bluuebunny/crossref_metadata_2025 huggingface dataset:
Modelling the Decision Process in Computer Simulation of Ship Navigation
Authors: James M. K.
Published: October 2009

1. INTRODUCTION. The Collision Regulations are designed to assist navigators to avoid collisions at sea. However, because of their qualitative nature it has been proposed that the Regulations should be supplemented by quantitative references to give practical meaning to concepts like ‘safe’ passing distance, ‘early’ action, etc. (Cockcroft and Lameijer, 1982). The problem of interpretation and quantification of the Regulations has been analysed in a recent paper by Wu (1984), considering in particular the concepts of ‘substantial’ action to avoid a collision, and the distance of ‘last-minute’ action in turning to avoid a collision. These analyses, along with many others, are concerned with developing prescriptive guidelines for mariners, in accordance with the Regulations.
Navigational Practice in the Vicinity of Offshore Installations
Authors: Pyman M. A. F. , Lyon P. R. , May G. Rowe
Published: October 2009

1. INTRODUCTION. This paper describes the results of a survey carried out to investigate the views and practices of mariners when navigating in the vicinity of offshore installations in the North Sea.
Presidential Address: Navigation Aids to Aircraft All-weather Landing
Authors: Charnley John
Published: October 2009

1. INTRODUCTION. In his Presidential address last year J. E. D. Williams treated us to a most absorbing, largely philosophical review of the development of the science of navigation over the last five centuries. In discussing the profound and enduring influence of radio waves on air navigation over the last century he commended as of ‘transcending importance’ the ‘homing quality’ of the radio beam in which the accuracy increases as distance from the transmitter decreases. He illustrated this ‘homing quality’ with references to the radio range for en-route navigation and the instrument landing system (ILS) for guidance to the runway. But he went further and remarked ‘Automatic landings in regular airline service are an example of how a perceived potential of the homing quality of radio has drawn to navigation a whole range of diverse applied sciences including, in this case, information theory, the properties of semi-conductors and the theory of servomechanisms and control, among many others.’
Optimizing Instrument Navigation in Restricted Waters
Authors: Gyldén Sven G.
Published: October 2009

1. INTRODUCTION. The object of open-ocean navigation is basically to find a ship's position. In coastal and confined waters, another dimension is added – the margins for errors are smaller, and actual ship handling must be integrated with the pure navigational disciplines. In restricted waters, the traditional philosophy of position fixing at intervals in terms of a point, e.g. cross-bearings, bearing and distance off a reference object, or latitude/longitude, is no longer a prime objective.
Omega Navigation in the Shadow of Antarctica
Authors: Barr R. , Young K. B.
Published: October 2009

1. INTRODUCTION. Very-low-frequency radio waves were used to implement the Omega navigation system because of their low attenuation (2–4 dB/1000 km) when propagating globally in the waveguide formed between the Earth and the ionosphere. However, it became apparent in the early seventies, throughout the period when the majority of the stations of the Omega network were commissioned, that VLF signals propagating over permafrost or glacial ice could suffer anomalously large attenuations, of greater than 20 dB/1000 km, especially during the daytime. In the Northern Hemisphere problems have arisen with the heavy attenuation of Omega signals propagating over the Greenland ice sheet. In particular a very bad region for Omega coverage occurs around Winnipeg in Canada (the ‘Winnipeg Hole’). In this area Omega North Dakota suffers from ‘near field’ effects, Omega Liberia is contaminated by trans-equatorial modal effects and Omega Norway is removed by the attenuation of its signals when crossing the Greenland ice-cap. There have even been discussions on the feasibility of constructing extra VLF transmitters in Canada to alleviate this problem.
Simulated Collision Avoidance Manoeuvres: a Parametric Study
Authors: Habberley John S. , Taylor Donald H.
Published: October 2009

John Habberley is Research Leader at the College of Maritime Studies, Warsash, Hampshire, UK, to which the study was contracted by the Marine Directorate of the Department of Transport. Don Taylor is consultant to the project.
The Navigator's Yeoman
Authors: Agnew H. J. , Woolley R. K. , Parfitt G.
Published: October 2009

This paper is concerned with potential improvements in the way man interacts with machines, maps and charts. Particular motivation comes from the new navigational challenges provided by the increasingly widespread use of electronic position-fixing aids in the marine field. Whilst automatic plotting tables and moving light spots have provided part of the solution in larger ships, much recent investment has been witnessed in the development of ‘electronic chart’-based systems.

For a number of practical reasons, among which are the lack of available data bases for these systems and little updating and distribution infrastructure for them, it is believed that there is unlikely to be a wide acceptance of such equipment as the primary or sole plotting aid for a considerable number of years to come.

