Si Deposition Research Articles

Structural and morphological instabilities of the Si(1 1 1)-7 × 7 surface during silicon growth and etching by oxygen and selenium

Using in situ reflection electron microscopy and ex situ atomic force microscopy, we have studied the morphological stability of large-scale (~10–100 μm) Si(111)-7 × 7 terraces during silicon growth and etching by oxygen and selenium. On the large-scale terraces, silicon growth at substrate temperatures T = 600–770 °C and Si deposition rates R = 0.002–0.2 BL/s proceeds in multilayer mode. Based on RMS surface roughness scaling W ∝ Θβ, we have discerned three modes of morphological instability caused by (I) effective adatom diffusion along step edges at low T and R (β ≈ 0.33), (II) effective diffusion and fast step motion along disordered “1 × 1” regions in 7 × 7 domain boundaries at intermediate T and R (β ≈ 0.2), and (III) accumulation of Si adatoms in high-atom-density “1 × 1” regions on the uppermost terraces at high T and R (β ≈ 0.5). The etching of the singular Si(111)-7 × 7 surface by oxygen leads to the slow development of multilayer morphology, while selenium-induced etching preserves flat surface morphology with periodic 2D vacancy island nucleation, growth, and coalesce, which is attributed to Se adatom diffusion. On the step-bunched surface, the Si or Se adatom diffusion to the step bunches leads to the self-organization of pyramidlike or valley-like morphology during Si growth or Se-induced etching, respectively.

High silicon concentrations in grasses are linked to environmental conditions and not associated with C4 photosynthesis.

The uptake and deposition of silicon (Si) as silica phytoliths is common among land plants and is associated with a variety of functions. Among these, herbivore defense has received significant attention, particularly with regard to grasses and grasslands. Grasses are well known for their high silica content, a trait which has important implications ranging from defense to global Si cycling. Here, we test the classic hypothesis that C4 grasses evolved stronger mechanical defenses than C3 grasses through increased phytolith deposition, in response to extensive ungulate herbivory ("C4 -grazer hypothesis"). Despite mixed support, this hypothesis has received broad attention, even outside the realm of plant biology. Because C3 and C4 grasses typically dominate in different climates, with the latter more abundant in hot, dry regions, we also investigated the effects of water availability and temperature on Si deposition. We compiled a large dataset of grasses grown under controlled environmental conditions. Using phylogenetically informed generalized linear mixed models and character evolution models, we evaluated whether photosynthetic pathway or growth condition influenced Si concentration. We found that C4 grasses did not show consistently elevated Si concentrations compared with C3 grasses. High temperature treatments were associated with increased concentration, especially in taxa adapted to warm regions. Although the effect was less pronounced, reduced water treatment also promoted silica deposition, with slightly stronger response in dry habitat species. The evidence presented here rejects the "C4 -grazer hypothesis." Instead, we propose that the tendency for C4 grasses to outcompete C3 species under hot, dry conditions explains previous observations supporting this hypothesis. These findings also suggest a mechanism via which anthropogenic climate change may influence silica deposition in grasses and, by extension, alter the important ecological and geochemical processes it affects.

PERKECAMBAHAN DAN PERTUMBUHAN AWAL BUDSET DAN BUDCHIP TEBU (Saccharum officinarum L.) YANG DITANAM PADA BERBAGAI POSISI MATA TUNAS

Germination phase is a crucial stage in the cultivation of sugarcane. This phase is influenced by numerous factors, such as the position of bud when the sugarcane seed is planted. This study aims to examine the responses of germination and early growth of sugarcane bud chip and budset seeds variety PS 862 that are grown in various bud positions, namely upward, downward, and side positions. Results explicated that there were significant differences in the seed germination that are grown with various bud positions. Seeds that are planted with a downward bud position germinate slower than the two other bud positions. However, the percentage of germination of all treatments were classified as vigorous since the numbers are more than 80%. There was a strong influence of the bud position on the number of tillers and root/shoot ratio. Seeds that are planted with upward and side bud position have more tillers than seeds grown with the two other positions. The root/shoot ratio was higher in seeds grown with upward positions than the other positions. Meanwhile, there were no significant effects of bud positions and the form of seed on plant and stem height, the number of leaves, as well as root, shoot, and total dry weight of the crop.

