Manganese activation of CaSO4:Dy

The influence of Mn activation on CaSO4:Dy thermoluminescent (TL) phosphor has been observed to study the basic TL characteristics such as TL output, fading, sensitivity, and dose response. The experimental results indicate that the TL characteristics are strongly influenced by the concentration of Mn dopant in CaSO4:Dy, especially for the low temperature trapping peak of the glow curves. The TL properties of CaSO4:Dy:Mn phosphor with a concentration ratio of 1:4 of Dy to Mn include not only high sensitivity, negligible fading, and linear dose response as compared to the CaSO4:Dy phosphor, but also two well-separated peaks and relative peak heights. This suggests that it can be used for accidental dose and elapsed time evaluations as well as for a routine personnel dosimeter. It was also found that 350 degrees C to 400 degrees C for 30 min is the optimum temperature and time in annealing treatment for this phosphor.     

Glow-peak stability in 6LiF:Mg,Ti (TLD-600) exposed to a Fe-ion beam

The stability of glow peaks in 6LiF:Mg,Ti (TLD-600) exposed to a high-energy Fe-ion beam was examined in comparison to 137Cs gamma-ray irradiation under changing annealing conditions. The peak areas induced by the Fe ions were much smaller than those by gamma-rays. The sizes and positions of peaks 3-5 in Fe-ion irradiated samples were hardly changed after post-annealing at 100 degrees C x 30 min, regardless of the pre-annealing conditions (fast quenching or subsequent pre-annealing at 100 degrees C x 2 h). Whereas, the peaks in gamma-ray irradiated samples were notably affected by post-annealing; the peak positions and peak-area sizes changed in different ways depending on the pre-annealing conditions. The effects of post-annealing on peak 6 were identical for Fe ions and gamma-rays. These facts suggest that peaks 3-5 in TLD-600 comprised both stable and unstable luminescent centers, and that the latter part would be easily depleted in highly dense ionization.     

A new phosphor Li2B4O7: Cu for TLD

The phosphor Li2B4O7: Cu (0.03% by weight) has an effective atomic number of 7.3, which is very similar to that of tissue (7.4). This suggests that the phosphor should have excellent properties for thermoluminescent dosimetry. The phosphor prepared by a sintering method shows two glow peaks composed of a dosimetric peak at 205 degrees C and a shoulder at 120 degrees C, and a broad emission band peaking at 368 nm. The material based on the stoichiometric compound of Li2O . 2B2O3 has a good moisture resistant property. The dosimetric characteristics are as follows: (1) The sensitivity of gamma rays is about 20 times higher than that of Li2B4O2: Mn prepared by the conventional melting method. (2) The dosimetry peak of 205 degrees C fades less than 9% in intensity at 25 degrees C after 60 days in dark. (3) The TL output is linear with exposure to about 10(5) R, becoming sublinear above it. (4) The sensitivity loss caused by humidity is about 10-25% after 2-6 months of storage in air of 90% relative humidity at 25 degrees C. (5) The energy dependence of TL output for photons is flat within the limit of 10% from 40 keV to 7 MeV. (6) The light induced fading is 10% after 3 h room lighting at 1000 lux.     

Determining optimal heat treatment of soybeans by measuring available lysine chemically and biologically with rats to maximize protein utilization by ruminants.

Soybeans were heated in a forced air oven at 120 and 130 degrees C for 60 and 180 min, and at 140, 150 and 160 degrees C for 10, 30, 60, 90 and 120 min. Two types of measurements were used to determine optimal heat treatment of soybeans to maximize protein utilization by ruminants. One was to estimate the rate and extent of protein degradation in the rumen using an in vitro ruminal system. The second was to determine the nutritional availability of lysine. Methods used to determine available lysine were an indirect fluorodinitro-benzene chemical method and a rat growth assay. The product of undegraded intake protein and available lysine content was used to estimate the amount of lysine that would escape ruminal degradation and be available for intestinal absorption. As heat input increased, ruminal undegraded intake protein increased, and protein degradation rates and total and available lysine decreased. As temperature increased, the time required to maximize post-ruminal available lysine decreased. The optimal heat treatment for soybeans heated in a forced air oven was: 140 degrees C for 120 min or greater, 150 degrees C for 60 min or 160 degrees C for 30 min. A loss of 15-22% of chemically determined available lysine was necessary to achieve the heat treatment that resulted in maximal post-ruminal available lysine.     

