Solvent-assisted size effect and defect engineering synergistically prepare high-efficiency microwave absorbers

Effects of artificial embedded defect size and position on the fatigue lives of additive manufacturing Ti–6Al–4V alloy

Microwave absorbing materials have attracted much attention in solving electromagnetic interference and pollution problems. Hierarchical cobalt selenides have been obtained through a facile selenization annealing process. The as-prepared samples exhibit distinct reflection losses (RL) and frequency responses via tailoring their crystalline configurations, with excellent absorption in Ku, X, or C band. All of the samples show RL greater than or near -50 dB with effective bandwidths more than 4 GHz, indicating that they may serve as high-efficient and frequency-tunable microwave absorbers. Especially, the sample annealed at 400 °C shows a competitive RL of -62.04 dB at 9.92 GHz with a thickness of 2.25 mm; meanwhile, its effective absorption bandwidth reaches 5.36 GHz with a thickness as small as 1.56 mm. The cobalt selenides as microwave absorbers exhibit a promising prospect applied in complex electromagnetic environments.

Background: Osteochondral allograft transplantation (OCA) is a successful knee joint preservation technique; however, the effects of defect size and defect size:condyle ratio (DSCR) are poorly understood. Purpose: To quantify clinical outcomes of isolated OCA of the knee based on defect size and DSCR. Study Design: Cohort study; Level of evidence, 3. Methods: Data from patients who underwent OCA of the knee without major concomitant procedures by a single surgeon were analyzed at a minimum follow-up of 2 years. Osteochondral defect size was measured intraoperatively, and femoral condyle size was measured with preoperative imaging. Patient-reported outcomes, reoperations, and survival rates were analyzed per defect size and DSCR, comparing males and females and patients <40 and ≥40 years old. Results: Sixty-eight patients were included, of whom 57% were male (mean ± SD: age, 34.5 ± 10.3 years; follow-up, 5.2 ± 2.6 years). Mean osteochondral defect size and DSCR were 3.48 ± 1.72 cm2 and 0.2 ± 0.1, respectively. Defect size was larger among males as compared with females (3.97 ± 1.71 cm2 vs 2.81 ± 1.16 cm2, P = .005), while DSCRs were not significantly different between sexes (P = .609). The cohort as a whole demonstrated improvements in the following scores: Lysholm, International Knee Documentation Committee, Knee injury and Osteoarthritis Outcome Score, Western Ontario and McMaster Universities Osteoarthritis Index, and 12-Item Short Form Health Survey Physical (P < .05). There were 27 reoperations (39.7%) at a mean of 2.5 ± 1.92 years and 8 failures (11.8%) at a mean of 2.62 ± 1.3 years. Mean DCSR was higher among patients with graft failure (0.26 ± 0.20 vs 0.19 ± 0.07, P = .049). After stratification by age, failures among patients ≥40 years old were associated with a larger defect size (mean 5.37 ± 3.50 cm2 vs 3.22 ± 1.32 cm2, P = .03) and higher DSCR (mean 0.30 ± 0.25 vs 0.19 ± 0.06, P = .05) when compared with nonfailures. Failures among patients <40 years old were not significantly associated with defect size or DSCR (P > .05) as compared with nonfailures. Conclusion: Patients undergoing isolated OCA transplantation demonstrated significant clinical improvements and a graft survival of 88.2% at 5.2 years. Failures overall were associated with a larger DSCR, and failures among patients ≥40 years old with a larger DSCR and larger defect size. Increasing defect size among males was positively correlated with some improved outcomes, although this was not maintained in analysis of the DSCR, suggesting similar prognosis after OCA regardless of sex. Clinical Relevance: Failed osteochondral allografts are associated with larger defect sizes and defect:condyle ratios in this study, providing additional information to surgeons for appropriate patient consultation.

Competition between surface defect and grain size under fatigue loading - ARMCO iron

Interaction between a surface defect and grain size under high cycle fatigue loading: Experimental approach for Armco iron

The effects of small artificial surface flaws on the fatigue strength of HAZ material are studied. The samples of coarse grain HAZ material were prepared using a welding thermal-cycle simulator. The artificial flaws were produced by indenting with a Vickers pyramid at different loads as either single indentations or as a series. The size of the flaws did not exceed the primary austenitic grain size of the material, which is the most relevant microstructural unit of carbon steels. The dependence of the experimentally determined bending fatigue strength of treated coarse grain HAZ materials on the properly evaluated size of the artificial flaws was compared with the law of long-crack propagation. The biggest flaws evaluated with the flaw-size parameter √area ≅ 100 m are still small for the studied coarse grain HAZ. In further experimental work, the effects of flaw size and the effects of residual stresses should be analysed separately.

