bluuebunny/crossref_metadata_2025 huggingface dataset:
MIRROR MATTER ADMIXTURES IN KL→μ+μ-
Authors: SÁNCHEZ-COLÓN G. , GARCÍA A.
Published: September 2007

Our previous analysis on the contributions of mirror matter admixtures in ordinary hadrons to KL→γγ is extended to study the relevance of such contributions to the KL→μ+μ-rare decay. The mixing angle of the admixtures previously determined to describe the enhancement phenomenon in two-body non-leptonic decays of strange hadrons is used, along with recent results for the description of the strong and electromagnetic interaction parts of the transition amplitudes. We find that these admixtures give a significant contribution with a small SU(2) breaking of only 2.8%, we also find a value of ~ -17.9° for the η–η′ mixing angle consistent with some of its determinations in the literature and a preferred negative value around -16 for the local counterterm contribution χ1+χ2consistent with the existence of a unique counterterm assuming lepton universality. We conclude that those mixings may be relevant in low energy physics and should not be ignored.
META-STABLE BRANE CONFIGURATION AND GAUGED FLAVOR SYMMETRY
Authors: AHN CHANGHYUN
Published: September 2007

Starting from an [Formula: see text] supersymmetric electric gauge theory with the gauge group Sp (N c ) × SO (2N′ c ) with fundamentals for the first gauge group factor and a bifundamental, we apply Seiberg dual to the symplectic gauge group only and arrive at the [Formula: see text] supersymmetric dual magnetic gauge theory with dual matters including the gauge singlets and superpotential. By analyzing the F-term equations of the dual magnetic superpotential, we describe the intersecting brane configuration of type IIA string theory corresponding to the meta-stable nonsupersymmetric vacua of this gauge theory.
MASS LIMITS FOR SCALAR AND GAUGE LEPTOQUARKS FROM $K^0_L\to e^{\mp}\mu^{\pm}$, B0→e∓τ± DECAYS
Authors: SMIRNOV A. D.
Published: September 2007

The contributions of scalar and gauge leptoquarks into widths of [Formula: see text], B0→e∓τ± decays are calculated in the models with the vectorlike and chiral four-color symmetry and with the Higgs mechanism of the quark–lepton mass splitting. From the current data on [Formula: see text] and B0 decays the mass limits for scalar and chiral leptoquarks and the updated vector leptoquark mass limits are obtained. It is shown that unlike the gauge leptoquarks the scalar leptoquark mass limits are weak, of order or below their direct mass limits. The search for such scalar leptoquarks at LHC and the further search for leptonic decays [Formula: see text] are of interest.
IRREDUCIBLE THREE-LOOP CONTRIBUTIONS TO THE PRESSURE IN YANG–MILLS THERMODYNAMICS
Authors: KAVIANI DARIUSH , HOFMANN RALF
Published: September 2007

In the effective theory for the deconfining phase of SU(2) Yang–Mills thermodynamics we compute estimates for the moduli of the irreducible three-loop diagrams contributing to the pressure. Our numerical results are in agreement with general expectations.
ON THE MODIFIED LOGISTIC EQUATION
Authors: BAKRI T.
Published: September 2007

A simple slow-fast system based on the logistic equation for which the exact solution is known, is considered here. We are especially interested in the lift-off point i.e. the point where the solution suddenly leaves the unstable slow manifold after being exponentially close to it for quite some time. Sharp estimates of this point are given. Also a slightly modified system is considered which has a periodic solution of canard type. The explicit expression of this periodic solution is given as well as estimates of its lift-off point. This type of equation can be valuable in modeling population dynamics. Lift-off points can then be used to predict outbreaks of epidemics, which nowadays is an important item in our society.
THE CUSP–HOPF BIFURCATION
Authors: HARLIM J. , LANGFORD W. F.
Published: September 2007

The coalescence of a Hopf bifurcation with a codimension-two cusp bifurcation of equilibrium points yields a codimension-three bifurcation with rich dynamic behavior. This paper presents a comprehensive study of this cusp-Hopf bifurcation on the three-dimensional center manifold. It is based on truncated normal form equations, which have a phase-shift symmetry yielding a further reduction to a planar system. Bifurcation varieties and phase portraits are presented. The phenomena include all four cases that occur in the codimension-two fold–Hopf bifurcation, in addition to bistability involving equilibria, limit cycles or invariant tori, and a fold–heteroclinic bifurcation that leads to bursting oscillations. Uniqueness of the torus family is established locally. Numerical simulations confirm the prediction from the bifurcation analysis of bursting oscillations that are similar in appearance to those that occur in the electrical behavior of neurons and other physical systems.
STABILITY COMPUTATIONS FOR NILPOTENT HOPF BIFURCATIONS IN COUPLED CELL SYSTEMS
Authors: GOLUBITSKY M. , KRUPA M.
Published: September 2007

Vanderbauwhede and van Gils, Krupa, and Langford studied unfoldings of bifurcations with purely imaginary eigenvalues and a nonsemisimple linearization, which generically occurs in codimension three. In networks of identical coupled ODE these nilpotent Hopf bifurcations can occur in codimension one. Elmhirst and Golubitsky showed that these bifurcations can lead to surprising branching patterns of periodic solutions, where the type of bifurcation depends in part on the existence of an invariant subspace corresponding to partial synchrony. We study the stability of some of these bifurcating solutions. In the absence of partial synchrony the problem is similar to the generic codimension three problem. In this case we show that the bifurcating branches are generically unstable. When a synchrony subspace is present we obtain partial stability results by using only those near identity transformations that leave this subspace invariant.
ELEMENTAL PERIODIC ORBITS ASSOCIATED WITH THE LIBRATION POINTS IN THE CIRCULAR RESTRICTED 3-BODY PROBLEM
Authors: DOEDEL E. J. , ROMANOV V. A. , PAFFENROTH R. C. , KELLER H. B. , DICHMANN D. J. , GALÁN-VIOQUE J. , VANDERBAUWHEDE A.
Published: September 2007

