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PubMed2005

Anharmonic motions of Kr in the clathrate hydrate.

The anomalous glass-like thermal conductivity of crystalline clathrates has been suggested to be the result of the scattering of thermal phonons of the framework by 'rattling' motions of the guests in the clathrate cages. Using the site-specific (83)Kr nuclear resonant inelastic scattering spectroscopy in combination with conventional incoherent inelastic neutron scattering and molecular-dynamics simulations, we provide unambiguous evidence and characterization of the effects on these guest-host interactions in a structure-II Kr clathrate hydrate. The resonant scattering of phonons led to unprecedented large anharmonic motions of the guest atoms. The anharmonic interaction underlies the anomalous thermal transport in this system. Clathrates are prototypical models for a class of crystalline framework materials with glass-like thermal conductivity. The explanation of the unusual molecular dynamics has a wide implication for the understanding of the thermal properties of disordered solids and structural glasses.

Computer Simulation↗
PubMed2001

85Kr measurement system for continuous monitoring at the Meteorological Research Institute, Japan.

A 85Kr measurement system for continuous monitoring based principally on the BfS-IAR method (activity measurement of 85Kr by gas counting coupled with gas chromatographic separation, using pure CH4 as carrier and Counting gas) was implemented for the first time in Japan. In this paper, a detailed description of the system and procedures is given and the inter-comparison results of our system with the BfS-IAR system are presented. A consistent temporal concentration change with high accuracy and consistency of the respective data with the BfS-IAR data (maximum difference of 5%) were achieved with the Meteorological Research Institute (MRI) system, which shows that the system is valid and reliable for the purpose of background monitoring for 85Kr in air. Also, the 85Kr monitoring record at the MRI during 1995-2001 is described. The record distinctively shows the Northern Hemispheric background 85Kr concentrations at the mid-latitude and the elevated concentrations affected by the operation of a nuclear fuel reprocessing plant in Tokai-mura, Ibaraki. Japan.

Air Pollutants, Radioactive↗
PubMed2006

Accurate potential energy curves for F(-)-Rg (Rg = He-Rn): spectroscopy and transport coefficients.

High-quality ab initio potential energy curves are presented for the F(-)-Rg series (Rg = He-Rn). Calculations are performed at the CCSD(T) level of theory, employing d-aug-cc-pV5Z quality basis sets, with "small core" relativistic effective core potentials being used for Kr-Rn. The quality of the curves is judged by agreement with recent high-level calculations in the case of F(-)-He and F(-)-Ne and by excellent agreement with mobility data for the systems F(-)-Rg (Rg = He-Xe). Except for these recent high-level calculations on the two lightest systems, we are able to deduce that all other previous potentials for the whole set of these systems are inadequate. We also present spectroscopic information for the titular species, derived from our potential energy curves.

Algorithms↗
PubMed1984

Picosecond spectroscopy: applications in biochemistry. Part I: Techniques.

A number of sources of picosecond optical pulses and the means by which they may be used to investigate fast molecular processes have been described. In addition, it should be pointed out that most of these techniques can be extended to take advantage of other properties of the laser pulses; in particular, the polarization is of use in measuring time-dependent antisotropy. The state of the art is now the generation of 30fs pulses; it seems likely that this is all the time resolution that one is likely to need for investigating biological and other molecular processes as at such short times the uncertainty principle leads to a considerable loss of spectral resolution.

Argon↗
PubMed1975

Permanent hypertension after renal homotransplantation in man.

1. In forty-one patients who underwent renal homotransplantation the following measurements were made: (a) blood flow and its distribution in the transplanted kidney as measured by the 85-Kr washout method; (b) renin release in the renal vein of the transplant; (c) arteriovenous difference in plasma renin activity (PRA) of the recipient's remaining left kidney. 2. Eleven transplanted patients were normotensive. Renal haemodynamic data were comparable with those obtained in potential kidney donors. 3. Three hypertensive patients had chronic rejection. The mean renal blood flow and the percentage flow in the first component of the washout curve were reduced. Renin release from the transplant, however, was normal. 4. Ten hypertensive patients had transplant artery stenosis. In eight of them renin release from the grafts as well as peripheral PRA were within normal range. This result is similar to experimental data obtained in Goldblatt renovascular hypertension. The two patients with the tightest artery stenosis had an elevated renin release from the transplant. 5. Thirteen hypertensive patients had elevated arteriovenous difference in PRA of the recipient's own left kidney. Peripheral PRA was significantly higher than in normotensive patients. Left nephrectomy relieved hypertension in ten of them; three have not so far undergone nephrectomy. 6. In four other cases hypertension was also relieved by removal of the patient's own kidney; however, the arteriovenous difference in PRA of that kidney fell within normal range.

Adult↗
PubMed1980

Regional lung function in bilateral diaphragmatic paralysis.

