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The influence of size effect on deformation behaviors at quasi-static strain rate has been widely studied in recent years. However, there is little research about size effect on deformation behaviors of metal foils at high strain rate. To clarify how the size effect influences the deformation behavior of metal foils over a wide range of strain rate, the tensile tests at different strain rates of pure titanium foil with various grain sizes were originally conducted using material testing system (MTS) and a specially designed Split Hopkinson Tension Bar. It is found that microstructure evolution and fracture mechanism show great differences between quasi-static and dynamic tensile tests. Moreover, size effect on flow stress of pure titanium foil also shows obvious distinctions between quasi-static and dynamic tensile tests and this phenomenon was well explained by the proposed twinning refinement physics model. Furthermore, the uniform strain for pure titanium foil is larger at high strain rate than that at quasi-static strain rate, and a larger uniform strain for pure titanium foil with larger grains was observed at high strain rate. A modified Johnson-Cook model coupling effects of grain size and strain rate was proposed to predict the flow stress of pure titanium foil, and the prediction matched well with the experimental results.

Organophosphorus pesticides (OPs) are one of the most frequently used pesticides in agriculture, and their residues in environment have caused serious human health and environmental concerns. In this work, we reported a dual-ratiometric electrochemical aptasensor based on carbon nanohorns/anthraquinone-2-carboxylic acid/Au nanoparticles (CNHs/AQ/AuNPs) for simultaneous detection of malathion (MAL) and omethoate (OMT). Here, CNHs/AQ/AuNPs composites were synthesized by a simple room temperature method, and used as a substrate to generate a reference signal (I

The wide-angle lens is widely used with the advantage of a large field of view, but it is difficult to solve the problem of large distortion. Therefore, the research on how to design a wide-angle low-distortion lens with excellent imaging quality is very meaningful. In this paper, we propose a high-performance wide-angle small distortion optical system, which has a horizontal field angle of 110° and a vertical field angle of 77°, focal length of 2.03mm, f number of 1.65, and a total length of 16.5mm. By introducing a non-rotational symmetric freeform surface into the last side of the wide-angle optical system and combining with several even aspheric surfaces, the f-tan(theta) distortion in the X direction is controlled to -6%~+1%, and the f-tan(theta) distortion in the Y direction is controlled to less than 1%. At the same time, the MTF of the system is greater than 0.35 at 125lp/mm, so that the circular image plane can better adapt to the rectangular sensor. In addition, due to the introduction of the freeform surface in the system, the change of system structure with temperature becomes more complex. We carry out thermal analysis for this surface and calculate the change of structure with temperature. Finally, we completed the athermalized design of the lens, so that the wide-angle lens can work in the range of -40℃~+80℃. This optical system has great development potential in security monitoring, UAV detection and other fields that may encounter extreme environments.

Global environmental pollution issue has boosted the development of novel analytical techniques with high efficiency and accuracy for detection of hazardous contaminants. Strategies based on electrochemical, electrochemiluminescent, or photoelectrochemical analysis are among the promising detection approaches to provide rapid and sensitive analysis. Currently, combining ratiometric assay with such strategies can further promote their sensing reliability and reproducibility in complex conditions. This review highlights recent advances of ratiometric electrochemical, electrochemiluminescent, and photoelectrochemical sensors in the past 2 years. Their signal generation strategies and analysis applications, particularly for the environmental contaminant detection, are discussed in detail, and a future prospect in this area from us is also provided.

We reported a carbon nanohorns/gold nanoparticles composites-based impedimetric aptasensor for carbendazim (CBZ) detection in lettuce and orange juice at picogram levels. The increased electron-transfer resistance, resulting from the formation of CBZ-aptamer complex, was recorded by electrochemical impedance spectroscopy as the aptasensor response for CBZ. Under the optimal conditions, the proposed aptasensor displayed a linear response for CBZ ranging from 1 to 1000 pg mL−1 with a detection limit of 0.5 pg mL−1. Noteworthy, the as-developed aptasensor displayed the lowest detection limit for CBZ among the previously reported methods. Common pesticides (atrazine, thiamethoxam, etc.) with 100-fold concentration did not interfere the CBZ detection. For CBZ detection in lettuce and orange juice, satisfactory recoveries were obtained with standard addition method. Statistics demonstrated that no significant differences were found between the data provided by standard HPLC-MS reference method and developed aptasensing method in term of accuracy and precision. We believe that the proposed aptasensor possesses a potential application for CBZ monitoring in agricultural product and food.

