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This paper reports the quasiparticle band structure and the optical absorption spectrum of SrO, using many-body perturbation theory. The quasiparticle band structure is calculated within the GW approximation. Taking the electron–hole interaction into consideration, electron–hole pair states and optical excitations are obtained by solving the Bethe–Salpeter equation for the electron–hole two-particle Green function. The calculated band gap for SrO is 6.0 eV, which is in good agreement with the corresponding experimental results. The theoretical result of optical absorption spectrum for SrO is also in close agreement with the experimental data. In particular, the calculated excitation energy for the lowest exciton peak in the optical absorption spectra of SrO reproduces very well the corresponding experimental result.

We report the calculated quasiparticle band structure and optical absorption spectrum of LiI, using many-body perturbation theory. Density-functional theory within local density approximation is used to calculate the ground-state properties of the system. The quasiparticle band structure is evaluated within the GW approximation. Taking the electron–hole interaction into account, electron–hole pair states and optical excitations are derived from the solution of the Bethe–Salpeter equation for the electron–hole two-particle Green function. The band gap is estimated within the GW approximation as 6.3 eV, which is in good agreement with the experimental result of 6.4 eV. And the calculated optical spectrum is also in agreement with experimental data.

I present a method to calculate the ballistic transport properties of atomic-scale structures under bias. The electronic structure of the system is calculated using the Kohn-Sham scheme of density functional theory (DFT). The DFT eigenvectors are then transformed into a set of maximally localized Wannier functions (MLWFs) [N. Marzari and D. Vanderbilt, Phys. Rev. B 56 (1997) 12847]. The MLWFs are used as a minimal basis set to obtain the Hamitonian matrices of the scattering region and the adjacent leads, which are needed for transport calculation using the nonequilibrium Green's function formalism. The coupling of the scattering region to the semi-infinite leads is described by the self-energies of the leads. Using the nonequilibrium Green's function method, one calculates self-consistently the charge distribution of the system under bias and evaluates the transmission and current through the system. To solve the Poisson equation within the scheme of MLWFs I introduce a computationally efficient method. The method is applied to a molecular hydrogen contact in two transition metal monatomic wires (Cu and Pt). It is found that for Pt the I–V characteristics is approximately linear dependence, however, for Cu the I–V characteristics manifests a linear dependence at low bias voltages and exhibits apparent nonlinearity at higher bias voltages. I have also calculated the transmission in the zero bias voltage limit for a single CO molecule adsorbed on Cu and Pt monatomic wires. While a chemical scissor effect occurs for the Cu monatomic wire with an adsorbed CO molecule, it is absent for the Pt monatomic wire due to the contribution of d-orbitals at the Fermi energy.

Laser excitation at 7.9 eV photon energy leads to the desorption of hydrogen atoms from the H:Si(0 0 1)-(2 × 1) monohydride surface [T. Vondrak, X.-Y. Zhu, Phys. Rev. Lett. 82 (1999) 1967]. In the present paper we address the electronic excitations relevant for this desorption process and investigate the corresponding force on the hydrogen atom. The excited state is described by ab-initio many-body perturbation theory. A particular problem is posed by the resonant character of the excited state in question, leading to delocalization and fast decay. Here we suggest to employ an additional short-range confinement potential to localize the excited state on the Si–H bond which is broken in the desorption process.

In field-effect transistors (FETs), charge trapping in the gate oxide is known to cause low-frequency noise and threshold shifts. Here we calculate the effect of single trapped charges in a carbon nanotube FET, using the nonequilibrium Greens function method in a tight-binding approximation. We find that a single charge can shift and even rescale the entire transfer characteristic of the device. This can explain both the large "random telegraph signal" noise and the large variations between nominally identical devices. We examine the dependence on both the thickness and dielectric constant of the gate dielectric, suggesting routes to reduce electrical noise.

We present an ab initio approach to electronic excitations of surface systems and to their dynamics. Based on a density-functional calculation for the electronic ground state, excitations are described by many-body perturbation theory, taking electronic correlation effects and electron–hole interaction into account. This approach yields highly reliable results for electronic spectra, optical excitations, and excited-state total energies. In addition, the femtosecond dynamics (like, e.g., charge-transfer processes) of excited states can be evaluated. As examples, we discuss surface excitons at the LiF(0 0 1)-(1 × 1) surface, as well as the initial decay of the first excited state of CO molecules due to adsorption of the molecules on the insulator surface MgO(0 0 1)-(1 × 1).

