Spin and orbital contributions to magnetically ordered moments in 5d layered perovskite Sr2IrO4.

The ratio of orbital (L) and spin (S) contributions to the magnetically ordered moments of a 5d transition metal oxide, Sr2IrO4 was evaluated by nonresonant magnetic x-ray diffraction. We applied an improved experimental setting that minimized the experimental error, in which we varied only the linear polarization of incident x ray at a fixed scattering angle. Strong polarization dependence of the intensity of magnetic diffraction was observed, from which we conclude that the ordered moments contain substantial contribution from the orbital degree of freedom with the ratio of /∼5.0, evidencing the pronounced effect of spin-orbit coupling. The obtained ratio is close to, but slightly larger than the expected value for the ideal J(eff) = 1/2 moment of a spin-orbital Mott insulator, ||/|| = 4, which cannot be accounted for by the redistribution of orbital components within the t(2g) bands associated with the elongation of the IrO6 octahedra.

A-type antiferro-orbital ordering with I4(1)/a symmetry and geometrical frustration in the spinel vanadate MgV2O4.

We conduct a detailed structural analysis of the S=1 pyrochlore antiferromagnet MgV2O4, which exhibits an antiferromagnetic ordering marginally at TN=40 K, triggered by a structural transition from cubic to tetragonal symmetry at TS=62 K, using high resolution synchrotron x-ray diffraction and convergent beam electron diffraction. We reveal that the tetragonal phase below TS has the symmetry of I4(1)/a and that the distortion pattern of VO6 octahedra is consistent with A-type antiferro-orbital ordering with alternating stacking of layers with yz/xy orbital chains and zx/xy orbital chains along the tetragonal c axis. This implies that an anisotropic coupling of V moments produced by the orbital ordering below TS primarily brings about the antiferromagnetic ordering.

Tetrahedral magnetic order and the metal-insulator transition in the pyrochlore lattice of Cd2Os2O7.

Cd2Os2O7 shows a peculiar metal-insulator transition at 227 K with magnetic ordering in a frustrated pyrochlore lattice, but its magnetic structure in the ordered state and the transition origin are yet uncovered. We observed a commensurate magnetic peak by resonant x-ray scattering in a high-quality single crystal. X-ray diffraction and Raman scattering experiments confirmed that the transition is not accompanied with any spatial symmetry breaking. We propose a noncollinear all-in-all-out spin arrangement on the tetrahedral network made of Os atoms. Based on this we suggest that the transition is not caused by the Slater mechanism as believed earlier but by an alternative mechanism related to the formation of the specific tetrahedral magnetic order on the pyrochlore lattice in the presence of strong spin-orbit interactions.

Two-dimensional Heisenberg behavior of J(eff)=1/2 isospins in the paramagnetic state of the spin-orbital Mott insulator Sr2IrO4.

The dynamical correlations of J(eff)=1/2 isospins in the paramagnetic state of spin-orbital Mott insulator Sr2IrO4 were revealed by resonant magnetic x-ray diffuse scattering. We found a two-dimensional antiferromagnetic fluctuation with a large in-plane correlation length exceeding 100 lattice spacings at even 20 K above the magnetic ordering temperature. In marked contrast to the naive expectation of the strong magnetic anisotropy associated with an enhanced spin-orbit coupling, we discovered an isotropic isospin correlation that is well described by the two-dimensional S=1/2 quantum Heisenberg model. The estimated antiferromagnetic coupling constant as large as J∼0.1 eV that is comparable to the small Mott gap (<0.5 eV) points out the weak and marginal Mott character of this spin-orbital entangled system.

Measurement of the ßß decay half-life of 130Te with the NEMO-3 detector.

We report results from the NEMO-3 experiment based on an exposure of 1275 days with 661 g of (130)Te in the form of enriched and natural tellurium foils. The ßß decay rate of (130)Te is found to be greater than zero with a significance of 7.7 standard deviations and the half-life is measured to be T(½)(2ν) = [7.0 ± 0.9(stat) ± 1.1(syst)] × 10(20) yr. This represents the most precise measurement of this half-life yet published and the first real-time observation of this decay.

Phase-sensitive observation of a spin-orbital Mott state in Sr2IrO4.

