bluuebunny/crossref_metadata_2025 huggingface dataset:
Ectomycorrhizal community effects on hybrid spruce seedling growth and nutrition in clearcuts
Authors: Kranabetter J M
Published: August 2004

A diverse community of ectomycorrhizal (ECM) fungi is generally considered beneficial to forest ecosystems, but the function of ECM communities should be considered within an ecological context. The growth of hybrid spruce (Picea glauca (Moench) Voss × Picea sitchensis (Bong.) Carrière) seedlings was compared after transplanting into recent clearcuts, where soil moisture and nitrogen are typically readily available. The seedlings had either a "forest" ECM community (taken from forest gap edges) or a "pioneer" ECM community (taken from disturbed road edges) and were planted at wide and close spacing. After 3 years, morphotype distribution and abundance (64% community similarity between "forest" and "pioneer" seedlings) overlapped considerably, but height growth was 25% greater for the "pioneer" seedlings. There was a reduction in diameter at close spacing, with little difference in competition effects between ECM communities. There were no differences detected in foliar nitrogen concentrations and no evidence of nitrogen or phosphorus deficiencies. The advantage of fungi such as Amphinema byssoides, Thelephora terrestris, and Laccaria laccata might be the proliferation of fine roots that allows for the fullest utilization of abundant soil resources. The results suggest that the ECM communities arising after clearcut disturbances are well adapted to these initial soil conditions.Key words: ectomycorrhiza, disturbance, diversity, productivity, competition, Picea glauca.
Seed-bank characteristics in mixed-mesophytic forest clearcuts and edges: Does "edge effect" extend to the seed bank?
Authors: Landenberger Rick E , McGraw James B
Published: August 2004

Little is known about the seed banks of mixed-mesophytic forest clearcuts or their associated forest edges. Seed banks were described and compared to better understand how seed density, species richness, and composition change with increasing distance from clearcuts. Thirty-two taxa were found in the seed bank of clearcuts, and 44 were found in adjacent forest edges. Annuals represented 41% of seeds in clearcuts, but only 8% in edges, while trees and shrubs represented 3% in both areas. Seed-bank density and species richness varied significantly within and between clearcuts, but clearcuts were no different in seed-bank density and richness from interior forest seed banks. Seed-bank density declined significantly with distance from clearcuts on west-facing forest edges, but demonstrated no discernable spatial pattern on south-facing edges. Overall, edge effects from clearcutting on adjacent forest seed banks were demonstrated in total seed density and in several common wind-dispersed, early-successional herbaceous species, including Erechtites hieraciifolia (L.) Raf. and Lobelia inflata L., and Vitis, a common ingestion-dispersed species. The seed-shadow edge effect may influence both current and future community characteristics and population dynamics of vegetation in mixed-mesophytic forest edges adjacent to clearcuts.Key words: seed banks, clearcutting, edge effects, mixed-mesophytic forest, West Virginia.
SINGLE EVENT EFFECTS IN AVIONICS AND ON THE GROUND
Authors: NORMAND EUGENE
Published: August 2004

Single event effects in electronics caused by the atmospheric neutrons have been an issue for systems using large blocks of random access memory (RAM) in avionics applications as well as those on the ground. At ground level there are two main sources of single event effects, alpha particles from the packaging materials as well as the neutrons, but at aircraft altitudes, where the neutron flux is about 300 times higher than the ground, the alpha particles make a negligible contribution. We review the trends over the last 5-10 years in the response of COTS computer systems to single event effects, taking into the response of devices as well as fault tolerant measures incorporated into the systems.
SYSTEM LEVEL SINGLE EVENT UPSET MITIGATION STRATEGIES
Authors: HEIDERGOTT W. F.
Published: August 2004

Use of a systems engineering process and the application of techniques and methods of fault tolerant systems are applicable to the development of a mitigation strategy for Single Event Upsets (SEU). Specific methods of fault avoidance, fault masking, detection, containment, and recovery techniques are important elements in the mitigation of single event upsets. Fault avoidance through the use of SEU hardened technology, fault masking using coding and redundancy provisions, and solutions applied at the subsystem and system level are available to the system developer. Validation and verification of SEU mitigation and performance of fault tolerance provisions are essential elements of systems design for operation in energetic particle environments.
TOTAL-DOSE AND SINGLE-EVENT EFFECTS IN SILICON-GERMANIUM HETEROJUNCTION BIPOLAR TRANSISTORS
Authors: CRESSLER JOHN D.
Published: August 2004

We present an overview of radiation effects in silicon-germanium heterojunction bipolar transistors ( SiGe HBT). We begin by reviewing SiGe HBTs, and then examine the impact of ionizing radiation on both the dc and ac performance of SiGe HBTs, the circuit-level impact of radiation-induced changes in the transistors, followed by single-event phenomena in SiGe HBT circuits. While ionizing radiation degrades both the dc and ac properties of SiGe HBTs, this degradation is remarkably minor, and is far better than that observed in even radiation-hardened conventional Si BJT technologies. This fact is particularly significant given that no intentional radiation hardening is needed to ensure this level of both device-level and circuit-level tolerance (typically multi-Mrad TID). SEU effects are pronounced in SiGe HBT circuits, as expected, but circuit-level mitigation schemes will likely be suitable to ensure adequate tolerance for many orbital missions. SiGe HBT technology thus offers many interesting possibilities for space-borne electronic systems.
RIGID AND GAUGE NOETHER SYMMETRIES FOR CONSTRAINED SYSTEMS
Authors: GARCÍA J. ANTONIO , PONS J. M.
Published: August 2004

