The sources of Mill's views of ratiocination and induction

Steffen Ducheyne and John P. McCaskey (2014). “The Sources of Mill’s Views of Ratiocination and Induction,” in: Antis Loizides (ed.), John Stuart Mill’s ‘A System of Logic’: A Critical Guide (London, Routledge), pp. 63-8

The Sources of Mill’s View of Ratiocination and Induction

The philosophical background important to Mill’s theory of induction has two major components: Richard Whately’s introduction of the uniformity principle into inductive inference and the loss of the idea of formal cause

Reactions and Surface Transformations of a Bone-Bioactive Material in a Simulated Microgravity Environment

A comprehensive program to investigate the expeditious in vitro formation of three-dimensional bone-like tissue is currently underway at the University of Pennsylvania. The study reported here forms a part of that program. Three-dimensional bone-like tissue structures may be grown under the simulated microgravity conditions of NASA designed Rotating Wall Bioreactor Vessels (RWV's). Such tissue growth will have wide clinical applications. In addition, an understanding of the fundamental changes that occur to bone cells under simulated microgravity would yield important information that will help in preventing or minimizing astronaut bone loss, a major health issue with travel or stay in space over long periods of time. The growth of three-dimensional bone-like tissue structures in RWV's is facilitated by the use of microcarriers which provide structural support. If the microcarrier material additionally promotes bone cell growth, then it is particularly advantageous to employ such microcarriers. We have found that reactive, bone-bioactive glass (BBG) is an attractive candidate for use as microcarrier material. Specifically, it has been found that BBG containing Ca- and P- oxides upregulates osteoprogenitor cells to osteoblasts. This effect on cells is preceded by BBG reactions in solution which result in the formation of a Ca-P surface layer. This surface further transforms to a bone-like mineral (i.e., carbonated crystalline hydroxyapatite (c-HA)). At normal gravity, time-dependent, immersion-induced BBG reactions and transformations are greatly affected both by variations in the composition of the milieu in which the glass is immersed and on the immersion conditions. However, the nature of BBG reactions and phase transformations under the simulated microgravity conditions of RWV's are unknown, and must be understood in order to successfully use BBG as microcarrier material in RWV'S. In this paper, we report some of our recent findings in this regard using experimental and numerical methods. BBG composition 45S5, the most reactive among known bone-bioactive glasses, was chosen for the study. BBG 45S5 behavior in physiological solutions was tested in simulated microgravity and compared with that at normal gravity. On the basis of our numerical study, we have chosen the BBG granule size to be in the range 40-70 microns, and a RWV rotational speed of 10 rpm. Our numerical study has shown that these parameters enable the microcarrier to remain suspended in the medium without experiencing collisions with the wall of the vessel. Immersion-induced changes in the solution composition and the material surface were analyzed after immersion

The effect of starch and starch-bioactive glass composite microparticles on the adhesion and expression of the osteoblastic phenotype of a bone cell line

There is a clear need for the development of microparticles that can be used simultaneously as carriers of stem/progenitor cells and as release systems for bioactive agents, such as growth factors or differentiation agents. In addition, when thinking on bone-tissueengineering applications, it would be very useful if these microparticles are biodegradable and could be made to be bioactive. Microparticles with all those characteristics could be cultured together with adherent cells in appropriate bioreactors to form in vitro constructs that can then be used in tissue-engineering therapies. In this work, we have characterized the response of MC3T3-E1 pre-osteoblast cells to starch-based microparticles. We evaluated the adhesion, proliferation, expression of osteoblastic markers and mineralization of cells cultured at their surface. The results clearly show that MC3T3-E1 pre-osteoblast cells adhere to the surface of both polymeric and composite starch-based microparticles and express the typical osteoblastic marker genes. Furthermore, the cells were found to mineralize the extracellular matrix (ECM) during the culture period. The obtained results indicate that starch-based microparticles, known already to be biodegradable, bioactive and able to be used as carriers for controlled release applications, can simultaneously be used as carriers for cells. Consequently, they can be used as templates for forming hybrid constructs aiming to be applied in bone-tissue-engineering applications

