Small Localized Defects Research Articles

Applications of maxillary tuberosity block autograft.

Autogenous bone grafts are considered the gold standard due to their compatibility and osteogenic potential to induce new bone formation through osteogenesis, osteoinduction, and osteoconduction. The aim of this paper was to describe clinical applications of the maxillary tuberosity block autograft in small and moderate localized defects of the alveolar process around implants and teeth. Maxillary tuberosity is often used as a particulate graft for augmentation of deficient alveolar ridge or maxillary sinus prior to or simultaneously with implant insertion, but not as a bone block graft. The maxillary tuberosity block autograft may also provide a valuable bone source for challenging situations such as immediate implant placement into types II and III extraction sockets, treatment of horizontal and vertical bone defects with simultaneous implantation, reconstruction of circumferential defects around implants, and preservation of alveolar ridge. The advantages of the maxillary tuberosity include intraoral corticocancellous autogenous graft with fewer intraoperative difficulties, no need for donor site restoration, less morbidity, and an excellent correction of localized alveolar ridge defects. Within the limitations of the presented case reports, the use of maxillary tuberosity block autograft has shown to be successful in alveolar ridges augmentation that lack both width and height.

Electron Microscopy of Nanoporous Crystals

ConspectusNanoporous crystals, such as silica mesoporous crystals (SMCs), zeolites, metal–organic frameworks (MOFs) and covalent organic frameworks (COFs), usually have unique geometrical features of periodically arranged pores from micro-, meso- to macro-scale. They have great potential to be structurally designed toward novel materials for various applications, such as storage, separation, and catalysis. In addition to the synthesis and applications of these materials, the structural analysis of nanoporous crystals is also critical for obtaining novel materials and unravelling their structure–property relationships. The crystal structure determines the pore size and connectivity of cages/channels, which are closely related to the performance of these materials in adsorption and catalysis. However, there are significant challenges in structural analysis due to small crystal size, electron-beam sensitivity, and local defects. Due to the strong interaction between electrons and matter, electron microscopy (EM) can provide rich structural information, which at the same time can also cause structural damage to samples. As early as 1960s, EM had been used to directly observe the lattice fringes of zeolites. Subsequently, the structures of many nanoporous crystals were solved and structural details such as defects, intergrowths, and surface structures were revealed by exploiting EM during the past decades. With the development of three-dimensional electron diffraction (3D ED) and low-dose high-resolution electron microscopy imaging, these approaches become more routine for solving the structure of nanocrystals and for revealing the local structural details. In this Account, we present our previous work on EM studies of several typical nanoporous materials, including SMCs, zeolites, MOFs, the TiO2@MIL-101 composite, and COFs. Various methods and strategies were developed and applied to different materials based on the characteristics of their structures. For example, 3D electrostatic potential maps of SMCs can be reconstructed by Fourier synthesis of crystal structure factors obtained from high-resolution TEM images, leading to the discovery of many 3D mesostructures. New zeolites/MOFs/COFs structures, which were not previously solved due to their structural complexity and small crystal size, have been determined using 3D ED data from nanosized crystals or using a combination of electron diffraction and high-resolution imaging. In addition, EM methods for determining the handedness of nanocrystals have also been developed and successfully applied to SMCs and STW zeolite based on high-resolution EM imaging or dynamical electron diffraction. Recently, a new strategy involving a combination of 3D ED and cryogenic protocol was proposed to study the structure, dynamics, and the host–guest interactions in a COF material. The direct-space strategy for structure solution, implemented using a genetic algorithm, was also demonstrated to be a successful approach for solving structures from low-resolution 3D ED data. By now, EM has become one of the most widely used methods in the study of nanoporous materials. We hope this Account will promote further developments of EM and stimulate the design and synthesis of new functional nanoporous materials.