We develop the general theory of Noether symmetries for constrained systems, that is, systems that are described by singular Lagrangians. In our derivation, the Dirac bracket structure with respect to the primary constraints appears naturally and plays an important role in the characterization of the conserved quantities associated to these Noether symmetries. The issue of projectability of these symmetries from tangent space to phase space is fully analyzed, and we give a geometrical interpretation of the projectability conditions in terms of a relation between the Noether conserved quantity in tangent space and the presymplectic form defined on it. We also examine the enlarged formalism that results from taking the Lagrange multipliers as new dynamical variables; we find the equation that characterizes the Noether symmetries in this formalism, and we also prove that the standard formulation is a particular case of the enlarged one. The algebra of generators for Noether symmetries is discussed in both the Hamiltonian and Lagrangian formalisms. We find that a frequent source for the appearance of open algebras is the fact that the transformations of momenta in phase space and tangent space only coincide on shell. Our results apply with no distinction to rigid and gauge symmetries; for the latter case we give a general proof of the existence of Noether gauge symmetries for theories with first and second class constraints that do not exhibit tertiary constraints in the stabilization algorithm. Among some examples that illustrate our results, we study the Noether gauge symmetries of the Abelian Chern–Simons theory in 2n+1 dimensions. An interesting feature of this example is that its primary first class constraints can only be identified after the determination of the secondary constraint. The example is worked out retaining all the original set of variables.
S-MATRICES FOR QUANTUM CHARGED MASSLESS SCALAR PARTICLES ON KERR BLACK HOLES
Authors: FIRSOVA N. E.
Published: August 2004

The scattering problems that arise when considering the contribution of the topologically inequivalent configurations (TIC's) of the massless complex scalar field on Kerr black holes to the Hawking radiation are studied. The corresponding S-matrices are examined and presented in the form convenient for numerical computations.
A STATISTICAL MECHANICAL STUDY OF THERMODYNAMIC PROPERTIES OF SOLID SODIUM UNDER PRESSURE BASED ON AN EFFECTIVE INTERIONIC POTENTIAL
Authors: ZUBOV V. I. , CAPARICA A. A.
Published: August 2004

Basing on the Schiff effective interionic potential that has an oscillatory character and the correlative method of unsymmetrized self-consistent field (CUSF) that enables one to take into account the strong anharmonicity of the crystal lattice vibrations, we have calculated a complete set of equilibrium thermodynamic properties of solid sodium as functions of pressure and temperature: the lattice parameter, the elastic moduli, the thermal expansion coefficient, the Grüneisen parameter and the isochoric and isobaric heat capacities. Our results are compared with available experimental data. We also discuss the thermodynamic stability of the BCC lattice, the mechanism of its loss and its change under pressure.
EXPERIMENTAL VERIFICATION OF HEAVY ION IRRADIATION SIMULATION
Authors: ZHU SHENGYUN , IWATA T. , XU YONGJUN , ZHENG YONGNAN , ZHOU DONGMEI , ZHU JIAZHENG , WANG ZHIQQIANG , YUAN DAQING , DU ENPENG , ZUO YI
Published: August 2004

The heavy ion irradiation simulation of neutron and/or proton irradiation has been verified experimentally by the detailed study of radiation damage in α- Al 2 O 3 irradiated at the equivalent dose by 5.28×1015 cm -285 MeV 19 F ions and by 3×1020 cm -2 En≥1 MeV neutrons, respectively. The radiation damage created by irradiation was examined by a positron annihilation lifetime technique. The positron annihilation parameters of lifetime and intensity obtained for both irradiations in α- Al 2 O 3 are all in good agreement. This demonstrates that the heavy ion irradiation can well simulate the neutron and/or proton irradiation.
ELECTRONIC TRANSPORT AND THERMOPOWER IN APERIODIC DNA SEQUENCES
Authors: ROCHE STEPHAN , MACIÁ ENRIQUE
Published: August 2004

A detailed study of charge transport properties of synthetic and genomic DNA sequences is reported. Genomic sequences of the Chromosome 22, λ-bacteriophage, and D1s80 genes of Human and Pygmy chimpanzee are considered in this work, and compared with both periodic and quasiperiodic (Fibonacci) sequences of nucleotides. Charge transfer efficiency is compared for all these different sequences, and large variations in charge transfer efficiency, stemming from sequence-dependent effects, are reported. In addition, basic characteristics of tunneling currents, including contact effects, are described. Finally, the thermoelectric power of nucleobases connected in between metallic contacts at different temperatures is presented.
COMPLEXITY OF SEMIGROUP IDENTITY CHECKING
Authors: KISIELEWICZ ANDRZEJ
Published: August 2004

