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As a novel X-ray focusing technology, lobster eye micro-pore optics (MPO) feature both a wide observing field of view and true imaging capability, promising sky monitoring with significantly improved sensitivity and spatial resolution in soft X-rays. Since first proposed by Angel (1979), the optics have been extensively studied, developed and trialed over the past decades. In this Letter, we report on the first-light results from a flight experiment of the Lobster Eye Imager for Astronomy ($LEIA$), a pathfinder of the wide-field X-ray telescope of the Einstein Probe mission. The piggyback imager, launched in July 2022, has a mostly un-vignetted field of view of $18.6^\circ \times 18.6^\circ $. Its spatial resolution is in the range of 4$-$7 arcmin in FWHM and the focal spot effective area is 2$-$3 cm$^2$, both showing only mild fluctuations across the field of view. We present images of the Galactic center region, Sco X-1 and the diffuse Cygnus Loop nebular taken in snapshot observations over 0.5$-$4 keV. These are truly wide-field X-ray images of celestial bodies observed, for the first time, by a focusing imaging telescope. Initial analyses of the in-flight data show excellent agreement between the observed images and the on-ground calibration and simulations. The instrument and its characterization are briefly described, as well as the flight experiment. The results provide a solid basis for the development of the present and proposed wide-field X-ray missions using lobster eye MPO., Comment: 11 pages, 4 figures. Accepted for publication in Astrophysical Journal Letter

A new type of composite concrete which can be called corundum-rubble concrete (CRC) was presented to improve the resistance of protective structure to the projectile impact. Comparative experiments were conducted between CRC and reinforced concrete, and a modified Taylor model was proposed to predict the penetration depth of CRC targets. Experimental results show that CRC is much higher than reinforced concrete in both strength and hardness and shows excellent resistance to the 0.125 m-diameter projectile impact. Theoretical analyses demonstrated that the modified Taylor model’s predicted results were in good agreement with the measured values.

Phase selection under far-from-equilibrium condition has been investigated in three Cr 2 Nb-20/30/40Ti (at. %) alloys processed by laser surface melting (LSM) with scanning speeds of 50–200 mm/s. Phase identification was performed by micro-area XRD technique combined with SEM plus EDS methods. The results show that, at all scanning speeds of 50–200 mm/s, the microstructure of Cr 2 Nb-20Ti alloy consisted of single-phase Cr 2 Nb, whereas it evolved to monolithic β-Ti in the Cr 2 Nb-40Ti alloy. Meanwhile, the microstructure of Cr 2 Nb-30Ti alloy solidified with eutectic β-Ti/Cr 2 Nb at 50 mm/s, which transited to monolithic β-Ti as scanning speeds increased to 100–200 mm/s. Microstructures evolution was interpreted based on Trivedi-Magnin-Kurz (TMK) and Kurz-Giovanola-Trivedi (KGT) models incorporating the effect of non-equilibrium solidification. After the process of LSM, the micro-hardness of Cr 2 Nb-20Ti alloy was improved to a level of 9.0 GPa, and the fracture toughness was reduced to about 3.1 MPa m 1/2 ; while for the Cr 2 Nb-30/40Ti alloys, the micro-hardness decreased within a range of 5.5–6.6 GPa, but with a great increase of facture toughness of 21–23 MPa m 1/2 .

Aflatoxin is a potent carcinogen commonly found in animal feeds that can impair rumen fermentation at high concentrations; however, its effects at physiologically relevant concentrations are unknown. This study examined the effects of aflatoxin B

The microstructures of binary Cr/Cr2Nb alloys doped with 0.1 at-% rare earth element (REE) Y were characterised by fine interlamellar spacing, and the growth morphology of Cr2Nb primary phase was transformed from faceted to non-faceted. Moreover, the lamellar spacing was observed to decrease with the decreasing of solidification rate with the addition of REE Y. Furthermore, the mechanical tests showed that the addition of REE Y has a beneficial effect on the room temperature fracture toughness of Cr2Nb/Cr alloys. The room temperature fracture toughness of the Y doped Cr/Cr2Nb hypoeutectic and hypereutectic alloys increased by ∼130 and 140% over that of the undoped alloys respectively, which was caused by the refinement of lamellar eutectic and strengthening of lamellar eutectic bonding strength.

