Anharmonic force constants extracted from first-principles molecular dynamics: applications to heat transfer simulations.

A systematic method to calculate anharmonic force constants of crystals is presented. The method employs the direct-method approach, where anharmonic force constants are extracted from the trajectory of first-principles molecular dynamics simulations at high temperature. The method is applied to Si where accurate cubic and quartic force constants are obtained. We observe that higher-order correction is crucial to obtain accurate force constants from the trajectory with large atomic displacements. The calculated harmonic and anharmonic force constants are, then, combined with the Boltzmann transport equation (BTE) and non-equilibrium molecular dynamics (NEMD) methods in calculating the thermal conductivity. The BTE approach successfully predicts the lattice thermal conductivity of bulk Si, whereas NEMD shows considerable underestimates. To evaluate the linear extrapolation method employed in NEMD to estimate bulk values, we analyze the size dependence in NEMD based on BTE calculations. We observe strong nonlinearity in the size dependence of NEMD in Si, which can be ascribed to acoustic phonons having long mean-free-paths and carrying considerable heat. Subsequently, we also apply the whole method to a thermoelectric material Mg2Si and demonstrate the reliability of the NEMD method for systems with low thermal conductivities.

Two-dimensional intrinsic ferromagnetism at nitride-boride interfaces.

We predict theoretically novel two-dimensional interface ferromagnetism at AlN/MgB(2)(0001) using first-principles calculations, where the interface is employed as an ordered structure of spin sites instead of point defects. Although N dangling bonds are apparently saturated, interfacial states exhibit spin polarization. Hund's coupling of the two N p(∥) orbitals as well as low density of states at the Fermi energy contribute to strong band ferromagnetism. Furthermore, first-principles electron transport calculations demonstrate that this interfacial spin polarization is responsible for quantum spin transport. The magnetization can be controlled by applied gate bias voltages.

Quantum electron transport through ultrathin Si films: effects of interface passivation on Fermi-level pinning.

We report first-principles calculations on electron transport through ultrathin silicon films between aluminum electrodes. The passivation of interface Si atoms at one side of the film with hydrogen makes the current-voltage characteristics asymmetric with quasirectifying properties. The low conductivity in this case can be explained by the weakened metal-induced gap states due to the passivation. We also demonstrate that the applied bias changes the strength of Fermi-level pinning for the passivated interface.

Charging of molecules during transport.

The possibility that a single molecule can acquire charge during steady-state transport is an open issue. We report first-principles calculations in a range of configurations of certain molecules and conclude the following. When a molecule is strongly coupled to the electrodes, charging is not sustainable. On the other hand, by using variable-length tunnel barriers (insulating tethers) one can enable and control charging. In particular, by using different combinations of "tethers", we demonstrate the possibility of charging by a single electron, sustainable over a wide bias range, and also the possibility of continuous linear charging when a gate voltage is applied.

Total energy distribution of field-emitted electrons from Al(100) surface with single-atom terminated protrusion.

We have analyzed field electron emission from Al(100) surfaces with a single-atom terminated protrusion on the basis of the density functional theory combined with real space scattering theory. We have obtained multiple peaks in total energy distribution of emission current from such a pure-metallic protrusion. Furthermore, we have also found that multiple peaks become pronounced as the size of a protrusion becomes larger, which explains the discrepancy among experiments. All the above results can be understood from two factors, the existence of localized states at the topmost Al atom and the potential barrier reduction in front of the topmost atom.

[A clinical study of posttraumatic hydrocephalus].

From 1989 to 1998, 721 patients with head injury were admitted to our department and 22 (3.1%) of them developed posttraumatic hydrocephalus. These patients included 16 males and 6 females, ranging in age from 17 to 86 years (mean age, 66 yrs) with peak incidence in the eighth decade. CT scan on admission immediately after head injury showed subarachnoid hemorrhage (SAH) in 18 cases. The other 4 cases without SAH had once suffered head injuries severe enough to give rise to consciousness disturbance. The typical clinical symptoms of hydrocephalus were observed in only 5 (23%) patients, and in the other 17 cases prolonged or deteriorated of consciousness disturbance were the main symptoms. Hydrocephalus was diagnosed between 1 and 3 months in 15 cases and in 7 cases after 4 months. Clinical improvement has been seen in 17 (77%) cases and marked recovery of consciousness was achieved in 12 cases after V-P shunt, but 5 cases with severe disturbance of consciousness revealed no improvement of clinical signs even after decrease of ventricular size. These results indicate that elderly patients with traumatic SAH should be followed up for at least 4 to 5 months, paying attention to development of hydrocephalus, and V-P shunt would be effective to improve consciousness disturbance in most of the cases.

