Sharif Digital Repository

The high Cr, Ni base superalloy IN738LC has been directionally solidified on both laboratory and industrial scales using Bridgman and liquid metal cooling (LMC) methods respectively. In the Bridgman experiments, cylindrical rods were grown using a graphite chill with temperature gradient G = 5·0 K mm-1 and a water cooled copper chill with G = 8·5 K mm-1, and a wide range of withdrawal rates of R = 60, 120, 240, 600, and 1200 mm h-1. In the LMC rigs, several turbine blades were grown using a wide range of withdrawal rates of R = 120, 225, 330, 420, and 630 mm h-1. Grain and dendritic structures in both cylindrical and turbine blade specimens were evaluated in longitudinal and transverse... 

The problem of finding a characterization of Cohen-Macaulay simplicial complexes has been studied intensively by many authors. There are several attempts at this problem available for some special classes of simplicial complexes satisfying some technical conditions. This paper is a survey, with some new results, of some of these developments. The new results about simplicial complexes with Serre's condition are an analogue of the known results for Cohen-Macaulay simplicial complexes  

Three new Cu(I) complexes containing bidentate N^N donor ligands with the general formula [Cu(N^N)2][PF6] (N^N = 2,3-diphenyl-6,7-di-p-tolyl-1,4,5,8-tetraazaphenanthrene (L1), 2,3-diphenyl-6,7-di(2-thienyl)-1,4,5,8-tetraazaphenanthrene (L2), and 2,3-diphenyl-6,7-di-p-fluorophenyl-1,4,5,8-tetraazaphenanthrene (L3), were prepared by the reaction of [Cu(CH3CN)4][PF6] with two equivalents of the N^N ligand. Single-crystal X-ray diffraction analysis confirmed that in each complex the metal displays a distorted tetrahedral geometry surrounded by the four N atoms of the two sterically hindered substituted tetraazaphenanthrene (TAP) ligands. Density functional theory (DFT) and time-dependent density... 

The solution equilibria of magnesium (II) complex formed with bidentate ligand of dopamine in acidic media (pH=∼4-∼6) have been studied in cosolvent systems at 15, 25, 35 ± 0.1° C and 1=0.2 mol.dm-3 sodium chloride, using phosphate buffer, with spectrophotometric methods. Evidence for the 2:1 complex was not observed for magnesium. The stability constant of the complex was determined KMg(HL)+ = ∼9 and the resulting free-energy changes obtained. The protonation constant of dopamine was determined under the above conditions. The results are discussed in terms of the effect of solvent on protonation and complexation  

The novel, unsymmetrical, mixed-donor, tetradentate amido, and oxo complexes of V(IV) of the general formula VOLx were synthesized by a nontemplate method and characterized by physico-chemical methods. The ligands were prepared by a two-stage aldol condensation reaction in the molar ratio 1:1 of 2-hydroxybenzaldehyde, 2′-hydroxyacetophenone, or 2′,4′- dihydroxyacetophenone and 1,2-diaminopropane of the general formula HA x (x = 1-3) as precursors. The tetradentate mixed donor ligands of the general formula H2Lx (x = 1-6) were obtained by condensation reaction of precursors with appropriate ketone or aldehyde. The synthesis of the ligand system, described here, is an efficient and easy method... 

A concept of Cohen–Macaulay in codimension t is defined and characterized for arbitrary finitely generated modules and coherent sheaves by Miller, Novik, and Swartz in 2011. Soon after, Haghighi, Yassemi, and Zaare-Nahandi defined and studied CMt simplicial complexes, which is the pure version of the abovementioned concept and naturally generalizes both Cohen–Macaulay and Buchsbaum properties. The purpose of this paper is to survey briefly recent results of CMt simplicial complexes. © 2021, Institute of Mathematics, Vietnam Academy of Science and Technology (VAST) and Springer Nature Singapore Pte Ltd  

A concept of Cohen–Macaulay in codimension t is defined and characterized for arbitrary finitely generated modules and coherent sheaves by Miller, Novik, and Swartz in 2011. Soon after, Haghighi, Yassemi, and Zaare-Nahandi defined and studied CMt simplicial complexes, which is the pure version of the abovementioned concept and naturally generalizes both Cohen–Macaulay and Buchsbaum properties. The purpose of this paper is to survey briefly recent results of CMt simplicial complexes. © 2021, Institute of Mathematics, Vietnam Academy of Science and Technology (VAST) and Springer Nature Singapore Pte Ltd  

