MICROSTRUCTURAL EFFECTS ON THE PHASE TRANSITIONS AND THE THERMAL EVOLUTION OF ELASTIC AND PIEZOELECTRIC PROPERTIES IN HIGHLY DENSE, SUBMICRON-STRUCTURED NaNbO3 CERAMICS

The dielectric, piezoelectric and elastic coefficients, as well as the electromechanical coupling factors, of NaNbO3 submicron-structured ceramics have been obtained by an automatic iterative method from impedance measurements at resonance. Poled thin disks were measured from room temperature up to the depoling one, close to 300ºC. Dielectric thermal behaviour was determined also for unpoled ceramics up to the highest phase transition temperature. Ceramics were processed by hot-pressing from mechanically activated precursors. Microstructural effects on the properties are discussed. The suppression of the classical maximum in dielectric permittivity in unpoled ceramics at the phase transition at 370ºC was found when a bimodal distribution of grain sizes, in which a population of average grain size of 110 nm in between much coarser grains is observed. The appearance of a phase transition at 150ºC took place when Na vacancies are minimized. The occurrence of a non-centrosymmetric, ferroelectric phase, in the unpoled ceramic from room temperature to ~300ºC, highly polarisable resulting in high ferro-piezoelectric properties was also observed in the ceramic which presents grain size below 160 nm. Maximum values of kp=14%, d31=-8.7•10-12 C•N-1 and Np=3772 Hz•m at room temperature, and kp=18%, d31=-25.4•10-12 C•N-1 and Np=3722 Hz•m at 295ºC were achieved in the best processing conditions of the ceramics.Peer reviewe

Photoplethysmographic sensors for perfusion measurements in spinal cord tissue

Sensors for recording photoplethysmographic signals from the nervous tissue of the spinal cord are described. The purpose of these sensors is to establish whether perfusion is compromised in various states of injury which occur in certain animal models of spinal cord injury, for example compression injury. Various measures of perfusion are applicable such as the amplitude of the photoplethysmograph signal and the oxygen saturation, measured using a dual wavelength configuration. Signals are usually compared to baseline measurements made in uninjured subjects. This paper describes two types of probe, one based on optical fibres, and one in which optotes are placed in direct contact with the tissue surface. Results from a study based on a compression model utilising a fibreoptic sensor are presented

Optical measurement of blood flow changes in spinal cord injury

Little is known about cell death in spinal cord tissue following compression injury, despite compression being a key component of spinal injuries. Currently models are used to mimic compression injury in animals and the effects of the compression evaluated by observing the extent and duration of recovery of normal motor function in the days and weeks following the injury. A fibreoptic photoplethysmography system was used to investigate whether pulsation of the small arteries in the spinal cord occurred before, during and after compressive loads were applied to the tissue. It was found that the signal amplitudes were reduced and this reduction persisted for at least five minutes after the compression ceased. It is hoped that results from this preliminary study may improve knowledge of the mechanism of spinal cord injury

Obesity and asthma: an association modified by age

[Abstract] Background. Some studies indicate some causal relationship between obesity and asthma, while others show inconsistent results. Our objective was to evaluate the prevalence of asthma according to obesity in children. Methods. A cross-sectional study, following the ISAAC study methodology, was conducted on two randomly selected groups consisting of 6–7 year-old children (n = 7485) and 13–14 year-old adolescents (n = 8496). The asthma symptoms and potential risk factors were determined from the questionnaire. Overweight and obesity were defined based on the body mass index. Multiple logistic regression was used to obtain adjusted prevalence odds ratios (OR) and 95% confidence intervals. Results. Obesity was associated with an increase in wheezing ever (OR: 1.35) and exercise-induced asthma (OR: 1.62) in the 6–7 year-old group. No significant relationship was observed in the adolescent population. Conclusion. Obesity was associated with a higher prevalence of asthma in young children, but not in adolescents