Yeoman, a navigation plotting system which uses existing conventional charts, was conceived and developed to provide a simple and effective man–chart interface with few drawbacks. This paper provides the background for the development, the product and potential future evolution.
Evaluating ILS and MLS Sites without Flight Tests
Authors: Mahapatra P. R. , Poulose M. M.
Published: October 2009

Instrument landing systems (ILS) and the upcoming microwave landing systems (MLS) are (or are planned to be) very important navigational aids at most major airports of the world. However, their performance is directly affected by the features of the site in which they are located. Currently, validation of the ILS performance is through costly and time-consuming experimental methods. This paper outlines a powerful and versatile analytical approach for performing the site evaluation, as an alternative to the experimental methods. The approach combines a multi-plate model for the terrain with a powerful and exhaustive ray-tracing technique and a versatile and accurate formulation for estimating the electromagnetic fields due to the array antenna in the presence of the terrain. It can model the effects of the undulation, the roughness and the impedance (depending on the soil type) of the terrain at the site. The results computed from the analytical method are compared with the actual measurements and good agreement is shown. Considerations for site effects on MLS are also outlined.
Night Observation in Automated Astronomical Navigation
Authors: Nastro V. , Russo A. , Santamaria R. , Sposito A. , Vultaggio M. , Giordano F.
Published: October 2009

In this paper two devices as applied to a marine sextant are presented. A night viewer replaces the usual telescope to allow observation of the horizon in darkness. In addition an automatic reading of altitude is made practicable by a ten-bit encoder mounted on the index arm. In this way the proposed Celestial Navigation Automated Global System may be included within an integrated navigation system.
The Eva G. R. Taylor Lecture: The English Pilot: English Sailing Directions and Charts and the Rise of English Shipping, 16th to 18th Centuries
Authors: Waters D. W.
Published: October 2009

In the mid-16th century the English began to expand their merchant and fighting navies to sail beyond the waters of north-west Europe. This necessitated mathematical navigation, charts, and written and illustrated sailing directions; all, from the 1580s, were embodied in the printed ‘waggoners’ of the Dutch and were used in translation by the English seamen.
Eurofix
Authors: Willigen Durk Van
Published: October 2009

Around 1992 Navstar/GPS will become fully operational. Public access is then provided in the Standard Precision Service, SPS, at a reduced accuracy of 100 metres for 95 per cent of the fixes. The exclusively US military-operated system and the deliberately introduced degradation (SA, selective availability) of the attainable accuracy have some drawbacks for European navigation. Neither the probability density function of the error amplitude, nor its power spectral density function is known. So, using Navstar/GPS as a sole-means precise and reliable navigational aid for high-risk transports is not possible.
Evaluating the Feasibility of a Radar Separation Minimum for a Long-Range SSR
Authors: Nagaoka Sakae , Amai Osamu , Watanabe Yasuo
Published: October 2009

This paper deals with an analytical method for establishing a separation minimum for air traffic control using a monopulse SSR (Secondary Surveillance Radar), namely the Long Range SSR (LSSR), of which coverage is extended to 250 n.m. The azimuth estimation accuracy of the monopulse SSR was significantly improved compared with that of conventional SSR.

As an index of a collision risk due to azimuth errors of the LSSR, the close approach probability (CAP) associated with the probability of overlap of aircraft in azimuth is used for evaluating the safety of the surveillance system. The CAPs for both the LSSR and the conventional SSR are estimated by modelling and comparing distributions of azimuth errors. The CAP for the LSSR is significantly smaller than that for the conventional one under 5 n.m. separation minimum.
Satellite Navigation for the Merchant Marine – a User's View
Authors: Boer H. B.
Published: October 2009

Navigation at sea and navigation in the air have much in common. There is, however, a marked limitation for the ship (with the exception of a submarine), as that kind of navigation is restricted to the surface of the sea. The ship has to navigate within areas defined by two dimensions only, always bearing in mind that the depth of the water has to be more than the draught of the vessel.
An Evil So Pregnant with Mischief: Some Influential Ups and Downs in the Development of Navigation Equipment and Practice
Authors: Fanning A. E.
Published: October 2009

This paper formed the 1988 Anderson Memorial Lecture, and was presented to the Boscombe Down Branch on 17 March.

Wing Commander Anderson, in addition to his many distinctions connected with our Institute (a Founder Member, President, Gold Medallist, Honorary Member and frequent office holder) was above all an indefatigable worker for the science and artistry of navigation, which he regarded as a basic activity of all mankind. In 1939 he was headmaster of a school and by 1945 had become one of the most outstanding operational navigators in the Royal Air Force. In that year he was chosen as navigator of the research aircraft, Aries I, for those epic flights over the North geographic and magnetic poles, investigating compass performance in high latitudes.
Radio Stars, What They are and The Prospects for their Use in Navigational Systems
Authors: Wallace Kevin
Published: October 2009

The chief failing of surface astronavigation in its traditional form is reliability – it needs clear skies! Any solution to this limitation must therefore centre on a more weather-independent means of both detecting and identifying astronomical objects. This implies that the detection process should be conducted not in the optical but in the radio waveband, although radio astronomy makes it clear that the rather simple distribution and ‘point’-like images seen visually do not exist at radio wavelengths.
Air Navigation Systems: Chapter I. Astronomical Navigation in the Air 1919–1969
Authors: Williams J. E. D.
Published: October 2009

