43,221 research outputs found
Development of sustainable biodegradable lignocellulosic hemp fiber/polycaprolactone biocomposites for light weight applications
Biocomposites with poly(Īµ-caprolactone) (PCL) as matrix and lignocellulosic hemp fiber with varying average aspect ratios (19, 26, 30 and 38) as reinforcement were prepared using twin extrusion process. The influence of fiber aspect ratio on the water absorption behavior and mechanical properties are investigated. The percentage of moisture uptake increased with the aspect ratio, following Fickian behavior. The hemp fiber/PCL biocomposites showed enhanced properties (tensile, flexural and low-velocity impact). The biocomposite with 26 aspect ratio showed the optimal properties, with flexural strength and modulus of 169% and 285% respectively, higher than those of neat PCL. However, a clear reduction on the mechanical properties was observed for water-immersed samples, with reduction in tensile and flexural moduli for the aspect ratio of 26 by 90% and 62%, respectively than those of dry samples. Summarily, the optimal sample provides an eco-friendly alternative to conventional, petroleum-based and non-renewable composites for various applications.Peer reviewedFinal Accepted Versio
Fluctuations, Saturation, and Diffractive Excitation in High Energy Collisions
Diffractive excitation is usually described by the Good--Walker formalism for
low masses, and by the triple-Regge formalism for high masses. In the
Good--Walker formalism the cross section is determined by the fluctuations in
the interaction. In this paper we show that by taking the fluctuations in the
BFKL ladder into account, it is possible to describe both low and high mass
excitation by the Good--Walker mechanism. In high energy collisions the
fluctuations are strongly suppressed by saturation, which implies that pomeron
exchange does not factorise between DIS and collisions. The Dipole Cascade
Model reproduces the expected triple-Regge form for the bare pomeron, and the
triple-pomeron coupling is estimated.Comment: 20 pages, 12 figure
Coopetition of software firms in Open source software ecosystems
Software firms participate in an ecosystem as a part of their innovation
strategy to extend value creation beyond the firms boundary. Participation in
an open and independent environment also implies the competition among firms
with similar business models and targeted markets. Hence, firms need to
consider potential opportunities and challenges upfront. This study explores
how software firms interact with others in OSS ecosystems from a coopetition
perspective. We performed a quantitative and qualitative analysis of three OSS
projects. Finding shows that software firms emphasize the co-creation of common
value and partly react to the potential competitiveness on OSS ecosystems. Six
themes about coopetition were identified, including spanning gatekeepers,
securing communication, open-core sourcing and filtering shared code. Our work
contributes to software engineering research with a rich description of
coopetition in OSS ecosystems. Moreover, we also come up with several
implications for software firms in pursing a harmony participation in OSS
ecosystems.Comment: This is the author's version of the work. Copyright owner's version
can be accessed at
https://link.springer.com/chapter/10.1007/978-3-319-69191-6_10, Coopetition
of software firms in Open source software ecosystems, 8th ICSOB 2017, Essen,
Germany (2017
Association Rule Learning Is an Easy and Efficient Method for Identifying Profiles of Traumas and Stressors that Predict Psychopathology in Disaster Survivors: The Example of Sri Lanka.
Research indicates that psychopathology in disaster survivors is a function of both experienced trauma and stressful life events. However, such studies are of limited utility to practitioners who are about to go into a new post-disaster setting as (1) most of them do not indicate which specific traumas and stressors are especially likely to lead to psychopathology; and (2) each disaster is characterized by its own unique traumas and stressors, which means that practitioners have to first collect their own data on common traumas, stressors and symptoms of psychopathology prior to planning any interventions. An easy-to-use and easy-to-interpret data analytical method that allows one to identify profiles of trauma and stressors that predict psychopathology would be of great utility to practitioners working in post-disaster contexts. We propose that association rule learning (ARL), a big data mining technique, is such a method. We demonstrate the technique by applying it to data from 337 survivors of the Sri Lankan civil war who completed the Penn/RESIST/Peradeniya War Problems Questionnaire (PRPWPQ), a comprehensive, culturally-valid measure of experienced trauma, stressful life events, anxiety and depression. ARL analysis revealed five profiles of traumas and stressors that predicted the presence of some anxiety, three profiles that predicted the presence of severe anxiety, four profiles that predicted the presence of some depression and five profiles that predicted the presence of severe depression. ARL allows one to identify context-specific associations between specific traumas, stressors and psychological distress, and can be of great utility to practitioners who wish to efficiently analyze data that they have collected, understand the output of that analysis, and use it to provide psychosocial aid to those who most need it in post-disaster settings
Quanta of Space-Time and Axiomatization of Physics
We consider Hilbert's sixth problem on the axiomatization of physics starting
with a higher degree Heisenberg commutation relation involving the Dirac
operator and the Feynman slash of scalar fields. The two sided version of the
commutation relation in dimension 4 implies volume quantization and determines
a noncommutative space which is a tensor product of continuous and discrete
spaces. This noncommutative space predicts the full structure of a unified
model of all particle interactions based on Pati-Salam symmetries or, as a
special case, the Standard Model. We study implications of this quantization
condition on Particle Physics, General Relativity, the cosmological constant
