Small Size Defects Research Articles

Optimal Methods for the Management of Iatrogenic Colonoscopic Perforation.

Background/Aims:Colonoscopic perforations have been managed with exploratory laparotomy, and have resulted in some morbidity and mortality. Recently, laparoscopic surgery is commonly performed for this purpose. The aim of this study was to compare the outcomes of several management strategies for iatrogenic colonoscopic perforations.Methods:We retrospectively reviewed the medical records of patients who had been treated for colonoscopic perforation between January 2004 and April 2013 at CHA Bundang Medical Center in Korea.Results:A total of 41 patients with colonoscopic perforation were enrolled. Twenty patients underwent conservative management with a success rate of 90%. Surgical management was performed in 23 patients including two patients who were converted to surgical management after the failure of the initial conservative management. Among 14 patients who underwent surgery at 8 hours after the perforation, there was no considerable difference in adverse outcomes between the laparotomy group and the laparoscopic surgery group. The medical costs and claim rate were 1.45 and 1.87 times greater in the exploratory laparotomy group, respectively.Conclusions:Conservative management of colonoscopic perforation could be an option for patients without overt symptoms of peritonitis or with a small defect size. If surgical management is required, laparoscopic surgery may be considered as the initial procedure even with a delayed diagnosis.

Revisit of Nasolabial Flap in the Reconstruction of Defects Involving the Oral Floor.

Aim:The aim of this article is to present the usefulness of the nasolabial flap (NL flap) along with a detailed review of the factors that lead to its selection for the reconstruction of post-ablative oral floor defects.Materials and Methods:The records of patients who underwent the procedure between June 2009 and June 2011 were retrospectively analyzed. A total of 16 reconstructive procedures were performed. NL flap was selected for reconstruction in all the cases due patient related factors mainly associated medical comorbidities, resource constraints, and the relatively small size of defects, which precluded the use of free flaps.Results:None of the flaps were lost, 26% of patients had flap related complications. Most of the complications were minor and managed conservatively.Conclusion:Data from this study suggest that NL flap is a reliable option for reconstruction of the oral floor, in form as well as function, without esthetic compromise and has a major role even in this era of free flaps.

Calvarial Reconstruction of Small-Size Skull Defects Performing "8 Cranioplasty" in Children: Surgical Experience, Clinical Results and Treatment Algorithm.

To report our clinical experience, surgical treatment algorithm and technique in the reconstruction of uncomplicated and small-size calvarial defects by performing autologous split-bone grafting technique on anatomical findings and patients" outcome. We covered the defective calvarial zone without bone (area, 3.8 to 7.5 centimetersquare; median area 4.2 centimetersquare) following the resection of pathological skull region with an inner table of horizontally split adjacent skull site in thirty-six patients (aged between 28 and 125 months; median age, 68.75 months, minimum follow-up 14 months). The donor site, the characteristics of skin incision such as length, shape, location and bone splitting technique were determined based on our treatment algorithm for "8 cranioplasty". Pre- and postoperative clinical outcomes and courses as well as radiological results are documented. Mean follow-up period for all children was 25 months. There was no mortality and 5.55% morbidity (n=2: 1 sterile wound dehiscence and 1 sterile wound discharge). No infected flap was seen and none of the patients required a second surgery. No graft failure, tumor recurrence or residue occurred. Almost all of our patients reported good surgical and clinical outcomes with this presented management and surgical algorithm. Autologous split bone grafting technique in small-size skull defects, with its proposed name "8 cranioplasty" is a safe and effective reconstructive procedure due to its short-term surgery, small-size surgical zone, low complication rate, good cosmetic results and cost effectiveness. In addition, our algorithm specified for this procedure is purposive and also saves the surgeon time in the surgical planning stage.

