Solid-state electron spin lifetime limited by phononic vacuum modes.

Longitudinal relaxation is the process by which an excited spin ensemble decays into its thermal equilibrium with the environment. In solid-state spin systems, relaxation into the phonon bath usually dominates over the coupling to the electromagnetic vacuum1-9. In the quantum limit, the spin lifetime is determined by phononic vacuum fluctuations 10 . However, this limit was not observed in previous studies due to thermal phonon contributions11-13 or phonon-bottleneck processes10, 14,15. Here we use a dispersive detection scheme16,17 based on cavity quantum electrodynamics18-21 to observe this quantum limit of spin relaxation of the negatively charged nitrogen vacancy (NV-) centre 22 in diamond. Diamond possesses high thermal conductivity even at low temperatures 23 , which eliminates phonon-bottleneck processes. We observe exceptionally long longitudinal relaxation times T1 of up to 8 h. To understand the fundamental mechanism of spin-phonon coupling in this system we develop a theoretical model and calculate the relaxation time ab initio. The calculations confirm that the low phononic density of states at the NV- transition frequency enables the spin polarization to survive over macroscopic timescales.

Critical Thermalization of a Disordered Dipolar Spin System in Diamond.

Statistical mechanics underlies our understanding of macroscopic quantum systems. It is based on the assumption that out-of-equilibrium systems rapidly approach their equilibrium states, forgetting any information about their microscopic initial conditions. This fundamental paradigm is challenged by disordered systems, in which a slowdown or even absence of thermalization is expected. We report the observation of critical thermalization in a three dimensional ensemble of ∼10^{6} electronic spins coupled via dipolar interactions. By controlling the spin states of nitrogen vacancy color centers in diamond, we observe slow, subexponential relaxation dynamics and identify a regime of power-law decay with disorder-dependent exponents; this behavior is modified at late times owing to many-body interactions. These observations are quantitatively explained by a resonance counting theory that incorporates the effects of both disorder and interactions.

Hybrid quantum circuit with a superconducting qubit coupled to a spin ensemble.

We report the experimental realization of a hybrid quantum circuit combining a superconducting qubit and an ensemble of electronic spins. The qubit, of the transmon type, is coherently coupled to the spin ensemble consisting of nitrogen-vacancy centers in a diamond crystal via a frequency-tunable superconducting resonator acting as a quantum bus. Using this circuit, we prepare a superposition of the qubit states that we store into collective excitations of the spin ensemble and retrieve back into the qubit later on. These results constitute a proof of concept of spin-ensemble based quantum memory for superconducting qubits.

Ultrahard diamond indenter prepared from nanopolycrystalline diamond.

Knoop indenters were prepared from nanopolycrystalline diamonds (NPDs) synthesized by direct conversion sintering from graphite under high pressure and high temperature. Owing to the fine structure (grain size: 10-100 nm) of NPD, high-accuracy sharp edges could be formed at the indenter tips. The indentation tests demonstrated that the NPD indenter can form normal (measurable) indentations on NPD samples without fracture or chipping even at high temperatures of up to 1000 degrees C, while conventional indenters made of single-crystal diamonds break easily above 600 degrees C. This suggests that the NPD indenter has greater potential in high-temperature hardness tests than the conventional single-crystal diamond indenters.

Note: Evaluation of microfracture strength of diamond materials using nano-polycrystalline diamond spherical indenter.

Ultra-hard and high-strength spherical indenters with high precision and sphericity were successfully prepared from nanopolycrystalline diamond (NPD) synthesized by direct conversion sintering from graphite under high pressure and high temperature. It was shown that highly accurate and stable microfracture strength tests can be performed on various super-hard diamond materials by using the NPD spherical indenters. It was also verified that this technique enables quantitative evaluation of the strength characteristics of single crystal diamonds and NPDs which have been quite difficult to evaluate.

Determination of flow and rate constants in a kinetic model of [99mTc]-hexamethyl-propylene amine oxime in the human brain.

