A Complex Network Approach to Topographical Connections

The neuronal networks in the mammals cortex are characterized by the coexistence of hierarchy, modularity, short and long range interactions, spatial correlations, and topographical connections. Particularly interesting, the latter type of organization implies special demands on the evolutionary and ontogenetic systems in order to achieve precise maps preserving spatial adjacencies, even at the expense of isometry. Although object of intensive biological research, the elucidation of the main anatomic-functional purposes of the ubiquitous topographical connections in the mammals brain remains an elusive issue. The present work reports on how recent results from complex network formalism can be used to quantify and model the effect of topographical connections between neuronal cells over a number of relevant network properties such as connectivity, adjacency, and information broadcasting. While the topographical mapping between two cortical modules are achieved by connecting nearest cells from each module, three kinds of network models are adopted for implementing intracortical connections (ICC), including random, preferential-attachment, and short-range networks. It is shown that, though spatially uniform and simple, topographical connections between modules can lead to major changes in the network properties, fostering more effective intercommunication between the involved neuronal cells and modules. The possible implications of such effects on cortical operation are discussed.Comment: 5 pages, 5 figure

Oscillator Strength of Metallic Carbon Nanotubes

Based on the tight binding method with hopping integral between the nearest-neighbor atoms, an oscillator strength \int_0^{\infty} \d \omega {\rm Re} \sigma (\omega) is discussed for armchair and metallic zigzag carbon nanotubes. The formulae of the oscillator strength are derived for both types of nanotubes and are compared with the result obtained by a linear chain model. In addition, the doping dependence is investigated in the absence of Coulomb interaction. It is shown that the oscillator strength of each carbon nanotube shows qualitatively the same doping dependence, but the fine structure is different due to it's own peculiar band structure. Some relations independent of the radius of the tube are derived, and a useful formula for determining the amount of doping is proposed.Comment: 4 pages, 4 figures, submitted to J. Phys. Soc. Jpn. at June 30, 200

FEMTOSECOND RESPONSE OF OPTICAL CONSTANTS DUE TO CHARGE-TRANSFER EXCITATIONS IN Nd 2 CuO 4

We have performed femtosecond reflectivity ∆R/R and transmissivity ∆T /T measurements in Nd 2 CuO 4 thin film at 80 and 300 K. We have derived time variations of ∆ and ∆ from transient data of ∆R/R and ∆T /T . Assuming a Lorentz oscillator model consisting of three oscillators, we obtain spectra of the real part and imaginary part of dielectric function from the measured reflectivity and absorption spectra in the visible-uv region. The absorption bands in the visible region are assigned to in-plane charge-transfer (CT) excitations, and relaxation times of CT excitations are found to be 0.6 and 1.0 ps

Left ventricular non-compaction: clinical features and cardiovascular magnetic resonance imaging

Background: It is apparent that despite lack of family history, patients with the morphological characteristics of left ventricular non-compaction develop arrhythmias, thrombo-embolism and left ventricular dysfunction. METHODS: Forty two patients, aged 48.7 +/- 2.3 yrs (mean +/- SEM) underwent cardiovascular magnetic resonance (CMR) for the quantification of left ventricular volumes and extent of non-compacted (NC) myocardium. The latter was quantified using planimetry on the two-chamber long axis LV view (NC area). The patients included those referred specifically for CMR to investigate suspected cardiomyopathy, and as such is represents a selected group of patients. RESULTS: At presentation, 50% had dyspnoea, 19% chest pain, 14% palpitations and 5% stroke. Pulmonary embolism had occurred in 7% and brachial artery embolism in 2%. The ECG was abnormal in 81% and atrial fibrillation occurred in 29%. Transthoracic echocardiograms showed features of NC in only 10%. On CMR, patients who presented with dyspnoea had greater left ventricular volumes (both p < 0.0001) and a lower left ventricular ejection fraction (LVEF) (p < 0.0001) than age-matched, healthy controls. In patients without dyspnoea (n = 21), NC area correlated positively with end-diastolic volume (r = 0.52, p = 0.0184) and end-systolic volume (r = 0.56, p = 0.0095), and negatively with EF (r = -0.72, p = 0.0001). CONCLUSION: Left ventricular non-compaction is associated with dysrrhythmias, thromboembolic events, chest pain and LV dysfunction. The inverse correlation between NC area and EF suggests that NC contributes to left ventricular dysfunction

