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An optimal dosage of nitrogen has long been known to play important roles in governing nitrogen-use efficiency and improving the yield of plants. However, there is limited information on the isolation and expression profiles of genes related to nitrogen metabolism in peach (Prunus persica L. Batsch). This study isolated five genes involved in nitrogen metabolism and evaluated the effects of a single foliar application of urea on levels of expression of these genes in the leaves of ‘Dazhenbaochiyue’ peach. Cloning resulted in the isolation of 1,767, 1,236, 1,074, 1,758, and 2,721 nt-long cDNAs with full-length open reading frames encoding 588, 411, 357, 585, and 906 amino acids representing the asparagine synthetase (AS), glutamate dehydrogenase (GDH), glutamine synthetase (GS), nitrite reductase (NiR), and nitrate reductase (NR) genes in peach, respectively. An alignment of multiple amino acid sequences revealed that the AS, GDH, GS, and NR proteins in peach shared high levels of sequence conserva...

Copper (Cu2+) ion was determined at micro level by diethyldithiocarbamate (DDTC) spectrophotometry after temperature-dependent solid–liquid separation using N-butyl pyridinium hexafluorophosphate ([BPy]PF6) as a solid solvent and DDTC as an extractant. The results showed that ions can be extracted 100% by DDTC–[BPy]PF6 at pH = 10·20. The extracted species was neutral Cu(DDTC)mCl2 (m = 1) based on slope analysis in the Cu2+–[BPy]PF6–DDTC temperature-dependent solid–liquid separation system. The recovery of Cu2+ extracted into DDTC–[BPy]PF6 can be achieved using 2 mol L−1 HNO3 as stripping agents. Back extraction method was adopted for the detection and quantification of Cu2+ ions using the DDTC spectrometry. The calibration curve was Y = 0·00328 + 0·10279X (correlation coefficient = 0·99922), the linear calibration range was 7·68 × 10−2 0·768 μg mL−1 and the limit of detection was 1·28 × 10−2 μg mL−1 for Cu2+. In this method, the contents of Cu2+ in Tieguanyin tea were determined with relative stan...

Summary Background Peginterferon-α–based therapy frequently leads to neutropenia. It remains unclear whether neutropenia is associated with bacterial infection in chronic hepatitis C (CHC). Aim To evaluate the risk of bacterial infection and neutropenia in patients with CHC treated with peginterferon-α/ribavirin. Methods In all, 207 patients with CHC with (group A, n = 30) and without (group B, n = 177) baseline neutropenia were treated with peginterferon-α/ribavirin. Results Group A had significantly higher rates of moderate (

This paper describes a system for the recognition of legal amounts on bank checks written in the Chinese language. It consists of subsystems that perform preprocessing, segmentation, and recognition of the legal amount. In each step of the segmentation and recognition phases, a list of possible choices are obtained. An approach is adopted whereby a large number of choices can be processed effectively and efficiently in order to achieve the best recognition result. The contribution of this paper is the proposal of a grammar checker for Chinese bank check amounts. It is found to be very effective in reducing the substitution error rate. The recognition rate of the system is 74.0%, the error rate is 10.4%, and the reliability is 87.7%.

An attempt on the use of secondary ion mass spectroscopy (SIMS) in studying ancient Chinese bronze is reported with an evaluation of the suitability of SIMS for the provenance study of ancient bronze objects. The advantage of using SIMS in the study of the lead isotope ratio is the high sensitivity that enables the examination of small fragments of valuable relics that are often difficult to collect. The application of SIMS in this direction widens the sampling area, which is limited by the use of thermal ionization mass spectroscopy (TIMS). The focus of the study has been placed on the precision of SIMS when compared to TIMS and the effect of sample matrices on the precision. Samples of Chinese bronze artefacts and a standard lead sample (SRM 981) were tested for their lead isotope ratios using both SIMS and TIMS. A comparison of the data obtained using the two techniques showed that SIMS results have a relatively large standard deviation, which was attributed to the non-uniformity of the ancient samples and the single-isotope detection system of the SIMS set-up used. Matrix effects were found to be small among bronze samples of different compositions. Non-conducting samples can also be analysed when a specimen isolation technique is employed. Although SIMS gave higher uncertainties than TIMS, the SIMS technique can be applied easily to differentiate the high radiogenic lead in Shang bronze artefacts from common lead. Copyright © 2000 John Wiley & Sons, Ltd.