We consider the [Formula: see text] problem, whose instance is a finite semigroup S and an identity I, and the question is whether I is satisfied in S. We show that the question concerning computational complexity of this problem is much harder, when restricted to commutative semigroups. We provide a relatively simple proof that in general the problem is co-NP-complete, and demonstrate, using some structure theory, that for a fixed commutative semigroup the problem can be solved in polynomial time. The complexity status of the general [Formula: see text] problem remains open.
THE INFORMATION MODELING OF THE ENCODING-DECODING PROCESSES AT TRANSFORMATION OF BIOLOGICAL INFORMATION
Authors: LERNER VLADIMIR S.
Published: August 2004

Using the Informational Macrodynamics (IMD), the paper focuses on information modeling DNA structure and code, encoding-decoding mechanisms for the transformation and synthesis of information, and the telomerase information functions that these mechanisms generate. As an alternative to experimental DNA discovery, the considered double spiral information structure (DSS) and its coding language implement the IMD analytical model. The transferred pieces of the DSS' information code are synthesized into meaningful units, integrated by an information network. The analysis of the cognitive information processing shows that the information synthesis mechanism includes the preliminary encoding-decoding procedure whose code embodies the total time required for the translation of information as well as characterizing its life-time duration. The paper emphasizes on the systemic nature of these biological mechanisms.
REVIEW OF HIV MODELS: THE ROLE OF THE NATURAL IMMUNE RESPONSE AND IMPLICATIONS FOR TREATMENT
Authors: CULSHAW REBECCA V.
Published: August 2004

We present a review and comparison of several recent differential equations models of treatment of HIV-1 infection. We seek to clarify the role of the natural anti-HIV immune response and determine its effect upon optimal treatment schemes. In this paper, we consider systems in which treatment is expressed as a forcing function, as well as those in which we determine optimal treatment via control theoretic techniques. The primary goal of this study is to compare treatment schemes for systems in which a natural nonconstant immune response of the patient is considered explicitly with those that consider implicitly a constant non-specific immune response. We find that when the natural immune response can be boosted sufficiently, drug levels may not need to be as high as previously supposed. This implies that a treatment scenario in which intervals of drug treatment are alternated with some form of immune-boosting therapy may be highly beneficial in terms of reducing toxicity to the patient. Additionally, in developing countries where HIV infection is widespread and sufficient funds are not available to supply rigourous drug regimens, the implications of these models are profound, as they suggest methods of treating HIV at a minimal cost.
PRELIMINARY HYDRAULIC PERFORMANCE CHARACTERIZATION OF AN AXIAL BLOOD PUMP
Authors: CHAN W. K. , WONG Y. W. , LUM M. F. , CHONG V. , KOH S. Y.
Published: August 2004

This paper presents preliminary results of hydraulic performance characterization of an axial blood pump. Two sets of inducer-impellers and 3 diffusers were designed and tested in a closed loop flow circuit. The results showed that the impellers tested can deliver 5 L/min at a head of 100 mmHg when operating at a rotational speed of 10,000 rpm. Based on the preliminary experiments, the double start inducer-impeller with the 100° wrap angle diffuser offers the greatest promise. However, regions of flow reversals and stagnation were noted from CFD simulations of the pump. The blade profile as well as the diffuser design has to be modified in further work to eliminate regions of flow reversals.
THE FAST FOURIER TRANSFORM AND THE CONTINUOUS WAVELET TRANSFORM ANALYSIS OF THE PHONOCARDIOGRAM SIGNAL
Authors: DEBBAL S. M. , BEREKSI-REGUIG F. , TANI A. MEZIANE
Published: August 2004

This paper is concerned with a synthesis study of the fast Fourier transform (FFT) and the continuous wavelet transform (CWT) in analysing the phonocardiogram signal (PCG). It is shown that the continuous wavelet transform provides enough features of the PCG signals that will help clinics to obtain qualitative and quantitative measurements of the time-frequency PCG signal characteristics and consequently aid to diagnosis. Similary, it is shown that the frequency content of such a signal can be determined by the FFT without difficulties.
LINEAR STABILITY ANALYSIS OF THE NEOCLASSICAL GROWTH MODEL TO SPATIALLY HOMOGENEOUS PERTURBATIONS
Authors: VADASZ ALISA S. , CARSKY MILAN , GUPTHAR ABIN S. , VADASZ PETER
Published: August 2004

A linear stability analysis of the stationary solutions for growth of populations with respect to Spatially Homogeneous Perturbations (SHoP) is presented. The Neoclassical growth theory is extended to apply to spatially heterogeneous populations. The latter includes the metabolic mass transfer effects and allows for the recovery of substantial and distinct phenomena observed experimentally, such as the mechanism controlling the LAG phase, a result that holds impressive future potential in diverse applications. The stability conditions are expressed explicitly in terms of the primitive parameters of the original nonlinear system. The results are necessary when undertaking a corresponding linear stability analysis for growth of populations with respect to Spatially Heterogeneous Perturbations (SHeP).
A RESOURCE-BASED STUDY OF NEW PRODUCT DEVELOPMENT: PREDICTING FIVE-YEAR LATER COMMERCIAL SUCCESS AND SPEED TO MARKET
Authors: KELLER ROBERT T.
Published: August 2004

