambipolar, blue‐emitting materials are lightly doped with a yellow‐orange‐emitting iridium complex, white organic light‐emitting diodes (WOLEDs) can be achieved, as well by the use of the incomplete energy transfer between the host and the dopant.     

High hole mobility from thiophene-thienopyrazine copolymer based thin film transistors

Surface morphologies and thin film transistor characteristics of three thiophene (TH)-thieno[3,4-b]pyrazine (TP) donor–acceptor conjugated copolymers (PTHTP-C7, PTHTP-C12, and PBTHTP-C7) are reported. The long alkyl side chain probably promoted PTHTP-C12 to become a fibrillar-like structure on the hexamethyldisilazane (HMDS)-modified surface and resulted in better charge transport properties than the other two copolymers. However, a nodule-like morphology on the octyltrichlorosilane (OTS)-modified surface was observed due to the strong interaction between the non-polar alkyl chains of PTHTP-C12 and highly hydrophobic surface. By further annealing at a higher temperature, a densely packed grain morphology on octyltrichlorosilane (OTS) modified SiO₂ surface was shown and led to the field effect mobility of 1.1 × 10⁻² cm² V⁻¹ s⁻¹ with the on/off ratio of 227. The present study suggests that thiophene based donor–acceptor conjugated polymers could have a high FET mobility through the manipulation of polymer morphology.