Faster acquisition of magnetic resonance imaging sequences of the knee via deep learning reconstruction: a volunteer study

AIM

To evaluate whether deep learning reconstruction (DLR) can accelerate the acquisition of magnetic resonance imaging (MRI) sequences of the knee for clinical use.

MATERIALS AND METHODS

Using a 1.5-T MRI scanner, sagittal fat-suppressed T2-weighted imaging (fs-T2WI), coronal proton density-weighted imaging (PDWI), and coronal T1-weighted imaging (T1WI) were performed. DLR was applied to images with a number of signal averages (NSA) of 1 to obtain 1DLR images. Then 1NSA, 1DLR, and 4NSA images were compared subjectively, and by noise (standard deviation of intra-articular water or medial meniscus) and contrast-to-noise ratio between two anatomical structures or between an anatomical structure and intra-articular water.

RESULTS

Twenty-seven healthy volunteers (age: 40.6 ± 11.9 years) were enrolled. Three 1DLR image sequences were obtained within 200 s (approximately 12 minutes for 4NSA image). According to objective evaluations, PDWI 1DLR images showed the smallest noise and significantly higher contrast than 1NSA and 4NSA images. For fs-T2WI, smaller noise and higher contrast were observed in the order of 4NSA, 1DLR, and 1NSA images. According to the subjective analysis, structure visibility, image noise, and overall image quality were significantly better for PDWI 1DLR than 1NSA images; moreover, the visibility of the meniscus and bone, image noise, and overall image quality were significantly better for 1DLR than 4NSA images. Fs-T2WI and T1WI 1DLR images showed no difference between 1DLR and 4NSA images.

CONCLUSION

Compared to PDWI 4NSA images, PDWI 1DLR images were of higher quality, while the quality of fs-T2WI and T1WI 1DLR images was similar to that of 4NSA images.

The Japanese Nationwide Cohort Data of Particle Beam Therapy for Liver Oligometastasis in Esophagogastric Cancer Patients

PURPOSE/OBJECTIVE(S)

A nationwide multicenter cohort study on particle therapy was launched by the Japanese Society for Radiation Oncology (JASTRO) in Japan in May 2016. We analyzed the outcome of proton beam therapy (PBT) for liver oligometastasis of esophagogastric cancers.

MATERIALS/METHODS

Cases in which PBT was performed at all PBT facilities in Japan between May 2016 and February 2019 were enrolled. The patients were selected based on the following criteria: controlled primary cancer; liver recurrence without extrahepatic tumors; and no more than three liver lesions. The dose and fraction of PBT were determined using unified treatment policy established by JASTRO. We used the following protocol, 64 gray (relative biological effect) (Gy (RBE))/8 fractions (fr) for the peripheral region, and 72.6 GyE/22fr for the central region. For safety aspect, the hepatocellular carcinoma irradiation protocols of 66 Gy (RBE)/10fr, 72.6-76 Gy (RBE)/20-22fr, and 74-76 Gy (RBE)/37-38fr could be allowed. The overall survival (OS), local control (LC), and adverse events (AEs) were examined. The OS and LC rates were calculated using the Kaplan-Meier method. Factors possibly related to OS, such as tumor size (for multiple lesions, the largest size), number of liver tumors, as well as the presence or absence of prior, concurrent, and post-PBT chemotherapy, were investigated. The cut-off values were estimated using the receiver operating characteristic curve and area under the curve. Univariate analysis was performed using the log-rank test. Statistical significance was P-values < 0.05.

RESULTS

Twenty-three males and two females with a median age of 69 (range, 52-80) years and 36 lesions were included. This study included six patients with esophageal and 19 patients with gastric cancer. The median lesion size, fraction size, and biological effective dose (BED)10 were 31 (7-104) mm, 3.8 gray (relative biological effect)/fractions (Gy (RBE)/fr) (2-8 Gy (RBE)/fr), and 96.9 (88.8-115.2) Gy, respectively. The median follow-up period was 18 (4-47) months. The 1-, 2-, and 3-year OS rates were 76.0, 49.5, and 43.3%, respectively, and the median OS was 19 months. The 1-, 2-, and 3-year OS rates of esophageal cancer were 83.3% for all. The 1-, 2-, and 3-year OS rates of gastric cancer were 73.7, 40.2, and 32.2%, respectively, and the median OS was 18 months. The 1-, 2-, and 3-year LC rates were 96.3, 91.5, and 91.5%, respectively. The 1-, 2-, and 3-year LC rates of esophageal cancer were 100% for all. The 1-, 2-, and 3-year LC rates of gastric cancers were 94.7, 88.0, and 88.0%, respectively. Tumor size was the only significant OS-related factor (P < 0.01). No grade 3 or higher adverse events were observed.

