In situ characterization of vertically oriented carbon nanofibers for three-dimensional nano-electro-mechanical device applications

We have performed mechanical and electrical characterization of individual as-grown, vertically oriented carbon nanofibers (CNFs) using in situ techniques, where such high-aspect-ratio, nanoscale structures are of interest for three-dimensional (3D) electronics, in particular 3D nano-electro-mechanical-systems (NEMS). Nanoindentation and uniaxial compression tests conducted in an in situ nanomechanical instrument, SEMentor, suggest that the CNFs undergo severe bending prior to fracture, which always occurs close to the bottom rather than at the substrate–tube interface, suggesting that the CNFs are well adhered to the substrate. This is also consistent with bending tests on individual tubes which indicated that bending angles as large as ~70° could be accommodated elastically. In situ electrical transport measurements revealed that the CNFs grown on refractory metallic nitride buffer layers were conducting via the sidewalls, whereas those synthesized directly on Si were electrically unsuitable for low-voltage dc NEMS applications. Electrostatic actuation was also demonstrated with a nanoprobe in close proximity to a single CNF and suggests that such structures are attractive for nonvolatile memory applications. Since the magnitude of the actuation voltage is intimately dictated by the physical characteristics of the CNFs, such as diameter and length, we also addressed the ability to tune these parameters, to some extent, by adjusting the plasma-enhanced chemical vapor deposition growth parameters with this bottom-up synthesis approach

Systematic Analysis Method for Color Transparency Experiments

We introduce a data analysis procedure for color transparency experiments which is considerably less model dependent than the transparency ratio method. The new method is based on fitting the shape of the A dependence of the nuclear cross section at fixed momentum transfer to determine the effective attenuation cross section for hadrons propagating through the nucleus. The procedure does not require assumptions about the hard scattering rate inside the nuclear medium. Instead, the hard scattering rate is deduced directly from the data. The only theoretical input necessary is in modelling the attenuation due to the nuclear medium, for which we use a simple exponential law. We apply this procedure to the Brookhaven experiment of Carroll et al and find that it clearly shows color transparency: the effective attenuation cross section in events with momentum transfer $Q^2$ is approximately $40\ mb\ (2.2\ GeV^2/Q^2)$. The fit to the data also supports the idea that the hard scattering inside the nuclear medium is closer to perturbative QCD predictions than is the scattering of isolated protons in free space. We also discuss the application of our approach to electroproduction experiments.Comment: 11 pages, 11 figures (figures not included, available upon request), report # KU-HEP-92-2

The cost of solving linear differential equations on a quantum computer: fast-forwarding to explicit resource counts

How well can quantum computers simulate classical dynamical systems? There is increasing effort in developing quantum algorithms to efficiently simulate dynamics beyond Hamiltonian simulation, but so far exact running costs are not known. In this work, we provide two significant contributions. First, we provide the first non-asymptotic computation of the cost of encoding the solution to linear ordinary differential equations into quantum states -- either the solution at a final time, or an encoding of the whole history within a time interval. Second, we show that the stability properties of a large class of classical dynamics can allow their fast-forwarding, making their quantum simulation much more time-efficient. We give a broad framework to include stability information in the complexity analysis and present examples where this brings several orders of magnitude improvements in the query counts compared to state-of-the-art analysis. From this point of view, quantum Hamiltonian dynamics is a boundary case that does not allow this form of stability-induced fast-forwarding. To illustrate our results, we find that for homogeneous systems with negative log-norm, the query counts lie within the curves $11900 \sqrt{T} \log(T)$ and $10300 T \log(T)$ for $T \in [10^6, 10^{15}]$ and error $\epsilon = 10^{-10}$, when outputting a history state.Comment: 8+22 pages, 3 figures. Comments welcome

Surface Tension at Finite Tempearture in the MIT Bag Model

At $T = 0$ the surface tension $\sigma ^{1/3}$ in the MIT bag model for a single hadron is known to be negligible as compared to the bag pressure $B^{1/4}$. We show that at finite temperature it has a substantial value of 50 - 70 MeV which also differ from hadron to hadron. We also find that the dynamics of the Quark-Gluon Plasma is such that the creation of hybrids $(s\bar{s}g)$ with massive quarks will predominate over the creation of $(s\bar{s})$ mesons.Comment: Substantial changes in the revised version and a new author included, 13 pages in Latex and one figur

Product assurance technology for custom LSI/VLSI electronics

The technology for obtaining custom integrated circuits from CMOS-bulk silicon foundries using a universal set of layout rules is presented. The technical efforts were guided by the requirement to develop a 3 micron CMOS test chip for the Combined Release and Radiation Effects Satellite (CRRES). This chip contains both analog and digital circuits. The development employed all the elements required to obtain custom circuits from silicon foundries, including circuit design, foundry interfacing, circuit test, and circuit qualification

Variação demográfica causada por exploração florestal no banco de mudas de espécies florestais em resposta a diferentes tamanhos de aberturas no dossel da floresta.

bitstream/item/57644/1/CPATU-PA170.pd

Banco de sementes de floresta tropical úmida no município de Moju, PA.

bitstream/item/57772/1/CPATU-PA185.pd

Monolithically Integrated, Mechanically Resilient Carbon-Based Probes for Scanning Probe Microscopy

Scanning probe microscopy (SPM) is an important tool for performing measurements at the nanoscale in imaging bacteria or proteins in biology, as well as in the electronics industry. An essential element of SPM is a sharp, stable tip that possesses a small radius of curvature to enhance spatial resolution. Existing techniques for forming such tips are not ideal. High-aspect-ratio, monolithically integrated, as-grown carbon nanofibers (CNFs) have been formed that show promise for SPM applications by overcoming the limitations present in wet chemical and separate substrate etching processes

Poly[3-methyl­pyridinium [(μ2-di­hydrogen phosphito)bis­(μ3-hydrogen phosphito)dizinc]]

Peer reviewe