Fujishima and Honda (1972) demonstrated the potential of titanium dioxide (TiO2) semiconductor materials to split water into hydrogen and oxygen in a photo-electrochemical cell. Their work triggered the development of semiconductor photocatalysis for a wide range of environmental and energy applications. One of the most significant scientific and commercial advances to date has been the development of visible light active (VLA) TiO2 photocatalytic materials. In this review, a background on TiO2 structure, properties and electronic properties in photocatalysis is presented. The development of different strategies to modify TiO2 for the utilization of visible light, including non metal and/or metal doping, dye sensitization and coupling semiconductors are discussed. Emphasis is given to the origin of visible light absorption and the reactive oxygen species generated, deduced by physicochemical and photoelectrochemical methods. Various applications of VLA TiO2, in terms of environmental remediation and in particular water treatment, disinfection and air purification, are illustrated. Comprehensive studies on the photocatalytic degradation of contaminants of emerging concern, including endocrine disrupting compounds, pharmaceuticals, pesticides, cyanotoxins and volatile organic compounds, with VLA TiO2 are discussed and compared to conventional UV-activated TiO2 nanomaterials. Recent advances in bacterial disinfection using VLA TiO2 are also reviewed. Issues concerning test protocols for real visible light activity and photocatalytic efficiencies with different light sources have been highlighted.

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A review on the visible light active titanium dioxide photocatalysts for environmental applications

Hydrogel delivery systems can leverage therapeutically beneficial outcomes of drug delivery and have found clinical use. Hydrogels can provide spatial and temporal control over the release of various therapeutic agents, including small-molecule drugs, macromolecular drugs and cells. Owing to their tunable physical properties, controllable degradability and capability to protect labile drugs from degradation, hydrogels serve as a platform in which various physiochemical interactions with the encapsulated drugs control their release. In this Review, we cover multiscale mechanisms underlying the design of hydrogel drug delivery systems, focusing on physical and chemical properties of the hydrogel network and the hydrogel-drug interactions across the network, mesh, and molecular (or atomistic) scales. We discuss how different mechanisms interact and can be integrated to exert fine control in time and space over the drug presentation. We also collect experimental release data from the literature, review clinical translation to date of these systems, and present quantitative comparisons between different systems to provide guidelines for the rational design of hydrogel delivery systems.

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Designing hydrogels for controlled drug delivery.

Nature’s hierarchical materials

Additive manufacturing (AM) alias 3D printing translates computer-aided design (CAD) virtual 3D models into physical objects. By digital slicing of CAD, 3D scan, or tomography data, AM builds objects layer by layer without the need for molds or machining. AM enables decentralized fabrication of customized objects on demand by exploiting digital information storage and retrieval via the Internet. The ongoing transition from rapid prototyping to rapid manufacturing prompts new challenges for mechanical engineers and materials scientists alike. Because polymers are by far the most utilized class of materials for AM, this Review focuses on polymer processing and the development of polymers and advanced polymer systems specifically for AM. AM techniques covered include vat photopolymerization (stereolithography), powder bed fusion (SLS), material and binder jetting (inkjet and aerosol 3D printing), sheet lamination (LOM), extrusion (FDM, 3D dispensing, 3D fiber deposition, and 3D plotting), and 3D bioprinting....

Polymers for 3D Printing and Customized Additive Manufacturing

MUCKE aims to mine a large volume of images, to structure them conceptually and to use this conceptual structuring in order to improve large-scale image retrieval. The last decade witnessed important progress concerning low-level image representations. However, there are a number problems which need to be solved in order to unleash the full potential of image mining in applications. The central problem with low-level representations is the mismatch between them and the human interpretation of image content. This problem can be instantiated, for instance, by the incapability of existing descriptors to capture spatial relationships between the concepts represented or by their incapability to convey an explanation of why two images are similar in a content-based image retrieval framework. We start by assessing existing local descriptors for image classification and by proposing to use co-occurrence matrices to better capture spatial relationships in images. The main focus in MUCKE is on cleaning large scale Web image corpora and on proposing image representations which are closer to the human interpretation of images. Consequently, we introduce methods which tackle these two problems and compare results to state of the art methods. Note: some aspects of this deliverable are withheld at this time as they are pending review. Please contact the authors for a preview.

http://ieeexplore.ieee.org/iel2/4524/12820/00592460.pdf

Image Processing

Robust mapping of relaxation parameters in ex vivo tissues is based on hydration and therefore requires control of the tissue treatment to ensure tissue integrity and consistent measurement conditions over long periods of time. One way to maintain the hydration of ex vivo tendon tissue is to immerse the samples in a buffer solution. To this end, various buffer solutions have been proposed; however, many appear to influence the tissue relaxation times, especially with prolonged exposure. In this work, ovine Achilles tendon tissue was used as a model to investigate the effect of immersion in phosphate-buffered saline (PBS) and the effects on the T1 and T2* relaxation times. Ex vivo samples were measured at 0 (baseline), 30 and 67 hours after immersion in PBS. Ultrashort echo time (UTE) imaging was performed using variable flip angle and echo train-shifted multi-echo imaging for T1 and T2* estimation, respectively. Compared with baseline, both T1 and T2* relaxation time constants increased significantly after 30 hours of immersion. T2* continued to show a significant increase between 30 and 67 hours. Both T1 and T2* tended to approach saturation at 67 hours. These results exemplify the relevance of stringently controlled tissue preparation and preservation techniques, both before and during MRI experiments.

