Giga-Hertz quantized charge pumping in bottom gate defined InAs nanowire quantum dots

Semiconducting nanowires (NWs) are a versatile, highly tunable material platform at the heart of many new developments in nanoscale and quantum physics. Here, we demonstrate charge pumping, i.e., the controlled transport of individual electrons through an InAs NW quantum dot (QD) device at frequencies up to $1.3\,$GHz. The QD is induced electrostatically in the NW by a series of local bottom gates in a state of the art device geometry. A periodic modulation of a single gate is enough to obtain a dc current proportional to the frequency of the modulation. The dc bias, the modulation amplitude and the gate voltages on the local gates can be used to control the number of charges conveyed per cycle. Charge pumping in InAs NWs is relevant not only in metrology as a current standard, but also opens up the opportunity to investigate a variety of exotic states of matter, e.g. Majorana modes, by single electron spectroscopy and correlation experiments.Comment: 21 page

Valley-spin blockade and spin resonance in carbon nanotubes

Manipulation and readout of spin qubits in quantum dots made in III-V materials successfully rely on Pauli blockade that forbids transitions between spin-triplet and spin-singlet states. Quantum dots in group IV materials have the advantage of avoiding decoherence from the hyperfine interaction by purifying them with only zero-spin nuclei. Complications of group IV materials arise from the valley degeneracies in the electronic bandstructure. These lead to complicated multiplet states even for two-electron quantum dots thereby significantly weakening the selection rules for Pauli blockade. Only recently have spin qubits been realized in silicon devices where the valley degeneracy is lifted by strain and spatial confinement. In carbon nanotubes Pauli blockade can be observed by lifting valley degeneracy through disorder. In clean nanotubes, quantum dots have to be made ultra-small to obtain a large energy difference between the relevant multiplet states. Here we report on low-disorder nanotubes and demonstrate Pauli blockade based on both valley and spin selection rules. We exploit the bandgap of the nanotube to obtain a large level spacing and thereby a robust blockade. Single-electron spin resonance is detected using the blockade.Comment: 31 pages including supplementary informatio

Dispersively detected Pauli Spin-Blockade in a Silicon Nanowire Field-Effect Transistor

We report the dispersive readout of the spin state of a double quantum dot formed at the corner states of a silicon nanowire field-effect transistor. Two face-to-face top-gate electrodes allow us to independently tune the charge occupation of the quantum dot system down to the few-electron limit. We measure the charge stability of the double quantum dot in DC transport as well as dispersively via in-situ gate-based radio frequency reflectometry, where one top-gate electrode is connected to a resonator. The latter removes the need for external charge sensors in quantum computing architectures and provides a compact way to readout the dispersive shift caused by changes in the quantum capacitance during interdot charge transitions. Here, we observe Pauli spin-blockade in the high-frequency response of the circuit at finite magnetic fields between singlet and triplet states. The blockade is lifted at higher magnetic fields when intra-dot triplet states become the ground state configuration. A lineshape analysis of the dispersive phase shift reveals furthermore an intradot valley-orbit splitting $\Delta_{vo}$ of 145 $\mu$eV. Our results open up the possibility to operate compact CMOS technology as a singlet-triplet qubit and make split-gate silicon nanowire architectures an ideal candidate for the study of spin dynamics

NRF2-driven miR-125B1 and miR-29B1 transcriptional regulation controls a novel anti-apoptotic miRNA regulatory network for AML survival

