Effects of atomic number Z on the energy distribution of hot electrons generated by femtosecond laser interaction with metallic targets

The effects of atomic number Z on the energy distribution of hot electrons generated by the interaction of 60fs, 130mJ, 800nm, and 7×10^17W/cm^2 laser pulses with metallic targets have been studied experimentally. The results show that the number and the effective temperature of hot electrons increase with the atomic number Z of metallic targets, and the temperature of hot electrons are in the range of 190-230keV, which is consistent with a scaling law of hot electrons temperature.

A study on compatibility of experimental effective atomic numbers with those predicted by ZXCOM

In this study, effective atomic numbers(Zeff) of materials determined at different experimental conditions by measuring the elastic-to-inelastic γ-ray scattering ratios are compared to ZXCOM predictions. It also presents the experimental data obtained via the transmission technique The agreement and disagreement between ZXCOM and experimental values are investigated. The theoretical basics of determining Zeffby scattering mode are outlined. The study shows that choosing appropriate experimental conditions can provide a good compatibility between the experimental results and theoretical ZXCOM

Quantitative parameters in novel spectral computed tomography:Assessment of Ki-67 expression in patients with gastric adenocarcinoma

BACKGROUND The level of Ki-67 expression has served as a prognostic factor in gastric cancer.The quantitative parameters based on the novel dual-layer spectral detector computed tomography(DLSDCT)in discriminating the Ki-67 expression status are unclear.AIM To investigate the diagnostic ability of DLSDCT-derived parameters for Ki-67 expression status in gastric carcinoma(GC).METHODS Dual-phase enhanced abdominal DLSDCT was performed preoperatively in 108 patients with gastric adenocarcinoma.Primary tumor monoenergetic CT attenuation value at 40-100 kilo electron volt(kev),the slope of the spectral curve(λ_(HU)),iodine concentration(IC),normalized IC(nIC),effective atomic number(Z^(eff))and normalized Z^(eff)(nZ^(eff))in the arterial phase(AP)and venous phase(VP)were retrospectively compared between patients with low and high Ki-67 expression in gastric adenocarcinoma.Spearman’s correlation coefficient was used to analyze the association between the above parameters and Ki-67 expression status.Receiver operating characteristic(ROC)curve analysis was performed to compare the diagnostic efficacy of the statistically significant parameters between two groups.RESULTS Thirty-seven and 71 patients were classified as having low and high Ki-67 expression,respectively.CT_(40 kev-VP),CT_(70 kev-VP),CT_(100 kev-VP),and Z^(eff)-related parameters were significantly higher,but IC-related parameters were lower in the group with low Ki-67 expression status than the group with high Ki-67 expression status,and other analyzed parameters showed no statistical difference between the two groups.Spearman’s correlation analysis showed that CT_(40 kev-VP),CT_(70 kev-VP),CT_(100 kev-VP),Z^(eff),and n Z^(eff) exhibited a negative correlation with Ki-67 status,whereas IC and nIC had positive correlation with Ki-67 status.The ROC analysis demonstrated that the multi-variable model of spectral parameters performed well in identifying the Ki-67 status[area under the curve(AUC)=0.967;sensitivity 95.77%;specificity 91.89%)].Nevertheless,the differentiating capabilities of singlevariable model were moderate(AUC value 0.630-0.835).In addition,the nZ_(VP)^(eff) and nIC_(VP)(AUC 0.835 and 0.805)showed better performance than CT_(40 kev-VP),CT_(70 kev-VP) and CT_(100 kev-VP)(AUC 0.630,0.631 and 0.662)in discriminating the Ki-67 status.CONCLUSION Quantitative spectral parameters are feasible to distinguish low and high Ki-67 expression in gastric adenocarcinoma.Z^(eff) and IC may be useful parameters for evaluating the Ki-67 expression.

Monte Carlo simulation of reflection effects of multi-element materials on gamma rays

To study the effects of the gamma reflection of multi-element materials,gamma ray transport models of single-element materials,such as iron and lead,and multielement materials,such as polyethylene and ordinary concrete,were established in this study.Relationships among the albedo factors of the gamma photons and energies and average energy of the reflected gamma rays by material type,material thickness,incident gamma energy,and incidence angle of gamma rays were obtained by Monte Carlo simulation.The results show that the albedo factors of single-element and multi-element materials increase rapidly with an increase in the material thickness.When the thickness of the material increases to a certain value,the albedo factors do not increase further but rather tend to the saturation value.The saturation values for the albedo factors of the gamma photons,and energies and the reflection thickness are related not only to the type of material but also to the incident gamma energy and incidence angle of the gamma rays.At a given incident gamma energy,which is between 0.2 and 2.5 MeV,the smaller the effective atomic number of the multi-element material is,the higher the saturation values of the albedo factors are.The larger the incidence angle of the gamma ray is,the greater the saturation value of the gamma albedo factor,saturation reflection thickness,and average saturation energy of the reflected gamma photons are.

