Nader Engheta, H. Nedwill Ramsey Professor in Electrical and Systems Engineering, Bioengineering and Materials Science and Engineering, has been awarded the 2020 Isaac Newton Medal and Prize by the Institute of Physics (IOP). The IOP is the professional body and scholarly society for physics in the UK and Ireland.
Engheta has been recognized for ” groundbreaking innovation and transformative contributions to electromagnetic complex materials and nanoscale optics, and for pioneering development of the fields of near-zero-index metamaterials, and material-inspired analogue computation and optical nanocircuitry.”
Speaker: Daniel Palanker, Ph.D.
Director of the Hansen Experimental Physics Laboratory and Professor of Ophthalmology
Date: Wednesday, November 18, 2020
Time: 1:00-2:00 PM EST
Zoom – check email for link or contact firstname.lastname@example.org
Title: “Photovoltaic Restoration of Sight in Age-related Macular Degeneration”
Retinal degenerative diseases lead to blindness due to loss of the “image capturing” photoreceptors, while neurons in the “image-processing” inner retinal layers are relatively well preserved. Information can be reintroduced into the visual system using electrical stimulation of the surviving inner retinal neurons. We developed a photovoltaic substitute of photoreceptors which convert light into pulsed electric current, stimulating the secondary retinal neurons. Visual information captured by a camera is projected onto the retina from augmented-reality glasses using pulsed near-infrared (~880nm) light. This design avoids the use of bulky electronics and wiring, thereby greatly reducing the surgical complexity. Optical activation of the photovoltaic pixels allows scaling the number of electrodes to thousands. In preclinical studies, we found that prosthetic vision with subretinal implants preserves many features of natural vision, including flicker fusion at high frequencies (>30 Hz), adaptation to static images, antagonistic center-surround organization and non-linear summation of subunits in receptive fields, providing high spatial resolution. Results of the clinical trial with our implants (PRIMA, Pixium Vision) having 100μm pixels, as well as preclinical measurements with 75 and 55μm pixels, confirm that spatial resolution of prosthetic vision can reach the pixel pitch. Remarkably, central prosthetic vision in AMD patients can be perceived simultaneously with peripheral natural vision. For broader acceptance of this technology by patients who lost central vision due to agerelated macular degeneration, visual acuity should exceed 20/100, which requires pixels smaller than 25μm. I will describe the fundamental limitations in electro-neural interfaces and 3-dimensional configurations which should enable such a high spatial resolution. Ease of implantation of these wireless arrays, combined with high resolution opens the door to highly functional restoration of sight.
Daniel Palanker is a Professor of Ophthalmology and Director of the Hansen Experimental Physics Laboratory at Stanford University. He received MSc in Physics in 1984 from the State University of Armenia in Yerevan, and PhD in Applied Physics in 1994 from the Hebrew University of Jerusalem, Israel. Dr. Palanker studies interactions of electrical field with biological cells and tissues, and develops optical and electronic technologies for diagnostic, therapeutic, surgical and prosthetic applications, primarily in ophthalmology. In the range of optical frequencies, his studies include laser-tissue interactions with applications to ocular therapy and surgery, and interferometric imaging of neural signals. In the field of electro-neural interfaces, he is developing highresolution photovoltaic retinal prosthesis for restoration of sight and implants for electronic control of organs. Several of his developments are in clinical practice world-wide: Pulsed Electron Avalanche Knife (PEAK PlasmaBlade, Medtronic), Patterened Scanning Laser Photocoagulator (PASCAL, Topcon), Femtosecond Laser-assisted Cataract Surgery (Catalys, J&J), and Neural Stimulator for enhancement of tear secretion (TrueTear, Allergan). Photovoltaic retinal prosthesis for restoration of sight (PRIMA, Pixium Vision) is in clinical trials.
See the full list of upcoming Penn Bioengineering events here.
New research finds that works of literature, musical pieces, and social networks have a similar underlying structure that allows them to share large amounts of information efficiently.
