Lateral Expansion Research Articles

Rapid Rotation of an Erupting Prominence and the Associated Coronal Mass Ejection on 13 May 2013

In this paper, we report the multiwavelength observations of an erupting prominence and the associated coronal mass ejection (CME) on 13 May 2013. The event occurs behind the western limb in the field of view of the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO) spacecraft. The prominence is supported by a highly twisted magnetic flux rope and shows rapid rotation in the counterclockwise direction during the rising motion. The rotation of the prominence lasts for ∼ 47 minutes. The average period, angular speed, and linear speed are ∼ 806 sec, ∼ 0.46 rad min−1, and ∼ 355 km s−1, respectively. The total twist angle reaches ∼ 7 $\pi$ , which is considerably larger than the threshold for kink instability. Writhing motion during 17:42 – 17:46 UT is clearly observed by SWAP in 174 Å and Extreme-UltraViolet Imager (EUVI) on board the behind Solar Terrestrial Relations Observatory (STEREO) spacecraft in 304 Å after reaching an apparent height of ∼ 405 Mm. Therefore, the prominence eruption is most probably triggered by kink instability. A pair of conjugate flare ribbons and post-flare loops are created and observed by STA/EUVI. The onset time of writhing motion is consistent with the commencement of the impulsive phase of the related flare. The 3D morphology and positions of the associated CME are derived using the graduated cylindrical shell (GCS) modeling. The kinetic evolution of the reconstructed CME is divided into a slow-rise phase (∼ 330 km s−1) and a fast-rise phase (∼ 1005 km s−1) by the writhing motion. The edge-on angular width of the CME is a constant (60∘), while the face-on angular width increases from 96∘ to 114∘, indicating a lateral expansion. The latitude of the CME source region decreases slightly from ∼ 18∘ to ∼ 13∘, implying an equatorward deflection during propagation.

A new hypercarnivorous hyaenodont from the Eocene of South China

A new hyaenodont Maocyon peregrinus, gen. et sp. nov., is described based on a partial skull and associated mandible from the upper Eocene Youganwo Formation at Maoming locality in Guangdong Province, China. It shows certain similarities with the Hyainailouroidea in the skull structure, including anteroposteriorly extended jugal/squamosal suture, presence of a preglenoid crest, a lateral expansion of the squamosal posterior to the zygomatic arch, a transversally expanded mastoid process, a nuchal crest that does not extend laterally to mastoid process, and large occipital condyles. The phylogenetic analysis clusters the new taxon with Orienspterodon dahkoensis from the late middle Eocene of China and Myanmar and places this clade within the Hyainailouridae in a polytomy with the Apternodontinae and the Hyainailourinae.

Insight into the decay mechanism of non-ultra-thin silicon film anode for lithium-ion batteries

Silicon thin-film is one of the most promising silicon anode materials for lithium-ion batteries, with the advantages of high cycle stability and initial coulombic efficiency. The excellent performance of silicon thin-films is due to their ultra-thin thickness (< 200 nm), but this results in their areal capacity too low to be compatible with commercial cathode materials, and only films thicker than 500 nm are practical. However, frequent volume changes in non-ultra-thin silicon films during cycling may cause layer misalignment and separation of the film from substrate. In this paper, silicon films with a thickness of ∼700 nm are prepared by magnetron sputtering on the inhomogeneous surface of a copper foil. The properties of the silicon films and mechanisms involved in the cycling process is investigated by combining experimental means during cycling with calculations of the atomic-scale amorphous lithium-silicon Zintl Phases’ structural volumes before and after cycling. The results show that the volume of silicon doesn't recover after delithiation and there is still significant swelling. The cyclic process causes a superimposed expansion of the volume, but the non-uniform film substrate causes the lateral expansion stresses to offset each other, thereby retaining a relatively stable structure. At the end of 100 cycles, the specific capacity of the silicon film electrode is 1461.5 mAh g −1 (areal capacity 0.242 mAh cm−2), with a capacity retention of 64.35%, and the silicon film thickness becomes 8.5 μm. We believe that by reducing the longitudinal expansion volume or stress of the silicon film, the cycle life of the silicon film can be further optimized.

