bluuebunny/crossref_metadata_2025 huggingface dataset:
INTERACTION OF D-STRING WITH F-STRING: A PATH-INTEGRAL FORMALISM
Authors: KAR SUPRIYA , KAZAMA YOICHI
Published: April 2003

A path integral formalism is developed to study the interaction of an arbitrary curved Dirichlet (D-) string with elementary excitations of the fundumental (F-) string in bosonic string theory. Up to the next-to-leading order in the derivative expansion, we construct the properly renormalized vertex operator, which generalizes the one previously obtained for a D-particle moving along a curved trajectory. Using this vertex, an attempt is further made to quantize the D-string coordinates and to compute the quantum amplitude for scattering between elementary excitations of the D- and F-strings. By studying the dependence on the Liouville mode for the D-string, it is found that the vertex in our approximation consists of an infinite tower of local vertex operators which are conformally invariant on their respective mass-shell. This analysis indicates that, unlike the D-particle case, an off-shell extension of the interaction vertex would be necessary to compute the full amplitude and that the realization of symmetry can be quite nontrivial when the dual extended objects are simultaneously present. Possible future directions are suggested.
PHASE TRANSITION IN EVOLUTIONARY GAMES
Authors: CAO ZHEN , HWA RUDOLPH C.
Published: April 2003

The evolution of cooperative behavior is studied in the deterministic version of the Prisoners' Dilemma on a two-dimensional lattice. The payoff parameter is set at the critical region 1.8<b<2.0, where clusters of cooperators are formed in all spatial sizes. Using the factorial moments developed in particle and nuclear physics for the study of phase transition, the distribution of cooperators is studied as a function of the bin size covering varying numbers of lattice cells. From the scaling behavior of the moments a scaling exponent is determined and is found to lie in the range where phase transitions are known to take place in physical systems. It is therefore inferred that when the payoff parameter is increased through the critical region the biological system of cooperators undergoes a phase transition to defectors. The universality of the critical behavior is thus extended to include also this particular model of evolution dynamics.
TOPOLOGICAL DEFECTS IN [SU(6)]3× Z3
Authors: GARCÍA-COMPEÁN H. , PÉREZ-LORENZANA A. , ZEPEDA A.
Published: April 2003

We study topological defects arising in the grand unification model SU (6)L⊗ SU (6)c⊗ SU (6)R× Z3. We show that the model does not contain domain walls, while it produces massive magnetic monopoles and it may, depending on the symmetry breaking chain, give rise to the formation of strings. We also discuss the possible relation of these topological defects with the origin of the highest energy cosmic rays detected.
DIRAC FIELDS ON SPACELIKE HYPERSURFACES, THEIR REST-FRAME DESCRIPTION AND DIRAC OBSERVABLES
Authors: BIGAZZI FRANCESCO , LUSANNA LUCA
Published: April 2003

Grassmann-valued Dirac fields together with the electromagnetic field (the pseudo-classical basis of QED) are reformulated on spacelike hypersurfaces in Minkowski space–time and then restricted to Wigner hyperplanes to get their description in the rest-frame Wigner-covariant instant form of dynamics. The canonical reduction to the Wigner-covariant Coulomb gauge is done in the rest frame. It is shown, on the basis of a geometric inconsistency, that the description of fermions is incomplete, because there is no bosonic carrier of the spin structure describing the trajectory of the electric current in Minkowski space–time, as it was already emphasized in connection with the first quantization of spinning particles in a previous paper.
INEQUIVALENT QUANTIZATIONS OF GAUGE THEORIES
Authors: HORIE KENICHI
Published: April 2003

It is known that the quantization of a system defined on a topologically nontrivial configuration space is ambiguous in that many inequivalent quantum systems are possible. This is the case for multiply connected spaces as well as for coset spaces. Recently, a new framework for these inequivalent quantizations approach has been proposed by McMullan and Tsutsui, which is based on a generalized Dirac approach. We employ this framework to the quantization of the Yang–Mills theory in the simplest fashion. The resulting inequivalent quantum systems are labelled by quantized nondynamical topological charges.
HARMONIC SUMS, MELLIN TRANSFORMS AND INTEGRALS
Authors: VERMASEREN J. A. M.
Published: April 2003

This paper describes algorithms to deal with nested symbolic sums over combinations of harmonic series, binomial coefficients and denominators. In addition it treats Mellin transforms and the inverse Mellin transformation for functions that are encountered in Feynman diagram calculations. Together with results for the values of the higher harmonic series at infinity the presented algorithms can be used for the symbolic evaluation of whole classes of integrals that were thus far intractable. Also many of the sums that had to be evaluated seem to involve new results. Most of the algorithms have been programmed in the language of FORM. The resulting set of procedures is called SUMMER.
REDUCED PHASE SPACE QUANTIZATION OF MASSIVE VECTOR THEORY
Authors: PAVEL H.-P. , PERVUSHIN V. N.
Published: April 2003

We quantize massive vector theory in such a way that it has a well-defined massless limit. In contrast to the approach by Stückelberg where ghost fields are introduced to maintain manifest Lorentz covariance, we use reduced phase space quantization with nonlocal dynamical variables which in the massless limit smoothly turn into the photons, and check explicitly that the Poincaré algebra is fulfilled. In contrast to conventional covariant quantization our approach leads to a propagator which has no singularity in the massless limit and is well behaved for large momenta. For massive QED, where the vector field is coupled to a conserved fermion current, the quantum theory of the nonlocal vector fields is shown to be equivalent to that of the standard local vector fields. An inequivalent theory, however, is obtained when the reduced nonlocal massive vector field is coupled to a nonconserved classical current.
ON THE ANOMALOUS U(1) IN FREE FERMIONIC SUPERSTRING MODELS
Authors: CLEAVER GERALD B. , FARAGGI ALON E.
Published: April 2003

