bluuebunny/crossref_metadata_2025 huggingface dataset:
Uncrossed actions of feline corticospinal tract neurones on hindlimb motoneurones evoked via ipsilaterally descending pathways
Authors: Stecina K. , Jankowska E.
Published: January 2007

Despite numerous investigations on the corticospinal system there is only scant information on neuronal networks mediating actions of corticospinal neurones on ipsilateral motoneurones. We have previously demonstrated double crossed pathways through which pyramidal tract neurones can influence ipsilateral motoneurones, via contralaterally descending reticulospinal neurones and spinal commissural interneurones. The aim of the present study was to examine the effects of stimulation of pyramidal tract (PT) fibres mediated via ipsilaterally descending pathways and to find out which neurones relay these effects. This was done by using intracellular recordings from 96 lumbar motoneurones in deeply anaesthetized cats. To eliminate actions of fibres descending on the side contralateral to the location of the motoneurones, the spinal cords were hemisected on this side at a low‐thoracic level. Stimuli that selectively activated ipsilateral PT fibres evoked EPSPs and/or IPSPs in 34/47 motoneurones tested. These PSPs were evoked at latencies indicating that the most direct coupling between PT neurones and motoneurones in uncrossed pathways is disynaptic. Occlusion and spatial facilitation between actions evoked by stimulation of ipsilateral PT and of reticulospinal tract fibres in the ipsilateral medial longitudinal fascicle (MLF) indicated that PT actions are mediated by reticulospinal neurones with axons in the MLF. However, after transection of the MLF in the caudal medulla, stimulation of the ipsilateral PT continued to evoke EPSPs and IPSPs with characteristics similar to when the MLF was intact (in 15/49 motoneurones) suggesting the existence of parallel disynaptic pathways via other relay neurones.
Uncrossed actions of feline corticospinal tract neurones on lumbar interneurones evoked via ipsilaterally descending pathways
Authors: Jankowska E. , Stecina K.
Published: January 2007

Effects of stimulation of ipsilateral pyramidal tract (PT) fibres were analysed in interneurones in midlumbar segments of the cat spinal cord in search of interneurones mediating disynaptic actions of uncrossed PT fibres on hindlimb motoneurones. The sample included 44 intermediate zone and ventral horn interneurones, most with monosynaptic input from group I and/or group II muscle afferents and likely to be premotor interneurones. Monosynaptic EPSPs evoked by stimulation of the ipsilateral PT were found in 12 of the 44 (27%) interneurones, while disynaptic or trisynaptic EPSPs were evoked in more than 75%. Both appeared at latencies that were either longer or within the same range as those of disynaptic EPSPs and IPSPs evoked by PT stimuli in motoneurones, making it unlikely that premotor interneurones in pathways from group I and/or II afferents relay the earliest actions of uncrossed PT fibres on motoneurones. These interneurones might nevertheless contribute to PT actions at longer latencies. Uncrossed PT actions on interneurones were to a great extent relayed via reticulospinal neurones with axons in the ipsilateral medial longitudinal fascicle (MLF), as indicated by occlusion and mutual facilitation of actions evoked by PT and MLF stimulation. However, PT actions were also relayed by other supraspinal or spinal neurones, as some remained after MLF lesions. Mutual facilitation and occlusion of actions evoked from the ipsilateral and contralateral PTs lead to the conclusion that the same midlumbar interneurones in pathways from group I or II muscle afferents may relay uncrossed and crossed PT actions.
Cutaneous afferents provide a neuronal population vector that encodes the orientation of human ankle movements
Authors: Aimonetti Jean‐Marc , Hospod Valérie , Roll Jean‐Pierre , Ribot‐Ciscar Edith
Published: January 2007

The aim of this study was to analyse the directional coding of two‐dimensional limb movements by cutaneous afferents from skin areas covering a multidirectional joint, the ankle. The activity of 89 cutaneous afferents was recorded in the common peroneal nerve, and the mean discharge frequency of each unit was measured during the outward phase of ramp and hold movements imposed in 16 different directions. Forty‐two afferents responded to the movements in the following decreasing order (SA2, n= 24/27; FA2, n= 13/17; FA1, n= 3/24; SA1, n= 2/21). All the units activated responded to a specific range of directions, defining their ‘preferred sector’, within which their response peaked in a given direction, their ‘preferred direction’. Based on the distribution of the preferred directions, two populations of afferents, and hence two skin areas were defined: the anterior and the external lateral parts of the leg. As the directional tuning of each population was cosine shaped, the neuronal population vector model was applied and found to efficiently describe the movement direction encoded by cutaneous afferents, as it has been previously reported for muscle afferents. The responses of cutaneous afferents were then considered with respect to those of the afferents from the underlying muscles, which were previously investigated, and an almost perfect matching of directional sensitivity was observed. It is suggested that the common movement‐encoding characteristics exhibited by cutaneous and muscle afferents, as early as the peripheral level, may facilitate the central co‐processing of their feedbacks subserving kinaesthesia.
Mechanosensitive channel properties and membrane mechanics in mouse dystrophic myotubes
Authors: Suchyna Thomas M. , Sachs Frederick
Published: January 2007

