bluuebunny/crossref_metadata_2025 huggingface dataset:
Electronic Charts for Oceangoing Vessels
Authors: Weeks Colin G.
Published: October 2009

It is probable that Congress will require oceangoing ships in US ports to use Differential GPS (DGPS) and electronic charts once DGPS is available on all coasts of the US, which is currently scheduled for completion by the end of 1996. The type of electronic chart currently envisaged, the Electronic Chart Display and Information System (ECDIS) under development by the IMO & IHO, is unsuitable for those ports which are entered through long dredged channels – a category that includes Houston, Gramercy and New Orleans, the three ports which handled the most foreign tonnage in 1991. A different type of electronic chart has been in daily use in such channels, with microwave positioning, since 1984; the combination of DGPS with such a software package has been called an Electronic Navigation System (ENS) and differs from ECDIS in that the ENS is designed to supplement the published chart, not replace it. The paper suggests that the utility of ECDIS would be enhanced if its specifications were modified to allow the entry of the data files used by the ENS, thus giving ECDIS a similar capability for blind navigation in confined waters. Standardization of the current data format would also permit alternative versions of ENS to be developed.
The Channel Navigation Information Service
Authors: Griffiths A. H.
Published: October 2009

The recent history and background of the Channel Navigation Information Service (CNIS) have been well documented in this journal by my illustrious forebears, Captain Richard Emden and Commander James Neill. Whilst this paper describes some of the changes in the service since those papers were published, it may be appropriate to review the key events in the introduction of what was once a unique initiative, and remind the reader of the operational doctrine and philosophy of the system.
The Russian Fleet's Navigational Aids in the Baltic Sea During the Eighteenth and Nineteenth Centuries
Authors: Afrossimova Vera N.
Published: October 2009

Russia has had a quite unique development as a sea power. The 20th of October 1696 has been considered as the date of the Russian Fleet's creation when the supreme legislative body of Russia – the Boyar Duma – decreed that there should be a ship-building programme for the State's need. So, in 1996, we celebrate the tercentenary of the founding of the Russian Fleet (Figure 1).
Air Navigation Systems Chapter 5. The Development of British Airborne Primary Radar, 1935–1945
Authors: Kendal Brian
Published: October 2009

This paper is the fifth chapter of a series on the history of air navigation systems. Comments on the content of the paper would be welcomed by the author and the editor.
The Impact of DGPS on Land, Marine and Air Navigation in Egypt
Authors: El-Saadawy Hassan
Published: October 2009

For half a century, the Egyptians have been concerned about the coverage of all their local waters in the Mediterranean and the Red Sea with visual and electronic aids to navigation. As a result, they constructed several lighthouses and landmarks as separate entities. Long years of political friction and military conflict in the Middle East resulted in damage to the majority of visual and primitive aids to navigation, particularly in the Gulf of Suez (GOS), the Gulf of Aqaba (GOA) and the Red Sea.
Modelling Navigational Risk and Oil Spill Probabilities
Authors: Quon Tony K. S. , Bushell George E.
Published: October 2009

This paper examines first a statistical modelling of the number of navigational accidents (collisons, groundings and strikings) involving tankers and freighters in Canadian waters; it then looks at a direct method of modelling oil spill frequency and magnitude, given a navigational accident. The former is used to examine various hypotheses in the literature regarding the impact of various factors on navigational risk. The latter is based on a direct probability tree analysis which allows the estimation of detailed oil spill impacts by facilitating the examination of representative spill sizes.
Small RCS Marine Surface Craft and their Radar Detection in Real (Estuary) Sea Conditions
Authors: Adamopoulos Panos G.
Published: October 2009

Human error accounts for a number of collisions at sea; nevertheless, it is widely accepted that vessels are inclined to produce widely varying ranges of radar echo strengths in real sea conditions, in contrast to their ‘true’ anechoic strength, which tends to be minimal for a small and structurally non-reflective craft; even for the calmest possible water conditions.

In this paper experimental results for small craft will be presented and analysed in an exploration of potentially influential parameters in such cases. These results are based on three series of sea trials. Furthermore, an attempt is to be made to portray the inherent, theoretical and/or practical, limitations in the radar detection of small craft in real (estuary) sea conditions.
Display Requirements for ECDIS/ARPA Overlay Systems
Authors: Smeaton G. P. , Dineley W. O. , Tucker S. M.
Published: October 2009

The International Maritime Consultative Organization (now IMO) carriage requirement for ARPA began to take effect in 1984 and became progressively mandatory worldwide; prior to this, for certain classes of vessels trading to the USA, a national requirement was introduced in 1982. These radar plotting aids perhaps constituted the first widespread use of computing power aboard merchant vessels. In implementation, even the early ARPAS were much more than the mere plotting aid which their name suggests. Sophisticated processing gave the navigator a system which offered significant assistance in scenario analysis, with the well known ability to display graphically the effect of a trial manoeuvre being the most active element of the system.
A Visual Interpretation of an ERS- I SAR Image of the Thames Estuary
Authors: Culshaw S. T.
Published: October 2009

