oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2020 ( 1 )

2019 ( 194 )

2018 ( 287 )

2017 ( 289 )

Custom range...

Search Results: 1 - 10 of 152946 matches for " Stephan H?fner "
All listed articles are free for downloading (OA Articles)
Page 1 /152946
Display every page Item
Estimation of Radio Channel Parameters in Case of an Unknown Transmitter
Stephan Hfner,Reiner Thom?
Mathematics , 2015,
Abstract: This paper investigates the estimation of radio channel parameters from receiver data, whereby the transmitter is fully unknown. We use a multipath model to describe the radio channel between transmitter and receiver. According to this model, we discuss the accessibility of parameters for estimation. Based on the Maximum-Likelihood principle, we derive a cost function. A second cost function is derived from the cross relation between the receiver channels. To estimate the parameters, we seek for the minimum of these cost functions. The performance of the presented cost functions are compared in simulations.
Vestibular Loss and Balance Training Cause Similar Changes in Human Cerebral White Matter Fractional Anisotropy
Nadine Hummel, Katharina Hüfner, Thomas Stephan, Jennifer Linn, Olympia Kremmyda, Thomas Brandt, Virginia L. Flanagin
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0095666
Abstract: Patients with bilateral vestibular loss suffer from severe balance deficits during normal everyday movements. Ballet dancers, figure skaters, or slackliners, in contrast, are extraordinarily well trained in maintaining balance for the extreme balance situations that they are exposed to. Both training and disease can lead to changes in the diffusion properties of white matter that are related to skill level or disease progression respectively. In this study, we used diffusion tensor imaging (DTI) to compare white matter diffusivity between these two study groups and their age- and sex-matched controls. We found that vestibular patients and balance-trained subjects show a reduction of fractional anisotropy in similar white matter tracts, due to a relative increase in radial diffusivity (perpendicular to the main diffusion direction). Reduced fractional anisotropy was not only found in sensory and motor areas, but in a widespread network including long-range connections, limbic and association pathways. The reduced fractional anisotropy did not correlate with any cognitive, disease-related or skill-related factors. The similarity in FA between the two study groups, together with the absence of a relationship between skill or disease factors and white matter changes, suggests a common mechanism for these white matter differences. We propose that both study groups must exert increased effort to meet their respective usual balance requirements. Since balance training has been shown to effectively reduce the symptoms of vestibular failure, the changes in white matter shown here may represent a neuronal mechanism for rehabilitation.
Cerebellar and Visual Gray Matter Brain Volume Increases in Congenital Nystagmus
Katharina Hüfner,Thomas Stephan,Marianne Dieterich,Michael Strupp,Thomas Brandt
Frontiers in Neurology , 2011, DOI: 10.3389/fneur.2011.00060
Abstract: Structural brain abnormalities associated with congenital nystagmus (CN) are still unknown. In some patients with CN additional sensory, metabolic, or gross structural alterations can be detected. In the present study voxel-based morphometry was used to compare the gray matter (GM) brain volumes of 14 individuals with CN without associated sensory, metabolic, or obvious structural alterations (i.e., idiopathic CN) to those of a group of controls. Further, GM brain volumes were correlated with nystagmus severity as measured by sway path. Intergroup comparison exhibited significant volume increases in the human motion sensitive complex V5/MT+, the fusiform gyrus, and the middle occipital gyrus bilaterally in CN. These volume increases may be associated with excess visual motion stimulation due to involuntary retinal slip of the visual scene. A positive correlation (linear model) of nystagmus sway path with cerebellar GM volume was seen in the following areas: vermal parts VIII-X as well as hemisphere lobule II, hemisphere VI, crus I, crus II, and lobule VII-IX bilaterally. There is evidence that the reported GM volume changes in the vestibulo-cerebellum, which correlated with nystagmus sway path, might be related to the subjects‘ attempt to maintain fixation, rather than be due to the generation of nystagmus.