By combining the techniques of directional solidification and coating Y2O3, a Cr–20Nb–40Ti alloy was manufactured successfully with various growth rates. The revolution of microstructures and corresponding mechanical properties was discussed to develop the Cr2Nb based alloys with good combination of mechanical properties. The results show that the favorable growth dynamics of plane (220) of Laves phase Cr2Nb was observed with the increase of growth rate. Phase selection took place in microstructures evolved from the primary Cr2Nb, via the dendrite-like eutectic Cr2Nb/β-Ti, and finally to the primary β-Ti, with increasing the growth rate from 5 to 200 µm/s. Based on the coupled zone of eutectic, the competitive growth of solidified phases in the directionally solidified Cr–20Nb–40Ti alloy was elucidated. In addition, the mechanical properties of alloy depended on the growth rate, and the fracture toughness of the alloy reached 16.50 MPa m1/2 at 200 µm/s, much larger than 1.40 MPa m1/2 for single-phase Cr2Nb.

By employing XRD, EDXS, TEM, HRTEM, and SADPs methods, the polytypic transition of Laves phase Cr2Nb alloyed with Ti has been investigated in the dual-phase Cr–20Nb–40Ti (in at.%) alloy. The solute Ti in Cr2Nb is shown to inhibit the polytypic transition of Cr2Nb by substituting onto the Cr sites. This leads to the occurrence of metastable structures of C36, 5R, 6H and 7R. On the contrary, the second phase β-Ti is suggested to prompt the polytypic transition of Cr2Nb based on the lattice mismatch calculation. The low lattice mismatch between the β-Ti and the C15 polytype is beneficial to the formation of single C15 polytype at the interface.

Synopsis The electron correlation effects are crucial to the two-electron one-photon transition of double K hole excited state. Appropriate correlation model was constructed to investigate this process of 11 selected He-like ions of Z from 10 to 47. Good agreement to the previous work and some new transition data were obtained.

Multilayered combination of protective structures is an important means of effectively weakening the explosive shockwave. On this basis, a “rigid-flexible-rigid” three-layer sealed structure was proposed in this paper and two models for the sealed structure were designed. Meanwhile, internal explosion tests of the two models were conducted. One model used foam concrete as the energy absorbing material and the other used dense sand. The comparisons between the test results and the computed results obtained from the formulae were made, and the test results agreed well with the computed results. Test results showed that both models had favorable energy-dissipating capacity, and the model that used foam concrete as the energy absorbing material had a superior energy-dissipating capacity.

This study aimed to determine the fermentation characteristics, nutrient composition and in vitro digestibility of desert wormwood (DW, Artemisia desertorum Spreng.) silage as the sole ingredient, or mixed with high-moisture maize (corn) straw (HMCS). Desert wormwood and HMCS were harvested and chopped (1–2 cm) then ensiled in laboratory silos (25 cm high with an internal diameter of 7·6 cm) at a density of 550 g L−1 at room temperature for 60 days. The proportions of DW in the DW/HMCS mixtures were 1, 0·75, 0·50, 0·25 and 0, based on fresh weight. The silages were analysed for fermentation characteristics, nutrient composition and in vitro digestibility. Desert wormwood ensiled with HMCS had lower pH and acetic acid concentration and higher lactic acid concentration as the proportion of DW decreased. As the proportion of DW decreased, the crude protein concentration and the in vitro digestibility of dry matter increased and the concentrations of neutral detergent fibre, acid detergent fibre and acid detergent lignin decreased. This study has indicated that mixing HMCS with DW can improve the fermentation quality and nutrient composition of these silage mixtures.

The effect of Ti content on the fracture toughness of the Cr 2 Nb–20/30/40Ti (in at.%) alloys has been investigated in the arc melting and heat treatment (1473 K for 48 h) conditions. The results show that the reduction of grain size and the facture toughness of the alloys increased with increasing the Ti content. After the heat treatment, the facture toughness of the Cr 2 Nb–20/30Ti alloys increased by almost twice, and the crack bridging was primarily observed as the toughening mechanism, and for the Cr 2 Nb–40Ti alloy, the fracture toughness increased by 77% and reached 18.80 MPa m 1/2 , and the toughening mechanism transited to the crack defection. The alleviation of deformation constraint during the heat treatment was elucidated to be effective in improving the fracture toughness of the alloys.