Muscular dystrophy is associated with increased activity of mechanosensitive channels (MSCs) and increased cell calcium levels. MSCs in patches from mdx mouse myotubes have higher levels of resting activity, compared to patches from wild‐type mice, and a pronounced latency of activation and deactivation. Measurements of patch capacitance and geometry reveal that the differences are linked to cortical membrane mechanics rather than to differences in channel gating. We found unexpectedly that patches from mdx mice are strongly curved towards the pipette tip by actin pulling normal to the membrane. This force produces a substantial tension (∼5 mN m−1) that can activate MSCs in the absence of overt stimulation. The inward curvature of patches from mdx mice is eliminated by actin inhibitors. Applying moderate suction to the pipette flattens the membrane, reducing tension, and making the response appear to be stretch inactivated. The pronounced latency to activation in patches from mdx mice is caused by the mechanical relaxation time required to reorganize the cortex from inward to outward curvature. The increased latency is equivalent to a three‐fold increase in cortical viscosity. Disruption of the cytoskeleton by chemical or mechanical means eliminates the differences in kinetics and curvature between patches from wild‐type and mdx mice. The stretch‐induced increase in specific capacitance of the patch, ∼80 fF μm−2, far exceeds the specific capacitance of bilayers, suggesting the presence of stress‐sensitive access to large pools of membrane, possibly caveoli, T‐tubules or portions of the gigaseal. In mdx mouse cells the intrinsic gating property of fast voltage‐sensitive inactivation is lost. It is robust in wild‐type mouse cells (observed in 50% of outside‐out patches), but never observed in mdx cells. This link between dystrophin and inactivation may lead to increased background cation currents and Ca2+ influx. Spontaneous Ca2+ transients in mdx mouse cells are sensitive to depolarization and are inhibited by the specific MSC inhibitor GsMTx4, in both the d and l forms.
Effects of muscle conditioning on position sense at the human forearm during loading or fatigue of elbow flexors and the role of the sense of effort
Authors: Allen Trevor J. , Ansems Gabrielle E. , Proske Uwe
Published: January 2007

In a forearm position‐matching task in the horizontal plane, when one (reference) arm is conditioned by contraction and length changes, subjects make systematic errors in the placement of their other, indicator arm. Here we describe experiments that demonstrate the importance not just of conditioning the reference arm, but of the indicator arm as well. Total errors from muscle conditioning represented up to a quarter of the angular range available to subjects. The sizes of the observed effects have led us to repeat other, previously reported experiments. In a matching task in the vertical plane, when muscles of both arms were conditioned identically, if the subject supported their arms themselves, or when the arms were loaded by the addition of weights, the loading did not introduce new position errors. To test the effect of exercise, subjects' elbow flexors were exercised eccentrically or concentrically by asking them to lower or raise a set of weights using forearm muscles. The exercise produced 25–30% decreases in maximum voluntary contraction strength of elbow flexors and this led to significant position‐matching errors. The directions and magnitudes of the errors were similar after the two forms of exercise and indicated that subjects perceived their exercised muscles to be longer than they actually were. To conclude, the new data from loading the arm are not consistent with the idea that the sense of effort accompanying support of a load, provides positional information in any simple way. Our current working hypothesis is that when muscles are active, position‐sense involves operation of a forward internal model. Loading the arm produces predictable changes in motor output and afferent feedback whereas changes after exercise are unpredictable. This difference leads to exercise‐dependent errors.
Brain–computer interfaces as new brain output pathways
Authors: Wolpaw Jonathan R.
Published: January 2007

Brain–computer interfaces (BCIs) can provide non‐muscular communication and control for people with severe motor disabilities. Current BCIs use a variety of invasive and non‐invasive methods to record brain signals and a variety of signal processing methods. Whatever the recording and processing methods used, BCI performance (e.g. the ability of a BCI to control movement of a computer cursor) is highly variable and, by the standards applied to neuromuscular control, could be described as ataxic. In an effort to understand this imperfection, this paper discusses the relevance of two principles that underlie the brain's normal motor outputs. The first principle is that motor outputs are normally produced by the combined activity of many CNS areas, from the cortex to the spinal cord. Together, these areas produce appropriate control of the spinal motoneurons that activate muscles. The second principle is that the acquisition and life‐long preservation of motor skills depends on continual adaptive plasticity throughout the CNS. This plasticity optimizes the control of spinal motoneurons. In the light of these two principles, a BCI may be viewed as a system that changes the outcome of CNS activity from control of spinal motoneurons to, instead, control of the cortical (or other) area whose signals are used by the BCI to determine the user's intent. In essence, a BCI attempts to assign to cortical neurons the role normally performed by spinal motoneurons. Thus, a BCI requires that the many CNS areas involved in producing normal motor actions change their roles so as to optimize the control of cortical neurons rather than spinal motoneurons. The disconcerting variability of BCI performance may stem in large part from the challenge presented by the need for this unnatural adaptation. This difficulty might be reduced, and BCI development might thereby benefit, by adopting a ‘goal‐selection’ rather than a ‘process‐ control’ strategy. In ‘process control’, a BCI manages all the intricate high‐speed interactions involved in movement. In ‘goal selection’, by contrast, the BCI simply communicates the user's goal to software that handles the high–speed interactions needed to achieve the goal. Not only is ‘goal selection’ less demanding, but also, by delegating lower‐level aspects of motor control to another structure (rather than requiring that the cortex do everything), it more closely resembles the distributed operation characteristic of normal motor control.
Spinal projection of spindle afferents of the longissimus lumborum muscles of the cat
Authors: Durbaba R. , Taylor A. , Ellaway P. H. , Rawlinson S.
Published: January 2007

