Peculiar Defect Research Articles

A peculiar unilateral inferior visual field defect in metastatic pituitary renal cell carcinoma located inferior to the optic chiasm

Abstract: Pituitary metastasis (PM) from clear cell renal cell carcinoma (ccRCC) has a rare occurrence of constituting only 0.03%–0.05% of all pituitary tumors. The patient, a 58-year-old man with a history of bilateral ccRCC and endocrine disorders, presented with progressive visual deterioration and headaches. Initial ophthalmological examination revealed a unilateral inferior altitudinal visual field defect, contrasting with typical PM cases. Brain magnetic resonance imaging and computed tomography exposed a large suprasellar lesion with a unique relationship to surrounding structures, notably the left A1 segment of the anterior cerebral artery. Surgical removal confirmed invasive ccRCC metastasis, addressing hormone dysregulation. The distinctive manifestation of a prechiasmal optic nerve compression resulting in an unusual visual field defect underscores the need for ophthalmologists to consider brain lesions in unexplained visual impairments. This case contributes novel insights into the complex interplay between PM and adjacent anatomical structures.

Evolution of microstructure and defects in sintering of tape-cast alumina laminates observed by synchrotron X-ray multiscale tomography

Processing-induced defects affect the performance and reliability of multilayered ceramics. They are introduced from the raw powder, or during tape casting, drying, thermo-compression, binder burnout, and sintering. Using synchrotron X-ray multiscale tomography, we investigated how the microstructural heterogeneities and various defects evolve in the sintering of tape-cast alumina laminate. The strength-limiting defects were identified as large defects at the layer interface and peculiar crack-like defects formed around large inclusions contained in the raw powder. Although a slurry might be uniform in colloidal processing, the particle packing in the tape was heterogeneous. This heterogeneity determined the spatial distribution of pores and formed complex pores in later stages. Moreover, we found the formation of flake-like sheets in slurry due to the self-assembly of polyhedral alumina crystals. This phenomenon has the potential to be applied in the manufacture of 2D micro-sheets controlled to the thickness of a single particle.

Micro-Raman Spectroscopy Study of Vertical GaN Schottky Diode

In this work, the physical and the electrical properties of vertical GaN Schottky diodes were investigated. Cathodo-luminescence (CL), micro-Raman spectroscopy, SIMS, and current-voltage (I-V) measurements were performed to better understand the effects of physical parameters, for example structural defects and doping level inhomogeneity, on the diode electrical performances. Evidence of dislocations in the diode epilayer was spotted thanks to the CL measurements. Then, using 2D mappings of the E2h and A1 (LO) Raman modes, dislocations and other peculiar structural defects were observed. The I-V measurements of the diodes revealed a significant increase in the leakage current with applied reverse bias up to 200 V. The combination of physical and electrical characterization methods indicated that the electrical leakage in the reverse biased diodes seems more correlated with short range non-uniformities of the effective doping than with strain fluctuation induced by dislocations.

Optimization of Single-Point Incremental Forming of Polymer Sheets through FEM

Incremental sheet forming represents a relatively new process appointed to form sheets of pure metals, alloys, polymers, and composites for the manufacture of components in fields where customized production in a short time and at a low cost is required. Its most common variant, named single-point incremental forming, is a flexible process using very simple tooling; the sheet is clamped along the edges and a hemispherical-headed tool follows a required path, to deform the sheet locally. In so doing, better formability is reached without any dedicated dies and for low-forming forces, which represent some of the attractive features of this process. Nevertheless, and with special reference to thermoplastic sheets, incremental formed parts suffer from peculiar defects like twisting and wrinkling. In this numerical work, analyses were conducted through a commercial finite element code by varying the toolpath strategy of the incremental forming of polycarbonate sheets. The investigation of some features like the forming forces, the deformation states, the energy levels, and the forming time was carried out, to determine the toolpath strategy able to optimize the incremental forming process of polymer sheets. The results of the numerical analyses highlight a reduction of the forming forces when using toolpaths alternating diagonal up and vertical down steps and, presumably, a reduced risk of failures and defects. Furthermore, these toolpath strategies solutions also have a positive impact on the environment in terms of energy and do not significantly increase the manufacturing time.

