Analysis of echo signal modulation characteristic parameters on aerial and space targets

Based on the scattering characteristic,the comparison of RCS(radar cross-section)at different positions of a target in the same direction of incidence can be obtained first by extruding or deleting part of the entity.A simulation method of aerial&space targets echo characteristics(A&STEC)is proposed that is universal to aerial and space targets.We utilize a fixed-wing UAV(unmanned aerial vehicle)and typical missiles in simulation.The echo signal modulation characteristic parameters are calculated theoretically by the atmospheric attenuation model,the finite element method and a MUMPS solver.The verification simulations show that this method can analyze the influence of the target shape,incident direction,detection position and detection frequency on echo waveform,intensity and energy distribution.The results show that the profile of echo waveform can invert the general shape of the target.The relationship between time and intensity can determine whether the target is moving towards or away from the detector in addition.These conclusions can provide a reference for the ballistic missile target tracking and the defense against UVA intrusion in theory.

Crosstalk between the tumor microenvironment and tumor cells through exosomes:Roles in tumor metabolism and progression

Tumor proliferation,metabolism,metastasis,and chemoresistance are intimately related to the tumor microenvironment(TME).The metabolic reprogramming of tumor cells is a hallmark of their adaptation to hypoxic and nutrient-deficient TMEs.Exosomes,a type of extracellular vesicle,have been found to regulate the crosstalk between tumor cells and the TME,affecting tumor metabolic reprogramming.In this review,we introduce the metabolic characteristics of tumor cells;describe the crosstalk between tumor cells and the TME in terms of glucose metabolism,lipid metabolism,and amino acid metabolism through exosomes;and provide an overview of the diagnostic and therapeutic potential of exosomes.A better understanding of tumor metabolism would provide a broader perspective about the mechanisms underlying tumor pathology and would facilitate the search for therapeutic targets and guide more individualized tumor treatment.

Three important components in the regeneration of the cavernous nerve： brain-derived neurotrophic factor, vascular endothelial growth factor and the JAK/STAT signaling pathway

Retroperitoneal operations, such as radical prostatectomy, often damage the cavernous nerve, resulting in a high incidence of erectile dysfunction. Although improved nerve-sparing techniques have reduced the incidence of nerve injury, and the administration of phosphodiesterase type 5 inhibitors has revolutionized the treatment of erectile dysfunction, this problem remains a considerable challenge. In recent years, scientists have focused on brain-derived neurotrophic factor and vascular endothelial growth factor in the treatment of cavernous nerve injury in rat models. Results showed that both compounds were capable of enhancing the regeneration of the cavernous nerve and that activation of the Janus kinase （JAK）/signal transducer and activator of transcription （STAT） pathway played a major role in the process.

Numerical investigation of fluid phase momentum transfer in carbonate acidizing

This work mainly studies the effect of fluid phase momentum transfer mechanisms on the acidizing results,including the retardation effect of the porous structure and the interaction between the fluid phase,such as viscous dissipation and inertial effect.The results show that the acid fluid momentum transfer is influenced by the complex porous structure and fluid viscous dissipation.Eventually,the Stokes-Darcy equation is recommended to be adopted to describe the fluid phase momentum transfer in the following numerical simulation studies of the carbonate acidizing process.Based on this model,a parametric research is carried out to investigate the impact of acid on rock physical characteristics in the stimulation process.Increasing the acid concentration appears to minimize the quantity of acid consumed for the breakthrough.The acid surface reaction rate has a considerable impact on the pore volume to breakthrough and the optimum acid injection rate.The influence of permeability on the acidizing results basically shows a negative correlation with the injection rate.The difference between the acidizing curves of different permeability gradually becomes insignificant with the decrease in injection rate.The existence of isolated fracture and vug significantly reduces acid consumption for the breakthrough.

