Abstract
The donor–acceptor (D-A) type of conjugated polymers has emerged as the paradigm of the third generation of electronically conducting polymers demonstrating improved infrared activity and ...intrinsic electronic conductivity. Judicious selection of donor (D) and acceptor (A) monomers for copolymerization can further fine-tune these properties. Notably, for such refinement, natural compounds provide many conjugated molecules with various functional groups. Berberine cation (Ber
+
) found in
Coscinium fenestratum
has extensive conjugation and contains both an electron deficient isoquinolium A moiety and electron-rich D-type methylenedioxy and methoxy groups. The incorporation of natural products in electronic materials is a novel area of research which opens a wide scope for future electronic and optoelectronic devices. Investigation of their fundamental properties via computer simulations is therefore important. In this study, quantum chemical calculations are performed using density functional theory (DFT) to investigate the electronic and optical properties of oligomers of Ber
+
and 3,4-ethylenedioxythiophene (EDOT) and to explore the possibilities for homo-polymerization of Ber
+
and its copolymerization with EDOT. It has been revealed that homo-polymerization is not favoured but copolymerization with EDOT is possible. As such, Ber
+
was copolymerized with EDOT and the copolymers formed by electro-polymerization are extensively characterised and the D-A behaviour of the copolymers verified. Furthermore, the theoretical predictions have been compared with the experimental data.
This paper reports the effect of using a mixed iodide salt system with two dissimilar cations to enhance the efficiency of dye-sensitized solar cells made with polyvinylidenefluoride (PVdF) based gel ...electrolyte. Instead of a single iodide salt, a mixture of potassium iodide (KI) with a small K+ cation and tetrapropylammonium iodide (Pr4NI) with a bulky Pr4N+ cation were used to provide the required iodide ion conductivity. Solar cells of configuration FTO/TiO2/Dye/electrolyte/Pt/FTO were fabricated using a mesoporous TiO2 electrode sensitized with a Ruthenium dye (N719). With identical electrolyte compositions, the cells with KI and Pr4NI alone gave efficiencies of 2.37% and 2.90% respectively. The cell with the mixed iodide system, KI:Pr4NI = 16.6:83.4 (% weight ratio), however, showed an enhanced efficiency of 3.92% with a short circuit current density of 9.16 mA cm−2, open circuit voltage of 674.4 mV and a fill factor of 63.4%.
•Efficiency enhancement in a dye-sensitized solar cell with mixed cations is reported.•KI and Pr4NI provided the small and large mixed cations in the PVdF electrolyte used.•16.6 KI: 83.4 Pr4NI (wt.%) mixture produced maximum Jsc and 3.92% efficiency.•K+ and Pr4N+ mixed cations produced 35% maximum efficiency enhancement.
Recent rainfall trend over Sri Lanka (1987–2017) Nisansala, W. D. S.; Abeysingha, N. S.; Islam, Adlul ...
International journal of climatology,
15 June 2020, Letnik:
40, Številka:
7
Journal Article
Recenzirano
Rainfall trend analysis provides useful information for effective planning, and management of water resources, and gives an insight into climate change of a region. This study investigates trends in ...annual and seasonal rainfall over Sri Lanka using an Innovative Trend Analysis (ITA) and Mann–Kendall (MK) test with Sen's slope estimator. The MK test showed increasing trends in annual rainfall at 24 stations (65%) with five stations showing significant increasing trend. Annual rainfall at 13 locations (35%) showed decreasing trend, but none were significant (p < .05). ITA results for annual rainfall showed increasing trend at 67% stations while 33% stations showed decreasing trend. MK test results for seasonal rainfall indicated increasing trend at 76, 51, 32, and 86% of stations during First Inter‐Monsoon (FIM), Second Inter‐Monsoon (SIM), South West Monsoon (SWM), and North East Monsoon (NEM) seasons, respectively. Seasonal analysis of rainfall trend using ITA method showed increasing trend in 81, 70, 32, and 65% stations during FIM, SIM, SWM, and NEM, respectively. ITA and MK tests exhibited similar trend results for 80% of the stations. Moreover, Spearman's rho correlation coefficient between ITA and MK test trends showed significant (p < .05) positive correlation. In general, eastern, south eastern, north and north central regions of the country showed increasing rainfall trend over the last 31 years (1987–2017) while western, part of north western and central part of the country indicated a decreasing rainfall trend during the same period.
