Distributed Adaptive Greedy Quasi-Newton Methods with Explicit Non-asymptotic Convergence Bounds

Though quasi-Newton methods have been extensively studied in the literature, they either suffer from local convergence or use a series of line searches for global convergence which is not acceptable in the distributed setting. In this work, we first propose a line search free greedy quasi-Newton (GQN) method with adaptive steps and establish explicit non-asymptotic bounds for both the global convergence rate and local superlinear rate. Our novel idea lies in the design of multiple greedy quasi-Newton updates, which involves computing Hessian-vector products, to control the Hessian approximation error, and a simple mechanism to adjust stepsizes to ensure the objective function improvement per iterate. Then, we extend it to the master-worker framework and propose a distributed adaptive GQN method whose communication cost is comparable with that of first-order methods, yet it retains the superb convergence property of its centralized counterpart. Finally, we demonstrate the advantages of our methods via numerical experiments

Removal of Mercury(II) from Aqueous Solutions by Adsorption on Poly(1-amino-5-chloroanthraquinone) Nanofibrils: Equilibrium, Kinetics, and Mechanism Studies

Poly(1-amino-5-chloroanthraquinone) (PACA) nanofibrils were applied as novel nanoadsorbents for highly toxic mercury removal from aqueous solutions. A series of batch adsorption experiments were conducted to study the effect of adsorbent dose, pH, contact time, and metal concentration on Hg(II) uptake by PACA nanofibrils. Kinetic data indicated that the adsorption process of PACA nanofibrils for Hg(II) achieved equilibrium within 2 h following a pseudo-second-order rate equation. The adsorption mechanism of PACA nanofibrils for Hg(II) was investigated by Fourier transform-infrared (FT-IR) spectra and X-ray photoelectron spectroscopy (XPS) analyses. The adsorption isotherm of Hg(II) fitted well the Langmuir model, exhibiting superb adsorption capacity of 3.846 mmol of metal per gram of adsorbent. Lastly, we found out that the as-synthesized PACA nanofibrils are efficient in Hg(II) removal from real wastewater. Furthermore, five consecutive adsorption-desorption cycles demonstrated that the PACA nanofibrils were suitable for repeated use without considerable changes in the adsorption capacity

Removal of Mercury(II) from Aqueous Solutions by Adsorption on Poly(1-amino-5-chloroanthraquinone) Nanofibrils: Equilibrium, Kinetics, and Mechanism Studies

Poly(1-amino-5-chloroanthraquinone) (PACA) nanofibrils were applied as novel nanoadsorbents for highly toxic mercury removal from aqueous solutions. A series of batch adsorption experiments were conducted to study the effect of adsorbent dose, pH, contact time, and metal concentration on Hg(II) uptake by PACA nanofibrils. Kinetic data indicated that the adsorption process of PACA nanofibrils for Hg(II) achieved equilibrium within 2 h following a pseudo-second-order rate equation. The adsorption mechanism of PACA nanofibrils for Hg(II) was investigated by Fourier transform-infrared (FT-IR) spectra and X-ray photoelectron spectroscopy (XPS) analyses. The adsorption isotherm of Hg(II) fitted well the Langmuir model, exhibiting superb adsorption capacity of 3.846 mmol of metal per gram of adsorbent. Lastly, we found out that the as-synthesized PACA nanofibrils are efficient in Hg(II) removal from real wastewater. Furthermore, five consecutive adsorption-desorption cycles demonstrated that the PACA nanofibrils were suitable for repeated use without considerable changes in the adsorption capacity

catena-Poly[zinc(II)-μ3-{hydrogen [1-hydr­oxy-2-(3-pyridinio)ethane-1,1-di­yl]diphospho­nato}]

In the polymeric title compound, [Zn(C7H9NO7P2)]n, the zinc(II) centre displays a tetra­hedral coordination geometry provided by four O atoms from three different phospho­nate groups. The crystal structure consists of ladder chains parallel to the b axis built up from vertex-sharing of ZnO4 and PO3C tetra­hedra. The chains are linked by strong intra- and inter­chain O—H⋯O and N—H⋯O hydrogen bonds, forming a three-dimensional supra­molecular assembly

