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PubMed2001

Effects of layer thickness for SAW, PSAW, and HVPSAW devices.

Considerable efforts in recent SAW device design and development have been aimed at obtaining high frequency, low loss, and high performance. A large number of applications relate to cellular and mobile telephony, pagers, local area networks, cordless phones, global positioning systems (GPS), and security systems. Pseudo-SAW (PSAW) and high velocity PSAW (HVPSAW) have received great attention because of their high phase velocities and, therefore, the high frequencies of operation that these modes provide. In addition to high phase velocities, the pseudomodes must also present low propagation losses and considerably high electromechanical coupling coefficients to be considered for surface acoustic wave (SAW) devices. This paper verifies that the metallic layer thickness is a relevant SAW device parameter, which must be considered to achieve lower losses for high frequency, low loss SAW devices. Popular PSAW and HVPSAW material orientations, such as 64 degrees YX LiNbO3 (0 degree -26 degrees 0 degree), 36 degrees YX LiTaO3 (0 degree -54 degrees 0 degree), LiNbO3 (90 degrees 90 degrees 36 degrees), LiTaO3 (90 degrees 90 degrees 31 degrees), and Li2B4O7 (0 degree 47.3 degrees 90 degrees), are considered as examples. In addition to the reduced loss analysis and the dispersion analysis for the pseudo modes, the present work discusses the transitions with respect to the layer thickness from the PSAWs and HVPSAWs to the generalized SAWs (GSAWs) and Rayleigh (sagittal particle motion) modes. In addition to contributing to the knowledge of the pseudomodes behavior with layer thickness, this mode transition analysis enlightens the situation in which the losses in the pseudo modes go to zero because of the merging of the pseudo modes into the SAWs (GSAWs and Rayleigh). The fact that the SAWs are a continuation as a function of thickness for the pseudo modes may be conveniently used in the fabrication of low loss devices. In addition, the effects of heavy layer metals, such as gold, in reducing the layer thickness at which the pseudo modes merge to the SAWs are discussed. Numerical results are compared with experimental data available in the literature, and the present analysis elucidates experimentally observed higher order pseudo modes and values of layer thickness for which lower losses are achieved.

Journal Article↗
PubMed1980

Purification of peptides: an efficient procedure for the separation of peptides from amino acids and salt.

A novel method for the separation of peptides from amino acids and salts has been developed. Separation is achieved by passage of the sample through a column of octadecasilyl-silica (ODS). Peptides, but not amino acids and salts, are strongly retained by ODS in an aqueous mobile phase and can be recovered by elution with an aqueous-alcoholic mobile phase. The method is applicable to most peptides and is fast and simple. Moreover, it is characterized by good recovery yields and high sample capacity.

Amino Acids↗
PubMed1998

FLT-3 ligand mobilizes hematopoietic primitive and committed progenitor cells into blood in mice.

We investigated the effects of the administration of FLT-3 ligand (FL) on mobilization of primitive and committed progenitor cells in mice. C57bl/6J mice were injected subcutaneously with FL once a day for 5 d at doses of 20, 100 and 200 microg/kg. After the collection of peripheral blood, we determined the number of white blood cells (WBCs) with the differential counts. The formation of colony-forming cells (CFCs) in peripheral blood, bone marrow and spleen was evaluated. Although the administration of FL, 20 microg/kg, did not stimulate leukocytosis, its administration at doses of 100 and 200 microg/kg increased the number of WBC up to 1.7- and 2.4-fold, respectively. Committed progenitor cells were mobilized into the peripheral blood dose-dependently and the number of CFCs was increased up to 5.5-fold by the administration of FL at 200 microg/kg on d 5. The number of CFCs in the bone marrow increased, but not dose-dependently. The number of CFCs in the spleen also increased up to 32-fold at a dose of 200 microg/kg FL. Mobilized peripheral blood mononuclear cells were transplanted into lethally irradiated mice and the number of CFU-S (d 12) was scored. A dose-dependent mobilization of CFU-S (d 12) into peripheral blood was also observed. These observations suggest that FL can mobilize hematopoietic primitive and committed progenitor cells into the peripheral blood of mice and those cells mobilized by FL may be applicable to peripheral blood stem cell transplantation.