The connections and monosynaptic projections of muscle spindle afferents of individual heads of the longissimus lumborum have been studied in cats by natural stimulation, by electrical stimulation and by spike‐triggered averaging from single identified afferents. The spindle afferents were classified by sensitivity to vibration and by the effect of succinylcholine on their response to ramp‐and‐hold muscle stretches. Axonal conduction and synaptic effects were recorded as field potentials and focal synaptic potentials during systematic exploration of the spinal cord in segments L1 to L4 with extracellular metal microelectrodes, singly and in linear arrays. Ascending branches of afferent axons within the cord had a significantly higher mean conduction velocity (CV: 56.5 m s−1) than descending branches (40.8 m s−1). The CV of ascending branches was significantly positively correlated with a measure of the strength of intrafusal bag2 muscle fibre contacts, but not to a measure of bag1 contacts. Two sites of monosynaptic excitatory projection in the cord were identified, namely to the intermediate region (laminae V, VI and VII) and to ventral horn region (laminae VIII and IX). In tests of 154 single afferents, signs of central projection were detected for 60, providing 122 regions of maximum negative focal synaptic potentials (FSPs) of mean amplitude 7.51 μV. Their longitudinal spacing indicated that axons gave off descending collaterals at intervals of 1.5–3.5 mm. Based on the amplitude of FSPs, the projection of secondary afferents is stronger than that of primaries in the intermediate region and possibly also in the ventral horn region. Evidence is also presented that spindle afferent input from different heads of the longissimus converges into any given spinal segment and that input in one spinal root projects to adjacent segments. It is concluded that the organization of the longissimus monosynaptic spindle input favours relatively tonic and diffuse stretch reflexes.
Useful signals from motor cortex
Authors: Schwartz Andrew B.
Published: January 2007

Historically, the motor cortical function has been explained as a funnel to muscle activation. This invokes the idea that motor cortical neurons, or ‘upper motoneurons’, directly cause muscle contraction just like spinal motoneurons. Thus, the motor cortex and muscle activity are inextricably entwined like a puppet master and his marionette. Recently, this concept has been challenged by current experimentation showing that many behavioural aspects of action are represented in motor cortical activity. Although this activity may still be related to muscle activation, the relation between the two is likely to be indirect and complex, whereas the relation between cortical activity and kinematic parameters is simple and robust. These findings show how to extract useful signals that help explain the underlying process that generates behaviour and to harness these signals for potentially therapeutic applications.
Ca2+ permeability of the channel pore is not essential for the δ2 glutamate receptor to regulate synaptic plasticity and motor coordination
Authors: Kakegawa Wataru , Miyazaki Taisuke , Hirai Hirokazu , Motohashi Junko , Mishina Masayoshi , Watanabe Masahiko , Yuzaki Michisuke
Published: January 2007

The δ2 glutamate receptor (GluRδ2) plays a crucial role in cerebellar functions; mice with a disrupted GluRδ2 gene (GluRδ2−/−) display impaired synapse formation and abrogated long‐term depression (LTD). However, the mechanisms by which GluRδ2 functions have remained unclear. Because a GluRδ2 mutation in lurcher mice causes channel activities characterized by Ca2+ permeability, GluRδ2 was previously suggested to serve as a Ca2+‐permeable channel in Purkinje cells. To test this hypothesis, we introduced a GluRδ2 transgene, which had a mutation (Gln618Arg) in the putative channel pore, into GluRδ2−/− mice. Interestingly, the mutant transgene rescued the major functional and morphological abnormalities of GluRδ2−/− Purkinje cells, such as enhanced paired‐pulse facilitation, impaired LTD at parallel fibre synapses, and sustained innervation by multiple climbing fibres. These results indicate that the conserved glutamine residue in the channel pore, which is crucial for all Ca2+‐permeable glutamate receptors, is not essential for the function of GluRδ2.
A Membrane Receptor for Retinol Binding Protein Mediates Cellular Uptake of Vitamin A
Authors: Kawaguchi Riki , Yu Jiamei , Honda Jane , Hu Jane , Whitelegge Julian , Ping Peipei , Wiita Patrick , Bok Dean , Sun Hui
Published: January 2007

Vitamin A has diverse biological functions. It is transported in the blood as a complex with retinol binding protein (RBP), but the molecular mechanism by which vitamin A is absorbed by cells from the vitamin A–RBP complex is not clearly understood. We identified in bovine retinal pigment epithelium cells STRA6, a multitransmembrane domain protein, as a specific membrane receptor for RBP. STRA6 binds to RBP with high affinity and has robust vitamin A uptake activity from the vitamin A–RBP complex. It is widely expressed in embryonic development and in adult organ systems. The RBP receptor represents a major physiological mediator of cellular vitamin A uptake.
Cadherin-11 in Synovial Lining Formation and Pathology in Arthritis
Authors: Lee David M. , Kiener Hans P. , Agarwal Sandeep K. , Noss Erika H. , Watts Gerald F. M. , Chisaka Osamu , Takeichi Masatoshi , Brenner Michael B.
Published: January 2007

