Login with your Social Account

Researchers plan to release black hole movie soon

Researchers plan to release black hole movie soon

Before releasing the first-ever image of a black hole, an international team of researchers were already scheduling a movie sequel depicting how huge clouds of gas are permanently absorbed into the void. The required observations have already been recorded by the Event Horizon Telescope Collaboration and scientists are currently processing the data for the release of the first video in 2020.

Shep Doeleman, the project director is hopeful that by the end of the next decade, it would be possible to make real-time movies of black holes that depict their action at a cosmic stage beside their appearance.

The complete group of 347 scientists from around the world won $3 million and were awarded the Breakthrough Prize in Fundamental Physics for the so-called “Oscar of science” image. Doeleman, a 52-year-old cosmologist at the Harvard-Smithsonian Centre for Astrophysics and the father of two joked that his wife might be finally convinced that he was doing something worthwhile as he worked on this for more than 20 years.

Astronomers did not have the sharpness in their images to detect the shape of the light which was being swallowed by the black holes. After the team linked multiple radio telescopes together, creating an Earth-sized massive telescope the barrier was finally overcome and thus objects that appear microscopic in the night sky could now be observed with high resolution.

The team used three telescopes to establish the evidence of concept and the first measurements of the black hole were published in 2008. They had combined eight radio telescopes in Chile, Spain, Mexico, the US, and the South Pole by April 2017. The astronomers were able to observe the boundaries of the black holes by using these massive instruments which observe high-frequency radio waves.

The group also observed the center of our own Milky Way: Sagittarius-A* in addition to its observations of the black hole in the Messier 87 (M87) galaxy. Doeleman explained that while orbits of matter around Sagittarius-A* takes only half an hour and can change during one night of observation, it takes about a month to orbit around M87. He also added that the first cut of the movie could be made by 2020 and researchers would need more telescopes on Earth as well as in orbit, to strengthen the resolution.

Doeleman is optimistic about the possibility of future funding from governments as well as possibly from private donors after the first image of M87 captured people’s imagination. He also said that the EHT has added more value than any other scientific project in history. As explorers, they are reporting what they have observed at the edges of the black hole with their instruments.

graphene structure

Researchers demonstrate production of graphene using bacteria

Researchers have figured out a novel method to produce graphene, an amazing substance in a cheaper way with the help of bacteria. Graphene is a very useful material in filtering water, dyeing hair and great strengthening of substances. The study has been published in ChemistryOpen.

When the bacterium Shewanella oneidensis is mixed with oxidized graphite or graphene oxide (which is comparatively easy to produce but not conductive due to oxygen groups), the oxygen groups are withdrawn and conductive graphene is obtained as the product. It is inexpensive, quicker and more eco-friendly than the existing methods to produce the substance. It can also be stored for a long period of time making it appropriate for various applications. Using this method, we can produce graphene at a scale required for computing and medical devices of the next generation.

“For real applications, you need large amounts,” says biologist Anne Meyer from the University of Rochester in New York.

Using the new method, Meyer and her colleagues were able to make graphene that’s thinner, more stable, and longer-lasting than graphene that’s produced by chemical manufacturing. This will unlock all sort of opportunities for less costly bacteria-produced graphene and can be used in field-effect transistor (FET) biosensors.  It is a tool that identifies specific biological molecule such as glucose tracking for diabetics.

Bacteria production method leaves back specific oxygen group. It makes resulting graphene compatible to link with specific molecules. Graphene material obtained from this method can be used as conductive ink in circuit boards, computer keyboards or in small wires to unfreeze car windscreen or to produce one-sided conductive graphene by twisting the bacteria process. It can also lead to the creation of innovative computer technologies and medical equipment.

At present, graphene is produced by different chemical methods using graphite or graphene oxide compared to the past method where graphite was extracted by graphite blocks using sticky tape. The new method of production is the most favorable one to date without the use of unpleasant chemicals. Prior to scaling up and using it to develop next-generation devices, lots of research needs to be done to study the bacteria process. However, the future of this extraordinary material continues to look bright. Meyer said that bacterially produced graphene material will guide to much better applicability for product development and development of nanocomposite materials.

Journal: https://onlinelibrary.wiley.com/doi/full/10.1002/open.201900186

Physics behind evaporation

Experiments reveal the physics of evaporation

It’s a process so fundamental to everyday life — in everything from your morning coffeemaker to the huge power plant that provides its electricity — that it’s often taken for granted: the way a liquid boils away from a hot surface.

Yet surprisingly, this basic process has only now, for the first time, been analyzed in detail at a molecular level, in a new analysis by MIT postdoc Zhengmao Lu, professor of mechanical engineering and department head Evelyn Wang, and three others at MIT and Tokyo University. The study appears in the journal Nature Communications.

