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The main magnetic fields in COMPASS – i.e. The Toroidal, Magnetising, Equilibrium, and Shaping Fields – are created by a set of four corresponding thyristor power supplies controlled in a 0.5 ms loop. The plasma position has to be controlled both radially and vertically by two additional magnetic fields provided by two fast amplifiers (FAs) based on MOSFET technology, each supplying ±100 V and up to ±5 kA. Currently, an ongoing project aims at ELM triggering by fast changes of the vertical position of the plasma column, also referred to as vertical kicks. For this purpose, a new Vertical Kicks Power Supply (VKPS) capable of quick change of vertical plasma position is being constructed. This power supply should operate at up to 1.2 kV with switching frequency up to 5 kHz. It is designed as a H-bridge but based on IGBT transistors which can be operated at higher voltages than MOSFETs. In this paper, we focus on the FAs and VKPS engineering design and required output parameters. Both the power supplies are based on modern components with highest available ratings in their categories. Unique design of the power supplies takes advantage of the short duration of the COMPASS discharge by overloading the transistors above their maximal steady-state rating. The FA is regularly operating, so that in addition to describing its design, we also describe the achieved performance parameters. Finally, the common controller unit, communication, and error handling is described.

Our investigations of the cation exchange resins based on styrene-divinylbenzene (DVB) have shown that because of its unfavorable reactivity towards styrene, the DVB causes great inhomogeneities in the copolymers formed with styrene. This affects, in a negative way, the mechanical stability of the strongly acid cation exchange resin produced. On the other hand, strongly acid cation exchange resins based on polystyrene may be produced by reacting polystyrene in two steps with chlorosulfonic acid in the presence of formaldehyde. Furthermore, it has been successfully tied to chloromethylate polystyrene in the presence of paraformaldehyde or methylal so that a cross-linked chloromethylated product was formed. It has been the aim of our investigations to make sure if, on the one hand, on the basis of polystyrene, it was possible by chloromethylation to get a cross-linked product that could be subsequently worked into a strongly acid cation exchange resin or, on the other hand, to verify if one could, based on polystyrene in the presence of a formaldehyde-releasing substance, sulfonate in one step so that the product is cross-linked at the same time. The quality criterion of all experiments is to guarantee that the characteristics of the final product, i.e., a strongly acid cation exchange resin, are comparable to those of the well-known resin types based on styrene-DVB.

Efficient computation in sheet metal forming or car crash analysis is obtained only by using shell elements instead of fully three-dimensional solid elements. However, many requirements in the investigations in particular when looking at edges and special situations like large stretching and bending with small radii – strains and stresses in thickness direction and general three-dimensional material laws – cannot be provided by shell elements even if they are based on the well-known degeneration concept. Therefore in Hauptman [Int. J. Numer. Meth. Engng. 42 (1998) 49] among others as Schoop [Ingenieur-Archiv 56 (1986) 427]; Parisch [Int. J. Numer. Meth. Engng. 38 (1995) 1855]; Miehe [Comp. Meth. Appl. Mech. Engng. 155 (1998) 193] a so-called `Solid-Shell' formulation which is described briefly in the following section, was proposed. It must be noted also that in the solid-shell formulation the use of rotational degrees of freedom can be avoided and it is based instead on displacement degrees of freedom belonging to the upper and lower shell surfaces. Thus a simple combination with solid elements is obtained and no problems concerning large rigid body motions appear.

In the present contribution we extend a previously proposed so-called solid–shell concept which incorporates only displacement degrees of freedom to the simulation of large elastic and large elastoplastic deformations of shells. Therefore, the modi cations necessary for hyper-elastic or elastoplastic material laws are discussed. These modi cations concern the right Cauchy–Green tensor for large elastic deformations, respectively, the deformation gradient for elastoplasticity which then are consistent to the modi ed Green–Lagrange strains that are necessary for transverse shear and membrane locking free solid–shell element formulations. However, in addition to the locking mentioned above especially in the range of plasticity incompressibility locking becomes important. Thus, the second major aspect of this contribution is the discussion of several ways to avoid incompressibility locking also including the investigation of eigenmodes. Finally, a selective reduced integration scheme with reduced integration for the volumetric term is employed and described in detail, although it is limited to material laws which allow the decomposition into a volumetric and a deviatoric part. Some numerical examples show the range of application for the proposed elements. Copyright ? 2000 John Wiley & Sons, Ltd.

