Search Results (368)

Flame impingement heat transfer is implemented in many industrial applications. The laminar premixed Bunsen flame, impinging on a flat cold surface, represents a basic model for the validation of computational fluid dynamics (CFD) codes, used for the simulation of industrial processes. Meanwhile, as the present paper demonstrates, some features of basic flame configurations are not well-reviewed. The present paper reports on the direct numerical simulation of the thermofluidic field in a laminar premixed impinging Bunsen flame in comparison with advanced optical measurements. The results reveal the phenomenon of the central recirculation zone formation between the tip of the Bunsen flame cone and the cold surface. Cooled combustion products concentrate inside this zone, resulting in reduced heat transfer near the flow axis. All three tested chemical kinetic mechanisms (GRI-Mech 3.0, SanDiego, RMech1) provide reasonable predictions of the observed phenomenon, which explain previous experimental observations on the reduced heat transfer at the central axis of impinging flames. Moreover, the most detailed mechanism, GRI-Mech 3.0, predicts an elevated concentration of NO_X pollutants caused by the mentioned phenomenon. Full article

Theta Pinch is one of the promising methods for the generation of hot and dense plasma. In this paper, we describe the results of experimental research on a small-scale Theta Pinch created with Helium or Hydrogen plasmas. Different plasma diagnostics, namely, optical, microwave cut-off, laser interferometry, visible spectroscopy, Thomson scattering, and Laser-Induced Fluorescence were used to characterize the time- and space-resolved evolution of the plasma parameters, and the specific features of these diagnostic results obtained are discussed. The measured plasma density and the electron and ion temperature evolution, obtained by these various diagnostic tools, agree to a satisfactory level. These methods will be applied for studies of the parameters of the plasma in the device that is being developed by the nT-Tao company towards fusion energy. Full article

Background: A phthalimide-functionalized heptamethine cyanine dye, named Ph790H, is used for targeted photothermal cancer therapy in vivo. We highlight that the chemical structure of Ph790H is newly designed and synthesized for the first time in this study. Objectives: By possessing a rigid chloro-cyclohexenyl ring in the heptamethine cyanine backbone, the bifunctional near-infrared (NIR) fluorescent dye Ph790H can be preferentially accumulated in tumor without the need for additional targeting ligands, which is defined as the “structure-inherent tumor targeting” concept. Methods: The phototherapeutic effect of Ph790H is evaluated in HT-29 human colorectal cancer xenografts to be used as a cancer-targeting photothermal agent. Results: The results reveal that the Ph790H shows enhanced tumor accumulation in HT-29 xenografts 48 h post-injection with a high tumor-to-background ratio. After determination of the optimal timing for photothermal therapy (PTT), the HT-29 tumor-possessing nude mice pretreated with Ph790H are subsequently irradiated with an 808 nm NIR laser for 5 min. The tumor-targeted PTT treatment can efficiently inhibit the tumor development compared with that of control groups. Moreover, no tumor regrowth or Ph790H-induced mortality occurs after the treatment of Ph790H and laser irradiation during a period of monitoring. Conclusions: Therefore, this work demonstrates that the bifunctional phototheranostic agent Ph790H can be utilized for targeted cancer imaging and fluorescence-guided phototherapy simultaneously. Full article

During the underwater movement of a submarine, cooling water at a specific temperature is discharged into the surrounding water through nuclear reactor secondary loop circulation, creating a thermal jet. Thermal jets are characterized by initial velocity and temperature properties that allow for complete mixing with the surrounding water through a combination of mixing and heat transfer processes. This paper aims to investigate the movement and diffusion of underwater thermal jets, specifically examining the temperature stratification of the ambient water, the initial velocity of the jet, and the effect of temperature on the velocity field and temperature field of the underwater thermal jet. This study utilizes particle velocity measurements and the laser-induced fluorescence method to measure the velocity field and temperature field of the thermal jet, as well as simulation methods to validate conclusions. The experimental and simulation conditions in this paper are mainly categorized into two types: uniform water body and thermally-stratified water body. Upon analysis and comparison of the experimental and simulation results, it has been observed that an increase in jet velocity will hinder the upward diffusion of jet temperature, decrease the floating height of the jet, and slow down the rate at which the jet temperature decays. Furthermore, as the difference between the jet temperature and the ambient water temperature increases, the upward diffusion of the jet temperature becomes predominant, resulting in a 40–50% increase in its floating rate. It is evident that the stratification conditions of the background environment have a significant impact on the jet temperature diffusion. When the jet temperature diffuses to the thermally-stratified interface of water in the tank, it ceases to float due to density differences; consequently, its temperature cannot diffuse further towards or reach the water surface. Full article

