Incidence of Venous Thromboembolism after Primary Total Hip Arthroplasty with Mechanical Prophylaxis in Hong Kong Chinese.

Purpose: The incidence of deep vein thrombosis (DVT) following total hip arthroplasty (THA) without chemoprophylaxis could be as high as 50% in Caucasians. However, according to several subsequent studies, the incidence of venous thromboembolic events (VTE) in Asians was much lower. The routine use of chemoprophylaxis, which could potentially cause increased bleeding, infection, and wound complications, has been questioned in low-incidence populations. The objective of this study is to determine the incidence of VTE after primary THA without chemoprophylaxis in an Asian population using a fast-track rehabilitation protocol and to verify the safety profile for use of 'mechanical prophylaxis alone' in patients with standard risk of VTE. Materials and Methods: This is a retrospective cohort study of 542 Hong Kong Chinese patients who underwent primary THA without chemoprophylaxis. All patients received intermittent pneumatic compression and graduated compression stockings as mechanical prophylaxis. Multimodal pain management was applied in order to facilitate early mobilisation. Routine duplex ultrasonography was performed between the fourth and seventh postoperative day for detection of proximal DVT. Results: All patients were Chinese (mean age, 63.0±11.9 years). Six patients developed proximal DVT (incidence rate, 1.1%). None of the patients had symptomatic or fatal pulmonary embolism. Conclusion: The incidence of VTE after primary THA without chemical prophylaxis can be low in Asian populations when following a fast-track rehabilitation protocol. Mechanical prophylaxis alone can be regarded as a reasonably safe practice in terms of a balanced benefit-to-risk ratio for Asian patients with standard risk of VTE.

Tibial tray thickness does not significantly increase medial tibial bone resorption: Using tibial bone density as an objective measurement method.

BACKGROUND: Recent studies have reported the occurrence of medial tibial bone resorption following total knee replacement. One study proposed that a thick tibial tray results in stress shielding and increases the risk of bone resorption, but its findings were based on subjective radiological assessment. This study aimed to verify this hypothesis and to objectively quantify medial tibial bone density by using serial measurements with digital radiological densitometry. METHODS: This was a retrospective cohort study involving 140 patients (70 thick tray vs. 70 thin tray) with cobalt-chromium implants with at least 24 months of follow-up. Standard radiographs were reviewed to look for incidence of medial tibial bone loss. Serial measurement of medial tibial bone density was also performed using the method of digital radiological densitometry. RESULTS: There was no significant difference in the incidence of medial tibial bone loss. Both groups showed a significant drop in medial tibial bone density after operation (P < 0.01). Medial tibial bone density of the thick-tray cohort was significantly higher than the thin-tray cohort at one year (93.3 vs. 83.1 Greyscale; P = 0.04), but not at two and three years. Clinical outcomes in terms of postoperative range of motion, Knee Society score and complication rates were similar. CONCLUSIONS: Medial tibial bone resorption is a common phenomenon. Implants with thicker tibial trays suffer less than those with thinner trays at one year, but the difference is transient and does not affect clinical outcome.

Increased Exciton Delocalization of Polymer upon Blending with Fullerene.

Interfaces between donor and acceptor in a polymer solar cell play a crucial role in exciton dissociation and charge photogeneration. While the importance of charge transfer (CT) excitons for free carrier generation is intensively studied, the effect of blending on the nature of the polymer excitons in relation to the blend nanomorphology remains largely unexplored. In this work, electroabsorption (EA) spectroscopy is used to study the excited-state polarizability of polymer excitons in several polymer:fullerene blend systems, and it is found that excited-state polarizability of polymer excitons in the blends is a strong function of blend nanomorphology. The increase in excited-state polarizability with decreased domain size indicates that intermixing of states at the interface between the donor polymers and fullerene increases the exciton delocalization, resulting in an increase in exciton dissociation efficiency. This conclusion is further supported by transient absorption spectroscopy and time-resolved photoluminescence measurements, along with the results from time-dependent density functional theory calculations. These findings indicate that polymer excited-state polarizability is a key parameter for efficient free carrier generation and should be considered in the design and development of high-performance polymer solar cells.

Langmuir-Blodgett Thin Films of Diketopyrrolopyrrole-Based Amphiphiles.