Hypotheses derived from a resource-based model of new product development were used to predict five-year later commercial success in the form of profitability and speed to market for a sample of 117 new products from four firms in different industries. The results found marketing capabilities to be the best predictor of profitability, and that technical capabilities and leadership capabilities were also significant predictors. Leadership capabilities were the only significant predictor of which products made it to market, and of speed to market. Implications for models of new product development and for its effective management are discussed.
IL-10 modulates intestinal damage and epithelial cell apoptosis in T cell-mediated enteropathy
Authors: Zhou Pengfei , Streutker Cathy , Borojevic Rajka , Wang Yufa , Croitoru Ken
Published: August 2004

In vivo T cell activation by anti-CD3 monoclonal antibody (mAb) results in intestinal damage characterized by loss of villi and epithelial cell apoptosis. The role of the increased interleukin (IL)-10 released during this process is not clear. We assessed the effects of IL-10 on T cell-induced mucosal damage in vivo using IL-10-deficient C57BL/6 [IL-10 knockout (KO)] mice. IL-10 KO and wild-type C57BL/6 mice were injected with anti-CD3 mAb and observed for diarrhea. Changes in serum cytokine levels were measured by ELISA. Histological changes and epithelial cell apoptosis were analyzed on hematoxylin- and eosin-stained tissue sections. Fas expression on intestinal epithelial cells was assessed by flow cytometry analysis of freshly isolated intestinal epithelial cells. Anti-CD3-treated IL-10 KO mice developed more severe diarrhea, a greater loss of intestinal villi, and an increase in the numbers of apoptotic cells in the crypt epithelium. This difference in IL-10 KO mice was associated with an increase in serum tumor necrosis factor-α and interferon-γ levels and with an increase in Fas expression on fresh, isolated, small intestinal epithelial cells. In addition, the enhanced intestinal tissue damage induced by anti-CD3 in IL-10 KO mice was significantly diminished by treatment with recombinant murine IL-10. Therefore, the lack of IL-10 allowed for an increased T cell-induced intestinal tissue damage, and this was associated with an increase in T cell cytokine release and an increase in epithelial cell Fas expression.
Complex Response to Afferent Excitatory Bursts by Nucleus Accumbens Medium Spiny Projection Neurons
Authors: Lape Remigijus , Dani John A.
Published: August 2004

The nucleus accumbens (NAc) of the ventral striatum is involved in attention, motivation, movement, learning, reward, and addiction. GABAergic medium spiny projection neurons that make up ∼90% of the neuronal population are commonly driven by convergent bursts of afferent excitation. We monitored spiny projection neurons in mouse striatal slices while applying stimulus trains to mimic bursts of excitation. A stimulus train evoked a simple, short-lived postsynaptic response from CA1 hippocampal pyramidal neurons, but the train evoked a complex series of excitatory postsynaptic potentials (EPSPs) or currents (EPSCs) from the NAc spiny projection neurons. As is commonly seen with projection neurons, the EPSC amplitudes initially displayed facilitation followed by depression, and that pattern was sensitive to the extracellular calcium concentration. In addition, there were two other novel observations. The spiny projection neurons responded to the stimulus train with a prolonged depolarization that was accompanied by a posttrain increase of spontaneous glutamatergic synaptic activity. Blocking AMPA/kainate glutamate receptors strongly inhibited the evoked EPSP/EPSCs, the posttrain spontaneous synaptic activity, and the prolonged depolarization. A potassium channel inhibitor increased and extended the prolonged postsynaptic depolarization, causing a long-lasting depolarized plateau potential. Our results indicate that burst-like activity along ventral striatal afferents is extended in time by additional spontaneous glutamate release that is integrated by the postsynaptic spiny projection neurons into a prolonged depolarization. The results suggest that the posttrain quantal glutamate release helps to blend and maintain multiple afferent inputs. That convergent excitation is further integrated by the postsynaptic neuron into a prolonged depolarization that may contribute to the depolarized “up state” observed in vivo.
Membrane Bistability in Thalamic Reticular Neurons During Spindle Oscillations
Authors: Fuentealba Pablo , Timofeev Igor , Bazhenov Maxim , Sejnowski Terrence J. , Steriade Mircea
Published: August 2004

