Unusual Orientation Research Articles

MOCVD Growth, Micro‐Structural, and Superconducting Properties of a‐Axis Oriented TlBaCaCuO Thin Films.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Influences of oxygen pressure and substrate temperature on the quality ofNdBa2Cu3Ox thin films prepared by pulsed laser deposition

Fabrication of c-axis oriented NdBa2Cu3Ox (Nd123) thin films with high critical temperature(Tc) prepared by using pulsed laser deposition (PLD) was investigated. Previousworks indicated that optimal deposition conditions of PLD-Nd123 films werequite different from those of PLD-Y123 films. We investigated systematicallythe influences of oxygen pressure and substrate temperature on both filmquality and superconducting properties. High-performance Nd123 films, withTc of 93 K, were successfully grown in an atmosphere with rather high oxygen pressureof 1.5 mbar. We observed an unusual crystal orientation behaviour wherebyc-axis oriented domains of the Nd123 films became dominant on loweringthe substrate temperature at oxygen pressure of 1.5 mbar and thea-axis oriented domains completely disappeared above 1.5 mbar. These tendencies areopposite to the behaviours reported in the fabrication of PLD-Y123 films. We discuss thecrystal orientation mechanism of PLD-Nd123 films.

MOCVD Growth, Micro-Structural, and Superconducting Properties of a-Axis Oriented TlBaCaCuO Thin Films

The fabrication of pure a-axis oriented Tl2Ba2Ca1Cu2O8 (Tl-2212) superconducting thin films, prepared ex-situ by a combined approach of metal−organic chemical vapor deposition (MOCVD) and thallium vapor diffusion, is reported. The unusual orientation has been obtained by depositing the superconducting films on LaAlO3 (100) buffer layers grown on SrTiO3 (100) substrates. The micro-structural and superconducting properties of a-axis oriented films have been investigated and compared with those of the c-axis oriented samples simultaneously deposited.

Abnormal extension of the femoral head epiphysis as a cause of cam impingement.

The etiology of an insufficient femoral head-neck offset has not been identified yet. It was investigated whether a decreased head-neck offset might be correlated with an unusual orientation of the physeal capital scar. Therefore, the femoral head-neck offset and the extension of the physeal scar onto the femoral neck were measured with specific magnetic resonance imaging arthrography. The measurements were done in 15 patients with anterior femoroacetabular impingement attributable to a nonspherical head and were compared with 15 age- and gender-matched control subjects. Eight serial magnetic resonance imaging sections perpendicular to the femoral neck axis were used in each hip to measure the head-neck offset and the epiphyseal extension toward the femoral neck at 16 measurement points. In both groups there was an inverse correlation between the amount of head-neck offset and the relative extension of the capital physeal scar in the cranial hemisphere of the head. Within the anterosuperior head quadrant, there was statistically significant different decrease of the head-neck offset and increase of the lateral epiphyseal extension in the patients compared with the control subjects. These findings suggest a growth abnormality of the capital physis as one probable underlying cause for a nonspherical head.

EPR detection of presumable magnetoelectric interactions in the liquid-crystalline state of an iron mesogen

The behavior of the iron-containing mesogenic molecules in the magnetic field was studied by EPR in ferroelectric-like smectic phases. The investigation of the angular dependence of the EPR spectra allows one to define the unusual orientation of the iron molecules in the external magnetic field. Different factors influencing the way of the molecules’ orientation in the magnetic field were considered and evaluated. It is shown that the unusual orientation is, most probably, caused by the action of the internal electric field (existing in the mesophases) on magnetic properties via the magnetoelectric effect. It is also found that the paramagnetic susceptibility of the iron complex in mesophases is increased, and that it has an anomaly in the same temperature range as the static dielectric permittivity does. It is supposed, that this anomaly is also associated with the creation of an additional magnetization by the internal electric field.

