Determination of distances of sugar protons from Mn2+ in concanavalin A

1H NMR spin-lattice relaxation time (T1) measurements have been carried out with various sugars, viz. methyl alpha-D-glucopyranoside (alpha-MeGluP), methyl beta-D-lucopyranoside (beta-MeGluP), methyl alpha--annopyranoside (alpha-MeManP), maltose (4-O-alpha-D-glucopyranosyl--glucose), nigerose (3-O-alpha-D-glucopyranosyl-D-glucose), p-nitrophenyl alpha-maltoside (PNP-alpha-maltoside) and p-nitrophenyl beta-maltoside (PNP-beta-maltoside) to determine the distances of sugar protons from Mn2+ in concanavalin A (Con A). With a rotational correlation time of 1.58 x 10(-10) s determined, distances were calculated using Solomon-Bloembergen equation. The data obtained indicated differences in disposition of different groups in the binding site of Con A. An average value of about 10 A was obtained for the distances of sugar protons from Mn2+ in Con A. In the case of mono and disaccharides, the non-reducing end sugar unit was found to be closer to Mn2+ than the reducing end one.

Kateuden luonne ja erityispiirteet filosofisessa pohdinnassa

Kateuden tunnetta ei ole tarkasteltu käytännöllisessä filosofiassa huolimatta sen määräävästä asemasta ihmisen normaalissa päivittäisessä elämässä. Kateus liittyy moniin ilmiöihin yksilöllisenä tai jopa kollektiivisena ryhmätunteena, kun siihen yhdistyvät epäoikeudenmukaisuus ja itsepetoksellisuus. Tutkielma pyrki osoittamaan kateuden vääjäämättömän monipuolisuuden kilpailullisena ja eriarvoisuutta lisäävänä vertailevana kompleksisena negatiivisena tunteena. Jo antiikin Kreikassa kateus liitettiin ihmisten ja jumalien väliseen eriarvoisuuteen, nykypäivänä taas kateutta leimaa liberaalisen yhteiskuntapolitiikan keskiössä ”tietämättömyyden verhon” takana egalitaarisuuden ihanne ja oikeudenmukaisuuden ja reiluuden taju. Tunnekokemuksena kateus on impotenttinen toisen paremmuudesta ja inferioi näin kateuden episodisuuden irrationaaliseen tilanteeseensa nähden antagonistiseksi. Tutkielman neljästä pääluvussa ensimmäisessä kateus yhdistetään poliittisen liberaalin yhteiskuntafilosofian yhdysvaltalaiseen kannattajaan John Rawlsiin (1921−2002). Hänen ajattelussaan ja pääteoksessaan A Theory of Justice (1971) ja siinä erityisesti kateutta käsittelevässä luvussa IX kateus on yhteiskunnassa vaikuttavaa erityispsykologista taipumusta tavoitella parempiosaisten asemaa oikeudenmukaisuuden kontraktuaalisessa valintajärjestelmässä. Rawlsille kateus ei ole tabu, vaan kateuden ongelma koskee kaikkia abstraktissa alkuasetelmassa yhteiskuntasopimuksen piiriin liittyviä sopija−agentteja. Rationaalinen agentti ei kärsi kateudesta, kun epäoikeudenmukaisuutta ei ole hänen ja muiden samojen vapaus− ja eroperiaatteiden nojalla toimivien ihmisten välillä sietämättömästi. Rawls tekee kuitenkin jaon pahantahoisessa kateudessa (proper) yleiseen ja erityiseen ja erottaa sekä emulatiivisen (emulative) eli motivoivan esimerkin sysäämän kilvoittelevan kateuden varsinaisesta kateudesta (proper). Myös anteeksiannettava kateus (excusable general envy) on Rawlsin onnellisuutta ja reiluutta tasa–arvoistavassa sopimusteorian ideaalissa varsinaisen kateuden alaluokkana mukana. Kateus ja tasa-arvo tulevat esille paremmin kilpailullisessa kateudessa, mistä myös viime vuosien merkittävin kateustutkija amerikkalainen Kentuckyn yliopiston psykologian professori Richard H. Smith on ollut kiinnostunut. Hänelle kateus on inferiorisen kompleksista ja liittyy oman arvon tunteeseen ja kognitiiviseen psykologiaan. Kateuden tutkimus on monialaistunut ja vilkastunut viime vuosikymmenen