Improved Measurements of Muonic Helium Ground-State Hyperfine Structure at a Near-Zero Magnetic Field.

Muonic helium atom hyperfine structure (HFS) measurements are a sensitive tool to test the three-body atomic system and bound-state quantum electrodynamics theory, and determine fundamental constants of the negative muon magnetic moment and mass. The world's most intense pulsed negative muon beam at the Muon Science Facility of the Japan Proton Accelerator Research Complex allows improvement of previous measurements and testing further CPT invariance by comparing the magnetic moments and masses of positive and negative muons (second-generation leptons). We report new ground-state HFS measurements of muonic helium-4 atoms at a near-zero magnetic field, performed for the first time using a small admixture of CH_{4} as an electron donor to form neutral muonic helium atoms efficiently. Our analysis gives Δν=4464.980(20) MHz (4.5 ppm), which is more precise than both previous measurements at weak and high fields. The muonium ground-state HFS was also measured under the same conditions to investigate the isotopic effect on the frequency shift due to the gas density dependence in He with CH_{4} admixture and compared with previous studies. Muonium and muonic helium can be regarded as light and heavy hydrogen isotopes with an isotopic mass ratio of 36. No isotopic effect was observed within the current experimental precision.

An experimental setup for creating and imaging 4He2 * excimer cluster tracers in superfluid helium-4 via neutron-3He absorption reaction.

For the purpose of future visualization of the flow field in superfluid helium-4, clusters of the triplet state excimer 4He2 * are generated along the micro-scale recoil tracks of the neutron-absorption reaction n + 3He → 3T + p. This reaction is induced by neutron irradiation of the 3He fraction contained in natural isotopic abundance liquid helium with neutron beams either from the Japan Proton Accelerator Research Complex, Materials and Life Science Experimental Facility (JPARC)/Materials and Life Science Experimental Facility or from the Kyoto University Institute for Integrated Radiation and Nuclear Science. These 4He2 * clusters are expected to be ideal tracers of the normal-fluid component in superfluid helium with several advantageous properties. Evidence of the excimer generation is inferred by detection of laser induced fluorescence emitted from the 4He2 * clusters excited by a purpose-built short pulse gain-switched titanium:sapphire (Ti:sa) laser operating at a wavelength of 905 nm. The setup and performance characteristics of the laser system including the Ti:sa and two continuous wave re-pumping lasers are described. Detection at the fluorescence wavelength of 640 nm is performed by using optical bandpass filtered photomultiplier tubes (PMT). Electrical noise in the PMT acquisition traces could successfully be suppressed by post-processing with a simple algorithm. Despite other laser-related backgrounds, the excimer was clearly identified by its fluorescence decay characteristics. Production of the excimer was found to be proportional to the neutron flux, adjusted via insertion of different collimators into the neutron beam. These observations suggest that the apparatus we constructed does function in the expected manner and, therefore, has the potential for groundbreaking turbulence research with superfluid helium.

Pulsed neutron time-dependent intensity modulation for quasi-elastic neutron scattering spectroscopy.

We propose a basic formula and demonstration for a high-resolution quasi-elastic neutron scattering (QENS) by combining the time-of-flight (TOF) method with Modulation of Intensity by Zero Effort (MIEZE) type neutron spin echo spectroscopy. The MIEZE technique has the potential to develop a unique approach to study on slow dynamics of condensed matter; however, the energy resolution is limited owing to the hypersensitivity of the MIEZE signal contrast to the echo condition, which is strongly affected by the alignment of the instruments and the sample. The narrow allowance of the optimal alignment is a major obstacle to the wide use of this technique. Combining the TOF method with MIEZE (TOF-MIEZE), the hypersensitivity of MIEZE signals is significantly alleviated with a short pulsed beam. This robustness is very useful to optimize experimental alignments and enables accurate measurements of QENS. The experimental results demonstrate the characteristic of the TOF-MIEZE technique and are well described by the formula presented in this study.

Observation of the spatial distribution of gravitationally bound quantum states of ultracold neutrons and its derivation using the Wigner function.

Ultracold neutrons (UCNs) can be bound by the potential of terrestrial gravity and a reflecting mirror. The wave function of the bound state has characteristic modulations. We carried out an experiment to observe the vertical distribution of the UCNs above such a mirror at the Institut Laue-Langevin in 2011. The observed modulation is in good agreement with that prediction by quantum mechanics using the Wigner function. The spatial resolution of the detector system is estimated to be 0.7 µm. This is the first observation of gravitationally bound states of UCNs with submicron spatial resolution.

Nuclear-matter modification of decay widths in the phi-->e+e- and phi-->K+K- channels.

The invariant mass spectra of phi-->K+K- are measured in 12 GeV p+A reactions in order to search for the in-medium modification of phi mesons. The observed K+K- spectra are well reproduced by the relativistic Breit-Wigner function with a combinatorial background shape in three betagamma regions between 1.0 and 3.5. The nuclear mass number dependence of the yields of the K+K- decay channel is compared to the simultaneously measured e+e- decay channel for carbon and copper targets. We parameterize the production yields as sigma(A)=sigma0Aalpha and obtain alphaphi-->K+K- -alphaphi-->e+e- to be 0.14+/-0.12. Limits are obtained for the partial decay widths of the phi mesons in nuclear matter.

Evidence for in-medium modification of the phi meson at normal nuclear density.

Invariant mass spectra of e(+) e(-) pairs have been measured in 12 GeV p + A reactions to detect possible in-medium modification of vector mesons. Copper and carbon targets are used to study the nuclear-size dependence of e(+) e(-) invariant mass distributions. A significant excess on the low-mass side of the phi meson peak is observed in the low betagamma(= beta/square root(1-beta(2))) region of phi mesons (betagamma < 1.25) with copper targets. However, in the high betagamma region (betagamma > 1.25), spectral shapes of phi mesons are well described by the Breit-Wigner shape when experimental effects are considered. Thus, in addition to our earlier publications on rho/omega modification, this study has experimentally verified vector meson mass modification at normal nuclear density.

Experimental signature of medium modifications for rho and omega mesons in the 12 GeV p+A reactions.

The invariant mass spectra of e+e- pairs produced in 12 GeV proton-induced nuclear reactions are measured at the KEK Proton Synchrotron. On the low-mass side of the meson peak, a significant enhancement over the known hadronic sources has been observed. The mass spectra, including the excess, are well reproduced by a model that takes into account the density dependence of the vector meson mass modification, as theoretically predicted.

Clinicogenetic study of PINK1 mutations in autosomal recessive early-onset parkinsonism.

The authors performed PINK1 mutation analysis of 51 families with autosomal recessive Parkinson disease (ARPD). They found two novel PINK1 mutations: one was a homozygous deletion (13516-18118del) and the other a homozygous missense mutation (C388R). Clinically, the patients with the deletion had dementia. Thus, early-onset PD with dementia may be considered PINK1-linked parkinsonism. Furthermore, patients with PINK1 mutations form 8.9% of parkin- and DJ-1-negative ARPD families.

Cerebral fat embolism after a nondisplaced tibial fracture: case report.

Fat embolism syndrome has been observed after traumatic or nontraumatic events. In traumatic cases, fat embolism syndrome is known to occur in patients with a fracture of a long bone. The case of a patient with a cerebral fat embolism associated with a nondisplaced fracture of the tibial shaft is reported.

Observation of rho/omega meson modification in nuclear matter.

We measured the invariant mass spectra of electron-positron pairs in the target rapidity region of 12-GeV p+A reactions. We have observed a significant difference in the mass spectra below the omega meson between p+C and p+Cu interactions. This difference indicates that the spectral shape of mesons is modified at normal nuclear-matter density.

[A case of linear sebaceous nevus syndrome associated with a cerebrovascular anomaly].