CONCLUSION

Owing to the low incidence of adverse events and the high LC rate, PBT is a feasible option for liver oligometastasis of esophagogastric cancers.

The Japanese Nationwide Cohort Data of Proton Beam Therapy for Liver Oligometastasis in Breast Cancer Patients

PURPOSE/OBJECTIVE(S)

A nationwide multicenter cohort study on particle therapy was launched by the Japanese Society for Radiation Oncology (JASTRO) in Japan. We analyzed the outcome of proton beam therapy (PBT) for liver oligometastasis in breast cancers.

MATERIALS/METHODS

Cases in which PBT was performed at all Japanese proton therapy facilities between May 2016 and February 2019 were enrolled. The patients were selected based on the following criteria: the primary cancer was controlled, liver recurrence without extrahepatic tumors, and no more than three liver lesions. The treatment indication and strategy were discussed at cancer boards in each institution. The dose and fraction of PBT were determined by referring to the unified treatment policy established by JASTRO. We used the following protocol: 64 gray (Gy) (relative biological effectiveness [RBE])/8 fraction (fr) for the hepatic periphery area away from the GI tract, and 72.6 GyE/22 fr for the adjacent hilar region type. Regarding safety, the HCC irradiation protocols of 66 GyE/10 fr, 72.6-76 GyE/20-22 fr, and 74-76 GyE/37-38 fr could be used. The local control (LC), overall survival (OS), and progression free survival (PFS) rates were calculated using the Kaplan-Meier method. Factors possibly related to OS, such as tumor size, number of liver tumors, intervention of chemotherapy, and/or hormone therapy, were investigated. The cut-off values were estimated using the receiver operating characteristic curve and area under the curve. Univariate analysis was performed using the log-rank test.

RESULTS

Fourteen females, with a median age of 57 (range, 44-73) years and twenty-two lesions were included. Nine patients had one lesion, two patients had two lesions, and three patients had three lesions. PBT was selected because nine patients had underlying disease and five patients had general conditions (age, etc.). The median lesion size, fraction size, and biological effective dose using the linear-quadratic model with α/β = 10 Gy ((BED)10) were 44 (20-130) mm, 6.6 (2-8) (relative biological effectiveness [RBE])/fraction (fr), and 109.6 (52.7-115.2) Gy, respectively. The median follow-up period of breast cancers was 22.8 (4-54) months. The 1-, 2-, and 3-year LC rates of liver metastasis from breast cancers were 100% for all. The 1-, 2-, and 3-year OS rates were 85.7%, 62.5%, and 62.5%, respectively. The 1-, 2-, and 3-year PFS rates were 50.0%, 33.3%, and 16.7%, respectively, and median PFS time was 16 months. Tumor size, the number of liver tumors, and the intervention of chemotherapy and/or hormone therapy at any time were not significantly related to the OS. Only one patient did not complete PBT due to current disease progression. The other patients completed PBT without interruption. One patient had grade 3 radiation-induced dermatitis.

CONCLUSION

Based on the low incidence of adverse events and the high LC rate, PBT appears to be a feasible option for liver oligometastasis in breast cancer patients.

RIB induced reactions: Studying astrophysical reactions with low-energy RI beam at CRIB

Astrophysical reactions involving radioactive isotopes (RI) often play an important role in high-temperature stellar environments. The experimental studies on the reaction rates for those are still limited mainly due to the technical difficulties in producing high-quality RI beams. A direct measurement of those reactions would be still challenging in many cases, however, we can make a reliable evaluation of the reaction rates by an indirect method or by studying the resonance prorerties. Here we ntroduce recent examples of experimental studies on such RI-involving astrophysical reactions, performed at Center for Nuclear Study, the University of Tokyo, using the low-energy RI beam separator CRIB. One is for the neutron-induced destruction reactions of 7Be in the Big-Bang nucleosynthesis, and the other is the study on the 22Mg(α, p) reaction relevant in X-ray bursts, which was performed with the resonant scattering method from the inverse reaction channel.

