This paper studies a novel design of user pairing and resource allocation in a simultaneous wireless information and power transfer (SWIPT)-enabled cooperative non-orthogonal multiple access (NOMA) ...system with coexisting power-splitting (PS) and time-switching (TS) users. In this system, near NOMA users (NUs) that are close to a source can assist the communications between the source and far NOMA users (FUs) using the energy harvested by either PS or TS strategy. The design aims to maximize the sum-rate of the system by optimizing user pairing and power allocation between NUs and FUs as well as performing PS and TS control at NUs, while guaranteeing the target data rates and the minimum harvested energy requirements of users. Since the joint design is formulated as a non-convex mixed-integer non-linear programming (MINLP) problem that is challenging to tackle, we propose a two-step user pairing and resource allocation algorithm. Specifically, we decouple the original problem into an inner resource allocation problem and an outer user pairing problem. For the inner problem, we propose successive convex approximation (SCA) and block coordinate descent (BCD)-based algorithms to perform power allocation as well as PS and TS control iteratively, with the algorithms' convergence being theoretically proved. By exploiting the characteristics of the outer problem of user pairing, this problem is well tackled by the Hungarian algorithm. Simulation results demonstrate the proposed joint design yields better performance gains than the existing schemes.
A major obstacle to industrial-scale astaxanthin production by the yeast Phaffia rhodozyma is the strong inhibitory effect of high glucose concentration on astaxanthin synthesis. We investigated, for ...the first time, the mechanism of the regulatory effect of high glucose (> 100 g/L) at the metabolite and transcription levels.
Total carotenoid, β-carotene, and astaxanthin contents were greatly reduced in wild-type JCM9042 at high (110 g/L) glucose; in particular, β-carotene content at 24-72 h was only 14-17% of that at low (40 g/L) glucose. The inhibitory effect of high glucose on astaxanthin synthesis appeared to be due mainly to repression of lycopene-to-β-carotene and β-carotene-to-astaxanthin steps in the pathway. Expression of carotenogenic genes crtE, pbs, and ast was also strongly inhibited by high glucose; such inhibition was mediated by creA, a global negative regulator of carotenogenic genes which is strongly induced by glucose. In contrast, astaxanthin-overproducing, glucose metabolic derepression mutant strain MK19 displayed de-inhibition of astaxanthin synthesis at 110 g/L glucose; this de-inhibition was due mainly to deregulation of pbs and ast expression, which in turn resulted from low creA expression. Failure of glucose to induce the genes reg1 and hxk2, which maintain CreA activity, also accounts for the fact that astaxanthin synthesis in MK19 was not repressed at high glucose.
We conclude that astaxanthin synthesis in MK19 at high glucose is enhanced primarily through derepression of carotenogenic genes (particularly pbs), and that this process is mediated by CreA, Reg1, and Hxk2 in the glucose signaling pathway.
With the development of the Internet of Things (IoT), it requires better performance from wireless sensor networks (WSNs), such as larger coverage, longer lifetime, and lower latency. However, a ...large amount of data generated from monitoring and long-distance transmission places a heavy burden on sensor nodes with the limited battery power. For this, we investigate an unmanned aerial vehicles assisted mobile wireless sensor network (UAV-assisted WSN) to prolong the network lifetime in this paper. Specifically, we use UAVs to assist the WSN in collecting data. In the current UAV-assisted WSN, the clustering and routing schemes are determined sequentially. However, such a separate consideration might not maximize the lifetime of the whole WSN due to the mutual coupling of clustering and routing. To efficiently prolong the lifetime of the WSN, we propose an integrated clustering and routing scheme that jointly optimizes the clustering and routing together. In the whole network space, it is intractable to efficiently obtain the optimal integrated clustering and routing scheme. Therefore, we propose the Monte-Las search strategy based on Monte Carlo and Las Vegas ideas, which can generate the chain matrix to guide the algorithm to find the solution faster. Unnecessary point-to-point collection leads to long collection paths, so a triangle optimization strategy is then proposed that finds a compromise path to shorten the collection path based on the geometric distribution and energy of sensor nodes. To avoid the coverage hole caused by the death of sensor nodes, the deployment of mobile sensor nodes and the preventive mechanism design are indispensable. An emergency data transmission mechanism is further proposed to reduce the latency of collecting the latency-sensitive data due to the absence of UAVs. Compared with the existing schemes, the proposed scheme can prolong the lifetime of the UAV-assisted WSN at least by 360%, and shorten the collection path of UAVs by 56.24%.
