Hasil untuk "math.OC"

E. V. Artem’eva, O. K. Sharutina, V. V. Sharutin et al.

Cindy Riou, Luiz Cordeiro, Nadine Gérard

Min Wu, Hermann B. Frieboes, Mark A.J. Chaplain et al.

H. D. Lutz

AbstractAus den IR‐Spektren (200–5000 cm−1) der Erdalkaliäthylate geht hervor, daß die Metall‐Sauerstoff‐Bindung bei Metallen mit kleinem Ionenradius (Magnesium) überwiegend kovalent ist (Wechselwirkung zwischen den (MeO)‐ und (CO)‐Schwingungen), während die Äthylatgruppe bei Metallen mit großem Ionenradius, also stark elektropositiven Elementen, weitgehend ionogen gebunden ist. Die Normalschwingungen des Äthylations können unter Zugrundelegung der Symmetriegruppe Cs zugeordnet werden. Die mit steigenden Kationenradius zunehmende, langwellige Verschiebung der CH‐Valenzschwingungen im Vergleich zum Äthanol läßt auf eine Verringerung der Bindungsfestigkeit der CH‐Bindung, vor allem bei der CH2‐Gruppe, schließen. Die in gleiche Richtung zunehmende Oxydationsempfindlichkeit der Äthylate steht damit in Zusammenhang.

Nozomu Matsubara

Chen Liu, Jinqiu Du, Wuhui Lin et al.

South Ural State University, V. Sharutin, A. Efremov

Tris[(2-methoxy)(5-bromo)phenyl]antimony dicarboxylates [(2-MeO)(5-Br)C6H3]3Sb[OC(O)C6H3F2-2,3]2 (1), [(2-MeO)(5-Br)C6H3]3Sb[OC(O)CH2OC6H2Cl3-2,4,5]2 ∙ ½ TolH (2) were synthesized by interaction of tris[(2-methoxy)(5-bromo)phenyl]antimony and car-boxylic acid in the presence of tert-butyl hydroperoxide (molar ratio 1:2:1) in ether at room tem-perature and structurally characterized after recrystallization from toluene. Crystallographic char-acteristics of 1 [C35H24Br3F4O7Sb, M = 994.00; triclinic syngony, space group P–1; cell parame-ters: a = 9.596(13) Å, b = 11.592(18) Å, c = 17.57(3) Å; a = 73.44(7)°, β = 86.25(7)°, g = 87.23(7)°, V = 1868(5) Å3, Z = 2; rcalc = 1.767 g/cm3; m = 4.011 mm–1; F(000) = 964.0; collection area by 2q: 5.54–48.88°; –11 ≤ h ≤ 11, –13 ≤ k ≤ 13, –20 ≤ l ≤ 20; total reflections 44182; independent reflections 6118 (Rint = 0.0341); GOOF = 1.039; R-factor = 0.0378]; 2 [C81H60Br6Cl12O18Sb2, M = 2469.61; triclinic system, space group Р–1; cell parameters: a = 12.214(7) Å, b = 14.000(9) Å, c = 15.358(6) Å; a = 95.32(2)°, β = 97.333(17)°, g = 111.15(3)°, V = 2402(2) Å3, Z = 1; rcalc = 1.707 g/cm3; m = 3.453 mm–1; F(000) = 1206.0; collection area by 2q: 5.84–56.998°; –16 ≤ h ≤ 16, –18 ≤ k ≤ 18, –20 ≤ l ≤ 20; total re-flections 74550; independent reflections 12138 (Rint = 0.0588); GOOF = 1.019 ; R-factor = 0.0384]. From the X-ray diffraction data it follows that crystals 1–2 consist of trigonal-bipyramidal molecules with the oxygen atoms of carboxylate ligands in axial positions (solvate molecules of toluene are present in crystal 2). The OSbO angles in 1 and 2 are 172.78(12)°, 175.51(8)°, the Sb-С equatorial bond lengths are 2.111(5)-2.130(5), 2.108(3)-2.126(3) Å; and the Sb-O axial lengths equal 2.096(4), 2.133(4) Å; 2.099(3), 2.121(3) Å, respectively. Due to the bi-dentate nature of the carboxylate ligands in structures 1 and 2 there are intramolecular contacts between the Sb and O atoms of the carbonyl groups [3.056(5), 3.070(5) Å; 3.129(4), 3.129(4) Å]. The formation of intramolecular contacts Sb⋅⋅⋅O(=C) occurs within two different CSbC equatorial angles, as a result of which the CSbC equatorial angles differ slightly from each other [108.44(19)-129.16(19)° for 1; 112.46(12)-123.88(11)° for 2]. In addition, in molecules 1 and 2 there are intramolecular contacts Sb⋅⋅⋅OMe, which are 3.043(6)-3.172(6) Å, 3.097(4)-3.189(4) Å, respectively, therefore it can be considered that the coordination number of the central metal atom increases to CN = 10. Complete tables of atomic coordinates, bond lengths and valence angles of compounds 1 and 2 are deposited in the Cambridge Crystallographic Data Centre (CCDC No. 2060290, No. 2067753 deposit@ccdc.cam.ac.uk; http://www.ccdc.cam.ac.uk).

GU Chianakwana, GU Chianakwana, Egwuonwu OA et al.

Pheochromocytomas are rare neuroendocrine tumors that arise from the adrenal medulla and rarely from extra-adrenal locations. Although rare, they are potentially lethal tumors [1]. The pathognomonic biochemical features of these tumors are markedly elevated plasma catecholamines and their metabolites. The high plasma catecholamines are the reasons for the hypertension seen in patients with these tumors.

Bora Farsak, Mehmet Oc, Bahar Oc et al.

Primary spontaneous coronary artery dissection is one of the rare causes of acute myocardial infarction and is mostly fatal. Previous studies report that it is mostly seen in middle-aged women in the last trimester of pregnancy and early postpartum period. Clinical presentation of the disease is variable in pattern, and its severity is related to extent and development rate of dissection. Herein we present three cases of primary spontaneous left main coronary artery dissection. Two of the patients are men and the third patient is a non-pregnant 69-year-old woman. The cases were presented and discussed with review of the pertinent literature.

Jon Petrescu

T.H. Dunigan

S.W. Seetharam, G.J. Minden, J.B. Evans