Surface plasmons in suspended graphene: launching with in-plane gold nanoantenna and propagation properties.

Graphene physics and plasmonics are two fields which, once combined, promise a variety of exciting applications. One of those applications is the integration of active nano-optoelectronic devices in electronic systems, using the fact that plasmons in graphene are tunable, highly confined and weakly damped. A crucial challenge remains before achieving these active devices: finding a platform enabling a high propagation of Graphene Plasmons Polaritons (GPPs). Suspended graphene presenting ultrahigh electron mobility has given rise to increasing interest. We numerically studied the plasmonic properties of suspended graphene. We propose a hybrid configuration and a set of conditions to launch graphene plasmons via an in-plane gold nanoantenna, for micrometric propagation of surface plasmons in suspended graphene. Finally, we propose a realistic optoelectronic device based on the use of suspended graphene.

Growth and characterization of bamboo-shaped carbon nanotubes using nanocluster-assembled ZnO:Co thin films as catalyst.

Bamboo-shaped carbon nanotubes (CNTs) had been successfully fabricated by a plasma enhanced chemical vapor deposition method, in which nanocluster-assembled ZnO:Co thin film was used as catalyst. It was found that bamboo-shaped CNTs were generally grown in a direction perpendicularly to the substrate surface with the tops of CNTs dominated by the droplet-like catalyst covered by the carbon layer. The diameter of CNTs was ranged from 20-50 nm. High resolution of TEM image showed that the typical CNT had a multi-walled structure with an inner core presented. The ordered graphite layers were inclined to an axis of CNT about 18 degrees and the interlayer space of a CNT was about 0.35 nm. Two peaks in Raman spectrum at 1586 cm(-1) and 1372 cm(-1) were identified as G-band and D-band for graphite, respectively. The results showed that catalyst based on ZnO:Co thin films could be used for the growth of CNTs with bamboo-shaped structure.

Dewetting of polymer films by ion implantation.

We report dewetting of thermodynamically stable, thick (approximately 100 nm) polystyrene films by titanium ion implantation. The dynamic dewetting patterns in time evolution are recorded. The dewetting mechanism is determined to be heterogeneous nucleation, where the defects and Ti nanoparticles formed by ion implantation serve as the nuclei. In addition, we observe abundant rims with regular polygonal shapes in dewetting patterns. This is attributed to fingering instability, which results from the balance between the driving force arisen from thermally induced surface tension gradient and the resistive forces from the combination of friction force, Laplace pressure and long-range van der Waals interactions. Finally, a model based on mass conservation is used to qualitatively describe the transition from circular to polygonal shaped rims at a critical diameter for holes.

A novel amperometric biosensor based on ZnO:Co nanoclusters for biosensing glucose.

ZnO:Co nanoclusters were synthesized by nanocluster-beam deposition with averaged particle size of 5 nm and porous structure, which were for the first time adopted to construct a novel amperometric glucose biosensor. Glucose oxidase was immobilized into the ZnO:Co nanocluster-assembled thin film through Nafion-assisted cross-linking technique. Due to the high specific active sites and high electrocatalytic activity of the ZnO:Co nanoclusters, the constructed glucose biosensor showed a high sensitivity of 13.3 microA/mA cm2. The low detection limit was estimated to be 20 microM (S/N=3) and the apparent Michaelis-Menten constant was found to be 21 mM, indicating the high affinity of the enzyme on ZnO:Co nanoclusters to glucose. The results show that the ZnO:Co nanocluster-assembled thin films with nanoporous structure and nanocrystallites have potential applications as platforms to immobilize enzyme in biosensors.

A comparison of teriparatide and calcitonin therapy in postmenopausal Asian women with osteoporosis: a 6-month study.

