Small Stripe Research Articles

Performance, radiation damage, and future plans of the BABAR silicon vertex tracker

The BABAR silicon vertex tracker (SVT) has been in operation for four years at the PEP-II electron-positron storage ring. During this time the SVT modules have accumulated a radiation dose up to 2 Mrad. We study the degradation in the performance of the SVT due to this accumulated dose which is highly non uniform across the device and also within the individual silicon detectors. To extrapolate the performance of the device to the future we study separately the effect of the irradiation on silicon detectors, front end integrated circuits and on a complete detector module under controlled radiation conditions, using a /sup 60/Co source and a 0.9 GeV e/sup -/ beam. We compare the results to the data from the SVT. In particular we show the dependence of the charge collection efficiency on the radiation dose even when a small stripe of the module is irradiated up to space charge sign inversion. Since the modules that are located in the plane of the beams will suffer significant radiation damage, we will describe our plans for their replacement in 2005 and for the operation of the SVT through the lifetime of the BABAR experiment.

Paraxial protocadherin coordinates cell polarity during convergent extension via Rho A and JNK.

Convergent extension movements occur ubiquitously in animal development. This special type of cell movement is controlled by the Wnt/planar cell polarity (PCP) pathway. Here we show that Xenopus paraxial protocadherin (XPAPC) functionally interacts with the Wnt/PCP pathway in the control of convergence and extension (CE) movements in Xenopus laevis. XPAPC functions as a signalling molecule that coordinates cell polarity of the involuting mesoderm in mediolateral orientation and thus selectively promotes convergence in CE movements. XPAPC signals through the small GTPases Rho A and Rac 1 and c-jun N-terminal kinase (JNK). Loss of XPAPC function blocks Rho A-mediated JNK activation. Despite common downstream components, XPAPC and Wnt/PCP signalling are not redundant, and the activity of both, XPAPC and PCP signalling, is required to coordinate CE movements.

Effects of passive cardiac containment on left ventricular structure and function: verification by volume and flow measurements

Background: The cardiac support device (CSD, Acorn) is a compliant, textile-mesh graft placed around the ventricles to prevent further dilatation and to improve function in congestive heart failure. The aim of this study was to verify post-operative changes in left ventricular volumes, ejection fraction, blood flow, and myocardial mass. Methods: Fourteen patients underwent contrast-enhanced, electrocardiography-triggered electron-beam computerized tomography before and 6 to 9 months after CSD implantation. We measured volume and flow using the slice-summation method and the indicator-dilution technique. Results: We found significant changes for the following parameters: end-diastolic volume decreased from 382.9 ± 140.2 ml to 311.3 ± 138.7 ml, end-systolic volume from 310.4 ± 132.4 ml to 237.4 ± 133.8 ml, end-diastolic diameter from 75.3 ± 7.8 mm to 70.7 ± 11.6 mm, end-systolic diameter from 65.8 ± 7.8 mm to 60.0 ± 14.0 mm, and myocardial mass from 298.6 ± 79.6 g to 263.1 ± 76.8 g. Ejection fraction increased from 20.3% ± 6.4% to 27.8% ± 13.1%. We found no significant differences for stroke volume (from 72.5 ± 24.6 ml to 73.8 ± 23.6 ml), heart rate (from 80.5 ± 11.0 beats per minute to 76.5 ± 6.8 beats per minute), and total cardiac output (from 5.8 ± 1.9 liter/min to 5.6 ± 1.8 liter/min). Mitral regurgitation fraction decreased from 30.5% ± 15.5% to 15.6% ± 12.8%, increasing antegrade cardiac output from 3.8 ± 0.9 liter/min to 4.7±1.5 liter/min. For most parameters, pre- and post-operative values in these patients differed significantly from those in an age- and gender-matched control group. In each patient, we observed a small hyperdense stripe along the pericardium after surgery, but we observed no local complications. Conclusion: Three-dimensional structural and functional data obtained by computerized tomography volume and flow measurements confirm the safety and efficacy of CSD implantation.

