Pit-like Structures Research Articles

Evolving properties of pits on 67P/C-G due to illumination induced mass loss I: Isolated shape morphology

Abstract Our aim is to characterize patterns of evolution of morphological units on the nucleus of 67P-CG such as pits, sink-holes or, more generally, pit-like features. This work focuses on developing suitable metrics to contrast different stages and changes during the time evolution. We adopt a 3D mass loss evolution model (MONET) assuming water ice sublimation is the primary driver of erosion activity. This paper considers isolated pit-like structures without the process of merging which will be addressed in our subsequent work. The modeling study cases investigate how latitude, obliquity and initial pit shape converge in defining the final morphology of the pits, for a spherical nucleus as well as shape model of 67P/C-G. Our results corroborate to some extent the previous studies quantifying exes heat retention due to the concavity of these pit features, however, we demonstrate a clear dependence of ‘smoothing’ or ‘deepening’ effects on the orientation and initial shape. Furthermore, it is shown that the diameter evolution of the pits is influenced by a combination of factors such as solar incidence, shadowing, and/or self-heating acting on its walls. Under certain circumstances, we also observe pronounced asymmetry in mass loss at the pit floors, a weak effect of terracing. Mass loss-induced evolution may result in the transformation of circular depressions into elongated ones due to specific solar illumination directions. The modeling results presented here represent the first explicit simulators of the deepening, widening, and smoothing processes in the context of 67P-C-G.

Droplet free self-assembling of high density nanoholes on GaAs(100) via thermal drilling

Droplet free self-assembling of high density nanoholes on GaAs(100) via thermal drilling

FIVE SEASONS OF EXCAVATIONS IN AREAS 2A AND G OF SARUQ AL HADID (DUBAI, UAE): IRON AGE II EVIDENCES OF COPPER PRODUCTION, WORKSHOP AREA AND CEREMONIAL ACTIVITIES

Within five years of excavations in Area 2A and G of Saruq al-Hadid, several pit-like structures used in combustion activities were found whose purpose is still unclear. Near these, a rich collection of metal objects from the Iron Age II was gathered, along with evidences of their production at the site. Frequent identification of raw materials and working tools, mainly for jewellery production, suggests that the site was also a production centre for these kind of objects, as well as a site with religious connotation as suggested by the votive objects discovered, such as copper anthropomorphic figurines, snakes, miniature weaponry, and soft stone and ceramic vessels with parallels in other places of worship.

Investigation of Dislocations Inducing Leakage Current on SiC Junction Barrier Schottky Diode by Two-Photon-Excited Band-Edge Photoluminescence

Tilt angles of threading dislocations (TDs) which induce leakage of current on SiC junction barrier schottky diodes (SiC-JBSs) were investigated by two-photon-excited photoluminescence (2PPL) and transmission electron microscopy (TEM). Observation of leakage spots measured by atomic force microscopy (AFM) revealed that pit-like structures were certainly formed but the depths were considerably shallow, indicating that influence of local electric field due to the structures was negligible on our SiC-JBSs. It became clear that tilt angles of the TDs inducing leakage were relatively larger than about 11° by 2PPL and that the TD was the threading mixed dislocation by TEM.

Paradoxical antifungal activity and structural observations in biofilms formed by echinocandin-resistant Candida albicans clinical isolates

