In this letter, we apply the concept of media-based modulation with radio frequency mirrors to uncoded space-time labeling diversity (USTLD). Several configurations are investigated. Results ...demonstrate a significant improvement in the error performance over USTLD and the recently proposed space-time channel modulation for fast frequency-flat Rayleigh fading channels with and without channel estimation error. Improvement is also shown for the quasi-static channel case. The analytical average bit error probability is formulated for the scheme and is shown to agree well with Monte Carlo simulation results at moderate-to-high signal-to-noise ratios. Furthermore, the detection computational complexity of each configuration is analyzed in terms of the number of real operations.
The first contribution of this letter is to correct an error in the formulation of the Low-Complexity Euclidean Distance optimized Antenna Selection scheme for Spatial Modulation (SM), (SM-EDAS-LC). ...Secondly, due to a simulation error the Monte Carlo simulation results presented in the above letter for SM-EDAS-LC are erroneous, thus we present the correct results for the scheme, which demonstrates that the error performance in fact outperforms that of Capacity Optimized Antenna Selection for SM. The third contribution is to propose two modifications to SM-EDAS-LC that significantly reduce the computational complexity.
In this letter, we apply labeling diversity to a space-time block coded system, which does not require channel coding or bit interleaving. The proposed system is investigated for both Rayleigh ...frequency-flat fast and quasi-static fading channels. The theoretical average bit error probability of the system is formulated using the union bound approach. A possible optimization criterion for the design of the mappers for both M-ary quadrature amplitude modulated and M-ary phase shift keying modulated systems is suggested; however, due to a large solution space, a simple method is investigated.
Manipulation of magnetization by electric‐current‐induced spin–orbit torque (SOT) is of great importance for spintronic applications because of its merits in energy‐efficient and high‐speed ...operation. An ideal material for SOT applications should possess high charge‐spin conversion efficiency and high electrical conductivity. Recently, transition metal dichalcogenides (TMDs) emerge as intriguing platforms for SOT study because of their controllability in spin–orbit coupling, conductivity, and energy band topology. Although TMDs show great potentials in SOT applications, the present study is restricted to the mechanically exfoliated samples with small sizes and relatively low conductivities. Here, a manufacturable recipe is developed to fabricate large‐area thin films of PtTe2, a type‐II Dirac semimetal, to study their capability of generating SOT. Large SOT efficiency together with high conductivity results in a giant spin Hall conductivity of PtTe2 thin films, which is the largest value among the presently reported TMDs. It is further demonstrated that the SOT from PtTe2 layer can switch a perpendicularly magnetized CoTb layer efficiently. This work paves the way for employing PtTe2‐like TMDs for wafer‐scale spintronic device applications.
PtTe2, a layered type‐II Dirac semimetal, is successfully synthesized in a scalable and controllable manner. High spin–orbit torque and large spin Hall conductivity are found in these PtTe2 thin films, which manifest the potential of PtTe2 thin film for energy‐efficient magnetization switching. The experiments establish a primary basis for further research on similar systems for high‐performance spintronic devices.
To obtain new insights into the mechanisms of the positive effects of exogenous melatonin applications to cucumber seedlings during chilling, we investigated its role in regulating photosynthesis, ...the transcription level of csZat12 and the metabolism of polyamines (PAs) and of abscisic acid (ABA). The negative effects of chilling were clearly alleviated in cucumber seedlings by irrigation with 200 μM melatonin solution. This was evidenced by alleviation of the decline in net photosynthesis rate and also in electrolyte leakage in chilled plants. The reasons for this can be explained as follows. First, melatonin up-regulates CsZat12, an important stress-related gene. Second, melatonin increases the content of putrescine (Put) and spermidine (Spd) and stabilized spermine (Spm) by altering the activity of the PA metabolic enzymes. And, third, ABA is also involved in these effects as melatonin modulated the expression of the key ABA biosynthesis genes (CsNCED1 and CsNCED2) and also the key ABA catabolism genes (CsCYP707A1 and CsCYP707A2). This study provides new evidence suggesting melatonin mitigates chilling stress in cucumber by up-regulating the expression of CsZat12 and by modulating the metabolism of PAs and ABA.
Motivated to enhance the error performance (EP) of generalised complex quadrature spatial modulation (GCQSM) systems, this study proposes a scheme that builds on GCQSM and uses hexagonal quadrature ...amplitude modulation (H-QAM) constellations which have the advantages of a maximised Euclidean distance with relatively low peak-to-average power ratio, compared to conventional QAM (C-QAM) systems. This in turn, leads to an enhancement of the EP of GCQSM schemes. The proposed scheme utilises a rotated hexagonal 8QAM (H-8QAM) set. Thus, the proposed scheme is herein named; Generalised QSM using H-8QAM (GQSM-H-8QAM). In this study, the EP of the proposed GQSM-H-8QAM scheme is investigated over Rayleigh frequency flat-fading channels with additive white Gaussian noise. Additionally, a theoretical average bit error probability (ABEP) expression of the GQSM-H-8QAM scheme is formulated and validated using Monte Carlo simulations. Compared to simulation results, the ABEP proves to be increasingly tight at high signal-to-noise ratio values. Obtained simulation results also show an improvement in the EP of the GQSM-H-8QAM scheme over various SM schemes like GCQSM, C-QSM and conventional-generalized spatial modulation (C-GSM), at the same spectral efficiency (SE). An improvement in the EP of 0.61 dB with SE of 8 bits/s/Hz is seen in Formula: see text GQSM-H-8QAM over Formula: see text GCQSM using C-8QAM, 2.58 dB over Formula: see text C-QSM-C-64QAM and a gain of 4.85 dB over Formula: see text C-GSM-C-64QAM.