“It turns out that for the process of liquid-to-vapor phase change, a fundamental understanding of that is still relatively limited,” Wang explains. “While there’s been a lot of theories developed, there actually has not been experimental evidence of the fundamental limits of evaporation physics.”

It’s an important process to understand because it is so ubiquitous. “Evaporation is prevalent in all sorts of different types of systems such as steam generation for power plants, water desalination technologies, membrane distillation, and thermal management, like heat pipes, for example,” Wang says. Optimizing the efficiency of such processes requires a clear understanding of the dynamics at play, but in many cases engineers rely on approximations or empirical observations to guide their choices of materials and operating conditions.

By using a new technique to both control and detect temperatures at the surface of an evaporating liquid, the researchers were able to identify a set of universal characteristics involving time, pressure and temperature changes that determine the details of the evaporation process. In the process, they discovered that the key factor determining how fast the liquid could evaporate was not the temperature difference between the surface and the liquid, but rather the difference in pressure between the liquid surface and the ambient vapor.

The “rather simple question” of how a liquid evaporates at a given temperature and pressure, has remained unanswered despite many decades of study, says Pawel Keblinski, professor and head of Department of Materials Science and Engineering at Rensselaer Polytechnic Institute (RPI), who was not involved in this work. “While theorists speculated for over a century, experiment was of little help, as seeing the evaporating liquid-vapor interface and knowing the temperature and pressure near the interfaces is extremely challenging,” he says.

This new work, Keblinski says, “brings us closer to the truth.” Along with other new observational techniques developed by others, the new insights will “put us on the path to finally quantify the evaporation process after a century of efforts,” he says.

The researchers’ success was partly the result of eliminating other factors that complicate the analysis. For example, evaporation of liquid into air is strongly affected by the insulating properties of the air itself, so for these experiments the process was observed in a chamber with only the liquid and vapor present, isolated from the surrounding air. Then, in order to probe the effects right at the boundary between the liquid and the vapor, the researchers used a very thin membrane riddled with small pores to confine the water, heat it up, and measure its temperature.

That membrane, just 200 nanometers (billionths of a meter) thick, made of silicon nitride and coated with gold, carries water through its pores by capillary action, and is electrically heated to cause the water to evaporate. Then, “we also use that membrane as the sensor, to sense the temperature of the evaporating surface in an accurate and noninvasive way,” Lu says.

The gold coating of the membrane is crucial, he adds. The electrical resistance of the gold varies directly as a function of the temperature, so by carefully calibrating the system before the experiment, they are able to get a direct reading of the temperature at the exact point where evaporation is taking place, moment by moment, simply by reading the membrane’s resistance.

The data they gathered “suggests that the actual driving force or driving potential in this process is not the difference in temperature, but actually the pressure difference,” Wang says. “That’s what makes everything now aligned to this really nice curve, that matches well with what theory would predict,” she says.

While it may sound simple in principle, actually developing the necessary membrane with its 100-nanometer-wide pores, which are made using a method called interference lithography, and getting the whole system to work properly took two years of hard work, she says.

Overall, the findings so far “are consistent with what theory predicts,” Lu says, but it is still important to have that confirmation. “While theories have predicted things, there’s been no experimental evidence that the theories are correct,” Wang adds.

The new findings also provide guidance for engineers designing new evaporation-based systems, providing information on both the selection of the best working fluids for a given situation, as well as the conditions of pressure and removal of ambient air from the system. “Using this system as a guideline you can sort of optimize the working conditions for certain kinds of applications,” Lu says.

This team did a series of elegant experiments designed to confirm theoretical predictions,” says Joel Plawsky, professor of chemical and biological engineering at RPI, who was not involved in this work. “The apparatus was unique and painstakingly difficult to fabricate and operate. The data was exceptional in its quality and detail. Any time one can collapse a large spread of data by developing a dimensionless formulation,” that is, one that applies equally well under a wide variety of conditions, “that represents a major advance for engineering,” he says.

Plawsly adds, “There are many questions that this work opens up about the behavior of different fluids and of fluid mixtures.  One can imagine many years’ worth of follow-on work.”

The team also included Ikuya Kinefuchi at the University of Tokyo and graduate students Kyle Wilke and Geoffrey Vaartstra at MIT. The work was supported by the Air Force Office of Scientific Research and the National Science Foundation.