The normal synovium forms a membrane at the edges of joints and provides lubrication and nutrients for the cartilage. In rheumatoid arthritis, the synovium is the site of inflammation, and it participates in an organized tissue response that damages cartilage and bone. We identified cadherin-11 as essential for the development of the synovium. Cadherin-11–deficient mice have a hypoplastic synovial lining, display a disorganized synovial reaction to inflammation, and are resistant to inflammatory arthritis. Cadherin-11 therapeutics prevent and reduce arthritis in mouse models. Thus, synovial cadherin-11 determines the behavior of synovial cells in their proinflammatory and destructive tissue response in inflammatory arthritis.
Photoelectron Spectroscopy on Small Anionic Copper-Carbonyl Clusters
Authors: Stanzel Jörg , Aziz Emad F. , Neeb Matthias , Eberhardt Wolfgang
Published: January 2007

Anion photoelectron spectroscopy in combination with density functional theory (DFT) calculations has been used to study mono- and dinuclear copper-carbonyl clusters Cun(CO)m- (n = 1, 2; m = 2-5). The adiabatic detachment energies of the anions have been measured which correspond to the electron affinities of the respective neutral species. The corresponding values are 0.95 eV for Cu(CO)2, 1.02 eV for Cu(CO)3, 1.04 eV for Cu(CO)4, 1.43 eV for Cu2(CO)4, and 1.19 eV for Cu2(CO)5. All spectra exhibit a pronounced vibrational fine structure on the adiabatic photodetachment peak. The energy splitting is close to the energy of the C-O stretching vibration of the neutral cluster (final state). The DFT calculations clearly indicate that in all clusters the highest occupied molecular orbital (HOMO) is a CO-derived π* orbital. Furthermore the calculations are used to give insight into geometry, frontier orbitals, vibrational frequencies and spin multiplicity of the neutral and anionic clusters.
Comparison of the Conformational Stability for Several Vinylhalomethanes and Silanes with Experiment Using MP2 Perturbation Theory and DFT
Authors: Förner Wolfgang , Badawi Hassan M.
Published: January 2007

In recent literature it was reported that the valence triple zeta basis set augmented by polarization functions is not too reliable for vinyl monohalo- and dihalomethanes and -silanes, the halogen being fluorine and chlorine. The major conclusion was that a valence triple zeta basis is too small to be augmented by polarization functions in a balanced way, at least on vinylmonofluoromethane. Thus we decided to apply the 6-311++G** basis set to the complete series of methanes, silanes and germanes (the latter ones are just added for completeness because no experimental data are available for them and, moreover, we published them already previously) and to compare the results to experimental data available in the literature to see whether the failures of this basis set show up in the complete series of molecules. In the literature we found five such molecules and the information which of the conformers is the most stable. Indeed we found that predictions on the relative stability of conformers in those systems with this basis set and MP2 as well as DFT are with a 60:40 chance, three being correct predictions and two being incorrect ones out of the five. However, since the energy differences are rather small in these systems and due to the fact that - as a consequence of twofold degeneracy of the gauche conformer on the potential curve of the torsional vibration - the abundances of the conformers in equilibrium do not change too much, we decided to calculate also vibrational spectra for three examples and to compare them also to experiment. It is reported that besides the failures in total energy (we have chosen two examples where predictions of the nature of the stable conformer are correct, and one where it is not), the vibrational spectra are rather well reproduced, especially when experimental energies are used to calculate abundances in equilibrium in the case where the prediction of the stable conformer failed.
ELECTRODE MATERIAL EFFECT ON CAPACITANCE AND LOSS TANGENT OF THE ORGANIC ZnPc SEMICONDUCTING THIN FILMS
Authors: ABU-HILAL A. O. , GOULD R. D. , ABU-TAHA M. I. , SALEH A. M.
Published: January 2007

The capacitance and loss tangent of thermally evaporated zinc phthalocyanine, ZnPc , semiconducting thin films were measured in the temperature range of 180–430 K and frequency between 0.1 and 20 kHz. Aluminum and gold electrical contact electrodes were employed to sandwich ZnPc films. For both electrode types, the capacitance and loss tangent showed strong dependence on both temperature and frequency. Such dependence is related to the relevant temperature and frequency range under consideration. The capacitance has strong temperature dependence for T>240 K and frequency below 3 kHz, while it becomes a constant at higher frequencies and all temperatures. The loss tangent dependence on temperature is more evident at low frequencies and a minimum or an indication of a minimum was observed in tan δ versus f curves. Loss tangent variation with temperature was not monotonic for all frequencies. An anomaly (maximum) in tan δ was observed approximately between 300 and 360 K. This maximum was attributed to the presence of oxygen molecules in the sample and their subsequent exhaustion as the temperature is increased. The behavior of capacitance and loss tangent (for both Al and Au -electrodes) may be explained qualitatively and successfully in terms of an equivalent circuit model.
DIAGRAMMATICS AND FEYNMAN RULES IN THE LAGRANGIAN THEORY BASED ON THE spl(2,1) GRADED ALGEBRA
Authors: ABECASIS C. , ZANDRON O. S.
Published: January 2007

From the path-integral method, the diagrammatics and Feynman rules for the Lagrangian theory based on the spl(2,1) graded algebra are constructed. The first-order Lagrangian we have obtained is written in terms of the graded Hubbard operators. By using functional techniques, the correlation generating functional is given in terms of the proper effective Lagrangian of the model. Once the Feynman rules, propagators and vertices were found, a physical discussion about the free propagators is given. Finally, the expressions of the boson self-energy and the renormalized boson propagator are used to study the hole effects on the magnetic properties of the high-T c cuprates.
MAGNETIC RESISTIVITY IN Bi2Sr2Ca(Cu1-xCox)2Od EPITAXIAL THIN FILMS
Authors: YANG T. R. , ILONCA G. , TOMA V. , BALINT P. , BODEA M.
Published: January 2007

