Key Hole Research Articles

Osteomyelitis After Robotically Assisted Laparoscopic Sacral Colpopexy

Dear Editor, Osteomyelitis following robot assisted sacral colpopexy is a rare entity. Till now only two cases have been reported (1, 2). In 2010, Muffly et al described a life-threatening case of osseous infection (L5/S1) and epidural abscess 4 months after robot assisted sacral colpopexy using a synthetic mesh. The correction of complications required surgical intervention, including sacral debridement, discectomy, mesh removal and abscess drainage. However, in the case reported by Nosseir, the sacral osteomyelitis did not require neither reoperation or mesh removal. The infection was treated with 8 weeks of outpatient antibiotic treatment. Sacral osseous infections after colpopexy are likely to have a multifactorial origin. Innovative surgical procedures, such as robotic assisted laparoscopic operations, present the advantage of a key hole operation which have as a consequence significantly less pain, less blood loss, better aesthetic result, more precise surgical manipulations and shorter hospital stay as well as shorter recovery time. Nevertheless, the absence of haptic feedback in manipulations through robot can lead the surgeon to place sutures deeper in the tissues, especially in periosteum of the sacral promontory, creating a site of potential infection. In theory, another risk factor that could lead to this complication is the possible ischemia resulted from the devascularization during routine dissection and the foreign body implantation. At this point, this disadvantage could be bypassed with the palpation of the promontory by the assistant surgeon, who through conventional laparoscopy, can direct the surgeon to the precise position for suture placement. Moreover, the utilization of braided sutures in the vaginal fibromuscular tissue for the attachment of the mesh may represent another possible risk factor of osteomyelitis. There is a hypothesis that with the use of braided sutures, the bacterial adherence of suture materials is increased (3, 4). In addition, the use of monofilament sutures can avoid surgical infections from any microorganisms. The concurrent placement of the mesh immediately after hysterectomy could also be considered as another potential risk factor of sacral osteomyelitis (5). The creation of multiple layers of tissue over vaginal apex before attaching the mesh could form an extra tissue barrier that may avoid vaginal mesh erosion. Furthermore, the immunologic status of the patient as well as various medical comorbidities (such as diabetes mellitus) could be another reason for the appearance of infections in this type of surgical operations. In sacrocolpopexy, the suspension of the vaginal vault most frequently is performed by attaching the vault to the anterior longitudinal ligament of the sacrum by utilizing sutures. In order to facilitate laparoscopic procedures, the sacral fixation is realized with the insertion of bone anchors, which very often are made by titanium (6). The use of titanium tacks have been used in pubic fixation during urinary incontinence procedures for more than 10 years. In addition, these types of bone anchors decrease the total operative time and reduce the risk of life-threatening haemorrhage from the vessels collocated at the sacrum area. Until now, the rate of pubic osteomyelitis related to such procedures has been reported to be 1.3% (7). Though, the anatomic difference between sacral and pubic bone fixation may differs in the fact that it is a clean procedure as opposed to urinary incontinence operations as clean contaminated procedure. Thus, the relative infection rate may also be different. In the treatment of sacral bone infections, the surgical debridement of the infected area from the necrotic materials might be necessary, while proper antimicrobial therapy should be established as soon as possible. Currently, the antibiotic treatment may include prolonged antibiotic courses, which according to the available recommendations in the literature for management of lumbar osteomyelitis, should durate at least 4 to 6 weeks of parenteral administration, in order to penetrate bone and joint cavities (8). For example, in the case reports identified in the current literature, the cultures revealed either methicillin-resistant coagulase-negative Staphylococcus aureus treated with intravenous vancomycin and ampicillin–sulbactam for 6 weeks or methicillin-sensitive Staphylococcus aureus treated with intravenous nafcillin for 8 weeks (1, 2). In conclusion, patients with referred back pain and vaginal drainage subsequent sacral colpopexy with use of synthetic mesh and fixation materials should be evaluated with a high level of suspicion for osteomyelitis. Clinical decisions as well as follow-up can be assisted by the assessment of magnetic resonance imaging, white cells blood count and c-reactive protein. Nevertheless, surgeons should always inform, independently of the surgical route selected, their patients about the possible complications of such procedures including sacral osteomyelitis.