Optimizing the use of LiF:Mg,Cu,P (GR-200 P) to measure low dose irradiation in nuclear medicine

We undertook a study in order to determine the optimal conditions under which thermoluminescent powder LiF:Mg,Cu,P (GR-200 P) could be used for applications in nuclear medicine and for dosimetric needs. First, we defined the conditions chiefly related to the readout chain, namely the optimal mass of GR-200 material used for each readout, which is between 15 and 30 mg, and the optimal glow curve readout, which corresponds to heating in two phases: a rise in temperature at the rate of 10 degrees C s(-1) up to 150 degrees C followed by a plateau lasting 10 s and then another rise in temperature at the rate of 25 degrees C s(-1) up to 260 degrees C followed by a second plateau lasting 6 s. The optimum conditions for using TL material were also studied: using GR-200 P without annealing and performing two successive readouts of the same sample only led to a 0.1% loss in sensitivity per re-use cycle, and the good reproducibility of measurements was preserved with stable and weak residual TL signal. The response of the sample irradiated at three different dose levels with a 60Co gamma photon beam remained constant over 40 d. Sensitivity was preserved to within +/-4% between a few tenths of a microGy and 1 Gy. Our observations concur with the results of the literature and show how to optimize the conditions for using the GR-200 thermoluminescent dosimeter to measure low doses with a simple procedure that preserves the sensitivity of material.     

Gamma radiation dosimetry using a NaCl:Ba(T) thermoluminescent phosphor

A detailed examination is presented of the thermoluminescence (TL) characteristics of untreated and heat-treated pure and Ba-doped NaCl exposed to gamma radiation at room temperature. The NaCl:Ba (10(-2) molar fraction) phosphor quenched from 750 degrees C, designated as NaCl:Ba(T), is found to give a pronounced TL output with a well-defined glow peak around 220 degrees C (peak III) along with other peaks at lower temperatures. It is suggested that the TL centre associated with glow peak III is comprised of an impurity-vacancy dipole with a negative ion vacancy in its vicinity. The TL centres are presumed to be located in the dislocation region. The dosimetric properties of peak III after gamma irradiation have also been examined. It is observed that most of the basic requirements of an efficient TLD material are fulfilled by the phosphor.     

Simultaneous estimation of exposure and time elapsed since exposure using multipeaked thermoluminescent phosphors

Knowledge of the time elapsed since a radiation exposure may be useful in personnel monitoring, as for example in determining the time for occurrence of an over exposure or a nuclear accident, or in the choice of a therapy procedure, etc. This paper describes the application of the multipeaked thermoluminescent phosphors, such as natural CaF2, and Harshaw's type of LiF, for the simultaneous estimation of the exposure and the time elapsed since this exposure. Natural CaF2 used for this purpose has three types of traps, so that the glow curve shows three maxima at about 100, 180 and 260 degrees C. These can easily supply data for the computation of both results. From the area under the 260 degrees peak the exposure can be calculated with good precision within the range from a few millirads to some kilorads. The spontaneous decay of the electrons from shallow traps at normal temperatures (fading) with time after exposure leads to the decrease of the peak areas. The 100 degree peak decays most rapidly, and after about a month the decay of the 180 degree peak is observable. By measuring the ratios of the areas under the peaks, or of the peak heights, the time elapsed since the exposure may be assessed with a precision of about 10% for the range from a few hours up to a thousand days. These ratios are independent of the exposure, the LET, and the dose rate. LiF phosphor offers similar possibilities.(ABSTRACT TRUNCATED AT 250 WORDS)     

Characterization of Al2O3 sintered pellets for dosimetric applications in radiotherapy.

Al2O3 sintered pellets were tested in relation to their thermoluminescent properties, to investigate the possibility of their use for dosimetry in the radiotherapy cases of 60Co and x-radiation. The material is inexpensive and has a glow peak at about 280 degrees C, a linear dose response between 0.1 and 100 Gy, suitable reproducibility and a low detection limit. The thermoluminescent response can easily be corrected for fading and the energy dependence, when necessary.     

Synthesis, anti-HIV and antitubercular activities of lamivudine prodrugs

The synthesis of a novel series of lamivudine prodrugs involving N4-substitution with isatin derivatives is described. The in-vitro antiretroviral activities indicated that compound 3b was found to be equipotent to lamivudine with EC50 of 0.0742+/-0.04 microM. Lamivudine prodrugs bearing fluoroquinoles antibacterial showed 92-100% inhibition against Mycobacterium tuberculosis strain H37Rv at 6.25 microg ml(-1). At pH 7.4, 37 degrees C, the hydrolytic t(1/2) ranged between 120 and 240 min.     