We report ab initio calculations of the quasiparticle band structure and the optical excitation spectrum of bulk MgO, the MgO(001) surface, and CO molecules adsorbed on MgO(001). Many-body exchange and correlation effects are included within the GW approximation of the electron self-energy operator and the corresponding electron–hole interaction. The excited electron–hole states are obtained from the Bethe–Salpeter equation. At the clean MgO(001) surface exciton states are found with binding energies that are significantly stronger than in the bulk. The exciton spectrum of the adsorbate system CO : MgO is dominated by charge-transfer excitons, which couple strongly to the molecular excitations of CO.

The current through a carbon nanotube field-effect transistor (CNFET) with cylindrical gate electrode is calculated using the nonequilibrium Greens function method in a tight-binding approximation. The obtained result is in good agreement with the experimental data. The theoretical approach is used to calculate the amplitude of the random-telegraph-signal (RTS) noise due to a single defect in the gate oxide of a long channel p-type CNFET. Considering a composite structure of gate insulators, which contains an inner insulator with a large dielectric constant (ϵ > 3.9) and an outer insulator with a dielectric constant of 3.9 (as for SiO2), the dependence of the RTS noise amplitude on the structure of composite gate insulators is investigated. It is found that the RTS amplitude increases apparently with the decreasing thickness of the inner gate insulator. If the inner insulator is too thin, even though its dielectric constant is as large as 80, the amplitude of the RTS noise caused by the charge of Q = +1e may amount to around 80% in the turn-on region.

Random telegraph signals corresponding to activated charge traps were observed with liquid-gated CNT FETs. The high signal-to-noise ratio that we observe demonstrates that single electron charge sensing is possible with CNT FETs in liquids at room temperature. We have characterized the gate-voltage dependence of the random telegraph signals and compared to theoretical predictions. The gate-voltage dependence clearly identifies the sign of the activated trapped charge.

A constrained local plasma density approximation is presented for the calculation of the stopping power of solids for slow ions. Using the density-functional theory with the local density approximation for exchangecorrelation in the scattering potential and the constrained local plasma density approximation for averaging over effective solid-state electron densities, the stopping power for slow hydrogen and helium projectiles in different solids are calculated. The obtained results of the stopping powers for slow H and He projectiles, and the stopping power ratio R5( 1 )@(2dE/dx)He /(2dE/dx)H# in some solids are in agreement with recent experimental predictions. @S0163-1829~98!02330-3#

The energy widths of the states of protons and antiprotons moving at arbitrary velocities in a homogeneous electron gas are evaluated within a quadratic response theory and the random-phase approximation (RPA). It is found that at low and intermediate velocities the Z13 correction causes a considerable reduction in the energy width of the states of antiprotons, though it is found to be less important than in the evaluation of both the stopping power and the energy-loss straggling.

The stopping powers for slow H and He projectiles in different solids are calculated using density-functional theory with local density approximation for exchange correlations in the scattering potential and the concept of local plasma density approximation for excitation channels. The calculated results for the stopping power ratio R=(1/4)[({minus}dE/dx){sub He}/({minus}dE/dx){sub H}] in some solids are in agreement with recent experimental predictions. {copyright} {ital 1997} {ital The American Physical Society}

The energy-loss straggling and energy width of states of slow ions interacting with a homogeneous electron gas are evaluated within a quadratic response theory and the random-phase approximation. These results are compared with corresponding results determined from a fully nonlinear scattering theory approach. The quadratic response theory is shown to be a good approximation for high electron densities and small ion charges. {copyright} {ital 1997} {ital The American Physical Society}

The energy-loss straggling of protons in an electron gas is calculated by using the linear-response theory and dynamic local-field correction in the dielectric function. A comparison of the theoretical results obtained with the predictions of density-functional theory and experimental data is made.

Electronic stopping powers for fixed-charge-state He ions, ${\mathrm{He}}^{2+}$ and ${\mathrm{He}}^{+}$ , in Al target are calculated within the framework of linear-response dielectric theory by using the dynamic local-field correction in the dielectric function and the concept of local plasma density approximation. An average stopping power has been defined by weighting the fixed-charge-state results with theoretical occupation probabilities. Satisfactory agreement between this average stopping power and experimental data, measured for He-ion beam, is found.

We report the quasiparticle band structure and optical absorption spectrum of bulk LiBr calculated from first-principles approaches. The quasiparticle band structure is calculated within the GW approximation. Taking the electron-hole interaction into consideration, the optical excitation is investigated by solving the Bethe-Salpeter equation for the electron-hole two-particle Green’s function. The obtained results for the band gap and optical absorption spectrum are in good agreement with experimental measurements.

By taking into account the finite-size effect rationally in the framework of the Hartree–Fock theory, compression properties at zero and finite temperatures of finite nuclear matter are investigated with the Skyrme force SKM*. Energies of the isoscalar giant monopole resonance of nuclei at zero temperature calculated are found to be in agreement with experimental and empirical values.