Measurement of the quantum-mechanical phase in quantum matter provides the most direct manifestation of the underlying abstract physics. We used resonant x-ray scattering to probe the relative phases of constituent atomic orbitals in an electronic wave function, which uncovers the unconventional Mott insulating state induced by relativistic spin-orbit coupling in the layered 5d transition metal oxide Sr2IrO4. A selection rule based on intra-atomic interference effects establishes a complex spin-orbital state represented by an effective total angular momentum = 1/2 quantum number, the phase of which can lead to a quantum topological state of matter.

First results of the search for neutrinoless double-beta decay with the NEMO 3 detector.

The NEMO 3 detector, which has been operating in the Fréjus underground laboratory since February 2003, is devoted to the search for neutrinoless double-beta decay (beta beta 0v). The half-lives of the two neutrino double-beta decay (beta beta 2v) have been measured for 100Mo and 82Se. After 389 effective days of data collection from February 2003 until September 2004 (phase I), no evidence for neutrinoless double-beta decay was found from approximately 7 kg of 100Mo and approximately 1 kg of 82Se. The corresponding limits are T1/2(beta beta0v) > 4.6 x 10(23) yr for 100Mo and T1/2(beta beta 0v) > 1.0 x 10(23) yr for 82Se (90% C.L.). Depending on the nuclear matrix element calculation, the limits for the effective Majorana neutrino mass are < 0.7-2.8 e/v for 100Mo and < 1.7-4.9 eV for 82Se.

Ferro-type orbital state in the Mott transition system Ca2-xSrxRuO4 studied by the resonant x-ray scattering interference technique.

We have succeeded in detecting ferro-type orbital states in Ca2-xSrxRuO4, which is the first outcome in a 4d Mott transition system by the resonant x-ray scattering interference technique. For x=0 (Mott insulator), the resonant signal for d(xy) orbital ordering is observed even at room temperature, in which the Jahn-Teller distortion is negligible. The signal disappears near the metal-insulator transition. On the other hand, in a metallic phase for x=0.5, orbital polarization with d(yz/zx) character dominates. With lowering temperature, the magnitude of the resonant signal slightly decreases owing to the additional influence of the gamma band with d(xy) character.

[Postoperative epidural fentanyl administration in patients for hysterectomy with para-aortic lymph node resection].

In our experience, continuous epidural administration of fentanyl in doses of 12.5 micrograms.h-1, has not been sufficient to relieve postoperative pain in patients after hysterectomy with para-aortic lymph node resection. Thus, a prospective, randomized, single-blind study was performed to compare the analgesic efficacy of fentanyl 25 micrograms.h-1 with 12.5 micrograms.h-1 in these patients for 48 hours after surgery. Twenty-one women undergoing hysterectomy with para-aortic lymph node resection were allocated into three groups; Group C (control, n = 7): fentanyl 12.5 micrograms.h-1, infusion rate 2 ml.h-1, Group S2 (double speed, n = 7): fentanyl 25 micrograms.h-1, infusion rate 4 ml.h-1, and Group C2 (double concentration, n = 7): fentanyl 25 micrograms.h-1, infusion rate 2 ml.h-1. At postoperative 0, 2, 6, 12, 24, and 48 hours, the degree of analgesia was evaluated by visual analogue scale (VAS) and verbal pain scores at both rest and movement. Groups S2 and C2 showed significantly lower VAS scores than group C at the postoperative 6- and 24-hour points. At movement, the analgesic efficacy was not sufficient in any groups, but, at rest, groups S2 and C2 experienced significantly less pain than the group C. The degree of pain relief was not different between groups S2 and C2. In conclusion, epidural fentanyl 25 micrograms.h-1 provided significantly superior analgesia compared with epidural fentanyl 12.5 micrograms.h-1.

[Epidural catheterization dose not meet our expectation].

