ZnFe2 O4 Dendrite/SnO2 Helix 3D Hetero-Structure Photoanodes for Enhanced Photoelectrochemical Water Splitting: Triple Functions of SnO2 Nanohelix.

An array of SnO2 nanohelix structures is employed to fabricate a SnO2 helix@ZnFe2 O4 dendrite core-shell 3D heterostructure photoanode for photoelectrochemical (PEC) water splitting. The SnO2 helix provides triple critical functions to enhance the PEC performance of the photoanode. First, it scatters the incident light to achieve a higher light harvesting efficiency. Second, it provides a facile electron pathway as an electron transfer layer (ETL) while blocking hole transport to mitigate charge recombination in the bulk of ZnFe2 O4 . Finally, it becomes a template for the formation of ZnFe2 O4 dendrite nanostructure shell. The ZnFe2 O4 dendrite/SnO2 helix photoanode exhibits a remarkable increase in incident photon-to-electron conversion efficiency compared to unmodified ZnFe2 O4 with no ETL and modified one with "flat" SnO2 ETL. The surface of the ZnFe2 O4 /SnO2 helix photoanode is further modified with TiO2 passivation layer and NiFeOx oxygen evolution co-catalyst to achieve one of the best PEC performances among reported ZnFe2 O4 -based photoanodes.

Multiple Heterojunction in Single Titanium Dioxide Nanoparticles for Novel Metal-Free Photocatalysis.

Despite a longstanding controversy surrounding TiO2 materials, TiO2 polymorphs with heterojunctions composed of anatase and rutile outperform individual polymorphs because of the type-II energetic band alignment at the heterojunction interface. Improvement in photocatalysis has also been achieved via black TiO2 with a thin disorder layer surrounding ordered TiO2. However, localization of this disorder layer in a conventional single TiO2 nanoparticle with the heterojunction composed of anatase and rutile has remained a big challenge. Here, we report the selective positioning of a disorder layer of controlled thicknesses between the anatase and rutile phases by a conceptually different synthetic route to access highly efficient novel metal-free photocatalysis for H2 production. The presence of a localized disorder layer within a single TiO2 nanoparticle was confirmed for the first time by high-resolution transmission electron microscopy with electron energy-loss spectroscopy and inline electron holography. Multiple heterojunctions in single TiO2 nanoparticles composed of crystalline anatase/disordered rutile/ordered rutile layers give the nanoparticles superior electron/hole separation efficiency and novel metal-free surface reactivity, which concomitantly yields an H2 production rate that is ∼11-times higher than that of Pt-decorated conventional anatase and rutile single heterojunction TiO2 systems.

Spatially graded TiO2-SiO2 Bragg reflector with rainbow-colored photonic band gap.

A simple single-step method to fabricate spatially graded TiO2-SiO2 Bragg stack with rainbow colored photonic band gap is presented. The gradation in thickness of the Bragg stack was accomplished with a modified glancing angle deposition (GLAD) technique with dynamic shadow enabled by a block attached to one edge of the rotating substrate. A linear gradation in thickness over a distance of about 17 mm resulted in a brilliant colorful rainbow pattern. Interestingly, the photonic band gap position can be changed across the whole visible wavelength range by linearly translating the graded Bragg stack over a large area substrate. The spatially graded Bragg stack may find potential applications in the tunable optical devices, such as optical filters, reflection gratings, and lasers.

Isolated acetabular revision with ceramic-on-ceramic bearings using a ceramic head with a metal sleeve.

The purpose of this study is to evaluate results of isolated acetabular revision with ceramic-on-ceramic bearings using a ceramic head with a metal sleeve. A retrospective review of fifty-three hips was performed. The mean patient age was 49.9years and the mean follow-up period was 5.7years. The mean modified Harris hip score improved from 47.5, pre-operatively, to 84.7 at the time of last follow-up (P<0.001). Two patients reported squeaking of the hip. Three patients experienced loosening cup, necessitating re-revision surgery. There was a significant difference of acetabular bone defect between loose cup group and stable cup group (P=0.018). There were no ceramic fractures and no osteolysis. The survival rate of the acetabular cup at the mid-term follow-up was 94.3%. In conclusion, ceramic head with a metal sleeve can be a reliable option for isolated acetabular revision.

Is second generation metal-on-metal primary total hip arthroplasty with a 28 mm head a worthy option?: a 12- to 18-year follow-up study.