This paper examines a Synthetic Aperture Radar (SAR) image of the Thames Estuary aided by the relevant nautical chart, tidal, weather and shipping information of the area. By correlating this information it is possible to identify gross sediment transport which would otherwise be hard and financially expensive to detect. Seabed topography, seabed pipelines, some shipping, coastal zone features and different water parcels can be identified.
GRI Ranking Based on Cross-Rate Interference in Loran-C
Authors: Nieuwland Andre K.
Published: October 2009

This paper starts with a brief overview of cross-rate interference (CRI) and methods developed in the past for estimating the CRI between two Group Repetition Intervals (GRIS). It presents an algorithm for fast calculation of the loss of pulses due to blanking in dual-rate stations. These stations broadcast on the GRIS of two chains but, if pulses of both chains overlap, one GRI is not transmitted at that instant. Furthermore, it will discuss the impact of this blanking on the use of Loran-C signals for transmitting data. A strategy is given for selecting GRIS, based on the presented theory. The paper is based on papers presented at the 1993 WGA technical symposium and the 1993 INA conference.
Presidential Address: Around The World In Less Than Eighty Days
Authors: Knox-Johnston Robin
Published: October 2009

In January 1993 our target for a circumnavigation was eighty days but, having been struck halfway between Africa and Australia by an object which holed our starboard hull, we were forced to pull out, and a Frenchman – Commodore Explorer – got round first in just 18 hours under the magic Jules Verne figure. It all seemed to be over, except that we were convinced it could be done more quickly – in seventy-seven days anyway, and perhaps (holding our breath) even seventy-five with some luck. We were keen to have another go at winning the Trophy and fortunately so was our sponsor – the New Zealand Apple and Pear Marketing Board. Preparations began immediately.
GPS Wide Area Augmentation System (WAAS)
Authors: Loh Robert
Published: October 2009

Today, no single technology has more broad-reaching potential for worldwide civil aviation than the future applications of satellite technology. These applications represent the greatest opportunity to enhance aviation system capacity, efficiency and safety since the introduction of radio-based navigation systems more than 50 years ago. The foundation for this optimism is the Global Positioning System (GPS), a satellite-based radio navigation system operated and controlled by the United States Department of Defense (DoD). In December 1993, DoD declared GPS to be in initial operational capability (10c), which means 24 satellites are now in orbit, available and usable for satellite navigation. The Federal Aviation Agency (FAA) responded to this potential through initiation of a comprehensive satellite programme involving government, industry and users to expedite research, development and field implementation of satellite-based navigation services.
Meeting Mariners' Needs for Electronic Charts
Authors: Wright Peter
Published: October 2009

During the last 5 years there has been a rapid growth in the market for electronic charts. All of the systems that currently use these charts, regardless of their size and complexity, have one thing in common: they are all officially classified as Electronic Chart Systems (ECS). By definition, these systems are not considered to be equivalent to conventional paper charts for the purposes of satisfying SOLAS regulations. For all vessels bound by these regulations, ECS cannot be used in place of paper charts. Consequently, it has been left to commercial companies to provide data for use in these systems. Such data have been of variable quality, and no commercial company currently provides a correction service that matches that provided by most hydrographic offices for paper charts.
Institutional Requirements for a Global Navigation Satellite System
Authors: Blanchard W. F. , Broughton D. W.
Published: October 2009

This paper, and the following paper, were presented at the 8th Congress of the International Association of Institutes of Navigation held in Beijing, 6–11 September 1994.
The Future of Electronic Charts in Merchant Ships
Authors: Beattie J. H.
Published: October 2009

Reduced manning levels, the lack of skilled maritime labour and new satellite navigation systems have created a need for electronic charts in merchant ships. Developments in information technology have made it possible to design and produce these charts and the equipment to display them. It is essential that shipowners and others understand the issues which affect the use of these charts and equipment. It is also important for users to understand the effects that the revolution in satellite technology is having on all types of charts, paper and electronic. Only with this knowledge can shipowners appreciate the economic and operational benefits of using electronic charts, and IMO complete its work on the safety rules for the carriage and operation of all types of electronic charts and equipment for merchant ships.
Orientation and the Young Orienteer
Authors: Walsh S. E. , Martland J. R.
Published: October 2009

Orientation within orienteering is dependent on the use of two basic strategies; that is, either a compass or Magnetic-North-based strategy, which relies on the use of one set of information; or the use of a map and landmark-based strategy which relies on the use of at least two sets of information. Walsh and found that, when given the choice, young children use the compass-based strategy when following complex potentially disorientating routes.

The efficacy of these two basic orientation strategies was investigated within three different orienteering environments: (1) a familiar known environment; (2) a familiar unknown environment and (3) an unfamiliar unknown environment.

Subjects, age range from 9 to 10·5 years, completed an appropriate orienteering route in each of the environments. Individual mini-cassette recorders and tie-pin microphones were used to record data using a ‘think aloud’ technique as subjects followed their selected routes. Transcripts of the taped data produced a total number of uttered statements for each subject within each environment. A qualitative analysis of these statements identified the following groups of statements expressed as percentages of the total number of statements (as reported by Thorndyke and Stasz): (a) Orientation statements; (b) Relocation or error correction statements; (c) Statements about distractions; (d) Self-efficacy statements.

