Science/Technology celerating rate at which smaller par ticles, aerosols, or minute volatiles become targets for collection," McTaggart says. "We can now mea sure contaminants to incredibly small sizes and percentages. But we don't necessarily have the matching solutions for what we can now mea sure in the way of problems/' Semiconductor makers, for exam ple, are squeezing more and more megabytes on their memory chips. Contamination control is critical. As circuitry dimensions go down, so does critical particle size. "Three years ago, everybody was sort of hap py using a 0.2- or O.l-μπι microfilter," McTaggart says. "Now they've got to go to 0.05 Mm and still get adequate flow rates with a decent pressure drop." The recent trend to demand im proved performance will continue through the 1990s. "Thus, we see markets growing for premium sub strates and devices to get the job done," McTaggart says. But at the same time, he complains of "a mad dening array of products and engi neered specialties provided by hun dreds of companies," with "so many overlapping technologies that can do a similar job." Among that "maddening array," however, certain newer technolo gies appear to have "noteworthy po tential," McTaggart observes. He in cludes gas membrane separation, pervaporation (a membrane-based way of avoiding distillation), inor ganic membranes and media, sur face-modified or sorptive media, nonwovens, and microfibers on his list of promising candidates. What sets these technologies apart is "their fit with one or several of the needs associated with exceptional growth opportunities," McTaggart says. "These needs relate to demands for higher-temperature performance, reduced-energy-intensive processes, specific molecular or organic binding properties, and increased retention capacities for target objects to be har vested or cleaned from a liquid or air stream." Several companies, including Millipore, Pall, W. L. Gore, and Gelman Science have their principal focus in the separations business. In addi tion, and significantly, McTaggart says, it's become apparent to a num28
December 2, 1991 C&EN
SOFTWARE/DATABASE UPDATE • Periodic Plus (Spectral Intelli gence Corp., $100, Circle 301) provides chemical, thermody namic, and spectroscopic data on 105 elements in a series of graph ical displays that includes 3-D representations and electronic structure diagrams. X-ray absorp tion energies, environmental im pact data, and over 300 unit con version factors are also included. It runs on MS-DOS systems. • Beilstein Current Facts in Chemistry ( S p r i n g e r - V e r l a g , $490 and up annual subscription, Circle 302) is a CD-ROM of chem ical and physical data and struc tures from recent organic chemis try literature, starting in 1990. It provides capabilities for data and substructure searches, including stereochemical searches. • Dry Lab Gl plus (LC Resources Inc., $2495, Circle 303) simulates gradient HPLC separations for methods development. Following entry of retention time from two experimental runs, the user exam ines the effects of changes in gra dient time, mobile phase compo sition, column dimensions, flow rate, and particle size by viewing simulated chromatograms. It runs on IBM PCs. • TOT ($820, Circle 304) simu lates and graphically displays ti trations and other chemical equi librium problems. It was devel oped, and is being marketed, by Robert H. Rosset of Ecole Superieure de Physique et Chimie de Paris, France, and coworkers. The IBM PC-based program can plot pH, concentrations, reparti tion curves, electrode potentials, solubilities, and other equilibri um phenomena. • 3DB (Tripos Associates, price unavailable, Circle 305) is a 3-D molecular-search system that in cludes structure registration, stor age, and retrieval, in addition to database access, integration with molecular modeling, and report generation. The graphical inter face accesses 3-D structure search
ing, substructure (2-D) searching, and relational databases. Struc ture-property relationships can be shown by displaying chemical structures with testing or physical property data. The program runs on DEC, Silicon Graphics, Evans & Sutherland, IBM PC, and Mac intosh computers. • Slide Write Plus Science Figure Packs (Advanced Graphics Soft ware, $99 each, Circle 306) pro vide hundreds of scientific clip art images. The images can be ed ited and incorporated into slides and figures with the company's Slide Write Plus program. • SigmaPlot (Jandel Scientific, $395, Circle 307), a scientific graphing program formerly avail able only in an MS-DOS version, is now available for the Macin tosh as well. Program features in clude error bars, curve fitting, re gressions, and confidence inter vals. Data may be input from the keyboard and from Excel, text, or SigmaPlot (DOS version) files. • Chemdraft III (C_Graph Soft ware Inc., $295, Circle 308), an IBM PC-based molecular editor program, has been upgraded with a Macintosh-like user interface with icons and pull-down menus. The software can construct and manipulate 2-D and 3-D chemical structures and supports user- and predefined libraries. • CAChe Worksystem (Tektron ix Inc., $14,000 to $60,000, Circle 309) has been enhanced with spectral prediction and visualiza tion capabilities. These make it possible to display molecular properties and visually analyze calculated vibrational spectra from MOPAC a n d calculated electronic spectra from ZINDO. CAChe is a Macintosh-based reac tivity m o d e l i n g system t h a t builds and displays 3-D confor mations and electronic structures. For information on these items or numbered ads, see Reader Service Card
