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ed by J. MINOR GWYNN "The TVA ProgramThe Regional Approach to General Welfare." Julius Yourman, Editor. The Journal of Educational Sociology, 15:129-192. November, 1941. This issue of the Journal is devoted to the newer approach to the solution of educational problems. As an experiment it is unique in that it has rich facilities for the accomplishment of its aims, yet it has not attempted to superimpose upon the people concerned a culture and educational pattern entirely foreign to their traditions and background. The scope of the project may be realized from a glance at the aspects treated in this issue: "The Tennessee River Valley, Its People, and Institutions," by William E. Cole and S. E. T. Lund. "The Approach of the TVA to the Solution of Regional Problems," by Gordon R. Clapp and Howard K. Menhinick. This content downloaded from 157.55.39.176 on Sat, 09 Apr 2016 06:38:57 UTC All use subject to http://about.jstor.org/terms The High School Journal 43 "Community Education Improvement Under the Impact of the Construction Program," by Eugene L. Bishop, Raymond F. Leonard, and Malcolm G. Little. "Education for Sustained Regional Productivity," by Willis M. Baker and William M. Landess. "Education in the Adaptation of the Valley People to New Factors in the Environment," by George D. Munger, Carroll A. Towne, and Philip W. Voltz. "The Adaptation of Regional Research to Educational Uses," by Ellis F. Hartford and Maurice F. Seay. The TV A program might be termed a working demonstration of the educational approach to problems of regional and national welfare. As such, it is of interest to all school administrators and teachers. "It Takes Time to Learn." John Franklin Donnelly. The Journal of the National Education Association, 30:253-34. November, 1941. How long does it take for a young child to learn to make up his own bed well and as a matter of habit? For a beginner in piano to lay the groundwork for playing voluntarily for pleasure? For an adult to learn to turn a light on at a new location of a switch? How long does it take to change or help children to change habits which have been in operation for one, two, three or more years? Can the teacher alone cause undesirable habits to be broken down and new desirable ones to be set up? Is the teacher prone to consider that the development of good habits can take place in a shorter time than is really possible? The assistant principal of a junior high school considers aspects of these problems from a working and observational point of view. "Multiple Texts Multiply Textbook Problems." Harry A. Becker. The Social Studies, XXII: 294-6. November, 1941. The influence of the textbook on teaching has always been large; whether it has been more of a help than a hindrance to good teaching is still debated in educational circles. The author of this article presents and discusses the plan of using several texts in a class instead of one. His approach considers critically multiple text employment as (1) a modern plan of providing instructional material; (2) breaking down slavish dependence upon a single text; (3) opening to the student more avenues of information and different points of view; (4) increasing pupil interest; (5) offering better comparison of information and points of view in developing critical thinking; (6) furnishing a better learning situation for students. "Why Go to College Now?" Levering Tyson. School and Society, 54:453-7November 22, 1941. Under present conditions of world-wide unrest and uncertainty, the question of whether one should go to college now is indeed pertinent. To many of those registered in college in the fall of 1941 has often come the feeling of "What is the use of these courses I am taking, world conditions being what they are?" Though this has been true primarily of those youth who are of draft age or approaching it, it has created a serious problem for collegiate administrative officials and for high-school teachers, to a lesser extent. In this brief article, the address of the president of Muhlenberg College to his students, one may find a sane discussion of the opportunities, the responsibilities, and the challenge which the existing crisis offers to youth graduating from secondary school and to young people in college. This content downloaded from 157.55.39.176 on Sat, 09 Apr 2016 06:38:57 UTC All use subject to http://about.jstor.org/terms 44 The High School Journal "Regional Vocational Business Schools." Anson B. Barber. Education, 62:13341. November, 1941. For some time a serious questioning has been made of the attempt to give real vocational business training in small high schools. The types of training now needed to prepare youth for useful lives in business require broad facilities. As a matter of fact, the Regents Inquiry recommended for the State of New York much less highly specialized vocational training in the secondary school. The author presents the assumptions, principles, and criteria for the establishment of such regional training centers. "Economic Enterprises for High School Students." S. R. Logan. Curriculum Journal, 12:301-4. November, 1941. In this account of the economic enterprises of the Skokie Junior High School, one may get ideas for types of services which children need and may obtain for themselves. Each "corporation" is set up under the school representatives government. The types of corporate organization are the profit corporation, the cooperative corporation, and the public-ownership organization. Described in detail are the Livestock Company, Student Insurance through the Cooperative Corporation, the Biology Bureau of Bees, and the Credit Union. The relation of the Student Council to these activities is also presented. "The School Follows Through. A Post-School Adjustment of Youth." Byron C. Hayes, Edward Landy, and John R. Beery. The Bulletin of the National Association of Secondary -School Principals, Vol. 25, No. 101, pp. 1-84. November, 1941. This is the second and final report of the Occupational Adjustment Study, sponsored by the Implementation Commission of the National Association of Secondary School Principals. The first Report was published in November, 1940 (Bulletin No. 93), Occupational Adjustment and the School. In this bulletin three aspects are emphasized: (1) a special study of the follow-up plan in operation in forty selected high schools; (2) the experiences of these schools as throwing light on the techniques involved in the Occupational Follow-up and Adjustment Service Plan; and (3) a technical study of the post-school inventory. The Appendix contains valuable data in the form of the instruments used and revised during the study. "Tennessee Probes Placement of Farm Youth." E. B. Knight. Occupations, 20:116-21. November, 1941. What factors cause vocational students to enter either related or non-related fields instead? What local or sectional opportunities exist for pupils trained specifically for certain occupations? One of the first state-wide studies to acquire definite placement data for Tennessee rural youth in farming and related fields is described by Knight. The survey, made in 1940, included some 70 per cent of the 246 Tennessee communities served by white and negro teachers of vocational agriculture. 13,054 farm operators and 1,568 individuals owning or managing local businesses closely related to agriculture were interviewed. The fifteen major types of farming areas of the state were sampled. The trends, the related businesses, the rural county group, and the industrial county group are presented with their opportunities. Of major interest are the new departure and it simplications for secondary-education vocational work. This content downloaded from 157.55.39.176 on Sat, 09 Apr 2016 06:38:57 UTC All use subject to http://about.jstor.org/terms

