Volume 45, Number 12, 2000
General Physics  Quantum Theory
A New Interpretation of the TwoPhoton Entangled Experiments via Quantum Mirrors D.B. Ion, P. Constantin, M. L. D. Ion Romanian Journal of Physics 45,
314 (2000)
In this paper the coherence and crossing symmetry of the electromagnetic interaction of photons involved in the spontaneous parametric down conversion (SPDC) phenomena in nonlinear crystals, are investigated. On this basis a new interpolation of the recent results on the two photon entangled experiment is obtained. A new field of applications is suggested.
Plane SPDCQuantum Mirror M. L. D. Ion, D. B. Ion Romanian Journal of Physics 45,
1523 (2000)
In this paper the kinematical correlations from the phase conjugated optics (equivalently with crossing symmetric spontaneous parametric down conversion(SPDC) phenomena) in the nonlinear crystals are used for the description of a new kind of optical device called SPDCquantmn mirrors. Then, some important laws of the plane SPDCquantum mirrors combined with usual mirrors or lens are proved only by using geometric optics concepts. In particular, these results allow us to obtain a new interpretation of the recent experiments on the twophoton geometric optics.
General Physics  Fields Theory
Fermion Systems Interacting with Time Periodic Fields II. Green Functions in Zero Temperature Formalism Radu Paul Lungu Romanian Journal of Physics 45,
2540 (2000)
The Green functions for an interacting fermion system which is coupled to a time periodic external field are defined and the most interesting preperties of the oneparticle Green functions are discussed. The general expression of the free oneparticle Green function is derived and it is presented the perturbation theory with its diagrammatic interpretation for the evaluation of the interacting Green function.
General Physics  Particles and Fields
Irreducible Canonical Approach to FirstStage Reducible SecondClass Constraints. The Example of GaugeFixed Two and OneForms with Stueckelberg Coupling C. Bizdadea, A. Constantin, S. O. Saliu Romanian Journal of Physics 45,
4149 (2000)
The Dirac bracket for gaugeﬁxed two and oneforms with Stueckelberg coupling is derived along an irreducible manner. The inferred results coincide with those from the reducible approach, hence our method puts on equal footing the irreducible and reducible secondclass constraints.
Hamiltonian BRSTAntiBRST Approach to YangMills Theory C. Bizdadea Romanian Journal of Physics 45,
5155 (2000)
The Hamiltonian BRSTantiBRST symmetry for YangMills theory is constructed. Finally, the gaugefixing procedure is discussed and the gaugeﬁxed action is derived.
Nuclear Physics
Parity Nonconservation in $^{10}$BeNucleus Dan Mihăilescu, Daniel Radu, Ovidiu Dumitrescu Romanian Journal of Physics 45,
5768 (2000)
The $\gamma$circular polarization ($P_\gamma$) and asymmetries ($A_\gamma$) of the parity forbidden M1 + E2 $\gamma$decays:
$^{10}$B$^*$($J^\pi = 2^$ $T = 0$; $E_x = 5.11$ MeV) $\to$ $^{10}$B$^*$($J^\pi = 1^+$ $T=0$; $E_x=0.72$ MeV) as well as the PNC analyzing powers for $^9$Be($\bar{p},\alpha$)$^6$Li resonance reraction populating the parity ($2^\pm$) doublet at 7.47 MeV have been investigated theoretically. We use the recently proposed WarburtonBrown shell model interaction
[1]. For the weak forces we discuss comparatively different weak interaction models based on different assumptions for evaluating the weak meson—hadron coupling constants. The results determine a range of $P_\gamma$  values from which we ﬁnd the most probable values: $P_\gamma = 3.7 \cdot 10^{4}$ for the 5.11 MeV doublet and $A_{L(b)} \simeq 0.6 \cdot 10^{5}$ for the 7.47 MeV doublet. These cases seem to be promising for further experimental tests of parity nonconservation in nuclei.