(Invited) Evolutionary Applications of Functional Porous Silicon

Nanostructured porous silicon (PS) shows varied tunable functions leading to diversification of silicon technology. Among these functions, the emissions of photon, electron, and sound relate to the optical, electrical, and thermal properties of PS, respectively, as a quantum-confined material [1]. Some topics on further usefulness based on the functional combination is presented here.PS is composed of thermally isolated Si quantum dots (Si QDs) with a very high packing density. Due to a strong phonon confinement and interfacial scattering in PS, the thermal conductivity of PS layers is drastically lowered in comparison to that of bulk single-crystalline Si (c-Si). At the same time, its volumetric heat capacity is also significantly decreased. When combined with the mechanically metastable nature, it becomes possible to produce Si QDs with a considerably low external thermal energy. Actually, PS layers prepared by a standard electrochemical anodization of c-Si wafers in ethanoic HF solutions followed by peeling off from the wafer were dipped into organic solvents mixed with HF aqueous solution, and then in-situ heat treatment was made. It has been confirmed that PS layers are almost completely transformed into colloidal Si QDs with a significantly high yield even at a moderate temperature. The surfaces of as-prepared colloidal Si QDs are autonomously and organically passivated and they exhibit brighter PL emission than original PS. The dispersibility of Si QDs in solvents can be controlled by using organic solutions with appropriate function groups. Being a practical, clean, and low-power approach, this process provides a way for the scalable use of colloidal Si QDs as a printable material in optoelectronic, photoelectric, and biological applications. The thermal stability of PS with a controlled mesoporous surface structure, on the other hand, is useful as a substrate for epitaxial deposition of Si, Ge, SiC, diamond films, GaN, ZnO, and other III–V and II–VI semiconductors. The study has been extended to thin film deposition of ceramics like ferroelectric and ferrite materials. Recently [2], thin films of spinel ferrite (ZnFe2O4) were deposited on PS layers by pulsed laser deposition with an Nd:YAG laser of 266 nm for application to gas sensing. According to the structural and compositional characterizations, deposited thin films were polycrystalline and stoichiometric. Its average grain size and resistivity were smaller and higher, respectively, than those in the case of deposition on c-Si wafers. Obviously, the density of nucleation sites on the PS surface is much higher than that on the c-Si substrate. The measured sensitivity of a PS based device for liquefied petroleum gas was two-times higher than that of the c-Si based one. The sensitivity at high temperatures was comparable to that of ZnFe2O4 nanotubes and powder. It is important from a technological viewpoint that a reducing gas was detected effectively using the thin-film device configuration on c-Si wafer. In the high-porosity PS layer, thermal constants become close to the lower limit of solid state materials. When a temperature fluctuation is produced by electrical input to the heater electrode formed on the PS layer, an acoustic wave is generated near the surface via the thermos-acoustic transfer effect. A significant sound pressure amplitude is produced without any mechanical vibrations. The PS thermos-acoustic emitter shows a sufficiently flat frequency response in a wide ultrasonic band. One possible application is to reproduce complicated ultrasonic vocalization (USV) calls for clarifying the mechanism of mice communication and male-female interactions. As previously demonstrated, mouse mothers were attracted by pup USVs reproduced by a PS emitter, while they did not respond to other synthesized sounds. It was also found that the response to pup USVs was enhanced by social experiences. Studies on mutual recognition between mother and infant suggest that pup USVs looks to have an individual signature used in pup differentiation by mouse mothers, similar to acoustic communication between human mothers and their infants. It has also been reported that female mice exhibit disassortative social preferences in response to male USVs, and that the acoustic features that affect these social preferences are different between mouse strains [3].The author NK thank Prof. Wakiya, and Prof. Kikusui for their continuing cooperation.[1] N. Koshida and T. Nakamura, Frontiers in Chemistry “Advances in Porous Semiconductors Science and Technology” Vol. 7, 273 (2019).[2] H. Ishigami, T. Kawaguchi, N. Sakamoto, S. Che, N. Koshida, K. Shinozaki, H. Suzuki, and N. Wakiya, J. Ceramic Soc. of Japan 128, 2020.[3] K. Nomoto, A. Hashiguchi, A. Asaba, M. Kato, N. Koshida, K. Mogi, and T. Kikusui, Experimental Animals, Published online, Feb 26, 2020.

