Persistent luminescence dosimetry performance of solid state synthesized BaZrO3 phosphors.

This work reports for the first time on the thermoluminescence (TL) and persistent luminescence (PLu) characterization of BaZrO3 synthesized through solid state reaction. X-Ray diffraction confirmed the crystalline structure of the synthesized phosphors. The characteristic glow curves of the synthesized samples exhibit TL maxima located at 85 and 165 °C, whose fading after radiation exposure gives rise to intense PLu. PLu decay curves were recorded after beta particle irradiation in the dose range from 1.0 up to 1024 Gy. Both TL and PLu exhibit remarkable reproducibility. The integrated persistent luminescence (IPLu) as a function of the irradiation dose exhibits a linear dependence in the 1.0-16 Gy dose range, followed by a sublinear behavior from 16 to 128 Gy. From the experimental evidence here presented, it is concluded that solid state synthesized BaZrO3 is an interesting phosphor material to be implemented as a PLu-based detector and dosimeter.

Beta radiation excited thermoluminescence of solid-state synthesized SrZrO3 phosphors.

In this work, we report on the solid-state reaction synthesis of SrZrO3 phosphors, and their beta particle irradiation excited thermoluminescence (TL) characterization. X-ray diffraction data confirmed the obtention of the orthorhombic phase of SrZrO3. Through computational glow curve deconvolution, the whole glow curve was resolved into six individual first order kinetics peaks. This is the first report concerning the usefulness of SrZrO3 as TL dosimeter. The synthesized phosphors exhibit TL emission from below 100 °C up to above 300 °C, being the most intense TL between 200 and 300 °C, as well as a remarkable reproducibility of the TL response in repeated irradiation-TL readout cycles.

Prevalence and risk factors of Neospora caninum and Toxoplasma gondii infection in breeding ewes from central western Mexico.

The objective of the study was to analyse the prevalence of infection by N. caninum and T. gondii in breeding ewes from central western Mexico. For this purpose, 184 blood samples were collected from sheep in the reproductive stage, which were analysed by ELISA and PCR tests, respectively, and the association between seroprevalence and some management factors was estimated by means of a logistic regression analysis. For N. caninum, a seroprevalence of 15.22% was identified, while the DNA detection in blood was 14.13% (26/184); positive animals were found in 75% of the farms (6/8). The variables poor placental waste management (OR 8.4), abortion history (OR 1.5) and presence of rodents (OR 1.3) were identified as risk factors for N. caninum infection. In the case of T. gondii, a seroprevalence of 61.96% was found, and antibodies were detected in eight farms included in the study; no positive samples were identified for T. gondii by the PCR test. The main identified risk factors for T. gondii were as follows: poor hygiene conditions (OR 12.5), presence of cats (OR 9.5), presence of other domestic animals (OR 5.7), urban context of the farm (OR 9.5) and public water supply (OR 5.3). The seroprevalence of co-infection of T. gondii and N. caninum in breeding ewes was 7% (13/184; 95% CI 6.92-7.20). T. gondii has a high seroprevalence while N. caninum was of lower proportion, and both may be associated with reproductive losses for these herds studied.

Beta radiation excited thermoluminescence of SrB4O7 phosphors synthesized through solid state reaction.

In this work, the synthesis of SrB4O7 through solid state reaction and its beta particle excited thermoluminescence (TL) are reported. The glow curves show maxima around 200 and 300 -considered suitable for TL dosimetry-, and a remarkable reproducibility in successive irradiation - TL readout cycles. The integrated TL exhibits a linear dependence upon the irradiation dose in the tested dose range (from 1.0 up to 8.0 Gy). The lower detection limit and the sensitivity relative to the TLD-100 dosimeter are 88 mGy and 0.49, respectively. From the results here presented, we conclude that SrB4O7 synthesized through solid state reaction can be considered a phosphor material interesting to develop TL dosimeters.

Beta particle excited thermoluminescence of CaZrO3 phosphors synthesized by solid state reaction.

In this work, the synthesis through solid state reaction and the thermoluminescence (TL) characterization of pellet shaped CaZrO3 samples is reported. X-ray diffraction confirms that orthorhombic CaZrO3 was obtained. The glow curve has two maxima located at 149 and 216 °C as well as a less intense maximum around 350 °C when a 5.0 °C/s heating rate is used after 64 Gy of beta particle exposure. A remarkably reproducibility of the TL response is observed in repeated irradiation - TL readouts cycles. The TL as a function of the dose displays linear dependence in the dose range from 0.5 to 256 Gy. The intensity of the maximum located around 216 °C remains 61% 14 days after irradiation, and then remains closely constant for longer times. The synthesized CaZrO3 exhibits TL properties potentially of interest for use in radiation detection and dosimetry.

