71 research outputs found
Optimising Event-Driven Spiking Neural Network with Regularisation and Cutoff
Spiking neural networks (SNNs), a variant of artificial neural networks
(ANNs) with the benefit of energy efficiency, have achieved the accuracy close
to its ANN counterparts, on benchmark datasets such as CIFAR10/100 and
ImageNet. However, comparing with frame-based input (e.g., images), event-based
inputs from e.g., Dynamic Vision Sensor (DVS) can make a better use of SNNs
thanks to the SNNs' asynchronous working mechanism. In this paper, we
strengthen the marriage between SNNs and event-based inputs with a proposal to
consider anytime optimal inference SNNs, or AOI-SNNs, which can terminate
anytime during the inference to achieve optimal inference result. Two novel
optimisation techniques are presented to achieve AOI-SNNs: a regularisation and
a cutoff. The regularisation enables the training and construction of SNNs with
optimised performance, and the cutoff technique optimises the inference of SNNs
on event-driven inputs. We conduct an extensive set of experiments on multiple
benchmark event-based datasets, including CIFAR10-DVS, N-Caltech101 and DVS128
Gesture. The experimental results demonstrate that our techniques are superior
to the state-of-the-art with respect to the accuracy and latency
Room-Temperature Spin-Valve Effect in FeGaTe/MoS/FeGaTe 2D van der Waals Heterojunction Devices
Spin-valve effect has been the focus of spintronics over the last decades due
to its potential in many spintronic devices. Two-dimensional (2D) van der Waals
(vdW) materials are highly expected to build the spin-valve heterojunction.
However, the Curie temperatures (TC) of the vdW ferromagnetic 2D crystals are
mostly below room temperature (~30-220 K). It is very challenging to develop
room temperature, ferromagnetic (FM) 2D crystals based spin-valve devices which
are still not available to date. We report the first room temperature, FM 2D
crystal based all-2D vdW Fe3GaTe2/MoS2/Fe3GaTe2 spin valve devices. The
Magnetoresistance (MR) of the all- devices is up to 15.89% at 2.3 K and 11.97%
at 10 K, 4-30 times of MR from the spin valves of
FeGaTe/MoS/FeGaTe and conventional NiFe/MoS/NiFe.
Typical spin valve effect shows strong dependence on MoS2 spacer thickness in
the vdW heterojunction. Importantly, the spin valve effect (0.31%) still
robustly exists at 300 K with low working currents down to 10 nA (0.13
A/cm). The results provide a general vdW platform to room temperature, 2D
FM crystals based 2D spin valve devices
Room-temperature and tunable tunneling magnetoresistance in Fe3GaTe2-based all-2D van der Waals heterojunctions with high spin polarization
Magnetic tunnel junctions (MTJs) based on all-two dimensional (2D) van der
Waals heterostructures with sharp and clean interfaces in atomic scale are
essential for the application of next-generation spintronics. However, the lack
of room-temperature intrinsic ferromagnetic crystals with perpendicular
magnetic anisotropy has greatly hindered the development of vertical MTJs. The
discovery of room-temperature intrinsic ferromagnetic 2D crystal Fe3GaTe2 has
solved the problem and greatly facilitated the realization of practical
spintronic devices. Here, we demonstrate a room-temperature MTJ based on
Fe3GaTe2/WS2/Fe3GaTe2 heterostructure. The tunnelling magnetoresistance (TMR)
ratio is up to 213% with high spin polarization of 72% at 10 K, the highest
ever reported in Fe3GaTe2-based MTJs up to now. The tunnelling spin-valve
signal robustly exists at room temperature (300 K) with bias current down to 10
nA. Moreover, the spin polarization can be modulated by bias current and the
TMR shows a sign reversal at large bias current. Our work sheds light on the
potential application for low-energy consumption all-2D vdW spintronics and
offers alternative routes for the electronic control of spintronic devices
Cream roll-inspired advanced MnS/C composite for sodium-ion batteries: encapsulating MnS cream into hollow N,S-co-doped carbon rolls
Giant 2D Skyrmion Topological Hall Effect with Ultrawide Temperature Window and Low-Current Manipulation in 2D Room-Temperature Ferromagnetic Crystals
The discovery and manipulation of topological Hall effect (THE), an abnormal
magnetoelectric response mostly related to the Dzyaloshinskii-Moriya
interaction (DMI), are promising for next-generation spintronic devices based
on topological spin textures such as magnetic skyrmions. However, most
skyrmions and THE are stabilized in a narrow temperature window either below or
over room temperature with high critical current manipulation. It is still
elusive and challenging to achieve large THE with both wide temperature window
till room temperature and low critical current manipulation. Here, by using
controllable, naturally-oxidized, sub-20 and sub-10 nm 2D van der Waals
room-temperature ferromagnetic Fe3GaTe2-x crystals, robust 2D THE with
ultrawide temperature window ranging in three orders of magnitude from 2 to 300
K is reported, combining with giant THE of ~5.4 micro-ohm cm at 10 K and ~0.15
micro-ohm cm at 300 K which is 1-3 orders of magnitude larger than that of all
known room-temperature 2D skyrmion systems. Moreover, room-temperature
current-controlled THE is also realized with a low critical current density of