OBJECTIVE: The number of hip fractures is expected to double in the next 20 years, with current estimates that Asia will account for 37% of these cases. As bone mineral density (BMD) may be used as a measure of fracture risk, we sought to compare the effects of teriparatide with salmon calcitonin treatment on changes in BMD, biochemical bone markers, and safety in postmenopausal Asian women with osteoporosis. METHODOLOGY: A total of 104 patients (n = 47 teriparatide [20 g/day subcutaneously] and n = 57 calcitonin [100 IU/day subcutaneously]) were enrolled in Hong Kong, Singapore, Philippines, Malaysia, and Thailand. Calcium (> or = 500 mg/day) and vitamin D (200-400 IU/day) supplements were taken throughout the 6-month controlled, randomized study. RESULTS: Teriparatide was associated with a 5.03 +/- 4.77% increase in lumbar spine BMD (p < 0.0001, mean +/- SD change from baseline), whereas changes in lumbar spine BMD for patients on calcitonin were not statistically significant (mean change of 0.36 +/- 4.12%, p = 0.16). Comparison of the two groups indicated that teriparatide treatment improved lumbar spine BMD statistically significantly more than calcitonin (p < 0.0001). No statistically significant changes were observed for total hip or femoral neck BMD. Serum bone-specific alkaline phosphatase (BSAP) increased by 55.9% (median change from baseline, p < 0.0001) in the teriparatide group, and remained stable with calcitonin (5.0% change, p = 0.24); osteocalcin increased by 156.15% (median change from baseline, p < 0.0001) with teriparatide, and decreased with calcitonin (-15.25%, p = 0.03). Similar rates of adverse events were observed, with nausea and dizziness the most commonly reported for both groups (teriparatide versus calcitonin, 13.0% versus 23.2% p = 0.21, 10.9% versus 21.4% p = 0.19, respectively). There were no clinically relevant changes observed in laboratory parameters. CONCLUSIONS: Both treatments were similarly tolerated, however teriparatide was associated with greater increases in lumbar spine BMD and bone formation markers, demonstrating the unique mechanism of action and safety of this treatment for osteoporosis in these Asian women.

Comparing 2-year outcomes of anterior cruciate ligament reconstruction using either patella-tendon or semitendinosus-tendon autografts: a non-randomised prospective study.

PURPOSE: To compare the results of anterior cruciate ligament (ACL) reconstructions using either a patella-tendon autograft or a semitendinosus-tendon autograft. METHODS: Based on surgeon experience and preference, 68 patients underwent ACL reconstruction using either a quadruple-strand semitendinosus autograft (n = 34) or a central one-third bone-patella tendon-bone autograft (n = 34). Each patient was assessed preoperatively and postoperatively at 3, 6, and 24 months using the International Knee Documentation Committee (IKDC) knee score, Biodex muscle strength and endurance testing, and the KT1000 instrumented arthrometer test of knee laxity to anterior translation. All assessments at the 2-year follow-up were performed by the same physician and physiotherapist. RESULTS: While ACL reconstruction improved knee stability and IKDC knee scores significantly, there was no statistically significant difference between semitendinosus- and patella-tendon autograft reconstructions in terms of long-term knee score or laxity to anterior translation. Semitendinosus graft reconstruction was associated with less donor-site morbidity and hamstring weakness. Meniscectomy was associated with poorer long-term knee scores. CONCLUSION: ACL reconstruction is associated with a significantly better IKDC knee score and laxity measurement at 2-year follow-up. However, we were unable to demonstrate a significantly better long-term outcome in knee score or laxity to anterior translation with either a patella-tendon autograft or a semitendinosus-tendon autograft.

Histochemical and molecular analyses of distraction osteogenesis in a mouse model.

A tibial lengthening scheme in the mouse was used to study the molecular and cellular events regulating tissue regeneration during distraction osteogenesis. Here, we report on the surgical technique and frame design and describe the histochemical and molecular aspects of distraction during different phases of treatment. A total of 26 mice were used in this study. The treatment protocol was divided into a latency period of 7 days, a phase of active distraction that lasted 10 days with a distraction rate of 0.42 mm/day, and a maturation phase of 9 days. During latency, the distraction site resembled a stabilized fracture callus on both a histochemical and a molecular level. During active distraction, the gap was characterized by a central fibrous interzone bordered by primary matrix fronts, regenerate bone aligned with the distraction force, parallel columns of vascular sinusoids, and a medullary cavity. Alkaline phosphatase activity was detected in the endosteal and periosteal surfaces of the bone ends. Tartrate resistant acid phosphatase staining revealed that osteoclasts remodeled the bone regenerate as it formed. Collagen type I was expressed in the periosteum and the primary matrix front during distraction, whereas collagen type-II transcripts were localized to discrete regions on the periosteal surfaces, immediately adjacent to the osteotomy ends. Collagen type-II transcripts were not detected in the fibrous interzone. During the maturation phase, cells within the fibrous interzone expressed collagen type I and exhibited abundant alkaline phosphatase activity, suggesting that they had begun to terminally differentiate. Collectively, these data demonstrate the utility of a mouse model to study the molecular and cellular bases for the regeneration and remodeling of tissue.

The effect of surgically implanted bullet fragments on the spinal cord in a rabbit model.

