Most biomechanical studies on bicycle ergonomics focused on racing efficiency and often neglected the investigation of cycling comfort, due to the difficulties related to the people's subjective ...feelings. This research work aims at analyzing the comfort on bicycle from an objective viewpoint; specifically, an attempt to relate subject's preferences, determined in a dynamic way, with his/her physical features, acquired by means of anthropometric measurements, was carried out. The validity of some existing and commonly used "rules of thumb" for bicycle fitting is discussed and investigated, and new indications are also proposed to achieve an optimal bike configuration.
A group of 120 volunteers was considered in this study; they were non-professional cyclists. First, the participants' anthropometric features were acquired; afterwards, the volunteers were asked to cycle on a bicycle fitting system (adjustable gym bike) and then to modify the simulator settings till the optimal subjective feelings of comfort are reached. The linear correlation coefficient between the measured anthropometric features and the geometrical preferences adopted on the cycling simulator was calculated.
On one hand, the data analysis allows to propose new indications to achieve an optimal postural comfort on the basis of the physical features of the subject, but, on the other hand, the results confirm that the comfort on bicycles is highly related to personal preferences and, therefore, it is strongly subjective.
The main conclusions and implications of this study can be summarized as follows: 1) the comfort on bicycle is strongly subjective as it is highly related to personal preferences; 2) an optimal bicycle setting can be achieved only by taking in to account the most relevant anthropometric features of every single cyclist; 3) a station for acquiring cyclists' anthropometric measurements and a bicycle simulator (adjustable gym bike) can act as very useful tools for designing optimal and custom-made bicycle configurations.
Caffeine-photosensitized degradation has been studied in the presence of bio-based materials derived from urban biowaste after aerobic aging. A peculiar fraction (namely bio-based substances (BBSs)), ...soluble in all the pH range, has been used as photosensitizing agent. Several caffeine photodegradation tests have been performed, and positive results have been obtained in the presence of BBSs and H
2
O
2
, without and with additional Fe(II) (photo-Fenton-like process). Moreover, hybrid magnetite-BBS nanoparticles have been synthesized and characterized, in order to improve the sensitizer recovery and reuse after the caffeine degradation. In the presence of such nanoparticles and H
2
O
2
and Fe(II), the complete caffeine degradation has been attained in very short time. Both homogeneous and heterogeneous processes were run at pH = 5, milder condition compared to the classic photo-Fenton process.
This work focuses on the synthesis and characterization of a novel bioresorbable glass ceramic phosphate-based material (GC-ICEL). More specifically, its solubility in different aqueous media (water, ...Tris-HCl and acellular simulated body fluid) and the response of human stromal cells cultured on it were investigated. X-ray diffraction analysis showed the presence of two crystalline phases identified as Na2Mg(PO4)3 and Ca2P2O7 and dissolution tests highlighted a preferential dissolution of the Na2Mg(PO4)3 phase and of the residual amorphous phase in all the chosen media. Soaking tests in simulated body fluid showed precipitation of a hydroxyapatite layer, demonstrating the bioactivity of GC-ICEL, which is partially due to the reported bioactivity of Ca2P2O7. The effect of GC-ICEL on adhesion, proliferation and osteoblastic gene expression of human bone marrow-derived stromal cells was also studied. Combining molecular and biochemical analyses, it was found that bone marrow cell differentiation was stimulated over proliferation on GC-ICEL. Moreover, the expression of bone-related genes in cells cultured on GC-ICEL confirmed the bioactivity of this phosphate-based glass ceramic, which might have a stimulatory effect on osteogenesis.
Composite systems have been prepared, combining the drug up-take and release properties of MCM-41 silica sub-micron spheres with those of a bioactive glass–ceramic macroporous scaffold belonging to ...the SiO
2–CaO–K
2O (SCK) system (potentially able to promote successful osteointegration in tissue engineering).
The systems are prepared by dipping the glass–ceramic scaffold into the MCM-41 synthesis solution. To this purpose, the pH of the MCM-41 synthesis solution has been lowered with respect to the usual literature procedure to minimize the detrimental effects of the impregnation treatment on glass–ceramic scaffolds that were observed in a previous work by the author.
MCM-41–SCK composite scaffolds have been characterized by means of XRD, N
2 adsorption, thermogravimetry and Scanning Electron Microscopy (coupled with EDS analysis).
The adsorption capacity toward ibuprofen, tested as model drug, is three times higher than that of the MCM-41-free scaffold, because of the presence of the ordered mesoporous silica. Also the release behaviour in SBF at 37
°C is strongly affected by the presence of MCM-41 inside the scaffold macropores.
