DS-K3DOM: 3-D Dynamic Occupancy Mapping with Kernel Inference and Dempster-Shafer Evidential Theory

Occupancy mapping has been widely utilized to represent the surroundings for autonomous robots to perform tasks such as navigation and manipulation. While occupancy mapping in 2-D environments has been well-studied, there have been few approaches suitable for 3-D dynamic occupancy mapping which is essential for aerial robots. This paper presents a novel 3-D dynamic occupancy mapping algorithm called DSK3DOM. We first establish a Bayesian method to sequentially update occupancy maps for a stream of measurements based on the random finite set theory. Then, we approximate it with particles in the Dempster-Shafer domain to enable real time computation. Moreover, the algorithm applies kernel based inference with Dirichlet basic belief assignment to enable dense mapping from sparse measurements. The efficacy of the proposed algorithm is demonstrated through simulations and real experiments.Comment: 7 pages, 2 figures, submitted to ICRA 202

Probing the Importance of Charge Balance and Noise Current in WSe2/WS2/MoS(2)van der Waals Heterojunction Phototransistors by Selective Electrostatic Doping

Heterojunction structures using 2D materials are promising building blocks for electronic and optoelectronic devices. The limitations of conventional silicon photodetectors and energy devices are able to be overcome by exploiting quantum tunneling and adjusting charge balance in 2D p–n and n–n junctions. Enhanced photoresponsivity in 2D heterojunction devices can be obtained with WSe2 and BP as p-type semiconductors and MoS2 and WS2 as n-type semiconductors. In this study, the relationship between photocurrent and the charge balance of electrons and holes in van der Waals heterojunctions is investigated. To observe this phenomenon, a p-WSe2/n-WS2/n-MoS2 heterojunction device with both p–n and n–n junctions is fabricated. The device can modulate the charge carrier balance between heterojunction layers to generate photocurrent upon illumination by selectively applying electrostatic doping to a specific layer. Using photocurrent mapping, the operating transition zones for the device is demonstrated, allowing to accurately identify the locations where photocurrent generates. Finally, the origins of flicker and shot noise at the different semiconductor interfaces are analyzed to understand their effect on the photoresponsivity and detectivity of unit active area (2.5 µm2, λ = 405 nm) in the p-WSe2/n-WS2/n-MoS2 heterojunction device. © 2020 The Authors. Published by Wiley-VCH GmbH1

Lithography-Free Fabrication of Large Area Subwavelength Antireflection Structures Using Thermally Dewetted Pt/Pd Alloy Etch Mask

We have demonstrated lithography-free, simple, and large area fabrication method for subwavelength antireflection structures (SAS) to achieve low reflectance of silicon (Si) surface. Thin film of Pt/Pd alloy on a Si substrate is melted and agglomerated into hemispheric nanodots by thermal dewetting process, and the array of the nanodots is used as etch mask for reactive ion etching (RIE) to form SAS on the Si surface. Two critical parameters, the temperature of thermal dewetting processes and the duration of RIE, have been experimentally studied to achieve very low reflectance from SAS. All the SAS have well-tapered shapes that the refractive index may be changed continuously and monotonously in the direction of incident light. In the wavelength range from 350 to 1800 nm, the measured reflectance of the fabricated SAS averages out to 5%. Especially in the wavelength range from 550 to 650 nm, which falls within visible light, the measured reflectance is under 0.01%

The musculoskeletal effect of exercise and soluble activin receptor type 2b in mouse models of osteogenesis imperfecta

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Osteogenesis Imperfecta (OI) is a heritable connective tissue disorder primarily due to mutations in the type I collagen containing tissues, such as bone, skin and blood vessels. The clinical manifestations of OI include skeletal deformity and fragility, scoliosis, growth retardation, and hearing loss. There is no cure for OI and current treatment is limited with anti-resorptive drugs, the bisphosphonates, and/or surgical intervention, which comes with adverse side-effects and high risk of device failure, respectively. Thus identifying an alternative strategy to strengthen the skeletal properties of OI is still critically needed. Bone and muscle are intimate tissues in a relation to their proximate locations and biochemical cross-talks. Bone responds and adapts to external stimuli, mainly the muscle mass and contractile strength, to alter its shape and mass due to its mechanosensing characteristic, and this makes muscle and bone mass to be positively correlated in normal condition. As a potential therapeutic option, we sought to enhance the muscle mass and function via physical exercise to indirectly improve the bone properties in OI. We have investigated the effects of the threadmill exercise in G610C OI mouse model, which has a glycine to cysteine substitution at position 610 of pro[alpha]2 collagen chain and mimics the phenotype of mild type I/IV OI individuals. Treadmill exercised heterozygous G610C (+/G610C) mice exhibited similar exercise capacity as wildtype littermates and had increased femoral stiffness without altering bone biomechanical strength. Muscle mass can be regulated by myostatin, a negative regulator of muscle growth, and deficiency of myostatin in mice lead to abnormal muscle fiber growth. As an alternative approach, we have investigated the effects of pharmacological myostatin inhibition by using a soluble fusion protein activin receptor type IIB-mFc (sActRIIB-mFc). Myostatin signals through activin receptor type IIB (ActRIIB) on cell surface to regulate downstream signaling pathways and the sActRIIB-mFc act as "ligand trap" to bind any circulating myostatin proteins and prevent them from binding to their endogenous cellular receptors. As first part of this study, we investigated the effects of sActRIIB-mFc on muscle properties of two molecularly distinct OI mouse models, G610C and oim. Unlike G610C mouse model, homozygous oim (oim/oim) has a mutation in col1[alpha]2 genes thus synthesizing nonfunctional pro[alpha]2(I) collagen chain and leading to synthesis of homotrimeric [alpha]1(I)3, instead of normal heterotrimeric [alpha]1(I)2[alpha]2(I). oim/oim also exhibit muscle atrophy with compromised muscle contractile strength. 8 weeks of bi-weekly sActRIIB-mFc (10mg/kg) treatment in +/G610C and oim/oim mice was able to induce the increase in body weight and skeletal muscle mass. In addition, oim/oim mice exhibited increase in absolute contractile strength without altering relative and specific muscle function, suggesting a potential therapeutic option for muscle weakness in oim/oim mice. As second part of this study, we investigated the effects of sActRIIB-mFc on skeletal properties of these two OI mouse models. sActRIIB-mFc treated +/G610C and oim/oim mice exhibited increase in trabecular bone microarchitecture, and +/G610C mice had further increase in cortical bone geometry and biomechanical strength. Overall, my current study demonstrated that sActRIIB-mFc treatment was effective in both G610C and oim mouse models to enhance their muscle and bone properties, although they exhibited different responses in such that G610C mice did not show a statistically significant increase in muscle contractile function while the oim mice did not show increase in cortical bone geometry and biomechanical strength. I postulate that this was potentially due to the differences in molecular mutation and severity of the phenotype, thus more thorough investigation in molecular and cellular mechanisms of sActRIIB-mFc in these two different OI mouse models will hold promise in developing more targeted therapeutic option for OI.Includes biblographical reference

