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T Fuchs

Publications and source records attributed to T Fuchs.

At least 55 records · Page 3Linked to original sources
PubMed2000

Attentional focus in complex skill learning.

Experiment 1 examined whether it is more advantageous to direct learners' attention to the external effects of their movements relative to other external cues. Two groups of participants hit tennis balls at a target, with one group focusing on the ball coming toward them (antecedent) and the other group focusing on the ball leaving the racket (effect). The effect group demonstrated more effective learning. Experiment 2 examined whether it is more beneficial if the movement effect is related to the movement technique, relative to other movement effects (e.g., outcome). Two groups of participants hit golf balls at a target. The attention of these groups was directed to the club or the ball trajectory, respectively. The club group showed more effective learning than the target group, suggesting that focusing on technique-related effects is more effective.

Adolescent↗
PubMed2000

Measurement of the radiative cooling rates for high-ionization species of krypton using an electron beam ion trap

We describe a measurement of the radiative cooling rate for krypton made at the Berlin electron beam ion trap (EBIT). The EBIT was tuned to a charge-state distribution approaching the ionization balance of a plasma at a temperature of about 5 keV. To determine the cooling rate, we made use of EBIT's capabilities to sample a wide range of electron-beam energies and distinguish between different radiation channels. We have measured the x-ray emission from bremsstrahlung, radiative recombination, dielectronic recombination, and line radiation following electron-impact excitation. The dominant contribution to the cooling rate is made by the n=3-2, n=4-2, ellipsis x rays of the L-shell spectra of krypton, which produce more than 75% of the total radiation loss. A difference with theoretical calculations is noted for the measured total cooling rate. The predicted values are lower by a factor of 1.5-2, depending on the theoretical model. For our measurement of the cooling rate, we estimate an uncertainty interval of 22-30 %.

Journal Article↗
PubMed2000

Spiral interpolation algorithm for multislice spiral CT--part I: theory.

This paper presents the adaptive axial interpolator (AAI), a novel spiral interpolation approach for multislice spiral computed tomography (CT) implemented in a clinical multislice CT scanner, the SOMATOM Volume Zoom (Siemens Medical Systems, Forchheim, Germany). The method works on parallel-beam data generated from the acquired fan-beam data by azimuthal rebinning. Spiral interpolation is performed by distance-dependent weighting; i.e., for each ray, its distance to the image plane is evaluated and serves as an argument to a freely selectable weighting function, resulting in a weight factor. A normalization step is applied to the weight factors to ensure that the sum of all corresponding weights (i.e., the weights applied to rays that contribute to the same ray in the interpolated sinogram) is 1. By selection of appropriate weighting functions and suitable adjustment of the tube current, it is possible to keep the slice sensitivity profiles (SSP) as well as the pixel noise constant for all pitch values in the relevant range. Also, a large range of slice-thickness can be reconstructed from a given collimation. The method is, thus, very versatile. Further advantages are that it uses the entire applied dose for imaging and allows for efficient implementation using a table lookup approach.

Algorithms↗
PubMed2000

Spiral interpolation algorithms for multislice spiral CT--part II: measurement and evaluation of slice sensitivity profiles and noise at a clinical multislice system.

The recently introduced multislice data acquisition for computed tomography (CT) is based on multirow detector design, increased rotation speed, and advanced z-interpolation and z-filtering algorithms. We evaluated slice sensitivity profiles (SSPs) and noise of a clinical multislice spiral CT (MSCT) scanner with M = 4 simultaneously acquired slices and adaptive axial interpolator (AAI) reconstruction software. SSPs were measured with a small gold disk of 50 microm thickness and 2-mm diameter located at the center of rotation (COR) and 100 mm off center. The standard deviation of CT values within a 20-cm water phantom was used as a measure of image noise. With a detector slice collimation of S = 1.0 mm, we varied spiral pitch p from 0.25 to 2.0 in steps of 0.025. Nominal reconstructed slice thicknesses were 1.25, 1.5, and 2.0 mm. For all possible pitch values, we found the full-width at half maximum (FWHM) of the respective sensitivity profile at the COR equivalent to the selected nominal slice thickness. The profiles at 100 mm off center are broadened less than 7 % on the average compared with the FWHM at the COR. In addition, variation of the full-width at tenth maximum (FWTM) at the COR was below 10% for p < or = 1.75. Within this range, image noise varied less than 10% with respect to the mean noise level. The slight increase in measured slice-width above p = 1.75 for nominal slice-widths of 1.25 and 1.50 mm is accompanied by a decrease of noise according to the inverse square root relationship. The MSCT system that we scrutinized provides reconstructed slice-widths and image noise, which can be regarded as constant within a wide range of table speeds. With respect to this, MSCT is superior to single-slice spiral CT. These facts can be made use of when defining and optimizing clinical protocols: the spiral pitch can be selected almost freely, and scan protocols can follow the diagnostic requirements without technical restrictions. In summary, MSCT offers constant image quality while scan times are reduced drastically. Volume scans with three-dimensional (3-D) isotropic resolution are routinely feasible for complete anatomical regions.

