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121.
Weerasekara A Rinzan M Matsik S Perera AG Buchanan M Liu HC von Winckel G Stintz A Krishna S 《Optics letters》2007,32(10):1335-1337
Terahertz detection using the free-carrier absorption requires a small internal work function of the order of a few millielectron volts. A threshold frequency of 3.2 THz (93 microm or approximately 13 meV work function) is demonstrated by using a 1 x 10(18) cm(-3) Si-doped GaAs emitter and an undoped Al(0.04)Ga(0.96)As barrier structure. The peak responsivity of 6.5 A/W, detectivity of 5.5 x 10(8) Jones, and quantum efficiency of 19% were obtained at 7.1 THz under a bias field of 0.7 kV/cm at 6 K, while the detector spectral response range spans from 3.2 to 30 THz. 相似文献
122.
Shridhar H. Thorat Sanjay Kumar Sahu Rajesh G. Gonnade 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(11):1010-1016
The synthesis of pharmaceutical cocrystals is a strategy to enhance the performance of active pharmaceutical ingredients (APIs) without affecting their therapeutic efficiency. The 1:1 pharmaceutical cocrystal of the antituberculosis drug pyrazinamide (PZA) and the cocrystal former p‐aminobenzoic acid (p‐ABA), C7H7NO2·C5H5N3O, (1), was synthesized successfully and characterized by relevant solid‐state characterization methods. The cocrystal crystallizes in the monoclinic space group P21/n containing one molecule of each component. Both molecules associate via intermolecular O—H...O and N—H...O hydrogen bonds [O...O = 2.6102 (15) Å and O—H...O = 168.3 (19)°; N...O = 2.9259 (18) Å and N—H...O = 167.7 (16)°] to generate a dimeric acid–amide synthon. Neighbouring dimers are linked centrosymmetrically through N—H...O interactions [N...O = 3.1201 (18) Å and N—H...O = 136.9 (14)°] to form a tetrameric assembly supplemented by C—H...N interactions [C...N = 3.5277 (19) Å and C—H...N = 147°]. Linking of these tetrameric assemblies through N—H...O [N...O = 3.3026 (19) Å and N—H...O = 143.1 (17)°], N—H...N [N...N = 3.221 (2) Å and N—H...N = 177.9 (17)°] and C—H...O [C...O = 3.5354 (18) Å and C—H...O = 152°] interactions creates the two‐dimensional packing. Recrystallization of the cocrystals from the molten state revealed the formation of 4‐(pyrazine‐2‐carboxamido)benzoic acid, C12H9N3O3, (2), through a transamidation reaction between PZA and p‐ABA. Carboxamide (2) crystallizes in the triclinic space group P with one molecule in the asymmetric unit. Molecules of (2) form a centrosymmetric dimeric homosynthon through an acid–acid O—H...O hydrogen bond [O...O = 2.666 (3) Å and O—H...O = 178 (4)°]. Neighbouring assemblies are connected centrosymmetrically via a C—H...N interaction [C...N = 3.365 (3) Å and C—H...N = 142°] engaging the pyrazine groups to generate a linear chain. Adjacent chains are connected loosely via C—H...O interactions [C...O = 3.212 (3) Å and C—H...O = 149°] to generate a two‐dimensional sheet structure. Closely associated two‐dimensional sheets in both compounds are stacked via aromatic π‐stacking interactions engaging the pyrazine and benzene rings to create a three‐dimensional multi‐stack structure. 相似文献
123.
Sanjay Kumar Ankur Jain Yoshitsugu Kojima 《Journal of Thermal Analysis and Calorimetry》2017,128(2):721-733
This paper studies the addition (0–40% w/w) of natural zeolite (NZ, 84% clinoptilolite) in blended cements made with Portland cement (PC) with low and medium C3A content. The isothermal calorimetry was used to understand the effect of NZ on the early cement hydration. For low C3A cement, the addition of NZ produces mainly a dilution effect and then the heat released curve is similar to plain cement with lower intensity. For medium C3A cement, the curve shows the C3S peak in advance and a high intensity of third peak attributed to C3A hydration. The high cation fixed of NZ reduces the ions concentration (especially alkalis) in the mixing water stimulating the PC hydration. The flowability decreases when the NZ replacement level increases. Results of Fratini’s test show that NZ with both PCs used presents slow pozzolanic activity. At early age, XRD and FTIR analyses confirm that hydration products are the same as that of the corresponding PC and the CH is progressively reduced after 28 days and some AFm phases (hemi- and monocarboaluminate) appear depending on the NZ percentage and the PC used. For low replacement levels, the compressive strength is higher than the corresponding PC from 2 to 28 days. For high replacement levels, the early compressive strength is lower than that of corresponding plain PC and the pozzolanic reaction improves the later compressive strength of blended cements. 相似文献
124.
125.