The scaling behavior of the effective activation energy of high-quality epitaxial c-oriented Bi 2 Sr 2 Ca ( Cu 1-x Co x)2 O d thin films with 0≤x ≤0.025 has been studied as a function of temperature and magnetic field. For all samples, the effective activation energy scales as U(T, μoH)=Uo(1-T/T c )mHn with exponent m=1.25±0.03, n=-1/2 and the field scaling 1/μoH and -UμoH for thick films and ultra thin films, respectively. The results are discussed taking into account of the influence of the Co substitution with a model in which U(T, H) arises from plastic deformations of the viscous flux liquid above the vortex-glass transition temperature.
INFRARED, STRUCTURAL AND MAGNETIC PROPERTIES OF La0.67Ca0.33MnO3 COMPOUND
Authors: ADIGÜZEL H. İ , KOLAT V. S. , GENCER H. , SEÇKIN T. , ATALAY S.
Published: January 2007

La 0.67 Ca 0.33 MnO 3 samples prepared by polymeric precursor route method are investigated using the thermogravimetric, differential thermal analysis, X-ray powder diffraction, scanning electron microscope, infrared spectroscopy and magnetic measurements. The unit cell parameters and grain size for all the samples are refined using X-ray diffraction and scanning electron microscope. It is observed that the IR bands at about 400 cm-1 is are most likely due to Mn – O – Mn bending mode and the band at 600 cm-1 is the result of the in plane Mn – O stretching mode. Magnetization measurements indicated that the Curie temperature increases from 241.3 K for the sample sintered at 600°C to 268.86 K for the sample sintered at 1000°C as a function of sintering temperature. The magnetic entropy change reaches the maximum value of about 4.8 J/kg · K for the sample sintered at 1150°C at an applied field of 1 T.
DIAGONALIZATION OF A HAMILTONIAN DESCRIBING A SINGLE TWO-LEVEL ATOM INTERACTING WITH A TWO MODE AMPLIFIER
Authors: BRACKEN PAUL
Published: January 2007

A Hamiltonian which describes the interaction of a single atom with two photon modes is introduced. It is shown that the Hamiltonian can be diagonalized in a particular basis. The energies and an eigenvector basis set are obtained. Some quasi-probability densities are calculated using amplitudes determined with respect to the rotated basis. Some of the physical phenomena which are manifested in the calculations are discussed.
PERTURBATION OF AN INFINITE NETWORK OF IDENTICAL CAPACITORS
Authors: HIJJAWI R. S. , ASAD J. H. , SAKAJI A. J. , KHALIFEH J. M.
Published: January 2007

The capacitance between any two arbitrary lattice sites in an infinite square lattice is studied when one bond is removed (i.e. perturbed). A connection is made between the capacitance and the lattice Green's function of the perturbed network, where they are expressed in terms of those of the perfect network. The asymptotic behavior of the perturbed capacitance is investigated as the separation between the two sites goes to infinity. Finally, numerical results are obtained along different directions and a comparison is made with the perfect capacitances.
MAGNETIC RESPONSE IN 1D NON-INTERACTING MESOSCOPIC RINGS: LONG-RANGE HOPPING IN SHORTEST PATH
Authors: MAITI SANTANU K.
Published: January 2007

Persistent current and low-field magnetic susceptibility in single-channel normal metal rings threaded by a magnetic flux ϕ are studied in the tight-binding model considering long-range hopping of the electrons in shortest path. The higher order hopping integrals try to reduce the effect of disorder by delocalizing the energy eigenstates and accordingly, current amplitude in disordered rings is comparable to that of an ordered ring. The calculations of low-field magnetic susceptibility predict that the sign of the currents can be mentioned precisely for the rings with fixed number of electrons even in the presence of impurity in the rings. At low-fields current shows only diamagnetic sign in perfect rings irrespective of the total number of electrons, Ne. On the other hand, in disordered rings it exhibits diamagnetic and paramagnetic sign, respectively, for the rings with odd and even Ne. In the rings described by fixed chemical potentials μ, the sign of the low-field currents cannot be predicted precisely since then it strongly depends on the values of μ and the specific realizations of disordered configurations.
POSSIBLE QUANTITATIVE CRITERIA FOR THE MOTT AND ANDERSON TRANSITIONS IN DOPED UNCOMPENSATED SYSTEMS
Authors: DZHUMANOV S. , KURBANOV U. T. , KURMANTAYEV A.
Published: January 2007

