881 research outputs found
Effects of light and soil flooding on the growth and photosynthesis of ramin (Gonystylus bancanus) seedlings in Malaysia
We studied the ecophysiology of ramin (Gonystylus bancanus) seedlings in an experimental set up at the Forest Research Centre in Kuching, Sarawak, Malaysia. Ramin seedlings were grown on flooded and drained peat soil under 100, 76, 46 and 23% sunlight, thus simulating effects of different light conditions (canopy gap size) and drainage that occur in natural ramin populations. Seedling growth was highest in partial sunlight (76%) and reduced with reducing light levels. Aboveground productivity and fine root development were significantly higher in seedlings grown on flooded soil compared with those on drained soil. In contrast, investment in coarse root biomass was significantly higher in seedlings grown on drained soil. It appeared that the aboveground growth benefits in flooded conditions were the result of more advantageous conditions for allocation of carbon to leaves, thus enhancing overall relative growth rates through higher light interception rates despite lower photosynthetic capacity. The results of this experiment suggested that drainage of peat swamp forests would seriously hamper natural regeneration of ramin by limiting the growth of seedlings. It is also suggested that selective logging operations which produce medium-size canopy gaps improve ramin regeneration in hydrologically undisturbed mixed swamp forest
Why do high jumpers use a curved approach?
Currently all elite high jumpers use the Fosbury Flop technique with a curved approach.
This suggests that the curved approach presents some clear advantage although there is no
general agreement upon the mechanism or the mechanics. This study aimed to determine the
characteristics of the approach curve and to investigate how it contributes to the generation
of somersault rotation. A simple theoretical model was used to demonstrate that a tightening
approach curve would change the inward lean towards the centre of the curve into outwards
lean. Three-dimensional video analysis was conducted on performances of two elite male
high jumpers in competition. It was found that in each case the radius of the approach curve
and the inward lean angle both decreased towards the end of the approach (p < 0.01). The
amount of outward lean angular velocity generated was shown to be a major proportion of
the required somersault angular velocity for a jump. It was concluded that the main
advantage of a curved approach was that it resulted in the generation of somersault velocity
providing the curve tightened towards the end of the approach
Structural and electrical properties of Nb-substituted LiTa1-xNbxO3
Single phase LiTa1-xNbxO3 solid solution with 0.00 ≤ x ≤ 1.00 was successfully synthesised via conventional solid-state method at 950°C for 24 h. These materials were refined and fully indexed with hexagonal crystal system, space group of R3c; lattice parameters, a ranging from 5.1410(6) Ǻ to 5.1471(3) Ǻ and c ranging from 13.7467(1) Ǻ to 13.8341(1) Ǻ; with α = β = 90° and γ = 120°. Variation of the lattice parameters in these materials was found to be negligibly small throughout the subsolidus solution. No thermal event was detected within the studied temperature range of 50 to 1000°C. The electrical properties of samples were characterised by AC impedance analyser, HP4192A at temperature ranging from room temperature to 850°C over a frequency range of 5 Hz to 13 MHz. LiTa1-xNbxO3 materials exhibited bulk response with associated capacitances in the order of 10-12 F cm-1 and the temperature-dependent conductivities were found to increase with increasing temperatures. The results showed that LiTa1-xNbxO3 samples were of typical ferroelectrics
Influence of Nb2O5 substitution on the structural and electrical properties of Bi3TaO7 ceramics
Herein we report the doping mechanism and impedance study of the Nb-substituted Bi3Ta1-xNbxO7 (0 ≤ x ≤ 0.5) prepared via conventional solid-state method at 900 °C over 24 h. The substitutional solid solution crystallised in a cubic fluorite structure, space group Fm-3m and with lattice parameter, a = b = c, in the range 5.4477 (±0.0037)–5.4654 (±0.0011) Å. An insignificant unit cell expansion was observed with increasing Nb2O5 content and the linear correlation between lattice parameter and composition variable showed that the Vegard's Law was obeyed. Both TGA and DTA analyses confirmed that the Bi3Ta1-xNbxO7 solid solution was thermally stable as neither phase transition nor weight loss was observed within the studied temperature range, ∼28 °C–1000 °C. The electrical conductivities of these samples were found to increase with increasing Nb concentration; the Bi3Ta0.5Nb0.5O7 exhibited the highest conductivity, ∼1.2 × 10−2 S cm−1 at 700 °C with a low activation energy of 1.03 eV
