3,786 research outputs found
Effect of Sulfur Concentration on the Morphology of Carbon Nanofibers Produced from a Botanical Hydrocarbon
Carbon nanofibers (CNF) with diameters of 20–130 nm with different morphologies were obtained from a botanical hydrocarbon: Turpentine oil, using ferrocene as catalyst source and sulfur as a promoter by simple spray pyrolysis method at 1,000 °C. The influence of sulfur concentration on the morphology of the carbon nanofibers was investigated. SEM, TEM, Raman, TGA/DTA, and BET surface area were employed to characterize the as-prepared samples. TEM analysis confirms that as-prepared CNFs have a very sharp tip, bamboo shape, open end, hemispherical cap, pipe like morphology, and metal particle trapped inside the wide hollow core. It is observed that sulfur plays an important role to promote or inhibit the CNF growth. Addition of sulfur to the solution of ferrocene and turpentine oil mixture was found to be very effective in promoting the growth of CNF. Without addition of sulfur, carbonaceous product was very less and mainly soot was formed. At high concentration of sulfur inhibit the growth of CNFs. Hence the yield of CNFs was optimized for a given sulfur concentration
Facile one-pot synthesis of amoxicillin-coated gold nanoparticles and their antimicrobial activity
Nanomaterials have been the object of intense study due to promising applications in a number of different disciplines. In particular, medicine and biology have seen the potential of these novel materials with their nanoscale properties for use in diverse areas such as imaging, sensing and drug vectorisation. Gold nanoparticles (GNPs) are considered a very useful platform to create a valid and efficient drug delivery/carrier system due to their facile and well-studied synthesis, easy surface functionalization and biocompatibility. In the present study, stable antibiotic conjugated GNPs were synthesised by a one-step reaction using a poorly water soluble antibiotic, amoxicillin. Amoxicillin, a member of the penicillin family, reduces the chloroauric acid to form nanoparticles and at the same time coats them to afford the functionalised nanomaterial. A range of techniques including UV-vis spectroscopy, dynamic light scattering (DLS), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA) were used to ascertain the gold/drug molar ratio and the optimum temperature for synthesis of uniform monodisperse particles in the ca. 30-40 nm size range. Amoxicillin-conjugated gold showed an enhancement of antibacterial activity against Escherichia coli compared to the antibiotic alone
Generalized Flows around Neutron Stars
In this chapter, we present a brief and non-exhaustive review of the
developments of theoretical models for accretion flows around neutron stars. A
somewhat chronological summary of crucial observations and modelling of timing
and spectral properties are given in sections 2 and 3. In section 4, we argue
why and how the Two-Component Advective Flow (TCAF) solution can be applied to
the cases of neutron stars when suitable modifications are made for the NSs. We
showcase some of our findings from Monte Carlo and Smoothed Particle
Hydrodynamic simulations which further strengthens the points raised in section
4. In summary, we remark on the possibility of future works using TCAF for both
weakly magnetic and magnetic Neutron Stars.Comment: 15 pages, 7 figures. arXiv admin note: text overlap with
arXiv:1901.0084
Blockchain-Based Transaction Validation Protocol for a Secure Distributed IoT Network
Funding Agency: 10.13039/501100010418-Institute for Information and Communications Technology Promotion (IITP), Ministry of Science and ICT (MSIT); 10.13039/501100003621-Korea Government;Peer reviewedPublisher PD
SSMap: A new UniProt-PDB mapping resource for the curation of structural-related information in the UniProt/Swiss-Prot Knowledgebase
<p>Abstract</p> <p>Background</p> <p>Sequences and structures provide valuable complementary information on protein features and functions. However, it is not always straightforward for users to gather information concurrently from the sequence and structure levels. The UniProt knowledgebase (UniProtKB) strives to help users on this undertaking by providing complete cross-references to Protein Data Bank (PDB) as well as coherent feature annotation using available structural information. In this study, SSMap – a new UniProt-PDB residue-residue level mapping – was generated. The primary objective of this mapping is not only to facilitate the two tasks mentioned above, but also to palliate a number of shortcomings of existent mappings. SSMap is the first isoform sequence-specific mapping resource and is up-to-date for UniProtKB annotation tasks. The method employed by SSMap differs from the other mapping resources in that it stresses on the correct reconstruction of the PDB sequence from structures, and on the correct attribution of a UniProtKB entry to each PDB chain by using a series of post-processing steps.</p> <p>Results</p> <p>SSMap was compared to other existing mapping resources in terms of the correctness of the attribution of PDB chains to UniProtKB entries, and of the quality of the pairwise alignments supporting the residue-residue mapping. It was found that SSMap shared about 80% of the mappings with other mapping sources. New and alternative mappings proposed by SSMap were mostly good as assessed by manual verification of data subsets. As for local pairwise alignments, it was shown that major discrepancies (both in terms of alignment lengths and boundaries), when present, were often due to differences in methodologies used for the mappings.</p> <p>Conclusion</p> <p>SSMap provides an independent, good quality UniProt-PDB mapping. The systematic comparison conducted in this study allows the further identification of general problems in UniProt-PDB mappings so that both the coverage and the quality of the mappings can be systematically improved for the benefit of the scientific community. SSMap mapping is currently used to provide PDB cross-references in UniProtKB.</p
Women's input and decision-making in agriculture are associated with diet quality in rural Tanzania.
