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The microstructure of particle-reinforced metal matrix composites (PMMCs) and its parameters (such as particle size distribution, particle volume fraction, particle shape, etc.) have a great influence on the elastic modulus of PMMC. In this paper, the intermingled fractal units (IFU) model was used to describe the microstructure of PMMCs. Based on the spring series-parallel connection model, an analytical method of predicting the elastic modulus was proposed, and the area fraction, size distribution, and interface of the reinforced particles were taken into consideration. The tensile experiments performed on three groups of the SiC/Al composite specimens with different microstructure (namely, of different particle shape, size, and volume fraction of reinforcing particles) were conducted to evaluate the elastic modulus and strength properties. The comparison between the predicted and experimental results has proved the applicability and effectiveness of the method proposed in this paper.

We propose an improved adaptive Type-II progressive censoring scheme, which can effectively guarantee that the test time will not exceed a certain threshold time. And the adaptive Type-II progressive censoring scheme is its special case. Based on this censoring scheme, the parameters, reliability and hazard functions of Burr-XII distribution were estimated. Firstly, we obtain the estimators of parameters, reliability and hazard functions by using the maximum likelihood estimation method. Subsequently, the approximate confidence intervals of the above statistics are obtained by using the asymptotic normality properties of maximum likelihood estimation and the Bootstrap method. Furthermore, based on the square loss function and the LINEX loss function, the point estimators and approximate confidence intervals of parameters are derived by using Bayesian method. A real data is used to illustrate and validate the advantages of the proposed improved adaptive Type-II progressive censoring scheme. Finally, the Monte Carlo simulations are performed to compare the behavior of improved adaptive Type-II progressive censoring scheme with adaptive Type-II progressive censoring scheme for different evaluation methods.

In order to reduce the vibration fatigue test time of aeronautical engineering components made of aluminum-alloy, a random vibration fatigue acceleration model under narrow-band excitation is proposed in this paper. A three-parameter S- N curve is adopted to consider the effect of small stress response, while a scale factor α is introduced to consider the effect of stress distribution. The random vibration fatigue tests of 2024-T3 and 7075-T6 aluminum-alloy specimens with elliptical holes are performed, where the vibration fatigue lives of load spectra with the same bandwidth and different excitation acceleration levels are obtained. The test results show that the proposed model is in sound agreement with the test results.

Background Cancer patients are at a high risk of being infected with severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), and are more likely to develop severe illness and have higher mortality once infected. In the COVID‐19 pandemic, it is urgent to understand the effects of antitumor therapy on the prognosis of patients with COVID‐19. Methods A systematic literature search was conducted in PubMed, Cochrane Library, Embase, MedRxiv, and Chinese National Knowledge Infrastructure (CNKI) until 21 June 2020. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were evaluated using a random effects model to analyze the effects of antitumor therapies on COVID‐19 patients. Results For cancer patients with COVID‐19, the death events related to antitumor treatment were higher than those with no antitumor treatment (OR = 1.55; 95% CI 1.07–2.25; p = 0.021). Compared with patients in the survival group, the non‐survival group showed no significant differences in patients who received antitumor therapy. Compared with patients in the non‐severe group, the severe group was more likely to receive antitumor therapy (OR = 1.50; 95% CI 1.02–2.19; p = 0.037) and there was a significant difference. The incidence of severe events was higher in the subgroup of chemotherapy (OR = 1.73; 95% CI 1.09–2.73). Conclusion The synthesized evidence suggests that cancer patients with COVID‐19 who received antitumor treatment shortly before symptom onset are more likely to experience severe symptoms and have high mortality. Receiving chemotherapy is an unfavorable factor for the prognosis of cancer patients with COVID‐19., Patients with cancer and COVID‐19 who received anti‐tumor treatment shortly before symptom onset are more likely to develop severe illness and have high a mortality. Receiving chemotherapy is an unfavorable factor for the prognosis of patients with COVID‐19.

