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Video quality based link adaptation for low latency video transmission over WLANs

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2006年第5期7卷 847-856页

作者： FERR Pierre DOUFEXI Angela chung-HOW James NIX Andrew BULL david University of Bristol Department of Electrical and Electronic Engineering Centre for Communications Research Bristol BS8 1UB UK ProVision Communication Technologies Bristol BS4 4EU UK

Wireless Local Area Networks (WLANs) such as IEEE 802.11a/g and Hiperlan/2 utilise numerous transmission modes, each providing different throughputs and reliability levels. Many link adaptation algorithms proposed in the literature either maximise the error-free data throughput based on channel conditions or are based on the number of failed transmissions. However, these algo- rithms do not take into account the content of the data stream and strongly rely on the use of Automatic Repeat Requests (ARQs). Low latency video applications such as real-time video transmission may require no retransmission, or only a limited number of retrans- missions. Moreover, completely error-free communication is not essential, especially if robust video compression techniques are applied. In such scenarios, improved decoded video quality can be obtained with a video stream transmitted at a higher bit rate using a higher link speed but with some degree of transmission error, rather than an error-free video stream at a lower bit rate using a lower link speed. In this work, we investigate a link adaptation scheme that improves the Quality of Service (QoS) for video transmission, based on the overall received video quality (Peak Signal to Noise Ratio, PSNR), rather than by maximising the error-free throughput. We also study a practical link adaptation approach that uses PER thresholds at the PHY layer. An empirical study showed that thresholds for switching from one mode to another are much lower (almost error free) than those currently used by throughput based schemes. We show that traditional link adaptation strategies are not appropriate for real-time video transmission with no retransmis- sion. Simulation results using the H.264 video compression standard over IEEE 802.11a are presented.

关键词： Link adaptation Wireless LAN Video quality Peak Signal to Noise Ratio (PSNR) Packet Error Rate (PER)

Effect of thickness of planar nozzles on erosion depth of levee soils subjected to plunging water

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International Journal of Sediment Research 2018年第3期33卷 243-249页

作者： chung Rak Song Jinwon Kim James Tyler Kidd Alexander Cheng david Admiraal Department of Civil Engineering University of Nebraska-Lincoln

In this study, the effect of the thickness of a planar jet on the erosion depth when the jet impinges on a surface composed of cohesive soil was analytically and numerically evaluated. The results showed that the erosion depth was practically independent of the nozzle thickness for erosion depths shallower than the potential core length(i.e. the region of the jet in which the central flow velocity is the same as the nozzle velocity). The relation between nozzle thickness and erosion depth was non-linear with continuously variable slope for erosion depths deeper than the potential core length. Finally, the relation was approximately linear when the erosion depth converged to the equilibrium erosion depth. The findings of this study indicate that direct and fast prediction of the erosion depth in the field is possible using the data from a small scale soil erosion test with similar flow velocities.

关键词： Nozzle thickness Levee erosion Erosion depth Plunging water Planar nozzle

Fluorescence lifetime imaging of molecular rotors to map microviscosity in cells

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Chinese Optics Letters 2010年第10期8卷 926-930页

作者： James A. Levitt Marina K. Kuimova Gokhan Yahioglu Pei-Hua chung Klaus Suhling david Phillips Department of Physics King's College London Department of Chemistry Imperial College London PhotoBiotics Ltd.

Fluorescence liftime imaging （FLIM） of modified hydrophobic bodipy dyes that act as fluorescent molecular rotors shows that the fluorescence lifetime of these probes is a function of the microviscosity of their environment. Incubating cells with these dyes, we find a punctate and continuous distribution of the dye in cells. The viscosity value obtained in what appears to be endocytotic vesicles in living cells is around 100 times higher than that of water and of cellular ***-resolved fluorescence anisotropy measurements also yield rotational correlation times consistent with large microviscosity values. In this way, we successfully develop a practical and versatile approach to map the microviscosity in cells based on imaging fluorescent molecular rotors.

