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We examine the influence of noise on the propagation of harmonic signals with two frequencies through discrete bistable media. We show that random fluctuations enhance propagation of this kind of signals for low coupling strengths, similarly to what happens with purely monochromatic signals. As a more relevant finding, we observe that the frequency being propagated with better efficiency can be selected by tuning the intensity of the noise, in such a way that for large noises the highest frequency is transmitted better than the lower one, whereas for small noises the reverse holds. Such a noise-induced frequency selection can be expected to exist for general multifrequency harmonic signals.
We report on the effect of vibrational resonance in a spatially extended system of coupled noisy oscillators under the action of two periodic forces, a low-frequency one (signal) and a high-frequency one (carrier). Vibrational resonance manifests itself in the fact that for optimally selected values of high-frequency force amplitude, the response of the system to a low-frequency signal is optimal. This phenomenon is a synthesis of two effects, a noise- induced phase transition leading to bistability, and a conventional vibrational resonance, resulting in the optimization of signal processing. Numerical simulations, which demonstrate this effect for an extended system, can be understood by means of a zero-dimensional "effective" model. The behavior of this "effective" model is also confirmed by an experimental realization of an electronic circuit.
We show that external fluctuations are able to induce propagation of harmonic signals through monostable media. This property is based on the phenomenon of doubly stochastic resonance, where the joint action of multiplicative noise and spatial coupling induces bistability in an otherwise monostable extended medium, and additive noise resonantly enhances the response of the system to a harmonic forcing. Under these conditions, propagation of the harmonic signal through the unforced medium i observed for optimal intensities of the two noises. This noise-induced propagation is studied and quantified in a simple model of coupled nonlinear electronic circuits.
Our every-day experience is connected with different acoustical noise or music. Usually noise plays the role of nuisance in any communication and destroys any order in a system. Similar optical effects are known: strong snowing or raining decreases quality of a vision. In contrast to these situations noisy stimuli can also play a positive constructive role, e.g. a driver can be more concentrated in a presence of quiet music. Transmission processes in neural systems are of especial interest from this point of view: excitation or information will be transmitted only in the case if a signal overcomes a threshold. Dr. Alexei Zaikin from the Potsdam University studies noise-induced phenomena in nonlinear systems from a theoretical point of view. Especially he is interested in the processes, in which noise influences the behaviour of a system twice: if the intensity of noise is over a threshold, it induces some regular structure that will be synchronized with the behaviour of neighbour elements. To obtain such a system with a threshold one needs one more noise source. Dr. Zaikin has analyzed further examples of such doubly stochastic effects and developed a concept of these new phenomena. These theoretical findings are important, because such processes can play a crucial role in neurophysics, technical communication devices and living sciences.
In this paper, the problem on formation and construction of a shock wave for three dimensional compressible Euler equations with the small perturbed spherical initial data is studied. If the given smooth initial data satisfies certain nondegenerate condition, then from the results in [20], we know that there exists a unique blowup point at the blowup time such that the first order derivates of smooth solution blow up meanwhile the solution itself is still continuous at the blowup point. From the blowup point, we construct a weak entropy solution which is not uniformly Lipschitz continuous on two sides of shock curve, moreover the strength of the constructed shock is zero at the blowup point and then gradually increases. Additionally, some detailed and precise estimates on the solution are obtained in the neighbourhood of the blowup point.
This note is devoted to the study on the global existence of a shock wave for the supersonic flow past a curved wedge. When the curved wedge is a small perturbation of a straight wedge and the angle of the wedge is less than some critical value, wwe show that a shock attached at the wedge will exist globally.