The values for flow and rate constants for a kinetic model of [99mTc]-hexamethylpropyleneamine oxime (HM-PAO) distribution in the human brain were determined. The single-pass extraction ratio of HM-PAO was also determined in the rat brain by the indicator diffusion method; a value of 0.90 +/- 0.02 (mean +/- SEM, n = 5) was obtained. Time course data of brain activity and arterial blood activity of the tracer were fitted to a four compartment model: Values of blood flow and the first-order rate constants for backdiffusion of the diffusible tracer from brain to blood (k2), conversion of the lipophilic tracer to the hydrophilic one in brain (k3), and conversion of the diffusible tracer to the nondiffusible one in blood (k5) were determined. Conversion of hydrophilic tracer back to a lipophilic form in both blood and brain was assumed to be negligible during the course of the experiment. The values obtained for blood flow, k2, and k3 were, respectively, 0.40 +/- 0.03 ml/g/min, 0.38 +/- 0.04 min-1, and 0.92 +/- 0.05 min-1 in the gray matter (n = 4), and 0.23 +/- 0.01 ml/g/min, 0.17 +/- 0.01 min-1, and 1.01 +/- 0.05 min-1 in the white matter (n = 2) in patients with cerebrovascular disorder. The k5 value was 1.14 +/- 0.06 min-1 (n = 4). These experimentally determined values agree well with the theoretical ones previously reported by Lassen et al. The results suggest the relative constancy of the k3 and k5 values and the more prominent initial backdiffusion of the lipophilic HM-PAO from brain to blood in high flow regions compared to low flow regions.

Histochemical examination of expression of ras p21 protein and R 1881-binding protein in human prostatic cancers.

Expression of ras p21 was examined with monoclonal antibody RASK-3 in normal, benign hyperplasic, and cancerous prostates. In patients with stage D2 disease who received endocrine therapy, the relation between ras p21 expression, response to therapy, and prognosis was studied. In these patients, R 1881-binding protein (androgen receptor and progestin-binding protein) was also examined. Non-cancerous cells and most cancer cells from stage A patients did not express ras p21, while expression increased with both higher staging and grading. Staging pelvic lymphadenectomy was done in some stage A2-C cases, and presence of nodal metastasis was correlated with ras p21 expressions in the primary tumours. In stage D2, there was no correlation between ras p21 expression and R 1881-binding protein. Response to therapy and survival did not correlate with expression of ras p21, but was influenced by presence of R 1881-binding protein.

Brain perfusion SPECT in Lyme neuroborreliosis.

SPECT imaging brain perfusion using 99mTc-HMPAO was performed on a 38-yr-old women with Lyme neuroborreliosis confirmed by autopsy. The patient had been suspected of spinocerebellar degeneration. Cerebral blood flow was diffusely decreased throughout cerebral cortices but cerebellar blood flow was not impaired, which indicated that the diagnosis was unlikely spinocerebellar degeneration. These findings suggested that brain perfusion SPECT provides useful information in diagnosing the patients with Lyme neuroborreliosis, especially when spinocerebellar degeneration is included in the differential diagnosis.

Evaluating benign and malignant bone and soft-tissue lesions with technetium-99m-MIBI scintigraphy.

