Molecular spin resonance in the geometrically frustrated magnet MgCr2O4 by inelastic neutron scattering.

We measured two magnetic modes with finite and discrete energies in an antiferromagnetic ordered phase of a geometrically frustrated magnet MgCr2O4 by single-crystal inelastic neutron scattering, and clarified the spatial spin correlations of the two levels: one is an antiferromagnetic hexamer and the other is an antiferromagnetic heptamer. Since these correlation types are emblematic of quasielastic scattering with geometric frustration, our results indicate instantaneous suppression of lattice distortion in an ordered phase by spin-lattice coupling, probably also supported by orbital and charge. The common features in the two levels, intermolecular independence and discreteness of energy, suggest that the spin molecules are interpreted as quasiparticles (elementary excitations with energy quantum) of highly frustrated spins, in analogy with the Fermi liquid approximation.

Kagomé ice state in the dipolar spin ice Dy2Ti2O7.

We have investigated the kagomé ice behavior of the dipolar spin-ice compound Dy2Ti2O7 in a magnetic field along a [111] direction using neutron scattering and Monte Carlo simulations. The spin correlations show that the kagomé ice behavior predicted for the nearest-neighbor interacting model, where the field induces dimensional reduction and spins are frustrated in each two-dimensional kagomé lattice, occurs in the dipole interacting system. The spins freeze at low temperatures within the macroscopically degenerate ground states of the nearest-neighbor model.

Observation of modulated quadrupolar structures in PrPb3.

Neutron diffraction measurements have been performed on the cubic compound PrPb(3) in a [001] magnetic field to examine the quadrupolar ordering. Antiferromagnetic components with q = (1/2 +/- delta 1/2 0), (1/2 1/2 +/- delta 0) (delta approximately 1/8) are observed below the transition temperature T(Q) (0.4 K at H = 0) whose amplitudes vary linear with H and vanish at zero field, providing the first evidence for a modulated quadrupolar phase. For H < 1 T, a nonsquare modulated state persists even below 100 mK suggesting quadrupole moments associated with a Tau(3) doublet ground state to be partially quenched by hybridization with conduction electrons.

Magnetic structure, phase diagram, and a new type of spin-flop transition dominated by higher order interaction in a localized 5f system U3Pd20Si6.

The magnetic structure of the localized-5f uranium intermetallic compound U3Pd20Si6 has been determined by means of a neutron diffraction experiment. Our data demonstrate that this compound has a collinear coupling of the sublattice ordering of the uranium spins on the 4a and 8c sites. We conclude that higher-order exchange and/or quadrupole interactions are necessary to stabilize this unique collinear structure. We discovered a new type of spin-flop transition against the uniaxial anisotropy induced by this collinear coupling.

Spin-triplet superconductivity in UNi(2)Al(3) revealed by the (27)Al Knight shift measurement.

We report (27)Al Knight shift ( (27)K) measurement on a single-crystal UNi(2)Al(3) that reveals a coexistence of superconductivity and a spin-density-wave (SDW) type of magnetic ordering ( T(SDW) = 4.5 K). The spin part of (27)K, (27)K(s), does not change down to 50 mK across the superconducting (SC) transition temperature T(c) approximately 0.9 K. In contrast with the isostructural compound UPd(2)Al(3) ( T(c) approximately 2 K), which was identified to be a spin-singlet d-wave superconductor, the behavior of (27)K strongly supports that UNi(2)Al(3) , like UPt(3) and Sr(2)RuO(4), belongs to a class of spin-triplet SC pairing state superconductors.

Dzyaloshinski-Moriya interaction in the 2D spin gap system SrCu(2)(BO(3))(2).

The Dzyaloshinski-Moriya interaction partially lifts the magnetic frustration of the spin-1/2 oxide SrCu(2)(BO(3))(2). It explains the fine structure of the excited triplet state and its unusual magnetic field dependence, as observed in previous ESR and new neutron inelastic scattering experiments. We claim that it is mainly responsible for the dispersion. We propose also a new mechanism for the observed ESR transitions forbidden by standard selection rules, which relies on an instantaneous Dzyaloshinski-Moriya interaction induced by spin-phonon couplings.

Strong coupling between local moments and superconducting 'heavy' electrons in UPd2Al3.