Seroprevalence of Toxoplasma gondii Infection and Associated Factors in Sheep from Jalisco, Mexico.

The objective of the study was to identify the seroprevalence of anti-Toxoplasma gondii antibodies in sheep herds from 3 municipalities from Jalisco, Mexico, as well as estimate the association between seroprevalence and certain factors presents in the farms. In total, 12 sheep farms that maintain only hair breeds were included in the work. From these farms, 336 blood samples were collected, corresponding 324 to ewes and 12 rams. Serum samples were subjected to ELISA test, and the association between the frequency of antibodies and some potential risk factors was estimated. The overall seroprevalence to anti-T. gondii antibodies in the population studied was 17.8% (60/336; 95% confidence interval [C.I.] 14-22), all farms had positive animals, and the seroprevalence of antibodies ranged between 7 to 32%. Seroprevalence in specific municipalities was 18.7% in Lagos de Moreno, 17.8% in Encarnación de Díaz, and 16.9% in San Juan de los Lagos. Seroprevalence in ewes was 17.5% (57/324; 95% C.I. 13-22), and seroprevalence in rams was 25% (3/12; 95% C.I. 6-57), while among breeds it was 17.8% in Pelibuey (20/112; 95% C.I. 11-26), 16.6% in Kathadin (14/84; 95% C.I. 9-26), 15.4% in Blackbelly (13/84; 95% C.I. 8-25), and 23.2% in Dorper (13/56; 95% C.I. 13-36); no differences were observed among breeds (p < 0.05). The presence of cats on the farms was associated with seroprevalence (odds ratio [OR] 2.8; 95% C.I. 1.8-7.3, p < 0.001), as was the absence of a rodent-control program (OR 1.5; 95% C.I. 0.8-3.2, p < 0.05). No other factors were identified as associated with seroprevalence.

Prevalence, Incidence, and Risk Factors for Infection by Neospora caninum in Dairy Farm Dogs in North-Central Mexico.

The purpose of this study was to describe the prevalence and incidence of Neospora caninum infection in dogs that are in close contact with dairy cattle and to identify possible risk factors associated with the infection in this population. Twenty-four dogs located in 8 different dairy farms of Aguascalientes, Mexico, were evaluated for a 6-mo period. Once a month a sample of serum and a sample of peripheral blood was collected. The serum was used to detect antibodies against N. caninum by means of the indirect immunofluorescence technique, and the blood was used to detect parasite's DNA. The association between seroprevalence and possible risk factors was estimated using logistic regression. The prevalence of anti-N. caninum antibodies was 54% in the first month, 62% in the last month, and the incidence was 8.69%. One farm had no positive cases. Antibody titers ranged from 1:50 to 1:800. Parasite DNA was not detected in any of the samples. Only the age (>6 yr) of the dogs was identified as a risk factor for infection by N. caninum (P ≤ 0.05).

Susceptibility of entomopathogenic nematodes to ivermectin and thiabendazole.

The objective of the present study was to determine the susceptibility of entomopathogenic nematodes to ivermectin and thiabendazole. Soil samples collected from the municipalities of Irapuato and León, Guanajuato, Mexico, were obtained, from which the entomopathogenic nematodes (EPNs) of the Steinernematidae and Heterorhabditidae families were isolated. The samples were classified from livestock and nonlivestock soils, and the susceptibility of EPNs to anthelmintics was determined with the larval motility assay (LMA, 24 h) and the larval migration inhibition assay (LMI assay, 48 h). Sterile distilled water (T1) and treatments with 1% ivermectin diluted in 5% DMSO (dimethyl sulfoxide) (T2) and 5% thiabendazole diluted in 5% DMSO (T3) were applied to infective juvenile larvae. Analysis of variance was performed with a factorial design and Tukey's test at 0.05 probability. In addition, different concentrations of ivermectin (0.1, 0.5, 1, 1.2, 1.5, and 2 µg) and thiabendazole (1, 5, 10, 12, 15, and 20 mg) were evaluated to perform a Probit analysis to determine their LC50. All strains of EPNs were susceptible to ivermectin in both the LMA and LMI assay. The results show that EPNs are susceptible to ivermectin and thiabendazole, and the degree depends on the type of test performed, the chemical product used, and the origin of the strain of EPN.

