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The temperature dependence of the Hall plateaus at microwave frequencies (∼ 30 GHz) and their disappearance at 160 GHz suggest a unified phenomenological model of the integral quantum Hall effect at zero and high frequencies. In laterally structured samples depolarization effects as well as the Hall plateaus are observed in the Hall conductivity.

The objective of this survey was to obtain a self-reported assessment of the use of information technology (IT) by final year medical students. Two hundred and sixty five students responded to a questionnaire survey. 81.5% of students considered their computer skills adequate, while 87.9% had access to computers outside the campus. Most students reported adequate skills at word processing, e-mailing and surfing the Internet. Fifty three percent of students spent three hours or more each week on the computer. While students indicated a general willingness to access Internet-based materials, further steps need to be taken to increase the use of this method of instruction.

Anaesthetizing patients with Long QT Syndrome is a major challenge, as the potential for sudden catastrophic cardiovascular collapse is well known. We present a 15-year-old boy with Long QT Syndrome who presented for an elective renal transplant. All electrolyte concentration abnormalities were corrected preoperative and adequate beta-blockade was maintained. The patient was given a target controlled infusion of propofol, together with opioids and atracurium. Anaesthesia was uneventful and the patient was extubated at the end of the surgical procedure.

We investigated concerted evolution of rRNA genes in multiple populations of Tragopogon mirus and T. miscellus, two allotetraploids that formed recurrently within the last 80 years following the introduction of three diploids (T. dubius, T. pratensis, and T. porrifolius) from Europe to North America. Using the earliest herbarium specimens of the allotetraploids (1949 and 1953) to represent the genomic condition near the time of polyploidization, we found that the parental rDNA repeats were inherited in roughly equal numbers. In contrast, in most present-day populations of both tetraploids, the rDNA of T. dubius origin is reduced and may occupy as little as 5% of total rDNA in some individuals. However, in two populations of T. mirus the repeats of T. dubius origin outnumber the repeats of the second diploid parent (T. porrifolius), indicating bidirectional concerted evolution within a single species. In plants of T. miscellus having a low rDNA contribution from T. dubius, the rDNA of T. dubius was nonetheless expressed. We have apparently caught homogenization of rDNA repeats (concerted evolution) in the act, although it has not proceeded to completion in any allopolyploid population yet examined.

High quality GaAs layers with excellent crystal quality and surface morphology were grown on InP substrates (GaAs/InP) using liquid phase epitaxy. Thin GaAs buffer layers heavily doped with Se were utilized to prevent the substrate meltback and the InP substrates patterned with gratings to reduce the dislocation density. Double crystal x‐ray diffraction showed about 230 arcsec full width at half maximum of the (400) reflection, which represents significant improvement compared to the previously reported 350 arcsec of the GaAs/InP layer grown by chemical beam epitaxy using strained superlattice buffer layers.

By using femtosecond laser pulses at a wavelength range from 720 to 780 nm, we have observed absorptive and refractive nonlinearities in a film of multi-walled carbon nanotubes grown mainly along the direction perpendicular to the surface of quartz substrate. The Z-scans show that both absorptive and refractive nonlinearities are of negative and cubic nature in the laser irradiance range from a few to 300 GW/cm^2. The magnitude of the third-order nonlinear susceptibility,chi-(3), is of an order of 10^-11 esu. The degenerate pump-probe measurement reveals a relaxation time of 2 ps., 12 pages, 4 figures, submitted to Appl. Phys. Lett. (2003)

Nicotiana rustica (2n = 4x = 48) is a natural allotetraploid composed of P and U genomes which are closely related to genomes of diploid species N. paniculata and N. undulata. Genomic in situ hybridization (GISH) also confirms that the diploid parents, or close relatives, are the ancestors of N. rustica. In order to study genetic interactions between ancestral genomes in the allotetraploid, we isolated three families of repetitive sequences, two from N. paniculata (NPAMBE and NPAMBO) and one from N. undulata (NUNSSP). Southern blot hybridization revealed that the sequences are digested with a range of restriction enzymes into regular ladder patterns indicating a tandem arrangement of high copy repeats possessing monomeric units of about 180 bp. The three-tandem sequences belong to a larger Nicotiana tandem repeat family called here the HRS-60 family. Members of this family are found in all Nicotiana species studied. Fluorescence in situ hybridization (FISH) analysis localized the satellite repeats to subtelomeric regions of most chromosomes of N. paniculata and N. undulata. The pattern of sequence distribution on the P- and U-genomes of N. rustica was similar to the putative parents N. paniculata and N. undulata respectively. However, NPAMBO repeats appear to be reduced and rearranged in N. rustica that may suggest evolution within the P genome. GISH and FISH with the tandem repeat probes failed to reveal intergenomic translocations as might be predicted from the nucleocytoplasmic interaction hypothesis.