BackgroundOsteochondral lesion of the talus (OLT) is one of the most common ankle injuries, which will lead to biomechanical changes in the ankle joint and ultimately affect ankle function. Finite element analysis (FEA) is used to clarify the effect of talus osteochondral defects on the stability of the ankle joint at different depths. However, no research has been conducted on talus osteochondral defect areas that require prompt intervention. In this research, FEA was used to simulate the effect of the area size of talus osteochondral defect on the stress and stability of the ankle joint under a specific depth defect.MethodsDifferent area sizes (normal, 2 mm* 2 mm, 4 mm* 4 mm, 6 mm* 6 mm, 8 mm* 8 mm, 10 mm* 10 mm, and 12 mm* 12 mm) of the three-dimensional finite element model of osteochondral defects were established. The model was used to simulate and calculate joint stress and displacement of the articular surface of the distal tibia and the proximal talus when the ankle joint was in the heel-strike, midstance, and push-off phases.ResultsWhen OLT occurred, the contact pressure of the articular surface, the equivalent stress of the proximal talus, the tibial cartilage, and the talus cartilage did not change significantly with an increase in the size of the osteochondral defect area when the heel-strike phase was below 6 mm * 6 mm. Gradual increases started at 6 mm * 6 mm in the midstance and push-off phases. Maximum changes were reached when the defect area size was 12 mm * 12 mm. The same patterns were observed in the talus displacement.ConclusionsThe effect of the defect area of the ankle talus cartilage on the ankle biomechanics is evident in the midstance and push-off phases. When the size of the defect reaches 6 mm * 6 mm, the most apparent change in the stability of the ankle joint occurs, and the effect does not increase linearly with the increase in the size of the defect.

The vertical rectus abdominis myocutaneous (VRAM) flap has been frequently used for perineal reconstruction given the high potential for wound complications associated with direct closure of this area. However, the relationship between defect size and postoperative complications remains undefined. A retrospective chart review of the last 20 years for VRAM flaps was performed. Defect size, age, body mass index (BMI), cause of defect, sex, radiation, and flap donor laterality were recorded. Complications of infection, partial flap loss, total flap loss, minor wounds, treated nonoperatively, and major wound, which required reoperation, were analyzed with respect to defect size. Descriptive statistics were used to summarize the demographic and clinical characteristics of the included patients. Associations were assessed using binary logistic regression analysis, and difference in means for compared groups was assessed using the independent samples t test. P values were set at 5% for all comparisons. There were 65 patients with VRAM flaps identified during the review period. Mean defect size was 204.71 cm2. Mean age was 63.97, and mean BMI was 27.18. History of prior radiation was noted in 90.77% of patients (n = 59). When adjusted for age and BMI, mean defect area was significantly different for patients with minor or major wounds. Larger perineal defects were associated with increased risk of major wound complications (odds ratio, 1.012; 95% confidence interval, 1.003-1.022). The vertical rectus abdominis flap has been a workhorse flap for perineal reconstruction. Defect size does not affect risk of partial flap necrosis, complete flap loss, infection, abdominal fascial dehiscence, ventral hernia, or seroma, which supports the utility of VRAM flap for perineal reconstruction. Larger perineal defects are associated with increased risk for major wound complications, which required reoperation, regardless of age or BMI. Future studies should be performed to determine if there is a maximum defect size cutoff that limits the utility of VRAM flap reconstruction or to develop a predictive model to assess the risk of major wound complications based on defect size.

Strong microwave absorption performance of simply grinding FAPbI3/CNTs composite absorbers

