Production of hard tissue scaffolds using three-dimensional printing method

Synthesised bone replacement scaffolds provide the possibility to individually tailor properties, overcome limited donor availability and improve osteointegration. The aim of bone tissue engineering is to provide solutions to these problems by making available high quality transplants that can be supplied in larger quantities. In these applications both the internal and external geometry of the scaffold are very important since they have significant effect on mechanical properties, permeability and cell proliferation. Rapid Prototyping technologies allow the use of customised materials with predetermined and optimised geometries to be fabricated with good accuracy. This work investigates the ability of the 3D printing technology to manufacture intricate bone scaffold geometries from biocompatible calcium phosphate based materials. Initial investigations with the proprietary materials showed that predicted directional mechanical behaviour can be realised. Practical measurements investigating the directional mechanical properties of the manufactured samples showed trends identical with the results of the Finite Element Analysis (FEA). The ability of 3D Printing technology to fabricate tissue engineering scaffold geometries made of biocompatible calcium phosphate cements was also demonstrated in this work. Scaffolds were manufactured by printing aqueous sodium phosphate dibasic solution on the powder bed consisting of a homogeneous mixture of dicalcium phosphate and calcium hydroxide. The wet-chemical reaction of precipitation took place in the powder bed of the 3D Printer. Solid specimens were manufactured in order to measure the bulk compressive mechanical properties of the fabricated Calcium Phosphate Cement (CPC). The average elastic modulus for the so produced parts was 3.59 MPa, and the average compressive strength was 0.147 MPa. Sintering resulted in significantly increased compressive properties (E = 9.15 MPa, σy = 0.483 MPa), but it decreased the specific surface area of the material. As a result of sintering, the calcium phosphate cement decomposed to β-Tricalcium Phosphate (β-TCP) and Hydroxyapatite (HA) as confirmed by Thermogravimetric Analysis and Differential Thermal Analysis (TGA/DTA) as well as with X-Ray Diffraction (XRD). The obtained mechanical properties are not sufficient for high load bearing implants, where the required strength in ranging between 1.5 -150 MPa and compressive stiffness is above 10 MPa. However further post processing such as infiltration with biodegradable polymers may allow these structures to be used for scaffold applications

Functional definition of the N450 event-related brain potential marker of conflict processing: a numerical stroop study

BACKGROUND: Several conflict processing studies aimed to dissociate neuroimaging phenomena related to stimulus and response conflict processing. However, previous studies typically did not include a paradigm-independent measure of either stimulus or response conflict. Here we have combined electro-myography (EMG) with event-related brain potentials (ERPs) in order to determine whether a particularly robust marker of conflict processing, the N450 ERP effect usually related to the activity of the Anterior Cingulate Cortex (ACC), is related to stimulus- or to response-conflict processing. EMG provided paradigm-independent measure of response conflict. In a numerical Stroop paradigm participants compared pairs of digits and pressed a button on the side where they saw the larger digit. 50% of digit-pairs were preceded by an effective cue which provided accurate information about the required response. 50% of trials were preceded by a neutral cue which did not communicate the side of response. RESULTS: EMG showed that response conflict was significantly larger in neutrally than in effectively cued trials. The N450 was similar when response conflict was high and when it was low. CONCLUSIONS: We conclude that the N450 is related to stimulus or abstract, rather than to response conflict detection/resolution. Findings may enable timing ACC conflict effects.This research has been supported by a grant from the Medical Research Council (G90951)

An ALMA Survey of faint disks in the Chamaeleon I star-forming region: Why are some Class II disks so faint?

