12,431 research outputs found
Ion beam induced enhanced diffusion from gold thin films in silicon
Enhanced diffusion of gold atoms into silicon substrate has been studied in
Au thin films of various thicknesses (2.0, 5.3, 10.9 and 27.5 nm) deposited on
Si(111) and followed by irradiation with 1.5 MeV Au2+ at a flux of 6.3x10^12
ions cm-2 s-1 and fluence up to 1x10^15 ions cm-2. The high resolution
transmission electron microscopy measurements showed the presence of gold
silicide formation for the above-mentioned systems at fluence greater than
equal to 1x1014 ions cm-2. The maximum depth to which the gold atoms have been
diffused at a fluence of 1x10^14 ions cm-2 for the cases of 2.0, 5.3, 10.9 and
27.5 nm thick films has been found to be 60, 95, 160 and 13 nm respectively.
Interestingly, at higher fluence of 1x1015 ions cm-2 in case of 27.5 nm thick
film, gold atoms from the film transported to a maximum depth of 265 nm in the
substrate. The substrate silicon is found to be amorphous at the above fluence
values where unusually large mass transport occurred. Enhanced diffusion has
been explained on the basis of ion beam induced, flux dependent amorphous
nature of the substrate, and transient beam induced temperature effects. This
work confirms the absence of confinement effects that arise from spatially
confined structures and existence of thermal and chemical reactions during ion
irradiation.Comment: 15 pages, 3 figure
Flux dependent 1.5 MeV self-ion beam induced sputtering from Gold nanostructured thin films
We discuss four important aspects of 1.5 MeV Au2+ ion-induced flux dependent
sputtering from gold nanostrcutures (of an average size 7.6 nm and height 6.9
nm) that are deposited on silicon substrates: (a) Au sputtering yield at the
ion flux of 6.3x10^12 ions cm-2 s-1 is found to be 312 atoms/ion which is about
five times the sputtering yield reported earlier under identical irradiation
conditions at a lower beam flux of 10^9 ions cm-2 s-1, (b) the sputtered yield
increases with increasing flux at lower fluence and reduces at higher fluence
(1.0x10^15 ions cm-2) for nanostructured thin films while the sputtering yield
increases with increasing flux and fluence for thick films (27.5 nm Au
deposited on Si) (c) Size distribution of sputtered particles has been found to
vary with the incident beam flux showing a bimodal distribution at higher flux
and (d) the decay exponent obtained from the size distributions of sputtered
particles showed an inverse power law dependence ranging from 1.5 to 2.5 as a
function of incident beam flux. The exponent values have been compared with
existing theoretical models to understand the underlying mechanism. The role of
wafer temperature associated with the beam flux has been invoked for a
qualitative understanding of the sputtering results in both the nanostructured
thin films and thick films.Comment: 25 pages, 5 figures, 1 table To be Appeared in J. Phys. D: Appl. Phy
Hyperfine interaction and electronic spin fluctuation study on SrLaFeCoO (x = 0, 1, 2) by high-resolution back-scattering neutron spectroscopy
The study of hyperfine interaction by high-resolution inelastic neutron
scattering is not very well known compared to the other competing techniques
viz. NMR, M\"ossbauer, PACS etc. Also the study is limited mostly to
magnetically ordered systems. Here we report such study on
SrLaFeCoO (x = 0, 1, 2) of which first (SrFeCoO with x
= 0) has a canonical spin spin glass, the second (SrLaFeCoO with x = 1) has
a so-called magnetic glass and the third (LaFeCoO with x = 2) has a
magnetically ordered ground state. Our present study revealed clear inelastic
signal for SrLaFeCoO, possibly also inelastic signal for SrFeCoO
below the spin freezing temperatures but no inelastic signal at all
for for the magnetically ordered LaFeCoO in the neutron scattering
spectra. The broadened inelastic signals observed suggest hyperfine field
distribution in the two disordered magnetic glassy systems and no signal for
the third compound suggests no or very small hyperfine field at the Co nucleus
due to Co electronic moment. For the two magnetic glassy system apart from the
hyperfine signal due only to Co, we also observed electronic spin fluctuations
probably from both Fe and Co electronic moments. \end{abstract
Optical absorption and photoluminescence spectroscopy of the growth of silver nanoparticles
