Type Of Barrier Research Articles

The (Paleo)Geography of Evolution: Making Sense of Changing Biology and Changing Continents

Abstract During the voyage of the H.M.S. Beagle, Charles Darwin quickly realized that geographic isolation led to significant changes in the adaptation of local flora and fauna (Darwin 1859). Genetic isolation is one of the well-known mechanisms by which adaptation (allopatric speciation) can occur (Palumbi, Annu Rev Ecol Syst 25:547–72, 1994; Ricklefs, J Avian Biol 33:207–11, 2002; Burns et al., Evolution 56:1240–52, 2002; Hendry et al., Science 290:516–8, 2009). Evolutionary changes can also occur when landmasses converge or are “bridged.” An important and relatively recent (Pliocene Epoch) example known as the “Great American Biotic Interchange” allowed for the migration of previously isolated species into new ecological niches between North and South America (Webb 1985, Ann Mo Bot Gard 93:245–57, 2006; Kirby and MacFadden, Palaeogeogr Palaeoclimatol Palaeoecol 228:193–202, 2005). Geographic isolation (vicariance) or geographic merging (geodispersal) can occur for a variety of reasons (sea level rise, splitting of continents, mountain building). In addition, the growth of a large supercontinent (or breakup) may change the climatic zonation on the globe and form a different type of barrier for species migration. This short review paper focuses on changing paleogeography throughout the Phanerozoic and the close ties between paleogeography and the evolutionary history of life on Earth.

Structural features of transversal barrier in central channel of nuclear pore complex

The most important entity of the selective behavior of the nuclear pore complex (NPC) is considered to be the matter called “barrier,” “meshwork” or “sieve.” This part of NPC has not been well elucidated by using electron microscopy methods to date. In the present study, we demonstrated the presence of a coherent transversal barrier in the central channel of NPC, using high resolution transmission electron microscopy. It was found that the barrier is located in the middle of the central channel, i.e. at the level where the outer and inner nuclear membranes fuse. The thickness of this layer is evidently different in various NPCs and usually varies between 20 and 30nm and its diameter is approximately 40nm. The cytoplasmic and nuclear surfaces of the barrier are roughly parallel and plane. Moreover we suggest that the barrier may not be interrupted by any channel(s), at least not with a diameter above 10nm. Further various appearances of the central channel with different particles were observed, presumably cargos and karyopherins captured in transit. A different type of central channel barrier with lipid bilayer membrane-like appearance is also discussed.

Noise Reduction Effect of Low Barriers Installed Adjacent to Rails

Recently, complaints regarding railway noise have increased from residents living in high-rise buildings facing railway tracks. However, reducing noise for locations high above the tracks with conventional noise barriers is difficult, because the noise sources are directly visible from these elevated positions. This paper investigated the effect on noise of low barriers installed adjacent to rails. It was evident through acoustic tests using scale models and field tests on existing railways that this type of noise barrier is able to reduce noise even in locations high above the track. Furthermore, a prediction model of the effect of these noise barriers was proposed based on the results of the field tests.

OPTICAL CHARACTERIZATION OF 50 Hz ATMOSPHERIC PRESSURE SINGLE DIELECTRIC BARRIER DISCHARGE PLASMA

A low frequency (50Hz) dielectric barrier discharge (DBD) system with a single dielectric cover on copper coil anode is designed to generate and sustain the micro-discharge plasma which is very practical for material processing applications. The DBD system is powered by a high tension ac source consisting of a conventional step up transformer and variac. The dielectric barriers (quartz and glass) between the conducting electrodes appreciably influences the discharge plasma characterized by optical emission spectroscopy technique. Using intensity ratio method, the electron temperature and electron number density are determined from recorded spectra as function of ac input voltage, type and thickness of dielectric barrier and inter-electrode gap. It is observed that both the electron temperature and electron number density increase with the increase in ac input voltage and r/d ratio, while a decreasing trend is observed with increase in inter-electrode gap.

Structural and physical properties of microwave synthesized orthorhombic perovskite erbium chromite ErCrO3

Abstract Rare-earth chromite ErCrO 3 powder was synthesized from metal nitrate precursors using microwave synthesis. (Micro-) structural characterizations were performed using X-ray diffraction, Rietveld refinement, High Resolution Transmission Electron Microscopy and Electron Micro-Diffraction. Magnetization vs. temperature measurements revealed anti-ferromagnetism with T Neel ≈ 135 K. An anti-ferrimagnetic moment of ≈0.4 μ B was determined from magnetization vs. applied field measurements. Temperature dependent impedance spectroscopy (IS) indicated 3 dielectric relaxation processes: electrode interface, grain boundary and bulk. The intrinsic bulk activation energy was found to be 0.27 eV and the dielectric permittivity ɛ r was ≈23 in excellent agreement with Clausius–Mossotti predictions and showed no perceptible temperature dependence. This and the low ɛ r value suggested that ErCrO 3 is a dielectric rather than ferroelectric compound. IS measurements with applied dc bias revealed the signs of an unconventional type of Schottky barrier at the metallic Au electrode/ceramic ErCrO 3 interface.

