100-Phones: A Large VI-SLAM Dataset for Augmented Reality Towards Mass Deployment on Mobile Phones.

Visual-inertial SLAM (VI-SLAM) is a key technology for Augmented Reality (AR), which allows the AR device to recover its 6-DoF motion in real-time in order to render the virtual content with the corresponding pose. Nowadays, smartphones are still the mainstream devices for ordinary users to experience AR. However the current VI-SLAM methods, although performing well on high-end phones, still face robustness challenges when deployed on a larger stock of mid- and low-end phones. Existing VI-SLAM datasets use either very ideal sensors or only a limited number of devices for data collection, which cannot reflect the capability gaps that VI-SLAM methods need to solve when deployed on a large variety of phone models. This work proposes 100-Phones. the first VI-SLAM dataset covering a wide range of mainstream phones in the market. The dataset consists of 350 sequences collected by 100 different models of phones. Through analysis and experiments on the collected data, we conclude that the quality of visual-inertial data vary greatly among the mainstream phones, and the current open source VI-SLAM methods still have serious robustness issues when it comes to mass deployment on mobile phones. We release the dataset to facilitate the robustness improvement of VI-SLAM and to promote the mass popularization of AR. Project page: https://github.com/zju3dv/100-Phones.

MagLoc-AR: Magnetic-Based Localization for Visual-Free Augmented Reality in Large-Scale Indoor Environments.

Accurate localization of a display device is essential for AR in large-scale environments. Visual-based localization is the most commonly used solution, but poses privacy risks, suffers from robustness issues and consumes high power. Wireless signal-based localization is a potential visual-free solution, but its accuracy is not enough for AR. In this paper, we present MagLoc-AR, a novel visual-free localization solution that achieves sufficient accuracy for some AR applications (e.g. AR navigation) in large-scale indoor environments. We exploit the location-dependent magnetic field interference that is ubiquitous indoors as a localization signal. Our method requires only a consumer-grade 9-axis IMU, with the gyroscope and acceleration measurements used to recover the motion trajectory, and the magnetic measurements used to register the trajectory to the global map. To meet the accuracy requirement of AR, we propose a mapping method to reconstruct a globally consistent magnetic field of the environment, and a localization method fusing the biased magnetic measurements with the network-predicted motion to improve localization accuracy. In addition, we provide the first dataset for both visual-based and geomagnetic-based localization in large-scale indoor environments. Evaluations on the dataset demonstrate that our proposed method is sufficiently accurate for AR navigation and has advantages over the visual-based methods in terms of power consumption and robustness. Project page: https://github.com/zju3dv/MagLoc-AR/.

Dynamics of green economic development in countries joining the belt and road initiative: Is it driven by green investment transformation?

Green investment transformation is the main interval difference of the Belt and Road Initiative, however, its actual effects are still uncertain. Finding out its utility, mechanism and improvement on green economy may accelerate green development. In this paper, Slack Based Measure model is used to obtain original results, Super-Efficiency model is used to sort effective decision-making units for stronger efficient frontier and Minimum Distance to Strong Efficient Frontier model is used to narrow gaps between non-effective ones and real situations. Then Global Malmquist-Lunberger index makes results dynamisation. Samples of 51 countries joining the Belt and Road Initiative from 2008 to 2022 are used in above-mentioned models to portray green economic dynamics. Then utility, mechanism and improvement of green investment transformation on green economy are studied through econometric model. The findings show that (i) Green Belt and Road Initiative makes green economic development more stable. The standard deviation decreases by 96.53% and mean maintains in 1.5. However, disconnection between a 36.36% increase of pure technological change and a 24.83% decline of its scale effect inhibits technical advance. (ii) Share of countries obtaining green scale revenues reaches 56.86%, which realizes a 52.64% increase. Furthermore, gaps between countries with positive status and those with negative status narrow 68.42%. Positive group accounts for 50% in developed countries and 46.15% in developing countries. (iii) Performance of Green Belt and Road Initiative is better than the Belt and Road Initiative. A one standard deviation increase in green investment transformation increases green economic development by 0.2705 (0.2105), which is a 18.57% (14.45%) increase relative to average green economic development of 1.457. Former's strengths also reflect in different quantiles, lagging effect and heterogeneity analysis. (iv) Green investment transformation of Green Belt and Road Initiative broadens more reliable mechanism (Promote Innovation - Strict Regulation - Ensure Commercialization) based on original one (Improve Efficiency - Decrease Costs - Increase Revenues) of the Belt and Road Initiative. (v) For the green investment transformation with government subsidies, property rights protection, investment environment stability and exchange cooperation, magnitudes of its effects on green economic development have significant increases by 25.03%, 31.77%, 8.01% and 10.12% respectively. The findings not only help understand green economic status, but also support some policy insights for achieving green economy by discovering utility, mechanism and improvement of green investment transformation.

