Analysis on the effectiveness of the 20-H rule for printed-circuit-board layout to reduce edge-radiated coupling

This paper presents the quantified study of the electromagnetic radiation mechanism of the 20-H rule using a numerical approach that has not yet been systematically addressed. The 20-H rule is a rule-of-thumb layout technique recommended to minimize radiated fields propagating from the edges of a printed circuit board (PCB) coupling onto nearby structures. Propagating electromagnetic fields may corrupt adjacent cable assemblies, sheet metal enclosures, and aperture openings. The magnitude of this design rule is investigated using the full-wave finite-difference time-domain (FDTD) method. An analysis on whether benefits exist from use of this rule is examined and under what conditions the rule is valid when correctly implemented. The purpose of this paper is to provide insight into the validity of the 20-H rule, recognizing that every PCB will have different simulation results. FDTD is used to capture a snapshot view of field propagation. This view allows one to determine the validity of the 20-H rule at a single point of time within a dynamic structure and what may be expected when digital components are finally added to a PCB assembly, which generally negates simulated results.     

Transepithelial SCFA fluxes link intracellular and extracellular pH regulation of mouse colonocytes

We have studied pH regulation in both intracellular and extracellular compartments of mouse colonic crypts, using distal colonic mucosa with intact epithelial architecture. In this work, we question how transepithelial SCFA gradients affect intracellular pH (pHi) and examine interactions between extracellular pH (pHo) and pHi regulation in crypts of distal colonic epithelium from mouse. We studied pH regulation in three adjacent compartments of distal colonic epithelium (crypt lumen, crypt epithelial cell cytosol, and lamina propria) with SNARF-1 (a pH sensitive fluorescent dye), digital imaging microscopy (for pHi), and confocal microscopy (for pHo). Combining results from the three compartments allows us to find how pHi and pHo are regulated and related under the influence of physiological transepithelial SCFA gradients, and develop a better understanding of pH regulation mechanisms in colonic crypts. Results suggest a complex interdependency between SCFA fluxes and pHo values, which can directly affect how strongly SCFAs acidify colonocytes.     

Subcellular redistribution is involved in acute regulation of the brush border Na+/H+ exchanger isoform 3 in human colon adenocarcinoma cell line Caco-2. Protein kinase C-mediated inhibition of the exchanger

Na+/H+ exchanger isoform 3 (NHE3), an epithelial brush border isoform of the Na+/H+ exchanger gene family, plays an important role in reabsorption of Na+ in the small intestine, the colon, and the kidney. In several cell types, phorbol 12-myristate 13-acetate (PMA) acutely inhibits NHE3 activity by changes in Vmax, but the mechanism of this inhibition is unknown. We investigated the role of subcellular redistribution of NHE3 in the PMA-induced inhibition of endogenous brush border NHE3 in a model human colon adenocarcinoma cell line, Caco-2. Subcellular localization of NHE3 was examined by confocal morphometric analysis complemented with cell surface biotinylation and compared with NHE3 activity evaluated by fluorometric measurement of intracellular pH. PMA inhibited NHE3 activity by 28% (p < 0.01), which was associated with a decrease of the ratio of the brush border/subapical cytoplasmic compartment of NHE3 from approximately 4.3 to approximately 2.4. This translocation resulted in 10-15% of the total cell NHE3 being shifted from the brush border pool to the cytoplasmic pool. These effects were mediated by protein kinase C, since they were blocked by the protein kinase C inhibitor H7. We conclude that inhibition of NHE3 by protein kinase C in Caco-2 cells involves redistribution of the exchanger from brush border into a subapical cytoplasmic compartment, and that this mechanism contributes approximately 50% to the overall protein kinase C-induced inhibition of the exchanger.     

Cosmic ray soft error rates of 16-Mb DRAM memory chips

Manufactured 16-Mb DRAM memory chips use three different cell technologies for bit storage: stacked capacitors, trenches with internal charge, and trenches with external charge. We have measured the soft fail probability of 26 different 16-Mb chips produced by nine vendors to evaluate whether the different cell technologies have an impact on the chip soft error rate. This testing involved irradiation with neutrons, protons, and pions, the principle hadrons of terrestrial cosmic rays. The results show clear differences in soft-fail sensitivity, which appears to be related to the cell structure     

Extracellular pH regulation in microdomains of colonic crypts: effects of short-chain fatty acids

It has been suggested that transepithelial gradients of short-chain fatty acids (SCFAs; the major anions in the colonic lumen) generate pH gradients across the colonic epithelium. Quantitative confocal microscopy was used to study extracellular pH in mouse distal colon with intact epithelial architecture, by superfusing tissue with carboxy SNARF-1 (a pH-sensitive fluorescent dye). Results demonstrate extracellular pH regulation in two separate microdomains surrounding colonic crypts: the crypt lumen and the subepithelial tissue adjacent to crypt colonocytes. Apical superfusion with (i) a poorly metabolized SCFA (isobutyrate), (ii) an avidly metabolized SCFA (n-butyrate), or (iii) a physiologic mixture of acetate/propionate/n-butyrate produced similar results: alkalinization of the crypt lumen and acidification of subepithelial tissue. Effects were (i) dependent on the presence and orientation of a transepithelial SCFA gradient, (ii) not observed with gluconate substitution, and (iii) required activation of sustained vectorial acid/base transport by SCFAs. Results suggest that the crypt lumen functions as a pH microdomain due to slow mixing with bulk superfusates and that crypts contribute significant buffering capacity to the lumen. In conclusion, physiologic SCFA gradients cause polarized extracellular pH regulation because epithelial architecture and vectorial transport synergize to establish regulated microenvironments.     

Rapid computerized analysis of Na+/H+ exchange flux

The regulation of intracellular pH (pHi) is mediated by membrane transporters whose activity is directly controlled by pHi. Therefore, transport rates must be compared at identical pHi values in functional studies of these transporters. This is conventionally performed using scatter plots showing initial rates of proton flux versus intracellular pH. We present justification for determining proton flux over a wide range of pHi, by digitally smoothing a pHi trace and then directly taking the first derivative versus time of smoothed data. Compared to conventional least-squares analysis of initial rates, the derivative method generates much more information per experiment. Compared to other methods which fit pHi traces to a defined equation prior to rate calculation, the new method does not require that the pHi trace be well fit by any given mathematical function. The derivative technique is illustrated in an analysis of Na+/H+ exchange in Caco-2 cells. Intracellular pH is measured fluorometrically in cells loaded with BCECF (2',7'-bis[2-carboxyethyl]-5-(and-6)carboxyfluorescein). To validate the analysis of Na+/H+ exchange over an extended time range, we demonstrate that cellular acidification with NH4Cl does not change steady state Na+ content. We find that proton flux rates analyzed by the derivative method are equivalent to initial rates measured by least-squares analysis.     

Contour measurement using retrographic imaging

A new experimental method called retrographic imaging has been developed which uses retroreflected light for visualising minute irregularities in reflective opaque surfaces. This paper provides a qualitative explanation of this phenomenon, the experimental setup required for such imaging, and describes an experiment which was devised to determine how this type of imaging can be correlated to actual surface topography. Results indicate that grey level intensity is proportional to an average between the surface contour and its rate of change of slope.     

The political boundaries of strategic decision support systems

Decision support systems have begun to impact the healthcare strategic planning environment. What are the repercussions to the chief financial officer as these systems make further headway?