Single Site Research Articles

Multivalent Calixarene Complexation of a Designed Pentameric Lectin.

We describe complex formation between a designed pentameric β-propeller and the anionic macrocycle sulfonato-calix[8]arene (sclx8), as characterized by X-ray crystallography and NMR spectroscopy. Two crystal structures and 15N HSQC experiments reveal a single calixarene binding site in the concave pocket of the β-propeller toroid. Despite the symmetry mismatch between the pentameric protein and the octameric macrocycle, they form a high affinity multivalent complex, with the largest protein-calixarene interface observed to date. This system provides a platform for investigating multivalency.

Pharmacodynamic evaluation of the etonogestrel contraceptive implant initiated midcycle with and without ulipristal acetate: An exploratory study

ObjectiveTo estimate the incidence of ovulation suppression within five days of etonogestrel 68 mg implant insertion in the presence of a dominant follicle with and without same-day ulipristal acetate. Study designThis single site non-masked, exploratory randomized trial recruited people age 18–35 years with regular menstrual cycles, no pregnancy risk, and confirmed ovulatory function. We initiated transvaginal ultrasound examinations on menstrual day 7–9 and randomized participants 1:1 to etonogestrel implant alone or with concomitant ulipristal acetate 30 mg oral when a dominant follicle reached ≥14 mm in diameter. We completed daily sonography and serum hormone levels for up to seven days or transitioned to labs alone if sonographic follicular rupture occurred. We defined ovulation as follicular rupture followed by progesterone >3 ng/mL. We calculated point estimates, risk ratios and 95% confidence intervals for ovulation for each group. Ovulation suppression of ≥44% in either group (the follicular rupture suppression rate with oral levonorgestrel emergency contraception), would prompt future method testing. ResultsFrom October 2020 to October 2022, we enrolled 40 people and 39 completed primary outcome assessments: 20 with etonogestrel implant alone (mean follicular size at randomization: 15.2 mm ± 0.9 mm) and 19 with etonogestrel implant + ulipristal acetate (mean follicular size at randomization: 15.4 mm ± 1.2 mm, p = 0.6). Ovulation suppression occurred in 13 (65%) of etonogestrel implant-alone participants (Risk ratio 0.6 (95% CI: 0.3, 1.1), p = 0.08) and seven (37%) of implant + ulipristal acetate participants. ConclusionsOvulation suppression of the etonogestrel implant alone exceeds threshold testing for future research while the implant + ulipristal acetate does not. ImplicationsData are lacking on midcycle ovulation suppression for the etonogestrel implant with and without oral ulipristal acetate. In this exploratory study, ovulation suppression occurred in 65% of implant participants and 37% of implant + ulipristal acetate participants. Ovulation suppression of the implant alone exceeds threshold testing for future emergency contraception research.

Impact of Metastatic Site in Favorable-Risk Renal Cell Carcinoma Receiving Sunitinib or Pazopanib

BackgroundAlthough in metastatic renal cell carcinoma (mRCC) patients with intermediate and poor risk the benefit of combination strategies versus tyrosine kinase inhibitor (TKI) has been ascertained, in those with favorable risk data are ambiguous. Herein, we investigated the impact of number and type of metastatic site in patients with favorable risk to contribute to the best therapeutic choice. Material and MethodsMulticenter data regarding patients with favorable risk mRCC carcinoma receiving first-line TKIs, sunitinib or pazopanib, were retrospectively collected. We divided our population into 2 groups based on the number of metastatic sites and analyzed its impact on tumor response and efficacy outcome. The Kaplan-Meier method was used to estimate efficacy outcomes and the log-rank test to examine differences between subgroups. ResultsA total of 107 patients with a median age of 69 years were included in the final analysis. Patients with 1 metastatic site, compared with patients with > 1 site, had a significantly longer overall survival (OS) (not reached vs. 66 months) and a trend, although not statistically significant, of better progression-free survival (PFS) (31 vs. 17 months). In patients with 1 metastatic site, liver involvement was correlated with worse PFS and OS at the univariate analysis (P = .01) and was confirmed as independent poor prognostic factor for PFS at multivariate analysis. ConclusionIn conclusion, we reported a longer OS in favorable risk mRCC patients receiving TKI with only 1 metastatic site. Nevertheless, in patients with a single metastatic site, hepatic involvement correlated with worse PFS compared to other metastatic sites.