aikana. Sosiaali−psykologia, sosiologia, kulttuuriantropologia ja tunnefilosofia ovat kiinnostuneet ymmärtämään tätä kompleksista negatiivista tunnetta paremmin. Kulttuurissamme kateus toimii universaalisesti yhteydessä muihin rinnakkaistunteisiin, kuten moraaliseen paheksuntaan tai sitä lievempään närkästymiseen. Kateus ei ole perustunne, mutta sille on löydettävissä prototyypillisiä piirteitä, joskin kateus ei helposti antaudu propositionaaliseen tai kognitiiviseen arvostelmasisältöön yksin mentaalisen analyysin välityksellä (Solomon 1976). Siitä pitää huolen kateuden affektuaalnen instrumentaalisuus (feeling) ja kognitiivisen komponentiaalisen tulkinnan vaikeus kateellisen väistellessä oman itsetunnon inferiorisuuden tai omaa toimintavalmiutta heikentävien ilkeämielisten motiiviensa alaisuudessa. Kateelliselle ei ns. perisyntinä riitä, että kadehditulta olisi saatu pois haluttu myönteinen ominaisuus, kohde−esine tai asema, vaan lähietäisyydellä toimivasta kadehditusta pitäisi päästä kokonaan eroon (ns. venäläinen kateus). Siksi kateus approksimoi naapureita, ystäviä, kollegoita tai myös toisen ihmisen aviopuolisoa, mutta usein arkiyhteydessä käsitteellisesti väärinymmärrettynä, koska jälkimmäisessä on kyse kolmepaikkaisesta mustasukkaisuuden tunteesta. Kaksipaikkaisena tunteena (kateellinen & kadehdittu) ja sen vastatunteenaan usein mainittu kiittämättömyys saavat aikaan sen, että kateellinen on myös taipuvainen aggressiivisuuteen ja vihaisuuteen, mutta kun asiaa tarkastelee tarkemmin taustalta paljastuu itsepetoksen elementtejä. Kateellinen hyödyntää itsepetoksen paradoksia eli kahden vastakkaisen uskomuksen (Kateellinen, koska P & Kateellinen, koska ~P) samanaikaista voimassaoloa tilanteessa, jossa omat teot ovat suuntautuneet intentionaalisesti muualle kuin kadehditun komparatiiivisesti parempana näyttäytyvien arvostuserojen kuromiseksi tilanteen tasavertaistamiseksi kiinni. Kateellinen voi olla deliberatiivisen ahne ja nopea epäreilussa reaktiossaan kadehdittua kohtaan. Näin uppiniskainen kateustunne voi tulla eriäväksi havaitun arvioivan arvostelman kanssa. Kateustunne olisi näin määritelmällisesti intensiivistä puutetta (toistuvissa) epätasa−arvoisissa ja irrationalisoituneissa ihmiskohtaamisissa. Tutkimus esitteli kateustunteen adekvaattisena käsitteenä ja toi havaintoja kognitiivisen tunneteorian riittämättömyydestä kateustunteen tutkimukselle. Kiinnostavaa oli, että poliittisessa yhteiskuntafilosofiasta löytyi myös Rawlsin psykologisten erityistaipumuksien ja erityisesti kateuden yhteiskuntapoliittista kritiikkiä. Tunneteoreettisesti kateustunne on kognitiivista perustunnetta holistisempi, intensiivisempi ja intentionaalisempi sekä lisäksi affektuaalisesti motivoiva, joka mahdollistaa myös inhimillisen toiminnan kehittymisen, mutta myös kadehtijan tuhoamisen. Itsepetos sen sijaan tekee kateudesta haavoittuvan ja myös narsismia ruokkivan tunnetilan, jossa kateellinen toimii hedonistisesti ei−kognitiivisen irrationaalisen tietämyksen (envious feeling proper) varassa ja kieltää tunteen konsekventionaaliset usein negatiiviset seuraukset itselleen ja lähiympäristölleen.

Superconducting Y--Ba--Cu--O Thin Films by RF Sputtering

Thin films of Y--Ba--Cu--O have been prepared by conventional methods of RF sputtering. The films exhibit superconducting onset temperatures as high as 91K, midpoint at 80K and a zero resistance state at 35K. Critical current measurements implied critical current densities of the order of 31 A/cm exp 2 . An attempt has been made to establish the role of substrate and various deposition parameters. 7 ref.--AA.