Morphology of the middle ear of golden moles (Chrysochloridae)

The middle ear structures of nine species of golden moles (family Chrysochloridae) were examined under the light microscope. Auditory structures of several of these species are described here for the first time in detail, the emphasis being on the ossicular apparatus. Confirming previous observations, some golden moles (e.g. Amblysomus species) have ossicles of a morphology typical of mammals, whereas others (Chrysospalax, Chrysochloris, Cryptochloris and Eremitalpa species) have enormously hypertrophied mallei. Golden moles differ in the nature and extent of the interbullar connection, the shape of the tympanic membrane and that of the manubrium. The stapes has an unusual orientation, projecting dorsomedially from the incus. It has been proposed that hypertrophied ossicles in golden moles are adapted towards the detection of seismic vibrations. The functional morphology of the middle ear apparatus is reconsidered in this light, and it is proposed that adaptations towards low‐frequency airborne hearing might have predisposed golden moles towards the evolution of seismic sensitivity through inertial bone conduction. The morphology of the middle ear apparatus sheds little light on the disputed ordinal position of the Chrysochloridae.

Peculiar spectral and power spectral behaviour of the LMXB GX 13+1

We present results of an analysis of all 480 ks of Rossi X-ray Timing Explorer Proportional Counter Array data obtained from 17 May 1998 to 11 October 1998 on the luminous low mass X-ray binary GX 13+1. We analysed the spectral properties in colour-colour diagrams (CDs) and hardness-intensity diagrams (HIDs) and fitted the power spectra with a multi-Lorentzian model. GX 13+1 traces out a curved track in the CDs on a time scale of hours, which is very reminiscent of a standard atoll track containing an island, and lower and upper banana branch. However, both count rate and power spectral properties vary along this track in a very unusual way, not seen in any other atoll or Z source. The count rate, which varied by a factor of ~1.6, along a given track first decreases and then increases, causing the motion through the HIDs to be in the opposite sense to that in the CD, contrary to all other Z and atoll sources. Along a CD track, the very low frequency noise uniquely decreases in amplitude from ~5 to ~2% (rms). The high frequency noise amplitude decreases from ~4% to less than 1% and its characteristic frequency decreases from ~10 to \~5 Hz. The 57-69 Hz quasi-periodic oscillation (QPO) found earlier is also detected, and no kHz QPOs are found. In addition the entire track shows secular motion on a time scale of about a week. The average count rate as well as the amplitude of the very low frequency noise correlate with this secular motion. We discuss a possible explanation for the peculiar properties of GX 13+1 in terms of an unusual orientation or strength of a relativistic jet.

On the conformation of the COOH-terminal domain of the large mechanosensitive channel MscL.

COOH-terminal (S3) domains are conserved within the MscL family of bacterial mechanosensitive channels, but their function remains unclear. The X-ray structure of MscL from Mycobacterium tuberculosis (TbMscL) revealed cytoplasmic domains forming a pentameric bundle (Chang, G., R.H. Spencer, A.T. Lee, M.T. Barclay, and D.C. Rees. 1998. Science. 282:2220–2226). The helices, however, have an unusual orientation in which hydrophobic sidechains face outside while charged residues face inside, possibly due to specific crystallization conditions. Based on the structure of pentameric cartilage protein , we modeled the COOH-terminal region of E. coli MscL to better satisfy the hydrophobicity criteria, with sidechains of conserved aliphatic residues all inside the bundle. Molecular dynamic simulations predicted higher stability for this conformation compared with one modeled after the crystal structure of TbMscL, and suggested distances for disulfide trapping experiments. The single cysteine mutants L121C and I125C formed dimers under ambient conditions and more so in the presence of an oxidant. The double-cysteine mutants, L121C/L122C and L128C/L129C, often cross-link into tetrameric and pentameric structures, consistent with the new model. Patch-clamp examination of these double mutants under moderately oxidizing or reducing conditions indicated that the bundle cross-linking neither prevents the channel from opening nor changes thermodynamic parameters of gating. Destabilization of the bundle by replacing conservative leucines with small polar residues, or complete removal of COOH-terminal domain (Δ110–136 mutation), increased the occupancy of subconducting states but did not change gating parameters substantially. The Δ110–136 truncation mutant was functional in in vivo osmotic shock assays; however, the amount of ATP released into the shock medium was considerably larger than in controls. The data strongly suggest that in contrast to previous gating models (Sukharev, S., M. Betanzos, C.S. Chiang, and H.R. Guy. 2001a. Nature. 409:720–724.), S3 domains are stably associated in both closed and open conformations. The bundle-like assembly of cytoplasmic helices provides stability to the open conformation, and may function as a size-exclusion filter at the cytoplasmic entrance to the MscL pore, preventing loss of essential metabolites.

