Record Low Energy Research Articles

Alkali Silicates Codoped with NIR-Emitting RE (Nd3+ and Yb3+) Ions for Thermometry Applications.

In the present study, the synthesis of BaSrSiO4 co-doped Yb3+ and Nd3+ nanophosphors (NPs) was successfully achieved through the conventional sol-gel method, as confirmed by X-ray diffraction and SEM analysis, verifying the formation of pure NPs. The FTIR and Raman spectra analysis confirm the formation of silicates, as different modes and vibrations of Si-O and Si-O-Si were seen at 800-1000cm-1. The energy transfer (ET) mechanism between Nd3+ and Yb3+ ions was seen as the emission spectra showed a rise in intensity of one over another. PLE emission spectra showed transitions at 2F7/2-2F5/2 for Yb3+ and from 4F3/2 to (4I9/2, 4I11/2, and 4I13/2) for Nd3+ when excited at 785nm. All the samples record low activation energy, which shows that the rate of reaction will be higher in all the samples, and it will be highest for 1mol% Nd3+ and 1mol% Yb3+. An increasing value of τ was seen with increasing Yb3+ concentration, which confirms the increase in the population of trap centers. The positron annihilation lifetime (PAL) curve showed that 1mol% Yb3+ and 2mol Nd3+ have single vacancies or shallower positron traps, whereas 3mol% Yb3+ and 2mol% Nd3+ have larger defects like surface oxygen vacancy clusters. The other two samples have balance vacancies, which makes them best for thermometry applications. The fluorescence intensity ratio (FIR) was calculated to get sensitivity for thermometry application. 2.13% K-1 sensitivity achieved at 303-333K temperature.

High-speed and energy-efficient non-volatile silicon photonic memory based on heterogeneously integrated memresonator.

Recently, interest in programmable photonics integrated circuits has grown as a potential hardware framework for deep neural networks, quantum computing, and field programmable arrays (FPGAs). However, these circuits are constrained by the limited tuning speed and large power consumption of the phase shifters used. In this paper, we introduce the memresonator, a metal-oxide memristor heterogeneously integrated with a microring resonator, as a non-volatile silicon photonic phase shifter. These devices are capable of retention times of 12 hours, switching voltages lower than 5 V, and an endurance of 1000 switching cycles. Also, these memresonators have been switched using 300 ps long voltage pulses with a record low switching energy of 0.15 pJ. Furthermore, these memresonators are fabricated on a heterogeneous III-V-on-Si platform capable of integrating a rich family of active and passive optoelectronic devices directly on-chip to enable in-memory photonic computing and further advance the scalability of integrated photonic processors.

Kubernetes for the Deep Underground Neutrino Experiment Data Acquisition

The Deep Underground Neutrino Experiment (DUNE) is a next-generation long-baseline neutrino experiment based in the USA which is expected to start taking data in 2029. DUNE aims to precisely measure neutrino oscillation parameters by detecting neutrinos from the LBNF beamline (Fermilab) at the Far Detector, 1,300 kilometres away, in South Dakota at the Sanford Underground Research Facility. The Far Detector will consist of four cryogenic Liquid Argon Time Projection Chamber detectors of 17 kT, each producing more than 1 TB/sec of data. The main requirements for the data acquisition system are the ability to run continuously for extended periods of time, with a 99% up-time requirement, and the functionality to record both beam neutrinos and low energy neutrinos from the explosion of a neighbouring supernova, should one occur during the lifetime of the experiment. The key challenges are the high data rates that the detectors generate and the deep underground environment, which places constraints on power and space. To overcome these challenges, DUNE plans to use a highly optimised C++ software suite and a server farm of about 110 nodes continuously running about two hundred multicore processes located close to the detector, 1.5 kilometres underground. Thirty nodes will be at the surface and will run around two hundred processes simultaneously. DUNE is studying the use of the Kubernetes framework to manage containerised workloads and take advantage of its resource definitions and high up-time services to run the DAQ system. Progress in deploying these systems at the CERN neutrino platform on the prototype DUNE experiments is reported.