Background: Women's empowerment is one critical pathway through which agriculture can impact women's nutrition; however, empirical evidence is still limited. We evaluated the associations of women's participation, input, and decision-making in key agricultural and household activities with women's diet quality.Methods: We analyzed data from a cross-sectional study of 870 women engaged in homestead agriculture. We used food frequency questionnaires to assess women's diets and computed women's diet quality using the Prime Diet Quality Score (PDQS) (range 0–42), which captures healthy and unhealthy foods. We evaluated women's decision-making in 8 activities, food crop farming, cash crop farming, livestock raising, non-farm economic activities, wage/salary employment, fishing, major household expenditures, and minor household expenditures. Generalized estimating equations (GEE) linear models were used to evaluate associations between (a) women's participation, (b) decision-making, (c) adequate input, (d) adequate extent of independence in decision-making in agriculture, and (e) adequate input in use of agricultural income with their PDQS. Adequate input was defined as input into some, most or all decisions compared to input into few decisions or none. Adequate extent of independence was defined as input to a medium or high extent compared to input to a small extent or none.Findings: Median PDQS was 19 (IQR: 16–21). Women's adequate input in decision-making on wage and salary employment (estimate: 4.19, 95% CI: 2.80, 5.57) and minor expenditures were associated with higher PDQS vs. inadequate input. Women with independence in decision-making on livestock production (estimate: 0.97, 95% CI: 0.05, 1.90) and minor household expenditures, and women with adequate decision-making in the use of income from wages/salaries (estimate: 3.16, 95% CI: 2.44, 3.87) had higher PDQS. Participation in agricultural activities was positively associated with PDQS.Conclusions: Women's participation and input in decision-making in wage and salary employment, livestock production, and minor household expenditures were strongly associated with the consumption of better-quality diets. Women participating in multiple farm activities were also likely to have better diet quality. This study adds to the growing evidence on the pathways through which women's empowerment may influence women's nutrition in rural Tanzania
Sources of Relativistic Jets in the Galaxy
Black holes of stellar mass and neutron stars in binary systems are first
detected as hard X-ray sources using high-energy space telescopes. Relativistic
jets in some of these compact sources are found by means of multiwavelength
observations with ground-based telescopes. The X-ray emission probes the inner
accretion disk and immediate surroundings of the compact object, whereas the
synchrotron emission from the jets is observed in the radio and infrared bands,
and in the future could be detected at even shorter wavelengths. Black-hole
X-ray binaries with relativistic jets mimic, on a much smaller scale, many of
the phenomena seen in quasars and are thus called microquasars. Because of
their proximity, their study opens the way for a better understanding of the
relativistic jets seen elsewhere in the Universe. From the observation of
two-sided moving jets it is inferred that the ejecta in microquasars move with
relativistic speeds similar to those believed to be present in quasars. The
simultaneous multiwavelength approach to microquasars reveals in short
timescales the close connection between instabilities in the accretion disk
seen in the X-rays, and the ejection of relativistic clouds of plasma observed
as synchrotron emission at longer wavelengths. Besides contributing to a deeper
comprehension of accretion disks and jets, microquasars may serve in the future
to determine the distances of jet sources using constraints from special
relativity, and the spin of black holes using general relativity.Comment: 39 pages, Tex, 8 figures, to appear in vol. 37 (1999) of Annual
Reviews of Astronomy and Astrophysic
Holographic phase diagram of quark-gluon plasma formed in heavy-ions collisions
The phase diagram of quark gluon plasma (QGP) formed at a very early stage
just after the heavy ion collision is obtained by using a holographic dual
model for the heavy ion collision. In this dual model colliding ions are
described by the charged shock gravitational waves. Points on the phase diagram
correspond to the QGP or hadronic matter with given temperatures and chemical
potentials. The phase of QGP in dual terms is related to the case when the
collision of shock waves leads to formation of trapped surface. Hadronic matter
and other confined states correspond to the absence of trapped surface after
collision.
