1,224 research outputs found
Intrinsic Metastabilities in the Charge Configuration of a Double Quantum Dot
We report a thermally activated metastability in a GaAs double quantum dot
exhibiting real-time charge switching in diamond shaped regions of the charge
stability diagram. Accidental charge traps and sensor back action are excluded
as the origin of the switching. We present an extension of the canonical double
dot theory based on an intrinsic, thermal electron exchange process through the
reservoirs, giving excellent agreement with the experiment. The electron spin
is randomized by the exchange process, thus facilitating fast, gate-controlled
spin initialization. At the same time, this process sets an intrinsic upper
limit to the spin relaxation time.Comment: 4 pages, 5 figures (color
GaAs Quantum Dot Thermometry Using Direct Transport and Charge Sensing
We present measurements of the electron temperature using gate defined
quantum dots formed in a GaAs 2D electron gas in both direct transport and
charge sensing mode. Decent agreement with the refrigerator temperature was
observed over a broad range of temperatures down to 10 mK. Upon cooling nuclear
demagnetization stages integrated into the sample wires below 1 mK, the device
electron temperature saturates, remaining close to 10 mK. The extreme
sensitivity of the thermometer to its environment as well as electronic noise
complicates temperature measurements but could potentially provide further
insight into the device characteristics. We discuss thermal coupling
mechanisms, address possible reasons for the temperature saturation and
delineate the prospects of further reducing the device electron temperature.Comment: 8 pages, 3 (color) figure
Versatile Surface Electrodes for Combined Electrophysiology and Two-Photon Imaging of the Mouse Central Nervous System
Understanding and modulating CNS function in physiological as well as
pathophysiological contexts remains a significant ambition in research and clinical
applications. The investigation of the multifaceted CNS cell types including their
interactions and contributions to neural function requires a combination of the state-ofthe-art in vivo electrophysiology and imaging techniques. We developed a novel type of
liquid crystal polymer (LCP) surface micro-electrode manufactured in three customized
designs with up to 16 channels for recording and stimulation of brain activity. All designs
include spare central spaces for simultaneous 2P-imaging. Nanoporous platinumplated contact sites ensure a low impedance and high current transfer. The epidural
implantation of the LCP micro-electrodes could be combined with standard cranial
window surgery. The epidurally positioned electrodes did not only display long-term
biocompatibility, but we also observed an additional stabilization of the underlying CNS
tissue. We demonstrate the electrode’s versatility in combination with in vivo 2P-imaging
by monitoring anesthesia-awake cycles of transgenic mice with GCaMP3 expression
in neurons or astrocytes. Cortical stimulation and simultaneous 2P Ca2+ imaging in
neurons or astrocytes highlighted the astrocytes’ integrative character in neuronal activity
processing. Furthermore, we confirmed that spontaneous astroglial Ca2+ signals are
dampened under anesthesia, while evoked signals in neurons and astrocytes showed
stronger dependency on stimulation intensity rather than on various levels of anesthesia.
Finally, we show that the electrodes provide recordings of the electrocorticogram (ECoG) with a high signal-to noise ratio and spatial signal differences which help to decipher brain
activity states during experimental procedures. Summarizing, the novel LCP surface
micro-electrode is a versatile, convenient, and reliable tool to investigate brain function
in vivo
Metallic Coulomb Blockade Thermometry down to 10 mK and below
We present an improved nuclear refrigerator reaching 0.3 mK, aimed at
microkelvin nanoelectronic experiments, and use it to investigate metallic
Coulomb blockade thermometers (CBTs) with various resistances R. The high-R
devices cool to slightly lower T, consistent with better isolation from the
noise environment, and exhibit electron-phonon cooling ~ T^5 and a residual
heat-leak of 40 aW. In contrast, the low-R CBTs display cooling with a clearly
weaker T-dependence, deviating from the electronphonon mechanism. The CBTs
agree excellently with the refrigerator temperature above 20 mK and reach a
minimum-T of 7.5 +/- 0.2 mK.Comment: 3 pages, 3 (color) figure
Ferritic Nb-alloyed Cr-Steel in simulated strip casting process
Nb alloyed ferritic Cr-steel is usually produced by continuous casting with following hot and cold rolling procedure. In the laboratory scale the possible new route via strip casting was studied. The scope of the investigation in simulated process route was the development of microstructure and precipitations. In the experiments process parameters similar to those of the real strip caster were chosen, then those of hot rolling and cold rolling of such cast strips. The quickly solidified layer was produced by immersion of a steel substrate under vacuum into melt. The microstructure showed small niobium precipitates in the grain matrix and at the grain boundaries. Their size and distribution was evaluated for different niobium contents and cooling rates in the as-solidified structure. The diffusion controlled change of the precipitate morphology was also analysed after preheating and rolling. Reprecipitation and precipitate growth, as well as dissolution of precipitations at the grain boundaries were observed. The effect of various cooling rates and niobium content on the shape and formation of niobium containing precipitates and on the grain boundary is discussed. Thermodynamic calculations using FactSage were carried out in order to predict the precipitation of Nb-rich phases in ferritic stainless steels. The effect of the chemical composition and temperature on the thermodynamic stability of these precipitates was evaluated
Marrow adipose tissue expansion coincides with insulin resistance in MAGP1-deficient mice