The preparation of two new bis(N-heterocyclic carbene) platinum(ii) complexes, in which NHC rings are joined by a CH2 linker group, is described. While, the chelate complex [PtMe2(bis-NHC1)], 1, was formed with large tert-butyl wingtips, the iso-propyl N-substituent analogue favors formation of the cluster complex [Pt2Me4(μ- SMe2)(μ-bis-NHC2)]2(μ-Ag2Br2), 2, in which two binuclear platinum(ii) complexes are linked together by an Ag2Br2 unit. The chelating platinum complex 1 undergoes aerial CO2 fixation and forms platinum(ii) carbonate complex [Pt(CO3)(bis-NHC1)], 3  

A new mononuclear molybdenum(VI)-oxodiperoxo complex [MoO(O 2)2(phox)] with a simple bidentate ligand, 2-(2′-hydroxyphenyl)-5,6-dihydro-1,3-oxazine (Hphox), has been synthesized and characterized by X-ray structure analysis, elemental analysis, infrared, and 1H NMR spectroscopy. A triclinic space group P-1 was determined by X-ray crystallography from single-crystal data of this complex. The resulting complex functioned as a facile sulfide oxidation catalyst with urea hydrogen peroxide as terminal oxidant at room temperature. The catalyst showed efficient reactivity in oxidation of sulfides giving high yield and selectivity  

In this paper, we report that a known dinuclear Fe complex, [tpa(H2O)FeOFe(H2O)tpa](ClO4)4 (tpa: tris(2-pyridylmethyl)amine), is an efficient catalyst toward organic sulfide oxidation in the presence of urea-hydrogen peroxide  

This study reports synthesis and characterization of polymeric [MoO2(Salen)] complexes that combine MoO2(acac)2 and polymeric ligands bearing N2O2 coordination sites, abbreviated herein as [piperazinCH2{MoO2(Salen)}]n (6), [piperazinCH2{MoO2(Salophen)}]n (7), and [piperazinCH2{MoO2(Salpn)}]n (8). The epoxidation of alkenes using tert-butyl hydroperoxide and oxidation of sulfides to sulfoxides by urea hydrogen peroxide were enhanced with excellent selectivity under the catalytic influence of these coordination polymers. No relevant difference in activity was found due to change in the diamine in the Schiffs base ligands. The stability of polymeric catalysts was assessed by recycling a sample... 

New dioxomolybdenum(VI) complex was prepared by reacting 1-(2,4-dihydroxybenzylidene)-N-methyl-N-phenylthiosemicarbazone (H2L) as ligand and [MoO2(acac)2] in acetonitrile solution. The doubly deprotonated ligand is coordinated to molybdenum through sulfur atom, hydrazinic nitrogen atom and phenolic oxygen atom. The resulting complex with the formula [MoO2L(CH3CN)] which contains an acetonitrile molecule in sixth site of coordination, was characterized by elemental analyses, 1H NMR, IR and electronic spectroscopic studies and single crystal X-ray diffraction analysis. This complex was tested as a catalyst for the homogeneous epoxidation of olefins using tert-butyl hydrogen peroxide (TBHP) as... 

A new mononuclear oxo-peroxo complex of molybdenum(VI) of the formula [MoO(O2)(phox)2] (where phox = 2-(2′-hydroxyphenyl) oxazoline) has been synthesized and characterized by X-ray structure analysis, elemental analysis, infrared, UV-visible and 1H, 13C NMR spectroscopy. A monoclinic space group P-1 was determined by X-ray crystallography from single-crystal data of this complex. Complex functions as facile alkane oxidation catalyst with hydrogen peroxide as terminal oxidant at room temperature. The catalyst shows very much efficient reactivity in the oxidation reactions giving high yield, turnover number (TON) and selectivity  

A new cis-dioxo molybdenum(VI) complex was obtained by reaction of 2,4-dihydroxybenzylidene(5-N,N-methylphenylamino-1,3,4-thiadiazol-2-yl)hydrazone as ligand and [MoO2(acac)2] in methanol and was characterized by elemental analyses, 1H NMR, IR, and electronic spectroscopic studies. The complex was also analyzed by single-crystal X-ray diffraction. The structure determination revealed a distorted octahedral coordination geometry around molybdenum in which the tridentate NNO donor (L2-) is bonded to [MoO2]2+ through phenolic oxygen, hydrazinic nitrogen, and thiadiazole nitrogen. The sixth coordination site is occupied by a weakly bonded methanol. The complex was tested as a catalyst for... 