Regenerating Codes for Distributed Storage Networks

In a storage system where individual storage nodes are prone to failure, the redundant storage of data in a distributed manner across multiple nodes is a must to ensure reliability. Reed-Solomon codes possess the reconstruction property under which the stored data can be recovered by connecting to any k of the n nodes in the network across which data is dispersed. This property can be shown to lead to vastly improved network reliability over simple replication schemes. Also of interest in such storage systems is the minimization of the repair bandwidth, i.e., the amount of data needed to be downloaded from the network in order to repair a single failed node. Reed-Solomon codes perform poorly here as they require the entire data to be downloaded. Regenerating codes are a new class of codes which minimize the repair bandwidth while retaining the reconstruction property. This paper provides an overview of regenerating codes including a discussion on the explicit construction of optimum codes.

A Triggering Mechanism for Enhanced Star-Formation in Colliding Galaxies

We propose a physical mechanism to explain the origin of the intense burst of massive-star formation seen in colliding/merging, gas-rich, field spiral galaxies. We explicitly take account of the different parameters for the two main mass components, H-2 and H I, of the interstellar medium within a galaxy and follow their consequent different evolution during a collision between two galaxies. We also note that, in a typical spiral galaxy-like our galaxy, the Giant Molecular Clouds (GMCs) are in a near-virial equilibrium and form the current sites of massive-star formation, but have a low star formation rate. We show that this star formation rate is increased following a collision between galaxies. During a typical collision between two field spiral galaxies, the H I clouds from the two galaxies undergo collisions at a relative velocity of approximately 300 km s-1. However, the GMCs, with their smaller volume filling factor, do not collide. The collisions among the H I clouds from the two galaxies lead to the formation of a hot, ionized, high-pressure remnant gas. The over-pressure due to this hot gas causes a radiative shock compression of the outer layers of a preexisting GMC in the overlapping wedge region. This makes these layers gravitationally unstable, thus triggering a burst of massive-star formation in the initially barely stable GMCs.The resulting value of the typical IR luminosity from the young, massive stars from a pair of colliding galaxies is estimated to be approximately 2 x 10(11) L., in agreement with the observed values. In our model, the massive-star formation occurs in situ in the overlapping regions of a pair of colliding galaxies. We can thus explain the origin of enhanced star formation over an extended, central area approximately several kiloparsecs in size, as seen in typical colliding galaxies, and also the origin of starbursts in extranuclear regions of disk overlap as seen in Arp 299 (NGC 3690/IC 694) and in Arp 244 (NGC 4038/39). Whether the IR emission from the central region or that from the surrounding extranuclear galactic disk dominates depends on the geometry and the epoch of the collision and on the initial radial gas distribution in the two galaxies. In general, the central starburst would be stronger than that in the disks, due to the higher preexisting gas densities in the central region. The burst of star formation is expected to last over a galactic gas disk crossing time approximately 4 x 10(7) yr. We can also explain the simultaneous existence of nearly normal CO galaxy luminosities and shocked H-2 gas, as seen in colliding field galaxies.This is a minimal model, in that the only necessary condition for it to work is that there should be a sufficient overlap between the spatial gas distributions of the colliding galaxy pair.

Purification and characterization of an extracellular β-glucosidase from the thermophilic fungus Sporotrichum thermophile and its influence on cellulase activity

Multiple forms of beta-glucosidase (EC 3.2.1.21) of Sporotrichum thermophile were produced when the fungus was grown in a cellulose medium. One beta-glucosidase was purified 16-fold from 6-d-old culture filtrates by ion-exchange and gel-filtration chromatography. The purified enzyme was free of cellulase activity. It hydrolysed aryl beta-D-glucosides and beta-D-linked diglucosides. It was optimally active at pH 5.4, at 65-degrees-C. The apparent K(m) values for p-nitrophenyl beta-D-glucoside (PNPG) and cellobiose were 0.29 and 0.83 mm, respectively. Glucose, fucose, nojirimycin and gluconolactone inhibited beta-glucosidase competitively. At high (> 1 mm) substrate concentration, beta-glucosidase catalysed a parallel transglycosylation reaction. The transglycosylation product formed from cellobiose appeared to be a beta-linked tetramer of glucose. Admixtures of beta-glucosidase and cellulase components showed that the concept of cellobiose inhibition of cellulases was not valid for all components of the cellulase system of S. thermophile. Beta-Glucosidase supplementation also stimulated cellulose hydrolysis by cellulases when there was no accumulation of cellobiose in reaction mixture.

