The dynamics of magnetically trapped fluids. I - Implications for umbral dots and penumbral grains

A study of the magnetohydrodynamic system in which a nonmagnetized fluid in a gravitational field is surrounded by a fluid carrying a vertical magnetic field is presented. It is pointed out that this study can throw some light on the fine-structural features of a sunspot. The equilibrium configuration of the field-free fluid is a tapering column ending at an apex. The regions away form the apex can be studied by the slender flux tube approximation. A scheme developed to treat the apex indicates that, just below the apex, the radius of the tapering column opens up with a 3/2 power dependence on the depth below the apex. If the internal pressure of the field-free fluid is increased, the apex rises, and a static equilibrium may not be possible beyond a limit if the magnetic pressure drops quickly above a certain height. The nature of steady-flow solutions beyond this limit is investigated. Under conditions inside a sunspot, a column of field-free gas is found to rise with a velocity of about 100 km/hr. If umbral dots and penumbral grains are interpreted as regions where the field-free gas ultimately emerges, a very natural explanation of most of their observed properties is obtained.

Hirsitaloteollisuuden kehityshaasteet

Pientalobarometri 2/2008 ennustaa omakotitalorakentamisen jatkavan laskuaan rakentamiskustannusten kasvamisesta, kaavoituksesta, tonttitarjonnasta ja talouden tilasta johtuen. Kustannusten odotetaan edelleen nousevan mm. energia­tehokkuuden kohentumisen myötä. Työ- ja elinkeinoministeriön Puutalojen ja rakennuspuusepäntuotteiden valmistus –toimialaraportissa 2008 oletetaan myös, että lämmöneristysvaatimukset ovat saattaneet lisätä massiivihirsitalojen kysyntää, koska uusien määräysten voimaantulon jälkeen niitä ei mahdollisesti enää tehdä. Kehityksen voidaan olettaa johtavan rakennusten koon ja varustetason järkevöittämiseen. Oma­koti­talorakentamisen tarpeeksi pientalobarometri laskee 20 000 asuntoaloitusta, mutta toimialaraportissa määrän arvioidaan vuonna 2008 jäävän 12 500 oma­kotitalon aloitukseen. Avaimet käteen –rakentaminen on kasvusuunnassa ja talo­paketit ovat kehittymässä selvemmiksi rakennusosakokonaisuuksiksi. Pientalobarometri kertoo suomalaisten toivovan yksilöllisyyttä. Talotehtaiden toimituksista yksilöllisiä suunnitteluratkaisuja on kolmannes ja tyyppimuunnoksia puolet. Valmisosatalojen osuus asunnoista on noin 68 % ja teollisen hirren osuus valmisosatalojen markkinoista on nyt kutakuinkin samoissa 10 % lukemissa kuin 20 vuotta sitten. Korkeimmillaan teollisen hirren osuus valmisosataloista kävi 17 % tasolla kymmenen vuotta sitten, vuosina 1995 ja 1996. Siporex-, betoni,- tiili- ja harkkotalojen osuus on noussut kahdessakymmenessä vuodessa 4 %:sta 12 %:iin ja precut-talojen osuus 2 %:sta 16 %:iin, kun taas puuelementtien osuus on laskenut 85 %:sta 62 %:iin. Talopaketin keskimääräinen kuluttajahinta on Toimialaraportin mukaan noin 83 000 euroa ja niitä valmistuu vuodessa alle 10 000. Talopakettimarkkinat ovat Pientalobarometrin mukaan vuonna 2008 hieman laskeneet vuosien 2006 ja 2007 huippulukemista alle 800 miljoonan euron. Teollisten hirsivalmistajien liikevaihto laski myös vuodesta 2007 alle 350 miljoonan. Toimialaraportin mukaan puutalojen valmistus työllistää vajaa 4000 henkeä 251 toimipaikassa (2006). Alan liikevaihto vuonna 2006 oli 812 miljoonaa euroa ja viennin arvo 178 miljoonaa euroa. Viennin kasvun todettiin riippuvan hirsitaloteollisuudesta. Viennin kannalta tärkeitä alueita ovat Keski-Eurooppa, Venäjä, Japani ja Pohjoismaat. Puutalojen vienti on Toimialaraportin mukaan kohonnut 90-luvun alun noin 30 miljoonasta yli 200 miljoonaan euroon, josta hirsitalojen viennin arvo ylittää 160 miljoonaa. Tutkimus- ja kehittämiskuluiksi arvioidaan puutalon valmistajilla 0–2 % tuotannon arvosta. Puutalojen mediaanikäyttökate oli Toimialaraportin mukaan vuonna 2006 noin 6 % kun teollisuuden vastaava luku on 10 %. Finnveran tilastointi hirsitalojen kustannusrakenteesta ja kannattavuudesta ei poikkea tästä, vaan hirsitalojen käyttökatteeksi ilmoitetaan 6,4 % ja kokonaistulokseksi 3,4 % vuonna 2007. Toimialaraportin mukaan teollisuuden omavaraisuusaste on noin 43 % kun taas puutaloteollisuuden omavaraisuusaste jää 26,5 %:iin ja hirsitalojen Finnveran mukaan 27,7 %:iin. Hirsitaloja valmistaa Toimialaraportin mukaan noin 150 yritystä. Alan kahden suurimman yrityksen osuus on lähes puolet koko alan liikevaihdosta.