BACKGROUND: Whether or not to remove bullets or bullet fragments from the spinal column of a neurologically intact patient has been a subject of continual debate. The controversy is due in part to a lack of information about the long-term effects of bullet fragments on spinal cord tissue. Although many studies have demonstrated the toxic effects of metal fragments on brain tissue, to our knowledge no one has evaluated the effects of the metals contained in commercially available bullets on spinal cord tissue. METHODS: Copper, aluminum, and lead fragments from three commercially available bullet cartridges were implanted in intradural and extradural locations in seventeen New Zealand White rabbits. At an average of 9.8 months, the metal content of specimens of blood, cerebrospinal fluid, and liver were determined. The spinal cords were harvested and examined histologically. RESULTS: There was a significant increase in the copper level of blood from the rabbits with an implanted copper fragment compared with that of the control animals (p = 0.007). Concentrations of copper and lead were not elevated, compared with the control values, in the serum or liver. Histological examination of the spinal cords revealed major destruction of both the axons and the myelin of the dorsal column adjacent to the intradural copper fragments. Intradural fragments of lead caused similar destruction of myelin and axons in the dorsal column, but to a lesser degree. Minimal spinal cord or meningeal histological changes were noted around the aluminum intradural fragments, and no pathological changes were found near any fragments placed in an extradural location. CONCLUSIONS: The results of this study show that certain metals contained in commercially available bullets can cause varying degrees of neural destruction independent of the initial mechanical injury caused by implantation. Of the three metals tested, copper fragments consistently caused a substantial localized area of neural injury within the spinal cord. CLINICAL RELEVANCE: In our study, copper fragments caused local neural toxicity involving as much as 10% of the spinal cord area, suggesting that there may be a scientific basis for removal of copper fragments lodged in the spinal cord, even in the absence of a neurological deficit.

Use of a collagen-hydroxyapatite matrix in spinal fusion. A rabbit model.

STUDY DESIGN: The efficacy of a specially designed mineralized bovine collagen matrix as a carrier for bone marrow stem cells was studied in a rabbit posterolateral spinal fusion model. OBJECTIVES: To determine if bone marrow cells added to Healos matrix will lead to fusion rates, biomechanical properties, and histologic properties comparable with those of fusions using autologous iliac crest bone graft; and to determine if the addition of preservative-free heparin to anticoagulate the bone marrow during harvest will adversely affect the fusion rate. SUMMARY OF BACKGROUND DATA: Although the development of new preparations of osteoinductive agents has advanced rapidly in recent years, the carrier systems that have been used in their application have received less attention. The composition and structure of the matrix used are key components affecting the ability of the matrix to function as a scaffold on which cells can migrate, adhere, proliferate, and form bone. The composition and design of matrix components also determine the ability of osteoinductive agents to influence local and hematogenously derived osteogenic precursor cells, which migrate to or are brought into the fusion site. Thus, the properties of the carrier can affect the behavior and efficacy of the osteoinductive agent that is used. The authors studied the properties of a new mineralized collagen matrix called Healos, which has been engineered specifically for spinal fusion application. METHODS: Forty-four adult female New Zealand white rabbits were divided into five groups. Groups 1-4 underwent bilateral intertransverse fusion between L5 and L6. The fusions were augmented with either autologous iliac crest bone graft, Healos matrix alone, Healos matrix mixed with autologous bone marrow, or Healos matrix combined with heparinized autologous bone marrow. At 8 weeks after surgery, the fusions were characterized radiographically, histologically, and biomechanically. The rate of fusion was determined by radiographic analysis. The fifth group consisted of two animals whose bone marrow was aspirated from their tibias and femurs and then sent for determination of total nucleated cell count. RESULTS: At 8 weeks, the radiographically determined fusion rate for autologous bone graft was 75% (9/12 animals), compared with 100% (10/10 and 9/9 animals) for groups in which fusions were done by using Healos matrix augmented with bone marrow (P < or = 0.1). Matrix used alone yielded a fusion rate of 18% (2/11 animals, P < or = 0.006). Histologically, the most mature bone was seen in the group augmented with autologous iliac crest graft, followed in decreasing order by the groups augmented with Healos with heparinized bone marrow, Healos with unheparinized bone marrow, and Healos alone. Biomechanically, the group augmented with autologous graft had the highest mean stiffness, followed by the groups augmented with Healos with heparinized bone marrow, Healos with untreated bone marrow, and finally Healos matrix alone. However, the differences in stiffness between groups were not statistically significant with the number of spines tested. CONCLUSIONS: These results show that Healos is an osteoconductive matrix that can be a useful carrier in the biologic and mechanical environment of a posterolateral intertransverse fusion site. In combination with bone marrow, it produces fusion rates that are comparable with those of autologous bone graft. However, it must be combined with an osteoinductive or osteogenic agent to ensure reliable fusion rates and alone cannot produce reliable osteogenesis. The Healos matrix was not compared with other commercially available matrices currently in use. Therefore, the efficacy of Healos relative to these other materials could not be determined.

