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R Hübner

Publications and source records attributed to R Hübner.

At least 19 recordsLinked to original sources
PubMed2004

Comparison of the annealing behavior of thin Ta films deposited onto Si and SiO2 substrates.

Structural changes at annealing temperatures (T(an)) of 500-1,100 degrees C were investigated for thin Ta films which were sputter-deposited onto pure Si substrates and onto thermally oxidized Si. In the as-deposited state, the Ta layers predominantly consist of metastable tetragonal beta-Ta, whereby the [001] texture is independent of the substrate material. At lower annealing temperatures, the microstructural evolution is essentially the same for both Ta films. Incorporation of O atoms causes an increase of the intrinsic compressive stress, and diffusion of C atoms into the Ta layer leads to the formation of Ta(2)C. Additionally, a partial transformation of the original beta-Ta phase into a second phase with tetragonal unit cell (denoted as beta'-Ta) occurs. For the Ta/Si system, the formation of a Ta-Si intermixing layer is initiated at T(an)=550 degrees C, and nucleation of crystalline TaSi(2) occurs at T(an)=620 degrees C. The formation of a second Ta silicide was not detected up to T(an)=900 degrees C. In the case of the Ta film deposited onto the SiO(2) substrate, the metastable beta-Ta and the beta'-Ta transform completely into the thermodynamically stable cubic alpha-Ta at T(an)=750 degrees C. A marked reaction with the substrate indicated by the formation of Ta(2)O(5) and Ta(5)Si(3) occurs at T(an)=1,000 degrees C.

Alloys↗
PubMed2003

[Guidelines for inpatient adenoidectomy].

BACKGROUND: Adenoidectomy, with or without tonsillectomy, remains as one of the most common surgical procedures. This study was undertaken to determine whether or not the criteria for adenoidectomy based on an inpatient basis in our hospital have to be revised and to evaluate the incidence of postoperative bleeding. MATERIAL AND METHODS: The data of 470 patients who underwent adenoidectomy during 1 year were analyzed in a prospective study. Age <1 year; age >16 years; underlying diseases that put the patient at increased pre-or postoperative cardiopulmonary, metabolic or general risk; >20 minutes driving time between hospital and home, lack of compliance; request of the patients/parents were criteria for adenoidectomy to be performed as an inpatient procedure. Due to the rarity of postoperative bleeding the rate of post-adenoidectomy hemorrhage was calculated in a retrospective study on the basis of the data of 8131 patients who had undergone adenoidectomy. RESULTS: A total of 249 patients underwent adenoidectomy on an outpatient basis (53%). Two patients required surgical treatment for postoperative bleeding under general anesthesia (0.43%), one of whom was initially scheduled for outpatient surgery. The parents of 17 children initially scheduled for outpatient surgery refused to take responsibility of postoperative care on the day of surgery. These children were admitted. Inpatient observation was scheduled in most cases because of the distance to the hospital (115 patients) or underlying diseases (7 patients). The rate of post-adenoidectomy hemorrhage in our retrospective study was 0.23%. There was only one adult with repeated bleeding on the day of surgery and 6 days postoperatively. 15 of 19 episodes of bleeding occurred on the day of surgery, the latest episode 6 days postoperatively. There was no case with lethal outcome. No blood transfusions or major surgical procedures at the neck were required to stop the bleeding. CONCLUSIONS: Inpatient observation should be considered in patients with underlying general diseases, postoperative bleeding, poor compliance or request of the patients/parents. Age, general risk of post-adenoidectomy hemorrhage and distance to the hospital are not criteria significant enough to indicate inpatient observation in patients who undergo adenoidectomy.

Adenoidectomy↗
PubMed2001

The effect of familiarity on visual-search performance: evidence for learned basic features.

In this study, the effects of familiarity on visual search were investigated. To avoid any confounding between familiarity and visual-feature differences between item pairs, Ns and mirror-Ns were presented as target and as distractors to a group of German participants and to a group of Slavic participants. For the Germans only N was familiar, whereas for the Slavs both N and mirror-N were familiar. The results show that search was difficult only when the Germans had to find an N among mirror-Ns. In any other case, search was efficient. Therefore, our results demonstrate that, contrary to earlier suggestions, search for a familiar item among familiar distractors can be easy. This supports the hypothesis that familiarity improves distractor grouping. However, the data are also compatible with the idea that letters are standard or basic features, which implies that basic features can be learned.

Adult↗
PubMed2001

How to produce an absent-advantage in visual search.