Algorithms↗
PubMed2000

Direct comparison of a xenon and a solid-state CT detector system: measurements under working conditions.

Measurements of various image quality parameters were carried out with two different detector systems in an otherwise unchanged medical computed tomography (CT) scanner. As all other components of the scanner and the image reconstruction system remained identical, we were able to quantify the difference in performance between a Xenon gas ionization detector and a new solid-state scintillation detector in an isolated fashion. We determined noise, spatial resolution, and artifact behavior and assessed the potential for dose reduction. No significant impact of the detector change on absolute CT values of a calibration phantom was observed. Spatial resolution was improved by more than 10% for the solid-state system. As the system's modulation transfer functions were measured with a wire phantom and otherwise unchanged scanner geometry and image reconstruction algorithm, the increase of resolution is explained by the improved temporal response of the solid-state detector. At the same time, noise was reduced by 12% for a 20-cm diameter water phantom. The noise reduction corresponds to a possible reduction of patient dose by 23% for constant image quality, which is in good agreement with our prediction by estimations of both systems total detective quantum efficiency. Also, a significant improvement of scatter rejection was found for the solid-state system.

Ceramics↗
PubMed2000

[The influence of computer supervision of deliveries on the medical procedures during labor and neonatal post-delivery status].

OBJECTIVES: The aim of the study was estimation of the influence of computer supervision of delivery on the way of medical management during partus. MATERIALS AND METHODS: Authors analyzed 10,983 labours which took place in years 1990-1999 in University Clinic of Reproduction and Obstetrics of Medical Academy in Wrocław. Cases of labours without computer monitoring was the first analyzed group, and the cases of computer monitoring deliveries was the second group. In both groups, the count of cesarean sections performed because of first symptoms of fetal asphyxia, and Apgar score gained by newborns, were taken into consideration. RESULTS AND CONCLUSIONS: The frequency of cesarean sections and neonatal Apgar score gained by newborns were compared in two characterized group in order to evaluation the influence of computer monitoring deliveries on the neonatal status. No impact of computer supervision on the way of delivery procedures, quality of work and neonatals state was observed.

Apgar Score↗
PubMed2000

[Fibronectin level in amniotic fluid as an index of unavoidable labor].

During uterus contractions detaching of amino-chorionic layer from uterus wall occurs and released fibronectin penetrates into amniotic fluid. The aim of this study was to estimate in a quantity mode the presence of fibronectin in amniotic fluid and to find the dependence between the fibronectin level in amniotic fluid and the period of time from collecting the sample to the labor. We wanted also to find the dependence between fibronectin level in amniotic fluid and duration of pregnancy, preterm rupture of amniotic membranes, patients' age, parity and number of deliveries. We analysed 86 pregnant women where we estimated the fibronectin level in specimens of amniotic fluid. During carrying out the experiment we noted that fibronectin is present in amniotic fluid and can be identified in a quantity mode. We have proved dependence between fibronectin level in amniotic fluid and the period of time from collecting the sample, up to the delivery. Fibronectin level in amniotic fluid in pregnancies uncomplicated with premature delivery was on the average 350 mg/ml. Increase of fibronectin in amniotic fluid above 700 mg/ml points at detaching of amino-chorionic layer and the occurrence of unavoidable preterm labor at the time no longer than 24 hours. Fibronectin level in amniotic fluid doesn't depend of pregnancy duration, preterm rupture of amniotic membranes.