Metal-insulator transitions (MITs) in doped uncompensated systems are investigated in the Mott–Hubbard and Anderson impurity models by considering the intercarrier correlation and screening effect of carriers in the same hydrogenic impurity center, the formation of the superlattices with different coordination numbers (z=6, 8 and 12) and by studying the effect of randomness in impurity distribution. We have obtained simple and quite general criteria for the Mott and Anderson transitions and used these criteria to describe quantitatively the correlation and disorder-induced MITs in doped semiconductors and high-T c cuprates. We examine the validity of the obtained criteria for the Mott and Anderson MITs in these doped systems. It is found that the newly derived criteria for the Mott MIT are well satisfied in doped semiconductors, but they cannot be used to describe the observed MITs in the hole-doped high-T c cuprates, whereas the newly derived criteria for the Anderson MIT are applicable equally to describe the MITs observed both in doped semiconductors (at weak and intermediate disorders) and in doped cuprates (at intermediate and strong disorders). The new criteria for the Anderson MIT are extended to the polaronic systems in p-type cuprates. Our results are in quantitative agreement with the existing well-established experimental data and shed more light on the different types of MITs that occur in doped uncompensated semiconductors and cuprates.
POSITRONIUM FORMATION CROSS-SECTIONS FOR POSITRON SCATTERING BY RUBIDIUM ATOMS
Authors: EL-BAKRY SALAH YASEEN
Published: January 2007

Cross-sections for positron-rubidium (37Rb) scattering have been calculated using the Clementi–Roetti wavefunctions and a combination of the coupled-static and frozen-core approximations. The total cross-sections, calculated with eight partial waves corresponding to the total angular momentum ℓ=0 to ℓ=7, are determined over a wide region of scattering energies ranging from 2.7 to 300 eV. The resulting total cross-sections are compared with experimental results and those calculated by other authors. Our total collisional cross-sections display a pronounced peak at 5 eV, nearly consistent with the measurements of Parikh et al. [Phys. Rev. A47, 1535 (1993)] and also reveal another peak at 7 eV, consistent with the experimental cross-section of Stein et al.23 in the neighborhood of 7 eV. The oscillating behavior of our total collisional cross-sections supports the possible existence of resonance, especially at low energy region. The effect of positronium formation on the total collisional cross-sections diminishes when the incident energy is larger than 100 eV.
COMBINATION EFFECTS OF STRUCTURE NONUNIFORMITY OF PROTEINS ON THE SOLITON TRANSPORTED BIO-ENERGY
Authors: PANG XIAO-FENG , YU JIA-FENG , LAO YU-HUI
Published: January 2007

Combination effects of structure disorder of protein molecules containing the fluctuations of spring constant, dipole-dipole interaction constant and exciton-phonon coupling constant and diagonal disorder, resulting from nonuniform distribution of masses of amino acid residues and impurities, on the soliton transported the bio-energy in the proteins have been numerically simulated by fourth-order Runge–Kutta method in the improved model. The results obtained show that these structure disorders can change the states of solitons but as the solitons are quite robust against these disorder effects, they can only be dispersed or disrupted in the cases of quite large structure disorders. From these results and the properties of molecular structure of biological proteins we can conclude that the new soliton in the improved model is quite stable in normal conditions. Thus the soliton is possibly a carrier of bio-energy transport in the protein molecules.
HIERARCHICAL CUMULATIVE VOTING (HCV) — PRIORITIZATION OF REQUIREMENTS IN HIERARCHIES
Authors: BERANDER PATRIK , JÖNSSON PER
Published: January 2007

Decision support in requirements engineering is an activity that plays an important role in enabling the delivery of value to stakeholders. Requirements prioritization has been identified as an integral (and important) part of requirements negotiation and release planning in incremental software development, which makes prioritization a key issue in requirements engineering decision support. The Analytical Hierarchy Process (AHP) has for long been considered as the technique to use when prioritizing requirements on a ratio scale. Several studies have reported positively about AHP, but lately a number of studies have also reported about weaknesses, without identifying any better ratio-scale alternatives. In this paper, the strengths and weaknesses of AHP and another ratio-scale prioritization technique, Cumulative Voting (CV), are compared. Based on this comparison, a new technique for prioritizing hierarchically structured requirements on a ratio scale is presented, called Hierarchical Cumulative Voting (HCV). HCV addresses the weaknesses of AHP while inheriting the strengths of CV. The suitability of HCV is discussed theoretically as well as in the light of empirical results from using HCV and CV in industrial settings. It is concluded that HCV seems very promising, but additional empirical studies are needed to address some of the open questions about the technique.
BUILDING DECISION SUPPORT PROBLEM DOMAIN ONTOLOGY FROM NATURAL LANGUAGE REQUIREMENTS FOR SOFTWARE ASSURANCE
Authors: LEE SEOK-WON , MUTHURAJAN DIVYA , GANDHI ROBIN A. , YAVAGAL DEEPAK , AHN GAIL-JOON
Published: January 2007

The process of engineering software-intensive systems that comply with their Certification and Accreditation (C&A) requirements involves many critical decision-making activities for the related stakeholders. Considering the exhaustive nature of C&A activities together with the complexity of software-intensive systems, effective decision making relies heavily on the ways to understand and structure the problem domain concepts concerning decision points for interpretation, applicability, scope, evaluation, and impact of the enforced C&A requirements. These decision points are further complicated by natural language specifications of inherently non-functional C&A requirements scattered across multiple regulatory documents with complex interdependencies at different levels of abstractions in the organizational hierarchy, which often result in subjective interpretations and non-standard implementations of the C&A process. To address these issues, we define a systematic methodology using novel techniques from software Requirements Engineering (RE) and knowledge engineering for understanding and structuring the problem domain concepts based on a uniform representation format that promotes common understanding among stakeholders. Specifically, we use advanced ontological engineering techniques driven by theoretical RE foundations to systematically elicit, model, understand, and analyze problem domain concepts concerning significant and difficult decision points throughout the C&A process. We demonstrate the appropriateness of our methodology in creating decision support problem domain ontology using several examples derived from our experiences on automating the Department of Defense Information Technology Security C&A Process (DITSCAP).
A FRAMEWORK FOR THE EVALUATION OF REAL-TIME SPECIFICATION TECHNIQUES
Authors: KHWAJA AMIR A. , URBAN JOSEPH E.
Published: January 2007