CoLi-BA: Compact Linearization based Solver for Bundle Adjustment.

Bundle adjustment (BA) is widely used in SLAM and SfM, which are key technologies in Augmented Reality. For real-time SLAM and large-scale SfM, the efficiency of BA is of great importance. This paper proposes CoLi-BA, a novel and efficient BA solver that significantly improves the optimization speed by compact linearization and reordering. Specifically, for each reprojection function, the redundant matrix representation of Jacobian is replaced with a tiny 3D vector, by which the computational complexity, memory storage, and cache missing for Hessian matrix construction and Schur complement are significantly reduced. Besides, we also propose a novel reordering strategy to improve the cache efficiency for Schur complement. Experiments on diverse datasets show that the speed of the proposed CoLi-BA is five times that of Ceres and two times that of g2o without sacrificing accuracy. We further verify the effectiveness by porting CoLi-BA to the open-source SLAM and SfM systems. Even when running the proposed solver in a single thread, the local BA of SLAM only takes about 20ms on a desktop PC, and the reconstruction of SfM with seven thousand photos only takes half an hour. The source code is available on the webpage: https://github.com/zju3dv/CoLi-BA.

Ocean wave energy generator based on graphene/TiO2 nanoparticle composite films.

Harvesting ocean wave energy through carbon-based materials, particularly graphene, is receiving increasing attention. However, the complicated fabrication process and the low output power of the present monolayer graphene-based wave energy generators limit their further application. Here, we demonstrate the facile fabrication of a new type of wave energy generator based on graphene/TiO2 nanoparticle composite films using the doctor-blading method. The developed wave energy harvesting device exhibits a high open-circuit voltage of up to 75 millivolts and a high output power up to 1.8 microwatts. A systematic study was conducted to explore the optimal conditions for the energy harvesting performance.

Dual amplification enabled counting based ultrasensitive enzyme-linked immunosorbent assay.

ELISA is a predominant technique in the detection of biomarkers. Notwithstanding its ubiquity and numerous advantages, its application for detection of low abundant biomarkers requires the ultrasensitivity. To bridge the gap between the need and availability, an innovative dual amplification enabled counting based ELISA was developed for ultrasensitive detection of mouse total IgG (a model biomarker). The dual amplification strategy, which is compatible with conventional plate-based ELISA, was realized through tyramide signal amplification (TSA) and alkaline phosphatase enabled formation of fluorescent precipitates. The counting of fluorescent precipitates in 25 images of each well can correlate the number of precipitates to the concentration of IgG with good linearity and lower the limit of detection of the commercial mouse IgG kit (1.56 ng/mL) to 54.5 pg/mL. Recovery tests further demonstrate the reliability of the developed method. This study opens a new avenue to improve the sensitivity of conventional plate-based ELISA.

MOUNT: Learning 6DoF Motion Prediction Based on Uncertainty Estimation for Delayed AR Rendering.

The delay of rendering on AR devices requires prediction of head motion using sensor data acquired tens of even one hundred milliseconds ago to avoid misalignment between the virtual content and the physical world, where the misalignment will lead to a sense of time latency and dizziness for users. To solve the problem, we propose a method for the 6DoF motion prediction to compensate for the time latency. Compared with traditional hand-crafted methods, our method is based on deep learning, which has better motion prediction ability to deal with complex human motion. In particular, we propose a MOtion UNcerTainty encode decode network (MOUNT) that estimates the uncertainty of input data and predicts the uncertainty of output motion to improve the prediction accuracy and smoothness. Experiments on the EuRoC and our collected dataset demonstrate that our method significantly outperforms the traditional method and greatly improves AR visual effects.

A critical review: Recent advances in "digital" biomolecule detection with single copy sensitivity.

