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Kinetics and mechanism of alkaline hydrolysis of N-(o aminophenyl)phthalimide in the presence and absence of cationic micelles and sodium salts of aliphatic acids
No full textPseudo first-order rate constants, kobs, for the alkaline hydrolysis of N-(o-aminophenyl) phthalimide, obtained at constant [CTABr]T (total concentration of cetyltrimethylammonium bromide) and varying concentrations of inert salt MX (MX = sodium formate, sodium acetate, sodium propanoate, sodium butyrate, sodium valerate and sodium hexanoate) follow the relationship: kobs (K0 + θKX/S [MX])/(1 + KX/S [MX]) where θ and KX/S are empirical constants and S = HO-. The values of KX/S for each aliphatic acid decrease with an increase in [CTABr]T. This relationship gives an empirical constant whose magnitude is the measure of the ability of an ion, X- X/S, to expel another counterion S-, from the cationic micellar surface to the bulk aqueous phase. The values of the empirical constant, K X/S, are used to derive the ion exchange constant, KBr X
Factors Associated with Medical Doctors' Intentions to Discriminate Against Transgender Patients in Kuala Lumpur, Malaysia
No full textPurpose: Transgender people are frequent targets of discrimination. Discrimination against transgender people in the context of healthcare can lead to poor health outcomes and facilitate the growth of health disparities. This study explores factors associated with medical doctors' intentions to discriminate against transgender people in Malaysia. Methods: A total of 436 physicians at two major university medical centers in Kuala Lumpur, Malaysia, completed an online survey. Sociodemographic characteristics, stigma-related constructs, and intentions to discriminate against transgender people were measured. Bivariate and multivariate linear regression were used to evaluate independent covariates of discrimination intent. Results: Medical doctors who felt more fearful of transgender people and more personal shame associated with transgender people expressed greater intention to discriminate against transgender people, whereas doctors who endorsed the belief that transgender people deserve good care reported lower discrimination intent. Stigma-related constructs accounted for 42% of the variance and 8% was accounted for by sociodemographic characteristics. Conclusions: Constructs associated with transgender stigma play an important role in medical doctors' intentions to discriminate against transgender patients. Development of interventions to improve medical doctors' knowledge about and attitudes toward transgender people are necessary to reduce discriminatory intent in healthcare settings
Circulating MicroRNAs in Young Patients with Acute Coronary Syndrome
No full textCirculating microRNAs (miRNAs) hold great potential as novel diagnostic markers for acute coronary syndrome (ACS). This study sought to identify plasma miRNAs that are differentially expressed in young ACS patients (mean age of 38.5 ± 4.3 years) and evaluate their diagnostic potentials. Small RNA sequencing (sRNA-seq) was used to profile plasma miRNAs. Discriminatory power of the miRNAs was determined using receiver operating characteristic (ROC) analysis. Thirteen up-regulated and 16 down-regulated miRNAs were identified in young ACS patients. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) validation showed miR-183-5p was significantly up-regulated (8-fold) in ACS patients with non-ST-segment elevated myocardial infarction (NSTEMI) whereas miR-134-5p, miR-15a-5p, and let-7i-5p were significantly down-regulated (5-fold, 7-fold and 3.5-fold, respectively) in patients with ST-segment elevated myocardial infarction (STEMI), compared to the healthy controls. MiR-183-5p had a high discriminatory power to differentiate NSTEMI patients from healthy controls (area under the curve (AUC) of ROC = 0.917). The discriminatory power for STEMI patients was highest with let-7i-5p (AUC = 0.833) followed by miR-134-5p and miR-15a-5p and this further improved (AUC = 0.935) with the three miRNAs combination. Plasma miR-183-5p, miR-134-5p, miR-15a-5p and let-7i-5p are deregulated in STEMI and NSTEMI and could be potentially used to discriminate the two ACS forms
Physicochemical properties of acylated low molecular weight chitosans
No full textHydrophobically modified chitosans are developing progressively in drug delivery system due to their ability to encapsulate drugs with the amphiphilic architecture. In this study, low molecular weight chitosans were acylated with hexanoyl (LCh-C6), octanoyl (LCh-C8) and decanoyl (LCh-C10) groups to study their physicochemical properties for the potential as drug carriers. Both fourier transform-infrared (FT-IR) and 1H NMR (Nuclear Magnetic Resonance) analyses confirmed the successful acylation of alkyl chains onto chitosan backbone. LCh-C6, LCh-C8 and LCh-C10 showed the similar value of critical aggregation concentration around 40 µg L−1. The average particle size of LCh-C6, LCh-C8 and LCh-C10 obtained by dynamic light scattering measurement was compared to by mean of transmission electron microscopy. Acylated low molecular weight chitosans (LChA) showed higher encapsulation efficiency and drug loading toward hydrophobic salicylic acid as compared to hydrophilic caffeine, as well as exhibited higher increment in particle size due to possible inner volume expansion. Both long alkyl chains and high degree of substitution contributed to better drug encapsulation of LChA