We report a 34-year-old woman with linear sebaceous nevus syndrome and dolichomegalic artery. The patient was admitted to our hospital for evaluation of a headache and fever. Neurological examination revealed no focal sign except neck stiffness. She had had sebaceous nevi on the left side of her head, cheek and neck since she was born. A cranial CT scan showed high signal intensity in the subarachnoid space. Cranial MRI showed a dolichomegalic artery. The patient's past history included many episodes of headache and fever since her first decade of life and she had been diagnosed five times with cerebrovascular disease. At the present admission, subarachnoid hemorrhage was diagnosed and treated. The patient improved and was discharged on the 21st day. Linear sebaceous nevi are associated with many types of anomalies, but we found no other reported cases of linear sebaceous nevus syndrome associated with a cerebrovascular anomaly. This case suggests that a patient with sebaceous nevi who presents with headache and fever should be examined with careful attention to the cerebrovascular system.

[A case of isolated ACTH deficiency accompanied by generalized painful muscle cramp].

We report a patient who had generalized painful muscle cramps associated with isolated ACTH deficiency. A 68-year-old woman was hospitalized because of painful muscle cramps present for one year. Neurological examination revealed no abnormalities except for generalized painful muscle cramps. Serum electrolyte and CPK levels were normal. Serum ACTH and cortisol levels as well as urine 17-OHCS were low. An ACTH loading test employing insulin, TRH and LH-RH indicated isolated ACTH deficiency. Just after the muscle cramp, EMG revealed a low amplitude in the biceps muscle. Colon biopsy showed mild fibrosis and inflammatory cell infiltration in the lamina propria. Her muscle cramps improved markedly after two weeks of hydrocortisone replacement therapy and resolved after three weeks, suggesting that this symptom was closely related to isolated ACTH deficiency. Our case suggests that isolated ACTH deficiency may present with very similar clinical symptoms to Satoyoshi disease.

Abnormal evoked potentials of Kearns-Sayre syndrome.

We examined eight patients with Kearns-Sayre syndrome (KSS) to investigate a dysfunction in the central nervous system (CNS) using PTN-SEP, MN-SEP and BAEP. We found a significant increase in the P37 latency of PTN-SEPs and the central conduction time of MN-SEPs, and interpeak latencies of BAEPs. Delayed SEPs or BAEPs were caused by a dysfunction of the somatosensory or lateral lemniscus pathways which could be related to mitochondrial abnormalities in the CNS. Long-term therapy with CoQ showed an improvement of the latencies of SEPs after about half a year from the start of CoQ therapy in our patients. The improvement of the latencies of SEPs were preserved during CoQ therapy. It could be demonstrated that CoQ therapy had the beneficial effects on abnormal functions of the CNS in patients with KSS.

Magnetic resonance imaging and brain-stem auditory evoked potentials in neuro-Behçet's disease.

We studied central nervous system lesions in patients with neuro-Behcet's disease using magnetic resonance imaging (MRI) of the brain and recording of brain-stem auditory evoked potentials (BAEPs). MRI revealed abnormal findings in seven of eight patients. MRI studies demonstrated extensive regions with high intensity signal in the brain stem and/or basal ganglia on T2-weighted images obtained during the acute stage of the disease in three patients. One of these patients had a strongly gadolinum-enhanced round lesion in the lower pons. In four of the other five patients with chronic disease, brain-stem atrophy was observed on T1-weighted images. Atrophic changes were more severe in the brain stem than in the cerebellum. Abnormal BAEPs were observed in three patients and consisted of prolongation of interpeak latency of waves III-V and defects of wave III or V. Abnormal BAEPs were recorded in patients with severe inflammatory changes or progression of atrophic changes in the brain stem. Our findings show that MRI and BAEPs are useful in detecting the presence and assessing the degree of neurological involvement in patients with neuro-Behçet's disease.

[Studies on motor neuron disease with cranial magnetic resonance imaging].