The thalamic reticular (RE) nucleus is a major source of inhibition in the thalamus. It plays a crucial role in regulating the excitability of thalamocortical networks and in generating some sleep rhythms. Current-clamp intracellular recordings of RE neurons in cats under barbiturate anesthesia revealed the presence of membrane bistability in ∼20% of neurons. Bistability consisted of two alternate membrane potentials, separated by ∼17–20 mV. While non-bistable (common) RE neurons fired rhythmic spike-bursts during spindles, bistable RE neurons fired tonically, with burst modulation, throughout spindle sequences. Bistability was strongly voltage dependent and only expressed under resting conditions (i.e. no current injection). The transition from the silent to the active state was a regenerative event that could be activated by brief depolarization, whereas brief hyperpolarizations could switch the membrane potential from the active to the silent state. These effects outlasted the current pulses. Corticothalamic stimulation could also switch the membrane potential from silent to active states. Addition of QX-314 in the recording micropipette either abolished or disrupted membrane bistability, suggesting INa(p) to be responsible for its generation. Thalamocortical cells presented various patterns of spindling that reflected the membrane bistability in RE neurons. Finally, experimental data and computer simulations predicted a role for RE neurons' membrane bistability in inducing various patterns of spindling in target thalamocortical cells. We conclude that membrane bistability of RE neurons is an intrinsic property, likely generated by INa(p) and modulated by cortical influences, as well as a factor that determines different patterns of spindle rhythms in thalamocortical neurons.
Critical Points in the Forelimb Fictive Locomotor Cycle and Motor Coordination: Effects of Phasic Retractions and Protractions of the Shoulder in the Cat
Authors: Saltiel Philippe , Rossignol Serge
Published: August 2004

This study investigates the responses to phasic shoulder retractions or protractions given at different times in the fictive locomotor cycle of the forelimbs of decerebrate cats. Generally, the responses in flexor and extensor muscles acting at the shoulder or elbow were bilaterally coordinated according to a negative feedback scheme. Perturbations in the direction of the movements that would have taken place if the animal had not been paralyzed tended to shorten the duration of the burst of activity of the muscles active during that phase and vice versa in the opposite phase. Changes in response patterns took place around critical points corresponding to the critical points B–D described in the companion paper using tonic perturbations of the limb. Past point C, at 58% of the ipsilateral extensor burst, protractions no longer prolonged the burst and no longer delayed onset of the contralateral extensor. At point B, occurring at 41% of the contralateral extensor burst, ipsilateral protractions maximally shortened the ipsilateral flexor phase, advancing ipsilateral extensor onset (point D) to point C of the contralateral extensor burst. During a critical period from the end of the ipsilateral flexor (point D) until the contralateral flexor onset, retractions elicited two alternative responses. Either the contralateral extensor activity was abolished and the contralateral flexor turned on, or it persisted for another cycle. We argue that the critical points found here correspond to critical biomechanical events in real locomotion and may underlie a phase-dependent motor coordination.
Coordinated Excitatory Effect of GABAergic Interneurons on Three Feeding Motor Programs in the MolluskClione limacina
Authors: Norekian Tigran P. , Malyshev Aleksey Y.
Published: August 2004

Coordination between different motor centers is essential for the orderly production of all complex behaviors. Understanding the mechanisms of such coordination during feeding behavior in the carnivorous mollusk Clione limacina is the main goal of the current study. A bilaterally symmetrical interneuron identified in the cerebral ganglia and designated Cr-BM neuron produced coordinated activation of neural networks controlling three main feeding structures: prey capture appendages called buccal cones, chitinous hooks used for prey extraction from the shell, and the toothed radula. The Cr-BM neuron produced strong excitatory inputs to motoneurons controlling buccal cone protraction. It also induced a prominent activation of the neural networks controlling radula and hook rhythmic movements. In addition to the overall activation, Cr-BM neuron synaptic inputs to individual motoneurons coordinated their activity in a phase-dependent manner. The Cr-BM neuron produced depolarizing inputs to the radula protractor and hook retractor motoneurons, which are active in one phase, and hyperpolarizing inputs to the radula retractor and hook protractor motoneurons, which are active in the opposite phase. The Cr-BM neuron used GABA as its neurotransmitter. It was found to be GABA-immunoreactive in the double-labeling experiments. Exogenous GABA mimicked the effects produced by Cr-BM neuron on the postsynaptic neurons. The GABA antagonists bicuculline and picrotoxin blocked Cr-BM neuron-induced PSPs. The prominent coordinating effect produced by the Cr-BM neuron on the neural networks controlling three major elements of the feeding behavior in Clione suggests that this interneuron is an important part of the higher-order system for the feeding behavior.
Cortical Control of Sound Localization in the Cat: Unilateral Cooling Deactivation of 19 Cerebral Areas
Authors: Malhotra Shveta , Hall Amee J. , Lomber Stephen G.
Published: August 2004

