[Analysis of clinical features and the outcome of in-hospital mortality of myocardial infarction with non-obstructive coronary arteries]

Objective: To compare the clinical features and the outcome of in-hospital mortality between patients with myocardial infarction with non-obstructive coronary arteries(MINOCA)and myocardial infarction with obstructive coronary artery disease (MI-CAD). Methods: This is a retrospective study. The clinical data of acute myocardial infarction (AMI) patients admitted to Qilu Hospital of Shandong University from January 2017 to May 2021, who underwent coronary angiography, were collected. Patients were divided into MINOCA group and MI-CAD group according to the degree of coronary stenosis (<50% or ≥50%). Baseline clinical characteristics, electrocardiograph during hospitalization, myocardial bridge, length of stay in hospital, discharge medication and the outcome of in-hospital mortality were collected and compared between the two groups. Univariate and multivariate logistic regression analysis was used to screen the related factors of MINOCA and the factors predicting the nosocomial death outcome of patients with AMI. Results: A total of 3 048 AMI patients were enrolled, age was 62 (54, 69) years, 741 (24.3%) patients were women including 165 patients (5.4%) in the MINOCA group and 2 883 patients (94.6%) in the MI-CAD group. Compared with MI-CAD patients, MINOCA patients were younger, had a higher proportion of females and a higher incidence of NSTEMI, and had a lower history of smoking, diabetes, coronary heart disease and myocardial infarction. Baseline inflammatory markers such as neutrophil count, monocyte count, neutrophil count/lymphocyte count (NLR), and monocyte count/high-density lipoprotein count (MHR) were lower, creatinine, N-terminal pro-brain B-type Natriuretic peptides (NT-proBNP), creatine kinase-MB, hypersensitive troponin I, fibrinogen, baseline blood glucose levels were lower, high-density lipoprotein cholesterol was higher, and the incidence of myocardial bridge, arrhythmia, tachycardia and atrial fibrillation was higher (P<0.05). The application rates of calcium antagonists and non-vitamin K antagonists oral anticoagulants were higher in MINOCA group (P<0.05), and there was no statistical difference in hospitalization days and in-hospital death between the two groups (P>0.05). Multiple logistic regression analysis showed that young age, female, non-smoker, no history of coronary heart disease and low MHR were risk factors of MINOCA (P<0.05). MINCOA was not associated with higher in-hospital death (P>0.05). Patients with AMI and a history of coronary heart disease, chronic renal failure, higher baseline blood glucose, higher NLR, and higher D-dimer were risk factors of in-hospital death (P<0.05). Conclusions: Compared with MI-CAD patients, MINOCA patients are younger, more likely to be female and non-smokers and on history of coronary heart disease, and have lower baseline MHR. MINOCA is often associated with myocardial bridge and atrial fibrillation. The incidence of in-hospital death in MINCOA patients is similar as in MI-CAD patients.

Ordered stereom structure in sea urchin tubercles: High capability for energy dissipation

Tubercles in sea urchin shells serve as a base on the test plates connecting the spine; these undergo compressive or impact stress from the spines. As the volume fraction of the ordered stereom structure in a tubercle increases, the compressive load-displacement curves are gradually characterized by the typical behavior of ceramic foams. Although this ordered stereom structure only exhibits an average porosity of 50.6%, it also exhibits high fracture resistance and energy dissipation capacity. Such remarkable behavior of the ordered stereom structure is attributed to its unique hierarchical microstructure. Specifically, at the macroscale, the stereom structure is periodic. It has uniformly distributed pores that are typically round, which can effectively reduce the stress concentration around the pores, and the ordered arrangement of the trabeculae along the axial direction of the tubercle bears the most compressive stress. The trabeculae present a bottleneck shape with a specific dimension, ensuring the best fracture resistance with a relatively higher porosity. Furthermore, crack deflection in the trabeculae changes the local fracture mode of the mineral, thereby increasing the crack surface area. STATEMENT OF SIGNIFICANCE: The connecting bases of the spines in sea urchin shell, known as tubercle, effectively undergo the compressive stress or impact stress from the spines. An ordered stereom structure is found in the tubercle, and it shows an excellent fracture resistance and energy dissipation capacity. Such a fantastic behavior of the ordered stereom structure mainly takes advantage of its unique hierarchical microstructure. The stereom structure presents a periodic structure on macroscale, the trabeculae show a bottleneck shape with a specific dimension to guarantee the best fracture resistance with a relatively higher porosity, and the soft fillers among CaCO₃ nanoparticles in a trabecula cause consecutive crack deflections.

Kinking and cracking behavior in nacre under stepwise compressive loading

The damage evolution of nacre under compressive loading has not been well understood, despite numerous investigations on its compressive behavior. In the present work, quasi-in-situ loading-unloading-reloading stepwise compressive tests were performed on nacre in Pinctada maxima shell, which exhibits a distinctive gradient feature with the thickness of platelets decreasing from the external to internal parts. In the loading direction parallel to the platelets, multiple microcracks and kink bands can absorb much deformation energy, leading to a graceful failure. Kinking only occurs at the final stage of fracture process, and it thus has no obvious influence on the strength of nacre, but contributes to a much larger strain. In the loading direction perpendicular to the platelets, nacre exhibits concurrently much higher compressive strength and fracture strain, as the damage can be effectively restricted. This is attributed to the presence of gradient structure, which disperses the stress concentration in front of the crack tip, and arouses the toughening mechanisms including damage localization and crack deflection. The findings obtained in this study are expected to provide fundamental insights into the design of bio-inspired advanced engineering materials.

