Position Mismatch Research Articles

Double-Diffracted Spatially Separated Heterodyne Grating Interferometer and Analysis on its Alignment Tolerance

An optical configuration of double-diffracted spatially separated heterodyne grating interferometer with a mechanical fixture was designed. To further investigate its features and provide robust measurements, the alignment tolerance in double-diffracted spatially separated heterodyne grating interferometer was qualitatively and quantitatively analyzed. Except for the offset error causing no influence on the interfering signal, the effect of the other four errors, roll, yaw, pitch angles, and stand-off error were geometrically analyzed and mathematically modeled. The simulation result quantified the position mismatches of output beams in a double-diffracted configuration and found the crucial structural parameters related to the intensity of interfering signals. Experiments based on the grating interferometer with a mechanical fixture and the same optical configuration built by independent optical components were implemented, whose results agreed with the simulation. Besides, the results showed that the proposed grating interferometer structure could tolerate the ±1100 arcsec roll movement, ±440 arcsec yaw movement, ±280 arcsec pitch movement, and ±0.6 mm stand-off error when -10 dB intensity loss is afforded.

Topological data assimilation using Wasserstein distance

This work combines a level-set approach and the optimal transport-based Wasserstein distance in a data assimilation framework. The primary motivation of this work is to reduce assimilation artifacts resulting from the position and observation error in the tracking and forecast of pollutants present on the surface of oceans or lakes. Both errors lead to spurious effect on the forecast that need to be corrected. In general, the geometric contour of such pollution can be retrieved from observation while more detailed characteristics such as concentration remain unknown. Herein, level sets are tools of choice to model such contours and the dynamical evolution of their topology structures. They are compared with contours extracted from observation using the Wasserstein distance. This allows to better capture position mismatches between both sources compared with the more classical Euclidean distance. Finally, the viability of this approach is demonstrated through academic test cases and its numerical performance is discussed.

Development of an effective electrochemical platform for highly sensitive DNA detection using MoS2 - polyaniline nanocomposites

Molybdenum disulfide (MoS2) and its associated nanocomposites are widely explored in different applications like capacitance, batteries, sensing etc. However, the nanosheet formation of MoS2 exhibits excellent properties for DNA adsorption without any further surface or probe DNA modification which makes it a suitable matrix for the less explored DNA sensing application. In this present work, an ultrasensitive electrochemical DNA biosensor, based on few layered MoS2 nanosheets blended with conducting polymer, polyaniline is constructed as a sensing platform and used as a DNA sensing probe via differential pulse voltammetric technique. The sensor works well even at concentrations as low as 10−15 M of target DNA without labeling or any use of amplifiers. The sensing performances show highly satisfactory results in case of serum samples and in presence of other interferrants. In addition, the sensor can successfully recognize any positional mismatch in a known concentration of targeted DNA which can lead to a DNA mismatch senor in near future. The detection method described here expands the application of MoS2 in the biosensor field with a viable alternative for easy, cost effective electrochemical DNA detection technique with mismatch identification capability.

Information content of ship noise on a drifting volumetric array for passive environmental sensing

This study investigates the information content of ship noise received on a drifting volumetric array of hydrophones in shallow water marine environments for the purposes of conducting acoustic thermometry or other environmental inversions. Passive inversions for physical oceanographic parameters are conducted using travel time differences, determined by cross-correlating ship noise received on hydrophones suspended beneath drifting buoys. Ships are tracked using the Automatic Identification System (AIS). Information content gained from the inversion is assessed using traditional a-posteriori error analysis. Numerical simulations using a standard normal mode propagation model are used to test limitations of the proposed approach with respect to frequency band, drifting receiver configuration, precision and accuracy of the inversion results, along with sensitivity to environmental and position mismatch. Performance predictions using this model are compared with results from a field experiment using at-sea data collected off the coast of New London, CT in Long Island Sound. Information gathered using passive acoustic inversion methods on drifting arrays can be used to constrain general circulation models (GCMs), in coastal environments, where ship noise is ubiquitous, environmental data are sparse, and the oceanography is dynamic and important for understanding large-scale ocean processes.

