14,886 research outputs found
Laser extensometer
A drift compensated and intensity averaged extensometer for measuring the diameter or other properties of a substantially cylindrical sample based upon the shadow of the sample is described. A beam of laser light is shaped to provide a beam with a uniform intensity along an axis normal to the sample. After passing the sample, the portion of the beam not striking said sample is divided by a beam splitter into a reference signal and a measurement signal. Both of these beams are then chopped by a light chopper to fall upon two photodiode detectors. The resulting ac currents are rectified and then divided into one another, with the final output being proportional to the size of the sample shadow
An approach to market analysis for lighter than air transportation of freight
An approach is presented to marketing analysis for lighter than air vehicles in a commercial freight market. After a discussion of key characteristics of supply and demand factors, a three-phase approach to marketing analysis is described. The existing transportation systems are quantitatively defined and possible roles for lighter than air vehicles within this framework are postulated. The marketing analysis views the situation from the perspective of both the shipper and the carrier. A demand for freight service is assumed and the resulting supply characteristics are determined. Then, these supply characteristics are used to establish the demand for competing modes. The process is then iterated to arrive at the market solution
Superconductor-Nanowire Devices from Tunneling to the Multichannel Regime: Zero-Bias Oscillations and Magnetoconductance Crossover
We present transport measurements in superconductor-nanowire devices with a
gated constriction forming a quantum point contact. Zero-bias features in
tunneling spectroscopy appear at finite magnetic fields, and oscillate in
amplitude and split away from zero bias as a function of magnetic field and
gate voltage. A crossover in magnetoconductance is observed: Magnetic fields
above ~ 0.5 T enhance conductance in the low-conductance (tunneling) regime but
suppress conductance in the high-conductance (multichannel) regime. We consider
these results in the context of Majorana zero modes as well as alternatives,
including Kondo effect and analogs of 0.7 structure in a disordered nanowire.Comment: Supplemental Material here:
https://dl.dropbox.com/u/1742676/Churchill_Supplemental.pd
In-vivo magnetic resonance imaging of hyperpolarized silicon particles
Silicon-based micro and nanoparticles have gained popularity in a wide range
of biomedical applications due to their biocompatibility and biodegradability
in-vivo, as well as a flexible surface chemistry, which allows drug loading,
functionalization and targeting. Here we report direct in-vivo imaging of
hyperpolarized 29Si nuclei in silicon microparticles by MRI. Natural physical
properties of silicon provide surface electronic states for dynamic nuclear
polarization (DNP), extremely long depolarization times, insensitivity to the
in-vivo environment or particle tumbling, and surfaces favorable for
functionalization. Potential applications to gastrointestinal, intravascular,
and tumor perfusion imaging at sub-picomolar concentrations are presented.
These results demonstrate a new background-free imaging modality applicable to
a range of inexpensive, readily available, and biocompatible Si particles.Comment: Supplemental Material include
Main phase transition in lipid bilayers: phase coexistence and line tension in a soft, solvent-free, coarse-grained model
We devise a soft, solvent-free, coarse-grained model for lipid bilayer
membranes. The non-bonded interactions take the form of a weighted-density
functional which allows us to describe the thermodynamics of self-assembly and
packing effects of the coarse-grained beads in terms of a density expansion of
the equation of state and the weighting functions that regularize the
microscopic bead densities, respectively. Identifying the length and energy
scales via the bilayer thickness and the thermal energy scale, kT, the model
qualitatively reproduces key characteristics (e.g., bending rigidity, area per
lipid molecules, and compressibility) of lipid membranes. We employ this model
to study the main phase transition between the liquid and the gel phase of the
bilayer membrane. We accurately locate the phase coexistence using free energy
calculations and also obtain estimates for the bare and the thermodynamic line
tension.Comment: 21 pages, 12 figures. Submitted to J. Chem. Phy
Achieving minimum-error discrimination of an arbitrary set of laser-light pulses
Laser light is widely used for communication and sensing applications, so the
optimal discrimination of coherent states--the quantum states of light emitted
by a laser--has immense practical importance. However, quantum mechanics
imposes a fundamental limit on how well different coher- ent states can be
distinguished, even with perfect detectors, and limits such discrimination to
have a finite minimum probability of error. While conventional optical
receivers lead to error rates well above this fundamental limit, Dolinar found
an explicit receiver design involving optical feedback and photon counting that
can achieve the minimum probability of error for discriminating any two given
coherent states. The generalization of this construction to larger sets of
coherent states has proven to be challenging, evidencing that there may be a
limitation inherent to a linear-optics-based adaptive measurement strategy. In
this Letter, we show how to achieve optimal discrimination of any set of
coherent states using a resource-efficient quantum computer. Our construction
leverages a recent result on discriminating multi-copy quantum hypotheses
(arXiv:1201.6625) and properties of coherent states. Furthermore, our
construction is reusable, composable, and applicable to designing
quantum-limited processing of coherent-state signals to optimize any metric of
choice. As illustrative examples, we analyze the performance of discriminating
a ternary alphabet, and show how the quantum circuit of a receiver designed to
discriminate a binary alphabet can be reused in discriminating multimode
hypotheses. Finally, we show our result can be used to achieve the quantum
limit on the rate of classical information transmission on a lossy optical
channel, which is known to exceed the Shannon rate of all conventional optical
receivers.Comment: 9 pages, 2 figures; v2 Minor correction
Hole Spin Coherence in a Ge/Si Heterostructure Nanowire
Relaxation and dephasing of hole spins are measured in a gate-defined Ge/Si
nanowire double quantum dot using a fast pulsed-gate method and dispersive
readout. An inhomogeneous dephasing time
exceeds corresponding measurements in III-V semiconductors by more than an
order of magnitude, as expected for predominately nuclear-spin-free materials.
Dephasing is observed to be exponential in time, indicating the presence of a
broadband noise source, rather than Gaussian, previously seen in systems with
nuclear-spin-dominated dephasing.Comment: 15 pages, 4 figure
Nieuwe landgoederen; hoe passen ze in het landschap? : een beslisboom ter ondersteuning van het afwegingsproces
Nieuwe landgoederen kunnen een impuls betekenen voor het landschap en de leefbaarheid. Veel gemeenten zijn echter huiverig met het verlenen van een aanlegvergunning omdat ze niet goed weten hoe nieuwe landgoederen in het landschap ingepast moeten worden. In dit artikel wordt een beslisboom gepresenteerd die gemeenten en vergunningaanvragers hierbij kan helpen
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