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Engineered magnetic nanoparticles have been extensively explored for magnetic resonance imaging (MRI) diagnosis of a tumor to improve the visibility. However, most of these nanoparticles display "always-on" signals without tumor specificity, causing insufficient contrast and false positives. Here, we provide a new paradigm of MRI diagnosis using MnCO3 nanorhombohedras (MnNRs) as an ultrasensitive T1-weighted MRI contrast agent, which smartly enhances the MR signal in response to the tumor microenvironment. MnNRs would quickly decompose and release Mn2+ at mild acidity, one of the pathophysiological parameters associated with cancer malignancy, and then Mn2+ binds to surrounding proteins to achieve a remarkable amplification of T1 relaxivity. In vivo MRI experiments demonstrate that MnNRs can selectively brighten subcutaneous tumors from the edge to the interior may be because of the upregulated vascular permeation at the tumor edge, where cancer cell proliferation and angiogenesis are more active. Specially, benefiting from the T2 shortening effect in normal liver tissues, MnNRs can detect millimeter-sized liver metastases with an ultrahigh contrast of 294%. The results also indicate an effective hepatic excretion of MnNRs through the gallbladder. As such, this pH-activatable MRI strategy with facility, biocompatibility, and excellent efficiency may open new avenues for tumor malignancy and metastasis diagnosis and holds great promise for precision medicine.

We reported the magnetic, dielectric and magnetoelectric properties of NdCrO3 polycrystalline ceramics. Magnetization curves revealed two magnetic transitions at 227 K and 38 K, which corresponded to Cr3+ canted antiferromagnetic ordering and Cr3+ spin reorientation phase transition, respectively. At 11.5 K, a Schottky-type anomaly was observed, caused by Nd3+ ground doublet Zeeman splitting. High-temperature dielectric relaxation exhibited a type of thermally activated relaxation process, which mainly resulted from the Maxwell&ndash, Wagner effect. The spin-reorientation of Cr3+ ions and the Nd3+ ground doublet splitting were observed to be accompanied by an electric polarization. The polarization could be induced by the presence of the antiferromagnetic-type domain walls, which led to spatial inversion symmetry breaking.

High-brightness X-ray free-electron lasers (FELs) are perceived as fourth-generation light sources providing unprecedented capabilities for frontier scientific researches in many fields. Thin crystals are important to generate coherent seeds in the self-seeding configuration, provide precise spectral measurements, and split X-ray FEL pulses, etc. In all of these applications a high-intensity X-ray FEL pulse impinges on the thin crystal and deposits a certain amount of heat load, potentially impairing the performance. In the present paper, transient thermal stress wave and vibrational analyses as well as transient thermal analysis are carried out to address the thermomechanical issues for thin diamond crystals, especially under high-repetition-rate operation of an X-ray FEL. The material properties at elevated temperatures are considered. It is shown that, for a typical FEL pulse depositing tens of microjoules energy over a spot of tens of micrometers in radius, the stress wave emission is completed on the tens of nanoseconds scale. The amount of kinetic energy converted from a FEL pulse can reach up to ∼10 nJ depending on the layer thickness. Natural frequencies of a diamond plate are also computed. The potential vibrational amplitude is estimated as a function of frequency. Due to the decreasing heat conductivity with increasing temperature, a runaway temperature rise is predicted for high repetition rates where the temperature rises abruptly after ratcheting up to a point of trivial heat damping rate relative to heat deposition rate.

High temperature dielectric relaxation behaviors of single phase Mn3O4 polycrystalline ceramics prepared by spark plasma sintering technology have been studied. Two dielectric relaxations were observed in the temperature range of 200 K&ndash, 330 K and in the frequency range of 20 Hz&ndash, 10 MHz. The lower temperature relaxation is a type of thermally activated relaxation process, which mainly results from the hopping of oxygen vacancies based on the activation energy analysis. There is another abnormal dielectric phenomenon that is different from the conventional thermally activated behavior and is related to a positive temperature coefficient of resistance (PTCR) effect in the temperature region. In line with the impedance analyses, we distinguished the contributions of grains and grain boundaries. A comparison of the frequency-dependent spectra of the imaginary impedance with imaginary electric modulus suggests that both the long range conduction and the localized conduction are responsible for the dielectric relaxations in the Mn3O4 polycrystalline samples.