By use of the linear‐response dielectric theory and local electron density approximation, we calculate the energy straggling of protons in solids. The correlation and exchange interaction of electron gas in solids is taken into consideration by introducing a static local‐field‐correction function in the dielectric function. The theoretical results are compared with experimental and empirical data, as well as with other previous theoretical results.

We present an implementation of the ballistic Landauer-B\"uttiker transport scheme in one-dimensional systems based on density functional theory calculations within the full-potential linearized augmented plane-wave (FLAPW) method. In order to calculate the conductance within the Green's function method, we map the electronic structure from the extended states of the FLAPW calculation to Wannier functions, which constitute a minimal localized basis set. Our approach benefits from the high accuracy of the underlying FLAPW calculations, allowing us to address the complex interplay of structure, magnetism, and spin-orbit coupling and is ideally suited to study spin-dependent electronic transport in one-dimensional magnetic nanostructures. To illustrate our approach, we study ballistic electron transport in nonmagnetic Pt monowires with a single stretched bond including spin-orbit coupling, and in ferromagnetic Co monowires with different collinear magnetic alignment of the electrodes with the purpose of analyzing the magnetoresistance when going from tunneling to the contact regime. We further investigate spin-orbit scattering due to an impurity atom. We consider two configurations: a Co atom in a Pt monowire and vice versa. In both cases, the spin-orbit induced band mixing leads to a change of the conductance upon switching the magnetization direction from along the chain axis to perpendicular to it. The main contribution stems from ballistic spin scattering for the magnetic Co impurity in the nonmagnetic Pt monowire, and for the Pt scatterer in the magnetic Co monowire from the band formed from states with ${d}_{xy}$ and ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}$ orbital symmetry. We quantify this effect by calculating the ballistic anisotropic magnetoresistance, which displays values up to as much as 7$%$ for ballistic spin scattering and gigantic values of around 100$%$ for the Pt impurity in the Co wire. In addition, we show that the presence of a scatterer can reduce as well as increase the ballistic anisotropic magnetoresistance.

To analyze clinical characteristics and therapy of pan-resistant Acinetobacter baumannii (PDRAB) infection and explore the methods for effective therapy and prevention of this infection.Nine hospitalized patients with PDRAB infection confirmed by pathogen and susceptibility testing were analyzed for the risk factors and the treatment outcomes were assessed by case analysis.PDRAB infections occurred mainly in patients with severe complications, most of whom had complications by diabetes or hypertension or damaged mucosal integrity due to mechanical ventilation, surgery and catheterization. The polymyxin sensitivity were 100% for these infections, but all the bacteria identified showed a antimicrobial resistance rates of 100%. The majority of the infections were acquired during hospitalization occurring mainly in the lungs; all the patients had prolonged hospitalization and received antibiotic treatments with high proportions of broad-spectrum antimicrobial agents especially third-generation cephalosporins and quinolones. Exclusive or sequential use of carbapenems and sulbactam in combination with quinolone or aminoglycoside produced favorable effects.The prevalence of hospital-acquired pan-resistance of PDRAB infections increased significantly in recent years, particularly in patients with high risk factors. The widespread use of broad-spectrum antibiotics may have some relevance to drug resistant occurrence. The application of carbapenems or sulbactam, or their sequential use, in combination with other agents may produce good effects.

We investigate electronic excitations of the H:Si(001)-(2x1) monohydride surface using first-principles approaches. Density-functional theory is used to calculate the ground-state geometry of the system. The quasiparticle band structure is calculated within the GW approximation. Taking the electron-hole interaction into account, electron-hole pair states and optical excitations are obtained from the solution of the Bethe-Salpeter equation for the electron-hole two-particle Green's function. In this work we focus, in particular, on localized excitations of the silicon-hydrogen bonds at the surface layer. These excitations give rise to an outward-directed force on the hydrogen atoms, which may well explain their optically induced desorption from the surface as observed in recent experiments. The localization of the excitation is described by an artificial confinement potential in addition to standard many-body perturbation theory.

To investigate the relation between the epidemiological strains of meticillin-resistant Staphylococcus aureus (MRSA) and the strains isolated from the nasal fossa of the medical staff and inpatients.The MRSA strains were isolated from the nasal fossa of the medical staff and inpatients in the Department of Neurosurgery. The genes of the isolated strains were amplified by randomly amplified polymorphic DNA (RAPD) assay.Three and 12 MRSA strains were isolated from the nasal fossa of the medical staff and patients who were hospitalized for more than 1 week, respectively, and RAPD assay revealed high homology between the isolated strains.Cross infection can be present between the medical staff, inpatients, and the infected patients.