Self-nanomicellizing solid dispersion of edaravone: part I – oral bioavailability improvement
Background: Edaravone (EDR) is known for its free radical scavenging, antiapoptotic, antinecrotic, and anticytokine effects in neurological and non-neurological diseases. It is currently available clinically as Radicava® and Radicut®, intravenous medications, recently approved for the treatment of amyotrophic lateral sclerosis and cerebral infarction. However, the oral use of EDR is still restricted by its poor oral bioavailability (BA) due to poor aqueous solubility, stability, rapid metabolism, and low permeability. The present study reports the development of novel EDR formulation (NEF) using self-nanomicellizing solid dispersion (SNMSD) strategy with the aim to enable its oral use. Materials and methods: The selection of a suitable carrier for the development of NEF was performed based on the miscibility study. The optimization of EDR-to-carrier ratio was conducted via kinetic solubility study after preparing SNMSDs using solvent evaporation technique. The drug–polymer carrier interaction and self-nanomicellizing properties of NEF were investigated with advanced characterization studies. In vitro permeation, metabolism, and dissolution study was carried out to examine the effect of the presence of a carrier on physicochemical properties of EDR. Additionally, the dose-dependent pharmacokinetic study of NEF was conducted and compared with the EDR suspension. Results: Soluplus® (SOL) as a carrier was selected based on the potential for improving aqueous solubility. The NEF containing EDR and SOL (1:5) resulted in the highest enhancement in aqueous solubility (17.53-fold) due to amorphization, hydrogen bonding interaction, and micellization. Moreover, the NEF demonstrated significant improvement in metabolism, permeability, and dissolution profile of EDR. Furthermore, the oral BA of NEF showed 10.2-, 16.1-, and 14.8-fold enhancement compared to EDR suspension at 46, 138, and 414 µmol/kg doses. Conclusion: The results demonstrated that SNMSD strategy could serve as a promising way to enhance EDR oral BA and NEF could be a potential candidate for the treatment of diseases in which oxidative stress plays a key role in their pathogenesis.Ankit Parikh, Krishna Kathawala, Chun Chuan Tan, Sanjay Garg, Xin-Fu Zho
Phase formation and dielectric properties of pentavalent cation doped non-stoichiometric Bismuth Zinc Niobate (BZN) cubic pyrochlore.
In an attempt to synthesize new solid solutions and search for better performance materials, pentavalent cation dopants
were introduced into the non stoichiometric BZN cubic pyrochlore, Bi3Zn1.84Nb3O13.84. Extensive solid solutions were formed in Bi3Zn1.84Nb3-xDxO13.84 with limit at x = 3 and 2.6 for D = Ta and Sb, respectively. This illustrates the possibility of cationexchange solid solutions due to similarity in dopants’ ionic radii. The elemental analysis confirmed the stoichiometry of doped materials with no deleterious Bi2O3 loss. Ta / Sb doped samples were highly resistive with activation energies ranging from 1.2 - 1.9 eV. Temperature coefficient of capacitance, TCC, decreased from -396 ppm / oC to ~ -180 ppm / oC and ~ -90 ppm / oC for both end members, respectively
Quantum Cryptography Using Single Particle Entanglement
A quantum cryptography scheme based on entanglement between a single particle
state and a vacuum state is proposed. The scheme utilizes linear optics devices
to detect the superposition of the vacuum and single particle states. Existence
of an eavesdropper can be detected by using a variant of Bell's inequality.Comment: 4 pages, 3figures, revte
Single-particle nonlocality and entanglement with the vacuum
We propose a single-particle experiment that is equivalent to the
conventional two-particle experiment used to demonstrate a violation of Bell's
inequalities. Hence, we argue that quantum mechanical nonlocality can be
demonstrated by single-particle states. The validity of such a claim has been
discussed in the literature, but without reaching a clear consensus. We show
that the disagreement can be traced to what part of the total state of the
experiment one assigns to the (macroscopic) measurement apparatus. However,
with a conventional and legitimate interpretation of the measurement process
one is led to the conclusion that even a single particle can show nonlocal
properties.Comment: 6 pages, 5 figure
Immune-related genetic enrichment in frontotemporal dementia: An analysis of genome-wide association studies
Background