Software is as integral as a research paper, monograph, or dataset in terms of facilitating the full understanding and dissemination of research. This article provides broadly applicable guidance on software citation for the communities and institutions publishing academic journals and conference proceedings. We expect those communities and institutions to produce versions of this document with software examples and citation styles that are appropriate for their intended audience. This article (and those community-specific versions) are aimed at authors citing software, including software developed by the authors or by others. We also include brief instructions on how software can be made citable, directing readers to more comprehensive guidance published elsewhere. The guidance presented in this article helps to support proper attribution and credit, reproducibility, collaboration and reuse, and encourages building on the work of others to further research.

Software is as integral as a research paper, monograph, or dataset in terms of facilitating the full understanding and dissemination of research. This article provides broadly applicable guidance on software citation for the communities and institutions publishing academic journals and conference proceedings. We expect those communities and institutions to produce versions of this document with software examples and citation styles that are appropriate for their intended audience. This article (and those community-specific versions) are aimed at authors citing software, including software developed by the authors or by others. We also include brief instructions on how software can be made citable, directing readers to more comprehensive guidance published elsewhere. The guidance presented in this article helps to support proper attribution and credit, reproducibility, collaboration and reuse, and encourages building on the work of others to further research.

Organic Chemistry A typical chemist running a known reaction will start by finding the method described in a published paper. Mehr et al. report a software platform that uses natural language processing to translate the organic chemistry literature directly into editable code, which in turn can be compiled to drive automated synthesis of the compound in the laboratory. The synthesis procedure is intended to be universally applicable to robotic systems operating in a batch reaction architecture. The full process is demonstrated for synthesis of an analgesic as well as common oxidizing and fluorinating agents. Science , this issue p. [101][1] [1]: /lookup/doi/10.1126/science.abc2986

Organic Chemistry Catalysts can introduce asymmetry in the outcome of chemical reactions, favoring one mirror-image product over another. Many of the most effective catalysts for this application were optimized through trial and error, but more recently, parameterization and systematic analysis have played an increasing role. Singh et al. now showcase the predictive power of machine learning applied to the ligands used for asymmetric hydrogenation. A random forest algorithm trained on several different families of chiral binaphthyl phosphorus compounds predicted selectivity in hydrogenation of alkenes and imines with a root-mean-square error of just over 8%. Proc. Natl. Acad. Sci. U.S.A. 117 , 1339 (2020).

