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Author: Christian Sommer (32)


Feb
2018

Alcohol intoxication may affect self-reports of alcohol use and related constructs, such as impulsivity and dependence symptoms. Improved knowledge about potential systematic reporting biases induced by alcohol, e.g.

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Jan
2018

The influence of Pavlovian conditioned stimuli on ongoing behavior may contribute to explaining how alcohol cues stimulate drug seeking and intake. Using a Pavlovian-instrumental transfer task, we investigated the effects of alcohol-related cues on approach behavior (i.e.

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Dec
2017

The premature aging hypothesis of alcohol dependence proposes that the neurobiological and behavioural deficits in individuals with alcohol dependence are analogous to those of chronological aging. However, to date no systematic neurobiological evidence for this hypothesis has been provided. To test the hypothesis, 119 alcohol-dependent subjects and 97 age- and gender-matched healthy control subjects underwent structural MRI.

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Sep
2017

An array of N closely spaced dipole coupled quantum emitters exhibits super- and subradiance with characteristic tailorable spatial radiation patterns. Optimizing the emitter geometry and distance with respect to the spatial profile of a near resonant optical cavity mode allows us to increase the ratio between light scattering into the cavity mode and free space emission by several orders of magnitude. This leads to distinct scaling of the collective coherent emitter-field coupling vs the free space decay as a function of the emitter number.

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Oct
2017

Impulsive decision making relates to problematic substance use. Specifically, altered delay discounting (DD) has been suggested as a behavioral marker for addiction, while other relevant facets of choice impulsivity such as probability discounting (PD) or loss aversion are clearly understudied.
Two studies were performed collecting behavioral data on choice impulsivity with a value-based decision-making battery providing estimates of DD, PD for gains and losses, and loss aversion.

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Jul
2017

Alcohol-related cues can evoke explicit and implicit motivation to drink alcohol. Concerning the links between explicit and implicit motivation, there are mixed findings. Therefore, we investigated both concepts in 51 healthy 18- to 19-year-old males, who are less affected by neuropsychological deficits in decision-making that are attributed to previous alcohol exposure than older participants.

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Dec
2017

Addiction is supposedly characterized by a shift from goal-directed to habitual decision making, thus facilitating automatic drug intake. The two-step task allows distinguishing between these mechanisms by computationally modeling goal-directed and habitual behavior as model-based and model-free control. In addicted patients, decision making may also strongly depend upon drug-associated expectations.

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Oct
2017

Video fluoroscopy is a technique currently used to retrieve the in vivo three-dimensional kinematics of human joints during activities of daily living. Minimization of the radiation dose absorbed by the subject during the measurement is a priority and has not been thoroughly addressed so far. This issue is critical for the motion analysis of the hip joint, because of the proximity of the gonads.

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Jul
2017

Deep neck infections are among the most dangerous acute diseases in the head and neck region. This analysis gives an overview of the bacterial and histopathologic findings of deep neck infections.
From January 2002 to December 2012, 63 patients were diagnosed with and treated for deep neck infections at the University Medical Center Göttingen.

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Apr
2017


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Nov
2016

Many-body correlations govern a variety of important quantum phenomena such as the emergence of superconductivity and magnetism. Understanding quantum many-body systems is thus one of the central goals of modern sciences. Here we demonstrate an experimental approach towards this goal by utilizing an ultracold Rydberg gas generated with a broadband picosecond laser pulse.

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Sep
2016

Several classifications to identify and avoid use of potentially inappropriate medications (PIMs) in the elderly have been published. To what extent these classifications match each other and whether there are differences in the prevalence of PIM use at admission, during the inpatient stay and at discharge are largely unreported.
To determine the PIM prevalence in elderly patients at a university hospital, with a special focus on different classification systems and the chronological sequence, and to examine a possible association between PIM use and the reason for admission, as well as severe side effects and consequences of PIM use during hospitalization.

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Aug
2016

Adolescence is a critical period for the development of alcohol use disorders; drinking habits are rather unstable and genetic influences, such as male sex and a positive family history of alcoholism (FH), are often masked by environmental factors such as peer pressure.
We investigated how sex and FH modulate alcohol use in a sample of 18- to 19-year-olds from the Dresden Longitudinal Study on Alcohol use in Young Adults. Adolescents reported their real-life drinking in a TimeLine Follow-Back interview.

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Jun
2016

The purpose of this study was to evaluate the use of the tongue repositioning maneuver (TRM) during panoramic radiography so as to avoid the error of tongue shadow.
A total of 300 panoramic radiographs were evaluated. One hundred and fifty orthopantomograms with conventional positioning technique were used as a control group, while other 150 were taken with the patient performing the TRM.

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Dec
1969

We show that with an appropriate combination of two optical simulation techniques-classical ray-tracing and the finite difference time domain method-an optical device containing multiple diffractive and refractive optical elements can be accurately simulated in an iterative simulation approach. We compare the simulation results with experimental measurements of the device to discuss the applicability and accuracy of our iterative simulation procedure.

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Dec
2015

Insertion of reporter cassettes into the Lgr5 locus has enabled the characterization of mouse intestinal stem cells (ISCs). However, low cell surface abundance of LGR5 protein and lack of high-affinity anti-LGR5 antibodies represent a roadblock to efficiently isolate human colonic stem cells (hCoSCs). We set out to identify stem cell markers that would allow for purification of hCoSCs.

