Spectrophotometric study of the charge transfer complexation of tranexamic acid with 7,7,8,8-tetracyanoquinodimethane

A simple, sensitive and accurate spectrophotometric method for the determination of tranexamic acid (TXA) has been developed. The method was based on the charge transfer reaction between TXA as n-electron donor and 7,7,8,8-tetracyanoquinodimethane (TCNQ) as π-acceptor resulting in highly coloured stable complex, which showed maximum absorption band at wavelength of 419 nm. The formation of such complex was also confirmed by infrared measurement. The stoichiometry of the complex was found to be 1:1 between donor and acceptor as determined by Job’s continuous variation method and straight line method. The thermodynamic parameters were calculated as association constant KCT of 5109 mol−1 and Gibbs free energy ΔG° of 22.22 kJ mol−1. Different variables affecting the CT reaction were carefully studied and optimized. At the optimum reaction conditions, Beer’s law was obeyed in a concentration range of 1-18 µg mL−1 of TXA using TCNQ reagent and the limit of detection was 0.2 µg mL−1. Different analytical parameters, namely molar absorptivity (ε), relative standard deviation, correlation coefficient, limit of detection, and Sandell sensitivity, were calculated. The developed method could be applied successfully for the determination of TXA in its pharmaceutical dosage forms with a good precision and accuracy compared to the official method. KEY WORDS: Tranexamic acid, 7,7,8,8-Tetracyanoquinodimethane, Charge transfer complex, Spectrophotometry Bull. Chem. Soc. Ethiop. 2014, 28(2), 187-194.DOI: http://dx.doi.org/10.4314/bcse.v28i2.

ESTIMATION THE PREFERENCE OF ECOTOURISM FOR GAOMEI WETLAND IN TAIWAN

Gaomei Wetland is not only the biggest grassy coastal wetland, but also a wild‐animal protecting area, located on the west‐central coast of Taiwan.Wetlands are considered as one of the most important natural resource, which offer a lot of benefits for human and other creatures. However, it is believed that over-intensive recreational activities in Gaomei Wetland should be responsible for serious damages on natural environment and ecosystem. This study takes Gaomei wetland as an example, and aims to estimate its landscape and ecological services values through Choice experiment. The results of this research showed that Gaomei landscape’s economic value is $2.06 million (USD) per year, and$1.54 million (USD) for its value of ecological services. These findings can help to bring up the awareness of natural resource preservation, and hopefully to keep Gaomei Wetland substantial. The results also indicated that visitors with undergraduate degree or above were willing to pay $6.43 (USD) per year for entry fee to enjoy sunset scenery in Gaomei wetland

Comorbid Mental Disorders in Anxiety Disorders: Genetic Aspects of Bipolar Disorders and of Ethnicity

Anxiety disorder (AD) is commonly comorbid with other mental illness. It could be a state or trait, controversially. Evidence for an association between alcoholism and anxiety has emerged from clinical studies of patients with alcoholism, and those of patients with anxiety disorders. Alcohol dependence (or abuse) as well as bipolar disorder (BP) is usually comorbid with anxiety disorder and/or depressive disorder, which often coexist and are difficult to distinguish from one another. However, in Han Chinese population, the comorbidity rate either with alcoholism or bipolar disorder was not reported as much high as reported in Caucasians, this finding of comorbidity between anxiety/depressive disorders and alcohol dependence (or abuse) or/and bipolar disorders, possibly at the genetic level, makes the differentiation of their categorical diagnoses in the association study vitally important

Qi standard metasurface for free-positioning and multi-device supportive wireless power transfer

Free-positioning and multi-user supportive wireless power transfer systems represent the next-generation technology for wireless charging under the Qi standard. Traditional approaches employ multiple transmitting coils and multi-channel driving circuits with active control algorithms to achieve these goals. However, these traditional approaches are significantly limited by cost, weight, and heating due to their relatively low efficiency. Here, we demonstrate an innovative approach by using a metasurface to achieve free-positioning and multi-user compatibility. The metasurface works as a passive device to reform the magnetic field and enables high-efficiency free-positioning wireless power transfer with only a single transmitting coil. It shows up to 4.6 times improvement in efficiency. The metasurface also increases the coverage area from around 5 cm by 5 cm with over 40% efficiency to around 10 cm by 10 cm with over 70% efficiency. We further show that the system can support multiple receivers. Besides increasing the overall efficiency, we demonstrate tuning the power division between the multiple receivers, enabling compensation of receivers of different sizes to achieve their desired power

Dimensional crossover of thermal conductance in graphene nanoribbons: A first-principles approach

First-principles density-functional calculations are performed to investigate the thermal transport properties in graphene nanoribbons (GNRs). The dimensional crossover of thermal conductance from one to two dimensions (2D) is clearly demonstrated with increasing ribbon width. The thermal conductance of GNRs in a few nanometer width already exhibits an approximate low-temperature dependence of $T^{1.5}$, like that of 2D graphene sheet which is attributed to the quadratic nature of dispersion relation for the out-of-plane acoustic phonon modes. Using a zone-folding method, we heuristically derive the dimensional crossover of thermal conductance with the increase of ribbon width. Combining our calculations with the experimental phonon mean-free path, some typical values of thermal conductivity at room temperature are estimated for GNRs and for 2D graphene sheet, respectively. Our findings clarify the issue of low-temperature dependence of thermal transport in GNRs and suggest a calibration range of thermal conductivity for experimental measurements in graphene-based materials.Comment: 18 pages, 4 figure

Effects of immersing treatment of curcumin and piperine combined with vacuum packaging on the quality of salmon (Salmo salar) during cold chain logistics

In order to study the effects of the compound preservatives (curcumin and piperine (CP)) and vacuum packaging (VP) on the quality of salmon during cold chain logistics suffered from temperature abuse, the physiochemical indexes (texture, water holding capacity (WHC), total volatile basic nitrogen (TVB-N), thiobarbituric acid reactive substances (TBARS), free amino acids (FAA) contents), microbial indicators (total mesophilic bacteria count (MBC), total psychrotrophic bacteria count (PBC), H2S-producing bacteria count (HSBC)) were determined, and the moisture changes were explored by near-infrared (NIR) spectroscopy and low-field nuclear magnetic resonance (LF-NMR). The results showed that the treatment of curcumin and piperine in combination with vacuum packaging could maintain the quality of salmon suffered from temperature abuse most effectively. At the end of storage, the MBC of VP+CP was only 4.95 log CFU/g, which was about 1 log CFU/g lower than the control sample stored at the same condition. The combined treatment also retarded the increase of TVB-N, TBARS, and the decrease of hardness, springiness, and a* value, as well as water migration in salmon, contributing to higher water holding capacity and better appearance. Besides, VP+CP retarded the decrease of free glutamate, which contributed to umami taste. Due to the biological activity and safety of the preserves, the combined treatment could be a promising method for preservation of seafood.Peer reviewe