Search Results (249)

The design and implementation of a dynamic frequency sweeping algorithm for a 3 kW RF power source are underpinned by theoretical principles aimed at optimizing impedance matching under pulse-mode operation. The algorithm dynamically adjusts the output frequency within a predefined range to align the source impedance Z_source with the conjugate of the load impedance Z*_load, maximizing the power transfer efficiency and minimizing the reflection coefficient Γ. This is achieved by leveraging the maximum power transfer theorem and adapting to dynamic load variations, such as those induced by the plasma state transitions. The algorithm incorporates adaptive step size adjustments based on the rate of change of Γ, predictive frequency initialization using historical data, and real-time impedance monitoring to ensure efficient convergence within the constrained pulse “ON” time (TON). Integration with pulse mode requires synchronization with the pulse signal, fast convergence, and optimized search strategies. Experimental validation on a 13.56 MHz, 3 kW Automatic Sweep Generator testbed operating at 20 kHz pulse modulation with a 50% duty cycle demonstrates a linear and stable sweep, achieving impedance matching and low reflected power within 5.0172 ms. These findings highlight the algorithm’s potential for high-precision applications, such as RF plasma excitation, and underscore the importance of adaptive techniques in dynamic RF systems. Full article

Extraintestinal pathogenic Escherichia coli (ExPEC) poses escalating threats to human and veterinary health amid rising antimicrobial resistance. We isolated a highly virulent ExPEC strain RZ-13 (ST345, O134:H21) from diarrheic calves at a large beef cattle farm in Rizhao City, and conducted whole genome sequencing, conjugation experiments, and antimicrobial susceptibility testing to elucidate its genomic architecture and resistance mechanisms. The RZ-13 genome comprises one chromosome and four plasmids. The chromosome harbors virulence factors for adhesion, invasion, biofilm formation, and iron acquisition. Notably, plasmids pRZ13-1 (265,777 bp, IncHI2-IncHI2A) and pRZ13-3 (74,304 bp, IncFII) carry the majority of resistance genes. Plasmid pRZ13-1 carries 25 resistance genes, including bla_CTX-M-55, floR, qnrS1, sul3, and tet(A), as well as a complete tellurite resistance gene cluster, terABCDEFZY1. Its multidrug resistance (MDR) region features an IS26-mediated tandem amplification and an approximately 29 kb inverted structure. Comparative analysis indicated that the MDR region carried by this plasmid is highly prevalent in both animal-derived and human-derived isolates. Plasmid pRZ13-3 harbors an IS91-mediated mobile region that integrates both antimicrobial resistance and stress adaptation genes, which have been repeatedly identified in plasmids from diverse sources, including animals and humans. Conjugation experiments confirmed both pRZ13-1 and pRZ13-3 plasmids are self-transmissible and confer multidrug-resistant phenotypes to recipient strains, with pRZ13-3 exhibiting an exceptionally high transfer frequency of 8.9 × 10⁻², substantially exceeding that of previously reported IncFII plasmids. These findings demonstrate that pRZ13-1 and pRZ13-3 serve as critical vehicles for resistance dissemination through complex mobile genetic element structures and efficient horizontal transfer, highlighting the urgent need for surveillance of livestock-reservoir ExPEC to mitigate public health risks. Full article

Drought and salinity are among the most severe abiotic stresses limiting global agricultural productivity, and their frequency and intensity are expected to increase under ongoing climate change. Concurrently, the growing human population necessitates the development of crop varieties that combine high yield with enhanced stress tolerance. Jasmonates, including jasmonic acid (JA) and its derivatives, play pivotal roles in plant responses to abiotic stresses and are widely regarded as stress hormones. The bioactive conjugate jasmonoyl-isoleucine (JA-Ile) acts as a ligand for the coronatine insensitive 1 (COI1) receptor. Jasmonates regulate essential physiological processes, including leaf senescence, secondary metabolism, and nutrient homeostasis, which collectively contribute to plant adaptation to drought and salinity stress. In this review, we summarize recent advances in understanding the role of jasmonate signaling in plant responses to drought and salinity, with particular emphasis on the initiation and progression of leaf senescence and chlorophyll degradation pathways. By integrating genetic, biochemical, and physiological evidence, we discuss how targeted modulation of jasmonate levels and signaling components may be exploited to breed or engineer crops with improved tolerance to water-deficit and saline conditions. Full article