Lanthanum can reduce absorption of phosphate by forming lanthanum phosphate complexes after oral administration of lanthanum carbonate tablets (FOSRENOL®) in patients. Based on the pH-responsive interaction of phosphate and lanthanum ions, the chitosan coated siRNA-loaded lanthanum phosphate nanoparticles (CS/LaP/siRNA NPs) were prepared for improving cancer treatment, in which polysaccharide chitosan was used as the outer shell to control the excessive growth of lanthanum phosphate complexes, and enable intestinal mucoadhesion. The CS/LaP/siEGFR NPs exhibited significant biological activities in human colorectal cancer HT-29 cells by the synergistic effects of siEGFRs and lanthanum ions, such as downregulation of EGFR and upregulation of miR-34a. Furthermore, significant tumor growth inhibition was observed in both transgenic C57BL/6-ApcMinC/Nju cancer mouse model and AOM/DSS chemically induced orthotopic colorectal cancer mouse model after intestinal instillation administration of CS/LaP/siEGFR NPs. Therefore, the lanthanum-based siRNA delivery system would provide a potential and efficient strategy for the treatment of colorectal cancers.

Radiation-induced intestinal injury is a common and critical complication of radiotherapy for pelvic or abdominal tumors, with limited therapeutic strategies and effectiveness. Sitagliptin, a dipeptidyl peptidase IV (DPP4) inhibitor, has previously been reported to alleviate total body irradiation- (TBI-) induced damage of hematopoietic system in mice, but its effect on radiation-induced intestinal injury remains unclear. In this study, we confirmed that Sitagliptin could not only protect mice from death and weight loss caused by whole abdominal irradiation (WAI) but also improve the morphological structure of intestine and the regeneration ability of enterocytes. In addition, Sitagliptin significantly inhibited the production of radiation-induced proinflammatory cytokines and reduced the number of apoptotic intestinal epithelial cells and γ-H2AX expression. In vitro, we demonstrated that Sitagliptin protected HIEC-6 cells from ionizing radiation, resulting in increased cell viability and reduced DNA damage. Mechanistically, the radiation protection of Sitagliptin might be related to the upregulation of NRF2 level and the decrease of NLRP3 inflammasome activity. Importantly, Sitagliptin significantly restored radiation-induced changes in bacterial composition. In conclusion, our results suggested that Sitagliptin could reduce WAI-induced intestinal injury in mice, which may provide novel therapeutic strategy for radiation-induced intestinal injury.

Background Bladder cancer (BLCA) is one of the most common malignancies worldwide. One of the main reasons for the unsatisfactory management of BLCA is the complex molecular biological mechanism. Annexin A1 (ANXA1), a Ca2+-regulated phospholipid-binding protein, has been demonstrated to be implicated in the progression and prognosis of many cancers. However, the expression pattern, biological function and mechanism of ANXA1 in BLCA remain unclear. Methods The clinical relevance of ANXA1 in BLCA was investigated by bioinformatics analysis based on TCGA and GEO datasets. Immunohistochemical (IHC) analysis was performed to detect the expression of ANXA1 in BLCA tissues, and the relationships between ANXA1 and clinical parameters were analyzed. In vitro and in vivo experiments were conducted to study the biological functions of ANXA1 in BLCA. Finally, the potential mechanism of ANXA1 in BLCA was explored by bioinformatics analysis and verified by in vitro and in vivo experiments. Results Bioinformatics and IHC analyses indicated that a high expression level of ANXA1 was strongly associated with the progression and poor prognosis of patients with BLCA. Functional studies demonstrated that ANXA1 silencing inhibited the proliferation, migration, invasion and epithelial–mesenchymal transition (EMT) of BLCA cells in vitro, and suppressed the growth of xenografted bladder tumors in vivo. Mechanistically, loss of ANXA1 decreased the expression and phosphorylation level of EGFR and the activation of downstream signaling pathways. In addition, knockdown of ANXA1 accelerated ubiquitination and degradation of P-EGFR to downregulate the activation of EGFR signaling. Conclusions These findings indicate that ANXA1 is a reliable clinical predictor for the prognosis of BLCA and promotes proliferation and migration by activating EGFR signaling in BLCA. Therefore, ANXA1 may be a promising biomarker for the prognosis of patients with BLCA, thus shedding light on precise and personalized therapy for BLCA in the future.

