The Role of Branched-Chain Amino Acids in the Aquaculture of Red Drum, Sciaenops ocellatus L. ̶ Defining Dietary Requirements and Elucidating Antagonistic Effects

Five separate feeding trials were conducted to investigate branched-chain amino acid (BCAA) nutrition of red drum (Sciaenops ocellatus). First, the minimum dietary requirements of the BCAAs (leucine [Leu], isoleucine [Ile] and valine [Val]) were determined for juvenile red drum. Three independent 49-d feeding trials were conducted. Experimental diets were prepared by supplementing a basal diet containing 37 g/kg crude protein (CP) from red drum muscle (RDM) and crystalline amino acids (AAs) with incremental levels of Leu (9.0, 13.0, 17.0, 21.0, 25.0 and 29.0 g/kg of dry diet), Ile (5.0, 8.0, 11.0, 14.0, 17.0 and 20.0 g/kg of dry diet) and Val (6.8, 8.0, 9.2, 10.4, 11.6, 12.8 and 14.0 g/kg of dry diet). Fish in triplicate 30-L glass aquaria were fed each experimental diet to apparent satiation twice daily, after which growth performance parameters were measured. Incremental levels of dietary Leu, Ile and Val significantly affected weight gain, feed efficiency and protein retention. Analyses of the weight gain data using a broken-line regression model estimated the minimum Leu, Ile and Val requirements for maximum weight gain of juvenile red drum to be 15.7 ± 1.7 g/kg (± 95% confidence interval), 11.1 ± 2.3 g/kg and 12.4 ± 0.6 g/kg of dry diet, respectively. Secondly, the effects of high dietary levels of BCAAs on growth performance and AA utilization of juvenile red drum were determined. A semi-purified control diet (430 g/kg CP) was prepared by combining lyophilized RDM and crystalline AAs, while keeping the levels of Leu, Ile and Val at the minimum dietary requirement for red drum. Six experimental diets were prepared by supplementing the control diet with (1) an excess of Leu (62.0 g/kg of dry diet), (2) an excess of Ile (44.0 g/kg of dry diet), (3) an excess of Val (50.0 g/kg of dry diet), (4) an excess of Leu and Ile (62.0 and 44.0 g/kg), (5) an excess of Ile and Val (44.0 and 50.0 g/kg), and (6) an excess of Leu and Val (62.0 and 50.0 g/kg). Excess levels of Leu, Ile and Val corresponded to 200% of the amount found in a diet with 350 g/kg CP provided by RDM. Red drum juveniles were stocked in 38-L glass aquaria (12 fish/aquarium), and diets were fed to fish in triplicate aquaria at a rate approaching apparent satiation, twice daily, for 49 d. At the end of the feeding trial, growth performance parameters were calculated and the postprandial concentration of BCAAs in plasma was analyzed. Growth performance of the red drum was significantly affected by an excess of dietary Leu, alone or in combination (Leu+Ile and Leu+Val), confirming an antagonistic effect due to the imbalanced concentration of BCAAs in the diet. In addition, the postprandial concentration of plasma Leu, Ile and/or Val was significantly higher in fish fed an excess of Leu, Ile and/or Val, respectively. Nonetheless, postprandial levels of BCAAs in plasma did not indicate that an excess of Leu blocked the intestinal absorption or promoted the catabolism of Ile and/or Val in red drum, as has been reported in other species. Ultimately, the results obtained from this dissertation will facilitate the production of aquaculture feeds composed of alternative protein ingredients while maintaining an ideal AA profile for optimal performance of red drum

The Role of Branched-Chain Amino Acids in the Aquaculture of Red Drum, Sciaenops ocellatus L. ̶ Defining Dietary Requirements and Elucidating Antagonistic Effects