Acute encephalitis is a brain infection that can harm the nervous system if not recognized and treated promptly. However, the presence of the blood–brain barrier restricts therapeutic agent ...distribution from the bloodstream to the brain parenchyma, severely restricting effective therapy for this disease. Herein, a novel drug delivery system based on a macrophage (RAW 264.7 cells) artifactual diagnostic and therapeutic nanoparticles (IPD@RAW) drug‐loading approach is presented, which exploits RAW cells' ability to cross the blood–brain barrier and go toward inflammation, and efficiently realizes the targeted enrichment of diagnostic and therapeutic nanoparticles at the site of inflammation in the brain. This nano‐drug‐carrying technology can accurately depict the degree of inflammation in real time for an extended period due to the significant penetration depth and high signal‐to‐noise ratio of near‐infrared (NIR) imaging. Meanwhile, the modified polydopamine can trigger the controlled release of anti‐inflammatory drugs through photothermal conversion under NIR irradiation to reduce the expression of cellular inflammatory factors, such as TNF‐α, IL‐6, and IL‐1β, and alleviate the brain damage due to secretion of this inflammatory factor. As a result, this drug delivery system provides a reliable tool for overcoming the blood–brain barrier to achieve early diagnosis and treatment of acute encephalitis.
A novel drug delivery system is engineered based on a macrophage artifactual diagnostic and therapeutic nanoparticles (IPD@RAW) drug‐loading, which efficiently realizes the targeted enrichment of diagnostic and therapeutic nanoparticles at the site of inflammation in the brain. This drug delivery system provides a reliable tool for overcoming the blood–brain barrier to achieve early diagnosis and treatment of acute encephalitis.
It is generally believed that having high performance expectations is an effective means of motivating employees to pursue excellence and sustain the motivation driven by it, while ignoring the ...negative impact that hinders the incentive to sustain such expectations. Drawing on the conservation of resources theory, we constructed a moderated mediation model to examine the relationship between supervisor’s high performance expectations and the employee’s territoriality utilizing data from 291 supervisor–subordinate dyads from two companies in China. The results revealed that task autonomy moderated the indirect and positive effect of high performance expectations on employees’ territoriality through stress, such that this indirect effect was stronger when employees were assigned to higher levels of task autonomy. The theoretical of these findings, as well as future research directions, are discussed.
Misuse and abuse of veterinary antimicrobial agents have led to an alarming increase in bacterial resistance, clinical treatment failure, and drug residues. To address these problems, consistent and ...appropriate dosage regimens for veterinary antimicrobial agents are needed. Pharmacokinetics/Pharmacodynamics (PK/PD) models have been widely used to establish rational dosage regimens for veterinary antimicrobial agents that can achieve effective prevention and treatment of bacterial diseases and avoid the development of bacterial resistance. This review introduces building methods for PK/PD models and describes current PK/PD research progress toward rational dosage regimens for veterinary antimicrobial agents. Finally, the challenges and prospects of PK/PD models in the design of dosage regimens for veterinary antimicrobial agents are reviewed. This review will help to increase awareness of PK/PD modeling among veterinarians and hopefully promote its development and future use.
Display omitted
•Fe/Mn oxides loaded biochar could enhance the adsorption of tetracycline.•γ-Fe2O3 and MnO2 were the main crystalline phases of Fe/Mn oxides.•Fe/Mn oxides play complex acid and base ...roles to enhance the tetracycline adsorption.•Adsorption of tetracycline follow Elovich kinetic model and Langmuir isotherm.
