BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//CMSA - ECPv6.17.1//NONSGML v1.0//EN
CALSCALE:GREGORIAN
METHOD:PUBLISH
X-ORIGINAL-URL:https://cmsa.fas.harvard.edu
X-WR-CALDESC:Events for CMSA
REFRESH-INTERVAL;VALUE=DURATION:PT1H
X-Robots-Tag:noindex
X-PUBLISHED-TTL:PT1H
BEGIN:VTIMEZONE
TZID:America/New_York
BEGIN:DAYLIGHT
TZOFFSETFROM:-0500
TZOFFSETTO:-0400
TZNAME:EDT
DTSTART:20210314T070000
END:DAYLIGHT
BEGIN:STANDARD
TZOFFSETFROM:-0400
TZOFFSETTO:-0500
TZNAME:EST
DTSTART:20211107T060000
END:STANDARD
BEGIN:DAYLIGHT
TZOFFSETFROM:-0500
TZOFFSETTO:-0400
TZNAME:EDT
DTSTART:20220313T070000
END:DAYLIGHT
BEGIN:STANDARD
TZOFFSETFROM:-0400
TZOFFSETTO:-0500
TZNAME:EST
DTSTART:20221106T060000
END:STANDARD
BEGIN:DAYLIGHT
TZOFFSETFROM:-0500
TZOFFSETTO:-0400
TZNAME:EDT
DTSTART:20230312T070000
END:DAYLIGHT
BEGIN:STANDARD
TZOFFSETFROM:-0400
TZOFFSETTO:-0500
TZNAME:EST
DTSTART:20231105T060000
END:STANDARD
END:VTIMEZONE
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220707T090000
DTEND;TZID=America/New_York:20220707T100000
DTSTAMP:20240229T085211Z
CREATED:20240215T094540Z
LAST-MODIFIED:20240229T085211Z
UID:10002727-1657184400-1657188000@cmsa.fas.harvard.edu
SUMMARY:The phenotype of the last universal common ancestor and the evolution of complexity
DESCRIPTION:Interdisciplinary Science Seminar\n\n\n\n\n\nSpeaker: Fouad El Baidouri\, Broad Institute \nTitle: The phenotype of the last universal common ancestor and the evolution of complexity \nAbstract: A fundamental concept in evolutionary theory is the last universal common ancestor (LUCA) from which all living organisms originated. While some authors have suggested a relatively complex LUCA it is still widely assumed that LUCA must have been a very simple cell and that life has subsequently increased in complexity through time. However\, while current thought does tend towards a general increase in complexity through time in Eukaryotes\, there is increasing evidence that bacteria and archaea have undergone considerable genome reduction during their evolution. This raises the surprising possibility that LUCA\, as the ancestor of bacteria and archaea may have been a considerably complex cell. While hypotheses regarding the phenotype of LUCA do exist\, all are founded on gene presence/absence. Yet\, despite recent attempts to link genes and phenotypic traits in prokaryotes\, it is still inherently difficult to predict phenotype based on the presence or absence of genes alone. In response to this\, we used Bayesian phylogenetic comparative methods to predict ancestral traits. Testing for robustness to horizontal gene transfer (HGT) we inferred the phenotypic traits of LUCA using two robust published phylogenetic trees and a dataset of 3\,128 bacterial and archaeal species. \nOur results depict LUCA as a far more complex cell than has previously been proposed\, challenging the evolutionary model of increased complexity through time in prokaryotes. Given current estimates for the emergence of LUCA we suggest that early life very rapidly evolved cellular complexity.
URL:https://cmsa.fas.harvard.edu/event/iss_7722/
CATEGORIES:Interdisciplinary Science Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220714T090000
DTEND;TZID=America/New_York:20220714T100000
DTSTAMP:20240301T101549Z
CREATED:20240214T091545Z
LAST-MODIFIED:20240301T101549Z
UID:10002614-1657789200-1657792800@cmsa.fas.harvard.edu
SUMMARY:Topological and geometrical aspects of spinors in insulating crystals
DESCRIPTION:Abstract:  Introducing internal degrees of freedom in the description of crystalline insulators has led to a myriad of theoretical and experimental advances. Of particular interest are the effects of periodic perturbations\, either in time or space\, as they considerably enrich the variety of electronic responses. Here\, we present a semiclassical approach to transport and accumulation of general spinor degrees of freedom in adiabatically driven\, weakly inhomogeneous crystals of dimensions one\, two and three under external electromagnetic fields. Our approach shows that spatio-temporal modulations of the system induce a spinor current and density that is related to geometrical and topological objects — the spinor-Chern fluxes and numbers — defined over the higher-dimensional phase-space of the system\, i.e.\, its combined momentum-position-time coordinates. \nThe results are available here: https://arxiv.org/abs/2203.14902 \nBio: Ioannis Petrides is a postdoctoral fellow at the School of Engineering and Applied Sciences at Harvard University. He received his Ph.D. from the Institute for Theoretical Physics at ETH Zurich. His research focuses on the topological and geometrical aspects of condensed matter systems.
