Abstract
X-ray detectors are broadly utilized in medical imaging and product inspection. Halide perovskites recently demonstrate excellent performance for direct X-ray detection. However, ionic ...migration causes large noise and baseline drift, limiting the detection and imaging performance. Here we largely eliminate the ionic migration in cesium silver bismuth bromide (Cs
2
AgBiBr
6
) polycrystalline wafers by introducing bismuth oxybromide (BiOBr) as heteroepitaxial passivation layers. Good lattice match between BiOBr and Cs
2
AgBiBr
6
enables complete defect passivation and suppressed ionic migration. The detector hence achieves outstanding balanced performance with a signal drifting one order of magnitude lower than all previous studies, low noise (1/
f
noise free), a high sensitivity of 250 µC Gy
air
−1
cm
–2
, and a spatial resolution of 4.9 lp mm
−1
. The wafer area could be easily scaled up by the isostatic-pressing method, together with the heteroepitaxial passivation, strengthens the competitiveness of Cs
2
AgBiBr
6
-based X-ray detectors as next-generation X-ray imaging flat panels.
An X‐ray detector with high sensitivity would be able to increase the generated signal and reduce the dose rate; thus, this type of detector is beneficial for applications such as medical imaging and ...product inspection. The inorganic lead halide perovskite CsPbBr3 possesses relatively larger density and a higher atomic number in contrast to its hybrid counterpart. Therefore, it is expected to provide high detection sensitivity for X‐rays; however, it has rarely been studied as a direct X‐ray detector. Here, a hot‐pressing method is employed to fabricate thick quasi‐monocrystalline CsPbBr3 films, and a record sensitivity of 55 684 µC Gyair−1 cm−2 is achieved, surpassing all other X‐ray detectors (direct and indirect). The hot‐pressing method is simple and produces thick quasi‐monocrystalline CsPbBr3 films with uniform orientations. The high crystalline quality of the CsPbBr3 films and the formation of self‐formed shallow bromide vacancy defects during the high‐temperature process result in a large µτ product and, therefore, a high photoconductivity gain factor and high detection sensitivity. The detectors also exhibit relatively fast response speed, negligible baseline drift, and good stability, making a CsPbBr3 X‐ray detector extremely competitive for high‐contrast X‐ray detections.
The hot‐pressing fabrication method for quasi‐monocrystalline CsPbBr3 thick film and the performance of their X‐ray detection are introduced. The high crystalline quality of CsPbBr3 films and the formation of self‐formed shallow bromide vacancy defects during the high‐temperature process result in a large µτ product and therefore high photoconductivity gain factor and record‐high detection sensitivity.
The sensitive detection of X‐rays embodies an important research area, being motivated by a common desire to minimize the radiation doses required for detection. Among metal halide perovskites, the ...double‐perovskite Cs2AgBiBr6 system has emerged as a promising candidate for the detection of X‐rays, capable of high X‐ray stability and sensitivity (105 μC Gy−1 cm−2). Herein, the important photophysical pathways in single‐crystal Cs2AgBiBr6 are detailed at both room (RT) and liquid‐nitrogen (LN2T) temperatures, with emphasis made toward understanding the carrier dynamics that influence X‐ray sensitivity. This study draws upon several optical probes and an RT excitation model is developed which is far from optimal, being plagued by a large trap density and fast free‐carrier recombination pathways. Substantially improved operating conditions are revealed at 77 K, with a long fundamental carrier lifetime (>1.5 µs) and a marked depopulation of parasitic recombination pathways. The temperature dependence of a single‐crystal Cs2AgBiBr6 X‐ray detecting device is characterized and a strong and monotonic enhancement to the X‐ray sensitivity upon cooling is demonstrated, moving from 316 μC Gy−1 cm−2 at RT to 988 μC Gy−1 cm−2 near LN2T. It is concluded that even modest cooling—via a Peltier device—will facilitate a substantial enhancement in device performance, ultimately lowering the radiation doses required.
The sensitive detection of X‐rays using devices based on metal halide perovskite semiconductors embodies a rapidly emerging field of research. The photophysical pathways within a single‐crystal Cs2AgBiBr6 detector exhibiting high sensitivity to X‐rays are detailed. By evaluating carrier‐recombination pathways at both high and low temperatures, the dramatic enhancements to performance realized upon cooling the device are elucidated.