Optically stimulated luminescence dosimetry performance of novel MgO-La(OH)3 phosphors.

The aim of this work was to study the optically stimulated luminescence (OSL) properties of novel MgO co-doped with different lanthanides and lithium ions as well as to evaluate the feasibility of using the mentioned phosphors as OSL dosimeters. In this context, the OSL efficiency corresponding to different stimulation wavelengths and different filters was analyzed for all the samples. The properties of the most efficient material, namely, MgO-La(OH)3, were further studied. Moreover, the repeatability and linearity of the OSL response, the fading of the OSL signal and the minimum detectable dose were investigated. Finally, feasibility of using these compounds in OSL dosimetry was assessed.

Synthesis and thermoluminescence characterization of self-agglomerating CaSO4 exposed to beta radiation.

The synthesis and thermoluminescence (TL) characterization of self-agglomerating pellet-shaped CaSO4 phosphors, through a low cost and environmentally friendly method is reported. In order to investigate their TL features, some samples were exposed to beta particle irradiation in the dose range from 0.07 to 10 Gy. Characteristic TL glow curve consists of a single main maximum located at 216 °C, which is considered stable, hence, suitable for dosimetry applications. The dose-response was remarkable linear. Moreover, the lower detection limit was determined to be 6.0 µGy, and the relative TL sensitivity twice the one from the commercial TLD-100 dosimeter.

Afterglow based detection and dosimetry of beta particle irradiated ZrO2.

In this work, we report on the afterglow (AG) response characterization of commercially available ZrO2. Pellet shaped samples previously annealed in air at 1000°C during 24h were exposed to beta particle irradiation in the dose range from 0.5 up to 128Gy and their AG decay curves recorded during 600s after irradiation exposure. The characteristic glow curves of beta particle irradiated ZrO2 show two maxima located around 80°C and 150°C. The first one rapidly vanishes at room temperature, giving rise to AG. The integrated AG signal increases as dose increases from 0.5 to 128Gy, with a linear dependence from 0.5 up to ca. 32Gy. Excellent reproducibility of the AG response was observed in 10 irradiation - AG readout cycles, showing that the studied ZrO2 samples are reusable. The results here presented show that ZrO2 is a promising material for use as a radiation dosimeter based on the AG phenomenon.

Afterglow dosimetry performance of beta particle irradiated lithium zirconate.

In this work, we report for the very first time on the thermoluminescence (TL) and afterglow (AG) properties of Li2ZrO3. The ternary oxide Li2ZrO3 was synthesized by solid state reaction of a mixture of Li2CO3 and ZrO2 subjected to thermal annealing at 400°C for 2h and 1000°C during 24h in air. The characteristic glow curves of beta particle irradiated samples exhibit an intense TL emission located around 150°C. From the shape of the TL curve, a 0.4 form factor was determined, suggesting that first order kinetics processes are involved. The afterglow decay curves were recorded after exposure to beta particle irradiation in the dose range from 0.5 up to 2kGy. The AG integrated in the time interval from 510 to 600s after radiation exposure shows a linear dependence as a function of the irradiation dose from 0.5 up to 256Gy. A method is proposed to compute the lower detection limit and the AG sensitivity and applied to the studied phosphors. Structural and morphological characterization were carried out by X-ray diffraction and Scanning Electron Microscopy, respectively. From the results presented, it is concluded that the AG response of the synthesized Li2ZrO3 presents features suitable to develop radiation detectors and dosimeters.

Short communication: Relationship between serum cortisol concentration and defensive behavioral responses of dairy cows exposed to natural infestation by stable fly, Stomoxys calcitrans.

The aim of this study was conducted to evaluate the effect of natural infestation by Stomoxys calcitrans on the behavioral and adrenocortical responses of dairy cattle. Twenty Holstein cows randomly selected were individually sprayed with insecticide once every 7d, whereas no insecticide was applied to the other 20 animals. The average number of flies per cow was estimated daily, and the frequency of fly-avoidance behaviors was measured daily; plasma cortisol concentration was measured each morning. No flies were ever counted on the treated cows at any time during the experiment, whereas an average of 17.13±1.14 (±standard error) flies/d were recorded on untreated cows. Tail movement was the most frequent behavior displayed, with stamps or kicks showing the highest increment rate (41.2×) when fly population increased from zero to greater than 51 flies/cow. Cortisol concentration increased to a maximum of 56.81±39.53ng/mL with 26 to 30 flies/cow per day. Coefficients of determination between the number of flies, cortisol concentration, tail movements, and stamps or kicks were 0.73, 0.78, and 0.81, respectively. The multiple correlation coefficient was 0.90, with 81% of the variation in cortisol concentration explainable by variation in the number of flies per cow and the frequency of fly-avoidance behaviors. It was concluded that plasma cortisol concentration is linearly related to a combination of the number of flies and the frequency of fly-dislodging behaviors, producing a maximum response before reaching maximum fly loads.

