Search Results (42)

The Atacama Desert is emerging as an unexpected source of microbial life and, thus, a source of bioactive compounds and novel enzymes. Baeyer–Villiger monooxygenases (BVMOs), a subclass of flavin-dependent monooxygenases (FPMOs), have gained attention as promising biocatalysts for the biosynthesis of industrially relevant molecules for a wide range of applications, such as pharmaceuticals and polymers, among others. BVMOs catalyze the oxidation of ketones and cyclic ketones to esters and lactones, respectively, by using molecular oxygen and NAD(P)H. BVMOs may also catalyze heteroatoms oxidation including sulfoxidations and N-oxidations. This work aims to search for novel BVMOs in the genomes of new bacterial strains isolated from the Atacama Desert. Bioinformatic analysis led to the identification of 10 putative BVMOs, where the monooxygenase named MO-G35A was selected. Genome context showed, downstream of the MO-G35A, a gene encoding for an enzyme from the short-chain dehydrogenase/reductase family, suggesting a closer redox loop between both enzymes. MO-G35A was successfully expressed in three Escherichia coli expression systems, where higher yields were achieved using the E. coli Shuffle T7 as host, suggesting that correct disulfide bond formation is necessary for correct folding. Enzyme characterization showed that it operates optimally at 35–38 °C, exhibiting a Km of 0.06 mM and a kcat of 0.15 s⁻¹ for bicyclo [3.2.0] hept-2-en-6-one (BHC). Furthermore, the study revealed high stability in the presence of organic solvents, making it suitable for applications in various industrial processes, especially when the substrates have poor solubility in aqueous solutions. These results highlight the robustness and adaptability of enzymes in extreme environments, making them valuable candidates for biotechnological applications. Full article

This paper investigates the axial deformation characteristics and crashworthiness of thin-walled metal tubes (TWT) reinforced with Polyetherketoneketone (PEKK) honeycomb lattice structures consisting of bio-inspired hierarchical cellular topological features. Experimentally validated numerical results revealed that the specific energy absorption capacity (SEA) of these composite structures increased with filler volume corresponding to a specific cellular topology. This includes the bio-inspired hierarchical sparse (BHS) topology, which registered a remarkable improvement in SEA over the hollow tube of 202%. In contrast, the central (BHC) topology deformed in an unstable hex-dominated pattern and triggered catastrophic failure of the composite in global bending mode. Furthermore, rigid cells were shown to drastically increase the initial peak force (IPF), while cells with low stiffness were beneficial for maintaining a low level of IPF and moderately improving SEA. Moreover, the rib and wall thickness of the BHS honeycomb cells were suitably tailored to increase the SEA by 2.1%, while simultaneously reducing the IPF by 3.7%. These findings suggest that multi-functional mechanical attributes of PEKK hierarchical honeycomb lattice fillers can mutually benefit thin-walled tubes with superior energy absorption capability and lightweight features over conventional lattice-filled tubes or a hollow tube. Full article

5-Hydroxymethylfurfural (HMF) is a versatile carbohydrate-derived platform chemical that has been used for the synthesis of a number of commercially valuable compounds. In this study, several chromium (Cr)-doped, biomass-derived hydrochar catalysts were synthesized via the one-pot method using starch, eucalyptus wood, and bagasse as carbon sources. Then, the performance of these synthesized materials for the catalytic conversion of glucose into HMF was evaluated by, primarily, the yield of HMF. The synergistic interactions between the Cr salt and the different biomass components were investigated, along with their effects on the catalytic efficiency. The differences in the catalytic activity of the synthesized materials were analyzed through structural characterization, as well as assessments of the acid density and strength. Among the catalysts, Cr₅BHC₁₈₀ derived from bagasse presented the highest activity, achieving an HMF yield of 64.5% in an aqueous solvent system of dimethyl sulfoxide (DMSO) and saturated sodium chloride (NaCl) at 170 °C after 5 h. After four cycles, the HMF yield of Cr₅BHC₁₈₀ decreased to 38.7%. Characterization techniques such as N₂ adsorption–desorption and Py-FTIR suggested that such a decline in the HMF yield is due to pore blockage and acid site coverage by humic by-products, as demonstrated by the fact that regeneration by calcination at 300 °C restored the HMF yield to 50.5%. Full article