Dimethyl ether-steam assisted gravity drainage: Physical 2D heavy oil simulation

Steam-assisted gravity drainage (SAGD) is a mature heavy oil thermal recovery technology but inherently limited to low recovery efficiency at mid-late stage due to the increasing heat loss in the steam chamber. Here, the dimethyl ether (DME)-assisted SAGD technology and its relevant transport and interfacial properties are specifically investigated through physical 2D heavy oil simulation. A total of four-set physical experiments, with different DME injection ratios, were conducted and compared with the traditional SAGD. The experimental results indicate DME is capable of reducing the heavy oil’s viscosity and interfacial tension at high temperatures. Three stages, rising, lateral expansion, and descending stages, are determined in the SAGD steam chamber’s development; the mid-late SAGD stage is defined when the steam chamber extends to the caprock boundary. With DME additions at the mid-late SAGD stage, higher oil recovery factor and sweep efficiency could be reached and the dew point temperature of steam chamber’s lead decreases by 0.7–1.8 °C. The optimum gas–water ratio is determined to be 3:1, with the fastest oil recovery growth and the highest final cumulative oil-vapor ratio of 0.163. This study provides reliable experimental bases and valuable analyses for the DME-SAGD technology and its application in heavy oil reservoirs.

Clear aligner orthodontic force and conformity during lateral expansion

ABSTRACT Purpose: This study aimed to find the clear aligner form which buccal tipping is less likely to occur by experimentally comparing the marginal type of the aligners with the orthodontic force and conformity (flotation) on the first molars during lateral expansion. Materials and methods: Four different marginal types (conventional aligners with no palatal coverage, partial palatal coverage [with or without 2.0 mm buccal extension], and complete palatal coverage) and three levels of lateral expansion (no expansion, 0.25-mm expansion, and 0.50-mm expansion) were used. The force applied to the first molar was measured by attaching a pressure sensor to the palatal side of the left first molar on a modelled maxillary constricted dental arch. The conformity (flotation) was measured by micro-CT with each aligner attached to the model. Results: Conventional aligners showed no significant difference in force at 0.25-mm or 0.50-mm expansion, but significant flotation at the midpoint and cervical side. The force of all three types of palatal coverage aligners increased significantly (p < 0.01) with increasing expansion and showed less flotation (p < 0.01) compared to the conventional type. Complete palatal coverage aligners had little flotation at 0.25-mm expansion and no expansion. Conclusion: Conventional aligners should have greater buccal tipping of the molars due to increased flotation with expansion. Complete palatal coverage aligners with 0.25-mm expansion had the best conformity, suggesting that they may prevent unplanned buccal tipping of the molars and allow lateral expansion to occur as intended.

Faded landscape: unravelling peat initiation and lateral expansion at one of northwest Europe's largest bog remnants

Abstract. On the mainland of northwest Europe generally only remnants of former peat landscapes subsist. Due to the poor preservation of these landscapes, alternative approaches to reconstruct peat initiation and lateral expansion are needed compared to regions with intact peat cover. Here we aim (1) to find explanatory variables within a digital soil mapping approach that allow us to reconstruct the pattern of peat initiation and lateral expansion within (and potentially beyond) peat remnants, and (2) to reconstruct peat initiation ages and lateral expansion for one of the largest bog remnants of the northwest European mainland, Fochteloërveen. Basal radiocarbon dates were obtained from the peat remnant, which formed the basis for subsequent analyses. We investigated the relationship between peat initiation age and three potential covariates: (1) total thickness of organic deposits, (2) elevation of the Pleistocene mineral surface that underlies the organic deposits, and (3) a constructed variable representing groundwater-fed wetness based on elevation of the mineral surface and current hydraulic head. Significant relationships were found with covariates (1) and (3), which were then used for subsequent modelling. Our results indicate simultaneous peat initiation at several loci in Fochteloërveen during the Early Holocene and continuous lateral expansion until 900 cal BP. Lateral expansion accelerated between 5500–3500 cal BP. Our approach is spatially explicit (i.e. results in a map of peat initiation ages), and it allows for a quantitative evaluation of the prediction using the standard deviation and comparison of predictions with validation points. The applied method based on covariate (1) is only useful where remnant peat survived, whereas covariate (3) may ultimately be applied to reconstruct peat initiation ages and lateral peatland expansion beyond the limits of peat remnants.

