[A model of primary open-angle glaucoma: manifestations and outcomes].

OBJECTIVE: To determine the expected duration of the disease and the age of the patients with different stages ofprimary open-angle glaucoma complicated by pseudoexfoliation syndrome (PES) and/or patients with pseudoexfoliation glaucoma (PEG). METHODS: The study protocol included data from 120 patients (50 males (41.7%), 70 females (58.3%)); 189 eyes; 102 right eyes; 87 left eyes). The first study group (28 patients, 44 eyes) comprised patients with suspected glaucoma. The second group (53 patients, 84 eyes) consisted ofpatients with early glaucoma. The third group (21 patient, 33 eyes) included patients with advanced glaucoma, the forth group (18 patients, 28 eyes) comprised patients with terminal glaucoma. Mean age of the patients at diagnosis was 61.6 (58.4; 66.9) years and 66.9 (63.4; 72.8) years at the endpoint visit in 2013. In all cases, diagnosis was made in accordance with the differential diagnostics system and confirmed by special diagnostic techniques. The database included data from 3 qualified examinations taking account of the results of tonometry and static automated perimetry. RESULTS: The mean expected age of the patients age at the onset of blindness was 75.1 years. The occurrence of the event was limited to a period of 6.1 years. Mean age at the time of possible glaucoma development was 59.58 (56.14; 64.36) years. The disease itself could develop within 3.24 (-5.38; -1.2) years prior to diagnosis. CONCLUSION: Studies for glaucoma diagnosis should be focused on the age group of 55-60 years. The degree of IOP reduction in patients with advanced glaucoma does not agree with the Russian glaucoma society recommendations which accounts for progression of the disease.

Extraordinary magnetoresistance in graphite: experimental evidence for the time-reversal symmetry breaking.

We report a highly anisotropic in-plane magnetoresistance (MR) in graphite that possesses in-plane parallel line-like structural defects. In a current direction perpendicular to the line defects (LD), MR is negative and linear in low fields with a crossover to a positive MR at higher fields, while in a current direction parallel to LD, we observed a giant super-linear positive MR. These extraordinary MRs are respectively explained by a hopping magnetoresistance via non-zero angular momentum orbitals, and by the magnetoresistance of inhomogeneous media. The linear negative orbital MR is a unique signature of the broken time-reversal symmetry (TRS). We discuss the origin of the disorder-induced TRS-breaking in graphite.

Molecular dynamics simulations of oxide memory resistors (memristors).

Reversible bipolar nanoswitches that can be set and read electronically in a solid-state two-terminal device are very promising for applications. We have performed molecular dynamics simulations that mimic systems with oxygen vacancies interacting via realistic potentials and driven by an external bias voltage. The competing short- and long-range interactions among charged mobile vacancies lead to density fluctuations and short-range ordering, while illustrating some aspects of observed experimental behavior, such as memristor polarity inversion. The simulations show that the 'localized conductive filaments' and 'uniform push/pull' models for memristive switching are actually two extremes of the one stochastic mechanism.

Unconventional high-temperature superconductivity from repulsive interactions: theoretical constraints.

Unconventional symmetries of the order parameter allowed some researchers to maintain that a purely repulsive interaction between electrons provides superconductivity without phonons in a number of high-temperature superconductors. It is shown that the Cooper pairing in p and d states is not possible with the realistic Coulomb repulsion between fermions at relevant temperatures in any dimension.

Superconducting gap, normal state pseudogap, and tunneling spectra of bosonic and cuprate superconductors.

We develop a theory of normal metal-superconductor and superconductor tunneling in "bosonic" superconductors with strong attractive correlations taking into account coherence effects in single-particle excitation spectrum and disorder. The theory accounts for the existence of two energy scales, their temperature and doping dependencies, asymmetry, and inhomogeneity of tunneling spectra of underdoped cuprate superconductors.

Key pairing interaction in layered doped ionic insulators.

