Linear Dimension Research Articles

Broken Ice Photogrammetry in Model-Scale Experiments with Sloped Structure

Testing a physical model of an ice-resistant marine structure in an ice tank is one of the methods used for design validation. For a stationary structure design, not only is the possible global ice load of interest but also the processes of creation and evolution of ice rubble in front of the contacting surface. While the load registering technique in model-scale experiments is very well-developed, the photogrammetric analysis of broken ice morphometry and locomotion is not. The photographs taken to illustrate the breaking process do not usually accompany the information necessary for the photogrammetric reconstruction of the scene. This paper outlines a systematic approach to the photogrammetric analysis of the scenes in model-scale conditions. Using this approach, the broken ice dimensions were measured in seven model-scale experiments for which the model of a sloped marine structure was reconstructed. In these experiments, a 700 mm wide slope with an inclination angle of 53° caused an upward flexural failure of the model’s granular ice. Reference global load histories for these experiments are provided. For the first contact episodes, the successful reconstruction of the broken ice mosaic in the polynya showed the insignificant contribution of compressive failure. In continual ice–structure interaction, the morphometry of the ice blocks visible on the slope of the rubble pile and on the surface of the surrounding ice sheet was retrieved from orthorectified video frames. The results were compared with the after-test nadir drone view of the polynya. The error in estimating the top-side area and the maximum linear dimension of the ice block fell into the interval of 0–10%. The morphometric information of the broken ice floes obtained in ice tank experiments with physical models can be used for the improvement of the mechanical models of ice fracture and failure against inclined offshore ice-resistant structures.

Ion-channel degeneracy and heterogeneities in the emergence of complex spike bursts in CA3 pyramidal neurons.

Complex spike bursting (CSB) is a characteristic electrophysiological signature exhibited by several neuronal subtypes and has been implicated in neural plasticity, learning, perception, anaesthesia and active sensing. Here, we address how pronounced intrinsic and synaptic heterogeneities affect CSB, with hippocampal CA3 pyramidal neurons (CA3PNs), where CSB emergence and heterogeneities are well characterized, as a substrate. We randomly generated 12,000 unique models and found 236 valid models that satisfied 11 characteristic CA3PN measurements. These morphologically and biophysically realistic valid models accounted for gating kinetics and somatodendritic expression profiles of 10 active ion channels. This heterogeneous population of valid models was endowed with broad distributions of underlying parameters showing weak pairwise correlations. We found two functional subclasses of valid models, intrinsically bursting and regular spiking, with significant differences in the expression of calcium and calcium-activated potassium conductances. We triggered CSB in all 236models through different intrinsic or synaptic protocols and observed considerable heterogeneity in CSB propensity and properties spanning models and protocols. Finally, we used virtual knockout analyses and showed that synergistic interactions between intrinsic and synaptic mechanisms regulated CSB emergence and dynamics. Specifically, although there was a dominance of calcium and calcium-activated potassium channels in the emergence of CSB, individual deletion of none of the several ion channels or N-methyl-d-aspartate receptors resulted in the complete elimination of CSB across all models. Together, our analyses critically implicate ion-channel degeneracy in the robust emergence of CSB and other characteristic signatures of CA3PNs, despite pronounced heterogeneities in underlying intrinsic and synaptic properties. KEY POINTS: An unbiased stochastic search algorithm yielded a heterogeneous population of morphologically and biophysically realistic CA3 pyramidal neuronal models matching several signature electrophysiological characteristics. Two functional subclasses of valid models were identified with intrinsically bursting (IB) and regular spiking (RS) characteristics, which exhibited differential localization within the parametric space with linear and non-linear dimension reduction analyses. Calcium and calcium-activated potassium channels distinguished IB from RS models, apart from playing dominant roles in the emergence of complex spike bursting (CSB). The impact of deleting individual ion channels or N-methyl-d-aspartate receptors was variable across different models and differential for each channel/receptor, pointing to ion-channel degeneracy in the emergence of CSB. Biological heterogeneities across different neurons of the same subtype, ion-channel degeneracy and state-dependent changes (involving activity-dependent plasticity, pathology, and neuromodulation of intrinsic and synaptic properties) need to be considered carefully in assessing the propensity and dynamicsof CSB in different neuronal subtypes.

