Eric Sembrat's Test Bonanza

Physicist and adventurer Francis Slakey describes his decade long journey that led to his becoming the first person to both summit the highest mountain on every continent and surf every ocean.  The talk reviews some of the people he encounters and the challenges he endures – a Lama who gives him an amulet etched with “life’s meaning”, an ambush in the jungles of Indonesia, a life-or-death choice atop Everest – that culminate in a recognition that science is the most powerful tool we have to build a better world.  He will describe how that perspective now informs his work for the American Physical Society and Georgetown University.

Biography:

Francis Slakey received his PhD in physics from the University of Illinois, Urbana-Champaign in 1992.  He is the Associate Director of Public Affairs for the American Physical Society where he oversees APS legislative activities, specializing in energy and security policy.  He is also The Upjohn Lecturer on Physics and Public Policy and the Co-Director of the Program on Science in the Public Interest at Georgetown University.  He is a Fellow of the APS, a Fellow of the AAAS, a MacArthur Scholar, and a Lemelson Research Associate of the Smithsonian Institution.  In recognition of his adventures, in 2002, he was chosen to run the Olympic Torch from the steps of the US Capitol.  He recounts his global journey in his best-selling adventure memoir, To The Last Breath.

Curative cancer treatment requires radiotherapy (RT) in almost 2/3rd of all cases. Unfortunately, children are highly susceptible to the development of debilitating toxicities and secondary malignancies from RT. Normal tissue sparing with hadron-beam therapy is being actively investigated to reduce RT side-effects. The objective of this talk is to describe conventional and novel normal tissue-sparing applications of photon and proton beam therapy, respectively; radiobiological interplay with the tumor microenvironment will also be discussed.

Cells are sensitive to mechanical signals produced either by application of exogenous force, or by the resistance to cell-generated forces caused by the viscoelastic properties of the materials to which they adhere. The range of stiffness over which different cell types respond can vary over a wide range and generally reflects the elastic modulus of the tissue from which these cells were isolated. Many cell types can alter their own stiffness to match that of the substrate to which they adhere. The maximal elastic modulus that cells can attain is similar to that of crosslinked actin networks at the concentrations in the cell cortex. Mechanosensing appears to require an elastic connection between cell and substrate, mediated by transmembrane proteins. The viscoelastic properties of different extracellular matrices and cytoskeletal elements strongly influence the response of cells to mechanical signals, and the unusual non-linear elasticity of many biopolymer gels, characterized by strain-stiffening, leads to novel mechanisms by which cells alter their stiffness by engagement of molecular motors that produce internal stresses.

Motile immune cells like neutrophils (the most abundant type of white blood cell) track down invading microbes by chemotaxis, keep hold of them by adhesion, and neutralize them by phagocytosis.  We integrate concepts and tools from immunobiology and biophysics to examine the mechanistic underpinnings of this amazing, cross-disciplinary feat.  Single-live-cell experiments using micropipette manipulation, optical tweezers, and a new type of horizontal atomic force microscope allow us to assess the nano-to-microscale ingredients of one-on-one encounters between human neutrophils and their targets (such as opsonized particles or pathogenic fungi and bacteria).  We dissect such encounters by examining separately the immunophysical roles of opsonization, chemotaxis, immune-cell priming, adhesion, and phagocytosis, as well as their vital interplay.  Providing a fresh view of the initiation of host-pathogen interactions, this approach demonstrates how the integration of essential physical insight with immunobiology allows us to define tighter constraints on possible explanations of cell and molecular behavior. 

Reference:

Heinrich, V., and C.-Y. Lee.  (2011).  Blurred line between chemotactic chase and phagocytic consumption:  An immunophysical, single-cell perspective.  Journal of Cell Science  124(18):3041-3051.

mso-bidi-font-style:italic">The problem of speciation and species aggregation on a neutral landscape, subject to random mutational fluctuations without selective drive, has been a focus of research since the seminal work of Kimura on genetic drift. This problem, which has received increased attention due to the recent development of a neutral ecological theory by Hubbell, bears comparison with mathematical problems such as percolation and branching and coalescing random walks. I will discuss an agent-based computational model in which clustering (speciation) occurs on a neutral phenotype landscape. This model corresponds to sympatric speciation: organisms cluster phenotypically, but are not spatially separated. Moreover, clustering occurs not only in the case of assortative mating, but also in the case of asexual fission (bacterial splitting). In contrast, clusters fail to form in a control case where organisms mate randomly. The population size and the number of clusters (species) undergo a critical phase transition, most likely of the directed percolation universality class, as the maximum mutation size is varied, and cluster size appears to undergo a percolation transition.

