Showing papers on "Tripod (photography) published in 2022"

ZnIn2S4 QDs@TiO2 nanosphere-BiOI double heterojunction combined with unique tripod DNA walker amplification for photoelectrochemical biosensing of microRNA-21

Abstract: In this study, a new amplified signal probe of ZnIn2S4 quantum [email protected]2 nanosphere was used to sensitize the BiOI substrate, which was combined with a unique tripod DNA walker to develop a new photoelectrochemical (PEC) biosensor for microRNA-21 (miRNA-21) assay. TiO2 has good PEC activity for its narrow band gap, and a large number of ZnIn2S4 quantum dots (QDs) were attached to the TiO2 to form a good heterojunction, realizing double enhancement of PEC performance. Moreover, a tripod DNA walker for target-cycling amplification was synthesized using a simple catalytic hairpin assembly (CHA). After DNA hairpin 5 (HP5) was linked to the BiOI-modified electrode, the prepared three-legged DNA walker opened HP5 DNA, and formed a single-stranded DNA (ssDNA). Then the ZnIn2S4 [email protected]2 signal probe was linked to the electrode by specific hybridization of ssDNA with the tripod walker, realizing noticeable amplification of PEC signal for sensitive detection of miRNA-21. This work combined the excellent PEC characteristic, the amplified signal of ZnIn2S4 [email protected]2 heterojunction, and an enzyme-free tripod walker amplification technique to achieve sensitive detection of target, which opens a new PEC analysis method for clinical application.

An “On‐Demand”, Selective Dehydrogenative Borylation or Hydroboration of Terminal Alkynes Using Zn2+‐based Catalyst

Abstract: An air‐stable dicationic Zn2+ complex (1) in a tripod‐type ligand with non‐bound phosphorus base and three pyridinyl “arms” (TPPh) was synthesized. Remarkably, while 2 mol% of 1 at room temperature selectively catalyzed dehydrogenative borylation of terminal alkynes with HBPin, a lower loading of 1 (0.5 mol%) at 90 °C selectively promoted hydroboration reaction of the same alkynes skipping the dehydrogenative borylation step. The mode of action of 1 was proposed based on experimental observations as well as the mechanism of dehydrogenative borylation was studied by DFT computations.

X-ray imaging of the magnetic configuration of a three-dimensional artificial spin ice building block

Abstract: The extension of artificial spin systems to the third dimension offers advances in functionalities and opportunities for technological applications. One of the main challenges facing their realization is the fabrication of three-dimensional geometries with nanoscale resolution. In this work, we combine two-photon lithography with deformation-free pyrolysis and a GdCo coating to create a three-dimensional (3D) tripod structure that represents a building block of an 3D artificial spin ice, surrounded by a two-dimensional magnetic film. We map the three-dimensional magnetic configuration of the structure and its surroundings using soft x-ray magnetic laminography. In this way, we determine the magnetic configuration of the tripod nanostructure to be in the low-energy two-in-one-out spin ice state, observed at the 2D vertex of a kagome ice and predicted for three-dimensional vertices of magnetic buckyball structures. In contrast to isolated vertices, the degeneracy of this state can be lifted by the surrounding film, which also offers a route toward the controlled injection of emergent charges. This demonstration of the building block of a 3D spin system represents the first step toward the realization and understanding of more complex 3D artificial spin systems.

Numerical Study of Local Scour around Tripod Foundation in Random Waves

Abstract: In this study, the local scour around tripods in random waves is numerically investigated. The seabed-tripod-fluid numerical model with an RNG k−ε turbulence model is built and validated. Following that, the scour characteristics and flow velocity distribution are analyzed using the present numerical model. Finally, a revised stochastic model is proposed to predict the equilibrium scour depth, Seq, around tripods in random waves. The results indicate that the present seabed-tripod-fluid numerical model is capable of depicting the scour process and of capturing the flow field around tripods with high accuracy. Due to the blockage effects of the main column and structural elements, there is enhanced flow acceleration underneath the main column and the lower diagonal braces, which increases the turbulence intensity and seabed shear stress, causing more particles to be mobilized and transported, resulting in more severe scour at the site. The revised stochastic model shows the best agreement with the numerical and experimental results when n = 20, but more experimental data and numerical results are still needed to verify the adaptation of the revised stochastic model for larger Keulegan–Carpenter (KC) number conditions (KCrms,a > 4).

