bluuebunny/crossref_metadata_2025 huggingface dataset:
The Malawi 2002 food crisis: the rural development challenge
Authors: Dorward Andrew , Kydd Jonathan
Published: March 2008

The recent food crisis in Malawi has drawn stark attention to the failures of development policies over the last forty years to create wealth and develop a robust economy or the markets on which such an economy must depend. Current market liberalisation policies have achieved at best mixed success in addressing the generic problems inhibiting smallholder agricultural development: low returns to farmers' and service providers' investments, with high risks from natural shocks, price variations, coordination failure and opportunistic behaviour. Post-independence institutional mechanisms in Malawi were more successful in addressing some of these problems, in particular those of coordination risk, although external and internal difficulties led to increasing costs and declining effectiveness of these mechanisms, and to their collapse. They do provide, however, important lessons about the different failures of both market intervention and market liberalisation policies. We suggest and discuss a set of critical elements needed for economic development and wealth creation in poor rural areas, and propose four basic principles to guide the search for, and design and implementation of, effective rural development strategies and policies.
‘Old brooms can sweep too!’ An overview of rulers and public sector reforms in Uganda, Tanzania and Kenya
Authors: Mette Kjaer Anne
Published: March 2008

New leaders are often assumed to be better able to push for policy and sector reform because they are less tied in by established patronage networks. The article discusses this assumption by examining public sector reform in three East African countries under different leaders. It finds that while neo-patrimonialism is an important reason why public sector reform is often blocked, this paradigm cannot explain why some public sector reforms are actually implemented. New leaders are not always new brooms, and whether they are so depends as much on formal conditions, such as the existence of a political coalition, as on informal neo-patrimonial factors. The article also finds that in some cases, old brooms can sweep too. When succession is institutionalised, as the Tanzanian case shows, even a relatively weak leader can carry out reform effectively in his second term because he does not have to consider re-election.
Syntactic ambiguity resolution and the prosodic foot: Cross-language differences
Authors: PERRY CONRAD , KAN MAN-KIT , MATTHEWS STEPHEN , WONG RICHARD KWOK-SHING
Published: March 2008

In this study we examined syntactic ambiguity resolution in two different Chinese languages, Cantonese and Mandarin, which are relatively similar grammatically but very different phonologically. We did this using four-character sentences that could be read using two, two-syllable sequences (2-2) or a structure where the first syllable could be read by itself. The results showed that when both potential readings were semantically congruent, Mandarin speakers had a strong preference for the 2-2 structure and they preferred that structure much more than Cantonese speakers did. We attribute this to Mandarin having a more dominant bisyllabic prosodic foot than Cantonese. When the 2-2 meaning was semantically incongruent, however, the alternative structure was preferred by both Mandarin and Cantonese speakers. Overall, the results suggest that, in silent reading tasks and semantically neutral conditions, the prosodic foot is generated automatically and can affect syntactic choices when ambiguity arises.
Phonological development in lexically precocious 2-year-olds
Authors: SMITH BRUCE L. , MCGREGOR KARLA K. , DEMILLE DARCIE
Published: March 2008

To examine interactions between young children's vocabulary size and their phonological abilities, spontaneous language samples were collected from 24-month-olds with precocious lexicons, their age mates (24-month-olds with average-sized lexicons), and their vocabulary mates (30-month-olds with average-sized lexicons). Phonological ability was measured in a variety of ways, such as the number of different consonants that were targeted, the number of different consonants produced correctly, the percentage of consonants produced correctly, and the occurrence of phonological processes. The lexically precocious 24-month-olds were similar to their vocabulary mates on most measures of phonological ability, and both of these groups were generally superior to the 24-month-olds with smaller lexicons. These findings supported a hypothesized relationship between lexicon size and phonological performance, and demonstrated that 2-year-olds' phonological development is more closely related to size of the lexicon than chronological age.
The effect of perceptual availability and prior discourse on young children's use of referring expressions
Authors: MATTHEWS DANIELLE , LIEVEN ELENA , THEAKSTON ANNA , TOMASELLO MICHAEL
Published: March 2008

Choosing appropriate referring expressions requires assessing whether a referent is “available” to the addressee either perceptually or through discourse. In Study 1, we found that 3- and 4-year-olds, but not 2-year-olds, chose different referring expressions (noun vs. pronoun) depending on whether their addressee could see the intended referent or not. In Study 2, in more neutral discourse contexts than previous studies, we found that 3- and 4-year-olds clearly differed in their use of referring expressions according to whether their addressee had already mentioned a referent. Moreover, 2-year-olds responded with more naming constructions when the referent had not been mentioned previously. This suggests that, despite early social–cognitive developments, (a) it takes time to master the given/new contrast linguistically, and (b) children understand the contrast earlier based on discourse, rather than perceptual context.
Semantic encoding of spoken sentences: Adult aging and the preservation of conceptual short-term memory
Authors: LITTLE DEBORAH M. , McGRATH LAUREN M. , PRENTICE KRISTEN J. , WINGFIELD ARTHUR
Published: March 2008

