Ultrafast polarization control by terahertz fields via π-electron wavefunction changes in hydrogen-bonded molecular ferroelectrics.

Rapid polarization control by an electric field in ferroelectrics is important to realize high-frequency modulation of light, which has potential applications in optical communications. To achieve this, a key strategy is to use an electronic part of ferroelectric polarization. A hydrogen-bonded molecular ferroelectric, croconic acid, is a good candidate, since π-electron polarization within each molecule is theoretically predicted to play a significant role in the ferroelectric-state formation, as well as the proton displacements. Here, we show that a sub-picosecond polarization modulation is possible in croconic acid using a terahertz pulse. The terahertz-pulse-pump second-harmonic-generation-probe and optical-reflectivity-probe spectroscopy reveal that the amplitude of polarization modulation reaches 10% via the electric-field-induced modifications of π-electron wavefunctions. Moreover, the measurement of electric-field-induced changes in the infrared molecular vibrational spectrum elucidates that the contribution of proton displacements to the polarization modulation is negligibly small. These results demonstrate the electronic nature of polarization in hydrogen-bonded molecular ferroelectrics. The ultrafast polarization control via π-electron systems observed in croconic acid is expected to be possible in many other hydrogen-bonded molecular ferroelectrics and utilized for future high-speed optical-modulation devices.

Assessing infrared intensity using the evaporation rate of liquid hydrogen inside a cryogenic integrating sphere for laser fusion targets.

Infrared (IR) heating processes have been studied to form a deuterium layer in an inertial confinement fusion target. To understand the relationship between the IR intensity and the fuel layering time constant, we have developed a new method to assess the IR intensity during irradiation. In our method, a glass flask acting as a dummy target is filled with liquid hydrogen (LH2) and is then irradiated with 2-µm light. The IR intensity is subsequently calculated from the time constant of the LH2 evaporation rate. Although LH2 evaporation is also caused by the heat inflow from the surroundings and by the background heat, the evaporation rate due to IR heating can be accurately determined by acquiring the time constant with and without irradiation. The experimentally measured IR intensity is 0.66 mW/cm2, which agrees well with a value estimated by considering the IR photon energy balance. Our results suggest that the present method can be used to measure the IR intensity inside a cryogenic system during IR irradiation of laser fusion targets.

Ultrafast Photoinduced Electric-Polarization Switching in a Hydrogen-Bonded Ferroelectric Crystal.

Croconic acid crystals show proton displacive-type ferroelectricity with a large spontaneous polarization reaching 20 µC/cm^{2}, which originates from the strong coupling of proton and π-electron degrees of freedom. Such a coupling makes us expect a large polarization change by photoirradiations. Optical-pump second-harmonic-generation-probe experiments reveal that a photoexcited croconic-acid crystal loses the ferroelectricity substantially with a maximum quantum efficiency of more than 30 molecules per one absorbed photon. Based on density functional calculations, we theoretically discuss possible pathways toward the formation of a one-dimensional domain with polarization inversion and its recovery process to the ground state by referring to the dynamics of experimentally obtained polarization changes.

Novel electronic ferroelectricity in an organic charge-order insulator investigated with terahertz-pump optical-probe spectroscopy.

In electronic-type ferroelectrics, where dipole moments produced by the variations of electron configurations are aligned, the polarization is expected to be rapidly controlled by electric fields. Such a feature can be used for high-speed electric-switching and memory devices. Electronic-type ferroelectrics include charge degrees of freedom, so that they are sometimes conductive, complicating dielectric measurements. This makes difficult the exploration of electronic-type ferroelectrics and the understanding of their ferroelectric nature. Here, we show unambiguous evidence for electronic ferroelectricity in the charge-order (CO) phase of a prototypical ET-based molecular compound, α-(ET)2I3 (ET:bis(ethylenedithio)tetrathiafulvalene), using a terahertz pulse as an external electric field. Terahertz-pump second-harmonic-generation(SHG)-probe and optical-reflectivity-probe spectroscopy reveal that the ferroelectric polarization originates from intermolecular charge transfers and is inclined 27° from the horizontal CO stripe. These features are qualitatively reproduced by the density-functional-theory calculation. After sub-picosecond polarization modulation by terahertz fields, prominent oscillations appear in the reflectivity but not in the SHG-probe results, suggesting that the CO is coupled with molecular displacements, while the ferroelectricity is electronic in nature. The results presented here demonstrate that terahertz-pump optical-probe spectroscopy is a powerful tool not only for rapidly controlling polarizations, but also for clarifying the mechanisms of ferroelectricity.