In this paper, the influence of the bonding materials on the failure modes and the critical energy release rate (CERR) is studied through the double cantilever beam (DCB) test. The test results show that the failure mode and CERR of the bonded structure are closely related to the bonding materials, and three failure modes, i.e., the cohesive failure, the interface failure and the mixed-mode failure are identified on the bonding surface. The finite element method is used to simulate the interface debonding behavior of the DCB test specimens, and the influence of material randomness on the interface failure is introduced. A XFEM/CZM coupled approach is proposed to model the crack migration phenomena. The predicted results have a good agreement with the experimental results.

Two methods based on local stress responses are proposed to locate fatigue critical point of metallic notched components under non-proportional loading. The points on the notch edge maintain a state of uniaxial stress even when the far-field fatigue loading is multi-axial. The point bearing the maximum stress amplitude is recognized as fatigue critical point under the\ud condition of non-mean stress, otherwise the Goodman’s empirical formula is adopted to amend mean stress effect prior to the determination of fatigue critical point. Furthermore, the uniaxial stress state can be treated as a special multi-axial stress state. The Susmel’s fatigue damage parameter is employed to evaluate the fatigue damage of these points on the notch edge.\ud Multi-axial fatigue tests on thin-walled round tube notched specimens made of GH4169 nickel-base alloy and 2297 aluminum-lithium alloy are carried out to verify the two methods. The prediction results show that both the stress amplitude method and the Susmel’s parameter method can accurately locate the fatigue critical point of metallic notched components under multi-axial fatigue loading.

The design and development of civil aircraft is a systematic engineering project with high precision and high complexity. Traditional aircraft requirements are based on document transmission, which is not intuitive and logical, and are easy to miss requirements in different scenarios The Model-based function analysis is a method that can identify and define all elements of a certain function. In the process of function analysis, the relation between the function interfaces can be determined and the relative requirements can be obtained, which can consequently ensure the validity and integrity of aircraft functional requirements. The functional modeling analysis is carried out based on a SysML model in this paper, and the function is described from the perspective of structural level, behavioral level and activity level by using graphical and hierarchical expression. The internal logic of the function is analyzed in depth to obtain the functional requirements of the aircraft.

In order to study the nonlinear dynamic behaviors of Thermal Protection System (TPS) and the nonlinear dynamic strength of the strain-isolation-pad (SIP), a two degree-of-freedom nonlinear dynamic theoretical model was presented under the acoustic excitation and base excitation. The tile is simplified as a mass point, a linear spring and a damping element, and the SIP is simplified as a mass point, a nonlinear spring and a damping element. On this basis, the solving process of the nonlinear theoretical model and the iterative process of the equivalent linear stiffness coefficient of SIP were derived by the statistical linearization method. The dynamic responses analyzed by the nonlinear theoretical model and linear theoretical model are compared. The nonlinear stiffness of SIP shows obvious influence on behaviors of TPS and dynamic stress of SIP, and the equivalent linear stiffness of SIP is related to the types of excitations. Finally, the influences on above dynamic responses by the nonlinear stiffness level of SIP were studied. The equivalent linear stiffness coefficient of SIP, acceleration of TPS and dynamic stress of SIP decrease with the increase of the nonlinear level for the stiffness of SIP.

