Hiroshi Yamaguchi

Emission of Coherent THz Radiation from Superconductors

Compact solid-state sources of terahertz (THz) radiation are being sought for sensing, imaging, and spectroscopy applications across the physical and biological sciences. We demonstrate that coherent continuous-wave THz radiation of sizable power can be extracted from intrinsic Josephson junctions in the layered high-temperature superconductor Bi2Sr2CaCu2O8. In analogy to a laser cavity, the excitation of an electromagnetic cavity resonance inside the sample generates a macroscopic coherent state in which a large number of junctions are synchronized to oscillate in phase. The emission power is found to increase as the square of the number of junctions reaching values of 0.5 microwatt at frequencies up to 0.85 THz, and persists up to ∼50 kelvin. These results should stimulate the development of superconducting compact sources of THz radiation.

Characteristics of terahertz radiation emitted from the intrinsic Josephson junctions in high-Tc superconductor Bi2Sr2CaCu2O8+δ

Characteristic features of terahertz radiation emitted from a rectangular mesa comprised stacked intrinsic Josephson junctions in the layered high-Tc superconductor Bi2Sr2CaCu2O8+δ are reported. The emission with the total power of ∼5u2002μW at 0.63 THz shows a characteristic spatial distribution reflecting the rectangular shape. The stability of the emission was measured for at least 20 min. and the power fluctuation was found to be less than 4%. Furthermore, the radiation is highly polarized linearly with a ratio of 50:1. All features, including the spectral purity narrower than 4 GHz at full width at half maximum, promise a stable, coherent, and continuous terahertz source for various applications.

Intrathecal morphine dose-response data for pain relief after cholecystectomy

We studied the effect of low-dose intrathecal morphine (0.00–0.20 mg) on pain relief and the incidence of side effects after cholecystectomy in 139 patients divided into eight groups according to intrathecal morphine dose: groups 1 (0.00 mg), 2 (0.04 mg), 3 (0.06 mg), 4 (0.08 mg), 5 (0.10 mg), 6 (0.12 mg), 7 (0.15 mg), and 8 (0.20 mg). Preservative-free morphine hydrochloride mixed in hyperbaric tetracaine solution was administered at the time of induction of spinal anesthesia just before surgery. Pain relief was significantly greater for the first 24 h in groups 3, 4, 5, 6, 7, and 8 than in group 1. The incidence of respiratory depression was significantly greater in groups 7 and 8 than in the other groups in the first 48 h. Vomiting occurred significantly more often in group 1 than in groups 2, 3, 4, and 5. Intraoperative cholangiography and the postoperative clinical course indicated no increase in tone of the sphincter of Oddi in any patient. We conclude that 0.06–0.12-mg intrathecal morphine is the best dose range for pain relief after cholecystectomy without respiratory depression and with the lowest incidence of vomiting or pruritus, or both.

Preoperative small-dose ketamine prevented tourniquet-induced arterial pressure increase in orthopedic patients under general anesthesia

The mechanism of tourniquet-induced arterial pressure increase is not known. We investigated the effect of preoperative ketamine on tourniquet-induced arterial pressure and heart rate changes in 85 patients undergoing knee surgery with a tourniquet under general anesthesia. Patients were randomly assigned into three groups; Large Ketamine (n = 28; ketamine 1.0 mg/kg), Small Ketamine (n = 28; ketamine 0.25 mg/kg), and Control (n = 29; normal saline) groups. Anesthesia was maintained with 1.5%–2.5% sevoflurane and 66% N2O in oxygen with endotracheal intubation. Ketamine or normal saline was given in a double-blinded fashion before skin incision and tourniquet inflation. Arterial pressure and heart rate were recorded every 10 min until 60 min after the start of tourniquet inflation and again after deflation. Arterial pressure and heart rate were compared among the three groups by using repeated-measures analysis of variance. In the Large and Small Ketamine groups, arterial pressure was not significantly changed, but in the Control group arterial pressure was significantly increased 40, 50, and 60 min after the start of tourniquet inflation (P < 0.05). Development of more than a 30% increase in systolic arterial pressure during tourniquet inflation was more frequent in the Control group than the other groups. The results show that preoperative IV ketamine, 0.25 mg/kg or more, significantly prevented tourniquet-induced systemic arterial pressure increase in patients under general anesthesia.

The comparison of epidural fentanyl, epidural lidocaine, and intravenous fentanyl in patients undergoing gastrectomy.

