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The aim of this study is to investigate the open problem of classification laws and results. First, a comprehensive research method of quantitative analysis-Bayesian discrimination is used to reasonably and accurately investigate the classification laws of high potassium glass and lead-barium glass, obtaining the Bayesian discriminant for high potassium glass ????1 = 2.909????1 - 0.117????2 + 4.487 ????3 + 2.432????4 + 1.097????5 + 3.352????6 + 3.403????7 + 6.303????8 + 2.669????9 + 0.897????10 + 1.882????11 - 4.543????12 + 5.002????14 - 150.381 with the lead-barium glass Bayesian discriminant ????2 = 2.447????1 - 1.195????2 + 42.807????3 + 2.117????4 + 1.0971.534????5 + 3.221????6 + 3.299????7 + 4.830????8 + 2.513????9 + 1.226????10 + 1.590????11 - 5.628????12 + 3.087????13-111.481. Then, using the clustering process-Bayesian discrimination method, the number of sample clusters was roughly determined using systematic clustering, and the data were categorized in detail using K-Means clustering, resulting in the possibility of classifying each of the high-potassium and lead-barium glasses into Three subclasses were identified, and Bayesian discriminant functions were derived for each subclass, and the data were tested to justify the subclasses.

Most of the existing acoustic imaging studies in reverberant field ignore the influence of signal-to-noise ratio. As a result, commonly used beamforming algorithms in reverberant backgrounds have poor imaging accuracy for low signal-to-noise ratio sound sources. In response to that problem, an improved adaptive beamforming algorithm called SC-DAMAS is put forward in this paper. The algorithm replaces the free-field Green's function with the impulse response function, making the algorithm more suitable for acoustic imaging of low signal-to-noise ratio in a reverberant environment. Besides, the comparative simulation results with the conventional beamforming method and orthogonal matching pursuit algorithm-based DAMAS, as well as sound source acoustic imaging experiments are carried out to analyze its effectiveness. It is indicated that, in the reverberation field, the SC-DAMAS has no obvious sidelobes and achieves higher positioning accuracy for acoustic imaging of low signal-to-noise ratio sound source than the abovementioned counterparts, and its imaging test result is consistent with the actual situation, which verifies the effectiveness of the algorithm.

Emerging evidence has indicated that cognitive impairment is an underrecognized feature of multiple system atrophy (MSA). Mild cognitive impairment (MCI) is related to a high risk of dementia. However, the mechanism underlying MCI in MSA remains controversial. In this study, we conducted the amplitude of low-frequency fluctuation (ALFF) and seed-based functional connectivity (FC) analyses to detect the characteristics of local neural activity and corresponding network alterations in MSA patients with MCI (MSA-MCI). We enrolled 80 probable MSA patients classified as cognitively normal (MSA-NC, n = 36) and MSA-MCI (n = 44) and 40 healthy controls. Compared with MSA-NC, MSA-MCI exhibited decreased ALFF in the right dorsal lateral prefrontal cortex (RDLPFC) and increased ALFF in the right cerebellar lobule IX and lobule IV-V. In the secondary FC analyses, decreased FC in the left inferior parietal lobe (IPL) was observed when we set the RDLPFC as the seed region. Decreased FC in the bilateral cuneus, left precuneus, and left IPL and increased FC in the right middle temporal gyrus were shown when we set the right cerebellar lobule IX as the seed region. Furthermore, FC of DLPFC-IPL and cerebello-cerebral circuit, as well as ALFF alterations, were significantly correlated with Montreal Cognitive Assessment scores in MSA patients. We also employed whole-brain voxel-based morphometry analysis, but no gray matter atrophy was detected between the patient subgroups. Our findings indicate that altered spontaneous activity in the DLPFC and the cerebellum and disrupted DLPFC-IPL, cerebello-cerebral networks are possible biomarkers of early cognitive decline in MSA patients.

