A series of (1
0
0)-oriented gallium-doped germanium crystals has been grown by the vertical Bridgman method and under the influence of a rotating magnetic field (RMF). Time-dependent flow ...instabilities occur when the critical magnetic Taylor number (
T
m
c
) is exceeded, and this can be observed by noting the appearance of striations in the grown crystals.
T
m
c
decreases as the aspect ratio of the melt increases, and approaches the theoretical limit expected for an infinite cylinder. Intentional interface demarcations are introduced by pulsing the RMF on and off. The RMF has a marked effect on the interface shape, changing it from concave to nearly flat as the RMF strength is increased.
The Continuous Performance Test (CPT) has become an essential constituent of the neuropsychological investigation of schizophrenia. Also, a vast number of brain imaging studies, mostly PET ...investigations, have employed the CPT as a cognitive challenge and established a relative hypofrontality in schizophrenics compared to controls. The aim of the present investigation was to clarify whether this predescribed hypofrontality could also be verified using functional magnetic resonance imaging (fMRI). 20 healthy volunteers and 14 schizophrenics on stable neuroleptic medication were included. Imaging was performed using the CPT-double-T-version and a clinical 1.5 T MRI-scanner with a single slice technique and a T(2)*-weighted gradient-echo-sequence. The schizophrenics exhibited a decreased activation in the right mesial prefrontal cortex, the right cingulate and the left thalamus compared to controls. These results obtained by fMRI are discussed in relation to published findings using PET.
Abstract The efficacy and safety of Hypericum extract WS® 5570 in preventing relapse during 6 months' continuation treatment and 12 months' long-term maintenance treatment after recovery from an ...episode of recurrent depression were investigated in a double-blind, placebo controlled multicenter trial. Adult out-patients with a recurrent episode of moderate major depression, a 17-item Hamilton Depression Rating Scale (HAMD) total score ≥ 20 and ≥ 3 previous episodes in 5 years participated. After 6 weeks of single-blind treatment with 3 × 300 mg/day WS® 5570 patients with score ≤ 2 on item ‘Improvement’ of the Clinical Global Impressions (CGI) scale and a HAMD total score decrease ≥ 50% versus baseline were randomized to 3 × 300 mg/day WS® 5570 or placebo for 26 weeks. 426 patients were evaluated for efficacy. Relapse rates during continuation treatment were 51/282 (18.1%) for WS® 5570 and 37/144 (25.7%) for placebo. Average time to relapse was 177 ± 2.8 and 163 ± 4.4 days for WS® 5570 and placebo, respectively (time-to-event analysis; p = 0.034; α = 0.025 one-sided). Patients treated with WS® 5570 showed more favorable HAMD and Beck Depression Inventory time courses and greater over-all improvement (CGI) than those randomized to placebo. In long-term maintenance treatment a pronounced prophylactic effect of WS® 5570 was observed in patients with an early onset of depression as well as in those with a high degree of chronicity. Adverse event rates under WS® 5570 were comparable to placebo. WS® 5570 showed a beneficial effect in preventing relapse after recovery from acute depression. Tolerability in continuation and long-term maintenance treatment was on the placebo level.
Temporal information processing is a fundamental brain function, which might include central timekeeping mechanisms independent of sensory modality. Psychopharmacological and patient studies suggest ...a crucial role of the basal ganglia in time estimation. In this study, functional magnetic resonance imaging (fMRI) was applied in 15 healthy right-handed male subjects performing an auditory time estimation task (duration discrimination of tone pairs in the range of 1,000-1,400 ms) and frequency discriminations (tone pairs differing in pitch, around 1,000 Hz) as an active control task. Task difficulty was constantly modulated by an adaptive algorithm (weighted up-down method) reacting on individual performance. Time estimation (vs rest condition) elicited a distinct pattern of cerebral activity, including the right medial and both left and right dorsolateral prefrontal cortices (DLPFC), thalamus, basal ganglia (caudate nucleus and putamen), left anterior cingulate cortex, and superior temporal auditory areas. Most activations showed lateralisation to the right hemisphere and were similar in the frequency discrimination task. Comparing time and frequency tasks, we isolated activation in the right putamen restricted to time estimation only. This result supports the notion of central processing of temporal information associated with basal ganglia activity. Temporal information processing in the brain might thus be a distributed process of interaction between modality-dependent sensory cortical function, the putamen (with a timing-specific function), and additional prefrontal cortical systems related to attention and memory. Further investigations are needed to delineate the differential contributions of the striatum and other areas to timing.
Functional and structural changes in 10 DSM-III-R male schizophrenics and 10 healthy volunteers were investigated using magnetoencephalographically (MEG) detected long-latency (N100 m) auditory ...evoked fields (AEFs) and magnetic resonance imaging (MRI). The AEFs were characterized by single moving equivalent dipoles, which were superimposed on MRIs. There were significant differences in dipole orientations and in AEF latencies in the left hemisphere of schizophrenics, when compared to the controls. The MEG-detected alterations were found to be associated with a bilateral volume reduction of the posterior superior temporal gyrus (pSTG), which was more pronounced in the left hemisphere. Separate analysis of white and gray matter has shown that the pSTG volume reduction resulted from decreased gray matter volumes without white matter changes. Both the functional and the morphological data indicate a left-hemispheric disturbance in our patients.
The noradrenaline-selective antidepressant reboxetine in vitro is a weak inhibitor of both cytochrome P450 (CYP) 2D6 and CYP3A4. Thus, in this study the pharmacokinetics of reboxetine in relation to ...pharmacogenetics and the effects of reboxetine compared to paroxetine treatment on the CYP2D6 and CYP3A4 phenotype were analyzed in healthy control subjects.