We examined the ability of mature cats to accurately orient to, and approach, an acoustic stimulus during unilateral reversible cooling deactivation of primary auditory cortex (AI) or 1 of 18 other cerebral loci. After attending to a central visual stimulus, the cats learned to orient to a 100-ms broad-band, white-noise stimulus emitted from a central speaker or 1 of 12 peripheral sites (at 15° intervals) positioned along the horizontal plane. Twenty-eight cats had two to six cryoloops implanted over multiple cerebral loci. Within auditory cortex, unilateral deactivation of AI, the posterior auditory field (PAF) or the anterior ectosylvian sulcus (AES) resulted in orienting deficits throughout the contralateral field. However, unilateral deactivation of the anterior auditory field, the second auditory cortex, or the ventroposterior auditory field resulted in no deficits on the orienting task. In multisensory cortex, unilateral deactivation of neither ventral or dorsal posterior ectosylvian cortices nor anterior or posterior area 7 resulted in any deficits. No deficits were identified during unilateral cooling of the five visual regions flanking auditory or multisensory cortices: posterior or anterior ii suprasylvian sulcus, posterior suprasylvian sulcus or dorsal or ventral posterior suprasylvian gyrus. In motor cortex, we identified contralateral orienting deficits during unilateral cooling of lateral area 5 (5L) or medial area 6 (6m) but not medial area 5 or lateral area 6. In a control visual-orienting task, areas 5L and 6m also yielded deficits to visual stimuli presented in the contralateral field. Thus the sound-localization deficits identified during unilateral deactivation of area 5L or 6m were not unimodal and are most likely the result of motor rather than perceptual impairments. Overall, three regions in auditory cortex (AI, PAF, AES) are critical for accurate sound localization as assessed by orienting.
Serum Lipid Levels and the Risk of Venous Thrombosis
Authors: Doggen Carine J.M. , Smith Nicholas L. , Lemaitre Rozenn N. , Heckbert Susan R. , Rosendaal Frits R. , Psaty Bruce M.
Published: August 2004

Objective—

Lipids, through effects on the coagulation and fibrinolytic systems, may contribute to the development of venous thrombosis. This association has been investigated in a few studies, with conflicting results.

Methods and Results—

We conducted a population-based, case-control study at a health maintenance organization in Washington State, to assess the association of serum lipid levels with the risk of venous thrombosis. Cases were 477 postmenopausal women with a first venous thrombosis during January 1995 through December 2001. Control subjects (1986) were a random sample of postmenopausal women. Medical records, computerized pharmacy databases, and a cancer registry served to collect data on lipid levels and risk factors for thrombosis. Total cholesterol levels were not associated with venous thrombosis. Only high HDL cholesterol levels were associated with a decreased risk of venous thrombosis after adjustment for hospitalization, malignancy, height and weight, postmenopausal hormone therapy, and vascular disease (for high-density lipoprotein [HDL] cholesterol levels >1.79 mmol/L versus those <1.79 mmol/L; odds ratio [OR], 0.71; 95% confidence interval [CI], 0.52 to 0.97). In contrast, elevated triglyceride levels were associated with an increased risk (OR, 2.13; 95% CI, 1.34 to 3.37) for women with triglyceride levels >1.05 mmol/L compared with women with lower levels.

Conclusion—

Elevated triglyceride levels were associated with a doubling of risk of venous thrombosis in postmenopausal women, whereas elevated HDL cholesterol levels were associated with a decreased risk.
Reflections on Democracy: The Beginning of the End or the End of the Beginning?
Authors: Sa'adah Anne
Published: August 2004

Democratization represents both a sea change in the life of a society and an open-ended process. The order that it produces is never an unmitigated good or a natural outcome, and it is not likely to be self-sustaining in any time or place. The ability of the United States to foster democratization, whether at home or abroad, is modest because it is proportional to its limited ability to build and maintain the institutions that democracy requires.
Learning Eigenfunctions Links Spectral Embedding and Kernel PCA
Authors: Bengio Yoshua , Delalleau Olivier , Roux Nicolas Le , Paiement Jean-François , Vincent Pascal , Ouimet Marie
Published: August 2004

In this letter, we show a direct relation between spectral embedding methods and kernel principal components analysis and how both are special cases of a more general learning problem: learning the principal eigenfunctions of an operator defined from a kernel and the unknown data-generating density. Whereas spectral embedding methods provided only coordinates for the training points, the analysis justifies a simple extension to out-of-sample examples (the Nyström formula) for multidimensional scaling (MDS), spectral clustering, Laplacian eigenmaps, locally linear embedding (LLE), and Isomap. The analysis provides, for all such spectral embedding methods, the definition of a loss function, whose empirical average is minimized by the traditional algorithms. The asymptotic expected value of that loss defines a generalization performance and clarifies what these algorithms are trying to learn. Experiments with LLE, Isomap, spectral clustering, and MDS show that this out-of-sample embedding formula generalizes well, with a level of error comparable to the effect of small perturbations of the training set on the embedding.
Disambiguating Visual Motion Through Contextual Feedback Modulation
Authors: Bayerl Pierre , Neumann Heiko
Published: August 2004

Motion of an extended boundary can be measured locally by neurons only orthogonal to its orientation (aperture problem) while this ambiguity is resolved for localized image features, such as corners or nonocclusion junctions. The integration of local motion signals sampled along the outline of a moving form reveals the object velocity. We propose a new model of V1-MT feedforward and feedback processing in which localized V1 motion signals are integrated along the feedforward path by model MT cells. Top-down feedback from MT cells in turn emphasizes model V1 motion activities of matching velocity by excitatory modulation and thus realizes an attentional gating mechanism. The model dynamics implement a guided filling-in process to disambiguate motion signals through biased on-center, off-surround competition. Our model makes predictions concerning the time course of cells in area MT and V1 and the disambiguation process of activity patterns in these areas and serves as a means to link physiological mechanisms with perceptual behavior. We further demonstrate that our model also successfully processes natural image sequences.
Exact Solution for the Optimal Neuronal Layout Problem
Authors: Chklovskii Dmitri B.
Published: August 2004

