How to use graphene as a biosensor by increasing its chemical selectivity

Kurzweil AI - Fri, 26/06/2015 - 2:51am

The illustration shows how maleimide compounds (top) bind to the graphene surface to hold detector molecules. The graphene monolayer lies on a thin film of silicon nitride (red) that in turn is on a quartz microbalance (blue) and the graphene can be subjected to voltage via a gold contact (yellow). (credit: Marc Gluba/HZB)

Scientists at the HZB Institute for Silicon Photovoltaics in Berlin have succeeded in precisely measuring and controlling the thickness of an organic compound that has been bound to a graphene layer. This could enable graphene to be used as a sensitive detector for biological molecules in the future.

It has long been known that graphene is useful for detecting traces of organic molecules, because the electrical conductivity of graphene drops as soon as foreign molecules bind to it. The problem: graphene is not very selective, making it difficult to differentiate molecules.

The scientists found a way to increase the selectivity by electrochemically connecting graphene to host molecules that act as detector molecules functioning as selective binding sites. To accomplish this, para-maleimidophenyl groups (maleimide) from an organic solution were grafted to the surface of the graphene. These organic molecules behave like mounting brackets to which the selective detector molecules can be attached in the next step.

“Thanks to these molecules, graphene can now be employed for detecting various substances, similar to how a key fits a lock,” explains researcher Marc Gluba. The “lock” molecules on the surface are highly selective and absorb only the matching “key” molecules, allowing for  accurately measuring how many molecules actually were grafted to the surface of the graphene.

One use would be an inexpensive “lab-on-a-chip.” Using a single drop of blood could immediately provide data for medical diagnosis, says Prof. Norbert Nickel, head of the research team.

Abstract of Quantifying the electrochemical maleimidation of large area graphene

The covalent modification of large-area graphene sheets by p-(N-Maleimido)phenyl (p-MP) via electrochemical grafting of p-(N-Maleimido)benzenediazonium tetrafluoroborate (p-MBDT) is successfully demonstrated for the first time. The deposition process is monitored in-situ using the mass change of a graphene/SiNX:H/Au-coated quartz crystal microbalance(QCM) chip. The resulting mass increase correlates with a maleimide thickness of approximately 2.3 molecular layers. The presence of an infrared absorption band at 1726 cm-1 shows that maleimide groups were deposited on the substrates. Raman backscattering spectra reveal the presence of D and D′ modes of the graphene layer, indicating that p-MP forms covalent bonds to graphene. Using the mass change and charge transfer during the potential cycling the faradaic efficiency of the functionalisation process was deduced, which amounts to eta = 22%.

Categories: Science

Spintronics advance brings wafer-scale quantum devices closer to reality

Kurzweil AI - Fri, 26/06/2015 - 2:30am

Light polarizes silicon nuclear spins within a silicon carbide chip. This image portrays the nuclear spin of one of the atoms from the full crystal lattice below. (credit: Peter Allen)

Researchers at the University of Chicago’s Institute for Molecular Engineering have taken a crucial step toward nuclear spintronic technologies that use the “spin” — or magnetization — of atomic nuclei to store and process information. The new technologies could be used for ultra-sensitive magnetic resonance imaging, advanced gyroscopes, and quantum computers.

The researchers used infrared light to make nuclear spins line themselves up in a consistent, controllable way, using a high-performance semiconductor that is practical, convenient, and inexpensive.

The research was featured as the cover article of the June 17 issue of Physical Review Letters.

No cryogenic temperatures and high magnetic fields

Nuclear spins tend to be randomly oriented. Aligning them in a controllable fashion is usually a complicated and only marginally successful proposition. The reason, explains Paul Klimov, a co-author of the paper, is that “the magnetic moment of each nucleus is tiny, roughly 1,000 times smaller than that of an electron.”

This small magnetic moment means that little thermal kicks from surrounding atoms or electrons can easily randomize the direction of the nuclear spins. Extreme experimental conditions such as high magnetic fields and cryogenic temperatures (-238 degrees Fahrenehit and below) are usually required to get even a small number of spins to line up. In magnetic resonance imaging, for example, only one to 10 out of a million nuclear spins can be aligned and seen in the image, even with a high magnetic field applied.