Luminescence spectroscopy of anomalous Eu3+ in ternary aluminates: Experimental evidence for covalent bonding of 4f-orbitals of lanthanides

Luminescence spectroscopy of Eu3+ doped into strontium and calcium aluminate nanoparticles (NPs) sheds light on two longstanding arguments: 1) covalent bonding of the 4f-orbitals, and 2) the so-called anomalous luminescence of Eu3+ ion. Similar to a few reports on crystalline compounds in the literature, we observe an intense 5D0→7F0 emission accompanied by a low-energy oxygen to Eu3+ charge transfer (CT) band, however, in the amorphous phase. In the strontium aluminate NPs, the 5D0→7F0 transition appears at a record-high energy of 17675 cm−1 (565.75 nm), whereas its corresponding CT band can shift to a record-low energy of 29200 cm−1 (342 nm). Systematic investigation of these peculiarities leads to unprecedented information about the local environment of the anomalous Eu3+. Spectroscopic probing of the Eu3+ local environment suggests that the electropositivity of one specific neighboring metal ion determines the energy of the 5D0→7F0 transition through electron delocalization, which directly involves the 4f-orbitals of the Eu3+ ion.

Directly‐Deposited Ultrathin Solid Polymer Electrolyte for Enhanced CO2 Electrolysis

AbstractThe economic viability of carbon dioxide electroreduction (CO2R) relies on improved performance accompanied by scalable system design. Membranes are commonly used for the separation of reduction and oxidation products as well as to provide a suitable micro‐environment for CO2R. Commercial membranes often address only one of the key challenges in CO2R: either they offer a suitable micro‐environment for CO2R (e.g., anion exchange membrane) or suppress carbonate cross‐over (e.g., cation exchange membrane and bipolar membrane). This work presents a cation‐infused ultrathin (≈3 µm) solid polymer electrolyte (CISPE) that concomitantly addresses both challenges via a bidirectional ion transport mechanism and suppressed cathode flooding. This directly‐deposited CISPE (that substitutes the commonly used pre‐made membrane) enables record high full‐cell energy efficiency of 28% at 100 mA cm−2 for one‐step CO2 electrolysis to ethylene (C2H4) with ≈110 h of stable operation. This translates into a record low energy cost of 290 GJ per ton C2H4 for the end‐to‐end process (i.e., CO2 capture and electroreduction, carbonate regeneration, CO2 separation from anode and cathode streams) in a membrane electrode assembly CO2R. The present work offers a versatile design paradigm for functional polymer electrolytes, opening the door to stable, and efficient electrolysis of high‐value feedstock chemicals and fuels using low‐cost catalysts.

Exploiting flocculation and membrane filtration synergies for highly energy-efficient, high-yield microalgae harvesting

High energy consumption during harvesting is one of the main bottlenecks for sustainable microalgae production. Membranes can efficiently separate microalgae from liquids with low energy consumption, but membrane fouling remains an important issue. Flocculation prior to membrane filtration can increase membrane fluxes and decrease fouling, thus offering a low-cost and efficient solution to harvest microalgae. Biobased cationic cellulose nanocrystals were successfully used as flocculants for microalgae and were effective over a wide pH-range and for both freshwater and marine microalgae. Such flocculation was for the first time combined with vibration-assisted filtration using a charged, surface patterned membrane, enabling operation at very high flux (95 L/m2 h) using a vibration frequency of only 1 Hz, and even under sub-optimal flocculation conditions. Intermittent vibration decreased energy consumption further while keeping excellent filtration performance to finally achieve a record-low energy consumption for the membrane filtration of only 6.7 Wh/m3, which is >25-times lower than that of normal membrane filtration. Interaction forces revealed that increasing particle size through flocculation prior to membrane filtration can significantly prevent microalgae attachment on the vibrating membrane surface. This work opens a new direction for sustainable microalgae harvesting with an ultra-low energy consumption, combined with a very high microalgae recovery, reduced use of chemicals, and lower membrane investment cost.

Late Quaternary mud‐dominated, basin‐floor sedimentation of the Gulf of Corinth, Greece: Implications for deep‐water depositional processes and controls on syn‐rift sedimentation