Fabrication of ideal geometric-phase holograms with arbitrary wavefronts

Throughout optics and photonics, phase is normally controlled via an optical path difference. Although much less common, an alternative means for phase control exists: a geometric phase (GP) shift occurring when a light wave is transformed through one parameter space, e.g., polarization, in such a way as to create a change in a second parameter, e.g., phase. In thin films and surfaces where only the GP varies spatially—which may be called GP holograms (GPHs)—the phase profile of nearly any (physical or virtual) object can in principle be embodied as an inhomogeneous anisotropy manifesting exceptional diffraction and polarization behavior. Pure GP elements have had poor efficiency and utility up to now, except in isolated cases, due to the lack of fabrication techniques producing elements with an arbitrary spatially varying GP shift at visible and near-infrared wavelengths. Here, we describe two methods to create high-fidelity GPHs, one interferometric and another direct-write, capable of recording the wavefront of nearly any physical or virtual object. We employ photoaligned liquid crystals to record the patterns as an inhomogeneous optical axis profile in thin films with a few μm thickness. We report on eight representative examples, including a GP lens with F/2.3 (at 633 nm) and 99% diffraction efficiency across visible wavelengths, and several GP vortex phase plates with excellent modal purity and remarkably small central defect size (e.g., 0.7 and 7 μm for topological charges of 1 and 8, respectively). We also report on a GP Fourier hologram, a fan-out grid with dozens of far-field spots, and an elaborate phase profile, which showed excellent fidelity and very low leakage wave transmittance and haze. Together, these techniques are the first practical bases for arbitrary GPHs with essentially no loss, high phase gradients (∼rad/μm), novel polarization functionality, and broadband behavior.

Large-area synthesis of high-quality and uniform monolayer WS2 on reusable Au foils.

Large-area monolayer WS2 is a desirable material for applications in next-generation electronics and optoelectronics. However, the chemical vapour deposition (CVD) with rigid and inert substrates for large-area sample growth suffers from a non-uniform number of layers, small domain size and many defects, and is not compatible with the fabrication process of flexible devices. Here we report the self-limited catalytic surface growth of uniform monolayer WS2 single crystals of millimetre size and large-area films by ambient-pressure CVD on Au. The weak interaction between the WS2 and Au enables the intact transfer of the monolayers to arbitrary substrates using the electrochemical bubbling method without sacrificing Au. The WS2 shows high crystal quality and optical and electrical properties comparable or superior to mechanically exfoliated samples. We also demonstrate the roll-to-roll/bubbling production of large-area flexible films of uniform monolayer, double-layer WS2 and WS2/graphene heterostructures, and batch fabrication of large-area flexible monolayer WS2 film transistor arrays.

Application of Hilbert–Huang transform for defect recognition in pulsed eddy current testing

Defect recognition plays an important role in the structure integrity and health monitor of in-service equipment. However, it is difficult to recognise deep-layer defect or small-size defect in conductive structure during pulsed eddy current (PEC) testing. Aiming at the issue, this article proposes a method based on Hilbert–Huang transform which consists of two modules: data processing and defect recognition. In the data processing module, the PEC response signal is decomposed into a few of intrinsic mode functions (IMFs) using ensemble empirical mode decomposition method. The IMFs whose variance contribution rates are bigger than 1% are chosen to reconstruct signal in order to remove noise. In the defect recognition module, the features based on specific frequency components of marginal spectrum (MS) of the reconstructed signals are extracted to discriminate those defects in surface and subsurface. Furthermore, the normalisation MS energy ratio is proposed to quantify defects which cannot be distinguished using peak value in time domain. Experiments show that the proposed method can achieve better de-noising effect and defect evaluation, which contributes to the recognition of those complicated defects such as deep-layered and small-sized defect.

Computational Study of the A0 Scattered Field Due to an Edge Delamination

Delamination detection presents a pertinent problem for SHM (structural health monitoring), as in most cases, there may be no visible signs of the damage on the surface of the structure. This study investigates the scattering of a zeroth-order anti-symmetric (A0) Lamb wave mode by an edge delamination using the commercial FE (finite element) package ABAQUS. The A0 Lamb mode is chosen because the corresponding stress distribution is more sensitive to delamination than is the case for symmetric modes. The paper presents results for the scatter field for various angles of incidence, and for varying defect sizes. The regime of small defect size relative to the incident wavelength is of particular interest for SHM as it corresponds to early damage detection. It is shown that, in this regime the scattered field appears to originate from a point source at the origin of the delamination, and the corresponding amplitude is linearly proportional to area of the delamination. These results can be used to guide the use of Lamb waves to detect and quantify edge delamination in plate-like structures.