By Erica K. Brockmeier
To an English scholar or avid reader, the Shakespeare Canon represents some of the greatest literary works of the English language. To a network scientist, Shakespeare’s 37 plays and the 884,421 words they contain also represent a massively complex communication network. Network scientists, who employ math, physics, and computer science to study vast and interconnected systems, are tasked with using statistically rigorous approaches to understand how complex networks, like all of Shakespeare, convey information to the human brain.
New research published in Nature Physics uses tools from network science to explain how complex communication networks can efficiently convey large amounts of information to the human brain. Conducted by postdoc Christopher Lynn, graduate students Ari Kahn and Lia Papadopoulos, and professor Danielle S. Bassett, the study found that different types of networks, including those found in works of literature, musical pieces, and social connections, have a similar underlying structure that allows them to share information rapidly and efficiently.
Technically speaking, a network is simply a statistical and graphical representation of connections, known as edges, between different endpoints, called nodes. In pieces of literature, for example, a node can be a word, and an edge can connect words when they appear next to each other (“my” — “kingdom” — “for” — “a” — “horse”) or when they convey similar ideas or concepts (“yellow” — “orange” — “red”).
The advantage of using network science to study things like languages, says Lynn, is that once relationships are defined on a small scale, researchers can use those connections to make inferences about a network’s structure on a much larger scale. “Once you define the nodes and edges, you can zoom out and start to ask about what the structure of this whole object looks like and why it has that specific structure,” says Lynn.
Building on the group’s recent study that models how the brain processes complex information, the researchers developed a new analytical framework for determining how much information a network conveys and how efficient it is in conveying that information. “In order to calculate the efficiency of the communication, you need a model of how humans receive the information,” he says.
Before CRISPR became a household name as a tool for gene editing, researchers had been studying this unique family of DNA sequences and its role in the bacterial immune response to viruses. The region of the bacterial genome known as the CRISPR cassette contains pieces of viral genomes, a genomic “memory” of previous infections. But what was surprising to researchers is that rather than storing remnants of every single virus encountered, bacteria only keep a small portion of what they could hold within their relatively large genomes.
In recent years, CRISPR has become the go-to biotechnology platform, with the potential to transform medicine and bioengineering. In bacteria, CRISPR is a heritable and adaptive immune system that allows cells to fight viral infections: As bacteria come into contact with viruses, they acquire chunks of viral DNA called spacers that are incorporated into the bacteria’s genome. When the bacteria are attacked by a new virus, spacers are copied from the genome and linked onto molecular machines known as Cas proteins. If the attached sequence matches that of the viral invader, the Cas proteins will destroy the virus.
Bacteria have a different type of immune system than vertebrates, explains senior author Vijay Balasubramanian, but studying bacteria is an opportunity for researchers to learn more about the fundamentals of adaptive immunity. “Bacteria are simpler, so if you want to understand the logic of immune systems, the way to do that would be in bacteria,” he says. “We may be able to understand the statistical principles of effective immunity within the broader question of how to organize an immune system.”
Danielle Bassett has been named the J. Peter Skirkanich Professor of Bioengineering.
Dr. Bassett is a Professor in the department of Bioengineering at the School of Engineering and Applied Science. She holds a Ph.D. in Physics from the University of Cambridge and completed her postdoctoral training at the University of California, Santa Barbara, before joining Penn in 2013.
Dr. Bassett has received numerous awards for her research, including an Alfred P Sloan Research Fellowship, a MacArthur Fellowship, an Office of Naval Research Young Investigator Award, a National Science Foundation CAREER Award and, most recently, an Erdos-Renyi Prize in Network Science to name but a few. She has authored over 190 peer-reviewed publications as well as numerous book chapters and teaching materials. She is the founding director of the Penn Network Visualization Program, a combined undergraduate art internship and K-12 outreach program bridging network science and the visual arts.