Application of nanodiamonds in human body fluid analysis by matrix-assisted laser desorption/ionization mass spectrometry

Direct mass spectrometric analysis of complex biological samples is very important and challenging.In this paper,nanodiamonds have been successfully used in matrix-assisted laser desorption/ionization mass spectrometric analysis of human serum and urine.As a practical tool and platform,it can be widely used in the field of humoral proteomics,and it plays a very promising role in clinical diagnosis,including identification of novel disease-associated biomarkers.     

The dissociative ionization and Coulomb explosion of ethane by a femtosecond laser field

Femtosecond laser-induced dissociation and Coulomb explosion of polyatomic molecule C_2H_6 were systematically investigated using a time-of-flight mass spectrometer and a chirped pulse amplifier laser. With the laser intensity varying from 2.4×10^{15}W/cm^{2} to 1.2×10^{16}W/cm^2, strong molecular ions C_2H_n^+ (n=0－6) and atomic ions C^{m+} (m=1－3) signals were observed. The double-peak structure of atomic ions indicated the occurrence of Coulomb explosion. Compared with the nearly isotropic distribution of C^{+}, highly charged ions C^{m+} (m=2－3) exhibited a sharply anisotropic angular distribution, which was attributed to the geometric alignment.     

Characterization and electromagnetic response of a ?-shaped metamaterial

In this paper we experimentally and numerically study the left-handed behavior in a biplanar metamaterial operating at microwave frequency. The metamaterial consists of ϕ-shaped metallic patterns on both sides of a dielectric spacer. The origin of negative refractive index is elucidated by performing the effective medium analysis. Additionally, the dependence of the left-handed transmission on geometric parameters, such as the periodicities, the shapes of metallic slabs and continuous wires, and the impact of spacer separation, is examined.     

T1? in nuclear quadrupole resonance: a theoretical study

A new NQR method of measuring the spectral density of slow motions in solids is proposed. It is shown that also in NQR a 90 ° phase shift of a resonant rf magnetic field following a 90 ° pulse locks the nuclear magnetization in a ‘rotating frame’ similarly as in NMR. The spin-lattice relaxation time T_1? of the locked magnetization is calculated in general for an arbitrary spin. It is assumed that the fluctuations of the EFG tensor dominate the spin-lattice relaxation. The calculations show that T_1? depends on the spectral density J(ω) of the electric quadrupole fluctuations at the NQR frequencies, and also at a low frequency Ω. Here kHz depends on the orientation of the rf magnetic field in the principal-axis system of the EFG tensor. The term containing in the expression for T_1?⁻¹ depends on the orientation of the rf magnetic field in the principal-axis system of the EFG tensor, only through the orientation dependence of Ω. This term vanishes when the electric quadrupole fluctuations do not modulate the frequency of the NQR transition excited by the rf magnetic field. Two particular examples: are worked out in details.     

Synthesis of crystalline TiN and Si particles by laser ablation in liquid nitrogen

Laser ablation of titanium and silicon targets immersed in liquid nitrogen was carried out using a YAG laser at 1.06 μm. Synthesized particles were collected and were characterized by TEM, SEM, EDS, XRD, and XPS. In the case of a titanium target, the synthesized particles had an atomic ratio of N/Ti=0.4 and a polycrystalline structure with many XRD peaks of TiN. This result indicates the usefulness of laser ablation in liquid nitrogen for synthesizing nitrides. On the other hand, in the case of a silicon target, the nitridation of the synthesized particles was negligible, and the synthesized particles had a polycrystalline structure of pure cubic silicon. This means that the oxygen-free environment realized by liquid nitrogen is useful for synthesizing particles with negligible oxidation.     

Stochastic resonance of bias signal-modulated noise in a single-mode laser＊

Stochastic resonance (SR) for bias signal modulation is studied in a single-mode laser system. By investigating a gain-noise model driven by correlated pump noise and quantum noise, we find that, whether the correlation coefficient between both the noises is positive or negative, SR always appears in the dependence of signal-to-noise ratio (SNR) upon the noise correlation time and the frequency of the modulation signal. However, only when the correlation coefficient between both noises is negative can SR occur in the dependence of SNR upon the quantum noise intensity and pump noise intensity, while when the correlation coefficient between both noises is positive, it shows monotonically.     

