79 research outputs found
Too Many Unknown Molecules In The Laboratory Itself
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Over the last few years, we have generated considerable theoretical data on CH (n = 5, 7, and 9)\footnote{Thimmakondu, V. S.; Ulusoy, I.; Wilson, A. K.; Karton, A. Theoretical Studies of Two Key Low-Lying Carbenes of CH Missing in the Laboratory, {\emph{J. Phys. Chem. A}}, {\bf 2019}, 123, 6618-6627.}\footnote{Thimmakondu, V. S.; Karton. A. Energetic and Spectroscopic Properties of the Low-Lying CH Isomers: A High-Level Ab Initio Perspective, {\emph{Phys. Chem. Chem. Phys.}}, {\bf 2017}, 19, 17685-17697.}\footnote{Thirumoorthy, K. and Karton, A. and Thimmakondu, V. S. From High-Energy CH Isomers with A Planar Tetracoordinate Carbon Atom to An Experimentally Known Carbene, {\emph{J. Phys. Chem. A}}, {\bf 2018}, 122, 9054-9064.}\footnote{Thirumoorthy, K.; Viji, M.; Pandey, A. P.; Netke, T. G.; Sekar, B.; Yadav, G.; Deshpande, S.; Thimmakondu, V. S. Many Unknowns Below or Close to the Experimentally Known Cumulene Carbene - A Case Study of CH Isomers, {\emph {Chem. Phys.}} {\bf 2019}, 527, 110496.} and SiCH\footnote{Job, N. and Karton, A. and Thirumoorthy, K.; Cooksy, A. L.; Thimmakondu, V. S. Theoretical Studies of SiCH Isomers Delineate Three Low-Lying Silylidenes Are Missing in the Laboratory, {\emph {J. Phys. Chem. A}} {\bf 2020}, 124, 987-1002.}isomers, in view of their astronomical relevance. An overview of these results will be discussed in this meeting. Although the potential target molecules have been theoretically identified, lack of their experimental data, especially the infrared and microwave spectra, is a serious concern. To unambiguously confirm molecules in astrophysical sources, precise laboratory rest frequencies will be required. To the best of our knowledge, all of the new isomers we theoretically identified so far remain elusive in the laboratory itself to date.Made available in DSpace on 2021-09-24T21:09:30Z (GMT). No. of bitstreams: 2
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Previous issue date: 2021-06-2
Ferrocene-quinoxaline Y-shaped chromophores as fascinating second-order NLO building blocks for long lasting highly active SHG polymeric films
No full textThe first example of a Y-shaped ferrocene quinoxaline derivative with a surprisingly high and stable second harmonic generation (SHG) response in composite polymeric films is reported. The interesting quadratic hyperpolarizability values of different substituted Y-shaped chromophores are also investigated in solution by the EFISH technique
New Internal-Charge-Transfer Second-Order Nonlinear Optical Chromophores Based on the Donor Ferrocenylpyrazole Moiety
No full textA series
of new N-arylated ferrocenepyrazole structures, carrying
different donor or acceptor substituents in the para position of the
aryl ring, has been synthesized by the Chan–Lam cross-coupling
reaction. The nonplanar geometric molecular structure of some of these
chromophores together with their crystal packing was determined by
X-ray diffraction, and the HOMO and LUMO energy levels were evaluated
by electrochemical and optical measurements and by density functional
theoretical (DFT) calculations. By the investigation of solvent effects
and time-dependent DFT (TD-DFT) calculations, the intense electronic
absorption band around 270–310 nm was confirmed to be an internal-charge-transfer
(ICT) band, showing a significant red shift by increasing the electron
withdrawing properties of the substituent on the para position of
the aryl ring. TD-DFT calculations and electric field induced second
harmonic generation (EFISH) measurements of the quadratic hyperpolarizability
have shown that also the second-order nonlinear optical (NLO) response
of these new ICT chromophores can be tuned by changing the nature
of the substituent. Both theoretical μβ and β and
experimental EFISH μβ1907 and β1907 values are significant, with a quite satisfactory correlation of
the general trend of theoretical μβ and EFISH μβ1907 values. The highest value of EFISH μβ1907 (410 × 10–48 esu) was measured
for the chromophore carrying the strong electron withdrawing NO2 group
Organomagnesium Crown Ethers and Their Binding Affinities with Li+, Na+, K+, Be2+, Mg2+, and Ca2+ Ions - a Theoretical Study
No full textNovel organomagnesium crown ether molecules have been computationally
characterized for the first time using density functional theory (DFT).
