19672 research outputs found
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Non‐native mangroves support carbon storage, sediment carbon burial, and accretion of coastal ecosystems
No full textMangrove forests play an important role in climate change adaptation and mitigation by maintaining coastline elevations relative to sea level rise, protecting coastal infrastructure from storm damage, and storing substantial quantities of carbon (C) in live and detrital pools. Determining the efficacy of mangroves in achieving climate goals can be complicated by difficulty in quantifying C inputs (i.e., differentiating newer inputs from younger trees from older residual C pools), and mitigation assessments rarely consider potential offsets to CO2 storage by methane (CH4) production in mangrove sediments. The establishment of non-native Rhizophora mangle along Hawaiian coastlines over the last century offers an opportunity to examine the role mangroves play in climate mitigation and adaptation both globally and locally as novel ecosystems. We quantified total ecosystem C storage, sedimentation, accretion, sediment organic C burial and CH4 emissions from ~70 year old R. mangle stands and adjacent uninvaded mudflats. Ecosystem C stocks of mangrove stands exceeded mudflats by 434 ± 33 Mg C/ha, and mangrove establishment increased average coastal accretion by 460%. Sediment organic C burial increased 10-fold (to 4.5 Mg C ha−1 year−1), double the global mean for old growth mangrove forests, suggesting that C accumulation from younger trees may occur faster than previously thought, with implications for mangrove restoration. Simulations indicate that increased CH4 emissions from sediments offset ecosystem CO2 storage by only 2%–4%, equivalent to 30–60 Mg CO2-eq/ha over mangrove lifetime (100 year sustained global warming potential). Results highlight the importance of mangroves as novel systems that can rapidly accumulate C, have a net positive atmospheric greenhouse gas removal effect, and support shoreline accretion rates that outpace current sea level rise. Sequestration potential of novel mangrove forests should be taken into account when considering their removal or management, especially in the context of climate mitigation goals. © 2019 John Wiley & Sons Lt
Modeling of the nanocrystalline-sized mesoporous zinc oxide catalyst using an artificial neural network for efficient biodiesel production
No full textThe sulfonated mesoporous zinc oxide catalyst (SO 3 H–ZnO) was hydrothermally fabricated and functionalized by sulfonation to catalyze the palm fatty acid distillate (PFAD) to esters. The effect of different reaction parameters including reaction time, reaction temperature, metal ratio, and calcination temperature was modeled by artificial neural networks (ANNs) to find out the possible relative optimum conditions of the synthesized mesoporous SO 3 H–ZnO catalyst for the prediction of the nanocrystalline size. Under the optimized conditions of calcine temperature 700 °C, 18 min reaction time, 160 °C reaction temperature, and 4 mmol of Zn concentration predicted a 56.41 nm size of the mesoporous SO 3 H–ZnO catalyst. The acquired model was statistically verified for its utility. The quick propagation model with four nodes in the input layer, six nodes in the hidden layer and one node in the output layer (QP-4-6-1) was chosen as the final model due to its optimum statistical characteristics. Furthermore, the most effective parameter was found to be the zinc concentration whilst the reaction time demonstrated the least influence. The optimized mesoporous SO 3 H–ZnO catalyst was further utilized for esterification of PFAD, depicting a high fatty acid methyl ester yield (96.11%). It shows a valuable application for the conversion of discarded oils/fats containing high free fatty acids for the production of renewable green biodiesel. © 2018, © 2018 Taylor & Francis
The Multidimensional Poverty Measure among Malaysian Employee Provident Fund (EPF) Retirees
No full textAssessing poverty using multiple dimensions of deprivation provides a comprehensive picture of poverty. No one factor, like income or any monetary-based indicator is uniquely able to capture all of the factors that contribute to poverty. This study attempts to evaluate the multidimensional poverty measure among Malaysian Employee Provident Fund (EPF) retirees by using Alkire and Foster multidimensional poverty index to a set of deprivation dimensions. The findings indicate that around 84% of EPF retirees were identified as multidimensionally poor, meaning that they are in acute poverty. On average, poor retirees are deprived of 48% of weighted indicators. The results also show that women are more multidimensionally poor compared to men in terms of transportation, income, home ownership and education. The study discovered that Indian retirees are more deprived than other ethnic groups, followed by Malays. In this regard, it is necessary to strengthen current retirement savings institutions to reduce the impacts of the retirement crisis. The government needs to provide a Social Security system that rolls back the decline of Malaysian’s retirement savings. © 2018, Springer Nature B.V. and The International Society for Quality-of-Life Studies (ISQOLS)
