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PubMed2004

Plasma cleaning of dental instruments.

The theoretical risk of prion transmission via surgical instruments is of current public and professional concern. These concerns are further heightened by reports of the strong surface affinity of the prion protein, and that the removal of organic material by conventional sterilization is often inadequate. Recent reports of contamination on sterilized endodontic files are of particular relevance given the close contact that these instruments may make with peripheral nerve tissue. In this paper, we report the effective use of a commercial gas plasma etcher in the cleaning of endodontic files. A representative sample of cleaned, sterilized, files was screened, using scanning electron microscopy and energy-dispersive X-ray analysis, to determine the level of contamination before plasma cleaning. The files were then exposed for a short-term to a low-pressure oxygen-argon plasma, before being re-examined. In all cases, the amount of organic material (in particular that which may have comprised protein) was reduced to a level below the detection limit of the instrument. This work suggests that plasma cleaning offers a safe and effective method for decontamination of dental instruments, thus reducing the risk of iatrogenic transmission of disease during dental procedures. Furthermore, whilst this study focuses on dental files, the findings indicate that the method may be readily extended to the decontamination of general surgical instruments.

Argon↗
PubMed1999

Re-analysis of magic angle spinning nuclear magnetic resonance determination of interlamellar waters in lipid bilayer dispersions.

A recent method to obtain the number of water molecules of hydration of multilamellar lipid vesicles using magic angle spinning nuclear magnetic resonance has been re-examined. The previous interpretation divided the water into bulk and interlamellar water and ignored water in defects (lakes) that are intrinsic to multilamellar lipid vesicles; the result was inconsistent with x-ray results for the lipid DOPC. The new interpretation takes advantage of the reduction of lake water with increased spinning and it uses osmotic pressure measurements to determine the loss of interlamellar water. The new result for DOPC from magic angle spinning is consistent with x-ray results.

Centrifugation↗
PubMed2001

Characterization of the hydroxypropylmethylcellulose-nicotinamide binary system.

The effect of hydroxypropylmethylcellulose (HPMC) on the thermal behaviour of nicotinamide was studied. Binary mixtures of nicotinamide and HPMC, composed of various weight fractions of HPMC (X(HPMC)), were heated, cooled and subsequently re-heated. HPMC dissolved in fused nicotinamide at 140 degrees C. The binary mixture at compositions 0<==X(HPMC)<==0.3 formed a film structure on cooling. At X(HPMC)>==0.4, the molten nicotinamide at 140 degrees C was saturated with HPMC. These heated mixtures did not form a homogeneous film by cooling to ambient temperature. At X(HPMC)<0.4, differential scanning calorimetry peaks originating from recrystallization and melting of nicotinamide were observed in the cooling and re-heating scans, respectively. These peaks became smaller with increase in X(HPMC) and disappeared at X(HPMC) approximately 0.4. Decrease in crystallinity with increase in X(HPMC) was confirmed by X-ray diffraction. The glass transition temperature of the cooled mixture (T(g)) increased with increase in X(HPMC). When the enthalpy of melting of nicotinamide and 1/T(g) were plotted against X(HPMC), inflections were observed at similar X(HPMC) values, 0.37-0.38. Dissolution of HPMC in molten nicotinamide was accompanied by hydrogen bond formation, which was confirmed by infrared studies.

Algorithms↗
PubMed1999

A New Rare-Earth Indium Antimonide, (RE)In(1)(-)(x)()Sb(2) (RE = La-Nd), Featuring In Zigzag Chains and Sb Square Nets.

A new series of ternary rare-earth indium antimonides, (RE)In(1)(-)(x)()Sb(2) (RE = La-Nd), has been synthesized through reaction of the elements at 950 degrees C. The structure of LaIn(0.81(1))Sb(2) has been determined by single-crystal X-ray diffraction (monoclinic space group -P2(1)/m, Z = 2, a = 4.521(3) Å, b = 4.331(3) Å, c = 11.913(7) Å, beta = 99.6680(11) degrees ). The structure is built up of alternating layers of compositions and separated by the La atoms. The layer is described as a nearly square net of Sb atoms held by weak one-electron bonds, while the layer is derived from edge-sharing InSb(4) tetrahedra distorted in such a way as to produce In-In zigzag chains. Extended Hückel band structure calculations are used to explain the bonding and predict that anisotropic metallic behavior should be observed.

Journal Article↗
PubMed2005

d0 Re-based olefin metathesis catalysts, Re([triple bond]CR)(=CHR)(X)(Y): the key role of X and Y ligands for efficient active sites.