A controversial issue on whether the electron-phonon interaction (EPI) is crucial for high-temperature superconductivity or it is weak and inessential has remained one of the most challenging problems of contemporary condensed matter physics. We employ a continuum random phase approximation for the dielectric response function allowing for a self-consistent semianalytical evaluation of the EPI strength, electron-electron attractions, and the carrier mass renormalization in layered high-temperature superconductors. We show that the Fröhlich EPI with high-frequency optical phonons in doped ionic lattices is the key pairing interaction, which is beyond the BCS-Migdal-Eliashberg approximation in underdoped superconductors, and it remains a significant player in overdoped compounds.

Electron-phonon coupling in high-temperature cuprate superconductors determined from electron relaxation rates.

We determined electronic relaxation times via pump-probe optical spectroscopy using sub-15 fs pulses for the normal state of two different cuprate superconductors. We show that the primary relaxation process is the electron-phonon interaction and extract a measure of its strength, the second moment of the Eliashberg function λ[ω2] = 800 ± 200 meV2 for La(1.85)Sr(0.15)CuO4 and λ[ω2] = 400 ± 100 meV2 for YBa(2)Cu(3)O(6.5). These values suggest a possible fundamental role of the electron-phonon interaction in the superconducting pairing mechanism.

Theory of extrinsic and intrinsic tunnelling in cuprate superconductors.

There has been a huge theoretical and experimental push to try to illuminate the mechanism behind the high-temperature superconductivity of copper oxides. Cuprates are distinguishable from conventional metallic superconductors in originating from the doping of the parent charge-transfer insulators. The superconducting parts are weakly coupled two-dimensional doped layers held together by the parent lattice. Apart from their high-T(c) they have other characteristic features including the 'superconducting' gap (SG) which develops below the superconducting critical temperature and can be seen in extrinsic and intrinsic tunnelling experiments as well as using high-resolution angle-resolved photoemission (ARPES); there also exists another energy gap, the 'pseudogap' (PG), which is a large anomalous gap that exists well above T(c). We present a brief review of recent theories behind the pseudogap and discuss in detail one specific (polaronic) approach which explains the SG, PG and unusual tunnelling characteristics of cuprate superconductors.

Diamagnetism of real-space pairs above T(c) in hole doped cuprates.

The nonlinear normal state diamagnetism reported by Li et al (2010 Phys. Rev. B 81 054510) is shown to be incompatible with a claimed Cooper pairing and vortex liquid above the resistive critical temperature. However, it is perfectly compatible with the normal state Landau diamagnetism of real-space composed bosons, which provides a description of the nonlinear magnetization curves of the less anisotropic cuprates La-Sr-Cu-O (LSCO) and Y-Ba-Cu-O (YBCO) as well as for strongly anisotropic bismuth-based cuprates over the whole range of available magnetic fields.

Increased plasma endothelin level as an endothelial marker of cardiovascular risk in patients with active acromegaly: a comparison with plasma homocysteine.

The aim of the present study was to evaluate the plasma endothelin-1 (ET-1) and total homocysteine (tHcy) levels as biochemical markers of endothelial dysfunction and atherosclerosis in patients with active and cured acromegaly in order to assess the relationship between the secretory status of growth hormone (GH)/insulin-like growth factor I (IGF-I) and ET-1/tHcy levels. The patients were divided in two subgroups: 1) patients with active disease (n = 30); and 2) patients with nonactive cured acromegaly (n = 21). Plasma ET-1 levels were directly determined by a highly sensitive enzyme immunoassay and plasma tHcy concentrations were measured by a fluorescence polarization immunoassay. In active acromegaly subjects, plasma ET-1 levels were 1.24 +/- 0.2 pmol/L, significantly higher than in both nonactive acromegalics (0.39 +/- 0.1 pmol/L) and age-matched healthy controls (0.49 +/- 0.2 pmol/L) (P < 0.001). Plasma tHcy concentrations, however, did not differ significantly in all studied groups: nonactive acromegalics: 9.54 +/- 4.42 micromol/L; active acromegalics: 9.0 +/- 3.14 micromol/L; and control subjects: 9.96 +/- 2.95 micromol/L (P > 0.05). In conclusion, our study demonstrated that elevated ET-1 levels probably contributed to premature atherosclerosis and cardiovascular disease and represent a new risk factor for endothelial dysfunction and early vascular complications in acromegaly. We propose that GH and IGF-I secretory status are important determinants of plasma ET-1 but not tHcy levels.