Modelling local areas of exposure to Schistosoma japonicum in a limited survey data environment

BackgroundSpatial modelling studies of schistosomiasis (SCH) are now commonplace. Covariate values are commonly extracted at survey locations, where infection does not always take place, resulting in an unknown positional exposure mismatch. The present research aims to: (i) describe the nature of the positional exposure mismatch in modelling SCH helminth infections; (ii) delineate exposure areas to correct for such positional mismatch; and (iii) validate exposure areas using human positive cases.MethodsTo delineate exposure areas to Schistosoma japonicum, a spatial Bayesian network (sBN) was constructed. It uses data on exposure risk factors such as: potential sites for snails’ accessibility, geographical distribution of snail infection rate, and cost of the community to access nearby water bodies. Prior and conditional probabilities were obtained from the literature and inserted as weights based on their relative contribution to exposure; these probabilities were then used to calculate joint probabilities of exposure within the sBN.ResultsHigh values of probability of S. japonicum exposure correspond to polygons where snails could potentially be present, for instance in wet soils and areas with low slopes, but also where people can easily access water bodies. Low correlation (R2 = 0.3) was found between the percentage of human cases and the delineated probabilities of exposure when validation buffers are generated over the human cases.ConclusionsThe utility of a probabilistic method for the identification of exposure areas for S. japonicum, with wider application for other water-borne infections, was demonstrated. From a public health perspective, the schistosomiasis exposure sBN developed in this study could be used to guide local schistosomiasis control teams to specific potential areas of exposure, and improve efficiency of mass drug administration campaigns in places where people are likely to be exposed to the infection.

F36. Imaging fascicle traffic in peripheral nerve using fast neural EIT

Fast neural Electrical Impedance Tomography (EIT) is a promising technique which can potentially be used for imaging neural activity over milliseconds with unprecedented spatial resolution without penetrating nervous tissue. Here we present the first cross-sectional images of fascicular neural activity measured during compound action potentials acquired in rat sciatic nerve in in vivo experiments. EIT was collected with a cylindrical cuff electrode wrapped around the sciatic nerve in the thigh in 4 adult Sprague-Dawley rats anaesthetized with Isoflurane nerve made of silicone rubber. 16 electrodes were placed around the circumference, each 2 × 0.1 mm, made of laser-cut stainless steel foil which was then platinised. Distal fibular and tibial branches were electrically stimulated with square pulses with 0.2 ms duration, 1 mA amplitude, and 200 ms inter–stimulus interval. EIT data was acquired during consecutive injection of alternating current, with amplitude 5–75 μA and frequency 3–15 kHz, through a pair of electrodes at a time with simultaneous voltage recordings on the remaining electrodes. 16 independent current injections with 50 pulses per injection were recorded, resulting in 160 s image acquisition time. Acquired data was demodulated with 4 kHz bandwidth, averaged, and reconstructed with >0.5 ms temporal resolution. 1M-element 3D forward mesh, and 20k-element inverse mesh was used for reconstruction; 0-th order Tikhonov regularisation with coefficient of variance correction was employed. Results were displayed as a Z-score with respect to the inter-stimulus noise. Reproducible time-series images were reconstructed in each experiment, showing neural activity onset in ∼0.3–0.6 ms, after stimulus, peak at 0.6–1.5 ms, and subsequent decay at 1–2 ms. Images were obtained following electrical stimulation of the tibial or peroneal branches distally. Spatially distinguishable activity with centre-to-centre separation distance of 0.57 ± 0.04 mm (mean ± S.E.) was obtained in N = 24 experiments in n = 3 rats. EIT were much superior to those collected by Inverse Source Analysis (ISA) performed on CAPs recorded simultaneously to the EIT. Images were cross-validated with co-registered histological images. Comparison showed the position mismatch was 0.1 mm ± 0.03 mm between EIT and histology, and 0.14 mm ± 0.06 mm between EIT and inverse source imaging. Nerve fascicular traffic can be successfully imaged using EIT. This offers a potential means to identify the function of fascicles in autonomic nerve in vivo and so avoid off-target effect by selective stimulation. This could yield significant benefits in vagal nerve stimulation in epilepsy, where hoarseness is a limiting factor, and in the new field of Electroceutical treatment of disease by electrical stimulation of autonomic nerve.