In this work we produced wollastonite-containing glass-ceramic coatings on alumina substrates by airbrush spraying of glass-based aqueous suspensions followed by sintering. Investigations by scanning ...electron microscopy revealed that layer-wise slurry deposition is a suitable technique to manufacture homogeneous and continuous bioceramic coatings without flaws or cracks at the coating/substrate interface. Coating thickness can be designed by controlling the number of spraying cycles. The bonding strength of the coating (about 22MPa) was found adequate for biomedical applications. A mechanical model based on the innovative concepts of quantized fracture mechanics was developed to predict the bonding strength and estimate the fracture toughness of the coating on the basis of experimental data from tensile tests. The approach proposed in this work can contribute to optimize the design and manufacturing of bioceramic coatings with the aim of improving their mechanical properties and suitability for clinical applications.
Silver nanocluster silica composite coatings were deposited by radio frequency co-sputtering technique on several substrates. This versatile method allows tailoring of silver content and ...antibacterial behaviour of coatings deposited on glasses, ceramics, metals and polymers for several applications. Coating morphology and composition as well as nanocluster size were analyzed by means of UV-Visible absorption, X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), electron dispersive spectroscopy (EDS), X-ray Photoelectron Spectroscopy (XPS) and Atomic Force Microscopy (AFM). The antibacterial effect was verified through the inhibition halo test against standard bacterial strain, Staphylococcus aureus, before and after sterilization process. Tape test demonstrated a good adhesion of the coatings to the substrates.
Ceramics for oculo-orbital surgery Baino, Francesco; Vitale-Brovarone, Chiara
Ceramics international,
05/2015, Letnik:
41, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Ceramics are an extremely versatile class of materials with an extraordinarily broad spectrum of applications, ranging from building industry to medicine. Ceramics began to be systematically ...investigated as implantable biomaterials in the 1950s and soon revealed surprising properties. Orthopaedics and dentistry are the preferred areas of surgical applications of ceramics, due to their suitable strength for load-bearing applications, wear resistance (e.g. alumina and alumina/zirconia composites) and, in some cases, bone-bonding ability (e.g. hydroxyapatite and bioactive glasses). Another clinical field where ceramics are playing a significant role is oculo-orbital surgery, a highly interdisciplinary medical area that focuses on the management of injured eye orbit, with particular regard to the repair of orbital floor/wall fractures and/or the placement of orbital implants after removal of a diseased eye. Especially in the latter case, implants are not intended for bone repair but have to be biointegrated in soft ocular tissues; therefore, suitable ceramics for this application are required to go beyond the “traditional” bone-bonding ability. This article provides a picture of the currently-used ceramics for such applications and explores new emerging perspectives, highlighting the promises for the future disclosed by the recent advances in nanobioceramics science.
In this work, the use of foam-like glass–ceramic scaffolds as trabecular coatings on ceramic prosthetic devices to enhance implant osteointegration is proposed. The feasibility of this innovative ...device was explored in a simplified, flat geometry: glass–ceramic scaffolds, prepared by polymeric sponge replication and mimicking the trabecular architecture of cancellous bone, were joined to alumina square substrates by a dense glass coating (interlayer). The role played by different formulations of starting glasses was examined, with particular care to the effect on the mechanical properties and bioactivity of the final coating. Microindentations at the coating/substrate interface and tensile tests were performed to evaluate the bonding strength between the sample’s components. In vitro bioactive behaviour was assessed by soaking in simulated body fluid and evaluating the apatite formation on the surface and inside the pores of the trabecular coating. The concepts disclosed in the present study can have a significant impact in the field of implantable devices, suggesting a valuable alternative to traditional, often invasive bone-prosthesis fixation.
One of the key purposes of bone tissue engineering is the development of new biomaterials that can stimulate the body's own regenerative mechanism for patient's anatomical and functional recovery. ...Bioactive glasses, due to their versatile properties, are excellent candidates to fabricate porous 3-D architectures for bone replacement. In this work, morphological and structural investigations are carried out on Bioglass®- and CEL2-derived scaffolds produced by sponge replication (CEL2 is an experimental glass developed at Politecnico di Torino). Synchrotron radiation X-ray microtomography is used to study the samples 3-D architecture, pores size, shape, distribution and interconnectivity, as well as the growth kinetics on scaffolds struts of a newly formed apatitic phase during in vitro treatment in simulated body fluid, in order to describe from a quantitative viewpoint the bioactive potential of the analyzed biomaterials. An accurate comparison between architectural features and bioactive behaviour of Bioglass®- and CEL2-derived scaffolds is presented and discussed.
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