739 research outputs found
Time-domain Brillouin scattering assisted by diffraction gratings
Absorption of ultrashort laser pulses in a metallic grating deposited on a
transparent sample launches coherent compression/dilatation acoustic pulses in
directions of different orders of acoustic diffraction. Their propagation is
detected by the delayed laser pulses, which are also diffracted by the metallic
grating, through the measurement of the transient intensity change of the first
order diffracted light. The obtained data contain multiple frequency components
which are interpreted by considering all possible angles for the Brillouin
scattering of light achieved through the multiplexing of the propagation
directions of light and coherent sound by the metallic grating. The emitted
acoustic field can be equivalently presented as a superposition of the plane
inhomogeneous acoustic waves, which constitute an acoustic diffraction grating
for the probe light. Thus, the obtained results can also be interpreted as a
consequence of probe light diffraction by both metallic and acoustic gratings.
The realized scheme of time-domain Brillouin scattering with metallic grating
operating in reflection mode provides access to acoustic frequencies from the
minimal to the maximal possible in a single experimental configuration for the
directions of probe light incidence and scattered light detection. This is
achieved by monitoring of the backward and forward Brillouin scattering
processes in parallel. Applications include measurements of the acoustic
dispersion, simultaneous determination of sound velocity and optical refractive
index, and evaluation of the samples with a single direction of possible
optical access.Comment: 21 pages, 4 figures, 1 tabl
Research on ignition and flame spread of solid materials in Japan
Fire safety is one of the main concerns for crewed missions such as the space station. Materials used in spacecraft may burn even if metalic. There are severe restrictions on the materials used in spacecraft from the view of fire safety. However, such restrictions or safety standards are usually determined based on experimental results under normal gravity, despite large differences between the phenomena under normal and microgravity. To evaluate the appropriateness of materials for use in space, large amount of microgravity fire-safety combustion data is urgently needed. Solid material combustion under microgravity, such as ignition and flame spread, is a relatively new research field in Japan. As the other reports in this workshop describe, most of microgravity combustion research in Japan is droplet combustion as well as some research on gas phase combustion. Since JAMIC, the Japan Microgravity Center, (which offers 10 seconds microgravity time) opened in 1992, microgravity combustion research is robust, and many drop tests relating to solid combustion (paper combustion, cotton string combustion, metal combustion with Aluminium or Magnesium) have been performed. These tests proved that the 10 seconds of microgravity time at JAMIC is useful for solid combustion research. Some experiments were performed before JAMIC opened. For example, latticed paper was burned under microgravity by using a 50 m drop tower to simulate porous material combustion under microgravity. A 50 m tower provides only 2 seconds microgravity time however, and it was not long enough to investigate the solid combustion phenomena
Flame spread over thin hollow cylindrical fuels in microgravity
This work presents experimental study on opposed flow flame spread over thin
hollow cylindrical cellulosic fuel of diameters varying from 10 mm to 49 mm in
microgravity environment. To understand the effect of flow and geometry on
flame spread, experiments are conducted in low convective opposed flow
conditions ranging from 10 cm/s to 30 cm/s for both hollow cylindrical and
planar fuels at oxygen concentration of 21% and 1 atm pressure. In the
microgravity environment the flame length and the flame spread rate are seen to
increase with increase in hollow cylindrical fuel diameter over the flow range
studied here. The flame spread rate exhibited a non-monotonic trend with flow
speed, for flow of large diameter whereas a monotonic increasing trend is noted
for small diameters. The flame spread rate over hollow cylindrical fuel is
noted to be higher or at most equal compared to planar fuels over the matrix of
experiments conducted in this study. A simplified analysis is carried out to
arrive at an expression for flame spread rate over thin hollow cylindrical
fuels. The analysis shows that the radiation heat transfer from the hot char to
the inner surface of hollow virgin fuel dictates flame spread rate trend with
fuel diameter of the hollow cylindrical fuels. Higher overall equivalence ratio
in the inner section of the hollow fuels is responsible for higher char length
in hollow fuels and also influence the flame spread rate for smaller fuel
diameters.Comment: 40 pages, 14 figure
Influence of Substrate Surface Roughness on Synthesized Diamond Films by Flame Combustion on Ti Substrate for Dental Implants
The flame combustion method enables the synthesis of diamonds via acetylene-oxygen gas flame combustion in ambient air, and this method has various advantages over other methods. However, most diamond films synthesized by this method delaminate because of thermal stress during cooling. Titanium (Ti) has recently been utilized as a dental implant in the dental industry. In this study, to improve the strength, wear resistance, and biocompatibility of dental implant surfaces, diamond films were synthesized on a Ti substrate, a dental implant material, by the flame combustion method. Moreover, to obtain high-quality diamond films and achieve good adhesion on the Ti substrate, as a pretreatment of the substrate to prevent delamination, scratch processing, in which a substrate is ground with emery paper in one direction, was performed to roughen the surface. The surface roughness of the Ti substrates was varied by scratching with emery paper of #180, #400, and #1500 grain sizes. According to these results, diamond films were synthesized on the Ti substrate surface by flame combustion. The surface morphology of the synthesized films could be altered by varying the scratching process using emery paper. Delamination of the synthesized films during the scratching process with emery paper #180 (Case A) and #400 (Case B) grain size was completely prevented. However, delamination occurred during the scratching process with a grain size of emery paper #1500 (Case C). To investigate the reason for this result, the surface roughness of the pretreated Ti substrate was observed, and it affected the surface roughness of pretreated Ti substrate affected the surface morphology and delamination of the synthesized diamond films