The electronic structure of heavy-fermion compounds arises from the interaction of nearly localized 4f- or 5f-shell electrons (with atomic magnetic moments) with the free-electron-like itinerant conduction-band electrons. In actinide or rare-earth heavy-fermion materials, this interaction yields itinerant electrons having an effective mass about 100 times (or more) the bare electron mass. Moreover, the itinerant electrons in UPd2Al3 are found to be superconducting well below the magnetic ordering temperature of this compound, whereas magnetism generally suppresses superconductivity in conventional metals. Here we report the detection of a dispersive excitation of the ordered f-electron moments, which shows a strong interaction with the heavy superconducting electrons. This 'magnetic exciton' is a localized excitation which moves through the lattice as a result of exchange forces between the magnetic moments. By combining this observation with previous tunnelling measurements on this material, we argue that these magnetic excitons may produce effective interactions between the itinerant electrons, and so be responsible for superconductivity in a manner analogous to the role played by phonons in conventional superconductors.

[CT-guided needle biopsy of the lung: factors affecting risk of complications].

PURPOSE: To analyze factors influencing the risk of complications associated with CT-guided percutaneous needle biopsy for lung lesions. MATERIALS AND METHODS: Sixty patients, aged 24-85 years (37 men and 23 women), underwent CT-guided needle biopsy. A definite diagnosis was made in 49 of 60 cases (81.7%), including 38 of 43 malignant lesions (88.4%) and 11 of 17 benign lesions (64.7%). Complications associated with biopsy were observed in 35 patients (58.3%). Major complications included pneumothorax (n = 26) and pulmonary hemorrhage (n = 20). Chest tube placement was needed in 5 (19.2%) of 26 pneumothorax cases (8.3% of all biopsies). RESULTS: The high frequency of pneumothorax (43.3%) in this series had several contributing factors, including the presence of pulmonary emphysema, lesion size, and traversal of aerated lung. Chest tube replacement was necessary more frequently in patients with pulmonary emphysema. The number of pleural passes, location of lesions, and size of needles were not correlated with the incidence of pneumothorax. CONCLUSION: The presence of pulmonary emphysema, lesion size, and traversal of aerated lung are the predominant risk factors for pneumothorax in patients with CT-guided lung biopsy.

Lobar atelectasis: diagnostic pitfalls on chest radiography.

This pictorial review looks at the pitfalls in the diagnosis of lobar atelectasis on chest radiographs. Lobar atelectasis with marked volume loss is hard to recognize and may be easily missed. Lobar atelectasis presenting as a mass-like opacity may be misdiagnosed as mediastinal or lung tumour. Lobar atelectasis in an unusual location may also be misdiagnosed as other entities. Familiarity with such manifestations and consideration of anatomical alterations as the signs of lobar atelectasis are important in making the correct diagnosis.

A phase II trial of oral UFT plus cisplatin (CDDP) in patients with non-small cell lung cancer (NSCLC).

Based on the results of our previous pilot study, we conducted a multi-institutional phase II study of combination chemotherapy consisting of oral UFT (Taiho Pharmaceutical Co. Ltd, Tokyo) plus cisplatin (CDDP) in patients with advanced non-small cell lung cancer (NSCLC). UFT capsule containing 100 mg tegafur and 224 mg uracil was orally administered in two divided doses on days 1 through 21 making the total tegafur dose 400 mg/m(2)/day (maximum 600 mg/body). CDDP was administered by drip infusion at a dose of 20 mg/m(2) on a 5-day schedule from day 8 to 12. Treatment was repeated every 4 weeks as long as the criteria for initiation of therapy were still met. Between April 1995 and March 1997, 51 patients were entered into the study. The mean age of all 50 eligible patients was 64 years(range: 40-78). There were 21 patients with clinical stage IIIB disease and 29 patients with IV disease. Thirty-two patients had adenocarcinoma, 14 had epidermoid carcinoma, and four had large cell carcinoma. Of the 47 assessable patients, 18 achieved a partial response with an overall response rate of 38.3% (95% confidence interval: 24.4-52.2%). The median response duration was 113 days. The median survival time of the eligible patients was 12.8 months, and the 1-year survival rate was 54%. Among the 51 patients enrolled, grade 3 or 4 leukopenia developed in one patient (2%), neutropenia in six patients (11. 8%), thrombocytopenia in six patients (11. 8%), and anemia in three patients (5. 9%). Non-hematological grade 3 or 4 toxicities included anorexia in 10 patients (19.6%), nausea in ten (19.6%), vomiting in two (3.9%), and diarrhea in two (3. 9%). Grade 3 abnormal laboratory data included bilirubinemia in four (7. 8%), GPT elevation in one (2.0%), and hematuria in one (2.0%). In conclusion, combination of CDDP plus oral UFT is efficacious, with low toxicity, in the treatment of advanced NSCLC. In particular, the low hematological toxicity may warrant application of this regimen to the treatment of elderly patients and in trials of concurrent chemoradiotherapy in patients with locally advanced NSCLC.