AbstractSyn‐rift deep‐water muds and mudstones preserve a relatively complete stratigraphic record of tectonic and climatic events. This paper investigates mud‐dominated deposits and stratigraphy using core from International Ocean Discovery Program (IODP) Expedition 381 sites M0078 and M0079 in the Gulf of Corinth, Greece. Millimetre‐scale logging defined several bed types: homogeneous and laminated mud beds, bioturbated beds, a variety of graded beds, and rare matrix‐supported conglomerates and slumps. Homogeneous muds and light grey to black laminated muds record deposition from distal, waning low density turbidity currents and terminal mud‐rich quasi‐laminar or laminar plug flows. Graded beds, interpreted as turbidites, range from beds several millimetre to a few centimetres of mud with silt to fine sand bases, to metre‐scale mud beds with coarser sand and pebble bases. Conglomerate and slumped beds record cohesive debris flows, transitional flows and slope failure. Three stratal package types are distinguished: bioturbated, bedded and laminated, recording distinct hydrological conditions. Bioturbated packages record interglacial marine conditions with well oxygenated waters. Bedded packages record hemipelagic processes and low energy density underflows in a mainly dysoxic, stratified, lacustrine setting (glacial phases). In laminated packages, white mm‐scale laminae of calcite or aragonite from varved, hemipelagic sediments demonstrating seasonal variability in a dysoxic non‐marine or transitional setting. Rift stratigraphy is linked to eustatically controlled connections to the global ocean across rift segment boundaries. The ca. 780 to 330 ka succession is dominated by laminated packages with thin bioturbated packages and distinct conglomerates and slumps, suggesting high sills, making ocean connections brief and transitional to lacustrine conditions prolonged. The ca. 330 ka to present succession shows well developed bioturbated and bedded packages, separated by thin laminated packages, suggesting brief transitions and well‐developed marine conditions due to lower sills. Results indicate that structurally controlled rift segment boundaries exert a first‐order control on syn‐rift stratigraphic evolution, with fault segment growth and linkage driving intra‐rift facies and sequence variability.

An Electrochemical Hydrogen-Looping System for Low-Cost CO2 Capture from Seawater

Carbon dioxide (CO2) capture from seawater is a viable, long-term solution for addressing legacy carbon pollution on the planet. However, significant challenges to widespread applicability exist in terms of efficiency, cost, and scalability. In this work, we have developed an electrochemical hydrogen-looping (EHL) system that capitalizes on the generation of proton and OH– from seawater. A CO2 capture efficiency as high as 91% is achieved for our EHL flow cell. We have demonstrated that the electrochemical hydrogen-looping flow cell can remove CO2 from simulated seawater at a record low electric energy consumption of 660 kWh ton–1 CO2, which is a significant reduction of 56% compared with the currently used bipolar membrane electrodialysis technology. The electrochemical hydrogen-looping flow cell with its much lower energy consumption provides an economical approach for direct removal of CO2 from seawater at practical scale.

Palaeoecological reconstruction of the Late Devonian Lebedjan biota

ABSTRACT Palaeozoic fossil-bearing deposits in Russia record important and rare insights into pre-Mesozoic palaeoecological systems. Among the known formations, the Late Devonian (Famennian) deposits exposed in the central part of Russian platform have been under-documented. To expand the record of these formations, some of which show evidence of soft-bodied preservation, we revisit the Famennian-aged Lebedjan Formation from the Lipetsk region, central European Russia. We examine and record three outcrops lithologically and stratigraphically. In re-considering the Lebedjan Formation, we illustrate novel evidence for macrophytic algae, crustaceans, fishes, stromatolites, and xiphosurans preserved within the deposit. In doing so, we present a more complete reconstruction of this Late Devonian palaeoecosystem and demonstrate that sections of the Lebedjan Formation record low energy, lagoonal palaeoenvironments that had limited influence from the open ocean.

Intrinsic Planar Defects in Germanium and Their Contribution to the Excess Specific Heat at High Temperatures

Excessively high specific heat is usually observed in solids at comparatively high temperatures. It is believed to be associated with anharmonic effects. Using the simple case of elemental germanium with archetypical diamond structure, it is demonstrated that the anharmonicity effect can not fully describe the excess specific heat in germanium. Instead, two types of extended planar defects with a record low formation energy () are proposed, which can account for the discrepancy between theoretical and observed specific heat. These planar defects can be considered as finite distortion of crystal lattice produced by shear phonon modes accompanied by specific reconstruction of interatomic bonds on certain atomic planes. By comparison of experimental and theoretical specific heat, it is found that the germanium sample is subdivided into domains with intrinsic planar defects aligned along a single crystallographic direction.

Extended Defects in Graphene and Their Contribution to the Excess Specific Heat at High Temperatures.

The recent experiments on fast (microsecond) pulse heating of graphite suggest the existence of sharp maximum (6500K at 1-2GPa) on its melting curve. To check the validity of these findings, we propose to investigate the accumulation of extended in-plane defects in graphene. Such defects would contribute to thermodynamic properties of graphene and impose the upper limit on its melting temperature. We propose a type of extended defect of graphene, consisting of pentagonal and heptagonal rings with record low formation energy, whose accumulation leads to the loss of shear rigidity of graphene at temperatures above 6400K, thus setting the upper limit on its melting temperature. We found that this model satisfactorily explains the increase of specific heat observed in the premelting region of graphite in slow (millisecond) pulse heating experiments. However, in fast (microsecond) pulse heating experiments such an increase of specific heat was not observed, which is a strong indication of overheating that takes place in these experiments.

