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Rigid System (rigid + system)
Selected AbstractsHelical Bis(N-Confused Porphyrins) with Subunits Fused by Double Orthometalation with Platinum: Adaptability of an Apparently Rigid System,ANGEWANDTE CHEMIE, Issue 46 2009Piotr Starr und doch flexibel: Wegen der Flexibilität der Porphyrinringe gelingen Racemisierung oder chirale Induktion auch noch bei helicalen metallierten N-invertierten Biporphyrinen, obwohl das Bipyrrolfragment starr ist. Die Porphyrine sind peripher doppelt mit Platin(II) orthometalliert, und einige Produkte ihrer oxidativen Addition wurden ebenfalls erhalten (siehe die Strukturen des Iodmethyladdukts: grau und braun C; blau N; orange Pt; violett I). [source] Processability and mechanical properties of commercial PVC plastisols containing low-environmental-impact plasticizersJOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 3 2009Paola Persico Preliminary results are presented concerning the use of less-toxic plasticizers such as dioctyl adipate (DOA) and acetyl tributyl citrate (ATBC) in plastisol formulations for rotational molding technology. The DOA and ATBC plasticizers have been studied by comparing the effects of their content, molecular architecture, and polarity on the rheological behavior of liquid plastic systems and on the mechanical properties of the ultimate products prepared with PVCs having different particle sizes and molecular-weight distributions. Rheological tests have confirmed the differences in solvent power of the diethylhexyl phthalate (DOP), DOA, and ATBC plasticizers. The glass transition temperatures measured on rotomolded samples have shown that the use of ATBC leads to a more nearly rigid system as a consequence of the branched structure and polarity of this plasticizer when compared with DOA. Mechanical tests carried out on final products after natural and forced environmental aging revealed a slight decrease in their performance. J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers [source] Perspective: The Stage-Gate® Idea-to-Launch Process,Update, What's New, and NexGen Systems,THE JOURNAL OF PRODUCT INNOVATION MANAGEMENT, Issue 3 2008Robert G. Cooper Stage-Gate has become a popular system for driving new products to market, and the benefits of using such a robust idea-to-launch system have been well documented. However, there are many misconceptions and challenges in using Stage-Gate. First, Stage-Gate is briefly outlined, noting how the system should work and the structure of both stages and gates. Next, some of the misconceptions about Stage-Gate,it is not a linear process, nor is it a rigid system,are debunked, and explanations of what Stage-Gate is and is not are provided. The challenges faced in employing Stage-Gate are identified, including governance issues, overbureaucratizing the process, and misapplying cost-cutting systems such as Six Sigma and Lean Manufacturing to product innovation. Solutions are offered, including better governance methods such as "gates with teeth," clearly defined gatekeepers, and gatekeeper rules of engagement, as well as ways to deal with bureaucracy, including leaner gates. Next-generation versions of Stage-Gate are introduced, notably a scalable system (to handle many different types and sizes of projects), as well as even more flexible and adaptable versions of Stage-Gate achieved via spiral development and simultaneous execution. Additionally, Stage-Gate now incorporates better decision-making practices including scorecards, success criteria, self-managed gates, electronic and virtual gates, and integration with portfolio management. Improved accountability and continuous improvement are now built into Stage-Gate via a rigorous postlaunch review. Finally, progressive companies are reinventing Stage-Gate for use with "open innovation," whereas others are applying the principles of value stream analysis to yield a leaner version of Stage-Gate. [source] Synthesis, chiroptical properties, and their theoretical simulation of some highly rotating benzotricamphor derivatives,,CHIRALITY, Issue 1E 2009Giuseppe Mazzeo Abstract The large molecules 1,3 (69, 90, and 102 atoms, respectively), prepared by cyclotrimerization of enantiomerically pure derivatives of (,)-bornyl acetate, show intense ECD spectra, high optical rotation (OR) values (200,1300, in absolute value) dominated in sign and order of magnitude by the lowest-energy Cotton effects, that is, they are the ideal candidates to test the reliability of our "approximate" (TDDFT/B3LYP/6-31G* or smaller basis set) approach to the calculation of chiroptical properties. As a matter of fact, a correct simulation of the OR values and ECD spectra of 1 and 2 can be obtained even using STO-3G basis set and semiempirical or molecular mechanics input geometries: for 1, at the TDDFT/B3LYP/STO-3G level, the OR values are of the order of 500,550, versus an experimental value ranging between 660 and 690, depending on the solvent. On the contrary, the case of 3 (exp. OR between ,1330 and ,1500) is really complex (for instance, the OR values range between ,3216 and ,729 (TDDFT/B3LYP/6-31G* calculations) or ,1824 and ,444 (TDDFT/B3LYP/STO-3G calculations)), making the comparison between calculated and experimental values more difficult. The behavior of 3 is due to its molecular flexibility, whereas 1 is a really rigid molecules and 2 behaves (vide infra) as it were a rigid system. These observations strongly indicate that the conformational freedom constitutes one of the major difficulties for a correct but simple simulation of the chiroptical properties. Chirality 21:E86,E97, 2009. © 2009 Wiley-Liss, Inc. [source] The rheological properties of modified microcrystalline cellulose containing high levels of model drugsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 6 2009Paul E. Knight Abstract The rheological properties of different types of microcrystalline cellulose (MCC) mixed with model drugs and water have been evaluated to identify the influence of sodium carboxymethylcellulose (SCMC) added to the cellulose during preparation. A ram extruder was used as a capillary rheometer. The mixtures consisted of 20% spheronizing agent (standard grade MCC or modified types with 6% or 8% of low viscosity grade SCMC) and 80% of ascorbic acid, ibuprofen or lactose monohydrate. The introduction of SCMC changed all rheological parameters assessed. It produced more rigid systems, requiring more stress to induce and maintain flow. Degree of non-Newtonian flow, angle of convergence, extensional viscosity, yield and die land shear stress at zero velocity, and static wall friction were increased, but recoverable shear and compliance were decreased. The presence of SCMC did not remove the influence of the type of drug. The mixture of ibuprofen and standard MCC had the lowest values for shear stress as a function of the rate of shear, extensional viscosity, and angle of convergence, but the highest values for recoverable shear and compliance. The findings indicate that the system has insufficient rigidity to form pellets. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:2160,2169, 2009 [source] | ||||||||||