GROUND BASED AUGMENTATION SYSTEM (GBAS)

The purpose of this article is to introduce the new technology of Ground Based Augmentation System by taking many factors into consideration such as, what this system is, the system equipment, its operating principle, installation costs, and advantages compared to other systems. Nowadays, many airports are not able to use their capacity adequately due to some disadvantages of approach systems, which is a serious cost for the enterprises. On the other hand, the fact that the number of equipment in the GBAS system is low and the transceiver signals are not influenced by the air traffic around the system ensures the system to be more reliable and preferable in low visibility conditions while reducing the costs greatly

Tipin-Replication Protein A Interaction Mediates Chk1 Phosphorylation by ATR in Response to Genotoxic Stress

Mammalian Timeless is a multifunctional protein that performs essential roles in the circadian clock, chromosome cohesion, DNA replication fork protection, and DNA replication/DNA damage checkpoint pathways. The human Timeless exists in a tight complex with a smaller protein called Tipin (Timeless-interacting protein). Here we investigated the mechanism by which the Timeless-Tipin complex functions as a mediator in the ATR-Chk1 DNA damage checkpoint pathway. We find that the Timeless-Tipin complex specifically mediates Chk1 phosphorylation by ATR in response to DNA damage and replication stress through interaction of Tipin with the 34-kDa subunit of replication protein A (RPA). The Tipin-RPA interaction stabilizes Timeless-Tipin and Tipin-Claspin complexes on RPA-coated ssDNA and in doing so promotes Claspin-mediated phosphorylation of Chk1 by ATR. Our results therefore indicate that RPA-covered ssDNA not only supports recruitment and activation of ATR but also, through Tipin and Claspin, it plays an important role in the action of ATR on its critical downstream target Chk1

Multiple ATR-Chk1 Pathway Proteins Preferentially Associate with Checkpoint-Inducing DNA Substrates

The ATR-Chk1 DNA damage checkpoint pathway is a critical regulator of the cellular response to DNA damage and replication stress in human cells. The variety of environmental, chemotherapeutic, and carcinogenic agents that activate this signal transduction pathway do so primarily through the formation of bulky adducts in DNA and subsequent effects on DNA replication fork progression. Because there are many protein-protein and protein-DNA interactions proposed to be involved in activation and/or maintenance of ATR-Chk1 signaling in vivo, we systematically analyzed the association of a number of ATR-Chk1 pathway proteins with relevant checkpoint-inducing DNA structures in vitro. These DNA substrates included single-stranded DNA, branched DNA, and bulky adduct-containing DNA. We found that many checkpoint proteins show a preference for single-stranded, branched, and bulky adduct-containing DNA in comparison to undamaged, double-stranded DNA. We additionally found that the association of checkpoint proteins with bulky DNA damage relative to undamaged DNA was strongly influenced by the ionic strength of the binding reaction. Interestingly, among the checkpoint proteins analyzed the checkpoint mediator proteins Tipin and Claspin showed the greatest differential affinity for checkpoint-inducing DNA structures. We conclude that the association and accumulation of multiple checkpoint proteins with DNA structures indicative of DNA damage and replication stress likely contribute to optimal ATR-Chk1 DNA damage checkpoint responses

AgNOR increase in buccal epithelial cells of trisomy 21 infants

The aim of this study is to compare the Argilophilic Nucleolus Organizer Regions (AgNORs) level between Down syndrome (DS) patients and controls in a tissue sharing the same embryonic origin with the central nervous system and compare the results with those obtained recently by us from DS's lymphocytes. For this, buccal desquamating epithelial cells well known as the ectodermic origin were used. Since the AgNOR staining intensity is an indicator of the ribosomes biosynthesis rate, comparison of the image analysis values of the AgNOR area/total nuclear area (NORa/TNa) in buccal desquamating epithelial cells of DS patients and controls provided a plausible conclusion about the regulation/deregulation of the rRNA genes (rDNA) in these cells of DS babies/infants. The (NORa/TNa) proportion was calculated using an in-house computer program. Fifty buccal desquamating cells were analysed for each individual to determine the average NORa/TNa value per individual. In contrast to healthy controls, NORa/TNa proportion value of buccal epithelia] cells from DS patients found significantly higher than that of the controls: (4.08 +/- 1.16)% and (2.13 +/- 0.55)%, respectively. This 92% increase is far higher than the expected value due to the extra rRNA genes on the extra-chromosome 21. Finally DS babies/infants exhibit very higher AgNOR expression increase in their buccal epithelial cells compared to controls. This is the first study that is available on the comparison of AgNOR expression levels in buccal epithelial cells between DS infants and their controls. (C) 2008 Elsevier Ltd. All rights reserved

Collaboration among small shippers in a transportation market

Intense competition in markets is pushing companies to increase their operational efficiency. One possible way to achieve increased efficiency is through cooperation with other companies. We study the coalition formation among small shippers in a transportation market characterized by uncertain demand. We analyze the decisions taken by the coalition and study the effect of shipper characteristics on the benefit of collaboration. Analysis shows that the shippers always benefit from the coalition, but when the benefits are to be allocated, the coalition may not always guarantee the budget balance, which is elementary for sustainability of any coalition. Using a game theoretical approach this study proposes saving allocation mechanisms and discusses the conditions that lead to a balanced budget

Mechanical behaviour and wear resistance of Ce-PSZ alumina matrix composites

Transformation toughening is one of the methods for improving the strength of alumina which has a hardness value of similar to2000 HV. In this study, 0wt.%, 5wt.%, 15wt.%, 25wt.% and 35wt.% of Ce-partially stabilised ZrO2 powders were dispersed homogeneously in alumina powder matrix. Pure alpha-Al2O3 and alpha-Al2O3/ZrO2 mixtures were shaped by using slip casting method and then they were sintered at 1550degreesC. Specimens were tested in order to determine apparent porosity and bulk density, micro-hardness, flexural strength and fracture toughness. Later, wear tests were carried out on specimens by using 60 and 120 mesh abrasive papers, 64.5N, 33.3N and 14.4N loads. By this procedure, the effects of composition, load and mesh size of abrasive paper on abrasive wear behaviour was inspected throughly. Finally, surface analyses were carried out by using SEM to determine the characteristics of worn specimens