We present an overview of detailed computational results for families of periodic orbits that emanate from the five libration points in the Circular Restricted 3-Body Problem, as well as for various secondary bifurcating families. Our extensive overview covers all values of the mass-ratio parameter, and includes many known families that have been studied in the past. The numerical continuation and bifurcation algorithms employed in our study are based on boundary value techniques, as implemented in the numerical continuation and bifurcation software AUTO.
INSTABILITIES OF WAVE TRAINS AND TURING PATTERNS IN LARGE DOMAINS
Authors: RADEMACHER JENS D. M. , SCHEEL ARND
Published: September 2007

We classify generic instabilities of wave trains in reaction–diffusion systems on the real line as the wavenumber and system parameters are varied. We find three types of robust instabilities: Hopf with nonzero modulational wavenumber, sideband and spatio-temporal period-doubling. Near a fold, the only other robust instability mechanism, we show that all wave trains are necessarily unstable. We also discuss the special cases of homogeneous oscillations and reflection symmetric, stationary Turing patterns.
DARBOUX POLYNOMIALS AND ALGEBRAIC INTEGRABILITY OF THE CHEN SYSTEM
Authors: LÜ TINGHUA , ZHANG XIANG
Published: September 2007

In this paper, we characterize all the Darboux polynomials of the Chen system, [Formula: see text], and prove that the system is not algebraic integrability. For proving the results, we use the weight homogeneous polynomials and the method of characteristics.
NOISE-INDUCED INTERMITTENCY IN CELLULAR PATTERN-FORMING SYSTEMS
Authors: GASNER SCOTT , BLOMGREN PETER , PALACIOS ANTONIO
Published: September 2007

We study the effects of thermal noise in a stochastic, Langevin formulation, of a spatio-temporal pattern-forming Partial Differential Equation (PDE) model with circular domain. Modification of a recently developed numerical integration scheme reveals that the pattern-forming model exhibits, in the presence of noise, a greater tendency towards dynamic states and towards intermittent patterns in which ordered states appear randomly, preceded and succeeded by disorganized states. In order to gain additional insight, we focus on a region of parameter space where the patterns of the deterministic system arise from the steady-state interaction of two pairs of modes with wave numbers in a 1:2 ratio. Analysis of the associated stochastic normal form equations allows us to explain the underlying bifurcations of the noise-induced patterns, some of which had only been observed, until now, in laboratory experiments.
ANALYSIS ON TOPOLOGICAL PROPERTIES OF THE LORENZ AND THE CHEN ATTRACTORS USING GCM
Authors: YU PEI , YAO WEIGUANG , CHEN GUANRON
Published: September 2007

This letter reports a study on some topological properties of chaos using a generalized competitive mode (GCM). The Lorenz system and the Chen system are used as examples for comparison. It is shown that for typical parameter values used in the two systems, the Lorenz attractor has one pair of GCMs in competition, while the Chen attractor has two pairs of GCMs in competition. This explains why the two attractors are topologically different, and furthermore indicates that the Chen attractor is more complex than the Lorenz attractor from the dynamics point of view.
PSEUDO-OSCILLATOR ANALYSIS OF SCALAR NONLINEAR TIME-DELAY SYSTEMS NEAR A HOPF BIFURCATION
Authors: WANG ZAI HUA , HU HAI YAN
Published: September 2007

In this paper, a novel method named pseudo-oscillator analysis is developed for the local dynamics near a Hopf bifurcation of scalar nonlinear dynamical systems with time delays. For this purpose, a pseudo-oscillator that is slightly perturbed from an undamped oscillator is firstly constructed, its fundamental frequency is the same as the frequency at the bifurcation point, and the disturbance is associated with the original system. Next, the pseudo-power function, defined as the power function of the pseudo-oscillator, is estimated along a harmonic function. Then we conclude that the local dynamics near the Hopf bifurcation can be justified from the variation of the averaged pseudo-power function. The new method features a clear physical intuition and easy computation, and it yields very accurate prediction for the periodic solution resulted from the Hopf bifurcation, as shown in three illustrative examples.
A NONPARAMETRIC STATISTICAL TEST FOR CHAOS: CUMULATIVE PERIODOGRAM UNDER AN ORDER TRANSFORMATION
Authors: LAI DEJIAN
Published: September 2007

In this article, we study the empirical power of Bartlett's Kolmogorov–Smirnov test statistic derived from cumulative periodograms in detecting chaos. In our study, we simulated 10 000 time series of i.i.d. standard normal random variable, logistic map and Gaussian chaotic map of various lengths with and without measurement errors. The empirical power was assessed for the original series and its order transformed series. Although our results showed that the Bartlett's test statistic was not a powerful test statistic in detecting chaos when it is applied directly to the original series generated by the logistic map and the Gaussian chaotic map, the order transformation technique can significantly increase the power of the Bartlett's test statistic.
SOURCES AND SINKS IN THE VICINITY OF A WEAKLY INVERTED INSTABILITY
Authors: CISTERNAS JAIME , DESCALZI ORAZIO
Published: September 2007

