Localized Necking Research Articles

Effects of Peripheral Haptic Feedback on Intracortical Brain-Computer Interface Control and Associated Sensory Responses in Motor Cortex.

Intracortical brain-computer interfaces (iBCIs) provide people with paralysis a means to control devices with signals decoded from brain activity. Despite recent impressive advances, these devices still cannot approach able-bodied levels of control. To achieve naturalistic control and improved performance of neural prostheses, iBCIs will likely need to include proprioceptive feedback. With the goal of providing proprioceptive feedback via mechanical haptic stimulation, we aim to understand how haptic stimulation affects motor cortical neurons and ultimately, iBCI control. We provided skin shear haptic stimulation as a substitute for proprioception to the back of the neck of a person with tetraplegia. The neck location was determined via assessment of touch sensitivity using a monofilament test kit. The participant was able to correctly report skin shear at the back of the neck in 8 unique directions with 65% accuracy. We found motor cortical units that exhibited sensory responses to shear stimuli, some of which were strongly tuned to the stimuli and well modeled by cosine-shaped functions. In this article, we also demonstrated online iBCI cursor control with continuous skin-shear feedback driven by decoded command signals. Cursor control performance increased slightly but significantly when the participant was given haptic feedback, compared to the purely visual feedback condition.

Damage and Cracking Prediction of AISI 410 Martensitic Stainless Steel at Elevated Temperatures

Combining Gleeble hot compression and tensile tests with finite‐element (FE) simulations, this study delivers a robust assessment of the elevated temperature damage and cracking of AISI 410 martensitic stainless steel. The effects of hot deformation parameters on the macroscopic flow and deformation behaviors as well as microscopic damage and fracture characteristics are discussed, determining the critical damage values with the aid of FE calculations. Furthermore, a novel critical damage value model is proposed using the Zener–Hollomon parameter to establish the normalized Oyane fracture criterion coupling hot deformation parameters. The results reveal that the flow stress and tensile load both increase, as the strain rate increases and the temperature decreases and vice versa. The occurrence of localized necking and internal damage cracking causes the tensile load to decline drastically. The hot deformation parameters manipulate not only the plat and dimple fractures, each caused by intergranular and transgranular fractures, but also the internal damage cracking before the final fracture. The established criterion predicts outcomes in good agreement with experimental results. This work provides essential information and a model for the cracking prediction of AISI 410 steel at elevated temperatures, helping to derive a rational hot forming design to prevent cracking.

Degenerative Cervical Myelopathy: Insights into Its Pathobiology and Molecular Mechanisms.

Degenerative cervical myelopathy (DCM), earlier referred to as cervical spondylotic myelopathy (CSM), is the most common and serious neurological disorder in the elderly population caused by chronic progressive compression or irritation of the spinal cord in the neck. The clinical features of DCM include localised neck pain and functional impairment of motor function in the arms, fingers and hands. If left untreated, this can lead to significant and permanent nerve damage including paralysis and death. Despite recent advancements in understanding the DCM pathology, prognosis remains poor and little is known about the molecular mechanisms underlying its pathogenesis. Moreover, there is scant evidence for the best treatment suitable for DCM patients. Decompressive surgery remains the most effective long-term treatment for this pathology, although the decision of when to perform such a procedure remains challenging. Given the fact that the aged population in the world is continuously increasing, DCM is posing a formidable challenge that needs urgent attention. Here, in this comprehensive review, we discuss the current knowledge of DCM pathology, including epidemiology, diagnosis, natural history, pathophysiology, risk factors, molecular features and treatment options. In addition to describing different scoring and classification systems used by clinicians in diagnosing DCM, we also highlight how advanced imaging techniques are being used to study the disease process. Last but not the least, we discuss several molecular underpinnings of DCM aetiology, including the cells involved and the pathways and molecules that are hallmarks of this disease.