Animals↗
PubMed1999

Discrimination of subtype B and non-subtype B strains of human immunodeficiency virus type 1 by serotyping: correlation with genotyping.

The ability of a peptide-based serotyping assay to differentiate human immunodeficiency virus (HIV) type 1 (HIV-1) subtype B infections from non-subtype B infections was investigated with 166 anti-HIV-1- and HIV RNA-positive (by PCR) serum or plasma specimens. The specimens were divided genetically into those infected with subtype B and non-subtype B by application of a screening heteroduplex mobility assay (HMA) that used plasmids for subtypes A and B alone. Specimens that were not clearly infected with HIV-1 subtype B by HMA or for which the two methods had discordant results in distinguishing those infected with subtype B from those infected with non-subtype B were then investigated with a full HMA plasmid panel and, for selected specimens, env sequencing. For the 141 genotyped and serotypically reactive specimens, the correlation between genotyping and serotyping (all subtypes) was 69%. Of the 67 specimens that reacted monotypically as serotype B, 64 were shown to be infected with genotype B (positive predictive value, 96%). Of the 82 specimens that contained genotype B nucleic acid, 64 reacted monotypically as serotype B (sensitivity, 78%), and 4 specimens reacted with a single non-subtype B peptide; the viruses in 14 specimens could not be assigned a serotype. Initial screening results had indicated that 12 samples had results discordant between restricted HMA and serotyping. The V3 loop amino acids of the infecting HIV strains from the seven specimens with discordant serology results were analyzed. For five specimens discordance occurred when the amino acid sequence of the infecting virus closely resembled those of more than one consensus peptide antigen or when the observed V3 crown motif of the strain was atypical for the genetic subtype present. For the other two specimens no explanation for the discordance was identified. Five specimens gave unclear or discordant results in the initial HMA screen, but the results were resolved when the full plasmid panel was used. Serotyping, although of limited sensitivity, distinguishes between subtype B and non-subtype B infections with a high degree of specificity. However, it poorly differentiates the major non-subtype B subtypes, particularly subtypes A and C. When HIV-1 subtype B predominates, serological typing and/or subtype-restricted HMA screening usefully distinguishes between subtype B and non-subtype B infections.

Amino Acid Sequence↗
PubMed2004

Physiological concentrations of bile salts inhibit recovery of ischemic-injured porcine ileum.

We have previously shown rapid in vitro recovery of barrier function in porcine ischemic-injured ileal mucosa, attributable principally to reductions in paracellular permeability. However, these experiments did not take into account the effects of luminal contents, such as bile salts. Therefore, the objective of this study was to evaluate the role of physiological concentrations of deoxycholic acid in recovery of mucosal barrier function. Porcine ileum was subjected to 45 min of ischemia, after which mucosa was mounted in Ussing chambers and exposed to varying concentrations of deoxycholic acid. The ischemic episode resulted in significant reductions in transepithelial electrical resistance (TER), which recovered to control levels of TER within 120 min, associated with significant reductions in mucosal-to-serosal (3)H-labeled mannitol flux. However, treatment of ischemic-injured tissues with 10(-5) M deoxycholic acid significantly inhibited recovery of TER with significant increases in mucosal-to-serosal (3)H-labeled mannitol flux, whereas 10(-6) M deoxycholic acid had no effect. Histological evaluation at 120 min revealed complete restitution regardless of treatment, indicating that the breakdown in barrier function was due to changes in paracellular permeability. Similar effects were noted with the application of 10(-5) M taurodeoxycholic acid, and the effects of deoxycholic acid were reversed with application of the Ca(2+)-mobilizing agent thapsigargin. Deoxycholic acid at physiological concentrations significantly impairs recovery of epithelial barrier function by an effect on paracellular pathways, and these effects appear to be Ca(2+) dependent.

