bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of learning on the oviposition preference of field-collected and laboratory-reared Chilo partellus (Lepidoptera: Crambidae) populations
Authors: Glas J.J. , van den Berg J. , Potting R.P.J.
Published: July 2007

Recent studies show that Vetiver grass, (Vetiveria zizanioides (L.) Nash), may have potential as a dead-end trap crop in an overall habitat management strategy for the spotted stem borer, Chilo partellus (Swinhoe) (Lepidoptera: Crambidae). Vetiver grass is highly preferred for oviposition, in spite of the fact that larval survival is extremely low on this grass. The oviposition behaviour of female Chilo partellus moths was investigated by determining the amount and size of egg batches allocated to maize and Vetiver plants and studying the effect of rearing conditions and oviposition experience on host plant selection. Two-choice preference tests were used to examine the effect of experience of maize (a suitable host plant) and Vetiver plants on the oviposition choice of C. partellus. For both field-collected and laboratory-reared moths, no significant differences were found in the preference distributions between the experienced groups. It is concluded that females do not learn, i.e. that they do not change their preference for Vetiver grass after having experienced oviposition on either maize or this grass, which supports the idea that trap cropping could have potential as a control method for C. partellus. Differences observed between field-collected and laboratory-reared moths in the amount and size of egg batches laid on maize and Vetiver grass indicate that data obtained from experiments with laboratory-reared insects should be treated with caution.
Seasonal mortality factors of the coffee leafminer,Leucoptera coffeella
Authors: Pereira E.J.G. , Picanço M.C. , Bacci L. , Crespo A.L.B. , Guedes R.N.C.
Published: July 2007

Seasonal population fluctuation of the coffee leafminer,Leucoptera coffeella(Guérin-Méneville & Perrottet) (Lepidoptera: Lyonetiidae), led to an investigation of its natural mortality factors during the rainy season when the population level is low and during the dry season when population peaks occur. Life-table data were colleted from insecticide-free plots within a 3 ha coffee plantation on the upper, medium and lower canopy. Leafminer mortality was similar among the canopy parts but varied in the two seasons studied. During the rainy season, the generational mortality averaged 94.3%, with 50.2, 33.7 and 10.4% occurring during egg, larval and pupal stages, respectively. During the dry season, total mortality was 89%, with 13.2, 61.0 and 14.8% occurring during egg, larval and pupal stages, respectively. Marginal mortality rates during the rainy season were highest for physiological disturbances, rainfall and egg inviability; but, in the dry season, they were highest for predaceous wasps, physiological disturbances and parasitoids. Egg and larval stages accounted for most of the mortality variation in the rainy season, while the combination of larval and pupal mortality better described the generational mortality in the dry season. Variation in mortality during the rainy season was primarily associated with egg inviability, rainfall and parasitoids. In contrast, predatory wasps and physiological disturbances were the main factors associated with mortality variation during the dry season. These results suggest that weather conditions, natural enemies and plant quality attributes are the main determinants of the population dynamics ofL. coffeella.
AdultBemisia tabacibiotype B can induce silverleafing in squash
Authors: De Barro P. , Khan S.
Published: July 2007

Bemisia tabacibiotype B is one of three genetic groups able to induce silverleafing in squash. Several earlier studies had observed that this physiological change was induced only through the feeding of juvenile whiteflies. This study uses adult males only to show that after 11 days the adult males were able to begin to induce silverleafing. Further, the response was density dependant with 120 adults inducing the first signs of silverleafing in 11 days, 90 adults in 13 days and 60 adults in 15 days.
Theoretical analysis of the zigzag instability of a vertical co-rotating vortex pair in a strongly stratified fluid
Authors: OTHEGUY PANTXIKA , BILLANT PAUL , CHOMAZ JEAN-MARC
Published: July 2007

A long-wavelength stability analysis of two co-rotating Gaussian vertical vortices in an inviscid strongly stratified fluid is conducted for vortices separated by a large distance b compared to their radius a (b ≫ a). This analysis predicts and explains the zigzag instability found by a numerical stability analysis in a companion paper (Otheguy, Chomaz & Billant, J. Fluid. Mech. vol. 553, 2006, p. 253). The zigzag instability results from the coupling between the bending perturbations of each vortex and the external strain that one vortex induces on the other S = Γ/2 π b2, where Γ is the circulation of the vortices. The analysis predicts that the maximum growth rate of the instability is twice the strain S and that the most unstable vertical wavelength λ scales as the buoyancy length, defined by LB = Γ/πaN, multiplied by the ratio b/a, i.e. λ ∝ Fhb, where Fh = Γ/πa2N is the horizontal Froude number. The asymptotic results are in very good agreement with the numerical results.
Recurrence of travelling waves in transitional pipe flow
Authors: KERSWELL R. R. , TUTTY O. R.
Published: July 2007