We conducted experiments to screen annual forage oats suitable for cultivation at high altitude (4200 m), and to establish a green fertilization system with microbial fertilizers and manure organic fertilizers in order to provide technical support for a sustainable forage production system in the pastoral areas of the Qinghai–Tibetan Plateau. The experiment followed the principle of randomized block design to systematically analyze the agronomic traits, yield quality, and soil health of oats among different treatments, and to screen for adaptable oat varieties and the optimal application rate of microbial fertilizers with organic manure. The results showed that the following: (1) The results of the oat variety screening test showed that the yield and quality indexes of ‘Qing Yin No. 2’ and ‘Bai Yan No. 7’ introduced in high altitude areas were higher than those of other oat varieties, with high membership function values of 0.69 and 0.65, respectively. (2) The combined application of microbial fertilizer and organic fertilizer showed that the combined application could significantly improve the growth and photosynthetic characteristics of ‘Bai Yan No. 7’. The combination of the two also improved the yield quality of ‘Bai Yan No. 7’; the hay yield with the BHC3 treatment was 8508.00 kg·hm⁻², significantly higher than the BCK treatment (p < 0.05). Regarding soil fertility, under the BHC3 treatment, compared with the BCK, soil nutrient contents and soil enzyme activities were also significantly improved (p < 0.05). At the same time, the combination of the two treatments also significantly improved the growth and photosynthetic characteristics of ‘Qing Yin No. 2’. The combination of the two also improved the yield quality of ‘Qing Yin No. 2’, and the hay yield with the QDY4 treatment was 8707.67 kg·hm⁻², which was significantly increased by 25.37%, compared with that of QCK. Regarding soil fertility, under the QHC2 treatment, compared with the QCK treatment, soil nutrient contents and soil enzyme activities were also significantly improved. To sum up, ‘Qing Yin No. 2’ and ‘Bai Yan No. 7’ can better adapt to the ecological environment in high altitude areas, and are suitable for planting in areas with an altitude of 4200 m. The combined application of Trichoderma harzianum, Bacillus licheniformis, and organic fertilizer can improve the yield, nutritional quality, and soil fertility of ‘Qing Yin No. 2’ and ‘Bai Yan No. 7’. The best treatment for ‘Qing Yin No. 2’ is QDY4, that is, 15.00 kg of Bacillus licheniformis is applied per hectare, and 18,000 kg of cattle and sheep manure organic fertilizer is applied per hectare. The best treatment for ‘Bai Yan No. 7’ is BHC3, that is, 6.00 kg of Trichoderma harzianum is applied per hectare, and 18,000 kg of cattle and sheep manure organic fertilizer is applied per hectare. With the above treatment, the forage grass grows best, the soil nutrient content in the forage grass field is the highest, and the input–output ratio is the highest. Full article

This research explores the relationship between credit risk and bank value within the framework of horizontal mergers and acquisitions (M&A), employing a quantile regression approach to analyze how horizontal M&A activities moderate this relationship across 110 operational Bank Holding Companies (BHCs) over 23 years. This paper stands out from previous studies by extending the scope beyond linear approaches and using the Quantiles via Moments estimator to address potential endogeneity concerns. The results demonstrate a significant negative link between credit risk and bank value, which decreases in magnitude as moving higher in the value distribution. Conversely, there is a consistent positive connection between M&A activities and bank value that is stable across different quantiles of value. Mergers and acquisitions worsen the negative impact of credit risk on bank value, affecting banks with both low and high values similarly. The findings provide useful information for investors, practitioners, and policymakers in the banking industry. Investors may use credit risk and value proposition assessments to make well-informed investment decisions, or to construct well-diversified portfolios, and identify appropriate institutions for mergers and acquisitions to enhance value. It is recommended that practitioners prioritize efficient credit risk management, especially before engaging in M&A activities and aligning them with the bank’s value proposition. Policymakers should develop guidelines to regulate M&A transactions, using established dynamic credit risk standards that correspond to banks’ value propositions, to promote financial stability and drive industry expansion. Full article