Renewable Energy Modern wind turbines already represent a tightly optimized confluence of materials science and aerodynamic engineering. Veers et al. review the challenges and opportunities for further expanding this technology, with an emphasis on the need for interdisciplinary collaboration. They highlight the need to better understand atmospheric physics in the regions where taller turbines will operate as well as the materials constraints associated with the scale-up. The mutual interaction of turbine sites with one another and with the evolving features of the overall electricity grid will furthermore necessitate a systems approach to future development. Science , this issue p. [eaau2027][1] [1]: /lookup/doi/10.1126/science.aau2027

Electrochemistry Plants that grow in the ground make all their carbon-based infrastructure from carbon dioxide (CO2). By contrast, plants built by chemists use petroleum and natural gas as their carbon feedstock. In a review, De Luna et al. explore the prospective challenges and opportunities for manufacturing commodity chemicals such as ethylene and alcohols by direct electrochemical reduction of CO2. They estimate that production costs would be competitive with fossil technologies if renewable electricity costs drop below 4 cents per kilowatt-hour and electrical-to-chemical conversion efficiencies reach 60%. Science , this issue p. [eaav3506][1] [1]: /lookup/doi/10.1126/science.aav3506

Laser Physics The shortest laser pulses—with durations measured in attoseconds—arise from a process termed high-harmonic generation (HHG). Essentially, a longer, “driving” pulse draws electrons out of gaseous atoms like a slingshot, and, when they ricochet back, light emerges at shorter wavelengths. Most HHG has been carried out using light near the visible/infrared boundary for the driving pulse. Popmintchev et al. used an ultraviolet driving pulse instead, which yielded an unexpectedly efficient outcome. These results could presage a more generally efficient means of creating x-ray pulses for fundamental dynamics studies as well as technological applications. Science , this issue p. [1225][1] [1]: /lookup/volpage/350/1225?iss=6265

Chemistry Chemists spend a great deal of time tweaking the conditions of known reactions. Small changes to temperature and concentration can have a big influence over product yield. Bedard et al. present a flow-based reaction platform that carries out this laborious task automatically. By using feedback from integrated analytics, the system converges on optimal conditions that can then be applied with high precision afterward. A series of modules with heating, cooling, mixing, and photochemical capabilities could be configured for a broad range of reactions. These include homogeneous and heterogeneous palladium-catalyzed cross-coupling, reductive amination, and the generation of sensitive intermediates under an inert atmosphere. Science , this issue p. [1220][1] [1]: /lookup/doi/10.1126/science.aat0650

Scholarly Publishing How do we gauge the importance of a scientific publication? Citation counts are, by their nature, crowdsourced, but their inherent meaning is somewhat unclear. To explore this question in more depth, Borchardt et al. asked chemists in a survey to look back at a 10-year-old issue of the Journal of the American Chemical Society ( JACS ) and predict, without checking, which three papers had been most highly cited. Respondents were also asked which papers they construed as most important and which they would share with other chemists or the public more broadly. Citations not only proved rather hard to predict, but also correlated poorly with the papers chosen to share. PLOS ONE 13 , e0194903 (2018).

Organic Chemistry How does a chemist plan a synthesis? In principle, it is an exercise in breaking down the targeted product into smaller pieces that look feasible to stitch together. Computer programs that offer such advice on the basis of a set of reaction precedents have been around for decades

Biophysics Once green fluorescent protein has unleashed its eponymous green glow, a proton must journey back to the chromophore to reset the photophysical cycle. Salna et al. have now timed that journey over a temperature range from ambient temperature to down below −190 °C. Based on the large and temperature-dependent rate differences associated with isotopic substitution by deuterium, they conclude that quantum-mechanical tunneling plays a central role in the process. Specifically, the OH group on a serine residue participates in the proton transfer chain, despite its comparatively low acidity. Deep tunneling by serine's proton, at energies well below the threshold for classical deprotonation, helps bias overall transport in the right direction. Nature Chem. 10.1038/NCHEM.2527 (2016).

Applied Physics Electrical engineers can finetune the energetics of rigid photovoltaics and transistors by blending different semiconducting materials. However, it's hard to apply this tuning protocol to the flexible class of carbon-based semiconductors. Schwarze et al. now show that continuous band

Applied Physics Modern pulsed lasers make it possible to time molecular processes that happen even faster than trillionths of a second. A pump pulse starts off the process, while an investigative probe pulse gets sent on a steadily lengthened detour to delay its arrival by precise increments.

