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Gervasio S.,University of Aalborg | Farina D.,University of Gottingen | Sinkjaer T.,University of Aalborg | Sinkjaer T.,Danish National Research Foundation | Mrachacz-Kersting N.,University of Aalborg
Journal of Neurophysiology | Year: 2013

During human walking, precise co-ordination between the two legs is required in order to react promptly to any sudden hazard that could threaten stability. The networks involved in this coordination are not yet completely known, but a direct spinal connection between soleus (SOL) muscles has recently been revealed. For this response to be functional, as previously suggested, we hypothesize that it will be accompanied by a reaction in synergistic muscles, such as gastrocnemius lateralis (GL), and that a reversal of the response would occur when an opposite reaction is required. In the present study, surface EMGs of contralateral SOL and GL were analyzed after tibial nerve (TN), sural nerve (SuN), and medial plantar nerve (MpN) stimulation during two tasks in which opposite reactions are functionally expected: normal walking (NW), just before ipsilateral heel strike, and hybrid walking (HW) (legs walking in opposite directions), at ipsilateral push off and contralateral touchdown. Early crossed facilitations were observed in the contralateral GL after TN stimulation during NW, and a reversal of such responses occurred during HW. These results underline the functional significance of short-latency crossed responses and represent the first evidence for short-latency reflex reversal in the contralateral limb for humans. Muscle afferents seem to mediate the response during NW, while during HW cutaneous afferents are likely involved. It is thus possible that different afferents mediate the crossed response during different tasks. © 2013 the American Physiological Society. Source


News Article
Site: http://www.nanotech-now.com/

Abstract: Quantum technology has the potential to revolutionize computation, cryptography, and simulation of quantum systems. However, quantum physics places a new demand on information processing hardware: quantum states are fragile, and so must be controlled without being measured. Researchers at the Niels Bohr Institute have now demonstrated a key property of Majorana zero modes that protects them from decoherence. The result lends positive support to the existence of Majorana modes, and goes further by showing that they are protected, as predicted theoretically. The results have been published in the prestigious scientific magazine, Nature. Normal computers are limited in their ability to solve certain classes of problems. The limitation lies in the fact that the operation of a conventional computers is based on classical states, or bits, the fundamental unit of information that is either 0 or 1. In a quantum computer, data is stored in quantum bits, or qubits. According to the laws of quantum mechanics, a qubit can be in a superposition of states --- a 0 and 1 at the same time. By taking advantage of this and other properties of quantum physics, a quantum computer made of interconnected qubits should be able to tackle certain problems much more efficiently than would be possible on a classical computer. There are many different physical systems that could in principle be used as quantum bits. The problem is that most quantum systems lose coherence very quickly--the qubit becomes a regular bit once measured. This is why researchers are still searching for the best implementation of quantum hardware. Enter the Majorana zero mode, a delocalized state in a superconductor that resists decoherence by sharing quantum information between separated locations. In a Majorana mode, the information is stored in such a way that a disturbance of either location leaves the quantum information intact. "We are investigating a new kind of particle, called a Majorana zero mode, which can provide a basis for quantum information that is protected against measurement by a special and who knows, perhaps unique property of these particles. Majorana particles don't exist as particles on their own, but they can be created using a combination of materials involving superconductors and semiconductors. What we find is that, first of all, the Majorana modes are present, verifying previous experiments, but more importantly that they are protected, just as theory predicts," says Villum Kann Rasmussen Professor Charles Marcus, Director of the Center for Quantum Devices (QDev) and Station Q Copenhagen, at the Niels Bohr Institute, University of Copenhagen. Nanowires for quantum technology The Center for Quantum Devices is a leading research center in quantum information technology - with activities in theory, experiment, and materials research. Semiconductor nanowires around 10 micrometers long and around 0.1 micrometers in diameter, coated with superconducting aluminum were used to form isolated islands of various lengths. By applying a strong magnetic field along the axis of the wire, and cooling the wires to below a tenth of a kelvin, a new kind of superconducting state, called a topological superconductor, was formed. Quantum states are protected In 2012, physicists at Delft University in the Netherlands found the first signatures of Majorana zero modes in a similar system, with further evidence revealed in subsequent experiments around the world. Now, researchers at the Center for Quantum Devices have demonstrated critical predictions regarding their behavior, namely that their quantum states are protected in a fundamentally different manner from conventional quantum states. The experiments were carried out by PhD Candidate Sven Albrecht and postdoc Andrew Higginbotham, now at the University of Colorado/NIST, USA, using new superconductor-semiconductor hybrid nanowires developed by Assistant Professor Peter Krogstrup in collaboration with Marcus and Professor Jesper Nygard. "The protection is related to the exotic property of the Majorana mode that it simultaneously exists on both ends of the nanowire, but not in the middle. To destroy its quantum state, you have to act on both ends at the same time, which is unlikely", says Sven Albrecht. Albrecht explains that it was a challenging effort to demonstrate the protection experimentally. The researchers had to repeat their experiment many times with nanowires of different lengths in order to show that the protection improved with wire length. "Exponential protection is an important check as we continue our basic exploration, and ultimately application, of topological states of matter. Two things have pushed the field forward--from the first Majorana sightings at Delft to the present results--the first is strong interaction between theory and experiment. The second is remarkable materials development in Copenhagen, an effort that predates our Center. Without these new materials, the field was rather stuck. That's behind us now." says Charles Marcus. ### The research at the Center for Quantum Devices and Station Q Copenhagen was supported by Microsoft Research and the Danish National Research Foundation and the Villum Foundation. For more information, please click Contacts: Gertie Skaarup 45-28-75-06-20 Charles Marcus Professor Director Center for Quantum Devices QDev Niels Bohr Institute Univeresity of Copenhagen +45 2034-1181 Sven Albrecht PhD Candidate Center for Quantum Devices QDev Niels Bohr Institutet Københavns Universitet +45 2155-2975 If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.