Using their new technique, David Awschalom, the Liew Family Professor in Spintronics and Quantum Information, and his associates aligned more than 99 percent of spins in certain nuclei in silicon carbide. Equally important, the technique works at room temperature — no cryogenics or intense magnetic fields needed. Instead, the research team used light to “cool” the nuclei.

While nuclei do not interact with light themselves, certain imperfections, or “color-centers,” in the silicon carbide crystals do. The electron spins in these color centers can be readily optically cooled and aligned, and this alignment can be transferred to nearby nuclei.

Getting spins to align in room-temperature silicon carbide brings practical spintronic devices a significant step closer, said Awschalom. The material is already an important semiconductor in the high-power electronics and opto-electronics industries. Sophisticated growth and processing capabilities are already mature. So prototypes of nuclear spintronic devices that exploit the IME researchers’ technique may be developed in the near future.

“Wafer-scale quantum technologies that harness nuclear spins as subatomic elements may appear more quickly than we anticipated,” Awschalom said.

Abstract of Optical Polarization of Nuclear Spins in Silicon Carbide

We demonstrate optically pumped dynamic nuclear polarization of Si29 nuclear spins that are strongly coupled to paramagnetic color centers in 4H- and 6H-SiC. The 99%±1% degree of polarization that we observe at room temperature corresponds to an effective nuclear temperature of 5 μK. By combining ab initio theory with the experimental identification of the color centers’ optically excited states, we quantitatively model how the polarization derives from hyperfine-mediated level anticrossings. These results lay a foundation for SiC-based quantum memories, nuclear gyroscopes, and hyperpolarized probes for magnetic resonance imaging.

Categories: Science

Could nanowires be the LEDs of the future?

Kurzweil AI - Fri, 26/06/2015 - 2:03am

(a) Sketch of an LED nanowire showing the onion-like structure of the layers; (b) Finite element method simulation of strain distribution (credit: Tomas Stankevic, Niels Bohr Institute, University of Copenhagen)

LEDs made from nanowires with an inner core of gallium nitride (GaN) and a outer layer of indium-gallium-nitride (InGaN) — both semiconductors — use less energy and provide better light, according Robert Feidenhans’l, professor and head of the Niels Bohr Institute at the University of Copenhagen.

The studies were performed using nanoscale X-ray microscopy in the electron synchrotron at DESY in Hamburg, Germany. The results are published in the journal ACS Nano.

The nanowires could also be used as displays in smart phones, TVs and other forms of lighting within five years, according to the researchers.

A series of nanowires were scanned in a nanofocused X-ray while reflections from the different crystal planes of the nanowires were measured (credit: Tomas Stankevic, Niels Bohr Institute, University of Copenhagen)

Abstract of Fast Strain Mapping of Nanowire Light-Emitting Diodes Using Nanofocused X-ray Beams

X-ray nanobeams are unique nondestructive probes that allow direct measurements of the nanoscale strain distribution and composition inside the micrometer thick layered structures that are found in most electronic device architectures. However, the method is usually extremely time-consuming, and as a result, data sets are often constrained to a few or even single objects. Here we demonstrate that by special design of a nanofocused X-ray beam diffraction experiment we can (in a single 2D scan with no sample rotation) measure the individual strain and composition profiles of many structures in an array of upright standing nanowires. We make use of the observation that in the generic nanowire device configuration, which is found in high-speed transistors, solar cells, and light-emitting diodes, each wire exhibits very small degrees of random tilts and twists toward the substrate. Although the tilt and twist are very small, they give a new contrast mechanism between different wires. In the present case, we image complex nanowires for nanoLED fabrication and compare to theoretical simulations, demonstrating that this fast method is suitable for real nanostructured devices.

Categories: Science

Stellar Rejuvenation: Some Exoplanets May Get Facelifts

Slashdot - Fri, 26/06/2015 - 2:03am
astroengine writes: Astronomers may have discovered an exoplanet that has found the elixir to planetary youth, knocking billions of years off its age. Until now, stellar rejuvenation has been pure conjecture, but after studying a white dwarf star called PG 0010+280, it turns out that one very interesting explanation for an excess in detected infrared radiation may be down to the presence of an exoplanet that was given a facelift. "When planets are young, they still glow with infrared light from their formation," said Michael Jura of the University of California, Los Angeles, co-author of the study published in The Astrophysical Journal. "But as they get older and cooler, you can't see them anymore. Rejuvenated planets would be visible again." This rejuvenation happens when stellar material shedding from a dying red giant star falls onto an exoplanet, causing heating and making it appear younger.

