Functional characterization of developing heart in embryos using Electric Potential Sensors

The characterization of the electrocardiographic activity of the living zebrafish heart during early developmental stages is a challenging task. Most of the available techniques are limited to heartbeat rate quantification being this inaccurate. Other invasive methodologies require the insertion of electrodes noise isolated environments and advanced amplification stages making these techniques very expensive. In this paper, we present a novel and non-invasive sensor development to characterize the functional activity of the developing heart of in vivo zebrafish embryos. The design is based on the Electric Potential Sensing technology patented at Sussex which has been developed to achieve reproducibility and continuous detection. We present preliminary functional characterization data of the developing zebrafish heart starting at 3 days-post-fertilization. Results show that using the proposed system for mapping the electrocardiographic activity of the zebrafish heart at early developmental stages is successfully accomplished. This is the first time that such a sensitive sensor has been developed for measuring the electrical changes occurring on micron sized (< 100 µm) living samples such as the zebrafish heart

Electric field phase sensing for wearable orientation and localisation applications

We show how to sense the phase of the ambient electric field from a body-worn sensor with respect to a reference and discuss how phase information could contribute to relative orientation sensing and indoor localisation. Our system uses 7mW and can be enclosed in a plastic case which makes it suitable for new wearable devices

Cooling an electron gas using quantum dot based electronic refrigeration

Studies of two-dimensional electron gases (2DEGs) in semiconductors form an active and productive field of condensed matter physics research. As well as having interesting inherent properties, they are used as the foundation for constructing various nano-scale electronic devices, such as quantum wires and quantum dots. Conventionally, low temperature measurements of 2DEGs are made by cooling the sample to 1.5 K with liquid Helium-4, to 300 mK with liquid Helium-3, or even down to a few mK using a dilution refrigerator. However, at lower temperatures the electron gas becomes increasingly decoupled from the lattice in which it resides. Below ~ 1 K the coupling can be weak enough for the electron gas to be significantly elevated in temperature due to parasitic heating. In this thesis we present the experimental and theoretical investigation of a refrigeration scheme that has the potential to cool 2DEGs below the temperatures currently available. Cooling to ever lower temperatures would be beneficial for studying fragile fractional quantum Hall states, non-Fermi-liquid behaviour in bilayer 2DEGs, or interactions like the Kondo effect that occur between quantum dots and 2DEGs. The scheme we investigate is called the Quantum Dot Refrigerator (or QDR) and is based upon the energy selective transport of electrons through the singleparticle states of quantum dots. By using a pair of dots, both hot electrons and hot holes can be selectively removed from an otherwise electrically isolated 2DEG. The result is a net current that continuously removes heat. This type of refrigerator is best suited to be used in conjunction with a dilution fridge or Helium-3 system to provide a final stage of cooling. The scheme was first investigated theoretically in 1993 by Edwards et al. but, to our knowledge, has never before been demonstrated experimentally. We detail the fabrication and measurement of a QDR device that is designed to cool an isolated 6 µm2 2DEG. In order to interpret the behaviour of the device, a model was developed to take account of electrostatic interactions between the components of the system (the quantum dots and the isolated 2DEG). Electrostatic interactions were found to be significant for our design, but were neglected in previous work. Our model predicts that their presence complicates, but does not invalidate, the principle of operation of a QDR. By comparing measurements of the current through the QDR with predictions of the model, we show that the observed behaviour is consistent with cooling of the isolated 2DEG by up to 100 mK at ambient temperatures around 250 mK. Although these temperatures are well within the reach of conventional refrigeration techniques, the results are a compelling proof-of-concept demonstration that the QDR principle is sound and can achieve significant refrigeration in the right conditions. Finally, we discuss future directions for improving QDR performance and characterisation, and for lowering the achievable base temperature. We also suggest how QDRs could be used to provide cold reservoirs for a nano-scale electronic device, and explore the limitations that would apply to such an experiment

Single-shot measurement of triplet-singlet relaxation in a Si/SiGe double quantum dot

