1,722,933 research outputs found
Modeling estuarine morphodynamics under combined river and tidal forcing
No full textEstuarine morphodynamics are of broad importance to estuaries’ functions related to navigation, human settlement and ecosystems. Inspired by the Yangtze River estuary (YRE), this study aims to explore the impact of river discharge, tides and their interaction on long-term estuarine morphodynamics. Use is made of 1D and 2D process-based models. In first instance we focus on purely hydrodynamic characteristics in a 560 km long basin. We analyze the non-stationary river tides in the YRE by harmonic analysis and continuous wavelet transformation which reveals a wide range of subtidal variations and non-linear modulation by varying river discharges. An intermediate river discharge could be defined at which the amplitudes of the internally generated overtides and compound tides reach maxima. Based on these hydrodynamic insights we conduct long-term (millennia time scale) morphodynamic simulations in schematized long basins. Vanishing spatial gradients in tidal residual sediment transport indicate an approach towards morphodynamic equilibrium. Morphodynamic equilibrium is also reached in case of a seasonally varying river discharge, which is reflected by a balance between erosion and accretion during low and high river discharge periods, respectively. River flow supplies sediment, accelerates ebb currents, and alters tidal asymmetries. Each of these processes has its own effects on tidal residual transport and morphodynamics. For example, the interaction between a mean flow (i.e., Stokes return flow or river flow) and tidal currents induces significant tidal residual sediment transport which explains net ebb transport dominance in the presence of a flood tidal asymmetry. A larger river discharge does not necessarily lead to deeper equilibrium bed profiles. An intermediate river discharge is found which induces largest residual sediment transport gradients along the estuary leading to deepest equilibrium bed profile. Quantification of this medium river discharge is case dependent because of the non-linearities involved. The 2D model approach applied in a large scale fluvio-deltaic system reveal river, estuarine and deltaic types of morphodynamic features, such as alternating sand bars, meandering channels inside the estuary and more elongated sand bars and distributary channels in the mouth zone and delta. The cross-sectionally averaged depth of the 2D model responds in a similar way to increased river discharge as a 1D model. Furthermore, a high river discharge induces ebb transport dominance, restricts development of flood channels and prolongs meander wavelength. In summary, this research unveils the fundamental effects of tidal asymmetries, river discharge, and river-tide interaction in governing residual sediment transport and associated long-term estuarine morphodynamics under combined river and tidal forcing.Hydraulic EngineeringCivil Engineering and Geoscience
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Differential expression of toll-like receptor mRNA in treatment non-responders and sustained virologic responders at baseline in patients with chronic hepatitis C
No full textBackground/Aims: The contribution of the host immune response to sustained virologic response is not clear in patients with chronic hepatitis C (CHC). The aim of this study was to explore the relationship of the toll-like receptor (TLR) expression with the outcome of antiviral therapy in hepatitis C viral infection. Methods: Peripheral blood mononuclear cells (PBMC) were obtained from 15 CHC patients before a 48-week treatment with pegylated interferon (PEG IFN) alpha-2a and ribavirin. A multiplex semi-quantitative reverse-trancriptase polymerase chain reaction (RT-PCR) was used to compare the relative abundance of TLR2-9 transcripts. Results: mRNA levels of TLR2, 3 and 6 were significantly higher in CHC subjects compared with normal controls (n=8). When patients were classified into non-responders (n=8) and sustained virological responders (n=7) according to the virological outcome of the treatment, there was a clear difference in baseline mRNA expression of TLRs and T-helper (Th) 1/2 cytokines. In addition, the mRNA expression of IFN-gamma and nuclear factor of activated T cells (NFAT), which is exclusively expressed in activated T cells, was inversely correlated with that of TLR4, 6 and 9 in non-responders. Conclusions: TLRs mRNA levels are differentially expressed in baseline PBMC of chronic HCV-infected subjects with or without responsiveness to antiviral therapy
Differential Expression of Toll-Like Receptors mRNA in Baseline Peripheral Blood Mononuclear Cells (PBMC) of Chronic Hepatitis C Patients with Differential Responsiveness to Pegylated Interferon Plus Ribavirin Therapy
No full textVariations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Ethanol affects NMDA receptor signaling at climbing fiber-Purkinje cell synapses in mice and impairs cerebellar LTD
No full textEthanol profoundly influences cerebellar circuit function and motor control. It has recently been demonstrated that functional N-methyl-D-aspartate (NMDA) receptors are postsynaptically expressed at climbing fiber (CF) to Purkinje cell synapses in the adult cerebellum. Using whole cell patch-clamp recordings from mouse cerebellar slices, we examined whether ethanol can affect NMDA receptor signaling in mature Purkinje cells. NMDA receptor-mediated currents were isolated by bath application of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptor antagonist 2,3-dihydroxy-6-nitro-7-sulfamoylbenzol[f]quinoxaline (NBQX). The remaining D-2-amino-5-phosphonovaleric acid (D-APV)-sensitive current was reduced by ethanol at concentrations as low as 10 mM. At a concentration of 50 mM ethanol, the blockade of D-APV-sensitive CF-excitatory postsynaptic currents was significantly stronger. Ethanol also altered the waveform of CF-evoked complex spikes by reducing the afterdepolarization. This effect was not seen when NMDA receptors were blocked by D-APV before ethanol wash-in. In contrast to CF synaptic transmission, parallel fiber (PF) synaptic inputs were not affected by ethanol. Finally, ethanol (10 mM) impaired long-term depression (LTD) at PF to Purkinje cell synapses as induced under control conditions by paired PF and CF activity. However, LTD induced by pairing PF stimulation with depolarizing voltage steps (substituting for CF activation) was not blocked by ethanol. These observations suggest that the sensitivity of cerebellar circuit function and plasticity to low concentrations of ethanol may be caused by an ethanol-mediated impairment of NMDA receptor signaling at CF synapses onto cerebellar Purkinje cells. © 2013 the American Physiological Society
Exploring dynamics of stakeholder salience and functional roles in megaproject collaborative innovation system: insights from the Hong Kong-Zhuhai-Macao Bridge
No full textPurposeMegaprojects provide an ideal context for exploring the dynamic characteristics of stakeholders within a collaborative innovation system. This research aims to examine the changes in stakeholder salience and functional roles during the evolution of such a system.Design/methodology/approachThis study is empirically grounded on the Hong Kong-Zhuhai-Macao Bridge (HZMB) megaproject in China, analyzed with the stakeholder salience, stakeholder functional role, stakeholder dynamics and collaborative innovation system theoretical lens.FindingsThe megaproject collaborative innovation system can be divided into four stages: the birth stage, development stage, mature stage and re-innovation stage. Stakeholder salience generally remains unchanged throughout the lifecycle of the collaborative innovation system, except for engineering consulting firms (ECF). ECF transitioned from a definitive stakeholder to an expectant stakeholder upon project completion. The number of definitive stakeholders during the first three stages increases gradually. Besides, stakeholder functional roles shift in eight different directions throughout the lifecycle of the megaproject collaborative innovation system because they possess different core resources necessary for implementing innovations and are positioned differently within the collaborative innovation system.Originality/valueThis study contributes to the theory and practice of collaborative innovation in megaprojects. First, it offers insights into the evolution of megaproject collaborative innovation systems from the perspective of stakeholder interactions. Second, it has significant implications for managing stakeholder relationships based on their salience and functional roles at different stages of the collaborative innovation system
- …