Influence of laser power on bonding strength for low purity copper wire bonding technology
No full textThe drive for improving copper wire bonding has been more rampant with continued rise in gold prices. The global increase in gold price directly resulted the semiconductor packaging industry to rapidly replace gold as a medium of interconnection to copper wire. This is a cost effective solution for creating viable interconnections for integrated circuit packaging. However, through past research it is well known the hardness of copper wire is significantly higher compared to gold wire and the usage of copper poses various challenges in electronic packaging. These challenges, resulting from the usage of copper wire is primarily due to the high hardness of copper. Higher hardness of copper as compared to gold will require higher bonding force and ultrasonic energy to create bonding to the bond pads. The higher bonding force makes copper wire bonding unsuitable for fragile structures and possible damage to underlying circuitry. Past research has also exhibited the hardness of copper wire decreases as the purity levels increase, however the usage of higher purity copper wires in high volume manufacturing may significantly increase manufacturing cost. This research therefore investigates the application of laser assisted heating for enabling improved copper wire bonding strength and improved grain structures for low purity copper wires. Experimentations were conducted accordingly on three copper wire purity types, 99.9% purity (3 N), 99.99% purity (4 N) and 99.999% purity (5 N) copper wires, so as to evaluate the impact of laser assisted heating on various copper purity levels. The result of this study shows laser assisted heating is able to improve the bonding strength and improve the grain structure by means of reduced columnar grains for copper wires with lower purity levels. It is shown, higher as-bonded ball shear strengths with fewer columnar grains were observed when the highest laser heating intensity was applied. The results of this study can be helpful for integrated circuit packaging especially to enable interconnections using copper wire materials with lower purity levels, enabling a more cost effective manufacturing. © 2019 Elsevier B.V
Quantile range-based volatility measure for modelling and forecasting volatility using high frequency data
No full textVolatility of asset prices in financial market is not directly observable. Return-based models have been proposed to estimate the volatility using daily closing prices. Recently, many new range-based volatility measures were proposed to estimate the financial volatility. This paper proposes quantile Parkinson (QPK) measure to estimate daily volatility and to show how it can robustify the Parkinson (PK) measure in the presence of intraday extreme returns. Results from extensive simulation studies show that the QPK measure is more efficient than intraday (open-to-close) squared returns and PK measures in the presence of intraday extreme returns. To demonstrate the applicability of QPK measure, we analyse the daily Standard and Poor 500 index by fitting the QPK measure to the conditional autoregressive range (CARR) models. Results show that choosing a suitable interquantile level width for the QPK measure will reduce its variance and hence improve its efficiency. In addition, the QPK measure using asymmetric CARR model gives the best in-sample model fit based on Akaike information criterion and provides the best out-of-sample forecast based on root mean squared forecast error and other measures. Mincer Zarnowitz test is carried out to confirm the unbiasedness of the forecasted volatility. Different levels of value-at-risk and conditional value-at-risk forecasts are also provided and tested. © 2018 Elsevier Inc
Association between non‐alcoholic fatty liver disease evaluated by transient elastography with extracranial carotid atherosclerosis in a multiethnic Asian community