The tumour suppressor gene l(2)giant discs is required to restrictthe activity of Notch to the dorsoventral boundaryduring Drosophila wing development

During the development of the Drosophila wing, the activity of the Notch signalling pathway is required to establish and maintain the organizing activity at the dorsoventral boundary (D/V boundary). At early stages, the activity of the pathway is restricted to a small stripe straddling the D/V boundary, and the establishment of this activity domain requires the secreted molecule fringe (fng). The activity domain will be established symmetrically at each side of the boundary of Fng-expressing and non-expressing cells. Here, I present evidence that the Drosophila tumour-suppressor gene lethal (2) gaint discs (lgd) is required to restrict the activity of Notch to the D/V boundary. In the absence of lgd function, the activity of Notch expands from its initial domain at the D/V boundary. This expansion requires the presence of at least one of the Notch ligands, which can activate Notch more efficiently in the mutants. The results further suggest that Lgd appears to act as a general repressor of Notch activity, because it also affects vein, eye, and bristle development.

Possible implication of Hox genes Abdominal-B and abdominal-A in the specification of genital and abdominal segments in cirripedes.

The crustaceans cirripedes (barnacles) are characterised by the lack of fully developed abdominal segments at any stage of their life cycle. However, in nauplius larvae of the cirripede Sacculina carcini, we detected five small engrailed stripes in a postero-dorsal region behind the sixth thoracic segment, that we interpreted as a vestigial abdomen. Here, we present additional morphological and genetic data on Sacculina to further characterise this structure. Scanning electron microscopy analysis confirms the existence of a segmented region in this part of the naupliar body. However, at the late naupliar stage, this structure stops its development and degenerates. This region expresses the Hox gene Abdominal-B, which may indicate that it actually corresponds to the posterior-most part of the Sacculina trunk. In addition, Abdominal-B expression differentiates two types of larvae that probably correspond to male and female larvae, respectively. In contrast, no abdominal-A expression can be detected in the vestigial abdomen. We discuss the possible implication of the loss or divergence of the Abdominal-A protein in the impaired development of abdominal segments in cirripedes.

Ordering of nitrogen molecules on the nanostructured Cu(1 1 0)/Cu(1 1 0)–(2×1)O stripe phase

The influence of the confinement induced by the finite width of the Cu and CuO domains on the Cu(1 1 0)/Cu(1 1 0)–(2×1)O stripe phase on the structure of the N 2 monolayer was investigated using both, He atom diffraction and interaction potential calculations. Above large size domains of Cu or CuO, the 4 1 1 3 pinwheel structure and the (4×3) phase already observed for the homogeneous Cu(1 1 0) and Cu(1 1 0)–(2×1)O substrates are recovered. If the width of one or the other domain type decreases, confinement effects lead to the progressive disappearance of the superstructure diffraction peaks tied to these ordered structures. Calculations show that the pinwheel structure is replaced by a hexagonal incommensurate phase on the Cu stripes whereas the (4×3) phase is only slightly disturbed even on small CuO stripes.

Coryphaeschna huaoraniaspec. nov. from central Ecuador with keys to all species in the genus (Odonata: Aeshnidae)

Abstract Coryphaeschna huaorania sp. n. (holotype ♂ Ecuador, Morona Santiago Prov., pond 5 km N of Mendez jet., 6 Nov 1997; allotype ♀ same data; both to be deposited in FSCA, Gainesville, FL, USA) is described and compared with C. amazonica, C. apeora and C. perrensi. The new species can be recognized by having 3 transverse rows of cells in the fork of Rs for a distance of 2 to 4 cells, and a combination of reddish frons without a dark spot, green thorax with small brown mesepisternal stripes, a reddish abdomen, and epiproct about half as long as the cerci. Separate keys are provided to males and females of the eight species currently recognized in the genus.

