bluuebunny/crossref_metadata_2025 huggingface dataset:
Mixed kinematic and dynamic sideslip angle observer for accurate control of fast off‐road mobile robots
Authors: Lenain Roland , Thuilot Benoit , Cariou Christophe , Martinet Philippe
Published: October 2009

Automation in outdoor applications (farming, surveillance, military activities, etc.) requires highly accurate control of mobile robots, at high speed, although they are moving on low‐grip terrain. To meet such expectations, advanced control laws accounting for natural ground specificities (mainly sliding effects) must be derived. In previous work, adaptive and predictive control algorithms, based on an extended kinematic representation, have been proposed. Satisfactory experimental results have been reported (accurate to within ±10 cm, whatever the grip conditions), but at limited velocity (below 3 m·s−1). Nevertheless, simulations reveal that control accuracy is decreased when vehicle speed is increased (up to 10 m·s−1). In particular, oscillations are observed at curvature transition. This drawback is due to delays in sideslip angle estimation, unavoidable at high speed because only an extended kinematic representation was used. In this paper, a mixed backstepping kinematic and dynamic observer is designed to improve observation of these variables: the slow‐varying data are still estimated from a kinematic representation, which is then injected into a dynamic observer to supply reactive and reliable sliding variable (namely sideslip angle) estimation, without increasing the noise level. The algorithm is evaluated via advanced simulations (coupling Adams and MatLab software) investigating high‐speed capabilities. Actual experiments at lower speed (experimental platform maximum velocity) demonstrate the benefits of the proposed approach. © 2009 Wiley Periodicals, Inc.
Selection and bias—Two hostile brothers
Authors: Bauer Peter , Koenig Franz , Brannath Werner , Posch Martin
Published: October 2009

We consider the situation where in a first stage of a clinical trial several treatments are compared with a single control and the ‘best’ treatment(s) are selected in an interim analysis to be carried on to the second stage. We quantify the mean bias and mean square error of the conventional estimates after selection depending on the number of treatments and the selection time during the trial. The cases without or with reshuffling the planned sample size of the dropped treatments to the selected ones are investigated. The mean bias shows very different patterns depending on the selection rule and the unknown parameter values. We stress the fact that the quantification of the bias is possible only in designs with planned adaptivity where the design allows reacting to new evidence, but the decision rules are laid down in advance. Finally, we calculate the mean bias which arises in a simple but influential regulatory selection rule, to register a new medical therapy only when two pivotal trials have both proven an effect by a statistical test. Copyright © 2009 John Wiley & Sons, Ltd.
Exploring the concept of value creation in program planning and systems engineering processes
Authors: Patanakul Peerasit , Shenhar Aaron
Published: October 2009

Almost every large system is initiated with an intention of building something, which has new value to its stakeholders. Yet, turning this simple statement into reality is often problematic since the concept of value is not always explicitly defined or structually incorporated in the formal frameworks of program planning and systems engineering. Quite often, beyond traditional financial measures or technical and operational requirements, there is little agreement of what program value really means, and there are limited theoretical models that could help conceptualize and focus its essence. In this exploratory study, we investigated the components of program value in several major defense programs that were nominated for Aviation Week's Program Excellence Award. Among other things, these programs had to declare what value their product created. Our findings resulted in an initial framework, which identifies program value according to three major groups: value to the customer, value to the performing organization, and value to the team. The specific value components identified in our data suggest that program value could be formally and explicitly integrated into program planning and systems engineering processes. It can also lead to further research and new applications that will be focused on value creation, rather than just meeting performance and technical specifications. © 2009 Wiley Periodicals, Inc. Syst Eng
Intraoperative fluorescent imaging using indocyanine green for liver mapping and cholangiography
Authors: Aoki Takeshi , Murakami Masahiko , Yasuda Daisuke , Shimizu Yoshinori , Kusano Tomokazu , Matsuda Kazuhiro , Niiya Takashi , Kato Hirohisa , Murai Noriyuki , Otsuka Koji , Kusano Mitsuo , Kato Takashi
Published: October 2009

Background

Preoperative imaging is widely used and extremely helpful in hepatobiliary surgery. However, transfer of preoperative data to a intraoperative situation is very difficult. Surgeons need intraoperative anatomical information using imaging data for safe and precise operation in the field of hepatobiliary surgery. We have developed a new system for mapping liver segments and cholangiograms using intraoperative indocyanine green (ICG) fluorescence under infrared light observation.

Method

The imaging technique for mapping liver segments and cholangiogram based on ICG fluorescence used an infrared‐based navigation system. Eighty one patients with liver tumors underwent hepatectomy from 2006, January to 2009, March. In liver surgery, 1 ml of ICG was injected via the portal vein under observation by the fluorescent imaging system. Fourteen patients were underwent laparoscopic cholecystectomy for chronic cholecystitis with gallstones. In laparoscopic cholecystectomy, 5 ml of ICG was administered intravenously just before operation and the bile duct was observed using the infrared‐based navigation system.

