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The gray contrast between the liver and other soft tissues is low, and the boundary is not obvious. As a result, it is still a challenging task to accurately segment the liver from CT images. In recent years, methods of machine learning have become a research hotspot in the field of medical image segmentation because they can effectively use the “gold standard” personalized features of the liver from different data. However, machine learning usually requires a large number of data samples to train the model and improve the accuracy of medical image segmentation. This paper proposed a method for liver segmentation based on the Gabor dictionary of sparse image blocks with prior boundaries. This method reduced the number of samples by selecting the test sample set within the initial boundary area of the liver. The Gabor feature was extracted and the query dictionary was created, and the sparse coefficient was calculated to obtain the boundary information of the liver. By optimizing the reconstruction error and filling holes, a smooth liver boundary was obtained. The proposed method was tested on the MICCAI 2007 dataset and ISBI2017 dataset, and five measures were used to evaluate the results. The proposed method was compared with methods for liver segmentation proposed in recent years. The experimental results show that this method can improve the accuracy of liver segmentation and effectively repair the discontinuity and local overlap of segmentation results.

Purpose Situations of vessel wall in IVUS images after Chocolate balloon dilatation remains unknown and 12-month following-up results would be performed. Materials and Methods 25 patients were enrolled in this observational study. Angiography and intravascular ultrasound were performed before Chocolate balloon inflation and post inflation. Dissections were quantified and classified according to the iDissection classification on intravascular ultrasound (IVUS) and National Heart, Lung, and Blood Institute classification on angiography. The elastic recoil rate, plaque burden and luminal gain were calculated in each patient too. Doppler ultrasound was presented in 30days, 3months, 6months and 12months each patient during follow-up. Results The mean lesion length was 168.3 ± 26.6 mm and arc of calcium was 115.1 ± 84.6°. 7 of the 25 patients required stents because of flow-limiting dissections and another 8 patients used stents with residual narrowing > 30%. Post Chocolate balloon angioplasty, the elastic recoil rate was 32.4 ± 13.1% and luminal gain was 6.1 ± 2.8mm2. The plaque burden volume reduction was 7.0 ± 4.6%. Diameters on cine were 5.1 ± 0.7mm and 5.9 ± 0.6mm on IVUS. Total number of dissections were 2.9 times (114/40) on IVUS images than cine film, more non-flow-limiting dissections observed on IVUS compared cine (102/31). 2 patients lost follow-up because of death, primary patency in patients was 52.2% (12/23) and secondary patency was 82.6% (19/23) in 12-month. Conclusion Vessel injury from Chocolate balloon angioplasty and diameter in femoropopliteal artery lesions were grossly underestimated on angiography. Severe elastic recoil performed in most of patients according to IVUS images after Chocolate. Further randomized controlled trials are needed to support their use.

This study assessed the effectiveness and safety of percutaneous mechanical thrombectomy and catheter-directed thrombolysis combined with stent placement in the management of iliac vein compression syndrome with acute iliofemoral deep venous thrombosis (DVT).From December 2014 to April 2016, there were 46 patients with DVT who underwent percutaneous mechanical thrombectomy and catheter-directed thrombolysis and stenting for acute proximal DVT with computed tomography-verified iliofemoral stenosis. The Venous Registry Index was used for evaluating the degree of patency after pharmacomechanical thrombolysis; the prevalence of post-thrombotic syndrome (PTS) in the follow-up was assessed according to the Villalta scale. For up to 24 months, conditions of the patients were assessed using periodic duplex ultrasound scans.For all patients, the technical success rate was 100%; no major bleeding or 30-day mortality was observed. Overall, the 6-, 12-, and 24-month primary patency rates were 97.8%, 95.7%, and 91.1%, respectively. There was a significant reduction in Venous Registry Index (9.82 ± 1.74 to 1.15 ± 1.02; P .05) after the procedure. According to the Villalta score, only one patient developed mild PTS and none developed severe PTS. Symptomatic pulmonary embolism was not observed during the hospitalization. The mean hospital stay was 6.5 ± 1.7 days.This technique provides a safe and effective treatment option for patients with acute proximal DVT caused by vein compression syndrome.