Endonuclease IV recognizes single base mismatch on the eighth base 3' to the abasic site in DNA strands for ultra-selective and sensitive mutant-type DNA detection.

Since single nucleotide polymorphism (SNP) is related with many diseases and drug metabolic polymorphous and SNP genotyping is rising rapidly in many biological and medical areas, various methods of discriminating SNPs have been developed, one of which is an enzyme-based method. We uncovered a unique property of endonuclease IV due to which it can discriminate single base mismatches in different positions of DNA strands containing an abasic site, and we also discovered a new property: a mismatch in the +8 position could inhibit the cleavage of endonuclease IV. Then, we coupled +8 mismatch with other mismatches along with the discrimination effect of melting temperature to develop a new ultra-selective and sensitive genotyping system, which showed high discrimination factors. The detection limit was as low as 0.05–0.01%. Our new discovery improves the understanding of endonuclease IV. Also, the method could be applied to clinical real samples; thus, it merits further investigation and improvement for application in clinical utilization for early screening of specific diseases.

Overcoming Source Limitations in Drainage Delineation by Combining the Streams of Toposheet and DEM in River Morphometric Studies

ABSTRACT This paper suggests an approach that combines the drainages of DEM and toposheets, by matching streams (number and length) and spatial coincidence, the critical aspects of such operations, for overcoming source limitation in river morphometric studies. We illustrate the approach taking Gaurang, a Himalayan river basin, as an example where the toposheets for the uppermost part is inaccessible. Stream matching in terms of number and length is controlled by a method of automatic stream generation from downscaled DEM and flow accumulated rasters. Stream estimated by this method are tested, verified and finally applied to the portion of the basin where the data is unavailable. The other critical aspect-spatial coincidence is controlled by commonly used method of GCPs. In the present case, use of the nodal points of the major tributaries generated from DEM as GCPs for georeferencing of toposheets have restricted the positional mismatch to much less than a pixel. With the consent of both the aspects i.e. stream matching and spatial coincidence, the DEM generated stream is considered to combine with the stream of toposheets to get the drainage of entire basin.

Peritoneal Dialysis Catheter Position Evaluated by Ultrasound: Can it Replace Abdomen X-Ray in Patients Presenting Catheter Misplacement?

Background Malfunction of the peritoneal dialysis catheter is frequently caused by dislocation. The diagnostic approach is classically based on abdomen X-ray together with detailed case history and physical examination. Despite being rarely applied in clinical practice to evaluate catheter misplacement, ultrasound is a noninvasive, radiation-free technique that ispotentially useful also to explore reasons for catheter malfunction. Consequently, we aimed to evaluate the diagnostic accuracy of ultrasound to identify peritoneal catheter misplacement. Methods In a multicenter observational blinded study, we compared ultrasound to abdomen X-ray for catheter localization in 93 consecutive peritoneal dialysis patients with dialysate outflow problems enrolled in two nephrology and dialysis units. The position of the catheter was annotated on a standard scheme of nine abdominopelvic regions. The sensitivity, specificity, positive and negative predictive value and Kappa coefficient were calculated. Results Dislocation out of the inferior abdominopelvic regions was present in 19 patients (20 %) at X-ray and 23 patients (25 %) at ultrasound. Correct determination of the position of the catheter in the lower abdomen by ultrasound had a sensitivity of 93 % (95 % CI 84 - 97 %), specificity of 95 % (95 % CI 72 - 100 %), positive predictive value of 99 % (95 % CI 91 - 100 %), negative predictive value of 78 % (95 %CI 56 - 92 %) and Kappa coefficient of 0.82 (95 % CI 0.67 - 0.96). In 10 out of 93 patients (11 %), there was a position mismatch between X-ray and ultrasound in an adjacent abdominopelvic region. Conclusion Our results suggest that abdomen X-ray for the evaluation of peritoneal catheter position can be replaced by ultrasound in experienced hands. This bedside diagnostic procedure might reduce costs, the time necessary for diagnosis and lifetime radiation exposure.

