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PubMed1999

Medical dissolution and prevention of canine struvite urolithiasis. Twenty years of experience.

Two types of canine struvite uroliths have been recognized: infection-induced struvite is the most common type; sterile struvite is uncommonly recognized. Infection-induced struvite is most commonly associated with urease-producing staphylococcal UTI. For dogs that qualify, medical dissolution is an effective method of treatment. Medical dissolution protocols encompass: (1) eradication or control of UTI; (2) use of calculolytic diets; and (3) administration of urease inhibitors to patients with persistent UTI caused by urease-producing microbes.

Animals↗
PubMed2003

Palygorskite as a feasible amendment to stabilize heavy metal polluted soils.

The sorption behaviour of palygorskite has been studied with respect to lead, copper, zinc and cadmium in order to consider its application to remediate soils polluted with these metals. The Langmuir model was found to describe well the sorption processes offering maximum sorption values of 37.2 mg/g for lead, 17.4 mg/g for copper, 7.11 mg/g for zinc and 5.83 mg/g for cadmium at pH 5-6. In addition the effect of palygorskite amendment in a highly polluted mining soil has been studied by means batch extractions and leaching column studies. The soluble metal concentrations as well as the readily-extractable metal concentrations were substantially decreased at any concentration of palygorskite applied to soil (1, 2, 4%), although the highest decrease is obtained at the 4% dose. The column studies also showed a high reduction in the metal leaching (50% for lead, 59% for copper, 52% for zinc and 66% for cadmium) when a palygorskite dose of 4% was applied.

Cadmium↗
PubMed1991

Citrate and renal calculi: new insights and future directions.

Citrate is pathogenetically important in stone formation, because it retards the crystallization of stone-forming calcium salts and because its level in urine is low in many patients with nephrolithiasis. Potassium citrate is useful therapeutically, because it can often restore normal urinary citrate. Hypocitraturia often results from dietary aberrations, including sodium excess, and exaggerated intake of animal proteins. Hypocitraturia is frequently accompanied by a low net gastrointestinal absorption of alkali. New drugs are under development as improvements or refinements of currently available potassium citrate. They are potassium citrate 10-mEq-tablet preparation, effervescent calcium citrate, and potassium-magnesium citrate.

Animals↗
PubMed1985

Evaluation of a flushing solution designed to protect kidneys from in situ ischemia.

An in situ flushing solution was evaluated with regard to the following: (1) its ability to protect the kidney during 60, 90, and 120 minutes of normothermic ischemia; (2) the effects of using an intracellular versus extracellular electrolyte composition in the flushing solution; and (3) the ability of the flushing solution to complement in situ hypothermia as a protective measure during long-term ischemia. Rat kidneys were briefly flushed in situ with an isotonic phosphate buffered solution (pH 7.2) containing 50 milliosmole of sucrose. The left renal pedicle was then immediately clamped to render the kidney ischemic and to hold the flushing solution in the kidney. Following removal of the pedicle clamp, a contralateral nephrectomy of the right kidney was performed and daily serum creatinine levels determined to evaluate postischemic renal function. The results indicate the following: (1) the flushing procedure is very effective in preventing postischemic acute renal failure following 60 minutes of normothermic ischemia, but is considerably less effective for ischemic times of 90 minutes or more; (2) an intracellular electrolyte composition in the flushing solution does not improve the protective effects of this solution; and (3) the flushing procedure can significantly improve on the protection otherwise provided by in situ hypothermia.

Acute Kidney Injury↗
PubMed1999

Investment strength as a function of time and temperature.

OBJECTIVES: The purpose of this investigation was to evaluate and compare the compressive strength characteristics of selected investments and to determine if these change as a function of time and temperature after mixing. METHODS: Two phosphate-bonded investments and one gypsum-bonded investment were selected and 288 cylindrical specimens were fabricated (n = 9). Baseline compressive strength values were determined for each material at room temperature and compressive strength measurements were made for all materials at 700 degrees C, and at 872 degrees C only for phosphate-bonded investments. Each material was tested at 2, 6, 12, and 24 h after mixing. Specimens were heated at 15 degrees C/min and heat soaked for 5 min in a burnout oven at the applicable testing temperature. They were transferred to a preheated chamber on an Instron testing machine and subjected to a compressive load at a crosshead speed of 2 mm/min until failure. The resulting strength data are presented in MN/m2. RESULTS: The gypsum-bonded investment did not exhibit marked differences in strength as a function of either time or temperature. The phosphate-bonded investments, on the other hand, demonstrated considerable changes in compressive strength and differed in compressive strength characteristics at 700 degrees C and 872 degrees C respectively. CONCLUSIONS: At elevated temperatures, all materials approximated peak strength 2 h after initial mixing. At room temperature, the phosphate-bonded investments in this study were not significantly stronger than the gypsum-bonded investment material. However, they exhibited increased compressive strength as a function of time and temperature that was considerably higher than that exhibited by the gypsum-bonded investments.