A two degree-of-freedom uncertainty dynamic theoretical model under the acoustic and base excitations was presented to analyze the uncertainty dynamic behaviors of thermal protection system (TPS) and the uncertainty dynamic strength of strain-isolation-pad (SIP). The tile and SIP are both simplified as the combination of a mass point, a linear spring and a damping element, and all the dynamic parameters obey the normal distribution. The probability distributions of responses were derived from adopting the perturbation method. The difference method is used to analyze the sensitivity of the mean responses to random parameters, and the reasonable sensitivity values are obtained under a difference step which is equal to the standard deviation of the random parameter. The probability distributions calculated by the uncertainty theoretical model match well with the Monte Carlo numerical results, so the accuracy of the uncertainty dynamic theoretical model is verified. The researches in this paper provide a theoretical foundation for studying the uncertainty dynamic behaviors of TPS, analyzing uncertainty dynamic strength of SIP and intensifying the integrity and security of TPS.

A loosely coupled fluid-structural thermal numerical method is introduced for the thermal protection system (TPS) gap thermal control analysis in this paper. The aerodynamic heating and structural thermal are analyzed by computational fluid dynamics (CFD) and numerical heat transfer (NHT) methods respectively. An interpolation algorithm based on the control surface is adopted for the data exchanges on the coupled surface. In order to verify the analysis precision of the loosely coupled method, a circular tube example was analyzed, and the wall temperature agrees well with the test result. TPS gap thermal control performance was studied by the loosely coupled method successfully. The gap heat flux is mainly distributed in the small region at the top of the gap which is the high temperature region. Besides, TPS gap temperature and the power of the active cooling system (CCS) calculated by the traditional uncoupled method are higher than that calculated by the coupled method obviously. The reason is that the uncoupled method doesn't consider the coupled effect between the aerodynamic heating and structural thermal, however the coupled method considers it, so TPS gap thermal control performance can be analyzed more accurately by the coupled method.

The misorientation of nickel-base single crystal (NBSX) superalloy is always ignored in the current research, which in fact has a certain influence on the fatigue life of NBSXs. To investigate this influence, the fatigue tests of NBSX superalloy DD5 with different misorientation angles have been carried out at 980 °C, and the failure mechanism has been investigated based on the fractographic observation and crystal plastic finite element (CPFE) analysis. The effect of real misorientation on the fatigue life of NBSX has been quantified, which is also reported for the first time.

The fatigue damage of composite sandwich panels is divided into two parts: the face sheet damage and the core damage. Both the two kinds of damage cause the performance degradation of panels, however only the core damage results in the ultimate failure. In this paper, a fatigue damage model of the face sheet and the core is proposed and three-point bending tests are carried out to obtain the deflection evolution curves. With the proposed model, the fatigue damage can be predicted accurately, which proves the validity of the fatigue damage model proposed in this paper.

Microporosity is one of the most common defects in nickel base single crystal (N-SC) superalloys, which is a great threat to fatigue performance. In this paper, nine porosity-related fatigue damage parameters for N-SC superalloys were selected by referring to those parameters originally proposed for casting and 3D printing metal materials as well as the critical plane damage parameters commonly used in N-SC superalloys. According to the plastic constitutive model of single crystals, a crystal plastic finite element (CPFE) model was established to evaluate these different fatigue damage parameters, and the parameters of CPFE were calibrated by the low cycle fatigue (LCF) hysteresis loop obtained from the fatigue test. The evaluation results showed that the geometric mean of stress–strain concentration factor (GCF) k g was a satisfactory parameter to quantify the effect of porosity defects on fatigue. Inspired by the discovery and considering the slip systems characteristics of N-SC superalloys, the geometric mean of resolved stress–strain concentration factor (GRCF) k rg on slip systems was proposed, and it was found that the max ( k rg , k g ) could be used to predict the fracture modes of N-SC superalloys. Based on the max ( k rg , k g ) , a porosity-related fatigue life prediction method which can distinguish the fracture modes was put forward. The prediction results showed that the fracture mode prediction results were consistent with the test results, and the life prediction results were also improved compared with the GCF parameter.