Study on gamma-ray attenuation characteristics of some amino acids for 133Ba,137Cs, and 60Co sources

Amino acids are the building blocks of proteins,which are the most abundant macromolecules in living cells.From the standpoint of the photon interaction cross sections of amino acids,the mass attenuation coefficients,half and tenth value layers,mean free path,effective atomic and electronic cross sections,effective atomic number,and effective electron density of fifteen essential amino acids have been determined for 133Ba,137Cs,and 60Co gamma-ray sources.The MCNP-4C code and the XCOM program have been used to calculate these parameters.The results have been compared to the available experimental and theoretical data.The theoretical results agreed with the experimental data,with RD values of ≤±7%.In the energy region of 81-1332.5 keV,it was found that the μm,σa,and revalues of the amino acids decreased as the photon energy increased,and the increasing density of amino acids had no steady effect on these quantities.Additionally,results demonstrated that the HVL,TVL,and MFP values increased with the increase in photon energy.The μm,σa,and Zeff values of aspartic acid were the highest among those of all amino acids,and they were the lowest for isoleucine.The Zeff value of each sample containing H,C,N,and O atoms was nearly constant in the studied energy region.The Neffvalues of the studied amino acids varied in the range of 3.14×10^23-3.44×10^23 electron/g.Furthermore,the Neffvalues were approximately independent of the amino acid type in this energy region.

Comparative Study between Lead Oxide and Lead Nitrate Polymer as Gamma-Radiation Shielding Materials

In this work, the Styrene-butadiene rubber (SBR)/lead oxide and the Styrene-butadiene rubber (SBR)/lead nitrate composites were prepared as gamma-radiation shielding materials. The investigated materials were prepared with three different weight percentage of lead oxide and lead nitrate (30, 50 and 70 wt%). The mass attenuation coefficients (μm) for all composite samples were measured experimentally at 511 and 661.6 keV photon energies. The measurements were made by performing transmission experiments with a 3'' × 3'' NaI (Tl) scintillation detector, which had an energy resolution of 7% at 0.662 MeV for the gamma-rays from the decay of 137Cs. The effective atomic numbers (Zeff) and the effective electron densities (Neff) were determined experimentally. Also they were determined theoretically using the obtained μm values for the studied composites samples by WinXCom program. The obtained results show that the experimental values of the composites are found to be in a good agreement with the theoretical values. It is recognized that the mass attenuation coefficient (μm), effective atomic numbers (Zeff) and the effective electron densities (Neff) are increased in the composite samples which contain lead oxides than which contain lead nitrates. Finally, the Styrene-butadiene rubber (SBR)/lead oxide is better than Styrene-butadiene rubber (SBR)/lead nitrate polymer as gamma radiation shielding.

Radiation Parameters of Some Potential Bioactive Compounds

In this study,we aimed to determine the radiation parameters of some potential bioactive compounds.1-Aryl-3-dibenzylamino-propane-1-on hydrochloride type Mannich bases were synthesized via classical conventional heating method.Aryl part was changed as phenyl(C6H5),4-methylphenyl(4-CH3C6H4),4-fluorophenyl(4-FC6H4),4-nitrophenyl(4-NO2C6H4),4-chlorophenyl(4-ClC6H4),4-bromophenyl(4-BrC6H4),and 2-thienyl(C4H3S-2-yl).Mass attenuation coefficient(μm),effective atomic number(Zeff)and effective electron density(Nel)of compounds were determined experimentally and theoretically for at 8.040,8.910,13.40,14.96,17.48,19.61,22.16,24.94,32.19,36.38,44.48,50.38and 59.54keV photon energies by using an HPGe detector with a resolution of 182eV at 5.9keV.Radiation parameters of these compounds which can be anti-cancer drug candidate were given in the tables.The results show that phenyl ring behave like thiophene ring in terms of radiation absorption.It is thought that the results of study may drive allow the development of drug candidate new compounds in medical oncology.

