228 research outputs found
GROWTH OF InAsxSb1-x LAYERS ON GaAs SUBSTRATES BY HOT WALL EPITAXY
We have studied the structural and electrical characteristics of InAsSb
ternary layers grown on GaAs (001) substrates by hot wall epitaxy (HWE) at
arsenic (As) reservoir temperature in the range from 220 to 290 °C. The
growth rate of the epilayer is found to be decreased with increasing As
temperature. This is attributed to the abundance of group V molecules to the
growth surface, which suppresses the mass transport of Indium (In) atoms. A
dramatic change in the surface morphologies of the samples has been observed
by scanning electron microscopy. X-ray diffraction studies indicate that the
arsenic composition of the layer can be controlled by manipulating As
temperature. Hall effect results of the samples show that the electron
mobility of the layer decreases with increasing As temperature
A trial of somatic gene targeting in vivo with an adenovirus vector
BACKGROUND: Gene targeting in vivo provides a potentially powerful method for gene analysis and gene therapy. In order to sensitively detect and accurately measure designed sequence changes, we have used a transgenic mouse system, MutaMouse, which has been developed for detection of mutation in vivo. It carries bacteriophage lambda genome with lacZ(+ )gene, whose change to lacZ-negative allele is detected after in vitro packaging into bacteriophage particles. We have also demonstrated that gene transfer with a replication-defective adenovirus vector can achieve efficient and accurate gene targeting in vitro. METHODS: An 8 kb long DNA corresponding to the bacteriophage lambda transgene with one of two lacZ-negative single-base-pair-substitution mutant allele was inserted into a replication-defective adenovirus vector. This recombinant adenovirus was injected to the transgenic mice via tail-vein. Twenty-four hours later, genomic DNA was extracted from the liver tissue and the lambda::lacZ were recovered by in vitro packaging. The lacZ-negative phage was detected as a plaque former on agar with phenyl-beta-D-galactoside. RESULTS: The mutant frequency of the lacZ-negative recombinant adenovirus injected mice was at the same level with the control mouse (~1/10000). Our further restriction analysis did not detect any designed recombinant. CONCLUSION: The frequency of gene targeting in the mouse liver by these recombinant adenoviruses was shown to be less than 1/20000 in our assay. However, these results will aid the development of a sensitive, reliable and PCR-independent assay for gene targeting in vivo mediated by virus vectors and other means
GRAVITATIONAL EFFECT ON GROWTH OF InX Ga1-XSb TERNARY BULK CRYSTALS
The effect of gravity on dissolution of GaSb in InSb melt and growth of
InGaSb was experimentally investigated using GaSb(seed)/InSb/GaSb(feed)
sandwich samples. Two parameters were considered: (1) the inclination angle
of the sample for gravity as 0°, 53° and 90°, (2) the sample diameter (D) as 9 mm and 5mm. When θ
=0°, the interface was almost flat whereas the interfaces were strongly
distorted when θ = 53° and 90°. The undissolved GaSb(feed)
remained for \theta = 0 °. However, it dissolved completely for
θ
=
90°, and partially for θ = 53°. As the gravitational angle
was increased, the growth length of uniform composition became long. The
decrease of sample diameter reduced the dissolution area of GaSb. These
facts indicated that the dissolution and growth processes were strongly
influenced by gravity
Three-dimensional observation and analysis of remineralization in dentinal caries lesions
The remineralization mechanism in dental caries lesions is not completely understood. This study reports on ultrastructural and chemical changes observed within arrested caries lesions. Carious human teeth were observed using scanning electron microscopy (SEM) and focused-ion-beam (FIB)-SEM. The crystals detected in the caries lesions were characterized by transmission electron microscopy (TEM), along with chemical element mapping using energy-dispersive spectroscopy (EDS)-STEM. FIB-SEM 3D reconstructions revealed a severely damaged dentin surface abundantly covered by bacteria. Although the dentin tubules were clogged up to a depth of 100 mu m, bacterial invasion into dentin tubules was not observed. TEM crystal analysis and EDS-STEM revealed the presence of Ca and P, as well as of Mg within the HAp crystals deposited inside the dentin tubules. It was concluded that extensive remineralization with deposition of Mg-HAp crystals had occurred in dentin tubules of caries-arrested dentin. Understanding the natural remineralization process is thought to be helpful for developing clinical biomimetic remineralization protocols
From Supermembrane to Matrix String
We develop a systematic method of directly embedding supermembrane wrapped
around a circle into matrix string theory. Our purpose is to study connection
between matrix string and membrane from an entirely 11 dimensional point of
view. The method does neither rely upon the DLCQ limit nor upon string
dualities. In principle, this enables us to construct matrix string theory with
