DDPG-Based Throughput Optimization with AoI Constraint in Ambient Backscatter-Assisted Overlay CRN.

The combination of ambient backscatter (AB) communications (ABCs) and RF-powered cognitive radio networks (CRNs) deals with challenges of both energy supply and spectrum shortage, and improves the network performances. With the expansion of wireless networks, many applications raise requirements for both high-throughput and timely data. Driven by these facts, we study the long-term throughput optimization of the secondary network in the AB-assisted overlay CRN (ABO-CRN), ABCs, and CRNs with the age of information (AoI) constraint, which is a novel metric for measuring the freshness of data received by receivers. Due to the dynamic environment, complete knowledge of the environment could not be obtained. Then, the deep deterministic policy gradient (DDPG), a deep reinforcement learning (DRL) method that addresses decision issues in both continuous and discrete spaces, is deployed to address the throughput optimization. We consider the impacts of time and energy allocation on the reward when the AoI constraint can not be satisfied, and develop the corresponding reward functions. Furthermore, we analyze the impacts of the minimum throughput requirement and maximum allowable AoI on the throughput and AoI of the secondary networks in the ABO-CRN, ABCs, and CRNs. We compare the throughput optimization scheme under the AoI constraint with two baseline schemes (i.e., throughput-optimal (T-O) and AoI-optimal (A-O) baseline schemes), and the simulation results show that the throughput of the ABO-CRN is close to the optimal throughput of the T-O baseline scheme, and the AoI of the ABO-CRN is close to the optimal AoI of the A-O baseline scheme.

Joint Optimizations of Relays Locations and Decision Threshold for Multi-Hop Diffusive Mobile Molecular Communication With Drift.

In this paper, we study diffusive multi-hop mobile molecular communication (MMC) with drift in one-dimensional channel by adopting amplify-and-forward (AF) relay strategy. Multiple and single molecules type are used in each hop to transmit information, respectively. Under these two cases, the mathematical expressions of average bit error probability (BEP) of this system based on AF scheme are derived. We implement joint optimization problem whose objective is to minimize the average BEP with (Q + 2) optimization variables including (Q + 1) -hop distance ratios and decision threshold. Q is the number of relay nodes. Furthermore, considering that more optimization variables result in higher computation complexity, we use efficient algorithm which is adaptive genetic algorithm (AGA) to solve the optimization problems to search the location of each relay node and the decision threshold at destination node simultaneously. Finally, the numerical results reveal that AGA has a faster convergence speed and it is more efficient with fewer iterations compared with Bisection algorithm. The performances of average BEP with optimal distance ratio of each hop and decision threshold are evaluated. These results can be used to design multi-hop MMC system with optimal optimization variables and lower average BEP.

Mobile Two-Way Molecular Communication via Diffusion Using Amplify-and-Forward and Analog Network Coding.

Mobile molecular communication via diffusion (MCvD) has attracted lots of attentions due to its time-varying channels. In this paper, we investigate a mobile two-way MCvD model, which consists of two mobile source nanomachines and a mobile relay nanomachine. The amplify-and-forward (AF) relaying and analog network coding (ANC) are utilized to implement the exchange of information between two source nanomachines in this model. To explore the performance of the mobile two-way MCvD system, we first adopt the depleted molecule shift keying (D-MoSK) modulation, and then the mathematical expressions of symbol error probability (SEP) and mutual information are derived by using AF and ANC scheme on the basis of maximum a posteriori (MAP) probability detection. Finally, we present the numerical and simulation results. Compared with the AF-No-ANC scheme which is without use of ANC scheme, the scheme of combining AF and ANC can significantly improve the performance of SEP and mutual information. Moreover, the D-MoSK modulation outperforms the molecule shift keying (MoSK) modulation for this mobile two-way MCvD system. In addition, we propose the evaluation and discussion about the impacts of several important parameters on the performance of this system. These results can be used to design mobile two-way MCvD system with lower SEP and higher mutual information.

