Bone tissue engineering : reconstruction of critical sized segmental bone defects in the ovine tibia

Well-established therapies for bone defects are restricted to bone grafts which face significant disadvantages (limited availability, donor site morbidity, insufficient integration). Therefore, the objective was to develop an alternative approach investigating the regenerative potential of medical grade polycaprolactone-tricalcium phosphate (mPCL-TCP) and silk-hydroxyapatite (silk-HA) scaffolds. Critical sized ovine tibial defects were created and stabilized. Defects were left untreated, reconstructed with autologous bone grafts (ABG) and mPCL-TCP or silk-HA scaffolds. Animals were observed for 12 weeks. X-ray analysis, torsion testing and quantitative computed tomography (CT) analyses were performed. Radiological analysis confirmed the critical nature of the defects. Full defect bridging occurred in the autograft and partial bridging in the mPCL-TCP group. Only little bone formation was observed with silk-HA scaffolds. Biomechanical testing revealed a higher torsional moment/stiffness (p < 0.05) and CT analysis a significantly higher amount of bone formation for the ABG group when compared to the silk-HA group. No significant difference was determined between the ABG and mPCL-TCP groups. The results of this study suggest that mPCL-TCP scaffolds combined can serve as an alternative to autologous bone grafting in long bone defect regeneration. The combination of mPCL-TCP with osteogenic cells or growth factors represents an attractive means to further enhance bone formation.

Atomistic investigations of single-crystal silicon with pre-existing defects

Molecular dynamics (MD) simulations have been employed to investigate the single-crystal Si properties with different pre-existing cavities under nanoindentation. Cavities with different radii and positions have been considered. It is found that pre-existing cavities in the Si substrate would obviously influence the mechanical properties of Si under nanoindentation. Furthermore, pre-existing cavities would absorb part of the strain energy during loading and then release during unloading. It would decrease plastic deformation to the substrate. Particularly, the larger of the cavity or the nearer of the cavity to the substrate’s top surface, the larger decrease of Young’s modulus and hardness is usually observed. Just as expected, the larger offset of the cavity in the lateral direction, the less influence is usually seen.

Effect of caffeine on adenosine-induced reversible perfusion defects assessed by automated analysis

Objectives This prospective study investigated the effects of caffeine ingestion on the extent of adenosine-induced perfusion abnormalities during myocardial perfusion imaging (MPI). Methods Thirty patients with inducible perfusion abnormalities on standard (caffeine-abstinent) adenosine MPI underwent repeat testing with supplementary coffee intake. Baseline and test MPIs were assessed for stress percent defect, rest percent defect, and percent defect reversibility. Plasma levels of caffeine and metabolites were assessed on both occasions and correlated with MPI findings. Results Despite significant increases in caffeine [mean difference 3,106 μg/L (95% CI 2,460 to 3,752 μg/L; P < .001)] and metabolite concentrations over a wide range, there was no statistically significant change in stress percent defect and percent defect reversibility between the baseline and test scans. The increase in caffeine concentration between the baseline and the test phases did not affect percent defect reversibility (average change −0.003 for every 100 μg/L increase; 95% CI −0.17 to 0.16; P = .97). Conclusion There was no significant relationship between the extent of adenosine-induced coronary flow heterogeneity and the serum concentration of caffeine or its principal metabolites. Hence, the stringent requirements for prolonged abstinence from caffeine before adenosine MPI—based on limited studies—appear ill-founded.

The persistence of phase-separation in LiFePO4 with two-dimensional Li+ transport : the Cahn-Hilliard-reaction equation and the role of defects

We examine the solution of the two-dimensional Cahn-Hilliard-reaction (CHR) equation in the xy plane as a model of Li+ intercalation into LiFePO4 material. We validate our numerical solution against the solution of the depth-averaged equation, which has been used to model intercalation in the limit of highly orthotropic diffusivity and gradient penalty tensors. We then examine the phase-change behaviour in the full CHR system as these parameters become more isotropic, and find that as the Li+ diffusivity is increased in the x direction, phase separation persists at high currents, even in small crystals with averaged coherency strain included. The resulting voltage curves decrease monotonically, which has previously been considered a hallmark of crystals that fill homogeneously.

Consecutive days of cold water immersion: effects on cycling performance and heart rate variability.

