Voltammetric properties of boron carbide electrodes

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Correlating Gene Transfection Efficiency and the Physical Properties of Various Cationic Poly(methacrylate) Systems

Transfection efficiencies of several polymeric gene carriers were compared and correlated quantitatively to the amounts of cellular accumulation of plasmid DNA and to the expression of mRNA by quantitative real time PCR. Three cationic methacrylate polymer systems with similar chemical structure were used in this study, namely: poly(dimethylamino)ethyl methacrylate (PDMA) homopolymer, PEO-b-PDMA copolymer and PEO-b-poly(diethylamino)ethyl methacrylate (PEO-b-PDEA) copolymer. Despite their similar chemical structures, their transfection efficiencies were significantly different. PEO-b-PDEA copolymer was significantly less efficient as gene carrier compared to both PDMA and PEO-b-PDMA systems. Results from quantitative real-time polymerase chain reaction (real-time PCR), cytotoxicity and Zeta potential measurements showed correlations between the physical properties of the polymers and the efficiencies of cellular uptake of the transgene and transfections. In the case of PEO-b-PDEA system, cytotoxicity was due primarily to the excess polymers that did not participate in the DNA binding. In addition, the inability of the polymer/DNA complexes to interact with cell effectively was identified as the main barrier for high efficiency of transfection. This study demonstrated that the use of quantitative real-time PCR in combination with other physical characterization techniques can provide greater insights into the transfection barrier at different cellular levels.Singapore-MIT Alliance (SMA

A CFD analysis of the effective plume-chimney height of lazy plumes and its implications to clear air turbulence

Plume chimney is a plume that has chimney characteristics due to stack effects of plumes. In this study, CFD simulation was carried out for three different heights of chimney, three different diameters of chimney at various heat loads to cover a range of source Richardson number from 0.034 to 0.33, and Plume Function from 1.01 to 7.16. Reynold’s average Navier-Stokes’s conservation equations were solved in modelling the plume. A zero-gravity forced convection plume model was applied to obtain the overall total pressure drop. Effective Plume-Chimney Height (EPCH) was correlated with several parameters to obtain an empirical correlation. It was found that EPCH was related to the square root diameter of the chimney, as predicted by dimensional analysis in a pioneering plume rise study and concurred with all existing prediction methods. Through this finding a scaling formula for plume characteristic height is proposed. The power indices of volumetric coefficient of expansion, temperature differences, mean density of plume source density difference of air between ambient and plume source were 0.45, 0,80, 1.09 and -0.97 respectively; and correlation with the air velocity was negligible. The EPCH predicted by the correlation derived using the current method was found to be very close to previous correlations at the same Richardson number and plume function. For improved applicability, the range of parameters should be sufficiently broad and evenly distributed in future analysis. The theory of effective plume-chimney height is strongly supported by this CFD analysis, in addition to experimental data from industrial tests. Implications of the phenomenon of effective plume-chimney height, where a lazy plume has invisible walls causing a stack effect, generates a sizeable up thrust that is recommended to be investigated as it may be one of several factors contributing to mesoscale Clear Air Turbulence phenomenon experienced by aircrafts

Photoelectrochemical cells based on inherently conducting polymers

This review of photoelectrochemical cells (PECs) based on inherently conducting polymers (ICPs) deals with the mechanisms of operation and the various factors that influence the overall efficiency of PECs. The factors addressed include ICP composition and oxidation state, the use of nanostructured surfaces and interfaces, and the PEC electrolyte and redox mediator

Association Behavior of Biotinylated and Non-Biotinylated PolyEthylene Oxide-b-Poly(2-(Diethylamino)Ethyl Methacrylate)

