566 research outputs found
All-optical modulation of laser light in amorphous silicon-filled microstructured optical fibers
No full textAmorphous silicon is deposited within optical fibers by a high pressure microfluidic deposition process and characterized via Raman spectroscopy. All-optical modulation of 1.55 µm light guided through the silicon core is demonstrated using the free carrier absorption generated by a 532 nm pump pulse. Modulation depths of up to 8.26 dB and modulation frequencies of up to 1.4 MHz are demonstrated
El Tlacuache Núm. 4 (2001). 4 Año 1 (2001) julio. El Tlacuache
No full text- Del hecho al dicho por Alfredo López Austin. - Desde Tetelcingo un cuentito de como fue el Diluvio Universal por Adriana Saldaña Ramirez. - El Yahuatli. Aihuitl o hierba del agua. Hierba del ángel. Eupator um sp. familia: Asteraceae/Compositae por Biol. Margarita Avilés y Biol. Macrina Fuentes. - Nuestro Patrimonio desconocido por Teresita Loera y Anaite Monterforte. - La conversión de los indios de la Nueva España por Arqueóloga Laura Ledesma
Effect of the degree of polymerization of polyglycerol on the emulsifying capacity of polyglycerols ester of saturated carboxylic acids of different lengths of carboned chain*
No full textLa creciente oferta de glicerol crudo proveniente de la industria del biodiesel ha reducido drásticamente su valor comercial. Como una opción para afrontar esta problemática esta la síntesis de productos de valor agregado tales como los poligliceroles éster de ácidos carboxílicos, los cuales son polímeros versátiles que presentan buen desempeño como emulsificantes no-iónicos. En el presente trabajo se estudió el efecto del grado de polimerización de poliglicerol y la longitud de la cadena carbonada de los ácidos carboxílicos saturados utilizados en la síntesis de poliglicerol éster sobre su capacidad emulsificante. Debido a que las moléculas de emulsificante sintetizadas deben poseer una zona hidrófila y otra lipófila, el estudio se dividió en tres temas; en el primero se abordan la formación de la zona hidrófila, en el segundo se describen los conceptos de la formación de la zona lipófila y el tercer tema se dedicó a evaluar los emulsificantes sintetizados. En el Tema I se analizó la etapa de polimerización utilizando ácido sulfúrico e hidróxido de sodio como catalizadores. Se estimaron los parámetros cinéticos a través de análisis termogravimétrico TGA y calorimetría diferencial de barrido DSC. Posteriormente los parámetros cinéticos estimados fueron validados usando métodos de titulación, FTIR y espectrometría de masas. En el Tema II se realizaron diseños experimentales variando el tiempo de reacción y la longitud de la cadena del ácido carboxílico para evaluar su efecto sobre la síntesis de poligliceroles éster; se trabajó con ácidos saturados para no tener la perturbación adicional de otros grupos funcionales. En el Tema III se evaluó el efecto del grado de polimerización y longitud de la cadena carbonada del ácido carboxílico sobre la capacidad emulsificante del poliglicerol éster sintetizado, para lo cual se utilizaron técnicas de microscopia óptica, tensión superficial y tiempo de estabilidad de las emulsiones.MaestríaMagíster en Ingeniería QuímicaThe growing supply of crude glycerol from the biodiesel industry has drastically reduced its commercial value. One of the options to address this problem is the synthesis of value-added product such as polyglycerol ester of carboxylic acids, wich are versatile polymers that can present a good performance as nonionic emulsifiers. In this work, the effect of degree of polymerization of polyglycerol and the length of the carbon chain of the saturated carboxylic acids used in the synthesis of polyglycerol ester on their emulsifying capacity was studied. Because the emulsifier molecules synthesized must possess a hydrophilic and a lipophilic zone, the study was divided into three topics; in the first, the formation of the hydrophilic zone is analyzed, in the second, the concepts of the lipophilic zone formation was described and the third topic was devoted to the evaluation of the synthesized emulsifiers. In topic I polymerization step was studied using sulfuric acid and sodium hydroxide as catalysts. Kinetic parameters were estimated by thermogravimetric analysis and differential scanning calorimetry. Subsequently the estimated