Tag Archives: Northwestern University

Sticky-flares nanotechnology to track and observe RNA (ribonucleic acid) regulation

I like the name ‘sticky-flares’ and had hoped there was an amusing story about its origins. Ah well, perhaps I’ll have better luck next time.

This work comes out of Chad Mirkin’s lab at Northwestern University (Chicago, US) according to a July 21, 2015 news item on Azonano,

RNA [ribonucleic acid] is a fundamental ingredient in all known forms of life — so when RNA goes awry, a lot can go wrong. RNA misregulation plays a critical role in the development of many disorders, such as mental disability, autism and cancer.

A new technology — called “Sticky-flares” — developed by nanomedicine experts at Northwestern University offers the first real-time method to track and observe the dynamics of RNA distribution as it is transported inside living cells.

A July 20, 2015 Northwestern University news release by Erin Spain, which originated the news item, describes the research in a little more detail also including information about predecessor technology,

Sticky-flares have the potential to help scientists understand the complexities of RNA better than any analytical technique to date and observe and study the biological and medical significance of RNA misregulation.

Previous technologies made it possible to attain static snapshots of RNA location, but that isn’t enough to understand the complexities of RNA transport and localization within a cell. Instead of analyzing snapshots of RNA to try to understand functioning, Sticky-flares help create an experience that is more like watching live-streaming video.

“This is very exciting because much of the RNA in cells has very specific quantities and localization, and both are critical to the cell’s function, but until this development it has been very difficult, and often impossible, to probe both attributes of RNA in a live cell,” said Chad A. Mirkin, a nanomedicine expert and corresponding author of the study. “We hope that many more researchers will be able to use this platform to increase our understanding of RNA function inside cells.”

Sticky-flares are tiny spherical nucleic acid gold nanoparticle conjugates that can enter living cells and target and transfer a fluorescent reporter or “tracking device” to RNA transcripts. This fluorescent labeling can be tracked via fluorescence microscopy as it is transported throughout the cell, including the nucleus.

In the … paper, the scientists explain how they used Sticky-flares to quantify β–actin mRNA in HeLa cells (the oldest and most commonly used human cell line) as well as to follow the real-time transport of β–actin mRNA in mouse embryonic fibroblasts.

Sticky-flares are built upon another technology from Mirkin’s group called NanoFlares, which was the first genetic-based approach that is able to detect live circulating tumor cells out of the complex matrix that is human blood.

NanoFlares have been very useful for researchers that operate in the arena of quantifying gene expression. AuraSense, Inc., a biotechnology company that licensed the NanoFlare technology from Northwestern University, and EMD-Millipore, another biotech company, have commercialized NanoFlares. There are now more than 1,700 commercial forms of NanoFlares sold under the SmartFlareä name in more than 230 countries.

The Sticky-flare is designed to address limitations of SmartFlares, most notably their inability to track RNA location and enter the nucleus. The Northwestern team believes Sticky-flares are poised to become a valuable tool for researchers who desire to understand the function of RNA in live cells.

Based on the paragraph about the precursor technology’s commercial success , I gather they are excited about similar possibilities for sticky-flares.

Here’s a link to and a citation for the paper,

Quantification and real-time tracking of RNA in live cells using Sticky-flares by William E. Briley, Madison H. Bondy, Pratik S. Randeria, Torin J. Dupper, and Chad A. Mirkin. Published online before print July 20, 2015, doi: 10.1073/pnas.1510581112 PNAS July 20, 2015

This paper is behind a paywall.

Northwestern University’s (US) International Institute for Nanotechnology (IIN) rakes in some cash

Within less than a month Northwestern University’s International Institute for Nanotechnology (IIN) has been granted awarded two grants by the US Department of Defense.

4D printing

The first grant, for 4D printing, was announced in a June 11, 2015 Northwestern news release by Megan Fellman (Note: A link has been removed),

Northwestern University’s International Institute for Nanotechnology (IIN) has received a five-year, $8.5 million grant from the U.S. Department of Defense’s competitive Multidisciplinary University Research Initiative (MURI) program to develop a “4-dimensional printer” — the next generation of printing technology for the scientific world.

Once developed, the 4-D printer, operating on the nanoscale, will be used to construct new devices for research in chemistry, materials sciences and U.S. defense-related areas that could lead to new chemical and biological sensors, catalysts, microchip designs and materials designed to respond to specific materials or signals.

“This research promises to bring transformative advancement to the development of biosensors, adaptive optics, artificially engineered tissues and more by utilizing nanotechnology,” said IIN director and chemist Chad A. Mirkin, who is leading the multi-institution project. Mirkin is the George B. Rathmann Professor of Chemistry in the Weinberg College of Arts and Sciences.

The award, issued by the Air Force Office of Scientific Research, supports a team of experts from Northwestern, the University of Miami, the University of California, San Diego, and the University of Maryland.

In science, “printing” encodes information at specific locations on a material’s surface, similar to how we print words on paper with ink. The 4-dimensional printer will consist of millions of tiny elastomeric “pens” that can be used individually and independently to create nanometer-size features composed of hard or soft materials.

The information encoded can be in the form of materials with a defined set of chemical and physical properties. The printing speed and resolution determine the amount and complexity of the information that can be encoded.

Progress in fields ranging from biology to chemical sensing to computing currently are limited by the lack of low-cost equipment that can perform high-resolution printing and 3-dimensional patterning on hard materials (e.g., metals and semiconductors) and soft materials (e.g., organic and biological materials) at nanometer resolution (approximately 1,000 times smaller than the width of a human hair).

“Ultimately, the 4-D printer will provide a foundation for a new generation of tools to develop novel architectures, wherein the hard materials that form the functional components of electronics can be merged with biological or soft materials,” said Milan Mrksich, a co-principal investigator on the grant.

Mrksich is the Henry Wade Rogers Professor of Biomedical Engineering, Chemistry and Cell and Molecular Biology, with appointments in the McCormick School of Engineering and Applied Science, Weinberg and Northwestern University Feinberg School of Medicine.