This paper is the first of a series on Air Navigation Systems during the fifty years from the early oceanic flights and the inception of commercial aviation to the introduction of INS in civil aircraft. These papers are intended as critical commentaries. A definitive history has yet to be written. The writer would be grateful to receive criticisms of the paper or comments on the subject.
Radionav 2000 – A European Dimension
Authors: Bridge R. W.
Published: October 2009

The Institute’s NAV 88 Conference, with the above title, was held in London from 22 to 24 March. It included nearly 40 papers concerned broadly with the way ahead for radionavigation in Europe. The Jull proceedings of the Conference are available on application to the Director, price £30 (plus £3 p & p) for Members (£60 plus p & p for non-Members). A summary of the Conference is presented below, and this is followed by one of the Conference papers which describes a rationalization of radionavigation in the USA.
The Integration of GPS and Loran-C
Authors: Polhems Wiliam L.
Published: October 2009

This briefing presents an overview of one section of a recently enacted Statute (US Public Law 100–223 signed into Law by the President of the United States on 30 December 1987) which directs the US Secretary of Transportation to effect certain improvements in US-provided radio navigation systems.
The ‘Automatic Gun Laying System’ – A Quantum Enhancement for the Royal Artillery
Authors: Symonds G. B.
Published: October 2009

abstract

This paper was presented at an Ordinary Meeting of the Institute, held at the Royal Entomological Society, London, on Wednesday 20 April 1988.

The current method of artillery survey is reviewed and its limitations examined in the light of both the system error budget and the envisaged battlefield threat. The concept of the Automatic Gun Laying System (AGLS) is introduced as a means of enhancing the effectiveness and survivability of the self-propelled gun element through the application of modern inertial navigation (IN) technology. As a complement to this, the use of IN technology to provide a vehicle-mounted target observation capability is also presented. The paper describes a unified treatment of the artillery system, leading to the selection of the respective IN solutions, and concludes that a standard module is both appropriate and optimal. Environmental factors are discussed, together with the alternative sensors and systems considered. The paper concludes with brief comments on the status of inertial navigation within the military land area.
Aircraft Automatic Landing Systems Using GPS
Authors: Parkinson B. W. , Fitzgibbon K. T.
Published: October 2009

abstract

This paper is based on a presentation made at the IAIN International Navigation Congress held in Sydney, Australia, in February 1988.

The global positioning system (GPS) offers a new opportunity for the automation of aircraft landing systems. The position and velocity measurements provided by a state-of-the-art GPS receiver using the C/A code and working in a normal or differential mode (D-GPS) and aided by one or two ground-based PseudoLites (PLS), may be able to satisfy the landing accuracy requirements of the FA A.

This paper describes the design and simulation of an aircraft automatic landing system. Aircraft position and velocity are assumed to be measured using a (carrier-tracking) GPS receiver. The hypothesized capability is based on measurements taken at Stanford and elsewhere, using the Trimble 4000SX, five-channel receiver in an integrated-doppler-aiding mode. For some of the autopilot designs, either ground-based GPS transmitters (pseudolites) or a radar altimeter have also been incorporated.

Included in the landing simulations are wind shears and a gust model, creating realistic landing situations. The performances of the lateral and vertical displacements are presented with their 1σ r.m.s. estimation errors during the glide-slope and flare phases. Included are different wind conditions, GPS configurations and controllers. The results are compared with the FAA requirements for various categories of automatic landing systems.
Automatic Conflict Detection Logic for Future Air Traffic Control
Authors: Ratcliffe S.
Published: October 2009

Air traffic control (ATC) makes extensive use of computer technology in subordinate roles for processing flight-plan and radar data and for message switching. It is usual to stress that such computers are aids to human controllers who take the decisions. It can, however, be argued that computers are, in fact, already encroaching on the decision-taking processes. The SSR plot extractor, for example, produces a censored summary which amounts to only a few per cent of the torrent of radar data from which it is derived. This summary is then subjected to code conversion and coordinate transformation before it reaches the controllers who cannot refer back to the data sources. Once computer-processing has been introduced, the issue is no longer whether a computer may take some of the decisions involved in ATC, but merely the extent of the authority it can exercise.
Navigating Along Geodesic Paths on the Surface of a Spheroid
Authors: Williams R. , Phythian J. E.
Published: October 2009

Hairawa in the Journal made the statement that there is no easy method of calculating the length of a geodesic line on the surface of a spheroid and this is true. Nevertheless, it is the purpose here to attempt to devise a method and then to leave it to the reader to judge whether or not the amount of work involved justifies the method as an alternative to the correction methods of Andoyer and Lambert and to the work of Hairawa himself.
Risk of Collision at Sea
Authors: Hinsch Werner
Published: October 2009

Vessel traffic service systems (VTS systems) have been established, throughout the world, in areas of high traffic density. These systems, operating with such tools as VHF radiotelephony, land-based radar installations and ship's data processing, gather information to respond to collision and grounding danger, to organize traffic flow and assist allied activities. It is expected that VTS systems should effectively reduce the number of collisions in the VTS area. But efforts for collision avoidance can only be successful if the VTS operator in front of the shoreside radar screen is precisely instructed as to which measurements he has to make to identify a risk-of-collision situation. Uncertainties about the direction in which ships must take evasive action arise in VTS areas, where ships are free to engage in encounters.
Excitation of 4‐min periodic ionospheric variations following the great Sumatra‐Andaman earthquake in 2004
Authors: Choosakul Nithiwatthn , Saito Akinori , Iyemori Toshihiko , Hashizume Michio
Published: October 2009

