Fourth Form Research Articles

J-aggregates and liquid crystal structures of cyanine dyes

Low-angle X-ray diffraction and NMR measurements have been carried out on liquid crystals formed by four cyanine dyes dissolved in water. Three of the dyes form layer (smectic/lamellar-type) phases, while the fourth forms columnar nematic/hexagonal phases. The NMR measurements of water (2H2O) quadrupole splittings give information on the phase equilibria, while X-ray diffraction has been employed to determine the long-range structure. Both the columnar and the layer phases can form at solute concentrations as low as 0.1 wt.% of dye. The dye aggregates are significantly more rigid than surfactant micelles. They self-associate via σ–π interactions between adjacent molecules rather than the hydrophobic effect. Using NMR, the layer phases were found to exist to higher temperatures in the presence of added electrolytes, while the columnar phases are known to be unaltered or destabilised. The two-phase solution/mesophase co-existence regions are much larger for the layer phases than for the columnar phases. In these respects the dye mesophases resemble amphiphilic ones. It appears that a simple aggregation model originally developed for different surfactant micelle shapes can be applied to describe dye aggregates. One dye shows unusual NMR behaviour, with time-dependent and overlapping spectra. This indicates the coexistence of two mesophases in a manner which contradicts the phase rule. Possible explanations of this phenomenon are discussed.

Chemical Applications of Topology and GroupTheory.29.Low Density PolymericCarbon Allotropes Based on Negative CurvatureStructures

The construction of graphite and fullerene structures from networks of trigonal sp2 carbon atoms of zero and positive curvature can be extended to a fourth form of carbon, provisionally called schwarzites, consisting of networks of trigonal sp2 carbon atoms decorating infinite periodic minimal surfaces (IPMS's) of negative curvature and topological genus 3 such as the so-called D and P surfaces. The carbon networks of the simplest schwarzite structures contain only six- and seven-membered rings analogous to the fullerene networks containing only six- and five-membered rings. The stable structures of both fullerenes and schwarzites contain enough six-membered rings so that no two five-membered rings in the fullerene structures or no two seven-membered rings in the schwarzite structures share edges leading to unstable pentalene and heptalene units, respectively. The smallest unit cell of a viable schwarzite structure of this type contains 168 carbon atoms and is constructed by applying a leapfrog transforma...

Progress in preventing death from colorectal cancer

Colorectal cancer is the fourth commonest form of cancer worldwide with an estimated 678 000 new cases diagnosed in 1985 (Parkin et al., 1993). High incidence rates are found in Western Europe, North America and Australasia and intermediate rates in Eastern Europe, with the lowest rates found in sub-Saharan Africa (Boyle et al., 1985). The disease is not uniformly fatal although there are large differences in survival according to stage of disease. In advanced colorectal

An integrable normal form for water waves in infinite depth

Abstract We consider the Birkhoff normal form for the water wave problem posed in a fluid of infinite depth, with the starting point of our analysis a version of the Hamiltonian given by Zakharov. We verify that in the fourth order normal form, the coefficients vanish for all non-generic resonant terms, and we show that the resulting truncated system is completely integrable. In contrast we show that there are resonant fifth order terms with nonvanishing coefficients, answering to the negative the conjecture of Dyachenko & Zakharov on the integrability of free surface hydrodynamics. We analyse all solutions of the fourth order integrable system. In particular, the bifurcation structures of standing wave and travelling wave solutions are remarkably explicit due to the normal form.

Polarization suppression in Pb(Zr,Ti)O3 thin films

Switchable polarization can be suppressed in Pb(Zr,Ti)O3 thin films by optical, thermal, electrical, and reducing processes. The optical suppression effect occurs by biasing the ferroelectric near the switching threshold and illuminating the material with band gap light; the thermal suppression effect occurs by biasing the ferroelectric near the switching threshold and heating the material to ≊100 °C. The electrically induced suppression effect, known as electrical fatigue, occurs by subjecting the ferroelectric capacitor to repeated polarization reversals. We find that the suppressed polarization in these three cases can be restored to essentially its initial polarization value by creating electronic charge carriers in the ferroelectric. This strongly suggests that all three forms of degradation largely involve locking domains by electronic charge trapping at domain boundaries. The fourth form of polarization suppression, a reducing treatment, was obtained by annealing the crystallized PZT films at 400 °C in nitrogen. The suppressed polarization could not be restored by injecting electronic charge into the reduced films, indicating that the mechanism for polarization suppression is different. In this case, it appears as though ionic defects, such as oxygen vacancies, are responsible for locking the domains, and hence, suppressing the polarization.

