The progress of research

When I ran and wrote for Physics Today‘s Search and Discovery department, I’d often end news stories with a look toward the future. Such endings not only sound a note of hope and optimism, they also reflect the progressive nature of scientific research: A solution doesn’t just resolve an existing problem; it also leads to new problems and new applications.

I became the head of Search and Discovery in January 2003. To find concrete examples of how research progresses, I picked three of my stories from that year and got back in touch with the principal investigators whose work I’d covered.

My story “Ultrashort laser pulses beget even shorter bursts in the extreme ultraviolet” appeared in the April 2003 issue. The subject was a Nature paper by a team led by Ferenc Krausz, who was then at the Vienna University of Technology. Having achieved the ability to control the phase of the electric field of few-femtosecond laser pulses, Krausz and his colleagues used the pulses to induce argon atoms to emit bursts of UV light that lasted a mere few hundred attoseconds.

I already knew about some of Krausz’s subsequent work—because I’d written about it. In 2004 his team used 250-as pulses to trace the petahertz oscillations of an optical pulse’s electric field. Two years later he collaborated with Marc Vrakking of the FOM Institute for Atomic and Molecular Physics in Amsterdam on an experiment that controlled the light-induced breakup of a singly charged deuterium molecule D₂⁺. Thanks to their ability to control the phase of short laser pulses, Krausz and Vrakking could predetermine which of the two disassociated D atoms inherited the molecule’s lone electron.

But I was unfamiliar with—or had forgotten about—Krausz’s more recent work. Using attosecond pulses as a probe, he and his team discovered that when a 100-eV light pulse impinges on a neon atom, electrons from the atom’s 2p orbitals take 21 ± 5 attoseconds longer to be kicked out than do electrons from the 2s orbital. Subtle, electron–electron correlations are the delay’s most likely cause. That same year, 2010, the researchers resolved the motion of valence electrons in krypton ions.

More recently, Krausz and his collaborators demonstrated the ability to change the AC conductivity of a dielectric, silica, by 18 orders of magnitude within 1 femtosecond. The feat has implications for ultrahigh-frequency signal processing.

Three-dimensional optical storage

When I did my PhD thesis back in the mid 1980s, astronomical data were stored on magnetic tapes. Although the tapes’ information density was orders of magnitude lower than that of today’s optical and magnetic disks, wound-up tape, unlike the surface of a disk, exploits all three spatial dimensions.

In the summer of 2003 I came across a paper in the Proceedings of the National Academy of Sciences that reported on a potential technology that combined a tape reel’s 3D storage with a disk drive’s far speedier access to stored information. The paper, by Yongchao Liang, Alexander Dvornikov, and Peter Rentzepis of the University of California, Irvine, was the subject of my September 2003 story “Composite molecules store rewritable digital data.”

The concept behind the research was simple. Find a dye molecule whose ability to fluoresce can be switched on and off by light of different wavelengths. Embed the molecules in transparent plastic. The storage bits would correspond to voxels of the dye-embedded plastic. Access to individual voxels would be effected by aiming two perpendicular lasers at them. Where the beams converged, two-photon absorption would ensure that only the intended bit would be read, written, or erased.

Rentzepis and his colleagues couldn’t find a single molecule that had all the right properties, so they grafted two different ones together: a molecule that can be optically switched between polar and nonpolar states and a dye molecule that fluoresces only in a nonpolar environment. Back in 2003 Rentzepis, Liang, and Dvornikov demonstrated that the concept worked. The prototype that they built reliably wrote, read, and erased data over 10 000 cycles. Where, I wondered, had the research gone in the past 10 years?

Rentzepis told me in an email that he and his colleagues developed the technology to the point that they could store more than 10 terabytes in a plastic cylinder with a bit error rate that surpassed the industry standard. They also devised and developed a path toward boosting both capacity and switching rates. After being granted several patents, which were assigned to the University of California, Rentzepis concluded that the research had reached the point at which a company should pursue it. Call/Recall took over the project and introduced its first 3D storage device in 2007.

Cancer-fighting nanoparticles

In August 2003 the American Association for Cancer Research held its annual meeting in Washington, DC. Out of curiosity and because the meeting was local, I spent a day there. My decision paid off. One of the talks I attended was by Greg Lanza of Washington University in St. Louis.

Like others, Lanza and his Washington University collaborator Sam Wickline were investigating the use of nanoparticles to diagnose and treat cancer. The approach is promising. Nanoparticles can be coated with anticancer drugs, with molecules that stick to cancer’s molecular markers, and with contrast agents that enhance the visibility of even tiny tumors in x-ray or other types of medical image. And thanks to their size, the nanoparticles can be injected into a patient’s bloodstream. In principle, a tumor could be destroyed without the doctor knowing at first where it is.

Lanza and Wickline’s nanoparticles were coated with antibodies for integrin, a transmembrane protein. Integrins take part in angiogenesis, the process by which tumors assemble the blood vessels they need to gain access to nutrients. If angiogenesis is thwarted, tumors cannot grow. The nanoparticles were also coated with gadolinium ions that serve as a potent contrast agent in magnetic resonance imaging.

Using those two coatings was not especially novel. What attracted me to the research was the nanoparticles themselves. Lanza and Wickline made their nanoparticles from an emulsion of an octane derivative and water. In my October 2003 story, “Nanoparticles locate and flag the blood vessels that nourish tumors,” I likened the production process to making salad dressing from olive oil and balsamic vinegar.

Lanza and Wickline are still pursuing emulsion-based nanoparticles, and they’ve made considerable progress. In an email, Lanza told me that their nanoparticles are in phase I clinical trials both for imaging the sites of angiogenesis and for delivering an antiangiogenesis drug that they and their colleagues developed and licensed. Once they pass further health and safety tests, the nanonparticles will be submitted to the US Food and Drug Administration for evaluation as an investigational new drug .

Is it any wonder?

Search and Discovery publishes about 40 stories a year that more or less represent the full range of research conducted by physicists and their close professional relatives. The department’s reporters must be highly selective in choosing what to cover. It is therefore not surprising that research covered in the department turns out to be fruitful.

Still, I think my modest investigation has revealed aspects of scientific research that need restating, especially to the politicians who control research funding. First, the time scale over which basic research bears fruit is usually long and unpredictable. Funding short-term, applied research at the expense of basic research—Canada’s policy under Prime Minister Stephen Harper—will likely curtail the development of promising applications.

Second, the universities play an important role in developing promising lines of research. Spending 10 or more years on a project that expands our knowledge of the natural world yet doesn’t necessarily yield a new product is far riskier for an industrial lab than it is for a university lab.

Lastly, the progress made in just 10 years by the three groups in my investigation reminds me at least that science and its relative technology are the fields of human endeavor that have advanced the most. Despite the passage of centuries, no English writer has significantly surpassed William Shakespeare in skill. Some musicians proclaim Johann Sebastian Bach (1685–1750) as the greatest composer of all time.

And in the 1780s, when James Madison and others were writing the first US Constitution, Antoine Lavoisier was writing world’s first chemistry textbook. Whereas the current US constitution is clearly superior to the unamended original, the leap from Lavoisier’s textbook, which listed just seven known elements, to today’s chemical knowledge is far, far greater.

There is no Moore’s law for art, music, or politics.