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Search Results: 1 - 10 of 461822 matches for " A. Chavarria "
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First Neotropical Mutualistic Associations in Bumblebee Nests(Hymenoptera: Apidae)
Gabriela Chavarria
Psyche , 1994, DOI: 10.1155/1994/41890
Abstract:
Phoresy on a Neotropical Bumblebee (Hymenoptera: Apidae) byAntherophagus (Coleoptera: Cryptophagidae)
Gabriela Chavarria
Psyche , 1994, DOI: 10.1155/1994/84604
Abstract:
Solar Neutrinos in 2011
Alvaro Chavarria
Physics , 2012,
Abstract: I give an overview of the recent developments in the solar neutrino field. I focus on the Borexino detector, which has uncovered the solar neutrino spectrum below 5 MeV, providing new tests and confirmation for solar neutrino oscillations. I report on the updated measurements of the 8B solar neutrino flux by water Cherenkov and organic scintillator detectors. I review the precision measurement of the 7Be solar neutrino flux by Borexino and the search for its day-night asymmetry. I present Borexino's latest result on the study of pep and CNO neutrinos. Finally, I discuss the outstanding questions in the field and future solar neutrino experiments.
índice de área foliar em canola cultivada sob varia??es de espa?amento e de densidade de semeadura
Chavarria, Geraldo;Tomm, Gilberto Omar;Muller, Alexandre;Mendon?a, Heloisa Ferro;Mello, Naiana;Betto, Maico Serafini;
Ciência Rural , 2011, DOI: 10.1590/S0103-84782011001200008
Abstract: the aim of this work was to estimate leaf area index of the canola cultivar 'hyola 61' under variations of row spacing and density of sowing by a non-destructive method. the experimental design consisted of a split plot with four blocks with row widths of 17, 34, 51 and 68cm and plant populations of 15, 30, 45 and 60m2. two hundred and fifth leaves were collected at random and mesure width (c), length (l) and leaf area (la) and the parameters were correlated. also the leaves of four plants of each plot, selected at random, were measured l and c and estimated the leaf area index (lai). width leaf was the biometric parameter that shows highest correlation with la. there is a linear relation between plant density and leaf area index in spacing of 34, 51 and 68cm in 'hyola 61'. the row width of 17cm and plant population of 60 plants per square meter to reduces the lai. however, aiming lai maintenance in hyola 61 is recommended uses of row width of 17cm and plant population of 45 plants per square meter.
Evaluación espacial y temporal de la diversidad de los ascomicetes dulceacuícolas del canal turístico Santa Cruz, Xochimilco, México
Chavarria, Allan;González, María C.;Dantán, Edgar;Cifuentes, Joaquín;
Revista mexicana de biodiversidad , 2010,
Abstract: the diversity of freshwater ascomycetes was determined in the touristic channel santa cruz, xochimilco, mexico. two surveys were conducted in 2007 during the dry and wet season. four sampling sites were selected in the channel margin, based on the level of urbanization. at each sampling site, wood panels of tabebuia donnell-smithii, bucida buceras, pinus sp., cupressus lindlei and abies religiosa were submerged during 8 weeks. water temperature, dissolved oxygen, organic matter, phosphorus and most probable number of coliform bacteria were determined. results were evaluated using the diversity index of shannon and the index of similarity of s?rensen. the highest ascomycete diversity recorded (h' = 1.152) was found at the third sampling site, located near commercial florist greenhouses. the lowest diversity (h' = 0.976) was obtained at the first sampling site, in front of santa cruz pier. both values of diversity were in agreement with the urbanization level and physicochemical and bacteriological data. the wet season had the lowest diversity of freshwater ascomycetes, perhaps due to the effect of the rainfall in this aquatic environment.