Silicon deposition on guard cells increases stomatal sensitivity as mediated by K+ efflux and consequently reduces stomatal conductance.

Silicon (Si) has been widely reported to improve plant resistance to water stress via various mechanisms including cuticular Si deposition to reduce leaf transpiration. However, there is limited understanding of the effects of Si on stomatal physiology, including the underlying mechanisms and implications for resistance to water stress. We grew tall fescue (Festuca arundinacea Schreb. cv. Fortuna) hydroponically, with or without Si, and treated half of the plants with 20% polyethylene glycol to impose physiological drought (osmotic stress). Scanning electron microscopy in conjunction with X-ray mapping found that Si was deposited on stomatal guard cells and as a sub-cuticular layer in Si-treated plants. Plants grown in Si had a 28% reduction in stomatal conductance and a 23% reduction in cuticular conductance. When abscisic acid was applied exogenously to epidermal leaf peels to promote stomatal closure, Si plants had 19% lower stomatal aperture compared to control plants (i.e. increased stomatal sensitivity) and an increased efflux of guard cell K+ ions. However, the changes in stomatal physiology with Si were not substantial enough to improve water stress resistance, as shown by a lack of significant effect of Si on water potential, growth, photosynthesis and water-use efficiency. Our findings suggest a novel underlying mechanism for reduced stomatal conductance with Si application; specifically, that Si deposition on stomatal guard cells promotes greater stomatal sensitivity as mediated by guard cell K+ efflux.

Design and formation of SiC (0001)/SiO2 interfaces via Si deposition followed by low-temperature oxidation and high-temperature nitridation

We report an effective approach to reduce defects at a SiC/SiO2 interface. Since oxidation of SiC may inevitably lead to defect creation, the idea is to form the interface without oxidizing SiC. Our method consists of four steps: (i) H2 etching of SiC, (ii) Si deposition, (iii) low-temperature (∼750 °C) oxidation of Si to form SiO2, and (iv) high-temperature (∼1600 °C) N2 annealing to introduce nitrogen atoms. The interface state density estimated by a high (1 MHz)–low method is in the order of 1010 cm−2 eV−1, two orders of magnitude lower than that of an interface formed by SiC oxidation.

For examination and dietetics pregnant women and women who have recently given birth.

The author praises the Thure Brandt's method of treatment diseases of female genital organs and says that he has come to the development of this method to such perfection that new work in this area can only be directed at the discovery of the newest information on the physiology and pathology of the female genital apparatus, for the Thure Brandt's method to be shown to the indications for method and the reason for his success. It is also known that in case of uterine prolapse, in old and neglected cases, this method of raising the uterus and massage can give an amazingly quick and perfect result, in other cases it is not. Obviously, failure is the result of various anatomical relationships, and, according to the author, the bending of the uterus back and its side positions, where pessaries and surgical methods of treatment are more intelligent.

Quantum Transport in Air-Stable Na3Bi Thin Films.

Na3Bi has attracted significant interest in both bulk form as a three-dimensional topological Dirac semimetal and ultrathin form as a wide-band gap two-dimensional topological insulator. Its extreme air sensitivity has limited experimental efforts on thin and ultrathin films grown via molecular beam epitaxy to ultrahigh vacuum environments. Here, we demonstrate air-stable Na3Bi thin films passivated with magnesium difluoride (MgF2) or silicon (Si) capping layers. Electrical measurements show that deposition of MgF2 or Si has minimal impact on the transport properties of Na3Bi while in ultrahigh vacuum. Importantly, the MgF2-passivated Na3Bi films are air-stable and remain metallic for over 100 h after exposure to air, as compared to near instantaneous degradation when they are unpassivated. Air stability enables transfer of films to a conventional high-magnetic field cryostat, enabling quantum transport measurements, which verify that the Dirac semimetal character of Na3Bi films is retained after air exposure.