Colorectal cancer liver metastasis (CRLM) was one of the cancers with high mortality. Clinically, the target point was determined by invasive detection, which increased the suffering of patients and the cost of treatment. If the target point was found through the relationship between early radiomic information and genetic information, it was expected to assist doctors in diagnosing disease, formulating treatment plans, and reducing the pain and burden of patients. In this study, gene coexpression analysis and hub gene mining were first performed on the gene data; secondly, quantitative radiomic features were extracted from CT-enhanced radiomic data to obtain features highly correlated with CRLM; and finally, we analyzed the relationship between gene features and radiomic feature correlations by establishing a link between early radiomic features and gene sequencing and finding highly correlated expressions. This experiment demonstrated that radiomic features could be used to mine gene attributes. Based on the four previously identified genes (NRAS, KRAS, BRAF, and PIK3CA), we identified two novel genes, MAPK1 and STAT1, highly associated with CRLM. There were specific correlations between these 6 genes and radiomic features (shape_elongation, glcm, glszm, firstorder_10percentile, gradient, exponent_firstorder_Range, and gradient_glszm_SmallAreaLowGrayLevel). Therefore, this paper established the correlation between radiomic features and genes, and through radiomic features, we could find the genes associated with them, which was expected to achieve noninvasive prediction of liver metastasis.

Object To distinguish combined hepatocellular cholangiocarcinoma (cHCC-CC), hepatocellular carcinoma (HCC) and cholangiocarcinoma (CC) before operation using MRI radiomics. Method This study retrospectively analyzed 196 liver cancers: 33 cHCC-CC, 88 HCC and 75 CC. They had confirmed by pathological analysis in the Affiliated Hospital of Hebei University. MRI lesions were manually segmented by a radiologist.1316 features were extracted from MRI lesions by Pyradiomics. Useful features were retained through two-level feature selection to establish a classification model. Receiver operating characteristic (ROC), area under curve (AUC) and F1-score were used to evaluate the performance of the model. Results Compared with low-order image features, the performance of the model based on high-order features was improved by about 10%. The model showed better performance in identifying HCC tumors during the delay phase (AUC = 0.91, sensitivity = 0.88, specificity = 0.89, accuracy = 0.89, F1-Score = 0.88). Conclusion The classification ability of cHCC-CC, HCC and CC can be further improved by extracting MRI high-order features and using a two-level feature selection method.

Background To evaluate the effect of stent compression on in-stent restenosis (ISR) and clinical outcomes in patients with iliac vein compression syndrome (IVCS) after iliac vein stenting. Methods Fifty patients with IVCS treated with iliac vein stenting (Smart Control, Cordis, USA) between March 2017 and October 2018 were consecutively enrolled in this study. Computed tomography venography (CTV) was performed to assess stent compression and ISR. Based on the degree of stent compression, patients were allocated to a significant stent compression (SSC) group and an insignificant stent compression (ISC) group. The incidence of ISR was analyzed between the SSC and ISC groups. Patients' venous clinical severity scores (VCSSs) and responses to the chronic venous insufficiency questionnaire (CIVIQ) one year after stenting were compared between the two groups to evaluate the clinical improvement of venous insufficiency. Results In total, 34% of patients had SSC. There were significant differences in the incidence of ISR (52.9% vs. 21.2%, P=0.023), and in each group, there was one case of stent occlusion (5.88% vs. 3.03%, P=0.999). Patients in the SSC group had a higher VCSS score (8.41±5.92 vs. 3.15±2.87, P=0.04) and a lower CIVIQ score (83.35±8.86 vs. 92.21±4.32, P=0.001). Conclusions SSC has a significant effect on the incidence of ISR and the clinical outcomes of venous insufficiency. Thus, a dedicated iliac venous stent with sufficient radial resistive force, crush resistance, and outward radial force is needed to prevent the occurrence of stent compression.

