Resistive switching modulation by incorporating thermally enhanced layer in HfO2-based memristor.

Oxide-based memristors by incorporating thermally enhanced layer (TEL) have showed great potential in electronic devices for high-efficient and high-density neuromorphic computing owing to the improvement of multilevel resistive switching. However, research on the mechanism of resistive switching regulation is still lacking. In this work, based on the method of finite element numerical simulation analysis, a bilayer oxide-based memristor Pt/HfO2(5 nm)/Ta2O5(5 nm)/Pt with the Ta2O5TEL was proposed. The oxygen vacancy concentrates distribution shows that the fracture of conductive filaments (CF) is at the interface where the local temperature is the highest during the reset process. The multilevel resistive switching properties were also obtained by applying different stop voltages. The fracture gap of CF can be enlarged with the increase of the stopping voltage, which is attributed to the heat-gathering ability of the TEL. Moreover, it was found that the fracture position of oxygen CF is dependent on the thickness of TEL, which exhibits a modulation of device RS performance. These results provide a theoretical guidance on the suitability of memristor devices for use in high-density memory and brain-actuated computer systems.

Al and Ta co-doped LLZO as active filler with enhanced Li+conductivity for PVDF-HFP composite solid-state electrolyte.

Battery safety calls for solid state batteries and how to prepare solid electrolytes with excellent performance are of significant importance. In this study, hybrid solid electrolytes combined with organic PVDF-HFP and inorganic active fillers are studied. The modified active fillers of Li7-x-3yAlyLa3Zr2-xTaxO12are obtained by co-element doping with Al and Ta when LLZO is synthesized by calcination. And an high room temperature ionic conductivity of 5.357 × 10-4S cm-1is exhibited by ATLLZO ceramic sheet. The composite solid electrolyte PVDF-HFP/LiTFSI/ATLLZO (PHL-ATLLZO) is prepared by solution casting method, and its electrochemical properties are investigated. The results show that when the contents of lithium salt LiTFSI and active filler ATLLZO are controlled at 40 wt% and 10%, respectively, the ionic conductivity of the resulting composite solid electrolyte is as high as 2.686 × 10-4S cm-1at room temperature, and a wide electrochemical window of 4.75 V is exhibited. The LiFePO4/PHL-ATLLZO/Li all-solid-state battery assembled based on the composite solid-state electrolyte exhibits excellent cycling stability at room temperature. The cell assembled by casting the composite solid-state electrolyte on the cathode surface shows a discharge specific capacity of 134.3 mAh g-1and 96.2% capacity retention after 100 cycles at 0.2 C. The prepared composite solid-state electrolyte demonstrates excellent electrochemical performance.

Computed Tomography Perfusion Imaging Quality Affected by Different Input Arteries in Patients of Internal Carotid Artery Stenosis.

BACKGROUND The aim of this study was to explore the influence of different input arteries on the parameters of computed tomography (CT) perfusion imaging for patients with different degree of stenosis of internal carotid artery (ICA). MATERIAL AND METHODS Forty patients were enrolled in the present study and divided into mild, moderate, severe stenosis and occlusion groups respectively with each 10 patients in each group. In reconstruction of cerebral CT perfusion (CTP) images, each raw perfusion image was reconstructed 3 times based on different reference input artery, including bilateral middle cerebral artery (MCA) and basilar arteries (BA). Region of interest (ROI) was drawn in the central territories of bilateral anterior cerebral artery, middle cerebral artery and posterior cerebral artery. And regional cerebral blood flow (rCBF) regional cerebral blood volume (rCBV), mean transit time (MTT), time to peak (TTP) and delay time (DT) were obtained from those ROI corresponding perfusion images. RESULTS In patients with mild and moderate ICA stenosis, there was no significant difference of perfusion parameters based on different input arteries (P>0.05). However, in severe ICA stenosis and occlusion CBF, MTT, and DT were significant different in affect side of the MCA group compared to the others (P<0.05). CONCLUSIONS Large intracranial artery can be selected as the input artery for patients with mild to moderate ICA stenosis, while for patients with severe stenosis and occlusion of ICA, the contra lateral middle cerebral artery or basilar artery would be better choice.

A meta-analysis of contrast-enhanced computer tomography in the diagnosis of colorectal cancer.

