2,091 research outputs found
Biodiesel Produced from Catalyzed Transesterification of Triglycerides Using ion-Exchanged Zeolite Beta and MCM-22
AbstractIn this work, biodiesel production from catalyzed transesterification of triglycerides with excess methanol was studied by using ion-exchanged Zeolite Beta and MCM-22 as heterogeneous catalysts. Zeolite Beta and MCM-22 were synthesized with hydrothermal processes and, subsequently, modified by ion-exchanged with alkali ions. These as-obtained zeolite catalysts could yield a high conversion of triglycerides to biodiesel. The conversion efficiency was largely affected by crystallinity and frameworks of zeolite support, pH value of alkali ion-exchange solutions and alkali loadings onto the zeolite support. Furthermore, the effects of the duration of the sodium ion-exchange process on the final conversion efficiency of triolein to biodiesel, both the as-prepared Zeolite MCM-22 and Zeolite Beta catalysts were used. The effect of the duration of the sodium ion-exchange process is insignificant in transesterification using Na-ion-exchanged Zeolite MCM-22 catalysts from 0.5 to 4h. In contrast, the conversion efficiency of triolein to biodiesel reached ca. 95% in 0.5hours of transesterification using Zeolite Beta ion-exchanged with 3 mmol-eq. Na+/g cat for 0.5hours
Integral and Rxte/Asm Observations on Igr J17098-3628
To probe further the possible nature of the unidentified source IGR
J17098-3628, we have carried out a detailed analysis of its long-term time
variability as monitored by RXTE/ASM, and of its hard X-ray properties as
observed by INTEGRAL. INTEGRAL has monitored this sky region over years and
significantly detected IGR J17098-3628 only when the source was in this dubbed
active state. In particular, at 20 keV, IBIS/ISGRI caught an outburst in
March 2005, lasting for 5 days with detection significance of 73
(20-40 keV) and with the emission at 200 keV. The ASM observations reveal
that the soft X-ray lightcurve shows a similar outburst to that detected by
INTEGRAL, however the peak of the soft X-ray lightcurve either lags, or is
preceded by, the hard X-ray (20 keV) outburst by 2 days. This
resembles the behavior of X-ray novae like XN 1124-683, hence it further
suggests a LMXB nature for IGR J17098-3628. While the quality of the ASM data
prevents us from drawing any definite conclusions, these discoveries are
important clues that, coupled with future observations, will help to resolve
the as yet unknown nature of IGR J17098-3628.Comment: 15 pages, 7 figure, accepted in PAS
THE EFFECTS OF EXTERNAL LOAD ON LOWER EXTREMiTY ELECTROMYOGRAPHY AMPLITUDE DURING COUNTERMOVEMENT JUMP
The purpose of this study was to investigate the effects of different loads on the mean electromyography (EMG) amplitude of the gluteus maximus, biceps fernoris, vastus medialis, gastrocnemius, soleus, and tibialis anterior during the deceleration phase and the acceleration phase of the countermovement jumps (CMJ). Ten male physical education students performed different CMJs with and without an external load (0,2.5,5.0, 7.5, or 10.0 kg hold in arms). The results s h o w the amplitude of the gluteus maximus with load of 7.5 kg was higher than with load of 2.5 kg during the deceleration phase (p < .05), and the amplitude of the soleus with load of 10.0 kg was higher than with load of 2.5 kg during the acceleration phase (p < .05). It indicated that the activities of lower limb muscles were not influenced by the relative lower of external loading during CMJ
Effect of Hawthorn on Drosophila Melanogaster Antioxidant-Related Gene Expression
Purpose: To study the effects of various doses of hawthorn extract on Drosophila lifespan, antioxidant enzyme activity and expression of antioxidant-related regulation genes.Methods: Experiments with Drosophila as an animal model were conducted. The effects of hawthorn on Drosophila melanogaster antioxidant related gene expression were investigated by lifespan tests of Drosophila, antioxidant enzyme activity assay of Drosophila, and mRNA expression of antioxidant genes by real time-PCR assay.Results: The results indicate that hawthorn extract prolonged the life span of Drosophila, with 50 % survival time of 0.8 and 4 mg/mL groups being increased from 52 days (control) to 56 and 62 days, respectively. Addition of 0.8 mg/mL hawthorn extract increased CuZn-SOD enzyme activity significantly (p < 0.05); the 4 mg/mL extract significantly increased CuZn-SOD enzyme (p < 0.01) and CAT enzyme activity (p < 0.05), but decreased MDA levels. Real time-PCR results show that the 4 mg/mL extract significantly improved the expression levels of CuZn-SOD and CAT mRNA (p < 0.05); on the other hand, both extract concentrations improved PHGSH-Px mRNA level significantly compared with that of control group (p < 0.05).Conclusion: The antioxidant activity of hawthorn in vivo may be achieved by increasing endogenous antioxidant enzymes.Keywords: Drosophila melanogaster, Hawthorn, Lifespan, Enzyme, Gene expression, Phospholipid hydroperoxide glutathione peroxidase, Superoxide dismutase, Catalas