Traditional models of human memory have postulated the need for a brief phonological or verbatim representation of verbal input as a necessary gateway to a higher level conceptual representation of the input. Potter has argued that meaningful sentences may be encoded directly in a conceptual short-term memory (CSTM) running parallel in time to such a phonological store. The primary aim of the current study was to evaluate two main tenets of the CSTM model: that linguistic context biases selection of information entering the conceptual store, and that information not integrated into a coherent structure is rapidly forgotten. Results confirmed these predictions for spoken sentences heard by both young and older adults, supporting the generality of the model and suggesting that CSTM remains stable in normal aging.
Guest Editor's Preface: Second International Conference on the
Frontiers of Plasma Physics and Technology
Authors: Desai Tara , Pant H.C.
Published: March 2008

The Second International Conference on the Frontiers of Plasma Physics
and Technology was held in Goa, India, from February 21–25, 2005.
This conference explored a number of fundamental and applied plasma
physics topics. Special attention was focused on the exploration of
frontiers in physics and technology of high energy density plasmas—a
topic growing at a very fast pace due to the emergence of extremely
powerful laser sources. Reviews on activities and new opportunities for
large laser facilities in prominent laboratories of Asia, Europe, and
Canada were presented. Talks on recent advances on laser driven Wakefield
particle acceleration scheme were very exciting. This technology has a
strong potential of revolutionizing the existing accelerator physics,
technology, and radiation sources such as synchrotrons and X-ray
free-electron lasers. Discussions were also given on the generation of
extreme physical conditions similar to those existing in astrophysical
objects, under laboratory conditions using intense lasers. This technique
may lead to an easy and inexpensive way to simulate and understand a
variety of astrophysical phenomena. This aspect of realization of
astrophysical conditions in a laboratory has now become reality, and soon
may lead to routine experiments. New applications of laser in the designs
of light-crafts may soon become reliable.
From laser produced Debye layers in plasma to a theory of nuclear forces and quark-gluon plasmas
Authors: HORA HEINRICH
Published: March 2008

A new theory for the nuclear forces for confining the nucleons in a nucleus was derived from a generalization of the Debye layer as known from the plasma ablation at laser irradiation where the temperature is substituted by the Fermi energy of the statistics of nucleons. The first convincing proof is by using the empirical density of the nucleons defining their Fermi energy to arrive at a Debye length of about 3 fm as measured by Hofstadter for the decay of the nucleon density at the surface of heavy nuclei. Taking then the surface tension of plasmas with the same steps of substituting temperature by Fermi energy, the surface energy of nuclei is always too small against the nucleon enthalpy to confine the nucleons until equilibrium is reduced at about such high densities reproducing the well known radii of nuclei. The Hofstadter decay can be interpreted as the inhomogeneous wave of the nucleons by Wigner scattering at the nuclear surface similar to the Goos-Haenchen effect. By this way, nuclei are possible only until uranium or curium by a Boltzmann equilibrium process explaining the endothermic generation of heavy nuclei. At about six times higher nucleon density, the Fermi statistics changes into its relativistic branch resulting in a surface energy always smaller than before, and the mass and density independence indicates that one cannot distinguish between the state as in a neutron star or as a quark-gluon plasma. The steps from the ablation of laser produced plasma via a quantum theory of the surface tension in metals to the new nuclear force theory are explained. A consideration of the magic numbers indicates a quark-shell structure of nuclei.
Pico- and microsecond laser ablation of dental restorative
materials
Authors: WIEGER V. , STRASSL M. , WINTNER E.
Published: March 2008

For biological hard tissues as well as for artificial restoration
materials, ultra-short laser pulses (USLP) have proven their suitability
for ablation with negligible collateral damage providing many advantages.
For this paper, it was the aim to investigate the suitability of scanned
USLP for the ablation of dental restorative materials compared to the
microsecond pulses of conventional Erbium lasers. Scanning electron
microscopy allowed analyzing the quality of the cavity surfaces with
respect to structural properties as well as temperature exposition.
Quantitative results about the ablation efficiency are given for different
laser parameters on dental hard tissue and a broad variety of dental
restoration materials, the latter being reported for the first time.
Transport of heavy-ion beams in a 1 m free-standing plasma
channel
Authors: NEFF S. , KNOBLOCH R. , HOFFMANN D.H.H. , TAUSCHWITZ A. , YU S.S.
Published: March 2008

The transport of high-current heavy-ion beams in plasma channels is a
promising option for the final transport in a heavy-ion fusion reactor,
since it simplifies the construction of the reactor chamber significantly.
Our experiments at the Gesellschaft für Schwerionenforschung
demonstrate the creation of 1 m long stable plasma channels and the
transport of heavy-ion beams. The article outlines the experimental setup
used at GSI and reports the results of beam transport measurements using
these long channels. The experiments demonstrate good beam transport
properties of the channel, indicating that channel transport is a viable
alternative to neutralized-ballistic transport.
Experimental prospects at the Canadian advanced laser light source
facility
Authors: OZAKI T. , KIEFFER J.-C. , TOTH R. , FOURMAUX S. , BANDULET H.
Published: March 2008