Raman scattering in the quarter-filled spin ladder system ${\ensuremath{\alpha}}^{\ensuremath{'}}\ensuremath{-}{\mathrm{NaV}}_{2}{\mathrm{O}}_{5}$ shows in the dimerized singlet ground state $(Tl~{T}_{\mathrm{SP}}=35 \mathrm{K})$ an unexpected sequence of three magnetic bound states. Our results suggest that the recently proposed mapping onto an effective spin chain for $Tg{T}_{\mathrm{SP}}$ has to be given up in favor of the full topology and exchange paths of a ladder in the dimerized phase for $Tl{T}_{\mathrm{SP}}.$ As the new ground state we propose a dynamic superposition of energetically nearly degenerate dimer configurations on the ladder.

Neutron and X-ray diffraction experiments have shown that NaV 2 O 5 consists of zig-zag V chains of average valence 4.5 rather than a charge ordered state at room temperature. Both these experiments revealed superlattice reflections below the phase transition temperature T SP ≈34 K. The modulation below T SP is due to displacements predominantly of V atoms for which we propose a model.

In the present contribution we propose a so-called solid-shell concept which incorporates only displacement degrees of freedom. Thus, some major disadvantages of the usually used degenerated shell concept are overcome. These disadvantages are related to boundary conditions—the handling of soft and hard support, the need for special co-ordinate systems at boundaries, the connection with continuum elements—and, in geometrically non-linear analyses, to a complicated update of the rotation vector. First, the kinematics of the so-called solid-shell concept in analogy to the degenerated shell concept are introduced. Then several modifications of the solid-shell concept are proposed to obtain locking-free solid-shell elements, leading also to formulations which allow the use of general three-dimensional material laws and which are also able to represent the normal stresses and strains in thickness direction. Numerical analyses of geometrically linear and non-linear problems are finally performed using solely assumed natural shear strain elements with a linear approximation in in-plane direction. Although some considerations are needed to get comparable boundary conditions in the examples analysed, the solid-shell elements prove to work as good as the degenerated shell elements. The numerical examples show that neither thickness nor shear locking are present even for distorted element shapes. © 1998 John Wiley & Sons, Ltd.

We present results of high-resolution thermal-expansion and specific-heat measurements on single crystalline ${\ensuremath{\alpha}}^{\ensuremath{'}}$-${\mathrm{NaV}}_{2}$O${}_{5}$. We find clear evidence for two almost degenerate phase transitions associated with the formation of the dimerized state around 33 K: A sharp first-order transition at ${T}_{1}=(33\ifmmode\pm\else\textpm\fi{}0.1)$ K slightly below the onset of a second-order transition at ${T}_{2}^{\mathrm{onset}}\ensuremath{\approx}(34\ifmmode\pm\else\textpm\fi{}0.1)$ K. The latter is accompanied by pronounced spontaneous strains. Our results are consistent with a structural transformation at ${T}_{1}$ induced by the incipient spin-Peierls order parameter above ${T}_{2}{=T}_{\mathrm{SP}}.$

By means of Raman scattering, we investigated single-crystalline samples of the new inorganic spin-Peierls compound α′-NaV2O5 = 34 with TSP = 34 K. Phonons with anomalous broad line shape indicating a strong spin-phonon coupling above TSP were detected. Below TSP several additional modes could be observed. Different temperature dependencies of these modes are interpreted as a first hint that low-energy modes are related to the opening of the spin-Peierls gap observed in neutron scattering experiments while other modes are related to the lowering of the lattice symmetry due to the spin-Peierls transition.

The effect of Si doping on the magnetic properties of the spin-Peierls SP system CuGeO3 was found to differ strongly between polycrystals PC’s and single crystals SC’s. In SC’s, the SP state is suppressed much more strongly, whereas the existence region of the antiferromagnetic AF state is enhanced. We investigated the origin of this difference by means of magnetic susceptibility, specific heat, thermal expansion, Raman scattering, elastic neutron scattering, and x-ray measurements on CuGe1xSixO3 samples prepared under different conditions. The partial oxygen pressure and the temperature during the synthesis were found to have a profound influence on the magnetic properties: preparation under reduced oxygen pressure leads to a stabilization of the AF state, whereas heating above the melting point results in a strong decrease of TSP in Si-doped samples. Therefore, both the AF stabilization and the TSP reduction observed in SC’s are not an intrinsic effect of Si doping PC samples, which can be prepared at lower temperatures and more oxidizing conditions, reflect much better the intrinsic properties of CuGe1xSixO3. We were able to prepare PC samples up to 50 at. % Si and found a continuous decrease of the one-dimensional character of the magnetic properties without pronounced changes in the structure. S0163-18299705321-6