DIAGNOSTICS OF STRUCTURAL DAMAGE BASED ON THE NATURAL FREQUENCIES RATIO CHANGE

The problems of vibration diagnostics based on the change of natural frequencies of structures are connected with the influence of ambient and operational factors (temperature, humidity, wind, heavy traffic etc.) on the natural frequencies. In some cases, this effect is comparable with the effect of damage itself and reliable diagnostics of damage becomes problematic. To solve this problem, the use of the ratio change between natural frequencies of different mode shapes is proposed as a characteristic of damage. The study has demonstrated that this ratio is unaffected by the environmental and operational factors. Application of the proposed method is illustrated using the example of Z24 reinforced concrete bridge. As the characteristic feature of the reinforced concrete structures damage is the occurrence of multiple cracks, in the analytical model, apart from the size and location of the cracks, the possibility of several locally located cracks was taken into account.The analytical study was performed to calculate the mode shapes and natural frequencies of damaged multi-span beam-like structure. The results reveal that, in order to identify local damage of subcritical size, natural frequency data of at least four modes of vibration are necessary. The eigenfrequencies obtained experimentally in the study of the Z24 bridge were used to confirm that the change in the eigenfrequency ratio can be used to diagnose relatively small local defects in complex structures. At this the reliability of such vibration diagnostics is much higher than based on the change of natural frequencies and mode shapes, since the change in the ratio of natural frequencies does not depend on the environmental conditions and operating conditions of the structure.

A multicenter randomized controlled trial: matrix-augmented bone marrow stimulation with a polyglycolic acid membrane with hyaluronan vs. microfracture alone in local femoral cartilage defects of the femoral condyles

Aims and Objectives:Microfracture is the gold standard for the treatment of small localized chondral defects of the knee joint. There is evidence from animal studies that the augmentation of bone marrow stimulation by a matrix improves the quality of the repair tissue (matrix-augmented bone marrow stimulation = m-BMS). Aim of this randomized controlled trial was to examine the outcome of a matrix made of polyglycolic acid and hyaluronan in comparison to a conventional microfracture technique.Materials and Methods:In a randomized controlled trail (RCT) patients between 18-60 years with an articular femoral cartilage defect of 1-4 cm2 in the weight bearing area of the femoral condyles with indication for MF were enrolled and randomized to MF or m-BMS using a polyglycolic acid membrane with hyaluronan. Defect filling in MRI assessment at 12 weeks postoperatively was defined as primary outcome measure. MRI scans and follow up examinations including patient reported clinical outcome scores (VAS pain, KOOS, IKDC and SF-36) were performed at 12, 54 and 108 weeks after surgery.Results:There was no statistically significant difference between both groups in terms of defect filling assessed by MRI at 12, 54 and 108 weeks postoperatively. At 12 weeks there was a tendency towards higher degree of defect filling in the MF group when compared to the m-BMS group, whereas no difference was found after 54 and 108 weeks. The m-BMS group revealed superiority in terms of improvement over time in the KOOS subscales pain, knee-related symptoms, activity of daily living, sports and recreation and quality of life at 54 weeks and 108 weeks after treatment.Conclusion:This is the first RCT comparing m-BMS using a polyglycolic acid membrane with hyaluronan to any different treatment strategy in localized cartilage defects of any human joint. The use of the Chondrotissue® membrane in m-BMS of cartilage defects has proven to be a safe procedure with side effects comparable to those of MF. There seems to be an accelerated formation of cartilage repair tissue after MF when compared to m-BMS at 12 weeks postoperatively, whereas at one and two years after treatment there was no difference concerning the quantity of repair tissue. The improvement in clinical outcome scores over time after m-BMS might be due to the formation of cartilage repair tissue of higher quality. Long term follow up studies including histological assessment are desirable for further investigation.