Equivocators or zealots? Post-revolutionary re-imaging colonial languages, names and name change in Ireland and South Africa

Successful revolutionaries often find themselves in a distinctly uneasy position vis-à-vis the cultural burden of the pre-revolution which they inherit. Establishing a stable and effective government often means alienating their own ‘wild men screaming through the key hole’. Yet, they also need to stamp their revolutionary credentials both on the new society they wish to construct and as a territorialising edict to the defeated. This also serves as an implicit edict to the defeated that their day has passed. To achieve this, manipulation of imagery is fundamental in the successful revolutionary’s arsenal. This article documents the reaction of two very different counties, Ireland and South Africa, in their post-revolutionary eras. It notes their differing, and at times bizarre, attempts at re-branding nationhood in the image of the successful revolution. Ireland after 1922 was on the whole more restrained in its image-making than was South Africa after 1994, yet both, for reasons of revolutionary fervour, revenge or strategy, showed the old order that change was non-negotiable, be it in language policy, civic honours and titles, emblems and symbols of state, or simply in place and street names. In such instances heritage is frequently the handmaiden of political necessity, often crude but sometimes subtle.

Diode Lasers and Aluminum — A Success Story on the Rise

AbstractDiode lasers, in spite of their prefix “high‐power”, until a few years ago, were applicable merely as systems for surface modification, heat treatment, and in applications with low prerequisites in terms of beam quality. Today, they are widely used in key hole welding as well.

Allograft Meniscus Transplantation

Menisci function to manage load transmission, provide secondary mechanical stability as well as nutrition, and lubricate the joint. Meniscus transplantation techniques continue to evolve and include: free soft tissue allograft implantation; separate anterior and posterior bone plugs; and bone bridges including key hole, trough, dovetail, and bridge-in-slot variations. The senior author's preference is for the bridge-in-slot technique for lateral and medial menisci, owing to its simplicity and secure bony fixation, flexibility in allowing concomitant procedures as osteotomy and ligament reconstruction, and the ability to maintain the native anterior and posterior meniscal horn attachments. Meniscal allograft transplantation yields fair to excellent results in almost 85% of patients. Patients demonstrate significant decrease in pain, as well as an increase in activity. Long-term success is encouraging in well-selected patients but is unknown whether transplantation is protective against the progression of degenerative changes.

Temperature Distribution Simulation for Pulsed Laser Spot Welding of Dissimilar Stainless Steel AISI 302 to Low Carbon Steel AISI 1008

This paper describes the development of a computer model used to analyze the heat flow during pulsed Nd:YAG laser spot welding of dissimilar metals; stainless steel AISI 302 to low carbon steel AISI 1008. The model is built using ANSYS FLUENT 6.3 software where almost all the environments simulated to be similar to the experimental environments. A simulation analysis was implemented, based on conduction heat transfer, out of the key hole where no melting occurs. The effect of laser power and pulse duration was studied. Four peak powers 5, 5.5, 6.5 and 7 kW were varied during pulsed laser spot welding (keeping the energy constant), also the effect of four pulse durations 5, 6, 6.5 and 7 ms (with constant peak power), on the transient temperature distribution and weld pool dimensions was predicted ,using the present simulation. It was found that the present simulation model can give an indication for choosing the suitable laser parameters (i.e. pulse duration, peak power) during pulsed laser spot welding of dissimilar metals.

T Tail Configuration Of Opsite On Suction Tubing Outlet For Modified Vacuum Assisted Closure.

