The Effect of Mn, Al Doping on the CO2 Hydrogenation Performance of CaCO3 -Supported Fe-Based Catalysts.

With increasingly serious environmental problems caused by the greenhouse effect, it has also become essential to reduce the concentration of CO2 in the atmosphere. In this paper, CaCO3 -supported Fe-based catalysts doped with Mn, Al, and K are prepared by a straightforward method and used for CO2 hydrogenation. The fresh and spent catalysts were characterized by SEM-EDS, BET, TG, CO2 -TPD, XRD, and XPS. The experimental results show that the highest CO2 conversion rate of Fe10Mn2Al10Ca is 35.99 %, the maximum FTY value is 293.98 µmolCO2 ⋅ g Fe - 1 ${{\rm{g}}_{{\rm{Fe}}}^{ - 1} }$ ⋅ s-1 , the maximum O/P value is 6.61, and the lowest CO selectivity is 32.21 %. At the same time, according to the characterization results, the doping of Mn and Al increased the Fe3 O4 /FeCx ratio. As the Fe3 O4 /FeCx ratio increases, the proportion of short-chain hydrocarbons (CH4 , C2-4 ) in the products increases, and the proportion of long-chain hydrocarbons (C5+ ) decrease. Therefore, the co-doping of Mn and Al promotes the conversion of CO and reduces its selectivity, and promotes the formation of light olefins. Finally, it is hoped that this study can provide a reference for further research on CaCO3 -supported Fe catalysts.

Interleaved signal multiplexing readout in depth encoding Prism-PET detectors.

BACKGROUND: Given the large number of readout pixels in clinical positron emission tomography (PET) scanners, signal multiplexing is an indispensable feature to reduce scanner complexity, power consumption, heat output, and cost. PURPOSE: In this paper, we introduce interleaved multiplexing (iMux) scheme that utilizes the characteristic light-sharing pattern of depth-encoding Prism-PET detector modules with single-ended readout. METHODS: In the iMux readout, four anodes from every other silicon photomultiplier (SiPM) pixels across rows and columns, which overlap with four distinct light guides, are connected to the same application-specific integrated circuit (ASIC) channel. The 4-to-1 coupled Prism-PET detector module was used which consisted of a 16 ×  16 array of 1.5 × 1.5 × 20 mm3 lutetium yttrium oxyorthosilicate (LYSO) scintillator crystals coupled to an 8 × 8 array with 3 ×  3 mm2 SiPM pixels. A deep learning-based demultiplexing model was investigated to recover the encoded energy signals. Two different experiments were performed with non-multiplexed and multiplexed readouts to evaluate the spatial, depth of interaction (DOI), and timing resolutions of our proposed iMux scheme. RESULTS: The measured flood histograms, using the decoded energy signals from our deep learning-based demultiplexing architecture, achieved perfect crystal identification of events with negligible decoding error. The average energy, DOI, and timing resolutions were 9.6 ± 1.5%, 2.9 ± 0.9 mm, and 266 ± 19 ps for non-multiplexed readout and 10.3 ± 1.6%, 2.8 ± 0.8 mm, and 311 ± 28 ps for multiplexed readout, respectively. CONCLUSIONS: Our proposed iMux scheme improves on the already cost-effective and high-resolution Prism-PET detector module and provides 16-to-1 crystal-to-readout multiplexing without appreciable performance degradation. Also, only four SiPM pixels are shorted together in the 8 ×  8 array to achieve 4-to-1 pixel-to-readout multiplexing, resulting in lower capacitance per multiplexed channel.

The Effect Of Ca Doping On The CO2 Hydrogenation Performance Of CaxZn10-xFe20 Catalysts (x=0, 0.5, 1 and1.5).

In this paper, CaxZn10-xFe20 catalysts were prepared by the co-precipitation method and applied to CO2 hydrogenation. The experimental results show that the CO2 conversion of the catalyst Ca1Zn9Fe20 at a Ca doping amount of 1 mmol can reach 57.91 %, which is 13.5 % more than the CO2 conversion of the catalyst Zn10Fe20. Moreover, the catalyst Ca1Zn9Fe20 has the lowest selectivity for both CO and CH4, with 7.40 % and 6.99 %, respectively. The catalysts were characterized by XRD, N2 adsorption-desorption, CO2 -TPD, H2 -TPR, and XPS. The results demonstrate that the doping of Ca increases the basic sites on the catalyst surface and thus allows the catalyst to adsorb more CO2 to promote the reaction. Besides, the Ca doping amount of 1 mmol can suppress the formation of graphitic carbon on the catalyst surface and prevent the excess graphitic carbon from covering the active site Fe5 C2 .

