19672 research outputs found
Sort by
Acid Hydrazide: A Potential Reagent for the Synthesis of Semicarbazones
No full textComplex semicarbazone derivatives were successfully synthesized from substituted semicarbazides in acidic ethanol upon heating in the presence of aldehyde. The reaction is functional group tolerant and chemoselective because no terminal hydrazine moiety is present in the substituted semicarbazides. Thus, functional groups such as esters and acetyls, which are prone to reaction with hydrazine, can also be used in this reaction because the terminal hydrazine moiety of the acid hydrazide was protected by aryl isocyanates in order to prepare substituted semicarbazides. In addition, neither of the aryl groups of semicarbazone are dependent on the starting materials (acid hydrazide) and can be changed upon demand. Thus, this reaction protocol provides a simple and effective alternative for the preparation of a wide variety of semicarbazones that could not be synthesized by utilizing conventional methods
Avoidance of sponsored posts on consumer-generated content: a study of personal blogs
No full textPurpose: This study aims to conceptualise and empirically examine how blog users engage with the sponsored posts on consumer-generated content, specifically blogs. Design/methodology/approach: This paper empirically tested the proposed hypotheses using the structural equation modelling using a sample of 399 blog users. Findings: The need for cognition, perceived interactivity and perceived credibility of blogs has been found to directly influence consumers’ attitude towards blogs. Innovativeness has been found to have a weak negative link with the attitude towards blogs. Blog users were more favourable towards the sponsored posts if the blogs were more interactive. Attitude towards blogs has been found to mediate the relationship between users’ perceived interactivity and their avoidance of the sponsored posts and also between perceived credibility and avoidance of the sponsored posts on blogs. The most significant finding of this study is that the positive attitude towards a blog results in a higher avoidance of the sponsored posts. Research limitations/implications: This study focuses on the sponsored posts on blogs. It does not look at other forms of advertising on blogs such as banner ads, or other forms of consumer-generated content. Practical implications: Marketers and bloggers should carefully consider the suitability of the sponsored posts on blogs as they risk alienating the regular users of the blogs. Sponsored posts which are perceived as honest reviews (as opposed to paid advertorials) might be more acceptable to blog users. Social implications: This study highlights the importance of credibility of bloggers to blog users. There are some serious ethical issues related to the sponsored posts which have not been discussed here but need to be examined further. Originality/value: This study represents one of the first attempts to conceptualise and empirically examine how blog users engage with customer-generated advertising – sponsored posts. It contributes to marketing literature by enhancing the understanding of how consumers perceive consumer-generated content and more specifically, with regard to consumer attitudes towards online consumer-generated advertising. This study enhances the theoretical and empirical knowledge on how consumers react to advertisements on social media, with important suggestions for future research and implications for practitioners
Transcriptional responses of Streptococcus gordonii and Fusobacterium nucleatum to coaggregation
No full textCell-cell interactions between genetically distinct bacteria, known as coaggregation, are important for the formation of mixed-species biofilms such as dental plaque. Interactions lead to gene regulation in the partner organisms that may be critical for adaptation and survival in mixed-species biofilms. Here, gene regulation responses to coaggregation between Streptococcus gordonii and Fusobacterium nucleatum were studied using dual RNA-Seq. Initially, S. gordonii was shown to coaggregate strongly with F. nucleatum in buffer or human saliva. Using confocal laser scanning microscopy and transmission electron microscopy, cells of different species were shown to be evenly distributed throughout the coaggregate and were closely associated with one another. This distribution was confirmed by serial block face sectioning scanning electron microscopy, which provided high resolution three-dimensional images of coaggregates. Cell-cell sensing responses were analysed 30 minutes after inducing coaggregation in human saliva. By comparison with monocultures, 16 genes were regulated following coaggregation in F. nucleatum whereas 119 genes were regulated in S. gordonii. In both species, genes involved in amino acid and carbohydrate metabolism were strongly affected by coaggregation. In particular, one 8-gene operon in F. nucleatum encoding sialic acid uptake and catabolism was up-regulated 2- to 5-fold following coaggregation. In S. gordonii, a gene cluster encoding functions for phosphotransferase system-mediated uptake of lactose and galactose was down-regulated up to 3-fold in response to coaggregation. The genes identified in this study may play key roles in the development of mixed-species communities and represent potential targets for approaches to control dental plaque accumulation