UNLABELLED: This study compares the ability of 201TI and 99mTc-MIBI to detect and assess tumor response to chemotherapy in malignant and benign bone and soft-tissue lesions. METHODS: Forty-two patients with various bone and soft-tissue pathologies (29 malignant and 13 benign lesions) were studied with 201TI and 99mTc-MIBI. Planar 201TI scintigraphy was performed 15 min after injection of 111 MBq of 201TI. Within 1 wk of the 201TI study, radionuclide angiography with 600-740 MBq of 99mTc-MIBI was performed and planar imaging was done 15 min later. RESULTS: In visual analysis, 31 of 42 patients showed similar uptake of both tracers, 8 showed more intense uptake of 99mTc-MIBI than 201TI and 3 showed more intense uptake of 201TI than 99mTc-MIBI. In quantitative analysis, similar 201TI and 99mTc-MIBI uptake ratios were obtained (1.96 +/- 1.25 versus 1.96 +/- 1.02, respectively; p = ns). The perfusion index derived from 99mTc-MIBI radionuclide angiography was higher than 99mTc-MIBI uptake ratio (2.33 +/- 1.23 versus 1.96 +/- 1.02, respectively; p < 0.005), but correlated well with 99mTc-MIBI uptake ratio (r = 0.75). In 11 patients with malignant tumors, 201TI and 99mTc-MIBI scintigraphy was repeated after chemotherapy and the uptake of both tracers was significantly suppressed in patients with complete response confirmed by histological evaluation. In patients with complete response (n = 3), the uptake ratio of both tracers was reduced by more than 50%, whereas, less than 20% reduction of uptake ratio was observed in patients with nonresponse (n = 6). CONCLUSION: The ability of 99mTc-MIBI to detect malignant and benign bone and soft-tissue lesions and to assess tumor response to chemotherapy was comparable to that of 201TI. In addition, blood flow could be assessed by radionuclide angiography with 99mTc-MIBI. Technetium-99m-MIBI is a promising radiopharmaceutical for the evaluation of bone and soft-tissue lesions.

Midcourse thallium-201 scintigraphy to predict tumor response in bone and soft-tissue tumors.

UNLABELLED: The purpose of this study was to assess the predictive power of 201TI scintigraphy in the midcourse of chemotherapy for the final tumor response to chemotherapy in malignant bone and soft-tissue tumors. METHODS: The 21 patients studied with 201TI scintigraphy were 14 males and 7 females (average age 39.8+/-22.1 yr; age range 8-74 yr). Planar scintigraphy was performed 15 min after injection of 111 MBq 201TI before chemotherapy, after the third chemotherapy cycle (midcourse) in all 21 patients and after the final chemotherapy cycle but before surgery in 11 patients. The 201TI uptake ratio was calculated by dividing the count density of the lesion by that of the contralateral normal area. The percent reduction of the 201TI uptake ratio calculated by 100 x [(prechemotherapy ratio - postchemotherapy ratio)/prechemotherapy ratio] in the midcourse was compared with that after the final course of chemotherapy, and it also was compared with the histologic response. RESULTS: In patients with histologically complete response [(CR), n=6] and with partial response [(PR), n=5], the percent reduction in 201TI uptake ratio after three cycles of chemotherapy was 64.1%+/-14.4% and 50.9% +/-10.5%, respectively. In patients with histologically no change [(NC), n=10], the percent reduction was 0.40%+/-18.2% after the third cycle; -5.3%+/-20.9% in four patients with full courses of chemotherapy (p < 0.0001 and p < 0.005 compared with the CR and PR groups, respectively). After the final cycle of chemotherapy, the percent reduction in 201TI uptake ratio was 68.6%+/-14.7%, 56.2%+/-6.1% and -0.3%+/-17.2% in the CR, PR and NC groups, respectively (NC versus CR, p < 0.0005; NC versus PR, p < 0.005). CONCLUSION: Thallium-201 scintigraphy performed in the midcourse of chemotherapy is predictive of the final response to chemotherapy that can be demonstrated histologically. Serial 201TI scintigraphy in the midcourse of chemotherapy is useful in assessing final chemotherapeutic response in the early stage of chemotherapy, and it helps clinicians when choosing the most appropriate treatment strategies in patients with bone and soft-tissue tumors.

Assessment of P-glycoprotein in patients with malignant bone and soft-tissue tumors using technetium-99m-MIBI scintigraphy.

