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Biomedical subjects

R Gellert

Publications and source records attributed to R Gellert.

At least 19 recordsLinked to original sources
PubMed2004

Chemistry of rocks and soils at Meridiani Planum from the Alpha Particle X-ray Spectrometer.

The Alpha Particle X-ray Spectrometer on the Opportunity rover determined major and minor elements of soils and rocks in Meridiani Planum. Chemical compositions differentiate between basaltic rocks, evaporite-rich rocks, basaltic soils, and hematite-rich soils. Although soils are compositionally similar to those at previous landing sites, differences in iron and some minor element concentrations signify the addition of local components. Rocky outcrops are rich in sulfur and variably enriched in bromine relative to chlorine. The interaction with water in the past is indicated by the chemical features in rocks and soils at this site.

Alpha Particles↗
PubMed2004

Jarosite and hematite at Meridiani Planum from Opportunity's Mossbauer Spectrometer.

Mossbauer spectra measured by the Opportunity rover revealed four mineralogical components in Meridiani Planum at Eagle crater: jarosite- and hematite-rich outcrop, hematite-rich soil, olivine-bearing basaltic soil, and a pyroxene-bearing basaltic rock (Bounce rock). Spherules, interpreted to be concretions, are hematite-rich and dispersed throughout the outcrop. Hematitic soils both within and outside Eagle crater are dominated by spherules and their fragments. Olivine-bearing basaltic soil is present throughout the region. Bounce rock is probably an impact erratic. Because jarosite is a hydroxide sulfate mineral, its presence at Meridiani Planum is mineralogical evidence for aqueous processes on Mars, probably under acid-sulfate conditions.

Extraterrestrial Environment↗
PubMed2004

Soils of Eagle crater and Meridiani Planum at the Opportunity Rover landing site.

The soils at the Opportunity site are fine-grained basaltic sands mixed with dust and sulfate-rich outcrop debris. Hematite is concentrated in spherules eroded from the strata. Ongoing saltation exhumes the spherules and their fragments, concentrating them at the surface. Spherules emerge from soils coated, perhaps from subsurface cementation, by salts. Two types of vesicular clasts may represent basaltic sand sources. Eolian ripples, armored by well-sorted hematite-rich grains, pervade Meridiani Planum. The thickness of the soil on the plain is estimated to be about a meter. The flatness and thin cover suggest that the plain may represent the original sedimentary surface.

Extraterrestrial Environment↗
PubMed2004

Basaltic rocks analyzed by the Spirit Rover in Gusev Crater.

The Spirit landing site in Gusev Crater on Mars contains dark, fine-grained, vesicular rocks interpreted as lavas. Pancam and Mini-Thermal Emission Spectrometer (Mini-TES) spectra suggest that all of these rocks are similar but have variable coatings and dust mantles. Magnified images of brushed and abraded rock surfaces show alteration rinds and veins. Rock interiors contain </=25% megacrysts. Chemical analyses of rocks by the Alpha Particle X-ray Spectrometer are consistent with picritic basalts, containing normative olivine, pyroxenes, plagioclase, and accessory FeTi oxides. Mössbauer, Pancam, and Mini-TES spectra confirm the presence of olivine, magnetite, and probably pyroxene. These basalts extend the known range of rock compositions composing the martian crust.

Extraterrestrial Environment↗
PubMed2004

Chemistry of rocks and soils in Gusev Crater from the alpha particle x-ray spectrometer.

The alpha particle x-ray spectrometer on the Spirit rover determined major and minor elements of soils and rocks in Gusev crater in order to unravel the crustal evolution of planet Mars. The composition of soils is similar to those at previous landing sites, as a result of global mixing and distribution by dust storms. Rocks (fresh surfaces exposed by the rock abrasion tool) resemble volcanic rocks of primitive basaltic composition with low intrinsic potassium contents. High abundance of bromine (up to 170 parts per million) in rocks may indicate the alteration of surfaces formed during a past period of aqueous activity in Gusev crater.