Analysis of Variance↗
PubMedDate not supplied

Giant urethral calculus: a rare cause of acute urinary retention.

We present a case of a 98-yr-old woman with acute urinary retention secondary to a large urethral calculus. This is a unique cause of obstructive uropathy for several reasons. First, urethral calculi are extremely rare in American-born Caucasian females. Second, urethral stones in females are nearly always associated with underlying genitourinary pathology; however, subsequent work up failed to reveal any strictures, diverticula, or related processes that may have predisposed this patient to urethral calculus formation. The epidemiology, pathogenesis, clinical presentation, and emergency management of large urethral calculi are reviewed.

Acute Disease↗
PubMed2000

Through-bond connectivity in solids by continuous-wave spin lock.

A simple two-dimensional correlation experiment that enables determination of through-bond connectivity in the solid state is described. The experiment is performed under fast magic angle spinning (MAS) conditions. After the initial pi/2 pulse, the magnetization develops freely under the MAS Hamiltonian. The t1-period is followed by a strong spin locking pulse used as mixing period. The dipolar coupling is averaged out by magic angle spinning, and the chemical shifts and r.f.-offsets are scaled by the applied spin locking field. Hence, for strong locking conditions, the isotropic J-coupling is the dominant interaction. The mixing Hamiltonian is thus identical to the well-known TOCSY-Hamiltonian, resulting in a net through-bond magnetization transfer. The mixing-time dependence of the exchange rates is investigated. Applications to crystalline P4S7 and MgP4O11 are shown.

Magnesium Compounds↗
PubMed2003

Advanced physico-chemical treatment experiences on young municipal landfill leachates.

In this study, Membrane Filtration (UF+RO), Struvite (MAP) precipitation and ammonia stripping alternatives were studied on biologically pre-treated Landfill Leachate. The results indicated that the system including the Upflow Anaerobic Sludge Blanket Reactor (UASBR) and Membrane Reactors (UF+RO) has been offered as an appropriate treatment alternative for young landfill leachates. This system provided high removals of COD, colour and conductivity (>98-99%). For ammonia removal, struvite precipitation was applied at the stoichiometric ratio (Mg:NH4:PO4=1:1:1) to anaerobically pre-treated raw landfill leachate effluent having an influent ammonium concentration of 2240 mg/l. Maximum ammonium nitrogen removal was observed as 85% at pH of 9.2. In ammonia stripping following 2 h of aeration, the removal was 72% at pH=12 while the removals were around 20% at pH=10 and pH=11. When membrane reactor, and struvite precipitation or ammonia stripping was applied to anaerobically pre-treated effluents, the results indicated that each system could be used as an appropriate post-treatment option for young landfill leachates. In economic aspect, ammonia stripping was found as the cheapest alternative with high ammonium removal. However, when both high COD and ammonium removals were to be achieved membrane technology such as UF+RO (SW) could be considered as the most appropriate system due to the fact that COD removal could be obtained very low by ammonia stripping.

Ammonia↗
PubMed2001

A new method for conservation of nitrogen in aerobic composting processes.

Several factors, such as pH, C/N ratio, temperature, mixing and turning, and aeration rate, could affect the loss of ammonia in composting reactions. Substantial loss of ammonia can reduce the nutrient value of the compost product and may lead to a severe odor problem in the composting facility. A new method for conservation of ammonia in composting was proposed and tested in this study. The ammonia being produced during the composting was precipitated into struvite crystals by addition of Mg and P salts. Ammonia volatilization was greatly reduced by this method and it also contributed to a remarkable increase in total ammoniacal-N (TAN) content in the compost, reaching up to 1.4% of dry mass. This value of TAN content was 3-5 times higher than that in normal compost. The scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analyses confirmed the formation of struvite crystals in the aerobic composting process.

Air↗
PubMed2003

Struvite precipitation in anaerobic swine lagoon liquid: effect of pH and Mg:P ratio and determination of rate constant.