Zircon SHRIMP U-Pb dating of the Neogene coral reefs,Xisha Islands,South China Sea:implications for tectonic evolution

The Xisha Block is a minor one in the South China Sea and an important tectonic unit in the northwestern part of the region.Zircon SHRIMP U-Pb ages for three volcanic intrusive core samples from Xike-1,an exploratory well penetrating the bioherms of the Xisha Islands.The core samples are from the Miocene reef carbonate bedrock and are recognized as dark-gray biotite-hornblende gabbro,gray fne-grained biotite diorite,and gray fine-grained granite,respectively.Zircon cathodoluminescence (CL)images and trace Th,U and Pb compositions of the zircons show that these rocks are of volcanic intrusive origin.Zircon SHRIMP U-Pb dating yielded six groups of ages,ranging from 2451-1 857 Ma to early Cretaceous, which indicate that the formation and evolution of the Xisha Block was affected by the evolution and closure of Neotethys Ocean,probably within its eastern extension into South China Sea.Both old,deepsourced material,including fragments from Rodina supercontinent,and recent mantle-derived magma products contributed to the emergence and formation of the Xisha block.The SHRIMP U-Pb results also proved that this process differed from that of the Kontum massif,the Hainan Block,and the South China Block,but is similar to that of the Nansha and Zhongsha blocks.The process was associated with the effects of Yanshanian magmatism induced by subduction mechanisms of the Paleo-Pacific Plate or the reworking of the multiple magmatisms since the Early to mid-Yanshanian,possibly jointly experienced by the Xisha-Zhongsha-Nansha Block.

Effect and safety of mark-guided vs standard peroral endoscopic myotomy: A retrospective case control study

BACKGROUND Peroral endoscopic myotomy(POEM)is a promising therapeutic modality for esophageal achalasia worldwide.However,clinical failure and adverse events of POEM have still been concerned.AIM To compare the efficacy and safety of a novel mark-guided POEM with standard POEM.METHODS A total of 133 patients with esophageal achalasia who underwent POEM from May 2013 to May 2019 were enrolled in this retrospective study.Of the 133 patients,there were 64 patients in the mark-guided POEM group and 69 patients in the standard POEM group.The clinical success,procedural duration and adverse events were compared between the two groups at 3 mo,12 mo and 24 mo postoperatively.RESULTS Characteristic baseline was similar in the mark-guided POEM group and standard POEM group.The clinical success was comparable between the two groups,ranging from 92%to 98%,at 3 mo,12 mo and 24 mo postoperatively(all P>0.5).Eckart score,Gastroesophageal Reflux Disease Questionnaire score and SF-36 score were not different between the two groups after treatment(all P>0.05).No severe adverse events occurred in the two groups.However,markguided POEM required shorter procedural duration,and less use of proton pump inhibitors and lower incidence of reflux symptoms than the standard POEM(all P<0.001).CONCLUSION Mark-guided POEM and standard POEM were both effective and safe for the treatment of esophageal achalasia.However,the mark-guided POEM was characterized by shorter procedural duration,less use of proton pump inhibitors and lower incidence of reflux symptoms.

低速风洞轴流风扇研制进展

CARDC(China Aerodynamics Research and Development Center)has designed and developed various kinds of axial fans for specific wind tunnels in the previous decade.This paper not only gives summary about it,but also talks its future development.First,the contents are presented about high aerodynamic performance low-noise fan,including the methods of designing fan and ways of controlling noise generation and propagation,and how to reconcile the difficulties between noise control and fan efficiency raise.Then a simplified method of adjusting fan-blade angle during commissioning test is proposed and validated in practice.Contrary to usually used method,this simplified method can be implemented without using any test instruments of the fan,thus significantly reducing the commissioning test time of the fan.This is followed by the design of high pressure low Reynolds number axial fan.By using the method discussed in the paper,the restriction of Ma at blade tip not higher than 0.5 is relaxed.Accordingly,the pressure ratio obtained through one stage fan was raised above to 1.08,realizing the design target of Ma as 0.7 of the air in the test section.In addition,the topics about fan array,low hub-tip ratio fan and high pressure fan have been briefly covered for the future work.