Read more of this story at Slashdot.

Categories: Science

Google Asks Android Developers To Show Sensitivity To Disasters and Atrocity

Slashdot - Fri, 26/06/2015 - 12:31am
Mark Wilson writes: Today Google revealed an updated version of its Google Play Developer Program Policies. There aren't actually all that many changes or additions, but those that are present are quite interesting. Google is clamping down on the problem of impersonation, making it clearer that it is not permissible to mislead users by imitating other apps, making false claims, or suggesting endorsements that do not exist. One of the more intriguing changes to the document sees Google calling on developers to show sensitivity to evens such as natural disasters, war, and death. Any apps or other content that attempt to benefit by exploiting such events are explicitly banned.

Read more of this story at Slashdot.

Categories: Science

WiFi Offloading is Skyrocketing

Slashdot - Thu, 25/06/2015 - 11:50pm
dkatana writes: WiFi Offloading is skyrocketing. This is the conclusion of a new report from Juniper Research, which points out that the amount of smartphone and tablet data traffic on WiFi networks will will increase to more than 115,000 petabytes by 2019, compared to under 30,000 petabytes this year, representing almost a four-fold increase. Most of this data is offloaded to consumer's WiFi by the carriers, offering the possibility to share your home internet connection in exchange for "free" hotspots. But this article on InformationWeek Network Computing also warns that "The capacity of the 2.4GHz band is reaching its limit. [...] the growing number of WiFi devices using unlicensed bands is seriously affecting network efficiency. Capacity is compromised by the number of simultaneously active devices, with transmission speeds dropping as much as 20% of the nominal value. With the number of IoT and M2M applications using WiFi continuously rising, that could become a serious problem soon."

Read more of this story at Slashdot.

Categories: Science

DARPA Is Already Working On Designer Organisms To Terraform Mars

Slashdot - Thu, 25/06/2015 - 11:08pm
MarkWhittington writes: Space visionaries dream of a time when human beings will not only settle Mars, but will terraform the Red Planet into something more Earth-like, with a breathable atmosphere, running water, and a functioning biosphere. Evidence exists that Mars was more or less Earth-like billions of years ago before the atmosphere leached away into space and the water became frozen under the ground and at the poles. Terraforming Mars is decades away from the beginning and probably centuries away from the end. But DARPA, the Defense Advanced Research Projects Agency, is already genetically engineering organisms that will help turn the Red Planet blue, according to a story in Motherboard.

Read more of this story at Slashdot.

Categories: Science

Astronauts Need Flexible Spacesuits for Mars - Thu, 25/06/2015 - 11:01pm
The next couple of decades could see astronauts go to many places: an asteroid, the moon, even Mars. But the current spacesuits used on the International Space Station will likely need replacing to get those exploration jobs done.
Categories: Science

Average Duration of Hiring Process For Software Engineers: 35 Days

Slashdot - Thu, 25/06/2015 - 10:24pm
itwbennett writes: Despite the high demand for tech workers of pretty much all stripes, the hiring process is still rather drawn out, with the average time-to-hire for Software Engineers taking 35 days. That's one of the findings of a new study from career site Glassdoor. The study, led by Glassdoor's Chief Economist Dr. Andrew Chamberlain, analyzed over 340,000 interview reviews, covering 74,000 unique job titles, submitted to the site from February 2009 through February 2015. Glassdoor found that the average time-to-hire for all jobs has increased 80% (from 12.6 days to 22.9 days) since 2010. The biggest reason for this jump: The increased reliance on screening tests of various sorts, from background checks and skills tests to drug tests and personality tests, among others.

Read more of this story at Slashdot.

Categories: Science

Why Supreme Court Interns Still Sprint to Deliver News

Wired News - Thu, 25/06/2015 - 10:20pm

When it comes to the Supreme Court, paper hand-offs still reign.

The post Why Supreme Court Interns Still Sprint to Deliver News appeared first on WIRED.

Categories: Science

Google Tests Code Repository Service

Slashdot - Thu, 25/06/2015 - 9:41pm
An anonymous reader writes: VentureBeat notes that Google has begun testing an unannounced service to host and edit source code repositories as part of its cloud platform. It's called Cloud Source Repositories, and it's currently being beta-tested. "Google is taking a gradual approach with the new service: It can serve as a 'remote' for Git repositories sitting elsewhere on the Internet or locally. Still, over time the new tool could help Google become more of an all-in-one destination for building and deploying applications."