Secrecy Performance Maximization for Underlay CR Networks with an Energy Harvesting Jammer.

This paper investigates the secrecy communication in an underlay cognitive radio (CR) networks with one primary user (PU) as well as multiple PUs, where the radio frequency (RF) energy-harvesting secondary user (SU) transmits the confidential information to the destination in the presence of a potential eavesdropper. We introduce a RF energy-harvesting secondary jammer (SJ) to secure the SU transmissions. The system works in time slots, where each time slot is divided into the energy transfer (ET) phase and the information transfer (IT) phase. In ET phase, the SU and SJ capture energy from the PU transmissions; in the IT phase, the SU uses the harvested energy to transmit information to the destination without causing the harmful interference to the PU transmissions, while the SJ utilizes the captured energy to generate jamming signals to the eavesdropper to secure the SU transmissions. We aim to maximize the secrecy rate for SU transmissionsby jointly optimizing the time allocation between ET phase and IT phase and the transmit power allocation at the SU and SJ. We first formulate the secrecy rate maximization as non-convex optimization problems. Then, we propose efficient nested form algorithms for the non-convex problems. In the outer layer, we obtain the optimal time allocation by the one dimension search method. In the inner layer, we obtain the optimal transmit power allocation by the DC programming, where the Lagrange duality method is employed to solve the convex approximation problem. Simulation results verify that the proposed schemes essentially improve the secrecy rate of the secondary network as compared to the benchmark schemes.

Human action recognition based on HOIRM feature fusion and AP clustering BOW.

In this paper, we propose a human action recognition method using HOIRM (histogram of oriented interest region motion) feature fusion and a BOW (bag of words) model based on AP (affinity propagation) clustering. First, a HOIRM feature extraction method based on spatiotemporal interest points ROI is proposed. HOIRM can be regarded as a middle-level feature between local and global features. Then, HOIRM is fused with 3D HOG and 3D HOF local features using a cumulative histogram. The method further improves the robustness of local features to camera view angle and distance variations in complex scenes, which in turn improves the correct rate of action recognition. Finally, a BOW model based on AP clustering is proposed and applied to action classification. It obtains the appropriate visual dictionary capacity and achieves better clustering effect for the joint description of a variety of features. The experimental results demonstrate that by using the fused features with the proposed BOW model, the average recognition rate is 95.75% in the KTH database, and 88.25% in the UCF database, which are both higher than those by using only 3D HOG+3D HOF or HOIRM features. Moreover, the average recognition rate achieved by the proposed method in the two databases is higher than that obtained by other methods.

Energy Storage Overflow-Aware Data Delivery Scheme for Energy Harvesting Wireless Sensor Networks.

In Energy-Harvesting Wireless Sensor Networks (EH-WSNs), energy storage with limited capacity is used in the nodes to store the harvested energy. Energy storage overflow (ESO) happens when the energy storage is full, which causes the nodes to be unable to store the newly harvested energy. In traditional data delivery schemes, there is the problem of "energy hungry and surplus coexistence", meaning that some nodes in the network are hungry for energy while some other nodes continue to waste energy due to ESO. To alleviate this problem, in this paper, we present the ESO-aware multiple path (EAMP) data delivery scheme so that more data can be delivered to the sink. With the EAMP, multiple disjoint paths from the source node to the sink are constructed, and the source node splits data into multiple pieces with each going through one of the paths, which helps in mitigating ESO. Simulation results show that the proposed EAMP scheme can deliver more data than the existing ones.

Comparison of Intraperitoneal and Intraepididymal Quercetin for the Prevention of Testicular Torsion/Detorsion-induced Injury.