Sedimentation motion of sand particles in moving water (I): The resistance on a small sphere moving in non-uniform flow

In hydraulics, when we deal with the problem of sand particles moving relative to the surrounding water, Stokes’ formula of resistance has usually been used to render the velocity of sedimentation of the particles. But such an approach has not been proved rigorously, and its accuracy must be carefully considered. In this paper, we discuss the problem of a sphere moving in a non-uniform flow field, on the basis of the fundamental theory of hydrodynamics. We introduce two assumptions: i) the diameter of the sphere is much smaller than the linear dimension of the flow field, and ii) the velocity of the sphere relative to the surrounding water is very small. Using these two assumptions, we solve the linearized Navier-Stokes equations and equations of continuity by the method of Laplace transform, and finally we obtain a formula for the resistance acting on a sphere moving in a non-uniform flow field.

Local support vector machine based dimension reduction

AbstractMotivated by several recent work that adopt support vector machines into the sufficient dimension reduction research, we propose a local support vector machine based dimension reduction approach. The proposal deals with continuous and binary responses, linear and nonlinear dimension reduction in a unified framework. The localization can also help relax the stringent probabilistic assumptions required by the global methods. Numerical experiments and a real data application demonstrate the efficacy of the proposed approach.

Label-Retention Expansion Microscopy (LR-ExM) Enables Super-Resolution Imaging and High-Efficiency Labeling.

Expansion microscopy (ExM) is a sample preparation technique that can be combined with most light microscopy methods to increase the resolution. After embedding cells or tissues in swellable hydrogel, samples can be physically expanded three-to sixteen-fold (linear dimension) compared to the original size. Therefore, the effective resolution of any microscope is increased by the expansion factor. A major limitation of the previously introduced ExM is reduced fluorescence after polymerization and the digestion procedure. To overcome this limitation, label-retention expansion microscopy (LR-ExM) has been developed, which prevents signal loss and greatly enhances labeling efficiency using a set of novel trifunctional anchors. This technique allows one to achieve higher resolution when investigating cellular or subcellular structures at a nanometric scale with minimal fluorescent signal loss. LR-ExM can be used not only for immunofluorescence labeling, but also with self-labeling protein tags, such as SNAP- and CLIP-tags, thus achieving higher labeling efficiency. This work presents the procedure and troubleshooting for this immunostaining-based approach, as well as discussion of self-labeling tagging approaches of LR-ExM as an alternative.

Label-Retention Expansion Microscopy (LR-ExM) Enables Super-Resolution Imaging and High-Efficiency Labeling

Expansion microscopy (ExM) is a sample preparation technique that can be combined with most light microscopy methods to increase the resolution. After embedding cells or tissues in swellable hydrogel, samples can be physically expanded three-to sixteen-fold (linear dimension) compared to the original size. Therefore, the effective resolution of any microscope is increased by the expansion factor. A major limitation of the previously introduced ExM is reduced fluorescence after polymerization and the digestion procedure. To overcome this limitation, label-retention expansion microscopy (LR-ExM) has been developed, which prevents signal loss and greatly enhances labeling efficiency using a set of novel trifunctional anchors. This technique allows one to achieve higher resolution when investigating cellular or subcellular structures at a nanometric scale with minimal fluorescent signal loss. LR-ExM can be used not only for immunofluorescence labeling, but also with self-labeling protein tags, such as SNAP- and CLIP-tags, thus achieving higher labeling efficiency. This work presents the procedure and troubleshooting for this immunostaining-based approach, as well as discussion of self-labeling tagging approaches of LR-ExM as an alternative.