Calcium sulfate- and calcium phosphate-based bone substitutes. Mimicry of the mineral phase of bone.

Calcium sulfate and calcium phosphate have provided the orthopedic surgeon a viable alternative to autogenous bone grafting as either an osteoconductive bone void filler or a bone graft extender. These materials mimic the mineral phase of bone and are resorbed at a rate similar to the rate of bone formation. Thus, they are able to provide some structural support and prevent ingrowth of fibrous tissue while facilitating creeping substitution by the host bone.

Clinical experience with automated percutaneous discectomy.

This study was performed to evaluate a group of patients undergoing automated percutaneous lumbar discectomy. All patients had disc pathology at L4/L5 and L5/S1 documented on CT scan and/or MRI. The range of follow-up was between 3 months and 20 months. The average hospital stay was 2 days (range 1-3 days). A total of 21 patients underwent the procedure and 18 were available for assessment. Of these, 12 patients improved. Of the patients that did not, two subsequently underwent surgical discectomy. There was one failed procedure but no other intra- or post-operative complications. The results of the study indicate that percutaneous discectomy has a demonstrable low morbidity and can be performed under local anaesthesia. However, proper patient selection is important for successful results.

Piriformis pyomyositis: a rare cause of sciatica.

A 30-year-old Thai woman with piriformis pyomyositis presented with sciatica. Computed tomography showed swelling and enhancement of the right gluteus medius and piriformis muscles. She made a complete recovery after a course of intravenous antibiotics. This condition has only been reported three other times and is often diagnosed with difficulty. It could be erroneously dismissed as a lumbar disc prolapse. If untreated, it could lead to prolonged hospital stay and death. A high index of suspicion, early diagnosis and appropriate antibiotic or surgical treatment leads to full recovery.

Wide versus selective decompression in the operative treatment of lumbar spinal stenosis.

The early post-operative results of wide versus selective decompression in a group of 64 patients with lumbar spinal stenosis were studied with the aim of ascertaining whether a more limited approach gives comparable results to the more traditional method of wide decompression. Wide decompression involved complete removal of a vertebral lamina at the stenotic level. Selective decompression refers to removal of the lower part of the superior lamina and the upper part of the inferior lamina at the stenotic level together with limited facetectomies. Patients were compared with respect to post-operative relief of back pain and sciatica/claudication as well as the ability to return to their pre-morbid level of functional activity. Follow up ranged from 4 months to 26 months. Results showed that both wide and selective decompression were able to achieve complete or considerable relief of symptoms and return to pre-morbid level of activity in 74% to 84% of patients. The results in the 2 groups were not statistically different. It appears that within the first 2 years of surgery, the vast majority of our post-decompression patients had good results regardless of whether wide or selective decompression was used.

Autologous marrow injection in the treatment of delayed and non-union in long bones.

A retrospective study of the use of autologous bone marrow injection for the treatment of delayed and non-union of long bones in an Orthopaedic Department, Singapore General Hospital from 1990-1991 is presented. There were 10 patients with 11 fractures (8 tibia and one each of humerus, femur and radius-ulna) available for study. Percutaneous injection of autologous marrow alone was used to stimulate healing of delayed and non-unions treated initially by plating, external fixation and in one case, by plaster cast. Marrow injection stimulated a callus formation sufficient to unite 9 of the fractures. The median time to clinical union was 10 weeks (range 4-23 weeks) and radiological union 17 weeks (range 9-29 weeks). Most patients had discomfort at the donor and injected sites for one to two days. There was one case of infection but none of the significant donor site morbidity was associated with standard open autologous grafting. Bone marrow injection was effective in stimulating bony union, with numerous advantages and considerably lower morbidity compared with standard open autologous grafting. Shorter inpatient stay was a significant feature.

Results of arthroscopic abrasion arthroplasty in osteoarthritis of the knee joint.

This paper is a retrospective review of arthroscopic abrasion arthroplasty plus debridement. This procedure was performed on 52 knees in 44 patients during the period January 1985 to June 1987 in the Sinagpore General Hospital. Follow-up period ranged from 3 to 27 months. All patients had moderate to severe degenerative osteoarthritis of the knees. Overall results were: 51%--improved; 23%--no change; 26%--worse. The results were better in the older age group and in those without significant deformity. There was improvement in 74% of the patients with normal alignment. Results were compared with those in world literature. Although results are encouraging, further research is required to reduce the proportion of patients with unsatisfactory results.

Giant cell tumours of the sacrum.