No full textBackground and Aim: There is not much data on the association between non-alcoholic fatty liver disease (NAFLD) and advanced fibrosis assessed using Fibroscan with carotid intima-media thickness (CIMT) in the general population. The objective of this study was to evaluate the association between NAFLD and advanced fibrosis, as diagnosed by Fibroscan, with an increased CIMT in the Malaysian population. Methods: A cross-sectional study of government officers and their family members attending a health screening at a public healthcare facility was conducted. All subjects underwent clinical evaluation, biochemical testing, anthropometry, ultrasound carotid Doppler, and Fibroscan examination. Results: Data for 251 subjects were analyzed (mean age 47.1 ± 12.4 years, 74.1% male). Prevalence of NAFLD and advanced fibrosis were 57.4 and 17.5%, respectively. Independent factors associated with NAFLD were waist circumference (odds ratio [OR] = 1.077, 95% confidence interval [CI] 1.038–1.118, P < 0.001) and serum alanine aminotransferase (ALT) (OR = 1.039, 95% CI 1.005–1.074, P = 0.024). Independent factors associated with advanced fibrosis were male gender (OR = 4.847, 95% CI 1.369–17.155, P = 0.014) and serum aspartate aminotransferase (AST) (OR = 1.057, 95% CI 1.003–1.113, P = 0.036). Prevalence of increased CIMT was 29.0%. Independent factor associated with increased CIMT was older age (OR = 1.146, 95% CI 1.067–1.231, P < 0.001). Of the subjects, 34.5% with NAFLD had increased CIMT compared to 19.1% of the subjects without NAFLD (P = 0.063). Advanced fibrosis was not associated with increased CIMT. Conclusions: Prevalence of NAFLD, advanced liver fibrosis, and increased CIMT were high. NAFLD and advanced liver fibrosis appeared not to be associated with increased CIMT. However, a larger sample size is needed to demonstrate whether there is any association. © 2018 The Authors. JGH Open: An open access journal of gastroenterology and hepatology published by Journal of Gastroenterology and Hepatology Foundation and John Wiley & Sons Australia, Ltd
The utility of Guillain‐Barré syndrome prognostic models in Malaysian patients
No full textGuillain-Barré syndrome (GBS) is an acute immune-mediated neuropathy that has variable disease course and outcome. The Erasmus GBS outcome score (EGOS), modified EGOS (mEGOS), and Erasmus GBS respiratory insufficiency score (EGRIS) are prognostic models designed to predict the functional outcome of GBS patients at 6 months (EGOS and mEGOS) and the need for mechanical ventilation within a week of admission (EGRIS). The models were primarily developed in the Dutch GBS population, and thus the usefulness of these models in other GBS cohorts is less clear. In the current study, we aimed to validate mEGOS, EGOS, and EGRIS in Malaysian GBS patients. A total of 107 patients with GBS and its variants were consecutively recruited. Patients with GBS and Miller Fisher syndrome (MFS) were analysed separately. In the GBS cohort, high mEGOS and EGOS scores were significantly correlated with poor outcome at 6 months (mEGOS on admission: r =.381, P =.005; mEGOS at day 7 of admission: r =.507, P <.001; EGOS: r =.484, P <.001). However, there were no significant correlations between mEGOS or EGOS and outcome in patients with MFS (mEGOS on admission: r =.152, P =.523; mEGOS at day 7 of admission: r =.008, P =.973; EGOS: r =.110; P =.644). The score of EGRIS for GBS patients with mechanical ventilation was significantly higher than those patients without mechanical ventilation (4 ± 2 vs 3 ± 1; P <.001). We conclude that mEGOS and EGOS are clinically useful and relevant to the Malaysian GBS population but not in patients with classic MFS. EGRIS could be used to predict the need for mechanical ventilation in our local GBS patients. © 2019 International Society of Travel Medicin
Pt, Pd and Cu metal-amidine coordination
No full textAmidines, R’NH-C(R)=NR’, as for the isoelectronic carboxylic acids, form a variety of compounds incorporating transition metals from lower to higher oxidation states. Many studies reveal that Platinum, palladium and copper metals are very active in bonding with amidine moieties. The novelty of work presented here resides in an unified approach that deals with the interpretation of various types of bonding modes shown by amidine moieties and particularly the most remarkable achievements in the design and development of platinum, palladium and copper (II) complexes of substituted amidines. Special emphasis has been focused on the identification of structural relationships for the complexes formed. © 2019 Editura Academiei Romane. All rights reserved
Theoretical Study on Passively Mode-Locked Fiber Lasers with Saturable Absorber
No full textIn this paper, passively mode-locked erbium-doped fiber lasers based on saturable absorber (SA) have been theoretically studied. The energetics and pulse properties for different fiber laser cavity configurations have been investigated and the effects of each component (active fiber, passive fiber, and SA) in the laser cavity have been studied. This numerical study takes into account the temporal change in the saturable absorption (dq/dt).The presented simulations could be highly useful for understanding, optimizing, and improving passively mode-locked fiber lasers with SA. © 2018, © 2018 Taylor & Francis