1,442 research outputs found
Chiron: A Robust Recommendation System with Graph Regularizer
Recommendation systems have been widely used by commercial service providers
for giving suggestions to users. Collaborative filtering (CF) systems, one of
the most popular recommendation systems, utilize the history of behaviors of
the aggregate user-base to provide individual recommendations and are effective
when almost all users faithfully express their opinions. However, they are
vulnerable to malicious users biasing their inputs in order to change the
overall ratings of a specific group of items. CF systems largely fall into two
categories - neighborhood-based and (matrix) factorization-based - and the
presence of adversarial input can influence recommendations in both categories,
leading to instabilities in estimation and prediction. Although the robustness
of different collaborative filtering algorithms has been extensively studied,
designing an efficient system that is immune to manipulation remains a
significant challenge. In this work we propose a novel "hybrid" recommendation
system with an adaptive graph-based user/item similarity-regularization -
"Chiron". Chiron ties the performance benefits of dimensionality reduction
(through factorization) with the advantage of neighborhood clustering (through
regularization). We demonstrate, using extensive comparative experiments, that
Chiron is resistant to manipulation by large and lethal attacks
Negative Link Prediction in Social Media
Signed network analysis has attracted increasing attention in recent years.
This is in part because research on signed network analysis suggests that
negative links have added value in the analytical process. A major impediment
in their effective use is that most social media sites do not enable users to
specify them explicitly. In other words, a gap exists between the importance of
negative links and their availability in real data sets. Therefore, it is
natural to explore whether one can predict negative links automatically from
the commonly available social network data. In this paper, we investigate the
novel problem of negative link prediction with only positive links and
content-centric interactions in social media. We make a number of important
observations about negative links, and propose a principled framework NeLP,
which can exploit positive links and content-centric interactions to predict
negative links. Our experimental results on real-world social networks
demonstrate that the proposed NeLP framework can accurately predict negative
links with positive links and content-centric interactions. Our detailed
experiments also illustrate the relative importance of various factors to the
effectiveness of the proposed framework
More is Better in Modern Machine Learning: when Infinite Overparameterization is Optimal and Overfitting is Obligatory
In our era of enormous neural networks, empirical progress has been driven by
the philosophy that more is better. Recent deep learning practice has found
repeatedly that larger model size, more data, and more computation (resulting
in lower training loss) improves performance. In this paper, we give
theoretical backing to these empirical observations by showing that these three
properties hold in random feature (RF) regression, a class of models equivalent
to shallow networks with only the last layer trained.
Concretely, we first show that the test risk of RF regression decreases
monotonically with both the number of features and the number of samples,
provided the ridge penalty is tuned optimally. In particular, this implies that
infinite width RF architectures are preferable to those of any finite width. We
then proceed to demonstrate that, for a large class of tasks characterized by
powerlaw eigenstructure, training to near-zero training loss is obligatory:
near-optimal performance can only be achieved when the training error is much
smaller than the test error. Grounding our theory in real-world data, we find
empirically that standard computer vision tasks with convolutional neural
tangent kernels clearly fall into this class. Taken together, our results tell
a simple, testable story of the benefits of overparameterization, overfitting,
and more data in random feature models
The occurrence of wakefieldite, a rare earth element vanadate, in the rhyolitic Joe Lott Tuff, Utah, USA
The high-silica rhyolitic Joe Lott Tuff was erupted at 19.2 ± 0.4 Ma from the Mount Belknap caldera, SW Utah. Certain units in the tuff contain two species of wakefieldite, the Nd- A nd Y-dominant types. They occur in disseminated streaks and patches in association with rhodochrosite, calcite, Fe oxide, cerite-(Ce), and a Mn silicate (caryopilite?), thought to have been deposited from hydrothermal fluids. The wakefieldites contain the highest levels of As (≤15.34 wt.% As2O5) and P (≤5.7 wt.% P2O5) yet recorded in this mineral, indicating significant solid solution towards chernovite-(Y) and xenotime-(Y). Thorium levels are also unusually high (≤14.2 wt.% ThO2). The source of the hydrothermal fluid(s) is unknown but might be related to uranium mineralisation in the region, in that As, V and U are commonly associated in such deposits. © 2019 Mineralogical Society of Great Britain and Ireland
Smoothed Analysis of Tensor Decompositions
Low rank tensor decompositions are a powerful tool for learning generative
models, and uniqueness results give them a significant advantage over matrix
decomposition methods. However, tensors pose significant algorithmic challenges
and tensors analogs of much of the matrix algebra toolkit are unlikely to exist
because of hardness results. Efficient decomposition in the overcomplete case
(where rank exceeds dimension) is particularly challenging. We introduce a
smoothed analysis model for studying these questions and develop an efficient
algorithm for tensor decomposition in the highly overcomplete case (rank
polynomial in the dimension). In this setting, we show that our algorithm is
robust to inverse polynomial error -- a crucial property for applications in
learning since we are only allowed a polynomial number of samples. While
algorithms are known for exact tensor decomposition in some overcomplete
settings, our main contribution is in analyzing their stability in the
framework of smoothed analysis.
