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关键词： ride-sharing platform   differential pricing   two-sided markets   price fairness  

摘要： Ride-sharing platforms, such as Uber and Didi Chuxing, widely use differential pricing strategies to encourage platform participation. However, it remains unclear whether differential pricing strategies in ride sharing are reasonable when users care about price fairness. Moreover, platforms face a unique dilemma when considering differential pricing: should it be used for customers, drivers, or both? On the demand side, platforms must deal with taxi competition, while the supply side contends with government regulation;it is this dilemma that motivates our work. Using a stylized model that includes price fairness, market conditions, and government policies, we consider four ride-sharing platform pricing strategies: uniform pricing, differential customer pricing, differential driver pricing, and bilateral differential pricing. We present results from three perspectives. For platforms, we obtain feasible regions in all four pricing strategies. If the maximal number of potential drivers is below certain thresholds, a platform will use differential driver pricing. Conversely, differential customer pricing is optimal when the maximal number of potential drivers is sufficiently large. Moreover, when customers have stronger fairness concerns, platforms tend to use differential driver pricing to reduce competition. From the government perspective, when a platform charges customers differently, the government can achieve a win-win solution for sustainable development and market stability by setting a proper taxi rate. Interestingly, we find that, for the demand and supply sides, an increase in fairness concerns may hurt customers and drivers under certain conditions.

关键词： infinite delay   integro-differential equation   optimal control   resolvent operator   time optimal control  

摘要： We study in this work the optimal control and time optimal control problems for a semi-linear integro-differential evolution system with infinite delay in Hilbert space. We first study the existence and uniqueness result of mild solutions in space X alpha for the considered system, and the main tools here are the theory of resolvent operators and fractional powers of operators and alpha-norm. In this way the obtained results are more general and can be applied to the systems involving terms having spatial derivatives. Then we discuss the Lagrange optimal control problem for the system via limit arguments. The time optimal control problem is also proposed and investigated deliberately for it. Finally, an example is provided to show the applications of the obtained results.

关键词： genome evolution   gene clusters   gene regulation   chemodiversity   histone modifications   pathogenicity   metabolomics   feature-based molecular network  

摘要： The genome of the wheat-pathogenic fungus Zymoseptoria tritici represents extensive presence-absence variation in gene content. Here, we addressed variation in biosynthetic gene cluster (BGC) content and biochemical profiles among three isolates. We analyzed secondary metabolite properties based on genome, transcriptome, and metabolome data. The isolates represent highly distinct genome architecture but harbor similar repertoires of BGCs. Expression profiles for most BGCs show comparable patterns of regulation among the isolates, suggesting a conserved biochemical infection program. For all three isolates, we observed a strong upregulation of a putative abscisic acid (ABA) gene cluster during biotrophic host colonization, indicating that Z. tritici interferes with host defenses by the biosynthesis of this phytohormone. Further, during in vitro growth, the isolates show similar metabolomes congruent with the predicted BGC content. We assessed if secondary metabolite production is regulated by histone methylation using a mutant impaired in formation of facultative heterochromatin (H3K27me3). In contrast to other ascomycete fungi, chromatin modifications play a less prominent role in regulation of secondary metabolites. In summary, we show that Z. tritici has a conserved program of secondary metabolite production, contrasting with the immense variation in effector expression, and some of these metabolites might play a key role during host colonization. IMPORTANCE Zymoseptoria tritici is one of the most devastating pathogens of wheat. So far the molecular determinants of virulence and their regulation are poorly understood. Previous studies have focused on proteinaceous virulence factors and their extensive diversity. In this study, we focus on secondary metabolites produced by Z. tritici. Using a comparative framework, we characterize core and noncore metabolites produced by Z. tritici by combining genome, transcriptome, and metabolome data sets. Our findings indicate

关键词： cytology   fluorescence in situ hybridization   lipoma   MDM2   well-differentiated liposarcoma  