Few-Layer Graphene As an Electrode, Electrode Additive and an Interfacial Layer in Aqueous Supercapacitors

The intermittent nature of many renewable energy sources such as wind and solar, coupled with fluctuations in energy demand, creates a pressing need for efficient, low-cost energy storage technologies. Supercapacitors are promising candidates to play a role in next-generation energy storage systems. They have a higher power density and better cycle life (although lower energy density) than batteries making them ideal for rapid energy storage and deployment [1]. Activated carbon is a favoured electrode material due to high surface area, although low conductivity requires use of a conductive additive (often carbon black), reducing available surface area for charge storage. In contrast, the high conductivity and specific surface area of graphene has made it a promising material for electrochemical double layer supercapacitors (EDLCs) [2], however, performance is limited by restacking of the graphene sheets, reducing available surface area.In this work, high-shear exfoliated few layer graphene (FLG) [3] is investigated both as an electrode material and as a conductive additive/interfacial layer for EDLCs. FLG suspensions were produced under a variety of exfoliation conditions, with platelet thickness and linear dimension determined from Raman spectroscopy based on metrics developed by Backes et al. [4] and through scanning electron microscopy (SEM).The FLG suspensions were used in three ways: i) to create thin ‘graphene paper’ electrodes; ii) as a conductive additive, mixed into the activated carbon electrode material; iii) deposited onto the back of (and diffused within) activated carbon electrodes. These electrodes were investigated by Raman spectroscopy and Scanning Electron Microscopy, before being assembled into symmetric two-terminal aqueous cells then evaluated by cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS), and their electrochemical performance related to structure and composition.As expected, pure FLG electrodes often showed excellent low series resistance values, however specific capacitance was low, due to restacking. Directly mixing 5% FLG into activated carbon as a conventional conductive additive led to a specific capacitance of 63 F/g (from CV at 10 mV/s), and a series resistance of 19 W (from GCD at 1 A/g) - markedly inferior to those with 5% carbon black as a conductive additive (95 F/g and 2 Ohm) and inferior even to electrodes with no conductive additive (87 F/g and 10 Ohm).However, post fabrication deposition/infusion of FLG offers comparable performance to carbon black (90 F/g and 1 Ohm) at 7% FLG by weight. As the quantity of FLG is increased the specific capacitance decreases sharply. This behaviour is attributed to FLG restacking on the rear of the electrode, so adding mass whilst providing limited additional capacitance, and compression of the electrode.Adding high-shear exfoliated FLG to activated carbon electrodes shows promise for obtaining the benefits of both materials. At present, FLG/activated carbon electrodes can match the performance of those produced from activated carbon with a carbon black conductive additive and, with further optimization, we expect will be able to exceed them.Figure: a) Cross sectional SEM image of activated carbon electrode with graphene interfacial layer; b) magnified cross sectional SEM image of graphene interfacial layer; c) cyclic voltammograms at 10 mV/s of the different electrodes mentioned in the abstract.

Active target classification using a shallow neural network with dimension reduction

Techniques for automatically identifying sonar targets using machine learning algorithms are being actively developed, and modern algorithms based on deep learning are often considered first. However, deep learning based algorithms require a lot of data to train a neural network, and if there is not enough data, overfitting easily occurs and the performance on real data can be degraded. In fact, in the case of active target detection where there is not enough data, it has been reported that using a shallow neural network after extracting appropriately designed features from the raw data showed better detection performance than applying deep learning directly to the raw data. With regard to this, we investigate the performance of a shallow neural network combined with dimensionality reduction techniques for active sonar target classification. In particular, several linear and nonlinear dimension reduction techniques are compared in terms of target classification performance, and the effects of the characteristics of background noise and the presence of reverberation on the target classification performance are discussed. [This work was supported by the research project PES4380 funded by KRISO.]

Reference ranges of tricuspid annulus geometry in healthy adults using a dedicated three-dimensional echocardiography software package.