Failure envelope method is comprehensively used in failure mode prediction of multi-bolt composite joints. The method is based on the assumption that bolt load distribution proportion is constant till failure. However, bearing damage and net-section damage must have some influence on the load distribution and then change structure failure mode. In this paper, tensile experiments of two-bolt and three-bolt joints were conducted to obtain the failure modes and other properties. Three dimensional (3D) finite element models involving damage were constructed, and the results were consistent with experimental data. Then, the models were used to study the effect of damage on failure mode of multi-bolt composite joints. The results show that failure mode prediction with failure envelope method should involve the effect of composite damage. Compared with net-section damage, bearing damage has greater influence on failure mode. Based on conventional failure envelope method, a new evaluation procedure involving damage was proposed.

In this paper, tensile behavior of box-joint structure fabricated by resin transfer moulding (RTM) was investigated. A finite element model (FEM) of the box joint based on cohesive zone model was established to study the joint tensile behavior. Hashin failure criterion and degradation rules were applied to simulate damage modes and to predict failure strength. The FEM results show a good agreement with experimental results. Based on the model, the influences of bolt location and lap length on the joint tensile performances were analyzed. The results show that the delamination between the L-shape part and box-shape parts is the main failure mode. Bolt location affects the damage modes, ultimate load and structure stiffness of the joint, and longer lap length has a tendency to promote ultimate load and structure stiffness.

In this paper, tensile experiments were conducted into single-lap bolted joint between composite laminate and steel with countersunk fastener, and two three-dimensional explicit finite element models were developed using Abaqus/Explicit. Continuum shell elements (SC8R) were used to model in-plane ply failure with built-in damage model while cohesive elements were selected to predict interlaminar damage in model I. 8-node reduced integration solid elements (C3D8R) were chosen to model all the parts with 3D Hashin-type initiation criteria and Camanho degradation law implemented in a VUSDFLD subroutine in model II. The results simulated by both models accurately predicted the elastic loading response and captured overall damage profile compared with the experimental results. The numerical analysis using explicit solver provided acceptable accuracy which highlighted the robust nature and high computational efficiency without convergence issues compared with implicit solver. In addition, the effect of cohesive elements on computational efficiency was investigated to simplify the countersunk joints analysis.

Reversals of magnetization and exchange bias field were observed around 19 K in polycrystalline perovskite chromite YbCrO3. Both the reversals can be elucidated based on the antiferromagnetic interaction between the ferromagnetic component of Cr3+ moments and the Yb3+ moments. The low field magnetization exhibits a perfect linear correlation with the magnetization shift resulted from the exchange bias effect. Distinguished from other exchange bias systems, the dependence of HE at 10 K on the cooling field shows an almost undamped feature up to 85 kOe, indicating the stable exchange bias states in respective temperature region.

Single lap bolted joints subjected to tensile load are essential joining methods in engineering design. Lateral displacement of the grip in single lap bolted joint experiment was examined and analyzed. This was different from early investigations that considered the joint fully gripped with no lateral degree of freedom. The lateral stiffness of the grip was tested to obtain the test machine properties. Tensile experiments on single lap composite-to-aluminum bolted joints were conducted, and the lateral displacement of the grip measured. Other measurements included tensile displacement, out-of-plane displacement, and surface strains. By allowing for lateral displacement, the novel finite element model predicted good results. The influence of lateral displacement of the grip was analyzed using the novel and traditional models. The novel model predicted 13 % smaller joint stiffness than traditional model. The parameters related to secondary bending were found different and the failure load of the joint was delayed because of lateral displacement of the grip.

Glassy magnetic behavior and exchange bias phenomena are observed in single phase Mn3O4 nanoparticles. Dynamics scaling analysis of the ac susceptibility and the Henkel plot indicate that the observed glassy behavior at low temperature can be understood by taking into account the intrinsic behavior of the individual particles consisting of a ferrimagnetic (FIM) core and a spin-glass surface layer. Field-cooled magnetization hysteresis loops display both horizontal and vertical shifts. Dependence of the exchange bias field (H E) on the cooling field shows an almost undamped feature up to 70 kOe, indicating the stable exchange bias state in Mn3O4. H E increases as the particle size decreases due to the higher surface/volume ratio. The occurrence of the exchange bias can be attributed to the pinning effect of the frozen spin-glass surface layer upon the FIM core.