We present a comparison of the effect of different dopants on both spin-Peierls and the Neel transition in CuGeO3. The composition dependence of the Neel-transition temperature TN can be scaled to a universal dependence for both in- and off-chain dopants taking into consideration the changes of the ionic radii. This suggests local distortions to play an important role for the effect of the doping. All in-chain dopants lead to a similar linear decrease of TSP; the slope differing only slightly within a factor of 1.5 for different dopands. The much weaker effect on TSP of the two off chain dopants Si and Ti scales to a common behaviour if the chemical pressure is taken into account. Furthermore, we found for in-chain dopants a clear correlation between the transition temperature TSP and the spin-Peierls gap.

The barrier properties of electron cyclotron resonance plasma deposited silicon oxide (SiO), silicon oxynitride (SiON) and silicon nitride (SiN) films against moisture and water penetration were studied as a function of the deposition parameters gas flux ratios, microwave power and reactor pressure. Three methods were used to quantify these barrier properties: measurement of film etch rate in water at different temperatures and pH values, determination of moisture permeation coefficient and electrical characterization of samples during humidity exposure. Although the dissolution rate of SiN in water is slightly higher compared with SiO the lower moisture permeation coefficient and the higher electrical stability during exposure to humidity of silicon nitride make it an attractive passivation material for different applications.

C27H60K4N3O12Sn9, monoclinic, P121/n1(No. 14), a = 10.410(2) Å, b = 25.659(5) Å, c = 20.636(4) Å, β = 102.56(3)°, V = 5380.2 Å3, Z = 4, Rgt(F) = 0.030, wRref(F2) = 0.072, T = 150 K.

C28H68Cs2K2N8O8Sn9, monoclinic, P121/c1 (No. 14), a = 13.897(3) Å, b = 16.091(3) Å, c = 26.432(5) Å, β = 91.03(3)°, V = 5909.7 Å3, Z = 4, Rgt(F) = 0.050, wRref(F2) = 0.127, T = 153 K.

C24H60Ge9K3N8O6, triclinic, P1̅ (No. 2), a = 9.408(2) Å, b = 13.606(3) Å, c = 19.507(4) Å, α = 84.74(3)°, β = 81.35(3)°, γ = 80.18(3)°, V = 2426.8 Å3, Z = 2, Rgt(F) = 0.064, wRref(F2) = 0.192, T = 150 K.

Annexin VIII is a calcium-dependent phospholipid-binding protein previously identified as a blood anticoagulant based on in vitro studies. However, the physiologic function of annexin VIII remains unknown. In acute promyelocytic leukemia (APL) the annexin VIII gene is highly expressed, but its expression is undetectable in the blasts of other acute leukemias. In the present investigation, we showed using the APL-derived NB4 cell line that expression of the annexin VIII gene is regulated at the transcription level during induced differentiation by all-trans retinoic acid (ATRA). The half-life of the annexin VIII mRNA is about 5 to 6 hours, as determined by using actinomycin D as a transcription inhibitor. Analysis of the expression of annexin VIII protein in NB4 cells and in APL samples showed a consistent expression of a predominant 36-kD protein and a weak 72-kD protein. After ATRA- induced differentiation of NB4 cells, the annexin VIII protein level reduced gradually, but a detectable level persisted even after 4 days of induction. Because annexin VIII mRNA becomes undetectable after 48 hours of ATRA induction, this result indicates that annexin VIII is a relatively stable protein. A multiple tissue Northern blot analysis was performed, and we found that annexin VIII is normally expressed in the placenta and the lung. Cellular localization of the annexin VIII protein was determined by immunofluorescence staining and subcellular fractionation. These results indicated that annexin VIII is predominantly localized to the plasma membrane. The annexin VIII is neither an extracellular protein nor associated with the cell surface suggesting that it does not play a role in blood coagulation in vivo. The plasma membrane localization and its property as a phospholipase inhibitor suggests that annexin VIII may have a role in the signal transduction pathway in the APL cells.