Slip deformation is the predominant fatigue damage form of nickel-based single crystals at intermediate temperature range (near 760℃). Under different crystal orientations, the dominant slip system may be an octahedral or cubic slip system. This paper explores the dominant slip systems under different crystal orientations through crystal plastic finite element analysis, and determines the fatigue damage parameter that can characterize both the octahedral deformation and the cubic deformation. The results show that within a certain orientation range close to the orientation, the dominant slip system of the nickel-based single crystal is the cubic slip system. For an orientation far deviating from the orientation, the dominant slip system is the octahedral slip system. Through finite element calculation, this paper gives the distribution diagram of the dominant slip system in the standard pole figure. The fatigue data of nickel-based single crystals with different orientations in the existing literature are used for verification, and the results show that the dominant slip system can be effectively determined by using the distribution diagram, and the proposed fatigue damage parameter can effectively characterize the fatigue damage of different slip systems. Compared with the condition where the distribution of the dominant slip system is not considered, the method proposed in this paper has effectively improved the fatigue life prediction ability.

A numerical simulation on the deformation behavior of AZ31 magnesium alloy during backward extrusion with counter pressure was investigated by FE software DEFORM. The results show that the steady load increases nonlinearly with the increment of counter pressure. The equivalent strain gradient decreases significantly results from the counter pressure and the unevenness in the top of wall disappeared approximately when the counter pressure is 10~15MPa. Furthermore, there are obviously shear band along the inner fillet to outer fillet of workpiece. Higher hydrostatic pressure generated with counter pressure compared that of no counter pressure leads to improve the plastic deformation limit. The damage factor is reduced significantly in the backward extrusion with counter pressure, which is beneficial to the improvement of crack.

In this paper, the bending fatigue tests of honeycomb sandwich panels are carried out by using an improved three-point bending test fixture, and the S-N curves at different stress ratios are obtained. Through the records of fatigue damage in the experiment, the failure mode of the honeycomb sandwich panels and the source of fatigue damage are determined. At the same time, through the calculation of the shear stress distribution on the honeycomb wall, the reasons for the difference in the failure morphology of the L-direction and W-direction sandwich panels are clarified. Besides, a life prediction method is proposed and its effectiveness in predicting the fatigue life of sandwich panels has been verified.

Fifteen multiaxial critical-plane fatigue damage parameters of isotropic metal materials are applied to the life evaluation of nickel-base single crystal superalloys. These parameters are classified into stress-, strain- and strain-energy parameters, and their predictive abilities are evaluated by 12 groups of single crystal fatigue data obtained from mainly an intermediate temperature range (500–760 °C) where the slip deformation is the main damage mode. The results show that the strain energy group exhibits the best fitting characteristics with correlation coefficients. A topologized resolved shear stress method (TRSS) considering the interaction of main slip systems is further proposed. The dispersion degree of resolved shear stress among the main slip systems is quantified by a dispersion factor, and the real driving capacity of resolved shear stress is amended according to the topology of driving force. The obtained results show that the proposed method has achieved an improvement of correlation ability.

The advanced volumetric approaches are reviewed briefly to state the stress/strain-based or energy-based parameters of fatigue damage region are critical. A new approach is proposed to distinguish crack initiation and propagation stage. The angles of crack initiation are predicted by notch critical plane (NCP) approach (Luo et al. Fatigue Fract Eng Mater Struct, 2019, 42(4): 854–870). NCP is the plane which passes through the fatigue critical point (FCP) and undergoes the maximum shear stress amplitude. The experiment of thin-walled round tube components is conducted to check these approaches. The direction of crack initiation is basically the same as that of NCP. Most of the predicted lives fall within an error factor of 3.

Based on the matrix crack density evolution, a theoretical model is proposed to study the natural frequency degradation of woven fabric composite subjected to very high cycle vibration loading. A very high cycle bending fatigue test of woven fabric composite is designed, and the existence of crack saturated state is verified. An on-line natural frequency measurement test is proposed, which proved the validity of the proposed natural frequency degradation model.