Remodeling of the Proximal Tibia Subsequent to Bone Graft Harvest: Postoperative CT Study.

Proximal tibia bone autograft (PTBG) is regularly used in reconstructive foot, ankle, and maxillofacial surgery. Although many surgeons prefer PTBG rather than the conventional iliac crest, little is known about the remodeling capacity of the proximal tibia after harvesting cancellous bone. Via bilateral postoperative computed tomography of 17 harvesting sites, comparing the defect side with the healthy side, we measured the repair capacity of the proximal tibia in response to bone defect created by the harvest at medium-term follow-up (mean 29 months; range, 7-55 months). 16 of 17 (94%) cortical defects showed complete consolidation. Cancellous remodeling was graded 0 to 3, with 2 defects showing complete remodeling (grade 3), 4 defects partial remodeling (more than 50%), 8 defects partial remodeling (less than 50%) and 3 defects no remodeling at all (grade 0). The proximal tibia has the potential to form new cancellous bone after cancellous bone graft harvesting. More data are required to identify possible variables influencing this remodeling capacity. When performing knee surgery, knee surgeons should take into account the relatively small defect size and the consolidation of the cortical window after proximal tibia bone harvesting. Level IV, case series.

A review of the development of porous substrate-supported carbon membranes

Carbon membranes have attracted extensive attention because of their outstanding performance and excellent stability in the separation of gases, particularly of those with molecular sizes close to that of the membrane pores. However, they suffer from problems such as difficulty in fabrication, low permeability and poor physical strength, which greatly limit their industrial applications. These problems may be solved by supporting the thin carbon membrane on a porous substrate, forming a composite carbon membrane. The properties of the substrate play a key role, especially in the surface properties. A low surface roughness, high porosity, small pore size and fewer defects of the supporting substrate significantly favor membrane fabrication and performance. It is important to develop an effective and low cost surface modification of porous substrates to meet the requirements of membrane fabrication to optimize the selective permeability and economics of the composite carbon membranes. Research progress on the substrate materials, such as material selection, pore size distribution and surface modification, as well as membrane fabrication including precursor selection, coating, carbonization and post-treatment are summarized. [New Carbon Materials 2014, 29(6): 409–418]

Microstructural evolution of RPV steels under proton and ion irradiation studied by positron annihilation spectroscopy

The microstructural evolution of reactor pressure vessel (RPV) steels induced by proton and heavy ion irradiation at low temperature (∼373K) has been investigated using positron annihilation spectroscopy (PAS), atom probe tomography (APT), transmission electron microscopy (TEM) and nanoindentation. The PAS results indicated that both proton and heavy ion irradiation produce a large number of matrix defects, which contain small-size defects such as vacancies, vacancy-solute complexes, dislocation loops, and large-size vacancy clusters. In proton irradiated RPV steels, the size and number density of vacancy cluster defects increased rapidly with increasing dose due to the migration and agglomeration of vacancies. In contrast, for Fe ion irradiated steels, high density, larger size vacancy clusters can be easily induced at low dose, showing saturation in PAS response with increasing dose. No clear precipitates, solute-enriched clusters or other forms of solute segregation were observed by APT. Furthermore, dislocation loops were observed by TEM after 1.0dpa, 240keV proton irradiation, and an increase of the average nanoindentation hardness was found. It is suggested that ion irradiation produces many point defects and vacancy cluster defects, which induce the formation of dislocation loops and the increase of nanoindentation hardness.

Photocatalytically Active YBa2Cu3O7−x Nanoparticles Synthesized via a Soft Chemical Route

YBa2Cu3O7−x (YBCO) nanoparticles (NPs) were synthesized via a soft chemical approach and they were found photocatalytically active at room temperature. Using metal acetate as precursors, a well‐designed soft chemical procedure was carried out to produce YBCO NPs. The very small particle size and/or large number of defects might have led the NPs to semiconductors with vigorous photocatalytic activities. This work provides a direct and efficient route to obtain multifunction in YBCO based nanomaterials which are based on specific size and surface effects.

