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PubMed1996

Synchrotron radiation in the study of the variation of dose response in thermoluminescence dosimeters with radiation energy.

Thermoluminescence dosimetry (TLD) is a versatile technique with many applications for dosimetry of ionising radiation. However, in the range of kilovoltage x-rays which is widely used for diagnostic and therapeutic medical applications, problems arise from the differing dose response of most TL dosimeters with the radiation energy. The dose response of various TL detector types was investigated in mono-energetic x-ray beams of 26.8, 33.2, 40, 80.4 and 99.6keV from a synchrotron radiation source at the National Laboratory for High Energy Physics in Japan. This response was studied as a function of TL material (LiF:Mg,Ti, LiF:Mg,Cu,P and Al2O3), the detector geometry and size, and their thermal history. Due to the asymmetric diffraction from a Si crystal employed to produce monoenergetic photons there was more than 50% dose inhomogeneity in some of radiation fields used. Therefore, the different TL dosimeter types were rotated around and the results related to the reading of a set of "standard" LiF:Mg,Ti ribbons which were included in all experiments as reference detectors. No significant influence of the detector shape (physical size, thickness) on the dose response with energy could be found. However, the pre-irradiation thermal history influences the dose response with radiation energy: a fast cool down of LiF:Mg,Ti after a high temperature anneal will increase the sensitivity by more than a factor of two. The relatively new TLD material LiF:Mg,Cu,P (GR-200, obtained from Solid Dosimeter & Detector Laboratories, Beijing) was found to be approximately 100 times more sensitive than the standard LiF:Mg,Ti. In addition it proved to be more tissue equivalent for photon radiation between 27keV and 40keV. The performance of LiF:Mg,Cu,P makes it a very interesting TL material deserving further evaluation for applications in diagnostic and therapeutic x-rays.

Aluminum Oxide↗
PubMed1997

Reflections on antireflection films.

BACKGROUND: The development of antireflection films 50 years ago was based on interference of light waves. Antireflection films have broad ophthalmic applications by increasing transmittance and decreasing reflection as a function of wavelength and polarization. Design considerations of thin films are enormous, as are the rigors of successful film production. METHODS: A computer search of optometric and ophthalmologic databases produced very few pertinent references. Discussions with optical engineers led to extensive publications in optical engineering journals and texts. RESULTS: Literature search and interviews with optical engineers provided the historical development, design, and production considerations of optical antireflection coatings. CONCLUSIONS: Ophthalmic thin-film antireflection coatings have a long but unknown development. Many design and production parameters must be considered in producing effective, long-lived ophthalmic coatings, which do offer significant improvement in optical performance.

Eyeglasses↗
PubMed1997

Randomized, controlled comparison of two forms of preparation for screening flexible sigmoidoscopy.

OBJECTIVE: There is a paucity of data regarding the optimal form of bowel preparation for flexible sigmoidoscopy. Most endoscopists recommend enemas. A simpler preparation that is easy, acceptable, and that reduces patient encounter time would be desirable, and might be cost-effective. Our objective in this study was to evaluate a simple oral form of preparation for screening flexible sigmoidoscopy. METHODS: In this randomized, single-blind, controlled trial, we compared two forms of preparation in consecutive male patients referred for screening flexible sigmoidoscopy. The oral preparation consisted of one bottle of magnesium citrate and two "Dulcolax" tablets on the evening before flexible sigmoidoscopy. This was compared with the standard form of preparation, namely, two Fleet's enemas given on arrival at the endoscopy suite. Thirty-seven patients received the oral preparation [mean age, 62.8 +/- 8.9 (SD) yr]; 33 received enemas (mean age, 65.2 +/- 7.3 yr). Endoscopists were blinded to the preparation. RESULTS: Mean time between arrival and starting flexible sigmoidoscopy was 36 +/- 22 (SD) min for patients on oral preparation, and 62 +/- 25 min for patients receiving enemas (p < 0.0001). Mean times performing flexible sigmoidoscopy were 10 +/- 3 min and 13 +/- 4 min, respectively (p = 0.004). Mean patient satisfaction score (range 0-13) was higher for patients given the oral preparation (11.4 +/- 1.8) than for patients receiving enemas (9.6 +/- 2.4) (p = 0.001). Fifteen patients randomized to receive the oral preparation had previous flexible sigmoidoscopy with an enema preparation; all preferred the oral form. Mean technical difficulty (range 1-10) was 3 +/- 2.2 for patients given the oral preparation and 4.9 +/- 3.1 for patients receiving the enema preparation (p = 0.01). Polyps were identified in 10/37 patients who received the oral preparation and in 3/33 patients who received enemas (p = 0.05). Quality of colon preparation was judged "good" in 29, "fair" in four, and "poor" in four, among the 37 patients given the oral form; corresponding values for 33 patients given enemas were 16, 10, and 7 (p = 0.03). CONCLUSION: Patient acceptance, encounter time, technical ease, and quality of colon preparation were significantly better with the oral form of colon preparation than with the standard Fleet enema preparation.