Result

This new technique successfully identified stained subsegments and segments of the liver in 73 of 81 patients (90.1%). Moreover, clear mapping of liver segments was obtained even against a background of liver cirrhosis. Fluorescent cholangiography clearly showed the common bile duct and cystic duct in 10 of 14 patients (71.4%). No adverse reactions to the ICG were encountered.

Conclusion

Application of this technique allows intraoperative identification of anatomical landmark in hepatobiliary surgery.
Ab Initio Prediction of Boron Compounds Arising from Borozene: Structural and Electronic Properties
Authors: Forte G , La Magna A , Deretzis I , Pucci R
Published: October 2009

Structure and electronic properties of two unusual boron clusters obtained by fusion of borozene rings have been studied by means of first principles calculations based on the generalized-gradient approximation of the density functional theory. Moreover, a semiempirical tight-binding model has been appropriately calibrated for transport calculations on these clusters. Results show that the pure boron clusters are topologically planar and characterized by (3c–2e) bonds, which can explain, together with the aromaticity (estimated by means of NICS), the remarkable cohesive energy values obtained. Such feature makes these systems competitive with the most stable boron clusters to date. The energy gap values indicate that these clusters possess a semiconducting character, while when the larger system is considered, zero-values of the density of states are found exclusively within the HOMO–LUMO gap. Electron transport calculations within the Landauer formalism confirm these indications, showing semiconductor-like low bias differential conductance for these structures. Differences and similarities with carbon clusters are highlighted in the discussion.
The pre-transitional Klebanoff modes and other boundary-layer disturbances induced by small-wavelength free-stream vorticity
Authors: RICCO PIERRE
Published: October 2009

The response of the Blasius boundary layer to free-stream vortical disturbances of the convected gust type is studied. The vorticity signature of the boundary layer is computed through the boundary-region equations, which are the rigorous asymptotic limit of the Navier–Stokes equations for low-frequency disturbances. The method of matched asymptotic expansion is employed to obtain the initial and outer boundary conditions. For the case of forcing by a two-dimensional gust, the effect of a wall-normal wavelength comparable with the boundary-layer thickness is taken into account. The gust viscous dissipation and upward displacement due to the mean boundary layer produce significant changes on the fluctuations within the viscous region. The same analysis also proves useful for computing to second-order accuracy the boundary-layer response induced by a three-dimensional gust with spanwise wavelength comparable with the boundary-layer thickness. It also follows that the boundary-layer fluctuations of the streamwise velocity match the corresponding free-stream velocity component. The velocity profiles are compared with experimental data, and good agreement is attained.

The generation of Tollmien–Schlichting waves by the nonlinear mixing between the two-dimensional unsteady vorticity fluctuations and the mean flow distortion induced by localized wall roughness and suction is also investigated. Gusts with small wall-normal wavelengths generate significantly different amplitudes of the instability waves for a selected range of forcing frequencies. This is primarily due to the disparity between the streamwise velocity fluctuations in the free stream and within the boundary layer.
On the logarithmic mean profile
Authors: KLEWICKI J. , FIFE P. , WEI T.
Published: October 2009

Elements of the first-principles-based theory of Weiet al. (J. Fluid Mech., vol. 522, 2005, p. 303), Fifeet al. (Multiscale Model. Simul., vol. 4, 2005a, p. 936;J. Fluid Mech., vol. 532, 2005b, p. 165) and Fife, Klewicki & Wei (J. Discrete Continuous Dyn. Syst., vol. 24, 2009, p. 781) are clarified and their veracity tested relative to the properties of the logarithmic mean velocity profile. While the approach employed broadly reveals the mathematical structure admitted by the time averaged Navier–Stokes equations, results are primarily provided for fully developed pressure driven flow in a two-dimensional channel. The theory demonstrates that the appropriately simplified mean differential statement of Newton's second law formally admits a hierarchy of scaling layers, each having a distinct characteristic length. The theory also specifies that these characteristic lengths asymptotically scale with distance from the wall over a well-defined range of wall-normal positions,y. Numerical simulation data are shown to support these analytical findings in every measure explored. The mean velocity profile is shown to exhibit logarithmic dependence (exact or approximate) when the solution to the mean equation of motion exhibits (exact or approximate) self-similarity from layer to layer within the hierarchy. The condition of pure self-similarity corresponds to a constant leading coefficient in the logarithmic mean velocity equation. The theory predicts and clarifies why logarithmic behaviour is better approximated as the Reynolds number gets large. An exact equation for the leading coefficient (von Kármán coefficient κ) is tested against direct numerical simulation (DNS) data. Two methods for precisely estimating the leading coefficient over any selected range ofyare presented. These methods reveal that the differences between the theory and simulation are essentially within the uncertainty level of the simulation. The von Kármán coefficient physically exists owing to an approximate self-similarity in the flux of turbulent force across an internal layer hierarchy. Mathematically, this self-similarity relates to the slope and curvature of the Reynolds stress profile, or equivalently the slope and curvature of the mean vorticity profile. The theory addresses how, why and under what conditions logarithmic dependence is approximated relative to the specific mechanisms contained within the mean statement of dynamics.
Two new species of spiruroid nematodes in birds from Kangean Island, Indonesia
Authors: Dewi K. , Zhang L.
Published: October 2009