Aflatoxin B1 (AFB1) contamination has raised global concerns in agricultural and food industry; thus, sensitive, accurate and rapid AFB1 sensors are essential in many circumstances. Herein, we developed a label-free and immobilization-free ratiometric homogeneous electrochemical aptasensor based on hybridization chain reaction (HCR) for facile and rapid determination of AFB1. Methylene blue (MB) and ferrocene (Fc) were used as label-free probes to produce a response signal (IMB) and a reference signal (IFc) in solution phase, respectively. The ratio of IMB/IFc was used as a yardstick to quantify AFB1. HCR was exploited to enlarge the intensity of IMB as well as ratiometric signal. By combining label-free homogeneous assay and ratiometric strategy, the resulting aptasensor offered sensitive, rapid, and reliable determinations of AFB1 with a detection limit of 38.8 pg mL−1. The aptasensor was then used to determine AFB1 in cereal samples with comparable reliability as HPLC-MS.

A panoramic annular lens can provide abundant spatial information in real time with its compact and scalable structure. To deal with extreme temperature environments and to improve the utilization of an image plane, we propose a high-performance compact athermal panoramic annular lens with separated radial optical power. By introducing multiple free-form surfaces, the system achieves a field of view of ( 40 ∘ ∼ 100 ∘ ) × 360 ∘ , an f -number of 2.2, and a total length of 40 mm. The modulation transfer function of the system’s full fields of view is greater than 0.5 at 200 lp/mm, and the distortion is less than 2.5%. It can work stably in the range of − 30 ∘ C to 70°C. The proposed system is compact, athermal, and high-performing and has broad application prospects in the fields of visual positioning and biomedicine.

It has been revealed that the grain size effect has a great effect on the formability of metal foils during quasi-static forming processes. However, there is little research on how size effects influence the formability of metal foils during the high-speed forming process, e.g., electromagnetically-assisted forming. To characterize the grain size effect in electromagnetically assisted micro-bulging, a miniaturized Nakazima test was conducted using a specially designed device. Pure titanium foils of thickness 103 μm and different grain sizes were utilized in the experiment. In addition, SEM and TEM methods were used to clarify how grain size influences the fracture surface and microstructure in electromagnetic forming.

The simultaneous detection of multiple mycotoxins in grains is significant due to the enhanced toxicity induced by their synergistic effects. In this work, a dual-ratiometric electrochemical aptasensing strategy for the simultaneous detection of aflatoxin B1 (AFB1) and ochratoxin A (OTA) was developed. Here, an anthraquinone-2-carboxylic acid (AQ)-labelled complementary DNA (cDNA) was used to provide separate and specific binding sites to assemble the ferrocene-labelled AFB1 aptamer (Fc-Apt1) and methylene blue-labelled OTA aptamer (MB-Apt2). The target-induced current ratios of IFc/IAQ and IMB/IAQ were then used to quantitatively relate to AFB1 and OTA, respectively. Following this principle, two types of aptasensors involving the hairpin DNA (hDNA) and linear single-stranded DNA (ssDNA) as the cDNA were fabricated for performance comparisons. The results revealed that hairpin DNA with a rigid 2D structure can greatly improve the assembly and recognition efficiency of the sensing interface, which makes the hDNA-based aptasensor possess high sensitivity, reliability and anti-interference ability. The hDNA-based aptasensor exhibited a detection range of 10-3000 pg mL−1 for AFB1 and 30-10000 pg mL−1 for OTA, respectively, with no observable cross-reactivity. Furthermore, the aptasensor was applied to analyze corn and wheat samples, and the reliability was validated by HPLC-MS/MS. Our work has presented a novel way for fabricating a high-performance aptasensor for simultaneous detection of multiple mycotoxins.

