bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of fractals and moments to describe olive cultivars
Authors: BARI A. , MARTIN A. , BOULOUHA B. , GONZALEZ-ANDUJAR J. L. , BARRANCO D. , AYAD G. , PADULOSI S.
Published: January 2004

Morphological description based on features of the olive stone, such as its surface and shape, can help to determine an olive cultivar's identity. The description, however, is based on visual examination and is thus affected by the examiner's expertise. Although the eye has the capacity to discern texture and shape, the values that are assigned to score different levels or descriptor states, such as a highly scabrous to smooth surface or a circular to elliptic shape, are categorical values. Studies on scoring methodology have shown that the assignment to categories or classes is problematic. The purpose of the present work was to classify olive cultivars by computer-image analysis of olive stone characteristics using mathematical tools, such as fractal geometry and moments. Fractals were used to extract texture information, and moments were used to extract shape information. The results revealed an overall classification accuracy of more than 90% using a Mahalanobis distance. The fractals and moments calculated for stones from genetically identical trees of the same cultivar did not show any statistically significant differences. As environmentally independent and robust morphological descriptors, both fractals and moments showed potential for accurate and efficient classification of olive cultivars and eventual description of olive diversity.
Frontal plane algorithms for dynamic bipedal walking
Authors: Chew Chee-Meng , Pratt Gill A.
Published: January 2004

This paper presents two frontal plane algorithms for 3D dynamic bipedal walking. One of which is based on the notion of symmetry and the other uses reinforcement learning algorithm to learn the lateral foot placement. The algorithms are combined with a sagittal plane algorithm and successfully applied to a simulated 3D bipedal robot to achieve level ground walking. The simulation results showed that the choice of the local control law for the stance-ankle roll joint could significantly affect the performance of the frontal plane algorithms.
Anxiety detecting robotic system – towards implicit human-robot collaboration
Authors: Rani Pramila , Sarkar Nilanjan , Smith Craig A. , Kirby Leslie D.
Published: January 2004

A novel affect-sensitive human-robot cooperative framework is presented in this paper. Peripheral physiological indices are measured through wearable biofeedback sensors to detect the affective state of the human. Affect recognition is performed through both quantitative and qualitative analyses. A subsumption control architecture sensitive to the affective state of the human is proposed for a mobile robot. Human-robot cooperation experiments are performed where the robot senses the affective state of the human and responds appropriately. The results presented here validate the proposed framework and demonstrate a new way of achieving implicit communication between a human and a robot.
A unified dynamics-based motion planning algorithm for autonomous underwater vehicle-manipulator systems (UVMS)
Authors: Podder Tarun Kanti , Sarkar Nilanjan
Published: January 2004

A new unified motion planning algorithm for autonomous Underwater Vehicle-Manipulator Systems (UVMS) has been presented in this paper. Commonly, a UVMS
consists of two sub-systems, a vehicle and a manipulator, having vastly different dynamic responses. The proposed algorithm considers the variability in dynamic bandwidth of the complex UVMS system and generates not only kinematically admissible but also dynamically feasible reference trajectories. Additionally, this motion planning algorithm exploits the inherent kinematic redundancy of the whole system and provides reference trajectories that accommodates other important criteria such as thruster/actuator faults and saturations, and also minimizes hydrodynamic drag. Effectiveness of the proposed unified motion planning algorithm has been verified by extensive computer simulation. The results are quite promising.
A new approach using sensor data fusion for mobile robot
navigation
Authors: Jin Tae-Seok , Lee Jang Myung , Tso S. K.
Published: January 2004

To fully utilize the information from the sensors, this paper proposes a new sensor-fusion technique where the data sets for the previous moments are properly transformed and fused into the current data sets to enable an accurate measurement.
Exploration of an unknown environment is an important task for the new generation of mobile service robots. The mobile robots may navigate by means of a number of monitoring systems
such as the sonar-sensing system or the visual-sensing system. Note that in the conventional fusion schemes, the measurement is dependent on the current data sets only. Therefore, more of sensors are required to measure a certain physical parameter or to improve the accuracy of the measurement. However, in this approach, instead of adding more sensors to the system, the temporal sequence of the data sets are stored and utilized for the accurate measurement. The theoretical basis is illustrated by examples and the effectiveness is proved through the simulations and experiments. The newly proposed, STSF (Space and Time Sensor Fusion) scheme is applied to the navigation of a mobile robot in an unstructured environment, as well as in structured environment, and the experimental results show the performance of the system.
Dynamic simulation and experiments for the design of a new
7-dofs biped walking leg module
Authors: Carbone Giuseppe , Ogura Yu , Lim Hun-ok , Takanishi Atsuo , Ceccarelli Marco
Published: January 2004

In this paper the mechanical design for a new 7-dofs leg is investigated
as a walking module for a humanoid robot. In particular, a dynamic simulation is deduced by means of a Newton-Euler formulation and implemented numerically in order to compute the needed input actuator torques. A simulation is carried out for a similar built leg prototype that is used as a walking module for WABIAN-RIV (WAseda BIped humANoid robot-Revised IV). Experimental tests are carried out on this existing leg in order to validate the proposed formulation for a similar application. Thus, the validated formulation has been used in order to design the actuators for a new leg prototype.
Assessment of various display devices on a virtual reality-based hand
rehabilitation system
Authors: Huang Wei-Shin , Shing Chang-Yih , Fung Chin-Ping , Chuang Tien-Yow , Jeng Ming-Chang , Doong Ji-Liang
Published: January 2004

