Horocycle Decision Boundaries for Large Margin Classification in Hyperbolic Space

Hyperbolic spaces have been quite popular in the recent past for representing hierarchically organized data. Further, several classification algorithms for data in these spaces have been proposed in the literature. These algorithms mainly use either hyperplanes or geodesics for decision boundaries in a large margin classifiers setting leading to a non-convex optimization problem. In this paper, we propose a novel large margin classifier based on horocycle (horosphere) decision boundaries that leads to a geodesically convex optimization problem that can be optimized using any Riemannian gradient descent technique guaranteeing a globally optimal solution. We present several experiments depicting the performance of our classifier

Thickness changes in the corneal epithelium and Bowman’s layer after overnight wear of silicone hydrogel contact lenses

Abstract Background To investigate thickness changes in the corneal epithelium and Bowman’s layer after overnight silicone hydrogel contact lens (CL) wear by using ultra-high resolution optical coherence tomography (UHROCT). Methods Eleven subjects without CL wearing history were recruited for this study. An UHROCT was used to measure the thickness of the epithelium (ET), Bowman’s layer (BT), stroma (ST), and total cornea (CCT) at the center of both eyes. A silicone hydrogel CL was inserted in the right eye of each subject, and the fellow non-CL wearing left eye served as the control. The lens was inserted at 9:30 pm and removed at 8:00 am the next morning. The subjects were evaluated at 9:00 pm (baseline), 9:30 pm (lens insertion), 10:00 pm (before sleep), 7:00 am (waking), 7:30 am, and 8:00 am (lens removal). Results Compared to the lens insertion level, the ET of the lens-wearing eye increased by 5.73% at eye opening (P = 0.001). The ET of the non-CL wearing eye and the BT in both eyes did not change after overnight CL wear. Compared to baseline, the CCT of the lens-wearing eye increased by 2.87% upon waking (P = 0.003) and recovered 30 min later (P = 0.555). In contrast, compared to baseline, the CCT of the non-CL wearing eye did not increase upon waking (P = 0.105). Conclusions By using UHROCT, we found that overnight CL wear induced different swelling responses in the various sublayers of the cornea. Trial registration Retrospectively registered. Registration number: ChiCTR1800015115. Registered 07 March 2018

Cortical bone viscoelastic damping assessed with resonant ultrasound spectroscopy reflects porosity and mineral content

International audienceViscoelasticity is an essential property of bone related to fragility, which is altered in aging and bone disease. Bone viscoelastic behavior is attributed to several mechanisms involving collagen and mineral properties, porosities, and bone hierarchical tissue organization. We aimed to assess the relationships between cortical bone viscoelastic damping measured with Resonant Ultrasound Spectroscopy (RUS), microstructural and compositional characteristics. We measured 52 bone specimens from the femur of 26 elderly human donors. RUS provided a shear damping coefficient at a frequency of the order of 150 kHz. The characteristics of the structure of the vascular pore network and tissue mineral density were measured using synchrotron radiation high-resolution computed tomography (SR-μCT). Fourier transformed infrared microspectroscopy (FTIRM) was used to quantify mineral-to-organic phase ratio, mineral maturity, crystallinity, and collagen maturity. Cross-links were quantified from biochemistry. Viscoelastic damping was found to increase with vascular porosity (r=0.68), to decrease with the degree of mineralization of the extravascular matrix (r=-0.68), and was marginally affected by collagen. We built a multilinear model suggesting that when porosity is controlled, the variation of mineral content explains a small additional part of the variability of damping. The work supports the consideration of viscoelasticity measurement as a potential biomarker of fragility and provides a documentation of bone viscoelastic behavior and its determinants in a frequency range rarely investigated

Bulk wave velocities in cortical bone reflect porosity and compression strength

International audienceThe goal of this study was to evaluate whether ultrasonic velocities in cortical bone can be considered as a proxy for mechanical quality of cortical bone tissue reflected by porosity and compression strength. Micro-computed tomography, compression mechanical testing and resonant ultrasound spectroscopy were used to assess, respectively, porosity, strength and velocity of bulk waves of both shear and longitudinal polarisations propagating along and perpendicular to osteons, in 92 cortical bone specimens from tibia and femur of elderly human donors. All velocities were significantly associated with strength (r = 0.65–0.83) and porosity (r = –0.64 to –0.77). Roughly, according to linear regression models, a decrease in velocity of 100 m/s corresponded to a loss of 20 MPa in strength (which is approximately 10% of the largest strength value) and to an increase in porosity of 5%. These results provide a rationale for the in vivo measurement of one or several velocities for the diagnosis of bone fragility

Associated risk factors in the early stage of Chick for diabetic retinopathy

Background: To investigate the retinal capillary density (RCD) of the macula using optical coherence tomography angiography (OCT-A) in type 2 diabetic patients and to further determine the association with risk factors. Methods: A total of 212 eyes from 212 subjects were recruited; subjects included diabetics with no retinopathy (NDR, n = 90 eyes), diabetics with mild retinopathy DR (MDR, n = 36 eyes), and healthy participants (Control, n = 86 eyes). All participants underwent OCT-A scanning. RCD was quantified by superficial and deep retinal capillary layers (SRCL and DRCL) from OCT-A images. Results: RCD in SRCL and DRCL was lower in NDR (P 55y, HbA1c > 7% had significantly reduced DRCL (P 8.2 mmol/L had significantly reduced SRCL and DRCL when compared to the other group of diabetics. Conclusions: Risk factors including older age, higher level of HbA1c, LDL-C and BUN, were associated with lower RCDs found in type 2 diabetic patients with and without mild DR by OCT-A. The impairment of retinal capillary by OCT-A may play a key role in the early monitoring of management in diabetes