Animals↗
PubMed1995

Potentiation of a slow Ca(2+)-dependent K+ current by intracellular Ca2+ chelators in hippocampal CA1 neurons of rat brain slices.

1. In hippocampal CA1 neurons of rat brain slices, a Ca(2+)-dependent slow afterhyperpolarization (sAHP) and underlying K+ current (IsAHP) are activated by Ca2+ influx and presumably reflect the time course of the intracellular Ca2+ signal produced by neuronal stimulation. We tested the hypothesis that when exogenous Ca2+ chelators become the predominant mobile Ca2+ buffer in the neuron, they alter the shape of intracellular Ca2+ signals responsible for IsAHP. The nature of this alteration provides insight into the mechanism of IsAHP generation. 2. Derivatives of 1,2-bis-[2-amino phenoxy] ethane N,N,N',N' tetraacetic acid (BAPTA) with different dissociation constants (KDS) for Ca2+ ranging from 0.15 to 7,000 microM were used to test this hypothesis. We also examined the effects of ethylene glycolbis (beta-aminoethyl either)-N,N,N',N'-tetraacetic acid (EGTA), which has a KD similar to that of BAPTA for Ca2+, but which binds and releases Ca2+ 100 times more slowly. When delivered to the cytoplasm by dialysis from a patch pipette, these chelators potentiated, inhibited, or had no effect on IsAHP depending on their concentration, affinity, and binding kinetics. 3. IsAHP decayed exponentially over much of its time course, with a half-decay time of 0.9 +/- 0.1 s (mean +/- SE, n = 22). Immediately after breakthrough into the whole cell configuration, there was an initial period of approximately 5 min during which IsAHP magnitude increased approximately 3.5-fold with no change in time course. Thereafter, the time course and amplitude of IsAHP were stable for > 45 min. 4. Addition of 1 mM of the high-affinity chelators 5,5'-dimethyl BAPTA or BAPTA to the pipette solution first increased the decay time of IsAHP 1.5-fold. However, within 10-15 min after break-through, the current was abolished. Addition of Ca2+ (0.1-1.0 mM) to the patch pipette containing the BAPTA derivatives reduced the ability of a given concentration of high-affinity chelator to inhibit IsAHP and also prolonged the period of IsAHP enhancement. A similar prolongation of the period of enhancement with even less attenuation of IsAHP was apparent with 0.1 mM 5,5'-dimethyl BAPTA and 0.1 mM Ca2+. 5. The intermediate-affinity chelator 4.4'-difluoro BAPTA (1 mM) prolonged the decay phase of the sAHP/IsAHP without attenuating the current. A twofold prolongation of IsAHP also was observed in neurons dialyzed with internal solution containing 3 mM EGTA and 0.3 mM Ca2+. Dialysis with 1 mM of the low-affinity chelators 2-amino-5-fluorophenol-N,N,O-triacetic acid (5-fluoro APTRA) or 5,5'-dinitro BAPTA had no apparent effect on IsAHP. All of the chelators that prolonged the decay phase of IsAHP also induced a rising phase such that a well-defined peak of IsAHP could be discerned at approximately 0.6 s after the end of the stimulus used to evoke the current. 6. Weak stimulation of muscarinic receptors selectively inhibits IsAHP. Thus the uncontaminated time course of IsAHP can be deduced by subtracting currents recorded before and after such muscarinic stimulation. With minimal exogenous buffer in the pipette (0.1 mM EGTA), the muscarinic-receptor-sensitive current exhibited a rising phase lasting approximately 300 ms and then decayed with a half-time of approximately 1 s. Both the rising and decay phases of the muscarinic-receptor-sensitive current were prolonged at least twofold by dialysis with BAPTA or 4,4'-difluoro BAPTA. Thus the effect of the chelators on the time course of IsAHP is not simply and artifact of inhibition of early components of the outward current. 7. The effects of BAPTA analogues on the time course of IsAHP are not due to changes in mobilization of intracellular Ca2+. External application of caffeine (10 mM), ryanodine (20 microM), dantrolene (20 microM), or thapsigargin (100 microM) had no effect on IsAHP recorded with the standard pipette solution or