Because of increased concern about surface water eutrophication from nutrient-enriched agricultural runoff, many swine producers are encouraged to decrease application rates of waste-based P. Precipitation and subsequent removal of magnesium ammonium phosphate (MgNH(4)PO(4) x 6H(2)O), commonly known as struvite, is a promising mechanism for N and P removal from anaerobic swine lagoon effluent. The objectives of this research were to (i) quantify the effects of adjusting pH and Mg:P ratio on struvite precipitation and (ii) determine the rate constant pH effect for struvite precipitation in anaerobic swine lagoon liquid. Concentrations of PO(4)-P in liquid from two anaerobic swine lagoons were determined after 24 h of equilibration for a pH range of 7.5-9.5 and Mg:P ratios between 1:1 and 1.6:1. Struvite formation reduced the PO(4)-P concentration in the effluents to as low as 2 mgl(-1). Minimum concentrations of PO(4)-P occurred between pH 8.9 and 9.25 at all Mg:P ratios. Struvite precipitation decreased PO(4)-P concentrations by 85% within 20 min at pH 9.0 for an initial Mg:P ratio of 1.2:1. The rate of PO(4)-P decrease was described by a first-order kinetic model, with rate constants of 3.7, 7.9, and 12.3 h(-1) at pH 8.4, 8.7 and 9.0 respectively. Our results indicate that induced struvite formation is a technically feasible method to remove N and P from swine lagoon liquid and it may allow swine producers to recover nutrients for off-farm sale.

Anaerobiosis↗
PubMed1998

Use of Chinese LiF:Mg,Cu,P (GR-200) TL detectors at therapy-level absorbed doses.

The objective was to find out whether or not the highly radiation-sensitive Chinese thermoluminescent (TL) LiF:Mg,Cu,P (GR-200) detector pellets can be used in therapy-level dosimetry. For this purpose the precision was investigated at an absorbed dose level of 1 Gy using a commercial TL read-out instrument. Relative standard deviations, sigma rel, of the individual calibration factors were found to be in the range between 0.2% and 0.6% from 30 randomly selected detectors, with the mean at 0.37%. Apart, linearity checks between 1 and 6 Gy resulted into a sublinear response of up to -4% which was successfully corrected for by a third-order polynomial curve fit. The residual signal turned out to be about 0.1% after one annealing cycle almost independent of the applied dose, and this figure could be reduced by two more decades after repeated annealing cycles.

Copper↗
PubMed2000

Dosimetric characterisation of a new production of MgB4O7:Dy,Na thermoluminescent material.

Thermoluminescent dosimetric characteristics of MgB4O7:Dy,Na are presented. MgB4O7:Dy,Na is a newly prepared TL material with attractive features for dosimetric applications, such as near-tissue equivalence, simple glow curve, high sensitivity and low fading. The dosimetric properties of this material examined in this study include glow curve shape, TL sensitivity, annealing procedure, photon dose response, minimum detectable dose, precision of TL measurements, reproducibility, energy response and fading characteristics.

Borates↗
PubMed1996

Susceptibility of electro-optic components to degradation in a space environment.

Possible causes of degradation of electro-optic systems operating in a space environment include not only the effects of radiation but also the effects of temperature, temperature cycling, atomic oxygen effects (for low-Earth orbits), micrometeoroid impacts, and contamination effects. For the majority of electro-optic components, the radiation environment in space does not present a significant problem. For a few components, or for electro-optic systems that must operate in a high radiation environment, special precautions must be observed. The effects of radiation, as well as other problems of the space environment, on electro-optic components, including recent results from the LDEF satellite experiments and some later measurements, are reviewed. Guidelines for materials and component selection shielding are presented.

Extraterrestrial Environment↗
PubMed2000

Single crystal EPR study of VO(II)-doped magnesium.

Single crystal EPR studies of VO(II)-doped magnesium potassium Tutton's salt have been carried out at room temperature. The results indicate that the paramagnetic impurity has entered the lattice, both substitutionally and interstitially and the maximum hyperfine for the substitutional site along the a axis corresponds to the minimum hyperfine for interstitial site and vice versa. The spin Hamiltonian parameters obtained from single crystal data for these sites are: Site 1, gparallel = 1.954(1); gperpendicular = 1.998(1), Aparallel = 19.80(2) mT; Aperpendicular = 7.61(2) mT; Site 2, gparallel = 1.997(1); gperpendicular = 1.952(1), Aparallel = 7.66(2) mT; Aperpendicular = 19.85(2) mT. Superhyperfine from ligand protons have been observed at certain orientations for Site 2 impurity. Powder spectrum shows a set of eight parallel and perpendicular features indicating the presence of only one site and these values matched with Site 1 values. From these observations, it has been concluded that the two vanadyl impurities are approximately at right angles to each other. Cooling the sample to 77 K does not change the spectra appreciably. The admixture coefficients have been calculated from Site 1 data, which agree well with the reported values.