With the inherent advantages of micromachining technologies such as small size, small mass, low cost, low power consumption and high reliability, there will be radical changes to biomedical devices and how clinical diagnoses are made. One of the most promising applications of microtechnologies is in the biomedical field. This paper presents a low-voltage high-torque MEMS 2D scanner well suited for in vivo biomedical imaging.

This paper presents a novel 2D-scanning micro-mirror used in ECOM for in vivo and in situ tissue imaging using MEMS technology. The 2D scanner accomplishes Raster Scanning with just one mirror. The size of the mirror is 1mm by 1mm and is rotated about two axes giving it two degree of freedom. The scanning mirror is actuated electrostatically. The inherent disadvantages of electrostatic actuation such as high crosstalk between electrodes, and large nonlinearity in voltage to angle relationship are systematically addressed. In the context of biomedical applications, it is desirable to minimize the driving voltage requirements of the electrostatic actuators while maintaining the same scan angle. The optical scanner described in this paper is capable of generating large scan angles with low driving voltages, thus making it highly suitable for biomedical imaging.

Yttrium-90 ((90)Y) internal pair production can be imaged by positron emission tomography (PET)/CT and is superior to bremsstrahlung single-photon emission CT/CT for evaluating hepatic (90)Y microsphere biodistribution. We illustrate a case of (90)Y imaging using first generation PET/CT technology, producing high-quality images for qualitative diagnostic purposes.

We studied the influence of the sample structure on the photoluminescence intensity in terms of carrier diffusion and transfer phenomena in InxGa1−xAs/GaAs multi‐quantum‐well structures. Carrier injection from the barrier, cap, or buffer layers dominates the generation in the well when the well thicknesses are small and the excitation energy is larger than the band gap of the barrier layer. The carrier transport between wells also plays an important role in the photoluminescence particularly in the shallow wells and can be accounted for by phenomenologically introduced hopping time between wells. The hopping time varies from a few tens of picoseconds to a few hundreds of nanoseconds depending on the well composition and width. The strain relaxation of these strained layer quantum‐well structures also leads to the intensity variation as well as the change in the peak position.

Nicotiana tabacum (tobacco, Solanaceae) has two 5S ribosomal DNA (rDNA) families, one of unit length ~646 bp and the other ~430 bp, that differ in the length of the 5S rDNA non-transcribed spacer (NTS). The long 5S rDNA family, found on the T genome of tobacco and in Nicotiana tomentosiformis, contains a GC-rich subregion that is absent in the short family. We designed primers for this subregion and generated a probe that we used against a range of Nicotiana and related Solanaceous species. We demonstrated the presence of the GC-rich subregion in a range of Nicotiana species, but it was absent in Nicotiana sylvestris, Nicotiana longiflora, and two closely related genera, Petunia and Solanum. These data suggest that this subregion of the NTS is likely to have evolved with the genus Nicotiana. The absence of the subregion in N. sylvestris and N. longiflora is likely to have arisen by a deletion event in the evolution of section alatae. We demonstrate patterns of evolution in the 5S rDNA unit cluster in relation to a phylogenetic reconstruction of species relationships in section tomentosae. Nicotiana glutinosa diverged early from the section and contains a 5S rDNA family based on a 550-bp unit. After this divergence, 430- and 650-bp rDNA unit families evolved. The 650-bp family is found in all species of tomentosae (except N. glutinosa) and in tobacco. The 430-bp family within tomentosae includes the GC-rich subregion and is thus unrelated to the 430-bp family in N. sylvestris. Nicotiana setchellii is unusual in that it has three 5S rDNA loci, including one locus that is exceptionally large. This species, unique to tomentosae, has a very abundant 900-bp unit family. It is possible that this 900-bp family occurs on this one large locus. In N. tomentosa and N. kawakamii, the 650-bp family is predominant, whereas N. tomentosiformis and N. otophora have only the 650-bp family. There is no clear relationship between the number of 5S families and the number of 5S rDNA loci. Certainly the replacement of 5S rDNA units, perhaps by gene conversion, has occurred repeatedly in the evolution of genus Nicotiana.Key words: 5S rDNA, evolution, Nicotiana, Solanaceae, satellite homogenization.