BackgroundTricuspid annulus (TA) sizing is essential for planning percutaneous or surgical tricuspid procedures. According to current guidelines, TA linear dimension should be assessed using two-dimensional echocardiography (2DE). However, TA is a complex three-dimensional (3D) structure.AimIdentify the reference values for TA geometry and dynamics and its physiological determinants using a commercially available three-dimensional echocardiography (3DE) software package dedicated to the tricuspid valve (4D AutoTVQ, GE).MethodsA total of 254 healthy volunteers (113 men, 47 ± 11 years) were evaluated using 2DE and 3DE. TA 3D area, perimeter, diameters, and sphericity index were assessed at mid-systole, early- and end-diastole. Right atrial (RA) and ventricular (RV) end-diastolic and end-systolic volumes were also measured by 3DE.ResultsThe feasibility of the 3DE analysis of TA was 90%. TA 3D area, perimeter, and diameters were largest at end-diastole and smallest at mid-systole. Reference values of TA at end-diastole were 9.6 ± 2.1 cm2 for the area, 11.2 ± 1.2 cm for perimeter, and 38 ± 4 mm, 31 ± 4 mm, 33 ± 4 mm, and 34 ± 5 mm for major, minor, 4-chamber and 2-chamber diameters, respectively. TA end-diastolic sphericity index was 81 ± 11%. All TA parameters were correlated with body surface area (BSA) (r from 0.42 to 0.58, p < 0.001). TA 3D area and 4-chamber diameter were significantly larger in men than in women, independent of BSA (p < 0.0001). There was no significant relationship between TA metrics with age, except for the TA minor diameter (r = −0.17, p < 0.05). When measured by 2DE in 4-chamber (29 ± 5 mm) and RV-focused (30 ± 5 mm) views, both TA diameters resulted significantly smaller than the 4-chamber (33 ± 4 mm; p < 0.0001), and the major TA diameters (38 ± 4 mm; p < 0.0001) measured by 3DE. At multivariable linear regression analysis, RA maximal volume was independently associated with both TA 3D area at mid-systole (R2 = 0.511, p < 0.0001) and end-diastole (R2 = 0.506, p < 0.0001), whereas BSA (R2 = 0.526, p < 0.0001) was associated only to mid-systolic TA 3D area.ConclusionsReference values for TA metrics should be sex-specific and indexed to BSA. 2DE underestimates actual 3DE TA dimensions. RA maximum volume was the only independent echocardiographic parameter associated with TA 3D area in healthy subjects.

Biomimetic folding of triangular deployable membranes

Deployable membranes are being increasingly applied in numerous space projects owing to their light weight, small stowage volume and capacity for use at large scales. The geometric design of biomimetic folding is studied to design crease patterns for triangular deployable membranes applied in space. Various crease designs for triangular membranes based on leaf-in, leaf-out and orthogonal patterns are put forward, especially patterns composed of triangular and hexagonal units. In order to analyse the membrane folding method based on biomimetic folding, a set of evaluation indices, including linear dimension ratio, deployment ratio, crease length and junction number, are established. The indices for various membrane folding patterns are calculated according to the crease distributions and geometric relations. Furthermore, a parametric study of crease parameters is performed to determine how the parameters affect folding behaviour and deployment efficiency. These indices can provide an indication to help with the selection of crease patterns and folding parameters for triangular deployable membranes according to the required performance and space mission requirements.

The effect of sodium hypochlorite disinfectant on the linear dimensional stability of alginate impression material.

Objective: To compare changes, in linear dimension of Alginate impression by disinfection with immersion in 0.525% Sodium Hypochlorite solution and no disinfection. Study Design: Randomized Control Trial. Setting: Department of Prosthodontics, Punjab Dental Hospital Lahore. Period: April 2018 to September 2018. Material &amp; Methods: Sixty alginate impressions were made of a stainless steel die and were randomly divided into two groups. The 30 control group impressions were poured only after rinsing with tap water, whereas the 30 experimental group impressions were first immersed in 0.525% Sodium Hypochlorite solution for 10 minutes and then poured after rinsing with tap water. The distance between two engraved lines C and D on die were measured in the casts of both groups. Results: The mean difference of mean dimensional changes between both methods was 0.01mm. Conclusion: The disinfection of the alginate impression material by immersion in 0.525% Sodium Hypochlorite solution does not cause significant effect on dimensional stability of alginate impression material.

