Cyclic ADP-ribose and NAADP:fraternal twin messengers for calcium signaling

The concept advanced by Berridge and colleagues that intracellular Ca2+-stores can be mobilized in an agonist-dependent and messenger(IP3)-mediated manner has put Ca 2+-mobilization at the center stage of signal transduction mechanisms.During the late 1980s,we showed that Ca2+-stores can be mobilized by two other messengers unrelated to inositol trisphosphate(IP 3) and identified them as cyclic ADP-ribose(cADPR),a novel cyclic nucleotide from NAD,and nicotinic acid adenine dinucleotide phosphate(NAADP),a linear metabolite of NADP.Their messenger functions have now been documented in a wide range of systems spanning three biological kingdoms.Accumulated evidence indicates that the target of cADPR is the ryanodine receptor in the sarco/endoplasmic reticulum,while that of NAADP is the two pore channel in endolysosomes. As cADPR and NAADP are structurally and functionally distinct,it is remarkable that they are synthesized by the same enzyme.They are thus fraternal twin messengers.We first identified the Aplysia ADP-ribosyl cyclase as one such enzyme and,through homology,found its mammalian homolog,CD38.Gene knockout in mice confirms the important roles of CD38 in diverse physiological functions from insulin secretion,susceptibility to bacterial infection,to social behavior of mice through modulating neuronal oxytocin secretion.We have elucidated the catalytic mechanisms of the Aplysia cyclase and CD38 to atomic resolution by crystallography and site-directed mutagenesis.This article gives a historical account of the cADPR/NAADP/CD38-signaling pathway and describes current efforts in elucidating the structure and function of its components.

Inhibition of CD38/Cyclic ADP-ribose Pathway Protects Rats against Ropivacaine-induced Convulsion

Background： The CD38/cyclic ADP-ribose （cADPR） pathway plays a role in various central nervous system diseases and in morphine tolerance, but its role in local anesthetic intoxication is unknown. The aim of this study was to determine the role of the CD38/cADPR pathway in ropivacaine-induced convulsion. Methods： Forty male Sprague-Dawley rats were randomly divided into five groups （n = 8 per group）： sham group, ropivacaine group, ropivacaine＋8-Br-cADPR （5 nmol） group, ropivacaine＋8-Br-cADPR （10 nmol） group, and ropivacaine＋8-Br-cADPR （20 nmol） group （no rats died）. Rats were intracerebroventricularly injected with normal saline or 8-Br-cADPR 30 min before receiving an intraperitoneal injection of ropivacaine. Electroencephalography and convulsion behavior scores were recorded. The hippocampus was harvested from each group and subjected to nicotinamide adenine dinucleotide and cADPR assays, Western blotting analysis, and malondialdehyde （MDA） and superoxide dismutase （SOD） assays. Results： Intraperitoneal injection of ropivacaine （33.8 mg/kg） induced convulsions in rats. CD38 and cADPR levels increased significantly following ropivacaine-induced convulsion （P = 0.031 and 0.020, respectively, compared with the sham group）. Intraventricular injection of 8-Br-cADPR （5, 10, and 20 nmol） significantly prolonged convulsion latency （P = 0.037, 0.034, and 0.000, respectively）, reduced convulsion duration （P = 0.005, 0.005, and 0.005, respectively）, and reduced convulsion behavior scores （P = 0.015, 0.015, and 0.000, respectively）. Intraventricular injection of 8-Br-cADPR （10 nmol） also increased the B-cell lymphoma-2 （Bcl-2）/Bcl-2-associated X protein ratio （P = 0.044） and reduced cleaved Caspase 3/Caspase 3 ratio, inducible nitric oxide synthase, MDAand SOD levels （P = 0.014, 0.044, 0.001, and 0.010, respectively） compared with the ropivacaine group. Conclusions： The CD38/cADPR pathway is activated in ropivacaine-induced convulsion. Inhibiting this pathway alleviates ropivacaine-induced convulsion and protects the brain from apoptosis and oxidative stress.

Structure-activity relationship of cyclic ADP-ribose, an update

Cyclic ADP-ribose (cADPR) is a universal Ca2+ mobilizing second messenger in many different cell types and organisms. cADPR activates Ca2+ release from endo/sarcoplasmic reticulum via ryanodine receptors. In addition, Ca2+ entry secondary to Ca2+ depletion is at least one of the mechanisms in which cADPR triggers Ca2+ inflow, too. Analogues of cADPR have been prepared by chemical and chemo-enzymatic routes. Most of the analogues were analyzed for biological activity in intact or permeabilized Jurkat T cells (a human T-lymphoma cell line). As a systematic approach, analogues were grouped according to alterations in the base, the northern ribose, the southern ribose, the pyrophosphate backbone, or in complex modifications, comprising more than one part of the molecule. Biological activity of the analogues is reviewed, with special emphasis on Jurkat T cells.

