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Increasing net patient revenues from teaching clinics is one of the alternatives available to dental schools seeking to alleviate economic pressures. Managerial decisions directed to this end require accurate and useful data on clinic finances and economic organization. An important step in this direction can be taken by defining the teaching clinic as a cost center, that is as an economic entity in a dental school with identifiable specific resources, costs, and revenues. This paper describes the accounting and economics frameworks within which resources and costs are classified and allocated into direct and indirect, and fixed and variable categories. The development and structure of a cost-revenue model designed for the teaching clinics at the University of Connecticut School of Dental Medicine is described to illustrate an application of the cost center concept.

The title molecule, 3,7-bis(2-thienyl)-1,5,2,4,6,8-dithiatetrazocine, C 10 H 6 N 4 S 4 , is planar within 0.069 (5) A and crystallizes in the monoclinic space group P2 1 /c. There are two centrosymmetric molecules in the cell; these are stacked such that each eight-membered C 2 N 4 S 2 ring has a thienyl ring above and below it. The mean interplanar separation is 3.55 (2) A.

The present paper deals with the microstructural parameters calculated from X-ray diffraction data, electrical and optical investigations, and scanning tunneling microscopy (STM) studies on ZnIn2S4 IIIa layer type CdIn2S4-xSex (1.75 ≤ x ≤ 2.75) quaternary chalcogenides. Microstructural parameters such as dislocation density, root-mean-square strain, stacking fault probability, crystallite size anisotropy, and layer disorder parameters of these compounds have been calculated. The temperature variation of electrical conductivity (25−400 °C) confirmed semiconducting behavior. The band gaps of all these compounds obtained from STM and optical measurements are in the range 1.57−1.77 eV and are comparable to each other irrespective of the technique used.

The title molecule, 3,7-bis(2-thienyl)-1,5,2,4,6,8-dithiatetrazocine, C 10 H 6 N 4 S 4 , is planar within 0.069 (5) A and crystallizes in the monoclinic space group P2 1 /c. There are two centrosymmetric molecules in the cell; these are stacked such that each eight-membered C 2 N 4 S 2 ring has a thienyl ring above and below it. The mean interplanar separation is 3.55 (2) A.

The radical units Se 2 N 2 CMe dimerize with long Se...Se distances of 3.159(3) and 3.187(3) A to give the title compound, C 4 H 6 N 4 Se 4 . There are two crystallographically independent dimers in the unit cell. The dimers adopt a twisted conformation with parallel ring planes. One ring is rotated on the axis between ring centers by approximately 90° from the eclipsed position to give Se-Se-Se-Se torsion angles of 86.81(15) and 88.95 (17)°. Se-Se bond lengths within the radicals vary from 2.306 (3) to 2.330 (3) A.

The title compound, [Cu(C 10 H 14 N 4 O 2 P) 2 ], consists of pairs of bis(dimethylpyrazolyl)phosphinato groups coordinated to copper(II) atoms sitting on inversion centers. The compound has Cu-N bond distances of 2.009 (4) and 2.010 (4) A and an N-Cu-N angle of 89.27 (13)° . The phosphinato O atoms weakly coordinate the copper ions with bond distances of 2.490 (3) A.

The title phosphazene, P 3 N 3 R 4 XX, where R is 3,5-dimethylpyrazole and XX is a spiro-bonded −NHCH 2 CH 2 CH 2 NH− ring, has P−N bonds of 1.554 (5)-1.614 (5) A in the phosphazene ring with exocyclic bonds of 1.609 (5) and 1.635 (5) A to the spiro ring and 1.683 (4)-1.708 (5) A to the pyrazole groups. The N−P−N angle within the phosphazene ring at the unique P atom is 6.9 (3)° smaller than those at the other P atoms. One of the pyrazole-substituted P atoms is displaced by 0.252 (5) A from the best plane of the other five ring atoms, which are coplanar to within 0.087 (6) A. The −PNCCCN− ring conformation is intermediate between a boat and a twist-boat

The title compound [Ru(C 5 H 5 )(C 2 H 5 NS)(C 18 H 15 P) 2 ]BF 4 crystallizes in the space group P2 1 /c. The Ru atom has pseudotetrahedral coordination geometry formed by the cyclopentadienyl centroid, the two PPh 3 ligands and the S atom of the neutral thioacetamide molecule. The Ru-S and C=S distances are 2.3820 (13) and 1.671 (5) A, respectively, and the Ru-S=C angle is 116.3 (2) o . The Ru atom is at a distance of 0.405 (9) A from the plane formed by the atoms of the thioacetamide group