The interface debonding is a major failure mode of composite structures. In this paper, the debonding behavior of the structurally asymmetric interfaces is studied, and the calculating method of the critical energy release rate of such debonding interfaces is proposed. The experimental results show that the critical energy release rate calculated in this paper is more in line with its intrinsic physical attribute of being a material constant, which proves the effectiveness of the proposed method.

Although multidisciplinary treatment is widely applied in colorectal cancer (CRC), the prognosis of patients with advanced CRC remains poor. Immunotherapy blocking of programmed cell death ligand 1 (PD-L1) is a promising approach. Binding of the transmembrane protein PD-L1 expressed by tumor cells or tumor microenvironment cells to its receptor programmed cell death 1 (PD-1) induces immunosuppressive signals and reduces the proliferation of T cells, which is an important mechanism of tumor immune escape and a key issue in immunotherapy. However, the regulation of PD-L1 expression is poorly understood in CRC. Fibroblast growth factor (FGF) receptor (FGFR) 2 causes the tyrosine kinase domains to initiate a cascade of intracellular signals by binding to FGFs and dimerization (pairing of receptors), which is involved in tumorigenesis and progression. In this study, we showed that PD-L1 and FGFR2 were frequently overexpressed in CRC, and FGFR2 expression was significantly associated with lymph node metastasis, clinical stage, and poor survival. In the current study, PD-L1 expression was positively correlated with FGFR2 expression in CRC. Tumor-derived–activated FGFR2 induced PD-L1 expression via the JAK/STAT3 signaling pathway in human CRC cells (SW480 and NCI-H716), which induced the apoptosis of Jurkat T cells. FGFR2 also promoted the expression of PD-L1 in a xenograft mouse model of CRC. The results of our study reveal a novel mechanism of PD-L1 expression in CRC, thus providing a theoretical basis for reversing the immune tolerance of FGFR2 overexpression in CRC.

In order to detect the electrothermal heating tube internal electrothermal film resistance and the relationship between the two electrode gap, this thesis used design using a testing equipment: The two ends of the measurement period from two electrodes, and the probe spacing can be adjusted ; The two measuring points into hair heat pipe internal contact with the resistive film, using the bleeder circuit, the indirect measuring resistance membrane resistance and the relationship between the two measuring points spacing; then analyze the measurement data, the relationship between the two electrode gap and electrothermal film resistance. The use of such equipment, the measured data, we can analyze the electrothermal film heating pipe internal heating membrane resistance and two measurement of the end head distance is linear change. The linear relationship between the use of electrothermal film heating tube internal electrothermal membrane resistance, can estimate the range of internal electric heating film heating pipe resistance from two the distance between the electrodes, get the change range of heating tube power.

Astragalus polysaccharides (APS) have been shown to possess a variety of biological activities including anti-oxidant and anti-inflammation functions in a number of diseases. However, their function in pulmonary arterial hypertension (PAH) is still unknown. Rats received APS (200[Formula: see text]mg/kg once two days) for 2 weeks after being injected with monocrotaline (MCT; 60[Formula: see text]mg/kg). The pulmonary hemodynamic index, right ventricular hypertrophy, and lung morphological features of the rat models were examined, as well as the NO/eNOS ratio of wet lung and dry lung weight and MPO. A qRT-PCR and p-I[Formula: see text]B was used to assess IL-1[Formula: see text], IL-6 and TNF-[Formula: see text] and WB was used to detect the total I[Formula: see text]B. Based on these measurements, it was found that APS reversed the MCT-induced increase in mean pulmonary arterial pressure (mPAP) (from 32.731[Formula: see text]mmHg to 26.707[Formula: see text]mmHg), decreased pulmonary vascular resistance (PVR) (from 289.021[Formula: see text]mmHg[Formula: see text][Formula: see text] min/L to 246.351[Formula: see text]mmHg[Formula: see text][Formula: see text][Formula: see text]min/L), and reduced right ventricular hypertrophy (from 289.021[Formula: see text]mmHg[Formula: see text][Formula: see text][Formula: see text]min/L to 246.351 mmHg[Formula: see text][Formula: see text][Formula: see text]min/L) ([Formula: see text]0.05). In terms of pulmonary artery remodeling, the WT% and WA% decreased with the addition of APS. In addition, it was found that APS promoted the synthesis of eNOS and the secretion of NO, promoting vasodilation and APS decreased the MCT-induced elevation of MPO, IL-1[Formula: see text], IL-6 and TNF-[Formula: see text], reducing inflammation. Furthermore, APS was able to inhibit the activation of pho-I[Formula: see text]B[Formula: see text]. In couclusion, APS ameliorates MCT-induced pulmonary artery hypertension by inhibiting pulmonary arterial remodeling partially via eNOS/NO and NF-[Formula: see text]B signaling pathways.