Oral fat exposure increases the first phase triacylglycerol concentration due to release of stored lipid in humans

Oral exposure to dietary fat (through modified sham feeding, which entails mastication and expectoration of foods) augments the postprandial triacylglycerol (TAG) concentration, in part, though augmented lipid absorption. This study was designed to characterize early events in this process. At 2200 h, 25 healthy adults (13 men, 12 women) consumed 80 g of almonds (high oleic acid content) and fasted until approximately 0700 h. After placement of a catheter in a hand vein and 4 blood draws at 10-min intervals, 50 1-g safflower oil (high linoleic acid content) capsules were consumed. After another blood draw, modified sham feeding was initiated with a cracker only or cracker with cream cheese in random order with 1 wk between trials. Oral exposures occurred at 5-min intervals for 60 min then at 15-min intervals from min 60 to 120. Additional blood draws occurred at 2, 4, 6, 8, 10, 12, 14, 30, 60, 120, 240, 360 and 480 min. Oral stimulation, especially by fat, prompted the rapid (mean approximately 23 min) release of lipid stored from the previous meal (almonds) in all participants. This resulted in multimodal postprandial triacylglycerol (TAG) peaks generally occurring at 0-30 min, 60-120 min and 240-480 min after loading and initiation of oral stimulation. TAG magnitudes during these times were correlated (r = 0.40-0.89, P < 0.001-P = 0.053). It is proposed that the sensory-enhanced release of lipid from the residual pool initiates an early TAG rise, which augments the peak attributable to absorption of meal lipid; this in turn supplements a later peak associated with release of endogenously synthesized TAG because lipid from all three sources competed for a common clearance mechanism. If substantiated, additional understanding of the behavioral factors (e.g., eating patterns) that initiate this cascade will be warranted.     

Dosimetric properties of europium-doped potassium bromide thermoluminescent crystals.

The dosimetric thermoluminescent properties of potassium bromide crystals doped with europium have been investigated. Nominal concentrations of europium ions varied between 0.01% and 1%. The crystals were annealed prior to irradiation following different thermal treatments. We report the glow curve and dose-response characteristics to 60Co gamma rays. After a particular annealing, the crystals showed a strong thermoluminescent peak near 100 degrees C and a linear response for doses between 0.03 cGy and 10 cGy. The sensitivity is approximately 10 times that of lithium fluoride (TLD-100).     

Effect of deep-fat frying on ascorbic acid, carotenoids and potassium contents of plantain cylinders

The influence of thermal treatment (frying of plantain) on the micronutrients ascorbic acid, potassium and carotenoids is evaluated. Cylinders (diameter 30 mm, thickness 10 mm) of plantain (Musa AAB 'barraganete') were fried at four thermal treatments (120-180 degrees C and from 24 to 4 min) to obtain products with approximately the same water content (approximately 0.8+/-0.02 kg/kg1) and fat content (approximately 0.15+/-0.06 kg/kg). The thermal study used the cook value and the mean cook value as indicators of the effect of several different treatment temperatures and times on quality. Deep-fat frying had no significant effect on carotenoid contents at any frying conditions, and on potassium content, except at 120 degrees C and 24 min (loss 相似文献   

Conservative evaluation of space radiation dose equivalent using the glow curve of 7LiF:Mg, Ti (TLD-700)

For conservative evaluation of dose equivalent in space, a simple method using two glow peaks in TLD-700 has been proposed. This method is superior to the method using the two-peak ratio in terms of following the 1990 ICRP recommendation. Dependence of each peak on LET was confirmed using relativistic heavy-ion beams (He, C, Ne, Ar, and Kr) at NIRS-HIMAC. TL values as gamma-ray absorbed-dose equivalent of both peak areas were additionally combined to conservatively estimate a dose equivalent over a range of LET of 0.5-440 keV microm(-1). This method was tested in an 8.8-d Shuttle-Mir mission (STS-89) at 400 km x 51.65 degrees. The dose-equivalent rates obtained at two positions in the Spacehab module were about 0.9 mSv d(-1); this result is reasonable in a conservative sense.     