We describe here the present status of the Advanced Laser Light Source
(ALLS) facility, a state-of-the-art multi-beam Ti:sapphire laser system
presently under construction in Canada. ALLS is a national user facility
to be commissioned in 2005 at the INRS campus near Montreal. The 25 fs
ALLS multi-beam laser system has three components, each with different
repetition rate and output energy. These multiple laser beams will be used
to generate a “rainbow” of femtosecond pulses from the far
infrared to hard X-rays, which can be combined to perform unique
experiments, such as dynamic molecular imaging. In this paper, we describe
two examples of experiments that are planned by our group with the ALLS
facility. The first is the highly efficient generation of high-order
harmonics using ablation medium. We demonstrate the generation of up to
the 53rd harmonics (λ = 15 nm) of a Ti:sapphire laser pulse
(150 fs, 10 mJ), using pre-pulse (210 ps, 24 mJ) produced boron ablation
as the nonlinear medium. The second example is the demonstration of
in-line phase-contrast imaging with an ultrafast (300 fs) laser-based hard
X-ray source (Mo K-α line). Images of biological samples have shown
great enhancement of contrast due to this technique, distinguishing
details that are barely observable or even undetectable in absorption
images.
Particle simulation of acceleration of quasineutral plasma blocks by short laser pulses
Authors: KLIMO O. , LIMPOUCH J.
Published: March 2008

Acceleration of quasineutral plasma blocks by ponderomotive force induced by normally incident short laser pulse is studied here via 1D3V Particle-In-Cell (PIC) simulations. Very high current densities 109–1011Acm−2of accelerated ions are observed for maximum laser intensities in the range 1016–1018Wcm−2on solid hydrogen target. Ion acceleration process is traced here via evolution of ion density and of ion velocity distribution. Basic parameters of the accelerated plasma blocks are determined from temporally integrated ion distributions. Our results provide more detailed information than the previous analytical estimates (Hora, 2003) and the two-fluid 1D hydrodynamic simulations (Glowaczet al., 2004).
Electromagnetic solitary waves in the saturation regime of
stimulated Brillouin backscattering
Authors: LONTANO M. , PASSONI M. , RICONDA C. , TIKHONCHUK V.T. , WEBER S.
Published: March 2008

Recent particle-in-cell simulations of the stimulated Brillouin
backscattering (SBBS) of electromagnetic radiation have shown that even at
sub-relativistic intensities (Iλ2 =
1016 Wμm2/cm2) non-drifting
solitary waves, “solitons” for short, are easily produced, and
remain almost unchanged all along the simulation time, typically for
several thousands of optical cycles. They appear in the form of stable
local concentrations of electromagnetic radiation trapped inside
quasi-neutral density holes. The plasma density inhomogeneity associated
with their presence disrupts the resonant SBBS amplification. The
cavitation process is accompanied by strong electron and ion heating. The
physical characteristics of such solitons are discussed and they are
compared with the theoretical predictions of an analytical model for
localized solution of the Maxwell equations in warm plasma.
Modeling of the electrostatic sheath shape on the rear target
surface in short-pulse laser-driven proton acceleration
Authors: BRAMBRINK ERIK , ROTH MARKUS , BLAZEVIC ABEL , SCHLEGEL THEODOR
Published: March 2008

Proton beams, generated in the interaction process of short
ultra-intense laser pulses with thin foils, carry imprints of rear side
target structures. These intensity patterns, imaged with a particle
detector, sometimes show slight deformations. We propose an analytical
model to describe these deformations by the spatial shape of a
monoenergetic layer of protons in the beginning of free proton
propagation. We also present results of simulations, which reproduce the
detected structures and allow finally making quantitative conclusions on
the shape of the layer. In experiments with electrically conducting
targets, the shape is always close to a parabolic one independently on
target thickness or laser parameters. Since the protons are pulled by the
free electrons, there must be a strong correlation to the electron space
charge distribution on the rear side of the illuminated foil. Simulations
demonstrate that the deformations in the detected patterns of the proton
layers are very sensitive to the initial layer shape. Analyzing spatial
structures of the generated proton beams we can indirectly conclude on
electron transport phenomena in the overdense part of the target.
Editorial from the Editor in Chief
Authors: Hoffmann Dieter H.H.
Published: March 2008

The journal ofLaser and Particle Beamswants to take this opportunity to congratulate Dr. Max Tabak and Dr. Joseph D. Kilkenny on the occasion of being selected by the American Nuclear Society as winners of the 2005 Edward Teller award. Both scientists were recognized for their pioneering work in the field of fusion research. Nuclear fusion and especially inertial confinement fusion constitutes a specific field of interest which is frequently discussed in this Journal. Both scientists have previously contributed to this journal, and we are very proud that our recent December 2005 issue carried an article by Kilkennyet al.(2005), related to this topic. The same issue carries articles by two former Teller Award winners (Hora, 2005; Mileyet al., 2005).
Kinematic analysis and path planning of a new kinematically redundant planar parallel manipulator
Authors: Ebrahimi Iman , Carretero Juan A. , Boudreau Roger
Published: March 2008