Our main technical contribution is to show that tensor products of perturbed
vectors are linearly independent in a robust sense (i.e. the associated matrix
has singular values that are at least an inverse polynomial). This key result
paves the way for applying tensor methods to learning problems in the smoothed
setting. In particular, we use it to obtain results for learning multi-view
models and mixtures of axis-aligned Gaussians where there are many more
"components" than dimensions. The assumption here is that the model is not
adversarially chosen, formalized by a perturbation of model parameters. We
believe this an appealing way to analyze realistic instances of learning
problems, since this framework allows us to overcome many of the usual
limitations of using tensor methods.Comment: 32 pages (including appendix
M-CSF and GM-CSF Regulation of STAT5 Activation and DNA Binding in Myeloid Cell Differentiation is Disrupted in Nonobese Diabetic Mice
Defects in macrophage colony-stimulating factor (M-CSF) signaling disrupt myeloid cell differentiation in nonobese diabetic (NOD) mice, blocking myeloid maturation into tolerogenic antigen-presenting cells (APCs). In the absence of M-CSF signaling, NOD myeloid cells have abnormally high granulocyte macrophage colony-stimulating factor (GM-CSF) expression, and as a result, persistent activation of signal transducer/activator of transcription 5 (STAT5). Persistent STAT5 phosphorylation found in NOD macrophages is not affected by inhibiting GM-CSF. However, STAT5 phosphorylation in NOD bone marrow cells is diminished if GM-CSF signaling is blocked. Moreover, if M-CSF signaling is inhibited, GM-CSF stimulation in vitro can promote STAT5 phosphorylation in nonautoimmune C57BL/6 mouse bone marrow cultures to levels seen in the NOD. These findings suggest that excessive GM-CSF production in the NOD bone marrow may interfere with the temporal sequence of GM-CSF and M-CSF signaling needed to mediate normal STAT5 function in myeloid cell differentiation gene regulation
Non-Redundant Spectral Dimensionality Reduction
Spectral dimensionality reduction algorithms are widely used in numerous
domains, including for recognition, segmentation, tracking and visualization.
However, despite their popularity, these algorithms suffer from a major
limitation known as the "repeated Eigen-directions" phenomenon. That is, many
of the embedding coordinates they produce typically capture the same direction
along the data manifold. This leads to redundant and inefficient
representations that do not reveal the true intrinsic dimensionality of the
data. In this paper, we propose a general method for avoiding redundancy in
spectral algorithms. Our approach relies on replacing the orthogonality
constraints underlying those methods by unpredictability constraints.
Specifically, we require that each embedding coordinate be unpredictable (in
the statistical sense) from all previous ones. We prove that these constraints
necessarily prevent redundancy, and provide a simple technique to incorporate
them into existing methods. As we illustrate on challenging high-dimensional
scenarios, our approach produces significantly more informative and compact
representations, which improve visualization and classification tasks
Reaction of benzylidenephenylsulfonylacetophenone with trimethyl phosphite and tris(dimethylamino) phosphine
1. Benzylidenephenylsulfonylacetophenone (I) reacts with trimethyl phosphite (80°, C6H6) to give 2,2,2-trimethoxy-3,5-diphenyl-4-phenylsulfonyl-1,2-oxa-4-phospholene (II). 2. Two processes take place simultaneously at high temperatures (160°): isomerization of phosphorane (II) to give the dimethyl ester of 1,3-diphenyl-2-phenylsulfonyl-3-methoxy-2-propenephosphonic acid (VI), and decomposition of phosphorane (II) to the starting reactants with a cleavage of the P-C bond. 3. When phosphorane (II) is reacted with proton-donor reagents the phosphorane ring is opened at the P-O bond to give the dimethyl ester of 1-phenyl-2-benzoyl-2-phenylsulfonylethanephosphonic acid (III). 4. Benzylidenephenylsulfonylacetophenone (I) reacts with tris(dimethylamino)phosphine to give the 1:1 adduct with a bipolar structure (VII) and containing the P-C bond. Its hydrolysis and reaction with dry HCl gas were studied. © 1973 Consultants Bureau
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