Thermodynamics of Fe-C-j (j=Al, Si, P, S) Melts

Based on a proposed method, the mathematical expressions between carbon solubility in Fe-C-j (j=Al, Si, P, S) melts and temperature were obtained. The expressions show the relation of the affecting factors of component j and temperature on carbon solubility, and the activity interaction coefficient of j upon carbon depends on atomic number, covalent radius and electro-negativity. The affecting factors of four elements on carbon solubility are all negative. There is a linear relationship between covalent radius and electro-negativity.

Studies of Structural and Thermodynamic Properties for Polychlorinated Thianthrenes by Density Functional Theory

The structural and thermodynamic （PCTAs） in the ideal gas state at 298.15 K and 1.013 properties of 75 polychlorinated thianthrenes ×10^5 Pa have been calculated at the B3LYP/6- 31G＊ level using Gaussian 98 program. Based on the output data of Gaussian, the isodesmic reactions were designed to calculate standard enthalpy of formation （△fH^θ） and standard free energy of formation （△fH^θ） of PCTAs congeners. The relations of these thermodynamic parameters with the number and position of C1 atom substitution （Npcs） were discussed, and it was found that there exists high correlation between thermodynamic parameters （total energy （TE）, zero-point vibrational energy （ZPE）, thermal correction to energy （Eth）, heat capacity at constant volume （Cv^θ）, entropy （S^θ）, enthalpy （H^θ）, free energy （G^θ）, standard enthalpies of formation （△fH^θ） and standard Gibbs energies of formation （△fG^θ）） and Npcs. On the basis of the relative magnitude of their △fG^θ, the order of relative stability of PCTA congeners was theoretically proposed. In addition, the correlations between structural parameters and Npcs were also discussed. The good correlations were found between molecular average polarizability （α）, energy of the highest occupied molecular orbital （EHOMO）, molecular volume （Vm） and Npcs, and all R^2 values are larger than 0.95. Moreover, it was supposed that the isomer groups with higher toxicity should be Tri-CTA and TCTA.

Studies of Thermodynamic Properties and Relative Stability of Polybrominated Xanthones by Density Functional Theory

The thermodynamic properties of xanthone（XTH） and 135 polybrominated xanthones（PBXTHs） in the standard state have been calculated at the B3LYP/6-31G＊ level using Gaussian 03 program.The isodesmic reactions were designed to calculate the standard enthalpy of formation（△fHθ） and standard free energy of formation（△fGθ） of PBXTH congeners.The relations of these thermodynamic parameters with the number and position of Br atom substitution（NPBS） were discussed,and it was found that there exist high correlation between thermodynamic parameters（entropy（Sθ）,△fHθ and △fGθ） and NPBS.According to the relative magnitude of their △fGθ,the relative stability order of PBXTH congeners was theoretically proposed.The relative rate constants of formation reactions of PBXTH congeners were calculated,Moreover,the values of molar heat capacity at constant pressure（Cp,m） from 200 to 1000 K for PBXTH congeners were also calculated,and the temperature dependence relation of them was obtained,suggesting very good relationships between Cp,m and temperature（T,T^1 and T^2） for almost all PBXTH congeners.

Structure, Plastic Deformation of Polyethylene: A Molecular Dynamics Method

This paper studies the influence factors of atoms number (N) at temperature (T) and after annealing time (t) on the structure shape and the plastic deformation of Polyethylene C2H4 (PE) by the Molecular Dynamics (MD) method with Dreading pair interaction, cyclic boundary conditions and plastic deformation of Polyethylene (PE) be done by stretching method according to the z-axis. The results of structure, plastic deformation of PE are analyzed through size (l), the total energy of the system (Etot), shape and associated energy (Ebond), angular binding energy (Eangle), energy Edihedral, interactive energy Vander Walls (Enon-bonding). When increasing N, t leads to the number of structural units of Face-Centred Cubic (FCC), Body-Centered Cubic (BCC) and Hexagonal Close-Packed (HCP) increasing, but Amorphous (Amor) decreases while the angle between the atoms is a constant corresponding to 109.5°. Besides, the length of the link (r) increases from r = 1.529 Å to r = 1.558 Å while the plastic deformation energy of PE gets an enormous change and the bonding angle at 109.27°. The length of the link r = 1.529 Å and the size (l) of the PE material increase from l = 3.73 nm to l = 6.63 nm while the total energy of system (Etotal) decreases from Etotal = −1586 eV to Etotal = −7891 eV with the transition temperature is T = 103 K. Increasing the number of atoms leads to increasing the length of the link. The total energy Etotal of the system decreases, but the number of structural units in FCC, HCP, BCC and Amor increase, which leads to the length of the link increases, the Etotal decreases, and there is a change in the plastic deformation characteristics of PE. In contrast, increasing T leads to the plastic deformation increases, and PE moves from the amorphous state to the liquid state. The obtained results are very significant for future experimental research.