Starch-based microparticles as vehicles for the delivery of active platelet-derived growth factor

In a previous work, we described the use of starch-based microparticles as vehicles for the controlled release of corticosteroids. The goal of the present work is to evaluate the potential of these microparticles to incorporate and release platelet-derived growth factor (PDGF). The loading efficiency and release profile were evaluated, and PDGF was incorporated into and released from the matrix of starch-based microparticles. The release profile shows rapid release of PDGF in the first 24 h, after which there was a slow but constant release for up to 8 weeks. The maintenance of the PDGF biological activity after incorporation and release was evaluated by itsmitogenic effect over osteoblastic cells, and it was shown to be comparable to that of PDGF supplemented to the culture medium. This proves that the incorporation and release did not affect the biological activity of the growth factor (GF). The results clearly demonstrate that starchbased microparticles are suitable vehicles for the incorporation and release of GFs. When combined with previous results, these materials also suggest their ability to enhance the regenerating potential of tissue engineering hybrid constructs

Starch-based microparticles as carriers for the delivery of platelet-derived growth factor aimed to stimulate the proliferation of osteoblastic-like cells

We have previously shown that starch-based microparticles are bioactive [1], serve as substrates for the culture of osteoblast-like cells [2], and are suitable for controlled release applications [3]. In this way, we postulate that if we combine these different properties we could generate hybrid constructs with enhanced properties. Hence, we describe herein the encapsulation and release of Platelet-Derived Growth Factor (PDGF), as well as its mitogenic effect over osteoblast-like cells. PDGF was encapsulated into starch-based microparticles composed of a blend of 50:50 (wt/wt) starch with polylactic acid (SPLA). The loaded microparticles were tested for released PDGF up to 8 weeks and the released PDGF was quantified using ELISA specific for this growth factor. Bioactivity of released PDGF was assessed using a mouse calvaria cell line (MC3T3-E1) possessing a pre-osteoblastic phenotype. PDGF could be effectively encapsulated into SPLA microparticles. The release profile of PDGF shows there is a burst release in the first hours, and then a reduction in the released levels, with a steady release after 7 days. The release was quantified up to 8 weeks, with reduced, steady-level amounts being released. This release profile is typical for hydrophilic, biodegradable polymers, where the water uptake controls the first release stages, where the encapsulated agent is released by diffusion. In this particular application this behavior is desirable, since PDGF mitogenic effect over osteoblasts is only observed with an intermittent, higher-level supplementation, followed by a low-level, continuous one. The released PDGF bioactivity, evaluated by the response of MC3T3-E1 cells to culture medium supplemented with a defined dosage of either exogenous or released PDGF, reveals that PDGF encapsulated and released from SPLA microparticles is capable of stimulating the proliferation of MC3T3-E1 cells in levels comparable to those of exogenous PDGF. Both conditions significantly enhance the proliferation of osteoblastic cells, as compared to control conditions. In conclusion, we clearly demonstrate the potential of starch-based microparticles to be used as carriers for growth factors. These systems encapsulate, release and maintain the bioactivity of the entrapped growth factor. PDGF was effectively released in a defined profile compatible with the final goal of stimulating the proliferation of cells within a hybrid construct aimed to be used in tissue engineering applications.FCT (SFRH/BD/2001/4698) and European Union funded STREP Project Hippocrates (NNM-3-CT-2003-505758)

Elastic Membrane That Undergoes Mechanical Deformation Enhances Osteoblast Cellular Attachment and Proliferation

The main objective of this paper was to investigate the effect of transmission of force on bone cells that were attached to a deformable membrane. We functionalized a silastic membrane that measured 0.005 inches thickness and coated it with an extra cellular matrix (ECM) protein, fibronectin (FN). MC3T3-E1 osteoblast-like cells were cultured on the functionalized FN-coated membrane after which cell attachment and proliferation were evaluated. We observed an immediate attachment and proliferation of the bone cells on the functionalized membrane coated with FN, after 24 hours. Upon application of a mechanical force to cells cultured on the functionalized silicone membrane in the form of a dynamic equibiaxial strain, 2% magnitude; at 1-Hz frequency for 2 h, the osteoblast cells elicited slightly elevated phalloidin fluorescence, suggesting that there was reorganization of the cytoskeleton. We concluded from this preliminary data obtained that the engineered surface transduced applied mechanical forces directly to the adherent osteoblast cells via integrin binding tripeptide receptors, present in the FN molecules, resulting in the enhanced cellular attachment and proliferation