Five separate feeding trials were conducted to investigate branched-chain amino acid (BCAA) nutrition of red drum (Sciaenops ocellatus). First, the minimum dietary requirements of the BCAAs (leucine [Leu], isoleucine [Ile] and valine [Val]) were determined for juvenile red drum. Three independent 49-d feeding trials were conducted. Experimental diets were prepared by supplementing a basal diet containing 37 g/kg crude protein (CP) from red drum muscle (RDM) and crystalline amino acids (AAs) with incremental levels of Leu (9.0, 13.0, 17.0, 21.0, 25.0 and 29.0 g/kg of dry diet), Ile (5.0, 8.0, 11.0, 14.0, 17.0 and 20.0 g/kg of dry diet) and Val (6.8, 8.0, 9.2, 10.4, 11.6, 12.8 and 14.0 g/kg of dry diet). Fish in triplicate 30-L glass aquaria were fed each experimental diet to apparent satiation twice daily, after which growth performance parameters were measured. Incremental levels of dietary Leu, Ile and Val significantly affected weight gain, feed efficiency and protein retention. Analyses of the weight gain data using a broken-line regression model estimated the minimum Leu, Ile and Val requirements for maximum weight gain of juvenile red drum to be 15.7 ± 1.7 g/kg (± 95% confidence interval), 11.1 ± 2.3 g/kg and 12.4 ± 0.6 g/kg of dry diet, respectively. Secondly, the effects of high dietary levels of BCAAs on growth performance and AA utilization of juvenile red drum were determined. A semi-purified control diet (430 g/kg CP) was prepared by combining lyophilized RDM and crystalline AAs, while keeping the levels of Leu, Ile and Val at the minimum dietary requirement for red drum. Six experimental diets were prepared by supplementing the control diet with (1) an excess of Leu (62.0 g/kg of dry diet), (2) an excess of Ile (44.0 g/kg of dry diet), (3) an excess of Val (50.0 g/kg of dry diet), (4) an excess of Leu and Ile (62.0 and 44.0 g/kg), (5) an excess of Ile and Val (44.0 and 50.0 g/kg), and (6) an excess of Leu and Val (62.0 and 50.0 g/kg). Excess levels of Leu, Ile and Val corresponded to 200% of the amount found in a diet with 350 g/kg CP provided by RDM. Red drum juveniles were stocked in 38-L glass aquaria (12 fish/aquarium), and diets were fed to fish in triplicate aquaria at a rate approaching apparent satiation, twice daily, for 49 d. At the end of the feeding trial, growth performance parameters were calculated and the postprandial concentration of BCAAs in plasma was analyzed. Growth performance of the red drum was significantly affected by an excess of dietary Leu, alone or in combination (Leu+Ile and Leu+Val), confirming an antagonistic effect due to the imbalanced concentration of BCAAs in the diet. In addition, the postprandial concentration of plasma Leu, Ile and/or Val was significantly higher in fish fed an excess of Leu, Ile and/or Val, respectively. Nonetheless, postprandial levels of BCAAs in plasma did not indicate that an excess of Leu blocked the intestinal absorption or promoted the catabolism of Ile and/or Val in red drum, as has been reported in other species. Ultimately, the results obtained from this dissertation will facilitate the production of aquaculture feeds composed of alternative protein ingredients while maintaining an ideal AA profile for optimal performance of red drum

Formability of the 5754-aluminum alloy deformed by a modified repetitive corrugation and straightening process

Sheets of 5754-aluminum alloy processed by a modified repetitive corrugation and straightening (RCS) process were tested in order to measure their formability. For this purpose, forming limit curves were derived. They showed that the material forming capacity decreased after being processed by RCS. However, they kept good formability in the initial stages of the RCS process. The formability study was complemented with microstructural analysis (derivation of texture) and mechanical tests to obtain the strain-rate sensitivity. The texture analysis was done by employing X-ray diffraction, obtaining pole figures, and the orientation distribution function. It was noticed that the initial texture was conserved after successive RCS passes, but the intensity dropped. RCS process did not induce ß-fiber, contrary to common deformation process. The strain-rate sensitivity coefficient was measured through tensile tests at different temperatures and strain rates; the coefficient of the samples processed after one and two passes were still relatively high, indicating the capacity to delay necking, in agreement with the good formability observed in the initial passes of the RCS processPeer ReviewedPostprint (published version

