Effects of arbitrarily directed field on spin phase oscillations in biaxial molecular magnets

Quantum phase interference and spin-parity effects are studied in biaxial molecular magnets in a magnetic field at an arbitrarily directed angle. The calculations of the ground-state tunnel splitting are performed on the basis of the instanton technique in the spin-coherent-state path-integral representation, and complemented by exactly numerical diagonalization. Both the Wentzel-Kramers-Brillouin exponent and the preexponential factor are obtained for the entire region of the direction of the field. Our results show that the tunnel splitting oscillates with the field for the small field angle, while for the large field angle the oscillation is completely suppressed. This distinct angular dependence, together with the dependence of the tunnel splitting on the field strengh, provide an independent test for spin-parity effects in biaxial molecular magnets. The analytical results for the molecular Fe$_{8}$ magnet, are found to be in good areement with the numerical simulations, which suggests that even the molecular magnet with total spin S=10 is large enough to be treated as a giant spin system.Comment: 19 pages, 5 figure

Macroscopic quantum coherence in antiferromagnetic molecular magnets

The macroscopic quantum coherence in a biaxial antiferromagnetic molecular magnet in the presence of magnetic field acting parallel to its hard anisotropy axis is studied within the two-sublattice model. On the basis of instanton technique in the spin-coherent-state path-integral representation, both the rigorous Wentzel-Kramers-Brillouin exponent and preexponential factor for the ground-state tunnel splitting are obtained. We find that the quantum fluctuations around the classical paths can not only induce a new quantum phase previously reported by Chiolero and Loss (Phys. Rev. Lett. 80, 169 (1998)), but also have great influnence on the intensity of the ground-state tunnel splitting. Those features clearly have no analogue in the ferromagnetic molecular magnets. We suggest that they may be the universal behaviors in all antiferromagnetic molecular magnets. The analytical results are complemented by exact diagonalization calculation.Comment: 6 pages, 1 figur

Low energy exciton states in a nanoscopic semiconducting ring

We consider an effective mass model for an electron-hole pair in a simplified confinement potential, which is applicable to both a nanoscopic self-assembled semiconducting InAs ring and a quantum dot. The linear optical susceptibility, proportional to the absorption intensity of near-infrared transmission, is calculated as a function of the ring radius $$. Compared with the properties of the quantum dot corresponding to the model with a very small radius $R_0$, our results are in qualitative agreement with the recent experimental measurements by Pettersson {\it et al}.Comment: 4 pages, 4 figures, revised and accepted by Phys. Rev.

Online Container Scheduling for Low-Latency IoT Services in Edge Cluster Upgrade: A Reinforcement Learning Approach

In Mobile Edge Computing (MEC), Internet of Things (IoT) devices offload computationally-intensive tasks to edge nodes, where they are executed within containers, reducing the reliance on centralized cloud infrastructure. Frequent upgrades are essential to maintain the efficient and secure operation of edge clusters. However, traditional cloud cluster upgrade strategies are ill-suited for edge clusters due to their geographically distributed nature and resource limitations. Therefore, it is crucial to properly schedule containers and upgrade edge clusters to minimize the impact on running tasks. In this paper, we propose a low-latency container scheduling algorithm for edge cluster upgrades. Specifically: 1) We formulate the online container scheduling problem for edge cluster upgrade to minimize the total task latency. 2) We propose a policy gradient-based reinforcement learning algorithm to address this problem, considering the unique characteristics of MEC. 3) Experimental results demonstrate that our algorithm reduces total task latency by approximately 27\% compared to baseline algorithms

{2-[(Benzylphenyl­phosphanyl-κP)methyl]phenyl-κC 1}iodidobis(trimethyl­phos­phane)cobalt(II)