Echinocandin-resistant clinical isolates of Candida albicans have been reported, and key-hot spot mutations in the FKS1 gene, which encodes a major glucan synthase subunit, have been identified in these (caspofungin-resistant [CAS-R]) strains. Although these mutations result in phenotypic resistance to echinocandins in planktonic cells, there is little data on antifungal susceptibilities of CAS-R C. albicans strains within biofilms. Thus, we analyzed biofilms formed by 12 C. albicans CAS-R clinical strains in which we previously identified FKS1 hot-spot mutations and compared the sessile antifungal and paradoxical activity of anidulafungin (ANID), caspofungin (CAS), and micafungin (MICA). Biofilms were formed in a 96-well static microplate model and assayed using both tetrazolium-salt reduction and crystal violet assays, as well as examination by scanning electron microscopy. We first sought to assess biofilm formation and structure in these fks1 mutants and found that the biofilm mass and metabolic activities were reduced in most of the fks1 mutants as compared with reference strain SC5314. Structural analyses revealed that the fks1 mutant biofilms were generally less dense and had a clear predominance of yeast and pseudohyphae, with unusual "pit"-like cell surface structures. We also noted that sessile minimum inhibitory concentrations (MICs) to ANID, CAS, and MICA were higher than planktonic MICs of all but one strain. The majority of strains demonstrated a paradoxical effect (PE) to particular echinocandins, in either planktonic or sessile forms. Overall, biofilms formed by echinocandin-resistant clinical isolates demonstrated varied PEs to echinocandins and were structurally characterized by a preponderance of yeast, pseudohyphae, and pit-like structures.

Ultra-thin MoS2 irradiated with highly charged ions

Abstract Single MoS 2 layers exfoliated on KBr have been irradiated with highly charged Xe ions, i.e. with Xe 35+ and Xe 40+ . By atomic force microscopy (AFM) we identified pits and hillocks induced by single ion impacts. The latter ones appear on single layer and bulk-like MoS 2 after both irradiations, whereas their diameter and height apparently depend on the charge state q and layer number. By comparison of contact mode and tapping mode AFM measurements we deduce that these ion induced defects are topographical hillocks accompanied by an enhanced friction. In contrast to this, pit-like structures were only observed on single layer MoS 2 irradiated with q = 40. Taking into account the well known ion induced pit formation on KBr due to defect mediated sputtering, we deduce that pit formation takes place in the substrate and not in the MoS 2 layer.

Effect of sputtering power on the properties of ZnO:Ga transparent conductive oxide films deposited by pulsed DC magnetron sputtering with a rotating cylindrical target

Abstract Effect of sputtering power on the properties of ZnO:Ga (GZO) transparent conductive oxide (TCO) films was investigated on the films deposited by pulsed DC magnetron sputtering with a rotating cylindrical target. At lower sputtering power up to 2.0 kW, the films showed flat surfaces with some pit-like structures. However, films morphology deteriorated with higher sputtering power up to 3.5 kW as reflected in the rough porous surfaces. Microstructures of the films evolved into the uniformly shaped columnar grains well aligned with the c -axis with the increasing sputtering power up to 2.0 kW, but further increasing the sputtering power caused the irregularity of the grain shapes and their orientations. Accordingly, the film deposited at 2.0 kW showed the lowest electrical resistivity of 4.89 × 10 −4 Ω cm achieved through the highest Hall mobility of 25.9 cm 2 V −1 s −1 . All the GZO films in this study showed the optical transmittances higher than 80%.

Mechanisms of Defect Generation and Clustering in CH3S Self-Assembled Monolayers on Au(111).

Periodic density functional calculations probe that step edges play a key role as source of defects during self-assembly. It is shown that the self-assembly process strongly reduces the energy required to strip an atom from the gold surface, locally increasing the concentration of surface defects. The thermodynamic driving force for the atom stripping is considerably more favorable along step-edge lines within the self-assembly than on the higher-coordinated terrace sites. Furthermore, the clustering of surface defects is considered, and we probe that the formation of aggregates of vacancies in the form of vacancy pits significantly stabilizes the self-assembly on the terraces of gold, where the role of the step edges is expected to be less significant. The high stability of pit-like structures arises from a balance between the corrugation and the enhanced bonding of defect-rich substrates. Our results demonstrate the important role that step edges play during assembly and could be very valuable for discovering defect-free assembled structures.