Monomer units of MgC6 have been used as building blocks. The potential
energy surface of the parent elemental composition, MgC6H2, has been
extensively explored using both DFT and coupled-cluster methods. It is
concluded that the seven-membered ring isomer,
1-magnesacyclohept-4-en-2,6-diyne, is the thermodynamically most stable
molecule at all levels. Thus, the latter has been used as the building
block for organomagnesium crown ethers. Both alkali (Li+, Na+, and K+)
and alkaline-earth (Be2+, Mg2+, and Ca2+) metal ions selective complexes
have been theoretically identified. Binding energies (Delta E at 0 K) and
thermally corrected Gibbs free energies (Delta G at 298.15 K) havebeen computed for these metal ions with MgC6-9-crown-3 and MgC6-12-crown-4 to gauge their binding affinities.Novel organomagnesium crown ether molecules have been computationally
characterized for the first time using density functional theory (DFT).
Monomer units of MgC6 have been used as building blocks. The potential
energy surface of the parent elemental composition, MgC6H2, has been
extensively explored using both DFT and coupled-cluster methods. It is
concluded that the seven-membered ring isomer,
1-magnesacyclohept-4-en-2,6-diyne, is the thermodynamically most stable
molecule at all levels. Thus, the latter has been used as the building
block for organomagnesium crown ethers. Both alkali (Li+, Na+, and K+)
and alkaline-earth (Be2+, Mg2+, and Ca2+) metal ions selective complexes
have been theoretically identified. Binding energies (Delta E at 0 K) and
thermally corrected Gibbs free energies (Delta G at 298.15 K) have been computed for these metal ions with MgC6-9-crown-3 and MgC6-12-crown-4 to gauge their binding affinities
Properties of Pulse Plated CdS<sub>x</sub>Te<sub>1-x</sub> Films
No full textThin films of CdSxTe1-x were deposited by the pulse electrodepsoition technique using cadmium sulphate, sodium thiosulphate and tellurium di oxide on titanium and conducting glass substrates. Structural studies indicated the formation of polycrystalline films possessing hexagonal structure. The resistivity varies from 53 ohm cm to 8 ohm cm as the stochiometric co-efficient 'x' value decreases from 1 to 0. It is observed that a post heat treatment temperature of 550 C results in high photosensitivity as well as low light resistance. The optical constants, refractive index(n) and extinction coefficient(k) were evaluated from the transmission spectra of the films of different composition.</jats:p
Marburg hemorrhagic fever associated with multiple genetic lineages of virus.
No full textBACKGROUND: An outbreak of Marburg hemorrhagic fever was first observed in a gold-mining village in northeastern Democratic Republic of the Congo in October 1998. METHODS: We investigated the outbreak of Marburg hemorrhagic fever most intensively in May and October 1999. Sporadic cases and short chains of human-to-human transmission continued to occur until September 2000. Suspected cases were identified on the basis of a case definition; cases were confirmed by the detection of virus antigen and nucleic acid in blood, cell culture, antibody responses, and immunohistochemical analysis. RESULTS: A total of 154 cases (48 laboratory-confirmed and 106 suspected) were identified (case fatality rate, 83 percent); 52 percent of cases were in young male miners. Only 27 percent of these men reported having had contact with other affected persons, whereas 67 percent of patients who were not miners reported such contact (P<0.001). Most of the affected miners (94 percent) worked in an underground mine. Cessation of the outbreak coincided with flooding of the mine. Epidemiologic evidence of multiple introductions of infection into the population was substantiated by the detection of at least nine genetically distinct lineages of virus in circulation during the outbreak. CONCLUSIONS: Marburg hemorrhagic fever can have a very high case fatality rate. Since multiple genetic variants of virus were identified, ongoing introduction of virus into the population helped perpetuate this outbreak. The findings imply that reservoir hosts of Marburg virus inhabit caves, mines, or similar habitats
Isothermal kinetic study of nitric oxide adsorption and decomposition on Pd(111) surfaces: molecular beam experiments
No full textThe kinetics of NO adsorption and dissociation on Pd(111) surfaces and the NO sticking coefficient (sNO) were probed by isothermal kinetic measurements between 300 and 525 K using a molecular beam instrument. NO dissociation and N2 productions were observed in the transient state from 425 K and above on Pd(111) surfaces with selective nitrogen production. Maximum nitrogen production was observed between 475 and 500 K. It was found that, at low temperatures, between 300 and 350 K, molecular adsorption occurs with a constant initial sNO of 0.5 until the Pd(111) surface is covered to about 70-80% by NO. Then sNO rapidly decreases with further increasing NO coverage, indicating typical precursor kinetics. The dynamic adsorption - desorption equilibrium on Pd(111) was probed in modulated beam experiments below 500 K. CO titration experiments after NO dosing indicate the diffusion of oxygen into the subsurface regions and beginning surface oxidation at ≥475 K. Finally, we discuss the results with respect to the rate-limiting character of the different elementary steps of the reaction system
Financial situation of people living with HIV in Europe.