ALMA surveys of nearby star-forming regions have shown that the dust mass in the disk is correlated with the stellar mass, but with a large scatter. This scatter could indicate either different evolutionary paths of disks or different initial conditions within a single cluster. We present ALMA Cycle 3 follow-up observations for 14 Class II disks that were low S/N detections or non-detections in our Cycle 2 survey of the $\sim 2$ Myr-old Chamaeleon I star-forming region. With 5 times better sensitivity, we detect millimeter dust continuum emission from six more sources and increase the detection rate to 94\% (51/54) for Chamaeleon I disks around stars earlier than M3. The stellar-disk mass scaling relation reported in \citet{pascucci2016} is confirmed with these updated measurements. Faint outliers in the $F_{mm}$--$M_*$ plane include three non-detections (CHXR71, CHXR30A, and T54) with dust mass upper limits of 0.2 M$_\oplus$ and three very faint disks (CHXR20, ISO91, and T51) with dust masses $\sim 0.5$ M$_\oplus$. By investigating the SED morphology, accretion property and stellar multiplicity, we suggest for the three millimeter non-detections that tidal interaction by a close companion ($<$100 AU) and internal photoevaporation may play a role in hastening the overall disk evolution. The presence of a disk around only the secondary star in a binary system may explain the observed stellar SEDs and low disk masses for some systems.Comment: ApJ accepte

Representational change and strategy use in children's number line estimation during the first years of primary school

BACKGROUND: The objective of this study was to scrutinize number line estimation behaviors displayed by children in mathematics classrooms during the first three years of schooling. We extend existing research by not only mapping potential logarithmic-linear shifts but also provide a new perspective by studying in detail the estimation strategies of individual target digits within a number range familiar to children. METHODS: Typically developing children (n = 67) from Years 1-3 completed a number-to-position numerical estimation task (0-20 number line). Estimation behaviors were first analyzed via logarithmic and linear regression modeling. Subsequently, using an analysis of variance we compared the estimation accuracy of each digit, thus identifying target digits that were estimated with the assistance of arithmetic strategy. RESULTS: Our results further confirm a developmental logarithmic-linear shift when utilizing regression modeling; however, uniquely we have identified that children employ variable strategies when completing numerical estimation, with levels of strategy advancing with development. CONCLUSION: In terms of the existing cognitive research, this strategy factor highlights the limitations of any regression modeling approach, or alternatively, it could underpin the developmental time course of the logarithmic-linear shift. Future studies need to systematically investigate this relationship and also consider the implications for educational practice.This research was conducted as part of the PhD project completed by Sonia White at the University of Cambridge, who was supported by the Cambridge Commonwealth Trust. This research was also partly funded by the Medical Research Council, Ref. G90951

A critical analysis of design, facts, bias and inference in the approximate number system training literature: A systematic review

© 2016 Elsevier GmbHA popular suggestion states that an evolutionarily grounded analogue magnitude representation, also called an approximate number system (ANS) or ‘number sense’ underlies human mathematical knowledge. During recent years many studies aimed to train the ANS with the intention of transferring improvements to symbolic arithmetic. Here we critically evaluate all published studies. We conclude that there is no conclusive evidence that specific ANS training improves symbolic arithmetic. We provide a citation analysis demonstrating that highly controversial results often get cited in support of specific claims without discussion of controversies. We suggest ways to run future training studies so that clear evidence can be collected and also suggest that data should be discussed considering both supporting and contrary evidence and arguments

Food additives and consumer preferences: A cross-cultural choice based conjoint analysis

Important differences have been reported in several countries about the level of concern in connection with food additives. In order to better understand the consumer preferences related to foodstuffs containing food additives, five hypotheses were tested with the help of a choice-based conjoint analysis. The study was performed in three European countries (Hungary, Romania, and Spain) having different risk perceptions concerning food additives. Two “model foodstuffs” were involved in the analysis: pre-packed sliced cheese (natural image) and chips (artificial image). For the creation of the conjoint cards, three attributes were selected: “preservatives” (natural/artificial), “packaging gases” (contains/does not contain) and “price” (average based on market data/+10%/+20%). Results were collected via Internet simultaneously and a total of 500 valid questionnaires were received in case of pre-packed cheese and 468 regarding chips. In the analysed countries “preservatives” had an outstanding importance — mainly in Hungary and Romania —, while “packaging gases” got lower importance during the shopping intention. “Natural preservatives” very positively contributed to the choosing of both pre-packed sliced cheese and chips. High level of willingness to pay was not observed, as well as the “price” was less important factor than the additives. Comparison of the data from three countries showed notable differences, which can determine the direction of the product planning and development

A comparison of three techniques (local anesthetic deposited circumferential to vs. above vs. below the nerve) for ultrasound guided femoral nerve block