The purpose of the present study is to assess the effect of an auxiliary lateral image and display devices on manipulation performance in a virtual reality-based hand rehabilitation system. The system consists of a personal computer, a tracker, a data glove, and a display device. For this study, a projector, a monitor, and a head-mounted display were respectively used as the display devices to present three-dimensional virtual environments. Twelve volunteers were recruited to take a pick-and-place procedure at different levels of difficulty. Task time and collision frequency were the parameters used to evaluate the manipulation performance. It was found that the presence of an auxiliary lateral image was a significant factor only for the performance of the projector group and the monitor group. In addition, no statistically significant difference was found in the comparison between the projector group and the monitor group.
Tracking a joint path for the walk of an underactuated
biped
Authors: Chevallereau Christine , Formal'sky Alexander , Djoudi Dalila
Published: January 2004

This paper presents a control law for the tracking of a cyclic reference path by an under-actuated biped robot. The robot studied is a five-link planar biped. The degree of under-actuation is one during the single support phase. The control law is defined in such a way that only the geometric evolution of the biped configuration is controlled, but not the temporal evolution. To achieve this objective, we consider a parametrized control. When a joint path is given, a five degree of freedom biped in single support becomes similar to a one degree of freedom inverted pendulum. The temporal evolution during the geometric tracking is completely defined and can be analyzed through the study of a model with one degree of
freedom. Simple analytical conditions, which guarantee the existence of a cyclic motion and the convergence towards this motion, are deduced. These conditions are defined on the reference trajectory path. The analytical considerations are illustrated with some simulation results.
Only sixteen years…
Authors: McArthur Tom
Published: January 2004

Responses to articles in ET typically reach me three months after the relevant issue comes out. Each issue contains around ten contributions, and presents a wide and shifting range of topics, backgrounds, styles, perspectives, lengths, and densities of expression. In addition, we know from experience that, while some contributors approach ET because for them it is a comfortable and suitable vehicle, others do so because they see it as the only outlet available for what they have to say.
Selling English: advertising and the discourses of ELT
Authors: PEGRUM MARK
Published: January 2004

FOR SOME time, a growing chorus of voices has been expressing concern over the way in which English is promoted by English-speaking countries, primarily the UK, the US, Canada, Australia and New Zealand (cf. Phillipson 1992, Pennycook 1994 & 1998, Canagarajah 1999, Skutnabb-Kangas 2000). Identified by Kachru (1985) as the ‘inner circle’ countries, these make vast profits from linguistic sales to ‘outer circle’ countries such as Singapore and India – despite the fact that the latter have largely developed their own Englishes – and even more so to the ‘expanding circle’ of countries which require access to the default international lingua franca.
The ‘katakana effect’ and teaching English in Japan
Authors: MARTIN ASSUNTA
Published: January 2004

THIS discussion of the condition of English teaching in Japan looks at some deeply rooted national educational and cultural attitudes, including in particular the impact of ‘the katakana effect’ on speaking and listening among teachers and students alike. A unique configuration of cultural, historical, sociological, and linguistic factors presents Japanese teachers with serious challenges. The Ministry of Education, faced with a rising dropout rate, cases of bullying, accusations against irresponsible teachers, and complaints from parents, agreed in 2000 to adopt reforms. The resulting curriculum and methodology changes necessarily address issues relating to English. Although the reforms aim to produce a generation able to thrive socially and professionally in the international community, entrenched beliefs and values threaten their implementation, particularly with regard to a more natural and creative way of teaching and learning Japan's international language of choice.
Jeremy Sandford: a Docu-Retrospect
Authors: Paget Derek
Published: January 2004

Containing an Explanation, an (Undelivered) Funeral Oration, Divers Reminiscences, a Draft

Treatment for a Docudrama (and Some Dialogue Therefrom), and Some Shandyan Digressions. When,

back in 1972, the original Theatre Quarterly devoted one of its earliest issues (TQ6)

to television drama, the strongest reactions were to remarks by Tony Garnett concerning the

recently developed form already being dubbed documentary drama. Subsequent issues featured both

an attack on the form from Paul Ableman, and a vigorous defence from its leading practitioner–

Jeremy Sandford, author of the seminal Cathy Come Home (1966) and Edna the Inebriate

Woman (1972). The debate continues, but despite the critical esteem in which Sandford's

work is held, the man himself became persona non grata on national television, and

devoted himself to his many other concerns, notably the traditions and present treatment of the

gypsy people. He died on 12 May 2003 – an apparent recluse, yet with websites devoted to

hundreds of loving tributes from young and old alike. The leading historian of docudrame,

Derek Paget – author of True Stories: Documentary Drama on Radio, Stage, and

Television (Manchester University Press, 1990) – here offers a tribute which refuses to

fit a ‘proper’ academic format, and takes on something of the variegated style of

Sandford's own work.
British Radio Dramaturgy and the Effects of the New Conservatism
Authors: Stanton William
Published: January 2004