In a series of four experiments, we investigated the conditions under which target-absent responses are faster than target-present responses in visual search. Previous experiments have shown that such an absent-advantage occurs mainly for homogeneous distractors arranged in a regular pattern. From these results, it has been concluded that the absent-advantage is due to perceptual processes, such as grouping by similarity. Our data show that such processes are not sufficient. Rather, the absent-advantage is the result of interactions between perceptual and decisional processes. Certain perceptual conditions, such as randomizing stimulus patterns, lead to specific criteria settings that produce an absent-advantage. That such an account can explain our main results is demonstrated by modeling our data with a modified version of the Guided Search 2 model.

Adult↗
PubMed2001

A formal version of the Guided Search (GS2) model.

Guided Search 2 (GS2) is currently one of the most detailed models of visual search and has been used to predict search times for different stimulus conditions by means of detailed computer simulations. The present article goes a step further and presents formulas that allow for the calculation of the search times and their variances. Moreover, these formulas can be applied to fit GS2 to data. An example is provided in which GS2 is fitted to search functions representing search asymmetries.

Computer Simulation↗
PubMed2001

On attentional control as a source of residual shift costs: evidence from two-component task shifts.

It is widely assumed that supervisory or attentional control plays a role only in the preparatory reconfiguration of the mental system in task shifting. The well-known fact that residual shift costs are still present even after extensive preparation is usually attributed to passive mechanisms such as cross talk. The authors question this view and suggest that attentional control is also responsible for residual shift costs. The authors hypothesize that, under shift conditions, tasks are executed in a controlled mode to guarantee reliable performance. Consequently, the control of 2 task components should require more resources than the control of only 1. A series of 4 experiments with 2-component tasks was conducted to test this hypothesis. As expected, more residual shift costs were observed when 2 components rather than 1 varied across trials. Interference effects and sequential effects could not account for these results.

Adult↗
PubMed1999

Perceiving spatially inseparable objects: evidence for feature-based object selection not mediated by location.

In 4 experiments, stimulus elements were arranged into an LED-like array, and letters were defined within the array by feature similarity between the elements with respect to color and form. These stimuli allowed the display of a target and a distractor letter simultaneously at the same location. They were spatially inseparable but could be separated in feature space. Participants had to identify the letter on a prespecified feature dimension (color or form). As a result, the distractors produced specific compatibility effects. This showed that nontarget features could not be ignored at an early stage (i.e., that color and form were processed automatically and in parallel up to a high stage). The target was selected from the resulting objects according to the prespecified feature dimension. Results demonstrate that object selection is possible without selecting absolute spatial arrays.

Adult↗
PubMed1999

Diagnosis of cutaneous T-cell lymphoma detecting T-cell receptor gamma chain gene monoclonality by denaturing gradient gel electrophoresis.

Cutaneous T-cell lymphomas represent a group of malignant lymphoproliferative disorders characterised by the occurrence of a monoclonal population of T-lymphocytes. Diagnosis of early stages of this disease is a difficult challenge for both the dermatologist and the dermatopathologist. With the aid of the polymerase chain reaction it is possible to amplify specific regions of the T-cell receptor gamma gene. The amplification products can then be separated by denaturing gradient gel electrophoresis in order to detect a monoclonal population of T-lymphocytes in the infiltrate. We studied 4 patients with the clinicopathologic diagnosis of mycosis fungoides and 2 patients diagnosed as large plaque parapsoriasis. A monoclonal population was detected in 3 of the 4 mycosis fungoides cases and in 1 of the patients with large plaque parapsoriasis. This indicates that our analysis can help us establishing a diagnosis, and it can also help us to identify patients with a possible early stage of the disease, which clinically or histologically is not yet recognised as such.

Aged↗
PubMed1998

Telomerase activity in human pleural mesothelioma.