Evaluation of the middle ear in water buffaloes (Bubalus bubalis) by gross anatomy and cone-beam computed tomography

The purpose of this study was to provide a description of gross middle ear morphology in water buffaloes, augmented with additional data on the osseous structures of middle ear derived from cone-beam computed tomography (CBCT). Skulls of 10 young adult male water buffaloes were used to examine their middle ears. Anatomical features noted included the presence of tympanic cells in the tympanic bulla, the location of malleus head and neck, and all of incus in the dorsal epitympanic recess, the oval tympanic membrane, absence of a prominent notch on the articular surface of malleus, positional variations of the lateral process of malleus relative to the muscular process and muscular process relative to the rostral process of malleus, absence of complete coverage of the articular facet of malleus head by incus body, and presence of the lenticular process of incus. In CBCT images, the osseous part of external acoustic meatus, the petrous part of temporal bone and the details of the ossicles were seen, except for stapes. Although tympanic membrane, malleus and stapes of water buffaloes are similar to those of ox, the incus of water buffaloes is more similar to that of goats. The heaviest ossicles among the ruminants studied belonged to water buffaloes; the mean length of malleus head and neck, total length and width of incus body as well as length of stapes head were greatest in water buffaloes too. The auditory ossicles of water buffaloes show 'transitional type' morphological characteristics. These features suggest a relatively wide frequency range of hearing, but not one biased towards especially low or especially high frequencies.

The patient-reported outcome measures in oropharyngeal, laryngeal and hypopharyngeal cancer patients treated with Volumetric Modulated Arc based simultaneous integrated boost radiotherapy.

To assess the change in the quality of life (QOL) in head and neck cancer patients treated with Simultaneous Integrated Boost (SIB) by Volumetric Modulated Arc Therapy (VMAT) technique. Thirty patients with localised head and neck cancers (Stage II- IVa) were treated with VMAT and SIB technique. The three-dose levels prescribed were 68.2 Gy at 2.2 Gy/fraction, 62 Gy at 2 Gy/fraction and 55.8 Gy at 1.8 Gy/fraction to the high, intermediate and low-risk volumes respectively. Concurrent chemotherapy with cisplatin 100 mg/m2 was administered once in three weeks. Acute toxicities were evaluated and scored according to the RTOG grading system. Quality of life (QOL) was assessed using European Organization of Research and Treatment of Cancer (EORTC) QLQC30 and HN35 questionnaires at baseline and in three instances (immediately, one month and three months after the radiotherapy). Out of the total 30, 80% patients had a complete response (CR) at the median follow up of 12 months, while three patients died because of progression, and the remaining 3 had stable disease. All planning objectives were achieved for organs at risk and planning target volume(PTV). There was a statiscally significant(p value < 0.001) reduction in global quality of life scores at the end of treatment when compared to baseline scores, but by three months, there was the return in the QOL scores in most scales similar to the baseline value. VMAT based Simultaneous boost radiotherapy is a feasible and safe strategy in terms of toxicityprofile with an acceptable transient change in the quality of life and allows a faster return to baseline quality of life.

Flow behaviors and deformation mechanism of WQ-tempered Al–Li alloy at cryogenic temperatures

Abstract Cryogenic forming is a promising technique for fabricating complex components using high-strength aluminum alloys. In this work, the flow behaviors and microstructure evolution of a WQ-tempered (solution treatment followed by water quenching) 2195 Al–Li alloy was studied by uniaxial tension tests from −196 to 25 °C and strain rates from 2.5 × 10−4 to 1 × 10−2 s−1. The results showed that the ductility gradually increased after decreasing the deformation temperature, while the strain rate had a limited effect on the ductility. Serrated flow caused by dynamic strain aging occurred from −60 to 25 °C, which increased the flow stress due to additional pinning of mobile dislocations by solute atom clusters. Smooth flow curves were obtained from −196 to −90 °C due to the suppression of dynamic strain aging. The microstructure observations indicated that more homogeneous plastic strain and grain rotation occurred in the cryogenically-deformed sample, leading to the formation of weaker fiber texture compared with the sample deformed at room temperature. A higher work hardening rate was achieved at cryogenic temperature, which delayed local necking. The suppression of serrated flow and homogeneous plastic deformation significantly improved the ductility at −196 °C, with a uniform elongation of 35.2%, which was 84.3% higher than that at 25 °C.

Multilayer Maraging/CoCrNi Composites With Synergistic Strengthening-Toughening Behavior

A novel multilayer maraging/CoCrNi composite with good mechanical properties was successfully fabricated by a vacuum hot-rolling and aging treatment. The yield strength, tensile strength, uniform elongation, and fracture elongation reached 1,151, 1,380 MPa, 15.7, and 24% respectively, realizing the aim of synergistic strengthening–toughening by effectively improving the yield strength of the CoCrNi alloy and strain-hardening capacity of the maraging steel. The vacuum state, high rolling reduction ratio, and alloy element diffusion are beneficial in strengthening the clad interface. The good work-hardening capacity of the CoCrNi alloy compensates for the poor strain-softening behavior of the maraging steel, effectively delaying the premature localized necking of the multilayer composites. The strengthening–toughening mechanism of the multilayer maraging/CoCrNi composites is mainly attributed to the strong interface, nanoscale precipitation, and strain-induced twinning.