A July 10, 2015 article about the ‘4D printer’ grant  by Madeline Fox for the Daily Northwestern features a description of 4D printing from Milan Mrksich, a co-principal investigator on the grant,

Milan Mrksich, one of the project’s five senior participants, said that while most people are familiar with the three dimensions of length, width and depth, there are often misconceptions about the fourth property of a four-dimensional object. Mrksich used Legos as an analogy to describe 4D printing technology.

“If you take Lego blocks, you can basically build any structure you want by controlling which Lego is connected to which Lego and controlling all their dimensions in space,” Mrksich said. “Within an object made up of nanoparticles, we’re controlling the placement — as we use a printer to control the placement of every particle, our fourth dimension lets us choose which nanoparticle with which property would be at each position.”

Thank you Dr. Mrksich and Ms. Fox for that helpful analogy.

Designing advanced bioprogrammable nanomaterials

The second grant, announced in a July 6, 2015 Northwestern news release by Megan Fellman, is apparently the only one of its kind in the US (Note: A link has been removed),

Northwestern University’s International Institute for Nanotechnology (IIN) has been awarded a U.S. Air Force Center of Excellence grant to design advanced bioprogrammable nanomaterials for solutions to challenging problems in the areas of energy, the environment, security and defense, as well as for developing ways to monitor and mitigate human stress.

The five-year, $9.8 million grant establishes the Center of Excellence for Advanced Bioprogrammable Nanomaterials (C-ABN), the only one of its kind in the country. After the initial five years, the grant potentially could be renewed for an additional five years.

“Northwestern University was chosen to lead this Center of Excellence because of its investment in infrastructure development, including new facilities and instrumentation; its recruitment of high-caliber faculty members and students; and its track record in bio-nanotechnology and cognitive sciences,” said Timothy Bunning, chief scientist at the U.S. Air Force Research Laboratory (AFRL) Materials and Manufacturing Directorate.

Led by IIN director Chad A. Mirkin, C-ABN will support collaborative, discovery-based research projects aimed at developing bioprogrammable nanomaterials that will meet both military and civilian needs and facilitate the efficient transition of these new technologies from the laboratory to marketplace.

Bioprogrammable nanomaterials are structures that typically contain a biomolecular component, such as nucleic acids or proteins, which give the materials a variety of novel capabilities. [emphasis mine] Nanomaterials can be designed to assemble into large 3-D structures, to interface with biological structures inside cells or tissues, or to interface with existing macroscale devices, for example. These new bioprogrammable nanomaterials and the fundamental knowledge gained through their development will ultimately lead to the creation of wearable, portable and/or human-interactive devices with extraordinary capabilities that will significantly impact both civilian and Air Force needs.

In one research area, scientists will work to understand the molecular underpinnings of vulnerability and resilience to stress. They will use bioprogrammable nanomaterials to develop ultrasensitive sensors capable of detecting and quantifying biomarkers for human stress in biological fluids (e.g., saliva, perspiration or blood), providing means to easily monitor the soldier during times of extreme stress. Ultimately, these bioprogrammable materials may lead to methods to increase human cellular resilience to the effects of stress and/or to correct genetic mutations that decrease cellular resilience of susceptible individuals.

Other research projects, encompassing a wide variety of nanotechnology-enabled goals, include:

Developing hybrid wearable energy-storage devices;
Developing devices to identify chemical and biological targets in a field environment;
Developing flexible bio-electronic circuits;
Designing a new class of flat optics; and
Advancing understanding of design rules between 2-D and 3-D architectures.

The analysis of these nanostructures also will extend fundamental knowledge in the fields of materials science and engineering, human performance, chemistry, biology and physics.

The center will be housed under the IIN, providing researchers with access to IIN’s strong entrepreneurial community and its close ties with Northwestern’s renowned Kellogg School of Management.

This second news release provides an interesting contrast to a recent news release from Sweden’s Karolinska Intitute where the writer was careful to note that the enzymes and organic electronic ion pumps were not living as noted in my June 26, 2015 posting. It seems nucleic acids (as in RNA and DNA) can be mentioned without a proviso in the US. as there seems to be little worry about anti-GMO (genetically modified organisms) and similar backlashes affecting biotechnology research.

TRIUMF accelerator used by US researchers to visualize properties of nanoscale materials

The US researchers are at the University of California at Los Angeles (UCLA) and while it’s not explicitly stated I’m assuming the accelerator they mention at TRIUMF (Canada’s national laboratory for particle and nuclear physics) has something special as there are accelerators in California and other parts of the US.

A July 15, 2015 news item on Nanotechnology Now announces the latest on visualizing the properties of nanoscale materials,

Scientists trying to improve the semiconductors that power our electronic devices have focused on a technology called spintronics as one especially promising area of research. Unlike conventional devices that use electrons’ charge to create power, spintronic devices use electrons’ spin. The technology is already used in computer hard drives and many other applications — and scientists believe it could eventually be used for quantum computers, a new generation of machines that use quantum mechanics to solve complex problems with extraordinary speed.

A July 15, 2015 UCLA news release, which originated the news item, expands on the theme and briefly mentions TRIUMF’s accelerator (Note: A link has been removed),

Emerging research has shown that one key to greatly improving performance in spintronics could be a class of materials called topological insulators. Unlike ordinary materials that are either insulators or conductors, topological insulators function as both simultaneously — on the inside, they are insulators but on their exteriors, they conduct electricity.

But topological insulators have certain defects that have so far limited their use in practical applications, and because they are so tiny, scientists have so far been unable to fully understand how the defects impact their functionality.

The UCLA researchers have overcome that challenge with a new method to visualize topological insulators at the nanoscale. An article highlighting the research, which was which led by Louis Bouchard, assistant professor of chemistry and biochemistry, and Dimitrios Koumoulis, a UCLA postdoctoral scholar, was published online in the Proceedings of the National Academy of Sciences.

The new method is the first use of beta‑detected nuclear magnetic resonance to study the effects of these defects on the properties of topological insulators.

The technique involves aiming a highly focused stream of ions at the topological insulator. To generate that beam of ions, the researchers used a large particle accelerator called a cyclotron, which accelerates protons through a spiral path inside the machine and forces them to collide with a target made of the chemical element tantalum. This collision produces lithium-8 atoms, which are ionized and slowed down to a desired energy level before they are implanted in the topological insulators.

