Characteristics investigation on heat transfer growth of sonochemically synthesized ZnO-DW based nanofluids inside square heat exchanger

Journal of Thermal Analysis and Calorimetry - In recent decades, the growth of heat transfer using nanomaterials in the conventional base fluid has caught the attention of researchers...     

Host–guest inter­action in a thio­urea–dimethyl oxalate (2/1) complex at 300 and 100 K

The title complex, 2CH₄N₂S·C₄H₆O₄, is a host–guest system. The asymmetric unit consists of one complete thio­urea mol­ecule and one‐half of a dimethyl oxalate mol­ecule lying on an inversion centre. The host thio­urea mol­ecules are connected to form zigzag chains by N—H⋯S hydrogen bonds. The guest dimethyl oxalate mol­ecules provide O‐atom acceptors for N—H⋯O hydrogen bonds, thus inter­connecting the chains of thio­urea mol­ecules to form completely connected sheets. The reduction in temperature from 300 to 100 K leaves the structure unchanged and still isostructural with that previously determined for the analogous thio­urea–diethyl oxalate (2/1) complex. It does, however, induce closer packing of the mol­ecules, general shrinkage of the unit cell and shortening of the hydrogen bonds, these last two to the extent of 1–2%.     

On-line cysteine modification for protein analysis: new probes for electrochemical tagging nanospray mass spectrometry

A series of electrogenerated selective electrophiles based on substituted benzoquinones has been characterized as tags for l-cysteine and cysteine residues in proteins. The electrophiles are generated electrochemically from the corresponding hydroquinones. It is shown from mass spectrometry analysis that the electrogenerated benzoquinone can tag the biomolecules. The rate constants pertaining to the addition of l-cysteine onto the electrogenerated benzoquinones have been determined using electrochemical techniques. The substitution patterns have been unraveled leading to the assessment of site-specific rate constants. It is shown that the rate constants are primarily dependent on the electronic nature of the substituents as expressed by the Hammett substitution constant. The apparent tagging yields observed for l-cysteine in nanospray mass spectrometry experiments do not correspond to the yields expected from the electrochemical study, as the ionisation efficiencies are highly dependent on the tag. Finally, the on-line tagging has been tested using β-lactoglobulin A and myoglobin. Based on these results, it is concluded that the tagging reaction is selective towards cysteine when it takes place in the nanospray interface. The results show that the methodology presented can be used for a rapid characterization and identification of reactive sites in biomolecules.     

The effect of rapid rotation on a vertical bridgman furnace at large Rayleigh number

In quasi-steady operation, convection currents in a Bridgmandevice, used for producing a semi-conductor crystal, createinhomogeneities that may make the crystal unusable. It has oftenbeen suggested that additional forces due to rotation or magnetismmight be efficacious in reducing the segregation of the elementsof the alloy. It has been found that, over a wide range of rotationrates, there is no improvement in performance due to rotationabout the vertical axis. However, numerical results that havebeen obtained previously (Lee & Pearlstein, J. Crys. Growth240, 2002) indicate that, when effects of centrifugal buoyancyare introduced, a substantial reduction in segregation is achieved.In the work reported here, by contrast, in which we extend previouslarge-Rayleigh-number asymptotic analysis to include centrifugalbuoyancy, we find no improvement in radial segregation, butrather increasing segregation with increasing rotation rate.     

One-pot synthesis of an ionic half-sandwich complex of neodymium. Application to isoprene polymerisation catalysis

The reaction of one equivalent of Nd(BH₄)₃(THF)₃ with an half equivalent of dialkylmagnesium in the presence of a stoichiometric amount of pentamethylcyclopentadiene cleanly affords a new kind of half-sandwich of neodymium that is stable toward comproportionation. This strategy can be advantageously applied to generate in situ catalysts allowing the controlled polymerisation of isoprene.     

Revised analysis of the structure of the v1 band of methane

The CARS spectrum of the v₁ band of ₁₂CH₄ at a pressure of 14 mbar was recorded using cw excitation in the cavity of a ring argon ion laser. The analysis of the intensity profile of the obarred spectrum led to the detection of inconsistencies with the hitherto proposed calculated positions of transitions with J = 7 to J = 10 and to a relocation of the corresponding lines.     

Hétérocyclisations intramoléculaires par réaction d'oxymercuration. I — synthèse et configurations des hétérocycles

We have accomplished the intramolecular oxymercuration of γ-δ ethylenic alcohols, with different mercuric salts under different conditions. By “in situ” reduction, or by direct reduction of isolated mercuric compounds, we obtain, in some cases, diastereoisomers with different relative yields.     

Reducing a chemical master equation by invariant manifold methods

We study methods for reducing chemical master equations using the Michaelis-Menten mechanism as an example. The master equation consists of a set of linear ordinary differential equations whose variables are probabilities that the realizable states exist. For a master equation with s(0) initial substrate molecules and e(0) initial enzyme molecules, the manifold can be parametrized by s(0) of the probability variables. Fraser's functional iteration method is found to be difficult to use for master equations of high dimension. Building on the insights gained from Fraser's method, techniques are developed to produce s(0)-dimensional manifolds of larger systems directly from the eigenvectors. We also develop a simple, but surprisingly effective way to generate initial conditions for the reduced models.     

Simultaneous microbatch screening of enantiorecognition on solid chiral selectors using selected mixtures of test-racemates: a case study on cellulose tris(alpha-phenylpropionate) with configurational diversity

An improved methodology for microbatch screening in the liquid-solid enantioselective adsorption of racemates by solid chiral selector is presented and illustrated by the evaluation of a series of six cellulose tris(alpha-phenylpropionate) presenting a configurational diversity and cellulose tris (4-methylbenzoate). Analyses were performed on 5 mg scale of chiral selector and 150 microL of supernatant containing a mixture of three test-racemates. Fifteen test-racemates were chosen according to their molecular diversity using a hierarchical clustering approach for seven selected three-dimensional molecular properties. The 15 racemates were sorted in five test mixtures composed of three racemates each according to the following constraints: each triplet of test-racemates can be analyzed without peak overlap on a commercially available chiral stationary phase (CSP). The designed five groups of three racemates may be used for the evaluation of other chiral selectors in view of the preparation of CSPs. This methodology improves the throughput of the evaluation and could be automated.     

Gear effect—10 : Conformational aspects of the positive or negative buttressing effects of methyl groups: polymethylpyridines

The effect of the shape of a methyl group on reactivity, which cannot be accounted for by considering a methyl group as a spherical substituent with the appropriate van der Waals radius, was considered in kinetics of alkylalion of substituted pyridines and barriers to rotation and ground state conformations of an isopropyl group attached to a planar framework. The perturbation of a methyl group by an o-methyl group is accounted for by a unique conformational explanation which involves the polyhedral shape of the methyl group.