Effects of natto extract on endothelial injury in a rat model
Vascular endothelial damage has been found to be associated with thrombus formation, which is considered to be a risk factor for cardiovascular disease. A diet of natto leads to a low prevalence of cardiovascular disease. The aim of the present study was to investigate the effects of natto extract on vascular endothelia damage with exposure to laser irradiation. Endothelial damage both in vitro and in vivo was induced by irradiation of rose bengal using a DPSS green laser. Cell viability was determined by MTS assay, and the intimal thickening was verified by a histological approach. The antioxidant content of natto extract was determined for the free radical scavenging activity. Endothelial cells were injured in the presence of rose bengal irradiated in a dose-dependent manner. Natto extract exhibits high levels of antioxidant activity compared with purified natto kinase. Apoptosis of laser-injured endothelial cells was significantly reduced in the presence of natto extract. Both the natto extract and natto kinase suppressed intimal thickening in rats with endothelial injury. The present findings suggest that natto extract suppresses vessel thickening as a synergic effect attributed to its antioxidant and anti-apoptosis properties
Evaluation of unilateral cage-instrumented fixation for lumbar spine
<p>Abstract</p> <p>Background</p> <p>To investigate how unilateral cage-instrumented posterior lumbar interbody fusion (PLIF) affects the three-dimensional flexibility in degenerative disc disease by comparing the biomechanical characteristics of unilateral and bilateral cage-instrumented PLIF.</p> <p>Methods</p> <p>Twelve motion segments in sheep lumbar spine specimens were tested for flexion, extension, axial rotation, and lateral bending by nondestructive flexibility test method using a nonconstrained testing apparatus. The specimens were divided into two equal groups. Group 1 received unilateral procedures while group 2 received bilateral procedures. Laminectomy, facectomy, discectomy, cage insertion and transpedicle screw insertion were performed sequentially after testing the intact status. Changes in range of motion (ROM) and neutral zone (NZ) were compared between unilateral and bilateral cage-instrumented PLIF.</p> <p>Results</p> <p>Both ROM and NZ, unilateral cage-instrumented PLIF and bilateral cage-instrumented PLIF, transpedicle screw insertion procedure did not revealed a significant difference between flexion-extension, lateral bending and axial rotation direction except the ROM in the axial rotation. The bilateral group's ROM (-1.7 ± 0. 8) of axial rotation was decreased significantly after transpedicle screw insertion procedure in comparison with the unilateral group (-0.2 ± 0.1). In the unilateral cage-instrumented PLIF group, the transpedicle screw insertion procedure did not demonstrate a significant difference between right and left side in the lateral bending and axial rotation direction.</p> <p>Conclusions</p> <p>Based on the results of this study, unilateral cage-instrumented PLIF and bilateral cage-instrumented PLIF have similar stability after transpedicle screw fixation in the sheep spine model. The unilateral approach can substantially reduce exposure requirements. It also offers the biomechanics advantage of construction using anterior column support combined with pedicle screws just as the bilateral cage-instrumented group. The unpleasant effect of couple motion resulting from inherent asymmetry was absent in the unilateral group.</p
Loading effects of anterior cervical spine fusion on adjacent segments
AbstractAdjacent segment degeneration typically follows anterior cervical spine fusion. However, the primary cause of adjacent segment degeneration remains unknown. Therefore, in order to identify the loading effects that cause adjacent segment degeneration, this study examined the loading effects to superior segments adjacent to fused bone following anterior cervical spine fusion. The C3–C6 cervical spine segments of 12 sheep were examined. Specimens were divided into the following groups: intact spine (group 1); and C5–C6 segments that were fused via cage-instrumented plate fixation (group 2). Specimens were cycled between 20° flexion and 15° extension with a displacement control of 1°/second. The tested parameters included the range of motion (ROM) of each segment, torque and strain on both the body and inferior articular process at the superior segments (C3–C4) adjacent to the fused bone, and the position of the neutral axis of stress at under 20° flexion and 15° extension. Under flexion and