Sensitivity of the Power Spectra of Thermal Magnetization Fluctuations in Low Barrier Nanomagnets Proposed for Stochastic Computing to In-Plane Barrier Height Variations and Structural Defects

Nanomagnets with small in-plane shape anisotropy energy barriers on the order of the thermal energy have unstable magnetization that fluctuates randomly in time. They have recently emerged as promising hardware platforms for stochastic computing and machine learning because the random magnetization states can be harnessed for probabilistic bits. Here, we have studied how the statistics of the magnetization fluctuations (e.g., the power spectral density) is affected by (i) moderate variations in the barrier height of the nanomagnet (caused by small size variations) and (ii) the presence of structural defects — both localized and delocalized — in order to assess how robust the stochastic computing platform based on Low Barrier Nanomagnets (LBM) is. We found that the power spectral density is relatively insensitive to moderate barrier height change and also relatively insensitive to the presence of small localized defects. However, extended (delocalized) defects, such as thickness variations over a significant fraction of the nanomagnet, affect the power spectral density very noticeably. That means extended defects can significantly alter the fluctuation rate of the magnetization in low barrier nanomagnets. Since the fluctuation rate is crucial for stochastic computing applications, this has very serious implications for the latter. Thickness variations are difficult to avoid in real nanomagnets with in-plane anisotropy since they must be thin to keep the barrier height small and the substrate on which they are fabricated may have surface roughness comparable to the nanomagnet thickness. This raises questions about the viability of stochastic computing with low barrier nanomagnets possessing in-plane anisotropy. Our results establish that small variations in the shape (causing small variations in the barrier height), or small localized defects, are relatively innocuous and tolerable but extended defects are not. The latter must be avoided for stochastic computing applications.

Alterations to the Foveal Cone Mosaic of Diabetic Patients.

PurposeWe measured localized changes occurring in the foveal cone photoreceptors and related defects in the cone mosaic to alterations in the nearby retinal vasculature.MethodsThe central 4° of the retina of 54 diabetic (53.7 ± 12.5 years) and 85 control (35.8 ± 15.2 years) participants were imaged with the Indiana adaptive optics scanning laser ophthalmoscope. Foveal cones and overlying retinal capillaries were imaged and infrared scanning laser ophthalmoscopy (IR SLO) images and optical coherence tomography (OCT) B-scans were obtained. Follow-up imaging sessions were performed with intervals from 4 to 50 months for 22 of the 54 diabetic participants.ResultsThe foveal cone mosaics of 49 of 54 diabetic participants were of sufficient quality to assess the absence or presence of small localized defects in the cone mosaic. In 13 of these 49 diabetic participants we found localized defects, visualized as sharp-edged areas of cones with diminished reflectivity. These small, localized areas ranged in size from 10 × 10 μm to 75 × 30 μm. Of these 13 participants with cone defects, 11 were imaged over periods from 4 to 50 months and the defects remained relatively stable. These dark regions were not shadows of overlying retinal vessels, but all participants with these localized defects had alterations in the juxtafoveal capillary network.ConclusionsThe foveal cone mosaic can show localized areas of dark cones that persist over time, that apparently correspond to either missing or nonreflecting cones, and may be related to local retinal ischemia.

Non-Uniformity Behaviors of Commercial Large-Format Batteries: Performance and Durability

Coin cells and small pouch cells are commonly fabricated in laboratory to study performance and degradation mechanisms of battery materials. However, for real world applications such as hybrid electric vehicles large-format Li-ion based batteries are used currently. Performance, durability, and safety are more complex in these large-format batteries than in small ones. For example, temperature spatial profile can be significantly varied in large-format batteries during high-rate charging and discharging periods. In addition, non-uniform battery material distribution, small local defects, and inappropriate cell assembly designs may magnify the non-homogeneous behaviors in large-format batteries. Better understanding of large-format commercial batteries is essential to ensure safety and performance reliability.Both in-situ and ex-situ techniques utilizing synchrotron X-ray diffraction and Neutron diffraction are being developed at Argonne National Laboratory and Oak Ridge National Laboratory, respectively. Under various operating conditions, 3-D profiles of temperature, internal stress, and electrode SOC% can be collected on large-format Li-ion based prismatic cells. Both techniques, complementary to each other, will be briefly described. We will focus on discussing non-uniformity behaviors of local battery performance and changes of local material structure and chemistry before and after storage tests and charge-discharge cycles. These results will be correlated to the diffraction data, to understand the effects of non-uniform profiles of temperature, internal stress, and electrode SOC% on battery life-time durability. Important implications on battery quality, safety, and controls will also be mentioned. Acknowledgement This project is partially funded by US-CHINA Clean Energy Research Center (CERC)-Clean Vehicles Consortium.