We investigate the lifetime of two-electron spin states in a few-electron Si/SiGe double dot. At the transition between the (1,1) and (0,2) charge occupations, Pauli spin blockade provides a readout mechanism for the spin state. We use the statistics of repeated single-shot measurements to extract the lifetimes of multiple states simultaneously. At zero magnetic field, we find that all three triplet states have equal lifetimes, as expected, and this time is ~10 ms. At non-zero field, the T0 lifetime is unchanged, whereas the T- lifetime increases monotonically with field, reaching 3 seconds at 1 T.Comment: 4 pages, 3 figures, supplemental information. Typos fixed; updated to submitted versio

Neo-SENSE: a non-invasive smart sensing mattress for cardiac monitoring of babies

Within the first minute of life a newborn must take its first breath to make the transition from life inside the womb to the outside world. If a baby does not start breathing, its heart rate will drop and the circulation of blood carrying oxygen to the organs will be seriously affected. The damage done to a newborn who is deprived of oxygen happens so quickly that rapid response is imperative. During birth, the attending neonatal staff manually listen to the baby´s heart and count the heart rate; however, this has proven inaccurate and inefficient. Nowadays, there is not a reliable method to monitor newborn heart rate promptly throughout birth. In this paper, we report the design and development of a novel smart mattress device to measure the babies’ electrocardiogram and respiration non-invasively. The device is based on electrometer-based amplifier sensors combined with novel screen-printing techniques. Proof of concept tests are carried out to demonstrate the suitability of the smart-mattress for new born ECG monitoring. We perform tests with a young infant and demonstrate the potential of this sensing technology to provide a quick and reliable application as ECG readings were displayed within a time < 30 seconds. This will aid the neonatal staff to assess the success of the resuscitation technology aiming to lower the incidence of long-term consequences of poor adaptation to life outside the womb

Estudo eletroforético da dinâmica de variação genética em três taxa ribeirinhos ao longo do rio Solimões, América do Sul

An electrophoretic study was undertaken to determine the extent of genetic variability in three taxa of legumes (Aeschynomene sensitiva Sw. var. sensitiva, Aeschynomene sensitiva Sw. var. amazonica Rudd, Papilionoideae: Mimosa pigra L , Mimosoideae) along a 2,174 Km reach of the Amazon River from Iquitos, Peru, to Manaus, Brazil. Genetic variability was expressed in terms of: 1) degree of enzyme polymorphism (P, and 2) average populational heterozygosity (H. Five enzyme systems were examined: leucine aminopeptidase (LAP), glutamate dehydrogenase (GDH), phosphoglucomutase (PGM), phosphoglucoisomerase (PGI). and acid phosphotase (AcPH). Riverine taxa provide a unique system for the experimental study of population biology and evolution. The origin, perpetuation, and dynamics of genic variation within and among populations is used as an indicator of evolutionary change. Gene flow in these entomophilous, water dispersed legumes is undirectional and linear, with minor blackflow by pollen vectors. Of the enzymes examined, LAP was a monomer for all three taxa with low polymorphic values. AcPH, also a codominant monomer, had no detectable isoenzyme fraction; a situation also found in PGM systems. PGI is a very complex system controlled by several loci. GDH is monomorphic with one resolvable band. Mean polymorphism for the two Aeschynomene taxa is 21.3% (P' = 0.213), and for the Mimosa is 24.5% (P' = 0.245). Average populational heterozygosity (Nei statistic, H varied between 0.10 to 0.43 for Aeschynomene. This value was significantly higher for the Mimosa, which ranged between 0.33 and 0.50. Heterozygosity index, genetic similarity index, demographic patterns, and biology show a concise correlation between genetic variability and adaptative strategy. Populations with a high extinction probability are more homozygous than populations with greater survival probability. Homozygosity is favored in perturbed populations along the Rio Amazonas.", 'enAo longo de um trecho de 2.174 km do rio Solimões, partindo de Iquitos. Peru, a Manaus, Brasil, foi realizado um estudo eletroforético para determinação da quantidade de variação genética em três taxa de leguminosas (Aeschynomene sensitiva Sw. var. amazonica Rudd, Papilionoideae; Mimosa Pigra L., Mimosoideae). A variabilidade genética foi expressa em termos de1) grau de polimorfismo enzimático (P, e 2) heterozigosidade populacional média (H. Foram examinados cinco sistemas enzimáticosleucina-aminopeptidase (LAP), glutamato-dehidrogenase (GDH). fosfoglucomutase (PGM), fosfoglucoisomerase (PGI), e fosfatase ácida (AcPH). Os taxa ribeirinhos apresentam condições excepcionais para estudos experimentais sobre biologia de população e evolução. A origem, perpetuação e dinâmica de variação gênica intra e interpopulacional são usadas como indicadores de mudança evolutiva. O fluxo gênico entre essas leguminosas entomolfílicas e dispersas na água é unidirecional e linear, com fluxo regressivo mínimo por vetores de pólen. Entre as enzimas examinadas, LAP foi um monômero para todos os três taxa, com valores polimórficos baixos. AcPH, outro monômero codominante, não apresentou fração isoenzimática detectável, situação semelhante à encontrada em sistemas PGM. PGI é um sistema muito complexo controlado por diversos loci. GDH é monomórfico, com uma faixa detectável. O polimorfismo médio para os dois taxa de Aeschynomene é 21.3% (P' = 0.213). e para Mimosa é 24.% (P' = 0.245). A heterozigosidade populacional média (estatística Nei H variou entre 0.10 e 0.43 para Aeschynomene Esse valor foi significativamente maior para Mimosa, variando entre 0.33 e 0.50. Os índices de heterozigosidade e de similaridade genética, os padrões demográficos e a biologia, indicam uma estreita correlação entre a variabilidade genética e a estratégia adaptativa. As populações com alta probabilidade de extinção são mais homozigóticas do que aquelas com maior probabilidade de sobrevivência. A homozigosidade é favorecida em populações que sofrem perturbações ao longo do rio Solimões

