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Plant-derived natural products are an important source of potential medicines and continue to have a major impact on the drug discovery process. Natural product discovery assignments provide an opportunity to present various experimental techniques to undergraduate students in introductory medicinal chemistry. This assignment was developed to serve as a meaningful hands-on exercise to introduce undergraduate Chemistry students to the common procedure in the early phase of drug discovery using inexpensive corn silk, in which the final year undergraduate student used Recycling Preparative High-Performance Liquid Chromatography to separate and purify steroids from corn silk. The student used advanced spectroscopic methods such as UV, IR, and one- and two-dimensional NMR to elucidate the structures of these steroids. The cytotoxic activity of these steroids was also evaluated and found to be non-cytotoxic to normal human MRC-5 cells at 60 µg/mL via 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. With this assignment, students gain meaningful multidisciplinary hands-on exercises with the common procedure in the early stages of drug discovery and understand the process of isolating natural compounds that may lead to the development of new drugs.

Low student engagement and motivation in online classes are well-known issues many universities face, especially with distance education during the COVID-19 pandemic. The online environment makes it even harder for teachers to connect with their students through traditional verbal and nonverbal behaviours, further decreasing engagement. Yet, addressing such problems with 24/7 synchronous communication is overly demanding for faculty. This paper details an automated Question-Answering chatbot system trained in synchronous communication and instructor immediacy techniques to determine its suitability and effectiveness in attending to students undergoing an online Chemistry course. The chatbot is part of a new wave of affective focused chatbots that can benefit students' learning process by connecting with them on a relatively more humanlike level. As part of the pilot study in the development of this chatbot, qualitative interviews and self-report data capturing student-chatbot interactions, experiences and opinions have been collected from 12 students in a Singaporean university. Thematic analysis was then employed to consolidate these findings. The results support the chatbot's ability to display several communication immediacy techniques well, on top of responding to students at any time of the day. Having a private conversation with the chatbot also meant that the students could fully focus their attention and ask more questions to aid their learning. Improvements were suggested, in relation to the chatbot's word detection and accuracy, accompanied by a framework to develop communication immediacy mechanics in future chatbots. Our findings support the potential of this chatbot, once modified, to be used in a similar online setting.

The handling of chemicals in the laboratory presents a challenge in instructing large class sizes and when students are relatively new to the laboratory environment. In this work, we describe and demonstrate an augmented reality colorimetric titration tool that operates out of the smartphone or tablet of students. It allows multiple students to conduct the exercise at the same time, respond quickly to actions made, and correctly depict the colors associated with changes in pH values for the indicator used. The tool imbues unparalleled realism in the conduct of the experiment and offers to strongly help students acquire bench skills with minimal use of liquid chemicals, thereby reducing handing risks for them and resulting in lower negative impacts on the environment. The feedback received from undergraduate students that participated in an initial small test exercise with the tool corroborates this.

The appreciation and understanding of gas generation through processes is vital in biochemical education. In this work, an augmented reality tool is reported to depict the redox reaction between hydrogen peroxide and sodium hypochlorite solutions, two ubiquitous oxidizing agents, to create oxygen, a combustible gas. As it operates out of smartphones or tablets, students are able to conduct the exercise collaboratively, respond in a manner similar to an actual physical experiment, and able to depict the oxygen volume changes in relation to the volume of hydrogen peroxide of different concentrations used. The tool offers to help students acquire bench skills by limiting handing risks and to mitigate possible student anxiety on handling chemical materials and implements in the laboratory. The feedback received from Year 11 and 12 high school student participants in an outreach exercise indicate the overall effectiveness of this tool.

Recent studies have shown that songs may enhance learning as they function as mnemonic devices to increase memorability. In this research, songs based on the more difficult subtopics in Chemistry were composed, encompassing many formulas, equations and facts to be remembered. This technique of song composition can be used in any subject, any point of time and any tune can be used. Songs can be utilized for any class size, from tutorials to lecture halls. It was found in this study that students understood and retained key information better. In addition, songs added variety to classroom learning experiences, lowered students' stress levels, increased enjoyment and engaged students more effectively by catering for students with different learning styles.

This study presents an analysis of alternative conceptions (ACs) on acid--base chemistry harbored by grade 9 students in Singapore. The ACs were obtained by the development and validation of a 4-tier diagnostic instrument. It is among the very few studies in the science education literature that have focused on examining results based also on measures used in the educational psychology literature. The results indicate that the students harbor a range of ACs of varying strengths in relation to the properties of acids and bases, strengths of acids and bases, pH, neutralization, indicators, and sub-microscopic views of acids and bases. The 25-item instrument uncovered 30 ACs. A novel insight from this study is that when students are presented with a test item with all incorrect answer and reason responses but with a blank space for them to fill up their own answer and reason if they disagree with any of these responses, hardly any chose to do so. ACs were also identified from this question. Overall, the results reiterate the utility of the 4-tier format for identifying ACs and getting some indication of their strengths.

