Breaking the Nyquist barrier

The author discusses the concept that data sampled beyond the Nyquist frequency is meaningless. A simple signal processing scheme to extend resolution to nearly twice the Nyquist without the problem of alias emerged. It starts by placing one-dimensional signals into a simulated sample-and-hold process in a Mathcad application     

The Study of Heterogeneous Catalysts by High-Resolution Transmission Electron MicroscoDV

Advances in instrumentation have made it possible in recent years to study the microstructure of inorganic materials at atomic resolution using the technique of high-resolution electron microscopy (HREM). Details of instrumentation have been described elsewhere [l], and applications and trends for HREM have recently been reviewed [2]. Although HREM is primarily a technique for studying bulk defects, it is increasingly also being applied in the profile-imaging mode to derive information about surfaces [3]. The high spatial resolution of the electron microscope makes it a valuable tool for the characterization of heterogeneous catalysts. This is evidenced by the growing number of studies wherein electron micrographs are being used to describe the morphology of a particular catalyst. Profile imaging is proving particularly useful in this regard for following changes in surface structure as a function of treatment conditions [4].     

Hip impact velocities and body configurations for voluntary falls from standing height

OBJECTIVE: To determine prevalence of various pheno- and genotypes of Serpulina sp in young pigs in relation to diarrhea and feed medication in Swedish pig-rearing herds. DESIGN: Isolation of spirochetes. Phenotypical and genotypical classification. SAMPLE POPULATION: Young pigs (n = 358) in 19 pigrearing herds. PROCEDURE: Serpulina isolates were classified according to a biochemical scheme based on hemolysis, indole production, hippurate hydrolysis, and alpha-galactosidase, alpha-glucosidase, and beta-glucosidase activities. The 16S rRNA sequences for 10 of the field strains and 2 type strains of Serpulina spp were aligned and compared. Minimum inhibitory concentrations of olaquindox for 9 of the strains were determined. RESULTS: Weakly beta-hemolytic intestinal spirochetes (WBHIS) were isolated from 17 of the herds and 65% of the samples. More than 1 phenotype of WBHIS was found in 12 of the 19 herds. S hyodysenteriae was not isolated in any of the herds. Hippurate-positive WBHIS were isolated in 6 of 7 herds affected by diarrhea, but in only 1 of 8 herds without diarrhea. Hippurate-positive strains were closely related to the pathogenic strain P43 if judged from sequence comparisons. Strains with the same biochemical profile isolated within a herd had identical sequences, but when isolated from different herds, sequence differences were observed. The prevalence of WBHIS was reduced in herds medicated with olaquindox. Investigated field strains had minimum inhibitory concentration values < or = 1 microgram/ml for olaquindox. CONCLUSION: The presence of WBHIS, with the ability to hydrolyze hippurate, was related to diarrhea in pig herds. CLINICAL RELEVANCE: Potentially pathogenic WBHIS can be distinguished from nonpathogenic strains by the hippurate hydrolysis test.     

Effects of viscosity on the bitterness and astringency of grape seed tannin

To examine the separate effects of viscosity and sweetness on astringency, aqueous solutions of grape seed tannin (GST) were thickened with carboxymethyl cellulose (CMC) from 2 to 45 cP (experiment 1) or sweetened with 0 to 1.8 g/L aspartame (experiment 2). Trained subjects continuously rated astringency and bitterness in duplicate. Subjects were categorized by the salivary flow induced by citric acid and ability to taste n-propyl thiouracil (PROP). In experiment 1, maximum intensity and total duration of astringency were significantly decreased as viscosity rose, although time to maximum intensity of astringency was not affected. Maximum intensity and total duration of bitterness were not significantly affected by increasing viscosity; however, the onset of bitterness was significantly delayed. In experiment 2, increasing sweetness had no affect on any astringency parameter, although maximum intensity of bitterness was significantly decreased. Neither PROP nor salivary flow-status had any effect on perception of bitterness or astringency in either experiment.     

