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1.
Sebastian Grieger Beata M. Szydowska Vaishnavi J. Rao Eva Steinmann Marcus Dodds Zahra Gholamvand Georg S. Duesberg Jana Zaumseil Claudia Backes 《Angewandte Chemie (International ed. in English)》2020,59(33):13785-13792
In recent years, various functionalization strategies for transition‐metal dichalcogenides have been explored to tailor the properties of materials and to provide anchor points for the fabrication of hybrid structures. Herein, new insights into the role of the surfactant in functionalization reactions are described. Using the spontaneous reaction of WS2 with chloroauric acid as a model reaction, the regioselective formation of gold nanoparticles on WS2 is shown to be heavily dependent on the surfactant employed. A simple model is developed to explain the role of the chosen surfactant in this heterogeneous functionalization reaction. The surfactant coverage is identified as the crucial element that governs the dominant reaction pathway and therefore can severely alter the reaction outcome. This study shows the general importance of the surfactant choice and how detrimental or beneficial a certain surfactant can be to the desired functionalization. 相似文献
2.
Vaishnavi Rajagopal Chris Stokes Alessandra Ferzoco 《Journal of the American Society for Mass Spectrometry》2018,29(2):260-269
We report a custom-geometry linear ion trap designed for fluorescence spectroscopy of gas-phase ions at ambient to cryogenic temperatures. Laser-induced fluorescence from trapped ions is collected from between the trapping rods, orthogonal to the excitation laser that runs along the axis of the linear ion trap. To increase optical access to the ion cloud, the diameter of the round trapping rods is 80% of the inscribed diameter, rather than the roughly 110% used to approximate purely quadrupolar electric fields. To encompass as much of the ion cloud as possible, the first collection optic has a 25.4 mm diameter and a numerical aperture of 0.6. The choice of geometry and collection optics yields 107 detected photons/s from trapped rhodamine 6G ions. The trap is coupled to a closed-cycle helium refrigerator, which in combination with two 50 Ohm heaters enables temperature control to below 25 K on the rod electrodes. The purpose of the instrument is to broaden the applicability of fluorescence spectroscopy of gas-phase ions to cases where photon emission is a minority relaxation pathway. Such studies are important to understand how the microenvironment of a chromophore influences excited state charge transfer processes. 相似文献
3.
Jagadeesh B Prabhakar A Sarma GD Chandrasekhar S Chandrashekar G Reddy MS Jagannadh B 《Chemical communications (Cambridge, England)》2007,(4):371-373
Residue based control of specific helical folding is explored in hybrid peptide oligomers consisting of alternating L-Ala and cis-beta-furanoid sugar amino acid (FSAA) residues as building blocks; two series of these hybrid oligomers are designed, synthesized and extensively characterized by using NMR, CD, FT-IR and MD simulation studies; results show the co-existence of left-handed 11- and 14/15-helical conformations in these short oligomers of Boc-(alpha/beta) and Boc-(beta/alpha) series. 相似文献
4.
Murthy GS Johnston DB Rausch KD Tumbleson ME Singh V 《Applied biochemistry and biotechnology》2012,166(1):87-111
Ethanol from corn is produced using dry grind corn process in which simultaneous saccharification and fermentation (SSF) is
one of the most critical unit operations. In this work an optimal controller based on a previously validated SSF model was
developed by formulating the SSF process as a Bolza problem and using gradient descent methods. Validation experiments were
performed to evaluate the performance of optimal controller under different process disturbances that are likely to occur
in practice. Use of optimal control algorithm for the SSF process resulted in lower peak glucose concentration, similar ethanol
yields (13.38±0.36% v/v and 13.50±0.15% v/v for optimally controlled and baseline experiments, respectively). Optimal controller
improved final ethanol concentrations as compared to process without optimal controller under conditions of temperature (13.35±1.28
and 12.52±1.19% v/v for optimal and no optimal control, respectively) and pH disturbances (12.65±0.74 and 11.86±0.49% v/v
for optimal and no optimal control, respectively). Cost savings due to lower enzyme usage and reduced cooling requirement
were estimated to be up to $1 million for a 151 million L/yr (40 million gal/yr) dry grind plant. 相似文献
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Time consuming portions in the computation of transport properties of rigid and flexible molecules are the evaluation of subunit hydrodynamic interaction tensors Q and σ, and the procedure for satisfying subunit-subunit distance constraints. Vector algorithms to speed up these parts of the computation are given. Using these algorithms, a vector version of the Ermak-McCammon Brownian dynamics code has been developed on a Cyber-205. To demonstrate the order of speedups that can be achieved, the code was tested on a rigid “trimer” system comprising 24 spherical subunits with a fixed geometry. A speedup of about 14 times for the whole program, and of 45, 6, and 18 times for the computation of Q , σ, and for the procedure to enforce the constraints, respectively, were obtained. 相似文献
7.