parameters were validated with reaction monitoring using titration methods, FTIR and mass spectrometry. In topic II experimental designs were made varying the reaction time and the length of the carboxylic acid chain to evaluate their effect on the synthesis of polyglycerol ester; The author worked with saturated acids to avoid additional disturbance of other functional groups. In topic III, O / W were evaluated the effect of the degree of polymerization and length of the carboxylic acid carbon chain on the emulsifying capacity of the polyglycerol ester synthesized, for which optical microscopy techniques, surface tension measurements and stability time of the emulsions were used
Mission analysis of space-based telescopes to detect impacting near-earth objects
No full textRecognising the threat of near-Earth objects (NEOs) to life on Earth, many projects have been developed worldwide with the aim of detecting potential impactors, most of which are focused on ground-based surveys. However, _20% of the Earth-threatening NEOs are estimated to be approaching Earth from the day-side, and are thus very difficult to detect using ground surveys. Over the last decade, several space-based capabilities have emerged in an effort to discover and catalogue NEOs in order to better quantify their risk of impact, yet little research has gone into dealing with imminent-impacting NEOs. The aim of this paper is to design a space mission that places a telescope in-orbit in order to detect and provide warning for Earth-impacting NEOs down to 20m in size, by determining the performance of both a visible and an infrared (IR) space-based telescope used in two mission candidates. The first mission candidate consists of a halo orbit about the artificial equilibrium point sub-L1 of the Sun-Earth (SE) system, which is displaced with respect to the classical L1 point, along the SE direction towards the Sun, through the use of solar-sail propulsion. As second mission candidate, three vertical Lyapunov orbits about the libration points L3, L4 and L5 of the Sun-Venus system are considered. A trade-off between detection rates and warning times is conducted to determine the most suitable space-based NEO survey system. It is concluded that an IR space-based telescope placed at the SE solar-sail displaced L1 point is the best option because of the long warning times obtained and the beneficial contribution to existing ground-based NEO surveys. A preliminary mission analysis is also performed to determine a solar-sail propelled transfer trajectory to the SE sub-L1 region, assuming a ride-share launch on ESA’s Euclid mission.Astrodynamics & Space Mission
Aqueous Solvation of SmI2: A Born-Oppenheimer Molecular Dynamics Density Functional Theory Cluster Approach
No full textbibtex: ISI:000397546100011 bibtex\location:'1155 16TH ST, NW, WASHINGTON, DC 20036 USA',publisher:'AMER CHEMICAL SOC',type:'Article',affiliation:'Ramirez-Solis, A (Reprint Author), Univ Autonoma Estado Morelos, Ctr Invest Ciencias IICBA, Dept Fis, Cuernavaca 62209, Morelos, Mexico. Ramirez-Solis, A., Univ Autonoma Estado Morelos, Ctr Invest Ciencias IICBA, Dept Fis, Cuernavaca 62209, Morelos, Mexico. Amaro-Estrada, J. I.; Hernandez-Cobos, J., UNAM, Inst Ciencias Fis, Cuernavaca 62210, Morelos, Mexico. Maron, L., Univ Toulouse, INSA CNRS UPS, Lab Phys & Chim Nano Objets, 135 Ave Rangueil, F-31077 Toulouse, France.','author-email':'[email protected]',da:'2018-12-05','doc-delivery-number':'EP7GM','funding-acknowledgement':'CONACYT Basic Science project [253679]; DGAPA-UNAM','funding-text':'We thank E. Sanchez-Marcos and the reviewers for their valuable comments. A.R.-S. acknowledges support from CONACYT Basic Science project number 253679. J.I.A.