Geochemical properties of blue carbon sediments through an elevation gradient: study of an anthropogenically impacted coastal lagoon

Global research is showing that coastal blue carbon ecosystems are vulnerable to climate change driven threats including accelerated sea-level rise and prolonged periods of drought. Furthermore, direct anthropogenic impacts present immediate threats through deterioration of coastal water quality, land reclamation, long-term impact to sediment biogeochemical cycling. These threats will invariably alter the future efficacy of carbon (C) sequestration processes and it is imperative that currently existing blue carbon habitats be protected. Knowledge of underlying biogeochemical, physical and hydrological interactions occurring in functioning blue carbon habitats is essential for developing strategies to mitigate threats, and promote conditions to optimise C sequestration/storage. In this current work, we investigated how sediment geochemistry (0–10 cm depth) responds to elevation, an edaphic factor driven by long-term hydrological regimes consequently exerting control over particle sedimentation rates and vegetation succession. This study was performed in an anthropogenically impacted blue carbon habitat along a coastal ecotone encompassing an elevation gradient transect from intertidal sediments (un-vegetated and covered daily by tidal water), through vegetated salt marsh sediments (periodically covered by spring tides and flooding events), on Bull Island, Dublin Bay. We determined the quantity and distributions of bulk geochemical characteristics in sediments through the elevation gradient, including total organic carbon (TOC), total nitrogen (TN), total metals, silt, clay, and also, 16 individual polyaromatic hydrocarbon’s (PAH’s) as an indication of anthropogenic input. Elevation measurements for sample sites were determined on this gradient using a LiDAR scanner accompanied by an IGI inertial measurement unit (IMU) on board a light aircraft. Considering the gradient from the Tidal mud zone (T), through the low-mid marsh (M) to the most elevated upper marsh (H), there were significant differences between all zones for many measured environmental variables. The results of significance testing using Kruskal–Wallis analysis revealed, that %C, %N, PAH (µg/g), Mn (mg/kg), TOC:NH4+ and pH are significantly different between all zones on the elevation gradient. The highest values for all these variables exists (excluding pH which followed a reverse trend) in zone H, decreasing in zone M and lowest in the un-vegetated zone T. TC content is 16 fold higher overall in vegetated (3.43 -21.84%) than uninhabited (0.21–0.56%) sediments. TN was over 50 times higher (0.24–1.76%), more specifically increasing in % mass on approach to the upper salt marsh with distance from the tidal flats sediments zone T (0.002–0.05%). Clay and silt distributions were greatest in vegetated sediments, increasing in % content towards upper marsh zones The retention of water, metals, PAHs, mud, chloride ions, NH4+, PO43− and SO42− increased with elevated C concentrations, concurrently where pH significantly decreased. Sediments were categorized with respect to PAH contamination where all SM samples were placed in the high polluted category. The results highlight the ability of Blue C sediments to immobilise increasing levels of C, N, and metals, and PAH with over time and with both lateral and vertical expansion. This study provides a valuable data set for an anthropogenically impacted blue carbon habitat predicted to suffer from sea-level rise and exponential urban development.Graphical abstractSummarized results from this study demonstrating the geochemical changes through an elevation gradient, with a transect encompassing intertidal sediments through supratidal salt marsh sediments within Bull Island’s blue carbon lagoon zones.

A search for the resting conformation of the bacterial mechanosensitive channel MSCs.