AimsThe Hub genes highly related to the disease were found from the gene co-expression module, and the potential high expression genes were analyzed to predict the liver metastasis of colorectal cancer, so as to provide reference for subsequent targeted therapy.MethodsIn this study, we used the public data set of GEO database (GSE50760) to analyze the gene co-expression of liver metastasis of colon cancer, primary colon cancer and normal colon tissue (54 cases) and 50 cases of clinical cases. The functional annotations based on GO database are enriched, and the functional annotations of five gene modules are obtained through the enrichment of biological processes. Then the data mining is carried out to find the sub-networks with high adjacency in the gene co-expression network. At the same time, these sub-networks are annotated to find oncogenes related to liver metastasis of colorectal cancer.ResultsThis experiment found that KRAS, APC, FBXW7, PIK3CA, TP53 were highly correlated with liver metastasis of colorectal cancer. Finally, two protein genes STAT1 and MAPK1 were found by MCODE, which may be highly correlated with liver metastasis of colorectal cancer. Two new genes with high expression proteins found in this experiment have potential cancer, which has not been reflected in previous studies.Conclusion According to clinical data, KRAS, APC, FBXW7, PIK3CA, TP53 are related to colorectal cancer liver metastasis, and the analysis of the data set shows that STAT1 and MAPK1 are not only related to colorectal cancer liver metastasis oncogene but also related to clinically obtained genes.

Aims Oscillatory wall shear stress (WSS)-linked oxidative stress promotes intimal hyperplasia (IH) development, but the underlying mechanisms are not completely understood. Materials and methods We used an in vivo rabbit carotid arterial stenosis model representing different levels of WSS and found that WSS was increased at 1 month with 50% stenosis and was accompanied by VSMCs proliferation and interstitial collagen accumulation. Increased WSS promoted the expression of NOX, AKT, and survivin (SVV) and the proliferation/migration of VSMCs and reduced apoptosis. Key findings Our in vitro study suggested that H2O2 promoted proliferation and migration while suppressing apoptosis in cultured human umbilical vascular endothelial cells. Significance We demonstrated that the elevation of WSS promotes VSMC proliferation and migration through the H2O2-mediated NOX-AKT-SVV axis, thereby accelerating IH development.

Objective To improve the accuracy of the prediction of primary liver cancer by radiomics employing non invasive hyperspectral imaging technology. Methods This retrospective study was approved by the IRB committee of our institution, and the rule of informed consent was put forward. This paper analyzes the hyperspectral images (HSI) of patients with primary liver cancer and finds that the spectral reflectance curve of tumor and non-tumor locations are significantly different at different wavelengths. By using the ISODATA algorithm to predict tumor, it is found that the result is obvious. It is speculated that the use of HSI to select computed tomography (CT) images can improve the accuracy of radiomics in the prediction of primary liver cancer. Therefore, we employed HSI in combination with radiomic features to complete this task. We use the attention mechanism to concentrate computing resources into highly correlated features and use these features to predict tumor. Results Using the hyperspectral-attention mechanism feature selection method, we were able to achieve an AUC of 0.96. Our study shows that HSI and radiomic features could aid in the prediction of liver cancer.

Hypoxia following arteriovenous fistulization results in venous neointimal hyperplasia (VNH), potentially causing early arteriovenous fistula (AVF) dysfunction. In this study, we used hyperbaric oxygen (HBO) in a rabbit model of AVF to determine whether it could ameliorate early AVF failure. Chronic renal failure was induced by adenine in 96 adult rabbits randomly divided into 3 groups (n=32 in each group). The sham + HBO group underwent sham operation and received HBO. The AVF alone group underwent fistulization, but did not receive HBO. The AVF + HBO group underwent fistulization and received HBO. Each group was further divided into 4 subgroups of 8 rabbits each that were euthanized at 1, 7, 14 or 28 days post-operatively. At each time point, blood flow changes in the AVF venous segment were detected using a high-frequency duplex ultrasonography system. Immunohistochemical staining for proliferating cell nuclear antigen (PCNA), and hematoxylin and eosin staining were performed to evaluate VNH. Western blot analysis was performed to confirm the expression of hypoxia-inducible factor (HIF)-1α. At 14 and 28 days following HBO treatment, blood flow in the AVF + HBO group was greater than that at day 0. The AVF + HBO group had a smaller ratio of intima to media area, a lower HIF-1α protein expression, and a smaller percentage of PCNA-positive cells in the proximal vein than did the AVF alone group. Our results thus suggest that continuous HBO treatment following AVF significantly inhibits VNH and promotes blood flow. Therefore, early AVF failure may be prevented by the use of HBO therapy.

Background/Aims: Skeletal muscle ischemia/reperfusion (I/R) injury is a common and severe disease. Sonic hedgehog (Shh) plays a critical role in post-natal skeletal muscle regeneration. In the present study, the role of Shh in skeletal muscle I/R injury and the mechanisms involved were investigated. Methods: The expression of Shh, AKT/mTOR/p70S6K and apoptosis pathway components were evaluated following tourniquet-induced skeletal muscle I/R injury. Then, mice were subjected to systemic administration of cyclopamine or one-shot treatment of a plasmid encoding the human Shh gene (phShh) to examine the effects of Shh on I/R injury. Moreover, mice were subjected to systemic administration of NVP-BEZ235 to investigate the role of the AKT/mTOR/p70S6K pathway in Shh-triggered skeletal muscle protection. Results: We found that the levels of Shh, AKT/mTOR/p70S6K pathway components and Cleaved Caspase 3 and the Bax/Bcl2 ratio initially increased and then decreased at different time points post-I/R injury. Moreover, Shh protected skeletal muscle against I/R injury by alleviating muscle destruction, reducing interstitial fibrosis and inhibiting apoptosis, and these protective effects were abrogated when the AKT/mTOR/p70S6K pathway was inhibited. Conclusion: Collectively, these data suggest that Shh signaling exerts a protective role through the AKT/mTOR/p70S6K signaling pathway during skeletal muscle I/R injury. Thus, Shh signaling may be a therapeutic target for protecting skeletal muscle from I/R injury.

Lichtenstein repair (LR), mesh-plug repair (MPR), and prolene hernia system (PHS) are three common open tensionless repair techniques for inguinal hernia (IH); each technique has its supporters and controversies never stop. It is necessary to perform a meta-analysis to evaluate the clinical efficacy of these three open tensionless repair techniques. RCTs comparing at least any two of the three open tensionless repair techniques for IH were searched in online databases. Literature screening and quality assessment were carried out basing on the established inclusion criteria and exclusion criteria. Statistical analyses were carried out using RevMan software 5.3. The primary outcomes were recurrence, chronic pain and time to return to work. Secondary outcomes were inguinal paresthesia, testicular and scrotal problems, hematoma, seroma and wound infection. Twenty-two references on fifteen RCTs involving a total of 3716 hernias were selected for the meta-analysis. In these trials, seven comparing LR and MPR, five comparing LR and PHS, and three comparing LR, MPR and PHS. All primary and secondary outcomes could be pooled analyzed in comparison of MPR and PHS with LR, while only two primary outcomes (recurrence and chronic pain) and one secondary outcome (wound infection) could be pooled analyzed in comparison of MPR with PHS. Results of this meta-analysis demonstrated that MPR and PHS were comparable to LR in all primary and secondary outcomes, and MPR and PHS were comparable in terms of recurrence, chronic pain and wound infection. This meta-analysis indicates that MPR and PHS seem comparable to LR in terms of recurrence, chronic pain, time to return to work, inguinal paresthesia, testicular and scrotal problems, hematoma, seroma and wound infection. MPR and PHS seem comparable in terms of recurrence, chronic pain and wound infection.