Microstructural refinement of β-sintered and Ti-6Al-4V porous-coated by temporary alloying with hydrogen

A series of thermochemical treatments, in which hydrogen was used as a temporary alloying element to refine the lamellar microstructure of β-sintered and porous-coated Ti-6Al-4V was formulated. Each step of the treatment sequence (hydrogenation, eutectoid decomposition and dehydrogenation) was studied separately, on uncoated specimens and then on porous-coated specimens. The resultant microstructures can have α-grain sizes less than 1 μm, aspect ratios near unity and discontinuous grain boundary α (GBα), microstructural attributes which increase the fatigue strength. Microstructural refinement occurs because hydrogen-alloying reduces the (α+β)↔β transition temperature and enables a eutectoid decomposition reaction to occur. The optimal hydrogenation temperature is 850 °C, because hydrogen concentrations of 0.71 to 0.85 wt% are in-diffused and β-transformation is achieved. These weight percentages are in the optimal range for efficient eutectoid decomposition kinetics, β-transformation obviates the need for a separate β-transformation treatment step. A separate eutectoid decomposition treatment step may be used, or eutectoid decomposition may be combined with dehydrogenation. The finest eutectoid microstructures are obtained if hydrogen concentrations are in the range 0.5 to 0.8 wt%. The criteria for dehydrogenation are efficient removal of hydrogen, with minimal grain growth and absence of GBα. These criteria are best met by using dehydrogenation temperatures <700 °C. Altering the sintering temperature or adding a porous coating does not affect the parameters of the hydrogen-alloying treatment steps.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44704/1/10853_2004_Article_BF00576555.pd

Acoustic emission during fatigue of Ti-6Al-4V: Incipient fatigue crack detection limits and generalized data analysis methodology

The fundamentals associated with acoustic emission monitoring of fatigue crack initiation and propagation of Ti-6Al-4V were studied. Acoustic emission can detect and locate incipient fatigue crack extensions of approximately 10 μm. The technique therefore can serve as a sensitive warning to material failure. There are three distinct stages during which acoustic emission is generated. These stages are: crack initiation, slow crack propagation and rapid crack propagation. The distinction between the stages is based primarily on the rate of acoustic emission event accumulation. These three stages of acoustic emission correspond to the three stages of the failure process that occurs during fatigue loading. That is, changes in acoustic emission event rate correspond to changes in crack extension rate. Acoustic emission event intensities are greater during crack initiation than during slow crack propagation and greatest during rapid crack propagation. In a given fatigue cycle, event intensities increase with increasing stress and most high-intensity events occur near or at the maximum stress. Acoustic emission may therefore be used with confidence to detect, monitor and anticipate failure, in real-time.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44713/1/10853_2005_Article_BF01116003.pd

Suitability of European climate for the Asian tiger mosquito Aedes albopictus: recent trends and future scenarios

The Asian tiger mosquito (Aedes albopictus) is an invasive species that has the potential to transmit infectious diseases such as dengue and chikungunya fever. Using high-resolution observations and regional climate model scenarios for the future, we investigated the suitability of Europe for A. albopictus using both recent climate and future climate conditions. The results show that southern France, northern Italy, the northern coast of Spain, the eastern coast of the Adriatic Sea and western Turkey were climatically suitable areas for the establishment of the mosquito during the 1960–1980s. Over the last two decades, climate conditions have become more suitable for the mosquito over central northwestern Europe (Benelux, western Germany) and the Balkans, while they have become less suitable over southern Spain. Similar trends are likely in the future, with an increased risk simulated over northern Europe and slightly decreased risk over southern Europe. These distribution shifts are related to wetter and warmer conditions favouring the overwintering of A. albopictus in the north, and drier and warmer summers that might limit its southward expansion