A reliable method for the treatment of lower third soft tissue defects of the leg: Use of a posterior tibial artery perforator flap

Management of lower third limb defects is a common challenge for the reconstructive surgeon due to a lack of soft tissue in that anatomic area. Traditionally, lower third of the limb defects were usually reconstructed with free flaps. The evolution of reconstructive surgery enabled thinner and pliable flaps to be harvested for the purpose of minimizing morbidity from muscle inclusion into the flap. With the introduction of perforator flaps, repairing of small and medium size defects of the distal lower third of leg and ankle region is possible with minimal donor site morbidity. Perforator flaps are based on cutaneous, small diameter vessels that arise from a main pedicle that adjacently perforates the fascia to reach the skin. In this article, we present our experience with two cases involving the repair of these defects by using posterior tibial artery perforator flaps.

Combined study on conductive AFM and damascene process to visualize Nano-Scaled defects in Cr thin films on polymer substrate

The evolution of a direct observation technique for small-sized defects in a thin film is important in understanding of a water-vapor barrier layers. An investigation into the availability of direct observation techniques for detecting nano-scaled defects in a chromium thin film on a polymer substrate was performed. The best images of nano-scaled defects in Cr thin films were obtained using conductive atomic force microscopy (C-AFM) in conjunction with a damascene process. When a dielectric Al2O3 layer was filled into the defects, such as voids or grain boundaries, in the Cr coating via this damascene process, a distinctive conductivity image was obtained from C-AFM. The major role of the dielectric material of the Al2O3 layer, when filled into the nano-scaled defects in the Cr coating, was the generation of different values in conductivity during the C-AFM analysis. The results confirmed that the combination of C-AFM and the filling of the dielectric Al2O3 layer into the defects via the damascene process is a useful method for the direct observation of nano-scaled defects comprised of deep and narrow trenches in metallic thin films on a polymer substrate.

Genetic algorithm optimization of defect clusters in crystalline materials

A real-space genetic algorithm for the optimization of defect structures embedded in bulk crystalline materials is developed. The purpose of this method is to enable automated prediction of stable structures for a range of embedded clusters, including radiation induced defect clusters, dopant clusters, and small precipitates. The method is applied to the prediction of small interstitial clusters in cubic SiC, BCC Fe, and BCC Fe–Cr random alloys for radiation damage applications. The performance of the method is analyzed and compared to alternative techniques such as basin hopping. The technique is able to reproduce small-size defects that had been previously identified as stable or metastable structures as well as predict new mid-size defects. The structure optimization program (StructOpt) developed in this study is available under open source licensing as part of the MAterials Simulation Toolkit (MAST) and can be obtained from https://pypi.python.org/pypi/MAST.

Pullulan/dextran/nHA Macroporous Composite Beads for Bone Repair in a Femoral Condyle Defect in Rats

The repair of bone defects is of particular interest for orthopedic, oral, maxillofacial, and dental surgery. Bone loss requiring reconstruction is conventionally addressed through bone grafting. Depending on the size and the location of the defect, this method has limits and risks. Biomaterials can offer an alternative and have features supporting bone repair. Here, we propose to evaluate the cellular penetration and bone formation of new macroporous beads based on pullulan/dextran that has been supplemented with nanocrystalline hydroxyapatite in a rat model. Cross-linked beads of 300–500 µm diameters were used in a lateral femoral condyle defect and analyzed by magnetic resonance imaging, micro-computed tomography, and histology in comparison to the empty defects 15, 30, and 70 days after implantation. Inflammation was absent for both conditions. For empty defects, cellularisation and mineralization started from the periphery of the defect. For the defects containing beads, cellular structures filling out the spaces between the scaffolds with increasing interconnectivity and trabecular-like organization were observed over time. The analysis of calcified sections showed increased mineralization over time for both conditions, but was more pronounced for the samples containing beads. Bone Mineral Density and Bone Mineral Content were both significantly higher at day 70 for the beads in comparison to empty defects as well as compared with earlier time points. Analysis of newly formed tissue around the beads showed an increase of osteoid tissue, measured as percentage of the defect surface. This study suggests that the use of beads for the repair of small size defects in bone may be expanded on to meet the clinical need for a ready-to-use fill-up material that can favor bone formation and mineralization, as well as promote vessel ingrowth into the defect site.

