131 research outputs found
Dynamic and Static Transmission Electron Microscopy Studies on Structural Evaluation of Au nano islands on Si (100) Surface
Transmission electron microscopy (TEM) study on morphological changes in gold
nanostructures deposited on Si (100) upon annealing under different vacuum
conditions has been reported. Au thin films of thickness ~2.0 nm were deposited
under high vacuum condition (with the native oxide at the interface of Au and
Si) using thermal evaporation. In-situ, high temperature (from room temperature
(RT) to 850\degreeC) real time TEM measurements showed the evaluation of gold
nanoparticles into rectangular/square shaped gold silicide structures. This has
been attributed to selective thermal decomposition of native oxide layer.
Ex-situ annealing in low vacuum (10-2 mbar) at 850\degreeC showed no growth of
nano-gold silicide structures. Under low vacuum annealing conditions, the
creation of oxide could be dominating compared to the decomposition of oxide
layers resulting in the formation of barrier layer between Au and Si.Comment: 15 pages, 4 figure
Growth of Oriented Au Nanostructures: Role of Oxide at the Interface
We report on the formation of oriented gold nano structures on Si(100)
substrate by annealing procedures in low vacuum (\approx10-2 mbar) and at high
temperature (\approx 975^{\circ} C). Various thicknesses of gold films have
been deposited with SiOx (using high vacuum thermal evaporation) and without
SiOx (using molecular beam epitaxy) at the interface on Si(100). Electron
microscopy measurements were performed to determine the morphology, orientation
of the structures and the nature of oxide layer. Interfacial oxide layer, low
vacuum and high temperature annealing conditions are found to be necessary to
grow oriented gold structures. These gold structures can be transferred by
simple scratching method.Comment: 13 pages, 3 figures, Accepted in J. Appl. Phy
RP-HPLC METHOD DEVELOPMENT AND VALIDATION FOR SIMULTANIOUS ESTIMATION AND FORCED DEGRADATION STUDIES OF LAMIVUDINE AND RALTEGRAVIR IN SOLID DOSAGE FORM
Objective: A stability indicating reverse phase high-performance liquid chromatography (RP-HPLC) method was developed and validated for the estimation of the combined tablet formulation of lamivudine (LAM) and raltegravir (RAL) in dosage forms and its API.Methods: Chromatographic separation was achieved on inertsil ODS C18 5 µm (4.6 X 150 mm) using a mobile phase (MP) consisting of a mixture of mixed orthophosphoric acid (OPA): acetonitrile (ACN) in the ratio 50:50 v/v which was determined at 242 nm respectively. Results: The assay of LAM and RAL was performed with tablets, and the % assay was found to be 100.12 and 99.89 which shows that the method is useful for routine analysis. The linearity of LAM and RAL was found to be linear with a correlation coefficient of 0.998 and 0.999, which shows that the method is capable of producing good sensitivity. The retention time of LAM and RAL was 1.99 min and 4.34 min respectively; linearity range was found to lie from 15 µg/ml to 75 µg/ml for LAM, 30 µg/ml to 150 µg/ml for RAL with a correlation coefficient of 0.999 respectively. Forced degradation studies were conducted in acidic, basic, thermal, photolytic and peroxide where all the degradation peaks were monitored.Conclusion: The proposed HPLC method was found to be simple, specific, precise, accurate, rapid and economical for simultaneous estimation of LAM and RAL in bulk and tablet dosage form. Thus the validated economical method was applied for forced degradation study of LAM and RAL tablet
Nanodot to Nanowire: A strain-driven shape transition in self-organized endotaxial CoSi2 on Si (100)
We report a phenomenon of strain-driven shape transition in the growth of
nanoscale self-organized endotaxial CoSi2 islands on Si (100) substrates. Small
square shaped islands as small as 15\times15 nm2 have been observed. Islands
grow in the square shape following the four fold symmetry of the Si (100)
substrate, up to a critical size of 67 \times 67 nm2. A shape transition takes
place at this critical size. Larger islands adopt a rectangular shape with ever
increasing length and the width decreasing to an asymptotic value of ~25 nm.