High seroprevalence of Toxoplasma gondii infection in a subset of Mexican patients with work accidents and low socioeconomic status

<p>Abstract</p> <p>Background</p> <p><it>Toxoplasma gondii </it>has been associated with reflex impairment and traffic accidents. It is unknown whether <it>Toxoplasma </it>infection might be associated with work accidents. Therefore, using a case-control seroprevalence study design, 133 patients with a recent work accident and 266 control subjects of the general population from the same region were examined with enzyme-linked immunoassays for the presence and levels of anti-<it>Toxoplasma </it>IgG antibodies and anti-<it>Toxoplasma </it>IgM antibodies. Socio-demographic, work, clinical and behavioral characteristics from each worker were obtained.</p> <p>Results</p> <p>Eleven (8.3%) of 133 patients, and 14 (5.3%) of 266 controls had anti-<it>T. gondii </it>IgG antibodies. Anti-<it>T. gondii </it>IgG levels were higher than 150 IU/ml in 8 (6%) patients and 10 (3.8%) controls. Anti-<it>T. gondii </it>IgM antibodies were found in one (0.8%) of the workers, and in 6 (2.3%) of the controls. No statistically significant differences in the IgG seroprevalences, frequencies of high IgG levels, and IgM seroprevalences among patients and controls were found. In contrast, a low socio-economic level in patients with work accidents was associated with <it>Toxoplasma </it>seropositivity (<it>P </it>= 0.01). Patients with work accidents and low socioeconomic status showed a significantly (OR = 3.38; 95% CI: 0.84-16.06; <it>P </it>= 0.04) higher seroprevalence of <it>T. gondii </it>infection than controls of the same socioeconomic status (15.1% vs. 5%, respectively). Multivariate analysis showed a positive association of <it>T. gondii </it>infection with boar meat consumption (OR = 3.04; 95% CI: 1.03-8.94; <it>P </it>= 0.04). In contrast, a negative association between <it>T. gondii </it>infection and national trips (OR = 0.40; 95% CI: 0.17-0.96; <it>P </it>= 0.04), sausage consumption (OR = 0.20; 95% CI: 0.05-0.68; <it>P </it>= 0.01), and ham consumption (OR = 0.16; 95% CI: 0.05-0.51; <it>P </it>= 0.002) was found.</p> <p>Conclusions</p> <p>In the study described here seropositivity to <it>T. gondii </it>was associated to work accidents in a subset of patients with low socioeconomic status. This is the first report of an association of <it>T. gondii </it>infection and work accidents. Further studies to confirm our results are needed. Results may help in designing optimal prevention strategies to avoid <it>T. gondii </it>infection.</p

Toxoplasma gondii infection in workers occupationally exposed to unwashed raw fruits and vegetables: a case control seroprevalence study