Two new species of spiruroid nematodes in birds from Kangean Island, Indonesia are reported:Diplotriaena anthreptissp. nov. is found from the abdominal cavity ofAnthreptes malacensis malacensis. The new species is similar toD. ozouxi,D. bargusinica,D. delta,D. isabellinaandD. obtusain the size of tridents and the length of spicules. However, it differs from the five similar species in the structure of the tridents, in the morphology of the right spicule, in the spicule ratio and in the size of the eggs.Acuaria irhamisp. nov. is described based on two male specimens from under the gizzard lining ofDicrurus hottentottus jentincki. The new species can be distinguished easily from all congeners except fromA. microecae, in having equal rather than subequal or dissimilar spicules. However, the new species can be differentiated fromA. microecaein the number of postanal papillae, in the median preanal papilla and in the length of the cordons.
Efficacy of laser occlusion of posterior semicircular canal for benign paroxysmal positional vertigo: case report
Authors: Lin S-Z , Fan J-P , Sun A-H , Guan J , Liu H-B , Zhu Q-B
Published: October 2009

Objective:

To observe the long-term effect of laser occlusion of the posterior semicircular canal for benign paroxysmal positional vertigo.

Method:

Case report and review of the relevant world literature.

Results:

We treated a patient with refractory benign paroxysmal positional vertigo using laser occlusion of the posterior semicircular canal, and achieved satisfactory results. Three months after the operation, the patient was able to lead a normal life. There was no recurrence over five years of follow up.

Conclusion:

To our knowledge, this is the first report in the world literature of a patient with refractory benign paroxysmal positional vertigo being treated with laser occlusion of the posterior semicircular canal. This method had long-term effectiveness, and may be one of the most effective methods of treating patients with refractory benign paroxysmal positional vertigo.
Prospective study of sensorineural hearing loss following radiotherapy for nasopharyngeal carcinoma
Authors: Li J-J , Guo Y-K , Tang Q-L , Li S-S , Zhang X-L , Wu P-A , Yang X-M
Published: October 2009

Objectives:

To investigate the severity and incidence of sensorineural hearing loss in patients with nasopharyngeal carcinoma treated with radiotherapy.

Methods:

Forty-two patients with nasopharyngeal carcinoma were treated with conventional radiotherapy. Audiological testing was performed to compare patients' hearing before and at varying stages after radiotherapy.

Results:

At one month post-radiation, a significant hearing threshold increase was seen only for high frequencies. At 12, 24 and 60 months post-radiation, significant threshold increases were observed at speech frequencies (4.0 and 8.0 kHz), compared with pre-radiation data. The mean values of wave I, III and V latencies and of the I–V interpeak latency intervals were not significantly altered at one month post-radiation, but were significantly prolonged at 12, 24 and 60 months post-radiation, compared with pre-radiation data.

Conclusion:

In patients with nasopharyngeal carcinoma treated with radiotherapy, the severity and incidence of radiation-induced sensorineural hearing loss increased with time, especially at high frequencies. This hearing impairment may be due to changes in the cochlea and/or the retrocochlear auditory pathway.
Multinodular goitre in lingual thyroid: case report
Authors: Zackaria M , Chisholm E J , Tolley N S , Rice A , Chhatwani A
Published: October 2009

Objective:

We report a case of a multinodular goitre developing in a lingual thyroid.

Method:

Case report, and discussion of the embryology and treatment of lingual thyroids.

Case report:

A 66-year-old woman presented with dysphagia secondary to a multinodular lingual goitre. A previously silent lingual thyroid had undergone multinodular change to cause dysphagia and eventually airway compromise. The goitre was excised via a midline, mandible-splitting approach.

Conclusion:

Lingual thyroids have an incidence of one in 3000 to 10 000. There has not previously been a reported case of such an ectopic gland undergoing multinodular changes and presenting in later life.
Perforation after rigid pharyngo-oesophagoscopy: when do symptoms and signs develop?
Authors: Daniel M , Kamani T , Nogueira C , Jaberoo M-C , Conboy P , Johnston M , Bradley P
Published: October 2009

Background:

Perforation after pharyngo-oesophagoscopy is a serious complication, and its identification, through close patient monitoring, is essential. Yet little is known about when symptoms and signs develop, and thus how long any close monitoring should last.

Aim:

To examine the timing of individual symptoms and signs of perforation after rigid pharyngo-oesophagoscopy.

Methodology:

Three-centre, retrospective study.

Results:

Of 3459 patients undergoing rigid pharyngo-oesophagoscopy, 10 (0.29 per cent) developed perforations, nine of which were suspected intra-operatively. Symptoms and signs developed at 1.5 hours post-operatively at the earliest, and at 36 hours at the latest. Three patients were asymptomatic. The majority of procedures (n = 8) were undertaken for food bolus obstruction or foreign body ingestion.