Composite integrative and conjugative elements (ICEs) frequently mediate the co-transfer of multiple antibiotic resistance genes during horizontal gene transfer, but their formation mechanisms remain unclear. This study investigated the site-specific integration of Tn1806 into ICESa2603-family ICEs in Streptococcus agalactiae by conjugation experiments. PCR screening of 161 S. agalactiae clinical isolates identified potential Tn1806-like ICE carriers; whole-genome sequencing was performed to further characterize the macrolide-resistance isolates from this group. PCR detection resulted in 24 carrying Tn1806-like ICEs being found, five of which were macrolide-resistant. Genomic analysis for these five revealed distinct Tn1806-like ICEs (ICESag16, ICESag57, ICESag139, ICESag167, and ICESag220), three of which were found nested within another ICE (ICESpy009, an ICESa2603-family ICE). Conjugation experiments confirmed ICESag167 could integrate into the snf2 (methyltransferase containing a SNF2 helicase domain) of ICESpy009 in recipient cells, generating a composite ICE. Re-conjugation verified the transferability of composite ICE at low frequencies (8.63 × 10⁻⁸), during which some nested ICESag167 were excised and transferred independently. This work provides first experimental evidence supporting Tn1806 nesting within another ICE as a mechanism for resistance accumulation and mobile element evolution in S. agalactiae. The spread of such composite ICEs may confer multiple forms of resistance to new hosts, challenging infection treatment and raising public health concerns. Full article

Background/Objectives: Plasmids are autonomous DNA molecules that can replicate independently and transfer horizontally between bacterial cells. They play a key role in disseminating adaptive traits, such as antimicrobial resistance and virulence. Our study investigates the fundamental differences between plasmid populations originating from clinical/isolates and environmental/metagenomes. Methods: We compare three distinct plasmid genome datasets—the NCBI Reference Sequence Database (RefSeq), the Integrated Microbial Genomes & Microbiomes system (IMG/PR) from bacterial isolates (I) and microbiomes (M)—to assess how plasmid origin shapes their characteristics, including mobility types, antimicrobial resistance genes (ARGs), virulence genes (VGs) and host taxonomy. Results: We show that plasmids originating from bacterial isolates, more enriched in clinical samples, are fundamentally distinct from recovered from metagenomic data. Plasmids from isolates are larger, enriched in conjugative plasmids and display a higher frequency of ARGs and VGs than the ones assembled from metagenomes. Furthermore, ARGs are more frequently associated with highly mobile plasmids, particularly pCONJ. Conclusions: These findings highlight the importance of plasmid origins in studies of plasmid epidemiology, functional potential and mobility. Full article

Generative artificial intelligence (AI) models including GPT, Gemini, and DeepSeek are reshaping embodied agents, temporal prediction, and autonomous driving, demanding a ten-fold annual growth in training FLOPS that Moore’s law can no longer sustain. Consequently, scale-out GPU clusters require >400 Gb/s lane-rate optical interconnects within AI data-centers (AIDCs). Single-photodiode direct detection offers density, latency, and energy advantages, but DAC bandwidth remains limited to around 70 GHz. We present an optical triple-band multiplexing scheme that replaces high-frequency radio frequency (RF) mixers and local oscillators (LOs) with photonic components. A Mach–Zehnder modulator (MZM) generates 80-GBd PS-PAM-20 signal while an in-phase/quadrature (IQ) modulator driven by a wavelength-offset laser creates two independent 35-GBd PS-64-QAM bands. The proposed optical multiplexing method breaks conjugate symmetry and enhances dispersion tolerance of the direct detection system. After 200 m SSMF transmission and single 70-GHz photodiode (PD) detection, digital signal-signal beating interference (SSBI)/cross-beating compensation enables the recovery of net 543.9 Gb/s signal (line rate of 686.6 Gb/s) using only 45-GHz DACs. The optical multiplexing architecture provides a path to beyond-400 Gb/s lanes and demonstrates a scalable, energy-efficient solution for next-generation AI clusters. Full article

