Suitable Gradient Research Articles

Delineation of groundwater prospective zones using multivariate and spatial analysis techniques in Henan Province North China Plain

Groundwater is an essential resource that meets all of humanity’s daily water demands, supports industrial development, influences agricultural output, and maintains ecological equilibrium. The objective behind this research is to find groundwater prospective zones and their sustainable development in Henan Province, located in the North China Plain, with the help of analytical hierarchical process (AHP) and frequency ratio (FR) models. Consequently, a groundwater inventory map was created, utilizing 70% of the data for training and 30% for testing purposes. The resulting maps were overlaid with groundwater levels and the locations of wells within the study area. The performance and validation of the models were assessed using the Area Under Curve (AUC) curve, which indicated an accuracy of 70% for the AHP model and 69% for the FR model. The study indicates that areas with suitable gradients and rainfall patterns generally have high groundwater prospective zonation (GWPZ), i.e., Zhumadian and Nanyang (ZN). However, AHP demonstrated a higher predictive capability in comparison to FR the broader context. Whereas GIS-RS methodology aligns with existing wells and field data that validate it in range of good and excellent. In conclusion, this study provides valuable insights for effective groundwater exploration and sustainable water supply planning in Henan Province.

Self-Powered MAPbI3 Heterojunction Photodetector with Gradient-Level Electron Transport Layers and Dual Pyro-Phototronic Effects.

An electron transport layer (ETL) with a suitable gradient energy level can enhance electron transfer, suppress carrier recombination, and effectively improve the photoresponse of photodetectors (PDs). In this letter, a series of ITO/ZnO/CdS/MAPbI3/Spiro-OMeTAD heterojunction PDs were prepared by incorporating a ZnO layer at the CdS/ITO interface upon varying the thickness from 0 to 95 nm. The optimized band arrangement in the PD results in an excellent self-powering ability and improved photoresponse. Moreover, both the photovoltaic and pyroelectric responses strongly correlate with the thickness of the ZnO layer. The PD with an optimal ZnO thin film thickness of 50 nm achieves a huge responsivity (R) of 1.19 × 104 V/W and detectivity (D) of 2.22 × 109 Jones, primarily due to the strengthened pyro-phototronic effects enabled by the dual ETL layers. In addition, the enhanced pyroelectric effect broadens the spectral range of the PD to 360-1550 nm, largely surpassing the band gap of the heterojunction.

A general-purpose spectroscopic camera for single-board computers

A low-cost consumer-grade spectroscopic system offers potential applications in many fields. Linear variable optical filters (LVOFs) placed in front of imaging sensors are one of the most promising avenues to realize this goal. In this work, we built a spectroscopic system by depositing an LVOF directly onto the protective window of OV5647 color and OV9281 monochrome imaging sensors for the Raspberry Pi. The ¼” sensors cost $15-$80 CAD at the time of writing and have linear dimensions of only 2.7 – 3.6 mm. To achieve a suitable gradient over such small sensors, an ultra-slow shutting system was built for the physical vapor deposition of an SiO2 gradient layer between two partially transparent silver mirrors to form a miniature LVOF. The resulting devices operated as effective low-cost spectrometers that were single-moded in the visible spectrum. These simple systems were finally used to measure spectra from sample light sources, clearly illustrating the advantages and limitations of this simple and economical approach towards everyday consumer spectroscopy.

Prediction of compressive comfort of graded compression sleeves based on calf feature classification

This study explored the relationship between the design of calf compression sleeves and the comfort of young women in long sitting and standing work environments. By studying the relationship between material elongation and comfort pressure, a prediction model was obtained. The characteristics of the calf models of 94 women were classified, and the influence of different calf characteristics on the pressure distribution and tensile value design was objectively analyzed through simulation tests. The samples were then produced based on the simulation results, and subjective and objective try-on tests and evaluations were carried out. The results show that the difference in the shape of the calf has a certain impact on the pressure distribution and comfort. The predicted value of the theoretical model is in good agreement with the actual test value. The sample can bring a suitable gradient pressure and meet the comfort requirements and safety standards.

Acoustophoretic Characterization and Separation of Blood Cells in Acoustic Impedance Gradients.