P-doped ZnO was fabricated by means of the ion-implantation method. At the Raman measurement, the blue shift of the E2high mode and A1(LO) phonon of the inactive mode were observed after the P-ion implantation. It suggested to be caused by the compressive stress. Thus, Hall effect measurement indicates that the acceptor levels exists in P-doped ZnO while still maintaining n-type ZnO. From the X-ray photoelectron spectroscopy, the chemical bond formation of the P2p3/2 spectrum consisted of 2(P2O5) molecules. Therefore, the implanted P ions were substituted to the Zn site in ZnO. From the photoluminescence (PL) spectra, P-related PL peaks were observed in the energy ranges of 3.1 and 3.5 eV, and its origin was analyzed at PZn-2VZn complexes, acting as a shallow acceptor. With increasing temperatures, the neutral-acceptor bound-exciton emission, (A0, X), shows a tendency to quench the intensity and extend the emission linewidth. From the relations of the intensity and the linewidth as a function of temperatu...

Cytosine methylation levels and susceptibility to drug-induced hypomethylation have been studied in several Nicotiana tabacum (tobacco) DNA repetitive sequences. It has been shown using HapII, MspI, BamHI and Sau3AI methylation-sensitive restriction enzymes that the degree of 5'-mCmCG-3' methylation varied significantly between different repeats. There were almost saturation levels of 5-methylcytosine at the inner (3') cytosine position and variable degrees of methylation at the outer (5') cytosine at the enzyme recognition sites. The non-transcribed high copy satellite sequences (HRS60, GRS) displayed significant heterogeneity in methylation of their basic units while middle repetitive sequences (R8.1, GRD5, 5S rDNA) were more uniformly modified at both cytosine residues. Dihydroxypropyladenine (DHPA) treatment, which is thought to reduce DNA methyltransferase activity by increasing S-adenosylhomocysteine levels, resulted in extensive demethylation of the outer cytosine in all repeats, and the partial hypomethylation of cytosines at the inner positions in less densely methylated repeats such as HRS60 and GRS. The results suggest that hypomethylation of 5'-mCmCG-3' sites with DHPA is a gradual non-random process proceeding in the direction mCmCG--CmCG--CCG. The 18S-5.8S-25S rDNA was remarkably hypomethylated relative to the 5S rDNA at all restriction sites studied. Fluorescence in-situ hybridization showed that DNA decondensation within and between the 18S-5.8S-25S and 5S rDNA loci was variable in different nuclei. All nuclei had condensed and decondensed sequence. The chromatin of 18S-5.8S-25S rDNA was more readily digested with micrococcal nuclease than the 5S rDNA suggesting that the overall levels of decondensation were higher for 18S-5.8S-25S rDNA. Variable decondensation patterns within and between loci were also observed for GRS and HRS60. Cytosine methylation of the tobacco repeats is discussed with respect to transcription, overall levels of condensation and overall structure.