Non-contact heart rate estimation technology based on frequency-modulated continuous wave (FMCW) radar has garnered extensive attention in single-target scenarios, yet it remains underexplored in multi-target environments. Accurate discrimination of multiple targets and precise estimation of their heart rates constitute key challenges in the multi-target domain. To address these issues, we propose a novel scheme for multi-target heart rate estimation. First, a high-precision distance-bin selection (HDBS) method is proposed for target localization in the range domain. Next, multiple-input multiple-output (MIMO) array processing is combined with the Root-multiple signal classification (Root-MUSIC) algorithm for angular domain estimation, enabling accurate discrimination of multiple targets. Subsequently, we propose an efficient method for interference suppression and vital sign extraction that cascades variational mode decomposition (VMD), local mean decomposition (LMD), and wavelet thresholding (WT) termed as VLW, which enables high-quality heartbeat signal extraction. Finally, to achieve high-precision and super-resolution heart rate estimation with low computational burden, an improved fast iterative interpolated beamforming (FIIB) algorithm is proposed. Specifically, by leveraging the conjugate symmetry of real-valued signals, the improved FIIB algorithm reduces the execution time by approximately 60% compared to the standard version. In addition, the proposed scheme provides sufficient signal-to-noise ratio (SNR) gain through low-complexity accumulation in both distance and angle estimation. Six experimental scenarios are designed, incorporating densely arranged targets and front-back occlusion, and extensive experiments are conducted. Results show this scheme effectively discriminates multiple targets in all tested scenarios with a mean absolute error (MAE) below 2.6 beats per minute (bpm), demonstrating its viability as a robust multi-target heart rate estimation scheme in various engineering fields. Full article

The increasing frequency, duration, and intensity of wildfires over the past decade have raised significant concerns about widespread exposure to wildfire smoke. Inhalation of wildfire smoke poses a substantial risk to human health, with epidemiological studies linking exposure to cardiovascular, respiratory, and neurological dysfunction. Wildfire smoke contains hundreds of chemical compounds across diverse classes, with concentrations varying by fuel type and combustion conditions. Phenolic compounds are prominent constituents of wood smoke, and catechol is especially abundant under smoldering conditions that produce dense smoke. In this study, ¹⁴C-labeled catechol was spiked into smoldering eucalyptus wood smoke extract (WSE) and administered to rats via intranasal instillation. Plasma was collected at 5 min and 2 h post-exposure. Samples were analyzed using parallel accelerator and molecular mass spectrometry (PAMMS). Major catechol-derived metabolites identified included benzene oxide, catechol-cysteine conjugate, and catechol-glutamine conjugate; the parent compound was not detected. These results indicate that inhaled catechol in wood smoke is quickly metabolized upon entry into circulation. PAMMS enabled both identification and relative quantification of circulating catechol metabolites, demonstrating feasibility for biomarker discovery and exposure assessment. Full article

BU–MIT whistler wave injection experiments, which were conducted at Arecibo Observatory, started with the joint US–USSR Active Space Plasma Program Experiment on 24 December 1989. In this experiment, a satellite-borne VLF transmitter injected radio waves at the frequency and power of 10 kHz and 10 kW. A series of controlled whistler wave experiments with the Arecibo HF heater were subsequently carried out during 1990–1998 until the HF heater was damaged by Hurricane Georges in 1998. In these ionospheric HF heating experiments, 28.5 kHz whistler waves were launched from the nearby naval transmitter (code-named NAU) located at Aguadilla, Puerto Rico. HF heater waves were used to create ionospheric ducts (in the form of parallel-plate waveguides) to facilitate the entry of NAU whistler waves from the neutral atmosphere into the ionosphere. Conjugate whistler wave propagation experiments were conducted between Arecibo, Puerto Rico and Trelew, Argentina in 1997. After 1999, whistler wave experiments in the absence of an HF heater had been conducted. Naturally-occurring large-scale ionospheric irregularities due to spread F or Traveling Ionospheric Disturbances (TIDs) were relied on to guide NAU launched 40.75 kHz whistler waves to propagate from the ionosphere further into the radiation belts, to cause 390 keV charged-particle precipitation. A train of TIDs, resulting from the 9.2 Mw earthquake off the west coast of Sumatra, Indonesia, was observed in our 26 December 2004 Arecibo experiments, about a day after the earthquake-launched tsunami waves traveled across the Indian Ocean, then into remote parts of the Atlantic Ocean. The author’s recent research efforts, motivated by Arecibo experiments, focus on Solar Powered Microwave Transmitting Systems, to simulate Solar Energy Harvesting via Solar Power Satellite (SPS) (also known as Space Based Solar Power (SBSP)) These experiments involved a large number of the author’s BU and MIT students working on theses and participating in the Undergraduate Research Opportunities Program (UROP), in collaboration with other colleagues at several universities and national laboratories. Full article