Direct evidence for the localized single-triplet excitations and the dispersive multitriplet excitations in SrCu2(BO3)2.

We performed inelastic neutron scattering on the 2D Shastry-Sutherland system SrCu2(11BO3)2 with an exact dimer ground state. Three energy levels at around 3, 5, and 9 meV were observed at 1.7 K. The lowest excitation at 3.0 meV is almost dispersionless with a bandwidth of 0.2 meV at most, showing a significant constraint on a single-triplet hopping owing to the orthogonality of the neighboring dimers. In contrast, the correlated two-triplet excitations at 5 meV exhibit a more dispersive behavior.

[An autopsy case of AIDS complicated with cytomegalovirus infection and multiple Kaposi's sarcoma].

Cutaneous Kaposi's sarcoma (KS) is a well-known complication of the acquired immunodeficiency syndrome. KS in the internal organs, however, is rare in Japan. We present here a 33-years-old Japanese homosexual man who had AIDS complicated with cytomegalovirus (CMV) infection and KS. He was found to be HIV-seropositive, when he was 31-years-old. He visited our hospital in June 1996 because of high fever. The peripheral blood CD4+ lymphocyte counts were 2 per cubic millimeter, and CMV antigenemia was noted (p65 antigen positive cells; 240/50,000 white blood cells). Thereafter he was successfully treated with parental ganciclovir. On admission, some brown-colored flat nodules were found on the skin, and the diagnosis of KS was made by skin biopsy. We administrated human chorionic gonadotropin (hCG) for the treatment of KS, but had no clinical response. In September 1996, he complained of severe cough, shortness of breath, and vomiting. A chest radiogram showed nodular lesions and pleural effusion in bilateral lungs. A computed tomography of his chest also revealed nodular and linear densities distributed along the bronchovascular bundles. The ultrasonic examination of his abdomen revealed a duodenal nodule. Both nodules in the lungs and duodenum were proved to be KS based on the autopsy findings. Intranuclear inclusionbodies pathognomonic for CMV infections were detected in the stomach and the colon.

Role of somatosensory feedback from tools in realizing movements by patients with ideomotor apraxia.

In order to investigate the underlying mechanism of ideomotor apraxia, we studied 9 patients who could not mime using tools despite the ability to manipulate actual tools normally. In all the mime tasks, visually presented tools or model gestures by examiners were fundamentally ineffectual in improving the patients' performances. Even the remarkable improvement demonstrated when using actual tools disappeared immediately after the subjects took their hands off them. In a further experiment, 4 of the 9 patients were required to pretend to use tools while holding a stick, resulting in significant improvements or normal miming. These findings suggest that the somatosensory feedback continuously supplied from a handheld tool is a crucial component in enabling patients with ideomotor apraxia to actually use tools.

[Findings of MR and MR cholangiopancreatography in acute cholecystitis].

We retrospectively reviewed magnetic resonance cholangiopancreatography (MRCP) of 25 patients with acute cholecystitis based on clinical, sonographic and surgical findings. Intramural high signal intensity on MRCP was demonstrated in 22 of the 25 patients (88%), and pericholedochal high signal intensity was observed in 6 of the 25 patients (24%). Pericholecystic or perihepatic fluid was demonstrated in 6 of the 25 patients (24%). Gallbladder stones were identified in all 21 patients (100%) by sonography, in 19 of the 21 (90%) by MRCP and in 11 of 18 patients by CT (CT was not performed in other 3 patients). Common bile duct calculi were detected in all 6 patients (100%) by MRCP, in 2 of the 6 (33%) by sonography, and in 5 of the 6 (50%) by CT with confirmation of surgical finding or endoscopic retrograde cholangiography (ERC). MRCP had a high accuracy in diagnosing acute cholecystitis with the finding of intramural high signal intensity. MRCP is an excellent method to evaluate acute biliary disease and may replace CT and ERC in the preoperative evaluation of acute cholecystitis.