Deformation and fracture behavior of a natural shell ceramic: Coupled effects of shell shape and microstructure

Common seashells possess their most adaptive functions benefiting from the macro-geometry and unique microstructures. The Cymbiola nobilis shell exhibits a logarithmic spiral-like shape and it is hierarchically constructed by the fiber-like crossed-lamellar structure. Three-point bending tests are conducted on three groups of samples taken from different locations (G1 with two macro-layers, G2 with three macro-layers, and G3 containing three macro-layers but with an arch-like curved shape). A novel method was developed to evaluate the bending stress of the curved samples and understand the bending fracture resistance of such curved samples. Due to the presence of a horizontal force that can decrease or shield the bending moment at the bottom center of samples, the arch-like G3 samples demonstrate the highest bending fracture resistance, revealing the significance of the curved shape of shell in the protection against the external attacks. The number of macro-layers and the curved shape of shell play an important role in the mechanical properties of the shell. The orientation of building blocks in a single crossed-lamellar layer is critical to the fracture resistance, and five types of fracture modes based on interfacial debonding, inter- and trans-lamella fracture are identified. The results obtained in this study would help open a new pathway to the development of bio-inspired high-performance structural materials.

Mechanical properties of crossed-lamellar structures in biological shells: A review

The self-fabrication of materials in nature offers an alternate and powerful solution towards the grand challenge of designing advanced structural materials, where strength and toughness are always mutually exclusive. Crossed-lamellar structures are the most common microstructures in mollusks that are composed of aragonites and a small amount of organic materials. Such a distinctive composite structure has a fracture toughness being much higher than that of pure carbonate mineral. These structures exhibiting complex hierarchical microarchitectures that span several sub-level lamellae from microscale down to nanoscale, can be grouped into two types, i.e., platelet-like and fiber-like crossed-lamellar structures based on the shapes of basic building blocks. It has been demonstrated that these structures have a great potential to strengthen themselves during deformation. The observed underlying toughening mechanisms include microcracking, channel cracking, interlocking, uncracked-ligament bridging, aragonite fiber bridging, crack deflection and zig-zag, etc., which play vital roles in enhancing the fracture resistance of shells with the crossed-lamellar structures. The exploration and utilization of these important toughening mechanisms have attracted keen interests of materials scientists since they pave the way for the development of bio-inspired advanced composite materials for load-bearing structural applications. This article is aimed to review the characteristics of hierarchical structures and the mechanical properties of two kinds of crossed-lamellar structures, and further summarize the latest advances and biomimetic applications based on the unique crossed-lamellar structures.

Broadband tunable InAs/InP quantum dot external-cavity laser emitting around 1.55 μm

We report a broadband tunable external-cavity laser based on InAs/InP quantum dots (QDs) grown by metal-organic vapor phase epitaxy. It is found that high AsH₃ flow during the interruption after QD deposition greatly promotes QD ripening, which improves the optical gain of QD active medium in lower energy states. Combined with anti-reflection/high-reflection facet coatings, a broadly tunable InAs/InP QD external-cavity laser was realized with a tuning range of 140.4 nm across wavelengths from 1436.6 nm to 1577 nm at a maximum output power of 6 mW.

High performance 2150 nm-emitting InAs/InGaAs/InP quantum well lasers grown by metalorganic vapor phase epitaxy

We demonstrate high performance 2150 nm InAs/InGaAs/InP quantum well (QW) lasers grown by metalorganic vapor phase epitaxy. The laser structure consists of two InAs/InGaAs QWs, with a 30 μm-wide ridge waveguide and two cleaved cavity facets. The continuous wave operation at room temperature (RT) is achieved, with an output power of larger than 160 mW per facet and with a low threshold current density of 90.4 A/cm(2) per QW derived for the infinite cavity length. Under pulse injection mode, the maximal peak power per facet is as high as 1.35 W. By varying the cavity length, the lasing wavelength can be tuned in a range from 2142 nm to 2154 nm. Moreover, the highest operating temperature reaches up to 100 °C, and characteristic temperatures are 50 K (T(0)) and 132 K (T(1)) in the temperature range of 20-70 °C, respectively.

A thin-layer electrochemical detector coated with nafion film for liquid chromatography

The selectivity and analytical application of a thin-layer electrochemical detector comprised of glassy carbon electrode coated with Nafion film were investigated. As a result of the ion-exchange characteristics of the Nafion polymer, the selectivity and stability were improved greatly. The coated electrode has a good response only for cations with the same sensitivity as an uncoated (bare) electrode, but not for anions, and the response for neutral molecules is decreased three-fold. The diffusion of electroactive compounds in Nafion film is discussed based on the results of flow injection experiments. The peak current at the coated electrode was independent of the flow-rate of the mobile phase. Electrode poisoning due to protein adsorption was minimized. The use of 30% methanol or 10% acetonitrile in the mobile phase did not affect the performance of the coated electrode. Various analytes having three kinds of charge state, i.e., anionic, cationic and neutral, were tested. Liquid chromatography with electrochemical detection of ascorbic acid, norepinephrine, epinephrine, dopamine and uric acid was demonstrated.