BACKGROUND: Gradual telomere erosion eventually limits the replicative life span of somatic cells and is regarded as an ultimate tumour suppressor mechanism, eliminating cells that have accumulated genetic alterations. Telomerase, which has been found in over 85% of human cancers, elongates telomeres and may be required for tumorigenesis by the process of immortalisation. Malignant mesothelioma is an incurable malignancy with a poor prognosis. The disease becomes symptomatic decades after exposure to carcinogenic asbestos fibres, suggesting the long term survival of pre-malignant cell clones. This study investigated the presence of telomerase in pleural malignant mesothelioma, which may be the target for future anti-telomerase drugs. METHODS: Telomerase activity was semiquantitatively measured in extracts from 22 primary pleural mesotheliomas, two benign solitary fibrous tumours of the pleura, four mesothelioma cell lines, and six short term mesothelial cell cultures from normal pleura using a non-isotopic dilution assay of the telomeric repeat amplification protocol. RESULTS: Twenty of the 22 primary mesotheliomas (91%) and all tumour derived mesothelioma cell lines were telomerase positive. Different levels of enzyme activity were observed in the tumours of different histological subtypes. Telomerase activity could not be detected in the six normal mesothelial cell cultures or in the two mesotheliomas. Both benign solitary fibrous tumours showed strong telomerase activity. CONCLUSIONS: Telomerase activity is found in a high proportion of mesotheliomas and anti-telomerase drugs might therefore be useful clinically. The results are consistent with the hypothesis that telomerase activity may be a feature of carcinogenesis in mesotheliomas and possibly in many other cancers.

Electrophoresis, Polyacrylamide Gel↗
PubMed1997

Visuelle Welt: a Windows program for demonstrating visual-perception phenomena.

The Windows program Visuelle Welt allows the demonstration of various visual phenomena such as geometrical-optical illusions, subjective contours, apparent movement, and Gestalt principles. One of the program's most interesting features is that the illusion-inducing context can be switched off, and in addition for many phenomena parameters can be varied interactively.

Computer Terminals↗
PubMed1997

The effect of spatial frequency on global precedence and hemispheric differences.

There are many conditions in which identification proceeds faster for the global form of a hierarchical pattern than for it's local parts. Since the global form usually contains more lower spatial frequencies than do the local forms, it has frequently been suggested that the higher transmission rate of low spatial frequencies is responsible for the global advantage. There are also functional hemispheric differences. While the right hemisphere is better at processing global information, the left hemisphere has an advantage with respect to local information. In accordance with the spatial-frequency hypothesis, it has been speculated that this difference is due to a differential capacity of the hemispheres for processing low and high spatial frequencies. To test whether low spatial frequencies were responsible for the global advantage and/or for the observed hemispheric differences, two experiments were carried out with unfiltered and highpass-filtered compound-letter stimuli presented at the left, right, or center visual field. The first experiment, in which the target level was randomized in each trial block, revealed that low spatial frequencies were not necessary for either global advantage or for hemispheric differences. Highpass filtering merely increased the response times. In the second experiment, the target level was held constant in each block. This generally increased the speed of responding and produced interactions between filtering and global-local processing. It was concluded that both sensory and attentional or control mechanisms were responsible for global precedence and that the hemispheres differed with respect to the latter.

Adult↗
PubMed1997

Pharmacokinetics of candesartan after single and repeated doses of candesartan cilexetil in young and elderly healthy volunteers.

Candesartan cilexetil is rapidly and completely hydrolysed to the active compound candesartan during absorption from the gastrointestinal tract. Candesartan is a potent, long-acting, selective angiotensin II AT1 receptor blocker. The pharmacokinetics of candesartan were investigated after single and repeated once-daily doses of candesartan cilexetil in the dose range 2-16 mg in both younger (19-40 years) and elderly (65-78 years) healthy volunteers in five studies. Blood pressure, heart rate, and hormones associated with the renin-angiotensin system, and safety of candesartan cilexetil administration were also assessed. Placebo comparisons were made in four studies. Frequent blood samples were collected after the first single dose of candesartan cilexetil, and during the last dosing interval after 1 week repeated once-daily administration. Serum and plasma were analysed for candesartan cilexetil, candesartan and its inactive metabolite, CV-15959, as well as angiotensin I and II, aldosterone, plasma renin activity (PRA) and angiotensin-converting enzyme (ACE) activity. The AUC and Cmax of candesartan showed dose-proportional increases in the dose range of 2-16 mg candesartan cilexetil after both single and repeated once-daily tablet intake, indicating linear pharmacokinetics in both younger and elderly healthy subjects. The pharmacokinetics did not change on repeated dosing and, as expected from the half-life of candesartan of approximately 9 h in younger subjects, there was almost no accumulation after repeated once-daily dosing. The time to peak candesartan concentrations after tablet intake was consistently approximately 4 h at all dose levels. Both Cmax and AUC of candesartan were increased after single and repeated once-daily dosing in the elderly compared to younger subjects by approximately 50%. However, no accumulation after repeated once-daily dosing were seen in the elderly. The half-life of candesartan in the elderly (9-12 h) was somewhat longer than in the younger healthy adult volunteers (approximately 9 h) and no gender-related differences in the disposition of candesartan were observed. Serum concentrations of CV-15959 were much lower than candesartan, and reached peak serum concentrations later, about 4-9 h after dose intake. The elimination of CV-15959 was somewhat slower than that of candesartan. Candesartan cilexetil, the prodrug to candesartan, was not measurable in serum. No differences in ACE activity or serum aldosterone concentrations were observed between subjects receiving candesartan cilexetil and placebo tablets. Plasma angiotensin I and II concentrations and PRA were augmented after single doses and further increased after 1 week repeated candesartan cilexetil dosing. Single and repeated doses of candesartan cilexetil were well tolerated in the younger and elderly volunteers. Only mild adverse events were recorded, with 'headache' as the most commonly reported event, and no increase in the number of reported adverse events was observed with higher doses of candesartan cilexetil. No clinically significant changes in respect to vital signs, physical examination, ECG, and clinical laboratory tests were observed.