The present study was performed to examine the pyramidal tracts of the brain in both 51 normal subjects (21 male and 30 female subjects; mean age of 43.5 +/- 16.1 years) and 12 patients with motor neuron disease (6 male and 6 female patients; mean age of 57.4 +/- 7.9 years), using the magnetic resonance imaging (MRI). The 12 patients with motor neuron disease (MND) comprised 7 suffering from spinal progressive muscular atrophy (SPMA) and 5 from amyotrophic lateral sclerosis (ALS). The MRI used in this study was of both short spin echo and long spin echo sequence. Of the 52 normal subjects, 24 of them (47%) had the T2 prolonged small areas (high signal intensity areas) at the posterior limb of internal capsule. These findings were not found in the normal subjects over fifty years old. No similar finding was detected in the pyramidal tracts except the posterior limb of internal capsule. On the other hand, 8 patients with MND (67%) proved to have the high signal intensity areas in the pyramidal tracts. Moreover, these high intensity areas were extended from the crus cerebri to corona radiata in 7 patients (58%). In all patients with ALS, these areas were extended in whole areas of the pyramidal tracts, and the similar findings were also found in two patients with SPMA. These findings were demonstrated to be more extensive than those in the normal subjects. The results thus obtained warrant us to conclude that cranial MRI is useful to detect the degeneration of the pyramidal tracts of MND patients.

Improved inching method for the diagnosis and prognosis of carpal tunnel syndrome.

A modified sensory "inching" method for the electrodiagnosis of carpal tunnel syndrome (CTS) is described. The median nerve as stimulated at the cubital portion, with 8 channel recording electrodes placed along the nerve across the carpal tunnel. In most of the CTS cases, there was a conductive abnormality from 3 to 4.5 cm distal to the proximal ending of the flexor retinaculum. Subjects' values, obtained by subtracting the theoretical latency from the measured latency, which were more than 0.6 ms, could not be improved by conservative therapy. As we could determine from subtle change at the short span of nerve conduction, below the electrodes from the proximal to the affected site of the carpal tunnel, this method provides high sensitivity and specificity for the diagnosis of CTS.

Clinical utility of somatosensory evoked potentials in diabetes mellitus.

The posterior tibial nerve and median nerve somatosensory evoked potentials (PTN-SEPs and MN-SEPs) were investigated in 34 patients with diabetes mellitus (DM). We measured the latency of the first positive cortical potential (the cortical P37) of PTN-SEPs and that of the first negative cortical potential (the cortical N18) and Erb's potential of MN-SEPs. In 18 patients (52.9%), the cortical P37 latency was more than 3 SD longer than normal in the tibial nerve. There were positive correlations between the latency of cortical P37 and the duration of DM and the motor nerve conduction velocity of the posterior tibial nerve. Sensory action potentials of the posterior tibial nerve were not detectable in 21 patients, though cortical P37 potential was unambiguously recorded by stimulating the posterior tibial nerve even in those subjects. Diabetic retinopathy and nephropathy also tended to rise with increasing latency of cortical P37. The latency of cortical P37 is an important parameter in assessing diabetic neuropathy.

Brainstem auditory and somatosensory evoked potentials in neuro-Behçet's syndrome.

Brainstem auditory evoked potentials (BAEPs) and somatosensory evoked potentials after median nerve stimulation (MN-SEPs) and after posterior tibial nerve stimulation (PTN-SEPs) were studied in 17 patients with neuro-Behçet's syndrome (NB). Eleven patients (64.7%) showed an absence of wave I, III or V or a prolongation of the interpeak latency I-III, or III-V in BAEPs. Six patients (37.4%) showed a prolongation in the latency of cortical P37 of PTN-SEPs and/or the interpeak latency EP-N13 or N13-N18 of MN-SEPs. The BAEP and SEP abnormalities indicated a conduction failure of the acoustic lateral lemniscus pathway and the medial lemniscus pathway in the brainstem of the patients with NB. Abnormal EPs can provide sensitive information which shows the presence of subclinical lesions in the central nervous system.

Comparative study of evoked potentials in multiple sclerosis and neuro-Behçet's syndrome.

We studied somatosensory evoked potentials (SEPs) and brainstem auditory evoked potentials (BAEPs) in Japanese patients with multiple sclerosis (MS) and those with neuro-Behcet's disease (NB). Abnormal cortical P37 of posterior tibial nerve SEPs or cervical N13 of median nerve SEPs were more frequently found in the MS patients than in the NB patients. On the other hand, prolongation of the central conduction time of median nerve SEPs or abnormal BAEPs were more common in NB than in MS. The present data showed that lesions were mainly present in the spinal cord in MS and in the brainstem in NB. SEPs and BAEPs were considered of great value for detecting the involvement of the central nervous system in MS and NB and distinguishing between these diseases.