Transcription factor NRF2 is an important regulator of oxidative stress. It is involved in cancer progression, and has abnormal constitutive expression in acute myeloid leukaemia (AML). Posttranscriptional regulation by microRNAs (miRNAs) can affect the malignant phenotype of AML cells. In this study, we identified and characterised NRF2-regulated miRNAs in AML. An miRNA array identified miRNA expression level changes in response to NRF2 knockdown in AML cells. Further analysis of miRNAs concomitantly regulated by knockdown of the NRF2 inhibitor KEAP1 revealed the major candidate NRF2-mediated miRNAs in AML. We identified miR-125B to be upregulated and miR-29B to be downregulated by NRF2 in AML. Subsequent bioinformatic analysis identified putative NRF2 binding sites upstream of the miR-125B1 coding region and downstream of the mir-29B1 coding region. Chromatin immunoprecipitation analyses showed that NRF2 binds to these antioxidant response elements (AREs) located in the 5′ untranslated regions of miR-125B and miR-29B. Finally, primary AML samples transfected with anti-miR-125B antagomiR or miR-29B mimic showed increased cell death responsiveness either alone or co-treated with standard AML chemotherapy. In summary, we find that NRF2 regulation of miR-125B and miR-29B acts to promote leukaemic cell survival, and their manipulation enhances AML responsiveness towards cytotoxic chemotherapeutics

Nanoscale spin rectifiers controlled by the Stark effect

The control of orbital and spin state of single electrons is a key ingredient for quantum information processing, novel detection schemes, and, more generally, is of much relevance for spintronics. Coulomb and spin blockade (SB) in double quantum dots (DQDs) enable advanced single-spin operations that would be available even for room-temperature applications for sufficiently small devices. To date, however, spin operations in DQDs were observed at sub-Kelvin temperatures, a key reason being that scaling a DQD system while retaining an independent field-effect control on the individual dots is very challenging. Here we show that quantum-confined Stark effect allows an independent addressing of two dots only 5 nm apart with no need for aligned nanometer-size local gating. We thus demonstrate a scalable method to fully control a DQD device, regardless of its physical size. In the present implementation we show InAs/InP nanowire (NW) DQDs that display an experimentally detectable SB up to 10 K. We also report and discuss an unexpected re-entrant SB lifting as a function magnetic-field intensity

Infiltration efficiency and subsurface water processes of a sustainable drainage system and consequences to flood management

With increased intensity rainfall events globally and urban expansion decreasing permeable surfaces, there is an increasing problem of urban flooding. This study aims to better understand rainfall infiltration into a Sustainable Drainage System (SuDS) permeable pavement, compared with an adjacent Green Area of made ground, in relationship to groundwater levels below both areas. Both areas were instrumented with soil water content and matric potential sensors and four shallow boreholes were instrumented with groundwater level sensors. Surface infiltration rates were measured using a double‐ring infiltrometer. Results showed that average infiltration rates of the SuDS (1,925 mm/hr) were significantly higher than the Green Area (56 mm/hr). The SuDS was well designed to transfer rainfall rapidly to the aquifer below, where groundwater levels rapidly rose within 1 hr of a 1 in 30 year event (32.8 mm/hr). In comparison, soil compaction of the made ground Green Area decreased infiltration rates, but still enabled the majority of rainfall events to infiltrate. The aquifer below the Green Area responded more slowly, as lower matrix potentials facilitated water retention in the soil profile, slowing water draining to the aquifer. This work reiterates the importance of ensuring a 1 m separation depth between the base of the SuDS infiltration zone and aquifer depth

Effect of foot orthoses on lower extremity kinetics during running: a systematic literature review

<p>Abstract</p> <p>Background</p> <p>Throughout the period of one year, approximately 50% of recreational runners will sustain an injury that disrupts their training regimen. Foot orthoses have been shown to be clinically effective in the prevention and treatment of several running-related conditions, yet the physical effect of this intervention during running remains poorly understood. The aim of this literature review was therefore to evaluate the effect of foot orthoses on lower extremity forces and pressure (kinetics) during running.</p> <p>Methods</p> <p>A systematic search of electronic databases including Medline (1966-present), CINAHL, SportDiscus, and The Cochrane Library occurred on 7 May 2008. Eligible articles were selected according to pre-determined criteria. Methodological quality was evaluated by use of the Quality Index as described by Downs & Black, followed by critical analysis according to outcome variables.</p> <p>Results</p> <p>The most widely reported kinetic outcomes were loading rate and impact force, however the effect of foot orthoses on these variables remains unclear. In contrast, current evidence suggests that a reduction in the rearfoot inversion moment is the most consistent kinetic effect of foot orthoses during running.</p> <p>Conclusion</p> <p>The findings of this review demonstrate systematic effects that may inform the direction of future research, as further evidence is required to define the mechanism of action of foot orthoses during running. Continuation of research in this field will enable targeting of design parameters towards biomechanical variables that are supported by evidence, and may lead to advancements in clinical efficacy.</p

How to measure influence in social networks?