Many modified vacuum assisted closure methods have been proposed as an alternative to original VAC which are simple and cost-effective. M Singh et al has proposed the idea of a poor man’s VAC (1-2). We would like to suggest few modifications in the methodology considering which will improve the efficiency of poor man’s VAC. The port of exit of the suction tubing from the dressing remains a potential site of leakage. For the use of non electrical suction devices it is necessary to have complete leak proof dressing. Every attempt has to be made to minimize the leak. We recommend Ttailing of suction tubing which prevents leakage significantly from our experience. INTRODUCTION Many modified vacuum assisted closure methods have been proposed as an alternative to original VAC which are simple and cost-effective. M Singh et al has proposed the idea of a poor man’s VAC (1-2). We would like to suggest few modifications in the methodology considering which will improve the efficiency of poor man’s VAC. The port of exit of the suction tubing from the dressing remains a potential site of leakage. For the use of non electrical suction devices it is necessary to have complete leak proof dressing. Every attempt has to be made to minimize the leak. We recommend Ttailing of suction tubing which prevents leakage significantly from our experience. METHODOLOGY The opsite is applied in such a manner that the tubing is lifted one to two inches beyond the edge of the wound by the assistant, and the opsite is adhered to the whole circumference of the tubing and opposing beneath the suction tubing by the applicant in a key hole fashion creating an air tight seal towards the periphery. The “wings” of the opsite is adhered to the skin surface. Now the cross section appears a T shape (Figure 1 ). When this procedure is not performed there is always a chance of peritubal leak from the triangular dead space area tracking along the tubing into the wound especially when the opsite is streched. This procedure prevents the leakage and the efficiency of modified VAC remains same for varying size of tubing. This process is similar to creation of witzel tube for feeding jejunostomy. Figure 1 Figure 1. (T tail configuration in different views ) ADVANTAGES Avoids tunneling through the tissue as much as possible preventing the tissue damage and risk of spread of infection. Change of tubing easily, frequently with every change of dressing Avoiding pain and discomfort to the patient T Tail Configuration Of Opsite On Suction Tubing Outlet For Modified Vacuum Assisted Closure. 2 of 3 Avoids unnecessary usage of adhesive plasters in attempt to sealing the leak. It is easy, comfortable, cost-effective and decreases frequent monitoring for leakage. Patients are relatively ambulant when the negative suction can be maintained through using 50 cc syringes and romovac Though the leakage chances are more in regions involving ankle, groin, axilla, and uneven surfaces , pedal suction device with calibrated vacuum gauge can maintain for a longer period than usual. Figure 2 Figure 2: Measurement of negative pressure with suction gauge with syringe type, romovac and mucus sucker. The 50 cc syringe piston is held in position with a 20 cc syringe piston. A standard 50cc syringe is able to create a maximum amount of 450 mm hg pressure. A standard romovac drain is able to create a negative pressure of 75 mm hg pressure and a mucus sucker produces a vacuum of similar amount. We have used infant feeding tube, ryle’s tube and suction catheters as suction tubing’s with good efficacy and these materials are readily available in government hospitals. Figure 3 Figure 3: Wound healing after application of modified VAC with pedal suction. It is beyond doubt the results are gratifying with poor man’s VAC, we totally agree with the results. With the Ttailing the performance can be more enhanced in low resource setting. Wounds of extensive surface area is are the limiting factor for poor man’s VAC as there are multiple sites of leakage, hence may require a motorized suction device or central vacuum for maintaining the vacuum depending on the resource setting. Vacuum dressing has to be done with great caution or avoided in peripheral vascular disease (3). Further studies regarding the microbial clearance rate, wound contraction time, bed occupancy, patient’s compliance are required to formulate guidelines and standardize poor man’s VAC. Simpler Low cost vacuum devices like these need to be encouraged, educated and improved with modifications which are user as well as patient friendly.

Temperature Distribution Simulation for Pulsed Laser Spot Welding of Dissimilar Stainless Steel AISI 302 to Low Carbon Steel AISI 1008

This paper describes the development of a computer model used to analyze the heat flow during pulsed Nd:YAG laser spot welding of dissimilar metals; stainless steel AISI 302 to low carbon steel AISI 1008. The model is built using ANSYS FLUENT 6.3 software where almost all the environments simulated to be similar to the experimental environments. A simulation analysis was implemented, based on conduction heat transfer, out of the key hole where no melting occurs. The effect of laser power and pulse duration was studied. Four peak powers 5, 5.5, 6.5 and 7 kW were varied during pulsed laser spot welding (keeping the energy constant), also the effect of four pulse durations 5, 6, 6.5 and 7 ms (with constant peak power), on the transient temperature distribution and weld pool dimensions was predicted ,using the present simulation. It was found that the present simulation model can give an indication for choosing the suitable laser parameters (i.e. pulse duration, peak power) during pulsed laser spot welding of dissimilar metals.

Full mouth implant reconstruction for medically compromised patient with key hole access surgery

Demographic trends indicate that clinicians will be treating more edentulous geriatric patients many of whom will be medically compromised. Many such patients seek implant therapy for the purpose of their oral rehabilitation. When a patient is medically compromised, it is a generalized notion that dental implant treatment must be avoided. But in reality, dental implant treatment for such a patient must be curtailed to reduce invasiveness and surgical treatment time. Today's guidelines of pre- and post-implant therapy of such patients have still not been entirely clarified and consequently are not completely clear to dental practioners. This case report emphasizes the importance of diagnosis and its impact on proper treatment planning of both surgical and prosthetic phase of full mouth reconstruction with dental implants in a medically compromised geriatric patient.