The 12C +16 O fusion reaction in carbon burning: Study at energies of astrophysical interest using the Trojan Horse Method

The carbon-burning process in massive stars mainly occurs via the 12C +12 C. However, at temperatures higher than 109K and considering the increased abundance of 16O produced during the later stages of the heliumburning,the 12C+16O fusion can also become relevant. Moreover, 12C+16O also plays a role in the scenario of explosive carbon burning. Thus, the astrophysical energy region of interest ranges from 3 to 7.2 MeV in the center-of-mass frame. However, the various measurements of the cross-section available in the literature stop around 4 MeV, making extrapolation necessary. To solve this uncertainty and corroborate direct measurement we applied the Trojan Horse Method to three-body processes 16O(14N, α24Mg)2H and 16O(14N, p27Al)2H to study the 12C(16O, α)24Mg and 12C(16O, p)27Al reactions in their entire energy region of astrophysical interest. In this contribution, after briefly describing the method used, the experiment and the preliminary phases of the data analysis will be presented and discussed.

First measurement of 25Al+p resonant scattering relevant to the astrophysical reaction 22Mg(α,p)25Al

Type I X-ray bursts (XRBs) are the most frequently observed thermonuclear explosions in nature. The 22Mg(α,p)25Al reaction plays a critical role in XRB models. However, experimental information is insufficient to deduce a precise 22Mg(α,p)25Al reaction rate for the respective XRB temperature range. A new measurement of 25Al+p resonant scattring was performed up to the astrophysically interested energy region of 22Mg(α,p)25Al. Several resonances were observed in the excitation functions, and their level properties have been determined based on an R-matrix analysis. In particular, proton widths and spin-parities of four natural-parity resonances above the α threshold of 26Si, which can contribute the reaction rate of 22Mg(α,p)25Al, were first experimentally determined.

Experimental studies on astrophysical reactions at the low-energy RI beam separator CRIB

Experimental studies on astrophysical reactions involving radioactive isotopes (RI) often accompany technical challenges. Studies on such nuclear reactions have been conducted at the low-energy RI beam separator CRIB, operated by Center for Nuclear Study, the University of Tokyo. We discuss two cases of astrophysical reaction studies at CRIB; one is for the 7Be+n reactions which may affect the primordial 7Li abundance in the Big-Bang nucleosynthesis, and the other is for the 22Mg(α, p) reaction relevantin X-raybursts.

Iron lamination and interlaminar insulation for high-frequency pulsed magnets

In high-frequency pulsed magnets, such as kickers in particle accelerators, it is essential to reduce eddy currents that could be induced in the magnet core during excitation not to distort and attenuate the magnetic field pulse. A novel iron lamination scheme with additional interlaminar insulation is proposed for the magnet core of such pulsed magnets. A laminated steel sheet core is formed by alternately stacking thin steel and insulation sheets. For application to matched kicker magnets for accelerators, test magnets with the new and conventional iron lamination were designed, assembled, and extensively evaluated. The pulsed magnetic field waveforms of two test magnets with the new lamination successfully matched to below 0.1% over the entire pulse duration, which was significantly better than those with the conventional lamination. Among the applications of the developed high-frequency pulsed magnets, beam injection kickers for the coming next generation light sources and future colliders, where suppression of the transient stored-beam oscillation during beam injection is crucial, are considered to be promising.

Photoemission from Bialkali Photocathodes through an Atomically Thin Protection Layer

Photocathodes are essential components for various applications requiring photon-to-free-electron conversion, for example, high-sensitivity photodetectors and electron injectors for free-electron lasers. Alkali antimonide thin films are widely used as photocathode materials owing to their high quantum efficiency (QE) in the visible spectral range; however, their lifetime can be limited even in ultrahigh vacuum due to their high reactivity to residual gases and sensitivity to ion back-bombardment in these applications. An ambitious technical challenge is to extend the lifetime of bialkali photocathodes by coating them with suitable materials that can isolate the photocathode films from residual gases while still maintaining their highly emissive properties. We propose the use of graphene, an atomically thin two-dimensional material with gas impermeability, as a promising candidate for this purpose. Here, we report that high-quality bialkali antimonide can be grown on a two-layer (2L) suspended graphene substrate with a peak QE of 15%. More importantly, by comparing the photoemission through varying layers of graphene, we demonstrate that photoelectrons can transmit through few-layer graphene with a maximum QE of over 0.7% at 4.5 eV for 2L graphene, corresponding to a transmission efficiency of 5%. These results demonstrate important progress toward fully encapsulated bialkali photocathodes having both high QEs and long lifetimes using atomically thin protection layers.

