295 research outputs found
Trapping/Pinning of colloidal microspheres over glass substrate using surface features
Suspensions of micro and nano particles made of Polystyrene, Poly(methyl
methacrylate), Silicon dioxide etc. have been a standard model system to
understand colloidal physics. . These systems have proved useful insights into
phenomena such as self-assembly. Colloidal model systems are also extensively
used to simulate many condensed matter phenomena such as dynamics in a quenched
disordered system and glass transition. A precise control of particles using
optical or holographic tweezers is essential for such studies. However, studies
of collective phenomena such as jamming and flocking behaviour in a disordered
space are limited due to the low throughput of the optical trapping
techniques.In this article, we present a technique where we trap and pin
polystyrene microspheres ~ 10 {\mu}m over triangular-crest shaped
microstructures in a microfluidic environment. Trapping/Pinning occurs due to
the combined effect of hydrodynamic interaction and non-specific adhesion
forces. This method allows trapping and pinning of microspheres in any
arbitrary pattern with a high degree of spatial accuracy which can be useful in
studying fundamentals of various collective phenomena as well as in
applications such as bead detachment assay based biosensors
The determination and validation of population pharmacokinetic parameters of phenytoin in adult epileptic patients in the Western Cape using nonlinear mixed-effects modelling
The pharmacokinetics of phenytoin is complicated by the nonlinearity of the dose-concentration relationship which is a consequence of capacity-limited metabolism. Individualized therapy with phenytoin is therefore optimally required. As no data are available on the population pharmacokinetics of phenytoin in the Western Cape, this study was undertaken to address this issue. This study was conducted prospectively primarily to: (1) investigate the influence of various patient variables on the population pharmacokinetic parameters of phenytoin, (2) assess whether the parallel Michaelis-Menten and first-order elimination model provides a better fit to the data than the Michaelis-Menten model, (3) determine population pharmacokinetic parameter estimates of phenytoin representative of the patient population, and (4) validate and compare the clinical applicability of the parameter estimates and the models. The study population comprised 332 black and coloured, adult, male and female epileptic patients residing in the Western Cape, South Africa. All patients were on phenytoin monotherapy for the management of their epilepsy and no drugs known to interfere with phenytoin pharmacokinetics were taken concurrently. Clinical pharmacokinetic dosing services were initiated at 9 clinics from which patients were selected for this study. The service entailed a patient interview, a chart review, drug analysis and provision of either a written or verbal consultation report. The data were analyzed using NONMEM (nonlinear mixed-effects modelling), a computer programme designed for population pharmacokinetic analysis that allows pooling of data from many individuals. The Michaelis-Menten and the parallel Michaelis-Menten and first-order elimination models were fitted to 853 steady-state dose: serum concentration pairs
Tuning the torque-speed characteristics of bacterial flagellar motor to enhance the swimming speed
In a classic paper, Edward Purcell analysed the dynamics of flagellated
bacterial swimmers and derived a geometrical relationship which optimizes the
propulsion efficiency. Experimental measurements for wild-type bacterial
species E. coli have revealed that they closely satisfy this geometric
optimality. However, the dependence of the flagellar motor speed on the load
and more generally the role of the torque-speed characteristics of the
flagellar motor is not considered in Purcell's original analysis. Here we
derive a tuned condition representing a match between the flagella geometry and
the torque-speed characteristics of the flagellar motor to maximize the
bacterial swimming speed for a given load. This condition is independent of the
geometric optimality condition derived by Purcell and interestingly this
condition is not satisfied by wild-type E. coli which swim 2-3 times slower
than the maximum possible speed given the amount of available motor torque. Our
analysis also reveals the existence of an anomalous propulsion regime, where
the swim speed increases with increasing load (drag). Finally, we present
experimental data which supports our analysis
Close Range High Voltage Multiplier Device
This project has been implemented to create a sample, cheap and easy to make “Electroshock defensive device†.This is powered from a 9 volt DC source making use of basic electronic components. This voltage is multiplied through the Cockroft –Walton Voltage Multiplier Ladder.It generates a high voltage arc across its output electrodes ranging from 4.5KV to 75000KV.The output voltage is pulsating. Based on the prototype design this can be used for a plethora of applications. This must be handled with extreme precaution since misuse of device may lead to hazardous accidents
Stem Cell-Derived Regulatory T Cells for Therapeutic Use
CD4+ regulatory T cells (Tregs) are essential for normal immune surveillance, and their dysfunction can lead the development of autoimmune diseases. Pluripotent stem cells (PSCs) can be utilized to obtain a renewable source of healthy Tregs to treat autoimmune disorders as they have the ability to produce almost all cell types in the body, including Tregs. However, the right conditions for the development of antigen (Ag)-specific Tregs from PSCs (i.e., PSC-Tregs) have not been fully defined, especially the signaling mechanisms that the direct differentiation of such Tregs. Ag-specific PSC-Tregs can be tissue-associated and infiltrate to local inflamed tissue to suppress autoimmune responses after adoptive transfer, thereby avoiding potential overall immunosuppression from non-specific Tregs. Development of cell-based therapies using Ag-specific PSC-Tregs will provide an important step toward personalized therapies for autoimmune disorders
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Mucoadhesive maleimide-functionalised liposomes for drug delivery to urinary bladder
Intravesical drug administration is used to deliver chemotherapeutic agents via a catheter to treat bladder cancer. The major limitation of this treatment is poor retention of the drug in the bladder due to periodic urine voiding. In this work, maleimide-functionalised PEGylated liposomes (PEG-Mal) were explored as mucoadhesive vehicles for drug delivery to the urinary bladder. The retention of these liposomes on freshly excised porcine bladder mucosa in vitro was compared with conventional liposomes, PEGylated liposomes, two controls (dextran and chitosan), and evaluated through Wash Out50 (WO50) values. PEG-Mal liposomes exhibited greater retention on mucosal surfaces compared to other liposomes. The penetration abilities of conventional, PEG-Mal-functionalised and PEGylated liposomal dispersions with encapsulated fluorescein sodium into the bladder mucosa ex vivo were assessed using a fluorescence microscopy technique. PEGylated liposomes were found to be more mucosa-penetrating compared to other liposomes. All liposomes were loaded with fluorescein sodium salt as a model drug and the in vitro release kinetics was evaluated. Longer drug release was observed from PEG-Mal liposomes
Cellular transport of anti-inflammatory pro-drugs originated from a herbal formulation of Zingiber cassumunar and Nigella sativa
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