According to the roentgenographically confirmed intervertebral space at which an epidural catheter was placed, 241 patients who underwent abdominal or orthopedic hip surgery were allocated into 3 groups. Groups A, B, and C received epidural catheterization at Th7-10, Th10-L1, and L1-4, respectively. In each group, we examined the intervertebral space, which the anesthesiologist who had placed epidural catheter had determined, and the one which had been confirmed roentgenographically. We also investigated the catheter movement during the postoperative period. Catheters were barely placed at the same intervertebral space which had been confirmed roentgenographically. Considering the iliac crest as a landmark of L3-4 intervertebral space, the puncture point agreed with the roentgenographically confirmed intervertebral space with a percentage of 33 in group A. The extent of agreement increased up to 47 and 55 percent, in groups B and C, respectively. In contrast, when we counted down from the cervical prominent vertebra, a landmark of C7, the agreement was better in group A (55%) than in group C (33%). In the postoperative period, catheters came out more frequently in groups A and B than in group C, resulting from the early ambulation in abdominal surgery groups. There results suggest that, to place the epidural catheter more properly, (1) we should start to count from the landmark which is close to the puncture point and (2) we should keep it in mind that catheters come out accidently in patients who are encouraged to ambulate in the early postoperative period.

[Intraoperative ST-T depression during extreme hemodilution].

A 45 year old woman undergoing a removal of cerebral arterio-venous malformation, suffered an unexpected massive bleeding. With transfusion of plasma constituents, her hemoglobin concentration decreased to about 5 g.dl-1, but her hemodynamic parameters remained unchanged. Electrocardiogram showed a depressed ST segment, indicating myocardial ischemia, when hemoglobin concentration decreased to 2.2 g.dl-1. Accompanied with the ECG change, her blood pressure fell down from 110/70 mmHg to 70/40 mmHg and an elevation of CVP was observed. With rapid transfusion of concentrated red cell and whole blood, hemodynamic parameters as well as ECG change were restored to normal. With hemodilutional myocardial ischemia which is caused by acute massive bleeding, hemoglobin concentration of about 2 g.dl-1 would be critical.

[Anesthetic management using percutaneous cardiopulmonary support for cesarean section in a patient with severe pulmonary hypertension].

A 27-year-old female with severe pulmonary hypertension was scheduled to undergo an elective cesarean section at the 32-week gestational age. Since the preoperative assessment revealed that the patient could not tolerate the hemodynamic changes during the operation under general anesthesia without any cardiopulmonary support, the percutaneous cardiopulmonary support (PCPS) with a centrifugal pump was applied for the anesthetic management of the patient during the operation. After the induction of anesthesia, percutaneous cannulation was performed via the femoral artery and vein, and the PCPS was started with an assisted flow ranged 1.5-2.0 l.min-1. Then, the operation was performed, during which the cardiopulmonary function of the patient was well maintained with the aid of the PCPS. The operation was finished uneventfully, and the patient could successfully emerge from the PCPS immediately after the operation. The PCPS is thought to be very useful for the anesthetic management of the patients with poor cardiopulmonary tolerance.

[Anesthetic management and neurological outcomes of patient for open heart surgery with infective endocarditis and neurological complications].

No reports have focused on neurological outcomes after open heart surgery of patients with infective endocarditis (IE) and neurological complications. We evaluated parameters related to anesthetic management and neurological outcomes. The subjects analyzed were 24 patients who had undergone valvular surgeries under hypothermic cardiopulmonary bypass from April 1978 to December 1990. The patients were divided into two groups according to the interval between onset of neurological complication and the time of operation: 1) acute group (within one month before the surgery: n = 11, 9.4 +/- 9 days; means +/- SD) and 2) chronic group (more than one month before the surgery: n = 13, 120 +/- 80 days). After heart surgery, 5 patients in the acute group showed newly developed neurological abnormality including death from hemorrhagic transformation, hemiplegia or aphasia. No patients in the chronic group had newly developed neurological abnormality related to the surgery. In the neurologically deteriorated patients of the acute group, interval from the onset of neurological complication to surgery was 3.5 +/- 4.5 days, whereas that of the remainders of the acute group was significantly longer (14.4 +/- 9.0 days). Intraoperative events and anesthetic management of these patients were also analyzed. However, there were no significant differences in the parameters such as cerebral perfusion pressure, arterial PaCO2, doses of anesthetics and use of vasopressors. Our results suggest that the most important factor which may influence neurological outcome was the interval between the onset of neurological abnormality and the time of operation.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of midazolam and flumazenil on carotid sinus baroreflex control of circulation in rabbits.