Localised bifurcation in soft cylindrical tubes under axial stretching and surface tension

We investigate localised bulging or necking in an incompressible, hyperelastic cylindrical tube under axial stretching and surface tension. Three cases are considered in which the tube is subjected to different constraints. In case 1 the inner and outer surfaces are traction-free and under surface tension, whilst in cases 2 and 3 the inner and outer surfaces (respectively) are fixed to prevent radial displacement and surface tension. However, each free surface in these latter two cases is still under surface tension. We first state the analytical bifurcation conditions for localisation and then validate them numerically whilst determining whether localisation is preferred over bifurcation into periodic modes. It is shown that bifurcation into a localised solution is unattainable in case 1 but possible and favourable in cases 2 and 3. In contrast, in case 1 any bifurcation must necessarily take the form of a periodic mode with a non-zero wave number. Our results are validated using Finite Element Method (FEM) simulations.

Investigation of the unloading yield effect in 7075 Al alloys based on microstructural and digital image correlation analysis

The unloading yield effect (UYE), which indicates that the reloading flow stress overshoots the monotonically loaded flow stress during uniaxial tensile test, was investigated by evaluating three aluminum alloy 7075 sheets with different precipitate states: solution heat-treated (SHT), aged for 20 min (A20, underaged), aged for 80 min (A80, peak aged) and aged for 240 min (A240, overaged). The precipitate states of A20 and A240 specimens were characterized by transmission electron microscope (TEM) and small-angle neutron scattering (SANS) analyses. The UYE was exhibited only in artificially aged specimens, but not in the SHT specimen. It was confirmed that the root cause of UYE is the interaction between the precipitate and dislocation during unloading. In addition, it was observed that strain instability is inevitably generated during stress overshoot owing to temporal geometric softening. The temporal strain instability diffused to the neighboring region in the case of A20 specimen, but that of A240 specimen directly influenced the premature localized necking or failure, resulting in a significant reduction in elongation.

Large-deformation plasticity and fracture behavior of pure lithium under various stress states

Although lithium-metal anodes are being extensively examined in research projects aiming at pushing the energy density of lithium batteries to its limit, the knowledge about the mechanical properties of pure lithium is insufficient in two aspects. First, most of the available data focuses either on nano- and micro-scale single-crystalline lithium or on macro-scale bulk material. Second, those tests were commonly performed via uniaxial tests in which the stress states were simple or nanoindentation. This work aims at bridging these gaps by performing a systematic experimental program under various stress states on small-sized specimens and by developing a plasticity model that can capture the important characteristics. Based on these experimental and computational findings, the added value on the understanding of the deformation and failure mechanisms of lithium under various stress states and a first quantitative description on the plasticity anisotropy on lithium is provided. In order to manufacture the required complex-shaped specimens for the five different stress states (uniaxial tension, notched tension with two different radii, central hole tension, and simple shear), a method which allows safe laser cutting of thick lithium foil in argon atmosphere is developed. The tensile tests are conducted in pure argon as well as in air to quantify the effect of oxidation on the strength of lithium. By means of post-mortem microstructural examinations, two active slip systems and cross-slip are observed. Lithium fractures in a perfectly ductile manner when the specimen thickness is reduced to zero due to localized necking. Digital image correlation analysis shows that the lithium foil is highly anisotropic in the through-thickness direction although it is in-plane isotropic. By using a rate-dependent transverse isotropic model, a satisfactory prediction of the five experiments is provided.

Mechanical response of an high-strength automotive steel at different strain rates and evolution of damage-related parameters

The present work concerns a thin sheet high-strength steel of interest for automotive applications. The extended constitutive curves in static and dynamic conditions were determined by tensile tests on smooth specimens. Further tests carried out on notched specimens were simulated both to validate the elastoplastic response and to analyse the evolution of the relevant parameters related to ductile damage (triaxiality and Lode angle) in the critical areas of the specimens (diffuse and localized necking), studying the correlations between the trend of these quantities and the mode/location of the fracture initiation. The analysis of the images of the specimens acquired during the tests allowed to characterize in detail the behaviour of the material up to breakage, also providing different experimental references to validate the numerical simulations of the tests on the smooth and notched specimens.

