Spotlight - חוקרי הפקולטה משתפים

Graphical abstract -  thumbnail MicroRNA-targeted suppression of liver fat - Geula Hanin and Prof. Hermona Soreq

Fatty liver is a common disease, affecting 25% of the population, and is characterized by the accumulation of fat in the liver. Fatty liver may develop in people who are overweight or obese, or who have diabetes, high cholesterol, or high triglycerides, or those who inherited mutations in the cholesterol receptor gene. The first stage of the disease, called ‘hepatic steatosis’, can progress to a condition called NASH (non-alcoholic steatohepatitis) and eventually cirrhosis or liver cancer. Currently, there are no effective treatments for fatty liver disease. New research performed by Geula Hanin and colleagues from the laboratory of Prof. Hermona Soreq at the Life Sciences Institute, leans on molecular biology tools for identifying a novel cause for fatty liver disease.
The researchers studied a small gene product, called micoRNA which can "silence" or "turn off" genes – and may send brain-to-body commands for changing metabolism. They discovered that one particular microRNA, known as miRNA-132, accumulates both in brain neurons under acute stress and in fatty livers of fattened mice consuming a high-fat diet, a treatment which mimics the most common cause of the disease; and in human patients with fatty liver disease. Furthermore, injecting an ‘antisense’ oligonucleotide inverse to miRNA-132 to fattened mice reversed the fatty liver and hyperlipidemia states, retrieving normal lipid levels in the blood and in the liver; whereas engineering a mouse with inherited high levels of miRNA-132 led to fatty liver and high blood lipids.
So, does psychological stress induce fatty liver disease? This awaits further research; meanwhile, small DNA-based molecules are already used elsewhere to silence miRNAs, for example- to lower blood cholesterol to normal levels. This new molecular biology-based approach may soon become the next trend in precision medicine, solving challenging problems via exploiting the power of molecular biology


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stratosphere - thumbnail Stratospheric variability contributed to and sustained the recent hiatus in Eurasian winter warming - Dr. Chaim Garfinkel

The rate of surface warming over the most recent 15 or so years has been considerably less than that since the mid-20th century - the so-called hiatus. This effect is most pronounced over Eurasia in wintertime, where a series of cold winters has led some to cast doubt on the basic science behind anthropogenic climate change. The cause of this cooling is still not understood. In this paper, we demonstrate that the recent Eurasian cooling was caused, at least in part, by stratospheric processes. Similar hiatus events could happen again even in a future with high GHG concentrations.

Accepted by Geophysical Research Letters.


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thumnail Accessing human selenoproteins through chemical protein synthesis - Dr. Norman Metanis

The research group of Dr. Norman Metanis, from the Institute of Chemistry, specializes in organic and bioorganic chemistry and has recently published an article in Chemical Science, in which they describe for the first time a method to access human selenoproteins by total chemical protein synthesis. The human body contains 25 selenoproteins, which contain in their sequence the twenty-first encoded amino acid, selenocysteine. About a dozen of these proteins remain functionally uncharacterized or poorly studied. Challenges in accessing these selenoproteins using traditional recombinant expressions have prevented biological characterization thus far. The Metanis group reported the total chemical syntheses of two human selenoproteins, selenoprotein M (SELM) and selenoprotein W (SELW). The synthesis of the more challenging protein SELM, which is longer, was enabled using recent advances in the field of selenocysteine chemistry that was developed in the lab. This approach allows the preparation of selenoproteins in milligram quantities and in homogenous form, which should open new horizons for future studies to pursue a fuller biological understanding of their role in health and disease, which is currently ongoing in the Metanis group.

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3D printing - small image 3D printing of highly stretchable UV curable elastomers - Prof. Shlomo Magdassi

Elastomeric structures show a lot of interest in different research fields such as soft robotics, flexible electronics, and smart biomedical devices which require soft and deformable material properties. However, to date, the most widely used materials are silicon rubber based for e.g. PDMS. The fabrication methods using these materials are limited to traditional ways, such as cutting, molding and casting, thus constrains the design freedom and geometric complexity. In order to enrich the design and fabrication flexibility, researchers attempted to use 3D printing techniques, especially the UV curing based 3D printing techniques, to fabricate elastomeric 3D objects. Nevertheless, most of the commercially available UV curable thus 3D printable elastomers break at less than 200 %, which is insufficient to many applications.
In the recent publication published in the prestigious journal Advanced Materials, researchers from the group of Prof. Shlomo Magdassi, led by Dr. Dinesh Patel and Dr. Michael Layani showed the development of a family of highly stretchable and UV curable (SUV) elastomers that can be stretched by up to 1100%, and are suitable to Digital Light Processing (DLP) and other UV curing based 3D printing techniques. This enabled the researchers to print diverse structures such as a deformable 3D isotropic truss, a deformable 3D negative Poisson’s ratio structure, 3D printed soft actuators and stretchable grippers activated by pressure, Bucky ball electronic switches, and even a 3D printed balloon, which demonstrate the ink's elastomer advantage of high stretchability and compatibility with DLP printing technique. The research was performed in collaboration with Singapore University of Technology and Design (SUTD). We believe the SUV elastomers will significantly enhance the capability of the UV curing based 3D printing of fabricating soft and deformable 3D structures and devices including soft actuators and robots, flexible electronics, acoustic metamaterials, and many other applications.

