Shrinkage Compensation and Effect of Building Orientation on Mechanical Properties of Ceramic Stereolithography Parts.

Stereolithography additive manufacturing (SLA-AM) can be used to produce ceramic structures by selectively curing a photosensitive resin that has ceramic powder in it. The photosensitive resin acts as a ceramic powder binder, which is burned, and the remaining ceramic part is sintered during post-processing using a temperature-time-controlled furnace. Due to this process, the ceramic part shrinks and becomes porous. Moreover, additive manufacturing leads to the orthotropic behavior of the manufactured parts. This article studies the effect of the manufacturing orientation of ceramic parts produced via SLA-AM on dimensional accuracy. Scaled CAD models were created by including the calculated shrinkage factor. The dimensions of the final sintered specimens were very close to the desired dimensions. As sintering induces porosity and reduces the mechanical strength, in this study, the effect of orientation on strength was investigated, and it was concluded that the on-edge specimen possessed by far the highest strength in terms of both compression and tension.

Optimization of Wire Electric Discharge Machining (WEDM) Process Parameters for AISI 1045 Medium Carbon Steel Using Taguchi Design of Experiments.

With the growth of the manufacturing industry, the demand for alloy materials with high hardness, toughness, and impact strength has increased. Since products from such alloy materials are extremely difficult to manufacture with high accuracy and reduced surface roughness using traditional machining techniques, wire electric discharge machining can be used to machine such complex parts with more precision. In this case-study-based research, machining factors such as current, pulse-on time, and voltage are studied to determine their effects on the material removal rate for AISI 1045 medium carbon steel. The Taguchi L9 orthogonal array is used in the design of experiments for optimization. Statistical techniques such as analysis of variance and signal-to-noise ratio are used to identify the control parameters that matter most in bringing about optimal results. Based on the results, the current is the most crucial control variable in this investigation. Moreover, the maximum material removal rate obtained was 0.7112 mm3/min with the obtained optimized values of current (I) = 16 A, voltage (V) = 50 V, and pulse-on time (Ton) = 100 µs.

Nitrogen-Doped Carbon Nanosheets Decorated With Mn2O3 Nanoparticles for Excellent Oxygen Reduction Reaction.

The purpose of this study is to develop an active, low cost, non-precious, stable, and high-performance catalyst for oxygen reduction reaction (ORR). In this regard, Mn2O3-decorated nitrogen-doped carbon nanosheets (Mn2O3/NC) are fabricated by a two-step strategy involving a hydrothermal method and a solid-state method. In the resultant structures, very fine Mn2O3 nanoparticles with an average size of about 5 nm are strongly attached to nitrogen-doped carbon nanosheets. The role of the Mn2O3 nanoparticles is to provide active sites for ORR, while the presence of the nitrogen-doped carbon not only enhances the conductivity of the overall structure but is also helpful for overall stability. The Mn2O3/NC shows good onset potential (0.80 V@-1 mA/cm2), methanol crossover effect, and stability (90%).

The Gadolinium (Gd3+) and Tin (Sn4+) Co-doped BiFeO3 Nanoparticles as New Solar Light Active Photocatalyst.

The process of photocatalysis is appealing to huge interest motivated by the great promise of addressing current energy and environmental issues through converting solar light directly into chemical energy. However, an efficient solar energy harvesting for photocatalysis remains a critical challenge. Here, we reported a new full solar spectrum driven photocatalyst by co-doping of Gd3+ and Sn4+ into A and B-sites of BiFeO3 simultaneously. The co-doping of Gd3+ and Sn4+ played a key role in hampering the recombination of electron-hole pairs and shifted the band-gap of BiFeO3 from 2.10 eV to 2.03 eV. The Brunauer-Emmett-Teller (BET) measurement confirmed that the co-doping of Gd3+ and Sn4+ into BiFeO3 increased the surface area and porosity, and thus the photocatalytic activity of the Bi0.90Gd0.10Fe0.95Sn0.05O3 system was significantly improved. Our work proposed a new photocatalyst that could degrade various organic dyes like Congo red, Methylene blue, and Methyl violet under irradiation with different light wavelengths and gave guidance for designing more efficient photocatalysts.

Enhanced Thermoelectricity in High-Temperature ß-Phase Copper(I) Selenides Embedded with Cu2Te Nanoclusters.

We report remarkably enhanced thermoelectric performance of Te doped Cu2Se in midtemperature range. Through ball-milling process followed by spark plasma sintering (SPS), nanoscale Cu2Te clusters were embeded in the matrix of Cu2Se, inducing a drastic enhancement of thermoelectric performance by reducing the thermal conductivity without degrading the power factor. A large ZT value of 1.9 was achieved at 873 K for Cu2Se1.9Te0.1, which is about 2 times larger than that of the pure Cu2Se. The nanoscale heat management by Cu2Te nanoclusters in superionic conductors opens up an avenue for thermoelectric materials research.