Human interferon-alpha 2c (IFN-alpha 2c) was produced in Escherichia coli under the control of the alkaline phosphatase promoter using a periplasmic expression system. Compared with other leader sequences, the heat-stable enterotoxin II leader of E. coli (STII) resulted in the highest rate of correct processing as judged by Western-blot analysis. The fermentation was designed as a batch-fed process in order to obtain a high yield of biomass. The processing rate of IFN-alpha 2c could be increased from 25% to more than 50% by shifting the fermentation pH from 7.0 to 6.7. IFN-alpha 2c extracted from the periplasm was purified by a new four-step chromatographic procedure. Whereas cytoplasmically produced IFN-alpha 2c does not have its full native structure, IFN-alpha 2c extracted from the periplasm was found to be correctly folded, as shown by c.d. spectroscopy. Peptide-map analysis in combination with m.s. revealed the correct formation of disulphide bridges. N-terminal sequence analysis showed complete removal of the leader sequence, creating the authentic N-terminus starting with cysteine.

We have determined the complete cDNA sequence of rat plectin from a number of well-characterized overlapping lambda gt11 clones. The 4,140-residue predicted amino acid sequence (466,481 D) is consistent with a three-domain structural model in which a long central rod domain, having mainly an alpha-helical coiled coil conformation, is flanked by globular NH2- and COOH-terminal domains. The plectin sequence has a number of repeating motifs. The rod domain has five subregions approximately 200-residues long in which there is a strong repeat in the charged amino acids at 10.4 residues that may be involved in association between plectin molecules. The globular COOH-terminal domain has a prominent six-fold tandem repeat, with each repeat having a strongly conserved central region based on nine tandem repeats of a 19-residue motif. The plectin sequence has several marked similarities to that of desmoplakin (Green, K. J., D. A. D. Parry, P. M. Steinert, M. L. A. Virata, R. M. Wagner, B. D. Angst, and L.A. Nilles. 1990. J. Biol. Chem. 265:2,603-2,612), which has a shorter coiled-coil rod domain with a similar 10.4 residue charge periodicity and a COOH-terminal globular domain with three tandem repeats homologous to the six found in plectin. The plectin sequence also has homologies to that of the bullous pemphigoid antigen. Northern blot analysis indicated that there is a significant degree of conservation of plectin genes between rat, human, and chicken and that, as shown previously at the protein level, plectin has a wide tissue distribution. There appeared to be a single rat plectin gene that gave rise to a 15-kb message. Expression of polypeptides encoded by defined fragments of plectin cDNA in E. coli has also been used to localize the epitopes of a range of monoclonal and serum antibodies. This enabled us to tentatively map a sequence involved in plectin-vimentin and plectin-lamin B interactions to a restricted region of the rod domain.

We present results from magnetic-resonance measurements for 75--350 GHz in ${\ensuremath{\alpha}}^{\ensuremath{'}}\ensuremath{-}{\mathrm{NaV}}_{2}{\mathrm{O}}_{5}.$ The temperature dependence of the integrated intensity indicates that we observe transitions in the excited state. A quantitative description gives resonances in the triplet state at high-symmetry points of the excitation spectrum of this spin-Peierls compound. This energy has the same temperature dependence as the spin-Peierls gap. Similarities and differences with another inorganic compound ${\mathrm{CuGeO}}_{3}$ are discussed.

We present measurements on single- and polycrystalline samples of the spin-Peierls compound α′ -NaV 2 O 5 . The transition temperature T SP obtained in susceptibility measurements is strongly dependent on the Na-stoichiometry of the samples. The g -values obtained in ESR measurements are close to g ≈ 2. The crystallographic distortion due to the dimerisation at T SP is seen in thermal expansion as well as in Raman light scattering measurements.

