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Search Results: 1 - 10 of 91096 matches for " Neal X. Chen "
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Decreased MicroRNA Is Involved in the Vascular Remodeling Abnormalities in Chronic Kidney Disease (CKD)
Neal X. Chen, Kraiwiporn Kiattisunthorn, Kalisha D. O'Neill, Xianming Chen, Ranjani N. Moorthi, Vincent H. Gattone, Matthew R. Allen, Sharon M. Moe
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0064558
Abstract: Patients with CKD have abnormal vascular remodeling that is a risk factor for cardiovascular disease. MicroRNAs (miRNAs) control mRNA expression intracellularly and are secreted into the circulation; three miRNAs (miR-125b, miR-145 and miR-155) are known to alter vascular smooth muscle cell (VSMC) proliferation and differentiation. We measured these vascular miRNAs in blood from 90 patients with CKD and found decreased circulating levels with progressive loss of eGFR by multivariate analyses. Expression of these vascular miRNAs miR-125b, miR-145, and miR-155 was decreased in the thoracic aorta in CKD rats compared to normal rats, with concordant changes in target genes of RUNX2, angiotensin II type I receptor (AT1R), and myocardin. Furthermore, the expression of miR-155 was negatively correlated with the quantity of calcification in the aorta, a process known to be preceded by vascular de-differentiation in these animals. We then examined the mechanisms of miRNA regulation in primary VSMC and found decreased expression of miR-125b, 145, and 155 in VSMC from rats with CKD compared to normal littermates but no alteration in DROSHA or DICER, indicating that the low levels of expression is not due to altered intracellular processing. Finally, overexpression of miR-155 in VSMC from CKD rats inhibited AT1R expression and decreased cellular proliferation supporting a direct effect of miR-155 on VSMC. In conclusion, we have found ex vivo and in vitro evidence for decreased expression of these vascular miRNA in CKD, suggesting that alterations in miRNAs may lead to the synthetic state of VSMC found in CKD. The decreased levels in the circulation may reflect decreased vascular release but more studies are needed to confirm this relationship.
Cortical Bone Mechanical Properties Are Altered in an Animal Model of Progressive Chronic Kidney Disease
Christopher L. Newman, Sharon M. Moe, Neal X. Chen, Max A. Hammond, Joseph M. Wallace, Jeffry S. Nyman, Matthew R. Allen
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0099262
Abstract: Chronic kidney disease (CKD), which leads tocortical bone loss and increasedporosity,increases therisk of fracture. Animal models have confirmed that these changes compromise whole bone mechanical properties. Estimates from whole bone testing suggest that material properties are negatively affected, though tissue-level assessmentshavenot been conducted. Therefore, the goal of the present study was to examine changes in cortical bone at different length scales using a rat model with theprogressive development of CKD. At 30 weeks of age (~75% reduction in kidney function), skeletally mature male Cy/+ rats were compared to their normal littermates. Cortical bone material propertieswere assessed with reference point indentation (RPI), atomic force microscopy (AFM), Raman spectroscopy,and high performance liquid chromatography (HPLC). Bones from animals with CKD had higher (+18%) indentation distance increase and first cycle energy dissipation (+8%) as measured by RPI.AFM indentation revealed a broader distribution of elastic modulus values in CKD animals witha greater proportion of both higher and lower modulus values compared to normal controls. Yet, tissue composition, collagen morphology, and collagen cross-linking fail to account for these differences. Though the specific skeletal tissue alterations responsible for these mechanical differences remain unclear, these results indicate that cortical bone material properties are altered in these animals and may contribute to the increased fracture risk associated with CKD.
An ARX-Based PID-Sliding Mode Control on Velocity Tracking Control of a Stick-Slip Pi-ezoelectric-Driven Actuator  [PDF]
Y. Cao, X. B. Chen
Modern Mechanical Engineering (MME) , 2015, DOI: 10.4236/mme.2015.51002
Abstract: Piezoelectric-driven stick slip actuators have been drawn more and more attention in the nano- positioning application due to the high accuracy and theoretical unlimited displacement. However, the hysteresis of piezoelectric actuator (PEA) and the nonlinear friction force between the end- effector and the stage make control of piezoelectric-driven stick slip actuator challenge. This paper presents the development of an autoregressive exogenous (ARX)-based proportional-integral-derive (PID)-sliding mode control (SMC) for the velocity tracking control of the piezoelectric-driven stick slip actuator. Stability is guaranteed by rigorously choosing the appropriate PID parameters and the zero steady state error is achieved. To verify the effectiveness of the proposed method, experiments were carried out on a commercially-available piezoelectric-driven stick slip actuator. The tracking errors were compared with the traditional PID controller, illustrating that in spite of existing of modeling error, the ARX-based PID-SMC is able to better improve the velocity tracking performance of piezoelectric-driven stick slip actuator, compared with the traditional PID controller.