Optimum Design for External Seismic Stability of Geosynthetic Reinforced Soil Walls: Reliability Based Approach

In this paper, an analytical study considering the effect of uncertainties in the seismic analysis of geosynthetic-reinforced soil (GRS) walls is presented. Using limit equilibrium method and assuming sliding wedge failure mechanism, analysis is conducted to evaluate the external stability of GRS walls when subjected to earthquake loads. Target reliability based approach is used to estimate the probability of failure in three modes of failure, viz., sliding, bearing, and eccentricity failure. The properties of reinforced backfill, retained backfill, foundation soil, and geosynthetic reinforcement are treated as random variables. In addition, the uncertainties associated with horizontal seismic acceleration and surcharge load acting on the wall are considered. The optimum length of reinforcement needed to maintain the stability against three modes of failure by targeting various component and system reliability indices is obtained. Studies have also been made to study the influence of various parameters on the seismic stability in three failure modes. The results are compared with those given by first-order second moment method and Monte Carlo simulation methods. In the illustrative example, external stability of the two walls, Gould and Valencia walls, subjected to Northridge earthquake is reexamined.

Optimum Design for External Seismic Stability of Geosynthetic Reinforced Soil Walls: Reliability Based Approach

In this paper, an analytical study considering the effect of uncertainties in the seismic analysis of geosynthetic-reinforced soil (GRS) walls is presented. Using limit equilibrium method and assuming sliding wedge failure mechanism, analysis is conducted to evaluate the external stability of GRS walls when subjected to earthquake loads. Target reliability based approach is used to estimate the probability of failure in three modes of failure, viz., sliding, bearing, and eccentricity failure. The properties of reinforced backfill, retained backfill, foundation soil, and geosynthetic reinforcement are treated as random variables. In addition, the uncertainties associated with horizontal seismic acceleration and surcharge load acting on the wall are considered. The optimum length of reinforcement needed to maintain the stability against three modes of failure by targeting various component and system reliability indices is obtained. Studies have also been made to study the influence of various parameters on the seismic stability in three failure modes. The results are compared with those given by first-order second moment method and Monte Carlo simulation methods. In the illustrative example, external stability of the two walls, Gould and Valencia walls, subjected to Northridge earthquake is reexamined.

When sharing becomes a liability: An intellectual capital approach to describing the dichotomy of knowledge protection versus sharing in intra- and interorganizational relationships

The tension created when companies are collaborating with competitors – sometimes termed co-opetition - has been subject of research within the network approach. As companies are collaborating with competitors, they need to simultaneously share and protect knowledge. The opportunistic behavior and learning intent of the partner may be underestimated, and collaboration may involve significant risks of loss of competitive edge. Contrastingly, the central tenet within the Intellectual Capital approach is that knowledge grows as it flows. The person sharing does not lose the knowledge and therefore knowledge has doubled from a company’s point of view. Value is created through the interplay of knowledge flows between and within three forms of intellectual capital: human, structural and relational capital. These are the points of departure for the research conducted in this thesis. The thesis investigates the tension between collaboration and competition through an Intellectual Capital lens, by identifying the actions taken to share and protect knowledge in interorganizational collaborative relationships. More specifically, it explores the tension in knowledge flows aimed at protecting and sharing knowledge, and their effect on the value creation of a company. It is assumed, that as two companies work closely together, the collaborative relationship becomes intertwined between the two partners and the intellectual capital flows of both companies are affected. The research finds that companies commonly protect knowledge also in close and long-term collaborative relationships. The knowledge flows identified are both collaborative and protective, with the result that they sometimes are counteracting and neutralize each other. The thesis contributes to the intellectual capital approach by expanding the understanding of knowledge protection in interorganizational relationships in three ways. First, departing from the research on co-opetition it shifts the focus from the internal view of the company as a repository of intellectual capital onto the collaborative relationships between competing companies. Second, instead of the traditional collaborative and sharing point of departure, it takes a competitive and protective perspective. Third, it identifies the intellectual capital flows as assets or liabilities depending on their effect on the value creation of the company. The actions taken to protect knowledge in an interorganizational relationship may decrease the value created in the company, which would make them liabilities.