Application of neuroendoscopy combined with fluorescence angiography in anterior circulation aneurysm clipping

Objective: To explore the value of neuroendoscopy combined with fluorescence angiography in anterior circulation aneurysm clipping. Methods: A total of 15 patients with anterior circulation aneurysm from Department of Neurosurgery, Zhongnan Hospital of Wuhan University between October 2018 and January 2019 were enrolled. Neuroendoscopy combined with indocyanine green fluorescence angiography (ICGA) was used to determine the shape of the aneurysm, the specific location of the aneurysm neck and its relationship with the aneurysm-bearing artery during anterior circulation aneurysm clipping. Meanwhile, Neuroendoscopy combined with ICGA can be employed to observe whether there was stenosis and incomplete clamping of the aneurysm-bearing artery after clipping the aneurysm, and whether there was misclamping of the perforating branches hidden under the posterior wall of the aneurysm. Results: The success rate of aneurysm clipping in 15 cases was 15/15. After aneurysm clipping, ICGA and neuroendoscopy were performed. The residual aneurysm neck was detected in 3 cases, and the position of aneurysm clip was adjusted or aneurysm clips were added. In one case, the anterior choroidal aneurysm was found to be mistakenly clipped. After adjusting the aneurysm clip, ICGA and neuroendoscopy showed that the anterior choroidal artery was normal. In another case, the A1 segment aneurysm was clipped. ICGA and neuroendoscopy found that the perforating branch blood vessels were mistakenly clipped. After the adjustment of the aneurysm clip, the blood vessels recovered their patency. There were no surgical-related deaths, disability and coma cases in the study. Conclusions: During aneurysm clipping, neuroendoscopy combined with ICGA can reduce cerebral vasospasm, decrease the misclipping rate of perforation of blood vessels, and avoid residual neck of aneurysm, stenosis or occlusion of aneurysm-bearing artery by using neuroendoscopy to observe whether misclipping of the perforating branch vessels exist and whether the aneurysm is clipped. Therefore, it can reduce postoperative complications.

Evaluation of Localized Necking Models for Fracture Prediction in Punch-Loaded Steel Panels

This study compared the experimental test results on punch-loaded unstiffened and stiffened panels with numerical predictions using different localized necking modeling approaches with shell elements. The analytical models that were derived by Bressan–Williams–Hill (BWH) were used in their original form and extended version, which considers non-proportional loading paths while using the forming-severity concept and bending-induced suppression of through-thickness necking. The results suggest that the mesh size sensitivity depends on the punch geometry. Moreover, the inclusion of bending effects and the use of the forming-severity concept in the BWH criterion yielded improved estimations of fracture initiation with shell elements.

Tonsillar Epithelioid Haemangioendotelioma: Description of a Rare Clinical Case.

We present a rare case of tonsillar EHE with local recurrence and neck metastasis 30months after surgery, as well as further neck recurrence 27months later. We describe clinical, immunohistopathological, and therapeutic aspects of the tumor highlighting the diagnostic difficulties, lack of therapeutic guidelines and need for long-term follow-up.

Formability enhancement of 5052 aluminium alloy sheet in electromagnetic impaction forming

Electromagnetic impaction forming of 5052 aluminium alloy sheets using a V-shaped die and a conical die was performed. The conventional quasi-static forming limit curve (QS-FLC) is obtained according to the linear loading condition, which can only describe linear strain paths. However, it cannot accurately evaluate the formability of electromagnetic impaction forming, especially strain paths that have become highly non-linear. In this study, the formability of electromagnetic impaction forming, which considers a bilinear strain path and a continuous highly non-linear strain path, was investigated. The conventional QS-FLC is no longer suitable to evaluate the formability of electromagnetic impaction forming. Therefore, modified FLCs were established in strain space that follow bilinear strain paths and continuous non-linear strain paths. The actual formability improvement was compared with the modified FLC. The maximum safe strain of bilinear strain paths near the sidewall of V-shaped specimens increased in formability by approximately 30% at the discharge voltage of 20 kV compared with conventional QS forming. The maximum safe strains near the apex of the conical specimens increased in formability by approximately 100% at the same discharge energy. It should be noted that the increase in formability above the modified FLC is a conservative estimate, because the limit strains at the necking location were not known in the electromagnetic impaction forming. The influencing factors of the formability improvement of 5052 aluminium alloy sheet in electromagnetic impaction forming were also discussed.