From the root bark of Erythrina burttii three new isoflav-3-enes, 7,4'-dihydroxy-2'-methoxy-6- (1'',1''-dimethylallyl)isoflav-3-ene (trivial name, burttinol-A), 4'-hydroxy-2'- methoxy-(2'',2''-dimethylpyrano[5'',6'':8,7]isoflav-3-ene (trivial name, burttinol-B), 7,4'-dihydroxy-2'-methoxy-8-(3'',3''-dimethylallyl)isoflav-3-ene (trivial name, burttinol-C), and a new 2-arylbenzofuran, 6,4'-dihydroxy-2'-methoxy-5- (1'',1''-dimethylallyl)-2-arylbenzofuran (trivial name, burttinol-D) were isolated. In addition, the known compounds, abyssinone V-4'-methyl ether, bidwillol A, calopocarpin, erybraedin A, erythrabyssin II, isobavachalcone, phaseollidin and phaseollin were identified. The structures were determined on the basis of spectroscopic evidence.
Local asymptotic types
(2002)
Local asymptotic types
(2002)
We report the discovery of a new gravitationally lensed QSO, at a redshift z = 1.689, with four QSO components in a cross-shaped arrangement around a bright galaxy. The maximum separation between images is 2farcs 6, enabling a reliable decomposition of the system. Three of the QSO components have g =~ 19.6, while component A is about 0.6 mag brighter. The four components have nearly identical colours, suggesting little if any dust extinction in the foreground galaxy. The lensing galaxy is prominent in the i band, weaker in r and not detected in g. Its spatial profile is that of an elliptical galaxy with a scale length of ~ 12 kpc. Combining the measured colours and a mass model for the lens, we estimate a most likely redshift range of 0.3 < z < 0.4. Predicted time delays between the components are la 10 days. The QSO shows evidence for variability, with total g band magnitudes of 17.89 and 17.71 for two epochs separated by ~ 2 months. However, the relative fluxes of the components did not change, indicating that the variations are intrinsic to the QSO rather than induced by microlensing. Based in part on observations obtained with the Baade 6.5-m telescope of the Magellan Consortium. Also based in part on observations collected at the European Southern Observatory, La Silla, Chile.
Chiroptcial properties of poly(p-phenyleneethynylene) copolymers in thin films : large g-values
(2002)
Observational data of natural systems, as measured in medical measurements are typically quite different from those obtained in laboratories. Due to the peculiarities of these data, wellknown characteristics, such as power spectra or fractal dimension, often do not provide a suitable description. To study such data, we present here some measures of complexity, which are basing on symbolic dynamics. Firstly, a motivation for using symbolic dynamics and measures of complexity in data analysis based on the logistic map is given and next, two applications to medical data are shown. We demonstrate that symbolic dynamics is a useful tool for the risk assessment of patients after myocardial infarction as well as for the evaluation of th e architecture of human cancellous bone.
Human Rights
(2002)
Significant seasonal variation in size at settlement has been observed in newly settled larvae of Dreissena polymorpha in Lake Constance. Diet quality, which varies temporally and spatially in freshwater habitats, has been suggested as a significant factor influencing life history and development of freshwater invertebrates. Accordingly, experiments were conducted with field-collected larvae to test the hypothesis that diet quality can determine planktonic larval growth rates, size at settlement and subsequent post-metamorphic growth rates. Larvae were fed one of two diets or starved. One diet was composed of cyanobacterial cells which are deficient in polyunsaturated fatty acids (PUFAs), and the other was a mixed diet rich in PUFAs. Freshly metamorphosed animals from the starvation treatment had a carbon content per individual 70% lower than that of larvae fed the mixed diet. This apparent exhaustion of larval internal reserves resulted in a 50% reduction of the postmetamorphic growth rates. Growth was also reduced in animals previously fed the cyanobacterial diet. Hence, low food quantity or low food quality during the larval stage of D. polymorpha lead to irreversible effects for postmetamorphic animals, and is related to inferior competitive abilities.