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Jun
2015

While the utility of experimental free-access alcohol self-administration paradigms is well established, little data exist addressing the question of whether study participation influences subsequent natural alcohol consumption. We here present drinking reports of young adults before and after participation in intravenous alcohol self-administration studies.
Timeline Follow-back drinking reports for the 6 weeks immediately preceding the first, and the 6 weeks after the last experimental alcohol challenge were examined from subjects completing 1 of 2 similar alcohol self-administration paradigms.

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May
2016

In detoxified alcohol-dependent patients, alcohol-related stimuli can promote relapse. However, to date, the mechanisms by which contextual stimuli promote relapse have not been elucidated in detail. One hypothesis is that such contextual stimuli directly stimulate the motivation to drink via associated brain regions like the ventral striatum and thus promote alcohol seeking, intake and relapse.

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Dec
1969

Pavlovian processes are thought to play an important role in the development, maintenance and relapse of alcohol dependence, possibly by influencing and usurping ongoing thought and behavior. The influence of pavlovian stimuli on ongoing behavior is paradigmatically measured by pavlovian-to-instrumental transfer (PIT) tasks. These involve multiple stages and are complex.

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Jun
2014

In this study the applicability of an interface procedure for combined ray-tracing and finite difference time domain (FDTD) simulations of optical systems which contain two diffractive gratings is discussed. The simulation of suchlike systems requires multiple FDTD↔RT steps. In order to minimize the error due to the loss of the phase information in an FDTD→RT step, we derive an equation for a maximal coherence correlation function (MCCF) which describes the maximum degree of impact of phase effects between these two different diffraction gratings and which depends on: the spatial distance between the gratings, the degree of spatial coherence of the light source and the diffraction angle of the first grating for the wavelength of light used.

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Jul
2014

According to the Segré-Silberberg effect, spherical particles migrate to a lateral equilibrium position in parabolic flow profiles. Here, for the first time, the corresponding equilibrium velocity is studied experimentally for micro particles in channels with rectangular cross section. Micro channels are fabricated in PMMA substrate based on a hot embossing process.

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Dec
1969

Efficient fractionation of peptides is an essential prerequisite for comprehensive analysis of complex protein mixtures by shotgun mass spectrometry. The separation of peptides by isoelectric focusing is particularly attractive due to its orthogonality to reverse-phase HPLC. Here, we present a protocol for in-gel peptide isoelectric focusing using immobilized pH gradient strips.

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May
2013

For a systematic approach to improve the reliability and the white light quality of phosphor converted light-emitting diodes (LEDs) it is imperative to gain a better understanding of the individual parameters that affect color temperature constancy and maintenance. By means of a combined optical and thermal simulation procedure, in this contribution we give a comprehensive discussion on the impact of different current driving schemes on the thermal load of the color conversion elements (CCEs) of phosphor converted LEDs. We show that on the one hand a decreasing duty cycle under pulse width modulation driving conditions may cause a notable temperature variation and on the other hand also effects due to the non-linearity between the blue radiant flux and the current have to be considered for the thermal load of the CCEs.

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Nov
2012

Polar molecules have a rich internal structure and long-range dipole-dipole interactions, making them useful for quantum-controlled applications and fundamental investigations. Their potential fully unfolds at ultracold temperatures, where various effects are predicted in many-body physics, quantum information science, ultracold chemistry and physics beyond the standard model. Whereas a wide range of methods to produce cold molecular ensembles have been developed, the cooling of polyatomic molecules (that is, with three or more atoms) to ultracold temperatures has seemed intractable.

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Feb
2012

In order to produce recombinant microbial transglutaminase (rMTG) which is free of the activating protease, dispase was used to activate the pro-rMTG followed by immobilized metal affinity chromatography (IMAC). As shown by MALDI-MS, the dispase does not only cleave the pro-sequence, but unfortunately also cleaves within the C-terminal histidine-tag. Hence, the active rMTG cannot properly bind to the IMAC material.

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May
2011

A process for the production of a thermostable variant of a microbial transglutaminase was developed. The transglutaminase variant produced, carried a single amino acid exchange (serine replaced by proline at position 2) and showed a nearly doubled specific activity of 46.1 Umg(-1) compared to the wild-type enzyme.

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Dec
1969

We describe the combination of buffer-gas cooling with electrostatic velocity filtering to produce a high-flux continuous guided beam of internally cold and slow polar molecules. In a previous paper (L.D.

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Oct
2007

Recombinant activated factor VII (rFVIIa; NovoSeven) has been widely used to treat bleeding in patients with haemophilia with inhibitors. To increase the intrinsic activity, analogues of rFVIIa (rFVIIa Q, rFVIIa DVQ, and rFVIIa DVQA) with altered amino acid sequence at or near the active centre have been developed. The immunogenicity of these analogues was tested in a rat immune tolerance model.

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Jun
2004

Vocalizations with an emphasized fundamental are common in many species of animals. Such calls can presumably be sufficiently described by measures of their fundamental shape or 'contour'. Here we describe a software we developed to analyze such vocalizations semi-automatically.

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Feb
2004

Helicobacter pylori is the causative agent of a variety of gastric diseases, but the clinical relevance of bacterial virulence factors is still controversial. Virulent strains carrying the cag pathogenicity island (cagPAI) are thought to be key players in disease development. Here, we have compared cagPAI-dependent in vitro responses in H.

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Feb
2002

To determine the value of the bispectral index (BIS) in assessing the depth of sedation in sedated and mechanically ventilated ICU patients, compared with clinical sedation scores.
Prospective convenience sample in a 12-bed anesthesiological-surgical ICU of a university hospital.
19 consecutive patients without any central neurological diseases requiring mechanical ventilation for more than 24 h.

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