Results obtained from the optical absorption and photoluminescence (PL)
spectroscopy experiments have shown the formation of excitons in the
silver-exchanged glass samples. These findings are reported here for the first
time. Further, we investigate the dramatic changes in the photoemission
properties of the silver-exchanged glass samples as a function of postannealing
temperature. Observed changes are thought to be due to the structural
rearrangements of silver and oxygen bonding during the heat treatments of the
glass matrix. In fact, photoelectron spectroscopy does reveal these chemical
transformations of silver-exchanged soda glass samples caused by the thermal
effects of annealing in a high vacuum atmosphere. An important correlation
between temperature-induced changes of the PL intensity and thermal growth of
the silver nanoparticles has been established in this Letter through precise
spectroscopic studies.Comment: 15 pages,4 figures,PDF fil
Impact of an educational video as a consent tool on knowledge about cure research among patients and caregivers at HIV clinics in South Africa
Background: Despite increasing access to antiretroviral therapy in low- and middle-income countries, only 54% of eligible individuals were receiving treatment in Africa by 2015. Recent developments in HIV cure research have been encouraging. However, the complex science and procedures of cure research render the informed consent process challenging.
Objective: This study evaluates the impact of a video tool on educating participants about HIV cure.
Methods: A questionnaire assessing the content of the video was administered to adults recruited from two clinics in South Africa. Patients and their care partners, who provided voluntary informed consent, were included in the study. The questionnaire was administered in each participant‘s home language before, immediately after and at 3 months after viewing the video, in an uncontrolled quasi-experimental ‘one group pre-test–post-test’ design. Scoring was carried out according to a predetermined scoring grid, with a maximum score of 22.
Results: A total of 88 participants, median age 32.0 years and 86% female, were enrolled and completed the pre- and post-video questionnaires. Twenty-nine (33%) completed the follow-up questionnaire 3 months later to assess retention of knowledge. Sixty-three (72%) participants had a known HIV-positive status. A significant increase (10.1 vs 15.1, P=0.001) in knowledge about HIV and HIV cure immediately after viewing the video was noted. No statistically significant difference in knowledge between HIV-positive and -negative patients was noted at baseline. After 3 months, a decrease in performance participation (14 vs 13.5, P=0.19) was noted. However, knowledge scores achieved after 3 months remained significantly higher than scores at baseline (13.5 vs 9.5, P<0.01).
Conclusions: This research showed that a video intervention improved participants’ knowledge related to HIV, HIV cure research and ethics, and the improvement was sustained over 3 months. Video intervention may be a useful tool to add to the consent process when dealing with complex medical research questions
Presence of Phytol, a Precursor of Vitamin E in Chaetomorpha Antinnina
Phytol, a precursor of vitamin E was identified from green algae Chaetomorpha antinnina collected from Chullickal, Kochi Kerala coast, using GC-MS. Phytol is an acyclic diterpene alcohol that can be used as a precursor for the manufacture of synthetic forms of vitamin E and vitamin K1. The compound 3,7,11,15-tetramethylhexadec-2-en-1-ol also known as phytol which exist naturally only in single isomeric form having molecular formula C20H40O and molecular mass 296. From the total ion chromatogram more than twenty peaks were observed, the mass spectrum of the peak at Rt 21.53 was resolved and the major fragmentations were noted. Major fragmentation were m/z 71 the base peak, m/z 296 the molecular ion peak, m/z 43, m/z 57, m/z 81, m/z 95, and m/z 123. It was found that there are some other compounds apart from this identified phytol which are more complicated in structure and cannot be characterised using GC-MS. Phytol is reported to have both antimicrobial and anticancer activities. The green algae Chaetomorpha antinnina can be proposed to be a good natural source for production of phytol
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