154 research outputs found
Comparison of Monomethylhydrazine/Hydroxypropylcellulose and Hydrocarbon/Silica Gels
Experimental studies have been performed to investigate rheology and droplet burning with different types of gelled propellants. Monomethylhydrazine has been gelled with organic hydroxypropylcellulose. JP-8 and RP-1 hydrocarbon gels have been produced with inorganic fumed silica particles. Rheological characterization showed the differences in terms of viscosity and yield stress behavior due to different types of gelling agents. Herschel-Bulkley and Carreau-Yasuda models have been used to characterize the gels with inorganic and organic gelling agents, respectively. First experiments with the Monomethylhydrazine/hydroxypropylcellulose gels showed a typical swelling process during combustion with a flexible viscous droplet surface. Contrary to that, the hydrocarbon/silica gels burned while a rigid silica structure was built, which remained unburned. Burning drop measurements have been compared to the d^2-squared law
The universal red-giant oscillation pattern; an automated determination with CoRoT data
The CoRoT and Kepler satellites have provided thousands of red-giant
oscillation spectra. The analysis of these spectra requires efficient methods
for identifying all eigenmode parameters. The assumption of new scaling laws
allows us to construct a theoretical oscillation pattern. We then obtain a
highly precise determination of the large separation by correlating the
observed patterns with this reference. We demonstrate that this pattern is
universal and are able to unambiguously assign the eigenmode radial orders and
angular degrees. This solves one of the current outstanding problems of
asteroseismology hence allowing precise theoretical investigation of red-giant
interiors.Comment: Accepted in A&A letter
A Comprehensive Spectroscopic Analysis of DB White Dwarfs
We present a detailed analysis of 108 helium-line (DB) white dwarfs based on
model atmosphere fits to high signal-to-noise optical spectroscopy. We derive a
mean mass of 0.67 Mo for our sample, with a dispersion of only 0.09 Mo. White
dwarfs also showing hydrogen lines, the DBA stars, comprise 44% of our sample,
and their mass distribution appears similar to that of DB stars. As in our
previous investigation, we find no evidence for the existence of low-mass (M <
0.5 Mo) DB white dwarfs. We derive a luminosity function based on a subset of
DB white dwarfs identified in the Palomar-Green survey. We show that 20% of all
white dwarfs in the temperature range of interest are DB stars, although the
fraction drops to half this value above Teff ~ 20,000 K. We also show that the
persistence of DB stars with no hydrogen features at low temperatures is
difficult to reconcile with a scenario involving accretion from the
interstellar medium, often invoked to account for the observed hydrogen
abundances in DBA stars. We present evidence for the existence of two different
evolutionary channels that produce DB white dwarfs: the standard model where DA
stars are transformed into DB stars through the convective dilution of a thin
hydrogen layer, and a second channel where DB stars retain a helium-atmosphere
throughout their evolution. We finally demonstrate that the instability strip
of pulsating V777 Her white dwarfs contains no nonvariables, if the hydrogen
content of these stars is properly accounted for.Comment: 74 pages including 30 figures, accepted for publication in the
Astrophysical Journa
Micro-Hall Magnetometry Studies of Thermally Assisted and Pure Quantum Tunneling in Single Molecule Magnet Mn12-Acetate
We have studied the crossover between thermally assisted and pure quantum
tunneling in single crystals of high spin (S=10) uniaxial single molecule
magnet Mn12-acetate using micro-Hall effect magnetometry. Magnetic hysteresis
experiments have been used toinvestigate the energy levels that determine the
magnetization reversal as a function of magnetic field and temperature. These
experiments demonstrate that the crossover occurs in a narrow (~0.1 K) or broad
(~1 K) temperature interval depending on the magnitude and direction of the
applied field. For low external fields applied parallel to the easy axis, the
energy levels that dominate the tunneling shift abruptly with temperature. In
the presence of a transverse field and/or large longitudinal field these energy
levels change with temperature more gradually. A comparison of our experimental
results with model calculations of this crossover suggest that there are
additional mechanisms that enhance the tunneling rate of low lying energy
levels and broaden the crossover for small transverse fields.Comment: 5 pages, 5 figure
Subcellular compartmentation of glutathione in dicotyledonous plants
This study describes the subcellular distribution of glutathione in roots and leaves of different plant species (Arabidopsis, Cucurbita, and Nicotiana). Glutathione is an important antioxidant and redox buffer which is involved in many metabolic processes including plant defense. Thus information on the subcellular distribution in these model plants especially during stress situations provides a deeper insight into compartment specific defense reactions and reflects the occurrence of compartment specific oxidative stress. With immunogold cytochemistry and computer-supported transmission electron microscopy glutathione could be localized in highest contents in mitochondria, followed by nuclei, peroxisomes, the cytosol, and plastids. Within chloroplasts and mitochondria, glutathione was restricted to the stroma and matrix, respectively, and did not occur in the lumen of cristae and thylakoids. Glutathione was also found at the membrane and in the lumen of the endoplasmic reticulum. It was also associated with the trans and cis side of dictyosomes. None or only very little glutathione was detected in vacuoles and the apoplast of mesophyll and root cells. Additionally, glutathione was found in all cell compartments of phloem vessels, vascular parenchyma cells (including vacuoles) but was absent in xylem vessels. The specificity of this method was supported by the reduction of glutathione labeling in all cell compartments (up to 98%) of the glutathione-deficient Arabidopsis thaliana rml1 mutant. Additionally, we found a similar distribution of glutathione in samples after conventional fixation and rapid microwave-supported fixation. Thus, indicating that a redistribution of glutathione does not occur during sample preparation. Summing up, this study gives a detailed insight into the subcellular distribution of glutathione in plants and presents solid evidence for the accuracy and specificity of the applied method