A machine vision system for high speed sorting of small spots on grains

A sorting system was developed to detect and remove individual grain kernels with small localized blemishes or defects. The system uses a color VGA sensor to capture images of the kernels at high speed as the grain drops off an inclined chute. The image data are directly input into a field-programmable gate array that performs image processing and classification in real time. Spot detection is accomplished by a combination of color information and a simple, nonlinear spatial filter that detects small dips in pixel intensity along an image line. Color information is combined with spatial filtering to achieve a high level of accuracy. Testing was performed on popcorn with blue-eye damage, which is characterized by a small blue blemish on the germ. A two-camera system was developed to inspect the opposite sides of each kernel as they slide off the end of a chute. The chute was designed such that the kernels slide down the chute without tumbling, increasing the probability that a spot will be in the field of view of one of the cameras. The system’s accuracy is 89 % identification of blue-eye damaged kernels with a 6 % false positive rate. The throughput is approximately 180 kernels per second, or 100 kg/h.

Surface defect detection of 3D objects using robot vision

PurposeThe purpose of this paper is to develop a robot vision system for surface defect detection of 3D objects. It aims at the ill‐defined qualitative items such as stains and scratches.Design/methodology/approachA robot vision system for surface defect detection may counter: high surface reflection at some viewing angles; and no reference markers in any sensed images for matching. A filtering process is used to separate the illumination and reflection components of an image. An automatic marker‐selection process and a template‐matching method are then proposed for image registration and anomaly detection in reflection‐free images.FindingsTests were performed on a variety of hand‐held electronic devices such as cellular phones. Experimental results show that the proposed system can reliably avoid reflection surfaces and effectively identify small local defects on the surfaces in different viewing angles.Practical implicationsThe results have practical implications for industrial objects with arbitrary surfaces.Originality/valueTraditional visual inspection systems mainly work for two‐dimensional planar surfaces such as printed circuit boards and wafers. The proposed system can find the viewing angles with minimum surface reflection and detect small local defects under image misalignment for three‐dimensional objects.

Germanium Fin Structure Optimization for Future MugFET and FinFET Applications

(100) germanium wafers were patterned by e-beam lithography with various exposure doses, in combination with dry etch, resulting in fin structures with widths in the range of approximately 20-150 nm with a high aspect ratio, running in either the [100] or [110] direction. Fins were also subjected to various anneals in N2 to examine germanium desorption but little or no size reduction was observed for realistic thermal budgets. Other samples received a phosphorus implant (at 7°) that partially amorphized the structures. The amorphous depth was 120 nm. Subsequently a 400 °C 3 min furnace anneal in N2 recrystallized the wide fins completely, leading to the formation of various defects, including twin boundaries, small localized defects, and stacking faults. Recrystallization was retarded in narrow fins as was reported in silicon fins.

Characterisation of structured thin films made from complex materials by photoabsorption spectromicroscopy

Al3 and YBa2Cu3O7/PrBa2Cu3O7. To investigate devices built from these complex materials we applied element-sensitive photoemission electron microscopy (PEEM). Information about the chemical composition of the imaged sample can be obtained by PEEM via tuning the photon energy to X-ray absorption edges. To apply spectromicroscopy we acquired microscopic images using photon energies near and at the edges. Such images give the lateral distribution of a specific element. Microspectroscopy is performed by recording the intensity of the true secondary electrons in selected spots during a sweep of the photon energy. The main aim of our work was to observe oxygen-related defects and changes in the composition affecting the physical properties of the materials. Therefore, we applied both methods to micro-patterned devices using soft-X-ray synchrotron radiation and found that small local defects and chemical differences can be easily detected. Such defects and chemical differences are quite critical to the physical properties of the devices, since they simulate spurious effects thus influencing the reliability of the devices.

