Structure-activity relationship studies of dibromo phenolic derivatives as photosynthetic electron chain inhibitors     

Martha Albores-Velasco  Blas Lotina-Henssen  Arturo Zapien  Gilberto Gonzalez  Luis Migueles 《Pest management science》1986,17(4):396-402

A number of 2,6-dibromophenols with different substituents in the 4-position have been synthesised and their effect on the whole electron transport chain and on photosystem II have been determined. A study was made to relate the chemical characteristics of the 4-substituent group and the inhibition of the uncoupled electron transport of isolated chloroplasts from spinach plants. The chemical nature of the 4-substituent group varies greatly in the active compounds and it is therefore suggested that this group does not participate in the inhibitor-receptor interaction. The results indicated that the inhibiting power of these compounds increased with the electron-attracting capacity of the 4-substituent group, decreased with increase in its size and that there was no correlation with its hydrophobic nature.  相似文献   

Yield and yield components of saffron under different cropping systems   总被引：1，自引：0，他引：1  

Jos Arturo de Juan  Horacio Lpez Crcoles  Ramona Mª Muoz  Mª Raquel Picornell 《Industrial Crops and Products》2009,30(2):212-219

This study was conducted to evaluate yield and yield components of saffron (Crocus sativus L.) in response to (i) production system (PS) (irrigated vs. non-irrigated); (ii) corm size (CS) (medium −2.25 to 3 cm diameter vs. small corms <2.25 cm diameter); (iii) planting depth (PD) (10 cm vs. 20 cm); and iv) planting density (PDEN) (51 corms m⁻² vs. 69 corms m⁻²).This fully replicated multifactorial design was started in August 2000, and carried through November 2003, when the fourth saffron harvest took place. The total and average fresh weight of stigmas, and the number of flowers were measured at each harvest.Results indicate that three of the four factors tested (PS, CS and PD) had a significant effect on the quantitative yield during the two most productive flowering years (2001 and 2002) and on the total flowering. Irrigated cultivation, medium size corms and 10 cm planting depth had the greatest effect in increasing the quantitative production of saffron.Yield was also affected by planting density in contrasting ways. Whereas at high PDEN yield increased per unit of surface, at low PDEN, yield increased with respect to the initial number of corms planted.The fresh weight of stigmas per flower yield component, an important aspect that determines the quality of the spice, was enhanced when corms were planted at 20 cm depth and when irrigation was applied to the crop.  相似文献   

Influence of Bacillus thuringiensis application timing on population dynamics of gypsy moth in Mediterranean cork oak forests     

Roberto Mannu  Arturo Cocco  Pietro Luciano  Andrea Lentini 《Pest management science》2020,76(3):1103-1111

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Antioxidant activity of Rhizophora mangle bark     

Sánchez J  Melchor G  Martínez G  Escobar A  Faure R 《Fitoterapia》2006,77(2):141-143

The antioxidant activity of Rhizophora mangle bark aqueous extract and its majoritary component and high molecular weight polyphenols' fraction were studied using deoxyribose assay. The total extract and its fraction showed scavenging activity of hydroxyl radicals and hability to chelate iron ions.  相似文献   

Seasonal distribution of air-borne pathogenic and free-living amoebae in Mexico City and its suburbs     

Dr. Fermin Rivera  Patricia Bonilla  Elizabeth Ramirez  Arturo Calderon  Elvia Gallegos  Salvador Rodriguez  Ricardo Ortiz  Dolores Hernandez  Victor Rivera 《Water, air, and soil pollution》1994,74(1-2):65-87

A survey was carried out over a one-year period to isolate amoebae suspended in the air of Mexico City and its suburbs. Sampling stations were placed at the four cardinal points of the metropolitan area. Selective media were used to culture the amoebae isolated. Specialized taxonomic keys and physical and physiological tests were used for identification, and a statistical analysis was performed to determine the correlations between physico-chemical and biological parameters. 108 strains were isolated, of which 19 were pathogenic via intracerebral inoculation and 9 via intranasal inoculation. Species of the generaAcanthamoeba, Vahlkampfia andHartmannella were most abundant.Acanthamoeba polyphaga showed the highest abundance. Several times during the period of the study SO₂ O₃, CO, NO and NO₂ exceeded the permissible levels established by the Mexican government. The ability of amoebae to form cysts and cyst size were important factors for their presence, survival, abundance and diversity in the atmosphere. The main source of air-borne amoebae was the soil. Factors that favored the incidence and diversity of the isolates were wind speed and direction, low relative humidity, generation of frequent dust-storms, resuspension of amoebae by vehicular traffic, proximity to garbage dumps and large extensions of bare soil. Soil cover was a factor associated with a reduction in the incidence and diversity of the aerial amoebae. This study demonstrates that there are viable cysts of amoebae in the atmosphere of Mexico City, that may have potential importance in the case of certain kinds of human allergies and diseases. Further research is needed to find out the aerial presence of viable cysts of obligatory, amphizoic or opportunistic amoebic parasites, and to clarify the qualitative and quantitative effects of the local meteorological and physico-chemical environment on the free-living amoebae present in the atmosphere.  相似文献   