[Fe(CO) 4 (SO 2 )(C 5 H 5 ) 2 ]•H 2 O cristallise dans P2 1 /n avec a=10,884, b=12,424, c=12,658 A, β=103,35 o , Z=4; affinement jusqu'a R=0,0355. Les liaisons hydrogene entre l'eau et SO 2 lient les complexes entre eux. L'eau provoque la cristallisation du complexe dans usne conformation trans, en opposition a la forme gauche du materiau anhydre

C 18 H 14 Mn 2 O 6 Si cristalline dans P1 avec a=7,649, b=11,119 et c=12,203 A, α=98,39, β=104,68 et γ=96,29 o , Z=2; affinement jusqu'a R=0,039. Les deux cycles forment des angles diedres de 89,5 et 144,0 o avec le plan central et une unite Mn(CO) 3 est liee η 5 a chaque cycle

C 8 H 4 N 4 Se 2 2+ •2SbF 6 − •3C 7 H 5 N cristallise dans P1 avec a=6,829, b=13,981, c=21,320 A, α=72,26, β=89,03, γ=88,78 o , Z=2; affinement jusqu'a R=0,049. La maille cristalline contient quatre anions, six molecules de solvant et deux cations situes sur les centres d'inversion cristallographiques

[Rh(C 13 H 23 ) {(PCC 6 H 5 ) 3 } 2 ]•0,5 C 6 H 6 cristallise dans P1 avec a=12,260, b=13,05, c=15,91 A, α=71,30, β=76,24, γ=67,71 o , τ=2; affinement jusqu'a R=0,043. Les atomes du cycle a 13 chai←nons sont dans une configuration trans. Les distances des 3 atomes de ce cycle lies au metal sont de 2,120; 2,180; 2,231 A, et les angles formes par ces atomes sont de 123,9 et 125,7 o

C 24 H 20 ClN 3 P 2 Se cristallise dans P1 avec a=9,759, b=11,046, c=13,332 A, α=65,50, β=64,89, γ=74,96 o , Z=2; affinement jusqu'a R=0,036. Dans le cycle a 5 chai←nons, l'un des liens entre P et N est presque plan (a 0,053 A pres), tandis que l'atome Se soit de ce plan de 0,499 A du cote du chlore. Les longueurs des liaisons de la sequence Se−N−P−N sont en moyenne de 1,730; 1,637 et 1,584 A. Les angles des liaisons du cycle autour des atomes Se et P sont respectivement de 111,5 o et 117,8 o

Cristallisation dans C2/c avec a=11,578, b=22,122 et c=13,672 A, β=110,31 o , Z=4; affinement jusqu'a R=0,046. Le cation est localise sur un centre cristallographique de symetrie et deux anions SbF 6 − independants sont localises chacun sur un axe de rotation d'ordre 2. L'un des anions est desordonne

C 16 H 22 S 2 cristallise dans P2 1 /n avec a=8,851, b=15,398 et c=11,590 A, Z=4; affinement jusqu'a R=0,036. Presence de quatre contacts intramoleculaires entre les atomes H et le cycle phenylene dans le domaine 2,53 a 2,68 A, contribuent au «benzene courbe» typique des paracyclophanes

The Ru atom of the title complex, [Ru(C10H8N2)2-(H2O)2](PF6)2, is located on a crystallographic inversion center; the bipyridine ligands are bowed [dihedral angle between C5N planes is 162.68 (12) degrees] due to the interligand steric interactions of the trans bipyridyl units. The Ru--O distance is 2.116 (2) A and the mean Ru--N distance is 2.074 (2) A.

