Joint Frequency and DOA Estimation with Automatic Pairing Using the Rayleigh–Ritz Theorem

This paper presents a novel scheme for joint frequency and direction of arrival (DOA) estimation, that pairs frequencies and DOAs automatically without additional computations. First, when the property of the Kronecker product is used in the received array signal of the multiple-delay output model, the frequency-angle steering vector can be reconstructed as the product of the frequency steering vector and the angle steering vector. The frequency of the incoming signal is then obtained by searching for the minimal eigenvalue among the smallest eigenvalues that depend on the frequency parameters but are irrelevant to the DOAs. Subsequently, the DOA related to the selected frequency is acquired through some operations on the minimal eigenvector according to the Rayleigh–Ritz theorem, which realizes the natural pairing of frequencies and DOAs. Furthermore, the proposed method can not only distinguish multiple sources, but also effectively deal with other arrays. The effectiveness and superiority of the proposed algorithm are further analyzed by simulations

Nonobese Male Patients with Alzheimer’s Disease Are Vulnerable to Decrease in Plasma Leptin

Background:Metabolic dysfunction links to cognitive deficits in Alzheimer’s disease (AD). Leptin is an anti-obesity hormone that modulates energy homeostasis and memory function. Although leptin deregulation is implicated in mouse models of AD-like brain pathology, clinical studies have shown inconsistent results regarding an association of leptin with the development of this neurodegenerative disorder. Objective:We investigated the changes of plasma leptin and the correlation of sex-stratified circulating leptin with cognitive performance, AD-related biological markers, and metabolic status in patients with AD and cognitively unimpaired (CU) counterparts. Methods:We used nonobese AD patients and CU controls in a University of Kansas Medical Center (KUMC) cohort. Plasma leptin levels, circulating AD-related molecules and metabolic profiles were examined and analyzed. Results:In contrast to unchanged circulating leptin in females, male patients exhibited decreased plasma leptin levels compared with male CU counterparts. Moreover, plasma leptin showed no correlation with cognitive performance and AD blood biomarkers in patients with either sex. Of note, females but not males demonstrated an association of plasma leptin with body mass index, high density lipoprotein-cholesterol and its ratio with total cholesterol and triglycerides. Conclusion:Our findings suggest that leptin deficiency is associated with nonobese male AD patients, supporting systemic dysmetabolism in the development of this neurodegenerative disorder in certain populations. Although plasma leptin may have limited capacity to reflect disease severity or progression, future mechanistic studies on the regulation of leptin in nonobese patients with AD would deepen our understanding of the sex-related disparity of AD etiopathogenesis

An effective strategy for the synthesis of biocompatible gold nanoparticles using danshensu antioxidant: prevention of cytotoxicity via attenuation of free radical formation

Abstract To suppress the cytotoxicity of gold nanoparticles (AuNPs), danshensu, a naturally occurring polyphenol antioxidant isolated from Chinese herb, was used to provide a fundamental protection layer for AuNPs, to alleviate oxidative stress and as a reducing agent to react with chloroauric acid. Besides danshensu, gum arabic was chosen as an auxiliary stabilising agent to improve the stability of AuNPs against aggregation. As expected, the prepared GA-DS-AuNPs (gum arabic-danshensu-gold nanoparticle) was remarkably stable in various buffer solutions. More interestingly, the GA-DS-AuNPs not only did not show any appreciable cytotoxicity, but also could alleviate the oxidative damage induced by AuNPs. Meanwhile, the ROS/RNS scavenging activities of GA-DS-AuNPs was evaluated by electron spin resonance spectroscopy (ESR), potentiometric nitric oxide (NO) sensor and cell confocal imaging. The results suggest that GA-DS-AuNPs might have effectively reduced the AuNPs-induced cytotoxicity and oxidative stress by downregulation of ROS/NOS production. The GA-DS-AuNPs may provide potential opportunities for the application in nanomedicine and nanobiology.postprin

High temperature performance of a piezoelectric micro cantilever for vibration energy harvesting

Energy harvesters withstanding high temperatures could provide potentially unlimited energy to sensor nodes placed in harsh environments, where manual maintenance is difficult and costly. Experimental results on a classical microcantilever show a 67% drop of the maximum power when the temperature is increased up to 160 °C. This decrease is investigated using a lumped-parameters model which takes into account variations in material parameters with temperature, damping increase and thermal stresses induced by mismatched thermal coefficients in a composite cantilever. The model allows a description of the maximum power evolution as a function of temperature and input acceleration. Simulation results further show that an increase in damping and the apparition of thermal stresses are contributing to the power drop at 59% and 13% respectively

Liver-expressed antimicrobial peptide 2 elevation contributes to age-associated cognitive decline