This study was conducted prospectively to compare the effect of epidural fentanyl (EP-F), epidural lidocaine (EP-L), and intravenous fentanyl (IV-F) on hemodynamic and hormonal responses to surgery and postoperative analgesic requirement in 30 patients undergoing gastrectomy during isoflurane anesthesia. An epidural catheter was placed via the T8-9 interspace. Group EP-F received fentanyl 2 micro gram/kg in 10 mL saline, and Group EP-L, 10 mL 1.5% lidocaine, epidurally; Group IV-F was given fentanyl, 2 micro gram/kg, IV. Fifty percent of the original dose was repeated every hour. Hemodynamic data and plasma hormonal levels were compared between those before and those at 1 h after skin incision. The total number of analgesic administrations within the first 48 h post-operatively were compared. Group EP-L developed more frequent episodes of hypotension. Group IV-F required higher isoflurane concentrations and the plasma epinephrine levels increased more than in Groups EP-F and EP-L. In Groups EP-L and IV-F, the plasma antidiuretic hormone (ADH) level increased more than in Group EP-F. In Groups EP-F and IV-F, the plasma cortisol and adrenocorticotropic hormone (ACTH) levels increased more than in Group EP-L. The use of postoperative analgesics was significantly less in Group EP-F. In conclusion, in Group EP-F, attenuated hormonal responses to surgery was accompanied with less hypotension and postoperative analgesic requirements were reduced. (Anesth Analg 1995;81:1169-74)

Minimal Effective Dose of Intrathecal Morphine for Pain Relief Following Transabdominal Hysterectomy

Intrathecal morphine is useful for relief of various types of pain. Postoperative pain relief is one of the most common indications (1). The dose range suggested for postoperative pain relief has ranged from 0.1 to 20 mg morphine (2-6), with the resulting pain relief lasting as much as 24 hours (7-10). Intrathecal morphine is also, however, accompanied by complications such as nausea, vomiting, urinary retention, pruritus, and delayed respiratory depression (1 1-15), the latter potentially life threatening (16). As side effects cannot be predicted (17) and because respiratory depression may be delayed by as much as 20 hours, careful observation for side effects is required (5,18,19). As a result, intrathecal morphine may not be as widely used as it deserves to be for postoperative pain relief because of lack of data on doseresponse relationships for intrathecal morphine, in which responses included both delayed respiratory depression as well as potentially less lethal side effects. In this study, we prospectively investigated the effects of low doses of intrathecal morphine, 0.10 mg as the maximum, on pain relief after transabdominal hysterectomy. We report the minimum effective intrathecal morphine dose defined as that amount of morphine that provides relief of postoperative pain with the least incidence of side effects.

Antinociceptive synergistic interaction between morphine and nω-nitro 1-arginine methyl ester on thermal nociceptive tests in the rats

PurposeThis study was conducted to demonstrate if subeffective dose of Nω Nitro L-arginine methyl ester (L-NAME), a nitric oxide synthase inhibitor, interacts with morphine when given intrathecaly (IT), epidurally (EP), and intravenously (IV) to produce a synergistic antinociceptive effect in normal rats.MethodsChronically catheterized 72 male Wistar rats were used in this study. We measured the tail flick latency in response to thermal stimulation of the tail on a hot plate (53°C), and determined dose-response functions of IT, EP and IV morphine, L-NAME, and morphine co-administered with subeffective doses of L-NAME. The antinociceptive effect was evaluated using the doses for 50% maximum probable effect (ED50). The interaction between morphine and L-NAME was evaluated using an isobolographic approach. ANOVA was used for the statistical analysis. Significance was taken at P < 0.05.ResultsMorphine and L-NAME produced dose-related antinociceptive effects in the IT (ED50 = 1.23 ±0.18 μg (Mean ± SEM) and 76.0 ± 14.5 μg), EP (ED50 = 32.6 + 2.4 μg and 560 ± 97 μg), and IV (ED50 = 563 ± 71.8μ and 16.0 ± 4.0 mg) groups, respectively. Co-administration of small doses of L-NAME and morphine produced reductions in the ED50 values for morphine (0.16 ± 0.03 μg in IT, 1.18 ± 0.32 μg in EP, and 50.5 ± 11.4 μg in TV groups) (P < 0.01), suggesting a multiplicative interaction of L-NAME with morphine.ConclusionL-NAME has a synergistic antinociceptive interaction with morphine in response to thermal stimulation when given intrathecally, epidurally or intravenously in rats.RésuméObjectifRechercher si le Nω nitro L-arginine méthyl ester (L-NAME), un inhibiteur de la synthétase de l’oxyde nitrique administré à doses réduites avec de la morphine par la voie intrathécale (IT), épidurale (EP) ou intraveinesuse (IV) agissait en synergie avec celle-ci sur l’effet antinociceptif chez le rat normal.MéthodesCette étude a été réalisées chez 72 rats Wistar porteurs de cathéters à demeure. Nous avons utilisé l’épreuve de latence de la déviation de la queue en réponse à la stimulation thermique sur plaque chauffante (53%), et déterminé les caractéristiques dose-effet de la morphine IT, EP et IV, du L-NAME, et de la morphine et des doses réduites de L-NAME administrées conjointement. L’effet antinociceptif était évalué avec la moitié des doses de L-NAME susceptibles de produire 50% de l’effet maximal attendu (ED50). L’interaction entre la morphine et la L-NAME était évaluée par isobolographie. L’ANOVA a servi pour l’analyse statistique. La valeur P < 0,05 était considérée comme significative.RésultatsLa morphine et L-NAME avaient une activité antinociceptive proportionnelle à la dose dans les groupes IT (ED50 = 1,23 ± 0,18 μg (moyenne ± SEM) et 76 ± 14.5 μg), EP (ED50 = 32,6 ±2,4 μg et 560 ± 97 μg) et IV(ED50 = 563 ±71,8 μg et 16,0 ± 4,0 mg). L’administration conjointe de petites doses de L-NAME et de morphine réduisait les valeurs d’ED50 pour la morphine (0,15 ± 0,03 μg en IT, 1,18 ± 0,32 μg en EP et 50 ± 11,4 μg en IV; P < 0,01) suggérant une interaction multiplicatrice de L-NAME avec morphine.ConclusionLe L-NAME posséde une interaction antinociceptive synergique avec la morphine en réponse à la stimulation thermique lorsqu’ils sont administrés conjointement par la voie intrathécale, épidurale ou intraveineuse.