Four vanadyl pyrophosphate (VPO) catalysts were prepared via the sesquihydrate precursor route using direct microwave irradiation and reflux synthesis methods. The synthesis of the sesquihydrate precursor was carried out in 2 stages. The synthesized catalysts were denoted as VPOs-DD, VPOs-RR, VPOs-RD, and VPOs-DR; where VPOs represented VPO catalysts produced through sesquihydrate precursor, and D and R represented direct microwave irradiation and reflux synthesis methods, respectively. The direct microwave irradiation synthesis method was found to reduce the synthesis duration significantly for both stages of the precursor synthesis, from 48 to 4 h. An exclusive secondary configuration, akin to a needle-shaped form in chrysanthemums, is specifically noted in VPOs-DD could increase the specific surface area by 35.4% compared to the bulkier structure of VPOs catalyst produced via the conventional reflux synthesis method (VPOs-RR). Direct microwave irradiation could induce the removal of more than 4 times the total amount of oxygen atoms from the lattice of V4+ and V5+ phases, as compared to the conventional reflux method counterpart. This ultimately produced VPOs catalysts with greater catalytic performances and TON. In summary, employing direct microwave irradiation could generate VPOs catalysts with increased efficiency, improved activity and selectivity as compared to the conventional reflux method.

Abstract Phonon dispersion in crystals determines many important material properties, but its measurement usually requires large-scale facilities and is limited to bulk samples. Here, we demonstrate the measurement of full phonon dispersion along the stacking direction in nanoscale systems by using picosecond acoustics. A heterostructure sample was prepared consisting of layers of hexagonal boron nitride (hBN) sandwiching a thin layer of black phosphorus (BP), within which a strain pulse was generated by photoexcitation and observed with an optical probe in the BP layer. The strain pulse traverses to the few nanometer thick hBN layers, where it propagates to the edge and echoes back, like acoustic waves in Newton’s cradle. The echoes returning to the BP layer provide information on the frequency-dependent time-of-flight and group velocity dispersion of the sample system. The microscopic origin of the photoinduced strain pulse generation and its propagation is revealed from first principles. Phonon frequency combs observed in the Fourier transform spectrum confirm the strain wave round trips and demonstrate the feasibility of determining group velocity dispersion through photoacoustics.

This case is based on an article that considered the problems that would arise if a person were to cross over into a mirror-image environment (Yee 2002). Some of the stereochemistry problems posed in that article are woven into this case study. (Contains 8 figures.)

Abstract Halogenation of pyrrole requires strong electrophilic reagents and often leads to undesired polyhalogenated products. Biocatalytic halogenation is a highly attractive approach given its chemoselectivity and benign reaction conditions. While there are several reports of enzymatic phenol and indole halogenation in organic synthesis, corresponding reports on enzymatic pyrrole halogenation have been lacking. Here we describe the in vitro functional and structural characterization of PrnC, a flavin-dependent halogenase that can act on free-standing pyrroles. Computational modeling and site mutagenesis studies identified three key residues in the catalytic pocket. A moderate resolution map using single-particle cryogenic electron microscopy reveals PrnC to be a dimer. This native PrnC can halogenate a library of structurally diverse pyrrolic heterocycles in a site-selective manner and be applied in the chemoenzymatic synthesis of a chlorinated analog of the agrochemical fungicide Fludioxonil.

This article describes the projects on solar hydrogen powered vehicles using water as fuel conducted by teams at Brooklyn Technical High School. Their investigations into the pure and applied chemical thermodynamics of hydrogen fuel cells and bio-inspired devices have been consolidated in a new and emerging sub-discipline that they define as solar hydrogen electric bio-mimetic energetics. They have designed and are developing the following autonomous or remote-controlled/bio-inspired devices: (1) Remote Controlled Hovercraft; (2) Air Sampling Craft; (3) Tranquilizing Dart Projector; (4) Autonomous Buoyant Micro-power Plant; (5) Remote Controlled Electric Water Sampling Boat; and (6) Inflatable Electric Kite. A short description of each device is given.

Previous conventional mist devices can induce a detrimental effect of leaf burn by intense, focused sunlight in summer. A mist generator is designed to prevent particulate matter (PM) damage to trees by combining mist with PM during high PM episodes. We measured changes in microclimate conditions and the concentration of PM before, during, and after mist spraying in urban parks (Yangjae Citizen Forest, YCF; Cheongdam Road Park, CRP) from May 6 to 8, 2020. PM changes in YCF and CRP were observed immediately after mist spraying and were found to return to the previous concentrations. Mist spraying had no significant effects on the meteorological traits of air temperature, humidity, and wind speed but had significant effects on the concentration of PMx and the ratio of PM during a short time. Also, the ratio of PMx was partially affected by mist spraying. During the morning rush hour and lunch, mist, high wind speed, and low relative humidity conditions were related to the increase in mist movement, resulting in increasing PM (2.5–10 μm) and the deposition of these PM. During the evening rush hour, high relative humidity and low wind speed affected PM concentrations more than mist. This prototype of mist spraying could effectively condense and deposit the PM during high PM episodes.

