bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Investigation of Three-Dimensional Clocking Effects in a Low Pressure Turbine
Authors: Arnone Andrea , Marconcini Michele , Del Greco Alberto Scotti , Spano Ennio
Published: September 2004

One and a half stages of a low pressure turbine were investigated using a three-dimensional time-accurate viscous solver. Unsteady analyses were carried out by varying the circumferential relative position of consecutive vanes to study the effects of clocking on performance. Assuming that efficiency improvements by clocking are linked to the wake tangential position with respect to the successive blade, a certain circumferential shift in this position can be observed along the blade height due to blade twist and nonradial stacking, giving different contributions. In order to assess this phenomenon, results from three-dimensional computations were compared with a quasi-three-dimensional analysis at mid-span. The effects of clocking on wake interaction mechanisms and unsteady blade loadings are presented and discussed.
Vortex Transport and Blade Interactions in High Pressure Turbines
Authors: Chaluvadi V. S. P. , Kalfas A. I. , Hodson H. P.
Published: September 2004

This paper presents a study of the three-dimensional flow field within the blade rows of a high-pressure axial flow steam turbine stage. Half-delta wings were fixed to a rotating hub to simulate an upstream rotor passage vortex. The flow field is investigated in a low-speed research turbine using pneumatic and hot-wire probes downstream of the blade row. The paper examines the impact of the delta wing vortex transport on the performance of the downstream blade row. Steady and unsteady numerical simulations were performed using structured three-dimensional Navier-Stokes solver to further understand the flow field. The loss measurements at the exit of the stator blade showed an increase in stagnation pressure loss due to the delta wing vortex transport. The increase in loss was 21% of the datum stator loss, demonstrating the importance of this vortex interaction. The transport of the stator viscous flow through the rotor blade row is also described. The rotor exit flow was affected by the interaction between the enhanced stator passage vortex and the rotor blade row. Flow underturning near the hub and overturning towards the midspan was observed, contrary to the classical model of overturning near the hub and underturning towards the midspan. The unsteady numerical simulation results were further analyzed to identify the entropy producing regions in the unsteady flow field.
Salmonella: a continuing problem
Authors: Hardy A
Published: September 2004

Salmonella was the archetypal food poisoning organism of the 20th century. It achieved a high public profile following the salmonella-in-eggs crisis of 1988–89, but by then had been the subject of public health concern and scientific interest for over a century. Early associated with animal foods, the advent of phage typing in the 1940s began to reveal the complexity of its environmental associations. This paper explores the story of salmonella as a continuing problem in epidemiology, microbiology and public health, in the food chain, and in the kitchen.
Thrombotic thrombocytopenic purpura associated with statin treatment
Authors: Sundram F , Roberts P , Kennedy B , Pavord S
Published: September 2004

Thrombotic thrombocytopenic purpura (TTP) is a rare condition but associated with 90% mortality if left untreated. The diagnosis is usually made when there is thrombocytopenia and microangiopathic haemolytic anaemia, although the full pentad also includes fever, renal impairment, and neurological dysfunction. A variety of underlying causes have been implicated in acquired TTP including bacterial and viral infections, bone marrow and organ transplantation, pregnancy, immune disorders, and certain drugs. To date there is just one case report of TTP associated with statin treatment. The clinical course of a patient who presented with TTP after being started on simvastatin, a HMG-CoA inhibitor, is described.
A MINIMAL SUPERSTRING STANDARD MODEL I: FLAT DIRECTIONS
Authors: CLEAVER G. B. , FARAGGI A. E. , NANOPOULOS D. V.
Published: September 2004

Three family SU (3)C× SU (2)L× U (1)Y string models in several constructions generically possess two features: (i) an extra local anomalous U (1)A and (ii) numerous (often fractionally charged) exotic particles beyond those in the minimal supersymmetric model (MSSM). Recently, we demonstrated that the observable sector effective field theory of such a free fermionic string model can reduce to that of the MSSM, with the standard observable gauge group being just SU (3)C× SU (2)L× U (1)Y and the SU (3)C× SU (2)L× U (1)Y-charged spectrum of the observable sector consisting solely of the MSSM spectrum. An example of a model with this property was shown. We continue our investigation of this model by presenting a large set of different flat directions of the same model that all produce the MSSM spectrum. Our results suggest that even after imposing the conditions for the decoupling of exotic states, there may remain sufficient freedom to satisfy the remaining phenomenological constraints imposed by the observed data.
RENORMALIZABILITY AND SEARCHING FOR THE ABELIAN Z′ BOSON IN FOUR-FERMION PROCESSES
Authors: GULOV A. V. , SKALOZUB V. V.
Published: September 2004

A model independent search for Abelian Z′ gauge boson in four-fermion processes is analyzed. It is based on a low energy effective Lagrangian parametrizing the Z′ interactions with the fermion and scalar fields of the Standard Model. These parameters are related due to the requirement of renormalizability (gauge invariance). It is found that the absolute value of the Z′ coupling to the axial-vector currents is the same for all fermions and it is strongly correlated with the Z′ coupling to the scalar field. On the base of these relations the dependences between the parameters of the effective Lagrangian constructed from dimension-six operators are derived.
A CONSISTENT CALCULATION OF HEAVY MESON DECAY CONSTANTS AND TRANSITION WAVE FUNCTIONS IN THE COMPLETE HQEFT
Authors: WANG W. Y. , WU Y. L.
Published: September 2004