Single-cell phenotyping based on biophysical properties is a promising tool to distinguish cell types and their response to a given condition, and charting such properties also enables optimization of cell separations. Isoacoustic focusing, where cells migrate to their points of zero acoustic contrast in an acoustic impedance gradient, added the effective acoustic impedance of cells to the directory of biophysical properties that can be utilized to categorize or separate cells. This study investigates isoacoustic focusing in a stop-flow regime and shows how cells migrate towards their isoacoustic point. We introduce a numerical model that we use to estimate the acoustic energy density in acoustic impedance gradient media by tracking particles of known properties, and we investigate the effect of acoustic streaming. From the measured trajectories of cells combined with fluorescence intensity images of the slowly diffusing gradient, we read out the effective acoustic impedance of neutrophils and K562 cancer cells. Finally, we propose suitable acoustic impedance gradients that lead to a high degree separation of neutrophils and K562 cells in a continuous-flow configuration.

Imaging Saturation Transfer Difference (STD) NMR: Affinity and Specificity of Protein-Ligand Interactions from a Single NMR Sample.

We have combined saturation transfer difference NMR (STD NMR) with chemical shift imaging (CSI) and controlled concentration gradients of small molecule ligands to develop imaging STD NMR, a new tool for the assessment of protein-ligand interactions. Our methodology allows the determination of protein-ligand dissociation constants (KD) and assessment of the binding specificity in a single NMR tube, avoiding time-consuming titrations. We demonstrate the formation of suitable and reproducible concentration gradients of ligand along the vertical axis of the tube, against homogeneous protein concentration, and present a CSI pulse sequence for the acquisition of STD NMR experiments at different positions along the sample tube. Compared to the conventional methodology in which the [ligand]/[protein] ratio is increased manually, we can perform STD NMR experiments at a greater number of ratios and construct binding epitopes in a fraction (∼20%) of the experimental time. Second, imaging STD NMR also allows us to screen for non-specific binders, by monitoring any variation of the binding epitope map at increasing [ligand]/[protein] ratios. Hence, the proposed method does carry the potential to speed up and smooth out the drug discovery process.

Assembly of NiFe-PBA nanoparticles on nanoflower-like NiFe-PBA@IF as enhanced oxygen evolution electrocatalyst at room temperature

Oxygen Evolution Reaction (OER) catalysts that overcome low energy barriers to improve the reaction efficiency of the OER are important for the development of future green energy sources. Herein, NiFe-PBA@IF layered nanoflowers were successfully prepared by etching iron foam (IF) using Prussian blue-like (PBA) material as a precursor. Notably, the fractured PBA nanosheets prepared by etching at room temperature had a suitable growth gradient and growth environment with the homogeneous nucleation environment, compared to the conventional method. In this environment, a layered NiFe-PBA structure can be formed on the surface of IF, enabling efficient green synthesis, reducing ecological and economic costs, and providing a clear source of catalytic activity. More importantly, NiFe-PBA@IF has a nanoparticle structure anchored on NiFe-PBA stacked nanoflowers, which can expand the surface roughness and electrochemical active area of the sample, so the OER performance in 1 M KOH is 253 mV@10 mA·cm−2. The green and direct synthesis of PBA electrocatalysts can provide new ideas for the efficient synthesis of other OER electrocatalysts at room temperature and will further provide an effective template for the industrial application of OER electrocatalysts.

Simultaneously enhancing strength and hydrogen embrittlement resistance of pure iron via gradient microstructure

Hydrogen embrittlement (HE) of gradient-structured pure iron was studied by slow strain rate tensile tests, microstructural analysis and time-of-flight secondary ion mass spectrometry. As pre-torsion angles increase from 0° to 1400°, yield strength of alloys monotonically increases, but the HE susceptibility first decreases and then increases, with optimal match of improved strength and HE-resistance for pre-torsioned sample at 400°. This correlates with gradient distributions of grain boundary and dislocation hydrogen traps. These results indicate that the construction of suitable gradient structure in alloys is a promising strategy to maximize the strength and HE-resistance synergy.

