Crystal Structure and Electronic Properties of Ammine[tris(2-aminoethyl)amine]copper(i~) Diperchlorate and Potassium Penta-amminecopper( 11) Tris( hexaf luorophosphate)By M a r y Duggan, Noel Ray, Brian Hathaway,' and (in part)
The effect of pre-heating resin composite on pre-cured viscosity and post-cured surface hardness was evaluated. Groups of uncured specimens were heated to 60 degrees C and compared with control groups (24 degrees C) with respect to viscosity and surface hardness. Mean (SD) viscosities of the pre-heated specimens (n = 15) were in the range of 285 (13)-377 (11) (Pa) compared with 642 (35)-800 (23) (Pa) at ambient temperature. There was a statistically significant difference between the two groups (P < 0.001). Mean (SD) Vickers microhardness (VHN) of the pre-heated group (n = 15) was 68.6 (2.3) for the top surface and 68.7 (1.8) for the bottom surface measured at 24 h post curing (specimen thickness = 1.5 mm). The corresponding values for the room temperature group were 60.6 (1.4) and 59.0 (3.5). There was a statistically significant difference between corresponding measurements taken at the top and bottom for the pre-heated and room temperature groups (P < 0.001). There was no significant difference between top and bottom measurements within each group. Pre-heating resin composite reduces its pre-cured viscosity and enhances its subsequent surface hardness. These effects may translate as easier placement together with an increased degree of polymerization and depth-of-cure.
The crystal structure of the title compounds [Cu(bipy)(C204)]-2H20 (1) and [Cu(bipy)(C204) (OH2)].2H20 (2) have been determined by X-ray analysis. Compound (1) crystallises in the triclinic space group P i with a = 9.673(3), b = 8.940(3), c = 9.103(3) A, a = 105.718(3), p = 110.347(3), y = 97.539(3)', and2 = 2. The six-co-ordinate C U N ~O ~O ' ~ chromophore of (1 ) involvesan elongated rhombic octahedralstereochemistryinvolving a symmetrically co-ordinated bipy ligand (mean CU-N 2.007 A) and unsymmetrically co-ordinated bridging oxalate groups (mean Cu-0 1.988 and 2.320 A). Compound (2) crystallises in the triclinic space group Pi with a = 10.565(3), b = 7.246(3), c = 10.806(3) A, a = 102.467(3), p = 62.119(3), y = 98.134(3)", and 2 = 2. TheCuN2020' chromophore of (2) is basically square pyramidal with a symmetrically co-ordinated bipy ligand (mean CU-N 1.989 A), and a symmetrically co-ordinated oxalate group (mean Cu-0 1.953 A) in the plane of the square pyramid, and a water molecule at 2.341 A out of the plane. The electronic reflectance spectrum of (1) involves a main band at 14 500 cm-' with a resolved broad band at 9 300 cm-l, while that of (2) involves a single broad band at 15 600 cm-I, a difference that is consistent with the structures and suggests an ' electronic criterion of stereochemistry ' to distinguish these two structures.
As dental practice management becomes more computer-based, the efficient functioning of the dentist will become dependent on adequate computer literacy. A survey has been carried out into the computer literacy of a cohort of 140 undergraduate dental students at a University Dental School in Ireland (years 1-5), in the academic year 1997-98. Aspects investigated by anonymous questionnaire were: (1) keyboard skills; (2) computer skills; (3) access to computer facilities; (4) software competencies and (5) use of medical library computer facilities. The students are relatively unfamiliar with basic computer hardware and software: 51.1% considered their expertise with computers as "poor"; 34.3% had taken a formal typewriting or computer keyboarding course; 7.9% had taken a formal computer course at university level and 67.2% were without access to computer facilities at their term-time residences. A majority of students had never used either word-processing, spreadsheet, or graphics programs. Programs relating to "informatics" were more popular, such as literature searching, accessing the Internet and the use of e-mail which represent the major use of the computers in the medical library. The lack of experience with computers may be addressed by including suitable computing courses at the secondary level (age 13-18 years) and/or tertiary level (FE/HE) education programmes. Such training may promote greater use of generic softwares, particularly in the library, with a more electronic-based approach to data handling.
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