Acquired Optic Nerve and Peripapillary Pits in Pathologic Myopia

To examine the incidence and characteristics of pit-like structures around the optic disc and myopic conus in eyes with high myopia. Prospective, observational case series. We evaluated 198 eyes of 119 patients with pathologic myopia (spherical equivalent >-8 diopters [D]). We also evaluated 32 eyes of 32 subjects with emmetropia (refractive error ≤±3 D) as controls. The papillary and peripapillary areas were examined with a prototype swept-source optical coherence tomography (OCT) system with a center wavelength of 1050 nm. We studied the structural characteristics of pit-like changes. The incidence and characteristics of the optic nerve (ON) pits in eyes with high myopia. Pit-like clefts were found at the outer border of the ON or within the adjacent scleral crescent in 32 of 198 highly myopic eyes (16.2%) but in none of the emmetropic eyes. The eyes with these pits were more myopic, had significantly longer axial lengths, and had significantly larger optic discs than the highly myopic eyes without pits. The pits were located in the optic disc area (optic disc pits) in 11 of 32 eyes and in the area of the conus outside the optic disc (conus pits) in 22 of 32 eyes. One eye had both optic disc pits and conus pits. The optic disc pits existed in the superior or inferior border of the optic disc. All but 1 eye with conus pits had a type IX staphyloma, and the location of the conus pits were present nasal to the scleral ridge or outside the ridge temporal to the nerve. The optic disc pits were associated with discontinuities of the lamina cribrosa, whereas the conus pits appeared to develop from a scleral stretch-associated schisis or to emissary openings for the short posterior ciliary arteries in the sclera. The nerve fiber tissue overlying the pits was discontinuous at the site of the pits. Optic nerve pits are common in highly myopic eyes. The ON pits are barely visible ophthalmoscopically but can be demonstrated by using swept-source OCT.

Synthesis and characterization of iron oxide nanoparticles using amphiphilic diblock copolymer PS-b-PAA micelle as soft template

By hydrothermal treatment, α-Fe2O3 with club and date pit-like structures were successfully prepared using amphiphilic diblock copolymer poly(styrene-b-acrylic acid) (PS-b-PAA) micelle as soft template. The particles were characterized by fourier transform infrared (FTIR), powder X-ray diffraction (XRD), scanning electron microscopy (SEM). The influence of factors on the morphologies of α-Fe2O3 particles, such as the compositions and concentration of copolymer, and existence of citric acid, has been discussed.

Super-Resolution Imaging of Membrane Topology using Small Molecule Lipophilic Dye

Plasma membrane of any cell supports a vast array of biomolecules on its surface. These are crucial in response and adaptation to the external environmental cues of the cell. The process of determining these cues is done by a plethora of plasma membrane associated proteins including receptors, channels and pores. The spatial organization including compartmentalization of these proteins is critical for cellular function. In order to generate a high spatial resolution topological map of a plasma membrane we use wide-field fluorescence super-resolution imaging technique known as Stochastic optical reconstruction microscopy (STORM). STORM works on the principle of stochastic switching of single-molecule fluorophores and precise localization of the centers of these spots. Here we labeled the plasma membrane using a small molecule lipophilic carbocyanine dye, DiD, which can photoswitch under similar conditions as previously used for Cy5 photoswitching. We stained Drosophila Schneider 2 cells with DiD and imaged them under both fixed and live conditions using 3D STORM imaging and/or single-particle tracking modes. We observed plasma membrane features including clathrin coated pit-like structures. Further experiments using multicolor STORM to image DiD together with membrane proteins will shed light on how membrane protein distribution is correlated with membrane topology.

Image-enhanced endoscopy for diagnosis of colorectal tumors in view of endoscopic treatment

Recently, image-enhanced endoscopy (IEE) has been used to diagnose gastrointestinal tumors. This method is a change from conventional white-light (WL) endoscopy without dyeing solution, requiring only the push of a button. In IEE, there are many advantages in diagnosis of neoplastic tumors, evaluation of invasion depth for cancerous lesions, and detection of neoplastic lesions. In narrow band imaging (NBI) systems (Olympus Medical Co., Tokyo, Japan), optical filters that allow narrow-band light to pass at wavelengths of 415 and 540 nm are used. Mucosal surface blood vessels are seen most clearly at 415 nm, which is the wavelength that corresponds to the hemoglobin absorption band, while vessels in the deep layer of the mucosa can be detected at 540 nm. Thus, NBI also can detect pit-like structures named surface pattern. The flexible spectral imaging color enhancement (FICE) system (Fujifilm Medical Co., Tokyo, Japan) is also an IEE but different to NBI. FICE depends on the use of spectral-estimation technology to reconstruct images at different wavelengths based on WL images. FICE can enhance vascular and surface patterns. The autofluorescence imaging (AFI) video endoscope system (Olympus Medical Co., Tokyo, Japan) is a new illumination method that uses the difference in intensity of autofluorescence between the normal area and neoplastic lesions. AFI light comprises a blue light for emitting and a green light for hemoglobin absorption. The aim of this review is to highlight the efficacy of IEE for diagnosis of colorectal tumors for endoscopic treatment.