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New light source at the NGC4993 Galaxy The First Discovery of a Binary Neutron Star Merger and an Electromagnetic Counterpart - Dr. Assaf Horesh

On August 17 2017 the LIGO detector has made the first discovery of gravitational waves from a Neutron star merger. This type of event was predicted about 30 years ago by several scientists including Prof. Tsvi Piran (Hebrew University). Before this discovery only three gravitational wave events have been detected (since 2015), all of them originating from black hole mergers. This discovery is also unique as this is the first time that electromagnetic emission has been discovered from a gravitational wave source. Two seconds after GW170817 was detected, the space satellite Fermi has detected a short gamma-ray burst in a location consistent with the location of the gravitational wave event. Following this discovery, astronomers around the world have started searching for electromagnetic emission across the spectrum including the ultra-violet, optical, infra-red, X-rays and radio. A team from the U.S. was the first to announce the discovery of an optical counterpart for GW170817. This discovery helped to pinpoint the source to a galaxy at a distance of 130 million light years. Many other groups have detected the counterpart shortly after in optical, infrared and ultraviolet light and have undertaken follow-up campaigns for many days after the event, collecting every bit of information they can. Dr. Assaf Horesh and Prof. Tsvi Piran are members of one of the international teams that performed a detailed analysis of the infrared and optical emission from the source. The team found that as predicted, a large amount of heavy elements have been forged in the merger event, elements such as gold and platinum. Dr. Horesh is also a member of a small team of scientists that has been conducting a search for radio emission from the merger event. Radio emission is expected to arise at late time as the material that is ejected during the merger, interacts with the surrounding material, creating a shockwave. Initially, the radio team did not detect any radio emission. Only 16 days after the initial discovery, radio emission has finally been detected, also for the first time in this type of event. The radio emission is now getting brighter and analysis of this emission can answer many questions such as whether a powerful jet has been formed in the event, and what is the velocity and energy in the ejected material. Overall this discovery symbolizes a new era of gravitational wave astronomy.

Surfant micellar solution Metallic nanoparticles are materials of many uses - Prof. Daniel Mandler

Metallic nanoparticles are materials of many uses; ranging from catalyzing chemical reactions to forming unique dyes that can be used for sensing and electro-optics. These particles are usually synthesized in solution but it is also possible to form them directly on surfaces.  Since the shape and size of the nanoparticles determine their properties, it is of major importance to understand the mechanism controlling these features.
In a paper by Prof. Daniel Mandler’s group, they present a method for patterning gold nanoparticles of different shapes on non-conducting surfaces. The particles are grown by dipping a thin gold electrode in a solution of a reducing agent. Concurrently, a surface modified with thiols –chemical groups with high affinity to gold, is dipped in the same solution. Once formed, the particles bind to the thiols, anchoring themselves to the surface.
In addition, the researchers examined the conditions affecting the shape of the particles. Changing the reductants and their concentrations, as well as altering the electrode voltage, resulted in particles that differed in size and shape. For example, under different concentrations and voltages, sodium borohydride gave cubical, spherical and pentagonal crystals. It turned out that the rate of the redox reaction influenced the crystal structure of the particles. A strong reductant induced a fast uncontrolled redox that lead to simple structures like spheres, whereas a weak reductant induced slow controlled reaction that resulted in more complexed geometrical structures such as cubes and hexagons.
By utilizing these nanoparticles properties (e.g. optical, catalytic…) it is now possible to use this methodology to functionalize non-conducting surfaces for various fields.

Group Mandler's site

Thumbnail of supernova A Young Supernova Reveals the Secrets of a Dying Star - Dr. Assaf Horesh

Massive stars end their lives in an explosion called supernova. Understanding the last stages of evolution in a star life, leading to a supernova, and understanding the explosion itself, are some of the leading questions in astrophysics today. Not knowing when and where a supernova will occur makes it even harder to study this phenomena. Nowadays, we have the capability to discover many supernovae a night thanks to many dedicated experiments. Our detection capability has improved recently and we can now discover supernovae only a few hours after explosion!

Supernova SN2013fs was discovered by the Palomar Transient Factory project three hours after explosion. The early discovery allowed us to perform followup observations with more advanced telescopes such as the Keck telescope, which provided several optical spectra over a few hours after detection. These spectra revealed the existence of dense gas in the close vicinity around the supernova (10^15 cm) that was ionized by the flash from the supernova explosion. The spectral signatures of this gas have disappeared a few days after the discovery, leading to the conclusion that there was a dense massive shell of gas around the supernova which was swept away by the stellar material that was ejected in the explosion. Late-time radio observations support this conclusion.

Massive stars loose mass along their lives thus enriching their surroundings with low density gas. Discovering a dense shell of gas so close to the star that exploded suggests that massive stars go through major dynamical processes which make the star loose a lot of mass in a short time, during the last year of their lives. These processes are still not well understood and there are several theories explaining them. Understanding these processes is critical to our understanding of the processes inside dying stars which lead to supernova explosions.
The results of this research have been recently published in Nature (the research was performed by an international team of researchers led by Dr. Ofer Yaron from the Weizmann Institute and in collaboration with Dr. Assaf Horesh from the Hebrew University)

Ubiquitin Accumulation on Disease Associated Protein Aggregates Is Correlated with Nuclear Ubiquitin Depletion, Histone De-Ubiquitination and Impaired DNA Damage Response A possible link between neurodegeneration associated aggregates and cellular aging - Prof. Michael Brandeis