Effect of Stalling after Mismatches on the Error Catastrophe in Nonenzymatic Nucleic Acid Replication

The frequency of errors during genome replication limits the amount of functionally important information that can be passed on from generation to generation. During the origin of life, mutation rates are thought to have been quite high, raising a classic chicken-and-egg paradox: could nonenzymatic replication propagate sequences accurately enough to allow for the emergence of heritable function? Here we show that the theoretical limit on genomic information content may increase substantially as a consequence of dramatically slowed polymerization after mismatches. As a result of postmismatch stalling, accurate copies of a template tend to be completed more rapidly than mutant copies and the accurate copies can therefore begin a second round of replication more quickly. To quantify this effect, we characterized an experimental model of nonenzymatic, template-directed nucleic acid polymerization. We found that most mismatches decrease the rate of primer extension by more than 2 orders of magnitude relative to a matched (Watson-Crick) control. A chemical replication system with this property would be able to propagate sequences long enough to have function. Our study suggests that the emergence of functional sequences during the origin of life would be possible even in the face of the high intrinsic error rates of chemical replication

Serum uric acid distribution according to SLC22A12 W258X genotype in a cross-sectional study of a general Japanese population

<p>Abstract</p> <p>Background</p> <p>Although <it>SLC22A12 258X </it>allele was found among those with hypouricemia, it was unknown that serum uric acid distribution among those with <it>SLC22A12 258X </it>allele. This study examined serum uric acid (SUA) distribution according to <it>SLC22A12 </it>W258X genotype in a general Japanese population.</p> <p>Methods</p> <p>Subjects were 5,023 health checkup examinees (3,413 males and 1,610 females) aged 35 to 69 years with creatinine < 2.0 mg/dL, who were participants of a cohort study belonging to the Japan Multi-Institutional Collaborative Cohort Study (J-MICC Study). <it>SLC22A12 </it>W258X was genotyped with a polymerase chain reaction with confronting two-pair primers.</p> <p>Results</p> <p>The genotype frequency was 4,793 for <it>WW</it>, 225 for <it>WX</it>, and 5 for <it>XX</it>, which was in Hardy-Weinberg equilibrium (p = 0.164) with <it>X </it>allele 0.023 (95% confidence interval [0.021-0.027]). Mean (range) SUA was 6.2 (2.1-11.4) mg/dL for <it>WW</it>, 3.9 (0.8-7.8) mg/dL for <it>WX</it>, and 0.8 (0.7-0.9) mg/dL for <it>XX </it>among males, and 4.5 (1.9-8.9) mg/dL, 3.3 (2.0-6.5) mg/dL, and 0.60 (0.5-0.7) mg/dL among females, respectively. Six individuals with SUA less than 1.0 mg/dL included two males with <it>XX </it>genotype, one male with <it>WX </it>genotype, and three females with <it>XX </it>genotype. Subjects with <it>WX </it>genotype were 14 (77.8%) of 18 males with a SUA of 1.0-2.9 mg/dL, and 28 (34.6%) of 81 females with the same range of SUA. The corresponding values were 131 (25.1%) of 522 males and 37 (3.5%) of 1,073 females for SUA 3.0-4.9 mg/dL, and 8 (0.4%) of 2,069 males and 5 (1.1%) of 429 females for SUA 5.0-6.9 mg/dL. The <it>X </it>allele effect for SUA less than 3 mg/dL was significantly (p < 0.001) higher in males (OR = 102.5, [33.9-309.8]) than in females (OR = 25.6 [14.4-45.3]).</p> <p>Conclusions</p> <p>Although <it>SLC22A12 </it>W258X was a determining genetic factor on SUA, SUA of those with <it>WX </it>genotype distributed widely from 0.8 mg/dL to 7.8 mg/dL. It indicated that other genetic traits and/or lifestyle affected SUA of those with <it>WX </it>genotype, as well as those with <it>WW </it>genotype.</p

