The aim of this study is to point to the very large improvements that are taking place in a range of modelling applications in the urban areas. The particular phenomenon chosen in this study is a supercell, but it cou...
详细信息
The aim of this study is to point to the very large improvements that are taking place in a range of modelling applications in the urban areas. The particular phenomenon chosen in this study is a supercell, but it could well have been any other aspect of urban modelling. The Sydney hailstorm of 14 April 1999 was a long-lived, high precipitation supercell that produced a massive damage bill of over 2 billion Australian dollars from its hail swath. The Sydney hailstorm was poorly forecast for a number of reasons including: the severe weather season had officially ended so there were no specialist staff on duty when the hailstorm struck Sydney;the storm proved very difficult to predict and it was expected to continue heading out to sea;and the forecast guidance from all available operational numerical models was inadequate at the resolution required for a supercell simulation. Here, our interest is on the last of the problems, namely, the quality of the operational numerical model guidance, especially given the impact it had on a densely populated urban region. In this study, we compare the numerical guidance available at the time with current modeling capability which, although in research mode at present, will soon be available in real-time mode. The operational models were hydrostatic models run at horizontal resolutions of 25 km at best, compared with 1 km horizontal resolution for the non-hydrostatic research model. The research model also had a high-order differencing scheme and a sophisticated six phase cloud physics scheme compared with the much simpler parameterized convection in the operational models. The operational model produced very little convective precipitation and it was displaced well to the north of Sydney. The research model generated a supercell with a track and a hail size distribution that was encouragingly close to the observed.
The purpose of this editorial is to give an update on various issues relating to the running of the The Journal of Pathology. In particular, ethical issues are discussed, forthcoming changes to the manuscript submissi...
详细信息
The purpose of this editorial is to give an update on various issues relating to the running of the The Journal of Pathology. In particular, ethical issues are discussed, forthcoming changes to the manuscript submission, tracking, and peer-review system are outlined, and guidance on the submission of illustrations for publication is provided. Copyright (C) 2004 Pathological Society of Great Britain and Ireland. Published by John Wiley Sons, Ltd.
We evaluated the value of CT-guided transthoracic core biopsy for the diagnosis of mycobacterial pulmonary nodules. The 30 subjects in this study had pulmonary nodules that had been either diagnosed histopathologicall...
详细信息
We evaluated the value of CT-guided transthoracic core biopsy for the diagnosis of mycobacterial pulmonary nodules. The 30 subjects in this study had pulmonary nodules that had been either diagnosed histopathologically as tuberculosis or were suspected as tuberculosis based on a specimen obtained by CT-guided transthoracic core biopsy. The histopathological findings, the existence of acid-fast bacilli in the biopsy specimens, and the clinical course of the patients after the biopsy were reviewed retrospectively. Two of the three histological findings for tuberculosis that included epithelioid cells, multinucleated giant cells and caseous necrosis were observed in 21 of the nodules which were therefore diagnosed as histological tuberculosis. Six of these 21 nodules were positive for acid-fast bacilli, confirming the diagnosis of tuberculosis. Thirteen of the 2 1 nodules did not contain acid-fast bacilli but decreased in size in response to antituberculous treatment and were therefore diagnosed as clinical tuberculosis. Seven nodules with only caseous necrosis were diagnosed as suspected tuberculosis, with a final diagnosis of tuberculosis being made in 4 of the nodules and a diagnosis of old tuberculosis in 2 nodules. Two nodules with only multinucleated giant cells were diagnosed as suspected tuberculosis with I of these nodules being diagnosed finally as tuberculosis and the other nodule as a nonspecific granuloma. When any two of the three following histopathological findings-epithelioid cells, multinucleated giant cells or caseous necrosis-are observed in a specimen obtained by CT-guided transthoracic core biopsy, the diagnosis of tuberculosis can be established without the detection of acid-fast bacilli or Mycobacterium tuberculosis.
Neurotrophins have been known to play a pivotal role in axonal guidance. Recent research has implicated the role of extracelluar matrix molecules in co-ordinating axonal movement. In this study, we examined the influe...
详细信息
Neurotrophins have been known to play a pivotal role in axonal guidance. Recent research has implicated the role of extracelluar matrix molecules in co-ordinating axonal movement. In this study, we examined the influence of neurotrophins (nerve growth factor (NGF) and neurotrophin-3 (NT-3)) and extracellular matrix molecules (laminin, fibronectin, and poly-L-lysin) on sensory neurite outgrowth in thoracic dorsal root ganglia (DRG) dissected from rats at embryonic day 13. Adjacent DRG were embedded in a collagen gel matrix and supplemented with NGF or NT-3. Under NT-3 conditions, DRG axons extended towards each other and intermingled, while neurites from NGF-treated DRG demonstrated a strong repellent effect, resulting in turning responses and growth cone collapse. This effect was not observed on a collagen culture surface. Interestingly, the composition of the extracellular matrix strongly influenced the observed repellent effect. Sensory neurites from NGF-stimulated DRG again demonstrated a repellent effect when plated on a laminin surface, but showed intermingling behavior when plated on poly-L-lysin or fibronectin. This observation suggests that a factor secreted by NGF-treated DRG axons interacts with laminin, enabling repulsion. This factor and its interaction with the extracellular matrix play an important role in the mechanism of sensory axonal-pathfinding. (C) 2004 ISDN. Published by Elsevier Ltd. All rights reserved.