Effect of Peclet Number on the Thermo Capillary Convection and Molten Pool Shape Formation during Laser Welding Using CFD

A mathematical model is developed for the simulation of keyhole and molten pool formation during laser beam welding. Heat transfer from the key hole to the weld pool and details of the fluid flow play a major role in determining the weld bead profile. The simulation is performed based on the control volume method (CVM) and a volumetric heat source is used to model the laser beam and the equations of mass, momentum and energy are solved. The effect of Peclet number, Marangoni number, and Nusselt number is studied by varying process parameters like welding speed and beam power. The simulated bead profiles are compared with the experimental profile and are found to be acceptable.

Tungsten Film Chemical Mechanical Polishing Using MnO2 Slurry

It has been demonstrated that MnO2 abrasive can polish tungsten films without using an oxidizer solution. The polishing rate of MnO2 slurry is 1.5 times higher than that of commercially available Al2O3 slurry. A W plug is formed without etching holes (keyholes) during chemical mechanical polishing with MnO2 abrasive slurry. With MnO2 slurry, no key holes were formed even after overpolishing by an additional 0.6 µm. On the other hand, with conventional Al2O3 slurry, keyholes were formed after overlpolishing by an additional 0.4 µm. The residual MnO2 abrasive on the surface after chemical mechanical polishing was completely removed by the cleaning process because MnO2 abrasive easily dissolves in a cleaning solution of HCl, H2O2, and H2O. These results indicate that, since MnO2 is in itself a solid oxidizer, MnO2 abrasive can polish W films without using an oxidizer solution and does not etch the seam.

The Low-Cycle Fatigue Strength of Laser-Welded Ultra-High-Strength Steel

The UUltra -high -strength (UHS) steels are used in booms, transport vechicles and other light weight structures. It is well -known that it is possible to achieve a strong weld statically, as the base material, by using laser welding as a weld method [1]. The design strength of the light weight structure is often rather high. In the case of booms and transport vechilevehicles, there can be very high dynamic forces in the structure. Therefore it is necessary to study how much fatigue stress the weld seam can resist and at the same time find the optimal welding parameters. The 4 mm bainitic-martensitic UHS steel was welded with laser without filler material to lasercut seam edges by using different weld parameters. Argon gas was blown by pipe onr coaxial nozzle near the key hole and through a 60 mm gas nozzle after the keyhole. Also, the root side of the weld was shielded with argon. The welds were tested by using the bending fatigue test. The test stresses were 800 MPa and 700 MPa. The fatigue strength results showed that with the laser welded seams, the number of cycles wereas about three times lower than with the base material. The fatigue strength was slightly better in welds which were welded with lower energy input. In the case of the weld seam which was welded with lowest energy input by using 300 mm optics, there was some incomplete penetration due to tooexcessively high surface roughness ofat the weld seam edges.

Anchoring of Methylmethacrylate Filler to the Calvarium -Technical Note-

Implanted methylmethacrylate may be unexpectedly displaced due to poor adherence to the bone. We developed a simple technique to fix the material plugging the burr holes for use primarily in cosmetically important areas. At the closure of craniotomy, 2-3 small drill holes are made at the rim of the craniotomy burr hole. To address cranial defects in the pterional region, small holes are placed on the bone surface around the key burr hole. The holes extend into the diploic layer and have no parallel relationship. After fixation of the bone flap, a methylmethacrylate filler mixture is manually plugged into the burr hole and pushed into the small holes, thereby forming horns for secure fixation. None among over 100 patients developed an objectionable bulge attributable to displacement of the filler. Our technique requires no special instruments or materials and decreases the risk of cosmetic problems.

Morphology of Actinocyclus and Lobodiscus species (Bacillariophyta) from the Miocene deposits of the Vitim Plateau, Russia

