Comparison of the Numerical Model with Experimental Data for a Beam-Loss Monitor Based on an Optical Fiber

Physics of Particles and Nuclei Letters - Abstract—The principle of operation of a distributed beam-loss monitor based on Cherenkov radiation in an optical fiber is considered. This device...     

Methods for Increasing the Spatial Resolution of a Distributed Beam-Loss Monitor Based on Cherenkov Radiation in an Optical Fiber

Physics of Particles and Nuclei Letters - Abstract—The principle of operation of a distributed beam-loss monitor based on the Cherenkov radiation in optical fiber is considered. The monitor...     

Ionization state and structure of l-1,2-dipalmitoylphosphatidylglycerol monolayers at the liquid/air interface

Phosphatidylglycerols are components of biological membranes. The phase behavior of these phospholipids was extensively investigated. However, there is still no definite picture about the dependence of the ionization state and monolayer structure on subphase composition. The major problem of previous investigations is that none of the methods used allow obtaining the ionization degree directly. In the present work we apply techniques developed in the past decades for Langmuir monolayers: infrared reflection absorption spectroscopy (IRRAS) as well as X-ray diffraction and reflectivity techniques, which provide straightforward information about structure and ionization state of a L-1,2-dipalmitoylphosphatidylglycerol (DPPG) monolayer. The Gouy-Chapman model is applied to evaluate the intrinsic pKa. Therewith, the ionization degree can be determined even at low pH values. The experimental titration curves are in good agreement with theoretical curves based on the Gouy-Chapman model. The obtained instrinic pKa amounts to 1. The ionization degree of a DPPG monolayer is independent of the monovalent cation size. In contrast, the structure of a DPPG monolayer is strongly affected by the type of divalent cations.     

Influence of assembling pH on the stability of poly(L-glutamic acid) and poly(L-lysine) multilayers against urea treatment

Polyelectrolyte multilayers of poly(L-glutamic acid) (PGA) and poly(L-lysine) (PLL) were built up using the layer-by-layer (LbL) technique in low pH (3.6, PM3.6) and in neutral pH (7.4, PM7.4) solutions. The multilayers were then treated with a concentrated urea (one kind of denaturant for proteins and polypeptides) solution (8M) and rinsed with corresponding buffer. The buildup and treatment processes were investigated by ultraviolet visible spectroscopy and ellipsometry. The surface morphology was observed by scanning force microscopy (SFM). The inner structures were determined by X-ray reflectometry and circular dichroism spectroscopy (CD). An exponential growth of the optical mass and the layer thickness was observed for both PM3.6 and PM7.4. After urea treatment, a significant mass loss for PM3.6 was found, while no mass change was recorded for PM7.4. The dominant driving force for PM7.4 is electrostatic interaction, resulting in multilayers with an abundant beta-sheet structure, which has higher stability against urea treatment. By contrast, the dominant driving force for PM3.6 is hydrogen bonding and hydrophobic interaction, which are sensitive to the urea treatment. The mechanism is substantiated by molecular mechanics calculation. This has offered a convenient pathway to mediate the multilayer properties, which is of great importance for potential applications.     

Nondestructive diagnostics of charged particle beams in accelerators

The basic techniques for nondestructive diagnostics and detection of losses of charged particle beams used in accelerator engineering are reviewed. The data provided may help choose the systems for diagnostics and detection of losses of beams and give a qualitative picture of the operation principles of such devices. Quantitative characteristics that define the limits of applicability of each diagnostic technique are outlined.     

Optimizing Parameters of the Fiber-Optic Beam-Loss Monitor for the VEPP-5 Injection Complex

Physics of Particles and Nuclei Letters - The distributed beam-loss monitor based on the Cherenkov radiation in an optical fiber installed on the e–e+ Injection Complex at the Budker...     

Porphyrin-based molecular receptors for alkali metal cations: synthesis and chemical modification

A synthetic approach leading to the meso-arylporphyrins containing a conformationally mobile polyether fragment on the benzene ring with a terminal pyridine ring has been developed, which opens the possibility for design of new porphyrin-based molecular receptors for detection and selective binding of alkali metal cations.     

Determination of Discontinuities of a Function in a Domain with Refraction from Its Attenuated Ray Transform

Some results of numerical investigations are presented for the problem of determination of discontinuities of an unknown function that has the meaning of the internal source distribution and is given in a domain with absorption and refraction, on using the attenuated ray transform of the function. The refraction and the absorption coefficient are assumed to be given. The behavior of the available and newly constructed discontinuity indicator operators is investigated in some numerical tests. Some modification of discontinuity indicators was carried out for the purpose of applying them in the model of refractive tomography with absorption. Numerical methods are applied to investigate the possibility of using the operators of this kind for solving the problem of finding the discontinuities of a function from its attenuated ray transform; the degree is investigated of the influence on the recovery quality of such factors as the level of the noise introduced into the generated data, the parameters of metrics, the magnitude and variation of the absorption coefficient.     

Complexes of Erbium and Lutetium of Different Compositions with 4-R-5-Nitro-substituted Phthalocyanines

Metal complexes (metal: ligand = 1 : 1) have been obtained via the reaction of 4-R-5-nitrophthalonitriles with erbium and lutetium acetates and chlorides. 1 : 2 heteroleptic complexes have been synthesized based on them, containing unsubstituted and octasubstituted phthalocyanine ligands at the metal atom. The products have been characterized by a set of physico-chemical methods.