<p>Abstract</p> <p>Background</p> <p>Through a case control seroprevalence study, we sought to determine the association of <it>Toxoplasma gondii </it>infection with occupational exposure to unwashed raw fruits and vegetables.</p> <p>Methods</p> <p>Subjects, numbering 200, who worked growing or selling fruits and vegetables, and 400 control subjects matched by age, gender, and residence were examined by enzyme immunoassays for the presence of anti-<it>Toxoplasma </it>IgG and IgM antibodies. Socio-demographic, clinical, and behavioral characteristics from the study subjects were obtained.</p> <p>Results</p> <p>Of the 200 fruit and vegetable workers, 15 (7.5%) of whom, and 31 (7.8%) of the 400 controls were positive for anti-<it>Toxoplasma </it>IgG antibodies (<it>P </it>= 0.96). Anti-<it>Toxoplasma </it>IgM antibodies were found in 2 (1%) of the fruit workers and in 11 (2.8%) of the control subjects (<it>P </it>= 0.23). Seroprevalence of <it>Toxoplasma </it>antibodies increased with age (<it>P </it>= 0.0004). In addition, seropositivity to <it>Toxoplasma </it>was associated with ill status (<it>P </it>= 0.04), chronic tonsillitis (<it>P </it>= 0.03), and reflex impairment (<it>P </it>= 0.03). Multivariate analysis showed that <it>Toxoplasma </it>infection was associated with consumption of raw meat (OR = 5.77; 95% CI: 1.15-28.79; <it>P </it>= 0.03), unwashed raw fruits (OR = 2.50; 95% CI: 1.11-5.63; <it>P </it>= 0.02), and living in a house with soil floors (OR = 3.10; 95% CI: 1.22-7.88; <it>P </it>= 0.01), whereas <it>Toxoplasma </it>infection was negatively associated with traveling abroad (OR = 0.28; 95% CI: 0.12-0.67; <it>P </it>= 0.005).</p> <p>Conclusions</p> <p>This is the first report of seroprevalence and contributing factors for <it>Toxoplasma </it>infection in workers occupationally exposed to unwashed raw fruits and vegetables, and the results may help in the design of optimal preventive measures against <it>Toxoplasma </it>infection especially in female workers at reproductive age.</p

Probabilistic dynamic analysis of steel buildings with long duration earthquakes

El análisis probabilista del comportamiento sísmico de una estructura requiere cuantificar las incertidumbres de las variables y parámetros involucrados, incluyendo la acción sísmica y las propiedades mecánicas de sus elementos. En este artículo se analiza el comportamiento sísmico de edificios de acero bajos, medianos y altos, sometidos a las acciones sísmicas de larga duración probables de la Ciudad de México. El análisis se efectúa bajo una perspectiva probabilista. Las acciones sísmicas se han seleccionado de forma que sean compatibles con los espectros de diseño, para suelos blandos y sismos de larga duración de esta área. Los análisis dinámicos, se llevan a cabo usando simulaciones Monte Carlo. La resistencia y la ductilidad de vigas y columnas se consideran como variables aleatorias; las acciones sísmicas también se consideran de forma probabilista. El daño esperado es evaluado con el índice de Park y Ang. Los resultados muestran que las incertidumbres esperadas en la respuesta son significativas, siendo la aleatoriedad de la acción sísmica la principal causa. De la comparación entre los valores medianos del enfoque probabilista con los del caso determinista se observa una buena consistencia de los resultados correspondientes a edificios de baja y mediana altura, siendo menor en el comportamiento no lineal de los edificios altos. Los edificios bajos y medianos analizados tienen un comportamiento adecuado antes las acciones sísmicas de la zona de estudio, pero los edificios altos tienen un mayor riesgo sísmico y podrían tener daños leves o moderados. Se concluye que el enfoque probabilista proporciona información más rica sobre la respuesta estructural.The probabilistic analysis of the seismic performance of a structure requires quantifying the uncertainties of the involved variables and parameters, including the seismic action and mechanical properties of its elements. In this article, the seismic performance of high-rise, mid-rise and low-rise of steel buildings, subjected to long duration seismic actions like those of Mexico City, is analyzed. The analysis is conducted by using a probabilistic approach. The seismic actions are selected to be compatible with the design spectra of the Mexican seismic code for soft soils and long duration earthquakes, characteristic for this region. The dynamic analyses are performed by using Monte Carlo simulations. The strength and ductility of the beams and columns are considered random variables; the seismic actions are also modelled in a probabilistic way. The damage index of Park and Ang is used. The results show that the uncertainties expected in the response are significant, being the randomness of the seismic action the main cause. From the comparison between the mean values of the probabilistic approach and those corresponding to the deterministic case, a good consistency of the result obtained for low-rise and mid-rise buildings is observed. Nevertheless, the consistency is lower in the case of high-rise buildings. The analyzed low-rise and mid-rise buildings show a good seismic performance to seismic actions, but the high-rise buildings show slight or moderate damage. It is concluded that the probabilistic approach provides a more complete information on the structural response.Peer ReviewedPostprint (published version