Deactivation mechanism of Fe/Al2O3 catalyst during the ozonation of reverse osmosis concentrates (ROCs): Effect of silicate

Catalytic ozonation is regarded as a promising process for the treatment of heavily contaminated industrial wastewater, but has not been widely implemented at full-scale due to the high expense of catalyst. In this paper, the catalysts from a fix-bed catalytic ozonation reactor were collected and analyzed after the consecutive operation of three and a half years. The reactor was fed with 200 m3/h of Reverse osmosis concentrates (ROC) from a coal refinery plant located in mid-west China. The deactivation mechanism of the Fe/Al2O3 catalyst is revealed. It was found that the deposition of Si on the catalyst surface (an increase of about 40 times) was the main cause of deactivation. Herein, the role of typical functional sites of Fe/Al2O3 formed under various physicochemical conditions, for the silicate adsorption was studied based on the adsorption isotherms and theoretical analyses using density functional theory (DFT) calculation. The sites associated with catalytic activation of ozone: Fe-OOH (-0.66 eV) and Fe-O-Al (-0.49 eV) sites have much higher binding energy of silicate than non-reactive Fe-OH (-0.05 eV) sites. As a relatively strong Brönsted acid, silicic acid preferentially interacts with Fe-O-Al and Fe-OOH to reduce the abundance of Lewis acidity on the catalyst surface, which leads to the catalyst poisoning. This work points out the deactivation mechanism of the ozonation catalyst when treating wastewater with high salinity or alkalinity, and will lead to the new direction on the design of heterogenous ozonation catalysts.

Dry synthesis of single-nanometer-scale Pt Si fine particles for electrocatalysis

Abstract Single-nanometer-scale Pt Si fine particles (Pt Si NPs) were synthesized via the arc-plasma deposition of Si on a highly oriented pyrolytic graphite at a fixed substrate temperature of 600 °C, followed by electron-beam deposition of Pt at the temperatures between 100 and 600 °C in ultra-high vacuum. X-ray diffraction patterns of the vacuum-synthesized Pt Si NPs showed that a solid solution of Pt Si was the major component of the particles. Minor diffraction peaks, due to the intermetallic compounds (Pt3Si1 and Pt12Si5), at the Pt-deposition temperature (Tsub-Pt) of 500 °C, were also observed. Scanning tunneling microscopic images exhibited that Pt Si NPs with an average diameter less than 10 nm were dispersed in the substrate at Tsub-Pt temperatures up to 500 °C. The Pt Si NPs synthesized at a Tsub-Pt of 300 and 450 °C showed 1.7 times higher initial mass activity for oxygen reduction reaction (ORR) compared to commercial carbon-supported Pt NPs catalysts and showed better electrochemical stability than pure Pt NPs. These results demonstrate that the arc-plasma deposition of Si NPs, followed by e-beam deposition of metal elements (Pt) in ultra-high vacuum is a new class dry-synthesis for the single-nanometer-scale fine particles of Pt Si for electrocatalysis, e.g. ORR.

New evidence defining the evolutionary path of aquaporins regulating silicon uptake in land plants.

Understanding the evolution events defining silicon (Si) uptake in plant species is important for the efficient exploration of Si-derived benefits. In the present study, Si accumulation was studied in 456 diverse plant species grown in uniform field conditions, and in a subset of 151 species grown under greenhouse conditions, allowing efficient comparison among the species. In addition, a systematic analysis of nodulin 26-like intrinsic proteins III (NIP-III), which form Si channels, was performed in >1000 species to trace their evolutionary path and link with Si accumulation. Significant variations in Si accumulation were observed among the plant species studied. For their part, species lacking NIP-IIIs systematically showed low Si accumulation. Interestingly, seven NIP-IIIs were identified in three moss species, namely Physcomitrella patens, Andreaea rupestris, and Scouleria aquatica, indicating that the evolution of NIP-IIIs dates back as early as 515 million years ago. These results were further supported from previous reports of Si deposition in moss fossils estimated to be from around the Ordovician era. The taxonomical distribution provided in the present study will be helpful for several other disciplines, such as palaeoecology and geology, that define the biogeochemical cycling of Si. In addition to the prediction of Si uptake potential of plant species based on sequence information and taxonomical positioning, the evolutionary path of the Si uptake mechanism described here will be helpful to understand the Si environment over the different eras of land plant evolution.

