A fast version of 'CONTACT' for normal problem calculations

[EN] In its different versions, the CONTACT method developed by Prof. Kalker is the primary reference in wheel-rail contact mechanics. Despite adopting simplifications associated with the elastic behaviour of the solids and being a non-conformal contact theory, CONTACT provides precise solutions for most wheel-rail contact conditions, with lower computational and modelling costs than other numerical methods such as Finite Elements. Nevertheless, the computational cost of CONTACT is still too high for its implementation in dynamic simulation. The present work proposes a fast and accurate wheel-rail contact method for normal problems based on Kalker's CONTACT algorithm. Dissimilarly to CONTACT, the new method formulates the normal traction distribution through a suitable basis, which reduces the dimension of the problem. This method is able to faithfully reproduce the contact patch and the normal traction distribution, even when the yaw angle of the wheelset is non-zero. Results obtained with this method are compared with the ones calculated with CONTACT, and errors about 0.05% are obtained in normal contact forces, with a reduction on the computation cost between 30 and 60 times.Grant PRE2018-084067 funded by MCIN/AEI/10.13039/501100011033 and by the EU program "ESF Investing in your future". Grant PID2020-118013RB-C21 funded by MCIN/AEI/10.13039/501100011033. Grant PROMETEO/2021/046 funded by Generalitat Valenciana.Giner Navarro, J.; Gómez-Bosch, J.; Alonso, A.; Baeza González, LM. (2023). A fast version of 'CONTACT' for normal problem calculations. Wear. 530-531:1-12. https://doi.org/10.1016/j.wear.2023.205074112530-53

G287.84-0.82: an infrared star cluster in the Carina nebula

We have studied the properties of an infrared cluster embedded in the gas and dust of the southern part of the Carina nebula (NGC 3372), where the probable existence of current star formation has already been predicted. We used mid-infrared (A and C bands) and near-infrared (JHKs) images from the Midcourse Space Experiment and the Two-Micron All-Sky Survey, respectively, combined with an optical Ha narrow-band filter image obtained at the Cerro Tololo Inter-American Observatory. The infrared star cluster has at least 17 members, and its parameters, radius and stellar density are in very good agreement with high- to intermediate-mass star formation scenarios. The detected infrared sources have roughly the same intrinsic infrared excess determined from their position in colour-colour and colour-magnitude diagrams, suggesting that these objects could be related to pre-main-sequence stars of high to intermediate mass. Furthermore, we present a low-dispersion spectrum of the LS 1883 (O9.5V) star located near the centre of the infrared cluster. The position of this object in the colour-colour and colour-magnitude infrared diagrams lies close to the reddening vector of a zero-age main-sequence O9V spectral-type star, and it seems to be the first star of this cluster to emerge. All these facts are consistent with the current star-forming scenarios associated with highly embedded star clusters.Facultad de Ciencias Astronómicas y Geofísica

Maximum expected ramp rates using cloud speed sensor measurements

Large ramps and ramp rates in photovoltaic (PV) power output are of concern and sometimes even explicitly restricted by grid operators. Battery energy storage systems can smooth the power output and maintain ramp rates within permissible limits. To enable PV plant and energy storage system design and planning, a method to estimate the largest expected ramps for a given location is proposed. Because clouds are the dominant source of PV power output variability, an analytical relationship between the worst expected ramp rate, cloud motion vector, and the geometrical layout of the PV plant is developed. The ability of the proposed method to bracket actual ramp rates is assessed over 10 months under different meteorological conditions, demonstrating an average compliance rate of 98.9% for a 2 min evaluation time window. The largest observed ramp of 29.7% s(-1)is contained with the worst case estimate of 34.3% s(-1). This method provides a convenient yet economical approach to worst-case PV ramp rate modeling and is compatible with solar irradiance measured at coarse temporal resolution.Juan Bosch was financed in part by Project No. PID2019-108953RB-C21, funded by the Ministerio de Ciencia e Innovación and co-financed by the European Regional Development Fund. In addition, Iñigo de la Parra was partially supported by the Spanish State Research Agency (AEI) and FEDER-UE under Grant Nos. DPI2016-80641-R and DPI2016-80642-R

3D features of modified photostructurable glass-ceramic with infrared femtosecond laser pulses

