Crystal structure of tetrakis(μ3-2-{[1,1-bis(hydroxymethyl)-2-oxidoethyl]iminomethyl}-6-methoxyphenolato)tetrakis[aquacopper(II)]: a redetermination at 200 K

The crystal structure of the tetranuclear title compound, [Cu4(C12H15NO5)4(H2O)4], has been previously reported by Back, Oliveira, Canabarro & Iglesias [Z. Anorg. Allg. Chem.(2015),641, 941–947], based on room-temperature data. In the previously published structure, no standard uncertainties are recorded for the deprotonated hydroxymethyl group and water molecule O atoms coordinating to the metal atom indicating that they were not refined; furthermore, the H atoms of some OH groups and water molecules have not been positioned accurately. Since the current structure was determined at a lower temperature, all atoms, including the H atoms of these hydroxy groups and the water molecule, have been determined more accurately resulting in improved standard uncertainties in the bond lengths and angles. Diffraction data were collected at 200 K, rather than the more usual 100 K, due to apparent disordering at lower temperatures. In addition, it is now possible to report intra- and intermolecular O—H...O interactions. In the title complex molecule, which has crystallographic -4 symmetry, the CuIIions are coordinated by the tridentate Schiff base ligands and water molecules, forming a tetranuclear Cu4O4cubane-like core. The CuIIion adopts a CuNO5elongated octahedral environment. The coordination environment of CuIIat 200 K displays a small contraction of the Cu—N/O bonds, compared with the room-temperature structure. In the crystal lattice, the neutral clusters are linked by intermolecular O—H...O hydrogen bonds into a one-dimensional hydrogen-bonding network propagating along thebaxis.

Relations of Normal Bundles and Flips of Small Contractions on Projective Manifolds

Let X be a smooth projective variety over the complex number field. Let f : X → Y be a small contraction, and suppose that each irreducible component Ei of the exceptional locus E of f is a smooth subvariety. Assume that dim E ≤ ½ ( dim X + 1), and the normal bundle [Formula: see text]. Then each Ei ≅ P dim Ei or Q dim Ei. Moreover, the flip f+ : X+ → Y of f exists.

HUGE MAGNETOVOLUME EFFECT IN AN INVERTED Mn LAYER ON Ag(001) STUDIED BY LEED

The surface structure obtained by deposition of a Ag monolayer on the ideal c(2 × 2) antiferromagnetic Mn monolayer on Ag(001) at 100 K and subsequent annealing at room temperature is determined by low energy electron diffraction. It is established that this system is actually a good realization of an inverted monolayer, i.e. a pseudomorphic Ag/Mn/Ag(001) structure that corresponds to a reversed composition of the two topmost layers with respect to the Mn overlayer. The Ag–Mn and Mn–Ag interlayer distances, d12 = 1.97 ± 0.015 Å and d23 = 1.97 ± 0.02 Å respectively, indicate only a fairly small contraction of ~ 3.5% (~ 1.5%) with respect to the ideal Ag bulk lattice (Mn monolayer on top) as compared to ~ 10% expected from atomic radii in bulk Mn and Ag. This clearly reveals a spectacular magnetovolume effect related to the high spin state of Mn in this two-dimensional structure.

Musculoskeletal Pain from Repetitive Strain in Musicians: Insights into an Alternative Approach

In dealing with the symptoms of repetitive strain suffered by musicians, the focus has been primarily on assessing prevalence and developing means of prevention. While these are useful endeavors, the etiology of repetitive strain at the cellular level has not been well understood. As a consequence, the well-established forms of therapy--drugs, exercise, stretching, splinting, and rest--have gone largely unquestioned, even though they fail to solve the problems of many musicians. Chronic pain continues to ruin musical careers, in spite of everything the medical community has to offer. It may be worth questioning whether the medical community is overlooking something of value outside the boundaries of accepted practice. There is reason to believe that a significant proportion of the aches, pains, and other symptoms caused by repetitive strain are actually generated by myofascial trigger points, or small contraction knots, in the muscles of the body. This article is an effort to acquaint the readers with the basic tenets of myofascial trigger points.

Human Isolated Coronary Artery Contraction To Sumatriptan: A Post Hoc Analysis

A post hoc analysis was performed on concentration response curves to sumatriptan in 62 human isolated coronary arteries. We determined whether donor-related clinical characteristics (age, sex, cause of death) and properties of the coronary artery (functional endothelial integrity, muscle mass) were related to the potency and efficacy of sumatriptan in contracting the human isolated coronary artery. The efficacy of sumatriptan was inversely related to the functional integrity of the vessel endothelium. Thus, contrary to expectation, coronary artery constriction to sumatriptan seems to be more pronounced in patients with nondiseased coronary arteries where the endothelium is intact. Nevertheless, in view of the high coronary reserve in these patients, myocardial ischemia after the use of sumatriptan is unlikely to occur, whereas in patients with coronary artery disease even a small contraction may be deleterious.