Characteristics of Retinal Pigment Epithelium Elevations Preceding Exudative Age-Related Macular Degeneration in Japanese

Introduction: Drusen and pigmentary abnormality are found as the hallmark to predict progression of age-related macular degeneration (AMD). In Asian populations, exudative AMD often appears in the absence of drusen but is rather accompanied by pigmentary abnormality. Recently, shallow irregular retinal pigment epithelium (RPE) elevations (SIRE) have been shown as a sign of subclinical nonexudative macular neovascularization. In this study, we aimed to investigate the characteristics of optical coherence tomography (OCT) findings including SIRE before the appearance of exudative AMD. Methods: We retrospectively reviewed 32 cases of exudative AMD that occurred in the fellow eye within the 5-year-observation period. Color fundus photography, OCT, and fluorescein/indocyanine-green angiography at the beginning of observation and at the time when exudative AMD appeared were examined to diagnose SIRE and the subtype of exudative AMD. Results: Exudative AMD was found in 19 eyes with large drusen and 13 eyes without large drusen. Mean sub-foveal choroidal thickness without large drusen was significantly thicker than that with large drusen (336 ± 109 and 220 ± 96 μm, respectively; mean ± SD). Six eyes with pachychoroid neovasculopathy, 4 eyes with type 1 macular neovascularization, and 3 eyes with PCV had occurred in the fellow eye without large drusen. Among those, 6 eyes had been accompanied by SIRE with a greatest transverse linear dimension of 1 mm or more at the beginning of observation period. Besides, small RPE elevations with a longest diameter of less than 1 mm had been observed in other 5 eyes. Three cases of polypoidal choroidal vasculopathy had originated from small RPE elevations. Moreover, pachyvessels, choriocapillaris thinning, or choroidal hyperpermeability were observed with SIRE or small RPE elevations. Conclusions: There is a non-drusen type of exudative AMD that originates from small RPE elevations as well as SIRE.

Characteristics of choroidal neovascularization in elderly eyes with high myopia not meeting the pathologic myopia definition

The META-Analysis of Pathologic Myopia Study group proposed a new classification system for myopic maculopathy (MM) with pathologic myopia (PM) defined as MM equal to/more serious than diffuse atrophy or the presence of plus lesions and myopic choroidal neovascularization (mCNV) defined as CNV in the eye with PM. However, CNV in elderly eyes with high myopia (HM) not meeting the PM definition (high-myopia CNV) are not classified as age-related macular degeneration (nAMD) or mCNV. This retrospective study included 39 eyes with high-myopia CNV, 20 eyes with mCNV, and 20 eyes with AMD. All patients were at least 40 years old. We compared the clinical characteristics and treatment outcomes among three groups. The high-myopia CNV group had significantly more CNV types, shorter axial length and fewer lacquer cracks (P < 0.0001, respectively); larger baseline greatest linear dimension (P = 0.0002), more fellow-eye drusen (P = 0.0106), more men (P = 0.0029), and more treatments (24 months, P = 0.0098) compared to the mCNV group. Compared with the nAMD group, the high-myopia CNV group was significantly younger (P = 0.0041), and had fewer CNV types (P = 0.0316), more lacquer cracks (P = 0.0079) and fewer drusen (affected-eye, P = 0.0006 and fellow-eye, P = 0.0222), and fewer treatments (24 months, P = 0.0030). Because the CNV in elderly eyes with HM not meeting the PM definition is classified as combined mCNV and nAMD, the clinical and angiographic findings are critical to determine the treatment strategy.

Mylohyoid Ridge as a Predictor of Available Bone for Implant Placement: A Cone-Beam Computed Tomography (CBCT) Retrospective Observational Study.