Neurodegenerative diseases, like Parkinson and Alzheimer are associated with cellular protein aggregation. A method to follow aggregation in living cultured cells in real time was developed in the laboratory of Prof. Michael Brandeis of the Department of Genetics of the Life Science Institute. This method enables to study the effect of aggregates on cellular proteins and organelles. Ubiquitin is a small protein playing an essential role in protein degradation and DNA damage repair. The omnipresence of ubiquitin in disease associated aggregates is well established. This method enabled, for the first time to characterize the dynamics ubiquitin accumulation on aggregates. Research by the master students Adi Ben Yehuda and Marwa Risheq revealed that this accumulation leads to the depletion of nuclear ubiquitin. Given the role of ubiquitin for DNA repair, this observation suggested that aggregates compromises genome repair. Such a defect is particularly significant in brain neurons that suffer from extensive DNA damage. Ofra Novoplansky, another student in the lab, showed that aggregates puncture the nuclear lamina thereby disrupting the nuclear cytoplasmic compartmentalization. In contrast to most cells in the body, brain neurons hardly regenerate throughout life, their aging is exceedingly slow and their number does hardly decline in old age. Impaired DNA repair, disruption of the nuclear lamina, as well as the reduced capacity to degrade proteins, discovered in a previous research done by this approach, are all well-established hallmarks of aging. The observed correlation between protein aggregation and the appearance of these hallmarks suggests that aggregates cause premature neuron aging and could lead to neurodegeneration. It is important to stress that these are preliminary observations and that their possible application for treating neurodegeneration lay still a far way ahead. This research, published last week in PlosONE, was funded by the Israeli Ministry of Health and the Israeli Science Foundation.

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N-acetylcysteine amide (AD4) reduces cocaine-induced reinstatemen - small image N-acetylcysteine amide (AD4) reduces cocaine-induced reinstatement - Prof. Daphne Atlas

We prepared a non-toxic small-molecular weight compound, with combined anti-inflammatory, and metal chelating activities.  The new compound is the amide form of N-acetylcysteine (NAC).   NAC itself is being used in the clinic for over 40 years but displays a relatively low efficacy.

The amide form of NAC, NAC-amide, is called AD4 or NACA, and is highly effective because it is both water-soluble and crosses cell membranes.  A large number of in vivo and in vitro studies have shown that AD4 is significantly more effective than NAC.

In this new study, AD4 (NAC-amide) was examined in intravenous cocaine self-administration and extinction/reinstatement procedures in rats.

We investigated the behavioral effects of AD4 in the olfactory bulbectomized (OBX) rats, considered an animal model of depression. We also tested rats injected with AD4 or NAC during 10-daily extinction training sessions to examine subsequent cocaine seeking.

We found that AD4 is highly effective in reducing cocaine-induced reinstatement in rats with preexisting depression. It is more potent than NAC in reducing cocaine-induced reinstatement in rats with preexisting depression

AD4 is very effective because it was also shown to inhibit metalloproteinase 9 (MMP-9), which is required for cocaine relapse and relapse-associated synaptic plasticity

AD4 treatment represents a new approach to treat substance-use disorders through affecting the glutaminergic pathway aimed at improving the dopaminergic system.  In addition AD4 helps the cells to better manage drug-induced changes through increasing the reductive state and lowering inflammatory insults.

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Magnetic imaging - thumbnail Imaging of super-fast dynamics and flow instabilities of superconducting vortices - Dr. Yonathan Anahory

Researchers have made the first direct visual observation and measurement of ultra-fast vortex dynamics in superconductors. Their technique, detailed in the journal Nature Communications, could contribute to the development of novel practical applications by optimizing superconductor properties for use in electronics.


An international team of researchers, led by Prof. Eli Zeldov from the Weizmann Institute of Science and Dr. Yonathan Anahory, senior lecturer at the Hebrew University of Jerusalem’s Racah Institute of Physics, has shown for the first time how these vortices move in superconducting materials and how fast they may travel.


They used a novel microscopy technique called scanning SQUID-on-tip, which allows magnetic imaging at unprecedented high resolution (about 50 nm) and magnetic sensitivity. The technique was developed over the last decade at the Weizmann Institute by a large team including Ph.D. student Lior Embon and Ella Lachman and is currently being implemented at the Hebrew University in Dr. Anahory’s lab as well.


Using this microscope, they observed vortices flowing through a thin superconducting film at rates of tens of GHz, and traveling at velocities much faster than previously thought possible — up to about 72 000 km/hr.

This is not only much faster than the speed of sound, but also exceeds the pair-breaking speed limit of superconducting condensate


In photos and videos shown for the first time, the vortex trajectories appear as smeared lines crossing from one side of the film to another. This is similar to the blurring of images in photographs of fast-moving objects. They show a tree-like structure with a single stem that undergoes a series of bifurcations into branches. This channel flow is quite surprising since vortices normally repel each other and try to spread out as much as possible.

Here vortices tend to follow each other, which generates the tree-like structure.



Chart image that compairs Tolerance, Resistance and Survival Physicists unveil how bacteria can evolve fast towards antibiotic resistance - Prof. Nathalie Balaban

A new research appearing this week in SCIENCE, led by PhD student Irit Levin-Reisman in Prof. Nathalie Balaban's lab, show that bacteria first evolve to "sleep" for most of the antibiotic treatment, and then this "sleeping mode" not only transiently protected them from the lethal action of the drug, but also actually worked as a stepping stone for the later acquisition of resistance factors. The experiments were performed by a team of physicists, who developed a theoretical model and computer simulations that enabled a deep understanding of the reason behind the fast evolution of resistance that was observed. These findings may have important implications for the development of new antibiotics, as they suggest news way to delay the evolution of resistance, one of the burning health issues today. It is important to note that these dormant bacteria would go undetected in the current tests done in the clinic. In order to bridge this gap, a complementary study from the same lab, and led by Scholar-Teacher Dr. Orit Gefen, demonstrates a new and easy method for the detection of dormant bacteria in the clinical setting and may help avoid the evolution of resistance in real time.
Irit Levin-Reisman et al., Science (2017)
Orit Gefen et al. Scientific Reports (2017)

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Accessing Human Selenoproteins through Chemical Protein Synthesis - small photo Accessing Human Selenoproteins through Chemical Protein Synthesis - Dr. Norman Metanis

The human body contains 25 selenoproteins. This is a small family of proteins which contain in their sequence the twenty-first encoded amino acid, selenocysteine. About a dozen of these proteins remain functionally uncharacterized or poorly studied. The bottleneck in studying selenoproteins is the challenges in accessing these proteins using traditional recombinant expressions, which have prevented biological characterization thus far. Chemical protein synthesis has the potential to overcome these hurdles. In a recent seminal paper published in the journal Chemical Science, our group report the first total chemical syntheses of two human selenoproteins, selenoprotein M (SELM) and selenoprotein W (SELW). The synthesis of the more challenging protein SELM was enabled using recent advances in the field of selenocysteine chemistry, which we mastered in our lab. This approach allow the preparation of selenoproteins in milligram quantities and in homogenous form, which should open new horizons for future studies to pursue a fuller biological understanding of their role in health and disease.