Nanoscale heterogeneity in thermoelectrics: the occurrence of phase separation in Fe-doped Ca3Co4O9.

The misfit layered cobaltate thermoelectrics are good candidates for high temperature thermoelectric applications. Ca3Co4O9 is a typical compound of this family, which consists of rock salt Ca2CoO3 slabs alternating with hexagonal CoO2 slabs with a large lattice mismatch along the b axis. Each slab is 0.3-0.5 nm thick and shows an inherent structural heterogeneity at the nanoscale. The latter is a key parameter that affects the electrical transport and the heat flow in these misfit structured thermoelectrics. To clarify the physical origin of the thermoelectric performance of iron doped Ca3Co4O9 we combined X-ray near-edge absorption spectroscopy (XANES) and quantum modeling using density functional theory. In contrast to single-site doping, the iron doping first occurs at the Co1 site of the rock salt slab at low doping while at higher doping it prefers the Ca1 site of the rock salt slab. Doping at the Ca1 site modifies the electronic structure tuning the nanoscale structural heterogeneity. This mechanism may open a new route to optimizing the thermoelectric performance of misfit layered thermoelectrics.

The use of ultrasound in comparison to radiography in magnetically controlled growth rod lengthening measurement: a prospective study.

PURPOSE: This study investigated whether ultrasound (U/S) is an alternative to radiography when measuring magnetically controlled growth rod (MCGR) length in order to reduce radiation exposure. Distractible spinal growth rods are the gold standard when treating early-onset scoliosis (EOS). METHODS: This was a prospective series. Patients were already undergoing EOS treatment using MCGRs. Forty-eight data points measured using radiography and U/S were compared. Each U/S data point was measured three times by three observers to assess intra- and inter-observer reliability. The radiation dose of the pre-lengthening and post-lengthening radiographs was recorded. RESULTS: The average rod lengths were 1.322 cm with U/S and 1.329 cm with radiography. The ICC (radiography vs. U/S) was 0.992 (95 % confidence interval (CI) 0.976, 1.000). The inter- and intra-rater reliability of U/S had an ICC of 0.987 (95 % CI 0.966, 1.000) and 0.983 (95 % CI 0.956, 1.000), respectively. The mean total effective radiation dose of the pre-lengthening and post-lengthening PA spinal radiographs was 0.26 mSv with a mean attributable lifetime cancer risk of one in 39,686 per lengthening. CONCLUSION: U/S highly agrees with radiography when measuring MCGR length. It has a high inter- and intra-observer reliability and does not require radiation exposure. Although U/S allows accurate MCGR measurement and soft tissue assessment, patients will still need occasional radiographs to assess spine bony elements, overall spinal balance and scoliosis correction. Combining radiography and U/S allows patient monitoring and accurate MCGR measurement whilst decreasing patients' radiation exposure.

MDCT of acute subaxial cervical spine trauma: a mechanism-based approach.

Injuries to the spinal column are common and road traffic accidents are the commonest cause. Subaxial cervical spine (C3-C7) trauma encompasses a wide spectrum of osseous and ligamentous injuries, in addition to being frequently associated with neurological injury. Multidetector computed tomography (MDCT) is routinely performed to evaluate acute cervical spine trauma, very often as first-line imaging. MDCT provides an insight into the injury morphology, which in turn reflects the mechanics of injury. This article will review the fundamental biomechanical forces underlying the common subaxial spine injuries and resultant injury patterns or "fingerprints" on MDCT. This systematic and focused analysis enables a more accurate and rapid interpretation of cervical spine CT examinations. Mechanical considerations are important in most clinical and surgical decisions to adequately realign the spine, to prevent neurological deterioration and to facilitate appropriate stabilisation. This review will emphasise the variables on CT that affect the surgical management, as well as imaging "pearls" in differentiating "look-alike" lesions with different surgical implications. It will also enable the radiologist in writing clinically relevant CT reports of cervical spine trauma. Teaching Points • Vertebral bodies and disc bear the axial compression forces, while the ligaments bear the distraction forces.• Compressive forces result in fracture and distractive forces result in ligamentous disruption.• Bilateral facet dislocation is the most severe injury of the flexion-distraction spectrum.• Biomechanics-based CT reading will help to rapidly and accurately identify the entire spectrum of injury.• This approach also helps to differentiate look-alike injuries with different clinical implications.

Avulsion fracture of the anterior superior iliac spine: misdiagnosis of a bone tumour.