Adult↗
PubMed2000

[Useful of cerebral placental ratio in pregnancies complicated by intrauterine growth retardation and it correlation with perinatal outcome].

OBJECTIVE: The aim of this study was to asses usefulness of cerebro-placental ratio in the estimation of the intrauterine fetal well being in pregnancies complicated by intrauterine growth retardation and prediction of perinatal outcome. MATERIAL AND METHODS: We investigated 22 pregnant women between 28th and 40th week of pregnancy with IUGR detected by ultrasound examination. 19 pregnant women between 28th and 41st week of pregnancy was control group. We measured parameters blood flow in umbilical arteries and in middle cerebral arteries in both groups. We calculated cerebro placental ratios(CPR, CPP). We divided pregnant women with IUGR int 2 groups depending on correct (CPR, CPP > 1.08) or incorrect (CPR, CPP < 1.08). In both groups we analyzed perinatal outcome. RESULTS: In group pregnancies complicated with IUGR cerebro-placental ratios (CPR and CPP) were statistically significant lower than in control group. (for CPR p < 0.015 and for CPP p < 0.033). Sensitivity of cerebro placental ratio in screening small gestational age fetuses was 59% and specificity 89%. Sensitivity of cerebro placental ratio in predicting adverse perinatal outcome was 85% and specificity was 82%. CONCLUSIONS: Statistically significant decrease of cerebro-placental ratios is observed in pregnancies complicated wit IUGR. Cerebro placental ratio is very useful tool for prediction of adverse perinatal outcome.

Blood Flow Velocity↗
PubMed1999

Reaction of the hypoxia-selective antitumor agent tirapazamine with a C1'-radical in single-stranded and double-stranded DNA: the drug and its metabolites can serve as surrogates for molecular oxygen in radical-mediated DNA damage reactions.

The compound 3-amino-1,2,4-benzotriazine 1,4-dioxide (1, tirapazamine; also known as SR4233, WIN 59075, and tirazone) is a clinically promising anticancer agent that selectively kills the oxygen-poor (hypoxic) cells found in tumors. When activated by one-electron enzymatic reduction, tirapazamine induces radical-mediated oxidative DNA strand cleavage. Using the ability to generate a single deoxyribose radical at a defined site in an oligonucleotide, we recently provided direct evidence that, in addition to initiating the formation of DNA radicals, tirapazamine can react with these radicals and convert them into base-labile lesions [Daniels et al. (1998) Chem. Res. Toxicol. 11, 1254-1257]. The rate constant for trapping of a C1'-radical in single-stranded DNA by tirapazamine was shown to be approximately 2 x 10(8) M(-1) s(-1), demonstrating that tirapazamine can substitute for molecular oxygen in radical-mediated DNA strand damage reactions. Because reactions of tirapazamine with DNA radicals may play an important role in its ability to damage DNA, we have further characterized the ability of the drug and its metabolites to convert a C1'-DNA radical into a base-labile lesion. We find that tirapazamine reacts with a C1'-radical in double-stranded DNA with a rate constant of 4.6 x 10(6) M(-1) s(-1). The mono-N-oxide (3) stemming from bioreductive metabolism of tirapazamine converts the C1'-radical to an alkaline-labile lesion more effectively than the parent drug. Compound 3 traps a C1'-radical in single-stranded DNA with a rate constant of 4.6 x 10(8) M(-1) s(-1) and in double-stranded DNA with a rate constant of 1.4 x 10(7) M(-)(1) s(-)(1). We have also examined the rate and mechanism of reactions between the C1'-radical and representatives from two known classes of "oxygen mimetic" agents: the nitroxyl radical 2,2,6, 6-tetramethylpiperidin-N-oxyl (4, TEMPO) and the nitroimidazole misonidazole (5). TEMPO traps the C1'-radical in single-stranded DNA (7.2 x 10(7) M(-1) s(-1)) approximately 3 times less effectively than tirapazamine, but 2 times as fast in double-stranded DNA (9.1 x 10(6) M(-1) s(-1)). Misonidazole traps the radical in single- (6. 9 x 10(8) M(-1) s(-1)) and double-stranded DNA (2.9 x 10(7) M(-1) s(-1)) with rate constants that are roughly comparable to those measured for the mono-N-oxide metabolite of tirapazamine. Finally, information regarding the chemical mechanism by which these compounds oxidize a monomeric C1'-nucleoside radical has been provided by product analysis and isotopic labeling studies.