A significant seasonal variation in size at settlement has been observed in newly settled larvae of Dreissena polymorpha in Lake Constance. Diet quality, which varies temporally and spatially in freshwater habitats, has been suggested as a significant factor influencing the life history and development of freshwater invertebrates. Accordingly, experiments were conducted with field-collected larvae to test the proposal that diet quality can determine planktonic larval growth rates, size at settlement and subsequent post-metamorphic growth rates. Larvae were fed one of two diets or starved. One diet was composed of cyanobacterial cells, which are de; cient in polyunsaturated fatty acids (PUFAs) and the other was a mixed diet rich in PUFAs. Freshly metamorphosed animals from the starvation treatment had a carbon content per individual 70% lower than that of larvae fed the mixed diet. This apparent exhaustion of larval internal reserves resulted in a 50% reduction of the post-metamorphic growth rates. Growth was also reduced in animals previously fed the cyanobacterial diet. Hence, low food quantity or low food quality during the larval stage of D. polymorpha, lead to irreversible effects for post-metamorphic animals and are related to inferior competitive abilities.
Food quality effects of unsaturated fatty acids on larvae of the zebra mussel Dreissena polymorpha
(2002)
In standardized growth experiments, newly hatched larvae of the zebra mussel Dreissena polymorpha were fed diets representing different biochemical compositions. Algae that were rich in (n-3) polyunsaturated fatty acids (PUFAs), except for long-chained (.C18) PUFAs (Chlorella minutissima and Monoraphidium minutum) were of low food quality. Higher growth than on C. minutissima or M. minutum was supported by a culture of the cyanobacterium Aphanothece sp., which contained traces of a long-chained (n-3) PUFA, docosahexaenoic acid (DHA, 22 : 6n-3). The alga Isochrysis aff. galbana, which contained high amounts of the longchained (n-3) PUFAs DHA and eicosapentaenoic acid (EPA, 20 : 5n- 3), supported the highest growth. The alga Nannochloropsis limnetica, which differed from I. galbana by a defi- ciency in DHA, allowed slightly, but significantly lower, growth. Growth of larvae on N. limnetica was increased by enrichment of N. limnetica cells with a lipid extract of I. galbana, showing that larval growth on N. limnetica was limited by the deficiency of a compound that was present in I. galbana. Growth was also enhanced by feeding N. limnetica cells supplemented with DHA, but not by cells enriched with EPA, indicating that DHA was the limiting factor. We conclude that, on DHA-deficient food, the larvae of D. polymorpha were not able to sufficiently convert C18-PUFAs into long- chained (n-3) PUFAs and that the rates for elongation and desaturation of EPA into DHA limited growth.
A simple synthetic route to a new poly(diallylammonium) salt functionalized by a styrene group is presented. This reactive polymer was employed for polyelectrolyte multilayer films using electrostatical layer-by-layer self- assembly, together with an inorganic polyanion, namely an exfoliated hectorite clay. To enhance their stability, the final hybrid multilayers were cross-linked by exposure to UV light, leading only to a minor shrinkage. Alternatively, the reactive polycation was cross-linked after each adsorption step. X-ray reflectometry revealed that the two types of films dispose of an internal order with a short length scale, that seems insensitive to the photo-cross-linking. Cross- linking after each adsorption step, however, results in more regular film growth, and reduces the films? roughness and the amount of polyanion deposited. Under these conditions, the films seem to grow by deposition of submonolayers with a combined vertical and lateral expansion, resulting in the self-healing of previously deposited, incomplete layers.
Yet another Theta-System
(2002)
Thermal properties of block copolymer, poly(N-isopropyl acrylamide)-block-poly(3-[N-(3-methacrylamido-propyl)- N,N-dimethyl]-ammonio propane sulfonate), PNIPA-b-PSPP have been studied in pure and saline (NaCl) aqueous solutions by dynamic laser light scattering (DLS). The copolymer [Mw(PNIPA) 10800 g/mol and Mw(PSPP) 9700 g/mol] exhibits both an upper (UCST 9 oC) and lower (LCST 32 oC) critical solution temperatures in pure water. The addition of NaCl enhances the solubility of the zwitterionic polymer, PSPP, leading to the disappearance of the UCST. On the other hand, the solubility of PNIPA in water decreases as NaCl is added. At 20 oC the copolymer shows a bimodal size distribution through the NaCl concentration range of 0-0.93 M above a certain limiting polymer concentration. The slow and fast components of the diffusion coefficients of the polymer have been calculated. A gradual addition of salt turns the mutual interactions from zwitterionic attractions between PSPP blocks to hydrophobic attractions between PNIPA blocks. The formation of the aggregates and the aggregate sizes at T < UCST and T > LCST are influenced by polymer and salt concentrations. Below UCST the aggregates in saline polymer solutions are larger than those in pure polymer solutions. Above LCST the aggregate size is determined by the salt concentration.