关键词： Fluorescence lifetime imaging of molecular rotors to map microviscosity in cells

The role of complement C5a receptor in DPSC odontoblastic differentiation and in vivo reparative dentin formation

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International Journal of Oral Science 2022年第1期14卷 71-79页

作者： Muhammad Irfan Ji-Hyun Kim Hassan Marzban david AReed Anne George Lyndon FCooper Seung chung Department of Oral Biology University of Illinois at ChicagoChicagoUSA Department of Human Anatomy and Cell Science University of ManitobaWinnipegCanada

Therapeutic dentin regeneration remains difficult to achieve,and a majority of the attention has been given to anabolic strategies to promote dentinogenesis directly,whereas,the available literature is insufficient to understand the role of inflammation and inflammatory complement system on *** aim of this study is to determine the role of complement C5a receptor(C5aR)in regulating dental pulp stem cells(DPSCs)differentiation and in vivo dentin *** DPSCs were subjected to odontogenic differentiation in osteogenic media treated with the C5aR agonist and C5aR *** vivo dentin formation was evaluated using the dentin injury/pulp-capping model of the C5a-deficient and wildtype *** vitro results demonstrate that C5aR inhibition caused a substantial reduction in odontogenic DPSCs differentiation markers such as DMP-1 and DSPP,while the C5aR activation increased these key odontogenic genes compared to control.A reparative dentin formation using the C5a-deficient mice shows that dentin regeneration is significantly reduced in the C5a-deficient *** data suggest a positive role of C5aR in the odontogenic DPSCs differentiation and tertiary/reparative dentin *** study addresses a novel regulatory pathway and a therapeutic approach for improving the efficiency of dentin regeneration in affected teeth.

关键词： C5a vivo inflammation

Steroid for chronic subdural hematoma? A prospective phase IIB pilot randomized controlled trial on the use of dexamethasone with surgical drainage for the reduction of recurrence with reoperation

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Chinese Neurosurgical Journal 2015年第1期1卷 -页

作者： david Yuen chung Chan Tin Fung david Sun Wai Sang Poon Division of Neurosurgery Department of Surgery Prince of Wales HospitalThe Chinese University of Hong Kong 30-32 Ngan Shing Street Shatin NTHong Kong

Background: Chronic subdural hematoma is a common neurosurgical condition especially in the aging *** hole for drainage is an effective treatment, yet recurrence is reported at 8 to 22 ％ worldwide, and 1-year mortality rates could be as high as 32 ％.Our previous study on the use of dexamethasone as a primary nonsurgical treatment showed good response in selected group of *** study aims to assess the efficacy of dexamethasone with surgical drainage in the reduction of recurrence requiring ***: From October 2000 to September 2006, patients with chronic subdural hematoma admitted to the Prince of Wales Hospital, The Chinese University of Hong Kong, were randomized to surgical drainage with steroid versus surgical drainage *** primary endpoint was symptomatic recurrence requiring ***: Two hundred forty-eight patients were recruited and consented for the randomization during the study *** hundred twenty-two received both surgery and steroid (the intervention arm) while 126 received surgery only (the control arm).The recurrence rate requiring reoperation was 6.6 ％ (8/122) and 13.5 ％ (17/126),respectively (p =0.109).There was no significant difference in complications such as chest infection (p =0.201) or wound infection (p =0.987).Favorable outcome (Glasgow Outcome Score 4-5) was 104/122 (85.2 ％) in the intervention group versus 105/126 (83.3 ％) in the control group, respectively (p =0.811).Based on the recurrence rate in our study, we generate a potential sample size of at least 594 patients (type Ⅰ error =5 ％, power =80 ％,two-sided test) to detect a significant ***, brief summary, and potential implications: In this prospective pilot phase IIB randomized controlled study, steroid with surgical drainage had a lower recurrence with reoperation though statistically *** was safe with no significant difference in complication *** pilot study generates a potential sample s

关键词： Chronic subdural hematoma Steroid Burr hole for drainage

Is quantum capacitance in graphene a potential hurdle for device scaling？

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Nano Research 2014年第4期7卷 453-461页