To determine whether MoM THA with a small head is still worthy of use, we investigated survivorship, complications, and factors influencing failure. Of 149 consecutive patients (195 hips), 141 (180 hips) of mean age 43 (19-55) years were available for review at a mean of 14.4 years postoperatively. Survivorship for cup revision for any cause was 97.8% at 18.4 years postoperatively. Nine hips generated complaints of groin pain; six showed periacetabular osteolysis, one had pain without radiological change, and two were diagnosed as symptomatic pseudotumors. Four of six hips with periacetabular osteolysis or aseptic loosening were revised. Surgery- and patient-related factors had no effect in results. Our results are encouraging, however, further study will be necessary to determine the incidence and fates of pseudotumors after MoM THA with a small head.

Total hip arthroplasty using cementless grit-blasted femoral component: a minimum 10-year follow-up study.

The grit-blasted cementless Spotorno (CLS) stem, which has excellent survival rates up to 10 years, is widely used in total hip arthroplasty (THA). We investigated the survivorships of CLS stems in THA at a minimum follow-up of 10 years and sought to identify factors that influence outcomes. A total of 227 hips of 191 patients who underwent cementless THA with a CLS stem were retrospectively reviewed at a mean follow-up of 12.3 years. All patients were evaluated clinically and radiographically according to implant type and surgery-related and patient-related factors. Survivorship was 97.2% when femoral revision for any reason was defined as the end point. Femoral revisions were performed in 3 hips because of periprosthetic fractures. Survivorship for all hips, using revision for any reason as the end point, was 92.6%. Two metal-on-metal THAs were revised because of aseptic loosening or osteolysis around the cup. No significant differences were evident for type of stem, type of bearing surface, stem alignment, or patient-related factors. However, a canal fill index of 80% or less was found to affect cortical remodeling, subsidence, and a change in stem position of 5° or more, which indicates that care must be taken not to undersize stems. In addition, in view of the revisions performed, bearing surfaces appear to importantly influence THA survivorship.

The cartilage degeneration and joint motion of bipolar hemiarthroplasty.

PURPOSE: The outcomes of bipolar hemiarthoplasty for osteonecrosis of femoral head have been disappointing due to cartilage degeneration and osteolysis. We investigated the cartilage degeneration, joint motion, and factors associated with osteolysis. METHODS: We retrospectively reviewed 134 bipolar hemiarthroplasties. The wear rate of acetabular cartilage was calculated. The ranges of motion of outer bearing and inner bearing were determined, and the ratio (O/I ratio) was calculated. RESULTS: The mean degeneration rate of acetabular cartilage was 0.34 ± 0.35 mm/year. We could observe that the outer bearing motion was dominant, but decreased over time. In addition, the degeneration rate of cartilage and the decline rate of outer bearing motion of the osteolysis group were significantly higher than those of the control group. CONCLUSIONS: Close observation is needed in cases of high degeneration rate of cartilage and rapid decline of outer bearing motion due to possibility of osteolysis.

Is bipolar hemiarthroplasty a reliable option for Ficat stage III osteonecrosis of the femoral head? 15- to 24-year follow-up study.

PURPOSE: The long-term results of a bipolar hemiarthroplasty (BHA) for osteonecrosis (ON) of the femoral head have not been favorable. The causes have been attributed to cup migration and osteolysis or groin pain. The purpose of this study was to analyze the long-term outcomes and the survivorships of bipolar hemiarthroplasty applied to Ficat stage III ON. MATERIALS AND METHODS: Between 1985 and 1993, 49 patients (63 hips) underwent cementless BHA for Ficat stage III ON. Of these 49 patients, 43 patients (55 hips) of mean age 42.2 years were available for follow-up review at a mean duration of 20.3 years post operation. Anteroposterior hip serial (including extreme abduction/adduction) radiographs were used to evaluate osteolysis, migration, cartilage wear rate, and the ratio of outer/inner bearing motion (O/I ratio) at the latest follow-up. RESULTS: The mean Harris hip score improved to 80.8 points at the latest follow-up. Survivorship at 24 years was 79 and 69 % with revision for any reason and development of acetabular osteolysis as the end point. Groin pain was present in 20 (36.4 %) of the 55 hips, and isolated groin pain was not a reason for revision. The patients had revision surgery performed, which showed that the cartilage wear rate was significantly high, and that the O/I ratio was significantly low (p < 0.05). CONCLUSION: Survivorship determined in this study was more favorable than that of previous studies, and exceeded expectation. The BHA for Ficat stage III ON is not reliable option anymore, considering low survival rate and high osteolysis developmental rate.

Cementless total hip arthroplasty with a metal-on-metal bearing in patients younger than 50 years.