This paper presents the design of a high speed, high resolution silicon based thermal imaging instrument and its application to thermally image the temperature distributions of an electron beam melting additive manufacturing system. Typically, thermal images are produced at mid or long wavelengths of infrared radiation. Using the shorter wavelengths that silicon focal plane arrays are sensitive to allows the use of standard windows in the optical path. It also affords fewer modifications to the machine and enables us to make use of mature silicon camera technology. With this new instrument, in situ thermal imaging of the entire build area has been made possible at high speed, allowing defect detection and melt pool tracking. Melt pool tracking was used to implement an emissivity correction algorithm, which produced more accurate temperatures of the melted areas of the layer.

Identifying grain size and specimen thickness effects on the twinning characteristics and texture evolution of ultra-thin pure titanium sheet is essential for its extensive applications in many industries. In this research, ultra-thin pure titanium sheet with different grain sizes and thicknesses were deformed to different strain by electromagnetic-assisted bulging. Then the deformation twins were analyzed on a grain-by-grain basis to determine both the volume fraction of twins and the Schmid factor of twin variants in each grain. Results indicate that twin density of ultra-thin pure titanium sheet decreases when sample thickness decreases from 205 μm to 45 μm. Moreover, deformation twinning can be promoted when grain size increases from 7.5 μm to 27.4 μm but also can be restricted to a certain extent when grain size increases to 38.2 μm. In addition, grain size plays an evidently positive effect on multiple twin variants activation so as to affect the misorientation distributions. Furthermore, the frequency of twin variants with lower Schmid factor decreases with the increase of grains size from 7.5 μm to 38.2 μm. This is well explained by the strain accommodation criterion. By affecting the deformation mechanism of ultra-thin pure titanium sheet, size effects also play significant roles in the texture evolution.

A compact varifocal panoramic annular lens (PAL) system based on the four-component mechanical zoom method is proposed, which solves the problem that the traditional PAL system cannot zoom in to the region of interest. By moving the zoom group and the compensation group, our design achieves continuous zooming, in which the focal length changes from 3.8 to 6 mm. It can keep the position of the image surface unchanged while maintaining a compact structure. The system has a field of view (FoV) of 25°–100° in wide-angle mode and an FoV of 25°–65° in telephoto mode. The modulation transfer function of the wide-angle view is higher than 0.22 at 147 lp/mm. The F -theta distortion is less than 3%, and the relative illuminance is higher than 0.9 in the zoom process. Compared with the zoom PAL system with multiple free-form aspheric surfaces, the proposed system uses multiple spherical lenses and only one Q -type asphere lens to achieve outstanding panoramic zoom imaging results. It is practical and straightforward, easy to manufacture, detect, and mass produce.

Aflatoxin contamination causes tremendous economic losses and seriously threatens human health due to its prevalence in agricultural products and foods coupled with the severe toxicity of aflatoxins. Thus, sensitive, reliable, and rapid methods for aflatoxin analysis are urgently required. In recent years, electrochemical biosensors have emerged as a suitable alternative to gold standard methods that rely on sophisticated instruments (e.g. HPLC-MS). This review aims to describe recent advances (2016–2019) in electrochemical biosensors for aflatoxins detection in novel sensing strategies, recognition reporters, and integrated platforms. Particular emphasis is placed on the utilization of novel sensing strategies including dual-mode detection and ratiometric sensing in the fabrication of biosensors based on electrochemistry, photoelectrochemistry, and electrochemiluminescence. Meanwhile, a comprehensive discussion is provided on the challenges and perspectives related to electrochemical biosensing of aflatoxins.

We present a wide field of view (FOV) infrared scanning system, designed for single-pixel near-infrared thermal imaging. The scanning system consisted of a two-axis micro-electromechanical system (MEMS) mirror that was incorporated within the lens. The optical system consisted of two groups of lenses and a silicon avalanche photodiode. The system was designed for both the production of thermal images and also to utilize the techniques of radiation thermometry to measure the absolute temperature of targets from 500°C to 1100°C. Our system has the potential for real-time image acquisition, with improved data acquisition electronics. The FOV of our scanning system was ±30° when fully utilizing the MEMS mirror’s scanning angle of ±5°. The pixel FOV (calculated from the distance to target size ratio) was 100:1. The image quality was analyzed, including the modulation transfer function, spot diagrams, ray fan plots, lateral chromatic aberrations, distortion, relative illumination, and size-of-source effect. The instrument was fabricated in our laboratory, and one of the thermal images, which was taken with the new lens, is presented as an example of the instrument optical performance.