Chemical Engineering The infrastructure for chemical synthesis typically lies at either end of a spectrum: small-scale studies in ad hoc assemblies of glassware or large-scale production in capital-intensive custom reactors. Kitson et al. report a hybrid protocol that customizes a blueprint for

Laser Physics Dual-comb spectroscopy relies on a pair of laser pulses with multiple frequencies distributed like tines in a comb. It is a rapid means of characterizing atoms and molecules in fine detail, but, when applied to complex mixtures, it can produce a sea of peaks that are hard to discriminate. Lomsadze and Cundiff present a protocol to extend dual comb spectroscopy into the nonlinear regime. The cross-peaks that appear in the resulting two-dimensional spectra allow assignment of crowded features to common sources, as demonstrated for an isotopic mixture of 87Rb and 85Rb. Science , this issue p. [1389][1] [1]: /lookup/doi/10.1126/science.aao1090

Solar Cells Certain tunable coatings can render windows “smart” by modulating the amount of heat and light passing through them, depending on the desired temperature indoors. Powering these windows with photovoltaics seems sensible, but it is inefficient for the power source to absorb the same light that the coating is meant to regulate. Davy et al. resolve this conundrum by preparing a class of solar cells that absorb at the boundary between violet and ultraviolet. Composed from hexabenzocoronene organic semiconductors, these cells interfaced effectively with electrochromic window coatings on square-centimeter scales, leaving the rest of the optical and near-infrared regime open for modulation. Nat. Energy 2 , 17104 (2017).

Laser Physics Combs of light divide the optical frequency spectrum into closely spaced tines that can measure molecular absorption spectra with exceptional precision. One appealing method to extend this precision down into the microwave regime is to simultaneously use two slightly distinct combs

Chemical Engineering Although many commodity chemicals are manufactured using continuous flow techniques, pharmaceuticals are still mostly produced in large single batches. Cole et al. report a protocol for the small-volume continuous preparation of multi-kilogram quantities of a cancer drug candidate, prexasertib monolactate monohydrate, under current good manufacturing practices. Advantages of the approach include safer handling of hazardous reagents and intermediates, as well as yield and selectivity improvements in both the reaction and purification stages. Concurrent analytical monitoring also facilitated rapid trouble-shooting during the manufacturing process. Science , this issue p. [1144][1] [1]: /lookup/doi/10.1126/science.aan0745

Electrochemistry Widespread use of solar power will require a convenient means of storing energy for use at night and on rainy days, and making hydrogen fuel from water is a clean prospective solution. Most current approaches split the water into hydrogen and oxygen in the same apparatus, with a membrane keeping the two mutually explosive gases apart. Landman et al. instead separated the half reactions entirely, linking the two cells with a pair of nickel-based electrodes of the sort used in rechargeable alkaline batteries. Because these cells require only an electrical connection, the setup could potentially enable centralized hydrogen production powered by far-flung arrays of solar cells where the oxygen would be released. Nat. Mater. 10.1038/NMAT4876 (2017).

Electrochemistry Chemists have known how to use electricity to split water into hydrogen and oxygen for more than 200 years. Nonetheless, because the electrochemical route is inefficient, most of the hydrogen made nowadays comes from natural gas. Seh et al. review recent progress in electrocatalyst development to accelerate water-splitting, the reverse reactions that underlie fuel cells, and related oxygen, nitrogen, and carbon dioxide reductions. A unified theoretical framework highlights the need for catalyst design strategies that selectively stabilize distinct reaction intermediates relative to each other. Science , this issue p. [10.1126/science.aad4998][1] [1]: /lookup/doi/10.1126/science.aad4998

Ultrafast Dynamics Conceptually, the electronic structure of matter is a fixed scaffold of energy levels, which electrons climb with the help of light absorption. In reality, the light's electromagnetic field distorts the scaffold, a phenomenon that becomes increasingly evident with rising field

Flow Chemistry Commodity chemicals tend to be manufactured in a continuous fashion. However, the preparation of pharmaceuticals still proceeds batch by batch, partly on account of the complexity of their molecular structures. Adamo et al. now present an apparatus roughly the size of a household refrigerator that can synthesize and purify pharmaceuticals under continuous-flow conditions (see the Perspective by Martin). The integrated set of modules can produce hundreds to thousands of accumulated doses in a day, delivered in aqueous solution. Science , this issue p. [61][1]; see also p. [44][2] [1]: /lookup/doi/10.1126/science.aaf1337 [2]: /lookup/doi/10.1126/science.aaf3065