73 Joint pains revealing a dysautonomic syndrome

BackgroundPrimary dysautonomia is a disorder of the autonomic nervous system with nonspecific manifestations, mainly affecting blood pressure and heart rate.ObjectiveWe report the diagnostic odyssey in an 11-year-old girl starting with arthralgia and leading to the final diagnosis of a rare dysautonomia.MethodsA 13-year-old girl, with no pathologic history, was admitted to pediatrics for diffuse arthralgia without clinical inflammatory signs.Biological exploration unmasked a morning proteinuria without hypoalbuminemia and with a normal electrophoretic profile, microcytic anaemia and orthostatic hypotension authenticated during his hospitalization.Exhaustive explorations were undertaken (including autoimmune panel, ophthalomological examination, full metabolic screen and even renal biopsy), without any conclusive result.ResultsThe development—after one year of follow up—of arterial hypertension, associated with orthostatic hypotension and proteinuria, points toward the extremely rare defect in baroreceptors.The management, in collaboration with the cardiology department, enhanced the patient’s quality of life with a reduction in hypertensive peaks. An appropriate lifestyle also amended the intensity of orthostatic hypotension.The close multidisciplinary follow-up over >48 months is reassuring.ConclusionThe peculiar baroreceptor defect in a context of dysautonomia should be kept in mind in the (long) list of differential diagnosis of arthralgias, as joint pain can be triggered by dysautonomia. Management is mainly symptomatic.

Lipid anchoring and electrostatic interactions target NOT-LIKE-DAD to pollen endo-plasma membrane.

Phospholipases cleave phospholipids, major membrane constituents. They are thus essential for many developmental processes, including male gamete development. In flowering plants, mutation of phospholipase NOT-LIKE-DAD (NLD, also known as MTL or ZmPLA1) leads to peculiar defects in sexual reproduction, notably the induction of maternal haploid embryos. Contrary to previous reports, NLD does not localize to cytosol and plasma membrane of sperm cells but to the pollen endo-plasma membrane (endo-PM), a specific membrane derived from the PM of the pollen vegetative cell that encircles the two sperm cells. After pollen tube burst, NLD localizes at the apical region of the egg apparatus. Pharmacological approaches coupled with targeted mutagenesis revealed that lipid anchoring together with electrostatic interactions are involved in the attachment of NLD to this atypical endo-PM. Membrane surface-charge and lipid biosensors indicated that phosphatidylinositol-4,5-bisphosphate is enriched in the endo-PM, uncovering a unique example of how membrane electrostatic properties can define a specific polar domain (i.e., endo-PM), which is critical for plant reproduction and gamete formation.

Simulations of primary damage in a High Entropy Alloy: Probing enhanced radiation resistance

High Entropy Alloys (HEA) attract attention as possible radiation resistant materials, a feature observed in some experiments that has been attributed to several unique properties of HEA, in particular to the disorder-induced reduced thermal conductivity and to the peculiar defect properties originating from the chemical complexity. To explore the origin of such behavior we study the early stages (less than 0.1 ns), of radiation damage response of a HEA using molecular dynamics simulations of collision cascades induced by primary knock-on atoms (PKA) with 10, 20 and 40 keV, at room temperature, on an idealized model equiatomic quinary fcc FeNiCrCoCu alloy, the corresponding “Average Atom” (AA) material, and on pure Ni. We include accurate corrections to describe short-range atomic interactions during the cascade. In all cases the average number of defects in the HEA is lower than for pure Ni, which has been previously used to help claiming that HEA is radiation resistant. However, simulated defect evolution during primary damage, including the number of surviving Frenkel Pairs, and the defect cluster size distributions are nearly the same in all cases, within our statistical uncertainty. The number of surviving FP in the alloy is predicted fairly well by analytical models of defect production in pure materials. All of this indicates that the origin of radiation resistance in HEAs as observed in experiments may not be related to a reduction in primary damage due to chemical disorder, but is probably caused by longer-time defect evolution.