Chemical microimaging and microspectroscopy of surfaces with a photoemission microscope

We applied element sensitive photoemission electron microscopy (PEEM) to investigate surfaces of devices built from complex materials. Conventional PEEM suffers from lack of information about the chemical composition of the imaged surface. Such information can be obtained by PEEM via tuning the photon energy to X-ray absorption edges. To apply spectromicroscopy we acquired and subtracted microscopic images using photon energies just below and at the edges. The resulting difference gives a micro-image of the lateral distribution of a specific element. Microspectroscopy is performed by recording the intensity of secondary electrons in selected spots during a sweep of the photon energy. We applied both methods to microstructured devices using soft X-ray synchrotron radiation and found that small local defects and chemical differences can be easily detected.

The Use of Gore-Tex for Nasal Augmentation

Numerous implant materials have been used in nasal surgery, including autogenous, homogeneous, and alloplastic grafts. Autogenous cartilage remains the ideal graft material; however, situations exist where an alternative or an additional grafting material is needed. Homogeneous materials have demonstrated significant resorption. Alloplastic grafts have offered varying degrees of success but have resulted in significant complications as well. Gore-Tex has undergone extensive research and clinical application in various surgical fields with reported success. This analysis examines 106 patients over a 5-year time period in which the Gore-Tex soft-tissue patch was used in a wide variety of situations from extensive nasal dorsal reconstruction to small localized nasal defects or irregularities. Postoperative follow-up has revealed a stable implant material with no complications relating to the graft material.

Evaluation of the retinal nerve fiber layer in early glaucoma. Physiological and pathological findings

In this study on retinal nerve fiber layer (RNFL) evaluation in early glaucoma we investigated whether the greatest retinal vein width is a usable measure to distinguish physiological findings from beginning pathological defects. Seven normal control eyes and 23 glaucomatous eyes with small relative Octopus defects (greater than 10 db and less than 20 db) were photographed. In the control group 3 eyes had no RNFL loss, 4 eyes had localized defect less than 1 vein width. In the glaucoma group 1 eye had a localized defect less than 1 vein width, 7 eyes had localized defects greater than or equal to 1 vein width and 12 eyes had diffuse defects. Based on the present study it seems reasonable to define small localized defects as pathological if they at any point are greater than or equal to 1 vein width. According to this definition our study showed a specificity of 100% and sensitivity of 95% which means that the method is usable as an extra parameter in the diagnosis of early glaucoma.

Recurrent Inguinal Hernia

An analysis of 584 operations for recurrent inguinal hernia was made in an attempt to determine the cause of the recurrence based on the anatomic findings. The recurrence was indirect in 300, direct in 241, and various other in 43 operations. The causes of the indirect recurrences appeared to be an unrecognized hernia, incomplete dissection or improper ligation of the sac, failure to narrow the cord, or inadequate reconstruction of the internal ring. No cause for the diffuse direct recurrences was apparent. Of the 241 hernias in Hesselbach's triangle, 144 were small localized defects, usually (112) just lateral to the symphysis. These were considered to be caused by the cutting action of a suture placed under tension. On the basis of these findings, suggestions are made for primary inguinal hernia operations.

Natural frequency measurements for production quality control of fibre composites

The use of natural frequency measurements for the production quality control of fibre-reinforced plastics has been investigated. Tests have been carried out on filament wound carbon fibre-reinforced plastic tubes with a variety of defects and on a honeycomb panel fabricated from pre-impregnated fibre. The results show that a test taking under ten seconds to set up and one second to carry out can detect general defects such as incorrect fibre volume fraction and winding angle in filament wound components, and incorrect lay-up in components constructed from pre-impregnated fibre. The sensitivity of the test is limited by the degree of scatter in the properties of good components. At present, the scatter is too high for small localized defects to be detected.