In beta‑detected nuclear magnetic resonance, ions (in this case, the ionized lithium-8 atoms) of various energies are implanted in the material of interest (the topological insulator) to generate signals from the material’s layers of interest.

Bouchard said the method is particularly well suited for probing regions near the surfaces and interfaces of different materials.

In the UCLA research, the high sensitivity of the beta‑detected nuclear magnetic resonance technique and its ability to probe materials allowed the scientists to “see” the impacts of the defects in the topological insulators by viewing the electronic and magnetic properties beneath the surface of the material.

The researchers used the large TRIUMF cyclotron in Vancouver, British Columbia.

According to the UCLA news release, there were also researchers from the University of British Columbia, the University of Texas at Austin and Northwestern University involved with the work.

Here’s a link to and a citation for the paper,

Nanoscale β-nuclear magnetic resonance depth imaging of topological insulators by Dimitrios Koumoulis, Gerald D. Morris, Liang He, Xufeng Kou, Danny King, Dong Wang, Masrur D. Hossain, Kang L. Wang, Gregory A. Fiete, Mercouri G. Kanatzidis, and Louis-S. Bouchard. PNAS July 14, 2015 vol. 112 no. 28 doi: 10.1073/pnas.1502330112

This paper is behind a paywall.

Nanoscale imaging gets rough

Smooth is easier than rough when imaging at the nanoscale according to a June 17, 2015 Northwestern University news release by Megan Fellman (also on EurekAlert),

A multi-institutional team of scientists has taken an important step in understanding where atoms are located on the surfaces of rough materials, information that could be very useful in diverse commercial applications, such as developing green energy and understanding how materials rust.

Researchers from Northwestern University, Brookhaven National Laboratory, Lawrence Berkeley National Laboratory and the University of Melbourne, Australia, have developed a new imaging technique that uses atomic resolution secondary electron images in a quantitative way to determine the arrangement of atoms on the surface.

Many important processes take place at surfaces, ranging from the catalysis used to generate energy-dense fuels from sunlight and carbon dioxide to how bridges and airplanes corrode, or rust. Every material interacts with the world through its surface, which is often different in both structure and chemistry from the bulk of the material.

The real focus of the work is on corrosion, according to the news release,

“We are excited by the possibilities of applying our imaging technique to corrosion and catalysis problems,” said Laurence Marks, a co-author of the paper and a professor of materials science and engineering at Northwestern’s McCormick School of Engineering and Applied Science. “The cost of corrosion to industry and the military is enormous, and we do not understand everything that is taking place. We must learn more, so we can produce materials that will last longer.”

To understand these processes and improve material performance, it is vital to know how the atoms are arranged on surfaces. While there are many good methods for obtaining this information for rather flat surfaces, most currently available tools are limited in what they can reveal when the surfaces are rough.

Scanning electron microscopes are widely used to produce images of many different materials, and roughness of the surface is not that important. Until very recently, instruments could not obtain clear atomic images of surfaces until a group at Brookhaven managed in 2011 to get the first images that seemed to show the surfaces very clearly. However, it was not clear to what extent they really were able to image the surface, as there was no theory for the imaging and many uncertainties.

The new work has answered all these questions, Marks said, providing a definitive way of understanding the surfaces in detail. What was needed was to use a carefully controlled sample of strontium titanate and perform a large range of different types of imaging to unravel the precise details of how secondary electron images are produced.

“We started this work by investigating a well-studied material,” said Jim Ciston, a staff scientist at Lawrence Berkeley National Laboratory and the lead author of the paper, who obtained the experimental images. “This new technique is so powerful that we had to revise much of what was already thought to be well-known. This is an exciting prospect because the surface of every material can act as its own nanomaterial coating, which can greatly change the chemistry and behavior.”

“The beauty of the technique is that we can image surface atoms and bulk atoms simultaneously,” said Yimei Zhu, a scientist at Brookhaven National Laboratory. “Currently, no existing methods can achieve that.”

Les Allen, who led the theoretical and modeling aspects of the new imaging technique in Melbourne, said, “We now have a sophisticated understanding of what the images mean. It now will be full steam ahead to apply them to many different types of problems.”

Here’s a link to and citation for the paper,

Surface determination through atomically resolved secondary-electron imaging by J. Ciston, H. G. Brown, A. J. D’Alfonso, P. Koirala, C. Ophus, Y. Lin, Y. Suzuki, H. Inada, Y. Zhu, L. J. Allen, & L. D. Marks. Nature Communications 6, Article number: 7358 doi:10.1038/ncomms8358 Published 17 June 2015

This paper is open access.

Liquid nanolaser: the first one

According to an April 24, 2015 news item on Nanowerk, there has been a big discovery at Northwestern University (located in Chicago, Illinois, US),

Northwestern University scientists have developed the first liquid nanoscale laser. And it’s tunable in real time, meaning you can quickly and simply produce different colors, a unique and useful feature. The laser technology could lead to practical applications, such as a new form of a “lab on a chip” for medical diagnostics.

To understand the concept, imagine a laser pointer whose color can be changed simply by changing the liquid inside it, instead of needing a different laser pointer for every desired color.

In addition to changing color in real time, the liquid nanolaser has additional advantages over other nanolasers: it is simple to make, inexpensive to produce and operates at room temperature.

An April 24, 2015 Northwestern University news release by Megan Fellman (also on EurekAlert), which originated the news item, offers a little history buttressed by some technical details (Note: Links have been removed),

Nanoscopic lasers — first demonstrated in 2009 — are only found in research labs today. They are, however, of great interest for advances in technology and for military applications.

“Our study allows us to think about new laser designs and what could be possible if they could actually be made,” said Teri W. Odom, who led the research. “My lab likes to go after new materials, new structures and new ways of putting them together to achieve things not yet imagined. We believe this work represents a conceptual and practical engineering advance for on-demand, reversible control of light from nanoscopic sources.”

The liquid nanolaser in this study is not a laser pointer but a laser device on a chip, Odom explained. The laser’s color can be changed in real time when the liquid dye in the microfluidic channel above the laser’s cavity is changed.