The dynamics of perturbations around sinks and sources of traveling waves (TW) is studied in the cubic-quintic Ginzburg–Landau equation from an analytical point of view. Perturbations generically propagate in a direction opposite to the TW. Thus, a sink of TW is a source of perturbations and vice versa. For small values of time we predict there is a lower bound for the group velocity. For large values of time we predict the asymptotic value of the group velocity of the wave packet. Both predictions are in good agreement with direct numerical simulations.
ROBUST DESIGNS FOR GRAY-SCALE GLOBAL CONNECTIVITY DETECTION CNN TEMPLATES
Authors: LIU JINZHU , MIN LEQUAN
Published: September 2007

The cellular neural/nonlinear network (CNN) is a powerful tool for image and video signal processing, as well as robotic and biological visions. Practically, an engineer always hopes to design a CNN that has both universality and robustness. Based on research on the designs for the global connectivity detection (GCD) CNN [Chua, 1997] used in binary pattern, this paper establishes a theorem on robust designs for gray-scale global connectivity detection (GGCD) CNN templates. The theorem provides template parameter inequalities for determining parameter intervals for implementing the GCD functions. As a first example, two gray-scale labyrinth patterns with Gaussian noise are constructed. Using the GGCD, CNN designed by the theorem detects the connectivity of the two labyrinth patterns with gray-scales. In the other three examples, using GGCD CNNs simulate the spreads of an infectious diseases at nonuniform speeds.
GENERIC COMPLEXITY OF THE CONJUGACY PROBLEM IN HNN-EXTENSIONS AND ALGORITHMIC STRATIFICATION OF MILLER'S GROUPS
Authors: BOROVIK ALEXANDRE V. , MYASNIKOV ALEXEI G. , REMESLENNIKOV VLADIMIR N.
Published: September 2007

We discuss time complexity of the Conjugacy Problem in HNN-extensions of groups, in particular, in Miller's groups. We show that for "almost all", in some explicit sense, elements, the Conjugacy Problem is decidable in cubic time. It is worth noting that the Conjugacy Problem in a Miller group may be undecidable. Our results show that "hard" instances of the problem comprise a negligibly small part of the group.
THE GROUP OF AUTOMORPHISMS OF THE SEMIGROUP OF ENDOMORPHISMS OF FREE COMMUTATIVE AND FREE ASSOCIATIVE ALGEBRAS
Authors: BERZINS A.
Published: September 2007

Let W(X) be a free commutative or a free associative algebra. The group of automorphisms of the semigroup End (W(X)) is studied.
BURNSIDE-TYPE PROBLEMS RELATED TO SOLVABILITY
Authors: GURALNICK ROBERT , PLOTKIN EUGENE , SHALEV ANER
Published: September 2007

In the paper we pose and discuss new Burnside-type problems, where the role of nilpotency is replaced by that of solvability.
SOME RESULTS AND PROBLEMS RELATED TO UNIVERSAL ALGEBRAIC GEOMETRY
Authors: PLOTKIN BORIS
Published: September 2007

In universal algebraic geometry (UAG), some primary notions of classical algebraic geometry are applied to an arbitrary variety of algebras Θ and an arbitrary algebra H ∈ Θ. We consider an algebraic geometry in Θ over the distinguished algebra H and we also analyze H from the point of view of its geometric properties. This insight leads to a system of new notions and stimulates a number of new problems. They are new with respect to algebra, algebraic geometry and even with respect to the classical algebraic geometry.

In our approach, there are two main aspects: the first one is a study of the algebra H and its geometric properties, while the second is focused on studying algebraic sets and algebraic varieties over a "good", particular algebra H.

Considering the subject from the second standpoint, the main goal is to get forward as far as possible in a classification of algebraic sets over the given H. The first approach does not require such a classification which is itself an independent and extremely difficult task. We also consider some geometric relations between different H1 and H2 in Θ.

The present paper should be viewed as a brief review of what has been done in universal algebraic geometry. We also give a list of unsolved problems for future work.
FIXED VECTORS FOR ELEMENTS IN MODULES FOR ALGEBRAIC GROUPS
Authors: SUPRUNENKO IRINA D. , ZALESSKI ALEXANDRE E.
Published: September 2007

We provide conditions guaranteeing that a given element of a simple algebraic group G has a fixed vector in every nonzero G-module, and deduce similar results for finite Chevalley groups.
COMMUTATIVE RINGS OF PRIME CHARACTERISTIC IN WHICH SUBRINGS OF MONOGENIC SUBRINGS ARE MONOGENIC
Authors: FREIDMAN P. A. , HMEL'NITSKII I. L.
Published: September 2007

We describe commutative rings of prime characteristic with the property indicated in the title of the paper.
COMMUTATOR SUBGROUPS OF FREE NILPOTENT GROUPS
Authors: GUPTA N. , PASSI I. B. S.
Published: September 2007

