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.

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.

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.

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.

Adipogenesis inhibitory factor. A novel inhibitory regulator of adipose conversion in bone marrow.

Recombinant adipogenesis inhibitory factor (AGIF) was purified to homogeneity from the conditioned medium of COS-1 cells transfected with human AGIF cDNA. The amino-terminal sequence analysis of the mature AGIF revealed that AGIF was produced as a precursor consisting of 199 amino acids and processed into a mature form of 178 amino acids by a cleavage between Ala(-1) and Pro(+1). The purified AGIF inhibited the process of adipogenesis in mouse 3T3-L1 preadipocytes, indicating that AGIF directly acts on the cells. AGIF acted as an adipogenic antagonist not only on the extramedullary cell line 3T3-L1 but also on the mouse bone marrow stroma-derived cell line H-1/A, suggesting that this cytokine may regulate adipogenesis in bone marrow.

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.

Preoperative estimation of cerebral blood flow autoregulation curve for control of cerebral circulation after cerebral revascularization.

In this report, the anesthetic management for cerebral revascularization in 3 patients with ischemic cerebral vascular disease was presented. Arterial pressure was maintained above their ordinary level before revascularization. To prevent cerebral hemorrhage or edema due to the breakthrough phenomenon, the arterial pressure was reduced to the lower limit pressure of cerebral blood flow (CBF) autoregulation which was measured preoperatively. The patients did not show any new neurological deficit after the operations.

[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.

[A computerized anesthesia record system: four years' experience].

A computerized anesthesia record system is in routine use for cardiovascular procedures in our operating rooms. This system is implemented on an NEC PC-9801 personal computer and automatically collects hemodynamic variables from a polygraph as well as from intraoperative laboratory reports via RS-232C ports. Events such as intubation can be entered manually using a standard keyboard. Since the introduction of the system in 1987, the system has been used in 90 percent of the total cases performed and 2941 electronic data files were recorded in a four-year period. Excluding some short procedures for which the system was not used, failure to store records on disks resulted from system errors due to power-line troubles in the operating rooms as well as users' omission to command the system. User-acceptance of event entry was poor. In 74 percent of the cases, not a single event was entered. Advantage of an automated anesthesia record system over a hand-written record is being recognized. Wide-spread use of such a system will require ergonomic design of the system and man-machine interfaces suitable for use in an operating room.

[Does rate of urine flow influence the difference between bladder temperature and nasopharyngeal temperature during cardiac surgery with cardiopulmonary bypass?].

Recently, bladder temperature (BT) monitoring is employed instead of rectal temperature because it is possible to keep the probe clean. The relationship between BT and core temperature is different in patients with steady state compared with those with rapid changes in temperatures. This study evaluated BT compared with nasopharyngeal temperature (NPT) reflecting brain temperature during cardiac surgery with induced hypothermia using cardiopulmonary bypass. During the steady state, after induction of anesthesia and immediately before cooling or rewarming, BT was equivalent to NPT independent of urine flow rate. In rapid cooling or rewarming phase of cardiopulmonary bypass, BT was not equivalent to NPT. BT preceded NPT in case of a very high urine flow rate, and with a lower urine flow rate delayed BT lagged behind NPT. During rapid changes in core temperature during cardiopulmonary bypass, the difference of BT to NPT depends on urine flow rate.

[Monitoring of peripheral tissue oxygenation with near infrared spectrophotometry during abdominal or iliac aortic cross-clamping surgery].

Peripheral tissue oxygenation was monitored with near infrared spectrophotometry during abdominal or common iliac aortic cross-clamping surgery. Six patients who had abdominal aortic aneurysm (AAA) and eight patients who had aortic sclerotic occlusive disease (ASO) were studied. At the beginning of cross-clamping, oxyhemoglobin was decreasing and deoxyhemoglobin was increasing in all AAA patients. Average of 37 minutes following cross-clamping of abdominal aorta, both hemoglobin values were stabilized. On the other hand, changes in both hemoglobin values were delayed or missing in ASO patients. The results suggest that the duration from cross-clamping to stabilization is related to co-lateral blood flow. During operation, monitoring of peripheral blood flow with near infrared spectrophotometry is useful for detection of peripheral ischemia and for the estimation of postoperative local blood flow.

[Maintenance doses of vecuronium and pancuronium during hypothermic cardiopulmonary bypass].

In 31 patients undergoing coronary artery bypass grafting, we investigated the maintenance doses of pancuronium and vecuronium during hypothermic cardiopulmonary bypass. For all patients, the height of the first twitch of the train-of-four (T1) was measured with evoked electromyogram. During operation, T1 was kept from 5 to 15 per cent of control. Infusion doses of both muscle relaxants were controlled with a personal computer. During hypothermic cardiopulmonary bypass (body temperature 28 degrees C), requirement of both muscle relaxants decreased for about 90 per cent compared with pre bypass values. We consider that the prolongation of neuromuscular blockade is attributable to hypothermia rather than to other factors of cardiopulmonary bypass. After rewarming, maintenance dose of vecuronium remained about a half of the dose required in pre-bypass period. It suggests that elimination of vecuronium from liver and kidney is hindered not only during hypothermia but also after rewarming.

[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.

[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.

[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)

[Difference of arterial pressure regulatory mechanism between awake and anesthetized human subjects].

This experiment was conducted to clarify difference of arterial pressure regulatory mechanism between awake and anesthetized human subjects. In 18 subjects who were scheduled for surgical operations, passive tilting test was performed both in awake and anesthetized conditions. Arterial pressure and heart rate were measured during four types of tilting test, i.e., 1. supine-10 degrees head down tilt 2. 10 degrees head down tilt-supine 3. supine-10 degrees head up tilt 4. 10 degrees head up tilt-supine. Relative changes in arterial pressure and heart rate in response to these four tilting tests were compared. After postural changes, all anesthetized subjects showed significant arterial pressure changes followed by restoration of arterial pressure towards control level with opposite changes of heart rate. This initial arterial pressure changes were mainly induced by shift of blood due to gravity and subsequent arterial pressure and heart rate changes were mainly by baro-receptor reflex. On the other hand, awake subjects showed transient increase of heart rate immediately after tilting followed by arterial pressure rise 2 to 3 seconds later in all four tilting tests. However, arterial pressure did not change so remarkably as in anesthetized condition and remained almost constant during tilting test. In awake subjects, their arterial pressure was regulated rapidly and reflex control of arterial pressure was masked. This rapid regulation of arterial pressure may be induced directly by higher central nervous system.