Characterizing a fast-response, low-afterglow liquid scintillator for neutron time-of-flight diagnostics in fast ignition experiments.

The characteristics of oxygen-enriched liquid scintillators with very low afterglow are investigated and optimized for application to a single-hit neutron spectrometer for fast ignition experiments. It is found that 1,2,4-trimethylbenzene has better characteristics as a liquid scintillator solvent than the conventional solvent, p-xylene. In addition, a benzophenon-doped BBQ liquid scintillator is shown to demonstrate very rapid time response, and therefore has potential for further use in neutron diagnostics with fast time resolution.

Excitation-photon-energy selectivity of photoconversions in halogen-bridged Pd-chain compounds: Mott insulator to metal or charge-density-wave state.

Ultrafast photoinduced transitions of a one-dimensional Mott insulator into two distinct electronic phases, metal and charge-density-wave (CDW) state, were achieved in a bromine-bridged Pd-chain compound [Pd(en)2Br](C5-Y)2H2O (en=ethylenediamine and C5-Y=dialkylsulfosuccinate), by selecting the photon energy of a femtosecond excitation pulse. For the resonant excitation of the Mott-gap transition, excitonic states are generated and converted to one-dimensional CDW domains. For the higher-energy excitation, free electron and hole carriers are produced, giving rise to a transition of the Mott insulator to a metal. Such selectivity in photoconversions by the choice of initial photoexcited states opens a new possibility for the developments of advanced optical switching and memory functions.

Revealing the photorelaxation mechanism in a molecular solid using density-functional theory.

Photorelaxation in a molecular crystal is investigated by a density-functional theory for the first time. A quasi-one-dimensional molecular compound, (EDO-TTF)(2)PF(6), is known to exhibit a photoinduced phase transition, which is characterized as a transition from a (0110)-type charge-ordering insulator phase to a high-temperature metallic phase. First, we apply the method of embedding a cluster in a self-consistent environment and succeed in constructing a stable tetramer structure of EDO-TTF molecules. The reliance of this cluster is ensured by a vibrational analysis that well reproduces the IR and Raman frequencies particularly for C=C stretching modes including a relatively large degree of electron-'molecular vibration' coupling. Second, relaxations in the photoexcited states of this cluster are investigated by adiabatic potential-surface analyses and full structural optimization. A reaction coordinate is found to be quite unique for a relatively high-energy excitation, namely, the so-called CT2 excitation, which is interpreted as leading to the photoinduced phase transition.

Detection of domain dynamics by high energy photons: proposals in one-dimensional photoinduced phase transition systems.

We propose the detection of domain dynamics in a one-dimensional system by using high energy photons such as synchrotron radiation. The domain here means that of a different phase formed in the background of an original phase. Using high energy photons, it is expected that not only k=0 states with k being the momentum of its center of gravity motion, but also finite k states are possible to be detected. We theoretically demonstrate how they are observed, with nonresonant inelastic x-ray scattering and valence photoemission as concrete examples. In the former, we mainly detect charge excitations, particularly, the center of gravity and the spatial size of the domain as its basic two degrees of freedom, while, in the latter, spin excitations inside the domain also play an essential role.

Kudo type-5 total elbow arthroplasty in mutilating rheumatoid arthritis: a 5- to 11-year follow-up.