Speech emotion recognition research: an analysis of research focus
No full textThis article analyses research in speech emotion recognition (“SER”) from 2006 to 2017 in order to identify the current focus of research, and areas in which research is lacking. The objective is to examine what is being done in this field of research. Searching on selected keywords, we extracted and analysed 260 articles from well-known online databases. The analysis indicates that SER research is an active field of research, dozens of articles being published each year in journals and conference proceedings. The majority of articles concentrate on three critical aspects of SER, namely (1) databases, (2) suitable speech features, and (3) classification techniques to maximize the recognition accuracy of SER systems. Having carried out association analysis of the critical aspects and how they influence the performance of the SER system in term of recognition accuracy, we found that certain combination of databases, speech features and classifiers influence the recognition accuracy of the SER system. We have also suggested aspects of SER that could be taken into consideration in future works based on our review
Integrated database approach in multi-objective network reconfiguration for distribution system using discrete optimisation techniques
No full textReconfiguring the link between buses is a crucial task to enhance the distribution system performance. Reconfiguration is a complex combinatorial process due to numerous feasible solutions. Therefore, to consistently find global optimum solutions within a short span of time is a challenging task. One of the factors that cause time consumption in finding optimal network configurations is the elimination of non-radiality network solutions during the optimisation process. To address this issue, this work proposes to store pre-determined network radiality solutions in a database. These sets of solutions are used in the network reconfiguration optimisation by a discrete evolutionary programming and a discrete evolutionary particle swarm optimisation techniques. These optimisation methods are based on a multi-objective problem which minimises power loss, voltage deviation, and a number of switching actions. Moreover, the quality of the solutions is measured in terms of computational time and consistency. To demonstrate the efficiency of the proposed technique, a comparative assessment is carried out on 33-bus and 118-bus distribution systems. It is found that the proposed technique outperforms other existing methods in terms of quality of the solutions
1500-nm Q-switched fibre laser with carbon nanotubes
No full textA Q-switched fibre laser operating at 1500 nm is proposed and demonstrated. The laser uses a saturable absorber (SA) based on carbon nanotubes (CNTs) to generate Q-switched pulses, while a 30-m-long depressed-cladding erbium-doped fibre (DC-EDF) provides the necessary gain in the desired wavelength region. The proposed laser has lasing and pulsed thresholds of 30 mW and 50 mW respectively, along with a maximum output power, pulse energy and peak power of 0.5 mW, 7.6 nJ and 2.2 mW. Additionally, the output of the system also has a maximum repetition rate of 59.4 kHz with the shortest pulse duration measured at 3.4 ms. The output pulses are smooth and uniform, with no indication of self mode-locking
Effect of sodium dodecyl sulphate and polyoxyethylene dodecyl ether on the rheological behaviour and stability of natural rubber latex
No full textSurfactants are important class of material used in latexes to impart stability at the solid/liquid interface. Ionic surfactants and nonionic surfactants are known to provide elec- trostatic and steric stabilisation. In this study, two surfactants having chain length of twelve hydrocarbons were added to the natural rubber latex (NRL) respectively to determine its zeta potential values, adsorption isotherm and rheological properties. Previous study has shown that optimum stability was observed when the alkyl chain of surfactant contains twelve car- bon atoms. The zeta potential magnitude of NRL in the presence of sodium dodecyl sulphate increased as the surfactant concentration increases, while polyoxyethylene dodecyl ether did not show a significant change in zeta potential. The isotherms were of Langmuir Type 1, the amount of surfactant adsorbed per unit area at the plateau region was 6.0 × 10-6 mol m-2 for sodium dodecyl sulphate and 2.1 × 10-6 mol m-2 for polyoxyethylene dodecyl ether. The elastic modulus and relative viscosity of the NRL suspensions increased significantly in the presence of sodium dodecyl sulphate and also with polyoxyethylene dodecyl ether as compared to the NRL system due to stronger colloidal forces. The maximum packing volume fractions of the NRL stabilised with sodium dodecyl sulphate and polyoxyethylene dodecyl ether were found to be lower than NRL itself