URL:https://cmsa.fas.harvard.edu/event/7-14-2022-interdisciplinary-science-seminar/
CATEGORIES:Interdisciplinary Science Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Interdisciplinary-Science-Seminar-07.14.22-1583x2048-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220721T090000
DTEND;TZID=America/New_York:20220721T100000
DTSTAMP:20240301T092042Z
CREATED:20240214T111802Z
LAST-MODIFIED:20240301T092042Z
UID:10002694-1658394000-1658397600@cmsa.fas.harvard.edu
SUMMARY:Infants’ sensory-motor cortices undergo microstructural tissue growth coupled with myelination
DESCRIPTION:Abstract: The establishment of neural circuitry during early infancy is critical for developing visual\, auditory\, and motor functions. However\, how cortical tissue develops postnatally is largely unknown. By combining T1 relaxation time from quantitative MRI and mean diffusivity (MD) from diffusion MRI\, we tracked cortical tissue development in infants across three timepoints (newborn\, 3 months\, and 6 months). Lower T1 and MD indicate higher microstructural tissue density and more developed cortex. Our data reveal three main findings: First\, primary sensory-motor areas (V1: visual\, A1: auditory\, S1: somatosensory\, M1: motor) have lower T1 and MD at birth than higher-level cortical areas. However\, all primary areas show significant reductions in T1 and MD in the first six months of life\, illustrating profound tissue growth after birth. Second\, significant reductions in T1 and MD from newborns to 6-month-olds occur in all visual areas of the ventral and dorsal visual streams. Strikingly\, this development was heterogenous across the visual hierarchies: Earlier areas are more developed with denser tissue at birth than higher-order areas\, but higher-order areas had faster rates of development. Finally\, analysis of transcriptomic gene data that compares gene expression in postnatal vs. prenatal tissue samples showed strong postnatal expression of genes associated with myelination\, synaptic signaling\, and dendritic processes. Our results indicate that these cellular processes may contribute to profound postnatal tissue growth in sensory cortices observed in our in-vivo measurements. We propose a novel principle of postnatal maturation of sensory systems: development of cortical tissue proceeds in a hierarchical manner\, enabling the lower-level areas to develop first to provide scaffolding for higher-order areas\, which begin to develop more rapidly following birth to perform complex computations for vision and audition. \nThis work is published here: https://www.nature.com/articles/s42003-021-02706-w
URL:https://cmsa.fas.harvard.edu/event/7-21-2022-interdisciplinary-science-seminar/
CATEGORIES:Interdisciplinary Science Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220728T090000
DTEND;TZID=America/New_York:20220728T100000
DTSTAMP:20240229T084527Z
CREATED:20240215T094315Z
LAST-MODIFIED:20240229T084527Z
UID:10002726-1658998800-1659002400@cmsa.fas.harvard.edu
SUMMARY:Statistical Mechanical theory for spatio-temporal evolution of Intra-tumor heterogeneity in cancers: Analysis of Multiregion sequencing data
DESCRIPTION:CMSA Interdisciplinary Science Seminar \nSpeaker: Sumit Sinha\, Harvard University \nTitle: Statistical Mechanical theory for spatio-temporal evolution of Intra-tumor heterogeneity in cancers: Analysis of Multiregion sequencing data (https://arxiv.org/abs/2202.10595) \nAbstract: Variations in characteristics from one region (sub-population) to another are commonly observed in complex systems\, such as glasses and a collection of cells. Such variations are manifestations of heterogeneity\, whose spatial and temporal behavior is hard to describe theoretically. In the context of cancer\, intra-tumor heterogeneity (ITH)\, characterized by cells with genetic and phenotypic variability that co-exist within a single tumor\, is often the cause of ineffective therapy and recurrence of cancer. Next-generation sequencing\, obtained by sampling multiple regions of a single tumor (multi-region sequencing\, M-Seq)\, has vividly demonstrated the pervasive nature of ITH\, raising the need for a theory that accounts for evolution of tumor heterogeneity. Here\, we develop a statistical mechanical theory to quantify ITH\, using the Hamming distance\, between genetic mutations in distinct regions within a single tumor. An analytic expression for ITH\, expressed in terms of cell division probability (α) and mutation probability (p)\, is validated using cellular-automaton type simulations. Application of the theory successfully captures ITH extracted from M-seq data in patients with exogenous cancers (melanoma and lung). The theory\, based on punctuated evolution at the early stages of the tumor followed by neutral evolution\, is accurate provided the spatial variation in the tumor mutation burden is not large. We show that there are substantial variations in ITH in distinct regions of a single solid tumor\, which supports the notion that distinct subclones could co-exist. The simulations show that there are substantial variations in the sub-populations\, with the ITH increasing as the distance between the regions increases. The analytical and simulation framework developed here could be used in the quantitative analyses of the experimental (M-Seq) data. More broadly\, our theory is likely to be useful in analyzing dynamic heterogeneity in complex systems such as supercooled liquids. \nBio: I am a postdoctoral fellow in Harvard SEAS (Applied Mathematics) and Dana Farber Cancer Institute (Data Science) beginning Feb 2022. I finished my PhD in Physics (Theoretical Biophysics) from UT Austin (Jan 2022) on “Theoretical and computational studies of growing tissue”.  I pursued my undergraduate degree in Physics from the Indian Institute of Technology\, Kanpur in India (2015). Boradly\, I am interested in developing theoretical models\, inspired from many-body statistical physics\, for biological processes at different length and time scales. \n 
URL:https://cmsa.fas.harvard.edu/event/iss_72822/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Interdisciplinary Science Seminar
END:VEVENT
END:VCALENDAR