Conclusion:

Pharyngo-oesophagoscopy for food bolus obstruction and foreign body ingestion accounts for a large number of perforations, but symptoms and signs may take longer than 24 hours to develop. A contrast swallow should be considered in high risk patients, and a high index of suspicion maintained in order to detect this complication.
Roll-over-Beethoven: Johnnie Ray in context
Authors: HERR CHERYL
Published: October 2009

The American Johnnie Ray (1927–1990) is best known for his emotional rendition of Churchill Kohlman's song ‘Cry’, a tune that Ray recorded with Mitch Miller in 1951. This song, along with Ray's own composition, ‘The Little White Cloud That Cried’, earned Ray nicknames such as ‘The Nabob of Sob’ and ‘The Cry Guy’. Although wildly popular in the mid-1950s, Johnnie Ray was soon overshadowed by his contemporaries and has been virtually ignored by scholars.

This essay situates Ray's music and his hearing impairment in the material and mediated conditions of his life. In addition to interpreting Ray's signature performances, the essay deals with Ray's childhood musicality, his appearances on The Ed Sullivan Show, the influence of televangelism on Ray, cinematic contexts for his life and art, and the hearing aid technology of the 1940s and 1950s.
‘Crippled with nerves’: popular music and polio, with particular reference to Ian Dury
Authors: McKAY GEORGE
Published: October 2009

This article looks at a remarkable cluster of popular musicians who contracted and survived poliomyelitis (‘infantile paralysis’) epidemics through the twentieth century, and ways in which they managed and, to varying extents, explored their polio-related impairments and experiences in their music. Drawing on medical history and disability studies, it focuses largely on the pop and rock generation of polio survivors – the children and young people from the 1940s and 1950s who were among the last to contract the disease prior to the successful introduction of mass vaccination programmes (in the West). These include Neil Young, Steve Harley, Joni Mitchell, and Israel Vibration. The article then looks in detail at the work of Ian Dury, who was for a while the highest profile visibly physically disabled pop artist in Britain, and who produced a compelling body of works exploring the experiences of disability.
Tragic but brave or just crips with chips? Songs and their lyrics in the Disability Arts Movement in Britain
Authors: CAMERON COLIN
Published: October 2009

Disability culture is a site within which social and positional identities are struggled for and dominant discourses rejected; in which mainstream representations of people with impairments – as victims of personal tragedy – are held to the light and revealed as hegemonic constructions within a disabling society. Drawing upon styles that range from jazz, blues and folk to reggae, performance poetry and punk, disabled singers and bands in the Disability Arts Movement in Britain have been central to the development of an affirmative disability discourse rooted in ideas of pride, anger and strength. Examining lyrics by Johnny Crescendo, Ian Stanton and the Fugertivs – performers emerging as part of this movement in the 1980s and 1990s – this article considers the dark humour which runs through much of this work. It is suggested that these lyrics' observational reflections on everyday experiences of being oppressed as disabled people have been overlooked within critical disability studies to date, but are important in developing an understanding of positive disability identity as a tool available to disabled people in order to make sense of, and express themselves within, the world in which they find themselves.
A natural ear for music? Hearing (dis)abled masculinities
Authors: LOESER CASSANDRA , CROWLEY VICKI
Published: October 2009

Musical performances on the bass guitar, able to be felt bodily beyond the ear, connect into the many layers of affect that music excites; but they are particularly potent as a means of communicating embodied masculinity for one young man with a hearing disability. Masculinity as a social code enacted within practices of the everyday involves both the affect and the effect of difference. The bass guitar, the instrument which drives a band's sound and rhythm, is part of the performativity of masculinity within popular music – visually, and at the level of sound, as auricular materiality – an embodied sensation where the ‘feel’ of sound through the body constitutes a language in which ‘desirable’ and ‘undesirable’ modes of masculinity become appropriated and defined.

Displays of musical prowess on the bass guitar open a space for becoming ‘unfixed’ from the identity and abject status of the hearing-disabled Other. This ‘Othering’ occurs primarily in everyday spoken encounters where difficulties with hearing and speech limit opportunities for occupying a viable masculine positioning. By contrast, the capacity to ‘fit’ the sensory and sensual prompts that trigger recognition of masculinity within popular music enables the re-assembling of an embodied masculine identity for a hearing-disabled young man. Masculinity and disability are rendered reversible and exchangeable – performative productions that are excessive and transgressive, contingent on the sensory perceptions of self and others.

This emphasis on embodied communicative practice through the play of bass guitar provides an important counterweight to representational forms of embodied gendered subjectivity that continue to predominate in some modes of disability and gender theorising. It constitutes a forceful assertion of how everyday embodied interactions are irrevocably coupled with mobile and transient masculine and disabled aesthetic identifications.
4. Needs and the deployment of services
Authors: Wykes T. , Creer C. , Sturt E.
Published: October 2009

An assessment of need for services on the census day, and whether any identified need was being met, was made on the basis of all the information collected from patients, staff, relatives and case-records. Staff judgements that there was unmet need were given considerable weight, since they were usually made when the need was particularly serious or long-lasting. However, in several instances the team rated unmet need as present when staff had not mentioned it. Occasionally, it was necessary to reconcile conflicting information from different sources, as when a relative gave details of problems not known to staff.
Nicht jede Hirnleistungsschwäche ist demenzbedingt.
Authors: Wettstein
Published: October 2009