Lead halide perovskites have recently emerged as promising X/γ-ray scintillators. However, the small Stokes shift of exciton luminescence in perovskite scintillators creates problems for the light ...extraction efficiency and severely impedes their applications in hard X/γ-ray detection. Dopants have been used to shift the emission wavelength, but the radioluminescence lifetime has also been unwantedly extended. Herein, we demonstrate the intrinsic strain in 2D perovskite crystals as a general phenomenon, which could be utilized as self-wavelength shifting to reduce the self-absorption effect without sacrificing the radiation response speed. Furthermore, we successfully demonstrated the first imaging reconstruction by perovskites for application of positron emission tomography. The coincidence time resolution for the optimized perovskite single crystals (4 × 4 × 0.8 mm
) reached 119 ± 3 ps. This work provides a new paradigm for suppressing the self-absorption effect in scintillators and may facilitate the application of perovskite scintillators in practical hard X/γ-ray detections.
Lead halide perovskites have exhibited excellent performance in solar cells, LEDs and detectors. Thermal properties of perovskites, such as heat capacity and thermal conductivity, have rarely been ...studied and corresponding devices have barely been explored. Considering the high absorption coefficient (10
~10
cm
), low specific heat capacity (296-326 J kg
K
) and small thermal diffusion coefficient (0.145 mm
s
), herein we showcase the successful use of perovskite in optoacoustic transducers. The theoretically calculated phonon spectrum shows that the overlap of optical phonons and acoustic phonons leads to the up-conversion of acoustic phonons, and thus results in experimentally measured low thermal diffusion coefficient. The assembled device of PDMS/MAPbI
/PDMS simultaneously achieves broad bandwidths (-6 dB bandwidth: 40.8 MHz; central frequency: 29.2 MHz), and high conversion efficiency (2.97 × 10
), while all these parameters are the record values for optoacoustic transducers. We also fabricate miniatured devices by assembling perovskite film onto fibers, and clearly resolve the fine structure of fisheyes, which demonstrates the strong competitiveness of perovskite based optoacoustic transducers for ultrasound imaging.
Effective scheduling of multiple agricultural machines in emergencies can reduce crop losses to a great extent. In this paper, cooperative scheduling based on deep reinforcement learning for ...multi-agricultural machines with deadlines is designed to minimize makespan. With the asymmetric transfer paths among farmlands, the problem of agricultural machinery scheduling under emergencies is modeled as an asymmetric multiple traveling salesman problem with time windows (AMTSPTW). With the popular encoder-decoder structure, heterogeneous feature fusion attention is designed in the encoder to integrate time windows and asymmetric transfer paths for more comprehensive and better feature extraction. Meanwhile, a path segmentation mask mechanism in the decoder is proposed to divide solutions efficiently by adding virtual depots to assign work to each agricultural machinery. Experimental results show that our proposal outperforms existing modified baselines for the studied problem. Especially, the measurements of computation ratio and makespan are improved by 26.7% and 21.9% on average, respectively. The computation time of our proposed strategy has a significant improvement over these comparisons. Meanwhile, our strategy has a better generalization for larger problems.
The continuous solar collector is a promising heater and reactor for the hydrothermal liquefaction (HTL) of microalgae biomass. To enhance the heat transfer and hydrothermal conversion of microalgae ...slurry in solar-driven reactors, a static mixer is inserted in the flow channel of the solar collector. A numerical model combining CFD and HTL reactions of microalgae biomass is proposed. Six composition equations of protein, carbohydrates, lipids, biocrude, aqueous phase and biogas were proposed, while corresponding HTL kinetics were utilized to simulate the conversion rate of the reactants and products. The effects of the twist ratio of the static mixer (3–10), flow rate (30–80 L/h) and solar intensity (650, 750, 850 W/m2) on the flow resistance, heat transfer and organics formation of microalgae slurry were investigated. The swirl flow caused by the static mixer with a twist ratio of three increased the convective heat transfer coefficient (97 W·m−2·K−1) by 2.06 times, while the production rate of biocrude (0.074 g·L−1·s−1) increased by 2.05 times at 50 L/h and 750 W/m2. This investigation gives guidance for utilizing static mixers in solar-driven reactors to optimize the heat transfer and HTL of microalgae biomass with solar heat sources.
