Long-distance Tunnel Research Articles

The Influence of Pressure Pipe Diameter and Orifice Size of Surge Chamber Optimization on the Pressure at Volute

For a long-distance convey tunnel hydropower station, the changes of its convey tunnel diameter will impact on the pressure at the turbine volute, due to the influence of upper room of surge chamber, surge pressure is difficult to be the controlling value of the pressure at volute, the results also indicate that the influence of pressure pipe diameter on the pressure is more significant than the diversion tunnel diameter. This paper focuses on the pressure pipe diameter by the calculation of a numerical example, the increasing of the pressure at volute caused by the reduction of pressure pipe diameter can be adjusted for security requirements by optimizing the orifice size of surge chamber. Combined with the calculation of the combinational conditions, optimization results are satisfactory. That will reduce the investment of pressure pipe, so it has a certain reference value to the project.

DNA and RNA Charge Transport Effect of Sequence, Stacking, Structure and Hg Incorporation

In this work experimental and theoretical approaches have been combined for unique study and comparison of charge transfer efficiency in standard and modified (Hg incorporated) DNA duplexes and DNA/RNA hybrids. Specific mechanism proposed to account for the on-chain oligonucleotide charge transport is based on polaron formation-charge is transported coherently by long-distance tunneling (superexchange). A key parameter in this approach is how the bridge orbitals of the intervening DNA bases couple the charge donor and acceptor - this is strongly controlled by specific oligomeres structures and conformation. The RNA/DNA system flexibility also improves the conditions for polaron creation and thus may facilitate rapid (coherent) charge transport in the DNA/RNA hybrids. All our observations demonstrate that charge transfer characteristics of oligonucleotide duplexes are able to reveal the presence of structure changes in the sequence, which may help to elucidate possible disturbance identification in the cell or even in potential technological applications.

Long-Distance Tunneling Nanotubules Shuttle Viral Immunoglobulin Class Switch-Suppressing Factors from HIV-Infected Macrophages to B Cells.

Class switching from immunoglobulin M (IgM) to IgG, IgA or IgE is central to immunity against viruses and requires activation of B cells by CD4+ T cells through CD40 ligand (CD40L). Human immunodeficiency virus (HIV) evades protective T cell-dependent IgG and IgA responses against viral proteins and vaccines through mechanisms that remain unknown. Recent findings from our lab suggested the involvement of negative factor (Nef), an HIV accessory protein that suppresses CD40 signaling in B cells. The present work addressed the mechanism by which Nef invades B cells. Fluorescence microscopy-based studies showed that accumulation of Nef in infected lymphoid follicles was associated with severe loss of activation-induced cytidine deaminase (AID), a Nef-targeted DNA-editing enzyme essential for class switching. Loss of follicular AID correlated with in vivo inactivation of CD40 signaling and formation of long-distance membrane tethers connecting Nef-positive B cells with HIV-infected macrophages. By combining confocal microscopy, videomicroscopy and electron microscopy with standard molecular biology techniques, we demonstrated that macrophages harboring HIV or expressing a chimeric Nef-green-fluorescent protein were capable of transferring Nef-containing cargos to B cells via long-distance, actin-propelled and energy-dependent membrane channels, including tunneling nanotubules. Transfer of Nef to B cells involved a clathrin-dependent pathway that required the guanine nucleotide exchange factor Vav as well as downstream Rho, Rac and Ccd42 small GTPases. This pathway led to Nef-mediated inhibition of CD40-induced AID expression and IgG and IgA class switching. In summary, our findings indicate that HIV evades T cell-dependent IgG and IgA responses by shuttling virus-encoded Ig class switch-suppressing factors from infected macrophages to non-infected B cells via long-range membrane tethers, including tunneling nanotubules.

Safety in quick construction of a long water conveyance channel by shield tunneling method

The new Ishioka Tunnel project (in the second work section) involves the construction of a water conveyance tunnel with an inner diameter of 3.5 m by the slurry shield tunneling method. The project has two characteristics, long-distance excavation and quick construction. The tunnel has a length of 5,000 m without any intermediate shafts. This is one of Japan’s leading long-distance tunnelling projects. Construction including design is carried out quickly over a period of 36 months. Permanent excavation was started in late April 2004. A highest rate of monthly shield advance of 500.85 m was recorded. Construction was carried out rapidly at an average rate of monthly shield advance of 338 m, higher than 320 m as planned. The shield reached the reception shaft approximately two months earlier than scheduled. This paper provides an outline of construction and describes the major techniques applied. (A) This paper was presented at Safety in the underground space - Proceedings of the ITA-AITES 2006 World Tunnel Congress and the 32nd ITA General Assembly, Seoul, Korea, 22-27 April 2006. For the covering abstract see ITRD E129148. “Reprinted with permission from Elsevier”.

Long-distance electron tunneling in proteins

Long-distance tunneling is the major mechanism of electron transfer (ET) in proteins. For a number of years, a major question has been whether specific electron tunneling pathways exist. This question is still debated in the literature, because the pathways are not observed directly, and interpretation of experimental results on ET rates involves ambiguities. The extremely small tunneling interactions are difficult to calculate accurately. Recently, there has been remarkable progress in the area; however, some problems still remain unresolved. The accurate prediction of the absolute rates of long-distance ET reactions and other biological charge-transfer reactions is a particularly pressing issue. The current theoretical calculations indicate that the specific paths do exist in static protein structures. However, the protein motions can result in significant averaging of the spatial tunneling patterns, and it is not clear how accurately subtle quantum interference effects are described by the present theories. The key to resolving these issues is to perform accurate, first-principles calculations of electron tunneling that include the dynamics of the protein. This paper reviews some of theoretical issues of electron tunneling dynamics in inhomogeneous organic media.

Long-distance electron tunneling in proteins

Long-distance electron tunneling in proteins

Reductively activated cleavage of DNA mediated by o, o'-diphenylenehalonium compounds.

o,o'-Diphenylenehalonium (DPH) cations represent a novel class of DNA-affinic compounds characterized by binding constants within the range of 10(5)-10(6) M(-1). The maximum binding capacity of 2-2.5 base pairs per DPH cation and about 30% hypochromic reduction in the optical absorption of DPH cations upon binding to DNA suggest intercalation as a likely binding mode. In a DNA-bound form, DPH cations induce strand breaks upon reduction by radiation-produced electrons in aqueous solutions. In keeping with this mechanism, the cleavage is strongly inhibited by oxygen and is not affected by OH radical scavengers in the bulk. The yields of DPH-mediated base release significantly exceed the yield of base release caused by hydroxyl radical (in the absence of scavenger) in anoxic solutions. The yields are weakly dependent on DNA loading within the range from 5 to 50 base pairs per intercalator, which indicates the ability of excess electrons in DNA to react with a scavenger separated by tens of base pairs from the electron attachment site. The question regarding the mechanism by which the distant reactants reach each other in DNA remains unanswered, although it most likely involves electron hopping rather than a single-step long-distance tunneling. The latter conclusion is based on our finding that the electron affinity of DPH cations does not affect their properties as electron scavengers in DNA as would be expected if the direct long-distance tunneling is involved.

Ab initio calculations of long-distance electron tunneling in organometallic systems of biological origin

Ab initio calculations of long-distance electron tunneling in organometallic systems of biological origin

Ab initio calculations of long-distance electron tunneling in organometallic systems of biological origin

Ab initio calculations of long-distance electron tunneling in organometallic systems of biological origin