Hans Noordsij, a Dutch Tesla driver, uploaded a Dec. 27 dashcam video that dramatically shows the new radar processing capacity of Tesla’s Autopilot and resulting auto-breaking, DarkVision Hardware reports. The system’s radar saw ahead of the car in front and tracked two cars ahead on the road. Note the audible warning a second or so before the accident.
Scientists at Stanford University and the Department of Energy’s SLAC National Accelerator Laboratory have discovered a way to use diamondoids* — the smallest possible bits of diamond — to self-assemble atoms, LEGO-style, into the thinnest possible electrical wires, just three atoms wide.
The new technique could potentially be used to build tiny wires for a wide range of applications, including fabrics that generate electricity, optoelectronic devices that employ both electricity and light, and superconducting materials that conduct electricity without any loss. The scientists reported their results last week in Nature Materials.
The researchers started with the smallest possible diamondoids —interlocking cages of carbon and hydrogen — and attached a sulfur atom to each. Floating in a solution, each sulfur atom bonded with a single copper ion — creating a semiconducting combination of copper and sulfur known as a chalcogenide.
That created the basic nanowire building blocks, which then drifted toward each other, drawn by “unusually strong” van der Waals attraction between the diamondoids, and attached themselves to the growing tip of the nanowire. The attached diamondoids formed an insulating shell — creating the nanoscale equivalent of a conventional insulated electrical wire.
Although there are other ways to get materials to self-assemble, this is the first one shown to make a nanowire with a solid, crystalline core that has good electronic properties, said study co-author Nicholas Melosh, an associate professor at SLAC and Stanford and investigator with SIMES, the Stanford Institute for Materials and Energy Sciences at SLAC.
The team also included researchers from Lawrence Berkeley National Laboratory, the National Autonomous University of Mexico (UNAM) and Justus-Liebig University in Germany. The work was funded by the DOE Office of Science and the German Research Foundation.
* Found naturally in petroleum fluids, they are extracted and separated by size and geometry in a SLAC laboratory.
Citation: Yan et al., Nature Materials, 26 December 2016 (10.1038/nmat4823)
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Abstract of Hybrid metal–organic chalcogenide nanowires with electrically conductive inorganic core through diamondoid-directed assembly
Controlling inorganic structure and dimensionality through structure-directing agents is a versatile approach for new materials synthesis that has been used extensively for metal–organic frameworks and coordination polymers. However, the lack of ‘solid’ inorganic cores requires charge transport through single-atom chains and/or organic groups, limiting their electronic properties. Here, we report that strongly interacting diamondoid structure-directing agents guide the growth of hybrid metal–organic chalcogenide nanowires with solid inorganic cores having three-atom cross-sections, representing the smallest possible nanowires. The strong van der Waals attraction between diamondoids overcomes steric repulsion leading to a cis configuration at the active growth front, enabling face-on addition of precursors for nanowire elongation. These nanowires have band-like electronic properties, low effective carrier masses and three orders-of-magnitude conductivity modulation by hole doping. This discovery highlights a previously unexplored regime of structure-directing agents compared with traditional surfactant, block copolymer or metal–organic framework linkers.
Swiss researchers have succeeded in measuring changes in strong magnetic fields with unprecedented precision, they report in the open-access journal Nature Communications. The finding may find widespread use in medicine and other areas.
In their experiments, the researchers at the Institute for Biomedical Engineering, which is operated jointly by ETH Zurich and the University of Zurich, magnetized a water droplet inside a magnetic resonance imaging (MRI) scanner, a device used for medical imaging. The researchers were able to detect even the tiniest variations of the magnetic field strength within the droplet. These changes were up to 10-12 (1 trillion) times smaller than the 7 tesla field strength of the MRI scanner used in the experiment.
“Until now, it was possible only to measure such small variations in weak magnetic fields,” says Klaas Prüssmann, Professor of Bioimaging at ETH Zurich and the University of Zurich. An example of a weak magnetic field is that of the Earth, where the field strength is just a few dozen microtesla. For fields of this kind, highly sensitive measurement methods are already able to detect variations of about a trillionth of the field strength, says Prüssmann. “Now, we have a similarly sensitive method for strong fields of more than one tesla, such as those used … in medical imaging.”
The scientists based the sensing technique on the principle of nuclear magnetic resonance (NMR), which also serves as the basis for magnetic resonance imaging and the spectroscopic methods that biologists use to elucidate the 3D structure of molecules, but with 1000 times greater sensitivity than current NMR methods.