During chicken embryonic development the metanephros forms from the uretic duct at embryonic day (E) 7. As the metanephric tissue develops between E7 and E10, it comes into close apposition with lumbosacral nerves. Co...
详细信息
During chicken embryonic development the metanephros forms from the uretic duct at embryonic day (E) 7. As the metanephric tissue develops between E7 and E10, it comes into close apposition with lumbosacral nerves. Coculturing of metanephric and nerve explants demonstrated that the Schwann cells of the sciatic nerve inhibit the migration of metanephric cells in a contact-dependent manner. Conversely, metanephric cells inhibit dorsal root ganglion axon extension in a contact-dependent manner. However, metanephric cells are not inhibited by contact with growth cones or axons. Dorsal root ganglion growth cones become sensitive to the inhibitory signals on the surfaces of metanephric cells around E8, a time when the metanephros is expanding into the territory occupied by nerves in vivo. These observations demonstrate inhibitory bidirectional tissue-tissue interactions in vitro and provide a novel model system for the study of contact-based guidance of both neuronal and non-neuronal cell migration. (C) 2004 Wiley-Liss, Inc.
In Belgium, between 3% and 8% of the children in elementary schools have mathematics learning disabilities (MLD). Many of these children have less developed linguistic, procedural, and mental representation skills. Mo...
详细信息
In Belgium, between 3% and 8% of the children in elementary schools have mathematics learning disabilities (MLD). Many of these children have less developed linguistic, procedural, and mental representation skills. Moreover, a majority of the children have been found to show inaccurate prediction and evaluation skills in Grade 3. MLD often become obvious in elementary school. Whereas some children are retained, others are referred to special education. During the last 10 years, the number of children in special education and the number of children with learning disabilities who are following a special guidance program in general education (inclusive education) have increased. Children in Belgium with MLD can get therapy for about 2 years. Nevertheless, many problems continue unresolved even in high school and adulthood.
We present the on-orbit performance results of the Pointing Calibration and Reference Sensor (PCRS) for the Spitzer Space Telescope. A cryogenic optical (center wavelength 0.55 mum) imager, the PCRS serves as the Obse...
详细信息
ISBN:
(纸本)0819454192
We present the on-orbit performance results of the Pointing Calibration and Reference Sensor (PCRS) for the Spitzer Space Telescope. A cryogenic optical (center wavelength 0.55 mum) imager, the PCRS serves as the Observatoryis fine guidance sensor by providing an alignment reference between the telescope boresight and the external spacecraft attitude determination system. The PCRS makes precision measurements of the positions of known guide stars;these are used to calibrate measurements from Spitzeris star tracker and gyroscopes to obtain the actual pointing of the Spitzer telescope. The PCRS calibrates out thermomechanical drifts between the 300 K spacecraft bus and the 5.5 K telescope. By using only 16 pixels, the PCRS provides high precision centroiding with extremely low (similar to64 muW) power dissipation, resulting in minimal impact to Spitzeris helium lifetime. We have demonstrated that the PCRS meets its centroiding accuracy requirement of 0.14 arcsec 1-sigma radial, which represents similar to1/100 pixel centroiding. The Spitzer Space Telescope was launched on 25 August, 2003 and completed its In-Orbit Checkout phase two months later;the PCRS has been operating failure-free ever since.
The European Agency under its Aurora programme is about to undertake bold and unprecedented steps towards exploring the outer planets of our solar system. A very important step in this programme is a Mars sample retur...
详细信息
The European Agency under its Aurora programme is about to undertake bold and unprecedented steps towards exploring the outer planets of our solar system. A very important step in this programme is a Mars sample return mission lead by the European Space Agency. One main point in this mission is transporting samples from mars with and without humans back to Earth. Transporting these samples and humans from the hostile Mars environment to low Mars orbit and then back to Earth will require some means of transportation based on rockets. In this respect the Surrey Space Centre is exploring alternatives to design a low cost, modular Planetary Ascent Vehicle (PAV). This paper will briefly describe the following: Sizing and systems design of a Mars Ascent Vehicle Issues on the design of the Navigation, guidance and Control System of a Mars Ascent Vehicle (MAV).
In this paper, a system for vision based autonomous navigation is presented which is capable of obstacle avoidance as well as self-localization. At first a ground plane detection method is proposed which is capable of...
详细信息
In this paper, a system for vision based autonomous navigation is presented which is capable of obstacle avoidance as well as self-localization. At first a ground plane detection method is proposed which is capable of working on different most commonly occurring indoor/outdoor ground textures. The benefit of ground plane detection is that the system is not dependent on some specific property of obstacle to detect (such as size and orientation). Next, a strategy for vehicle localization and implementation of proposed method is discussed.
At first the advance of Chinese spacecraft control systems in the last decade is summarized in this paper, which include the technical progress of the control systems of geostationary double-spin stabilized meteorolog...
详细信息
At first the advance of Chinese spacecraft control systems in the last decade is summarized in this paper, which include the technical progress of the control systems of geostationary double-spin stabilized meteorological satellites, geostationary three-axis stabilized communication and broadcast satellites, Medium Earth Orbit(MEO) solar synchronous three-axis stabilized Earth resource satellites, scientific experiment small satellites and etc, and the technical progress of the guidance, navigation and control system of Shenzhou manned spaceship. Secondly the study and the applications of modern information process technologies and control theories in spacecraft control are introduced. At last future technical development trend in China is prospected.
暂无评论