Intensity inhomogeneity image segmentation based on the gradient-based spaces and the prior constraint

Image segmentation is a fundamental task in computer vision and image processing. How to efficiently decrease the effect such as high noise, low resolution and intensity inhomogeneity is the key to improve the accuracy of segmentation. To this end, we propose a novel segmentation model by assuming the image to be the product of a piecewise-constant function and a smooth function and then the model can be proposed based on the suitable gradient spaces. To improve the robustness of the proposed model, we add a prior constraint for the smooth function and then analyse the existence of the solution based on the functional theory. Since the proposed model includes two nonsmooth terms, we use a heat kernel convolution to approximately replace the length regularization term and then the alternating direction method of multipliers can be employed to solve it. Numerical experiments on several testing images demonstrate that the effectiveness and the robustness of the proposed model compared to some state-of-the-art segmentation models.

Efficient methodology with potential uses of Fresnel diffractometry for real-time study of uniaxial nematic liquid crystal phase transitions

Due to the different features of their various phases and expanding physical understanding, liquid crystals (LCs) play a fundamental and crucial role in contemporary technology. Recently, they have also been utilised in adaptive optics, active switching, and next-generation displays for augmented and virtual reality. In order to determine relevant quantities for thermotropic uniaxial nematic liquid crystals (NLCs), our aim is to assess the applicability of a ground-breaking method. The method being discussed is based on Fresnel diffraction (FD) from phase objects, which has been employed over the past 20 years in several accurate and precise metrological applications. Using a phase step and quantitatively registering the visibility of the diffraction patterns, diffractometry can transform any change in the order of LCs brought on by a change in temperature into a change in the optical phase. Owing to its low sensitivity to environmental vibrations, inherent compactness, and ease of set up, diffractometry can be used much more effectively than interferometry. Additionally, as a special major feature, if the various phases of a LC have the required transparency, it is possible to record the number of phases in the bulk of the LC, the surface ordering, and the approximate temperature of the phase transitions in a single-shot imaging by applying a suitable temperature gradient. The numerical computations and practical data comparisons from our theoretical considerations demonstrate a very high level of agreement with the output from other currently used methodologies. As we shall see, by addressing some of the faults and inadequacies of existing techniques, this strategy has the potential to both complement and strengthen them.

Nanoparticles for co-delivery of paclitaxel and curcumin to overcome chemoresistance against breast cancer

As a prominent cause of morbidity and mortality in women, breast cancer continues to be challenging to treat due to the lack of effective drugs. Paclitaxel (PTX) is an effective chemotherapeutic agent for treating breast cancer patients. The effectiveness of PTX against breast cancer is nevertheless diminished by multidrug resistance (MDR). In addition to having potent reversal effects on the MDR brought by PTX in breast cancer, curcumin (CUR) has demonstrated therapeutic and/or adjuvant in treating patients with breast cancer. In this study, amphiphilic di-block copolymer poly(ethylene glycol)-block-poly (lactide-co-glycolide) (PEG-PLGA) was employed for encapsulating PTX and CUR into nanoparticles (PC-NPs) to boost anticancer activity against MDR. The nanoparticles exhibited potential advantages, including a spherical shape, small diameter (85.8 ± 0.21 nm), exceptionally high encapsulation efficiency (83.05 ± 1.35% for PTX and 85.84 ± 0.87% for CUR), and drug loading (38.70 ± 0.97% for PTX and 32.22 ± 0.53% for CUR), a smooth-surface morphology, suitable negative charge (−20.3 ± 1.3 mV), gradient release, and optimum stability. The proliferation of 4T1 and MDA-MB-231 cells implicated in the suppression of the NF-κB signaling pathway was slowed down by PC-NPs. CUR could inhibit the production of P-glycoprotein and reverse MDR in breast cancer cells. Most importantly, CUR and PTX, both in free and nanoparticulate forms, were found to be less toxic on RAW mononuclear macrophages in comparison to both 4T1 and MDA-MB-231 cells. Furthermore, compared to single-nanoparticle formulations, in vivo investigations have revealed that PC-NPs exhibited enhanced tumor suppression and therapeutic outcomes. These findings suggested that PTX and CUR nanoparticle co-delivery is a potentially suitable approach for effectively eradicating breast cancer.