For fixed m, n ≥ 2, we examine the structure of the nth lower central subgroup γn(F) of the free group F of rank m with respect to a certain finite chain F = F(0) > F(1) > ⋯ > F(l-1) > F(l) = {1} of free groups in which F(k) is of finite rank m(k) and is contained in the kth derived subgroup δk(F) of F. The derived subgroups δk(F/γn(F)) of the free nilpotent group F/γn(F) are isomorphic to the quotients F(k)/(F(k) ∩ γn(F)) and admit presentations of the form 〈xk,1,…,xk,m(k): γ(n)(F(k))〉, where γ(n)(F(k)), contained in γn(F), is a certain partial lower central subgroup of F(k). We give a complete description of γn(F) as a staggered product Π1 ≤ k ≤ l-1(γ〈n〉(F(k))*γ[n](F(k)))F(k+1), where γ〈n〉(F(k)) is a free factor of the derived subgroup [F(k),F(k)] of F(k) having countable infinite rank and generated by a certain set of reduced commutators of weight at least n, and γ[n](F(k)) is the subgroup generated by a certain finite set of products of non-reduced ordered commutators of weight at least n. There are some far-reaching consequences.
BREADTH IN POLYCYCLIC GROUPS
Authors: MANN AVINOAM , SEGAL DAN
Published: September 2007

The breadth of a polycyclic group is the maximum of h(G) - h(CG(x)) for x ∈ G, where h(G) is the Hirsch length. We prove a number of results that bound the class of a finitely generated nilpotent group, and the Hirsch length of the derived group in a polycyclic group, in terms of the breadth. These results are analogues of well-known results in finite group theory.
ON AUTOMORPHISMS OF CATEGORIES OF UNIVERSAL ALGEBRAS
Authors: PLOTKIN BORIS , ZHITOMIRSKI GRIGORI
Published: September 2007

Let [Formula: see text] be a variety of universal algebras. We suggest an approach for describing automorphisms of a category [Formula: see text] of free [Formula: see text]-algebras. In particular, this approach allows us to answer the question: is an automorphism of such a category inner? Most of the results actually deal with arbitrary categories supplied with a represented forgetful functor.
AUTOMORPHIC EQUIVALENCE OF ALGEBRAS
Authors: TSURKOV A.
Published: September 2007

This paper is adjacent to [5] and motivated by the following question arising in universal algebraic geometry: when do two algebras have the same geometry? This question requires considering algebras in a variety Θ and the category Θ0of all finitely generated free algebras in Θ. The notions of geometrically equivalent algebras and weakly geometrically equivalent algebras (cf. [2]) are intimately related to the above problem (the latter notion being related to automorphisms of the category Θ0is replaced in the present paper by a more natural one: "automorphic equivalence").

Two algebras are said to have the same algebraic geometry if they are automorphically equivalent. If an automorphic equivalence of algebras is provided by an inner automorphism of Θ0, then this equivalence coincides with the geometric equivalence. However, not all automorphisms of Θ0are inner (see [5, Theorem 2]). In this paper we study the situation when the automorphic equivalence of algebras is provided by a non-inner automorphism.

Assuming Θ to be an IBM variety of one-sorted algebras we prove that two algebras H1and H2are automorphically equivalent in Θ if and only if H1is geometrically equivalent to [Formula: see text], where [Formula: see text] is the algebra with the same domain as H2and with the new operations induced by some system of words W = {wω(x)|ω ∈ Ω, Ω is the signature of algebras in Θ. Thus, the notion of automorphic equivalence is reduced to a more simple one of geometric equivalence.
EQUILIBRIUM, STABILITY AND DYNAMICAL RESPONSE IN A MODEL OF THE EXTRINSIC APOPTOSIS PATHWAY
Authors: CAROTENUTO LUCIANO , PACE VINCENZA , BELLIZZI DINA , DE BENEDICTIS GIOVANNA
Published: September 2007

In the past few years several mathematical models have been proposed to formally represent the biochemical processes that lead to the programmed death of the cell (apoptosis) starting from an intrinsic or extrinsic stimulus. In this paper we consider the model proposed by Eissing and colleagues in 2004 and, compared to the previously published results, provide several original contributions. We prove formally that the model can have one, two or three equilibrium states; one of these (the life equilibrium) represents the normal state of the cell: we state a stability criterion for this equilibrium and prove that its stability/instability is related to the number of equilibrium states. A large sample of models with randomly generated parameter vectors (representative of a population of cells) is numerically analyzed as regards both the equilibria and respective stability properties, and the dynamical behavior. Many patterns of stable/unstable equilibrium states, and different types of bifurcations are discovered. Correlations between model parameters, equilibrium patterns and equilibrium concentration of a critical protein are also carried out. The analysis of the dynamical time responses shows that the richness of behaviors accounted by the model is much larger than that implied by the classification into life-monostable, bistable, death-monostable models.
THE BEST DOSAGE SCHEME ON MULTIPLE RAPID VEIN INJECTION
Authors: LIN DONGRONG , HUI JING
Published: September 2007

In this paper, we mainly consider the compartment models of the multiple rapid vein injection. Applying the theory of impulsive differential equation, we study the steady drug concentration in the blood, its maximum, minimum and mean value, dosing interval, etc. to design the best dosage schemes on these models. This paper is useful in instructing the use of pharmaceuticals in clinical practice and enriches the research of pharmacokinetics.
ANALYSIS OF SIMILARITY/DISSIMILARITY OF DNA SEQUENCES BY A NEW 3D GRAPHICAL REPRESENTATION
Authors: SONG JIE
Published: September 2007