Panel Cointegration of Chinese A and B Shares

This paper uses panel unit root and cointegration methods to test the stationarity of the premium on domestic investors’ A shares over foreign investors’ B shares and cointegration between the A and B share prices on the Chinese stock exchanges. We find that the A share price premium is nonstationary until 2001, when the A and B share markets were partially merged, and that the A and B share prices are cointegrated in the panel.Cointegration is more likely to be found for firms in the service sector and for firms that issued B shares recently.

Synthesis and structural aspects of quasicrystals in Mg-Al-Ag system: Mg4Al6Ag

The existence of an icosahedral phase in Mg−Al−Ag is better understood on a crystallographic basis rather than on a quantum structural diagram basis. The quasicrystalline structure is delineated in terms of quasiperiodic arrangement of Pauling triacontahedra, which can be identified in the equilibrium structure. Subtle differences in the electron diffraction patterns have been recorded compared to the ideal quasicrystalline pattern. The misalignment of spots and distortions are better attributed to higher order rational approximate structure than anisotropic phason strain. Ares of diffuse intensity have been related to the ordering among the atoms in the clusters.

A Method for Purifying Bulk Gallium Arsenide by Chemical Vapour Transport

The need for high purity materials for the growth of epitaxial layers of GaAs and the limitations of present source materials are discussed. A for purifying bulk quantitites of GaAs using chemical vapour transport is presented. GaAs is contained in a silica capsule which has a small orifice allow movement of gas between inside and outside. The capsule is contained in a heated tube and hydrogen chloride is used as the transporting agent. Growth rates of 0.1 g/h have been obtained and evidence for the purification is presented along with a discussion of the principles involved. The potentialities of the method for both purification and for the growth of single crystal substrate material are stressed.--AA

Visiting the cell biology of Salmonella infection

Salmonella, a Gram-negative facultative intracellular pathogen is capable of infecting vast array of hosts. The striking ability of Salmonella to overcome every hurdle encountered in the host proves that they are true survivors. In the host, Salmonella infects various cell types and needs to survive and replicate by countering the defense mechanism of the specific cell. In this review, we will summarize the recent insights into the cell biology of Salmonella infection. Here, we will focus on the findings that deal with the specific mechanism of various cell types to control Salmonella infection. Further, the survival strategies of the pathogen in response to the host immunity will also be discussed in detail. Better understanding of the mechanisms by which Salmonella evade the host defense system and establish pathogenesis will be critical in disease management. (C) 2010 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.

Neural network approach for the two-dimensional assignment problem

A neural network approach for solving the two-dimensional assignment problem is proposed. The design of the neural network is discussed and simulation results are presented. The neural network obtains 10-15% lower cost placements on the examples considered, than the adjacent pairwise exchange method.

Analysis of heat and mass transfer during bulk hydraircooling of spherical food products

Hydraircooling is a technique used for precooling food products. In this technique chilled water is sprayed over the food products while cold unsaturated air is blown over them. Hydraircooling combines the advantages of both air- and hydrocooling. The present study is concerned with the analysis of bulk hydraircooling as it occurs in a package filled with several layers of spherical food products with chilled water sprayed from the top and cold unsaturated air blown from the bottom. A mathematical model is developed to describe the hydrodynamics and simultaneous heat and mass transfer occurring inside the package. The non-dimensional governing equations are solved using the finite difference numerical methods. The results are presented in the form of time-temperature charts. A correlation is obtained to calculate the process time in terms of the process parameters.

Ac conductivity studies of lithium thioborate glasses

The variation in the exponent s in σa.c. agr ωs as a function of temperature is reported for lithium thioborate glasses. The origin of the observed minimum in s is discussed using the diffusion-controlled relaxation (DCR) model. An entirely new model for the a.c. conductivity of highly modified ionic glasses has been proposed and expressions for relaxation identical with those of the DCR model have been obtained, providing a new explanation for the temperature behaviour of s. The origin of two activation barriers generally observed in a.c. conductivity studies is examined in the light of the new model.