Nanoelectromechanical Membranes for Multimode Mass Spectrometry

Nanoelectromechanical systems (NEMS) represent the next wave in miniaturizing various electrical and mechanical devices used in a variety of fields, such as physics, biology, and engineering. In particular, NEMS devices have high surface area to volume ratios, low power consumption, low mass, and extremely small footprints. These properties allow NEMS to explore more fundamental regimes of matter. Current NEMS mass spectrometry advancements have only utilized doubly-clamped beams and cantilevers. However to expand the measurement capabilities of NEMS mass spectrometry, we utilize a circular membrane geometry in order to build upon the existing measurements in 1 spatial dimension to measure mass spatially in 2-dimensions. Furthermore, membranes should provide a larger potential mass dynamic range. For this experiment, we utilize circular piezoelectric membranes of aluminum nitride and molybdenum stacks. For mass deposition, we utilize a technique known as matrix-assisted laser desorption/ionization (MALDI), which focuses a pulsed UV laser onto the desired sample embedded in a corresponding matrix. The energy causes a plume of particles to desorb off the sample and towards the device. As a particle lands on the device, we are able to deduce its mass from the shift in its resonant frequency. In particular we need to measure the first three resonant frequencies, since the frequency shifts also depend on the location the particle landed on the device. Here we show the viability of our detection setup, mass deposition setup, and our mass deposition results

N=1N=1 formal genus 00 Gromov-Witten theories and Givental's formalism

In [Gi3] Givental introduced and studied a space of formal genus zero Gromov-Witten theories $GW_0$, i.e. functions satisfying string and dilaton equations and topological recursion relations. A central role in the theory plays the geometry of certain Lagrangian cones and a twisted symplectic group of hidden symmetries. In this note we show that the Lagrangian cones description of the action of this group coincides with the genus zero part of Givental's quantum Hamiltonian formalism. As an application we identify explicitly the space of $N=1$ formal genus zero GW theories with lower-triangular twisted symplectic group modulo the string flow.Comment: 15 page