This essay, which is informed by the author's own practice as a playwright working in the medium of radio drama, looks at some effects of the enforced merger of radio with TV drama to create a ‘bi-media’ department at the BBC, and considers the evolution of commissioning policy since the imposition of the internal market under the Director Generalship of John Birt (from 1992 to 2000). Considering radio drama, after Adorno, as a producer in the culture industry, he suggests that the neo-conservatism of the 1980s, as described by Habermas, is a significant factor in understanding current commissioning practices and the dramaturgy of new realism in some radio drama. William Stanton is a Lecturer in Drama at Exeter University, where he teaches and researches writing for performance and intercultural performance practice through a research/practice link with the University of Santa Catarina, Florianópolis, Brazil, where he has an AHRB award for a new project in 2004. He is also a writer of fiction and plays for stage and radio. His most recent play for BBC Radio 4 was Dead Line in 2002, and his Route 23 is forthcoming.
‘Out Vile Jelly’: Sarah Kane's ‘Blasted’ and
Shakespeare's ‘King Lear’
Authors: Saunders Graham
Published: January 2004

Sarah Kane's notorious 1995 debut, Blasted, has been widely though belatedly
recognized as a defining example of experiential or ‘in-yer-face’ theatre. However,
Graham Saunders here argues that the best playwrights not only innovate in use of language and
dramatic form, but also rewrite the classic plays of the past. He believes that too much stress
has been placed on the play's radical structure and contemporary sensibility, with the
effect of obscuring the influence of Shakespearean tradition on its genesis and content. He
clarifies Kane's gradually dawning awareness of the influence of Shakespeare's King
Lear on her work and how elements of that tragedy were rewritten in terms of dialogue, recast
thematically, and reworked in terms of theatrical image. He sees Blasted as both a
response to
contemporary reality and an engagement with the history of drama. Graham Saunders is Senior
Lecturer in Theatre Studies at the University of the West of England, Bristol, and author of the
first full-length study of Kane's work: ‘Love Me or Kill Me’: Sarah Kane and
the Theatre of Extremes (Manchester University Press, 2002). An earlier version of this
article was given as a paper at the ‘Crucible of Cultures: Anglophone Drama at the Dawn
of a New Millennium’ conference in Brussels, May 2001. Saunders is currently working on
articles about Samuel Beckett and Edward Bond.
‘Me and My Mates’: the State of English Playwriting, 2003
Authors: Sierz Aleks
Published: January 2004

Since his account of the Birmingham Theatre Conference in NTQ51, Aleks Sierz has taken the temperature of British playwriting in articles about ‘Cool Britannia’ (NTQ56) – from which developed his influential book, In Yer Face Theatre: British Drama Today (Faber, 2001) – ‘Still In-Yer-Face? Towards a Critique and a Summation’ (NTQ69), and a report on the Bristol conference (NTQ73). At a time when more new writing is being staged than probably at any period of British theatre history, here he laments the insular social realism which once more characterizes English (as distinct from Irish, Scottish, and American) playwriting, however modishly its characters may now be drawn from the underclass rather than the upper; and he identifies a ‘hunger for ideas’ among British audiences which is ill-satisfied by the dystopian despair of many would-be political dramatists.
Intensive Actor Training in Costa Rica
Authors: Avila Roxana , Korish David
Published: January 2004

Report on ‘Learning to Live’, an Intensive Actor Training Workshop for Central
American actors, held in Costa Rica from 19 June to 10 July
2003.
Biological stoichiometry: a theoretical framework connecting ecosystem ecology, evolution, and biochemistry for application in astrobiology
Authors: Elser James J.
Published: January 2004

Astrobiology is an extremely wide-ranging field and thus is in special need of conceptual and theoretical frameworks that can integrate its various arenas of study. In this paper I review recent work associated with a conceptual framework known as ‘ecological stoichiometry’ and even more recent extensions in the development of ‘biological stoichiometry’. Ecological stoichiometry is the study of the balance of energy and multiple chemical elements in ecological interactions and has developed rapidly in the study of nutrient cycling and energy flow in aquatic food webs. It identifies the elemental composition of interacting biota as central in understanding the nature of their interactions and dynamics, including key feedbacks via nutrient recycling. Biological stoichiometry extends this mode of thinking to all types of biological systems. It especially seeks to better understand, at the biochemical and genetic levels, the factors influencing the elemental composition of living things and the evolutionary forces that drive and constrain that elemental composition. By connecting key concepts of ecosystem ecology, evolutionary biology and biochemistry, stoichiometric theory integrates biological information into a more coherent whole that holds considerable promise for application in astrobiology. Several examples of potential astrobiological applications of stoichiometric analysis are offered, including ones related to pre-biotic evolution, the Cambrian explosion, biosignatures and biological feedbacks on planetary carbon cycling.
Did silicon aid in the establishment of the first bacterium?
Authors: Wainwright M. , Al-Wajeeh K. , Wickramasinghe N.C. , Narlikar J.V.
Published: January 2004

Silicic acid increased numbers of both aerobic and facultatively anaerobic bacteria in ultrapure water incubated under strict oligotrophic conditions; soil extracts acted as the bacterial inoculum. The results are discussed in relation to the possibility that silicic acid, produced by the hydrolysis of silicates on the early Earth, could have stimulated the growth of the first bacterium, thereby allowing it to become established in the then prevailing conditions (presumed to be oligotrophic).
Where is the nitrogen on Mars?
Authors: Mancinelli Rocco L. , Banin Amos
Published: January 2004