Open or partially open boundary conditions in fully or partially saturated rocks possibly occur in many realistic geologic scenarios, and it is critical to understand the influences of wave-induced fluid pressure diffusion and anelasticity for many fields of earth science and engineering applications. Under the framework of Biot’s poroelasticity, by proposing a scale factor to represent the opening degree of the boundary, we have investigated the influences of boundary conditions on the seismic wave dispersion and attenuation in partially saturated rocks. It is found that there exist two types of fluid pressure diffusion taking place simultaneously: the mesoscopic fluid pressure diffusion between the two immiscible fluids (e.g., gas and brine) and the fluid flow associated with the outer boundary. The boundary conditions significantly control the seismic wave dispersion and attenuation signatures. The coupled fluid pressure diffusion of mesoscopic flow and outer boundary flow expedite the pore pressure equilibration processes and make the characteristic frequency one order of magnitude higher than the undrained scenario. The drained and partially drained conditions also significantly decrease the velocity of partially saturated rocks, which can be even lower than that of Gassmann’s prediction and dry rock. The reliability of the theoretical model also is validated by comparing it with the numerical simulation for drained and undrained conditions. We have determined that the proposed model is capable of better interpreting the logging data of velocity-saturation relationship for a partially saturated carbonate reservoir and experimental data of wave dispersion for a fully saturated sandstone, both of which are possibly exposed to the open boundary conditions.

Natural fractures are usually multiscale in size, orientations and distribution, resulting in complex anisotropic characteristics. Analytical methods for quantifying the associated effective elastic properties are based on some assumptions, such as dilute fracture concentration and regular-shaped fractures, which do not occur in actual reservoirs. Here, we conduct anisotropic finite-element modeling of effective elastic properties of complex fractured rocks using the least-square fitting method. The algorithm is developed for a 3D case and validated by classical effective medium theories for models with different fracture densities. The results of the 3D numerical method agree well with the theoretical predictions at low fracture density. The model also considers the interactions among fractures to calculate equivalent stiffness tensors at high fracture density. Three 2D fracture models are simulated to demonstrate the basic behavior of stress interactions and their effect on the overall elasticity under different fracture densities. We applied the developed model to 3D natural fractures built from a real outcrop, and we found that the fracturing pattern significantly affects the effective anisotropy properties. The resultant P-wave phase velocities as functions of the incidence angle and frequency are anisotropic. This study provides a great potential to calculate equivalent stiffness tensors and anisotropic properties of 3D multiscale natural fractures.

Generally, local stress induced by individual crack hardly disturbs their neighbours for small crack densities, which, however, could not be neglected as the crack density increases. The disturbance becomes rather complex in saturated porous rocks due to the wave‐induced diffusion of fluid pressures. The problem is addressed in this study by the comparison of two solutions: the analytical solution without stress interactions and the numerical method with stress interactions. The resultant difference of effective properties can be used to estimate the effect of stress interactions quantitatively. Numerical experiments demonstrate that the spatial distribution pattern of cracks strongly affects stress interactions. For regularly distributed cracks, the resulting stress interaction (shielding or amplification) shows strong anisotropy, depending on the arrangement and density of cracks. It has an important role in the estimation of effective anisotropic parameters as well as the incident‐angle‐dependency of P‐ and SV‐wave velocities. Contrarily, randomly distributed cracks with a relative small crack density generally lead to a strong cancellation of stress interactions across cracks, where both the numerical and analytical solutions show a good agreement for the estimation of effective parameters. However, for a higher crack density, the incomplete cancellation of stress interactions is expected, exhibiting an incidence‐angle dependency, slightly affecting effective parameters, and differentiating the numerical and analytical solutions.

We examine the effect of poroelastic boundary conditions when determining elastic properties of fluid‐saturated porous rocks from forced‐oscillation laboratory experiments. One undesired yet often unavoidable complication in the estimation of the undrained bulk modulus is due to the presence of the so‐called dead volume. It implies that some fluid mass can escape the rock sample under applying a confining pressure perturbation. Thus, the dead volume compromises the undrained state required to unambiguously determine the undrained bulk modulus. In this paper, we model data of recently performed low‐frequency (0.1 Hz) measurements. Therein, the dead volume has been systematically varied from 10% to 1000% of the pore volume. For the smallest dead volume, the inferred bulk modulus is close to the Biot–Gassmann undrained bulk modulus. With increasing dead volume, the experimentally inferred bulk modulus approaches the drained bulk modulus. We show that the transition from undrained to drained state as a function of dead volume can be modelled with a 1D poroelastic model for the rock sample‐dead volume system with a boundary condition that honours the continuity of the fluid volume flux. We discuss the limitations of the 1D model when applied to data recorded at higher frequencies (up to 100 Hz).