Digital Twin Brain: a simulation and assimilation platform for whole human brain

In this work, we present a computing platform named digital twin brain (DTB) that can simulate spiking neuronal networks of the whole human brain scale and more importantly, a personalized biological brain structure. In comparison to most brain simulations with a homogeneous global structure, we highlight that the sparseness, couplingness and heterogeneity in the sMRI, DTI and PET data of the brain has an essential impact on the efficiency of brain simulation, which is proved from the scaling experiments that the DTB of human brain simulation is communication-intensive and memory-access intensive computing systems rather than computation-intensive. We utilize a number of optimization techniques to balance and integrate the computation loads and communication traffics from the heterogeneous biological structure to the general GPU-based HPC and achieve leading simulation performance for the whole human brain-scaled spiking neuronal networks. On the other hand, the biological structure, equipped with a mesoscopic data assimilation, enables the DTB to investigate brain cognitive function by a reverse-engineering method, which is demonstrated by a digital experiment of visual evaluation on the DTB. Furthermore, we believe that the developing DTB will be a promising powerful platform for a large of research orients including brain-inspiredintelligence, rain disease medicine and brain-machine interface.Comment: 12 pages, 11 figure

A Survey on Fundamental Limits of Integrated Sensing and Communication

The integrated sensing and communication (ISAC), in which the sensing and communication share the same frequency band and hardware, has emerged as a key technology in future wireless systems due to two main reasons. First, many important application scenarios in fifth generation (5G) and beyond, such as autonomous vehicles, Wi-Fi sensing and extended reality, requires both high-performance sensing and wireless communications. Second, with millimeter wave and massive multiple-input multiple-output (MIMO) technologies widely employed in 5G and beyond, the future communication signals tend to have high-resolution in both time and angular domain, opening up the possibility for ISAC. As such, ISAC has attracted tremendous research interest and attentions in both academia and industry. Early works on ISAC have been focused on the design, analysis and optimization of practical ISAC technologies for various ISAC systems. While this line of works are necessary, it is equally important to study the fundamental limits of ISAC in order to understand the gap between the current state-of-the-art technologies and the performance limits, and provide useful insights and guidance for the development of better ISAC technologies that can approach the performance limits. In this paper, we aim to provide a comprehensive survey for the current research progress on the fundamental limits of ISAC. Particularly, we first propose a systematic classification method for both traditional radio sensing (such as radar sensing and wireless localization) and ISAC so that they can be naturally incorporated into a unified framework. Then we summarize the major performance metrics and bounds used in sensing, communications and ISAC, respectively. After that, we present the current research progresses on fundamental limits of each class of the traditional sensing and ISAC systems. Finally, the open problems and future research directions are discussed

Eye movement characteristics in a mental rotation task presented in virtual reality

IntroductionEye-tracking technology provides a reliable and cost-effective approach to characterize mental representation according to specific patterns. Mental rotation tasks, referring to the mental representation and transformation of visual information, have been widely used to examine visuospatial ability. In these tasks, participants visually perceive three-dimensional (3D) objects and mentally rotate them until they identify whether the paired objects are identical or mirrored. In most studies, 3D objects are presented using two-dimensional (2D) images on a computer screen. Currently, visual neuroscience tends to investigate visual behavior responding to naturalistic stimuli rather than image stimuli. Virtual reality (VR) is an emerging technology used to provide naturalistic stimuli, allowing the investigation of behavioral features in an immersive environment similar to the real world. However, mental rotation tasks using 3D objects in immersive VR have been rarely reported.MethodsHere, we designed a VR mental rotation task using 3D stimuli presented in a head-mounted display (HMD). An eye tracker incorporated into the HMD was used to examine eye movement characteristics during the task synchronically. The stimuli were virtual paired objects oriented at specific angular disparities (0, 60, 120, and 180°). We recruited thirty-three participants who were required to determine whether the paired 3D objects were identical or mirrored.ResultsBehavioral results demonstrated that the response times when comparing mirrored objects were longer than identical objects. Eye-movement results showed that the percent fixation time, the number of within-object fixations, and the number of saccades for the mirrored objects were significantly lower than that for the identical objects, providing further explanations for the behavioral results.DiscussionIn the present work, we examined behavioral and eye movement characteristics during a VR mental rotation task using 3D stimuli. Significant differences were observed in response times and eye movement metrics between identical and mirrored objects. The eye movement data provided further explanation for the behavioral results in the VR mental rotation task

