Single electron charge sensitivity of liquid-gated carbon nanotube transistors.

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.

Electronic excitations of bulk LiCl from many-body perturbation theory.

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.

[Clinical characteristics and therapy of pan-drug resistant Acinetobacter baumannii infection].

OBJECTIVE: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Random-telegraph-signal noise and device variability in ballistic nanotube transistors.

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.

[Homology analysis of the epidemiological strains of meticillin-resistant Staphylococcus aureus and the strains isolated from the nasal fossa of the medical staff and inpatients].

OBJECTIVE: 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. METHODS: 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. RESULTS: 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. CONCLUSION: Cross infection can be present between the medical staff, inpatients, and the infected patients.

Electromigration forces on ions in carbon nanotubes.

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.

Fast initial decay of molecular excitations at insulator surfaces.

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.

[Survey on drug resistance of Staphylococcus to commonly used antibiotics].

OBJECTIVE: 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. METHOD: 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. RESULTS: 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 (all>50%) to the antibiotics erythromycin, imipenem, amikacin, SXT, ciprofloxacin, which fell into 4 categories according to their different antibiotic mechanisms. CONCLUSIONS: 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.

Image states and excitons at insulator surfaces with negative electron affinity.

We discuss electronic excitation processes at two ionic insulator surfaces, LiF(001)-(1x1) and MgO(001)-(1x1), 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).

[Survey on drug resistance to ciprofloxacin in common pathogenic bacteria].

OBJECTIVE: To obtain primary knowledge of drug resistance to ciprofloxacin in the common pathogenic bacteria in this hospital thereby to bring the situation under control. METHODS: 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. RESULTS: 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. CONCLUSION: 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.