Phase conjugation by degenerate four wave mixing in disodium fluorescein solution in methanol

Organic dyes are known to show the resonant type of nonlinear optical properties, including phase conjugation. In the present work, disodium fluorescein in methanol is used as an organic nonlinear medium for degenerate four wave mixing at 532 nm to see the intensity dependence of the phase conjugate signal at different concentrations of the solution. It is observed that the maximum reflectivity of the signal occurs in a concentration range of 5 x 10(exp -3)/cu cm to 1.2 x 10(exp -2) g/cu cm. It is also observed that the intensity of the signal drops suddenly to less than half of its maximum outside the concentration range mentioned above. An investigation of the phase conjugate signal intensity by changing the delay time between probe signal and the forward pump is also examined. Briefly discussed is the possibility of population grating in dye liquids as a source of enhancing the third order susceptibility besides the other techniques mentioned in reference. The experiment is done by beam splitting the second harmonic (532 nm) of Nd:YAG laser, Q-switched at 20 pulses/sec (pulse width is approximately 8 and 200 mJ per pulse)

A case of reversed polarity in the embryo-sac

This article does not have an abstract

Optimum culture medium composition for lipopeptide production by Bacillus subtilis using response surface model-based ant colony optimization

Central composite rotatable design (CCRD) of experiments was used to obtain data for Lipopeptide and Biomass concentrations from fermentation medium containing the following five components: glucose, monosodium glutamate, yeast extract, MgSO4⋅7H2O, and K2HPO4. Data was used to develop a second order regression response surface model (RSM) which was coupled with ant colony optimization (ACO) to optimize the media compositions so as to enhance the productivity of lipopeptide. The optimized media by ACO was found to yield 1.501 g/L of lipopeptide concentration which was much higher compared to 1.387 g/L predicted by Nelder–Mead optimization (NMO). The optimum from ACO was validated experimentally. RSM-based ACO is thus shown to be an effective tool for medium optimization of biosurfactant production

Mechanical property evaluation of an Al-2024 alloy subjected to HPT processing

An aluminum-copper alloy (Al-2024) was successfully subjected to high-pressure torsion (HPT) up to five turns at room temperature under an applied pressure of 6.0 GPa. The Al-2024 alloy is used as a fuselage structural material in the aerospace sector. Mechanical properties of the HPT-processed Al-2024 alloy were evaluated using the automated ball indentation technique. This test is based on multiple cycles of loading and unloading where a spherical indenter is used. After two and five turns of HPT, the Al-2024 alloy exhibited a UTS value of ~1014 MPa and ~1160 MPa respectively, at the edge of the samples. The microhardness was measured from edges to centers for all HPT samples. These results clearly demonstrate that processing by HPT gives a very significant increase in tensile properties and the microhardness values increase symmetrically from the centers to the edges. Following HPT, TEM examination of the five-turn HPT sample revealed the formation of high-angle grain boundaries and a large dislocation density with a reduced average grain size of ~80 nm. These results also demonstrate that high-pressure torsion is a processing tool for developing nanostructures in the Al-2024 alloy with enhanced mechanical propertie

Endemic Fluorosis and Occurrence Gastrointestinal Disorders in Prakasam District A.P.

Fluoride has been known to cause significant effect on human health through drinking water. Excessive ingestion of fluorides not only causes dental and skeletal fluorosis but also leads to gastro intestinal disturbances. Prakasam district of Andhra Pradesh, India is having severe fluorosis. In the present study epidemiological survey was conducted in five villages of Prakasam district regarding the incidence of Gastrointestinal symptoms such as loss of appetite, indigestion, nausea, vomiting, bloody vomiting, Pain in the upper part of the abdomen and blotting in the upper abdomen after eating. The results showed that nausea was found in 23 % of population. Loss of appetite was found in 18 % of villagers. Indigestion, bloody vomit was very low (6%) Experimental results show that male albino rats with ingestion of 4mg/L of fluorides for 120 days caused damage to the intestinal mucosa and sub mucosa. The possible reasons for the gastrointestinal problems and mechanism of action of fluorides on gastrointestinal tract was discussed

Remarks on the k-error linear complexity of p(n)-periodic sequences

Recently the first author presented exact formulas for the number of 2ⁿn-periodic binary sequences with given 1-error linear complexity, and an exact formula for the expected 1-error linear complexity and upper and lower bounds for the expected k-error linear complexity, k >2, of a random 2ⁿn-periodic binary sequence. A crucial role for the analysis played the Chan-Games algorithm. We use a more sophisticated generalization of the Chan-Games algorithm by Ding et al. to obtain exact formulas for the counting function and the expected value for the 1-error linear complexity for pⁿn-periodic sequences over Fp, p prime. Additionally we discuss the calculation of lower and upper bounds on the k-error linear complexity of pⁿn-periodic sequences over Fp

Development of Aluminium based Metal Matrix Composites

A detailed study on the processing of Al-metal matrix comp, cites with the reinforcement of different parti-culates such as SiC, TiN and Ti02 was carried out. The Al-SiC composite powder prepared through atomisation route is expected to limit the interfacial reaction bet-ween the matrix and the ceramic particulate and help in making customer tailored components by powder metallurgy route. An attempt to avoid the interfacial reaction of matrix and ceramic is investigated by impregnating the Al matrix with TiN particulates. Similarly, Al-Ti02.composite is investigated by new spray forming technique, where the interfacial reaction between Al and Ti02 is expected to form intermetallic compounds and improve the bonding and mechanical properties. The results of the present studies show that the Al based composites prepared through various techniques exhibits excellent mechanical, physical and tribological properties and could emerge as promising materials for defence, aerospace and other engineering applications

Embryological studies in the lythraceae I. Lawsonia inermis linn

This article does not have an abstract

Development and Characterization of Ag-Cu-Ti Alloys for Ceramic Brazing

In the present investigation, silver and copper base alloys with varying compositions of Ag:Cu = 72:28, 60:40, 50:50 and 30:70 (by wt%) are prepared. In each set, 1, 2 and 3w1% of active filler element, i.e. titanium is incorporated by powder metallurgical route. The samples are characterised by XRD, DTA-TGA, SEM and EDX. The XRD results show that titanium and its related phases are not present due to the lower concentration of Ti in these samples. Energy dispersive X-ray analyses reveal that most of the titanium is present in the copper rich phase and very little in the silver rich phase. The rolled brazing alloys are used for./pining the alumina to alumina, that showed excellent joining characteristics