Total hip arthroplasty (THA) longevity is the primary concern in young patients. Metal-on-metal articulations were reintroduced to reduce polyethylene particle-induced osteolysis and improve survivorship; to date, based on issued reports, this strategy appears to have been successful. In this study, the authors investigated metal-on-metal articulation survivorship and osteolysis incidence in young patients (19-50 years old at index operations) and retrospectively reviewed cementless metal-on-metal THAs in 70 patients (78 hips) with a mean follow-up of 12.4 years. Metasul articulation was used with the Wagner acetabular component in all. Survivorship with revision for any cause was 98.7% (95% confidence interval, 98%-100%), and survivorship due to the development of osteolysis for any lesion was 97.5% (95% confidence interval, 95%-99%). Mean Harris hip score improved from 51 to 95 points at final follow-up. The findings of this study indicate that outcomes of cementless THA with a metal-on-metal bearing in young patients are satisfactory. However, longer-term studies in larger cohorts are required to determine whether metal-on-metal articulations are really a favorable option in young patients.

Incidence and factors associated with squeaking in alumina-on-alumina THA.

BACKGROUND: The alumina-on-alumina bearing surface, which has a high wear resistance and a good biocompatibility, is widely used in THA but recently has been associated with squeaking. While various authors have reported factors associated with squeaking, they remain poorly understood. QUESTIONS/PURPOSES: To contribute to the debate on squeaking we therefore asked the following questions: (1) What is the incidence of squeaking in alumina-on-alumina THA? (2) What factors are associated with squeaking in alumina bearings in our practice? METHODS: We retrospectively reviewed 168 patients (173 hips) who had primary alumina-on-alumina THAs. The mean age of the patients was 53 years (range, 18 to 81 years). Minimum followup was 5.6 years (average, 7.3 years; range, 5.6-9.4 years). All patients were evaluated clinically and radiographically with attention to periprosthetic osteolysis, squeaking, and ceramic fracture. When the patient reported squeaking, we determined the onset, reproducibility, and activities associated with the squeaking. We recorded patient (gender, age, height, weight, and body mass index) and surgical factors (abduction angle of cup, size and length of ceramic head component, and diameter of cup in the implant). RESULTS: Eight of the 168 patients (5%) had squeaking hips. Squeaking was more common in males and in those with large ceramic heads. There were no complications or revisions in the squeaking group. One ceramic liner fracture was associated with trochanteric nonunion. CONCLUSIONS: When recommending alumina-on-alumina bearing surfaces to patients they should be clearly informed of the possibility of squeaking. Patients with risk factors for squeaking should be followed at regular intervals.

Isolated acetabular revision hip arthroplasty with the use of uncemented cup.

We evaluated the clinical and radiological results of isolated acetabular revision hip arthroplasty. Forty-three hips underwent isolated acetabular revision with uncemented cup and were followed up for an average of 76 months. The monoblock femoral stems were used in 20 hips and modular femoral stems in 23 hips. The average Harris Hip Score improved to 87 at last follow-up from 57 preoperatively. All femoral stems maintained stable fixation with bone ingrowth and no subsidence at last follow-up. Five hips with the monoblock stem underwent rerevision due to loosening of cup with osteolysis. The isolated acetabular revision is encouraging, but in reflection of the results of the monoblock head, the visual inspection of the femoral head is not enough for evaluation of its surface status.

Amorphous Tin Oxide Nanohelix Structure Based Electrode for Highly Reversible Na-Ion Batteries.

An array of amorphous tin oxide (a-SnOx) nanohelixes (NHs) was fabricated on copper foil as an electrode for Na-ion batteries via the oblique angle deposition method, a solution- and surfactant-free process. The combination of the amorphous phase SnOx with a low oxidation number and its vertically aligned NH geometry with a large surface area and high porosity, which facilitate Na-ion dynamics and accommodate the volume changes, enabled a reversible capacity of up to 915 mA h g-1 after 50 cycles, fast rate capability with 48.1% retention at 2 A g-1, and high stability, which are superior to those of crystalline nanoparticle-based electrodes.

Unassisted photoelectrochemical water splitting exceeding 7% solar-to-hydrogen conversion efficiency using photon recycling.

Various tandem cell configurations have been reported for highly efficient and spontaneous hydrogen production from photoelectrochemical solar water splitting. However, there is a contradiction between two main requirements of a front photoelectrode in a tandem cell configuration, namely, high transparency and high photocurrent density. Here we demonstrate a simple yet highly effective method to overcome this contradiction by incorporating a hybrid conductive distributed Bragg reflector on the back side of the transparent conducting substrate for the front photoelectrochemical electrode, which functions as both an optical filter and a conductive counter-electrode of the rear dye-sensitized solar cell. The hybrid conductive distributed Bragg reflectors were designed to be transparent to the long-wavelength part of the incident solar spectrum (λ>500 nm) for the rear solar cell, while reflecting the short-wavelength photons (λ<500 nm) which can then be absorbed by the front photoelectrochemical electrode for enhanced photocurrent generation.

