Rotaxane Probes for the Detection of Hydrogen Peroxide by 129Xe HyperCEST NMR Spectroscopy

The development of sensitive and chemically selective MRI contrast agents is imperative for the early detection and diagnosis of many diseases. Conventional responsive contrast agents used in ¹H MRI are impaired by the high abundance of protons in the body. ¹²⁹Xe hyperCEST NMR/MRI comprises a highly sensitive complement to traditional ¹H MRI because of its ability to report specific chemical environments. To date, the scope of responsive ¹²⁹Xe NMR contrast agents lacks breadth in the specific detection of small molecules, which are often important markers of disease. Herein, we report the synthesis and characterization of a rotaxane‐based ¹²⁹Xe hyperCEST NMR contrast agent that can be turned on in response to H₂O₂, which is upregulated in several disease states. Added H₂O₂ was detected by ¹²⁹Xe hyperCEST NMR spectroscopy in the low micromolar range, as well as H₂O₂ produced by HEK 293T cells activated with tumor necrosis factor.     

Interaction of light with subwavelength apertures: a comparison of approximate and rigorous approaches

The interaction of an electromagnetic wave with various classes of subwavelength one dimensional apertures is studied in detail, using several approximate and rigorous approaches. The attention is given to a comparison of the revealing basic physical features of the interaction. Several semi-analytical models which are able to predict the enhanced transmission phenomenon are reviewed, applied, and extended: the one-mode periodic model, the model based on the composite diffracted evanescent wave approach, and the so called combined model. Then, a detailed rigorous modeling is performed, using the finite difference time domain method, to study the parametrical dependencies of all critical parameters (i.e. the parameters of the aperture—diameter and thickness, and also the parameters of the surrounding corrugations). The transmission properties of the subwavelength single apertures and apertures with the supporting corrugations on the input side and on both sides of the structure are compared in detail, and the options for their optimizations are discussed. Finally, the results of approximate models are compared with that from the rigorous finite difference time domain modeling, for the case of two important cases, a periodic array of slits and the slit-groove diffraction problem, i.e. a combination of the aperture and one corrugation.     

Normal equivalent to an arbitrary diagonalizable matrix

The aim of this paper is to reduce the eigenvalue problem of a diagonalizable matrix to the eigenvalue problem of an equivalent normal matrix. We use for this purpose a minimization strategy, which is also applicable for transforming an arbitrary nondiagonalizable matrix to an almost normal one.     

The influence of proper mechanical vibrations on some properties of TGS tandel

In the present paper the existence is proved of mechanical vibrations in TGS tandels in the frequency range from 5 kc/s to 1000 kc/s. A number of resonances was found in the given range of frequencies. Mainly plane and flexural vibrations occur. A study is made of their influence on the course of the frequency dependence of the complex effective permittivity, dielectric non-linearities of the tandel, and the thermoelectric force measured by a thermocouple on its surface. From the study of the frequency dependences of these parameters at various temperatures the conclusion is drawn that the probable cause of the origin of mechanical vibrations in a tandel is the piezoeffect.At the 2^nd International Conference on Piezoelectricity in Liberec on Sept. 1^st, 1965 the main results of this paper were presented.In conclusion the authors would like to express their deep gratitude to Ing. J. Janta of the Institute of Radio Engineering and Electronics, Czechoslovak Academy of Sciences, to Associate Professor Dr. J. Tichý of the Technical University in Liberec and to Dr. J. Mastner of the Institute of Radio Engineering and Electronics for valuable discussions and suggestions, and to Associate Professor Dr. O. Taraba of the Czech Technical University also for facilitating the ultrasonic experiments and his help in arranging them in his laboratory. We are also indebted to all our colleagues for their friendly help.     

Hydrogen bonding effects on the (15)N and (1)H shielding tensors in nucleic acid base pairs

The results of systematic ab initio calculations of (15)N and (1)H chemical shielding tensors in the GC base pair as a function of hydrogen bond length are presented for the first time. The hydrogen bond length characterized by the distance r(N...N) between purine N1 and pyrimidine N3 was varied between 2.57 and 3.50 A and the chemical shift tensors were calculated by the sum-over-states density functional perturbation theory. It is shown that the hydrogen bond length has a strong effect on the chemical shielding tensor of both imino proton and nitrogen, on their orientation, and, as a consequence, on the relaxation properties of both nuclei. For a nitrogen nucleus not involved in hydrogen bonding, the shielding tensor is nearly axially symmetric and almost collinear with the bond vector. As the length of the hydrogen bond decreases, the least shielding component sigma(11) deflects from the N-H vector and the shielding tensor becomes increasingly asymmetric. The significance of the presented results for the analysis of relaxation data and the efficiency of TROSY effects together with a summary of the relevant shielding parameters are presented and discussed.     