Poly (ADP-ribose): A double-edged sword governing cancer cell survival and death

Poly(ADP-ribose)(PAR),a polymer of ADP-ribose,is synthesized by PAR po-lymerase and is crucial for the survival of cancer cells due to its vital functions in DNA repair and post-translational modifications.Beyond its supportive role,PAR also triggers cancer cell death by excessive accumulation of PAR leading to an energy crisis and parthanatos.This phenomenon underscores the potential of targeting PAR regulation as a novel anticancer strategy,and the rationale would present an engaging topic in the field of anticancer research.Therefore,this editorial provides an overview of the mechanisms determining cancer cell fate,emphasizing the central role of PAR.It further introduces promising methods for modulating PAR concentrations that may pave the way for innovative anticancer therapies.

Low testing rates and high BRCA prevalence: Poly (ADP-ribose) polymerase inhibitor use in Middle East BRCA/homologous recombination deficiency-positive cancer patients

BACKGROUND Poly(ADP-ribose)polymerase inhibitors(PARPis)are approved as first-line therapies for breast cancer gene(BRCA)-positive,human epidermal growth factor receptor 2-negative locally advanced or metastatic breast cancer.They are also effective for new and recurrent ovarian cancers that are BRCA-or homologous recombination deficiency(HRD)-positive.However,data on these mutations and PARPi use in the Middle East are limited.AIM To assess BRCA/HRD prevalence and PARPi use in patients in the Middle East with breast/ovarian cancer.METHODS This was a single-center retrospective study of 57 of 472 breast cancer patients tested for BRCA mutations,and 25 of 65 ovarian cancer patients tested for HRD.These adult patients participated in at least four visits to the oncology service at our center between August 2021 and May 2023.Data were summarized using descriptive statistics and compared using counts and percentages.Response to treatment was assessed using Response Evaluation Criteria in Solid Tumors criteria.RESULTS Among the 472 breast cancer patients,12.1%underwent BRCA testing,and 38.5%of 65 ovarian cancer patients received HRD testing.Pathogenic mutations were found in 25.6%of the tested patients:26.3%breast cancers had germline BRCA(gBRCA)mutations and 24.0%ovarian cancers showed HRD.Notably,40.0%of gBRCA-positive breast cancers and 66.0%of HRD-positive ovarian cancers were Middle Eastern and Asian patients,respectively.PARPi treatment was used in 5(33.3%)gBRCA-positive breast cancer patients as first-line therapy(n=1;7-months progression-free),for maintenance(n=2;>15-months progression-free),or at later stages due to compliance issues(n=2).Four patients(66.6%)with HRD-positive ovarian cancer received PARPi and all remained progression-free.CONCLUSION Lower testing rates but higher BRCA mutations in breast cancer were found.Ethnicity reflected United Arab Emirates demographics,with breast cancer in Middle Eastern and ovarian cancer in Asian patients.

Exploring the interaction between the gut microbiota and cyclic adenosine monophosphate-protein kinase A signaling pathway:a potential therapeutic approach for neurodegenerative diseases

The interaction between the gut microbiota and cyclic adenosine monophosphate(cAMP)-protein kinase A(PKA)signaling pathway in the host's central nervous system plays a crucial role in neurological diseases and enhances communication along the gut–brain axis.The gut microbiota influences the cAMP-PKA signaling pathway through its metabolites,which activates the vagus nerve and modulates the immune and neuroendocrine systems.Conversely,alterations in the cAMP-PKA signaling pathway can affect the composition of the gut microbiota,creating a dynamic network of microbial-host interactions.This reciprocal regulation affects neurodevelopment,neurotransmitter control,and behavioral traits,thus playing a role in the modulation of neurological diseases.The coordinated activity of the gut microbiota and the cAMP-PKA signaling pathway regulates processes such as amyloid-β protein aggregation,mitochondrial dysfunction,abnormal energy metabolism,microglial activation,oxidative stress,and neurotransmitter release,which collectively influence the onset and progression of neurological diseases.This study explores the complex interplay between the gut microbiota and cAMP-PKA signaling pathway,along with its implications for potential therapeutic interventions in neurological diseases.Recent pharmacological research has shown that restoring the balance between gut flora and cAMP-PKA signaling pathway may improve outcomes in neurodegenerative diseases and emotional disorders.This can be achieved through various methods such as dietary modifications,probiotic supplements,Chinese herbal extracts,combinations of Chinese herbs,and innovative dosage forms.These findings suggest that regulating the gut microbiota and cAMP-PKA signaling pathway may provide valuable evidence for developing novel therapeutic approaches for neurodegenerative diseases.

