Collective evolution of submicron hillocks during the early stages of anisotropic alkaline wet chemical etching of Si(100) surfaces

We address experimentally the large-scale dynamics of Si(100) surfaces during the initial stages of anisotropic wet (KOH) chemical etching, which are characterized through atomic force microscopy. These systems are known to lead to the formation of characteristic pyramids, or hillocks, of typical sizes in the nanometric/micrometer scales, thus with the potential for a large number of applications that can benefit from the nanotexturing of Si surfaces. The present pattern formation process is very strongly disordered in space. We assess the space correlations in such a type of rough surface and elucidate the existence of a complex and rich morphological evolution, featuring at least three different regimes in just 10 min of etching. Such a complex time behavior cannot be consistently explained within a single formalism for dynamic scaling. The pyramidal structure reveals itself as the basic morphological motif of the surface throughout the dynamics. A detailed analysis of the surface slope distribution with etching time reveals that the texturing process induced by the KOH etching is rather gradual and progressive, which accounts for the dynamic complexity. The various stages of the morphological evolution can be accurately reproduced by computer-generated surfaces composed by uncorrelated pyramidal structures. To reach such an agreement, the key parameters are the average pyramid size, which increases with etching time, its distribution and the surface coverage by the pyramidal structures.We gratefully acknowledge discussions with David Nečas, leader of the Gwyddion project. This work was supported by Council of Scientific and Industrial Research (India) Scheme No. 03(1289)/13/EMR-II, and by MINECO/FEDER (Spain/UE) Grants Nos. FIS2012-38866-C05-01, MAT2014-54231-C4-1-P, BIO2016-79618-R, and FIS2015-66020-C2-1-P, as well as by Comunidad Autónoma de Madrid (Spain) Grant NANOAVANSENS S2013/MIT-3029

A close encounter of the massive kind

We have used (a) HST ACS imaging and STIS spectroscopy, (b) ground-basedPIONIER/VLT long-baseline interferometry, and (c) ground-basedspectroscopy from different instruments to study the orbit of theextreme multiple system HD 93 129 Aa,Ab, which is composed of (at least)two very massive stars in a long-period orbit with e>0.92 that willpass through periastron in 2017/2018. In several ways, the system is aneta Car precursor. Around the time of periastron passage the two verystrong winds will collide and generate an outburst of non-thermal hardX-ray emission without precedent in an O+O binary since astronomers havebeen able to observe above Earth's atmosphere. A coordinatedmultiwavelength monitoring in the next two years will enable abreakthrough understanding of the wind interactions in such extremeclose encounters. Furthermore, we have found evidence that HD 93 129 Aamay be a binary system itself. In that case, we could witness athree-body interaction that may yield a runaway star or a stellarcollision close to or shortly after the periastron passage. Either ofthose outcomes would be unprecedented, as they are predicted to below-frequency events in the Milky Way.Instituto de Astrofísica de La Plat

A close encounter of the massive kind

We have used (a) HST ACS imaging and STIS spectroscopy, (b) ground-basedPIONIER/VLT long-baseline interferometry, and (c) ground-basedspectroscopy from different instruments to study the orbit of theextreme multiple system HD 93 129 Aa,Ab, which is composed of (at least)two very massive stars in a long-period orbit with e>0.92 that willpass through periastron in 2017/2018. In several ways, the system is aneta Car precursor. Around the time of periastron passage the two verystrong winds will collide and generate an outburst of non-thermal hardX-ray emission without precedent in an O+O binary since astronomers havebeen able to observe above Earth's atmosphere. A coordinatedmultiwavelength monitoring in the next two years will enable abreakthrough understanding of the wind interactions in such extremeclose encounters. Furthermore, we have found evidence that HD 93 129 Aamay be a binary system itself. In that case, we could witness athree-body interaction that may yield a runaway star or a stellarcollision close to or shortly after the periastron passage. Either ofthose outcomes would be unprecedented, as they are predicted to below-frequency events in the Milky Way.Instituto de Astrofísica de La Plat

The first orbital solution for the massive colliding-wind binary HD 93162 (≡WR 25)