No full textThe objective was to investigate the financial situation of people living with HIV in Europe. Two surveys using an anonymous questionnaire were organized in Europe among people living with HIV, the first in 1996-97 and the second in 1998-99. One thousand one hundred and sixty-one people from the 1996-97 survey and 899 from the 1998-99 survey were included. Four hundred and fifty-seven (42%) of the 1996-97 participants reported that their income had decreased since HIV diagnosis. The latter participants reported significantly more often difficulties in paying for housing (27% vs 20%), food (18% vs 12%) and transport (17% vs 12%) compared to 1998-99 participants. In multiple regression analysis, severity of HIV disease, not being on highly active antiretroviral therapy (HAART), younger age, lower education level and living in the South of Europe were associated with having financial difficulties. We concluded that since the introduction of HAART, the financial situation of persons living with HIV in Europe has improved, but a relatively large percentage of them still have financial difficulties
Documentation of clinical data and its transference from Ebola and Marburg wards: health care workers' experiences and preferences
No full textReproductive health for refugees by refugees in Guinea II: sexually transmitted infections.
No full textBACKGROUND: Providing reproductive and sexual health services is an important and challenging aspect of caring for displaced populations, and preventive and curative sexual health services may play a role in reducing HIV transmission in complex emergencies. From 1995, the non-governmental "Reproductive Health Group" (RHG) worked amongst refugees displaced by conflicts in Sierra Leone and Liberia (1989-2004). RHG recruited refugee nurses and midwives to provide reproductive and sexual health services for refugees in the Forest Region of Guinea, and trained refugee women as lay health workers. A cross-sectional survey was conducted in 1999 to assess sexual health needs, knowledge and practices among refugees, and the potential impact of RHG's work. METHODS: Trained interviewers administered a questionnaire on self-reported STI symptoms, and sexual health knowledge, attitudes and practices to 445 men and 444 women selected through multistage stratified cluster sampling. Chi-squared tests were used where appropriate. Multivariable logistic regression with robust standard errors (to adjust for the cluster sampling design) was used to assess if factors such as source of information about sexually transmitted infections (STIs) was associated with better knowledge. RESULTS: 30% of women and 24% of men reported at least one episode of genital discharge and/or genital ulceration within the past 12 months. Only 25% correctly named all key symptoms of STIs in both sexes. Inappropriate beliefs (e.g. that swallowing tablets before sex, avoiding public toilets, and/or washing their genitals after sex protected against STIs) were prevalent. Respondents citing RHG facilitators as their information source were more likely to respond correctly about STIs; RHG facilitators were more frequently cited than non-healthcare information sources in men who correctly named the key STI symptoms (odds ratio (OR) = 5.2, 95% confidence interval (CI) 1.9-13.9), and in men and women who correctly identified effective STI protection methods (OR = 2.9, 95% CI 1.5-5.8 and OR = 4.6, 95% CI 1.6-13.2 respectively). CONCLUSION: Our study revealed a high prevalence of STI symptoms, and gaps in sexual health knowledge in this displaced population. Learning about STIs from RHG health facilitators was associated with better knowledge. RHG's model could be considered in other complex emergency settings
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