SlPGR5/SlPGRL1 pathway-dependent cyclic electron transport regulates photoprotection and chloroplast quality in tomato plants

The essential photoprotective role of proton gradient regulation 5(PGR5)-dependent cyclic electron flow(CEF)has been reported in Arabidopsis,rice,and algae.However,its functional assessment has not been performed in tomato yet.In this study,we focused on elucidate the function of SlPGR5 and SlPGR5-like photosynthetic phenotype 1(PGRL1)in tomato.We performed RNA interference and found that SlPGR5/SlPGRL1-suppressed transformants exhibited extremely low CO_(2)assimilation capacity,their photosystem I(PSI)and PSII were severely photoinhibited and chloroplasts were obviously damaged.The SlPGR5/SlPGRL1-suppressed plants almost completely inhibited CEF and Y(ND),and PSII photoinhibition may be directly related to the inability to produce sufficient proton motive force to induce NPQ.The transgenic plants overexpressing SlPGR5 and SlPGRL1 driven by 35S promoter capable alleviate photoinhibition of plants under low night temperature.The transcriptomic and proteomic analyses suggested that the nuclear gene transcription and turnover of chloroplast proteins,including the plastoglobule-related proteins,were closely related to SlPGR5/SlPGRL1 pathway dependent CEF.The bridge relationship between CEF and chloroplast quality maintenance was a novel report to our knowledge.In conclusion,these results revealed the regulatory mechanism of the SlPGR5/SlPGRL1 pathway in photoprotection and maintenance of chloroplast function in tomato,which is crucial for reduce yield loss,especially under adverse environmental conditions.

Bidirectional regulation of the cyclic guanosine monophosphateadenosine monophosphate synthase-stimulator of interferon gene pathway and its impact on hepatocellular carcinoma

BACKGROUND Hepatocellular carcinoma(HCC)ranks as the fourth leading cause of cancerrelated deaths in China,and the treatment options are limited.The cyclic guanosine monophosphate-adenosine monophosphate synthase(cGAS)activates the stimulator of interferon gene(STING)signaling pathway as a crucial immune response pathway in the cytoplasm,which detects cytoplasmic DNA to regulate innate and adaptive immune responses.As a potential therapeutic target,cGASSTING pathway markedly inhibits tumor cell proliferation and metastasis,with its activation being particularly relevant in HCC.However,prolonged pathway activation may lead to an immunosuppressive tumor microenvironment,which fostering the invasion or metastasis of liver tumor cells.AIM To investigate the dual-regulation mechanism of cGAS-STING in HCC.METHODS This review was conducted according to the PRISMA guidelines.The study conducted a comprehensive search for articles related to HCC on PubMed and Web of Science databases.Through rigorous screening and meticulous analysis of the retrieved literature,the research aimed to summarize and elucidate the impact of the cGAS-STING pathway on HCC tumors.RESULTS All authors collaboratively selected studies for inclusion,extracted data,and the initial search of online databases yielded 1445 studies.After removing duplicates,remaining 964 records were screened.Ultimately,55 articles met the inclusion criteria and were included in this review.CONCLUSION Acute inflammation can have a few inhibitory effects on cancer,while chronic inflammation generally promotes its progression.Extended cGAS-STING pathway activation will result in a suppressive tumor microenvironment.

Poly(ADP-ribose) polymerase inhibition reveals a potential mechanism to promote neuroprotection and treat neuropathic pain

Neuropathic pain is triggered by the lesions to peripheral nerves which alter their structure and function. Neuroprotective approaches that jimit the pathological changes and improve the behavioral outcome have been well explained in different experimental models of neuropathy but translation of such strategies to clinics has been disappointing. Experimental evidences revealed the role of free radicals, especially per- oxynitrite after the nerve injury. They provoke oxidative DNA damage and consequent over-activation of the poly（ADP-ribose） polymerase （PARP） upregulates pro-inflammatory pathways, causing bioenergetic crisis and neuronal death. Along with these changes, it causes mitochondrial dysfunction leading to neu- ronal apoptosis. In related preclinical studies agents that neutralize the free radicals and pharmacological inhibitors of PARP have shown benefits in treating experimental neuropathy. This article reviews the in- volvement of PARP over-activation in trauma induced neuropathy and therapeutic significance of PARP inhibitors in the experimental neuropathy and neuropathic pain.