Localization and release of ?-glucosidase in the thermophilic and cellulolytic fungus, Sporotrichum thermophile

In a medium containing cellulose as the carbon source, the rapid growth of Sporotrichum thermophile, the secretion of cellulases and the utilization of cellulose were well-correlated events. The production of beta-glucosidase in culture medium lagged behind cellulases, coinciding with the time of extensive autolysis of mycelia. By contrast, neither apparent autolysis nor secretion of beta-glucosidase occurred when S. thermophile was grown in medium containing cellobiose; the enzyme activity remained associated with mycelia. The release of beta-glucosidase in cellulose-grown cultures was correlated with the activity of the lytic enzyme in the cell wall. Immunocytochemical localization and biochemical characterization showed that a beta-glucosidase released in the cellulose medium was the same as that which remained associated with mycelia grown on cellobiose. The results indicated that the release of beta-glucosidase in the cellulose culture is incidental to the activity of the lytic enzymes which are strongly induced by cellulose. The observations minimize a functional role of the culture fluid beta-glucosidase in cellulolysis by the fungus. Rather, the available information suggests that the cellulases and beta-glucosidases associated with the hyphal cell wall may play a role in cellulolysis by the fungus. (C) 1994 Academic Press, Inc.

Entanglement and nonclassicality for multimode radiation-field states

Nonclassicality in the sense of quantum optics is a prerequisite for entanglement in multimode radiation states. In this work we bring out the possibilities of passing from the former to the latter, via action of classicality preserving systems like beam splitters, in a transparent manner. For single-mode states, a complete description of nonclassicality is available via the classical theory of moments, as a set of necessary and sufficient conditions on the photon number distribution. We show that when the mode is coupled to an ancilla in any coherent state, and the system is then acted upon by a beam splitter, these conditions turn exactly into signatures of negativity under partial transpose (NPT) entanglement of the output state. Since the classical moment problem does not generalize to two or more modes, we turn in these cases to other familiar sufficient but not necessary conditions for nonclassicality, namely the Mandel parameter criterion and its extensions. We generalize the Mandel matrix from one-mode states to the two-mode situation, leading to a natural classification of states with varying levels of nonclassicality. For two-mode states we present a single test that can, if successful, simultaneously show nonclassicality as well as NPT entanglement. We also develop a test for NPT entanglement after beam-splitter action on a nonclassical state, tracing carefully the way in which it goes beyond the Mandel nonclassicality test. The result of three-mode beam-splitter action after coupling to an ancilla in the ground state is treated in the same spirit. The concept of genuine tripartite entanglement, and scalar measures of nonclassicality at the Mandel level for two-mode systems, are discussed. Numerous examples illustrating all these concepts are presented.

Swing amplification of nonaxisymmetric perturbations in stars and gas in a sheared galactic disk

We present a study of the growth of local, nonaxisymmetric perturbations in gravitationally coupled stars and gas in a differentially rotating galactic disk. The stars and gas are treated as two isothermal fluids of different velocity dispersions, with the stellar velocity dispersion being greater than that for the gas. We examine the physical effects of inclusion of a low-velocity dispersion component (gas) on the growth of non-axisymmetric perturbations in both stars and gas, as done for the axisymmetric case by Jog & Solomon. The amplified perturbations in stars and gas constitute trailing, material, spiral features which may be identified with the local spiral features seen in all spiral galaxies. The formulation of the two-fluid equations closely follows the one-fluid treatment by Goldreich & Lynden-Bell. The local, linearized perturbation equations in the sheared frame are solved to obtain the results for a temporary growth via swing amplification. The problem is formulated in terms of five dimensionless parameters-namely, the Q-factors for stars and gas, respectively; the gas mass fraction; the shearing rate in the galactic disk; and the length scale of perturbation. By using the observed values of these parameters, we obtain the amplifications and the pitch angles for features in stars and gas for dynamically distinct cases, as applicable for different regions of spiral galaxies. A real galaxy consisting of stars and gas may display growth of nonaxisymmetric perturbations even when it is stable against axisymmetric perturbations and/or when either fluid by itself is stable against non-axisymmetric perturbations. Due to its lower velocity dispersion, the gas exhibits a higher amplification than do the stars, and the amplified gas features are slightly more tightly wound than the stellar features. When the gas contribution is high, the stellar amplification and the range of pitch angles over which it can occur are both increased, due to the gravitational coupling between the two fluids. Thus, the two-fluid scheme can explain the origin of the broad spiral arms in the underlying old stellar populations of galaxies, as observed by Schweizer and Elmegreen & Elmegreen. The arms are predicted to be broader in gas-rich galaxies, as is indeed seen for example in M33. In the linear regime studied here, the arm contrast is shown to increase with radius in the inner Galaxy, in agreement with observations of external galaxies by Schweizer. These results follow directly due to the inclusion of gas in the problem.

