Ferrites with Rectangular and Square Hysteresis Loops

We have formulated the requirements for ferrites that must be met to obtain rectangular and square hysteresis loops. We have studied the effect of micro-inhomogeneities on the rectangularity and squareness of the hysteresis loop. We have established a negative effect from -Fe₂O₃ inclusions, local tetragonal distortions of the cubic lattice, and linear micro-inhomogeneities. We have shown that the general reason for the high degree of squareness of the hysteresis loop for ferrites of all compositions having a rectangular hysteresis loop is granulated micro-inhomogeneities with an elevated concentration of cationic vacancies relative to the matrix. We have studied the conditions for the formation of such inhomogeneities.__________Translated from Poroshkovaya Metallurgiya, Nos. 1–2(441), pp. 80–89, January–February, 2005.     

Investigation of the Cauchy-Riemann equations for one-dimensional image recovery in intensity interferometry

A method of image recovery using noniterative phase retrieval is proposed and investigated by simulation. This method adapts the Cauchy-Riemann equations to evaluate derivatives of phase based on derivatives of magnitude. The noise sensitivity of the approach is reduced by employing a least-mean-squares fit. This method uses the analytic properties of the Fourier transform of an object, the magnitude of which is measured with an intensity interferometer. The solution exhibits the degree of nonuniqueness expected from root-flipping arguments for the one-dimensional case, but a simple assumption that restricts translational ambiguity also restricts the space of solutions and permits essentially perfect reconstructions for a number of non-symmetric one-dimensional objects of interest. Very good reconstructions are obtained for a large fraction of random objects, within an overall image flip, which may be acceptable in many applications. Results for the retrieved phase and recovered images are presented for some one-dimensional objects and for different noise levels. Extensions to objects of two dimensions are discussed. Requirements for signal-to-noise ratio are derived for intensity interferometry with use of the proposed processing.     

Reflection of light at structured chiral interfaces

Modified boundary conditions and general surface constitutive equations are derived for a very thin interface with some internal structure that separates two different media. The modified boundary conditions are reduced to the standard ones for an idealized steplike sharp interface without additional structure. These modified boundary conditions together with surface constitutive equations and Maxwell equations in the bulk form a complete set of macroscopic equations to describe optical properties of planar interfaces with thicknesses much less then the wavelength of light. In particular, two-dimensional chiral surfaces are considered that are characterized by surface gyrotropic coefficients even if the two different bulk media and the interface are made of nonchiral materials. It is shown that the rotation of the polarization state should occur for the light reflected from such a surface. This result is supported by recent experimental data.     

Physicochemical properties determining the detection probability of tryptic peptides in Fourier transform mass spectrometry. A correlation study

Sequence verification and mapping of posttranslational modifications require nearly 100% sequence coverage in the "bottom-up" protein analysis. Even in favorable cases, routine liquid chromatography-mass spectrometry detects from protein digests peptides covering 50-90% of the sequence. Here we investigated the reasons for limited peptide detection, considering various physicochemical aspects of peptide behavior in liquid chromatography-Fourier transform mass spectrometry (LC-FTMS). No overall correlation was found between the detection probability and peptide mass. In agreement with literature data, the signal increased with peptide hydrophobicity. Surprisingly, the pI values exhibited an opposite trend, with more acidic tryptic peptides detected with higher probability. A mixture of synthesized peptides of similar masses confirmed the hydrophobicity dependence but showed strong positive correlation between pI and signal response. An explanation of this paradoxal behavior was found through the observation that more acidic tryptic peptide lengths tend to be longer. Longer peptides tend to acquire higher average charge state in positive mode electrospray ionization than more basic but shorter counterparts. The induced-current detection in FTMS favors ions in higher charge states, thus providing the observed pI-FTMS signal anticorrelation.     

Detection of polyomavirus DNA in human brain tumors

AIM: To investigate surgically resected human brain tumors for the presence of polyomavirus DNA. MATERIALS AND METHODS: 65 samples of surgically resected human brain tumors (57 tumors were of neuroectodermal genesis, 4--mesenchimal, 4--metastatic tumors) were examined for the presence of viral DNA by PCR analysis. RESULTS: DNA of polyomaviruses was found in oligodendroligomas (66.7% of cases), oligodendroastrocytomas (66.7% of cases) and glioblastomas (40% of cases). In metastatic tumors viral infection had not been detected. No correlation between the grade of brain tumors and infection with polyomavirus DNA has been revealed. CONCLUSION: Our data point to importance of investigation of the brain tumors and cerebrospinal fluid for determination of viral infection.     

Development of a gallium-doped germanium far-infrared photoconductor direct hybrid two-dimensional array

To our knowledge, we are the first to successfully report a direct hybrid two-dimensional (2D) detector array in the far-infrared region. Gallium-doped germanium (Ge:Ga) has been used extensively to produce sensitive far-infrared detectors with a cutoff wavelength of approximately equal to 110 microm (2.7 THz). It is widely used in the fields of astronomy and molecular and solid spectroscopy. However, Ge:Ga photoconductors must be cooled below 4.2 K to reduce thermal noise, and this operating condition makes it difficult to develop a large format array because of the need for a warm amplifier. Development of Ge:Ga photoconductor arrays to take 2D terahertz images is now an important target in such research fields as space astronomy. We present the design of a 20 x 3 Ge:Ga far-infrared photoconductor array directly hybridized to a Si p-type metal-oxide-semiconductor readout integrated circuit using indium-bump technology. The main obstacles in creating this 2D array were (1) fabricating a monolithic Ge:Ga 2D array with a longitudinal configuration, (2) developing a cryogenic capacitive transimpedance amplifer, and (3) developing a technology for connecting the detector to the electronics. With this technology, a prototype Ge:Ga photoconductor with a direct hybrid structure has shown a responsivity as high as 14.6 A/W and a minimum detectable power of 5.6 x 10(-17) W for an integration time of 0.14 s when it was cooled to 2.1 K. Its noise is limited by the readout circuit with 20 microV/Hz(1/2) at 1 Hz. Vibration and cooling tests demonstrated that this direct hybrid structure is strong enough for spaceborne instruments. This detector array will be installed on the Japanese infrared satellite ASTRO-F.     

Development of alternative fuel assembly for WWER-1000 reactor

An alternative design of fuel assembly has been developed for the WWER-1000 reactor with the aim of assuring a geometrical stability of the core during operation. The fuel assembly provides enhanced safety and substantial improvement in the WWER-1000 fuel cycle economics.     

Unified finite element analysis

A special matrix is introduced, the elements of which are zero or first-order differential operators. This matrix is used to define a boundary value problem which covers a wide class of engineering applications. An equivalent variational formulation is found using an extension of the Gauss theorem. From this variational principle the equations of the elements are derived. The unified formulae presented here can be useful for educational purposes and for the design of a finite element system for total analysis.     

Stress and experimental ulcer: Critique of psychological literature.

Although several authors have claimed that the psychological procedures of conflict, conditioned fear, and avoidance could be used to develop ulcers in rats, the present authors' evaluation of these procedures suggests that the physical factors of shock and food deprivation were the primary agents responsible for the observed lesions. It is concluded that a convincing demonstration that psychological factors per se are sufficient to induce ulcers and the pathophysiological changes necessary for their formation is lacking at present in the experimental literature. (French summary) (49 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)