DFT(B3PW91) calculations show that the reaction pathways for ethylene metathesis with Re([triple bond]CMe)(=CHMe)(X)(Y) (X/Y = CH2CH3/CH2CH3; CH2CH3/OSiH3; OSiH3/CH2CH3; OCH3/OCH3, CH2CH3/OCH3, and OCF3/OCF3) occur in two steps: first, the pseudo-tetrahedral d0 Re complexes distort to a trigonal pyramid to open a coordination site for ethylene, which remains far from Re (early transition state for C-C bond formation). The energy barrier, determined by the energy required to distort the catalyst, is the lowest for unsymmetrical ligands (X not equal Y) when the apical site of the TBP is occupied by a good sigma-donor ligand (X) and the basal site by a poor sigma-donor (Y). Second, the formation of metallacyclobutanes (late transition state for C-C bond formation) has a low energy barrier for any type of ligands, decreasing for poor sigma-donor X and Y ligands, because they polarize the Re-C alkylidene bond as Re(+delta)=C(-delta), which favors the reaction with ethylene, itself polarized by the metal center in the reverse way. The metallacyclobutane is also a TBP, with apical alkylidyne and Y ligands, and it is stabilized by poor sigma-donor X and Y. The best catalyst will have the more shallow potential energy surface, and will thus be obtained for the unsymmetrical set of ligands with X = a good sigma-donor (alkyl) and Y = a poor sigma-donor (O-based ligand). This rationalizes the high efficiency of well-defined Re alkylidene supported on silica, compared to its homogeneous equivalent, Re([triple bond]CMe)(=CHMe)(OR)2.

Alkenes↗
PubMed1992

[A case of re-expansion pulmonary edema following water seal drainage for spontaneous pneumothorax--management with right and left-separated mechanical ventilation].

A 23-year-old male with complete collapse of the right lung due to spontaneous pneumothorax was admitted 11 days after its onset. Paying close attention to the re-expansion pulmonary edema (REPE), water seal drainage was performed. Following couple episodes of persistent severe cough, four hours later, he developed dyspnea and began to expectorate frothy massive sputum. Chest X-ray revealed pulmonary edema of the entire right lung field. Measurement of total proteins and neutrophil elastase in airway exudates showed 5.5 g/dl (ratio to plasma, 0.89) and 7000 micrograms/l, respectively. Because of marked difference of compliance between bilateral lungs, management with right and left-separated mechanical ventilation and PEEP applied only to the right lung was performed. Although transient mediastinal deviation to the left was observed, successful management was achieved by the maneuver. High concentrations of total proteins and neutrophil elastase in edema fluid suggest that increased vascular permeability due to endothelial cell injury via activated neutrophils is mainly responsible for REPE. In the present case, rapid expansion of the collapsed lung accelerated by severe cough seems to be a predisposing factor of REPE. In patient with prolonged pneumothorax, suppression of cough is thought to be important for the prevention of REPE even with water seal drainage.

Adult↗
PubMed2003

Production, purification and preliminary X-ray crystallographic studies of adeno-associated virus serotype 4.

Adeno-associated virus (AAV) serotypes 1 to 5 are currently under development as clinical gene delivery vectors for the treatment of human diseases. However, the ubiquitous nature of their cell surface receptors, heparin sulfate (AAV2 and 3) and sialic acids (AAV4 and 5), can preclude specific tissue targeting in vivo. Structural studies of AAV4 were initiated to characterize its capsid surface for re-targeting manipulations. Crystals obtained diffracted synchrotron radiation to 3.2 A resolution. The unit cell is body-centered orthorhombic, I222, with a = 339.6, b = 319.2 and c = 285.0 A. The virus particle orientation and position have been determined.

Animals↗
PubMedDate not supplied

Some epidemiological and socio-medical peculiarities of pulmonary tuberculosis (pTB) among individuals from war affected areas (WAA)--experiences and results from north-west Yugoslavia (NWYU).