Periodic variations of the ionosphere were detected by ground‐based GPS total electron content (TEC) measurements after the Sumatra‐Andaman earthquake in 2004. The observational data showed that the 4‐min periodic TEC variations occurred 1 h after the earthquake and continued for longer than 4 h. At the PHKT station, about 30 cycles of the 4‐min periodic TEC variations were observed from 0230 to 0430 UT. The maximum peak‐to‐peak amplitude of the variations was about 0.6 total electron content unit (TECU; 1 TECU = 1016 el m−2) around 0320 UT. The frequency of these periodic variations was 3.9 mHz. They were detected by the SAMP station in the northern Sumatra and the PHKT and BNKK stations in Thailand with the signal from seven GPS satellites: PRN 8, 11, 13, 19, 23, 27, and 31. They were observed in a limited area from 4°N to 15°N in latitude and from 96°E to 101°E in longitude, although the western boundary was not certain because of the limit of the observational field of view. The amplitude of these TEC variations showed the dependence on the zenith angle of the path between the GPS receiver and satellite. The amplitude had a maximum when the zenith angle was the smallest. This could be caused by the vertical structure of the electron density variations. This also suggested that the electrons were oscillating along the geomagnetic field. The 4‐min periodic TEC variations were interpreted to be induced by the long‐lasting free oscillation of the atmosphere set up by the earthquake. Their long duration also indicates that they were generated by a nontransient process like resonance.
An explanation for parallel electric field pulses observed over thunderstorms
Authors: Kelley M. C. , Barnum B. H.
Published: October 2009

Every electric field instrument flown on sounding rockets over a thunderstorm has detected pulses of electric fields parallel to the Earth's magnetic field associated with every strike. This paper describes the ionospheric signatures found during a flight from Wallops Island, Virginia, on 2 September 1995. The electric field results in a drifting Maxwellian corresponding to energies up to 1 eV. The distribution function relaxes because of elastic and inelastic collisions, resulting in electron heating up to 4000–5000 K and potentially observable red line emissions and enhanced ISR electron temperatures. The field strength scales with the current in cloud‐to‐ground strikes and falls off as r−1 with distance. Pulses of both polarities are found, although most electric fields are downward, parallel to the magnetic field. The pulse may be the reaction of ambient plasma to a current pulse carried at the whistler packet's highest group velocity. The charge source required to produce the electric field is very likely electrons of a few keV traveling at the packet velocity. We conjecture that the current source is the divergence of the current flowing at mesospheric heights, the phenomenon called an elve. The whistler packet's effective radiated power is as high as 25 mW at ionospheric heights, comparable to some ionospheric heater transmissions. Comparing the Poynting flux at the base of the ionosphere with flux an equal distance away along the ground, some 30 db are lost in the mesosphere. Another 10 db are lost in the transition from free space to the whistler mode.
An analytical solution of two‐dimensional reactive solute transport in an aquifer‐aquitard system
Authors: Zhan Hongbin , Wen Zhang , Gao Guangyao
Published: October 2009

This article presents an analytical study of two‐dimensional reactive solute transport in an aquifer‐aquitard system. Advection, longitudinal and vertical dispersion, first‐order irreversible decay, and linear sorption are included for aquifer transport. Advection, vertical diffusion, first‐order irreversible decay, and linear sorption are considered for aquitard transport. This study solves transport equations in the aquifer and aquitards simultaneously and maintains continuities of concentration and mass flux at the aquifer‐aquitard interfaces. The transport equations are first solved in Laplace domain, and the solutions are then inverted numerically to yield solutions in the real time domain (the Zhan solution). Concentration profiles in the aquifer and the aquitards are obtained and mass transported to the aquitards is also calculated. Closed‐form steady state solutions of concentration and mass have been obtained. The Zhan solution is compared with solutions derived with the averaged volumetric sink/source approach (the AA solution). The AA solution substantially overestimates the concentration and the mass in the upper aquitard when an upward velocity exists in the aquitard. The penetrating depths of the solute in the aquitard are similar for the AA solution and the Zhan solution.
First observations of X‐mode suppression of O‐mode HF enhancements at 6300 Å
Authors: Gustavsson B. , Newsome R. , Leyser T. B. , Kosch M. J. , Norin L. , McCarrick M. , Pedersen T. , Watkins B. J.
Published: October 2009

We present observations of radio induced optical emissions from a HAARP experiment with simultaneous transmission in X and O‐mode. The additional transmission of X‐mode with a frequency 700 kHz higher than the O‐mode, reduces the enhancement of the 6300 Å emission. This suggests that the wave‐plasma process that energizes the electrons, which excites oxygen to the O(1D) state, is closely connected to the excitation of upper‐hybrid waves, whose onset and initial growth are reduced by additional X‐mode pumping.
Early Ischemia Enhances Action Potential-Dependent, Spontaneous Glutamatergic Responses in CA1 Neurons
Authors: Ye Hui , Jalini Shirin , Zhang Liang , Charlton Milton , Carlen Peter L
Published: October 2009

