bluuebunny/crossref_metadata_2025 huggingface dataset:
Scratch Resistance and Localised Damage Characteristics of Polymer Surfaces – a Review
Authors: Briscoe B. J. , Sinha S. K.
Published: October 2003

The “Scratch Test” is, arguably, the earliest and amongst the now most widely used techniques for evaluating a wide range of surface mechanical properties. Some of the areas where this test has been successfully used in the engineering field, both by research and industry, include the determination of the relative hardness of materials, characterizations of coatings, paints and thin‐films, modeling of the wear of materials and the estimation of different material deformation characteristics when subjected to hard asperity damage. In this paper we have reviewed the “state‐of‐the‐art” in the scratch method for polymeric materials. The paper provides some important theoretical models that have been developed in the field of scratching for material property characterizations. Results from different types of scratch tests (macro, micro and nano scales) on a range of polymeric materials are presented with critical discussion on the usefulness of each result. Finally, various areas for further research in scratching of polymer surfaces have been identified.
Reibungs‐ und Verschleißverhalten von randschichtmodifizierter HfO2‐verstärkter Al2O3‐Keramik im ungeschmierten Gleitkontakt
Authors: Schneider J.
Published: October 2003

Eine handelsübliche Aluminiumoxidkeramik wurde durch CO2‐lasergestütztes Umschmelzen und Einlegieren von Hafniumoxid mit unterschiedlichen Anteilen an Yttriumoxid gezielt oberflächenmodifiziert. In Folge der Laserbehandlung entstanden bis zu 400 μm dicke Randschichten mit einem mehrphasigen Gefüge, das durch eine Al2O3‐Matrix und eine feinlamellare, eutektische Reaktionsphase aus HfO2 und Al2O3 entlang der Kristallitgrenzen der Al2O3‐Matrix gekennzeichnet war. Das tribologische Verhalten der legierten Keramik wurde im ungeschmierten, reversierenden Gleitkontakt in Paarung mit Al2O3‐Kugeln bei Raumtemperatur und einer relativen Luftfeuchte von 50 % charakterisiert. Das Abrasivverschleißverhalten wurde unter furchender Beanspruchung durch SiC‐Abrasivpartikel untersucht. Das Reibungs‐ und Verschleißverhalten der lasermodifizierten Keramik wurde sowohl durch den Anteil als auch die Zusammensetzung des Legierungszusatzes beeinflusst. Die Untersuchungen zeigten für die randschichtmodifizierte Keramik im Vergleich zu einer kommerziell erhältlichen Al2O3‐Keramik bzw. Al2O3‐ZrO2‐Mischkeramik (ZTA) deutlich verbesserte tribologische Eigenschaften. Die Reibungszahl konnte verringert und der Verschleißwiderstand erhöht werden.
Effect of conversion from cyclosporine A to mizoribine on transplant arteriosclerosis in rat aortic allograft models
Authors: Shimizu Hisashi , Takahashi Masafumi , Takeda Shinichi , Tahara Kazunori , Inoue Seiichiro , Hakamata Yoji , Kaneko Takashi , Takeyoshi Izumi , Morishita Yasuo , Kobayashi Eiji
Published: October 2003

Recent studies suggested that conversion from cyclosporine A (CsA) to antimetabolic agents protects allograft vasculopathy. However, the mechanism of this beneficial effect by the conversion therapy is not fully understood. In the present study, we investigated the effects of conversion from CsA to antimetabolic agent mizoribine (MZR) on the formation of transplant arteriosclerosis in rat aortic allografts. Conversion from CsA to MZR significantly prevented intimal hyperplasia and perivascular inflammatory cell infiltration at 28 days after aortic transplantation. These findings suggest that conversion therapy from CsA to antimetabolic agents might have therapeutic potential in transplant patients with chronic vascular rejection. © 2003 Wiley‐Liss, Inc. MICROSURGERY 23:454–457 2003
Light‐emitting diodes and lasers based on polymer films doped with small organic molecules and rare‐earth complexes
Authors: Díaz‐García María A.
Published: October 2003

We investigated the lasing properties of optically pumped polymer films. Amplified spontaneous emission (ASE) around 400 nm was observed in polymer films of polystyrene (PS) and poly(N‐vinylcarbazole) (PVK) doped up to 20% with the hole‐transporting organic molecule N,N′‐bis(3‐methylphenyl)‐N,N′‐diphenylbenzidine (TPD). Thus, TPD‐based films are candidates for blue‐emitting organic diode lasers. Films containing several semiconducting organic molecules and polymers and rare‐earth complexes were also investigated. Energy transfer was observed in PVK films doped with various europium and samarium complexes. PS films containing the electron‐transporting organic molecule 2‐(4‐biphenylyl)‐5‐(4‐tert‐butylphenyl)‐1,3,4‐oxadiazole and small amounts of TPD also showed energy transfer to the europium complexes, but not to the samarium ones. None of these films demonstrated ASE; therefore, they are not appropriate for lasing purposes. However, because rare‐earth ions have very sharp emission spectra, these materials are candidates for very monochromatic light‐emitting diodes. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2706–2714, 2003
Organic light‐emitting diodes with multiple photocrosslinkable hole‐transport layers
Authors: Domercq Benoit , Hreha Richard D. , Zhang Ya‐Dong , Haldi Andreas , Barlow Stephen , Marder Seth R. , Kippelen Bernard
Published: October 2003