Group 2, torque, ROM, and strain on both the bodies and facets of superior segments adjacent to the fused bone were higher than those of Group 1. Under extension and Group 2, ROM for the fused segment was less than that of Group 1; torque, ROM, and stress on both the bodies and facets of superior segments adjacent to the fused bone were higher than those of Group 1. These analytical results indicate that the muscles and ligaments require greater force to achieve cervical motion than the intact spine following anterior cervical spine fusion. In addition, ROM and stress on the bodies and facets of the joint segments adjacent to the fused bone were significantly increased. Under flexion, the neutral axis of the stress on the adjacent segment moved backward, and the stress on the bodies of the segments adjacent to the fused bone increased. These comparative results indicate that increased stress on the adjacent segments is caused by stress-shielding effects. Furthermore, increased stress and ROM of the adjacent segments after long-term bone fusion may accelerate degeneration in adjacent segment
SeaEval for Multilingual Foundation Models: From Cross-Lingual Alignment to Cultural Reasoning
We present SeaEval, a benchmark for multilingual foundation models. In
addition to characterizing how these models understand and reason with natural
language, we also investigate how well they comprehend cultural practices,
nuances, and values. Alongside standard accuracy metrics, we investigate the
brittleness of foundation models in the dimensions of semantics and
multilinguality. Our analyses span both open-sourced and closed models, leading
to empirical results across classic NLP tasks, reasoning, and cultural
comprehension. Key findings indicate (1) Most models exhibit varied behavior
when given paraphrased instructions. (2) Many models still suffer from exposure
bias (e.g., positional bias, majority label bias). (3) For questions rooted in
factual, scientific, and commonsense knowledge, consistent responses are
expected across multilingual queries that are semantically equivalent. Yet,
most models surprisingly demonstrate inconsistent performance on these queries.
(4) Multilingually-trained models have not attained "balanced multilingual"
capabilities. Our endeavors underscore the need for more generalizable semantic
representations and enhanced multilingual contextualization. SeaEval can serve
as a launchpad for more thorough investigations and evaluations for
multilingual and multicultural scenarios.Comment: 15 pages, 7 figure
High energy properties of PKS 1830-211
We report on an analysis of X- and -ray observations of PKS 1830-211,
based on the long-term campaigns carried out by \emph{INTEGRAL} and COMPTEL.
The \emph{INTEGRAL} data currently available present a significance
detection in the 20-100 keV band, while the COMPTEL 6-years data provide a
significance detection in the 1-3 MeV energy band. At hard X-rays,
\emph{INTEGRAL} and supplementary \emph{SWIFT} observations show flux
variability on timescales of months. At -rays, the source shows
persistent emission over years. The hard X-ray spectrum is well represented by
a power-law model, with in the 20-250 keV band. This photon
index is well consistent with the previous report of obtained
at keV from the best fit of \emph{XMM-Newton} data with a broken
power law model. The joint \emph{XMM-Newton}/\emph{INTEGRAL} spectrum presented
here is then fit with a broken power-law model and the parameters are refined
compared to the previous. The results show the photon index changes from to at a break energy keV. At MeV energies, the
spectrum softens to . These results, together with the EGRET
measurement at MeV, constitute a broad-band spectrum containing the
peak of the power output at MeV energies, similar to most high-luminosity
-ray blazars. The measured spectral characterstics are then discussed
in the framework of the gravitational lens effects.Comment: accepted for Ap
Phase-resolved spectral analysis of 4U 1901+03 during its outburst
The high mass X-ray binary 4U 1901+03 was reported to have the pulse profile
evolving with the X-ray luminosity and energy during its outburst in
February-July 2003: the pulse peak changed from double to single along with the
decreasing luminosity. We have carried out a detailed analysis on the
contemporary phase-resolved energy spectrum of 4U 1901+03 as observed by Rossi
X-ray Timing Explorer (RXTE). We find that, both the continuum and the pulse
spectra are phase dependent. The optical depth derived from the pulse spectrum
is in general larger than that from the continuum. Fe Ka emission line is only
detected in the spectrum of the continuum and is missing in the pulse spectrum.
This suggests an origin of Fe emission from the accretion disk but not the
surface of the neutron star.Comment: 18 pages, 8 figures, accepted by Ap
- …