The value of 18F-FDG PET/CT in Langerhans cell histiocytosis.

To investigate the value of 18F-FDG PET/CT in diagnosis and disease evaluation of Langerhans cell histiocytosis (LCH). A retrospective analysis of 31 patients with LCH confirmed by histopathology was performed. A systematic analysis of the PET/CT imaging manifestations of LCH was performed, recording patients who were treated and receiving PET/CT for efficacy evaluation. In addition, clinical and laboratory data of LCH patients were collected, and the correlation between these data and PET/CT metabolic parameters was initially investigated. Of the 31 patients, thirty had at least 1 PET/CT positive lesions (96.7%), and one had only skin damage without abnormalities on PET/CT. Of 31 patients, fifteen (48.4%) had single system (SS) disease (9 cases with a single site and 6 cases with multiple sites) and 16 (51.6%) had multisystem (MS) disease (6 low risk and 10 high risk cases). The incidence of LCH lesions in the bone, lymphatic system, pituitary gland, liver, soft tissue, thyroid gland, thymus, and lungs was 20 cases (64.5%), 12 cases (38.7%), 3 cases (9.7%), 2 cases (6.5%), 2 cases (6.5%), 1 case (3.2%), 1 case (3.2%), and 8 cases (25.8%), respectively. A total of 21 PET/CT follow-up scanning were performed in 13 patients receiving chemotherapy, with 13 (61.9%) partial metabolic remission (PMR), 6 (28.6%) progressive metabolic disease (PMD), and 2 (9.5%) stable metabolic disease (SMD), according to PET Response Evaluation Criteria in Solid Tumors (PRECIST) 1.0. Erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and Lactic Dehydrogenase (LDH) were positively correlated with TTLG (total TLG) (R2 = 0.3256, 0.2409, 0.4205, P < 0.05). The Re-examine SUVmax is positively correlated with re-examine LDH (R2 = 0.7285, P < 0.05). 18F-FDG PET/CT is an effective way to diagnose and evaluate LCH. PET metabolic parameters were associated with laboratory inflammatory markers, suggesting that 18F-FDG PET/CT may be helpful in evaluating disease activity of LCH.

Single atom sites as CO scavenger to allow for crude hydrogen usage in PEMFC

Nanosized Pt catalysts are the catalyst-of-choice for proton exchange membrane fuel cell (PEMFC) anode, but are limited by their extreme sensitivity to CO in parts per million (ppm) level, thereby making the use of ultrapure H2 a prerequisite to ensure acceptable performance. Herein, we confront the CO poisoning issue by bringing the Ir/Rh single atom sites to synergistically working with their metallic counterparts. In presence of 1000 ppm CO, the catalyst represents not only undisturbed H2 oxidation reaction (HOR) catalytic behavior in electrochemical cell, but also unparalleled peak power density at 643 mW cm−2 in single cell, 27-fold in mass activity of the best PtRu/C catalysts available. Pre-poisoning experiments and surface-enhanced Raman scattering spectroscopy (SERS) and calculation results in combine suggest the presence of adjacent Ir/Rh single atom sites (SASs) to the nanoparticles (NPs) as the origin for this prominent catalytic behavior. The single sites not only exhibit superb CO oxidation performance by themselves, but can also scavenge the CO adsorbed on approximated NPs via supplying reactive OH* species. We open up a new route here to conquer the formidable CO poisoning issue through single atom and nanoparticle synergistic catalysis, and pave the way towards a more robust PEMFC future.

Atmospheric Air Dust Concentration, Composition And Size Distribution Data At Breathing Heights In Yekaterinburg.

Accurate information on air quality serves as the foundation for making regulatory and legal decisions aimed at reducing air pollution. This study investigates the vertical distribution of dust particle concentration, their elemental composition, and size distribution in the atmospheric surface layer in Yekaterinburg. Over eight days in April 2021, 64 dust samples were collected on filters at heights ranging from 0.5 m to 10 m at a single site using a mobile post. The mass concentration of the dust, characterized by heterogeneous data with a coefficient of variation exceeding 30%, exhibited a weak tendency to decrease with height. The proportion of particles smaller than 1 µm decreased with increasing altitude, except for 10 m, where their proportion increased. Conversely, the concentration of p articles ranging from one to two microns decreased closer to the surface. Dust grains of other sizes were nearly evenly distributed at various heights. Dust particles smaller than PM2.5 accounted for approximately 45% of the total particles. X-ray fluorescence analysis identified 12 elements in dust particles, with S, Ca, and Fe showing the most substantial content. The proportion of most metals and Ca in solid particles decreased with height, while the content of S and As increased. The Cu, Zn, and Sb content in dust particles remained constant at all measured heights.

