Dark Pits Research Articles

Multiscale revelation of asphalt morphology and adhesion performance evolution during stress relaxation process

The objective of this study is to investigate the evolution of asphalt morphology and adhesion properties during stress relaxation using atomic force microscopy (AFM) and molecular dynamics (MD) simulations. Changes in surface roughness, Derjaguin-Muller-Toporov (DMT) modulus, adhesion force, and force-distance curves were analyzed. Morphological and adhesion property evolution was assessed using correlation length and Lyapunov exponent. MD simulations provided insights into the internal stress-time relationship and free volume fraction of asphalt during relaxation. Results indicate that under constant tensile strain, the “bee structure” on the asphalt surface elongates, dark pits transform into light protrusions, microcracks heal, and surface roughness stabilizes after 10 h. Under compressive strain, similar changes occur but are more pronounced during tensile relaxation. The combined use of AFM and MD simulations offers a comprehensive understanding of the microscopic evolution mechanisms of asphalt under stress relaxation, providing valuable insights for optimizing asphalt pavement design and maintenance.

DARK SOIL PITS AND GRAVES IN VOLCANIC CAVE C6.1, KRONG NO, DAK NONG PROVINCE: DOCUMENTATION AND DISCUSSION

Dark soil pits and graves are critical documents discovered in volcanic cave C6.1. As a result of the investigation and excavation of cave C6.1 conducted in 2017, 2018, and 2019, we have discovered vestiges of nine dark soil pits and seven relatively intact graves, together with teeth and other human remains scattered in the cultural layer. This is an important source of information on the racial composition of the prehistoric inhabitants of the Central Highlands during the Neolithic period, as well as the paleoenvironment, environmental adaptations, and flora and fauna that prehistoric inhabitants exploited for their livelihoods. This article introduces documents and reconstructs the socioeconomic picture of the prehistoric inhabitants of cave C6.1. It also contributes scientific documents for the general conservation and promotion of heritage to develop sustainable cultural tourism in Dak Nong Province.

Effects of Ga on the microstructure and magnetostriction of Fe-Ga alloys for actuators

The microstructure and magnetostrictive properties of Arc melted Fe100-x-Gax alloys (x = 20, 25) were studied. The results of the X-Ray Diffraction study confirm the presence of the A2 and DO3 phases in the body-centered cubic structure, which is consistent with previous findings. The increased lattice parameter of the alloy containing 25% Ga results in an increase in the alloy's total magnetic moment. According to the results of an optical microscopy study, the substitution of more Ga atoms results in an increase in grain size and a decrease in the number of dark pits. Due to interactions between domain walls, the coercivity (HC) of the Fe80-Ga20 alloy is lower than that of its counterpart alloy. Fe atoms' magnetic moments are directly proportional to the distance between them and their nearest neighbours in the local environment, and Ga does interrupt the Fe's nearest neighbours, resulting in an increase in saturation magnetization. The formation of the Ga-rich phase is also responsible for the increase in saturation and remanent magnetization. The alloy exhibited enhanced magnetostriction because of the structure and local symmetry placed at different lattices. Its improved magnetostriction makes the Fe75-Ga25 alloy particularly well suited for use in sensor and actuator applications.

GENESIS OF THE GENRE OF TALES

The article deals with the problem of the increasing emphasis on the genre of tales, a deeper analysis of reality, a look at the deep and dark pits of the human soul, and the essence of life. When we research the nature of the genre of tales, we can observe the versatility of images, the intensity of conflict, the depth of psychological analysis, the diversity of artistic and visual means, and the diversity of themes. Studying the development of the genre of the story, the stages of development further strengthens the view of the genre. Allah, possessor of the Exalted in Power, revealed in the Divine Book the knowledge of the universe to men. The scholars and scientists of the world are still astounded with the miracles of the Holy Word. The message of the creation of man is found in the holy verses of the Koran in a form of a compact narrative. It clearly shows human's inner and outer character. The secret of the place and time contains the underlying hint at centuries old mysteries. The criterion of time, which does not exist in the present, was also first shown on the pages of the Holy Book. The birth of the Prophets, the Divine Gospel has been synthesized in chronotopes, such as heaven, ocean, mountains, and earth. During their journeys, they show the character of the Prophecy and the Prophets, their intelligence and power. The story focuses on the origins and the core of such sciences as religion, history, philosophy, psychology, medicine, geography, logic, and art. In the Koran, the word narrative is used in Surahs, and presupposes the interpretation of events at a global scale, at a human level, from the celestial depth to the earthly layer, from the first Adam to the last messenger Muhammad. A particular attention is paid to the significance of narratives and tales in folklore and classical literature.