We present experimental results related to the features and geophysical conditions for the occurrence of the long-delay echo (LDE) signals in the medium-wave (MW) frequency range observed on 20 January 2025, at the Gor’kovskaya observatory near St. Petersburg (60.27° N, 29.38° E). A total of 19 series of experiments on guiding MF in the magnetosphere were carried out, while LDE signals were only registered on January 20, 2025, in evening hours, when the most disturbed conditions were observed (Kp = 4+, ΣKp = 27−). It was found that the LDE signals, with delay times of 310–322 ms, were observed in the evening hours under disturbed magnetic conditions. In such a case, the MW propagates into the magnetosphere to the magnetically conjugate point, is reflected from the topside ionosphere, and returns. The frequency of sounding signal f_SS exceeded the critical frequency of the F2 layer at Gor’kovskaya observatory foF2_GRK but was less than the critical frequency at the magnetic conjugated point foF2_MCP, foF2_GRK < f_SS < foF2_MCP. The LDE signals were observed in the narrow frequency range from 2100 to 2400 kHz. The background geophysical conditions during the occurrence of LDE signals were analyzed using the CADI ionosonde data and Swarm satellite observations. The plausible generation mechanisms for MW guiding in the magnetosphere are discussed. Full article

Background/Objectives: Single-domain antibodies (sdAbs) are derived from camelid heavy-chain antibodies (HCAb). Their small size, high stability, and ease of production, among other properties, makes them highly valuable in biomedical research and therapeutic development. Several sdAb-based molecules are currently progressing through clinical trials, highlighting their translational relevance. As sdAbs originate from HCAb of Camelidae family, they can originate from multiple species including Vicugna pacos, Lama glama, Camelus dromedarius and Camelus bactrianus. Although several reports and databases analyze the structure of sdAbs, comprehensive evaluations on species-dependent structural differences remain scarce. Methods: We assembled MO-IISA, an open-access curated database of sdAbs with known antigen targets by integrating six public resources (iCAN, INDI, SAbDab-nano, sdAb-DB, PLabDab-nano, NbThermo) under harmonized eligibility criteria. Results: The final dataset comprises 2053 sdAbs derived from llamas (Lama glama, n = 1316); alpacas (Vicugna pacos, n = 325), dromedary camels (Camelus dromedarius, n = 377) and Bactrian camels (Camelus bactrianus, n = 35). We quantified region lengths, amino acid frequency, and conservation/entropy across frameworks (FR1–FR4). The average length of all sdAbs was about 124 ± 8 amino acids, with minor interspecies differences. We observed a consistent enrichment of lysines in FR3 (and secondarily FR2) and cysteines primarily in FR1 and FR3, with non-canonical cysteines more frequent in Bactrian and dromedary sdAbs CDRs. CDR2 and, particularly CDR3, contributed most to inter- and intra-species variability, whereas FRs were highly conserved. Conclusions: Species-neutral framework constraints and species-tuned loop adaptations have practical implications for sdAb engineering, species selection, and conjugation strategies. These features are captured in MO-IISA, an open-access database of known-target sdAbs from different species. Full article

Understanding the molecular determinants of antioxidant activity in natural phenolic compounds is essential for explaining their biological performance and designing new radical scavengers. In this work, the radical-scavenging mechanisms of three major ginger phenolics—6-gingerol (GIN), 6-shogaol (SHO), and 6-paradol (PAR)—were systematically investigated using density functional theory (DFT) thermochemistry at the M06-2X/6-31+G(d,p) level in the gas phase, benzene, and water. Three canonical pathways—hydrogen atom transfer (HAT), single-electron transfer followed by proton transfer (SET–PT), and sequential proton loss–electron transfer (SPLET)—were evaluated through full optimization and frequency calculations at 298.15 K, combined with the SMD solvation model. Frontier molecular orbital (FMO), molecular electrostatic potential (MEP), and quantum theory of atoms in molecules (QTAIM) analyses were employed to correlate electronic structure with reactivity. The results reveal a distinct solvent-dependent mechanistic crossover. In the gas phase and benzene, the low dielectric constant suppresses charge separation, making HAT the thermodynamically dominant pathway. In water, strong stabilization of ionic species lowers both the ionization and deprotonation barriers, allowing SPLET and SET–PT to become competitive or even preferred. Across all media, the phenolic O–H group is the principal reactive site, while the aliphatic O–H of GIN remains inactive. SHO exhibits the most versatile redox profile, combining a highly conjugated α,β-unsaturated chain with favorable charge delocalization; PAR is somewhat less redox-active, while GIN shows intermediate performance governed by intramolecular hydrogen bonding. The assembled thermodynamics for HOO• scavenging confirm that all three phenolics are thermodynamically competent antioxidants (ΔG° ≈ −4 kcal mol⁻¹ in water), with comparable driving forces; electronic descriptors indicate SHO is the most redox-flexible, GIN(phenolic) is moderately and PAR is somewhat less charge-transfer-prone, while GIN(aliphatic) remains inactive. These findings provide a comprehensive structure-to-mechanism correlation for ginger phenolics and establish a predictive framework for solvent-controlled antioxidant behavior in phenolic systems. Full article