-E. acknowledges a DGAPA-UNAM postdoctoral fellowship.','journal-iso':'J. Phys. Chem. A','keywords-plus':'SAMARIUM DIIODIDE; ELECTRON-TRANSFER; ORGANIC-SYNTHESIS; PROTON DONORS; REDUCTION; IODIDE; PSEUDOPOTENTIALS; CYCLIZATIONS; DERIVATIVES; CHEMISTRY','number-of-cited-references':'39','orcid-numbers':'Ramirez-Solis, Alejandro/0000-0002-8428-5714','research-areas':'Chemistry; Physics','times-cited':'7','unique-id':'ISI:000397546100011','usage-count-last-180-days':'1','usage-count-since-2013':'16','web-of-science-categories':'Chemistry, Physical; Physics, Atomic, Molecular & Chemical'\International audienceWe report the results of Born-Oppenheimer molecular dynamics (BOMD) simulations on the aqueous solvation of the SmI2 molecule at room temperature using the cluster microsolvation approach including 32 water molecules. The electronic structure calculations were done using the M062X hybrid exchange-correlation functional in conjunction with the 6-31G** basis sets for oxygen and hydrogen. For the iodine and samarium atoms the Stuttgart Koln relativistic effective core potentials were utilized with their associated valence basis sets. Starting from the optimized geometry of SmI2 embeded in the microsolvation environment, we find a swift substitution of the iodine ions by eight tightly bound water molecules around Sm(II). Through the Sm-O radial distribution function and the evolution of the Sm-O distances, the present study predicts a first rigid Sm(II) solvation shell from 2.6,to 3.4 (A) over circle, whose integration leads to a coordination number of 8.4 water molecules, and a second softer solvation sphere from 3.5 to ca. 6 (A) over circle. The Sm(II)-O radial distribution function is in excellent agreement with that reported for Sr2+ from:EXATS studies, a fact that can be explained because Sr2+ and Sm2+ have almost identical ionic radii (ca. 1.26 (A) over circle) and coordination numbers: 8 for Sr2+ and 8.4 for Sm2+. The theoretical EXAFS spectrum was obtained from the BOMD trajectory and is discussed in the light ofthe experimental spectra for Sm(III). Once microsolvation is achieved, no water exchange events were found to occur around Sm2+, in agreement with the experimental data for Eu2+ (which has a nearly identical charge-to-ionic radius relation as Sm2+),-where the mean residence time of a water molecule in [Eu(H2O)(8)](2+) is known to be ca. 230 ps
Aqueous Solvation of SmI2: A Born-Oppenheimer Molecular Dynamics Density Functional Theory Cluster Approach
No full textbibtex: ISI:000397546100011 bibtex\location:'1155 16TH ST, NW, WASHINGTON, DC 20036 USA',publisher:'AMER CHEMICAL SOC',type:'Article',affiliation:'Ramirez-Solis, A (Reprint Author), Univ Autonoma Estado Morelos, Ctr Invest Ciencias IICBA, Dept Fis, Cuernavaca 62209, Morelos, Mexico. Ramirez-Solis, A., Univ Autonoma Estado Morelos, Ctr Invest Ciencias IICBA, Dept Fis, Cuernavaca 62209, Morelos, Mexico. Amaro-Estrada, J. I.; Hernandez-Cobos, J., UNAM, Inst Ciencias Fis, Cuernavaca 62210, Morelos, Mexico. Maron, L., Univ Toulouse, INSA CNRS UPS, Lab Phys & Chim Nano Objets, 135 Ave Rangueil, F-31077 Toulouse, France.','author-email':'[email protected]',da:'2018-12-05','doc-delivery-number':'EP7GM','funding-acknowledgement':'CONACYT Basic Science project [253679]; DGAPA-UNAM','funding-text':'We thank E. Sanchez-Marcos and the reviewers for their valuable comments. A.R.-S. acknowledges support from CONACYT Basic Science project number 253679. J.I.A.-E. acknowledges a DGAPA-UNAM postdoctoral fellowship.','journal-iso':'J. Phys. Chem. A','keywords-plus':'SAMARIUM DIIODIDE; ELECTRON-TRANSFER; ORGANIC-SYNTHESIS; PROTON DONORS; REDUCTION; IODIDE; PSEUDOPOTENTIALS; CYCLIZATIONS; DERIVATIVES; CHEMISTRY','number-of-cited-references':'39','orcid-numbers':'Ramirez-Solis, Alejandro/0000-0002-8428-5714','research-areas':'Chemistry; Physics','times-cited':'7','unique-id':'ISI:000397546100011','usage-count-last-180-days':'1','usage-count-since-2013':'16','web-of-science-categories':'Chemistry, Physical; Physics, Atomic, Molecular & Chemical'\International audienceWe report the results of Born-Oppenheimer molecular dynamics (BOMD) simulations on the aqueous solvation of the SmI2 molecule at room temperature using the cluster microsolvation approach including 32 water molecules. The electronic structure calculations were done using the M062X hybrid exchange-correlation functional in conjunction with the 6-31G** basis sets for oxygen and hydrogen. For the iodine and samarium atoms the Stuttgart Koln relativistic effective core potentials were utilized with their associated valence basis sets. Starting from the optimized geometry of SmI2 embeded in the microsolvation environment, we find a swift substitution of the iodine ions by eight tightly bound water molecules around Sm(II). Through the Sm-O radial distribution function and the evolution of the Sm-O distances, the present study predicts a first rigid Sm(II) solvation shell from 2.6,to 3.4 (A) over circle, whose