Extraction and recovery of phytochemical components and antioxidative properties in fruit parts of Dacryodes rostrata influenced by different solvents
No full textThis study investigated the recovery of phytochemical antioxidants in Dacryodes rostrata fruit using different extraction solvents. The effects of solvent of varying polarities with sequential extraction method on the recovery of phenolics, flavonoids, carotenoids and anthocyanins from different parts of the fruit (seed, pulp and peel) were determined. Their antioxidant activities were further determined using DPPH radical, ferric reducing antioxidant power (FRAP), hydroxyl radical scavenging, superoxide anion radical scavenging and phosphomolybdenum method. Dacryodes Rostrata seed had the highest total phenolic content with 50% ethanol as the most efficient extraction solvent. The highest total flavonoid content was obtained in ethyl acetate extract of fruit pulp, whereas peel extracted with hexane and 50% ethanol was the highest in total carotenoid content and total anthocyanin content, respectively. The seed extracted with 50% ethanol exhibited the strongest DPPH radical scavenging activity. Iron chelating activity measured by FRAP assay was the best in seed extracts, particularly in those polar extracts derived from water and 50% ethanol. Antioxidant activities of 50% ethanol extract of D. rostrata seed was the highest when determined by FRAP and phosphomolydenum assays. However, the influence of extraction solvents is not distinctly shown by hydroxyl radical and superoxide anion radical scavenging activities. This is the first report on the effect of various extraction solvents on the recovery of phytochemicals in D. rostrata fruit parts and the seed of D. rostrata is a potential source of polar antioxidants
Improved Differential Evolution-Based MPPT Algorithm Using SEPIC for PV Systems Under Partial Shading Conditions and Load Variation
No full textPhotovoltaic arrays subject to partial shading conditions have more than one maximum power point (MPP), and conventional algorithms are unable to track the global maximum power point (GMPP) accurately. Thus, an improved global search space differential evolution algorithm for tracking the GMPP is introduced in this paper. The main contribution of the proposed algorithm are the following: capability in tracking GMPP and faster respond against load variation; optimization algorithm can search for the GMPP within a larger operating region as it is implemented by using a single-ended primary-inductor converter; and easy tuning as less parameter has to be set in the algorithm. The proposed system is first simulated in PSIM to ensure its capability. The feasibility of the approach is validated through physical implementation and experimentation. Results demonstrate that the proposed algorithm has the capability to track the GMPP within 2 s with an accuracy of 99% and respond to load variation within 0.1 s
Impact of Partial Shading on the P-V Characteristics and the Maximum Power of a Photovoltaic String
No full textA photovoltaic system is highly susceptible to partial shading. Based on the functionality of a photovoltaic system that relies on solar irradiance to generate electrical power, it is tacitly assumed that the maximum power of a partially shaded photovoltaic system always decreases as the shading heaviness increases. However, the literature has reported that this might not be the case. The maximum power of a partially shaded photovoltaic system under a fixed configuration and partial shading pattern can be highly insusceptible to shading heaviness when a certain critical point is met. This paper presents an investigation of the impact of partial shading and the critical point that reduce the susceptibility of shading heaviness. Photovoltaic string formed by series-connected photovoltaic modules is used in this research. The investigation of the P-V characteristic curve under different numbers of shaded modules and shading heaviness suggests that the photovoltaic string becomes insusceptible to shading heaviness when the shaded modules irradiance reaches a certain critical point. The critical point can vary based on the number of the shaded modules. The formulated equation in this research contributes to determining the critical point for different photovoltaic string sizes and numbers of shaded modules in the photovoltaic string
Design and implementation of a non-invasive real-time microwave sensor for assessing water hardness in heat exchangers
