Biofilm-producing ability of methicillin-resistant Staphylococcus aureus clinically isolated in China.

BACKGROUND: Staphylococcus aureus, a commensal bacterium, colonizes the skin and mucous membranes of approximately 30% of the human population. Apart from conventional resistance mechanisms, one of the pathogenic features of S. aureus is its ability to survive in a biofilm state on both biotic and abiotic surfaces. Due to this characteristic, S. aureus is a major cause of human infections, with Methicillin-Resistant Staphylococcus aureus (MRSA) being a significant contributor to both community-acquired and hospital-acquired infections. RESULTS: Analyzing non-repetitive clinical isolates of MRSA collected from seven provinces and cities in China between 2014 and 2020, it was observed that 53.2% of the MRSA isolates exhibited varying degrees of ability to produce biofilm. The biofilm positivity rate was notably high in MRSA isolates from Guangdong, Jiangxi, and Hubei. The predominant MRSA strains collected in this study were of sequence types ST59, ST5, and ST239, with the biofilm-producing capability mainly distributed among moderate and weak biofilm producers within these ST types. Notably, certain sequence types, such as ST88, exhibited a high prevalence of strong biofilm-producing strains. The study found that SCCmec IV was the predominant type among biofilm-positive MRSA, followed by SCCmec II. Comparing strains with weak and strong biofilm production capabilities, the positive rates of the sdrD and sdrE were higher in strong biofilm producers. The genetic determinants ebp, icaA, icaB, icaC, icaD, icaR, and sdrE were associated with strong biofilm production in MRSA. Additionally, biofilm-negative MRSA isolates showed higher sensitivity rates to cefalotin (94.8%), daptomycin (94.5%), mupirocin (86.5%), teicoplanin (94.5%), fusidic acid (81.0%), and dalbavancin (94.5%) compared to biofilm-positive MRSA isolates. The biofilm positivity rate was consistently above 50% in all collected specimen types. CONCLUSIONS: MRSA strains with biofilm production capability warrant increased vigilance.

Advances in co-pathogenesis of the united airway diseases.

According to the concept of "united airway diseases", the airway is a single organ in which upper and lower airway diseases are commonly comorbid. A range of inflammatory factors have been found to play an important role in the chain reaction of upper and lower airway diseases. However, the amount of research on this concept remains limited. The underlying mechanism of the relationship between typical diseases of the united airway, such as asthma, allergic rhinitis, and chronic sinusitis, also needs to be further explored. This review highlights the interaction between upper and lower respiratory diseases gathered from epidemiological, histoembryology, neural mechanistic, microbiological, and clinical studies, revealing the relationship between the upper and lower respiratory tracts.

Effects of HMGB1/TLR4 on secretion IL-10 and VEGF in human jaw bone-marrow mesenchymal stem cells.

OBJECTIVE: We aimed to investigate the regulatory effects of HMGB1/TLR4 signaling pathway on the expression of IL-10 and VEGF in human bone marrow mesenchymal stem cells. METHODOLOGY: Human JBMSCs were isolated and cultured. Then, HMGB1 was added into the JBMSCs culture medium, and the protein and mRNA expression levels of IL-10 and VEGF were assessed. Moreover, cells were pretreated with a specific TLR4 inhibitor (TAK-242), and the expression changes of IL-10 and VEGF were compared. RESULTS: Compared with the control group, exposure to HMGB1 in human JBMSCs up-regulated TLR4, IL-10, and VEGF secretion at both protein and mRNA levels (P<0. 05). In addition, the increased expression of IL-10 and VEGF could be restrained in TAK-242 group compared with the HMGB1 group (P<0.05). CONCLUSIONS: The results indicated that HMGB1 activate TLR4 signaling pathway in Human JBMSCs, which plays a regulatory role in cytokines expression.

Single-pixel p-graded-n junction spectrometers.