The realistic free fermionic models have had an intriguing success in explaining different properties of the observed particle spectrum. In this paper we discuss in some detail the anomalous U(1) symmetry which exists in these models. We study the properties of the anomalous U(1) in both the more realistic NAHE-based free fermionic models and those in a general NAHE class. Appearance of an anomalous U(1) in the more realistic NAHE models is shown to be an effect of reduction of world sheet supersymmetry from (2,2) to (2,0). We show, however, that in more general (2,1) and (2,0) models, all U(1) can remain anomaly-free under certain conditions. Several phenomenological issues related to the anomalous U(1) are discussed. In particular, we note that in some examples the anomalous U(1) arises from the breaking E6 → SO (10)× U(1) A, resulting in U(1) A being family universal.
DISPERSIVE BOUNDS ON THE SHAPE OF $\Lambda_b\to
\Lambda_b l\bar{\nu}_l$ FORM FACTORS
Authors: CHAKRAVERTY DEBRUPA , DE TRIPTESH , DUTTA-ROY BINAYAK , GUPTA K. S.
Published: April 2003

We derive a theoretically allowed domain for the charge radius ρ and the curvature c of the Isgur–Wise function describing the decay [Formula: see text]. Our method uses crossing symmetry, dispersion relations and analyticity in the context of the heavy quark effective theory (HQET), but is independent of the specifics of any given model. The experimentally determined values of the ϒ masses have been used as input information. The results are of interest for testing different models employed to calculate the heavy baryon form factors which are used for the extraction of |Vcb| from experimental data.
U DUALITY AND NETWORK CONFIGURATIONS OF BRANES
Authors: KUMAR ALOK , MUKHOPADHYAY SUBIR
Published: April 2003

We explicitly write down the invariant supersymmetry conditions for branes with generic values of moduli and U duality charges in various space–time dimensions D≤10. We then use these results to obtain new BPS states, corresponding to the network type structure of such branes.
SUPER WEYL ANOMALIES IN THE AdS/CFT CORRESPONDENCE
Authors: NISHIMURA MADOKA , TANII YOSHIAKI
Published: April 2003

Anomalies of N=(4,4) superconformal field theories coupled to a conformal supergravity background in two dimensions are computed by using the AdS/CFT correspondence. We find that Weyl, axial gauge and super Weyl transformations are anomalous, while general coordinate, local Lorentz, vector gauge and local supertransformations are not. The coefficients of the anomalies show that the superconformal field theories have the central charge expected in the AdS/CFT correspondence.
FOKKER-TYPE CONFINEMENT MODELS FROM EFFECTIVE LAGRANGIAN IN CLASSICAL YANG–MILLS THEORY
Authors: DUVIRYAK A.
Published: April 2003

Abelian potentials of pointlike moving sources are obtained from the nonstandard theory of Yang–Mills field. They are used for the construction of the time-symmetric and time-asymmetric Fokker-type action integrals describing the dynamics of two-particle system with confinement interaction. The time-asymmetric model is reformulated in the framework of the Hamiltonian formalism. The corresponding two-body problem is reduced to quadratures. The behavior of Regge trajectories is estimated within the semiclassical consideration.
U DUALITY AS GENERAL COORDINATE TRANSFORMATIONS, AND SPACE–TIME GEOMETRY
Authors: LAVRINENKO I. V. , LÜ H. , POPE C. N. , TRAN T. A.
Published: April 2003

We show that the full global symmetry groups of all the D-dimensional maximal supergravities can be described in terms of the closure of the internal general coordinate transformations of the toroidal compactifications of D=11 supergravity and of type IIB supergravity, with type IIA/IIB T duality providing an intertwining between the two pictures. At the quantum level, the part of the U duality group that corresponds to the surviving discretized internal general coordinate transformations in a given picture leaves the internal torus invariant, while the part that is not described by internal general coordinate transformations can have the effect of altering the size or shape of the internal torus. For example, M theory compactified on a large torus Tn can be related by duality to a compactification on a small torus, if and only if n≥3. We also discuss related issues in the toroidal compactification of the self-dual string to D=4. An appendix includes the complete results for the toroidal reduction of the bosonic sector of type IIB supergravity to arbitrary dimensions D≥3.
TEMPORAL GENERALIZATION WITH DOMAIN GENERALIZATION GRAPHS
Authors: RANDALL D. J. , HAMILTON H. J. , HILDERMAN R. J.
Published: April 2003

This paper addresses the problem of using domain generalization graphs to generalize temporal data extracted from relational databases. A domain generalization graph associated with an attribute defines a partial order which represents a set of generalization relations for the attribute. We propose formal specifications for domain generalization graphs associated with calendar (date and time) attributes. These graphs are reusable (i.e. can be used to generalize any calendar attributes), adaptable (i.e. can be extended or restricted as appropriate for particular applications), and transportable (i.e. can be used with any database containing a calendar attribute).
A GAUSSIAN DERIVATIVE OPERATOR FOR AUTHENTIC EDGE DETECTION AND ACCURATE EDGE LOCALIZATION
Authors: KENNEDY LESA M. , BASU MITRA
Published: April 2003