Proliferation of vascular smooth muscle cells (VSMCs) plays an important role in various vascular diseases. Abnormal hemodynamic factors are important stimulus for promoting proliferation of VSMCs. In this study, we show that transmural pressure (TP) promotes the proliferation of human arterial smooth muscle cells (HASMCs) and its related mechanism. HASMCs were treated with different TPs (0,100,120,140,160,180 and 200 mmHg) in a custom-made pressure loading apparatus for 6 h. Results showed that proliferation of HASMCs was significantly promoted when the TP was over 160 mmHg compared with 0 mmHg (atmosphere pressure). In like manner, the expressions of NADPH oxidase 2(Nox2) and Survivin (SVV) and production of intracellular reactive oxygen species (ROS) were all elevated distinctly when TP exceeded 160 mmHg. Moreover, ROS scavenger NAC reduced TP-induced proliferation of HASMCs and expression of SVV largely, and slightly down-regulated expression of NOX2. NOX inhibitor apocynin (Apo) also significantly reduced TP-induced proliferation of HASMCs and expression of SVV and almost completely eliminated TP-induced production of ROS. These results demonstrate that TP drives proliferation of HASMCs via mechanism associated with NOX and SVV.

Medical ultrasound images are corrupted by speckle noise, which is multiplicative. This noise limits the contrast resolution in these images and complicates image-based quantitative measurement and diagnosis. In this study, the speckle noise in the ultrasound image is modeled by local statistics of the intensity distribution. And the non-local mean (NLM) filter is utilized to filter additional noise by applying the redundancy information in noisy images. A hybrid denoising method is proposed in consideration of the characteristics of both the local statistics of speckle noise and the NLM filter. The study combines local statistics with the NLM filter to reduce speckle in ultrasound images. The local statistics of speckle noise is estimated by local patches, while the intensity of the denoising pixel is computed by the weighted average of all the pixels by using the NLM. The weight is determined according to the similarity measures between the intensities of the local patches. The performance of the proposed method is evaluated on synthetic data, simulated images, and real images. Results of quantitative analysis and visual inspection of the synthetic data and of the real images demonstrate that the proposed method outperforms the original NLM, as well as many previously developed methods.

Eleven denoising filters, proposed during last fifteen years, are introduced and compared for magnetic resonance images. Among them, the state-of-art denoising algorithms, NLM and BM3D, have attracted much attention. Several expansions are proposed to improve the noise reduction based on these two algorithms. On the other hand, optimal dictionaries, sparse representations and appropriate shapes of the transform's support are also considered for the image denoising. Based on the estimated noise variance, the comparison of various filters is implemented by measuring the signal-noise-ratio (SNR), resolution and uniformity of a phantom image. The subjective judgment of denoising effectiveness is executed for a clinical image. And the computational time is finally evaluated

In optical transmission imaging, even a very thin layer of a scattering material can appear opaque make the image blurry, which restricts the positioning of heterogeneity in transmission images. Aiming at the problem, an exploratory method based on frame accumulation and multiband information fusion was proposed and proven, which can be used to detect the edge of heterogeneity in transmission images. Treating the trichromatic image as an example, the following experiment was designed: Firstly, the transmission video of phantom is collected by camera. Then, single-band images are decoded at “R∖G∖B” and further accumulated by frame accumulation technology to obtain the image with high grayscale level, respectively. Lastly, the information fusion of the three single-band images is realized through neural network, and further the edge could be detected by the established model. The experimental result shows that the heterogeneity edge can be detected more accurately by this method. Therefore, the validity of this method for detecting heterogeneity in transmission images is demonstrated. It is expected to provide an idea for the future clinical diagnosis of breast tumor by transmission method.

The heating methods currently used at oil delivery sites and transfer stations on North China Oilfield include electric bar heating, fuel oil heating, gas heating, etc. The traditional heating methods have adverse effect on energy conservation and environmental protection. They have low energy efficiency of heating and produces great pollution to the environment. The air source heat pump technology uses the heat in the air as the low-temperature heat source and transforms it to the high-temperature hot water, which will later serve as a heat tracing for crude oil gathering and transportation. No combustion effluent is produced in operation and the energy-saving effect is outstanding with high social-benefit.

