Optical Absorption Characteristics of Ni2+ in Mixed-Alkali Borate Glasses

Nickel-containing mixed-alkali borate glasses were prepared and their spectral absorption in the visible and near-ir were measured and used to determine the ligand field strength, Racah parameter, and state of coordination of Ni²⁺ ions. The change in these parameters with alkali content is discussed in terms of mixed-alkali effect. Nickel ions were found to occupy octahedral sites in the 20 mol% (Li₂O+Na₂O) glasses, whereas in the 30 mol% (Na₂O+K₂O) glasses Ni^Z+ ions are believed to occupy both octahedral and tetrahedral sites. In most cases slight deviations were observed which increased with increasing alkali content. The results obtained suggest that the substitution of one alkali for another in alkali borate glasses did not produce gross alterations of the glass network sufficient to induce deviations from linearity in property-composition relations.     

MEASUREMENT BY COMPRESSION TEST OF IMPACT DAMAGE TO CITRUS FRUITS*

Abstract. Oranges and grapefruit were subjected to single and repeated impact drops from three heights. Subsequent measurements of the force-deformation ratio and hysteresis loss were made with quasi-static compression tests on the impacted whole fruit. Internal damage was indicated by a reduction in the force-deformation ratio and an increase in the hysteresis loss for a single 100 cm drop and two or more drops from 25 or 50 cm heights.     

Beef muscle osmotic pressure as assessed by differential scanning calorimetry (DSC)

Osmotic pressure, an important physiological characteristic of plant and animal tissues, is difficult to measure, and no convenient and efficient method is so far available. In the present work we developed a differential scanning calorimetry (DSC) method, and estimated the physiological osmotic pressure of intact bovine muscle and post-mortem variation during the conversion of muscle into meat. We also examined the major role of sample pH in this variation. This method, based on the determination of the melting onset point of frozen muscle's indigenous water, was compared to a freezing point osmometric method and a soaking method. It was concluded that the DSC method appeared more practical and reliable than other methods and could be applied to various animal and plant tissues and fluids.     

Electric-field induced fluctuations in laser generated plasma plume

The effect of an external electric field on laser-generated plasma has been studied. It is observed that the laser-generated plasma can be used for the ignition of a spark in the presence of a low voltage external electric field. An eight-fold emission intensity enhancement in Cu Ⅰ spectral lines are measured as compared to the signal intensity in the absence of an external electric field.The plasma parameters remain the same initially, up to a few microseconds after the generation of plasma, and this feature makes it more interesting for the quantitative analysis of any sample using laser induced breakdown spectroscopy(LIBS). In the presence of an external electric field,fluctuations(contraction and expansion) in the laser-generated plasma are observed which increase the plasma decay time and consequently result in enhanced signal intensity.     

Application of ferrous sulfate alleviates negative impact of cadmium in rice (<i>Oryza sativa</i> L.)

Soil contamination with toxic heavy metals [such as cadmium (Cd)] is becoming a serious global problem due to rapid development of social economy. Iron (Fe), being an important element, has been found effective in enhancing plant tolerance against biotic and abiotic stresses. The present study investigated the extent to which different levels of Ferrous sulphate (FeSO₄) modulated the Cd tolerance of rice (Oryza sativa L.), when maintained in artificially Cd spiked regimes. A pot experiment was conducted under controlled conditions for 146 days, by using natural soil, mixed with different levels of CdCl₂ [0 (no Cd), 0.5 and 1 mg/kg] together with the exogenous application of FeSO₄ at [0 (no Fe), 1.5 and 3 mg/kg] levels to monitor different growth, gaseous exchange characteristics, oxidative stress, antioxidative responses, minerals accumulation, organic acid exudation patterns of O. sativa. Our results depicted that addition of Cd to the soil significantly (P < 0.05) decreased plant growth and biomass, gaseous exchange parameters, mineral uptake by the plants, sugars (soluble, reducing, and non-reducing sugar) and altered the ultrastructure of chloroplasts, plastoglobuli, mitochondria, and many other cellular organelles in Cd-stressed O. sativa compared to those plants which were grown without the addition of Cd in the soil. However, Cd toxicity boosted the production of reactive oxygen species (ROS) by increasing the contents of malondialdehyde (MDA), which is the indication of oxidative stress in O. sativa and was also manifested by hydrogen peroxide (H₂O₂) contents and electrolyte leakage to the membrane bounded organelles. Although, activities of various antioxidative enzymes like superoxidase dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) and non-enzymatic antioxidants like phenolics, flavonoid, ascorbic acid, anthocyanin and proline contents increased up to a Cd level of 0.5 mg/kg in the soil but were significantly diminished at the highest Cd level of 1 mg/kg in the soil compared to those plants which were grown without the addition of Cd in the soil. The negative impacts of Cd injury were reduced by the application of FeSO₄ which increased plant growth and biomass, improved photosynthetic apparatus, antioxidant enzymes, minerals uptake together with diminished exudation of organic acids as well as oxidative stress indicators in roots and shoots of O. sativa by decreasing Cd retention in different plant parts. These results shed light on the effectiveness of FeSO₄ in improving the growth and upregulation of antioxidant enzyme activities of O. sativa in response to Cd stress. However, further studies at field levels are required to explore the mechanisms of FeSO₄-mediated reduction of the toxicity of not only Cd, but possibly also other heavy metals in plants.     

States of Sulfur in Alkali Borate Glasses

Simple binary alkali borate glasses of differing alkali content (alkali = Li, Na, or K) containing sulfur were prepared and their absorption spectra were measured in the range of 200 to 700 nm. The absorption bands obtained were used to determine the stable states of sulfur in these glasses by directly comparing them with published data. The following states of sulfur were identified and their ranges of stability were determined: the S₂ molecule in glasses containing at least 15 mol% alkali oxide, the S₃⁻ and S₂⁻ in glasses containing 20 to 30 mol% Na₂O or K₂O, and the polysulfide ion (S x ²⁻) in glasses of 30 to 35 mol% Na₂O or K₂O.