A Fe/Mn oxides loaded biochar (FeMn-BC) was prepared to enhance the adsorption of tetracycline (TC). γ-Fe2O3 and MnO2 were assigned to the Fe and Mn oxides, respectively. The enhanced adsorption of TC was dominated by the loaded γ-Fe2O3 and MnO2. According to Akaike-Information-Criteria evaluation, Elovich kinetic and Langmuir isotherm models could best describe the adsorption with a maximum capacity of 14.24 mg/g. During adsorption process, the γ-Fe2O3 and MnO2 hydrolyzed into hydroxides (FeOOH and MnOOH) which acted as bases to complex with TC2− ion under alkaline condition (pH = 11). After the adsorption, the concentrations of leached Fe and Mn could meet the requirements PRC standards GB13456-2012 and GB8978-1996, respectively. The FeMn-BC had ~24% on TC removal (initial concentration of 20 mg/L) after four-cycles regeneration. The FeMn-BC was also available for TC adsorptions in column tests and actual wastewater.
Anatase and rutile, two major polymorphs of TiO2, have been used widely for environmental remediation, while anatase is apparently less effective for As(III) pollution management and needs ...substantial improvement. Herein, DFT calculations show that (001) rather than (101) and (100) facets of anatase are highly selective for As(III) adsorption. Facet control plays critical role during As(III) adsorption over pristine anatase surfaces and remains for mono doping, while diminishes substantially for dual doping. The second doping profoundly enhances As(III) adsorption for anatase facets with low activities and proves to be a viable strategy. Distinct from pristine surfaces where bidentate binuclear complexes prevail, monodentate complexes may become preferred due to doping, especially for dual doping where Fe site promotes adsorption via electronic effects. Doping causes As(III) oxidation when As centers interact directly with surfaces, and for mono doping, electron back-donation re-reduces As(V) to As(IV), while As(IV) occurs less for dual doping due to electron reservoir of Fe site that inhibits As(V) re-reduction. Regulatory mechanisms of facet control and effects of mono and dual doping for As(III) adsorption are further unraveled at molecular level. Results provide significant new insights for As(III) pollution management, and conduce to design As(III) scavengers and manage As-associated pollution.
Display omitted
Mobile edge computing (MEC) enables the caching of various services close to users, thereby reducing service delay for emerging applications. However, realizing efficient and secure computation ...offloading is challenging due to the limited storage capacity of MEC servers and the offloading security issue arising from the open nature of wireless channels. In this letter, we investigate a MEC network with an eavesdropper, where the MEC server caches service programs required for task execution. Moreover, we propose a cooperative jamming-assisted scheme to enhance the security of computation offloading, in which a friendly jammer actively transmits signals to disrupt eavesdropping. Considering the limited caching capacity of the MEC server and the security concerns of computation offloading, we formulate a delay minimization problem by jointly optimizing service caching placement, transmit power, and devices' computation offloading decisions. To tackle this problem, we develop an efficient layered algorithm using successive convex approximation and the cross entropy-based technique. Numerical results demonstrate the effectiveness of our proposed scheme in reducing the overall delay in completing devices' computation tasks compared to baseline schemes.
This paper investigates secure offloading for a wireless powered mobile edge computing (MEC) system. Specifically, an energy-constrained user is first charged by a power beacon (PB) via wireless ...power transfer (WPT) and then leverages the harvested energy to offload its computation tasks to a MEC server in the presence of multiple eavesdroppers. To enhance the security of computation offloading, we propose a novel physical layer security-assisted scheme, in which the PB can also play the role of a cooperative jammer by transmitting jamming signals to interfere with the eavesdroppers. The objective is to maximize secrecy energy efficiency (SEE) of the MEC system by jointly optimizing the transmit power for WPT, offloading, and jamming, the time allocated for WPT and offloading, and the computation task partition while satisfying the secrecy offloading rate constraint and the energy causality constraint. To deal with the highly non-convex problem, we develop an efficient two-layer algorithm by resorting to variable substitutions, successive convex approximation, and the Dinkelbach method. Simulation results demonstrate that our designed scheme yields a SEE performance enhancement as compared to benchmarks.
PDF