作者： Jaeho Lee Hyun-Jong chung david H. Seo Jaehong Lee Hyungcheol Shin Sunae Seo Seongjun Park Sungwoo Hwang Kinam Kim Samsung Advanced Institute of Technology Samsung Electronics Yongin-Si Gyeonggi-Do 446-712 Korea Inter-University Semiconductor Research Center (ISRC) School of Electrical Engineering and Computer Science Seoul National University Seoul 151-742 Korea Division of Quantum Phases and Devices Department of Physics Konkuk University Seou1143-701 Korea Semiconductor R&D Center Somsung Electronics Hwasung-City Gyeonggi-Do 446-711 Korea Department of Physics Sejong University Seou1143-74 7 Korea Memory Division Samsung Electronics Hwasung-City Gyeonggi-Do 446-711 Korea

Transistor size is constantly being reduced to improve performance as well as power consumption. For the channel length to be reduced, the corresponding gate dielectric thickness should also be reduced. Unfortunately, graphene devices are more complicated due to an extra capacitance called quantum capacitance （CQ） which limits the effective gate dielectric reduction. In this work, we analyzed the effect of CQ on device-scaling issues by extracting it from scaling of the channel length of devices. In contrast to previous reports for metal-insulator- metal structures, a practical device structure was used in conjunction with direct radio-frequency field-effect transistor measurements to describe the graphene channels. In order to precisely extract device parameters, we reassessed the equivalent circuit, and concluded that the on-state model should in fact be used. By careful consideration of the underlap region, our device modeling was shown to be in good agreement with the experimental data. CQ contributions to equivalent oxide thickness were analyzed in detail for varying impurity concentrations in graphene. Finally, we were able to demonstrate that despite contributions from CQ, graphene＇s high mobility and low-voltage operation allows for ~raphene channels suitable for next generation transistors.

关键词： graphene equivalent circuit quantum capacitance intrinsic delay

Functional magnetic resonance imaging in an animal model of pancreatic cancer

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World Journal of Gastroenterology 2010年第26期16卷 3292-3298页

作者： Robert J Lewandowski Aaron C Eifler david J Bentrem Johnathan C chung Gayle E Woloschak Robert Ryu Riad Salem Andrew C Larson Reed A Omary Department of Radiology Northwestern University Feinberg School of Medicine Chicago IL 60611 United States Department of Surgical Oncology Northwestern University Feinberg School of Medicine Chicago IL 60611 United States Department of Radiation Oncology Northwestern University Feinberg School of Medicine Chicago IL 60611 United States

AIM: To test the hypotheses that diffusion weighed (DW)and transcatheter intraarterial perfusion (TRIP)magnetic resonance imaging (MRI) can each be used to assess regional differences in tumor function in an animal pancreatic cancer ***: VX2 tumors were implanted in pancreata of 6 rabbits. MRI and digital subtraction angiography (DSA) were performed 3 wk following implantation. With a 2-French catheter secured in the rabbit's gastroduodenal artery, each rabbit was transferred to an adjacent 1.5T MRI scanner. DWand TRIP-MRI were performed to determine if necrotic tumor core could be differentiated from viable tumor periphery. For each, we compared mean differences between tumor core/ periphery using a 2-tailed paired t-test (α = 0.05). Imaging was correlated with histopathology. RESULTS: Tumors were successfully grown in all rabbits, confirmed by necropsy. On DW-MRI, mean apparent diffusion coeffi cient (ADC) value was higher in necrotic tumor core (2.1 ± 0.3 mm2/s) than in viable tumor periphery (1.4 ± 0.5 mm2/s) (P < 0.05). On TRIP-MRI, mean perfusion values was higher in tumor periphery (110 ± 47 relative units) than in tumor core (66 ± 31 relative units) (P < 0.001). CONCLUSION: Functional MRI can be used to differentiate necrotic from viable tumor cells in an animal pancreatic cancer model using ADC (DW-MRI) and perfusion (TRIP-MRI) values.

