Quasi-SMILES: quantitative structure–activity relationships to predict anticancer activity

Molecular Diversity - Reliable prediction of anticancer potential of different substances for different cells using unambiguous algorithms is attractive alternative of experimental investigation of...     

Jet activity versus alignment

The hypothesis of the relation between the observed alignment of spots in x-ray films in cosmic ray emulsion experiments and the features of events in which jets prevail at super-high energies is tested. Due to the strong dynamical correlation between jet axis directions and that between the momenta of jet particles (almost collinearity), the evaluated degree of alignment is considerably larger than that for randomly selected chaotically located spots in the x-ray film. It appears to be comparable with the experimental data provided that the height of the primary interaction, the collision energy and the total energy of the selected clusters meet certain conditions. The Monte Carlo generator PYTHIA, which basically well describes jet events in hadron-hadron interactions, was used for the analysis.Received: 25 February 2005, Revised: 18 April 2005, Published online: 2 August 2005     

X-ray detected optical activity

Optical Activity (OA) was only measured quite recently in the X-ray range using electric dipole–electric quadrupole interference terms that mix multipoles of opposite parity but are only present in systems with broken inversion symmetry. Natural OA refers to effects that are even with respect to time-reversal symmetry, whereas non-reciprocal OA is concerned with time-reversal odd contributions. Various types of X-ray dichroism related to either natural or non-reciprocal OA have been detected and are reviewed in the present paper. To cite this article: A. Rogalev et al., C. R. Physique 9 (2008).     

ILC activity at JINR

JINR is an active participant in the massive new international project ILC. JINR physicists are taking part in several fields of activity in the International Linear Collider (ILC), such as work on the photo injector prototype, the design and construction of cryomodules, laser metrology, cryodiagnostics, etc. The Joint Institute is one of the potential candidates for hosting the ILC, near Dubna, Russia. The status and progress of the above topics are discussed in the report. The text was submitted by the authors in English.     

Conductivity in an activity gradient

A procedure to evaluate conductivity measurements on a sample exposed to an activity gradient is presented The method allows the measured mean conductivity to be subsequently associated with a denned activity It offers not only an experimentally simple alternative to the Wagner-Hebb experiment, but also enables detailed information to be obtained about the activity dependence of the conductivity in polarization measurements with two blocking electrodes as well as in concentration cell experiments, no matter whether a two- or four-point arrangement is used It is further shown how the steady-state activities, which are necessary to compute the desired mean value, can be obtained from the initial and boundary conditions     

Optimal control of neuronal activity

We investigate the optimal control of neuronal spiking activity for neurons receiving a class of random synaptic inputs, characterized by a positive parameter alpha. Optimal control signals and optimal variances are found exactly for the diffusion process approximating an integrate and fire model. When synaptic inputs are "sub-Poisson" (alpha<0.5), we find that the optimal synaptic input is a delta function (corresponding to bang-bang control) and the optimal signal is not unique. Poisson synaptic input is the critical case: The control signal is unique, but the control signal is still a delta function. For "supra-Poisson" (alpha>0.5) inputs, the optimal control is smooth and unique. The optimal variance obtained in the current paper sets the lowest possible bound in controlling the stochasticity of neuronal activity. We also discuss how to implement the optimal control signal for certain model neurons.     

Automatic optical activity measurement system

The present note proposes a simple, fast and accurate experimental technique to measure the specific optical activity coefficients in fibre-like crystals. The system is based on the automatic electronic phase shift detection by a lock-in amplifier in a dynamic polarimetric system.     

Laser-induced stimulation of chymotrypsin activity

Experimental evidence supporting Frölich's conjecture of a metastable state in enzymes is provided.     

Optical activity and time reversal

The rôle of time reversal symmetry in natural and magnetic optical activity is discussed. Natural optical rotation is shown to be generated by an anti-hermitian odd parity time-even operator and magnetic optical rotation by an anti-hermitian even parity time-odd operator. This shows that lack of time reversal invariance is not the source of natural optical rotation and that free atoms can show natural optical rotation without violating reversality, which leads to a fundamental distinction between the conditions necessary for natural optical rotation and a permanent space-fixed electric dipole moment. General transition optical activity and polarizability tensors between components of degenerate states are discussed with reference to possible new Raman experiments and new contributions to discriminating intermolecular forces between chiral molecules. Time reversal symmetry also leads to a new criterion for chiral objects and to the concept that natural optical activity provides an example of spontaneous symmetry breaking with respect to CP.     

MWCNT-oxazolidinone conjugates with antibacterial activity

Journal of Nanoparticle Research - The electronic and optical properties of the iron-doped bismuth nanoclusters having less than 15 atoms are presented here. This doping is especially interesting...     

Magnetoacoustic activity of rhombohedral antiferromagnets

A quantitative theory of magnetic acoustic birefringence in rhombohedral antiferromagnets is developed. It is shown that acoustic activity and the Faraday effect associated with it are determined by the joint action of piezomagnetism and magnetostriction. The effect is estimated quantitatively, and the method of experimental determination of the piezomagnetic constant is indicated. The conditions for the transformation of linear polarization into circular polarization and for the rotation of linear polarization through 90° are determined.     

Self-induced optical activity in crystals

We have observed non-linear rotation of the plane of polarization of a linearly polarized light beam in GaAs crystals ($\text{4}$3m). The effect has been investigated by means of YAG : Nd^3- laser and pulse polarimeter with accuracy to non-linear rotation angle 0.02°. Two mechanisms caused by the non-linearity of the spatial dispersion and the anisotropy of two-photon's absorption have been distinguished and corresponding susceptibilities have been calculated.     

Photodynamic activity of different dyes

Photodynamic therapy (PDT) is a technique for inducing tissue damage with light irradiation of a drug selectively retained in malignant tissue. Many kinds of compounds are known with photosensitizing properties including dyes, drugs, cosmetics, chemicals, and many natural substances. There are different classes of sensitizers used for medical purposes such as tetrapyrroles (porphyrins and derivatives, chlorophyll, phylloerythrin, phthalocyanines), tricyclic dyes with different meso-atoms (acridine orange, proflavine, riboflavine, methylene blue, fluorescein, eosine, erythrosine, rose bengal), and furocoumarins (psoralen and its methoxyderivatives xanthotoxin, bergaptene). In this work, we performed one comparative cytotoxic study of the photodynamic activity presented by tricyclic dyes (methylene blue, fluorescein and erythrosine) and the commercial Russian photosensitizer Photogem® (hematoporphyrin derivative). For this purpose, three cell lines were used: HEp-2 (tumor cells), VERO and McCoy (nontumor cells), and a yeast strain. The wavelength used for irradiation was 630 nm, the same as used in PDT for medical purposes, since it is in the therapeutic window, i.e., where light can penetrate more into the tissues. The results suggest that Photogem® is more cytotoxic and more photocytotoxic than the studied tricyclic dyes in nontumor and tumor cells. These dyes present less cytotoxicity (around half) in normal cells (dark and light) than in tumor cells. In the experiments with microorganisms, methylene blue presented a better photodynamic effect than Photogem®. These results can be explained by the fact that it is more difficult for Photogem® to penetrate in microorganism membranes than mammalian cell membranes. As for Photogem®, these tricycle dyes present a higher cytotoxicity in tumor cells. These data suggest that methylene blue can be an option in photodynamic inactivation as well as in photodynamic therapy, mainly for superficial lesions.