Accurately monitoring of aflatoxin B1 (AFB1), the most hazardous mycotoxin in agricultural products, is essential for the public health, but various testing demands (e.g. detection range, sensitivity) for different samples can be challenging for sensors. Here, we developed a sensitivity-programmable ratiometric electrochemical aptasensor for AFB1 analysis in peanut. Thionine functionalized reduced graphene oxide (THI-rGO) served as reference signal generator, ferrocene-labelled aptamer (Fc-apt) output the response signal. During analysis, the formation of Fc-apt-AFB1 complex led to its stripping from the electrode and faded the current intensity of Fc (IFc), while the current intensity of THI (ITHI) was enhanced. And ratiometric detection of AFB1 was achieved by using the current intensity ratio (ITHI/IFc) as quantitative signal. Compared with ratiometric strategies that highly rely on the labelled aptamers, the proposed strategy could regulate the value of ITHI/IFc by changing the modification of Fc-apt. And the detection sensitivity was found to be closely related to ITHI/IFc. Under the optimal conditions, the fabricated aptasensor with a dynamic range from 0.05–20 ng mL−1 and a detection limit of 0.016 ng mL−1 for AFB1 analysis. Besides, it exhibited excellent selectivity, reliability and reproducibility. The proposed sensitivity-programmable biosensor can be applied to detect various aptamer-recognized mycotoxins in agricultural sensing.

Conventional thermal imaging cameras, based on focal-plane array (FPA) sensors, exhibit inherent problems: such as stray radiation, cross-talk and the calibration uncertainty of ensuring each pixel behaves as if it were an identical temperature sensor. Radiation thermometers can largely overcome these issues, comprising of only a single detector element\ud \ud that can be optimised and calibrated. Although the latter approach can provide excellent accuracy for single-point temperature measurement, it does not provide a temperature image of the target object. In this work, we present a micromechanical systems (MEMS) mirror and silicon (Si) avalanche photodiode (APD) based single-pixel camera, capable of producing quantitative thermal images at an operating wavelength of 1 μm. This work utilises a custom designed f-theta wide-angle lens and MEMS mirror, to scan +/− 30° in both x- and ydimensions, without signal loss due to vignetting at any point in the field of view (FOV). Our single-pixel camera is shown to perform well, with 3 °C size-of-source effect (SSE) related temperature error and can measure below 700 °C whilst achieving ± 0.5 °C noise related measurement uncertainty. Our measurements were calibrated and traceable to the International Temperature Scale of 1990 (ITS-90). The combination of low SSE and absence of vignetting enables quantitative temperature measurements over a spatial field with measurement uncertainty at levels lower than would be possible with FPA based thermal imaging cameras.

Accurate quantitative temperature measurements are difficult to achieve using focal-plane array sensors. This is due to reflections inside the instrument and the difficulty of calibrating a matrix of pixels as identical radiation thermometers. Size-of-source effect (SSE), which is the dependence of an infrared temperature measurement on the area surrounding the target area, is a major contributor to this problem and cannot be reduced using glare stops. Measurements are affected by power received from outside the field-of-view (FOV), leading to increased measurement uncertainty. In this work, we present a micromechanical systems (MEMS) mirror based scanning thermal imaging camera with reduced measurement uncertainty compared to focal-plane array based systems. We demonstrate our flexible imaging approach using a Si avalanche photodiode (APD), which utilises high internal gain to enable the measurement of lower target temperatures with an effective wavelength of 1 µm and compare results with a Si photodiode. We compare measurements from our APD thermal imaging instrument against a commercial bolometer based focal-plane array camera. Our scanning approach results in a reduction in SSE related temperature error by 66 °C for the measurement of a spatially uniform 800 °C target when the target aperture diameter is increased from 10 to 20 mm. We also find that our APD instrument is capable of measuring target temperatures below 700 °C, over these near infrared wavelengths, with D* related measurement uncertainty of ± 0.5 °C.