One of the nice properties of the Gaussian scale space map is its well behavedness. This rather well-behaved nature is somewhat deceptive, however, as portions of the map may not have any direct relationship to the features in the unfiltered image.4 It has been shown that not all zero-crossing surface patches can be associated with intensity changes in the unfiltered image. Zero-crossings give rise to both authentic and phantom scale map contours. Recently, we proposed an edge enhancement operator, the LWF, which is a weighted combination of the Gaussian and its second derivative.6 In this paper, we prove analytically and demonstrate experimentally that the LWF produces the authentic scale map contours only. We also show that the LWF has excellent edge localization (i.e. the points marked by the operator is very close to center of the true edge). A performance comparison between the Laplacian of Gaussian and LWF operators with respect to the localization property is also presented.
FEATURES OF DERIVATIVE CONTINUITY IN SHAPE
Authors: HENSHAW PHILIP F.
Published: April 2003

Derivative continuity is a distributed invariant relationship between parts of flowing shapes. The original techniques presented here were developed for making the behavioral dynamics of complex processes more recognizable, but are equally applicable to assisting in the recognition of shapes in images. Regularizing a sequence using a constraint of derivative continuity is equivalent to using a bimodal smoothing kernel, producing a distinct bias for reducing variation on higher derivative levels, sharply defining shape with minimal suppression of shape. To help determine where reconstructing shapes in this way is valid, a test was developed to help distinguish combinations of noise and smooth flows from random walks. This helps distinguish between illusory and genuine, data shapes but also exposes a flair in using this and other measures of scaling behavior for diagnostic purposes. Gaussian scale space techniques in use for some time in image recognition, for identifying reliable landmarks in the shapes of outlines, are demonstrated for use in identifying key features of shape in time series.
DYNAMIC STOCHASTIC GAMES OF RESOURCE ALLOCATION BETWEEN PRODUCTION AND CONSUMPTION
Authors: DOMANSKY VICTOR
Published: April 2003

Controlled by several agents, multistage processes of resource allocation between production and consumption with random production functions are considered as non-cooperative dynamic stochastic games. For these games, the Nash Equilibria are constructed satisfying the criteria of maximisation of some kind of "public utility". Both finite and infinite horizons of planning are examined.
CONGESTION GAMES AND POTENTIALS RECONSIDERED
Authors: VOORNEVELD MARK , BORM PETER , VAN MEGEN FREEK , TIJS STEF , FACCHINI GIOVANNI
Published: April 2003

In congestion games, players use facilities from a common pool. The benefit that a player derives from using a facility depends, possibly among other things, on the number of users of this facility. The paper gives an easy alternative proof of the isomorphism between exact potential games and the set of congestion games introduced by Rosenthal (1973). It clarifies the relations between existing models on congestion games, and studies a class of congestion games where the sets of Nash equilibria, strong Nash equilibria and potential-maximising strategies coincide. Particular emphasis is on the computation of potential-maximising strategies.
OPTIMUM DESIGN OF SPACE FRAMES UNDER SEISMIC LOADING
Authors: PAPADRAKAKIS MANOLIS , LAGAROS NIKOS D. , PLEVRIS VAGELIS
Published: April 2003

The objective of this paper is to perform structural optimization under seismic loading. Combinatorial optimization methods and in particular algorithms based on Evolution Strategies are implemented for the solution of large-scale structural optimization problems under seismic loading. In this work the efficiency of a rigorous approach in treating dynamic loading is investigated and compared with a simplified dynamic analysis in the framework of finding the optimum design of structures with minimum weight. In this context a number of accelerograms are produced from the elastic design response spectrum of the region. These accelerograms constitute the multiple loading conditions under which the structures are optimally designed. This approach is compared with an approximate design approach based on simplifications adopted by the seismic codes. The results obtained for a characteristic test problem indicate a substantial improvement in the final design when the proposed optimization procedure is implemented.
FUNDAMENTALS OF BIOMETRIC AUTHENTICATION TECHNOLOGIES
Authors: WAYMAN JAMES L.
Published: April 2003

Biometric authentication technologies are used for the machine identification of individuals. The human-generated patterns used may be primarily physiological or behavioral, but usually contain elements of both components. Examples include voice, handwriting, face, eye and fingerprint identification. In this paper, we look at these technologies and their applications in general, developing a systematic approach to classifying, analyzing and evaluating them. A general system model is shown and test results for a number of technologies are considered.
TOM: TOTALLY ORDERED MESH A MULTIRESOLUTION STRUCTURE FOR TIME CRITICAL GRAPHICS APPLICATIONS
Authors: BOUVIER ERIC , GOBBETTI ENRICO
Published: April 2003

Tridimensional interactive applications are confronted to situations where very large databases have to be animated, transmitted and displayed in very short bounded times. As it is generally impossible to handle the complete graphics description while meeting timing constraint, techniques enabling the extraction and manipulation of a significant part of the geometric database have been the focus of many research works in the field of computer graphics. Multiresolution representations of 3D models provide access to 3D objects at arbitrary resolutions while minimizing appearance degradation. We describe the TOM (Totally Ordered Mesh), a multiresolution triangle mesh structure tailored to the support of time-critical adaptive rendering. The structure grants high speed access to the continuous levels of detail of a mesh and allows very fast traversal of the list of triangles at arbitrary resolution so that bottlenecks in the graphic pipeline are avoided. Moreover, and without specific compression, the memory footprint of the TOM is small (about 108% of the single resolution object in face-vertex form) so that large scenes can be handled effectively. The TOM structure also supports storage per vertex (or per corner of triangle) attributes such as colors, normals, texture coordinates or dynamic properties. Implementation details are presented along with the results of tests for memory needs, approximation quality, timing and efficacy.
SEMICONDUCTOR JUNCTION NOISE REVISITED: WHERE HAVE ALL THE PHYSICAL NOISE SOURCES GONE?
Authors: EDWARDS PAUL J.
Published: April 2003