Absolute Measurement of X and GammaRay Exposure Rate with FreeAir and Cavity Ionization Chambers M. R. Călin Romanian Journal of Physics 45,
6976 (2000)
The problem of radiation doses measurement arises both in research and in practical circumstances whenever one needs to evaluate the effects of irradiation from the energy deposited by radiation into substance. Within the many approaches currently available, those using open—air ionization chambers and cavity ionization chambers (developed by the ionization Chambers Group, at NIPNEHH) are the most viable inasmuch as they constitute primary (reference) standards that are used in national laboratories for the metrology of ionizing radiation. Both types of chamber rely on the electronic balance principle and the Bragg—Gray relation and are basic detectors for
measuring exposure rates and/or absorbed dose rates in various materials, including air.
The experimental data provided by both chamber types are in agreement with market requirements and international data. Both are used as primary standards in national metrological laboratories. By using these two measuring procedures for gamma, X and beta radiation, one can determine various quantities such as exposure, exposure rate, dose, dose rate, activity, etc.
Depending on intended use, radiation field, ambient conditions, kind of radiation, etc., the parameters of both chambers can be improved by varying the types of gas or gas mixture that are introduced in the sensitive volume.
Optics
Color Processing of a Gravity Map by Zero and First Order ﬁltering in Partially Spatial Coherent White Light Constantin Dănciulescu Romanian Journal of Physics 45,
7787 (2000)
The processing of data using a white light source partially spatial coherent is relied on the possibility to implement spatial filtering operators similar to those deﬁned in optical data processing using a monochromatic light source.
By this optical filtering is defined a linear operation in order to improve the signal/noise ratio, to emphasize the signal characteristics and the extraction, and recognize some specific features of the signal.
Mössbauer Spectroscopy  Instrumentation
An Improved Proportional Counter for Conversion Electron and Transmission Mössbauer Spectroscopy I. Bibicu, M. S. Rogalski, G. Nicolescu Romanian Journal of Physics 45,
8997 (2000)
An improved version of proportional counter for simultaneous conversion electron and transmission Mössbauer spectroscopy is presented. Its characteristics and test measurements carried out at room temperature are reported.
Condensed Matter
ElectronOptical Phonon Interaction in an Anisotropic Uniaxial Slab D. E. N. Brâncuş, E. R. Racec Romanian Journal of Physics 45,
99109 (2000)
In a particular geometry of an anisotropic uniaxial semiconductor slab (the optical axis is directed along the normal to the faces) the eigenfrequencies and the eigenvectors of the optical phonon field are obtained as solutions of a system of integral equations derived in the frame of continuum dielectric model. In contradistinction with the situation encountered for an isotropic slab four major new features are found: the degeneracy of the conﬁned modes is lifted, their frequencies being distributed in two domains which correspond to the frequencies of the so—called quasilongitudinal and quasi—transverse modes in the case of a 3Dcrystal; for some strong anisotropic materials the character of some modes (surface or conﬁned) depends on the domain of values of the inplane wave vector; an electron placed outside the slab strongly interacts with some conﬁned modes; an unexpected large interaction between an electron situated inside the slab and the quasi—transverse modes is obtained. The results are particularized for layeredtype semiconductors PbI$_2$ and SnS$_2$.
Field Emission in Diamond Structures Deposited Onto Si111 Tips Ioan Stamatin, Silviu Grecu, Irina Kleps, Mihnea Ionescu, Anca Dumitru Romanian Journal of Physics 45,
111119 (2000)
A simple equipment and method are described for diamond deposition onto silicon111  specially etched pyramidal tips. Electron field emission from metals is affected by surface morphology and the properties of any dielectric coating. Recent results have demonstrated low field electron emission from ptype diamond, aD and photoemission measurements have identified surface treatments that result in a negative electron affinity (NEA). In this study, the ﬁeld emission from diamond, correlated with surface treatment, surface roughness, and film properties (doping and defects) is shortly reviewed. Electron emission measurements are reported on diamond films synthesized by plasma RRCVD and deposited onto a Si111  matrixed tips area. Field emission currentvoltage measurements indicate "threshold voltages" ranging from, approximately, 28 V/$\mu$m to 42 V/$\mu$m with $0.120.8$ mA/cm$^2$ current density.