Alpha Particles↗
PubMed2004

Mineralogy at Gusev Crater from the Mössbauer spectrometer on the Spirit Rover.

Mössbauer spectra measured on Mars by the Spirit rover during the primary mission are characterized by two ferrous iron doublets (olivine and probably pyroxene) and a ferric iron doublet (tentatively associated to nanophase ferric iron oxide). Two sextets resulting from nonstoichiometric magnetite are also present, except for a coating on the rock Mazatzal, where a hematite-like sextet is present. Greater proportions of ferric-bearing phases are associated with undisturbed soils and rock surfaces as compared to fresh rock surfaces exposed by grinding. The ubiquitous presence of olivine in soil suggests that physical rather than chemical weathering processes currently dominate at Gusev crater.

Extraterrestrial Environment↗
PubMed2004

Magnetic properties experiments on the Mars exploration Rover Spirit at Gusev Crater.

The magnetic properties experiments are designed to help identify the magnetic minerals in the dust and rocks on Mars-and to determine whether liquid water was involved in the formation and alteration of these magnetic minerals. Almost all of the dust particles suspended in the martian atmosphere must contain ferrimagnetic minerals (such as maghemite or magnetite) in an amount of approximately 2% by weight. The most magnetic fraction of the dust appears darker than the average dust. Magnetite was detected in the first two rocks ground by Spirit.

Atmosphere↗
PubMed2003

[Graduated compression stockings in surgery -- optional or obligatory?].

BACKGROUND: Graduated compression stockings (GCS) can effectively reduce postoperative deep vein thrombosis (DVT) and their use is recommended by expert committees. However, it appears that GCS are not frequently used. The objectives of this study are to evaluate the customary use of GCS in surgical settings in the City of Hamburg, Germany, and to present evidence on the effectiveness of GCS. METHODS: A questionnaire on the use of thromboprophylaxis was sent to 48 surgeons in Hamburg. In addition, a comprehensive search for randomized-controlled trials, reviews, and meta-analyses indexed in MEDLINE (1984-06/2002) and the Cochrane Library (Issue 2, 2002) was conducted to show the effectiveness of GCS compared to nontreatment, other antithrombotic methods, or combined treatment. RESULTS: Of 48 surgeons 39 responded. Seven surgeons dismissed the use of GCS for thromboprophylaxis, 3 used GCS alone, 25 GCS in combination with heparin, and 4 used GCS only for patients at high risk. The review of the literature revealed the effectiveness of GCS in general and for abdominal surgical patients. Enhanced benefit is suggested when combining GCS with another intervention such as low-dose unfractionated heparin. Single application of GCS in orthopedic surgical or neurosurgical patients using venography showed no effect when compared to combined treatment of GCS and low molecular weight heparin. Trials with patients undergoing gynecological and urological surgeries are rare. There is a lack of trials investigating health-related quality of life and costs associated with the use of GCS. Complications are poorly reported. A determination as to the appropriate length of stockings is presently not possible. CONCLUSIONS: GCS should be integral part of DVT prophylaxis in surgical departments. Their ineffectiveness is likely in some surgical populations.

Anticoagulants↗
PubMed2003

Effects of novel manufacturing technology on blood and dialysate flow distribution in a new low flux "alpha Polysulfone" hemodialyzer.