Advancement of Photospheric Radius Expansion and Clocked Type-I X-Ray Burst Models with the New ^{22}Mg(α,p)^{25}Al Reaction Rate Determined at the Gamow Energy

We report the first (in)elastic scattering measurement of ^{25}Al+p with the capability to select and measure in a broad energy range the proton resonances in ^{26}Si contributing to the ^{22}Mg(α,p) reaction at type I x-ray burst energies. We measured spin-parities of four resonances above the α threshold of ^{26}Si that are found to strongly impact the ^{22}Mg(α,p) rate. The new rate advances a state-of-the-art model to remarkably reproduce light curves of the GS 1826-24 clocked burster with mean deviation <9% and permits us to discover a strong correlation between the He abundance in the accreting envelope of the photospheric radius expansion burster and the dominance of ^{22}Mg(α,p) branch.

Mesoscopic engineering materials for visual detection and selective removal of copper ions from drinking and waste water sources

The monitoring and removal of abundant heavy metals such as Cu ions are considerable global concerns because of their severe impact on the health of humans and other living organisms. To meet this global challenge, we engineered a novel mesoscopic capture protocol for the highly selective removal and visual monitoring of copper (Cu²⁺) ions from wide-ranging water sources. The capture hierarchy carriers featured three-dimensional, microsized MgO mesoarchitecture rectangular sheet-like mosaics that were randomly built in horizontal and vertical directions, uniformly arranged sheet faces, corners, and edges, smoothly quadrilateral surface coverage for strong Cu²⁺-to-ligand binding exposure, and multidiffusible pathways. The Cu²⁺ ion-selectively active captor surface design was engineered through the simple incorporation/encapsulation of a synthetic molecular chelation agent into hierarchical mesoporous MgO rectangular sheet platforms to produce a selective, visual mesoscopic captor (VMC). The nanoscale VMC dressing of MgO rectangular mosaic hierarchy by molecularly electron-enriched chelates with actively double core bindings of azo- and sulfonamide- groups and hydrophobic dodecyl tail showed potential to selectively trap and efficiently remove ultratrace Cu²⁺-ions with an extreme removal capability of ~233 mg/g from watery solutions, such as drinking water, hospital effluent, and food-processing wastewater at specific pH values. In addition to the Cu²⁺ ion-selective removal, the VMC design enabled the continuous visual monitoring of ultratrace Cu²⁺ ions (~3.35 × 10^-8 M) as a consequence of strong chelate-to-Cu²⁺ binding events among all accumulated matrices in water sources. Our experimental recycle protocol provided evidence of reusability and recyclability of VMC (≥10 cycles). With our mesoscopic capture protocol, the VMC can be a promising candidate for the selective decontamination/removal and sensitive detection of hazardous inorganic pollutants from different water sources with indoor or outdoor applications.

Body Weight Loss After Orthognathic Surgery: Comparison Between Postoperative Intermaxillary Fixation with Metal Wire and Elastic Traction, Factors Related to Body Weight Loss

INTRODUCTION

The aim of this study was to compare body weight loss between postoperative intermaxillary fixation with metal wire and elastic traction and to investigate factors related to body weight loss after orthognathic surgery.

MATERIALS AND METHODS

Subjects were 59 patients with dentofacial deformity, comprising 31 patients treated with intermaxillary fixation (IMF) and 28 patients treated with elastic traction without IMF (ELT) just after surgery. Body weight loss was measured at 1 week (T1) and 2 weeks (T2) after surgery. Body weight loss was compared between IMF and ELT, and factors related to body weight loss were statistically analyzed.

RESULTS

Body weight loss ratio was significantly increased in IMF (2.6%) rather than in ELT (1.4%) at T1, but only tended to be increased in both groups at T2, showing no statistical difference. Body weight loss ratio was significantly increased at T2 compared to T1 in both groups. Body weight loss was significantly greater at T2 than at T1.

CONCLUSION

Both IMF and ELT cause body weight loss after orthognathic surgery, but IMF causes body weight loss earlier than ELT and increased early body weight loss increases continuous body weight loss after orthognathic surgery.