Self-consistent density functional calculation of field emission currents from metals

We have developed a fully self-consistent method which is suitable to examine field emission currents, on the basis of the density functional theory. In our method, the nearby counterelectrode is not necessary. By using this method, we have investigated field emission currents from a biased metallic surface represented by the jellium model. We have found that the energy barrier between the jellium and vacuum becomes lower than the Fermi energy under strong electric fields (e.g., 10 V/nm for r(s) = 4 bohr). In this situation, the slope of the Fowler-Nordheim plot becomes flatter than that under a weaker field.

Tetrahydrobiopterin inhibits copper-induced oxidation of low density lipoprotein.

The effect of tetrahydrobiopterin (BPH4) on Cu2+-induced oxidation of low density lipoprotein (LDL) prepared from rabbit plasma was examined. BPH4 (0.5-10 microM) inhibited the formation of thiobarbituric acid-reactive substances (TBARS) in LDL induced by 5 microM Cu2+ in a dose-dependent manner. BPH4 also suppressed the increase in relative electrophoretic mobility (REM) of LDL in the presence of 5 microM Cu2+. The potency of inhibitions of BPH4 on TBARS formation and REM was the same as or stronger than that of ascorbic acid and alpha-tocopherol, which are known as endogenous inhibitors of LDL oxidation. These results suggest that BPH4 could act as an efficacious endogenous inhibitor of atherogenic LDL modification.

Role of type III iodothyronine 5-deiodinase gene expression in temporal regulation of Xenopus metamorphosis.

To elucidate the role of type III iodothyronine 5-deiodinase (5-D) in the temporal regulation of amphibian metamorphosis, the regulation of gene expression of 5-D and thyroid hormone receptor beta (TRbeta) in organs of Xenopus laevis was investigated. High levels of TRbeta mRNA in the respective organs were observed at the times of their major morphological changes. Expression of the 5-D gene was highly regulated among the organs during metamorphosis, including up-regulation in the tail and down-regulation in the liver. The tail and liver expressed 5-D gene before their metamorphic changes. These precocious expressions correlated with the lower responsiveness to exogenously added triiodo-L-thyronine (T3) for inducing a high level of TRbeta mRNA expression. However, the same organs responded to lower doses of T3 to regulate 5-D gene expression as seen in spontaneous metamorphosis. The induction of 5-D gene expression was considerably delayed in the intestine, even at an excess dose of T3. Thus, the two genes in a given organ appeared to respond to T3 either with different dose dependencies or with different timetables. The results obtained are also discussed in respect to recent findings in Rana catesbeiana.

Outcome after external decompression for massive cerebral infarction.

Acute ischemic stroke involving the entire vascular distribution of a carotid or middle cerebral artery can cause massive cerebral edema. This study evaluated external decompression for the treatment of massive stroke and analyzed possible prognostic factors. Twenty-four patients with acute massive cerebral infarction, which had progressed to tentorial herniation and impending death, underwent external decompression after medical therapy failed to achieve an effective response. The neurological outcome 2 months after surgery using the Glasgow Outcome Scale was severe disability in 14 patients, vegetative state in two, and death in eight. The overall mortality was 33%. Various characteristics (age, sex, etiology, side of hemispheric infarction, pupillary asymmetry, Japan Coma Scale, distribution of infarction, hemorrhagic infarction, midline shift, tentorial herniation) were evaluated to determine the factors associated with high mortality after surgical intervention. There was no statistically significant relationship between any variable and mortality. Mortality was especially high in the patients with preoperative consciousness level of 200, anterior, middle, and posterior cerebral artery territory infarction, and stage III of tentorial herniation. Postoperatively, all patients with severe disability returned to a clear level of consciousness. Six patients with dominant hemisphere stroke had some measure of communicative skills in spite of aphasia. External decompression is a life-saving treatment for patients with massive cerebral infarction and can provide a reasonable quality of life even for those with dominant hemisphere strokes. Decompressive surgery should be considered and performed as soon as possible if computed tomography demonstrates signs of descending tentorial herniation.

Synthesis and structure-activity relationships of CP-122,721, a second-generation NK-1 receptor antagonist.

The synthesis and SAR of benzylamine side chain analogs of the NK-1 receptor antagonist CP-99,994 are described. The 5-trifluoromethoxy analog, CP-122,721, shows superior in vivo blockade of NK-1 receptor mediated responses.

Percutaneous transluminal angioplasty for intracranial atherosclerotic stenosis.

SUMMARY: Eleven patients with symptomatic intracranial atherosclerotic stenotic lesions underwent percutaneous transluminal angioplasty (PTA). Seven patients had stenosis in M1 segment of the middle cerebral artery (MCA), two in the cavernous internal carotid artery, one in M2 segment of the MCA and one in the P2 segment of the posterior cerebral artery. Initial successful dilatation (less than 50% residual stenosis) was obtained in nine patients (81.8%). Permanent neurological deficit related to PTA was seen in one patient and transient symptoms were observed in two. Re-stenosis was revealed in two cases (18.2%) in the early followup period. All patients with successful dilatation and without re-stenosis never had TIA or stroke after PTA. Intracranial PTA is an effective procedure, but several problems remain to be solved.