A finned-riser design to avoid the capillarity effect in multi-jet fusion technology

PurposeMulti-jet fusion (MJF) process is based on a polymeric powder bed that is heated and irradiated by infra-red lamps. The layer under construction is jetted with inks to provide the desired heat management conditions for selective melting. Depending on several process variables, manufactured parts can exhibit lifting of the borders of the top surface of the shape under construction. This phenomenon is related to the capillarity effect. As a result, the top surface of MJF-manufactured parts can present a peculiar convex shape. This study aims to propose a solution that instead induces the capillarity effect outside of the part under construction.Design/methodology/approachA specific design is developed to avoid the capillarity effect in MJF. It is based on an analytical model that was previously developed by the authors to estimate the shape and extent of the capillary on top surfaces of benchmark components. The proposed methodology is established by the predicted calculation of maximum values of capillarity rise and length, and safety factors. A fin-shaped geometry is designed to avoid the capillarity effect. An experimental campaign is implemented to verify the effectiveness of the proposed solution. Prototypes are manufactured by an HP MultiJet 4200 in the original design and the so-called finned-riser design, by adding a well-dimensioned appendage on the top surface to shift the capillarity effect outside the border of the part under construction. Measurements are done by a CAM2 ScanArm contactless measuring system to achieve the real shape of top surfaces. Geomagic Control X software by 3D systems is used to evaluate the quality of measured surfaces in comparison with the expected geometry of the top plane of the benchmark.FindingsThe investigated approach involves adding an auxiliary finned-shape appendage, which acts similarly to the risers in foundry technology, to the top surface of the part that is being produced by MJF technology. The procedure and rules for determining the dimensions of the fin are established based on physical considerations and process modelling. The method is then applied to a prototype part, which is designed to highlight the effectiveness of the finned-riser design for improving the dimensional accuracy of the top surfaces of products manufactured by the MJF process. Experimental measurements of top surfaces of the original benchmark are compared to the same ones in the case of the finned-riser benchmark. Reported results are satisfactory, and the capillary effect occurred in the fins outside the border edges of the part. Further developments are planned to extend the proposed design.Originality/valueMJF technology is attracting large interest from manufacturers to produce mass customised products. The quality of manufactured parts could be affected by peculiar defects related to process parameters. The present work aims to show a method to avoid the capillarity effect. It is based on an original analytical model developed by the authors and implemented successfully in the case of a benchmark geometry.

On the origin of the premature breakdown of thermal oxide on 3C-SiC probed by electrical scanning probe microscopy

The dielectric breakdown (BD) of thermal oxide (SiO2) grown on cubic silicon carbide (3C-SiC) was investigated comparing the electrical behavior of macroscopic metal–oxidesemiconductor (MOS) capacitors with nanoscale current and capacitance mapping using conductive atomic force (C-AFM) and scanning capacitance microscopy (SCM). Spatially resolved statistics of the oxide BD events by C-AFM revealed that the extrinsic premature BD is correlated to the presence of peculiar extended defects, the anti-phase boundaries (APBs), in the 3C-SiC layer. SCM analyses showed a larger carrier density at the stacking faults (SFs) the 3C-SiC, that can be explained by a locally enhanced density of states in the conduction band. On the other hand, a local increase of minority carriers concentration was deduced for APBs, indicating that they behave as conducting defects having also the possibility to trap positive charges. The results were explained with the local electric field enhancement in correspondence of positively charged defects.

Transparent ZnO-coated polydimethylsiloxane-based material for photocatalytic purification applications

We describe production and photocatalytic properties of a material based on polydimethylsiloxane (PDMS) as a carrier substrate coated with microparticles of zinc oxide (ZnO). The ZnO microparticles are fabricated by our original hydrothermal method and intentionally have a defect structure. According to our understanding, this peculiar defect structure contributes to the greatly enhanced photocatalytic properties of the ZnO material. The resulting photocatalyst demonstrates high activity under visible light (410 nm) in the process of phenol degradation in water solution, while generally ZnO is inactive below the UV range. In addition, we compare the photocatalytic activity of our ZnO/PDMS composite to that of the same ZnO powder suspension in a similar setup. We find that the same activity is achieved by three orders of magnitude smaller amount of ZnO in our composite compared to the powder suspension. The ZnO/PDMS interface exhibits sufficiently strong bonding for stable operation that is ensured during material production. The obtained photocatalytic material preserves the transparency of PDMS due to the low amount of attached ZnO (about 0.1% by mass). The transparency of the photocatalytic ZnO/PDMS material enables easy performance upgrades by constructing multilayer or manifold fluid treatment devices.