Gas Barrier Properties of Chemical Vapor-Deposited Graphene to Oxygen Imparted with Sub-electronvolt Kinetic Energy

Graphene gas-barrier performance holds great interest from both scientific and technological perspectives. Using in situ synchrotron X-ray photoelectron spectroscopy, we demonstrate that chemical vapor-deposited monolayer graphene loses its gas-barrier performance almost completely when oxygen molecules are imparted with sub-electronvolt kinetic energy but retains its gas-barrier performance when the molecules are not energized. The permeation process is nondestructive. Molecular dynamics-based simulation suggests kinetic energy-mediated chemical reactions catalyzed by common graphene defects as a responsible mechanism.

Performance of the newly installed vertical neutron cameras for low neutron yield discharges in the Large Helical Device

Two new vertical neutron cameras characterized by high detection efficiency were developed on the Large Helical Device in order to observe poloidal structures of helically trapped beam ions created by the perpendicularly injected positive-ion based neutral beam (P-NB) and are newly operated since 2018. In this work, the neutron fields at the vertical neutron cameras are investigated using the Monte Carlo N-particle transport code to evaluate the performance of its collimators. The results indicate that neutrons are attenuated by the heavy concrete and are well collimated through the collimator to detectors. Neutron spectra at the detector position show over 99% of uncollided 2.45 MeV neutrons. Time evolution of neutron emission profiles during the short pulse of P-NB injection is measured by the vertical neutron cameras. Peaks on the neutron emission profiles corresponding to the helically trapped beam ion are successfully obtained, as designed. The decrease in line integrated neutron flux at the peak positions after the P-NB stops is consistent with the behavior of the total neutron emission rate measured by the neutron flux monitor.

Graphene Supported MoS2 Structures with High Defect Density for an Efficient HER Electrocatalysts

The development of novel efficient and robust electrocatalysts with sufficient active sites is one of the key parameters for hydrogen evolution reactions (HER) catalysis, which plays a key role in hydrogen production for clean energy harvesting. Recently, two-dimensional (2D) materials, especially those based upon transition metal dichalcogenides such as molybdenum disulfide (MoS₂), have gained attention for the catalysis of hydrogen production because of their exceptional properties. Innovative strategies have been developed to engineer these material systems for improvements in their catalytic activity. Toward this aim, the facile growth of MoS₂ clusters by sulfurization of molybdenum dioxide (MoO₂) particles supported on reduced graphene oxide (rGO) foams using the chemical vapor deposition (CVD) method is reported. This approach created various morphologies of MoS₂ with large edges and defect densities on the basal plane of rGO supported MoS₂ structures, which are considered as active sites for HER catalysis. In addition, MoS₂ nanostructures on the surface of the porous rGO network show robust physical interactions, such as van der Waals and π-π interactions between MoS₂ and rGO. These features result in an improved process to yield a suitable HER catalyst. In order to gain a better understanding of the improvement of this MoS₂-based HER catalyst, fully atomistic molecular dynamics (MD) simulations of different defect geometries were also performed.

Angular scattering of protons through ultrathin graphene foils: Application for time-of-flight instrumentation

Space plasma instruments often rely on ultrathin carbon foils for incident ion detection, time-of-flight (TOF) mass spectrometry, and ionization of energetic neutral atoms. Angular scattering and energy loss of ions or neutral atoms in the foil can degrade instrument performance, including sensitivity and mass resolution; thus, there is an ongoing effort to manufacture thinner foils. Using new 3-layer graphene foils manufactured at the Los Alamos National Laboratory, we demonstrate that these are the thinnest foils reported to date and discuss future testing required for application in space instrumentation. We characterize the angular scattering distribution for 3-30 keV protons through the foils, which is used as a proxy for the foil thickness. We show that these foils are ∼2.5-4.5 times thinner than the state-of-the-art carbon foils and ∼1.6 times thinner than other graphene foils described in the literature. We find that the inverse relationship between angular scattering and energy no longer holds, reaffirming that this may indicate a new domain of beam-foil interactions for ultrathin (few-layer) graphene foils.