Today, social networks are a valued resource of social data that can be used to understand the interactions among people and communities. People can influence or be influenced by interactions, shared opinions and emotions. How-ever, in the social network analysis, one of the main problems is to find the most influential people. This work aims to report on the results of literature review whose goal was to identify and analyse the metrics, algorithms and models used to measure the user influence on social networks. The search was carried out in three databases: Scopus, IEEEXplore, and ScienceDirect. We restricted pub-lished articles between the years 2014 until 2020, in English, and we used the following keywords: social networks analysis, influence, metrics, measurements, and algorithms. Backward process was applied to complement the search consid-ering inclusion and exclusion criteria. As a result of this process, we obtained 25 articles: 12 in the initial search and 13 in the backward process. The literature review resulted in the collection of 21 influence metrics, 4 influence algorithms, and 8 models of influence analysis. We start by defining influence and presenting its properties and applications. We then proceed by describing, analysing and categorizing all that were found metrics, algorithms, and models to measure in-fluence in social networks. Finally, we present a discussion on these metrics, al-gorithms, and models. This work helps researchers to quickly gain a broad per-spective on metrics, algorithms, and models for influence in social networks and their relative potentialities and limitations.This work has been supported by IViSSEM: POCI-01-0145-FEDER-28284, COMPETE: POCI-01-0145-FEDER-007043 and FCT – Fundação para a Ciência e Tecnologia within the R&D Units Project Scope: UIDB/00319/2020

Terrain, politics, history

This article is based on the 2019 Dialogues in Human Geography plenary lecture at the Royal Geographical Society. It has four parts. The first discusses my work on territory in relation to recent work by geographers and others on the vertical, the volumetric, the voluminous, and the milieu as ways of thinking space in three-dimensions, of a fluid and dynamic earth. Second, it proposes using the concept of terrain to analyse the political materiality of territory. Third, it adds some cautions to this, through thinking about the history of the concept of terrain in geographical thought, which has tended to associate it with either physical or military geography. Finally, it suggests that this work is a way geographers might begin to respond to the challenge recently made by Bruno Latour, where he suggests that ‘belonging to a territory is the phenomenon most in need of rethinking and careful redescription; learning new ways to inhabit the Earth is our biggest challenge’. Responding to Latour continues this thinking about the relations between territory, Earth, land, and ground, and their limits

The necessity of historical inquiry in educational research: the case of Religious Education

publication-status: PublishedThis is an Author's Original Manuscript of an article whose final and definitive form, the Version of Record, has been published in the British Journal of Religious Education, July 2010. Available online at: http://www.tandfonline.com/ or DOI: 10.1080/01416200.2010.498612This article explores the mixed fortunes of historical inquiry as a method in educational studies and exposes evidence for the neglect of this method in religious education research in particular. It argues that historical inquiry, as a counterpart to other research methods, can add depth and range to our understanding of education, including religious education, and can illuminate important longer‐term, broader and philosophical issues. The article also argues that many historical voices have remained silent in the existing historiography of religious education because such historiography is too generalised and too biased towards the development of national policy and curriculum and pedagogical theory. To address this limitation in educational research, this article promotes rigorous historical studies that are more substantially grounded in the appropriate historiographical literature and utilise a wide range of original primary sources. Finally, the article explores a specific example of the way in which a historical approach may be fruitfully applied to a particular contemporary debate concerning the nature and purpose of religious education