UNLABELLED: Overexpression of P-glycoprotein (Pgp) has been detected in many malignant tumors including bone and soft-tissue tumors. Technetium-99m-MIBI has proved to be a transport substrate for Pgp. The purpose of our study was to explore 99mTc-MIBI as a functional imaging agent reflecting Pgp expression in malignant bone and soft-tissue tumors. METHODS: Technetium-99m-MIBI scintigraphy was performed in 30 patients with malignant bone and soft-tissue tumors. Radionuclide angiography with 99mTc-MIBI was done and, at 15 min and 3 hr postinjection of the radiopharmaceutical, imaging was performed. The 99mTc-MIBI uptake ratio was calculated by dividing the lesion count by the background count. The washout rate (WR) for 99mTc-MIBI was calculated by the following formula: WR = 100 x [(Te-Be)-(Td-Bd)]/(Te-Be) (%), where Te and Td = decay-corrected count density of the tumor in the 15-min and 3-hr images, respectively. Be and Bd = decay-corrected count density of the background in the 15-min and 3-hr images, respectively. The lesions were resected by open biopsy to obtain a histopathological diagnosis, and immunohistochemical staining was performed to detect Pgp. RESULTS: Twenty-four of 30 patients showed significant uptake at the 15-min image. In these 24 patients, the lesions with a high Pgp expression showed a similar 99mTc-MIBI perfusion index (3.00 +/- 1.04) and uptake ratio (2.05 +/- 0.58) at the 15-min image to those of lesions without a high Pgp expression (2.65 +/- 0.85 and 2.28 +/- 0.64, respectively). On delayed images, the 99mTc-MIBI uptake ratio was lower in patients with a high Pgp expression than in patients without a high Pgp expression (1.37 +/- 0.41 versus 1.87 +/- 0.39, p < 0.01). The washout ratio of 99mTc-MIBI was higher in patients with a high Pgp expression than in patients without a high Pgp expression (66% +/- 25% versus 29% +/- 18%, p < 0.001). None of the 6 patients without 99mTc-MIBI uptake at the 15-min imaging showed 201TI uptake, and only 2 had a high Pgp expression. CONCLUSION: In malignant bone and soft-tissue tumors, perfusion and initial 99mTc-MIBI uptake were not related to the Pgp expression; however, washout of 99mTc-MIBI from the tumor was related to Pgp expression. Technetium-99m-MIBI scintigraphy with washout analysis may be a useful method for the evaluation of Pgp overexpression and its function.

Age-related changes in the cerebral distribution of 99mTc-ECD from infancy to adulthood.

UNLABELLED: Although cerebral blood flow in infants differs from that in older individuals, the distribution of 99mTc-ethyl cysteinate dimer (ECD) in infants has not been well studied. This study compared 99mTc-ECD distribution in infants and children with that in young adults. METHODS: 99mTc-ECD SPECT was performed on 37 patients suspected of having epilepsy, ranging in age from 3 mo to 26 y. The patients were divided into two age-matched groups, a drug-free group (n = 19) and a drug-taking group (n = 18), according to their anticonvulsant medication status at the time of examination. 99mTc-ECD (100-740 MBq) was injected interictally, and SPECT data were acquired using a triple-head gamma camera. Mean whole-brain counts were obtained from 10 sequential SPECT images. Regions of interest were set bilaterally on five areas of the cerebral cortex and on the basal ganglia, thalamus and cerebellum. The brain perfusion index (BPI) was obtained as a ratio of the mean counts in each region of interest to the mean whole-brain counts. The relationship between BPI and age in each region in the drug-free and drug-taking groups was analyzed separately and together using linear regression. The relationship between five patient age groups (<1 y, n = 4; 1-4 y, n = 9; 5-9 y, n = 8; 10-15 y, n = 7; >15 y, n = 9) and BPI in each region was also examined using multiple comparison analyses. RESULTS: Significant positive correlations between BPI and age in the frontal cortex and cerebellum were confirmed in the drug-free group. Anticonvulsant drugs did not affect the regression lines of BPI in the frontal cortex and cerebellum. Significant differences in BPI between age groups were seen in the parietal cortex, frontal cortex, occipital cortex, basal ganglia, thalamus and cerebellum in all patients. CONCLUSION: Age-related changes in cerebral 99mTc-ECD distribution were confirmed and found to be unaffected by the administration of anticonvulsant drugs. 99mTc-ECD uptake in children and infants is different from cerebral blood flow glucose metabolism as previously reported, especially in the cerebellum.