Three Laves phase-based alloys with nominal compositions of Cr2Nb–xTi (x = 20, 30, 40, in at%) have been prepared through vacuum non-consumable arc melting. The results show that the microstructures of Cr2Nb-(20, 30) Ti alloys are composed of the primary Laves phase C15–Cr2(Nb,Ti) and bcc solid solution phase, while the microstructure of Cr2Nb–40Ti alloy is developed with the eutectic phases C15–Cr2(Nb,Ti)/bcc solid solution. The measured fracture toughness of ternary Laves phase C15–Cr2(Nb,Ti) is about 3.0 MPa m1/2, much larger than 1.4 MPa m1/2 for binary Laves phase Cr2Nb. Meanwhile, the fracture toughness of Cr2Nb–xTi (x = 20, 30, 40) alloys increases with increasing Ti content and reaches 10.6 MPa m1/2 in Cr2Nb–40Ti alloy. The eutectic microstructure and addition of Ti in Cr2Nb are found to be effective in toughening Laves phase-based alloys.

The microstructure and room temperature fracture toughness of binary Cr/Cr2Nb alloys annealed at 1653 K for 30 h were investigated at both the hypo- and hypereutectic compositions. The experimental results indicate that the high temperature heat treatment has a beneficial effect on the room temperature fracture toughness of the Cr2Nb/Cr alloys. After the heat treatment, the room temperature fracture toughness of the hypo- and hypereutectic alloys are increased by about 212 and 203%, which are 15 and 8 times higher than that of as-cast Cr2Nb Laves phase (1·2 MPa m1/2). The fractographic analysis indicates that in the annealed condition, the strengthen of lamellar eutectic cohesive strength can provide significant toughening of the matrix by crack deflection, crack blunting and crack bridging mechanisms.

The microstructure and mechanical properties of Cr2Nb-based intermetallic matrix composites fabricated by laser surface remelting were investigated at hypoeutectic and hypereutectic compositions. In the hypoeutectic composition, the molten zones under different laser scanning velocities consist of fully α-Cr dendrites, whereas a series of morphology evolutions perpendicular to the scanning direction occurred in the hypereutectic composition: Cr2Nb primary phase + Cr/Cr2Nb eutectic → Cr/Cr2Nb eutectic → α-Cr primary phase + Cr/Cr2Nb eutectic → fully α-Cr dendrite. Based on the maximum growth rate criterion, the microstructure evolutions of the molten zones were analyzed by considering the competitive growth among the α-Cr phase, Cr2Nb Laves phase, and the Cr/Cr2Nb eutectic, which are in agreement with the experimental results. More importantly, the room-temperature fracture toughness values of the hypoeutectic and hypereutectic alloys attain 11.2 MPa m1/2 and 7.9 MPa m1/2, respectively, which increase by eight and six times over the as-cast Cr2Nb Laves phase (1.2 MPa m1/2), respectively. The remarkable enhancements in room-temperature fracture toughness were explained in terms of fine-grain toughening, second Cr phase toughening, and point defects toughening.

The phase stability of the Laves phase Cr2Nb in a two-phase Cr-Cr2Nb alloy produced by arc-melting was investigated using X-ray diffraction, transmission electron microscopy and selected area electron diffraction. The experimental results indicated that the as-cast ingot was consisted of C15-Cr2Nb and Cr phases; the intermediate C36 and high-temperature C14 modifications of Cr2Nb, reported in literatures, were not detected in this study. These results, combined with a detailed analysis of the actual solidification conditions, revealed that the C14-Cr2Nb was a metastable rather than a stable high-temperature modification. Moreover, a kind of extremely fine lamellar structure was found to be randomly distributed in the eutectic cells, which may be formed by decomposition of the supersaturated C15-Cr2Nb via a discontinuous precipitation reaction.

A series of microstructures including fully coupled eutectic, both α-Cr and β-Cr2Nb primary dendrites embedded in eutectic and only β-Cr2Nb primary dendrites plus eutectic were observed in the arc-melted Cr-Cr2Nb eutectic alloy. By employing EPMA analysis performed at the eutectic regions, the eutectic composition of the Cr-Cr2Nb system was indicated to contain less than 18 at.%Nb. Based on the solidification phase selection involving phase competitive nucleation and growth, the α-Cr phase was predicted to be the primary nucleating phase and the β-Cr2Nb the primary growing phase. Under large undercooling conditions, the solidification process was controlled by nucleation, which led to the formation of α-Cr primary particles. With the decrease in undercooling, the solidification process developed into growth controlling, which caused the occurrence of β-Cr2Nb primary phase since the actual solidification path of the alloy lay within the hypereutectic region. The explanation was confirmed by the experimental composition analysis.

