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A photoactivated ZnO nanomesh with precisely controlled dimensions and geometries is fabricated by using nanosphere lithography process. The nanomesh structures effectively increase the surface-to-volume ratio to improve the sensing response under the same testing gas. And the periodical nanostructures also increase the effective light path and lead to more efficient light activation for gas sensing. With the increase of the photoinduced oxygen ions by UV illumination, a distinguished sensing response is observed at room temperature. In the optimized case, the sensing response (△R/R0) of the ZnO nanomesh at the butanol concentration of 500 ppm is 97.5%, which is 4.54 times higher than the unpatterned one.
Congenital anomalies of the coronary arteries are present in 0.2–1.4% of the general population. These anomalies represent one of the most confusing issues in the field of cardiology and challenges for interventional cardiologists and cardiac surgeons if the anomalies are unrecognised. Double right coronary artery is one of the rarest coronary arteries. Previously, the probability of developing atherosclerotic changes in patients with a double right coronary artery was considered to be equal to that in those without it. In reality, however, a high prevalence of atherosclerotic coronary artery disease was found in patients with a double right coronary artery originating from a single ostium after our comprehensive literature search through the PubMed database. Owing to the fact that double right coronary artery is both a congenital and potentially atherosclerotic coronary artery disease at diagnosis, coronary intervention or cardiac operation is more complicated than previously believed. Individuals with a double right coronary artery may be unaware of its presence until an accidental finding during coronary angiography or cardiac operation and are at risk for unsuspected complications of atherosclerotic coronary artery disease or during cardiac operation. Therefore, it is important to obtain information on the anatomic variants of this congenital coronary anomaly in patients who are undergoing either coronary intervention, aortic root operation or myocardial revascularisation. To our knowledge, this is the first comprehensive article to discuss the anomalies and their clinical implications.
The challenges associated with meeting 20nm technology requirements for better Cu CMP process uniformity and lower defectivity have been studied. Required improvements in uniformity were obtained through platen process optimization along with evaluation & selection of specific Cu slurries and pads and their performance reported. The principal factors influencing defect formation, including Cu barrier metallurgy, interconnect pattern density and process queue times were studied. Specific new post CMP clean chemistries were evaluated to assess their capability to suppress defect formation and their performance reported. The trade off between uniformity and defect suppression as a function slurry, pad and post Cu CMP clean chemistry is described.
Kennedy's disease (KD) is an X-linked recessive polyglutamine disease. Traditionally, it is a lower motor neuron syndrome with additional features such as gynecomastia and tremor. Sensory symptoms are minimal if ever present. We used multimodal evoked potential (EPs) tests to study the distribution of the involvement of the disease.
Visual, brainstem auditory, somatosensory and motor EPs were studied in six KD patients. All of them had typical presentations and had been proved genetically.
Abnormal findings were noted as follows: prolonged peak latencies of visual EPs, increased hearing threshold level, inconsistent brainstem auditory EPs, decreased amplitudes of cortical potentials of somatosensory EPs, and increased motor threshold to transcranial magnetic stimulation.
Our multimodal EP studies showed that KD involved multiple levels of the nervous system. It implies the widespread effects of the mutant androgen receptors.
Methicillin-resistant Staphylococcus aureus (MRSA) has become an important nosocomial pathogen in our neonatal intensive care units (NICUs) and accounts for almost all S. aureus clinical isolates. The objective of this study was to assess the relatedness of these MRSA strains.
MRSA clinical isolates were collected from infants hospitalized in our NICUs. Pulsed-field gel electrophoresis with SmaI digestion was used to fingerprint these isolates.
Level-III NICUs in a university-affiliated children's hospital.
Between 1998 and 2000, a total of 122 MRSA clinical isolates were collected from 104 infants hospitalized in our NICUs. Fifteen infants had multiple isolates (range, 2 to 4 isolates). The sources of specimens included blood (72), pus (23), sputum (15), body fluids (3), and catheter tips (9). A total of 4 genotypes with 20 subtypes were identified. There were 2 genotypes in 1998, 2 genotypes in 1999, and 4 genotypes in 2000. All but 2 isolates belonged to either genotype A (63.1%; 7 subtypes) or genotype C (35.2%; 11 subtypes). Among the 15 infants with multiple isolates, the genotypes of the isolates from a single episode of MRSA infection were different in 2 of 12 cases, and reinfection with a new strain was noted in 3 of 5 cases with recurrent infections.
Two predominant MRSA clones prevailed in our NICUs between 1998 and 2000. Polyclonal bacteremia and reinfection with a new strain were noted.
This paper describes a bi-layer deposition technique to reduce the strain gradient of polycrystalline silicon-germanium (poly-SiGe) thin films without the use of any post-deposition annealing. By adjusting deposition conditions such as temperature, pressure, and/or flow rates of reactants, poly-SiGe films with required low average stresses can be obtained. Using the bi-layer technique, a strain gradient of 1.1×10-5 μm-1 (equivalent to 88 mm radius-of-curvature) has been achieved in 3.9 μm-thick poly-SiGe. This strain gradient would cause only 0.055 μm tip deflection for a 100 μm-long cantilever. The thermal budget was ∼10 hours at 425 °C, and no post-deposition annealing was required. The bi-layer film also exhibits low compressive average stress (-36 MPa) and low resistivity (0.55 mΩ-cm).