Tuberculosis (TB) remains a significant worldwide health challenge due to the limitations of conventional treatments and the rising incidence of drug-resistant Mycobacterium tuberculosis strains. This review consolidates the advancements in nanotechnology-based therapeutics, inhalable formulations, CRISPR–Cas tools, host-directed therapies (HDTs), and nanoparticle-based vaccine development aimed at enhancing TB management. Novel nanocarriers such as liposomes, solid-lipid nanoparticles (SLNs), dendrimers, and polymeric nanoparticles (NPs) offer enhanced bioavailability of drugs, sustained release, as well as targeted delivery to infected macrophages, thereby reducing systemic toxicity and dosing frequency. Inhalable nanomedicines provide localized delivery to the pulmonary site, enhancing the concentration of the drug at the primary site of infection. CRISPR–Cas technology is emerging as a transformative approach to disabling drug-resistant genes and enhancing diagnostic precision. HDTs, including agents like vitamin D and metformin, show potential in modulating host immune responses and enhancing pathogen clearance. Nanoparticle-based vaccines, including mRNA and antigen-conjugated platforms, aim to overcome the limitations of the BCG vaccine by enhancing antigen presentation and eliciting stronger, longer-lasting immunity. Collectively, these modalities mark a shift toward more personalized, effective, and less toxic TB therapies. However, challenges such as regulatory approval, safety, scalability, and accessibility remain. This review highlights the integrated potential of nanomedicine, gene editing, and immunomodulation to transform TB care and combat drug resistance, paving the way for more robust and durable treatment strategies. Full article

The widespread use of plastics has caused severe environmental pollution, driving interest in biodegradable alternatives like polylactic acid (PLA). However, incomplete degradation of biodegradable plastics under natural conditions may generate micro/nanoplastics that could exacerbate ecological risks. This study investigated the combined effects of UV-aged microplastics from biodegradable PLA and conventional PET, along with sulfamethoxazole (SMX), on the conjugative transfer of antibiotic resistance genes (ARGs) between bacteria. Using UV aging to simulate environmental weathering, the microplastic morphology, adsorption behavior, and interaction with SMX were characterized. The study further evaluated the bacterial viability, ROS level, membrane permeability, and the expression of conjugative transfer-related genes to elucidate the underlying mechanisms. Results showed that aged PLA released significantly more nanoplastics and exhibited higher adsorption affinity for SMX than PET. Combined exposure to aged PLA and SMX significantly enhanced ARG transfer frequency by approximately 14.5-fold compared to the control. Mechanistic studies revealed that this promotion was associated with increased intracellular ROS levels, elevated membrane permeability, and upregulation of conjugative related genes. These findings underscore that biodegradable plastics, after environmental aging, may pose greater ecological risks than conventional plastics, and highlight the importance of considering environmental aging in the risk assessment of plastics. Full article

Poly(lactic-co-glycolic acid) (PLGA) sustained-release systems for intra-articular (IA) delivery aim to extend joint residence time and reduce the reinjection frequency of conventional IA therapies. This review synthesizes current understanding of PLGA degradation, the acidic microenvironment inside degrading microspheres, and release behavior in joints, and surveys clinical experience with extended-release corticosteroid depots alongside emerging platforms for nonsteroidal and biologic agents. To situate PLGA within the broader IA field, we briefly summarize selected non-PLGA sustained-release approaches—such as multivesicular liposomes, hyaluronic acid conjugates, and hybrid matrices—to contextualize comparative performance and safety. For proteins and peptides, central barriers include acidification inside degrading microspheres, aggregation during fabrication and storage, and incomplete or delayed release, as illustrated by glucagon-like peptide-1 analog formulations. Mitigation strategies span pH buffering, excipient-based stabilization, and gentler manufacturing that improve encapsulation efficiency and preserve bioactivity. Translation hinges on manufacturing scale-up and quality systems that maintain critical particle attributes and enable informative in vitro–in vivo interpretation. Clinically, prolonged symptom relief after single dosing has been demonstrated for corticosteroid depots (e.g., ~50% pain reduction over 12 weeks with a single PLGA–triamcinolone injection), whereas repeat-dose safety and indication expansion beyond the knee remain active needs best addressed through multicenter trials incorporating imaging and patient-reported outcomes. Consistent real-world performance will depend on controlling batch-to-batch variability and implementing pharmacovigilance approaches suited to long dosing intervals, enabling broader clinical adoption. Full article