ESTADO NUTRICIONAL DE TRABAJADORES BAJO TURNOS ROTATIVOS O PERMANENTES NUTRITIONAL STATE OF WORKERS UNDER STEADY OR ROTATING SHIFTS
Marcela Ruiz de la F,María Trinidad Cifuentes M,Orieta Segura B,Pamela Chavarria S
Revista Chilena de Nutricíon , 2010,
Abstract: Restricciones del sue o predisponen a padecer, a largo plazo, malnutrición por exceso y enfermedades crónicas no transmisibles. El objetivo fue estudiar la influencia del turno laboral sobre estado nutricional, perfil lipídico y glicemia en ayuno. Estudio exploratorio del tipo de serie de casos, 47 reclutados; 31 turnos rotativos (día y noche), y 16 turno permanente (día). La evaluación nutricional se efectuó mediante el IMC, la circunferencia cintura-cadera y los pliegues tricipital, bícipital, subescapular y suprailiaco. Se estudió las horas sue o mediante un registro semanal, la ingesta dietética por encuesta de recordatorio de 24 horas. Se determinó el colesterol total, c-HDL, c-LDL, triglicéri-dos séricos y glicemia. La muestra estuvo representada en un 87% mujeres y 13% por hombres, cuya mediana de edad fue de 38,7 a os [19,0] y 44,7[25,2] (p=0,420) en turno rotativo y permanente, respectivamente. El turno rotativo no mostró diferencias significativas respecto al turno permanente en los parámetros antropométricos a excepción, del pliegue subescapular que fue significativamente superior (p=0,032), respecto a ingesta de macronutrientes, perfil lipídico y glicemia tampoco mostró diferencias significativas (p=> 0,05). La prevalencia del estado nutricional en el turno rotativo fue en 35,4% normal, en 45,1% sobrepeso y en 19,5% obesidad, y turno permanente: 43,7% normal y 56,3% sobrepeso. La antigüedad laboral sólo en el turno rotativo se correlacionó positivamente con IMC (r=0,436 p<0,005), grasa corporal (r=0,454 p<0,005), el colesterol total (r= 0,394 p<0,005) el LDL (r=0,484 p<0,005) y la glicemia (r=0,405 p<0,005). En conclusión, los funcionarios del turno rotativo y permanente no mostraron diferencias significativas entre las variables estudiadas, a excepción del pliegue subescapular que fue significativamente mayor en el turno rotativo, lo que podría asociarse a la distribución de la grasa predominantemente central. Restrictions of sleep predispose to experience, in the long-term, excess malnutrition and non-transmissible chronic diseases. The objective of this research has to study the influence of working shifts on nutritional status lipid profile and fasting blood glucose (FBG). Study of a series of cases considered a total of47 recruited workers from which 31 of them had a rotating shift (day and night) and 16 a steady shift (day). The nutritional assessment involved: BMI (Body Mass index), waist and hip circumference, tricipital, bicipital, sub scapular and supra iliac skin folds. Sleep hours were studied with a weekly record, food intake was
Evaluación espacial y temporal de la diversidad de los ascomicetes dulceacuícolas del canal turístico Santa Cruz, Xochimilco, México Spatial and temporal evaluation of the diversity of freshwater Ascomycetes from the touristic channel Santa Cruz, Xochimilco, Mexico
Allan Chavarria,María C. González,Edgar Dantán,Joaquín Cifuentes
Revista mexicana de biodiversidad , 2010,
Abstract: Se investigó la diversidad de los ascomicetes del canal Santa Cruz, considerado el de mayor importancia turística en Xochimilco, Distrito Federal. En 2007 se realizaron 2 muestreos en las épocas de menor y mayor precipitación. En el márgen del canal se establecieron 4 estaciones de muestreo con diferente grado de urbanización y en cada una se sumergieron bloques de madera de Virola sp., Tabebuia donnell-smithii, Bucida buceras, Pinus sp., Cupressus lindlei y Abies religiosa durante 8 semanas. Se midió la temperatura, el pH, el oxígeno disuelto, la materia orgánica y el fósforo, y se determinó el número más probable de bacterias coliformes del agua. Para evaluar los datos, se aplicaron el índice de diversidad de Shannon y el índice de similitud de S rensen. La mayor diversidad de ascomicetes (H' = 1.152) se registró en la tercera estación, ubicada en la zona de viveros con flores y la menor diversidad (H' = 0.976) se obtuvo en la primera estación, localizada frente al embarcadero Santa Cruz, ambos valores de diversidad coincidieron con el grado de urbanización y con los datos fisicoquímicos y bacteriológicos. La temporada de lluvias presentó la diversidad más baja debido probablemente al efecto de la precipitación en este ambiente acuático. The diversity of freshwater Ascomycetes was determined in the touristic channel Santa Cruz, Xochimilco, Mexico. Two surveys were conducted in 2007 during the dry and wet season. Four sampling sites were selected in the channel margin, based on the level of urbanization. At each sampling site, wood panels of Tabebuia donnell-smithii, Bucida buceras, Pinus sp., Cupressus lindlei and Abies religiosa were submerged during 8 weeks. Water temperature, dissolved oxygen, organic matter, phosphorus and most probable number of coliform bacteria were determined. Results were evaluated using the diversity index of Shannon and the index of similarity of S rensen. The highest Ascomycete diversity recorded (H' = 1.152) was found at the third sampling site, located near commercial florist greenhouses. The lowest diversity (H' = 0.976) was obtained at the first sampling site, in front of Santa Cruz pier. Both values of diversity were in agreement with the urbanization level and physicochemical and bacteriological data. The wet season had the lowest diversity of freshwater Ascomycetes, perhaps due to the effect of the rainfall in this aquatic environment.