Atomic-Scale Observations of the Manganese Porphyrin/Au Catalyst Interface Under the Electrocatalytic Process Revealed with Electrochemical Scanning Tunneling Microscopy

© 2021 Wiley-VCH GmbH.As a promising molecular catalyst for oxygen evolution reaction (OER), metalloporphyrin is a good model system that is extensively studied. The catalytic efficiency of metalloporphyrin can be improved with deeper insight into its complex issues, such as structural stability and catalytic activity. Using in situ electrochemical scanning tunneling microscopy (EC-STM) and X-ray photoelectron spectroscopy, the morphological evolution of the manganese porphyrin/Au(111) interface affected by the electrocatalytic reaction is revealed. In alkaline solution, the catalytic performance is dramatically enhanced after the first potential sweep, directly related to the formation of the MnOx-porphyrin complexes, driven by an irreversible oxidation–reduction process. These newly formed catalytically active materials exhibit synergistic effects with the Au interface. In situ EC-STM imaging provides the molecular evidence for the formation of the real active metalloporphyrin-based catalyst, showing the complicated interrelation of the morphology, structure, catalytic activity, and electrolyte in OER catalysts.11Nsciescopu

Restructuring of Porphyrin Networks Driven by Self-Assembled Octanoic Acid Monolayer on Au(111)

We report time-dependent surface restructuring of bicomponent domain structures of 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine (H2OEP) and cobalt(II) 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine (CoOEP) (H-2/Co OEP) driven by self-assembled octanoic acid on the surface of Au(111). Scanning tunneling microscopy (STM) visualized molecular adsorption/desorption and rearrangement of supramolecular architectures in real-time in a solution of octanoic acid. We found that unique domain structures emerged at an initial state guided by adsorbed octanoic acid on the Au surface. Moreover, the desorption of octanoic acid occurred in solution, leading to the surface restructuring of porphyrin molecular networks. This molecular evidence is well- manifested in the time-dependent phase transitions, monitored by in situ STM11Nsciescopu

Low Power Coherent Ising Machine Based on Mechanical Kerr Nonlinearity

Finding a reliable Ising machine for solving nondeterministic polynomial-class problems has attracted great attention in recent years, where an authentic system can be expanded with polynomial-scaled resources to find the ground state Ising Hamiltonian. In this Letter, we propose an extremely low power optomechanical coherent Ising machine based on a new enhanced symmetry breaking mechanism and highly nonlinear mechanical Kerr effect. The mechanical movement of an optomechanical actuator induced by the optical gradient force greatly increases the nonlinearity by a few orders and significantly reduces the power threshold using conventional structures capable of fabrication via photonic integrated circuit platforms. With the simple but strong bifurcation mechanism and remarkably low power requirement, our optomechanical spin model opens a path for chip-scale integration of large-size Ising machine implementations with great stability. © 2023 American Physical Society.FALS

Water-Assisted Growth of Cobalt Oxide and Cobalt Hydroxide Overlayers on the Pt3Co(111) Surface

© 2019 American Chemical Society.Bimetallic platinum-cobalt (Pt-Co) catalysts have highly enhanced performance for the oxygen reduction reaction (ORR), where this peculiar surface alloy structure contributes to efficient energy conversion processes. However, the detailed catalytic reaction steps and adsorbate-driven interactions on the surface morphology under practical operating conditions are still unclear. Here, we report the water-assisted surface reconstruction of the bimetallic Pt3Co(111) surface using near-ambient pressure scanning tunneling microscopy (NAP-STM) in a humid O2 environment. The segregated CoOx clusters are selectively transferred to the Co(II) oxide/hydroxide layer at 0.1 Torr of H2O/O2 gas mixture at elevated temperature. In contrast, this drastic phase transition is limited and dependent on the partial pressure of water because the nanoscale CoO islands are formed with 0.1 Torr of the N2/O2 gas mixture. Synchrotron radiation in-situ X-ray photoelectron spectroscopy measurements also support the water-assisted evolution of the Co(OH)2 species. These morphologic modulations not only explain the surface degradation process of the bimetallic Pt-Co catalysts but also indicate the active formation of CoOx/CoOOH intermediates during energy conversion11sciescopu