关键词： Animal model Functional magnetic resonance imaging Pancreatic cancer

Determinants of the impact of blood pressure variability on neurological outcome after acute ischaemic stroke

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Stroke & Vascular Neurology 2017年第1期2卷 1-6页

作者： Adam de Havenon Alicia Bennett Gregory J Stoddard Gordon Smith Lee chung Steve O’Donnell J Scott McNally david Tirschwell Jennifer J Majersik Department of Neurology University of UtahSaltLake CityUtahUSA University of Utah SaltLake CityUtahUSA University of Washington SeattleWashingtonUSA

Introduction: Increased blood pressure variability (BPV) is detrimental after acute ischaemic stroke, but the interaction between BPV and neuroimaging factors that directly influence stroke outcome has not been explored. Methods: We retrospectively reviewed inpatients from 2007 to 2014 with acute anterior circulation ischaemic stroke, CT perfusion and angiography at hospital admission, and a modified Rankin Scale (MRS) 30- 365 days after stroke onset. BPV indices included SD, coefficient of variation and successive variation of the systolic blood pressure between 0 and 120 hours after admission. Ordinal logistic regression models were fitted to MRS with predictor variables of BPV indices. Models were further stratified by CT perfusion volumetric measurements, proximal vessel occlusion and collateral score. Results: 110 patients met the inclusion criteria. The likelihood of a 1-point rise in the MRS increased with every 10 mm Hg increase in BPV (OR for the 3 BPV indices ranged from 2.27 to 5.54), which was more pronounced in patients with larger ischaemic core volumes (OR 8.37 to 18.0) and larger hypoperfused volumes (OR 6.02 to 15.4). This association also held true for patients with larger mismatch volume, proximal vessel occlusion and good collateral vessels. Conclusions: These results indicate that increased BPV is associated with worse neurological outcome after stroke, particularly in patients with a large lesion core volume, concurrent viable ischaemic penumbra, proximal vessel occlusion and good collaterals. This subset of patients, who are often not candidates for or fail acute stroke therapies such as intravenous tissue plasminogen activator or endovascular thrombectomy, may benefit from interventions aimed at reducing BPV.

关键词： impaired perfusion cerebral

Tumor-associated methylation of the putative tumor suppressor AJAP1 gene and association between decreased AJAP1 expression and shorter survival in patients with glioma

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Chinese Journal of Cancer 2011年第4期30卷 247-253页

作者： david Cogdell Woonbok chung Yuexin Liu J. Matthew McDonald Kenneth Aldape Jean-Pierre J. Issa Gregory N. Fuller Wei Zhang Department of Pathology The University of Texas MD Anderson Cancer Center Houston Texas 77030 USA Department of Leukemia The University of Texas MD Anderson Cancer Center Houston Texas 77030 USA.

Allelic loss of the short arm of chromosome 1 has been observed frequently in a wide spectrum of cancers,most frequently in *** our previous studies,we evaluated 177 oligodendroglial tumor samples and identified the AJAP1 gene(formerly Shrew1) in the consensus region of ***1 is a transmembrane protein found in adheren junctions and functions to inhibit glioma cell adhesion and *** a putative tumor suppressor gene,we did not detect AJAP1 gene *** subsequent studies,we found that AJAP1 was underexpressed in oligodendrogliomas relative to normal brain *** analysis revealed the presence of CpG islands in the promoter of *** analysis of the AJAP1 promoter identified hypermethylation in 21% of oligodendrogliomas(n = 27),and the degree of methylation correlated with low levels of AJAP1 expression(P = 0.045).The AJAP1 promoter was also highly methylated in a wide spectrum of cell lines(n = 22),including cell lines of *** of the National Cancer Institute's REMBRANDT dataset,which contains 343 glioma samples,indicated that low AJAP1 gene expression was associated with decreased ***,both genetic(gene deletion) and epigenetic alterations(promoter methylation) are likely mechanisms that inactivate the putative tumor suppressor AJAP1 in gliomas,which contributes to poor prognosis.

关键词：甲基化分析脑胶质瘤抑癌基因 P1基因肿瘤患者协会少突胶质细胞