Ultrafast Dynamics Diodes are central components of modern electronic circuits. They essentially consist of two semiconductors sandwiched together, with one deficient in electrons (p), the other enriched (n). Najafi et al. used ultrafast electron microscopy to study the dynamics in a silicon diode

Water Splitting The light-driven splitting of water into hydrogen and oxygen is a widely studied approach toward storing solar energy for use at night and on cloudy days. Hill et al. constructed cells in which n -doped silicon absorbed the light and a cobalt catalyst on top helped accelerate the

[Smarter Pest Control Special Issue Index][1] Pesticides—a vast range of chemicals that kill insects, weeds, fungi, and other organisms humans would rather do without—bring some great benefits to society. They have made it possible to feed a growing human population, and they protect millions from malaria and other insect-borne diseases. They also support important economic sectors such as the cotton and flower industries and help make our lives easier and more enjoyable; for instance, by reducing mosquito, ant, and cockroach populations. Yet the potentially serious threats they pose to human health and the environment have led to a series of bans on the most dangerous chemicals and to calls to go much further. This spring, the European Union took a new step by issuing a partial ban on three neonicotinoids, a widely used group of insecticides suspected of harming bees, butterflies, and other nontarget species. Although science is guiding some policy changes, there is still room for major improvement when it comes to pesticides, by more carefully tracking their effects, using them more judiciously, reducing their negative impacts, and finding alternatives. Scientists are making strides in precisely understanding the effects of the chemicals now in our arsenal, including the myriad ways in which they are broken down in the environment and the harm they cause to wildlife. Meanwhile, cohort studies in the United States are beginning to map out their troubling effects on the young developing brain. Reducing the negative fallout from pesticides is possible in many ways. Australia's wheat farmers are tackling one of the worst weed problems in the world (a crisis that, ironically, partly arose from overreliance on herbicides) by using a more diverse set of tools. Pesticide overuse is a big problem in Asia, too; although cheap, they hurt the farmer's bottom line in the long run. Vietnam has developed a pioneering program that is paying dividends to farmers who spray less. Also in Asia, scientists are tackling one of the biggest problems: More than 300,000 people are believed to commit suicide every year by swallowing pesticides. Others, meanwhile, are looking ahead. New synthetic chemicals to protect crops hold the promise of stronger and more specific protection with less collateral damage. And some crops won't need pesticides at all: Scientists are developing plants whose immune systems can ward off fungal, bacterial, or viral diseases, and they are using RNA interference to help plants fight insects—a new technology that could hit the market before the decade ends. We may never be able to abandon pesticides altogether, but as this collection of Reviews, News stories, and research papers shows, pest control can become much smarter, and science has a major role to play. [1]: http://www.sciencemag.org/site/special/pesticides/index.xhtml

Solar Cells Solar cells made from carbon-based polymers are helpfully flexible. However, there's been a frustrating tradeoff between cell stability and efficiency when converting solar power to electrical power. Page et al. offer a strategy to partially resolve this dilemma by inserting a layer of polar organic compound (a fullerene derivative) between the cathode (the positive pole in the circuit) and the rest of the cell. Aluminum is an efficient cathode material but is prone to oxidative degradation. The easily applied polar layer enables the use of more stable metals, such as silver and copper, for the cathode, while counteracting their tendencies to diminish power conversion efficiency. Science , this issue p. [441][1] [1]: /lookup/doi/10.1126/science.1255826

Nanomaterials When you shrink semiconductors down to quantum dots—particles a few billionths of a meter in diameter—their color becomes very sensitive to their size. Over the past decade, scientists have exploited this property in numerous optical devices without knowing the precise atomic structure of the particles they were using. Beecher et al. now report detailed structures of three classes of cadmium selenide quantum dots, each with a different size and light absorption spectrum. The key was to use a selenium precursor that facilitated the synthesis of highly uniform samples. In the past, the dots in a single sample tended to range too much in size for this degree of characterization. J. Am. Chem. Soc. 10.1021/ja503590h (2014).

