CT based three-dimensional measurement of adult orbit in Hospital Universiti Sains Malaysia

Purpose: To correlate the orbital parameters with age, race and gender of the HUSM population for forensic radiology future reference. Materials and methods: In an institutional review board-approved study, the authors obtained 126 samples referred to HUSM Radiology Department for CT scan of the head. Measurement of the orbital parameters is done on reconstructed 3D images using electronic calipers on workstation screen with the supervision of the supervisor, a senior radiologist with more than 30 years of experience in the Head and Neck imaging. Correlation and regression was used to assess the association between the orbital parameters with patient’s age, race and gender. Results: We were able to obtain 126 patients in which 113 were Malays, 13 were non-Malays, 68 were male and 58 were female. There was a significant correlation between the left and right orbital height (regression line 0.877), orbital width (regression line 0.759) and orbital perimeter (regression line 0.850). There was no significant statistical difference with race correlation and the orbital anthropometry. In terms of correlation with gender, independent t-test showed there was significant statistical difference in the left orbital height (mean difference 0.05), right orbital height (mean difference 0.06) and right orbital perimeter (mean difference 0.16). One way ANOVA showed that in terms of age, there was a significant statistical difference between the left orbital width (mean difference 0.16), right orbital width (mean difference 0.15) and left orbital perimeter (mean difference 0.43). Conclusions: This study provided useful baseline anthropometric data that will be of clinical and surgical interest in ophthalmology, oral and maxillofacial surgery in Kelantan. We recommended that anthropologists, clinicians and forensic experts to obtain this data and use them in any way deemed necessary for the quest of research and knowledge

Coherent quantum transport in disordered systems: A unified polaron treatment of hopping and band-like transport

Quantum transport in disordered systems is studied using a polaron-based master equation. The polaron approach is capable of bridging the results from the coherent band-like transport regime governed by the Redfield equation to incoherent hopping transport in the classical regime. A non-monotonic dependence of the diffusion coefficient is observed both as a function of temperature and system-phonon coupling strength. In the band-like transport regime, the diffusion coefficient is shown to be linearly proportional to the system-phonon coupling strength, and vanishes at zero coupling due to Anderson localization. In the opposite classical hopping regime, we correctly recover that the dynamics are described by the Fermi's Golden Rule (FGR) and establish that the scaling of the diffusion coefficient depends on the phonon bath relaxation time. In both the hopping and band-like transport regimes, it is demonstrated that at low temperature the zero-point fluctuations of the bath lead to non-zero transport rates, and hence a finite diffusion constant. Application to rubrene and other organic semiconductor materials shows a good agreement with experimental mobility data.Comment: 19 pages, 4 figure

Non-Canonical Statistics of a Spin-Boson Model: Theory and Exact Monte-Carlo Simulations

Equilibrium canonical distribution in statistical mechanics assumes weak system-bath coupling (SBC). In real physical situations this assumption can be invalid and equilibrium quantum statistics of the system may be non-canonical. By exploiting both polaron transformation and perturbation theory in a spin-boson model, an analytical treatment is advocated to study non-canonical statistics of a two-level system at arbitrary temperature and for arbitrary SBC strength, yielding theoretical results in agreement with exact Monte-Carlo simulations. In particular, the eigen-representation of system's reduced density matrix is used to quantify non-canonical statistics as well as the quantumness of the open system. For example, it is found that irrespective of SBC strength, non-canonical statistics enhances as temperature decreases but vanishes at high temperature.Comment: 8 pages, 6 figures, to appear in Phys. Rev.

The Enhancement of Interfacial Exciton Dissociation by Energetic Disorder is a Nonequilibrium Effect

The dissociation of excited electron-hole pairs is a microscopic process that is fundamental to the performance of photovoltaic systems. For this process to be successful, the oppositely charged electron and hole must overcome an electrostatic binding energy before they undergo ground state recombination. Here we use a simple model of charge dynamics to investigate the role of molecular disorder in this process. This model reveals that moderate spatial variations in electronic energy levels, such as those that arise in disordered molecular systems, can actually increase charge dissociation yields. We demonstrate that this is a nonequilibrium effect that is mediated by the dissipation driven formation of partially dissociated intermediate states that are long-lived because they cannot easily recombine. We present a kinetic model that incorporates these states and show that it is capable of reproducing similar behavior when it is parameterized with nonequilibrium rates.Comment: 25 pages, 7 figure

Quantum Diffusion on Molecular Tubes: Universal Scaling of the 1D to 2D Transition

The transport properties of disordered systems are known to depend critically on dimensionality. We study the diffusion coefficient of a quantum particle confined to a lattice on the surface of a tube, where it scales between the 1D and 2D limits. It is found that the scaling relation is universal and independent of the disorder and noise parameters, and the essential order parameter is the ratio between the localization length in 2D and the circumference of the tube. Phenomenological and quantitative expressions for transport properties as functions of disorder and noise are obtained and applied to real systems: In the natural chlorosomes found in light-harvesting bacteria the exciton transfer dynamics is predicted to be in the 2D limit, whereas a family of synthetic molecular aggregates is found to be in the homogeneous limit and is independent of dimensionality.Comment: 10 pages, 6 figure

Hedging Strategy in Petro Summit - Is It Effective?

This paper attempts to find out the hedging strategy of Petro Summit and explore its effectiveness. Was the income volatility due to some risks that cannot be hedged and that it is masking the effectiveness of the hedging strategy in Petro Summit? Could the company have done better in hedging their risks (i.e. was the hedging in Petro Summit effective)

Hedging Strategy in Petro Summit - Is It Effective?

This paper attempts to find out the hedging strategy of Petro Summit and explore its effectiveness. Was the income volatility due to some risks that cannot be hedged and that it is masking the effectiveness of the hedging strategy in Petro Summit? Could the company have done better in hedging their risks (i.e. was the hedging in Petro Summit effective)

Hierarchical Graph Transformer with Adaptive Node Sampling

The Transformer architecture has achieved remarkable success in a number of domains including natural language processing and computer vision. However, when it comes to graph-structured data, transformers have not achieved competitive performance, especially on large graphs. In this paper, we identify the main deficiencies of current graph transformers:(1) Existing node sampling strategies in Graph Transformers are agnostic to the graph characteristics and the training process. (2) Most sampling strategies only focus on local neighbors and neglect the long-range dependencies in the graph. We conduct experimental investigations on synthetic datasets to show that existing sampling strategies are sub-optimal. To tackle the aforementioned problems, we formulate the optimization strategies of node sampling in Graph Transformer as an adversary bandit problem, where the rewards are related to the attention weights and can vary in the training procedure. Meanwhile, we propose a hierarchical attention scheme with graph coarsening to capture the long-range interactions while reducing computational complexity. Finally, we conduct extensive experiments on real-world datasets to demonstrate the superiority of our method over existing graph transformers and popular GNNs.Comment: Accepted by NeurIPS 202