Ventral hernia repair (VHR) is a commonly performed operation, but analysis of patient outcomes based upon hernia size is lacking. We sought to identify differences in operative repair and post-operative morbidity and mortality after open VHR based on hernia defect size. Patient and operative data were retrospectively reviewed on all patients undergoing open incisional VHR between January 2008 and February 2015 by a single surgeon at the Johns Hopkins Hospital. Patient variables were described by means for continuous variables and percentages for discrete variables, with differences between groups calculated by Chi-squared analysis. During the study period, 228 patients underwent open VHR during which intraoperative defect size was measured. Patients were split into four groups based upon defect size: less than 200cm2, 200-300cm2, 301-400cm2, and over 400cm2. Patients with large defects were more likely to present with a recurrent hernia (P=0.007) and trended towards a history of wound infections (P=0.07). Operative time was significantly longer as defect size increased (P<0.001). Component separation was most frequently used in patients with defects 200-300cm2 in size (P=0.001), in whom primary closure was most likely to occur. While mesh was used in almost all patients, the specific location (overlay only, underlay only, or overlay with underlay) depended on hernia size (P<0.001). Mean length of stay increased with defect size (P<0.001). Larger defect size was associated with increased 30-day morbidity (P=0.03) but not readmission (P=0.53), recurrence (P=0.99), or mortality (P=0.99). Hernia defect size affects operative time and surgical technique for repair of a ventral hernia. Larger defect size is associated with increased post-operative morbidity and length of stay but not readmission, recurrence, or mortality. Hernia size greater than 400cm2 should not be a limitation to operative repair.

Compositional and morphological design of heterojunction modified by Schottky junction as highly efficient microwave absorbers

Effect of size of a secundum atrial septal defect on shunt volume

In this study, hollow three-dimensional CuS hierarchical microspheres were prepared via a facile galvanic replacement reaction. The hollow flower-like CuS microspheres were characterized by XRD, Raman, XPS, SEM and TEM techniques, which revealed that numerous nanoflakes were self-assembled to construct hollow flowers. Based on time-dependent experiments, a plausible formation mechanism (galvanic replacement reaction) was proposed. Paraffin-based composites, containing 50 wt% hollow CuS, exhibited outstanding microwave absorption capabilities, which were attributed to the suitable impedance match and dielectric loss. The minimal reflection loss was −17.5 dB and the effective bandwidth was 3.0 GHz with thin absorber thickness of 1.1 mm. In addition, we put forward a novel solution to evaluate the microwave absorption efficiency. The high efficiency microwave absorption properties originate from the electric/dielectric polarization and unique hollow flower-like structure. The hollow structures can adjust the dielectric properties to obtain good impedance matching. Moreover, the two-dimensional flakes and hollow flowers can induce more multiple reflection and scattering, which consumes more microwave energy. This study has led to a novel useful method for the design of hollow structures used as high efficiency microwave absorbers.

It has been successfully investigated the effect of intensity and size of defect on GL free energy density for type II superconductor. The investigation was carried out numerically based on the TDGL equation. The physical system under study square type II superconductor of niobium (κ = 1,3) with size 12ξ×12ξ with defects placed at the center of the material. This material is placed in a vacuum, where an external magnetic field H = 0.7Hck̂, is applied to the material. The intensity and size of the defect is varied. Its effect on the density of GL free energy is discussed based on the average curve of free energy density and the contour of the dynamics of GL free energy in the material.

The purpose of this study was to determine the relationship between bony stability and percentage of anterior glenoid bone loss and the effect of bone loss orientation. Twelve cadaveric shoulders were studied. Glenoid bone defects were simulated in two different osteotomy angles: 0° and 45° to the superoinferior (SI) axis of the glenoid. The force and displacement required for dislocation were measured under two compressive forces of 40 and 60N. Testing was performed for the intact glenoid and glenoid defects of 2, 4, 6, 8, and 10 mm from the anterior margin. The maximum force for dislocation with the 2-mm glenoid defect was significantly decreased compared with intact glenoid (p = 0.01), and this force also significantly decreased with each increase in defect size (p < 0.05). The dislocation force for 45° osteotomy was significantly higher than that for 0° osteotomy for all defect widths up to 8 mm with 40N compression and 6 mm with 60N compression (p < 0.001). The displacement at dislocation did not significantly decrease until the 8-mm defect with the 45° osteotomy but significantly decreased with the 4-mm defect with the 0° osteotomy. The required force for dislocation with 60N compression was significantly higher than that with 40N compression for all osteotomy sizes and orientations. The decrease in stability even with glenoid bone loss as small as 2 mm or 7.5 % of the glenoid width suggests that bony restoration is recommended whenever any bone loss exists. Bone defects parallel to SI axis may be more susceptible to recurrent instability, and shoulder muscle strengthening exercises may increase glenohumeral compressive force and thus improve glenohumeral stability. Bony restoration is recommended whenever bone loss exists even with small bone fragments particularly those in line with the superior-inferior axis of the glenoid.