Materials provided by Massachusetts Institute of Technology

hyphens in research papers

Warning to academics: Hyphens in paper titles harm citation counts and journal impact factors

According to the latest research results, the presence of simple hyphens in the titles of academic papers adversely affects the citation statistics, regardless of the quality of the articles. The phenomenon applies to all major subject areas. Thus, citation counts and journal impact factors, commonly used for professorial evaluations in universities worldwide, are unreliable.

This breakthrough finding poses a fundamental challenge to the rule of the game in determining the contributions of papers, journals, and professors. It is unveiled in a paper titled Metamorphic Robustness Testing: Exposing Hidden Defects in Citation Statistics and Journal Impact Factors” by Zhi Quan Zhou, T.H. Tse, and Matt Witheridge, recently published in IEEE Transactions on Software Engineering, the top journal in the field.

T.H. Tse is an honorary professor in computer science at the University of Hong Kong (HKU). Zhi Quan Zhou received the PhD degree from HKU and is currently an associate professor in software engineering at the University of Wollongong, Australia. Matt Witheridge is a PhD student at the University of Wollongong.

Scopus and Web of Science are the two leading citation indexing systems. Scopus provides the citation statistics to support the Times Higher Education World University Rankings and the QS World University Rankings. Web of Science provides the journal impact factor that supports the ranking of major journals. Because of the importance of these two indexing systems, it is essential to assure their quality. In particular, robustness testing refers to the verification of the systems’ ability to deal with erroneous inputs or unexpected situations. For example, can the indexing system handle a citation properly if there is a minor typo when quoting the paper title?

Professor Tse and team members proposed an innovative method named “metamorphic robustness testing” to verify Scopus and Web of Science. The in-depth study uncovered robustness defects in both systems that might produce erroneous citation counts for papers with hyphens in the titles, so that the journal impact factors subsequently computed are problematic.

Back in 2015, Letchford and colleagues conducted a large-scale study on Scopus, and found that papers with shorter titles tended to be cited more than those with longer titles. Their results were widely reported in international media including Science and Nature.

On the contrary, Professor Tse and the present team find that it is actually the number of hyphens in the title that serves as the more dominating factor for citation counts. Usually, the number of hyphens is correlated to a paper’s title length, thus giving the misinterpretation that citation counts depend on title length.

Citation practices vary across subject areas. Publications in certain fields may have systematically higher citation counts than in other fields. For example, one may argue that papers in chemistry (where paper titles often carry hyphens as part of the chemical nomenclature) only receive relatively limited numbers of citations, giving rise to a spurious negative correlation between hyphens and citations. Hence, the team carried out focused studies on journals in specific subject areas. The results indicated that hyphens adversely affect the citation counts of papers even if the study is only limited to some particular discipline.

To build on the findings at the article and discipline levels, the team investigated the impact of hyphens in paper titles at the journal level. Journal impact factor (JIF) is a common metric for determining the citation frequency of an academic journal. It is frequently used to represent the relative importance of a journal within its field. A software engineering field-wide study reveals that the higher JIF-ranked journals are publishing a lower percentage of papers with hyphenated titles.

The team further conducted an analysis of the validity of the research to avoid falling into the trap of equating correlation with causation.

“Our results question the common belief by the academia, governments, and funding bodies that citation counts are a reliable measure of the contributions and significance of papers. In fact, they can be distorted simply by the presence of hyphens in article titles, which has no bearing on the quality of research. Similarly, our results also challenge the validity of journal impact factors,” said Professor Tse.

“These surprising results are of interest not only to professors seeking tenure or promotion, but also to the senior management such as presidents, deans, and heads. They are applicable to all faculties in any university,” he added.

Materials provided by the University of Hing Kong

MIT Household

Pantry ingredients can help grow carbon nanotubes

Baking soda, table salt, and detergent are surprisingly effective ingredients for cooking up carbon nanotubes, researchers at MIT have found.

In a study published this week in the journal Angewandte Chemie, the team reports that sodium-containing compounds found in common household ingredients are able to catalyze the growth of carbon nanotubes, or CNTs, at much lower temperatures than traditional catalysts require.

The researchers say that sodium may make it possible for carbon nanotubes to be grown on a host of lower-temperature materials, such as polymers, which normally melt under the high temperatures needed for traditional CNT growth.

“In aerospace composites, there are a lot of polymers that hold carbon fibers together, and now we may be able to directly grow CNTs on polymer materials, to make stronger, tougher, stiffer composites,” says Richard Li, the study’s lead author and a graduate student in MIT’s Department of Aeronautics and Astronautics. “Using sodium as a catalyst really unlocks the kinds of surfaces you can grow nanotubes on.”

