Quantitative analysis of intermodulation product interference

An analytical technique for estimating the absolute signal strength of externally generated intermodulation (IM) product interference is given. The modeling approach detailed is intended to augment previously published work by providing greater insight into the mechanisms generating IM product interference and may find direct application for siting situations in which equipment parameters and layout are well defined. The layout for a simplified model used to determine externally generated IM product levels is shown; a transmitting antenna illuminates a dipole antenna terminated in a nonlinearity, which reradiates IM product interference that is coupled into the receiving antenna. Actual signal levels are calculated for a canonic case involving a parasitic, center-fed dipole terminated in a nonlinear diode-type junction. The results can be applied readily to any nonlinear function and radiating system     

An interactive demonstration of electromagnetic wave propagationusing time-domain finite differences

The finite difference time-domain (FDTD) method is one of the most widely used computational methods in electromagnetics. Using FDTF, Maxwell's equations are solved directly in the time domain via finite differences and time stepping. the basic approach is relatively easy to understand and is an alternative to the more usual frequency-domain approaches. In order to take advantage of this, an interactive personal computer program based on FDTD has been developed. The program directly solves Maxwell's equation via finite differences. The solution is for one dimension, corresponding to normal incidence propagation through a planar stratified medium. The program displays an electromagnetic pulse as it propagates through the medium. Since Maxwell's equations are solved directly, the reflected and transmitted pulse amplitudes demonstrate how the reflection and transmission coefficients determine reflected and transmitted wave amplitudes. Since lossy material layers can be included, frequency dispersion can be demonstrated     

Extension of the thermodynamics of small systems to open metastable states: an example

By using a simplified model of small open liquid-like clusters with surface effects, in the gas phase, it is shown how the statistical thermodynamics of small systems can be extended to include metastable supersaturated gaseous states not too far from the gas-liquid equilibrium transition point. To accomplish this, one has to distinguish between mathematical divergence and physical convergence of the open-system partition function.     

Graphic applications of the Standard Generalized Markup Language (SGML)

The Standard Generalized Markup Language (SGML) is a language for representing document structure. This paper discusses ways in which the SGML language might be used to represent graphic as well as textual contents of a document. By using SGML markup for both graphics and text, a document processing application can achieve a more uniform treatment and tighter coupling between these two types of materials.     

Subclinical hypocalcemia,plasma biochemical parameters,lipid metabolism,postpartum disease,and fertility in postparturient dairy cows

A study was conducted to evaluate the potential association between Ca status at calving and postpartum energy balance, liver lipid infiltration, disease occurrence, milk yield and quality parameters, and fertility in Holstein cows. One hundred cows were assigned to 1 of 2 groups based on whole-blood ionized Ca concentration ([iCa]) on the day of calving [d 0; hypocalcemic [iCa] <1.0 mmol/L (n = 51); normocalcemic [iCa] ≥1.0 mmol/L (n = 49)]. Cows were blocked based on calving date and parity. Blood samples were collected approximately 14 d from expected calving date (d −14), the day of calving (d 0), and on d 3, 7, 14, 21, and 35 postpartum for measurement of plasma nonesterified fatty acid, iCa, total Ca, glucose, and total and direct bilirubin concentrations, and plasma aspartate aminotransferase and gamma glutamyl transferase activities. Liver biopsies were obtained from a subset of cows on d 0, 7, and 35 for quantification of lipid content. Milk samples were collected on d 3, 7, 14, 21, and 35 postpartum for measurement of somatic cell count and percentages of protein, fat, and solids-not-fat. Data for peak test-day milk yield, services per conception, and days open were obtained from Dairy Herd Improvement Association herd records. Disease occurrence was determined based on herd treatment records. Hypocalcemic cows had significantly higher nonesterified fatty acids on d 0. Hypocalcemic cows also had significantly more lipid in hepatocytes on d 7 and 35 postpartum. However, no statistically significant differences were observed between groups for plasma aspartate aminotransferase and gamma glutamyl transferase activities or total and direct bilirubin concentrations. Milk protein percentage was lower in hypocalcemic cows on d 21 and 35. However other milk quality variables (somatic cell count, milk fat percentage, and solids-not-fat) and milk yield variables (peak test-day milk yield and 305-d mature-equivalent 4% fat-corrected milk yield) did not differ between groups. No differences were observed between groups in the occurrence of clinical mastitis, ketosis, displaced abomasum, dystocia, retained placenta, metritis, or fertility measures (percentage cycling at 50–60 d postpartum, services per conception, or days open). These data suggest that early lactation fatty acid metabolism differs between cows with subclinical hypocalcemia and their normocalcemic counterparts.     