Low-field vortex melting in a single crystal of Ba0.6K0.4Fe2As2

Theoretically, the vortex melting phenomenon occurs at both low and high magnetic fields at a fixed temperature. While the high field melting has been extensively investigated in high Tc cuprates, the low field melting phenomena in the presence of disorder hasn't been well explored. Using bulk magnetization measurement and high-sensitivity differential magneto-optical imaging technique, we detect a low-field vortex melting phenomenon in a single crystal of Ba0.6K0.4Fe2As2. The low field melting is accompanied by a significant change in local magnetization ~ 3 G, which decreases with increasing applied field. The observed vortex melting phenomena is traced on a field temperature phase diagram and which lies very close to theoretically predicted Lindemann criteria based low field melting line. Our analysis shows a Lindemann number cL = 0.14 associated with the low field melting. Imaging of low-field vortex melting features shows the process nucleates via formation of extended finger-like projections which spreads across the sample with increasing field or temperature, before entering into an interaction-dominated vortex solid phase regime. Magnetization scaling analysis shows that the dimensionality of melting vortex state is close to one. Angular dependence of bulk magnetization hysteresis loop in our sample shows the presence of extended defects. From our studies, we propose the sample contains a peculiar geometry of extended defects arranged in a plane in the sample, with these planes extending through the sample thickness. In the weak intervortex interaction limit, we argue that reduced vortex dimensionality due to pinning by these peculiar extended defect planes strongly enhances thermal fluctuations. It is these extended defects planes, which we propose are promoting low dimensional vortex melting in the pnictide system.

Advanced Fabrication Processes for Superconductor Electronics: Current Status and New Developments

In superconductor electronics fabrication processes developed at MIT Lincoln Laboratory, Josephson junctions (JJs) are placed near the top of the stack composed of nine or ten superconducting layers. We discuss the effects of this placement and other processing factors on uniformity of JJ critical current across 200-mm wafers; specifically, nonuniformity of residual stress in Nb films, wafer bow and warpage caused by accumulated stress in the underlying dielectric and superconducting layers, and effects of accumulated topography caused by patterning and planarization of wiring layers. We describe the typical fabrication defects, focusing primarily on the peculiar defects caused by electrochemical corrosion of dissimilar metals. To increase the integration scale and enhance fabrication capabilities, we are developing a new process, titled SC1, in which Nb/Al/AlO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> /Nb JJs are placed near the bottom of the layer stack, preceded only by two planarized layers: resistor layer and superconducting ground plane. Six planarized Nb wiring layers are placed above the JJs. This layer stack should simplify routing of data and clock in integrated circuits, and allow for improvements in uniformity of small JJs. The SC1 process has a 250-nm minimum feature size for inductors, three sheet resistance options for resistors, and two options for JJ critical current density: 100 and 200 μA/μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . We present fabrication details and process optimization aimed at improving JJ uniformity, increasing circuit yield, and reducing occurrence of corrosion defects to below the 1 ppm level.

Transition pathways between defect patterns in confined nematic liquid crystals

Confined nematic liquid crystals can admit multiple stable equilibria. These equilibrium states usually exhibit peculiar defect patterns in order to satisfy the topological constraints imposed by the boundary conditions. In this work, we systematically investigate transition pathways between different stable equilibria of nematic liquid crystals confined in a cylinder with homeotropic boundary condition. To do so, we implement spectral method to minimize the Landau-de Gennes free energy and develop a multiscale string method to accurately compute both minimal energy path and transition state. We first compute the transition pathways under the assumption that system state is invariant along the axial direction of the cylinder. This axial invariant assumption allows us to reduce the simulation domain to a two-dimensional disk. We subsequently remove the axial invariant assumption to search the transition pathways in the three-dimensional cylinder. Numerical simulations demonstrate that there exists a threshold for the cylinder height above which a domino-like transition pathway is more energetically favored than the axial invariant transition pathway. Moreover, we show that the transition pathway from escape radial with ring defects (ERRD) to escape radial has a lower energy barrier than the one from ERRD to planar polar, even though the free energy of the planar polar state is lower than that of the escape radial state. Our approach provides an accurate and efficient method to compute minimal energy path and transition state of confined nematic liquid crystals.