Two types of quantal spontaneous neurotransmitter release are present in the nervous system, namely action potential (AP)-dependent release and AP-independent release. Previous studies have identified and characterized AP-independent release during hypoxia and ischemia. However, the relative contribution of AP-dependent spontaneous release to the overall glutamate released during transient ischemia has not been quantified. Furthermore, the neuronal activity that mediates such release has not been identified. Using acute brain slices, we show that AP-dependent release constitutes approximately one-third of the overall glutamate-mediated excitatory postsynaptic potentials/currents (EPSPs/EPSCs) measured onto hippocampal CA1 pyramidal neurons. However, during transient (2 mins) in vitro hypoxia–hypoglycemia, large-amplitude, AP-dependent spontaneous release is significantly enhanced and contributes to 74% of the overall glutamatergic responses. This increased AP-dependent release is due to hyper-excitability in the presynaptic CA3 neurons, which is mediated by the activity of NMDA receptors. Spontaneous glutamate release during ischemia can lead to excitotoxicity and perturbation of neural network functions.
Mutant Ubiquitin-Mediated β-Secretase Stability via Activation of Caspase-3 is Related to β-Amyloid Accumulation in Ischemic Striatum in Rats
Authors: Zhang Yong , Xiong Man , Yan Ri-Qiang , Sun Feng-Yan
Published: October 2009

Previous studies have demonstrated that ischemic stroke increases β-amyloid (Aβ) production by increasing β-secretase (BACE1) through activation of caspase-3, and stimulates generation of mutant ubiquitin (UBB+1) in rat brains. In this study, we examined whether caspase-3 activation participates in the regulation of UBB+1 generation and UBB+1-mediated BACE1 stability in ischemic injured brains. The results showed that UBB+1 and activated caspase-3-immunopositive-stained cells were time dependently increased in the ipsilateral striatum of rat brains after middle cerebral artery occlusion. UBB+1-immunopositive cells could be co-stained with caspase-3, Aβ (UBB+1–Aβ), and BACE1 (UBB+1–BACE1). BACE1 protein could also be pulled down by immunoprecipitation with UBB+1 antibody. Z-DEVD-FMK (DEVD), a caspase-3 inhibitor, significantly decreased the level of UBB+1 protein and the number of UBB+1–Aβ and UBB+1–BACE1 double-stained cells in the ischemic striatum, as well as the level of UBB+1/BACE1 protein complex. We conclude that activation of caspase-3 might be upstream of UBB+1 formation and that excessive UBB+1 could bind to BACE1 and increase the stability of BACE1, thereby increasing Aβ in ischemic injured brains. These results suggest new biological and pathological effects of caspases and regulation of the ubiquitin–proteasome system in the brain. Our results provide new therapeutic targets to prevent further neurodegeneration in patients after stroke.
Spatial correlation as an early warning signal for transitions in ecosystems
Authors: Dakos Vasilis , van Nes Egbert , Scheffer Marten
Published: October 2009

An increasing number of sudden transformations triggered by small forces has been identified in a variety of ecological systems. Such changes are usually termed regime shifts between alternative states and their unexpected nature makes them challenging to handle from a management perspective. In the face of our limited mechanistic insight on the dynamics of such transitions, developing generic early warning signals for ecosystem regime shifts becomes a formidable task. So far, most of the research has focused on developing potential early warnings in simple models which ignore spatial interactions. In this work we spatially extended three well studied models that belong to the class of systems which undergo regime shifts through a fold bifurcation. All models were run on a two dimensional lattice with different spatial distributions of an environmental factor (e.g., soil fertility, water level). Where each patch in the lattice is individually governed by the same dynamics which eventually lead to alternative stable states, the response of the global spatial system is modified due to connectivity between patches. Our aim was to investigate whether we could identify a leading indicator of the imminent shift in the global spatial system.We followed the evolution of both spatial correlation between patches and temporal correlation within patches, obtained from stationary distributions, as we gradually increased a control parameter which causes the system to switch to its alternative attractor. We evaluated whether spatial correlation between neighboring patches can be used as a leading indicator of a system approaching a transition. Our analyses showed that spatial correlation between neighboring patches increases before the transition of the global spatial system into its alternative stable state. We demonstrated that spatial correlation between neighbors performs better as an indicator to an impending regime shift in heterogeneous conditions when compared to temporal correlation indicators. Despite differences between the three models, spatial correlation between neighbors appears to be a parsimonious and reliable early warning signal for transitions in spatial systems.
Intersection of the tocopherol and plastoquinol metabolic pathways at the plastoglobule
Authors: Zbierzak Anna Maria , Kanwischer Marion , Wille Christina , Vidi Pierre-Alexandre , Giavalisco Patrick , Lohmann Antje , Briesen Isabel , Porfirova Svetlana , Bréhélin Claire , Kessler Felix , Dörmann Peter
Published: October 2009