A conformal TOF-DOI Prism-PET prototype scanner for high-resolution quantitative neuroimaging.

BACKGROUND: Positron emission tomography (PET) has had a transformative impact on oncological and neurological applications. However, still much of PET's potential remains untapped with limitations primarily driven by low spatial resolution, which severely hampers accurate quantitative PET imaging via the partial volume effect (PVE). PURPOSE: We present experimental results of a practical and cost-effective ultra-high resolution brain-dedicated PET scanner, using our depth-encoding Prism-PET detectors arranged along a compact and conformal gantry, showing substantial reduction in PVE and accurate radiotracer uptake quantification in small regions. METHODS: The decagon-shaped prototype scanner has a long diameter of 38.5 cm, a short diameter of 29.1 cm, and an axial field-of-view (FOV) of 25.5 mm with a single ring of 40 Prism-PET detector modules. Each module comprises a 16 × 16 array of 1.5 × 1.5 × 20-mm3 lutetium yttrium oxyorthosillicate (LYSO) scintillator crystals coupled 4-to-1 to an 8 × 8 array of silicon photomultiplier (SiPM) pixels on one end and to a prismatoid light guide array on the opposite end. The scanner's performance was evaluated by measuring depth-of-interaction (DOI) resolution, energy resolution, timing resolution, spatial resolution, sensitivity, and image quality of ultra-micro Derenzo and three-dimensional (3D) Hoffman brain phantoms. RESULTS: The full width at half maximum (FWHM) DOI, energy, and timing resolutions of the scanner are 2.85 mm, 12.6%, and 271 ps, respectively. Not considering artifacts due to mechanical misalignment of detector blocks, the intrinsic spatial resolution is 0.89-mm FWHM. Point source images reconstructed with 3D filtered back-projection (FBP) show an average spatial resolution of 1.53-mm FWHM across the entire FOV. The peak absolute sensitivity is 1.2% for an energy window of 400-650 keV. The ultra-micro Derenzo phantom study demonstrates the highest reported spatial resolution performance for a human brain PET scanner with perfect reconstruction of 1.00-mm diameter hot-rods. Reconstructed images of customized Hoffman brain phantoms prove that Prism-PET enables accurate radiotracer uptake quantification in small brain regions (2-3 mm). CONCLUSIONS: Prism-PET will substantially strengthen the utility of quantitative PET in neurology for early diagnosis of neurodegenerative diseases, and in neuro-oncology for improved management of both primary and metastatic brain tumors.

Significantly improved antifouling capability of silicone rubber surfaces by covalently bonded acrylated agarose towards biomedical applications.

Bacteria have the extraordinary ability to adhere to biomaterial surfaces and form multicellular structures known as biofilms, which have a detrimental impact on the performance of medical devices. Herein, an investigation highlighted the effective inhibition of bacteria adhesion and overgrowth on silicone rubber surface by grafting polysaccharide, agarose (AG), to construct hydrophilic and negatively charged surfaces. Because of the strong hydration capacity of agarose, the water contact angle of the modified silicone rubber surfaces was significantly reduced from 107.6 ± 2.7° to 19.3 ± 2.6°, which successfully limited bacterial adherence. Most importantly, the durability and stability of coating were observed after 10 days of simulated dynamic microenvironment in vivo, exhibiting a long service life. This modification method did not compromise biocompatibility of silicone rubber, opening a door to new applications for silicone rubber in the field of biomedical materials.

High-resolution and high-sensitivity PET for quantitative molecular imaging of the monoaminergic nuclei: A GATE simulation study.

