967 resultados para Scour at bridges.
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Työ käsittelee Rooman laivaston kehitystä, toimintaa ja osallistumista laajenemispolitiikkaan, jossa Rooma kasvoi kaupunkivaltiosta Välimeren hallitsijaksi. Rooma on aikaisemmissa tutkimuksissa nähty maavaltiona vailla kiinnostusta merenkulkuun. On katsottu, että ainoa merkittävä merisota Rooman historiassa on ensimmäinen puunilaissota (264-241 eKr.) ja että siinäkin roomalaiset (jotka historioitsija Polybius kuvaa vasta-alkajiksi) menestyivät Karthagoa vastaan turvautumalla laskusiltoihin, joiden avulla he saattoivat muuttaa meritaistelun maataisteluksi. Polybiuksen kuvaukseen on aina tähän asti luotettu. On katsottu että Roomalla ei ollut laivastoa ennen ensimmäistä puunilaissotaa ja että Rooma kaikissa sodissaan panosti merisodankäyntiin mahdollisimman vähän. Tämä työ pyrkii kumoamaan nämä käsitykset. Laivasto oli osallisena ja ehdottoman välttämätön kaikissa Rooman laajenemispolitiikan käänteissä. Arkeologian tiedot osoittavat, että ennen ensimmäistä puunilaissotaa Rooma kehittyi ja siitä tuli merkittävä kaupunki nimenomaan kaupankäynnin ja ulkomaisten kontaktien seurauksena. Se ei siis ollut puhdas agraarivaltio. Roomalaisilla oli laivasto jo viimeistään 500-luvulta lähtien eKr. ja sitä käytettiin Rooman laajentaessa valtaansa Italiassa. Näin ollen ensimmäisessä puunilaissodassa läntisen Välimeren herruudesta kilpaili kaksi merivaltiota, Rooma ja Karthago. Toinen puunilaissota (218-201) tunnetaan yleensä Hannibalin tulosta Alppien yli Italiaan, mutta se oli myöskin merkittävä merisota ja karthagolaiset hävisivät sen nimenomaan merellä. Rooma osallistui kilpailuun itäisen Välimeren hallinnasta ja kukisti Makedonian ja Syyrian laivastot, jotka eivät olleet mitenkään Rooman laivaston veroisia. Kaikista Rooman vastustajista Karthagolla olisi ollut suurin mahdollisuus pysäyttää Rooman laivaston voittokulu toisessa puunilaissodassa. Laivastoa käytettiin moniin eri tarkoituksiin. Suuret meritaistelut eivät ole ainoa osoitus laivastojen mukanaolosta ja merkityksestä, vaan on myös otettava huomion sotalaivojen rakenne ja toimintaedellytykset. Sotalaivat oli rakennettu taisteluita varten ja niissä oli hyvin niukasti säilytystilaa. Niiden oli päästävä laskemaan maihin aina kun miehistö tarvitsi vettä, ruokaa ja lepoa. Laivastot saattoivat toimia vain niiden rannikoiden tuntumassa, joiden satamiin ja laskupaikkoihin niillä oli turvallinen pääsy. Roomalaiset olivat hyvin tietoisia tästä. Suuret merentakaiset sotaretket Afrikkaan, Espanjaan, Kreikkaan ja Vähän-Aasian rannikolle perustuivat kaikki siihen, että Rooman laivasto hallitsi purjehdusreittejä ja sopivia laskupaikkoja ja saattoi huolehtia joukkojen ja varusteiden kuljettamisesta kaukana taisteleville armeijoille. Samalla Rooman laivasto kävi itsenäistä sotaa merellä ja haastoi ja kukisti kaikki Välimeren merivaltiot. 130-luvulle eKr. tultaessa se oli lyönyt vihollisensa ja riisunut aseista liittolaisensa; Rooman laivasto hallitsi Välimerta yksin.
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The accuracy of synoptic-based weather forecasting deteriorates rapidly after five days and is not routinely available beyond 10 days. Conversely, climate forecasts are generally not feasible for periods of less than 3 months, resulting in a weather-climate gap. The tropical atmospheric phenomenon known as the Madden-Julian Oscillation (MJO) has a return interval of 30 to 80 days that might partly fill this gap. Our near-global analysis demonstrates that the MJO is a significant phenomenon that can influence daily rainfall patterns, even at higher latitudes, via teleconnections with broadscale mean sea level pressure (MSLP) patterns. These weather states provide a mechanistic basis for an MJO-based forecasting capacity that bridges the weather-climate divide. Knowledge of these tropical and extra-tropical MJO-associated weather states can significantly improve the tactical management of climate-sensitive systems such as agriculture.