News Article
Site: http://phys.org/biology-news/

All science students learn how human cell division takes place. The copying or replication of the genome, the cell's DNA, has until now been believed only to take place during the so-called S-phase in the cell cycle. The new results show that this is not the case, because some regions of the genome are copied only after the cell enters the next crucial phase in the cell cycle called mitosis. "It has radically altered our views and requires that the textbook view of the human cell cycle be revised", says Professor Ian Hickson, Director of the Centre for Chromosome Stability and affiliated with the Center for Healthy Aging. The research project was funded by the Danish National Research Foundation and was just published in the international scientific journal Nature. This unusual pathway for copying of the DNA occurs at specific regions of the human genome called fragile sites, and during mitosis, chromosomes in these fragile areas have a tendency to break. The fragile sites are conserved across species and are frequently associated with undesirable genome rearrangements in connection with the development of cancer. "We now know that these so-called 'chromosome breaks' are not actually broken, but instead comprise a region of DNA that is newly synthesized in mitosis. They appear broken because they are far less compacted than the rest of the chromosome," adds Professor Hickson. Cancer cells utilize this unusual form of DNA replication because one of the side effects of the genetic changes that cause cancer is so-called 'replication stress'. The scientists weren't specifically looking for this but fortunately they saw something very unusual when looking at human cancer cells under the microscope. "When we realized what was happening, it took us about 3 years to determine the mechanism underlying this phenomenon." "All science students learn that DNA is replicated in S-phase. Our results show that this is not the case, because some regions are replicated only after the cell enters mitosis," he adds. The scientists already know of two proteins that are essential for this unusual pathway for DNA replication, but now aim to define the full 'toolbox' of factors that are required. They can then proceed with studies to identify chemical compounds that block the process. This would constitute the first stage in identifying potential new treatments for cancer. "Although it has not yet been proven, it seems that the growth of many, or indeed most, cancers in humans is dependent on this process. Hence, the development of a reliable, therapeutic drugs strategy would likely have wide applicability in cancer therapy." "Our aim is to generate results that will lead to the development of new approaches to treatments of various types of cancer," concludes Professor Hickson. Explore further: Infradian oscillation of circadian genes in a mouse model of bipolar disorder More information: Sheroy Minocherhomji et al. Replication stress activates DNA repair synthesis in mitosis, Nature (2015). DOI: 10.1038/nature16139


News Article
Site: http://www.scientificcomputing.com/rss-feeds/all/rss.xml/all

Since researchers first succeeded in mapping the human genome back in 2003, the technological development has moved at warp speed, and the process, which at that time took several years and billions of dollars, can now be performed in a few days. In the Klaus Hansen research group at the Biotech Research & Innovation Centre, University of Copenhagen, researchers have developed a new type of software, which enables a much faster analysis and interpretation of the vast amounts of data provided by sequencing technology. “The amount of information that a genome researcher creates and which makes the basis of his scientific work has grown a million times during the last two decades. Today, the challenge does not consist in creating the data, but in exploring them and deducing meaningful conclusions. We believe that this analytical tool, which we have called “EaSeq” can help researchers in doing so,” said Associate Professor Klaus Hansen. ChIP sequencing — an insight into the workflow of human cells The EaSeq software has been developed for analysis of so called ChIP sequencing. DNA sequencing is used for mapping the sequence of the base pairs, which our DNA consists of, and ChIP sequencing is a derived method in which the sequences are used to determine the presence of different cell components in the genome at a given time. “Roughly speaking, ChIP sequencing can be compared to a microscope, which enables us to observe the presence of different cell components in the entire genome at a given time. The method is still quite young and holds the potential to be applied within many more scientific fields, which can benefit from understanding how healthy and pathological cells control and uses genes,” said Associate Professor Mads Lerdrup. While ChIP sequencing has made it possible to produce enormous amounts of data very fast, the analysis of these data has — until now — been a tedious process. Most of the analytical software being used requires knowledge of computer programming and researchers have, therefore, been dependent on specialists in order to decode and analyze their data. EaSeq offers a far more visual and intuitive alternative, which makes it possible for biomedical researchers to study and test hypotheses using their own data. This means that, instead of waiting for weeks for others to carry out an analysis, researchers will be able to perform the analyses themselves in a matter of hours. Today, DNA sequencing is gaining ground within the clinical area where it is e.g. being used for diagnosis and targeting of treatment within the cancer area. The developers of EaSeq see similar perspectives for ChIP sequencing in the clinical work and, in that context, strong analytical tools will be pivotal. “The DNA sequence itself tells us very little about how cells actual decodes the DNA and, to understand this, we need to map out which cell components are present in different parts of the genome at a specific time. It is our hope that we, by increasing feasibility, can enable researchers to faster uncover such knowledge and apply it clinically,” said Associate professor Mads Lerdrup. The research project has been financed by the Danish National Research Foundation and the results have been published in the journal Nature Structural & Molecular Biology.