Trends of the annual and seasonal precipitation of Sri Lanka were analysed using data recorded at 37 stations during the recent 31 years with the use of two different trend tests, namely, the Mann–Kendal and Innovative Trend Analysis (ITA) methods.
As shown in the figure, annual rainfall in dry zone, particularly in the eastern area, has an increasing trend in the recent 31 years.
ITA results of annual rainfall over Sri Lanka showed that high and medium rainfall values have increasing trend in those stations where rainfall trend is increasing.
Quasi-solid-state polymer electrolytes can be used in dye sensitized solar cells (DSSCs) in order to overcome various problems associated with liquid electrolytes. Prior to fabricating commercially ...viable solar cells, the efficiency of quasi solid state DSSCs needs to be improved. Using electrolytes with a binary iodide mixture is a novel technique used to obtain such efficiency enhancement. In this work we report both conductivity and solar cell performance enhancements due to incorporation of a mixture containing LiI and tetrahexylammonium iodide in a quasi-solid-state electrolyte. The conductivity of the electrolyte increases with added amounts of LiI and thus the highest conductivity, 3.15 × 10−3 S cm−1 at 25 °C, is obtained for the electrolyte 100 wt% LiI. The predominantly ionic behavior of the electrolytes was established from dc polarization measurements. The iodide ion conductivity, measured using iodine pellet electrodes decreased somewhat with increasing amount of LiI even though the overall conductivity increased. However, the highest efficiency was obtained for the DSSC containing a polymer electrolyte with Hex4N+I¯:LiI = 1:2 mass ratio. This cell had the largest short circuit current density of about 13 mA cm−2 and more than 4% overall energy conversion efficiency. The results thus show that electrolytes with Hex4N+I¯/LiI mixed iodide system show better DSSC performance than single iodide systems.
•DSSCs were fabricated by using a gel polymer electrolyte with mixed iodides system.•Incorporation of LiI into the electrolyte contributes to conductivity enhancement.•DSSC performance cannot directly be related to the conductivity of the electrolyte.•Results show that cations in the electrolyte have an influence on DSSC performance.•Quasi-sold-state DSSC prepared with the mixed iodide system showed 4.2% efficiency.
Lifestyle factors associated with hypertension (HT) in South Asian populations are relatively unknown. The objective of the current study was to investigate the prevalence rates of undiagnosed HT and ...factors associated with it in a cohort of males from the Central Province of Sri Lanka.
The study group consisted of 2462 males (mean age 31 years, range: 16-72 years) who underwent a routine medical examination at the National Transport Medical Institute, Kandy, Sri Lanka. Participants with previously diagnosed heart disease, diabetes, hypertension or other chronic illnesses were excluded from this study. Dietary and other lifestyle factors were studied using validated self-administered questionnaires. Body Mass Index (BMI) cut-off values for Asians were used to categorize the subjects according to weight status. The association of individual dietary and lifestyle patterns with HT was assessed by fitting into binary logistic regression models.
The mean systolic (SBP) and diastolic blood pressures (DBP) of the individuals were 125.9 mmHg and 80.5 mmHg, respectively. The prevalence rate of undiagnosed HT was 31.7%. Both SBP and DBP showed significant positive correlations with age, weight, BMI and waist circumference. After adjusting for potential confounders, HT was associated with older age (p = 0.001) and increased weight status (p < 0.001) with trends of association for level of education (p = 0.058). Level of income, alcohol consumption, sleeping hours, smoking, physical activity level, ethnic difference, consumption of fruits, fish, meat, dairy, sweets or fried snacks were not significantly associated with HT. Obese males were 92.1% odds ratio: 1.9 (1.4-2.7) more likely to be hypertensive compared to normal weight males.