Designing and Engineering Atomically Dispersed Metal Catalysts for CO2 to CO Conversion: From Single to Dual Metal Sites

AbstractThe electrochemical CO2 reduction reaction (CO2RR) is a promising approach to achieving sustainable electrical‐to‐chemical energy conversion and storage while decarbonizing the emission‐heavy industry. The carbon‐supported, nitrogen‐coordinated, and atomically dispersed metal sites are effective catalysts for CO generation due to their high activity, selectivity, and earth abundance. Here, we discuss progress, challenges, and opportunities for designing and engineering atomic metal catalysts from single to dual metal sites. Engineering single metal sites using a nitrogen‐doped carbon model was highlighted to exclusively study the effect of carbon particle sizes, metal contents, and M−N bond structures in the form of MN4 moieties on catalytic activity and selectivity. The structure‐property correlation was analyzed by combining experimental results with theoretical calculations to uncover the CO2 to CO conversion mechanisms. Furthermore, dual‐metal site catalysts, inheriting the merits of single‐metal sites, have emerged as a new frontier due to their potentially enhanced catalytic properties. Designing optimal dual metal site catalysts could offer additional sites to alter the surface adsorption to CO2 and various intermediates, thus breaking the scaling relationship limitation and activity‐stability trade‐off. The CO2RR electrolysis in flow reactors was discussed to provide insights into the electrolyzer design with improved CO2 utilization, reaction kinetics, and mass transport.

Designing and Engineering Atomically Dispersed Metal Catalysts for CO2 to CO Conversion: From Single to Dual Metal Sites.

The electrochemical CO2 reduction reaction (CO2 RR) is a promising approach to achieving sustainable electrical-to-chemical energy conversion and storage while decarbonizing the emission-heavy industry. The carbon-supported, nitrogen-coordinated, and atomically dispersed metal sites are effective catalysts for CO generation due to their high activity, selectivity, and earth abundance. Here, we discuss progress, challenges, and opportunities for designing and engineering atomic metal catalysts from single to dual metal sites. Engineering single metal sites using a nitrogen-doped carbon model was highlighted to exclusively study the effect of carbon particle sizes, metal contents, and M-N bond structures in the form of MN4 moieties on catalytic activity and selectivity. The structure-property correlation was analyzed by combining experimental results with theoretical calculations to uncover the CO2 to CO conversion mechanisms. Furthermore, dual-metal site catalysts, inheriting the merits of single-metal sites, have emerged as a new frontier due to their potentially enhanced catalytic properties. Designing optimal dual metal site catalysts could offer additional sites to alter the surface adsorption to CO2 and various intermediates, thus breaking the scaling relationship limitation and activity-stability trade-off. The CO2 RR electrolysis in flow reactors was discussed to provide insights into the electrolyzer design with improved CO2 utilization, reaction kinetics, and mass transport.

Constructing fully exposed Pt atomically dispersed catalysts for enhanced multifunctional selective hydrogenation reactions

Constructing highly efficient and low-cost catalysts is essential for the selective hydrogenation reaction. Herein, we developed fully exposed Pt atomically dispersed catalysts (PtAD/C-Al2O3) by a simple carbon modified strategy. Importantly, the co-existence of Pt-O1C2 single atoms and Pt nanoclusters in the PtAD/C-Al2O3 system could exhibit excellent catalytic activity in the selective hydrogenation of quinoline and p-nitrophenol. Notably, the quinoline conversion and the corresponding selectivity of 1,2,3,4-tetrahydroquinoline is 99.6 % and 99.3 %, respectively. Meanwhile, the turnover frequency of PtAD/C-Al2O3 (1081 h−1) is 3.8 and 5.7 times higher than that of Pt single-atom catalysts (PtSA/C-Al2O3) and Pt nanoparticles (PtNPs/C-Al2O3), respectively, during quinoline hydrogenation. Besides, the rate constant of PtAD/C-Al2O3 could reach 192.5 min-1mgPt-1 for p-nitrophenol hydrogenation, which is much better than most of the reported catalysts. Mechanism studies revealed the synergistic effect between Pt-O1C2 single atoms and Pt nanoclusters acts as the main role in enhancing the hydrogenation activity. Specifically, Pt single atoms sites mainly adsorb and activate quinoline molecules, while Pt nanoclusters boost the dissociation of H2 molecules to H atoms. This work paves an origin carbon modified method to construct Pt atomically dispersed catalysts for efficient multifunctional hydrogenation.

