





Volume 49, Number 78, 2004 ~ Contents only ~


THEORETICAL PHYSICS  GRAVITATION 

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Title & Author(s) 
549 
Motion of the Mass Centers in a Scalar Theory of Gravitation: the PointParticle Limit
MAYEUL ARMINJON
We investigate the pointparticle limit of the equations of motion valid for a system of extended bodies in a scalar alternative theory of gravitation: the size of one of the bodies being a small parameter $\xi$. we calculate the limit, as $\xi$ tends towards 0, of the postNewtonian (PN) acceleration of this small body. We use the asymptotic scheme of PN approximation, that expands all fields. We find that the PN acceleration A of the small body keeps a structuredependent part at this limit. In particular, if the only massive body is static and spherical, then A differs from the PN acceleration of a test particle in a Schwarzschild field only by this structuredependent part. The presence of the latter is due to the fact that the PN metric depends on the first spatial derivatives of the Newtonian potential. Since just the same form of PN metric is valid for the standard form of Schwarzschild's solution, the acceleration of a small body might keep a structuredependent part at the point limit in general relativity also, depending on the gauge. The magnitude of the structuredependent acceleration is already challenging on Earth. For the Pioneer spacecrafts, it is likely to discard the current version of the scalar theory. A modified version has been outlined in a quoted reference.


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GENERAL PHYSICS  HYDRODYNAMICS 

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Title & Author(s) 
573 
Thermosolutal Instability Problem in RivlinEricksen ElasticoViscous Fluid: A Characterization Theorem
HARI MOHAN, PARDEEP KUMAR, PUSHPA DEVI
The thermosolutal instability of a layer of RivlinEricksen elasticoviscous fluid is considered. A mathematical theorem disallowing the existence of neutral or unstable oscillatory motions in an initially bottom heavy thermosolutal convection configuration of the Veronis' [1] type with a quite general nature of bounding surfaces whenever the thermosolutal Rayleigh number is less than a critical value, is established.


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GENERAL PHYSICS  MAGNETIC FLUIDS 

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Title & Author(s) 
583 
Some New Experimental Results on MagnetoOptical Effects in Ferrofluids
G. FOSA, R. BĂDESCU, GH. CĂLUGĂRU
In an applied magnetic field the ferrofluids behave optically anisotropic. In this work we present the microscopically observed patterns in transformeroil magnetic fluid films in applied parallel and perpendicular magnetic fields and optically effects of these, especially the optical transmittance. The most interesting experimental observation is that concerning the time dependence of relative transmissivity, $\bar{T}_r$. For kerosene base ferrofluids $\bar{T}_r$ relax rapidly at coupling and decoupling magnetic field, but for a transformeroil magnetic fluid the relaxation times can attain 35 minutes, depending on intensity of applied magnetic field.


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NUCLEAR PHYSICS 

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Title & Author(s) 
589 
Perspectives for Positron Emission Tomography with RPCs
ILIE CRUCERU, IOANA MANEA, CARMEN NICORESCU, FLORIN CONSTANTIN
Several detecting structures based on Resistive Plate Counters (RPCs) are evaluated for the use in a positron emission 3D Complete Body Scan tomograph. The coincidence matrix is built for the specific detecting structure by means of random gamma pair rays generation, and then the filtered backprojection algorithm is used to reconstruct the original picture. The accuracy of image reconstruction is examined for the four different detecting structures.


597 
Measuring System for the Production of Gaseous Standards
E. SANDU, D. STÂNGA, R. MĂRGINEANU
Gaseous standards are necessary for the calibration of gas monitoring instruments used for the activity measurement of the gases discharged by nuclear power plants. A measuring system has been developed to standardize these radionuclides by the internal gas proportional counting method of measurement. It is simple and easy to operate. Using this measuring system, the activity per unit volume of the beta emitting gaseous radionuclides, such as ^{3}H, ^{85}Kr and ^{133}Xe, can be measured accurately. Thus, samples of tritium gas were measured with a relative standard uncertainty less than 0.8%.


601 
Customization of RODOS 5.0 System for the Assessment of a CANDUNPP Cernavoda Nuclear Accident Scenario
GH. MATEESCU, D. GALERIU, D. SLAVNICU, D. VAMANU, T. CRACIUNESCU, CATRINEL TURCANU, ANCA MELINTESCU, DORINA GHEORGHIU, ADRIANA GHEORGHIU
The RODOS is projected to run for multiuser operation at European scale in national nuclear emergency centres (responsible for offsite nuclear emergency management). Its development involves different stages of increasing complexity each of them called a prototype (PRTY) version which have to be customized by each participant country and validated in adequate accident scenarios. The present work underlines the results obtained by the Romanian RODOS Team at IFINHH with customization and validation of the most recent RODOS version (PRTY 5.0) taking into account tbe accident scenario for CANDU reactor and other specific Romanian conditions (the tritium issue, a more detailed geographical data base, associated costs of countermeasures, etc.).