Synthesis and structure of oxygen-deficient La2NiCoO5 and LaSrCo2O5 phases

The La2NiCoO5 and LaSrCo2O5 phases have been synthesized by the temperature-programmed reduction (TPR) of the parent mixed perovskites LaNi0.5Co0.5O3 and La0.5Sr0.5CoO3, respectively, under an ammonia atmosphere. While La2NiCoO5 adopts a structure similar to the vacancy-ordered La2Ni2O5, LaSrCo2O5 crystallized in a brownmillerite-like structure. The reactivity of the perovskite oxides towards reduction by ammonia and the structure of the product oxides are found to be guided by factors such as the coordination and oxidation state of the transition-metal cations.

The steady state nuclear Overhauser effect revisited

The steady state of a two spin system coupled to an isotropic environment and to each other through a dipolar interaction and under irradiation by a monochromatic, circularly polarized radio frequency field is determined ab initio using thermodynamic arguments. This steady state is used to describe the well known nuclear Overhauser effect in liquids. The steady state is also derived from the Solomon-Bloch set of equations used to describe the driven spin. It is shown that in the limit of weak driving, the two solutions coincide. (C) 1999 American Institute of Physics. [S0021-9606(99)71210-9].

Distributed Storage Codes With Repair-by-Transfer and Nonachievability of Interior Points on the Storage-Bandwidth Tradeoff

Regenerating codes are a class of recently developed codes for distributed storage that, like Reed-Solomon codes, permit data recovery from any subset of k nodes within the n-node network. However, regenerating codes possess in addition, the ability to repair a failed node by connecting to an arbitrary subset of d nodes. It has been shown that for the case of functional repair, there is a tradeoff between the amount of data stored per node and the bandwidth required to repair a failed node. A special case of functional repair is exact repair where the replacement node is required to store data identical to that in the failed node. Exact repair is of interest as it greatly simplifies system implementation. The first result of this paper is an explicit, exact-repair code for the point on the storage-bandwidth tradeoff corresponding to the minimum possible repair bandwidth, for the case when d = n-1. This code has a particularly simple graphical description, and most interestingly has the ability to carry out exact repair without any need to perform arithmetic operations. We term this ability of the code to perform repair through mere transfer of data as repair by transfer. The second result of this paper shows that the interior points on the storage-bandwidth tradeoff cannot be achieved under exact repair, thus pointing to the existence of a separate tradeoff under exact repair. Specifically, we identify a set of scenarios which we term as ``helper node pooling,'' and show that it is the necessity to satisfy such scenarios that overconstrains the system.

Interference Alignment in Regenerating Codes for Distributed Storage: Necessity and Code Constructions

Regenerating codes are a class of recently developed codes for distributed storage that, like Reed-Solomon codes, permit data recovery from any arbitrary of nodes. However regenerating codes possess in addition, the ability to repair a failed node by connecting to any arbitrary nodes and downloading an amount of data that is typically far less than the size of the data file. This amount of download is termed the repair bandwidth. Minimum storage regenerating (MSR) codes are a subclass of regenerating codes that require the least amount of network storage; every such code is a maximum distance separable (MDS) code. Further, when a replacement node stores data identical to that in the failed node, the repair is termed as exact. The four principal results of the paper are (a) the explicit construction of a class of MDS codes for d = n - 1 >= 2k - 1 termed the MISER code, that achieves the cut-set bound on the repair bandwidth for the exact repair of systematic nodes, (b) proof of the necessity of interference alignment in exact-repair MSR codes, (c) a proof showing the impossibility of constructing linear, exact-repair MSR codes for d < 2k - 3 in the absence of symbol extension, and (d) the construction, also explicit, of high-rate MSR codes for d = k+1. Interference alignment (IA) is a theme that runs throughout the paper: the MISER code is built on the principles of IA and IA is also a crucial component to the nonexistence proof for d < 2k - 3. To the best of our knowledge, the constructions presented in this paper are the first explicit constructions of regenerating codes that achieve the cut-set bound.