Antineoplastic Agents↗
PubMed1999

A cross-sectional study of workers in the chemical industry with occupational exposure to hexamethylenetetramine.

OBJECTIVES: To assess the health effects of hexamethylenetetramine (HMT) on the airways and the skin of workers in the chemical industry. METHODS: A cross-sectional study was performed with 17 employees of a HMT-producing chemical plant and 16 control subjects from the plant. In addition, we examined 4 out of 5 subjects who had left the production for medical reasons during the last 10 years. Anamnestic data, total and specific IgE to four environmental allergens, lung function and bronchial responsiveness to methacholine were assessed by standard procedures. Skin prick tests (SPT) and patch tests were performed with known sensitizing substances and HMT 100 mg/ml and 2% pet and aq. RESULTS: A high number of exposed subjects and controls reported symptoms during the previous year (64.7% vs 68.8%), most of them were not related to work. Work-related symptoms and objective parameters did not show differences between groups. No sensitizations to HMT as assessed by SPT or patch tests were found. Among those who had left the HMT production for medical reasons, 2 former baggers showed sensitizations to HMT by patch tests. These reported eczema during exposure but lost symptoms after removal from exposure. Geometric mean HMT concentrations as assessed by personal sampling were 0.3 [95% confidence intervals (CI) 0.1; 0.9] mg/m(3) in shiftleaders and 0.6 (95% CI 0.3; 1.1) mg/m(3) in baggers. CONCLUSION: High exposures to HMT may cause allergic contact dermatitis. There was no evidence of an increased risk for occupational asthma at mean airborne HMT concentrations below 1 mg/m(3).

Adult↗
PubMed1999

Photosensitization of guanine-specific DNA damage by a cyano-substituted quinoxaline di-N-oxide.

The cyano-substituted quinoxaline di-N-oxide (2) is a potential antitumor agent, which selectively kills hypoxic cells. While investigating this drug's potential ability to act as a surrogate for O(2) in DNA damage processes, we discovered that 2 produces alkali-labile lesions selectively at 2'-deoxyguanosine positions upon irradiation in the UV-A (lambda(max) = 350 nm) region. Strand damage is induced in single-stranded and double-stranded substrates, with the latter being slightly more susceptible to lesion formation. Alkaline-labile lesions are formed under aerobic and anaerobic conditions. The efficient formation of alkali-labile lesions by 2 suggests that this molecule may exhibit phototoxicity. Subsequent investigation of this process suggests that photoexcited 2 damages DNA via a type I process. The results of experiments aimed at determining the involvement of singlet O(2) are ambiguous and indicate that commonly used experimental tests for this species may be less definitive than often thought. The involvement of other reactive oxygen species in strand damage, such as hydroxyl radical, is ruled out.

Antineoplastic Agents↗
PubMed1999

Combined analysis of polymorphisms of the tumor necrosis factor-alpha and interleukin-10 promoter regions and polymorphic xenobiotic metabolizing enzymes in psoriasis.

