אפריל 29, 2015
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Date:26ראשוןאפריל 201529רביעיאפריל 2015כנסים
Cortical Development in Health and Disease
More information שעה 08:00 - 18:00מיקום מרכז כנסים על-שם דויד לופאטי
Kimmel Auditoriumיושב ראש Orly Reinerדף בית צרו קשר -
Date:29רביעיאפריל 2015הרצאה
Cell competition and Tumorigenesis
More information שעה 10:00מיקום בניין ארתור ורושל בלפר למחקר ביורפואי
Botnar Auditoriumמרצה Dr. Gines Morata
Centro de Biología Molecular, CSIC-UAM, Universidad Autónoma de Madrid, Spainמארגן מדעי החייםצרו קשר -
Date:29רביעיאפריל 2015הרצאה
Turbulent Magnetic Field Amplification in Young Galaxies
More information שעה 10:15 - 11:15מיקום מעבדה על-שם דני נ. היינמן
Benoziyo Center for Astrophysics Seminar Roomמרצה Jennifer Schoberמארגן מרכז לאסטרופיסיקה עש נלה וליאון בנוזיוצרו קשר תקציר Show full text abstract about Magnetic fields play an important role in present-day galaxi...» Magnetic fields play an important role in present-day galaxies, for instance by influencing the star formation process. In models of young galaxies magnetic fields are usually not considered as they were assumed not to be dynamical important at high redshifts. In the presence of turbulence, however, the small-scale or turbulent dynamo can amplify weak magnetic seed fields by randomly stretching, twisting, and folding the field lines. The details of this process depend on the nature of turbulence, i.e. on the hydrodynamic and magnetic Reynolds numbers, and on the compressibility of the gas. In my talk I will introduce the basics of the turbulent dynamo and sketch our recent progress in describing it analytically and numerically. With a model of a typical young galaxy, where turbulence is driven by accretion and by supernova explosions, we determine the growth rate of the small-scale dynamo. We follow the exponential growth of the magnetic field on the viscous scale and also the subsequent transport of the magnetic energy to larger scales in the non-linear dynamo phase. Depending on the parameters of our model we find that equipartition of magnetic and kinetic energy, which corresponds to a field strength of roughly 10^(-5) G, is reached within 4 to 270 Myr. Thus, we expect that the turbulent dynamo can generate strong unordered fields already in very young galaxies which should be considered in future models of galaxy evolution. -
Date:29רביעיאפריל 2015סימפוזיונים
Special Chemistry Colloquium - "Bond, Chemical Bond"
More information שעה 11:00 - 12:30מיקום אולם הרצאות ע"ש גרהרד שמידטמרצה Prof. Wilson Ho
Department of Physics and Astronomy, University of California/USAמארגן הפקולטה לכימיהצרו קשר -
Date:29רביעיאפריל 2015הרצאה
Deviation from identity of macroscopic properties of enantiomers –via water chiral preference. (Is water chiral?)
More information שעה 14:00מיקום בניין פרלמן למדעי הכימיה
Room 404מרצה Dr. Yosef Scolnik
IYAR (Israel Institute for Advanced Research). Weizmann Instituteמארגן המחלקה לכימיה מולקולרית ולמדע חומריםצרו קשר פרטים נוספים Show full text description of Abstract Mirror-image asymmetric molecules, i.e. enantiomer...» Abstract
Mirror-image asymmetric molecules, i.e. enantiomers, are classically considered as chemically identical. Parity violation by the nuclear weak force induces a tiny energy difference between chiral isomers. Upon combination with a massive amplification process, expansion of this difference to a detectable macroscopic level may be achieved. In our studies we have prove this in several systems: Stearoylserine "quasi peptide" formation
Solubility and cluster formation of Alanine
Peptide Transitions to alpha –helix, shortly described hereafter and others
We compared structural and dynamic features of synthetic D- and L-polyglutamic acid and polylysine molecules each of 24 identical residues. The helix and random coil configurations and their transition were determined in this study by circular dichroism (CD) and isothermal titration calorimetry (ITC) in water and deuterium oxide. Distinct differences in structure and transition energies between the enantiomer polypeptides were detected by both CD and ITC when dissolved in water. Intriguingly, these differences were by and large abolished in deuterium oxide. Our findings suggest that deviation from physical invariance between the D- and L-polyamino acids is induced in part by different hydration in water which is eliminated in deuterium oxide. We suggest that ortho-H2O, which constitutes 75% of bulk H2O, has a preferential affinity to L-enantiomers.In other words, these studies, prove that indeed water has chiral preferences, Accordingly, Heavy Water has no chiral preference. Differential hydration of enantiomers may have played a role in the selection of L-amino acids by early forms of life.
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Date:29רביעיאפריל 2015הרצאה
Investigations of Implosions on the National Ignition Facility and discussion on the fusion yield from NIF
More information שעה 15:15מיקום בניין הפיסיקה ע"ש עדנה וק.ב. וייסמן
Drory Auditoriumמרצה H. A. Scott, B. A. Hammel
Lawrence Livermore National Laboratory, Livermore, CA USAמארגן המחלקה לפיסיקה של חלקיקים ואסטרופיסיקה
Plasma Seminarצרו קשר פרטים נוספים Show full text description of 15:00 – Light refreshments ...» 15:00 – Light refreshmentsתקציר Show full text abstract about Hydrodynamic instabilities are a primary impediment to the s...» Hydrodynamic instabilities are a primary impediment to the success of inertial confinement fusion (ICF), as they can severely degrade capsule performance [1]. Even with perfectly smooth capsules, the fill tube and capsule support provide perturbations that seed instabilities. Consequently,
understanding the evolution of perturbations and their effects on capsule performance is critical to the success of an ICF program. We discuss here the use of spectroscopic methods to diagnose the growth of hydrodynamic instabilities in imploding capsules. To understand capsule evolution and guide experimental design and interpretation, we use high-resolution HYDRA [2] simulations, postprocessed with Cretin [3], to simulate the spectra produced by capsules with specified initial perturbations. The
spectral simulations cover a wide range of conditions, from the multi-keV hot spot to the cold dense pusher.
For capsules with mid-Z dopants, the resulting X-ray spectrum can be analyzed to obtain information about the plasma conditions. An analysis of the dopant K-shell line emission has been used to estimate the mass of ablator material mixed into the hot spot [4]. Other spectral features can be used to provide information about the shell and further constrain the mixed mass. Other recent work has focused on using spectroscopy to quantitatively characterize the growth of perturbations. Capsules containing a small amount of argon in the gas produce sufficient emission before peak compression to provide radiographic information. The analysis of simulated spectra from capsules with machined perturbations demonstrates the possibility of extracting quantitative measures of perturbation growth.
References
[1] B.A. Hammel, et al, High Energy Density Physics, 6 (2010) 171.
[2] M. Marinak, et al, Phys. Plasmas 8 (2001) 2275.
[3] H.A. Scott, J Quant Spectrosc Radiat Transfer 71 (2001) 681.
[4] S.P. Regan et al. Phys. Rev, Lett. 111, 045001 (2013).