There was a higher reported use of the compass-based strategy for orientation within the familiar known environment which supported the earlier findings of Walsh and Martland. Although the percentage of compass-based orientation statements was smaller in the familiar unknown and the unfamiliar unknown environments, there was a pattern in the use of orientation strategies within these two environments. Typically, the compass-based orientation strategy was used for initial orientation at the beginning of the route and at the pre-defined control points along the route, whilst the landmark and map-based strategy was used as a means of maintaining and reinforcing orientation within the route. Relocation statements typically reported an awareness of disorientation and were generally followed by attempts to reorientate. Whilst none of the subjects used relocation statements within the familiar known environment, relocation statements were used within the familiar unknown and the unfamiliar unknown environments.

This evidence suggests that both orientation strategies are used in orienteering routes, but that each strategy is used selectively depending on the environment. These findings clearly have implications for the sport of orienteering – particularly the introduction of basic skills to young performers. They support the argument that is essential to introduce the map and compass simultaneously and that relocation and orientation skills should be coached concurrently.
Columbus's Method of Determining Longitude: An Analytical View
Authors: Pickering Keith
Published: October 2009

On 14 September 1494, Christopher Columbus observed a lunar eclipse while at the island of Saona near the eastern tip of Hispaniola. He later recorded in his Libro de las Profecias that, from his timing of the eclipse, he determined his longitude to be ‘five hours and more than one half’west of Cape San Vicente. His actual longitude was three hours and 59 minutes west of Cape San Vicente, so Columbus was off by over an hour and a half, some 23 degrees of longitude.
Vehicle Location Systems in Urban Traffic Control
Authors: Marsden Greg
Published: October 2009

This short paper discusses briefly the role of the current forms of bus priority used in the United Kingdom and how these strategies are incorporated within our urban traffic control systems.

The philosophy behind the SCOOT (Split, Cycle and Offset Optimization Technique) demand-responsive signal timings program is discussed, and the latest results from the bus priority trials carried out in London by the University of Southampton and London's Traffic Control Systems Unit (TCSU) are appraised. The system installed in London is compared with current dead reckoning vehicle location systems and the major differences highlighted.
The Australian REEFREP System: A Coastal Vessel Traffic Information Service and Ship Reporting System for the Torres Strait Region and the Inner Route of the Great Barrier Reef
Authors: Macdonald John C.
Published: October 2009

The new Australian ship reporting system, identifier ‘REEFREP’, will be the core component of a Vessel Traffic Information Service (VTIS) covering the Torres Strait region and the Great Barrier Reef (GBR). It is the first such system to be considered by the International Maritime Organization (IMO) under the terms of the new SOLAS 74 regulation v/8-1, which entered into force on 1 January 1996 and allows for ship reporting systems adopted by the Organization to be made mandatory for all, or certain categories of vessels.

The REEFREP system, planned for implementation on 1 January 1997, extends for some 900 n.m. or about 1500 km along the Queensland coastline. It will be a VHF radio-based system with radars covering three selected focal points in the Torres Strait, off Cairns and in the southern approaches to the inner route. The system will provide a capability for a single Ship Reporting Centre to interact with shipping, enabling the provision of improved information on the presence, movements and patterns of shipping in the area and the ability to respond more quickly to an incident or pollution should this occur.

An interesting feature and a major factor in the system design is the remoteness of most equipment sites and the limited infrastructure available to support communications and data transmission requiring the application of advanced technology and video transmission, solar power generation and software engineering skills of a high order.
Ship—Shore and Ship—Ship Data Transfer
Authors: Heikkilä Martti
Published: October 2009

During recent years there has been significant development in several technologies which can contribute to the efficiency and safety of maritime traffic. The most important of these are accurate positioning systems (DGPS), digital data transmission/transponder technology, electronic chart systems (ECDIS), control of ships using electronic passage plans, and ship path prediction. With a widespread implementation of these new techniques, combined with advanced ship-shore and ship-ship data transfer, significant improvements can be achieved in traffic situation awareness both in a VTS and onboard. This paper describes the research carried out at VTT on VTS development, and especially gives an outline of new VTS functions using ship—shore and ship—ship data transfer.
Transponders and their Impact on the Future of Navigation
Authors: Crichton T. , Redfern A.
Published: October 2009

The introduction of a transponder-based ship identification system may have far-reaching effects on the way navigation is carried out. Fundamental changes to the underlying principles of collision avoidance become a reality, offering the potential for a new set of sailing and anticollision rules that allow unprecedented levels of control for maritime traffic.
U.S. Programme for Development of Satellite Services for Air Traffic Control
Authors: Miller Clyde A.
Published: October 2009