Biotinylated and non-biotinylated copolymers of ethylene oxide (EO) and 2-(diethylamino)ethyl methacrylate (DEAEMA) were synthesized by the atom transfer radical polymerization technique (ATRP). The chemical compositions of the copolymers as determined by NMR are represented by PEO₁₁₃PDEAEMA₇₀ and biotin-PEO₁₀₄PDEAEMA₉₃ respectively. The aggregation behavior of these polymers in aqueous solutions at different pHs and ionic strengths was studied using a combination of potentiometric titration, dynamic light scattering (DLS), static light scattering (SLS), and transmission electron microscopy (TEM). Both PEO-b-PDEAEMA and biotin-PEO-b-PDEAEMA diblock copolymers form micelles at high pH with hydrodynamic radii (Rh) of about 19 and 23 nm, respectively. At low pH, the copolymers are dispersed as unimers in solution with Rh of about 6-7 nm. However, at a physiological salt concentration (cs) of about 0.16M NaCl and a pH of 7-8, the copolymers form large loosely packed Guassian chains, which were not present at the low cs of 0.001M NaCl. The critical micelle concentrations (CMC) and the cytotoxicity of the copolymers were investigated to determine a suitable polymer concentration range for future biological applications. Both PEO-b-PDEAEMA and biotin-PEO-b-PDEAEMA diblock copolymers possess identical CMC values of about 0.0023 mg/g, while the cytotoxicity test indicated that the copolymers are not toxic up to 0.05mg/g (> 83% cell survival at this concentration).Singapore-MIT Alliance (SMA

Size reduction of selected spices using knife mill: Experimental investigation and model fitting.

The process of size reduction is significant in numerous industries to improve performance and meet specification. This research is undertaken to study the size reduction of three spices, namely cinnamon, coriander and star anise as influenced by loading weight and grinding time. Grinding was conducted in a knife mill. The dependent variables used for assessing performance were grinding efficiency, size reduction ratio and grinding rate. Simple experimental model was built using Microsoft Excel for showing the relationship between cumulative size reduction function (Bij) and selectivity function (Si) with the physical properties like density, moisture content and hardness of spices used. It was observed that there was a gradual decrease in size of spices up to grinding of 1 min and then became constant. Among the three spices, cinnamon achieved the highest size reduction as evaluated by efficiency, size reduction rate and size reduction ratio. The optimum loading weight for grinding was found 30 g irrespective of the type of spices. The data of cumulative size reduction function, selectivity and particle size fitted to second-order polynomial equation with the highest goodness of fit. This study indicated that the size reduction/grinding using knife mill was greatly influenced by physical properties of spices among the factors studied

Living with AIDS in Uganda: a qualitative study of patients' and families' experiences following referral to hospice

Background: Globally, the majority of people with HIV/AIDS live in sub-Saharan Africa. While the increasing availability of antiretroviral therapy is improving the outlook for many, its effects are yet to reach all of those in need and patients still present with advanced disease. This paper reports findings from qualitative interviews with patients living with AIDS and their caregivers who were receiving palliative care from Hospice Africa Uganda (HAU). We aimed to understand what motivated patients and their families to seek formal healthcare, whether there were any barriers to help- seeking and how the help and support provided to them by HAU was perceived. Methods: We invited patients with AIDS and their relatives who were newly referred to HAU to participate in qualitative interviews. Patients and carers were interviewed in their homes approximately four weeks after the patient’s enrolment at HAU. Interviews were translated, transcribed and analysed using narrative and thematic approaches. Results: Interviews were completed with 22 patients (10 women and 12 men) and 20 family caregivers, nominated by patients. Interviews revealed the extent of suffering patients endured and the strain that family caregivers experienced before help was sought or accessed. Patients reported a wide range of severe physical symptoms. Patients and their relatives reported worries about the disclosure of the AIDS diagnosis and fear of stigma. Profound poverty framed all accounts. Poverty and stigma were, depending on the patient and family situation, both motivators and barriers to help seeking behaviour. Hospice services were perceived to provide essential relief of pain and symptoms, as well as providing rehabilitative support and a sense of caring. The hospice was perceived relieve utter destitution, although it was unable to meet all the expectations that patients had. Conclusion: Hospice care was highly valued and perceived to effectively manage problems such as pain and other symptoms and to provide rehabilitation. Participants noted a strong sense of being “cared for”. However, poverty and a sense of stigma were widespread. Further research is needed to understand how poverty and stigma can be effectively managed in hospice care for patients for advanced AIDS and their families

Anti-tumour activity of tachykinin NK1receptor antagonists on human glioma U373 MG xenograft