Hydraulic jump in channel contraction

The hydraulic jump in a linearly contracting channel is studied in relation to choking flow. For a contraction intended to perform under supercritical flow, choking is an important design consideration because of the increase of flow depth and modified upstream conditions. Based on the momentum equation, a relation for the sequent depths ratio is determined and verified with extended experiments. Further, the mechanisms of both hydraulic jump and the choking flow are described. The wall surface profile is shown to be similar and equal to the profile of the classical hydraulic jump for a relatively small contraction rate. The lengths of roller and jump are determined, and substantial agreement with the classical jump is again found. The choking of a channel contraction is discussed as the limit condition of the hydraulic jump. A simplified model is shown to agree with observations. A design equation for choking is proposed. Key words: channel, choking, contraction, hydraulic jump, supercritical flow, water flow.

A remark on elementary contractions

Let X be a smooth projective variety of dimension n over the field of complex numbers. We denote by Kx the canonical bundle of X. By Mori's theory, if Kx is not numerically effective (i.e. if there exists a curve on X which has negative intersection number with Kx), then there exists an extremal ray ℝ+[C] on X and an elementary contraction fR: X → Y associated with ℝ+[C].fR is called a small contraction if it is bi-rational and an isomorphism in co-dimension one.

Endothelin-Induced Contraction and Relaxation of Rat Isolated Basilar Artery: Effect of BQ-123

In ring segments from rat basilar artery (BA) the endothelin (ET) peptides ET-1, ET-2, and ET-3 induced concentration-related contractions. The order of potency was ET-1 = ET-2 > ET-3, while no differences occurred in the maximum contraction. The selective ETA receptor antagonist, BQ-123 (10−10-10−4 M) alone elicited a small contraction only at 10−4 M. In the presence of BQ-123 (10−7-10−5 M), the concentration-response curve for ET-1 was shifted to the right without any decrease in maximum contraction, indicating competitive inhibition of ET-1 binding to the ETA receptor by BQ-123. The pA2 value calculated for BQ-123 was 6.935; the slope of the regression curve was 0.734. In contrast to ET-1, the contractile action of ET-3 was abolished by 10−5 M BQ-123. In segments precontracted with 10−6 M serotonin, ET-3, but not ET-1, induced relaxation at low concentrations (10−11-10−8 M), with maximum relaxation amounting to 17.8 ± 14.7% of precontraction (mean ± SD; n = 16). The relaxant action of ET-3 was abolished in vessels incubated with NG-nitro-l-arginine (10−5 M), an inhibitor of nitric oxide synthase. These results indicate that the ET-induced contraction of the isolated rat BA involves activation of the ETA receptor. The ET-3-induced relaxation of precontracted rat BA is apparently mediated by release of nitric oxide from the endothelium.

Influence of hydroxyl radical on rabbit airway smooth muscle chronically exposed to H2O2 in vivo

The effects of .OH on the isolated tracheal smooth muscles (TSM), from control, polyethylene glycol (PEG)-glucose oxidase (GO)-, and GO+PEG catalase-treated rabbits were investigated. GO or GO+catalase were given intravenously each week for 4 mo. .OH produced relaxation of basal and ACh-precontracted tension in TSM of control rabbits. The relaxant effect was attenuated by removal of epithelium, whereas it was converted to contraction in the indomethacin-pretreated muscle. .OH produced contraction of TSM and ACh-precontracted muscle in GO-treated rabbits. The contractile response was abolished in preparations denuded of epithelium or pretreated with indomethacin. .OH produced relaxation in basal tension, but a small contraction in ACh-precontracted muscle of GO+catalase-treated rabbits. The contractile response to .OH was unaffected by indomethacin pretreatment; however, it was converted to relaxation in the preparations denuded of epithelium. Contractile response of TSM to ACh was augmented in deepithelialized, indomethacin-, or GO-treated preparations. H2O2 damaged the tracheal epithelium. These results suggest that 1) .OH-induced relaxation/contraction of TSM is partly epithelium dependent and is mediated by bronchodilator/bronchoconstrictor arachidonic acid metabolites, 2) the airway smooth muscle with healthy epithelium responds to .OH differently from those with dysfunctional or damaged epithelium, and 3) hyperresponsiveness of the airways to ACh may be related to the epithelial dysfunction.