A pixelated liquid perovskite array for high-sensitivity and high-resolution X-ray imaging scintillation screens.

Scintillators with high spatial resolution at a low radiation dose rate are desirable for X-ray medical imaging. A low radiation dose rate can be achieved using a sufficiently thick scintillator layer to absorb the incident X-ray energy completely, however, often at the expense of low spatial resolution due to the issue of optical crosstalk of scintillation light. Therefore, to achieve high sensitivity combined with high-resolution imaging, a thick scintillator with perfect light guiding properties is in high demand. Herein, a new strategy is developed to address this issue by embedding liquid scintillators into lead-containing fiber-optical plates (FOPs, n = 1.5) via the siphon effect. The liquid scintillator is composed of perovskite quantum dots (QDs)/2,5-diphenyloxazole (PPO) and the non-polar high-refractive index (n = 1.66) solvent α-bremnaphthalene. Benefiting from the pixelated and thickness-adjustable scintillators, the proposed CsPbBr3 QDs/PPO liquid scintillator-based X-ray detector achieves a detection limit of 79.1 µGy s-1 and a spatial resolution of 4.6 lp mm-1. In addition, it displays excellent tolerance against radiation (>34 h) and shows outstanding stability under ambient conditions (>160 h). This strategy could also be applied to other liquid scintillators (such as CsPbCl3 QDs and Mn:CsPbCl3 QDs). The combination of high sensitivity, high spatial resolution and stability, easy fabrication and maintenance, and a reusable substrate matrix makes these liquid scintillators a promising candidate for practical X-ray medical imaging applications.

Deep Point Set Resampling via Gradient Fields.

3D point clouds acquired by scanning real-world objects or scenes have found a wide range of applications including immersive telepresence, autonomous driving, surveillance, etc. They are often perturbed by noise or suffer from low density, which obstructs downstream tasks such as surface reconstruction and understanding. In this paper, we propose a novel paradigm of point set resampling for restoration, which learns continuous gradient fields of point clouds that converge points towards the underlying surface. In particular, we represent a point cloud via its gradient field-the gradient of the log-probability density function, and enforce the gradient field to be continuous, thus guaranteeing the continuity of the model for solvable optimization. Based on the continuous gradient fields estimated via a proposed neural network, resampling a point cloud amounts to performing gradient-based Markov Chain Monte Carlo (MCMC) on the input noisy or sparse point cloud. Further, we propose to introduce regularization into the gradient-based MCMC during point cloud restoration, which essentially refines the intermediate resampled point cloud iteratively and accommodates various priors in the resampling process. Extensive experimental results demonstrate that the proposed point set resampling achieves the state-of-the-art performance in representative restoration tasks including point cloud denoising and upsampling.

High-performance x-ray source based on graphene oxide-coated Cu2S nanowires grown on copper film.

Full static x-ray computed tomography (CT) technology has enabled higher precision and resolution imaging and has been applied in many applications such as diagnostic medical imaging, industrial inspection and security screening. In this technique, the x-ray source section is mainly composed of a thermionic cathode and electron beam scanning system. However, they have several shortcomings such as limited scanning angle, long response time and large volume. Distributed and programmable cold cathode (i.e. carbon nanotubes, ZnO nanowires (NWs)) field-emission x-ray sources are expected to solve these problems. However, there have been several long-standing challenges to the application of such cold field emitters for x-ray sources, such as the short lifetime and rigorous fabrication process, which have fundamentally prevented their widespread use. Here, we propose and demonstrate a cold field-emission x-ray source based on a graphene oxide (GO)-coated cuprous sulfide nanowire (Cu2S NW/GO) cathode. The proposed Cu2S NW/GO x-ray source provides stable emission (>18 h at a direct voltage of 2600 V) and has a low threshold (4.5 MV m-1 for obtaining a current density of 1 µA cm-2), benefiting from the demonstrated key features such as in situ epitaxy growth of Cu2S NWs on Cu, nanometer-scale sharp protrusions within GO and charge transfer between the Cu2S NWs and GO layer. Our research provides a simple and robust method to obtain a high-performance cold field emitter, leading to great potential for the next generation of x-ray source and CT.

[Coagulation and prothrombotic state parameters: clinical analysis in early pregnancy].

OBJECTIVE: To assess the changes in coagulation, thrombosis, anti-coagulation and fibrinolysis during early pregnancy. METHODS: A total of 105 gravidas with monocytic pregnancies between 10 and 12 weeks gestational age at Sun Yat-sen Memorial Hospital, Sun Yat-sen University during April 2005 to June 2009 were recruited for study group and another 82 non-pregnant women as control group. Coagulation parameters, including thrombin time (TT), activated partial thromboplastin time (APTT), prothrombin (PT) and fibrinogen (Fg), were measured. We also tested the prothrombotic state parameters, including prothrombin fragment 1+2 (F1+2), thrombomodulin (TM), thrombin-antithrombin complex (TAT), antithrombin III(AT-III), GMP140, thromboxane B2 (TXB2), plasminogen activator inhibitor (PAI-2; performed by enzyme-linked immunosorbent assay) and D-dimer (D2; tested by latex turbidimetric immunoassay). RESULTS: Fg (4.00 vs 2.52 g/L), F1+2 (0.66 vs 0.31 nmol/L), TAT (179.95 vs 39.46 µg/L), GMP140 (9.42 vs 19.13 µg/L), D2 (201.51 vs 125.02 µg/L) and PAI-2 (0.047 vs 0.006 g/L) were statistically different between the study and control groups (P < 0.01). CONCLUSIONS: The coagulation, fibrinolysis and anti-fibrinolysis functions of healthy pregnant women become enhanced during early pregnancy while anti-coagulation function slightly increases. These four basic functions are balanced at a higher level so that the activation of platelets stays at a lower level.

[Clinical experience of using oxytocin antagonist atosiban in the rescue therapy of preterm labour].

OBJECTIVE: To investigate the effectiveness of oxytocin antagonist atosiban in the alternative rescue therapy of preterm labor. METHODS: Alternative tocolysis atosiban was given as rescue therapy to 35 women, who had received ritodrine or magnesium sulphate but failed, due to either progression of labour or intolerable adverse events. Atosiban was administered for up to 48 hours. Efficacy and tolerability were assessed based on the proportion of women who did not deliver and did not need alternative tocolytic therapy at 48 hours and 7 days after therapy initiation. The numbers of maternal adverse events and neonatal morbidity were also assessed. RESULTS: Efficacy and tolerability at 48 hours and 7 days after atosiban initiation were 77% (27/35) and 60% (21/35). One woman presented drug-related side effects with mild nausea and vomiting. Thirty-four women have delivered and one bigemina (28 weeks) is being followed-up. In 34 women, 11 delivered before 28 gestational weeks, 17 delivered after 28 gestational weeks, 3 delivered after 34 weeks and 3 had term delivery. Pregnancies were prolonged by 4 hours to 14(+2) weeks. There were nine neonatal deaths, with gestational ages less than 28 weeks at delivery. CONCLUSION: Oxytocin antagonist atosiban could be given as alternative rescue therapy if therapy with ritodrine or magnesium sulphate fails in the treatment of preterm labor, and it is safe and effective.