Zero-temperature phase transitions in dilute bosonic superfluids on a lattice.

Kinetic energy driven phase transitions in Bose superfluids occur at low values of the repulsion when the values of the next-to-nearest and next-to-next-to-nearest hopping term attain certain critical values, resulting in alterations in the wavevector of the condensate. We map out the space of possible phases allowed by particular forms of the single-particle energy dispersion in the superfluid state, noting the appearance of a new phase, and examine in more detail the effects of additional repulsive terms on the form of the condensate wavefunction. We also examine the effect of these additional hopping terms on the formation of inhomogeneities in the condensate.

Superlight small bipolarons in the presence of a strong Coulomb repulsion.

We study a lattice bipolaron on a staggered triangular ladder and triangular and hexagonal lattices with both long-range electron-phonon interaction and strong Coulomb repulsion using a novel continuous-time quantum Monte Carlo algorithm to solve the two-particle Coulomb-Fröhlich model. The algorithm is preceded by an exact integration over phonon degrees of freedom, and as such is extremely efficient. The bipolaron effective mass and radius are computed. Bipolarons on lattices constructed from triangular plaquettes have a novel crablike motion, and are small but very light over a wide range of parameters. We discuss the conditions under which such particles may form a Bose-Einstein condensate with high transition temperature, proposing a route to room temperature superconductivity.

Simulating focal demyelinating neuropathies: membrane property abnormalities.

Membrane properties such as potentials (intracellular, extracellular, electrotonic) and axonal excitability indices (strength-duration and charge-duration curves, strength-duration time constants, rheobasic currents, recovery cycles) can now be measured in healthy subjects and patients with demyelinating neuropathies. They are regarded here in two cases of simultaneously reduced paranodal seal resistance and myelin lamellae in one to three consecutive internodes of human motor nerve fiber. The investigations are performed for 70 and 96% myelin reduction values. The first value is not sufficient to develop a conduction block, but the second leads to a block and the corresponding demyelinations are regarded as mild and severe. For both the mild and severe demyelinations, the paranodally internodally focally demyelinated cases (termed as PIFD1, PIFD2, and PIFD3, respectively, with one, two, and three demyelinated internodes) are simulated using our previous double-cable model of the fiber. The axon model consists of 30 nodes and 29 internodes. The membrane property abnormalities obtained can be observed in vivo in patients with demyelinating forms of Guillain-Barré syndrome (GBS) and multifocal motor neuropathy (MMN). The study confirms that focal demyelinations are specific indicators for acquired demyelinating neuropathies. Moreover, the following changes have been calculated in our previous papers: (1) uniform reduction of myelin thickness in all internodes (Stephanova et al. in Clin Neurophysiol 116: 1153-1158, 2005); (2) demyelination of all paranodal regions (Stephanova and Daskalova in Clin Neurophysiol 116: 1159-1166, 2005a); (3) simultaneous reduction of myelin thickness and paranodal demyelination in all internodes (Stephanova and Daskalova in Clin Neurophysiol 116: 2334-2341, 2005b); and (4) reduction of myelin thickness of up to three internodes (Stephanova et al., in J Biol Phys, 2006a,b, DOI: 10.1007/s10867-005-9001-9; DOI: 10.1007/s10867-006-9008-x). The membrane property abnormalities obtained in the homogeneously demyelinated cases are quite different and abnormally greater than those in the case investigated here of simultaneous reduction in myelin thickness and paranodal demyelination of up to three internodes. Our previous and present results show that unless focal demyelination is severe enough to cause outright conduction block, changes are so slight as to be essentially indistinguishable from normal values. Consequently, the excitability-based approaches that have shown strong potential as diagnostic tools in systematically demyelinated conditions may not be useful in detecting mild focal demyelinations, independently of whether they are internodal, paranodal, or paranodal internodal.