Effect of variable doses of ultraviolet radiation (253.7 nm) on thermoluminescence NaCl:Ca(T) material

This paper studies the thermoluminescence (TL) glow curves of NaCl:Ca(T) phosphors to various doses of 253.7-nm ultraviolet (UV) radiation at room temperature. TLD grade NaCl:Ca(T) material was obtained by crystallization from solution and was subsequently annealed at 750 degrees C for 2 h, followed by sudden quenching. We undertook measurement of the effect of variable UV radiation doses (10(2) to 10(6) J m-2) on the TL behaviour of NaCl:Ca(T) phosphors. It was observed that the phosphor exhibits a dominant peak around 167 degrees C along with a weak peak at lower temperature. The high-temperature peak (Peak II) is found to grow linearly with the increase in UV dose in the range of 10(2) to 10(6) J m-2. Since the nature of the glow curves under the influence of different doses remains more or less identical, it is believed that the phosphor does not undergo radiation damage and displays high intrinsic TL around Peak II. Examination of the system for fundamental dosimetry requirements shows that it can be used in dosimetry work at 253.7 nm.     

Study of stabilizing CaF2:Dy ultraviolet sensitivity by double annealing treatment

The intrinsic thermoluminescent response to ultraviolet radiation of CaF2:Dy phosphor is enhanced by pre-irradiation high-temperature annealing treatment. The thermoluminescent response is stabilized by adding a medium temperature annealing treatment after the previous annealing. The experimental results show that the annealing treatment of 1 h 850 degrees C high-temperature annealing followed by 1 h 350 degrees C medium-temperature annealing is the optimum treatment to have high thermoluminescent response and good stability. The results also show that (1) the thermoluminescent response to 253.7 nm ultraviolet radiation is increased and stabilized, (2) the thermoluminescent sensitivity and glow curve distribution to 235.7 nm ultraviolet radiation are retained, and (3) the thermoluminescent response to 253.7 nm ultraviolet is linear from 3 to 1 x 10(3) Jm(-2), but there is no linear response with respect to 365 nm ultraviolet.     

高温、苯并芘-7,8-二醇-9,10-环氧化物单独作用对人肺腺癌细胞Hsp27、Hsp70表达的影响

目的研究不同温度和不同浓度B(a)P7,8二醇9,10环氧化物(BPDE)作用A549细胞后,热休克蛋白27(HSP2)、热休克蛋白70(Hsp70)的表达规律。方法体外培养的A549细胞分为高温应激组和BPDE组。37℃培养的细胞作对照,高温应激组细胞置于高温(39℃、42℃、43℃)应激2小时。BPDE组用不同浓度的BPDE(0、2、4、8μmolL)染毒2h。利用Westernblot技术分析A549细胞株中Hsp27、Hsp70的表达水平。结果高温应激组细胞Hsp27的表达较37℃对照明显升高,差异均有显著性(P<0.05)。在39℃,Hsp27的表达水平达到峰值。高温处理后,Hsp70的表达也增加,在42℃达到最高,且与对照相比差异有显著性(P<0.05)。BPDE组Hsp27、Hsp70的表达均较对照明显升高,其中Hsp27的表达水平在实验用最高浓度8μmolL达到最高,且与对照比较差异有显著性(P<0.05),但仍处于上升阶段。Hsp70在4μmolL达到最高,在4μmolL和8μmolL时,Hsp70的表达水平与对照比较差异有显著性(P<0.05)。结论高温和BPDE均能诱导A549细胞Hsp27、Hsp70的表达。高温应激时,Hsp27和Hsp70的表达水平分别在39℃和42℃达到峰值。BPDE处理时,Hsp27在8μmolL时表达最高,但仍处于上升趋势,而Hsp70在4μmolL时表达最高。     

Convective heat processing of turkey roll: effects on sensory quality and energy usage

Twenty-four frozen, raw, boneless, ready-to-cook turkey rolls were cooked in an institutional electric convection oven to an internal temperature of 77 degrees C. Six treatment combinations of three cooking temperatures (105 degrees C, 135 degrees C, and 165 degrees C) and two holding conditions (not chilled and chilled for 24 hours) were studied. Turkey rolls from each treatment combination were subjected to three hot-holding times (0, 60, and 120 minutes). Electrical energy usage was monitored during heat processing of the turkey rolls, reheating the turkey slices, and hot holding the turkey slices. Aroma, juicy mouthfeel, texture, flavor, and flavor off-notes of the cooked turkey were evaluated by seven judges using 150-mm unstructured line scales. Chew counts also were recorded. Turkey cooked at 105 degrees C took significantly more time to cook (331 vs. 227 and 203 minutes) but consumed significantly less energy (3.4 vs. 3.8 and 4.5 kWh) than turkey rolls cooked at 135 degrees C and 165 degrees C, respectively. Significantly higher juicy mouthfeel scores were obtained when the turkey roll was cooked in the convection oven at an oven temperature of 105 degrees C, the turkey was not chilled, and the slices were held hot for 60 minutes or less.     

