3,034 research outputs found
Split-cross-bridge resistor for testing for proper fabrication of integrated circuits
An electrical testing structure and method is described whereby a test structure is fabricated on a large scale integrated circuit wafer along with the circuit components and has a van der Pauw cross resistor in conjunction with a bridge resistor and a split bridge resistor, the latter having two channels each a line width wide, corresponding to the line width of the wafer circuit components, and with the two channels separated by a space equal to the line spacing of the wafer circuit components. The testing structure has associated voltage and current contact pads arranged in a two by four array for conveniently passing currents through the test structure and measuring voltages at appropriate points to calculate the sheet resistance, line width, line spacing, and line pitch of the circuit components on the wafer electrically
Charge sensing in carbon nanotube quantum dots on microsecond timescales
We report fast, simultaneous charge sensing and transport measurements of
gate-defined carbon nanotube quantum dots. Aluminum radio frequency single
electron transistors (rf-SETs) capacitively coupled to the nanotube dot provide
single-electron charge sensing on microsecond timescales. Simultaneously, rf
reflectometry allows fast measurement of transport through the nanotube dot.
Charge stability diagrams for the nanotube dot in the Coulomb blockade regime
show extended Coulomb diamonds into the high-bias regime, as well as even-odd
filling effects, revealed in charge sensing data.Comment: 4 pages, 4 figure
Mechanics of Mineralized Collagen Fibrils upon Transient Loads
Collagen is a key structural protein in the human body, which undergoes mineralization during the formation of hard tissues. Earlier studies have described the mechanical behavior of bone at different scales, highlighting material features across hierarchical structures. Here we present a study that aims to understand the mechanical properties of mineralized collagen fibrils upon tensile/compressive transient loads, investigating how the kinetic energy propagates and it is dissipated at the molecular scale, thus filling a gap of knowledge in this area. These specific features are the mechanisms that nature has developed to passively dissipate stress and prevent structural failures. In addition to the mechanical properties of the mineralized fibrils, we observe distinct nanomechanical behaviors for the two regions (i.e., overlap and gap) of the D-period to highlight the effect of the mineralization. We notice decreasing trends for both wave speeds and Young's moduli over input velocity with a marked strengthening effect in the gap region due to the accumulation of the hydroxyapatite. In contrast, the dissipative behavior is not affected by either loading conditions or the mineral percentage, showing a stronger damping effect upon faster inputs compatible to the bone behavior at the macroscale. Our results offer insights into the dissipative behavior of mineralized collagen composites to design and characterize bioinspired composites for replacement devices (e.g., prostheses for sound transmission or conduction) or optimized structures able to bear transient loads, for example, impact, fatigue, in structural applications
Parity measurement of one- and two-electron double well systems
We outline a scheme to accomplish measurements of a solid state double well
system (DWS) with both one and two electrons in non-localised bases. We show
that, for a single particle, measuring the local charge distribution at the
midpoint of a DWS using an SET as a sensitive electrometer amounts to
performing a projective measurement in the parity (symmetric/antisymmetric)
eigenbasis. For two-electrons in a DWS, a similar configuration of SET results
in close-to-projective measurement in the singlet/triplet basis. We analyse the
sensitivity of the scheme to asymmetry in the SET position for some
experimentally relevant parameter, and show that it is realisable in
experiment.Comment: 18 Pages, to appear in PR
Defining signal thresholds in DNA microarrays: exemplary application for invasive cancer
BACKGROUND: Genome-wide or application-targeted microarrays containing a subset of genes of interest have become widely used as a research tool with the prospect of diagnostic application. Intrinsic variability of microarray measurements poses a major problem in defining signal thresholds for absent/present or differentially expressed genes. Most strategies have used fold-change threshold values, but variability at low signal intensities may invalidate this approach and it does not provide information about false-positives and false negatives. RESULTS: We introduce a method to filter false-positives and false-negatives from DNA microarray experiments. This is achieved by evaluating a set of positive and negative controls by receiver operating characteristic (ROC) analysis. As an advantage of this approach, users may define thresholds on the basis of sensitivity and specificity considerations. The area under the ROC curve allows quality control of microarray hybridizations. This method has been applied to custom made microarrays developed for the analysis of invasive melanoma derived tumor cells. It demonstrated that ROC analysis yields a threshold with reduced missclassified genes in microarray experiments. CONCLUSIONS: Provided that a set of appropriate positive and negative controls is included on the microarray, ROC analysis obviates the inherent problem of arbitrarily selecting threshold levels in microarray experiments. The proposed method is applicable to both custom made and commercially available DNA microarrays and will help to improve the reliability of predictions from DNA microarray experiments
Endothermic salts integrated in impermeable suits do not reduce heat strain during exercise
Wearing impermeable garments during work inherently leads to heat strain, even in cold
environments [1]. Phase change materials (mainly paraffin’s or salt [4]) may be used as a thermal
buffer (e.g. [2]) to reduce initial heat stress. Salts can also be used to absorb sweat, which may
enhance the cooling power from the skin.