Buried defects induced by plasma assisted molecular beam epitaxy of AlN and GaN on Silicon

The present work is dedicated to the study of peculiar defects observed in GaN/AlN structures grown on Silicon substrate using the plasma assisted Molecular Beam Epitaxy under metal-rich conditions. Optical microscopy shows that these defects have undefined shape when AlN is grown on Silicon. On the contrary such defects are not observed with AlN films grown under nitrogen-rich plasma assisted or ammonia source Molecular Beam Epitaxy, but triangular shape defects appear in case of GaN regrowth on the latter. As scanning electron microscopy is not able to evidence these defects but only protuberances connected with them, we deduce that they are located in the Silicon substrate. Complementary analysis with atomic force microscopy and energy dispersive X-ray analysis lead us to propose a scenario involving the etching of the Silicon substrate with Ga or Al diffusing through weak points in the nucleation layer.

Analysis of Concentric Flow Mark Occurrence Phenomena in Injection-molded Samples Produced with a Hot Runner System

Molded products using a hot runner can have peculiar defects such as flow marks, gate marks, flow imbalance, and the like, caused by melt staying in the manifold channel. These phenomena have been noted, but the systematic analysis of their generation mechanisms have not been adequately shown. In this study, we focused on the generation mechanism of concentric flow marks around the gate that were observed on the surface of molded products using acrylonitrile-butadiene-styrene resin (ABS) with a side-fed type hot runner mold. An analysis was conducted using a dynamic flowing visualization method developed by the authors and a two-color molding method. A correlation between these flow patterns and flow mark generation areas was then derived. A unique stagnant behavior of the flow front was observed in the filling process, and it was thought that this caused a change in the deformation of the rubber particles in the melt during the transcription process. Results indicate a glossy unevenness on the surface. The stagnant behavior of the flow front was presumed to be a phenomenon that occurs due to the reversal of the temperature distribution between the inner and the outer layers of the cavity when the low-temperature, high-viscosity resin stagnating around the valve pin of the hot runner begins flowing into the cavity.

Improving the Bulk Emission Properties of CH3NH3PbBr3 by Modifying the Halide-Related Defect Structure

The peculiar defect chemistry of hybrid organic–inorganic lead halide perovskites is believed to be partially responsible for the outstanding performance of this solution-processed material in optoelectronic devices. While most effort has been put on the management of halide defects (the ones presenting the highest mobility) for CH3NH3PbI3, its bromide counterpart has not been so widely studied. Although the former is the material of choice for photovoltaics, the latter is present in most light-emitting applications. Here, we report how the exposure of CH3NH3PbBr3 single crystals to a bromine atmosphere strongly affects its emission properties. Such improvement takes place in the absence of apparent signs of degradation and remains for tens of hours. We propose an explanation based on the defect structure for this material where bromine-related defects can act as deep or shallow traps. These results are of relevance for a material expected to be present in a new generation of solution-processed light-emitting devices.

Topological Defects in Helical Magnets

Helical magnets which violated space inversion symmetry have rather peculiar topological defects. In isotropic helical magnets with exchange and Dzyaloshinskii-Moriya interactions there are only three types of linear defects: $\pm\pi$ and $2\pi$-disclinations. Weak crystal anysotropy suppresses linear defects on large scale. Instead planar defects appear: domain walls that separate domains with different preferential directions of helical wave vectors. The appearance of such domain walls in the bulk helical magnets and some of their properties were predicted in the work \cite{Li 2012}. In a recent work by an international team of experimenters and theorists \cite{Schoenherr 2018} the existence of new types of domain walls on crystal faces of helical magnet FeGe was discovered. They have many features predicted by theory \cite{Li 2012}, but display also unexpected properties, one of them is the possibility of arbitrary angle between helical wave vectors. Depending on this angle the domain walls observed in \cite{Schoenherr 2018} can be divided in two classes: smooth and zig-zag. This article contains a mini-review of the existing theory and experiment. It also contains new results that explain why in a system with continuos orientation of helical wave vectors domain walls are possible. We discuss why and at what conditions smooth and zig-zag domain walls appear, analyze spin textures associated with helical domain walls and find the dependence of their width on angle between helical wave vectors.

