446494 research outputs found
Sort by
Investigating The Molecular Dynamics Of Caffeine In Protic And Aprotic Solvents Using
No full textCoffee is renowned for its rich composition of bioactive compounds, including caffeine. While the macroscopic effects of caffeine are well documented, a comprehensive understanding of molecular dynamics at the microscopic level remains limited, particularly regarding solvent effects and spin-lattice relaxation time (T1), which are critical for quality control/authentication of coffee. This study addresses this gap by developing a Benchtop Nuclear Magnetic Resonance (NMR) spectroscopy method to investigate the molecular dynamics of caffeine by determining the spin-lattice relaxation time (T1). Our approach focuses on comparing the T1 values of pure caffeine in two distinct solvent environments, the protic heavy water (D2O) and the aprotic deuterated chloroform (CDCl3). Experimental procedures involved preparing caffeine samples in both solvents and measuring T1 values using the inversion-recovery method with relaxation delays of 3, 5.5, 11, 20, and 25 seconds. Preliminary results show that the T1 value of caffeine is influenced by both the solvent type and the relaxation delay. Specifically, the T1 values in CDCl3 were more uniform than those in D2O, suggesting substantial differences in the molecular interactions and motional dynamics of caffeine in these two environments. These findings can contribute to understanding the molecular dynamics of complex coffee, especially its caffeine behaviour
Integrating ethno-VR wedhang uwuh into an inquiry project learning model to actualize science and technology literacy in accordance with sustainable development goal 4
No full textScience and technology literacy among Indonesian students remains low, limiting their engagement with Sustainable Development Goal (SDG) 4 on quality education. This study aimed to develop Ethno–Virtual Reality (Ethno-VR) learning media based on the Wedhang Uwuh Spice Museum to enhance students' literacy while integrating cultural knowledge and local wisdom. Using a research and development approach, data were collected through case studies, observations, interviews, and literature review to explore sociocultural, economic, health, and educational aspects of Wedhang Uwuh, informing the design of interactive content, including virtual museum tours, organoleptic tests, phytochemical analysis, structural observations, and aroma profiling, enriched with multimedia learning materials. The Ethno-VR media successfully created a valid, engaging, and contextually rich virtual learning environment, and students responded positively, finding it innovative and effective in improving their science and technology literacy. Based on the results of the research and discussion, it can be concluded that (1) an integrated pattern of IPjLM and Ethno-SSI has been identified in the form of an integrated model; (2) the development of the Ethno-VR Wedhang Uwuh media successfully produced a valid, attractive, and contextually rich virtual learning environment that integrates scientific, cultural, and health perspectives along with experimental explorations; (3) students responded positively to the media, finding it engaging, innovative, and effective in enhancing their science and technology literacy; and (4) these findings indicate that the Ethno-VR media contributes to achieving Sustainable Development Goal 4 by supporting inclusive, equitable, and quality education
Conceptualisation nosologique et étiologique des troubles et maladies mentales
No full textL’article analyse la conceptualisation nosologique et étiologique des troubles mentaux à la fin du Moyen Âge. Les médecins médiévaux concevaient l’homme comme composé d’un corps et d’une âme unis et présentant une interrelation étroite. Ils situaient les opérations psychiques dans différents lieux du cerveau, variant selon des facultés de l’âme (imagination, raison/jugement, mémoire notamment). Les maladies mentales étaient quant à elles distinguées et diagnostiquées en fonction d’une symptomatologie complexe et subtile et leurs causes constituèrent le sujet de réflexions approfondies afin de les inscrire dans le cadre des théories physiologiques de l’époque. En effet, la nosologie médiévale distinguait principalement trois catégories de maladies mentales : la phrénésie, la manie et la mélancolie, en tenant compte des comportements observés et en s’appuyant sur une étiologie multifactorielle. L’examen de ces conceptualisations médiévales permet d’inscrire dans une histoire de longue durée la recherche d’une classification fine des troubles et maladies mentaux, et d’une étiologique cohérente avec le cadre conceptuel physiologique. Cet article apporte des éléments de réflexion relevant de l’épistémologie historique et met en évidence la résonance existante entre les préoccupations des médecins médiévaux et celles des psychiatres actuels
Minkowski space dynamics and light-front projection
No full textWe explore the connection between the four-dimensional Minkowski-space Bethe–Salpeter equation and its light-front projection, emphasizing the implications for bound-state dynamics. Our approach incorporates dressed particles, such as quarks, via the integral representation of the corresponding propagator. We analyze the light-front dynamics of the valence component of the physical state using a hierarchical set of Green’s functions, which reveals its coupling to higher Fock components when dressed particles are considered. We also present the light-front Faddeev–Bethe–Salpeter equations for three-body systems with dressed constituents. Furthermore, we discuss formal developments that are central to connecting the three-dimensional light-front dynamics onto the null-plane and the four-dimensional Minkowski-space framework, based on the Nakanishi integral representation. Selected applications to hadron structure are also reviewed
Tribological performance and energy savings in sustainable machining of duplex stainless steel via hybrid Cryo-MQL
No full textThe most reliable industrial uses of duplex stainless steels (DSS), including energy systems, maritime engineering, and chemical processing, are on the rise due to the material’s exceptional corrosion resistance and high mechanical strength. Tool wear is rapid, surface integrity is poor, and energy demand is high when machining these materials due to their bi-phase microstructure and high alloy content. This work analyzes the performance of these four cooling and lubrication techniques and compares their effectiveness in improving the machinability of DSS turning: dry, Minimum Quantity Lubrication (MQL), cryogenic cooling, and the hybrid Cryo-MQL (CMQL). Extensive tests for tool wear, surface roughness, microhardness profiles, chip morphology, and machining energy consumption were carried out. CMQL was found to be the best among all methods, reducing tool wear by 54%, surface roughness to a lower level of 0.558 µm, and energy consumption by 32.3%, while increasing the subsurface microhardness by 31.7%. The results support the use of CMQL as an eco-friendly, high-efficiency alternative for the precision machining of DSS parts