Skill Transfer Between Industrial Robots by Learning from Demonstration

Industrial robots are the key role in modern manufacture. In order to allow different robots to perform the same task, they must be programmed manually which is time-consuming and cumbersome. The ability to transfer robotic skills between heterogeneous robots would provide significances to industry. This paper presents a prototype control architecture for industrial robots which allows multiple heterogeneous robots of different morphologies to perform the same task without manually programming each robot separately. We selected three articulated industrial manipulators with different degree of freedoms (Yaskawa Motoman HP3JC: 6, Universal Robot UR5: 6 and Rethink Robotics Baxter: 7) to test our approach. Two simple tasks were chosen for implementation and analysis. Results indicate that our approach works with some errors. Maximum and average position mismatch errors for UR5 are 4.9380 cm and 4.4761 cm. For Baxter, maximum and average position mismatch errors are 1.7770 cm and 1.6068 cm. Baxter has a different range of motion therefore some places could not be reached with it.

Effect of Patient-Prosthesis Mismatch in Aortic Position on Late-Onset Tricuspid Regurgitation and Clinical Outcomes after Double Valve Replacement.

PurposeSignificant late-onset tricuspid regurgitation (TR) is unfortunately common after double valve replacement (DVR); however, its underlying factors remain undefined. We evaluated the effect of aortic patient-prosthesis mismatch (PPM) on late-onset TR and clinical outcomes after DVR.Materials and MethodsOf the 2392 consecutive patients who underwent aortic valve replacement between January 1990 and May 2014 at our institution, we retrospectively studied 462 patients who underwent DVR (excluding concomitant tricuspid valvular annuloplasty or replacement). Survival and freedom from grade >3 TR were compared between PPM (n=152) and non-PPM (n=310) groups using the Kaplan-Meier method.ResultsAlthough the overall survival rates were similar between the two groups at 5 and 10 years (95%, 91% vs. 96%, 93%, p=0.412), grade >3 TR-free survival was significantly lower in the PPM group (98%, 91% vs. 99%, 95%, p=0.014). Small body-surface area, atrial fibrillation, PPM, and subaortic pannus were risk factors for TR progression. However, aortic prosthesis size and trans-valvular pressure gradient were not significant factors for either TR progression or overall survival.ConclusionAortic PPM in DVR, regardless of mitral prosthesis size, was associated with late TR progression, but was not significantly correlated with overall survival. Therefore, we recommend careful echocardiographic follow-up for the early detection of TR progression in patients with aortic PPM in DVR.

QCM-based rupture force measurement as a tool to study DNA dehybridization and duplex stability.

The stability of double-stranded DNA (dsDNA) was assessed on the basis of unwinding force measurement. Unwinding force was measured directly with a quartz crystal microbalance (QCM). The amplitude of its surface oscillations was controlled by supplying variable alternate voltage. Under smoothly increasing amplitude of QCM surface oscillations, dsDNA fixed on QCM surface through one of its ends got unwound. This procedure allows reliable measurement of rupture force as small as 5-10 pN. It was demonstrated that oscillations of the surface, with dsDNA bound through one of its ends to this surface, at a frequency of 14MHz, cause helix unwinding to form two complementary parts due to viscous forces of the liquid medium. Unwinding starts at the upper end. This was proven using oligonucleotide duplexes containing mismatches in different positions. For duplexes containing complementary 20 base pairs, the helix unwinding force is equal to 30-40 pN, which is in agreement with the data obtained by means of atomic-force microscopy (AFM) for the case of unzipping mode. Graphical Abstract Rupture force depending on mismatch position in dsDNA.