A new 3D graphical representation of DNA sequences according to chemical structures of the bases is proposed, reflecting the distribution of bases with different chemical structure, preserving information on sequential adjacency of bases, avoiding loss of information accompanying alternative 3D representations in which the curve standing for DNA overlaps and intersects itself. Based on this representation, a numerical characterization approach is presented by constructing a six-component vector whose components are the normalized leading eigenvalues of the L/L matrices associated with the DNA sequences. The examination of similarities among the coding sequences of the first exon of β-globin gene of different species illustrates the utility of the approach.
LENGTH DISTRIBUTIONS OF SIMPLE TANDEM REPEATS IN GENOMES
Authors: NYEO SU-LONG , YU JUI-PING
Published: September 2007

The length distributions of simple tandem repeats in the genomes of several organisms are evaluated and found to exhibit long-range correlations in A and T nucleotide bases related repeats for most eukaryotes. In particular, the length distributions of the mononucleotide A/T repeat units have longer tails than those of the C/G repeat units. Also, the length distributions of the dinucleotide repeat unit CG show a simple monotonously fast decreasing behavior, while those of repeat units AT, AG and AC have complicated structures at larger repeat lengths, especially for human, mouse and rat chromosomes. These distributive behaviors are due to the CpG deficiency in different genomes with different methylation activities. Especially, methyltransferases in vertebrates appear to methylate specifically the cytosine in CpG dinucleotides, and the methylated cytosines is prone to mutate to thymine by spontaneous deamination. The dinucleotide CpG would gradually decay into TpG and CpA. In addition, there is a peak in the distributions of repeat unit A at repeat-repeat separation 153 nt for humans and chimpanzees. We show that the long-tail behavior of mononucleotide repeat unit A and the peak at repeat separation 153 nt are due to the interspersed repetitive DNA sequences in humans and chimpanzees.
IMPULSIVE DISPERSAL OF PLANT SEEDS IN SINGLE SPECIES MODEL
Authors: WANG LIMIN , TAN YUANSHUN , CHEN LANSUN
Published: September 2007

In this paper, a single species model with impulsive diffusion between two patches is proposed, which provides a more natural description of plant seeds dynamics compared with the continuous or discrete ones. By using the discrete dynamical system generated by a monotone, concave map for the dispersal model and a ∊1 - ∊2 variation, it is proved that the Poincare map has a globally stable positive fixed point. This implies that the system considered here has a globally stable positive periodic solution under some sufficient conditions. Further numerical simulations show that the diffusion can save the extinction though the species has a negative growth rate in one patch.
Discovering Earth’s future in its past: palaeohydrology and global environmental change
Authors: Baker V. R.
Published: September 2007

Palaeohydrology is the study of various past aspects of the hydrological cycle. It is accomplished by interpreting indices of past hydrological processes. By its focus on the effects of
realized
processes, palaeohydrology provides a critical scientific complement to studies that
idealize
hydrological systems in order to predict future change. Future habitability of the planet will surely require the guidance of scientific concepts, but it will also require a basis in the perception of change that compels people to act. Human perception is grounded in the concrete particulars of reality, not in the abstract idealizations of theoretical science. While we scientists may wish otherwise, say for a more enlightened public and political sector, it is pragmatic not to expect such on the short time scale of potential detrimental changes for Earth’s habitability to humankind.

The greatest repository of scientific knowledge for stimulating human perception is the geological past. This experience of the Earth is the only real evidence of global environmental change available. It can function scientifically as a source of data with which to test models of change, confirming or falsifying theoretical extrapolations to past states (retrodictions). However, its more important role is as a source of discovery. In the geological record the scientist can discover previously unanticipated realizations of hydrological processes that will require new or revised models (hypotheses) for their explanation. It is our challenge as scientists to devote as much effort to exploring this real world of Earth experience as we currently apply to idealizing the abstract world of Earth systems.
Climate change and flood sensitivity in Spain
Authors: Benito G. , Machado M. J. , Pérez-González A.
Published: September 2007

The temporal and spatial distribution of more than 2500 records of historical floods in Spain, gathered within a database, were analyzed. Our results suggest that the last millennium can be divided into periods with similar flood frequency, magnitude and distribution. This flood variability seems to correspond to changes of the prevailing atmospheric circulation patterns affecting the Iberian Peninsula. The present climatic flood-generating conditions were used in order to identify those changes for each period. In the Atlantic river basins, large floods between
AD
1400–1500 and
AD
1850–1910 resulted from intense, widespread rainfalls associated with Atlantic west and northwest frontal systems transported by the westerlies. In fact, both periods seem to experience a high hydrological variance, corresponding to a transition between different climatic conditions. Between
AD
1150 and 1400 two hydroclimatic periods were distinguished: the first (
AD
1150–1290) was characterized by a high flood frequency, especially over the Atlantic basins, some of these floods affecting more than one drainage basins. The flood distribution pattern for the second phase between
AD
1290 and 1400, was characterized by a decrease in the number of floods in the Atlantic basins and a relative increase of flooding in the Ebro and J%ucar basins. Finally, the
AD
1500–1850 interval was characterized by a higher flood frequency, especially in the south and southeastern basins, due to cold pool conditions, as well as by a high irregularity of large floods associated with a high temperature contrast between winter and summer.
A preliminary palaeohydraulic model applied to late Quaternary gravel dunes: Altai Mountains, Siberia
Authors: Carling Paul A.
Published: September 2007