OBJECTIVE: To investigate the diagnostic value of contrast-enhanced computer tomography in diagnosis of colorectal cancer. METHODS: All the diagnostic studies about contrast-enhanced computer tomography in diagnosis of colorectal cancer were searched in the PubMed, Medline, EMBASE, CNKI, and Wanfang databases and included in this meta-analysis. The diagnostic sensitivity and specificity were pooled. The data were analyzed by statistic software Meta-DiSc1.4. RESULTS: After searching the databases, eight studies with 4764 cases were finally included in this meta-analysis. The combined results showed the pooled diagnostic sensitivity and specificity were 0.73 (95% confidence interval [CI] of 0.69-0.76) and 0.86 (95% CI of 0.85-0.87). Moreover, the area under the receiver operating characteristic was 0.896. CONCLUSION: Contrast-enhanced computer tomography was a good method for detection colorectal cancer.

Evaluation of Hepatic Tumors Using Intravoxel Incoherent Motion Diffusion-Weighted MRI.

BACKGROUND This study aimed to evaluate the diagnostic value of the D value, D* value, and f magnitude for identifying benign and malignant hepatic tumors using intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI). MATERIAL AND METHODS Data of 89 cases (123 lesions) with hepatic tumor confirmed by surgical pathology and postoperative follow-up were retrospectively collected. Among these cases, 40 cases were benign hepatic tumors (57 lesions) and 49 cases were malignant hepatic tumors (66 lesions). All subjects underwent conventional MRI with T1WI, T2WI, multi-b-value DWI, and dynamic enhanced LAVA scan. Diffusion-weighted images with 11 b values (0, 10, 20, 30, 50, 80, 100, 200, 400, 800, and 1000 s/mm2) were obtained to calculate true molecular diffusion (D), perfusion-related diffusion coefficient (D*), and perfusion fraction (f). The diagnostic performance in differentiating between malignant and benign hepatic lesions was analyzed. RESULTS Malignant lesions had a significantly lower D value ([1.04±0.34]×10-3 mm2/s) and D* value ([16.5±7.7]×10-3 mm2/s) compared to benign lesions (D value: [1.70±0.55]×10-3 mm2/s, P<0.01; D* value: [21.7±9.9]×10-3 mm2/s, P<0.01). There was no statistically significant difference in f values between malignant (23.3±9.5) and benign lesions (33.5±14.9, P=0.13). In addition, D exhibited a better diagnostic performance than D* in terms of the area under the curve, sensitivity, and specificity when identifying malignancies from benign lesions. CONCLUSIONS D and D* are significant parameters for diagnosing hepatic tumors. Moreover, the D value is a more reliable parameter in distinguishing benign and malignant hepatic tumors.

3.0 T MRI arterial spin labeling and magnetic resonance spectroscopy technology in the application of Alzheimer's disease.

The purpose of this study was to investigate the changes in the cerebral blood flow (CBF) and spectrum variables in the posterior cingulate region of patients with AD under the detection of arterial spin labeling (ASL) and magnetic resonance spectroscopy (MRS). A total of 20 AD patients (8 males and 12 females; mean age, 64.84±8.82 years) and 20 healthy controls (9 males and 11 females; mean age, 64.94±7.93 years) were included in this study for analysis. All images were obtained using a 3.0-T MR imager and an 8-channel head array receiving coil. MRS measurements were conducted exploring variables of metabolite ratios. Statistical analyses were conducted with the SPSS 11.0 statistical software package. Findings in the present study revealed a significant difference in the mean MMSE scores between the AD group and the healthy control group (16.21±4.01 vs. 27.35±1.01, P<0.01). Compared with the healthy control group, CBF in the bilateral frontal region showed a significant decrease in the AD group (right frontal: 83.5±7.2 vs. 110±11.5, P<0.05; left frontal: 85.6±8.1 vs. 108.7±12.2, P<0.05, respectively), and a similar association was also observed in the TL, TPJ, parietal, and hippocampal regions (all P<0.05). MRS imaging in the posterior cingulate region showed a significant reduction in the NAA/Cr ratio in the AD group (1.43±0.1 vs. 1.49±0.0, P<0.05). Additionally, we found that the MI/Cr and Cho/Cr ratios were higher than normal controls in patients with AD (all P<0.05). Our results suggested that 3D ASL detection combined with MRS in studying AD could show the regional hypo-perfusion with the decrease of CBF and the abnormal metabolic changes of the posterior cingulate cortex.