Substituent Effects Impact Surface Charge and Aggregation of Thiophenol-Labeled Gold Nanoparticles for SERS Biosensors

SERS immunoassay biosensors hold immense potential for clinical diagnostics due to their high sensitivity and growing interest in multi-marker panels. However, their development has been hindered by difficulties in designing compatible extrinsic Raman labels. Prior studies have largely focused on spectroscopic characteristics in selecting Raman reporter molecules (RRMs) for multiplexing since the presence of well-differentiated spectra is essential for simultaneous detection. However, these candidates often induce aggregation of the gold nanoparticles used as SERS nanotags despite their similarity to other effective RRMs. Thus, an improved understanding of factors affecting the aggregation of RRM-coated gold nanoparticles is needed. Substituent electronic effects on particle stability were investigated using various para-substituted thiophenols. The inductive and resonant effects of functional group modifications were strongly correlated with nanoparticle surface charge and hence their stability. Treatment with thiophenols diminished the negative surface charge of citrate-stabilized gold nanoparticles, but electron-withdrawing substituents limited the magnitude of this diminishment. It is proposed that this phenomenon arises by affecting the interplay of competing sulfur binding modes. This has wide-reaching implications for the design of biosensors using thiol-modified gold surfaces. A proof-of-concept multiplexed SERS biosensor was designed according to these findings using the two thiophenol compounds with the most electron-withdrawing substitutions: NO2 and CN.

Assessment of radiative heating errors in Tropical Atmosphere Ocean array marine air temperature measurements

We assess the radiative heating error affecting marine air temperature (MAT) measurements in the Tropical Atmosphere Ocean array. The error in historical observations is found to be ubiquitous across the array, spatially variable and approximately stationary in time. The error induces spurious warming during daytime hours, but does not affect night-time temperatures. The range encompassing the real, unknown daily- and monthly-mean values is determined using daytime and night-time mean temperatures as upper and lower limits. The uncertainty in MAT is less than or equal to 0.5 °C and 0.2 °C for 95% of daily and monthly estimates, respectively. Uncertainties impact surface turbulent heat flux estimates, with potentially significant influences on the quantification of coupled ocean-atmosphere processes.

Experimental Study and Numerical Analysis on Impact Resistance of Civil Air Defense Engineering Shear Wall

In order to study the impact resistance of civil air defense engineering shear wall, the impact resistance of civil air defense engineering shear wall was studied by combining finite element numerical simulation with pendulum impact test. The effects of impact height, pendulum mass, and impact times on the impact resistance of civil air defense engineering shear walls were analyzed. It was shown that when the impact height increased from 0.4 m to 2.5 m, the failure mode of civil air defense engineering shear wall tended to be local impact failure, and the horizontal displacement in the middle of the wall span increased. The concrete crushing occurred in the impact area of the back of the civil air defense engineering shear wall. The increase in the impact height is a negative factor for the impact resistance of the civil air defense engineering shear wall. With the increase of pendulum weight, the number of concrete horizontal cracks in the back of the civil air defense engineering shear wall increased, while the number of vertical cracks decreased, but the impact surface was destroyed. Through multiple impact tests on the civil air defense engineering shear wall, the civil air defense engineering shear wall had accumulated damage. The longitudinally loaded steel on the back reached the ultimate strength, and there are large cracks at the bottom and even collapses. The increase of impact times has a great influence on the impact resistance of the civil air defense engineering shear wall. Through the analysis of the factors affecting the impact resistance of civil air defense engineering shear wall, it provides guidance for civil air defense engineering shear wall to resist impact load.

Effect of coherent structures on convective heat transfer in a swirling impinging jet

The present paper reports on the detailed investigation of the flow dynamics and unsteady heat transfer in an impinging jet in regimes with high swirl and vortex breakdown. A combination of the time-resolved stereoscopic PIV, time-resolved PLIF and high-speed IR-thermometry methods is used. Two cases of distances between the jet nozzle and impingement surface are considered, H = d and H = 2d. The Reynolds number is fixed as Re = 5000. The temperature distribution in the flow has a maximum on the jet axis near the surface in the region of the central recirculation zone. The data are processed using the POD method to extract coherent flow structures and quantify temperature fluctuations on the impact surface. The helical vortex structure in the case of H = d influences heat transfer between the swirling jet and the surface, the temperature fluctuations on the surface reach 0.05 degrees.

Projecting land use changes and its consequences for hydrological response in the New Capital City of Indonesia

The Indonesian government intends to build a New Capital City in East Kalimantan Province, with a total development area of 56.000 ha located in existing forest and palm oil plantations. This study will look at the fast changes in land use throughout the urbanization process from 2020 to 2045. They will impact surface runoff and increase flood risk in the future. However, this study primarily focuses on modelling to simulate and predict land use changes in the landscape of the primary river basin in the New Capital City. Land use maps for the years 2013 to 2020 were generated using image classification from Landsat images. The CLUE-S semi-empirical model was used for simulations. The modelling effort included a land use/cover change with three scenarios. The simulation revealed that mainland use/cover types will rapidly increase from 2020 to 2045, particularly in converting forest, fishpond, and plantation areas into urban areas and open fields. According to the New Capital scenario model, the built-up area would continue to expand dramatically with a 742.46 % change. In a future study, a surface runoff will be estimated using the HEC-HMS and SCS-CN models.