Microtubule-organizing center-mediated structural atypia in low- and high-grade urothelial carcinoma

Urothelial carcinoma (UC) comprises two subtypes, low grade (LG-UC) and high grade (HG-UC), with different pathological and clinical behavior. LG-UC and HG-UC are classified based on cellular and structural atypia of pathological findings. The mechanisms responsible for maintaining structural atypia, such as the disturbance of nuclear polarity, remain unclear. In this study, we studied microtubule-organizing center (MTOC)-mediated nuclear polarity in UC subtypes. We evaluated six cases with normal urothelium (NU), 10 LG-UC cases, and 10 HG-UC cases by double immunofluorescence staining of γ-tubulin as a marker of MTOC and E-cadherin as a marker of each cell border. The number and position of γ-tubulin dots of expression in more than 100 cells per case were assessed using the spatial relationship with the nucleus and surface-basal axis. We found one γ-tubulin dot in most normal and tumor cells, and more than two γ-tubulin dots in 4.6% of NU cells, 6.1% of LG-UC cells, and 9.8% of HG-UC cells. More than three γ-tubulin dots were found only in 1.2% of HG-UC cells. Surface side positioning of γ-tubulin was found in 77.4% of normal urothelial cells, 63.8% of LG-UC cells, and 39.2% of HG-UC cells, whereas aberrant lateral and basal side positioning of γ-tubulin was found in 22.6% of normal urothelial cells, 36.1% of LG-UC cells, and 60.8% of HG-UC cells. We concluded that numerical and positional aberrations of MTOC in UC cases were strongly correlated with both cellular and structural atypia as well as abnormal cell proliferation.

Preliminary development and technical evaluation of a belt-actuated robotic rehabilitation platform.

BACKGROUND: To provide effective rehabilitation in the early post-injury stage, a novel robotic rehabilitation platform is proposed, which provides full-body arm-leg rehabilitation via belt actuation to severely disabled patients who are restricted to bed rest.OBJECTIVE: To design and technically evaluate the preliminary development of the rehabilitation platform, with focus on the generation of various leg movements.METHODS: Two computer models were developed by importing the components from SolidWorks into Simscape Multibody in MATLAB. This allowed simulation of various stepping movements in supine-lying and side-lying positions. Two belt-actuated test rigs were manufactured and automatic control programs were developed in TIA Portal. Finally, the functionality of the test rigs was technically evaluated. RESULTS: Computer simulation yielded target positions for the generation of various stepping movements in the experimental platforms. The control system enabled the two-drive test rig to provide three modes of stepping in a supine position. In addition, the four-drive test rig produced walking-like stepping in a side-lying position.CONCLUSIONS:This work confirmed the feasibility of the mechanical development and control system of the test rigs, which are deemed applicable for further development of the overall novel robotic rehabilitation platform.

Catalytically mediated epitaxy of 3D semiconductors on van der Waals substrates

The formation of well-controlled interfaces between materials of different structure and bonding is a key requirement when developing new devices and functionalities. Of particular importance are epitaxial or low defect density interfaces between two-dimensional materials and three-dimensional semiconductors or metals, where an interfacial structure influences electrical conductivity in field effect and optoelectronic devices, charge transfer for spintronics and catalysis, and proximity-induced superconductivity. Epitaxy and hence well-defined interfacial structure has been demonstrated for several metals on van der Waals-bonded substrates. Semiconductor epitaxy on such substrates has been harder to control, for example during chemical vapor deposition of Si and Ge on graphene. Here, we demonstrate a catalytically mediated heteroepitaxy approach to achieve epitaxial growth of three-dimensional semiconductors such as Ge and Si on van der Waals-bonded materials such as graphene and hexagonal boron nitride. Epitaxy is “transferred” from the substrate to semiconductor nanocrystals via solid metal nanocrystals that readily align on the substrate and catalyze the formation of aligned nuclei of the semiconductor. In situ transmission electron microscopy allows us to elucidate the reaction pathway for this process and to show that solid metal nanocrystals can catalyze semiconductor growth at a significantly lower temperature than direct chemical vapor deposition or deposition mediated by liquid catalyst droplets. We discuss Ge and Si growth as a model system to explore the details of such hetero-interfacing and its applicability to a broader range of materials.