Within the complete heavy quark effective field theory (HQEFT), the QCD sum rule approach is used to evaluate the decay constants including 1/mQcorrections and the Isgur–Wise function and other additional important wave functions concerned at 1/mQfor the heavy–light mesons. The number of unknown wave functions or form factors in HQEFT is shown to be much less than the one in the usual heavy quark effective theory (HQET). The values of wave functions at zero recoil are found to be consistent with the ones extracted from the interesting relations (which are resulted from the HQEFT) between the hadron masses and wave functions at zero recoil. The results for the decay constants are consistent with the ones from full QCD sum rule and Lattice calculations. The 1/mQcorrections to the scaling law [Formula: see text] are found to be small in HQEFT, which demonstrates again the validity of 1/mQexpansion in HQEFT. It is also shown that the residual momentum v·k of heavy quark within heavy–light hadrons is indeed around the binding energy [Formula: see text] of the heavy hadrons, which turns out to be in agreement with the expected one in the HQEFT. Therefore such a calculation provides a consistent check on the HQEFT and shows that the HQEFT is more reliable than the usual HQET for describing a slightly off-mass shell heavy quark within hadron as the usual HQET seems to lead to large 1/mQcorrections in evaluating the meson decay constants. It is emphasized that the introduction of the "dressed heavy quark" mass is useful for the heavy–light mesons (Qq) with [Formula: see text], while for heavy–heavy bound states (ψ1ψ2) with masses m1, [Formula: see text], like bottom-charm hadrons or similarly for muonium in QED, one needs to treat both particles as heavy effective particles via 1/m1and 1/m2expansions and redefine the effective bound states and modified "dressed heavy quark" masses within the HQEFT.
(2, 0)-SUPER-YANG–MILLS COUPLED TO NONLINEAR σ-MODELS
Authors: GÓES-NEGRÃO M. S. , NEGRÃO M. R. , PENNA-FIRME A. B.
Published: September 2004

Considering a class of (2, 0)-super-Yang–Mills multiplets that accommodate a pair of independent gauge potentials in connection with a single symmetry group, we present here their coupling to ordinary matter and to nonlinear σ-models in (2, 0)-superspace. The dynamics and the couplings of the gauge potentials are discussed and the interesting feature that comes out is a sort of "chirality" for one of the gauge potentials once light-cone coordinates are chosen.
HIDDEN SYMMETRIES OF THE OPEN N=2 STRING
Authors: IVANOVA TATIANA A. , LECHTENFELD OLAF
Published: September 2004

It is known for ten years that self-dual Yang–Mills theory is the effective field theory of the open N=2 string in (2+2)-dimensional space–time. We uncover an infinite set of Abelian rigid string symmetries, corresponding to the symmetries and integrable hierarchy of the self-dual Yang–Mills equations. The twistor description of the latter naturally connects with the BRST approach to string quantization, providing an interpretation of the picture phenomenon in terms of the moduli space of string backgrounds.
CASIMIR EFFECT IN BACKGROUND OF STATIC DOMAIN WALL
Authors: SETARE M. R. , SAHARIAN A.
Published: September 2004

In this paper we investigate the vacuum expectation values of energy–momentum tensor for conformally coupled scalar field in the standard parallel plate geometry with Dirichlet boundary conditions and in the background of planar domain wall case. First we calculate the vacuum expectation values of energy–momentum tensor by using the mode sums, then we show that corresponding properties can be obtained by using the conformal properties of the problem. The vacuum expectation values of energy–momentum tensor contain two terms which come from the boundary conditions and the the gravitational background. In the Minkowskian limit our results agree with those obtained in Ref. 3.
ON THE PERTURBATIVE EXPANSION OF BOUNDARY REFLECTION FACTORS OF THE SUPERSYMMETRIC SINH–GORDON MODEL
Authors: ABLIKIM M. , CORRIGAN E.
Published: September 2004

The supersymmetric sinh–Gordon model on a half-line with integrable boundary conditions is considered perturbatively to verify conjectured exact reflection factors to one loop order. Propagators for the boson and fermion fields restricted to a half-line contain several novel features and are developed as prerequisites for the calculations.
YANG–MILLS DUALITY AND THE GENERATION PUZZLE
Authors: CHAN HONG-MO
Published: September 2004

The fermion generation puzzle has survived into this century as one of the great mysteries in particle physics. We consider here a possible solution within the Standard Model framework based on a non-Abelian generalization of electric–magnetic duality. First, by constructing in loop space a non-Abelian generalization of the Abelian dual transform (Hodge *), one finds that a "magnetic" symmetry exists also in classical Yang–Mills theory dual to the original ("electric") gauge symmetry. Secondly, from a result of 't Hooft's, one obtains that for confined color SU(3), the dual symmetry [Formula: see text] is spontaneously broken and can play the role of the "horizontal symmetry" for generations. Thirdly, such an identification not only offers an explanation why there should be three and apparently only three generations of fermions with the remarkable mass and mixing patterns seen in experiment, but allows even a calculation of the relevant parameters giving very sensible results. Other testible predictions follow ranging from rare hadron decays to cosmic ray air showers.
GENERAL RELATIVITY AND QUANTUM MECHANICS
Authors: HARTLE J. B.
Published: September 2004