Plastoglobules, lipid–protein bodies in the stroma of plant chloroplasts, are enriched in non-polar lipids, in particular prenyl quinols. In the present study we show that, in addition to the thylakoids, plastoglobules also contain a considerable proportion of the plastidial PQ-9 (plastoquinol-9), the redox component of photosystem II, and of the cyclized product of PQ-9, PC-8 (plastochromanol-8), a tocochromanol with a structure similar to γ-tocopherol and γ-tocotrienol, but with a C-40 prenyl side chain. PC-8 formation was abolished in the Arabidopsis thaliana tocopherol cyclase mutant vte1, but accumulated in VTE1-overexpressing plants, in agreement with a role of tocopherol cyclase (VTE1) in PC-8 synthesis. VTE1 overexpression resulted in the proliferation of the number of plastoglobules which occurred in the form of clusters in the transgenic lines. Simultaneous overexpression of VTE1 and of the methyltransferase VTE4 resulted in the accumulation of a compound tentatively identified as 5-methyl-PC-8, the methylated form of PC-8. The results of the present study suggest that the existence of a plastoglobular pool of PQ-9, along with the partial conversion of PQ-9 into PC-8, might represent a mechanism for the regulation of the antioxidant content in thylakoids and of the PQ-9 pool that is available for photosynthesis.
An electrical impedance tomography-based approach to monitor in vitro sodium chloride dissolution from pharmaceutical tablets
Authors: Rimpiläinen Ville , Heikkinen Lasse M. , Kuosmanen Marko , Lehikoinen Anssi , Voutilainen Arto , Vauhkonen Marko , Ketolainen Jarkko
Published: October 2009

An approach to monitor in vitro dissolution process from pharmaceutical tablets utilizing electrical impedance tomography (EIT) is introduced. In the demonstration, a tablet containing sodium chloride (NaCl) was dissolution tested using tap water as a dissolution medium within an apparatus similar to the United States Pharmacopoeia dissolution apparatus II. During the process, the three-dimensional sodium chloride concentration distribution was monitored with EIT measurements as a function of time. For EIT measurements, an array of electrodes was attached on the boundary of the dissolution vessel, a set of alternating electric currents was injected through the electrodes, and the resulting voltages were measured. With these data and by applying mathematical algorithms, an approximation for the spatial/temporal concentration distribution inside the vessel was computed. It was found that the computed distributions were relatively homogeneous. A NaCl release curve was computed by integrating the concentration distribution over the vessel volume, and the final value of the curve matched well with the reference point based on the weight loss of the tablet. Finally, EIT monitoring is suggested to be used for research and product development purposes.
Development and testing of a fast Fourier transform high dynamic-range spectral diagnostics for millimeter wave characterization
Authors: Thoen D. J. , Bongers W. A. , Westerhof E. , Oosterbeek J. W. , de Baar M. R. , van den Berg M. A. , van Beveren V. , Bürger A. , Goede A. P. H. , Graswinckel M. F. , Hennen B. A. , Schüller F. C.
Published: October 2009

A fast Fourier transform (FFT) based wide range millimeter wave diagnostics for spectral characterization of scattered millimeter waves in plasmas has been successfully brought into operation. The scattered millimeter waves are heterodyne downconverted and directly digitized using a fast analog-digital converter and a compact peripheral component interconnect computer. Frequency spectra are obtained by FFT in the time domain of the intermediate frequency signal. The scattered millimeter waves are generated during high power electron cyclotron resonance heating experiments on the TEXTOR tokamak and demonstrate the performance of the diagnostics and, in particular, the usability of direct digitizing and Fourier transformation of millimeter wave signals. The diagnostics is able to acquire 4 GHz wide spectra of signals in the range of 136–140 GHz. The rate of spectra is tunable and has been tested between 200 000 spectra/s with a frequency resolution of 100 MHz and 120 spectra/s with a frequency resolution of 25 kHz. The respective dynamic ranges are 52 and 88 dB. Major benefits of the new diagnostics are a tunable time and frequency resolution due to postdetection, near-real time processing of the acquired data. This diagnostics has a wider application in astrophysics, earth observation, plasma physics, and molecular spectroscopy for the detection and analysis of millimeter wave radiation, providing high-resolution spectra at high temporal resolution and large dynamic range.
Isochronal sampling in non-Boltzmann Monte Carlo methods
Authors: Abreu Charlles R. A.
Published: October 2009