Oscillatory wall shear stress (WSS)-linked oxidative stress promotes intimal hyperplasia (IH) development, but the underlying mechanisms are not completely understood.We used an in vivo rabbit carotid arterial stenosis model representing different levels of WSS and found that WSS was increased at 1 month with 50% stenosis and was accompanied by VSMCs proliferation and interstitial collagen accumulation. Increased WSS promoted the expression of NOX, AKT, and survivin (SVV) and the proliferation/migration of VSMCs and reduced apoptosis.Our in vitro study suggested that HWe demonstrated that the elevation of WSS promotes VSMC proliferation and migration through the H

Angiographic image is the perspective projection of the whole body from a 3D space to a 2D imaging plane, in which X-ray is used. As such, topological vasculature information has been lost. In 2D angiograms, foreshortening and overlapping are commonly observed in tubular-like structures. Hence, an optimum viewing angle should be determined to observe an interesting vessel segment (IVS) or an interesting vessel bifurcation (IVB) with minimized foreshortening and overlapping from a limited number of angiographic images. In this study, a novel integrated optimization method is proposed to calculate the optimum viewing angle. In the proposed method, the irregular shape and inter-branch distance of vasculatures are considered. Furthermore, three optimized conditions, including projection foreshortening rate, projection stenosis rate, and projection overlapping rate, are designed and integrated to determine the optimum viewing angle in a single vessel segment. The three conditions, including projection foreshortening, projection stenosis, and projection adjacent spacing rates, are also designed to optimize the viewing angle of bifurcations. To evaluate the performance of the proposed method, we simulated an angiographic image based on X-ray propagating principle by integrating 3D coronary artery tree models and the respective CT volume data. Experimental results demonstrate that the proposed method is very effective and robust; hence, this method can be used to determine the optimum viewing angle of IVS or IVB with irregular stenosis. The proposed method can also help physicians observe the branching structure or stenosis clearly in clinical practice.

This study proposes a new liver segmentation method based on a sparse a priori statistical shape model (SP-SSM). First, mark points are selected in the liver a priori model and the original image. Then, the a priori shape and its mark points are used to obtain a dictionary for the liver boundary information. Second, the sparse coefficient is calculated based on the correspondence between mark points in the original image and those in the a priori model, and then the sparse statistical model is established by combining the sparse coefficients and the dictionary. Finally, the intensity energy and boundary energy models are built based on the intensity information and the specific boundary information of the original image. Then, the sparse matching constraint model is established based on the sparse coding theory. These models jointly drive the iterative deformation of the sparse statistical model to approximate and accurately extract the liver boundaries. This method can solve the problems of deformation model initialization and a priori method accuracy using the sparse dictionary. The SP-SSM can achieve a mean overlap error of 4.8% and a mean volume difference of 1.8%, whereas the average symmetric surface distance and the root mean square symmetric surface distance can reach 0.8 mm and 1.4 mm, respectively.

Objective To assess the effects of survivin (SVV)in vascular endothelial cells. Methods In this study, we applied a gain-of-function approach and ectopically expressed SVV in rat aortic endothelial cells (RAECs) using a SVV-expressing adenovirus. The resulting SVV expression on the steady-state mRNA and protein level in RAECs was determined by reverse transcription quantitative PCR and Western blot, respectively. Cell viability, apoptosis, and migration were assessed in vitro by CCK-8 assay, flow cytometry, and transwell assay, respectively. The effect of SVV on in vivo angiogenesis was evaluated by immunohistochemistry in nude mice. Non-infected RAECs and those infected with GFP-expressing control adenovirus were used as controls. Results Compared to non-infected or control adenovirus-infected RAECs in vitro, SVV-expressing cells had increased viability and migratory capability, but reduced apoptosis. In vivo, SVV-expressing RAECs were associated with a higher level of angiogenesis. Conclusion SVV is a positive regulator of endothelial cell survival and migration, and thus, stabilizes endothelial cells and stimulates angiogenesis.