Studies on rheological, structural, optical, electrical and surface properties of LiMn2O4thin films by varied spin rates

AbstractLiMn2O4thin films prepared by cost-effective spin coating method using optimized coating conditions are reported. Spin rate was varied and spin rate dependent properties were studied. Prepared films were characterized for their structural, morphological and optical properties. X-ray diffraction study of LiMn2O4thin films confirmed the cubic spinel structure with the preferred orientation along (1 1 1) plane. Optical absorption studies showed band gap energy of 3.02 eV for the grown LiMn2O4films. FT-IR bands assigned to asymmetric stretching modes of MnO6group were located around 623 cm-1and 514 cm-1for the LiMn2O4thin films. The weak band observed at 437 cm-1was attributed to the LiO4tetrahedra. The films showed high conductivity value 0.79 S/cm indicating the generation of effective network of the film for enhanced charge transport. AFM micrographs of the LiMn2O4films deposited at 3000 rpm and 3500 rpm showed uniform distribution of fine grains throughout the surface without any dark pits, pinholes and cracks.

Identification of open lenticels in apples after harvest in relation to lenticel breakdown development during storage

Lenticel breakdown (LB), appearing as dark brown pits on apple skin, occurs following storage, and the factors associated with LB have not yet been identified. It was assumed that open lenticels at harvest and following postharvest treatments contribute to this phenomenon and therefore a method was developed using SO2 treatment, to detect air-exposed tissue in Red Delicious apples. The efficiency of detection was assessed on artificial openings, created by pricking the apple surface, which caused bleaching around these openings with enlargement of their dimensions. Similarly, SO2 treatment of intact apples caused a bleaching around few of the lenticels, indicating that the underlying parenchyma cells were exposed to air. The percentage of open lenticels decreases after harvest during cold storage. A calcium chloride, but not potassium chloride, immersion at harvest resulted in significantly more SO2 damaged lenticels, indicating that calcium enhances lenticel opening. There was a high correlation between the percentage of open lenticels at harvest and the severity of LB after storage (Pearson’s correlation coefficient of r2=0.80). This suggests that LB might occur due to exposure of parenchyma cells to air at harvest. In conclusion, these results indicate that the SO2 treatment at harvest might be used as an efficient method for the prediction of lenticel damage after storage.

Geotechnical and Geoacoustic Properties of Volcanic Soil in Ulleung Island, East Sea of Korea

The unique material properties of volcanic soils may cause stability problems within the soil. However, few studies have examined the composition and engineering characteristics of volcanic soils below sea level. The objective of this study is to investigate the engineering properties of volcanic soils sampled from Ulleung Island. For the volcanic soils, the index properties, particle geometry, and mineralogy are analyzed in the laboratory. An oedometer cell incorporated with bender elements is used to measure the small-strain stiffness and compressibility of the volcanic soils. To obtain the large strain strength parameter and hydraulic conductivity of the volcanic soils, direct shear tests, and constant head permeability tests are performed. The experimental results show that the basic index properties of volcanic soils sampled from Ulleung Island are very similar to the values of previously published reference data: poorly graded with a median grain size, very low fine fraction, and slightly high specific gravity. In addition, the particle surface texture features and elementary analysis indicates a dark grain color, small pits or holes in the grain, and relatively low SiO2 and high Fe2O3 contents. The friction angle of the volcanic soils depends on the relative density, and the hydraulic conductivity varies according to e3/(1 + e) and D102. The characterization of the electrical properties in Ulleung Island needs to be conducted with caution due to the high Fe2O3 content in the volcanic soils.

Preparation and characterization of ceria magnesium aluminate nano powder for thermal barrier application

The present work deals with the preparation of CeMgAl11O19 nano powder by sol gel citric acid route and to investigate its structural, surface and thermo-mechanical properties, to access its suitability for thermal barrier application. The XRD profile of the CeMgAl11O19 powder heat treated at different temperatures confirms polycrystalline structure. From the XRD data, mean grain size, lattice strain energy, dislocation density and other structural parameters have been investigated and reported. Thermal properties of the as synthesized CeMgAl11O19 powder have been studied from the TG-DTA and DSC measurement and the results are presented. Thermal conductivity of the CeMgAl11O19 specimen heat treated at different temperatures has been evaluated using the physical property measurement system and the results have been discussed. Hardness of the pelletized CeMgAl11O19 specimen heat treated at different temperatures has been measured in the Vickers scale and the results have been discussed. The influence of annealing temperature on the tensile strength and wear resistance of the CeMgAl11O19 specimen have been investigated and reported. The 2D and 3D AFM image of the CeMgAl11O19 specimen heat treated at 750°C shows the uniform surface pattern without any dark pits and pinholes. The surface roughness and grain size evaluated from the AFM data have been analyzed and presented.