Usual quantum mechanics requires a fixed background spacetime geometry and its associated causal structure. A generalization of the usual theory may therefore be needed at the Planck scale for quantum theories of gravity in which spacetime geometry is a quantum variable. The elements of generalized quantum theory are briefly reviewed and illustrated by generalizations of usual quantum theory that incorporate spacetime alternatives, gauge degrees of freedom, and histories that move forward and backward in time. A generalized quantum framework for cosmological spacetime geometry is sketched. This theory is in fully four-dimensional form and free from the need for a fixed causal structure. Usual quantum mechanics is recovered as an approximation to this more general framework that is appropriate in those situations where spacetime geometry behaves classically.
NONLINEAR SIGMA MODEL APPROACH FOR PHASE DISORDER TRANSITIONS IN CHIRAL GROSS–NEVEU, NAMBU–JONA-LASINIO MODELS AND STRONG-COUPLING SUPERCONDUCTORS
Authors: BABAEV EGOR
Published: September 2004

We briefly review the nonlinear sigma model approach for the subject of increasing interest: "two-step" phase transitions in the Gross–Neveu and the modified Nambu–Jona-Lasinio models at low N and condensation from pseudogap phase in strong-coupling superconductors. Recent success in describing of "Bose-type" superconductors that possess two characteristic temperatures and a pseudogap above Tc is the development approximately comparable with the BCS theory. One can expect that it should have influence on high-energy physics, similar to impact of the BCS theory on this subject. Although first generalizations of this concept to particle physics were made recently, these results were not systematized. In this review we summarize this development and discuss similarities and differences of the appearance of the pseudogap phase in superconductors and the Gross–Neveu and Nambu–Jona-Lasinio-like models. We discuss its possible relevance for chiral phase transition in QCD and color superconductors. This paper is organized in three parts. In the first part, we briefly review the separation of temperatures of pair formation and pair condensation in strong-coupling and low carrier density superconductors (i.e. the formation of the pseudogap phase). The second part is a review of nonlinear sigma model approach to an analogous phenomenon in the chiral Gross–Neveu model at small N. In the third part we discuss the modified Nambu–Jona-Lasinio model where the chiral phase transition is accompanied by a formation of a phase analogous to the pseudogap phase.
SO(10)-INSPIRED SEESAW MECHANISM
Authors: ABUD MARIO , BUCCELLA FRANCO
Published: September 2004

We determine the νR Majorana mass matrix from the experimental data on neutrino oscillations in the framework of a see-saw SO(10) model, where we impose the condition (MR)33=0 to avoid too large fine-tunings in the see-saw formula. We find a class of solutions with the two lowest neutrino masses almost degenerate and the scale of the matrix elements of MR in the range 1011–1012 GeV in agreement with Pati–Salam intermediate symmetry. We find also solutions with smaller neutrino masses, for which the scale of MR depends on the solution to the "solar neutrino problem" and on the value of the component of νe along the highest mass eigenstate, Ue3.
A FORMULATION OF THE YANG–MILLS THEORY AS A DEFORMATION OF A TOPOLOGICAL FIELD THEORY BASED ON THE BACKGROUND FIELD METHOD AND QUARK CONFINEMENT PROBLEM
Authors: KONDO KEI-ICHI
Published: September 2004

By making use of the background field method, we derive a novel reformulation of the Yang–Mills theory which was proposed recently by the author to derive quark confinement in QCD. This reformulation identifies the Yang–Mills theory with a deformation of a topological quantum field theory. The relevant background is given by the topologically nontrivial field configuration, especially, the topological soliton which can be identified with the magnetic monopole current in four dimensions. We argue that the gauge fixing term becomes dynamical and that the gluon mass generation takes place by a spontaneous breakdown of the hidden supersymmetry caused by the dimensional reduction. We also propose a numerical simulation to confirm the validity of the scheme we have proposed. Finally we point out that the gauge fixing part may have a geometric meaning from the viewpoint of global topology where the magnetic monopole solution represents the critical point of a Morse function in the space of field configurations.
COMPILATION OF RELATIONS FOR THE ANTISYMMETRIC TENSORS DEFINED BY THE LIE ALGEBRA COCYCLES OF su(n)
Authors: DE AZCÁRRAGA J. A. , MACFARLANE A. J.
Published: September 2004

This paper attempts to provide a comprehensive compilation of results, many new here, involving the invariant totally antisymmetric tensors (Omega tensors) which define the Lie algebra cohomology cocycles of su (n), and that play an essential role in the optimal definition of Racah–Casimir operators of su (n). Since the Omega tensors occur naturally within the algebra of totally antisymmetrized products of λ-matrices of su (n), relations within this algebra are studied in detail, and then employed to provide a powerful means of deriving important Omega tensor/cocycle identities. The results include formulas for the squares of all the Omega tensors of su (n). Various key derivations are given to illustrate the methods employed.
ONE-PION EVENTS BY ATMOSPHERIC NEUTRINOS: A THREE-FLAVOR ANALYSIS
Authors: BALAJI K. R. S. , RAJASEKARAN G. , SANKAR S. UMA
Published: September 2004

We study the one-pion events produced via neutral current (NC) and charged current (CC) interactions by the atmospheric neutrinos. We analyze the ratios of CC events to the NC events in the framework of neutrino oscillations. These ratios can distinguish between different combinations of neutrino mixing angles in the case of three-flavor oscillations. They also provide a good diagnostic method to distinguish νμ→ντ oscillations from νμ→νs oscillations.
A STUDY OF TWO-/ONE-FORM SUPERFIELDS
Authors: PARK JEONG-HYUCK
Published: September 2004

We study two supersymmetric toy models of a k-form superfield, k=2,1 separately. By "solving" Jacobi identities, we show that each model is completely solvable, possesses a severely constrained kinematics, and gives a rigid representation of the supersymmetry algebra. This study of the toy models is motivated by our reanalysis on supersymmetry algebras in gauge theories where we discuss internal symmetry generators carrying space–time/spinor indices.
MORE ON GENERALIZED SIMPLICIAL CHIRAL MODELS
Authors: ALIMOHAMMADI M. , SAAIDI KH.
Published: September 2004