C 24 H 20 ClN 3 P 2 Se cristallise dans P1 avec a=9,759, b=11,046, c=13,332 A, α=65,50, β=64,89, γ=74,96 o , Z=2; affinement jusqu'a R=0,036. Dans le cycle a 5 chai←nons, l'un des liens entre P et N est presque plan (a 0,053 A pres), tandis que l'atome Se soit de ce plan de 0,499 A du cote du chlore. Les longueurs des liaisons de la sequence Se−N−P−N sont en moyenne de 1,730; 1,637 et 1,584 A. Les angles des liaisons du cycle autour des atomes Se et P sont respectivement de 111,5 o et 117,8 o

The synthesis and crystal structure of 2,5-diamino-3,6-dichloropyrazine, C4H4Cl2N4, are described. The centrosymmetric molecule has an exocyclic C—N distance of 1.362 (3) A, and a nearly planar amine group [the angles at N sum to 351 (2)°]. Within the crystal, the molecules form a ribbon through two centrosymmetric pairs of N—H⋯N hydrogen-bond interactions, where the N⋯N distance is 3.110 (3) A.

A crystallographic twofold rotation axis passes through the C-C bond joining the imidazole rings of the title compound, C10H10N4O2. The molecule crystallizes in a cis disposition. The planar acetyl group is twisted by 5.0 (3)° with respect to the imidazole ring and the two imidazole rings are tilted by 60.53 (5)° in relation to one another.

The title molecules, C 6 H 4 N 6 O 4 .2C 3 H 7 NO, lie on a center of inversion. One N atom of the ring is hydrogen bonded to the O atom of the dimethylformamide (DMF) solvate molecule [N-H...O = 2.699 (4) A]. The nitro group is tilted by 4.11 (18)° with respect to the imidazole ring.

Ru(HSO3)2(NH3)4), Mr=331.3, mono- clinic, P21/c, a = 6.2019 (15), b = 7.0213 (11), c = 11.761 (2)A, fl= 115.30(2) °, V= 463.0 (3) A 3, Z= 2, Dx = 2-38 g cm -3, A(Mo Kte) = 0.71073 A,, /z = 21-0 cm- 1, F(000) = 332, T = 293 K, R = 0.019 for 1179 reflections with Fo 2 > 3o'(Fo2). The complex lies on an inversion center with Ru-N distances of 2.141 (2) A, and a Ru-S distance of 2-2785 (5) A.. All of the H atoms are linked to O atoms of neighboring hydrogensulfite ligands in an extensive network of H bonds. Experimental. The title complex (I) was obtained by the procedure described by Vogt, Katz & Wiberley (1965). Colorless crystals were obtained by slow cooling of the reaction mixture. Data crystal was 0.12 x 0-20 x 0-32 mm and was mounted with epoxy on a glass fiber. Intensities measured with an Enraf- Nonius CAD-4 diffractometer using o~--20 scans of 4-16 ° min-~ in 0. Unit cell determined from least- squares analysis of angle data for 25 reflections with 17 < 20 < 22 °. Analytical absorption correction varied from 0-79 to 1.00. Data collected to (sin0)/A =0.68A.-', 0_

K[RuCl 4 (C 10 H 8 N 2 )] cristallise dans Pbcn avec a=14,382, b=13,980 et c=7,491 A, Z=4; affinement jusqu'a R=0,051. L'anion [Ru(bpy)Cl 4 ] − est sur un axe cristallographique d'ordre 2. Les cycles organiques des anions voisins se recouvrent avec des espacements entre les plans 3,27 et 3,36 A

Cu(C 7H9N)(C 12H8N2)2 ) (CIO4)2, M r = 730.0, monoclinic, P2,/n, a = 18.430 (3), b = 9.122(2), c=18.744(8)A, fl=97.92(3) °, V= 3121 (3) A 3, z = 4, Dm = 1.56 (1), D x = 1.55 gcm -3, 2(Mo Ka) = 0.71073 A, g = 9.3 cm -l, F(000) = 1492, T=293K, R=0.081 for 1312 unique observed reflections. The Cu-atom environment is approxi- mately square pyramidal, with the apical position occupied by an N atom of a 1,10-phenanthroline (phen) molecule. The Cu atom is 0.256 (3)A above the basal

(I), C 18 H 12 Mn 2 O 6 , cristallise dans P2 1 /C avec a=12,045, b=14,169 et c=11,468 A, β=115,91 o , Z=4, affinement jusqu'a R=0,043. (II), C 8 H 12 Mn 2 O 6 •1/2 C 6 H 6 , cristallise dans P1 avec a=7,850, b=9,205 et c=14,291 A, α=85,42, β=85,79 et γ=75,50 o , Z=2; affinement jusqu'a R=0,028. Ces deux cristaux presentent de grandes differences de conformation dans le coordinat dicyclopentadiene