Determination of the some electronic parameters of nanostructure copper selenide and Cu/Cu3Se2/n-GaAs/In structure

The nanostructure copper selenide thin film has been grown on n-type gallium arsenide substrate by Successive Ionic Layer Adsorption and Reaction (SILAR) method. The film has been characterized by X-ray Diffraction (XRD), Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM) measurements. X-ray diffraction analysis of the film confirms a polycrystalline with preferred orientation. The AFM and SEM micrographs of the film reveal smooth and uniform surface pattern without any dark pits, pinholes and microcracks. The Cu/Cu3Se2/n-GaAs/In structure has been thermally formed in evaporating system after the SILAR process. The electrical analysis of Cu/Cu3Se2/n-GaAs/In structure has been investigated by means of current–voltage (I–V) measurements in the temperature range of 60–400K in dark conditions. The values of barrier height (BH) and ideality factor (n) ranged from 0.21eV and 4.97 (60K) to 0.83eV and 1.14 (400K), respectively. In the calculations, the electrical parameters of the experimental forward bias I–V characteristics of the Cu/Cu3Se2/n-GaAs/In with the homogeneity in the 60–400K range have been explained by means of the thermionic emission (TE), considering Gaussian distribution (GD) of BH with linear bias dependence.

Improvement of electrical properties of AlGaN/GaN heterostructures using multiple high‐temperature AlN interlayers

AbstractAlGaN/GaN heterostructures with multiple AlN interlayers deposited at a high‐temperature (HT) of 900 °C were grown by metalorganic chemical vapor deposition. Flat surface with few dark pits was obtained by using multiple HT‐AlN interlayers. Hall effect measurements and non‐contact sheet resistance mappings demonstrated the improvement of the electrical properties of AlGaN/GaN heterostructure. The sheet carrier density and Hall mobility continuously increased with the increase of the AlN interlayer number. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

High-Sensitivity Nitride-Based Ultraviolet Photosensors with a Low-Temperature AlGaN Interlayer

Nitride-based ultraviolet (UV) photosensors with a low-temperature (LT) AlGaN interlayer were fabricated and characterized. Material analysis results showed that dark pits corresponding to threading dislocation (TD) terminations were almost invisible after inserting the LT AlGaN interlayer. It was also found that we could significantly suppress the dark leakage current by using the LT AlGaN interlayer owing to TD annihilation and demultiplication processes. For photosensors with the LT AlGaN interlayer, the responsivity at 360 nm and UV-to-visible rejection ratio were found to be 0.12 A/W and 2.45 × 10 3 , respectively, under 5 V applied bias.

Distribution and symptoms of epiphyte infection in major carrageenophyte-producing farms

High density commercial farming of carrageenophyte Kappaphycus alvarezii is often plagued with “ice-ice” disease and epiphyte infection, which eventually leads to reduced production and in some cases collapse of crop. Epiphyte outbreak has been occurring regularly in major carrageenophyte farms in the Philippines, Indonesia, Malaysia and Tanzania. Infected materials from these countries were studied to establish baseline information on the epiphyte’s identity, density, symptoms and secondary infection on the host seaweed. The causative organism was identified as Neosiphonia apiculata (Hollenberg) Masuda et Kogame, based on its morphological features. Epiphyte density on host seaweed materials decreased in the following order: the Philippines (88.5 epi cm−2), Tanzania (69.0 epi cm−2), Indonesia (56.5 epi cm−2) and Malaysia (42.0 epi cm−2). Initial symptoms were the presence of tiny black spots, indicating the embedded tetrasporeling in seaweed cortex layer. Vegetative form emerged after 2 weeks measuring less than 0.5 mm in length with a density of less than 25.0 epi cm−2. Upon maturation, infected seaweed takes on a “hairy” appearance with “goose-bumps” like cortical swellings. The epiphyte appears as a solitary plant with multiple secondary rhizoids or as multiple epiphytes appearing from a single cortical opening. At the end of infection, the epiphytes left dark pits on the cortical swelling, and the carrageenophytes are infected by opportunistic bacteria. Bacterial enumeration of healthy and infected seaweed materials showed an increase of more than 300% in total bacterial count on infected materials dominated by Alteromonas sp., Flavobacterium sp. and Vibrio sp.

