A High-Sensitivity Microwave-Single-Photon Detector with Rydberg Atoms at Low Temperature

A high-sensitivity microwave-single-photon detector was developed in Kyoto, in which microwave photons in a resonant cavity cooled at very low temperatures are absorbed by highly excited Rydberg atoms and the Rydberg atoms thereby promoted to a higher excited state are then selectively field-ionized and detected. This scheme allows us to count microwave photons one by one, thus provide a single-photon counting without the limit of standard quantum limit (SQL). The apparatus “CARRACK” for the single-photon detector was constructed based on this scheme, where the cavity was cooled down to 10 mK range to reduce the background of thermal blackbody photons from the cavity wall. The apparatus has served for years to search for dark matter axions in the 10 μeV (∼2.4 GHz) mass region. Thermal blackbody photons in a microwave resonant cavity at temperatures as low as 70 mK have been measured, the sensitivity being below the SQL limit. A number of improvements in the detection efficiency and sensitivity have been planned and will be reported. Applications of the detector to fundamental physics are also discussed shortly.      

Benchmark models for criticalities of FCA-IX assemblies with systematically changed neutron spectra

New benchmark models with respect to criticality data are established on the basis of seven uranium-fueled assemblies constructed in the ninth experimental series at the fast critical assembly (FCA) facility. By virtue of these FCA-IX assemblies, where the simple combinations of uranium fuel and diluent (graphite and stainless steel) in their core regions were systematically varied, the neutron spectra of these benchmark models cover those of various reactor types, from fast to sub-moderated reactors. The sample calculations of the benchmark models by a continuous-energy Monte Carlo (MC) code showed obvious differences between even the latest versions of two major nuclear data libraries, JENDL-4.0 and ENDF/B-VII.1. The present benchmark models would be well suited for the assessment and improvement of the nuclear data for ²³⁵U, ²³⁸U, graphite, and stainless steel. In addition, the verification of the deterministic method was performed on the benchmark models by comparison with the MC calculations. The present benchmark models are also available to users of deterministic calculation codes for the assessment and improvement of nuclear data.     

Effect of addition of commercial rosemary extracts on potent odorants in cooked beef

Solid-phase microextraction-gas chromatography-olfactometry (SPME-GCO) and aroma extract dilution analysis (AEDA) were applied to measure the effects of the addition of two commercial rosemary extracts (RE) on the potent odorants in cooked beef extracts (BE). On the basis of the results of SPME-GCO and AEDA, the addition of RE imparted sweet and floral notes to BE as a result of the addition of esters and terpenes of RE. In addition, RE suppressed the formation of odorants derived via lipid oxidation and Maillard reactions. The most potent lipid oxidation volatiles consisted of 1-octen-3-one (mushroom-like), (E)-2,4-epoxy-(E)-2-decenal (metallic), and eight different aldehydes (fatty). The Maillard reaction volatiles, necessary for typical cooked beef flavor, included compounds with meaty [2-methyl-3-furanthiol, 2-methyl-3-(methylthio)furan, 2-methyl-3-(methyldithio)furan], roasty (2-furanmethanethiol), caramel-like [4-hydroxy-2,5-dimethyl-3(2H)-furanone], baked potato-like [3-(methylthio)propanal], and spicy [3-hydroxy-4,5-dimethyl-2(5H)-furanone] attributes. The suppressive effects of RE may be caused by the action of antioxidative substances in RE alone or in combination with the pH increase in BE induced by the matrix components of RE.     

Dicyano-functionalized chlorophyll derivatives with ambipolar characteristic for organic photovoltaics

Two ambipolar chlorophyll derivatives, namely, 3²,3²-dicyano-pyropheophorbide-a (Chl-1) and methyl 13¹-deoxo-13¹-(dicyanomethylene) pyropheophorbide-a (Chl-2), were synthesized for use as either the electron acceptor or the electron donor in organic planar-heterojunction solar cells. Despite the higher electron mobilities of these chlorophyll derivatives compared with their hole mobilities, devices using them as the electron donor with fullerene C₇₀ give much better photovoltaic performance than when they are used as the electron acceptor with copper phthalocyanine. In these Chl-based solar cells, the energy gap between the LUMO levels of the donor and acceptor molecules substantially affects the charge separation and resultant photocurrent and photovoltaic performance. The highest solar energy-to-electricity conversion efficiency of up to 2.3% has been achieved using the Chl-2/C₇₀ solar cell, under AM1.5 solar illumination (100 mW/cm²) after thermal annealing of the device. It was also confirmed that the electron mobility of blend films containing Chls and fullerene derivative PC₇₀BM was determined not only by the electron mobility of PC₇₀BM but also by that of Chls.     