Involvement of STAT3 in Bladder Smooth Muscle Hypertrophy Following Bladder Outlet Obstruction
We examined the involvement of the signal transducer and activator of transcription 3 (STAT3) in bladder outlet obstruction (BOO)-induced bladder smooth muscle hypertrophy using a rat in vivo and in vitro study. BOO induced increases in bladder weight and bladder smooth muscle thickness 1 week after the operation. By using antibody microarrays, 64 of 389 proteins blotted on the array met our selection criteria of an INR value between > or = 2.0 and < or = 0.5. This result revealed up-regulation of transcription factors, cell cycle regulatory proteins, apoptosis-associated proteins and so on. On the other hand, down-regulation (INR value < or = 0.5) of proteins was not found. In a profiling study, we found an increase in the expression of STAT3. A significant increase in nuclear phosphorylated STAT3 expression was confirmed in bladder smooth muscle tissue by immunohistochemistry and Western blot analysis. Cyclical stretch-relaxation (1 Hz) at 120% elongation significantly increased the expression of STAT3 and of alpha-smooth muscle actin in primary cultured bladder smooth muscle cells. Furthermore, the blockade of STAT3 expression by the transfection of STAT3 small interfering RNA (siRNA) significantly prevented the stretch-induced increase in alpha-smooth muscle actin expression. These results suggest that STAT3 has an important role in the induction of bladder smooth muscle hypertrophy
Mis16 and Mis18 Are Required for CENP-A Loading and Histone Deacetylation at Centromeres
AbstractCentromeres contain specialized chromatin that includes the centromere-specific histone H3 variant, spCENP-A/Cnp1. Here we report identification of five fission yeast centromere proteins, Mis14–18. Mis14 is recruited to kinetochores independently of CENP-A, and, conversely, CENP-A does not require Mis14 to associate with centromeres. In contrast, Mis15, Mis16 (strong similarity with human RbAp48 and RbAp46), Mis17, and Mis18 are all part of the CENP-A recruitment pathway. Mis15 and Mis17 form an evolutionarily conserved complex that also includes Mis6. Mis16 and Mis18 form a complex and maintain the deacetylated state of histones specifically in the central core of centromeres. Mis16 and Mis18 are the most upstream factors in kinetochore assembly as they can associate with kinetochores in all kinetochore mutants except for mis18 and mis16, respectively. RNAi knockdown in human cells shows that Mis16 function is conserved as RbAp48 and RbAp46 are both required for localization of human CENP-A
Band structures of P-, D-, and G-surfaces
We present a theoretical study on the band structures of the electron
constrained to move along triply-periodic minimal surfaces. Three well known
surfaces connected via Bonnet transformations, namely P-, D-, and G-surfaces,
are considered. The six-dimensional algebra of the Bonnet transformations [C.
Oguey and J.-F. Sadoc, J. Phys. I France 3, 839 (1993)] is used to prove that
the eigenstates for these surfaces are interrelated at a set of special points
in the Brillouin zones. The global connectivity of the band structures is,
however, different due to the topological differences of the surfaces. A
numerical investigation of the band structures as well as a detailed analysis
on their symmetry properties is presented. It is shown that the presence of
nodal lines are closely related to the symmetry properties. The present study
will provide a basis for understanding further the connection between the
topology and the band structures.Comment: 21 pages, 8 figures, 3 tables, submitted to Phys. Rev.
Negative Impact of Gemtuzumab Ozogamicin on CD33-Positive Early T-Cell Precursor Acute Lymphoblastic Leukemia: A Case Report
Introduction: Early T-cell precursor acute lymphoblastic leukemia (ETP-ALL) is a rare subtype of T-cell leukemia that phenotypically expresses mature T-cell markers and immature myeloid markers such as CD33. Gemtuzumab ozogamicin (GO) is a novel agent for the CD33 molecular targeting antibody conjugated to the cytotoxic agent calicheamicin. GO is anticipated to be effective against ETP-ALL. In vivo studies promise antileukemic effects in cell lines; however, clinical reports to support this research are lacking. We treated a patient who suffered from CD33-positive ETP-ALL using GO. Case Presentation: We treated an 81-year-old man who suffered from ETP-ALL. The patient’s leukemia expressed T cell and myeloid markers including cyCD3, CD5, CD7, CD33, and HLA-DR. Initially, the patient was treated using a standard chemotherapy regimen for acute lymphoblastic leukemia comprising cyclophosphamide, daunorubicin, vincristine, l-asparaginase, and prednisolone. The induction chemotherapy produced the expected complete hematological response; however, bone marrow blasts remained. Following consolidation chemotherapy, the patient maintained a full hematological response. Thereafter, we changed the consolidation regimen to nelarabine, which did not reduce bone marrow blasts effectively. After two courses of nelarabine therapy, we finally used GO at an 8 mg/m2 weekly dose after confirming that CD33 expression was still positive in the patient’s residual leukemic cells. GO was ineffective in treating the patient’s leukemia, and peripheral blasts increased 30 days following treatment. The patient died 81 days after initiating GO therapy. Conclusion: This is the first clinical case of GO having a negative impact on ETP-ALL. Because the GO resistance mechanism for ETP-ALL has not been fully elucidated, treatment modification should be considered to achieve optimal clinical efficacy
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