Nitrogen is an essential element for life. Specifically, fixed nitrogen (i.e. NH3, NH4+, NOx or N that is chemically bound to either inorganic or organic molecules and can be released by hydrolysis to form NH3 or NH4+) is useful to living organisms. Nitrogen on present-day Mars has been analysed only in the atmosphere. The inventory is a small fraction of the amount of nitrogen presumed to have been received by the planet during its accretion. Where is the missing nitrogen? Answering this question is crucial for understanding the probability of the origin and evolution of life on Mars, and for its future astrobiological exploration. The two main processes that could have removed nitrogen from the atmosphere include: (1) non-thermal escape of N atoms to space and (2) burial within the regolith as nitrates and ammonium salts. Nitrate would probably be stable in the highly oxidized surface soil of Mars and could have served as an NO3− sink. Such accumulations are observed in certain desert environments on Earth. Some NH4+ nitrogen may also be fixed and stabilized in the soil by inclusion as a structural cation in the crystal lattices of certain phyllosilicates replacing K+. Analysis of the Martian soil for traces of NO3− and NH4+ during future missions will provide important information regarding the nitrogen abundance on Mars. We hypothesize that Mars soil, as typical of extremely dry desert soils on Earth, is likely to contain at least some of the missing nitrogen as nitrate salts and some fixed ammonium bound to aluminosilicate minerals.
Unfrozen subsurface water on Mars: presence and implications
Authors: Möhlmann Diedrich T.F.
Published: January 2004

It has been concluded from measurements, recently made by Mars Odyssey experiments, that there is water in the upper few metres of the Martian surface at mid- and equatorial latitudes with regionally high contents of up to about 9 wt%. This Martian subsurface water is shown to be in the form of adsorption (or sorption) water. The adsorptive bond of water molecules is about twice as strong on mineral surfaces compared with on water ice. Therefore, evaporation of adsorption water in porous soil happens on time scales, which exceed those of sublimation of water ice by orders of magnitude. Consequently, sorption water can have survived in the near-surface layers of the Martian soil at mid- and equatorial latitudes over geological time scales, where ice must have been lost by sublimation. Sorption water is unfrozen, i.e. liquid-like, down to temperatures of −40°C and below. It must, at least regionally and temporarily, be an important and not a trace constituent of the upper-surface Martian soil. The presence of liquid-like sorption water on Mars is also discussed in view of exobiological implications.
Precession-driven migration of water in the surficial layers of Mars
Authors: Tokano Tetsuya
Published: January 2004

A linear correlation analysis between the Mars Odyssey neutron fluxes and various surface parameters indicates that the annual maximum surface temperature is the most important factor controlling the soil water content in the surficial (upper few tens of centrimetres) layers of the Martian soil. This is likely to be associated with the higher enthalpy of hydration of minerals in comparison with the enthalpy of sublimation of ice, which is presumably almost absent in the surficial layer. While presently the maximum surface temperature occurs near 30° S because of perihelion in late southern spring, the season of perihelion periodically migrates by virtue of precession. Consequently, the maximum surface temperature as well as the driest place on Mars should move from one hemisphere to the other with a period of about 51 000 yr. A significant amount of surficial (adsorbed) water would then be exchanged between the hemispheres and between the soil and other reservoirs, especially the polar caps and the polar layered deposits, and is probably borne out by the stratigraphic structure of these deposits. It is suggested that the water migration driven by the orbital eccentricity and precession may be as important as the obliquity-driven exchange of water, particularly very close to the surface, where ground ice is unstable.

The zones of liquid water stability oscillate somewhat in a north–south direction in the course of the precession cycle, but are most prevalent in parts of the low and mid northern latitudes as well as in the Hellas Basin. The thermal stability of liquid water tends to be high where the near-surface soil water content is low, indicating that the periodic melting of ground ice by solar heating is not a likely source of liquid water on the surface, but some episodic processes should provide water, if any.

An enhanced soil water content near the surface is always accompanied with a reduced peak ultraviolet flux, both reducing the chemical reactivity of the soil. In the present epoch the northern hemisphere may represent astrobiologically more clement environmental conditions.
A deforming block model for the present‐day tectonics of Tibet
Authors: Chen Qizhi , Freymueller Jeffrey T. , Wang Qi , Yang Zhiqiang , Xu Caijun , Liu Jingnan
Published: January 2004