Effectiveness of Nesting on Posture Comfort among Low Birth Weight Babies in Neonatal Intensive Care Unit

An infant is the most helpless gathering to get acclimates to the new condition. Following birth, during the initial months, they act as a momentary period during which the baby adjusts from the aquatic to the aerial environment. Nesting positions keeps up the flexion pose as such as intrauterine position and stances. As a fundamental obligation of the nurses, it is one of the most significant nursing procedures, positioning by nesting utilizes a non-pharmacological methodology to diminish torment and push and improve comfort. The present study aims to assess the effectiveness of nesting on posture comfort among low birth weight babies. A quantitative quasiexperimental research design was conducted among 30 low birth weight babies. Convenient sampling technique was used to select samples. A semistructured interview was used to collect demographic data, and posture comfort was assessed using a comfort scale. The babies in the experimental group were placed in a side-lying position inside the nest, which is then rolled blanket. After an hour, the posture comfort was re-assessed. The study results show significant improvement in the posture comfort among the experimental group than the control group after the intervention at the level of p<0.001. This reveals that nesting is highly signiϑicant in the experimental group because it improves posture comfort of the newborn, which in turn promotes growth and development of the low birth weight babies. This indicates that nesting is an effective and secure method to improve posture comfort, maintains the vital signs and helps in the development of low birth weight babies & promotes sound sleep in low birth weight babies.><0.001. This reveals that nesting is highly significant in the experimental group because it improves posture comfort of the newborn, which in turn promotes growth and development of the low birth weight babies. This indicates that nesting is an effective and secure method to improve posture comfort, maintains the vital signs and helps in the development of low birth weight babies & promotes sound sleep in low birth weight babies.

Reliability Of Ultrasound Panoramic Imaging Of Muscle Size For The Transversus Abdominis

PURPOSE: The transversus abdominis (TrA) is a key muscle in core stability. Measurements of its morphology might shed some light on structure, function and pathology of core muscles. A new ultrasound technique, panoramic imaging, could be used to visualize the whole length of the muscle in one image. The purpose of this study is to assess the degree to which this technique produces stable and consistent results. METHODS: 6 female participants; age(years)= 21.3 ± 1.6; height(cm)= 167.5 ± 5.1; weight(kg) = 65.5 ± 11.0 volunteered for this study. With the participants in side-lying position, muscle length, muscle area and thickness were scanned using GE Logic S8 (6-15 MHz probe). The right and left TrA muscles were imaged twice on each subject at spinal levels L1, L3 and L5 and later measured by two separate investigators. Test-retest reliability was calculated using interclass correlation coefficient (ICC) (random subjects and fixed raters) along with the Standard Error of Measurement (SEM). RESULTS: Our panoramic measures showed excellent intertester reliability for length, area and thickness measurements (ICC=0.981, 0.982, 0.985, respectively). In addition, the SEM for length, area and thickness were SEM= 0.178, 0.078, 0.046, respectively. CONCLUSIONS: Our method of assessing TrA morphology showed excellent reliability in the three dimensions measured and had low error rates that were equal to or better than those associated with other muscles previously measured. Panoramic imaging seems to be a reliable technique that could be used to visualize the whole TrA muscle in one image. Comparison to MRI images would further help establish its validity.

Silicon: its ameliorative effect on plant defense against herbivory

Plants protect themselves against pest attack utilizing both direct and indirect modes of defense. The direct mode of defense includes morphological, biochemical, and molecular barriers that affect feeding, growth, and survival of herbivores whereas the indirect mode of defense includes release of a blend of volatiles that attract natural enemies of the pests. Both of these strategies adopted by plants are reinforced if the plants are supplied with one of the most abundant metalloids, silicon (Si). Plants absorb Si as silicic acid (Si(OH)4) and accumulate it as phytoliths, which strengthens their physical defense. This deposition of Si in plant tissue is up-regulated upon pest attack. Further, Si deposited in the apoplast, suppresses pest effector molecules. Additionally, Si up-regulates the expression of defense-related genes and proteins and their activity and enhances the accumulation of secondary metabolites, boosting induced molecular and biochemical defenses. Moreover, Si plays a crucial role in phytohormone-mediated direct and indirect defense mechanisms. It is also involved in the reduction of harmful effects of oxidative stress resulting from herbivory by accelerating the scavenging process. Despite increasing evidence of its multiple roles in defense against pests, the practical implications of Si for crop protection have received less attention. Here, we highlight recent developments in Si-mediated improved plant resistance against pests and its significance for future use in crop improvement.