Nanocellulose (CNF) has emerged as a promising alternative to synthetic petroleum-based polymers, but the conventional preparation process involves multiple tedious steps, heavily dependent on chemical input, and proves cost-inefficient. This study presented an, in situ ultrasound-assisted extraction using deep eutectic solvent (DES) based on choline chloride and oxalic acid for more facile production of CNF from raw durian husk fibers. FESEM analysis confirmed the successful extraction of web-like nanofibril structure with width size ranging from 18 to 26 nm. Chemical composition analysis and FTIR revealed the selective removal of lignin and hemicellulose from the raw fiber. As compared to post-ultrasound treatment, in situ ultrasound-assisted extraction consistently outperforms, yielding a higher CNF yield with finer fiber width and significantly reduced lignin content. Integrating this eco-friendly in situ ultrasonication-assisted one-pot extraction method with a 7.5 min interval yielded the highest CNF yield of 58.22 % with minimal lignin content. The superior delignification ability achieved through the proposed in situ ultrasound-assisted protocol surpasses the individual efficacy of DES and ultrasonication processes, neither of which yielded CNF in our experimental setup. This single-step fabrication process significantly reduces chemical usage and streamlines the production steps yielding web-structured CNF that is ideal for sustainable application in membrane and separator.

The feasibility of the laboratory production of copper metal from a readily available, naturally occurring mineral malachite utilizing techniques that are consistent with the time period of around 4000 B.C.E. is presented. The starting materials are inexpensive and convenient and the procedure involves no hazardous reagents and produces no hazardous wastes, thus representing a safe and compelling introduction to metallurgy in the laboratory.

This paper proposes a model-based method for real-time automatic mood estimation in video sequences. The approach is customized by learning the person’s specific facial parameters, which are transformed into facial Action Units (AUs). A model mapping for mood representation is used to describe moods in terms of the PAD space: Pleasure, Arousal, and Dominance. From the intersection of these dimensions, eight octants represent fundamental mood categories. In the experimental evaluation, a stimulus video randomly selected from a set prepared to elicit different moods was played to participants, while the participant’s facial expressions were recorded. From the experiment, Dominance is the dimension least impacted by facial expression, and this dimension could be eliminated from mood categorization. Then, four categories corresponding to the quadrants of the Pleasure–Arousal (PA) plane, “Exalted”, “Calm”, “Anxious” and “Bored”, were defined, with two more categories for the “Positive” and “Negative” signs of the Pleasure (P) dimension. Results showed a 73% of coincidence in the PA categorization and a 94% in the P dimension, demonstrating that facial expressions can be used to estimate moods, within these defined categories, and provide cues for assessing users’ subjective states in real-world applications.

While fluorescent sensors have been developed for monitoring metal ions in health and diseases, they are limited by the requirement of an excitation light source that can lead to photobleaching and a high autofluorescence background. To address these issues, bioluminescence resonance energy transfer (BRET)-based protein or small molecule sensors have been developed; however, most of them are not highly selective nor generalizable to different metal ions. Taking advantage of the high selectivity and generalizability of DNAzymes, we report herein DNAzyme-based ratiometric sensors for Zn2+ based on BRET. The 8-17 DNAzyme was labeled with luciferase and Cy3. The proximity between luciferase and Cy3 permitted BRET when coelenterazine, the substrate for luciferase, was introduced. Adding samples containing Zn2+ resulted in a cleavage of the substrate strand, causing dehybridization of the DNAzyme construct, thus increasing the distance between Cy3 and luciferase and changing the BRET signals. Using these sensors, we detected Zn2+ in serum samples and achieved Zn2+ detection with a smartphone camera. Moreover, since the BRET pair is not the component that determines the selectivity of the sensors, this sensing platform has the potential to be adapted for the detection of other metal ions with other metal-dependent DNAzymes.

Cancer, also known as malignant tumour or neoplasm, is a leading cause of death worldwide. One distinct feature from normal cells is that cancerous cells often overexpress protein on the cell membrane—for instance, the overexpression of human epidermal growth factor receptor 2. The expression of a specific protein on the cancerous cell surface acts as a marker that differentiates the normal cell and facilitates the recognition of cancerous cells. An emerging anticancer treatment, Antibody–Drug Conjugates (ADCs), utilises this unique feature to kill cancerous cells. ADCs consist of an antibody linked with a cytotoxic payload, mainly targeting the antigen found on cancerous cells. This design can increase the specificity in delivering the cytotoxin to the drug target, thus increasing the drug efficacy and reducing the side effect of cancer treatment due to off-target toxicities. There are tremendous quantities of clinical trials conducted to evaluate the safety and effectiveness of this magic drug in treating different types of cancers. However, only 12 ADCs have been approved by the FDA until now. This review provides the principles of ADCs and highlights the ADCs that FDA has approved. In addition, some of the ADCs that undergo clinical trials are discussed in this review. The application of computational techniques in addressing ADCs’ challenges and neoantigen-targeted cancer vaccines is also highlighted. Although ADCs have been seen as promising magic drugs in cancer treatment, the problems such as toxicity, the stability of the linker, the specificity of an antibody with antigen, and so on, remain a challenge in developing ADCs.