Ultra-compact spectrometers are becoming increasingly popular for their promising applications in biomedical analysis, environmental monitoring, and food safety. In this work, we report a single-pixel-photodetector spectrometer with a spectral range from 480 nm to 820 nm, based on the AlGaAs/GaAs p-graded-n junction with a voltage-tunable optical response. To reconstruct the optical spectrum, we propose a tailored method called Neural Spectral Fields (NSF) that leverages the unique wavelength and bias-dependent responsivity matrix. Our spectrometer achieves a high spectral wavelength accuracy of up to 0.30 nm and a spectral resolution of up to 10 nm. Additionally, we demonstrate the high spectral imaging performance of the device. The compatibility of our demonstration with the standard III-V process greatly accelerates the commercialization of miniaturized spectrometers.

Dynamic Structural Change of Plant Epidermal Cell Walls under Strain.

The molecular foundations of epidermal cell wall mechanics are critical for understanding structure-function relationships of primary cell walls in plants and facilitating the design of bioinspired materials. To uncover the molecular mechanisms regulating the high extensibility and strength of the cell wall, the onion epidermal wall is stretched uniaxially to various strains and cell wall structures from mesoscale to atomic scale are characterized. Upon longitudinal stretching to high strain, epidermal walls contract in the transverse direction, resulting in a reduced area. Atomic force microscopy shows that cellulose microfibrils exhibit orientation-dependent rearrangements at high strains: longitudinal microfibrils are straightened out and become highly ordered, while transverse microfibrils curve and kink. Small-angle X-ray scattering detects a 7.4 nm spacing aligned along the stretch direction at high strain, which is attributed to distances between individual cellulose microfibrils. Furthermore, wide-angle X-ray scattering reveals a widening of (004) lattice spacing and contraction of (200) lattice spacing in longitudinally aligned cellulose microfibrils at high strain, which implies longitudinal stretching of the cellulose crystal. These findings provide molecular insights into the ability of the wall to bear additional load after yielding: the aggregation of longitudinal microfibrils impedes sliding and enables further stretching of the cellulose to bear increased loads.

Optical ReLU-like activation function based on a semiconductor laser with optical injection.

Artificial neural networks usually consist of successive linear multiply-accumulate operations and nonlinear activation functions. However, most optical neural networks only achieve the linear operation in the optical domain, while the optical implementation of activation function remains challenging. Here we present an optical ReLU-like activation function (with 180° rotation) based on a semiconductor laser subject to the optical injection in an experiment. The ReLU-like function is achieved in a broad regime above the Hopf bifurcation of the injection-locking diagram and is operated in the continuous-wave mode. In particular, the slope of the activation function is reconfigurable by tuning the frequency difference between the master laser and the slave laser.

The nonlinear mechanics of highly extensible plant epidermal cell walls.

Plant epidermal cell walls maintain the mechanical integrity of plants and restrict organ growth. Mechanical analyses can give insights into wall structure and are inputs for mechanobiology models of plant growth. To better understand the intrinsic mechanics of epidermal cell walls and how they may accommodate large deformations during growth, we analyzed a geometrically simple material, onion epidermal strips consisting of only the outer (periclinal) cell wall, ~7 µm thick. With uniaxial stretching by >40%, the wall showed complex three-phase stress-strain responses while cyclic stretching revealed reversible and irreversible deformations and elastic hysteresis. Stretching at varying strain rates and temperatures indicated the wall behaved more like a network of flexible cellulose fibers capable of sliding than a viscoelastic composite with pectin viscosity. We developed an analytic framework to quantify nonlinear wall mechanics in terms of stiffness, deformation, and energy dissipation, finding that the wall stretches by combined elastic and plastic deformation without compromising its stiffness. We also analyzed mechanical changes in slightly dehydrated walls. Their extension became stiffer and more irreversible, highlighting the influence of water on cellulose stiffness and sliding. This study offers insights into the structure and deformation modes of primary cell walls and presents a framework that is also applicable to tissues and whole organs.

Emergence of KPC-2 and NDM-5-coproducing hypervirulent carbapenem-resistant Klebsiella pneumoniae with high-risk sequence types ST11 and ST15.