Context. Since the discovery, with the EINSTEIN satellite, of strong X-ray emission associated with HD 93162 (≡WR 25), this object has been predicted to be a colliding-wind binary system. However, radial-velocity variations that would prove the suspected binary nature have yet to be found. Aims. We spectroscopically monitored this object to investigate its possible variability to address this discordance. Methods. We compiled the largest available radial-velocity data set for this star to look for variations that might be due to binary motion. We derived radial velocities from spectroscopic data acquired mainly between 1994 and 2006, and searched these radial velocities for periodicities using different numerical methods. Results. For the first time, periodic radial-velocity variations are detected. Our analysis definitively shows that the Wolf-Rayet star WR 25 is an eccentric binary system with a probable period of about 208 days.Facultad de Ciencias Astronómicas y Geofísica

The first orbital solution for the massive colliding-wind binary HD 93162 (≡WR 25)

Context. Since the discovery, with the EINSTEIN satellite, of strong X-ray emission associated with HD 93162 (≡WR 25), this object has been predicted to be a colliding-wind binary system. However, radial-velocity variations that would prove the suspected binary nature have yet to be found. Aims. We spectroscopically monitored this object to investigate its possible variability to address this discordance. Methods. We compiled the largest available radial-velocity data set for this star to look for variations that might be due to binary motion. We derived radial velocities from spectroscopic data acquired mainly between 1994 and 2006, and searched these radial velocities for periodicities using different numerical methods. Results. For the first time, periodic radial-velocity variations are detected. Our analysis definitively shows that the Wolf-Rayet star WR 25 is an eccentric binary system with a probable period of about 208 days.Facultad de Ciencias Astronómicas y Geofísica

Mal-positioned nasogastric feeding tubes : are medical students safe to identify them?

OBJECTIVES: Nasogastric tube (NGT) placement is listed against Clinical Imaging in the upcoming Medical Licensing Assessment-compulsory for every graduating UK medical student from 2025. This study aims to establish the ability of medical students to correctly identify the position of an NGT on Chest X-ray (CXR) and to evaluate a learning tool to improve student outcome in this area. METHODS: Fourth-year (MB4) and fifth-year (MB5) medical students were invited to view 20 CXRs with 14 correctly sited and 6 mal-positioned NGT. MB5 students (Intervention) were exposed to an online interactive learning tool, with MB4 students kept as control. One week later, both groups of students were invited to view 20 more CXRs for NGT placement. RESULTS: Only 12 (4.8%) of 249 MB5 students and 5 (3.1%) of 161 MB4 students correctly identified all the NGTs on CXRs. The number of students misidentifying 1 or more mal-positioned NGT as "safe to feed" was 129 (51.8%) for MB5 and 76 (47.2%) for MB4 students. This improved significantly (P < .001) following exposure to the learning tool with 58% scoring all CXRs correctly, while 28% scored 1 or more mal-positioned NGT incorrectly. Students struggled to determine if the NGT tip had adequately passed into the stomach. However, they failed to identify an NG tube in the lung ("never event") in just one out of 1,108 opportunities. CONCLUSION: Medical students' ability to determine if the NGT was in the stomach remains suboptimal despite exposure to over 60 CXRs. Feeding NGT should be formally reported before use. ADVANCES IN KNOWLEDGE: This is the first attempt at quantifying graduating medical students', and by inference junior doctors', competence in safely identifying misplaced nasogastric feeding tubes. An online, experiential learning resource significantly improved their ability

Mal-positioned nasogastric feeding tubes: are medical students safe to identify them?