Pt nanoparticle-loaded carbon nanohorns (Pt/CNHs) nanocomposites were synthesized by using formic acid as reducing agent at room temperature. Taking the advantage of the high surface area and excellent electronic conductivity, CNHs were used as support without any pretreatments for the enhancement of catalytic performance. By adjusting the feeding amount of H2PtCl6, the mass, size and distribution of Pt nanoparticles could be effectively controlled on CNHs. Compared with commercial Pt/C, the synthesized Pt/CNHs exhibit higher catalytic activity and improved long-term stability toward both methanol and formic acid oxidations. Among the Pt/CNHs, 13% wt. Pt/CNHs exhibit the best catalytic performances for the small size (2.4 nm) and uniform distribution of Pt NPs on CNHs. Our work reveals the superior catalytic performance of Pt/CNHs which may be a promising substitute for commercial Pt/C.

A novel ratiometric electrochemical aptasensor was developed for Ochratoxin A (OTA) detection based on the binding of methylene blue (MB) to DNA with a dual signal amplification strategy. The formation of dsDNA structures between ferrocene-labeled complementary DNA (Fc-cDNA), the OTA aptamer, and complementary helper DNA (hDNA) caused Fc away from the electrode, and allowed dsDNA to bind with a certain amount of MB. Here, a small oxidation current of Fc (IFc) and a large oxidation current of MB (IMB) were obtained. In the presence of OTA, its specific recognition with the aptamer induced the release of aptamer and hDNA from the electrode and subsequently the formation of hairpin structure for cDNA, which caused Fc close to the electrode and a weaker binding ability with MB. Then, an increased IFc and a decreased IMB were obtained. Based on this principle, OTA could be accurately quantified by measuring the ratiometric signal of IFc/IMB. Herein, the dual signal amplification strategy of the introduction of hDNA and the binding with MB after the OTA recognition was exploited to amplify the response signal. The obtained aptasensor showed a linear detection range from 10 pg mL−1 to 10 ng mL−1 and a detection limit of 3.3 pg mL−1. The aptasensor was successfully applied to determine OTA in wheat, and the results were validated through HPLC-MS. Furthermore, by changing the target aptamers, this strategy could be universally used for the determination of various mycotoxins, showing promising potential applications for mycotoxins monitoring in agricultural products and foods.

Comparisons between observational surveys and galaxy formation models find that the mass of dark matter haloes can largely explain galaxies' stellar mass. However, it remains uncertain whether additional environmental variables, generally referred to as assembly bias, are necessary to explain other galaxy properties. We use the Illustris Simulation to investigate the role of assembly bias in producing galactic conformity by considering 18,000 galaxies with $M_{stellar}$ > $2 \times 10^9$ $M_{\odot}$. We find a significant signal of galactic conformity: out to distances of about 10 Mpc, the mean red fraction of galaxies around redder galaxies is higher than around bluer galaxies at fixed stellar mass. Dark matter haloes exhibit an analogous conformity signal, in which the fraction of haloes formed at earlier times (old haloes) is higher around old haloes than around younger ones at fixed halo mass. A plausible interpretation of galactic conformity can be given as a combination of the halo conformity signal with the galaxy color-halo age relation: at fixed stellar mass, particularly toward the low-mass end, Illustris' galaxy colors correlate with halo age, with the reddest galaxies (often satellites) being preferentially found in the oldest haloes. In fact, we can explain the galactic conformity effect with a simple semi-empirical model, by assigning stellar mass based on halo mass (abundance matching) and by assigning galaxy color based on halo age (age matching). We investigate other interpretations for the galactic conformity, particularly its dependence on the isolation criterion and on the central-satellite information. Regarding comparison to observations, we conclude that the adopted selection/isolation criteria, projection effects, and stacking techniques can have a significant impact on the measured amplitude of the conformity signal., 15 pages, 8 figures; accepted for publication in MNRAS (minor revisions to match accepted version)