Fitness consequences of divorce in the azure-winged magpie depends on the breeding experience of a new mate

Sexual conflict in producing and raising offspring is a critical issue in evolutionary ecology research.Individual experience affects their breeding performance,as measured by such traits of provisioning of offspring and engagement in extra-pair copulations,and may cause an imbalance in sexual conflict.Thus,divorce is hypothesized to occur within aged social pairs,irrespective of current reproductive success.This concept was explored in the azure-winged magpie Cyanopica cyanus by investigating the divorce of a social pair and its relationship to their changes in breeding performance with prior experience.Females engaging in extra-pair copulation may intensify sexual conflicts and may be the main reason for divorce.Once divorced,females repairing with an inexperienced male realized higher reproductive success than that repairing with an experienced male;males repairing with an experienced female realized higher reproductive success than that repairing with an inexperienced female.This finding indicates that the fitness consequence of divorce depends on the breeding experience of new mates.Divorced females can obtain more extra-pair copulations,whereas divorced males cannot,when they repair with inexperienced breeders.Divorced females provisioned a brood at lower rates than inexperienced females whereas divorced males had no such difference.It appears that divorced females can obtain an advantage in sexual conflicts with inexperienced mates in future reproduction.Consequently,females are probably more active than males in divorcing their aged mates so as to select an inexperienced male as a new mate.Azure-winged magpies thus provide novel insights into the implicaticns of sexual conflict in birds.

Parental dependence on the nest's spatial cues in offspring recognition decreases with nestling growth in the azure-winged magpie

In altricial birds,to address which cues are used by parents to recognize their offspring,and when they switch between cues during reproduction,it has not been well determined.In this study,we address this questi on in a Tibetan populatio n of the azure-winged magpie Cyanopica cyan us f by examining the dependence of parents on a nest's spatial position in offspring recognition.During the egg and nestling phases,azure-winged magpie nests were translocated to new positions across various distances from their original site,and parental responses to the translocated nests were investigated.Our findings show that a nesfs spatial position is not connected with the survival of its young,but might be used as a cue in parental offspring recognition.When nests are translocated to a new position within a certain distance,parents could recognize their nests and returned to resume their parenting behaviors.Parental dependence on the nest's spatial position in offspring recognition is higher during the egg phase than during the nestling phase,and it decreases with the growth of nestlings.After nestlings reach a certain age,the nest's spatial position was no longer used by pare nts as the single cue for offspring recog nition.These findings suggest that azure-winged magpies switch their cues in offspring recog nition during the differe nt stages of reproduction.After parent-offspring communication has been established,the offspring's phenotypic traits may become a more reliable cue than the nests spatial position in offspring recognition.

Coherent Control of the Hartman Effect through a Photonic Crystal with Four-Level Defect Layer

In this paper, we examine the transmission of a probe field through a one dimensional photonic crystal (1DPC) when the sixth layer of the crystal is doped with four level atoms. We analyze effects of the external driving field on the passage of weak probe field across the photonic crystal. It is found that for the phase time delay of the probe photons, intensity of the driving field switches the Hartman effect from sub to superluminal character. It is interesting to note that in our model, the superluminal transmission of the probe pulse is accompanied by a negligibly small absorption of the incident beam. It ensures that the probe field does not attenuate while passing through the photonic crystal. A similar switching of the Hartman effect may be obtained by adjusting detuning of the probe field related to the excited states of the four-level doping atoms.

Fecal consumption by adults of altricial birds in relation to the temporal change in nestling gut microbiota

Nest sanitation behavior of altricial birds has been selected to reduce the exposure of young to pathogens,parasites,or predators,and thus to maintain the health and safety of nestlings(Guigueno and Sealy 2012).During the process of nest sanitation,caregivers either carry away the fecal sacs of nestlings or directly eat them.Given that adults endure higher risk of being infected by pathogens during fecal consumption(Potti et al.2007),it remains a puzzle about why adults consume the nestling feces when they can transport them.Several hypotheses have been proposed to explain the fecal consumption behavior of altricial birds,including the nutrition hypothesis(Gliick 1988),economic hypothesis(Hurd et al.1991),and predation hypothesis(Ibanez-Alamo et al.2013).