Histopathological patterns of skin adnexal tumours in Ibadan, South-West Nigeria

Background: Skin adnexal tumours (SATs) are tumours that differentiate towards one or more of the adnexal structures of the skin. The aim of this study was to determine the incidence of SATs in Ibadan and to correlate them with age, sex and anatomic location. Methods: This is a 10-year retrospective study of all SATs in the Department of Pathology, University College Hospital, Ibadan. The clinicopathological data were obtained from the department's records for the given period. Haematoxylin and eosin-stained sections obtained from formalin-fixed paraffin-embedded tissue blocks were examined to confirm the diagnosis and special stains such as periodic acid Schiff staining done where necessary. Cases of SATs were further classified into benign and malignant tumours. Results: Twenty-seven cases of SATs were reviewed over the study period. Tumours from the sweat glands formed the largest group (55.6%) with trichoepithelioma being the most common subtype, followed by tumours with follicular differentiation (40.7%) and sebaceous tumours (3.7%). There was a slight female predominance with a male-to-female ratio 1:1.07. The highest number of tumours was seen in the fourth decade of life (23%). Benign tumours made up the majority of cases (85.2%). The most common location was the head and neck with 40.8% of cases. Conclusion: SATs are not uncommon among Nigerian patients. These tumours are mostly benign and are present commonly in the head and neck location.

A rare case of echinococcus granulosus cyst at an unusual location of neck

A rare case of echinococcus granulosus cyst at an unusual location of neck

An effective method for determining necking and fracture strains of sheet metals

Biaxial tensile testing methods using cruciform specimens have been developed in the last few decades for the determination of forming limit diagrams (FLDs) and fracture forming limit diagrams (FFLDs) for sheet metals. One of the difficulties associated with this test geometry is the lack of a widely accepted method to determine the necking and fracture strains which are necessary to construct these diagrams. In this study, a novel spatio-temporal method has been proposed for the determination of necking and fracture strains. In the method, two rectangular zones: the base zone (BZ) and the reference zone (RZ) are selected at the location where fracture initiates. The zone RZ includes the zone BZ and both zones have the same side length in the direction parallel to the necking band but different side length in the perpendicular direction. By plotting the thickness reduction within RZ against that in BZ, the onset of localised necking can be determined by finding the intersection of the two straight lines fitted separately using the data in the initial and final stages of deformation. The corresponding limit strains are then determined using the strains within the zone BZ. The method has been successfully applied to uniaxial tensile tests on AA6082 and boron steel dog-bone specimens, and to equi-biaxial tensile tests on AA5754 cruciform specimens.• Compared to widely used existing methods, the novel spatio-temporal method has greater simplicity, stability and accuracy with regard to the determination of localised necking strains.• The spatio-temporal method has good potential to become a standard method for the determination of limit strains for sheet metals.

Separate tensile tests of ACSR at high and low temperatures

In order to ensure the accuracy of the test and avoid the errors caused by the slip between the steel and aluminum materials, the mechanical properties of ACSR at different temperatures were studied by the method of separate experiment of steel strand and aluminum strand. The test results show that with the increase of temperature, the elastic modulus of aluminum strand and steel strand decreases, but the elastic modulus of steel strand decreases more. There is no obvious strengthening stage and yield stage for aluminum strand, but obvious elastic stage, yield stage, strengthening stage and local necking stage for steel strand. The failure parts of aluminum strands are concentrated in the position of 1 / 2 ∼ 1 / 3 of the samples, and the failure parts of each strand tend to develop along the twisting direction. The failure position of the steel strand is basically in the same cross section of the middle area of the sample. The experimental results of steel and aluminum strands are basically consistent with the results of the whole steel reinforced aluminum strand, which proves that the experimental method is feasible.

Pediatric Nasopharyngeal Rhabdomyosarcoma: About a Case and Review of Literature

Introduction: Rhabdomyosarcoma (RMS) is the most common soft tissue tumor in children, with the head and neck location accounting for up to 40% of cases. The embryonal and alveolar histologic variants are more commonly seen in pediatric patients. The treatment is multimodal and the prognosis of this clinical entity is always gloomy. We report the case of nasopharyngeal rhabdomyosarcoma in a 7-year-old boy child with a good response to early post-therapy. Case Presentation: The patient was diagnosed with nasopharyngeal RMS revealed by a congested nose, ptosis and bilateral blindness, and who received induction chemotherapy followed by concurrent radiotherapy followed by adjuvant chemotherapy. The evolution is marked by a good clinical course but persistence of bilateral blindness. Conclusion: The RMS nasopharyngeal often presents with nonspecific symptoms. Multimodal therapy should be performed including surgery, chemotherapy and radiotherapy.