An unusual orientation for Tyr75 in the active site of the aspartic proteinase from Saccharomyces cerevisiae

The structures of the native Saccharomyces cerevisiae proteinase A have been solved by molecular replacement in the monoclinic and trigonal crystal forms and refined at 2.6–2.7 Å resolution. These structures agree overall with those of other uninhibited aspartic proteinases. However, an unusual orientation for the side chain of Tyr75, a conserved residue on the flexible “flap” that covers the active site and is important for the activity of these enzymes, was found in the trigonal crystals. A similar conformation of Tyr75 occupying the S 1 substrate-binding pocket was previously reported only for chymosin (where it was interpreted as representing a “self-inhibited” state of the enzyme), but for no other aspartic proteinases. Since this orientation of Tyr75 has now been seen in the structures of two members of the family of aspartic proteinases, it might indicate that the placement of that residue in the S 1 substrate-binding pocket might have some functional significance, analogous to what was seen for self-inhibited structures of serine proteinases.

Oblique vegetation banding in the Australian arid zone: implications for theories of pattern evolution and maintenance

This paper describes strongly developed vegetation bands that are not aligned along the contour. This previously unreported oblique vegetation banding is developed in an arid region of mixed tussock grasses and chenopod shrubs in western New South Wales, Australia. In two of four contour-mapped, 0·5 ha quadrats, the vegetation bands are oriented at angles of 45–70° to the direction of slope. Various soil features indicative of a runoff and runon hydrology, very similar to those classically reported from contour-parallel vegetation banding, suggest that the oblique configurations have been stable for a considerable time. In addition to the unusual band orientation, marked variations in the ratio of intergrove width to grove width were found within the study area, spanning the range 0·21–4·95, and there was generally no correlation between intergrove width and the width of the grove receiving runoff water from it. These findings cast doubt on the supposed close adjustment of intergrove dimensions to grove water requirements. In nearby plots having ordinary contour-parallel vegetation banding, the absence of any upslope motion of the pattern was demonstrated using monuments installed at band margins 6 years previously. These properties do not accord with the predictions of many models of the development of vegetation banding. However, soil changes associated with the runoff–runon system operating within vegetation bands may be involved in stabilizing their configurations. Thus, future investigations into the origin of vegetation banding must distinguish between their form and hydrologic functioning once established, and the fundamental origin of the vegetation pattern, which may be altogether different. In addition, pedologic and other processes which may inhibit free pattern adjustments must be incorporated into models addressing the development of vegetation banding.

Molecular Nanomagnets

Quantum mechanical tunneling of the direction of magnetization is discussed for several examples of single-molecule magnets (SMM's). Magnetization tunneling is described for two crystallographically different forms of [Mn 12 O 12 (O 2 CC 6 H 4 - p -Me) 16 (H 2 O) 4 ] solvate. The two Mn 12 complexes are isomers. The magnetization versus magnetic field hysteresis loops are quite different for the two isomeric Mn 12 complexes. One Mn 12 complex exhibits a magnetization hysteresis loop that is characteristic of considerably faster magnetization tunneling than in the other Mn 12 isomer. The unusual orientation of Jahn-Teller elongation axes in one isomer leads to greater rhombic zero-field splitting that is the origin of the faster magnetization tunneling. In addition to data for Mn 12 complexes, magnetization relaxation rate versus temperature responses of three mixed-valence Mn 4 complexes are also reported. In all three cases the Arrhenius plot of the logarithm of the magnetization relaxation rate versus the inverse absolute temperature shows a temperature-independent region as well as a temperature-dependent region. The temperature-independent relaxation rate is definitive evidence of magnetization tunneling in the lowest-energy zero-field component of the ground state.

Synthesis and characterization of a disulfide-linked c(5)-symmetric [5]carceplex.

The synthesis and characterization of the first disulfide-linked and C5-symmetric carceplex.(guests)2 using the recently described [5]cavitands as building blocks is reported. The solution behavior of the new carceplexes was explored by 1D NOSEY (EXSY) experiments. The disulfides have unusually high energy barriers to interconversion due to their cooperativity. The guests (2 DMF or 2 DMA) reside in an unusual orientation in parallel planes that are perpendicular to the principal axis of the host.

An interesting diagnostic dilemma: Double right coronary artery or high take off of a large right ventricular branch

We would like to present and discuss the dilemma of an unusual right coronary artery anomaly in two cases. Double right coronary artery or a high take off of a large right ventricular branch are two diagnostic possibilities that may provide difficulty in differentiating such an unusual orientation of coronary arteries based on angiographic views.