The carbon emissions from the pelletizing process are much lower than those from the sintering process. Moreover, increasing the proportion of fired pellets in the feedstock fed into the blast furnace can reduce carbon emissions, augment the capacity (the ability of a blast furnace to produce molten iron using the same weight of iron ore) and decrease slag generation. Therefore, much more attention has been paid to the pelletizing process. However, the shortage of high-quality feeds remains a bottleneck in the pelletization industry. Supplying more hematite for fired pellet production is of significant importance. In this study, the physicochemical properties and mineralogical characteristics of Brazilian hematite concentrate (BHC) were systematically analyzed. We simulated the traveling grate process and investigated the effect of BHC dosage on the balling behavior of mixed concentrates, the firing performance of the dry balls and the metallurgical properties of the fired pellets. The results indicate that substituting 20–30% BHC with magnetite concentrates improves the drop number and thermal stability of green balls with a slightly higher dosage of bentonite. The firing characteristics of the dry balls and the reduction index and reduction degradation index of the fired pellets were enhanced, although a slightly adverse effect on the reduction swelling index of the fired pellets was observed. Overall, the mechanical and metallurgical properties of the fired pellets can meet the requirements for blast furnace operations. Substituting magnetite concentrates with 20–30% hematite concentrate in the traveling grate for the pelletization process is technically feasible. Full article

The Santiago-Guadalajara River Basin (SGRB), located in western Mexico, is one of the most polluted rivers in the country. A pesticide monitoring program was carried out from January 2022 to September 2022, during which time water samples collected at 25 sites in the main stem and tributaries revealed the presence of 13 of the 24 pesticides analyzed, including α-BHC, β-BHC, γ-BHC (Lindane), γ-Chlordane, Hexachlorobenzene, Heptachlor, Aldrin, α-Endosulfan, DDT, -4,4, Methoxychlor, Chlorpyrifos-methyl, Endosulfan sulfate, and Dicofol. A high level of correlation was found between the identified pesticides, which could mean that several of these pesticides reached a stable level within the monitored water bodies. Most of the identified pesticides are classified as high environmental risk according to the Stockholm Convention because of their persistence and high degree of toxicity to the environment and human health. A Pesticide Toxicity Index (PTI) was applied to identify the streams considered to be of concern due to the presence of pesticides exceeding the threshold limits established by national and international guidelines. Performing a calculation for the entire Santiago-Guadalajara River Basin, the PTI reached a value of 0.833, which, according to the criteria of this method, classifies it as a “Moderate” level of risk for aquatic life. Increased regulatory and surveillance measures by state and federal authorities are required to prevent the use of these pesticides, which have been restricted globally. Full article

Photoactive N-hydroxysulfonamides photocaged with the (6-bromo-7-hydroxycoumarin-4-yl)methyl chromophore have been successfully synthesized, and the mechanisms of photodecomposition investigated for two of the compounds. Upon irradiation up to 97% of a diagnostic marker for (H)NO release, sulfinate was observed for the trifluoromethanesulfonamide system. In the absence of a species that reacts rapidly with (H)NO, (H)NO instead reacts with the carbocation intermediate to ultimately generate (E)-BHC-oxime and (Z)-BHC-oxime. Alternatively, the carbocation intermediate reacts with solvent water to give a diol. Deprotonation of the N(H) proton is required for HNO generation via concerted C-O/N-S bond cleavage, whereas the protonation state of the O(H) does not affect the observed photoproducts. If the N(H) is protonated, C-O bond cleavage to generate the parent N-hydroxysulfonamide will occur, and/or O-N bond cleavage to generate a sulfonamide. The undesired competing O-N bond cleavage pathway increases when the volume percentage of water in acetonitrile/water solvent mixtures is increased. Full article