Aharonov-Bohm spectral features and coherence lengths in carbon nanotubes

The electronic properties of carbon nanotubes are investigated in the presence of disorder and a magnetic field parallel or perpendicular to the nanotube axis. In the parallel field geometry, the $\phi_{0}(=hc/e)$-periodic metal-insulator transition (MIT) induced in metallic or semiconducting nanotubes is shown to be related to a chirality-dependent shifting of the energy of the van Hove singularities (VHSs). The effect of disorder on this magnetic field-related mechanism is considered with a discussion of mean free paths, localization lengths and magnetic dephasing rate in the context of recent experiments.Comment: 22 pages, 6 Postscript figures. submitted to Phys. Rev.

The effect of crack orientation on the nonlinear interaction of a P wave with an S wave

Cracks, joints, fluids, and other pore-scale structures have long been hypothesized to be the cause of the large elastic nonlinearity observed in rocks. It is difficult to definitively say which pore-scale features are most important, however, because of the difficulty in isolating the source of the nonlinear interaction. In this work, we focus on the influence of cracks on the recorded nonlinear signal and in particular on how the orientation of microcracks changes the strength of the nonlinear interaction. We do this by studying the effect of orientation on the measurements in a rock with anisotropy correlated with the presence and alignment of microcracks. We measure the nonlinear response via the traveltime delay induced in a low-amplitude P wave probe by a high-amplitude S wave pump. We find evidence that crack orientation has a significant effect on the nonlinear signal

A Comprehensive Resource for Induced Pluripotent Stem Cells from Patients with Primary Tauopathies.

Primary tauopathies are characterized neuropathologically by inclusions containing abnormal forms of the microtubule-associated protein tau (MAPT) and clinically by diverse neuropsychiatric, cognitive, and motor impairments. Autosomal dominant mutations in the MAPT gene cause heterogeneous forms of frontotemporal lobar degeneration with tauopathy (FTLD-Tau). Common and rare variants in the MAPT gene increase the risk for sporadic FTLD-Tau, including progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD). We generated a collection of fibroblasts from 140 MAPT mutation/risk variant carriers, PSP, CBD, and cognitively normal controls; 31 induced pluripotent stem cell (iPSC) lines from MAPT mutation carriers, non-carrier family members, and autopsy-confirmed PSP patients; 33 genome engineered iPSCs that were corrected or mutagenized; and forebrain neural progenitor cells (NPCs). Here, we present a resource of fibroblasts, iPSCs, and NPCs with comprehensive clinical histories that can be accessed by the scientific community for disease modeling and development of novel therapeutics for tauopathies

Chlorotetracycline As An Indicator Of The Interaction Of Calcium With Brain Membrane Fractions

The fluorescence of chlorotetracycline (CTC) in the presence of synaptosomes isolated from sheep brain is selectively increased by Ca2+ under conditions in which Mg2+, Na+, K+, Li+ or choline have only a small effect. The monovalent cations release bound Ca2+ from synaptosomes, and this effect is reflected by a decrease in the CTC fluorescence. Under optimal conditions there is a near parallelism between Ca2+ and CTC binding to the synaptosomes membranes, and Li+ is the monovalent cation tested which interferes the most with the binding of both substances. These results obtained in a predominantly sucrose medium become less distinct when media simulating physiological composition are utilized, which limits the usefulness of the method. Brain mitochondria and myelin also bind Ca2+ and CTC. The ratio of the fluorescence signal (or CTC bound) to Ca2+ bound is highest of all for mitochondrial membranes, and the apparent fluorescence quantum yield of CTC is also the highest in these membranes, which suggests that the Ca2+ in these membranes is localized in a more apolar region than is the case for synaptosomes and myelin