We investigated performance and heart rate (HR) variability (HRV) over consecutive days of cycling with post-exercise cold water immersion (CWI) or passive recovery (PAS). In a crossover design, 11 cyclists completed two separate 3-day training blocks (120 min cycling per day, 66 maximal sprints, 9 min time trialling [TT]), followed by 2 days of recovery-based training. The cyclists recovered from each training session by standing in cold water (10 °C) or at room temperature (27 °C) for 5 min. Mean power for sprints, total TT work and HR were assessed during each session. Resting vagal-HRV (natural logarithm of square-root of mean squared differences of successive R-R intervals; ln rMSSD) was assessed after exercise, after the recovery intervention, during sleep and upon waking. CWI allowed better maintenance of mean sprint power (between-trial difference [90 % confidence limits] +12.4 % [5.9; 18.9]), cadence (+2.0 % [0.6; 3.5]), and mean HR during exercise (+1.6 % [0.0; 3.2]) compared with PAS. ln rMSSD immediately following CWI was higher (+144 % [92; 211]) compared with PAS. There was no difference between the trials in TT performance (-0.2 % [-3.5; 3.0]) or waking ln rMSSD (-1.2 % [-5.9; 3.4]). CWI helps to maintain sprint performance during consecutive days of training, whereas its effects on vagal-HRV vary over time and depend on prior exercise intensity.

The effect of post-exercise hydrotherapy on subsequent exercise performance and heart rate variability

We investigated the effect of hydrotherapy on time-trial performance and cardiac parasympathetic reactivation during recovery from intense training. On three occasions, 18 well-trained cyclists completed 60 min high-intensity cycling, followed 20 min later by one of three 10-min recovery interventions: passive rest (PAS), cold water immersion (CWI), or contrast water immersion (CWT). The cyclists then rested quietly for 160 min with R-R intervals and perceptions of recovery recorded every 30 min. Cardiac parasympathetic activity was evaluated using the natural logarithm of the square root of mean squared differences of successive R-R intervals (ln rMSSD). Finally, the cyclists completed a work-based cycling time trial. Effects were examined using magnitude-based inferences. Differences in time-trial performance between the three trials were trivial. Compared with PAS, general fatigue was very likely lower for CWI (difference [90% confidence limits; -12% (-18; -5)]) and CWT [-11% (-19; -2)]. Leg soreness was almost certainly lower following CWI [-22% (-30; -14)] and CWT [-27% (-37; -15)]. The change in mean ln rMSSD following the recovery interventions (ln rMSSD(Post-interv)) was almost certainly higher following CWI [16.0% (10.4; 23.2)] and very likely higher following CWT [12.5% (5.5; 20.0)] compared with PAS, and possibly higher following CWI [3.7% (-0.9; 8.4)] compared with CWT. The correlations between performance, ln rMSSD(Post-interv) and perceptions of recovery were unclear. A moderate correlation was observed between ln rMSSD(Post-interv) and leg soreness [r = -0.50 (-0.66; -0.29)]. Although the effects of CWI and CWT on performance were trivial, the beneficial effects on perceptions of recovery support the use of these recovery strategies.

Influence of pre-exsiting surface defects on the vibrational properties of Ag nanowires

Large-scale molecular dynamics simulations are performed to characterize the effects of pre-existing surface defects on the vibrational properties of Ag nanowires. It is found that the first order natural frequency of the nanowire appears insensitive to different surface defects, indicating a defect insensitivity property of the nanowire’s Young’s modulus. In the meanwhile, an increase of the quality (Q)-factor is observed due to the presence of defects. Particular, a beat phenomenon is observed for the nanowire with the presence of a surface edge defect, which is driven by a single actuation. It is concluded that different surface defects could act as an effective mean to tune the vibrational properties of nanowires. This study sheds lights on the better understanding of nanowire’s mechanical performance when surface defects are presented, which would benefit the development of nanowire-based devices.

Striving to achieve best practice in heart failure disease management

Based on a national audit of chronic heart failure (CHF) management programmes (CHF-MPs) conducted in 2006, Driscoll et al identified a disproportionate distribution ranging from 0 to 4.2 programmes/million population in the various states of Australia with many programmes not following best practice.1 We welcome their proposal to develop national benchmarks for CHF management and acknowledge the contributions of the Heart Foundation and health professionals in finalising these recommendations.2 We would like to share the Queensland experience in striving towards best practice with the number of CHF-MPs increasing from four (at the time of the 2006 survey) to 23, equating to 5.0 programmes/million population. Queensland now has a state-wide heart failure service steering committee with a focus on the development of CHF-MPs supported by a central coordinator...