A compact, robust, and transportable ultra-stable laser with a fractional frequency instability of $1\times10^{-15}$
Qun-Feng Chen,Alexander Nevsky,Marco Cardace,Stephan Schiller,Thomas Legero,Sebastian Hfner,Andre Uhde,Uwe Sterr
Physics , 2014, DOI: 10.1063/1.4898334
Abstract: We present a compact and robust transportable ultra-stable laser system with minimum fractional frequency instability of $1\times10^{-15}$ at integration times between 1 to 10 s. The system was conceived as a prototype of a subsystem of a microwave-optical local oscillator to be used on the satellite mission STE-QUEST (Space-Time Explorer and QUantum Equivalence Principle Space Test, http://sci.esa.int/ste-quest/). It was therefore designed to be compact, to sustain accelerations occurring during rocket launch, to exhibit low vibration sensitivity, and to reach a low frequency instability. Overall dimensions of the optical system are $40\textrm{ cm}\times20\textrm{ cm}\times30\textrm{ cm}$. The acceleration sensitivities of the optical frequency in the three directions were measured to be $1.7\times10^{-11}/g$, $8.0\times10^{-11}/g$, and $3.9\times10^{-10}/g$, and the absolute frequency instability was determined via a three-cornered hat measurement. The design is also appropriate and useful for terrestrial applications.
8E-17 fractional laser frequency instability with a long room-temperature cavity
Sebastian Hfner,Stephan Falke,Christian Grebing,Stefan Vogt,Thomas Legero,Mikko Merimaa,Christian Lisdat,Uwe Sterr
Physics , 2015, DOI: 10.1364/OL.40.002112
Abstract: We present a laser system based on a 48 cm long optical glass resonator. The large size requires a sophisticated thermal control and optimized mounting design. A self balancing mounting was essential to reliably reach sensitivities to acceleration of below $\Delta \nu / \nu$ < 2E-10 /g in all directions. Furthermore, fiber noise cancellations from a common reference point near the laser diode to the cavity mirror and to additional user points (Sr clock and frequency comb) are implemented. Through comparison to other cavity-stabilized lasers and to a strontium lattice clock an instability of below 1E-16 at averaging times from 1 s to 1000 s is revealed.
The early Kraepelin´s dichotomy of schizophrenia and affective disorder - Evidence of separate diseases?a
Hfner,H.;
The European Journal of Psychiatry , 2010,
Abstract: background and objectives: testing kraepelin′s dichotomy model, we studied the separability of schizophrenia and affective disorders by their symptoms and course. methods: to this end symptoms and illness course were assessed retrospectively in individually matched untreated probands with schizophrenia and depression (n=130 each) from first admission back to illness onset in comparison with 130 "healthy" controls. in a second study these same variables were studied prospectively in 107 patients with schizophrenia over a homogenised follow-up of 134 months (11.2 years). the actual mean length of the follow-up period was 12.3 years. results: the symptom most frequently marking the onset of both schizophrenia and depression was depressive mood. both disorders exhibited the same prodromal core syndrome. it was not until the emergence of positive symptoms that the disorders became separable by the international classification systems. depression remained the most frequent syndrome over the course of schizophrenia. conclusions: obviously, depression does not represent comorbidity, but an integral part of psychosis. a dimensional disease model based on (successively emerging) hierarchical symptom patterns of the human brain with increasing brain dysfunction in the course of schizophrenia and several neuro-degenerative disorders, not unknown to the later kraepelin, is offered as an explanation.
The early Kraepelin′s dichotomy of schizophrenia and affective disorder - Evidence of separate diseases?a
H. Hfner
The European Journal of Psychiatry , 2010,