Control-canonical-form method applied to generating systems to improve dynamic stability characteristics

Contents The control-canonical-form (CCF) method is introduced for the purpose of applying it to high-order state-space single-input single or multiple-output (SISO or SIMO) and multiple-input multiple-output (MIMO) linear time-invariant system models to determine closed-loop systems (i.e. design robust controllers) from which enchanced dynamic stability characteristics and overall performance of these systems is achieved. The method has been applied successfully to a SISO 6th-order linearized state-space open-loop model (representing a simplified hydro power system), and to a MIMO 8th-order linearized state-space open-loop model (representing an 87.5 kVA synchronous machine with conventional exciter supplying power to an electric utility system through an interconnection network)

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Anwendung der kanonischen Form der Zustandsrückführung auf Erzeugersysteme zur Verbesserung der dynamischen Stabilitätseigenschaften

Übersicht Die Methode der kanonischen Form wird auf lineare zeitinvariante Systeme höherer Ordnung im Zustandsraum angewendet, die eine oder mehrere Eingangsgrößen bei einer oder mehreren Ausgangsgrößen aufweisen. Damit werden robuste Regler entworfen, welche die dynamische Stabilität und das gesamte Betriebsverhalten verbessern. Die Methode wurde erfolgreich auf ein linearisiertes Modell sechster Ordnung mit einem Eingang und einem Ausgang angewendet, das vereinfachend eine Wasserkraftanlage darstellt; außerdem auf ein linearisiertes Zustandsmodell achter Ordnung einer Synchronmaschine 87,5kVA mit konventioneller Erregung, die über ein Verbindungsnetzwerk in das öffentliche Netz einspeist.

     

Primary cell culture of human type II pneumonocytes: maintenance of a differentiated phenotype and transfection with recombinant adenoviruses

Studies of the regulation of surfactant lipoprotein metabolism and secretion and surfactant protein gene expression have been hampered by the lack of a cell culture system in which the phenotypic properties of type II cells are maintained. We have developed a primary culture system that facilitates the maintenance of a number of morphologic and biochemical properties of type II pneumonocytes for up to 2 wk. Cells were isolated by collagenase digestion of midgestation human fetal lung tissue that had been maintained in organ culture in the presence of dibutyryl cyclic AMP (Bt2cAMP) for 5 days. The isolated cells were enriched for epithelial components by treatment with DEAE-dextran, plated on an extracellular matrix (ECM) derived from Madin-Darby canine kidney (MDCK) cells, and incubated at an air/liquid interface in a minimal amount of culture medium containing Bt2cAMP. The cell cultures were comprised of islands of round epithelial-like cells containing numerous dense osmiophilic granules, surrounded by sparse spindle-shaped cells with the appearance of fibroblasts. Ultrastructural examination revealed that the osmiophilic granules had the appearance of lamellar bodies, the distinguishing feature of type II pneumonocytes. Additionally, the cultures maintained elevated levels of SP-A gene expression for up to 2 wk. The expression of mRNAs encoding SP-A, SP-B, and SP-C were regulated in the cultured cells by glucocorticoids and cyclic AMP in a manner similar to that observed in fetal lung tissue in organ culture. The differentiated phenotype was most apparent when the cells were cultured at an air/liquid interface. In order to utilize the cultured type II cells for study of the effects of overexpression of various proteins and for promoter analysis, it is of essence to transfect DNA constructs into these cells with high efficiency. Unfortunately, we found the cells to be refractory to efficient transfer of DNA using conventional methods (i.e., lipofection, electroporation, or calcium phosphate-mediated transfection). However, replication-defective recombinant human adenoviruses were found to provide a highly efficient means of introducing DNA into the type II pneumonocytes. Furthermore, we observed in type II cell-enriched cultures infected with recombinant adenoviruses containing the lacZ gene under control of a cytomegalovirus promoter, that beta-galactosidase was expressed uniformly in the islands of type II cells and surrounding fibroblasts. By contrast, in cultures infected with recombinant adenoviruses containing the human growth hormone (hGH) gene under control of the SP-A gene promoter and 5'-flanking region, hGH was expressed only in the type II cells. Thus, this culture system provides an excellent means for identifying genomic elements that mediate type II cell-specific gene expression.     

Loudness balance between acoustic and electric stimulation by a patient with a multichannel cochlear implant

Estimates of loudness balance were obtained for acoustically and electrically presented 250 Hz sine signals from a patient who uses the Ineraid multichannel cochlear implant. Acoustic and electric loudness matching was possible because the patient evidenced a 25 dB HL threshold at 250 Hz in his nonimplanted ear. The level of the electrical stimulus in microamperes required for a balance of loudness grew linearly with equal increments in decibels for the acoustic stimulus. These data, in concert with the very limited data from previous studies, provide a rationale for using a logarithmic transformation of acoustic to electric intensity in signal processors for cochlear implants.