The exclusive ability of laser radiation to be focused inside transparent materials makes lasers a unique tool to process inner parts of them unreachable with other techniques. Hence, laser direct-write can be used to create 3D structures inside bulk materials. Infrared femtosecond lasers are especially indicated for this purpose because a multiphoton process is usually required for absorption and high resolution can be attained. This work studies the modifications produced by 450 fs laser pulses at 1027 nm wavelength focused inside a photostructurable glass-ceramic (Foturan®) at different depths. Irradiated samples were submitted to standard thermal treatment and subsequent soaking in HF solution to form the buried microchannels and thus unveil the modified material. The voxel dimensions of modified material depend on the laser pulse energy and the depth at which the laser is focused. Spherical aberration and selffocusing phenomena are required to explain the observed results

Prosthetic joint infection by Bordetella holmesii: Case report and a review of the literature

Introduction: Bordetella holmesii is a Gram-negative coccobacillus involved in different infections mostly described in case reports. Prosthetic joint infections in relation to this pathogen are rare. Here, we present the third case of B. holmesii in a patient without anatomical or functional spleen dysfunction. Case report: The patient was a 62-year-old female with a total knee prosthesis implanted in 1997 that required multiple replacements of the femoral component due to aseptic loosening in the past years. The patient was admitted to our hospital for an elective replacement surgery due to new radiological signs of loosening. B. holmesii was isolated from synovial fluid obtained during surgery. The identification was performed by matrix-assisted laser desorption ionization-time of flight mass spectrometry and confirmed by 16S rRNA gene amplification and sequencing. Antibiotic treatment was started but 14 days after surgery the patient presented pain and joint effusion. An arthrocentesis was performed and synovial fluid culture was positive again for B. holmesii. Surgical debridement including polyethylene replacement was performed and antibiotic treatment was continued for 3 months. After a 2-year follow-up period, the patient remained asymptomatic and physical examination showed normal function of the prosthesis. Conclusion: B. holmesii is an uncommon cause of bone and joint infections. This case indicates that this microorganism is a potential pathogen of prosthetic or native arthritis, and it should be considered when cultures are negative and in cases presenting torpid evolution

G287.84-0.82: an infrared star cluster in the Carina nebula

We have studied the properties of an infrared cluster embedded in the gas and dust of the southern part of the Carina nebula (NGC 3372), where the probable existence of current star formation has already been predicted. We used mid-infrared (A and C bands) and near-infrared (JHKs) images from the Midcourse Space Experiment and the Two-Micron All-Sky Survey, respectively, combined with an optical Ha narrow-band filter image obtained at the Cerro Tololo Inter-American Observatory. The infrared star cluster has at least 17 members, and its parameters, radius and stellar density are in very good agreement with high- to intermediate-mass star formation scenarios. The detected infrared sources have roughly the same intrinsic infrared excess determined from their position in colour-colour and colour-magnitude diagrams, suggesting that these objects could be related to pre-main-sequence stars of high to intermediate mass. Furthermore, we present a low-dispersion spectrum of the LS 1883 (O9.5V) star located near the centre of the infrared cluster. The position of this object in the colour-colour and colour-magnitude infrared diagrams lies close to the reddening vector of a zero-age main-sequence O9V spectral-type star, and it seems to be the first star of this cluster to emerge. All these facts are consistent with the current star-forming scenarios associated with highly embedded star clusters.Facultad de Ciencias Astronómicas y Geofísica

Increased Cortical Thickness and Caudate Volume Precede Atrophy in PSEN1 Mutation Carriers

Neuroimaging studies of familial Alzheimer's disease allow investigation of the disease process before clinical onset. We performed semi-automated MRI analysis to evaluate cortical thickness (CTh), grey matter (GM) volumes, and GM diffusivity indexes in PSEN1 mutation carriers (MC). We recruited 11 MC from 4 families with PSEN1 mutations (L286P, M139T, K239N) and 6 familial and 12 non-familial healthy controls. MC were classified as either asymptomatic (n=6) or symptomatic (n=5). Subjects underwent structural and diffusion-weighted 3-Tesla MRI scanning. CTh and GM volumes of subcortical structures and diffusivity indexes were calculated and group comparisons were performed. Structural images were reanalyzed with voxel-based morphometry methodology. Cerebrospinal fluid amyloid-β1-42 levels (Aβ) were measured. We found that symptomatic MC presented widespread cortical thinning, especially in precuneus and parietotemporal areas (p<0.01) and increased mean diffusivity (MD) in these areas compared to controls. Unexpectedly, asymptomatic MC, 9.9 years prior to the predicted age of disease onset, presented increased CTh in the precuneus and parietotemporal areas (p<0.01), increased caudate volumes (p<0.01), and decreased MD (p<0.05) in these areas compared to HC. In MC, CTh correlated with adjusted age. Aβ values were within normal limits in AMC. In conclusion, at early preclinical stages, CTh in the precuneus and parietotemporal regions and caudate volume increase in PSEN1 MC and decrease thereafter with disease progression. The different trends in MD in asymptomatic and symptomatic MC suggest that different microstructural changes underlie the contrasting morphometric findings. Reactive neuronal hypertrophy or/and inflammation may account for increased CTh and decreased MD in asymptomatic MC