The morphology and granulometry of large ‘fossil’ late-Quaternary gravel dunes at Kuray in Siberia are used to estimate the hydraulic conditions associated with dune building and stabilization. To accomplish this, an algorithm is tested which provided reasonable predictions of the flow characteristics measured above small gravel dunes in the Toutle River, Washington State. Palaeoflow depths and velocities above the ‘fossil’ dunes as the bedforms finally stabilized are estimated using a simple force balance for initial motion and the partitioning of the flow resistance between the drag owing to the duneform and grain resistance. Flow parameters for peak discharge conditions when dunes actively developed are assessed with respect to the dune-upper plane bed transition and the entrainment of over-passing blocks. These data, coupled with an assessment of the lateral extent of the flood, provide estimates of the discharge magnitude of the glacial out-break flood which was responsible for the dunefield. Sensitivity analyses indicate the stability of the estimates and demonstrate that the dunes were initiated and finally stabilized when the flood was of the order of 5 × 10
4
m
3
s
−1
and 2 × 10
4
m
3
s
−1
respectively. The flood peak need not have exceeded 750 000 m
3
s
−1
with a maximum depth of a few tens of metres.
River response to the last neoglacial (the ‘Little Ice Age’) in northern, western and central Europe
Authors: Rumsby Barbara T. , Macklin Mark G.
Published: September 2007

Climate changes since AD 1200 have been of high magnitude. Significant lowering of temperatures occurred during the neoglacial (‘Little Ice Age’), between AD 1200–1400 and AD 1600–1800 with maximum cooling in the mid-late eighteenth century. At this time many European valley/cirque glaciers reached their maximum extent since the late Pleistocene. Neoglaciation was followed by an overall warming trend, although with significant reversals superimposed. Alongside these temperature changes were variations in the nature and amount of precipitation, and in consequence, river basins in north, west and central Europe experienced enhanced fluvial activity between 1250 and 1550 and particularly between 1750 and 1900. These phases coincide with periods of climatic transition; cooling after the Medieval optimum and warming during the latter stages of the Little Ice Age respectively. In contrast, the intervening period (1550–1750), which corresponds with the most severe phases of the last neoglacial, was associated with lower rates of fluvial activity.
Drawing a line in the sand: identifying and characterizing boundaries in the geological record
Authors: Beaudoin Alwynne B. , Head Martin J.
Published: September 2007

The identification and characterization of boundaries is a fundamental activity in geoscience. Spatial and temporal boundaries are rarely sharp but are more usually zones of transition, which may have variable characteristics. The examination of palynological and micropalaeontological data is often crucial for the delineation of geological boundaries, especially for the definition of Global Boundary Stratotype Sections and Points (GSSPs). The sixteen papers in this volume highlight many productive methodological approaches to boundary identification. This essay reviews the theoretical background to boundary identification in geology, and provides the contextual perspective for the subsequent papers.
Late Cambrian and Early Ordovician conodont communities from platform and slope facies, western Newfoundland: a statistical approach
Authors: Zhang Shunxin , Barnes Christopher R.
Published: September 2007

Twelve conodont communities and assemblages in the Cambrian-Ordovician interval of western Newfoundland are recognized by four cluster analyses, which include 18 468 identifiable conodont specimens recovered from 230 conodont-bearing samples from four stratigraphic sections. Each section represents a different facies: platform, upper proximal slope, lower proximal slope, and distal slope. The 12 conodont communities and assemblages were differentiated into pelagic and nektobenthic communities as well as both the assemblages with a mixture of pelagic and nektobenthic communities and transported assemblage. The distribution of conodont communities along the platform-to-slope environmental gradient shows some gradational relationships. Relative sea-level curves derived in part from the distribution pattern of conodont communities reveal a major sea-level drop in the latest
Cordylodus proavus
Zone time, and two major sea-level rises in the early
Iapetognathus fluctivagus
Zone time and early
Cordylodus angulatus
Zone time, respectively.
Tropical environmental changes at the mid-Pleistocene transition: insights from lipid biomarkers
Authors: Schefuß Enno , Jansen J. H. F. , Sinninghe Damsté J. S.
Published: September 2007

Mid-Pleistocene (1250–450 ka) lipid biomarker accumulation rates and bulk organic geochemical records have been examined from the Angola Basin in the eastern tropical Atlantic to assess the low-latitude environmental changes associated with the onset of the Middle Pleistocene ice ages. In combination with information on lipid sources, we use principal component and spectral analyses to evaluate the main forcing factors of phytoplankton productivity and lipid transport changes. Cross-spectral analyses reveal the phasing in orbitally driven climatic cycles. The average export of marine productivity remained high and unchanged throughout the mid-Pleistocene transition. However, the relative lipid contributions indicate a significant change in the primary-producing ecosystem. Before the growth of mean global ice volume, enhanced siliceous marine production was mainly controlled by monsoonal variations in river runoff, and oceanic upwelling was forced by variations in trade wind zonality. Both precession-driven processes were suppressed by the enlarged global ice mass after the beginning of the mid-Pleistocene transition. With the onset of 100 ka cyclicity, aeolian transport of terrigenous plant waxes and wind-driven coastal and oceanic upwelling strongly increased. From this time onwards, aridification of the continent and strengthening of the trade winds caused profound environmental changes in the tropical realm.
The stratigraphic transition and suggested boundary between the Early and Middle Pleistocene in the loess record of northern Eurasia
Authors: Dodonov A. E.
Published: September 2007