We calculate the electromigration forces on ions such as adsorbed alkali metal atoms in a carbon nanotube transistor. The forces are especially large in the turn-on regime of the transistor and much smaller in the off and on states. Electromigration in the channel is driven almost exclusively by the wind force. The sign of the "effective valence" Z* is independent of the actual charge sign but can be reversed with gate voltage, providing a dramatic illustration of the quantum character of the wind force. Our self-consistent nonequilibrium Green's function calculations treat a ballistic device within a tight-binding approximation.

We have investigated the time development of excited electronic states of $\mathrm{C}\mathrm{O}$ molecules adsorbed on the $\mathrm{Mg}\mathrm{O}(001)\text{--}(1\ifmmode\times\else\texttimes\fi{}1)$ surface using a state-of-the-art first principles approach. Density-functional theory is used to calculate the ground state geometry of the clean surface and of the molecules adsorbed on the surface. Thereafter, the quasiparticle band structures of bulk MgO, of the $\mathrm{Mg}\mathrm{O}(001)\text{--}(1\ifmmode\times\else\texttimes\fi{}1)$ surface, and of $\mathrm{C}\mathrm{O}$ adsorbed on the surface are calculated within the GW approximation. Taking the electron-hole interaction into consideration the electron-hole excitations and their optical spectrum are obtained from the solution of the Bethe-Salpeter equation for the electron-hole two-particle Green function. The optical spectra of bulk MgO, the $\mathrm{Mg}\mathrm{O}(001)\text{--}(1\ifmmode\times\else\texttimes\fi{}1)$ surface, and $\mathrm{C}\mathrm{O}$ adsorbed on the surface are calculated, yielding good agreement with available experimental data. Finally, based on the solution of the BSE for the adsorbate system $\mathrm{C}\mathrm{O}:\mathrm{Mg}\mathrm{O}(001)\text{--}(1\ifmmode\times\else\texttimes\fi{}1)$, the time propagation of molecular excitations is studied employing the time-dependent Schr\"odinger equation. An initial $\mathrm{C}\mathrm{O}$ excitation exhibits a very fast decay due to its coupling to charge-transfer exciton states between the substrate and the adsorbate. The decay is characterized by a lifetime of about 1.6 fs, which is a factor of 5 faster than the decay of single-particle states.

We discuss electronic excitation processes at two ionic insulator surfaces, LiF(001)-(1 × 1) and MgO(001)-(1 X 1), within ab initio many-body perturbation theory. Because of the negative electron affinity of the surfaces,the lowest unoccupied electronic states are image states located in the vacuum outside the surface. Excitations of electrons from the surface layer into these image states are much lower in energy than the bulk excitons. They are responsible for characteristic surface features in the electron energy-loss spectra of LiF(001) and MgO(001).

We investigate the initial decay of electron-hole excitations in a molecular layer after adsorption on an insulator substrate surface. This is done within ab initio many-body perturbation theory by calculating the time propagation of excited two-particle states. For a CO monolayer adsorbed on the MgO(001) surface we find very fast decay processes with lifetimes that are about 5 times shorter than the transfer of single charge carriers. This is due to a strong coupling of the molecular excitations to charge-transfer-exciton states between the adlayer and the substrate.

We present the quasiparticle band structure and optical excitation spectrum of bulk $\mathrm{Ca}{\mathrm{F}}_{2}$ using first-principles methods. The quasiparticle band structure is evaluated in Hedin's $GW$ approximation [Phys. Rev. 139, A796 (1965)]. Thereafter, the electron-hole interaction is calculated and the Bethe-Salpeter equation is solved, yielding the optical-absorption spectrum. Particular attention is paid to the $\mathrm{Ca}\phantom{\rule{0.2em}{0ex}}3d$ states, which contribute to the lower conduction bands, and to the $\mathrm{Ca}\phantom{\rule{0.2em}{0ex}}3s$ and $3p$ semicore states, which are included in the $GW$ method as valence states. The calculated quasiparticle band gap is $11.5\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$, which is in agreement with experiment $(11.8\phantom{\rule{0.3em}{0ex}}\mathrm{eV})$ and greatly improves the local-density approximation result $(6.85\phantom{\rule{0.3em}{0ex}}\mathrm{eV})$. The calculated optical-absorption spectrum and reflectivity spectrum, which consist of an exciton peak at $10.7\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ and several resonant-exciton peaks between 12 and $16\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$, are in good agreement with experiment.

