scholarly journals Observation of non-Hermitian topology and its bulk–edge correspondence in an active mechanical metamaterial

2020 ◽  
Vol 117 (47) ◽  
pp. 29561-29568 ◽  
Author(s):  
Ananya Ghatak ◽  
Martin Brandenbourger ◽  
Jasper van Wezel ◽  
Corentin Coulais
Keyword(s):  
Transport Properties ◽  
Cold Atoms ◽  
Topological Invariant ◽  
Geophysical Flows ◽  
Topological Phases ◽  
Topological Phase ◽  
Edge Mode ◽  
Mode Localization ◽  
Open Questions ◽  
Wide Range

Topological edge modes are excitations that are localized at the materials’ edges and yet are characterized by a topological invariant defined in the bulk. Such bulk–edge correspondence has enabled the creation of robust electronic, electromagnetic, and mechanical transport properties across a wide range of systems, from cold atoms to metamaterials, active matter, and geophysical flows. Recently, the advent of non-Hermitian topological systems—wherein energy is not conserved—has sparked considerable theoretical advances. In particular, novel topological phases that can only exist in non-Hermitian systems have been introduced. However, whether such phases can be experimentally observed, and what their properties are, have remained open questions. Here, we identify and observe a form of bulk–edge correspondence for a particular non-Hermitian topological phase. We find that a change in the bulk non-Hermitian topological invariant leads to a change of topological edge-mode localization together with peculiar purely non-Hermitian properties. Using a quantum-to-classical analogy, we create a mechanical metamaterial with nonreciprocal interactions, in which we observe experimentally the predicted bulk–edge correspondence, demonstrating its robustness. Our results open avenues for the field of non-Hermitian topology and for manipulating waves in unprecedented fashions.

scholarly journals Ways into Understanding HIF Inhibition

Cancers ◽  
2021 ◽  
Vol 13 (1) ◽  
pp. 159
Author(s):  
Tina Schönberger ◽  
Joachim Fandrey ◽  
Katrin Prost-Fingerle
Keyword(s):  
Protein Interactions ◽  
Target Genes ◽  
Protein Protein Interactions ◽  
Low Oxygen ◽  
Drug Candidates ◽  
Open Questions ◽  
Wide Range ◽  
Hif Pathway

Hypoxia is a key characteristic of tumor tissue. Cancer cells adapt to low oxygen by activating hypoxia-inducible factors (HIFs), ensuring their survival and continued growth despite this hostile environment. Therefore, the inhibition of HIFs and their target genes is a promising and emerging field of cancer research. Several drug candidates target protein–protein interactions or transcription mechanisms of the HIF pathway in order to interfere with activation of this pathway, which is deregulated in a wide range of solid and liquid cancers. Although some inhibitors are already in clinical trials, open questions remain with respect to their modes of action. New imaging technologies using luminescent and fluorescent methods or nanobodies to complement widely used approaches such as chromatin immunoprecipitation may help to answer some of these questions. In this review, we aim to summarize current inhibitor classes targeting the HIF pathway and to provide an overview of in vitro and in vivo techniques that could improve the understanding of inhibitor mechanisms. Unravelling the distinct principles regarding how inhibitors work is an indispensable step for efficient clinical applications and safety of anticancer compounds.

Computational Strategies for Analyzing Data in Gene Expression Microarray Experiments

2003 ◽  
Vol 01 (03) ◽  
pp. 541-586 ◽  
Author(s):  
Tero Aittokallio ◽  
Markus Kurki ◽  
Olli Nevalainen ◽  
Tuomas Nikula ◽  
Anne West ◽  
...  
Keyword(s):  
Gene Expression ◽  
Data Analysis ◽  
Microarray Data ◽  
Microarray Data Analysis ◽  
Biological Research ◽  
Microarray Experiments ◽  
Dna Microarray Data ◽  
Open Questions ◽  
Analysis Technique ◽  
Wide Range

Microarray analysis has become a widely used method for generating gene expression data on a genomic scale. Microarrays have been enthusiastically applied in many fields of biological research, even though several open questions remain about the analysis of such data. A wide range of approaches are available for computational analysis, but no general consensus exists as to standard for microarray data analysis protocol. Consequently, the choice of data analysis technique is a crucial element depending both on the data and on the goals of the experiment. Therefore, basic understanding of bioinformatics is required for optimal experimental design and meaningful interpretation of the results. This review summarizes some of the common themes in DNA microarray data analysis, including data normalization and detection of differential expression. Algorithms are demonstrated by analyzing cDNA microarray data from an experiment monitoring gene expression in T helper cells. Several computational biology strategies, along with their relative merits, are overviewed and potential areas for additional research discussed. The goal of the review is to provide a computational framework for applying and evaluating such bioinformatics strategies. Solid knowledge of microarray informatics contributes to the implementation of more efficient computational protocols for the given data obtained through microarray experiments.

Self-reports of health-care utilization: Diary or questionnaire?