integration leads to a coordination number of 8.4 water molecules, and a second softer solvation sphere from 3.5 to ca. 6 (A) over circle. The Sm(II)-O radial distribution function is in excellent agreement with that reported for Sr2+ from:EXATS studies, a fact that can be explained because Sr2+ and Sm2+ have almost identical ionic radii (ca. 1.26 (A) over circle) and coordination numbers: 8 for Sr2+ and 8.4 for Sm2+. The theoretical EXAFS spectrum was obtained from the BOMD trajectory and is discussed in the light ofthe experimental spectra for Sm(III). Once microsolvation is achieved, no water exchange events were found to occur around Sm2+, in agreement with the experimental data for Eu2+ (which has a nearly identical charge-to-ionic radius relation as Sm2+),-where the mean residence time of a water molecule in [Eu(H2O)(8)](2+) is known to be ca. 230 ps
Classification of agricultural systems based on pesticide use intensity and safety
No full textAn analysis of socio-economic driving forces in crop protection is proposed to improve the implementation of sustainable strategies. The analysis includes: (1) a classification of agricultural systems based on pesticide use intensity and safety, (2) an evaluation of the profitability of farming systems and identification of socio-economic factors that influence pesticide use and (3) formulation of policy recommendations. We find that for cereals and for fruit trees alike, crop yields are much higher for agricultural systems with high doses of pesticides. The safety of applied pesticides does not affect crop protection costs significantly. For cropping systems characterised by low-intensity in pesticide use, the application of safer products has a positive effect on reduction of crop protection costs.pesticide use, driving forces in crop protection, economic analysis of agricultural systems, Crop Production/Industries,
Probabilistic analysis of uncertainties in the disposal of nuclear waste
No full textTo determine a probabilistic analysis of the safety of a nuclear waste repository, a separated and sequential treatment of the waste migration problem is developed. The new approach consists of a description of the transmission of waste nuclei from interface to interface by a transfer kernel. The separation provides valuable information about the performance of each individual medium and how they contribute to the overall system performance. It also provides a framework for comparison of other safety assessment studies. The equations to describe the release rate of radionuclides for a simplified two-region model are obtained. The two-region model simulates the release of radionuclides from the repository and its subsequent transport through an overlying aquifer. Data that characterizes an actual proposed repository emplaced in a salt dome is used. A probabilistic analysis to investigate the parameter uncertainties at the level of the transfer kernel attempts to calculate the average release rates based on probability distributions assigned to the controlling variables. The widely considered scenario of accidental intrusion of water from the overlying rock into the filled repository during the post-operational period is generalized to have a probability distribution for possible intrusion times. Averaging over the brine intrusion time distribution gives the \u27overall\u27 average release rate. Numerical results for two important \u27waste\u27 nuclides, both with long half-life, are provided. The results include the average release rates from the aquifer and the repository for I-129 and Np-237 for five different brine intrusion times. The average release rates from the aquifer are quite different than the release calculated with a set of single conservative values. A reduction of about two orders of magnitude is observed, pointing out the significance of the probabilistic results over a single deterministic calculation. The release rates averaged over a brine intrusion distribution are also provided for three different mean times of brine intrusion, resulting in a further smearing out of the release rate. The averaging has a lesser effect in the repository region than in the aquifer domain. Thus, in general, the release rates from the aquifer are only slightly lower than the release rates from the repository. (Abstract shortened with permission of author.