The insulin-like growth-factor-1 (IGF-1) receptor, which is widely expressed in cells that have undergone oncogenic transformation, is emerging as a novel target in cancer therapy. IGF-1-induced receptor activation results in autophosphorylation of cytoplasmic kinase domains and enhances their capability to phosphorylate downstream substrates. Structures of the homologous insulin receptor kinase (IRK) exist in an open, unphosphorylated form and a closed, trisphosphorylated form.We have determined the 2.1 A crystal structure of the IGF-1 receptor protein tyrosine kinase domain phosphorylated at two tyrosine residues within the activation loop (IGF-1RK2P) and bound to an ATP analog. The ligand is not in a conformation compatible with phosphoryl transfer, and the activation loop is partially disordered. Compared to the homologous insulin receptor kinase, IGF-1RK2P is trapped in a half-closed, previously unobserved conformation. Observed domain movements can be dissected into two orthogonal rotational components.Conformational changes upon kinase activation are triggered by the degree of phosphorylation and are crucially dependent on the conformation of the proximal end of the kinase activation loop. This IGF-1RK structure will provide a molecular basis for the design of selective antioncogenic therapeutic agents.

Vascular anticoagulant alpha (VAC alpha, annexin V) is a member of the family of calcium and phospholipid binding proteins, the annexins. The binding properties of VAC alpha to phospholipid bilayers were studied by ellipsometry. Adsorption was calcium-dependent and completely reversible upon calcium depletion. Half-maximal adsorptions to phospholipid bilayers consisting of 100, 20, 5, and 1% dioleoyl-phosphatidylserine (DOPS) supplemented with dioleoyl-phosphatidylcholine (DOPC) were reached at Ca2+ concentrations of 0.04, 0.22, 1.5, and 8.6 mM. These surfaces all showed the same maximal adsorption of 0.22 +/- 0.01 micrograms of VAC alpha/cm2 (mean +/- S.D.). The adsorption to bilayers containing more than 10% DOPS was independent of VAC alpha concentrations in the range of 0.5-100 nM. Dissociation constants for VAC alpha binding to these surfaces were estimated to be below 2 x 10(-10) M. No adsorption was observed on pure DOPC bilayers at a Ca2+ concentration of 3 mM. The ability to mediate VAC alpha binding to 20% DOPS/80% DOPC bilayers was highly specific for Ca2+. The use of other divalent cations resulted in decreased binding in the order Cd2+ greater than Zn2+ greater than Mn2+ greater than Co2+ greater than Ba2+ greater than Mg2+. Zinc ions had a synergistic effect on Ca2(+)-dependent VAC alpha binding. The Ca2+ concentration needed for half-maximal binding to cardiolipin, dioleoyl-phosphatidylglycerol, DOPS, phosphatidylinositol, phosphatidic acid, dioleoyl-phosphatidylethanolamine, and sphingomyelin increased in that order. Adsorption was independent of the overall surface charge of the phospholipid membrane.

Vielen effizienten Schalenelementen fur FE-Anwendungen liegt das Degenerationskonzept zugrunde, dessen wesentliche Merkmale eine Kinematik mit Rotationsfreiheitsgraden und die Beschrankung auf einen ebenen Spannungszustand sind. Somit erfordern bereits geometrisch nichtlineare Berechnungen aufgrund der Verdrehungsfreiheitsgrade relativ aufwendige Formulierungen, die bei materiell nichtlinearen Berechnungen durch die Forderung nach einem ebenen Spannungszustand wesentlich komplexer werden. Ziel der Studie ist, eine Schalenformulierung vorzustellen, die diese nicht Nachteile aufweist.

We report on two top-gate defined, coupled quantum dots in a semiconducting single wall carbon nanotube, constituting a tunable double quantum dot system. The single wall carbon nanotubes are contacted by titanium electrodes, and gated by three narrow top-gate electrodes as well as a back-gate. We show that a bias spectroscopy plot on just one of the two quantum dots can be used to extract the addition energy of both quantum dots. Furthermore, honeycomb charge stability diagrams are analyzed by an electrostatic capacitor model that includes cross capacitances, and we extract the coupling energy of the double quantum dot., Comment: Published in Applied Physics Letters 4 December 2006. http://link.aip.org/link/?APL/89/232113

We have undertaken the production of recombinant soluble Fc epsilon receptor II (Fc epsilon RII) as a secretory protein, but not as a cleavage product of membrane-bound receptor. Several plasmid constructs containing soluble receptor sequence were prepared. Only a chimeric gene containing the sequences encoding IL-6 signal peptide and the soluble moiety of Fc epsilon RII could be expressed in Xenopus laevis oocytes and CHO cells, resulting in the secretion of soluble Fc epsilon RII. The recombinant soluble Fc epsilon RII was also produced in the yeast expression system. The NH2-terminal sequence analysis of the chimeric gene product generated by oocytes demonstrated the correct cleavage of IL-6 leader sequence by a signal peptidase. Moreover, most of CHO cell and all of the yeast-derived recombinant molecules were products identical with the native B cell-derived soluble Fc epsilon RII. These recombinant products as well as the natural soluble receptor derived from a human B cell line could bind both human IgE and two different anti-Fc epsilon RII mAb and could competitively inhibit the binding of IgE to Fc epsilon RII-expressing cells. However, the recombinant soluble Fc epsilon RII and highly purified native molecules did not display any B cell growth-promoting activity.