Marrow adipose tissue (MAT) is an endocrine organ with the potential to influence skeletal remodeling and hematopoiesis. Pathologic MAT expansion has been studied in the context of severe metabolic challenge, including caloric restriction, high fat diet feeding, and leptin deficiency. However, the rapid change in peripheral fat and glucose metabolism associated with these models impedes our ability to examine which metabolic parameters precede or coincide with MAT expansion. Microfibril-associated glycoprotein-1 (MAGP1) is a matricellular protein that influences cellular processes by tethering signaling molecules to extracellular matrix structures. MAGP1-deficient (Mfap2(−/−)) mice display a progressive excess adiposity phenotype, which precedes insulin resistance and occurs without changes in caloric intake or ambulation. Mfap2(−/−) mice were, therefore, used as a model to associate parameters of metabolic disease, bone remodeling, and hematopoiesis with MAT expansion. Marrow adiposity was normal in Mfap2(−/−) mice until 6 months of age; however, by 10 months, marrow fat volume had increased fivefold relative to wild-type control at the same age. Increased gonadal fat pad mass and hyperglycemia were detectable in Mfap2(−/−) mice by 2 months, but peaked by 6 months. The development of insulin resistance coincided with MAT expansion. Longitudinal characterization of bone mass demonstrated a disconnection in MAT volume and bone volume. Specifically, Mfap2(−/−) mice had reduced trabecular bone volume by 2 months, but this phenotype did not progress with age or MAT expansion. Interestingly, MAT expansion in the 10-month-old Mfap2(−/−) mice was associated with modest alterations in basal hematopoiesis, including a shift from granulopoiesis to B lymphopoiesis. Together, these findings indicate MAT expansion is coincident with insulin resistance, but not excess peripheral adiposity or hyperglycemia in Mfap2(−/−) mice; and substantial MAT accumulation does not necessitate a proportional decrease in either bone mass or bone marrow cellularity
Electron attachment to valence-excited CO
The possibility of electron attachment to the valence state of CO
is examined using an {\it ab initio} bound-state multireference configuration
interaction approach. The resulting resonance has symmetry;
the higher vibrational levels of this resonance state coincide with, or are
nearly coincident with, levels of the parent state. Collisional
relaxation to the lowest vibrational levels in hot plasma situations might
yield the possibility of a long-lived CO state.Comment: Revtex file + postscript file for one figur
Bisphosphonates Inhibit Expression of p63 by Oral Keratinocytes
Osteonecrosis of the jaw (ONJ), a side-effect of bisphosphonate therapy, is characterized by exposed bone that fails to heal within eight weeks. Healing time of oral epithelial wounds is decreased in the presence of amino-bisphosphonates; however, the mechanism remains unknown. We examined human tissue from individuals with ONJ and non-bisphosphonate-treated controlindividuals to identify changes in oral epithelium and connective tissue. Oral and intravenous bisphosphonate-treated ONJ sites had reduced numbers of basal epithelial progenitor cells, as demonstrated by a 13.8 ± 1.1% and 31.9 ± 5.8% reduction of p63 expression, respectively. No significant differences in proliferation rates, vessel density, or macrophage number were noted. In vitro treatment of clonal and primary oral keratinocytes with zoledronic acid (ZA) inhibited p63, and expression was rescued by the addition of mevalonate pathway intermediates. In addition, both ZA treatment and p63 shRNA knock-down impaired formation of 3D Ex Vivo Produced Oral Mucosa Equivalents (EVPOME) and closure of an in vitro scratch assay. Analysis of our data suggests that bisphosphonate treatment may delay oral epithelial healing by interfering with p63-positive progenitor cells in the basal layer of the oral epithelium in a mevalonate-pathway-dependent manner. This delay in healing may increase the likelihood of osteonecrosis developing in already-compromised bone
The use of biomedicine, complementary and alternative medicine, and ethnomedicine for the treatment of epilepsy among people of South Asian origin in the UK
Studies have shown that a significant proportion of people with epilepsy use complementary and alternative medicine (CAM). CAM use is known to vary between different ethnic groups and cultural contexts; however, little attention has been devoted to inter-ethnic differences within the UK population. We studied the use of biomedicine, complementary and alternative medicine, and ethnomedicine in a sample of people with epilepsy of South Asian origin living in the north of England.
Interviews were conducted with 30 people of South Asian origin and 16 carers drawn from a sampling frame of patients over 18 years old with epilepsy, compiled from epilepsy registers and hospital databases. All interviews were tape-recorded, translated if required and transcribed. A framework approach was adopted to analyse the data.
All those interviewed were taking conventional anti-epileptic drugs. Most had also sought help from traditional South Asian practitioners, but only two people had tried conventional CAM. Decisions to consult a traditional healer were taken by families rather than by individuals with epilepsy. Those who made the decision to consult a traditional healer were usually older family members and their motivations and perceptions of safety and efficacy often differed from those of the recipients of the treatment. No-one had discussed the use of traditional therapies with their doctor. The patterns observed in the UK mirrored those reported among people with epilepsy in India and Pakistan.
The health care-seeking behaviour of study participants, although mainly confined within the ethnomedicine sector, shared much in common with that of people who use global CAM. The appeal of traditional therapies lay in their religious and moral legitimacy within the South Asian community, especially to the older generation who were disproportionately influential in the determination of treatment choices. As a second generation made up of people of Pakistani origin born in the UK reach the age when they are the influential decision makers in their families, resort to traditional therapies may decline. People had long experience of navigating plural systems of health care and avoided potential conflict by maintaining strict separation between different sectors. Health care practitioners need to approach these issues with sensitivity and to regard traditional healers as potential allies, rather than competitors or quacks
Reaction rates for Neutron Capture Reactions to C-, N- and O-isotopes to the neutron rich side of stability
The reaction rates of neutron capture reactions on light nuclei are important
for reliably simulating nucleosynthesis in a variety of stellar scenarios.
Neutron capture reaction rates on neutron-rich C-, N-, and O-isotopes are
calculated in the framework of a hybrid compound and direct capture model. The
results are tabulated and compared with the results of previous calculations as
well as with experimental results.Comment: 33 pages (uses revtex) and 9 postscript figures, accepted for
publication in Phys. Rev.
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