We report on two π-conjugated donor-acceptor-donor (D-A-D) molecules of amphiphilic nature, aiming to promote intermolecular ordering and carrier mobility in organic electronic devices. Diketopyrrolopyrrole was selected as the acceptor moiety that was disubstituted with nonpolar and polar functional groups, thereby providing the amphiphilic structures. This structural design resulted in materials with a strong intermolecular order in the solid state, which was confirmed by differential scanning calorimetry and polarized optical microscopy. Langmuir-Blodgett (LB) films of ordered mono- and multilayers were transferred onto glass and silicon substrates, with layer quality, coverage, and intermolecular order controlled by layer compression pressure on the LB trough. Organic field-effect transistors and organic photovoltaics devices with active layers consisting of the amphiphilic conjugated D-A-D-type molecules were constructed to demonstrate that the LB technique is an effective layer-by-layer deposition approach to fabricate self-assembled, ordered thin films.

Morphology Control in Films of Isoindigo Polymers by Side-Chain and Molecular Weight Effects.

The performance of devices relying on organic electronic materials, such as organic field-effect transistors (OFET) and organic photovoltaics (OPV), is strongly correlated to the morphology of the conjugated material in thin films. For instance, several factors such as polymer solubility, weak intermolecular forces between polymers and fullerene derivatives, and film drying time impact phase separation in the active layer of a bulk heterojunction OPV device. In an effort to probe the influence of polymer assembly on morphology of polymer thin films and phase separation with fullerene derivatives, five terthiophene-alt-isoindigo copolymers were synthesized with alkyl side-chains of varying lengths and branching on the terthiophene unit. These P[T3(R)-iI] polymers were designed to have similar optoelectronic properties but different solubilities in o-dichlorobenzene and were predicted to have different tendencies for crystallization. All polymers with linear alkyl chains exhibit similar thin film morphologies as investigated by grazing-incidence wide-angle X-ray scattering (GIWAXS) and atomic force microscopy (AFM). The main differences in electronic and morphological properties arise when P[T3(R)-iI] is substituted with branched 2-ethylhexyl (2EH) side-chains. The bulky 2EH substituents lead to a blue-shifted absorption, a lower ionization potential, and reduced ordering in polymer thin films. The five P[T3-iI] derivatives span hole mobilities from 1.5 × 10-3 to 2.8 × 10-2 cm2 V-1 s-1 in OFET devices. In OPV devices, the 2EH-substituted polymers yield open-circuit voltages of 0.88 V in BHJ devices yet low short-circuit currents of 0.8 mA cm-2, which is explained by the large phase separation observed by AFM in blends of P[T3(2EH)-iI] with PC71BM. In these P[T3(R)-iI] systems, the propensity for the polymers to self-assemble prior to aggregation of PC71BM molecules was key to achieving fine phase separation and increased short-circuit currents, eventually resulting in power conversion efficiencies of 5% in devices processed using a single solvent.

High efficiency air-processed dithienogermole-based polymer solar cells.

The effect of air processing, with air exposure varying from minutes to hours prior to encapsulation, on photovoltaic device performance has been studied through a series of electrical characterizations and optical simulations for a donor/acceptor polymer-based organic solar cell based on poly(dithienogermole-alt-thienopyrrolodione) p(DTG-TPD)/PC71BM blends. A ∼10% degradation in power conversion efficiency was observed due to air processing with 10 min exposure time, with AM1.5 power conversion efficiencies (PCEs) decreasing from 8.5 ± 0.25% for devices processed in inert nitrogen atmosphere to 7.7 ± 0.18% for devices processed in ambient air. After 3 h air exposure, the PCE leveled off at 7.04 ± 0.1%. This decrease is attributed partially to interface issues caused by exposure of the electrode materials to oxygen and water and partially to a degradation of the hole transport in the active layer.

Tetracyano isoindigo small molecules and their use in n-channel organic field-effect transistors.

N,N'-Dihexyl-6,6'-dicyanoisoindigo, N,N'-didecyl-5,5',6,6'-tetracyanoisoindigo, N,N'-dihexyl-5,5',6,6'-tetracyanoisoindigo, and N,N'-dihexyl-5,5',6,6'-tetracyanothienoisoindigo have been synthesised in moderate yields by the reaction of corresponding di and tetrabromo species with CuCN, with microwave heating leading to higher yields and fewer side products for the tetrasubstituted species. Di- and tetracyano substitution anodically shifts the molecular reduction potential relative to the unsubstituted cores by ca. 0.4 and 0.8 V, respectively, with the resultant values for the tetracyano derivatives (-0.58 to -0.67 V vs. FeCp2(+/0)) suggesting the possibility of air-stable electron transport. All the synthesised cyano derivatives operate in n-channel OFETs, while the tetrabromothienoisoindigo derivative functions in a p-channel transistor. The tetracyanothienoisoindigo derivative exhibits the highest field-effect electron mobility values - up to 0.04 and 0.09 cm(2) V(-1) s(-1) in spin-coated and inkjet-printed devices respectively - and OFETs incorporating this compound have been shown to operate in air without significant degradation of their mobility values in the saturation regime.