Video-Based Vibration Measurement for Large Structure: A Spatiotemporal Disturbance-Adaptive Morphological Component Analysis

Abstract: Recently, phase-based motion estimation method is able to extract the full-field vibration of large structure from video, which has attracted widely attention. However, it suffers from diverse disturbances in the realistic measurement, such as periodic texture pattern from the surface and shake caused by unstable tripod. To address this issue, a spatiotemporal disturbance-adaptive morphological component analysis (DAMCA) is proposed in this article. This method focuses on separating texture component from structure component in each video frame and separating shake component from vibration component in the global motion signal extracted from video. First, it constructs a spatiotemporal model to remove the disturbances, respectively, from the space domain and time domain of the video. Subsequently, it incorporates morphological component analysis (MCA) into this model, aiming to obtain the optimal separation results in the space domain and time domain by finding the sparsest representations of different components. Finally, to adapt to various texture surfaces, MCA is developed in the space domain by exploiting the low-rank structure of the texture’s sparse representation. Similarly, to adapt to various shake, MCA is also developed in the time domain. Simulated and actual test demonstrate the effectiveness and accuracy of the proposed method. Spatiotemporal DAMCA has valuable potential to acquire video-based vibration measurement for large structure with the disturbances involving texture surface and tripod shake.

Vector beam polarization rotation control using resonant magneto optics.

Abstract: Vector beam propagation through a four-level tripod atomic system has been investigated. The three transitions of the tripod atomic system are coupled by a strong control field and the two constituent orthogonally polarized components of a weak probe vector beam. An external magnetic field induces anisotropy, creating a difference in the refractive indices of the two polarization components of the beam. This difference in refractive indices varies with the magnetic field strength and directly relates to the polarization orientation at any transverse plane. Thus, the transverse polarization structure can be rotated as desired with appropriate magnetic field strength. We further study the effect of nonlinearity and inhomogeneous broadening on the vector beam's polarization rotation. Therefore, the mechanism of efficient polarization control and manipulation of a vector beam can open up a new avenue for high-resolution microscopy and high-density optical communications.

Computing vertex resolvability of benzenoid tripod structure

Abstract: In this paper, we determine the exact metric and fault-tolerant metric dimension of the benzenoid tripod structure. We also computed the generalized version of this parameter and proved that all the parameters are constant. Resolving set $ {L} $ is an ordered subset of nodes of a graph $ {C} $, in which each vertex of $ {C} $ is distinctively determined by its distance vector to the nodes in $ {L} $. The cardinality of a minimum resolving set is called the metric dimension of $ {C} $. A resolving set $ L_{f} $ of $ {C} $ is fault-tolerant if $ {L}_{f}\setminus{b} $ is also a resolving set, for every $ {b} $ in $ {L}_{f}. $ Resolving set allows to obtain a unique representation for chemical structures. In particular, they were used in pharmaceutical research for discovering patterns common to a variety of drugs. The above definitions are based on the hypothesis of chemical graph theory and it is a customary depiction of chemical compounds in form of graph structures, where the node and edge represents the atom and bond types, respectively.

Static LiDAR Assisted UWB Anchor Nodes Localization

Abstract: The paper presents an indoor mapping and UWB (ultra-wideband) anchor localization method. The method, unlike most of the solutions described it the literature uses a static LiDAR (Light Detection and Ranging) mounted on a tripod rather than a robotic platform. It can be used at an any place, where employing a robot would be difficult (e.g. private homes), but since it requires manual LiDAR placement it would be most efficient in spaces of moderate areas. The proposed concept consists in mapping the environment of system installation while performing ranging measurements with deployed UWB anchor nodes. The SLAM (Simultaneous Location and Mapping) algorithm used for map integration and device localization relies only on LiDAR results. The matching is performed in two steps by finding an initial match based on corresponding landmarks extracted from the scans (intersections of the detected wall lines) and refining the results using an Iterative Closest Point algorithm. The anchors are localized based on the ranging results and SLAM-derived device locations using a Least-Squares based optimizer. The experiments have shown that the algorithm allows to construct a comprehensive map of the environment and localize the anchors with a root mean square error of 0.34 m, which is at similar level to analogous methods described in other works. The impact of anchor localization error on the systems performance was not significant. In both static and dynamic scenarios the difference in median errors obtained using reference and mapped anchors’ locations was about 0.05 m.