This review focuses on the loess-palaeosol record across the Early-Middle Pleistocene transition to show the main structural features in key sections from the Loess Plateau of China via central Asia to Europe. Loess-palaeosol sequences in general demonstrate an impressive coherence with oxygen isotope osillations, providing a high-resolution terrestrial record for stratigraphic subdivision. Accordingly, they are considered useful for detailed climatostratigraphy and correlation. Nonetheless, there are many uncertainties in loess-palaeosol stratigraphic correlation across the Early-Middle Pleistocene transition from region to region within northern Eurasia. The interval between the top of the Jaramillo Subchron and the Matuyama-Brunhes (M-B) Chron boundary is discussed in detail because it embraces suitable horizons for placing the Early-Middle Pleistocene boundary. This interval contains a variable number of loess and palaeosol horizons in sections along the different loess provinces from east to west. A distinctive palaeosol unit just below the M-B reversal can serve as a marker horizon for establishing the Early-Middle Pleistocene boundary. In south Tajikistan, it corresponds to the pedocomplex 10 (PC10) and to palaeosol S8 in the Loess Plateau of China. The base of this soil horizon correlated with the base of Marine Isotope Stage 21 can be considered as a distinctive geological level for recognizing the Early-Middle Pleistocene boundary on the continent.
Environmental change across the Early-Middle Pleistocene transition: small mammalian evidence from the Trinchera Dolina cave, Atapuerca, Spain
Authors: Cuenca-Bescós G. , Rofes J. , Garcia-Pimienta J.
Published: September 2007

The sites of Atapuerca are well known for their hominin-bearing localities of Early to Middle Pleistocene age. Trinchera Dolina yields western Europe’s oldest fossil hominin, the 850 ka
Homo antecessor
; and at Sima de los Huesos there occurs the best collection of the Middle Pleistocene hominin
Homo heidelbergensis
. However, small mammals (Rodentia, Insectivora, Chiroptera and Lagomorpha) represent the largest number of species and greatest fossil abundance in the deposits of the Atapuerca cave complex. The small mammals are grouped by habitat categories, but because the ecology of mammals is complex, we base our study on the evolution of these categories throughout the sequence. The assemblage distribution at the Trinchera Dolina site reflects landscape and environmental changes during the past million years. Shifts between woodland, open land and moorland are indicated by the relative abundance of species based on diagnostic elements such as first lower molars. These data are combined with the distribution of large mammals, pollen, sediments and geological context of the Trinchera Dolina site. From this interdisciplinary approach, we conclude that the first hominins from western Europe (
Homo antecessor
) lived during a warm, wet and wooded interval, probably corresponding to Marine Isotope Stages 21 to 19. The transition from Early to Middle Pleistocene at Atapuerca is characterized by palaeoenvironmental changes recorded between levels TD5–6 and TD8–10, respectively. The general opening of the landscape at the beginning of the Middle Pleistocene could have favoured the dispersal of hominins (
Homo heidelbergensis
) across western Europe.
Femtobiology
Authors: Sundström Villy
Published: September 2007

Functions of biologically active molecules are frequently initiated by elementary chemical reactions such as energy and electron transfer, cis-trans isomerizations, and proton transfer. The nature of these reactions generally makes them very fast and efficient, occurring on picosecond and femtosecond timescales. Ultrafast spectroscopy has played an important role in the study of a number of biological processes and has provided unique information about several of nature's responses to light. Here I review the current understanding of light-energy collection and conversion in photosynthesis, the function of carotenoid molecules in photosynthesis, and the primary light-initiated reactions of the photoreceptors rhodopsin, bacteriorhodopsin, photoactive yellow protein, phytochrome, and a new type of blue-light receptor based on flavin chromophores.
Organic Peracid Etches: A New Class of Chromium Free Etch Solutions for the Delineation of Defects in Different Semiconducting Materials
Authors: Possner Daniel , Kolbesen Bernd O. , Cerva Hans , Kluppel V
Published: September 2007

Defect etching is a well-established method used to reveal different kinds of crystalline defects in semiconducting materials. Most of the etch solutions used today have two disadvantages. They contain hexavalent chromium which is highly toxic and they are not suitable for application on thin films. There is a demand for environmentally friendly etch solutions which can also be used for new materials like SOI. Due to their properties Organic Peracid Etches (OPE), mixtures which contain a short-chain alkanoic acid like acetic or propionic acid, hydrogen peroxide and hydrofluoric acid are suitable for defect delineation in thin and very thin (<50 nm) films. Such solutions were also tested on CZ and FZ silicon substrates. In this case characteristic square-shaped etch figures caused by D-defects (COPs) were found after etching.
Surface Microdefects Control during Chemical Mechanical Polishing of Silicon Wafers: an Example of in line Manufacturing Process Control
Authors: Borionetti Gabriella , Corradi Alessandro , Mainardi Nicola , Rinaldi Antonio M. , Takami Keiichi
Published: September 2007

For the process control / improvement in Chemical Mechanical Polishing in silicon wafer production line, the automatic laser inspection tool (SP1) and on-time manufacturing database system are utilized for monitoring of various defects. In order to improve the most relevant defect, polishing scratch, the modeling on the morphology of the defect was developed and connected to SP1 and the database system, so that the source and mechanism of defect generation are easily and quickly identified and analyzed. The validity of the modeling was further confirmed with the microscopic instruments such as Nomarsky Microscope and AFM with sophisticated data transfer function from SP1 and database system. Several examples of their application during the continuous process improvement activity are reported
Molybdenum Contamination in Indium and Boron Implantation Processes
Authors: Codegoni Davide , Polignano Maria Luisa , Soncini Valter , Bresolin Camillo
Published: September 2007