It's a True Kinda Love: Steven Universe and How Its LGBTQ Characters Shows a Positive Representation of Gender Non-Conforming Identities and Lesbian Relationships
No full textThe author has granted permission for their work to be available to the general public.This research effort analyzed different representations of queerness, mainly same-sex relationships and gender non-conforming identities, in Steven Universe through the different characters in the show. It examined the representations of LGBTQ (Lesbian, Gay, Bisexual, Transgender and Queer) characters for children to watch, due to most LGBTQ youth facing homelessness because of their identity, along with isolation from friends and family, as well as harassment from their peers in school. Using different theoretical perspectives from queer theorists Judith Butler and Cathy Cohen we can discover themes in Steven Universe that correlate with the theoretical concepts, mainly the analysis of nonnormative identities that the show depicts. A content analysis of forty selected episodes with twenty episodes depicting important queer moments throughout the show was conducted, in contrast of 20 episodes that did not contain queer content will be conducted to determine if queer content is prevalent within Steven Universe. The findings illustrated positive representations of lesbian relationships, characters that challenge gender norms, or even blur the gender binary, and safe spaces for queer individuals in the show.Sociolog
Rhinobatesia rugicollis Clarke 2018, n. comb.
No full textRhinobatesia rugicollis (Bates, 1880) n. comb. (Fig. 35–40) Odontocera rugicollis Bates 1880: 43; Monné 2017: 446 (cat.). Odontocera nevermanni Fisher 1930: 8; Monné 2017: 445 (cat.). n. syn. Species concept. Based on Bates (1880) original description and photographs of the male holotype (Fig. 35), and Fisher (1930) description of his holotype of O. nevermanni (Fig. 36), both available on Bezark (2017), and examination of a male and female identified as O. nevermanni (Fig. 37–40) kindly loaned to the author by EMEC. Comment. Fisher stated that his species was described from a single male in which (quote), “Eyes separated from each other on the front by about the width of the labrum.” The author’s male specimen has the eyes separated by about half the width of the labrum, and in his female the space between the eyes is 1/5 narrower than the labrum. Fisher also stated that the length of his specimen was 15 mm, and its width 3.2 mm, the quotient length/width = 4.69; close to the author’s female quotient of 4.58; the quotient for the author’s male is 5.16. These data (and other minor ones described by Fisher) indicate that his holotype is a female. Measurements (mm). 1 male / 1 female: total length, 15.75/16.95; length of prothorax, 3.00/3.15; width of prothorax, 2.35/2.55; length of elytra, 7.60/8.80; width at humeri, 2.75/3.30. Specimens analyzed. MEXICO, Veracruz, Est. Biol. Los Tuxtlas, 480 m, male, 13.IV.1986, E. Ramirez col. (EMEC 202,862). COSTA RICA, Puntarenas, Monteverde, 1300 m, female, 18.V.1986 (EMEC 202,861).Published as part of Clarke, Robin O. S., 2018, Provisional revision of the genus Odontocera Audinet-Serville, 1834 (Coleoptera: Cerambycidae). I: exclusions, new rank, synonymies and the description of two new genera, pp. 1-27 in Insecta Mundi 637 on page 18, DOI: 10.5281/zenodo.370813
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