Abstract
Background
New-onset neurological symptoms such as numbness and pain in lower extremities might appear immediately after conventional lumbar interbody fusion (LIF) surgery performed in ...patients with lumbar spinal stenosis.
Methods and analysis
This is a multicenter, randomized, open-label, parallel-group, active-controlled trial investigating the clinical outcomes of modified LIF sequence versus conventional LIF sequence in treating patients with lumbar spinal stenosis. A total of 254 eligible patients will be enrolled and randomized in a 1:1 ratio to either modified LIF sequence or conventional LIF sequence group. The primary outcome measure is the perioperative incidence of new-onset lower extremity neurological symptoms, including new adverse events of pain, numbness, and foot drop of any severity. Important secondary endpoints include visual analogue scale (VAS) pain score and lumbar Japanese Orthopaedic Association (JOA) recovery rate. Other safety endpoints will also be evaluated. The safety set used for safety data analysis by the actual surgical treatment received and the full analysis set for baseline and efficacy data analyses according to the intent-to-treat principle will be established as the two analysis populations in the study.
Conclusion
This study is designed to investigate the clinical outcomes of modified LIF sequences in patients with lumbar spinal stenosis. It aims to provide clinical evidence that the modified “fixation-fusion” sequence of LIF surgery is effective in treating lumbar spinal stenosis.
Trial registration
http://www.chictr.org.cn/index.aspx
ID: ChiCTR2100048507.
Spontaneous abortions (SA) is amongst the most common complications associated with pregnancy in humans, and the underlying causes cannot be identified in roughly half of SA cases. We found ...miR-135a-5p to be significantly upregulated in SA-associated villus tissues, yet the function it plays in this context has yet to be clarified. This study explored the function of miR-135a-5p and its potential as a biomarker for unexplained SA.
RT-qPCR was employed for appraising miR-135a-5p expression within villus tissues with its clinical diagnostic values being assessed using ROC curves. The effects of miR-135a-5p in HTR-8/SVneo cells were analyzed via wound healing, Transwell, flow cytometry, EdU, CCK-8, and tube formation assays. Moreover, protein expression was examined via Western blotting, and interactions between miR-135a-5p and PTPN1 were explored through RIP-PCR, bioinformatics analyses and luciferase reporter assays.
Relative to normal pregnancy (NP), villus tissue samples from pregnancies that ended in unexplained sporadic miscarriage (USM) or unexplained recurrent SA (URSA) exhibited miR-135a-5p upregulation. When this miRNA was overexpressed in HTR-8/SVneo cells, their migration, proliferation, and cell cycle progression were suppressed, as were their tube forming and invasive activities. miR-135a-5p over-expression also downregulated the protein level of cyclins, PTPN1, MMP2 and MMP9. In RIP-PCR assays, the Ago2 protein exhibited significant miR-135a-5p and PTPN1 mRNA enrichment, and dual-luciferase reporter assays indicated PTPN1 to be a bona fide miR-135a-5p target gene within HTR-8/SVneo cells.
miR-135a-5p may suppress trophoblast migratory, invasive, proliferative, and angiogenic activity via targeting PTPN1, and it may thus offer value as a biomarker for unexplained SA.
Background
This study presents findings on improvements of both the X-axis and Z-axis posture in a young female with adolescent idiopathic, scoliosis suffering from pain complaints who was treated ...with a multidisciplinary approach.
Case Presentation
The 15-year-old patient reported low back pain for several months. Full spine radiographic assessment revealed a cervical kyphosis, forward head translation, a right ribcage translation, a left higher shoulder, and a dextroconvex lumbar scoliosis with a Cobb angle of 23°. The patient was treated with novel ASPINE Systems treatment protocols incorporating posture exercises, muscle balancing exercises, spinal 3D traction, and spinal manipulation.
Results
Assessment after 50 treatment sessions over 32 weeks revealed a dramatic improvement in postural distortions. The cervical kyphosis was reduced by 9° and was accompanied by a reduction in forward head posture, centering of the thoracic spine, leveling off her shoulders, and a reduction in the dextroconvex scoliosis by 10°. The lower back pain was relieved.
Conclusion
A reduction of postural distortions including idiopathic adolescent scoliosis resulted from a multidisciplinary approach utilizing ASPINE Systems.
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