Chitinase B (ChiB) from Serratia marcescens is a family 18 exochitinase whose catalytic domain has a TIM-barrel fold with a tunnel-shaped active site. We have solved structures of three ChiB complexes that reveal details of substrate binding, substrateassisted catalysis, and product displacement. The structure of an inactive ChiB mutant (E144Q) complexed with a pentameric substrate (binding in subsites 22 to 13) shows closure of the ''roof'' of the active site tunnel. It also shows that the sugar in the 21 position is distorted to a boat conformation, thus providing structural evidence in support of a previously proposed catalytic mechanism. The structures of the active enzyme complexed to Allosamidin (an analogue of a proposed reaction intermediate) and of the active enzyme soaked with pentameric substrate show events after cleavage of the glycosidic bond. The latter structure shows reopening of the roof of the active site tunnel and enzyme-assisted product displacement in the 11 and 12 sites, allowing a water molecule to approach the reaction center. Catalysis is accompanied by correlated structural changes in the core of the TIM barrel that involve conserved polar residues whose functions were hitherto unknown. These changes simultaneously contribute to stabilization of the reaction intermediate and alternation of the pKa of the catalytic acid during the catalytic cycle.
A close comparative analysis of the attrition of inflections in historical English and Welsh reveals that Welsh had already lost its entire NP inflection when it surfaces in writing in the 7c AD, while English was still fully inflected both in the NP and VP. The comparison of the modern English and Welsh morphological categories shows that English overtook Welsh in its rate of analyticising drift. This shows first in writing during the Middle English period. Thus in English, the attrition bothfully affected the NP and the VP, while in modern Welsh the attrition of the verbal inflection in the VP is much less advanced than in English. Both languages, however, share the shift in the VP from the synthetism of verbal tense, mood (and voice) marking towards analytic aspect marking, which continues to gain in importance in both languages today. The question is raised, whether this joint development may have been due to the influence of the 'Late British' speaking shifters to Old English, to prolongued areal contactin the island of Britain ("Sprachbund") and/or to a more general drift from syntheticity to analycity in (Western) IE languages in Europe, which affects some languages more than others. The Appendix prints the earliest Old English and Old Welsh texts (dated by absolute chronology) and marks their loss of inflections, in order to highlight the advanced analycity in the Old Welsh NP as opposed to the Old English NP.
The continued linguistic contact in the islands of Britain and Ireland over the past two millenia has led to linguistic convergence processes between the Insular Celtic and West Germanic languages involved. While the Latin, Old Norse and Norman French contact scenarios were recognised and have been well studied since the 19c, the Celtic component received much less scholarly attention until the 1990s because of the continued linguistic bias, once fostered by 19c Anglo-Saxonisms and the idea of racial purity of the Egnlish population. It is only in the very recent past that the many different contact areas between English and the Insular Celtic languages have received recognition after New Labour's post-1997 introduction of "devolution" politics. The closest and longest interaction took of course place between English and Welsh. The present article looks at three major types of interaction which led to convergence in a number of important linguistic features: (1) mutual retention of shared archaic features, (2) mutual shared innovations, and (3) transfer from one language to another, either by unilateral or by bilateral transfer. The exemplary contact features discussed in this article relate to the retention of interdental fricatives, the shared innovation of analycity and multi-word verb formation, and clefting as feature transfer. Transfer is likely to have taken place under the following conditions: (a) earlier written documentation in the donor language, (b) higher frequency of occurrence in the donor language, (c) conformity with other structures in the donor language, and (d) grammaticalisation in the donor language. The conclusion endorses Salikoko Mufwene's claim that the making of English in the island of Britain was subject to the same contact processes which created the English based creoles from indigenised Englishes during the colonial period.