Theoretical Study on Thermodynamic Properties and Hydrophilicity of Polychorinated Phenothiazines (PCPTZs)

The thermodynamic properties of 135 polychlorinated phenothiazines （PCPTZs） in the standard state are calculated using a combination of quantum mechanical computations performed with the Gaussian 03 program at the B3LYP/6-311G^＊＊ level, and their octanol-water partition coefficients （logKow） are calculated based on group contributions. The chlorine substitution pattern strongly influenced the thermodynamic properties and hydrophilicity of the compounds. The thermodynamic properties of congeners also depend on the chlorine substitution pattern. The effect of chlorine substitution pattern is quantitatively studied by considering the mmaber and position of Cl atom substitution （Npcs）. The results show that the Npcs model may be used to predict the thermodynamic properties and hydrophilicity for all 135 PCPTZ congeners.

DFT Study on Some Properties of Polybrominated Phenoxathiin 10-Oxides

With the B3LYP calculation method of density functional theory（DFT）and the 6-31G＊ basis set,full optimization calculation was made for phenoxathiin10-oxide（PTO）and 135 polybromine phenoxathiin 10-oxides（PBPTOs）with the Gaussian 03 program and molar heat capacity in constant volume（CVθ）value of each molecule in the standard state was obtained.The relation between CVθ and the substitution position and number of bromine atom（NPBS）was studied,and the results indicated good correlation（R2 = 1.000）between CVθ and NPBS of PBPTO compounds.Based on the output file of Gaussian 03 program,molar heat capacity at constant pressure（Cp,m）of PBPTO compounds from 200 to 1,000 K was calculated with the statistical thermodynamics program,and the correlation equation between Cp,m and temperature（T,T-1 and T-2）was obtained with the least-squares method,and the correlation coefficient of the correlation equation（R2）was 1.000.In addition,based on the partition function of each molecule calculated by vibration analysis,the relative rate constant of formation of each molecule was calculated.

Simulation of epitaxial growth on convex substrate using phase field crystal method

Phase field crystal （PFC） model is employed to simulate the process of growth of epitaxial layer on plane-convex substrate with a lattice mismatch and a small inclination angle. The variation of the systematic free energy, the total atomic number of the epitaxial layer, and the effect of the curvature and the angle of the substrate are analyzed. The results show that when the surface of the substrate is plane, the free energy increases with the increase of the substrate inclination angle, and also the total atomic number of the epitaxial layer increases; while the surface of the substrate is convex, the free energy decreases with the increase of substrate angle and so also the total atomic number of the epitaxial layer decrease. This is the reason that the frontier of surface of epitaxial layer changes from the step bunching to the hill-and-valley facet structure with the increasing of the inclination angle of convex substrate. These results are in good agreement with the other method results.

Spectral and attenuation studies of ^(204)Tl bremsstrahlung in thick target barium compounds

Objective:This study is aimed to measure the Bremsstrahlung spectrum produced by ^(204)Tl in barium compounds such as BaCl_(2),BaCO_(3),Ba(NO_(3))_(2),BaSO_(4) and BaTiO_(3).It is also aimed to study the attenuation of bremsstrahlung in the given compounds.Materials and methods:Bremsstrahlung spectrum and yield ^(204)Tl in barium compounds such as BaCl_(2),BaCO_(3),Ba(NO_(3))_(2),BaSO_(4) and BaTiO_(3) have been measured using NaI(Tl)detector and multichannel analyzer(MCA).The beta stopper technique is employed to measure the bremsstrahlung spectrum.Liden-Starfelt procedure is used to unfold the measured raw spectrum.The unfolded spectra were compared with Tseng–Pratt theory.Results:The measured spectra agree with the theory at low energy end of spectrum and some deviation(less than 10%)at higher energy end of spectrum.Attenuation of the bremsstrahlung,excited by ^(204)Tl beta emitters in the same compounds,is also studied.The measured attenuation parameter is not constant with absorber thickness and it increases with increasing Zmod of the absorber.Conclusion:The discrepancy between measured spectrum and theory increases with Zmod of the target compound and photon energy.The attenuation of bremsstrahlung may be represented as a combination of a large number of exponential terms rather than single term.