OBJECTIVE: To compare the effects of intraepididymal quercetin (IE-QE) with those of intraperitoneal quercetin (IP-QE) on testicular torsion/detorsion (TD)-induced ischemia/reperfusion (IR) injury of the testes in an experimental rat model. METHODS: Twenty-four rats were divided into 4 groups: sham (S), TD, TD treated with IP-QE, and TD treated with IE-QE. The IP-QE group received 20 mg/kg QE intraperitoneally, whereas the IE-QE group received quercetin (QE) epididymally. After surgically induced TD, sera and testicular tissues were obtained for the analysis of biochemical parameters including glutathione peroxidase (GPx), malondialdehyde, total antioxidant status, total oxidant status, oxidative stress index, histologic changes, and evaluation of germ cell apoptosis. RESULTS: The oxidative stress index and oxidants (malondialdehyde and total oxidant status) were increased with a concomitant decrease in the antioxidants (GPx and total antioxidant status) in the TD group. Severe histopathological damage, indicated by low Johnsen scores and high testicular injury grades, and germ cell apoptosis were found in the TD group compared with the other groups. Rats treated with QE showed significantly less IR injury, with moderately altered biochemical parameters, histopathological damage, and germinal cell apoptosis compared with the TD group. Most importantly, we found no significant differences in the biochemical parameters, histopathological changes, and germinal cell apoptosis between the IP-QE and IE-QE groups. CONCLUSION: IE-QE was comparable to IP-QE in the treatment of testicular TD. Local QE therapy should be considered as a new approach to treating testicular IR injury due to TD.

Dcsbis (PA2771) from Pseudomonas aeruginosa is a highly active diguanylate cyclase with unique activity regulation.

C-di-GMP (3',5' -Cyclic diguanylic acid) is an important second messenger in bacteria that influences virulence, motility, biofilm formation, and cell division. The level of c-di-GMP in cells is controlled by diguanyl cyclases (DGCs) and phosphodiesterases (PDEs). Here, we report the biochemical functions and crystal structure of the potential diguanylase Dcsbis (PA2771, a diguanylate cyclase with a self-blocked I-site) from Pseudomonas aeruginosa PAO1. The full-length Dcsbis protein contains an N-terminal GAF domain and a C-terminal GGDEF domain. We showed that Dcsbis tightly coordinates cell motility without markedly affecting biofilm formation and is a diguanylate cyclase with a catalytic activity much higher than those of many other DGCs. Unexpectedly, we found that a peptide loop (protecting loop) extending from the GAF domain occupies the conserved inhibition site, thereby largely relieving the product-inhibition effect. A large hydrophobic pocket was observed in the GAF domain, thus suggesting that an unknown upstream signaling molecule may bind to the GAF domain, moving the protecting loop from the I-site and thereby turning off the enzymatic activity.

Comparison of quercetin and resveratrol in the prevention of injury due to testicular torsion/detorsion in rats.

Quercetin (QE) and resveratrol (RSV) are powerful antioxidants with the potential to protect the testes against ischemia/reperfusion (I/R) injury. We compared their effects in testicular torsion/detorsion (T/D) in adult rats. Twenty-four male Wistar rats were divided into four groups: sham (group A), T/D (group B), T/D treated with QE (group C), and T/D treated with RSV (group D). QE (20 mg kg-1 ) and RSV (20 mg kg-1 ) were injected intra-peritoneally at 60 min of torsion. After 90 min of surgically induced torsion, the testicular cord was restored to its anatomical position. Twenty-four hour after torsion, blood and tissue samples were obtained for further examination. Testicular tissue malondialdehyde (MDA) and nitric oxide (NO) levels and serum total oxidant status (TOS) were higher in group B than in group A (P < 0.05). Group A had higher serum total antioxidant status (TAS) than group B. (P < 0.05) QE and RSV significantly lowered MDA, NO, and TOS levels and TAS consumption (P < 0.05). QE reduced the MDA and TOS levels more than RSV (P < 0.05), but their effects on NO reduction and TAS consumption were similar (P > 0.05). Group A had normal testicular architecture (grade 1). Groups C (mean grade 2.60) and D (mean grade 3.00) had lower testicular injury grades than group B (mean grade 3.45) (P < 0.05). Group C had lower testicular injury grade than group D (P < 0.05). Treatment with QE and RSV protects against I/R injury after testicular T/D. QE may exhibit better function than RSV at the doses tested in this study.