Converging evidence suggests that immune-mediated dysfunction plays an important role
in the pathogenesis of frontotemporal dementia (FTD). Although genetic studies have
shown that immune-associated loci are associated with increased FTD risk, a systematic
investigation of genetic overlap between immune-mediated diseases and the spectrum of
FTD-related disorders has not been performed. Methods and findings
Using large genome-wide association studies (GWASs) (total n = 192,886 cases and controls) and recently developed tools to quantify genetic overlap/pleiotropy, we systematically
identified single nucleotide polymorphisms (SNPs) jointly associated with FTD-related disorders—namely, FTD, corticobasal degeneration (CBD), progressive supranuclear palsy
(PSP), and amyotrophic lateral sclerosis (ALS)—and 1 or more immune-mediated diseases
including Crohn disease, ulcerative colitis (UC), rheumatoid arthritis (RA), type 1 diabetes
(T1D), celiac disease (CeD), and psoriasis. We found up to 270-fold genetic enrichment
between FTD and RA, up to 160-fold genetic enrichment between FTD and UC, up to 180-
fold genetic enrichment between FTD and T1D, and up to 175-fold genetic enrichment
between FTD and CeD. In contrast, for CBD and PSP, only 1 of the 6 immune-mediated diseases produced genetic enrichment comparable to that seen for FTD, with up to 150-fold
genetic enrichment between CBD and CeD and up to 180-fold enrichment between PSP
and RA. Further, we found minimal enrichment between ALS and the immune-mediated diseases tested, with the highest levels of enrichment between ALS and RA (up to 20-fold). For
FTD, at a conjunction false discovery rate < 0.05 and after excluding SNPs in linkage disequilibrium, we found that 8 of the 15 identified loci mapped to the human leukocyte antigen
(HLA) region on Chromosome (Chr) 6. We also found novel candidate FTD susceptibility
loci within LRRK2 (leucine rich repeat kinase 2), TBKBP1 (TBK1 binding protein 1), and
PGBD5 (piggyBac transposable element derived 5). Functionally, we found that the expression of FTD–immune pleiotropic genes (particularly within the HLA region) is altered in postmortem brain tissue from patients with FTD and is enriched in microglia/macrophages
compared to other central nervous system cell types. The main study limitation is that the
results represent only clinically diagnosed individuals. Also, given the complex interconnectedness of the HLA region, we were not able to define the specific gene or genes on Chr 6
responsible for our pleiotropic signal.
Conclusions
We show immune-mediated genetic enrichment specifically in FTD, particularly within the
HLA region. Our genetic results suggest that for a subset of patients, immune dysfunction
may contribute to FTD risk. These findings have potential implications for clinical trials target
Associations of Leisure-Time Physical Activity and Television Viewing With Life Expectancy Free of Nonfatal Cardiovascular Disease: The ARIC Study
Background High levels of physical activity have been associated with longer life expectancy free of cardiovascular disease (CVD), but specific types of CVD and sedentary behavior have not been examined. We examined associations of leisure-time moderate-to-vigorous physical activity (LTPA) and television viewing with life expectancy free of 3 types of CVD. Methods and Results We included 13 534 participants from the ARIC (Atherosclerosis Risk in Communities) cohort. We used multistate survival models to estimate associations of LTPA in the past year (no LTPA, less than the median, equal to or greater than the median) and television viewing (often or very often, sometimes, seldom or rarely) with life expectancy at age 50 free of nonfatal coronary heart disease (CHD), stroke, and heart failure (HF). Over 27 years of follow-up, 4519 participants developed one of the 3 nonfatal CVDs and 5475 deaths occurred. Compared with participants who engaged in no LTPA, participants who engaged in LTPA equal to or greater than the median had longer life expectancy free of nonfatal CHD (men: 1.5 years [95% CI, 1.0-2.0]; women: 1.6 years [95% CI, 1.1-2.2]), stroke (men: 1.8 years [95% CI, 1.2-2.3]; women: 1.8 years [95% CI, 1.3-2.3]), and HF (men: 1.6 years [95% CI, 1.1-2.1]; women: 1.7 years [95% CI, 1.2-2.2]). Compared with viewing more television, watching less television was associated with longer life expectancy free of CHD, stroke, and HF (≈0.8 year). Conclusions Higher levels of LTPA and less television viewing were associated with longer life expectancy free of CHD, stroke, and HF. Engaging in LTPA and watching less television may increase the number of years lived free of CHD, stroke, and HF
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