A Model for Investigating Developmental Eye Repair in Xenopus Laevis

Vertebrate eye development is complex and requires early interactions between neuroectoderm and surface ectoderm during embryogenesis. In the African clawed frog, Xenopus laevis, individual eye tissues such as the retina and lens can undergo regeneration. However, it has been reported that removal of either the specified eye field at the neurula stage or the eye during tadpole stage does not induce replacement. Here we describe a model for investigating Xenopus developmental eye repair. We found that tailbud embryos can readily regrow eyes after surgical removal of over 83% of the specified eye and lens tissues. The regrown eye reached a comparable size to the contralateral control by 5 days and overall animal development was normal. It contained the expected complement of eye cell types (including the pigmented epithelium, retina and lens), and is connected to the brain. Our data also demonstrate that apoptosis, an early mechanism that regulates appendage regeneration, is also required for eye regrowth. Treatment with apoptosis inhibitors (M50054 or NS3694) blocked eye regrowth by inhibiting caspase activation. Together, our findings indicate that frog embryos can undergo successful eye repair after considerable tissue loss and reveals a required role for apoptosis in this process. Furthermore, this Xenopus model allows for rapid comparisons of productive eye repair and developmental pathways. It can also facilitate the molecular dissection of signaling mechanisms necessary for initiating repair

Optimum sizing of PV/Wind hybrid system (I) CAD method

2003-2004 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

A comparative study of optical/ultraviolet variability of narrow-line Seyfert 1 and broad-line Seyfert 1 active galactic nuclei

The ensemble optical/ultraviolet variability of narrow-line Seyfert 1 (NLS1) type active galactic nuclei (AGNs) is investigated, based on a sample selected from the Sloan Digital Sky Survey (SDSS) Stripe-82 region with multi-epoch photometric scanning data. As a comparison a control sample of broad-line Seyfert 1 (BLS1) type AGNs is also incorporated. To quantify properly the intrinsic variation amplitudes and their uncertainties, a novel method of parametric maximum-likelihood is introduced, that has, as we argued, certain virtues over previously used methods. The majority of NLS1-type AGNs exhibit significant variability on timescales from about ten days to a few years with, however, on average smaller amplitudes compared to BLS1-type AGNs. About 20 NLS1- type AGNs showing relatively large variations are presented, that may deserve future monitoring observations, for instance, reverberation mapping. The averaged structure functions of variability, constructed using the same maximumlikelihood method, show remarkable similarity in shape for the two types of AGNs on timescales longer than about 10 days, which can be approximated by a power-law or an exponential function. This, along with other similar properties, such as the wavelength-dependent variability, are indicative of a common dominant mechanism responsible for the long-term optical/UV variability of both NLS1- and BLS1-type AGNs. Towards the short timescales, however, there is tentative evidence that the structure function of NLS1-type AGNs continues declining, whereas that of BLS1-type AGNs flattens with some residual variability on timescales of days. If this can be confirmed, it may suggest that an alternative mechanism, such as X-ray reprocessing, starts to become dominating in BLS1-type AGNs, but not in NLS1-, on such timescales.Comment: 53 pages, 13 figures, 3 tables, accepted for pulication in A

Optimum design of PV/Wind hybrid system II. A case study

2003-2004 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Optimization of six strand tundish based on inclusions motion

Inclusion transport and the influence of structural parameters of baffle holes on inclusion removal rate are discussed. The physical modeling experiments give two optimal integrated tundish structural parameters of baffle holes. From the further study of Inclusion trajectories, the tundish should be optimized in the structural parameters of baffle holes in the condition of height 300 mm, angle 30° and diameter 20 mm

The influential factor studies on the cooling rate of roller quenching for ultra-heavy plate

In this paper, the gradient temperature rolling (GTR) method is used to establish the 12-pass rolling model by Deform- 3D finite element (FE) software. The variation of temperature field and strain field of ultra-heavy plate slab under different conditions is systematically studied. The result shows that the more the number of water cooling between the passes during the rolling process, the greater the deformation of the core of slab, and the one of plate rolling with large temperature difference does not appear on near surface but gradually moves to the central part of the plate as cooling times increase

Vibration analysis of a beam on a moving vehicle under the road excitation with different contact models

Dynamic analysis of a beam on a moving vehicle is presented in this paper. The vehicle is simulated by a four degrees-of-freedom mass-spring system and the beam on top is supported by spring-damping systems. Two contact models named the ‘point contact’ and the ‘patch contact’ respectively, are adopted to simulate the interaction between road surface and vehicular tyres. The equation of motion of the beam-vehicle system is formulated and the dynamic response on the beam under the excitation of the irregular road surface is derived. Numerical simulations are conducted to demonstrate the influence of different factors, such as the length of the contact, the velocity of vehicle, the road condition and the bracing stiffness, etc. on the vibration level of the beam structure, which aims to provide references on the vibration problem in transporting a beam-shaped package

A Statistical Study on Force-Freeness of Solar Magnetic Fields in the Photosphere

It is an indisputable fact that solar magnetic fields are force-free in the corona, where force free fields means that current and magnetic fields are parallel and there is no Lorentz force in the fields. While the force-free extent of photospheric magnetic fields remains open. In this paper, the statistical results about it is given. The vector magnetograms (namely, $B_{x}$, $B_{y}$ and $B_{z}$ in heliocentric coordinates) are employed, which are deduced and calibrated from Stokes spectra, observed by Solar Magnetic Field Telescope (SMFT) at Huairou Solar Observing Station (HSOS) are used. We study and calibrated 925 magnetograms calibrated by two sets of calibration coefficients, that indicate the relations between magnetic fields and the strength of Stokes spectrum and can be calculated either theoretically or empirically. The statistical results show that the majority of active region magnetic fields are not consistent with the force-free model.Comment: 10 pages, 5 figures, has been accepted by PAS