Addtional information

A novel technique for endoscopic imaging through multicore fibers - thumbnail A novel technique for endoscopic imaging through multicore fibers - Dr. Uri Katz

Researchers from the Hebrew University Applied Physics Department in collaborations with researchers from the Weizmann Institute and from Paris, France, have developed a novel technique for endoscopic imaging through multicore fibers, using no lenses or optical elements besides the fiber. The technique is based on exploiting inherent correlations of coherent light propagating in such fibers.


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In the light of a neutron star, astronomers have found evidence for a quantum effect discovered in the 1930s. - smal image The discovery of weird quantum effects in the vacuum around neutron stars - Prof. Nir Shaviv

A prediction made by Prof. Nir Shaviv from the Racah Institute of Physics at the Hebrew University and Prof. Jeremy Heyl from the University of British Columbia in Vancouver Canada is reaffirmed through the measurement of polarized light from a neutron star. As a result of the very strong magnetic fields around neutron stars, the light rays can interact with the virtual electrons in the Vacuum. This interaction gives rise to very strange effects, the evidence of which was only recently seen for the first time.


Habitability of exoplanets Habitability of exoplanets - Dr. Amri Wandel

The recent detection of small planets within the Habitable Zone of Proxima Centauri and many other M-dwarf stars makes such planets prime candidates to look for life. In a recent article Joseph Gale and Amri Wandel discuss the potential of planets orbiting red dwarf stars to support photosynthesis and complex life. They combine the latest findings from the Kepler space telescope on the number of Earth-sized planets, with calculations showing that the appearance of life clement conditions on planets of red dwarf stars is possible and more probable than previously thought. In a recently submitted paper Wandel argues that Proxima b and other planets in the Habitable Zone of M dwarfs may support liquid water for a wide range of properties, including their atmosphere, irradiation and heat redistribution. This work also suggest a method that could give a quantitative estimation of the abundance of life on exoplanets, using the future telescopes JWST and TESS, planned for launch by 2018.


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Regeneration Vs. Tail - thumbnail Heads or tails? The whole body regeneration scheme of the sea-anemone Nematostella. - Dr. Uri Gat

Whole-body regeneration is the ability of some animals to reconstruct entire body parts after major damage such as cutting into two fragments. This may seem incredible to us but several very different animals are able to perform this feat quite easily, a phenomenon that has attracted the interest of naturalists and scientists for ages. In our lab we are studying the whole-body regeneration process of a simple animal called the sea anemone Nematostella. This animal belongs to cnidarians (e.g: medusas, corals) and has a remarkable ability to regenerate even after cutting it into several parts. Surprisingly the genome sequence of Nematostella revealed a large extent of genes and even genome segments that are very similar to those of man, especially genes that function in embryonic development.
To better understand this mystery we have explored the genetic program, in which after bisection in the middle, the "tail" half reconstructs the head and the "head" part rebuilds the tail. In this project we have charted the genes that are induced at different time points along the regeneration process and compared their action in the head versus the tail forming parts. This screen identified many genes that are involved in the formation of the basic body axis in the embryonic development stage and also discovered new genes that may be specific to the regeneration program.
In this research we have also characterized the main genetic networks that are involved in regeneration and we now know more about which gene tools are responsible for the head and tail reconstruction jobs as well as their logic of operation. A large proportion of these genes are common to us, and thus this information can lead in the future to better wound healing treatments in people and may even allow some organ repair after major injuries.

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Abstact The claustrum supports resilience to distraction - Dr. Ami Citri

In Brief:
The world we live in is dense with sensory stimulation, yet we largely manage to remain resilience to these distractors and achieve our goals. A new study from the Hebrew University finds that this capacity is mediated by the claustrum, a mysterious thin sheet of neurons comprising the brain’s most vastly connected structure. This discovery could have implications for diagnosis and therapy of ADHD and other psychiatric disorders of attention.

