Polysaccharide‐based artificial extracellular matrix: Preparation and characterization of three‐dimensional,macroporous chitosan,and heparin composite scaffold

Scaffold‐guided tissue engineering based on synthetic and natural occurring polymers has gained many interests in recent year. In this study, the development of a chitosan‐heparin artificial extracellular matrix (AECM) is reported. Three‐dimensional, macroporous composite AECMs composed of heparin (Hep) and chitosan (Chito) were prepared by an interpolyelectrolyte complex/lyophilization method. The Chito‐Hep composite AECMs were, respectively, crosslinked with glutaraldehyde, as well as cocrosslinked with N,N‐(3‐dimethylaminopropyl)‐N′‐ethyl carbodiimide (EDC/NHS) and N‐hydroxysuccinimide (NHS). The crosslinking reactions were examined by FT‐IR analysis. In physiological buffer solution (PBS), the EDC/NHS‐crosslinked Chito‐Hep composite AECM showed a relative lower water retention ratio than its glutaraldehyde‐crosslinked counterparts. The EDC/NHS‐crosslinked Chito‐Hep composite AECMs showed excellent biocompatibility, according to the results of the in vitro cytotoxic test. This result suggested that the EDC/NHS‐crosslinked Chito‐Hep composite AECMs might be a potential biomaterial for scaffold‐guided tissue engineering applications. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Einfluss der Wechselwirkung von Reaktion und Fluiddynamik auf das Verhalten von Strahlschlaufenreaktoren

Jet loop reactors are used as apparatus to facilitate chemical or biological reactions. This type of apparatus is characterized by an internal circulation flow, essentially driven by the injection of liquid. The nozzle can also be used to inject and disperse gas. The internal fluid dynamics and thus the reactor behavior is significantly determined by the introduced momentum and by the internal gas distribution. To describe the mutual influence of a gas-consuming reaction and the internal fluid dynamics, a simplified model based on a momentum balance and a material balance was used. From the exemplary calculations, a critical range for non-selective reactions and for fluid dynamic stability is given.     

Highly accurate frequency estimation of brief duration signals in noise

A highly accurate frequency estimation providing suppression of windowing effects, denoising performances and frequency resolutions in excess of Gabor–Heisenberg limit, is proposed for brief duration signals. It is shown that unbiased frequency estimation with vanishing frequency variances is achieved far below Cramer–Rao lower bound when signal-to-noise ratio reaches vicinity of threshold values. Observed performances provide novel and valuable perspectives for efficient and accurate frequency estimation for brief duration signals in noise.     

Selective Laser Melting process optimization of Ti–Mo–TiC metal matrix composites

Selective Laser Melting (SLM) was used to process a powder mixture of CP Ti, 6.5 wt% Mo and 3.5 wt% Mo₂C. The process parameters were optimized to obtain full-density, crack free parts. After the in situ decomposition of Mo₂C in favor of the formation of TiC, the material consisted of a homogeneous dispersion of submicrometer sized TiC platelets in a β-(Ti,Mo) matrix exhibiting a high hardness up to 550 HV and compressive yield stress of 1164 ± 37 MPa. The microstructure and mechanical properties could be tailored by variation of the process parameters within the high-density processing window, as well as through post-process heat treatments.     

Prognostic implications of downstaging following preoperative radiation therapy for operable T3-T4 rectal cancer