DO-Periphrasis in Irish
(2002)
Periphrastic DO constructions are very common both in English and in the Neo-Brittonic languages and are used for various functional purposes. These form part of a larger linguistic area in western and northern Europe. The literature does not mention comparable constructions for Irish and Scottish Gaelic. Irish informants, however, confirm orally that they are in common use among present day Gaeltacht speakers. They appear also to have been common in late spoken Manx. This study is based on the "Caint Chonamara" electronic corpus, the field work for which was first untertaken by Hans Hartmann (Hamburg) and Tomás de Bhaldraithe (Dublin) in the early 1960s und brought to a close by Arndt Wigger (Wuppertal) in the 1990s. The file for the Ros Muc dialogues yielded a very low return of potential DO constructions, i.e. 14 tokens of DÉAN + VN out of 494 DÉAN tokens altogether in the file. This shows that the DÉAN + VN construction was grammatically correct and acceptable to the native speakers, but was not grammaticalised and had a very low frequency. This result is interesting, but not surprising, since the informants chosen for this file conformed to the NORMS category (non-mobile old rural males. They were born around the turn of the 19c/20c and acquired their language now more than 100 years ago. This was well before the independence of the Republic. They would have acquired their Irish orally from native speakers and underwent very little formal training in Irish, or none. This small sample confirms that Irish did not belong to the broad linguistic area in Western Europe which makes use of periphrastic DO constructions, at least not until very recently.
A report of Mikhail Gasparov's 1989 book on the 'History of European Versification' is the starting point of the discussion in this article of the types of versification found in the Insular Celtic literatures from their first documenation in the early middle ages to the present day, as Gasparov's survey does not cover these poetries. It is claimed here that their metrical constraints were pre-literate and first and foremost geared at aural reception. The introduction of writing led to an increase in metrical sophistication which, while still basically oral, because of the process of "prelecting" (i.e. reading out aloud to illiterate or semi-literate audiences), required a very careful appreciation of their metrical skills. Contact with English and French syllabic poetry in the later middle ages and particularly in the modern period produced so-called "free verse" poetry. The word "free" in this particular context meant that the rather loose metrical constraints of these majority literatures in no way compared with the extraordinarily high metrical sophistication of the native oral derived or "bardic" poetry.
In this article, the synthesis of analogs of N,N',N''-triacetylchitotriose in which the central sugar residue was replaced by a succinic acid is presented. Mol. modeling calcns. revealed that the pseudotrisaccharides exist in low energy extended conformations which show similar space filling as N,N',N''-triacetylchitotriose. Of the N,N',N''-triacetylchitotriose pseudosugar analogs tested as chitinase inhibitors, none showed any appreciable competition (numerical data not presented). The conformational anal. along with further synthetic efforts will hopefully lead to more efficient pseudosaccharides as chitinase inhibitors.
Anisotropic edge problems
(2002)
Anisotropic edge problems
(2002)
We investigate elliptic pseudodifferential operators which degenerate in an anisotropic way on a submanifold of arbitrary codimension. To find Fredholm problems for such operators we adjoint to them boundary and coboundary conditions on the submanifold.The algebra obtained this way is a far reaching generalisation of Boutet de Monvel's algebra of boundary value problems with transmission property. We construct left and right regularisers and prove theorems on hypoellipticity and local solvability.