Accuracy of Machine Learning Assisted Detection of Keratoconus: A Systematic Review and Meta-Analysis

Abstract: (1) Background: The objective of this review was to synthesize available data on the use of machine learning to evaluate its accuracy (as determined by pooled sensitivity and specificity) in detecting keratoconus (KC), and measure reporting completeness of machine learning models in KC based on TRIPOD (the transparent reporting of multivariable prediction models for individual prognosis or diagnosis) statement. (2) Methods: Two independent reviewers searched the electronic databases for all potential articles on machine learning and KC published prior to 2021. The TRIPOD 29-item checklist was used to evaluate the adherence to reporting guidelines of the studies, and the adherence rate to each item was computed. We conducted a meta-analysis to determine the pooled sensitivity and specificity of machine learning models for detecting KC. (3) Results: Thirty-five studies were included in this review. Thirty studies evaluated machine learning models for detecting KC eyes from controls and 14 studies evaluated machine learning models for detecting early KC eyes from controls. The pooled sensitivity for detecting KC was 0.970 (95% CI 0.949–0.982), with a pooled specificity of 0.985 (95% CI 0.971–0.993), whereas the pooled sensitivity of detecting early KC was 0.882 (95% CI 0.822–0.923), with a pooled specificity of 0.947 (95% CI 0.914–0.967). Between 3% and 48% of TRIPOD items were adhered to in studies, and the average (median) adherence rate for a single TRIPOD item was 23% across all studies. (4) Conclusions: Application of machine learning model has the potential to make the diagnosis and monitoring of KC more efficient, resulting in reduced vision loss to the patients. This review provides current information on the machine learning models that have been developed for detecting KC and early KC. Presently, the machine learning models performed poorly in identifying early KC from control eyes and many of these research studies did not follow established reporting standards, thus resulting in the failure of these clinical translation of these machine learning models. We present possible approaches for future studies for improvement in studies related to both KC and early KC models to more efficiently and widely utilize machine learning models for diagnostic process.

Diving into the business strategy: The strategy tripod's influence on supply chain sustainability orientation

Abstract: Firm orientation is a key factor in the implementation of sustainability in supply chains (SCs). Although firms recognize the need to define strategies for success, they often overlook whatever strategies they do develop in their decision-making process. To address this gap, we argue that the strategy tripod comprising the industry-based view (IBV), resource-based view (RBV), and institutional-based view (INSBV) can influence SC orientation toward sustainability. This paper describes an investigation into this strategy tripod's impact on the cashew industry's SC sustainability orientation. Multiple case studies were conducted by gathering data from various cashew SC stakeholders. A deductive content analysis showed that, despite the existing influences from the three legs of the strategy tripod, emphasis was placed on the firm perspective (i.e., RBV), which affected SC sustainability orientation in that the industry- (i.e., IBV) and institutional- (i.e., INSBV) level views received less consideration in the creation of SC strategies. This research contributes to theory and practice by shedding light on under-explored relations between business strategy and SC sustainability. Our results show that firms should move from pressure responsiveness to strategy management to implement sustainability-oriented initiatives.

Automatic geometric inspection in digital fabrication

Abstract: Abstract. Additive Manufacturing in construction allows to create complex objects of different materials. Accordingly, an appropriate co-registration and comparison between the printed object and its digital model is needed for several purposes: quality control (QC) to ensure that tolerances are maintained and the realisation of a digital twin which holds the actual geometry. In this paper, we introduce an automated robotic data capturing and direct co-registration method. That is, a terrestrial laser scanner (TLS) is mounted on a robot to be moved freely in the printing room. In addition, various strategies are employed for quality control. The scanner is also mounted on the tripods, to validate the accuracy of our data capturing and co-registration solution. Furthermore, the experiment on real data is conducted for two different objects: a shotcrete printed object and a wax material object. Our experiments revealed that there is almost no influence on the scanner position accuracy compared to classical setup (mounting the TLS on tripod). The scanner position accuracy when mounted on tripods is 0.76 mm and the accuracy achieved by mounting the scanner on the robot is 1.03 mm. From the simulation it is noticed that C2M cannot detect missing extruded parts. To cope this problem, we used C2C and M3C2 algorithms. For real data scenario, without edge trimming and surface finishing it is challenging to interpret the data directly. However, M3C2 provided better results but it requires parameters tuning. In case of the surface finished object C2M and M3C2 algorithms have almost similar results.