In more detail:
A barrage of information constantly assaults our senses, of which only a fraction is relevant at any given point in time. How do we remain resilient in the face of all these potential distractors, maintaining goal-directed behavior? Consider a young mother taking her children at the mall – how is it that she can maintain her attention to her children, making sure she does not lose them, when she is surrounded by all the sensory information that is assaulting her?
New research from the Hebrew University has identified a role for the claustrum in supporting resilience to distraction, a central aspect of selective attention. This mysterious brain region, a thin sheet of neurons located under the cortex, has been famously suggested to be the location where the conscious experience arises. However, until now, no-one has been able to directly study the role of this brain structure, because of its unique structure.
Working with mice, the team, spearheaded by PhD students Gal Atlan, Anna Terem and Noa Peretz-Rivlin, in the lab of Dr. Ami Citri at the Hebrew University, identified a unique mode of genetic access to neurons of the claustrum, supporting the first investigation the function of this structure.
They found that activity of the claustrum was essential to enable mice to perform an attention-demanding task in the presence of a distracting stimulus. To this end, they utilized two tasks in mice. In the first task, mice had to wait patiently for the presentation of a very short visual cue, informing them of the identity of a port at which they would be given the opportunity to drink water. Mice, even those in which the claustrum had been inhibited, learned this task efficiently. However, mice, whose claustrum had been inhibited, were selectively sensitive to the addition of a distracting sound (a short segment of the song Pluto, by Bjork).
In a second task, the investigators addressed the role of the claustrum in the behavior of mommy mice, which will naturally retrieve their pups to their nest if they are left in an open area (remember the example of the mother in a mall?). The investigators took the pups away from young mice mothers, returning them one by one. Mother mice, even those whose claustrum was deficient, successfully retrieved the pups back to the nest. However, with Bjork in the background, the performance of claustral-deficient mommy mice was severely disrupted. Thus, the investigators concluded that the activity of the claustrum is crucial to enable mice to maintain attention to the task at hand, and remain resilient to the presentation of a distractor.
This study has implications for the diagnosis and therapy of the myriad of brain disorders that involve disruptions of attention. These obviously include Attention Deficit Hyperactivity Disorder (ADHD), as well as psychotic disorders, in which hallucinations and delusions occur. Indeed, the region of the claustrum has been observed to be hyperactive in patients with Attention Deficit Hyperactivity Disorder (ADHD), and temporary lesions of the claustrum have been associated with lapses in attention, as well as disrupted communication and hallucinations.

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Rota's basis conjecture - thumbnail Solution of the Rota conjecture - Karim Adiprasito

 We recently solved the so-called Rota conjecture, a 45 year old problem in  combinatorics that has baffled generations of researchers. The methods developped surprised even more, as they extended classical results of algebraic geometry to purely combinatorial settings
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mage of diamonds with different properties ready to be measured. Credit: Dima Farfurnik Enhancing the sensing capabilities of diamonds with quantum properties - Prof. Nir Bar-Gil

Pure diamond consists of carbon atoms in a perfect crystal lattice. But remove a few carbons and swap some others for nitrogen, and you get a diamond with special quantum-sensing properties. These properties are useful for quantum information applications and sensing magnetic fields, and as a platform for probing the mysteries of quantum physics.
When a nitrogen atom is next to the space vacated by a carbon atom, it forms what is called a nitrogen-vacancy (NV) center. Now, researchers have shown how they can create more NV centers, which makes sensing magnetic fields easier, using a relatively simple method that can be done in many labs. They describe their results this week in Applied Physics Letters.
Magnetic field sensing presents a prime example for the importance of this sensing. Green light can induce the NV centers to fluoresce and emit red light, but the amount of this fluorescence changes in the presence of a magnetic field. By measuring the brightness of the fluorescence, diamond NV centers can help determine magnetic field strength. Such a device can make magnetic images of a range of sample types, including rocks and biological tissue.
The sensitivity of this type of magnetic detection is determined by the concentration of NV centers while vacancies that are not paired with nitrogen create noise. Efficient conversion of vacancies into NV centers, therefore, as well as maximizing the concentration of NV centers, plays a key role in advancing these detection methods.
Researchers typically purchase nitrogen-doped diamonds from a separate company. They then bombard the diamond with electrons, protons or other particles, which strip away some of the carbon atoms, leaving behind vacancies. Finally, a heating process called annealing nudges the vacancies next to the nitrogen atoms to form the NV centers. The problem is that irradiation often requires sending your sample to a separate facility, which is expensive and time-consuming.
"What is special about our approach is that it's very simple and very straightforward," said Dima Farfurnik of the Hebrew University of Jerusalem in Israel. "You get sufficiently high NV concentrations that are appropriate for many applications with a simple procedure that can be done in-house."

Their method uses high energy electron bombardment in a transmission electron microscope (TEM), an instrument accessible to many researchers, to locally create NV centers. Normally, a TEM is used to image materials down to subnanometer resolutions, but its narrow electron beam can also irradiate diamonds.
Others have shown TEMs can create NV centers in specialized diamond samples, but the researchers in this study successfully tested the method on several commercially available diamond samples.
In a typical, untreated sample, less than 1 percent of the nitrogen atoms form NV centers. But by using a TEM, the researchers increased this conversion efficiency to as high as 10 percent. In certain cases, the samples reached their saturation limit, and more irradiation was no longer effective. For other samples, however, the researchers didn't hit this limit, suggesting that additional irradiation could boost efficiencies further. With higher conversion efficiencies, and small irradiation volumes possible with a TEM, devices like magnetic sensors could be more compact.
To make sure the method didn't hinder the effectiveness of NVs in applications like sensing magnetic fields, the researchers confirmed that the length of time the NV centers remain in their states—the coherence time—didn't change.
Packing enough NV centers in a diamond would allow physicists to probe the quantum interactions among the centers themselves. This research could enable the creation of a unique quantum state called a squeezed state, which has never been demonstrated before in a solid and could push the sensing capabilities of these systems beyond today's classical limits.
"We hope the enhanced number of NV centers due to irradiation will serve as a stepping stone for this long-term and ambitious goal," Farfurnik said.

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NS NS Merge Comparison New Radio Observations Shed New Light on Neutron Star Mergers - Dr. Assaf Horesh

On last August, gravitational waves together with electromagnetic radiation originating from a merger of two neutron stars, have been observed for the first time. The discovery of the gravitational waves has been made possible thanks to the advanced LIGO experiment. Now, a team of international scientists, including researchers from The Hebrew University and Tel-Aviv University, reveals new radio observations that shed new light on what has occurred during the neutron star merger.

This event, named GW170817, and that exhibited electromagnetic radiation across the spectrum (including gamma-rays, X-rays, ultra-violet light, and optical and infra-red light) provided a unique opportunity to study neutron star merger like never before. For example, optical and infra-red observations of the event provided evidence (for the first time) that heavy elements indeed form in this type of mergers.

