A novel reconstruction method combining multi-detector SPECT with an elliptical orbit and computer tomography for cardiac imaging.

The myocardial single photon emission computed tomography (SPECT) is a good study due to its clinical significance in the diagnosis of myocardial disease and the requirement for improving image quality. However, SPECT imaging faces challenges related to low spatial resolution and significant statistical noise, which concerns patient radiation safety. In this paper, a novel reconstruction system combining multi-detector elliptical SPECT (ME-SPECT) and computer tomography (CT) is proposed to enhance spatial resolution and sensitivity. The hybrid imaging system utilizes a slit-slat collimator and elliptical orbit to improve sensitivity and signal-to-noise ratio (SNR), obtains accurate attenuation mapping matrices, and requires prior information from integrated CT. Collimator parameters are corrected based on CT reconstruction results. The SPECT imaging system employs an iterative reconstruction algorithm that utilizes prior knowledge. An iterative reconstruction algorithm based on prior knowledge is applied to the SPECT imaging system, and a method for prioritizing the reconstruction of regions of interest (ROI) is introduced to deal with severely truncated data from ME-SPECT. Simulation results show that the proposed method can significantly improve the system's spatial resolution, SNR, and image fidelity. The proposed method can effectively suppress distortion and artifacts with the higher spatial resolution ordered subsets expectation maximization (OSEM); slit-slat collimation.

Building community-centered social infrastructure: a feminist inquiry into China's COVID-19 experiences.

The global COVID-19 pandemic has revealed the essential role of care work in sustaining life, health, and maintaining the basics of everyday existence. It has also made visible the disproportionate burden of care work on women that existed before the outbreak, which has intensified rapidly and been gravely exposed during the pandemic. In this article, we take China as a case study to investigate the gendered impact of this pandemic and further problematize the landscape of care provision. With a feminist political economy perspective, we introduce China's provisioning of care prior to the outbreak and investigate how the care crisis has further deepened in the pandemic. Drawing on the most recent data available on China's experience, we explore the role and function of community-centered social infrastructure, an assemblage of state, family, and local resources, in effectively combating the virus and providing care. We further provide comparative international evidence to demonstrate the essential role of community care infrastructure in this pandemic. Building social infrastructure to deliver care at the community level presents important policy implication, especially for many developing countries. Therefore, a critical reflection and discussion on pandemics and women is not only more vital than ever, but also sheds light on the endeavour to develop long-term solutions for the care crisis that will almost certainly outlive the current pandemic.

Photosensitive cross-linked block copolymers with controllable release.

We intend to form photosensitive block copolymer micelles for controllable release of encapsulated substances. Here, we designed and synthesized a new photocleavable cross-linker (2-nitrophenyl ethylene glycol dimethacrylate) for methyl methacrylate (MMA) atom transfer radical polymerization. Four different ratios (0:1, 1:26, 1:16, 1:8.8) of the photocleavable cross-linker to MMA monomer were used and four block copolymers (P0, P1, P2, P3) were synthesized with PEO-Br as the macroinitiator. Gel permeation chromatography and (1) H NMR studies showed that linear polymer molecules could be cross-linked by the photocleavable linker. The fluorescence studies of the encapsulated Nile Red (NR) showed that there were lower critical micelle concentrations for the polymer P1, P2 and P3 than polymer P0. And dynamic light scattering and SEM confirmed the formation of polymer micelles. Photolysis experiments demonstrated that NR encapsulated in the polymer micelles could be released upon UV irradiation (365 nm, 11 mW cm(-2)) due to the breakage of the photocleavable linker and the generation of more hydrophilic acid moieties, which destabilized polymer micelles. Our study shows a new strategy for the possibility of photocontrollable drug release for hydrophobic drugs.

Photomodulating RNA cleavage using photolabile circular antisense oligodeoxynucleotides.

Caged antisense oligodeoxynucleotides (asODNs) are synthesized by linking two ends of linear oligodeoxynucleotides using a photocleavable linker. Two of them (H30 and H40) have hairpin-like structures which show a large difference in thermal stability (Delta T(m) = 17.5 degrees C and 11.6 degrees C) comparing to uncaged ones. The other three (C20, C30 and C40) without stable secondary structures have the middle 20 deoxynucleotides complementary to 40-mer RNA. All caged asODNs have restricted opening which provides control over RNA/asODN interaction. RNase H assay results showed that 40-mer RNA digestion could be photo-modulated 2- to 3-fold upon light-activation with H30, H40, C30 and C40, while with C20, RNA digestion was almost not detectable; however, photo-activation triggered >20-fold increase of RNA digestion. And gel shift assays showed that it needed >0.04 microM H40 and 0.5 microM H30 to completely bind 0.02 microM 40-mer RNA, and for C40 and C30, it needed >0.2 microM and 0.5 microM for 0.02 microM 40-mer RNA binding. However, even 4 microM C20 was not able to fully bind the same concentration of 40-mer RNA. By simple adjustment of ring size of caged asODNs, we could successfully photoregulate their hybridization with mRNA and target RNA hydrolysis by RNase H with light activation.

[FTIR and XRD analysis of the enzymatic degradation of crosslinked starch microspheres].

Crosslinked starch microspheres (CSM) were prepared by crosslinking of soluble starch and N, N'-methylene-bis-acrylamide in inverse suspension. In order to describe the enzymatic degradation of CSM in this experiment, soluble starch, CSM and CSM's degradation product obtained from the simulated intestinal fluid in different time were analysed by Fourier transform infrared spectroscopy (FTIR) and X-ray diffractometer (XRD). The FTIR and SEM results showed that the CSM's crosslinking structure could be maintained steady in digested liquid within 3 hours. The intensity at 1,090 cm(-1) related to bending vibration bands of C--O--C, the amide band I and the amide band II became weaker in 3-12 hours along with the process of the enzymatic degradation, indicating the degradation of the molecular chain of starch and the depolymerization of the cross-linking structure. And then the disappearing of the amide band I and the amide band II indicated that the crosslinking structure was totally destructed after 12 hours and thereafter the enzymatic degradation was consistent with soluble starch. The XRD results proved that after 12 hours the CSM's degradation was similar to starch's degradation, their non-crystalline parts were decomposed, and their degree of crystallinity increased with the development of the degradation, but did not exceed the crystallinity of soluble starch.