Adaptation, Physiological↗
PubMed1978

Noninvasive recording of His-Purkinje activity in man by ORS-triggered signal averaging.

Mobile instrumentation and a clinically applicable method have been developed for external His bundle recording. High gain signal amplification (10)(5) filtering (30--300 HZ) and averaging (128 or 256 consecutive cycles) are used. Acquisition of signals arising in the P-R interval is triggered by the patient's QRS signal at the end of that interval. The precordial bipolar electrodiogram is digitized at 5k HZ with 8 bit resolution and transferred to a 1,024 word, 18 bit signal averager. The averaged signal is then displayed on an oscilloscope and photographed. Good correlations were obtained between direct intracardiac and precordial recordings in experimental animals and in humans. Noise level after averaging was below 0.3 microV, and there was good elimination of asynchronous atrial and ectopic ventricular activity. With averaging of 128 or 256 consecutive cycles, the signal attenuation after propagation to the chest wall was in the range 1:2000 to 1:4000 in comparison with the directly recorded His bundle activity deflections. The noninvasive method may be of value in follow-up of acute and chronic disturbances of atrioventricular conduction, as well as in studies of effects of pharmacologic interventions.

Animals↗
PubMed2005

Blind and sighted pedestrians' judgments of gaps in traffic at roundabouts.

This paper reports two experiments about street crossing under conditions of free flowing traffic, with a focus on modem roundabout intersections. Experiment 1 was conducted at three roundabouts varying in size and traffic volume. Six totally blind and six sighted adults judged whether gaps in traffic were long enough to permit crossing to the median (splitter) island before the next vehicle arrived. Gap distributions and measures of judgment quality are reported. Overall, blind participants were about 2.5 times less likely to make correct judgments than sighted participants, took longer to detect crossable gaps, and were more likely to miss crossable gaps altogether. However, the differences were significant only at the two higher volume roundabouts. In Experiment 2, we evaluated the response of drivers to pedestrians with and without mobility devices (i.e., long canes, dog guides). The experiment was conducted at a single-lane roundabout, a midblock crossing, and a two-way-stop-controlled intersection. Site-specific characteristics appeared to have a greater impact on drivers' yielding than did a mobility device. Actual or potential applications of this research include the development of methods for assessing pedestrian safety and driver behavior as well as identifying intersections that may require modification in order to be accessible to blind pedestrians.

Accidents, Traffic↗
PubMed1992

A technique for embedding undecalcified bone samples for detecting alpha-emitters using vacuum impregnation with Spurr's resin.

A method has been developed by which large samples of mineralized bone, containing an alpha-emitter, can be embedded in Spurr's resin in a fraction of the time required by conventional methods. Bone samples were freeze-dried or fixed and dried prior to impregnation with Spurr's resin under vacuum. Sections were cut for the preparation of either alpha-track or fission-track autoradiographs using the solid state detector CR-39. This method is applicable to samples containing a mobile form of a radionuclide that may be translocated during the processes of fixation and dehydration of the specimen.

Alpha Particles↗
PubMed2002

Information technology can enhance quality in regional health delivery.