Efficacy of the entomopathogenic fungi Metarhizium anisopliae in the control of infestation by stable flies Stomoxys calcitrans (L.), under natural infestation conditions.

The objective of this study was to evaluate the efficacy of an isolate of Metarhizium anisopliae applied by aspersion to control of Stomoxys calcitrans flies in dairy cattle naturally infested. Was applied by aspersion an aqueous formulation of M. anisopliae sensu lato (Ma134), at a concentration of 1×10(8)conidia/ml, four times with seven day intervals, on a group of eight Holstein cows; a control group of eight Holstein cows, received a water solution with Tween 80 (0.1%). The average number of flies per animal was estimated one day before each application, and then daily counts were done in both groups. The effectiveness of the formulation was calculated using the Abbott's formula. At the same time, defensive behaviors of stamp/kicks and tail movements were evaluated daily, estimating relative frequency per hour. The Ma134 formulation had an infestation control efficacy of 73%, taking into consideration the four study weeks. The population reduction effect was observed since the first week post-application (p<0.05), and the effect increased with the subsequent applications. Defensive behaviors were reduced beginning from the first application, reaching a reduction of 66% and 70%, respectively, during the four weeks of study. These results demonstrated the effectiveness of the formulation to control infestation by S. calcitrans, as well as reduce defensive behaviors which involves the infestation.

Efficacy of entomopathogenic fungi (Ascomycetes: Hypocreales) against adult Haematobia irritans (Diptera: Muscidae) under stable conditions in the Mexican dry tropics.

The purpose of this paper is to evaluate the effect of five strains of Metarhizium anisopliae (Ma) and three strains of Isaria fumosorosea (Ifr) at a concentration of 1×10(8)colony-forming units/ml applied by spraying onto bovines with controlled infestation of Haematobia irritans under stable conditions in the Mexican dry tropics. Four experiments were performed, in each of which three treatments (two fungal strains and one control) were evaluated with eight repetitions for each one, by carrying out a single application of the aqueous suspension of each strain. The animals were isolated in individual cages and direct counts of the infestation were carried out for 13 days. It was observed that strains Ma2, Ma6, Ma10, Ma14, and Ma34 caused 94-100% reduction in infestation between days 12 and 13 post-treatment, while strains Ifr19, Ifr11, and Ifr12 reduced infestation from 90% to 98% up to day 13 post-application. There was an effect in the generation of horn flies from the excrement of bovines that were treated with different strains, reducing the reproduction of subsequent generations. It was concluded that the strains of M. anisopliae and I. fumosorosea evaluated in this study can be used as biocontrol agents in infestations of H. irritans in stabled bovines.

Frequency of infection by Neospora caninum in wild rodents associated with dairy farms in Aguascalientes, Mexico.

The purpose of this study was to detect the presence of Neospora caninum in tissues from wild rodents associated with dairy farms in Aguascalientes, Mexico. Individuals from Mus musculus, Rattus novergicus and Spermophilus variegatus were caught in dairy farms with history of positive status to N. caninum. A total of 33 rodents were caught from which samples were taken of brain, spinal cord, liver and heart and were tested with nested PCR and Immunohistochemistry (IHC). Results obtained with PCR showed that M. musculus had 77% (10/13) positive samples to N. caninum, S. variegatus had 71% (10/14) and R. novergicus had 50% (3/6). The results obtained with IHC showed that 15% (2/13) of M. musculus individuals were positive, while 43% (6/14) of S. variegatus and 33% (2/6) R. novergicus were also positive. This is the first report of the presence of N. caninum in S. variegatus.

Virulence of Mexican isolates of entomopathogenic fungi (Hypocreales: Clavicipitaceae) upon Rhipicephalus=Boophilus microplus (Acari: Ixodidae) larvae and the efficacy of conidia formulations to reduce larval tick density under field conditions.