Abstract: Background and Objectives: Testing Kraepelin′s dichotomy model, we studied the separability of schizophrenia and affective disorders by their symptoms and course. Methods: To this end symptoms and illness course were assessed retrospectively in individually matched untreated probands with schizophrenia and depression (n=130 each) from first admission back to illness onset in comparison with 130 "healthy" controls. In a second study these same variables were studied prospectively in 107 patients with schizophrenia over a homogenised follow-up of 134 months (11.2 years). The actual mean length of the follow-up period was 12.3 years. Results: The symptom most frequently marking the onset of both schizophrenia and depression was depressive mood. Both disorders exhibited the same prodromal core syndrome. It was not until the emergence of positive symptoms that the disorders became separable by the international classification systems. Depression remained the most frequent syndrome over the course of schizophrenia. Conclusions: Obviously, depression does not represent comorbidity, but an integral part of psychosis. A dimensional disease model based on (successively emerging) hierarchical symptom patterns of the human brain with increasing brain dysfunction in the course of schizophrenia and several neuro-degenerative disorders, not unknown to the later Kraepelin, is offered as an explanation.
Psychosis and cannabis
Hfner, Heinz;
Revista de Psiquiatria Clínica , 2005, DOI: 10.1590/S0101-60832005000200001
Abstract: alcohol and cannabis misuse is currently the most frequent co-morbidity disorder of schizophrenia. the following four issues will be dealt with: 1) the neurobiological basis of the psychosis-inducing, pathogenic effects of thc, the agent contained in cannabis products. 2) can cannabis use - and for comparison alcohol abuse - prematurely trigger or even cause schizophrenia? 3) are persons genetically liable to schizophrenia, psychosis-prone individuals or young persons before completion of brain development at an increased risk? 4) what consequences does cannabis use have on the symptomatology and further course of schizophrenia? results from recent literature and the abc schizophrenia study show that the risk for cannabis use in schizophrenia is about twice the size in healthy controls. in most cases cannabis use starts before first admission, in a third of cases before schizophrenia onset. there is an increased affinity to misuse already at the prodromal stage. cannabis can prematurely trigger schizophrenia onset - on average eight years earlier than in non-use - and cause the illness partly in interaction with predisposing factors. cannabis use in the course of schizophrenia increases positive symptoms and reduces affective flattening, thus leading to dysfunctional coping in some cases.
Schizophrenia: do men and women suffer from the same disease?
Hfner, Heinz;
Revista de Psiquiatria Clínica , 2002, DOI: 10.1590/S0101-60832002000600002
Abstract: this article reviews the literature on normal brain development and behavioural development in men and women as well as on aetiological risk factors for schizophrenia, such as pre-, peri- and postnatal complications. the male-female comparisons of age and type of onset, symptomatology, course and outcome were based on a population-based sample of 232 first illness episodes - the abc schizophrenia study sample. the probands were assessed using the iraos interview and other instruments retrospectively at first admission and prospectively at six cross sections over five years after first contact. a representative subsample of 130 first admissions or 115 first illness episodes were compared with 130 controls, matched by age, sex and area of residence. women, 3 to 4 years older than men at illness onset, showed a second peak of onsets in age group 45 to 50 years. after animal experiments and a controlled clinical study this finding was explained by a protective effect of oestrogen persisting until menopause. the underlying neurobiological mechanism consisted in a sensitivity reducing effect of oestrogen on d2 receptors in the brain. the effect of oestrogen, meanwhile confirmed in randomised control trials, also includes genomic effects as well as interactions with free-radical detoxifying systems, thus demonstrating the neuroprotective capabilities of oestrogen. postmenopausal schizophrenia was more frequent and more severe in women. men fell ill more frequently and more severely at young age and less frequently and more mildly later in life. illness course, too, was more unfavourable in postmenopausal women than in their male peers. the protective effect of oestrogen in women depended on the degree of their predisposition to the illness: the higher the familial load for schizophrenia, the weaker the protection by oestrogen. the more favourable illness course in premenopausal women resulted from their higher level of social development at illness onset - determined by th
Endoskopie-Bilder-Quiz - Aufl sung aus 4/2004
Hfner M
Journal für Gastroenterologische und Hepatologische Erkrankungen , 2005,
Abstract:
Page 1 /152946
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.