Adult↗
PubMed1997

Candesartan cilexetil, a new generation angiotensin II antagonist, provides dose dependent antihypertensive effect.

Candesartan is a new generation angiotensin II type 1 receptor blocker, characterised by tight binding to and slow dissociation from the receptor. In order to delineate the dose-response curve for candesartan cilexetil (the orally administered prodrug), results from six European placebo-controlled, dose-response studies were pooled. These were of a double-blind, randomised, parallel group design, with a treatment duration of 4-12 weeks. A total of 1482 patients with mild to moderate primary hypertension were treated with candesartan cilexetil 2 mg (n = 80), 4 mg (n = 216), 8 mg (n = 455) or 16 mg (n = 294), or with placebo (n = 437). Blood pressure (BP) measurements were performed 24 h after dose. The differences in BP change (baseline vs end of the studies) between the placebo group and the groups treated with candesartan cilexetil were assessed using analysis of covariance and dose response curves were estimated by fitting the data to an Emax model. The placebo-corrected mean reductions in sitting diastolic BP were approximately 2.5 mm Hg with 2 mg, 4.5 mm Hg with 4 mg, 6 mm Hg with 8 mg, and 8 mm Hg with 16 mg of candesartan cilexetil. For sitting systolic BP, the placebo-corrected mean reductions were in the order of 5, 7, 10 and 12 mmHg, respectively, with 2, 4, 8 and 16 mg of candesartan cilexetil. The BP reductions were similar in the standing position with no indication of postural hypotension. Age or gender did not influence the BP response to candesartan cilexetil. In conclusion, candesartan cilexetil provides a clinically significant, dose-dependent antihypertensive effect in doses ranging from 4-16 mg once daily.

Adolescent↗
PubMed1997

Candesartan cilexetil: safety and tolerability in healthy volunteers and patients with hypertension.

The tolerability and safety of candesartan cilexetil has been evaluated in over 5000 subjects enrolled into double-blind or open-label clinical studies. In double-blind clinical trials in patients with primary hypertension, candesartan cilexetil 2-16 mg once-daily was associated with a low incidence of adverse events and drug-related withdrawals, similar to placebo. The drug showed no evidence of dose-dependent adverse events and it was equally well tolerated by men and women and by elderly (> or =65 years) and younger (<65 years) patients alike. Candesartan cilexetil had no effect on blood glucose control or serum lipid profile in patients with type II diabetes. It was very well tolerated also when given in combination with hydrochlorothiazide or amlodipine and during long-term open-label therapy (up to 1 year). Candesartan cilexetil therefore possesses an excellent tolerability profile that extends to a wide variety of patients including the elderly and it does not aggravate co-existing risk factors such as hyperlipidaemia or glucose intolerance. It therefore appears to offer a better tolerated alternative to other commonly used antihypertensive agents.

Angiotensin Receptor Antagonists↗
PubMed1996

The efficiency of different cue types for reducing spatial-frequency uncertainty.

Detection experiments reveal that performance is decreased when the signal's spatial frequency varies unpredictably across trials compared with conditions where it is held constant. However, this effect can more or less be compensated by presenting cues shortly before each trial. To investigate the efficiency of different sensory and symbolic cue types a signal-detection experiment with spatial-frequency uncertainty was carried out. The inter-stimulus interval between cue and signal as well as for the sensory cue types, the spatial overlap between cue and signal, was varied. The results reveal appreciable efficiency differences. While some cues were only of little help, others reduced uncertainty almost entirely. However, the efficiency of cues which were identical to the signals was severely restricted by forward-masking effects when they were presented at the same position as the signal.

Adult↗