Aminoacylase I from porcine kidney: Identification and characterization of two major protein domains

The domain structure of hog-kidney aminoacylase I was studied by limited proteolytic digestion with trypsin and characterization of the resulting fragments. In the native enzyme, the sequences from residue 6 to 196 and 307 to 406 are resistant to trypsin and remain tightly bound in nondenaturing solvents, while the intervening sequence (197-306) is efficiently degraded by trypsin. We conclude that the N-terminal half of the molecule and its C-terminal fourth form two independently folded domains. Both contain a peculiar PWW(A,L) sequence motif preceded by several strongly polar residues. We propose that these sequences form surface loops that mediate the membrane association of aminoacyclase I. We further show that the three free cysteine residues and the essential Zn2+ ion reside in the trypsin-resistant domains, while the intervening sequence contains the only disulfide H bond of the protein.

Insertion anomalies and the justification for 4NF in relational databases

The issue of providing a formal justification for the use of fourth normal form (4NF) in relational database design is investigated. Extending earlier work by other authors that provided formal definitions of an insertion anomaly in the case of functional dependency (FD) constraints, formal definitions are provided for two types of an insertion anomaly for the case when both FD and multivalued dependency (MVD) constraints are permitted. It is shown that both types of insertion anomaly are equivalent conditions on a relation scheme and a relation scheme is in 4NF if and only if both anomalies are absent. It is also shown that another type of insertion anomaly that does not reflect the symmetrical nature of MVDs is a weaker condition than 4NF.

Physical and functional interaction between wild-type p53 and mdm2 proteins.

The mdm2 oncogene, which is often amplified in mammalian tumors, produces a number of transcripts that encode distinct protein forms. Previous studies demonstrating that overexpression of the mdm2 gene can activate its transforming potential, and can inhibit the transcriptional activation function of p53, prompted us to begin to explore possible functional differences among the various mdm2 products. Utilizing a transient transfection assay, we have evaluated four naturally occurring murine mdm2 forms for their ability to inhibit p53-mediated transcriptional activation of reporter genes regulated by p53 response elements. Three of these mdm2 forms were found to physically associate with the wild-type p53 protein and to possess the ability to inhibit its transactivation function. A fourth form failed to exhibit either of these functions. This last mdm2 form lacks the N-terminal protein domain that is present in the other three splice forms examined, pointing to this region as one that is critical for complex formation with the p53 protein. Identifying such differences among mdm2 proteins provides important clues for dissecting their functional domains, and emphasizes that defining the individual properties of these products will be critical in elucidating the overall growth control function of the mdm2 gene.

Physical and functional interaction between wild-type p53 and mdm2 proteins.

The mdm2 oncogene, which is often amplified in mammalian tumors, produces a number of transcripts that encode distinct protein forms. Previous studies demonstrating that overexpression of the mdm2 gene can activate its transforming potential, and can inhibit the transcriptional activation function of p53, prompted us to begin to explore possible functional differences among the various mdm2 products. Utilizing a transient transfection assay, we have evaluated four naturally occurring murine mdm2 forms for their ability to inhibit p53-mediated transcriptional activation of reporter genes regulated by p53 response elements. Three of these mdm2 forms were found to physically associate with the wild-type p53 protein and to possess the ability to inhibit its transactivation function. A fourth form failed to exhibit either of these functions. This last mdm2 form lacks the N-terminal protein domain that is present in the other three splice forms examined, pointing to this region as one that is critical for complex formation with the p53 protein. Identifying such differences among mdm2 proteins provides important clues for dissecting their functional domains, and emphasizes that defining the individual properties of these products will be critical in elucidating the overall growth control function of the mdm2 gene.

REDUNDANCY AND THE JUSTIFICATION FOR FOURTH NORMAL FORM IN RELATIONAL DATABASES

The relationship between the absence of redundancy in relational databases and fourth normal form (4NF) is investigated. A relation scheme is defined to be redundant if there exists a legal relation defined over it which has at least two tuples that are identical on the attributes in a functional dependency (FD) or multivalued dependency (MVD) constraint. Depending on whether the dependencies in a set of constraints or the dependencies in the closure of the set is used, two different types of redundancy are defined. It is shown that the two types of redundancy are equivalent and their absence in a relation scheme is equivalent to the 4NF condition.