The first objective was laboratory evaluation of the virulence of 53 Mexican isolates of fungi against larvae of Rhipicephalus (Boophilus) microplus. Thirty-three isolates of Metarhizium anisopliae var. anisopliae (Metschnickoff) Sorokin (Hypocreales: Clavicipitaceae) and 20 isolates of Isaria (Paecilomyces) fumosorosea (fumosoroseus) (Wize) (Eurotiales: Trichomaceae) were tested on 7-day-old larvae under laboratory conditions. Larvae were immersed in a suspension containing 10(8)conidia/mL and the CL(50) values were estimated. Then, field tests were conducted to determine the efficacy of formulations of the isolate with the highest virulence. M. anisopliae (Ma 14 isolate) was formulated with four carriers: Tween, Celite, wheat bran, and Citroline (mineral oil) and applied on pasture beds of Cynodon plectostachyus (L.), at a dose of 2 x 10(9)CFU/m(2). In the first trial, M. anisopliae was applied on plots naturally infested with larvae; in the second trial, tick populations in the experimental plots were eliminated and then re-infested with 20,000 7-day-old larvae. In the laboratory, all M. anisopliae isolates infected larvae with a mortality range between 2 and 100%; also, 13 of 20 I. fumosorosea isolates caused mortality rates between 7 and 94%. In the first field trial, 14 days post-application, conidial formulations in Celite and wheat bran caused 67.8 and 94.2% population reduction, respectively. In the second trial, the Tween formulation caused the highest larval reduction, reaching up to 61% (28 days post-application). Wheat bran formulation caused 58.3% larval reduction (21 days post-application) and was one of the most effective. The carriers and emulsifiers have a large impact on the effectiveness of conidial formulations.

Thermoluminescence of Tequila-based nanodiamond.

Nanodiamond thin films were deposited onto Si (100) substrates using Tequila as precursor by pulsed-liquid injection chemical vapour deposition at 850 degrees C. Some samples were exposed to beta particle irradiation in the dose range from 100 to 1600 Gy, and it was found that the thermoluminescence (TL) response is a linear function of dose. The glow curve displays two maxima centred at 170 and 350 degrees C, which does not shift when dose changes, indicating that first-order kinetics processes are involved. From the results, it is concluded that the new nanodiamond films are promising high-dose TL dosimeters.

Seroepidemiological study of Neospora caninum infection in dogs found in dairy farms and urban areas of Aguascalientes, Mexico.

The objective of this study was to describe the seroepidemiology of Neospora caninum infection in dogs in close contact with dairy cattle and dogs from urban areas of Aguascalientes, Mexico, as well as to estimate the possible association between age, gender and size of these groups and seroprevalence. Sera were obtained from samples of 152 dogs in dairy farms and 116 in the urban area, and were subjected to ELISA test. General seroprevalence reached 32%, while the seroprevalence in farm dogs (41%) was significantly higher than in dogs from the urban area (20%) (p<0.05). Regarding age groups, general seroprevalence was greater among dogs between 11 and 15 years of age (67%) remaining equal between males and females (32 and 31%, respectively). Nevertheless, females resident in farms had a higher seroprevalence (42%) than female resident in the urban area. Regarding size, large-sized animals had greater seroprevalence in farms (58%), while in the urban area medium-sized animals were those that had the highest seroprevalence (27%). It was found that dairy farm dogs had a higher risk of infection (OR=2.79; p=0.0004), and that in said group, the age range from <1 to 5 years of age was identified as a risk factor (OR=3.11, p=0.001).

Relationships between stable fly infestation with some physical facility characteristics and sanitation practices in several dairy farms in the State of Aguascalientes, Mexico.

The possible relationships between stable fly infestation with dairy farm facilities and sanitation practices were studied using path analysis. Twelve dairies located in four counties of Aguascalientes dairy region were selected. The dairies were monitored from May to November 2003. In each occasion, fly infestation, individual physical facility characteristics, and sanitation practices were recorded. In all, 11 independent variables were involved in the study and related variables were grouped together and analyzed in two blocks by path analysis for each one of five population events (begin of fly season, first peak, fluctuation, second peak and decrease). There were significant regression coefficients only in the second peak for two variables, the distance to the silos and the distance to the dung heap (r(2)=0.96 for the full model). Among the 11 variables examined in the study, none had a statistical significant indirect contribution to fly infestation; direct contribution was observed for distance to the silos and for distance to the dung heap variables. However, only the distance to the silos variable was significantly related to stable fly Infestation.