The recent theoretical discovery of families of unstable travelling-wave solutions in pipe flow at Reynolds numbers lower than the transitional range, naturally raises the question of their relevance to the turbulent transition process. Here, a series of numerical experiments are conducted in which we look for the spatial signature of these travelling waves in transitionary flows. Working within a periodic pipe of 5D (diameters) length, we find that travelling waves with low wall shear stresses (lower branch solutions) are on a surface in phase space which separates initial conditions which uneventfully relaminarize and those which lead to a turbulent evolution. This dividing surface (a separatrix if turbulence is a sustained state) is then minimally the union of the stable manifolds of all these travelling waves. Evidence for recurrent travelling-wave visits is found in both 5D and 10D long periodic pipes, but only for those travelling waves with low-to-intermediate wall shear stress and for less than about 10% of the time in turbulent flow at Re = 2400. Given this, it seems unlikely that the mean turbulent properties such as wall shear stress can be predicted as an expansion solely over the travelling waves in which their individual properties are appropriately weighted. Instead the onus is on isolating further dynamical structures such as periodic orbits and including them in any such expansion.
Stability of an evaporating thin liquid film
Authors: SHKLYAEV OLEG E. , FRIED ELIOT
Published: July 2007

We use a newly developed set of interface conditions to revisit the problem of an evaporating thin liquid film. In particular, instead of the conventional Hertz–Knudsen–Langmuir equation for the evaporation mass flux, we impose a more general equation expressing the balance of configurational momentum. This balance, which supplements the conventional conditions enforcing the balances of mass, momentum and energy on the film surface, arises from a consideration of configurational forces within a thermodynamical framework. We study the influence of two newly introduced terms on the evolution of the liquid film. One of these terms accounts for the transport of energy within the liquid–vapour interface. The other term, which we refer to as the effective pressure, accounts for vapour recoil. Both new terms are found to be stabilizing. Furthermore, the effective pressure is found to affect a time-dependent base state of the evaporating film and to be an important factor in applications involving liquid films with thicknesses of one or two monolayers. Specifically, we demonstrate that consideration of the effective pressure makes it possible to observe the influence of the van der Waals interactions on film evolution close to the instant of rupture. Dimensional considerations indicate that one of the most significant influences of these effects occurs for molten metals.
Effects of polymer stresses on eddy structures in drag-reduced turbulent channel flow
Authors: KIM KYOUNGYOUN , LI CHANG-F. , SURESHKUMAR R. , BALACHANDAR S. , ADRIAN RONALD J.
Published: July 2007

The effects of polymer stresses on near-wall turbulent structures are examined by using direct numerical simulation of fully developed turbulent channel flows with and without polymer stress. The Reynolds number based on friction velocity and half-channel height is 395, and the stresses created by adding polymer are modelled by a finite extensible nonlinear elastic, dumbbell model. Both low- (18%) and high-drag reduction (61%) cases are investigated. Linear stochastic estimation is employed to compute the conditional averages of the near-wall eddies. The conditionally averaged flow fields for Reynolds-stress-maximizing Q2 events show that the near-wall vortical structures are weakened and elongated in the streamwise direction by polymer stresses in a manner similar to that found by Stone et al. (2004) for low-Reynolds-number quasi-streamwise vortices (‘exact coherent states: ECS’). The conditionally averaged fields for the events with large contribution to the polymer work are also examined. The vortical structures in drag-reduced turbulence are very similar to those for the Q2 events, i.e. counter-rotating streamwise vortices near the wall and hairpin vortices above the buffer layer. The three-dimensional distributions of conditionally averaged polymer force around these vortical structures show that the polymer force components oppose the vortical motion. More fundamentally, the torques due to polymer stress are shown to oppose the rotation of the vortices, thereby accounting for their weakening. The observations also extend concepts of the vortex retardation by viscoelastic counter-torques to the heads of hairpins above the buffer layer, and offer an explanation of the mechanism of drag reduction in the outer region of wall turbulence, as well as in the buffer layer.
Gravity currents over fractured substrates in a porous medium
Authors: PRITCHARD DAVID
Published: July 2007

We consider the behaviour of a gravity current in a porous medium when the horizontal surface along which it spreads is punctuated either by narrow fractures or by permeable regions of limited extent. We derive steady-state solutions for the current, and show that these form part of a long-time asymptotic description which may also include a self-similar ‘leakage current’ propagating beyond the fractured region with a length proportional to t1/2. We discuss the conditions under which a current can be completely trapped by a permeable region or a series of fractures.
Velocity and vorticity in weakly compressible isotropic turbulence under longitudinal expansive straining
Authors: XANTHOS SAVVAS , GONG MINWEI , ANDREOPOULOS YIANNIS
Published: July 2007

The response of homogeneous and isotropic turbulence to streamwise straining action provided by planar expansion waves has been studied experimentally in the CCNY shock tube research facility at several Reynolds numbers. The reflection of a propagating shock wave at the open endwall of the shock tube generated an expansion fan travelling upstream and interacting with the induced flow behind the incident shock wave which has gone through a turbulence generating grid.

A custom-made hot-wire vorticity probe was designed and developed capable of measuring the time-dependent highly fluctuating three-dimensional velocity and vorticity vectors, and associated total temperature, in non-isothermal and inhomogeneous flows with reasonable spatial and temporal resolution. These measurements allowed the computations of the vorticity stretching/tilting terms, vorticity generation through dilatation terms, full dissipation rate of kinetic energy term and full rate-of-strain tensor. The longitudinal size of the straining zone was substantial so that measurements within it were possible. The flow accelerated from a Mach number of 0.23 to about 0.56, a value which is more than twice the initial one.