Platelet-derived growth factor (PDGF) is known to induce phenotypic switching of vascular smooth muscle cells (VSMCs) from contractile to a pathological synthetic state, which played an essential role in proliferation of VSMCs. Sonic hedgehog (Shh) contributes to the proliferation of VSMCs when induced by PDGF. Here, we investigated the probable role of Shh in PDGF-induced VSMC dedifferentiation and its underlying mechanisms. We found that PDGF stimulated Shh expression in VSMCs, which was mediated by activation of PDGFRβ/ERK1/2 cell signaling pathway. Further, we found PDGF-induced VSMC phenotypic modulation was accompanied by up-regulation of Shh/Gli family zinc finger 2 (Gli2) signaling and Kruppel-like factor 4 (KLF4). When inhibited Shh in the presence of PDGF, the expressions of KLF4 and VSMC dedifferentiation markers were down-regulated and the effect of PDGF in inducing VSMC dedifferentiation was blocked. In the absence of PDGF, Shh signaling activation increased the expression of KLF4 and promoted VSMC dedifferentiation. The results indicate Shh participated in the regulation of PDGF-induced VSMC dedifferentiation. Finally, we found that KLF4 was closely involved in this process. On inhibition of KLF4, PDGF induced VSMC dedifferentiation was abrogated, even in the presence of Shh. Taken together, the results provide critical insights into the newly discovered role of Shh in phenotypic modulation of VSMCs which depends on KLF4.

Three new 20-electron bis-α-diimine nickel (II) complexes containing chloro-substituted ligands, bis{bis[N,N′-(3-chloro-2-methylphenyl)imino]-1,2-dimethylethane}dibromonickel 2a, bis{bis[N,N′-(3-chloro-2,6-dimethylphenyl)imino]-1,2-dimethylethane}dibromonickel 2b and bis{bis[N,N′-(4-chloro-2,6-dimethyl-phenyl)imino]-1,2-dimethylethane}dibromonickel 2c, were synthesized and characterized. The molecular structure of complex 2a was determined by X-ray crystallography. In the solid state, complex 2a has a pseudo-octahedral geometry about the nickel center, containing two α-diimine ligands in the pseudo-equatorial plane and two trans bromide ligands occupying the axial positions. These complexes, activated by diethylaluminum chloride (DEAC) were tested in the polymerization of ethylene under mild conditions. NMR analysis shows that highly branched polyethylenes are obtained using these bis-α-diimine nickel(II) complexes containing electron-withdrawing Cl groups in the aryl groups (e.g. 84 branches/1000 C, at 20 °C). The catalytic activity, polymer molecular weight and polymer degree of branching were significantly affected by the number of methyl substituents in the ortho-aryl position and the chlorine substituent position in the aryl rings of the coordinated α-diimine ligands.

The long-term patency rates in vascular transplants (diameter3.0-4.0mm) are very low due to thrombus formation and intimal hyperplasia. A possible mechanism is the loss of the endothelial cells (ECs) lining. Previous attempts to reseed ECs had poor results due to seeded cell loss, severe antigenicity, and low compliance. The objectives of this study were to generate an allogeneic vascular substitution with autogenic ECs and low antigenicity.ECs from mongrels were obtained and multiplied in vitro, then seeded to the allogeneic vein luminal surface, which was preserved by freeze-drying radiation. The cultivated cells' secretory function was confirmed by von Willebrand factor detection. The allogeneic vascular was then transplanted into animals' necks in situ. The physical properties, EC state, and vascular structure of the allogeneic vascular grafts were studied.The secretory function of ECs did not vary in vitro. The expression level of MHC-II antigen in freeze-dried radiation-treated vasculature was lower than normal fresh vasculature (P0.05). ECs covered the vascular inner surface and adhered tightly after implantation. As assessed by scanning electron micrograph, most ECs adhered tightly, and the cell polarity changed in accordance with the direction of the force. Allograft blood vessels with autogenic ECs implanted showed significant decreases in both thrombosis and intimal hyperplasia.Allograft blood vessels seeded with autogenic ECs improved the patency of small-diameter grafts in a canine model. Our study showed a significant decrease in both thrombosis and intimal hyperplasia.