Epithelial spreading is a common and fundamental aspect of various developmental and disease-related processes such as epithelial closure and wound healing. A key challenge for epithelial tissues ...undergoing spreading is to increase their surface area without disrupting epithelial integrity. Here we show that orienting cell divisions by tension constitutes an efficient mechanism by which the enveloping cell layer (EVL) releases anisotropic tension while undergoing spreading during zebrafish epiboly. The control of EVL cell-division orientation by tension involves cell elongation and requires myosin II activity to align the mitotic spindle with the main tension axis. We also found that in the absence of tension-oriented cell divisions and in the presence of increased tissue tension, EVL cells undergo ectopic fusions, suggesting that the reduction of tension anisotropy by oriented cell divisions is required to prevent EVL cells from fusing. We conclude that cell-division orientation by tension constitutes a key mechanism for limiting tension anisotropy and thus promoting tissue spreading during EVL epiboly.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Perovskite solar cells (PSCs) have now achieved efficiencies in excess of 22%, but very little is known about their long-term stability under thermal stress. So far, stability reports have hinted at ...the importance of substituting the organic components, but little attention has been given to the metal contact. We investigated the stability of state-of-the-art PSCs with efficiencies exceeding 20%. Remarkably, we found that exposing PSCs to a temperature of 70 °C is enough to induce gold migration through the hole-transporting layer (HTL), spiro-MeOTAD, and into the perovskite material, which in turn severely affects the device performance metrics under working conditions. Importantly, we found that the main cause of irreversible degradation is not due to decomposition of the organic and hybrid perovskite layers. By introducing a Cr metal interlayer between the HTL and gold electrode, high-temperature-induced irreversible long-term losses are avoided. This key finding is essential in the quest for achieving high efficiency, long-term stable PSCs which, in order to be commercially viable, need to withstand hard thermal stress tests.
Perovskites have been demonstrated in solar cells with a power conversion efficiency of well above 20%, which makes them one of the strongest contenders for next generation photovoltaics. While there ...are no concerns about their efficiency, very little is known about their stability under illumination and load. Ionic defects and their migration in the perovskite crystal lattice are some of the most alarming sources of degradation, which can potentially prevent the commercialization of perovskite solar cells (PSCs). In this work, we provide direct evidence of electric field-induced ionic defect migration and we isolate their effect on the long-term performance of state-of-the-art devices. Supported by modelling, we demonstrate that ionic defects, migrating on timescales significantly longer (above 103 s) than what has so far been explored (from 10-1 to 102 s), abate the initial efficiency by 10-15% after several hours of operation at the maximum power point. Though these losses are not negligible, we prove that the initial efficiency is fully recovered when leaving the device in the dark for a comparable amount of time. We verified this behaviour over several cycles resembling day/night phases, thus probing the stability of PSCs under native working conditions. This unusual behaviour reveals that research and industrial standards currently in use to assess the performance and the stability of solar cells need to be adjusted for PSCs. Our work paves the way for much needed new testing protocols and figures of merit specifically designed for PSCs.
Meiotic maturation is a crucial step of oocyte formation allowing its potential fertilization and embryo development. Elucidating this process is important both for fundamental research and assisted ...reproductive technology. Few computational tools based on non-invasive measurements are however available to characterize oocyte meiotic maturation. Here, we develop a computational framework to phenotype oocytes based on images acquired in transmitted light. We trained neural networks to segment the contour of oocytes and their zona pellucida using oocytes from diverse species. We defined a comprehensive set of morphological features to describe an oocyte. These steps are implemented in an open-source Fiji plugin. We present a feature based machine learning pipeline to recognize oocyte populations and determine their morphological differences. We first demonstrate its potential to screen oocyte from different strains and automatically identify their morphological characteristics. Its second application is to predict and characterize the maturation potential of oocytes. We identify the texture of the zona pellucida and the cytoplasmic particles size as features to assess mouse oocyte maturation potential and tested whether these features were applicable to human oocyte's developmental potential.