We report on photocrosslinkable hole‐transport polymers and their use as photodefinable hole‐transport layers in organic light‐emitting diodes. The polymers were obtained by copolymerization of bis(diarylamino)biphenyl‐based acrylate monomers with cinnamate‐functionalized acrylate moieties. Polymers with a range of redox potentials were obtained by varying the substitution patterns of the bis(diarylamino)biphenyl units. The 2 + 2 cycloaddition of the cinnamate moieties following UV irradiation renders the material insoluble. This allows for patterning of the polymer and simultaneously enables the fabrication of multilayer structures from solution. Hole mobilities were measured in these copolymers with the time‐of‐flight technique. Their performance as hole‐transport layers in light‐emitting diodes, with tris(8‐hydroxyquinolinato)aluminum as the emitter and electron‐transport layer, is evaluated. Electroluminescent devices with multiple hole‐transport layers having different ionization potentials were fabricated from solution, and the quantum efficiency of these devices was greater than that for devices based on a single hole‐transport layer. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2726–2732, 2003
Temperature dependence of19F NMR and ion transport parameters of fluoride ion conductors SnF2—PbF2and 2SnF2—NH4F prepared by mechanical milling
Authors: Kumar M. , Yamada K. , Okuda T. , Sekhon S. S.
Published: October 2003

19F NMR studies have been carried out on mixed metal fluorides composed of SnF2—PbF2and 2SnF2—NH4F and prepared by mechanical milling. Motional narrowing observed in the variation of19F NMR linewidth as a function of temperature for both the systems suggests the occurrence of F−ion diffusion. The variation of different ion transport parameters calculated from NMR results like jump frequency, diffusion coefficient, and conductivity with temperature has been found to be closely related with experimentally measured conductivity results.
Cation distribution and magnetic properties of natural chromites
Authors: Rais A. , Yousif A. A. , Al‐shihi M. H. , Al‐rawas A. D. , Gismelseed A. M. , El‐zain M. E.
Published: October 2003

Ten specimens of chromites from Oman ophiolites have been studied using magnetic susceptibility χ measurements, Mössbauer spectroscopy (MS), Scanning electron microscopy (SEM), and X‐ray diffraction (XRD). XRD shows that all samples have a face‐centered cubic spinel structure. MS analysis and SEM data at room temperature enabled to derive the chemical formula and the cations distribution among tetrahedral (A1 and A2) and octahedral (B) sites. For all specimens, paramagnetic variations of 1/χ with the temperature T show a systematic curve bending at a critical temperature T0, which indicates a change of the effective paramagnetic moment μeff. This deviation from Curie–Weiss law is interpreted as due to spin inversion of a fraction δ of Cr3+ cations located in the octahedral sites of the spinel structure. This interpretation is supported by a decrease in the Mössbauer peak areas of Fe2+ located in A1 sites from 300 to 80 K at the expense of Fe2+ located in A2 sites. The values of δ and μeff for each specimen are calculated by fitting this model separately to the experimental 1/χ versus T above and below T0.
The effect of a nonmagnetic cap layer on the spin‐polarized tunneling and magnetoresistance in double‐barrier planar junctions
Authors: Xie Zheng‐wei , Li Bo‐zang , Li Yu‐xian
Published: October 2003

Within the framework of the free‐electron model, the tunneling magnetoresistance (TMR) and tunneling conductance (TC) in double magnetic tunnel junctions (DMTJ) with nonmagnetic cap layer, i.e. the NM/FM/I/NM/(FM)/I/FM/NM junction is investigated. FM, NM and I represent the ferromagnetic metal, nonmagnetic metal and insulator, respectively, NM(FM) indicates that the middle layer can be NM or FM. Our results show that, due to the spin‐dependent interfacial potential barriers, the influences of the thickness of the FM layer on TC and TMR in DMTJ are large, and when the thicknesses of these two FM layers are suitable a large TMR can be obtained. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Prospects for carrier‐mediated ferromagnetism in GaN
Authors: Graf Tobias , Goennenwein Sebastian T. B. , Brandt Martin S.
Published: October 2003

Theoretical predictions of room‐temperature ferromagnetism in Mn‐doped GaN and other wide band gap semiconductors suggest that these materials might be useful for spintronic applications. In this short review, we summarize recent observations on the gap states of GaN:Mn, which make it impossible that the two main prerequisites of these predictions can be fulfilled at the same time, which are (1) a large concentration of localized Mn2+ spins coexisting with (2) a high density of free holes in the valence band. Such conditions have been observed in only a few materials like e.g. GaAs:Mn. More typically, transition‐metal impurities act as traps for free carriers, thus pinning the Fermi level in the semiconductor band gap far from the valence or conduction band. Alternatively to ferromagnetism mediated by free carriers, the interactions between bound magnetic polarons and the double‐exchange mechanism have been suggested to possibly lead to ferromagnetism in GaN:Mn. Because of the energy position and the character of its gap states, Mn seems to be rather unsuitable for these two mechanisms. Better candidates would be GaN:Fe:Mg for a system of magnetic polarons, and GaN:Cr for a double‐exchange ferromagnet. Because of its short‐range nature, the double‐exchange interaction requires rather concentrated alloys and does not offer significant advantages of GaN:Mn over the established ferromagnetic materials. However, microscopic ferromagnetic inclusions observed in many SQUID measurements of GaN:Mn could possibly help to achieve spin injection in nitride semiconductors. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Designing Problems to Promote Higher‐Order Thinking
Authors: Weiss Renée E.
Published: October 2003