Intrinsic Planar Defects in Germanium and Their Contribution to the Excess Specific Heat at High Temperatures

Excessively high specific heat is usually observed in solids at comparatively high temperatures. It was believed to be associated with the anharmonic effects. Using the simple case of elemental germanium with archetypical diamond structure we demonstrate that anharmonicity effect can not fully describe its excess specific heat. Instead we propose the two type of extended planar defects with the record low formation energy (ΔE = 1900-1950 K) which can account for the discrepancy between theoretical and observed specific heat. By comparison of experimental and theoretical specific heat it was found that germanium sample is subdivided into domains where intrinsic planar defects are aligned along the single crystallographic direction.

(Invited) Electrochemical Extraction and Conversion of CO2 from Seawater

Capture and conversion of CO2 from anthropogenic emission is becoming an increasingly important social responsibility as the concentration of atmospheric CO2 continues to rise above record high levels. To achieve carbon negative conditions in the long term, capture and extraction of CO2 directly from air and seawater will likely play a much bigger role. The concentration of the present CO2 in the atmosphere is ~400 ppm, or 0.00079 kg m−3. As a result, a large volume of air needs to be processed in direct air capture processes. In contrast, world ocean constitutes the largest carbon sink, absorbing about 40% of anthropogenic CO2 since the beginning of industrial era with an effective CO2 concentration of 2.1 mmol kg−1, or 0.095 kg m−3 in seawater, which is a factor of 120 times larger than in the atmosphere. Thus, extraction of CO2 from seawater provides an alternative and unique approach in the global carbon removal technological landscape.Herein, a new bipolar membrane electrodialysis (BPMED) cell design, in which the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) at the electrodes were replaced with reversible redox couple reactions with minimal thermodynamic and kinetic voltage losses, was designed, constructed and evaluated. At an operating current density of 3.3 mA cm−2, and a seawater flow rate of 37 ml min−1, a record low electrochemical energy consumption of 155.4 kJ mol−1 or 0.98 kWh kg−1 of CO2 was achieved. The demonstrated BPMED cell also exhibited a high CO2 extraction efficiency of 71% of total dissolved inorganic carbon (DIC). We also demonstrated, for the first time, the direct coupling between the CO2 extraction from seawater via BPMED and electrochemical CO2 reduction (CO2R) into fuels and chemicals. The outlet CO2 stream from the BPMED was fed into tandem custom-built vapor-fed GDE cells to first perform the oxygen reduction reaction (ORR) using a nanoparticle Ag-based catalyst followed by CO2R using Cu or Ag as the electrocatalyst. This configuration allowed us to convert CO2 from seawater to fuels and valuable chemicals such as carbon monoxide, ethylene, ethanol, and propanol with total Faradaic efficiency (FE) of up to 73% at current densities of 58 mA cm−2 using CO2R Cu electrocatalyst and to carbon monoxide with selectivity of up to 95% at current densities of 11.15 mA cm−2 using CO2R Ag electrocatalyst. Figure 1

20-Gbit/s direct modulation of GaInAsP/InP membrane distributed-reflector laser with energy cost of less than 100 fJ/bit

We demonstrated 20-Gbit/s direct modulation with a low energy cost of the membrane distributed-reflector (DR) laser whose static lasing characteristics were previously reported by Tomiyasu et al. in Appl. Phy. Express 10, 062702 (2017). As a small-signal modulation characteristic, a modulation current efficiency of 12 GHz/mA1/2 was obtained. In 20-Gbit/s direct modulation using a non-return-to-zero 211 − 1 word-length pseudorandom bit sequence signal, a clear eye opening with a bit-error rate of 6.4 × 10−10 was obtained with a bias current of 1.06 mA and a bias voltage of 1.76 V, which resulted in a record low energy cost of 93 fJ/bit among membrane distributed-feedback (DFB) and DR lasers ever reported.

DAC-Less 32-GBd PDM-256-QAM Using Low-Power InP IQ Segmented MZM

We demonstrate DAC-less generation and transmission of 256-quadrature amplitude modulation signals at a symbol rate of 32 GBd using an indium phosphide segmented Mach–Zehnder modulator with 15 active sections and dedicated BiCMOS driver arrays. The linear quantization characteristic of the segmented modulator with 4-bit resolution allows the generation of spectrally efficient modulation formats without any transmitter side signal processing. The chip power consumption of 1.64 W translates into the record-low energy per bit of 6.4 pJ/b. Back-to-back performance is evaluated and two different low-density parity check codes enable error-free transmission over 80 and 120 km with a net data rate of 320 and 240 Gb/s, respectively.