Silver Ions in Non-canonical DNA Base Pairs: Metal-Mediated Mismatch Stabilization of 2'-Deoxyadenosine and 7-Deazapurine Derivatives with 2'-Deoxycytidine and 2'-Deoxyguanosine.

Novel silver-mediated dA-dC, dA*-dC, and dA*-dG base pairs were formed in a natural DNA double helix environment (dA* denotes 7-deaza-dA, 7-deaza-7-iodo-dA, and 7-cyclopropyl-7-deaza-dA). 7-Deazapurine nucleosides enforce silver ion binding and direct metal-mediated base pair formation to their Watson-Crick face. New phosphoramidites were prepared from 7-deaza-dA, 7-deaza-7-iodo-dA, and 7-cyclopropyl-7-deaza-dA, which contain labile isobutyryl protecting groups. Solid-phase synthesis furnished oligonucleotides that contain mismatches in near central positions. Increased thermal stabilities (higher Tm values) were observed for oligonucleotide duplexes with non-canonical dA*-dC and dA-dC pairs in the presence of silver ions. The stability of the silver-mediated base pairs was pH dependent. Silver ion binding was not observed for the dA-dG mismatch but took place when mismatches were formed between 7-deazaadenine and guanine. The specific binding of silver ions was confirmed by stoichiometric UV titration experiments, which proved that one silver ion is captured by one mismatch. The stability increase of canonical DNA mismatches might have an impact on cellular DNA repair.

SU‐F‐J‐33: On‐Line Daily KV Image Protocol of Lung Patient Setup with Minimal CBCT

Purpose:This study's intent is to test if the first 3 fractions of an IGRT protocol consisting of a kV orthogonal pair and subsequent CBCT are representative of all remaining treatment fractions.Methods:At our institution the standard IGRT protocol includes CBCT after kV imaging for the first 3 fractions followed by daily kV and weekly CBCT. We randomly selected 20 lung patients who have at least 8 CBCTs in the entire treatment course (total 187 sets of orthogonal kV images plus CBCT). Our evaluation criterion is the fraction of kV‐vs‐CBCT position mismatches in the first 3 fractions. An additional CBCT is acquired if only 1 fraction mismatches among the first three. We define as 'protocol eligible’ (eGroup) the group of patients for whom the setups with kV images match within the pre‐selected thresholds of 3, 4 and 5 mm those of the consecutive CBCTs for at least 60% of the fractions. A protocol ineligible (iGroup) is defined as the group of patients other than eGroup.Results:The fractions of patients in the eGroup were 70%, 85% and 95%, when the setup thresholds selected were 3, 4 and 5mm respectively. The sensitivities of determining iGroup from the first 3 fractions of kV and CBCT were 0.83, 1.0, and 1.0, and the specificities were 0.93, 0.94 and 0.89 with thresholds 3, 4 and 5 mm respectively.Conclusion:The method suggested here well categorized cases for our kV‐based on‐line IGRT protocol. More patients are eGroup eligible if larger setup threshold is used. CBCT frequency in the on‐line daily kV plus weekly CBCT protocol may need to increase for protocol ineligible patients. Also, our IGRT CBCT frequency could be decreased when position differences between kVs and CBCTs are less than 1.5mm, the average positional standard deviation of out kV‐CBCT sets.