The effect of exercise on sleep quality in heart failure

Purpose The primary objective of this study was to examine the effect of exercise on subjective sleep quality in heart failure patients. Methods This study used a randomised, controlled trial design with blinded end-point analysis. Participants were randomly assigned to a 12-week programme of education and self-management support (control) or to the same programme with the addition of a tailored physical activity programme designed and supervised by an exercise specialist (intervention). The intervention consisted of 1 hour of aerobic and resistance exercise twice a week. Participants included 108 patients referred to three hospital heart failure services in Queensland, Australia. Results Patients who participated in supervised exercise classes showed significant improvement in subjective sleep quality, sleep latency, sleep disturbance and global sleep quality scores after 12 weeks of supervised hospital based exercise. Secondary analysis showed that improvements in sleep quality were correlated with improvements in geriatric depression score (p=0.00) and exercise performance (p=0.03). General linear models were used to examine whether the changes in sleep quality following intervention occurred independently of changes in depression, exercise performance and weight. Separate models adjusting for each covariate were performed. Results suggest that exercise significantly improved sleep quality independent of changes in depression, exercise performance and weight. Conclusion This study supports the hypothesis that a 12 week program of aerobic and resistance exercise improves subjective sleep quality in patients with heart failure. This is the first randomised controlled trial to examine the role of exercise in the improvement of sleep quality for patients with this disease. While this study establishes exercise as a therapy for poor sleep quality, further research is needed to investigate exercise as a treatment for other parameters of sleep in this population. Study investigators plan to undertake a more in-depth examination within the next 12 months

Drugs for hypertension, angina and heart failure

12.1 Drugs for hypertension 12.1.1 Epidemiology and pathophysiology 12.1.2 Diuretics for hypertension 12.2.3 Vasodilators for hypertension 12.4.4 β-Adrenoceptor blockers for hypertension 12.2. Drugs for angina 12.2.1 Typical angina 12.2.2 Drugs to treat an attack of typical angina 12,2.3 Drugs to prevent an attack of typical angina 12.2.4 Atypical angina 12.3 Drugs for heart failure 12.3.1 The heart failure epidemic 12.3.2 Compensatory changes in heart failure 12.3.3 Diuretics for heart failure 12.3.4 ACE inhibitors and AT1-receptor antagonists 12.3.5 β-adrenoceptor antagonists 12.3.6 Digoxin

Telephone support to rural and remote patients with heart failure : the Chronic Heart failure Assessment by Telephone (CHAT) study

Background Heart failure (HF) remains a condition with high morbidity and mortality. We tested a telephone support strategy to reduce major events in rural and remote Australians with HF, who have limited healthcare access. Telephone support comprised an interactive telecommunication software tool (TeleWatch) with follow-up by trained cardiac nurses. Methods Patients with a general practice (GP) diagnosis of HF were randomised to usual care (UC) or UC and telephone support intervention (UC+I) using a cluster design involving 143 GPs throughout Australia. Patients were followed for 12 months. The primary end-point was the Packer clinical composite score. Secondary end-points included hospitalisation for any cause, death or hospitalisation, as well as HF hospitalisation. Results Four hundred and five patients were randomised into CHAT. Patients were well matched at baseline for key demographic variables. The primary end-point of the Packer Score was not different between the two groups (P=0.98), although more patients improved with UC+I. There were fewer patients hospitalised for any cause (74 versus 114, adjusted HR 0.67 [95% CI 0.50-0.89], p=0.006) and who died or were hospitalised (89 versus 124, adjusted HR 0.70 [95% CI 0.53 – 0.92], p=0.011), in the UC+I vs UC group. HF hospitalisations were reduced with UC+I (23 versus 35, adjusted HR 0.81 [95% CI 0.44 – 1.38]), although this was not significant (p=0.43). There were 16 deaths in the UC group and 17 in the UC+I group (p=0.43). Conclusions Although no difference was observed in the primary end-point of CHAT (Packer composite score), UC+I significantly reduced the number of HF patients hospitalised amongst a rural and remote cohort. These data suggest that telephone support may be an efficacious approach to improve clinical outcomes in rural and remote HF patients.

Heart beats and economic decisions : Observing mental stress in the ultimatum bargaining game

One aim of experimental economics is to try to better understand human economic decision making. Early research of the ultimatum bargaining game (Gueth et al., 1982) revealed that other motives than pure monetary reward play a role. Neuroeconomic research has introduced the recording of physiological observations as signals of emotional responses. In this study, we apply heart rate variability (HRV) measuring technology to explore the behaviour and physiological reactions of proposers and responders in the ultimatum bargaining game. Since this technology is small and non-intrusive, we are able to run the experiment in a standard experimental economic setup. We show that low o�ers by a proposer cause signs of mental stress in both the proposer and the responder, as both exhibit high ratios of low to high frequency activity in the HRV spectrum.