Molecular Co-Catalyst Confined within a Metallacage for Enhanced Photocatalytic CO2 Reduction.

The construction of structurally well-defined supramolecular hosts to accommodate catalytically active species within a cavity is a promising way to address catalyst deactivation. The resulting supramolecular catalysts can significantly improve the utilization of catalytic sites, thereby achieving a highly efficient chemical conversion. In this study, the Co-metalated phthalocyanine (Pc-Co) was successfully confined within a tetragonal prismatic metallacage, leading to the formation of a distinctive type of supramolecular photocatalyst (Pc-Co@Cage). The host-guest architecture of Pc-Co@Cage was unambiguously elucidated by single-crystal X-ray diffraction (SCXRD), NMR, and ESI-TOF-MS, revealing that the single cobalt active site can be thoroughly isolated within the space-restricted microenvironment. In addition, we found that Pc-Co@Cage can serve as a homogeneous supramolecular photocatalyst that displays high CO2 to CO conversion in aqueous media under visible light irradiation. This supramolecular photocatalyst exhibits an obvious improvement in activity (TONCO = 4175) and selectivity (SelCO = 92%) relative to the nonconfined Pc-Co catalyst (TONCO = 500, SelCO = 54%). The present strategy provided a rare example for the construction of a highly active, selective, and stable photocatalyst for CO2 reduction through a cavity-confined molecular catalyst within a discrete metallacage.

Advantages of single-site laparoscopic orchiopexy for palpable undescended testes in children: a prospective comparison study

PurposeTo evaluate the feasibility of single-site laparoscopic orchiopexy for palpable undescended testes in children.MethodsWe prospectively studied patients with undescended testes between July 2021 and June 2022. In total, 223 patients were included in our study: 105 underwent single-site laparoscopic orchiopexy and 118 underwent conventional laparoscopic orchiopexy. During single-site laparoscopic orchiopexy, 3 ports were inserted within the umbilicus.ResultsNo differences were observed between the groups in terms of age and laterality. For unilateral undescended testes, the operating time was longer in the single site group than in the conventional group at the early stages (55.31 ± 12.04 min vs. 48.14 ± 14.39 min, P = 0.007), but it was similar to the conventional group at the later stages (48.82 ± 13.49 min vs. 48.14 ± 14.39 min, P = 0.78). Testicular ascent occurred in one patient from each group. There was no significant difference in the success rate between the single-site group and the conventional group (99.0% vs. 99.2%, P = 0.93). In the single-site group, no visible abdominal scarring was observed, while in the conventional group, there were two noticeable scars on the abdomen.ConclusionSingle-site laparoscopic orchiopexy offers superior cosmetic results and comparable success rates compared to conventional laparoscopic orchiopexy for palpable undescended testes.

Catalytic reactivity of Pt sites for non-oxidative coupling of methane (NOCM)