We use GPS data from 45 sites across the Tibetan Plateau surveyed between 1991 and 2001 to study the distribution of strain in that part of the India‐Eurasia collision zone. The plateau is cut by a few major, rapidly slipping strike‐slip fault zones, with broadly distributed strain between those zones. The GPS velocities can be fit well by a simple deforming block model that combines uniform strain with the motion of blocks separated by the major known fault zones within the plateau. The boundaries of the four blocks in this model correspond to the major, rapidly slipping faults. A rigid block model with a smaller number of blocks fits the data poorly and can be rejected. We estimate that 5.9 ± 0.7 mm/yr of extension in the N69°W direction occurs on the Yadong‐Gulu rift south of the plateau; localized extension may extend as far north as the Nyainqêntanglha Range. We find 7.4 ± 0.7 mm/yr of right‐lateral slip on the Karakorum‐Jiali fault zone, significantly slower than that previously estimated from offset geologic features. Our deforming block model and a two‐dimensional single‐fault screw dislocation model give lower and upper bounds of 4.4 ± 1.1 and 10.3 ± 0.4 mm/yr on the slip rate on the Kunlun fault, respectively, comparable, in its highest, to the long‐term slip rate observed geologically. The distributed deformation is surprisingly uniform over the Tibetan Plateau, Qaidam Basin, and Qilian Shan and approximates a combination of pure shear and uniaxial contraction with the same axes of maximum contraction, ∼N32°E. This strain field is a combination of shortening and extension that produces little net dilatation (1% area loss per million years) at present. The broadly distributed strain most likely represents slip on many faults, each with a relatively low slip rate. Distributed conjugate strike‐slip faulting is the most plausible mechanism to produce the observed strains, as supported by the record of medium to large earthquakes within the plateau. The distributed deformation is just as important in the accommodation of the total India‐Eurasia convergence as is slip on the major faults. The eastward motion of central Tibet is as large as 50% of the convergence rate between India and Eurasia. However, this eastward motion is not motion of a relatively undeforming block bounded by rapidly moving strike‐slip faults, as suggested by past extrusion models. Instead, much of this eastward extrusion is driven by the internal extension of the plateau. Our inference is in agreement with the model of F. Shen et al. [2001] that suggested east‐west extension, north‐south contraction, and eastward plateau growth dominate the present tectonics of the Tibetan Plateau.
The Alhama de Murcia fault (SE Spain), a seismogenic fault in a diffuse plate boundary: Seismotectonic implications for the Ibero‐Magrebian region
Authors: Masana E. , Martínez‐Díaz J. J. , Hernández‐Enrile J. L. , Santanach P.
Published: January 2004

The shortening between the African and the Iberian plates is absorbed by a number of faults distributed over a very wide zone with very low slip rates and long periods of seismic loading. Thus a seismotectonic map based only on faults associated with seismicity or with expressive geomorphic features is incomplete. It is possible to characterize seismogenic faults using paleoseismology. First, paleoseismological results based on trenching analysis in the eastern Betics (Lorca‐Totana segment of the Alhama de Murcia fault) are presented. The main paleoseismic parameters of this fault segment are (1) a minimum of two to threeMw6.5–7 earthquakes in the last 27 kyr (shortly before 1650 A.D., between 830 and 2130 B.C. and shortly before 16.7 ka, respectively), with a mean recurrence period of 14 kyr, and a very short elapsed time, and (2) a net slip rate of 0.07–0.6 mm/yr during the last 30 kyr. These results were extrapolated to the rest of the known active faults in the eastern Betics and were added to the slip rates of the active faults at the African margin. The total slip rate of the transect, which crosses de Alhama de Murcia fault in Spain and reaches the Cheliff basin (Algeria), would represent 21–82% of the total shortening between Africa and Eurasia estimated from plate motion models and seismic moment summation. A number of factors could account for this discrepancy: (1) hidden seismogenic faults in the emerged areas, (2) absence of correlation between current and late Pleistocene slip rates, (3) extensive small faults that are undetected and that absorb a significant amount of the deformation, and (4) possible overestimation of the convergence rates.
Hydroplaning and submarine debris flows
Authors: De Blasio Fabio V. , Engvik Lars , Harbitz Carl B. , Elverhøi Anders
Published: January 2004

Examination of submarine clastic deposits along the continental margins reveals the remnants of holocenic or older debris flows with run‐out distances up to hundreds of kilometers. Laboratory experiments on subaqueous debris flows, where typically one tenth of a cubic meter of material is dropped down a flume, also show high velocities and long run‐out distances compared to subaerial debris flows. Moreover, they show the tendency of the head of the flow to run out ahead of the rest of the body. The experiments reveal the possible clue to the mechanism of long run‐out. This mechanism, called hydroplaning, begins as the dynamic pressure at the front of the debris flow becomes of the order of the pressure exerted by the weight of the sediment. In such conditions a layer of water can intrude under the sediment with a lubrication effect and a decrease in the resistance forces between the sediment and the seabed. A physical‐mathematical model of hydroplaning is presented and investigated numerically. The model is applied to both laboratory‐ and field‐scale debris flows. Agreement with laboratory experiments makes us confident in the extrapolation of our model to natural flows and shows that long run‐out distances can be naturally attained.
Impact melts and glasses on Mars
Authors: Schultz Peter H. , Mustard John F.
Published: January 2004

