Intersheet Distance Modeling and Thermal Characterization of New Micro/Nano-Composites Composed by Clay Matrix and PEG 6000 Addition

Nowadays, the energetic efficiency becomes one of the major interests of the global society. Thus, the energetic challenges of the new century enforce the scientific and industrial environment to the development of new efficient materials, which present more than the classical thermal properties, according to the energy storage, energy consumption and other specific needs. In this context, the present work constitutes the third step of the development of a new kind of composite materials (micro-composites and nano-composites), using natural marl (clay) clay and biodegradable polymer, which is the PolyEthylene Glycol 6000 (PEG 6000). This step corresponds to characterization of the variation of the specific heat (denoted Cp) of the materials elaborated. So, in order to estimate the capacity of thermal energy adsorption, we utilized a SHIMATZU-DSC 60 Differential Scanning Calorimeter. The main results present the evolution of the Cp according to the PEG 6000 doping and also the specific melting enthalpy of the polymer within the natural clay matrix;by the way this enthalpy constitutes the specific heat stocked in the materials.

In Vitro Screening of Cactus [Opuntia ficus-indicia (L.) Mill] Genotypes for Drought Tolerance

Drought is one of the complex environmental factors affecting growth and yield of crops in arid and semi-arid areas of the world. In this context, this investigation was carried out to select drought tolerance cactus genotypes under in vitro condition. An experiment was carried out at Laboratory of Mekelle Agricultural Research Center, Northern Ethiopia. Six cactus pear genotypes namely, Gerao, Keyih Beles, Shenkor, Limo, Lemats Beles and Suluhna were used. Areoles were used as explants in tissue culture. The non-ionic water soluble polymer polyethylene glycol (PEG) of molecular weight 6000 was used as osmoticum to simulate water stress. In the first culture, the MS medium was supplemented with (2, 4-D (4 mg/l) and BA (0.5 mg/l) for callus induction. In all cultures MS medium was supplemented with 0, 10, 20 and 40 g/l polyethylene glycol (PEG) and was solidified with 0.8% agar and 30 g of sucrose. Significant differences were observed among the genotypes, PEG levels. In the first culture highest number of explants initiated callus on medium supplemented with no PEG but had not shown significant difference with 10 g/l PEG. At 10 g/l PEG, the callus induction frequency, callus fresh weight and plantlet regeneration were recorded highest for Suluhna (83.3%, 5.5 g and 63.3%), respectively. At 40 g/l PEG, callus induction frequency, callus fresh weight and plantlet regeneration were produced highest for Suluhna (41.7%, 2.75 g and 45%), respectively but no significant difference with Gerao, Limo and Lemats Beles. However, Shenkor and Keyih Beles were induced callus but became reddish black within 35 days supplemented with 40 g/l PEG. Both shoot and root production decreased with increased PEG level in the medium. At 40 g/l PEG in MS medium, the highest shoot number was in Suluhna genotype (4.33) followed by Gerao (3.67). The highest shoot length was in Suluhna (2.11 cm) with no significant difference with Gerao (2.02 cm). Root number (5.00 and root length (1.41 cm) were in the genotype Suluhna. Survival percentage of in vitro regenerated plantlets was 100% during hardening. By taking into consideration, all the growth parameter tested revealed that Suluhna, Gerao, Limo and Lemats Beles showed better drought stress tolerance at the highest level of PEG while Keyih Beles and Shenkor appeared to be drought sensitive at the highest level of PEG.

The Influence of Induced Drought Stress on Germination of Cenchrus ciliaris L.and Cenchrus setigerus Vahl.:Implications for Rangeland Restoration in the Arid Desert Environment of Kuwait

Drought impacts in arid desert ecosystems can result in decreased ecosystem productivity and biodiversity.Imple­mentation of restoration projects in arid desert environments is largely dependent on water availability and soil mois­ture condition.This study investigated the influence of induced drought stress by using polyethylene glycol(PEG-6000)solution on germination viz.Cenchrus ciliaris and Cenchrus setigerus as the important rangeland species.The water stress potential treatments were 0(control),-0.5 MPa,-1.0 MPa,-1.5 MPa,and-2.0 MPa.The extent of seed germi­nation was severely affected by decreased water stress potential.As drought increased,the percentage of germination decreased in both Cenchrus’species.The water deficit at-0.5 MPa showed a significant(P<0.001)reduction in the final germination percentage in the case of C.setigerus and C.ciliaris by 65%and 42.5%,respectively.At-1.0 MPa to-1.5 MPa,changes in intermediate germination were observed in C.ciliaris(from 35%to 17.5%,respectively)and C.setigerus(from 22.5%to 11.25%respectively).Higher levels of water stress(-2.0 MPa)prevented the survival of both species.Understanding the germination strategies of native desert plant species associated with drought stress and identifying favorable conditions during the germination process can be useful for restoration practices and rangeland management actions to improve desert ecosystems and maintain biodiversity.