We have studied the effects of midazolam and flumazenil on the carotid sinus baroreflex, by examining mean arterial pressure (MAP) and heart rate (HR) responses to partial or complete bilateral carotid occlusion (BCO) in 12 conscious rabbits after aortic denervation. In eight rabbits, the responses to complete BCO were evaluated before and after cumulative doses of midazolam 0.5 and 1.0 mg kg-1, and after flumazenil 0.3 mg kg-1 following administration of midazolam. Midazolam and flumazenil had no effect on MAP or HR before complete BCO and neither affected the MAP response to complete BCO. Midazolam 0.5 and 1.0 mg kg-1 decreased the HR response to 60% and 58% of control, respectively. Flumazenil restored the midazolam-induced depression of the HR response to the control level. In the other four rabbits, we examined the MAP and HR responses to partial BCO (carotid artery pressure reduced by 5, 10 and 20 mm Hg) before and after midazolam 0.5 mg kg-1 and after flumazenil 0.3 mg kg-1 following administration of midazolam. The response to partial occlusion showed the same tendency as the response to complete BCO. These results indicate that midazolam attenuated the HR response of the carotid sinus baroreflex, flumazenil restored this midazolam-induced depression and neither drug affected the MAP response.

Internal jugular bulb blood velocity as a continuous indicator of cerebral blood flow during open heart surgery.

BACKGROUND: Most techniques for measuring cerebral blood flow (CBF) can not be performed rapidly enough to detect sudden changes in CBF. However, measurement of internal jugular bulb (IJB) blood velocity may offer real-time information on changes in CBF. In the current study, we measured IJB blood velocity and CBF in anesthetized humans. METHODS: In protocol 1, IJB blood velocity was continuously measured using an intravascular Doppler catheter during cardiac surgery under hypothermic cardiopulmonary bypass (CPB). CBF values obtained with a Kety-Schmidt method using inhalation of 30% argon in oxygen gas were compared with concurrent IJB blood velocity values in ten patients. A 3-French intravascular Doppler catheter was placed in the right IJB, and CBF measurements were made before CPB, in a stable hypothermic period during CPB, at rewarming during CPB, and after CPB. In protocol 2, dimensions of right IJB were observed before and during CPB using an intravascular rotating A scan ultrasonic catheter (5-French) in three patients. RESULTS: IJB blood velocity responded quickly to changes in arterial pressure or body temperature during CPB. The percent change in IJB blood velocity relative to pre-CPB value showed a good linear correlation with the percent change in CBF (%CBF = 0.87 x %IJB velocity + 17, r = 0.87). The mean difference between percent changes in CBF and IJB blood velocity was -5.6% and the standard deviation was 16%. Despite a large reduction in arterial pressure or IJB pressure, there were no significant changes in the IJB dimension. CONCLUSIONS: The results suggest that IJB blood velocity may represent a clinically useful monitor of changes in CBF in anesthetized humans.

Accuracy of continuous jugular bulb venous oximetry during cardiopulmonary bypass.

We evaluated the accuracy of fiberoptic catheter oximetry in the jugular bulb during conditions of normothermia, hemodilution, and hypothermia in 11 patients who underwent cardiac surgery with cardiopulmonary bypass (CPB). An oximetry catheter was inserted into the right jugular bulb under general anesthesia, calibrated by the in vitro (n = 7) or in vivo (n = 4) mode. Jugular bulb oxygen saturation (SjO2) with the catheter oximeter was compared with a concurrent laboratory CO-oximeter value from a blood sample during surgery. Nasopharyngeal temperature (NPT) and hemoglobin concentration (Hb) were also measured. The oximetric catheter SjO2 correlated closely with the CO-oximeter determinations in both calibration modes (in vitro, r2 = 0.88; in vivo; r2 = 0.96). Data in the in vitro calibrated group were grouped into three conditions; 1) normothermia and no hemodilution, 2) normothermia and hemodilution, and 3) hypothermia and hemodilution, and showed good correlations between SjO2 values measured by the two methods (r2 = 0.90, r2 = 0.81, r2 = 0.79, respectively). The difference in SjO2 values by the two methods was not significantly affected by changes in NPT and Hb during CPB. In conclusion, the continuous SjO2 monitoring with catheter oximetry during CPB would be accurate and reliable under either calibration mode. Moderate hypothermia and hemodilution during CPB did not significantly influence the accuracy.

Cerebral vascular reactivity to carbon dioxide before and after cardiopulmonary bypass in children with congenital heart disease.