611 
Structure Investigations on Portland Cement Paste by Small Angle Neutron Scattering
C. A. DRAGOLICI, A. LEN


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CONDENSED MATTER 

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Title & Author(s) 
617 
A Mössbauer Study of FeC Steel Corrosion in Diluted Ammoniac Solutions
I. BIBICU, A. SAMIDE, M. PREDA
The corrosion product formed on surface of the industrial FeC steel with low carbon concentration, after immersion in diluted ammonia solutions, have been investigated by means of ^{57}Fe Mössbauer spectroscopy. The amorphous Fe^{3+} oxyhydroxide is the major constituent of the corrosion layers. The corrosion product thickness increases with the change of the NH_{3} concentration from 10^{1} M to 10^{4} M. All CEMS spectra show that there is a magnetic anisotropy on the surface of the samples.


625 
Simple Phenomenological Theory for the ReEntrance Phenomenon in Lyotropic Liquid Crystals
RODICA MOLDOVAN, MIHAELA ŢÎNŢARU , MĂDĂLINA ROXANA PUICA, T. BEICA, IRINA ZGURA
A phenomenological theory based on the Landau  de Gennes expansion of the free energy density, for the reentrance in lyotropics, is presented. The phenomenological coefficients and the order parameter temperature and concentration dependence for potassium laurate/decanol/water system showing reentrant isotropic discotic nematic phase transition, are obtained.


631 
Structural Investigations of FayaliteTephroite Series from the Razoare MnFe Ore Deposit
S. CONSTANTINESCU, N. POPESCUPOGRION, G. UDUBASA, P. HARTOPANU, S. T. REDFERN
The paper reports the results of local structure and microchemistry aspects of manganoan fayalite samples extracted from the MnFe deposit of Razoare in the Romanian Carpathians. The microstructure of natural samples have been investigated by ^{57}FeMössbauer technique (NGR), electron microscopy (BFTEM, DFTEM, SAED). A NGRrefined analysis of samples at room (RT) and LHetemperature (LHeT), evidenced the several magnetic phases corresponding to olivines, the Fe and FeMn oxides, the effects of superparamagnetism in some samples, the ordering degree of Fe in cationic site of olivine structure. In correlation with the XRD and ND data on some synthetic FeMn olivines, one established the dependencies of the unit cell parameters and M1, M2 polyhedron volume deformation around the metallic cations relative to iron content. The TEM investigations of natural mangangrunerite (formerly danemorite) assemblage (DA/138) have revealed the presence of precipitates and its identification: the FeO (wustite) and magnetite (Fe_{3}O_{4}).


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OPTICS 

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Title & Author(s) 
641 
The Optical Fibers  New Possibilities in Spectrometry
CAMELIALAURA SAVA, NICOLAE REZLESCU
In conventional spectrometers the transmission of light from the plasma to the spectrometer is done by lenses and/or mirrors. Fiber optics offer, in addition to low light loss on transport, the excellent opportunity of simultaneously coupling multiple spectrometer systems to the plasma without enormous space requirements or alignment difficulties. In this article we will describe an experiment using spark and ICP excitation to determine the advantages use the optical fibers. The use of optical fibers for light capture and transmission to the optics increases accuracy, reproducibility, sensitivity, long term stability, and flexibility of analytical system.


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THEORETICAL PHYSICS  SCATTERING 

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Title & Author(s) 
653 
Saturation of Optimality Limits in HadronHadron Scatterings
D. B. ION, M. L. ION
In this paper the optimal unitarity lower bound on logarithmic slope of the diffraction peak is investigated. It is shown that the unitarity lower bound is just the optimal logarithmic slopes predicted by the principle of least distance in space of states. A systematic tendency towards the saturation of the most forwardpeaked limit is observed from all the available experimental data of all principal hadronhadron (e.g., $PP$, $\bar{P}P$, $K^{\pm}P$, $\pi^{\pm}P$) scatterings practically at all laboratory momenta.


671 
Dual Coherent Particle Emission as Generalised CherenkovLike Effect in High Energy Particle Collisions
D. B. ION, E. K. SARKISYAN
In this paper we introduce a new kind of nuclear/hadronic coherent particle production mechanism in highenergy collisions called dual coherent particle emission (DCPE) which takes place when the phase velocities of the emitted particle $v_{Mph}$ and that of particle source $v_{B_1 ph}$ satisfy the dual coherence condition: $v_{Mph} \le v^{1}_{B_1 ph}$. The general signatures of the DCPE in the nuclear and hadronic media are established and some experimental evidences are given.


681 
On Simple Parameterizations of $f_n(\alpha)=\int_{0}^{\infty}e^{\alpha^2 x^2} x^{2n+1} K_{n}^{2}(x) dx$
I. BULBOACA, R. J. LOMBARD, J.P. MAILLET
Studying integrals of the form $f_n(\alpha)=\int_{0}^{\infty}e^{\alpha^2 x^2} x^{2n+1} K_{n}^{2}(x) dx$ with $n$ = 0, 1, ... an analytical expression for $n$ = 0 is first examined. Subsequently, simple parameterizations are proposed, which are valid to the percent level over a wide range of a values.


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EARTH PHYSICS 

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Title & Author(s) 
691 
Amplification Factors in Oscillatory Motion
B.F. APOSTOL
The forced oscillatory motion with damping is reviewed and amplification factors are defined and computed at resonance for displacement, velocity and acceleration. The amplification for external shocks is also estimated.


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