Order bounds for second derivative approximations

Rational approximations to the exponential function with denominator (1−λz−μz 2)s arise as stability functions of second derivative generalizations of Runge–Kutta methods. The purpose of this paper is to derive order barriers for approximations of this and related forms. Although some of these barriers are already known, we will analyse them in a new way. Order arrows were originally proposed as a complement to order stars for establishing barriers for A-stable methods but they are shown also to be a powerful tool for analysing the type of order barrier considered in this paper.

Influence of randomly distributed geofibers on the integrity of clay-based landfill covers: a centrifuge study

ABSTRACT: The main objective of this paper is to examine the influence of discrete and randomly distributed geofiber reinforcement on the integrity of clay-based landfill covers subjected to differential settlements in a geotechnical centrifuge. A series of centrifuge tests was performed on model clay-based landfill covers with and without geofiber reinforcement at 40 gravities. A hydraulic-based differential settlement simulator was used to induce continuous differential settlements with a distortion level up to 0.125. The type and moist-compacted conditions of the soil barrier and fiber content were held constant, and the thickness of the soil barrier and the fiber type are varied. The performance of the soil barrier with and without geofiber reinforcement having an overburden pressure equivalent to that of landfill covers was monitored by measuring water breakthrough at the onset of differential settlement. With an increase in the thickness of the geofiber-reinforced soil barrier, and with the provision of an overburden equivalent to that of landfill cover, the integrity of the geofiber-reinforced soil barrier was found to be retained, even after inducing a distortion level of 0.125. Analysis and interpretation of the test results indicate the significant potential for geofiber reinforcement to decrease and to retard soil crack potential in a discrete and randomly distributed soil barrier reinforced with geofibers, while retaining its hydraulic performance.

Proximity effect in electron-doped cuprate Josephson junctions

We study the proximity effect in Josephson junctions made of electron-doped cuprates Pr2–xCexCuO4 (PCCO). With superconducting electrodes at a fixed doping x = 0.15, we explore the variation of the Josephson coupling with the doping and the thickness of the barrier. We observe Josephson coupling for any type of barrier: antiferromagnetic (AF) metal, AF insulator, or paramagnetic metal. For an x = 0.05 barrier, we can estimate the normal coherence length, ξn = 12 ± 3 nm. Comparing this value with the theoretical prediction, ξn,max = 4.5 nm, we conclude that the proximity effect through a barrier of PCCO x = 0.05 is stronger than expected.

Internal and external electron transport barriers in the RFX-mod reversed field pinch

An interesting result of magnetic chaos reduction in RFX-mod high current discharges is the development of strong electron transport barriers. An internal heat and particle transport barrier is formed when a bifurcation process changes the magnetic configuration into a helical equilibrium and chaos reduction follows, together with the formation of a null in the q shear. Strong temperature gradients develop, corresponding to a decreased thermal and particle transport. Turbulence analysis shows that the large electron temperature gradients are limited by the onset of micro-tearing modes, in addition to residual magnetic chaos. A new type of electron transport barrier with strong temperature gradients develops more externally (r/a = 0.8) accompanied by a 30% improvement of the global confinement time. The mechanism responsible for the formation of such a barrier is still unknown but it is likely associated with a local reduction of magnetic chaos. These external barriers develop primarily in situations of well-conditioned walls so that they might be regarded as attempts towards an L–H transition. Both types of barriers occur in high-current low-collisionality regimes. Analogies with tokamak and stellarators are discussed.