The REC domain mediated dimerization is critical for FleQ from Pseudomonas aeruginosa to function as a c-di-GMP receptor and flagella gene regulator.

FleQ is an AAA+ ATPase enhancer-binding protein that regulates both flagella and biofilm formation in the opportunistic pathogen Pseudomonas aeruginosa. FleQ belongs to the NtrC subfamily of response regulators, but lacks the corresponding aspartic acid for phosphorylation in the REC domain (FleQ(R), also named FleQ domain). Here, we show that the atypical REC domain of FleQ is essential for the function of FleQ. Crystal structure of FleQ(R) at 2.3Å reveals that the structure of FleQ(R) is significantly different from the REC domain of NtrC1 which regulates gene expression in a phosphorylation dependent manner. FleQ(R) forms a novel active dimer (transverse dimer), and mediates the dimerization of full-length FleQ in an unusual manner. Point mutations that affect the dimerization of FleQ lead to loss of function of the protein. Moreover, a c-di-GMP binding site deviating from the previous reported one is identified through structure analysis and point mutations.

Expression, purification and preliminary crystallographic analysis of a haem-utilizing protein, HutX, from Vibrio cholerae.

Vibrio cholerae, the causative agent of cholera, has developed a variety of mechanisms to obtain the limited-availability iron from human hosts. One important method for iron acquisition is through haem-uptake systems. Although the transport of haem has been widely studied, the fate of haem once it enters the cytoplasm remains an open question. Here, preliminary X-ray crystallographic analysis was performed on HutX, a member of the conserved haem-utilization operon from V. cholerae strain N16961. The crystals of HutX were found to belong to the orthorhombic space group C2221, with unit-cell parameters a = 50.1, b = 169.0, c = 81.8 Å. There are two protein molecules in the asymmetric unit, with a corresponding Matthews coefficient VM of 2.06 Å(3) Da(-1) and a solvent content of 40.28%.

Correlation between preferentially expressed antigen of melanoma and tumour necrosis factor-related apoptosis-inducing ligand gene expression in different types of leukaemia patients.

INTRODUCTION: Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) down-regulation by preferentially expressed antigen of melanoma (PRAME) is a general phenomenon in different types of solid tumours, but research on the correlation between PRAME and TRAIL gene expression in leukaemia patients is rare. METHOD: PRAME and TRAIL expression was detected in bone marrow samples from 80 newly diagnosed acute leukaemia (AL) patients and 40 chronic myeloid leukaemia (CML) patients using TaqMan-based real-time quantitative PCR methods, and a linear correlation analysis was performed on their levels of expression. A total of 15 normal bone marrow samples from individuals with non-malignant haematological diseases served as normal controls. RESULTS: PRAME expression was higher in both AL and CML patients compared to controls (both p < 0.001). CML patients in both blast crisis (BC) and the accelerated phase (AP) had significantly higher PRAME levels than CML patients in the chronic phase (CP) (p = 0.006 and 0.0461, respectively). TRAIL expression was higher in both the acute myeloid leukaemia (AML) group and the acute lymphoblastic leukaemia (ALL) group than in the controls (p = 0.039 and 0.047, respectively). In contrast, CML patients had lower TRAIL levels than controls (p = 0.043), and TRAIL expression in CML patients in the advanced phases (BC and AP) was significantly lower than in CML-CP patients (p = 0.006). In CML patients, there was a significant inverse correlation (Spearman's R = -0.6669, p < 0.0001) between PRAME and TRAIL gene expression, while a greater significant inverse correlation was found in patients in the advanced phases (BC and AP) (R = -0.6764). In addition, no correlation was observed in AML and ALL patients. CONCLUSION: The simultaneous detection of PRAME and TRAIL gene expression may be helpful to monitor condition changes in leukaemia patients and evaluate therapeutic effects in clinical practice, particularly in CML patients.