Normal-state diamagnetism of charged bosons in cuprate superconductors.

Normal-state orbital diamagnetism of charged bosons quantitatively accounts for recent high-resolution magnetometery results near and above the resistive critical temperature T(c) of superconducting cuprates. The parameter-free descriptions of normal-state diamagnetism, T(c), upper critical fields, and specific heat anomalies support the 3D Bose-Einstein condensation of preformed real-space pairs with a zero off-diagonal order parameter above T(c) at variance with phase fluctuation scenarios of cuprates.

Phase coexistence and resistivity near the ferromagnetic transition of manganites.

Pairing of oxygen holes into heavy bipolarons in the paramagnetic phase and their magnetic pair breaking in the ferromagnetic phase (the so-called current-carrier density collapse) has accounted for the first-order ferromagnetic-phase transition, colossal magnetoresistance, isotope effect, and pseudogap in doped manganites. Here we propose an explanation of the phase coexistence and describe the magnetization and resistivity of manganites near the ferromagnetic transition in the framework of the current-carrier density collapse. The present quantitative description of resistivity is obtained without any fitting parameters, by using the experimental resistivities far away from the transition and the experimental magnetization, and is essentially model-independent.

Simulating mild systematic and focal demyelinating neuropathies: membrane property abnormalities.

This study provides numerical simulations of some of the abnormalities in the potentials and axonal excitability indices of human motor nerve fibers in simulated cases of internodal, paranodal and simultaneously of paranodal internodal demyelinations, each of them systematic or focal. A 70% reduction of the myelin lamellae (defining internodal demyelination), or of the paranodal seal resistance (defining paranodal demyelination), or simultaneously both of them (defining paranodal internodal demyelination) was uniform along the fiber length for the systematically demyelinated subtypes. These permutations were termed internodal systematic demyelination (ISD), paranodal systematic demyelination (PSD) and paranodal internodal systematic demyelination (PISD). In other tests, the same reductions of the myelin sheath parameters were used but restricted to only three (8th, 9th and 10th) consecutive internodes. Such fiber demyelinations were termed internodal focal demyelination (IFD), paranodal focal demyelination (PFD) and paranodal internodal focal demyelination (PIFD). The computations used our previous double cable model of the fibers. The axon model was comprised of 30 nodes and 29 internodes. The 70% reduction value was not sufficient to develop conduction block in all investigated demyelinations, which were regarded as mild. The membrane property abnormalities obtained in the ISD, PSD and PISD cases were quite different and abnormally greater than those in the IFD, PFD and PIFD cases. The changes in the excitability indices such as strength-duration time constants, rheobasic currents and recovery cycles in the focally demyelinated subtypes were so slight as to be essentially indistinguishable from normal values. Consequently, the excitability based approaches that have shown strong potential as diagnostic tools in systematically demyelinated conditions may not be useful in detecting mild focal demyelinations. The membrane property changes simulated in the systematically demyelinated subtypes are in good accordance with the data from patients with Charcot-Marie-Tooth disease type 1A (CMT1A) and chronic inflammatory demyelinating polyneuropathy (CIDP). The excitability abnormalities obtained in each focally demyelinated subtype match those observed in vivo in patients with demyelinating forms of Guillain-Barré syndrome (GBS). The results indicate that the model that was used is a rather promising tool in studying the membrane property abnormalities of hereditary, chronic and acquired demyelinating neuropathies, which up till now, have not been sufficiently well understood.

Differences in membrane properties in simulated cases of demyelinating neuropathies: internodal focal demyelinations without conduction block.

