Development of a Novel Classification Approach for Cow Behavior Analysis Using Tracking Data and Unsupervised Machine Learning Techniques.

Global Positioning Systems (GPSs) can collect tracking data to remotely monitor livestock well-being and pasture use. Supervised machine learning requires behavioral observations of monitored animals to identify changes in behavior, which is labor-intensive. Our goal was to identify animal behaviors automatically without using human observations. We designed a novel framework using unsupervised learning techniques. The framework contains two steps. The first step segments cattle tracking data using state-of-the-art time series segmentation algorithms, and the second step groups segments into clusters and then labels the clusters. To evaluate the applicability of our proposed framework, we utilized GPS tracking data collected from five cows in a 1096 ha rangeland pasture. Cow movement pathways were grouped into six behavior clusters based on velocity (m/min) and distance from water. Again, using velocity, these six clusters were classified into walking, grazing, and resting behaviors. The mean velocity for predicted walking and grazing and resting behavior was 44, 13 and 2 min/min, respectively, which is similar to other research. Predicted diurnal behavior patterns showed two primary grazing bouts during early morning and evening, like in other studies. Our study demonstrates that the proposed two-step framework can use unlabeled GPS tracking data to predict cattle behavior without human observations.

Defect-Rich Amorphous Iron-Based Oxide/Graphene Hybrid-Modified Separator toward the Efficient Capture and Catalysis of Polysulfides.

The sluggish sulfur reduction reaction, severe shuttle effect, and poor conductivity of sulfur species are three main problems in lithium-sulfur (Li-S) batteries. Functional materials with a strong affinity and catalytic effect toward polysulfides play a key role in addressing these issues. Herein, we report a defect-rich amorphous a-Fe3O4-x/GO material with a nanocube-interlocked structure as an adsorber as well as an electrocatalyst for the Li-S battery. The composition and defect structure of the material are determined by X-ray diffraction, high-resolution transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy measurements. The distinctive open framework architecture of the as-engineered composite inherited from the metal-organic framework precursor ensures the stability and activity of the catalyst during extended cycles. The oxygen defects in the amorphous structure are capable of absorbing polysulfides and similarly work as catalytic centers to boost polysulfide conversion. Taking advantage of a-Fe3O4-x/GO on the separator surface, the Li-S battery shows a capacity over 610 mA h g-1 at 1 C and a low decay rate of 0.12% per cycle over 500 cycles and superior rate capability. The functional material made via the low-cost synthesis process provides a potential solution for advanced Li-S batteries.

DFT study on the reaction mechanisms and stereoselectivities of NHC-catalyzed [2 + 2] cycloaddition between arylalkylketenes and electron-deficient benzaldehydes.

In this paper, two possible mechanisms (mechanisms A and B) on the stereoselective [2 + 2] cycloaddition of aryl(alkyl)ketenes and electron-deficient benzaldehydes catalyzed by N-heterocyclic carbenes (NHCs) have been investigated using density functional theory (DFT). Our calculated results indicate that the favorable mechanism (mechanism A) includes three processes: the first step is the nucleophilic attack on the arylalkylketene by the NHC catalyst to form an intermediate, the second step is the [2 + 2] cycloaddition of the intermediate and benzaldehyde for the formation of a ß-lactone, and the last step is the dissociation of the NHC catalyst and the ß-lactone. Notably, the [2 + 2] cycloaddition, in which two chiral centers associated with four configurations (SS, RR, SR and RS) are formed, is demonstrated to be both the rate- and stereoselectivity-determining step. Moreover, the reaction pathway associated with the SR configuration is the most favorable pathway and leads to the main product, which is in good agreement with the experimental results. Furthermore, the analysis of global and local reactivity indexes has been performed to explain the role of the NHC catalyst in the [2 + 2] cycloaddition reaction. Therefore, this study will be of great use for the rational design of more efficient catalysts for this kind of cycloaddition.