Introduction: The posterior mandibular region, due to the presence of vital structures, poses a high risk during implant placement because of its susceptibility to neurovascular injury and perforation of the lingual cortex. A breach in implant length and available bone height may lead to serious intraoperative and postoperative complications. Prediction of the exact location of the inferior alveolar nerve and submandibular fossa anatomy is a prerequisite for ideal implant placement, which is always not possible with conventional radiographic and clinical techniques.Materials and methods: One hundred ten cone-beam computed tomographies (CBCTs) of patients were acquired from the radiological archives of a radiological center in Chennai. DICOM files from CBCT were exported to Bly Sky Plan software. Cross-sections of the second molar and first molar were extracted following the inclusion criteria. The linear dimension between the mandibular canal and mylohyoid ridge and anatomic variables of the submandibular fossa were measured digitally on the left and right sides using software measuring tools. Descriptive statistics were done. The unilateral and bilateral site and gender differences were evaluated. Bone height superior to the mandibular canal was correlated with the submandibular fossa parameters; depth of undercut in the vertical and horizontal directions; and angle of the undercut.Results: The mandibular canal was on average 5.5 mm and 4 mm inferior to the Mylohyoid ridge in the second molar region and first molar region, respectively, with the right and left sides showing no statistically significant difference. The depth of fossa undercut in vertical and horizontal dimensions was higher in the second molar region compared to the first molar region. The height of the deepest point of the undercut in the vertical dimensions showed a positive correlation with the bone available between the mandibular canal and the mylohyoid ridge.Conclusion: Keeping 2 mm of safety factor in consideration, implants can be safely placed up to the mylohyoid ridge in 100% of cases and 2 mm below the mylohyoid ridge in 78.9% of cases in the mandibular second molar region. In keeping with a safety factor of 2 mm, implants can be safely placed up to the mylohyoid ridge in 82.6% of cases and 2 mm below the mylohyoid ridge in 43.1% of cases in the first molar region. A more pronounced undercut was seen in the second molar region than in the first molar region. Deeper fossa undercuts in vertical dimension are associated with more inferior positioning of the mandibular canal.

Construction and application of automobile user portrait based on k-mean clustering model

Abstract In the field of computer vision development, the core problem is how to obtain high-level semantic information from the lowest level of original video data, and make a correct understanding. At present, the research topics proposed at home and abroad are mainly focused on the visual analysis of moving objects. Especially for image research in automobile field, visual analysis of moving objects is one of the most common topics. Its focus is to use computer vision technology to detect moving objects, and describe and understand them after tracking and recognizing relevant user portraits and behaviors. In this paper, taking vehicle driving posture preference as an example, linear dimension parameters were used instead of human joint Angle parameters to simply present the driving posture of vehicle users, and corresponding dimension parameters were obtained to present the driving posture characteristics of vehicle users. By inviting 50 drivers to participate in the test of driving attitude preference, cluster analysis was carried out on three sample data representing upper body attitude, and the clustering results were presented by combining with three-dimensional images. The final results show that the k-means clustering model can eliminate the influence of body size difference, accurately distinguish the preference characteristics of driving posture, and scientifically design steering wheel and car seat according to the measurement data of target users.

&lt;em&gt;In vivo&lt;/em&gt; restoration and volumetric body mass estimate of &lt;em&gt;Mammuthus meridionalis&lt;/em&gt; from Madonna della Strada (Scoppito, L’Aquila)

In this contribution we present an in vivo reconstruction and volumetric body mass estimate for the mounted skeleton of Mammuthus meridionalis on exhibit at the east bastion of the Spanish Fortress at L’Aquila (Abruzzo, Central Italy). The reconstruction has been obtained starting from a 3D photogrammetric model of the skeleton acquired via a micro-drones and by digitally adding a percentage of soft tissues according to the conditions observed in wild specimens. By applying to the volume the density range proposed in literature for extant proboscideans we obtain an estimate of the body mass in the adult male specimen ranging from 11.3 t to 11.5 t, with average body mass equal to 11.43 t. In addition, we compare the volumetric BM estimate with the BM predictive values obtained by means of traditional regression equations based on long bones linear dimension and shoulder height. The results confirm that the volumetric method is always preferable if sufficiently complete mounted skeletons are available, since application of regression formulas to single bony element can lead to an underestimation or overestimation up to 130%. As a general indication, weight estimates in extinct tetrapods based on single measures and single bones should be totally avoided, especially in groups morphologically and phylogenetically distant from extant reference taxa.

A DFT-Based Quantitative and Geometric Analysis of the Effect of Pressure on Boron Arsenate.

Boron arsenate, BAsO4, is a β-cristobalite-like crystal which has been reported to exhibit the rather unusual property of negative linear compressibility behaviour at elevated pressures, that is expanding rather than shrinking in a linear dimension when subjected to pressure. This work proposes a ‘geometry—deformation mechanism’-based mathematical model to aid the discernment of the manner how this anomalous pressure behaviour is achieved. The model makes use of data obtained from DFT simulations over an extended range of pressures, including extreme pressure conditions, and rigorously explains the macroscopic properties of this material in terms of the nanoscale deformations. More specifically, through this model, it was possible to decipher the different contributions to the deformation mechanism and compressibility properties of BAsO4. Moreover, for the first time, it was shown that a rule related to the sum of angles of tetrahedrally coordinated atoms is so robust that it applies at the extreme pressures studied here.