Astrocytes harbour functional receptors to many neurotransmitters, including substance P (SP), an undecapeptide belonging to the tachykinin family of peptide transmitters. SP activates malignant glial cells to induce cytokine release and proliferation, both responses being relevant for tumour progression. In tumours developed in nude mice transplanted subcutaneously (s.c.) to U373 MG human glioma cells, the presence of SP was observed at immunohistochemistry. Although the administration of exogenous SP did not significantly affect the size or development of U373 MG xenograft, a role of SP in supporting glioma progression in vivo was highlighted by the tumour growth inhibition induced by highly specific and selective human tachykinin NK1receptor antagonists (MEN 11467 and MEN 11149). The anti-tumour activity of MEN 11467 was observed both with s.c. or intravenous treatments and was partially reverted by the concomitant administration of exogenous SP. Doxorubicin did not show any activity in controlling U373 MG growth in this in vivo model. A novel therapeutic approach to treat malignant gliomas with tachykinin NK1receptor antagonists is suggested by these findings. © 2000 Cancer Research Campaig

Age differences in physiological responses to self-paced and incremental V˙O2max\dot V O_{2max} testing

Purpose: A self-paced maximal exercise protocol has demonstrated higher $\dot V O_{2max}$ values when compared against traditional tests. The aim was to compare physiological responses to this self-paced $\dot V O_{2max}$ protocol (SPV) in comparison to a traditional ramp $\dot V O_{2max}$ (RAMP) protocol in young (18–30 years) and old (50–75 years) participants. Methods: Forty-four participants (22 young; 22 old) completed both protocols in a randomised, counter-balanced, crossover design. The SPV included 5 × 2 min stages, participants were able to self-regulate their power output (PO) by using incremental ‘clamps’ in ratings of perceived exertion. The RAMP consisted of either 15 or 20 W min$^{−1}$. Results: Expired gases, cardiac output (Q), stroke volume (SV), muscular deoxyhaemoglobin (deoxyHb) and electromyography (EMG) at the vastus lateralis were recorded throughout. Results demonstrated significantly higher $\dot V O_{2max}$ in the SPV (49.68 ± 10.26 ml kg$^{−1}$ min$^{−1}$) vs. the RAMP (47.70 ± 9.98 ml kg$^{−1}$ min$^{−1}$) in the young, but not in the old group (>0.05). Q and SV were significantly higher in the SPV vs. the RAMP in the young (0.05). No differences seen in deoxyHb and EMG for either age groups (>0.05). Peak PO was significantly higher in the SPV vs. the RAMP in both age groups (<0.05). Conclusion: Findings demonstrate that the SPV produces higher $\dot V O_{2max}$, peak Q and SV values in the young group. However, older participants achieved similar $\dot V O_{2max}$ values in both protocols, mostly likely due to age-related differences in cardiovascular responses to incremental exercise, despite them achieving a higher physiological workload in the SPV

Trials of large group teaching in Malaysian private universities: a cross sectional study of teaching medicine and other disciplines

<p>Abstract</p> <p>Background</p> <p>This is a pilot cross sectional study using both quantitative and qualitative approach towards tutors teaching large classes in private universities in the Klang Valley (comprising Kuala Lumpur, its suburbs, adjoining towns in the State of Selangor) and the State of Negeri Sembilan, Malaysia. The general aim of this study is to determine the difficulties faced by tutors when teaching large group of students and to outline appropriate recommendations in overcoming them.</p> <p>Findings</p> <p>Thirty-two academics from six private universities from different faculties such as Medical Sciences, Business, Information Technology, and Engineering disciplines participated in this study. SPSS software was used to analyse the data. The results in general indicate that the conventional instructor-student approach has its shortcoming and requires changes. Interestingly, tutors from Medicine and IT less often faced difficulties and had positive experience in teaching large group of students.</p> <p>Conclusion</p> <p>However several suggestions were proposed to overcome these difficulties ranging from breaking into smaller classes, adopting innovative teaching, use of interactive learning methods incorporating interactive assessment and creative technology which enhanced students learning. Furthermore the study provides insights on the trials of large group teaching which are clearly identified to help tutors realise its impact on teaching. The suggestions to overcome these difficulties and to maximize student learning can serve as a guideline for tutors who face these challenges.</p