252 research outputs found
New genera and species of gall midges (Diptera, Cecidomyiidae) from three restingas of Rio de Janeiro State, Brazil
Study of the reaction of grafting acrylamide onto xanthan gum
AbstractThe present study aimed to study the reaction conditions of grafting of acrylamide on xanthan gum. It was analyzed the influence of reaction conditions, mainly type of initiator activation, initiator concentration and initiator/acrylamide ratio, on graft parameters and copolymer properties. Potassium persulfate was employed as an initiator and heating or N,N,N′,N′-tetramethylethylenediamine was used to activate the initiator. Reaction time and initiator concentration were varied and final values for grafting percentage and grafting efficiency were the same for both methods, whereas speed in reaching these values differs from one technique to another. We found that reaction time was inversely proportional to intrinsic viscosity, likely due to main chain degradation promoted by potassium persulfate (KPS); furthermore, the increasing in the KPS concentration lowers grafting percentage, acrylamide conversion and chain degradation, possibly as a result of O2 formation at high KPS concentrations
Localization of gravity in brane world with arbitrary extra dimensions
We study the induced 4-dimensional linearized Einstein field equations in an
m-dimensional bulk space by means of a confining potential. It is shown that in
this approach the mass of graviton is quantized. The cosmological constant
problem is also addressed within the context of this approach. We show that the
difference between the values of the cosmological constant in particle physics
and cosmology stems from our measurements in two different scales, small and
large.Comment: 8 pages. arXiv admin note: substantial text overlap with
arXiv:gr-qc/0408004, arXiv:gr-qc/0607067, arXiv:0704.1035, arXiv:0707.3558,
arXiv:0710.266
Eugeniamyia dispar em pitangueira: parasitoides associados, dinâmica populacional e distribuição de galhas na planta
Alkaloids and volatile constituents from the stem of Fusaea longifolia (Aubl.) Saff. (Annonaceae)
Alcalóides de Duguetia trunciflora Maas (Annonaceae)
From the ethanolic extract of the leaves and thin branches of Duguetia trunciflora Maas (Annonaceae) six alkaloids were isolated, being one benzylisoquinoline: reticuline¹, four tetrahydroprotoberberine:,tetrahydro-palmatine², tetrahydrojathrorrizine³, discretamine4, thaicanine5, and one berberine: jathrorrizine6. These alkaloids were identified through ¹H and 13C NMR spectroscopic technics. The alkaloids 1, 3, 5 and 6 are being cited for the first time on Duguetia genus
Volatile and glycosidically bound composition of Loureiro and Alvarinho wines
Composition of Loureiro and Alvarinho wines from the Vinhos Verdes region,
respecting free volatile compounds as well as glycosidically bound aroma precursors,
was exhaustively determined by GC-MS after adsorption on XAD-2 resin. On the
whole, were identified and quantified 120 volatile compounds in the free fraction and
77 glycosidically bound compounds, belonging to C6-compounds, alcohols, fatty acids
ethyl esters, esters of organic acids, acetates, monoterpenic alcohols, monoterpenic
oxides and diols, C13-norisoprenoids, volatile phenols, volatile fatty acids and carbonyl
compounds. Globally, the wines of the two cultivars present similar composition on
volatiles. However, respecting varietal compounds, Loureiro wines are richer than
Alvarinho ones with regard to C6-compounds and monoterpenic compounds, occurring
the opposite for volatile phenols. It was also demonstrate that wines of both varieties
may benefit the aroma reserve, present as glycoconjugates, as it is susceptible of
being technologically explored. Linalool, Ho-trienol, α-terpineol, contributing with
fruity and floral notes, and β-damascenone mostly for Alvarinho, confering tropical
fruit notes, are the varietal compounds which may particularly influence the aroma of
these wines. Respecting fermentative compounds, Alvarinho is also particularly rich in
fatty acids ethyl esters related to lipid metabolism and acetates of fusel alcohols,
which can provide it a fruity character; Loureiro contains higher levels of esters of
organic acids and 2-phenylethanol, conferring fruity and floral notes. Sensory analysis
agree with chemical analyses showing a pronounced tree and tropical fruit character
for Alvarinho wines while Loureiro wines present more intense citrus fruit notes.Centre of Biological
Engineering of Universidade do Minho; Estação VitivinÃcola Amândio
Galhano (EVAG); Solar de Serrade; EVAG; Comissão de Viticultura da Região dos Vinhos Verdes
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