By generalizing the auxiliary field term in the Lagrangian of simplicial chiral models on a (d-1)-dimensional simplex, the generalized simplicial chiral models has been introduced in Ref. 1. These models can be solved analytically only in d=0 and d=2 cases at large-N limit. In the d=0 case, we calculate the eigenvalue density function in strong regime and show that the partition function computed from this density function is consistent with one calculated by path integration directly. In the d=2 case, it is shown that all V= Tr (AA†)n models have a third order phase transition, the same as the two-dimensional Yang–Mills theory.
ASPECTS OF ANOMALIES IN FIELD THEORY
Authors: FUJIKAWA KAZUO
Published: September 2004

We discuss some formal aspects of quantum anomalies with an emphasis on the regularization of field theory. We briefly review how ambiguities in perturbation theory have been resolved by various regularization schemes. To single out the true quantum anomaly among ambiguities, the combined ideas of PCAC, soft pion limit and renormalizability were essential. As for the formal treatment of quantum anomalies, we mainly discuss the path integral formulation both in continuum and lattice theories. In particular, we discuss in some detail the recent development in the treatment of chiral anomalies in lattice gauge theory.
LEFT–RIGHT ASYMMETRIES AND EXOTIC VECTOR–BOSON DISCOVERY IN LEPTON–LEPTON COLLIDERS
Authors: MONTERO J. C. , PLEITEZ V. , RODRIGUEZ M. C.
Published: September 2004

By considering left–right (L–R) asymmetries we study the capabilities of lepton colliders in searching for new exotic vector bosons. Specifically we study the effect of a doubly charged bilepton boson and an extra neutral vector boson appearing in a 3-3-1 model on the L–R asymmetries for the processes e-e-→e-e-, μ-μ-→ μ-μ- and e-μ-→e- μ- and show that these asymmetries are very sensitive to these new contributions and that they are in fact powerful tools for discovery of this sort of vector bosons.
EXTREME BLACK HOLE ENTROPY OBTAINED IN AN OPERATIONAL APPROACH
Authors: WANG BIN , SU RU-KENG , ABDALLA ELCIO
Published: September 2004

The entropy of anti-de Sitter Reissner–Nordström black hole is found to be stored in the material which gathers to form it and equals to A/4 regardless of material states. Extending the study to two kinds of extreme black holes, we find different entropy results for the first kind of extreme black hole due to different material states. However for the second kind of extreme black hole the results of entropy are uniform independently of the material states. Relations between these results and the stability of two kinds of extreme black holes have been addressed.
FUNDAMENTAL STRINGS AS NONCOMMUTATIVE SOLITONS
Authors: LARSEN FINN
Published: September 2004

The interpretation of closed fundamental strings as solitons in open string field theory is reviewed. Noncommutativity is introduced to facilitate an explicit construction. The tension is computed exactly and the correct spectrum is recovered at long wave length.
RS BRANEWORLDS IN TYPE IIB SUPERGRAVITY
Authors: STELLE K. S.
Published: September 2004

We show how the Randall-Sundrum geometry, which has been proposed as a scenario for the universe realized as a 3-brane embedded in a 5-dimensional spacetime, arises naturally as an S5 dimensional reduction of a supersymmetric 3-brane of type IIB supergravity. In this construction, the S5 scale-setting "breathing mode" plays a crucial rôle, permitting one to evade certain "no-go" claims for the possibility of such a supersymmetric realization.
SUPERSYMMETRY IN SINGULAR SPACES AND DOMAIN WALLS
Authors: KALLOSH RENATA
Published: September 2004

We discuss some recent work on brane world construction and supersymmetry issues. We introduce a concept of bulk & brane supersymmetry in the framework of 5-dimensional supergravity which allows to formulate the rules for supersymmetry in singular spaces. The original fine-tuning of the Randall-Sundrum world brane which provides the flatness of the brane is shown to follow from bulk & brane supersymmetry on [Formula: see text] orbifold. Examples of RS-type domain walls are presented.
${\mathcal N} =2$ GAUGE-GRAVITY DUALS
Authors: POLCHINSKI JOSEPH
Published: September 2004

We study the [Formula: see text] analog of the Klebanov-Strassler system. We first review the resolution of singularities by the enhançon mechanism, and the physics of fractional branes on an orbifold. We then describe the exact [Formula: see text] solution. This exhibits a duality cascade as in the [Formula: see text] case, but the singularity resolution is the characteristic [Formula: see text] enhançon. We discuss some related solutions and open issues.
COMPLEX GRAVITY AND NONCOMMUTATIVE GEOMETRY
Authors: CHAMSEDDINE ALI H.
Published: September 2004

The presence of a constant background antisymmetric tensor for open strings or D-branes forces the space-time coordinates to be noncommutative. An immediate consequence of this is that all fields get complexified. By applying this idea to gravity one discovers that the metric becomes complex. Complex gravity is constructed by gauging the symmetry U(1, D-1). The resulting action gives one specific form of nonsymmetric gravity. In contrast to other theories of nonsymmetric gravity the action is both unique and gauge invariant. It is argued that for this theory to be consistent one must prove the existence of generalized diffeomorphism invariance. The results are easily generalized to noncommutative spaces.
COVARIANT QUANTIZATION OF THE SUPERSTRING
Authors: BERKOVITS NATHAN
Published: September 2004