Four Highly Luminous Massive Star Forming Regions in the Norma Spiral Arm II. Deep NIR imaging
L. Chavarria,D. Mardones,G. Garay,A. Escala,L. Bronfman,S. Lizano
Physics , 2009, DOI: 10.1088/0004-637X/710/1/583
Abstract: We present sensitive NIR (J, H and K) imaging observations toward four luminous massive star forming regions in the Norma Spiral Arm: G324.201+0.119, G328.307+0.432, G329.337+0.147 and G330.949-0.174. We identify three clusters of young stellar objects (YSO) based on surface density diagnostics. We also find that sources detected only in the H and K-bands and with colors corresponding to spectral types earlier than B2, are likely YSOs. We analyze the spatial distribution of stars of different masses and find signatures in two clusters of primordial mass segregation which can't be explained as due to incompleteness effects. We show that dynamic interactions of cluster members with the dense gas from the parent core can explain the observed mass segregation, indicating that the gas plays an important role in the dynamics of young clusters.
PMS and ZAMS stars associated with the dark cloud LDN 1655
Carlos Chavarria-K,Marco A. Moreno-Corral,Estela de Lara,Eduardo de la Fuente
Physics , 2014, DOI: 10.1016/j.newast.2012.06.002
Abstract: We give results of a low-resolution optical spectroscopic study of the bright nebulous stars conforming the tight stellar trapezium embedded in IRAS06548-0815, of the exciting star of IRAS06547-0810, and of the stars associated with reflection nebulae (R-or N-stars) NJ065703.0-081421, NJ065714.1-081016, IRAS06548-0815 D and IRAS06548-0815 G, all objects scarcely observed and apparently pertaining to the dark cloud LDN 1655. Our results given here combined with the corresponding 2MASS near infrared photometry enables us to estimate a photometric distance to LDN1655 of 1.9 kpc and to locate the trapezium stars on the (log Lstar/Lsun, logTeff) or HR diagram in an attempt to disclose about their true nature. The spectroscopy of IRAS06548-0815 revealed two classic T Tauri, two Herbig Ae/Be stars, four weak-line T Tauri stars, and two probable lithium-rich stars. Additionally, we found that the R-star IRAS06547-0810 is excited by a single B1(V) star, that IRAS06548-0815 D is excited by a SpT. B2/B3(V) star, NJ065703.0-081421 and NJ065714.1-081016 are excited by a B3/B4(V) emission star and an A6(V) star, respectively. The brightest near infrared source of the trapezium, IRS1, has an infrared luminosity comparable to a highly reddened O8(V) star (Av of 29m). The second brightest near infrared source of the trapezium, IRAS06548-0815 C is, optically, a single classical T Tauri star of spectral type K4/K5, but is a resolved binary in the 2MASSKs band, both components being of about the same brightness.
A multiwavelength study of embedded clusters in W5-east, NGC7538, S235, S252 and S254-S258
L. Chavarria,L. Allen,C. Brunt,J. L. Hora,A. Muench,G. Fazio
Physics , 2014, DOI: 10.1093/mnras/stu224
Abstract: We present Spitzer, NIR and millimeter observations of the massive star forming regions W5-east, S235, S252, S254-S258 and NGC7538. Spitzer data is combined with near-IR observations to identify and classify the young population while 12CO and 13CO observations are used to examine the parental molecular cloud. We detect in total 3021 young stellar objects (YSOs). Of those, 539 are classified as Class I, and 1186 as Class II sources. YSOs are distributed in groups surrounded by a more scattered population. Class I sources are more hierarchically organized than Class II and associated with the most dense molecular material. We identify in total 41 embedded clusters containing between 52 and 73% of the YSOs. Clusters are in general non-virialized, turbulent and have star formation efficiencies between 5 and 50%. We compare the physical properties of embedded clusters harboring massive stars (MEC) and low-mass embedded clusters (LEC) and find that both groups follow similar correlations where the MEC are an extrapolation of the LEC. The mean separation between MEC members is smaller compared to the cluster Jeans length than for LEC members. These results are in agreement with a scenario where stars are formed in hierarchically distributed dusty filaments where fragmentation is mainly driven by turbulence for the more massive clusters. We find several young OB-type stars having IR-excess emission which may be due to the presence of an accretion disk.
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