Real-time and embedded software systems are becoming increasingly prevalent in everyday life. Well-defined and robust methods and methodologies are needed to support development and maintenance of such large and complex systems. Specification of a system is a critical phase of the development life cycle and has a major impact on the quality of a system. Formal specification languages and techniques are needed to be able to comprehensively and correctly define and prototype large and complex systems. The quality of a specification directly depends upon the capability of the language or technique used to express the specification. There is a need to determine language appropriateness for real-time systems. This paper establishes a real-time specification technique evaluation framework based on the features of real-time systems. The features are presented and the paper summarizes the result in terms of major features and their sub-features in a tabular form. This detailed list of features should serve not only to compare the techniques using a common framework, but also to determine the extent of real-time support that these techniques provide for specification. Application of the framework is demonstrated by testing a set of specification techniques for the specification of a real-time embedded cell phone software system.
Characterization of immunoisolated human gastric parietal cells tubulovesicles: identification of regulators of apical recycling
Authors: Lapierre Lynne A. , Avant Kenya M. , Caldwell Catherine M. , Ham Amy-Joan L. , Hill Salisha , Williams Janice A. , Smolka Adam J. , Goldenring James R.
Published: January 2007

Gastric parietal cells possess an amplified apical membrane recycling system dedicated to regulated apical recycling of H-K-ATPase. While amplified in parietal cells, apical recycling is critical to polarized secretory processes in most epithelial cells. To clarify putative regulators of apical recycling, we prepared immunoisolated parietal cell H-K-ATPase-containing recycling membranes from human stomachs and analyzed protein contents by tryptic digestion and mass spectrometry. We identified and validated by Western blots many of the proteins previously identified on immunoisolated rabbit tubulovesicles, including Rab11, Rab25, syntaxin 3, secretory carrier membrane proteins (SCAMPs), and vesicle-associated membrane protein (VAMP)2. In addition, we detected several previously unrecognized proteins, including Rab10, VAMP8, syntaxin 7, and syntaxin 12/13. We also identified the K+channel component KCNQ1. Immunostaining of human gastric mucosal sections confirmed the presence of each of these proteins in parietal cells and their colocalization with H-K-ATPase on tubulovesicles. To investigate the role of the identified soluble N-ethylmaleimide-sensitive factor attachment receptor (SNARE) proteins in apical recycling, we transfected them as DsRed2 fusions into an enhanced green fluorescent protein (EGFP)-Rab11a-expressing Madin-Darby canine kidney (MDCK) cell line. Syntaxin 12/13 and VAMP8 caused a collapse of the EGFP-Rab11a compartment, whereas a less dramatic effect was observed in cells transfected with syntaxin 3, syntaxin 7, or VAMP2. The five DsRed2-SNARE chimeras were also transfected into a MDCK cell line overexpressing Rab11-FIP2(129-512). All five of the chimeras were drawn into the collapsed apical recycling system. This study, which represents the first proteomic analysis of an immunoisolated vesicle population from native human tissue, demonstrates the diversity of putative regulators of the apical recycling system.
Caspase activity during cell stasis: avoidance of apoptosis in an invertebrate extremophile,Artemia franciscana
Authors: Menze Michael A. , Hand Steven C.
Published: January 2007

Evaluation of apoptotic processes downstream of the mitochondrion reveals caspase-9- and low levels of caspase-3-like activities in partly purified extracts of Artemia franciscana embryos. However, in contrast to experiments with extracts of human hepatoma cells, cytochrome c fails to activate caspase-3 or -9 in extracts from A. franciscana. Furthermore, caspase-9 activity is sensitive to exogenous calcium. The addition of 5 mM calcium leads to a 4.86 ± 0.19 fold (SD) ( n = 3) increase in activity, which is fully prevented with 150 mM KCl. As with mammalian systems, high ATP (>1.25 mM) suppresses caspase activity in A. franciscana extracts. A strong inhibition of caspase-9 activity was also found by GTP. Comparison of GTP-induced inhibition of caspase-9 at 0 and 2.5 mM MgCl2indicates that free (nonchelated) GTP is likely to be the inhibitory form. The strongest inhibition among all nucleotides tested was with ADP. Inhibition by ADP in the presence of Mg2+is 60-fold greater in diapause embryos than in postdiapause embryos. Because ADP does not change appreciably in concentration between the two physiological states, it is likely that this differential sensitivity to Mg2+-ADP is important in avoiding caspase activation during diapause. Finally, mixtures of nucleotides that mimic physiological concentrations in postdiapause and diapause states underscore the depressive action of these regulators on caspase-9 during diapause. Our biochemical characterization of caspase-like activity in A. franciscana extracts reveals that multiple mechanisms are in place to reduce the probability of apoptosis under conditions of energy limitation in this embryo.
Antagonistic effects of bone morphogenetic protein-4 and -7 on renal mesangial cell proliferation induced by aldosterone through MAPK activation
Authors: Otani Hiroyuki , Otsuka Fumio , Inagaki Kenichi , Takeda Masaya , Miyoshi Tomoko , Suzuki Jiro , Mukai Tomoyuki , Ogura Toshio , Makino Hirofumi
Published: January 2007