Diversity and abundance of
No full textBiting midges of the genus Culicoides Latreille (Ceratopogonidae) pose a significant threat to veterinary health as vectors of over 60 viruses, most of which affect livestock. In this study, we used light traps to sample Culicoides populations on cattle and goat farms from May to October 2023 at 15 sites in Gyeongsangnam-do, Jeollanam-do, and Jeju Island, South Korea. Diversity and abundance were analysed based on the collection date, environmental conditions, and host species. A total of 124,055 individuals were collected, comprising 14 previously recorded and two newly recorded species: C. asiana and C. palawanensis. The dominant species was C. arakawae, which accounted for 80.60% of the total collected individuals, followed by C. punctatus (10.25%), and C. tainanus (3.36%), while the remaining 13 species constituted 5.80% of the collection. Total Culicoides abundance peaked in August (40.15%), driven largely by fluctuations in C. arakawae abundance, but the seasonal abundances of individual species varied. Culicoides arakawae and C. punctatus were dominant on the mainland, while C. matsuzawai, C. lungchiensis, and C. tainanus were dominant on Jeju Island. The dominant species on cattle farms were C. arakawae and C. punctatus, while C. arakawae dominated in collections from goat farms. The detection of two new species records suggests that the fauna of South Korea is still incompletely understood
100 Glorious years of the Ising model
No full textThis is an editorial article from a special issue of the European Journal of Physics B dedicated to the Ising model and its applications in physics and interdisciplinary research over the last 100 years
PDRs4All. XVIII. JWST-NIRCam photometric properties of protoplanetary disks in the Orion Nebula Cluster
No full textThe Orion Nebula Cluster (ONC) provides the closest example of ongoing star and planet formation in highly irradiated environments. In particular, it is a key region for studying how ultraviolet (UV) radiation from massive stars can drive mass loss in protoplanetary disks through photo-evaporation. Far-UV (FUV, energy 6<E<13.6 eV) photons heat up the gas of the disk, forming a wind of neutral gas that is a photodissociation region (PDR). We used high-angular-resolution NIRCam images from the program and combined them with those of the guaranteed time observation (GTO) program 1256. From these images, we extracted key information on ONC disks, such as the radii of the disks observed in silhouette against the bright background, the presence and positions of the dissociation fronts (DFs), the presence and positions of ionization fronts (IFs), intensities of Paschen α lines, and their near-infrared spectral energy distributions (SEDs). From this information we constructed a typology for ONC disks: PDRs4All Type I sources show an IF and DF nearly merged at the disk surface; Type II sources have their DFs at the disk surface and IFs at a distance of several tens of astronomical units from the disk; and Type III sources also have their DF at the disk surface, but show no IF. For all types of disks, we find that PAH emission traces the PDR. We established that the SEDs of candidate Jupiter-mass binary objects (JuMBOs) observed as part of the PDRs4All program are similar to the SEDs of Type III ONC disks, except for one of them, JuMBO24, which is of Type I or II . A detailed look at this SED shows that it is compatible with a young low-mass binary star with an unresolved ionized disk: a microproplyd binary. We observe that the disk radius of ONC disks, r_̊m disk, increases with increasing projected distance to the ionizing source, d_̊m proj, following a power law, r_ ̊m disk ∝ d_ ̊m proj ^ 0.30 , which is interpreted as evidence of the truncation of the disks by the photoevaporation (as reported in previous studies). The disk radii measured at infrared wavelengths appear larger than the disk radii measured at millimeter wavelengths, which is interpreted as evidence of the dust radial segregation within the disks. In agreement with theoretical models and observations of PDRs in the interstellar medium, the thermal pressure within the PDRs of ONC disk increases with the intensity of the FUV radiation field, G_0, but with a flatter slope
How hard is dust in debris disks?
No full textThe observational appearance of debris disks is largely controlled by collisional grinding of their dust grains. However, the mechanical strength of dust at sizes in the micrometer to millimeter range is poorly known. Recent studies suggest that dust particles in the Solar System might have a higher critical fragmentation energy, QD, value than previously anticipated, while another recent study considered the Fomalhaut debris disk and found lower QD values to provide better fits to the data. In order to constrain the mechanical strength of dust, we investigate the collisional evolution of debris disks with QD prescriptions differing by about three orders of magnitude. We find that, above a certain threshold QD value, the disk's collisional evolution is dominated by rebounding -- rather than disruptive or cratering -- collisions. Rebounding (also known as bouncing) collisions are those in which both impactors survive, being only slightly eroded and producing fragments that only carry a minor fraction of their mass. We show that disks dominated by rebounding collisions would have brightness profiles increasing outward outside the parent belt. Since such profiles are not observed, this places an upper limit on how hard the debris dust is allowed to be in order not to violate the observations. We derived an approximate analytic expression for this limit, QD ≈ (1/8) v ^2(r) for grains close to the radiation pressure blowout size, where v K in the Keplerian circular speed at a distance r from the star. This implies QD łesssim 10^ 9...10 for micrometer-sized grains in typical debris disks. Even though rebounding collisions are not expected to affect debris disk evolution significantly, we emphasize that these collisions are actually much more frequent than disruptive and cratering ones in all debris disks