In this study, the photoelectric properties of a complete series of GaS1−xSex (0 ≤ x ≤ 1) layered crystals are investigated. The photoconductivity spectra indicate a decreasing bandgap of GaS1−xSex as the Se composition x increases. Time-resolved photocurrent measurements reveal a significant improvement in the response of GaS1−xSex to light with increasing x. Frequency-dependent photocurrent measurements demonstrate that both pure GaS crystals and GaS1−xSex ternary alloy crystals exhibit a rapid decrease in photocurrents with increasing illumination frequency. Crystals with lower x exhibit a faster decrease in photocurrent. However, pure GaSe crystal maintains its photocurrent significantly even at high frequencies. Measurements for laser-power-dependent photoresponsivity and bias-voltage-dependent photoresponsivity also indicate an increase in the photoresponsivity of GaS1−xSex as x increases. Overall, the photoresponsive performance of GaS1−xSex is enhanced with increasing x, and pure GaSe exhibits the best performance. This result contradicts the findings of previous reports. Additionally, the inverse trends between bandgap and photoresponsivity with increasing x suggest that GaS1−xSex-based photodetectors could potentially offer a high response and wavelength-selectivity for UV and visible light detection. Thus, this work provides novel insights into the photoelectric characteristics of GaS1−xSex layered crystals and highlights their potential for optoelectronic applications.

Abstract Multivitamin tablet certified reference material (CRM, 108-10-019) was developed for the analysis of seven water-soluble vitamins, including thiamine, riboflavin, nicotinamide, pantothenic acid, pyridoxine, biotin, and folic acid. The CRM was prepared in powder form by grinding multivitamin tablets and then mixing, sieving, and bottling the powder. For the certification of each water-soluble vitamin, the isotope dilution mass spectrometry based on the liquid chromatography was applied. The methods for each analyte were validated by confirming the repeatability and reproducibility and by comparing with other CRMs. The property values and uncertainties for the vitamins were determined with 10 units from sample stored at − 20 °C. The homogeneity of each certified component was also examined in the range of 0.48–2.2%. All certified values for the seven water-soluble vitamins were stable for 3 or 6 years after the initial certification under storage conditions at − 20 °C. For fat-soluble vitamins, including retinol, α-tocopherol, cholecalciferol, and phylloquinone, two expert laboratories participated in analyses based on official methods, and the mean values of the reported results were assigned as reference values. The multivitamin tablet CRM (108-10-019) will be useful for validating analytical methods and for ensuring the quality of results for vitamin analysis in multivitamin tablets or similar products.

Abstract In this study, we investigated Ni2+, Zn2+, and Co2+ mineralogical incorporation and its effect on green rust transformation to magnetite. Mineral transformation experiments were conducted by heating green rust suspensions at 85 °C in the presence of Ni2+, Zn2+, or Co2+ under strict anoxic conditions. Transmission electron microscopy and powder X-ray diffraction showed the conversion of hexagonal green rust platelets to fine grained cubic magnetite crystals. The addition of Ni2+, Zn2+, and Co2+ resulted in faster rates of mineral transformation. The conversion of green rust to magnetite was concurrent to significant increases in metal uptake, demonstrating a strong affinity for metal sorption/co-precipitation by magnetite. Dissolution ratio curves showed that Ni2+, Zn2+, and Co2+ cations were incorporated into the mineral structure during magnetite crystal growth. The results indicate that the transformation of green rust to magnetite is accelerated by metal impurities, and that magnetite is a highly effective scavenger of trace metals during mineral transformation. The implications for using diagenetic magnetite from green rust precursors as paleo-proxies of Precambrian ocean chemistry are discussed. Graphical Abstract

Information security has become a potential prospect that ensures information cannot be breached throughout the process of delivery while being exchanged over the Internet [...]

Due to a heightened interest in the field of earthquakes after two moderately sized earthquakes occurred in Gyeongju and Pohang, this study explores which ground motion prediction equations are compatible for the South Korea region. Due to data availability, ground motions from five earthquakes of moderate magnitude were used for comparing against selected ground motion models. Median rotated response spectral ordinates at a period of 0.2 s were extracted from these ground motions, which served as a basis for comparison. Twelve ground motion models were considered from the Next Generation Attenuation West, West2, and East programs due to their extensive databases and robust analytical techniques. A comparison of relative residuals, z-score, and each event found that the subset of Next Generation Attenuation—East ground motion prediction equations did not perform as well as the suite of Next Generation Attenuation—West2 ground motion prediction equations, most likely due to the regional simulations involved in developing the database. Interestingly, the ground motion models that performed relatively well were from the set designed for rock conditions.