Feed barrier design affects behaviour and physiology in goats

Among other things, feed barrier design for goats can differ with regard to ease of leaving, backward view, and presence of physical separation. The aim of our study was to investigate whether the type of feed barrier influences agonistic behaviour and stress. The study involved 55 adult non-lactating female goats of several Swiss dairy breeds. Three groups of 14 and one group of 13 goats (2 horned, 2 hornless) were rotated between four pens with different types of feed barriers (neck rail, metal palisade, wooden palisade, diagonal fence). Each group stayed four weeks with each feed barrier type. Social interactions in the feeding area were recorded for 12 h per group and feed barrier type (1.5 h on 8 days each group) and corrected by the average number of feeding animals. Heart rate and heart rate variability were measured in lying and undisturbed goats to evaluate chronic stress independently of actual levels of motor activity and agonistic interactions. Individual faecal samples were taken for analysis of the concentration of cortisol metabolites. Data were analysed by linear mixed-effect models taking into account interactions between the type of feed barrier and presence of horns. Hornless goats displayed the most agonistic behaviour with physical contact in the feeding area of the neck rail and diagonal fence and least in the feeding area of the metal palisade, whereas goats with horns showed much fewer interactions of this behaviour; thus, only slight differences depending on the type of feed barrier were found ( p < 0.0001). Hornless goats also displayed the most agonistic behaviour leading to displacements from the feeding place with the neck rail, whereas for horned goats the effect of the type of feed barrier was less distinctive ( p = 0.0009). The duration of leaving the feed barrier was longest with the diagonal fence for both horned and hornless goats, while the horned goats also took longer to leave the neck rail compared to the palisades ( p = 0.0194). The interaction of type of feed barrier and presence of horns showed an effect on heart rate variability in the parameters root mean square of successive interbeat interval differences (RMSSD; p = 0.0355), RMSSD in relation to the standard deviation of all interbeat intervals (RMSSD/SDNN; p = 0.0215) and determinism ( p = 0.0364). The metal palisade distinctly differed from the diagonal fence as well as from the neck rail in hornless goats, with highest heart rate variability (HRV) and thus lowest levels of chronic stress in the pen with the metal palisade. Independently of horn status, the concentration of faecal cortisol metabolites tended to be lowest for goats in the pen with the metal palisade ( p = 0.0600). In summary, the metal palisade showed the most beneficial effects, especially on hornless goats. In contrast to the neck rail and the diagonal fence, both types of palisades seem to be recommendable for feeding goats in loose housing.

Do Navigators’ Estimates of Navigation Intensity Predict Navigation Time for Cancer Care?

Patient navigation requires that patient load be equitably distributed. We examined whether navigators could predict the relative amount of time needed by different patients for navigation. Analysis of 139 breast and colorectal cancer patients randomized to the navigation arm of a trial evaluating the effectiveness of navigation. Navigators completed a one-item scale estimating how much navigation time patients were likely to require. Participants were mostly females (89.2%) with breast cancer (83.4%); barriers to cancer care were insurance difficulties (26.6%), social support (18.0%), and transportation (14.4%). Navigator baseline estimates of navigation intensity predicted total navigation time, independent of patient characteristics. The total number of barriers, rather than any specific type of barrier, predicted increased navigator time, with a 16% increase for each barrier. Navigators' estimate of intensity independently predicts navigation time for cancer patients. Findings have implications for assigning navigator case loads.

Simultaneous Dual Level Creation for Games

Recent research has shown that it is possible to design fitness functions, based on dynamic programming, that allow evolutionary computation to automatically generate level maps for games. In this study levels with multiple types of barriers are automatically designed. The levels are designed under the assumption that there are two agent types and that at least one agent type may ignore one type of barrier. A specification of multiple types of barriers thus creates two mazes, one for each agent type, that coexist in the same space. The design of these dual mazes is accomplished using different fitness functions for two mazes simultaneously. For example, this permits a level with a single long winding path for an agent that cannot walk through one type of barrier coexisting with a low-diameter maze with more complex connectivity for an agent that cannot cross another type of barrier. This study explores two representations for game levels with multiple barrier types using four different pairs of fitness functions. The system is shown to be able to design dual mazes whose properties depend substantially on both the choice of fitness function and representation used.

Seismic waves and seismic barriers

The basic idea of seismic barrier is to protect an area occupied by a building or a group of buildings from seismic waves. Depending on nature of seismic waves that are most probable in a specific region, different kinds of seismic barriers are suggested. For example, vertical barriers resembling a wall in a soil can protect from Rayleigh and bulk waves. The FEM simulation reveals that to be effective, such a barrier should be (i) composed of layers with contrast physical properties allowing “trapping” of the wave energy inside some of the layers, and (ii) depth of the barrier should be comparable or greater than the considered seismic wave length. Another type of seismic barrier represents a relatively thin surface layer that prevents some types of surface seismic waves from propagating. The ideas for these barriers are based on one Chadwick’s result concerning non-propagation condition for Rayleigh waves in a clamped half-space, and Love’s theorem that describes condition of non-existence for Love waves. The numerical simulations reveal that to be effective the length of the horizontal barriers should be comparable to the typical wavelength.