The incorporation of viscoelastic layers in laminates can markedly enhance the damped dynamic characteristics. This study focuses on integrating viscoelastic layers into the composite facesheet of the bowtie-shaped honeycomb core composite sandwich panel (BHC-CSP). The homogenization of the damped BHC-CSP is performed by employing the variational asymptotic method. Based on the generalized total energy equation, the energy functional of the representative unit cell of the damped BHC-CSP is asymptotically analyzed. The warping function, derived following the principle of minimum potential energy, provides a basis for obtaining the corresponding Euler–Lagrange equation to ascertain the equivalent elastic properties of the damped BHC-CSP. Utilizing the developed two-dimensional equivalent model, the free-vibration characteristics of the damped BHC-CSP are examined across diverse boundary conditions while delving into the impact of an external viscous damping layer on the natural frequency of the damped BHC-CSP. The results reveal that intensified boundary constraints effectively diminish the effective vibration region of the damped BHC-CSP, thereby enhancing its overall stability. The introduction of a PMI foam layer proves effective in adjusting the stiffness and mass distribution of the damped BHC-CSP. Resonance characteristics are explored through frequency and time-domain analyses, highlighting the pivotal roles of the excitation position and receiver point in influencing the displacement and velocity responses. Although the stiffness is improved by incorporating a PMI foam layer, its effect on the damping performance of the damped BHC-CSP is minimal when compared to the T-SW308 foam layer. Full article

Rainwater harvesting (RWH) systems offer an opportunity to diversify the water matrix under drought scenario. However, there is not a robust institutional framework for managing this new source of water. The objective of this study was to evaluate the influence of the catchment surface material on the quality of rainwater collected. Three systems were installed in south-central Chile, which collected rainwater from three different surfaces: gravel tile, zinc-polycarbonate sheets, and clay tiles. The RWH system consists of a first flush diverter and then a storage system with chlorination. The rainwater was characterized by its physicochemical and microbiological properties for its possible final use, considering the current regulations for drinking water and agricultural irrigation. The results indicate that the raw rainwater harvested from different surfaces presented a high mean conductivity of 232 ± 146 µS/cm. Meanwhile, fecal coliform values were <1 MPN/100 mL, which indicates good microbiological quality. Regarding the quality for use as drinking water, it was found that of 39 parameters evaluated according to a reference standard, only the pH was above the indicated limit. Meanwhile, the harvested water presents satisfactory quality for irrigation, except for its sodium (35–50% above the standard) and pesticide values (with respect to 0.028 µg Delta-BHC/L at Site 2). Full article

To enhance the impact resistance of high-performance concrete (HPC), a novel efficient solution was adopted by incorporating basalt fibers (BF) and polypropylene fibers (PF) as reinforcement materials in this work. To this end, the effects of single BF (BHC) and PF (PHC) as well as their combinations (BPHPC) on the impact energy consumption, ductility ratio, and toughness factor were explored through drop weight impact test of concrete considering fiber volume contents (0.1%, 0.15%, 0.2%) to evaluate the impact resistance of the concrete. The Weibull distribution function model is used to fit the drop weight impact test results and predict the probability of failure. Moreover, the fracture-resistance enhancement mechanism of fiber is analyzed at a microscopic level. Test results showed that the number of impacts resisted by the HPC can follow well the two-parameter Weibull distribution. Compared with the single BF and single PF, the combination of 0.15% BF and 0.1% PF yields favorable impact resistance, thus exhibiting a positive hybrid effect. Full article