Aldosterone and angiotensin II (ANG II) contribute to the development and progression of renal damage. Here we investigated the effects of bone morphogenetic proteins (BMPs) on renal cell proliferation evoked by aldosterone and ANG II with mouse mesangial cells, which express mineralocorticoid receptors (MR), ANG II type 1 receptors, and BMP signaling molecules. Aldosterone and ANG II stimulated mesangial cell mitosis and activated ERK1/2 and SAPK/JNK signaling. These aldosterone effects were neutralized by the MR antagonist eplerenone and inhibition of transcription or translation, suggesting the involvement of genomic activation via MR. BMP-4 and BMP-7 stimulated Smad1, -5, -8 signaling more potently than BMP-2 and BMP-6, leading to suppression of mesangial cell mitosis and MR expression. MAPK inhibitors including U-0126 and SP-600125, but not SB-203580, suppressed aldosterone-induced cellular DNA synthesis, implying that ERK1/2 and SAPK/JNK pathways play crucial roles in mesangial cell proliferation. BMP-4 and BMP-7 inhibited phosphorylation of ERK1/2 and SAPK/JNK induced by aldosterone while activating p38 pathway, resulting in inhibition of aldosterone-induced cell mitosis. In contrast, aldosterone modulated the mesangial BMP system by decreasing expression of ALK-3, BMP-4, and BMP-7 while increasing inhibitory Smad6 expression. Thus novel functional cross talk between the mesangial BMP system and aldosterone signaling was uncovered, in which inhibition of MAPK signaling and MR expression by BMP-4 and BMP-7 may be involved in ameliorating renal damage due to mesangial proliferation caused by aldosterone.
A single bout of exercise activates matrix metalloproteinase in human skeletal muscle
Authors: Rullman E. , Rundqvist H. , Wågsäter D. , Fischer H. , Eriksson P. , Sundberg C. J. , Jansson E. , Gustafsson T.
Published: January 2007

The aims of this study were 1) to characterize changes in matrix metalloproteinase (MMP), endostatin, and vascular endothelial growth factor (VEGF)-A expression in skeletal muscle in response to a single bout of exercise in humans; and 2) to determine if any exchange of endostatin and VEGF-A between circulation and the exercising leg is associated with a change in the tissue expression or plasma concentration of these factors. Ten healthy males performed 65 min of cycle exercise, and muscle biopsies were obtained from the vastus lateralis muscle at rest and immediately and 120 min after exercise. In the muscle biopsies, measurements of mRNA expression levels of MMP-2, MMP-9, MMP-14, and tissue inhibitor of metalloproteinase; VEGF and endostatin protein levels; and MMP activities were performed. Femoral arterial and venous concentrations of VEGF-A and endostatin were determined before, during, and 120 min after exercise. A single bout of exercise increased MMP-9 mRNA and activated MMP-9 protein in skeletal muscle. No measurable increase of endostatin was observed in the skeletal muscle or in plasma following exercise. A concurrent increase in skeletal muscle VEGF-A mRNA and protein levels was induced by exercise, with no signs of peripheral uptake from the circulation. However, a decrease in plasma VEGF-A concentration occurred following exercise. Thus 1) a single bout of exercise activated the MMP system without any resulting change in tissue endostatin protein levels, and 2) the increased VEGF-A protein levels are due to changes in the skeletal muscle tissue itself. Other mechanisms are responsible for the observed exercise-induced decrease in VEGF-A in plasma.
Effects of intensity and duration of exercise on muscular responses to training of thoroughbred racehorses
Authors: Rivero José-Luis L. , Ruz Antonio , Martí-Korff Silvia , Estepa José-Carlos , Aguilera-Tejero Escolástico , Werkman Jutta , Sobotta Mathias , Lindner Arno
Published: January 2007

This study examined the effects of the intensity and duration of exercise on the nature and magnitude of training adaptations in muscle of adolescent (2–3 yr old) racehorses. Six thoroughbreds that had been pretrained for 2 mo performed six consecutive conditioning programs of varying lactate-guided intensities [velocities eliciting blood lactate concentrations of 2.5 mmol/l (v2.5) and 4 mmol/l (v4), respectively] and durations (5, 15, 25 min). Pre- and posttraining gluteus muscle biopsies were analyzed for myosin heavy chain content, fiber-type composition, fiber size, capillarization, and fiber histochemical oxidative and glycolytic capabilities. Although training adaptations were similar in nature, they varied greatly in magnitude among the different training protocols. Overall, the use of v4 as the exercise intensity for 25 min elicited the most consistent training adaptations in muscle, whereas the minimal training stimulus that evoked any significant change was identified with exercises of 15 min at v2.5. Within this range, muscular adaptations showed significant trends to be proportional to the exercise load of specific training programs. Taken together, these data suggest that muscular adaptations to training in horses occur on a continuum that is based on the exercise intensity and duration of training. The practical implications of this study are that exercises for 15 to 25 min/day at velocities between v2.5 and v4 can improve in the short term (3 wk) the muscular stamina in thoroughbreds. However, exercises of 5–15 min at v4 are necessary to enhance muscular features related to strength (hypertrophy).