Retinal Microvascular Impairment in the Early Stages of Parkinson's Disease

To detect the retinal microvascular impairment using optical coherence tomography angiography (OCT-A) in patients with Parkinson's disease (PD) and find a correlation between the microvascular impairment and the neuronal damage. This is a prospective, observational study including 49 eyes from 38 PD patients in their early stages and 34 eyes from 28 healthy controls with comparable age range. Macula microvasculature was evaluated with the spectral-domain optical coherence tomography (SD-OCT) angiography and intraretinal layer thickness evaluated with the SD-OCT. A custom algorithm was used for custom segmentation of retinal thickness and quantification of the superficial and deep microvascular density of the macula, respectively. PD patients showed reduced microvascular density in most of the areas of the whole retina. In the superficial retinal capillary plexus, statistical difference (P < 0.01) was seen in the total annular zone (TAZ), superior, temporal, inferior, and nasal zones. In PD patients, there was a strong correlation between the average ganglion cell layer and inner plexiform (GCIP) thickness and the TAZ of the superficial microvascular density (r = 0.062, P = 0.032). We demonstrated that retinal microvascular density decreased in PD patients. The correlation between microvascular impairment in the superficial retinal capillary layer and GCIP thinning also revealed that the retinal microvascular abnormality may contribute to the neurodegeneration in PD patients. OCT-A with quantitative analysis offers a new path of study and will likely be useful in the future as an objective biomarker for detecting vessel impairment in early stages of PD

Characteristics of Retinal Structural and Microvascular Alterations in Early Type 2 Diabetic Patients

To investigate early retinal structural and microvascular changes in patients with type 2 diabetes mellitus (DM) and to analyze relationships among the retinal structure, microvasculature, and choroid. Seventy-seven patients with type 2 DM (40 with no diabetic retinopathy [DR], 37 with nonproliferative diabetic retinopathy [NPDR]), and 34 control subjects were enrolled. Spectral-domain optical coherence tomography, operating in radial 18-line mode, obtained macular images of the eight intraretinal layers and the choroid. The same system was equipped with Angiovue to obtain angiography images of the whole, superficial, and deep retinal capillary layers (WRCL, SRCL, and DRCL) in a 3-mm-diameter area around the macula. Algorithms quantified the thicknesses of the intraretinal layers and choroid as well as fractal dimensions (Dbox values) of the retinal capillary layers. Pearson's correlation was used to analyze the relationships. The choroidal thickness was significantly decreased in all the regions of the DM patients with no DR (P < 0.05). Compared to controls, the Dbox values of the SRCL and DRCL were significantly decreased in diabetic patients with no DR; however, only the nerve fiber layer in this group was slightly thinner than in the controls (P < 0.05). In the two diabetic groups, there was a weak correlation between the ganglion cell complex thickness and the SRCL (P < 0.05). In DM, changes of retinal microvasculature might occur earlier than changes in retinal structure. Thinning of the choroid may be the earliest sign in the diabetic patients with no clinical DR

Understanding Public Attention towards the Beautiful Village Initiative in China and Exploring the Influencing Factors: An Empirical Analysis Based on the Baidu Index

The implementation of China’s Beautiful Village Initiative was an extraordinary achievement and aroused extensive public attention. However, existing research mostly focuses on the construction and seldom on public attention towards the Beautiful Village Initiative. For this reason, this paper investigated the spatiotemporal characteristics of public attention based on the Baidu index using time-constrained clustering and the spatial autocorrelation test. Our results showed that the evolutionary process can be divided into three stages: very little national attention (2011–2012), injection of a strong impetus (2013–2015), and rooted in the people’s minds (2016–2020). Spatially, provincial public attention demonstrated obvious spatial differentiation and stable spatial autocorrelation, with Low–Low clusters in Northwest China and High–High Clusters in East, Central, and North China. Spatial econometric models were further utilized to quantify the effects of socioeconomic factors on public attention. The results of the SEM model proved the existence of spatial spillover effects and indicated that the urbanization rate, population density, education level, and network popularity rate all positively affected public attention. The relationship between Beautiful Village construction and public attention was uncoordinated and, in most provinces, advances in public attention were ahead of the construction level. Our findings contribute to the understanding of public attention towards the Beautiful Village Initiative, and policy suggestions we proposed would be applied to increasing public awareness and participation

Deep perifoveal vessel density as an indicator of capillary loss in high myopia

This study investigates the macular vasculature of both vascular layers in different degrees of myopia by optical coherence tomography angiography (OCTA). One hundred and forty-five eyes of 145 healthy subjects with spherical equivalents (SE) ranging from +0.50 to -16.50 dioptres were divided into three groups. The foveal avascular zone (FAZ) area and vessel density (VD) of OCTA images were compared. Compared with other groups, high myopia had a larger FAZ and less perifoveal VD in both layers and less deep total VD. Compared with other myopia, high myopia had less total VD in the superficial layer and parafoveal VD in the deep layer. Between emmetropia and low myopia, there was a difference only in the deep parafoveal VD. Except for the parafoveal VD in both layers and the superficial total VD, there were significant correlations of the FAZ with axial length (AL) and SE as well as VD. The deep perifoveal VD was most associated with high myopia. An increased FAZ and decreased VD in both layers were correlated with AL elongation. The decreasing deep perifoveal VD was most associated with high myopia. OCTA may provide additional information regarding the progression of pathologies in high myopia