Today, analytical chemistry does not longer consist of only the big measuring devices and methods which are time consuming and expensive, which can furthermore only be handled by the qualified staff and in addition the results can also only be evaluated by this qualified staff. Usually, this technique, which shall be described in the following as 'classic analytic measuring technique', requires also rooms equipped especially and often a relative big quantity of the test compounds which should be prepared especially. Beside this classic analytic measuring technique, limited on definite substance groups and requests, a new measuring technique has gained acceptance particularly within the last years, which one can often be used by a layman, too. Often the new measuring technique has very little pieces of equipment. The needed sample volumes are also small and a special sample preparation isn't required. In addition, the new measuring instruments are simple to handle. They are cheap both in their production and in the use and they permit even a continuous measurement recording usually. Numerous of this new measuring instruments base on the research in the field of Biosensorik during the last 40 years. Since Clark and Lyon in the year 1962 were able to measure glucose with a simple oxygen electrode, completed by an enzyme the development of the new measuring technique did not have to be held back any longer. Biosensors, special pickups which consists of a combination from a biological component (permits a specific recognition of the analyte also without purification of the sample previously) and a physical pickup (convert the primary physicochemical effect into an electronically measurable signal), conquered the market. In the context of this thesis different tyrosinasesensors were developed which fulfilling the various requests, depending on origin and features of the used tyrosinase. One of the tyrosinasesensors for example was used for quantification of phenolic compounds in river and sea water and the results could correlated very well with the corresponding DIN-test for the determination of phenolic compounds. An other developed tyrosinasesensor showed a very high sensitiveness for catecholamines, substances which are of special importance in the medical diagnostics. In addition, the investigations of two different tyrosinases, which were carried out also in the context of this thesis, have shown, that a special tyrosinase (tyrosinase from Streptomyces antibioticus) will be the better choice as tyrosinase from Agaricus bisporus, which is used in the area of biosensor research till now, if one wants to develop in future even more sensitive tyrosinasesensors. Furthermore, first successes became reached on a molecular biological field, the production of tyrosinasemutants with special, before well-considered features. These successes can be used to develop a new generation of tyrosinasesensors, tyrosinasesensors in which tyrosinase can be bound directionally both to the corresponding physical pickup or also to another enzyme. From this one expects to achieve ways minimized which the substance to be determined (or whose product) otherwise must cover. Finally, this should result in an clearly visible increase of sensitivity of the Biosensor.
Estimation of parameters and unobserved components for nonlinear systems from noisy time series
(2002)
We study the problem of simultaneous estimation of parameters and unobserved states from noisy data of nonlinear time-continuous systems, including the case of additive stochastic forcing. We propose a solution by adapting the recently developed statistical method of unscented Kalman filtering to this problem. Due to its recursive and derivative-free structure, this method minimizes the cost function in a computationally efficient and robust way. It is found that parameters as well as unobserved components can be estimated with high accuracy, including confidence bands, from heavily noise-corrupted data.
Photoaddressable alignment layers for fluorescent polymers in polarized electroluminescence devices
(2002)
1. Fussmann et al. (2000) presented a simple mechanistic model to explore predator-prey dynamics of a rotifer species feeding on green algae. Predictions were tested against experimental data from a chemostat system housing the planktonic rotifer Brachionus calyciflorus and the green alga Chlorella vulgaris. 2. The model accurately predicted qualitative behaviour of the system (extinction, equilibria and limit cycles), but poorly described features of population cycles such as the period and predator-prey phase relationship. These discrepancies indicate that the model lacked some biological mechanism(s) crucial to population cycles. 3. Here candidate hypotheses for the 'missing biology' are quantified as modifications to the existing model and are evaluated for consistency with the chemostat data. The hypotheses are: (1) viability of eggs produced by rotifers increases with food concentration, (2) nutritional value of algae increases with nitrogen availability, (3) algal physiological state varies with the accumulation of toxins in the chemostat and (4) algae evolve in response to predation. 4. Only Hypothesis 4 is compatible with empirical observations and thus may provide important insight into how prey evolution affects predator- prey dynamics.
A competitive immunoassay to detect a hapten using an enzyme-labelled peptide mimotope as tracer
(2002)
Mimotope peptides-peptides which mimic the binding of a hapten to its corresponding monoclonal antibody-were conjugated to peroxidase and used in competitive immunoassay. The established immunoassay was used to quantitatively determine the concentration of hapten. As model system in all the experiments described here, we used the binding of the monoclonal antibody B13-DE1 to fluorescein and the corresponding peptide mimotope.