Avulsion fractures of the anterior superior iliac spine are rare. This injury is usually seen in adolescents, as an avulsion fracture of the apophyses, a result of sudden vigorous contraction or repetitive contraction of the sartorius and tensor fasciae latae muscles. Treatment for this injury is usually conservative; however, surgical management has been reported in those with significant displacement. We present a 14 year old male patient who was referred to our unit for biopsy of a possible pathological fracture of his right ilium. The authors feel it is essential to understand the importance of ruling out a bone tumour, if the possibility has been raised, before managing a suspected fracture. If there is any doubt, the case should be referred to an appropriate sarcoma unit for review prior to any intervention.

Advantages and limitations of imaging the musculoskeletal system by conventional radiological, radionuclide, and hybrid modalities.

The endpoint of an efficient and accurate diagnosis of musculoskeletal pathology can take many different routes. Currently, conventional radiological techniques, such as plain radiography, ultrasonography, computed tomography, and magnetic resonance imaging are used in the assessment of patients with benign and malignant bone disease. An understanding of the advantages and limitations of the modalities available will help expedite diagnosis, and hence treatment. In this review, we discuss the advantages and limitations of the modalities available in investigating benign and malignant musculoskeletal pathology.

Metastatic pulmonary intimal sarcoma presenting as cauda equina syndrome: first report of a case.

STUDY DESIGN: Case report and clinical discussion. OBJECTIVE: To describe a rare case of metastatic pulmonary intimal sarcoma presenting as cauda equine syndrome. SUMMARY OF BACKGROUND DATA: Pulmonary artery sarcoma is a rare tumor, frequently misdiagnosed as pulmonary embolism, and although it is highly aggressive, metastasis to bone is very rare. In our case, the tumor metastasised to the vertebral column, which lead the patient to present with cauda equine-type symptoms. METHODS: We report the clinical and imaging features in a 38-year-old female presenting with back pain and weakness of the legs. Although initially misdiagnosed as a primary bone tumor of the vertebral column and a concurrent pulmonary embolism, the final diagnosis of pulmonary artery sarcoma with spinal metastasis, presenting as cauda equina syndrome was made. RESULTS: At surgery, the mass was excised with the pulmonary valve and replaced with a homograft. The histology demonstrated an undifferentiated intimal sarcoma of the pulmonary artery. When stable enough the patient underwent a posterior L4-S1 decompression laminectomy after which she regained the power in the legs. The histology also showed a metastatic undifferentiated intimal sarcoma likely to have come from the pulmonary artery. The patient went on to receive a more formal vertebrectomy, front and back repair, and radiotherapy. Her 1-year follow-up computed tomography (CT) chest showed evidence of further metastases. CONCLUSION: To our knowledge, this is the first case of metastatic pulmonary intimal sarcoma presenting as cauda equine syndrome described in the literature.

Angioleiomyoma: magnetic resonance imaging features in ten cases.

OBJECTIVES: Angioleiomyoma is a rare, benign smooth muscle tumour arising from the tunica media of small veins and arteries and can occur anywhere in the body. The histological appearances are well documented, but there are relatively few descriptions of the magnetic resonance imaging (MRI) findings. MATERIALS AND METHODS: A retrospective study of the clinical presentation, MRI appearances and histological findings of ten angioleiomyomas presenting as extremity soft tissue masses. RESULTS: MRI typically demonstrated a well-defined, oval mass located superficial to the fascia with the commonest sites being the hand (three cases) and ankle/foot (five cases). The lesion was isointense to muscle on T1-weighted spin echo images with heterogeneous increased internal T2W/short tau inversion recovery (STIR) signal intensity, which commonly appeared as multiple linear or branching areas of hyperintensity. Enhancement after IV gadolinium ranged from diffuse to heterogeneous. In a single case, central fat signal intensity was seen, while a further case showed marked T2W/STIR hypointensity due to diffuse hyalinisation within the lesion. CONCLUSIONS: This is the largest reported MRI series of extremity musculoskeletal angioleiomyoma. Angioleiomyoma should be considered in the differential diagnosis of a superficial mass in the hand or foot, particularly when characteristic linear or branching hyperintensity is seen on T2W or STIR images.

Stress fractures and related disorders in foot and ankle: plain films, scintigraphy, CT, and MR Imaging.

The accurate diagnosis of stress-induced changes in the foot and ankle requires careful and detailed clinical history and examination. This is of paramount importance in ensuring the correct imaging interpretation and for excluding other differential diagnoses. Advanced imaging (scintigraphy and MR imaging) plays a vital role in the early diagnosis of this type of injury, and CT has an important contributory role in the diagnosis of injury where imaging features by the other modalities are equivocal. An early diagnosis reached by judicious use of imaging techniques is the cornerstone of appropriate management, with a high probability of a full recovery, a low risk of complications, and a return to pre-disease activity.