Although the average value of the applied straining was only betweenS11= 130 s−1andS11= 240 s−1and the gradient Mach number was no more than 0.226, the amplitude of fluctuations of the strain rateS11were of the order of 4000 s−1before the application of straining and were reduced by about 2.5 times downstream of the interaction. This characteristic of high-amplitude bursts and the intermittent behaviour of the flow play a significant role in the dynamics of turbulence.

One of the most remarkable features of the suppression of turbulence is that this process peaks shortly after the application of the straining where the pressure gradient is substantial. It was also found that the total enthalpy variation follows very closely the temporal gradient of pressure within the straining region and peaks at the same location as the pressure gradient.

Attenuation of longitudinal velocity fluctuations has been observed in all experiments. It appears that this attenuation depends strongly on the characteristics of the incoming turbulence for a given straining strength and flow Mach number. The present results clearly show that in most of the cases, attenuation occurs at large times or distances from the turbulence generating grids where length scales of the incoming flow are high and turbulence intensities are low. Thus, large eddies with low-velocity fluctuations are affected the most by the interaction with the expansion waves. Spectral analysis has indicated that attenuation of fluctuations is not the same across all wavenumbers of the spectrum. The magnitude of attenuation appears to be higher in cases of finer mesh grids.
Wave-free motions of isolated bodies and the existence of motion-trapped modes
Authors: EVANS D. V. , PORTER R.
Published: July 2007

A motion trapping structure can be defined as a freely floating structure under natural or externally applied restoring forces, on or below the free surface of a heavy fluid extending to infinity in at least one direction, which generates a persistent local time-harmonic oscillation of the fluid of finite energy at a particular frequency, due to its own motion at that frequency. Such an oscillation is termed a motion-trapped mode. In this paper it is shown, using accurate numerical computations, that a submerged circular cylinder making forced time-harmonic two-dimensional heave or sway motions of small amplitude in a fluid of either finite or infinite depth, can create a local flow field in which no waves radiate to infinity at particular frequencies and depths of submergence of the cylinder. By tethering such a buoyant cylinder to the bottom of a fluid of finite depth, using a vertical inelastic mooring line, it is shown, by suitable choice of buoyancy and length of tether, how the cylinder, moving freely under its mooring forces, can operate as a motion trapping structure. Such a cylinder would, if displaced from its equilibrium position and released, ultimately oscillate indefinitely at the trapped mode frequency. This simple geometry is the first example of a submerged isolated motion trapping structure free to move under its natural mooring forces.
Acoustic and auditory correlates of non-pulmonic sound production in German
Authors: Simpson Adrian P.
Published: July 2007

Different types of non-pulmonic sound production found in read and spontaneous German are described and exemplified. Stop releases driven by a glottalic airstream are found in sequences of final plosive plus glottalized vowel onset. Both ingressive and egressive velaric stop releases are considered to arise from double occlusions involving partial articulatory overlap in sequences of dorsal stop followed by an apical or bilabial stop. Certain aspects of the articulatory and aerodynamic mechanisms involved remain unclear. However, it is argued that an identification of these patterns in the acoustic record alone provides an invaluable insight into aspects of articulatory synchronization in types of spoken language, such as conversation, which are not generally amenable to the more intrusive methods of articulatory analysis.
Role of heat-labile serum factor or host complement in the inhibition ofPlasmodium falciparumsporogonic stages inAnopheles stephensiby gametocyte carriers' serological factors
Authors: GOUAGNA L. C. , VAN DER KOLK M. , ROEFFEN W. , VERHAVE J.-P. , ELING W. , SAUERWEIN R. , BOUDIN C.
Published: July 2007

This study investigated the significance of serum complement on transmission-reducing activity (TRA) of field sera from 24 infectedPlasmodium falciparumgametocyte carriers (from Cameroon) against cultured NF54P. falciparum.Laboratory-rearedAnopheles stephensiwere given infectious blood meals prepared either with sera from naïve Dutch donor (AB type) or pair-matched field serum samples, both with and without active complement. TRA of serum factors and host complement on mosquito infection rate and oocyst intensity were divided into the various components involved in the early stages of sporogony. The majority (>80%) of sera tested showed positive antibody titres to Pfs230, the relevant complement-dependent target of transmission-reducing mechanisms. Regardless of the presence of active complement, bloodmeals with field sera exhibited significantly lower infection rates and oocyst intensity than the control group. Serological reactivity in Capture-ELISA against Pfs230 was significantly correlated with the reduction of parasite infectivity. Contrary to our expectation, the presence of active complement in the mosquito bloodmeal did not increase parasite losses and therefore the magnitude of transmission reduction by individual immune sera. Our findings onP. falciparumare consistent with previous studies on animal hosts ofPlasmodium, indicating that earlyP. falciparumsporogonic stages may be insensitive to the antibody-dependent pathways of complement in human serum.
Uniformly bounded components of normality
Authors: WANG XIAOLING , ZHOU WANG
Published: July 2007

Suppose that f(z) is a transcendental entire function and that the Fatou set F(f)≠∅. Set

and

where the supremum supU is taken over all components of F(f). If B1(f)<∞ or B2(f)<∞, then we say F(f) is strongly uniformly bounded or uniformly bounded respectively. We show that, under some conditions, F(f) is (strongly) uniformly bounded.
Spectral synthesis on discrete Abelian groups
Authors: LACZKOVICH M. , SZÉKELYHIDI L.
Published: July 2007