The emergence of Klebsiella pneumoniae carbapenemase-2 (KPC-2) and New Delhi metallo-ß-lactamase (NDM)-coproducing hypervirulent carbapenem-resistant Klebsiella pneumoniae (KPC-2-NDM-hv-CRKP) poses a certain threat to public health. Currently, only a few sporadic reports of such double-positive hv-CRKPs were available. In this study, we isolated two KPC-2-NDM-5-hv-CRKPs from elderly patients with serious underlying diseases and poor prognoses. We found both FK3122 and FK3127 were typical multidrug-resistant (MDR) isolates, exhibiting high-level resistance to both carbapenems and novel ß-lactamase inhibitors ceftazidime/avibactam. Notably, FK3122 is even resistant to cefiderocol due to multiple blaNDM-5 elements. Besides the MDR phenotype, A549 human lung epithelial cells and Galleria mellonella infection model all indicated that FK3122 and FK3127 were highly pathogenic. According to the whole-genome sequencing analysis, we observed over 10 resistant elements, and the uncommon co-existence of blaKPC-2, blaNDM-5, and virulence plasmids in both two isolates. Both virulence plasmids identified in FK3122 and FK3127 shared a high identity with classical virulence plasmid pK2044, harboring specific hypervirulent factors: rmpA and iuc operon. We also found that the resistance and virulence plasmids in FK3127 could not only be transferred to Escherichia coli EC600 independently but also together as a co-transfer, which was additionally confirmed by the S1-pulsed-field gel electrophoresis plasmid profile. Moreover, polymorphic mobile genetic elements were found surrounding resistance genes, which may stimulate the mobilization of resistance genes and result in the duplication of these elements. Considering the combination of high pathogenicity, limited therapy options, and easy transmission of KPC-2-NDM-5-hv-CRKP, our study emphasizes the need for underscores the imperative for ongoing surveillance of these pathogens.IMPORTANCEHypervirulent Klebsiella pneumoniae drug resistance has increased gradually with the emergence of carbapenem-resistant hypervirulent K. pneumoniae (hv-CRKP). However, little information is available on the virulence characteristics of the New Delhi metallo-ß-lactamase (NDM) and Klebsiella pneumoniae carbapenemase-2 (KPC-2) co-producing K. pneumoniae strains. In this study, we obtained two KPC-2-NDM-hv-CRKPs from elderly patients, each with distinct capsule types and sequence types: ST11-KL64 and ST15-KL24; these ST-type lineages are recognized as classical multidrug-resistant (MDR) K. pneumoniae. We found these KPC-2-NDM-hv-CRKPs were not only typical MDR isolates, including resistance to ceftazidime/avibactam and cefiderocol, but also displayed exceptionally high levels of pathogenicity. In addition, these high-risk factors can also be transferred to other isolates. Consequently, our study underscores the need for ongoing surveillance of these isolates due to their heightened pathogenicity, limited therapeutic options, and potential for easy transmission.

Two Undescribed Protostane Triterpenoids from the Rhizome of Alisma plantago-aquatica.

Two undescribed protostane triterpenoids, 11-deoxy-13(17),15-dehydro-alisol B 23-acetate (2) and alisol S (3), together with 21 known ones (1, 4-23), were isolated from the dried rhizome of Alisma plantago-aquatica. Of these compounds, 13(17),15-Dehydro-alisol B 23-acetate (1) and 11-deoxy-13(17),15-dehydro-alisol B 23-acetate (2) are two protostane triterpenoids containing conjugated double bonds in the five-membered ring D that are rarely found from nature resource, while alisol S (3) is a protostane triterpenoid with undescribed tetrahydrofuran moiety linked via C20 -O-C24 at the side chain. Additionally, compound 18 is a new natural product, and cycloartenol triterpenoid 23 is a non protostane triterpenoid firstly isolated from genus Alisma. Their structures were elucidated by extensive spectral analysis of the UV, IR, MS, 1D and 2D NMR, and comparison of the experimental and calculated CD curves.