In this work, the 3-RPRR, a new kinematically redundant planar parallel manipulator with six-degrees-of-freedom, is presented. First, the manipulator is introduced and its inverse displacement problem discussed. Then, all types of singularities of the 3-RPRR manipulator are analysed and demonstrated. Thereafter, the dexterous workspace is geometrically obtained and compared with the non-redundant 3-PRR planar parallel manipulator. Finally, based on a geometrical measure of proximity to singular configurations and the condition number of the manipulators' Jacobian matrices, actuation schemes for the manipulators are obtained. Different actuation schemes for a given path are obtained and the quality of their actuation schemes are compared. It is shown that the proposed manipulator is capable of following a path while avoiding the singularities.
Semantically routing queries in peer-based systems: the H-Link approach
Authors: MONTANELLI STEFANO , CASTANO SILVANA
Published: March 2008

A challenging issue to advance the existing P2P semantic routing protocols is related to the capability of developing mechanisms for focused selection of the query recipients by taking into account a semantically rich description of the context of each peer. In this article, we present the H-Link semantic routing approach designed to exploit the results of an ontology matchmaking process for providing a semantic overlay network where peers having similar contexts are recognized and interlinked as semantic neighbors. In particular, H-Linkaims at advancing the existing semantic routing protocols by combining ontology-based peer context descriptions and ontology matching techniques for providing query forwarding on a real semantic basis, in a completely decentralized way.
A context-sensitive framework for lexical ontologies
Authors: VEALE TONY , HAO YANFEN
Published: March 2008

Human categorization is neither a binary nor a context-free process. Rather, the criteria that govern the use and recognition of certain concepts may be satisfied to different degrees in different contexts. In light of this reality, the idealized, static structure of a lexical-ontology like WordNet appears both excessively rigid and unduly fragile when faced with real texts that draw upon different contexts to communicate different world-views. In this paper we describe a syntagmatic, corpus-based approach to redefining the concepts of a lexical-ontology like WordNet in a functional, gradable and context-sensitive fashion. We describe how the most diagnostic properties of concepts, on which these functional definitions are based, can be automatically acquired from the Web, and demonstrate how these properties are more predictive of how concepts are actually used and perceived than properties derived from other sources (such as WordNet itself).
Breakfast skipping is associated with differences in meal patterns, macronutrient intakes and overweight among pre-school children
Authors: Dubois Lise , Girard Manon , Potvin Kent Monique , Farmer Anna , Tatone-Tokuda Fabiola
Published: March 2008

Objectives

To examine the association between skipping breakfast, daily energy, macronutrients and food intakes, and BMI in pre-school children.

Design

A cross-sectional study using information on children’s food consumption and measured height and weight. Energy and macronutrient intakes of the children were derived from parent/day-care attendant’s responses to 24 h recall interviews and eating behaviour questionnaires.

Setting

Data obtained from a representative sample (n2103) of children born in Quebec (Canada) in 1998.

Subjects

One thousand five hundred and forty-nine children, with a mean age of 49 (sd3·12) months.

Results

Ten per cent of children ate breakfast on fewer than 7 days per week. This behaviour was associated with a lower diet quality and concentrated energy intakes through higher protein intakes at lunch and the consumption of snacks higher in energy and carbohydrate in the afternoon and evening; yet total daily energy intakes were not significantly different from those of pre-school children who ate breakfast every day. Breakfast skippers’ mean BMI increased as intake of energy, carbohydrates or servings of grain products increased; however, this was not the case for breakfast eaters. When Cole’s cut-off for overweight/obesity was used, overweight/obesity in breakfast skippers was related to the dinner-time consumption of approximately 3000 kJ (700 kcal) or more for energy intake, approximately 100 g or more of carbohydrates, or approximately 3 servings or more of grain products.

Conclusions

Eating breakfast every day is associated with having a healthy body weight, likely due to a more even distribution of energy intake across meals throughout the day.
Gender and Conditional Support for Torture in the War on Terror
Authors: Haider-Markel Donald P. , Vieux Andrea
Published: March 2008

The events of September 11 have clearly changed the way that Americans think about politics and policy and may have changed attitudes about the treatment of America's perceived enemies. At the same time, revelations about American interrogation techniques in the war on terror have forced a national dialogue on human rights during a time of war. Americans do tend to oppose a variety of harsh interrogation techniques, but opposition appears to be conditioned by gender, partisanship, and the context in which an interrogation might take place. We explore how conditions shape attitudes on interrogation techniques in the war on terror, with a particular focus on gender and contextual framing. We analyze data from a unique 2004 national survey of American adults to test several hypotheses. Our results suggest that gender strongly shapes opposition to harsh interrogation techniques, but contextual framing also shapes opposition. Partisanship and contextual framing also mediate the influence of gender on attitudes.
Sports Talk: How Gender Shapes Discursive Framing of Title IX
Authors: Rosenthal Cindy Simon
Published: March 2008

Existing scholarship has shown that the media and interest groups play an important role in the shaping of the public's perception of reality and in establishing the quality of democratic discourse on public policy questions. In turn, interest group actors employ different media and grassroots strategies in hopes of exploiting discursive opportunities that advance their cause. This study explores recent public policy debates over Title IX to illustrate how gender undergirds the discursive framing choices made by interest groups and presented in the media coverage. I find that framing, especially in the media, reinforces enduring cultural aspects of masculinity in sports.
Women in International Relations
Authors: Maliniak Daniel , Oakes Amy , Peterson Susan , Tierney Michael J.
Published: March 2008