In the title compound, [Co(C20H18P)I(C3H9P)2], the CoII atom has a distorted square-pyramidal geometry, the base of which is comprised of two trans PMe3 groups, an I atom, and a C atom of the benzyl group. This benzyl group is tethered to the P atom at the apex of the pyramid, thereby forming a five-membered chelated Co—C—C—C—P ring

Ethyl 6-methyl-2-p-tolyl­pyrazolo[1,5-a]pyridine-5-carboxyl­ate

In the title mol­ecule, C18H18N2O2, the bicyclic ring system and the benzene ring form a dihedral angle of 13.45 (3)°. In the crystal structure, weak inter­molecular C—H⋯O hydrogen bonds link mol­ecules into chains propagated along [201]

Efficient Serverless Function Scheduling at the Network Edge

Serverless computing is a promising approach for edge computing since its inherent features, e.g., lightweight virtualization, rapid scalability, and economic efficiency. However, previous studies have not studied well the issues of significant cold start latency and highly dynamic workloads in serverless function scheduling, which are exacerbated at the resource-limited network edge. In this paper, we formulate the Serverless Function Scheduling (SFS) problem for resource-limited edge computing, aiming to minimize the average response time. To efficiently solve this intractable scheduling problem, we first consider a simplified offline form of the problem and design a polynomial-time optimal scheduling algorithm based on each function's weight. Furthermore, we propose an Enhanced Shortest Function First (ESFF) algorithm, in which the function weight represents the scheduling urgency. To avoid frequent cold starts, ESFF selectively decides the initialization of new function instances when receiving requests. To deal with dynamic workloads, ESFF judiciously replaces serverless functions based on the function weight at the completion time of requests. Extensive simulations based on real-world serverless request traces are conducted, and the results show that ESFF consistently and substantially outperforms existing baselines under different settings

BASM: A Bottom-up Adaptive Spatiotemporal Model for Online Food Ordering Service

Online Food Ordering Service (OFOS) is a popular location-based service that helps people to order what you want. Compared with traditional e-commerce recommendation systems, users' interests may be diverse under different spatiotemporal contexts, leading to various spatiotemporal data distribution, which limits the fitting capacity of the model. However, numerous current works simply mix all samples to train a set of model parameters, which makes it difficult to capture the diversity in different spatiotemporal contexts. Therefore, we address this challenge by proposing a Bottom-up Adaptive Spatiotemporal Model(BASM) to adaptively fit the spatiotemporal data distribution, which further improve the fitting capability of the model. Specifically, a spatiotemporal-aware embedding layer performs weight adaptation on field granularity in feature embedding, to achieve the purpose of dynamically perceiving spatiotemporal contexts. Meanwhile, we propose a spatiotemporal semantic transformation layer to explicitly convert the concatenated input of the raw semantic to spatiotemporal semantic, which can further enhance the semantic representation under different spatiotemporal contexts. Furthermore, we introduce a novel spatiotemporal adaptive bias tower to capture diverse spatiotemporal bias, reducing the difficulty to model spatiotemporal distinction. To further verify the effectiveness of BASM, we also novelly propose two new metrics, Time-period-wise AUC (TAUC) and City-wise AUC (CAUC). Extensive offline evaluations on public and industrial datasets are conducted to demonstrate the effectiveness of our proposed modle. The online A/B experiment also further illustrates the practicability of the model online service. This proposed method has now been implemented on the Ele.me, a major online food ordering platform in China, serving more than 100 million online users

tert-Butyl N-(5-bromo-1H-imidazo[4,5-b]pyridin-2-ylmeth­yl)carbamate

In the mol­ecule of the title compound, C12H15BrN4O2, the imidazole and pyridine rings are strictly coplanar [maximum deviation 0.006 (3) Å]. In the crystal structure, mol­ecules are linked into chains running parallel to the a axis by inter­molecular N—H⋯O hydrogen bonds. Centrosymmetrically related chains are further connected by N—H⋯N hydrogen-bonding inter­actions to form a two-dimensional layer structure parallel to the ab plane