The laser’s cavity is made up of an array of reflective gold nanoparticles, where the light is concentrated around each nanoparticle and then amplified. (In contrast to conventional laser cavities, no mirrors are required for the light to bounce back and forth.) Notably, as the laser color is tuned, the nanoparticle cavity stays fixed and does not change; only the liquid gain around the nanoparticles changes.

The main advantages of very small lasers are:

• They can be used as on-chip light sources for optoelectronic integrated circuits;

• They can be used in optical data storage and lithography;

• They can operate reliably at one wavelength; and

• They should be able to operate much faster than conventional lasers because they are made from metals.

Some technical background

Plasmon lasers are promising nanoscale coherent sources of optical fields because they support ultra-small sizes and show ultra-fast dynamics. Although plasmon lasers have been demonstrated at different spectral ranges, from the ultraviolet to near-infrared, a systematic approach to manipulate the lasing emission wavelength in real time has not been possible.

The main limitation is that only solid gain materials have been used in previous work on plasmon nanolasers; hence, fixed wavelengths were shown because solid materials cannot easily be modified. Odom’s research team has found a way to integrate liquid gain materials with gold nanoparticle arrays to achieve nanoscale plasmon lasing that can be tuned dynamical, reversibly and in real time.

The use of liquid gain materials has two significant benefits:

• The organic dye molecules can be readily dissolved in solvents with different refractive indices. Thus, the dielectric environment around the nanoparticle arrays can be tuned, which also tunes the lasing wavelength.

• The liquid form of gain materials enables the fluid to be manipulated within a microfluidic channel. Thus, dynamic tuning of the lasing emission is possible simply by flowing liquid with different refractive indices. Moreover, as an added benefit of the liquid environment, the lasing-on-chip devices can show long-term stability because the gain molecules can be constantly refreshed.

These nanoscale lasers can be mass-produced with emission wavelengths over the entire gain bandwidth of the dye. Thus, the same fixed nanocavity structure (the same gold nanoparticle array) can exhibit lasing wavelengths that can be tuned over 50 nanometers, from 860 to 910 nanometers, simply by changing the solvent the dye is dissolved in.

Here’s a link to and a citation for the paper,

Real-time tunable lasing from plasmonic nanocavity arrays by Ankun Yang, Thang B. Hoang, Montacer Dridi, Claire Deeb, Maiken H. Mikkelsen, George C. Schatz, & Teri W. Odom. Nature Communications 6, Article number: 6939 doi:10.1038/ncomms7939 Published 20 April 2015

This paper is open access.

A more complex memristor: from two terminals to three for brain-like computing

Researchers have developed a more complex memristor device than has been the case according to an April 6, 2015 Northwestern University news release (also on EurekAlert),

Researchers are always searching for improved technologies, but the most efficient computer possible already exists. It can learn and adapt without needing to be programmed or updated. It has nearly limitless memory, is difficult to crash, and works at extremely fast speeds. It’s not a Mac or a PC; it’s the human brain. And scientists around the world want to mimic its abilities.

Both academic and industrial laboratories are working to develop computers that operate more like the human brain. Instead of operating like a conventional, digital system, these new devices could potentially function more like a network of neurons.

“Computers are very impressive in many ways, but they’re not equal to the mind,” said Mark Hersam, the Bette and Neison Harris Chair in Teaching Excellence in Northwestern University’s McCormick School of Engineering. “Neurons can achieve very complicated computation with very low power consumption compared to a digital computer.”

A team of Northwestern researchers, including Hersam, has accomplished a new step forward in electronics that could bring brain-like computing closer to reality. The team’s work advances memory resistors, or “memristors,” which are resistors in a circuit that “remember” how much current has flowed through them.

“Memristors could be used as a memory element in an integrated circuit or computer,” Hersam said. “Unlike other memories that exist today in modern electronics, memristors are stable and remember their state even if you lose power.”

Current computers use random access memory (RAM), which moves very quickly as a user works but does not retain unsaved data if power is lost. Flash drives, on the other hand, store information when they are not powered but work much slower. Memristors could provide a memory that is the best of both worlds: fast and reliable. But there’s a problem: memristors are two-terminal electronic devices, which can only control one voltage channel. Hersam wanted to transform it into a three-terminal device, allowing it to be used in more complex electronic circuits and systems.

The memristor is of some interest to a number of other parties prominent amongst them, the University of Michigan’s Professor Wei Lu and HP (Hewlett Packard) Labs, both of whom are mentioned in one of my more recent memristor pieces, a June 26, 2014 post.

Getting back to Northwestern,

Hersam and his team met this challenge by using single-layer molybdenum disulfide (MoS2), an atomically thin, two-dimensional nanomaterial semiconductor. Much like the way fibers are arranged in wood, atoms are arranged in a certain direction–called “grains”–within a material. The sheet of MoS2 that Hersam used has a well-defined grain boundary, which is the interface where two different grains come together.

“Because the atoms are not in the same orientation, there are unsatisfied chemical bonds at that interface,” Hersam explained. “These grain boundaries influence the flow of current, so they can serve as a means of tuning resistance.”

When a large electric field is applied, the grain boundary literally moves, causing a change in resistance. By using MoS2 with this grain boundary defect instead of the typical metal-oxide-metal memristor structure, the team presented a novel three-terminal memristive device that is widely tunable with a gate electrode.

“With a memristor that can be tuned with a third electrode, we have the possibility to realize a function you could not previously achieve,” Hersam said. “A three-terminal memristor has been proposed as a means of realizing brain-like computing. We are now actively exploring this possibility in the laboratory.”

Here’s a link to and a citation for the paper,

Gate-tunable memristive phenomena mediated by grain boundaries in single-layer MoS2 by Vinod K. Sangwan, Deep Jariwala, In Soo Kim, Kan-Sheng Chen, Tobin J. Marks, Lincoln J. Lauhon, & Mark C. Hersam. Nature Nanotechnology (2015) doi:10.1038/nnano.2015.56 Published online 06 April 2015

This paper is behind a paywall but there is a few preview available through ReadCube Access.

