Tutorial to SARAH

I give in this brief tutorial a short practical introduction to the Mathematica package SARAH. First, it is shown how an existing model file can be changed to implement a new model in SARAH. In the second part, masses, vertices and renormalisation group equations are calculated with SARAH. Finally, the main commands to generate model files and output for other tools are summarised.Comment: 8 pages, 1 figure; Tutorial (based on lecture arXiv:1509.07061) given at "School and Workshops on Elementary Particle Physics and Gravity", Corfu Summer Institute, September 201

Automatic Calculation of supersymmetric Renormalization Group Equations and Self Energies

SARAH is a Mathematica package for studying supersymmetric models. It calculates for a given model the masses, tadpole equations and all vertices at tree-level. Those information can be used by \SARAH to write model files for CalcHep/CompHep or FeynArts/FormCalc. In addition, the second version of SARAH can derive the renormalization group equations for the gauge couplings, parameters of the superpotential and soft-breaking parameters at one and two-loop level. Furthermore, it calculates the one-loop self energies and the one-loop corrections to the tadpoles. SARAH can handle all N=1 SUSY models whose gauge sector is a direct product of SU(N) and U(1) gauge groups. The particle content of the model can be an arbitrary number of chiral superfields transforming as any irreducible representation with respect to the gauge groups. To implement a new model, the user has just to define the gauge sector, the particle, the superpotential and the field rotations to mass eigenstates.Comment: 32 pages, some typoes corrected, matches published versio

For youth, by youth: a third student-run homeless shelter

This past winter, the third student-run homeless shelter in the United States came into being. Two recent Harvard graduates, Sam Greenberg and Sarah Rosenkrantz, who had volunteered at the Harvard Square Homeless Shelter as college students, saw a need within the Boston and Cambridge communities for a homeless shelter serving young adults. Drawing upon the Harvard Square Homeless Shelter’s student-run model, Sam and Sarah worked with Harvard College undergraduates to open Youth-to-Youth (Y2Y) Harvard Square, a homeless shelter exclusively for young adults ages 18–24. This article features an interview with Sam and Sarah about their work to establish Y2Y Harvard Square and the experiences of the college students leading and staffing the shelter

Retaliation

Prose by Sarah Coffing

Selected Poems

Selected poems by Sarah Jackson

Vista

Poetry by Sarah Switze

Merry Christimas, Papa

Prose by Sarah Coffing

Organic electrode coatings for next-generation neural interfaces

Traditional neuronal interfaces utilize metallic electrodes which in recent years have reached a plateau in terms of the ability to provide safe stimulation at high resolution or rather with high densities of microelectrodes with improved spatial selectivity. To achieve higher resolution it has become clear that reducing the size of electrodes is required to enable higher electrode counts from the implant device. The limitations of interfacing electrodes including low charge injection limits, mechanical mismatch and foreign body response can be addressed through the use of organic electrode coatings which typically provide a softer, more roughened surface to enable both improved charge transfer and lower mechanical mismatch with neural tissue. Coating electrodes with conductive polymers or carbon nanotubes offers a substantial increase in charge transfer area compared to conventional platinum electrodes. These organic conductors provide safe electrical stimulation of tissue while avoiding undesirable chemical reactions and cell damage. However, the mechanical properties of conductive polymers are not ideal, as they are quite brittle. Hydrogel polymers present a versatile coating option for electrodes as they can be chemically modified to provide a soft and conductive scaffold. However, the in vivo chronic inflammatory response of these conductive hydrogels remains unknown. A more recent approach proposes tissue engineering the electrode interface through the use of encapsulated neurons within hydrogel coatings. This approach may provide a method for activating tissue at the cellular scale, however, several technological challenges must be addressed to demonstrate feasibility of this innovative idea. The review focuses on the various organic coatings which have been investigated to improve neural interface electrodes