Synthesis and characterization of nanomagnetite particles and their polymer coated forms

Superparamagnetic nanoparticles were prepared by coprecipitation of ferrous (Fe(2+)) and ferric (Fe(3+)) aqueous solution by a base. Nanomagnetite particles were coated with poly(St/PEG-EEM/DMAPM) and poly(St/PEG-MA/DMAPM) layer by emulsifier-free emulsion polymerization. Chemical structure of nanoparticles was characterized by both FTIR and (1)H NMR. Particle morphologies were determined by Zeta Sizer, DLS, XRD and SAXS. Structural analysis showed that after polymer coating nanomagnetite particles kept their superparamagnetic property. Besides the synthesized magnetites, polymer coated forms of these particles are more biocompatible, well dispersable and uniform. These properties make them a very strong candidate for bioengineering applications, such as bioseparation, gene transfer.     

Studies on heat transfer and flow characteristics in subcooled flow boiling—Part 1. Boiling characteristics

Measurement of wall temperature profile and photographic observation are performed for R-113 subcooled boiling flow in a channel with heat fluxes up to the CHF. The incipient boiling superheats measured are little affected by mass velocity and liquid subcooling. Hysteresis in boiling observed by increasing and decreasing heat flux seems to be ascribed to variation in size of active nucleation cavities on the wall. Increasing heat flux up to the CHF, the bubble density on the heated surface increases and remarkably large coalescent bubbles appear periodically near the heating section outlet.     

Growth theorems and coefficient bounds for univalent holomorphic mappings which have parametric representation

Let B be the unit ball in Cn with respect to an arbitrary norm and let f(z,t) be a g-Loewner chain such that e−tf(z,t)−z has a zero of order k+1 at z=0. In this paper, we obtain growth and covering theorems for . Moreover, we consider coefficient bounds and examples of mappings in .     

Structure of methylphenylhydrazone form of 2-(2-methylphenylazo)-1,3-indandione

The molecule crystallizes in a ketohydrazone tautomeric form. The tautomeric form is stabilized by a strong intramolecular hydrogen bond of 2.709(2) Å binding the 3-oxo to the nearest nitrogen atom in the azine chain. The compound crystallizes in the monoclinic space group P2_l/c witha=7.0470(4),b=11.3090(9),c=16.2250(4) Å, =90.310(3)°, V=1293.0(1) ų, Z=4,Dx=1.3576 g cm^–3 and (Cu-K)=7.03 cm^–1. The molecule is nearly planar not regarding the methyl group; the small deviations from planarity are indicative of intramolecular interactions between the phenylazo group and indandione group. Some of the bond lengths and angles found in the molecule are distorted due to resonance, -electron delocalization and strain. The relation between these chemical effects and structural results are discussed.     

Ring-polymer Molecular Dynamics Simulation for the Adsorption of H2 on Ice Clusters (H2O)n (n=8, 10, and 12)

In the interstellar medium, the H₂ adsorption and desorption on the solid water ice are crucial for chemical and physical processes. We have recently investigated the probabilities of H₂ sticking on the (H₂O)₈ ice, which has quadrilateral surfaces. We have extended the previous work using classical MD and ring-polymer molecular dynamics (RPMD) simulations to the larger ice clusters, (H₂O)₁₀ and (H₂O)₁₂, which have pentagonal and hexagonal surfaces, respectively. The H₂ sticking probabilities decreased as the temperature increased for both cluster cases, whereas the cluster-size-independent profiles were observed. It is thought that the size independence of the probabilities is qualitatively understood from the similar binding energies for all the three cluster systems. Furthermore, the RPMD sticking probabilities are smaller than the classical ones because of the reduction in the binding energies owing to nuclear quantum effects, such as vibrational quantization.     

Reaction of the Mo3S4 cluster with dimethylacetylenedicarboxylate: an ESR-active cluster and an organometallic cluster formed by alpha,beta-conjugate addition

A seven-electron cluster [Mo3(mu3-S){mu3-SC(CO(2)CH(3))=C(CO(2)CH(3))S}{mu-SC(CO(2)CH(3))=CH(CO(2)CH(3))}(dtp)3(mu-OAc)] [2, S2P(OC(2)H(5))2-; dtp = diethyldithiophosphate] and an organometallic cluster [Mo3(mu3-S){mu3-SC(CO(2)CH(3))=C(CO(2)CH(3))S}{mu-SC(CO(2)CH(3))CH(OCH(3))(CO2)}(dtp)2(CH(3)OH)(mu-OAc)](Mo-C) (3) were obtained by reaction in methanol of the sulfur-bridged trinuclear complex [Mo3(mu3-S)(mu-S)3(dtp)3(CH(3)CN)(mu-OAc)] (1) with dimethylacetylenedicarboxylate (DMAD). The X-ray structures of 2 and 3 revealed the adduct formation of two DMAD molecules to the respective Mo(3)S(4) cores. 2 is paramagnetic and obeys the Curie-Weiss law: the mu(eff) value at 300 K is 1.90 muB. The electron spin resonance signal was observed at 173 K. The density functional theory calculation of 2 demonstrated that the main components of the singly occupied molecular orbitals of alpha and beta spins are Mo d electrons and the main components of lowest unoccupied molecular orbitals are of Mo and the olefin moiety with one C-S bond. A one-electron reversible oxidation process of 2 was observed at E1/2 = -0.11 V vs Fc/Fc+. The electronic spectrum of 2 has a peak at 468 nm (epsilon = 2170 M(-1) cm(-1)) and shoulders at 640 (918) and 797 (605) nm, and 3 has shoulders at 441 (1740) and 578 (625) nm and a distinct peak at 840 (467) nm. An intermediate [Mo3(mu3-S){mu3-SC(CO(2)CH(3))=C(CO(2)CH(3))S}{mu-SC(CO(2)CH(3))=CH(CO(2)CH(3))}(dtp)3(mu-OAc)]+ (4) is tentatively suggested: a one-electron reduction of 4 gives 2, and a nucleophilic conjugate addition of CH(3)O- to the alpha,beta-unsaturated carbonyl group of 4 gives 3.