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A strain gauge load cell with separate bridges for measurement of the pull and the bending moment in the plane containing the net neck load and pull was developed and fixed in the longitudinal member of an experimental cart. A cart fitted first with pneumatic wheels and then with steel-rimmed wooden wheels was tested on three terrains—tar road, mud road and grassy terrain. Pull vs time and moment vs time records were obtained in each test and analysed. It is found that the bullocks pull the cart rather discontinuously at the low velocities at which these carts normally operate. On the tar road and the grassy terrain, the mean static coefficient of friction is significantly higher for the cart with steelrimmed wooden wheels. The dynamic frictional resistance of the terrain for the cart with steel-rimmed wooden wheels is lower than for the cart with pneumatic wheels so long as the wheels do not dig or sink into the terrain. The fluctuation in the neck load is lower in the cart fitted with pneumatic wheels. Also, the ground-induced low-amplitude high-frequency vibratory load content in the neck load is lower in the cart with pneumatic wheels.
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C llH22 N 30 + . C2H302, orthorhombic, P2~2~2~, a = 5.511(2), b = 14.588(4), c = 21.109 (4)A, Z = 4. The structure has been solved using MULTAN and refined to R = 0.079 for 993 observed reflections. The fully extended lysine side chain in the molecule is staggered between the main-chain amino and carbonyl groups. The dipeptide molecules in the crystal structure are arranged in twofold helices centred on 21 screw axes. These helices are interconnected through interactions involving the acetate and the side-chain amino groups. Each acetate group bridges two adjacent side-chain amino groups, related by an a translation, giving rise to an infinitely long chain of alternating negatively charged carboxylate and positively charged amino groups.
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The isolation and characterization of the products formed during the irreversible thermal denaturation of enzyme RNAase-A are described. RNAase-A, when maintained in aqueous solution at pH 7.0 and 70° for 2 h, gives soluble products which have been fractionated by gel filtration on Sephadex G-75 into four components. These components are designated RNAase-At1, RNAase-At2, RNAase-At3 and RNAase-At4 according to the order of their elution from Sephadex G-75. RNAase-At4 shows the same specific activity towards yeast RNA as native RNAase-A and is virtually indistinguishable from it by the physical methods employed. However, chromatography on CM-cellulose separates it into three components that show the same u.v. spectra and specific activity towards yeast RNA as native RNAase-A. RNAase-At1, RNAase-At2and RNAase-At3 are all structurally altered derivatives of RNAase-A and they exhibit low specific activity (5–10%) towards yeast RNA. In the presence of added S-protein, all these derivatives show greatly enhanced enzymic activity. RNAase-At1 and RNAase-At2 are polymers, covalently crosslinked by intermolecular disulfide bridges; whereas RNAase-At3 is a monomer. Physical studies such as 1H-n.m.r., sedimentation analysis, u.v. absorption spectra and CD spectra reveal that RNAase-At3 is a unfolded derivative of RNAase-A. However, it is seen to possess sufficient residual structure which gives rise to a low but easily detectable enzymic activity.
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The experimental results of delay time of a vacuum gap triggered by an exploding wire plasma have been reported. It consists of explosion delay time and propagation delay time. The explosion delay time has been found to be dependent on the parameters of the exploding wire and the exploding wire circuit and is independent of vacuum gap configuration. The propagation delay time depends on the properties of the exploding wire plasma and vacuum gap parameters such as the number of injection slots, gap spacing, gap polarity, etc. In the absence of prebreakdown current in the vacuum gap, the breakdown can be initiated only after the plasma completely bridges the gap spacing. Under this specific condition, it has been shown that the delay time data can be used to calculate the plasma velocity.
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Octahedrally coordinated CoII and MoIV species are present on the surfaces of sulfided Co-Mo-Al2O3 catalysts used for hydrodesulfurization. They were characterized by XPE, EXAFS and XANES data. An excess of sulfur in the surface species can be explained in terms of the presence of S[stack 22 ] ions. Disulfide bridges could play a role in the hydrodesulfurization.