Research on Design of Neotype Wire Rope Safety Barrier

In order to research and develop a suitable wire rope safety barrier for our country, which will be used as the highway flexible safety barrier for two model demonstrative project of science and technology of Changsha-Xiangtan Highway, the paper presents a new type of wire rope safety barrier, by way of designing the shape of the post, the diameter of the rope, the arrangement and the number of ropes etc., on the basis of the form of structure of the most advanced foreign existing wire rope safety barrier — BRIFEN. The first part is devoted to prove the reliability of the finite element simulation, by comparing the simulation results of the finite element model of BRIFEN with the collision test data, which is published by U.S. Federal Highway Administration. After discussion and analysis, the neotype wire rope safety barrier, which has many posts with C-shaped cross section and 5 ropes, is invented with the post equivalent method. The finite element model of the neotype barrier is established and simulated to determine the dimension of the post. The simulation results achieve the design objective that the maximum dynamic deformation is less than 1.2m when the barrier is impacted by the 10 tons of bus in the speed of 60 kilometers per hour, and provide an important reference for Vehicle Crash Test.

Theoretical Consideration of Wetting on a Cylindrical Pillar Defect: Pinning Energy and Penetrating Phenomena

Wetting on a cylindrical pillar defect is discussed in terms of the free-energy difference ΔG. Wetting is divided into wetting on a flat surface, a pinning effect at the apex of the defect, and wetting on a pillar wall. First, we confirmed that ΔG between before and after ideal wetting on a flat surface can be derived as a function of the contact angle θ in which the free-energy minimum is obtained as the equilibrium contact angle θ(eq) described by Young's and Wenzel's laws. Second, the pinning effect at the apex in the cross section of the pillar defect is discussed in ΔG, where the pinning effect is shown to originate from the energy barrier by an increase in the air-liquid interfacial area of a pinned droplet induced by deformation. Next, the ΔG profiles of wetting on the pillar wall are drawn based on the theory of Carroll (Carroll, B. J. J. Colloid Interface Sci.1976, 57, 488-495) to better understand the ΔG profile during penetration. Differences in the manner of wetting between the wetting state on a flat surface and the pillar wall are reflected in ΔG. Finally, penetration of a droplet into a pillar defect is comprehensively discussed on the basis of wetting on a flat surface and a pillar wall. If we consider a simple manner of penetration, another type of energy barrier resulting from an anomalous deformation of the air-liquid interface of the penetrating droplet can be theoretically suggested. Consequently, two types of energy barrier are found. These energy barriers should play a significant role in the hysteresis of wetting, the liquid-repellent Cassie-Baxter state (CB), and the CB-Wenzel wetting transition on a microtextured surface.

Kinetics of Membrane Permeabilization by Human Antimicrobial Peptide LL-37

The molecular mechanism of membrane permeabilization by antimicrobial peptides (AMPs) has been an active field of research. There are suggestions that different AMPs might act with different mechanisms. One example used to support this hypothesis is LL-37 which was found by two independent studies that the helical peptide adsorbs to the membrane with its helical axis parallel to the membrane. Base on this result, it was concluded that LL-37 does not form pores, unlike many well studied AMPs, such as magainin. We have recently found that this result was due to the impediment of peptide rotation in the multilayers, because LL-37 is longer than the membrane thickness. We have detected pores by LL-37 in swollen multilayers by neutron in-plane scattering and also found that the helices were oriented normal to the membrane, exactly like magainin. We would like to know if the pore formation by long helices may exhibit kinetic potential barriers. By observing individual giant unilamellar vesicles (GUVs), we found that the pores are stable and of finite size consistent with neutron measurement. However, sometimes the pores reduce their sizes in time, allowing only partial leakage of large dye molecules, while small dye molecules completely leaked out. Both the formation of the pores and change of pore size occur stochastically as if there are potential barriers for each type of event. We also used the method of aspiration to correlate the leakage with the change of aspiration protrusion length. The maximum protrusion length before pore formation depends on the peptide concentration, exhibiting yet another type of potential barrier.