OBJECTIVES: a) The use of information technology (IT) based solutions for quality health delivery in regional health information networks and the study of the enabling factors for their use in a regional health care network from key classes of users such as the medical personnel and the citizens. b) Identification of potential technologies for usage from all citizens and health providers in a regional environment, in all aspects of everyday life. c) Presentation of a generic user model for reference when developing and assessing IT based health delivery solutions. METHODS: After defining the major questions to be addressed, an overview of tele-health and tele-medicine technologies and solutions currently available shall be presented. Further, a generic user model applied to the use of IT based regional health delivery solutions both for the daily life and home care, and for research and clinical routine purposes are presented. Enabling technologies for integration of different IT modules, medical data processing and management procedures and the wireless application protocol (WAP) technology is discussed. RESULTS: Different levels of user applications are presented such as mobile telephony driven health information monitoring and systems integrating electronic health care records with multimedia medical information management and processing modules. CONCLUSIONS: Although IT solutions are advanced and continue to evolve, still the user acceptance and user friendliness issues are unresolved. Mobile telecommunication solutions however may hold the key for wide scale implementation of IT solutions in regional health information networks and increased quality of health services.

Decision Support Systems, Clinical↗
PubMedDate not supplied

Technique, errors and safeguards in modern Küntscher nailing.

Intramedullary nailing after reaming of the medullary cavity according to Küntscher, provides a rigid fixation and makes early mobilization possible, and is even applicable to infected non-unions. Experience with 150 cases of fresh femoral fractures and more than 80 cases of non-union of the femur, the tibia, the humerus and the forearm, demonstrates that thorough familiarity with the instrumentation and the pitfalls of the technique, as well as the correct clinical indications of the method are critical to the achievement of good results.

Bone Diseases↗
PubMed1992

Abdominosacral resection for midrectal cancer.

Abdominosacral resection is the most reliable radical sphincter-saving operation for midrectal cancers which are too low for anterior resection. The posterior incision provides maximum exposure for wide resection of the tumor, a measured distal margin, and an accurate anastomosis. The procedure can be carried out consistently to the pelvic floor without disrupting the anal sphincters and their innervation. Sphincter function is consistently preserved. Mortality rate is no higher than for other radical rectal resections. Morbidity can be limited by the selective use of protective colostomy. The use of mechanical retractors and the end-to-end stapler facilitates the operation and should encourage its wider application. The transsacral approach allows mobilization of the rectum to the levators in every case, and resection is limited only by the distance of the tumor from the sphincter, and not by poor exposure due to obesity or a narrow pelvis. In the treatment of 926 consecutive patients with rectal cancer, sphincter-saving resection was possible in 79%. In our experience, abdominosacral resection extends the range of sphincter-saving resection beyond that which is possible by the abdominal approach alone, with no compromise in safety and no increased risk of local recurrence or death from cancer.

Abdomen↗
PubMedDate not supplied

Determination of trimetazidine dihydrochloride in the presence of its acid-induced degradation products.

Three methods are presented for the determination of trimetazidine dihydrochloride in the presence of its acid-induced degradation products. The first method was based on measurement of first-derivative D1 value of trimetazidine dihydrochloride at 282 nm over a concentration range of 8.00-56.00 microg/mL with mean percentage accuracy of 99.80+/-1.17. The second method was based on first derivative of the ratio spectra DD1 at 282 nm over the same concentration range with the percentage accuracy of 99.14+/-0.68. The third method was based on separation of trimetazidine dihydrochloride from its acid-induced degradation products followed by densitometric measurement of the spots at 215 nm. The separation was performed on silica gel 60 F254 using methanol-ammonia (100+/-1.5, v/v) as mobile phase. This method was applicable for determination of the intact drug in the presence of its degradation products over a concentration range of 2.00-9.00 microg/spot with mean percentage accuracy of 99.86+/-0.92. The proposed methods were successfully applied for the determination of trimetazidine dihydrochloride in bulk powder, laboratory-prepared mixtures containing different percentages of degradation products, and pharmaceutical dosage forms. The validity of results was assessed by applying the standard addition technique. The results obtained agreed statistically with those obtained by the reported method.