The design of the problem can be a key to success in using problem‐based learning. This chapter discusses characteristics of effective problems that will elicit higher‐order thinking among students.
Not All Metacognition Is Created Equal
Authors: Hacker Douglas J. , Dunlosky John
Published: October 2003

To promote metacognitive thinking, professors can help students articulate their motives and decisions during problem‐solving activities.
Convergence of biological and psychological perspectives on cognitive coordination in schizophrenia
Authors: Phillips William A. , Silverstein Steven M.
Published: October 2003

The concept of locally specialized functions dominates research on higher brain function and its disorders. Locally specialized functions must be complemented by processes that coordinate those functions, however, and impairment of coordinating processes may be central to some psychotic conditions. Evidence for processes that coordinate activity is provided by neurobiological and psychological studies of contextual disambiguation and dynamic grouping. Mechanisms by which this important class of cognitive functions could be achieved include those long-range connections within and between cortical regions that activate synaptic channels via NMDA-receptors, and which control gain through their voltage-dependent mode of operation. An impairment of these mechanisms is central to PCP-psychosis, and the cognitive capabilities that they could provide are impaired in some forms of schizophrenia. We conclude that impaired cognitive coordination due to reduced ion flow through NMDA-channels is involved in schizophrenia, and we suggest that it may also be involved in other disorders. This perspective suggests several ways in which further research could enhance our understanding of cognitive coordination, its neural basis, and its relevance to psychopathology.
Perceptual objects may have nonphysical properties
Authors: Ben-Ze’ev Aaron
Published: October 2003

Byrne & Hilbert defend color realism, which assumes that: (a) colors are properties of objects; (b) these objects are physical; hence, (c) colors are physical properties. I accept (a), agree that in a certain sense (b) can be defended, but reject (c). Colors are properties of perceptual objects – which also have underlying physical properties – but they are not physical properties.
Perceptual variation, realism, and relativization, or: How I learned to stop worrying and love variations in color vision
Authors: Cohen Jonathan
Published: October 2003

In many cases of variation in color vision, there is no nonarbitrary way of choosing between variants. Byrne & Hilbert insist that there is an unknown standard for choosing, whereas eliminativists claim that all the variants are erroneous. A better response relativizes colors to perceivers, thereby providing a color realism that avoids the need to choose between variants.
Schizophrenic cognition: Taken out of context?
Authors: Hemsley David R.
Published: October 2003

This commentary addresses: (a) the problems of definition which have been prominent in the use of the term context in schizophrenia research; (b) potentially useful distinctions and links with other theories of schizophrenic cognition; and (c) possible pathways to schizophrenic symptoms. It is suggested that at least two major aspects of the operation of context may be distinguished and that both may be impaired in schizophrenia.
Why not color physicalism without color absolutism?
Authors: Jakab Zoltán , McLaughlin Brian P.
Published: October 2003

We make three points. First, the concept of productance value that the authors propose in their defense of color physicalism fails to do the work for which it is intended. Second, the authors fail to offer an adequate physicalist account of what they call the hue-magnitudes. Third, their answer to the problem of individual differences faces serious difficulties.
Context, connection, and coordination: The need to switch
Authors: Oades Robert D. , Röpcke Bernd , Oknina Ljubov
Published: October 2003

Context, connection, and coordination (CCC) describe well where the problems that apply to thought-disordered patients with schizophrenia lie. But they may be part of the experience of those with other symptom constellations. Switching is an important mechanism to allow context to be applied appropriately to changing circumstances. In some cases, NMDA-voltage modulations may be central, but gain and shift are also functions that monoaminergic systems express in CCC.
Color as a material, not an optical, property
Authors: MacLennan Bruce J.
Published: October 2003

For all animals, color is an indicator of the substance and state of objects, for which purpose reflectance is just one among many relevant optical properties. This broader meaning of color is confirmed by linguistic evidence. Rather than reducing color to a simple physical property, it is more realistic to embrace its full phenomenology.
Clarifying the problem of color realism
Authors: Maund Barry
Published: October 2003

“The problem of color realism” as defined in the first section of the target article, is crucial to the argument laid out by Byrne & Hilbert. They claim that the problem of color realism “does not concern, at least in the first instance, color language or color concepts” (sect. 1.1). I argue that this claim is misconceived and that a different characterisation of the problem, and some of their preliminary assumptions makes their positive proposal less appealing.
Can a physicalist notion of color provide any insight into the nature of color perception?
Authors: Mausfeld Rainer , Niederée Reinhard
Published: October 2003

Byrne & Hilbert (B&H) conceive of color perception as the representation of a physical property “out there.” In our view, their approach does not only have various internal problems, but is also apt to becloud both the intricate and still poorly understood role that “color” plays within perceptual architecture, and the complex coupling to the “external world” of the perceptual system as an entirety. We propose an alternative perspective, which avoids B&H's misleading dichotomy between a purely subjective and a realist conception of “color.”
Color realism and color illusions
Authors: Todorovic Dejan
Published: October 2003