Simultaneous fluorometric determination of chlorophylls a and B and pheophytins a and B in olive oil by partial least-squares calibration     

Galeano Díaz T  Durán Merás I  Correa CA  Roldán B  Rodríguez Cáceres MI 《Journal of agricultural and food chemistry》2003,51(24):6934-6940

The resolution of quaternary mixtures of chlorophylls a and b and pheophytins a and b has been accomplished by partial least-squares (PLS) multivariate calibration, applied to the fluorescence signals of these pigments. The total luminescence information of the compounds has been used to optimize the spectral data set to perform the calibration. After preliminary studies, a method is described in acetone media, to avoid emulsions with the olive oil samples. Different scanning paths have been selected for each method. For the simultaneous determination of the pigments in olive oil samples, a comparative study of the results found by using excitation, emission, and synchronous spectral data, as analytical signal, was performed. The excitation spectra were selected as the better analytical signals for the determination of the pigments in olive oil samples. The optimum wavelength range to record the excitation spectra (lambda(em) = 662 nm) was selected to minimize the contribution of pheophytin a and to maximize the contribution of the other pigments, which are the minor constituents in olive oil. Determination of these pigments in olive oil samples was effected from the excitation spectra of dissolutions o suitable aliquots in acetone. Recovery values from olive oil, spiked with chlorophylls a and b and pheophytins a and b, were in the ranges of 70-112, 71-111, 76-105, and 82-109%, respectively.  相似文献   

Indirect biomass estimations in Collembola     

Marian Caballero  Enrique Baquero  Arturo H. Ario  Rafael Jordana 《Pedobiologia》2004,48(5-6):551-557

We propose coefficients for regressions relating dry weight to body or tergite length in Folsomia candida, Entomobrya schoetti, Sminthurus viridis, and Hypogastrura vernalis (Collembola). Measurements were made on large batches of preserved, identified specimens. Batches were dessicated completely by critical-point drying and weighed. We compare our data with other published models and critically review the literature, finding questionable records.  相似文献   

Compositional variation amongst sorghum hybrids: Effect of kafirin concentration on metabolizable energy     

Israel Salinas  Arturo Pr  Yolanda Salinas  Eliseo Sosa  Carlos Miguel Becerril  Manuel Cuca  Miguel Cervantes  Jaime Gallegos 《Journal of Cereal Science》2006,44(3):342-346

Kafirins are stored proteins that negatively affect the nutritional quality of sorghum grain. Kafirin concentration and other chemical characteristics were determined in 12 sorghum hybrids and varied significantly, from 58% (HB1) to 42% (HB12) as percent total protein. Kafirin concentration correlated negatively with crude protein (CP) (−0.49), with acid detergent fiber (−0.40), apparent metabolizable energy (−0.61), and true metabolizable energy corrected for N (−0.63). HB12 was the hybrid with the lowest content of kafirins, amylose and tannins, and the highest content of apparent metabolizable energy. No differences were observed in the concentration of starch, but differences were found in apparent metabolizable energy (3325–2944 kcal kg⁻¹) probably due to a greater availability of starch, related to differences in kafirin concentration.  相似文献   

COMPUTED TOMOGRAPHIC ANATOMY OF THE CANINE INNER AND MIDDLE EAR     

Marco  Russo  DVM  PHD  Eucenio M.  Covelli  MD  Leonardo  Meomartino  DVM  PHD  Christopher R.  Lamb  MA  Vetmb  Arturo Brunetti  MD 《Veterinary radiology & ultrasound》2002,43(1):22-26

A series of high-resolution computed x-ray tomography (CT) images of the normal canine middle and inner ear are presented to serve as a reference for optimal interpretation of clinical CT images of animals with diseases affecting this region.  相似文献   

A Procedure for Choosing Tree-Stem Volume Equations Previously Fitted in a Forest     

Arturo A. Alvarado-Segura  Karen I. De La Cruz-De La Cruz 《Journal of Sustainable Forestry》2020,39(6):595-607

ABSTRACT

Tree-stem volumes constitute critical measurements for forest management. We propose a general two-criterion procedure for choosing the most reliable and robust volume equation(s), among a set of them previously fitted in a forest. Also, the proposal can be used as an additional criterion when fitting new equations to a single sample. Through simulated volumes, we considered how well a model estimates the volume generated by itself (the more accurate estimation, the better) and measured a model’s variability of the mean errors when it estimates volumes rebuilt by other models (the lower variability, the better). The procedure is exemplified with volume equations of Pinus patula in the Forestry Management Unit 1302 in Hidalgo, Mexico. In the example, we found that a linearized form of the combined-variable equation results reliable and robust. This selection coincided with the one made with data of a recent 150 trees sample (validation), where the rebuilt-estimated mean volume differs 0.034 m3 from the observed mean volume; it represents around US$2.6. Therefore, it is shown that simulation becomes an effective tool to identify equations that do not reproduce the volume of trees well in the current forest and helps to choose reliable and robust equations.  相似文献