Undiagnosed HT is prevalent at an alarming rate among adult males in the Central Province of Sri Lanka. Its association with age and BMI (weight status) highlights the importance of routine screening for HT as well as interventions targeted at reducing obesity to curb the rise of this modifiable cardiovascular disease risk factor.
The design of an industrial water treatment system using sorption is based on laboratory column tests. To verify the applicability of a column sorption system at industrial scale, it is necessary to ...determine the system's breakthrough time (BT) in a laboratory setting. In a laboratory column set-up, BT is referred to as the time taken by the adsorbate to appear at column outlet for the first time. This is when the mass transfer zone (MTZ), where the equilibrium sorption occurs, reaches the end of the sorbent bed. However, such laboratory set-up requires significant resources including laboratory space, time and multiple trials, which is the opposite to the batch experimental approach that is commonly used to assess efficiency of sorbents. This study identified batch sorption parameters that can be used to determine BT for a column sorption setting for three toxic heavy metals commonly found in industrial wastewater, namely, Pb2+, Cd2+ and Cu2+. The study conducted a comprehensive evaluation of the relationships between column BT and its key influential factors, namely, equilibrium sorption capacity (qe), pseudo second-order kinetic rate constant (k2) and initial sorption rate (h). The results revealed that BT can be better estimated using h compared to qe and k2. As such, a batch experiment which is more resource efficient could be undertaken for an initial estimation of the experimental BT of a column system. Moreover, a simulation model developed to replicate column sorption could demonstrate the behaviour of the breakthrough curve, which is a key to the selection and assessment of the performance of a sorbent in an adsorbent column. The estimation errors in qe and k2 were found to influence the simulation outcomes. Hence, it is necessary to further investigate the other factors that can potentially influence sorption behaviour.
Display omitted
•Transferability between batch and column sorption was investigated.•Breakthrough time (BT) for column sorption was determined using batch experiments.•Mathematical formulation of BT using sorption rate, capacity and kinetics.•BT can be better estimated using initial sorption rate.
Performance of dye-sensitized nano-crystalline TiO
2
thin film-based photo-electrochemical solar cells (PECSCs) containing gel polymer electrolytes is largely governed by the nature of the cation in ...the electrolyte. Dependence of the photovoltaic performance in these quasi-solid state PECSCs on the alkaline cation size has already been investigated for single cation iodide salt-based electrolytes. The present study reports the ionic conductivity dependence on the nature of alkaline cations (counterion) in a gel polymer electrolyte based on binary iodides. Polyacrylonitrile-based gel polymer electrolyte series containing binary iodide salts is prepared using one of the alkaline iodides (LiI, NaI, KI, RbI, and CsI) and tetrapropylammonium iodide (Pr
4
NI). All the electrolytes based on binary salts have shown conductivity enhancement compared to their single cation counterparts. When combined with Pr
4
NI, each of the Li
+
, Na
+
, K
+
, Rb
+
, and Cs
+
cation containing iodide salts incorporated in the gel electrolytes has shown a room temperature conductivity enhancement of 85.59, 12.03, 12.71, 20.77, and 15.36%, respectively. The conductivities of gel electrolytes containing binary iodide systems with Pr
4
NI and KI/RbI/CsI are higher and have shown values of 3.28, 3.43, and 3.23 mS cm
−1
, respectively at room temperature. The influence of the nature of counterions on the performance of quasi-solid state dye-sensitized solar cells is investigated by assembling two series of cells. All the binary cationic solar cells have shown more or less enhancements of open circuit voltage, short circuit current density, fill factor, and efficiency compared to their single cation counterparts. This work highlights the importance of employing binary cations (a large and a small) in electrolytes intended for quasi-solid state solar cells. The percentage of energy conversion efficiency enhancement shown for the PECSCs made with electrolytes containing Pr
4
NI along with Li
+
, Na
+
, K
+
, Rb
+
, and Cs
+
iodides is 260.27, 133.65, 65.27, 25.32, and 8.36%, respectively. The highest efficiency of 4.93% is shown by the solar cell containing KI and Pr
4
NI. However, the highest enhancements of ionic conductivity as well as the energy conversion efficiency were exhibited by the PECSC made with Li
+
-containing binary cationic electrolyte.