Electrode-stress-induced nanoscale disorder in Si quantum electronic devices

Disorder in the potential-energy landscape presents a major obstacle to the more rapid development of semiconductor quantum device technologies. We report a large-magnitude source of disorder, beyond commonly considered unintentional background doping or fixed charge in oxide layers: nanoscale strain fields induced by residual stresses in nanopatterned metal gates. Quantitative analysis of synchrotron coherent hard x-ray nanobeam diffraction patterns reveals gate-induced curvature and strains up to 0.03% in a buried Si quantum well within a Si/SiGe heterostructure. Electrode stress presents both challenges to the design of devices and opportunities associated with the lateral manipulation of electronic energy levels

Edge currents shunt the insulating bulk in gapped graphene

An energy gap can be opened in the spectrum of graphene reaching values as large as 0.2 eV in the case of bilayers. However, such gaps rarely lead to the highly insulating state expected at low temperatures. This long-standing puzzle is usually explained by charge inhomogeneity. Here we revisit the issue by investigating proximity-induced superconductivity in gapped graphene and comparing normal-state measurements in the Hall bar and Corbino geometries. We find that the supercurrent at the charge neutrality point in gapped graphene propagates along narrow channels near the edges. This observation is corroborated by using the edgeless Corbino geometry in which case resistivity at the neutrality point increases exponentially with increasing the gap, as expected for an ordinary semiconductor. In contrast, resistivity in the Hall bar geometry saturates to values of about a few resistance quanta. We attribute the metallic-like edge conductance to a nontrivial topology of gapped Dirac spectra

Systematics Agenda 2020: The Mission Evolves

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial Licens

Combining experiment and optical simulation in coherent X-ray nanobeam characterization of Si/SiGe semiconductor heterostructures

The highly coherent and tightly focused x-ray beams produced by hard x-ray light sources enable the nanoscale characterization of the structure of electronic materials but are accompanied by significant challenges in the interpretation of diffraction and scattering patterns. X-ray nanobeams exhibit optical coherence combined with a large angular divergence introduced by the x-ray focusing optics. The scattering of nanofocused x-ray beams from intricate semiconductor heterostructures produces a complex distribution of scattered intensity. We report here an extension of coherent x-ray optical simulations of convergent x-ray beam diffraction patterns to arbitrary x-ray incident angles to allow the nanobeam diffraction patterns of complex heterostructures to be simulated faithfully. These methods are used to extract the misorientation of lattice planes and the strain of individual layers from synchrotron x-ray nanobeam diffraction patterns of Si/SiGe heterostructures relevant to applications in quantum electronic devices. The systematic interpretation of nanobeam diffraction patterns from semiconductor heterostructures presents a new opportunity in characterizing and ultimately designing electronic materials