Analysis of finite-differencing errors to determine cell size when modeling ferrites and other lossy electric and magnetic materials using FDTD

The focus of this paper is the modeling of materials that have both significant electric and magnetic losses, such as ferrites, using finite-difference time domain (FDTD). The primary contribution is identifying appropriate cell sizes when modeling these types of materials. It is shown that finite-differencing errors increase in lossy media compared to lossless media when sampling at the same number of cells per wavelength. Losses in a medium are defined by the ratio of the attenuation constant, /spl alpha/, to the phase constant, /spl beta/, since that ratio accounts for all losses, whether they be electric or magnetic. In addition to a detailed finite-differencing error analysis, a simple approximation is given for selecting a cell size in a lossy material that will give the same finite-differencing error as ten cells per wavelength in a lossless material. This paper also presents a means for deriving pure real constitutive parameters from complex constitutive parameters. Being able to make such calculations is useful in cases where complex constitutive parameters are given for a material, and the FDTD model being used only accepts pure real constitutive parameters, as is the case for several contemporary models. Comparisons of theoretical and FDTD-modeled reflection and transmission show that the derived, real constitutive parameters are valid.     

An empirical study of some election systems.

Uses presidential election data of the American Psychological Association for 5 yrs to compare a number of election systems in frequency of selecting Condorcet winners, consistency over subslates, and the effect of relevant and irrelevant candidates. The results from each system could be scaled in 1 dimension for each of the 5 elections, using the Kemeny metric. These scales were closely related to the weighting given to the variance of the candidates' rankings. An interpretation is given in terms of the polarizing effect of a candidate on an electorate. Election systems are discussed as strategies for the accumulation of subelectorates to reach a decisive set of voters. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recombinant adeno-associated virus vector: use for transgene expression and anterograde tract tracing in the CNS

Several signal transduction pathways have been implicated in the mechanism of protection induced by ischemic preconditioning (PC). For example, stimulation of a variety of G-protein coupled receptors results in stimulation of protein kinase C (PKC) which has been suggested to act as common denominator in eliciting protection. PC also significantly attenuated cAMP accumulation during sustained ischemia, suggesting involvement of an anti-adrenergic mechanism. The aim of this study was to evaluate the beta-adrenergic signal transduction pathway (as evidenced by changes in tissue cAMP and cAMP- and cGMP-phosphodiesterase) during the PC protocol as well as during sustained ischemia. Isolated perfused rat hearts were preconditioned by 3 x 5 min global ischemia (PC1,2,3) interspersed by 5 min reperfusion, followed by 25 min global ischemia. Tissue cAMP- and cGMP-PDE activity as well as cAMP and cGMP levels were determined at different time intervals during the PC protocol and sustained ischemia. Tissue cAMP increased with each PC ischemic event and normalized upon reperfusion, while PDE activity showed the opposite, viz a reduction during ischemia and an increase during reperfusion. Except for PC1, tissue cGMP showed similar fluctuations. Throughout 25 min sustained ischemia, cAMP- and cGMP-PDE activities were higher in PC than in nonpreconditioned hearts, associated with a significantly lesser accumulation in cAMP and higher cGMP levels in the former. Fluctuations in cyclic nucleotides during preconditioning were associated with concomitant changes in PDE activity, while the attenuated beta-adrenergic response of preconditioned hearts during sustained ischemia may partially be due to increased PDE activity.     

Sourcing Knowledge and Innovation in a Low-Technology Industry

This paper investigates the relationship between knowledge sourcing and innovation in a select low- to medium-technology industry, the forest sector. It is based on data from the Statistics Canada Survey of Innovation 2005. Econometric models are developed and tested, specifically logistic regression analyses, in order to probe the relationship between select forms of embodied and disembodied knowledge and levels of innovation intensity. Differences between single establishment Canadian firms, multi-establishment Canadian firms, Canada–USA multi-establishment firms and establishments belonging to multinational firms are studied in terms of the relationship between innovation and sources of knowledge. Findings indicate that establishment innovative performance is related to knowledge sourcing strategies and furthermore that organization ownership/structure impacts significantly upon this relationship.     

The Effect of Tree Cover on Air-Ground, VHF Propagation Path Loss

A theory accounting for attenuation caused by tree cover for line-of-sight propagation paths at VHF using vertical polarization is presented. An approach to implementing this theory using a terrainsensitive GTD propagation model is also given. Comparisons of model predictions and airborne measurements show that the approach is valid.