Detection of a single biomolecule, ranging from nucleic acids, proteins, viruses to bacteria, is of paramount importance in various fields including biology, environment, food and agriculture industry, public health, and medicine. With the understanding of the biological functions of these biomolecules (or bioparticles) and their impacts on public health, environmental pollution, and food safety, advanced detection techniques are unprecedentedly demanded for their early and/or sensitive detection. In this critical review, a series of elegant research about digital detection of biomolecules with potential single copy sensitivity is reviewed and summarized with the focus on the design principle and the innovation of how to accomplish the "digital" detection concept. Starting with a brief introduction on the importance of digital detection, recent advances in "digital" biomolecule detection with single copy sensitivity are grouped and discussed based on the difference of signal reporting systems, including surrogate signal development for "digital" detection, direct visualization for "digital" detection, and nucleic acid amplification enabled "digital" detection. Interdisciplinary combination and integration of different cutting-edge techniques are also discussed with details. The review is closed with the conclusion and future trends.

A whole area scanning-enabled direct-counting strategy for studying blocking efficiency in mitigating protein-solid surface binding.

The study of protein-solid surface binding as well as blocking efficiency of blocking agents plays an important role in the development of high-performance immunoassays. Although conventional colorimetric based assays are widely employed to monitor protein non-specific binding on the surface of microplate wells and evaluate the performance of blocking agents, there is still a great need to develop new methods to achieve the same goal from a new perspective. In this study, an innovative whole area scanning (WAS)-enabled direct-counting strategy was developed and validated through studying the blocking efficiency of different blocking agents on the non-specific binding of streptavidin-alkaline phosphatase conjugate (Strep-ALP, a model protein) to the surface of 96-well microplates. After non-specific binding of Strep-ALP in wells with or without blocking agents' treatment and loading of ELF™ 97 phosphate (ELFP), ALP in Strep-ALP conjugates converts ELFP to water-insoluble ELF™ 97 alcohol (ELFA), which precipitates locally, self-assembles into large needle structures, and glows green fluorescence upon excitation. After quenching the reaction, WAS of the whole wells allows us to directly count the number of individual fluorescent precipitates, which can be used to calculate and compare the blocking efficiency of three commonly used blocking agents (BSA, casein, and dry milk) based on mitigating the non-specific binding of Strep-ALP. WAS-enabled counting of individual needle-type precipitates opens a new avenue to investigate protein-solid surface binding as well as the efficiency of blocking agents with high sensitivity.

Revisiting China's provincial energy efficiency and its influencing factors.

Improving the energy efficiency is a fundamental way to ensure energy security and sustainable development, and is also the requirement of supply-side structural reform of China's energy. This paper uses the DEA-BCC model to estimate China's energy efficiency at the provincial level, analyzes its regional differences from 2006 to 2016, and applies a panel data model to analyze the influencing factors of energy efficiency. It selects labor, capital stock and total energy consumption as inputs and takes real GDP and comprehensive index of environmental pollution as desirable and undesirable outputs, respectively. The results show that (1) energy efficiency when undesirable output is included is generally lower than when undesirable output is excluded; (2) There is a considerable difference in energy efficiency among provinces, and China's energy efficiency, by and large, shows a trend of declining. The energy efficiency of four major regions demonstrates obvious regional differences: coastal region>northeastern region> middle region >western region; (3) The economic development level, technological progress, energy price and urbanization level are positively associated with energy efficiency, while the proportion of secondary industry and the energy consumption structure dominated by coal and oil are negatively correlated with energy efficiency.

Whole Slide Imaging for High-Throughput Sensing Antibiotic Resistance at Single-Bacterium Level and Its Application to Rapid Antibiotic Susceptibility Testing.

Since conventional culture-based antibiotic susceptibility testing (AST) methods are too time-consuming (typically 24-72 h), rapid AST is urgently needed for preventing the increasing emergence and spread of antibiotic resistant infections. Although several phenotypic antibiotic resistance sensing modalities are able to reduce the AST time to a few hours or less, concerning the biological heterogeneity, their accuracy or limit of detection are limited by low throughput. Here, we present a rapid AST method based on whole slide imaging (WSI)-enabled high-throughput sensing antibiotic resistance at single-bacterium level. The time for determining the minimum inhibitory concentration (MIC) was theoretically shortest, which ensures that the growth of each individual cell present in a large population is inhibited. As a demonstration, our technique was able to sense the growth of at least several thousand bacteria at single-cell level. Reliable MIC of Enterobacter cloacae against gentamicin was obtained within 1 h, while the gold standard broth dilution method required at least 16 h for the same result. In addition, the application of our method prevails over other imaging-based AST approaches in allowing rapid and accurate determination of antibiotic susceptibility for phenotypically heterogeneous samples, in which the number of antibiotic resistant cells was negligible compared to that of the susceptible cells. Hence, our method shows great promise for both rapid AST determination and point-of-care testing of complex clinical bacteria isolates.