Acoustic wave–liquid interactions

Surface acoustic waves (SAWs) are one of a broad class of acoustic wave (AW) techniques that have been applied to the study of physical changes at the solid–liquid interface. Other examples include shear horizontally polarised SAWs (SH-SAWs), acoustic plate modes, Love waves and quartz crystal microbalances (QCMs). Several factors motivate and favour these techniques. The sensing surface is highly mass sensitive, it is accessible and can be chemically modified, and it provides a rapid in situ method for studying dynamic chemical and biochemical changes. Moreover, for a Newtonian fluid, the AW only entrains fluid within a penetration depth of the interface, so that the technique truly probes interfacial changes. However, many studies of liquids using these acoustic techniques have been limited to fixed pools of liquid in contact with a device surface. In this work, a damped harmonic oscillator model is described, providing a unified view of the mass damping of the shear motion in SAW, SH-SAW, and QCM AW systems by finite thickness loadings of viscoelastic fluids. The simplicity of the model also allows the effect of fluid slip at the solid–liquid interface to be examined. In the limit of small relaxation time and thick fluid coating, the model recovers the expected limit with acoustic devices acting as sensors of the device area coated by the fluid. In the large relaxation time limit, the fluid acts as an amorphous solid and the influence of the acoustic shearing motion is able to extend to the free surface of the fluid, thus inducing shear wave resonances. To complement the theory, an experiment is described which uses pulses of high frequency (169 MHz) Rayleigh SAWs to probe a small stripe of a viscous fluid (polydimethylsiloxane [PDMS] oil with a viscosity between 10 000 and 100 000 centistokes [cSt]) as it dynamically evolves in shape. The cross-sectional profile of the liquid is a well-defined spherical cap shape and this is recorded using a video based interferometry arrangement. This allows a range of geometrical parameters to be obtained and correlated with the acoustic signals. The changing geometry of the stripe does not simply decrease the magnitude of the SAW transmission as the fluid wets a progressively larger area of the surface, but also specific significant attenuations are observed. Interpreting these attenuations within the damped harmonic oscillator model, data from a range of experiments can all be fitted by relaxation rates obtained from the viscosity and a high frequency shear modulus of μ=(1.5±0.1) GN m −2. Hence, with this type of viscous fluid, the acoustic method is not acting as a simple mass sensor, although it is probing the elasticity via the shear modulus.

3501 Endoscopic fibrin sealant injection with application of hemostatic clips: a novel method of closing a refractory gastrocutaneous fistula.

Background: Management of non-healing gastrocutanous fistula is difficult especially in debilitated patients. Methods: On an elderly man with advanced stage esophageal cancer and sever oxygen-dependent lung disease; who had persistent acid leakage from the percutaneous endoscopic gastrostomy site, small stripes of absorbable fiber(Surgicel)were introduced from the cutaneous side of the fistula and fibrin sealant(Tisseel® VH)with its two components was endoscopically injected through a specially designed syringe(Duploject® applicator) and catheter (Duplocath® 180, Immuno AG,Vienna, Austria) in addition to applying of four hemeostatic clips(Rotatable clip fixing device HX-5LR-1. Olympus,America INC,Melville,N.Y) on the gastric aspect of the fistula. Results: stopping of the leakage was successful,permanent and prevented more morbidity with no complication. Conclusion: We believe that our new technique is a novel and successful one, but large study is needed to define the proper candidates and success rate.

Self-defined AlAs oxide-current-aperture buried-heterostructure ridge waveguide InGaAs single-quantum-well diode laser

Techniques for fabricating a self-defined AlAs oxide-current-aperture that is applicable to very small stripe width edge emitting devices and small aperture vertical-cavity surface-emitting lasers are reported. InGaAs single-quantum-well buried-heterostructure edge-emitting lasers with a self-defined AlAs oxide-current-aperture were fabricated by a three-step metal-organic chemical vapor deposition growth to demonstrate the validity of the process. The AlAs layer for the AlAs oxide was grown by selective area growth techniques. The threshold current and differential quantum efficiency of 3-μm stripe width, 446-μm-long laser were 2 mA and 91%, respectively. The leakage current at -15 V was less than 20 nA.

