Search results for "Arid"
showing 10 items of 1382 documents
Assessment of soil particle erodibility and sediment trapping using check dams in small semi-arid catchments
2017
Check dams can be used as a source of information for studies on sediment characteristics and soil particle erodibility. In this study, sediment yield and grain size distribution (GSD) were measured in twenty small catchments draining into a rock check dam in NW Iran for different runoffs during 2010–2011. Significant correlations were found between sediment yield and slope steepness, vegetation cover and soil erodibility factor (K) of the catchments. The erodibility of soil particles was determined using the comparison of GSD between sediment and original soil. Clay was the most erodible soil particle which showed 2.05 times more percentage in sediment than the original soil. The erodibili…
SUOLI ANTROPOGENICI IN AMBIENTE IPERARIDO: EFFETTI DELLA COLTIVAZIONE SULLA PEDOGENESI DEI SUOLI TERRAZZATI
2012
Análisis del nivel de educación en participantes de turismo de tercera edad en Portugal
2017
El presente trabajo hace una caracterización de nivel de educación de participantes de turismo senior en Portugal. Así, se realizaron entrevistas a turistas mayores de diversas regiones de Portugal (Norte, Centro, Lisboa, Alentejo, Algarve e las Islas de Azores y Madeira). Para tal, se ha hecho un cuestionario acerca de comportamientos, lo cual se aplicó en 343 participantes. Los datos muestran que los turistas son, en su mayoría, mujeres, con edad media de 69.43 años (dp=5.28), casadas, que viven en la región norte de Portugal; y tienen como principal nivel de educación la enseñanza secundaria. La principal motivación para participar en el programa de turismo es el interés en las actividad…
Distribution of graminoids in open habitats in Tajikistan and Kyrgyzstan
2022
Aims: Landscapes of Middle Asia are exposed to human influence due to long-lasting pastoral tradition, and now are largely dominated by non-forest vegetation. Graminoids perform key ecosystem functions, and constitute an important feed source for livestock. We studied the distribution patterns of graminoids cover under climatic and grazing pressure gradients in different open vegetation types. Study area: Tajikistan, Kyrgyzstan. Methods: 1,525 vegetation plots representing five open vegetation types (mires, salt marshes, tall-forb communities, pseudosteppes and steppes) were extracted from the Vegetation of Middle Asia Database. We assessed the relative cover of graminoid species in each ve…
Orthotrichum pilosissimum (Orthotrichaceae), a new moss from arid areas of Nevada with unique axillary hairs
2011
Abstract Orthotrichum pilosissimum is described from herbarium material and recently collected specimens in the state of Nevada. Its specific epithet refers to the diagnostic hyper-developed axillary hairs, which are frequently longer than 1 mm, multiseriate and branched, covering most of the stems surface and sometimes protruding from the foliose shoots. These hairs are not only unique in the genus but also among mosses, providing a reliable diagnostic character for the new taxon. Additional gametophytic and sporophytic characters that contribute to its taxonomic delimitation are also given.
Synthesis of new fluorinated Tebufenpyrad analogs with acaricidal activity through regioselective pyrazole formation.
2008
In previous studies, our group has shown that the use of fluorinated alcohols such as trifluoroethanol (TFE) and hexafluoroisopropanol (HFIP) as solvents dramatically increases the regioselectivity in the pyrazole formation from 1,3-diketone with methylhydrazine. We have now applied this synthetic method to the preparation of new fluorinated pyrazoles, which have then been used as synthetic intermediates in the preparation of fluorinated analogs of Tebufenpyrad, a commercial acaricide. These compounds display a strong acaricidal activity that is either comparable to or better than that of the commercial compound.
Synthesis, mechanical and thermal rheological properties of new gellan gum derivatives
2017
New derivatives of gellan gum (GG) were prepared by covalent attachment of octadecylamine (C18- NH2) to polysaccharide backbone via amide linkage by using bis(4-nitrophenyl) carbonate (4-NPBC) as a coupling agent. The effect of the alkyl chain grafted onto hydrophilic backbone of high molecular weight GG was investigated in terms of physicochemical properties and ability of new derivatives to form hydrogels. A series of hydrogels was obtained in solutions with different kind and concentration of ions and their stability and mechanical properties were evaluated. The obtained derivatives resulted soluble at temperature lower than starting GG and physicochemical properties of obtained hydrogel…
An efficient acetylation of dextran using in situ activated acetic anhydride with iodine
2010
A facile, efficient, cost-effective and solvent-free acetylation method has been developed for the acetylation of dextran. Dextran acetates were successfully synthesized using different molar ratios of acetic anhydride in the presence of iodine as a catalyst without the use of any solvent. The reactions were realized at 50?C for 3 h under stirring and nitrogen. This efficient method yielded highly pure and organosoluble dextran esters. The reaction appears highly effective for obtaining higher degrees of substitution (DS) with great efficiency. Under solvent-free conditions, dextran triacetates were efficiently synthesized. It was also observed that the molar ratio can easily control the DS…
Synthesis of tumor-associated glycopeptide antigens for the development of tumor-selective vaccines
2004
In contrast to normal cells, the glycoprotein profile on epithelial tumor cells is distinctly altered. Due to an incomplete formation of the glycan side-chains resulting from a premature sialylation, additional peptide epitopes become accessible to the immune system in mucin-type glycoproteins on tumor cells. These tumor-associated structure alterations constitute the basis for a selective immunological attack on cancer cells. For the construction of immunostimulating antigens, glycopeptide partial structures from the mucins MUC1 and MUC4 carrying the tumor-associated sialyl-T(N), alpha2,6-sialyl-T and alpha2,3-sialyl-T antigens have been synthesized. Employing different linkers such as the…