1,183 research outputs found
Electric field and tip geometry effects on dielectrophoretic growth of carbon nanotube nanofibrils on scanning probes
Single-wall carbon nanotube (SWNT) nanofibrils were assembled onto a variety
of conductive scanning probes including atomic force microscope (AFM) tips and
scanning tunnelling microscope (STM) needles using positive dielectrophoresis
(DEP). The magnitude of the applied electric field was varied in the range of
1-20 V to investigate its effect on the dimensions of the assembled SWNT
nanofibrils. Both length and diameter grew asymptotically as voltage increased
from 5 to 18 V. Below 4 V, stable attachment of SWNT nanofibrils could not be
achieved due to the relatively weak DEP force versus Brownian motion. At
voltages of 20 V and higher, low quality nanofibrils resulted from
incorporating large amounts of impurities. For intermediate voltages, optimal
nanofibrils were achieved, though pivotal to this assembly is the wetting
behaviour upon tip immersion in the SWNT suspension drop. This process was
monitored in situ to correlate wetting angle and probe geometry (cone angles
and tip height), revealing that probes with narrow cone angles and long shanks
are optimal. It is proposed that this results from less wetting of the probe
apex, and therefore reduces capillary forces and especially force transients
during the nanofibril drawing process. Relatively rigid probes (force constant
>= 2 N/m) exhibited no perceivable cantilever bending upon wetting and
de-wetting, resulting in the most stable process control
Dimension of the Torelli group for Out(F_n)
Let T_n be the kernel of the natural map from Out(F_n) to GL(n,Z). We use
combinatorial Morse theory to prove that T_n has an Eilenberg-MacLane space
which is (2n-4)-dimensional and that H_{2n-4}(T_n,Z) is not finitely generated
(n at least 3). In particular, this recovers the result of Krstic-McCool that
T_3 is not finitely presented. We also give a new proof of the fact, due to
Magnus, that T_n is finitely generated.Comment: 27 pages, 9 figure
Automated analysis of Physarum network structure and dynamics
We evaluate different ridge-enhancement and segmentation methods to automatically extract the network architecture from time-series of Physarum plasmodia withdrawing from an arena via a single exit. Whilst all methods gave reasonable results, judged by precision-recall analysis against a ground-truth skeleton, the mean phase angle (Feature Type) from intensity-independent, phase-congruency edge enhancement and watershed segmentation was the most robust to variation in threshold parameters. The resultant single pixel-wide segmented skeleton was converted to a graph representation as a set of weighted adjacency matrices containing the physical dimensions of each vein, and the inter-vein regions. We encapsulate the complete image processing and network analysis pipeline in a downloadable software package, and provide an extensive set of metrics that characterise the network structure, including hierarchical loop decomposition to analyse the nested structure of the developing network. In addition, the change in volume for each vein and intervening plasmodial sheet was used to predict the net flow across the network. The scaling relationships between predicted current, speed and shear force with vein radius were consistent with predictions from Murray's law. This work was presented at PhysNet 2015
Integral Grothendieck-Riemann-Roch theorem
We show that, in characteristic zero, the obvious integral version of the
Grothendieck-Riemann-Roch formula obtained by clearing the denominators of the
Todd and Chern characters is true (without having to divide the Chow groups by
their torsion subgroups). The proof introduces an alternative to Grothendieck's
strategy: we use resolution of singularities and the weak factorization theorem
for birational maps.Comment: 24 page
Knowledge-driven stock trend prediction and explanation via temporal convolutional network
The authors would like to acknowledge that this work is funded by NSFC 61473260/91846204, national key research program YS2018YFB140004 as well as Natural Science Foundation of Zhejiang Province of China (LQ19F030001), and supported by Alibaba-Zhejiang University Joint Institute of Frontier Technologies.Publisher PD
Ligand-Independent HER2/HER3/PI3K Complex Is Disrupted by Trastuzumab and Is Effectively Inhibited by the PI3K Inhibitor GDC-0941
SummaryHerceptin (trastuzumab) is the backbone of HER2-directed breast cancer therapy and benefits patients in both the adjuvant and metastatic settings. Here, we describe a mechanism of action for trastuzumab whereby antibody treatment disrupts ligand-independent HER2/HER3 interactions in HER2-amplified cells. The kinetics of dissociation parallels HER3 dephosphorylation and uncoupling from PI3K activity, leading to downregulation of proximal and distal AKT signaling, and correlates with the antiproliferative effects of trastuzumab. A selective and potent PI3K inhibitor, GDC-0941, is highly efficacious both in combination with trastuzumab and in the treatment of trastuzumab-resistant cells and tumors
A model for reactive porous transport during re-wetting of hardened concrete
A mathematical model is developed that captures the transport of liquid water
in hardened concrete, as well as the chemical reactions that occur between the
imbibed water and the residual calcium silicate compounds residing in the
porous concrete matrix. The main hypothesis in this model is that the reaction
product -- calcium silicate hydrate gel -- clogs the pores within the concrete
thereby hindering water transport. Numerical simulations are employed to
determine the sensitivity of the model solution to changes in various physical
parameters, and compare to experimental results available in the literature.Comment: 30 page
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