10 research outputs found
An Exact Algorithm for Minimum Vertex Cover Problem
In this paper, we propose a branch-and-bound algorithm to solve exactly the minimum vertex cover (MVC) problem. Since a tight lower bound for MVC has a significant influence on the efficiency of a branch-and-bound algorithm, we define two novel lower bounds to help prune the search space. One is based on the degree of vertices, and the other is based on MaxSAT reasoning. The experiment confirms that our algorithm is faster than previous exact algorithms and can find better results than heuristic algorithms
Dual Intent Enhanced Graph Neural Network for Session-based New Item Recommendation
Recommender systems are essential to various fields, e.g., e-commerce,
e-learning, and streaming media. At present, graph neural networks (GNNs) for
session-based recommendations normally can only recommend items existing in
users' historical sessions. As a result, these GNNs have difficulty
recommending items that users have never interacted with (new items), which
leads to a phenomenon of information cocoon. Therefore, it is necessary to
recommend new items to users. As there is no interaction between new items and
users, we cannot include new items when building session graphs for GNN
session-based recommender systems. Thus, it is challenging to recommend new
items for users when using GNN-based methods. We regard this challenge as
'\textbf{G}NN \textbf{S}ession-based \textbf{N}ew \textbf{I}tem
\textbf{R}ecommendation (GSNIR)'. To solve this problem, we propose a
dual-intent enhanced graph neural network for it. Due to the fact that new
items are not tied to historical sessions, the users' intent is difficult to
predict. We design a dual-intent network to learn user intent from an attention
mechanism and the distribution of historical data respectively, which can
simulate users' decision-making process in interacting with a new item. To
solve the challenge that new items cannot be learned by GNNs, inspired by
zero-shot learning (ZSL), we infer the new item representation in GNN space by
using their attributes. By outputting new item probabilities, which contain
recommendation scores of the corresponding items, the new items with higher
scores are recommended to users. Experiments on two representative real-world
datasets show the superiority of our proposed method. The case study from the
real-world verifies interpretability benefits brought by the dual-intent module
and the new item reasoning module. The code is available at Github:
https://github.com/Ee1s/NirGNNComment: 10 Pages, 6 figures, WWW'202
Evolved Bacterial Biosensor for Arsenite Detection in Environmental Water
Arsenic, a ubiquitous presence in
the biosphere, often occurs from
both natural and anthropogenic sources. Bacterial biosensors based
on genetically engineered bacteria have promising applications in
detecting the chemical compound and its toxicity. However, most of
the bacteria biosensors take advantage of the existing wild-type substrate-induced
promoters, which are often low in specificity, affinity and sensitivity,
and thus limiting their applications in commercial or field use. In
this study, we developed an in vivo evolution procedure with a bidirectional
selection scheme for improving the sensitivity of an arsenite-responsive
bacterial biosensor through optimization of the inducible operon.
As a proof of concept, we evolved the arsenite-induced arsR operon
for both low background and high expression through three successive
rounds of fluorescence activated cell sorting (FACS) with bidirectional
strategy. An arsR operon variant with 12-fold higher activity over
the control was isolated, confirming multiple rounds of construction
and screening of mutation library, as described here, can be efficiently
applied to bacterial biosensor optimization. The evolved arsenite-responsive
biosensor demonstrated an excellent performance in the detection of
low trace arsenite in environmental water. These results indicate
that the technologies of directed evolution could be used to improve
the performance of bacterial biosensors, which will be helpful in
promoting the practical application of bacterial biosensors
Synergistic Effects Induced by a Low Dose of Diesel Particulate Extract and Ultraviolet‑A in <i>Caenorhabditis elegans</i>: DNA Damage-Triggered Germ Cell Apoptosis
Diesel exhaust has been classified
as a potential carcinogen and
is associated with various health effects. A previous study showed
that the doses for manifesting the mutagenetic effects of diesel exhaust
could be reduced when coexposed with ultraviolet-A (UVA) in a cellular
system. However, the mechanisms underlying synergistic effects remain
to be clarified, especially in an <i>in vivo</i> system.
In the present study, using <i>Caenorhabditis elegans</i> (<i>C. elegans</i>) as an <i>in vivo</i> system
we studied the synergistic effects of diesel particulate extract (DPE)
plus UVA, and the underlying mechanisms were dissected genetically
using related mutants. Our results demonstrated that though coexposure
of wild type worms at young adult stage to low doses of DPE (20 μg/mL)
plus UVA (0.2, 0.5, and 1.0 J/cm<sup>2</sup>) did not affect worm
development (mitotic germ cells and brood size), it resulted in a
significant induction of germ cell death. Using the strain of <i>hus-1::gfp</i>, distinct foci of HUS-1::GFP was observed in
proliferating germ cells, indicating the DNA damage after worms were
treated with DPE plus UVA. Moreover, the induction of germ cell death
by DPE plus UVA was alleviated in single-gene loss-of-function mutations
of core apoptotic, checkpoint HUS-1, CEP-1/p53, and MAPK dependent
signaling pathways. Using a reactive oxygen species (ROS) probe, it
was found that the production of ROS in worms coexposed to DPE plus
UVA increased in a time-dependent manner. In addition, employing a
singlet oxygen (<sup>1</sup>O<sub>2</sub>) trapping probe, 2,2,6,6-tetramethyl-4-piperidone,
coupled with electron spin resonance analysis, we demonstrated the
increased <sup>1</sup>O<sub>2</sub> production in worms coexposed
to DPE plus UVA. These results indicated that UVA could enhance the
apoptotic induction of DPE at low doses through a DNA damage-triggered
pathway and that the production of ROS, especially <sup>1</sup>O<sub>2</sub>, played a pivotal role in initiating the synergistic process