We prove that spectral synthesis holds on a discrete Abelian group G if and only if the torsion free rank of G is finite.
Total curvature, ropelength and crossing number of thick knots
Authors: DIAO Y. , ERNST C.
Published: July 2007

We first study the minimum total curvature of a knot when it is embedded on the cubic lattice. Let $\mathcal{K}$ be a knot or link with a lattice embedding of minimum total curvature $\tau(\mathcal{K})$ among all possible lattice embeddings of $\mathcal{K}$. We show that there exist positive constants c1 and c2 such that $c_1\sqrt{Cr(\mathcal{K})}\le \tau(\mathcal{K})\le c_2 Cr(\mathcal{K})$ for any knot type $\mathcal{K}$. Furthermore we show that the powers of $Cr(\mathcal{K})$ in the above inequalities are sharp hence cannot be improved in general. Our results and observations show that lattice embeddings with minimum total curvature are quite different from those with minimum or near minimum lattice embedding length. In addition, we discuss the relationship between minimal total curvature and minimal ropelength for a given knot type. At the end of the paper, we study the total curvatures of smooth thick knots and show that there are some essential differences between the total curvatures of smooth thick knots and lattice knots.
On a parametric family of Thue inequalities over function fields
Authors: FUCHS CLEMENS , JADRIJEVIĆ BORKA
Published: July 2007

In this paper we completely solve a family of Thue inequalities defined over the field of functions$\mathbb{C}(T)$, namely deg (X4−4cX3Y+(6c+2)X2Y2+4cXY3+Y4) ≤ degc, where the solutionsx,ycome from the ring$\mathbb{C}\left[ T\right] $and the parameter$c\in \mathbb{C}\left[ T\right] $is some non-constant polynomial.
Completely positive quantum stochastic convolution cocycles and their dilations
Authors: SKALSKI ADAM G.
Published: July 2007

Stochastic generators of completely positive and contractive quantum stochastic convolution cocycles on aC*-hyperbialgebra are characterised. The characterisation is used to obtain dilations and stochastic forms of Stinespring decomposition for completely positive convolution cocycles on aC*-bialgebra.
The fundamental solutions for irrotational and rotational Stokes flow in spheroidal geometry
Authors: DASSIOS G.
Published: July 2007

The Stokes operator E2 governs the irrotational axisymmetric Stokes flow and its square governs the corresponding rotational flow. In spheroidal coordinates the elements of the solution space ker E2 enjoy a spectral decomposition into separable eignefunction, while the elements of the ker E4 accept a spectral decomposition in terms of semiseparable eigensolutions involving 3D-by-3D eigenfunctions of the Gegenbauer operator. These spectral characteristics are utilized to construct the fundamental solutions for both the E2 and the E4 operators in spheroidal geometry. The fundamental solution for E2 is expressed in terms of the elements of the irrotational space ker E2, while the fundamental solution for E4 is expressed in terms of the corresponding generalized eigenfunctions alone.
The Hausdorff dimension of pulse-sum graphs
Authors: DEMICHEL YANN , FALCONER KENNETH
Published: July 2007

We consider random functions formed as sums of pulses

where Xn are independent random vectors, 0<α<1, and G is an elementary “pulse” or “bump”. Typically such functions have fractal graphs and we find the Hausdorff dimension of these graphs using a novel variant on the potential theoretic method.
Orthogonal pairs of weak*-closed inner ideals in a JBW*-triple
Authors: EDWARDS C. MARTIN
Published: July 2007

Pre-symmetric complex Banach spaces have been proposed as models for state spaces of physical systems. A neutral GL-projection on a pre-symmetric space represents an operation on the corresponding system, and has as its range a further pre-symmetric space which represents the state space of the resulting system. Two neutral GL-projectionsSandTon the pre-symmetric spaceA*are said to be L-orthogonal if for all elementsxinSA*andyinTA*,By studying the algebraic properties of the dual spaceAofA*, which is a JBW*-triple, it is shown that, provided that the orthogonal neutral GL-projectionsSandTsatisfy a certain geometrical condition, there exists a smallest neutral GL-projectionS∨Tmajorizing bothSandT, and thatS,TandS∨Tform a compatible family.
The automorphism group of an affine quadric
Authors: TOTARO BURT
Published: July 2007

We determine the automorphism group for a large class of affine quadrics over a field, viewed as affine algebraic varieties. The proof uses a fundamental theorem of Karpenko's in the theory of quadratic forms [13], along with some useful arguments of birational geometry. In particular, we find that the automorphism group of the n-sphere {x02+···+xn2=1} over the real numbers is just the orthogonal group O(n+1) whenever n is a power of 2. It is not known whether the same is true for arbitrary n. This result is reminiscent of Wood's theorem that when n is a power of 2, every real polynomial mapping from the n-sphere to a lower-dimensional sphere is constant [22].
The abelianization of the congruence IA-automorphism group of a free group
Authors: SATOH TAKAO
Published: July 2007