After reviewing the Green-Schwarz superstring using the approach of Siegel, the superstring is covariantly quantized by constructing a BRST operator from the fermionic constraints and a bosonic pure spinor ghost variable. Physical massless vertex operators are constructed and, for the first time, N-point tree amplitudes are computed in a manifestly ten-dimensional super-Poincaré covariant manner. Quantization can be generalized to curved supergravity backgrounds and the vertex operator for fluctuations around AdS5×S5 is explicitly constructed.
SUPERGRAVITY DESCRIPTION OF FIELD THEORIES ON CURVED MANIFOLDS AND A NO GO THEOREM
Authors: MALDACENA JUAN , NUÑEZ CARLOS
Published: September 2004

In the first part of this paper we find supergravity solutions corresponding to branes on worldvolumes of the form Rd×Σ where Σ is a Riemann surface. These theories arise when we wrap branes on holomorphic Riemann surfaces inside K3 or CY manifolds. In some cases the theory at low energies is a conformal field theory with two less dimensions. We find some non-singular supersymmetric compactifications of M-theory down to AdS5. We also propose a criterion for permissible singularities in supergravity solutions.

In the second part of this paper, which can be read independently of the first, we show that there are no non-singular Randall-Sundrum or de-Sitter compactifications for large class of gravity theories.
BLACK HOLE THERMODYNAMICS FROM CALCULATIONS IN STRONGLY COUPLED GAUGE THEORY
Authors: KABAT DANIEL , LIFSCHYTZ GILAD , LOWE DAVID
Published: September 2004

We develop an approximation scheme for the quantum mechanics of N D0-branes at finite temperature in the 't Hooft large-N limit. The entropy of the quantum mechanics calculated using this approximation agrees well with the Bekenstein-Hawking entropy of a ten-dimensional non-extremal black hole with 0-brane charge. This result is in accord with the duality conjectured by Itzhaki, Maldacena, Sonnenschein and Yankielowicz. Our approximation scheme provides a model for the density matrix which describes a black hole in the strongly-coupled quantum mechanics.
LIGHT CONE SUPERSTRINGS IN ADS SPACE
Authors: TSEYTLIN A. A.
Published: September 2004

We discuss light-cone gauge description of type IIB Green-Schwarz superstring in AdS5× S5 with a hope to make progress towards understanding spectrum of this theory. As in flat space, fixing light-cone gauge consists of two steps: (i) fixing kappa symmetry in such a way that the fermionic part of the action does not depend on x-; (ii) fixing 2-d reparametrizations by x+=τ and a condition on 2-d metric. In curved AdS space the latter cannot be the standard conformal gauge and breaks manifest 2-d Lorentz invariance. It is natural, therefore, to work in phase-space framework, imposing the GGRT light-cone gauge conditions x+=τ, P+= const. We obtain the resulting light-cone superstring Hamiltonian.
M-THEORY DUALITY AND BPS-EXTENDED SUPERGRAVITY
Authors: DE WIT BERNARD
Published: September 2004

We discuss toroidal compactifications of maximal supergravity coupled to an extended configuration of BPS states which transform consistently under the U-duality group. Under certain conditions this leads to theories that live in more than eleven space-time dimensions, with maximal supersymmetry but only partial Lorentz invariance. We demonstrate certain features of this construction for the case of nine-dimensional N=2 supergravity.
MEANING-CENTRIC FRAMEWORK FOR NATURAL TEXT/SCENE UNDERSTANDING BY ROBOTS
Authors: XIE M. , KANDHASAMY J. S. , CHIA H. F.
Published: September 2004

In the past fifty years, efforts in classical AI have focussed on computerizing human intelligence. Naturally, computerized human intelligence is not a proof of machine or robot intelligence because the programs underlying computerized human intelligence are still made by humans. So far, there is no computer nor robot which is creative enough to master its own language and to compose a text expressing its intentions. Thus, it is time to shift our research focus from computerizing human intelligence to developing machine intelligence. A first and necessary step towards this goal is to make machines or robots learn, manipulate, understand and create both elementary and composite meanings encoded in a natural language such as English. Elementary and composite meanings could be acquired through both sample texts and images. Hence, we propose a learning-synthesis-analysis framework which aims to enable a robot, or computer, to understand and convey meaning through texts or images. The main contribution of this paper is to lay out a sound foundation on which interdisciplinary research could effectively progress toward the development of machines or robots that understand meaning through texts or images.
DEVELOPMENTAL ROBOTICS: THEORY AND EXPERIMENTS
Authors: WENG JUYANG
Published: September 2004

A hand-designed internal representation of the world cannot deal with unknown or uncontrolled environments. Motivated by human cognitive and behavioral development, this paper presents a theory, an architecture, and some experimental results for developmental robotics. By a developmental robot, we mean that the robot generates its "brain" (or "central nervous system," including the information processor and controller) through online, real-time interactions with its environment (including humans). A new Self-Aware Self-Effecting (SASE) agent concept is proposed, based on our SAIL and Dav developmental robots. The manual and autonomous development paradigms are formulated along with a theory of representation suited for autonomous development. Unlike traditional robot learning, the tasks that a developmental robot ends up learning are unknown during the programming time so that the task-specific representation must be generated and updated through real-time "living" experiences. Experimental results with SAIL and Dav developmental robots are presented, including visual attention selection, autonomous navigation, developmental speech learning, range-based obstacle avoidance, and scaffolding through transfer and chaining.
TUTELAGE AND COLLABORATION FOR HUMANOID ROBOTS
Authors: BREAZEAL CYNTHIA , BROOKS ANDREW , GRAY JESSE , HOFFMAN GUY , KIDD CORY , LEE HANS , LIEBERMAN JEFF , LOCKERD ANDREA , CHILONGO DAVID
Published: September 2004