We examined cerebral vascular reactivity to carbon dioxide before and after cardiopulmonary bypass in 15 pediatric patients aged 2 to 9 years undergoing cardiac operations. Cerebral vascular reactivity was noninvasively assessed by transcranial Doppler ultrasonography. The cerebral blood flow velocity was plotted as a function of arterial carbon dioxide partial pressure. An exponential function was fitted for these plots and an exponent of curve was defined as the cerebral vascular reactivity to carbon dioxide. There was no significant change in this reactivity after cardiopulmonary bypass as compared with before bypass (before 0.028 +/- 0.003; after 0.030 +/- 0.016). For the entire series, we obtained best-fit curves of y = 2.8e0.046x (r = 0.91) and y = 3.4e0.031x (r = 0.89) (x; arterial carbon dioxide partial pressure, y; percent changes of cerebral blood flow velocity) before and after cardiopulmonary bypass. We conclude that the cerebral vascular reactivity to carbon dioxide was preserved before and after cardiopulmonary bypass in children undergoing cardiac operations. These results suggest that cerebral perfusion before and after cardiopulmonary bypass is not critically compromised.

Effects of vasopressin on the response to carotid occlusion in conscious rabbits.

To investigate the interaction between arginine vasopressin and the carotid sinus baroreflex, hemodynamic responses to bilateral carotid occlusion and to controlled reductions in carotid sinus pressure were examined. In the control state and during vasopressin infusion in conscious rabbits, mean arterial pressure, heart rate, mean aortic flow and total peripheral resistance were measured. Vasopressin infusion at 5 or 10 ng/kg/min did not raise arterial pressure, but increased resistance, and decreased heart rate and aortic flow in a dose-dependent manner. The pressure and resistance responses to carotid occlusion or changes in carotid pressure were not altered by vasopressin. The heart rate response was augmented significantly from 23 +/- 5 (mean +/- S.E.) to 40 +/- 8 and 43 +/- 8 beats/min with infusion of 5 and 10 ng/kg/min of vasopressin. Vasopressin did not augment the gain of carotid sinus reflex control of arterial pressure (3.7 +/- 0.5 in control and 3.5 +/- 0.5 during 5 ng/kg/min of vasopressin). With vasopressin infusion at 5 ng/kg/min, following vagal blockade with methylatropine both the arterial pressure and the heart rate responses to carotid pressure changes decreased to 73% and 32% of the response before blockade. The data indicate that vasopressin has little effect on control of arterial pressure by the carotid sinus baroreflex in conscious rabbits when vagal responses are activated.

Effects of sevoflurane on cerebral circulation and metabolism in patients with ischemic cerebrovascular disease.

BACKGROUND: Sevoflurane is a newly developed volatile anesthetic that has a low blood-gas partition coefficient. The effects of sevoflurane on the cerebral circulation or metabolism in humans have not been studied. The authors examined the cerebral blood flow (CBF) and cerebral metabolic rate for oxygen (CMRO2) during sevoflurane anesthesia. The carbon dioxide response and autoregulation of cerebral circulation were also examined. METHODS: Ten patients with ischemic cerebrovascular disease undergoing extra-intracranial artery anastomosis were studied. Cerebral blood flow and CMRO2 were determined by the Kety-Schmidt method using argon. These procedures were performed during the inhalation of 33% N2O, 33% argon, and oxygen with 1.5% sevoflurane (0.88 minimum alveolar concentration). To examine the relationship of CBF to a change in PaCO2, CBF was measured repeatedly at steady state PaCO2, of 40, 35, and 45 mmHg. Furthermore, CBF was measured before and after an increase in mean arterial pressure (MAP) caused by intravenous infusion of methoxamine to determine the relationship between CBF and MAP. RESULTS: Cerebral blood flow and CMRO2 were 28 +/- 4 ml x 100 g-1 x min-1 and 1.34 +/- 0.23 ml x 100 g-1 x min-1, respectively. Cerebral blood flow was found to vary directly with PaCO2 alteration. The slope of the regression line between PaCO2 and CBF was 1.29 ml x 100 g-1 x min-1 x mmHg-1. On the other hand, CBF was constant throughout the elevation of MAP with vasopressor. CONCLUSIONS: Both carbon dioxide response and cerebral autoregulation were well maintained under 0.88 MAC sevoflurane anesthesia in patients with ischemic cerebrovascular disease.