Autoradiographic analysis of iodoamphetamine redistribution in experimental brain ischemia.

The pathophysiologic significance of iodoamphetamine (IMP) redistribution was analyzed using a double radionuclide autoradiography technique in experimental brain ischemia in the rat. Within 4 hr after unilateral arterial occlusion, IMP almost completely redistributed at 150 min postinjection in the affected areas. At 2 min postinjection, both a remarkable decrease of IMP accumulation and histopathologic change of diminished staining were observed in these areas. The redistribution amplitude was higher in the affected hemisphere, especially in the regions surrounding the ischemic core than in the unaffected hemisphere. These findings were consistent with computer simulation studies of the time course of brain activity based on the standard diffusible tracer model. The results suggest that IMP redistribution in the ischemic area is due to differences of the temporal changes of the brain activity between the unaffected and affected areas and that it is a "physical" phenomenon (only flow related) rather than a "biologic" one.

Regional cerebral blood flow in male schizophrenic patients performing an auditory discrimination task.

Regional cerebral blood flow (rCBF) was measured in 11 schizophrenic patients amid 10 normal controls, both at rest and while performing an auditory discrimination task. Single photon emission computed tomography with technetium-99m hexamethylpropylene amine oxime was used for quantitative evaluation of rCBF. The schizophrenic patients showed greater rCBF in the temporal and parietal regions at rest than the controls, but no abnormalities were found in frontal perfusion. During task performance. on the other hand, the patients showed a reduced frontal rCBF. whereas there was no group difference in rCBF in the temporal and parietal regions. In addition, the left> right hemisphere asymmetries of rCBF observed in the controls during task performance were not present in the patients. although there was no group difference in hemisphere laterality in rCBF at rest. These findings suggest that the employment of a cognitive task for neuroimaging studies is useful for detecting abnormalities of brain activation. such as hypofrontality and altered hemisphere laterality. in patients with schizophrenia.

Simultaneous observation of regional cerebral blood flow and event-related potential during performance of an auditory task.

Reduced amplitude of the P300 component has been reported consistently in patients with neurological and psychiatric disorders. It is unclear, however, how such patients' cognitive dysfunction is related to their P300 abnormality. Further basic knowledge regarding neural substrates for P300 generation is required for gaining an understanding of the pathological significance of the P300 amplitude reduction. To determine the brain structures involved in P300 generation, we observed the event-related potential and the regional cerebral blood flow (rCBF) in 10 normal subjects performing an oddball discrimination of pure tones. The rCBF value was assessed quantitatively with the aid of single photon emission computed tomography using technetium-99m hexamethylpropylene amine oxime. During the task performance, significant activation was observed in the posterior superior temporal and inferior parietal regions of the right hemisphere. In addition, positive correlation of the task-related increase in rCBF with the simultaneously recorded P300 amplitude was observed in the right but not the left posterior superior temporal region. These findings indicate that activation of the right non-verbal auditory area might modulate P300 generation during pure-tone discrimination.

Klinefelter's syndrome with prepenile scrotum.

Two cases of Klinefelter's syndrome with prepenile scrotum were presented. They underwent the operation for prepenile scrotum according to Glenn and Anderson's method. Thereafter urethroplasty was performed in each case. The decrease in response to testosterone in the target organ was noticed in 1 patient, suggesting that some androgen resistance in this case was attributable in part to anomaly of genitalia.

Effect of vagal autotransplantation on quantitative [3H]-vesamicol binding image in rats with unilateral lesions of nucleus baslis magnocellularis.

