Self-assembly of magnetic iron oxide nanoparticles into cuboidal superstructures

This chapter describes the synthesis and some characteristics of magnetic iron oxide nanoparticles, mainly nanocubes, and focus on their self-assembly into crystalline cuboids in dispersion. The influence of external magnetic fields, the concentration of particles, and the temperature on the assembly process is experimentally investigated

Hierarchical fragmentation and differential star formation in the Galactic "Snake": infrared dark cloud G11.11-0.12

We present Submillimeter Array (SMA) $\lambda =$ 0.88 and 1.3 mm broad band observations, and the Jansky Very Large Array (VLA) observations in $\rm{NH_3}$ $(J,K) = (1,1)$ up to $(5,5)$, $\rm{H_2O}$ and $\rm{CH_3OH}$ maser lines toward the two most massive molecular clumps in infrared dark cloud (IRDC) G11.11-0.12. Sensitive high-resolution images reveal hierarchical fragmentation in dense molecular gas from the $\sim 1$ pc clump scale down to $\sim 0.01$ pc condensation scale. At each scale, the mass of the fragments is orders of magnitude larger than the Jeans mass. This is common to all four IRDC clumps we studied, suggesting that turbulence plays an important role in the early stages of clustered star formation. Masers, shock heated $\rm{NH_3}$ gas, and outflows indicate intense ongoing star formation in some cores while no such signatures are found in others. Furthermore, chemical differentiation may reflect the difference in evolutionary stages among these star formation seeds. We find $\rm{NH_3}$ ortho/para ratios of $1.1\pm0.4$, $2.0\pm0.4$, and $3.0\pm0.7$ associated with three outflows, and the ratio tends to increase along the outflows downstream. Our combined SMA and VLA observations of several IRDC clumps present the most in depth view so far of the early stages prior to the hot core phase, revealing snapshots of physical and chemical properties at various stages along an apparent evolutionary sequence.Comment: 21 pages, 11 figures, 8 tables, accepted to MNRAS; this version includes minor typo corrections from proo

Manipulating the motion of large neutral molecules

Large molecules have complex potential-energy surfaces with many local minima. They exhibit multiple stereo-isomers, even at very low temperatures. In this paper we discuss the different approaches for the manipulation of the motion of large and complex molecules, like amino acids or peptides, and the prospects of state- and conformer-selected, focused, and slow beams of such molecules for studying their molecular properties and for fundamental physics studies. Accepted for publication in Faraday Disc. 142 (2009), DOI: 10.1039/b820045aComment: 12 page

Effects of hemodialysis on plasma oxylipins

Chronic kidney disease (CKD) is an important risk factor for cardiovascular and all-cause mortality. Survival rates among end-stage renal disease (ESRD) hemodialysis patients are poor and most deaths are related to cardiovascular disease. Oxylipins constitute a family of oxygenated natural products, formed from fatty acid by pathways involving at least one step of dioxygen-dependent oxidation. They are derived from polyunsaturated fatty acids (PUFAs) by cyclooxygenase (COX) enzymes, by lipoxygenases (LOX) enzymes, or by cytochrome P450 epoxygenase. Oxylipins have physiological significance and some could be of regulatory importance. The effects of decreased renal function and dialysis treatment on oxylipin metabolism are unknown. We studied 15 healthy persons and 15 CKD patients undergoing regular hemodialysis treatments and measured oxylipins (HPLC-MS lipidomics) derived from cytochrome P450 (CYP) monooxygenase and lipoxygenase (LOX)/CYP omega/(omega-1)-hydroxylase pathways in circulating blood. We found that all four subclasses of CYP epoxy metabolites were increased after the dialysis treatment. Rather than resulting from altered soluble epoxide hydrolase (sEH) activity, the oxylipins were released and accumulated in the circulation. Furthermore, hemodialysis did not change the majority of LOX/CYP omega/(omega-1)-hydroxylase metabolites. Our data support the idea that oxylipin profiles discriminate ESRD patients from normal controls and are influenced by renal replacement therapies

Simultaneous optical polarimetry and X-ray data of the near synchronous polar RX J2115-5840

We present simultaneous optical polarimetry and X-ray data of the near synchronous polar RX J2115-5840. We model the polarisation data using the Stokes imaging technique of Potter et al. We find that the data are best modelled using a relatively high binary inclination and a small angle between the magnetic and spin axes. We find that for all spin-orbit beat phases, a significant proportion of the accretion flow is directed onto the lower hemisphere of the white dwarf, producing negative circular polarisation. Only for a small fraction of the beat cycle is a proportion of the flow directed onto the upper hemisphere. However, the accretion flow never occurs near the upper magnetic pole, whatever the orientation of the magnetic poles. This indicates the presence of a non-dipole field with the field strength at the upper pole significantly higher. We find that the brightest parts of the hard X-ray emitting region and the cyclotron region are closely coincident.Comment: 9 pages, accepted for publication in MNRAS 2 March 200

The Cauchy Problem for the Einstein Equations

Various aspects of the Cauchy problem for the Einstein equations are surveyed, with the emphasis on local solutions of the evolution equations. Particular attention is payed to giving a clear explanation of conceptual issues which arise in this context. The question of producing reduced systems of equations which are hyperbolic is examined in detail and some new results on that subject are presented. Relevant background from the theory of partial differential equations is also explained at some lengthComment: 98 page

Markov Properties of Electrical Discharge Current Fluctuations in Plasma

Using the Markovian method, we study the stochastic nature of electrical discharge current fluctuations in the Helium plasma. Sinusoidal trends are extracted from the data set by the Fourier-Detrended Fluctuation analysis and consequently cleaned data is retrieved. We determine the Markov time scale of the detrended data set by using likelihood analysis. We also estimate the Kramers-Moyal's coefficients of the discharge current fluctuations and derive the corresponding Fokker-Planck equation. In addition, the obtained Langevin equation enables us to reconstruct discharge time series with similar statistical properties compared with the observed in the experiment. We also provide an exact decomposition of temporal correlation function by using Kramers-Moyal's coefficients. We show that for the stationary time series, the two point temporal correlation function has an exponential decaying behavior with a characteristic correlation time scale. Our results confirm that, there is no definite relation between correlation and Markov time scales. However both of them behave as monotonic increasing function of discharge current intensity. Finally to complete our analysis, the multifractal behavior of reconstructed time series using its Keramers-Moyal's coefficients and original data set are investigated. Extended self similarity analysis demonstrates that fluctuations in our experimental setup deviates from Kolmogorov (K41) theory for fully developed turbulence regime.Comment: 25 pages, 9 figures and 4 tables. V3: Added comments, references, figures and major correction