it is always attempted to reduce the costs of comminution in mineral processing plants. one of thedifficulties in size reduction section is not to be designed properly. the key factor to design size reductionunits such as crushers and grinding mills, is ore’s work index. the work index, wi, presents the oregrindability, and is used in bond formula to calculate the required energy. bond has defi...

Ž . ABSTRACT: Bond-charge increments BCIs are additive parameters used to assign atomic charges for the MMFF force field. BCI parameters are classified parsimoniously according to two atom types and the bond order. We show how BCIs may be fitted rapidly by linear least squares to the calculated ab initio Ž . electrostatic potential ESP or to the electrostatic field. When applied simultaneously ...

[Bis(tri-methyl-sil-yl)amino](tert-butyl-imino)-thio-phospho-rane reacts in benzene with isopropyl alcohol via 1,2-addition of an (i) PrO-H bond across the P=N bond, resulting in the title compound, C13H35N2OPSSi2. In the mol-ecule, the P atom possesses a distorted tetra-hedral environment involving two N atoms from (Me3Si)2N- and (t) BuNH- groups, one O atom from an (i) PrO group and one S ato...

The title compound, C(6)H(8)FN(3)O(2), an analog of histidine, shows a reduced side-chain pK(a) (ca 1). The title structure exhibits a shortening of the bond between the proximal ring N atom and the F-substituted ring C atom, indicating an increase in π-bond character due to an inductive effect of fluorine.

Professor Dunitz questions the usefulness of ascribing crystalline structural stability to individual atom-atom intermolecular interactions viewed as bonding (hence stabilizing) whenever linked by a bond path. An alternative view is expressed in the present essay that articulates the validity and usefulness of the bond path concept in a crystallographic and crystal engineering context.

The present note is devoted to establish some extremal results for the zerothorder general Randić index of cacti, characterize the extremal polyomino chains with respect to the aforementioned index, and hence to generalize two already reported results.

The crystal structure of the ®rst reported non-substituted N-methyldioxazaborocane con®rms that the presence of a methyl group attached to the N atom introduces an N!B bond length that is longer than that in a simple dioxazaborocane ring. The presence of more N atoms in the vicinity of the B atom in the title compound [systematic name: 6a-(6bromopyridin-2-yl)-3a-methyl-2,3,4,5-tetrahydro-1,6-di...

Let T ∆ n denote the set of trees of order n, in which the degree of each vertex is bounded by some integer ∆. Suppose that every tree in T ∆ n is equally likely. We show that the number of vertices of degree j in T ∆ n is asymptotically normal with mean (μj + o(1))n and variance (σj + o(1))n, where μj , σj are some constants. As a consequence, we give estimate to the value of the general Zagre...

The general Randić index Rα(G) is the sum of the weight d(u)d(v)α over all edges uv of a graph G, where α is a real number and d(u) is the degree of the vertex u of G. In this paper, for any real number α = 0, the first three minimum general Randić indices among trees are determined, and the corresponding extremal trees are characterized.