Dark mobile materials on Mars are widely considered to be volcanically derived windblown particulates. Such a conclusion is consistent with the large volcanic edifices on Mars and the assumption that a volatile‐rich crust would not favor significant impact melt generation. Several post‐Viking discoveries, however, provide new perspectives for reconsidering alternative origins not only for some of the mobile dark veneers but also certain materials at the Pathfinder and Viking landing sites. First, certain dark materials on Mars do not exhibit the expected mafic absorption features in their reflectance spectra. Second, the Pathfinder mission revealed unexpected feldspathic compositions of vesicular blocks that lead to a preliminary conclusion that they represent andesites or basaltic andesites, rather than basalts. Third, recent discoveries of Holocene to Miocene impacts in Argentine loessoid deposits provide new insights for the nature of melts generated from eolian sediments. Fourth, global dispersal of impact melt products are now recognized in the terrestrial record throughout the Cenozoic. Consequently, the generation and preservation of impact glass on Mars should be reconsidered. Possible occurrences include possible tektite‐like strewnfields downrange from recent oblique impacts, dark avalanches emerging from backwasting cliffs of easily eroded unconformable deposits, global dispersal of glassy ejecta from Hesperian and Amazonian craters of Chicxulub scale, and dark mobile veneers emerging from Noachian craters. We propose that the mobile dark materials comprising many of the named features of Mars as well as some blocks at the Pathfinder/Viking landing sites may represent impact‐melt products.
Exploring Gusev Crater with Spirit: Review of science objectives and testable hypotheses
Authors: Cabrol Nathalie A. , Grin Edmond A. , Carr Michael H. , Sutter Brad , Moore Jeffrey M. , Farmer Jack D. , Greeley Ronald , Kuzmin Ruslan O. , DesMarais David J. , Kramer Marc G. , Newsom Horton , Barber Charles , Thorsos Ivan , Tanaka Kenneth L. , Barlow Nadine G. , Fike David A. , Urquhart Mary L. , Grigsby Brian , Grant Frederick D. , de Goursac Olivier
Published: December 2003

Gusev Crater was selected as the landing site for the Mars Exploration Rover (MER) Spirit mission. Located at the outlet of Ma'adim Vallis and 250 km south of the volcano Apollinaris Patera, Gusev is an outstanding site to achieve the goals of the MER mission. The crater could have collected sediments from a variety of sources during its 3.9 Ga history, including fluvial, lacustrine, volcanic, glacial, impact, regional and local aeolian, and global air falls. It is a unique site to investigate the past history of water on Mars, climate and geological changes, and the potential habitability of the planet, which are central science objectives of the MER mission. Because of its complex history and potential diversity, Gusev will allow the testing of a large spectrum of hypotheses with the complete suite of MER instruments. Evidence consistent with long‐lived lake episodes exist in the landing ellipse area. They might offer a unique opportunity to study, for the first time, Martian aqueous sediments and minerals formed in situ in their geological context. We review the geological history and diversity of the landing site, the science hypotheses that can be tested during the MER mission, and the relevance of Gusev to the MER mission objectives and payload.
A wind tunnel experiment of sand transport and its comparison with the Werner model
Authors: Hatano Y. , Kanda Y. , Udo K. , Takewaka S. , Ueki R. , Hatano N. , Mouri H. , Chiba M. , Kurihara K. , Nishimura H.
Published: January 2004

We carried out a wind tunnel experiment on aeolian transport of sand. Fluorescence‐dyed grains of sand were embedded in the sand bed in a wind tunnel, and their dispersion was recorded by a video camera. Dispersion of colored sand both downwind and in the crosswind direction are examined. The concentration of colored sand decreases as an exponential function of the downwind distance y, Ae−κy, whereas the cross‐sectional distribution is approximated by a Gaussian distribution with the standard deviation proportional to . The characteristic length scale is 1000 times greater in the downwind than in the crosswind direction. A simple stochastic model is proposed to explain these findings. We also found that our experimental results conform to the assumptions of the Werner model, which reproduces aeolian dune dynamics well. We derived conditions on the parameters of the Werner model from the experimental results and suggest the applicability of the Werner model to real problems such as sandy coasts, deserts, and regions whose surface is contaminated.
Scattering simulation for inhomogeneous layered canopy and random targets beneath canopies by using the Mueller matrix solution of the pulse radiative transfer
Authors: Jin Ya‐Qiu , Chen Fei
Published: December 2003

The Mueller matrix solution of vector radiative transfer for inhomogeneous random media of nonspherical scatterers under a pulse incidence is presented. Copolarized and cross‐polarized bistatic scattering echoes can be numerically simulated. Temporally varying echoes well demonstrate volumetric and surface scattering mechanism and depict the inhomogeneous fraction profile of random scatterers. The effective height of inhomogeneous canopy inverted from the pulse echoes is discussed. Pulse echo patterns are also numerically simulated for polarimetric scattering from the model of random metal targets beneath the layered vegetation canopies.
Modeling the global ocean iron cycle
Authors: Parekh Payal , Follows Michael J. , Boyle Edward
Published: January 2004

We describe a model of the ocean transport and biogeochemical cycling of iron and the subsequent control on export production and macronutrient distributions. Ocean transport of phosphorus and iron are represented by a highly idealized six‐box ocean model. Export production is parameterized simply; it is limited by light, phosphate, and iron availability in the surface ocean. We prescribe the regional variations in aeolian deposition of iron and examine three parameterizations of iron cycling in the deep ocean: (1) net scavenging onto particles, the simplest model; (2) scavenging and desorption of iron to and from particles, analogous to thorium; and (3) complexation. Provided that some unknown parameter values can be set appropriately, all three biogeochemical models are capable of reproducing the broad features of the iron distribution observed in the modern ocean and explicitly lead to regions of elevated surface phosphate, particularly in the Southern Ocean. We compare the sensitivity of Southern Ocean surface macronutrient concentration to increased aeolian dust supply for each parameterization. Both scavenging‐based representations respond to increasing dust supply with a drawdown of surface phosphate in an almost linear relationship. The complexation parameterization, however, asymptotes toward a limited drawdown of phosphate under the assumption that ligand production does not respond to increased dust flux. In the scavenging based models, deep water iron concentrations and, therefore, upwelled iron continually increase with greater dust supply. In contrast, the availability of complexing ligand provides an upper limit for the deep water iron concentration in the latter model.
Surface deformations as indicators of deep ebullition fluxes in a large northern peatland
Authors: Glaser P. H. , Chanton J. P. , Morin P. , Rosenberry D. O. , Siegel D. I. , Ruud O. , Chasar L. I. , Reeve A. S.
Published: January 2004