Dosimetry
The Response of LiF:Mg, Ti Detectors in a 7 MeV Photon Beam Cornelia Crăciun, Maria Sahagia, C. Turcuş, A. Stochioiu, D. Aranghel, F. Scarlat, A. Niculescu, N. Verga Romanian Journal of Physics 45,
121127 (2000)
In thispaper we have studied the response of the LiF:Mg, Ti thermoluminescent detectors (TLD) and bracelet dosimeters in a 7 MeV photon beam in order to extend their use from personal dosimetry to the dosimetry of relativistic electron and Xray beams. The detectors and dosimeters were irradiated in a mixed radiation field (about 60% photon contribution) generated by the 7 MeV NILPRP linear accelerator. The photon equivalent dose reference value within 0.01 Sv  6 Sv interval was determined with a maximum uncertainty of $\pm 3$%. The characterization of the field composition was made by separately measuring the photon and electron equivalent doses by means of a bracelet dosimeter containing two detectors.
The Inﬂuence of Ozone on the QuasiBiennial Oscillation Sabina Ştefan, Cristiana Stan Romanian Journal of Physics 45,
129144 (2000)
An equatorial betaplane model of the stratosphere is used to examine the effects of radiative cooling and ozone heating on the spatial and temporal evolution of the quasibiennial oscillation (QBO). The model atmosphere is described by coupled equations for the zonal and meridional momentum, temperature, mass continuity and ozone volumemixing ratio.
A simple expansion procedure is given for calculating corrections to the structure of equatorial waves in the presence of weak shear and dissipation.
For upwardpropagating Rossbygravity and Kelvin waves explicit results are obtained for the case of Newtonian cooling and ozone heating, corrected to the first two orders into ratio $\varepsilon$ ($\varepsilon \ll 1$) of wave to mean ﬂow height scale.
Results show that in the lower stratosphere, where the vertical ozone gradient is positive, the wave amplitude is enhanced, whereas in the upper stratosphere, where temperaturedependent ozone photochemistry predominates, the wave amplitude is reduced.
The effects of ozone enhanced flows from the Kelvin and Rossbygravity waves on the QBO are tested using a mechanistic 1D model of QBO. Model integrations show that in the lower stratosphere the ozone feedback increases the zonal wind amplitude by 12 m$\cdot$s$^{1}$ and increases the oscillation period by 2 months.
Geophysics
Source Parameters and Scaling Laws for the Crustal Microearthquake Swarm of January 13, 1997 in the Vrâncioaia Seismic Area Emilia Popescu, Mircea Radulian Romanian Journal of Physics 45,
145155 (2000)
The digital waveforms of the microearthquakes belonging to the crustal swarm generated on January 13, 1997 in the vicinity of the Vrâncioaia seismic station (Vrancea region) are analyzed both in time and frequency domains to find all possible information concerning the source parameters.
An efficient method to deconvolve the instrument response and noise is applied to reliably determine the seismic moment in time domain. Seismic moment, dynamic stress drop and P and Swave peak velocity parameters are estimated for 21 microearthquakes ($0.8 \le M_D \le 2.4$) of the swarm, and the corresponding scaling relations are subsequently obtained.
Source dimension (corner frequency) and consequently, static stress drop are not possible to be constrained for the considered magnitude range due to the limited frequency bandwidth of the S13 instruments belonging to the Romanian seismic network.
Biophysics
The Correlation's Matrix Determined Among Trace Elements Present in Human Fluid Maria Mihai, Ion V. Popescu Romanian Journal of Physics 45,
157160 (2000)
In this paper we calculate the correlation coefficients for the trace elements determined in the normal persons' blood comparatively with the persons suffering from diabetic disease. We calculate the matrix that contains the correlation coefficients relevant for the disease and normal state described by these trace elements. We represent graphically the values of the trace elements investigated in the blood.