Sonodynamic therapy (SDT) emerges as a promising non-invasive alternative for eradicating malignant tumours. However, its therapeutic efficacy remains limited due to the lack of sonosensitisers with high potency and biosafety. Previously, gold nanorods (AuNRs) have been extensively studied for their applications in photodynamic or photothermal cancer therapy, but their sonosensitising properties are largely unexplored. Here, we reported the applicability of alginate-coated AuNRs (AuNRsALG) with improved biocompatibility profiles as promising nanosonosensitisers for SDT for the first time. AuNRsALG were found stable under ultrasound irradiation (1.0 W/cm2, 5 min) and maintained structural integrity for 3 cycles of irradiation. The exposure of the AuNRsALG to ultrasound irradiation (1.0 W/cm2, 5 min) was shown to enhance the cavitation effect significantly and generate a 3 to 8-fold higher amount of singlet oxygen (1O2) than other reported commercial titanium dioxide nanosonosensitisers. AuNRsALG exerted dose-dependent sonotoxicity on human MDA-MB-231 breast cancer cells in vitro, with ∼ 81% cancer cell killing efficacy at a sub-nanomolar level (IC50 was 0.68 nM) predominantly through apoptosis. The protein expression analysis showed significant DNA damage and downregulation of anti-apoptotic Bcl-2, suggesting AuNRsALG induced cell death through the mitochondrial pathway. The addition of mannitol, a reactive oxygen species (ROS) scavenger, inhibited cancer-killing effect of AuNRsALG-mediated SDT, further verifying that the sonotoxicity of AuNRsALG is driven by the production of ROS. Overall, these results highlight the potential application of AuNRsALG as an effective nanosonosensitising agent in clinical settings.

Abstract Due to the widespread emergence of COVID-19, face masks have become a common tool for reducing transmission risk between people, increasing the need for sterilization methods against mask-contaminated microorganisms. In this study, we measured the efficacy of ultraviolet (UV) laser irradiation (266 nm) as a sterilization technique against Bacillus atrophaeus spores and Escherichia coli on three different types of face mask. The UV laser source demonstrated high penetration of inner mask layers, inactivating microorganisms in a short time while maintaining the particle filtration efficiency of the masks. This study demonstrates that UV laser irradiation is an efficient sterilization method for removing pathogens from face masks.

The construction industry, characterized by its intricate network of stakeholders and diverse workforce, grapples with the challenge of managing information effectively. This study delves into this issue, recognizing the universal importance of safeguarding data, particularly amid rising concerns around unauthorized access and breaches. Aiming to harness the potential of blockchain technology to address these challenges, this study used hypothetical biographical and safety data of construction workers securely stored on a Hyperledger Fabric blockchain. Developed within the Amazon Web Services (AWS) cloud platform, this blockchain infrastructure emerged as a robust solution for enhancing data security and privacy. Anchored in the core principles of data security, the model emerges as a potent defender against the vulnerabilities of traditional data management systems. Beyond its immediate implications, this study exemplifies the marriage of blockchain technology and the construction sector, and its potential for reshaping workforce management, especially in high-risk projects and optimizing risk assessment, resource allocation, and safety measures to mitigate work-related injuries. Practical validation through transaction testing using Hyperledger Explorer validates the model’s feasibility and operational effectiveness, thus serving as a blueprint for the industry’s data management. Ultimately, this research not only showcases the promise of blockchain technology in addressing construction data security challenges but also underscores its practical applicability through comprehensive testing, thus heralding a new era of data management that harmonizes security and efficiency for stakeholders’ benefit.

Understanding complex carbonate fracture networks and karstification at various geological scales is challenging, especially with limited multi-scale datasets. This paper aims to reduce uncertainty in the fracture architecture of Central Luconia karstified reservoirs by narrowing observational gaps between seismic and well data by using the discrete fracture models of exposed limestone outcrops as analogues for the subsurface carbonate reservoir. An outcrop-based fracture network characterisation of a near-surface paleo-karst at Subis Limestone combined with lineament analysis was conducted to extract fracture parameters. The karst structure was first delineated using a digital elevation map and outcrop examination. Then, topology analysis was performed, following the creation of two-dimensional discrete fracture models. Two main fracture sets oriented northeast–southwest and northwest–southeast and 79 potential dolines were identified. Fracture intersections, northeast–southwest major orientations, and drainage systems highly influenced the karst features. The Subis Limestone fracture model revealed that the highest number of fractures and total length of fractures were concentrated in the northern part of the Subis Limestone build-up (X: 250–350, Y: 150–250) and became denser towards the northwest direction of the outcrop (X: 600–800). The fractures in the Subis paleo-karsts appear isolated, with I-nodes ranging from 0.74 to 0.94. Hence, it is crucial to incorporate matrix porosity into multiple scales of fracture network modelling to improve upscaling and the modelling of fracture–vug networks, as well as to minimise the underestimation of discrete fracture networks in fractured and karstified limestone.