2005 ◽  
Vol 21 (3) ◽  
pp. 298-304 ◽  
Author(s):  
Mandy van den Brink ◽  
Wilbert B. van den Hout ◽  
Anne M. Stiggelbout ◽  
Hein Putter ◽  
Cornelis J. H. van de Velde ◽  
...  
Keyword(s):  
Health Care ◽  
Health Care Utilization ◽  
Convergent Validity ◽  
Cost Utility ◽  
Care Utilization ◽  
Economic Evaluations ◽  
Cost Diary ◽  
Open Questions ◽  
Wide Range ◽  
More Care

Objectives:The feasibility and convergent validity of a cost diary and a cost questionnaire was investigated.Methods:Data were obtained as part of a cost-utility analysis alongside a multicenter clinical trial in patients with resectable rectal cancer. A sample of 107 patients from 30 hospitals was asked to keep a weekly diary during the first 3 months after surgery, and a monthly diary from 3 to 12 months after surgery. A second sample of seventy-two patients from twenty-eight hospitals in the trial received a questionnaire at 3, 6, and 12 months after surgery, referring to the previous 3 or 6 months. Format and items of the questions were similar and included a wide range of medical and nonmedical items and costs after hospitalization for surgery.Results:Small differences were found with respect to nonresponse (range, 79 to 86 percent) and missing questions (range, 1 to 6 percent between the diary and questionnaire). For most estimates of volumes of care and of costs, the diary and questionnaire did not differ significantly. Total 3-month nonhospital costs were €1,860, €1,280, and €1,050 in the diary sample and €1,860, €1,090, and €840 in the questionnaire sample at 3, 6, and 12 months after surgery, respectively (p=.50). However, with respect to open questions, the diary sample tended to report significantly more care.Conclusions:For the assessment of health-care utilization in economic evaluations alongside clinical trials, a cost questionnaire with structured closed questions may replace a cost diary for recall periods up to 6 months.

Topological phase and thermoelectric properties of bialkali bismuthide compounds (Na,K)2RbBi from first-principles

2021 ◽  
Author(s):  
Shahram Yalameha ◽  
Zahra Nourbakhsh ◽  
Daryoosh Vashaee
Keyword(s):  
Density Functional ◽  
Transport Coefficients ◽  
Relaxation Times ◽  
Surface States ◽  
Topological Phase ◽  
Boltzmann Transport ◽  
Thermoelectric Power Factor ◽  
Practical Applications ◽  
Wide Range ◽  
P Type

Abstract We report the topological phase, thermal, and electrical properties of bialkali bismuthide compounds (Na,K)2RbBi, as yet hypothetical. The topological phase transitions of these compounds under hydrostatic pressure are investigated. The calculated topological surface states and Z2 topological index confirm the nontrivial topological phase. The electronic properties and transport coefficients are obtained using the density functional theory combined with the Boltzmann transport equation. The relaxation times are determined using the deformation potential theory to calculate the electronic thermal and electrical conductivity. The calculated mode Grüneisen parameters are substantial, indicating strong anharmonic acoustic phonons scattering, which results in an exceptionally low lattice thermal conductivity. These compounds also have a favorable thermoelectric power factor leading to a relatively flat p-type figure-of-merit over a broad temperature range. Furthermore, the mechanical properties and phonon band dispersions show that these structures are mechanically and dynamically stable. Therefore, they offer excellent candidates for practical applications over a wide range of temperatures.

scholarly journals Unveiling Signatures of Topological Phases in Open Kitaev Chains and Ladders

Nanomaterials ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 894 ◽  
Author(s):  
Alfonso Maiellaro ◽  
Francesco Romeo ◽  
Carmine Antonio Perroni ◽  
Vittorio Cataudella ◽  
Roberta Citro
Keyword(s):  
Electrical Response ◽  
Differential Conductance ◽  
Model Parameters ◽  
Topological Phases ◽  
Topological Order ◽  
Topological Phase ◽  
Moderate Amount ◽  
Topological System ◽  
Isolated Systems

In this work, the general problem of the characterization of the topological phase of an open quantum system is addressed. In particular, we study the topological properties of Kitaev chains and ladders under the perturbing effect of a current flux injected into the system using an external normal lead and derived from it via a superconducting electrode. After discussing the topological phase diagram of the isolated systems, using a scattering technique within the Bogoliubov–de Gennes formulation, we analyze the differential conductance properties of these topological devices as a function of all relevant model parameters. The relevant problem of implementing local spectroscopic measurements to characterize topological systems is also addressed by studying the system electrical response as a function of the position and the distance of the normal electrode (tip). The results show how the signatures of topological order affect the electrical response of the analyzed systems, a subset of which being robust also against the effects of a moderate amount of disorder. The analysis of the internal modes of the nanodevices demonstrates that topological protection can be lost when quantum states of an initially isolated topological system are hybridized with those of the external reservoirs. The conclusions of this work could be useful in understanding the topological phases of nanowire-based mesoscopic devices.