CT of neural plexus invasion in common bile duct carcinoma.

PURPOSE: Our purpose was to analyze the CT findings of neural plexus invasion in common bile duct carcinoma. METHOD: We studied 16 patients with common bile duct carcinoma who underwent surgery. Of these, neural invasion was seen in 10 patients. CT findings were retrospectively reviewed and correlated with the surgical and pathological findings. RESULTS: Irregular masses adjacent to the medial aspect of the uncinate process were observed in 4 of 14 patients with distal common bile duct carcinoma. These lesions extended medially and showed contiguity with the superior mesenteric artery and/or celiac axis, corresponding to neural plexus invasion with desmoplastic change. Increased attenuation of the fat between the common bile duct and the proper hepatic artery was seen in two of two patients with proximal common bile duct carcinoma, associated with neural plexus invasion in the hepatoduodenal ligament. CONCLUSION: The location and spread of neural plexus invasion in common bile duct carcinoma are characteristic and can be diagnosed by CT.

Complications associated with transcatheter arterial embolization for hepatic tumors.

Transcatheter arterial embolization (TAE) is widely used in the treatment of hepatic tumors. A total of 2,300 TAE procedures were performed with a 2-15-mL injection of a mixture or suspension of anticancer drugs and iodized oil, followed by administration of gelatin sponge particles. One or two chemotherapeutic drugs, including doxorubicin hydrochloride (10-30 mg), epirubicin hydrochloride (10-30 mg), mitomycin C (10-20 mg), and cisplatin (25-100 mg), were used for each procedure. Complications were encountered in 4.4% of cases (n = 102) and were related to the use of chemoembolic agents or the manipulation of a catheter or guide wire. These complications included acute hepatic failure (n = 6), liver infarction (n = 4) or abscess (n = 5), intrahepatic biloma (n = 20), multiple intrahepatic aneurysms (n = 6), cholecystitis (n = 7), splenic infarction (n = 2), gastrointestinal mucosal lesions (n = 5), pulmonary embolism or infarction (n = 4), tumor rupture (n = 1), variceal bleeding (n = 3), and iatrogenic dissection (n = 35) or perforation (n = 4) of the celiac artery and its branches. Knowledge of these complications is important for correct diagnosis and appropriate management.

Traction injuries of the brachial plexus: signal intensity changes of the posterior cervical paraspinal muscles on MRI.

PURPOSE: Our goal was to evaluate MR signal intensity change of the posterior cervical paraspinal muscles in brachial plexus traction injuries to determine the value of this finding in the diagnosis of nerve root avulsion. METHOD: MR images of 11 consecutive patients, 7 with nerve root avulsion and 4 without nerve root avulsion, were retrospectively analyzed, focusing on the signal intensity of the paraspinal muscles. RESULTS: Among the seven patients with nerve root avulsion, T2- or T2*-weighted MR images showed increased signal intensity in the deep posterior paraspinal muscles in five and traumatic meningocele in four. The signal intensity of the posterior paraspinal muscles was normal in all patients without nerve root injuries. CONCLUSION: MR signal intensity change in the deep posterior cervical paraspinal muscles is related to denervation and suggests the presence of nerve root avulsion.

[A clinical study of skin flora in patients with MRSA colonization after introduction of preventive measures of hospital infection in a geriatric ward].

In early 1980's methicillin-resistant Staphylococcus aureus (MRSA) was reported as a major pathogenic organism of geriatric hospital infection in Japan. At the same time in the geriatric hospital MRSA infection was prevalent. To decrease nosocomial infections some active preventive measures against hospital infection were taken since Oct. 1991. After introduction of preventive measures of hospital infection in the geriatric ward (190 beds) nosocomial bacteremia and pneumonia were markedly decreased in comparison of episode number before introduction of prevention. However several patients with MRSA colonization were observed every month. The aim of this clinical study was to clear how frequent MRSA was isolated from skin. Consequently 3 strains (3.4%) of MRSA were observed in 86 cultured skin. In conclusion we considered frequency of MRSA colonization frequency of MRSA colonization on skin was not so high but rather very low under the preventive measures.