13,646 research outputs found
A Monolithically Fabricated Combinatorial Mixer for Microchip-Based High-Throughput Cell Culturing Assays
We present an integrated method to fabricate 3-
D microfluidic networks and fabricated the first on-chip
cell culture device with an integrated combinatorial mixer.
The combinatorial mixer is designed for screening the
combinatorial effects of different compounds on cells. The
monolithic fabrication method with parylene C as the
basic structural material allows us to avoid wafer bonding
and achieves precise alignment between microfluidic
channels. As a proof-of-concept, we fabricated a device
with a three-input combinatorial mixer and demonstrated
that the mixer can produce all the possible combinations.
Also, we demonstrated the ability to culture cells on-chip
and performed a simple cell assay on-chip using trypan
blue to stain dead cells
Regularization Methods for Nuclear Lattice Effective Field Theory
We investigate Nuclear Lattice Effective Field Theory for the two-body system
for several lattice spacings at lowest order in the pionless as well as in the
pionful theory. We discuss issues of regularizations and predictions for the
effective range expansion. In the pionless case, a simple Gaussian smearing
allows to demonstrate lattice spacing independence over a wide range of lattice
spacings. We show that regularization methods known from the continuum
formulation are necessary as well as feasible for the pionful approach.Comment: 7 pp, 2 figs, to appear in Physics Letters
A 1.6 Gb/s, 3 mW CMOS receiver for optical communication
A 1.6 Gb/s receiver for optical communication has been designed and fabricated in a 0.25-μm CMOS process. This receiver has no transimpedance amplifier and uses the parasitic capacitor of the flip-chip bonded photodetector as an integrating element and resolves the data with a double-sampling technique. A simple feedback loop adjusts a bias current to the average optical signal, which essentially "AC couples" the input. The resulting receiver resolves an 11 μA input, dissipates 3 mW of power, occupies 80 μm x 50 μm of area and operates at over 1.6 Gb/s
A Spectral Algorithm for Latent Dirichlet Allocation
The problem of topic modeling can be seen as a generalization of the
clustering problem, in that it posits that observations are generated due to
multiple latent factors (e.g., the words in each document are generated as a
mixture of several active topics, as opposed to just one). This increased
representational power comes at the cost of a more challenging unsupervised
learning problem of estimating the topic probability vectors (the distributions
over words for each topic), when only the words are observed and the
corresponding topics are hidden.
We provide a simple and efficient learning procedure that is guaranteed to
recover the parameters for a wide class of mixture models, including the
popular latent Dirichlet allocation (LDA) model. For LDA, the procedure
correctly recovers both the topic probability vectors and the prior over the
topics, using only trigram statistics (i.e., third order moments, which may be
estimated with documents containing just three words). The method, termed
Excess Correlation Analysis (ECA), is based on a spectral decomposition of low
order moments (third and fourth order) via two singular value decompositions
(SVDs). Moreover, the algorithm is scalable since the SVD operations are
carried out on matrices, where is the number of latent factors
(e.g. the number of topics), rather than in the -dimensional observed space
(typically ).Comment: Changed title to match conference version, which appears in Advances
in Neural Information Processing Systems 25, 201
Estimating the Social Welfare Effects of New Zealand Apple Imports
This paper provides a demonstration of how a comprehensive economic framework, which takes into account both the gains from trade and the costs of invasive species outbreaks, can inform decision-makers when making quarantine decisions. Using the theoretical framework developed in Cook and Fraser (2008) an empirical estimation is made of the economic welfare consequences for Australia of allowing quarantine-restricted trade in New Zealand apples to take place. The results suggest the returns to Australian society from importing New Zealand apples are likely to be negative. The price differential between the landed product with SPS measures in place and the autarkic price is insufficient to outweigh the increase in expected damage resulting from increased fire blight risk. As a consequence, this empirical analysis suggests the net benefits created by opening up this trade are marginal.International Relations/Trade,
Association of PET-measured myocardial flow reserve with echocardiography-estimated pulmonary artery systolic pressure in patients with hypertrophic cardiomyopathy
BackgroundPulmonary hypertension (PH) is a known complication of HCM and is a strong predictor of mortality. We aim to investigate the relationship between microvascular dysfunction measured by quantitative PET and PH in HCM patients.MethodsEighty-nine symptomatic HCM patients were included in the study. Each patient underwent two 20-min 13N-NH3 dynamic PET scans for rest and stress conditions, respectively. A 2-tissue irreversible compartmental model was used to fit the segments time activity curves for estimating segmental and global myocardial blood flow (MBF) and myocardial flow reserve (MFR). Echocardiographic derived PASP was utilized to estimate PH.ResultsPatients were categorized into two groups across PASP: PH (PASP > 36 mmHg) and no-PH (PASP ≤ 36 mmHg). patients with PH had larger left atrium, ratio of higher inflow early diastole (E) and atrial contraction (A) waves, E/A, and ratio of inflow and peak early diastolic waves, E/e', significantly reduced global stress MBF (1.85 ± 0.52 vs. 2.13 ± 0.56 ml/min/g; p = 0.024) and MFR (2.21 ± 0.57 vs. 2.62 ± 0.75; p = 0.005), while the MBFs at rest between the two groups were similar. There were significant negative correlations between global stress MBF/MFR and PASP (stress MBF: r = -0.23, p = 0.03; MFR: r = -0.32, p = 0.002); for regional MBF and MFR measurements, the highest linear correlation coefficients were observed in the septal wall (stress MBF: r = -0.27, p = 0.01; MFR: r = -0.31, p = 0.003). Global MFR was identified to be independent predictor for PH in multivariate regression analysis.ConclusionEchocardiography-derived PASP is negatively correlated with global MFR measured by 13N-NH3 dynamic PET. Global MFR is suggested to be an index of PH in HCM patients.</div
Springback analysis of AA5754 after hot stamping: experiments and FE modelling
In this paper, the springback of the aluminium alloy AA5754 under hot stamping conditions was characterised under stretch and pure bending conditions. It was found that elevated temperature stamping was beneficial for springback reduction, particularly when using hot dies. Using cold dies, the flange springback angle decreased by 9.7 % when the blank temperature was increased from 20 to 450 °C, compared to the 44.1 % springback reduction when hot dies were used. Various other forming conditions were also tested, the results of which were used to verify finite element (FE) simulations of the processes in order to consolidate the knowledge of springback. By analysing the tangential stress distributions along the formed part in the FE models, it was found that the springback angle is a linear function of the average through-thickness stress gradient, regardless of the forming conditions used
Quantum Spin Hall Effect and Topological Field Effect Transistor in Two-Dimensional Transition Metal Dichalcogenides
We report a new class of large-gap quantum spin Hall insulators in
two-dimensional transition metal dichalcogenides, namely, MX with M=(Mo, W)
and X=(S, Se, and Te), whose topological electronic properties are highly
tunable by external electric field. We propose a novel topological field effect
transistor made of these atomic layer materials and their van der Waals
heterostructures. Our device exhibits parametrically enhanced charge-spin
conductance through topologically protected transport channels, and can be
rapidly switched off by electric field through topological phase transition
instead of carrier depletion. Our work provides a practical material platform
and device architecture for topological quantum electronics.Comment: 22 pages, 10 figures, submitted in May 201
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