The growth processes and crystal structure of Ca silicides films grown by MBE at 500 °C on a Si(001) substrate

This article investigates the growth of calcium (Ca) silicides on the Si(001)2x1 surface during molecular beam epitaxy (MBE) from two sources of Ca and Si with a variable flow ratio from three to 10 at a fixed substrate temperature of 500 °C. According to atomic force microscopy (AFM), the grown films consist of grains with a mutually perpendicular orientation and have pronounced grain boundaries with an inhomogeneous relief. The best crystalline qualities of the films, both CaSi and CaSi2, were confirmed for the minimum ratio (about 3.0) of Ca to Si deposition flows by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) data in both cross-sections and in planar sections. At the same time, according to XRD and HRTEM data, for all formed films over the CaSi(010) layer on Si(001), the growth of hR3-CaSi2 was observed with epitaxial relationships: hR3-CaSi2(001)//CaSi(010)//Si(001). An analysis of these studies showed that calcium monosilicide (CaSi) is the first silicide phase in the Ca–Si(001) system at 500 °C due to (1) the maximum modulus of its heat of formation, (2) a decrease in the Ca accommodation coefficient to silicon less than unity and the formation of a mixture close to CaSi, (3) a better matching between the parameters of the CaSi(010) plane lattice and the Si(001) plane lattice, and (4) lower CaSi (010)/Si (001) interface energy compared with the CaSi2(001)/Si(001) system. It is assumed that the formation of CaSi2 occurs in the subsurface region of the growing film at 500 °C due to increased diffusion of Ca atoms into the Si substrate and increased intergranular diffusion of Si atoms, which leads to the formation of a mixture with the CaSi2 composition. Both factors create conditions for the crystallization of CaSi2 on the surface of the CaSi layer at Т = 500 оС. The epitaxial ordering of CaSi2 on the CaSi surface and the decrease in the energy of hR3-CaSi2(001)/CaSi(010) interface is associated with small distortions of their lattices during superstructural matching, which is proved by modeling their matching.

Fire resistance of the vertical glass structures with thermal protection foil

PurposeDuring the building designing, it is very important to deal with the fire resistance of the structures. The designed materials for escape routes should be selected to ensure the usability of the structures until the time of escape. Planning affects the glass structures similarly, so these can also be partition walls and load bearing structures, although the latter is less applied on escape routes. The heat protection of the glasses can be improved with heat-protective foils, while fire protection is provided by gel intumescent material.Design/methodology/approachTo research the topic of fire resistance, laboratory experiments were carried out on small-scaled glass elements with thermal protection foil at Budapest University of Technology and Economics at the Department of Construction Materials and Technologies.FindingsFire protection of small model specimens was tested with blowtorch fire and furnace heat load. During the experiments, six foils were tested. Single pane glass, double layered and triple glazed specimens were tested with blowtorch fire.Originality/valueFire protection of small model specimens was tested with blowtorch fire and furnace heat load. During the experiments, six foils were tested. Single pane glass, double layered and triple glazed specimens were tested with blowtorch fire. In case of heat-protected glazing, the foils on the “protected” side of the single pane glass do not have a fire protection effect based on blowtorch fire test. For double glassed specimens, the P35 foil has a perceptible effect, even for the requirements of the flame breakthrough (E, integrity), when the foil is placed on the inner side (position 3) of the second glass layer. The stratification of each triple glazed specimens was effective against blowtorch fire load (3 M, S4&P35), so (EI, integrity and isolation) it can meet the requirements of flame breakthrough and thermal insulation.

Supracellular Actomyosin Mediates Cell-Cell Communication and Shapes Collective Migratory Morphology.

SummaryDuring collective cell migration, front cells tend to extend a predominant leading protrusion, which is rarely present in cells at the side or rear positions. Using Drosophila border cells (BCs) as a model system of collective migration, we revealed the presence of a supracellular actomyosin network at the peripheral surface of BC clusters. We demonstrated that the Myosin II-mediated mechanical tension as exerted by this peripheral supracellular network not only mediated cell-cell communication between leading BC and non-leading BCs but also restrained formation of prominent protrusions at non-leading BCs. Further analysis revealed that a cytoplasmic dendritic actin network that depends on the function of Arp2/3 complex interacted with the actomyosin network. Together, our data suggest that the outward pushing or protrusive force as generated from Arp2/3-dependent actin polymerization and the inward restraining force as produced from the supracellular actomyosin network together determine the collective and polarized morphology of migratory BCs.