Cementless bipolar hemiarthroplasty for unstable intertrochanteric fractures in octogenarians.

OBJECTIVE: The aim of this study was to evaluate the clinical and radiographic outcomes of bipolar hemiarthroplasty with cementless stem for the unstable intertrochanteric fracture in octogenarians and to determine the influencing factors associated with subsidence of the stem. METHODS: The study included the 143 hips of 139 patients (119 females, 20 males). Mean follow-up period was 3.8 (range: 2.2 to 9.0) years. The displaced lesser trochanteric fragment was reduced anatomically and fixed with 16-gauge stainless steel cerclage wire. Clinical outcomes included Harris Hip Score (HHS), thigh pain, groin pain and walking ability. Radiographic outcomes included stem fixation and stability, osteolysis, heterotopic ossification and subsidence. The stable reduction group was determined when anatomic reduction of posteromedial fragments was achieved with ≤1 mm gap of fragment. RESULTS: Mean HHS was 82 (range: 78 to 99) at the final follow-up. Thirty-one hips (21.7%) experienced thigh pain and 19 (13.3%) groin pain. One hundred and twelve patients (80.6%) regained their pre-injury level of ambulation. All femoral stems showed osseointegration without aseptic loosening and osteolysis. The mean stem subsidence was 3.1±2.4 (range: 0 to 18) mm. The extent of subsidence was significantly higher in patients with unstable reduction. The survival rate was 94.2%. CONCLUSION: Cementless bipolar hemiarthroplasty appears to be a suitable method for the treatment of intertrochanteric fracture in octogenarians. However, stable fixation of the posteromedial fragment is necessary to avoid stem subsidence.

The Comparison of Compression Hip Screw and Bipolar Hemiarthroplasty for the Treatment of AO Type A2 Intertrochanteric Fractures.

PURPOSE: The purpose of this study was to compare the outcomes of osteosynthesis using compression hip screw fixation versus bipolar hemiarthroplasty in AO type A2 intertrochanteric fractures. MATERIALS AND METHODS: From March 2003 to December 2009, 89 patients were included in this study. They were treated using compression hip screws (43 cases) or bipolar hemiarthroplasty (46 cases). The mean age of patients was 77.7 years (65-94 years) and the mean follow-up period was 5.9 years (1-8.3 years). For comparison of the outcomes in the two groups, statistical analyses were performed with parameters including anesthesia time, operation time, amount of transfusion, hospital stay, general complications, clinical outcome, time of partial weight-bearing using a walker, and radiological failure rate. RESULTS: Differences in the amount of transfusion, general complications, and clinical outcome (Merle d'Aubigné and Postel score) were not statistically significant between the two groups. The bipolar hemiarthroplasty group showed better results than the compression hip screw group for anesthesia time and the time of partial weight-bearing using a walker. Radiological failures were observed in hips in one case (2.2%) of bipolar hemiarthroplasty, and in four cases (9.3%) of compression hip screw fixation. CONCLUSION: Among elderly individuals with AO type A2 intertrochanteric fractures, patients treated with bipolar hemiarthroplasty were able to perform early ambulation. However, no significant difference in operation time, amount of postoperative transfusion, clinical results, hospital stay, and radiological failure rate was observed between the bipolar hemiarthroplasty and compression hip screw fixation groups.

Efficient photoelectrochemical hydrogen production from bismuth vanadate-decorated tungsten trioxide helix nanostructures.

Tungsten trioxide/bismuth vanadate heterojunction is one of the best pairs for solar water splitting, but its photocurrent densities are insufficient. Here we investigate the advantages of using helical nanostructures in photoelectrochemical solar water splitting. A helical tungsten trioxide array is fabricated on a fluorine-doped tin oxide substrate, followed by subsequent coating with bismuth vanadate/catalyst. A maximum photocurrent density of ~5.35±0.15 mA cm(-2) is achieved at 1.23 V versus the reversible hydrogen electrode, and related hydrogen and oxygen evolution is also observed from this heterojunction. Theoretical simulations and analyses are performed to verify the advantages of this helical structure. The combination of effective light scattering, improved charge separation and transportation, and an enlarged contact surface area with electrolytes due to the use of the bismuth vanadate-decorated tungsten trioxide helical nanostructures leads to the highest reported photocurrent density to date at 1.23 V versus the reversible hydrogen electrode, to the best of our knowledge.