Structure determination for membrane proteins remains not only technically challenging but is further complicated by potentially non-native conformations resulting from removal of stabilizing lipids. This is especially true for mechanosensitive channels, which are designed to undergo gating transitions under membrane tension that negates part of the bilayer's lateral pressure. At tensions near its activation threshold (5-7 mN/m), the MscS channel slowly transitions from the resting to the inactivated state, which is tension insensitive. This interconversion between the two non-conductive states is accompanied by an 8 nm2 lateral expansion, revealing that the resting state must be more compact. We attempt to relate these two functional states with existing MscS structures experimentally and computationally. Molecular dynamics simulations used to verify experimental conductance and in-plane area expansion revealed that the many MscS structures are non-conductive or semi-conductive. These non-conductive structures share a splayed conformation of lipid-facing TM1-TM2 helical pairs, deep crevices between TM2 and TM3, and a de-coupling of the TM3a gate from the TM1-TM2 tension-transmitting domains. Yet, functional studies demonstrate the necessity of close hydrophobic TM2-TM3 contact for the resting to open transition; hydrophilic mutations lead to immediate inactivation instead of opening. This prompted the modeling of a “compact” resting state characterized by “upright” rather than splayed TM1-TM2 pairs and tighter TM2-TM3 contact that would reconnect the gate to TM1-TM2 helices. Simulated transitions from structures with splayed TM1-TM2 pairs to this compact state revealed two conserved stabilizing salt bridges: R59-D67 and D62-R131. Charge-inverting and neutralizing mutations at these residues had drastic effects on opening and closing rates, inactivation, and especially recovery from inactivation. Disulfide pairs introduced at these salt bridge positions support their proximity as predicted by the model. A cryo-EM characterization of the disulfide cross-linked channel is in progress.

Landscape constraints on mire lateral expansion

Little is known about the long-term expansion of mire ecosystems, despite their importance in the global carbon and hydrogeochemical cycles. It has been firmly established that mires do not expand linearly over time. Despite this, mires are often assumed to have expanded at a constant rate after initiation simply for lack of a better understanding. There has not yet been a serious attempt to determine the rate and drivers of mire expansion at the regional, or larger spatial scales. Here we make use of a natural chronosequence, spanning the Holocene, which is provided by the retreating coastline of Northern Sweden. By studying an isostatic rebound area we can infer mire expansion dynamics by looking at the portion of the landscape where mires become progressively scarce as the land becomes younger. Our results confirms that mires expanded non-linearly across the landscape and that their expansion is related to the availability of suitably wet areas, which, in our case, depends primarily on the hydro-edaphic properties of the landscape. Importantly, we found that mires occupied the wettest locations in the landscape within only one to two thousand years, while it took mires three to four thousand years to expand into slightly drier areas. Our results imply that the lateral expansion of mires, and thus peat accumulation is a non-linear process, occurring at different rates depending, above all else, on the wetness of the landscape.

Homoepitaxial growth of 3-inch single crystalline AlN boules by the physical vapor transport process

Single crystalline aluminum nitride (sc-AlN or AlN) boules with a diameter of 3-inch (Φ76 mm) were successfully prepared by the physical vapor transport (PVT) process. The initial homoepitaxial growth run was performed on an aluminum nitride seed sliced from a Φ51 mm aluminum nitride boule, and diameter enlargement was conducted iteratively via the lateral expansion technique until a Φ76 mm boule was achieved. During the diameter expansion growth runs, the crystal shape transitioned from a hexagonal pyramid to a cylindrical pyramid. After the standard slicing and wafering processes, the as-obtained substrates were characterized by high-resolution X-ray diffraction (HRXRD), preferential chemical etching, and optical spectroscopy. The characterization results revealed that the aluminum nitride substrates showed good crystallinity and excellent UV transparency, although a slight quality deterioration was observed when the crystal size was expanded from Φ51 to Φ76 mm, while the deep-UV (DUV) transparency remained very similar to that of the aluminum nitride seeds. The Φ76 mm aluminum nitride boules obtained in this study are an important milestone towards achieving Φ100 mm (4-inch) aluminum nitride, which are essential for the rapid commercialization of deep-UV optoelectronics and ultra-wide bandgap (UWBG) electronics.