We studied 11 patients (14 elbows) with gross rheumatoid deformity of the elbow, treated by total arthroplasty using the Kudo type-5 unlinked prosthesis, and who were evaluated between five and 11 years after operation. Massive bone defects were augmented by autogenous bone grafts. There were no major complications such as infection, subluxation or loosening. In most elbows relief from pain and stability were achieved. The results, according to the Mayo Elbow Performance Score, were excellent in eight, good in five and fair in one. In most elbows there was minimal or no resorption of the grafted bone. There were no radiolucent lines around the stems of the cementless components. This study shows that even highly unstable rheumatoid elbows can be replaced successfully using an unlinked prosthesis, with augmentation by grafting for major defects of bone.

Kudo total elbow arthroplasty in patients with rheumatoid arthritis: a long-term follow-up study.

BACKGROUND: Improvements in the design of total elbow prostheses over the last two decades have led to better and more consistent results. The type-3 Kudo total elbow prosthesis was developed in 1980. The long-term results of use of this implant have not been reported. Because it is an unlinked prosthesis, it is not known whether preservation of the anterior oblique component of the ulnar collateral ligament at the time of implantation is important. METHODS: A type-3 Kudo total elbow arthroplasty with cement was performed in forty-seven patients (fifty elbows) with rheumatoid arthritis. Revision rates, clinical symptoms, postoperative complications, and radiographic changes were assessed eleven to sixteen years (mean, thirteen years) postoperatively. RESULTS: The overall survival rate of the prosthesis was 90% at sixteen years. The mean Mayo elbow performance scores were all poor (mean overall score, 43 points) initially. The overall score was substantially improved at both the intermediate follow-up examination (four to six years after the operation) and the late follow-up examination (eleven to sixteen years after the operation), to 81 and 77 points, respectively. The overall rate of radiolucency about the humeral component was 45% at the intermediate follow-up examination and 100% at the long-term follow-up examination. The rate of radiolucency about the ulnar component at the intermediate and late follow-up examinations was 4.3% and 8.9%, respectively. No great differences in results were found with preservation of the anterior oblique component of the ulnar collateral ligament. CONCLUSIONS: This long-term follow-up study showed acceptable results of the type-3 Kudo total elbow arthroplasty in patients with rheumatoid arthritis. Preservation of the ulnar collateral ligament does not seem to be necessary when performing this procedure.

[Prospective study of pulmonary embolism after total hip or knee arthroplasty].

We investigated the incidence of pulmonary embolism after total hip or knee arthroplasty. Arterial pO2 while the patient was breathing room air was measured at pre-operative day and 5 post-operative day using a Blood Gas Analyzer. Selection of patients for perfusion/ventilation scan during this study was dependent on the results of arterial blood gas determination that was more than 10 mmHg depression Of arterial pO2 level after surgery. More than depression of that was occurred in 11 patients (17.7%). Eight of them (72.7%) detected abnormalities (V/Q mismatch) in perfusion/ventilation scan, and we diagnosed them PE. More than 70% of PE was detected by only estimating the pre and post-operative arterial pO2. It was concluded that the estimation of arterial pO2 (pre and post-operation) was useful for the detection of PE, and combining estimation of arterial pO2 with the clinical feature evaluation method, low-invasive diagnosis and rapid treatment should be possible.

[Transient left ventricular dysfunction is still present one hour after exercise stress test: evaluation by gated SPECT with 99mTc-labeled perfusion agent].

It has been reported that quantitative gated SPECT (QGS) has revealed post-stress dysfunction of the left ventricle (LV) 30 minutes after a stress test. The purpose of this study was to determine whether post-stress dysfunction of LV is still present one hour after an exercise stress test. The subjects comprised 152 patients (124 males and 28 females, mean age 59 +/- 10 years). Exercise stress myocardial scintigraphy was performed using a one-day, stress and rest protocol. 99mTc labeled myocardial perfusion tracer, tetrofosmin, 370 MBq was injected at the end-point of a supine ergometer stress test for stress imaging. ECG gated SPECT was carried out 1 hour after injection. Three hours later, 740 MBq to 1100 MBq of 99mTc labeled myocardial perfusion tracer was injected for rest imaging. ECG gated SPECT was again performed 1 hour after injection. We divided the subjects into four groups according to the severity score of defects on the stress image and the presence or absence of fill-in; normal (NOR, n = 59), myocardial infarct (MI, n = 65), small ischemia (S-IS, n = 13) and large ischemia (L-IS, n = 15). Post-stress dysfunction is defined according to two criteria: 1) rest LVEF--post-stress LVEF > or = 5% and 2) post-stress ESV--rest ESV > or = 5 ml. The frequency of post-stress dysfunction was 3.4%, 9.1%, 23.1% and 40% in NOR, MI, S-IS and L-IS, respectively. Post-stress LV dysfunction was found to be more frequent in the large ischemia group. In conclusion, post-stress dysfunction was present 1 hour after the stress test and was more frequent in the large ischemia group.

