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Mathematical Modeling of Malaria and Typhoid Co-infection: Exploring Vector and Non-Vector Transmission Dynamics
No full textMalaria and typhoid fever are major infectious diseases that pose significant public health challenges in many parts of the world, particularly in sub-Saharan Africa. This study develops a mathematical model to investigate the dynamics of malaria–typhoid co-infection, incorporating both vector and non-vector malaria transmission routes and environmental transmission for typhoid. Model parameters were drawn from the literature, and simulations were conducted in MATLAB. The results show that vector-borne transmission accounts for over 80% of malaria infections, while typhoid transmission sustains a persistent infection level. Co-infected individuals constitute approximately 25–35% of the total infected population at peak conditions, underscoring the substantial burden of simultaneous infection. Sensitivity analysis identifies malaria and typhoid transmission rates as key drivers of co-infection prevalence. A backward bifurcation in the malaria subsystem indicates that malaria may persist even when its reproduction number is below one, thereby continually seeding co-infection and indirectly maintaining typhoid transmission through co-infected individuals. These findings highlight the need for integrated and sustained control strategies, including vector control, typhoid vaccination, and improved sanitation, to effectively reduce the dual disease burden. Overall, the model provides a useful analytical framework to support public health planning and evidence-based resource allocation in regions where both infections remain endemic
Digital micromirror device characterisation for ultrashort laser applications
No full textIn recent years, the wide variety of digital micromirror device (DMD) applications has extended significantly across various fields of optics, including ultrafast optics. Despite these advances, the interaction between DMDs and ultrashort pulses remains poorly understood. To address this gap, this study presents a comprehensive characterization of the behaviour of a DMD system when interacting with ultrashort laser pulses. In this work, the fluence threshold for multi-shot damage was first determined to be 0.12 J/cm-2. Regarding the temporal effects, the group delay dispersion (GDD) of intrinsic materials was experimentally measured for the zeroth order and was determined to be 190 fs2. The temporal dispersion introduced by the DMD was then theoretically quantified for higher diffraction orders, showing that it generates a broadening and a spatiotemporal shift that depend on the diffraction order. Concerning spatial effects, the lateral chromatic aberration for a broad wavelength range was analysed, revealing the spatial separation of different wavelength components due to the wavelength dependence of the order of diffraction. Finally, the capability of the DMD to analyse the intensity spatial distribution of the light beam was demonstrated using a single-pixel imaging technique. These findings contribute to the understanding of the effects resulting from the interaction of ultrashort pulses with the DMD, thereby facilitating applications
Research on pastoralism in France: state of knowledge and current issues
No full textThis article provides an overview of the current state of knowledge on pastoral systems and territories in France, focusing on the key issues that affect them. It provides a comprehensive analysis of the factors contributing to the decline of pastoralism in a context of intensified production and herd expansion, adaptation to climate change and market fluctuations, and the return of wild predators. Five priority areas for research are identified: animal selection and breeding in pastoral environments; pastoralism as a specific agroecological model, with its strengths and weaknesses; multi‐stakeholder pastoral territories, as spaces for confrontation and development of collective projects; pastoralism occupations and their attractiveness; and data derived from methods for monitoring changes in vegetation, biodiversity, and livestock systems. While not identical, many of these issues are notably similar to those in pastoral contexts in other parts of the world, particularly West Africa
A stellar prominence eruption associated with a white-light flare on an M dwarf observed simultaneously by LAMOST and TESS
No full textStellar coronal mass ejections (CMEs) are regarded as major drivers of space weather in exoplanetary systems. Their large-scale expulsions of magnetised plasma may erode planetary atmospheres and influence the long-term evolution of close-in exoplanets. Nevertheless, confirmed detections of stellar CMEs and prominence eruptions remain extremely rare compared to the frequent occurrence of stellar flares.
We investigated Doppler-shift signatures of stellar prominence eruptions associated with flares by combining simultaneous observations from LAMOST medium-resolution time-domain spectroscopy and TESS photometry.