Immersion of Achilles tendon in phosphate-buffered saline influences T1 and T2* relaxation times: An ex vivo study

Loading conditions physiologically approximating those acting on the normal masticatory system were incorporated into a new mandibular load simulator. Separate tension wires attached to each ramus of the mandible simulated the resultant force vectors of the masticatory musculature. The muscle insertion points were chosen in accordance with the anatomical situation, and the maximum in vivo forces acting on the joint. In a first application, the stability of a 2.4 mm LC-WDCP was compared with that of a 2.7 mm EDCP in plastic mandible models. It was found that under largely physiological loading, the 2.4 mm LC-EDCP exerted a stabilizing effect similar to that of a 2.7 mm EDCP. Although of smaller dimensions, the 2.4 mm LC-EDCP appears to enable an osteosynthesis of similar stability in the treatment of fractures of the mandibular angle.

[Physiological loading of the mandibular osteosynthesis: development of an improved mandibular load simulator].

The knee is the largest and one of the most biomechanically demanded joints in the human body, as it is located between the two longest lever arms of the body and its most powerful muscles. Knee stability through the range of motion is ensured by both static and dynamic structures that work in concert to prevent excessive movement or instability, which may occur across multiple planes of motion. While offering a wide range of motions, these structures have to meticulously balance the compressive forces across the knee joint. Orientation, shape, and material properties of the bony structure and dynamic stabilizers, including ligaments, the capsule, and musculotendinous soft tissues, are essential for knee stability. Even small changes to any of these parameters will alter the inherently complex interactions between these structures and ultimately distort overall movement patterns of the knee, consequently impacting alignment, load distribution, and wear of the components forming the knee joint.

Load, Alignment, and Wear

While the axolotl's ability to completely regenerate amputated limbs is well known and studied, the mechanism of axolotl bone fracture healing remains poorly understood. One reason might be the lack of a standardized fracture fixation in axolotl. We present a surgical technique to stabilize the osteotomized axolotl femur with a fixator plate and compare it to a non-stabilized osteotomy and to limb amputation. The healing outcome was evaluated 3 weeks, 3, 6 and 9 months post-surgery by microcomputer tomography, histology and immunohistochemistry. Plate-fixated femurs regained bone integrity more efficiently in comparison to the non-fixated osteotomized bone, where larger callus formed, possibly to compensate for the bone fragment misalignment. The healing of a non-critical osteotomy in axolotl was incomplete after 9 months, while amputated limbs efficiently restored bone length and structure. In axolotl amputated limbs, plate-fixated and non-fixated fractures, we observed accumulation of PCNA+ proliferating cells at 3 weeks post-injury similar to mouse. Additionally, as in mouse, SOX9-expressing cells appeared in the early phase of fracture healing and amputated limb regeneration in axolotl, preceding cartilage formation. This implicates endochondral ossification to be the probable mechanism of bone healing in axolotls. Altogether, the surgery with a standardized fixation technique demonstrated here allows for controlled axolotl bone healing experiments, facilitating their comparison to mammals (mice). 

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The specialist in regeneration—the Axolotl—a suitable model to study bone healing?

Der umgangssprachlich oft verwendete Begriff „Stabilitat“ wird im Zusammenhang mit Osteosynthesen und Frakturheilung genutzt, um den mechanischen Begriff der Steifigkeit zu umschreiben. Die Steifigkeit einer Osteosynthese hat neben Frakturmorphologie und biologischen Voraussetzungen erheblichen Einfluss auf die Heilungrate und -geschwindigkeit der Fraktur, sowie die biomechanischen Eigenschaften des Frakturkallus. Durch die unterschiedlichen verfugbaren Osteosyntheseverfahren ist in Hinblick auf Fraktur und physiologische Beanspruchung und Belastung des betroffenen Knochens eine Osteosynthese anzustreben, welche die Frakturheilung durch ihre biomechanischem Eigenschaften unterstutzt. Dieser Artikel gibt eine Einfuhrung in mechanische einflusse auf die Frakturheilung sowie Eigenschaften der haufigsten Osteosyntheseverfahren.

https://www.thieme-connect.com/products/ejournals/pdf/10.1055/a-0755-6202.pdf

Georg N. Duda

Papers

Immersion of Achilles tendon in phosphate-buffered saline influences T1 and T2* relaxation times: An ex vivo study

[Physiological loading of the mandibular osteosynthesis: development of an improved mandibular load simulator].

Load, Alignment, and Wear

The specialist in regeneration—the Axolotl—a suitable model to study bone healing?

Knochenbruchheilung und klinische Belastungsstabilität