Raptor Pit Mortality in Mongolia and a Call to Identify and Modify Death Traps Wherever they Occur

Raptor Pit Mortality in Mongolia and a Call to Identify and Modify Death Traps Wherever they Occur

Caveolae and neurotrophins in pulmonary artery smooth muscle

The mechanisms underlying pulmonary hypertension are still being explored. Recent studies suggest a role for caveolae (pit‐like plasma membrane structures), although it is not entirely clear whether they enhance or blunt pulmonary hypertension. The proteins caveolins ‐1, and ‐2, and polymerase I and transcription release factor (PTRF) are essential to forming caveolae. In other tissues, growth factors called neurotrophins (e.g. brain‐derived neurotrophic factor, BDNF) are thought to affect cell proliferation and structure. This study investigated caveolins and neurotrophins in human pulmonary artery. Western analysis of artery from a patient with primary pulmonary hypertension showed decreased levels of caveolin‐1, caveolin‐2, PTRF and RhoA. Exposure of human pulmonary artery to 1 nM BDNF increased protein levels of caveolin‐1 and PTRF. Isolated pulmonary artery smooth muscle cells exposed to BDNF showed decreased [Ca2+]i response to bradykinin (10 nM) and histamine (10 μM), but no change in caveolin or PTRF levels. These data suggest that decreased caveolin levels may contribute to increased pulmonary vascular contractility, while neurotrophins (potentially by increasing caveolin levels) may alleviate excessive constriction. Further studies are required to determine whether neurotrophins affect caveolae in endothelial cells or smooth muscle.Supported by FAMRI, NIH grant UL1RR024150, and the Department of Anesthesiology, Mayo Clinic.

γ-Aminobutryic Acid

γ-Aminobutryic Acid

Defect Mediated Desorption of the KBr(001) Surface Induced by Single Highly Charged Ion Impact

The individual impacts of slow (300 eV/amu) highly charged Xe ions induce nanometer sized pitlike structures on the KBr (001) surface. The volume of these structures shows a strong dependence on the ions potential energy. Total potential sputter yields from atomically flat (001) terraces are determined by imaging single ion impact sites. The dependence of the sputter yield on the ions initial charge state combined with structure formation at low and high-fluence irradiations indicates that agglomeration of defects into complex centers plays a major role in the desorption process induced by the potential energy.

Peripapillary Changes Detected by Optical Coherence Tomography in Eyes with High Myopia