Recently, single atom catalysts have been suggested as stable and non-coking catalysts for non-oxidative coupling of methane (NOCM) to ethylene and higher hydrocarbons. In this work, reaction kinetics coupled with microscopy and spectroscopy technique were used to understand the nature of the Pt single atom active sites under reaction conditions relevant to industrial applications of NOCM. Under NOCM conditions (975C, Space velocity = 30 L hr-1 gcat-1), single atom Pt supported on CeO2 (Pt SAs) and Pt nanoparticles (∼2nm) supported on SiO2 (Pt NPs) show similar ethylene formation rates and show similar gas phase selectivity to major and minor products like ethylene (∼60 %), ethane (∼20 %) and higher hydrocarbons (propylene, butene, etc.), suggesting that the single sites do not offer a superior performance as claimed in the literature. Power rate law reaction orders with respect to methane, ethylene and hydrogen show similar results for the two catalytic systems (nCH4 = 1, nC2H4 = 0 and nH2 = −0.5), indicating a surface-initiated gas phase radical mechanism for NOCM reactions. Transmission electron microscopy (TEM) of the spent samples (CH4 treated at 975C for 3 h) reveals that materials containing Pt (Pt SAs and Pt NPs) are found to sinter to particles approximately 5–7 nm in size, suggesting that the single atoms do not survive NOCM reaction conditions. Ethylene hydrogenation and CO-IR spectroscopy on fresh and spent catalysts suggest loss of surface Pt sites by coking following NOCM. These results shed light on the nature of the active sites during non-oxidative coupling of methane at industrially relevant conditions and motivate further research on catalyst development for this reaction.

Highly efficient, label free, ultrafast plasmonic SERS biosensor (silver nanoarrays/Si) to detect GJB2 gene expressed deafness mutations in real time validated with PCR studies

Rapid diagnostics of any gene mutations related to organ loss is highly demanded now-a days to consume time as well to reduce cost. Currently, Surface enhanced Raman spectroscopy (SERS) is evolved to be a rapid investigating tool to screen gene mutations down to single molecule sensing with regard to the design and development of substrates used for sensing. The current research focuses on particular towards direct detection of deafness mutations associated with single and dual sites related to GJB2 gene. SERS Sensor construction is achieved with plasmonic silver nanoarrays on Si (SNA/Si) substrate by effortless wet chemical methods (Reaction time: 35 s; Concentration: 20 mM). The fabricated SNA/Si facilitates direct sensing of the deafness mutations of GJB2 gene in single as well dual sites with the enhancement of plasmonic hotspots. Normal DNA DMF-33 (GGGGGG) as well as Mutant DNA at single site DMF-9 (GGGGG) were validated by their guanine fingerprint Raman bands intensity quenching for mutant DNA DMF-9 at 1366 cm−1 and 1595 cm−1 respectively. Likewise, double mutations in DMF-19 are substitutional from G to A, portrayed highly intense fingerprint of Adenine Raman bands at 739 cm−1, 1432 cm−1, 1572 cm−1 in comparison to normal DNA (DMF-33). The findings were well analyzed with Raman mapping data which carries almost 625 scans for each DNA sample. The fabricated sensor exhibited the highest sensitivity towards DNA detection down to 0.1 pg/μL with utmost reproducibility. The current study aims to bring in creation of library files for deafness mutations to facilitate clinical diagnostics in a simple and rapid approach.

Population genetic diversity of tomato spotted wilt orthotospovirus isolates from tobacco in Yunnan Province, China

We explored the genetic diversity and molecular evolutionary characteristics of tomato spotted wilt orthotospovirus (TSWV) on tobacco in Yunnan. In this study, 523 diseased tobacco leaf samples with suspected TSWV infection from nine different geographical sources in Yunnan were tested, and nucleocapsid protein (NP) of some isolates was amplified and cloned by reverse transcription-polymerase chain reaction (RT‒PCR). Bioinformatics tools were used to analyze the population genetic structure and molecular evolutionary relationships of the tobacco TSWV population. TSWV was detected in 284 of 523 samples, with an average positivity rate of 54.3%. NP gene sequences of the 159 tobacco TSWV isolates obtained were all 777 bp, with 265 nucleic acid polymorphic sites, with 197 variant sites, including 66 parsimony informative and 131 single variant sites. Results for virus consistency and variation analysis based on the NP gene showed that the nucleotide sequence consistency of Yunnan TSWV isolates was 96∼100%, the haplotype diversity 0.963, and the nucleic acid diversity 0.006. Phylogenetic analysis revealed that Yunnan tobacco TSWV isolates belong to the same group, with lower genetic differentiation and more frequent gene exchange among tobacco isolates of different geographical origins; their geographical characteristics were not obvious, and significant recombination signals were detected in the gene sequences of the DL-20 and DL-42 isolates. Many of the NP gene mutations of tobacco TSWV isolates from different geographic origins were deleterious in the nine different planting regions of Yunnan tobacco TSWV isolates, with only the population in the QJ planting region experiencing past population expansion events. The findings suggest that genetic recombination, mutation, and negative selection pressure are major drivers of the genetic diversity of tobacco TSWV in Yunnan. This study report of genetic variation in populations of TSWV isolates from various tobacco regions in Yunnan and provides information on the population structure of Yunnan tobacco TSWV isolates, which can help to prevent and control TSWV on Yunnan tobacco and provide a reference for research of disease-resistant varieties of tobacco.