The Federal Aviation Administration (FAA) is conducting experimental programmes to support introduction of satellite navigation and communications services into the air traffic control system during the 1990 time period. This work programme is closely related to the activities that have been conducted by the ICAO Future Air Navigation Systems (FANS) Committee and will result in development of standards for avionics systems and services for the Global Positioning System (GPS), as well as digital voice and digital data link services. This paper summarizes the FAA programmes supporting the introduction of the new satellite services.
Integration of Satellite and Inertial Positioning Systems
Authors: Napier M.
Published: October 2009

The Global Positioning System (GPS) offers an absolute positioning accuracy of 15 to 100 metres. Inertial navigation complements GPS in that it provides relative positioning and is totally self-contained. These two positioning sensors are ideally suited for system integration for although there is not necessarily an improvement in accuracy, the integration of GPS with inertial navigation systems (INS) does enable an increase in system performance.
GDOP, Ridge Regression and the Kalman Filter
Authors: Kelly R. J.
Published: October 2009

Multicollinearity and its effect on parameter estimators such as the Kalman filter is analysed using the navigation application as a special example. All position-fix navigation systems suffer loss of accuracy when their navigation landmarks are nearly collinear. Nearly collinear measurement geometry is termed the geometric dilution of position (GDOP). Its presence causes the errors of the position estimates to be highly inflated. In 1970 Hoerl and Kennard developed ridge regression to combat near collinearity when it arises in the predictor matrix of a linear regression model. Since GDOP is mathematically equivalent to a nearly collinear predictor matrix, Kelly suggested using ridge regression techniques in navigation signal processors to reduce the effects of GDOP. The original programme intended to use ridge regression not only to reduce variance inflation but also to reduce bias inflation. Reducing bias inflation is an extension of Hoerl's ridge concept by Kelly. Preliminary results show that ridge regression will reduce the effects of variance inflation caused by GDOP. However, recent results (Kelly) conclude it will not reduce bias inflation as it arises in the navigation problem, GDOP is not a mismatched estimator/model problem. Even with an estimator matched to the model, GDOP may inflate the MSE of the ordinary Kalman filter while the ridge recursive filter chooses a suitable biased estimator that will reduce the MSE. The main goal is obtaining a smaller MSE for the estimator, rather than minimizing the residual sum of squares. This is a different operation than tuning the Kalman filter's dynamic process noise covariance Q, in order to compensate for unmodelled errors. Although ridge regression has not yielded a satisfactory solution to the general GDOP problem, it has provided insight into exactly what causes multicollinearity in navigation signal processors such as the Kalman filter and under what conditions an estimator's performance can be improved.
The Economics of the North Atlantic Air Traffic System
Authors: Attwooll V. W.
Published: October 2009

1. INTRODUCTION. The North Atlantic air traffic system is the busiest and most important long-range system in operation today with a current total of 127 000 flights“annum. The combined effects of the total flight time and the difference in time zones on either side of the Atlantic makes it desirable for most passengers to fly westward in the day-time. Conversely, it is most convenient (or least inconvenient!) to fly eastbound during the hours of darkness. Thus the Atlantic traffic system is strongly tidal with the flow predominantly (though not entirely) westbound during the day and eastbound overnight. Currently the central core of the traffic in the busiest hours is organised into a parallel track structure – the Organized Track Structure (OTS), though nearly half the aircraft operate so-called random routes clear of the OTS.
Fish Migration: Orientation and Navigation or Environmental Transport?
Authors: Arnold G. P. , Metcalfe J. D.
Published: October 2009

This paper was presented at the RIN89 conference on Orientation and Navigation – Birds, Humans and other Animals held in Cardiff in April 1989.
Navigation of Tunnels
Authors: Kirkland C. J.
Published: October 2009

A number of factors need to be understood initially.

(1) Alignment is based upon the use of light, though not on being able to see where you are going!

(2) The theory relies upon three dimensional co-ordinate geometry.

(3) The knowledge that junction error will increase with distance, together with the commercial need to keep construction time short, normally means tunnelling from the ends towards a junction in the middle.

(4) Difficulties arise because of short baselines and no intermediate fixes.

(5) Terminology needs some explanation. Thus desired alignment is designed and then set out in the tunnel. Post-construction, a wriggle diagram is prepared and final alignment computed.
Magnetic Reference in Navigation – The Earth as a Magnet
Authors: Stuart W. F. , Barraclough D. R. , Preston J.
Published: October 2009

The magnetic field of the Earth originates in the motions of the fluid core of the planet. By good fortune it is predominantly dipolar and so has a simple topography. The core motions cause the field to change with time, and once charted it has to be charted again and again. Mathematical models can be made which represent the geomagnetic field to an accuracy of about one degree globally. Higher accuracy demands advanced techniques such as satellite surveys, and also attention to the detail of external fields caused by solar activity which disturb the main field, restricting the accuracy of mapping and producing magnetic deviations from the mean value from day to day. Understanding such effects is essential in preparing magnetic reference data for navigation.