Effects of HMGB1/TLR4 on secretion IL-10 and VEGF in human jaw bone-marrow mesenchymal stem cells

Abstract Objective: We aimed to investigate the regulatory effects of HMGB1/TLR4 signaling pathway on the expression of IL-10 and VEGF in human bone marrow mesenchymal stem cells. Methodology: Human JBMSCs were isolated and cultured. Then, HMGB1 was added into the JBMSCs culture medium, and the protein and mRNA expression levels of IL-10 and VEGF were assessed. Moreover, cells were pretreated with a specific TLR4 inhibitor (TAK-242), and the expression changes of IL-10 and VEGF were compared. Results: Compared with the control group, exposure to HMGB1 in human JBMSCs up-regulated TLR4, IL-10, and VEGF secretion at both protein and mRNA levels (P<0. 05). In addition, the increased expression of IL-10 and VEGF could be restrained in TAK-242 group compared with the HMGB1 group (P<0.05). Conclusions: The results indicated that HMGB1 activate TLR4 signaling pathway in Human JBMSCs, which plays a regulatory role in cytokines expression.

Regiospecific Cellulose Orientation and Anisotropic Mechanical Property in Plant Cell Walls.

Cellulose microfibrils (CMFs) are a major load-bearing component in plant cell walls. Thus, their structures have been studied extensively with spectroscopic and microscopic characterization methods, but the findings from these two approaches were inconsistent, which hampers the mechanistic understanding of cell wall mechanics. Here, we report the regiospecific assembly of CMFs in the periclinal wall of plant epidermal cells. Using sum frequency generation spectroscopic imaging, we found that CMFs are highly aligned in the cell edge region where two cells form a junction, whereas they are mostly isotropic on average throughout the wall thickness in the flat face region of the epidermal cell. This subcellular-level heterogeneity in the CMF alignment provided a new perspective on tissue-level anisotropy in the tensile modulus of cell wall materials. This finding also has resolved a previous contradiction between the spectroscopic and microscopic imaging studies, which paves a foundation for better understanding of the cell wall architecture, especially structure-geometry relationships.

Total glucosides of Rhizoma Smilacis Glabrae: a therapeutic approach for psoriasis by regulating Th17/Treg balance.

Total glucosides of Rhizoma Smilacis Glabrae (RSG) are selective immunosuppressants that exhibit primary efficacy in the treatment of rheumatoid arthritis through targeted inhibition of activated T cells. In this study, we aimed to investigate the potential application of RSG in the treatment of psoriasis and elucidate its mechanism of action and material basis. Our findings revealed significant improvements upon administration of RSG in an imiquimod (IMQ)-induced psoriasis model. These improvements were characterized by a remarkable increase in the number of tail scales in mice and a substantial amelioration of skin erythema, ulceration, and flaking. By transcriptome sequencing and T-cell flow sorting assay, we identified notable effects of RSG on the modulation of various cellular processes. Specifically, RSG prominently down-regulated the Th17/Treg ratio in damaged skin tissues and reduced the proportion of G2 phase cells. Furthermore, RSG exhibited a stimulatory effect on the proliferation and differentiation of epithelial cells. Of particular interest, we discovered that ß-sitosterol, sitostenone, stigmasterol, smiglanin, and cinchonain Ib displayed potent inhibitory effects on the IL-17-mediated inflammatory response in HaCaT cells. In summary, our study highlights the therapeutic potential of RSG in the treatment of psoriasis, attributed to its ability to regulate the Th17/Treg balance. These findings contribute to the development of new indications for RSG and provide a solid theoretical foundation for further exploration in this field.

Mupirocin enhances the biofilm formation of Staphylococcus epidermidis in an atlE-dependent manner.