Giant Cell Tumours (GCT) of the Bone is one of the commoner primary bone tumours. Although considered a benign tumour, it does occasionally metastasize to the lungs. Treatment modalities vary according to the surgical staging and the site of the tumour. Treatment is further complicated when the tumour occurs in difficult locations like the sacrum. The paper includes a review of literature into treatment options and the presentation of 3 patients with sacral GCTs, one of which also has multiple pulmonary metastases from a "benign" giant cell tumour.

Prospective trial of resurfaced patellaversus non-resurfaced patella in simultaneous bilateral total knee replacement.

INTRODUCTION: A prospective trial was carried out in simultaneous bilateral total knee replacement to compare the outcome of resurfaced versus non-surfaced patella. METHODS: Thirty-five patients between 1997 and 2002 had simultaneous bilateral total knee replacement with resurfaced patella on the left and non-resurfaced patella on the right knee using the same implant in both. RESULTS: There were 29 females and six males with a mean age of 65.3 years. Mean follow-up was 3.18 years. There was no significant difference between the resurfaced and non-resurfaced knees with respect to the overall Knee Society clinical score (p = 0.093 preoperative, 0.310 postoperative) or the pain (p = 0.715 preoperative, 0.395 postoperative) or function subscores (p = 0.126 preoperative, 0.317 postoperative). The postoperative range of motion was 109 and 110 degrees for the resurfaced patella and non-resurfaced patella respectively (p = 0.894). The post-operative knee scores between patients with or without pre-operative anterior knee pain (p = 0.238) and between those who were obese and non-obese (p = 0.387) were not significantly different. 82.9% of patients felt that the resurfaced knee and 80% felt that the non-resurfaced knee were much better than before. There was no major preference for either knee for climbing stairs and getting out of chair. CONCLUSION: The functional and symptomatic outcome of total knee replacement with or without patella resurfacing is the same in the local population. Also, the present study demonstrated no evidence that the weight of the patient or the presence of preoperative anterior knee pain should be considered as factors in the decision to resurface the patella.

Anterior cruciate ligament reconstruction using patellar tendon autografts--a review of results.

AIM: The aim of this retrospective study was to review the results of anterior cruciate ligament reconstruction using patellar tendon autografts. METHODS: Forty-one knees were available for evaluation at a minimum of 24 months follow-up. Objective, subjective, functional and KT-1000 arthrometric tests were performed. RESULTS: 92.7% had a negative or trace pivot shift at follow-up. None of the patients had rupture of the autografts at review. The mean post-operative single-legged hop was 81%. The KT-1000 arthrometric evaluation post-operatively revealed a mean maximum manual difference of 0.5 mm; 90.2% of these patients had a maximum manual difference of less than 4 mm. Five patients (12.2%) had a "tighter" reconstructed knee (a negative mean maximum manual difference). More than 70% of the patients in this series had good to excellent results on functional, subjective and objective evaluation scores. CONCLUSION: Excellent motion recovery, reliable stabilisation rates, good arthrometric results and encouraging post-operative functional, subjective and objective evaluation scores can be expected in patients undergoing anterior cruciate ligament reconstruction with patellar tendon autografts.

Patellar allografts in anterior cervical fusion - a two-year clinical and radiographic study.

Donor site morbidity, which occurs in 15% to 20% with the use of autografts for anterior cervical fusion, is eliminated with the use of allografts. While allografts from the iliac crest, ribs, fibula, femoral head and skull have been used in anterior cervical fusion, the use of patellar allografts has not been previously reported. Twenty-two patients underwent Cloward anterior cervical decompression and fusion using bicortical patellar allografts from 1993 to 1997. Fifteen patients, with a follow-up period of at least two years, were reviewed. Eleven patients (73.4%) had good or excellent results at an average of 42.8 months after surgery. Fourteen patients (93.4%) achieved union. Two patients (13.3%) developed collapse of the graft with extrusion, one of whom still achieved union. These results are comparable to those reported of anterior cervical fusion using autografts or other types of allografts.

The Mitchell distal metatarsal osteotomy for hallux valgus--the Singapore General Hospital experience.

BACKGROUND: Fifty-five Mitchell distal metatarsal osteotomies for hallux valgus performed over a period of four years have been retrospectively reviewed. The 38 patients were followed for an average of 30 months (range 12 to 60 months). RESULTS: The preoperative hallux valgus angle averaged 30.9 degrees +/- 8.2 degrees SD (range 18 degrees to 60 degrees) and the postoperative angle averaged 12.2 degrees +/- 4.6 degrees (range 5 degrees to 20 degrees). CONCLUSION: Ninety-two percent of the patients were satisfied with the result of the procedure. They stated that, given the identical situation, they would undergo the operation again.