A novel piezoelectric (PZ) immunosensor for the direct detection of malarial Plasmodium falciparum histidine rich protein-2 (PfHRP-2) antigen was developed. The mixed self-assembled monolayers (SAMs) of thioctic acid and 1-dodecanethiol were formed on gold surface of quartz crystal. Cyclic voltammetry, electrochemical impedance spectroscopy and surface Raman spectroscopy techniques were used to characterize the mixed SAMs. The rabbit anti-PfHRP-2 antibodies were coupled on mixed SAM modified gold surface of quartz crystal via NHS/EDC activation method. The PZ immunosensor was applied to detect PfHRP-2 in the linear range of 15-60 ng/ml with a detection limit of 12 ng/ml. It was also found that even after 14 days of storage, 50% of the activity still remained. Clinical human serum samples were tested with this method, and the results were in agreement with those obtained from commercially available ICT kit (NOW® Malaria). 相似文献
126.
The present work involves the adoption of an integrated approach for the purification of lactoperoxidase from milk whey by
coupling aqueous two-phase extraction (ATPE) with ultrasound-assisted ultrafiltration. The effect of system parameters of
ATPE such as type of phase system, polyethylene glycol (PEG) molecular mass, system pH, tie line length and phase volume ratio
was evaluated so as to obtain differential partitioning of contaminant proteins and lactoperoxidase in top and bottom phases,
respectively. PEG 6000-potassium phosphate system was found to be suitable for the maximum activity recovery of lactoperoxidase
150.70% leading to 2.31-fold purity. Further, concentration and purification of enzyme was attempted using ultrafiltration.
The activity recovery and purification factor achieved after ultrafiltration were 149.85% and 3.53-fold, respectively. To
optimise productivity and cost-effectiveness of integrated process, influence of ultrasound for the enhancement of permeate
flux during ultrafiltration was also investigated. Intermittent use of ultrasound along with stirring (2 min acoustic and
2 min stirring) resulted in increased permeate flux from 0.94 to 2.18 l/m2 h in comparison to the ultrafiltration without ultrasound. The use of ultrasound during ultrafiltration resulted in increase
in flux, but there was no significant change in activity recovery and purification factor. The integrated approach involving
ATPE and ultrafiltration may prove to be a feasible method for the downstream processing of lactoperoxidase from milk whey. 相似文献
127.
Sanjay Kumar Venkata Dasu Veeranki Kannan Pakshirajan 《Applied biochemistry and biotechnology》2011,163(3):327-337
Statistically based experimental design was applied to maximize the production of glutaminase-free L-asparaginase from Pectobacterium carotovorum MTCC 1428. The effect of physical process parameters (initial pH of the medium, temperature, rpm of the shaking incubator,
and inoculum size) on the production of L-asparaginase from P. carotovorum MTCC 1428 was studied using central composite design technique. The individual optimum levels of initial pH of the medium,
temperature, rpm of shaking incubator, and inoculum size were found to be 6.90, 29.8 °C, 157 rpm, and 2.61% (v/v), respectively, for the production of L-asparaginase. After physical process parameters optimization, the production and
productivity of L-asparaginase was enhanced by 26.39% (specific activity) and 10.19%, respectively. Maximization of L-asparaginase
production was achieved at 12 h under optimal levels of physical process parameters in shake flask level. 相似文献
128.
Singh A Mukherjee A Vermeulen HM Barkema GT Puri S 《The Journal of chemical physics》2011,134(4):044910
In this paper, we study the evolution of phase-separating binary mixtures which are subjected to alternate cooling and heating cycles. An initially homogeneous mixture is rapidly quenched to a temperature T(1)T(c). These cycles are repeated to create a domain morphology with multiple length scales, i.e., the structure factor is characterized by multiple peaks. For phase separation in d = 2 systems, we present numerical and analytical results for the emergence and growth of this multiple-scale morphology. 相似文献
129.
Kasture S Pawar A Kasture A Foddis C Frau MA Maxia A 《Natural product research》2011,25(20):1950-1954
In the traditional system of medicine in Sardinia, Rubia peregrina (RP) is reported as an aphrodisiac herb. Since aphrodisiacs may also have dopaminergic activity, and there can be a reciprocal relationship between dopaminergic and serotonergic functions in the central nervous system, the aim here was to study the effect of the ethanolic extract of the aerial parts of R. peregrina on monoamine-mediated behaviour. The RP (100 and 200?mg?kg(-1) intraperitoneally) significantly inhibited haloperidol (1?mg?kg(-1) i.p.) induced catalepsy in mice (p?0.01, dopamine-mediated response) lithium sulphate induced head twitches in rats (serotonin-mediated response) and was without effect on clonidine-induced hypothermia in rats (noradrenaline-mediated response). The study concludes that R. peregrina improves the dopaminergic function, diminishes the serotonin-mediated function and is devoid of any effect on the noradrenergic function. The study suggests that we should carry out further experiments to investigate the psychopharmacological profile of R. peregrina. 相似文献
130.
We present branching-on-hyperplane methods for solving mixed integer linear and mixed integer convex programs. In particular,
we formulate the problem of finding a good branching hyperplane using a novel concept of adjoint lattice. We also reformulate
the problem of rounding a continuous solution to a mixed integer solution. A worst case complexity of a Lenstra-type algorithm
is established using an approximate log-barrier center to obtain an ellipsoidal rounding of the feasible set. The results
for the mixed integer convex programming also establish a complexity result for the mixed integer second order cone programming
and mixed integer semidefinite programming feasibility problems as a special case. Our results motivate an alternative reformulation
technique and a branching heuristic using a generalized (e.g., ellipsoidal) norm reduced basis available at the root node. 相似文献