Comparison of time course changes in blood glucose, insulin and lipids between high carbohydrate and high fat meals in healthy young women

Few studies have examined short term responses to the different contents of carbohydrate or fat in the meal, although long term effects of the high fat meal have been considered as compound risk factor for metabolic disorders. The aim of this study was to investigate the postprandial changes of plasma glucose, insulin and lipids upon intakes of high carbohydrate or high fat meal in young healthy women. Subjects were randomly assigned to either the high carbohydrate meal (HCM, 75% carbohydrate, n=13) or the high fat meal (HFM, 60% fat, n=12) groups. The meals were prepared as isocaloric typical Korean menu. Blood samples were obtained prior to and 30, 60, 90, 120, 180 and 240 minute after the meal. There were no significant differences on fasting blood parameters including glucose, insulin, lipids concentrations between the groups prior to the test. The HCM had higher blood glucose and insulin concentrations, reached the peak at 30 min and maintained for 240 min compared to the HFM (P<0.05). The HFM had higher plasma triglyceride (TG) and free fatty acid (FFA) concentrations, reached the peak at 120 min and maintained for 240 min compared to the HCM (P<0.05). It is concluded that macronutrients content in the meal may be an important determinant of postprandial substrate utilization in healthy women.     

Thermal neutron fluence measurement in a research reactor using thermoluminescence dosimeter TLD-600.

A thermal neutron fluence in the range between 10(11) and 10(13) n cm(-2) in the reactor core of the Tehran research reactor has been measured using TLD-600 thermoluminescence dosimeters. After a thermal treatment of 1 h at 400 degrees C followed by 20 h cooling down to room temperature of pre-exposed dosimeters in the reactor, the accumulated TL light was measured after periods of storage of 24, 48 and 72 h. The influence of the irradiation-induced damage effect on the response of TLDs and their subsequent readings has been minimized in this manner. The induced TL light due to self-activity in the TLD-600 dosimeters, which is dependent on the neutron fluence, caused a conveniently measurable TL glow curve. The induced TL in the dosimeter due to the Q-value for the beta-decay of tritium Ebeta-max = 18.6 keV has been reproduced separately by a beta source to check the proportions of radionuclides in the chip. A short theoretical treatment is also presented.     

Effect of glycerol-induced hyperhydration on thermoregulation and metabolism during exercise in heat

This study examined the effect of glycerol ingestion on fluid homeostasis, thermoregulation, and metabolism during rest and exercise. Six endurance-trained men ingested either 1 g glycerol in 20 ml H2O x kg(-1) body weight (bw) (GLY) or 20 ml H2O x kg(-1) bw (CON) in a randomized double-blind fashion, 120 min prior to undertaking 90 min of steady state cycle exercise (SS) at 98% of lactate threshold in dry heat (35 degrees C, 30% RH), with ingestion of CHO-electrolyte beverage (6% CHO) at 15-min intervals. A 15-min cycle, where performance was quantified in kJ, followed (PC). Pre-exercise urine volume was lower in GLY than CON (1119 +/- 97 vs. 1503 +/- 146 ml x 120 min(-1); p < .05). Heart rate was lower (p < .05) throughout SS in GLY, while forearm blood flow was higher (17.1 +/- 1.5 vs. 13.7 +/- 3.0 ml x 100 g tissue x min(-1); p < .05) and rectal temperature lower (38.7 +/- 0.1 vs. 39.1 +/- 0.1 degrees C; p < .05) in GLY late in SS. Despite these changes, skin and muscle temperatures and circulating catecholamines were not different between trials. Accordingly, no differences were observed in muscle glycogenolysis, lactate accumulation, adenine nucleotide, and phosphocreatine degradation or inosine 5'-monophosphate accumulation when comparing GLY with CON. Of note, the work performed during PC was 5% greater in GLY (252 +/- 10 vs. 240 +/- 9 kJ; p < .05). These results demonstrate that glycerol, when ingested with a bolus of water 2 hours prior to exercise, results in fluid retention, which is capable of reducing cardiovascular strain and enhancing thermoregulation. Furthermore, this practice increases exercise performance in the heat by mechanisms other than alterations in muscle metabolism.