Dexter Johnson has written about this latest memristor development in an April 9, 2015 posting on his Nanoclast blog (on the IEEE [Institute for Electrical and Electronics Engineers] website) where he notes this (Note: A link has been removed),

The memristor seems to generate fairly polarized debate, especially here on this website in the comments on stories covering the technology. The controversy seems to fall along the lines that the device that HP Labs’ Stan Williams and Greg Snider developed back in 2008 doesn’t exactly line up with the original theory of the memristor proposed by Leon Chua back in 1971.

It seems the ‘debate’ has evolved from issues about how the memristor is categorized. I wonder if there’s still discussion about whether or not HP Labs is attempting to develop a patent thicket of sorts.

Gender gaps in science and how statistics prove and disprove the finding

A Feb. 17, 2015 Northwestern University news release by Hilary Hurd Anyaso (also on EurekAlert) features research suggesting that parity in the numbers of men and women students pursuing science degrees is being achieved,

Scholars from diverse fields have long proposed that interlocking factors such as cognitive abilities, discrimination and interests may cause more women than men to leave the science, technology, engineering and mathematics (STEM) pipeline after entering college.

Now a new Northwestern University analysis has poked holes in the much referenced “leaky pipeline” metaphor.

The research shows that the bachelor’s-to-Ph.D. pipeline in science and engineering fields no longer leaks more women than men as it did in the past

Curt Rice, a professor at Norway’s University of Tromsø, has challenged the findings in a Feb. 18, 2015 post on his eponymous website (more about that later).

The news release goes on to describe how the research was conducted and the conclusions researchers drew from the data,

The researchers used data from two large nationally representative research samples to reconstruct a 30-year portrait of how bachelor’s-to-Ph.D. persistence rates for men and women have changed in the United States since the 1970s. For this study, the term STEM persistence rate refers to the proportion of students who earned a Ph.D. in a particular STEM field (e.g. engineering) among students who had earlier received bachelor’s degrees in that same field.

They were particularly surprised that the gender persistence gap completely closed in pSTEM fields (physical science, technology, engineering and mathematics) — the fields in which women are most underrepresented.

Among students earning pSTEM bachelor’s degrees in the 1970s, men were 1.6 to 1.7 times as likely as women to later earn a pSTEM Ph.D. However, this gap completely closed by the 1990s.

Men still outnumber women by approximately three to one among pSTEM Ph.D. earners. But those differences in representation are not explained by differences in persistence from the bachelor’s to Ph.D. degree, said David Miller, an advanced doctoral student in psychology at Northwestern and lead author of the study.

“Our analysis shows that women are overcoming any potential gender biases that may exist in graduate school or undergraduate mentoring about pursing graduate school,” Miller said. “In fact, the percentage of women among pSTEM degree earners is now higher at the Ph.D. level than at the bachelor’s, 27 percent versus 25 percent.”

Jonathan Wai, a Duke University Talent Identification Program research scientist and co-author of the study, said a narrowing of gender gaps makes sense given increased efforts to promote gender diversity in science and engineering.

“But a complete closing of the gap was unexpected, especially given recent evidence of gender bias in science mentoring,” Wai said.

Consequently, the widely used leaky pipeline metaphor is a dated description of gender differences in postsecondary STEM education, Wai added.

Other research shows that gaps in persistence rates are also small to nonexistent past the Ph.D., Miller said.

“For instance, in physical science and engineering fields, male and female Ph.D. holders are equally likely to earn assistant professorships and academic tenure,” Miller said.

The leaky pipeline metaphor is inaccurate for nearly all postsecondary pathways in STEM, Miller said, with two important exceptions.

“The Ph.D.-to-assistant-professor pipeline leaks more women than men in life science and economics,” he said. “Differences in those fields are large and important.”

The implications of the research, Miller said, are important in guiding research, resources and strategies to explain and change gender imbalances in science.

“The leaking pipeline metaphor could potentially direct thought and resources away from other strategies that could more potently increase women’s representation in STEM,” he said.

For instance, plugging leaks in the pipeline from the beginning of college to the bachelor’s degree would fail to substantially increase women’s representation among U.S. undergraduates in the pSTEM fields, Miller said.

Of concern, women’s representation among pSTEM bachelor’s degrees has been decreasing during the past decade, Miller noted. “Our analyses indicate that women’s representation at the Ph.D. level is starting to follow suit by declining for the first time in over 40 years,” he said.

“This recent decline at the Ph.D. level could likely mean that women’s progress at the assistant professor level might also slow down or reverse in future years, so these trends will need to be watched closely,” Wai said.

While the researchers are encouraged that gender gaps in doctoral persistence have closed, they stressed that accurately assessing and changing gender biases in science should remain an important goal for educators and policy makers.

Before moving on to Rice’s comments, here’s a link to and citation for the paper,

The bachelor’s to Ph.D. STEM pipeline no longer leaks more women than men: a 30-year analysis by David I. Miller and Jonathan Wai. Front. Psychol., 17 February 2015, doi: 10.3389/fpsyg.2015.00037

This paper is open access (at least for now).

Maybe the situation isn’t improving after all

Curt Rice’s response titled, The incontinent pipeline: it’s not just women leaving higher education, suggests this latest research has unmasked a problem (Note: Links have been removed),

Freshly published research gives a more nuanced picture. The traditional recitation of percentages at various points along the pipeline provides a snapshot. The new research is more like a time-lapse film.

Unfortunately, the new study doesn’t actually show a pipeline being tightened up to leak less. Instead, it shows a pipeline that is leaking even more! The convergence in persistence rates for men and women is not a result of an increase in the rate of women taking a PhD; it’s the result of a decline in the rate of men doing so. It’s as though the holes have gotten bigger — they used to be so small that only women slipped through, but now men slide out, too.

Rice believes  that this improvement is ‘relative improvement’ i.e. the improvement exists in relation to declining numbers of men, a statistic that Rice gives more weight to than the Northwestern researchers appear to have done. ‘Absolute improvement’ would mean that numbers of women studying in the field had improved while men’s numbers had held steady or improved for them too.

To be fair, the authors of the paper seem to have taken at least some of this decline in men’s numbers into account (from the research paper),,

Reasons for the convergences in persistence rates remain unclear. Sometimes the convergence was driven by declines in men’s rates (e.g., in mathematics/computer science), increases in women’s rates (e.g., in physical science), or both (e.g., in engineering). help account for the changes in persistence rates. …

Overenthusiasm in the news release

Unfortunately, the headline and bullet list of highlights suggest a more ebullient research conclusion than seems warranted by the actual research results.