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In order to assess the structural reliability of bridges, an accurate and cost effective Non-Destructive Evaluation (NDE) technology is required to ensure their safe and reliable operation. Over 60% of the Australian National Highway System is prestressed concrete (PSC) bridges according to the Bureau of Transport and Communication Economics (1997). Most of the in-service bridges are more than 30 years old and may experience a heavier traffic load than their original intended level. Use of Ultrasonic waves is continuously increasing for (NDE) and Structural Health Monitoring (SHM) in civil, aerospace, electrical, mechanical applications. Ultrasonic Lamb waves are becoming more popular for NDE because it can propagate long distance and reach hidden regions with less energy loses. The purpose of this study is to numerically quantify prestress force (PSF) of (PSC) beam using the fundamental theory of acoustic-elasticity. A three-dimension finite element modelling approach is set up to perform parametric studies in order to better understand how the lamb wave propagation in PSC beam is affected by changing in the PSF level. Results from acoustic-elastic measurement on prestressed beam are presented, showing the feasibility of the lamb wave for PSF evaluation in PSC bridges.
Resumo:
C llH22 N 30 + . C2H302, orthorhombic, P2~2~2~, a = 5.511(2), b = 14.588(4), c = 21.109 (4)A, Z = 4. The structure has been solved using MULTAN and refined to R = 0.079 for 993 observed reflections. The fully extended lysine side chain in the molecule is staggered between the main-chain amino and carbonyl groups. The dipeptide molecules in the crystal structure are arranged in twofold helices centred on 21 screw axes. These helices are interconnected through interactions involving the acetate and the side-chain amino groups. Each acetate group bridges two adjacent side-chain amino groups, related by an a translation, giving rise to an infinitely long chain of alternating negatively charged carboxylate and positively charged amino groups.
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We study integral representations of Gaussian processes with a pre-specified law in terms of other Gaussian processes. The dissertation consists of an introduction and of four research articles. In the introduction, we provide an overview about Volterra Gaussian processes in general, and fractional Brownian motion in particular. In the first article, we derive a finite interval integral transformation, which changes fractional Brownian motion with a given Hurst index into fractional Brownian motion with an other Hurst index. Based on this transformation, we construct a prelimit which formally converges to an analogous, infinite interval integral transformation. In the second article, we prove this convergence rigorously and show that the infinite interval transformation is a direct consequence of the finite interval transformation. In the third article, we consider general Volterra Gaussian processes. We derive measure-preserving transformations of these processes and their inherently related bridges. Also, as a related result, we obtain a Fourier-Laguerre series expansion for the first Wiener chaos of a Gaussian martingale. In the fourth article, we derive a class of ergodic transformations of self-similar Volterra Gaussian processes.
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Wheat is at peak quality soon after harvest. Subsequently, diverse biota use wheat as a resource in storage, including insects and mycotoxin-producing fungi. Transportation networks for stored grain are crucial to food security and provide a model system for an analysis of the population structure, evolution, and dispersal of biota in networks. We evaluated the structure of rail networks for grain transport in the United States and Eastern Australia to identify the shortest paths for the anthropogenic dispersal of pests and mycotoxins, as well as the major sources, sinks, and bridges for movement. We found important differences in the risk profile in these two countries and identified priority control points for sampling, detection, and management. An understanding of these key locations and roles within the network is a new type of basic research result in postharvest science and will provide insights for the integrated pest management of high-risk subpopulations, such as pesticide-resistant insect pests.
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Neurotrophic factors (NTFs) are secreted proteins which promote the survival of neurons, formation and maintenance of neuronal contacts and regulate synaptic plasticity. NTFs are also potential drug candidates for the treatment of neurodegenerative diseases. Parkinson’s disease (PD) is mainly caused by the degeneration of midbrain dopaminergic neurons. Current therapies for PD do not stop the neurodegeneration or repair the affected neurons. Thus, search of novel neurotrophic factors for midbrain dopaminergic neurons, which could also be used as therapeutic proteins, is highly warranted. In the present study, we identified and characterized a novel protein named conserved dopamine neurotrophic factor (CDNF), a homologous protein to mesencephalic astrocyte-derived neurotrophic factor (MANF). Others have shown that MANF supports the survival of embryonic midbrain dopaminergic neurons in vitro, and protects cultured cells against endoplasmic reticulum (ER) stress. CDNF and MANF form a novel evolutionary conserved protein family with characteristic eight conserved cysteine residues in their primary structure. The vertebrates have CDNF and MANF encoding genes, whereas the invertebrates, including Drosophila and Caenorhabditis have a single homologous CDNF/MANF gene. In this study we show that CDNF and MANF are secreted proteins. They are widely expressed in the mammalian brain, including the midbrain and striatum, and in several non-neuronal tissues. We expressed and purified recombinant human CDNF and MANF proteins, and tested the neurotrophic activity of CDNF on midbrain dopaminergic neurons using a 6-hydroxydopamine (6-OHDA) rat model of PD. In this model, a single intrastriatal injection of CDNF protected midbrain dopaminergic neurons and striatal dopaminergic fibers from the 6-OHDA toxicity. Importantly, an intrastriatal injection of CDNF also restored the functional activity of the nigrostriatal dopaminergic system when given after the striatal 6-OHDA lesion. Thus, our study shows that CDNF is a potential novel therapeutic protein for the treatment of PD. In order to elucidate the molecular mechanisms of CDNF and MANF activity, we resolved their crystal structure. CDNF and MANF proteins have two domains; an amino (N)-terminal saposin-like domain and a presumably unfolded carboxy (C)-terminal domain. The saposin-like domain, which is formed by five α-helices and stabilized by three intradomain disulphide bridges, may bind to lipids or membranes. The C-terminal domain contains an internal cysteine bridge in a CXXC motif similar to that of thiol/disulphide oxidoreductases and isomerases, and may thus facilitate protein folding in the ER. Our studies suggest that CDNF and MANF are novel potential therapeutic proteins for the treatment of neurodegenerative diseases. Future studies will reveal the neurotrophic and cytoprotective mechanisms of CDNF and MANF in more detail.