Peatlands deform elastically during precipitation cycles by small (±3 cm) oscillations in surface elevation. In contrast, we used a Global Positioning System network to measure larger oscillations that exceeded 20 cm over periods of 4–12 hours during two seasonal droughts at a bog and fen site in northern Minnesota. The second summer drought also triggered 19 depressuring cycles in an overpressured stratum under the bog site. The synchronicity between the largest surface deformations and the depressuring cycles indicates that both phenomena are produced by the episodic release of large volumes of gas from deep semi‐elastic compartments confined by dense wood layers. We calculate that the three largest surface deformations were associated with the release of 136 g CH4 m−2, which exceeds by an order of magnitude the annual average chamber fluxes measured at this site. Ebullition of gas from the deep peat may therefore be a large and previously unrecognized source of radiocarbon depleted methane emissions from northern peatlands.
Noble gas signatures of abyssal gabbros and peridotites at an Indian Ocean core complex
Authors: Kumagai Hidenori , Dick Henry J. B. , Kaneoka Ichiro
Published: December 2003

We report some of the first noble gas data for in situ lower oceanic crust and shallow mantle. From a suite of gabbros and peridotites recovered from the Atlantis Bank oceanic core complex on the Southwest Indian Ridge, we measured He, Ne, Ar, Kr and Xe concentrations as well as 3He/4He and 40Ar/36Ar ratios, there by documenting the noble gas content and signature of oceanic lithosphere. Except for a single ultramylonite, the gabbros have higher 3He/4He ratios than atmospheric. Three gabbros have MORB‐like bulk 3He/4He ratios higher than 6RA despite variable helium concentrations, as much as two to three orders of magnitude lower than in MORB glasses. One of these is mylonitized, demonstrating that magmatic helium can be retained despite intense high‐temperature crystal‐plastic deformation in the lower crust. Of the gabbros measured, green amphibole‐bearing samples show relatively high helium abundances. Peridotite noble gas concentrations measured in clinopyroxene separates are dominantly lower than gabbros. Specifically, He abundances are similar to or greater than gabbros with MORB‐like 3He/4He isotopic ratios. All the gabbros and peridotite clinopyroxenes show severely contaminated 40Ar/36Ar values up to 1300. Magmatic 40Ar is enriched in the oxide‐olivine gabbro with the highest 40Ar/36Ar in the entire sample suit. These results suggest as an actual data that the recycling of the lower oceanic crust and shallow mantle should be considered in modeling mantle evolution at least for helium. Measured helium abundances, though lower than in basalt glasses, are greater than those in crystalline MORB. Even if entire upper crust retains primary magmatic signature, oceanic lower crust and lithospheric mantle may impact larger by recycling due to their large volumes.
Nitrogen isotopic composition of the MORB mantle: A reevaluation
Authors: Mohapatra Ratan K. , Murty S. V. S.
Published: January 2004

Nitrogen in the mantle source of mid oceanic ridge basalts (MORBs) is commonly believed to have δ15N∼−5‰. This is based on a (selective) statistical average drawn from nitrogen isotopic data obtained simultaneously with argon from MORBs. However, on critical evaluation, using the accompanying 40Ar/36Ar data, we show this approach to be somewhat ambiguous. Considering the fact that MORBs can have a number of geochemical components in them, as has been shown by several recent studies, the approach of statistical averaging may actually point to a mixture rather than the true mantle end‐member. A more reasonable approach, also used for deriving the mantle noble gas signatures, suggests nitrogen in the MORB mantle to be much lighter (∼−15‰) in its isotopic composition. Such a signature is consistent with nitrogen data from MORBs as well as from other mantle derived samples that are believed to have sampled volatiles from the MORB mantle.
Latitudinal dependence of diapycnal diffusivity in the thermocline estimated using a finescale parameterization
Authors: Hibiya Toshiyuki , Nagasawa Maki
Published: January 2004

The spatial distribution of diapycnal diffusivity in the thermocline over a large area in the interior of the North Pacific is obtained by incorporating the finescale vertical shear of horizontal velocity measured by expendable current profilers into the empirical formula proposed by Gregg [1989]. It is clearly shown that diapycnal diffusivity in the North Pacific strongly depends on the latitude. For example, the estimated diapycnal diffusivities near the Hawaiian Ridge and the Izu‐Ogasawara Ridge exceed 10−4 m2 s−1, whereas those near the Aleutian Ridge and the Emperor Seamounts are of the order of 0.1 × 10−4 m2 s−1, even though the available semidiurnal internal tidal energy is similar among all of these prominent topographic features. The observed results are consistent with the numerical prediction that the cascade of internal tidal energy down to dissipation scales is dominated by parametric subharmonic instability which is expected to occur only below 30°N.
Carbon isotope constraints on vertical mixing and air‐sea CO2 exchange
Authors: Fallon Stewart J. , Guilderson Thomas P. , Caldeira Ken
Published: December 2003