Think again about gender gap in science
Bachelor’s-to-Ph.D. pipeline in science, engineering no longer ‘leaks’ more women than men, new 30-year analysis finds

Research shows dated ‘leaky pipeline’ assumptions about gender imbalances in science

  • Men outnumber women as Ph.D. earners in science but no longer in doctoral persistence
  • Dramatic increase of women in science at Ph.D., assistant professorship levels since 1970s, but recent decline since 2010 may be of concern for future supply of female scientists
  • Assessing inaccurate assumptions key to correcting gender biases in science

Here’s the researchers’ conclusion,

Overall, these results and supporting literature point to the need to understand gender differences at the bachelor’s level and below to understand women’s representation in STEM at the Ph.D. level and above. Women’s representation in computer science, engineering, and physical science (pSTEM) fields has been decreasing at the bachelor’s level during the past decade. Our analyses indicate that women’s representation at the Ph.D. level is starting to follow suit by declining for the first time in over 40 years (Figure 2). This recent decline may also cause women’s gains at the assistant professor level and beyond to also slow down or reverse in the next few years. Fortunately, however, pathways for entering STEM are considerably diverse at the bachelor’s level and below. For instance, our prior research indicates that undergraduates who join STEM from a non-STEM field can substantially help the U.S. meet needs for more well-trained STEM graduates (Miller et al., under review). Addressing gender differences at the bachelor’s level could have potent effects at the Ph.D. level, especially now that women and men are equally likely to later earn STEM Ph.D.’s after the bachelor’s.

The conclusion seems to contradict the researchers’ statements in the news release,

“But a complete closing of the gap was unexpected, especially given recent evidence of gender bias in science mentoring,” Wai said.

Consequently, the widely used leaky pipeline metaphor is a dated description of gender differences in postsecondary STEM education, Wai added.

Other research shows that gaps in persistence rates are also small to nonexistent past the Ph.D., Miller said.

Incomplete pipeline

Getting back to Rice, he notes the pipeline in the Northwestern paper is incomplete (Note: Links have been removed),

In addition to the dubious celebration of the decline of persistence rates of men, the new research article also looks at an incomplete pipeline. In particular, it leaves aside the important issue of which PhD institutions students get into. For young researchers moving towards academic careers, we know that a few high-prestige universities are responsible for training future faculty members at nearly all other research universities. Are women and men getting into those high prestige universities in the same numbers? Or do women go to lower prestige institutions?

Following on that thought about lower prestige institutions and their impact on your career, there’s a Feb. 23, 2015 article by Joel Warner and Aaron Clauset in Slate investigating the situation, which applies to both men and women,

The United States prides itself on offering broad access to higher education, and thanks to merit-based admissions, ample financial aid, and emphasis on diverse student bodies, our country can claim some success in realizing this ideal.

The situation for aspiring professors is far grimmer. Aaron Clauset, a co-author of this article, is the lead author of a new study published in Science Advances that scrutinized more than 16,000 faculty members in the fields of business, computer science, and history at 242 schools. He and his colleagues found, as the paper puts it, a “steeply hierarchical structure that reflects profound social inequality.” The data revealed that just a quarter of all universities account for 71 to 86 percent of all tenure-track faculty in the U.S. and Canada in these three fields. Just 18 elite universities produce half of all computer science professors, 16 schools produce half of all business professors, and eight schools account for half of all history professors.

Then, Warner and Clauset said this about gender bias,

Here’s further evidence that the current system isn’t merely sorting the best of the best from the merely good. Female graduates of elite institutions tend to slip 15 percent further down the academic hierarchy than do men from the same institutions, evidence of gender bias to go along with the bias toward the top schools.

I suggest reading the Slate article, Rice’s post, and, if you have time, the Northwestern University research paper.

Coda: All about Curt Rice

Finally, this is for anyone who’s unfamiliar with Curt Rice (from the About page on his website; Note: Links have been removed),

In addition to my work as a professor at the University of Tromsø, I have three other roles that are closely related to the content on this website. I was elected by the permanent faculty to sit on the university board, I lead Norway’s Committee on Gender Balance and Diversity in Research, and I am the head of the Board for Current Research Information System in Norway (CRIStin). In all of these roles, I work to pursue my conviction that research and education are essential to improving society, and that making universities better therefore has the potential to make societies better.

I’m currently writing a book on gender balance. Why do men and women have different career paths? Why should we care? How can we start to make things better? Why is improving gender balance not only the right thing to do, but also the smart thing to do? For a taste of my approach, grab a copy of my free ebook on gender equality.

Beyond this book project, I use my speaking and writing engagements to reach audiences on the topics that excite me the most: gender balance, open access, leadership issues and more. These interests have grown during the past decade while I’ve had the privilege to occupy what were then two brand new leadership positions at the University of Tromsø.

From 2009–2013, I served as the elected Vice Rector for Research & Development (prorektor for forskning og utvikling). Before that, from 2002–2008, I was the founding director of my university’s first Norwegian Center of Excellence, the Center for Advanced Study in Theoretical Linguistics (CASTL). Given the luxury of being able to define those positions, I was able to pursue my passion for improving academic life by working to enhance conditions for education and research.

I’m part of the European Science Foundation’s genderSTE COST action (Gender, Science, Technology and Environment); I helped create the BALANSE program at the Research Council of Norway, which is designed to increase the numbers of women at the highest levels of research organizations. I am on the Advisory Board of the European Commission project EGERA (Effective Gender Equality in Research and Academia); I was on the Science Leaders Panel of the genSET project, in which we advised the European Commission about gender in science; I am a member of the Steering Committee for the Gender Summits.

I also led a national task force on research-based education that issued many suggestions for Norwegian institutions.

Bypassing nanofabrication methods for colourful silver

A new technique developed by researchers at Northwestern University (Chicago, US) would be faster and cheaper than nanofabrication methods according to a Feb. 14, 2015 news item on Azonano,

Northwestern University researchers have created a new technique that can transform silver into any color of the rainbow. Their simple method is a fast, low-cost alternative to color filters currently used in electronic displays and monitors.