As demonstrated by several example displays, color illusions challenge color realism, because they involve a one-to-many reflectance-to-color mapping. Solving this problem by differentiating between veridical and illusory colors corresponding to the same reflectance is hampered because of the lack of an appropriate criterion. However, the difference between veridical and illusory color perception can still be maintained.
A QUEUE WITH POSITIVE AND NEGATIVE ARRIVALS GOVERNED BY A
MARKOV CHAIN
Authors: Shin Yang Woo , Choi Bong Dae
Published: October 2003

We consider a single-server queue with exponential service
time and two types of arrivals: positive and negative. Positive
customers are regular ones who form a queue and a negative arrival
has the effect of removing a positive customer in the system.
In many applications, it might be more appropriate to assume
the dependence between positive arrival and negative arrival.
In order to reflect the dependence, we assume that the positive
arrivals and negative arrivals are governed by a finite-state
Markov chain with two absorbing states, say 0 and 0′. The
epoch of absorption to the states 0 and 0′ corresponds to
an arrival of positive and negative customers, respectively. The
Markov chain is then instantly restarted in a transient state,
where the selection of the new state is allowed to depend on the
state from which absorption occurred.

The Laplace–Stieltjes transforms (LSTs) of the sojourn
time distribution of a customer, jointly with the probability
that the customer completes his service without being removed,
are derived under the combinations of service disciplines FCFS
and LCFS and the removal strategies RCE and RCH. The service
distribution of phase type is also considered.
Physical control of chlorophyll a, POC, and TPN distributions in the pack ice of the Ross Sea, Antarctica
Authors: Arrigo Kevin R. , Robinson Dale H. , Dunbar Robert B. , Leventer Amy R. , Lizotte Michael P.
Published: October 2003

The pack ice ecosystem of the Ross Sea was investigated along a 1470‐km north‐south transect during the spring 1998 oceanographic program Research on Ocean‐Atmosphere Variability and Ecosystem Response in the Ross Sea (ROAVERRS). Snow and sea ice thickness along the transect varied latitudinally, with thinner snow and ice at the northern ice edge and thin new ice in the vicinity of the Ross Sea polynya. Relative to springtime observations in other sea ice regions, algal chlorophyll a (Chl a) concentrations were low. In contrast, particulate organic carbon (POC), total particulate nitrogen (TPN), and POC:Chl a were all high, indicating either that the ice contained substantial amounts of detritus or nonphotosynthetic organisms, or that the algae had a high POC:Chl a ratio. The abundance of Chl a, POC, and TPN in the sea ice was related to ice age and thickness, as well as to snow depth: older ice had thinner snow cover and contained higher algal biomass while new ice in the polynya had lower biomass. Older pack ice was dominated by diatoms (particularly Fragilariopsis cylindrus) and had vertical distributions of Chl a, POC, and TPN that were related to salinity, with higher biomass at the ice‐water interface. Fluorescence‐based measurements of photosynthetic competence (Fv/Fm) were higher at ice‐water interfaces, and photosynthesis‐irradiance characteristics measured for bottom ice algae were comparable to those measured in pack ice communities of other regions. Nutrient concentrations in extracted sea ice brines showed depletion of silicate and nitrate, depletion or regeneration of phosphate and nitrite, and production of ammonium when normalized to seawater salinity; however, concentrations of dissolved inorganic nitrogen, phosphorous, and silica were typically above levels likely to limit algal growth. In areas where pack ice and snow cover were thickest, light levels could be limiting to algal photosynthesis. Enrichment of δ13C‐POC in the sea ice was correlated with the accumulation of POC, suggesting that carbon sources for photosynthesis might shift in response to decreasing CO2 supply. Comparisons between new ice and underlying waters showed similar algal species dominance (Phaeocystis antarctica) implying incorporation of phytoplankton, with substantially higher POC and TPN concentrations in the ice.
Constraining the North Atlantic circulation between 4.5°S and 39.5°N with transient tracer observations
Authors: Li Xingwen , Wunsch Carl
Published: October 2003

A 1° horizontal resolution North Atlantic general circulation model (GCM) in the latitude band 4.5°S to 39.5°N is compared to, and then combined with, chlorofluorocarbon and tritium transient tracer data. The method of Lagrange multipliers (adjoint) is used. Tracer distribution within the model ocean interior is primarily sensitive to the flux through the open northern boundary. This flux is determined by the estimation method and is found to deviate from the initial estimate significantly for all tracers. An attempt to carry the model domain to 78.5°N showed the GCM inadequacy, believed to be primarily a problem of spatial resolution, to compute the convective injection of tracer into the deep ocean. Any such errors persist throughout the tracer integration and corrupt all further tracer concentrations. In general, and consistent with earlier much simpler computations, uncertainties in surface and northern boundary conditions dominate the computed tracer concentrations. The final results here are improved estimates of the three‐dimensional time histories of the tritium and CFCs and their boundary conditions over the model domain, with very little information available to constrain the GCM itself in the latitude band.
Erosion of the submarine flanks of the Canary Islands
Authors: Mitchell Neil C. , Dade W. Brian , Masson Douglas G.
Published: October 2003