Read more of this story at Slashdot.

Categories: Science

Why SpaceX Didn't Stick The Landing – But Soon Will | Video - Thu, 25/06/2015 - 9:35pm
A previously unreleased company video shows how challenging landing a Falcon 9 on a robot barge at sea can be. Many autonomous systems must act in concert and all must get their parts perfect.
Categories: Science

Paris Cabbies Show Their Dislike of Uber With Burning Tires

Wired News - Thu, 25/06/2015 - 9:31pm

In France, Uber has come up against a culture of resistance that doesn't share Silicon Valley's faith in the value of disruption.

The post Paris Cabbies Show Their Dislike of Uber With Burning Tires appeared first on WIRED.

Categories: Science

This Little Iron Tchotchke Can Help Cure a Big Health Issue

Wired News - Thu, 25/06/2015 - 9:27pm

In Cambodia, Lucky Iron Fish has cut down the cases of anemia.

The post This Little Iron Tchotchke Can Help Cure a Big Health Issue appeared first on WIRED.

Categories: Science

How to Stream Every Jon Stewart Daily Show Episode

Wired News - Thu, 25/06/2015 - 9:25pm

Comedy Central's not letting its bedrock of political satire go without a celebratory Viking funeral.

The post How to Stream Every Jon Stewart Daily Show Episode appeared first on WIRED.

Categories: Science

Tests vs. Fests: Students in 'learning celebrations' rather than exams scored higher and enjoyed themselves

Science Daily - Thu, 25/06/2015 - 9:07pm
A sociologist who reshaped "test day" in his class -- transforming it with balloons, streamers, treats and music -- found that students in "learning celebrations" scored higher than students who took standard-style exams in previous semesters.
Categories: Science

New strategies for combatting chronic kidney disease, other long-term conditions

Science Daily - Thu, 25/06/2015 - 9:07pm
New strategies for using electronic health records (EHRs) to treat patients with chronic kidney disease have been outlined by investigators. Their recommendations may help clinicians and hospitals better manage individual patients with chronic conditions and identify groups of patients most likely to benefit from different treatment strategies.
Categories: Science

Editor of 'Reason' Discusses Federal Subpoena To Unmask Commenters

Slashdot - Thu, 25/06/2015 - 9:00pm
mi points out an article from Nick Gillespie, editor of libertarian website Reason, who was recently asked by the federal government to provide identifying information on anonymous commenters from one of the site's blog posts. Not only was Reason issued a subpoena for the commenters's identities, but they were also placed under a gag order, preventing them from even mentioning it to somebody who wasn't their lawyer. Gillespie says the comments in question were "hyperbolic, in questionable taste–and fully within the norms of Internet commentary." He continues: To the extent that the feds actually thought these were serious plans to do real harm, why the hell would they respond with a slow-moving subpoena whose deadline was days away? By spending five minutes doing the laziest, George Jetson-style online "research" (read: Google and site searches), they would have found publicly available info on some of the commenters. I'm talking things like websites and Google+ pages. One of the commenters had literally posted thousands of comments at, from which it is clear that he (assuming it is a he) is not exactly a threat to anyone other than common decency."

Read more of this story at Slashdot.

Categories: Science

Destination Mars: NASA Asks Where Astronauts Should Land - Thu, 25/06/2015 - 8:28pm
The space agency will hold a workshop in Houston this October to kick off serious discussions about possible landing sites for NASA's first manned mission to the Red Planet, which the agency aims to launch by the mid- to late 2030s.
Categories: Science

Multiple pathways progressing to Alzheimer's disease

Science Daily - Thu, 25/06/2015 - 8:18pm
The amyloid cascade hypothesis of Alzheimer's disease (AD) posits that sticky aggregations or plaques of amyloid-beta peptides accumulate over time in the brain, triggering a series of events that ultimately result in the full-blown neurodegenerative disorder. The hypothesis has been a major driver of AD research for more than 20 years. However, in a new study, researchers suggest the picture is not so clear-cut, reporting that early indicators or biomarkers of AD development are not fixed in a specific sequence.
Categories: Science