The pathogenicity of Staphylococcus epidermidis is largely attributed to its exceptional ability to form biofilms. Here, we report that mupirocin, an antimicrobial agent widely used for staphylococcal decolonization and anti-infection, strongly stimulates the biofilm formation of S. epidermidis. Although the polysaccharide intercellular adhesin (PIA) production was unaffected, mupirocin significantly facilitated extracellular DNA (eDNA) release by accelerating autolysis, thereby positively triggering cell surface attachment and intercellular agglomeration during biofilm development. Mechanistically, mupirocin regulated the expression of genes encoding for the autolysin AtlE as well as the programmed cell death system CidA-LrgAB. Critically, through gene knockout, we found out that deletion of atlE, but not cidA or lrgA, abolished the enhancement of biofilm formation and eDNA release in response to mupirocin treatment, indicating that atlE is required for this effect. In Triton X-100 induced autolysis assay, mupirocin treated atlE mutant displayed a slower autolysis rate compared with the wild-type strain and complementary strain. Therefore, we concluded that subinhibitory concentrations of mupirocin enhance the biofilm formation of S. epidermidis in an atlE dependent manner. This induction effect could conceivably be responsible for some of the more unfavourable outcomes of infectious diseases.

The relationship between technology acceptance and self-regulated learning: the mediation roles of intrinsic motivation and learning engagement.

The current study assessed 495 middle school students in China using self-report questionnaires, to examine the multiple mediating effects of intrinsic motivation and learning engagement (vitality, dedication and absorption) in the relations between technology acceptance and students' self-regulated learning. The results indicated that technology acceptance had a significant impact on self-regulated learning, intrinsic motivation mediated the relations between technology acceptance and self-regulated learning, and learning engagement (vigor, dedication, and absorption) mediated the relations between technology acceptance and self- regulated learning. The findings suggested that students' perceived acceptance of technology can help them improve their ability to engage in self-regulated learning by enhancing intrinsic motivation and increasing learning engagement. The results expand our understanding of self-regulated learning for Chinese middle school students in the context of information technology, and have substantial theoretical and practical implications for educator and relevant researchers.

[Multivariate correlation analysis of T1S and C7S].

OBJECTIVE: To determine whether C7 angles (C7 slope, C7S) could replace T1 angles (T1 slope, T1S) by correlation analysis of T1S and C7S. METHODS: A total of 442 patients from July 2015 to July 2020 in outpatient and inpatient department were enrolled retrospectively, and 259 patients who could identify the upper endplate of T1 were screened out . Of them, there were 145 males and 114 females, aged from 20 to 83 years old with an average of (58.6±11.2) years, including 163 patients with cervical spine surgery and 96 non-surgical patients. Patients were stratified by sex, age, cervical kyphosis, cervical alignment imbalance, and cervical spine surgery. These 259 patients included 145 cases in the male group, 114 cases in the female group;76 cases in the youth group (<40 years old), 109 cases in the middle-aged group (40 to 60 years old), and 74 cases in the elderly group(>60 years old); 92 cases in the cervical kyphosis group, 167 cases in the non-kyphosis group;51 cases in the cervical sequence imbalance group, 208 cases in the non-imbalance group;163 cases in the cervical surgery group, 96 cases in the non-operation group. The correlations of C7S and T1S in various modalities groups were analyzed. RESULTS: Of 442 patients, the recognition rate of upper endplate of T1 was 58.6%(259/442), and that of C7 was 90.7%. The mean T1S and C7S of the 259 patients were (24.5±8.0)° [(25.9±7.7)° in the male group and (23.7±6.9)° in the female group] and (20.8±7.3)° [(22.5±7.5)° in the male group and(19.7±5.8)° in the female group], respectively. The total correlation coefficient between C7S and T1S was r=0.89, R2=0.79, and the linear regression equation was T1S=0.91×C7S+4.35. In the above general information and the grouping of deformity factors, T1S was highly correlated with C7S(r value 0.85 to 0.92, P<0.05). CONCLUSION: There is a high correlation between T1S and C7S in different factor groups. For cases where T1S cannot be measured, C7S can be used to provide guidance and reference for evaluating the sagittal balance of the spine, analyzing the condition, and formulating surgical plans.

