35 research outputs found
Oral citrulline as arginine precursor may be beneficial in sickle cell disease: early phase two results.
No full textL-Arginine may be a conditionally essential amino acid in children and adolescents with sickle cell disease, particularly as required substrate in the arginine-nitric oxide pathway for endogenous nitrovasodilation and vasoprotection. Vasoprotection by arginine is mediated partly by nitric oxide-induced inhibition of endothelial damage and inhibition of adhesion and activation of leukocytes. Activated leukocytes may trigger many of the complications, including vasoocclusive events and intimal hyperplasias. High blood leukocyte counts during steady states in the absence of infection are significant laboratory risk factors for adverse complications. L-Citrulline as precursor amino acid was given orally twice daily in daily doses of approximately 0.1 g/kg in a pilot Phase 11 clinical trial during steady states in four homozygous sickle cell disease subjects and one sickle cell-hemoglobin C disease patient (ages 10-1 8). There soon resulted dramatic improvements in symptoms of well-being, raised plasma arginine levels, and reductions in high total leukocyte and high segmented neutrophil counts toward or to within normal limits. Continued L-citrulline supplementation in compliant subjects continued to lessen symptomatology, to maintain plasma arginine concentrations greater than control levels, and to maintain nearly normal total leukocyte and neutrophil counts. Side effects or toxicity from citrulline were not experienced. Oral L-citrulline may portend very useful for palliative therapy in sickle cell disease. Placebo-controlled, long-term trials are now indicated. Originally published Journal of the National Medical Association, Vol. 93, No. 10, Oct 200
Asic gas sensors based on ratiometric principles
No full textThe wide-scale usage of VOCs in industrial processes requires monitoring the
concentrations of these vapours to keep a safe operating environment. Most combustible
hydrocarbons can be ignited as a gas-air mixture in the range of 0.5% to 15% by
volume. This has led to the development of several portable air quality monitoring
instruments. However, the high costs and lack of durability of these instruments has
remained an issue to be addressed. This PhD thesis reports on the development and
characterization of a novel low cost smart gas sensor technology adaptable for use in a
portable instrument. The smart gas sensor devices have been developed to target four
different VOCs in air.
The smart gas sensor device combines a smart ASIC (SRL 194 designed at
SRL, Warwick University) fabricated in standard 0.7 μm CMOS technology and two
alkyl-dithiol based self-assembled gold nanoparticle chemoresistive sensors (fabricated
at Sony Deutschland GmbH) in a ratiometric array to offer a robust system which can
address the common mode variations found in polymer based gas sensor systems. The
ratiometric ASIC sensor array architecture allows for the reduction of the baseline
value’s dependence on environmental variations and the elimination of baseline drift
due to long term application of DC voltage.
Three ratiometric array arrangements - mono-type uni-variate with only one
chemosensor per device, mono-type bi-variate with two chemosensors of the same film
material per device and duo-type with a polar and a non-polar chemosensor per device
and their variations were characterized in an automated FIA test station against
exposure to methanol, ethanol, propan-1-ol, and toluene at 30°C and 0-5% rh. It was
determined that the devices’ response output to VOC analytes was entirely dependent
on the variation of the resistance ratio of the chemoresistive sensors in the ratiometric
sensor array. The effects of variations of the temperature and rh on the smart sensor
output were calibrated. The mono-type devices gave a high magnitude response to the
vapours whereas the duo-type arrangement offered a high degree of discrimination
between the test analytes with little post-processing steps.
Three different alkyl-dithiol chemoresistive sensor films on gold electrodes
were successfully used as the VOC vapour sensitive elements in each arrangement. The
effects of using a silicone sealant gel as a partitioning layer were characterized and it
was observed that at vapour concentrations less than 3000 ppm the silicone
encapsulated chemosensor devices reported a larger response to the VOC analytes as
compared to those without the silicone. The test devices reported promising response
repeatability and reproducibility with excellent return to baseline properties, a negligible
hysteresis and an error margin of under 10%. Ideal operating temperature was
determined to be 40°C at which rh variations were found to be minimal. The test
devices were found to be robust with little variation in the quality of the device output
over the course of 18 months.
The novel research demonstrated that it is possible to get high level of
diversification between analytes from a low cost and robust gas sensor system for
monitoring VOCs. The work carried out here has opened the opportunity to develop
highly integrated programmable hand-held gas sensor and e-nose systems for
environmental monitoring use in health and safety applications
Micro-ATR-IR as a Probe of BCB Layers for MCM-D/L Applications
No full textAbstractTo lower the cost of multichip module packaging, hybridized substrate technologies have recently been reported which blend the desirable aspects of D and L fabrication (MCM-D/L). High performance dielectrics such as Cyclotene™3022 and photosensitive BCB have been shown to be compatible with laminate substrates used in MCM-DIL, however the cure levels of the dielectric on the laminates must be known for optimum processing.In this paper, the capability of attenuated reflection IR microscopy (micro-ATR-IR) to probe thin films of BCB polymers is demonstrated. This technique enables the polymer layer to be probed regardless of the characteristics of the substrate. Cure levels of both Cyclotene™ 3022 and photodefinable BCB polymer films are obtained with micro-ATR-IR on both silicon and laminate substrate. Micro-ATR-IR is also used to probe a rapid thermal cure of Cyclotene Tm 3022 and photodefinable BCB layers on copper-clad polyimide laminate; these measurements cannot be made with transmission IR due to the high reflectivity of the substrate.</jats:p