Objective There is increasing evidence of cognitive impairment (CI) frequently occurring in patients with multiple system atrophy (MSA); however, the neurobiological mechanisms underlying CI in patients with MSA remain unclear. Methods We enrolled 61 patients with probable MSA and 33 healthy controls (HC). We used degree centrality (DC) analysis to assess changes in the centrality level of MSA-CI related brain nodes. We conducted a secondary seed-based functional connectivity (FC) analysis to investigate dysfunctions in cognitive networks related to MSA. Further, we analysed the correlation between clinical symptoms and acquired connectivity measures. Results Compared with HC, patients with MSA-CI and those with MSA with normal cognition (MSA-NCI) exhibited lower DC values in the left calcarine and right postcentral regions and higher DC values in the bilateral caudate and left precuneus. There were significant differences in the DC values in the right middle prefrontal gyrus between the MSA-CI and MSA-NCI groups. The mean DC values in the right middle prefrontal gyrus (RMPFG) were correlated with clinical cognitive severity. Consequently, we used this brain region as a seed in secondary seed-based FC analysis and observed FC changes within the right precuneus, inferior parietal lobe, and right insula. Conclusions Decreased middle prefrontal cortex activity and its altered functional connectivity with the precuneus, inferior parietal lobe, and insula are possible biomarkers of cognitive dysfunction in patients with MSA-CI. Significance Cognitive impairment in MSA is associated with alterations in the dorsolateral prefrontal cortex network.

Enzymatic degradation of lignocelluloses into fermentable sugars to produce biofuels and other biomaterials is critical for environmentally sustainable development and energy resource supply. However, there are problems in enzymatic cellulose hydrolysis, such as the complex cellulase composition, low degradation efficiency, high production cost, and post-translational modifications (PTMs), all of which are closely related to specific characteristics of cellulases that remain unclear. These problems hinder the practical application of cellulases. Due to the rapid development of computer technology in recent years, computer-aided protein engineering is being widely used, which also brings new opportunities for the development of cellulases. Especially in recent years, a large number of studies have reported on the application of computer-aided protein engineering in the development of cellulases; however, these articles have not been systematically reviewed. This article focused on the aspect of protein engineering and PTMs of fungal cellulases. In this manuscript, the latest literatures and the distribution of potential sites of cellulases for engineering have been systematically summarized, which provide reference for further improvement of cellulase properties. KEY POINTS: •Rational design based on virtual mutagenesis can improve cellulase properties. •Modifying protein side chains and glycans helps obtain superior cellulases. •N-terminal glutamine-pyroglutamate conversion stabilizes fungal cellulases.

The effect of stress interactions on the effective poroelastic properties in saturated porous media has not been well-understood, especially for rocks with a fracture density larger than the dilute limit assumption. Frequency- and angle-dependent characteristics of stress interactions are analyzed by finite-element numerical tests with a least-squares procedure. We have investigated two types of fractured media: a stacked fractured model with stress shielding and a coplanar fractured model with stress amplification. We evaluate the effect of stress interactions from different spatial distributions of fractures on seismic attenuation and dispersion, with a specific focus on their frequency- and angle-dependent characteristics. We determine with numerical examples that a greater shielding effect corresponds to a larger frequency corresponding to maximum attenuation but a smaller peak attenuation. In contrast, a larger amplification effect leads to a higher attenuation. Due to the excluded diffusion energy outside the representative volume element, increasing the incidence angle ([Formula: see text]) leads to decreasing attenuation, whereas stress amplification is enhanced as the incidence angle increases continuously ([Formula: see text]), corresponding to increasing attenuation. This suggests that different incidence angles reshape the spatial distribution of stress interactions, in turn contributing to different frequency-dependent behaviors.

The variations of the static and dynamic moduli of porous rocks as a function of differential pressure have been described in terms of pore microstructure, i.e., the effects of cracks (soft pores) and intergranular (stiff) pores. Specifically, the first play a major role on the elastic properties of rocks. By using the Mori-Tanaka theory, this work relates rock elastic properties to the pore microstructure. Then, we estimate the distribution of pore aspect ratios by using the static bulk modulus instead of the dynamic one. The approach is applied to data from the Navajo and Weber sandstones. The results show that the cumulative crack porosity and density obtained from the static bulk modulus are higher than those estimated from the dynamic moduli, while the dominant crack aspect ratio is lower. The total porosity estimated from the static modulus agrees better with the experimental data. Furthermore, the cumulative crack (soft or compliant) porosity are estimated by the method, which also agrees with results from stress-strain relation and from bulk compressibility curves.