The energy distributions of electron emission from a Schottky emitter have been studied at tip temperatures from 1450 to 1800 K and angular current densities from 0.1 to 240 μA/sr. We have observed broadening of the energy distribution, with increase of angular current density and decrease of tip temperature, from 0.4 to 1.32 eV resulting from electron tunneling and electron–electron interaction. Good agreement between the experimental results and predictions from Monte Carlo simulation of the emission process is observed.

Distributed simulation of circuits in which the process interactions form a cyclic graph is addressed. The method described uses a dataflow network synthesized on the basis of the connectivity of the circuit components. The algorithm, called Yaddes (which stands for yet another asynchronous distributed discrete-event simulation algorithm), computes for each component a quantity time of next event, which permits the corresponding model to execute asynchronously as far ahead in simulation time as possible. The network ensures that a simulation process executing in a distributed processing environment will not deadlock. The algorithm, which also offers acceptable performance and provable correctness, is compared with the two other principal algorithms proposed to avoid deadlocks: the deadlock recovery algorithm and the exception-mode algorithm. Performance results for Yaddes are presented. >

The long-term benefits of interferon-based therapy on preventing cirrhosis at non-cirrhotic stage in chronic hepatitis C patients are not fully clarified.To evaluate the effectiveness of interferon-based therapy regarding to cirrhosis prevention in non-cirrhotic chronic hepatitis C patients.A total of 1386 biopsy-proven, non-cirrhotic chronic hepatitis C patients (892 received interferon-based therapy and 494 untreated) were enrolled.Fifty-six untreated and 51 treated (24 sustained virologic responders and 27 non-responders) patients developed cirrhosis during a mean follow-up period of 5.0 (1-16) and 5.1 (1-15.3) years, respectively. The annual incidences of cirrhosis in untreated and treated groups were 2.26 and 1.11% (non-responders: 1.99%, sustained responders: 0.74%), respectively. The 15-year cumulative incidence of cirrhosis was significantly lower in treated (9.9%) than untreated patients (39.8%, P = 0.0008, log-rank test). The 14.5-year cumulative incidence of cirrhosis was significantly lower in sustained responders (4.8%) compared with non-responders (21.6%, P = 0.0007) and untreated patients (36.6%, P0.0001). The difference was not significant between non-responders and untreated controls. Cox proportional hazards regression showed sustained virologic responders and younger age were independent negative factors for cirrhosis development.A sustained virologic response secondary to IFN-based therapy could reduce cirrhosis development in chronic hepatitis C patients.

This paper presents a SAS macro for a simulation study of comparing a new variant of hot-deck imputation with mean imputation for missing values, in which a simple algorithm proposed by Bebbington (Applied Statistics, 1975) for carrying out simple random sampling without replacement was employed to draw repeated random samples efficiently. A simulated example of drawing repeated random samples from a regional survey of obesity in school children was used to demonstrate the SAS macro.

In the analysis of complex survey data such as stratified multi-stage cluster samples, ignoring the design effects such as clustering and stratification usually will lead to erroneous conclusions. In this paper, we will demonstrate the consequences in the estimation of means and proportions by two examples from a stratified two-stage cluster sample. A brief review of methodology will be presented, and some suggestions on computational issues will be provided.

Vanadium pentoxide (V2O5) nanomaterials with various morphologies were prepared by chemical vapour deposition at a relatively low temperature (evaporation temperature of 250 °C and growth temperature of 500 °C) using vanadyl acetylacetonate (VO(acac)2) powder as the vanadium precursor. The obtained samples were characterized by scanning electron microscopy, x-ray diffraction, Raman scattering and photoluminescence spectra. The results revealed that the samples including a V2O5 nanocluster film, V2O5 nanowires and V2O5 nanospheres were synthesized at different distances from the source material. For our chemical vapour transport system, we suggested that VOx vapour and VO(acac)2 vapour existed simultaneously during the growth process, which resulted in different morphologies of V2O5 nanomaterials. The quite different supersaturation distributions of VOx vapour and VO(acac)2 vapour led to three main growth areas. The V2O5 film was grown in the region where the supersaturation of the VOx vapour was high, V2O5 nanowires were obtained where the supersaturation of the VOx vapour was relatively low and V2O5 nanospheres were synthesized in the region where the supersaturation of the VO(acac)2 vapour was high. The growth pressure that influenced the vapour concentration controlled the morphologies of the nanowires. It was found that a specific level of low concentration was necessary to ensure the growth of V2O5 nanowires.