Development of some hypersonic benchmark flows using CFD and experiment

Abstract. This paper presents a set of test cases in high speed aerodynamics that describe our perceived relationship between experiment and computation. Computational fluid dynamics, with sensible interpretation, can guide experimental design, so that wind tunnel studies can focus better on fundamental ‘benchmark’ studies. Likewise experimental data may be used as feed back to evaluate codes and to improve their physical modelling. Here we present several test cases, developed in our laboratory, that we regard as basic ‘building blocks’ for high speed aerodynamics. These include: design for boundary-layer/pressure-gradient interaction; cavity flows; shock-wave/boundary-layer interactions; techniques for a graduated and controlled study of three-dimensional separated flows. Received 10 October 2001/ Accepted 19 November 2002 Published online 4 February 2003 Correspondence to: R. Hillier (r.hillier@ic.ac.uk) An abridged version of this paper was presented at the 23rd Int. Symposium on Shock Waves at Fort Worth, Texas, from July 22 to 27, 2001     

Thermal cyclization of 4‐azido‐3‐nitropyridines to furoxanes

4‐Chloro‐3‐nitro‐2‐pyridines 3 and 10, obtained from 4‐hydroxy‐2‐pyridones 1 and 8 after nitration and chlorination, gave with sodium azide 4‐azido‐3‐nitropyridines 4 and 11 , which cyclized on thermolysis to furoxans 6 and 12 . Desoxygenation of the furoxan 6 with triphenylphosphane gave the furazan 7 . Thermal decomposition conditions of the azide 4 and the desoxygenation reaction of 6 to 7 were studied by differ ential scanning calorimetry (DSC).     

A theory of a receiving antenna in a moving isotropic plasma

We analyze the response of a dipole antenna to the noise-like and/or regular (quasimonochromatic) plasma oscillations and waves. The antenna is immersed in an isotropic plasma moving with velocity greater than the electron thermal velocity. In the case of a noise field, we calculate the squared spectral power density of the noise voltage at the input of a receiving antenna for frequencies close to the electron plasma frequency. It is shown that the main contribution to the noise is made by the radiation due to the excitation of waves at anomalous Doppler frequencies. In the case of an incident monochromatic wave, the mean square voltage at the antenna input is calculated as a function of the wave frequency and angle of arrival. It is shown that the effective antenna length can differ strongly from the geometrical length of the dipole. This fact results from the dispersion of longitudinal waves ensuring that many plane waves (a continuum, in the limiting case) contribute to the re-radiated field for a given direction of propagation of the radiation energy.     

Synchrotron radiation photoelectron spectroscopy study of metal-oxide thin film catalysts: Pt-CeO2 coated CNTs

The interaction of Pt with CeO₂ layers was investigated by using high resolution hard X-ray photoelectron spectroscopy. Pt doped CeO₂ layers were deposited simultaneously by rf-magnetron sputtering on a SiO₂/Si substrate and carbon nanotubes (CNTs) grown on a carbon diffusion layer of a polymer membrane fuel cell. In the case of the CNT support photoelectron spectra showed the formation of ionic platinum rich cerium oxide with Pt^2+,4+ species, and with the Pt²⁺/Pt⁴⁺ ratio strongly dependent on the amount of platinum. Ce reveals 4+/3+ mixed valent character with Ce³⁺ concentration increasing with Pt content. In the case of the SiO₂/Si substrate the film revealed Ce⁴⁺ and Pt⁴⁺ species only.     

A framework for solving network revenue management problems with customer choice behavior

Revenue management is the process of understanding, anticipating and influencing consumer behavior in order to maximize revenue. Network revenue management models attempt to maximize revenue when customers buy bundles of multiple resources. The dependence among the resources in such cases is created by customer demand. Network revenue management can be formulated as a stochastic dynamic programming problem whose exact solution is computationally intractable. Solutions are based on approximations of various types. Customer choice behavior modeling has been gaining increasing attention in the revenue management. A framework for solving network revenue management problems with customer choice behavior is proposed. The modeling and solving framework is composed from three inter-related network structures: basic network model, Petri net, and neural net.