Evolution perfected brain design by maximizing its functionality while minimizing costs associated with building and maintaining it. Assumption that brain functionality is specified by neuronal connectivity, implemented by costly biological wiring, leads to the following optimal design problem. For a given neuronal connectivity, find a spatial layout of neurons that minimizes the wiring cost. Unfortunately, this problem is difficult to solve because the number of possible layouts is often astronomically large. We argue that the wiring cost may scale as wire length squared, reducing the optimal layout problem to a constrained minimization of a quadratic form. For biologically plausible constraints, this problem has exact analytical solutions, which give reasonable approximations to actual layouts in the brain. These solutions make the inverse problem of inferring neuronal connectivity from neuronal layout more tractable.
Different Predictions by the Minimum Variance and Minimum Torque-Change Models on the Skewness of Movement Velocity Profiles
Authors: Tanaka Hirokazu , Tai Meihua , Qian Ning
Published: August 2004

We investigated the differences between two well-known optimization principles for understanding movement planning: the minimum variance (MV) model of Harris and Wolpert (1998) and the minimum torque change (MTC) model of Uno, Kawato, and Suzuki (1989). Both models accurately describe the properties of human reaching movements in ordinary situations (e.g., nearly straight paths and bell-shaped velocity profiles). However, we found that the two models can make very different predictions when external forces are applied or when the movement duration is increased. We considered a second-order linear system for the motor plant that has been used previously to simulate eye movements and single-joint arm movements and were able to derive analytical solutions based on the MV and MTC assumptions. With the linear plant, the MTC model predicts that the movement velocity profile should always be symmetrical, independent of the external forces and movement duration. In contrast, the MV model strongly depends on the movement duration and the system's degree of stability; the latter in turn depends on the total forces. The MV model thus predicts a skewed velocity profile under many circumstances. For example, it predicts that the peak location should be skewed toward the end of the movement when the movement duration is increased in the absence of any elastic force. It also predicts that with appropriate viscous and elastic forces applied to increase system stability, the velocity profile should be skewed toward the beginning of the movement. The velocity profiles predicted by the MV model can even show oscillations when the plant becomes highly oscillatory. Our analytical and simulation results suggest specific experiments for testing the validity of the two models.
Understanding the Cortical Specialization for Horizontal Disparity
Authors: Read Jenny C.A. , Cumming Bruce G.
Published: August 2004

Because the eyes are displaced horizontally, binocular vision is inherently anisotropic. Recent experimental work has uncovered evidence of this anisotropy in primary visual cortex (V1): neurons respond over a wider range of horizontal than vertical disparity, regardless of their orientation tuning. This probably reflects the horizontally elongated distribution of two-dimensional disparity experienced by the visual system, but it conflicts with all existing models of disparity selectivity, in which the relative response range to vertical and horizontal disparities is determined by the preferred orientation. Potentially, this discrepancy could require us to abandon the widely held view that processing in V1 neurons is initially linear. Here, we show that these new experimental data can be reconciled with an initial linear stage; we present two physiologically plausible ways of extending existing models to achieve this. First, we allow neurons to receive input from multiple binocular subunits with different position disparities (previous models have assumed all subunits have identical position and phase disparity). Then we incorporate a form of divisive normalization, which has successfully explained many response properties of V1 neurons but has not previously been incorporated into a model of disparity selectivity. We show that either of these mechanisms decouples disparity tuning from orientation tuning and discuss how the models could be tested experimentally. This represents the first explanation of how the cortical specialization for horizontal disparity may be achieved.
Decoding a Temporal Population Code
Authors: Knüsel Philipp , Wyss Reto , König Peter , Verschure Paul F.M.J.
Published: August 2004

Encoding of sensory events in internal states of the brain requires that this information can be decoded by other neural structures. The encoding of sensory events can involve both the spatial organization of neuronal activityanditstemporaldynamics. Here we investigate the issue of decoding in the context of a recently proposed encoding scheme: the temporal population code. In this code, the geometric properties of visual stimuli become encoded into the temporal response characteristics of the summed activities of a population of cortical neurons. For its decoding, we evaluate a model based on the structure and dynamics of cortical microcircuits that is proposed for computations on continuous temporal streams: the liquid state machine. Employing the original proposal of the decoding network results in a moderate performance. Our analysis shows that the temporal mixing of subsequent stimuli results in a joint representation that compromises their classification. To overcome this problem, we investigate a number of initialization strategies. Whereas we observe that a deterministically initialized network results in the best performance, we find that in case the network is never reset, that is, it continuously processes the sequence of stimuli, the classification performance is greatly hampered by the mixing of information from past and present stimuli. We conclude that this problem of the mixing of temporally segregated information is not specific to this particular decoding model but relates to a general problem that any circuit that processes continuous streams of temporal information needs to solve. Furthermore, as both the encoding and decoding components of our network have been independently proposed as models of the cerebral cortex, our results suggest that the brain could solve the problem of temporal mixing by applying reset signals at stimulus onset, leading to a temporal segmentation of a continuous input stream.
Minimal Models of Adapted Neuronal Response to In Vivo–Like Input Currents
Authors: Camera Giancarlo La , Rauch Alexander , Lüscher Hans-R. , Senn Walter , Fusi Stefano
Published: August 2004