Small-Molecule Compound CY-158-11 Inhibits Staphylococcus aureus Biofilm Formation.

Staphylococcus aureus is an important human pathogen and brings about many community-acquired, hospital-acquired, and biofilm-associated infections worldwide. It tends to form biofilms, triggering the release of toxins and initiating resistance mechanisms. As a result of the development of S. aureus tolerance to antibiotics, there are few drugs can availably control biofilm-associated infections. In this study, we synthesized a novel small-molecule compound CY-158-11 (C22H14Cl2NO2Se2) and proved its inhibitory effect on the biofilm formation of S. aureus at a subinhibitory concentration (1/8 MIC). The subinhibitory concentration of CY-158-11 not only did not affect the growth of bacteria but also had no toxicity to A549 cells or G. mellonella. Total biofilm biomass was investigated by crystal violet staining, and the results were confirmed by SYTO 9 and PI staining through confocal laser scanning microscopy. Moreover, CY-158-11 effectively prevented initial attachment and repressed the production of PIA instead of autolysis. RT-qPCR analysis also exhibited significant suppression of the genes involved in biofilm formation. Taken together, CY-158-11 exerted its inhibitory effects against the biofilm formation in S. aureus by inhibiting cell adhesion and the expression of icaA related to PIA production. IMPORTANCE Most bacteria exist in the form of biofilms, often strongly adherent to various surfaces, causing bacterial resistance and chronic infections. In general, antibacterial drugs are not effective against biofilms. The small-molecule compound CY-158-11 inhibited the biofilm formation of S. aureus at a subinhibitory concentration. By hindering adhesion and PIA-mediated biofilm formation, CY-158-11 exhibits antibiofilm activity toward S. aureus. These findings point to a novel therapeutic agent for combating intractable S. aureus-biofilm-related infections.

Phenotypic and genomic analysis of the hypervirulent ST22 methicillin-resistant Staphylococcus aureus in China.

ST22 MRSA (methicillin-resistant Staphylococcus aureus) strains are only sporadically reported in China. Through the phylogenetic reconstruction of 30 ST22 strains from China and 480 ST22 strains from global sources, we found that the global ST22 strains can be divided into three clades (I, II, and III). The China ST22 strains were found primarily in clade II (IIb and IIc) and also in clade III, indicating that the China ST22-MRSA clones have different origins. The China subclade IIb strains (SCCmec Vb-t309) may evolve from the native ST22 MSSA clone, while the China IIc strains may have spread from other countries. Subclade IIc (SCCmecIVa-t309) strains exhibited particularly strong lethality and invasiveness in Galleria mellonella infection and mouse skin abscess models in comparison to USA300 and other dominant China HA-MRSA (ST5 and ST239) or CA-MRSA (ST59) strains. This study described the emergence of a highly virulent ST22 MRSA subclade and improved our insight into the molecular epidemiology of ST22 strains in China. IMPORTANCE ST22 is a successful hospital-associated MRSA lineage which first appeared in the United Kingdom as EMRSA-15. At present, ST22 MRSA clones are spreading rapidly around the world and even replaced other dominant clones in some regions. We placed the Chinese ST22 in the worldwide phylogeny of ST22, demonstrating a distinctive molecular epidemiology and to our knowledge, this is the first time that a novel clade of ST22 has been found in China. Among the 15 ST22 MRSA strains belonging to the novel clade, 14 ST22 SCCmecIVa strains from different regions carried both pvl and tst and displayed significantly higher in vitro and in vivo virulence in comparison to other clade/subclade ST22 strains as well as other common China HA-MRSA or CA-MRSA strains. The further spread of this subclade of strains could pose a serious threat to the health system in China and other regions.

LiDAR-aid Inertial Poser: Large-scale Human Motion Capture by Sparse Inertial and LiDAR Sensors.