Administration, Oral↗
PubMed1997

[Urolithiasis in children in West Algeria].

We analyzed a series of 61 stones from children aged 3 to 14 years old using Fourier transform infrared spectroscopy. The calculi were collected from urology departments of the University Hospitals of Oran, Sidi-Bel-Abbès and Mostaganem in West Algeria. This series is the first investigation concerning the composition of stones in children based on infrared analysis. Calculi were more frequent in males (75.4%) and mainly localized in the bladder (55.8%). Upper urinary tract calculi were more frequent in children over the age of 10 years, and the sex ratio was about 1. Calcium oxalate monohydrate was present in 70.5% of stones and was the main component in 50.8% of cases both in whole stones and nuclei. In contrast, calcium oxalate dihydrate was the main component in only 9.8% of calculi although it was present in 75.4% of stones. Ammonium urate was detected in 29.5% of stones and was always the main component of nuclei. Uric acid, observed in 31.1% of calculi, was the major constituent in 14.7% of stones and 19.7% of nuclei. Magnesium ammonium phosphate was observed in 24.6% of stones as a consequence of urinary tract infection by urea-splitting bacteria. Our observations emphasized that the anatomical location of stone and their composition were in accordance with those previously reported in other countries.

Adolescent↗
PubMed1997

[Current information on the composition and breed distribution of urinary stones in dogs].

5706 canine urinary stones were analyzed by means of infrared spectroscopy from 1984-1996. The stones were sent in together with epidemiologic data (breed, age, sex, localisation of the stones, type of stone removal, stone frequency etc.) by more than 800 veterinarians from Germany, the Netherlands, Austria, and Switzerland. Irrespective of stone type, urinary stones were observed in almost all breeds, but small breeds like dachshound, poodle, terrier, schnauzer, and pekingese have a higher tendency to form stones. With 59.5% struvite is the most frequent stone type, followed by cystine with 15.5%. Cystine stones are becoming less frequent during the observation time, whereas the share of calcium oxalate (14.2%) and ammonium urate (6.0%) stones remains unchanged. The latter stone types are found predominantly in specific breeds. The stone formation appears predominantly at the age of 7. Male dogs form stones twice as often as female dogs. 98% of the stones were located in the lower urinary tract. About 90% of the urinary stones required surgical treatment.

Animals↗
PubMed1998

Accurate determination of chemical composition of urinary calculi by spiral computerized tomography.

PURPOSE: Choice of efficacious clinical management of symptomatic renal calculi can be facilitated by ascertaining the precise chemical composition of the calculus. Spiral computerized tomography (CT) is becoming a frequently used radiographic examination to establish the diagnosis and severity of calculus disease. Our objective for this study was to determine the precision of spiral CT in identifying the chemical composition of 6 different types of urinary calculi with region of interest measurements using spiral CT. MATERIALS AND METHODS: A total of 102 chemically pure stones were separated into 6 groups. The stones along with phantoms containing butter (fat) and jello (water) were mounted vertically in the scanner gantry. Then 1 mm. thickness scanning was performed with a high speed scanner at the 2 energy levels of 80 and 120 kV. The determination of the chemical composition was performed using the absolute CT value measured at 120 kV. and the dual kilovolt CT values measured at 80 and 120 kV. Hounsfield unit at 80 kV.-Hounsfield unit at 120 kV.). RESULTS: The absolute CT value measured at 120 kV. was able to identify precisely the chemical composition of uric acid, struvite and calcium oxalate stones. It was imprecise in differentiating calcium oxalate from brushite stone and struvite from cystine stone. However, dual kilovolt CT value was able to differentiate these latter stones with statistical significance (p < 0.03). Uric acid stones were easily differentiated from all other stones using the absolute CT value. CONCLUSIONS: This study demonstrates that the chemical composition of urinary calculi can be accurately determined by CT scanning in an in vitro setting.

Calcium Oxalate↗
PubMed1998

The effect of calprotectin on the nucleation and growth of struvite crystals as assayed by light microscopy in real-time.