Rate models are often used to study the behavior of large networks of spiking neurons. Here we propose a procedure to derive rate models that take into account the fluctuations of the input current and firing-rate adaptation, two ubiquitous features in the central nervous system that have been previously overlooked in constructing rate models. The procedure is general and applies to any model of firing unit. As examples, we apply it to the leaky integrate-and-fire (IF) neuron, the leaky IF neuron with reversal potentials, and to the quadratic IF neuron. Two mechanisms of adaptation are considered, one due to an after hyperpolarization current and the other to an adapting threshold for spike emission. The parameters of these simple models can be tuned to match experimental data obtained from neocortical pyramidal neurons. Finally, we show how the stationary model can be used to predict the time-varying activity of a large population of adapting neurons.
Advanced Fitness Landscape Analysis and the Performance of Memetic Algorithms
Authors: Merz Peter
Published: August 2004

Memetic algorithms (MAs) have demonstrated very effective in combinatorial optimization. This paper offers explanations as to why this is so by investigating the performance of MAs in terms of efficiency and effectiveness. A special class of MAs is used to discuss efficiency and effectiveness for local search and evolutionary meta-search. It is shown that the efficiency of MAs can be increased drastically with the use of domain knowledge. However, effectiveness highly depends on the structure of the problem. As is well-known, identifying this structure is made easier with the notion of fitness landscapes: the local properties of the fitness landscape strongly influence the effectiveness of the local search while the global properties strongly influence the effectiveness of the evolutionary meta-search.

This paper also introduces new techniques for analyzing the fitness landscapes of combinatorial problems; these techniques focus on the investigation of random walks in the fitness landscape starting at locally optimal solutions as well as on the escape from the basins of attractions of current local optima. It is shown for NK-landscapes and landscapes of the unconstrained binary quadratic programming problem (BQP) that a random walk to another local optimum can be used to explain the efficiency of recombination in comparison to mutation. Moreover, the paper shows that other aspects like the size of the basins of attractions of local optima are important for the efficiency of MAs and a local search escape analysis is proposed. These simple analysis techniques have several advantages over previously proposed statistical measures and provide valuable insight into the behaviour of MAs on different kinds of landscapes.
Reproductive Health in the Context of Economic and Democratic Development
Authors: Wang Guang-Zhen
Published: August 2004

This paper proposes a model of women's reproductive health in the context of economic and democratic development. Gender equality and reproductive rights were used as intervening factors. The analysis was done in three stages. First, a comparison of the mean values of the variables was conducted. Second, the parameters of the measurement model were assessed, in particular the reliability of the variables and the factor loadings on the constructs. Finally, the estimates of the structural parameters of the model were determined. Data used for this study were obtained from 129 developing countries. Empirical findings indicate the importance of economic development, gender equality, and personal marriage and divorce rights in predicting reproductive health. The path coefficients are high and statistically significant. The relationship between democracy and gender equality is positive and statistically significant as proposed. The results of this study throw some light on several long-standing concerns with regard to the role of economic development, democracy, gender equality, and reproductive rights in predicting women's reproductive health. Limitations of the study are discussed.
Does Human Capital Strongly Affect Economic Growth Rates? Yes, But Only If Assessed Properly
Authors: Weede Erich
Published: August 2004

Although modern growth theories regard human capital endowment as a determinant of economic growth rates, econometric research does not consistently support this view by empirical evidence. In principle, this discrepancy might arise either from misleading theories or from poor measurement of human capital endowment. Here, it is argued that poor measurement is the culprit, and that one should substitute results from psychological testing, i.e.IQ, for widely accepted measures based on schooling. In order to demonstrate both the superiority of IQ over schooling derived measures as well as the robustness of IQ effects on growth, the new measure is entered in the Mankiw, Romer and Weil and the De Long and Summers frameworks which differ in the specification of growth equations and, in particular, in their treatment of investment. It is demonstrated that IQ effects are at least about equally strong and robust determinants of growth as catch-up opportunities, whether investment is included or excluded, narrowly or broadly defined. If investment is included, its effects are in the same order of magnitude as those of catch-up opportunities or IQ. Since IQ is correlated with state antiquity, since state antiquity might offer
From Social Class and Religious Identity to Status Incongruence in Post-Industrial Societies
Authors: Dogan Mattei
Published: August 2004

In political behaviour, religion has played the role of a barrier against the lower social classes, at such a degree that in most democracies, the vertical cleavages (ethnicity, religion, language, race) have been stronger than the horizontal cleavage (income, education, professional status). Social changes in the last few decades have generated a decline of the social class as well as of the religious factor in the interpretation of political alignments. The concept of status incongruence appears to be a better explanation of contemporary social attitudes and political behaviour. Status imbalances are frequent in advanced pluralist societies, and rare in traditional societies of the Third World. For this reason, this analysis focuses on Western countries. Key words: social status, working class, decline of religious beliefs, status inconsistency, status crystallization, criss-crossing cleavages, downward mobility, individualization.