We fill a gap in the construction of the extended Johnson homomorphism, stated in Section 2 of the paper The abelianization of the congruence IA-automorphism group of a free group.
Drastic decrease of Salmonella Enteritidis isolated from humans in Belgium in 2005, shift in phage types and influence on foodborne outbreaks
Authors: COLLARD J. M. , BERTRAND S. , DIERICK K. , GODARD C. , WILDEMAUWE C. , VERMEERSCH K. , DUCULOT J. , VAN IMMERSEEL F. , PASMANS F. , IMBERECHTS H. , QUINET C.
Published: July 2007

In Belgium, non-typhoidal salmonellosis and campylobacteriosis are the two most frequently reported foodborne illnesses. During 2005, a 71% decrease of Salmonella Enteritidis infections compared with the average annual number cases in the period 2000–2004 was recorded by the Belgian National Reference Centre for Salmonella and Shigella. After the peak of 1999, the total number of salmonellosis cases decreased gradually, with the exception of 2003 when an increase was again recorded due to the rise of isolates belonging to the serotype Enteritidis. PT4, the predominant phage type of serotype Enteriditis over recent years (except in 2003), became the second most prevalent phage type in 2005 after PT21. We present in this paper the epidemiology (incidence and trends) of human salmonellosis in Belgium and assess the role of the vaccination programme in layer flocks on the decline of the incidence of human salmonellosis and foodborne outbreaks due to S. Enteritidis.
Sharing the load? Floods, droughts, and managing international rivers
Authors: JANMAAT JOHANNUS , RUIJS ARJAN
Published: July 2007

Rivers can be both givers of life and takers of life. Investments that provide protection against flooding are often beneficial during normal or low flows. Investments such as storage reservoirs are long lived, separating construction and management operations. With international rivers, the absence of enforcement mechanisms may preclude infrastructure collaboration. Where physical infrastructure is in an upstream nation, downstream impacts may be ignored after the structure has been completed. Using a game theoretic model, it is shown that downstream cooperation may only be rational when flooding is the primary downstream impact. A stylized arid developing region and humid developed region are compared. Potential gains from collaboration are greatest in arid regions, but may be difficult to achieve. There may be little scope for capturing the gains from basin level management if economic integration does not extend beyond water issues.
Are the poor benefiting from China's land conservation program?
Authors: UCHIDA EMI , XU JINTAO , XU ZHIGANG , ROZELLE SCOTT
Published: July 2007

This paper studies the impact of the largest conservation set-aside program in the developing world: China's Grain for Green program, on poverty alleviation in rural areas. Based on a large-scale survey, we find that the program was implemented mostly in the areas of China that are fairly poor. In addition, we show that income from livestock activities and some types of asset holdings of participants have increased significantly more than those of non-participants (due to program effects). Only weak evidence is provided demonstrating that participating households have begun to shift their labor into the off-farm sectors. Overall, the results suggest that the program has been moderately successful in achieving its poverty alleviation objectives.
The Four-States Model of Memory Retrieval Experiences
Authors: Erdfelder Edgar , Cüpper Lutz , Auer Tina-Sarah , Undorf Monika
Published: July 2007

Abstract. A memory measurement model is presented that accounts for judgments of remembering, knowing, and guessing in old-new recognition tasks by assuming four disjoint latent memory states: recollection, familiarity, uncertainty, and rejection. This four-states model can be applied to both Tulving's (1985) remember-know procedure (RK version) and Gardiner and coworker's ( Gardiner, Java, & Richardson-Klavehn, 1996 ; Gardiner, Richardson-Klavehn, & Ramponi, 1997 ) remember-know-guess procedure (RKG version). It is shown that the RK version of the model fits remember-know data approximately as well as the one-dimensional signal detection model does. In contrast, the RKG version of the four-states model outperforms the corresponding detection model even if unequal variances for old and new items are allowed for.We show empirically that the two versions of the four-statesmodelmeasure the same state probabilities. However, the RKG version, requiring remember-know-guess judgments, provides parameter estimates with smaller standard errors and is therefore recommended for routine use.
Culture of Peace and Mass Media
Authors: López Wilson López , Sabucedo José Manuel
Published: July 2007

Abstract. Currently, political violence is a central issue in the world-wide social agenda. This paper describes the psychosocial logic that legitimizes that violence, analyzed as a challenge for social and political psychology, implying that we have to work toward the construction of a culture of peace. Additionally, diverse concepts about peace are discussed. Finally, the transcendental role played by mass media in this dynamic and particularly the framing theory, are analyzed. Moreover, this paper considers how mass media and news are determinant factors in the beliefs, relational frames, and construction of feelings and are, thus, a barrier to coping and peacefully solving the conflicts that end in political violence.
Vertical group and phase velocities of ionospheric waves derived from the MU radar
Authors: Liu J. Y. , Hsiao C. C. , Liu C. H. , Yamamoto M. , Fukao S. , Lue H. Y. , Kuo F. S.
Published: July 2007

The middle‐ and upper‐atmosphere (MU) radar (34.85°N, 136.10°E) was operated in the incoherent scatter power‐only mode to observe the ionosphere during 17 June 2001. Pronounced 200‐ to 300‐min. waves in the echo power appeared in the F2 region during 0240–1250 local time on 17 June 2001. A procedure of Fourier analyses is conducted to derive power spectra, vertical phase, and group velocities of the pronounced waves. Results show that the center frequency of the waves is a function of the wave number. The opposite directions of the vertical phase and group velocities imply the presence of atmospheric gravity waves.
Toward forward modeling for paleoclimatic proxy signal calibration: A case study with oxygen isotopic composition of tropical woods
Authors: Evans M. N.
Published: July 2007