Li’s MIT co-authors are postdocs Erica Antunes, Estelle Kalfon-Cohen, Luiz Acauan, and Kehang Cui; alumni Akira Kudo PhD ’16, Andrew Liotta ’16, and Ananth Govind Rajan SM ’16, PhD ’19; professor of chemical engineering Michael Strano, and professor of aeronautics and astronautics Brian Wardle, along with collaborators at the National Institute of Standards and Technology and Harvard University.

Peeling onions

Under a microscope, carbon nanotubes resemble hollow cylinders of chicken wire. Each tube is made from a rolled up lattice of hexagonally arranged carbon atoms. The bond between carbon atoms is extraordinarily strong, and when patterned into a lattice, such as graphene, or as a tube, such as a CNT, such structures can have exceptional stiffness and strength, as well as unique electrical and chemical properties. As such, researchers have explored coating various surfaces with CNTs to produce stronger, stiffer, tougher materials.

Researchers typically grow CNTs on various materials through a process called chemical vapor deposition. A material of interest, such as carbon fibers, is coated in a catalyst — usually an iron-based compound — and placed in a furnace, through which carbon dioxide and other carbon-containing gases flow. At temperatures of up to 800 degrees Celsius, the iron starts to draw carbon atoms out of the gas, which glom onto the iron atoms and to each other, eventually forming vertical tubes of carbon atoms around individual carbon fibers. Researchers then use various techniques to dissolve the catalyst, leaving behind pure carbon nanotubes.

Li and his colleagues were experimenting with ways to grow CNTs on various surfaces by coating them with different solutions of iron-containing compounds, when the team noticed the resulting carbon nanotubes looked different from what they expected.

“The tubes looked a little funny, and Rich and the team carefully peeled the onion back, as it were, and it turns out a small quantity of sodium, which we suspected was inactive, was actually causing all the growth,” Wardle says.

Tuning sodium’s knobs

For the most part, iron has been the traditional catalyst for growing CNTs. Wardle says this is the first time that researchers have seen sodium have a similar effect.

“Sodium and other alkali metals have not been explored for CNT catalysis,” Wardle says. “This work has led us to a different part of the periodic table.”

To make sure their initial observation wasn’t just a fluke, the team tested a range of sodium-containing compounds. They initially experimented with commercial-grade sodium, in the form of baking soda, table salt, and detergent pellets, which they obtained from the campus convenience store. Eventually, however, they upgraded to purified versions of those compounds, which they dissolved in water. They then immersed a carbon fiber in each compound’s solution, coating the entire surface in sodium. Finally, they placed the material in a furnace and carried out the typical steps involved in the chemical vapor deposition process to grow CNTs.

In general, they found that, while iron catalysts form carbon nanotubes at around 800 degrees Celsius, the sodium catalysts were able to form short, dense forests of CNTs at much lower temperatures, of around 480 C. What’s more, after surfaces spent about 15 to 30 minutes in the furnace, the sodium simply vaporized away, leaving behind hollow carbon nanotubes.

“A large part of CNT research is not on growing them, but on cleaning them —getting the different metals used to grow them out of the product,” Wardle says. “The neat thing with sodium is, we can just heat it and get rid of it, and get pure CNT as product, which you can’t do with traditional catalysts.”

Li says future work may focus on improving the quality of CNTs that are grown using sodium catalysts. The researchers observed that while sodium was able to generate forests of carbon nanotubes, the walls of the tubes were not perfectly aligned in perfectly hexagonal patterns — crystal-like configurations that give CNTs their characteristic strength. Li plans to “tune various knobs” in the CVD process, changing the timing, temperature, and environmental conditions, to improve the quality of sodium-grown CNTs.

“There are so many variables you can still play with, and sodium can still compete pretty well with traditional catalysts,” Li says. “We anticipate with sodium, it is possible to get high quality tubes in the future. And we have pretty high confidence that, even if you were to use regular Arm and Hammer baking soda, it should work.”

For Shigeo Maruyama, professor of mechanical engineering at the University of Tokyo, the ability to cook up CNTs from such a commonplace ingredient as sodium should reveal new insights into the way the exceptionally strong materials grow.

“It is a surprise that we can grow carbon nanotubes from table salt!” says Maruyama, who was not involved in the research. “Even though chemical vapor deposition (CVD) growth of carbon nanotubes has been studied for more than 20 years, nobody has tried to use alkali group metal as catalyst. This will be a great hint for the fully new understanding of growth mechanism of carbon nanotubes.”

This research was supported, in part, by Airbus, Boeing, Embraer, Lockheed Martin, Saab AB, ANSYS, Saertex, and TohoTenax through MIT’s Nano-Engineered Composite aerospace STructures (NECST) Consortium.

Materials provided by Massachusetts Institute of Technology