Combination gemcitabine plus S-1 versus gemcitabine plus cisplatin for advanced/recurrent biliary tract cancer: the FUGA-BT (JCOG1113) randomized phase III clinical trial

BACKGROUND

Gemcitabine plus cisplatin (GC) is the standard treatment of advanced biliary tract cancer (BTC); however, it causes nausea, vomiting, and anorexia, and requires hydration. Gemcitabine plus S-1 (GS) reportedly has equal to, or better, efficacy and an acceptable toxicity profile. We aimed to confirm the non-inferiority of GS to GC for patients with advanced/recurrent BTC in terms of overall survival (OS).

PATIENTS AND METHODS

We undertook a phase III randomized trial in 33 institutions in Japan. Eligibility criteria included chemotherapy-naïve patients with recurrent or unresectable BTC, an Eastern Cooperative Oncology Group Performance Status of 0 - 1, and adequate organ function. The calculated sample size was 350 with a one-sided α of 5%, a power of 80%, and non-inferiority margin hazard ratio (HR) of 1.155. The primary end point was OS, while the secondary end points included progression-free survival (PFS), response rate (RR), adverse events (AEs), and clinically significant AEs defined as grade ≥2 fatigue, anorexia, nausea, vomiting, oral mucositis, or diarrhea.

RESULTS

Between May 2013 and March 2016, 354 patients were enrolled. GS was found to be non-inferior to GC [median OS: 13.4 months with GC and 15.1 months with GS, HR, 0.945; 90% confidence interval (CI), 0.78-1.15; P = 0.046 for non-inferiority]. The median PFS was 5.8 months with GC and 6.8 months with GS (HR 0.86; 95% CI 0.70-1.07). The RR was 32.4% with GC and 29.8% with GS. Both treatments were generally well-tolerated. Clinically significant AEs were observed in 35.1% of patients in the GC arm and 29.9% in the GS arm.

CONCLUSIONS

GS, which does not require hydration, should be considered a new, convenient standard of care option for patients with advanced/recurrent BTC.

CLINICAL TRIAL NUMBER

This trial has been registered with the UMIN Clinical Trials Registry (http://www.umin.ac.jp/ctr/index.htm), number UMIN000010667.

Diagnosis of fast ions produced by negative-ion neutral-beam injection with fast-ion deuterium-alpha spectroscopy

Negative-ion neutral-beam injection (NNBI) is an important source of heating and current drive for next-step fusion devices where the injected energy can range from hundreds of keV to 1 MeV. Few diagnostics are suitable for phase-space resolved measurements of fast ions with energy in excess of 100 keV. A study to assess the feasibility of fast-ion deuterium-alpha (FIDA) spectroscopy to diagnose high-energy ions produced by NNBI is presented. Case studies with the Large Helical Device (LHD) and JT-60SA illustrate possible solutions for the measurement. The distribution function of fast ions produced by NNBI is calculated for both devices, and the FIDA spectrum is predicted by synthetic diagnostic simulation. Results with 180 keV NNBI in LHD show that, with a judicious choice of viewing geometry, the FIDA intensity is comparable to that obtained with the existing FIDA system. The measurement is more challenging with the 500 keV NNBI in JT-60SA. Simulations predict the FIDA intensity to be about 1% of the background bremsstrahlung, which is small compared to existing FIDA implementations with positive neutral-beam injection where signal levels are an order of magnitude larger. The sampling time required to extract the small FIDA signal is determined using a probabilistic approach. Results indicate that long averaging periods, from ones to tens of seconds, are needed to resolve the FIDA signal in JT-60SA. These long averaging times are suitable in long-pulse (∼100 s), steady-state devices like JT-60SA where an important measurement objective is the spatial profile of the slowing-down distribution of fast ions.

Tuning the Fröhlich exciton-phonon scattering in monolayer MoS2

Charge carriers in semiconducting transition metal dichalcogenides possess a valley degree of freedom that allows for optoelectronic applications based on the momentum of excitons. At elevated temperatures, scattering by phonons limits valley polarization, making a detailed knowledge about strength and nature of the interaction of excitons with phonons essential. In this work, we directly access exciton-phonon coupling in charge tunable single layer MoS₂ devices by polarization resolved Raman spectroscopy. We observe a strong defect mediated coupling between the long-range oscillating electric field induced by the longitudinal optical phonon in the dipolar medium and the exciton. This so-called Fröhlich exciton phonon interaction is suppressed by doping. The suppression correlates with a distinct increase of the degree of valley polarization up to 20% even at elevated temperatures of 220 K. Our result demonstrates a promising strategy to increase the degree of valley polarization towards room temperature valleytronic applications.