The distinction between "physical" and "equivalent" noise sources in bipolar junction transistors and other semiconductor devices has become blurred in the current engineering textbooks. An unfortunate consequence of this is the emergence in the literature of fictitious noise sources such as the "the collector-current shot noise" and the "base-current shot noise". These are often assigned a physical reality and incorrectly treated as real physical noise sources, independent of circuit topology. Text-books have encouraged successive generations of students in this belief. Non-physical noise sources such as these are convenient and legitimate, even essential, for the effective modeling and simulation of circuit noise. However their naïve use in teaching and research is likely to continue to give rise to fallacious concepts and misleading conclusions. The physical. The physical modeling of the light-emitting diode, the photon transport transistor and the bipolar junction transistor are briefly discussed to illustrate this view.
Ezetimibe for Management of Hypercholesterolemia
Authors: Mauro Vincent F , Tuckerman Chad E
Published: April 2003

OBJECTIVE:

To review the primary literature describing the pharmacology of ezetimibe and clinical trials investigating its use in the management of hypercholesterolemia.

DATA SOURCES:

A MEDLINE search (1966–December 2002) was performed using SCH 48461, SCH 58235, ezetimibe, and 2-azetidinone as key words. English-language articles were identified and the references of these articles were used to further identify pertinent articles and abstracts. Given the paucity of published articles available on ezetimibe, many of the references cited are abstracts.

STUDY SELECTION:

All acquired articles that discussed the pharmacology, pharmacokinetics, chemistry, and clinical efficacy of ezetimibe were reviewed.

DATA EXTRACTION:

Articles were selected based on content regarding the medicinal chemistry, pharmacology, and clinical use of ezetimibe.

DATA SYNTHESIS:

Ezetimibe, approved for use in October 2002, belongs to a new class of antihyperlipidemic agents that uniquely inhibit the absorption of cholesterol by inhibiting the cholesterol transport system located within intestinal cell walls. In humans, ezetimibe reduced cholesterol absorption by >50%. In clinical trials, ezetimibe 10 mg/d reduced low-density lipoprotein cholesterol (LDL-C) by approximately 18% and further enhanced the LDL-C–lowering effect of statin medications by an additional 15–20%. In addition, ezetimibe lowered triglycerides about 5% and increased high-density lipoprotein cholesterol (HDL-C) approximately 3%. Ezetimibe is well tolerated. At present, no serious adverse effects have been directly attributable to ezetimibe.

CONCLUSIONS:

Based on the data currently available, it appears that ezetimibe has a potential role in the treatment of primary hypercholesterolemia; however further data are needed to determine its long-term tolerability and efficacy. The potential roles for ezetimibe include its concurrent use with a statin to further enhance the lowering of LDL-C. Other possible roles for ezetimibe include its concurrent use with a statin to permit a lowering of statin dosage to avoid statin-related complications or its use as monotherapy to treat hypercholesterolemia when statin use cannot be tolerated or is contraindicated. Outcome data demonstrating that cardiovascular morbidity and/or mortality are reduced by ezetimibe therapy have yet to be generated.
Holocene Relative Sea-Level History of Novaya Zemlya, Russia, and Implications for Late Weichselian Ice-Sheet Loading
Authors: Zeeberg JaapJan , Lubinski David J. , Forman Steven L.
Published: April 2003

We present six new radiocarbon-dated emergence curves that provide a detailed record of postglacial emergence of northern Novaya Zemlya and ages which constrain the emergence of Vaygach Island in the southern archipelago. Radiocarbon ages onHiatellasp. from a lateral moraine in Russkaya Gavan' and abundances of foraminifea in a marine core from Nordenskiold Bay, 300 km south of our study area, indicate that coastal deglaciation occurred prior to ∼10,000 cal yr B.P. However, postglacial emergence commenced ∼7000 cal yr B.P., with stabilization of global sea level. The total emergence is 13–11 m above sea level (asl) with apparent uplift rates of 1–2 mm/yr for the past 2000 yr, indicating modest glacier loads (<1 km), early (>11,000 cal yr B.P.) deglaciation, or both. The isobase pattern, showing no east–west tilt across Novaya Zemlya, and offshore moraines suggest a separate ice-dispersal center over Novaya Zemlya for the later stages of the Late Weichselian glacial cycle and possibly earlier.
Holocene Lake-Level Fluctuations of Lake Aricota, Southern Peru
Authors: Placzek Christa , Quade Jay , Betancourt Julio L.
Published: April 2003

Lacustrine deposits exposed around Lake Aricota, Peru (17° 22′S), a 7.5-km2 lake dammed by debris flows, provide a middle to late Holocene record of lake-level fluctuations. Chronological context for shoreline deposits was obtained from radiocarbon dating of vascular plant remains and other datable material with minimal 14C reservoir effects (<350 yr). Diatomites associated with highstands several meters above the modern lake level indicate wet episodes. Maximum Holocene lake level was attained before 6100 14C yr B.P. and ended ∼2700 14C yr B.P. Moderately high lake levels occurred at 1700 and 1300 14C yr B.P. The highstand at Lake Aricota during the middle Holocene is coeval with a major lowstand at Lake Titicaca (16°S), which is only 130 km to the northeast and shares a similar climatology. Comparisons with other marine and terrestrial records highlight emerging contradictions over the nature of mid-Holocene climate in the central Andes.
Raised Coral Terraces at Malakula, Vanuatu, Southwest Pacific, Indicate High Sea Level During Marine Isotope Stage 3
Authors: Cabioch Guy , Ayliffe Linda K.
Published: April 2003