Continued scaling of CMOS technology beyond the 100 nm technology node will rely on fundamental changes in transistor gate stack materials . Refractory metals and their metallic derivatives are among the only candidates suitable for use as transistor gate electrodes. In earlier publications, Mo has been proposed as a potential candidate for use as a MOSFET gate electrode and the implantation of nitrogen ions into the Mo film has been observed to lower the interfacial work function of Mo [2,3]. This observation indicates the potential application of Mo as a CMOS gate electrode. In this paper, the dependence of the interfacial work function on the nitrogen implant parameters (viz. energy and dose) is discussed. In general, metal work functions at dielectric interfaces depend on the permittivity of the dielectric [3,4,5]. This dependence of the gate work function on dielectric permittivity presents a significant challenge for the integration of metal gate electrodes into future CMOS technology. In light of this, the ability to engineer the Mo gate work function over a relatively large range makes it an attractive candidate for this application.
The change of surface profile during chemical-mechanical planarization (CMP) is monitored continuously in this study. The influences from pattemn dependency and substrate effects are discussed. Step height reduction rate is a function of pattern density and down force. The rate decreases with time until planarization is achieved. As the polish approaches the patterns underneath, the interaction between substrate effects and pattern dependency results in the resurgence of step height. The implication of this newly found phenomenon is discussed.
For embedded DRAM (E-DRAM) devices with feature sizes of 0.25 µm and beyond, contact processes with low contact resistance and low junction leakage current are required. The contact etch process needs to etch through multi-layer structures with SiO2, SiON/SiN layers and stop on Ti-polycide gate and Ti-salicide active regions at the same time. The key issues include high selectivity to TiSix, vertical profile, complete removal of SiON/SiN cap layer and no polymer residues. In this paper, multi-layer contact etching without attacking TiSix is reported. Using new process chemistry, the new contact etch process has been demonstrated for the manufacturing of 0.25 µm E-DRAM and beyond.
Nanohardness, modulus, and bonding structure of fluorinated silicon dioxides are characterized in order to evaluate their correlations with chemical-mechanical polishing (CM[P) performance. Alkaline-based slurry with adjusted pH is used for polishing in an attempt to delineate the chemical erosion from mechanical abrasion effects during CMIP of fluorinated oxides. The increase in CMIP removal rate and the reduction in refractive index with increasing fluorine content in the fluorinated oxides are related to the change in bonding configuration. The enhanced moisture absorption is due to the presence of fluorine in the oxide network.
A new sol-gel procedure using micellar solutions has been developed to
immobilize local anesthetic drugs in optically transparent glass. Dibucaine
was selected as a direct emission probe at 77 K for determining the forms of
the anesthetic drug (free base, monoprotonated, and/or diprotonated) and its
location (hydrophobic core, interfacial layer or hydrophilic region) in
micelles. The photophysical properties of local anesthetics obtained in gels
are compared to those in solutions. During the gelation stage, the
predominant drug species was identified as free base dibucaine embedded in
the hydrophobic core of neutral as well as charged micelles. This
observation suggests that the micellar interface was modified by the large
hydrophilic gel surface during the gelation stage. The modified micellar
interface allows an increase in the partition of free base dibucaine into
the hydrophobic region. At the xerogel stage, however, the collapse of
micellar structure provides a direct interaction of dibucaine with the
acidic gel surface, leading to a formation of diprotonated dibucaine. The
results are discussed in terms of molecular basis of pharmacological
implications such as drug delivery, release, and transport under
Deposition by aqueous acetate solution (DAAS) technique was used to synthesize undoped and 5 wt% Cr-, Mn-, Eu-, or Pr-doped Pb(Zr0.53Ti0.47O3 [PZT] thin films. The dopant was incorporated into PZT either in the precursor coating solution or via thermal diffusion into undoped PZT. X-ray diffraction shows that ion-doped PZT thin films on Pt<l 1 l>/Ti/SiO2/Si<100> (in particular, the Mn- and Eu- doped samples) display better crystallinity and smaller lattice parameters than those on sapphire substrates. The enhancement of photoconductivity at visible wavelengths measured by excitation photocurrent spectroscopy (EPS) goes as Cr-doped∼Mn-doped > Eu-doped ∼ Pr-doped. Only Mn-doped PZT perovskites have the band gap energy red-shifted to 360 nm from 330 nm. The space charge (or photovoltaic) field was estimated to be < 8 v when about 100 v was applied to ion-doped PZT thin films with 260 or 320 nm light. By using laser irradiation at selected wavelengths and switching the polarity of applied bias voltage, the expected changes in resistance (Ry) and remanent polarization (±Pr) states were observed in the P-E hysteresis loops. The possible applications of extrinsic ion-doped PZT thin films in optical memory devices are discussed.
Surface morphological and compositional evolution during the initial stages of Si growth on Ge(001)2×1 by cyclic gas-source molecular-beam epitaxy (GSMBE) from Si2H6 has been investigated using in-situ reflection high-energy electron diffraction (RHEED), Auger electron spectroscopy (AES), electron energy-loss spectroscopy (EELS), and scanning tunneling microscopy (STM). At 550 °C, single-step-height island growth was observed for nominal Si deposition thicknesses tsi up to ≃ 1.5 ML. The islands were essentially pure Ge which segregated to the surface as H was desorbed. At higher tsi, the Ge coverage decreased, the surface roughened, and two-dimensional multi-layer island growth was observed for tSi up to ≃8 ML above which three-dimensional island growth was obtained. For thick layers (t S: 75 ML), no Ge was detected at the surface.