Development of an HPLC Method for the Determination of Levothyroxine Applied to Four Different Preparations

HPLC is an important research tool that can identify, extract and measure the substance, its numerous components and drug-related additives that may occur during either the manufacture or storage of the medication. Understanding the chemistry of the drug ingredient is required for this, which makes it easier to create analytical methods. To find the most effective way to conduct the procedure, many chromatographic parameters were investigated and tested. It is essential to identify a suitable mobile phase, column, column temperature, wavelength, and gradient to achieve the desired suitability and durability of the medicine in addition to its degradants and contaminants. This study aims to develop simply and rapidly the HPLC method for the determination of levothyroxine and its different brands. Levothyroxine is the drug of choice for hypothyroidism. In this study, a high liquid chromatography method was developed for the quantification of different brands of levothyroxine. The chromatographic study was analyzed at an ambient temperature of 28°C with isocratic elution. The mobile phase of the chromatograph was water and methanol Me OH (45:55) (1:1V/V) or 0.01 M phosphate buffer, the solution with adjusted pH=3. The flow rate of the pump was set at 1.5ml/min, the volume of the solution was 20 ml injected into the HPLC column, and the wavelength at 225 nm. The accuracy (99.9% recovery), precision (99.9 to 100% recovery), linearity (³ 0.99), and retention time (16.8 min) were observed for all brands of levothyroxine. In this study, we have evaluated the HPLC method for the quantification of levothyroxine and its different brands. Levothyroxine is considered as a controversial drug throughout the globe. In the recent past, we have found no study that proved clinical and biological interchangeability between levothyroxine brands. Our study is its self-unique in its case. There is no such publication proving that generic drugs are equivalent.

Non-specular reflection of a narrow spatially phase-modulated Gaussian beam.

The lateral and angular Goos-Hänchen shifts undergone upon reflection on a dielectric plate by a spatially phase-modulated Gaussian beam are derived. It is shown that the amplitude and direction of both lateral and angular shifts are very sensitive to the degree of spatial phase modulation of the incident beam, so that such modulation thus provides a means to control those shifts. It is also shown that the modulation incurs some beam reshaping upon reflection. Analytical calculations of the lateral shift are found to be in good agreement with numerical simulations of beam propagation before and after reflection. In these simulations, the required spatial transverse phase modulation is achieved by focusing a microwave Gaussian beam onto the dielectric plate with a non-spherical lens or a flat-surfaced thin lamella exhibiting a suitable gradient of its refractive index. The optimal parameters governing the spatial phase modulation are discussed to achieve: (i) enhancement of the lateral shift of a spatially phase-modulated beam in comparison to that of a non-modulated beam and (ii) simultaneous large values of reflectivity and of the lateral shift, while keeping the reshaping of the reflected beam to a minimum.

Ion exchange chromatography hyphenated with fluorescence detector as a sensitive alternative to UV detector: Applications in biopharmaceutical analysis

Cation-exchange chromatography (CEX) is widely used for analysis of charge heterogeneity in monoclonal antibodies (mAbs) in the biopharmaceutical industry. Charge variant separation is typically achieved by either alteration of ionic strength or pH, and detection of the various species is performed using diode array detectors (DAD) at 280 nm. In this study, we investigate the suitability of fluorescence detector (FLD) as a sensitive alternative to traditional UV280 detection-based charge variant analysis. The objective of this work is to compare the performance of charge variants detection through cation exchange chromatography between FLD and DAD detectors. This was demonstrated for a mass spectroscopy compatible, pH based CEX method utilizing volatile ammonium acetate salt. The stability of FLD detection was tested as per method validation criteria set in the ICH Q2-(R1). LODFLD and LOQFLD were 59.07 and 59.64 times lower in comparison to LODUV and LOQUV, respectively (LODFLD: 0.13 µg, LOQFLD: 0.39 µg). The LinearityFLD was obtained in the range of 1–200 µg. Accuracy calculated as recovery value was between 93.38% and 103.35% and highest RSD value obtained for robustness was 2.54% (area under the curve). The application of FLD detection based CEX as a Process Analytical Technology (PAT) enabler in mAb biopharmaceutical analysis was demonstrated through direct charge variant profiling of CHO cell harvest supernatant (without pre purification through Pro-A). The method was also applied to and found suitable for biosimilarity assessment of drug products. While the present study is focused on analysis of trastuzumab biosimilars, the proposed method is expected to be applicable to any mAb product after suitable gradient modification.