The membrane properties (intracellular, extracellular, electrotonic potentials, strength-duration time constants, rheobasic currents and recovery cycles), which can now be measured in healthy subjects and patients with demyelinating neuropathies, are investigated in simulated cases of focal reduction (70%) of the myelin sheath in one, two and three successive internodal segments along the length of human motor fibres. The internodally focally demyelinated cases (termed as IFD1, IFD2 and IFD3, respectively) are simulated using our previous double cable model of the fibres. The results show that the intracellular potentials are with reduced amplitude and slowed conduction velocity in the vicinity of demyelinated segments, however the segmental conduction block is not achieved. The radial decline of the extracellular potential amplitudes slightly increases with the increase of the radial distance and demyelination. In contrast, the electrotonic potentials, strength-duration time constants and rheobases are normal. In the recovery cycles, the refractoriness, supernormality and less late subnormality are close to the normal, showing that the pathology is relatively minor. The obtained abnormalities in the potentials and excitability properties provide new information about the pathophysiology of the demyelinated human motor axons and can be observed in vivo in patients with acquired demyelinating neuropathies.

Differences in membrane properties in simulated cases of demyelinating neuropathies: internodal focal demyelinations with conduction block.

The aim of this study is to investigate the membrane properties (potentials and axonal excitability indices) in the case of myelin wrap reduction (96%) in one, two and three consecutive internodes along the length of human motor nerve fibre. The internodally focally demyelinated cases (termed as IFD1, IFD2 and IFD3, respectively, with one, two and three demyelinated internodes are simulated using our previous double cable model of the fibre. The progressively greater increase of focal loss of myelin lamellae blocks the invasion of the intracellular potentials into the demyelinated zones. For all investigated cases, the radial decline of the extracellular potential amplitudes increases with the increase of the radial distance and demyelination, whereas the electrotonic potentials show a decrease in the slow part of the depolarizing and hyperpolarizing responses. The time constants are shorter and the rheobases higher for the IFD2 and IFD3 cases than for the normal case. In the recovery cycles, the same cases have less refractoriness, greater supernormality and less late subnormality than the normal case. The simulated membrane abnormalities can be observed in vivo in patients with demyelinating forms of Guillain-Barré syndrome. The study provides new information about the pathophysiology of acquired demyelinating neuropathies.

Magnetic quantum oscillations in nanowires.

Analytical expressions for the magnetization and the longitudinal conductivity of nanowires are derived in a magnetic field, B. We show that the interplay between size and magnetic field energy-level quantizations manifests itself through novel magnetic quantum oscillations in metallic nanowires. There are three characteristic frequencies of de Haas-van Alphen (dHvA) and Shubnikov-de Haas (SdH) oscillations, F = F(0)/(1 + gamma)(3/2), and F(+/-) = 2F(0)/|1 + gamma +/- (1 + gamma)(1/2)|, in contrast with a single frequency F(0) = S(F)plankc/(2pie) in simple bulk metals. The amplitude of oscillations is strongly enhanced in some magic magnetic fields. The wire cross-section area S can be measured using the oscillations as S = 4pi(2)S(F)plank(2)c(2)/(gammae(2)B(2)) along with the Fermi-surface cross-section area, S(F).

The electrophysiological profile of hereditary motor and sensory neuropathy-Lom.

OBJECTIVE: To make electrophysiological observations on a large kindred with hereditary motor and sensory neuropathy-Lom (HMSN-L) containing 27 affected individuals. CLINICAL FINDINGS: Onset was in early childhood with gait difficulty related to progressive lower limb weakness. Upper limb weakness developed later. Bulbar involvement was present in one third of the patients, and deafness appeared during the second or third decades. ELECTROPHYSIOLOGICAL FINDINGS: Electromyographic evidence of denervation was progressive, more severe distally, and greater in the legs, being total in distal lower limb muscles in most patients. Sensory action potentials were absent and motor nerve conduction was severely slowed. This included proximal upper limb (musculocutaneous and axillary), hypoglossal, and facial nerves. The severity of slowing increased during childhood. M waves, often multiple, were recorded in all affected individuals. The blink reflex showed an unusual three component response. The latencies of all three components were prolonged. CONCLUSIONS: HMSN-L is shown to be a demyelinating neuropathy involving severe and early axonal loss. The progressive slowing of nerve conduction during childhood differs from the static reduction seen in type I HMSN.