Cloning, Sequencing, and Functional Studies of Phenobarbital-Inducible Forms of Cytochrome P450 2B and 4B Expressed in Rabbit Kidney

Expression of several forms of cytochrome P450 2B and of P450 4B1 in rabbit kidney was investigated by cloning from cDNA libraries constructed with renal mRNA from animals treated with phenobarbital. Isolation and sequencing of several cDNAs demonstrated that: (i) cytochrome P450 2B-B0 can be found in rabbit kidney along with a newly discovered form of P450 2B termed "P450 2B-Bx." P450 2B-Bx differs from P450 2B-B0 at 25 nucleotide positions and at four positions in the derived sequence of 491 amino acids. Two previously identified forms of cytochrome P450 2B, 2B-B1 and 2B-B2, are not detected in rabbit kidney. cDNA encoding cytochrome P450 4B1 was also cloned from the kidney library and found to be identical in sequence to cDNAs cloned from rabbit hepatic and pulmonary libraries. Analysis of renal mRNA indicates that forms of cytochrome P450 2B and P450 4B1 are expressed in a number of species but induced by phenobarbital in rabbit only (4B1) or rabbit and hamster (2B). Relatively high levels of mRNA related to P450 4B1 were detected in samples from untreated and phenobarbital-treated mice. Analysis of protein by immunoblotting was less sensitive but produced results consistent with those obtained by analysis of mRNA; protein related to cytochrome P450 2B was detected in renal microsomal samples from rabbit and hamster (phenobarbital > untreated), and protein related to P450 4B1 in samples from rabbits (phenobarbital > untreated) and mice (phenobarbital = untreated). The four forms of cytochrome P450 2B were expressed in COS-7 cells, and their activities were evaluated with androstenedione, testosterone, and 7-ethoxycoumarin as substrates. Three of the P450 2B forms, B0, B1, and Bx, metabolize these substrates in a manner characterized by preference for 16β-hydroxylation of androstenedione, low testosterone 16-hydroxylation, and high ethoxycoumann O-deethylation. The fourth form, P450 2B-B2, is catalytically distinct from the others, with activities characterized by high androstenedione 16α- and 15α-hydroxylation and high testosterone 16-hydroxylation. Since P450 2B-B2 is catalytically distinct from the other forms, the metabolic profiles of phenotypes that include P450 2B-B2 might differ significantly from those of phenotypes that lack P450 2B-B2.

VH gene organization in a relict species, the coelacanth Latimeria chalumnae: evolutionary implications.

The living coelacanth Latimeria chalumnae is a relict species whose higher-level phylogenetic relationships have not been resolved clearly by traditional systematic approaches. Previous studies show that major differences in immunoglobulin gene structure and organization typify different phylogenetic lineages. To date, mammalian-, avian-, and elasmobranch-type gene organizations have been identified in representatives of these different phylads. A fourth form or organization is found in Latimeria, which possesses immunoglobulin heavy-chain variable region (VH) elements separated by approximately 190 nucleotides from diversity (D) elements. Adjacency of VH and D elements is characteristic of the elasmobranch "clustered" arrangement, although many other features of coelacanth VH gene organization and structure are more similar to those of bony fishes and tetrapods. These observations strongly support a phylogenetic hypothesis in which Latimeria occupies a sister-group relationship with teleosts and tetrapods.

Cleavage of the α1-microglobulin-bikunin precursor is localized to the Golgi apparatus of rat liver cells

α 1-Microglobulin, a plasma protein with immunoregulatory properties, and bikunin, the light chain of the proteinase inhibitors inter-α-inhibitor and pre-α-inhibitor, are translated as a precursor protein from the same mRNA. The cosynthesis of α 1-microglobulin and bikunin is unique compared to other proproteins such as procomplement components and prohormones, since α 1-microglobulin and bikunin have no known functional connection. Different forms of intracellular rat liver α 1-microglobulin were isolated and characterized by amino acid sequence analysis, lectin binding and glycosidase treatment. Their subcellular distribution was studied by Nycodenz and sucrose gradient centrifugation, pulse-chase experiments, and electrophoresis with subsequent immunoblotting, using pro-C3 and prohaptoglobin as reference proteins. Two α 1-microglobulin-bikunin precursors (40 and 42 kDa), containing one and two N-linked oligosaccharides, respectively, were detected in the endoplasmic reticulum. After transport to the Golgi apparatus, the precursors were cleaved, probably C-terminal to the sequence Arg-Ala-Arg-Arg immediately preceding the bikunin part, yielding free sialylated 28 kDa α 1-microglobulin, representing the mature protein. The cleavage was almost complete in phosphatidylinositol 4-kinase-enriched membranes, previously identified as a post-Golgi compartment. A fourth intracellular form of α 1-microglobulin, 26 kDa, lacked sialic acid. None of the intracellular forms carried the yellow-brown chromophore associated with α 1-microglobulin when purified from serum and urine, suggesting that this chromophore becomes linked to the protein after its secretion from the liver cells.