Oxophilic Ce single atoms-triggered active sites reverse for superior alkaline hydrogen evolution

The state-of-the-art alkaline hydrogen evolution catalyst of united ruthenium single atoms and small ruthenium nanoparticles has sparked considerable research interest. However, it remains a serious problem that hydrogen evolution primarily proceeds on the less active ruthenium single atoms instead of the more efficient small ruthenium nanoparticles in the catalyst, hence largely falling short of its full activity potential. Here, we report that by combining highly oxophilic cerium single atoms and fully-exposed ruthenium nanoclusters on a nitrogen functionalized carbon support, the alkaline hydrogen evolution centers are facilely reversed to the more active ruthenium nanoclusters driven by the strong oxophilicity of cerium, which significantly improves the hydrogen evolution activity of the catalyst with its mass activity up to −10.1 A mg−1 at −0.05 V. This finding is expected to shed new light on developing more efficient alkaline hydrogen evolution catalyst by rational regulation of the active centers for hydrogen evolution.

Engineered serum markers for non-invasive monitoring of gene expression in the brain.

Measurement of gene expression in the brain requires invasive analysis of brain tissue or non-invasive methods that are limited by low sensitivity. Here we introduce a method for non-invasive, multiplexed, site-specific monitoring of endogenous gene or transgene expression in the brain through engineered reporters called released markers of activity (RMAs). RMAs consist of an easily detectable reporter and a receptor-binding domain that enables transcytosis across the brain endothelium. RMAs are expressed in the brain but exit into the blood, where they can be easily measured. We show that expressing RMAs at a single mouse brain site representing approximately 1% of the brain volume provides up to a 100,000-fold signal increase over the baseline. Expression of RMAs in tens to hundreds of neurons is sufficient for their reliable detection. We demonstrate that chemogenetic activation of cells expressing Fos-responsive RMA increases serum RMA levels >6-fold compared to non-activated controls. RMAs provide a non-invasive method for repeatable, multiplexed monitoring of gene expression in the intact animal brain.

Atomically dispersed Mn–Nx catalysts derived from Mn‐hexamine coordination frameworks for oxygen reduction reaction

AbstractMetal‐organic frameworks recently have been burgeoning and used as precursors to obtain various metal–nitrogen–carbon catalysts for oxygen reduction reaction (ORR). Although rarely studied, Mn–N–C is a promising catalyst for ORR due to its weak Fenton reaction activity and strong graphitization catalysis. Here, we developed a facile strategy for anchoring the atomically dispersed nitrogen‐coordinated single Mn sites on carbon nanosheets (MnNCS) from an Mn‐hexamine coordination framework. The atomically dispersed Mn–N4 sites were dispersed on ultrathin carbon nanosheets with a hierarchically porous structure. The optimized MnNCS displayed an excellent ORR performance in half‐cells (0.89 V vs. reversible hydrogen electrode (RHE) in base and 0.76 V vs. RHE in acid in half‐wave potential) and Zn–air batteries (233 mW cm−2 in peak power density), along with significantly enhanced stability. Density functional theory calculations further corroborated that the Mn–N4–C12 site has favorable adsorption of *OH as the rate‐determining step. These findings demonstrate that the metal‐hexamine coordination framework can be used as a model system for the rational design of highly active atomic metal catalysts for energy applications.