Digital, Rapid, Accurate, and Label-Free Enumeration of Viable Microorganisms Enabled by Custom-Built On-Glass-Slide Culturing Device and Microscopic Scanning.

Accurately measuring the number of viable microorganisms plays an essential role in microbiological studies. Since the conventional agar method of enumerating visible colonies is time-consuming and not accurate, efforts have been made towards overcoming these limitations by counting the invisible micro-colonies. However, none of studies on micro-colony counting was able to save significant time or provide accurate results. Herein, we developed an on-glass-slide cell culture device that enables rapid formation of micro-colonies on a 0.38 mm-thick gel film without suffering from nutrient and oxygen deprivation during bacteria culturing. Employing a phase contrast imaging setup, we achieved rapid microscopic scanning of micro-colonies within a large sample area on the thin film without the need of fluorescent staining. Using Escherichia coli (E. coli) as a demonstration, our technique was able to shorten the culturing time to within 5 h and automatically enumerate the micro-colonies from the phase contrast images. Moreover, this method delivered more accurate counts than the conventional visible colony counting methods. Due to these advantages, this imaging-based micro-colony enumeration technique provides a new platform for the quantification of viable microorganisms.

Secondary dialkylammonium salt/crown ether [2]pseudorotaxanes as nanostructured platforms for proton transport.

Multivalent secondary dialkylammonium salt/crown ether [2]pseudorotaxane, supramolecular polymer networks have been obtained by mixing surfactant-encapsulated clusters with dibenzo[24]crown-8 groups and star polymers end functionalized with dibenzylammonium ions. This induces remarkable enhancements and rational control of proton conductivity of the supramolecular networks.

Fixation of Zinc(II) Ion to Dioxygen in a Highly Deformed Porphyrin: Implications for the Oxygen Carrier Mechanism of Distorted Heme.

Three saddle-type nonplanar zinc porphyrins strapped by two short alkyl linkers have been synthesized. The deformation induced by the linkers can cause a spectral red shift of >30 nm compared with the absorption maxima of regular porphyrins and can also regulate the electronic structure of the central zinc(II) ion. The zinc(II) ion then complexes and activates a free dioxygen to form a superoxide group ligand by enlarging the splitting of energy levels of d orbitals under strong core deformation. The fixation of dioxygen can be reasonably explained by the Dewar-Chatt-Duncanson model. These results indicate that this type of saddle porphyrin has the potential to be used as a new model system of heme.

Fractional transfer of a free unpaired electron to overcome energy barriers in the formation of Fe(4+) from Fe(3+) during the core contraction of macrocycles: implication for heme distortion.

The free unpaired electron in Fe(3+) ions cannot be directly removed, and needs a transfer pathway with at least four steps to overcome the high energy barriers to form Fe(4+) ions. Fine changes in the electronic structure of Fe(3+) ions on spin conversion were identified through a deeper analysis of the diffraction, spectral and electrochemical data for six non-planar iron porphyrins. Fe(3+) ions can form four d electron tautomers as the compression of the central ion is increased. This indicates that the Fe(3+) ion undergoes a multistep electron transfer where the total energy gap of electron transfer is split into several smaller gaps to form high-valent Fe(4+) ions. We find that the interchange of these four electron tautomers is clearly related to the core size of the macrocycle in the current series. The large energy barrier to produce iron(iv) complexes is overcome through a gradient effect of multiple energy levels. In addition, a possible porphyrin Fe(3+)˙ radical may be formed from its stable isoelectronic form, porphyrin Fe(3+), under strong core contraction. These results indicate the important role of heme distortion in its catalytic oxidation functions.

Synthesis and biological evaluation of piperamide analogues as HDAC inhibitors.

Two natural piperamides (piperlonguminine and refrofractamide A) and their derivatives were synthesized and evaluated for inhibitory activity against histone deacetylases, as well as the HCT-116 human colon cancer cell line. The preliminary structure activity relationship was discussed. Compounds featuring a hydroxamic acid moiety exhibited moderate HDAC activity and in vitro cytotoxicity.