This paper presents an overview of our work towards building socially intelligent, cooperative humanoid robots that can work and learn in partnership with people. People understand each other in social terms, allowing them to engage others in a variety of complex social interactions including communication, social learning, and cooperation. We present our theoretical framework that is a novel combination of Joint Intention Theory and Situated Learning Theory and demonstrate how this framework can be applied to develop our sociable humanoid robot, Leonardo. We demonstrate the robot's ability to learn quickly and effectively from natural human instruction using gesture and dialog, and then cooperate to perform a learned task jointly with a person. Such issues must be addressed to enable many new and exciting applications for robots that require them to play a long-term role in people's daily lives.
MULTI-SENSORY SYNERGIES IN HUMANOID ROBOTICS
Authors: RUSSELL R. ANDREW , TAYLOR GEOFFREY , KLEEMAN LINDSAY , PURNAMADJAJA ANIES H.
Published: September 2004

Sensing is a key element for any intelligent robotic system. This paper describes the current progress of a project in the Intelligent Robotics Research Center at Monash University that has the aim of developing a synergistic set of sensory systems for a humanoid robot. Currently, sensing modes for colour vision, stereo vision, active range, smell and airflow are being developed in a size and form that is compatible with the humanoid appearance. Essential considerations are sensor calibration and the processing of sensor data to give reliable information about properties of the robot's environment. In order to demonstrate the synergistic use of all of the available sensory modes, a high level supervisory control scheme is being developed for the robot. All time-stamped sensor data together with derived information about the robot's environment are organized in a blackboard system. Control action sequences are then derived from the blackboard data based on a task description. The paper presents details of each of the robot's sensory systems, sensor calibration, and supervisory control. Results are also presented of a demonstration project that involves identifying and selecting mugs containing household chemicals. Proposals for future development of the humanoid robot are also presented.
An osteoclastic protein-tyrosine phosphatase may play a role in differentiation and activity of human monocytic U-937 cell-derived, osteoclast-like cells
Authors: Amoui Mehran , Suhr Sung-Min , Baylink David J. , Lau K.-H. William
Published: September 2004

This study investigated if an osteoclastic protein-tyrosine phosphatase (PTP), PTP-oc, plays a role in the functional activity and differentiation of osteoclastic cells by determining the effects of overexpression of wild-type (WT)- or phosphatase-deficient (PD)-PTP-oc on bone resorption activity and differentiation of human promyelomonocytic U-937 cells, which could be induced to differentiate into “osteoclast-like” cells by phorbol ester/1,25(OH)2D3 treatment. U-937 cells overexpressing WT- or PD-PTP-oc were produced with a transposon-based vector. The size and depth of resorption pits created by WT-PTP-oc-overexpressing osteoclast-like cells were greater, while those by PD-PTP-oc-overexpressing osteoclast-like cells were less, than those created by control osteoclast-like cells. Overexpression of WT-PTP-oc also enhanced, while overexpression of PD-PTP-oc suppressed, their differentiation into osteoclast-like cells. Overexpression of WT-PTP-oc increased apoptosis and proliferation of U-937 cells, and overexpression of PD-PTP-oc reduced cell proliferation. Cells overexpressing WT-PTP-oc has also led to greater c-Src and NF-κβ activation, whereas cells overexpressing PD-PTP-oc resulted in less c-Src and NF-κβ activation. c-Src activation and NF-κβ activation each correlated with resorption activity and differentiation into osteoclast-like cells. In summary, these results show that 1) PTP-oc regulates both the activity and the differentiation of osteoclast-like cells derived from U-937 cells; 2) PTP-oc enzymatic activity is important to these processes; 3) high PTP-oc enzymatic activity caused an increase in U-937 cell apoptosis and proliferation, leading to no significant changes in the number of viable cells; and 4) some of the PTP-oc actions are mediated in part by the c-Src and/or NF-κβ pathways.
The molecular basis of skeletal muscle atrophy
Authors: Jackman Robert W. , Kandarian Susan C.
Published: September 2004

Skeletal muscle atrophy attributable to muscular inactivity has significant adverse functional consequences. While the initiating physiological event leading to atrophy seems to be the loss of muscle tension and a good deal of the physiology of muscle atrophy has been characterized, little is known about the triggers or the molecular signaling events underlying this process. Decreases in protein synthesis and increases in protein degradation both have been shown to contribute to muscle protein loss due to disuse, and recent work has delineated elements of both synthetic and proteolytic processes underlying muscle atrophy. It is also becoming evident that interactions among known proteolytic pathways (ubiquitin-proteasome, lysosomal, and calpain) are involved in muscle proteolysis during atrophy. Factors such as TNF-α, glucocorticoids, myostatin, and reactive oxygen species can induce muscle protein loss under specified conditions. Also, it is now apparent that the transcription factor NF-κB is a key intracellular signal transducer in disuse atrophy. Transcriptional profiles of atrophying muscle show both up- and downregulation of various genes over time, thus providing further evidence that there are multiple concurrent processes involved in muscle atrophy. The purpose of this review is to synthesize our current understanding of the molecular regulation of muscle atrophy. We also discuss how ongoing work should uncover more about the molecular underpinnings of muscle wasting, particularly that due to disuse.
Early changes in insulin secretion and action induced by high-fat diet are related to a decreased sympathetic tone
Authors: Cruciani-Guglielmacci C. , Vincent-Lamon M. , Rouch C. , Orosco M. , Ktorza A. , Magnan C.
Published: September 2004