Environmental and genetic factors are thought to interact in the manifestation of psoriasis, but knowledge about the involved genes and antigens is incomplete. This study has focused on the association between psoriasis and inherited variations in xenobiotic metabolism and cytokine production as two components that may influence cutaneous immune responses to foreign substances. Polymorphisms of N-acetyltransferase 2, glutathione S-transferases T1 and M1, and promoter polymorphisms of the genes encoding for tumor necrosis factor-alpha and interleukin-10 were investigated in 151 Caucasian patients with psoriasis (100 with type I and 51 with type II psoriasis) and in 123 healthy controls. Polymorphisms were detected by polymerase chain reaction-based methods, restriction enzyme analysis, and direct sequencing. There were no significant differences in the distribution of enzyme polymorphisms or point mutations at position -1082 of the interleukin-10 promoter between the psoriasis groups and the control group. The G-->A polymorphism at position -238 of the tumor necrosis factor-alpha promoter (TNF alpha-238*A allele) was more common in type I psoriasis (27%) than in the controls [9.8%; odds ratio 3.4 (95% confidence interval 1.6-7.2); p = 0.0012; pcorr = 0.018]. Surprisingly, this overrepresentation of the tumor necrosis factor alpha-238*A allele was observed in male patients [4.1 (1.5-11.0); p = 0.0046; pcorr = 0.064] but not in female patients [1.8 (0.5-6.5); p = 0.5]. The G-->A polymorphism at position -308 of the tumor necrosis factor-alpha promoter was less frequent in type I psoriasis (23%) compared with controls (35.7%), although the negative association was weak [0.54 (0.3-0.97); p = 0.041; pcorr = not significant]. The distribution of the TNF alpha-238*A and TNF alpha-238*A alleles was similar in type II patients and controls. Our results suggest that male carriers of the G-->A polymorphism at position -238 of the tumor necrosis factor-alpha promoter are at an increased risk to develop early-onset psoriasis.

Adolescent↗
PubMed1999

B cell epitopes of the major timothy grass pollen allergen, phl p 1, revealed by gene fragmentation as candidates for immunotherapy.

Group 1 grass pollen allergens are recognized by IgE antibodies of almost 40% of allergic individuals and therefore belong to the most important elicitors of Type I allergy worldwide. We have previously isolated the cDNA coding for the group 1 allergen from timothy grass, Phl p 1, and demonstrated that recombinant Phl p 1 contains most of the B cell as well as T cell epitopes of group 1 allergens from a variety of grass and corn species. Here we determine continuous B cell epitopes of Phl p 1 by gene fragmentation. IgE antibodies of grass pollen allergic patients identified five continuous epitope-containing areas that on an average bound 40% of Phl p 1-specific IgE antibodies and were stably recognized in the course of disease. In contrast to untreated patients, patients undergoing grass pollen immunotherapy started to mount IgG(4) antibodies to the recombinant IgE-defined fragments in the course of immunotherapy. The protective role of these IgG(4) antibodies is demonstrated by observations that 1) increases in rPhl p 1 fragment-specific IgG(4) were in parallel with decreases in Phl p 1-specific IgE, and 2) preincubation of rPhl p 1 with patients sera containing rPhl p 1 fragment-specific IgG(4) blocked histamine release from basophils of an untreated grass pollen allergic patient. We propose to use recombinant Phl p 1 fragments for active immunotherapy in order to induce protective IgG responses against IgE epitopes in grass pollen allergic patients. This concept may be applied for the development of allergy vaccines whenever the primary sequence or structure of an allergen is available.

Allergens↗
PubMed1999

Patch test reactions at D4, D5 and D6.

In this retrospective study, patch test reactions in 3 groups of patients were analysed, in order to obtain information on the best day for the 2nd patch-test reading after day 2 (D2), on the usefulness of additional readings after D3, and on the dependence of patch-test reactions at D4, D5, or D6 on allergen and/or patient characteristics. In the years 1990 to 1995, patch tests were routinely read at D3 and D4 in 1096 patients, at D3 and D5 in 1243 patients, and at D3 and D6 in 1136 patients. In all of the 3 groups, significantly more positive reactions diminished than appeared de novo from D3 to the later reading. Virtually identical results were observed in subgroups of patients formed by sex, age or atopy. However, men might possibly react more slowly than women on patch testing, showing more increasing than diminishing reactions in the D3/D4- and the D3/D5-comparison. Reactions to individual allergens showed wide differences in this connection. Neomycin sulfate, cobalt salts, and p-phenylenediamine can be characterized as slow allergens, with more reactions increasing than diminishing from D3 to the later readings. With fragrance mix and balsam of Peru, the opposite pattern occurred. In all subgroups of patients, and with most allergens, the gain in positive reactions was biggest when an additional reading was performed at D5. We conclude that for a single 2nd patch test reading after D2, D3 is the best day, and especially better than D4. If a 3rd reading is performed, it should be done at D5 to get the maximum information out of patch testing. However, this extends the test procedure to at least 1 day of the weekend.

Adult↗