and dark matter. We demonstrate that, with little input, noncommutative
geometry gives a compelling and attractive picture about the nature and
structure of space-time.Comment: 47 pages. Contribution to the special issue of IJGMMP celebrating the
one century anniversary of the program announced in 1916 by Hilbert entitled
" Foundations of Mathematics and Physics", editors, Joseph Kouneiher, John
Stachel and Salvatore Capozzieol
Theory of the nodal nematic quantum phase transition in superconductors
We study the character of an Ising nematic quantum phase transition (QPT)
deep inside a d-wave superconducting state with nodal quasiparticles in a
two-dimensional tetragonal crystal. We find that, within a 1/N expansion, the
transition is continuous. To leading order in 1/N, quantum fluctuations enhance
the dispersion anisotropy of the nodal excitations, and cause strong scattering
which critically broadens the quasiparticle (qp) peaks in the spectral
function, except in a narrow wedge in momentum space near the Fermi surface
where the qp's remain sharp. We also consider the possible existence of a
nematic glass phase in the presence of weak disorder. Some possible
implications for cuprate physics are also discussed.Comment: 9 page, 4 figures, an error in one of expressions corrected and a new
author was added. New references and footnotes are added and this is the
version to appear in PR
High Energy Bounds on Soft N=4 SYM Amplitudes from AdS/CFT
Using the AdS/CFT correspondence, we study the high-energy behavior of
colorless dipole elastic scattering amplitudes in N=4 SYM gauge theory through
the Wilson loop correlator formalism and Euclidean to Minkowskian analytic
continuation. The purely elastic behavior obtained at large impact-parameter L,
through duality from disconnected AdS_5 minimal surfaces beyond the
Gross-Ooguri transition point, is combined with unitarity and analyticity
constraints in the central region. In this way we obtain an absolute bound on
the high-energy behavior of the forward scattering amplitude due to the
graviton interaction between minimal surfaces in the bulk. The dominant
"Pomeron" intercept is bounded by alpha less than or equal to 11/7 using the
AdS/CFT constraint of a weak gravitational field in the bulk. Assuming the
elastic eikonal approximation in a larger impact-parameter range gives alpha
between 4/3 and 11/7. The actual intercept becomes 4/3 if one assumes the
elastic eikonal approximation within its maximally allowed range L larger than
exp{Y/3}, where Y is the total rapidity. Subleading AdS/CFT contributions at
large impact-parameter due to the other d=10 supergravity fields are obtained.
A divergence in the real part of the tachyonic KK scalar is cured by
analyticity but signals the need for a theoretical completion of the AdS/CFT
scheme.Comment: 25 pages, 3 eps figure
NRL^{-/-} gene edited human embryonic stem cells generate rod-deficient retinal organoids enriched in S-cone-like photoreceptors
Organoid cultures represent a unique tool to investigate the developmental complexity of tissues like the human retina. NRL is a transcription factor required for the specification and homeostasis of mammalian rod photoreceptors. In Nrlādeficient mice, photoreceptor precursor cells do not differentiate into rods, and instead follow a default photoreceptor specification pathway to generate Sāconeālike cells. To investigate whether this genetic switch mechanism is conserved in humans, we used CRISPR/Cas9 gene editing to engineer an NRLādeficient embryonic stem cell (ESC) line (NRL^{ā/ā}), and differentiated it into retinal organoids. Retinal organoids selfāorganize and resemble embryonic optic vesicles (OVs) that recapitulate the natural histogenesis of rods and cone photoreceptors. NRLā/ā OVs develop comparably to controls, and exhibit a laminated, organized retinal structure with markers of photoreceptor synaptogenesis. Using immunohistochemistry and quantitative polymerase chain reaction (qPCR), we observed that NRL^{ā/ā} OVs do not express NRL, or other rod photoreceptor markers directly or indirectly regulated by NRL. On the contrary, they show an abnormal number of photoreceptors positive for SāOPSIN, which define a primordial subtype of cone, and overexpress other cone genes indicating a conserved molecular switch in mammals. This study represents the first evidence in a human ināvitro ESCāderived organoid system that NRL is required to define rod identity, and that in its absence Sāconeālike cells develop as the default photoreceptor cell type. It shows how gene edited retinal organoids provide a useful system to investigate human photoreceptor specification, relevant for efforts to generate cells for transplantation in retinal degenerative diseases
A study of blood contamination of Siqveland matrix bands
AIMS To use a sensitive forensic test to measure blood contamination of used Siqveland matrix bands following routine cleaning and sterilisation procedures in general dental practice. MATERIALS AND METHODS: Sixteen general dental practices in the West of Scotland participated. Details of instrument cleaning procedures were recorded for each practice. A total of 133 Siqveland matrix bands were recovered following cleaning and sterilisation and were examined for residual blood contamination by the Kastle-Meyer test, a well-recognised forensic technique. RESULTS: Ultrasonic baths were used for the cleaning of 62 (47%) bands and retainers and the remainder (53%) were hand scrubbed prior to autoclaving. Overall, 21% of the matrix bands and 19% of the retainers gave a positive Kastle-Meyer test, indicative of residual blood contamination, following cleaning and sterilisation. In relation to cleaning method, 34% of hand-scrubbed bands and 32% of hand-scrubbed retainers were positive for residual blood by the Kastle-Meyer test compared with 6% and 3% respectively of ultrasonically cleaned bands and retainers (P less than 0.001). CONCLUSIONS: If Siqveland matrix bands are re-processed in the assembled state, then adequate pre-sterilisation cleaning cannot be achieved reliably. Ultrasonic baths are significantly more effective than hand cleaning for these items of equipment
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