PURPOSE: To use light microscopy to observe the urease-induced growth of struvite crystals in real-time, and to compare the effects of various proteins on that growth. MATERIALS AND METHODS: Artificial urine, with and without citrate, and a minimal urine solution containing only urea and the components of struvite and apatite were incubated with urease and test proteins in the depressions of culture slides. The number and size of rectangular and X-shaped struvite crystals were recorded using a low-power phase contrast microscope. RESULTS: The formation of crystalline struvite appears to occur after the formation of an amorphous calcium- and magnesium-containing phase. The extent of this amorphous phase is dependent on the presence of calcium and citrate, both of which strongly promote its formation over the crystalline phase. alpha-globulin, gamma-globulin and chymotrypsin inhibitor all result in the same amount of crystalline struvite as bovine serum albumin which is used as a control. Calprotectin, on the other hand, causes consistent and significant reductions in the number and size of struvite crystals under a wide range of conditions. No changes in the morphology of the struvite crystals were observed. CONCLUSIONS: Calprotectin, the dominant protein of infection stone matrix, has distinctive properties which affect the formation and growth of struvite crystals. The presence of citrate in synthetic urine dramatically reduces the number of struvite crystals observed. The present method for observing the effects of putative infection stone inhibitors appears to have merit.

Crystallization↗
PubMedDate not supplied

[Early diagnosis of urolithiasis, assessment of its activity and composition of lithogenic urine salts (Litos system)].

Until recently, the diagnosis of urolithiasis has been made by its complication--an apparent calculus in the kidney. We have discovered the phenomenon of pathological crystallization of urinary lithogenetic salts. Now, basing on this phenomenon we are able to make a diagnosis of urolithiasis at its preclinical stage, i.e. before the appearance of renal calculus, to control the course of urolith formation and to find out composition of the stone. We propose a complex of original techniques (Litos system) which provides pathogenetic diagnosis of urolithiasis.

Apatites↗
PubMed1998

[Giant vesico-vaginal stone: a case report].

A 74-year-old female with the chief complaint of lower abdominal and anal pain had been suffering from total incontinence due to cerebral palsy since her childhood. A giant stone was palpable on vaginal examination. A radiograph showed a giant calcification in the pelvis. Magnetic resonance imaging (MRI) revealed a giant vesico-vaginal stone, which occupied most of the bladder and vagina. Cystolithotomy was performed. The removed stone weighed 435 g, and measured 9.0 x 6.5 x 5.5 cm, and was composed of magnesium ammonium phosphate. To our knowledge only eight cases of female giant vesical stone have been reported. We herein report a rare case of vesico-vaginal stone unrelated to gynecological procedures.

Aged↗
PubMed1998

A cystic calculus from a wild western spiny softshell turtle (Apalone [Trionyx] spiniferus hartwegi).

During a postmortem examination of a western spiny softshell turtle (Apalone [Trionyx] spiniferus hartwegi), a calculus (24 x 21 x 12-mm) with a dry weight of approximately 5 g was discovered in the urinary bladder. Chemically, the calculus was a mixture of apatite (basic calcium phosphate), struvite (magnesium ammonium phosphate hexahydrate), and unidentifiable crystals. This is the first report of a cystic calculus in a wild chelonian.

Animals↗
PubMed1998

Comparative experimental study of Mg lactate, vitamin B6 and their association on the permeability of a human membrane. 2. Effects on cellular and paracellular ionic transfer through isolated amniotic membrane.

The comparative effects of Mg lactate, pyridoxine chlorhydrate and their association were observed on the various components of the human transamniotic conductance Gt. The use of both microelectrodes and metabolic inhibitors indicates 12 components of Gt: 8 cellular components Gc (Na-K, ATPase, Na-H and Cl-HCO3 antiports, Na-K-2Cl cotransport, Na-Mg exchanger and Na, K, Cl channels), one coupling component and three paracellular components Gp (Na, K, Cl). Mg lactate had a monophasic action on some components (decrease or increase conductance), according to its concentration, on maternal side (MS): GpNa, GpK, GpCl, K channels, conductance due to Na-K, ATPase. On fetal side (FS), there is a monophasic action on GpK, Na channels and a biphasic action (decrease then increase conductance) on GpNa and Na/Mg (as on MS). Pyridoxine chlorhydrate had a monophasic action on GpNa (MS, FS), GpK (MS), Na/Mg (MS, FS) and a biphasic action on GpK (FS), Na channels (MS, FS). The association of both Mg lactate and pyridoxine chlorhydrate implicated a biphasic action on all cationic components on both sides (GpNa, GpK, Na and K channels, Na/H, Na-K-2Cl, Na/Mg. The anionic components were not modified with regard to agents. The Mg lactate + vitamin B6 association interferes specifically with the cationic conductance components with regard to individual components.