In Ga N ∕ Ga N multi-quantum-well ultraviolet photosensors by capping an unactivated Mg-doped GaN layer

In Ga N ∕ Ga N multi-quantum-well (MQW) metal-semiconductor-metal (MSM) photosensors with an unactivated Mg-doped GaN cap layer were fabricated and characterized. The experimental results showed that dark pits of threading dislocation termination was hardly observed after capping a thin Mg-doped GaN layer. It was also found that we could significantly suppress the dark leakage current by inserting an additional Mg-doped GaN layer due to a thicker and higher potential barrier and effective surface passivation. For InGaN∕GaN MQW MSM photosensors with the unactivated Mg-doped GaN cap layer, the responsivity at 380nm and UV to visible rejection ratio were found to be 0.366A∕W and 1.99×103 under 4V applied bias.

Studies on Spray Deposited SnO2, Pd:SnO2 and F:SnO2 Thin Films for Gas Sensor Applications

Undoped tin oxide (TO), palladium‐doped tin oxide (PTO) and fluorine‐doped tin oxide (FTO) thin films have been prepared by spray pyrolysis method, under optimized conditions. Transmission measurement of the TO, PTO and FTO films have been studied in the UV‐Visible region. Band gap energy evaluated from the spectral data lies between 3.15 eV and 3.8 eV. The X‐ray diffraction analysis of the films confirms a polycrystalline, tetragonal rutile structure of tin oxide, with preferred orientation along the (101) plane. The lattice constants, a and c, were evaluated as 4.7256 Å and 3.1768 Å. The average grain size lies between 470 nm and 850 nm and its variation as a function of annealing temperature have been studied and reported. The AFM micrographs of the films reveal smooth and uniform surface pattern without any dark pits, pinholes and micro‐cracks. The sheet resistance (R) and electrical resistivity (ρ) of the films under ambient condition and CO gas atmosphere have been studied at different operating temperatures, in a specially designed sensor test rig setup. From the resistance measurement, response and recovery characteristics, detection sensitivity and optimum operating temperature of the as‐coated TO, FTO and PTO films towards CO gas have been investigated and the results are discussed. Studies show a maximum detection sensitivity of 13.6% with a minimum response time of 110 sec. for the PTO thin films, at the operating temperature of 350°C.

Advanced characterization techniques of nonuniform indium distribution within InGaN/GaN heterostructures grown by MOCVD

AbstractNonuniform indium distribution within InGaN/GaN single quantum well (SQW) structures with nanoscale islands grown by metalorganic chemical vapor deposition (MOCVD) have been characterized by advanced characterization techniques. Robinson backscattered electron (BSE) measurements show cluster‐like BSE contrast of high brightness regions, which are not centered at small dark pits in a SQW structure of spiral growth mode. By comparing with the secondary electron (SE) images, the bright cluster areas from the BSE images were found to have higher indium content compared to the surrounding dark areas. Temperature dependant photoluminescence (PL) measurement shows typical “S‐shape” curve, which shows good correlation with nonuniform indium distribution from BSE measurement. Optical evaluation of the samples show increased PL slope efficiency of the spiral mode SQW, which can be attributed to the presence of Indium inhomogeneities. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Studies on pyrolytically sprayed SnO2 and Sb-SnO2 thin films for LPG sensor applications

Undoped and antimony doped tin oxide thin films of different thicknesses were prepared on mineral glass substrate by spray pyrolysis method via sol-gel route. Both the films show good transmittance in the visible region. Band gap energy of both films lies between 3 to 3.5 eV. X-ray diffraction studies of undoped and antimony doped tin oxide thin films for various annealing temperature show polycrystalline tetragonal structure of SnO2 with preferred orientation of (110) and (101), respectively and from the XRD data, grain size were also evaluated. AFM images of Undoped and antimony doped tin oxide thin films annealed at 375 °C depict the film thickness and indicate uniform surface pattern without dark pits and with strains of some ups exceeding the specified limit. The prepared films were tested in a specially developed test rig for Liquefied Petroleum Gas detection at different operating temperatures. The response characteristics of the films for LPG detection show maximum sensitivity and minimum response time at the operating temperature 400 °C. Studies indicate that antimony doped tin oxide thin film are one among the suitable candidates for LPG detection with a detection sensitivity and response time (t90) of 11 and 140 seconds, respectively.