On K?hler manifolds with positive orthogonal bisectional curvature
X. X. Chen
Mathematics , 2006,
Abstract: In this paper, we study any K\"ahler manifold where the positive orthogonal bisectional curvature is preserved on the K\"ahler Ricci flow. Naturally, we always assume that the first Chern class $C_1$ is positive. In particular, we prove that any irreducible K\"ahler manifold with such property must be biholomorphic to $\mathbb{C}\mathbb{P}^n. $ This can be viewed as a generalization of Siu-Yau\cite{Siuy80}, Morri's solution \cite{Mori79} of the Frankel conjecture. According to [8], note that any K\"ahler manifold with 2-positive traceless bisectional curvature operator is preserved under Kahler Ricci flow; which in turns implies the positivity of orthogonal bisectional curvature under the flow.
Space of K?hler metrics III--On the lower bound of the Calabi energy and geodesic distance
X. X. Chen
Mathematics , 2006,
Abstract: In this paper, we first prove a folklore conjecture on a greatest lower bound of the Calabi energy in all K\"ahler manifold. Similar result in algebriac setting was obtained by S. K. Donaldson. Secondly, we give an upper/lower bound estimate of the K energy in terms of the geodesic distance and the Calabi energy. This is used to prove a theorem on convergence of K\"ahler metrics in holomorphic coordinates, with uniform bound on the Ricci curvature and the diameter. Thirdly, we set up a framework for the existence of geodesic rays when an asymptotic direction is given. I
Synthetic Pattern of Fish Diversity in Alabama, USA
Chen, X.
Wildlife Biology in Practice , 2006,
Abstract: The state of Alabama has a rich fish fauna. Analyzing the current distributional patterns of fish diversity by synthesizing information and integrating different spatial and temporal scales is important for understanding the underlying mechanisms of diversity and making strategies for fish conservation. Basing the study on long-term intensive samples (9,244 collections) of fish species at 3,716 field stations across Alabama from 1845 to 1994, I analyzed the general pattern of fish diversity in Alabama at the county level. The results indicate that more than half the area of Alabama has high fish diversity, including fish species endemic to the USA. Most of the counties with the highest fish diversity are in southwestern Alabama. Nonnative fish species occurred mainly in the southernmost counties, such as Mobile and Baldwin. Twelve counties have the rare species which has only one occurence location in each country, with Lauderdale County having the most (10 rare species); the counties with the rare species are generally distributed at the four corner areas of the state boundaries, particularly on the northern and southern boundaries. A high positive correlation exists between species diversity and endemic species, but there is no significant correlation between species diversity and diversification. Both Power-law and logarithmic relationships exist between class of species diversity and its frequency; counties with higher fish diversity tend to have low human-population densities, and are located at or nearby the Alluvial-deltaic Plain and Gulf Coast floodplain.
Topological properties in the spatial distribution of amphibians in Alabama USA for the use of large scale conservation
X. Chen
Animal Biodiversity and Conservation , 2008,
Abstract: Large-scale biodiversity conservation is urgently needed due to increasing habitat loss and fragmentation. Understanding topological perspectives of species' distribution patterns can provide useful information for linking conservation studies at larger scales. We studied topological properties of localities in Alabama where 60 species of 12 families of amphibians were present. Analysis included a clustering coefficient which measures the strength of a population group, the relationship between occurrence localities and species number, the fractal dimension of occurrence localities (which emphasizes spatial irregularity), and distance to nearest-neighbor. The results indicate that the clustering coefficients of most amphibian species were low, but were higher for species with few occurrence localities, such as Rana sylvatica and Limnaoedus ocularis. The general relationship between species number and occurrence localities was that the majority of species held few localities in their distribution, while the remaining species occupied a greater number of localities. The fractal dimension (FD) for all amphibian localities was about 1.58, although FD was low for most individual species. We identified four relationships in the distribution of distance to nearest-neighbor: linear, logarithmic, power and polynomial. These topological properties may indicate intrinsic features about amphibians in Alabama and provide useful information for regional planning. Enhancing landscape linkages across a large area using undisturbed areas, such as 300-500 km in diameter may be a good approach to conservation practice in this region. Steps needed for biodiversity conservation planning in Alabama include creating or conserving small habitats across agricultural and urban land, and maintaining suitable spatial complexity and distance to nearest neighbors.