Grout voids in the tendons of a post-tensioning bridge reduce their strength. Grout voids are also severe flaws causing corrosion of the steel strands in the tendons. Detecting voids during construction and operation of the tendons is essential to prevent tendon failure, which is critical to bridge safety. This study presents a method for inspecting external tendons for voids in the grout below the protective duct pipe using terahertz electromagnetic waves. Due to low attenuation in the high-density polyethylene duct and the large reflectivity difference between the duct/grout and the duct/void interfaces, terahertz waves are suitable for detecting voids in the grout inside tendons. For this study, we developed a mobile frequency-domain terahertz A-scanner that can be used to measure terahertz A-scan data in real time. It is shown that the mobile terahertz A-scanner can be used to assess the area of the grout void in external bridge tendons.

Biosurfactants have been used in various industries due to their high surface activity, high biodegradability and low toxicity. However, the applications of biosurfactants are still limited due to their production and cost. This work aimed to determine the viability of palm kernel fatty acid distillate (PKFAD) as an alternative substrate for biosurfactant production using locally isolated Pseudomonas sp. LM19. Optimum conditions for biosurfactant production and characteristics of produced biosurfactants were studied. The results showed a 3.2-fold increase in biosurfactant concentration under optimum conditions: 2% (v/v) of PKFAD, pH 7.5, 170 rpm and 192 h incubation time, producing 1.6 g/L of biosurfactant. The produced biosurfactant was capable of reducing the surface tension to 27.7 mN/m with a critical micelle concentration (CMC) of 28 mg/L. Thin-layer chromatography showed presence of both lipid and sugar moieties, thus indicating the produced biosurfactant was glycolipid. Gas chromatography-mass spectrometry recorded the presence of rhamnolipid precursors, thereby revealing that the glycolipid produced was rhamnolipid. High-performance liquid chromatography determined the rhamnolipids produced was a combination of mono-rhamnolipids and di-rhamnolipids. The lipid moiety of both rhamnolipids produced boasted C10-C10 lipid chain majority. To conclude, PKFAD could be a potential substrate for biosurfactant production and add value to the industry.

Ultrasound-assisted solvent extraction (UAE) was applied to extract underutilized Madhuca longifolia seed oil. The effect of extraction time, temperature, solvent type, solvent/sample ratio, and amplitude on the oil yield and recovery were investigated. Approximately 56.97% of oil yield and 99.54% of oil recovery were attained using mild conditions of 35 min, 35 °C, 40% amplitude, isopropanol to acetone (1:1), and solvent to sample (20 mL/g). UAE oil yield and recovery were comparable with Soxhlet extraction (SXE) whilst mechanical pressing (ME) yielded

Camptothecin derivatives are precursors of potent anticancer agents, but their biosynthesis remains largely unknown. Here two cytochrome P450 monooxygenases are shown to regiospecifically oxidize camptothecin, yielding 10- and 11- hydroxylated derivatives, which are subsequently used to produce a suite of known anticancer drugs and derivatives.

With rising consumer demand for natural products, a greener and cleaner technology, i.e., ultrasound-assisted extraction, has received immense attention given its effective and rapid isolation for nanocellulose compared to conventional methods. Nevertheless, the application of ultrasound on a commercial scale is limited due to the challenges associated with process optimization, high energy requirement, difficulty in equipment design and process scale-up, safety and regulatory issues. This review aims to narrow the research gap by placing the current research activities into perspectives and highlighting the diversified applications, significant roles, and potentials of ultrasound to ease future developments. In recent years, enhancements have been reported with ultrasound assistance, including a reduction in extraction duration, minimization of the reliance on harmful chemicals, and, most importantly, improved yield and properties of nanocellulose. An extensive review of the strengths and weaknesses of ultrasound-assisted treatments has also been considered. Essentially, the cavitation phenomena enhance the extraction efficiency through an increased mass transfer rate between the substrate and solvent due to the implosion of microbubbles. Optimization of process parameters such as ultrasonic intensity, duration, and frequency have indicated their significance for improved efficiency.