SummaryEmbryo-free cotyledons of cv Red Delicious apple produced callus and adventitious shoots when they were cultured on a unique medium consisting of Nitsch and Nitsch (1969) salts supplemented with micronutrient solution, 6-benzylamino purine (4.0 mg l-1), several vitamins, as well as malt extract (400 mg l-1), myo-inositol (300 mg l-1). coconut milk (40 mg h-1) and glucose (25 g l-1). When the explanted cotyledons were placed in the dark for four days and then moved to lighted conditions, they formed a hard green callus which, differentiated into shoots within three weeks. The progress of shoot formation was delayed when the cotyledons were placed directly under lighted conditions. Seeds taken from slightly immature, freshly harvested apples formed shoots very quickly. The young shoots rooted readily on a medium which was free of coconut milk and malt extract but supplemented with 0.2 mg l-1 indoleacetic acid. These rooted shoots could be easily transplanted to the greenhouse. Cotyledons grown on a m...

The following possible techniques of nitrate removal from drinking water are compared with respect to their efficiency: reserved osmosis, electrodialysis and ion exchange. It can be shown by test products that it is possible, in principle, to synthesize nitrate-selective anion exchange resins. Today it is assumed that from this a preferential position of the technology of ion exchange can be expected for the elimination of nitrate from drinking water.

From sulphate-containing process solutions, such as CuSO4-solutions, nitrate can be removed by ion exchange resulting in residual contents not higher than trace amounts ( 1 M CuSO4-solution, 70 % to 80 % of the capacity of traditional ion exchange resins is utilized for adsorbing the NO3 − Even higher adsorption degrees have been achieved by the use of resins type wofatit SN 35 L that are selective for nitrate or a weakly basic resin with di-n-butyl amine functional groups. The resins loaded can be regenerated with alkalies and H2SO4. For the latter case, a closed loading-regeneration cycle is proposed which allows the separated NO3 to be reused as HNO3.

Protoplast fusion methodology has been used to produce inter and intraspecific heterokaryons from a large number of plant species. Although this is a potentially useful tool for the transfer of genetic information, the selection of heterokaryons from the homologous fusions and unfused protoplasts which are also present is a frequent problem (1). One successful method has employed the use of amino acid analog resistance complementation in the selection of fusion hybrids.

p-nitrophenylcarbamyl-methionyl-tRNAfMet is shown to act as an analogue of fMet-tRNAfMet in initiation complex formation. It binds to E. coli ribosomes in the presence of initiation factors and R 17-RNA as messenger. Covalent bond formation occurs in the complex between the Met-tRNAfMet derivative and protein of the 50 S ribosomal subunit. The protein labeled predominantly in the reaction has been identified as L 27 indicating that this protein is located at the donor-site of the ribosome.

Escherichia coli plays a central role in modern biotechnology i.e. gene technology and fermentation. This article summarizes the basic principles of genetic engineering using human type I interferon genes as an example. The second part describes the advantages and the problems encountered using E. coli as a production organism.

As part of an investigation into the molecular basis of attenuation in the Sabin poliovirus vaccines, the genomes of three strains of type 3 poliovirus differing in neurovirulence were cloned in Escherichia coli. The nucleotide sequence of the region of the genome encoding the virion protein 1 (VP1) polypeptide from each of these strains is presented. Very few changes were observed, a finding suggesting that the mutation(s) involved in the attenuation of type 3 poliovirus probably lies elsewhere in the genome. The complete nucleotide sequence of one of the strains, P3/Sabin, has been obtained and is compared with the published sequences of type 1 poliovirus. Between serotypes 1 and 3, there is 77% homology in nucleotide sequence and 90% homology in the amino acid sequence predicted for viral proteins.