Lateral Hydrological Connectivity Driven by Tidal Flooding Regulates Range-Expansion of Invasive Spartina alterniflora in Tidal Channel-Salt Marsh Systems

Understanding how hydrological features affect habitat invasibility is crucial for predicting whether variations of such hydrological features may act as important inducement regulating range-expansion of invasive species in tidal channel-salt marsh systems. Although lateral hydrological connectivity (LC), or the hydrological connections between tidal channels and adjacent marsh flats, is an important hydrological feature, its effect on plant invasion has rarely been studied in depth. Here, we examined the effects of lateral hydrological connectivity on range-expansion of Spartina alterniflora ( S. alterniflora ) in tidal channel margins of a typical tidal channel-salt marsh system, in the Yellow River Delta, China. Field surveys and transplanting experiments showed that high LC greatly favors S. alterniflora to expand its invasion ranges along tidal channel margins by mediating such habitat physical forms of stress as soil salinity, soil moisture and soil hardness. In contrast, low LC, exacerbates those forms of stress, thereby significantly checking the lateral expansion of S. alterniflora . Moreover, human-made and naturally formed geomorphic structures in salt marshes (e.g., artificial ditches, pools, and hollow microtopography), particularly at high elevations, could potentially enhance LC over time, thereby making such sites prone to invasion by S. alterniflora . These results highlight the importance of lateral hydrological connectivity as an essential driver to regulate S. alterniflora lateral expansion along with the tidal channels. Our results imply that considering the relationships between hydrological processes and spread processes of exotic species should be incorporated into future management frameworks for risk assessment and ecological control of invasive plant species.

Performance of Concrete Building Structure Exposed to Localized Fire

Concrete structures have a favorable position in the building industry with regard to their performance of fire resistance. The understanding of their behavior is essential for reliable analysis and design. This paper is mainly concerned with concrete building performance subjected to localized fire arrangement. Special attention has been given to the finite element model of a seven-story concrete building representing a typical commercial office building designed to European Standard. Very large displacements happened on horizontal direction of the floor slabs due to thermal expansions. The large displacement induced lateral movement of the floor slabs and created additional moments to external columns. Design engineers should ensure that the external columns have ability to accommodate lateral displacements during fire. Although, the thin external columns of the model can withstand these movements due to beneficial effect of membrane action developed to the floor slabs. Present analysis indicates that the performance of the whole structure is substantially different from the single isolated structural member behavior during fire. Although the current design procedures are conservative, design engineers have to consider the detrimental and beneficial effects of lateral slabs' thermal expansion in complete structure.

Evolution of pressure and cavitation in transition region walls for supercritical flow

Abstract Geometrical changes and high flow velocity cause flow separation and cavitation in the transition regions of hydraulic structures. A few studies have been conducted on the flow pressure and cavitation index in these regions, and the results need to be still improved. The present study examined the flow pressure and cavitation index variations for expansion angles between 0° and 10° and Froude numbers up to 20.1. Several relevant equations were also suggested to predict permissible angles in the transition regions. The results showed that negative pressure occurred at all lateral expansion angles except 0° when the Froude number was equal to or greater than ≥6.5. The cavitation phenomenon did not occur on the side walls for Froude number up to 4.49. However, the values of the cavitation index were reduced to less than the critical value for the Froude number of 14 when expansion angle was greater than 6°. The results also revealed that the side walls should not be expanded when Froude number was equal to or greater than 17.5. The occurrence of the cavitation on these walls substantially increased for Froude number of 20.1 even as expansion angle equals 0°.

팬 형상 막냉각 홀의 원형부 내부 거칠기가 막냉각 효율 변화에 미치는 영향

An experimental study on the effect of surface roughness inside a fan-shaped film cooling hole on the film cooling performance was conducted. The inside roughness was modeled using a groove pattern and the test plate with film cooling hole was manufactured by an additive manufacturing technique. The film cooling effectiveness was measured using the pressure sensitive paint technique. Considered hole was a fan-shaped film cooling hole with the diameter of 4.5 mm, the forward expansion angle of 3.54 degrees, the lateral expansion angle of 12.64 degrees, and the injection angle of 30 degrees. The density r atio w as 1 .5 and t he b lowing r atio w as r anged from 0.5 to 2.0. T ests were conducted in a l ow s peed w ind tunnel, and the mainstream speed was 20 m/s and the turbulence intensity was measured to be 4 %. The experimental results showed that the best film cooling effectiveness was achieved when the groove pattern was not applied inside the film cooling hole. If the blowing ratio was 1.0 or higher, the closely distributed groove cases showed higher film cooling effectiveness near the hole exit. When the blowing ratio was 1.5 or less, the sparsely distributed grooves resulted in higher film cooling effectiveness in the downstream region.

