Search results for "STAR"

The Influence of Brassinosteroid, a Growth-promoting Steroidal Lactone, on Development and CO2-fixation Capacity of Intact Wheat and Mustard Seedlings

1984

In 1970, Mitchell et al. isolated a lipoidal complex from the pollen of rape (Brassica napus L.). This complex, called “Brassins” was found to have partly powerful growth-promoting properties. The novel growth response of young bean plants in the second internode assay (Worley, Mitchell 1971; Mitchell, Gregory 1972) and other physiological changes following Brassin-treatment have been studied under several aspects (Krizek, Worley 1981; Gregory 1981).

Carotenoid-based colour polyphenism in a moth species: search for fitness correlates

2007

Carotenoid-based integumental coloration is often associated with individual performance in various animals. This is because the limited amount of the pigment has to be allocated to different vital functions. However, most of the evidence for the carotenoid-based trade-off comes from vertebrate studies, and it is unclear if this principle can be applied to insects. This possibility was investigated in Orgyia antiqua L. (Lepidoptera: Lymantriidae). The larvae of this species are polyphenic in their coloration, varying from a highly conspicuous combination of yellow hair tufts on black background to cryptic appearance with brown hair tufts. The conspicuous larvae are aposematic, advertising t…

Creep and recovery experimental investigation of low oil content food emulsions

2008

Abstract Creep and recovery tests have been performed to study the viscoelastic behavior of low oil content food emulsions. Formulations of salad dressings usually include modified starch (MS) due to its low cost and the special creamy texture if affords. The combination of starch with other natural gums may improve the quality of the product. A reference emulsion containing 4% MS, and four other formulations in which the starch was partially replaced by xanthan gum (XG), locust bean gum (LBG) and two synergistic blends of these gums were formulated. Gels prior to emulsification were studied for comparative purposes. The viscoelastic behavior of all the systems was characterized by means of…

2018

Star-shaped polymers show a continuous change of properties from flexible linear chains to soft colloids, as the number of arms is increased. To investigate the effect of macromolecular architecture on the flow properties, we employ computer simulations of single chain and star polymers as well as of their mixtures under Poiseuille flow. Hydrodynamic interactions are incorporated through the multi-particle collision dynamics (MPCD) technique, while a bead-spring model is used to describe the polymers. For the ultradilute systems at rest, the polymers are distributed uniformly in the slit channel, with a weak dependence on their number of arms. Once flow is applied, however, we find that the…

Improvement of the mechanical properties of photo-oxidized films after recycling

2002

Mechanical recycling of post-consumer plastics gives rise, in most cases, to secondary materials with mechanical properties worse than those of the reclaimed polymer. This is mostly due to the thermomechanical treatment undergone during the melt reprocessing operations. In this work, low density polyethylene films have been photo-oxidized in artificial accelerated ageing conditions and then the brittle films have been melt reprocessed. It is shown that the secondary material, after reprocessing, shows mechanical properties, in particular elongation at break, better than those of the photo-oxidized films. This behaviour has been attributed to the fact that the melt reprocessing has the effec…

Durability of a strach-based biodegradable polymer

2007

Abstract The photo-oxidation and the photo-stabilization of a commercial biodegradable polymer have been investigated in order to establish the possibility of using this polymer as raw material for films for agriculture. The degradation has been followed by measuring the mechanical properties as a function of photo-oxidation time and in particular by following the elongation at break. The virgin polymer, made from maize starch and a synthetic biodegradable polyester, shows poor resistance to the UV irradiation as observed by the fast decay of the elongation at break, but the presence of small amounts of conventional UV stabilizers strongly improves the durability of this polymer. The UV sta…

Natural Anti-oxidants for Bio-polymeric Materials

2017

In this work, three different bio-polymers, i.e. a commercial starch-based polymer (Mater-Bi®) a bio-polyester (PLA), and a bio-polyether (PEO) were additivated with quercetin, a natural flavonoid antioxidants, in order to formulate biobased films for eco-sustainable packaging and outdoor applications. The photo-oxidation behavior of unstabilized and quercetin stabilized films has been evaluated and compared with that of films additivated with a commercial synthetic light stabilizer. Obtained results show that quercetin molecules are able to slow down the photodegradation rate of all investigated bio-polymeric films, opening new avenues in the formulation of fully renewable polymer-based sy…

Biopolymer interactions affect the functional properties of edible films based on agar, cassava starch and arabinoxylan blends

2009

Abstract Edible films based on the binary combination of agar (AG), cassava starch (CAS) and arabinoxylan (AX) were studied with regard to their microstructure, moisture barrier and mechanical properties. Though the films appear macroscopically homogeneous, electron microscopy observations reveal a phase separation and dispersion, respectively, in AG–CAS and AG–AX blend film structures, whereas the structure of CAS–AX blend films seems homogeneous. In case high moisture (84% and 99% RH), neither the combination of AG and CAS nor the addition of AX into CAS can improve film moisture barrier properties, except at a lower RH (57%). Conversely, water vapor permeability (WVP) of AG based film is…

Determination of biological characteristics of Tunisian Artemia salina populations

2012

In this study, Artemia salina cysts collected from four Tunisian hypersaline environments were characterized using biometrical, biological and biochemical descriptors. Biometrical analysis revealed that the mean diameter value ranged from 220.25 to 237.76 μm, for the untreated cysts, from 199 to 224.52 μm for decapsulated cysts and that the chorion thickness ranged from 6.62 to 10.58 μm. 48 h after hatching, Artemia from Sebkha El Meleh, Sebha Moknine, Sfax saltworks and Sahline saltworks presented a hatching percentage of 52.7%, 53.75%, 70.16% and 43.74%, respectively. The length of the freshly hatched instar I nauplii varied from 429 to 449.34 μm. The fatty acids profile showed that the n…

(Co-)solvent selection for single-wall carbon nanotubes: best solvents, acids, superacids and guest-host inclusion complexes.

2011

Analysis of 1-octanol-water, cyclohexane-water and chloroform (CHCl(3))-water partition coefficients P(o-ch-cf) allows calculation of molecular lipophilicity patterns, which show that for a given atom log P(o-ch-cf) is sensitive to the presence of functional groups. Program CDHI does not properly differentiate between non-equivalent atoms. The most abundant single-wall carbon nanotube (SWNT), (10,10), presents a relatively small aqueous solubility and large elementary polarizability, P(o-ch-cf) and kinetic stability. The SWNT solubility is studied in various solvents, finding a class of non-hydrogen-bonding Lewis bases with good solubility. Solvents group into three classes. The SWNTs in so…