The main target for low flux hemodialyzers is an efficient low molecular weight solutes clearance. Such efficiency is largely dependent on the optimization of diffusion between blood and dialysis solution. The diffusion process can be impaired if there is a mismatch between blood and dialysate flow distribution in the dialyzer. Thus optimized flow distribution both in the blood and dialysate compartment becomes quintessential for the maximal efficiency of the diffusion process within the hemodialyzer. The present paper describes the distribution of the blood and dialysate flows in a new low flux polysulfone hollow fiber hemodialyzer characterized by a specific undulation of the fibers and a new cutting technology of the fibers for an improved micro-flow condition in the blood compartment headers. Twelve Diacap alpha Polysulfone LO PS 15 (1.5 sqm) (B. Braun Medizintechnologie, Melsungen Germany) were employed for the study. Six were analyzed in vitro and six were studied in vivo. Blood flow distribution was studied in vitro by dye injection in the blood compartment during experimental extracorporeal circulation utilizing human blood with hematocrit adjusted at 33%. Sequential images were obtained with a helical scanner in a fixed longitudinal section of the dialyzer 1 cm thick. Average and regional blood flow velocities were measured utilizing the reconstructed imaging sequence. The method allowed the calculation of single fiber blood flow (SF Qb) and the mass transfer zone (MTR) definition in digitally subtracted images. The patterns 20-10 and 40-30 were utilized. The same technology was used to evaluate flow distribution in the dialysate compartment after dye injection in the Hansen's connector. Regional dialysate flow was calculated in central and peripheral sample areas of 1 cm2. Six in vivo hemodialysis treatments on patients with end stage renal disease were performed at three different blood flow rates (250-350 and 450 ml/min) in order to measure urea, creatinine and phosphate clearance. Macroscopic and densitometrical analysis revealed that flow distribution was homogeneous in the blood compartment while in the dialysate compartment a slight difference between the peripheral and central regions in terms of flow velocity was observed. This however was not generating channeling phenomena. Urea creatinine and phosphate clearances were remarkably high and so were the Kt/V observed in all sessions, especially in relation to the studied blood flows. In conclusion, a significant blood to dialysate flow match with optimized countercurrent flow condition was observed in the studied hollow fiber hemodialyzers. Such optimization might be due both to the improved dialyzer design at the level of the blood header and to the specific fiber undulation that prevents dialysate channeling.

Biocompatible Materials↗
PubMed2001

[Recurrent Zieve's syndrome: a case report].

We report a case of recurrent Zieve's syndrome, consisting of jaundice, hemolytic anemia and hyperlipoproteinemia, initiated by alcohol abuse. The crucial feature of this syndrome, which allows differentiation with common acute alcoholic hepatitis, is the presence of hemolysis. There is no specific treatment, and restraining from alcohol consumption remains the basic prophylactic measure.

Alcoholism↗
PubMed2001

[Uremic neuropathy is more frequent in male patients].

The aim of this study was to analyse the relationship between clinical and electrophysiological features of somatic and autonomic neuropathy and gender of 51 patients on chronic hemodialysis. Apart from basic neurological examination, conduction velocities in peripheral nerves were determined, and the function of the autonomic nervous system was assessed with the help of two tests: R-R interval variation (RRIV) and sympathetic skin response (SSR). The incidence and intensity of clinical and electrophysiological signs of sensomotor neuropathy were statistically significantly more prevalent among male patients, whereas the symptoms suggesting autonomic involvement were more frequent in women. Results of parasympathetic electrophysiological tests were similar in both groups, but abnormal SSR results prevailed in male patients.

Adult↗
PubMed2000

Magnetic phase in the near-surface region of an FeBO3 single crystal

An FeBO3 single crystal was studied from 291 K up to the Neel temperature T(N) = 348.35 K by depth selective conversion electron Mossbauer spectroscopy in ultrahigh vacuum (10(-9) mbar). A new magnetic near-surface phase was found. Its thickness D diverges on approaching T(N) and gives a critical exponent for the correlation length of nu = 0.59(4). The phase boundary between the bulk and near-surface phase could be identified.

Journal Article↗
PubMed2000

Distribution of primary renal diseases leading to end-stage renal failure in the United States, Europe, and Australia/New Zealand: results from an international comparative study.

This report notes the differences in the classification of the primary renal disease (PRD) used in different renal dialysis and transplant registries worldwide. The heterogeneity of coding systems complicates the comparative analysis of end-stage renal disease from different regions. Using data collected over two decades in the United States, Europe, and Australia/New Zealand, we present a method for reorganization of the classes of PRD that allows a straightforward comparison of retrospective data from these registries.