Eine 55-jährige Frau lebte bis zu deren Tod bei den Eltern. In den letzten Wochen öffnet sie niemandem die Türe, auch nicht dem Sanitärinstallateur, der das WC reparieren soll. Nach einer Gefährdungsmeldung gelingt ein Hausbesuch nur dank Polizeihilfe. Die Untersuchung ergibt einen guten Allgemeinzustand. Die Gedächtnisleistungen sind intakt, aber die Exekutivfunktionen beeinträchtigt, keine Wahnvorstellungen, aber anerzogene Angst vor Fremden. Die Berufs- und Fremdanamnese bestätigt die klinische Verdachtsdiagnose einer Debilität. Mit der Errichtung einer vormundschaftlichen Massnahme kann die früher von den Eltern geleistete Anleitung in den Alltagsangelegenheiten gewährt werden.
Geomagnetic activity and polar surface air temperature variability
Authors: Seppälä A. , Randall C. E. , Clilverd M. A. , Rozanov E. , Rodger C. J.
Published: October 2009

Here we use the ERA‐40 and ECMWF operational surface level air temperature data sets from 1957 to 2006 to examine polar temperature variations during years with different levels of geomagnetic activity, as defined by the Ap index. Previous modeling work has suggested that NOx produced at high latitudes by energetic particle precipitation can eventually lead to detectable changes in surface air temperatures (SATs). We find that during winter months, polar SATs in years with high Ap index are different than in years with low Ap index; the differences are statistically significant at the 2‐sigma level and range up to about ±4.5 K, depending on location. The temperature differences are larger when years with wintertime Sudden Stratospheric Warmings (SSWs) are excluded. We take into account solar irradiance variations, unlike previous analyses of geomagnetic effects in ERA‐40 and operational data. Although we cannot conclusively show that the polar SAT patterns are physically linked by geomagnetic activity, we conclude that geomagnetic activity likely plays a role in modulating wintertime surface air temperatures. We tested our SAT results against variation in the Quasi Biennial Oscillation, the El Niño Southern Oscillation and the Southern Annular Mode. The results suggested that these were not driving the observed polar SAT variability. However, significant uncertainty is introduced by the Northern Annular Mode, and we cannot robustly exclude a chance linkage between sea surface temperature variability and geomagnetic activity.
Spatiotemporal distribution of seismic energy radiation from low‐frequency tremor in western Shikoku, Japan
Authors: Maeda Takuto , Obara Kazushige
Published: October 2009

The spatiotemporal patterns of the radiated seismic energy from low‐frequency tremor associated with slow slip events in western Shikoku, Japan, have been estimated. A spatially decaying mean square amplitude and differential traveltime measurement from envelope correlations observed at Hi‐net stations were used to locate tremors and to estimate their seismic energies. Tremor amplitude was corrected for the site amplification factors estimated using the coda normalization method. The location of the tremor is estimated as the position where both the decay of the observed energy and the differential travel times are well explained. The temporal pattern of the total energy released agrees very well with the observed tilt records. Although the spatial patterns of the energy radiation vary strongly among the six slow slip events (SSEs) in western Shikoku, the region where they overlap always radiates relatively high levels of energy. The estimated band‐limited energy rate of the tremor for a 2 to 10 Hz bandwidth was typically between 105 and 106 J/min, though there is temporal variation of the radiation energy. The released total energy associated with the SSEs whose magnitude is 5.9–6.1 is on the order of 108 J within the duration of SSEs of 8–13 days. This is quite small energy radiation compared to the moment release of accompanying SSE. The scaled energy, which is the ratio of the seismic moment and the seismic energy, for the slow slip and a very low frequency earthquake was estimated to be 5 orders of magnitude smaller than that of a regular earthquake.
Measurements and simulation of ionospheric scattering on VHF and UHF radar signals: Coherence times, coherence bandwidths, and S4
Authors: Rogers Neil C. , Cannon Paul S. , Groves Keith M.
Published: October 2009

Irregularities in the electron density of the ionosphere cause phase and amplitude scintillation on transionospheric VHF and UHF radar signals, particularly at lower radio frequencies. The design of radar and other transionospheric systems requires good estimates of the coherence bandwidth (CB) and coherence time (CT) imposed by a turbulent ionosphere. CB and CT measurements of the equatorial ionosphere, made using the Advanced Research Project Agency Long‐range Tracking and Identification Radar 158 MHz and 422 MHz phase coherent radar located on Kwajalein (9.4°N, 167.5°E), are presented as a function of the two‐way S4 scintillation index at 422 MHz The log linear regression equations are CT = 1.46 exp(−1.40 S4) s at 158 MHz and CT = 2.31 exp(−1.10 S4) s at 422 MHz. CT also varies by a factor of 2–3 depending on the effective scan velocity through the ionosphere, veff. The CT and CB, as a function of S4, have been compared to those from the Trans‐Ionospheric Radio Propagation Simulator, a phase screen model. A close agreement is achieved using appropriate values of veff and midrange values of phase spectral index and outer scale. Validation of CB is, however, limited by insufficient radar chirp bandwidth. Formulating the model in terms of the two‐way S4 index (an easily measurable parameter) rather than more fundamental phase screen parameters (which are difficult to obtain), improves its utility for the systems engineer. The frequency dependencies (spectral indices) of S4 and of CT are also presented to allow interpolation and some extrapolation of these results to other frequencies.
Real‐time management of a multipurpose water reservoir with a heteroscedastic inflow model
Authors: Pianosi F. , Soncini‐Sessa R.
Published: October 2009