Background and aims – In 2006, during a field expedition in the Amalat (Southern) paleovalley of the Vitim Plateau, 85 samples were taken from sediments of a new key hole 7236. The composition and distribution of siliceous microfossils were studied with light microscope (Usoltseva et al. 2008). The prevailence of species of the planktonic genera of Actinocyclus Ehr. and Aulacoseira Thw. was recorded. The aims of this paper were electron-microscopic investigations of fossil freshwater species Actinocyclus and Lobodiscus from the Miocene lacustrine sediments of a new key hole 7236, and the comparison of our morphological data with formerly published descriptions of known freshwater taxa of these genera. Methods – Samples from the section 7236 were examined using LM and SEM. Abundance was calculated based on the LM slides. Key results – Valve ultrastructure of dominant biostratigraphically valuable species of Actinocyclus and Lobodiscus from the Miocene freshwater sediments of the Vitim Plateau was for the first time studied with SEM. The comparison of results of carried out investigations with formerly published descriptions of known freshwater taxa of Actinocyclus and Lobodiscus permits to belong the studied species to Actinocyclus gorbunovii (Sheshukova) Moisseeva & Sheshukova and A. krasskei (Krasske) Bradbury & Krebs, to expand their certain morphometric data, as well as to describe A. vitimicus Usoltseva & Khursevich sp. nov., A. intermedius Usoltseva & Khursevich sp. nov. and Lobodiscus peculiaris Usoltseva & Khursevich sp. nov., with definite diagnostic features. Cоnclusion – Freshwater extinct species of Actinocyclus can be used as stratigraphic markers. Thus, occurred planktonic taxa of Actinocyclus, including the new species of A. vitimicus and A. intermedius, described above, as well as Lobodiscus peculiaris together with dominant accompanying planktonic representatives of Aulacoseira represent the characteristic diatom complex in lacustrine sediments of the Upper Dzhilinda subformation recovered from key hole 7236 within the Amalat paleovalley (the Vitim Plateau). The Middle-Late Miocene age of studied lacustrine deposits agrees with K-Ar dating of lavas in this part of section.

Keyhole depth instability in case of CW CO2 laser beam welding of mild steel

The study of keyhole (KH) instability in deep penetration laser beam welding (LBW) is essential to understand welding process and appearance of weld seam defects. The main cause of keyhole collapse is the instability in KH dynamics during the LBW process. This is mainly due to the surface tension forces associated with the KH collapse and the stabilizing action of vapour pressure. A deep penetration high power CW CO2 laser was used to generate KH in mild steel (MS) in two different welding conditions i.e. ambient atmospheric welding (AAW) and under water welding (UWW). KH, formed in case of under water welding, was deeper and narrower than keyhole formed in ambient and atmospheric condition. The number and dimensions of irregular humps increased in case of ambient and under water condition due to larger and rapid keyhole collapse also studied. The thermocapillary convection is considered to explain KH instability, which in turn gives rise to irregular humps.

Arteriovenous Micromalformation of the Trigeminal Root

To report on a single case of arteriovenous micromalformation (micro-AVM) of the trigeminal root that was diagnosed during microvascular decompression for trigeminal neuralgia with the use of indocyanine green (ICG) videoangiography. A 52-year-old woman with drug-resistant trigeminal neuralgia underwent a key hole suboccipital cerebellopontine angle exploration after the usual magnetic resonance imaging (MRI) screening had raised the suspicion of a vascular compression. In surgery, the petrosal vein was found to be bigger than usual and arterialized; the trigeminal root was embedded in a tangle of abnormal arterialized vessels. Intraoperative ICG videoangiography showed that the direction of flow in the arterialized petrosal vein was anterograde, thus allowing for the differential diagnosis between micro-AVM and tentorial dural fistula. It was possible to achieve only a partial nerve decompression because of the intimate relationship between the trigeminal root and the pathological vessels. Postoperative angiography and MRI with contrast administration confirmed the intraoperative diagnosis of micro-AVM. The patient was discharged neurologically intact on postoperative day 4. One month after surgery, she remains pain-free despite a 50% reduction in antiepileptic drugs. Surgeons performing microvascular decompression should be aware that a diagnosis of vascular compression based on MRI without contrast administration could not exclude the presence of a pontine micro-AVM. ICG videoangiography provides an elegant means of showing the flow dynamics of these pathological vessels. An MRI protocol that is suitable to avoid this kind of intraoperative drawback should be defined and systematically used in the preoperative evaluation of all such surgical candidates.

Contact mechanical studies on continuous wave CO 2 laser beam weld of mild steel with ambient and under water medium

Laser induced keyhole (KH) and weld pool formation during laser beam welding (LBW) can alter mechanical properties of weld seams. In this regard, deep penetration high power continuous wave (CW) CO 2 laser induced KH was generated in mild steel (MS) in both ambient and under water medium. Under water, KH was deeper and narrower as compared with KH formed in ambient condition. Contact mechanical studies of both the types of weld zones were carried out by measuring hardness and frictional properties. A significant rise in hardness was observed in fusion zone (FZ) regardless of the medium used. The KH and weld pool mediated LBW fusion zone showed lower coefficient of friction. Scratch size was also found to decrease in FZ due to increased hardness. The mechanical properties of FZ such as hardness, coefficient of friction and scratch size were correlated with microstructure composed of fine grained structure in the weld zones.