Healthy male volunteers were treated with either 6 mg reboxetine (n = 26) or 30 mg paroxetine (n = 25). On Days 10/11 of treatment, serum concentrations of the antidepressants were measured and pharmacokinetic parameters calculated. Volunteers were phenotyped at the end of treatment and after at least 3 weeks washout (true phenotype) using 30 mg dextromethorphan (DM) hydrobromide given orally and measuring DM and metabolites in serum 2 h after intake. CYP2D6 and CYP2C19 genotypes were determined in parallel.
Reboxetine serum concentrations showed no correlation with the CYP2D6 genotype and the CYP2D6 phenotype, whereas paroxetine concentrations showed some dependence on CYP2D6. In contrast to in vitro investigations, indicating a major role of CYP3A4 in reboxetine metabolism, reboxetine concentrations in serum showed no correlation with the respective DM metabolic ratios. There was also no correlation between paroxetine concentrations and the CYP3A4 phenotype data. The CYP2C19 genotype (only heterozygosity) had no influence on reboxetine and paroxetine pharmacokinetics. There were only minor changes in the DM metabolite pattern on treatment with reboxetine and no evidence of enzyme inhibition was obtained. In contrast and as expected, paroxetine strongly inhibited CYP2D6. Thus, reboxetine treatment has no effect on the CYP2D6 genotype and no clinically relevant drug interactions involving CYP2D6 are anticipated.
This paper describes a new method for detecting structural brain differences based on the analysis of deformation fields. Deformations are obtained by an intensity-based nonlinear registration ...routine that transforms one brain onto another one. We present a general multivariate statistical approach to analyze deformation fields in different subjects. This method was applied to the brains of 85 schizophrenic patients and 75 healthy volunteers to examine whether low frequency deformations are sufficiently sensitive to detect regional deviations in the brains of both groups. We observed significant changes caused by volume reduction in brains of schizophrenics bilaterally in the thalamus and in the superior temporal gyrus. On the left side, the superior frontal gyrus and precentral gyrus are found to be changed, while on the right side, the middle frontal gyrus was altered. In addition, there were significant changes in the occipital lobe (left lingual gyrus) and in the left cerebellum. Volume enlargement in brains of schizophrenics was observed in the right putamen and in the adjacent white matter of the thalamic region. Our data suggest a disturbance in the nodes of a prefrontal–thalamic–cerebellar circuitry. This provides further support for the model of “cognitive dysmetria,” which postulates a disruption in these nodes. We have demonstrated the application of deformation-based morphometry by detecting structural changes in the whole brain. This technique is fully automatic, thus allowing for the inclusion of large samples, with no user bias ora priori-defined regions of interest.
The thermal fields of two Bridgman-like configurations, representative of real systems used in prior experiments for the detached growth of CdTe and Ge crystals, are studied. These detailed heat ...transfer computations are performed using the CrysMAS code and expand upon our previous analysis C. Stelian, A. Yeckel, J.J. Derby, Influence of thermal phenomena on crystal reattachment during the dewetted Bridgman growth, J. Cryst. Growth, in press that posited a new mechanism involving the thermal field and meniscus position to explain stable conditions for dewetted Bridgman growth. Computational results indicate that heat transfer conditions that led to successful detached growth in both of these systems are in accordance with our prior assertion, namely that the prevention of crystal reattachment to the crucible wall requires the avoidance of any undercooling of the melt meniscus during the growth run. Significantly, relatively simple process modifications that promote favorable thermal conditions for detached growth may overcome detrimental factors associated with meniscus shape and crucible wetting. Thus, these ideas may be important to advance the practice of detached growth for many materials.
It has been demonstrated by single photon emission computed tomography (SPECT) and positron emission tomography (PET) that frontal brain regions are stimulated during performance of the Wisconsin ...Card Sorting Test (WCST). The WCST is also regarded as one of the standard tests for the assessment of frontal activity in brain imaging studies of schizophrenia. In this study cerebral activation was assessed by means of functional magnetic resonance imaging (fMRI). In healthy volunteers WCST stimulation resulted in a right lateralized frontal activation. In 13 chronic schizophrenics on stable neuroleptic medication, a lack of activation in the right prefrontal cortex and — as a trend — an increased left temporal activity during execution of the WCST was noted compared to controls. Since a one-slice technique was used, no information about the activation pattern in adjacent brain regions was obtained. However, as fMRI possesses a superior spatial resolution compared to SPECT and PET, the anatomical localization of the activation effect in the measured slice can be defined more precisely. Beside these methodological considerations, the results are discussed in relation to prior findings of a reduced ability of schizophrenics to coordinate cerebral function.
This paper treats the steady axisymmetric flow and mass transport in a cylindrical liquid bridge between the melting end of a feed rod and the solidifying end of an alloyed semiconductor crystal. ...There is a strong, uniform, steady, axial magnetic field. The surface tension depends on the temperature and the concentration of the species, while variations of the concentration occur because one species is rejected into the liquid during solidification. The thermocapillary and solutocapillary convections tend to cancel over part of the liquid bridge. For certain parameter ranges, there are two different stable solutions: one where the concentration gradient along the free surface leads to dominance by the solutocapillary convection and one where the mass transport due to the thermocapillary convection makes the concentration gradient along the free surface small, so that the thermocapillary convection is dominant.
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