Chromatography, High Pressure Liquid↗
PubMed2004

Operational variables in high-performance liquid chromatography-electrospray ionization mass spectrometry of peptides and proteins using poly(styrene-divinylbenzene) monoliths.

Capillary reversed-phase high-performance liquid chromatography (RP-HPLC) utilizing monolithic poly(styrene-divinylbenzene) columns was optimized for the coupling to electrospray ionization mass spectrometry (ESI-MS) by the application of various temperatures and mobile phase additives during peptide and protein analysis. Peak widths at half height improved significantly upon increasing the temperature and ranged from 2.0 to 5.4 s for peptide and protein separations at 70 degrees. Selectivity of peptide elution was significantly modulated by temperature, whereas the effect on proteins was only minor. A comparison of 0.10% formic acid (FA), 0.050% trifluoroacetic acid (TFA), and 0.050% heptafluorobutyric acid (HFBA) as mobile phase additives revealed that highest chromatographic efficiency but poorest mass spectrometric detectabilities were achieved with HFBA. Clusters of HFBA, water, and acetonitrile were observed in the mass spectra at m/z values >500. Although the signal-to-noise ratios for the individual peptides diverged considerably both in the selected ion chromatograms and extracted mass spectra, the average mass spectrometric detectabilities varied only by a factor of less than 1.7 measured with the different additives. Limits of detection for peptides with 500 nl sample volumes injected onto a 60 mm x 0.20 mm monolithic column were in the 0.2-13 fmol range. In the analysis of hydrophobic membrane proteins, HFBA enabled highest separation selectivity at the cost of lower mass spectral quality. The use of 0.050% TFA as mobile phase additive turned out to be the best compromise between chromatographic and mass spectrometric performance in the analysis of peptides and proteins by RP-HPLC-ESI-MS using monolithic separation columns.

Chromatography, High Pressure Liquid↗
PubMed2004

From SARS to systems: developing advanced knowledge management for public health.

Historically, public health has been at the forefront of data processing applications but it is lagging behind other areas of health care in the application of advanced interconnected and mobile information technologies. Ready to use technologies are lacking not only for the management of emerging infections or bio-terrorism but also for the coordination of prevention and chronic care initiatives. Advanced information and knowledge management for community health should expedite the transfer of research evidence to practice and provide essential logistical support for action. We need to find ways to integrate new scientific knowledge into our environment in order to expedite the translation of research to practice.

Decision Support Techniques↗
PubMed2005

[Stem cell therapy for chronic cardiac insufficiency--therapy of the future?].

The incidence of chronic cardiac insufficiency is constantly increasing. However, the current therapeutic possibilities during the terminal stage are limited by a lack of donor organs. For this reason, stem cell therapy is seen as a potent therapeutic option for the future. Catheter application or cytokine-mediated mobilization of autologous adult stem cells is for acute myocardial infarction safe and potentially effective; however, for chronic cardiac insufficiency, the successes have not yet been verifiable. Hence, embryonic stem cells offer a therapeutic option that cannot be ignored: These cells are pluripotent and are, theoretically, able to continue dividing in cell culture indefinitely. Through "tissue engineering" they could generate new myocardium that could be transplanted into patients suffering from chronic cardiac insufficiency to support the pump function.

Animals↗
PubMedDate not supplied

Letterer-Siwe disease: report of case.

Initial oral symptoms of Letterer-Siwe disease reveal the importance of a dentist in establishing this diagnosis. This case is important in that the patient was five months old, at which time an early diagnosis was made and treatment had begun. Because most cases occur in young children, a high level of suspicion is necessary, because the oral manifestations and radiographic findings in children may often resemble the periapical, periodontal or cystic involvements frequently seen first by the dentist. The oral lesions were necrotic, hemorrhagic, and degenerative gingival tissues in the maxillary molar area. Loss of alveolar bone was evident. There was precocious eruption of seven primary teeth, which were slightly mobile. Dentally, prophylaxis and fluoride applications were supportive measures.

Bone Marrow↗