Total elbow arthroplasty with use of a nonconstrained humeral component inserted without cement in patients who have rheumatoid arthritis.

BACKGROUND: Most total elbow prostheses that are currently in use require cement for fixation of each component. We developed a new (type-5) prosthesis that does not need cement for fixation. METHODS: The humeral component is made of cobalt-chromium alloy, and its stem is porous-coated with a plasma spray of titanium alloy. There are two options for the ulnar component: an all-polyethylene type and a metal-backed type with a porous-coated stem. Forty-three elbows in thirty-seven patients who had rheumatoid arthritis were treated with total elbow replacement arthroplasty with use of the type-5 prosthesis. The humeral component was implanted without cement in all elbows, whereas the ulnar component was implanted without cement in eleven elbows and was fixed with cement in the remaining thirty-two. The elbows were followed for an average of three years and ten months (range, two years and six months to five years and six months). RESULTS: The clinical results were assessed according to a modification of the Mayo Clinic Performance Index. At the time of the latest follow-up, the overall result was excellent for six elbows, good for thirty-one, and fair for six. All elbows had been rated as poor before the operation. There was almost complete relief of pain in twenty-nine elbows and mild or occasional pain in the remaining fourteen. Flexion increased markedly, from an average of 104 degrees preoperatively to an average of 133 degrees postoperatively; this difference was highly significant (p < 0.001, Student t test). In contrast, extension (flexion contracture) worsened slightly, from an average of 38 degrees preoperatively to an average of 42 degrees postoperatively; this difference was significant (p < 0.05). There was one postoperative dislocation of the elbow, and ectopic bone formed in another, with recurrence of ankylosis. Both elbows had a reoperation, and a good result eventually was obtained. There were no instances of postoperative infection or neuropathy of the ulnar nerve. Radiographically, there were no radiolucent lines at the bone-metal interface of any of the humeral or ulnar stems that had been implanted without cement, suggesting solid fixation by osseointegration. CONCLUSIONS: The results of total elbow arthroplasty with use of this prosthesis appear promising. There was a high rate of relief of pain as well as of restoration of adequate function in patients in whom the elbow was severely affected by rheumatoid arthritis.

Purification and characterization of a feruloylesterase from Aspergillus awamori.

A feruloylesterase was purified from the extracellular broth of Aspergillus awamori grown on wheat bran culture. The purified enzyme gave a single band on SDS-polyacrylamide gel electrophoresis and isoelectric focusing, with an apparent M(r) of 35,000 and a pI of 3.8, respectively. The substrate specificity of the purified enzyme differed obviously from that of acetylesterase of A. awamori. The enzyme bound to microcrystalline cellulose.

Left coronary artery-left ventricle fistula with right coronary artery spasm.

A 72-year-old woman was admitted to our hospital for evaluation of chest pain. Coronary angiography showed a left coronary artery-left ventricle fistula. An acetylcholine provocation test induced vasoconstriction of the right but not the left coronary artery. Her chest pain was not relieved by combined therapy with isosorbide dinitrate, diltiazem and nicorandil. Because of the coronary spasm, beta-blockers could not be used. However, her chest pain was relieved after the administration of a minor tranquilizer. Thus, the patient's chest pain was unlikely to be associated with either the fistula or the coronary spasm.