Multiple facets of poly(ADP-ribose) polymerase-1 in neurological diseases

The highly conserved abundant nuclear protein poly （ADP-ribose） polymerase-1 （PARP-1） is activated by DNA damage. PARP-1 activation is associated in DNA repair, cell death and inflammation. Since oxidative stress induced robust DNA damage and wide spread inflamma- tory responses are common pathologies of various CNS diseases, the attention towards PARP-1 as a therapeutic target has been amplifying. This review highlights the multiple roles of PARP- 1 in neurological diseases and po- tential of PARP- 1 inhibitors to enter clinical translation.

Mechanical responses of anchoring structure under triaxial cyclic loading

Dynamic load on anchoring structures(AS)within deep roadways can result in cumulative damage and failure.This study develops an experimental device designed to test AS under triaxial loads.The device enables the investigation of the mechanical response,failure mode,instability assessment criteria,and anchorage effect of AS subjected to combined cyclic dynamic-static triaxial stress paths.The results show that the peak bearing strength is positively correlated with the anchoring matrix strength,anchorage length,and edgewise compressive strength.The bearing capacity decreases significantly when the anchorage direction is severely inclined.The free face failure modes are typically transverse cracking,concave fracturing,V-shaped slipping and detachment,and spallation detachment.Besides,when the anchoring matrix strength and the anchorage length decrease while the edgewise compressive strength,loading rate,and anchorage inclination angle increase,the failure intensity rises.Instability is determined by a negative tangent modulus of the displacement-strength curve or the continued deformation increase against the general downward trend.Under cyclic loads,the driving force that breaks the rock mass along the normal vector and the rigidity of the AS are the two factors that determine roadway stability.Finally,a control measure for surrounding rock stability is proposed to reduce the internal driving force via a pressure relief method and improve the rigidity of the AS by full-length anchorage and grouting modification.

Inhibition of poly(ADP-Ribose)polymerase:A promising strategy targeting pancreatic cancer with BRCAness phenotype

The use of chemotherapeutic regimens for the treatment of pancreatic cancer is still limited because pancreatic cancer is usually diagnosed at an advanced stage as a refractory disease in which symptoms are difficult to recognize in the early stages.Furthermore,at advanced stages,there are important challenges to achieve clinical benefit and symptom resolution,even with the use of an expanded spectrum of anticancer drugs.Recently,a point of reduced susceptibility to conventional chemotherapies by breast cancer susceptibility gene(BRCA)mutations led to a new perspective for overcoming the resistance of pancreatic cancer within the framework of increased genome instability.Poly(ADP-Ribose)polymerase(PARP)-1 is an enzyme that can regulate intrinsic functions,such as response to DNA damage.Therefore,in an environment where germline mutations in BRCAs(BRCAness)inhibit homologous recombination in DNA damage,resulting in a lack of DNA damage response,a key role of PARP-1 for the adaptation of the genome instability could be further emphasized.Here,we summarized the key functional role of PARP-1 in genomic instability of pancreatic cancer with the BRCAness phenotype and listed clinical applications and outcomes of PARP-1 inhibitors to highlight the importance of targeting PARP-1 activity.

Poly(ADP-ribose) polymerase-1 gene polymorphism in various Chinese nationalities

Poly （ADP-ribose） polymerase-1 （PARP-1） can exacerbate ischemic brain injury and lessen ischemic neuronal death, which may be associated with PARP-1 polymorphisms. The present study investigated human PARP-1 gene polymorphisms in various Chinese nationalities, the results of which could potentially help in the treatment and prevention of neurologic diseases. Genetic polymorphisms of seven exons in the PARP-1 gene, in 898 Chinese Han, Buyi, Shui, Miao, and Zhuang subjects, were investigated by PCR-single-strand conformation polymorphism. A single-strand conformation polymorphism variant in exons 12, 13, 16, and 17 of the PARP-1 gene was identified in 148 people, with two stationary bands showing three degenerative single strands. Results showed that the PARP-1 gene polymorphisms exist in various nationalities, and may act as a biomarker for susceptibility to disease.