We analysed temporal Hα line profiles obtained with LAMOST's medium-resolution spectrograph. Blue-wing enhancements were identified through double-Gaussian fitting, and the integrated Hα blue-wing emission was used to estimate the mass and kinetic energy of the erupting prominence. In parallel, flares were identified in the TESS light curves, from which bolometric flare energies were derived. The temporal relationship between the Hα blue-wing signatures and the TESS flares was then examined and compared with solar eruptive events and existing theoretical models.
In the active M-type dwarf LAMOST J063150.73+412942.2, we detect a white-light flare associated with a stellar prominence eruption. The flare has a bolometric energy of 2.94 α=-1.52. The flare associated with the prominence eruption lies towards the lower-energy end of this distribution and corresponds to a relatively frequent event. The comparable magnitudes of the flare radiative energy and the prominence kinetic energy indicate a near equipartition between these two components in an active M dwarf, resembling solar eruptive events. These results provide an observational constraint on magnetic reconnection and mass-ejection processes in low-mass stars and have potential implications for the space-weather environments of close-in exoplanets
Eruptive mass loss less than a year before the explosion of superluminous supernovae. II. A systematic search for pre-explosion eruptions with VLT/X-shooter
No full textWe present X-shooter spectroscopic and photometric observations of a sample of 21 hydrogen-poor superluminous supernovae (SLSNe-I), spanning a redshift range of z = 0.13-0.95, aimed at searching for shells of circumstellar material (CSM). Specifically, we focused on identifying broad absorption features that are blueshifted by several thousand kilometers per second relative to the narrow absorption lines associated with the host galaxy. These broad features have previously been interpreted to arise from resonance line scattering of the SLSN continuum by rapidly expanding CSM ejected shortly before explosion. Utilizing high-quality near-ultraviolet spectra, we modeled the region around 2800 Å to characterize the Mg II Mg II line profiles, enabling us to either confirm their presence or place constraints on undetected CSM shells. We identified five objects in our sample that show broad absorption features consistent with the presence of CSM. While SN,2018ibb, SN,2020xga, and SN,2022xgc have been previously reported, we identified previously undiscovered CSM shells in DES15S2nr and DES16C3ggu. In the case of DES15S2nr, the CSM shell is located at ∼ 3.4 Mg II 10^ 15 ̊m cm and is moving with a maximum velocity of ∼ 4800̊m km s^ -1 . For DES16C3ggu, the shell lies at ∼ 4.8 ̊m cm and reaches up to ∼ 4700 ̊m km s^ 10^ 15 -1 . These shells were likely expelled approximately two and three months before the explosion of their respective associated SNe on timescales consistent with late-stage eruptive mass-loss episodes. We further found evidence that the velocities of the CSM shells in all objects lie within 3000-5000 ̊m km s^ -1 , which may reflect an intrinsic property and could hint at a similar mass-ejection mechanism. We did not find any correlations between the shell properties and the SN properties, except for a marginal correlation between the light curve decline timescale and the shell velocities. This correlation needs further work; however, if it applies, it is a powerful link between the late-time mass ejection and eventual explosion. We further demonstrate that CSM configurations similar to the majority of the detected shells would have been observable in spectra with a signal-to-noise per resolution element, and that the lines from a shell are, in general, detectable except in cases where the shell is either very geometrically and/or optically thin. Therefore, we conclude that the non-detections are unlikely to arise from selection effects but they may instead point to the existence of a subclass of SLSN-I progenitors undergoing late-stage shell ejections shortly before explosion
Re-visiting the Canis Major star-forming region with Gaia data release 3 data
No full textThe Canis Major (CMa) star-forming region, a remote molecular cloud complex within the recently discovered Radcliffe Wave, remains under-explored in the literature.
We revisit the stellar census in the CMa region, characterizing its stellar population, kinematics, and age using recent astrometric and photometric data from the third data release of the Gaia space mission (Gaia DR3).
We conducted a membership analysis of Gaia DR3 sources across a 16 deg2 field encompassing the youngest subgroups in CMa. This new stellar census, combined with spectroscopic observations, allowed us to investigate the structure, kinematics, and age of this region.