The microstructure and mechanical properties of a binary Cr based alloy containing the Laves phase Cr2Nb and Cr phase have been studied in the arc melted condition. Microstructure consisting of fine directional divorced eutectic was observed at the bottom of the ingot, while it developed into coarse Cr primary dendrites plus interdendritic lamellar eutectic containing Cr2Nb and Cr phases in the middle and top parts of the ingot. Meanwhile, the fracture toughness values of the top and bottom parts of the ingot attained 4·5 and 7·8 MPa m1/2 at room temperature, which were about three and five times than that of monolithic Cr2Nb respectively. The enhancement was explained by the second Cr phase toughening and grain refinement toughening mechanisms. In addition, the formation mechanism of the divorced eutectic and the microstructure–property relationships were also discussed.

Haloes of Laves phase Cr2Nb around the primary dendrites Cr were observed in the arc-melted Cr–12% Nb hypoeutectic alloy, while no halo of non-faceted Cr phase around the Cr2Nb Laves phase occurred in the Cr–20% Nb hypereutectic alloy. This observation differs from the haloes formed in metal–intermetallic alloy systems. An explanation on the formation of Cr2Nb halo was presented by considering the solidification behavior of the leading phase and non-reciprocal nucleation characteristics of the Cr2Nb/Cr eutectic. In the Cr–12% Nb alloy, primary dendrites Cr worked as a good nucleant available for the occurrence of the halo Cr2Nb that subsequently solidified as the leading phase in the eutectic. For the Cr–20% Nb alloy, primary dendrites Cr2Nb first precipitated as the leading phase inducing the eutectic formation, resulting in no halo growth. In addition, the coupled zone of the Cr–Nb alloy was theoretically predicted in agreement with the experimental results.

For improving the performance of a miniature loudspeaker, engineers have been pursuing a goal of lowering its first damped frequency to have a broad and smooth region of its sound-pressure-level response. This article applies the approach of electro-mechano-acoustical analogy to study the first damped frequency of a miniature loudspeaker used for cellular phones. Using the analogy approach, the authors derive an explicit formulation for the sound-pressure-level of a typical miniature loudspeaker of dynamic type. The veracity of the derived formulation is verified by comparing with the experimental result recorded by B and K apparatus. The derived formulation is further simplified by neglecting factors that are either irrelevant or insignificant for the first damped frequency. Through basic algebraic and calculus operations, this article also presents an explicit form of the first damped frequency. This work has laid the platform for engineers to tailor the design in pursuit of improving the performance of miniature loudspeakers.

The great mass of machining allowance for blisk is removed in the rough milling, so improving the rough machining efficiency for the blisk’s tunnel is the key of realizing high-efficiency machining of blisk. According to the structure characteristic of open blisk’s tunnel, a four-axis plunge slot rough milling with high-efficiency and low machining cost is advanced. First, the plunge slot process for blisk and the generation process of the ruled enveloping surface for the freeform surface of the blisk’s blade are put forward. Then, the generating method of the ruled enveloping surface for the blade’s freeform surface and the tool path generation method of four-axis plunge slot milling for blisk are studied. The rough milling region of open blisk’s tunnel is determined by generating the ruled enveloping surface of blade’s offset surface, and the algorithm of tool path for four-axis plunge milling is given. When using a ruled surface to approach a freeform surface, the problem of getting boundary is solved, and the error from the calculation of tool path is avoided by the algorithm. At last, the experiment shows that comparing to the traditional side slot milling, the cutting force of four-axis plunge milling can be reduced by 60% and even the rough machining efficiency can be increased to more than double.

To study the growth and secretion of pancreatic B cell line BTC6-F7 in the alginate polylysine-alginate (APA) microcapsules and explore the possibility of utilizing it as bioartificial islets.Microencapsulated BTC6-F7 cells prepared with electric droplet generator were cultured in vitro, and the growth and insulin secretion of them were measured periodically.Over the 90-day observation period, BTC6-F7 cells were able to grow and survive as cell clusters in the microcapsules and finally fulfill the capsules. But the microcapsules remained well after the long-time culture. The average total cell number per capsule were increasing with time, but the cell viability was decreasing. The changes of insulin secretion and average live cell number per capsule were in a same manner: for the first two weeks they increased rapidly and then maintained in a relatively constant levels for the rest time.The microencapsulated pancreatic B cells prepared by us could survive, grow and secretion for a long time. This has made a basis for further development of bioartificial islets, and also can be used to study the mechanism and therapy of diabetes mellitus.