Surveying with multibeam echo sounders around old (≫1 Ma) volcanic ocean islands reveals that their submarine flanks contain a strong downslope‐oriented ridge‐and‐valley corrugation, which modifies the original volcanic morphology of lava terraces and cones. By analogy with canyons in other settings, this corrugation was probably caused by channel incision by erosive sedimentary mass flows such as turbidity currents and debris flows. We adapt a method first used in subaerial geomorphology to isolate the erosion depth (exhumation) and apply it to the eroded flanks of the 6–8 Ma Anaga massif of Tenerife. The channels formed around this massif divert around local topographic highs. These highs, which are probably original volcanic cones, are therefore preferentially preserved during erosion, so that their elevations can be used to construct an artificial reference surface. Terrain depth was calculated by subtracting this reference surface from measured bathymetry. Comparison of the terrain depth of the old, eroded submarine flank of Anaga with that of the young, mostly unaltered submarine flank of El Hierro allows us to infer the mean depth of Anaga's submarine erosion, which is ∼100 m. Volcanic terrains can be dated by radiometric methods, so they also provide a way of quantifying long‐term denudation rates. We infer that submarine denudation of Anaga has occurred at comparable rates to that of subaerial lowlands and much slower than denudation of highlands, illustrated locally by the more extensive erosion of the subaerial Anaga edifice.
Integrated hydrologic and hydrochemical observations of Hidden Creek Lake jökulhlaups, Kennicott Glacier, Alaska
Authors: Anderson Suzanne P. , Walder Joseph S. , Anderson Robert S. , Kraal Erin R. , Cunico Michelle , Fountain Andrew G. , Trabant Dennis C.
Published: October 2003

Hidden Creek Lake (HCL), an ice‐marginal lake impounded by Kennicott Glacier, Wrangell Mountains, Alaska, fills annually to ∼20 to 30 × 106 m3 and then drains subglacially within 2 to 3 days. During the 1999 and 2000 jökulhlaups, we carried out a series of planned observations around the lake and in the Kennicott River, which drains the glacier. Approximately 20% of the lake volume was contained within a subglacial water “wedge” beneath the ice dam. The entire volume of the lake drains through the wedge; hydraulic head loss through this constriction may be responsible for the fairly symmetrical shape of the HCL outflow hydrographs, deduced from lake level records, basin hypsometry, and collapse of the ice dam. The flood hydrographs in the Kennicott River are similar in shape to the outflow hydrographs, and within error, lake volume matched the river flood volume in both years. Up to 12 × 106 m3 of water was temporarily stored within the glacier during the 2000 jökulhlaup. During the 2000 jökulhlaup the background flow in the Kennicott River shifted to a dilute chemical composition. As the HCL jökulhlaup progressed, Donoho Falls Lake filled with water whose chemistry was closer to that of the background flow in Kennicott River than to HCL water. Comparison of these chemical signals with typical summer variations in Kennicott River chemistry suggests that the jökulhlaup created high subglacial water pressure that impeded normal drainage of solute‐rich water from a distributed drainage system into a conduit system at the glacier bed and even caused flow direction locally to reverse.
North Africa‐West Asia (NAWA) sea‐level pressure patterns and their linkages with the Eastern Mediterranean (EM) climate
Authors: Paz Shlomit , Tourre Yves M. , Planton Serge
Published: October 2003

Monthly mean SLP anomalies are analyzed from the 1958–1997 record covering the Mediterranean Basin. From point‐correlation technique, a significant winter anomalous SLP oscillation between North Africa (NA) and West Asia (WA) or NAWA, is identified. Insight into the inter‐annual variability of NAWA is obtained from the detrended and composited patterns. During P/N, positive/negative values of the index, higher/lower SLP values over the Mediterranean and lower/higher values east of the Caspian Sea are displayed respectively. In both cases, maximum SLP gradients are found over the Eastern Mediterranean (EM). During P/N phases, decrease/increase in winter rainfall amounts and cooler/warmer temperatures are found and could be associated with enhanced northerlies/southeasterlies over the EM. The original and undetrended NAWA indices display mostly P phases during the second half of the period. The regional trend of NAWA index could explain increased drought processes in the EM after the late 70s, in relation with northern hemispheric circulation.
Evaluation of the agreement between the first global remotely sensed soil moisture data with model and precipitation data
Authors: Wagner Wolfgang , Scipal Klaus , Pathe Carsten , Gerten Dieter , Lucht Wolfgang , Rudolf Bruno
Published: October 2003