Estimation of uncertainty in computation of importance factors and probability of undesirable events for safety-critical multi-unit systems, based on Binary Decisions Diagrams

This paper addresses current needs of the Multi-Unit Probabilistic Safety Assessment (MUPSA) methodology, which consists of a series of eight essential steps for conducting Probabilistic Safety Assessment (PSA) in the context of a multi-unit Nuclear Power Plant (NPP), co-located on a single site. The focus of this study revolves around one of the steps of the MUPSA methodology, which includes the examination of the importance factors and uncertainty analysis. Emphasizing the role of this step within MUPSA, the paper highlights the hypothesis and estimations made, along with the determination of system importance factors and failure frequency. To illustrate the practical application of these concepts, the paper presents three illustrative examples. The first example involves a 3-terminal reliability network, while the second example features an illustrative calculation applied to a system designed for potential use in a real NPP, compared to a Monte-Carlo simulation. Moreover, the second example involves the evaluation of a medium voltage distribution system (MVDS) designed to meet the auxiliary supply requirements of a nuclear power plant. This analysis is performed using a binary decision diagram (BDD), and the results derived from the BDD evaluation are then verified with those obtained through a Monte Carlo simulation for a comprehensive comparative analysis. Finally, an uncertainty analysis is achieved using a BDD reliability model, using the results of fault trees developed by National Company SN Nuclearelectrica S.A. (SNN), Department of Nuclear Safety, in the context of the Coordinated Research Project (CRP- I31031).

Investigating the binding of caffeic acid to human hemoglobin using multispectroscopic and molecular docking approaches

Caffeic acid (CA) is a hydroxycinnamic acid derivative that possess a wide variety of biological properties and is non-toxic to humans. The binding mechanism of CA with human hemoglobin (HHb) was studied for the first time using multispectroscopic and molecular docking methods. The UV–visible absorption spectra showed that CA interacts with HHb through the formation of ground state complex. The fluorescence studies revealed that CA quenches HHb fluorescence by the static mechanism and confirmed the presence of a single CA binding site on the HHb molecule. The negative values of thermodynamics parameters (ΔH,ΔSand ΔG) showed that the binding of CA to HHb is a spontaneous and exothermic process. Hydrogen bonds and van der Waal interactions are the major intermolecular forces that stabilize the HHb-CA complex. Synchronous fluorescence experiments showed that binding of CA altered the microenvironment around tryptophan residues of HHb. Fluorescence resonance energy transfer studies indicated a high propensity of energy transfer from tryptophan residues of HHb to CA. Circular dichroism spectra and catalytic esterase activity confirmed that only minor changes occur in the secondary structure of HHb in the presence of CA. Molecular docking study identified the HHb amino acid residues involved in binding to CA. Analysis of the binding mode of CA with HHb represents an important step in elucidating the molecular mechanism of the protection of HHb from oxidative damage. This will help in understanding the potential role of CA and related antioxidants as therapeutic agents in various blood-related diseases.

Atomically-dispersed manganese anchored on B,N co-doped carbon for the sensitive electrochemical detection of levodopa

Metal single-atom catalysts offer the dual advantages of high electrochemical activity and near 100 % metal atom utilization, leading to their potential use in low-cost electrochemical sensor development. Herein, a novel electrocatalyst comprising atomically-dispersed Mn on B,N co-doped bamboo-derived carbon (MnSAs-BN-BC) was synthesized via a facile pyrolysis procedure. A high dispersion of Mn single atoms in MnSAs-BN-BC was confirmed by aberration-corrected transmission electron microscopy and elemental mapping. The Mn loading in the MnSAs-BN-BC determined by inductively coupled plasma mass spectrometry was 255 mg kg−1. MnSAs-BN-BC displayed outstanding electrocatalytic performance for levodopa (LD) oxidation, allowing a robust electrochemical sensing platform for LD detection to be established. The MnSAs-BN-BC/GCE sensing platform offered a wide LD detection range (concentrations from 2 to 683 µM) and a very low limit of detection (LOD) of 0.45 µM, outperforming almost all electrochemical sensors reported to date for LD sensing. The MnSAs-BN-BC/GCE platform also featured outstanding repeatability, reproducibility, selectivity, and stability. The as-developed sensing platform was successfully applied to LD quantification in commercial tablets with satisfactory recoveries (85.2–102.4 %), with the analytical precision of method validated against a traditional UV–vis spectrophotometry method. Density functional theory (DFT) calculations showed that Mn single atom sites lowered the reaction energy barrier for LD oxidation, with the favorable d-band center position of Mn single atom sites in MnSAs-BN-BC contributing to the enhanced LD sensing performance. This work encourages the use of single-atom metal catalysts in design of high-performance electrochemical sensors for the rapid detection of LD.