The advent of cluster ion beams has paved the way to the routine 3D analysis of organic heterojunctions. Alternatively, organic thin layers have also been successfully depth profiled with a ...low-energy cesium ion beam (Cs
+
), to exploit the high chemical reactivity of cesium atoms, acting as free-radical scavengers. Despite of this, little is known about the depth resolution associated with low-energy Cs
+
sputtering on organic multilayers. In this work, amino acids multilayers, consisting of phenylalanine delta layers alternated with tyrosine spacers, were used as model systems to assess the depth resolution associated with 500 eV Cs
+
depth profiles. High yields were obtained for quasi-molecular ions from both amino acids, and no significant chemical alteration was noticed under the monoatomic bombardment. A depth resolution as low as 4 nm is demonstrated without sensible degradation on a rather long profile depth (300 nm). Limited depth resolution (> 10 nm) along with high molecular degradation was previously reported on similar systems by combining low-energy Cs
+
with Ga
+
analysis beam. The use of the Bi
3
+
analysis beam results in a dramatic improvement of both the characteristic molecular signal intensities and the depth resolution. Even though the analysis beam fluence is very low compared to the sputtering beam fluence, data suggest that further reducing the analysis Bi
3
+
fluence could improve the depth resolution by ~ 1 nm.
The ventricular zone (VZ) of the developing cerebral cortex is a pseudostratified epithelium that contains progenitors undergoing precisely regulated divisions at its most apical side, the ...ventricular lining (VL). Mitotic perturbations can contribute to pathological mechanisms leading to cortical malformations. The HeCo mutant mouse exhibits subcortical band heterotopia (SBH), likely to be initiated by progenitor delamination from the VZ early during corticogenesis. The causes for this are however, currently unknown. Eml1, a microtubule (MT)-associated protein of the EMAP family, is impaired in these mice. We first show that MT dynamics are perturbed in mutant progenitor cells in vitro. These may influence interphase and mitotic MT mechanisms and indeed, centrosome and primary cilia were altered and spindles were found to be abnormally long in HeCo progenitors. Consistently, MT and spindle length regulators were identified in EML1 pulldowns from embryonic brain extracts. Finally, we found that mitotic cell shape is also abnormal in the mutant VZ. These previously unidentified VZ characteristics suggest altered cell constraints which may contribute to cell delamination.
Perovskites have been demonstrated in solar cells with a power conversion efficiency of well above 20%, which makes them one of the strongest contenders for next generation photovoltaics. While there ...are no concerns about their efficiency, very little is known about their stability under illumination and load. Ionic defects and their migration in the perovskite crystal lattice are some of the most alarming sources of degradation, which can potentially prevent the commercialization of perovskite solar cells (PSCs). In this work, we provide direct evidence of electric field-induced ionic defect migration and we isolate their effect on the long-term performance of state-of-the-art devices. Supported by modelling, we demonstrate that ionic defects, migrating on timescales significantly longer (above 10
3
s) than what has so far been explored (from 10
−1
to 10
2
s), abate the initial efficiency by 10-15% after several hours of operation at the maximum power point. Though these losses are not negligible, we prove that the initial efficiency is fully recovered when leaving the device in the dark for a comparable amount of time. We verified this behaviour over several cycles resembling day/night phases, thus probing the stability of PSCs under native working conditions. This unusual behaviour reveals that research and industrial standards currently in use to assess the performance and the stability of solar cells need to be adjusted for PSCs. Our work paves the way for much needed new testing protocols and figures of merit specifically designed for PSCs.
Perovskite cells benefit from a good night's sleep.