News Article
Site: http://www.scientificcomputing.com/rss-feeds/all/rss.xml/all

Quantum technology has the potential to revolutionize computation, cryptography and simulation of quantum systems. However, quantum physics places a new demand on information processing hardware: quantum states are fragile, and so must be controlled without being measured. Researchers at the Niels Bohr Institute have demonstrated a key property of Majorana zero modes that protects them from decoherence. The result lends positive support to the existence of Majorana modes, and goes further by showing that they are protected, as predicted theoretically. The results have been published in the scientific magazine, Nature. Normal computers are limited in their ability to solve certain classes of problems. The limitation lies in the fact that the operation of a conventional computers is based on classical states, or bits, the fundamental unit of information that is either 0 or 1. In a quantum computer, data is stored in quantum bits, or qubits. According to the laws of quantum mechanics, a qubit can be in a superposition of states — a 0 and 1 at the same time. By taking advantage of this and other properties of quantum physics, a quantum computer made of interconnected qubits should be able to tackle certain problems much more efficiently than would be possible on a classical computer. There are many different physical systems that could, in principle, be used as quantum bits. The problem is that most quantum systems lose coherence very quickly — the qubit becomes a regular bit once measured. This is why researchers are still searching for the best implementation of quantum hardware. Enter the Majorana zero mode, a delocalized state in a superconductor that resists decoherence by sharing quantum information between separated locations. In a Majorana mode, the information is stored in such a way that a disturbance of either location leaves the quantum information intact. “We are investigating a new kind of particle, called a Majorana zero mode, which can provide a basis for quantum information that is protected against measurement by a special and who knows, perhaps unique property of these particles. Majorana particles don’t exist as particles on their own, but they can be created using a combination of materials involving superconductors and semiconductors. What we find is that, first of all, the Majorana modes are present, verifying previous experiments, but more importantly that they are protected, just as theory predicts,” says Villum Kann Rasmussen Professor Charles Marcus, Director of the Center for Quantum Devices (QDev) and Station Q Copenhagen, at the Niels Bohr Institute, University of Copenhagen. The Center for Quantum Devices is a leading research center in quantum information technology — with activities in theory, experiment and materials research. Semiconductor nanowires around 10 micrometers long and around 0.1 micrometers in diameter, coated with superconducting aluminum were used to form isolated islands of various lengths. By applying a strong magnetic field along the axis of the wire, and cooling the wires to below a tenth of a kelvin, a new kind of superconducting state, called a topological superconductor, was formed. In 2012, physicists at Delft University in the Netherlands found the first signatures of Majorana zero modes in a similar system, with further evidence revealed in subsequent experiments around the world. Now, researchers at the Center for Quantum Devices have demonstrated critical predictions regarding their behavior, namely that their quantum states are protected in a fundamentally different manner from conventional quantum states. The experiments were carried out by Ph.D. Candidate Sven Albrecht and postdoc Andrew Higginbotham, now at the University of Colorado/NIST, using new superconductor-semiconductor hybrid nanowires developed by Assistant Professor Peter Krogstrup in collaboration with Marcus and Professor Jesper Nygard. “The protection is related to the exotic property of the Majorana mode that it simultaneously exists on both ends of the nanowire, but not in the middle. To destroy its quantum state, you have to act on both ends at the same time, which is unlikely,” says Albrecht. Albrecht explains that it was a challenging effort to demonstrate the protection experimentally. The researchers had to repeat their experiment many times with nanowires of different lengths in order to show that the protection improved with wire length. “Exponential protection is an important check as we continue our basic exploration, and ultimately application, of topological states of matter. Two things have pushed the field forward — from the first Majorana sightings at Delft to the present results — the first is strong interaction between theory and experiment. The second is remarkable materials development in Copenhagen, an effort that predates our Center. Without these new materials, the field was rather stuck. That’s behind us now.” says Charles Marcus. The research at the Center for Quantum Devices and Station Q Copenhagen was supported by Microsoft Research and the Danish National Research Foundation and the Villum Foundation.

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