Surface acoustic wave resonances in the spreading of viscous fluids

Reflection and attenuation of a Rayleigh surface acoustic wave from a small stripe of viscous fluid spreading across the acoustic path have been observed. As the stripe spreads across the acoustic path, with an accompanying decrease in stripe height to conserve volume, the reflected and attenuated acoustic signals show a distinct pattern of resonances. This paper reports experimental results for the spreading of highly viscous poly(dimethyl)siloxane oils (100 000 cS) in the propagation path of a 169 MHz Rayleigh wave operating in pulse mode and develops a model to explain the observed resonances of the transmission coefficient. Simultaneous optical observations enable the time evolution of the shape of the stripe to be converted into changes in geometric parameters (contact width, spherical radius, height, and contact angle). To model the acoustic attenuation, an approach treating the fluid as a viscoelastic fluid with a single relaxation time (Maxwell model) is developed. This approach is able to explain the structure of the observed transmitted signal. Resonances in the transmission coefficient occur cyclically and correspond to the stripe height matching $n{\ensuremath{\lambda}}_{s}/4,$ where n is odd and ${\ensuremath{\lambda}}_{s}$ is the shear wavelength in the fluid.

An acoustic technique for the monitoring of dynamic wetting behavior

A small stripe of a viscous fluid deposited on a high-energy surface spreads with an increasing contact width that follows a characteristic 1/7th power law with time. At any instant, the fluid has a spherical cap cross-sectional profile with well-defined values of the spherical radius and dynamic contact angle. The evolution of such stripes has been followed using optical interferometry. Simultaneously, the changing contact area has been monitored using an alternative method based on high-frequency (~ 170 MHz) surface acoustic waves. Such waves have their energy confined to within one wavelength of the surface and are potentially an in-plane technique for monitoring dynamic wetting. Acoustic signals that originate from reflections from the advancing oil, and from transit along the solid-liquid interface, are reported. The changes in these acoustic signals are compared with the optically measured parameters and are interpreted using a viscoelastic model of the fluid.

Infection of mottled stripe disease‐susceptible and resistant sugar cane varieties by the endophytic diazotroph Herbaspirilium

SUMMARYLeaves of a mottled stripe disease‐susceptible cultivar (B‐4362) and of a mottled stripe disease‐resistant cultivar (SP 70–1143) of sugar cane (interspecific hybrids of Saccharum) were inoculated with the diazotrophic endophytes, Herbaspirillum rubrisubalbicans or Herbaspirillum seropedicae, via injection into the apex of the stem. At 7 and 20 d.a.i., H. seropedicae could be isolated only from a small necrotic area around the point of inoculation, where there was considerable degradation of host cells, and was not detected in any other part of the leaves. This suggested a hypersensitive response by the host to this bacterium, and no disease symptoms formed on either cultivar. By contrast, H. rubrisubalbicans could be re‐isolated from throughout the infected leaves of both cultivars at both harvests and produced widespread disease symptoms on the leaves of cv. B‐4362.Symptoms consisted of necrotic regions near the point of inoculation, and red stripes and red patches along the vertical axis of the leaves, where the bacteria had spread in the primary and secondary veins. The xylem–conducting elements in diseased regions of leaves were filled with bacteria and, at the edges of disease symptoms, the vessels were filled with a gum which stained blue‐green with toluidine blue. This material probably contained phenolic compounds, and was produced as a host defence response. Leaves of cv. SP 70–1143 only developed small red stripes near the point of inoculation. These symptoms did not spread along the leaves, and the infected xylem vessels were never seen to be completely full of bacteria. Instead, the vessels contained encapsulated bacterial colonies attached to secondary wall deposition; these colonies were surrounded by blue‐green material that might have been host‐defence gums. In cv. B‐4362, bacteria were abundant in the intercellular spaces of mesophyll adjacent to infected xylem, and also filled sub–stomatal cavities. Immunogold labelling using polyclonal antisera raised against H. rubrisubalbicans gave a weak signal with the bacteria in cv. SP 70–1143, showing that few binding sites were available to the antibodies. By contrast, bacteria in cv. B‐4362 reacted strongly with the antibody, suggesting that they had a denser coating of immunoreactive mucus. In the later stages of infection of cv. B–4362, lysed bacteria were seen within degraded plant cells surrounded by a matrix of plant gums and bacterial mucus. This matrix reacted strongly to the H. rubrisubalbicans antibodies. Immunogold labelling using antibodies against nitrogenase component II showed that nitrogenase was expressed by bacteria in the early stages of infection of cv. B–362, but not in later stages, or by bacteria infecting cv. SP 70–1143.