Sinus pericranii associated with a cerebellar venous angioma--case report.

A 64-year-old male presented with sinus pericranii associated with a venous angioma draining through a large venous lake. Increased venous pressure and flow in the dural venous lake in contact with the venous sinus may have developed the sinus pericranii. Three-dimensional computed tomography was very useful in determining the site of the transcranial venous anastomotic channels, and magnetic resonance imaging was also very useful in detecting the intracranial vascular anomalies.

Progress in the management of patients with aneurysmal subarachnoid hemorrhage: a single hospital review for 20 years. Part I: Younger patients.

BACKGROUND: This study was carried out to clarify if there has been any improvement in the outcome of patients with aneurysmal subarachnoid hemorrhage during the past 20 years. Because elderly patients have apparently poorer prognoses than younger patients, patients older than 70 years were analyzed separately in the following article. METHODS: Five hundred seventy-one patients with aneurysmal subarachnoid hemorrhage, under 70 years, who were consecutively admitted to Kagawa Prefectural Central Hospital from July 1972 to December 1992, were reviewed. These patients were divided into four groups according to the time of admission. The ultimate outcome was evaluated by means of Glasgow Outcome Scale 6 months after the ictus. RESULTS: Changes in treatment protocol in this period included the induction of early surgery and the invention of a variety of modalities for the treatment of cerebral vasospasm. This resulted in a distinct increase in patients who actually underwent direct aneurysm clipping. Outcome has been significantly improved during this period, especially in patients with Hunt and Kosnik grade III (p<0.05, chi2). Patients in good clinical condition at follow-up (Glasgow Outcome Scale: good recovery) increased from 8.7% to 60.7%. Mortality decreased from 28.7% to 10.7%. CONCLUSIONS: Current therapeutic modalities have significantly improved the outcome of patients with aneurysmal subarachnoid hemorrhage. Rebleeding before early surgery remains as a major cause of unfavorable outcome and further progress on this subject is mandatory.

Progress in the management of patients with aneurysmal subarachnoid hemorrhage: a single hospital review for 20 years. Part II: Aged patients.

BACKGROUND: We have reported improvement in the outcome of the younger patients with aneurysmal subarachnoid hemorrhage in the preceding article. The purpose of this article is to study if the same management protocol has simultaneously benefited the elderly patients. METHODS: One hundred twenty-nine patients with aneurysmal subarachnoid hemorrhage, over 70 years old, who were consecutively admitted to Kagawa Prefectural Central Hospital from July 1972 to December 1992, were reviewed. Patient grouping and outcome evaluation were the same as those of younger patients. RESULTS: Changes in treatment protocol in this period, which were similar to those of the younger counterparts, resulted in an increased number of patients who actually underwent aneurysm clipping. Although the outcome evaluated at 6 months after initial hemorrhage was significantly poorer than that of the younger counterparts, there have been some improvements during the study period. Patients in good clinical condition at 6 months' follow-up (Glasgow Outcome Scale: Good Recovery) increased from 37.5% to 42.9% in grades I-II and from 0% to 23.1% in grade III, respectively. CONCLUSIONS: The improvement in the outcome of elderly patients was less remarkable than that observed in younger patients. Significantly higher incidence of preoperative rebleeding and postoperative symptomatic vasospasm has proven to be the major cause of mortality and major morbidity at present. More careful and sophisticated perioperative care is required in elderly patients with aneurysmal subarachnoid hemorrhage.

Combined cisternal drainage and intrathecal urokinase injection therapy for prevention of vasospasm in patients with aneurysmal subarachnoid hemorrhage.

The effect of cisternal drainage and intrathecal urokinase injection in preventing symptomatic vasospasm (SVS) after aneurysmal subarachnoid hemorrhage was studied in 60 patients with uniform background (Hunt & Kosnik grade III, younger than 70 yrs, undergoing surgery within 72 hrs after hemorrhage). The incidence of permanent neurological deficits caused by vasospasm was 5/16 without cisternal drainage, 5/34 with drainage alone, and 1/10 with drainage and urokinase injection. Analysis of patients without postoperative cisternal drainage showed the amount of subarachnoid clot on the initial computed tomographic scan was closely related to the occurrence of SVS (p < 0.05, unpaired t test). Analysis of patients with cisternal drainage showed the amount of bloody cerebrospinal fluid (CSF) drained during the 10 days after surgery and the duration of drainage placement were critical in preventing vasospasm (p < 0.05, unpaired t test). Greater CSF drainage significantly reduced the incidence of permanent neurological deficits caused by vasospasm (p < 0.01, chi 2), but significantly increased the incidence of hydrocephalus requiring shunt procedures (p < 0.01, chi 2). Urokinase injection via cisternal drainage achieved a further reduction in the occurrence of SVS. Intrathecal thrombolytic therapy after aneurysmal surgery is an effective method for SVS prophylaxis, and CSF drainage (> 1500 ml for 10 days) enhances the effect.