Ultra-sensitive recordings of heart contractions in an MRI machine
The scientists carried out an experiment in which they positioned their sensor in front of the chest of a volunteer test subject inside an MRI scanner. They were able to detect periodic changes in the magnetic field, which pulsated in time with the heartbeat. The measurement curve is similar to an electrocardiogram (ECG), but measures a mechanical process (the contraction of the heart) rather than electrical conduction.
“We are in the process of analyzing and refining our magnetometer measurement technique in collaboration with cardiologists and signal processing experts,” says Prüssmann. “Ultimately, we hope that our sensor will be able to provide information on heart disease — and do so non-invasively and in real time.”
The new measurement technique could also be used in the development of new contrast agents for magnetic resonance imaging and improved nuclear magnetic resonance (NMR) spectroscopy for applications in biological and chemical research.
A radiation-free approach to imaging molecules in the brain
In a related development, MIT scientists hoping to get a glimpse of molecules that control brain activity have devised a new sensor that allows them to image these molecules without using any chemical or radioactive labels (which feature low resolution and can’t be easily used to watch dynamic events).
The new sensors consist of enzymes called proteases designed to detect a particular target, which causes them to dilate blood vessels in the immediate area. This produces a change in blood flow that can be imaged with magnetic resonance imaging (MRI) or other imaging techniques.*
“This is an idea that enables us to detect molecules that are in the brain at biologically low levels, and to do that with these imaging agents or contrast agents that can ultimately be used in humans,” says Alan Jasanoff, an MIT professor of biological engineering and brain and cognitive sciences. “We can also turn them on and off, and that’s really key to trying to detect dynamic processes in the brain.”
Monitoring neurotransmitters at 100 times lower levels
In a paper appearing in the Dec. 2 issue of open-access Nature Communications, Jasanoff and his colleagues explain that they used proteases (sometimes used as biomarkers to diagnose diseases such as cancer and Alzheimer’s disease) to demonstrate the validity of their approach. But now they’re working on adapting these imaging agents to monitor neurotransmitters, such as dopamine and serotonin, which are critical to cognition and processing emotions.
“What we want to be able to do is detect levels of neurotransmitter that are 100-fold lower than what we’ve seen so far. We also want to be able to use far less of these molecular imaging agents in organisms. That’s one of the key hurdles to trying to bring this approach into people,” Jasanoff says.
“Many behaviors involve turning on genes, and you could use this kind of approach to measure where and when the genes are turned on in different parts of the brain,” Jasanoff says.
His lab is also working on ways to deliver the peptides without injecting them, which would require finding a way to get them to pass through the blood-brain barrier. This barrier separates the brain from circulating blood and prevents large molecules from entering the brain.
Jeff Bulte, a professor of radiology and radiological science at the Johns Hopkins School of Medicine, described the technique as “original and innovative,” while adding that its safety and long-term physiological effects will require more study.
“It’s interesting that they have designed a reporter without using any kind of metal probe or contrast agent,” says Bulte, who was not involved in the research. “An MRI reporter that works really well is the holy grail in the field of molecular and cellular imaging.”
The research was funded by the National Institutes of Health BRAIN Initiative, the MIT Simons Center for the Social Brain, and fellowships from the Boehringer Ingelheim Fonds and the Friends of the McGovern Institute.
* To make their probes, the researchers modified a naturally occurring peptide called calcitonin gene-related peptide (CGRP), which is active primarily during migraines or inflammation. The researchers engineered the peptides so that they are trapped within a protein cage that keeps them from interacting with blood vessels. When the peptides encounter proteases in the brain, the proteases cut the cages open and the CGRP causes nearby blood vessels to dilate. Imaging this dilation with MRI allows the researchers to determine where the proteases were detected.
Another possible application for this type of imaging is to engineer cells so that the gene for CGRP is turned on at the same time that a gene of interest is turned on. That way, scientists could use the CGRP-induced changes in blood flow to track which cells are expressing the target gene, which could help them determine the roles of those cells and genes in different behaviors. Jasanoff’s team demonstrated the feasibility of this approach by showing that implanted cells expressing CGRP could be recognized by imaging.