Some examples of contamination by mass interference are studied in this work, specifically the molybdenum contamination in indium and boron implantations. This contamination is detected by Elymat and DLTS analyses, whereas it is missed by SPV, which is commonly used for routine line monitoring. Both Elymat and DLTS analyses consistently show molybdenum contamination clearly related to indium implantation conditions and to high dose boron implantations.
Current Status and Perspective of High-k Gate Stack Materials Engineering for Further Scaled CMOS
Authors: Toriumi Akira
Published: September 2007

High-k dielectric materials and technology have been intensively investigated over the past ten years, and are now just at the stage before production. A number of new challenges and hopes have been found. Some of these challenges are related to processing or material optimization issues. This is because the optimal process parameters must be different from those currently used in poly-Si/SiO2/Si system. However, most issues seem to be related to the intrinsic properties of high-k dielectric materials. We would, therefore, like to discuss some key challenges that must be addressed to further advance Si-CMOS.
Does Strain Engineering Impact the Gate Stack Quality and Reliability?
Authors: Claeys C. , Simoen Eddy , Crupi Felice , Giusi Gione
Published: September 2007

Most state-of-the-art high-performance technologies are relying on strain engineering, based on either a global approach using high-mobility substrates or the implementation of local stressors. It has been reported that strain in the channel region has an impact on not only the carrier mobility and the drive current but also on key parameters such as gate oxide quality, hot carrier performance, negative bias temperature instabilities, low frequency noise, radiation hardness, etc. This paper reviews recent insights concerning the reliability and gate oxide quality of strained CMOS technologies. Impact of different strain engineering approaches will be illustrated and critically discussed.
Increase of Carbon Substitutionality and Silicon Strain by Molecular Ion Implantation
Authors: Li-Fatou Andrei , Jain Amitabh , Krull Wade , Ameen Mike , Harris Mark , Jacobson Dale
Published: September 2007

We have shown that molecular carbon ion implantation instead of the atomic species enhances the substitutional fraction of carbon upon solid phase epitaxial regrowth. Ultra-high temperature annealing by a laser was used for the first time, to produce the regrowth.
A Cost-Effective CMOS Technology Utilizing Gate Work Function Control with Hafnium
Authors: Tsutsui Gen , Nakamura Hidetatsu , Fukase Tadashi , Imai Kiyotaka
Published: September 2007

A cost-effective integration technique enabling Poly/Hf/SiON gate stack is demonstrated. Four advantages of an introduction of hafnium dielectric are discussed; (i) Ion enhancement, (ii) reduction of gate induced drain leakage (GIDL), (iii) suppression of reverse narrow channel effect, and (iv) mask steps reduction realized by identical ion implantation processes between core logic (transistors used in logic circuit) and I/O transistors. In addition, mobility improvement techniques by process-induced stress control and surface roughness reduction are discussed. These techniques realize highly cost-effective integrated CMOS platform for 45 nm node.
Improvement of Thermal Stability of Ni Silcide by Additive Metals with Specific Introduction Processes
Authors: Tsutsui Kazuo , Nagahiro Koji , Shiozawa Takashi , Ahmet Parhat , Kakushima Kuniyuki , Iwai Hiroshi
Published: September 2007

A new processe to improve thermal stability of Ni silicide, so called PSMD (post silicidation metal doping) in which additive metals were introduced to pre-formed NiSi was proposed. In situ deposition of thin Hf or Pt layer on the NiSi layer resulted in improvement of thermal stability evaluated by sheet resistance and morphology in the following RTA process at higher temperatures.
In Situ Dry Chemical Clean to Improve NiSi and Ni(Pt)Si Integration
Authors: Wood Bingxi S. , Lei Jianxin , Phan See-Eng , Ninan Biju , Lavu Kishore , Smayling Michael , Kao Chien-Teh , Gandikota Srinivas
Published: September 2007

Pre-Silicide clean is a critical step in NiSi integration to keep silicide/Si interface clean and defect-free for good device performance. Traditional pre-silicide clean uses HF wet clean which requires tight queue time control to prevent native oxide growth before Ni deposition. We present in this paper an in situ dry chemical clean technology and its impact on NiSi and Ni(Pt)Si Integration, compared with traditional HF wet clean. The new in situ dry pre-silicide clean selectively etches away oxide, and prepare the surface for subsequent Ni PVD deposition without leaving its vacuum environment. The electrical results show lower silicide resistance, tighter resistance distribution, and better diode characteristics with in situ dry clean than with HF clean.
High-Performance CMP Slurry with CeO2/Resin Abrasive for STI Formation
Authors: Matsui Yukiteru , Tateyama Yoshikuni , Iwade Kenji , Nishioka Takeshi , Yano Hiroyuki
Published: September 2007

Novel CMP slurry with CeO2/resin abrasive was investigated for STI formation. The slurry showed high selectivity of removal rate and better planarity compared to conventional CeO2/surfactant slurry. These advantages are attributable to the unique character of the inactive resin. The resin particle whose surface has anionic functional group absorbed to SiN film electrically and SiN surface is covered with the resin particle and protected strongly form CeO2 abrasion, therefore the selectivity was enhanced drastically. The resin particle also absorbed to CeO2 abrasive. In the convex area of STI patterned wafer, higher pressure is applied and CeO2-resin aggregation is destroyed and higher CMP removal rate is performed. In the concave area, lower pressure is applied and CMP removal rate is low because of protection of CeO2 surface by inactive resin. Therefore, the selectivity of removal rate between convex and concave areas is increased and planarity is improved.