Elderly individuals frequently report cognitive decline, while various studies indicate hippocampal functional declines with advancing age. Hippocampal function is influenced by ghrelin through hippocampus-expressed growth hormone secretagogue receptor (GHSR). Liver-expressed antimicrobial peptide 2 (LEAP2) is an endogenous GHSR antagonist that attenuates ghrelin signaling. Here, we measured plasma ghrelin and LEAP2 levels in a cohort of cognitively normal individuals older than 60 and found that LEAP2 increased with age while ghrelin (also referred to in literature as “acyl-ghrelin”) marginally declined. In this cohort, plasma LEAP2/ghrelin molar ratios were inversely associated with Mini-Mental State Examination scores. Studies in mice showed an age-dependent inverse relationship between plasma LEAP2/ghrelin molar ratio and hippocampal lesions. In aged mice, restoration of the LEAP2/ghrelin balance to youth-associated levels with lentiviral shRNA Leap2 downregulation improved cognitive performance and mitigated various age-related hippocampal deficiencies such as CA1 region synaptic loss, declines in neurogenesis, and neuroinflammation. Our data collectively suggest that LEAP2/ghrelin molar ratio elevation may adversely affect hippocampal function and, consequently, cognitive performance; thus, it may serve as a biomarker of age-related cognitive decline. Moreover, targeting LEAP2 and ghrelin in a manner that lowers the plasma LEAP2/ghrelin molar ratio could benefit cognitive performance in elderly individuals for rejuvenation of memory

Focused Local Search for Random 3-Satisfiability

A local search algorithm solving an NP-complete optimisation problem can be viewed as a stochastic process moving in an 'energy landscape' towards eventually finding an optimal solution. For the random 3-satisfiability problem, the heuristic of focusing the local moves on the presently unsatisfiedclauses is known to be very effective: the time to solution has been observed to grow only linearly in the number of variables, for a given clauses-to-variables ratio $\alpha$ sufficiently far below the critical satisfiability threshold $\alpha_c \approx 4.27$. We present numerical results on the behaviour of three focused local search algorithms for this problem, considering in particular the characteristics of a focused variant of the simple Metropolis dynamics. We estimate the optimal value for the ``temperature'' parameter $\eta$ for this algorithm, such that its linear-time regime extends as close to $\alpha_c$ as possible. Similar parameter optimisation is performed also for the well-known WalkSAT algorithm and for the less studied, but very well performing Focused Record-to-Record Travel method. We observe that with an appropriate choice of parameters, the linear time regime for each of these algorithms seems to extend well into ratios $\alpha > 4.2$ -- much further than has so far been generally assumed. We discuss the statistics of solution times for the algorithms, relate their performance to the process of ``whitening'', and present some conjectures on the shape of their computational phase diagrams.Comment: 20 pages, lots of figure

Utilising Nonlinear Air Damping as a Soft Mechanical Stopper for MEMS Vibration Energy Harvesting

This paper reports on the theory and experimental verification of utilising air damping as a soft stopper mechanism for piezoelectric vibration energy harvesting to enhance shock resistance. Experiments to characterise device responsiveness under various vibration conditions were performed at different air pressure levels, and a dimensionless model was constructed with nonlinear damping terms included to model PVEH response. The relationship between the quadratic damping coefficient ζ n and air pressure is empirically established, and an optimal pressure level is calculated to trade off harvestable energy and device robustness for specific environmental conditions

Present-day Geostress Characteristics of the Central Region of the 1605 Qiongshan M 7.5 Earthquake and their Implications for Regional Fault Activity

Continuous subsidence, which has occurred over more than 100 km2 of the Dongzhai Harbor area, northeast Hainan Island, is likely to be associated with tectonic movement arising from the 1605 Qiongshan M 7.5 earthquake. It is the only earthquake in the history of China to have caused large-scale land subsidence into the sea, and the disaster led to the sinking of 72 villages. To understand the dynamic environment of this subsidence, a 300-meter-deep borehole was established on the eastern side of the Puqian town on the east coast of Dongzhai Harbor. A series of 10 in-situ stress measurements and 4 impression orientation measurements were carried out by the hydraulic fracturing method in the borehole. The results show that the maximum horizontal principal stress, SH, is between 5.70 to 12.07 MPa, and the minimum horizontal principal stress, Sh, is between 4.13 to 8.16 MPa. Compared with the magnitude of in-situ stress in the South China coastal area, the magnitude of the in-situ stress for Dongzhai Harbor is considered to be of a medium to upper level. The maximum horizontal principal stress direction is in the northwest direction (33.96°NW). The maximum and minimum horizontal lateral pressure coefficient values are both greater than 1, which indicates that the stress field at the measured point is mainly horizontal, with the principal stress increasing with the depth. The NW-trending principal compressive stress is likely to be one of the dynamic sources of the activity of the Puqian - Qinglan fault and the subsidence of the Dongzhai Harbor graben

A Serine/Threonine Protein Kinase Encoding Gene KERNEL NUMBER PER ROW6 Regulates Maize Grain Yield

Increasing grain yield of maize (Zea mays L.) is required to meet the rapidly expanding demands for maize-derived food, feed, and fuel. Breeders have enhanced grain productivity of maize hybrids by pyramiding desirable characteristics for larger ears. However, loci selected for improving grain productivity remain largely unclear. Here, we show that a serine/threonine protein kinase encoding gene KERNEL NUMBER PER ROW6 (KNR6) determines pistillate floret number and ear length. Overexpression of KNR6 or introgression of alleles lacking the insertions of two transposable elements in the regulatory region of KNR6 can significantly enhance grain yield. Further in vitro evidences indicate that KNR6 can interact with an Arf GTPase-activating protein (AGAP) and its phosphorylation by KNR6 may affect ear length and kernel number. This finding provides knowledge basis to enhance maize hybrids grain yield