PURPOSE: Quantitative in vivo molecular imaging of fine brain structures requires high-spatial resolution and high-sensitivity. Positron emission tomography (PET) is an attractive candidate to introduce molecular imaging into standard clinical care due to its highly targeted and versatile imaging capabilities based on the radiotracer being used. However, PET suffers from relatively poor spatial resolution compared to other clinical imaging modalities, which limits its ability to accurately quantify radiotracer uptake in brain regions and nuclei smaller than 3 mm in diameter. Here we introduce a new practical and cost-effective high-resolution and high-sensitivity brain-dedicated PET scanner, using our depth-encoding Prism-PET detector modules arranged in a conformal decagon geometry, to substantially reduce the partial volume effect and enable accurate radiotracer uptake quantification in small subcortical nuclei. METHODS: Two Prism-PET brain scanner setups were proposed based on our 4-to-1 and 9-to-1 coupling of scintillators to readout pixels using 1.5 × 1.5 × 20 $1.5 \times 1.5 \times 20$  mm3 and 0.987 × 0.987 × 20 $0.987 \times 0.987 \times 20$  mm3 crystal columns, respectively. Monte Carlo simulations of our Prism-PET scanners, Siemens Biograph Vision, and United Imaging EXPLORER were performed using Geant4 application for tomographic emission (GATE). National Electrical Manufacturers Association (NEMA) standard was followed for the evaluation of spatial resolution, sensitivity, and count-rate performance. An ultra-micro hot spot phantom was simulated for assessing image quality. A modified Zubal brain phantom was utilized for radiotracer imaging simulations of 5-HT1A receptors, which are abundant in the raphe nuclei (RN), and norepinephrine transporters, which are highly concentrated in the bilateral locus coeruleus (LC). RESULTS: The Prism-PET brain scanner with 1.5 mm crystals is superior to that with 1 mm crystals as the former offers better depth-of-interaction (DOI) resolution, which is key to realizing compact and conformal PET scanner geometries. We achieved uniform 1.3 mm full-width-at-half-maximum (FWHM) spatial resolutions across the entire transaxial field-of-view (FOV), a NEMA sensitivity of 52.1 kcps/MBq, and a peak noise equivalent count rate (NECR) of 957.8 kcps at 25.2 kBq/mL using 450-650 keV energy window. Hot spot phantom results demonstrate that our scanner can resolve regions as small as 1.35 mm in diameter at both center and 10 cm away from the center of the transaixal FOV. Both 5-HT1A receptor and norepinephrine transporter brain simulations prove that our Prism-PET scanner enables accurate quantification of radiotracer uptake in small brain regions, with a 1.8-fold and 2.6-fold improvement in the dorsal RN as well as a 3.2-fold and 4.4-fold improvement in the bilateral LC compared to the Biograph Vision and EXPLORER, respectively. CONCLUSIONS: Based on our simulation results, the proposed high-resolution and high-sensitivity Prism-PET brain scanner is a promising cost-effective candidate to achieve quantitative molecular neuroimaging of small but important brain regions with PET clinically viable.

Sub-2 mm depth of interaction localization in PET detectors with prismatoid light guide arrays and single-ended readout using convolutional neural networks.

PURPOSE: Depth of interaction (DOI) readout in PET imaging has been researched in efforts to mitigate parallax error, which would enable the development of small diameter, high-resolution PET scanners. However, DOI PET has not yet been commercialized due to the lack of practical, cost-effective, and data efficient DOI readout methods. The rationale for this study was to develop a supervised machine learning algorithm for DOI estimation in PET that can be trained and deployed on unique sets of crystals. METHODS: Depth collimated flood data was experimentally acquired using a Na-22 source with a depth-encoding single-ended readout Prism-PET module consisting of lutetium yttrium orthosilicate (LYSO) crystals coupled 4-to-1 to 3×3  mm 2 silicon photomultiplier (SiPM) pixels on one end and a segmented prismatoid light guide array on the other end. A convolutional neural network (CNN) was trained to perform DOI estimation on data from center, edge and corner crystals in the Prism-PET module using (a) all non-zero readout pixels and (b) only the 4 highest readout signals per event. CNN testing was performed on data from crystals not included in CNN training. RESULTS: An average DOI resolution of 1.84 mm full width at half maximum (FWHM) across all crystals was achieved when using all readout signals per event with the CNN compared to 3.04 mm FWHM DOI resolution using classical estimation. When using only the 4 highest signals per event, an average DOI resolution of 1.92 mm FWHM was achieved, representing only a 4% dropoff in CNN performance compared to using all non-zero pixels per event. CONCLUSIONS: Our CNN-based DOI estimation algorithm provides the best reported DOI resolution in a single-ended readout module and can be readily deployed on crystals not used for model training.