The common theory suggests that in this type of an event, a large amount of energy will be carried out by a relativistic narrow jet (moving close to the speed of light). This jet is expected to penetrate the material around it (that is ejected during the merger process) and when the jet is pointing towards us, we expect to see gamma-ray emission. For many years, this was the model that has been used to explain short gamma-ray bursts that are observed once every few weeks (without any associated gravitational events).

Indeed, about two seconds after the discovery of GW170817, a short gamma ray burst emission has been observed. However, the emission was atypical compared to previous short bursts, as it was much fainter.

Scientists around the world tried to explain the weak gamma-ray emission by suggesting that the narrow relativistic jet is not pointing straight at us, but it is slightly off-axis. If this is true, then this model predicts that the radio emission from such a jet should decay by now, a few months after the merger.

It was therefore clear to the international radio observing team (that includes Dr. Assaf Horesh, an experimental astrophysicist from the Hebrew University) that prolonged radio observations can help solve this mystery. Also, radio observations can be undertaken during the day. This was important since GW170817 position on the sky has gotten closer to the sun these last few months, causing the observations in all other wavelengths (besides the radio) to cease, during a critical phase in gathering information on the event.

Now the team of researchers who performed the radio observations claim (in their new paper published in Nature) that in light of the new radio measurements a narrow jet was formed, but we have not seen it, as the radio emission has continued to rise over the last 100 days instead of fading away.

The jet quickly lost its energy as it deposited it into a wide-angle cocoon, created by the jet itself (according to a theoretical model developed by Prof. Tsvi Piran from the Hebrew University and Prof. Ehud Nakar and Ore Gottelib from Tel-Aviv University). This cocoon moves at a fast velocity but as fast as the jet that formed it. In fact, the jet lost all of its energy and quickly ceased to exist.

The radio observations, therefore, shed new light on the processes that take place when two neutron stars merge. Moreover, due to this result, it is clear that the connection between neutron star mergers and normal short gamma-ray bursts is far from being proven. However, at least now we know what to expect from neutron star mergers and what to look for in future events

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Unique properties of Human neurons - small image Unique properties of Human neurons - Idan Segev

A new modeling study shows that human cortical neurons have distinctive membrane properties, suggesting important implications for signal processing in the human neocortex, The theoretical results were validated in experiments perfumed in fresh human cortex following brain operations at the Fry University Hospital in Amsterdam. The study was performed by Guy Eyal, a Ph.D. student of Prof. Idan Segev at the Department of Neurobiology the Hebrew University of Jerusalem.

Aditional information

asymmetry image Light asymmetry explains the effect of nutrient enrichment on grassland diversity - Niv Demalach

One of the most ubiquitous patterns in plant ecology is species loss following nutrient enrichment.
A common explanation for this universal pattern is an increase in the size asymmetry of light partitioning (the degree to which large plants receive more light per unit biomass than smaller plants), which accelerates the rates of competitive exclusions. This ‘light asymmetry hypothesis’ has been confirmed by mathematical models, but has never been tested in natural communities due to the lack of appropriate methodology for measuring the size asymmetry of light partitioning in natural communities. Here, we use a novel approach for quantifying the asymmetry of light competition which is based on measurements of the vertical distribution of light below the canopy. Using our approach, we demonstrate that an increase in light asymmetry is the main
mechanism behind the negative effect of nutrient enrichment on species richness. Our results provide a possible explanation for one of the main sources of contemporary species loss in terrestrial plant communities.

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 neutron stars Does a merger of two neutron stars leads to the formation of a magnetar? - Assaf Horesh

The recent discovery of gravitational waves by LIGO opens a new era in astrophysics. While the event discovered by LIGO originated from the merger of two black holes, LIGO is also capable and is expected to discover mergers of Neutron stars. In a Neutron star merger, a small amount of material will be ejected at velocities of about 30,000 km/s. This material will be radioactively heated and hence will emit a weak and brief (1 day to a weak) optical/infra-red signal, named macronovae. Such a macronovae signal was first detected only a few years ago as the counterpart of short gamma-ray bursts (which are believed to also originate from compact binary mergers). The same material that is responsible for the macro novae signal, will also interact with environment, create a shockwave, and lead to radio emission. It is possible that in the merger process a magnetar will form (and not necessarily a black hole). A magnetar is a fast rotating neutron star (1 ms period) with a large magnetic field (> 10^15 Gauss). In this case, the magnetar will deposit its energy into the ejecta and will drive a much stronger shockwave, thus increasing, by at least an order of magnitude, the radio emission. We recently observed two macronoave candidates, in search for this radio emission. Our results suggest that at least in the events that we observed, no standard magnetar was formed, unless the magnetar had different properties than theory predicts. Following this results, we are conducting further radio observations of similar events, in an attempt to better characterize them and to unveil their nature.


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Tethered twistacenes Helically Locked Tethered Twistacenes - Dr. Uri Gidron

Acenes are linear molecules comprised of benzene rings. These rings are known for their resonance: a state in which their electrons are delocalized. Unlike other molecules, in which the electrons are associated with specific atoms and therefore restricted in space, the delocalized electrons are free to move throughout the molecule. The delocalization of electrons leads to the electrical semiconductivity of the molecule. Semiconductors are materials that conduct only under specific conditions. These materials (e.g. Silicon) are widely used in the electronics industry.                                                                          Acenes can be either planar (2D) or twisted (3D). It is known that twisting affects the electronic and optical properties, however, measuring this effect is difficult as changing planarity results in a new molecular structure with modified properties.