PURPOSE: Squamous cancer of the upper aerodigestive tract is a disheartening disease. Despite our best efforts, the long-term survival rate remains only 15% to 40%, and surgical cures often decrease the quality of life owing to the loss of swallowing and speech organs. A better understanding of tumor dynamics and the discovery that thiosulfate can neutralize cisplatin led us to develop a treatment plan that combines a rapid superselective high-dose intraarterial delivery of cisplatin (CDDP), simultaneous intravenous infusion of its antagonist, thiosulfate, and radiation therapy. METHODS: Patients with advanced head and neck squamous cancer were entered into the protocol after a multidisciplinary evaluation that included CT or MR imaging. Forty-two patients constituted the first cohort. After baseline angiography, an arterial acceptance test determined the maximum infusion rate that the tumor's nutrient artery would accept. CDDP was then infused at that rate, usually within 3 to 5 minutes, while the antagonist thiosulfate was given intravenously. In the second cohort of 85 patients with stage 3 or 4 previously untreated and unresectable disease, local radiation was added to the treatment plan. The radiation dose (180-200 cGy/d x 35) was delivered regionally on the basis of the known radiosensitizing effect of CDDP. RESULTS: Cohort 1 allowed us to develop the infusion technique and to establish a dose quantity and delivery frequency. When 150 mg/m2 was administered weekly for 4 weeks, no severe toxicity was found. In cohort 2, 72 (92%) of the remaining 78 patients had complete disappearance of their tumor. Seventeen severe toxic events were associated with 323 femoral catheterizations. One patient died of pulmonary embolus, precluding follow-up evaluation. Six patients had neurologic sequelae, three with transient and three with permanent strokes. CONCLUSION: Rapid superselective chemotherapy with CDDP combined with a circulatory systemic antagonist allowed delivery of an antitumoral drug directly into the lesion while protecting the kidneys and bone marrow from the agent's systemic effects. Use of a dose regimen of 150 mg CDDP/m2 per week for 4 weeks resulted in the disappearance of a large percentage of advanced squamous cancers.     

Facile Synthesis and Characterization of Palm CNF-ZnO Nanocomposites with Antibacterial and Reinforcing Properties

Cellulose nanofibers (CNF) isolated from plant biomass have attracted considerable interests in polymer engineering. The limitations associated with CNF-based nanocomposites are often linked to the time-consuming preparation methods and lack of desired surface functionalities. Herein, we demonstrate the feasibility of preparing a multifunctional CNF-zinc oxide (CNF-ZnO) nanocomposite with dual antibacterial and reinforcing properties via a facile and efficient ultrasound route. We characterized and examined the antibacterial and mechanical reinforcement performances of our ultrasonically induced nanocomposite. Based on our electron microscopy analyses, the ZnO deposited onto the nanofibrous network had a flake-like morphology with particle sizes ranging between 21 to 34 nm. pH levels between 8–10 led to the formation of ultrafine ZnO particles with a uniform size distribution. The resultant CNF-ZnO composite showed improved thermal stability compared to pure CNF. The composite showed potent inhibitory activities against Gram-positive (methicillin-resistant Staphylococcus aureus (MRSA)) and Gram-negative Salmonella typhi (S. typhi) bacteria. A CNF-ZnO-reinforced natural rubber (NR/CNF-ZnO) composite film, which was produced via latex mixing and casting methods, exhibited up to 42% improvement in tensile strength compared with the neat NR. The findings of this study suggest that ultrasonically-synthesized palm CNF-ZnO nanocomposites could find potential applications in the biomedical field and in the development of high strength rubber composites.     

The influence of molecular structure modification on the photoluminescence and optical absorption of thin copper phthalocyanine films in the near-IR range

We have studied the luminescence and optical absorption of thin films of copper phthalocyanine (CuPc) with a modified molecular structure of the peripheral fragments. The coefficient of absorption in the near-IR and visible range (absorption by defects) and the photoluminescence spectra exhibit correlated changes depending on the modification of the CuPc structure.     

hp-version discontinuous Galerkin methods for hyperbolic conservation laws: A parallel adaptive strategy

This paper describes a parallel algorithm based on discontinuous hp-finite element approximations of linear, scalar, hyperbolic conservation laws. The paper focuses on the development of an effective parallel adaptive strategy for such problems. Numerical experiments suggest that these techniques are highly parallelizable and exponentially convergent, thereby yielding efficiency many times superior to conventional schemes for hyperbolic problems.