Stereolithographic Ceramic Manufacturing of High Strength Bioactive Glass

Bioactive glasses and glass ceramics like the 45S5 formulation have been studied toward biocompatibility and biodegradability for years. Nevertheless, clinical applications as bone substitute or scaffold material are highly limited because of the often poor mechanical behavior of bioactive glasses. In this study, we are able to provide a new production alternative for 45S5 bioactive glass structures resulting in parts with high density and strength. Using the stereolithographic ceramic manufacturing (SLCM) process, it is possible to additively produce solid bulk glass ceramics as well as delicate scaffold structures. Recent developments in SLCM slurry preparation together with an appropriate selection of raw materials led to 3D parts with a very homogeneous microstructure and a density of about 2.7 g/cm³. Due to the low number and small size of defects, a high biaxial bending strength of 124 MPa was achieved. Weibull distribution also underlines good process control showing a Weibull modulus of 8.6 and a characteristic strength of 131 MPa for the samples tested here. By reaching bending strength values of natural cortical bone, bioactive glasses processed with SLCM could eventually advance to be an interesting bone substitute material even in load‐bearing applications, valuing the huge efforts undertaken to understand their bioactive behavior.

Facial artery musculomucosal flap in head and neck reconstruction: A systematic review.

The facial artery musculomucosal (FAMM) flap has emerged as a popular option in head and neck reconstruction in the last decade. The purpose of this study was to conduct a literature review of the FAMM flap. We have conducted a search on PubMed using specific key words to identify all articles related to the FAMM flap. We reviewed the modifications of the FAMM flap, its indications, contraindications, complications, and outcomes. Thirty-eight articles published from 1992 to 2013 were included for review. A total of 441 FAMM flaps were reported in the literature and the most commonly reconstructed site was the floor of the mouth. Functional and aesthetic outcomes were judged to be excellent. The FAMM flap is a versatile reconstructive option for small and medium size defects in the head and neck. Recent studies have explored new applications for this flap, such as in skull base reconstruction.

Factors Predictive of Improved Patient Reported Outcomes Following Distal Femoral Osteochondral Allograft Transplantation

Objectives:Osteochondral injury is associated with pain and/or dysfunction and has been implicated as a factor leading to early degenerative joint disease. Fresh osteochondral allograft (OCA) transplantation is a well-described surgical replacement therapy for patients with large osteochondral defects. Optimal selection of patients and factors most associated with a successful outcome is of clinical importance. Previous studies have found age and prior surgery to be predictive of graft failure; however, the potential influence of BMI, coronal plane alignment, and degree of osteoarthritis as well as donor factors such as donor age, graft age and donor match for gender and specific graft locations on patient reported outcomes remains less well characterized.Methods:We utilized a prospective database of 97 consecutive patients receiving osteochondral allograft transplantation to the distal femur from a single surgeon practice over 5 years (2006-2011). Patient and donor characteristics were routinely collected, as were patient reported outcome measures (PRO) including KOOS and IKDC. Pre-operative full length standing lower extremity radiographs were measured. Values were considered as both continuous (degrees of varus/valgus) and dichotomous variables (WB axis through the recipient condyle). We used AP X-rays to grade osteoarthritis using the Kellgren-Lawrence scale. Responder analysis was applied to individual patient scores using solitary and dual threshold criteria. Logistic regression was then applied to determine relationships between the candidate variables and response according to the responder analysis threshold. We considered 19 candidate variables in the analysis (Figure 1) and used a forward process for variable selection and multivariate model building based on Akaike Information Criterion (AIC) as the measure of relative goodness-of-fit for the models.Results:53 patients (36 male, 17 female, mean age 38.6 years) with a minimum of 24-month data (mean 35.7 months) and without concurrent osteotomy are reported. A statistically significant improvement from baseline to final follow-up (p<.006) was seen for KOOS (Pain: +14.6, ADL: +15.6, Sports: +33.8, QOL: +27.8) and IKDC (+18.7). Patient factors independently associated with greater improvement included a BMI of less than 30 (p<.047), prior cartilage surgery (p=.019), and Kellgren-Lawrence score of 2-4 (p=.024). Valgus alignment trended to greater improvement (p=.08), but medial vs lateral condyle did not. We built predictive multivariate models for our six dependent variables (KOOS, IKDC) and identified 4 significant contributors within patient and donor characteristics. Amongst the factors, the most prominent predictors were valgus alignment (p=.03), smaller defect size (p=.03), younger age (p=.01), and no additional simultaneous procedure (p=.01).Conclusion:We confirm that at an average of 3 years after surgery, patients undergoing OCA to the distal femur can expect significantly improved PRO scores. Independent factors resulting in greater patient improvement in this cohort included the absence of obesity, a history of prior cartilage surgery, and, to our surprise, advanced osteoarthritis (Kellgren-Lawrence 2-4). In the multivariate model, younger age, valgus alignment, smaller defect size, and no simultaneous procedure were predictive of better PRO. Surgeons may use this data to select and advise potential patients under consideration for OCA transplant.