The lack of global soil moisture data has spurred research in the field of microwave remote sensing. Both passive (radiometers) and active (scatterometer) microwave data are very sensitive to the moisture content of the surface soil layer. To retrieve soil moisture, the effects of vegetation, surface roughness, and heterogeneous land cover must be taken into account. Field experiments have shown that passive microwave data at long wavelengths (L‐band) are best suited for soil moisture retrieval. Nevertheless, the first global, multiannual soil moisture data set (1992–2000) has been derived from active microwave data acquired by the European Remote Sensing Satellites (ERS) ERS‐1 and ERS‐2 scatterometer (C‐band). The retrieval algorithm is based on a change detection approach that naturally accounts for surface roughness and heterogeneous land cover. In this paper the scatterometer‐derived soil moisture data are compared to gridded precipitation data and soil moisture modeled by a global vegetation and water balance model. The correlation between soil moisture and rainfall anomalies is observed to be best over areas with a dense rainfall gauge network. Also, the scatterometer‐derived and modeled soil moisture agree reasonably well over tropical and temperate climates. The fact that the algorithm performs equally well for regions with summer rain and Mediterranean areas indicates that dynamic vegetation effects are correctly represented in the retrieval. More research is needed to better understand the backscattering behavior over dry (steppe, deserts) and cold (boreal zone, tundra) climatic regions. The scatterometer‐derived soil moisture data are available to other research groups at http://www.ipf.tuwien.ac.at/radar/ers-scat/home.htm.
Cold surface layer thinning on Storglaciären, Sweden, observed by repeated ground penetrating radar surveys
Authors: Pettersson Rickard , Jansson Peter , Holmlund Per
Published: October 2003

A characteristic feature of ground penetrating radar (GPR) surveys on polythermal glaciers is an internal reflection presumably caused by the cold temperate transition surface (CTS), hence providing a possible tool for mapping thermal structure with high accuracy. Comparison of detailed temperature measurements in bore holes and GPR profiles at 345 MHz and 800 MHz center frequencies on Storglaciären, Sweden, show that the CTS can be detected and mapped with an accuracy of about ±1 m at both frequencies. A comparison between comprehensive GPR surveys of the cold surface layer, separated by 12 years (1989–2001), shows a substantial and complex thinning of the cold layer. An overall decrease of 8.3 m (22% of average thickness) of the CTS depth is much larger than uncertainties in CTS depth determinations. The stability of the cold surface layer depends on the net ice ablation at the surface and the downward migration of CTS. There is no evidence of substantial increased net ablation between the survey dates that could explain the observed thinning. However, small increase in average winter air temperature, a limiting factor for the temperature gradient through the cold surface layer, may provide a partial explanation. The weaker temperature gradient reduces the transport of latent heat from the CTS, thus slowing down its downward migration.
Polarimetric synthetic aperture radar study of the Tsaoling landslide generated by the 1999 Chi‐Chi earthquake, Taiwan
Authors: Czuchlewski Kristina R. , Weissel Jeffrey K. , Kim Yunjin
Published: October 2003

We employ L‐band airborne synthetic aperture radar (SAR) polarimetry to detect surface changes produced by the Tsaoling landslide, the largest slope failure triggered by the September 1999 Chi‐Chi earthquake in central Taiwan. Imaging polarimeters provide a complete description of the scattering properties of radar target materials. Resurfacing of forested hillslopes by landslides alters scattering mechanisms from those dominated by backscatter from trees to mechanisms associated with scatter from rough, bare surfaces. Scattering mechanism information on a per‐pixel basis is extracted by decomposing matrices formed as the outer product of the complex scattering vector measured for each resolution cell. We classify surface cover type and thereby identify the extent of the landslide, using such polarimetric parameters as scattering entropy, anisotropy, and pedestal height, derived from the eigenvalues of the decomposition, as well as the weighted average scattering mechanism derived from the eigenvectors. We address the utility of full polarimetry versus dual polarimetry for landslide mapping purposes and show that fully polarimetric SAR is necessary for distinguishing water surfaces of varying roughness from the bare surfaces created by landsliding. We show that scattering entropy and average scattering mechanism, for example, can be used to identify the Tsaoling landslide source, run out area and impounded lakes as proficiently as maps obtained using satellite optical sensors, such as Landsat and the Indian Research Satellite. However, the operational advantages of radar over optical sensing techniques (namely, its day‐night, all‐weather data acquisition capability) suggest that SAR polarimetry could play a leading role in the rapid assessment of landslide disasters.
Periodic Mesoporous Organosilicas Containing Interconnected [Si(CH
2
)]
3
Rings
Authors: Landskron Kai , Hatton Benjamin D. , Perovic Doug D. , Ozin Geoffrey A.
Published: October 2003

A periodic mesoporous organosilica composed of interconnected three-ring [Si(CH
2
)]
3
units built of three SiO
2
(CH
2
)
2
tetrahedral subunits is reported. It represents the archetype of a previously unknown class of nanocomposite materials in which two bridging organic groups are bound to each silicon atom. It can be obtained with powder and oriented film morphologies. The nanocomposite is self-assembled from the cyclic three-ring silsesquioxane [(EtO)
2
Si(CH
2
)]
3
precursor and a surfactant mesophase to give a well-ordered mesoporous framework. Low dielectric constants and good mechanical stability of the films were measured, making this material interesting for microelectronic applications. Methylene group reactivity of the three-ring precursor provides entry to a family of nanocomposites, exemplified by the synthesis and self-assembly of [(EtO)
2
Si(CHR)][(EtO)
2
Si(CH
2
)]
2
(where R indicates iodine, bromine, or an ethyl group).
A Neurexin-Related Protein, BAM-2, Terminates Axonal Branches in
C. elegans
Authors: Colavita Antonio , Tessier-Lavigne Marc
Published: October 2003