Use TRIPOD when validating clinical prediction models

Abstract: It is with great interest that we have read the article from Schinkel et al in which the Netherlands Triage System (NTS) was compared with the Modified Early Warning Score (MEWS) to predict hospital admission and 30day mortality in Emergency Department (ED) patients. Although the results showed that the MEWS performed better than complaintsbased triage in terms of discrimination, we disagree with the conclusion that MEWS may replace the NTS score for triage of patients. The authors could have strengthened the methodology and conclusions by following the ‘transparent reporting of a multivariable prediction model for individual prognosis or diagnosis’ (TRIPOD) guidelines. For example, in the study by Schinkel et al, patients were excluded if no or an incomplete MEWS score was registered, resulting in 40 654 patients being excluded from the analysis (76.6%). Why MEWS was not complete or not recorded at all remains uncertain. Although the authors state that the MEWS was recorded across the entire spectrum of disease severity, in a large multicentre quality registry of the Netherlands, we found the number of missing vital signs to be associated with mortality and admission. Excluding observations with incomplete MEWS may therefore have caused considerable selection and information bias and might have been mitigated by reporting missing value proportions or by multiple imputations of missing values following appropriate analyses, as recommended by TRIPOD. Additionally, for the validation of clincial prediction models, such as risk scores, calibration is as important as discrimination. A stepwise approach to validation has been proposed that includes calibration, discrimination and clinical usefulness. The latter is essential to evaluate whether using MEWS instead of a triage tool like NTS will benefit the reclassification of patients from low to high risk and vice versa. We consider the comparison of MEWS with a complaintbased system to be challenging and even harder to interpret. Complaintbased triage will likely always be inferior in terms of discrimination for outcomes such as 30day mortality or hospital admission, because they are designed to detect multiple, often nonprocess outcomes. For example, an NTS score of U3 may be triggered for ‘humane reasons’ if the patient is stable, but is in pain, or simply feeling unwell. Alhough such complaints can be related to mortality, they may also be unrelated to one’s risk of death or admission but trigger appropriate responses to relieve physical or mental suffering. Relieving suffering should be a core task for any ED, but it challenges our conception of urgency. Authors thoughtfully reflect on this and acknowledge that the ‘lack of a consensus definition about which patients require urgent care makes research in this field inherently difficult’. Authors suggest that a criterion validity method, such as a comparison with an expert team, is preferable to construct validity for surrogate markers but that such methods have limited applicability in the ED setting. We agree with the authors and believe this study highlights the need for a core set of outcome variables that combined or individually represents urgency, as perceived by both patients and experts. When deciding on a core set, careful consideration should be paid to shortterm outcomes that guide timecritical intervention. Such efforts should be coordinated across multiple settings and as part of an international effort.

Design and fabrication of lightweight additively manufactured mirrors for aviation.

Abstract: This paper proposes a design process for additively manufactured mirrors. A central support aspheric mirror and tripod support structure were manufactured via selective laser melting. To achieve substantial weight reduction, an additively manufactured body-centered cubic lattice structure was used in the mirror design. Simulation analysis showed that the mirror had good rigidity. Single-point diamond turning was applied to obtain an optical quality mirror. After assembly, the rms surface shape accuracy of the mirror was 0.069λ (λ=632.8nm). The surface roughness (Ra) of the additively manufactured metal mirror was 8.125 nm. These findings provide a strong theoretical basis and technical support for the preparation and application of lightweight metal mirrors.