Recently, specific encapsulated salts utilising KSCN (potassium thiocyanate) have been developed
that consume energy when the KSCN dissolves in water. The heat consumed when the KSCN
(present inside 150 g of capsules containing 60% KSCN salt) dissolves in water is 22410 J (249 J/g *
60% * 150 g). When this solving takes place over a period of 30 minutes, the average power
transfer is 12 W. One (1) g of KSCN-containing capsules absorbs close to 1 g of moisture. If we
assume that 150 g sweat extra can be evaporated from the skin, this yields an extra cooling power
of 182 W for 30 minutes. However this evaporated water from the skin is subsequently absorbed
by the KSCN in the capsules. During this absorption from the gas phase, the condensation heat is
released to the KSCN salt: about 182 W for 30 minutes. However, we hypothesise that this
condensation heat will be partly transferred to the body and partly to the environment [3],
providing a net benefit to the body.
Thus, the total cooling effect due to the salt capsules is composed of two parts:
• The cooling effect of about 12 W due to the heat consumption by the dissolving of the salts in
water;
• The cooling effect of maximal 182 W, which equals the difference between the evaporative
heat and the condensation heat. The latter is generated in the salt capsules that transfer part
of the heat to the environment.
The overall cooling effect should therefore be in between 12 W and 194 W.
The purpose of our study was to test the efficacy of a KSCN-based absorbing salt as a PCM for use
within impermeable protective clothing. We tested the PCM during 20 min of moderate exercise
in a hot (35°C, 40% relative humidity) environment, and hypothesized that thermal strain would be
lower in the PCM compared to the non-PCM condition
Observing sub-microsecond telegraph noise with the radio frequency single electron transistor
Telegraph noise, which originates from the switching of charge between
meta-stable trapping sites, becomes increasingly important as device sizes
approach the nano-scale. For charge-based quantum computing, this noise may
lead to decoherence and loss of read out fidelity. Here we use a radio
frequency single electron transistor (rf-SET) to probe the telegraph noise
present in a typical semiconductor-based quantum computer architecture. We
frequently observe micro-second telegraph noise, which is a strong function of
the local electrostatic potential defined by surface gate biases. We present a
method for studying telegraph noise using the rf-SET and show results for a
charge trap in which the capture and emission of a single electron is
controlled by the bias applied to a surface gate.Comment: Accepted for publication in Journal of Applied Physics. Comments
always welcome, email [email protected], [email protected]
Development and operation of the twin radio frequency single electron transistor for solid state qubit readout
Ultra-sensitive detectors and readout devices based on the radio frequency
single electron transistor (rf-SET) combine near quantum-limited sensitivity
with fast operation. Here we describe a twin rf-SET detector that uses two
superconducting rf-SETs to perform fast, real-time cross-correlated
measurements in order to distinguish sub-electron signals from charge noise on
microsecond time-scales. The twin rf-SET makes use of two tuned resonance
circuits to simultaneously and independently address both rf-SETs using
wavelength division multiplexing (WDM) and a single cryogenic amplifier. We
focus on the operation of the twin rf-SET as a charge detector and evaluate the
cross-talk between the two resonance circuits. Real time suppression of charge
noise is demonstrated by cross correlating the signals from the two rf-SETs.
For the case of simultaneous operation, the rf-SETs had charge sensitivities of
and .Comment: Updated version, including new content. Comments most welcome:
[email protected] or [email protected]
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
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