AIM: 1. To find out the differences between patients (pts) from WAA and the general population (GP) suffering from pTB. 2. To evaluate the proportion and characteristics of pts from WAA in pulmonary TB (pTB) hospital mortality rate. 3. To evaluate how many refugees (RE) and displaced persons consider TB as a social "stigma". METHODS: 1. Analysis of the medical files of pts with pTB--137 from WAA and 212 from the GP. 2. Analysis of clinical data of pts who died of pTB from 1990 to 1999. 3. A questionnaire about knowledge and social attitude towards TB. RESULTS: 1. The main characteristics of pts with pTB from WAA (both those who were dismissed from hospital and those with fatal outcome) are: male dominance, prolonged hospital treatment, high prevalence of relapses, very extended forms of the disease and presence of cavernous lesions on chest X-ray. 2. Deterioration of life conditions, impoverishment, demographic changes, shortage of anti-TB drugs and supplies for diagnosis led to increase hospital mortality rate of TB between 1990 and 1999 in NWYU (36% of all pts who died of TB in the mentioned period originated from WAA). 4. RE from former Yugoslavia consider TB more as a social "stigma" than the GP. CONCLUSION: The prevention, treatment and follow up of pts with pTB from WAA must be a priority in the Yugoslav national TB programme.

Adult↗
PubMedDate not supplied

The effect of environmental pollution on the respiratory system of lignite miners: a diachronic study.

BACKGROUND: It is not known whether working in surface lignite mines can cause x-ray lesions or disorders of respiratory function. OBJECTIVES: The aim of the study was to investigate the diachronic impact of environmental pollution on the respiratory system of lignite miners at mines in Eordea, Greece. METHODS: Cases of 199 workers (Group A) residing permanently in the Eordea valley and 151 (Group B) living outside the Eordea valley were studied during Phase I and then re-examined after three years (Phase II). These cases were compared to those of 71 office workers living in Eordea valley (Group C) and to 96 living in Grevena, a region without pollution (Group D). The study included the completion of the MRC questionnaire for the detection of respiratory diseases, pulmonary function tests, measurement of diffusion capacity, otorhinolaryngologic examination, rhinomanonetry as well as chest and paranasal cavity X-rays. RESULTS: Chronic bronchitis was reported by 26.8%, 24.8%, 17.9% and 10.6% respectively of the subjects of groups A, B, C and D according to the answers of the questionnaire (p<0.001). The spirometry and diffusion capacity findings presented no considerable differences either in the 4 groups or between phases I and II of the study. The main problems were detected in the upper airways. A very high prevalence of severe nasal obstruction (73%, 71.2%, 55.7% and 19.3% in Groups A, B, C and D respectively) was detected. Furthermore, a high percentage of atrophic rhinitis (14%) was detected both among workers (Groups A and B) and subjects living in the Eordea valley who participated as controls (Group C). From the X-rays, hypertrophy of nasal turbinates-cartilage and polyposis was observed as follows: Group A: 53.9%, Group B: 48.1%, Group C: 46.5% and Group D: 20.3% (p<0.001). The findings related to the upper respiratory system may be due to excessive pollution by airborne particles (fly ash) pollution in the region and particularly to chromium, nickel, cobalt and lead found at high concentration levels in airborne dust. A marked association between the total air-flow in the nose and the mid-expiratory flow (p<0.01) was detected. CONCLUSIONS: We conclude that subjects working in lignite mines under conditions of excessive pollution by airborne contaminants have a high prevalence of atrophic rhinitis and, in addition to other standard examinations, should undergo rhinomanometry testing and X-ray imaging of the paranasal cavities.

Adult↗
PubMed2002

Performance analysis and determination of the p(wall) correction factor for 60Co gamma-ray beams for Wellhöfer Roos-type plane-parallel chambers.

The wall perturbation correction factor p(wall) in 60Co for Wellhöfer Roos-type plane-parallel ionization chambers is determined experimentally and compared with the results of a previous study using PTW-Roos chambers (Palm et al 2000 Phys. Med. Biol. 45 971-81). Five ionization chambers of the type Wellhöfer PPC-35 (or its equivalent PPC-40) are used for the analysis. Wall perturbation correction factors are obtained by assuming N(D,air) chamber factors determined by cross-calibration in a high-energy electron and in a 60Co gamma-ray beam to be equal, and by assigning any differences to the wall perturbation factor. The procedure yields a p(wall) value of 1.018 (u(c) = 0.010), which is slightly higher than the value 1.014 (u(c) = 0.010) formerly obtained for the PTW-Roos chambers using the N(D,air) method. The chamber-to-chamber variation in p(wall) for the Wellhöfer-Roos chambers is found to be very small, with a maximum difference of 0.3%. The effect of using new p(cav) values for graphite-walled Farmer-type chambers used in water in electron beams is to decrease p(wall) by approximately 0.5%. The long- and short-term stability of the Roos-type chambers manufactured by Wellhöfer is investigated by measurements at the IAEA Dosimetry Laboratory in Vienna, Austria, and at the Sahlgrenska University Hospital in Göteborg, Sweden. Calibrations made at the IAEA over several months show variations in the N(D,w) calibration factors larger than expected. based on previous experiences with PTW-Roos chambers. Measurements of the short-term stability of the Wellhöfer-Roos chambers show a marked increase in chamber response for the time the chambers are immersed in water, pointing to a possible problem in the chamber design. As a consequence of these findings, Wellhöfer is currently working on a re-design of the chamber to solve the stability problem.