This produces long wires of nearly constant width.We have observed nanowire
islands with aspect ratios as large as ~ 20:1. The long nanowire
heterostructures grow partly above (~ 3 nm) the surface, but mostly into (~17
nm) the Si substrate. These self-organized nanostructures behave as nanoscale
Schottky diodes. They may be useful in Si-nanofabrication and find potential
application in constructing nano devices.Comment: 9 pages, 7 figure
Evaluation of thermogravimetric analysis as a rapid tool for the detection of rhizobacteria biostimulants used in precision agriculture
Publication history: Accepted - 31 October 2020; Published online - 17 January 2021Six-week-old root samples were evaluated using high resolution (maximum resolution [MaxRes]) thermogravimetric
analyses (TGA) of the cell wall compositions of Gram-positive (Bacillus mucilaginosus, Bacillus amyloliquefaciens,
and Bacillus subtilis) and Gram-negative (Burkholderia sp., Rahnella aquatilis strain H 2.6, and R. aquatilis strain
RC 2.5) root colonizing plant growth promoting rhizobacteria (PGPR) commercial inoculant strains (biostimulants)
applied to pot grown wheat plants. TGA discriminated the strains within the two types of rhizobacterial cohorts and
thus provided a rapid non-molecular means for the detection of PGPR inoculant biostimulants within hours of root
sampling. The latter was due to the greater degree of definition of TGA fingerprints of individual thermal weight
loss events occurring over a degradation range, and heightened the corresponding peak temperature divergences
within strains of either type of bacteria themselves for their unequivocal identification. Confirmation of biostimulant
rhizobacteria identity in concomitant root samples was achieved through either cultural methods or direct tissue
PCR molecular protocols within 5 days and 2 days of sampling, respectively. The results suggested that MaxRes
TGA could serve as a rapid, inexpensive stand-alone tool or as combinatorial utility alongside pyrolysis gas
chromatography mass spectra, and Fourier transform infrared analytics for the early detection of PGPR biostimulants
in precision farmingWe thank EU-BIOFECTOR (Grant Agreement No. 312117) funded by the European Commission within the 7th Framework Programme, and the Department of Agriculture, Environment and Rural Affairs (DAERA), Northern Ireland, UK for their Evidence and Innovation grant (activity 48125) to carry out the study at the Agri-Food & Biosciences Institute laboratories (AFBINI.GOV.UK
Nano scale phase separation in Au-Ge system on ultra clean Si(100) surfaces
We report on the formation of lobe-lobe (bi-lobed) Au-Ge nanostructures under
ultra high vacuum (UHV) conditions (\approx 3\times 10^{-10} mbar) on clean
Si(100) surfaces. For this study, \approx 2.0 nm thick Au samples were grown on
the substrate surface by molecular beam epitaxy (MBE). Thermal annealing was
carried out inside the UHV chamber at temperature \apprx 500{\deg}C and
following this, nearly square shaped Au_{x}Si_{1-x} nano structures of average
length \approx 48 nm were formed. A \approx 2 nm Ge film was further deposited
on the above surface while the substrate was kept at a temperature of \approx
500{\deg}C. Well ordered Au-Ge nanostructures where Au and Ge residing side by
side (lobe-lobe structures) were formed. In our systematic studies, we show
that, gold-silicide nanoalloy formation at the substrate (Si) surface is
necessary for forming phase separated Au-Ge bilobed nanostructures. Electron
microscopy (TEM, STEM-EDS, SEM) studies were carried out to determine the
structure of Au - Ge nano systems. Rutherford backscattering Spectrometry
measurements show gold inter-diffusion into substrate while it is absent for
Ge.Comment: 23 pages, 6 Figures, 1 Tabl
Antimicrobial resistance to 14 antimicrobials in marine coastal waters around Northern Ireland: Use of the novel Relative Resistance Index as a marker of ecological status
Relatively little work has been published on the incidence of antibiotic resistance (ABR) in the marine microbiological environment, which is of importance to animal (fish, mammals, birds) health, zoonotic transmission, distribution of ABR bacteria with oceanic drift, and ultimately human health. A study was performed to determine the diversity of total ABR (intrinsic and acquired resistance) in marine bacteria in shallow coastal waters surrounding Northern Ireland through the use of a novel Relative Resistance Index (RRI) as a surrogate marker for ecological change, particularly in comparing marine water in commercial versus non-commercial sites. Total antibiotic resistance was observed to varying degrees in all marine water specimens and specific resistance levels were as follows, in order of diminishing antibacterial effectiveness: fluoroquinolones \u3e rifampicin \u3e polymyxin \u3e tetracycline \u3e sulphamethoxazole/trimethoprim \u3e third generation cephalosporin and streptomycin \u3e carbapenem \u3e macrolide \u3e clindamycin \u3e vancomycin \u3e fucidic acid \u3e penicillin. None of the sampling sites contained endogenous bacteria that were resistant to ciprofloxacin, while nearly all (19 of 20 sites; 95%) contained bacteria that were resistant to penicillin. Commercial sites had a higher mean RRI score of 6.57±3.58 than non-commercial sites (RRI = 4.08 ± 2.02), which was statistically significant (p = 0.037), indicating that bacteria isolated from seawater in commercial coastal harbors had a higher frequency of antibiotic resistance than non-commercial sources. This novel RRI marker may be useful in assessing ecological change in marine water environments. In conclusion, this study demonstrated that there can be a high level of total ABR (intrinsic and acquired) in bacterial populations in marine water environments, which are multi- and pan-resistant to up to 11 major classes of antibiotics simultaneously. Ecological studies are urgently needed to help define the fate of ABR marine bacteria in their natural environment and their ability to act as reservoirs and donors of ABR to pathogenic bacteria, many of which transiently inhabit the natural environment
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