Elastic interactions between fractures will greatly affect the effective elasticity, which, in turn, reshape the effective fracture parameters. The disturbance will be more complex in the fault zone due to the complicated fracture distributions. The problem is addressed in this study by the comparison of two solutions: the analytical solution without stress interactions and the numerical method considering the stress interactions. The resultant difference between the two solutions allows the estimation of stress interactions on elasticity quantitatively. Furthermore, based on the orthorhombic assumption for fracture clustering in the damage zone, effect of stress interaction on the equivalent fractures parameter is estimated. We firstly characterize the fracture parameters in the fault damage zone considering more realistic distributions of fractures. Then, a series of numerical simulations are conducted to study the effective parameters of the fractured model. Finally, assuming the orthorhombic system of the fracture clustering, we invert the crack density and validate the accuracy of the inversion through the incidence-angle seismic velocities. Our numerical results suggest that, the size of fractures will determine the dominated type of stress interactions, and thus significantly reshape the effective properties of the models regardless of the fracture spatial distribution. Furthermore, the stress interactions tend to underestimate the fracture density for models containing long fractures, but generate a relatively satisfactory inverted fracture density for short fractures.

Objective This study aimed to develop an automatic classifier to distinguish different motor subtypes of Parkinson's disease (PD) based on multilevel indices of resting-state functional magnetic resonance imaging (rs-fMRI). Methods Ninety-six PD patients, which included thirty-nine postural instability and gait difficulty (PIGD) subtype and fifty-seven tremor-dominant (TD) subtype, were enrolled and allocated to training and validation datasets with a ratio of 7:3. A total of five types of index, consisting of mean regional homogeneity (mReHo), mean amplitude of low-frequency fluctuation (mALFF), degree of centrality (DC), voxel-mirrored homotopic connectivity (VMHC), and functional connectivity (FC), were extracted. The features were then selected using a two-sample t-test, the least absolute shrinkage and selection operator (LASSO), and Spearman's rank correlation coefficient. Finally, support vector machine (SVM) models based on the separate index and multilevel indices were built, and the performance of models was assessed via the area under the receiver operating characteristic curve (AUC). Feature importance was evaluated using Shapley additive explanation (SHAP) values. Results The optimal SVM model was obtained based on multilevel rs-fMRI indices, with an AUC of 0.934 in the training dataset and an AUC of 0.917 in the validation dataset. The AUCs of the models based on the separate index were ranged from 0.783 to 0.858 for the training dataset and from 0.713 to 0.792 for the validation dataset. SHAP analysis revealed that functional activity and connectivity in frontal lobe and cerebellum were important features for differentiating PD subtypes. Conclusions Our findings demonstrated multilevel rs-fMRI indices could provide more comprehensive information on brain functionalteration. Furthermore, the machine learning method based on multilevel rs-fMRI indices might be served as an alternative approach for automatically classifying clinical subtypes in PD at the individual level.

ObjectiveThis study aimed to investigate the morphometric alterations in the cortical and subcortical structures in multiple system atrophy (MSA) patients with mild cognitive impairment (MCI), and to explore the association with cognitive deficits.MethodsA total of 45 MSA patients (25 MSA-only, 20 MSA-MCI) and 29 healthy controls were recruited. FreeSurfer software was used to analyze cortical thickness, and voxel-based morphometry was used to analyze the gray matter volumes. Cortical thickness and gray matter volume changes were correlated with cognitive scores.ResultsCompared to healthy controls, both MSA subgroups exhibited widespread morphology alterations of brain structures in the fronto-temporal regions. Direct comparison of MSA-MCI and MSA-only patients showed volume reduction in the left superior and middle temporal gyrus, while cortical thinning was found in the left middle and inferior temporal gyrus in MSA-MCI patients. Cortical thinning in the left middle temporal gyrus correlated with cognitive assessment and disease duration.ConclusionStructural changes in the brain occur in MSA-MCI patients. The alteration of brain structure in the left temporal regions might be a biomarker of cognitive decline in MSA-MCI patients.