Amnion↗
PubMed1999

Urolithiasis in dogs V: regional comparisons of breed, age, sex, anatomic location, and mineral type of calculus.

OBJECTIVE: To determine extent and nature of regional differences in distribution of canine urinary calculi. SAMPLE POPULATION: 13,552 calculus specimens: 7,056 (52.1%) from females, 6,492 (47.9%) from males, and 4 from dogs of unrecorded sex. Procedure Records were used to compile information from all specimens submitted between July 1981 and December 1995. Results from mixed-breed and various breeds of stone-forming dogs were analyzed. Interrelations of breed, sex, and age of dogs, and anatomic location and mineral composition of specimens were analyzed and compared for 6 US geographic regions. RESULTS: Struvite-, apatite-, and urate-containing calculi were reported significantly most often from female dogs of the Mountain/Pacific region. Oxalate-, silica-, and brushite-containing calculi were reported significantly most often from male dogs in the New England/mid-Atlantic (NEMA) region. Cystine-containing calculi were reported most frequently from the NEMA and South Central (SC) regions. Dogs from the NEMA region were oldest in average age at diagnosis. Significant regional differences in distribution were found for several breeds. Sex distribution of renal calculi in 11 breeds of dogs (Lhasa Apso, Yorkshire Terrier, Shih Tzu, Basset Hound, Pug, Mastiff, Bichon Frise, Doberman Pinscher, Dalmatian, English Bulldog, and Pekingese) reported to be at high risk of renal lithiasis differed among the 6 geographic regions. Renal and ureteral calculi were reported significantly most often from dogs in the South Atlantic region, and bladder and urethral calculi were reported most often from dogs in the SC region. CONCLUSIONS: Wide regional differences exist in distribution of stone-forming dogs by sex, average age at diagnosis, breed, and minerals contained within and anatomic location of calculi.

Age Factors↗
PubMed1991

Increased responsiveness of rat mast cells to compound 48/80 due to removal of extracellular magnesium. Effects of ouabain and EGTA.

A decreased secretory response of mast cells to compound 48/80 (12% of control value) after preincubation of the cells with magnesium but without calcium was partially restored by removal of magnesium. EGTA (10 microM) blocked the restoration and decreased the restored secretory activity again, while this was further increased by ouabain (1 mM). Furthermore, ouabain completely restored the decreased secretion (50% of control value) due to preincubation without the divalent cations. This may indicate that magnesium influences a pool of cellular calcium that is involved in the stimulus-secretion coupling and is available to EGTA, and ouabain did not counteract the inhibitory mechanism of magnesium.

Animals↗
PubMed2002

Nanocrystalline metal oxides as destructive adsorbents for organophosphorus compounds at ambient temperatures.

Nanocrystals of magnesium oxide react with organophosphorus compounds at room temperature by dissociative chemisorption, which we term "destructive adsorption". This process involves cleavage of P-O and P-F bonds (but not P-C bonds) and immobilization of the resultant molecular fragments. These ultrafine powders have unusual crystalline shapes and possess high surface concentrations of reactive edge/corner and defect sites, and thereby display higher surface reactivity, normalized for surface area, than typical polycrystalline material. This high surface reactivity coupled with high surface area allows their use for effective decontamination of chemical warfare agents and related toxic substances. Herein data is presented for paraoxon, diisopropylfluorophosphate (DFP), and (CH3CH2O)2P(O)CH2-SC6H5 (DEPTMP). Solid-state NMR and IR spectroscopy indicate that all OR and F groups dissociate; this leaves bound -PO4, -F, and -OR groups for paraoxon, DFP, and DEPTMP, respectively. For paraoxon, it was shown that one monolayer reacts. For DEPTMP, the OR groups dissociate, but not the P-CH2SC6H5 group. The nanocrystalline MgO reacts much faster and in higher capacity than typical activated carbon samples, which physisorb but do not destructively adsorb these phosphorous compounds.

Adsorption↗
PubMed2002

Aqua(phthalocyaninato)magnesium.

The title compound, [Mg(C(32)H(16)N(8))(H(2)O)], crystallizes with two MgPc(H(2)O) molecules (Pc is phthalocyaninate) in the asymmetric unit. The geometries of the two molecules are very similar, with the Mg atoms each 4+1-coordinated by four isoindole N atoms at the base and by the O atom of the water molecule. The Mg atoms are displaced by 0.447 (1) and 0.468 (1) A from the basal coordination planes towards the water O atoms. O-H.N hydrogen bonds form dimers stacked along the b axis in a herring-bone fashion.

Journal Article↗