Photoemission has often been proposed as a promising approach for achieving arrays of independently modulated photocathodes for electron-beam lithography applications. In most such proposals the modulation of the photocurrent is assumed to be achieved by controlling the incident light energy reaching each photocathode. For many applications, however, the optical complexity of such a scheme limits the attractiveness of the photocathode approach. In this article we propose a novel gated photocathode structure which resolves this concern. It allows stable and reproducible electrical modulation of the photocurrent from each photocathode in a thin-film array under continuous optical illumination. In addition, by using illumination of the photocathodes through a transparent substrate, the position, the size, and the shape of each photocathode can be accurately determined during fabrication rather than being determined by the size of the optical illumination spot on the photocathode material. A number of structu...

Experimental measurements of emission stability and energy distributions from a Schottky emitter have been conducted at a tip temperature range from 1330 to 1800 K. The changes of emission properties have been observed at reduced tip temperatures. Noise fluctuations of the probe current increase with decrease of the tip temperature at a constant extraction voltage. The work function of the Schottky emitter increases with decrease of tip temperature. The energy distribution measurements show that the energy width at a given temperature increases with increasing angular emission current density. The energy width also increases with decreasing tip temperature at a given angular emission current density. The results indicate that the energy broadening is mainly contributed by electron tunneling. A comparison of the measured energy width with the theoretical predictions is discussed.

Lithography with an array of miniaturized scanning electron‐beam columns presents one of the most promising high‐throughput possibilities for fabrication of devices with feature sizes less than 100 nm. With scanning electron beams no mask is required and the necessary resolution and alignment of overlay structures are realizable. With arrays of microcolumns, the lithography throughput of a single column can be multiplied. The approach can also be used for a number of lithography related applications such as metrology, inspection, testing, etc. We review the status of the microcolumn program and discuss opportunities and challenges of this approach to high‐throughput nanolithography and related applications. Special emphasis is given to lithography in the 100 nm regime.

A miniaturized 1 kV electron beam column with a 20×20 mm square footprint for application in arrayed lithography was developed. The actual beam forming optics measured from the electron emitter to the last electrode in the beam focusing Einzel lens is only 3.5 mm in length. The electron source is a miniaturized, high brightness (120 μA/sr), low heating power (

We have measured the energy distributions of electrons field emitted from tungsten carbide, HfC〈100〉, and ZrC〈100〉 tips, and tungsten field emitters with diamondlike carbon coatings. Multiple‐peaked energy distributions were observed from instability induced emission sites on the carbide tips. Energy distributions of electrons field emitted from the diamondlike carbon coated tungsten tips were broader than those from metal tips. They also showed a shift towards lower energies with increases in the emission current.

A miniature Schottky electron source has been developed and evaluated for applications in a new generation of scanning tunneling microscope aligned field emission microcolumns. Both the physical dimensions and the heating power of this source have been significantly reduced from a conventional source of the same kind. Operating parameters for such a source in a microcolumn environment in terms of emission characteristics, suppressor operating range, etc., have been evaluated. Test results show that very good emission stability at ≥100 μA emission current over several hours, and axial angular current densities in excess of 100 μA/sr can be obtained. Energy distributions have been measured using a carefully calibrated analyzer, and the results show a full width at half‐maximum of 0.4 to 0.76 eV for a 0.3 μm radius Schottky source operating over an angular current density range of 1 to over 100 μA/sr. A significant change in the shape of the energy distribution was observed over this range of operation, indi...

We have built and tested a 1 keV electron‐beam microcolumn that focuses 1 nA of beam current into a 10 nm full width half‐maximum beam diameter at a working distance of 1 mm. The electron source is a miniaturized Zr/O/W Schottky field emitter with 150 μA/sr angular emission current density operating at about 1800 K at a distance of only 100 μm from a silicon membrane extractor electrode. The actual microcolumn is 3.5 mm long assembled mainly from silicon membrane electrodes. Improved einzel lens design and fabrication allowed the operation of this beam focusing element in the accelerating mode. Spherical and chromatic aberrations were reduced by factors of about 2–3, respectively, as compared to the retarding lens mode. Excellent beam current stability with less than 1% variation over several hours has been observed.

Schottky emission tips have been evaluated with microlenses for applications in scanning tunneling microscope aligned field emission microcolumns. Operation of Zr/O/W 〈100〉 Schottky emission tips at 1800 K with an axial separation of 50–100 μm between the tip and a microlens has been successfully tested. The microlens consists of an extraction electrode with a 5‐μm‐diam hole in a 1‐μm‐thick silicon membrane. The preliminary results of this study show that thermal field emission tips can be operated continuously in close proximity to a microlens over a long period of time, and that good emission stability of less than 1% noise fluctuation over 10 h is achieved with emission currents up to at least 100 μA.