An Aspergillus awamori acetylesterase: purification of the enzyme, and cloning and sequencing of the gene.

An inducible acetylesterase was purified from the culture medium of Aspergillus awamori strain IFO4033 growing on wheat-bran culture by ion-exchange, gel-filtration and hydrophobic-interaction chromatographies. The purified enzyme had an Mr of 31000 and contained Asn-linked oligosaccharides. The enzyme liberated acetic acid from wheat bran, hydrolysed only alpha-naphthyl acetate and propionate when aromatic esters were used for the substrate, and was tentatively classified as a carboxylic esterase (EC 3.1.1.1). The gene encoding acetylesterase was cloned and sequenced. The deduced amino acid sequence showed that acetylesterase was produced as a 304-amino-acid-residue precursor, which was converted post-translationally into a 275-amino-acid-residue mature protein. Part of the sequence of acetylesterase was similar to the region near the active-site serine of lipases of Geotrichum candidum and Candida cylindracea. A unique site of putative Asn-linked oligosaccharides was presented.

Infection with hepatitis GB virus C in patients on maintenance hemodialysis.

BACKGROUND: A recently discovered non-A-E hepatitis virus has been designated hepatitis GB virus C (HGBV-C), but little is known about its mode of transmission and its clinical manifestations. We studied 519 patients on maintenance hemodialysis to determine whether they were infected with HGBV-C. METHODS: HGBV-C RNA was identified in serum by a reverse-transcription-polymerase-chain-reaction assay with nested primers deduced from a non-structural region. A nucleotide sequence of 100 bp in the nonstructural region was determined on HGBV-C clones. RESULTS: HGBV-C RNA was detected on 3.1 percent of the patients on hemodialysis (16 of 519), as compared with 0.9 percent of healthy blood donors (4 of 448, P<0.03). None of the 16 patients had evidence of active liver disease, although 7 were also infected with hepatitis C virus. Eight patients with HGBV-C infection were followed for 7 to 16 years. In two patients the virus was present at the start of hemodialysis. One had a history of transfusion, and HGBV-C persisted over a period of 16 years; the other became free of HGBV-C after 10 years. In five patients, HGBV-C RNA was first detected 3 to 20 weeks after blood transfusion and persisted for up to 13 years. One patient with no history of transfusion was infected with an HGBV-C variant with the same sequence as in two of the patients with post-transfusion HGBV-C infections. CONCLUSIONS: Patients on maintenance hemodialysis are at increased risk for HGBV-C infection. This virus produces persistent infections, which may be transmitted by transfusions but may also be transmitted by other means.

Cloning and sequencing of cellulase cDNA from Aspergillus kawachii and its expression in Saccharomyces cerevisiae.

The cDNA encoding the endo-beta-1,4-glucanase (carboxymethylcellulase; CMCase-I) from Aspergillus kawachii IFO 4308 was cloned. Nucleotide-sequence analysis of the cloned cDNA insert showed a 717-bp open reading frame that encoded a protein of 239 amino-acid residues. The predicted amino-acid sequence of the mature protein had considerable homology with the protein sequence of the FI-CMCase of Aspergillus aculeatus. The cDNA was introduced into Saccharomyces cerevisiae. The expressed enzyme had carboxylmethylcellulase activity, identified by clear zones on a CMC-agar plate after Congo Red staining.

Cholesterol emboli following percutaneous transluminal coronary angioplasty as speculated by toe skin biopsy.

A 55-year-old man required hemodialysis for acute renal failure 3 days after repeat percutaneous transluminal coronary angioplasty (PTCA). Bilateral acrocyanosis and necrotic lesions of the toes occurred 10 days after PTCA. Skin biopsy samples revealed needle-shaped cholesterol crystals of the intraluminal clefts in his small arteries. He was diagnosed with cholesterol emboli presenting as blue toe syndrome. The conditions improved with anticoagulation and vasodilation, but improvement in renal function was temporary. He later required maintenance hemodialysis. Cholesterol emboli following PTCA are life threatening because they are difficult to diagnose and can cause severe complications.