Estimates of mechanical properties of human motor units have usually been made indirectly, using the technique of “spike-triggered averaging” (STA). In this method, a single motor unit action potential is used to synchronize the accumulation of an ensemble average of correlated force transients. However, under most realizable conditions, these transients are recorded during periods of sustained motor unit discharge, in which each motor unit is producing a partially fused tetanus. Therefore, the STA technique extracts the characteristics of the unfused force transient, instead of the desired single motor unit twitch. Although the STA method has been widely used, there is as yet no wellestablished relation between the force transient in the unfused tetanus, and the twitch contraction properties of the motor unit. To evaluate the accuracy of the STA as a measure of the motor unit mechanical properties, we applied two types of muscle models to the force transients recorded in an unfused tetanus, using data derived from experiments in which the response to a single twitch was also recorded. Our objective was to see whether accurate predictions of single motor unit mechanical characteristics are possible, working backward from the STA. The models chosen for this task were a linear second order model, and the distribution-moment (DM) model. These model predictions were then compared with the STA response, and with the twitch properties of the individual motor units. We also evaluated the utility of extrapolating the initial slope of the STA backward to improve the accuracy of the mechanical estimates. The results of our simulation suggest that there is no straightforward relation bwtween the characteristics of the unfused tetanus and the mechanical properties of the single twitch. Although our attempts to predict the properties of the single twitch from the STA were only partly successful, the results of the simulations were far more accurate than those derived from the STA alone. Because the errors in the use of the STA method were so substantial, we would urge that the STA technique be used with great caution as a measure of twitch contraction properties, unless accompanied by appropriate simulations of muscle mechanical behavior.© 1995 John Wiley &Sons, Inc.

The width of the QHE plateaus ΔB is investigated in GaAs/-AlGaAs using DC and microwave (MW) techniques. ΔB is narrower at MW frequencies than at DC and saturates below 2.4K. No fractional plateaus were observed at MW frequencies where they appeared at DC.

The paper proposes that some current problems in recruiting human factors methods to system design might be alleviated by means of a structured human factors design framework. The explicit stage-wise design scope of such a framework would support the assignment of appropriate human factors methods to specific system design needs. As an illustration, the design framework of an in-house structured human factors methodology is reviewed followed by the assignment of a set of existing human factors methods against its design stages. Subsequent steps to develop the assigned methods into a similar methodology are then described. The potential of such a methodology for facilitating human factors input is discussed.

Quadratic voltage coefficient of capacitance (VCC) for ZrO2–SiO2 multilayered dielectric metal-insulator-metal capacitors depends strongly on the stacking sequence of the layered dielectrics. The quadratic VCC of an optimized SiO2/ZrO2/SiO2 stack and ZrO2/SiO2/ZrO2 stack were +42 and −1094 ppm/V2, respectively, despite the same total SiO2 and ZrO2 dielectric thickness in the stack. The observed difference in quadratic VCC depending on dielectric stacking sequence is explained by taking into account both the interface and bulk dielectric responses to the applied voltage.

In the past, the electronic transport in quantum wires has mostly been studied using d.c. or low-frequency measuring techniques (Washburn and Webb, 1986; Heinrich et al., 1988). The use of high-frequency electric fields, however, is of particular interest if the product ωτϕ ∼ 1, where 1/τϕ is the phase-breaking rate which determines the phase coherence of the wave function (Altshuler et al., 1981; Khmelnitskii, 1988). In quantum wires, high-frequency effects were studied using narrow silicon MOSFETs and GaAs epitaxial layers (Bykov et al., 1989) and metal films (Liu et al., 1988; Lindelof et al., 1987). In the first experiments on heterostructure quantum wires the influence of a microwave field on the weak electron localization (WEL) and the universal conductance fluctuations (UCF) was studied (Kuchar et al., 1989, 1990).

Erratum

The dc characteristics of the AlGaN∕GaN heterostructure field-effect transistors were examined at temperatures ranging from 25 to 260 °C under white light illumination. Drain current collapse measured was defined by the difference of drain current between light on and light off at Vgs=1V and Vds=5V. The surface-passivated device showed no drain current collapse, but the unpassivated device showed severe drain current collapse at 25 °C. Drain current and drain current collapse with an increase in temperature reduced, which resulted from the reduction of the electron mobility or saturation velocity and the thermal activation of the trapped electrons, respectively. Eventually, drain current collapse disappeared completely above 250 °C. The behavior of the temperature-dependent drain current collapse showed that the surface states for trapping electrons were continuously distributed with the temperature not having specific energy states.