Though now losing ground to other methods, magnetic compasses still have a valuable role to play in many situations, so long as the limitations are fully appreciated and taken into account. Modern technology in standard geomagnetic observatories offers ways of updating a datum very accurately in automatic navigational systems and even of forecasting disturbances, and may bring magnetic reference back to the forefront of many navigational systems.
Operational Considerations and Constraints in Ship-based Weather Routeing Procedures
Authors: Motte R. , Calvert S.
Published: October 2009

Weather-related ship loss statistics are assessed as a proportion of total losses to ascertain the requirement for route planning. A routeing assessment for suitability of on-board application is undertaken and a moveable grid is then proposed incorporating a time optimization procedure for the on-board system.
Precise Navigation, Guidance and Control Services within the Agricultural Community
Authors: Palmer R. J.
Published: October 2009

This paper was presented at the 44th Annual Meeting of the US Institute of Navigation in Annapolis, June 1988.

Navigational systems are usually thought of in terms of locating vehicles and craft over a range of hundreds or thousands of miles. There are, however, applications where navigation systems with a range of a few miles and an accuracy of inches can be very useful. Farming is one of these applications and this paper identifies the specific operational aspects that can benefit. Precise navigation could facilitate a lowering of input costs by an estimated jo per cent on a western dryland farm.
The Ship's Wheelhouse of the Nineties: the Navigation Performance and Mental Workload of the Officer of the Watch
Authors: Schuffel H. , Boer J. P. A. , van Breda L.
Published: October 2009

The search for more efficient ship operation has increased over the last decade. One trend towards reducing operational costs is to conceive the wheelhouse as an operational centre for performing both navigational and supervisory tasks, such as monitoring the propulsion plant status and the condition of ship and cargo.

Under contract to the National Foundation for the Coordination of Maritime Research in The Netherlands, a study was conducted on the feasibility of a highly automated wheelhouse for single-handed navigation. In a series of simulation experiments, and by analysis, the effects on efficiency and safety of performance were investigated.

Results show that a careful function allocation can lead to an automated wheelhouse concept suitable for safe navigation in landfall conditions. Questions concerning the effects of monotonous watches on operator's alertness and the effects of the change in task structure on the operator's skill and interest in the job need further attention.
Benefits of ‘Area Navigation’ in Regional Aviation
Authors: Wallace D. M.
Published: October 2009

This paper was presented at the Annual Meeting of the US Institute of Navigation held in Annapolis, June 1988

The following is an assessment of Area Navigation Systems, or RNAV, as they apply to regional aviation.

Regional aviation, in this context, refers to that third sector of the airline industry which concentrates on short haul, high frequency, so-called ‘hub and spoke’ operations. Now amounting to over j per cent all airline passenger traffic, regional operations by their nature have more to gain from the use of RNAV than any other segment of the airline business. In particular we look at how RNAV systems provide business opportunities to regional operators, not only to manage aircraft more effectively, but in the process to improve a firm's viability.
A record of eruption and intrusion at a fast spreading ridge axis: Axial summit trough of the East Pacific Rise at 9–10°N
Authors: Soule S. Adam , Escartín Javier , Fornari Daniel J.
Published: October 2009

High‐resolution side‐scan sonar, near‐bottom multibeam bathymetry, and deep‐sea photo and bathymetry traverses are used to map the axial summit trough (AST) at the East Pacific Rise between 9 and 10°N. We define three ridge axis morphologic types: no AST, narrow AST, and wide AST, which characterize distinct ridge crest domains spanning tens of kilometers along strike. Near‐bottom observations, modeling of deformation above intruding dikes, and comparisons to the geologic and geophysical structure of the ridge crest are used to develop a revised model of AST genesis and evolution. This model helps constrain the record of intrusive and extrusive magmatism and styles of lava deposition along the ridge crest at time scales from hundreds to tens of thousands of years. The grabens in the narrow‐AST domain (9°43′–53′N) are consistent with deformation above the most recent (<10) diking events beneath the ridge crest. Frequent high–effusion rate extrusive volcanism in this domain (several eruptions every ∼100 years) overprints near‐axis deformation and maintains a consistent AST width. The most recent eruption at the ridge crest occurred in this area and did not significantly modify the physical characteristics of the AST. The grabens in the wide‐AST domain (9°23′–43′N) originated with similar dimensions to the narrow AST. Spreading, driven primarily by the intrusion of shallow dikes within a narrow axial zone, causes the initial graben bounding faults to migrate away from the axis. Infrequent extrusive volcanism (several eruptions every ∼1000 years) fills a portion of the subsidence that accumulates over time but does not significantly modify the width of the AST. Outside of these domains, lower–effusion rate constructional volcanism without efficient drain‐back fills and erases the signature of the AST. The relative frequency of intrusive versus extrusive magmatic events controls the morphology of the ridge crest and appears to remain constant over millennial time scales within the domains we have identified; however, over longer time scales (∼10–25 ka), domain‐specific intrusive‐to‐extrusive ratios do not appear to be fixed in space, resulting in a fairly consistent volcanic accretion over the length scale of the second‐order ridge segment between 9°N and 10°N.
Deformation of western Turkey from a combination of permanent and campaign GPS data: Limits to block‐like behavior
Authors: Aktug B. , Nocquet J. M. , Cingöz A. , Parsons B. , Erkan Y. , England P. , Lenk O. , Gürdal M. A. , Kilicoglu A. , Akdeniz H. , Tekgül A.
Published: October 2009