Tomography of AM Herculis
(2002)
Contents: Introduction 1 Operators with the transmission property 1.1 Operators on a manifold with boundary 1.2 Conditions with pseudodifferential projections 1.3 Projections and Fredholm families 2 Boundary value problems not requiring the transmission property 2.1 Interior operators 2.2 Edge amplitude functions 2.3 Boundary value problems 3 Operators with global projection conditions 3.1 Construction for boundary symbols 3.2 Ellipticity of boundary value problems with projection data 3.3 Operators of order zero
This MA thesis examines novels by Native American authors of the 20th century in regard to their representation of conflicts between the indigenous population of North America and the dominant Christian religion of the mainstream society. Several major points can be followed throughout the century, which have been presented repeatedly and discussed in various perspectives. Historical conflicts of colonization and Christianization, as well as the perpetual question of Native American Christians -- 'How can you go to a church that killed so many Indians?' [Alexie, Reservation Blues] -- are debated in these novels and analyzed in this paper. Furthermore, I have tried to position and classify the works according to their representation of these problems within literary history. Following Charles Larson's chronologic and thematic examination of American Indian Fiction, the categories rejection, (syncretic) adaptation, and postmodern-ironic revision are introduced to describe the various forms of representation. On the basis of five main examples, we can observe an evolution of contemporary Native American literature, which has liberated itself from the narrow definition of the 1960s and 1970s, in favor of a broader and more varied approach. In so doing, and by means of intercultural and intertextual referencing, postmodern irony, and a new Indian self-confidence, it has also taken a new position towards the religion of the former colonizer.
We study an elliptic differential operator on a manifold with conical singularities, acting as an unbounded operator on a weighted Lp-space. Under suitable conditions we show that the resolvent (λ - A )-¹ exists in a sector of the complex plane and decays like 1/|λ| as |λ| -> ∞. Moreover, we determine the structure of the resolvent with enough precision to guarantee existence and boundedness of imaginary powers of A. As an application we treat the Laplace-Beltrami operator for a metric with striaght conical degeneracy and establish maximal regularity for the Cauchy problem u - Δu = f, u(0) = 0.
We present a data set of images of the gravitationally lensed quasar Q2237+0305, that was obtained at the Apache Point Observatory (APO) between June 1995 and January 1998. Although the images were taken under variable, often poor seeing conditions and with coarse pixel sampling, photometry is possible for the two brighter quasar images A and B with the help of exact quasar image positions from HST observations. We obtain a light curve with 73 data points for each of the images A and B. There is evidence for a long (ga 100 day) brightness peak in image A in 1996 with an amplitude of about 0.4 to 0.5 mag (relative to 1995), which indicates that microlensing has been taking place in the lensing galaxy. Image B does not vary much over the course of the observation period. The long, smooth variation of the light curve is similar to the results from the OGLE monitoring of the system (Wozniak et al. cite{Wozniak00}). Based on observations obtained with the Apache Point Observatory 3.5-meter telescope, which is owned and operated by the Astrophysical Research Consortium.
Two Hybrid cDNA Cloning
(2002)
Contrary to naive expectation, diluting the stellar component of the lensing galaxy in a highly magnified system with smoothly distributed ``dark'' matter increases rather than decreases the microlensing fluctuations caused by the remaining stars. For a bright pair of images straddling a critical curve, the saddle point (of the arrival time surface) is much more strongly affected than the associated minimum. With a mass ratio of smooth matter to microlensing matter of 4:1, a saddle point with a macromagnification of ;=9.5 will spend half of its time more than a magnitude fainter than predicted. The anomalous flux ratio observed for the close pair of images in MG 0414+0534 is a factor of 5 more likely than computed by Witt, Mao, & Schechter, if the smooth matter fraction is as high as 93%. The magnification probability histograms for macroimages exhibit a distinctly different structure that varies with the smooth matter content, providing a handle on the smooth matter fraction. Enhanced fluctuations can manifest themselves either in the temporal variations of a light curve or as flux ratio anomalies in a single epoch snapshot of a multiply imaged system. While the millilensing simulations of Metcalf & Madau also give larger anomalies for saddle points than for minima, the effect appears to be less dramatic for extended subhalos than for point masses. Moreover, microlensing is distinguishable from millilensing because it will produce noticeable changes in the magnification on a timescale of a decade or less.