To evaluate the relationship between the development of obesity, nervous system activity, and insulin secretion and action, we tested the effect of a 2-mo high-fat diet in rats (HF rats) on glucose tolerance, glucose-induced insulin secretion (GIIS), and glucose turnover rate compared with chow-fed rats (C rats). Moreover, we measured pancreatic and hepatic norepinephrine (NE) turnover, as assessment of sympathetic tone, and performed hypothalamic microdialysis to quantify extracellular NE turnover. Baseline plasma triglyceride, free fatty acid, insulin, and glucose concentrations were similar in both groups. After 2 days of diet, GIIS was elevated more in HF than in C rats, whereas plasma glucose time course was similar. There was a significant increase in basal pancreatic NE level of HF rats, and a twofold decrease in the fractional turnover constant was observed, indicating a change in sympathetic tone. In ventromedian hypothalamus of HF rats, the decrease in NE extracellular concentration after a glucose challenge was lower compared with C rats, suggesting changes in overall activity. After 7 days, insulin hypersecretion persisted, and glucose intolerance appeared. Later (2 mo), there was no longer insulin hypersecretion, whereas glucose intolerance worsened. At all times, HF rats also displayed hepatic insulin resistance. On day 2 of HF diet, GIIS returned to normal after treatment with oxymetazoline, an α2A-adrenoreceptor agonist, thus suggesting the involvement of a low sympathetic tone in insulin hypersecretion in response to glucose in HF rats. In conclusion, the HF diet rapidly results in an increased GIIS, at least in part related to a decreased sympathetic tone, which can be the first step of a cascade of events leading to impaired glucose homeostasis.
Effects of glucagon-like peptide-1 on endothelial function in type 2 diabetes patients with stable coronary artery disease
Authors: Nyström Thomas , Gutniak Mark K. , Zhang Qimin , Zhang Fan , Holst Jens Juul , Ahrén Bo , Sjöholm Åke
Published: September 2004

GLP-1 stimulates insulin secretion, suppresses glucagon secretion, delays gastric emptying, and inhibits small bowel motility, all actions contributing to the anti-diabetogenic peptide effect. Endothelial dysfunction is strongly associated with insulin resistance and type 2 diabetes mellitus and may cause the angiopathy typifying this debilitating disease. Therefore, interventions affecting both endothelial dysfunction and insulin resistance may prove useful in improving survival in type 2 diabetes patients. We investigated GLP-1's effect on endothelial function and insulin sensitivity (SI) in two groups: 1) 12 type 2 diabetes patients with stable coronary artery disease and 2) 10 healthy subjects with normal endothelial function and SI. Subjects underwent infusion of recombinant GLP-1 or saline in a random crossover study. Endothelial function was measured by postischemic FMD of brachial artery, using ultrasonography. SI [in (10−4 dl·kg−1·min−1)/(μU/ml)] was measured by hyperinsulinemic isoglycemic clamp technique. In type 2 diabetic subjects, GLP-1 infusion significantly increased relative changes in brachial artery diameter from baseline FMD(%) (3.1 ± 0.6 vs. 6.6 ± 1.0%, P < 0.05), with no significant effects on SI (4.5 ± 0.8 vs. 5.2 ± 0.9, P = NS). In healthy subjects, GLP-1 infusion affected neither FMD(%) (11.9 ± 0.9 vs. 10.3 ± 1.0%, P = NS) nor SI (14.8 ± 1.8 vs. 11.6 ± 2.0, P = NS). We conclude that GLP-1 improves endothelial dysfunction but not insulin resistance in type 2 diabetic patients with coronary heart disease. This beneficial vascular effect of GLP-1 adds yet another salutary property of the peptide useful in diabetes treatment.
Mest/Peg1 imprinted gene enlarges adipocytes and is a marker of adipocyte size
Authors: Takahashi Mayumi , Kamei Yasutomi , Ezaki Osamu
Published: September 2004

Obesity is a common and serious metabolic disorder in the developed world that is occasionally accompanied by type II diabetes, atherosclerosis, hypertension, and hyperlipidemia. We have found that mesoderm-specific transcript (Mest)/paternally expressed gene 1 (Peg1) gene expression was markedly enhanced in white adipose tissue of mice with diet-induced and genetically caused obesity/diabetes but not with streptozotocin-induced diabetes, which does not cause obesity. Administration of pioglitazone, a drug for type II diabetes and activator of peroxisome proliferator-activated receptor (PPAR)γ, in obese db/ db mice reduced the enhanced expression of Mest mRNA in adipose tissue, concomitant with an increase in body weight and a decrease in the size of adipose cells. Ectopic expression of Mest in 3T3-L1 cells caused increased gene expression of adipose markers such as PPARγ, CCAAT/enhancer binding protein (C/EBP)α, and adipocyte fatty acid binding protein (aP)2. In transgenic mice overexpressing Mest in adipose tissue, enhanced expression of the adipose genes was observed. Moreover, adipocytes were markedly enlarged in the transgenic mice. Thus Mest appears to enlarge adipocytes and could be a novel marker of the size of adipocytes.
Smooth muscle F-actin disassembly and RhoA/Rho-kinase signaling during endotoxin-induced alterations in pulmonary arterial compliance
Authors: Boer Christa , van Nieuw Amerongen Geerten P. , Groeneveld A. B. Johan , Scheffer Gert Jan , de Lange Jaap J. , Westerhof Nico , van Hinsbergh Victor W. M. , Sipkema Pieter
Published: September 2004