Various types of dielectrophoresis (DEP) cell separation devices using AC electric fields have been proposed and developed. However, its capability is still limited by a lack of quantitative characterization of the relationship between frequency and force. In the present study, this limitation was addressed by developing a method capable of fast and accurate quantification of the dielectric properties of biological cells. A newly designed Creek-gap electrode device can induce constant DEP forces on cells, realizing the isomotive movement of cells suitable for DEP analysis. The real number part of the Clausius–Mossotti (CM) factor of cells, $\mathrm{R}\mathrm{e}\left(\beta \right)$, was obtained by simple cell velocimetry together with the numerical three-dimensional (3D) electric field analysis. Human mammary cells, MCF10A, and its cancer cells, MCF7 and MDAMB231, were used as model cells to evaluate the capability of the proposed device. The estimation of $\mathrm{R}\mathrm{e}\left(\beta \right)$ using the Creek-gap electrode device showed good agreement with previously reported values. Furthermore, the thermal behavior of the Creek-gap electrode device, which is crucial to cell viability, was investigated by adopting micro laser-induced fluorescence (LIF) thermometry using Rhodamine B. The temperature rise in the device was found to be approximately several degrees Celsius at most. The results demonstrate that the proposed method could be a powerful tool for fast and accurate noninvasive measurement of the DEP spectrum and the determination of the dielectric properties of biological cells. Full article

Background/Objectives: The objective of this study was to assess the role of a secreted serine protease, kallikrein-related peptidase 6 (KLK6), during colorectal tumorigenesis driven by a mutant Adenomatous polyposis coli (APC) tumor suppressor gene. A first analysis of KLK6 expression in the intestinal tract of Apc-mutant multiple intestinal neoplasia (Apc^Min/+) mice revealed up to four-fold induction of Klk6 mRNA levels in adenomas relative to its level in the adjacent mucosa. Methods and Results: The presence of KLK6 protein in the adenomatous areas was confirmed by immunohistochemistry and optical coherence tomography/laser-induced fluorescence (OCT/LIF) imaging. To assess the contribution of the KLK6 expression on the Apc-mutant intestinal and colon tumorigenesis, we engineered a mouse with floxed alleles of the Klk6 gene (Klk6^lox/lox) and crossed it with a mouse expressing the truncated APC protein under control of the intestinal tract-specific human CDX2P9.5-NLS Cre transgene (CPC;Apc^fl/fl;Klk6^+/+). We found that CPC;Apc^fl/fl mice with disrupted Klk6 gene expression (CPC;Apc^fl/fl;Klk6^fl/fl) had a significantly smaller average size of the small intestinal and colon crypts (p < 0.001 and p = 0.04, respectively) and developed a significantly fewer adenomas (p = 0.01). Moreover, a decrease in high-grade adenomas (p = 0.03) and adenomas with a diameter above 2 mm (p < 0.0001) was noted in CPC;Apc^fl/fl;Klk6^fl/fl mice. Further molecular analysis showed that Klk6 gene inactivation in the small intestine and colon tissues of CPC;Apc^fl/fl;Klk6^fl/fl mice resulted in a significant suppression of transforming growth factor β2 (TGF-β2) protein (p ≤ 0.02) and mitogen-activated protein kinase (MAPK) phosphorylation (p ≤ 0.01). Conclusions: These findings demonstrate the oncogenic role of KLK6 in the mutant Apc-mediated intestinal tumorigenesis and suggest the utility of KLK6 for early diagnosis of colorectal tumors. Full article

This paper presents the results of an experimental study of the possibility of remote visualization of traces of some nitro-group-containing explosives (TNT, RDX, HMX, Composition-B, and Tetryl) on the surface of aluminum foil using the laser fragmentation/laser-induced fluorescence (LF/LIF) method. A tunable excimer KrF laser with a narrow generation line was used to fragment explosives and excite fluorescence of their NO fragments (nitric oxide molecules) from the second vibrationally excited state (v″ = 2). When recording optical responses, spectral selection of the γ(0, 0) fluorescence band of NO was carried out. The LF/LIF method is shown to be promising for creating scanning detectors that will allow remote detection of trace amounts of explosives with a concentration of up to 1 μg/cm² on the surfaces of objects at a distance of several meters and simultaneously determine their location. The sensitivity of the one-color LF/LIF detection method can be increased by increasing the energy density of the probing radiation and/or by optimizing the LF/LIF excitation process. Full article