[Dual mobility total hip arthroplasty for the treatment of femoral neck fracture with hemiplegia].

OBJECTIVE: To investigate the clinical effects of dual mobility total hip prosthesis in treating femoral neck fracture patients with hemiplegia. METHODS: A retrospective analysis was performed on 18 patients with femoral neck fracture combined with hemiplegia who underwent dual mobility total hip prosthesis replacement from March 2014 to December 2016. The follow up data of these patients was complete. There were 5 males and 13 females, aged 65 to 70 years old with an average of (66.50±1.38) years. The left side was involved in 12 cases, while the right side in 6 cases. There were 4 cases with Garden Ⅲ type and 14 cases with type Ⅳ. Limb muscle strength of hemiplegia were in grade Ⅳ. The posterior-lateral approach of hip joint was used in surgery for all patients. The implant position, dislocation and loosening of the prosthesis were evaluated by X-ray examination. Harris hip score and the Merle D'aubigne score were used to assess the hip function in the follow up. RESULTS: The operation duration was for 70-90 (81.56±7.48) min and the blood loss during the operation was for 160-200 (170.32± 12.56) ml. No blood was transfused during the operation. Postoperative incisions were healed at the first stage. The follow-up time was for 28-60(36.0±3.5) months. Harris hip score increased from 16.94±0.73 preoperatively to 96.19±1.27 at the final follow-up(P<0.05). Merle D 'Aubigne score increased from 3.96±0.06 preoperatively to 16.81±0.63 at the final follow-up(P< 0.05). No fracture or nerve or vascular injury were found during the operation. The postoperative X-ray showed that the prosthesis was in good position. No complications such as joint dislocation, dislocation of prosthesis, loosening of prosthesis, fracture around the prosthesis, pain in the front of thethigh, fracture of the self tapping screw in the ilium, and delayed infection occurred in the patients after operation. CONCLUSION: Dual mobility total hip prosthesis has the advantages of both good initial stability and low dislocation rate of the prosthesis, and the clinical application of total hip replacement in hemiplegic femoral neck fracture is satisfactory.

High-Resolution Depth-Encoding PET Detector Module with Prismatoid Light-Guide Array.

Depth-encoding detectors with single-ended readout provide a practical, cost-effective approach for constructing high-resolution and high-sensitivity PET scanners. However, the current iteration of such detectors uses a uniform glass light-guide to achieve depth encoding, resulting in nonuniform performance throughout the detector array due to suboptimal intercrystal light sharing. We introduce Prism-PET, a single-ended-readout PET detector module with a segmented light-guide composed of an array of prismatoids that introduce enhanced, deterministic light sharing. Methods: High-resolution PET detector modules were fabricated with single-ended readout of polished multicrystal lutetium yttrium orthosilicate scintillator arrays directly coupled 4-to-1 and 9-to-1 to arrays of 3 × 3 mm silicon photomultiplier pixels. Each scintillator array was coupled at the nonreadout side to a light-guide (one 4-to-1 module with a uniform glass light-guide, one 4-to-1 Prism-PET module, and one 9-to-1 Prism-PET module) to introduce intercrystal light sharing, which closely mimics the behavior of dual-ended readout, with the additional benefit of improved crystal identification. Flood histogram data were acquired using a 3-MBq 22Na source to characterize crystal identification and energy resolution. Lead collimation was used to acquire data at specific depths to determine depth-of-interaction (DOI) resolution. Results: The flood histogram measurements showed excellent and uniform crystal separation throughout the Prism-PET modules, whereas the uniform glass light-guide module had performance degradation at the edges and corners. A DOI resolution of 5.0 mm full width at half maximum (FWHM) and an energy resolution of 13% FWHM were obtained in the uniform glass light-guide module. By comparison, the 4-to-1 coupled Prism-PET module achieved a DOI resolution of 2.5 mm FWHM and an energy resolution of 9% FWHM. Conclusion: PET scanners based on our Prism-PET modules with segmented prismatoid light-guide arrays can achieve high and uniform spatial resolution (9-to-1 coupling with ∼1-mm crystals), high sensitivity (20-mm-thick detectors and intercrystal Compton scatter recovery), good energy and timing resolutions (using polished crystals and after applying DOI correction), and compact size (depth encoding eliminates parallax error and permits smaller ring-diameter).