Non-Boltzmann sampling (NBS) methods are usually able to overcome ergodicity issues which conventional Monte Carlo methods often undergo. In short, NBS methods are meant to broaden the sampling range of some suitable order parameter (e.g., energy). For many years, a standard for their development has been the choice of sampling weights that yield uniform sampling of a predefined parameter range. However, Trebst et al. [Phys. Rev. E 70, 046701 (2004)] demonstrated that better results are obtained by choosing weights that reduce as much as possible the average number of steps needed to complete a roundtrip in that range. In the present work, we prove that the method they developed to minimize roundtrip times also equalizes downtrip and uptrip times. Then, we propose a discrete-parameter extension using such isochronal character as our main goal. To assess the features of the new method, we carry out simulations of a spin system and of lattice chains designed to exhibit folding transition, thus being suitable models for proteins. Our results show that the new method performs on a par with the original method when the latter is applicable. However, there are cases in which the method of Trebst et al. becomes inapplicable, depending on the chosen order parameter and on the employed Monte Carlo moves. With a practical example, we demonstrate that our method can naturally handle these cases, thus being more robust than the original one. Finally, we find an interesting correspondence between the kind of approach dealt with here and the committor analysis of reaction coordinates, which is another topic of rising interest in the field of molecular simulation.
Modal response of 4-rod type radio frequency quadrupole linac
Authors: Chatterjee Avik , Mahapatra Abhijit , Mondal Manas , Chakrabarti Alok
Published: October 2009

This paper deals with the analysis and experimental study of natural frequencies of vibration of a 4-rod type radio frequency quadrupole (RFQ) linear accelerator. The eigenvalue analysis of the structure has been done both analytically (multispan beam concept) as well as using blocked Lanczos eigenvalue finite element solver with an ability to extract the rigid body modes. This has been done in the mechanical design phase to find the level of agreement between the output of simplified analytical analysis results and the output of a commercial finite element method (FEM) solver, since a full scale RFQ structure is too complex to handle analytically. Experimental validation of the analysis results has been done on the physical 1.7 m RFQ at the installation site. The experimental data obtained were later analyzed and found to be in close agreement with the predicted frequencies in the lower frequency ranges. It gets more and more deviated in the higher frequency ranges. Also some frequencies were observed during experimentation, which were not found in the finite element analysis results. The source of those frequencies are to be further investigated as it may play a predominant role in the design high quality factor beam line cavities for higher operational efficiency.
Purely analytic solutions of the compressible boundary layer flow due to a porous rotating disk with heat transfer
Authors: Turkyilmazoglu M.
Published: October 2009

The motivation of the present study is to obtain exact analytical solution of the steady laminar flow of a compressible viscous fluid over a rotating disk subjected to a uniformly applied suction or blowing. Classical Von Karman problem of a rotating disk is extended to account for the compressibility effects with insulated and isothermal wall conditions. Using Von Karman similarity transformation the compressible nonlinear equations of motion are reduced to a boundary value problem whose solution was first obtained by Ackroyd [J. A. D. Ackroyd, “On the steady flow produced by a rotating disc with either surface suction of injection,” J. Eng. Phys. 12, 207 (1978)] for the velocity field in terms of a series of exponentially decaying functions. This kind of an approach, however, besides being incapable of resolving the velocity field for higher values of injection (see the conclusion of Ackroyd) is also shown not to be suitable for the temperature distribution of the compressible flow, necessitating the use of a Chebyshev collocation technique in such circumstances. A universally valid analytical technique based on the homotopy analysis method is next applied to obtain solutions corresponding to both velocity and temperature fields. This method yields explicit analytic solutions converging uniformly to the exact solution having the form of exponentially decaying functions for the full range of parameters considered. The effects of suction and blowing together with compressibility on the physically relevant and significant parameters are rigorously explored from the exact formulas extracted.
Resonating valence bond wave function with molecular orbitals: Application to first-row molecules
Authors: Marchi Mariapia , Azadi Sam , Casula Michele , Sorella Sandro
Published: October 2009

We introduce a method for accurate quantum chemical calculations based on a simple variational wave function, defined by a single geminal that couples all the electrons into singlet pairs, combined with a real space correlation factor. The method uses a constrained variational optimization, based on an expansion of the geminal in terms of molecular orbitals. It is shown that the most relevant nondynamical correlations are correctly reproduced once an appropriate number n of molecular orbitals is considered. The value of n is determined by requiring that, in the atomization limit, the atoms are described by Hartree–Fock Slater determinants with Jastrow correlations. The energetics, as well as other physical and chemical properties, are then given by an efficient variational approach based on standard quantum Monte Carlo techniques. We test this method on a set of homonuclear (Be2, B2, C2, N2, O2, and F2) and heteronuclear (LiF and CN) dimers for which strong nondynamical correlations and/or weak van der Waals interactions are present.
Controllable local modification of fractured Nb-doped SrTiO3 surfaces
Authors: Chien TeYu , Santos Tiffany S. , Bode Matthias , Guisinger Nathan P. , Freeland John W.
Published: October 2009

Nanoscale surface modification of a fractured Nb-doped SrTiO3 surface is demonstrated in a controlled way by scanning tunneling microscopy. By applying positive voltage pulses, holes can be created and the width and depth of the hole can be controlled by selecting the appropriate bias and pulse duration. The process shows a threshold condition for creation of the holes and change in the local electronic density of state consistent with exposure of the underlying TiO2 layer by removal of SrO. By applying negative bias, the hole can be partially refilled from the transfer of adsorbates on the tip.
Microwave magnetoabsorption in two-dimensional electron systems
Authors: Iñarrea Jesús , Platero Gloria
Published: October 2009