摘要： Background Adipocytic tumors are the most common soft tissue tumors, with lipomas and atypical lipomatous tumor/well-differentiated liposarcomas (ALT/WDL), which comprise most cases. Preoperative differential diagnosis of lipoma or ALT/WDL can provide important information for decisions regarding treatment. We evaluated the cytological findings of 20 cases of lipoma and ALT/WDL. Methods Fluorescence in situ hybridization (FISH) was performed on formalin-fixed paraffin-embedded specimens (FFPE) to examine mouse double minute 2 homolog (MDM2) amplification in all cases. Tissue samples were collected from the center of the surgical materials, stained with Pap, and evaluated for 12 cytological parameters by six cytotechnologists. Results The findings regarding large atypical cells, multinucleated cells, and nuclear pleomorphism were highly concordant among the cytotechnologists and were associated with MDM2 amplification. Large atypical cells, considered a highly specific feature of ALT/WDL, were not observed in lipoma cases. However, the sensitivity of the large atypical cell findings was not high (67%);therefore, comprehensive evaluation of multinucleated cells and pleomorphism is crucial for predicting ALT/WDL diagnosis. FISH of MDM2 on Pap-stained specimens was performed in four cases. In two, the results were similar to those of MDM2 FISH performed on FFPE sections and were reproducible, whereas in the other two, the signal could not be evaluated because of the strong background coloration. Conclusions Cytology specimens may be useful for the preoperative diagnosis of adipocytic tumors, particularly if the FISH conditions for Pap-stained specimens and the detection accuracy of MDM2 amplification can be improved.

关键词： impulsive fractional stochastic differential systems   optimal controls   Rosenblatt process   semigroup theory  

摘要： The objective of this article is to consider a new class of fractional stochastic differential systems driven by the Rosenblatt process with impulses. We used fractional calculus, stochastic analysis, and Krasnoselskii's fixed point theorem to study the existence of piecewise continuous mild solutions for the proposed system. Further, we discussed the existence of optimal controls for the considered system. Our main results are well supported by an illustrative example.

关键词： bacteria   global change   microdiversity  

摘要： Global change experiments often observe shifts in bacterial community composition based on 16S rRNA gene sequences. However, this genetic region can mask a large amount of genetic and phenotypic variation among bacterial strains sharing even identical 16S regions. As such, it remains largely unknown whether variation at the sub16S level, sometimes termed microdiversity, responds to environmental perturbations and whether such changes are relevant to ecosystem processes. Here, we investigated microdiversity within Curtobacterium, the dominant bacterium found in the leaf litter layer of soil, to simulated drought and nitrogen addition in a field experiment. We first developed and validated Curtobacterium-specific primers of the groEL gene to assess microdiversity within this lineage. We then tracked the response of this microdiversity to simulated global change in two adjacent plant communities, grassland and coastal sage scrub (CSS). Currobacterium microdiversity responded to drought but not nitrogen addition, indicating variation within the genus of drought tolerance but not nitrogen response. Further, the response of microdiversity to drought depended on the ecosystem, suggesting that litter substrate selects for a distinct composition of microdiversity that is constrained in its response, perhaps related to tradeoffs in resource acquisition traits. Supporting this interpretation, a metagenomic analysis revealed that the composition of Curtobacterium-encoded carbohydrate-active enzymes (CAZymes) varied distinctly across the two ecosystems. Identifying the degree to which relevant traits are phylogenetically conserved may help to predict when the aggregated response of a 16S-defined taxon masks differential responses of finer-scale bacterial diversity to global change. IMPORTANCE Microbial communities play an integral role in global biogeochemical cycling, but our understanding of how global change will affect microbial community structure and functioning remains li

关键词： Microbiology   Biotechnology  

摘要： Acinetobacter baumannii is a multidrug-resistant bacteria responsible for nosocomial infections with significant fatality rates globally. Therapeutic failure and relapse of infection has been associated with persister cells formation which can also lead to resistance in A. baumannii. In the present study, we observed that A. baumannii ATCC 17978 in exponential phase survived lethal concentrations of amikacin, rifampicin and ciprofloxacin by generating persister cells but was unable to survive tobramycin treatment. The transcriptome of A. baumannii ATCC 17978 was analyzed following exposure to a high concentration of tobramycin (10 x MIC) for a short period of time to study the possible mechanisms responsible for lethality. Tobramycin reduced the expression of genes involved in energy production (nuoH, nuoN, nuoM, cydA, sucC), oxidative stress protection (tauD, cysD), and nutrition uptake (ompW) significantly. In addition, hemerythrin (non-heme di-iron oxygen-binding protein) was found to be the most downregulated gene in response to tobramycin which needs to be further studied for its role in susceptibility to antibiotics. Tobramycin upregulated the expression of genes that are mainly involved in stress response (leucine catabolism, DNA repair and HicAB toxin-antitoxin system). The differentially expressed genes highlighted in the study provided insight into the probable molecular mechanism of tobramycin-induced cell death and revealed some novel targets that can be explored further for their potential to control A. baumannii.