Turbulent entrainment: the development of the entrainment assumption, and its application to geophysical flows

1986 ◽  
Vol 173 ◽  
pp. 431-471 ◽  
Author(s):  
J. S. Turner
Keyword(s):  
Turbulent Flow ◽  
Laboratory Experiments ◽  
Geophysical Flows ◽  
Natural Phenomena ◽  
Mean Velocity ◽  
Background Theory ◽  
Turbulent Entrainment ◽  
Wide Range ◽  
Buoyancy Forces ◽  
Local Mean

The entrainment assumption, relating the inflow velocity to the local mean velocity of a turbulent flow, has been used successfully to describe natural phenomena over a wide range of scales. Its first application was to plumes rising in stably stratified surroundings, and it has been extended to inclined plumes (gravity currents) and related problems by adding the effect of buoyancy forces, which inhibit mixing across a density interface. More recently, the influence of viscosity differences between a turbulent flow and its surroundings has been studied. This paper surveys the background theory and the laboratory experiments that have been used to understand and quantify each of these phenomena, and discusses their applications in the atmosphere, the ocean and various geological contexts.

scholarly journals On fast and slow Earth’s magnetospheric dynamics during geomagnetic storms: a stochastic Langevin approach

2018 ◽  
Vol 8 ◽  
pp. A56 ◽  
Author(s):  
Tommaso Alberti ◽  
Giuseppe Consolini ◽  
Paola De Michelis ◽  
Monica Laurenza ◽  
Maria Federica Marcucci
Keyword(s):  
Geomagnetic Storms ◽  
State Function ◽  
Topological Phase ◽  
H Index ◽  
First Order ◽  
Topological Phase Transition ◽  
Multiscale Dynamics ◽  
Wide Range ◽  
Langevin Approach ◽  
State Functions

The Earth’s magnetosphere responds to the external changes of interplanetary magnetic field and solar wind conditions showing a multiscale dynamics, manifesting in the occurrence of fluctuations over a very wide range of timescales. Here, using an approach based on a Langevin/Fokker-Planck description we investigate the nature of the fast (short-) and slow (long-timescale) fluctuations of SYM-H index during geomagnetic storms. The results point towards a different origin of the fast (τ < 200 min) and slow (τ > 200 min) fluctuations, which are characterized by state functions of different nature. In detail, the state function associated with the slow dynamics shows the evidence of the occurrence of first-order-like topological phase transition during the different phases of a geomagnetic storm, while the fast dynamics seems to be characterized by a quasi-invariant quadratic state function. A modeling in terms of stochastic Langevin equation is discussed and the relevance of our results in the framework of Space Weather studies is outlined.

scholarly journals Effect of mixed anions on the transport properties and performance of an ionic liquid-based electrolyte for lithium-ion batteries

2019 ◽  
Vol 91 (8) ◽  
pp. 1361-1381 ◽  
Author(s):  
Victor Chaudoy ◽  
Johan Jacquemin ◽  
François Tran-Van ◽  
Michaël Deschamps ◽  
Fouad Ghamouss
Keyword(s):  
Transport Properties ◽  
Lithium Ion Batteries ◽  
Salt Concentration ◽  
Lithium Salt ◽  
Nuclear Overhauser Effect ◽  
Lithium Ion ◽  
Activation Energies ◽  
The Self ◽  
Self Diffusion ◽  
Wide Range

Abstract In this work, the physical, transport and electrochemical properties of various electrolytic solutions containing the 1-propyl-1-methylpyrrolidinium bis[fluorosulfonyl]imide ([C3C1pyr][FSI]) mixed with the lithium bis[(trifluoromethyl)sulfonyl]imide (Li[TFSI]) over a wide range of compositions are reported as a function of temperature at atmospheric pressure. First, the ionicity, lithium transference number, and transport properties (viscosity and conductivity) as well as the volumetric properties (density and molar volume) were determined as a function of lithium salt concentration from 293 to 343 K. Second, the self-diffusion coefficient of each ion in solution was measured by nuclear magnetic resonance (NMR) spectroscopy with pulsed field gradients (PFG). Moreover, an analysis of the collected nuclear Overhauser effect (NOE) data along with ab initio and COSMO-RS calculations was conducted to depict intra and intermolecular neighbouring within the electrolytic mixtures. Based on this analysis, and as expected, all activation energies increase with the Li[TFSI] concentration in solution, and all activation energies were determined from the self-diffusion data for all ions. Interestingly, regardless of the composition in solution, these activation energies were similar, except for those determined for the [FSI]− anion. The activation energy of [FSI]− self-diffusion relatively decreases compared to the other ions as the lithium salt concentration increases. Furthermore, the lithium transference was strongly affected by the lithium salt concentration, reaching an optimal value and an ionicity of approximately 50 % at a molality close to 0.75 mol · kg−1. Finally, these electrolytes were used in lithium-ion batteries (i.e. Li/NMC and LTO/NMC), demonstrating a clear relationship between the electrolyte formulation, its transport parameters and battery performance.

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