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Molecular dynamics simulations have been carried out on all the jacalin-carbohydrate complexes of known structure, models of unliganded molecules derived from the complexes and also models of relevant complexes where X-ray structures are not available. Results of the simulations and the available crystal structures involving jacalin permit delineation of the relatively rigid and flexible regions of the molecule and the dynamical variability of the hydrogen bonds involved in stabilizing the structure. Local flexibility appears to be related to solvent accessibility. Hydrogen bonds involving side chains and water bridges involving buried water molecules appear to be important in the stabilization of loop structures. The lectin-carbohydrate interactions observed in crystal structures, the average parameters pertaining to them derived from simulations, energetic contribution of the stacking residue estimated from quantum mechanical calculations, and the scatter of the locations of carbohydrate and carbohydrate-binding residues are consistent with the known thermodynamic parameters of jacalin-carbohydrate interactions. The simulations, along with X-ray results, provide a fuller picture of carbohydrate binding by jacalin than provided by crystallographic analysis alone. The simulations confirm that in the unliganded structures water molecules tend to occupy the positions occupied by carbohydrate oxygens in the lectin-carbohydrate complexes. Population distributions in simulations of the free lectin, the ligands, and the complexes indicate a combination of conformational selection and induced fit. Proteins 2009; 77:760-777.
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Two new neutral copper-azido polymers [Cu-3(N-3)(6)(tmen)(2)](n)(1)and [Cu-6(N-3)(12)(deen)(2)](n) (2) [tmen = N,N,N, N-tetramethylethylenediamine and deen = N,N-diethylethylenediamine] have been synthesized by using lower molar equivalents of the chelating diamine ligands with Cu(NO3)(2)center dot 3H(2)O and an excess of NaN3. The single crystal X-ray structure shows that in the basic unit of the 1D complex 1, the three Cu-II ions are linked by double end-on azido bridges with Cu-N-EO-Cu angles on both sides of the magnetic exchange critical angle of 108 degrees. Complex 2 is a 3D framework of a basic u-6 cluster. Cryomagnetic susceptibility measurements over a wide range of temperature exhibit dominant ferromagnetic behavior in both the complexes. Density functional theory calculations (B3LYP functional) have been performed on the trinuclear unit to provide a qualitative theoretical interpretation of the overall ferromagnetic behavior shown by the complex 1.
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A versatile affinity matrix in which the ligand of interest is linked to the matrix through a connector arm containing a disulfide bond is described. It can be synthesized from any amino-substituted matrix by successive reaction with 2-imino-thio-lane, 5, 5'-dithiobis(2-nitrobenzoic acid), and a thiol derivative of the ligand of choice. The repertoire of ligands can be significantly increased by the appropriate use of avidin-biotin bridges. After adsorption of the material to be fractionated, elution can be effected by reducing the disulfide bond in the connector arm with dithiothreitol. Examples of the preparation and use of various affinity matrices based on amino-substituted Sepharose 6MB are given. One involves the immobilization of the Fab' fragment of a monoclonal antibody against Aspergillus oryzae β-galactosidase and the specific binding of that enzyme to the resulting immunoaffinity matrix. Another involves the immobilization of N-biotinyl-2-thioethylamine followed by complex formation with avidin. The resulting avidin-substituted matrix was used for the selective adsorption and subsequent recovery of mouse hybridoma cells producing anti-avidin antibodies. By further complexing the avidin-substituted matrix with appropriate biotinylated antigens, it should be possible to fractionate cells producing antibodies against a variety of antigens.