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PubMed1999

Computer aided design and fabrication of models for in vitro studies of vascular fluid dynamics.

An integrated computer aided design/computer aided manufacture system has been used to model the complex geometry of blood vessel anastomoses. Computer models are first constructed with key dimensions derived from radiological images of bypass grafts, and from casts of actual blood vessel anastomoses. Physical models are then fabricated in one of two ways: the surface geometry data can be used to control the movement of a three-axis milling machine; alternatively, the same data can be exported in a form that can be interpreted by a stereolithography apparatus. Both methods produce geometrically defined solid investments that can be used in a multistep casting process that yields high-quality physical models for vascular fluid dynamic studies. This technique is useful for parametric studies.

Anastomosis, Surgical↗
PubMed2002

Fractional Design Wizard: a computer program for cost-effective experimental research design.

The computer program Fractional Design Wizard creates fractional factorial designs that are cost-effective and especially useful for discarding irrelevant factors from a large number of possible candidates. The program is intended for researchers who are relatively new to the field of fractional design and who want to acquaint themselves with the use of fractions for the reduction of large experimental designs. Fractional designs allow estimation of main effects, and sometimes two-way interactions, without one's having to examine all treatment conditions. The program needs Microsoft Windows 95 or better and 32 MB of memory. In a step-by-step fashion, the user can specify the required properties of the fractional design. When there are more valid designs, the user can generate these successively. If necessary, the user can go back to diminish the requirements. The output can be copied, printed, and saved. The program generates all the information that is needed for the use and interpretation of fractional designs. A help file explains the use of the program and also the purpose, the analysis, and the interpretation of fractional designs. The program, which is written in Object Pascal, is available as freeware on www.fss.uu.nl/ms/hl/fracdes.htm.

Algorithms↗
PubMed2004

Computer-aided design, synthesis, and anti-HIV-1 activity in vitro of 2-alkylamino-6-[1-(2,6-difluorophenyl)alkyl]-3,4-dihydro-5-alkylpyrimidin-4(3H)-ones as novel potent non-nucleoside reverse transcriptase inhibitors, also active against the Y181C variant.

Dihydro-alkoxy-benzyl-oxopyrimidines (DABOs) are a family of potent NNRTIs developed in the past decade. Attempts to improve their potency and selectivity led to thio-DABOs (S-DABOs), DATNOs, and difluoro-thio-DABOs (F(2)-S-DABOs). More recently, we reported the synthesis and molecular modeling studies of a novel conformationally constrained subtype of the S-DABO series characterized by the presence of substituents on the methylene linkage connecting the pyrimidine ring to the aryl moiety (Mai, A., et al. J. Med. Chem. 2001, 44, 2544-2554). Now we report the computer-aided design, synthesis, and biological evaluation of four new DABO prototypes (5-alkyl-2-cyclopentylamino-6-[1-(2,6-difluorophenyl)alkyl]-3,4-dihydropyrimidin-4(3H)-ones, F(2)-NH-DABOs) in which the sulfur atom of the related F(2)-S-DABOs is replaced by an amino group. For these studies, we used as a reference model the cocrystallized MKC-442/RT complex. Docking studies with Autodock of the newly designed F(2)-NH-DABOs on the ligand-derived RT confirmed the findings previously described for the F(2)-S-DABOs. The F(2)-NH-DABO binding mode resembles that reported for F(2)-S-DABOs, with the difference that the NH moiety at the C-2 position represents a new anchor site for ligand/enzyme complexation. The predicted inhibition constant (K(i)) values by the internal scoring function of Autodock, and the predicted IC(50) values by the application of a VALIDATE II/HIV-RT model strongly suggested the synthesis of the designed amino-DABOs. F(2)-NH-DABOs were shown to be highly active in both anti-RT and anti-HIV biological assays with IC(50) and EC(50) comparable with that of the reference compound MKC-442. Interestingly, 2-cyclopentylamino-6-[1-(2,6-difluorophenyl)ethyl]-3,4-dihydro-5-methyl pyrimidin-4(3H)-one (9d) was active against the Y181C HIV-1 mutant strain at submicromolar concentration, with a resistance value similar to that of efavirenz, the last FDA-approved NNRTI for AIDS therapy, and 2-fold lower than that of its 2-cyclopentylthio counterpart 8d. The introduction in 9d of a new anchor point (pyrimidine C-2 NH group), with the formation of a new hydrogen bond with Lys101, could compensate for the lack of positive hydrophobic ligand/NNBP interactions due to the Tyr181 to Cys181 mutation.

Cell Line↗
PubMed1991

Computer-aided design and manufacture of an above-knee amputee socket.