Physiological vortices in the sinuses of Valsalva: An in vitro approach for bio-prosthetic valves

PurposeThe physiological flow dynamics within the Valsalva sinuses, in terms of global and local parameters, are still not fully understood. This study attempts to identify the physiological conditions as closely as possible, and to give an explanation of the different and sometime contradictory results in literature. MethodsAn in vitro approach was implemented for testing porcine bio-prosthetic valves operating within different aortic root configurations. All tests were performed on a pulse duplicator, under physiological pressure and flow conditions. The fluid dynamics established in the various cases were analysed by means of 2D Particle Image Velocimetry, and related with the achieved hydrodynamic performance. ResultsEach configuration is associated with substantially different flow dynamics, which significantly affects the valve performance. The configuration most closely replicating healthy native anatomy was characterised by the best hemodynamic performance, and any mismatch in size and position between the valve and the root produced substantial modification of the fluid dynamics downstream of the valve, hindering the hydrodynamic performance of the system. The worst conditions were observed for a configuration characterised by the total absence of the Valsalva sinuses. ConclusionThis study provides an explanation for the different vortical structures described in the literature downstream of bioprosthetic valves, enlightening the experimental complications in valve testing. Most importantly, the results clearly identify the fluid mechanisms promoted by the Valsalva sinuses to enhance the ejection and closing phases, and this study exposes the importance of an optimal integration of the valve and root, to operate as a single system.

Invited Commentary

Patient–prosthesis mismatch after mitral valve replacement is still of uncertain relevance because the long-term outcome and underlying potential pathomechanisms are not identified. The evidence is conflicting that patient–prosthesis mismatch is a clinically relevant phenomenon and affects long-term prognosis. The hemodynamic mechanisms of compensation in patient–prosthesis mismatch in the mitral position are different from those of patient–prosthesis mismatch in the aortic position. As nicely shown by Ho Young and colleagues [1Hwang H.Y. Kim Y.H. Kim K.H. et al.Patient–prosthesis mismatch after mitral valve replacement: a propensity score analysis.Ann Thorac Surg. 2016; 101: 1796-1803Abstract Full Text Full Text PDF Scopus (23) Google Scholar], there is a shift from a cardiac type toward a respiratory type of clinical presentation, inasmuch as pulmonary congestion and residual hypertension were more frequent in patients with mitral patient–prosthesis mismatch. This indicates congestion in the pulmonary vascular system with a negative impact on pulmonary recovery. Unfortunately, the authors could not provide information about the incidence of new-onset atrial fibrillation after surgery, which may have an impact on the postoperative clinical course. As in the aortic position, patient–prosthesis mismatch in the mitral valves seems to relate to the presence of bioprostheses rather than mechanical prostheses; however, the data failed to prove this statistically. The most striking new information in this study is the negative impact of patient–prosthesis mismatch in the mitral position on long-term survival. In the past, this clinical issue has been underestimated in the long-term follow-up after mitral valve replacement, and we will now be forced to rethink the concepts of intraoperative decision making. Patient-Prosthesis Mismatch After Mitral Valve Replacement: A Propensity Score AnalysisThe Annals of Thoracic SurgeryVol. 101Issue 5PreviewWe evaluated the impact of patient-prosthesis mismatch (PPM) after mitral valve replacement on the clinical outcomes using propensity score models. Full-Text PDF

Passive ocean acoustic tomography using ships as sources of opportunity recorded on an irregularly spaced free-floating array: A feasibility study

This presentation investigates the practical feasibility of using an adaptive volumetric array, such as a series of free-floating buoys with suspended hydrophones, which record ships as acoustic sources of opportunity in coastal waters for performing acoustic thermometry or other environmental inversions in near-shore environments in a totally passive manner. Ships are tracked using the Automatic Identification System (AIS). Numerical simulations using a standard normal mode propagation model were first used to test limitations of the proposed approach with respect to frequency band, drifting receiver configuration, signal to noise ratio, precision, and accuracy of the inversion results, along with sensitivity to environmental and position mismatch. Performance predictions using this model are compared with experimental results using at-sea data collected off the coast of New London, CT, in Long Island Sound during August of 2015.