We identified 1 531 objects as members of the CMa region, confirming 401 previously known members and introducing 1,130 new candidate members. These objects have magnitudes ranging from 10 to 18 mag in the G band from Gaia DR3. We identified two subgroups of CMa stars in our sample labelled as Cluster A and Cluster B. They are located at roughly the same distance A = 1,150^ +79 _ -88 pc and d_ B = 1,183^ +103 _ -108 pc) and exhibit similar space motions that can be derived thanks to the precise radial velocities obtained in this study. The subgroups have a mean isochronal age of about 2-3 Myr. However, based on infrared photometry we show that Cluster A has a higher fraction of disc-bearing stars suggesting that it could be somewhat younger than Cluster B.
Our analysis provides new insights into the stellar population of the Canis Major region, by identifying new members, characterizing their kinematics, and assessing their evolutionary stages. Future studies incorporating additional data from upcoming Gaia data releases, multi-wavelength and high-resolution spectroscopic observations will be essential to further advance our understanding of the history of star formation in this region
Unveiling the nature of SN 2022jli: The first double-peaked stripped-envelope supernova showing periodic undulations and dust emission at late times
No full textWe present optical and infrared observations from maximum light until around days of supernova (SN),2022jli, a peculiar stripped-envelope (SE) SN showing two maxima, each one with a peak luminosity of about 3 10^ 42 ,erg,s -1 , separated by 50 days. The second maximum is followed by unprecedented periodic undulations with a period of P ∼ 12.5 days. The spectra and the photometric evolution of the first maximum are consistent with the behaviour of a standard SE SN with an ejecta mass of ∼ 1.5,M_⊙ and a radioactive 56 Ni mass of ∼ 0.12M_⊙. The optical spectra after ,days relative to the first maximum correspond to a standard SN,Ic event, and at late times SN,2022jli exhibits a significant drop in the optical luminosity, implying that the physical phenomena that produced the secondary maximum have ceased to power the SN light curve. Among other potential scenarios, we discuss how the second maximum could be powered by a magnetar, while the light curve periodic undulations could be produced by accretion of material from a companion star onto the neutron star in a binary system. The near-infrared spectra shows clear first CO overtone emission from about days after the first maximum, and it becomes undetected at ,days. A significant near-infrared excess from hot dust emission is detected at ,days, having been produced by either newly formed dust in the SN ejecta or a strong near-infrared dust echo. Depending on the assumptions of the dust composition, the estimated dust mass is 2-16 10^ -4 ,M_⊙. The potential magnetar power of the second maximum can fit into a more general picture in which magnetars are the power source of SE super-luminous SNe, and could explain bumps, undulations, and late-time excess emission in SE SNe. The CO detection and the dust emission of SN 2022jli are key to understanding the molecule and dust formation in the ejecta of SE SNe and in their environment
A complete survey of filaments in Cygnus X
No full textFilamentary gas structures are widely observed in molecular clouds and are suggested to play a key role in the star formation processes. However, existing observations of molecular filaments are still biased toward case studies and small samples, and a large sample study from a single giant molecular cloud is lacking.
We aim to carry out a complete census of filaments in Cygnus X and obtain their physical properties, relations with dense cores, magnetic field (B field), and HII regions.
