Supersymmetric Mean-Field Theory of t-J Model

The supersymmetric formulation of t-J model is studied in this paper at the mean-field level where $\delta$-T phase diagram is computed. We find that slave-fermion-like spiral phase is stable at low doping concentration, and the slave-boson-like d-wave fermionic spin pairing state becomes energetically favourable when $\delta\geq$ 0.23. An improvement in free energy using Gutzwiller's method lowers the transition doping concentration to 0.06. We also point out the existence of new branches of excitations in the supersymmetric theory.Comment: 11 pages and 2 figure

Laser Surface Modification of NiTi for Medical Applications

Regarding the higher demand of the total joint replacement (TJR) and revision surgeries in recent years, an implant material should provide much longer lifetime without failure. Nickel titanium (NiTi) is the most popular shape memory alloy in the industry, especially in medical devices due to its unique mechanical properties such as pseudo-elasticity, damping capacity, shape memory and good biocompatibility. However, concerns of nickel ion release of this alloy still exist if it is implanted for a prolonged period of time. Nickel is well known for the possibility of causing allergic response and degeneration of muscle tissue as well as being carcinogenic for the human body beyond a certain threshold. Therefore, drastically improving the surface properties (e.g. wear resistance) of NiTi is a vital step for its adoption as orthopaedic implants. To overcome the above-mentioned risks, different surface treatment techniques have been proposed and investigated, such as Physical Vapour Deposition (PVD), Chemical Vapour Deposition (CVD), ion implantation, plasma spraying, etc. Yet all of these techniques have similar limitations such as high treatment temperature, poor metallurgical bonding between coated film and substrate, and lower flexibility and efficiency. As a result, laser gas nitriding would be an ideal treatment method as it could overcome these drawbacks. Moreover, the shape memory effect and pseudo-elasticity of NiTi from a reversible phase transformation between the martensitic phase and the austenitic phase are very sensitive to heat. Hence, NiTi implant is subjected to the following provisions of the thermo-mechanical treatment process, and this implant provides desired characteristics. It is important to suggest a surface treatment, which would not disturb the original build-in properties. As a result, the low-temperature methods for substrate have to be employed on the surface of NiTi. This present study aims to investigate the feasibility of applying diffusion laser gas nitriding technique to improve the wettability and wear resistance of NiTi as well as establish the optimization technique. The current report summaries the result of laser nitrided NiTi by continuous-wave (CW) fibre laser in nitrogen environment. The microstructure, surface morphology, wettability, wear resistance of the coating layer has been analysed using scanning electron microscopy (SEM), X-ray diffractometry (XRD), sessile drop technique, 3-D profile measurement and reciprocating wear test. The resulting surface layer is free of cracks, and the wetting behaviour is better than the bare NiTi. The wear resistance of the optimised nitride sample with different hatch patterns is also evaluated using reciprocating wear testing against ultra-high-molecular-weight polyethylene (UHMWPE) in Hanks’ solution. The results indicate that the wear rates of the nitride samples and the UHMWPE counter-part were both significantly reduced. It is concluded that the diffusion laser gas nitriding is a potential low-temperature treatment technique to improve the surface properties of NiTi. This technique can be applied to a femoral head or a bone fixation plates with relatively large surface area and movable components

Treating of Rayon-flocked Fabric by Atmospheric Pressure Plasma

This study investigates hydrophobisation of the surface of rayon-flocked fabric by means of atmospheric pressure plasma (APP) treatment with tetramethylsilane (TMS). Plasma deposition of TMS is regarded as an effective, single-step low pollution method. A detailed study of the process parameters was conducted. A highly hydrophobic surface was successfully fabricated on rayon-flocked fabric and the hydrophobic surface was found to have good stain resistance to coffee and milk tea

Association between serum uric acid and prostate cancer mortality in androgen deprivation therapy: A population‐based cohort study

Objective This population-based study examined the association between baseline uric acid (UA) and prostate cancer (PCa)-related mortality amongst PCa patients receiving androgen deprivation therapy (ADT). Methods Adults with PCa who received ADT in Hong Kong between December 1999 and March 2021 were identified. Patients with missing baseline UA were excluded. Patients were followed up until September 2021. The outcome was PCa-related mortality. Results Altogether, 4126 patients (median follow-up 3.1[interquartile range 1.4–6.0] years) were included. A J-shaped association was observed between baseline UA level and PCa-related mortality risk, with a direct association in those with mean(0.401 mmol/L) or above-mean baseline UA levels (hazard ratio (HR) per standard deviation-increase 1.35 [95% confidence interval 1.21,1.51], p < 0.001), and an inverse association in those with below-mean baseline UA levels (HR 0.78[0.67,0.92], p = 0.003). The former remained significant on competing risk regression, but not the latter. Conclusions A J-shaped relationship between baseline UA level and PCa-related mortality risk was identified. This study was mainly limited by potential unmeasured and residual confounders. Further validation studies are warranted

The Polished MS-30 Stem With a Solid Centralizer: A Minimum 10-year Review of Radiological and Clinical Outcomes 拋光 MS-30 假體固體與實心置中器的結合:最少術後十年的造影和臨床結果