Despite the remarkable progress in the modification and application of polyvinyl chloride (PVC), developing processing aids for the induced crystallization of PVC and characterizing its interfacial layer remain challenges. Herein, we propose a new polymeric nucleating agent, polyamidea12-graft-styrene–maleic anhydride copolymer (PA12-g-SMA), which possesses high compatibility and crystallinity, effectively improving the crystallinity to 15.1%, the impact strength to 61.03 kJ/m², and the degradation temperature of PVC to 267 °C through a single and straightforward processing step. Additionally, after the introduction of two different fluorescent sensors in PA12-g-SMA and PVC, the interfacial layer of the induced crystallization can be monitored in situ via a confocal laser scanning microscope (CLSM). This study highlights a rare strategy for significantly enhancing the physical properties of rigid PVC through simply adding a polymeric nucleating agent during processing, while also emphasizing the importance of visualizing the interfacial layer to understand various polymer crystallization processes. Full article

In this paper, we present the results of an experimental study on the characterization of holmium-doped silica fiber. A standard acousto-optic modulator controls the output power of the ytterbium-doped fiber laser operating at 1134.5 nm and serving as a pump source of the holmium-doped fiber under test. This technique allows us to measure the lifetimes of ⁵I₇ and ⁵I₈ energy levels of Ho³⁺ ions. The effects of the fiber length and the concentration-dependent pair-induced quenching on the accuracy of the fluorescence lifetime measurement are considered. The results of this study are compared with those obtained using the exponential and Förster decay functions used for such types of measurements. It is demonstrated that the knowledge of two fiber parameters, the pump saturation power and the fluorescence saturation power, together with the fiber absorption spectrum, permits one to obtain the absorption cross-sections at the pump and other key wavelengths, the effective concentration of the active ions, and the quantum efficiency of the fluorescence from the laser level. The results of this study are applicable to the reliable characterization of any type of heavily doped gain fibers and to the further numerical modeling and optimization of fiber lasers. Full article

The fluorescence intensity of fluorescent dyes typically employed in the dual-emission laser-induced fluorescence (DELIF) method gradually degrades as the excitation time increases, and the degradation rate depends on the type of fluorescent dye used. Therefore, the DELIF method is unsuitable for long-term temperature measurements. In this study, we focused on the fluorescence intensity ratio of a single fluorescent dye at two fluorescence wavelengths and developed a DELIF method for long-term temperature measurements based on this ratio. The fluorescence intensity characteristics of Fluorescein disodium and Rhodamine B, which are typically used in the DELIF method, in the temperature range of 10–60 °C were comprehensively investigated using two high-speed monochrome complementary metal-oxide semiconductor cameras and narrow bandpass filters. Interestingly, the ratio of the fluorescence intensity of each fluorescent dye at the peak emission wavelength of the fluorescence spectrum, λ, to the fluorescence intensity at wavelengths very close to the peak wavelength (λ ± 10 nm) was highly sensitive to temperature variations but not excitation time. Particularly, when Rhodamine B was used, the selection of the fluorescence intensity ratios at a wavelength combination of 589 and 600 nm enabled highly accurate temperature measurements with a temperature resolution of ≤0.042 °C. Moreover, the fluorescence intensity ratio varied negligibly throughout the excitation time of 180 min, with a measurement uncertainty (95% confidence interval) of 0.045 °C at 20 °C. The results demonstrate that the proposed DELIF method enables highly accurate long-term temperature measurements. Full article

Peanut seeds are harvested at different development stages (early and late) due to their uneven maturation. At the time of harvest, approximately 30% of the seeds are still immature, meaning they are not completely filled with compounds (e.g., oil and minerals) and exhibit reduced vigor. Hypothetically, these compounds can be detected as a “chemical fingerprinting” to classify seed maturation stages. Here, we investigated whether non-destructive techniques such as benchtop nuclear magnetic resonance (NMR), laser-induced breakdown spectroscopy (LIBS), and energy-dispersive X-ray fluorescence (ED-XRF) can identify chemical patterns unique to mature seeds with superior vigor. Field-grown seeds were classified into early (R5 and R6) and late (R7, R8, and R9) stages. Seed weight, germination, vigor, H₂O₂, and MDA (oxidative stress) were analyzed. Oil, potassium (K), and calcium (Ca) were measured digitally using spectroscopy techniques. We found that: (i) oxidative stress and K levels were higher in seeds from the early stages; (ii) seed oil and Ca were proportional to high-vigor seedlings and successful plant establishment in the field; and (iii) the seed chemical composition could be identified autonomously with 87% to 100% accuracy. In conclusion, LIBS, ED-XRF, and NMR technologies can effectively screen peanut seeds with superior vigor through “chemical fingerprinting”. Full article