Beginnings of Astigmatism Understanding and Management in the 19th Century.

Within the last 200 years, the perception of astigmatism has evolved from that of an infrequent and peculiar defect of the eye to a distortion almost as common as spherical refractive errors. Most of the significant findings on this condition were made in the 19th century, including the first description by Thomas Young (1773-1829) and the introduction of the treatment methods used today. The purpose of this study was to investigate the milestones in the understanding and management of astigmatism that occurred up to the year 1900. This fascinating history illustrates how knowledge evolves across time, geographical areas, and interdisciplinary boundaries. The first article looking at the use of a cylindrical lens to correct astigmatism was written by George Airy (1801-1892) in 1825. The term "astigmatism" was introduced in by William Whewell (1794-1866) in 1846. Methods for subjective and objective evaluation were subsequently established, including the introduction of a cross cylinder, keratoscope, astigmatic dial, and the development of retinoscopy and ophthalmoscopy. In the last two decades of the 19th century, the first attempt to alter the refraction in astigmatic patients by changing the shape of the cornea was made. It must be noted that diverse challenges were encountered in this field on the way to the development of a treatment, including the technical manufacture of a lens, the precise measurement of the refractive error, and understanding the optical properties of the eye. The importance of the 19th century was that interdisciplinary cooperation, such as that seen in this study, between physicists and astronomers, and mathematicians and physicians, led to the development of comprehensive knowledge on astigmatism.

Effect of d electrons on defect properties in equiatomic NiCoCr and NiCoFeCr concentrated solid solution alloys

The role of $d$ electrons in determining distributions of formation and migration energies for point defects in equiatomic NiCoCr and NiCoFeCr concentrated solid solution alloys (CSAs) are studied regarding electron density deformation flexibility based on first-principles calculations. The disordered state is taken into account by constructing special quasirandom structures. The migration barriers are determined by directly optimizing the saddle point. It is found that the formation energies of interstitials in CSAs are lower than those in pure Ni, whereas the formation energies of vacancies are higher. In both NiCoCr and NiCoFeCr, Co-related dumbbell interstitials exhibit lower formation energies. Notably, the distributions of migration energies for Cr interstitials and vacancies exhibit a remarkable overlap region. A detailed analysis of electronic properties reveals that the electronic charge deformation flexibility regarding ${e}_{g}$ to ${t}_{2}$g transition has a dominant effect on defect energetics for different elements in CSAs. Thus the electron deformation ability is suggested as a key factor in understanding the peculiar defect behavior in CSAs.

Defects controlled hole doping and multivalley transport in SnSe single crystals

SnSe is a promising thermoelectric material with record-breaking figure of merit. However, to date a comprehensive understanding of the electronic structure and most critically, the self-hole-doping mechanism in SnSe is still absent. Here we report the highly anisotropic electronic structure of SnSe investigated by angle-resolved photoemission spectroscopy, in which a unique pudding-mould-shaped valence band with quasi-linear energy dispersion is revealed. We prove that p-type doping in SnSe is extrinsically controlled by local phase segregation of SnSe2 microdomains via interfacial charge transferring. The multivalley nature of the pudding-mould band is manifested in quantum transport by crystallographic axis-dependent weak localisation and exotic non-saturating negative magnetoresistance. Strikingly, quantum oscillations also reveal 3D Fermi surface with unusual interlayer coupling strength in p-SnSe, in which individual monolayers are interwoven by peculiar point dislocation defects. Our results suggest that defect engineering may provide versatile routes in improving the thermoelectric performance of the SnSe family.