Experimental study of the damage characteristics of rocks containing non-penetrating cracks under cyclic loading

The damage evolution process of non-penetrating cracks often causes some unexpected engineering disasters.Gypsum specimens containing non-penetrating crack(s)are used to study the damage evolution and characteristics under cyclic loading.The results show that under cyclic loading,the relationship between the number of non-penetrating crack(s)and the characteristic parameters(cyclic number,peak stress,peak strain,failure stress,and failure strain)of the pre-cracked specimens can be represented by a decreasing linear function.The damage evolution equation is fitted by calibrating the accumulative plastic strain for each cycle,and the damage constitutive equation is proposed by the concept of effective stress.Additionally,non-penetrating cracks are more likely to cause uneven stress distribution,damage accumulation,and local failure of specimen.The local failure can change the stress distribution and relieve the inhibition of non-penetrating crack extension and eventually cause a dramatic destruction of the specimen.Therefore,the evolution process caused by non-penetrating cracks can be regarded as one of the important reasons for inducing rockburst.These results are expected to improve the understanding of the process of spalling formation and rockburst and can be used to analyze the stability of rocks or rock structures.

Damage evolution of rock-encased-backfill structure under stepwise cyclic triaxial loading

Rock-encased-backfill(RB)structures are common in underground mining,for example in the cut-andfill and stoping methods.To understand the effects of cyclic excavation and blasting activities on the damage of these RB structures,a series of triaxial stepwise-increasing-amplitude cyclic loading experiments was conducted with cylindrical RB specimens(rock on outside,backfill on inside)with different volume fractions of rock(VF=0.48,0.61,0.73,and 0.84),confining pressures(0,6,9,and 12 MPa),and cyclic loading rates(200,300,400,and 500 N/s).The damage evolution and meso-crack formation during the cyclic tests were analyzed with results from stress-strain hysteresis loops,acoustic emission events,and post-failure X-ray 3D fracture morphology.The results showed significant differences between cyclic and monotonic loadings of RB specimens,particularly with regard to the generation of shear microcracks,the development of stress memory and strain hardening,and the contact forces and associated friction that develops along the rock-backfill interface.One important finding is that as a function of the number of cycles,the elastic strain increases linearly and the dissipated energy increases exponentially.Also,compared with monotonic loading,the cyclic strain hardening characteristics are more sensitive to rising confining pressures during the initial compaction stage.Another finding is that compared with monotonic loading,more shear microcracks are generated during every reloading stage,but these microcracks tend to be dispersed and lessen the likelihood of large shear fracture formation.The transition from elastic to plastic behavior varies depending on the parameters of each test(confinement,volume fraction,and cyclic rate),and an interesting finding was that the transformation to plastic behavior is significantly lower under the conditions of 0.73 rock volume fraction,400 N/s cyclic loading rate,and 9 MPa confinement.All the findings have important practical implications on the ability of backfill to support underground excavations.

Liquefaction susceptibility and deformation characteristics of saturated coral sandy soils subjected to cyclic loadings-a critical review

Coral sandy soils widely exist in coral island reefs and seashores in tropical and subtropical regions.Due to the unique marine depositional environment of coral sandy soils,the engineering characteristics and responses of these soils subjected to monotonic and cyclic loadings have been a subject of intense interest among the geotechnical and earthquake engineering communities.This paper critically reviews the progress of experimental investigations on the undrained behavior of coral sandy soils under monotonic and cyclic loadings over the last three decades.The focus of coverage includes the contractive-dilative behavior,the pattern of excess pore-water pressure(EPWP)generation and the liquefaction mechanism and liquefaction resistance,the small-strain shear modulus and strain-dependent shear modulus and damping,the cyclic softening feature,and the anisotropic characteristics of undrained responses of saturated coral sandy soils.In particular,the advances made in the past decades are reviewed from the following aspects:(1)the characterization of factors that impact the mechanism and patterns of EPWP build-up;(2)the identification of liquefaction triggering in terms of the apparent viscosity and the average flow coefficient;(3)the establishment of the invariable form of strain-based,stress-based,or energy-based EPWP ratio formulas and the unique relationship between the new proxy of liquefaction resistance and the number of cycles required to reach liquefaction;(4)the establishment of the invariable form of the predictive formulas of small strain modulus and strain-dependent shear modulus;and(5)the investigation on the effects of stress-induced anisotropy on liquefaction susceptibility and dynamic deformation characteristics.Insights gained through the critical review of these advances in the past decades offer a perspective for future research to further resolve the fundamental issues concerning the liquefaction mechanism and responses of coral sandy sites subjected to cyclic loadings associated with seismic events in marine environments.