We present a new geodetic velocity field covering western Turkey, south of the North Anatolian fault. Our velocity field is derived from a combination of continuously recording GPS stations operating since 2003, survey‐type GPS measurements carried out in the period 1997–2005, and velocities from Reilinger et al. (2006). The velocity field indicates that western Turkey currently undergoes extension whose rate increases from the Anatolia plateau to the Aegean coast. The overall extension in westernmost Turkey is about 20 mm/yr, making it one of the fastest areas of continental extension in the world. We test whether the observed deformation is better represented by the rotation of crustal blocks or by more distributed deformation. While no deformation is detected in the central Anatolian plateau, we observe a deformation field west of the plateau that cannot be explained by block models, unless the blocks are so small as to be essentially indistinguishable from a continuum. Although concentration of strain rates (up to 140 nstrain/yr) are found across the major grabens, strain rates above 50 nstrain/yr are found throughout western Turkey. The distributions of topography and crustal thickness in western Turkey agree with the distributions expected if the crust there had a constant thickness at 5 Ma, equal to that of the present central Anatolian plateau, and had subsequently been thinned at the present‐day distribution of strain rates. Our results, therefore, suggest that extensional strain affects the whole continental lithosphere of western Turkey, rather than being restricted to a small number of block boundaries.
Beginning of the Apennine subduction system in central western Mediterranean: Constraints from Cenozoic “orogenic” magmatic activity of Sardinia, Italy
Authors: Lustrino Michele , Morra Vincenzo , Fedele Lorenzo , Franciosi Luigi
Published: October 2009

Major and trace element analyses plus six new40Ar/39Ar data obtained on feldspar separates for selected igneous rocks belonging to the Oligo‐Miocene igneous activity of Sardinia are reported here. The rocks show “subduction‐related” geochemical characteristics, ascribed to the metasomatic modification of a mantle wedge developed above a W/NW directed subduction system involving the recycling of Neo‐Tethyan oceanic lithosphere beneath the southern European margin. The40Ar/39Ar data shift back the beginning of the igneous activity in Sardinia to late Eocene (38.28 ± 0.26 Ma), whereas the end of the igneous activity is possibly shifted forward to late middle Miocene (12.24 ± 0.98 Ma). We therefore propose to rename the Oligo‐Miocene igneous phase as the “late Eocene–middle Miocene” phase. Rare earth element inversion modeling on subduction‐related volcanic rocks of Sardinia requires equilibrium with spinel‐lherzolite facies, therefore implying depths of formation lower than ∼80 km. To reach these depths, a 45° dipping slab needs ∼11 to ∼4 Myr (with 1 to 3 cm/yr subduction velocity, respectively), reducing the beginning of Apennine subduction to the ∼49–42 Ma interval. The different models proposed in literature to explain the origin and the evolution of the central western Mediterranean basins are here reviewed and critically discussed.
Rotation period of Jupiter from the observation of its magnetic field
Authors: Yu Z. J. , Russell C. T.
Published: October 2009

To determine the Jovian internal rotation rate, historically one has used the repetition period (periodicity) of decametric and decimetric radio waves. The period with which decametric and decimetric radio waves recur on Jupiter (the System III period) was defined by the IAU in 1965 to be 9h 55m 29.71s, based on early radio astronomical data. A more direct way to determine this period is to examine the rotation rate of the dipole field. We have done this using Galileo, Pioneer 10 and 11, Voyager 1 and 2, and Ulysses data over a 25‐year period. We find a small drift in the apparent longitude of the dipole axis that is statistically significant, consistent with there being a small error in the original IAU period, one within the error expected in the defined period. The newly derived period is 9h 55m 29.704 ± 0.003s, 6ms shorter than the 1965 IAU definition, and inconsistent with the value of 9h 55m 29.685s proposed by Higgins et al. (1997).
Absolute plate motions constrained by shear wave splitting orientations with implications for hot spot motions and mantle flow
Authors: Kreemer Corné
Published: October 2009

Here, I present a new absolute plate motion model of the Earth's surface, determined from the alignment of present‐day surface motions with 474 published shear wave (i.e., SKS) splitting orientations. When limited to oceanic islands and cratons, splitting orientations are assumed to reflect anisotropy in the asthenosphere caused by the differential motion between lithosphere and mesosphere. The best fit model predicts a 0.2065°/Ma counterclockwise net rotation of the lithosphere as a whole, which revolves around a pole at 57.6°S and 63.2°E. This net rotation is particularly well constrained by data on cratons and/or in the Indo‐Atlantic region. The average data misfit is 19° and 24° for oceanic and cratonic areas, respectively, but the normalized root‐mean‐square misfits are about equal at 5.4 and 5.2. Predicted plate motions are very consistent with recent hot spot track azimuths (<8° on many plates), except for the slowest moving plates (Antarctica, Africa, and Eurasia). The difference in hot spot propagation vectors and plate velocities describes the motion of hot spots (i.e., their underlying plumes). For most hot spots that move significantly, the motions are considerably smaller than and antiparallel to the absolute plate velocity. Only when the origin depth of the plume is considered can the hot spot motions be explained in terms of mantle flow. The results are largely consistent with independent evidence of subasthenospheric mantle flow and asthenospheric return flow near spreading ridges. The results suggest that, at least where hot spots are, the lithosphere is decoupled from the mesosphere, including in western North America.
Interannual variability of the Mediterranean outflow observed in Espartel sill, western Strait of Gibraltar
Authors: García‐Lafuente J. , Delgado J. , Sánchez Román A. , Soto J. , Carracedo L. , Díaz del Río G.
Published: October 2009