Crystallization↗
PubMed2002

The Renner effect in triatomic molecules with application to CH+, MgNC and NH2.

We have developed a computational procedure, based on the variational method, for the calculation of the rovibronic energies of a triatomic molecule in an electronic state that become degenerate at the linear nuclear configuration. In such an electronic state the coupling caused by the electronic orbital angular momentum is very significant and it is called the Renner effect. We include it, and the effect of spin-orbit coupling, in our program. We have developed the procedure to the point where spectral line intensities can be calculated so that absorption and emission spectra can be simulated. In order to gain insight into the nature of the eigenfunctions, we have introduced and calculated the overall bending probability density function f(p) of the states. By projecting the eigenfunctions onto the Born-Oppenheimer basis, we have determined the probability density functions f+(rho) and f-(rho) associated with the individual Born-Oppenheimer states phi(-)elec and phi(+)elec. At a given temperature the Boltzmann averaged value of the f(p) over all the eigenstates gives the bending probability distribution function F(rho), and this can be related to the result of a Coulomb Explosion Imaging (CEI) experiment. We review our work and apply it to the molecules CH2+, MgNC and NH2, all of which are of astrophysical interest.

Algorithms↗
PubMed2004

A Raman spectroscopic study of thermally treated glushinskite--the natural magnesium oxalate dihydrate.

Raman spectroscopy has been used to study the thermal transformations of natural magnesium oxalate dihydrate known in mineralogy as glushinskite. The data obtained by Raman spectroscopy was supplemented with that of infrared emission spectroscopy. The vibrational spectroscopic data was complimented with high resolution thermogravimetric analysis combined with evolved gas mass spectrometry. TG-MS identified two mass loss steps at 146 and 397 degrees C. In the first mass loss step water is evolved only, in the second step carbon dioxide is evolved. The combination of Raman microscopy and a thermal stage clearly identifies the changes in the molecular structure with thermal treatment. Glushinskite is the dihydrate phase in the temperature range up to the pre-dehydration temperature of 146 degrees C. Above 397 degrees C, magnesium oxide is formed. Infrared emission spectroscopy shows that this mineral decomposes at around 400 degrees C. Changes in the position and intensity of the CO and CC stretching vibrations in the Raman spectra indicate the temperature range at which these phase changes occur.

Hot Temperature↗
PubMed2004

Theoretical studies of the spin Hamiltonian parameters and the local structures for M2+ (M=Co, Mn, V and Ni) ions in CsMgCl3.

The spin Hamiltonian parameters (zero-field splitting D, g factors g parallel, g perpendicular and hyperfine structure constants A parallel, A perpendicular) for M2+ (M=Co, Mn, V and Ni) ions in CsMgCl3 are studied by using the perturbation formulas of the spin Hamiltonian parameters for 3dn (n=7, 5, 3, 8) ions in trigonal symmetry based on the cluster approach. In these formulas, the contributions to the spin Hamiltonian parameters from the admixture of d orbitals of the central ions with the p orbitals of the ligands and from the trigonal distortion are included and the parameters related to these effects can be obtained from the optical spectra and the local structures of the studied systems. Based on the studies, it is found that the local trigonal distortion angle beta in the M2+ impurity center is unlike that betaH (approximately 51.71 degrees) in the host CsMgCl3. The spin Hamiltonian parameters for these divalent ions in CsMgCl3 are also satisfactorily explained by using the local angle beta. The validity of the results is discussed.

Cesium↗
PubMed2004

Investigations of EPR parameters and local lattice distortions for both Co2+ centers in La2Mg3(NO3)12.24H2O crystal.

The EPR g factors, g parallel and g perpendicular, of Co2+ and hyperfine structure constants (A parallel, A perpendicular) of 59Co2+ and 60Co2+ isotopes in both trigonal Mg2+ sites of La2Mg3(NO3)12.24H2O crystal are calculated from the high-order perturbation formulas of EPR parameters based on the cluster approach for 3d7 ion. It is found that to explain reasonably all these EPR parameters, the local relaxation effects (particularly, those related to the trigonal distortion angles thetai) in the vicinity of both Co2+ impurities should be considered. The local angles thetai are obtained from the calculations and the results are discussed.

Cobalt↗