We have developed a ∼45 year carbon isotope record (δ13C, Δ14C) from the coralline sponge Acanthochaetetes wellsi from Vanuatu in an effort to examine air‐sea CO2 exchange using both the δ13C Suess effect and the bomb‐14C transient. From 1953 to 1999 δ13C decreased by 0.9‰. Pre‐bomb Δ14C is ‐59‰, consistent with coral based estimates from the same region and the post‐bomb maximum (+121‰) is achieved in 1973. A 1‐D box‐diffusion model was employed to quantify vertical diffusivity and air‐sea exchange rates. The model suggests that a low vertical diffusion rate (0.1 cm2 s‐1) coupled with a moderate CO2 exchange rate produces the overall observed shape of the pre‐post bomb Δ14C record and the general large scale features of the δ13C time series. These parameters are on the low end of values used in ocean‐carbon GCMs but are consistent with microscale tracer experiments.
A prognostic model of cloud cover based on Satellite Data
Authors: Goswami P. , Liberti G. L.
Published: January 2004

Large uncertainties still remain about the mechanisms of genesis and interaction of clouds in a large scale environment. Through a semi‐empirical dynamical model using hourly data from TOGA‐COARE IOP (130E–180E and 15S–15N, 01.11.91–28.02.92), we show that the convective activity leading to clouds is a self‐regulating, threshold process embedded in a large‐scale environment. The convective activity is prescribed through a of hourly fractional cloud cover while the environmental forcings are defined in terms large‐scale moist state defined in terms of the average brightness temperature. A prognostic model is then developed for cloud cover as the dynamical variable. To validate the model we integrate it with a given initial condition from observed data. The model reproduces the observed spatio‐temporal structure of the cloud with a remarkable degree of success. We identify and quantify two thresholds for large‐scale forcing for genesis and intensity of high clouds.
Anisotropy of water cloud reflectance: A comparison of measurements and 1D theory
Authors: Horváth Ákos , Davies Roger
Published: January 2004

Bi‐directional reflectances of marine liquid water clouds, as measured by the Multiangle Imaging SpectroRadiometer (MISR), are compared with plane‐parallel radiative transfer model calculations. We define an angular consistency test that requires measured and modeled radiances to agree within ±5% for all chosen view angles for the observations to be classified as plane‐parallel. When all nine MISR angles are used at the full 275 m resolution, 1 in 6 pixels (17%) pass the test. There is a slight dependence on effective radius Re, with Re = 8 μm resulting in the highest pass rate. As the resolution is degraded, clouds appear more plane‐parallel, and the passing rate increases to 38% at the coarsest 17.6 km scale. The passing rate quickly decreases as the number of angles used in the angular test increases. Requiring a match at only the nadir and two near‐nadir angles immediately eliminates half of the full resolution pixels.
Biological response of the sea around Sri Lanka to summer monsoon
Authors: Vinayachandran P. N. , Chauhan P. , Mohan M. , Nayak S.
Published: January 2004

Chlorophyll‐a concentration (chl a) maps derived from the Ocean Color Monitor (OCM) on board Indian Remote Sensing Satellite (IRS‐P4) and Seaviewing Wide field of View sensor (SeaWiFS) show increased chl a in the waters around Sri Lanka during summer monsoon. Physical processes that can lead to the phytoplankton bloom are investigated using upper ocean temperature profiles and satellite derived winds, sea surface temperature (SST) and sea level anomalies (SLA). There is a chl a bloom attached to the southern coast of Sri Lanka accompanied by cool SST, low SLA and upsloping of isotherms towards the coast. Coastal upwelling driven by monsoon winds is identified as the physical mechanism causing nutrient enrichment in the surface layer. The Southwest Monsoon Current (SMC) which flows eastward south of Sri Lanka and then into the Bay of Bengal advects the upwelled water eastward along its path. The chl a rich waters from the Indian coast also advects along with the SMC towards Sri Lanka. East of Sri Lanka the open ocean upwelling associated with the Sri Lanka Dome is also found to be an important process that upwell nutrients.
The pathway and circulation of North Pacific Intermediate Water
Authors: You Yuzhu
Published: December 2003

It has been speculated that the subtropical North Pacific Intermediate Water (NPIW) was formed by a shortcut of Okhotsk Sea source into the western subtropical gyre because this is the geographically shortest distance, and based on incomplete data. This mechanism is contradictory to the distribution of seawater properties, and, dynamically, is inconsistent with a basin‐wide distribution of NPIW and associated gyre circulation. A lengthy transpacific pathway has been identified for the transformed NPIW source waters that first enter the eastern subtropical gyre, which is robust in a water‐mass age distribution. Using an updated hydrography and a water‐mass mixing scheme combining property distribution with flow streamfunction the present study establishes a dynamically self‐consistent gyre circulation of NPIW and its pathway from the subpolar formation regions (source) to the Indonesian Throughflow (sink).