We have examined the field emission characteristics of oxygen‐processed and thermal‐field buildup W 〈111〉 tips. Good emission angular confinement was found to correlate with the global geometry of the tip. Emission stability was related to the atomic arrangement at the apex. This phenomenon is described by the different driving forces for atomic surface diffusion. We also showed that tip apexes can be engineered to form flat (111) facets at the tip end for improved stability.

An oxygen induced sharpening process of field emitter tips, W〈111〉, for use in a scanning tunneling microscope aligned field emission microcolumn system has been developed. The sharpening process which depends on processing temperature and oxygen pressure can be used to control tip radius accurately with reliability and reproducibility. The measured tungsten removal rate was ∼13 A/min at a processing temperature of ≂1650 K and at an oxygen pressure of ≂4×10−5 Torr. The process is primarily intended for more accurate control of the tip radius and hence performance of newly etched tips, although damaged or blunt tips can also be resharpened in situ with this process. Favorable emission characteristics of the oxygen processed tips have been observed with microcolumn operation: (1) reasonably stable emission current, (2) low extraction voltage, (3) reproducible threefold symmetric emission patterns, and (4) small emission angle.

A three-dimensional close-packed array of Josephson junctions was successfully produced in the form of a bulk granular superconductor. The granular system is a tightly compressed solid of oxide coated small tin particles in the thousand A range. The three-dimensional array of Josephson junctions thus formed showed coherent Josephson oscillations when external rf radiation was imposed, rf induced constant voltage steps were observed on its I-V characteristics at voltages a few thousand times the Josephson voltage hv/2e. The external rf radiation also induced Stable dc voltages on unbiased bulk samples, suggesting a practical mode of microwave detection. The analogy of this bulk superconducting system with a magnetic spin system will be discussed.

Common ion sputtering techniques for depth profiles can cause buildup of charge in low‐conductivity regions such as p‐n junctions in semiconductors, leading to erroneous results. We analyzed Ga0.1Al0.9As liquid phase epitaxial (LPE) layers on GaAs with secondary ion mass spectrometry (SIMS) and observed that the profiles of 69Ga+ and 27Al+ in the low‐conductivity region of these Zn‐diffused LPE layers were a function of the sample bias. We noticed that this artifact was due to the shift and broadening of the secondary ion energy distributions caused by positive charging of the specimen surface. We also found that this could be effectively remedied by integrating the secondary ion yields over a wide energy range. The use of an electron flood gun reduced this charging effect, but complete charge compensation was not achieved even at electron current densities far exceeding the ion current density. This can be explained by the fact that the electron‐induced secondary electron coefficient of GaAlAs is larger ...

The authors examine the limitations of the timing semantics in the conventional behavioral simulators and present a preemptive scheduling mechanism for accurate behavioral simulation results. They consider two signal transitions at the input ports of a component, where the second input transition arrives later than the first transition. The first and second input transitions cause first output signal transitions O/sub 1/ and O/sub 2/, respectively, to be generated at the output port of the component. When the logical values of O/sub 1/ and O/sub 2/ conflict with each other and O/sub 1/ arrives later than O/sub 2/, O/sub 1/ is preempted by O/sub 2/. In addition, an input signal to a component whose pulse duration is smaller than the inertial delay of the component, T/sub mip/, is discarded during simulation. Empirical measures for T/sub mip/ relative to the high-to-low and low-to-high propagation delays of the component for TL (transistor-transistor logic), NMOS, and CMOS technologies are presented. This approach has been implemented in the ADLIB-SABLE simulator at Stanford University. >

Normalized ionization probabilities α+ are reported for binary Fe‐Ni alloys under O+2 bombardment at a 45° incidence angle. It is shown that the dependence of α+ on the composition is much smaller than at normal incidence. Photoemission spectroscopy reveals that both nickel and iron remain essentially metallic under oblique‐incidence bombardment, whereas almost complete oxidation occurs at normal incidence. This is attributed to our observation that sputter yields under oxygen bombardment increase much faster than cos α−1.

A new way to use Josephson junctions for parametric amplification with phase control is proposed. The dc current bias of the junction is adjusted such that the Josephson oscillation automatically synchronizes with the input signal and oscillates at twice the signal frequency with the proper relative phase. The impedance of the junction then has a negative resistive component which can be used for amplification. Extension to other phase sensitive circuits is also discussed.