In order to solve the problem of 3D intricate product design and mold development, an approach based on UG NX was proposed. The design platform and modular technology of UG MoldWizard were introduced. How to add and edit attributes of the standard part library was explained by using sankyo lifter as example. As an application, a lamp set and its injection mold were rapidly designed by UG MoldWizard. How to patch surfaces, define parting lines and how to extract mold core and mold cavity were illustrated step by step. It proved that UG MoldWizard efficiently promoted work and integrated complex elements of design technology into automated sequences.

In Tang and Wang (Computers and Operations Research, pp. 413–422, 1997), they tried to develop an interactive approach for quadratic programming problems with fuzzy objective and resources. Based on their approach, they claimed that the exact optimal solution for inventory model under fuzzy objective and resources is useless. We will point out that their approach is questionable, from complete and contains severe drawbacks so that their comments about the exact optimal solution should be treated as seriously questionable.

This work examines the interactions between a large polypeptide, oxidized insulin chain A (ICA), and several metal ions (Na + , K + , Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ , and Pd 2+ ) by using tandem mass spectrometry. Fragmentation spectra of the anionic complexes show that each metal ion complex undergoes specific types of interactions, suggesting that different conformations are favored for each complex. The overall results are consistent with the data obtained from ion mobility measurements. Thus, the tandem mass spectrometry approach represents a complementary method for probing the conformations of metal–peptide complexes. The fragmentation spectra obtained from the complexes of the enzyme-digested ICA fragments with metal ions also reflect specific metal–peptide interactions parallel with those for corresponding metal–ICA complexes.

The effects of different NO3- concentrations (CK, 16 mmol x L(-1) NO3-; T1, 48 mmol x L(-1) NO3-; T2, 96 mmol x L(-1) NO3-; T3, 144 mmol x L(-1) NO3-) on the growth properties and antioxidant enzymes activities of strawberry seedlings were studied by sand culture. The results indicated that the plant height, leaf area, dry matter accumulation and root/shoot ratio of strawberry seedlings in T1, T2 and T3 were significantly decreased compared to the control (CK) after 15 days of treatment. The plant heights in T1, T2 and T3 decreased by 16.1%, 36.8% and 43.9%, and the areas of functional leaf decreased by 19.7%, 34.3% and 47.5% respectively, compared to the control. With the increasing NO3- concentration, the malondialdehyde (MDA), proline, soluble protein content and relative electronic leakage of the strawberry seedlings first increased and then decreased, but all those parameters in T1, T2 and T3 were higher than in the control. The activities of antioxidant enzymes, superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX) in both root and leaf, and catalase (CAT) in the root first increased and then decreased, but the CAT activity in the leaf gradually decreased with the increasing NO3 concentration. In T3, the activity of SOD in both root and leaf, APX in the root were lower than in the control. In sum, the osmolytes of strawberry seedlings increased and the plants become weaker under nitrate stress, and some antioxidant enzymes in strawberry seedlings increased at the low level of nitrate stress and decreased at the high level. The strawberry plants were stunted when growing under 48 mmol x L(-1) NO(3-) condition.