The Main Directives of the Process of Unification Commercial Contracts Law in Europe – The Path for Serbian National Private Law Legislation

International character of economic relations is in discrepancy with the limitation of their national legislation. During the whole last century and especially since World War II enormous grow of international trade created inevitable need for attempts of harmonization and even unification of commercial contract law. The unknown law of the different countries and contradictions and discrepancies among the legal families of common and civil law were the big risk which increased enormously transactional costs of the business arrangements in the trade between nations, especially in the trade among European countries. Existed varieties of contract law in European countries become a special type of non-tariff barrier which opposed to the free flow of goods, services, persons and capital and at the end decreased wealth. Legal scholars, practitioners and lawyers in Europe realized the need for harmonizing contract law in a way to create and adopt uniform rules for commercial activities, in one word to Europeanize the law of commercial contracts and create uniform legal environments. The problem of appropriate method of the unification divides many academics between idea of codification method in the way of legislation or by so called “creeping” method which uses common customs and practices in order to create unified system of generally accepted principles of commercial contracts law (lex mercatoria). In spite the first stages of unification was realized by way of directives, such as the law of consumer contracts, later on creation of the body of European competition law, emanation of the idea of Europeanized contract law took another direction emanating itself through the legal instrument of the so called “soft law” such as Principles of European Contract Law (PECL) created by the Commission of European Contract Law (so called Lando Commission). The Lando Principles which in their 17 Chapters content the common core of the all national legal systems of European countries are nowadays regarded as the nucleus of a European Civil Code. In Serbian attempts to join the EU it is the process of Europeanizing its commercial contract law which creating a challenge which obstacles should be overcome thankfully to the healthy roots of Serbian Law of Obligations-de lege lata which is the best part of Serbian positive private law founded on European legal tradition.

Laboratory investigation of hydraulic performance of silt screens

Silt screen is a type of flexible barrier that has been widely deployed for the purpose of sediment containment in an aquatic environment. Yet, its working mechanism is still largely unknown. In this study, the authors presented the findings of an investigation of the hydraulic performance of silt screen using Particles Imaging Velocimetry (PIV) technique.The experiments were conducted in a 30 cm-wide flume, with a silt screen spanned across the whole width, normal to the flow. Three average flow velocities, U0 of 0.5 m/s, 0.1 m/s, and 0.2 m/s and different values of the penetration ratio (the ration between screen's penetration depth and flow depth) were simulated in the experiments. PIV images of the flow approaching the screen and that at the lee side of the silt screen were captured in the vertical mid-plane of the flume. The images were then processed, and analyzed to determine the velocity distribution, turbulence characteristics and streamlines patterns of the flow in the vicinity of the silt screen. Preliminary results showed that underflow through the gap between silt screen's lower end and the flume's bottom could be large. The experimental results also suggested a distinct change of flow patterns with the formation of recirculation areas at both sides of the screen. This paper attempts to elucidate the hydraulic performance of silt-screen in response to the magnitude of the environmental flow and different scenarios of screen configurations.

CMP for Cu Interconnect with Advanced Barrier Materials

In this paper, we discuss CMP technology for Cu interconnects with a Co seed enhancement liner (SEL) and Cu with a Ru barrier. Typical forms of galvanic corrosion for each type of barrier are also reviewed. To meet CMP performance requirements, specific polishing and cleaning processes for each CMP step were developed. The overall performance of CMP was evaluated using a variety of patterned wafers, and results are presented.

Client perceived barriers to change of the construction process

PurposeThe purpose of this paper is to identify client‐perceived barriers to a change towards increased client influence on the end result of the construction process. Additionally, the variables of size of clients' markets and the extent of external project management are investigated in order to see how they influence the perceptions concerning important barriers to change.Design/methodology/approachEmpirical data were collected through a survey responded to by 87 Swedish construction clients.FindingsIdentified barriers are divided into three types: attitudinal, industrial and institutional. Attitudinal barriers (adversarial attitudes, lack of ethics and morality, focus on projects instead of processes and a short‐term focus) and industrial barriers (traditional organization of the construction process, conservative industry culture, industry structure and traditional production processes) are perceived to be important, whereas institutional barriers (standard contracts, laws and traditional procurement procedures) are not perceived to be critical. Each different type of barrier is tested against the use of internal or external project management and the sphere of activity of the client. Attitudinal barriers are perceived as being more critical by clients using external project management. “Nearness” in terms of the sphere of activity (e.g. how large is the client's market?) also has an effect on how clients perceive the barriers. Locally, active clients do not consider attitudinal barriers to be as influential on the end result of the construction process as nationally active clients.Research limitations/implicationsSince the empirical results are based on data collected only from Swedish clients, international generalizations should be made with caution.Practical implicationsClients wishing to act as change agents need to be aware that their use of internal versus external project management affects their chances to influence the other construction actors and implement change and innovation. Large national and international client organizations, which due to their size have significant opportunities to influence the industry, rely heavily on external project management, which may hamper their change agent role. Hence, such clients should make careful and purposeful selections of project management companies. Another more influential alternative is to strengthen their organisation and rely less on external project management.Originality/valueThis paper presents a unique investigation of the connections between the use of internal/external project management and perceived barriers to change.