A forward model of the oxygen isotopic composition (δ18O) of wood cellulose is parameterized for time series prediction in tropical environments and driven with meteorological data observed at La Selva Biological Research Station, Costa Rica, for 1985–2001. Monthly‐resolution model results correlate modestly (r = 0.34, p < 0.05) with observed isotopic data, with higher correlation (r = 0.45, p < 0.01) over the earliest 10 years of comparison and nonsignificant correlation over the most recent 6 years of record. Analysis of model output for La Selva suggests that isotopic variations are strongly controlled by rainfall amount. The model simulates an analogous but stronger than observed negative isotopic anomaly associated with positive July–September rainfall anomalies during El Niño–Southern Oscillation (ENSO) warm phase event years. Simulated tree isotope data for the global tropics suggest that a network of well‐replicated data series from selected locations may resolve the large‐scale precipitation anomaly pattern associated with ENSO.
Influence of the 17 April 2006 Asian dust storm on Moderate Resolution Imaging Spectroradiometer data for land cover identification
Authors: Zha Yong , Li Lin
Published: July 2007

China suffers from some of the most harmful dust storms. Dust storms occur every year in China and have significant effects on remote sensing of land surface. This study addresses the effect of dust storms on Moderate Resolution Imaging Spectroradiometer (MODIS) imagery for land cover identification. Results from supervised classification of two MODIS data sets acquired before and during a dust storm of April 2006 are compared, and the mechanism responsible for such effects is analyzed. An index called influence intensity was proposed to quantify the effect of dust storms on different MODIS bands for land cover identification. Results from this study indicate that dust storms modified spectral characteristics of land cover types and resulted in decreased spectral contrast among land cover types. Out of 10 MODIS bands used in this study, dust storm yielded the most significant effect on MODIS bands 3, 18, and 19 for land cover identification. Conversely, MODIS bands 4, 5 and 6 were affected to a low degree.
Atmospheric effects of the total solar eclipse of 4 December 2002 simulated with a high‐altitude global model
Authors: Eckermann S. D. , Broutman D. , Stollberg M. T. , Ma J. , McCormack J. P. , Hogan T. F.
Published: July 2007

The atmosphere's response to the total solar eclipse of 4 December 2002 is studied using a prototype high‐altitude global numerical weather prediction model (NOGAPS‐ALPHA). Local reductions in solar ultraviolet (UV) radiation during the eclipse are estimated using astronomical calculations of umbral and penumbral surface trajectories and observed solar limb darkening at ∼200–300 nm. In NOGAPS‐ALPHA these UV eclipse shadows yield stratospheric radiative cooling rate footprints peaking near 27 K day−1, a value 2–3 times larger than assumed in previous modeling. Difference fields between NOGAPS‐ALPHA runs with and without this eclipse forcing reveal vertically deep middle atmospheric responses, with three‐dimensional horizontal structures very similar to the large‐scale “bow‐wave” response first proposed by Chimonas (1970). Such structure appears clearly only at later times when total eclipses have abated and gravity waves generated in the stratosphere have had time to propagate vertically. Bow‐wave amplitudes and direct thermal cooling responses are both small (≲1 K for temperature and ≲2–3 m s−1 for horizontal winds), contradicting some rocketsonde measurements that suggest much larger responses near 50–60 km altitude. We also find clear evidence of a bow‐wave‐like response in the model's surface pressure fields, with an amplitude ∼0.1–0.5 hPa, while surface air temperatures in NOGAPS‐ALPHA show ∼4 K cooling over Africa during the eclipse. Both findings are consistent with surface atmospheric data acquired during previous eclipse passages.
Bedrock channel geometry along an orographic rainfall gradient in the upper Marsyandi River valley in central Nepal
Authors: Craddock William H. , Burbank Douglas W. , Bookhagen Bodo , Gabet Emmanuel J.
Published: July 2007

Pronounced rainfall gradients combined with spatially uniform exhumation of rocks at Quaternary timescales and uniform rock strength make the upper Marsyandi River valley in central Nepal a useful natural laboratory in which to explore variations in bedrock channel width. We focus on small catchments (0.6–12.4 km2) along a more than tenfold gradient in monsoon rainfall. Rainfall data are gathered from a dense weather network and calibrated satellite observations, the pattern of Quaternary exhumation is inferred from apatite fission track cooling ages, and rock compressive strength is measured in the field. Bedrock channel widths, surveyed at high scour indicators, scale as a power law function of discharge (w αQw0.38±0.09) that is estimated by combining rainfall data with 90‐m digital topography. The results suggest that power law width scaling models apply (1) to regions with pronounced rainfall gradients, (2) to tributary catchments distributed across a climatically diverse region, and (3) to large, rapidly denuding orogens. An analysis of rainfall data indicates that the regional gradient of rainfall during storms that drive erosive discharge events is about half as large as the gradient of seasonal rainfall across the same area. Finally, numerical models in which the maximum rainfall is displaced significantly downstream from the headwaters predict a midcatchment zone of relatively rapid decreases in channel gradient and increases in channel concavity that are driven by locally enhanced discharge. Because differential rock uplift can produce analogous changes in gradients, the influence of rainfall gradients should be assessed before tectonic inferences are drawn.
Valence state fossils in Proterozoic stromatolites by L‐edge X‐ray absorption spectroscopy
Authors: Brotton Stephen J. , Shapiro Russell , van der Laan Gerrit , Guo Jinghua , Glans Per‐Anders , Ajello Joseph M.
Published: July 2007