Recent advancements in computational fluid dynamics have enabled researchers to efficiently explore problems that involve moving elastic boundaries immersed in fluids for problems such as cardiac fluid dynamics, fish swimming, and the movement of bacteria. These advances have also made modeling the interaction between a fluid and an electromechanical model of an elastic organ feasible. The tubular hearts of some ascidians and vertebrate embryos offers a relatively simple model organ for such a study. Blood is driven through the heart by either peristaltic contractions or valveless suction pumping through localized periodic contractions. Models considering only the fluid-structure interaction aspects of these hearts are insufficient to resolve the actual pumping mechanism. The electromechanical model presented here will integrate feedback between the conduction of action potentials, the contraction of muscles, the movement of tissues, and the resulting fluid motion.

Granular materials exhibit large spatial variations in their response to external loading, whether static or dynamic. As such, continuum models of properties such as the shear modulus and sound speed often fail. A promising alternative is to build an understanding of bulk behaviors from measurements at the particle scale, by analogy with the statistical mechanics of thermal systems. I will describe experiments in which we utilize photoelastic particles and piezo-embedded 'smart' particles to explore how two familiar properties -- temperature equilibration and densities of states -- might arise in this new context.

Cancer continues to elude us. Metastasis, relapse and drug resistance are all still poorly understood and clinically insuperable. Evidently, the prevailing paradigms need to be re-examined and out-of-the-box ideas ought to be explored. Recently, has become acknowledged that transformative convergence of physical sciences with life sciences can bring forth new perspectives for addressing major questions and challenges relating to cancer. Drawing upon recent discoveries demonstrating the parallels between collective behaviors of bacteria and cancer, I will present a new picture of cancer as a society of smart communicating cells motivated by the realization of bacterial social intelligence. There is growing evidence that cancer cells, much like bacteria do, rely on advanced communication, social networking and cooperation to grow, spread within the body, colonize new organs, relapse and develop drug resistance. I will address the role of communication, cooperation and decision-making in bacterial collective navigation, swarming logistics and colony development. This will lead to a new picture of cancer cell migration, metastasis colonization and cell fate determination. I will reason that the new understanding calls for “cyber war” on cancer – the developments of drugs to target cancer communication and control.

“Bacterial linguistic communication and social intelligence”

http://www.cell.com/trends/microbiology/abstract/S0966-842X(04)00138-6

 
"Bacterial survival strategies suggest rethinking cancer cooperativity"

 http://www.cell.com/trends/microbiology/abstract/S0966-842X(12)00101-1

 PLEASE NOTE: This is a WEBINAR

More than 125 years ago Osborne Reynolds launched the quantitative study of turbulent transition as he sought to understand the conditions under which fluid flowing through a pipe would be laminar or turbulent. Since laminar and turbulent flow have vastly different drag laws, this question is as important now as it was in Reynolds' day.  Reynolds understood how one should define ``the real critical value'' for the fluid velocity beyond which turbulence can persist indefinitely.  He also appreciated the difficulty in obtaining this value.  For years this critical Reynolds number, as we now call it, has been the subject of study, controversy, and uncertainty. Now, more than a century after Reynolds pioneering work, we know that the onset of turbulence in shear flows is properly understood as a statistical phase transition.  How turbulence first develops in these flows is more closely related to the onset of an infectious disease than to, for example, the onset of oscillation in the flow past a body or the onset of motion in a fluid layer heated from below.  Through the statistical analysis of large samples of individual decay and proliferation events, we at last have an accurate estimate of the real critical Reynolds number for the onset of turbulence in pipe flow, and with it, an understanding of the nature of transitional turbulence.

For many investigations like astronomical observations in various electromagnetic windows, atmospheric and high altitude research, it is necessary to reach the top of the atmosphere. Balloons have been used as a carrier for a long time. The Tata Institute of Fundamental Research has conducted regular balloon flights for over 60 years and operates the National Balloon Facility in Hyderabad. This facility has been used by Indian and international groups for a variety of investigations. Balloons provide a cost effective means for space research by a small group of scientists. I will talk about the adventures of ballooning with special reference to the flights conducted by TIFR. I will show slides of various aspects of the fabrication, launch and recovery operations and also show some of the instruments flown. I'll briefly talk about long duration flights. I'll conclude by showing a short video clip.