Dry etching of undoped, n- and p-type GaN films was carried out in Cl2-based inductively coupled plasmas (ICPs) using different rf excitation frequencies of 100 kHz and 13.56 MHz, in which the rf chuck power source operates. The etch rates with lower frequency of 100 kHz are somewhat greater than those with a higher frequency of 13.56 MHz due to higher ion bombarding energy with lower frequency. The highest etch rates with the 100 kHz frequency were obtained at moderately high ICP power of 700 W: ∼9300 A/min of n-GaN, ∼5300 A/min of p-GaN, and ∼7100 A/min of undoped GaN. The 13.56 MHz frequency of rf chuck power source produced maximum etch rates of ∼7900 A/min of n-GaN, ∼5800 A/min of p-GaN, and 6100 A/min of undoped GaN at 20 mTorr, 700 W ICP, and 150 W rf power. The surface roughness was relatively independent of the chuck power up to 150 W in 13.56 MHz and showed fairly smooth morphology (rms 1.1–1.3 nm), while etching at higher rf power (>200 W) produced rougher surface.

A new robust nonlinear controller that has the ability to enhance the transient stability and achieve voltage regulation simultaneously via excitation control for power systems is proposed. The structure of the controller is to add a proportional plus integral (PI) type voltage servo-compensator to the existing direct feedback linearisation (DFL) controller; a design procedure is proposed to guarantee the stability of the closed loop system in a possible working region. By using this robust nonlinear controller, direct measurement of the power angle for stabilising feedback control and calculation of the target power angle for voltage regulation are not necessary when employing the feedback linearisation technique. Performance analysis and simulation on a single-machine infinite-bus power system show that the proposed controller can retain the characteristic of the DFL controller and thus can enhance the transient stability as well as achieve voltage regulation of the power system.

Quantized values of the Hall conductivity exist in the two-dimensional electron and hole gases of GaAs/AlGaAs heterostructures at frequencies as high as 30 GHz. This is a proof that a low-frequency breakdown does not occur and that the intrinsic plateau width of σxy is non-zero. The microwave measurement also allows to separate effects connected with the boundary of the 2D carrier gas; no significant contribution was observed.

Microwave experiments with crossed waveguides allow measurement of the Hall conductivity Oxy of a two-dimensional electron gas. The quantized behavior of σxy is equivalent to that of πxy measured with DC. In this contribution we report on new results regarding phenomena not accessible to DC techniques.

The observation of integer quantum Hall, effect (IQHE) behavior of σxv at microwave frequencies (~30 GHz) is reported. This clears the discrepancy concerning the socalled low-frequency breakdown of the IQHE, It was observed in a.c, experiments in the MHz range whereas 100 ns pulse experiment did not show a deviation from the d.c. behavior. In this investigation, for the observation of σxy at microwave frequencies, a crossed waveguide arrangement is used. The common part of the cross-sections of the two waveguides is much smaller than the sample area. This is expected to minimize edge effects. From the observed quantized behavior of σxy we conclude that the mechanism of an effective delocalization at low frequencies has to be ruled out.

Human factors engineers complain that their contribution to interactive system design is typically sought late, that is following system implementation. Software engineers, in contrast, complain that the human factors contributions to system design are neither timely, appropriate nor implementable. One solution to this problem is for human factors contributions to be integrated with those of software engineering, that is presented at a time and in a form that contributes directly to system development, and in particular to the design of the user interface. This paper proposed how structured methods, in the form of Jackson System Development (JSD), might be used to integrate human factors generally into system development.

Quantum Hall effect (QHE) behavior of the Hall conductivity σxy is observed in multiple (MHS) and single heterostructures (SHS) of GaAs/AlxGa1-x As at microwave frequencies (Ka band). Integer plateaus with even filling factor i are observed in σxy of the MHS as well as of the SHS with 2D electron and hole gas layers. In the case of the 2DEG in a SHS also the i=3 plateau is resolved. With this SHS it is clearly shown that the σxy plateaus occur equidistant on a 1/B scale and that the σxy values on the plateaus are multiples of a fundamental value.

Efficient access to coherent information files is an important issue in mobile computing. In this paper we consider performance analysis of information access in a mobile computing environment. We employ a distributed directory scheme that permits uninterrupted use under disconnected and low bandwidth connections and minimizes invalidation and false sharing. This scheme allows for two invalidation schemes that avoid false sharing, and a mechanism for efficient maintenance of file details. We analyse the performance of the directory scheme in terms of time taken and energy consumed in executing operations such as read/write, connection, disconnection, and hoarding in mobile environments. The directory scheme is employed for facilitating efficient transfer of partially updated files in hierarchical networks. We also investigate quality of service issues related to file accesses in the mobile computing environment discussed in the paper. However, the scheme can be extended to any mobile computing environment.

Omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) provide significant health benefits and this has led to an increased consumption as dietary supplements. Omega-3 fatty acids EPA and DHA are found in animals, transgenic plants, fungi and many microorganisms but are typically extracted from fatty fish, putting additional pressures on global fish stocks. As primary producers, many marine microalgae are rich in EPA (C20:5) and DHA (C22:6) and present a promising source of omega-3 fatty acids. Several heterotrophic microalgae have been used as biofactories for omega-3 fatty acids commercially, but a strong interest in autotrophic microalgae has emerged in recent years as microalgae are being developed as biofuel crops. This paper provides an overview of microalgal biotechnology and production platforms for the development of omega-3 fatty acids EPA and DHA. It refers to implications in current biotechnological uses of microalgae as aquaculture feed and future biofuel crops and explores potential applications of metabolic engineering and selective breeding to accumulate large amounts of omega-3 fatty acids in autotrophic microalgae.

Purpose: We evaluated stone-free rate and complications after flexible ureteroscopy for renal stones, comparing thulium fiber laser and holmium:YAG laser with MOSES technology. Materials and Methods: Data from adults who underwent flexible ureteroscopy in 20 centers worldwide were retrospectively reviewed (January 2018-August 2021). Patients with ureteral stones, concomitant bilateral procedures, and combined procedures were excluded. One-to-one propensity score matching for age, gender, and stone characteristics was performed. Stone-free rate was defined as absence of fragments >2 mm on imaging within 3 months after surgery. Multivariable logistic regression was performed to evaluate independent predictors of being stone-free. Results: Of 2,075 included patients, holmium:YAG laser with MOSES technology was used in 508 patients and thulium fiber laser in 1,567 patients. After matching, 284 patients from each group with comparable baseline characteristics were included. Pure dusting was applied in 6.0% of cases in holmium:YAG laser with MOSES technology compared with 26% in thulium fiber laser. There was a higher rate of basket extraction in holmium:YAG laser with MOSES technology (89% vs 43%, P < .001). Total operation time and lasing time were similar. Nine patients had sepsis in thulium fiber laser vs none in holmium:YAG laser with MOSES technology (P = .007). Higher stone-free rate was achieved in thulium fiber laser (85% vs 56%, P < .001). At multivariable analysis, the use of thulium fiber laser and ureteral access sheath ≥8F had significantly higher odds of being stone-free. Lasing time, multiple stones, stone diameter, and use of disposable scopes showed significantly lower odds of being stone-free. Conclusions: This real-world study favors the use of thulium fiber laser over holmium:YAG laser with MOSES technology in flexible ureteroscopy for renal stones by way of its higher single-stage stone-free rate. Flexible ureteroscopy (F-URS) is a first-line option for kidney stones up to 2 cm in diameter1,2 and is suitable even for patients with larger stones,3 renal malformations,4 obesity, bleeding diathesis, and calyceal diverticula5 under general and spinal anesthesia,6 with good stone-free rate (SFR) and low morbidity. Over the past 3 decades, holmium laser lithotripsy has been predominantly carried out using standard-power machines (ie, 20 W). More recently, the availability of high power has allowed a wider range of pulse energy, frequency, and power settings to improve lithotripsy.7 In holmium:YAG laser (HL), variations in pulse modulation have introduced the concept of holmium:YAG laser with MOSES technology (HLM), virtual basket, and vapor tunnel allowing for more efficient stone ablation and less retropulsion.8 In vitro studies demonstrated that pulse modulation technology resulted in more efficient stone ablation together with less retropulsion for both hard and soft stones.9,10 Thulium fiber laser (TFL), which emerged in 2018,11 was found in preclinical studies to allow for ablation at twice the speed of HL with 4 times the amount of dust generated.12 Despite a recent single-center randomized clinical trial demonstrating no significant clinical advantage of one technology over the other,13 no direct comparison has been published comparing HLM with TFL in F-URS for renal stones in real-world practice, and much controversy continues to exist among experts in the field.14,15 The purpose of the present study was to evaluate outcomes and complications after F-URS for renal stones, comparing patients who were operated on using HLM vs TFL.