Stochastic dynamic programming has been extensively used as a method for designing optimal regulation policies for water reservoirs. However, the potential of this method is dramatically reduced by its computational burden, which often forces to introduce strong approximations in the model of the system, especially in the description of the reservoir inflow. In this paper, an approach to partially remedy this problem is proposed and applied to a real world case study. It foresees solving the management problem on‐line, using a reduced model of the system and the inflow forecast provided by a dynamic model. By doing so, all the hydrometeorological information that is available in real‐time is fully exploited. The model here proposed for the inflow forecasting is a nonlinear, heteroscedastic model that provides both the expected value and the standard deviation of the inflow through dynamic relations. The effectiveness of such model for the purpose of the reservoir regulation is evaluated through simulation and comparison with the results provided by conventional homoscedastic inflow models.
Changes in permeability caused by dynamic stresses in fractured sandstone
Authors: Liu Weiqun , Manga Michael
Published: October 2009

Shaking‐induced changes in permeability have been invoked to explain a wide range of hydrologic responses to earthquakes. We measure the evolution of permeability in fractured sandstone in response to repeated shaking under undrained conditions. The frequency and amplitude of the imposed shaking are similar to those from earthquakes at distances of ∼ a fault length from the ruptured fault. To assess the role of mobile particles, we also add silt‐sized particles to the fractures. We find that, in general, permeability decreases after shaking. The samples with added particles show larger changes in permeability. Shaking‐induced transport of particles to block narrow fracture apertures can explain some of the observations. We also find that decreases in permeability are often accompanied by a contraction of sample indicating that fracture apertures sometimes decrease, presumably by mobilizing particles and removing asperities that hold fractures open.
Mirror mode structures in the solar wind at 0.72 AU
Authors: Zhang T. L. , Baumjohann W. , Russell C. T. , Jian L. K. , Wang C. , Cao J. B. , Balikhin M. , Blanco‐Cano X. , Delva M. , Volwerk M.
Published: October 2009

Magnetic holes in the solar wind with little or no directional change across the magnetic depression are related to mirror mode structures. Recently, Zhang et al. (2008) determined the characteristic size and shape of such mirror mode structures in the solar wind at 0.72 AU. They found that the mirror mode structure in the solar wind is quite elongated along the field direction. In this report, we examine the size and shape of isolated magnetic holes and train of holes, separately. We find that the isolated holes are slightly smaller in width and more elongated than the multiple holes. This observation suggests a particular evolutionary history of mirror mode structures in the solar wind in which multiple holes coalesce with time into isolated structures more elongated parallel to the magnetic field.
Plasmoid‐like structures in multiple X line Hall MHD reconnection
Authors: Liu C. X. , Jin S. P. , Wei F. S. , Lu Q. M. , Yang H. A.
Published: October 2009

Driven by a waveform inflow, multiple X line reconnection is initiated in a long current layer, and the plasmoids are bound between two neighboring reconnection sites. We investigate the behaviors of the plasmoid‐like structures in the absence and presence of an initial guide field By0 normalized by B0 (B0 is the initial intensity of Bx field at the top and bottom boundaries of the simulation domain) using a Hall magnetohydrodynamic (MHD) code. For the case with By0 = 0 the profiles of the out‐of‐plane By component are the bipolar signature or the bipolar wavelike signature which is caused by Hall effect and independent of the external mechanism. Such By features are in line with the observed signature of a closed‐loop‐like plasmoid in the magnetotail. The bipolar and fluctuation signatures of By have an asymmetric feature in the presence of a small By0(= 0.1), and the By profile becomes a positive signature as By0 reaches or exceeds 0.3. In the case of By0 = 0.5, a By bulge appears in the By signature when the enhanced By regions caused by Hall effect take place in the plasmoid. The By bulge evolves into a peaking signature, whose maximum (By∣max) is quickly raised and approaches the lobe magnetic field strength. Such a significant enhancement of the By component in the central region of the plasmoid might be representative of the observed strong core field in the magnetic flux rope. The present results indicate the following implications: (1) Hall effect and a preexisting cross‐tail component By are two important factors controlling the occurrence of various plasmoid‐like structures in the magnetotail. (2) In the later phase the nonlinear interaction between Hall effect and the By flux added by the plasma inflow makes a most important contribution to the growth of the core By field.
Statistical analysis of solar activity variations of total electron content derived at Jet Propulsion Laboratory from GPS observations
Authors: Liu Libo , Chen Yiding
Published: October 2009