The rapid advancement of information technology (IT) has given rise to a new era of efficient and fast communication and transactions. However, the increasing adoption of and reliance on IT has led to the exposure of personal and sensitive information online. Safeguarding this information against unauthorized access remains a persistent challenge, necessitating the implementation of improved computer security measures. The core objective of computer security is to ensure the confidentiality, availability, and integrity of data and services. Among the mechanisms developed to counter security threats, authentication stands out as a pivotal defense strategy. Graphical passwords have emerged as a popular authentication approach, yet they face vulnerability to shoulder-surfing attacks, wherein an attacker can clandestinely observe a victim’s actions. Shoulder-surfing attacks present a significant security challenge within the realm of graphical password authentication. These attacks occur when an unauthorized individual covertly observes the authentication process of a legitimate user by shoulder surfing the user or capturing the interaction through a video recording. In response to this challenge, various methods have been proposed to thwart shoulder-surfing attacks, each with distinct advantages and limitations. This study thus centers on reviewing the resilience of existing recognition-based graphical password techniques against shoulder-surfing attacks by conducting a comprehensive examination and evaluation of their benefits, strengths, and weaknesses. The evaluation process entailed accessing pertinent academic resources through renowned search engines, including Web of Science, Science Direct, IEEE Xplore, ProQuest, Scopus, Springer, Wiley Online Library, and EBSCO. The selection criteria were carefully designed to prioritize studies that focused on recognition-based graphical password methods. Through this rigorous approach, 28 studies were identified and subjected to a thorough review. The results show that fourteen of them adopted registered objects as pass-objects, bolstering security through object recognition. Additionally, two methods employed decoy objects as pass-objects, enhancing obfuscation. Notably, one technique harnessed both registered and decoy objects, amplifying the security paradigm. The results also showed that recognition-based graphical password techniques varied in their resistance to different types of shoulder-surfing attacks. Some methods were effective in preventing direct observation attacks, while others were vulnerable to video-recorded and multiple-observation attacks. This vulnerability emerged due to attackers potentially extracting key information by analyzing user interaction patterns in each challenge set. Notably, one method stood out as an exception, demonstrating resilience against all three types of shoulder-surfing attacks. In conclusion, this study contributes to a comprehensive understanding of the efficacy of recognition-based graphical password methods in countering shoulder-surfing attacks by analyzing the diverse strategies employed by these methods and revealing their strengths and weaknesses.

Even though transition metals can activate Oxone to degrade toxic contaminants, bimetallic materials possess higher catalytic activities because of synergistic effects, making them more attractive for Oxone activation. Herein, nanoscale CuCo-bearing N-doped carbon (CuCoNC) can be designed to afford a hollow structure as well as CuCo species by adopting cobaltic metal organic frameworks as a template. In contrast to Co-bearing N-doped carbon (CoNC), which lacks the Cu dopant, CuCo alloy nanoparticles (NPs) are contained by the Cu dopant within the carbonaceous matrix, giving CuCoNC more prominent electrochemical properties and larger porous structures and highly nitrogen moieties. CuCoNC, as a result, has a significantly higher capability compared to CoNC and Co3O4 NPs, for Oxone activation to degrade a toxic contaminant, Rhodamine B (RDMB). Furthermore, CuCoNC+Oxone has a smaller activation energy for RDMB elimination and maintains its superior effectiveness for removing RDMB in various water conditions. The computational chemistry insights have revealed the RDMB degradation mechanism. This study reveals that CuCoNC is a useful activator for Oxone to eliminate RDMB.

Amitriptyline residue released into the aquatic ecosystem can have detrimental consequences on marine organisms and human wellbeing via consumption of polluted water. With a uniquely large surface area and abundant functionalities, graphene oxide adsorption offers a remediation solution for such water pollution. This study focused on synthesizing a novel graphene-based adsorbent via ice-templating of boron-doped graphene substrate. The batch adsorption performance of the as-synthesized adsorbent was explored by central composite design (CCD), while its potential large-scale application was evaluated with a packed-bed column study. The CCD optimized conditions of 12.5 mg dosage, 32 min adsorption time, 30 °C operating temperature and 70 ppm concentration produced the highest removal efficiency of 87.72%. The results of the packed-bed study indicated that continuous adsorption of amitriptyline was best performed at a graphene bed of 3.5 cm in height, with 100 ppm of the pharmaceutical solution flowing at 2 mL/min. Furthermore, the breakthrough curve was effectively portrayed by the Log Bohart–Adams model. The as-synthesized adsorbent showed a high regeneration potential using ethanol eluent via multiple adsorption–desorption cycles. The results suggest the boron-doped graphene adsorbent in packed-bed as a highly effective system to remediate amitriptyline in an aqueous environment.

This study aims to investigate a new shear reinforcement method which utilizes thin mild steel (TMS) plates as shear reinforcement in deep beams to replace conventional reinforcement. Thirteen reinforced concrete deep beam specimens with three different plate thicknesses and four varying perforated hole arrangements on the TMS plates were experimentally tested to determine the load-carrying capacity and crack pattern. The experimental results indicate that the 2.0 mm thick TMS plate has the highest load-carrying capacity. Among the four different hole arrangements on the TMS plates, the perforated plates with a three-column hole arrangement show the best performance in terms of load-carrying capacity, with a 2.9% increment against the control beam specimen. The specimens also demonstrated compatible elastic stiffness with the control beam that used conventional shear links. This shows that TMS plates have the potential to replace conventional shear links in deep beams. This proposed method also changed the failure mode from conventional diagonal shear tension failure to a combination of flexural failure and shear deformation. A numerical model was developed and was found to have a good correlation with the experimental results, demonstrating potential for use in future parametric investigations on deep beams and cost reduction in future experimental work.