Background: Fractured neck of femur generally requires operative fixation and is a common cause of admission to hospital. The combination of femoral nerve block and spinal anesthesia is a common anesthetic technique used to facilitate the surgical procedure. The optimal disposition of local anesthetic (LA) relative the femoral nerve (FN) has not been defined. Our hypothesis was: that the deposition of LA relative to the FN influences the quality of analgesia for positioning of the patient for performance of spinal anesthesia. The primary outcome was verbal rating (VRS) pain scores 0–10 assessed immediately after positioning the patient to perform spinal anesthesia. Methods: With Institutional ethical approval and having obtained written informed consent from each, 52 patients were studied. The study was registered with ClinicalTrials.gov (NCT01527812). Patients were randomly allocated to undergo to one of three groups namely: intention to deposit lidocaine 2% (15 ml) i. above (Group A), ii. below (Group B), iii. circumferential (Group C) to the FN. A blinded observer assessed i. the sensory nerve block (cold) in the areas of the terminal branches of the FN and ii. VRS pain scores on passive movement from block completion at 5 minutes intervals for 30 minutes. Immediately after positioning the patient for spinal anesthesia, VRS pain scores were recorded. Results: Pain VRS scores during positioning were similar in the three groups [Above group/Below group/Circumferential group: 2(0–9)/0(0–10)/3(0–10), median(range), p:0.32]. The block was deemed to have failed in 20%, 47% and 12% in the Above group, Below group and Circumferential group respectively. The median number of needle passes was greater in the Circumferential group compared with the Above group (p:0.009). Patient satisfaction was greatest in the Circumferential group [mean satisfaction scores were 83.5(19.8)/88.1(20.5)/93.8(12.3), [mean(SD), p=0.04] in the Above, Below and Circumferential groups respectively. Conclusions: We conclude that there is no clinical advantage to attempting to deposit LA circumferential to the femoral nerve (relative to depositing LA either above or below the nerve), during femoral nerve block in this setting

Symbolic number: the integration of magnitude and spatial representations in children aged 6 to 8 years

The process of learning symbolic Arabic digits in early childhood requires that magnitude and spatial information integrates with the concept of symbolic digits. Previous research has separately investigated the development of automatic access to magnitude and spatial information from symbolic digits. However, developmental trajectories of symbolic number knowledge cannot be fully understood when considering components in isolation. In view of this, we have synthesized the existing lines of research and tested the use of both magnitude and spatial information with the same sample of British children in Years 1, 2, and 3 (6-8 years of age). The physical judgment task of the numerical Stroop paradigm demonstrated that automatic access to magnitude was present from Year 1 and the distance effect signaled that a refined processing of numerical information had developed. Additionally, a parity judgment task showed that the onset of the spatial-numerical association of response codes effect occurs in Year 2. These findings uncover the developmental timeline of how magnitude and spatial representations integrate with symbolic number knowledge during early learning of Arabic digits and resolve inconsistencies between previous developmental and experimental research lines

Activation of transglutaminase and production of protein-bound gamma-glutamylhistamine in stimulated mouse mast cells

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The illusion of replacement in research into the development of thinking biases: the case of the conjunction fallacy

The conjunction fallacy is a violation of a very basic rule of probability. Interestingly, although committing the fallacy seems irrational, adults are no less susceptible to the fallacy than young children. In Experiment 1, by employing tasks where the conjunctive response option involved two non-representative items, we found a large reduction in fallacy rates as compared to traditional conjunction fallacy problems. Nevertheless, fallacy rates remained relatively high in both adolescents and adults, although adults showed more consistency in their normative responses. In Experiment 2, we demonstrated that children’s relatively good performance on the task was not the consequence of their missing knowledge of social stereotypes. Additionally, children were more strongly affected by explicitly presented frequency information than adults. Indeed, adults only took frequency information into account when frequencies were made relevant by a training in probabilistic reasoning. Overall, the results suggest that whereas the potential for normative reasoning increases with development, this potential is often overshadowed by a pervasive tendency in adolescence and adulthood to rely on contextual information, knowledge, and beliefs, even when conflicting information is available. By contrast, children are more strongly influenced by explicitly presented information than relevant knowledge cued by the tasks.This research, and the writing of this paper, was partially supported by a UK Economic and Social Research Council post-doctoral fellowship [PTA-026-27-2989] to KM