Auxetic metamaterials for bone-implanted medical devices: Recent advances and new perspectives

Auxetic metamaterials and structures are characterized by their negative Poisson's ratio meaning that they exhibit lateral expansion under tensile axial loads and densification under compressive loads. The unique properties of the auxetic metamaterials have been generated by designing the micro- and macro-structures with various materials/designs. These types of structures are attracting interest for different reasons such as high energy absorption and improvement in mechanical and biological properties of medical devices. However, some of their interesting characteristics have not been widely explored yet in the field of biomedical engineering. This review aims at highlighting the applications of the auxetic structures in various bone medical devices. Additionally, it investigates different unit cells that were introduced as auxetic designs. The potential of using the auxetic structures in bone tissue engineering is discussed as well.

The effect of duct size, sample size, and fuel composition on concurrent flame spread over large cellulose samples in microgravity

Concurrent flame spread data for thermally-thin charring solid fuels are presented from Saffire and BASS experiments performed in habitable spacecraft for three duct sizes, five sample sizes, two materials, and two atmospheres. The flame spread rates and flame lengths were strongly affected by duct size even for the relatively large ducts (> 30 cm tall). A transient excess pyrolysis length (i.e., flame length overshoot) was observed for the cotton fabric that burned away, which indicates that the transient excess pyrolysis length phenomenon is caused by more than just the flame moving into the developing boundary layer thickness as was the case with the SIBAL sample. A burnout time, defined as the pyrolysis length divided by the flame spread rate, normalized the pyrolysis length histories into a single curve with a steady burnout time of 22 s for the SIBAL fabric. The transient excess pyrolysis length is hypothesized to be a post-ignition flame growth transient for the essentially two-dimensional flames where the burnout time becomes very long until the preheat and pyrolysis lengths develop. The three-dimensional flames over narrow samples have lateral thermal expansion and lateral oxygen diffusion which allows them to transition to a steady state length without the transient excess pyrolysis length. Surface temperature profiles, nondimensionalized by the pyrolysis length, indicate that the temperature profiles exhibit the same shape across the pyrolysis zone. A surface energy balance calculation in the preheat region revealed that the heat flux increased rapidly at the pyrolysis front to near the critical heat flux for ignition. An estimate of the acceleration of the inviscid core flow in the duct due to thermal expansion and developing boundary layers on the duct walls and the SIBAL sample surface seems to explain the observed spread rate trends across three duct sizes and multiple sample sizes.

ON THE DISTRIBUTION OF STRESSES ON THE CONTOURS OF SINGLE UNDERGROUND HORIZONTAL WORKINGS OF VARIOUS CROSS-SECTIONS SUBJECTED TO ALL-ROUND UNIFORM PRESSURE

The formula for normal tangential stresses for single underground workings of different cross-sectional shapes, located at a given depth, with all-round tensile uniform pressure applied at the points of the contours of the workings, is derived. As a mapping function is considered a function of complex variable, which is a polynomial of natural degree n with a pole of first order in zero, allowing the construction of various families of simple closed curves, simulating configurations of the contours of underground workings. Examples are given of contours whose cross-section has the form of a straight and inverse trapezoid, triangle, vaults with vertical and sloping walls, rhombus, rectangle, square and ellipse. Based on the method proposed by the author, the coefficients of the polynomial of the seventh degree, which performs conformal mapping of the interior of a unit circle on a plane with a trapezoidal hole of a given dimensions, are calculated. The stress state of constructed workings at the points of its contour at different depths of laying, the values of the all-round tensile uniform pressure at two fixed values of the lateral expansion coefficient of the rock is investigated. The graphical representations of the stress acting on the contour of the working in question are given. The obtained results can be used to solve problems of determining the permissible depths of mine workings and calculating the values of permissible values of uniform pressure in the points of their contours. The criterion for determining the values of these values is the condition of absence of points on the contours of workings, in which the normal tangential stresses exceeding the limits of tensile and compressive strength of the host rock.