Pre-embarkment Prognostication for Acute Paraquat Poisoning

1 In order to assess which laboratory parameters could be related to the prognosis of patients with acute paraquat poisoning, we reviewed the medical records of 160 patients who had ingested paraquat in an attempt at suicide. 2 Serum creatinine and potassium concentrations, arterial blood bicarbonate and base excess levels, arterial blood pH, volume of paraquat ingested and the strength of the urinary paraquat qualitative test (sodium dithionate colour reaction) on admission in the surviving patients were significantly different from those of the patients who died within 48 h of ingestion. 3 The relationship of the quantity Eq1 defined as: Eq1 = ([K +] × [HCO- 3]) / ([Cre] × 0.088) (mEq l-1 ) against the interval of time after ingestion to admission (T) had a significant correlation with prognosis (P < 0.01). Patients with Eq1 > (1500 - 399 × LogT) had a 90% survival rate, Eq1: (930 - 399 × LogT) < Eq1 ≤ (1500 - 399 × LogT) 38% and Eq1 ≤ (930 - 399 × LogT) 3%, P < 0.01.

Longer-term diabetic patients have a more frequent incidence of nosocomial infections after elective gastrectomy

UNLABELLEDnDiabetes mellitus (DM) is one of the risk factors for the development of postoperative nosocomial infections in surgical patients. We conducted this retrospective study to elucidate the perioperative risk factors for postoperative nosocomial infections in diabetic patients undergoing elective gastrectomy. Chart review was performed on diabetic and nondiabetic patients undergoing elective gastrectomy for gastric malignancy from January 1992 through April 1999. Fourteen of the 83 diabetic patients, and 23 of the 284 nondiabetic patients developed postoperative nosocomial infections. Statistical comparisons of multiple variables were made between patients with and without postoperative nosocomial infections. In diabetic patients, univariate analysis showed that longer-term DM (especially longer than 10 yr) was associated with a significantly increased risk for postoperative nosocomial infections. Multiple logistic regression analysis showed that DM lasting longer than 10 yr was an independent risk factor for postoperative nosocomial infections (odds ratio, 6.8; 95% confidence interval, 1.7 to 27.1). In nondiabetic patients, similar analysis showed that age was an independent risk factor for postoperative nosocomial infections. We conclude that patients with longer-term DM had a significantly greater incidence of postoperative nosocomial infections after elective gastrectomy.nnnIMPLICATIONSnPostoperative nosocomial infection is one of the major problems in diabetic patients. This study demonstrated that postoperative nosocomial infections were more common in patients undergoing elective gastrectomy if they had diabetes mellitus longer than 10 yr.

Emission of Terahertz Waves From Stacks of Intrinsic Josephson Junctions

By patterning mesoscopic crystals of Bi2Sr2CaCu2O8 (BSCCO) into electromagnetic resonators the oscillations of a large number of intrinsic Josephson junctions can be synchronized into a macroscopic coherent state accompanied by the emission of strong continuous wave THz-radiation. The temperature dependence of the emission is governed by the interplay of self-heating in the resonator and by re-trapping of intrinsic Josephson junctions which can yield a strongly non-monotonic temperature dependence of the emission power. Furthermore, proper shaping of the resonators yields THz-sources with voltage-tunable emission frequencies.