Chemical Etching of {111} Surfaces of GaAs Crystals in H2SO4–H2O2–H2O System

The H2SO4–H2O2–H2O system, typically a solution with five parts H2SO4, one part H2O2 and one part H2O in volume ratio, is currently used for chemical polishing of a GaAs crystal to obtain microscopically smooth surfaces. However, the etching of the (111)Ga surface in this etchant leads to the formation of etch pits. In this study, the etching behavior of the (111)Ga surface in various compositions of the H2SO4–H2O2–H2O system at temperatures of 0–70°C is mainly re-examined. It is found that a microscopically smooth {111} surface can be obtained by etching in the solutions with 78+x parts H2SO4, two parts H2O2 and 20-x parts H2O (x=0–4) at 70°C. In contrast, dark and light pits are formed on the (111)Ga surface etched in a solution with two parts H2SO4, one part H2O2 and seven parts H2O at 0°C. Their origin is predicted on the basis of double-etching test results.

Atom force microscopy study on HTHP as-grown diamond single crystals

For understanding the mechanism of diamond growth at high temperature–high pressure (HTHP) from a metallic catalyst–graphite system, it is of great interest to perform atomic force microscopy (AFM) experiments, which provide a unique technique different from that of normal optical and electronic microscopy studies, to study the topography of HTHP as-grown diamond single crystals. In the present paper, we report first AFM results on diamond single crystals grown from a Fe-Ni-C system at HTHP to reveal the growth mechanism of diamond single crystals at HTHP. AFM images for as-grown diamond samples show dark etch pits on the (111) surface, indicating dislocations. Some fine particles about 100–300 nm in dimension were directly observed on the (100) diamond surface. These particles are believed to have been formed through transition of graphite to diamond under the effect of the catalyst and to have been transported to the growing diamond surface through a metallic thin film by diffusion. The roughness of the (100) diamond surface is found to be about several tens of nanometers through profile analysis. The diamond growth at HTHP, in a sense, could be considered as a process of unification of these fine diamond particles or of carbon-atom-cluster recombination on the growing diamond crystal surface. Successive growth interlayer steps on the (111) diamond surface were systemically examined. The heights of the growth interlayer steps were measured by sectional analysis. It was shown that the heights of the growth interlayer steps are quite different and range from about 10 to 25 nm. The source of the interlayer steps might be dislocations. The diamond-growth mechanism at HTHP could be indicated by the AFM topography of the fine diamond particles and the train-growth interlayer steps on the as-grown diamond surfaces.

GaP結晶(111)面におけるスパイラル・ピットの形成

The (111) wafers obtained from a Te-doped GaP crystal were etched at 60-80°C over a time period of 1.2×103 to 7.2×103 s with a solution composed of H2SO4+H2O2+H2O (5:1:1 in volume ratio) and the etch-figures were observed mainly by optical microscopy.At temperatures above 70°C, spiral etch-pits developed on the (\bar1\bar1\bar1)P surface of the wafers in addition to the normal etch-pits. The spiral etch-pits increased in size with increasing etching temperature and etching time, while the size of normal etch pits remained constant. On the (111)Ga surface rather small spiral etch-pits were also formed at 80°C, but their size remained unchanged with increasing etching time. From the experiments of double etching with a H2SO4+H2O2+H2O solution and an RC etchant, it was concluded that the former etching produces normal pits at edge dislocations and spiral pits at screw dislocations, respectively, and that the latter etching forms dark pits at edge dislocations and S-pits at small lattice defects, respectively.

Neodymium:YAG laser damage on silicone intraocular lenses: A comparison of lesions on explanted lenses and experimentally produced lesions

In this study we examined 17 explanted silicone intraocular lenses (IOLs) (two one-piece, 15 three-piece) that had evidence of neodymium:YAG (Nd:YAG) laser damage. The majority of lenses (47.1 %) had been explanted because of persistent pigment deposits and chronic inflammation. Decentration or IOL dislocation had occurred with 29.4% of lenses. All 17 patients had had Nd:YAG laser posterior capsulectomy, anterior surface polishing, or both; treatments ranged from one to 13 times. By both clinical and gross examination, the laser lesions appeared dark. This was misinterpreted by some ophthalmologists as pigment deposits and some patients had additional Nd:YAG laser treatment, which increased the severity of the laser damage. The mean depth of laser damage on the IOLs was 143 ± 113.4 gym. It was between 51 and 175 µm in approximately 61.0% and deeper than 300 lam (maximum 660 µm) in 9.3%. We compared the explanted IOLs with silicone IOLs that were experimentally damaged using standard power levels from 0.3 to 3.0 mJ and different focal areas. The appearance of the experimentally induced laser burns was equivalent to that on the explanted IOLs, especially the dark laser pits. Since the laser lesions may resemble pigment deposits on slitlamp examination, we recommend careful examination of patients prior to planned laser therapy.