Solar Cells Organic photovoltaics operate by transferring charge from a light-absorbing donor material to a nearby acceptor. Falke et al. show that molecular vibrations smooth the way for this charge transfer to proceed. A combination of ultrafast spectroscopy and theoretical simulations revealed an oscillatory signal in a model donor/acceptor blend that implicates carbon-carbon bond stretching in concert with the electronic transition. This vibrational/electronic, or vibronic, process maintains a quantum-mechanical phase relationship that guides the charge more rapidly and directly than an incoherent migration from donor to acceptor. Science , this issue p. [1001][1] [1]: /lookup/doi/10.1126/science.1249771

Chemistry Chemical reaction trajectories tend to be largely confined to a single electronic potential energy surface. Occasionally, though, two surfaces intersect when vibrations on the lower surface become vigorous enough to match the energy level of the higher one. Such conical intersections (so

Applied Physics Semiconducting nanocrystals, or quantum dots, are promising materials for use in laser, light-emitting diode (LED), and solar cell applications, partly because of the tunability of their photophysical properties with size. One important size-dependent property in this context is the

[Figure][1] CREDIT: SOLAR MILLENNIUM The end of the age of fossil fuels may be in sight, but what comes after is still a bit of a blur. There are numerous alternatives to coal, oil, and natural gas from electricity generated by solar farms to biofuels brewed from plants. Scaling up these alternative sources of energy, however, has proved a challenge. This special issue explores the progress that researchers are making in developing better alternatives, and the technical, political, and economic pitfalls associated with scaling them up. As Kerr (p. [780][2]) notes in a News feature, alternative energies have big shoes to fill. Fossil fuels are widely used in part because they have some unique advantages over other sources of energy. A coal-fired power plant, for instance, can keep running when the Sun isn't shining or the wind dies down, and fossil fuels typically get more energy out of a hectare of land or a liter of raw material than the alternatives. It took about a century to build the energy system that runs on fossil fuels, though, and Kerr reports that it could take just as long to develop alternatives. Still, both Kerr and Cho (p. [786][3]) report that there is potentially more than enough energy available from the Sun, wind, and other renewable sources to replace fossil fuels. Clery (p. [782][4]) reports on one ambitious multinational effort to harness renewable sources to generate electricity in North Africa and then transmit the power across the Mediterranean Sea to Europe. Service (p. [784][5]), however, reports on how high hopes in the United States for one emerging alternative, cellulosic biofuels, have waned because of technical and economic setbacks. Kintisch (p. [788][6]) notes that even a relatively mature alternative technology, wind power, is now encountering public opposition owing to the environmental and aesthetic impacts of wind turbines. Such grand visions rest in part on vigorous continuing research. Three Perspectives take an in-depth look at how researchers hope to scale up biofuels development successfully. Somerville et al. (p. [790][7]) survey the most promising land crops for large-scale development, and Wijffels and Barbosa (p. [796][8]) discuss algae: a source that holds promise because of both its high content of lipids (which more closely resemble petroleum than sugars do) and its low land-area requirements. Richard (p. [793][9]) considers the changes in transport and processing infrastructure that will be necessary to ship biofuels from field to fueling station. Finally, nuclear power is a perennial player in the carbon-neutral energy discussion. Grimes and Nuttall (p. [799][10]) review a two-stage approach to the expansion of fission-based electricity generation, with the upcoming 20 years focused on shoring up current technology, followed in later years by the design and construction of next-generation plants that reprocess spent fuel for greater efficiency and waste minimization. Together, all of these pieces show that interest in scaling up alternatives remains high and that many attractive new energy sources exist despite the considerable challenges involved in their development. [1]: pending:yes [2]: /lookup/doi/10.1126/science.329.5993.780 [3]: /lookup/doi/10.1126/science.329.5993.786 [4]: /lookup/doi/10.1126/science.329.5993.782 [5]: /lookup/doi/10.1126/science.329.5993.784 [6]: /lookup/doi/10.1126/science.329.5993.788 [7]: /lookup/doi/10.1126/science.1189268 [8]: /lookup/doi/10.1126/science.1189003 [9]: /lookup/doi/10.1126/science.1189139 [10]: /lookup/doi/10.1126/science.1188928

Chemistry Numerous conveniences available in the chemistry laboratory (magnetic stirrers, for instance) have been slow to make their way into the kitchen. Chefs can still brag, though, that the ultimate kitchen convenience—the microwave oven—has only recently been widely exploited in the lab.