We analyzed the data series of the total electron content (TEC) derived at Jet Propulsion Laboratory from Global Positioning System (GPS) observations to investigate the solar activity effects of TEC on a global scale. The daily values of the solar extreme ultraviolet (EUV) fluxes in 0.1–50 nm wavelengths, 10.7 cm radio flux F10.7, and F10.7P (the average of daily F10.7 and its 81‐day mean F10.7A) are adopted to represent the solar EUV variability, respectively. The EUV fluxes are measured by the Solar EUV Monitor (SEM) spectrometer aboard Solar Heliospheric Observatory (SOHO). Three kinds of patterns (linearity, saturation, and amplification) can be detected in TEC versus F10.7P and EUV. A saturation feature exists in TEC versus F10.7 in the daytime, more pronounced at low latitudes than at middle and high latitudes. The saturation in the equatorial anomaly regions is strongest in equinoxes and weakest in the June solstice. In contrast, the amplification in TEC, as a novel feature, is mainly distributed in the northern middle, and high latitudes in the December solstice and in the Southern Hemisphere in the June solstice and the March equinox. It is the first time to determine where and when the linear, saturation, and amplification patterns are distributed in TEC. Further, the solar activity sensitivity of TEC is stronger at day than at night and more evident at lower latitudes than at higher latitudes. The solar activity dependent rates of TEC in the equatorial and low‐latitude regions have a minimum around the dip equator and maxima on both sides of the dip equator (near the crest of the equatorial anomaly). This structure is roughly aligned along the dip equator, being strongest in equinoxes and weakest in the June solstice, which highlights the importance of ionospheric dynamics related with E × B drift. In addition, this analysis confirms that in a statistical sense, a quadrate polynomial can well capture the long‐term solar activity dependency of TEC at specified local time.
Patterns of snow, deposition, and soil nutrients at multiple spatial scales at a Rocky Mountain tree line ecotone
Authors: Liptzin Daniel , Seastedt Timothy R.
Published: October 2009

The forest‐alpine tundra ecotone in the Front Range of Colorado typically occurs as a gradual transition from the treeless tundra to the closed canopy coniferous subalpine forest. We evaluated the patterns of snow, deposition inputs, and soil properties at three spatial scales: across the entire ecotone, with distance from tree limit in the transitional krummholz zone, and around individual trees. Snow depth was deepest in the krummholz zone and lowest in the alpine tundra and upwind of trees near tree limit, but was not predictive of most soil properties except for surface litter decomposition. Inorganic deposition ranged from 0.7 to 7.7 g m−2 yr−1 across the ecotone and tended to be higher downwind than upwind of trees. The exchangeable acid cation concentrations were significantly higher in the forest and increased gradually toward the tundra. The exchangeable base cations (Ca, Mg, and K) were only predictable at the scale of individual trees with greater concentrations downwind of trees. Resin bag available N was rarely predictable at any spatial scale, but was correlated among seasons. While the ecotone is in many ways a gradual transition from alpine tundra to subalpine forest, patterns observed across this vegetation gradient were often replicated on the scale of individual trees: downwind of trees was more similar to the forest, and upwind of trees was more similar to the tundra. No single spatial scale or gradient can provide uniform generalities about the amounts or fluxes of materials that determine the soil properties of this ecotone.
The role of redox‐dependent mechanisms in the downregulation of ligand‐induced Toll‐like receptors 7, 8 and 4‐mediated HIF‐1α prolyl hydroxylation
Authors: Nicholas Sally A , Sumbayev Vadim V
Published: October 2009

Toll‐like receptors (TLRs) are key components of the innate immune system that allow immune cells to specifically detect pathogens by recognizing their specific molecular patterns. Hypoxia‐inducible factor‐1α (HIF‐1α) is known to have a critical role in TLR downstream signalling by promoting energy metabolism, expression of proinflammatory cytokines and proangiogenic factors. However, the molecular mechanisms leading to the accumulation of HIF‐1α are not fully understood. In this study, we report that R848 (specific ligand)‐induced activation of endosomal TLRs 7 and 8 (which recognize viral single‐stranded RNA) and lipopolysaccharide (LPS)‐induced activation of TLR4 (which specifically recognizes LPS as a ligand) leads to downregulation of degradative HIF‐1α prolyl hydroxylation. In the case of TLR7/8, this downregulation is achieved through redox‐ and reactive nitrogen species (RNS)‐dependent mechanisms. S‐nitrosation of HIF‐1α protein was also observed. In the case of LPS‐induced TLR4 activation, only a redox‐dependent mechanism is involved. RNS and p38 MAP kinase (known to contribute to LPS‐induced TLR4‐dependent accumulation of HIF‐1α protein) do not affect HIF‐1α prolyl hydroxylation. In both cases, downregulation of HIF‐1α prolyl hydroxylation correlates with a decrease in intracellular iron (II).
Energy Levels and Thermodynamic Functions for Molecules with Internal Rotation: II. Unsymmetrical Tops Attached to a Rigid Frame
Authors: Pitzer Kenneth S.
Published: October 2009

Formulas are derived which make the tables and equations of the first paper of this series applicable to this more general class molecules. Additional approximations are involved and these are examined carefully.
Homology recognition funnel
Authors: Lee Dominic , Kornyshev Alexei A.
Published: October 2009