Women now receive political science degrees in record numbers, but female representation among political science faculty still lags behind that of many other disciplines. Only 26% of the 13,000 political science professors in the United States today are women (Sedowski and Brintall 2007). According to our recent survey of international relations faculty in the United States—the 2006 Teaching, Research, and International Politics (TRIP) Survey—women comprise an even smaller proportion of IR scholars: 77% of the IR faculty respondents are men, while only 23% are women. Even more than their counterparts in the wider field of political science, women in IR tend to be more junior and less likely to hold tenure than their male colleagues. Women comprise a minority at every level of the profession, but they are most scarce at the full professor level: Only 17% of political science professors and 14% of IR professors are women (Maliniak et al. 2007c; Sedowski and Brintall 2007).
Widespread remagnetizations and a new view of Neogene tectonic rotations within the Australia‐Pacific plate boundary zone, New Zealand
Authors: Rowan Christopher J. , Roberts Andrew P.
Published: March 2008

Large, clockwise, vertical axis tectonic rotations of the Hikurangi margin, East Coast, New Zealand, have been inferred over both geological and contemporary timescales, from paleomagnetic and geodetic data, respectively. Previous interpretations of paleomagnetic data have laterally divided the margin into independently rotating domains; this is not a feature of the short‐term velocity field, and it is also difficult to reconcile with the large‐scale boundary forces driving the rotation. New paleomagnetic results, rigorously constrained by field tests, demonstrate that late diagenetic growth of the iron sulfide greigite has remagnetized up to 65% of sampled localities on the Hikurangi margin. When these remagnetizations are accounted for, similar rates, magnitudes, and timings of tectonic rotation can be inferred for the entire Hikurangi margin south of the Raukumara Peninsula in the last 7–10 Ma. Numerous large (50–80°) declination anomalies from magnetizations acquired in the late Miocene require much greater rates of rotation (8–14° Ma−1) than the presently observed rate of 3–4° Ma−1, which is only likely to be characteristic of the tectonic regime established since 1–2 Ma. These new results are consistent with both long‐ and short‐term deformation on the Hikurangi margin being driven by realignment of the subducting Pacific plate, with collision of the Hikurangi Plateau in the late Miocene potentially being key to both the initiation of tectonic rotations and the widespread remagnetization of Neogene sediments. However, accommodating faster, more coherent rotation of the Hikurangi margin in Neogene reconstructions of the New Zealand plate boundary region, particularly in the late Miocene, remains a challenge.
Dynamic theory of relativistic electrons stochastic heating by whistler mode waves with application to the Earth magnetosphere
Authors: Khazanov G. V. , Tel'nikhin A. A. , Kronberg T. K.
Published: March 2008

In the Hamiltonian approach, electron motion in a coherent packet of the whistler mode waves propagating along the direction of an ambient magnetic field is studied. The physical processes by which these particles are accelerated to high energy are established. Equations governing particle motion are transformed into a closed pair of nonlinear difference equations. The solutions of these equations show there exists a threshold in initial electron energy, below which electron motion is regular and above which electron motion is stochastic. Particle energy spectra and pitch angle electron scattering are described by the Fokker‐Planck‐Kolmogorov equations. A calculation of the stochastic diffusion of electrons due to a spectrum of whistler modes is presented. The parametric dependence of the diffusion coefficients on the plasma particle density, magnitude of wave field, and the strength of magnetic field is studied. It is shown that significant pitch angle diffusion occurs for the Earth radiation belt electrons with energies from a few keV up to a few MeV.
Electron temperature anisotropy constraints in the solar wind
Authors: Štverák Štěpán , Trávníček Pavel , Maksimovic Milan , Marsch Eckart , Fazakerley Andrew N. , Scime Earl E.
Published: March 2008

We have performed a statistical study of a substantial amount of electron data acquired in the solar wind to understand the constraints on electron temperature anisotropy by plasma instabilities and Coulomb collisions. We use a large data set of electron measurements from three different spacecraft (Helios I, Cluster II, and Ulysses) collected in the low ecliptic latitudes covering the radial distance from the Sun from 0.3 up to 4 AU. We estimate the electron temperature anisotropy using fits of the measured electron velocity distribution functions acquired in situ. We use a two population (core and halo) analytical model and properties of both populations are studied separately. We examine all the acquired data in terms of temperature anisotropy versus parallel electron plasma beta, and we relate the measurements to the growth rates of unstable modes. The effect of Coulomb collisions is expressed by the electron collisional age Ae defined as the number of collisions suffered by an electron during the expansion of the solar wind. We show that both instabilities and collisions are strongly related to the isotropisation process of the electron core population. In addition we examine the radial evolution of these effects during the expansion of the solar wind. We show that the bulk of the solar wind electrons are constrained by Coulomb collisions, while the large departures from isotropy are constrained by instabilities.
Two‐stage oscillatory response of the magnetopause to a tangential discontinuity/vortex sheet followed by northward IMF: Cluster observations
Authors: Farrugia C. J. , Gratton F. T. , Lund E. J. , Sandholt P. E. , Cowley S. W. H. , Torbert R. B. , Gnavi G. , Mann I. R. , Bilbao L. , Mouikis C. , Kistler L. , Smith C. W. , Singer H. J. , Watermann J. F.
Published: March 2008