Biophysics![Figure][1] CREDIT: KILARSKI ET AL., NAT. MED. 15 , 657 (2009) If Robert Moses, the driving force behind the construction of the congested artery known as the Brooklyn-Queens Expressway, were alive today, he would marvel at the cellular engineers who relocate still-functioning

APPLIED PHYSICS Many people find it hard to sit still for extended periods without fidgeting and shifting about. A similar problem plagues the widely used technique of atomic force microscopy: Though the probing tip can resolve individual atoms, it is fundamentally a mechanical device and so inevitably drifts in space over time. As a result, the period available for signal-averaging to improve data quality is limited; moreover, it is often impossible to deliberately shift the tip to a different portion of the sample and then return to precisely the same starting position during the course of an imaging session (for example, to monitor slow rearrangements in two or more distinct domains of a protein). King et al. address this shortcoming using a laser-based feedback scheme for tip stabilization. Specifically, they detect backscattered laser light from the tip as well as a reference marker (a silicon disk) on the sample. The tip is then adjusted to remain in a fixed position relative to the marker. Studies of gold nanospheres in room-temperature air demonstrate a lateral drift rate limited to just 5 pm/min over the course of more than an hour. The method is optimized for transparent substrates, due to the backscattering detection geometry, but could potentially be extended by incorporating the reference marker into the instrument's cantilever assembly. — JSY Nano Lett. 9 , 10.1021/nl803298q (2009).

ENGINEERING The Sun provides far more energy to Earth each day than the worldwide population currently uses, but directing this energy toward a more useful purpose than heating the ground is a considerable challenge. Though siliconbased cells can effectively convert absorbed light into electricity, the costs associated with isolating and purifying the silicon toward this end remain substantially higher than those associated with fossil fuel-based processes for electricity generation. Wadia et al. have analyzed the relative costs and efficiencies of a wide range of alternative materials for eventual use in solar cells. Specifically, they examined 21 metal oxides, sulfides, selenides, and sundry other inorganic semiconductors in comparison with crystalline and amorphous silicon. Their model considered overall electricity consumption, and so evaluated power-conversion efficiencies of individual cells in the context of comparative fabrication costs for multiple cells. Iron pyrite emerged as an especially favorable option on the basis of its abundance and low extraction cost, with Zn3P2 and copper oxides also showing potential for economical efficiency. — JSY Environ. Sci. Technol. 43 , 10.1021/es8019534 (2009).

[Figure][1] The precision attainable in timing events once depended on how fast a human being could press the button on a stopwatch. More recently, pulsed laser sources have taken the place of those hand-held devices for measuring the fastest phenomena. The technology for tracking the time scale of nuclear motion in free molecules and solids was limited by the duration of a single cycle of visible light: approximately 0.000000000000001 second, or 1 femtosecond. Electrons move even faster than that, and for a long time, scientists could only watch their rearrangements as an indiscrete blur. Over the past several years, however, laser technology has crossed the threshold into the attosecond regime (a thousandth of a femtosecond). This series of three Reviews highlights the methods underlying this advance and the scientific prospects they have enabled. Bucksbaum (p. [766][2]) lays out the essential physics of high harmonic generation, a technique whereby an intense laser field pulls an atomic electron away from the nucleus like a loaded slingshot and then sends it careening back, giving rise to the emission of an attosecond light pulse. The Review also describes in general terms what events such light pulses can be used to track, ranging from electron rearrangements in chemical bonding to conduction dynamics in metallic solids. Goulielmakis et al. (p. [769][3]) take a more in-depth look at the laser techniques that create and detect attosecond pulses. Their Review also details the prospects not only of passively probing electron motions, but of actively manipulating and controlling them. In keeping with the uncertainty principle, compressing a light pulse's duration must also broaden its spectral bandwidth. Thus, attosecond pulses extend into the x-ray region of the electromagnetic spectrum. Kapteyn et al. (p. [775][4]) describe efforts to harness this feature of the technology in diffraction and imaging experiments, which would otherwise depend on much more elaborate x-ray generation apparatus. Optical technology continues to evolve. It seems that just as events at the atomic scale are at last observed with precision, they bring into view a new series of blurs, previously unappreciated. Then the quest begins for an even faster stopwatch. [1]: pending:yes [2]: /lookup/doi/10.1126/science.1142135 [3]: /lookup/doi/10.1126/science.1142855 [4]: /lookup/doi/10.1126/science.1143679

The Cartoon Guide to Chemistry . By Larry Gonick and Craig Criddle . HarperResource (HarperCollins), New York, 2005. 255 pp. $16.95, C$23.95. ISBN 0-06-093677-0. The latest addition to Gornick's comic series provides an informative, graphic, and humorous introduction to the ideas, techniques, and history of chemistry.