Efficacy and safety of bilateral continuous theta burst stimulation (cTBS) for the treatment of chronic tinnitus: design of a three-armed randomized controlled trial
<p>Abstract</p> <p>Background</p> <p>Tinnitus, the perception of sound and noise in absence of an auditory stimulus, has been shown to be associated with maladaptive neuronal reorganization and increased activity of the temporoparietal cortex. Transient modulation of tinnitus by repetitive transcranial magnetic stimulation (rTMS) indicated that these areas are critically involved in the pathophysiology of tinnitus and suggested new treatment strategies. However, the therapeutic efficacy of rTMS in tinnitus is still unclear, individual response is variable, and the optimal stimulation area disputable. Recently, continuous theta burst stimulation (cTBS) has been put forward as an effective rTMS protocol for the reduction of pathologically enhanced cortical excitability.</p> <p>Methods</p> <p>48 patients with chronic subjective tinnitus will be included in this randomized, placebo controlled, three-arm trial. The treatment consists of two trains of cTBS applied bilaterally to the secondary auditory cortex, the temporoparietal associaction cortex, or to the lower occiput (sham condition) every working day for four weeks. Primary outcome measure is the change of tinnitus distress as quantified by the Tinnitus Questionnaire (TQ). Secondary outcome measures are tinnitus loudness and annoyance as well as tinnitus change during and after treatment. Audiologic and speech audiometric measurements will be performed to assess potential side effects. The aim of the present trail is to investigate effectiveness and safety of a four weeks cTBS treatment on chronic tinnitus and to compare two areas of stimulation. The results will contribute to clarify the therapeutic capacity of rTMS in tinnitus.</p> <p>Trial registration</p> <p>The trial was registered with the clinical trials register of <url>http://www.clinicaltrials.gov</url> (NCT00518024).</p
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Care planning for consumers on community treatment orders: an integrative literature review
Background
Case management is the established model for care provision in mental health and is delivered within current care philosophies of person-centred and recovery-oriented care. The fact that people with a mental illness may be forced to receive care and treatment in the community poses challenges for clinicians aiming to engage in approaches that promote shared decision-making and self-determination. This review sought to gain an in-depth understanding of stakeholders’ perspectives and experiences of care planning for consumers’ on CTOs.
Methods
An integrative review method allowed for inclusion of a broad range of studies from diverse empirical sources. Systematic searches were conducted across six databases. Following appraisal, findings from included papers were coded into groups and presented against a framework of case management.
Results
Forty-eight papers were included in the review. Empirical studies came from seven countries, with the majority reporting on qualitative methods. Many similarities were reported across studies. Positive gains from CTOs were usually associated with the nature of support received, highlighting the importance of the therapeutic relationship in care planning. Key gaps in care planning included a lack of connection between CTO, treatment and consumer goals and lack of implementation of focussed interventions.
Conclusions
Current case management processes could be better utilised for consumers on CTOs, with exploration of how this could be achieved warranted. Workers need to be sensitive to the ‘control and care’ dynamic in the care planning relationship, with person-centred approaches requiring core and advanced practitioner and communication skills, including empathy and trust
Tracking the Expression of Excitatory and Inhibitory Neurotransmission-Related Proteins and Neuroplasticity Markers after Noise Induced Hearing Loss
Excessive exposure to loud noise can damage the cochlea and create a hearing loss. These pathologies coincide with a range of CNS changes including reorganisation of frequency representation, alterations in the pattern of spontaneous activity and changed expression of excitatory and inhibitory neurotransmitters. Moreover, damage to the cochlea is often accompanied by acoustic disorders such as hyperacusis and tinnitus, suggesting that one or more of these neuronal changes may be involved in these disorders, although the mechanisms remain unknown. We tested the hypothesis that excessive noise exposure increases expression of markers of excitation and plasticity, and decreases expression of inhibitory markers over a 32-day recovery period. Adult rats (n = 25) were monaurally exposed to a loud noise (16 kHz, 1/10th octave band pass (115 dB SPL)) for 1-hour, or left as non-exposed controls (n = 5). Animals were euthanased at either 0, 4, 8, 16 or 32 days following acoustic trauma. We used Western Blots to quantify protein levels of GABAA receptor subunit α1 (GABAAα1), Glutamic-Acid Decarboxylase-67 (GAD-67), N-Methyl-D-Aspartate receptor subunit 2A (NR2A), Calbindin (Calb1) and Growth Associated Protein 43 (GAP-43) in the Auditory Cortex (AC), Inferior Colliculus (IC) and Dorsal Cochlear Nucleus (DCN). Compared to sham-exposed controls, noise-exposed animals had significantly (p<0.05): lower levels of GABAAα1 in the contralateral AC at day-16 and day-32, lower levels of GAD-67 in the ipsilateral DCN at day-4, lower levels of Calb1 in the ipsilateral DCN at day-0, lower levels of GABAAα1 in the ipsilateral AC at day-4 and day-32. GAP-43 was reduced in the ipsilateral AC for the duration of the experiment. These complex fluctuations in protein expression suggests that for at least a month following acoustic trauma the auditory system is adapting to a new pattern of sensory input
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