Preferred well-founded semantics for logic programming by alternating fixpoints : preliminary report
(2002)
The length of the vegetation period (VP) plays a central role for the interannual variation of carbon fixation of terrestrial ecosystems. Observational data analysis has indicated that the length of the VP has increased in the last decades in the northern latitudes mainly due to an advancement of bud burst (BB). This phenomenon has been widely discussed in the context of Global Warming because phenology is correlated to temperatures. Analyzing the patterns of spring phenology over the last century in Southern Germany provided two main findings: - The strong advancement of spring phases especially in the decade before 1999 is not a singular event in the course of the 20th century. Similar trends were also observed in earlier decades. Distinct periods of varying trend behavior for important spring phases could be distinguished. - Marked differences in trend behavior between the early and late spring phases were detected. Early spring phases changed as regards the magnitude of their negative trends from strong negative trends between 1931 and 1948 to moderate negative trends between 1948 and 1984 and back to strong negative trends between 1984 and 1999. Late spring phases showed a different behavior. Negative trends between 1931 and 1948 are followed by marked positive trends between 1948 and 1984 and then strong negative trends between 1984 and 1999. This marked difference in trend development between early and late spring phases was also found all over Germany for the two periods 1951 to 1984 and 1984 to 1999. The dominating influence of temperature on spring phenology and its modifying effect on autumn phenology was confirmed in this thesis. However, - temperature functions determining spring phenology were not significantly correlated with a global annual CO2 signal which was taken as a proxy for a Global Warming pattern. - an index for large scale regional circulation patterns (NAO index) could only to a small part explain the observed phenological variability in spring. The observed different trend behavior of early and late spring phases is explained by the differing behavior of mean March and April temperatures. Mean March temperatures have increased on average over the 20th century accompanied by an increasing variation in the last 50 years. April temperatures, however, decreased between the end of the 1940s and the mid-1980s, followed by a marked warming after the mid-1980s. It can be concluded that the advancement of spring phenology in recent decades are part of multi-decadal fluctuations over the 20th century that vary with the species and the relevant seasonal temperatures. Because of these fluctuations a correlation with an observed Global Warming signal could not be found. On average all investigated spring phases advanced between 5 and 20 days between 1951 and 1999 for all Natural Regions in Germany. A marked difference be! tween late and early spring phases is due to the above mentioned differing behavior before and after the mid-1980s. Leaf coloring (LC) was delayed between 1951 and 1984 for all tree species. However, after 1984 LC was advanced. Length of the VP increased between 1951 and 1999 for all considered tree species by an average of ten days throughout Germany. It is predominately the change in spring phases which contributes to a change in the potentially absorbed radiation. Additionally, it is the late spring species that are relatively more favored by an advanced BB because they can additionally exploit longer days and higher temperatures per day advancement. To assess the relative change in potentially absorbed radiation among species, changes in both spring and autumn phenology have to be considered as well as where these changes are located in the year. For the detection of the marked difference between early and late spring phenology a new time series construction method was developed. This method allowed the derivation of reliable time series that spanned over 100 years and the construction of locally combined time series increasing the available data for model development. Apart from analyzed protocolling errors, microclimatic site influences, genetic variation and the observers were identified as sources of uncertainty of phenological observational data. It was concluded that 99% of all phenological observations at a certain site will vary within approximately 24 days around the parametric mean. This supports to the proposed 30-day rule to detect outliers. New phenology models that predict local BB from daily temperature time series were developed. These models were based on simple interactions between inhibitory and promotory agents that are assumed to control the developmental status of a plant. Apart from the fact that, in general, the new models fitted and predicted the observations better than classical models, the main modeling results were: - The bias of the classical models, i.e. overestimation of early observations and underestimation of late observations, could be reduced but not completely removed. - The different favored model structures for each species indicated that for the late spring phases photoperiod played a more dominant role than for early spring phases. - Chilling only plays a subordinate role for spring BB compared to temperatures directly preceding BB.