“Our technique doesn’t require expensive nanofabrication techniques or a lot of materials,” said Koray Aydin, assistant professor of electrical engineering and computer science at the McCormick School of Engineering. “And it can be completed in a half hour or so.”

A Feb. 12, 2015 Northwestern University news release (also on EurekAlert but dated Feb. 13, 2015), which originated the news item, provides more details about the research,

The filter’s secret lies within its “sandwich-like” structure. Aydin and his team created a three-layer design, where glass is wedged two thin layers of silver film. The silver layers are thin enough to allow optical light to pass through, which then transmits a certain color through the glass and reflects the rest of the visible spectrum. By changing the thickness of the glass, Aydin was able to filter and produce different colors.

“Controlling the thickness of the glass controls the color,” Aydin said. “This way, we can create any color desired.”

By making the bottom silver layer even thicker, Aydin found that the structure also acts as a color absorber because it traps light between the two metal layers. The team demonstrated a narrow bandwidth super absorber with 97 percent maximum absorption, which could have potential applications for optoelectric devices with controlled bandwidth, such as narrow-band photodetectors and light-emitting devices. The performance of Aydin’s structure is comparable to that of nanostructure-based devices but bypasses the complications of nanotechnology.

“People in the nanophotonics community are dealing with nanostructures, making nanoparticles, and using lithography or chemistry techniques,” he said. “That can be really challenging. We’re combatting that difficulty with a simple design.”

Aydin is also developing a similar structure out of aluminum and glass to filter or absorb ultraviolet spectrum. By controlling the thickness of the materials, he plans to design devices for other wavelengths of light.

Here’s a link to and a citation for the paper,

Large-Area, Lithography-Free Super Absorbers and Color Filters at Visible Frequencies Using Ultrathin Metallic Films by Zhongyang Li, Serkan Butun, and Koray Aydin. ACS Photonics, Article ASAP DOI: 10.1021/ph500410u Publication Date (Web): January 28, 2015
Copyright © 2015 American Chemical Society

This paper is behind a paywall.

Bipolar disorder at the nanoscale

In all the talk generated by the various brain projects (BRAIN initiative [US], The Human Brain Project [European Union], Brain Canada), there’s remarkably little discussion about mental illness. So, this news is a little unusual.

Using super-high resolution technique scientists at Northwestern University (Chicago, Illinois, US) believe they’ve made a discovery which explains how bipolar disorder affects the brain according to an Oct. 22, 2014 Northwestern University news release (also on EurekAlert and ScienceDaily) by Erin White,

Scientists used a new super-resolution imaging method — the same method recognized with the 2014 Nobel Prize in chemistry — to peer deep into brain tissue from mice with bipolar-like behaviors. In the synapses (where communication between brain cells occurs), they discovered tiny “nanodomain” structures with concentrated levels of ANK3 — the gene most strongly associated with bipolar disorder risk. ANK3 is coding for the protein ankyrin-G.

“We knew that ankyrin-G played an important role in bipolar disease, but we didn’t know how,” said Northwestern Medicine scientist Peter Penzes, corresponding author of the paper. “Through this imaging method we found the gene formed in nanodomain structures in the synapses, and we determined that these structures control or regulate the behavior of synapses.”

Penzes is a professor in physiology and psychiatry and behavioral sciences at Northwestern University Feinberg School of Medicine. The results were published Oct. 22 in the journal Neuron.

High-profile cases, including actress Catherine Zeta-Jones and politician Jesse Jackson, Jr., have brought attention to bipolar disorder. The illness causes unusual shifts in mood, energy, activity levels and the ability to carry out day-to-day tasks. About 3 percent of Americans experience bipolar disorder symptoms, and there is no cure.

Recent large-scale human genetic studies have shown that genes can contribute to disease risk along with stress and other environmental factors. However, how these risk genes affect the brain is not known.

This is the first time any psychiatric risk gene has been analyzed at such a detailed level of resolution. As explained in the paper, Penzes used the Nikon Structured Illumination Super-resolution Microscope to study a mouse model of bipolar disorder. The microscope realizes resolution of up to 115 nanometers. To put that size in perspective, a nanometer is one-tenth of a micron, and there are 25,400 microns in one inch. Very few of these microscopes exist worldwide.

“There is important information about genes and diseases that can only been seen at this level of resolution,” Penzes said. “We provide a neurobiological explanation of the function of the leading risk gene, and this might provide insight into the abnormalities in bipolar disorder.”

The biological framework presented in this paper could be used in human studies of bipolar disorder in the future, with the goal of developing therapeutic approaches to target these genes.

Here’s a link to and a citation for the paper,

Psychiatric Risk Factor ANK3/Ankyrin-G Nanodomains Regulate the Structure and Function of Glutamatergic Synapses by Katharine R. Smith, Katherine J. Kopeikina, Jessica M. Fawcett-Patel, Katherine Leaderbrand, Ruoqi Gao, Britta Schürmann, Kristoffer Myczek, Jelena Radulovic, Geoffrey T. Swanson, and Peter Penzes. Neuron, Volume 84, Issue 2, p399–415, 22 October 2014 DOI: http://dx.doi.org/10.1016/j.neuron.2014.10.010

This paper is behind a paywall.

You can find more about super-high resolution and nanoscopy in my Oct. 8, 2014 post about the 2014 Nobel Chemistry prize winners.

‘Genius’ grant (MacArthur Fellowship) for reseacher Mark Hersam and his work on carbon nanotubes and the next generation of electronics

It took a few minutes to figure out why Mark Hersam, professor at Northwestern University (Chicago, Illinois, US) is being featured in an Oct. 21, 2014 news item on Nanowerk,

One of the longstanding problems of working with nanomaterials–substances at the molecular and atomic scale–is controlling their size. When their size changes, their properties also change. This suggests that uniform control over size is critical in order to use them reliably as components in electronics.

Put another way, “if you don’t control size, you will have inhomogeneity in performance,” says Mark Hersam. “You don’t want some of your cell phones to work, and others not.”