The occurrence of a series of raised coral reefs from the uplifted island of Malakula (Vanuatu, SW Pacific) provide an opportunity to examine sea-level fluctuations over at least the past 120,000 years. Thirteen fossil coral samples from Malakula were analyzed by the thermal ionization mass spectrometry (TIMS) U/Th dating technique, yielding information on sea levels during late marine isotope stage 3 and early stage 4. Our findings are in good agreement with sea-level estimates from raised coral terraces in Papua New Guinea and the recent sea-level reconstruction from the deep-sea sedimentary δ18O records. In particular, our coral data appear to confirm that sea levels at about 45,000–50,000 yr B.P. were only 30 to 60 m below the present level. Combined with other evidence of sea-level change, our data provide a strong case for much higher sea levels and therefore markedly reduced continental ice volume at 47,000 to 49,000 years ago.
Late Quaternary Iceberg Rafting along the Antarctic Peninsula Continental Rise and in the Weddell and Scotia Seas
Authors: Ó Cofaigh Colm , Dowdeswell Julian A. , Pudsey Carol J.
Published: April 2003

Sediment cores from the continental rise west of the Antarctic Peninsula and the northern Weddell and Scotia Seas were investigated for their ice-rafted debris (IRD) content by lithofacies logging and counting of particles >0.2 cm from core x-radiographs. The objective of the study was to determine if there are iceberg-rafted units similar to the Heinrich layers of the North Atlantic that might record periodic, widespread catastrophic collapse of basins within the Antarctic Ice Sheet during the Quaternary. Cores from the Antarctic Peninsula margin contain prominent IRD-rich units, with maximum IRD concentrations in oxygen isotope stages 1, 5, and 7. However, the greater concentration of IRD in interglacial stages is the result of low sedimentation rates and current winnowing, rather than regional-scale episodes of increased iceberg rafting. This is also supported by markedly lower mass accumulation rates (MAR) during interglacial periods versus glacial periods. Furthermore, thinner IRD layers within isotope stages 2–4 and 6 cannot be correlated between individual cores along the margin. This implies that the ice sheet over the Antarctic Peninsula did not undergo widespread catastrophic collapse along its western margin during the late Quaternary (isotope stages 1–7). Sediment cores from the Weddell and Scotia Seas are characterized by low IRD concentrations throughout, and the IRD signal generally appears to be of limited regional significance with few strong peaks that can be correlated between cores. Tentatively, this argues against pervasive, rapid ice-sheet collapse around the Weddell embayment over the last few glacial cycles.
The Taylor Dome Antarctic 18O Record and Globally Synchronous Changes in Climate
Authors: Grootes Pieter M. , Steig Eric J. , Stuiver Minze , Waddington Edwin D. , Morse David L. , Nadeau Marie-Josée
Published: April 2003

The 18O/16O profile of a 554-m long ice core through Taylor Dome, Antarctica, shows the climate variability of the last glacial–interglacial cycle in detail and extends at least another full cycle. Taylor Dome shares the main features of the Vostok record, including the early climatic optimum with later cool phase of the last interglacial period in Antarctica. Taylor Dome δ18O fluctuations are more abrupt and larger than those at Vostok and Byrd Station, although still less pronounced than those of the Greenland GISP2 and GRIP records. The influence of the Atlantic thermohaline circulation on regional ocean heat transport explains the partly “North Atlantic” character of this Antarctic record. Under full glacial climate (marine isotope stage 4, late stage 3, and stage 2), this marine influence diminished and Taylor Dome became more like Vostok. Varying degrees of marine influence produce climate heterogeneity within Antarctica, which may account for conflicting evidence regarding the relative phasing of Northern and Southern Hemisphere climate change.
Determination of 36Cl Production Rates Derived from the Well-Dated Deglaciation Surfaces of Whidbey and Fidalgo Islands, Washington
Authors: Swanson Terry W. , Caffee Marc L.
Published: April 2003

The 36Cl dating method is increasingly being used to determine the surface-exposure history of Quaternary landforms. Production rates for the 36Cl isotopic system, a critical component of the dating method, have now been refined using the well-constrained radiocarbon-based deglaciation history of Whidbey and Fidalgo Islands, Washington. The calculated total production rates due to calcium and potassium are 91±5 atoms 36Cl (g Ca)−1 yr−1 and are 228±18 atoms 36Cl (g K)−1 yr−1, respectively. The calculated ground-level secondary neutron production rate in air, Pf(0), inferred from thermal neutron absorption by 35Cl is 762±28 neutrons (g air)−1 yr−1 for samples with low water content (1–2 wt.%). Neutron absorption by serpentinized harzburgite samples of the same exposure age, having higher water content (8–12 wt.%), is ∼40% greater relative to that for dry samples. These data suggest that existing models do not adequately describe thermalization and capture of neutrons for hydrous rock samples. Calculated 36Cl ages of samples collected from the surfaces of a well-dated dacite flow (10,600–12,800 cal yr B.P.) and three disparate deglaciated localities are consistent with close limiting calibrated 14C ages, thereby supporting the validity of our 36Cl production rates integrated over the last ∼15,500 cal yr between latitudes of 46.5° and 51°N. Although our production rates are internally consistent and yield reasonable exposure ages for other localities, there nevertheless are significant differences between these production rates and those of other investigators.
A 4000-Year Lacustrine Record of Environmental Change in the Southern Maya Lowlands, Petén, Guatemala
Authors: Rosenmeier Michael F. , Hodell David A. , Brenner Mark , Curtis Jason H. , Guilderson Thomas P.
Published: April 2003