We discuss the motion and structure of the magnetopause/boundary layer observed by Cluster in response to a joint tangential discontinuity/vortex sheet (TD/VS) observed by the Advanced Composition Explorer spacecraft on 7 December 2000. The observations are then supplemented by theory. Sharp polarity reversals in the east‐west components of the field and flow By and Vy occurred at the discontinuity. These rotations were followed by a period of strongly northward interplanetary magnetic field (IMF). These two factors elicited a two‐stage response at the magnetopause, as observed by Cluster situated in the boundary layer at the duskside terminator. First, the magnetopause suffered a large deformation from its equilibrium position, with large‐amplitude oscillations of ∼3‐min period being set up. These are argued to be mainly the result of tangential stresses associated with ΔVy the contribution of dynamic pressure changes being small in comparison. This strengthens recent evidence of the importance to magnetospheric dynamics of changes in azimuthal solar wind flow. The TD/VS impact caused a global response seen by ground magnetometers in a magnetic local time range spanning at least 12 h. The response monitored on ground magnetometers is similar to that brought about by magnetopause motions driven by dynamic pressure changes. Second, Cluster recorded higher‐frequency waves (∼79 s). Two clear phases could be distinguished from the spectral power density, which decreased by a factor of ∼3 in the second phase. Applying compressible linearized MHD theory, we show that these waves are generated by the Kelvin‐Helmholtz (KH) instability. Varying the local magnetic shear at the Cluster locale, as suggested by the temporal profile of the IMF clock angle, we find that locally stability was reinstated, so that the reduced power in the second phase is argued to be due residual KH activity arriving from locations farther to the dayside.
Impact of ocean carbon system variability on the detection of temporal increases in anthropogenic CO2
Authors: Levine Naomi Marcil , Doney Scott C. , Wanninkhof Rik , Lindsay Keith , Fung Inez Y.
Published: March 2008

Estimates of temporal trends in oceanic anthropogenic carbon dioxide (CO2) rely on the ability of empirical methods to remove the large natural variability of the ocean carbon system. A coupled carbon‐climate model is used to evaluate these empirical methods. Both the ΔC* and multiple linear regression (MLR) techniques reproduce the predicted increase in dissolved inorganic carbon for the majority of the ocean and have similar average percent errors for decadal differences (24.1% and 25.5%, respectively). However, this study identifies several regions where these methods may introduce errors. Of particular note are mode and deep water formation regions, where changes in air‐sea disequilibrium and structure in the MLR residuals introduce errors. These results have significant implications for decadal repeat hydrography programs, indicating the need for subannual sampling in certain regions of the oceans in order to better constrain the natural variability in the system and to robustly estimate the intrusion of anthropogenic CO2.
Urban photochemistry in central Tokyo: 2. Rates and regimes of oxidant (O3 + NO2) production
Authors: Kanaya Yugo , Fukuda Masato , Akimoto Hajime , Takegawa Nobuyuki , Komazaki Yuichi , Yokouchi Yoko , Koike Makoto , Kondo Yutaka
Published: March 2008

Net photochemical production rates of oxidant (Ox = O3 + NO2), F‐D(Ox), were determined in Tokyo during the winter and summer of 2004 using observed and calculated HO2 radical concentrations. In both cases, calculated RO2 (organic peroxy) radical concentrations were used. The rates calculated using the two HO2 data sets are similar. In summer, morning F‐D(Ox) values on smog days (those with midday O3 concentrations exceeding 100 ppbv) were higher than those on smog‐free days (with typical midday O3 concentrations of 30 ppbv); however, the amount of ozone produced in a single day, as estimated by integrating F‐D(Ox) over the daytime, was not significantly different for the two periods. This analysis suggests that the occurrence of smog events in the city center cannot readily be explained by day‐to‐day variations in the strength of in situ photochemistry. On smog days, the coupling of photochemistry and meteorology appears to be important, as air masses in which oxidants accumulated over successive days arrive at the city center at approximately midday, transported by land‐sea breeze circulation. The average maximum daytime F‐D(Ox) values in summer, 11 and 13 ppbv h−1 using observed and calculated HO2 levels, respectively, were only 1.5 and 2.2 times higher than those in winter (8 and 6 ppbv h−1). In winter, an underestimation of HO2 levels at high NO concentrations resulted in an underestimation of F‐D(Ox) when calculated using modeled HO2. While the model predicted a volatile organic compounds (VOC)‐limited regime for Ox production in winter, F‐D(Ox) based on observed HO2 did not show features of the VOC‐limited regime and only steadily increased with increasing NO mixing ratio, even when it exceeded 20 ppbv. In summer, the dependence of F‐D(Ox) on nonmethane hydrocarbons (NMHCs) and NOx concentrations was similar in the two cases, in which observed and calculated HO2 levels were used. A VOC‐limited regime, predicted on smog‐free days, changed to a NOx‐limited regime on smog days. The F‐D(Ox) values determined for Tokyo are also compared with values for other cities.
Nucleation mode particles in upslope valley winds at Mount Norikura, Japan: Implications for the vertical extent of new particle formation events in the lower troposphere
Authors: Nishita Chiharu , Osada Kazuo , Kido Mizuka , Matsunaga Katsuji , Iwasaka Yasunobu
Published: March 2008