On the formation of vertically oriented MCM-22 zeolite crystal films

Growth of MCM-22 zeolite films on glass substrates was studied with the focus on the understanding of the unusual vertical crystal orientation. The films formed were characterized by scanning electron microscopy and X-ray diffraction. Separate thin disk-like MCM-22 crystals were found vertically oriented at the early crystallization stage. With crystallization the crystals grew into thick disks and finally into continuous films. The vertically oriented MCM-22 thin crystals could be developed from the orientation of columnar MCM-22 nuclei, which have larger parameters in their c-directions than those in a and b directions. The preferred orientation of MCM-22 nuclei and the fast growth rate in the layer direction are responsible for the vertical growth of MCM-22 zeolite films.

Molecular recognition of sialyl Lewis(x) and related saccharides by two lectins.

The interaction of sialyl Lewis(x), Lewis(x), and alpha-L-Fuc-(1-->3)-beta-D-GlcNAc with isolectin A from Lotus tetragonolobus (LTL-A), and with Aleuria aurantia agglutinin (AAA) was studied using NMR experiments and surface plasmon resonance. Both lectins are specific for fucose residues. From NMR experiments it was concluded that alpha-L-Fuc-(1-->3)-beta-D-GlcNAc and Lewis(x) bound to both lectins, whereas sialyl Lewis(x) only bound to AAA. Increased line broadening of 1H NMR signals of the carbohydrate ligands upon binding to AAA and LTL-A suggested that AAA bound to the ligands more tightly. Further comparison of line widths showed that for both lectins binding strengths decreased from alpha-L-Fuc-(1-->3)-beta-D-GlcNAc to Lewis(x) and were lowest for sialyl Lewis(x). Surface plasmon resonance measurements were then employed to yield accurate dissociation constants. TrNOESY, QUIET-trNOESY, and trROESY experiments delivered bioactive conformations of the carbohydrate ligands, and STD NMR experiments allowed a precise epitope mapping of the carbohydrates bound to the lectins. The bioactive conformation of Lewis(x) bound to LTL-A, or AAA revealed an unusual orientation of the fucose residue, with negative values for both dihedral angles, phi and psi, at the alpha(1-->3)-glycosidic linkage. A similar distortion of the fucose orientation was also observed for sialyl Lewis(x) bound to AAA. From STD NMR experiments it followed that only the L-fucose residues are in intimate contact with the protein. Presumably steric interactions are responsible for locking the sialic acid residue of sialyl Lewis(x) in one out of many orientations that are present in aqueous solution. The sialic acid residue of sialyl Lewis(x) bound to AAA adopts an orientation similar to that in the corresponding sialyl Lewis(x)/E-selectin complex.

Solution structure of Methylophilus methylotrophus cytochrome c″: insights into the structural basis of haem-ligand detachment

Cytochrome c″ from Methylophilus methylotrophus is a monohaem protein with 124 amino acid residues. The iron has two histidine ligands in the oxidised form, one of which detaches and picks up a proton when the protein is reduced. Thus, both forms are paramagnetic. The structure of the oxidised form in solution, determined from NMR data is presented. The family of structures has an average backbone rmsd value of 0.53 Å, and a heavy atom rmsd value of 0.95 Å, within a target function range of 32 %. This structure is related to class I cytochromes with an additional helix at the N terminus. The haem-binding site occurs in a domain essentially lacking secondary structure motifs and the axial histidinyl residues were found in an unusual near perpendicular orientation. Moreover, a disulfide bridge is present, an uncommon structural feature among c-type cytochromes. The disulfide bridge, linking cysteine residues 96 and 104, forms a loop that confers rigidity and is essential to the detachment of the axial histidine (His95) as demonstrated by chemical disruption of the S-S bond. A route for protonation of the distal histidine involving haem propionate 17 is proposed and discussed in the light of available models for complex membrane proton pumps.

Unusual anisotropy of negative Hall states in (TMTSF) 2PF 6

We report an unusual orientation dependence of the negative quantum Hall effect (QHE) phases of the organic conductor (TMTSF) 2 PF 6 . Rotations within the b-c crystallographic plane produce a strong enhancement of the negative QHE states as the sample is tilted away from the normal. For rotations within the a-c plane, an opposite but somewhat less pronounced effect is observed. However, no such orientation dependence is found in the positive QHE states. These results establish a fundamental difference between the negative and positive QHE states in (TMTSF) 2 PF 6 . We speculate on the possibility of charge ordering associated with the negative phases.