Objective: Freezing of gait (FOG) is a common disabling motor symptom in Parkinson's disease (PD), but the potential pathogenic mechanisms are still unclear. Methods: A total of 22 patients with PD with FOG (PD-FOG), 28 patients with PD without FOG (PD-nFOG), and 33 healthy controls (HCs) were recruited in this study. Degree centrality (DC)—a graph theory-based measurement of global connectivity at the voxel level by measuring the number of instantaneous functional connections between one region and the rest of the brain—can map brain hubs with high sensitivity, specificity, and reproducibility. DC was used to explore alterations in the centrality of PD-FOG correlated with brain node levels. PD-FOG cognitive network dysfunction was further revealed via a seed-based functional connectivity (FC) analysis. In addition, correlation analyses were carried out between clinical symptoms and acquired connectivity measurement. Results: Compared to the PD-nFOG group, the PD-FOG group showed remarkably increased DC values in the right middle frontal gyrus (RMFG). There were no significant differences in other gray matter regions. Importantly, the clinical severity of FOG was related to the mean DC values in the RMFG. This brain region served as a seed in secondary seed-based FC analysis, and we further found FC changes in the right precuneus, right inferior frontal gyrus, right superior frontal gyrus, and cerebellum. Conclusions: Increased RMFG activity and FC network alterations in the middle frontal cortex with the precuneus, inferior, and superior frontal gyrus, and the cerebellum may have great potential in brain dysfunction in PD with FOG.

The present study investigated the differences in clinical characteristics, treatments, and outcomes of patients with acute aortic dissection (AAD) in different age groups.The present single-center retrospective study was conducted from August 2014 to August 2020. The patients were divided into three groups: age 45 years (young group), age 45 to 59 years (middle-age group), and age59 years (elderly group). Type A (TAAD) and type B (TBAD) aortic dissection were evaluated separately using the latest definitions.The mean age at onset was 52.4 years in our cohort of 602 patients. The young group included a large proportion of male patients (86%). The body mass index and body surface area were higher in the young group. The proportion of non-true lumen blood supply of branches on the abdominal aorta in the young group (27%-55%) was greater than that in the others. In the young group, the distal extent of dissection in 84% of TAAD and 89% of TBAD exceeded the abdominal aortic branch cluster (AABC) compared with 36% of TAAD and 58% of TBAD in the elderly group. The multivariate analysis revealed that age 45 years (odds ratio, 5.15; P .001) and D-dimer level (odds ratio, 1.05; P = .001) were risk factors for intimal flap tear exceeding the AABC. The proportion of visceral and lower limb malperfusion increased from 4.8% to 36.9% as the intimal flap tear exceeded the AABC.Compared with middle-age and elderly patients, young patients with AAD had two characteristics (ie, obesity and an intimal flap that had frequently exceeded the branches of the aorta). These two factors resulted in a greater proportion of non-true lumen blood supply, increased visceral and lower limb malperfusion, and an increase in potential associated risks.

The wave-induced interlayer flow between mesoscopic-scale heterogeneities (i.e., larger than pore scale but smaller than the predominant wavelengths) is the most important cause of attenuation at frequencies below 1 kHz. According to the White's layered model ( White et al., 1975 ), the wave-induced flow at an interface is symmetrical in periodically layered porous media due to its symmetrical structure. However, in one-dimensional (1-D) randomly layered porous rocks, layers of various thicknesses lead to different types of the interlayer flow. The coexistence of various wave-induced interlayer flow patterns at different interfaces results in interactions. The numerical creep test and a volume average of White's analytical solution were used to analyse the interactions in the two kinds of models (i.e., representative elementary volumes and randomly layered models). One of the parameters used to build a randomly layered model is the standard deviation of the thickness of the water-saturated layer, which could control the interaction strength of the interlayer flow. The detailed characteristics of the interlayer flow interaction were demonstrated by analysing the relative fluid velocity, while the statistical characteristics of the interlayer flow interaction were demonstrated by analysing the average solid velocity. We investigated the effect of the interaction on the amplitude versus the deviation at the interface between a non-dispersive medium and a patchy-saturated dispersive medium in three types of reservoirs. These results are beneficial for describing the distribution of oil/gas patches based on the statistical seismic properties in a layered formation with random disorder.

All for underwater images, there are some drawbacks, such as low definition, serious color bias, dark brightness, etc. On the basis of in-depth analysis of common image enhancement algorithms, This paper uses the improved dark channel priority algorithm to enhance the underwater image, Improving the contrast of underwater images and color correction of underwater images. Color correction is added based on dark channel prior algorithm; Make the image look more even, higher contrast, more acceptable. The improved algorithm model has a higher transfer rate; PSNR is more balanced and has better contrast to meet the requirements of underwater image observation.