We extracted 2633 filaments and 6551 cores from the column-density map of Cygnus X, using the most updated algorithm. We then investigated the mass functions for the cores on and separate from the filaments, compared the orientations of the filaments with that of the B field obtained with the data, derived the radial column-density profiles of the filaments close to HII regions, and calculated the distances between the identified young stellar objects and filament spines. We also re-extracted filaments at the resolution of the 353 GHz dust-emission map to study their relationship with the B field. getsf Planck Planck
The filaments in Cygnus X have a typical width of 0.5 pc. More than 93 of high-mass cores (ge 20 M_ 353 GHz map are mostly perpendicular to the B field, except that those of the lowest column densities are parallel to the B field. The transition from parallel to perpendicular occurs at a column-density equivalent to A_V=10 mag. Most prominent filamentary gas structures and high-mass cores appear to be preferentially located along the boundaries of HII regions or at the intersections of multiple HII regions. The filaments close to the HII region boundaries show a steeper column-density profile on the side toward the HII region compared to that on the opposite side. are located on filaments. The core mass function constructed from the cores on the filaments (onCMF) shows a power law in the high-mass-end () with a slope of -2.30, whereas the high-mass end of the core mass function (CMF) derived from the cores outside the filaments (outCMF) has a much steeper power-law distribution with a slope of -2.83. The core mass corresponding to the peak of onCMF is much less than the Bonner-Ebert mass, but that corresponding to the peak of outCMF is well comparable to the Bonner-Ebert mass. Filaments re-extracted from the column-density map smoothed to an angular resolution identical to the Planck
The formation of more massive cores has a stronger dependence on filaments, and the latter may provide a mass reservoir for the former to grow in mass via accretion. The B field plays a crucial role in filament formation, and the type-O mode where filaments form at the tip of converging flows along an oblique MHD shock front may be prevalent in Cygnus X. In this context, expanding HII regions in the complex induces shocks that compress the surrounding gas, creating inhomogeneity and dense clumps, and forming filaments. The global picture of filaments, cores, and star formation in Cygnus X is apparently consistent with the bubble-filament paradigm proposed in the literature
Impact of charge transfer inefficiency on transit light curves. A correction strategy for PLATO
No full textPLATO is designed to detect Earth-sized exoplanets orbiting solar-type stars and to measure their radii (relative to the star radii) with an accuracy better than (2%) via the transit method. Charge transfer inefficiency (CTI), a by-product of radiation damage to charge-coupled devices (CCDs), can jeopardise this accuracy constraint and therefore must be corrected to reach scientific requirements.
We assessed and quantified the impact of CTI on transit depth measurements. Our objective was to demonstrate the need for CTI correction and to develop a correction strategy that restores CTI-biased transit depths with an acceptable residual within the accuracy budget.
r, k )). Smearing was then modelled with an exponential-plus-constant function and removed on a column-wise basis. We modelled the spatial variation in the trap density with a quadratic polynomial function of the radial distance from the centre of the focal plane. The polynomial coefficients ((a_ p,k )) of this model, the well-fill power index ((β)), and the release times ((τ_ r, k )) were subsequently adjusted via an iterative application of the extended pixel edge response method combined with a CTI correction algorithm. This yielded the final calibration model that underpins our correction strategy.
In the worst-case scenario (8-year mission, high CTI impact zone), we found that CTI induced a bias of approximately (4%) in the measured transit depth. The polynomial coefficients from our trap density model were then used to correct the CTI-affected transit depths. Our correction reduced the bias to a residual of (0.06%), which is comfortably within PLATO's accuracy requirements.
We quantified the CTI-induced bias in transit depth measurements and implemented a calibration strategy that incorporates spatial variations in trap density. From the calibrated parameters, we derived a correction scheme that brought the photometric measurements within PLATO's noise budget, ensuring that the mission's precision requirements are met
A statistical framework for the quantitative spectroscopy of luminous blue stars
No full textQuantitative spectroscopy of luminous blue stars relies on detailed non-local thermodynamic equilibrium (non-LTE) model atmospheres whose increasing physical realism makes direct iterative analyses computationally demanding.
We introduce Machine-learning assisted Uncertainty inference ( a statistical framework designed for an efficient Bayesian inference of stellar parameters using emulator-based spectral models.
employs Gaussian-process-based emulators trained on a limited set of non-LTE simulations, combined with Markov chain Monte Carlo sampling to explore posterior distributions. We validate the approach with recovery experiments and demonstrate it on Galactic late-type O dwarf and early-type B dwarf and subgiant stars.
The emulator reproduces the predictions of full atmosphere models within the quoted uncertainties while reducing computational cost by several orders of magnitude. Posterior distributions are well calibrated with a conservative coverage across all stellar parameters.
The emulator-driven Bayesian inference retains the accuracy of classical analyses at a fraction of the computational expense, which enables posterior sampling that would be prohibitive with direct model evaluations. This positions emulators as a practical tool for high-fidelity spectroscopy of massive stars as atmosphere models grow more demanding