Theoretical study of a phased-array system using the diffraction model

Abstract

The transformation of a diffusion photon density wave (DPDW) in an infinite homogenous medium with an absorber for a phased-array system is studied theoretically using the diffraction model. The theoretical results agree with the experiment results. The results prove that a small object in a highly scattering medium can be detected and localized precisely by amplitude cancellation phase modulation spectroscopy (PMS).     

Decisions and the evolution of memory: Multiple systems, multiple functions.

Memory evolved to supply useful, timely information to the organism's decision-making systems. Therefore, decision rules, multiple memory systems, and the search engines that link them should have coevolved to mesh in a coadapted, functionally interlocking way. This adaptationist perspective suggested the scope hypothesis: When a generalization is retrieved from semantic memory, episodic memories that are inconsistent with it should be retrieved in tandem to place boundary conditions on the scope of the generalization. Using a priming paradigm and a decision task involving person memory, the authors tested and confirmed this hypothesis. The results support the view that priming is an evolved adaptation. They further show that dissociations between memory systems are not--and should not be--absolute: Independence exists for some tasks but not others. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Optical investigations of physiology: a study of intrinsic and extrinsic biomedical contrast

The utility and performance of optical studies of tissue depends upon the contrast and the changes of contrast in health and disease and in functional activity. The contrast is determined both by the optical properties of extrinsic chromophores and scatterers but especially upon the changes evoked by physiological activity and pathological states. Here, we have focused upon absorption changes of the intrinsic probe, blood absorbance changes due to cortical hypoxia and to haematomas, giving, for particular conditions, absorbance changes of 0.15 and over 0.4 delta OD, respectively. Functional activity may give changes of blood volume of over 0.05 delta OD with some variability due to individual responses that is best expressed as histogram displays of the distribution of response among a significant population. Responses have been observed in prefrontal parietal and occipital functions (242 tests). Extrinsic probes afford signals dependent upon the dose tolerance of the subject and can readily equal or exceed the blood volume and oxygenation signals, and currently afford vascular volume and flow indications. However, contrast agents for the functional activity of cellular function are ultimately to be expected. Finally, light-scattering changes afford osmolyte-related responses and are here shown to indicate a larger signal attributed to cortical depolarization and K+ release in hypoxia/ischaemia. Thus, the optical method affords imaging of manifold contrasts that greatly enhance its specificity and sensitivity for diagnostic procedures.     

一种采用近红外激光相位阵列检测乳腺癌的新方法(二)

近红外光谱学技术是无损检测与诊断的重要方法。采用频率分辨光谱学技术，检测以相位表示的光源与探测器之间的传输延迟，与光强检测相比具有更高的灵敏度。当在均匀介质中存在两个幅值相等、初始相位相差１８０°的近红外光源阵列时，依据光学相干原理，两光源的中垂线即为幅值为零、相位突变的零线。但当均匀介质中存在光学性质不同的异物时，零线会发生偏折。这种差异性即可提供有关异物大小、位置等信息。乳腺癌被认为是存在于乳房这一均匀组织中的异物。因此，基于上述原理，我们已研制出可用于无损检测乳腺癌的新型医疗仪器。与目前用的Ｘ射线、ＣＴ等比较，本仪器具有体积小、价格便宜、易于推广等优点。     

CMOS automobile performance logger

A battery-powered CMOS data logger suitable for 2 000 h of unattended operation is described. This paper relates to a machine designed for research into motor vehicle usage. Complete hardware details are given along with software showing the generation of time, distance travelled and fuel consumed. Design techniques of general application are emphasized.     

Hydroperoxide-induced chemiluminescence of the perfused lung

Light-emission of the perfused lung is induced by t-butyl hydroperoxide, giving chemiluminescence yields that oscillate between 800 and 1500 counts/s depending on the site and position of the lung. The response of the perfused lung to infusion with different hydroperoxides gives a pattern similar to that observed with the liver microsomal fraction; ethyl hydroperoxide shows a much higher chemiluminescence yield than the tertiary (t-butyl and cumene)hydroperoxides. Alveolar oedema affected the light-emission of the perfused lung depending on the time at which oedema developed, decreasing light emission on infusion of hydroperoxide in the oedematous lung and increasing it when oedema appeared after the maximal chemiluminescence yield was already achieved. Paraquat, administered in vivo, augmented light-emission by approximately 2-fold. The effect of paraquat was a time-dependent process. Lung chemiluminescence, compared with liver chemiluminescence, needed higher hydroperoxide concentration to induce light-emission.     

Radiolytic modification of basic amino acid residues in peptides: probes for examining protein-protein interactions

Protein footprinting utilizing hydroxyl radicals coupled with mass spectrometry has become a powerful technique for mapping the solvent accessible surface of proteins and examining protein-protein interactions in solution. Hydroxyl radicals generated by radiolysis or chemical methods efficiently react with many amino acid residue side chains, including the aromatic and sulfur-containing residues along with proline and leucine, generating stable oxidation products that are valuable probes for examining protein structure. In this study, we examine the radiolytic oxidation chemistry of histidine, lysine, and arginine for comparison with their metal-catalyzed oxidation products. Model peptides containing arginine, histidine, and lysine were irradiated using white light from a synchrotron X-ray source or a cesium-137 gamma-ray source. The rates of oxidation and the radiolysis products were primarily characterized by electrospray mass spectrometry including tandem mass spectrometry. Arginine is very sensitive to radiolytic oxidation, giving rise to a characteristic product with a 43 Da mass reduction as a result of the loss of guanidino group and conversion to gamma-glutamyl semialdehyde, consistent with previous metal-catalyzed oxidation studies. Histidine was oxidized to generate a mixture of products with characteristic mass changes primarily involving rupture of and addition to the imidazole ring. Lysine was converted to hydroxylysine or carbonylysine by radiolysis. The development of methods to probe these residues due to their high frequency of occurrence, their typical presence on the protein surface, and their frequent participation in protein-protein interactions considerably extends the utility of protein footprinting.     

Electrical and optical properties of highly conducting charge-transfer complexes of poly(p-phenylene)

Electrical conductivity, Hall effectm and spectroscopic measurements have been made on AsF₅-doped poly(p-phenylene). Doping increases the conductivity of the parent polymer by as much as 14 orders of magnitude to values as high as 5 × 10⁴ S/m. Hall effect measurements indicate p-type conduction with a Hall mobility approaching 10^?4 m²/V s for doping levels between 0.24 and 0.42 moles of AsF₅ per mole of monomer. Doping with an electron donor, K, has increased the conductivity to about 10³ S/m for a doping level of 0.57 moles of K per mole of monomer. Using this conductivity value, with the assumption of total charge transfer from the donor, suggests a drift mobility for electrons which is significantly less than that for holes. The assumption of an intercalant structure analogous to that of polyacetylene and graphite leads to the conclusion that the presently achieved AsF₅-doping levels in poly(p-phenylene) correspond to a compound which is not wholly stage 1.     

A low-temperature firing thick film capacttor material based on lead iron niobate/tungstate

The preparation of solid solution perovskite 70% $\text{Pb(Fe}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{Nb}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{)}$$\text{O}{}_3\text{-30\%}\text{Pb(Fe}{}_{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}\text{W}{}_{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}\text{)}\text{O}{}_3$ is described for use as a thick film capacitor on ceramic chip carriers. The limited densification at the temperature range of interest (850 – 900°C) requires the addition of a sintering aid. It is shown that a small addition of PbO(7 vol.%) is sufficient to promote densification of this material and maintain a dielectric constant exceeding 4000 for a fired thick film. Other electrical and physical properties of this material are described.