Endotoxemia is associated with changed pulmonary vascular function with respect to vasoreactivity, endothelial permeability, and activation of inducible nitric oxide synthase II (NOSII). However, whether altered passive arterial wall mechanics contribute to this endotoxin-induced pulmonary vascular dysfunction is still unknown. Therefore, we investigated whether endotoxin affects the passive arterial mechanics and compliance of isolated rat pulmonary arteries. Pulmonary arteries of pentobarbital-anesthetized Wistar rats ( n = 55) were isolated and exposed to Escherichia coli endotoxin (50 μg/ml) for 20 h. Endotoxin increased pulmonary artery diameter and compliance (transmural pressure = 13 mmHg) in an endothelium-, Ca2+-, or NOSII-induced NO release-independent manner. Interestingly, the endotoxin-induced alterations in the passive arterial mechanics were accompanied by disassembly of the smooth muscle cell (SMC) F-actin cytoskeleton. Disassembly of F-actin by incubation of control arteries with the cytoskeleton-disrupting agent cytochalasin B or the Rho-kinase inhibitor Y-27632 induced a similar increase in passive arterial diameter and compliance. In contrast, RhoA activation by lysophosphatidic acid prevented the endotoxin-induced alterations in the pulmonary SMC F-actin cytoskeleton and passive mechanics. In conclusion, these findings indicate that disassembly of the SMC F-actin cytoskeleton and RhoA/Rho-kinase signaling act as mediators of endotoxin-induced changes in the pulmonary arterial mechanics. They imply the involvement of F-actin rearrangement and RhoA/Rho-kinase signaling in endotoxemia-induced vascular lung injury.
Minocycline reduces renal microvascular leakage in a rat model of ischemic renal injury
Authors: Sutton Timothy A. , Kelly K. J. , Mang Henry E. , Plotkin Zoya , Sandoval Ruben M. , Dagher Pierre C.
Published: September 2004

Tetracyclines exhibit significant anti-inflammatory properties, inhibit matrix metalloproteinases (MMPs), and are protective in models of ischemia-reperfusion injury (IRI). Both inflammatory cascades and MMP activation have been demonstrated to modulate microvascular permeability. Because increased microvascular permeability occurs during IRI in a variety of organ systems including the kidney, we hypothesized that minocycline, a semisynthetic tetracycline, would diminish microvascular leakage during renal IRI. To test this hypothesis, we used intravital 2-photon microscopy to examine leakage of fluorescent dextrans from the vasculature in a rodent model of IRI. Minocycline significantly reduced the extent of dextran (500 kDa) leakage from the renal microvasculature 24 h after ischemia. Although minocycline diminished leukocyte accumulation in the kidney following ischemia, areas of leukocyte accumulation did not correlate with areas of microvascular permeability in either the saline- or minocycline-pretreated animals. Minocycline diminished the perivascular increase in MMP-2 and MMP-9, as well as the increase in MMP-2 activity 24 h after ischemia. ABT-518, a specific inhibitor of MMP-2 and MMP-9, also significantly reduced the extent of dextran (500 kDa) leakage from the renal microvasculature 24 h after ischemia. Our results indicate that minocycline mitigates the renal microvascular permeability defect following IRI. This effect is spatially distinct from the effect of minocycline on leukocyte accumulation and may be related to diminished activity of MMPs on the integrity of the perivascular matrix.
A high-salt diet stimulates thick ascending limb eNOS expression by raising medullary osmolality and increasing release of endothelin-1
Authors: Herrera Marcela , Garvin Jeffrey L.
Published: September 2004

A high-salt diet increases renal endothelin (ET) production and thick ascending limb (THAL) endothelial nitric oxide synthase (eNOS) expression. ET stimulates THAL eNOS expression via ETBreceptors. The tonicity of the renal medulla is highly variable, and hyperosmolality stimulates ET-1 synthesis by endothelial cells. We hypothesized that a high-salt diet raises medullary osmolality, increases ET release by the THAL, and thus enhances eNOS expression. Seven days of high salt (1% NaCl in drinking water) increased eNOS expression in THALs by 125 ± 31%. High salt increased outer medullary osmolality from 362 ± 13 to 423 ± 6 mosmol/kgH2O ( P < 0.05). Bosentan, a dual-ET receptor antagonist, blocked the increase in THAL eNOS expression caused by high salt (2.66 ± 0.44 absorbance units with bosentan vs. 5.15 ± 0.67 for vehicle; P < 0.05). Conscious systolic blood pressure did not differ between the two groups. In primary cultures of medullary THALs, raising osmolality from 300 to 350 and 400 mosmol/kgH2O using NaCl increased eNOS expression by 39 ± 11% ( P < 0.05) and 71 ± 16%, respectively ( P < 0.05). In primary cultures of THALs, raising osmolality from 300 to 400 mosmol/kgH2O for 1 h increased ET-1 release from 62 ± 7 to 113 ± 2 pg/mg protein ( P < 0.05). BQ-788, an ETBreceptor antagonist (1 μM), blocked the stimulatory effect of 400 mosmol/kgH2O on eNOS expression (70 ± 13% vs. −5 ± 10%; paired difference, 74 ± 15%; P < 0.05). BQ-788 alone had no significant effect. We concluded that high salt stimulates THAL eNOS expression by increasing outer medullary osmolality, ET-1 release by the THAL and ETBreceptor activation. This may be an important regulatory mechanism of THAL NaCl absorption when dietary salt intake is increased.