The recognition of homologous sequences of DNA before strand exchange is considered to be the most puzzling stage of homologous recombination. A mechanism for two homologous dsDNAs to recognize each other from a distance in electrolytic solution without unzipping had been proposed in an earlier paper [A. A. Kornyshev and S. Leikin, Phys. Rev. Lett. 86, 366 (2001)]. In that work, the difference in the electrostatic interaction energy between homologous duplexes and between nonhomologous duplexes, termed the recognition energy, has been calculated. That calculation was later extended in a series of papers to account for torsional elasticity of the molecules. A recent paper [A. A. Kornyshev and A. Wynveen, Proc. Natl. Acad. Sci. U.S.A. 106, 4683 (2009)] investigated the form of the potential well that homologous DNA molecules may feel when sliding along each other. A simple formula for the shape of the well was obtained. However, this latter study was performed under the approximation that the sliding molecules are torsionally rigid. Following on from this work, in the present article we investigate the effect of torsional flexibility of the molecules on the shape of the well. A variational approach to this problem results in a transcendental equation that is easily solved numerically. Its solutions show that at large interaxial separations the recognition well becomes wider and shallower, whereas at closer distances further unexpected features arise related to an abrupt change in the mean azimuthal alignment of the molecules. The energy surface as a function of interaxial separation and the axial shift defines what we call the recognition funnel. We show that it depends dramatically on the patterns of adsorption of counterions on DNA.
Fowler–Nordheim analysis of oxides on 4H-SiC substrates using noncontact metrology
Authors: Oborina Elena I. , Benjamin Helen N. , Hoff Andrew M.
Published: October 2009

A noncontact corona-Kelvin metrology technique was applied to investigate stress-induced leakage current (SILC) on thermal and afterglow thermal oxides grown on n-type 4H-SiC substrates. The equivalent oxide thickness was extracted from noncontact C-V measurements and used to obtain the experimental Fowler–Nordheim (F-N) plots. Differences between characteristics calculated from theory and experimental plots were found. Modification of the theoretical F-N characteristics with respect to trapped charge phenomena effectively eliminated the offset between theoretically predicted and experimental curves for thermal oxides grown at atmosphere but was unable to achieve such agreement in the case of afterglow oxides. Only variations in the effective barrier and trapped charge combined provided overlay between calculated and experimental F-N plots for afterglow oxides. In addition, the SILC property VSASS, or self-adjusting steady state voltage, is suggested as a useful monitor characteristic for oxides on SiC. This parameter was larger for afterglow oxides compared to thermal oxides of similar thickness. The SASS voltage also showed that the afterglow oxide interface was stable to substrate injected stress fluence in accumulation compared to thermal oxide of comparable thickness.
Physical modeling of strain-dependent hole mobility in Ge p-channel inversion layers
Authors: Zhang Y. , Fischetti M. V. , Sorée B. , Magnus W. , Heyns M. , Meuris M.
Published: October 2009

We present comprehensive calculations of the low-field hole mobility in Ge p-channel inversion layers with SiO2 insulator using a six-band k⋅p band-structure model. The cases of relaxed, biaxially, and uniaxially (both tensily and compressively) strained Ge are studied employing an efficient self-consistent method—making use of a nonuniform spatial mesh and of the Broyden second method—to solve the coupled envelope-wave function k⋅p and Poisson equations. The hole mobility is computed using the Kubo–Greenwood formalism accounting for nonpolar hole-phonon scattering and scattering with interfacial roughness. Different approximations to handle dielectric screening are also investigated. As our main result, we find a large enhancement (up to a factor of 10 with respect to Si) of the mobility in the case of uniaxial compressive stress similarly to the well-known case of Si. Comparison with experimental data shows overall qualitative agreement but with significant deviations due mainly to the unknown morphology of the rough Ge-insulator interface, to additional scattering with surface optical phonon from the high-κ insulator, to Coulomb scattering interface traps or oxide charges—ignored in our calculations—and to different channel structures employed.
Ultrafast and low-power photonic crystal all-optical switching with resonant cavities
Authors: Liu Ye , Qin Fei , Zhou Fei , Li Zhi-Yuan
Published: October 2009

We theoretically investigate and discuss the response time, switching contrast, and pump power of all-optical switching in a nonlinear photonic crystal structure with high quality factor (high-Q) cavity. For the response time of all-optical switching, the drop and rise time are considered, respectively. Moreover, we find that when the duration of pump pulse is shorter than the lifetime, the response curve of all-optical switching is asymmetric, and the drop time is determined by both the lifetime of high-Q cavity and duration of pump pulse, and the rise time is mainly determined by lifetime of high-Q cavity. In contrast, when the duration of pump pulse is much longer than the lifetime, the dynamic response curve is symmetric, and both the drop and rise time are determined by the duration of pump pulse. On the other hand, the pump power can be significantly reduced by using a setup where the probe beam is located at the high-Q cavity mode with very narrow linewidth. Furthermore, if the central wavelength of pump pulse is also set to match with this or another high-Q cavity mode, the pump power will be reduced further due to the large field enhancement within the photonic crystal, and more importantly there is no extra prolonged response time of all-optical switching. By this method, the pump power as low as 210 KW/cm2 is observed in our model structure with the quality factor of only 32 096 for the ordinary polystyrene material.