To obtain primary knowledge of drug resistance of Staphylococcus, especially methicillin-resistant Staphylococcus (MRS), so as to facilitate clinical decision over the choice of appropriate antibiotics.A total of 105 strains of Staphylococcus aureus, Staphylococcus epidermidis and other coagulase-negative Staphylococcus,were isolated from blood, sputum, pus and secretion sample from in-patients of Nanfang Hospital from January to July, 2002, and their status of drug-resistance was examined.MRS was isolated from 68.8% of the samples, and 69.6% of these isolates were methicillin-resistant Staphylococcus aureus (MRSA) and 63.3% resistant Staphylococcus epidermidis (MRSE). The rate of multi-drug resistance for MRS was much higher than that for methicilllin-susceptible Staphylococcus (MSS), and MRSA showed high multidrug resistance rates (all50%) to the antibiotics erythromycin, imipenem, amikacin, SXT, ciprofloxacin, which fell into 4 categories according to their different antibiotic mechanisms.The prevalence and high MDR rate of MRS isolated form the samples suggest that in cases of infection, identification of the pathogenic bacterium should be routinely performed. Besides controlling MRS infection, importance should also be given to its prevention.

To obtain primary knowledge of drug resistance to ciprofloxacin in the common pathogenic bacteria in this hospital thereby to bring the situation under control.A total of 3 800 strains of pathogenic bacteria were isolated from in-patients from 1997 to 2000, and drug resistance of these strains to ciprofloxacin was examined.During the past 4 years, Staphylococcus aureus, Staphylococcus epidermidis and Enterococcus faecalis were found to be highly resistant to ciprofloxacin with the rates still on the rise from 50%, 25.6% and 40.3% in 1997 to 62.2%, 53.4% and 63.6% respectively in 2000. Over 40% of Escherichia coli, Klebsiella pneumoniae and Enterobacter were resistant to ciprofloxacin and the percentages for Pseudomonas aeruginosa and Acinetobacter reached 31.1% to 34.0% in 2000. Among the 189 strains of the pathogenic bacteria isolated from patients with sustained infection in our hospital in 2000, over 70% of Staphylococcus aureus, Staphylococcus epidermidis and Enterococcus faecalis were identified as having resistance to ciprofloxacin.The percentages of common pathogenic bacteria that are resistant to ciprofloxacin have been considerably high and tend to increase further. Ciprofloxacin abuse needs to be given appropriate attention.

The electronic energy-loss straggling of protons and antiprotons moving at arbitrary nonrelativistic velocities in a homogeneous electron gas are evaluated within a quadratic response theory and the random-phase approximation (RPA). These results show that at low and intermediate velocities quadratic corrections reduce significantly the energy-loss straggling of antiprotons, these corrections being, at low-velocities, more important than in the evaluation of the stopping power., 4 pages, 3 figures, to appear in Phys. Rev. A

We present the quasiparticle band structure and the optical excitation spectrum of bulk LiCl, using many-body perturbation theory. Density-functional theory is used to calculate the ground-state geometry of the system. The quasiparticle band structure is calculated within the GW approximation. Taking the electron-hole interaction into consideration, electron-hole pair states and optical excitations are obtained by solving the Bethe-Salpeter equation for the electron-hole two-particle Green function. The calculated band gap is 9.5 eV, which is in good agreement with the experimental result of 9.4 eV. And the calculated optical absorption spectrum, which contains an exciton peak at 8.8 eV and a resonant-exciton peak at 9.8 eV, is also in good agreement with experimental data.

We investigate channel-length scaling characteristics for effects of a single charged defect in a carbon nanotube field-effect transistor (CNFET), using the nonequilibrium Greens function method. We find that the threshold voltage shift due to a single charge in midchannel increases with the decreasing channel length. In a p-type CNFET, the relative current reduction in the on-state due to a positive charge and the relative current change in the turn-on region due to a negative charge increase apparently with the decreasing channel length. The threshold voltage shift and relative current change caused by a single charge for short channel CNFETs increases with the gate-oxide thickness much faster than that for long channel CNFETs. For a short channel p-type CNFET, the current reduction in the on-state due to a positive charge may be larger than 60% and the threshold voltage shift due to a negative charge may amount to 0.6 V.

We calculate the amplitude of the random-telegraph-signal (RTS) noise due to a single charged defect in a long-channel p-type carbon nanotube field-effect transistor, using the nonequilibrium Green function method in a tight-binding approximation. We find that the amplitude of the RTS noise caused by a positive charge close to the source (or drain) contact increases with the applied gate voltage and drain voltage. A positive charge located at the nanotube-oxide interface and close to the source (or drain) contact may cause a large RTS noise of about 50% in the on-state.