Immunological mechanisms and clinical implications of regulatory T cell deficiency in a systemic autoimmune disorder: roles of IL-2 versus IL-15.

Regulatory T cell deficiency is evident in patients with lupus, but the casual [corrected] relationship and underlying mechanism leading to Treg deficiency are unclear. We analyzed the Treg profile, induction and functions of Treg in a lupus mouse model. A characteristic age-dependent biphasic change of Treg frequency was observed in the MRL/lpr mice, which developed a spontaneous lupus-like disease. After an early increase, Treg frequency in the peripheral lymphoid organs rapidly declined with age. Functionally, Treg from both young and old MRL/lpr mice were fully competent in suppressing the wild-type MRL/+ T effector cell (Teff) responses. Adoptive transfer of MRL/+ Treg markedly suppressed clinical disease in the MRL/lpr mice. We demonstrated that the reduced Treg frequency was a result of insufficient peripheral Treg expansion due to defective MRL/lpr Teff in IL-2 production, and the associated defects in dendritic cells, which could be fully restored by exogenous IL-2. In the absence of IL-2, MRL/lpr Teff but not MRL/lpr Treg were highly responsive to IL-15 and could expand rapidly due to enhanced IL-15R expression and IL-15 synthesis. These findings thus provide a clear causal relationship and immunological mechanism underlying Treg deficiency and systemic autoimmunity.

A crucial role for dendritic cell (DC) IL-10 in inhibiting successful DC-based immunotherapy: superior antitumor immunity against hepatocellular carcinoma evoked by DC devoid of IL-10.

The dendritic cell (DC)-based tumor immunotherapy has been a new promise of cure for cancer patients, but animal studies and clinical trials have thus far only shown limited success, especially in treating established tumors. Certain immunosuppressive mechanisms triggered by tumor cells or the derivatives are believed to be a major obstacle. We studied the role of DC-derived IL-10 and its negative impact on vaccine efficacy in mouse models. Liver tumor cells were injected via the portal vein, giving rise to disseminated intrahepatic tumors, or s.c. to form solid but extrahepatic tumors. Bone marrow-derived DCs were generated from normal or IL-10-deficient mice and used as the vector to deliver tumor Ags. We demonstrate here that DCs devoid of IL-10, a potent immunosuppressive cytokine, are superior over conventional DCs in triggering antitumor immunity. The IL-10(-/-)DCs were highly immunogenic, expressed enhanced levels of surface MHC class II molecules, and secreted increased amounts of Th1-related cytokines. By inducing tumor-specific killing and through the establishment of immunological memory, the vaccines delivered by IL-10(-/-)DCs could evoke strong therapeutic and protective immunity against hepatocellular carcinoma in the mouse models. These findings will have great clinical impact once being translated into the treatment of malignant, and potentially infectious, diseases in humans.

Systemic autoimmune disease induced by dendritic cells that have captured necrotic but not apoptotic cells in susceptible mouse strains.

Systemic lupus erythematosus (SLE) is an autoimmune disorder of a largely unknown etiology. Anti-double-stranded (ds) DNA antibodies are a classic hallmark of the disease, although the mechanism underlying their induction remains unclear. We demonstrate here that, in both lupus-prone and normal mouse strains, strong anti-dsDNA antibody responses can be induced by dendritic cells (DC) that have ingested syngeneic necrotic (DC/nec), but not apoptotic (DC/apo), cells. Clinical manifestations of lupus were evident, however, only in susceptible mouse strains, which correlate with the ability of DC/nec to release IFN-gamma and to induce the pathogenic IgG2a anti-dsDNA antibodies. Injection of DC/nec not only accelerated disease progression in the MRL/MpJ-lpr/lpr lupus-prone mice but also induced a lupus-like disease in the MRL/MpJ-+/+ wild-type control strain. Immune complex deposition was readily detectable in the kidneys, and the mice developed proteinuria. Strikingly, female MRL/MpJ-+/+ mice that had received DC/nec, but not DC/apo, developed a 'butterfly' facial lesion resembling a cardinal feature of human SLE. Our study therefore demonstrates that DC/nec inducing a Th1 type of responses, which are otherwise tightly regulated in a normal immune system, may play a pivotal role in SLE pathogenesis.