Multiplicity of the ion collision process is estimated in the dual language
as area of the trapped surface. We show that a non-zero chemical potential
reduces the multiplicity. To plot the phase diagram we use two different dual
models of colliding ions, the point and the wall shock waves, and find
qualitative agreement of the results.Comment: 33 pages, 14 figures, typos correcte
Semi-analytic results for quasi-normal frequencies
The last decade has seen considerable interest in the quasi-normal
frequencies [QNFs] of black holes (and even wormholes), both asymptotically
flat and with cosmological horizons. There is wide agreement that the QNFs are
often of the form omega_n = (offset) + i n (gap), though some authors have
encountered situations where this behaviour seems to fail. To get a better
understanding of the general situation we consider a semi-analytic model based
on a piecewise Eckart (Poeschl-Teller) potential, allowing for different
heights and different rates of exponential falloff in the two asymptotic
directions. This model is sufficiently general to capture and display key
features of the black hole QNFs while simultaneously being analytically
tractable, at least for asymptotically large imaginary parts of the QNFs. We
shall derive an appropriate "quantization condition" for the asymptotic QNFs,
and extract as much analytic information as possible. In particular, we shall
explicitly verify that the (offset)+ i n (gap) behaviour is common but not
universal, with this behaviour failing unless the ratio of rates of exponential
falloff on the two sides of the potential is a rational number. (This is
"common but not universal" in the sense that the rational numbers are dense in
the reals.) We argue that this behaviour is likely to persist for black holes
with cosmological horizons.Comment: V1: 28 pages, no figures. V2: 3 references added, no physics changes.
V3: 29 pages, 9 references added, no physics changes; V4: reformatted, now 27
pages. Some clarifications, comparison with results obtained by monodromy
techniques. This version accepted for publication in JHEP. V5: Minor typos
fixed. Compatible with published versio
Classical kinetic energy, quantum fluctuation terms and kinetic-energy functionals
We employ a recently formulated dequantization procedure to obtain an exact
expression for the kinetic energy which is applicable to all kinetic-energy
functionals. We express the kinetic energy of an N-electron system as the sum
of an N-electron classical kinetic energy and an N-electron purely quantum
kinetic energy arising from the quantum fluctuations that turn the classical
momentum into the quantum momentum. This leads to an interesting analogy with
Nelson's stochastic approach to quantum mechanics, which we use to conceptually
clarify the physical nature of part of the kinetic-energy functional in terms
of statistical fluctuations and in direct correspondence with Fisher
Information Theory. We show that the N-electron purely quantum kinetic energy
can be written as the sum of the (one-electron) Weizsacker term and an
(N-1)-electron kinetic correlation term. We further show that the Weizsacker
term results from local fluctuations while the kinetic correlation term results
from the nonlocal fluctuations. For one-electron orbitals (where kinetic
correlation is neglected) we obtain an exact (albeit impractical) expression
for the noninteracting kinetic energy as the sum of the classical kinetic
energy and the Weizsacker term. The classical kinetic energy is seen to be
explicitly dependent on the electron phase and this has implications for the
development of accurate orbital-free kinetic-energy functionals. Also, there is
a direct connection between the classical kinetic energy and the angular
momentum and, across a row of the periodic table, the classical kinetic energy
component of the noninteracting kinetic energy generally increases as Z
increases.Comment: 10 pages, 1 figure. To appear in Theor Chem Ac
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