SiO(2) mesoporous molecular sieve SBA-15 with the incorporation of erbium ions is studied as a novel type of nanoscopic composite photoluminescent material in this paper. To enhance the photoluminescence efficiency, two schemes have been used for the incorporation of Er(3+) where (1) Er(3+) is ligated with bis-(perfluoromethylsulfonyl)-aminate (PMS) forming Er(PMS)(x)-SBA-15 and (2) Yb(3+) is codoped with Er(3+) forming Yb-Er-SBA-15. As high as 11.17 × 10(-21)cm(2) of fluorescent cross section at 1534 nm and 88 nm of "effective bandwidth" have been gained. It is a 29.3% boost in fluorescent cross section compared to what has been obtained in conventional silica. The upconversion coefficient in Yb-Er-SBA-15 is relatively small compared to that in other ordinary glass hosts. The increased fluorescent cross section and lowered upconversion coefficient could benefit for the high-gain optical amplifier. Finally, the Judd-Ofelt theory has also been used for the analyses of the optical spectra of Er(PMS)(x)-SBA-15.

Ageing of geotextile has attracted incessant attention from the engineering field. During the revision of Technical Specification for Application of Geotextile in Marine Works (JTJ239-98) published by the Ministry of Communications of China, artificially accelerated ageing tests in laboratory, natural insolating tests, measurement of underwater ultraviolet radiation energy, ageing tests of buried geotextile in sandy soil and tests of specimens sampled from practical engineering works were carried out for the monographic research on ageing resistance of geotextile. The paper is the summary of the test results, which can be of the reference for designers and contractors.

We investigate transmission of low-energy electrons (800 eV) through a paired parallel glass plates. The measurements were focused on the angular distributions of electrons transmitted through capillary. The present results indicate that the observation angle is larger than the tilted angle ψ.

This study examines the effects of xenografts of microencapsulated bovine chromaffin cells (BCCs) on the rotational behavior of hemiparkinsonian monkey recipients. In addition, it determines the content of monoamine neurotransmitters and their major metabolites in the neostriatum in hemiparkinsonian monkeys. The hemiparkinsonian model in monkeys was induced by a unilateral intracarotid injection of methyl-phenyl-tetrahydropyridine (MPTP). Unencapsulated BCCs, BCCs microencapsulated in alginate-polylysine-alginate (ALA) membranes as well as empty microencapsules were grafted into the neostriatum of the hemiparkinsonian monkeys. Following the transplantation the hemiparkinsonian symptoms subsided and the number of rotations induced by apomorphine decreased for up to nine months in the group of recipients grafted with microencapsulated BCCs, while only a temporary improvement (one month) was detected in the recipients of the unencapsulated BCCs. No change was observed in the recipients of empty microencapsules. Dopamine and its metabolites were found considerably depleted in the MPTP-lesioned side versus the unlesioned side of the neostriatum in the hemiparkinsonian monkeys(P

We analyze the sideband multiwave mixing process of an audio-frequency-modulated signal in an erbium-doped-fiber amplifier. The nearly resonant interaction of an audio-frequency-modulated signal with the doped erbium ions results in multiwave mixing, which induces the generation of new sideband frequencies. We show that the input signal is distorted by such a multiwave mixing process. The condition to reduce the distortion of an input modulated signal in an erbium-doped-fiber amplifier is evaluated.

We present a theory that enables us to account for the pump-induced change of refractive index in a rare-earth-doped fiber. Experimental results carried out on an erbium-doped fiber with cw pump and cw signal operation confirm the accuracy of this theory at the steady state. Both theoretical and experimental results show that significant index changes can be obtained for the order of 1–2 mW of cw optical pump or signal power. In addition we studied the transient dynamics of the resonance-enhanced refractive index in a wide range of pulse widths from millisecond to tens of femtoseconds. The result shows that a fast response of refractive-index changes is achievable since the effects of spontaneous emission and nonradiative decay are negligible in the short-pulse case.