Neuronal axons connect to multiple target cells through the formation of collateral branches, but the mechanisms that regulate this process are largely unknown. We show that BAM-2, a neurexin-related transmembrane protein, is required for development of VC motoneuron branches in the worm
Caenorhabditis elegans
. Expression analysis and ectopic expression experiments suggest that BAM-2 functions as a branch termination cue and reveal a mechanism for selective control of branches that sprout off a primary axon.
Hecke Groups, Polynomial Maps and Matings
Authors: Bullett Shaun , Freiberger Marianne
Published: October 2003

We show that there is a topological conjugacy between the action of the Hecke group Gn on the completed positive real axis and the action of the shift on base n-1 expressions of real numbers in the unit interval. This conjugacy is shown to occur in holomorphic dynamical systems: we construct (n-1:n-1) holomorphic correspondences (multivalued self-maps of the Riemann sphere) which are matings between Gn acting on the complex upper half plane, and polynomials of degree n-1 acting on their filled Julia sets. Certain of these correspondences split into unions of (2:2) and (1:1) correspondences: we present combinatorial descriptions of limit sets and the connectivity locus in the case n=4.
Discrete Breathers Close to the Anticontinuum Limit: Existence and Wave Scattering
Authors: Flach S. , Dorignac J. , Miroshnichenko A. E. , Fleurov V.
Published: October 2003

The anticontinuum limit (i.e. the limit of weakly coupled oscillators) is used to obtain two surprising results. First we prove the continuation of discrete breathers of weakly interacting harmonic oscillators, provided a suitable coupling is chosen. Secondly we derive an analytical result for the wave transmission by a breather of the discrete nonlinear Schrödinger equation at weak coupling. We obtain a resonant full reflection due to a Fano resonance.
Infection Dynamics on Growing Networks
Authors: Lai Ying-Cheng , Liu Zonghua , Ye Nong
Published: October 2003

We consider the entire spectrum of architectures for large, growing, and complex networks, ranging from being heterogeneous (scale-free) to homogeneous (random or small-world), and investigate the infection dynamics by using a realistic three-state epidemiological model. In this framework, a node can be in one of the three states: susceptible (S), infected (I), or refractory (R), and the populations in the three groups are approximately described by a set of nonlinear differential equations. Our heuristic analysis predicts that, (1) regardless of the network architecture, there exists a substantial fraction of nodes that can never be infected, and (2) heterogeneous networks are relatively more robust against spread of infection as compared with homogeneous networks. These are confirmed numerically. We have also considered the problem of deliberate immunization for preventing wide spread of infection, with the result that targeted immunization can be quite effective for heterogeneous networks. We believe these results are important for a host of problems in many areas of natural science and engineering, and in social sciences as well.
Stability Analysis of Collisional Granular Flow on a Slope
Authors: Mitarai Namiko , Nakanishi Hiizu
Published: October 2003

We analyze the linear stability of a collisional granular flow on a slope under gravity using hydrodynamical equations based on kinetic theory of inelastic particles. It is shown that the steady, uniform flow is unstable against longitudinal long-wavelength perturbations in lower density region. The results are compared with the instabilities found in numerical simulations of granular flows.
Bifurcation and Chaos Research on Dry Friction System in the Spring Fault Condition
Authors: Zhao Wenli , Zhou Xiaojun , Luo Guanwei
Published: October 2003

In this paper, the periodic solutions and stability in the dry friction dynamic system are researched by two-dimensional Poincaremap when the fault has happened in the system because of the spring failure. As a result of numerical computation and theoretical analysis, the bifurcation and chaos will arise when the parameters of system are changed. It is very important to analyze the dynamic behavior to conduct fault diagnosis.
Implementation of Boundary Conditions for Optimized High-Order Compact Schemes
Authors: Kim Jae Wook , Lee Duck Joo
Published: October 2003

The optimized high-order compact (OHOC) finite difference schemes, proposed as central schemes are used for aeroacoustic computations on interior nodes. On near-boundary nodes, accurate non-central or one-sided compact schemes are formulated and developed in this paper for general computations in domains with non-periodic boundaries. The near-boundary non-central compact schemes are optimized in the wavenumber domain by using Fourier error analysis. Analytic optimization methods are devised to minimize the dispersion and dissipation errors, and to obtain maximum resolution characteristics of the near-boundary compact schemes. With the accurate near-boundary schemes, the feasibility of implementing physical boundary conditions for the OHOC schemes are investigated to provide high-quality wave solutions. Characteristics-based boundary conditions and the free-field impedance conditions are used as the physical boundary conditions for direct computations of linear and nonlinear wave propagation and radiation. It is shown that the OHOC schemes present accurate wave solutions by using the optimized near-boundary compact schemes and the physical boundary conditions.
Numerical Study of Noise from Isotropic Turbulence
Authors: Witkowska A. , Juvé D. , Brasseur J. G.
Published: October 2003