A 4000-yr sediment core record from Lake Salpetén, Guatemala, provides evidence for Maya-induced forest clearance and consequent soil erosion between ∼1700 cal yr B.C. and 850 cal yr A.D. Radiocarbon ages of wood, seeds, and charcoal support an age-depth model with average errors of ±110 cal yr. Relatively low carbonate δ18O values between 1300 and 400 cal yr B.C. coincide with pollen evidence for forest loss, consistent with increased surface and groundwater flow to the lake. Minimum δ18O values between 400 cal yr B.C. and 150 cal yr A.D. suggest a high lake level, as do 14C-dated aquatic gastropods as much as 7.5 m above the present lake stage. High lake levels resulted from reduced evaporation-to-precipitation ratios, increased hydrologic input caused by anthropogenic deforestation, or both. The Preclassic abandonment (150 A.D.) and Early Classic/Late Classic boundary (550 A.D.) are marked by relatively high δ18O values indicating reduced lake levels. Oxygen isotope composition increased further coincident with the Terminal Classic Maya demographic decline between 800 and 900 A.D. This period of high δ18O may have been caused by the greater aridity that has been documented in northern Yucatán lakes or by decreased hydrologic input to the lake as a consequence of forest recovery. Reduced soil erosion after 850 cal yr A.D. coincided with the Terminal Classic Maya demographic decline and permitted forest recovery and resumption of organic sedimentation.
Changes in the Bathymetry and Volume of Glacial Lake Agassiz between 9200 and 7700 14C yr B.P.
Authors: Leverington David W. , Mann Jason D. , Teller James T.
Published: April 2003

Computer reconstructions of the bathymetry of the lake were used to quantify variations in the size and form of Lake Agassiz during its final two phases (the Nipigon and Ojibway phases), between about 9200 and 7700 14C yr B.P. (ca. 10,300–8400 cal yr B.P.). New bathymetric models for four Nipigon Phase stages (corresponding to the McCauleyville, Hillsboro, Burnside, and The Pas strandlines) indicate that Lake Agassiz ranged between about 19,200 and 4600 km3 in volume and 254,000 and 151,000 km2 in areal extent at those times. A bathymetric model of the last (Ponton) stage of the lake, corresponding to the period in which Lake Agassiz was combined with glacial Lake Ojbway to the east, shows that Lake Agassiz–Ojibway was about 163,000 km3 in volume and 841,000 km2 in areal extent prior to the final release of lake waters into the Tyrrell Sea. During the Nipigon Phase, a number of catastrophic releases of water from Lake Agassiz occurred as more northerly (lower) outlets were made available by the retreating southern margin of the Laurentide Ice Sheet; we estimate that each of the four newly investigated Nipigon Phase releases involved water volumes of between 1600 and 2300 km3. The final release of Lake Agassiz waters into the Tyrrell Sea at about 7700 14C yr B.P. is estimated to have been about 163,000 km3 in volume.
Holocene Climate Reconstructions from the Fennoscandian Tree-Line Area Based on Pollen Data from Toskaljavri
Authors: Seppä Heikki , Birks H.J.B
Published: April 2003

Due to its location on the eastern North Atlantic seaboard, the Fennoscandian tree-line area is an ideal area to use biological proxies to assess the relative roles of the Scandinavian ice sheet and of oceanic, atmospheric, and astronomic forcings on regional climate history. Here we report pollen-based July mean temperature (Tjul) and annual precipitation (Pann) reconstructions from a sediment core from a high-altitude tree-line lake in northwestern Finland. The reconstructions suggest that at 9600–8300 cal yr B.P. Tjul values were low but steadily rising while Pann was high. The period of warmest summers, with Tjul values ca. 1.8°–1.6°C higher than at present, occurred at ca. 8000–6500 cal yr B.P. Since then climate has become gradually cooler. Tjul values during the “Medieval Warm Period” (ca. 1400–1000 cal yr B.P.) were ca. 0.8°C higher that at present but decreased rapidly to the low “Little Ice Age” levels at 800 cal yr B.P. We compare these results with an earlier pollen-based climate reconstruction from the same region. The reconstructions indicate a similar general Holocene Tjul pattern with lower values in the reconstruction from the high-altitude lake. However, most of the small-scale variations are not synchronous, suggesting that they may represent noise rather than signal in our data.
Regulation of cytochrome c expression in the aerobic respiratory yeast Kluyveromyces lactis
Authors: Freire-Picos M.Angeles , Hollenberg Cornelis P. , Breunig Karin D. , Cerdan M.Esperanza
Published: April 2003

Transcriptional regulation of the KlCYC1 gene from the aerobic respiratory yeast Kluyveromyces lactis has been studied. The KlCYC1 gene produces two transcripts of different sizes, in contrast with the single transcripts found for CYC1 and CYC7 from Saccharomyces cerevisiae, and for the CYC gene from Schwanniomyces occidentali. Both KlCYC1 transcripts respond in the same way to the regulatory signals studied here. The transcription of KlCYC1 is regulated by oxygen and this control is mediated by heme. The KlCYC1 gene is also subject to catabolite repression. Heterologous expression in S. cerevisiae mutants reveals that the factors HAP1 and HAP2 take part in the regulatory mechanism.
Interaction of smooth muscle caldesmon with calmodulin mutants
Authors: Medvedeva Marina V. , Bushueva Tatyana L. , Shirinsky Vladimir P. , Lukas Thomas J. , Watterson D.Martin , Gusev Nikolai B.
Published: April 2003