It is considered that nodosal ganglion grafting improves learning and memory disorder in nucleus basalis magnocellularis lesioned rats, and that [3H]-vesamicol is one of the mapping agents for presynaptic cholinergic neurons. Quantitative autoradiography was performed using high sensitive imaging plate system to evaluate the effect of neurotransplantation on [3H]-vesamicol binding. The affected-side to unaffected-side ratio of [3H]-vesamicol in the nucleus basalis magnocellularis lesioned group was significantly lower than that in the sham-operated group at 1, 2 and 4weeks (P<0.01). In the transplanted group, the ratio was significantly higher than that in the untreated group at 4weeks (P<0.05). [3H]-vesamicol binding is one of the most sensitive indicators of nucleus basalis magnocellularis lesions and the effect of the nodosal ganglion grafting.

The potential of radioiodinated (-)-m-iodovesamicol for diagnosing cholinergic deficit dementia.

We investigated changes in the brain distribution of (-)-[(125)I]-m-iodovesamicol [(-)-[(125)I]mIV] in cholinergic denervation rats produced by a unilateral lesion of the nucleus basalis magnocellularis (NBM). Dual-tracer ex vivo autoradiographic analysis using (-)-[(125)I]mIV and [(99m)Tc]HMPAO was conducted to the effect of regional cerebral perfusion on the brain distribution of (-)-[(125)I]mIV in a unilateral NBM-lesioned rat. (-)-[(125)I]mIV binding in the ipsilateral cortex to the lesion significantly reduced by 10.4 %, compared with that in the contralateral cortex, while (-)-[(125)I]mIV binding in the ipsilateral caudate putamen, hippocampus and thalamus did not change. The rate of reduction in the (-)-[(125)I]mIV binding (10.4 %) was significantly higher than that of [(99m)Tc]HMPAO accumulation (4.0%) in the ipsilateral cortex to the lesion (P < 0.01). These results suggested that radioiodinated (-)-mIV may be useful in the study of dementia characterized by degeneration of the cholinergic neurotransmitter system, such as Alzheimer's disease.

Synthesis of radioiodinated analogs of 2-(4-phenylpiperidino)cyclohexanol (vesamicol) as vesamicol-like agent.

Three iodovesamicol analogs, iodinated at the ortho, meta, and para positions of the 4-phenylpiperidine moiety, were synthesized and labeled with 125I by isotopic exchange reaction. Their potencies as a vesamicol-like drug were evaluated with competitive inhibition studies using (-)[3H]vesamicol. The radiochemical yields were 40-85%, the radiochemical purities exceeded 95% and their specific activities were 370-740 GBq/mmol. The descending order of binding affinity of the tested compounds against the vesamicol receptor was m-iodovesamicol > o-iodovesamicol > p-iodovesamicol. The receptor binding affinity of m-iodovesamicol (IC50 = 133 nM) was comparable with that of vesamicol (IC50 = 109 nM). Therefore, the meta position of the 4-phenylpiperidinyl fragment of vesamicol was the optimum site for iodination, and radioiodinated m-iodovesamicol may serve as a useful radiopharmaceutical for in vitro and in vivo studies of presynaptic cholinergic neurons in rats.

Reduction of vesicular acetylcholine transporter in beta-amyloid protein-infused rats with memory impairment.

The aim of this study was to investigate spatial memory and quantitative acetylcholine transporter autoradiography using a high-sensitivity imaging plate system in rats treated with beta-amyloid protein, a model of Alzheimer's disease. An eight-arm radial maze was used to evaluate spatial memory. The performance of the eight-arm radial maze task was impaired in beta-amyloid protein-treated rats. In the parietal cortex, [3H]-vesamicol binding to the vesicular acetylcholine transporter was significantly lower in beta-amyloid protein-treated rats than in vehicle-treated rats, and was significantly correlated with the mean number of correct selections in the maze task of the first 5 days in the post-operative state. These results indicate that the reduction in [3H]-vesamicol binding to vesicular acetylcholine transporter is related to memory impairment induced by beta-amyloid protein. Beta-amyloid protein-infused rats with spatial memory impairment may be useful for the development of new radiolabelled vesamicol analogues for the objective evaluation of Alzheimer's disease.