Two new silver(I) complexes ((tptz)Ag2(NO3) 2 and [Ag5(tptz)4](NO3)5) with 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz) have been synthesized and characterized by X-ray diffraction, elemental analysis, 1H NMR, IR, fluorescence, UV-Vis spectroscopy and electrochemistry. Oxidation of alcohols to their corresponding aldehydes and ketones was conducted with one of the Ag complexes as a catalyst, soluble enough in organic solvent, using oxone (2KHSO5·KHSO4·K2SO4) as an oxidant under biphasic reaction conditions (CH2Cl 2/H2O) and tetra-n-butylammonium bromide as phase transfer agent under air at room temperature  

In this paper, we propose a new algorithm that minimizes the worst expected growth of an epidemic by reducing the size of the largest connected component (LCC) of the underlying contact network. The proposed algorithm is applicable to any level of available resources and, despite the greedy approaches of most immunization strategies, selects nodes simultaneously. In each iteration, the proposed method partitions the LCC into two groups. These are the best candidates for communities in that component, and the available resources are sufficient to separate them. Using Laplacian spectral partitioning, the proposed method performs community detection inference with a time complexity that rivals... 

Suppose n colored points with k colors in Rd are given. The Smallest Color-Spanning Ball (SCSB) is the smallest ball containing at least one point of each color. As the computation of the SCSB in Lp metric (p≥1) is time-consuming, we focus on approximately computing the SCSB in near-linear time. Initially, we propose a 3-approximation algorithm running in O(n logn) time. This algorithm is then utilized to present a (1+ε)-approximation algorithm with the running time of O((1/ε)dn logn). We improve the running time to O((1/ε)dn) using randomized techniques. Afterward, spanning colors with two balls is studied. For a special case where d=1, there is an algorithm with O(n2) time. We demonstrate... 

We consider d-dimensional simplicial complexes which can be PL embedded in the 2d-dimensional Euclidean space. In short, we show that in any such complex, for any three vertices, the intersection of the link-complexes of the vertices is linklessly embeddable in the (Formula presented.)-dimensional Euclidean space. In addition, we use similar considerations on links of vertices to derive a new asymptotic upper bound on the total number of d-simplices in an (continuously) embeddable complex in 2d-space with n vertices, improving known upper bounds, for all (Formula presented.). Moreover, we show that the same asymptotic bound also applies to the size of d-complexes linklessly embeddable in the... 

We consider d-dimensional simplicial complexes which can be PL embedded in the 2d-dimensional Euclidean space. In short, we show that in any such complex, for any three vertices, the intersection of the link-complexes of the vertices is linklessly embeddable in the (2 d- 1 ) -dimensional Euclidean space. In addition, we use similar considerations on links of vertices to derive a new asymptotic upper bound on the total number of d-simplices in an (continuously) embeddable complex in 2d-space with n vertices, improving known upper bounds, for all d≥ 2. Moreover, we show that the same asymptotic bound also applies to the size of d-complexes linklessly embeddable in the (2 d+ 1 ) -dimensional... 

A polymeric phenolato-bridged potassium compound, K(2-bromo-4,6 dinitrophenolate) (H2O), was obtained by reaction of methylammonium 2-bromo-4,6-dinitrophenolate and potassium chloride in water. 2-bromo-4,6 dinitrophenolate co-ordinates to the metal ion by phenolic O atom, Br, and O atoms of the nitro groups. K+ ion is eleven-coordinate in the compound. Single-crystal X-ray diffraction for methylammonium 2-bromo-4,6-dinitrophenolate and single-crystal X-ray diffraction, elemental analysis, IR, UV-Vis spectra, and fluorescence emission spectra for the complex have also been determined. Methylammonium 2-bromo-4,6-dinitrophenolate was solved in the monoclinic system, space group P21/c, with the...