14,852 research outputs found
Finite element simulation of powder compaction via shock consolidation using gas-gun system
Shock consolidation is a promising method for consolidation of nanocrystalline metallic powders since it can prevent grain growth of nanopowders during the process due to very short processing time. However, internal cracks often occurs in powder compacts during the shock consolidation process. In this paper, finite element simulations showed that reflected tensile wave causes spall phenomena resulting internal crack of powder compaction during shock compaction process. To reduce spall phenomena, FEM simulation with changing compaction die's geometry was performed to find out relationship between shape and tensile wave intensity. Based on FEM results, new compaction die was designed and bulk nanocrystalline Cu are obtained using new compaction die. (C) 2014 Published by Elsevier Ltd.open1111Ysciescopu
Body composition, IGF1 status, and physical functionality in nonagenarians: implications for osteosarcopenia
OBJECTIVES:
Body composition alterations occur during aging. The purpose of the present analysis was to explore the functional consequences of the overlap of sarcopenia and osteoporosis, and the potential role of insulin-like growth factor 1 (IGF1) in their development in the oldest old.
SETTING AND PARTICIPANTS:
Eighty-seven nonagenarians from the Louisiana Healthy Aging Study were included.
MEASURES:
The definition of sarcopenia was based on appendicular lean mass (ALM). Osteoporosis was diagnosed based on bone mineral density (BMD) T score. Four phenotypes were compared: (1) healthy body composition, that is, nonosteoporotic nonsarcopenic (CO, control group), (2) osteoporotic (O, low BMD T score), (3) sarcopenic (S, low ALM), and (4) osteosarcopenic (OS, low BMD T score and low ALM). Sex- and age-specific IGF1-Standard Deviation Scores (SDS) were calculated. The Continuous Scale-Physical Functional Performance (CS-PFP) test was performed.
RESULTS:
In OS men, IGF1-SDS values (-0.61 ±0.37 vs -0.04 ± 0.52, P = .02) were lower than those in CO males (control group), whereas IGF1-SDS were similar in the 4 body composition phenotypes in women. In men only, ALM was positively associated with IGF1-SDS values (P = .01) independent of age and C-reactive protein concentration. Regarding bone health, we found no association between IGF1-SDS values and BMD. IGF1-SDS was not associated with functional performance (CS-PFP) in men and women.
CONCLUSIONS/IMPLICATIONS:
IGF1 sensitivity in skeletal muscle and bone may differ by sex in the oldest old. IGF1 status did not appear to affect physical functionality. Determinants and clinical and functional characteristics of osteosarcopenia need to be further investigated in order to define conclusive diagnostic criteria
All-Optical Ultrafast Control and Read-Out of a Single Negatively Charged Self-Assembled InAs Quantum Dot
We demonstrate the all-optical ultrafast manipulation and read-out of optical
transitions in a single negatively charged self-assembled InAs quantum dot, an
important step towards ultrafast control of the resident spin. Experiments
performed at zero magnetic field show the excitation and decay of the trion
(negatively charged exciton) as well as Rabi oscillations between the electron
and trion states. Application of a DC magnetic field perpendicular to the
growth axis of the dot enables observation of a complex quantum beat structure
produced by independent precession of the ground state electron and the excited
state heavy hole spins
Spread Supersymmetry
In the multiverse the scale of SUSY breaking, \tilde{m} = F_X/M_*, may scan
and environmental constraints on the dark matter density may exclude a large
range of \tilde{m} from the reheating temperature after inflation down to
values that yield a LSP mass of order a TeV. After selection effects, the
distribution for \tilde{m} may prefer larger values. A single environmental
constraint from dark matter can then lead to multi-component dark matter,
including both axions and the LSP, giving a TeV-scale LSP lighter than the
corresponding value for single-component LSP dark matter.