Learning Zero-Sum Simultaneous-Move Markov Games Using Function Approximation and Correlated Equilibrium

We develop provably efficient reinforcement learning algorithms for two-player zero-sum finite-horizon Markov games with simultaneous moves. To incorporate function approximation, we consider a family of Markov games where the reward function and transition kernel possess a linear structure. Both the offline and online settings of the problems are considered. In the offline setting, we control both players and aim to find the Nash equilibrium by minimizing the duality gap. In the online setting, we control a single player playing against an arbitrary opponent and aim to minimize the regret. For both settings, we propose an optimistic variant of the least-squares minimax value iteration algorithm. We show that our algorithm is computationally efficient and provably achieves an [Formula: see text] upper bound on the duality gap and regret, where d is the linear dimension, H the horizon and T the total number of timesteps. Our results do not require additional assumptions on the sampling model. Our setting requires overcoming several new challenges that are absent in Markov decision processes or turn-based Markov games. In particular, to achieve optimism with simultaneous moves, we construct both upper and lower confidence bounds of the value function, and then compute the optimistic policy by solving a general-sum matrix game with these bounds as the payoff matrices. As finding the Nash equilibrium of a general-sum game is computationally hard, our algorithm instead solves for a coarse correlated equilibrium (CCE), which can be obtained efficiently. To our best knowledge, such a CCE-based scheme for optimism has not appeared in the literature and might be of interest in its own right. Funding: Q. Xie is partially supported by the National Science Foundation [Grant CNS-1955997] and by J.P. Morgan. Y. Chen is partially supported by the National Science Foundation [Grants CCF-1657420, CCF-1704828, and CCF-2047910]. Z. Wang acknowledges the National Science Foundation [Grants 2048075, 2008827, 2015568, and 1934931], the Simons Institute (Theory of Reinforcement Learning), Amazon, J.P. Morgan, and Two Sigma for their support.

Maxillary labial frenum and malocclusion: An overriding or an overlooked tissue?

The influence of the maxillary labial frenum in relation to the midline diastema has been a proven fact to clinicians for many years. A pilot study was carried out to investigate the relationship between a low maxillary labial frenum attachment and skeletal malocclusions (class I, II, and III). Astonishingly, it was observed that the class III malocclusion had a statistically high number of cases with low frenum attachments. The objective of the study was to understand the underlying skeletal class III dysplasia in these cases. A comparative cross-sectional study was performed on 300 consecutive subjects between 13-30-years of age. Based on the cephalometric parameters the participants were categorized into 98 skeletal class I, 102 class II, and 100 class III subjects. Variations in the frenum attachment were clinically evaluated using Placek classification. The insertion level and width of the frenum were also measured by using a caliper and the data were statistically analyzed for determining the association between the frenum attachment and skeletal malocclusion. The prevalence of low frenum attachment in class III subjects was found to be 64%. Also, the mean attachment level of the frenum was significantly closer to the gingival margin in skeletal class III subjects compared with that of the other groups (p&amp;#60;0.01). The study identified that the subjects with a low frenum attachment had a tendency towards a retruded maxilla in terms of linear dimension. Therefore the present study supports the hypotheses that the skeletal Class III malocclusion may be associated with low frenum attachment.

Exploring brand perception in COVID vaccine tweets using TOPSA-NMF model

COVID-19 vaccines are primary biomedical preventive measures to combat the pandemic. Social media can have either a positive or negative impact on vaccine uptake, depending on their opinions about vaccines. An algorithm is proposed that can use a linear dimension reduction technique such as non-negative matrix factorization (NMF) to identify topics while using the sentiment lexicon to classify the tweet topics as positive, negative, and neutral. This study aims to determine public attitudes towards each topic of tweets about COVID-19 vaccines.