Provider: - Institution: - Data provided by Europeana Collections- Dieses Video zeigt den Mechanismus mit der dmgId 3254025(http://www.dmg-lib.org/dmglib/handler?mcdsc=3254025). Beim Generieren des ...Videos wurde die Ansicht von vorn verwendet. Andere Positionen sind hier dargestellt P5(http://www.dmg-lib.org/dmglib/handler?image=45643023), P3(http://www.dmg-lib.org/dmglib/handler?image=45644023), P1(http://www.dmg-lib.org/dmglib/handler?image=45645023), P0(http://www.dmg-lib.org/dmglib/handler?image=45646023), P2(http://www.dmg-lib.org/dmglib/handler?image=45647023), P4(http://www.dmg-lib.org/dmglib/handler?image=45648023) (ebenfalls als Ansicht von vorn).- This video shows a mechanism named landing gear system(http://www.dmg-lib.org/dmglib/handler?mcdsc=3254025). For the rendering of the video the view from the front was used. Other positions are shown here P5(http://www.dmg-lib.org/dmglib/handler?image=45643023), P3(http://www.dmg-lib.org/dmglib/handler?image=45644023), P1(http://www.dmg-lib.org/dmglib/handler?image=45645023), P0(http://www.dmg-lib.org/dmglib/handler?image=45646023), P2(http://www.dmg-lib.org/dmglib/handler?image=45647023), P4(http://www.dmg-lib.org/dmglib/handler?image=45648023) (also as view from the front).- Cette vidéo montre un mécanisme nommé système de train d'atterissage(http://www.dmg-lib.org/dmglib/handler?mcdsc=3254025). Pour le rendu de la vidéo la vue de face a été utilisé. D'autres positions seront affichés ici P5(http://www.dmg-lib.org/dmglib/handler?image=45643023), P3(http://www.dmg-lib.org/dmglib/handler?image=45644023), P1(http://www.dmg-lib.org/dmglib/handler?image=45645023), P0(http://www.dmg-lib.org/dmglib/handler?image=45646023), P2(http://www.dmg-lib.org/dmglib/handler?image=45647023), P4(http://www.dmg-lib.org/dmglib/handler?image=45648023) (également en tant que vue de face).- All metadata published by Europeana are available free of restriction under the Creative Commons CC0 1.0 Universal Public Domain Dedication. However, Europeana requests that you actively acknowledge and give attribution to all metadata sources including Europeana
Provider: - Institution: - Data provided by Europeana Collections- Dieses Video zeigt den Mechanismus mit der dmgId 3254025(http://www.dmg-lib.org/dmglib/handler?mcdsc=3254025). Beim Generieren des ...Videos wurde die ISO-Ansicht verwendet. Andere Positionen sind hier dargestellt P1(http://www.dmg-lib.org/dmglib/handler?image=45636023), P0(http://www.dmg-lib.org/dmglib/handler?image=45637023), P3(http://www.dmg-lib.org/dmglib/handler?image=45638023), P5(http://www.dmg-lib.org/dmglib/handler?image=45639023), P2(http://www.dmg-lib.org/dmglib/handler?image=45640023), P4(http://www.dmg-lib.org/dmglib/handler?image=45641023) (ebenfalls als ISO-Ansicht).- This video shows a mechanism named landing gear system(http://www.dmg-lib.org/dmglib/handler?mcdsc=3254025). For the rendering of the video the ISO-view was used. Other positions are shown here P1(http://www.dmg-lib.org/dmglib/handler?image=45636023), P0(http://www.dmg-lib.org/dmglib/handler?image=45637023), P3(http://www.dmg-lib.org/dmglib/handler?image=45638023), P5(http://www.dmg-lib.org/dmglib/handler?image=45639023), P2(http://www.dmg-lib.org/dmglib/handler?image=45640023), P4(http://www.dmg-lib.org/dmglib/handler?image=45641023) (also as ISO-view).- Cette vidéo montre un mécanisme nommé système de train d'atterissage(http://www.dmg-lib.org/dmglib/handler?mcdsc=3254025). Pour le rendu de la vidéo la ISO vue a été utilisé. D'autres positions seront affichés ici P1(http://www.dmg-lib.org/dmglib/handler?image=45636023), P0(http://www.dmg-lib.org/dmglib/handler?image=45637023), P3(http://www.dmg-lib.org/dmglib/handler?image=45638023), P5(http://www.dmg-lib.org/dmglib/handler?image=45639023), P2(http://www.dmg-lib.org/dmglib/handler?image=45640023), P4(http://www.dmg-lib.org/dmglib/handler?image=45641023) (également en tant que ISO vue).- All metadata published by Europeana are available free of restriction under the Creative Commons CC0 1.0 Universal Public Domain Dedication. However, Europeana requests that you actively acknowledge and give attribution to all metadata sources including Europeana
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