Low-Profile 1-Piece Bifrontal Craniotomy for Anterior Skull Base Approach and Reconstruction

The anterior skull base is a location of many pathologic lesions. These pathologic lesions are treated by bifrontal craniotomy and anterior skull base approach, either primarily or combined with facial osteotomies. To obtain wide exposure, low-profile craniotomies are preferred. In this article, we attempt to describe our own technique of frontal craniotomy for anterior skull base approach. In this technique, the frontal bone, frontal sinus, and the superior supraorbital bar are elevated in en bloc fashion. Bicoronal skin incision is followed by dissection and retraction of the skin flap in the epigaleal plan. The pericranial galeal flap is dissected separately in subperiosteal fashion until the superior orbital rim. After dissection and retraction of the tip of the temporal muscles, bilateral pterional key burr holes and 1 or 2 parasagittal burr holes are opened. The sagittal burr hole(s) is placed in the point where the upper horizontal surface of the frontal bone slopes vertically downward the forehead. With the craniotome rotating tip (Midas F2/8TA23, Medtronic Inc, Ft Worth, TX), bone cut is made between the pterional key burr holes, passing through the superior orbital bar and the anterior wall of the frontal sinus. To minimize the brain retraction, the operating microscope is placed beside the head, and exposure from the lateral view angle is obtained. Reconstruction of the defect is performed by using pericranial galeal flap and/or Cortoss (Orthovita, Malvern, PA). With this approach, wide exposure of the anterior skull base pathologic lesions was achieved with minimal brain retraction. In the postoperative period, patients tolerated this approach well with favorable functional and cosmetic outcomes. No infections or adverse effects related to this technique or Cortoss were observed. Anterior skull base pathologic lesions can be widely exposed by low-profile bicoronal craniotomy and anterior skull base approach with minimal brain retraction. This wide exposure allows us to gain more control of the pathologic lesion with better resection and reconstruction, reflected on the prognosis of the patients.

Efficacy and Safety of Key Hole Craniotomy for the Evacuation of Spontaneous Cerebellar Hemorrhage

The efficacy and safety of cerebellar hemorrhage evacuation by key hole craniotomy and the importance of thorough evacuation and irrigation of the hematoma in the fourth ventricle to resolve obstructive hydrocephalus were assessed in 23 patients with spontaneous cerebellar hemorrhage (SCH) greater than 3 cm or with brainstem compression and hydrocephalus. A 5-cm elongated S-shaped scalp incision was made, and a 3-cm key hole craniotomy was performed over a cerebellar convexity area. The hematoma was immediately evacuated through a small corticotomy. The hematoma in the fourth ventricle was gently removed through the hematoma cavity, followed by thorough saline irrigation to release obstructive hydrocephalus. Patients classified retrospectively into favorable and poor outcome groups using the Glasgow Outcome Scale (GOS) scores of 4-5 vs. 1-3 showed significant differences with respect to the preoperative Glasgow Coma Scale, hematoma size and volume, and brainstem compression. Only 2 of the 23 patients required ventricular drainage and no postoperative complications were recorded. Patients treated by experienced and inexperienced surgeons showed no significant differences in the hematoma evacuation rate, postoperative GOS, and interval from skin incision to start of hematoma evacuation. Our simplified method of key hole craniotomy to treat SCH was less invasive but easy to perform, as even inexperienced neurosurgeons could obtain good surgical results. Thorough cleaning of the fourth ventricle minimized the necessity for ventricular drainage.

不锈钢/铝合金激光深熔焊接头微观组织与力学性能

不锈钢/铝合金激光深熔焊接头微观组织与力学性能

Investigation of the material flow and texture evolution in friction-stir welded aluminum alloy

The material flow and crystallographic orientation in aluminum alloy sheets joined by friction stir welding (FSW) were investigated by electron back scattered diffraction (EBSD). The microstructure and microtexture of the material near the stir zone was found to be influenced by the rotational behavior of the tool pin. It was found that, during FSW, the forward movement of the tool pin resulted in loose contact between the tool pin and the receding material at the advancing side. This material behavior inside the joined aluminum plates was also observed by an X-ray micrograph by inlaying a gold marker into the plates. As the advancing speed of the tool increases at a given rotation speed, the loose contact region widens. As the microtexture of the material near the stir zone is very close to the simple shear texture on the basis of the frame of the tool pin in the normal and tangent directions, the amount of incompletely rotated material due to the loose contact could be estimated from the tilt angle of the shear texture in the pole figure around the key hole.