THE STRENGTH OF UNDERGROUND HORIZONTAL WORKINGS OF ELLIPTICAL CROSS-SECTION SHAPE SUBJECTED TO ALL-ROUND UNIFORM PRESSURE

The paper presents the results of a study to determine the stress state on the contours of underground workings, the cross-section of which has the form of an ellipse with a fixed value of the large semi-axis. For workings of this type, at different values of the ellipse parameter, the permissible depths of laying and the values of uniform pressure at the points of their contours are determined, at which normal tangential stresses do not exceed the tensile and compressive strength limits of the host rock. Based on the strength condition used in the work, the values of the permissible depths of the workings are calculated for varying values of uniform pressure applied at the points of the workings contours and the specified values of the lateral expansion coefficient of the rock. The permissible values of the stretching uniform pressure at the points of the contours of the elliptical shape of the cross-section with a change in the depth of laying, the specified values of the lateral expansion coefficient of the rock and the ellipse parameter are given. In addition, the paper presents formulas on the basis of which the problem of stress distribution at the points of contours whose cross-section has the shape of an ellipse with a fixed value of the large semi-axis is considered. It is established that when the intensity of the stretching uniform pressure applied at the points of the contours of the workings of an elliptical cross-section shape changes, and the specified values of the ellipse parameter, the depth of the workings and the magnitude of the lateral expansion coefficient of the host rock, sections of the contours on which tensile and compressive stresses act are highlighted. When changing the depths of the workings of the elliptical cross-section shape, sections of contours are identified on which tensile and compressive stresses act at given values of the ellipse parameter, the intensity of the stretching uniform pressure applied to the points of the contours, and the values of the lateral expansion coefficient of the rock.

Lateral Thoracic Expansion for Jeune's Syndrome, Surgical Approach, and Technical Details

Jeune's syndrome, or asphyxiating thoracic dystrophy (ATD), is a rare autosomal recessive disorder characterized by skeletal dysplasia. Ribs are typically short and horizontal resulting-in lethal variant-in severe lung hypoplasia, progressive respiratory failure, and death. Lateral thoracic expansion (LTE) consists in staggered bilateral ribs osteotomy leading to chest expansion and lung development. Studies on LTE in ATD patients report encouraging data, but the rarity of ATD implies the lack of a standardized surgical path. The aim of this report is to present our experience with LTE, the technical modification we adopted, and patients' clinical outcome. We retrospectively reviewed data of 11 LTE performed in 7 ATD patients with lethal variant. Information regarding pre- and postoperative clinical conditions and surgical details was collected. We adopted a single-stage or a two-stage approach based on patient clinical condition. Computed tomography (CT) scan was performed before and after surgery and lung volume was calculated. Five patients are alive, while two died in intensive care unit for other than respiratory cause (sepsis). Most patients experienced clinical improvement in terms of decreased respiratory infections rate, need for ventilation, and improved exercise tolerance. Postoperative CT scan demonstrated a median lung volume increase of 88%. Mortality in ADT patients is high. However, LTE is a feasible and safe surgical approach, which could improve clinical conditions and survival rate. Survived patients showed postoperatively less oxygen requirement and improved clinical conditions.

Step pinning and hillock formation in (Al,Ga)N films on native AlN substrates

The influence of edge-type threading dislocations (TDs) on the epitaxial growth of AlGaN on native AlN substrates was investigated theoretically and experimentally. In the step flow growth regime, we find that pure edge-type TDs cause a pinning of surface steps, resulting in curved step segments. Theoretical calculations reveal that this pinning mechanism is solely mediated by the altered surface potential due the strain field imposed by the TD. Within the curved step segment, the step width is subject to changes resulting in an altered Ga/Al incorporation rate. According to the density functional theory calculation, this effect is related to the different surface diffusion length of Ga and Al and represents a further destabilization mechanism during step flow growth. Another consequence of surface step pinning is the occurrence of areas where the step width is increased. These areas serve as precursors for 2D nucleation due to an increased adatom density. Once nucleated, these nuclei grow along the c-direction via continuous 2D nucleation, while lateral expansion occurs due to adatom incorporation on the m-facets.