The clonal origin of the lateral meristem generating the ear shoot of maize

The ear shoot of maize (Zea mays L.) consists of the peduncle and reproductive tissues (ear). Genetic mosaics induced by the unstable allele of thech1 locus were used for cell lineage analysis of the ear shoot. The unstablech1-m1 allele, caused by the insertion of a transposable element, gives rise to yellow-green seedlings with many small revertant green stripes. Rare plants with large revertant sectors comprising 30–50% of the plant were selected. Nineteen plants showing large sectors on the main stem were subjected to sector boundary analysis. Sectoring was recorded for the main stem, leaf subtending the ear shoot, peduncle, prophyll and ear. The reproductive part of the ear shoot, the ear, was scored after removal of the husks and subsequent exposure to light. In 18 cases the ear was non-sectored yellow-green or green. In an additional four cases, peduncle cell lineages entered the ear, but only in the proximal part, while the tip of the ear was non-sectored. Two additional ears showed longitudinal sectors which reached the tip of the ear. These observations indicate that in the lateral meristem of the ear shoot two types of cellular clone exist. One will generate the peduncle, the other will found the ear. Sector boundary analysis indicates that for the vegetative part of the ear shoot the number of meristem founder cells is high, whereas only a few initials are recruited for the formation of the ear. The presence of ear sectors not starting in the peduncle and reaching the ear tip, and the finding that the ear is frequently non-sectored, suggest that this organ derives from an apical type of growth.

The spreading of small viscous stripes of oil

The dynamics of spreading of small amounts of viscous fluids are usually investigated using spherical droplets of oils. Recently we applied Frenkel's method to this problem and obtained a wide angle relation between the edge speed and the dynamic contact angle and this gave good agreement with literature data. In this work we give a simple extension of the method to the spreading of a stripe, rather than droplet, of oil. The small angle limit for the time dependence of the width of the stripe on a high energy surface is d0 varies as (t+t0 to)1/7 and is in agreement with previous work. Results of optical observations on the time dependence of the width of stripes of polydimethylsiloxane (PDMS) oils of viscosities of 10000, 30000 and 100000 cS on glass and on lithium niobate substrates are also presented. Fits to these data give a time dependence close to that predicted. Furthermore, order of magnitude estimates of the value of a logarithmic cut-off factor appearing in the theory are consistent with those obtained by previous studies on the spreading of spherical droplets of PDMS oils. This work establishes a spreading problem with a plane spreading liquid front and which is used in an accompanying paper to study the feasibility of a new surface acoustic wave technique for the study of dynamic wetting.