Adult↗
PubMed1999

Cancer in patients on dialysis for end-stage renal disease: an international collaborative study.

BACKGROUND: Previous studies have suggested that the frequency of cancer is higher in patients with end-stage renal disease (ESRD) than in the general population, but have not established whether this increase is confined to certain cancers or to certain categories of ESRD patients. The aim of this study was to examine the risk of cancer in a large cohort of patients treated by dialysis but not transplantation. METHODS: We assembled a cohort of 831,804 patients who received dialysis during the period 1980-94 for ESRD in the USA, Europe, Australia, or New Zealand. We compared the observed frequency of cancer among these patients during 2,045,035 person-years of follow-up with the frequency of cancer in the respective background populations. FINDINGS: During average follow-up of 2.5 years, 25,044 (3%) of 831,804 patients developed cancer compared with an expected number of 21,185 (standardised incidence ratio 1.18 [95% CI 1.17-1.20]). We observed a higher risk of cancer in patients younger than 35 years (3.68 [3.39-3.99]), and the risk gradually decreased with increasing age. High risks were observed for cancer of the kidney (3.60 [3.45-3.76]), bladder (1.50 [1.42-1.57]), and thyroid and other endocrine organs (2.28 [2.03-2.54]). Excess cancers appeared in several organs for which viruses have been suspected as causative agents, whereas cancers of the lung, colorectum, prostate, breast, and stomach were not consistently increased. INTERPRETATION: The overall risk of cancer is increased in patients with ESRD, and the distribution of tumour types resembles the pattern seen after transplantation (although we have no data to make the comparison with skin cancer). The excess risk can largely be ascribed to effects of underlying renal or urinary-tract disease, or of loss of renal function, on the kidney and bladder, and to increased susceptibility to viral carcinogenesis. The relative risk, which is especially high in younger patients, gradually diminishes with age.

Adolescent↗
PubMed1999

Epidemiological data of treated end-stage renal failure in the European Union (EU) during the year 1995: report of the European Renal Association Registry and the National Registries.

BACKGROUND: The new Centre Questionnaire, mainly based on the collection of epidemiological data, was launched in 1996 and the overall response rate of centres for the 15 countries constituting the European Union (EU) reached 82.2% (66-100%) for 1995. RESULTS: We could derive the following information for a general population of 372.6 million. In 1995, the incidence of new end-stage renal failure (ESRF) patients (Ni/P) was 120 p.m.p. (per million population) with a clear north to south/west gradient (69 in Ireland, 131 in Italy and 163 in Germany). The incidence of ESRF deaths (No/P) was 67 p.m.p. (from 35 in Ireland to 89 in Germany). The net increase of patients was therefore 53 p.m.p. (from 13 in Greece to 74 in Germany). The point prevalence of treated ESRF patients (Ns/P) alive on 31 December 1995 was 644 p.m.p. (from 444 in Finland to 773 in Italy). The mean increase in the stock of ESRF patients was +8.2% (4.6 to 13.0) as a linear rate and +0.085 as a fractional rate (exponential). The first treatment of new patients (Ni) was haemodialysis (HD; 81%), peritoneal dialysis (PD; 18%) and pre-emptive renal transplantation (Tx; 1%). The latest treatment for patients still alive was HD (58.5%), PD (9%) or functional Tx (32.5%). The number of Tx was 30 p.m.p. (from 14 in Greece to 45 in Spain). The death rate was 10.4% for all those with ESRF, with 14.4% for those dialysed and 2.2% for transplanted patients. In 1995, 6.5% of dialysed patients received a graft and 4.0% of transplant patients returned to dialysis. The linear expansion rate of the dialysis pool and the transplant pool was respectively 8.3% and 7.9%. CONCLUSIONS: This data shows considerable disparities among countries of the EU which merit further evaluation. Also this analysis by the ERA Registry provides data of value for health and economic purposes.

Europe↗