Effect of tempering temperature on impact energy of AISI 410 martensitic stainless steel at low temperatures

AISI 410 martensitic stainless-steel specimens were austenitized at 1253 K then oil quenched and tempered at 573, 673, 773 and 923 K for 3600 s. The impact energy of the specimens was tested at 298, 253, 223, 213 K and measured using ASTM E23 standard. After austenitizing and tempering, the microstructure of the specimens showed carbide precipitation. Tempering at 773 K resulted in the highest hardness due to secondary hardening, while tempering at 923 K resulted in the lowest hardness due to brittle carbide precipitation at the grain boundary which caused softening of the matrix by decreasing the solute carbon content. By contrast, the change in impact energy is inversely proportional to the hardness values. The impact surface of specimens tempered at 573, 673 and 773 K revealed transgranular fracture; on the other hand, the impact surface of the specimen tempered at 923 K revealed intergranular fracture. From our experimental results, the appropriate hardening and tempering procedure of AISI 410 for low temperatures applications is selectable.

Stochastic Response of a Vibro-Impact System via a New Impact-to-Impact Mapping

In this paper, a new impact-to-impact mapping is constructed to investigate the stochastic response of a nonautonomous vibro-impact system. The significant feature lies in the choice of Poincaré section, which consists of impact surface and codimensional time. Firstly, we construct a new impact-to-impact mapping to calculate the one-step transition probability matrix from a given impact to the next. Then, according to the matrix, we can investigate the stochastic responses of a nonautonomous vibro-impact system at the impact instants. The new impact-to-impact mapping is smooth and it effectively overcomes the nondifferentiability caused by the impact. A linear and a nonlinear nonautonomous vibro-impact systems are analyzed to verify the effectiveness of the strategy. The stochastic P-bifurcations induced by the noise intensity and system parameters are studied at the impact instants. Compared with Monte Carlo simulations, the new impact-to-impact strategy is accurate for nonautonomous vibro-impact systems with arbitrary restitution coefficients.

Evaluating the Homogeneity of Surface Features Induced by Impact-Based Surface Treatments

Impact surface treatments are well-known for their efficiency in enhancing the mechanical properties of metallic materials, especially under cyclic loadings. These processes, which encompass a wide range of surface treatments based on repetitive impacts of tools of various types, induce surface plastic deformation, compressive residual stresses, and grain refinement alter the surface roughness as a side effect. Thus, it is essential to have suitable indexes to quantify the surface features caused by the typically random nature of these treatments. Herein, we evaluated the rationality of using standard roughness parameters for describing the morphological characteristics of surfaces treated by shot peening as a representative and widely used treatment of the category. A detailed numerical model of the peening process was developed. The output data were elaborated to extract the surface roughness parameters following the standard procedures. The results revealed the validity of the surface roughness parameters to describe the topography of material treated with adequate surface coverage, also highlighting the necessity to use a set of parameters rather than the common practice of relying on single parameters. Not considering a comprehensive set of amplitude and spacing parameters can result in significant, inconsistent, and misleading results while comparing the performance of surfaces.

Improving the Properties of Laser-Welded Al–Zn–Mg–Cu Alloy Joints by Aging and Double-Sided Ultrasonic Impact Compound Treatment

To improve the loose structure and serious porosity of (Al–Zn–Mg–Cu) 7075 aluminum alloy laser-welded joints, aging treatment, double-sided ultrasonic impact treatment (DSUIT), and a combination of aging and DSUIT (A–DSUIT) were used to treat joints. In this experiment, the mechanism of A–DSUIT on the microstructure and properties of welded joints was analyzed. The microstructure of the welded joints was observed using optical microscopy, scanning electron microscopy, and electron backscatter diffraction (EBSD). The hardness and tensile properties of the welded components under the different processes were examined via Vickers hardness test and a universal tensile testing machine. The results showed that, after the aging treatment, the dendritic structure of the welded joints transformed into an equiaxed crystal structure. Moreover, the residual tensile stress generated in the welding process was weakened, and the hardness and tensile strength were significantly improved. After DSUIT, a plastic deformation layer of a certain thickness was generated from the surface downward, and the residual compressive stress was introduced to a certain depth of the joint. However, the weld zone unaffected by DSUIT still exhibited residual tensile stress. The inner microhardness of the joint surface improved; the impact surface hardness was the largest and gradually decreased inward to the weld zone base metal hardness, with a small improvement in the tensile strength. Compared with the single treatment process, the microstructural and mechanical properties of the welded joint after A–DSUIT were comprehensively improved. The microhardness and tensile strength of the welded joint reached 200 HV and 615 MPa, respectively, for an increase of 45.8% and 61.8%, respectively. Observation of the fractures of the tensile specimens under the different treatment processes showed that the fractures before the aging treatment were mainly ductile fractures while those after were mainly brittle fractures. After DSUIT of the welded joints, a clear and dense plastic deformation layer was observed in the fracture of the tensile specimens and effectively improved the tensile properties of the welded joints. Under the EBSD characterization, the larger the residual compressive stress near the ultrasonic impact surface, the smaller the grain diameter and misorientation angle, and the lower the texture strength. Finally, after A–DSUIT, the hardness and tensile properties improved the most.