In a new paper by Anjan Bedi from Ori Gidron’s lab, two types of acenes were connected by ‘molecular bridges’ of different lengths. Each bridge locked the molecule in a different twisting angle. This way, it was possible to monitor the effect of twisting on the electronic and optical properties. For example, as the twisting angle increased, the color changed and fluorescence dramatically decreased.  In addition, the chirality of the molecule alternated.

Locking the molecular structures allowed the isolation of two mirror imaged molecules, called enantiomers. Each enantiomer rotates polarized light in opposite direction. The normalized value of rotation is called the anisotropy factor. These enantiomers exhibited high anisotropy factor and thermal stability. Molecules with high anisotropy factor are considered promising materials for the field of quantum computing and may also serve as sensors for biological entities.

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Ori Gidron Research Group

Advnaced Imaging - small picture "The Marker" article on the research at the Advnaced Imaging Lab of the Applied Physics Department - Dr. Uri Katz

A special article on the research at the Advanced Imaging Lab in the Hebrew University Applied Physics Department, led by Dr. Ori Katz, was published in "The Marker" magazine
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Single Colloidal Nanopracticle - thumbnail Scientists Demonstrate a Compact, Efficient Single Photon Source That Can Operate at Ambient Temperatures On a Chip - Prof. Ronen Rapaport

Highly directional single photon source concept is expected to lead to a significant progress in producing compact, cheap, and efficient sources of quantum information bits for future applications

Quantum information science and technology has emerged as a new paradigm for dramatically faster computation and secure communication in the 21st century. At the heart of any quantum system is the most basic building block, the quantum bit or qbit, which carries the quantum information that can be transferred and processed (this is the quantum analogue of the bit used in current information systems). The most promising carrier qbit for ultimately fast, long distance quantum information transfer is the photon, the quantum unit of light.

The challenge facing scientists is to produce artificial sources of photons for various quantum information tasks. One of the biggest challenges is the development of efficient, scalable photon sources that can be mounted on a chip and operate at room temperature. Most sources used in labs today have to be very cold (at the temperature of liquid Helium, about -270C), which requires large and expensive refrigerators. Many sources also emit photons in undefined directions, making efficient collection a hard problem.

Now, a team of scientists from the Hebrew University of Jerusalem has demonstrated an efficient and compact single photon source that can operate on a chip at ambient temperatures. Using tiny nanocrystals made of semiconducting materials, the scientists developed a method in which a single nanocrystal can be accurately positioned on top of a specially designed and carefully fabricated nano-antenna.

In the same way large antennas on rooftops direct emission of classical radio waves for cellular and satellite transmissions, the nano-antenna efficiently directed the single photons emitted from the nanocrystals into a well-defined direction in space. This combined nanocrystals-nanoantenna device was able to produce a highly directional stream of single photons all flying to the same direction with a record low divergence angle. These photons were then collected with a very simple optical setup, and sent to be detected and analyzed using single photon detectors.

The team demonstrated that this hybrid device enhances the collection efficiency of single photons by more than a factor of 10 compared to a single nanocrystal without the antenna, without the need for complex and bulky optical collection systems used in many other experiments. Experimental results show that almost 40% of the photons are easily collected with a very simple optical apparatus, and over 20% of the photons are emitted into a very low numerical aperture, a 20-fold improvement over a freestanding quantum dot, and with a probability of more than 70% for a single photon emission. The single photon purity is limited only by emission from the metal, an obstacle that can be bypassed with careful design and fabrication.

The antennas were fabricated using simple metallic and dielectric layers using methods that are compatible with current industrial fabrication technologies, and many such devices can be fabricated densely on one small chip. The team is now working on a new generation of improved devices that will allow deterministic production of single photons straight from the chip into optical fibers, without any additional optical components, with a near unity efficiency.

"This research paves a promising route for a high purity, high efficiency, on-chip single photon source operating at room temperature, a concept that can be extended to many types of quantum emitters. A highly directional single photon source could lead to a significant progress in producing compact, cheap, and efficient sources of quantum information bits for future quantum technological applications", said Prof. Ronen Rapaport, of the Racah Institute of Physics, The Department of Applied Physics, and the Center of Nanoscience and Nanotechnology at the Hebrew University of Jerusalem.

The Hebrew University of Jerusalem is Israel’s leading academic and research institution, producing one-third of all civilian research in Israel. For more information, visit

FUNDING: The research was supported in parts by the Einstein Foundation Berlin; the U.S. Department of Energy: Office of Basic Energy Sciences, Division of Materials Sciences and Engineering; the European Cooperation in Science and Technology through COST Action MP1302 Nanospectroscopy;  and by the Ministry of Science and Technology, Israel.

REFERENCE: Highly Directional Room-Temperature Single Photon Device. Nitzan Livneh, Moshe G. Harats, Daniel Istrati, Hagai S. Eisenberg, and Ronen Rapaport. Nano Lett., 2016, 16 (4), pp 2527–2532. DOI: 10.1021/acs.nanolett.6b00082.

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Gene expression encodes experiences in the brain - Dr. Ami Citri

We studied the representation in the brain of mice of recent experiences, by gene expression. These experiences included repeated exposure to drugs of abuse, acquisition of the habit of drinking sugar, exploration of a new environment, acute pain, nausea, exposure to food after a period of restriction etc’.
We find that the brain represents information for long-term storage in specific patterns of gene expression throughout the brain. Experiences that share common attributes also share commonalities in this code. Using subsets of this gene expression code, it is possible to identify, with almost 100% certainty, the identity of the recent experience of individual mice.

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scenery picture One Small Particle, One Big Storm - Prof. Daniel Rosenfeld

Man-Made Pollution May have Greater Impact on Weather Systems than Previously Thought

(Jerusalem, January 25, 2018)—Even the tiniest of particles from human emissions can fuel powerful storms and influence weather and crops much more than previously thought, according to new research published in the Jan. 26 issue of the journal Science.