In the past we have reported significant cognitive deficits in mice receiving 5‐fluorouracil in combination with low‐dose methotrexate. To explain such interactions, a pharmacokinetic study was designed. A sensitive bio‐analytical method was therefore developed and validated for 5‐fluorouracil and methotrexate in mouse plasma, brain and urine with liquid chromatography coupled to a single quadrupole mass spectrometer. Chromatographic separation was accomplished by Agilent® Zorbax® SB‐C18 column, with isocratic elution (5 mM ammonium acetate and methanol, 70:30, %v/v) at a flow rate of 300 μL/min. The limit of quantitation for both drugs was 15.6 ng/mL (plasma and brain) and 78.1 ng/mL (urine), with interday and intraday precision and accuracy ≤15% and a total run time of 6 min. This bio‐analytical method was used for the pharmacokinetic characterization of 5‐fluorouracil and methotrexate in mouse plasma, brain and urine over a period of 24 h. This method allowed characterization of the brain concentrations of 5‐fluorouracil over a period of 24 h. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
8.
James T. Nurmi Vaishnavi Sarathy Paul G. Tratnyek Donald R. Baer James E. Amonette Abhi Karkamkar 《Journal of nanoparticle research》2011,13(5):1937-1952
Most methods currently being used to recover Fe0-core/oxide-shell nanoparticles from solutions (including the solvents they are synthesized or stored in) are potentially
problematic because they may alter the particle composition (e.g., depositing salts formed from solutes) or leave the particles
prone to transformations during subsequent storage and handling (e.g., due to residual moisture). In this study, several methods
for recovery of nanoparticles from aqueous solution were studied to determine how they affect the structure and reactivity
of the recovered materials. Simple washing of the nanoparticles during vacuum filtration (i.e., “flash drying”) can leave
up to ~17 wt% residual moisture. Modeling calculations suggest this moisture is mostly capillary or matric water held between
particles and particle aggregates, which can be removed by drying for short periods at relative vapor pressures below 0.9.
Flash drying followed by vacuum drying, all under N2, leaves no detectable residue from precipitation of solutes (detectable by X-ray photoelectron spectroscopy, XPS), no significant
changes in overall particle composition or structure (determined by transmission electron microscopy, TEM), and negligible
residual moisture (by thermogravimetric analysis, TGA). While this improved flash-drying protocol may be the preferred method
for recovering nanoparticles for many purposes, we found that Fe0-core/oxide-shell nanoparticles still exhibit gradual aging during storage when characterized electrochemically with voltammetry. 相似文献
9.
Chandrasekhar S Rao CL Reddy MS Sharma GD Kiran MU Naresh P Chaitanya GK Bhanuprakash K Jagadeesh B 《The Journal of organic chemistry》2008,73(23):9443-9446
Short homo-oligomers of a new building block, cis-beta(2,3)-furanoid sugar aminoxy acid, are designed, characterized, and found to exhibit rigid ribbon-like secondary structures composed of 5/7 bifurcated intramolecular hydrogen bonds. 相似文献
10.
Nageswara S. V. Rao Vijay K. Vaishnavi S. Sitharama Iyengar 《BIT Numerical Mathematics》1988,28(1):37-53
In this paper we present a simple dynamization method that preserves the query and storage costs of a static data structure and ensures reasonable update costs. In this method, the majority of data elements are maintained in a single data structure, and the updates are handled using smaller auxiliary data structures. We analyze the query, storage, and amortized update costs for the dynamic version of a static data structure in terms of a functionf, such thatf(n)<n, that bounds the sizes of the auxiliary data structures (wheren is the number of elements in the data structure). The conditions onf for minimal (with respect to asymptotic upper bounds) amortized update costs are then obtained. The proposed method is shown to be particularly suited for the cases where the merging of two data structures is more efficient than building the resultant data structure from scratch. Its effectiveness is illustrated by applying it to a class of data structures that have linear merging cost; this class consists of data structures such as Voronoi diagrams, K-d trees, quadtrees, multiple attribute trees, etc. 相似文献