Competition between multiphoton/tunnel ionization and filamentation induced by powerful femtosecond laser pulses in air

In this work we present experiments by focusing 42 femtosecond laser pulses in air using three differentfocal length lenses: f=100, 30 and 5 cm. For the longest focal length, only the filament, which is aweak plasma column,is observed. When the shorter focal length lens is used, a high density plasma isgenerated near the geometrical focus and coexists with a weak plasma channel of the filamemt. Under thetightest focusing condition, filamentation is prevented and only a strong plasma volume appears at tehgeometrical focus.     

Chirping-dependent ionization and dissociation of methane in an intense femtosecond laser field

We studied the ionization and dissociation of polyatomic molecule methane in an intense femtosecond laserfield with wavelength of 810 nm and intensities ranging from 1.4×10~(14)to 2.6×10~(15) W/cm~2 by massspeetroscopy.Abundant fragment inos were observed in addition to the strong parent ion.The effect offrequency chirp was investigated and it was found that the negatively chirped pulses dramatically enhancedthe dissociation probability,which might be used to control the dissociation pathways.     

High-order harmonic generation and multi-photon ionization of Na2 in laser fields

In this paper high-order harmonic generation （HHG） spectra and the ionization probabilities of various charge states of small cluster Na2 in the multiphoton regimes are calculated by using time-dependent local density approximation （TDLDA） for one-colour （1064 nm） and two-colour （1064 nm and 532 nm） ultrashort （25 fs） laser pulses. HHG spectra of Na2 have not the large extent of plateaus due to pronounced collective effects of electron dynamics. In addition, the two-colour laser field can result in the breaking of the symmetry and generation of the even order harmonic such as the second order harmonic. The results of ionization probabilities show that a two-colour laser field can increase the ionization probability of higher charge state.     

Possible generation of a γ-ray laser by electrons wiggling in a background laser

The possibility of γ-ray laser generation by the radiation of wiggling electrons in a usual background laser is discussed.     

Evaluation and analysis of the radiation force in laser trap

Forces exerted on a small transparent dielectric sphere in a Gaussian beam is an-alyzed.The stable position of the sphere in the Gaussian beam was calculated.The effects ofthe sphere size,the beam radius etc.on the exerted forces,on the equilibrium positions aswell as on other parameters of the sphere are discussed.     

α-particle spectrum in the reaction p + 11B → α + 8Be* → 3α

Using a simple phenomenological parametrization of the reaction amplitude we calculated α-particle spectrumin the reaction p + ¹¹B → α + ⁸Be* → 3α at the resonance proton energy of 675 keV. The parametrization includes Breit-Wigner factor with an energy-dependent width for intermediate ⁸Be* state and the Coulomb and the centrifugal factors in α-particle-emission vertices. The shape of the spectrum consists of a well-defined peak corresponding to emission of the primary α and a flat shoulder going down to very low energy. We found that below 1.5MeV there are 17.5% of α’s and below 1MeV there are 11% of them. The text was submitted by the author in English.     

Regge analysis of the ππ scattering amplitude

The theoretical predictions for the subtraction constants lead to a very accurate dispersive representation of the ππ scattering amplitude below 0.8 GeV. The extension of this representation up to the maximum energy of validity of the Roy equations (1.15 GeV) requires a more precise input at high energies. In this paper we determine the trajectories and residues of the leading Regge contributions to the ππ amplitude (Pomeron, f and ρ), using factorization, phenomenological parametrizations of the πN and NN total cross sections at high energy, and a set of sum rules which connect the high and low energy properties of ππ scattering. We find that nonleading Regge terms are necessary in order to achieve a smooth transition from the partial waves to the Regge representation at or below 2 GeV. We obtain thus a Regge representation consistent both with the experimental information at high energies and the Roy equations for the partial waves with ℓ≤4. The uncertainties in our result for the Regge parameters are sizable, but in the solutions of the Roy equations these only manifest themselves above the K[`]KK\hspace {0.03cm}\overline {\rule [0.7em]{0.6em}{0em}}\hspace {-0.8em}K threshold.     

