115,062 research outputs found
Specialization of the rostral prefrontal cortex for distinct analogy processes
Analogical reasoning is central to learning and abstract thinking. It involves using a more familiar situation (source) to make inferences about a less familiar situation (target). According to the predominant cognitive models, analogical reasoning includes 1) generation of structured mental representations and 2) mapping based on structural similarities between them. This study used functional magnetic resonance imaging to specify the role of rostral prefrontal cortex (PFC) in these distinct processes. An experimental paradigm was designed that enabled differentiation between these processes, by temporal separation of the presentation of the source and the target. Within rostral PFC, a lateral subregion was activated by analogy task both during study of the source (before the source could be compared with a target) and when the target appeared. This may suggest that this subregion supports fundamental analogy processes such as generating structured representations of stimuli but is not specific to one particular processing stage. By contrast, a dorsomedial subregion of rostral PFC showed an interaction between task (analogy vs. control) and period (more activated when the target appeared). We propose that this region is involved in comparison or mapping processes. These results add to the growing evidence for functional differentiation between rostral PFC subregions
Scanning tunneling microscopy and spectroscopy of sodium-chloride overlayers on the stepped Cu(311) surface: Experimental and theoretical study
The physical properties of ultrathin NaCl overlayers on the stepped Cu(311)
surface have been characterized using scanning tunneling microscopy (STM) and
spectroscopy, and density functional calculations. Simulations of STM images
and differential conductance spectrum were based on the Tersoff-Hamann
approximation for tunneling with corrections for the modified tunneling barrier
at larger voltages and calculated Kohn-Sham states. Characteristic features
observed in the STM images can be directly related to calculated electronic and
geometric properties of the overlayers. The measured apparent barrier heights
for the mono-, bi-, and trilayers of NaCl and the corresponding
adsorption-induced changes in the work function, as obtained from the distance
dependence of the tunneling current, are well reproduced by and understood from
the calculated results. The measurements revealed a large reduction of the
tunneling conductance in a wide voltage region, resembling a band gap. However,
the simulated spectrum showed that only the onset at positive sample voltages
may be viewed as a valence band edge, whereas the onset at negative voltages is
caused by the drastic effect of the electric field from the tip on the
tunneling barrier
Improving Landmark Localization with Semi-Supervised Learning
We present two techniques to improve landmark localization in images from
partially annotated datasets. Our primary goal is to leverage the common
situation where precise landmark locations are only provided for a small data
subset, but where class labels for classification or regression tasks related
to the landmarks are more abundantly available. First, we propose the framework
of sequential multitasking and explore it here through an architecture for
landmark localization where training with class labels acts as an auxiliary
signal to guide the landmark localization on unlabeled data. A key aspect of
our approach is that errors can be backpropagated through a complete landmark
localization model. Second, we propose and explore an unsupervised learning
technique for landmark localization based on having a model predict equivariant
landmarks with respect to transformations applied to the image. We show that
these techniques, improve landmark prediction considerably and can learn
effective detectors even when only a small fraction of the dataset has landmark
labels. We present results on two toy datasets and four real datasets, with
hands and faces, and report new state-of-the-art on two datasets in the wild,
e.g. with only 5\% of labeled images we outperform previous state-of-the-art
trained on the AFLW dataset.Comment: Published as a conference paper in CVPR 201
Force and energy dissipation variations in non-contact atomic force spectroscopy on composite carbon nanotube systems
UHV dynamic force and energy dissipation spectroscopy in non-contact atomic
force microscopy were used to probe specific interactions with composite
systems formed by encapsulating inorganic compounds inside single-walled carbon
nanotubes. It is found that forces due to nano-scale van der Waals interaction
can be made to decrease by combining an Ag core and a carbon nanotube shell in
the Ag@SWNT system. This specific behaviour was attributed to a significantly
different effective dielectric function compared to the individual
constituents, evaluated using a simple core-shell optical model. Energy
dissipation measurements showed that by filling dissipation increases,
explained here by softening of C-C bonds resulting in a more deformable
nanotube cage. Thus, filled and unfilled nanotubes can be discriminated based
on force and dissipation measurements. These findings have two different
implications for potential applications: tuning the effective optical
properties and tuning the interaction force for molecular absorption by
appropriately choosing the filling with respect to the nanotube.Comment: 22 pages, 6 figure
ImageSpirit: Verbal Guided Image Parsing
Humans describe images in terms of nouns and adjectives while algorithms
operate on images represented as sets of pixels. Bridging this gap between how
humans would like to access images versus their typical representation is the
goal of image parsing, which involves assigning object and attribute labels to
pixel. In this paper we propose treating nouns as object labels and adjectives
as visual attribute labels. This allows us to formulate the image parsing
problem as one of jointly estimating per-pixel object and attribute labels from
a set of training images. We propose an efficient (interactive time) solution.
Using the extracted labels as handles, our system empowers a user to verbally
refine the results. This enables hands-free parsing of an image into pixel-wise
object/attribute labels that correspond to human semantics. Verbally selecting
objects of interests enables a novel and natural interaction modality that can
possibly be used to interact with new generation devices (e.g. smart phones,
Google Glass, living room devices). We demonstrate our system on a large number
of real-world images with varying complexity. To help understand the tradeoffs
compared to traditional mouse based interactions, results are reported for both
a large scale quantitative evaluation and a user study.Comment: http://mmcheng.net/imagespirit
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