We propose a multi-sensor fusion method for capturing challenging 3D human motions with accurate consecutive local poses and global trajectories in large-scale scenarios, only using single LiDAR and 4 IMUs, which are set up conveniently and worn lightly. Specifically, to fully utilize the global geometry information captured by LiDAR and local dynamic motions captured by IMUs, we design a two-stage pose estimator in a coarse-to-fine manner, where point clouds provide the coarse body shape and IMU measurements optimize the local actions. Furthermore, considering the translation deviation caused by the view-dependent partial point cloud, we propose a pose-guided translation corrector. It predicts the offset between captured points and the real root locations, which makes the consecutive movements and trajectories more precise and natural. Moreover, we collect a LiDAR-IMU multi-modal mocap dataset, LIPD, with diverse human actions in long-range scenarios. Extensive quantitative and qualitative experiments on LIPD and other open datasets all demonstrate the capability of our approach for compelling motion capture in large-scale scenarios, which outperforms other methods by an obvious margin. We will release our code and captured dataset to stimulate future research.

An Arbitrary Scale Super-Resolution Approach for 3D MR Images via Implicit Neural Representation.

High Resolution (HR) medical images provide rich anatomical structure details to facilitate early and accurate diagnosis. In magnetic resonance imaging (MRI), restricted by hardware capacity, scan time, and patient cooperation ability, isotropic 3-dimensional (3D) HR image acquisition typically requests long scan time and, results in small spatial coverage and low signal-to-noise ratio (SNR). Recent studies showed that, with deep convolutional neural networks, isotropic HR MR images could be recovered from low-resolution (LR) input via single image super-resolution (SISR) algorithms. However, most existing SISR methods tend to approach scale-specific projection between LR and HR images, thus these methods can only deal with fixed up-sampling rates. In this paper, we propose ArSSR, an Arbitrary Scale Super-Resolution approach for recovering 3D HR MR images. In the ArSSR model, the LR image and the HR image are represented using the same implicit neural voxel function with different sampling rates. Due to the continuity of the learned implicit function, a single ArSSR model is able to achieve arbitrary and infinite up-sampling rate reconstructions of HR images from any input LR image. Then the SR task is converted to approach the implicit voxel function via deep neural networks from a set of paired HR and LR training examples. The ArSSR model consists of an encoder network and a decoder network. Specifically, the convolutional encoder network is to extract feature maps from the LR input images and the fully-connected decoder network is to approximate the implicit voxel function. Experimental results on three datasets show that the ArSSR model can achieve state-of-the-art SR performance for 3D HR MR image reconstruction while using a single trained model to achieve arbitrary up-sampling scales.

Full-Volume 3D Fluid Flow Reconstruction With Light Field PIV.

Particle Imaging Velocimetry (PIV) is a classical method that estimates fluid flow by analyzing the motion of injected particles. To reconstruct and track the swirling particles is a difficult computer vision problem, as the particles are dense in the fluid volume and have similar appearances. Further, tracking a large number of particles is particularly challenging due to heavy occlusion. Here we present a low-cost PIV solution that uses compact lenslet-based light field cameras as imaging device. We develop novel optimization algorithms for dense particle 3D reconstruction and tracking. As a single light field camera has limited capacity in resolving depth (z-dimension measurement), the resolution of 3D reconstruction on the x-y plane is much higher than along the z-axis. To compensate for the imbalanced resolution in 3D, we use two light field cameras positioned at an orthogonal angle to capture particle images. In this way, we can achieve high-resolution 3D particle reconstruction in the full fluid volume. For each time frame, we first estimate particle depths under a single viewpoint by exploiting the focal stack symmetry of light field. We then fuse the recovered 3D particles in two views by solving a linear assignment problem (LAP). Specifically, we propose an anisotropic point-to-ray distance as matching cost to handle the resolution mismatch. Finally, given a sequence of 3D particle reconstructions over time, we recover the full-volume 3D fluid flow with a physically-constrained optical flow, which enforces local motion rigidity and fluid incompressibility. We perform comprehensive experiments on synthetic and real data for ablation and evaluation. We show that our method recovers full-volume 3D fluid flows of various types. Two-view reconstruction results achieves higher accuracy than those with one view only.