Owing to the presence of a valley degree of freedom, atomically thin transition metal dichalcogenides show promise for room temperature valleytronic applications. Here, the authors use polarization-resolved Raman spectroscopy to gain insight to the exciton-phonon coupling in charge tunable single layer MoS₂.

Incidence of anterior disc displacement without reduction of the temporomandibular joint in patients with dentofacial deformity

The aim of this study was to investigate the incidence of anterior disc displacement without reduction (ADDwoR) of the temporomandibular joint (TMJ) in patients with dentofacial deformity. Eighty-eight female patients (176 joints) with skeletal class III malocclusion and 33 female patients (66 joints) with skeletal class II malocclusion, with or without anterior open bite and asymmetry, were evaluated. Magnetic resonance imaging (MRI) of the TMJ was used to diagnose ADDwoR. A statistical analysis was performed to examine the relationship between ADDwoR and skeletal structure. ADDwoR was present in 37 of the 66 joints (56.1%) in class II compared to 34 of the 176 joints (19.3%) in class III (P<0.05). In class III, ADDwoR was significantly more common in joints with mandibular asymmetry (24/74; 32.4%) than in joints with open bite (9/62; 14.5%) and joints with open bite and without mandibular asymmetry (1/38; 2.6%). In class II, ADDwoR was significantly less common in joints with mandibular asymmetry and without open bite (1/8; 12.5%). ADDwoR was only observed on the deviated side in both class III and class II with mandibular asymmetry. The prevalence of ADDwoR differed according to the dentofacial morphology.

Study of the contribution of the 7Be(d, p) reaction to the 7Li problem in the Big-Bang Nucleosynthesis

Our research goal is to measure the 7Be(d, p) reaction to shed light on the 7Li problem in the Big-Bang Nucleosynthesis. We are developing an unstable 7Be target for a high-resolution measurement of the 7Be(d, p)8Be reaction. We plan to compare two methods to producethe 7Be target: (1) Activation method, and (2) Implantation method. We performed an activation methodexperiment at the Van de Graaff at Osaka University, and obtained the cross-section data. A second experiment to obtain more accurate data will take place at the Tandem Electrostatic Accelerator, Kobe University. We have also made a 7Be target with implantation method at CRIB, Center for Nuclear Study, Univer-sity of Tokyo. An experiment to measure the (d, p) reaction with the implanted target is scheduled for 2018 at Japan Atomic Energy Agency, tandem facility.

Isomeric 26Al beam production with CRIB

We performed an experiment to measure proton resonant elastic scattering of a mixed 26m,gAl beam with a thick target in inverse kinematics by using CNS RI beam sep-arator, located at RIKEN Nishina Center. It aimed to search for strong proton resonances and determine level properties of low spin-parity states in 27Si. Diagnosis of the 26mAl purity of the beam by annihilation radiation are discussed.

7Be and 8B reaction dynamics at Coulomb barrier energies

We investigated the reaction dynamics induced by the 7Be,8B+208Pb collisions at energies around the Coulomb barrier. Charged particles originated by both the col- lisions were detected by means of 6 ΔE-Eres telescopes of a newly developed detector array. Experimental data were analysed within the framework of the Optical Model and the total reaction cross-sections were compared together and with the 6,7Li+208Pb colli-sion data. According to the preliminary results, 7Be nucleus reactivity is rather similar to the 7Li one whereas the 8B+208Pb total reaction cross section appears to be much larger than those measured for reactions induced by the other weakly-bound projectiles on the same target.

Direct measurements and detection techniques with low-energy RIBs

Astrophysical reactions involving radioactive isotopes (RI) are of importance for the stellar energy generation and nucleosynthesis especially in high-temperature astrophysical sites, such as X-ray bursts, core-collapse supernovae, and supermassive metalpoor stars. In spite of the essential diffculties in the experimental evaluation of those reaction rates, there are several successful approaches to study them, owing to the recent technical developments in the beam production, measurement method, and detectors. Among them, the measurements of α resonant scattering and (α, p) reactions using the thick-target method in inverse kinematics are discussed. The experiments at the low-energy RI beam separator CRIB, operated by Center for Nuclear Study (CNS), the University of Tokyo, are introduced as examples for such studies.