Experimental evidence to understand mechanical causes of retinal detachment following blunt trauma.

PURPOSE: This study aimed to perform an in vitro experiment to simulate retinal detachment caused by blunt impact, and provide experimental evidence to understand mechanical causes of traumatic retinal detachment. METHODS: The experiment was conducted on twenty-two fresh porcine eyes using a bespoke pendulum testing device at two energy levels (0.1J for low energy and 1.0J for high energy). We examined dynamic forces and mechanical responses to the impact, including global deformations, intraocular pressure changes and the energy absorption. Another set of twenty-two eyes underwent pathological examination immediately after being subjected to blunt impact. Twelve additional intact eyes were examined as controls. All pathological sections were scored to indicate whether retinal detachment had occurred. RESULTS: A dynamic variation in intraocular pressure was detected following impact and exhibited an approximate sinusoidal oscillation-attenuation profile. The peaks of impact force were 12.9 ± 1.9 N at low-energy level and 34.8 ± 9.8 N at high-energy level, showing a significant difference (p < 0.001). The positive and negative peaks of intraocular pressure were 149.4 ± 18.9 kPa and -10.9 ± 7.2 kPa at low-energy level, and 274.5 ± 55.2 kPa and -35.7 ± 23.7 kPa at high-energy level, showing significant differences (p < 0.001 for both levels). Retinal detachments were observed in damaged eyes while few detachments were found in control eyes. The occurrence rate of retinal detachment differed significantly (p < 0.05) between the high- and low-energy impact groups. CONCLUSIONS: This study provided experimental evidence that shockwaves produced by blunt trauma break the force equilibrium and lead to the oscillation and negative pressure, which mainly contribute to traumatic retinal detachment

Identification of miRs-143 and -145 that Is Associated with Bone Metastasis of Prostate Cancer and Involved in the Regulation of EMT

The principal problem arising from prostate cancer (PCa) is its propensity to metastasize to bone. MicroRNAs (miRNAs) play a crucial role in many tumor metastases. The importance of miRNAs in bone metastasis of PCa has not been elucidated to date. We investigated whether the expression of certain miRNAs was associated with bone metastasis of PCa. We examined the miRNA expression profiles of 6 primary and 7 bone metastatic PCa samples by miRNA microarray analysis. The expression of 5 miRNAs significantly decreased in bone metastasis compared with primary PCa, including miRs-508-5p, -145, -143, -33a and -100. We further examined other samples of 16 primary PCa and 13 bone metastases using real-time PCR analysis. The expressions of miRs-143 and -145 were verified to down-regulate significantly in metastasis samples. By investigating relationship of the levels of miRs-143 and -145 with clinicopathological features of PCa patients, we found down-regulations of miRs-143 and -145 were negatively correlated to bone metastasis, the Gleason score and level of free PSA in primary PCa. Over-expression miR-143 and -145 by retrovirus transfection reduced the ability of migration and invasion in vitro, and tumor development and bone invasion in vivo of PC-3 cells, a human PCa cell line originated from a bone metastatic PCa specimen. Their upregulation also increased E-cadherin expression and reduced fibronectin expression of PC-3 cells which revealed a less invasive morphologic phenotype. These findings indicate that miRs-143 and -145 are associated with bone metastasis of PCa and suggest that they may play important roles in the bone metastasis and be involved in the regulation of EMT Both of them may also be clinically used as novel biomarkers in discriminating different stages of human PCa and predicting bone metastasis