arbitrary backgrounds from the corresponding supermembrane theory. As a
simplest application of the formalism, the matrix-string action with a 7 brane
background (Kaluza-Klein Melvin solution) with nontrivial RR vector field is
given.Comment: 36 pages, 1 figur
pH-dependent Formation of Membranous Cytoplasmic Body-like Structure of Ganglioside GM1/Bis(Monoacylglycero)Phosphate Mixed Membranes
Membrane structures of the mixtures of ganglioside GM1 and endosome specific lipid, bis(monoacylglycero)phosphate (BMP, also known as lysobisphosphatidic acid, LBPA) were examined at various pH conditions by freeze-fracture electron microscopy and small-angle x-ray scattering (SAXS). At pH 8.5 – 6.5, a GM1/BMP (1/1 mol/mol) mixture formed small vesicular aggregates, whereas the mixture formed closely packed lamellar structures under acidic conditions (pH 5.5, 4.6) with the lamellar repeat distance of 8.06 nm. Since BMP alone exhibits a diffuse lamellar structure at a broad range of pH values and GM1 forms a micelle, the present results indicate that both GM1 and BMP are required to produce the closely stacked multilamellar vesicles. These vesicles resemble membranous cytoplasmic bodies (MCB) in cells derived from patients suffering from GM1 gangliosidosis. Similar to GM1 gangliosidosis, cholesterol was trapped in BMP vesicles in GM1- and in a low pH-dependent manner. Studies employing different gangliosides and a GM1 analog suggest the importance of sugar chains and a sialic acid of GM1 in the pH-dependent structural change of GM1/BMP membranes
ADAMTS13 gene deletion enhances plasma high-mobility group box1 elevation and neuroinflammation in brain ischemia-reperfusion injury
Highly adhesive glycoprotein von Willebrand factor (VWF) multimer induces platelet aggregation and leukocyte tethering or extravasation on the injured vascular wall, contributing to microvascular plugging and inflammation in brain ischemia-reperfusion. A disintegrin and metalloproteinase with thrombospondin type-1 motifs 13 (ADAMTS13) cleaves the VWF multimer strand and reduces its prothrombotic and proinflammatory functions. Although ADAMTS13 deficiency is known to amplify post-ischemic cerebral hypoperfusion, there is no report available on the effect of ADAMTS13 on inflammation after brain ischemia. We investigated if ADAMTS13 deficiency intensifies the increase of extracellular HMGB1, a hallmark of post-stroke inflammation, and exacerbates brain injury after ischemia-reperfusion. ADAMTS13 gene knockout (KO) and wild-type (WT) mice were subjected to 30-min middle cerebral artery occlusion (MCAO) and 23.5-h reperfusion under continuous monitoring of regional cerebral blood flow (rCBF). The infarct volume, plasma high-mobility group box1 (HMGB1) level, and immunoreactivity of the ischemic cerebral cortical tissue (double immunofluorescent labeling) against HMGB1/NeuN (neuron-specific nuclear protein) or HMGB1/MPO (myeloperoxidase) were estimated 24h after MCAO. ADAMTS13KO mice had larger brain infarcts compared with WT 24h after MCAO (p<0.05). The rCBF during reperfusion decreased more in ADAMTS13KO mice. The plasma HMGB1 increased more in ADAMTS13KO mice than in WT after ischemia-reperfusion (p<0.05). Brain ischemia induced more prominent activation of inflammatory cells co-expressing HMGB1 and MPO and more marked neuronal death in the cortical ischemic penumbra of ADAMTS13KO mice. ADAMTS13 deficiency may enhance systemic and brain inflammation associated with HMGB1 neurotoxicity, and aggravate brain damage in mice after brief focal ischemia. We hypothesize that ADAMTS13 protects brain from ischemia-reperfusion injury by regulating VWF-dependent inflammation as well as microvascular pluggin
Heliocentric Distance Dependence of Zodiacal Light Observed by Hayabusa2#
Zodiacal light (ZL) is sunlight scattered by interplanetary dust particles
(IDPs) at optical wavelengths. The spatial distribution of IDPs in the Solar
System may hold an important key to understanding the evolution of the Solar
System and material transportation within it. The number density of IDPs can be
expressed as , and the exponent was
obtained by previous observations from interplanetary space by Helios 1/2 and
Pioneer 10/11 in the 1970s and 1980s. However, no direct measurements of
based on ZL observations from interplanetary space outside Earth's
orbit have been performed since then. Here, we introduce initial results for
the radial profile of the ZL at optical wavelengths observed over the range
0.76-1.06 au by ONC-T aboard the Hayabusa2# mission in 2021-2022. The ZL
brightness we obtained is well reproduced by a model brightness, although there
is a small excess of the observed ZL brightness over the model brightness at
around 0.9 au. The radial power-law index we obtained is , which is consistent with previous results based on ZL observations. The
dominant source of uncertainty arises from the uncertainty in estimating the
diffuse Galactic light (DGL).Comment: 22 pages, 19 figures, 4 tables, accepted for publication by Earth,
Planets and Spac
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