A numerical study of sound radiation by isotropic turbulence is carried out by combining turbulence simulation with Lighthill's acoustic analogy. In the first study we analyze sound generation by decaying isotropic turbulence obtained both with 643 Direct Numerical Simulation (DNS) and 163 Large Eddy Simulation (LES). Both simulations lead to similar results for acoustic power, in agreement with the numerical results of Sarkar and Hussaini, but slightly different from theoretical predictions of Proudman and Lilley. In the second study we analyze sound generation by forced stationary turbulence, simulated with 1283 DNS using a forcing scheme which preserves turbulence structure. The acoustic power computed from the stationary turbulence is in good agreement with results obtained for decaying isotropic turbulence. The acoustic spectrum shows that the characteristic frequency of the generated sound is approximately four times the inverse eddy turnover time. The contributions of different turbulence scales to the generated noise are computed separately from filtered velocity fields. For the low Reynolds number turbulence analyzed, the scales which most contribute to noise generation are 2–3 times smaller than the energy-containing scales and lie between the energy and dissipation-rate spectral peaks.
Rat Skeletal Muscle Myoblasts are Target Cells for the Action of Native Bone Morphogenetic Protein
Authors: Jortikka L. , Laitinen M. , Wiklund J. , Lindholm T. S. , Marttinen A.
Published: October 2003

Bone morphogenetic proteins (BMPs) are multifunctional proteins capable of inducing an osteogenic phenotype in various cell lines and providing alternatives to bone grafts in the field of orthopaedics. Study was carried out here of the specific binding and stimulation of markers of bone metabolism by highly purified native bovine BMP in rat skeletal myoblasts (L6). Binding studies using 125I-labeled BMP and various concentrations of unlabeled BMP showed the existence of a single-class, one-binding-site BMP receptor. The binding was time-, temperature- and dose-dependent in various experiments. In assessing the capacity of BMP to induce myoblasts to differentiate into the osteoblast lineage, osteocalcin production was initiated, alkaline phosphatase activity increased approximately four-fold and calcium uptake almost three-fold compared with control cells during four days culturing with 12.5 μg/ml of BMP. These results indicate that the L6 myoblast is a target cell for the action of native BMP, and under the influence of BMP L6 myoblasts are capable of differentiating in the direction of osteoblasts. This BMP-induced differentiation of myoblasts offers a novel assay system for in vitro detection of osteoinductivity and investigation of the mechanism of ectopic bone formation.
On-Off Intermittency and Riddled Basins of Attraction in a Coupled Map System
Authors: Laugesen J. , Mosekilde E. , Maistrenko Yu. L. , Maistrenko V. L.
Published: October 2003

The paper examines the appearance of on-off intermittency and riddled basins of attraction in a system of two coupled one-dimensional maps, each displaying type-III intermittency. The bifurcation curves for the transverse destablilization of low periodic orbits embeded in the synchronized chaotic state are obtained. Different types of riddling bifurcation are discussed, and we show how the existence of an absorbing area inside the basin of attraction can account for the distinction between local and global riddling as well as for the distinction between hysteric and non-hysteric blowout. We also discuss the role of the so-called mixed absorbing area that exists immediately after a soft riddling bifurcation. Finally, we study the on-off intermittency that is observed after a non-hysteric blowout bifurcaton.
The geometric maximum traveling salesman problem
Authors: Barvinok Alexander , Fekete Sándor P. , Johnson David S. , Tamir Arie , Woeginger Gerhard J. , Woodroofe Russ
Published: October 2003

We consider the traveling salesman problem when the cities are points in ℝ

d

for some fixed
d
and distances are computed according to geometric distances, determined by some norm. We show that for any polyhedral norm, the problem of finding a tour of
maximum
length can be solved in polynomial time. If arithmetic operations are assumed to take unit time, our algorithms run in time
O
(
n

f
-2

log
n
), where
f
is the number of facets of the polyhedron determining the polyhedral norm. Thus, for example, we have
O
(
n
2
log
n
) algorithms for the cases of points in the plane under the Rectilinear and Sup norms. This is in contrast to the fact that finding a
minimum
length tour in each case is NP-hard. Our approach can be extended to the more general case of
quasi-norms
with a not necessarily symmetric unit ball, where we get a complexity of
O
(
n

2
f
-2

log
n
).For the special case of two-dimensional metrics with
f
= 4 (which includes the Rectilinear and Sup norms), we present a simple algorithm with
O
(
n
) running time. The algorithm does not use any indirect addressing, so its running time remains valid even in comparison based models in which sorting requires Ω(
n
log
n
) time. The basic mechanism of the algorithm provides some intuition on why polyhedral norms allow fast algorithms.Complementing the results on simplicity for polyhedral norms, we prove that, for the case of Euclidean distances in ℝ

d

for
d
≥ 3, the Maximum TSP is NP-hard. This sheds new light on the well-studied difficulties of Euclidean distances.
Dual domain extrapolation
Authors: Lévy Bruno
Published: October 2003

Shape optimization and surface fairing for polygon meshes have been active research areas for the last few years. Existing approaches either require the border of the surface to be fixed, or are only applicable to closed surfaces. In this paper, we propose a new approach, that computes natural boundaries. This makes it possible not only to smooth an existing geometry, but also to extrapolate its shape beyond the existing border. Our approach is based on a global parameterization of the surface and on a minimization of the squared curvatures, discretized on the edges of the surface. The so-constructed surface is an approximation of a minimal energy surface (MES). Using a global parameterization makes it possible to completely decouple the outer fairness (surface smoothness) from the inner fairness (mesh quality). In addition, the parameter space provides the user with a new means of controlling the shape of the surface. When used as a geometry filter, our approach computes a smoothed mesh that is discrete conformal to the original one. This allows smoothing textured meshes without introducing distortions.