Large Scale Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;-ZrO&lt;sub&gt;2&lt;/sub&gt; (Y&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;) Eutectic and Hypereutectic Achieved by Combustion Synthesis in High Gravity Field

By introducing ZrO2 (4Y) powder into the thermit, the solidified Al2O3-ZrO2 (4Y) ceramic composites with eutectic and hypereutectic microstructures were prepared via combustion synthesis in high gravity field, and the microstructures and mechanical properties of the solidified ceramic composites were discussed. XRD, SEM and EDS showed that the Al2O3-33%ZrO2 (4Y) as the eutectic were composed of random-orientated rod-shaped colonies consisting of a triangular dispersion of orderly submicron-nanometer t-ZrO2 fibers, surrounded by inter-colony regions consisting of spherically-shaped micrometer t-ZrO2 grains, whereas Al2O3-45%ZrO2 (4Y) as the hypereutectic were comprised of spherically-shaped micron-meter t-ZrO2 grains, surround by irregularly-shaped α-Al2O3 grains and a few colonies. Compared to the directionally solidified Al2O3-ZrO2 (Y2O3), the increase in hardness and flexural strength of the eutectic obtained in current experiment was due to high densification, small-size defect and high fracture toughness induced by residual stress toughening and transformation toughening mechanisms; meanwhile, in despite of the moderate decrease in hardness, high flexural strength of the hypereutectic was considered to be a result of small-size defect and high fracture toughness induced by transformation toughening and microcrack toughening mechanisms.

Electrical stimulation for difficult wounds: only an alternative procedure?

In the wound healing research, the exact mechanism of action of different modalities of electrical stimulation (ES) remains controversial and unresolved. In this study we discuss a particular ES, with a different type of waveform, corresponding to the principle of stochastic resonance. Between July 2008 and May 2010, 32 patients were enrolled and ES was applied to wounds using the bioelectrical signal therapy (BST) device (LifeWave, Petach Tiqwa, Israel). The outcome evaluated in group 1 (n = 21) was wound healing, while group 2 (n = 11) was evaluated for wound-related pain [Visual Number Scale (VNS) pain scale] during treatment. In group 1, 87% of the wounds closed in an average time of 97 days (range 10-150 days); three patients were lost to follow-up. In group 2, 45% of the patients experienced a complete pain disappearance after 7 days of treatment; 36% reported a reduction in VNS from 9·3 to 3·2 in 7 days; 19% stopped morphine-like painkillers after 2 weeks. The clinical application of the stochastic resonance enables the usage of easy-to-use, non-invasive, painless and pain-relief treatment. Our experience with ES has demonstrated the BST device to be a very good alternative in cases of small size defects, compared with other therapies such as surgery, dressing and negative pressure devices.