The interaction of avian smooth muscle caldesmon with calmodulin (CaM) was investigated by studying the ability of selected mutant calmodulins to induce fluorescence changes in caldesmon. Different types of CaM mutants were used including point charge mutants, cluster mutations, and mutations which alter the calcium binding of CaM. The caldesmon binding properties were only slightly affected by E84K‐CaM or by the double mutation E84Q/E120Q‐CaM. Affinity of calmodulin to caldesmon was decreased 2–4 times by point mutation G33V‐CaM, double mutation E84K/E120K‐CaM, deletion of residues 82–84, and by cluster mutations DEE118‐120 → KKK or EEE8284 → KKK. Mutations of the first (E31A‐CaM) and the second (E67A‐CaM) calcium binding sites reduced the affinity of calmodulin to caldesmon by at least 5‐fold; in addition these calmodulin mutants exhibited smaller changes in the fluorescence spectra of caldesmon. Simultaneous mutation of the two negatively charged clusters of calmodulin EEE82‐84 → KKK and DEE118‐120 → KKK resulted in a more than 15‐fold decrease in the affinity of calmodulin for caldesmon. The data indicate that charged and uncharged amino acids in both halves of CaM play an important role in the binding of calmodulin to caldesmon, and that Ca2+ binding must be maintained in the amino‐terminal sites for maximal interaction with caldesmon.
The potent mitogen Pasteurella multocida toxin is highly resistant to proteolysis but becomes susceptible at lysosomal pH
Authors: Smyth Martin G. , Pickersgill Richard W. , Lax Alistair J.
Published: April 2003

The susceptibility of the potent mitogen Pasteurella multocida toxin (PMT) to various proteases was investigated. PMT at a toxin to protease molar ratio of 1:1 was resistant to 8 of the 11 proteases tested after one hour. With longer incubation, PMT remained resistant to 7 proteases, and this correlated with a retention of biological activity, indicating that PMT might not require proteolytic cleavage at least until it bound to a cell receptor. Previous evidence had suggested that PMT is processed in the cell via an endosome or lysosome. We have shown that PMT became susceptible to proteolysis when the pH was lowered to 5 or below. This supports the previous suggestion that PMT is processed via a low pH compartment in the cell.
Removal of lactoferrin from plasma is mediated by binding to low density lipoprotein receptor‐related protein/α2‐macroglobulin receptor and transport to endosomes
Authors: Meilinger Melinda , Haumer Markus , Szakmary Kati A. , Steinböck Ferdinand , Scheiber Barbara , Goldenberg Hans , Huettinger Manfred
Published: April 2003

LDL receptor related protein (LRP) is a ubiquitously expressed cell surface receptor that binds, at least in vitro, a plethora of ligands among them α
2‐macroglobulin and lactoferrin (Lf). The function of LRP in internalisation and distribution of ligands within cellular metabolism is still unclear. We here investigated by combined ligand‐ and immunoblotting the participation of LRP/α
2MR and its associated protein (RAP) in receptor mediated endocytosis of Lf into rat liver. We found LRP highly enriched in sucrose density gradient fractions around density 1.10 g/ml, previously characterised as endosomal fractions. RAP was concentrated in distinct fractions around density 1.14 g/ml. This separation of RAP from LRP/α
2MR is physiologically meaningful as RAP avidly binds to LRP/α
2MR and by that shuts off all ligand binding function. In endosomal fractions we found one single binding protein for 125I‐labelled Lf. With a specific anti LRP/α
2MR antibody and ligand blotting with 125I‐labelled RAP this endosomal Lf binding site was verified to be LRP/α
2MR. Endosomes did not bind labelled Lf when prepared from rats that received an intravenous injection of Lf (20 mg per animal) 20 min prior to preparation. Surprisingly we immunodetected Lf in these endosomes at a position around 600 kDa, comigrating with LRP/α
2MR. We determined Lf binding to be optimal at pH 5.8, what led us to suggest the existence of a very stable LF‐LRP/α
2MR complex in endosomes. These data support the idea of effective binding of Lf at pH as found in inflamed tissue environment where Lf is reported to be involved in leukocyte mediated inflammation regulation.
Transcriptional regulation of the yeast vacuolar aminopeptidase yscI encoding gene (APE1) by carbon sources
Authors: Bordallo Javier , Cueva Rosario , Suárez-Rendueles Paz
Published: April 2003

Transcription of the vacuolar aminopeptidase yscI‐encoding gene (APE1) is regulated by the carbon source used for yeast growth, responding to carbon catabolite repression. By Northern blot analyses, we determined the kinetics of glucose repression in growth‐shift experiments. When added to induced cells, glucose leads to the disappearance of hybridizable aminopeptidase yscI RNA sequences within 30 min. However, the amount of inmunoreactive protein, once induced, is not affected by the addition of glucose. By deletion analysis of the fusion gene APE1‐lacZ we have identified a number of strong regulatory regions in the APE1 promoter. Consensus sequences for the binding of yAP1 and the HAP2/HAP3/HAP4 complex are contained in those regions. Control of the APE1 gene expression is not mediated by the HXK2 regulatory gene, but a strain bearing a deletion in the CAT1 gene can not derepress APE1 transcription to wild‐type levels.
Influence of DNA superstructural features and histone amino‐terminal domains on nucleosome positioning
Authors: Kropp Bruno , Leoni Luisa , Sampaolese Beatrice , Savino Maria
Published: April 2003

Nucleosome positioning has been studied on a strongly curved 268 by DNA fragment from a Crithidia fasciculata kinetoplast, complexed with a histone octamer either normal or lacking amino‐terminal domains. A very similar nucleosome multiple positioning, with the same rotational phasing, has been found, by Exo III mapping, in both cases. The experimental positioning is in fairly good agreement with that predicted using a theoretical method based on DNA distortion energy, derived from the nucleotide sequence. Taking into account that nucleosomes, without histone amino‐terminal domains, lack thirty percent of electrostatic interactions, these results suggest a dominant role on nucleosome positioning of DNA distortion energy with respect to modifications in histone domains.
The telomeric sequence is directly attached to the HRS60 subtelomeric tandem repeat in tobacco chromosomes
Authors: Fajkus Jiří , Královics Robert , Kovařík Aleš , Fajkusová Lenka
Published: April 2003