Biofilm stratification in counter-diffused membrane biofilm bioreactors (MBfRs) for aerobic methane oxidation coupled to aerobic/anoxic denitrification: Effect of oxygen pressure

Aerobic methane oxidation coupled with denitrification (AME-D) executed in membrane biofilm bioreactors (MBfRs) provides a high promise for simultaneously mitigating methane (CH4) emissions and removing nitrate in wastewater. However, systematically experimental investigation on how oxygen partial pressure affects the development and characteristics of counter-diffusional biofilm, as well as its spatial stratification profiles, and the cooperative interaction of the biofilm microbes, is still absent. In this study, we combined Optical Coherence Tomography (OCT) with Confocal Laser Scanning Microscopy (CLSM) to in-situ characterize the development of counter-diffusion biofilm in the MBfR for the first time. It was revealed that oxygen partial pressure onto the MBfR was capable of manipulating biofilm thickness and spatial stratification, and then managing the distribution of functional microbes. With the optimized oxygen partial pressure of 5.5 psig (25% oxygen content), the manipulated counter-diffusional biofilm in the AME-D process obtained the highest denitrification efficiency, due mainly to that this biofilm had the proper dynamic balance between the aerobic-layer and anoxic-layer where suitable O2 gradient and sufficient aerobic methanotrophs were achieved in aerobic-layer to favor methane oxidation, and complete O2 depletion and accessible organic sources were kept to avoid constraining denitrification activity in anoxic-layer. By using metagenome analysis and Fluorescence in situ hybridization (FISH) staining, the spatial distribution of the functional microbes within counter-diffused biofilm was successfully evidenced, and Rhodocyclaceae, one typical aerobic denitrifier, was found to survive and gradually enriched in the aerobic layer and played a key role in denitrification aerobically. This in-situ biofilm visualization and characterization evidenced directly for the first time the cooperative path of denitrification for AME-D in the counter-diffused biofilm, which involved aerobic methanotrophs, heterotrophic aerobic denitrifiers, and heterotrophic anoxic denitrifiers.

Reward shaping in multiagent reinforcement learning for self-organizing systems in assembly tasks

Self-organizing systems feature flexibility and robustness for tasks that may endure changes over time. Various methods, e.g., applying task-field and social-field, have been proposed to capture the complexity of task environments so that agents can remain simple. To expand to complex task domains, the multiagent reinforcement learning (MARL) approach has been taken to train agent teams to be more capable and intelligent, permitting reduced complexity in task descriptions. MARL depends on the design of reward functions, which has been a challenging endeavour thus far. This paper investigates the impact of reward shaping in the context of an “L-shape” assembly task that involves collision avoidance. After introducing a general form of reward shaping function, various types of reward shaping fields are studied empirically with agent teams of different sizes. The experiment results have shown that reward shaping can be highly effective, and the singularities, the proper forms of the fields, and the suitable shaping field gradients are essential for successful agent team training. Furthermore, the effect of reward shaping functions depends highly on the size of agent teams.

Optimizing fish-friendly flow pattern in vertical slot fishway based on fish swimming capability validation