Acid and Deep Eutectic Solvent (DES) extraction of pectin from pomelo (Citrus grandis (L.) Osbeck) peels
No full textPectin was extracted from pomelo peel using citric acid. A Box–Behnken design was employed to optimize the yield and the Degree of Esterification (DE) of pectin. The effects of pH, temperature, extraction time and liquid-solid ratio on the yield were investigated. It was found that under optimized conditions at pH 1.80, extraction time of 141 min, temperature of 88 °C and a liquid-solid ratio of 29:1 mL/g, a pectin yield of 39.72% and a DE value of 57.56% were obtained. The results indicate that the pectin extracted from pomelo peel is a slow set high methoxyl type of pectin. pH was found to have the greatest influence on pectin yield and DE. Varying pH at a narrow range between 1 and 2 interestingly showed the formation of diverse pectin functional groups with different structural modifications. The findings suggest that extraction conditions could influence pectin extraction performance, chemical structure, as well as morphological and gelling properties. This study also explored various acid based Deep Eutectic Solvents (DESs) in pectin extraction. The lactic acid–glucose–water DES with a ratio of 6:1:6 gave the highest pectin yield of 23.04%. Citric acid was found to have a better yield performance and more energy saving as compared to DES in pectin extraction
Can doctors and patients correctly estimate cardiovascular risk? A cross-sectional study in primary care
No full textAccurate cardiovascular risk estimations by patients and doctors are important as these affect health behaviour and medical decision making. We aimed to determine if doctors and patients were accurately estimating the absolute cardiovascular risk of patients in primary care. Methods A cross-sectional study was carried out in primary care clinics in Malaysia in 2014. Patients aged 35 years and above without known cardiovascular disease (CVDs) were included. Face-to-face interviews with a structured questionnaire were used to collect sociodemographic and clinical data as well as patients' perception and doctors' estimate of the patients' CVD risk. Associations were tested using ‡ 2, correlation and independent t-tests. Results We recruited 1094 patients and 57 doctors. Using the Framingham Risk Score (FRS) alone, 508 patients (46.4%) were in the high-risk group. When diabetes was included as high risk, the number increased to 776 (70.9%). Only 34.4% of patients and 55.7% of doctors correctly estimated the patient's CVD risk in comparison with the reference FRS. Of the high-risk patients, 664 (85.6%) underestimated their CV risk. Factors associated with underestimation by patients included not having family history of CVD (adjusted OR (AOR): 2.705, 95% CI 1.538 to 4.757), smaller waist circumference (AOR: 0.979,95% CI 0.960 to 0.999) and ethnicity in comparison with the Malay as reference group (indigenous/others: AOR: 0.129, 95% CI 0.071 to 0.235). Doctors underestimated risk in 59.8% of the high-risk group. Factors associated with underestimation by doctors were patients factors such as being female (AOR: 2.232, 95% CI 1.460 to 3.410), younger age (AOR: 0.908, 95% CI 0.886 to 0.930), non-hypertensive (AOR: 1.731, 95% CI 1.067 to 2.808), non-diabetic (AOR: 1.931, 95% CI 1.114 to 3.348), higher high-density lipoprotein levels (AOR: 3.546, 95% CI 2.025 to 6.209), lower systolic blood pressure (AOR: 0.970, 95% CI 0.957 to 0.982), non-smoker (AOR: 2.246, 95% CI 1.354 to 3.726) and ethnicity in comparison with the Malay as reference group (Indian: AOR: 0.430, 95% CI 0.257 to 0.720; indigenous/others: AOR: 2.498, 95% CI 1.346 to 4.636). Conclusions The majority of consultations occurring between doctors and patients are being informed by inaccurate cardiovascular risk estimation
Thermal conductivity of an ethylene glycol/water-based nanofluid with copper-titanium dioxide nanoparticles: An experimental approach
No full textHeat transfer fluid with low thermal conductivity limits the efficiency of thermal systems, such as heat exchangers, which require heat transfer fluid with high thermal conductivity. There is a demand to synthesize heat transfer fluids with high thermal conductivity. The emergence of nanoparticles has led to the development of nanofluids. Nanofluids can be classified as non-hybrid and hybrid nanofluids. This study investigated the thermal conductivity characteristics of a copper‑titanium dioxide (Cu-TiO2) hybrid nanofluid and compared with those of a non-hybrid (Cu and TiO2) nanofluid. In addition, the effects of various factors (weight percentages of the nanoparticles, types of surfactants, pH values of the base fluid solution and sonication times) on the thermal conductivity of theCu-TiO2 hybrid nanofluid were studied. The thermal conductivity of theCu-TiO2 hybrid nanofluid increased in accordance with an increment in the weight percentage of the nanoparticles. The hybrid nanofluid containing 0.8 wt% of Cu-TiO2 and polyvinylpyrrolidone (PVP) as surfactant showed the highest thermal conductivity, exhibiting an improvement of 9.8% compared to that of the base fluid