If SUSY breaking is mediated to the SM sector at order X^* X, only squarks,
sleptons and one Higgs doublet acquire masses of order \tilde{m}. The gravitino
mass is lighter by a factor of M_*/M_Pl and the gaugino masses are suppressed
by a further loop factor. This Spread SUSY spectrum has two versions; the
Higgsino masses are generated in one from supergravity giving a wino LSP and in
the other radiatively giving a Higgsino LSP. The environmental restriction on
dark matter fixes the LSP mass to the TeV domain, so that the squark and
slepton masses are order 10^3 TeV and 10^6 TeV in these two schemes. We study
the spectrum, dark matter and collider signals of these two versions of Spread
SUSY. The Higgs is SM-like and lighter than 145 GeV; monochromatic photons in
cosmic rays arise from dark matter annihilations in the halo; exotic short
charged tracks occur at the LHC, at least for the wino LSP; and there are the
eventual possibilities of direct detection of dark matter and detailed
exploration of the TeV-scale states at a future linear collider. Gauge coupling
unification is as in minimal SUSY theories.
If SUSY breaking is mediated at order X, a much less hierarchical spectrum
results---similar to that of the MSSM, but with the superpartner masses 1--2
orders of magnitude larger than in natural theories.Comment: 20 pages, 5 figure
Chemical pre-processing of cluster galaxies over the past 10 billion years in the IllustrisTNG simulations
We use the IllustrisTNG simulations to investigate the evolution of the
mass-metallicity relation (MZR) for star-forming cluster galaxies as a function
of the formation history of their cluster host. The simulations predict an
enhancement in the gas-phase metallicities of star-forming cluster galaxies
(10^9< M_star<10^10 M_sun) at z<1.0 in comparisons to field galaxies. This is
qualitatively consistent with observations. We find that the metallicity
enhancement of cluster galaxies appears prior to their infall into the central
cluster potential, indicating for the first time a systematic "chemical
pre-processing" signature for {\it infalling} cluster galaxies. Namely,
galaxies which will fall into a cluster by z=0 show a ~0.05 dex enhancement in
the MZR compared to field galaxies at z<0.5. Based on the inflow rate of gas
into cluster galaxies and its metallicity, we identify that the accretion of
pre-enriched gas is the key driver of the chemical evolution of such galaxies,
particularly in the stellar mass range (10^9< M_star<10^10 M_sun). We see
signatures of an environmental dependence of the ambient/inflowing gas
metallicity which extends well outside the nominal virial radius of clusters.
Our results motivate future observations looking for pre-enrichment signatures
in dense environments.Comment: 5 pages, 4 figures, accepted for publication in MNRAS Letter
Exploring Consumers’ Attitudes of Smart TV Related Privacy Risks
A number of privacy risks are inherent in the Smart TV ecosystem. It is likely that many consumers are unaware of these privacy risks. Alternatively, they might be aware but consider the privacy risks acceptable. In order to explore this, we carried out an online survey with 200 participants to determine whether consumers were aware of Smart TV related privacy risks. The responses revealed a meagre level of awareness. We also explored consumers’ attitudes towards specific Smart TV related privacy risks.
We isolated a number of factors that influenced rankings and used these to develop awareness-raising messages. We tested these messages in an online survey with 155 participants. The main finding was that participants were generally unwilling to disconnect their Smart TVs from the Internet because they valued the Smart TV’s Internet functionality more than their privacy. We subsequently evaluated the awareness-raising messages in a second survey with 169 participants, framing the question differently. We asked participants to choose between five different Smart TV Internet connection options, two of which retained functionality but entailed expending time and/or effort to preserve privacy
Discrete R-symmetries and Anomaly Universality in Heterotic Orbifolds
We study discrete R-symmetries, which appear in 4D low energy effective field
theory derived from hetetoric orbifold models. We derive the R-symmetries
directly from geometrical symmetries of orbifolds. In particular, we obtain the
corresponding R-charges by requiring that the couplings be invariant under
these symmetries. This allows for a more general treatment than the explicit
computations of correlation functions made previously by the authors, including
models with discrete Wilson lines, and orbifold symmetries beyond
plane-by-plane rotational invariance. Surprisingly, for the cases covered by
earlier explicit computations, the R-charges differ from the previous result.