Identification of novel isoforms of the delta subunit of Ca2+/calmodulin-dependent protein kinase II. Differential expression in rat brain and aorta

Two novel isoforms of the Ca2+/calmodulin-dependent protein kinase II delta subunit were detected in rat aorta. Identification of the subunits was based on two independent lines of evidence, i.e. detection by immunoblotting of differently sized delta subunits and DNA sequence analysis of partial cDNA clones of the kinase. Cytosolic extracts from rat brain, aorta, and cultured aortic cells were analyzed by Western blotting using a delta subunit-specific antipeptide antibody. Aortic extracts demonstrated a single 53-kDa cross-reactive band approximately 7 kDa smaller than the cross-reactive band seen in brain. To ascertain the structural basis for this difference, reverse-transcribed RNAs from rat aorta and brain were analyzed by polymerase chain reaction (PCR), and the PCR fragments were cloned and sequenced. When aortic cDNA was analyzed with a primer pair that spanned the known variable region of the brain kinase subunit, the amplified PCR products were smaller than the major product obtained from brain cDNA. The aortic PCR product was cloned and sequenced and found to represent two novel subunit sequences, designated delta 2 and delta 3 to distinguish them from the previously described delta sequence (now called delta 1) from brain. delta 2 was identical to the predicted delta 1 sequence except for a deletion of 102 base pairs (bp). This deletion corresponded to nearly the entire variable domain. In the sequence of delta 3, this 102-bp region was replaced by a sequence of 33 bp that had 79% nucleotide sequence identity to a portion of the gamma subunit variable domain. A fourth form of the delta subunit (delta 4) was identified in rat skeletal muscle. The delta 4 isoform was characterized by the deletion of a 42-bp sequence identical to the 42 bp at the 3' end of the 102-bp deletion of delta 2. Reverse-transcription PCR analysis of additional rat tissues indicated that alternatively spliced variants of the delta subunit of Ca2+/calmodulin-dependent protein kinase II are expressed in a tissue-specific pattern.

Preliminary Crystallographic Analysis of a Fab Specific for the O-antigen of Shigella flexneri Cell Surface Lipopolysaccharide with and without Bound Saccharides

The Fab a monoclonal anti-carbohydrate antibody, SYA/J6 (IgG 3, κ, murine), raised against the O-polysaccharide antigen of the cell surface lipopolysaccharide of variant Y Shigella flexneri, a Gram negative bacterium, has been crystallized in the unliganded form and in complex with tri- and pentasaccharide antigens. The three crystal forms belong to the tetragonal space group P4 32 12, or P 4 12 12, with very similar unit cell dimensions and an asymmetric unit that contains one molecule of about 50,000 Daltons, and a fourth crystal form belongs to monoclinic space group P2 1, that contains four molecules of Fab in an asymmetric unit. Whereas diffractions of these crystals on an area detector-rotating anode system extend to only about 3·5 Å resolution, those measured using an imaging plate and synchrotron radiation at the Photon Factory facility extend to 2·5 Å

Response to “Remarks on two new theorems of Date and Fagin”

In [DF92], we present simple conditions, which we now describe, for guaranteeing higher normal forms for relational databases. A key is simple if it consists of a single attribute. We show in [DF92] that if a relation schema is in third normal form (3NF) and every key is simple, then it is in projection-join normal form (sometimes called fifth normal form), the ultimate normal form with respect to projections and joins. We also show in [DF92] that if a relation schema is in Boyce-Codd normal form (BCNF) and some key is simple, then it is in fourth normal form (4NF). These results give the database designer simple sufficient conditions, defined in terms of functional dependencies alone, that guarantee that the schema being designed is automatically in higher normal forms.