关键词： tissue thyroid hormone (T3)   mild endurance exercise   fasting   tissue BHB   tissue BCAA  

摘要： Mild endurance exercise has been shown to compensate for declined muscle quality and may positively affect the brain under conditions of energy restriction. Whether this involves brain-derived neurotrophic factor (BDNF) and mammalian target of rapamycin (mTOR) activation in relation to central and peripheral tissue levels of associated factors such as beta hydroxy butyrate (BHB), branched-chain amino acids (BCAA) and thyroid hormone (T3) has not been studied. Thus, a subset of male Wistar rats housed at thermoneutrality that were fed or fasted was submitted to 30-min-mild treadmill exercise bouts (five in total, twice daily, 15 m/min, 0 degrees inclination) over a period of 66 h. Prefrontal cortex and gastrocnemius muscle BHB, BCAA, and thyroid hormone were measured by LC-MS/MS analysis and were related to BDNF and mammalian target of rapamycin (mTOR) signaling. In gastrocnemius muscle, mild endurance exercise during fasting maintained the fasting-induced elevated BHB levels and BDNF-CREB activity and unlocked the downstream Akt-mTORC1 pathway associated with increased tissue BCAA. Consequently, deiodinase 3 mRNA levels decreased whereas increased phosphorylation of the mTORC2 target FOXO1 was associated with increased deiodinase 2 mRNA levels, accounting for the increased T3 tissue levels. These events were related to increased expression of CREB and T3 target genes beneficial for muscle quality previously observed in this condition. In rat L6 myoblasts, BHB directly induced BDNF transcription and maturation. Mild endurance exercise during fasting did not increase prefrontal cortex BHB levels nor was BDNF activated, whereas increased leucine levels were associated with Akt-independent increased phosphorylation of the mTORC1 target P70S6K. The associated increased T3 levels modulated the expression of known T3-target genes involved in brain tissue maintenance. Our observation that mild endurance exercise modulates BDNF, mTOR and T3 during fasting provides molecular

关键词： Mathematical model   Multi-agent systems   Shape   Heating systems   Robot kinematics   Partial differential equations   PD control   Boundary control   decentralized   formation control   multiple robots   partial differential equation (PDE)   stability   swarm  

摘要： We propose a method of controlling the formation in a multiagent system using partial differential equations (PDEs). In this method, the behavior of the entire multiagent system is modeled by second-order or higher order PDEs. We also propose a boundary controller that exponentially stabilizes the PDE model. By discretizing the PDE model under the proposed controller, the follower agents' control laws can be derived. Moreover, the boundary controller corresponds to the leader agents' control laws. The use of higher order PDEs leads to the generation of various formations that cannot be generated by using lower order PDEs. Finally, we conduct numerical simulations and experiments to validate the proposed method.

关键词： coevolution   host exploitation   Polistes dominula   Polistes sulcifer   sensory brain regions   sensory systems   social parasite  

摘要： Obligate insect social parasites evolve traits to effectively locate and then exploit their hosts, whereas hosts have complex social behavioral repertoires, which include sensory recognition to reject potential conspecific intruders and heterospecific parasites. While social parasites and host behaviors have been studied extensively, less is known about how their sensory systems function to meet their specific selective pressures. Here, we compare investment in visual and olfactory brain regions in the paper wasp Polistes dominula, and its obligate social parasite P. sulcifer, to explore the links among sensory systems,brain and behavior. Our results show significant relative volumetric differences between these two closely related species, consistent with their very different life histories. Social parasites show proportionally larger optic lobes and central complex to likely navigate long-distance migrations and unfamiliar landscapes to locate the specific species of hosts they usurp. Contrastingly, hosts have larger antennal lobes and calyces of the mushroom bodies compared with social parasites, as predicted by their sensory means to maintain social cohesion via olfactory signals, allocate colony tasks, forage, and recognize conspecific and heterospecific intruders. Our work suggests how this tradeoff between visual and olfactory brain regions may facilitate different sensory adaptations needed to perform social and foraging tasks by the host, including recognition of parasites, or to fly long distances and successful host localizing by the social parasite.