1000-fold enhancement in proton conductivity of a MOF using post-synthetically anchored proton transporters.

Pyridinol, a coordinating zwitter-ionic species serves as stoichiometrically loadable and non-leachable proton carrier. The partial replacement of the pyridinol by stronger hydrogen bonding, coordinating guest, ethylene glycol (EG), offers 1000-fold enhancement in conductivity (10−6 to 10−3 Scm−1) with record low activation energy (0.11 eV). Atomic modeling coupled with 13C-SSNMR provides insights into the potential proton conduction pathway functionalized with post-synthetically anchored dynamic proton transporting EG moieties.

Low-Power Wearable ECG Monitoring System for Multiple-Patient Remote Monitoring

Many devices and solutions for remote electrocardiogram (ECG) monitoring have been proposed in the literature. These solutions typically have a large marginal cost per added sensor and are not seamlessly integrated with other smart home solutions. Here, we propose an ECG remote monitoring system that is dedicated to non-technical users in need of long-term health monitoring in residential environments and is integrated in a broader Internet-of-Things (IoT) infrastructure. Our prototype consists of a complete vertical solution with a series of advantages with respect to the state of the art, considering both the prototypes with integrated front end and prototypes realized with off-the-shelf components: 1) ECG prototype sensors with record-low energy per effective number of quantized levels; 2) an architecture providing low marginal cost per added sensor/user; and 3) the possibility of seamless integration with other smart home systems through a single IoT infrastructure.

Dependence of Voltage and Size on Write Error Rates in Spin-Transfer Torque Magnetic Random-Access Memory

The dependence of the write-error rate (WER) on the applied write voltage, write pulse width, and device size was examined in individual devices of a spin-transfer torque (STT) magnetic random-access memory (MRAM) 4 kbit chip. We present 10 ns switching data at the ${10^{ - 6}}$ error level for 655 devices, ranging in diameter from 50 nm to 11 nm, to make a statistically significant demonstration that a specific magnetic tunnel junction stack with perpendicular magnetic anisotropy is capable of delivering good write performance in junction diameters range from 50 to 11 nm. Furthermore, write-error-rate data on one 11 nm device down to an error rate of $7{\times}10^{ - 10}$ was demonstrated at 10 ns with a write current of $7.5\;\upmu{\rm A}$ , corresponding to a record low switching energy below 100 fJ.

The American Energy Revolution: Challenging Europe and the Middle East

The American energy revolution is depressing oil prices and disrupting global energy flows. The surge in shale gas and tight oil production will most probably help American energy imports and exports to come into balance within the next decade. The energy revolution has increased American self-reliance and strengthened US energy security, while record-low energy prices have boosted its competitive edge, especially over Europe. Moreover, diminishing oil imports are providing fertile ground for a revolution in the US's Middle Eastern policy, leading to a more independent and less engaging American role in the region. While the resulting security vacuum is hurting Europe, the increasingly shared regional interests may lead to enhanced cooperation between the US, the EU and China.

Temperature-Stable, Energy-Efficient, and High-Bit Rate Oxide-Confined 980-nm VCSELs for Optical Interconnects

We report 980-nm VCSELs that achieve temperature-stable, energy-efficient, and high-bit rate data transmission concurrently. Oxide-aperture-dependent static characteristics and high-speed modulation properties are analyzed at room temperature and also at high temperature. It is demonstrated that VCSELs with oxide-aperture diameters smaller than ∼5 μm are most suitable to achieve energy-efficient, temperature-stable, and high-bit rate operation concurrently. We demonstrate error-free data transmission (defined as a bit error ratio < 1 × 10 −12) at 38 Gb/s from 25 to 85 °C without any change of working point and modulation condition by using VCSELs with oxide-aperture diameters smaller than 5 μm. For VCSELs smaller than ∼7 μm, 42 Gb/s error-free data transmission at 25 °C is achieved. Record low energy dissipation at 85 °C is achieved with our ∼3 μm oxide-aperture diameter VCSELs. At room temperature, only 145, 147, and 217 fJ of dissipated heat energy per bit is needed for 35, 38, and 42 Gb/s error-free data transmission. Each of these bit rates is a record low heat dissipation for 980-nm VCSELs. Our VCSELs are especially well suited for very short reach (<2 m) optical interconnects in high-performance computers, for board-to-board and chip-to-chip input/output interfaces and data buses, and for on-chip integrated photonics.