A surface acoustic wave technique for the observation of dynamic wetting

The spreading of small quantities of viscous oils has traditionally been studied using side views and plan views to obtain contact angles and profiles. The techniques employed have included optical profiling, interferometry, x-ray reflectivity and ellipsometry. In this work we report an alternative method, based on surface acoustic waves, which has the advantage of working directly within the spreading plane. In these experiments 150 ns pulses of 250 MHz surface acoustic waves are emitted along the solid-vapour interface towards a stripe of viscous oil. Both reflections from the advancing front edge of the oil and from a double transit signal which passes through the oil are observed. As the stripe becomes wider, changes in surface acoustic wave path lengths occur and these are measured using a phase comparison method. Results for the spreading of a small stripe of 100 000 cS polydimethylsiloxane oil are presented. The results for the time dependence of the width of the stripe agree with both theory and optical experiments.

Analytic modeling and comparisons of striping strategies for replicated disk arrays

Data replication has been widely used as a means of increasing the data availability for critical applications in the event of disk failure. There are different ways of organizing the two copies of the data across a disk array. This paper compares strategies for striping data of the two copies in the context of database applications. By keeping both copies active, we explore strategies that can take advantage of the additional copy to improve not only availability, but also performance during both normal and failure modes. We consider the effects of small and large stripe sizes on the performance of disk arrays with two active copies of data under a mixed workload of queries and transactions with a skewed access pattern. We propose a dual (hybrid) striping strategy which uses different stripe sizes for the two copies and a disk queuing policy designed to exploit this organization for optimal performance. An analytical model is devised for this scheme, by treating the individual disks as independent, and applying an M/G/1 queuing model. Disks on which a large query scan is running are modeled by a variation of the queue with permanent customers, which leads to an iterative functional equation for the query scan delay distribution. A solution for this equation is given. The results are validated against simulations. And are shown to match well. Comparison with uniform striping strategies show that the dual striping scheme yields the most stable performance in a variety of workloads, out-performing the uniform striping strategy using either mirrored or chained dc-clustering under both normal and failure mode operations. >

Extremely small active stripe laser diodes (EXSAS-LDs) for 17 channel low threshold array

A uniform 17 channel array of low-threshold (3.5 mA,average) 1.3 µm-wavelength lasers was realised with submicrometre-wide bulk active stripes grown by selective MOVPE.

一方向性けい素鋼板の圧縮応力下における磁区構造変化

The effects of compressive stress on the magnetization in grain-oriented silicon iron sheets have been investigated. The magnetization changes due to compression are composed of two effects, reversible and irreversible magnetization changes. The magnetization changes due to compression for a sample cut at a declining angle of 35° from the rolling direction have peculiar characteristics. This sample shows two peaks of magnetization change due to compression. Changes in the domain structure due to compression were observed in order to determine the mechanism of magnetization change. A stripe domain pattern with 180° domain walls changes into a small perpendicular stripe pattern as a result of the application of both a magnetic field and compression, and the density of stripes changes as a result of compressive stress.

Dynamic Properties of Orientation to a Visually Fixated Target by Walking Colorado Beetles

ABSTRACT The dynamic components of the fixation behaviour of walking Colorado beetles were examined. The beetles walked on top of a locomotion compensator under closed-loop conditions. The fixation target was a yellow disk with small black stripes (‘Colorado dummy’). The paths of beetles walking towards the stationary dummy were characterized by oscillations, and were investigated by applying a fast Fourier transform to the turning-velocity time course. The power density peaks near 0.3 Hz with varying amplitude. Films of the fixation reaction revealed that this frequency was much slower than the stepping-pattern frequency of the beetles. During orientation to other stimuli (wind or gravity), the oscillations were not present, showing that they were not an artefact of the motor output. However, they were present in other forms of visual orientation, such as the optomotor response and during positive phototaxis. A frequency-response curve (Bode diagram) under closed-loop conditions was obtained for the fixation reaction by changing the dummy position sinusoidally and measuring the phase and amplitude of the tracking response. A simple model of this behaviour, including a low-pass filter and an integrator, describes the reaction. Hence, the reaction can be understood as the simple resonance behaviour of an underdamped closed-position loop. The question of whether this can explain zigzagging paths in other species is discussed.