Polyethylene Crystal Orientation Induced by Block Copolymer Cylinders

We examined the solid-state structures of two cylinder-forming semicrystalline diblock copolymers, where polyethylene forms the continuous matrix in both, using simultaneous small- and wide-angle X-ray scattering combined with transmission electron microscopy. The mesophase structure formed in the melt is largely retained upon cooling, whether the cylinders are glassy or rubbery during crystallization. Specimens in which the cylinders had been macroscopically oriented by flow revealed that the hexagonal packing of cylinders induces an unusual two-dimensional preferred orientation of the polyethylene crystals within the matrix. Specifically, the crystals tend to grow with their b axes parallel to the cylinder axes, while in the plane of the cylinder radii, the crystals tend to align their c axes parallel to the (10), (01), and (11̄) planes of the hexagonal macrolattice. By calculating various dimensions within the macrolattice, we conclude that the observed orientation allows the E crystals to best adopt their preferred thickness and spacing.

Seismic activity, inferred crustal stresses and seismotectonics in the Rana region, Northern Norway

The seismotectonic significance of the Rana region is known both from the fact that this was the location of the largest known earthquake in Fennoscandia in recent times, the M S 5.8–6.2 earthquake of August 31, 1819, and from its relatively high, constant seismic activity also in the 20th century. In order to study this region in more detail, a local seismic network has been in operation there since July 1997, as part of the NEONOR (Neotectonics in Norway) project. The network was primarily designed to detect possible activity on the Båsmoen fault which runs ∼50 km subparallel to the Rana fjord, and which shows signs of likely post glacial activity. The results have revealed a quite complex spatio-temporal distribution of seismic activity, and has also shown no activity on the Båsmoen fault itself. During the first 18 months of operation (July 1997–January 1999), the network has detected 373 locatable seismic events, of which 267 were local earthquakes. Most of these earthquakes occurred in five groups in the western parts of the network. All five groups had similar NNW-ESW trends in epicenter locations, and all have shallow foci (2–12 km), similar to what has also been found earlier for other concentrated earthquake zones in Northern Norway, and the magnitude range is between M L 0.1 and 2.8. Earthquake focal mechanism solutions within the network reveal a predominance for normal faulting with the tensional stress axis perpendicular do the coastline (implying an unusual coast-parallel orientation of the principal horizontal compressive stress). The earthquakes occur in a region of maximum post-glacial uplift gradients, which supports deglaciation flexure as a viable explanation for these earthquakes. A certain influence from more local factors, however, tied in general to crustal in homogeneities, cannot be ruled out.

Cyanide Binding to Lucina pectinata Hemoglobin I and to Sperm Whale Myoglobin: An X-Ray Crystallographic Study

The x-ray crystal structures of the cyanide derivative of Lucina pectinata monomeric hemoglobin I (L. pectinata HbI) and sperm whale ( Physeter catodon) myoglobin (Mb), generally taken as reference models for monomeric hemoproteins carrying hydrogen sulfide and oxygen, respectively, have been determined at 1.9 Å ( R-factor = 0.184), and 1.8 Å ( R-factor = 0.181) resolution, respectively, at room temperature ( λ = 1.542 Å). Moreover, the x-ray crystal structure of the L. pectinata HbI:cyanide derivative has been studied at 1.4-Å resolution ( R-factor = 0.118) and 100 K (on a synchrotron source λ = 0.998 Å). At room temperature, the cyanide ligand is roughly parallel to the heme plane of L. pectinata HbI, being located ∼2.5 Å from the iron atom. On the other hand, the crystal structure of the L. pectinata HbI:cyanide derivative at 100 K shows that the diatomic ligand is coordinated to the iron atom in an orientation almost perpendicular to the heme (the Fe-C distance being 1.95 Å), adopting a coordination geometry strictly reminescent of that observed in sperm whale Mb, at room temperature. The unusual cyanide distal site orientation observed in L. pectinata HbI, at room temperature, may reflect reduction of the heme Fe(III) atom induced by free radical species during x-ray data collection using Cu K α radiation.