Four‐year time series of observations in Espartel sill at the western part of the Strait of Gibraltar have been analyzed in order to investigate the variability of the Mediterranean outflow. It is assumed that the observed variability comes from the changing properties of the dense waters that are located at the maximum depth from where they can be uplifted in the upstream basin (Alborán Sea, inside the Mediterranean Sea) and evacuated through the strait. From this perspective, the following three mechanisms are investigated: (1) the replenishment of the deep basin by newly formed Western Mediterranean Deep Water that, depending on its density, can either uplift old resident waters or lay above them leaving in any case a cold signature in the temperature series; (2) the presence/absence of the energetic anticyclonic gyres in the Alborán Sea, particularly the western one, which can transfer momentum to the underlying Mediterranean vein and provide it with additional energy to ascend over the sills of the strait; and (3) the meteorologically enhanced flows that follow the rapid changes of atmospheric pressure over the western Mediterranean basin, which would be able to aspire deeper waters residing in the upstream basin. The three mechanisms act on different timescales, from annual in case (1) to monthly in case (2) to weekly in case (3) although these two latter are modulated annually by the seasonal prevalence of the western Alborán gyre in summer and of the strong meteorologically driven fluctuations in winter. The mechanisms overlap at annual timescales making it difficult to separate out the different contributions.
In vivo Validation of Reconstruction-Based Resolution Recovery for Human Brain Studies
Authors: Mourik Jurgen EM , Lubberink Mark , van Velden Floris HP , Kloet Reina W , van Berckel Bart NM , Lammertsma Adriaan A , Boellaard Ronald
Published: October 2009

The aim of this study was to validate in vivo the accuracy of a reconstruction-based partial volume correction (PVC), which takes into account the point spread function of the imaging system. The NEMA NU2 Image Quality phantom and five healthy volunteers (using [11C]flumazenil) were scanned on both HR+ and high-resolution research tomograph (HRRT) scanners. HR+ data were reconstructed using normalization and attenuation-weighted ordered subsets expectation maximization (NAW-OSEM) and a PVC algorithm (PVC-NAW-OSEM). HRRT data were reconstructed using 3D ordinary Poisson OSEM (OP-OSEM) and a PVC algorithm (PVC-OP-OSEM). For clinical studies, parametric volume of distribution ( VT) images were generated. For phantom data, good recovery was found for both OP-OSEM (0.84 to 0.97) and PVC-OP-OSEM (0.91 to 0.98) HRRT reconstructions. In addition, for the HR+, good recovery was found for PVC-NAW-OSEM (0.84 to 0.94), corresponding well with OP-OSEM. Finally, for clinical data, good correspondence was found between PVC-NAW-OSEM and OP-OSEM-derived VT values (slope: 1.02±0.08). This study showed that HR+ image resolution using PVC-NAW-OSEM was comparable to that of the HRRT scanner. As the HRRT has a higher intrinsic resolution, this agreement validates reconstruction-based PVC as a means of improving the spatial resolution of the HR+ scanner and thereby improving the quantitative accuracy of positron emission tomography.
Frontal Sinus Fractures: Current Concepts
Authors: Strong E. Bradley
Published: October 2009

Frontal sinus injuries may range from isolated anterior table fractures resulting in a simple aesthetic deformity to complex fractures involving the frontal recess, orbits, skull base, and intracranial contents. The risk of long-term morbidity can be significant. Optimal treatment strategies for the management of frontal sinus fractures remain controversial. However, it is critical to have a thorough understanding of frontal sinus anatomy as well as the current treatment strategies used to manage these injuries. A thorough physical exam and thin-cut, multiplanar (axial, coronal, and sagittal) computed tomography scan should be performed in all patients suspected of having a frontal sinus fracture. The most appropriate treatment strategy can be determined by assessing five anatomic parameters including the: frontal recess, anterior table integrity, posterior table integrity, dural integrity, and presence of a cerebrospinal fluid leak. A well thought out management strategy and meticulous surgical techniques are critical to success. The primary surgical goal is to provide a safe sinus while minimizing patient morbidity. This article offers an anatomically based treatment algorithm for the management of frontal sinus fractures and highlights the key steps to surgical repair.
Complementary ion and extreme ultra-violet spectrometer for laser-plasma diagnosis
Authors: Ter-Avetisyan S. , Ramakrishna B. , Doria D. , Sarri G. , Zepf M. , Borghesi M. , Ehrentraut L. , Stiel H. , Steinke S. , Priebe G. , Schnürer M. , Nickles P. V. , Sandner W.
Published: October 2009