Long-term effects of cografts of pretransected peripheral nerve with adrenal medulla in animal models of Parkinson's disease.

Trophic factor supplementation has been reported to enhance the survivability of grafted adrenal chromaffin cells. Because the content of nerve growth factor in the distal stump of a pretransected peripheral nerve increases markedly 1 day after transection, we injected cografts of adrenal medulla with pretransected peripheral nerve into the striata of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mice and performed follow-up histological and neurochemical analyses over a 12-month period. Adrenal medullary chromaffin cells cografted with pretransected peripheral nerve survived better than in adrenal grafts alone at 1, 3, and 12 months after transplantation. Host dopaminergic fiber recovery adjacent to the grafts was more prominent in mice with cografts than in mice with adrenal grafts alone at 1 and 3 months after transplantation. Twelve months after transplantation, however, there was no significant difference between the two groups of animals because of the natural recovery of intrinsic dopaminergic fibers from MPTP toxicity. Dopamine concentration in the striata of cografted mice was higher than in mice with adrenal grafts alone at 1 month after transplantation. At 3 and 12 months after transplantation, the natural recovery of dopamine concentration from MPTP toxicity was apparent in both groups of animals and no significant difference was observed between the groups. We conclude that adrenal medullary chromaffin cells can survive for at least 12 months after grafting when cografted with pretransected peripheral nerve. Cografts enhanced the recovery of the host nigrostriatal dopaminergic system up to 3 months after transplantation, but this enhancement was not apparent at 12 months because of the natural recovery of dopaminergic fibers from MPTP toxicity.

Enhanced recovery of the nigrostriatal dopaminergic system in MPTP-treated mice following intrastriatal injection of basic fibroblast growth factor in relation to aging.

Studies have suggested that the restorative effects of adrenal medullary chromaffin cell grafts in animal models of Parkinson's disease may be related to trophic factors contained within the chromaffin cells. Basic fibroblast growth factor (bFGF) is present in chromaffin cells and has been shown to exert trophic effects on dopaminergic neurons in vitro. Basic FGF was stereotaxically injected into the striatum of young (2-month-old) and aging (12-month-old) C57BL/6 mice which had been treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) 1 week earlier. MPTP treatment reduced tyrosine hydroxylase (TH)-immunoreactive (IR) fibers in the striatum and striatal dopamine (DA) concentration in both the young and older mice 5 weeks later. Computerized image analysis of striatal DA fibers in young mice treated with bFGF showed significant recovery of DA fibers up to 600 microns from the injection site 5 weeks after MPTP administration. Striatal DA fibers in older mice treated with bFGF showed significant recovery only up to 300 microns from the injection site, and the degree of recovery was very limited compared with young mice. HPLC analysis of DA concentration revealed that striatal DA in young mice recovered significantly when treated with bFGF, but no significant recovery was observed in older mice. It is concluded that bFGF enhances the recovery of striatal DA systems from MPTP toxicity both in young and in older mice, but that such benefits are very limited in older mice.

[Postoperative pain relief by preanesthetic administration of buprenorphine suppository in elective mastectomy].

Seventy female patients scheduled for elective mastectomy were divided into three groups: Buprenorphine suppository (BPS) 0.4 mg group (n = 29); BPS 0.2 mg (n = 23) group; and control (scopolia extract and tannic acid suppository) group (n = 18). Suppositories were administered rectally to patients of each group one hour before induction of anesthesia. Plasma buprenorphine concentrations, sedation scores at entering the operating room, postoperative pain scores and side effects were evaluated. There were no significant differences in sedation effects of suppository among the three groups. Although there were significant differences in pain scores except at the time when patients left the operating room between BPS 0.2 mg group and the control group, postoperative pain relief in BPS 0.2 mg group was judged not enough. However, postoperative pain relief was more satisfactory in the BPS 0.4 mg group. Plasma concentrations of the BPS 0.4 mg group were higher than those of the BPS 0.2 mg group. Although nausea and vomiting were observed in 5 patients (17.2%) of the BPS 0.4 mg group and 4 patients (17.4%) of the BPS 0.2 mg group, respiratory depression and changes in blood pressure and heart rate were not observed in all groups. In conclusion, preanesthetic administration of the BPS 0.4 mg seemed to be useful for postoperative pain relief after elective mastectomy.