Zero sound modes in the AdS/CFT correspondence

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 41-42).We examine the effects of zero sound wave excitations of charged fermion species living around the charged black hole of an AdS/CFT spacetime. In particular, we show that these bulk modes cause corresponding singularities in the correlation functions of boundary gauge fields. Possible implications for the study of non-Fermi liquids are discussed.by Thomas Roxlo.S.B

Advances in Non-Invasive Blood Pressure Monitoring

This paper reviews recent advances in non-invasive blood pressure monitoring and highlights the added value of a novel algorithm-based blood pressure sensor which uses machine-learning techniques to extract blood pressure values from the shape of the pulse waveform. We report results from preliminary studies on a range of patient populations and discuss the accuracy and limitations of this capacitive-based technology and its potential application in hospitals and communities

Quantum Optics and Electronics

Contains reports on three research projects.U.S. Air Force - Office of Scientific Research (Contract F49620-79-C-0071)Joint Services Electronics Program (Contract DAAG29-78-C-0020)Joint Services Electronics Program (Contract DAAG29-80-C-0104)U.S. Navy - Office of Naval Research (Contract N00014-79-C-0694

Surfactant-aided exfoliation of molybdenum disulfide for ultrafast pulse generation through edge-state saturable absorption

We use liquid phase exfoliation to produce dispersions of molybdenum disulphide (MoS2) nanoflakes in aqueous surfactant solutions. The chemical structures of the bile salt surfactants play a crucial role in the exfoliation and stabilization of MoS2. The resultant MoS2 dispersions are heavily enriched in single and few (<6) layer flakes with large edge to surface area ratio. We use the dispersions to fabricate free-standing polymer composite wide-band saturable absorbers to develop mode-locked and Q- switched fibre lasers, tunable from 1535-1565 and 1030-1070 nm, respectively. We attribute this sub-bandgap optical absorption and its nonlinear saturation behaviour to edge-mediated states introduced within the material band-gap of the exfoliated MoS2 nanoflakes.EJRK and TH acknowledge support from the Royal Academy of Engineering (RAEng).This is the author accepted manuscript. The final version is available from Wiley via http://dx.doi.org/10.1002/pssb.20155230

Probing the local nature of excitons and plasmons in few-layer MoS₂

Excitons and plasmons are the two most fundamental types of collective electronic excitations occurring in solids. Traditionally, they have been studied separately using bulk techniques that probe their average energetic structure over large spatial regions. However, as the dimensions of materials and devices continue to shrink, it becomes crucial to understand how these excitations depend on local variations in the crystal- and chemical structure on the atomic scale. Here, we use monochromated low-loss scanning-transmission-electron-microscopy electron-energy-loss spectroscopy, providing the best simultaneous energy and spatial resolution achieved to-date to unravel the full set of electronic excitations in few-layer MoS₂ nanosheets over a wide energy range. Using first-principles, many-body calculations we confirm the excitonic nature of the peaks at ~ 2 and ~ 3 eV in the experimental electron-energy-loss spectrum and the plasmonic nature of higher energy-loss peaks. We also rationalise the non-trivial dependence of the electron-energy-loss spectrum on beam and sample geometry such as the number of atomic layers and distance to steps and edges. Moreover, we show that the excitonic features are dominated by the long wavelength (q = 0) components of the probing field, while the plasmonic features are sensitive to a much broader range of q-vectors, indicating a qualitative difference in the spatial character of the two types of collective excitations. Our work provides a template protocol for mapping the local nature of electronic excitations that open new possibilities for studying photo-absorption and energy transfer processes on a nanometer scale

Molybdenum/cobalt/sulfur clusters: Models and precursors for hydrodesulfurization (HDS) catalysts

Sulfido clusters which incorporate molybdenum and a late transition metal, e.g. iron, cobalt or nickel, are readily prepared by the reactions of Cp 2 Mo 2 S 4 , Cp 2 Mo 2 S 2 (SR) 2 or Cp 2 Mo 2 (CO) 2 (SR) 2 with Fe 2 (CO) 9 , Co 2 (CO) 8 , Ni(CO) 4 , Cp 2 Ni, etc. The homogeneous reactions of the cluster Cp 2 Mo 2 Co 2 S 3 (CO) 4 with thiols, thiophene, and phosphines are reviewed, as are some reactions of the clusters with metal oxide surfaces to produce heterogeneous catalysts for CO hydrogenation or hydrodesulfurization.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/38296/1/590060504_ftp.pd