Multiparameter inversion for pre-stack seismic data plays a significant role in quantitative estimation of subsurface petrophysical properties. However, it remains a complicated problem due to the non-unique results and unstable nature of the processing; the pre-stack seismic inversion problem is ill-posed and band-limited. Combining the full Zoeppritz equation and additional assumptions with edge-preserving regularisation can help to alleviate these problems. To achieve this, we developed an inversion method by constructing a new objective function that includes edge-preserving regularisation and soft constraints based on anisotropic Markov random fields and is intended especially for layered formations. We applied a fast simulated annealing algorithm to solve the nonlinear optimisation problem. The method directly obtains reflectivity RPP values using the full Zoeppritz equation instead of its approximations and effectively controls the stability of the multiparameter inversion by assuming a sectionally constant S- and P-wave velocity ratio and using the generalised Gardner equation. We substituted the inverted parameters, i.e., the P-wave velocity, the fitting deviation of S-wave velocity, and the density were inverted instead of the P-wave velocity, the S-wave velocity, and the density, and the generalised Gardner equation was applied as a constraint. Test results on two-dimensional synthetic data indicated that our substitution obtained improved results for multiparameter inversion. The inverted results could be improved by utilising high-order anisotropic Markov random field neighbourhoods at early stages and low-order anisotropicMarkov random field neighbourhoods in the later stages. Moreover, for layered formations, using a large horizontal weighting coefficient can preserve the lateral continuity of layers, and using a small vertical weighting coefficient allows for large longitudinal gradients of the interlayers. The inverted results of the field data revealed more detailed information about the layers and matched the logging curves at the wells acceptably over most parts of the curves.

The thin-film quality is critical for obtaining high-performance perovskite solar cells (PSCs). The additive 1,8-diiodooctane (DIO) was used to control the morphology and structure of CH 3 NH 3 PbI 3 perovskite thin films, and planar heterojunction (PHJ) PSCs with an architecture of ITO/PEDOT: PSS/CH 3 NH 3 PbI 3 /PCBM/Al was fabricated. It was found that the DIO played an important role on CH 3 NH 3 PbI 3 thin-film quality and the performance of PHJ-PSCs. With the optimal volume ratio of 2%, the compact and uniform high-quality CH 3 NH 3 PbI 3 thin films with enhanced crystallinity and less roughness were achieved, resulting in the great improvement of power conversion efficiency ( PCE ) from about 4.5% to over 9.0%. The research results indicate that the additive DIO is a simple and effective method to produce high-quality perovskite thin film and accordingly develop high-performance PHJ-PSCs.

Highly efficient planar heterojunction perovskite solar cells (PHJ–PSCs) with a structure of ITO/PEDOT:PSS/CH3NH3PbI3–xClx/PCBM/C60/Ag was fabricated, in which the compact and pinhole-free CH3NH3PbI3–xClx perovskite thin film was obtained using a mixture of precursors containing lead iodide (PbI2), lead chloride (PbCl2), and methylammonium iodide (CH3NH3I) at an optimized ratio of 1:1:4. The morphology and formation process of CH3NH3PbI3–xClx thin film was closely related to the annealing temperature and time, which would result in the controllable performance for the PHJ–PSC devices. The morphology, crystallization process, and element analysis suggested that the chlorine gradually diffused and sublimated from the film surface while the iodine moved to the surface, together with the removal of the pinholes in the film. The PHJ–PSCs with the as-prepared CH3NH3PbI3–xClx thin film showed good performance and excellent repeatability. The power conversion efficiency (PCE) up to 14.03% was achieved without obv...

Interface is one of the most important factors to influence the device stability, which directly determines the commercialization of perovskite solar cells (PSCs). The research disclosed the degradation process and mechanism of planar heterojunction (PHJ) PSCs with a structure of ITO/PEDOT:PSS/CH 3 NH 3 PbI 3 /PCBM/Al using in-situ experiments. The degradation of PHJ-PSCs is mainly attributed to the interface decay of perovskite/cathode. Large amount of bubbles formed quickly at the interface and grew up as PHJ-PSCs exposed to air. The cathode electrode easily peeled off from the devices that led to lose the efficiency completely after only 1 h exposure to air. On the other hand, the degradation driven by intrinsic decomposition of perovskite itself under atmosphere (humidity ∼ 45 RH%) was not obvious and the power conversion efficiency ( PCE ) could retain almost the same when only the perovskite layer was exposed to air for 200 h. Furthermore, annealing-free TiO 2 nanocrystalline particles (TiO 2 NPs) as an interface modification layer was inserted into PHJ-PSCs and dramatically improved the stability, of which the PCEs retained over 75% of its initial values after exposure to air for 200 h. The results provide important information to understand the degradation of PSCs and the improvement of the stability, which may potentially accelerate the development and commercialization of PSCs.