Paleoproterozioc (ca. 1.9 Ga) stromatolites from the Biwabik Iron‐Formation (Minnesota, United States) contain fossil forms which in the literature have been attributed to ancient microbes including iron‐oxidising bacteria and cyanobacteria. To search for valence state fossils, we measured Fe3+/ΣFe (ΣFe = Fe2++ Fe3+) transverse to the laminae of a Biwabik, probably biogenic stromatolite and compared the results with a scan across the enclosing, likely abiotic sedimentary rock (or interstromatolite fill). To obtain Fe3+/ΣFe and information about the site symmetry and crystal field strength, we used L3(2p3/2→ 3d) soft X‐ray absorption spectroscopy and interpreted the measurements using our calculated spectra. We found that Fe3+/ΣFe is approximately constant at 0.3 within the stromatolite, increases steeply to around 0.6 in the region of the stromatolite‐fill boundary, and then reduces significantly in the interstromatolite fill. The crystal field strength for octahedral Fe3+increased and became more irregular as the scan moved from the stromatolite into the fill. Our results tentatively suggest that a combination of ancient biological and later diagenetic processes can produce steep gradients in Fe3+/ΣFe and alterations in the crystal field strength across a probable abiotic‐biotic boundary. To describe the L3absorption spectra in the stromatolite‐fill region, it was necessary to include a significant Fe3+tetrahedral component, which suggests the presence of magnetite. At other positions, fits using only octahedral Fe2+and Fe3+theoretical curves satisfactorily reproduce the spectra. The search for a possible new type of spatial biosignature in the valence state record for ancient stromatolites might help differentiate between the biogenic stromatolites and abiogenic stromatolite‐like structures and could even be relevant to the search for fossil evidence of life in extraterrestrial rocks.
Response of dimethylsulfide (DMS) in the ocean and atmosphere to global warming
Authors: Kloster S. , Six K. D. , Feichter J. , Maier‐Reimer E. , Roeckner E. , Wetzel P. , Stier P. , Esch M.
Published: July 2007

A global coupled ocean‐atmosphere modeling system is applied in a transient climate simulation to study the response to global warming of Dimethylsulfide (DMS) in the ocean, the DMS flux to the atmosphere, and the resulting DMS concentrations in the atmosphere. The DMS production and consumption processes in the ocean are linked to plankton dynamics simulated in the marine biogeochemistry model HAMOCC5.1, embedded in an ocean general circulation model (MPI‐OM). The atmospheric model ECHAM5 is extended by the microphysical aerosol model HAM, treating the sulfur chemistry in the atmosphere and the evolution of microphysically interacting internally and externally mixed aerosol populations. For future conditions (2000–2100) we assume greenhouse gas concentrations, aerosol and aerosol precursor emissions according to the SRES A1B scenario. We analyzed the results in terms of simulated changes between the period 1861–1890 and 2061–2090. For the global annual mean DMS sea surface concentration and the DMS flux we found a reduction by 10%. The DMS burden in the atmosphere is reduced by only 3%, owing to a longer lifetime of DMS in the atmosphere in a warmer climate (+7%). Regionally the response and the underlying mechanisms are quite inhomogeneous. The largest reduction in the DMS sea surface concentration is simulated in the Southern Ocean (−40%) caused by an increase in the summer mixed layer depth, leading to less favorable light conditions for phytoplankton growth. In the mid and low latitudes DMS sea surface concentrations are predominantly reduced due to nutrient limitation of the phytoplankton growth through higher ocean stratification and less transport of nutrients into the surface layers.
A study of the TEX86 paleothermometer in the water column and sediments of the Santa Barbara Basin, California
Authors: Huguet Carme , Schimmelmann Arndt , Thunell Robert , Lourens Lucas J. , Sinninghe Damsté Jaap S. , Schouten Stefan
Published: July 2007

Particulate organic matter collected during a 2‐year period, as part of an ongoing sediment trap study, and a high‐resolution sediment record from 1850 to 1987 A.D. from the Santa Barbara Basin were analyzed for TEX86, a temperature proxy based on marine crenarchaeotal membrane lipids. Highest fluxes of crenarchaeotal lipids in the water column were found in May–June 1996 and from October 1996 to January 1997 and, in general, showed a good correlation with mass fluxes. TEX86 reconstructed temperatures from the sediment trap series ranged from 8 to 11°C and were usually substantially lower than sea surface temperatures (SST), indicating that unlike in previous studies, the TEX86 corresponds to subsurface temperatures, likely between 100 and 150 m. TEX86 temperature variations observed in trap samples were not coupled to changes in SST or deep‐water temperatures and only to some degree with crenarchaeotal lipid fluxes. This suggests that a complex combination of different depth origins and seasonal growth periods of Crenarchaeota contributed to the variations in TEX86 signal during the annual cycle. TEX86 temperatures in the two sediment cores studied (8–13°C) were also substantially lower than those of instrumental SST records (14–17.5°C) confirming that TEX86 records a subsurface temperature signal in the Santa Barbara Basin. This result highlights the importance of performing calibration studies using sediment traps and core tops before applying the TEX86 temperature proxy in a given study area.
Structure of the Maláguide Complex near Vélez Rubio (Eastern Betic Cordillera, SE Spain)
Authors: Fernández‐Fernández E. M. , Jabaloy‐Sánchez A. , Nieto F. , González‐Lodeiro F.
Published: July 2007