Despite positive associations between micronutrient intake, status, and health outcomes, many randomized controlled trials (RCT) of vitamins are null. Standards to establish causality in biological systems include the Bradford Hill criteria, the experimental component of which relies on and promotes RCT-centred approaches. Such criteria may need adaptations to the specificities of nutrition science. Our objective, as part of a broader FENS initiative to improve the science of nutrition, was to conduct a case study to assess the Bradford Hill criteria (BHC) applied to clinical studies of vitamin D and cardiovascular disease endpoints and evaluate strengths and pitfalls for this approach. We conducted a systematic review of the recent literature on CVD and vitamin D supplementation, including both RCT, cohort studies (CT), or systematic reviews within Medline, Web of Science, and Cochrane libraries. Studies had to be conducted in adults, including hard CVD-relevant endpoints with a minimum sample size of n = 500 for RCT and n = 10,000 for CT. CT had to utilize quality-assured, analytical methods for serum 25-hydroxyvitamin D assessment and include verified clinical outcomes. We also evaluated and proposed plausible biochemical and physiological mechanisms for vitamin D and CVD. We graded the evidence according to BHC for the establishment of causality in biological systems and the identification of strengths and pitfalls of this approach. The search yielded 4170 papers, and 31 met the predefined criteria. The criteria “strength of association”, “consistency”, “temporality”, “biological gradient”, “plausibility”, “experiment”, “specificity”, “analogy”, and “coherence” were analyzed and appraised. While the logical framework of the BHC is perceived as useful, its direct applicability to the nutritional context is partly open to interpretation and could be further specified. The Bradford Hill criteria for establishing causality need adaptation for the nutritional context and to the advances in biological and social sciences in the last decades. Insights gained and methodological paradigms identified may have broad application to nutrition science. Full article

Holding companies legally separate the assets and owners of a company creating a layer of liability protection. Theoretically, this feature lowers the risk attributable to holding companies, enabling them to offer lower-cost debts compared to stand-alone alternatives. However, no study has ever tested this hypothesis due to its technical and practical difficulties. Testing this hypothesis requires a separate classification of holding and stand-alone companies’ outstanding debts to compare their risk spreads, controlling the bonds’ risk ranking, maturities, and issue sizes. Further, a model is needed to make the callable bond spreads with unknown maturity dates comparable to non-callable bonds. This work is the first attempt to evaluate the risk spreads of stand-alone banks and bank holding companies in Spain by including all outstanding rated bonds offered by Spanish banks. In order to make callable bond spreads comparable with noncallable bond spreads, we obtained the option-adjusted spreads for the bonds using a lattice option-pricing model that treats the callable bonds as a bond with embedded options. We then regressed to option-adjusted spreads on control variables and ownership structure dummy to see if there exists a statistically and economically significant coefficient for the introduced dummy variable. We found that bank-holding company bonds have higher risk spreads compared to the stand-alone alternatives in Spain. This may be attributable to the characteristics of holding companies that introduce other risks that offset the gains obtained from the added layer of liability protection. Full article

In this paper, a hybrid cuckoo search technique is combined with a single-layer neural network (BHCS-ANN) to approximate the solution to a differential equation describing the curvature shape of the cornea of the human eye. The proposed problem is transformed into an optimization problem such that the $L_2–$error remains minimal. A single hidden layer is chosen to reduce the sink of the local minimum values. The weights in the neural network are trained with a hybrid cuckoo search algorithm to refine them so that we obtain a better approximate solution for the given problem. To show the efficacy of our method, we considered six different corneal models. For validation, the solution with Adam’s method is taken as a reference solution. The results are presented in the form of figures and tables. The obtained results are compared with the fractional order Darwinian particle swarm optimization (FO-DPSO). We determined that results obtained with BHCS-ANN outperformed the ones acquired with other numerical routines. Our findings suggest that BHCS-ANN is a better methodology for solving real-world problems. Full article

In this study, a new fractional-order model for human skull heat conduction is tackled by using a neural network, and the results were further modified by using the hybrid cuckoo search algorithm. In order to understand the temperature distribution, we introduced memory effects into our model by using fractional time derivatives. The objective function was constructed in such a way that the $L_2-$error remained at a minimum. The fractional order equation was then calculated by using the proposed biogeography-based hybrid cuckoo search (BHCS) algorithm to approximate the solution. When compared to earlier simulations based on integer-order models, this method enabled us to examine the fractional-order (FO) cases, as well as the integer order. The results are presented in the form of figures and tables for the different case studies. The results obtained for the various parameters were validated numerically against the available literature, where our proposed methodology showed better performance when compared to the least squares method (LSM). Full article