Experimental study on inelastic mechanical behaviour of composite girders under hogging moment

Negative bending moments acting on the support regions of continuous composite girders generate tensile stresses in the concrete slab and compressive stresses in the lower steel profile. As a result, the mechanical behaviour of these girders becomes strongly nonlinear, which needs special study. In this paper, static experimental tests on four half-scale models of steel and concrete composite girders with different shear connectors such as studs and Perfo-Bond Strips (PBLs) under hogging moments are cautiously conducted in order to investigate the reduction of flexural stiffness and the inelastic behaviour after cracking. In the test results, crack development, crack widths and strains of the composite section before and after cracking were observed. The crack width evaluation methods based on design codes for steel and concrete composite girders under negative bending moment were compared. Crack widths should be controlled appropriately within an allowable value in the slab under service load. The strains in reinforcing bars obtained through the static tests agreed well with the values calculated through the application of the existing tension stiffening theory. The test specimens could be assumed to be a full composite section until the ultimate state on the basis of load and slip relationship results of shear connectors. It follows that analytical and experimental studies can be served as a basis for the design of continuous composite bridges.     

Experimental and analytical investigation of the turbulent burning velocity of two-component fuel mixtures of hydrogen,methane and propane

In this paper, we present some experimental and analytical model results of two-component fuel mixtures of methane, propane and hydrogen. Experimentally obtained turbulent burning velocity S_T for outwardly propagating spherical lean turbulent premixed flames is examined with an algebraic flame surface wrinkling reaction model using 1) mean local burning velocity, and 2) the critical chemical time scale from the leading edge model by Zel'dovich and Frank-Kamenetskii. Based on the latter approach, the time scale that characterizes the effects of preferential diffusion phenomenon in critically curved spherical flames is incorporated into the reaction model. For this, a proposed simple linear model is used for estimating the effective Lewis number of the two-component fuel (CH₄–H₂ and C₃H₈–H₂)/Air mixtures. In general, both approaches are effective ways in achieving qualitatively consistent S_T trends for both mixtures. However, in the second approach, model predictions show large S_T deviation especially at high turbulence. This may be attributed to the use of approximate values of activation temperature and for the use of the effective Lewis number of both mixtures based on the simple linear model.     

Dermoid cysts of the ovary with malignant transformation: MR appearance

OBJECTIVE: This study presents the MR appearances of five women with a total of six proven dermoid cysts of the ovary with malignant transformation. To our knowledge, the MR findings of this entity have not been reported. CONCLUSION: The lesions appeared to be fat-containing tumors with a solid component (4/6) that extended transmurally (4/6) and extensively invaded neighboring pelvic organs (3/6). The supervening malignancy was squamous cell carcinoma in four tumors, melanoma in one, and transitional cell carcinoma in one. The mode of spread differed from that of common ovarian tumors in that it included transmural extension and local invasion, reflecting squamous cell carcinoma.     

Intralaminar fracture mechanism in unidirectional CFRP composites: Part I: Intralaminar toughness and AE characteristics

Three types of representative carbon fiber reinforced unidirectional composite materials were used and their intralaminar fracture behavior was investigated using the double-cantilever beam specimen with a simultaneous acoustic emission measurement. The intralaminar fracture toughness was evaluated by both the compliance method and energy area method. As a result, it was found that the intralaminar fracture toughness without bridging fibers had a constant value during crack propagation but it increased greatly when bridging fibers were present. The effect of bridging fibers on the intralaminar fracture toughness was estimated quantitatively by cutting the bridging fibers. Distinct differences in load–displacement curves, compliance, crack propagating behavior and acoustic emission signal characteristics between these three types of unidirectional composite materials were observed. It was also found that bridging fiber failure generated relatively large power spectra and contributed to the peak frequencies of 600–700 kHz in the spectrum analysis of acoustic emission (AE) signals. This suggested that the bridging fibers were also an important source of AE signals. Furthermore, a linear relationship between crack length and normalized cumulative AE event count rate was obtained.     

Intralaminar fracture mechanism in unidirectional CFRP composites — part II: analysis

Three kinds of representative carbon fiber reinforced unidirectional composite materials are used, and their intralaminar fracture behavior is investigated by using the double-cantilever beam (DCB) specimen with a simultaneous acoustic emission measuring. In Part I, the experimental results on the crack propagation, the bridging fibers, the intralaminar fracture toughness acoustic emission characteristics and microscope observations were obtained. Here, we use a bridging fiber model to analyze the debonding force acting on a bridging fiber and try to estimate the number of bridging fibers during the crack propagating process. At the same time, the intralaminar fracture toughness is calculated by both the adhesive force model and the finite element analysis. As a result, it is found that the intralaminar fracture toughness without the bridging fibers will have a constant value during the crack propagation, but it increases greatly when bridging fibers exist. It is clear that the bridging fibers play an important role in the intralaminar fracture toughness. The debonding forces acting on the bridging fibers and the number of bridging fibers are obtained. Furthermore, the quantitative estimation of the increment of the intralaminar fracture toughness contributed by bridging fibers is made according to the adhesive force model and it is comparable with the results obtained by the finite element analysis.     

Increased-contrast, high-spatial-resolution, diffusion-weighted, spin-echo, echo-planar imaging

An insertable head gradient coil with a maximum gradient amplitude of 45 mT/m and a rise time of 150 musec along all three major axes was used to collect high-spatial-resolution, single-shot, spin-echo, echo-planar, diffusion-weighted magnetic resonance images with b values ranging from 0 to 2,200 sec/mm2. Improvements in spatial resolution allowed better visualization of large white matter tracts and their relation to adjacent anatomic structures. Excellent contrast and anatomic detail were revealed for most structures in the brain when a sufficient number of acquisitions were collected.