Synthese und Festkörperstruktur des Koordinationspolymers {Zn[Sn(CH2SMe)4]0.5Cl2}n

Synthesis and Solid State Structure of the Coordination Polymer {Zn[Sn(CH₂SMe)₄]_0.5Cl₂}_n The tin compounds Sn(CH₂SMe)₄ and Sn(CH₂PPh₂)₄ are accessible from reaction of SnCl₄ with LiCH₂SMe and LiCH₂PPh₂, respectively. X‐ray quality crystals of Sn(CH₂PPh₂)₄ (tetragonal, ) are obtained from a benzene solution at 4 °C. The lithium methanide [Li(PMDTA)CH₂PPh₂], which was a starting material in the synthesis of Sn(CH₂PPh₂)₄ crystallized from a mixture of diethyl ether and pentane at ?20 °C in the monoclinic space group P2₁/c. The coordination polymer {Zn[Sn(CH₂SMe)₄]_0.5Cl₂}_n was synthesized from Sn(CH₂SMe)₄ and ZnCl₂ in benzene. The solid state structure of this coordination polymer reveals that {Zn[Sn(CH₂SMe)₄]_0.5Cl₂}_n possesses an infinite [Zn‐SMe‐CH₂‐Sn‐CH₂‐SMe‐]‐chain as its backbone (monoclinic P2₁/c).     

The microscopic analysis of high forchheimer number flow in porous media

High Forchheimer number flow through a rigid porous medium is numerically analysed by means of the volumetric averaging concept. The microscopic flow mechanisms, which must be known in order to understand the macroscopic flow phenomena, are studied by utilising a periodic diverging-converging representative unit cell (RUC). The detailed information for the microscopic flow field, in association with the locally averaged momentum balance, makes it possible to quantitatively demonstrate that the microscopic inertial phenomenon, which leads to distorted velocity and pressure fields, is the fundamental reason for the onset of nonlinear (non-Darcy) effects as velocity increases. The hydrodynamic definitions for Darcy's law permeabilityk, the inertial coefficient and Forchheimer number Fo are obtained by applying the averaging theorem to the pore level Navier-Stokes equations. Finally, these macroscopic parameters are numerically calculated at various combinations of micro-geometry and flow rate, and graphically correlated with the relevant microscopic parameters.Nomenclature a _i body force acceleration (m/s²) - A viscous integral term defined in (4.6) - A _f area of entrance and exist of RUC (m²) - A _fs interfacial area between the fluid and solid phases (m²) - B pressure integral term defined in (4.4) - d throat diameter of RUC (m) - D pore diameter of RUC (m) - Fo Forchheimer number defined in (4.1) and (4.10) - g gravitational acceleration (m/s²) - i, j microscopic unit vector for RUC - k Darcy's law permeability (m²) - k _v velocity dependent permeability defined in (4.1) (m²) - L length of a unit cell (m) - L _p pore length of RUC (m) - L _t throat length of RUC (m) - n unit outwardly directed vector for the fluid phase - p microscopic fluid pressure (N/m²) - P macroscopic fluid pressure (N/m²) - _en mean pressure at entrance of RUC (N/m²) - _ex mean pressure at exit of RUC (N/m²) - r _i,r coordinate on the macroscopic scale (m) - Re _d Reynolds number defined in (4.5) - u _i,u microscopic velocity (m/s) - specific discharge (m/s) - _d mean velocity at the throat of RUC (m/s) - v microscopic velocity (m/s) - V _b representative elementary volume (REV) (m³) - V _f volume occupied by the fluid within REV (m³) - V _s volume occupied by the solid within REV (m³) - x _i,x coordinate on the microscopic scale (m) - X _i,X coordinate on the macroscopic scale (m) Greek the inertia coefficient (1/m) - viscosity coefficient (Ns/m²) - _i microscopic unit vector - areosity at the entrance and the exit cross-section of RUC - fluid density (kg/m³) - porosity - _f a general property of the fluid phase Symbols ^f intrinsic phase average - the fluctuating part of _f - the mean value of _f - _f ^* the dimensionless value of _f     

The râle of microscopic cross flow in idealized porous media

In this paper, results from a combined network/averaging study are presented. The emphasis is placed on understanding the flow phenomena, rather than predicting results for real porous media. Idealized porous media, consisting of networks of tubes, are used to interpret two of the terms in the averaged momentum equation. In particular, it is demonstrated that the pressure term accounts for microscopic cross flow, and that the magnitude of this term is proportional to the variation of the cross-sectional areas of the tubes in the macroscopic flow direction. For one-dimensional macroscopic flow in these idealized porous media, the agreement of network theory and averaging theory permeabilities depends on areosity (a term related to the area open to flow in a direction) remaining constant in the macroscopic flow direction; it may vary in other directions.     

Luminescent Cyclometalated Platinum(II) Complex Forms Emissive Intercalating Adducts with Double‐Stranded DNA and RNA: Differential Emissions and Anticancer Activities

Luminescent metallo‐intercalators are potent biosensors of nucleic acid structure and anticancer agents targeting DNAs. There are few examples of luminescent metallo‐intercalators which can simultaneously act as emission probes of nucleic acid structure and display promising anticancer activities. Herein, we describe a luminescent platinum(II) complex, [Pt(C^N^N)(C≡NtBu)]ClO₄ ( 1 a , HC^N^N= 6‐phenyl‐2,2′‐bipyridyl), that intercalates between the nucleobases of nucleic acids, accompanied by an increase in emission intensity and/or a significant change in the maximum emission wavelength. The changes in emission properties measured with double‐stranded RNA (dsRNA) are different from those with dsDNA used in the binding reactions. Complex 1 a exhibited potent anticancer activity towards cancer cells in vitro and inhibited tumor growth in a mouse model. The stabilization of the topoisomerase I–DNA complex with resulting DNA damage by 1 a is suggested to contribute to its anticancer activity.     

EPR of defects in semiconductors: Past, present, future

Important physical concepts learned from early EPR studies of defects in silicon are reviewed. Highlighted are the studies of shallow effective-mass-like donors and acceptors by Feher, of deep transition-element impurities by Ludwig and Woodbury, and of vacancies and interstitials by Watkins et al. It is shown that the concepts learned in silicon translate remarkably well to corresponding defects in the other elemental and compound semiconductors. The introduction of sensitive optical and electrical detection methods during the intervening years, and the recent progress in single-defect detection insure the continued vital role of EPR in the future. Fiz. Tverd. Tela (St. Petersburg) 41, 826–830 (May 1999) Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor.