Exploring the correlation of dynamic surface tension with antimicrobial activities of quaternary ammonium-based disinfectants.

Quaternary ammonium compound (QAC) disinfectants represent one of our first lines of defense against pathogens. Their killing activities are usually tested through minimum inhibitory concentration (MIC) and time-kill assays, but these assays can become cumbersome when screening compounds. We investigated how the dynamic surface tension (DST) measurements of QACs correlate with these antimicrobial activities by testing a panel of potent and structurally varied QACs against the gram-positive Staphylococcus aureus and the gram-negative Pseudomonas aeruginosa. We found that DST values correlated well with bactericidal activity in real-world disinfection conditions but not with MIC values. Moreover, no correlation between these two antimicrobial activities of QACs was observed. We also observed that the bactericidal activity of our QAC panel against the gram-negative P. aeruginosa was severely affected in the presence of hard water. Interestingly, we found that the counterion of the QAC affects the killing of bacteria in these conditions, a phenomenon not observed in most MIC assessments. Moreover, some of our best-in-class QACs show enhanced bactericidal activity when combined with a commercially available QAC. In conclusion, we determined that DST can be used as a technique to screen for bactericidal activity of QACs in conditions that mimic real-world disinfection conditions.

Chimeric Amphiphilic Disinfectants: Quaternary Ammonium/Quaternary Phosphonium Hybrid Structures.

Cationic biocides play a crucial role in the disinfection of domestic and healthcare surfaces. Due to the rise of bacterial resistance towards common cationic disinfectants like quaternary ammonium compounds (QACs), the development of novel actives is necessary for effective infection prevention and control. Toward this end, a series of 15 chimeric biscationic amphiphilic compounds, bearing both ammonium and phosphonium residues, were prepared to probe the structure and efficacy of mixed cationic ammonium-phosphonium structures. Compounds were obtained in two steps and good yields, with straightforward and chromatography-free purifications. Antibacterial activity evaluation of these compounds against a panel of seven bacterial strains, including two MRSA strains as well as opportunistic pathogen A. baumannii, were encouraging, as low micromolar inhibitory activity was observed for multiple structures. Alkyl chain length on the ammonium group was, as expected, a major determinant of bioactivity. In addition, high therapeutic indexes (up to 125-fold) for triphenyl phosphonium-bearing amphiphiles were observed when comparing antimicrobial activity to mammalian cell lysis activity.

In Situ ATR Spectroscopy Study of the Interaction of Acacia senegal Gum with Gold Nanoparticles Films at the Solid-Liquid Interface.

The adsorption process of Acacia gum (A. senegal), a complex heteropolysaccharide, was followed by using a spectroscopic method to unravel the relative contribution of the protein moieties and the carbohydrate blocks on the adsorption process. In situ ATR-FTIR was used to investigate the kinetics and conformational changes associated with the adsorption of A. senegal gum on gold nanoparticle films (Au-NPs) at different pHs. The results of this thorough study highlighted the adsorption of A. senegal gum through its protein moieties, in particular, AGPs of low molecular weight and high protein content, close to the Au-NPs surface. Isotherm experiments, by gradually increasing the concentration, showed that the gum adsorption was heterogeneous and followed the Freundlich model for the amide part, while the polysaccharide part followed the Langmuir model. In addition, the hydration and structural organization of the gum layer depended on the gum concentration. A. senegal gum adsorbed irreversibly on Au-NPs whatever the pHs, but the adsorbed layer presented a different behavior depending on pH. A more aggregated and less hydrated structure was observed at acidic pH, while a very hydrated and continuous layer was detected at higher pH. The secondary structure analysis through amide III band revealed a change in the gum secondary structure at high pH with the increase in ß-turn while random coil decreased.

Use of mouthguards in Latin American field hockey athletes during the ODESUR 2022 Games.

BACKGROUND/AIMS: Athletes are susceptible to oral injuries. To reduce the incidence and severity of oral trauma, a custom-made mouthguard, a device positioned in the mouth to prevent damage to teeth and surrounding structures, is recommended. In field hockey, according to the international rules of this sport, using mouthguards is not mandatory, but it is recommended to wear them at all times while practicing this discipline. We aimed to determine characteristics and differences regarding mouthguard usage among field hockey players from different countries participating in the XII ODESUR Games. METHODS: We conducted a cross-sectional study that included 78 voluntary hockey athletes that met the inclusion criteria. The questionnaire used was validated by Panam Sports, collecting information on the type of mouthguard (custom-made or prefabricated), and the time of use of the mouthguard (range of 5 years). RESULTS: Of the total number of athletes, 96% used mouthguards, of which 64% were custom-made type, and 32% were prefabricated (p < .001). Custom-made mouthguards were used by 100%, 89%, and 64% of athletes in Argentina, Chile, and Peru, respectively, while only 40% of athletes in Paraguay and Uruguay used them. It has also been observed that more than 50% of the individuals have not controlled and replaced their intraoral devices for more than 10 years. CONCLUSIONS: Our results reveal a problem with a public health dimension and thus invite the standardization of guidelines with an educational approach to promoting and adopting good sports practices. This report is the first on using mouthguards in high-performance athletes during an international multisport event.

[Pembrolizumab-induced gastritis with PDL1 histological expression]. / Gastritis inducida por pembrolizumab con expresión histológica de PDL1.

Immune-mediated gastritis is a rare adverse effect in patients treated with immune checkpoint inhibitors. We present a patient with a diagnosis of cervical carcinoma under treatment with pembrolizumab who was admitted with nausea, vomiting and weight loss; an endoscopy revealed a ulcerated lesion covered by mucus in the antrum and gastric body. The biopsy revealed extensive denudation of the gastric mucosa with fibrin leukocyte reaction. Into the lamina propria, an increased lymphocytic and polymorphonuclear inflammatory infiltrate was observed. Immunohistochemistry confirmed positivity for PDL1 (clone SP2630) and combined positive score of 35%, with a relative contribution of epithelial cells of 25% and inflammatory cells of 10%. After three weeks with 30 mg meprednisone, a new endoscopy revealed a stomach with clear mucus content; fundus and body without lesions, and an antrum with congestive mucosa and multiple superficial ulcers covered by fibrin. Diagnostic and therapeutic aspects of immune-mediated gastritis are described.

La gastritis inmunomediada es un efecto adverso raro en pacientes bajo tratamiento con inhibidores del punto de control inmunitario; se presenta el caso de una paciente con carcinoma de cuello uterino bajo tratamiento con pembrolizumab que ingresa con náuseas, vómitos y pérdida de peso. La endoscopía demostró una lesión ulcerada cubierta por moco en antro y cuerpo gástrico. La biopsia reveló una extensa denudación de la mucosa gástrica con material fibrinoleucocitario. La lámina propia presentó incremento del infiltrado inflamatorio linfocitario y polimorfonuclear. La inmunohistoquímica confirmó positividad para PDL1 (clon SP2630) y un score positivo combinado (CPS) del 35%, con una contribución relativa de células epiteliales de 25% y de células inflamatorias de 10%. Luego de tres semanas de tratamiento con 30 mg de meprednisona, la endoscopía constató un estómago con contenido mucoso claro; fundus y cuerpo sin lesiones, antro con mucosa congestiva y múltiples úlceras extensas y superficiales cubiertas por fibrina. Se describen los aspectos diagnósticos y terapéuticos de la gastritis inmunomediada.

A Novel Dependoparvovirus Identified in Cloacal Swabs of Monk Parakeet (Myiopsitta monachus) from Urban Areas of Spain.

The introduction of invasive birds into new ecosystems frequently has negative consequences for the resident populations. Accordingly, the increasing population of monk parakeets (Myiopsitta monachus) in Europe may pose a threat because we have little knowledge of the viruses they can transmit to native naïve species. In this study, we describe a new dependoparvovirus detected by metagenomic analysis of cloacal samples from 28 apparently healthy individuals captured in urban areas of Madrid, Spain. The genomic characterization revealed that the genome encoded the NS and VP proteins typical of parvoviruses and was flanked by inverted terminal repeats. No recombination signal was detected. The phylogenetic analysis showed that it was closely related to a parvovirus isolated in a wild psittacid in China. Both viruses share 80% Rep protein sequence identity and only 64% with other dependoparvoviruses identified in Passeriformes, Anseriformes, and Piciformes and are included in a highly supported clade, which could be considered a new species. The prevalence was very low, and none of the additional 73 individuals tested positive by PCR. These results highlight the importance of exploring the viral genome in invasive species to prevent the emergence of novel viral pathogenic species.

Genomic Characterization and Genetic Profiles of Salmonella Gallinarum Strains Isolated from Layers with Fowl Typhoid in Colombia.

Salmonella Gallinarum (SG) is the causative agent of fowl typhoid (FT), a disease that is harmful to the poultry industry. Despite sanitation and prophylactic measures, this pathogen is associated with frequent disease outbreaks in developing countries, causing high morbidity and mortality. We characterized the complete genome sequence of Colombian SG strains and then performed a comparative genome analysis with other SG strains found in different regions worldwide. Eight field strains of SG plus a 9R-derived vaccine were subjected to whole-genome sequencing (WGS) and bioinformatics analysis, and the results were used for subsequent molecular typing; virulome, resistome, and mobilome characterization; and a comparative genome study. We identified 26 chromosome-located resistance genes that mostly encode efflux pumps, and point mutations were found in gyrase genes (gyrA and gyrB), with the gyrB mutation S464T frequently found in the Colombian strains. Moreover, we detected 135 virulence genes, mainly in 15 different Salmonella pathogenicity islands (SPIs). We generated an SPI profile for SG, including C63PI, CS54, ssaD, SPI-1, SPI-2, SPI-3, SPI-4, SPI-5, SPI-6, SPI-9, SPI-10, SPI-11, SPI-12, SPI-13, and SPI-14. Regarding mobile genetic elements, we found the plasmids Col(pHAD28) and IncFII(S) in most of the strains and 13 different prophage sequences, indicating a frequently obtained profile that included the complete phage Gifsy_2 and incomplete phage sequences resembling Escher_500465_2, Shigel_SfIV, Entero_mEp237, and Salmon_SJ46. This study presents, for the first time, the genomic content of Colombian SG strains and a profile of the genetic elements frequently found in SG, which can be further studied to clarify the pathogenicity and evolutionary characteristics of this serotype.

Soft QPCs: Biscationic Quaternary Phosphonium Compounds as Soft Antimicrobial Agents.

Quaternary ammonium compounds (QACs) serve as a first line of defense against infectious pathogens. As resistance to QACs emerges in the environment, the development of next-generation disinfectants is of utmost priority for human health. Balancing antibacterial potency with environmental considerations is required to effectively counter the development of bacterial resistance. To address this challenge, a series of 14 novel biscationic quaternary phosphonium compounds (bisQPCs) have been prepared as amphiphilic disinfectants through straightforward, high-yielding alkylation reactions. These compounds feature decomposable or "soft" amide moieties in their side chains, anticipated to promote decomposition under environmental conditions. Strong bioactivity against a panel of seven bacterial pathogens was observed, highlighted by single-digit micromolar activity for compounds P6P-12A,12A and P3P-12A,12A. Hydrolysis experiments in pure water and in buffers of varying pH revealed surprising decomposition of the soft QPCs under basic conditions at the phosphonium center, leading to inactive phosphine oxide products; QPC stability (>24 h) was maintained in neutral solutions. The results of this work unveil soft QPCs as a potent and environmentally conscious new class of bisQPC disinfectants.

Maturation of demineralized arabinogalactan-proteins from Acacia seyal gum in dry state: Aggregation kinetics and structural properties of aggregates.

The aggregation in dry state of mineral-loaded arabinogalactan-proteins (AGPs) from Acacia seyal gum (GA) generally occurs above 70 °C. This study focuses on the aggregation sensitivity of AGPs after their demineralization. The dry incubation in mild temperature (25 °C to 70 °C) of demineralized AGPs induced the formation of aggregates, not observed with GA. AGPs aggregated following a self-assembly mechanism for which temperature only modulated the aggregation rate. The activation energy was around 90-100 kJ·mol-1 that could correspond to chemical condensation reactions induced by the AGPs surface dehydration. The aggregation kinetics were characterized by the formation of soluble aggregates during the first times of incubation, whose molar mass increased from 1 · 106 g·mol-1 to 6.7 · 106 g·mol-1 (SEC MALS) or 12 · 106 g·mol-1 (AF4 MALS) after 1.66 days of dry heating at 40 °C. These soluble aggregates revealed they adopted a similar conformation to that of not aggregated AGPs with a νh value around 0.45. Above 1.66 days at 40 °C, the soluble aggregates grew up to form microparticles with sizes ranging from 10 to around 200 µm. This study highlighted the protective role of cations from AGPs whose demineralization increased their sensibility to dry heating and their chemical reactivity for aggregation.

Atom Economical QPCs: Phenyl-Free Biscationic Quaternary Phosphonium Compounds as Potent Disinfectants.

Quaternary ammonium compounds (QACs) are vital disinfectants for the neutralization of pathogenic bacteria in clinical, domestic, and commercial settings. After decades of dependence on QACs, the emergence of antimicrobial resistance to this class of compounds threatens the ability of existing QAC products to effectively manage rising bacterial threats. The need for new disinfectants is therefore urgent, with quaternary phosphonium compounds (QPCs) emerging as a new class of promising antimicrobials that boast significant activity against highly resistant bacteria. Reported here is a series of twenty-one novel QPCs that replace phenyl substituents on the phosphorus center with alkyl groups yet allow for rapid synthetic routes in high yields. Within this series are structures containing methyl, ethyl, or cyclohexyl phosphonium substituents on bisphosphane scaffolds bearing ethyl linkers, affording atom economical structures and ones that represent exact analogs to nitrogenous amphiphiles. The resultant bisQPC structures display high antibacterial efficacy enjoyed by comparably constructed QACs, with three structures in the single-digit micromolar activity range despite structural simplification.

Double BAC and Triple BAC: A Systematic Analysis of the Disinfectant Properties of Multicationic Derivatives of Benzalkonium Chloride (BAC).

Over the past decades, the shortcomings of established quaternary ammonium disinfectants have become increasingly clear. Although benzalkonium chloride (BAC) has enjoyed nearly a century of significantly protecting human health through surgical preparation, home use, and industrial applications, increasing levels of bacterial resistance have rendered it decreasingly effective. In light of more recent efforts that have informed us that multicationic amphiphilic disinfectants show both higher activity as well as diminished susceptibility to resistance, we embarked on the preparation of 27 multicationic QACs in an attempt to clearly document structure-activity relationships of next-generation BAC structures. Select biscationic BAC derivatives demonstrate single-digit micromolar activity against all seven bacteria tested and MIC values of 2- to 32-fold better than BAC. Particularly notable is the improvement against the more concerning bacteria like Acinetobacter baumannii and Pseudomonas aeruginosa, which pose a modern threat to legacy disinfectants like BAC. With simple synthetic paths, consistently high yields (averaging ∼80 %), and strong biological activity, potent structures with clear SAR trends and strong therapeutic indices have been established.

Hypertrophic cardiomyopathy in a patient with secondary hypoparathyroidism: A case report.

Parathyroid hormone (PTH) has direct and indirect actions on cardiovascular cells. The effects of chronic hypoparathyroidism on cardiac morphology, function, and conduction are still unclear. Low PTH states are associated with multiple manifestations in the heart, acute or chronic. Acute hypocalcemic cardiomyopathy is a transient dilated cardiomyopathy with reduced ejection fraction and diffuse left ventricular hypokinesia. Chronic hypoparathyroidism-associated cardiomyopathy is a rare disease that may cause reduced myocardial tension, cardiac cavity enlargement, arrhythmias, and congestive heart failure. Here, we describe a 73-year-old woman with chronic hypoparathyroidism and hypocalcemia, who developed a hypertrophic cardiomyopathy, and not a dilated hypocalcemia-associated cardiomyopathy, which would be usually the case.

Quaternary Phosphonium Compound Unveiled as a Potent Disinfectant against Highly Resistant Acinetobacter baumannii Clinical Isolates.

Acinetobacter baumannii is classified as a highest threat pathogen, urgently necessitating novel antimicrobials that evade resistance to combat its spread. Quaternary ammonium compounds (QACs) have afforded a valuable first line of defense against antimicrobial resistant pathogens as broad-spectrum amphiphilic disinfectant molecules. However, a paucity of innovation in this space has driven the emergence of QAC resistance. Through this work, we sought to identify next-generation disinfectant molecules with efficacy against highly resistant A. baumannii clinical isolates. We selected 12 best-in-class molecules from our previous investigations of quaternary ammonium and quaternary phosphonium compounds (QPCs) to test against a panel of 35 resistant A. baumannii clinical isolates. The results highlighted the efficacy of our next-generation compounds over leading commercial QACs, with our best-in-class QAC (2Pyr-11,11) and QPC (P6P-10,10) displaying improved activities with a few exceptions. Furthermore, we elucidated a correlation between colistin resistance and QAC resistance, wherein the only pan-resistant isolate of the panel, also harboring colistin resistance, exhibited resistance to all tested QACs. Notably, P6P-10,10 maintained efficacy against this strain with an IC90 of 3 µM. In addition, P6P-10,10 displayed minimum biofilm eradication concentrations as low as 32 µM against extensively drug resistant clinical isolates. Lastly, examining the development of disinfectant resistance and cross-resistance, we generated QAC-resistant A. baumannii mutants and observed the development of QAC cross-resistance. In contrast, neither disinfectant resistance nor cross-resistance was observed in A. baumannii under P6P-10,10 treatment. Taken together, the results of this work illustrate the need for novel disinfectant compounds to treat resistant pathogens, such as A. baumannii, and underscore the promise of QPCs, such as P6P-10,10, as viable next-generation disinfectant molecules.

A rare case of sino-nasal aneurysmal bone cyst.

Aneurysmal bone cysts (ABC) are rare in the paranasal sinuses. They are benign expansile multicystic masses containing blood-filled spaces which typically occur in the long bones of pediatric patients. The lesion often produces symptoms due to the compression of adjacent structures or pathological fracture and depends on localization. In this case report, we discuss a 28-year-old female who presented with left-sided headache, left eye proptosis, and diplopia. Radiologic evaluation revealed a left paranasal sinus expansile multicystic mass with internal blood fluid levels displacing and thinning the left medial orbital wall which suggested the diagnosis of ABC. Radiologists should be familiar with and comfortable diagnosing ABC in the head and neck, and be able to differentiate this entity from others, such as telangiectatic osteosarcoma. Biopsy can be challenging since blood products may be the only material identified and may produce tissue that is difficult to interpret or misdiagnosed.

Estrategia educativa para elevar el conocimiento sobre hipertensión arterial en la población, de 20 años en adelante / Educational strategy to raise knowledge about arterial hypertension in the population aged 20 and over

En el mundo las enfermedades cardiovasculares son responsables de casi un tercio del total de las muertes por año. Cada vez son más las personas que padecen hipertensión arterial (HTA), desconociendo muchos su condición. Objetivo: Diseñar una estrategia educativa para elevar el conocimiento sobre hipertensión arterial en la población de 20 años y más en el consultorio 2 de Medicina Familiar y Comunitaria; Centro de Salud Luchadores del Norte, año 2021.Materiales métodos: Se realizó una investigación descriptiva, observacional, prospectiva y transversal con la población de adultos del Centro de Salud Luchadores Norte, para elaborar el diseño de una estrategia educativa que eleve el conocimiento sobre esta enfermedad; se midieron variables sociodemográficas, de estilos de vida y de conocimiento. Resultados: El grupo de edad más frecuente de 50 a 59 años 26,2%; sexo masculino 66,4%; escolaridad nivel básico 41,1%; estado civil unión libre 52,3%; etnia mestizo 58,9% y ocupación empleado privado 29,0%; no realizan actividad física 65,4%; consumo excesivo de sal 67,3%; grasa 58,9%; gaseosas y energizantes 52,8%; no conocen de la enfermedad 62,6%; técnica charla 39,3%; frecuencia una vez cada 15 días 43,9%; horario de mañana 57,0%; duración 30 minutos 52,3%; lugar centro de salud 50,5% y tamaño del grupo de 6 a 10 (42,1%). Conclusión: La bibliografía concuerda mayoritariamente con los resultados de la investigación, en consumo de sal elevado, grasas, gaseosas y bebidas energizantes; el conocimiento sobre la enfermedad es escaso en los hipertensos, concordando con las citas de referencia; concluyendo, que coexisten estilos de vida no saludables con desconocimiento; favoreciendo las complicaciones de la enfermedad, una intervención educativa elevaría conocimiento y cambia actitudes evitando consecuencias y daños irreversibles(AU)

In the world, cardiovascular diseases are responsible for almost a third of all deaths per year. More and more people suffer from high blood pressure (HBP), many unaware of their condition. Objective: To design an educational strategy to raise awareness about arterial hypertension in the population aged 20 and over in Family and Community Medicine office 2; Luchadores del Norte Health Center, year 2021. Materials and methods: A descriptive, observational, prospective and cross-sectional investigation was carried out with the adult population of the Luchadores Norte Health Center, to develop the design of an educational strategy that raises knowledge about this illness; sociodemographic, lifestyle and knowledge variables were measured. Results: The most frequent age group was 50 to 59 years old, 26.2%; male sex 66.4%; basic level schooling 41.1%; marital status free union 52.3%; mestizo ethnic group 58.9% and occupation private employee 29.0%; do not perform physical activity 65.4%; excessive consumption of salt 67.3%; fat 58.9%; soft drinks and energy drinks 52.8%; 62.6% do not know about the disease; talk technique 39.3%; frequency once every 15 days 43.9%; morning hours 57.0%; duration 30 minutes 52.3%; health center location 50.5% and group size from 6 to 10 (42.1%). Conclusion: The bibliography mostly agrees with the results of the investigation, in consumption of high salt, fat, soft drinks and energy drinks; knowledge about the disease is scarce in hypertensive patients, in agreement with the reference citations; concluding that unhealthy lifestyles coexist with ignorance; favoring the complications of the disease, an educational intervention would increase knowledge and change attitudes, avoiding consequences and irreversible damage(AU)

Rigidity-Activity Relationships of bisQPC Scaffolds against Pathogenic Bacteria.

Biscationic quaternary phosphonium compounds (bisQPCs) represent a promising class of antimicrobials, displaying potent activity against both Gram-negative and Gram-positive bacteria. In this study, we explored the effects of structural rigidity on the antimicrobial activity of QPC structures bearing a two-carbon linker between phosphonium groups, testing against a panel of six bacteria, including multiple strains harboring known disinfectant resistance mechanisms. Using simple alkylation reactions, 21 novel compounds were prepared, although alkene isomerization as well as an alkyne reduction were observed during the respective syntheses. The resulting bisQPC compounds showed strong biological activity, but were hampered by diminished solubility of their iodide salts. One compound (P2P-10,10 I) showed single-digit micromolar activity against the entire panel of bacteria. Overall, intriguing biological activity was observed, with less rigid structures displaying better efficacy against Gram-negative strains and more rigid structures demonstrating slightly increased efficacy against S. aureus strains.

Does Roux-en-Y Gastric Bypass Really Cure Gastroesophageal Reflux Disease? Analysis of Objective Data.

Background: Laparoscopic Roux-en-Y gastric bypass (LRYGB) is considered the treatment of choice for obesity with gastroesophageal reflux disease (GERD). There are few reports showing objective data based on esophageal function tests (EFTs). The aim of our study was to evaluate the influence of LRYGB on GERD. Methods: Candidates for laparoscopic sleeve gastrectomy (LSG) underwent preoperative esophageal manometry (EM) and 24-hour pH monitoring. Based on the negative influence of LSG on GERD, patients with abnormal pH were offered LRYGB. Those patients repeated EFTs, esophagogastroduodenoscopy, and symptom questionnaire 1 year after surgery. Results: Two hundred fifty LSG candidates underwent preoperative EFTs; 38% were redirected to LRYGB due to abnormal pH and 13 (18%) completed EFTs postoperatively. In ten women, age: 40 ± 7 years, body mass index: 41 ± 1 kg/m2. EM: lower esophageal sphincter (LES) length increased from 2.6 to 2.9 cm (P = not statistically significant [NS]), and LES pressure decreased from 15 to 14.2 mmHg (P = NS). Preoperatively, LES was normotensive in 12 (92%) patients and postoperatively in 11 (85%) (P = NS). DeMeester score decreased from 35.7 to 11 (P < .001). Postoperatively, 9 (69%) patients resolved their GERD, 3 (23%) improved, and 1 (8%) remained the same (P < .001). Symptoms decreased significantly after surgery. Two patients (15%) had Grade A esophagitis. One of them was able to resolve it, while the other 1 remained the same. Conclusions: Our preliminary data showed that after LRYGB, LES pressure remained the same and DeMeester score decreased, while 69% of patients resolved their GERD. Therefore, LRYGB seems to be an excellent option for obesity and GERD.

Adsorption Behavior of Arabinogalactan-Proteins (AGPs) from Acacia senegal Gum at a Solid-Liquid Interface.

Adsorption of five different hyperbranched arabinogalactan-protein (AGP) fractions from Acacia senegal gum was thoroughly studied at the solid-liquid interface using a quartz crystal microbalance with dissipation monitoring (QCM-D), surface plasmon resonance (SPR), and atomic force microscopy (AFM). The impact of the protein/sugar ratio, molecular weight, and aggregation state on the adsorption capacity was investigated by studying AGP fractions with different structural and biochemical features. Adsorption on a solid surface would be primarily driven by the protein moiety of the AGPs through hydrophobic forces and electrostatic interactions. Increasing ionic strength allows the decrease in electrostatic repulsions and, therefore, the formation of high-coverage films with aggregates on the surface. However, the maximum adsorption capacity was not reached by fractions with a higher protein content but by a fraction that contains an average protein quantity and presents a high content of high-molecular-weight AGPs. The results of this thorough study highlighted that the AGP surface adsorption process would depend not only on the protein moiety and high-molecular-weight AGP content but also on other parameters such as the structural accessibility of proteins, the molecular weight distribution, and the AGP flexibility, allowing structural rearrangements on the surface and spreading to form a viscoelastic film.

On Differential Imaging Using Electromagnetic Simulation for Vehicular Antenna Signature Analysis.

The current trend in vehicles is to integrate a wide number of antennae and sensors operating at a variety of frequencies for sensing and communications. The integration of these antennae and sensors in the vehicle platform is complex because of the way in which the antenna radiation patterns interact with the vehicle structure and other antennae/sensors. Consequently, there is a need to study the radiation pattern of each antenna or, alternatively, the currents induced on the surface of the vehicle to optimize the integration of multiple antennae. The novel concept of differential imaging represents one method by which it is possible to obtain the surface current distribution without introducing any perturbing probe. The aim of this study was to develop and confirm the assumptions that underpin differential imaging by means of full-wave electromagnetic simulation, thereby providing additional verification of the concept. The simulation environment and parameters were selected to replicate the conditions in which real measurements were taken in previous studies. The simulations were performed using Ansys HFSS simulation software. The results confirm that the approximations are valid, and the differential currents are representative of the induced surface currents generated by a monopole positioned on the top of a vehicle.