CSF glial biomarkers YKL40 and sTREM2 are associated with longitudinal volume and diffusivity changes in cognitively unimpaired individuals

Cerebrospinal fluid (CSF) YKL40 and sTREM2 are astroglial and microglial activity biomarkers, respectively. We assessed whether CSF YKL40 and sTREM2 baseline levels are associated with longitudinal brain volume and diffusivity changes in cognitively unimpaired adults. Two brain MRI scans of 36 participants (57 to 78-years old, 12 male) were acquired in a 2-year interval. A beta(42), p-tau, YKL40 and sTREM2 concentrations in CSF were determined at baseline. We calculated gray and white matter volume changes per year maps (Delta GM and Delta WM, respectively) by means of longitudinal pairwise registration, and mean diffusivity variation per year (Delta MD) by subtraction. We checked voxel-wise for associations between Delta GM, Delta WM and Delta MD and baseline CSF level of YKL40 and sTREM2 and verified to what extent these associations were modulated by age (YKL40xAGE and sTREM2xAGE interactions). We found a positive association between Delta GM and YKL40 in the left inferior parietal region and no association between sTREM2 and Delta GM. Negative associations were also observed between Delta GM and YKL40xAGE (bilateral frontal areas, left precuneus and left postcentral and supramarginal gyri) and sTREM2xAGE (bilateral temporal and frontal cortex, putamen and left middle cingulate gyrus). We found negative associations between Delta WM and YKL40xAGE (bilateral superior longitudinal fasciculus) and sTREM2xAGE (bilateral superior longitudinal fasciculus, left superior corona radiata, retrolenticular external capsule and forceps minor, among other regions) but none between Delta WM and neither YKL40 nor sTREM2. Delta MD was positively correlated with YKL40 in right orbital region and negatively with sTREM2 in left lingual gyrus and precuneus. In addition, significant associations were found between Delta MD and YKL40xAGE (tail of left hippocampus and surrounding areas and right anterior cingulate gyrus) and sTREM2xAGE (right superior temporal gyrus). Areas showing statistically significant differences were disjoint in analyses involving YKL40 and sTREM2. These results suggest that glial biomarkers exert a relevant and distinct influence in longitudinal brain macro- and microstructural changes in cognitively unimpaired adults, which appears to be modulated by age. In younger subjects increased glial markers (both YKL40 and sTREM2) predict a better outcome, as indicated by a decrease in Delta GM and Delta WM and an increase in Delta MD, whereas in older subjects this association is inverted and higher levels of glial markers are associated with a poorer neuroimaging outcome

Analysis of Ionospheric and Geomagnetic Response to the 2020 Patagonian Solar Eclipse

Total solar eclipses are unique opportunities to study how the ionospheric and external geomagnetic field responds to fast changes in the ionizing flux as the moon’s shadow travels through its path over the ionosphere at an average speed of 3,000 km/h. In this contribution, we describe our observing campaign in which we set up GNSS and geomagnetic stations at the city of Valcheta, Río Negro, Argentina (which was located right under the path of totality). We also describe the results obtained from the analysis of the combination of on-site data together with publicly available observations from geodetic and geomagnetic observatories. The large span in latitude of our data allowed us to analyze the different magnitudes of the drop in vertical total electron content (ΔVTEC) with varying occultation percentages. We found an expected reduction in this drop as we move away from totality path but we also detected a new increment in ΔVTEC as we got closer to Earth’s Magnetic Equator. We also compared our observations of the geomagnetic field variations with predictions that were based on the Ashour-Chapman model and we find an overall good agreement, although a ≈20 min delay with the eclipse maximum is evident beyond observing uncertainties. This suggests the presence of processes that delay the response of the lower ionosphere to the loss of the photoionization flux.Laboratorio de Meteorología espacial, Atmósfera terrestre, Geodesia, Geodinámica, diseño de Instrumental y AstrometríaInstituto de Astrofísica de La Plat