The K -complex symbol Golden codeword-based modulation ( K CSGC) scheme for multiple-input multiple-output systems has been recently proposed in the literature and is capable of achieving a high ...diversity order by transmitting the same K complex symbols in each of K time slots. In this paper, we investigate improving the spectral efficiency of a single-input multiple-output (SIMO) configuration of the scheme (SIMO- K CSGC) by employing radio frequency (RF) mirror assisted media-based modulation (MBM). Three schemes are investigated: Scheme 1 employs the same RF mirror activation pattern (MAP) in each of K time slots, Scheme 2 employs different MAPs in each of the K time slots, while Scheme 3 employs different MAPs in a subset k of the K time slots. A joint detector based on the sorted symbol set sphere decoder and maximum-likelihood detection rule is presented and its computational complexity is analyzed. The bit error rate versus signal-to-noise ratio (SNR) curves show that there is a negligible penalty incurred in SNR gain when the spectral efficiency is increased by a few bits per channel use. For higher increases in spectral efficiency, the penalty increases but is less significant with increasing K . Scheme 1 is found to be superior in terms of the error performance-spectral efficiency trade-off. The theoretical average bit error probability is derived for the SIMO- K CSGC-MBM scheme and demonstrates a very close match with simulation results.
Background Despite its known significance in plant abiotic stress responses, the role of the RAV gene family in the response of Capsicum annuum to chilling stress remains largely unexplored. Results ...In this study, we identified and characterized six members of the CaRAV gene subfamily in pepper plants through genome-wide analysis. Subsequently, the CaRAV subfamily was classified into four branches based on homology with Arabidopsis thaliana, each exhibiting relatively conserved domains within the branch. We discovered that light response elements accounted for the majority of CaRAVs, whereas low-temperature response elements were specific to the NGA gene subfamily. After pepper plants were subjected to chilling stress, qRT-PCR analysis revealed that CaRAV1, CaRAV2 and CaNGA1 were significantly induced in response to chilling stress, indicating that CaRAVs play a role in the response to chilling stress. Using virus-induced gene silencing (VIGS) vectors, we targeted key members of the CaRAV gene family. Under normal growth conditions, the MDA content and SOD enzyme activity of the silenced plants were slightly greater than those of the control plants, and the REC activity was significantly greater than that of the control plants. The levels of MDA and electrolyte leakage were greater in the silenced plants after they were exposed to chilling stress, and the POD and CAT enzyme activities were significantly lower than those in the control, which was particularly evident under repeated chilling stress. In addition, the relative expression of CaPOD and CaCAT was greater in V2 plants upon repeated chilling stress, especially CaCAT was significantly greater in V2 plants than in the other two silenced plants, with 3.29 and 1.10 increases within 12 and 24 h. These findings suggest that CaRAV1 and CaNGA1 positively regulate the response to chilling stress. Conclusions Silencing of key members of the CaRAV gene family results in increased susceptibility to chilling damage and reduced antioxidant enzyme activity in plants, particularly under repeated chilling stress. This study provides valuable information for understanding the classification and putative functions of RAV transcription factors in pepper plants. Keywords: RAV gene family, Transcription factor, Chilling stress, VIGS
Generalized spatial modulation (GSM) is a novel scheme developed from the conventional single-active antenna spatial modulation (SA-SM). The challenge of the GSM lies at the receiving end. Since more ...than one antenna is activated, the complexity of ML detection for GSM is much higher than that for SA-SM, especially if the number of antennas is large. Low complexity sub-optimal detections, such as ZF detection or MMSE detection, can be used to detect GSM. However, the performance of these detections is poor and cannot yet be applied in an underdetermined system. Spatial modulation has an inherent property of sparsity. However, to the best of our knowledge, this property has not been used for GSM. In this paper, we exploit this property and propose a sub-optimal detection algorithm. The traditional algorithm using sparsity is sensitive to noise and not suitable for the application to communication systems. Therefore, we employ a denoising scheme to counter the effect of the background noise.
Room temperature magnetic skyrmions in magnetic multilayers are considered as information carriers for future spintronic applications. Currently, a detailed understanding of the skyrmion ...stabilization mechanisms is still lacking in these systems. To gain more insight, it is first and foremost essential to determine the full real‐space spin configuration. Here, two advanced X‐ray techniques are applied, based on magnetic circular dichroism, to investigate the spin textures of skyrmions in Ta/CoFeB/MgOn multilayers. First, by using ptychography, a high‐resolution diffraction imaging technique, the 2D out‐of‐plane spin profile of skyrmions with a spatial resolution of 10 nm is determined. Second, by performing circular dichroism in resonant elastic X‐ray scattering, it is demonstrated that the chirality of the magnetic structure undergoes a depth‐dependent evolution. This suggests that the skyrmion structure is a complex 3D structure rather than an identical planar texture throughout the layer stack. The analyses of the spin textures confirm the theoretical predictions that the dipole–dipole interactions together with the external magnetic field play an important role in stabilizing sub‐100 nm diameter skyrmions and the hybrid structure of the skyrmion domain wall. This combined X‐ray‐based approach opens the door for in‐depth studies of magnetic skyrmion systems, which allows for precise engineering of optimized skyrmion heterostructures.
The skyrmionic spin textures in magnetic multilayers are determined using two advanced X‐ray techniques. First, the highly resolved two‐dimensional out‐of‐plane spin profile of the skyrmion is captured using ptychography. Second, the depth‐dependent chirality of the magnetic structure is directly measured using circular dichroism in resonant elastic X‐ray scattering. This combined X‐ray‐based approach opens the door for in‐depth studies of magnetic skyrmions.
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