Highly efficient and non-hysteresis organic/perovskite planar heterojunction solar cells was fabricated by low-temperature, solution-processed method with a structure of ITO/PEDOT:PSS/CH 3 NH 3 PbI 3 /PCBM/Al. The high-quality perovskite thin film was obtained using a solvent-induced-fast-crystallization deposition involving spin-coating the CH 3 NH 3 PbI 3 solution followed by top-dropping chlorobenzene with an accurate control to induce the crystallization, which results in highly crystalline, pinhole-free, and smooth perovskite thin film. Furthermore, it was found that the molar ratio of CH 3 NH 3 I to PbI 2 greatly influence the properties of CH 3 NH 3 PbI 3 film and the device performance. The equimolar or excess PbI 2 was facile to form a flat CH 3 NH 3 PbI 3 film and produced relatively uniform perovskite crystals. Perovskite solar cells (PSCs) with high-quality CH 3 NH 3 PbI 3 thin film showed good performance and excellent repeatability. The power conversion efficiency ( PCE ) up to 13.49% was achieved, which is one of the highest PCEs obtained for low-temperature, solution-processed planar perovskite solar cells based on the structure ITO/PEDOT:PSS/CH 3 NH 3 PbI 3 /PC 61 BM/Al. More importantly, PSCs fabricated using this method didn’t show obvious hysteresis under different scan direction and speed.

A unique Ag-bridged Ag2O nanowire network/TiO2 nanotube array p–n heterojunction (Ag–Ag2O/TiO2 NT) was fabricated by simple electrochemical method. Ag nanoparticles were firstly electrochemically deposited onto the surface of TiO2 NT and then were partly oxidized to Ag2O nanowires while the rest of Ag mother nanoparticles were located at the junctions of Ag2O nanowire network. The Ag–Ag2O/TiO2 NT heterostructure exhibited strong visible-light response, effective separation of photogenerated carriers, and high adsorption capacity. The integration of Ag–Ag2O self-stability structure and p–n heterojunction permitted high and stable photocatalytic activity of Ag–Ag2O/TiO2 NT heterostructure photocatalyst. Under 140-min visible light irradiation, the photocatalytic removal efficiency of both dye acid orange 7 (AO7) and industrial chemical p-nitrophenol (PNP) over Ag–Ag2O/TiO2 NT reached nearly 100% much higher than 17% for AO7 or 13% for PNP over bare TiO2 NT. After 5 successive cycles under 600-min simulated solar light irradiation, Ag–Ag2O/TiO2 NT remained highly stable photocatalytic activity.

By applying nonequilibrium Green’s functions in combination with the density functional theory, we have investigated the electronic transport properties of molecular devices consisting of the carbon atomic chain coupling with symmetry and asymmetry Au electrodes. The asymmetry Au electrodes systems display good rectifying behavior. The main origin of this phenomenon is that a molecular core coupling with asymmetry electrodes can generate two asymmetrical Schottky barriers at both extended molecule regions. This rectification is also explained by the calculated transmission spectrum and the spatial distribution of the LUMO and HOMO states.

Planar heterojunction perovskite solar cells (PHJ-PSCs) based on CH3NH3PbI3/TiO2 with high-quality CH3NH3PbI3 films were fabricated by two-step interdiffusion technology. The photovoltaic performance of PHJ-PSCs, including short-circuit-current (Jsc) and open-circuit-voltage (Voc), was found to be strongly dependent on the thickness of TiO2 layer. The largest Jsc was obtained at an optimized TiO2 thickness of 65 nm, resulting in a moderate power conversion efficiency (PCE) of 8.40% with a device structure of fluorine doped SnO2/compact TiO2/CH3NH3PbI3/Spiro-MeOTAD/Ag. A thicker compact TiO2 film could lead to a lower Voc, and the physical mechanism between the Voc and the thickness of compact TiO2 layer was disclosed.