Investigación, desarrollo e innovación IDI 3 y 4

Existen un gran número de establecimientos que comercializan productos o servicios que, de manera indirecta, tienen que ver con la manufactura de modelos y prototipos de manera artesanal y semi-artesanal. Se ha identificado la carencia de un lugar especializado en la manufactura de prototipos que ofrezca un servicio integral en la materia. Un lugar que conozca, opere y domine diversos materiales, procesos de manufactura, conceptos técnicos, software e incluso lenguaje de diseño y desarrollo de producto y que se especialice en apoyar a quien requiera de este tipo de servicios especializados. Lo que se propone en este proyecto es un establecimiento especializado en proveer materiales, insumos y servicios para la fabricación de prototipos en un solo lugar, con acceso completo a maquinaria y equipo para que el interesado pueda transformar su idea en realidad y pueda obtener asesoría constante en el uso de las máquinas, procesos de producción, materiales suplementarios y el manejo de los mismos

Microstructural evolution and mechanical behavior of an Al-6061 alloy processed by repetitive corrugation and straightening

The repetitive corrugation and straightening process is a severe plastic deformation technique that is particularly suited to process metallic sheets. With this technique, it is possible to develop nano/ultrafine-grained structured materials, and therefore, to improve some mechanical properties such as the yield strength, ultimate tensile strength, and fatigue lifetime. In this study, an Al-6061 alloy was subjected to the repetitive corrugation and straightening process. A new corrugation die design was proposed in order to promote a heterogeneous deformation into the metallic sheet. The evolution of the mechanical properties and microstructure obtained by electron backscatter diffraction of the alloy showed a heterogeneous distribution in the grain size at the initial cycles of the repetitive corrugation and straightening process. Uniaxial tensile tests showed a significant increase in yield strength as the number of repetitive corrugation and straightening passes increased. The distribution of the plastic deformation was correlated with the hardness distribution on the surface. The hardness distribution map matched well with the heterogeneous distribution of the plastic deformation obtained by finite element simulation. A maximum average hardness (147 HV) and yield strength (385 MPa) was obtained for two repetitive corrugation and straightening cycles samplePeer ReviewedPostprint (published version

Study on the formability and texture evolution of AA6061 alloy processed by repetitive corrugation and straightening

The enhanced mechanical properties obtained by refining the grain size down to the ultrafine-grained (UFG) regime have attracted considerable attention in recent years. The severe plastic deformation (SPD) techniques allow obtaining ultrafine-grained materials. Different SPD techniques permit processing sheet shape materials such as repetitive corrugation and straightening (RCS) and accumulative roll bonding (ARB). In this study, the formability of an AA 6061-T6 processed by RCS was evaluated. The forming limit diagrams (FLD) were obtained by Nakazima tests of samples in initial condition (T6 state) and after one and two RCS cycles. The FLD curves showed that the forming capacity decreased from the first RCS cycle. Likewise, uniaxial tensile tests at different temperatures and strain rates were conducted to analyze the effect of the RCS process on the strain rate sensitivity. They showed a relatively high strain rate sensitivity coefficient in the samples after one and two RCS cycles, which indicates an improvement of i) the capacity of the material to delay the onset of the necking and ii) the formability at increasing temperatures. Finally, texture analysis was carried out employing X-ray diffraction, calculating the orientation distribution functions (ODFs). The initial texture showed a predominant cube texture component, whereas, for further RCS cycles, a weakening of the cube texture and an increment of the S texture component were observed.Peer ReviewedPostprint (published version