We study the anomalies associated with these R-symmetries, and comment on the
results.Comment: 21 pages, 2 figures. Minor changes, typos corrected. Matches JHEP
published versio
Benchmark performance of low-cost Sb2Se3 photocathodes for unassisted solar overall water splitting
Determining cost-effective semiconductors exhibiting desirable properties for commercial photoelectrochemical water splitting remains a challenge. Herein, we report a Sb2Se3 semiconductor that satisfies most requirements for an ideal high-performance photoelectrode, including a small band gap and favourable cost, optoelectronic properties, processability, and photocorrosion stability. Strong anisotropy, a major issue for Sb2Se3, is resolved by suppressing growth kinetics via close space sublimation to obtain high-quality compact thin films with favourable crystallographic orientation. The Sb2Se3 photocathode exhibits a high photocurrent density of almost 30mAcm(-2) at 0V against the reversible hydrogen electrode, the highest value so far. We demonstrate unassisted solar overall water splitting by combining the optimised Sb2Se3 photocathode with a BiVO4 photoanode, achieving a solar-to-hydrogen efficiency of 1.5% with stability over 10h under simulated 1 sun conditions employing a broad range of solar fluxes. Low-cost Sb2Se3 can thus be an attractive breakthrough material for commercial solar fuel production. While photoelectrochemical water splitting offers an integrated means to convert sunlight to a renewable fuel, cost-effective light-absorbers are rare. Here, authors report Sb2Se3 photocathodes for high-performance photoelectrochemical water splitting devices
Composition, structure and stability of RuO_2(110) as a function of oxygen pressure
Using density-functional theory (DFT) we calculate the Gibbs free energy to
determine the lowest-energy structure of a RuO_2(110) surface in thermodynamic
equilibrium with an oxygen-rich environment. The traditionally assumed
stoichiometric termination is only found to be favorable at low oxygen chemical
potentials, i.e. low pressures and/or high temperatures. At realistic O
pressure, the surface is predicted to contain additional terminal O atoms.
Although this O excess defines a so-called polar surface, we show that the
prevalent ionic model, that dismisses such terminations on electrostatic
grounds, is of little validity for RuO_2(110). Together with analogous results
obtained previously at the (0001) surface of corundum-structured oxides, these
findings on (110) rutile indicate that the stability of non-stoichiometric
terminations is a more general phenomenon on transition metal oxide surfaces.Comment: 12 pages including 5 figures. Submitted to Phys. Rev. B. Related
publications can be found at http://www.fhi-berlin.mpg.de/th/paper.htm
Risk of seizure recurrence in people with single seizures and early epilepsy - Model development and external validation
PURPOSE: Following a single seizure, or recent epilepsy diagnosis, it is difficult to balance risk of medication side effects with the potential to prevent seizure recurrence. A prediction model was developed and validated enabling risk stratification which in turn informs treatment decisions and individualises counselling. METHODS: Data from a randomised controlled trial was used to develop a prediction model for risk of seizure recurrence following a first seizure or diagnosis of epilepsy. Time-to-event data was modelled via Cox's proportional hazards regression. Model validity was assessed via discrimination and calibration using the original dataset and also using three external datasets - National General Practice Survey of Epilepsy (NGPSE), Western Australian first seizure database (WA) and FIRST (Italian dataset of people with first tonic-clonic seizures). RESULTS: People with neurological deficit, focal seizures, abnormal EEG, not indicated for CT/MRI scan, or not immediately treated have a significantly higher risk of seizure recurrence. Discrimination was fair and consistent across the datasets (c-statistics: 0.555 (NGPSE); 0.558 (WA); 0.597 (FIRST)). Calibration plots showed good agreement between observed and predicted probabilities in NGPSE at one and three years. Plots for WA and FIRST showed poorer agreement with the model underpredicting risk in WA, and over-predicting in FIRST. This was resolved following model recalibration. CONCLUSION: The model performs well in independent data especially when recalibrated. It should now be used in clinical practice as it can improve the lives of people with single seizures and early epilepsy by enabling targeted treatment choices and more informed patient counselling
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