건물의 3차원 구조체에 대한 전열해석 프로그램 개발 중 3차원 모델의 해석 오류 저감을 위한 사전 수정 방법 연구

This study is part of three-dimensional(3D) heat transfer analysis program developmental process. The program is being developed without it's own built in 3D-modeller. So 3D-model must be created from another 3D-modeller such as generic CAD programs and imported to the developed program. After that, according to the 3D-geometric data form imported model, 3D-mesh created for numerical calculation. But the 3D-model created from another 3D-modeller is likely to have errors in it's geometric data such as mismatch of position between vertexes or surfaces. these errors make it difficult to create 3D-mesh for calculation. These errors are must be detected and cured in the pre-process before creating 3D-mesh. So, in this study four kinds of filters and functions are developed and tested. Firstly, 'vertex error filter' is developed for detecting and curing for position data errors between vertexes. Secondly, 'normal vector error filter' is developed for errors of surface's normal vector in 3D-model. Thirdly, 'intersection filter' is developed for extracting and creating intersection surface between adjacent objects. fourthly, 'polygon-line filter' is developed for indicating outlines of object in 3D-model. the developed filters and functions were tested on several shapes of 3D-models. and confirmed applicability. these developed filters and functions will be applied to the developed program and tested and modified continuously for less errors and more accuracy.

Identification of Forested Landslides Using LiDar Data, Object-based Image Analysis, and Machine Learning Algorithms

For identification of forested landslides, most studies focus on knowledge-based and pixel-based analysis (PBA) of LiDar data, while few studies have examined (semi-) automated methods and object-based image analysis (OBIA). Moreover, most of them are focused on soil-covered areas with gentle hillslopes. In bedrock-covered mountains with steep and rugged terrain, it is so difficult to identify landslides that there is currently no research on whether combining semi-automated methods and OBIA with only LiDar derivatives could be more effective. In this study, a semi-automatic object-based landslide identification approach was developed and implemented in a forested area, the Three Gorges of China. Comparisons of OBIA and PBA, two different machine learning algorithms and their respective sensitivity to feature selection (FS), were first investigated. Based on the classification result, the landslide inventory was finally obtained according to (1) inclusion of holes encircled by the landslide body; (2) removal of isolated segments, and (3) delineation of closed envelope curves for landslide objects by manual digitizing operation. The proposed method achieved the following: (1) the filter features of surface roughness were first applied for calculating object features, and proved useful; (2) FS improved classification accuracy and reduced features; (3) the random forest algorithm achieved higher accuracy and was less sensitive to FS than a support vector machine; (4) compared to PBA, OBIA was more sensitive to FS, remarkably reduced computing time, and depicted more contiguous terrain segments; (5) based on the classification result with an overall accuracy of 89.11% ± 0.03%, the obtained inventory map was consistent with the referenced landslide inventory map, with a position mismatch value of 9%. The outlined approach would be helpful for forested landslide identification in steep and rugged terrain.

Enabling Unassisted Solar Water Splitting By Hematite

As a photoelectrode material for solar water splitting, hematite has received tremendous attention. The appealing properties presented by hematite include earth abundance, stability against corrosion, suitable band gap, and nontoxicity. It, however, also presents a long list of challenges, such as notoriously short hole diffusion distance, poor catalytic activity, and low photovoltage. Among these challenge, the low photovoltage has received the least attention. We have shown that the low photovoltage is a result of combined effects of band edge position mismatch with water redox potentials and poor surface energetics. By interfacing with NiFeOx, an amorphous oxygen evolution catalyst, we have measured greatly improved photovoltages (from 0.24 V to 0.61 V). Importantly, the improved photovoltage was understood as a result of improvement in surface energetics, but not better water oxidation kinetics enabled by NiFeOx. To further test what is the true limit of the photovoltage generation capability by hematite, we recently carried out a detailed structural study on hematite and found that surface defects are responsbile for additional photovoltage lost. A facile regrowth strategy was developed to correct the deficiency. A record-low turn-on voltage of 0.45 V (vs. RHE) was achieved. The results permitted us to construct, for the first time, unassistant water splitting by hematite with a Si photocathode. An overall efficiency of 0.91% was measured.