Cavity enhanced absorption spectroscopy measurements of?pressure-induced broadening and shift coefficients in?the?υ1+υ3 combination band of ammonia

Cavity enhanced absorption spectroscopy is performed using an external cavity diode laser operating around 1516 nm. We demonstrate a sensitivity of 6×10⁻⁸ cm⁻¹ Hz^−1/2 and utilise a simple method to measure pressure-induced broadening and shift coefficients. The broadening and shift coefficients for six gases (helium, neon, argon, xenon, oxygen and nitrogen) have been determined at room temperature for four transitions in the υ ₁+υ ₃ combination band of ammonia. Comparisons of the broadening coefficients with previous work in this region, where it exists, show good agreement. The broadening and shift coefficients of nitrogen and oxygen are also in good agreement with calculated values using the Robert and Bonamy theory. Both the broadening and shift coefficients show a clear trend through the rare gases, which can be explained in terms of the varying magnitude of the long range attractive forces operating between the colliding partners. We also demonstrate the application of the Parmenter–Seaver formalism to estimate the potential well depth of the ammonia dimer from the obtained broadening coefficients. The obtained well depth agrees well with theoretical calculations.     

SEM and HRTEM analysis of ZnS nanoflakes produced by?a?simple route

In this work, we report the synthesis of ZnS nanostructures by a simple and eco-friendly method that makes possible producing nanoflakes at room temperature. Scanning electron microscopy and transmission electron microscopy methods (mainly bright-field, high resolution and high angle annular dark-field) were used to identify and study the obtained nanostructures. The structure of these nanoflakes consists of nanosized crystalline particles around 1.5 to 3 nm. Domains with different contrast of nanometer-size diameters are formed in the self-assembled nanoflakes as a result of a noncompact arrangement of nanocrystallites during agglomeration and differences in the presence of the organic passivation agent. Agglomeration can be attributed to the amount of crystallites generated at the beginning of the reaction or to an anisotropic interaction between phosphate ions and the surfaces of ZnS clusters, and consequently a bottom-up synthesis is considered, which opens a simple route for the production of nanomaterials with the inclusion of extra elements by a simple way.     

Experimental and theoretical indications for an intermediate σ-dressed dibaryon in the NN interaction

Numerous theoretical and experimental arguments in favor of the generation of intermediate σ-dressed dibaryon in NN interaction at middle and short distances are presented. We argue that this intermediate dibaryon should be responsible for the strong middle-range attraction and the short-range repulsion in the NN interaction, and also for the short-range correlations in nuclei. The suggested mechanism for the σ-dressing of the dibaryon is identical to that which explains the Roper-resonance structure, its dominant decay mode and its extraordinary low mass. It is arguing that the (partial) chiral symmetry restoration effects, common for the Roper resonance and dressed dibaryon, are responsible for strong renormalizing of their masses and widths and the observed σ-meson mass and decay width as well. The new experimental data on 2π-production in the scalar-isoscalar channel produced in pn- and pd-collisions and recent data on γγ correlations in pC and dC scattering in the GeV region seems to corroborate the existence of the σ-dressed dibaryon in two- and three-nucleon interactions. A similar transformation mechanism from the glue to the scalar field can be valid also in some J/Ψ decays and in enormous σ-meson production in central pp collisions at high energies.     

Low-temperature deposition of α-Al2O3 films by laser chemical vapor deposition using a diode laser

We prepared Al₂O₃ films by laser chemical vapor deposition (LCVD) using a diode laser and aluminum acetylacetonate (Al(acac)₃) precursors and investigated the effects of laser power (P_L), deposition temperature (T_dep), and total pressure (P_tot) in a reaction chamber on the crystal phase, microstructure, and deposition rate (R_dep). An amorphous phase was obtained at P_L = 50 W, whereas an α-phase was obtained at P_L > 100 W. At P_L = 150 and 200 W (1 0 4)- and (0 1 2)-oriented α-Al₂O₃ films were obtained, respectively. The R_dep of α-Al₂O₃ films increases with decreasing P_L and P_tot. Single-phase α-Al₂O₃ film was obtained at T_dep = 928 K, which is about 350 K lower than that obtained by conventional thermal CVD using Al(acac)₃ precursor.     

Emission time sequence of neutrons and protons as probes of α-clustering structure

Neutron–proton momentum correlation functions are constructed from a three-body photodisintegration channel, i.e., core\begin{document}$ + n + p$\end{document}, and used to explore the spatial-time information of the non-clustering Woods–Saxon spherical structure as well as the \begin{document}$\alpha$\end{document}-clustering structures of \begin{document}$^{12}{\rm{C}}$\end{document} or \begin{document}$^{16}{\rm{O}}$\end{document} based on an extended quantum molecular dynamics model. The emission time sequence of neutrons and protons is indicated by the ratio of velocity-gated neutron–proton correlation functions, demonstrating its sensitivity to \begin{document}$\alpha$\end{document}-clustering structures. This work sheds light on a new probe for \begin{document}$\alpha$\end{document}-clustering structures.