RF power design optimization in MRI system

Magnetic resonance image quality and patient safety have been the focus of engineering and research ever since the invention of equipment in the early 1970s.In high field(or ultrahigh field)MRI systems,the emerging techniques induced by B1 field challenges have promoted various potential solutions.This paper describes the relationship between RF power and B1þfield performance,and the overall requirements considered in RF subsystem design.The design of the RF in the MR system is systematically summarized,including the entire transmission chain,sequence algorithm and RF pulse design,and the probabilities for improvement and optimization in the system design are indicated.At the same time,the radio frequency related issues of the human whole-body 7 T MR and animal MR systems are discussed,especially the promising future showed by the technologies such as radio frequency parallel transmission technology in the ultrahigh field.

Quantitative characteristics of microorganisms in permafrost at different depths and their relation to soil physicochemical properties

Microorganisms in permafrost can live in cold environments due to coadapted physicochemical processes in this environment. In this paper, the relation between microbial number and soil physicochemical properties at the headwaters area of the Urumqi River is analyzed by using fluorescence microscopy counting and oligo-culture techniques. In total, 20 samples from a 200-cm permafrost core were used as study materials. The study reveals that the number of culturable bacteria has a significantly positive correlation with soil water content, total carbon and total nitrogen concentrations, and a significantly negative correlation with soil pH value. In addition, the ratio of culturable bacteria to total cell number decreases with depths. The results demonstrate that the number of culturable bacteria in permafrost is closely correlated with soil physicochemical properties and depositional age.

IL-13/IL-13RA2 signaling promotes colorectal cancer stem cell tumorigenesis by inducing ubiquitinated degradation of p53

Cancer stem cells(CSCs)are considered tumor-initiating cells and the main drivers of disease progression.Targeting these rare cancer cells,however,remains challenging with respect to therapeutic benefit.Here,we report the up-regulation of IL-13RA2 expression in colorectal cancer(CRC)tissues and spheroid cells.The expression of IL-13RA2 was positively correlated with canonical stemness markers in CRC.We further demonstrated that the level of IL-13 was up-regulated in the serum of CRC patients.Biologically,recombinant IL-13(rIL13)stimulation promoted the sphere formation,proliferation,and migration of CRC cells in vitro and enhanced tumorigenesis in vivo.This phenotype could be reversed by knocking down IL-13RA2.Mechanistically,IL-13 activated autophagy by inducing LC3I/LC3II transformation in CRC-CSCs,which was crucial for the biological functions of IL-13.We further demonstrated that IL-13RA2 acted as a modular link of the E3 ligase UBE3C and the substrate p53 protein,enhancing the interaction of UBE3C and p53,thereby inducing the K48-linked ubiquitination of p53.In conclusion,the IL-13/IL-13RA2 signaling cascade promotes CRC-CSC self-renewal and tumorigenesis by inducing p53 ubiquitination,adding an important layer to the connection between IL-13 and p53,which can be translated into novel targeted therapies.

Source apportionment of ambient PM_(10) in urban areas of Wuxi,China

A total of 168 PM_(10)samples were collected during the year of 2005 at eight sites in the city of Wuxi in China.Fifteen chemical elements,three water-soluble ions,total carbon and organic carbon were analyzed.Six source categories were identified and their contributions to ambient PM_(10)in Wuxi were estimated using a nested chemical mass balance method that reduces the effects of colinearity on the chemical mass balance model.In addition,the concentrations of secondary aerosols,such as secondary organic carbon,sulfate and nitrate,were quantified.The spatially averaged PM_(10)was high in the spring and winter(123μg·m^(-3)and low in the summer-fall(90μg·m^(-3)).According to the result of source apportionment,resuspended dust was the largest contributor to ambient PM_(10),accounting for more than 50%of the PM_(10)mass.Coal combustion(14.6%)and vehicle exhaust(9.4%)were also significant source categories of ambient PM_(10).Construction and cement dust,sulfates,secondary organic carbon,and nitrates made contributions ranging between 4.1%and 4.9%.Other source categories such as steel manufacturing dust and soil dust made low contributions to ambient PM_(10).

Fine-Grained Topography and Modularity of the Macaque Frontal Pole Cortex Revealed by Anatomical Connectivity Profiles

The frontal pole cortex(FPC)plays key roles in various higher-order functions and is highly developed in non-human primates.An essential missing piece of information is the detailed anatomical connections for finer parcellation of the macaque FPC than provided by the previous tracer results.This is important for understanding the functional architecture of the cerebral cortex.Here,combining cross-validation and principal component analysis,we formed a tractography-based parcellation scheme that applied a machine learning algorithm to divide the macaque FPC(2 males and 6 females)into eight subareas using high-resolution diffusion magnetic resonance imaging with the 9.4 T Bruker system,and then revealed their subregional connections.Furthermore,we applied improved hierarchical clustering to the obtained parcels to probe the modular structure of the subregions,and found that the dorsolateral FPC,which contains an extension to the medial FPC,was mainly connected to regions of the default-mode network.The ventral FPC was mainly involved in the social-interaction network and the dorsal FPC in the metacognitive network.These results enhance our understanding of the anatomy and circuitry of the macaque brain,and contribute to FPC-related clinical research.

猕猴脑网络组图谱:包含分区、连接和组织学的多层面全新大脑地图

The rhesus macaque(Macaca mulatta)is a crucial experimental animal that shares many genetic,brain organizational,and behavioral characteristics with humans.A macaque brain atlas is fundamental to biomedical and evolutionary research.However,even though connectivity is vital for understanding brain functions,a connectivity-based whole-brain atlas of the macaque has not previously been made.In this study,we created a new whole-brain map,the Macaque Brainnetome Atlas(MacBNA),based on the anatomical connectivity profiles provided by high angular and spatial resolution ex vivo diffusion MRI data.The new atlas consists of 248 cortical and 56 subcortical regions as well as their structural and functional connections.The parcellation and the diffusion-based tractography were evaluated with invasive neuronal-tracing and Nissl-stained images.As a demonstrative application,the structural connectivity divergence between macaque and human brains was mapped using the Brainnetome atlases of those two species to uncover the genetic underpinnings of the evolutionary changes in brain structure.The resulting resource includes:(1)the thoroughly delineated Macaque Brainnetome Atlas(MacBNA),(2)regional connectivity profiles,(3)the postmortem high-resolution macaque diffusion and T2-weighted MRI dataset(Brainnetome-8),and(4)multi-contrast MRI,neuronal-tracing,and histological images collected from a single macaque.MacBNA can serve as a common reference frame for mapping multifaceted features across modalities and spatial scales and for integrative investigation and characterization of brain organization and function.Therefore,it will enrich the collaborative resource platform for nonhuman primates and facilitate translational and comparative neuroscience research.