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41.
Lei Yao Khan R. Chodavarapu V.P. Tripathi V.S. Bright F.V. 《IEEE transactions on biomedical circuits and systems》2009,3(5):304-311
We present the design and implementation of a phase luminometry sensor system with improved and tunable detection sensitivity achieved using a complementary metal-oxide semiconductor (CMOS) integrated circuit. We use sol-gel derived xerogel thin films as an immobilization media to house oxygen (O2) responsive luminescent molecules. The sensor operates on the principal of phase luminometry wherein a sinusoidal modulation signal is used to excite the luminophores encapsulated in the porous xerogel films and the corresponding phase shift of the emission signals is monitored. The phase shift is directly related to excited state lifetimes of the luminophores which in turn are related to the concentration of the target analyte species present in the vicinity of the luminophores. The CMOS IC, which consists of a 16 times 16 high-gain phototransistor array, current-to-voltage converter, amplifier and tunable phase shift detector, consumes an average power of 14 mW with 5-V power supply operating at a 38-kHz modulation frequency. The output of the IC is a dc voltage that corresponds to the detected luminescence phase shift with respect to the excitation signal. As a prototype, we demonstrate an oxygen sensor system by encapsulating the luminophore tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) within the xerogel matrices. The sensor system showed a fast response on the order of few seconds and we obtained a detection sensitivity of 118 mV per 1% change in O2 concentration. The system demonstrates a novel concept to tune and improve the detection sensitivity for specific concentrations of the target analyte in many biomedical monitoring applications. 相似文献
42.
The Ferroelectric relaxor ternary system 0.5PZN-(0.5 – x)PFN-xBZN was prepared using the columbite precursor method. The stability of the perovskite phase was studied as a function of BZN content in the system. It was observed that BZN is a good stabilizer of perovskite phase because of the high value of electronegativity difference between its cation and anion. It has also been observed that addition of BZN increases the dielectric maxima peak value and decrease the Curie temperature of the ceramics. The ternary composition 0.5PZN-0.425PFN-0.075BZN has been identified for MLCs applications. It has a T
c of around room temperature with a peak dielectric constant 6400 and tan 0.05. The mechanical properties of relaxor materials have also been studied and reported. 相似文献
43.
Tripathi RM Mahapatra S Raghunath R Sastry VN Krishnamoorthy TM 《The Science of the total environment》2000,250(1-3):43-50
The daily intake of manganese (Mn) estimated through air, water and duplicate dietary analysis is found to range from 0.67 to 4.99 mg with a mean value of 2.21 mg. Ingestion through food contributed to the predominant fraction of the intake. The turnover rate of Mn through blood is approximately 2 h, based on the mean concentration of Mn in blood of 1.54 microg l(-1). The average concentrations of Mn in water and air were approximately 1.42 microg l(-1) and 37 ng m(-3), respectively. The daily intake of Mn by the adult population of Mumbai is closer to the lower bound of the recommended limit of 2-5 mg. Electro Thermal Atomic Absorption Spectrophotometry (ET-AAS), has been used for the determination of Mn in a variety of environmental and human biological fluids. The detection limit of Mn for a volume injection of 20 microl is 2 pg absolute. The precision of the method is established by analyzing a synthetic mixture containing various elements in different quantities (0.5-10 ppm) and is found to be within +/- 8%. The reliability of estimation is further assessed through the analysis of Standard Reference Materials (SRMs) of soil, hay, milk powder and fish tissue obtained from IAEA. 相似文献
44.
Tripathi RK Cucinotta FA Wilson JW 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》1999,152(4):425-431
A simple reliable formalism is presented for obtaining nucleon-nucleon cross sections within a nucleus in nuclear collisions for a given projectile and target nucleus combination at a given energy for use in transport, Monte Carlo and other calculations. The method relies on extraction of these values from experiments and has been tested for absorption experiments to give excellent results. 相似文献
45.
Amit Pratap Ajay Tripathi R. S. Tripathi 《Journal of Superconductivity and Novel Magnetism》1996,9(6):593-597
We have studied the role of interlayer attractive interaction in a high-T c system having two layers per unit cell. The single band two-layer tight binding model Hamiltonian is considered and the double time Green's function technique is applied within the mean field approximation. The expressions for the hole density, transition temperature, and intra- and interlayer order parameters are obtained which are found to be dependent on the interlayer interaction and other parameters appearing in the Hamiltonian. The numerical analysis shows that the coupling of the charge carriers (holes) between the layers provides better conditions for the stabilization of long-range order and high superconducting transition temperature in layered superconductors. It is also observed that superconductivity is confined to a narrow region of hole concentration and the single particle tunneling suppresses the transition temperature. 相似文献
46.
47.
The effect of interlayer interactions on the electronic specific heat of high-T
c layered superconductors has been studied within the framework of the Hirsch model. In the present paper we extend our previous work in order to evaluate the expression for specific heat. It is shown that the inclusion of interlayer interactions suppresses the height of the jump in the specific heat at T
c. 相似文献
48.
49.
N. Goyal Abdolali Zolanvari S. K. Tripathi 《Journal of Materials Science: Materials in Electronics》2001,12(9):523-526
The paper reports the effect of dissolution of silver into the chalcogenide As2S3. The conductivity of As2S3 decreases with doping at lower temperatures. The a.c. conductivity is proportional to s for undoped as well as doped samples. The value of the frequency exponent s increases with doping. On the other hand, the dielectric constant of As2S3 also increases with doping and the effect is quite prominent at higher temperatures. A new structural model together with the correlated barrier hopping model has been used to explain these results. © 2001 Kluwer Academic Publishers 相似文献
50.
Schmitt Neal; Oswald Frederick L.; Kim Brian H.; Imus Anna; Merritt Stephanie; Friede Alyssa; Shivpuri Smriti 《Canadian Metallurgical Quarterly》2007,92(1):165
To determine whether profiles of predictor variables provide incremental prediction of college student outcomes, the authors 1st applied an empirical clustering method to profiles based on the scores of 2,771 entering college students on a battery of biographical data and situational judgment measures, along with SAT and American College Test scores and high school grade point average, which resulted in 5 student groups. Performance of the students in these clusters was meaningfully different on a set of external variables, including college grade point average, self-rated performance, class absenteeism, organizational citizenship behavior, intent to quit their university, and satisfaction with college. The 14 variables in the profile were all significantly correlated with 1 or more of the outcome measures; however, nonlinear prediction of these outcomes on the basis of cluster membership did not add incrementally to a linear-regression-based combination of these 14 variables as predictors. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献