The study focuses on the power of man-made emissions to grow rain clouds and intensify storms.  These particles, known as aerosols, come from urban and industrial air pollution, wildfires and other sources. While scientists have known that these particles play an important role in shaping weather and climate, the new study shows that even the smallest of man-made particles can have an outsize effect, creating more severe thunderstorms which in turn, may lead to soil erosion, runoff and damaged crops.

These tiny pollutants—less than one-thousandth of the width of a human hair – were long considered too small to have much impact on raindrop formation. However, according to lead-author Dr. Jiwen Fan of the Department of Energy’s Pacific Northwest National Laboratory, “We showed that the presence of these particles is one reason why some storms become so strong and produce so much rain. In a warm and humid area where atmospheric conditions are otherwise very clean, the intrusion of very small particles can make quite an impact.”

This study was conducted in the Amazon, a largely pristine, untouched area. This setting provided scientists the rare opportunity to study the impact of pollution from nearby Manaus, a city of 2 million people in the Amazon, and to pinpoint the effects of human pollution on a heretofore pristine weather environment.

Scientists, including second-author Professor Daniel Rosenfeld, of The Hebrew University of Jerusalem’s Institute of Earth Sciences, studied the role of ultrafine particles on thunderstorms.  While larger particles were known to enhance thunderstorms, scientists had not observed – until now – that even smaller particles, like those produced by vehicles and industry, could have the same effect. Further, this new study revealed that the ultrafine particles could invigorate rain clouds and increase rainfall in a much more powerful way than their larger counterparts.

"This groundbreaking research strongly suggests that mankind has likely altered the rainfall and weather in densely populated tropical and summer monsoon areas such as India, Southeast Asia, Indonesia, and even southeastern USA," said Rosenfeld.  Significantly, this heavier downpour often leads to soil erosion and crop damage, affecting the lives and livelihoods of those living in the affected areas.

Through detailed computer simulations, the scientists showed how the smaller particles have a powerful impact on rain clouds. While small in size, these particles are large in number and serve as a platform upon which small water droplets congregate and excess water vapor condenses. This enhanced condensation releases more heat, which in turn cause updrafts to become more powerful. The updrafts cause more warm air to be pulled into the clouds, which ultimately produces more ice and snow pellets, lightning, and heavier rain in the regions.

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CITATION: Substantial convection and precipitation enhancements by ultrafine aerosol particles. Jiwen Fan, Daniel Rosenfeld, Yuwei Zhang, Scott E. Giangrande, Zhanqing Li, Luiz A.T. Machado, Scot T. Martin, Yan Yang, Jian Wang, Paulo Artaxo, Henrique M.J. Barbosa, Ramon C. Braga, Jennifer M. Comstock, Zhe Feng, Wenhua Gao, Helber B. Gomes, Fan Mei, Christopher Pöhlker, Mira L. Pöhlker, Ulrich Pöschl, and Rodrigo A.F. de Souza. Science, Jan. 26, 2018. DOI: 10.1126/science.aan8461. Link:

FUNDING: The work was funded by a grant from the BACCHUS European Commission FP7-603445.

To date, here's the international press coverage we got for your study: Man-Made Pollution May have Greater Impact on Weather Systems than Previously Thought:

•    From the Grapevine, Is man-made pollution making storms more severe?  
•    Eureka, Amazon rainforest provides a unique natural lab to study effects of aerosols
•    Drovers, Tiny Particles Have Outsize Impact on Precipitation
•    Green Car progress, PNNL-led international study finds ultrafine aerosols have outsize impact on storm clouds, precipitation
•    Xihhua, Tiniest emission particles may lead to big storms: study
•    Israel 21C, New multinational research reveals that even small amounts of manmade aerosol particles can wreak havoc.  
•    Jerusalem Online, New US-Israeli study shows how tiny man-emitted particles affect weather, crops


Comics image - thumbnail One out of ten most promising researchers for 2016 - TheMarker - Dan Cohen

A doctoral student in the Department of Physics at the Hebrew University (32) breakthrough PhD research of Dan Cohen will help realize one of the most important questions in nuclear physics of today: What is the size of particles called protons, which are in the nucleus of every atom. Various experiments to measure the radius of the proton, some of them in recent years have yielded different results without a satisfactory explanation; the trial of Cohen, led by Prof. Guy Ron, offering innovative technique and guarantees. Cohen is part of an international group which integrate and work at the particle accelerator PSI, Switzerland. this year he is expected to complete at the Hebrew university the construction of his special detector, which is a screen like detector, the two types of particles will scatter on it: electrons are elementary particles in nature, and muons are similar to electrons but heavier than them. the experiment will be carried out at a particle accelerator in Switzerland, which is the only site in the world where this can be done. the accelerator will shoot at the protons the two particle types (separately) from the information collected on the interaction between the protons and the particles using their dispersion on the detector, it will be possible to calculate the size of the proton. One can imagine this ball doused in water and then with oil, and from the different distribution of the oil and water drops splashing from the ball, we can calculate its size. The experiment is expected to be completed within three years. Cohen, who dreamed of being an astronaut from an early age, realized that the way to realize the dream goes through learning sciences. He is alumnus of Space Studies Program 2014, from the International Space University and volunteer as the head of landing site selection team at SpaceIL. This is a non-profit organization founded in 2011 by three young Israeli engineers, and aims to launch the first Israeli spaceship on the moon, and a way to inspire the next generation of scientists and engineers. After completing his doctorate one can assume that Cohen will do postdoctoral at the United States which leads the field, and then he wants to come back and to be a researcher at Israel. The dream of being an astronaut is still vivid in his blood.

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