This paper describes the initial test results obtained from a newly developed computer-aided socket design (CASD) and manufacturing (CASM) process for above-knee amputees. Anthropometric measures taken from an amputee provided input information to a CASD system. Using these measurements, data from a reference shape library stored in the computer were selected and modified to create a unique socket shape reflecting the particular characteristics of the amputation stump. The resultant shape was produced as a 'primitive' test socket by a CASM process. Numerical shape data were then transferred to a CNC milling machine to construct a negative cast, from which the primitive socket was produced by a vacuum-forming procedure. The resultant primitive socket shape was fitted and the amputee was able to load the socket without discomfort. Some shape discrepancies were identified and the shape data were modified interactively by the CASD system to create a final socket shape. The final socket shape was manufactured and worn by the amputee during a 35 min walking trial. Subjective evaluation was that the socket provided comfort and control comparable with that of the conventional socket, and proved to be acceptable to the amputee. This was followed by a 2-month home trial which was also successful. The CASD socket shapes were compared numerically in area, shape and volume with data taken from the original socket worn by the amputee, a new socket made by conventional methods and a topographic model of the amputation stump. The final CASD socket shape compared favourably with that of a socket manufactured by conventional methods.(ABSTRACT TRUNCATED AT 250 WORDS)

Anthropometry↗
PubMed1990

Optimization of an isocratic reversed phase liquid chromatographic system for the separation of fourteen steroids using factorial design and computer simulation.

An optimization strategy for an isocratic reversed phase high performance liquid chromatographic system (RP-HPLC) is described. Factorial design and a computer program are used to predict the retention time and resolution of fourteen steroids. An optimized rapid (less than 25 min) isocratic RP-HPLC system for the satisfactory separation of cortisone, cortisol, corticosterone, 11-deoxycortisol, 11-deoxycorticosterone, 17 alpha-hydroxyprogesterone, progesterone, androstenedione, testosterone, estrone, estradiol, estriol, prednisone acetate and dexamethasone acetate has been developed using this strategy through eight experiments.

Chromatography, High Pressure Liquid↗
PubMed2002

Chromatofocusing using micropellicular column packings with computer-aided design of the elution buffer composition.

Micropellicular, anion-exchange column packings are used in chromatofocusing to demonstrate the resolution and speed achieved when proteins are separated under these conditions. Linear or concave pH gradients are produced with simple mixtures containing four or fewer individual buffering species instead of the more commonly used polyampholyte buffers. Computer-aided design methods are demonstrated for selecting the composition of the elution buffer to produce a pH gradient of a desired shape. The method is applied to high-resolution, analytical- and preparative-scale separations involving horse myoglobin, human hemoglobin variants, and bovine carbonic anhydrase. A useful selection of buffering species is described capable of producing pH gradients of a variety of shapes in the range between pH 9.5 and 5.5.

Algorithms↗
PubMed1996

Effect of type of practice in a computer-aided design environment in visualizing three-dimensional objects from two-dimensional orthographic projections.

The purpose of this study was to determine the effect of practice in manipulating 2- and 3-dimensional (D) wireframe images on a learner's ability to visualize 3-D objects. Practice, either rotational or not, consisted of visualizing 2- and 3-D objects generated by personal computer (PC)-based computer-assisted design software. Results indicated that participants in the rotation treatment group performed significantly better than those in either the nonrotation or control group on measures of spatial ability and 3-D visualization ability. Both treatment groups performed significantly better than the control group on measures of metacognition, effort, and worry. These results support a conclusion that spatial ability can be improved through practice that allows the learner to see the relationship between the 2-D and 3-D features of objects.

Adult↗
PubMed2004

Fracture strength of all-ceramic crowns luted using two bonding methods.

STATEMENT OF THE PROBLEM: Excellent esthetic quality is one of the major advantages of all-ceramic restorations; however, catastrophic fracture of such restorations is still a disadvantage. Ceramic bonding systems using ceramic primers without the use of hydrofluoric acid have been introduced, but data about the efficiency of these systems are lacking. PURPOSE: This study investigated the influence of 2 bonding procedures on the fracture resistance of low-fusing ceramic and computer aided design-computer aided manufacturing (CAD-CAM) all-ceramic crowns. MATERIAL AND METHODS: Forty-two standardized all-ceramic crowns were fabricated on human maxillary premolars. Seven unprepared maxillary premolars were used as control. Three all-ceramic crown systems were used: 1 low-fusing ceramic (Duceram) and 2 machineable ceramics (Vita Mark II and ProCAD) using the Cerec 3 CAD-CAM system. The intaglio surfaces of fabricated crowns (n=7) were subjected to 2 different conditioning techniques: etching, using 4.9% hydrofluoric acid followed by application of Mirage ABC silane, or cleaning, using 65% phosphoric acid and application of primer (Porcelain Liner-M). The crowns were luted to the teeth using Superbond C&B luting agent. After 24 hours storage in water, specimens were loaded in a universal testing machine with the compressive load applied along the long axis of the specimen at a crosshead speed 1 mm/min until fracture. Fracture loads (N) were recorded. One-way analysis of variance (ANOVA) and the Tukey HSD test (alpha=.05) were used for statistical analysis of the data. RESULTS: The mean fracture load of control specimens (738.3+/-195.3 N) was not significantly different from that of the 2 CAD-CAM crowns (667.7+/-72.3 N, 715.9+/-105.2 N). However, fracture load of natural teeth and the 2 CAD-CAM crowns was significantly higher than the fracture load of the low-fusing ceramic crowns treated with HF acid and silane (465.5+/-101.1 N) and, when cleaned, using phosphoric acid and an application of primer (447.5+/-63.4 N) (P<.05). There was no significant difference in the mean fracture load of each ceramic material when bonded using the 2 different procedures, either treated with HF acid and silane or cleaned using phosphoric acid and application of primer (P>.05). CONCLUSION: The application of a primer (Procelain Liner-M) was an effective method for treating the intaglio surface of all-ceramic crowns before cementation.