Magnetoabsorption, microwave-induced resistance oscillations, and zero resistance states in two-dimensional systems are calculated in the framework of the same theory: the microwave driven Larmor orbit model. On one hand, this theory allows to obtain resistance oscillations with multiple peaks, depending on the microwave frequency. On the other hand, it also permits to calculate the microwave magnetoabsorption yielding only one broad peak at the cyclotron resonance condition.
Attention-Deficit Hyperactivity Disorder
Authors: Fox David , Scanlon Francesca
Published: October 2009

Attention-deficit hyperactivity disorder (ADHD) is characterized by inattention, hyperactivity and impulsivity leading to difficulties at home, education and daily activities. ADHD remains relatively young within paediatric psychiatry with its recognition and management developing over the last 20 years. A consensus towards diagnosis and management has come with recent NICE guidelines.
Hernias
Authors: Stubbs Ben , Hyder Zargham
Published: October 2009

A hernia is defined as an abnormal protrusion of a viscus, or part of a viscus, through the wall of its containing cavity. A hernia can therefore occur at many anatomical locations. Abdominal wall hernias are a common problem and prevalence of this condition has been estimated as approximately 2% for all ages. This review will concentrate on abdominal wall hernias, their presentation, diagnosis and management.
Pancreatic Disease
Authors: Stephenson James A. , Al-Taan Omer , Metcalfe Matthew S. , Dennison Ashley R.
Published: October 2009

The pancreas is a retroperitoneal organ with both endocrine and exocrine functions. It was first described by a Greek physician Herophilus between 335 and 280 BC and was given its name by Ruphos only a few hundred years later. In 1642, Wirsung discovered the pancreatic duct and within three decades Graff investigated its secretory properties. Paul Langerhans described ‘islets of Langerhans’ in 1869 and the first description of pancreatitis as a disease was by Fitz in 1889. Halstead performed the first operation on the pancreas in 1898.
Liver Failure
Authors: Rabindra Gayathri
Published: October 2009

With an increase in prevalence of alcohol abuse and obesity, cirrhosis is on the rise. To prevent progression to end-stage liver disease and liver failure, abnormalities must be picked up early. This article provides an overview of liver failure and how to approach investigation and management of patients at risk.
Autism and Asperger's Syndrome
Authors: Ashwell Gemma
Published: October 2009

Autism and Asperger's syndrome are part of a range of conditions incorporated under the term autistic spectrum disorders (ASDs). This article will aim to define these conditions and explain the differences between them, clarify some of the myths about their aetiology and equip the reader with the specific knowledge to diagnose, refer and manage patients with ASDs as effectively as possible.
Prevalence of Delirium with Dexmedetomidine Compared with Morphine Based Therapy after Cardiac Surgery
Authors: Shehabi Yahya , Grant Peter , Wolfenden Hugh , Hammond Naomi , Bass Frances , Campbell Michelle , Chen Jack
Published: October 2009

Background

Commonly used sedatives/analgesics can increase the risk of postoperative complications, including delirium. This double-blinded study assessed the neurobehavioral, hemodynamic, and sedative characteristics of dexmedetomidine compared with morphine-based regimen after cardiac surgery at equivalent levels of sedation and analgesia.

Methods

A total of 306 patients at least 60 yr old were randomized to receive dexmedetomidine (0.1-0.7 microg x kg(-1) x h(-1)) or morphine (10-70 microg x kg(-1) x h(-1)) with open-label propofol titrated to a target Motor Activity Assessment Scale of 2-4. Primary outcome was the prevalence of delirium measured daily via Confusion Assessment Method for intensive care. Secondary outcomes included ventilation time, additional sedation/analgesia, and hemodynamic and adverse effects.

Results

Of all sedation assessments, 75.2% of dexmedetomidine and 79.6% (P = 0.516) of morphine treatment were in the target range. Delirium incidence was comparable between dexmedetomidine 13 (8.6%) and morphine 22 (15.0%) (relative risk 0.571, 95% confidence interval [CI] 0.256-1.099, P = 0.088), however, dexmedetomidine-managed patients spent 3 fewer days (2 [1-7] versus 5 [2-12]) in delirium (95% CI 1.09-6.67, P = 0.0317). The incidence of delirium was significantly less in a small subgroup requiring intraaortic balloon pump and treated with dexmedetomidine (3 of 20 [15%] versus 9 of 25 [36%]) (relative risk 0.416, 95% CI 0.152-0.637, P = 0.001). Dexmedetomidine-treated patients were more likely to be extubated earlier (relative risk 1.27, 95% CI 1.01-1.60, P = 0.040, log-rank P = 0.036), experienced less systolic hypotension (23% versus 38.1%, P = 0.006), required less norepinephrine (P < 0.001), but had more bradycardia (16.45% versus 6.12%, P = 0.006) than morphine treatment.

Conclusion

Dexmedetomidine reduced the duration but not the incidence of delirium after cardiac surgery with effective analgesia/sedation, less hypotension, less vasopressor requirement, and more bradycardia versus morphine regimen.