Vertical slot fishways are increasingly common structures for the passage of a wide variety of migratory fish species, which account for 59.2% of all fish passage facilities in China. The slot structures and redirected flow in the pools are of great importance to guide the fish to swim through the fishway. To optimize the design of vertical slot fishways, physical experiments and numerical simulations were used to study the hydraulic characteristics for 10 different geometric configurations (referred to as designs D1-D10), combining with the study of fish behavior in the model. A comparative study on vertical slot fishway with L-shaped baffle (D1) and with a new vertical baffle (D2) was conducted. Flow patterns, velocity fields and other key hydraulic parameters including the maximum velocities and turbulence kinetic energy in the pools were analyzed. No obvious differences in all key hydraulic between designs D1 and D2 present in the study, which suggests an upgrade of the L-shaped baffle to the new vertical baffle with the advantage of being more compact and economical. When modifying design D2 in the baffle thickness and length (D3-D10), three typical flow patterns with the different area ratios of left recirculation region to right recirculation region (Scl/Scr) were observed in the pools, which were denoted as flow pattern 1 (FP1), flow pattern 2 (FP2) and flow pattern 3 (FP3). An analysis of the behavior of grass carp (Ctenopharyngodon Idella) in the scaled model clearly showed that the flow and structure in FP2, with the principal flow in the center position and suitable velocity gradient and recirculation area ratio, were more friendly to fish with better migrating efficiency, which present sufficient velocity gradient and area of cushion zone for migratory fish to pass with less energy consumption.

The synthesis of thermostable, strongly basic Anion-Exchange resins using Cross-Linked biguanide and its application in the extraction of Sodium copper chlorophyllin

Commercially available, strongly basic anion-exchange resins with quaternary ammonium groups have been widely used in the purification of natural plant extracts. However, under the condition of high temperature (greater than 60 °C), these resins could not be used for long periods because of the Hofmann degradation of the strongly basic groups. In this work, the synthesis of novel, thermally stable, strongly basic resins, which has a cross-link biguanide structure, was reported. The mechanism of thermal degradation was investigated, and the result indicated that not only the stability of the functional group but also the link mode between the functional group and the resin matrix should influence the thermal stability of the resin. In our experiment, the PDG2 resin was selected to separate sodium copper chlorophyllin (SCC), a type of edible pigment derived from plants, due to its optimal thermal stability and adsorption capacity. The adsorption mechanism and thermodynamics of PDG2 were also investigated. The results demonstrated that the main adsorption affinity of PDG2 toward SCC was due to the synergistic effects of the hydrophobic and ionic interactions, and the rise in temperature will benefit the adsorption equilibrium, which differed from the equilibrium for lutein. Therefore, under suitable gradient desorption conditions, a high-purity SCC extract was prepared. After eight cycles, the adsorption capacity of the PDG2 remained constant and reproducible at a high temperature (70 °C).

Equilibrium validation for triblock copolymers via inverse norm bounds for fourth-order elliptic operators

Block copolymers play an important role in materials sciences and have found widespread use in many applications. From a mathematical perspective, they are governed by a nonlinear fourth-order partial differential equation which is a suitable gradient of the Ohta–Kawasaki energy. While the equilibrium states associated with this equation are of central importance for the description of the dynamics of block copolymers, their mathematical study remains challenging. In the current paper, we develop computer-assisted proof methods which can be used to study equilibrium solutions in block copolymers consisting of more than two monomer chains, with a focus on triblock copolymers. This is achieved by establishing a computer-assisted proof technique for bounding the norm of the inverses of certain fourth-order elliptic operators, in combination with an application of a constructive version of the implicit function theorem. While these results are only applied to the triblock copolymer case, the obtained norm estimates can also be directly used in other contexts such as the rigorous verification of bifurcation points, or pseudo-arclength continuation in fourth-order parabolic problems.

Hydrogen spillover effect enhanced by carbon quantum dots activated MoS2

The weak hydrogen adsorption and slow catalytic kinetics are unfavorable for MoS2 as a catalyst for hydrogen evolution reaction (HER) in alkaline solution. Herein, carbon quantum dots (CQDs) with high proton adsorption energy were expected to enhance the proton adsorption of MoS2 during the HER process. The CQDs activated MoS2 can establish a suitable hydrogen adsorption gradient due to the surface charge redistribution to promote the hydrogen spillover pathway. After the CQDs were loaded on MoS2, the charge distribution would gradually transfer from the C sites of CQDs to the S sites on MoS2 surface, showing a charge gradient distribution calculated by density functional theory predictions. The adsorbed hydrogen can spill over from hydrogen-enriched CQDs to hydrogen-deficient MoS2 in HER. The process could be monitored by the quasi in-situ electrochemical impedance spectroscopy. The enhanced hydrogen spillover effect by CQDs activated MoS2 can pave the way for the design and preparation of efficient and low-cost catalysts.