Number‐size distributions of atmospheric aerosol particles of 9–300 nm diameter were observed along with SO2 and NH3 concentrations at Mount Norikura, Japan (36.1°N, 137.5°E, 2770 m asl), during September 2001 and August–September 2002. Particle size distributions between the free troposphere and the mixed layer were measured at the site under local wind system conditions, comprising downslope mountain and upslope valley winds. The local wind system was well developed under clear‐sky conditions and was determined according to temporal variation of the water vapor mixing ratio at the site. Nucleation mode particles were observed on 4 of 23 clear‐sky days during our observation periods. Nucleation mode particles were observed in the mixed layer air, but never in the free tropospheric air, suggesting that new particle formation occurred in the air transported from the mixed layer. Nucleation‐mode‐particle growth rates during new particle formation events were 2.6–3.1 nm h−1. Preexisting particle concentrations on event days were about half those of nonevent sunny days on average, but no positive correlation was found between the events and either SO2 or NH3 concentrations. The events always occurred in a cold air mass advected from the north behind cold fronts. Horizontal advection of the northern cold air mass might bring a clean air mass with low preexisting particle concentration in the mixed layer and trigger a new particle formation event at Mount Norikura.
Use of FLUXNET in the Community Land Model development
Authors: Stöckli R. , Lawrence D. M. , Niu G.‐Y. , Oleson K. W. , Thornton P. E. , Yang Z.‐L. , Bonan G. B. , Denning A. S. , Running S. W.
Published: March 2008

The Community Land Model version 3 (CLM3.0) simulates land‐atmosphere exchanges in response to climatic forcings. CLM3.0 has known biases in the surface energy partitioning as a result of deficiencies in its hydrological and biophysical parameterizations. Such models, however, need to be robust for multidecadal global climate simulations. FLUXNET now provides an extensive data source of carbon, water and energy exchanges for investigating land processes, and it encompasses a global range of ecosystem‐climate interactions. Data from 15 FLUXNET sites are used to identify and improve model deficiencies. Including a prognostic aquifer, a bare soil evaporation resistance formulation and numerous other changes in the model result in a significantly improved soil hydrology and energy partitioning. Terrestrial water storage increased by up to 300 mm in warm climates and decreased in cold climates. Nitrogen control of photosynthesis is revealed as another missing process in the model. These improvements increase the correlation coefficient of hourly and monthly latent heat fluxes from a range of 0.5–0.6 to the range of 0.7–0.9. RMSE of the simulated sensible heat fluxes decrease by 20–50%. Primary production is overestimated during the wet season in mediterranean and tropical ecosystems. This might be related to missing carbon‐nitrogen dynamics as well as to site‐specific parameters. The new model (CLM3.5) with an improved terrestrial water cycle should lead to more realistic land‐atmosphere exchanges in coupled simulations. FLUXNET is found to be a valuable tool to develop and validate land surface models prior to their application in computationally expensive global simulations.
Uncertainties in seawater thermometry deriving from intratest and intertest Mg/Ca variability in Globigerinoides ruber
Authors: Sadekov Aleksey , Eggins Stephen M. , De Deckker Patrick , Kroon Dick
Published: March 2008

Laser ablation inductively coupled plasma–mass spectrometry microanalysis of fossil and live Globigerinoides ruber from the eastern Indian Ocean reveals large variations of Mg/Ca composition both within and between individual tests from core top or plankton pump samples. Although the extent of intertest and intratest compositional variability exceeds that attributable to calcification temperature, the pooled mean Mg/Ca molar values obtained for core top samples between the equator and >30°S form a strong exponential correlation with mean annual sea surface temperature (Mg/Ca mmol/mol = 0.52 exp0.076SST°C, r2 = 0.99). The intertest Mg/Ca variability within these deep‐sea core top samples is a source of significant uncertainty in Mg/Ca seawater temperature estimates and is notable for being site specific. Our results indicate that widely assumed uncertainties in Mg/Ca thermometry may be underestimated. We show that statistical power analysis can be used to evaluate the number of tests needed to achieve a target level of uncertainty on a sample by sample case. A varying bias also arises from the presence and varying mix of two morphotypes (G. ruber ruber and G. ruber pyramidalis), which have different mean Mg/Ca values. Estimated calcification temperature differences between these morphotypes range up to 5°C and are notable for correlating with the seasonal range in seawater temperature at different sites.
On the cause of the 1908 Messina tsunami, southern Italy
Authors: Billi Andrea , Funiciello Renato , Minelli Liliana , Faccenna Claudio , Neri Giancarlo , Orecchio Barbara , Presti Debora
Published: March 2008

A century after the catastrophic event, the sources of the 1908 Messina, Southern Italy, earthquake and tsunami, which caused at least 60,000 deaths, remain uncertain. Through a simple backward ray‐tracing method, we convert the tsunami travel‐time data reported in a 100‐years‐old paper into distances and find that the sources of the earthquake and tsunami are different. Overturning a long‐held assumption, reconsideration of the available tsunami, bathymetric, seismic, and seismological data indicates that the tsunami was generated by an underwater landslide.
Zinc cysteine active sites of metalloproteins: A density functional theory and x-ray absorption fine structure study
Authors: Dimakis Nicholas , Farooqi Mohammed Junaid , Garza Emily Sofia , Bunker Grant
Published: March 2008