Obesity has become a global epidemic. The prevalence of obesity has also increased in the South Asian region in the last decade. However, dietary and lifestyle factors associated with obesity in Sri ...Lankan adults are unclear. The objective of the current study was to investigate the association of dietary and lifestyle patterns with overweight and obesity in a cohort of males from the Central Province of Sri Lanka.
A total of 2469 males aged between 16 and 72 years (Formula: see text) were included in the study. The sample comprised individuals who presented for a routine medical examination at the National Transport Medical Institute, Kandy, Sri Lanka. The Body Mass Index (BMI) cutoff values for Asians were used to categorize the participants into four groups as underweight, normal weight, overweight or obese. The data on dietary and lifestyle patterns such as level of physical activity, smoking, alcohol consumption, sleeping hours and other socio demographic data were obtained using validated self-administered questionnaires. Multinomial logistic regression model was fitted to assess the associations of individual lifestyle patterns with overweight and obesity.
The mean BMI of the study group was 22.7 kg m
and prevalence rates of overweight and obesity were 31.8 and 12.3%, respectively. Mean waist circumference of the participants was 78.6 cm with 17.1% of them being centrally obese. After adjusting for potential confounders, weight status was associated with older age (P < 0.0001), ethnicity (P = 0.0033) and higher income (P = 0.0006). While higher physical activity showed a trend for being associated with lower odds of being obese (odds ratio: 0.898 - confidence interval: 0.744-1.084), alcohol intake, consumption of fruits, level of education, sleeping hours, smoking, consumption of fish, meat, dairy, sweets or fried snacks were not significantly associated with the weight status.
The high prevalence rates of overweight and obesity in working-age males is a threatening sign for Sri Lanka. Since the prevalence rate is higher in certain ethnic groups and higher-income groups, targeted interventions for these groups may be necessary.
Activating mutations in the receptor tyrosine kinase KIT, most notably KIT D816V, are commonly observed in patients with systemic mastocytosis. Thus, inhibition of KIT has been a major focus for ...treatment of this disorder. Here we investigated a novel approach to such inhibition. Utilizing rational drug design, we targeted the switch pocket (SP) of KIT, which regulates its catalytic conformation. Two SP inhibitors thus identified, DP-2976 and DP-4851, were examined for effects on neoplastic mast cell proliferation and mast cell activation. Autophosphorylation of both wild-type and, where also examined, KIT D816V activation was blocked by these compounds in transfected 293T cells, HMC 1.1 and 1.2 human mast cell lines, and in CD34(+)-derived human mast cells activated by stem cell factor (SCF). Both inhibitors induced apoptosis in the neoplastic mast cell lines and reduced survival of primary bone marrow mast cells from patients with mastocytosis. Moreover, the SP inhibitors more selectively blocked SCF potentiation of FcɛRI-mediated degranulation. Overall, SP inhibitors represent an innovative mechanism of KIT inhibition whose dual suppression of KIT D816V neoplastic mast cell proliferation and SCF-enhanced mast cell activation may provide significant therapeutic benefits.
Polyacrylonitrile-based gel electrolytes were prepared using tetrapropylammonium iodide salt for dye-sensitized solar cells (DSSCs). The optimized gel electrolyte exhibited an ionic conductivity of ...2.6 mS cm
−1
at 25 °C and the DSSC fabricated with this gel electrolyte showed open-circuit voltage, short-circuit current density, fill factor, and efficiency of 0.71 V, 11.8 mA, 51, and 4.2 %, respectively, under one sun irradiation. The efficiency of the cell increases increased with decreasing solar irradiance achieving 10 % efficiency and 80 % fill factor at 3 mW cm
−2
a low irradiance value of 3 mW cm
−2
. Lower efficiencies at higher intensities were attributed to transport limitation of the redox mediators at high irradiation intensities. This work suggests that quasi-solid state DSSCs can reach efficiencies close to that of liquid electrolyte-based cells at low irradiance levels. The results open up new vistas on efficiency improvement in DSSCs by optical manipulation and control of DSSCs.
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