Biophysical Phenomena↗
PubMed2003

Heterobimetallic oxalato-bridged M(II)Re(IV) complexes (M = Mn, Fe, Co, Ni): synthesis, crystal structure, and magnetic properties.

Four rhenium(IV)-M(II) bimetallic complexes of formula [ReCl(4)(mu-ox)M(dmphen)(2)].CH(3)CN with M = Mn (1), Fe (2), Co (3), and Ni (4) (ox = oxalate anion, dmphen = 2,9-dimethyl-1,10-phenanthroline) have been synthesized and the crystal structures of 1 and 3 determined by single-crystal X-ray diffraction. 1 and 3 are isostructural and crystallize in the monoclinic system, space group P2(1)/c, with a = 16.008(4) A, b = 12.729(2) A, c = 18.909(5) A, beta = 112.70(2) degrees, and Z = 4 for 1 and a = 15.998(4) A, b = 12.665(2) A, c = 18.693(5) A, beta = 112.33(2) degrees, and Z = 4, for 3. The structure of 1 and 3 is made up of neutral [ReCl(4)(mu-ox)M(dmphen)(2)] bimetallic units (M = Mn (1), Co (3)) and acetonitrile molecules of crystallization. M(II) and Re(IV) metal ions exhibit distorted octahedral coordination geometries being bridged by a bis(bidentate) oxalato ligand. The magnetic behavior of 1-4 has been investigated over the temperature range 2.0-300 K. A very weak antiferromagnetic coupling between Re(IV) and Mn(II) occurs in 1 (J = -0.1 cm(-)(1)), whereas a significant ferromagnetic interaction between Re(IV) and M(II) is observed in 2-4 [J = +2.8 (2), +5.2 (3), and +5.9 cm(-)(1) (4)].

Journal Article↗
PubMed1998

Study of the interaction of dithranol with heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin in solution and in the solid state.

The interaction between dithranol and heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin (TMBCyD) has been investigated in aqueous solution containing isoascorbic acid (0.2% w/v) as antioxidant and in the solid state. The interaction in the solid state was studied by differential scanning calorimetry (DSC), infrared spectroscopy (IR), X-ray powder diffractometry (XPD) and a dissolution-rate method. The extent of complexation between the two substances was poor, as indicated by the low value of the slope of the linear part of the solubility curve. A phase diagram was constructed by measuring the thermal behaviour of various re-solidified physical mixtures of dithranol and of TMBCyD previously subjected to heating until melting of the TMBCyD. The loss of dithranol, owing to sublimation and degradation caused by the thermal treatment used, was less than 10%. In keeping with XPD and IR data, the phase diagram indicated that a complex was formed containing 13.7% dithranol (molar ratio 1:1) which had a congruent melting point at 164 degrees C. The drug dissolution rate from the 1:1 complex was measurable, unlike that of the corresponding physical mixture, and was significantly increased when the complex was dispersed in the glassy matrix of TMBCyD, as it was in re-solidified mixtures containing 2-7% dithranol. The results show that the solubility of dithranol is increased significantly as a consequence of its interaction with TMBCyD, despite the low extent of complexation between the two substances.

Administration, Topical↗
PubMed1983

A re-evaluation of the 'saturated scatter' method for estimating the energy imparted to patients during diagnostic radiology examinations.

Central-axis depth dose data for diagnostic qualities (1-4 mm Al HVL) have been used to calculate the total energy imparted to patients or phantoms during X-ray examinations. A 'saturated scatter' method has been used and allowance is made for the finite dimensions of the patient by using PDD data for large but finite field sizes. For the purpose of integration, PDD data have been represented as a function of depth by two exponential components. Data in the form of energy imparted per unit central-axis surface dose and per unit surface X-ray field are tabulated as functions of kVp, first HVL, phantom thickness and the field size of the original PDD data. Comparison with energy fluence calculations of total energy imparted made by other workers indicates good agreement under similar phantom and X-ray quality conditions, although it is noted that anatomical variations between patients will in practice lead to uncertainties in the total energy imparted.

Humans↗