No full textA non-invasive-monitoring of concentration and dielectric properties of calcium hardness in heat exchanger cooling water was conducted with a 2.5 GHz microwave cavity resonator designed and fabricated locally for the experiment. The principle of electric dipole moment theories were used to analyse the sample solution that occurs as a function of calcium ion content. Artificial difference of water hardness was prepared by mixing CaCl2 in deionised water. The sample was centrally positioned in the electric field of the TM010 mode of a resonant cylindrical cavity. COMSOL simulation package was used to compare and validate the experimental cavity resonator frequency. Transmission signal (S21) measurements via vector network analyser at different concentrations were observed a linear relationship in amplitude with different frequency changes. In addition, calcium absorption provides a first-order change in material polarisation (i.e. real permittivity), and second-order transitions associated dielectric losses (i.e. imaginary permittivity). These research findings introduce a novel technique of real-time monitoring of water hardness concentration by using non-invasive microwave sensor
Immobilisation of hydroxyapatite-collagen on polydopamine grafted stainless steel 316L: Coating adhesion and in vitro cells evaluation
No full textThe utilisation of hydroxyapatite and collagen as bioactive coating materials could enhance cells attachment, proliferation and osseointegration. However, most methods to form crystal hydroxyapatite coating do not allow the incorporation of polymer/organic compound due to production phase of high sintering temperature. In this study, a polydopamine film was used as an intermediate layer to immobilise hydroxyapatite-collagen without the introduction of high sintering temperature. The surface roughness, coating adhesion, bioactivity and osteoblast attachment on the hydroxyapatite-collagen coating were assessed as these properties remains unknown on the polydopamine grafted film. The coating was developed by grafting stainless steel 316L disks with a polydopamine film. Collagen type I fibres were then immobilised on the grafted film, followed by the biomineralisation of hydroxyapatite. The surface roughness and coating adhesion analyses were later performed by using AFM instrument. An Alamar Blue assay was used to determine the cytotoxicity of the coating, while an alkaline phosphatase activity test was conducted to evaluate the osteogenic differentiation of human fetal osteoblasts on the coating. Finally, the morphology of cells attachment on the coating was visualised under FESEM. The highest RMS roughness and coating adhesion were observed on the hydroxyapatite-collagen coating (hydroxyapatite-coll-dopa). The hydroxyapatite-coll-dopa coating was non-toxic to the osteoblast cells with greater cells proliferation, greater level of alkaline phosphate production and more cells attachment. These results indicate that the immobilisation of hydroxyapatite and collagen using an intermediate polydopamine is identical to enhance coating adhesion, osteoblast cells attachment, proliferation and differentiation, and thus could be implemented as a coating material on orthopaedic and dental implants
Risk of Preeclampsia and Pregnancy Complications in Women With a History of Acute Kidney Injury
No full textAn episode of clinically recovered acute kidney injury (r-AKI) has been identified as a risk factor for future hypertension and cardiovascular disease. Our objective was to assess whether r-AKI was associated with future preeclampsia and other adverse pregnancy outcomes and to identify whether severity of AKI or time interval between AKI and pregnancy was associated with pregnancy complications. We conducted a retrospective cohort study of women who delivered infants between 1998 and 2016 at Massachusetts General Hospital. AKI was defined using the 2012 Kidney Disease Improving Global Outcomes laboratory criteria with subsequent clinical recovery (estimate glomerular filtration rate, >90 mL/min per 1.73 m2 before conception). AKI was further classified by severity (Kidney Disease Improving Global Outcomes stages 1-3) and time interval between AKI episode and the start of pregnancy. Women with r-AKI had an increased rate of preeclampsia compared with women without previous r-AKI (22% versus 9%; P<0.001). Infants of women with r-AKI were born earlier (gestational age, 38.2±3.0 versus 39.0±2.2 weeks; P<0.001) and were more likely to be small for gestational age (9% versus 5%; P=0.002). Increasing severity of r-AKI was associated with increased risk of preeclampsia for stages 2 and 3 AKI (adjusted odds ratio, 3.5; 95% confidence interval, 2.1-5.7 and adjusted odds ratio, 6.5; 95% confidence interval, 3.5-12.0, respectively), but not for stage 1 (adjusted odds ratio, 1.7; 95% confidence interval, 0.9-3.2). A history of AKI before pregnancy, despite apparent full recovery, was associated with increased risk of pregnancy complications. Severity and timing of the AKI episode modified the risk