PCR and primers derived from the telomeric repeat (CCCTAAA)n and from the tobacco subtelomeric tandemly repetitive sequence HRS60 (EMBL X12489) were used to amplify the region linking the two loci. A 131 bp PCR product was obtained both from total tobacco DNA and from the DNA fraction enriched for telomeres. Its sequence only consists of the telomeric primer and the attached region of the HRS60 repetitive unit up to the end of the sequence complementary to the HRS60 primer. The site of direct continuity between the two sequences is formed by a (dA)7 tract.
Protein kinase C activation is not a key step in ADP‐mediated exposure of fibrinogen receptors on human platelets
Authors: Pulcinelli Fabio M. , Ashby Barrie , Gazzaniga Pier Paolo , Daniel James L.
Published: April 2003

A selective inhibitor of protein kinase C (PKC), Ro 31‐8220, blocks pleckstrin (P47) phosphorylation in platelets activated with either ADP, ADP plus synthetic thromboxane agonist U46619 and ADP plus U46619 plus epinephrine, while inducing a weak inhibition of platelet aggregation, and no significant effect on the fibrinogen binding. In platelets activated by U46619 alone, P47 phosphorylation, platelet aggregation, fibrinogen binding and serotonin release are all inhibited by Ro 318220. In the presence of an ADP scavenger system, U46619 induces pleckstrin phosphorylation, serotonin release and calcium mobilization but not platelet aggregation and fibrinogen binding, unless epinephrine is added. In conclusion: (1) PKC activation is required for ADP secretion; (2) ADP or epinephrine are essential for fibrinogen receptor exposure induced by U46619; (3) fibrinogen receptor exposure induced by ADP is independent of activation of PKC.
Redox states of DsbA in the periplasm of Escherichia coli
Authors: Kishigami Satoshi , Akiyama Yoshinori , Ito Koreaki
Published: April 2003

DsbA is a periplasmic, disulfide bond formation factor of E. coli. We studied in vivo redox states of its active site cysteines. When periplasmic contents were prepared from iodoacetic acid‐treated cells, according to the previously published procedures, variable but major proportions of DsbA were in the reduced form. We found that this was due to an artificial reduction that occurred after cell disruption; even purified and oxidized DsbA underwent reduction when incubated with cell extracts in the absence of any added reducing agent. Such DsbA‐reducing activities were detected in both the periplasmic and the cytoplasmic fractions. To circumvent the artifact, we analyzed redox states of DsbA under denaturing conditions. Now virtually all the DsbA molecules were detected as oxidized or reduced in the dsbB
+ background or in the dsbB
− background, respectively. Using the improved method, we also examined redox states of DsbA when it was overproduced, and followed the oxidation/reduction pathway that DsbA follows after biosynthesis. It is suggested that newly synthesized DsbA is rapidly oxidized by pre‐existing DsbA, while oxidation of mature (functional) DsbA requires DsbB, whose roles might include that of antagonizing the actions of DsbA‐reducing enzyme(s).
A C‐terminal domain, which prevents secretion of the neuroendocrine protein 7B2 in Saccharomyces cerevisiae, inhibits Kex2 yet is processed by the Yap3 protease
Authors: Chaudhuri Bhabatosh , Stephan Christine
Published: April 2003

Recent reports reveal that the C‐terminal half of the neuroendocrine polypeptide 7B2 selectively inhibits and binds PC2, a mammalian prohormone converting enzyme that is homologous to the yeast pro‐α‐factor processing protease Kex2. During attempted secretion of the 185 amino‐acid human 7B2 in Saccharomyces cerevisiae, we observe that the protein is mostly retained inside the cell. However a mutant polypeptide (7B2Δ1), where the C‐terminal 48 amino acids of 7B2 are deleted, is efficiently secreted. Two shorter C‐terminal truncations either permit poor secretion or no secretion at all. Surprisingly, full‐length 7B2 but not 7B2Δ1 abolishes the catalytic activity of Kex2, indicating that C‐terminal residues of 7B2 might also be important for inhibition of the yeast protease. When the KEX2 gene is disrupted, yeast cells unexpectedly secrete a 7B2 variant similar in size to 7B2Δ1, suggesting involvement of the alternate yeast prohormone convertase Yap3 in processing. Secretion is enhanced by overexpression of Yap3 and by the presence of a Lys‐Arg residue at the processing site of precursor 7B2. These results purport that, in neuroendocrine cells too, secretion of 7B2 could be mediated by a homologue of Yap3.
Nitric oxide synthase activity in molluscan hemocytes
Authors: Conte Angela , Ottaviani Enzo
Published: April 2003

The hemocytes of the freshwater snail Viviparus ater have nitric oxide synthase (NOS) activity, as demonstrated by [3H]citrulline and nitrite+nitrate formation. The enzyme is NADPH dependent and is competitively inhibited by the mammalian NOS inhibitor (K
i = 4.7 μM). The K
m for l‐arginine is 2.5 μM. 70% of the total activity is observed at very low free Ca2+ concentration (3 nM). LPS treatment increased total NOS activity 2.4 fold. The activity is partly present in the non‐soluble fraction of hemocytes (24% and 8% in non‐stimulated and LPS‐stimulated snails, respectively). An antiserum to the C‐terminal synthetic pentadecapeptide of the rat cerebellar NOS inhibited the enzyme activity in a concentration‐dependent manner. This is the first biochemical demonstration of the existance of NOS activity in molluscan hemocytes, the cells responsible for defence mechanisms.