~6.2*10^5 A cm^-2. First-principles calculations unveil natural
oxidation-induced highly-enhanced 2D interfacial DMI reasonable for robust
giant THE. This work paves the way to room-temperature, electrically-controlled
2D THE-based practical spintronic devices
A comparison of growth on mercuric chloride for three Lemnaceae species reveals differences in growth dynamics that effect their suitability for use in either monitoring or remediating ecosystems contaminated with mercury
Mercury (Hg) is a toxic heavy metal that can alter the ecological balance when it contaminates aquatic ecosystems. Previously, researchers have used various Lemnaceae species either to monitor and/or remove heavy metals from freshwater systems. As Hg contamination is a pressing issue for aquatic systems worldwide, we assessed its impact on the growth of three commonly species of Lemnaceae - Lemna gibba 6745, Lemna minor 6580 and Spirodela polyrhiza 5543. We exposed plants to different concentrations of mercuric chloride (HgClâ‚‚) and monitored their growth, including relative growth rate, frond number (FN), and fresh weight (FW). These data were coupled with measurements of starch content, levels of photosynthetic pigment and the activities of antioxidant substances. The growth of all three lines showed significant negative correlations with Hg concentrations, and starch content, photosynthetic pigment, soluble protein and antioxidant enzymes levels were all clearly affected. Our results indicate that the L. gibba line used in this study was the most suitable of the three for biomonitoring of water contaminated with Hg. Accumulation of Hg was highest in the S. polyrhiza line with a bioconcentration factor over 1,000, making this line the most suitable of the three tested for use in an Hg bioremediation system
Room-temperature van der Waals 2D ferromagnet switching by spin-orbit torques
Emerging wide varieties of the two-dimensional (2D) van der Waals (vdW)
magnets with atomically thin and smooth interfaces holds great promise for
next-generation spintronic devices. However, due to the lower Curie temperature
of the vdW 2D ferromagnets than room temperature, electrically manipulating its
magnetization at room temperature has not been realized. In this work, we
demonstrate the perpendicular magnetization of 2D vdW ferromagnet Fe3GaTe2 can
be effectively switched at room temperature in Fe3GaTe2/Pt bilayer by
spin-orbit torques (SOTs) with a relatively low current density of 1.3
10^7A/cm2. Moreover, the high SOT efficiency of \xi_{DL}~0.22 is quantitatively
determined by harmonic measurements, which is higher than those in Pt-based
heavy metal/conventional ferromagnet devices. Our findings of room-temperature
vdW 2D ferromagnet switching by SOTs provide a significant basis for the
development of vdW-ferromagnet-based spintronic applications
Development of Efficient Protocols for Stable and Transient Gene Transformation for Wolffia Globosa Using Agrobacterium
Members of the Wolffia genus are fascinating plants for many biologists as they are the smallest flowering plants on Earth and exhibit a reduced body plan that is of great interest to developmental biologists. There has also been recent interest in the use of these species for bioenergy or biorefining. Molecular and developmental studies have been limited in Wolffia species due to the high genome complexity and uncertainties regarding the stable genetic transformation. In this manuscript we present new protocols for both stable and transient genetic transformation for Wolffia globosa using Agrobacterium tumefaciens. For the transient transformation, we used Wolffia fronds whereas we used clusters for the stable transformation. As proof of concept we transformed two synthetic promoter constructs driving expression of the GUS marker gene, that have previously been used to monitor auxin and cytokinin output in a variety of species. Using these approaches we obtained a Transformation Efficiency (TE) of 0.14% for the stable transformation and 21.8% for the transient transformation. The efficiency of these two methods of transformation are sufficient to allow future studies to investigate gene function. This is the first report for successful stable transformation of W. globosa
Large room-temperature magnetoresistance in van der Waals ferromagnet/semiconductor junctions
The magnetic tunnel junction (MTJ) is the core component in memory technologies, such as the magnetic random-access memory, magnetic sensors and programmable logic devices. In particular, MTJs based on two-dimensional (2D) van der Waals (vdW) heterostructures offer unprecedented opportunities for low power consumption and miniaturization of spintronic devices. However, their operation at room temperature remains a challenge. Here, we report a large tunnel magnetoresistance (TMR) of up to 85% at room temperature (T = 300 K) in vdW MTJs based on a thin (< 10 nm) semiconductor spacer WSe2 layer embedded between two Fe3GaTe2 electrodes with intrinsic above-room-temperature ferromagnetism. The TMR in the MTJ increases with decreasing temperature up to 164% at T = 10 K. The demonstration of TMR in ultra-thin MTJs at room-temperature opens a realistic and promising route for next-generation spintronic applications beyond the current state of the art
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