1. The distribution of regional function in the lungs of six patient with bilateral diaphragmatic paralysis was investigated by continuous inhalation and infusion of the radioactive gases 81mKr and 85mKr during tidal breathing. 2. In the supine and right lateral decubitus postures the vertical distribution of ventilation per unit alveolar volume was less in the dependent zones, the reverse of that found in normal subjects. In the upright posture ventilation was slightly decreased at the lung base. Perfusion per unit alveolar volume was more uniformly distributed than normally in the upright posture, and decreased from superior to inferior in the supine posture. In the lateral decubitus posture, perfusion of the lower lung was greater than that of the upper. Ventilation/perfusion ratios were more uniformly distributed in the patients than in normal subjects, except in the right lateral decubitus posture. 3. Alterations in the distribution of ventilation may be explained in terms of the altered mechanical interaction of chest wall, mediastinal and abdominal contents, with selective use of intercostal and accessory muscles. The effects on the distribution of blood flow are probably related to the low end-expiratory lung volume.

Adult↗
PubMed1984

Radionuclide demonstration of ventilatory abnormalities in mild asthma.

The distribution of 5 microns 99mTc aerosol particles deposited in the lungs was compared with that of 81mKr gas in 20 asthmatic subjects (FEV1.0 greater than or equal to 75% predicted) whose asthma was mild or in remission. Sixteen normal non-smokers and 14 'normal' cigarette smokers were studied as control subjects. Radioaerosol lung penetration in the 'normal' smokers was the same as in the normal non-smokers but was reduced in the asthmatic subjects. Radioaerosol penetrated better than 81mKr to the lung apices of normal non-smokers and asthmatic subjects; it penetrated better than 81mKr to the lung bases of the asthmatic subjects. Uneven distribution of aerosol relative to 81mKr related strongly to maximal mid-expiratory flow rate (MMFR) in the asthmatic subjects. Aerosol deposition abnormalities in symptom-free asthmatic subjects may reflect basal airways closure at functional residual capacity and abnormal patterns of lung filling.

Adult↗
PubMed1986

Sensory mechanisms in the upper respiratory tract affect the inhalation of cigarette smoke in man.

Cigarette puffing parameters (puff volume, puff duration, number of puffs, total smoking time) and inhaled smoke volume (by a radiotracer technique) have been measured in a group of 11 asymptomatic smokers, once after topical anaesthesia of the upper airways and once without anaesthesia. Topical anaesthesia significantly reduced the mean inhaled smoke volume per puff for the group from 41.1 ml to 30.6 ml (P less than 0.05) and the total inhaled smoke volume from 575 ml to 528 ml (P = 0.05), but cigarette puffing parameters were unchanged. It is concluded that stimulation of upper airway sensory receptors, probably sensitive to nicotine, may be an important mechanism in determining the amount of cigarette smoke inhaled by smokers.

Adult↗
PubMed1986

Inhaled smoke volume, puffing indices and carbon monoxide uptake in asymptomatic cigarette smokers.

Nine asymptomatic smokers each smoked one cigarette of their usual brand on four separate occasions. The inhaled smoke volume was measured by tracing the smoke with the inert gas 81Krm. Puffing indices were recorded by using an electronic smoking analyser and flowhead/cigarette holder. The expired air carbon monoxide concentration was measured immediately before and within 5 min of finishing smoking. The inhaled smoke percentage (total inhaled smoke volume/total puff volume) averaged 46% to 85% in different subjects. Neither the mean inhaled smoke volume per puff nor the total inhaled smoke volume per cigarette was significantly correlated with any of the puffing indices. Smokers took significantly smaller and shorter puffs, left longer between puffs and inhaled less smoke as the cigarette was smoked (P less than 0.01), although the proportion of the puff which was subsequently inhaled did not change significantly. There was no significant intra-subject difference in any index from one visit to another.

Adolescent↗
PubMed1985

[Comparative scintigraphic analysis of 99mTc aerosol inhalation and 81m Kr ventilation in chronic obstructive bronchial disease].

The usefulness of 99mTc-labelled serum albumin aerosol as a ventilation agent was compared to that of 81mKr gas in normal subjects and in patients with a wide range of pathological pulmonary function. In addition to visual analysis of the scintigrams, lung activity distribution was quantified by an index. In healthy subjects aerosol distribution was very similar to that of 81mKr gas. In patients with persistent obstruction of bronchial air flow, the aerosol tended to penetrate less well than 81mKr gas to the lung periphery and to show a more uneven pulmonary tracer distribution. Consequently the 81mKr gas technique resulted in underestimating bronchial obstructive defects compared with the radioaerosol method. The results indicate that unlike 81mKr gas imaging, small-particle aerosol scintigraphy provides a useful diagnostic technique for the detection of even mild air flow obstructions.

Adult↗
PubMed2004

A computational study of the dihydrogen bonded complexes HBeH ... HArF and HBeH ... HKrF.

We report an ab initio computational study of the properties of two linear dihydrogen-bonded complexes of HBeH with the recently discovered rare gas compounds HArF and HKrF at the MP2(full)/6-311++G(2d,2p) level of theory. The HBeH ... HArF and HBeH ... HKrF complexes were found to have zero-point energy corrected binding energies of 27 and 12 kJ mol(-1), respectively. Large red shifts of the H-Rg vibrational stretching frequency in both complexes were also predicted. The electron density rearrangement of the rare gas compounds on complexation was also examined. We also consider the relative stabilities of D-containing isotopomers of the complexes by comparison of their computed zero-point vibrational energies.

Argon↗