Abstract of Dynamic nuclear magnetic resonance field sensing with part-per-trillion resolution
High-field magnets of up to tens of teslas in strength advance applications in physics, chemistry and the life sciences. However, progress in generating such high fields has not been matched by corresponding advances in magnetic field measurement. Based mostly on nuclear magnetic resonance, dynamic high-field magnetometry is currently limited to resolutions in the nanotesla range. Here we report a concerted approach involving tailored materials, magnetostatics and detection electronics to enhance the resolution of nuclear magnetic resonance sensing by three orders of magnitude. The relative sensitivity thus achieved amounts to 1 part per trillion (10−12). To exemplify this capability we demonstrate the direct detection and relaxometry of nuclear polarization and real-time recording of dynamic susceptibility effects related to human heart function. Enhanced high-field magnetometry will generally permit a fresh look at magnetic phenomena that scale with field strength. It also promises to facilitate the development and operation of high-field magnets.
Abstract of Molecular imaging with engineered physiology
In vivo imaging techniques are powerful tools for evaluating biological systems. Relating image signals to precise molecular phenomena can be challenging, however, due to limitations of the existing optical, magnetic and radioactive imaging probe mechanisms. Here we demonstrate a concept for molecular imaging which bypasses the need for conventional imaging agents by perturbing the endogenous multimodal contrast provided by the vasculature. Variants of the calcitonin gene-related peptide artificially activate vasodilation pathways in rat brain and induce contrast changes that are readily measured by optical and magnetic resonance imaging. CGRP-based agents induce effects at nanomolar concentrations in deep tissue and can be engineered into switchable analyte-dependent forms and genetically encoded reporters suitable for molecular imaging or cell tracking. Such artificially engineered physiological changes, therefore, provide a highly versatile means for sensitive analysis of molecular events in living organisms.
University of Virginia School of Medicine researchers have discovered a rare and powerful type of immune cell in the meninges (protective covering) of the brain that are activated in response to central nervous system injury — suggesting that these cells may play a critical role in battling Alzheimer’s, multiple sclerosis, meningitis, and other neurological diseases, and in supporting healthy mental functioning.
By harnessing the power of the cells, known as “type 2 innate lymphocytes” (ILC2s), doctors may be able to develop new treatments for neurological diseases, traumatic brain injury, and spinal cord injuries, as well as migraines, the researchers suggest. They also suspect the cells may be the missing link connecting the brain and the microbiota in our guts, a relationship that has been shown to be important in the development of Parkinson’s disease.
Important immune roles
ILC2 cells have previously been found in the gut, lung, and skin, the body’s barriers to disease. Their discovery by UVA researcher Jonathan Kipnis, PhD, in the meninges, the membranes surrounding the brain, comes as a surprise. They were found along the same vessels discovered by the Kipnis lab last year, which showed that the brain and the immune system are directly connected.
“This all comes down to immune system and brain interaction,” said Kipnis, chairman of UVA’s Department of Neuroscience. These where previously believed to be not communicating, but not only are these [immune] cells present in the areas near the brain, they are integral to its function, Kipnis said.
Immune cells play several important roles within the body, including guarding against pathogens, triggering allergic reactions, and responding to spinal cord injuries. But its their role in the gut that makes Kipnis suspect they may also be serving as a vital communicator between the brain’s immune response and our microbiomes (microbes in the body). That could be very important, because our intestinal flora is critical for maintaining our health and well being.
“These cells are potentially the mediator between the gut and the brain. They are the main responder to microbiota changes in the gut,” Kipnis said. “They may go from the gut to the brain, or they may just produce something that will impact those cells. We know the brain responds to things happening in the gut. Is it logical that these will be the cells that connect the two? Potentially.”
The findings have been published online by the Journal of Experimental Medicine. The work was supported by a National Institutes of Health grant.
Abstract of Characterization of meningeal type 2 innate lymphocytes and their response to CNS injury
The meningeal space is occupied by a diverse repertoire of immune cells. Central nervous system (CNS) injury elicits a rapid immune response that affects neuronal survival and recovery, but the role of meningeal inflammation remains poorly understood. Here, we describe type 2 innate lymphocytes (ILC2s) as a novel cell type resident in the healthy meninges that are activated after CNS injury. ILC2s are present throughout the naive mouse meninges, though are concentrated around the dural sinuses, and have a unique transcriptional profile. After spinal cord injury (SCI), meningeal ILC2s are activated in an IL-33–dependent manner, producing type 2 cytokines. Using RNAseq, we characterized the gene programs that underlie the ILC2 activation state. Finally, addition of wild-type lung-derived ILC2s into the meningeal space of IL-33R−/− animals partially improves recovery after SCI. These data characterize ILC2s as a novel meningeal cell type that responds to SCI and could lead to new therapeutic insights for neuroinflammatory conditions.