To investigate the morphologic alterations around the optic disc by optical coherence tomography (OCT) in eyes with high myopia. Observational case series. One hundred twenty-seven eyes (69 patients) with high (> or =-8.00 diopters [D]) myopia were included. In addition, 46 emmetropic (+1.00 to -1.00 D) eyes and 40 eyes with low (<-6.00 D) myopia were examined as controls. The participants had ophthalmologic examinations including stereoscopic fundus observations, OCT examinations, and perimetry. For OCT, multiple horizontal and vertical OCT scans were obtained around the optic disc and fovea in each patient. The presence of a peripapillary detachment in eyes with pathologic myopia (PDPM) around and within the area of myopic conus, and the vascular microfolds and retinoschisis at the site of the retinal vessels at the conus edge were evaluated. A PDPM was detected by OCT in 14 eyes (11.0%). A PDPM was seen in the OCT images as a hyporeflective space intrachoroidally and subretinally. Hyporeflective spaces resembling PDPMs were also observed within the tissue posterior to the conus in eyes without the typical ophthalmoscopic yellow-orange lesions. Eyes with PDPM had glaucomalike visual field defects more frequently than eyes without PDPM. Pitlike structures within the conus were observed ophthalmoscopically in 3 eyes with high myopia, and OCT examinations revealed the presence of cystic structures with an opening toward the vitreous cavity at the corresponding sites. Microfolds in the retinal vessels were detected at the conus edge in 58 of the highly myopic eyes (45.0%), and 28 of these eyes had retinoschisis at the site of the retinal vessels. Fifteen of these 28 eyes showed an extension of the retinoschisis along the temporal retinal vessels toward the macula, and 9 of these 15 eyes had myopic foveoschisis. None of these changes (PDPM, pitlike structures, microfolds, and retinoschisis) were detected in controls. The OCT examinations demonstrated different types of abnormalities around the optic disc in highly myopic eyes. These changes might be related to the visually disabling complications, such as visual field loss and myopic foveoschisis, seen in highly myopic eyes.

Investigation on GaAs(0 0 1) surface treated by As-free high temperature surface cleaning method

We have used in in situ scanning tunneling microscopy to study GaAs(0 0 1) surface treated by As-free high temperature surface cleaning method. The temperatures ranged from 575 to 655∘C and an optimum temperature of 605∘C was found. Its surface had ×6 structure parallel to [11¯0] direction and smooth morphology by congruent evaporation. However, many pit-like structures formed lower than 600∘C. On the other hand, with 610∘C and higher, the surface became rough, forming many grooves with {111}B and {111}A facets. At 655∘C, the roughness was reduced but the surface easily became milky because of rapid As desorption.

Endocytosis of Cadherin from Intracellular Junctions Is the Driving Force for Cadherin Adhesive Dimer Disassembly

The adhesion receptor E-cadherin maintains cell-cell junctions by continuously forming short-lived adhesive dimers. Here mixed culture cross-linking and coimmunoprecipitation assays were used to determine the dynamics of adhesive dimer assembly. We showed that the amount of these dimers increased dramatically minutes after the inhibition of endocytosis by ATP depletion or by hypertonic sucrose. This increase was accompanied by the efficient recruitment of E-cadherin into adherens junctions. After 10 min, when the adhesive dimer amount had reached a plateau, the assembly of new dimers stalled completely. These cells, in a striking difference from the control, became unable to disintegrate both their intercellular contacts and adhesive dimers in response to calcium depletion. The same effects, but after a slightly longer time course, were obtained using acidic media, another potent approach inhibiting endocytosis. These data suggest that endocytosis is the main pathway for the dissociation of E-cadherin adhesive dimers. Its inhibition blocks the replenishment of the monomeric cadherin pool, thereby inhibiting new dimer formation. This suggestion has been corroborated by immunoelectron microscopy, which revealed cadherin-enriched coated pit-like structures in close association with adherens junctions.

Unsmooth cuticles of soil animals and theoretical analysis of their hydrophobicity and anti-soil-adhesion mechanism

Soil adhesion is a natural phenomenon, and it is harmful to terrain machines and tillage equipment that have soil as their work medium, such as automobiles, tractors, earth-moving machines, spades, hoes, and plows. Soil adhesion increases motion resistance and energy consumption, quickens damage to the soil-engaging components, and lowers work quality. The biomimetic research has provided a promising method to solve the soil adhesion problem. In this work, the cuticles of typical soil animals were observed by scanning electron microscopy (SEM) and their wettability and mechanism of antiadhesion were analyzed in theory. The results of experimental observation have shown that the cuticles of soil animals have different unsmooth appearances, such as pimple-shaped, pit-like, and undee structures. But for the cross sections of the unsmooth cuticles, their common character is undee. Theoretical analysis has indicated that the larger the ratio of the amplitude of the wave to the period of the wave, the stronger the hydrophobicity, the more easily the composite interface between the liquid and the unsmooth cuticles forms, and the function of reducing soil adhesion of the unsmooth cuticles will be better.