The Maláguide Complex of the Betic Cordillera represents a tectonic element which mostly underwent brittle deformation during the Alpine orogeny, and that covers the high‐pressure/low‐temperature (HP/LT) complexes of the internal Betic Cordillera. The evolution of this complex can help to determine both when the lower HP/LT complexes began to exhume and the behavior of the upper plate during this process. Moreover, this complex is a key element to understanding the relationships between the late orogenic extension in the internal Betic Cordillera and the coeval compression in the External Zones of the same mountain chain. This paper focuses in the geometry and kinematics of the Alpine structures of this Maláguide Complex in the eastern Betic Cordillera, near the village of Vélez Rubio. We propose that these Alpine structures can be grouped into three main stages. First stage (Paleogene) began with a synmetamorphic slaty cleavage produced in anchizone conditions. This foliation is associated with northward vergent structures and was probably connected with the superposition of the Maláguide Complex over the Alpujárride during the middle Eocene. This first stage ended with the thinning of the Maláguide Complex (Oligocene) by an extensional detachment with a top‐to‐the‐NNW sense of movement. Second stage records the convergence of the External and Internal Zones during the Aquitanian‐Burdigalian. This convergence was a right‐lateral transpression that produced back thrusts and extensional structures that exhumed the HP/LT rocks of the Alpujárride Complex. Third stage corresponds to the evolution from the late Burdigalian to the present‐day, when the Internal and External zones were welded together.
Recovering tracer test input functions from fluid electrical conductivity logging in fractured porous rocks
Authors: Mathias S. A. , Butler A. P. , Peach D. W. , Williams A. T.
Published: July 2007

A radially convergent tracer test was carried out in an unconfined Chalk aquifer of Berkshire, United Kingdom. Fluorescent tracers were injected into two boreholes lying 32 m (PL10A) and 54 m (PL10B) from the abstraction hole. The tracers were also mixed with an NaCl solution so that vertical distributions of tracer within the injection wells could be monitored using fluid electrical conductivity (FEC) logging. The breakthrough curve (BTC) from PL10A was unimodal and had a first arrival time of 14 min. The BTC from PL10B exhibited two distinct peaks and a first arrival time of just 4 min. The tracer test input functions were derived by numerically modeling the observed FEC logs of the injection wells. These were then convoluted with a conventional, Fickian matrix diffusion dual‐porosity model. The results suggested that the multiple peaks were due to the way in which the tracers left the injection wells and migrated into the aquifer. FEC log inversion proved to be an effective method for predicting borehole flow data obtained by flowmeters and recovering tracer test input functions for radially convergent tracer tests.
Transatlantic temperature and salinity changes at 24.5°N from 1957 to 2004
Authors: Cunningham Stuart A. , Alderson Steve
Published: July 2007

In 2004 a fifth occupation of a transatlantic section at 24.5°N allows us to examine decadal temperature and salinity changes using high quality full‐depth hydrographic data since 1957. Waters shallower than 1750 dbar have been warming and salinifying at least since 1981 and in 2004 are significantly warmer and saltier than at any time since 1957, while deeper than 3000 dbar there has been continuous cooling and freshening since 1957. Temperature and salinity changes at constant pressures are partitioned into changes on isopycnal surfaces and changes due to the vertical movement of the isopycnals. Warming in the western Atlantic thermocline since 1957 at a rate of 0.0111 °C/yr dominates the transatlantic average, while deep water has cooled and freshened at rates of −0.0021 °C/yr and −0.0003 psu/yr respectively. We argue that the shallower and deeper changes are consistent with a recently reported increased southward thermocline circulation and reduced southward flux of deep water.
Is the gas‐particle partitioning in alpha‐pinene secondary organic aerosol reversible?
Authors: Grieshop Andrew P. , Donahue Neil M. , Robinson Allen L.
Published: July 2007

This paper discusses the reversibility of gas‐particle partitioning in secondary organic aerosol (SOA) formed from α‐pinene ozonolysis in a smog chamber. Previously, phase partitioning has been studied quantitatively via SOA production experiments and qualitatively by perturbing temperature and observing particle evaporation. In this work, two methods were used to isothermally dilute the SOA: an external dilution sampler and an in‐chamber technique. Dilution caused some evaporation of SOA, but repartitioning took place on a time scale of tens of minutes to hours–consistent with an uptake coefficient on the order of 0.001–0.01. However, given sufficient time, α‐pinene SOA repartitions reversibly based on comparisons with data from conventional SOA yield experiments. Further, aerosol mass spectrometer (AMS) data indicate that the composition of SOA varies with partitioning. These results suggest that oligomerization observed in high‐concentration laboratory experiments may be a reversible process and underscore the complexity of the kinetics of formation and evaporation of SOA.