Acid Etching, Dental↗
PubMedDate not supplied

Effect of surface finish on the flexural strength of feldspathic and aluminous dental ceramics.

The effects of surface finish on flexural strength of a feldspathic porcelain, aluminous porcelain, and a computer aided design-computer aided machining porcelain (Vitabloc MKI) were examined. A total of 105 bars of the feldspathic ceramic were made, randomly divided into seven groups, and sintered according to manufacturer's recommendations. The groups consisted of as-fired, self-glazed, overglazed, ground, polished, ground/annealed, and polished/annealed. A total of 45 bars of the aluminous ceramic and Vitabloc MKI were made and randomly divided into three groups: as-fired, ground, and polished. Overglazing, grinding, and polishing all significantly increased (P < .05) the flexural strength (four-point-bend test) of the tested materials (15% to 30%).

Aluminum Oxide↗
PubMed1996

[The rational computer-aided design of new drugs].

At present, searches are being made to accelerate the designing of new drugs and at the same time to considerably reduce the associated expenses. The process of designing a new drug generally consists of 3 stages: (1) search for a new agent having the required pharmacological activity; (2) experimental studies and pharmacological and toxological tests; (3) an appropriate pharmacological committee's approval for clinical tests of the agent. Stage 1 is the most expensive and labour-consuming, as it requires a half the total expenditures. Its clinical version consists in the synthesis of numerous homologues of the well-known biologically active compounds and in long-term and costly trials. At the same time, an investigator has a definite range of concepts of the structure of a new drug as a new representative of the known group that he already knows. The application of computer-aided analysis and design enables these disadvantages to be overcome. The introduction of methods for predesigning computer-aided drug design has permitted drastic reduction of expenses and accelerated designing of new drugs, by decreasing the number of unsuccessful syntheses and trials.

Computer Graphics↗
PubMedDate not supplied

Computer aided design of a polarised source for in vivo X-ray fluorescence analysis.

A system has been developed which uses Monte Carlo computer simulations to aid the design and optimisation of a polarised source for in vivo X-ray fluorescence (XRF) analysis of heavy metals: The system is based on a version of the Monte Carlo code EGS4 which includes polarised photon interactions, running on a personal computer. The code was used to construct a model of a clinical polarised XRF system (based on a 300 kV therapy X-ray source) under development at Swansea for the measurement of Pt-based chemotherapy drugs in head and neck tumours. Several simulations were performed to investigate the variation of XRF measurement sensitivity with the material composition and geometry of the system components. Pt XRF spectra generated by the model were found to be in good agreement with experimental data. The optimum operating voltage for the system, predicted by the simulations and confirmed by experiment, was approx. 200 kV. The accuracy of the results obtained to date indicates that this technique will greatly facilitate future design and optimisation studies of a wide variety of XRF systems.

Antineoplastic Agents↗
PubMedDate not supplied

Computer-aided design and transverse strength of screw-retained attachments.

Two commercially available, screw-retained attachments and an experimental attachment were modeled and analyzed by computerized finite element method. Mechanical test specimens were then developed. Cast rectangular bars were fabricated with the attachments or were joined by soldering at midspan as a control. These bars were subjected to three-point loading. The soldered connector was stronger than the three attachment designs, and the experimental attachment was stronger than the two commercial products. There was general agreement between the mechanical and finite element testing. The use of computer-aided technology to design dental devices with improved mechanical properties was demonstrated by this study.

Analysis of Variance↗
PubMed1992

Interface load analysis for computer-aided design of below-knee prosthetic sockets.

A finite-element analysis is made for the compression of soft tissues of the residual lower limb contained in a prosthetic socket. The analysis is relevant to static loading during stance in a patellar-tendon-bearing, below-knee design of socket. Values of Young's modulus are obtained experimentally for use in the model. One of the main objectives is to study the sensitivity of the loading to these values and also to other assumed conditions. Using direct pressure at the limb/socket interface and vertical stiffness as indicators, changes in material properties, socket alignment and socket rectification are investigated; assumptions about the frictional characteristic at the interface are seen to be critical in determination of load distribution. This type of analysis may provide the next stage of refinement for computer-aided socket design systems.

Artificial Limbs↗