Experimental and theoretical evaluation of in-depth damage distribution in sawn silicon wafers

As-sawn silicon wafers have surface damage that needs to be removed before any further processing into solar cells. This damage distribution can vary with cutting parameters such as wire size, slurry particle/diamond grit size, and wire usage. To date, there is no simple way to measure the degree of damage, damage depth, and damage distribution. But, this information is needed by the wafer manufacturers as well as solar cell manufacturers. A technique based on sequential etching of silicon wafers and minority carrier lifetime (τeff) measurements is used to determine damage depth. In this technique, samples are sequentially etched to remove thin layers from each surface and minority carrier lifetime is measured after each etch step. Lifetime increases after each layer of damage is removed and reaches a plateau once the damage is totally removed. The thickness-removed at which the lifetime reaches a peak value corresponds to the damage depth. An accurate measurement of τeff requires corrections to optical reflection, and transmission from silicon wafers to account for changes in the surface morphology and in the wafer thickness. This technique also allows the in-depth distribution of the damage to be quantified in terms of surface recombination velocity (SRV). Although this method is routinely used at the National Renewable Energy Laboratory to measure damage depth, determination of damage distribution from these data requires an accurate model that coverts the minority carrier lifetime data into carrier recombination distribution. Continuity equation for excess minority carrier density (Δn) is solved for the material of interest (silicon wafer with surface damage layer), and carrier concentration is integrated and normalized to match the normalized lifetime vs thickness removed curve. A simplified model for determining the recombination distribution within a wafer having surface damage is presented. Potential improvements for this model are discussed

Complexes of ruthenium(II) and ruthenium(III) with tertiary arsines

Ruthenium trichloride reacts with stoichiometric amounts of tertiary arsines in boiling ethanol to give paramagnetic complexes, RuCl3(Ph2RAs)3 (R = Me, Et, Pr, Bu), which react further with 2,2′-bipyridyl(bipy) and o-phenanthroline(phen) to yield brick red crystalline products, RuCl3 (N-N)(Ph2RAs) (N-N = bipy, phen). In the presence of excess arsine Ru(III) is reduced to Ru(II), and trichloro-bridged complexes of the formula [Ru2Cl3(Ph2RAs)6]Cl are formed. These on treatment with carbonylated solutions of rhodium chloride produce yellow crystals of [Ru2Cl3(Ph2RAs)6][RhCl2(CO)2] containing Ru(II) and Rh(I). Several dicarbonyl complexes cis-RuX2(CO)2(Ph2RAs)2 (X = Cl, Br; R = Pr, Bu) have also been isolated. © 1977

Spatio-temporal prediction of crimes using network analytic approach

It is quite evident that majority of the population lives in urban area today than in any time of the human history. This trend seems to increase in coming years. A study [5] says that nearly 80.7% of total population in USA stays in urban area. By 2030 nearly 60% of the population in the world will live in or move to cities. With the increase in urban population, it is important to keep an eye on criminal activities. By doing so, governments can enforce intelligent policing systems and hence many government agencies and local authorities have made the crime data publicly available. In this paper, we analyze Chicago city crime data fused with other social information sources using network analytic techniques to predict criminal activity for the next year. We observe that as we add more layers of data which represent different aspects of the society, the quality of prediction is improved. Our prediction models not just predict total number of crimes for the whole Chicago city, rather they predict number of crimes for all types of crimes and for different regions in City of Chicago

A study of factors associated with tokophobia and its effect on pregnancy

Background: Tokophobia is pathological fear of childbirth which has bearing on the women’s health with the physical and psychosocial morbidity. It includes fear of injury to the baby, genital tract, death and is a common cause for which a woman opts for caesarean section. Recognition of tokophobia and close liaison with  obstetricians/specialists can help to reduce its severity and ensure treatment. Aim of the current study was to assess the incidence of tokophobia and correlation with the sociodemographic variables to evaluate the possibility of reducing the requests for caesarean section.Methods: 150 pregnant women attending the antenatal OPD and labour ward in a tertiary care centre constituted the study population. Data was gathered using standard questionnaire to assess fear of child birth, anxiety associated and was analysed with chi-square test for statistical significance.Results: 150 women included in the study, the incidence of tokophobia was 55.3% and severe tokophobia was 30.7%. Of these 62% were primigravidae and 38% multigravidae.15.3% of the total requested for caesarean section with the major reason being fear of childbirth. However, 84.7% of the study population did so without any such request for caesarean section. Higher incidence of tokophobia was observed in women with intermediate education as against those who completed their graduation and post-graduation.Conclusions: Tokophobia is associated with pregnant women in different severity. It’s influenced by sociodemographic variables like educational and socioeconomic status. Improvement in sociodemographic conditions could reduce tokophobia

Complexes of osmium with tertiary arsines and carbonmonoxide

Osmium halides (Cl and Br) react with monotertiary arsines Ph2RAs (R=Me, Et, Pr and Bu) in alcoholic medium to give paramagnetic octahedral complexes of the type OsX3L3 (X=Cl, Br; L=Ph2RAs) which further react with carbonmonoxide to give dihalo dicarbonyl complexes of osmium(II) of the type OsX2 (CO)2 L2. Similarly, osmium halides react with tertiary arsines in the presence of formaldehyde to give monocarbonyl complexes of osmium(II) of the type OsX2 (CO)L3. Structures have been assigned to all these compounds on the basis of IR and NMR studies. © 1980 Indian Academy of Sciences

Comparison of microvascular endothelial function as measured by laser Doppler flowmeter among non-smoker and smoker males

Background: To understand the role of smoking in influencing endothelial function as assessed by LDF among non-smoker and smoker males. Methods: The LDF measurement for a total of 35 non-smokers and 16 smokers was done in the central research laboratory after written informed consent. The change in LDF signal in response to acetylcholine 100 µl, which was delivered to the forearm skin by iontophoresis, was measured as perfusion units (PU). Results: The pre-ACh LDF signal were statistically not significant between the groups. The increase in LDF signal was more prominent in non-smoker group. The LDF signal parameters such as differences in minimal response pre and post-ACh; difference in mean response pre and post ACh; the difference in maximal response pre and post ACh was not statistically significant between groups. However, the difference in the area under curve (AUC) pre and post-ACh (PU.min) (non-smoker 20089.34 (3438.92) vs smoker 13220.72 (3379.52); p=0.16) showed a trend towards statistical significance. Conclusions: Microvascular endothelial function as assessed by LDF signal among smokers (pack-years;1.9±1.44) and non-smokers is statistically insignificant. However, lower microvascular endothelial function is observed among smokers