Abstract Metal contacts to two-dimensional (2D) semiconductors are often plagued by the strong Fermi level pinning (FLP) effect which reduces the tunability of the Schottky barrier height (SBH) and degrades the performance of 2D semiconductor devices. Here, we show that MoSi2N4 and WSi2N4 monolayers—an emerging 2D semiconductor family with exceptional physical properties—exhibit strongly suppressed FLP and wide-range tunable SBH. An exceptionally large SBH slope parameter of S ≈ 0.7 is obtained which outperforms the vast majority of other 2D semiconductors. Such intriguing behavior arises from the septuple-layered morphology of MoSi2N4 and WSi2N4 monolayers in which the semiconducting electronic states are protected by the outlying Si–N sublayer. We identify Ti, Sc, and Ni as highly efficient Ohmic contacts to MoSi2N4 and WSi2N4 with zero interface tunneling barrier. Our findings reveal the potential of MoSi2N4 and WSi2N4 as a practical platform for designing high-performance and energy-efficient 2D semiconductor electronic devices.

Chatbots have become increasingly popular in recent years, but they also present security risks and vulnerabilities that need to be addressed. This systematic literature review examines the existing research relating to information security in chatbots, identifying the potential threats, proposed solutions, and future directions for research. The review finds that chatbots face various security threats, including malicious input, user profiling, contextual attacks, and data breaches, and that solutions such as blockchain technology, end-to-end encryption, and organizational controls can be used to mitigate these concerns. The review also highlights the importance of maintaining user trust and addressing privacy concerns for the successful adoption and continued use of chatbots. A taxonomy developed in this review provides a useful framework for categorizing the articles and their findings. The review concludes by identifying future research directions that include developing more sophisticated authentication and authorization mechanisms, exploring the use of privacy-enhancing technologies, and improving the detection and prevention of security threats, among others. This review contributes to the growing body of literature on information security in chatbots and can guide future research and practice in this field.

In today’s increasingly connected world, the demand for secure computing and data protection is soaring [...]

Existing routes to dibenzofurans have intrinsic regioselectivity, limiting the substitution patterns available in the products. Here a double 1,4-conjugate addition-annulation cascade between propargylamines and imidazolium methylides provides direct access to dibenzofurans with a complementary substitution pattern.

A 16-month (July 2018–October 2019) dataset of size-resolved aerosol composition is used to examine the sources and characteristics of five organic acids (oxalate, succinate, adipate, maleate, phthalate) and methanesulfonate (MSA) in Metro Manila, Philippines. As one of the most polluted megacities globally, Metro Manila offers a view of how diverse sources and meteorology impact the relative amounts and size distributions of these species. A total of 66 sample sets were collected with a Micro-Orifice Uniform Deposit Impactor (MOUDI), of which 54 sets were analyzed for composition. Organic acids and MSA surprisingly were less abundant than in other global regions that are also densely populated. The combined species accounted for an average of 0.80 ± 0.66 % of total gravimetric mass between 0.056 and 18 µm, still leaving 33.74 % of mass unaccounted for after considering black carbon and water-soluble ions and elements. The unresolved mass is suggested to consist of non-water-soluble metals as well as both water-soluble and non-water-soluble organics. Oxalate was approximately an order of magnitude more abundant than the other five species (149 ± 94 ng m−3 versus others being < 10 ng m−3) across the 0.056–18 µm size range. Both positive matrix factorization (PMF) and correlation analysis are conducted with tracer species to investigate the possible sources of organic acids and MSA. Enhanced biomass burning influence in the 2018 southwest monsoon resulted in especially high levels of submicrometer succinate, MSA, oxalate, and phthalate. Peculiarly, MSA had negligible contributions from marine sources but instead was linked to biomass burning and combustion. Enhanced precipitation during the two monsoon seasons (8 June–4 October 2018 and 14 June–7 October 2019) coincided with a stronger influence from local emissions rather than long-range transport, leading to notable concentration enhancements in both the sub- and supermicrometer ranges for some species (e.g., maleate and phthalate). While secondary formation via gas-to-particle conversion is consistent with submicrometer peaks for the organic acids and MSA, several species (i.e., phthalate, adipate, succinate, oxalate) exhibited a prominent peak in the coarse mode, largely owing to their association with crustal emissions (i.e., more alkaline aerosol type) rather than sea salt. Oxalate's strong association with sulfate in the submicrometer mode supports an aqueous-phase formation pathway for the study region. However, high concentrations during periods of low rain and high solar radiation suggest photo-oxidation is an important formation pathway.