Protein aggregation is associated with various diseases caused by protein misfolding. Among them, amylin deposition is a prominent feature of type 2 diabetes. At present, the mechanism of amylin aggregation remains unclear, and this has hindered the treatment of type 2 diabetes. In this study, we analyzed the aggregation process of amylin using the quantum dot (QD) imaging method. QD fluorescence imaging revealed that in the presence of 100 μM amylin, aggregates appeared after 12 h of incubation, while a large number of aggregates formed after 24 h of incubation, with a standard deviation (SD) value of 5.435. In contrast, 50 μM amylin did not induce the formation of aggregates after 12 h of incubation, although a large number of aggregates were observed after 24 h of incubation, with an SD value of 2.883. Confocal laser microscopy observations revealed that these aggregates were deposited in three dimensions. Transmission electron microscopy revealed that amylin existed as misfolded fibrils in vitro and that QDs were uniformly bound to the amylin fibrils. In addition, using a microliter-scale high-throughput screening (MSHTS) system, we found that rosmarinic acid, a polyphenol, inhibited amylin aggregation at a half-maximal effective concentration of 852.8 μM. These results demonstrate that the MSHTS system is a powerful tool for evaluating the inhibitory activity of amylin aggregation. Our findings will contribute to the understanding of the pathogenesis of amylin-related diseases and the discovery of compounds that may be useful in the treatment and prevention of these diseases. Full article

Blowoff limits are essential in establishing the combustor operating envelope. Hence, there is a great demand for practical aero-engines to extend the blowoff limits further. In this work, the behavior of non-premixed swirling flames under fuel flow rate oscillations was investigated experimentally close to its blowoff limits. The methane flame was stabilized on the axisymmetric bluff body and confined in a square quartz enclosure. External acoustic forcing at 400 Hz was applied to the fuel flow to induce a fuel mass flow rate fluctuation (FMFRF) with varying amplitudes. A high-speed burst-mode laser and cameras ran at 20 kHz for OH*-chemiluminescence (CL), CH₂O-, and SO₂-PLIF measurements, offering the visualization of the two-dimensional flame structure and heat release distribution, temporally and spatially. The results show that the effect of FMFRF is predominantly along the central axis without altering the time-averaged flame structure and blowoff transient. However, the blowoff limits are extended due to the enhanced temperature and longer residence time induced by FMFRF. This work allows us to explore the mechanism of flame instability further. Full article

In this study, we designed three promising platforms based on metal–organic frameworks (MOFs) to develop paper-based analytical devices (PADs) for biosensing applications. PADs have become increasingly popular in field sensing in recent years due to their portability, low cost, simplicity, efficiency, fast detection capability, excellent sensitivity, and selectivity. In addition, MOFs are excellent choices for developing highly sensitive and selective sensors due their versatility for functionalizing, structural stability, and capability to adsorb and desorb specific molecules by reversible interactions. These materials also offer the possibility to modify their structure and properties, making them highly versatile and adaptable to different environments and sensing needs. In this research, we synthesized and characterized three different amino-functionalized MOFs: UiO-66-NH₂ (Zr), MIL-125-NH₂ (Ti), and MIL-101-NH₂ (Fe). These MOFs were used to fabricate PADs capable of sensitive and portable monitoring of alkaline phosphatase (ALP) enzyme activity by laser-induced fluorescence (LIF). Overall, amino-derivated MOF platforms demonstrate significant potential for integration into biosensor PADs, offering key properties that enhance their performance and applicability in analytical chemistry and diagnostics. Full article

Rare earth elements (REEs) hold significant industrial, scientific, and modern technological worth. This study focused on detecting and quantifying REEs in various geological ore samples. These samples were collected from different REE-bearing locations recommended by geological experts. The analysis was conducted using laser-induced breakdown spectroscopy (LIBS) and laser ablation time-of-flight mass spectrometry (LA-TOF-MS). In this work, LIBS methodology was employed using three different configurations: standard LIBS, LIBS with an applied magnetic field, and LIBS with both an applied magnetic field and target sample heating within an optimal temperature range. Elements from the REE group, specifically lanthanum (La), cerium (Ce), and neodymium (Nd), were identified and quantified. To detect, quantify, and validate the results from LIBS and LA-TOF-MS, we utilized an array of analytical techniques—Energy-Dispersive X-ray Spectroscopy (EDX), Energy-Dispersive X-ray Fluorescence Spectrometer (ED-XRF), and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Interestingly, the quantitative results for REEs (La, Ce, and Nd) in the ore samples obtained using the LIBS technique with various configurations were found to be in agreement with those from LA-TOF-MS, EDX, XRF, and ICP-OES. In addition, LIBS enables detailed microchemical imaging, allowing the map of the spatial distribution of elements within the mineral–ore matrix. The high-resolution microscale elemental mapping of REEs was accomplished using the emission lines Ce (II) at 446.0 nm, La (II) at 492.1 nm, and Nd (II) at 388.8 nm. By integrating multiple analytical techniques, our study enabled the construction of a complete elemental distribution map, providing new insights into the geochemical processes and mineral composition of rare earth ores, while advancing geochemistry and contributing valuable data for rare earth resource exploration. Full article