Objectives: Nasogastric tube (NGT) placement is listed against Clinical Imaging in the upcoming Medical Licensing Assessment – compulsory for every graduating UK medical student from 2025. This study aims to establish the ability of medical students to correctly identify the position of an NGT on Chest Xray (CXR) and to evaluate a learning tool to improve student outcome in this area. Materials and Methods: Fourth (MB4) and Fifth-year (MB5) medical students were invited to view 20 CXRs with 14 correctly sited and 6 mal-positioned NGT. MB5 students (Intervention) were exposed to an online interactive learning tool, with MB4 students kept as control. One week later, both groups of students were invited to view 20 more CXRs for NGT placement. Results: Only 12 (4.8%) of 249 MB5 students and 5 (3.1%) of 161 MB4 students correctly identified all the NGTs on CXRs. The number of students misidentifying 1 or more mal-position NGT as “safe to feed” was 129 (51.8%) for MB5 and 76 (47.2%) for MB4 students. This improved significantly (p&lt;0.001) following exposure to the learning tool with 58% scoring all CXRs correctly while 28% scored 1 or more mal-positioned NGT incorrectly. Students struggled to determine if the NGT tip had adequately passed into the stomach. However, they failed to identify an NG tube in the lung (“Never event”) in just one out of 1,108 opportunities. Conclusion: Medical students’ ability to determine if the NGT was in the stomach remains suboptimal despite exposure to over 60 CXRs. Feeding NGT should be formally reported before use. Advances in Knowledge: This is the first attempt at quantifying graduating medical students’, and by inference junior doctors’, competence in safely identifying misplaced nasogastric feeding tubes. An online, experiential learning resource significantly improved their ability

Broad Balmer Wings in BA Hyper/Supergiants Distorted by Diffuse Interstellar Bands: Five Examples in the 30 Doradus Region from the VLT-FLAMES Tarantula Survey

Extremely broad emission wings at Hβ and Hα have been found in VLT-FLAMES Tarantula Survey data for five very luminous BA supergiants in or near 30 Doradus in the Large Magellanic Cloud. The profiles of both lines are extremely asymmetrical, which we have found to be caused by very broad diffuse interstellar bands (DIBs) in the longward wing of Hβ and the shortward wing of Hα. These DIBs are well known to interstellar but not to many stellar specialists, so that the asymmetries may be mistaken for intrinsic features. The broad emission wings are generally ascribed to electron scattering, although we note difficulties for that interpretation in some objects. Such profiles are known in some Galactic hyper/supergiants and are also seen in both active and quiescent Luminous Blue Variables (LBVs). No prior or current LBV activity is known in these 30 Dor stars, although a generic relationship to LBVs is not excluded; subject to further observational and theoretical investigation, it is possible that these very luminous supergiants are approaching the LBV stage for the first time. Their locations in the HRD and presumed evolutionary tracks are consistent with that possibility. The available evidence for spectroscopic variations of these objects is reviewed, while recent photometric monitoring does not reveal variability. A search for circumstellar nebulae has been conducted, with an indeterminate result for one of them

The first orbital solution for the massive colliding-wind binary HD 93162 (≡WR 25)

Context. Since the discovery, with the EINSTEIN satellite, of strong X-ray emission associated with HD 93162 (≡WR 25), this object has been predicted to be a colliding-wind binary system. However, radial-velocity variations that would prove the suspected binary nature have yet to be found. Aims. We spectroscopically monitored this object to investigate its possible variability to address this discordance. Methods. We compiled the largest available radial-velocity data set for this star to look for variations that might be due to binary motion. We derived radial velocities from spectroscopic data acquired mainly between 1994 and 2006, and searched these radial velocities for periodicities using different numerical methods. Results. For the first time, periodic radial-velocity variations are detected. Our analysis definitively shows that the Wolf-Rayet star WR 25 is an eccentric binary system with a probable period of about 208 days.Facultad de Ciencias Astronómicas y Geofísica

Typical and extreme weather datasets for studying the resilience of buildings to climate change and heatwaves

peer reviewedWe present unprecedented datasets of current and future projected weather files for building simulations in 15 major cities distributed across ten climate zones worldwide. The datasets include ambient air temperature, relative humidity, atmospheric pressure, direct and diffuse solar irradiance, and wind speed at hourly resolution, which are essential climate elements needed to undertake building simulations. The datasets contain typical and extreme weather years in the EnergyPlus weather file (EPW) format and multiyear projections in comma-separated value (CSV) format for three periods: historical (2001-2020), future mid-term (2041-2060), and future long-term (2081-2100). The datasets were generated from projections of one regional climate model, which were bias-corrected using multiyear observational data for each city. The methodology used makes the datasets among the first to incorporate complex changes in the future climate for the frequency, duration, and magnitude of extreme temperatures. These datasets, created within the IEA EBC Annex 80 “Resilient Cooling for Buildings”, are ready to be used for different types of building adaptation and resilience studies to climate change and heatwaves.11. Sustainable cities and communitie