Cyclic shear behavior of en-echelon joints under constant normal stiffness conditions

To reveal the mechanism of shear failure of en-echelon joints under cyclic loading,such as during earthquakes,we conducted a series of cyclic shear tests of en-echelon joints under constant normal stiffness(CNS)conditions.We analyzed the evolution of shear stress,normal stress,stress path,dilatancy characteristics,and friction coefficient and revealed the failure mechanisms of en-echelon joints at different angles.The results show that the cyclic shear behavior of the en-echelon joints is closely related to the joint angle,with the shear strength at a positive angle exceeding that at a negative angle during shear cycles.As the number of cycles increases,the shear strength decreases rapidly,and the difference between the varying angles gradually decreases.Dilation occurs in the early shear cycles(1 and 2),while contraction is the main feature in later cycles(310).The friction coefficient decreases with the number of cycles and exhibits a more significant sensitivity to joint angles than shear cycles.The joint angle determines the asperities on the rupture surfaces and the block size,and thus determines the subsequent shear failure mode(block crushing and asperity degradation).At positive angles,block size is more greater and asperities on the rupture surface are smaller than at nonpositive angles.Therefore,the cyclic shear behavior is controlled by block crushing at positive angles and asperity degradation at negative angles.

Cyclic Beam Direction of Arrival Estimation Method for Ship Propeller Noise

In underwater acoustic applications,the conventional cyclic direction of arrival algorithm faces challenges,including a low signal-to-noise ratio and high bandwidth when compared with modulated frequencies.In response to these issues,this paper introduces a novel,robust,and broadband cyclic beamforming algorithm.The proposed method substitutes the conventional cyclic covariance matrix with the variance of the cyclic covariance matrix as its primary feature.Assuming that the same frequency band shares a common steering vector,the new algorithm achieves superior detection performance for targets with specific modulation frequencies while suppressing interference signals and background noise.Experimental results demonstrate a significant enhancement in the directibity index by 81%and 181%when compared with the traditional Capon beamforming algorithm and the traditional extended wideband spectral cyclic MUSIC(EWSCM)algorithm,respectively.Moreover,the proposed algorithm substantially reduces computational complexity to 1/40th of that of the EWSCM algorithm,employing frequency band statistical averaging and covariance matrix variance.

Enhancing capacitive deionization performance and cyclic stability of nitrogen-doped activated carbon by the electro-oxidation of anode materials

Electrode materials with high desalination capacity and long-term cyclic stability are the focus of capacitive deionization(CDI) community. Understanding the causes of performance decay in traditional carbons is crucial to design a high-performance material. Based on this, here, nitrogen-doped activated carbon(NAC) was prepared by pyrolyzing the blend of activated carbon powder(ACP) and melamine for the positive electrode of asymmetric CDI. By comparing the indicators changes such as conductivity, salt adsorption capacity, pH, and charge efficiency of the symmetrical ACP-ACP device to the asymmetric ACP-NAC device under different CDI cycles, as well as the changes of the electrochemical properties of anode and cathode materials after long-term operation, the reasons for the decline of the stability of the CDI performance were revealed. It was found that the carboxyl functional groups generated by the electro-oxidation of anode carbon materials make the anode zero-charge potential(E_(pzc)) shift positively,which results in the uneven distribution of potential windows of CDI units and affects the adsorption capacity. Furthermore, by understanding the electron density on C atoms surrounding the N atoms, we attribute the increased cyclic stability to the enhanced negativity of the charge of carbon atoms adjacent to quaternary-N and pyridinic-oxide-N.

Influence of cyclic ignition and steady-state operation on a 1–2 A barium tungsten hollow cathode

Booming low-power electric propulsion systems require 1–2 A hollow cathodes.Such cathodes are expected to go through more frequent ignitions in the low orbit,but the impact of cyclic ignitions on such 1–2 A barium tungsten hollow cathodes with a heater was not clear.In this study,a 12,638-cyclic ignition test and a 6,000-hour-long life test on two identical cathodes were carried out.The discharge voltage of the cathode and the erosion of the orifice after cyclic ignition were all larger than that of the cathode after stable operation.This indicated that the impact of cycle ignition on the discharge performance of a low current BaO-W cathode with a heater was higher than that of stable operation.The results of the ion energy distribution function measured during the ignition period indicated that the main reason for the orifice expansion was ion bombardment.Therefore,it was necessary to pay attention to the number of ignitions for the lifetime of this kind of cathode.