Simultaneous detection of extreme ultra-violet (XUV) and ion emission along the same line of sight provides comprehensive insight into the evolution of plasmas. This type of combined spectroscopy is applied to diagnose laser interaction with a spray target. The use of a micro-channel-plate detector assures reliable detection of both XUV and ion signals in a single laser shot. The qualitative analysis of the ion emission and XUV spectra allows to gain detailed information about the plasma conditions, and a correlation between the energetic proton emission and the XUV plasma emission can be suggested. The measured XUV emission spectrum from water spray shows efficient deceleration of laser accelerated electrons with energies up to keV in the initially cold background plasma and the collisional heating of the plasma.
Effect of exciton self-trapping and molecular conformation on photophysical properties of oligofluorenes
Authors: Schumacher Stefan , Ruseckas Arvydas , Montgomery Neil A. , Skabara Peter J. , Kanibolotsky Alexander L. , Paterson Martin J. , Galbraith Ian , Turnbull Graham A. , Samuel Ifor D. W.
Published: October 2009

Electronic absorption and fluorescence transitions in fluorene oligomers of differing lengths are studied experimentally and using density functional theory (DFT) and time-dependent DFT. Experimental values are determined in two ways: from the measured molar absorption coefficient and from the radiative rate deduced from a combination of fluorescence quantum yield and lifetime measurements. Good agreement between the calculated and measured transition dipoles is achieved. In both theory and experiment a gradual increase in transition dipoles with increasing oligomer length is found. In absorption the transition dipole follows an ∼n0.5 dependence on the number of fluorene units n for the range of 2≤n≤12, whereas a clear saturation of the transition dipole with oligomer length is found in fluorescence. This behavior is attributed to structural relaxation of the molecules in the excited state leading to localization of the excitation (exciton self-trapping) in the middle of the oligomer for both twisted and planar backbone conformations. Twisted oligofluorene chains were found to adopt straight or bent geometries depending on alternation of the dihedral angle between adjacent fluorene units. These different molecular conformations show the same values for the transition energies and the magnitude of the transition dipole.
Buckling properties of carbon nanotubes under hydrostatic pressure
Authors: Natsuki Toshiaki , Fujita Naoki , Ni Qing-Qing , Endo Morinobu
Published: October 2009

An elastic continuum mechanics model is presented to study the elastic buckling of single- and double-walled carbon nanotubes (CNTs) subjected to hydrostatic pressure. It is shown that a pressure-induced instability can occur in CNTs when a circle cross-section of the CNTs is destroyed. In this paper, we investigate the effects of deformation modes and dimension of CNTs on their mechanical stability. The results show that the critical pressure depends largely on the buckling mode, the diameter and aspect ratio of CNTs. The critical pressure of the single-walled CNTs (SWCNTs) with a diameter 1.3 nm is about 1.6 GPa, which is in excellent agreement the results reported in the relative literatures. The critical pressure of the double-walled nanotubes (DWCNTs) with a diameter of 2.2 nm will increase by 26%, compared with that of an identical diameter SWCNT.
Polarization-induced charge carrier separation in polar and nonpolar grown GaN quantum dots
Authors: Marquardt Oliver , Hickel Tilmann , Neugebauer Jörg
Published: October 2009

We have performed systematic studies of wurtzite GaN/AlN quantum dots grown on polar and nonpolar surfaces. For this purpose, experimentally observed quantum dot geometries have been employed within an eight-band k⋅p model. The spatial separation of electrons and holes due to polarization potentials is found to be much larger in nonpolar than in polar grown quantum dots. In order to improve the electron-hole overlap and thus the recombination rates, we have varied the shape, size, and the periodic arrangement of nonpolar quantum dots. We observed the strongest improvement of the charge carrier overlap in nonpolar quantum dots that have a reduced dimension. If the size is reduced below 60% of the dimensions reported recently in literature, this increase is clearly more pronounced than for the polar quantum dots, indicating much better recombination rates in smaller nonpolar quantum dots.
Terahertz generation via optical rectification of x-mode laser in a rippled density magnetized plasma
Authors: Bhasin Lalita , Tripathi V. K.
Published: October 2009

A scheme of resonant terahertz radiation generation by the optical rectification of a picosecond laser pulse in rippled density magnetized plasma is examined. The x-mode laser pulse, propagating perpendicular to dc magnetic field, exerts a quasistatic ponderomotive force on electrons, imparting them a drift with finite transverse component. The drift velocity beats with the density ripple to produce a current, resonantly driving terahertz radiation at frequency comparable to the inverse pulse duration. The terahertz power scales as the square of density ripple amplitude and rises with magnetic field strength. In the case when magnetic field is azimuthal with appropriate r-dependence, the terahertz power has a ring shape intensity distribution. At laser intensity of ∼3×1015 W/cm2, in a 0.01% critical density plasma with 30 kG magnetic field and 30% density ripple, one may have power conversion efficiency of 0.04%.