Hersam, a professor of materials science engineering, chemistry and medicine at Northwestern University, has developed a method to separate nanomaterials by size, therefore providing a consistency in properties otherwise not available. Moreover, the solution came straight from the life sciences–biochemistry, in fact.

The technique, known as density gradient ultracentrifugation, is a decades-old process used to separate biomolecules. The National Science Foundation (NSF)-funded scientist theorized correctly that he could adapt it to separate carbon nanotubes, rolled sheets of graphene (a single atomic layer of hexagonally bonded carbon atoms), long recognized for their potential applications in computers and tablets, smart phones and other portable devices, photovoltaics, batteries and bioimaging.

The technique has proved so successful that Hersam and his team now hold two dozen pending or issued patents, and in 2007 established their own company, NanoIntegris, jump-started with a $150,000 NSF small business grant. The company has been able to scale up production by 10,000-fold, and currently has 700 customers in 40 countries.
“We now have the capacity to produce ten times the worldwide demand for this material,” Hersam says.

NSF supports Hersam with a $640,000 individual investigator grant awarded in 2010 for five years. Also, he directs Northwestern’s Materials Research Science and Engineering Center (MRSEC), which NSF funds, including support for approximately 30 faculty members/researchers.

Hersam also is a recent recipient of one of this year’s prestigious MacArthur fellowships, a $625,000 no-strings-attached award, popularly known as a “genius” grant. [emphases mine] These go to talented individuals who have shown extraordinary originality and dedication in their fields, and are meant to encourage beneficiaries to freely explore their interests without fear of risk-taking.

An Oct. 20, 2014 US National Science Foundation Discoveries article by Marlene Cimons, which originated the news item, describes Hersam’s research and his hopes for it in more detail,

The carbon nanotubes separation process, which Hersam developed, begins with a centrifuge tube. Into that, “we load a water based solution and introduce an additive which allows us to tune the buoyant density of the solution itself,” he explains.

“What we create is a gradient in the buoyant density of the aqueous solution, with low density at the top and high density at the bottom,” he continues. “We then load the carbon nanotubes and put it into the centrifuge, which drives the nanotubes through the gradient. The nanotubes move through the gradient until their density matches that of the gradient. The result is that the nanotubes form separated bands in the centrifuge tube by density. Since the density of the nanotube is a function of its diameter, this method allows separation by diameter.”

One property that distinguishes these materials from traditional semiconductors like silicon is that they are mechanically flexible. “Carbon nanotubes are highly resilient,” Hersam says. “That allows us to integrate electronics on flexible substrates, like clothing, shoes, and wrist bands for real time monitoring of biomedical diagnostics and athletic performance. These materials have the right combination of properties to realize wearable electronics.”

He and his colleagues also are working on energy technologies, such as solar cells and batteries “that can improve efficiency and reduce the cost of solar cells, and increase the capacity and reduce the charging time of batteries,” he says. “The resulting batteries and solar cells are also mechanically flexible, and thus can be integrated with flexible electronics.”

They likely even will prove waterproof. “It turns out that carbon nanomaterials are hydrophobic, so water will roll right off of them,” he says.

A Sept. 17, 2014 Northwestern University news release congratulates Hersam on his award while describing his response to the news and providing more information about his work as a researcher and teacher (Note: Links have been removed),

The phone call from the John D. and Catherine T. MacArthur Foundation delivering the very good news was so out of the blue that Hersam initially thought it was a joke.

“Then I went into shock, and, I think, to some extent I remain in shock,” said Hersam, who received the call in his Cook Hall office. “As time has gone on, I’ve appreciated, of course, that it’s a great honor and, more importantly, a great opportunity.”

A dedicated and popular teacher, Hersam is the Bette and Neison Harris Chair in Teaching Excellence and professor of materials science and engineering at the McCormick School of Engineering and Applied Science.

“There are very few awards that provide unrestricted resources, and this one does. No strings attached,” he said. “That’s a great opportunity for a researcher — to have that level of freedom.”

Hersam is one of 21 new MacArthur Fellows recognized today (Sept. 17) by the MacArthur Foundation for “extraordinary originality and dedication in their creative pursuits and a marked capacity for self-direction.”

“I am very grateful and thankful to the MacArthur Foundation, to current and previous members of my research group and to my colleagues and collaborators over the years,” Hersam said. “Scientific research is a team effort.”

Hersam views his principal job as that of an educator — a role in which he can have more impact on unsolved problems by harnessing the minds of hundreds of young scientists and engineers.

“I love to teach in the classroom, but I also believe that scientific research is a vehicle for teaching,” Hersam said. “Research exposes students to difficult unsolved problems, forcing them to be creative. I want them to come up with truly new ideas, not just regurgitate established concepts.”

Hersam, who joined Northwestern in 2000, also is professor of chemistry in the Weinberg College of Arts and Sciences, professor of medicine at the Northwestern University Feinberg School of Medicine and director of Northwestern’s Materials Research Center.

Taking an interdisciplinary approach that draws on techniques from materials science, physics, engineering and chemistry, Hersam has established himself as a leading experimentalist in the area of hybrid organic-inorganic materials, with a focus on the study of the electrical and optical properties of carbon and related nanomaterials.

Hersam and his research lab have been working primarily with carbon nanotubes and graphene, but the support of the MacArthur award will allow the lab to diversify its materials set to other elements in the periodic table.

Earlier this year Hersam testified before U.S. Congress to push for “coordinated, predictable and sustained federal funding” for nanotechnology research and development.

The MacArthur Foundation’s website hosts a video on its ‘Mark Hersam’ webpage,

Interestingly, Hersam, in the video, describes a carbon nanotube as a rolled up sheet of graphene (it’s also described that way on the Foundation’s ‘Hersam’ webpage),

Graphene, a single atomic layer of hexagonally bonded carbon atoms, and carbon nanotubes, rolled sheets of graphene in single or multiple layers, have long been recognized for their potential applications in electronics, photovoltaics, batteries, and bioimaging.

It’s a good way of describing carbon nanotubes but the odd thing is that carbon nanotubes were discovered in 1991 (Timeline of carbon nanotubes entry on Wikipedia and in The History of Carbon Nanotubes on nanogloss.com) before graphene was first isolated in 2004 (my Oct. 7, 2010 posting).