Density functional theory (DFT) and x-ray absorption fine structure (XAFS) spectroscopy are complementary tools for the biophysical study of active sites in metalloproteins. DFT is used to compute XAFS multiple scattering Debye Waller factors, which are then employed in genetic algorithm-based fitting process to obtain a global fit to the XAFS in the space of fitting parameters. Zn-Cys sites, which serve important functions as transcriptional switches in Zn finger proteins and matrix metalloproteinases, previously have proven intractable by this method; here these limitations are removed. In this work we evaluate optimal DFT nonlocal functionals and basis sets for determining optimal geometries and vibrational densities of states of mixed ligation Zn(His)4−n(Cys)n sites. Theoretical results are compared to experimental XAFS measurements and Raman spectra from the literature and tabulated for use.
Effect of Cr-doping on the magnetic and electrical properties of La0.4Ca0.6MnO3
Authors: Wenger L. E. , Tsoi G. M. , Suryanarayanan R. , Sudyoadsuk T.
Published: March 2008

The magnetic and electrical properties of electron-doped manganite La0.4Ca0.6Mn1−yCryO3 polycrystalline samples (y=0.02, 0.04, and 0.06) prepared by a sol-gel technique have been investigated between 5 and 325K in magnetic fields ranging from 0to5T. Both the M-T and M-H data indicate that these Cr-doped manganites exhibit multiple ferromagnetic phases in which the relative amounts of each phase and temperatures of their appearance change with Cr content. The temperature dependence of the zero-field resistivity indicates that a transition occurs below 150K from an insulating (semiconducting) behavior to a behavior exhibiting a temperature-independent plateau with the magnitude of a semimetal. In addition a large field-induced behavior is found in both the magnetoresistance and magnetization at temperatures correlated to the ferromagnetic semimetallic phase being induced, which results in a large magnetoresistance at the lowest temperatures.
Neutral depletion versus repletion due to ionization
Authors: Fruchtman A. , Makrinich G. , Raimbault J.-L. , Liard L. , Rax J.-M. , Chabert P.
Published: March 2008

Recent theoretical analyses which predicted unexpected effects of neutral depletion in both collisional and collisionless plasmas are reviewed. We focus on the depletion of collisionless neutrals induced by strong ionization of a collisionless plasma and contrast this depletion with the effect of strong ionization on thermalized neutrals. The collisionless plasma is analyzed employing a kinetic description. The collisionless neutrals and the plasma are coupled through volume ionization and wall recombination only. The profiles of density and pressure both of the plasma and of the neutral-gas and the profile of the ionization rate are calculated. It is shown that for collisionless neutrals the ionization results in neutral depletion, while when neutrals are thermalized the ionization induces a maximal neutral-density at the discharge center, which we call neutral repletion. The difference between the two cases stems from the relation between the neutral density and pressure. The pressure of the collisionless neutral-gas turns out to be maximal where its density is minimal, in contrast to the case of a thermalized neutral gas.
Edgeworth expansion of the largest eigenvalue distribution function of Gaussian unitary ensemble revisited
Authors: Choup Leonard N.
Published: March 2008

We derive expansions of the resolvent Rn(x,y;t)=(Qn(x;t)Pn(y;t)−Qn(y;t)Pn(x;t))∕(x−y) of the Hermite kernel Kn at the edge of the spectrum of the finite n Gaussian unitary ensemble (GUEn) and the finite n-expansion of Qn(x;t) and Pn(x;t). Using these large n-expansions, we give another proof of the derivation of an Edgeworth type theorem for the largest eigenvalue distribution function of GUEn. These large n-expansions are essential ingredients in the derivation of our results for Gaussian orthogonal ensemble (GOEn) (Choup, L. N., arXiv:0801.2620v1) where we give explicit n−1∕3 and n−2∕3 correction terms to the limiting GOE Tracy–Widom distribution function.
Abrupt InGaP∕GaAs heterointerface grown by optimized gas-switching sequence in metal organic vapor phase epitaxy
Authors: Nakano Takayuki , Shioda Tomonari , Abe Eiji , Sugiyama Masakazu , Enomoto Naomi , Nakano Yoshiaki , Shimogaki Yukihiro
Published: March 2008

Fabrication of abrupt InGaP∕GaAs heterointerfaces has been difficult using metal organic vapor phase epitaxy (MOVPE) due to the exchange of P and As during the fabrication steps. An optimized gas-switching sequence to fabricate heterointerface of InGaP on GaAs layer by MOVPE was previously developed in which the unstable top surface layer of GaAs is stabilized and the exchange of P and As between InGaP and GaAs layers is suppressed. In this study, the effect of this optimized gas-switching sequence was quantitatively evaluated by using scanning transmission electron microscopy (STEM). Changes in atomic composition from GaAs to InGaP at the interface at the atomic layer level were revealed by using Z-contrast method in STEM. Quantitative evaluation using the Z-contrast method confirmed that the abruptness of the GaAs∕InGaP interface was improved by this optimized gas-switching sequence.