AbstractBackground/PurposeMS-30 is a triple tapered cemented femoral stem. Before 2005, it was used together with a solid centralizer. We wanted to investigate its effect on the migration behaviour and survivorship of polished stem with a minimum of 10 years.MethodsTwenty-seven hips in 26 patients were available for follow-up. The mean length of follow-up was 12.1 years. Clinical outcomes were documented with the Harris Hip Score. Radiographs were examined for evidence of aseptic loosening.ResultsThe average Harris Hip Score was 74.8. No stem was revised for aseptic loosening. Two stems (7.4%) developed radiolucent lines of more than 2 mm width with osteolysis. The mean subsidence was 0.77 mm. The survival rate at the 10th postoperative year, with aseptic loosening as the end point, was 100%.ConclusionThe polished MS-30 stem with a solid centralizer has a satisfactory long-term outcome. Its mean subsidence was less than that of other polished tapered stems reported in the literature

Enhancement of Wear and Corrosion Resistance of Beta Titanium Alloy by Laser Technology

The relatively high elastic modulus coupled with the presence of toxic vanadium (V) in Ti6Al4V alloy has long been a concern in orthopaedic applications. To solve the problem, a variety of non-toxic and low modulus beta-titanium (beta-Ti) alloys have been developed. Among the beta-Ti alloy family, the quaternary Ti-Nb-Zr-Ta (TZNT) alloys have received the highest attention as a promising replacement for Ti6Al4V due to their lower elastic modulus and outstanding long term stability against corrosion in biological environments. However, the inferior wear resistance of TNZT is still a problem that must be resolved before commercialising in the orthopaedic market. In this work, a newly-developed laser surface treatment technique was employed to improve the surface properties of Ti-35.3Nb-7.3Zr-5.7Ta alloy. The surface microstructure and composition of the laser-treated TNZT surface were examined by grazing incidence x-ray diffraction (GI-XRD) and x-ray photoelectron spectroscopy (XPS). The wear and corrosion resistance were evaluated by pin-on-plate sliding test and anodic polarisation test in Hanks’ solution. The experimental results were compared with the untreated (or base) TNZT material. The research findings showed that the laser surface treatment technique reported in this work can effectively improve the wear and corrosion resistance of TNZT. The enhancement of such surface properties was due to the formation of a smooth and hard layer on the substrate surface. The laser-formed layer was metallurgically bonded to the substrate, and had no concern of coating delamination or peel-off.Acknowledgments The work described in this paper was supported by research grants from the Hong Kong Polytechnic University (G-YK36 and G-YM75), Hong Kong Special Administration Region, China, and the Queen’s University Belfast (Start-up Research Fund: D8201MAS), United Kingdom

Mainland Chinese Tourists’ Expectations, Perceived Performance of and Satisfaction towards Shopping Malls in Hong Kong

Tourists from mainland China constitute one of the world's biggest and fastest-growing travel markets. The Hong Kong Tourism Board expects the frequency of the mainland Chinese tourists to grow steadily. One of the beneficiaries of this phenomenon is Hong Kong’s shopping malls. However, understanding of tourists from mainland China’s expectations from, perceived performance of and satisfaction with the shopping malls’ attributes in Hong Kong is inadequate. This study intends to fill this important gap. A survey questionnaire was employed for data collection. The main results reveal the mainland Chinese tourists’ levels of satisfaction, indifference and dissatisfaction as well as the relationship between shopping malls’ attributes and customer satisfaction

Major adverse cardiovascular events of enzalutamide versus abiraterone in prostate cancer: a retrospective cohort study.

Background While the cardiovascular risks of androgen receptor pathway inhibitors have been studied, they were seldom compared directly. This study compares the risks of major adverse cardiovascular events (MACE) between enzalutamide and abiraterone among prostate cancer (PCa) patients. Methods Adult PCa patients receiving either enzalutamide or abiraterone in addition to androgen deprivation therapy in Hong Kong between 1 December 1999 and 31 March 2021 were identified in this retrospective cohort study. Patients who switched between enzalutamide and abiraterone, initiated abiraterone used without steroids, or experienced prior cardiac events were excluded. Patients were followed-up until 30 September 2021. The primary outcomes were MACE, a composite of stroke, myocardial infarction (MI), Heart failure (HF), or all-cause mortality and a composite of adverse cardiovascular events (CACE) not including all-cause mortality. The secondary outcomes were individual components of MACE. Inverse probability treatment weighting was used to balance covariates between treatment groups. Results In total, 1015 patients were analyzed (456 enzalutamide users and 559 abiraterone users; mean age 70.6 ± 8.8 years old) over a median follow-up duration of 11.3 (IQR: 5.3–21.3) months. Enzalutamide users had significantly lower risks of 4P-MACE (weighted hazard ratio (wHR) 0.71 [95% confidence interval (CI) 0.59–0.86], p < 0.001) and CACE (wHR 0.63 [95% CI: 0.42–0.96], p = 0.031), which remained consistent in multivariable analysis. Such an association may be stronger in patients aged ≥65 years or without diabetes mellitus and was independent of bilateral orchidectomy. Enzalutamide users also had significantly lower risks of MI (wHR 0.57 [95% CI: 0.33–0.97], p = 0.040) and all-cause mortality (wHR 0.71 [95% CI: 0.59–0.85], p < 0.001). Conclusion Enzalutamide was associated with lower cardiovascular risks than abiraterone in PCa patients