Guiding and polarization shaping of vector beams in anisotropic media

Abstract: We investigate a scheme to guide a weak vector beam using optically written waveguides inside atomic vapor, while controlling its polarization rotation. The atoms are prepared in the four-level tripod configuration in the presence of an external magnetic field. The three transitions of the tripod system are driven by a strong control beam and the two orthogonal polarization components of a weak vector beam (VB). A suitable spatial intensity profile and the detuning of the control field facilitate the generation of an optical fiberlike refractive index gradient across the atomic vapor. This enables waveguiding of the weak VB for a couple of Rayleigh lengths. Further, the magnetic-field-induced anisotropy of the tripod system creates a difference in the refractive indices of its two components. This is the reason behind the polarization shaping of VB. The mechanism of efficient guiding of VB with controllable polarization may have important applications in high-density optical communication and quantum information.

Bearing Characteristics of Tripod Bucket Jacket Foundation for Offshore Wind Turbines in Sand under Monotonic Loads

Abstract: Tripod bucket jacket foundation is an alternative foundation solution for deep-sea wind farms. This paper analyzes and compares the bearing characteristics of two tripod bucket jacket foundations with different height-diameter ratios, the tripod suction pile jacket foundation (TSPJF) and tripod bucket jacket foundation (TBJF), under different monotonic loads. The bearing modes of the two foundations under the vertical loads are different. The ultimate vertical load is mainly borne by the inside frictional resistance for the TSPJF, while it is mainly borne by the lid resistance for the TBJF. The foundations will take place translation and rotation under horizontal load. Under the positive x-axis loading, the vertical resistance of the TSPJF and TBJF is mainly composed of the soil resistance on the 1# bucket lid, the inside and outside frictional resistance. Under the negative x-axis loading condition, the vertical resistance is mainly composed of the inside and outside frictional resistance of buckets. The ultimate moment capacities of the TSPJF and TBJF in loading of the single bucket in compression is significantly larger than that in loading of the single bucket in tension. The failure mode of the TSPJF and TBJF in loading of the single bucket in tension is the pull-out failure of the bucket in tension.

Enzyme-free triple cycles triggered in-situ generation of nanospheres on DNA planar tripod for sensitive photoelectrochemical biosensor

Abstract: In this work, the non-sensitizer participated photoactive 3D DNA nanospheres in-situ generated on rigid planar DNA tripod was proposed for constructing a novel photoelectrochemical (PEC) biosensor to realize the ultrasensitive detection of miRNA-141. First, the slight targets could be efficiently converted into numerous output DNAs through the enzyme-free triple cycles, which thus opened the hairpin at apex of planar DNA tripod on electrode to trigger the rolling cycle amplification (RCA) for in-situ producing 3D DNA nanospheres with loading of plentiful positively charged photoactive species perylene derivative (PDA+). Impressively, the unique rigid planar DNA tripod could not only adjust the distance among each hairpin on vertexes for simply enhancing the hybridization efficiency toward output DNA with effective improvement in the generation of 3D DNA nanospheres, but also endow the highly efficient decoration of PDA+ approximated to electrode that beneficial to fast electron transport, thereby simply acquiring a low background and extremely high PEC signal without the need of sensitizers for improving detection sensitivity. As a result, the proposed approach showed a detection range from 0.1 fM to 100 pM for miRNA-141, providing a new and efficient strategy to construct sensitive PEC biosensor for potential application in early disease diagnosis and monitoring.

Design and optimization of the tripod flexure for a 2m lightweight mirror for space application.

Abstract: In order to ensure optimal optical performance, primary mirror assembly must be impervious to environmental influences. These environmental influences include gravity, assembly error, and thermal change, under which external loads are imposed on the mirror. The external loads degrade the mirror surface accuracy and cause misalignment between mirrors. In this paper, a tripod flexure with a flexible hinge is designed to alleviate the influence of the external load on the surface accuracy of a 2 m primary mirror. This structure can effectively release the rotational freedom, provide a certain translational flexibility, and yield high axial stiffness. The axial stiffness is used to increase the frequency of the primary mirror assembly. According to the fast optimization model, the derivation of close form compliance equations is developed to characterize the flexibility, and parameter optimization is done to achieve the maximum performance. Then a finite element analysis and test are used to verify the final design. The results show that the index requirements of the 2 m primary mirror have been met.