Effects of Concept and Vee Mappings Under Three Learning Modes on Students' Attitudes Towards the Mappings, Learning Modes, Ecology and Genetics

This study investigates the effects of concept and vee mappings under cooperative, cooperative-competitive and individualistic learning modes, ability levels and gender on students' attitudes towards concept and vee mappings, the three learning modes, ecology and genetics. A pre-test-post-test experiment, with control groups, involving 808 eleventh grade (fourth form) students, was used for data collection. Students taught the use of concept and vee mappings, under cooperative conditions, developed superior positive attitudes towards the two heuristics, ecology and genetics, compared with those taught under cooperative-competitive and individualistic conditions. Statistically significant differences in their attitudes were due mainly to treatment and ability. High ability students developed the most superior positive attitudes to concept and vee mappings, ecology and genetics. Students' attitudes towards cooperation were mostly positive but totally negative to individualisation and mostly negative to competition. Students' positive attitudes to ecology and genetics correlated negatively with their attitudes towards competition and individualisation. The implications of the study's findings for the teaching of science are addressed.

STUDIES IN THETABULARIA FASCICULATACOMPLEX

Original material of Diatoma fasciculatum C. A. Agardh 1812, Diatoma tabulatum C. A. Agardh 1832, and Synedra affinis Kützing 1844, has been studied. Lectotypes are selected for Diatoma fasciculatum and Diatoma tabulatum. The type material of Diatoma fasciculatum agrees with Tabularia fasciculata (C. A. Agardh) Williams & Round 1986. The new combinations Tabularia tabulata (C. A. Agardh) Snoeijs and Tabularia affinis (Kützing) Snoeijs are proposed. All three species are here treated as Tabularia Williams & Round, although it may be necessary to split the genus in the future. Further taxonomic and ecological observations on fasciculata-like diatoms were made from recently gathered material, including numerous samples along the salinity gradient of the Baltic Sea (from 11 down to <1°/oo), and year-round samples of living diatoms from a site with a salinity of 5°/oo. Frustule structure, chloroplasts, colony-type, ecological distribution, and cell morphometric data are discussed. Tabularia affinis was not found in the Baltic Sea; it is probably a marine species (type locality Adriatic Sea). In the Baltic Sea, four fasciculata-like forms with different salinity preferences and consistent morphologies can be recognised; Tabularia fasciculata, Tabularia tabulata, a third form which is best left as Tabularia of. laevis Kützing, and finally a fourth fasciculata-like form which was initially recognised on the basis of its chloroplast morphology.

Simple conditions for guaranteeing higher normal forms in relational databases

A key is simple if it consists of a single attribute. It is shown that if a relation schema is in third normal form and every key is simple, then it is in projection-join normal form (sometimes called fifth normal form), the ultimate normal form with respect to projections and joins. Furthermore, it is shown that if a relation schema is in Boyce-Codd normal form and some key is simple, then it is in fourth normal form (but not necessarily projection-join normal form). These results give the database designer simple sufficient conditions, defined in terms of functional dependencies alone, that guarantee that the schema being designed is automatically in higher normal forms.

O-glycosylation of the coronavirus M protein. Differential localization of sialyltransferases in N- and O-linked glycosylation.

It has previously been shown that the M (E1) glycoprotein of mouse hepatitis virus strain A59 (MHV-A59) contains only O-linked oligosaccharides and localizes to the Golgi region when expressed independently. A detailed pulse-chase analysis was made of the addition of O-linked sugars to the M protein; upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis, three different electrophoretic forms could be distinguished that corresponded to the sequential acquisition of N-acetylgalactosamine (GalNAc), galactose (Gal), and sialic acid (SA). A fourth and fifth form could also be detected which we were unable to identify. Following Brefeldin A treatment, the M protein still acquired GalNAc, Gal, and SA, but the fourth and fifth forms were absent, suggesting that these modifications occur in the trans-Golgi network (TGN). In contrast, in the presence of BFA, the G protein of vesicular stomatitis virus (VSV), which contains N-linked oligosaccharides, acquired Gal and fucose but not SA. These results are consistent with earlier published data showing that Golgi compartments proximal to the TGN, but not the TGN itself, relocate to the endoplasmatic reticulum/intermediate compartment. More importantly, our data argue that, whereas addition of SA to N-linked sugars occurs in the TGN the acquisition of both SA on O-linked sugars and the addition of fucose to N-linked oligosaccharides must occur in Golgi compartments proximal to the TGN. The glycosylation of the M protein moreover indicates that it is transported to trans-Golgi and TGN. This was confirmed by electron microscopy immunocytochemistry, showing that the protein is targeted to cisternae on the trans side of the Golgi and co-localizes, at least in part, with TGN 38, a marker of the TGN, as well as with a lectin specific for sialic acid.