Multi-Segment Direct Inject nano-ESI-LTQ-FT-ICR-MS/MS For Protein Identification
Jing Chen, Lorena Canales, Rachel E Neal
Proteome Science , 2011, DOI: 10.1186/1477-5956-9-38
Abstract: One of the major goals of proteomics is to be able to identify proteins of interest [1]. For protein spots on 1D- or 2D-SDS-PAGE gels this is a challenge due to the large diversity of protein spot abundances and the complexity of the matrix. The great number of protein spots or gel slices which can approach several hundred per experiment demands automated, high throughput, cost-effective analytical methods with high sensitivity [2].For the proteomics workflow, high performance liquid chromatography (HPLC) is typically coupled via an electrospray source (nanoESI or ESI) to either an ion trap or time-of-flight (TOF) mass analyzer with ion packet selection via mass filter (quadrapole or ion trap) [2-9]. Following parent mass feature selection, tandem mass spectrometry (MS/MS) based on collision induced dissociation (CID) or electron capture dissociation (ECD) of peptide parent mass/charge features are used to generate mixed ion populations of peptide fragments which are then utilized for protein identification. The acidified HPLC eluent serves two purposes: a) to separate peptide mixtures thus simplifying the parent mass composition of ion packet; and b) to competitively eliminate salts. However this workflow has several drawbacks including potential sample cross-contamination due to column carryover and the lengthy sample run time [2,8]. The cost of instrument time, columns, and solvents drives the total cost per sample.To address the problem of lengthy sample run time and expensive instrument time usage, direct infusion sample introduction methods without HPLC separation prior to the electrospray source has been developed [2,8,10-16]. The advantages of the chip-based ESI method include fully automated, high throughput, a lack of cross-contamination, enhanced spray stability and reproducibility, and constant sample matrix [2,8,13-16]. In each case, protein spots were analyzed with one broad mass range MS scan followed by MS/MS scans.In the current study, a method of d
A Legacy System Encapsulation Strategy Based on Web Service  [PDF]
D. J. Chen, X. Y. Li
Creative Education (CE) , 2012, DOI: 10.4236/ce.2012.37B014
Abstract:

In order to migrate the enterprise legacy system to the web, a multi-agent based legacy system encapsulation model is proposed.  Firstly, the characteristics of legacy system are analyzed, and then the data and functions that need to be published are confirmed. Secondly the legacy system is wrapped into web components with common interface, and these components are managed by the application server. Thirdly, the clients can send requests to the application server, and receive the return result from the application server.  Due to adoption of wrapping technology for legacy system, original security and stability of legacy system are guaranteed in the web components. Finally, the validity and practicability of the migration technology are verified through the application in the encapsulation of Matlab as web components.

Real-Time Timing Channel Detection in a Software-Defined Networking Virtual Environment  [PDF]
Anyi Liu, Jim X. Chen, Harry Wechsler
Intelligent Information Management (IIM) , 2015, DOI: 10.4236/iim.2015.76023
Abstract: Despite extensive research, timing channels (TCs) are still known as a principal category of threats that aim to leak and transmit information by perturbing the timing or ordering of events. Existing TC detection approaches use either signature-based approaches to detect known TCs or anomaly-based approach by modeling the legitimate network traffic in order to detect unknown TCs. Un-fortunately, in a software-defined networking (SDN) environment, most existing TC detection approaches would fail due to factors such as volatile network traffic, imprecise timekeeping mechanisms, and dynamic network topology. Furthermore, stealthy TCs can be designed to mimic the legitimate traffic pattern and thus evade anomalous TC detection. In this paper, we overcome the above challenges by presenting a novel framework that harnesses the advantages of elastic re-sources in the cloud. In particular, our framework dynamically configures SDN to enable/disable differential analysis against outbound network flows of different virtual machines (VMs). Our framework is tightly coupled with a new metric that first decomposes the timing data of network flows into a number of using the discrete wavelet-based multi-resolution transform (DWMT). It then applies the Kullback-Leibler divergence (KLD) to measure the variance among flow pairs. The appealing feature of our approach is that, compared with the existing anomaly detection approaches, it can detect most existing and some new stealthy TCs without legitimate traffic for modeling, even with the presence of noise and imprecise timekeeping mechanism in an SDN virtual environment. We implement our framework as a prototype system, OBSERVER, which can be dynamically deployed in an SDN environment. Empirical evaluation shows that our approach can efficiently detect TCs with a higher detection rate, lower latency, and negligible performance overhead compared to existing approaches.
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