Electrical Conductivity Studies on Individual Conjugated Polymer Nanowires: Two-Probe and Four-Probe Results

<p>Abstract</p> <p>Two- and four-probe electrical measurements on individual conjugated polymer nanowires with different diameters ranging from 20 to 190 nm have been performed to study their conductivity and nanocontact resistance. The two-probe results reveal that all the measured polymer nanowires with different diameters are semiconducting. However, the four-probe results show that the measured polymer nanowires with diameters of 190, 95&#8211;100, 35&#8211;40 and 20&#8211;25 nm are lying in the insulating, critical, metallic and insulting regimes of metal&#8211;insulator transition, respectively. The 35&#8211;40 nm nanowire displays a metal&#8211;insulator transition at around 35 K. In addition, it was found that the nanocontact resistance is in the magnitude of 10⁴&#937; at room temperature, which is comparable to the intrinsic resistance of the nanowires. These results demonstrate that four-probe electrical measurement is necessary to explore the intrinsic electronic transport properties of isolated nanowires, especially in the case of metallic nanowires, because the metallic nature of the measured nanowires may be coved by the nanocontact resistance that cannot be excluded by a two-probe technique.</p

Resonances in a chaotic attractor crisis of the Lorenz Flow

Local bifurcations of stationary points and limit cycles have successfully been characterized in terms of the critical exponents of these solutions. Lyapunov exponents and their associated covariant Lyapunov vectors have been proposed as tools for supporting the understanding of critical transitions in chaotic dynamical systems. However, it is in general not clear how the statistical properties of dynamical systems change across a boundary crisis during which a chaotic attractor collides with a saddle. This behavior is investigated here for a boundary crisis in the Lorenz flow, for which neither the Lyapunov exponents nor the covariant Lyapunov vectors provide a criterion for the crisis. Instead, the convergence of the time evolution of probability densities to the invariant measure, governed by the semigroup of transfer operators, is expected to slow down at the approach of the crisis. Such convergence is described by the eigenvalues of the generator of this semigroup, which can be divided into two families, referred to as the stable and unstable Ruelle--Pollicott resonances, respectively. The former describes the convergence of densities to the attractor (or escape from a repeller) and is estimated from many short time series sampling the state space. The latter is responsible for the decay of correlations, or mixing, and can be estimated from a long times series, invoking ergodicity. It is found numerically for the Lorenz flow that the stable resonances do approach the imaginary axis during the crisis, as is indicative of the loss of global stability of the attractor. On the other hand, the unstable resonances, and a fortiori the decay of correlations, do not flag the proximity of the crisis, thus questioning the usual design of early warning indicators of boundary crises of chaotic attractors and the applicability of response theory close to such crises

Molecular mechanisms of cell death: recommendations of the Nomenclature Committee on Cell Death 2018.

Over the past decade, the Nomenclature Committee on Cell Death (NCCD) has formulated guidelines for the definition and interpretation of cell death from morphological, biochemical, and functional perspectives. Since the field continues to expand and novel mechanisms that orchestrate multiple cell death pathways are unveiled, we propose an updated classification of cell death subroutines focusing on mechanistic and essential (as opposed to correlative and dispensable) aspects of the process. As we provide molecularly oriented definitions of terms including intrinsic apoptosis, extrinsic apoptosis, mitochondrial permeability transition (MPT)-driven necrosis, necroptosis, ferroptosis, pyroptosis, parthanatos, entotic cell death, NETotic cell death, lysosome-dependent cell death, autophagy-dependent cell death, immunogenic cell death, cellular senescence, and mitotic catastrophe, we discuss the utility of neologisms that refer to highly specialized instances of these processes. The mission of the NCCD is to provide a widely accepted nomenclature on cell death in support of the continued development of the field

Drug resistance profiles and trends in drug-resistant tuberculosis at a major hospital in Guizhou Province of China

Yuanbo Lan,1,* Yuqin Li,1,* Ling Chen,1 Jianyong Zhang,1 Hong Zhang1,2 1Department of Respiratory Medicine, Affiliated Hospital of Zunyi Medical College, Zunyi, Guizhou 563003, China; 2Z-BioMed, Inc., Rockville, MD 20855, USA *These authors contributed equally to this work Objectives: Tuberculosis (TB) is the leading cause of death from infectious diseases in the world, with an estimated 1.6 million deaths from TB in 2017. The objectives of this study were to determine drug resistance profiles of Mycobacterium tuberculosis clinical isolates and to analyze the trends in drug-resistant and multidrug-resistant tuberculosis (MDR-TB) from 2008 to 2015 at a major hospital in Guizhou, a high-TB burden and resource-limited province of China. Patients and methods: A total of 462 clinical isolates were collected from patients with pulmonary TB during the period from January 2013 to December 2015 and used for determining drug resistance profiles against four first-line and six second-line anti-TB drugs, and the results were compared with those of two previous studies. Results: Exactly 4.4% of new and 44.1% of previously treated TB cases were MDR/rifampicin-resistant TB (RR-TB), which were higher than the 2017 global average numbers of 3.5% and 18%, respectively. There were many drug-resistant patterns among MDR-TB isolates and most of them were resistant to three or four anti-TB drugs. The trends in drug-resistant and MDR-TB declined at the hospital from 2008 to 2015. Conclusion: Results of this study show that the prevalence of MDR/RR-TB at a major hospital in Guizhou is higher than the global average and confirm the existence of heterogeneity in drug resistance patterns of MDR-TB isolates. Additionally, three practical measures have played an important role in the overall decline of MDR-TB at the hospital from 2008 to 2015. Keywords: Mycobacterium tuberculosis, anti-TB drugs, drug resistance patterns, trend