Exposure to paracetamol and asthma symptoms

Multicenter study[Abstract] Background: Paracetamol is one of the factors that have been associated with the observed increase in asthma prevalence in the last few years. The influence of environmental or genetic factors in this disease may be different in some countries than in others. The purpose of this study was to analyse the relationship between the paracetamol consumption and asthma prevalence in our community. Methods: A cross-sectional study was conducted on more than 20,000 children and adolescents in Galicia, Spain. The International Study of Asthma and Allergies in Childhood methodology was used to collect the information on asthma symptoms in children, paracetamol consumption, body mass index (BMI), pets in the home, education level of the mother and parental asthma and smoking habits. The influence of paracetamol consumption on the prevalence of asthma symptoms was calculated using logistic regression, adjusted for the other parameters included in the study. Results: After adjusting for gender, BMI, having a cat or dog, maternal education, parental asthma and smoking, in 6- to 7-year-old children, the consumption of paracetamol during the first year of life is associated with asthma [odds ratio (OR) 2.04 (1.79-2.31) for wheezing at some time]. Paracetamol consumption in the previous year leads to a significant increase in the probability of wheezing at some time [OR 3.32 (2.51-4.41)] in young children and adolescents [OR 2.12 (1.68-2.67)]. Conclusions: Paracetamol consumption is associated with a significant increase in asthma symptoms. The effect is greater the more often the drug is taken

Impact of parental smoking on childhood asthma

[Abstract] Objective: To evaluate the exposure to environmental tobacco smoke (ETS) of the childhood population in this community and its relationship with asthma symptoms. Methods: A cross-sectional study was conducted using the International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire on children and adolescents in this community. The symptoms "wheezing ever", "current asthma", "severe asthma", and "exercise-induced asthma" were defined by this questionnaire. Parental smoking was classified into four mutually exclusive categories: 1) no parent smokes; 2) only the mother smokes; 3) only the father smokes; and 4) both parents smoke. The odds ratio of the prevalence of asthma symptoms according to ETS exposure was calculated using logistic regression. Results: A total of 10,314 children and 10,453 adolescents were included. Over 51% of the children and adolescents were exposed to ETS at home. ETS is associated with a higher prevalence of asthma symptoms, particularly if the mother or both parents smoke. Conclusion: The prevalence of ETS is still high in this community, although there has been a decreasing tendency in the last 15 years. ETS is associated with higher prevalence of asthma

Factors associated with therapeutic response in acromegaly diagnosed in the elderly in Spain

ContextSome reports suggest that acromegaly in elderly patients has a more benign clinical behavior and could have a better response to first-generation long-acting somatostatin receptor ligands (SRL). However, there is no specific therapeutic protocol for this special subgroup of patients. ObjectiveThis study aimed at identifying predictors of response to SRL in elderly patients. DesignMulticentric retrospective nationwide study of patients diagnosed with acromegaly at or over the age of 65 years. ResultsOne-hundred and eighteen patients (34 men, 84 women, mean age at diagnosis 71.7 +/- 5.4 years old) were included. Basal insulin-like growth factor type 1 (IGF-1) above the upper limit of normal (ULN) and growth hormone (GH) levels (mean +/- SD) were 2.7 +/- 1.4 and 11.0 +/- 11.9 ng/ml, respectively. The mean maximal tumor diameter was 12.3 +/- 6.4 mm, and up to 68.6% were macroadenoma. Seventy-two out of 118 patients (61.0%) underwent surgery as primary treatment. One-third of patients required first-line medical treatment due to a rejection of surgical treatment or non-suitability because of high surgical risk. After first-line surgery, 45/72 (63.9%) were in disease remission, and 16/34 (46.7%) of those treated with SRL had controlled disease. Patients with basal GH at diagnosis <= 6 ng/ml had lower IGF-1 levels and had smaller tumors, and more patients in this group reached control with SRL (72.7% vs. 33.3%; p < 0.04) [OR: 21.3, IC: 95% (2.4-91.1)], while male patients had a worse response [OR: 0.09, IC 95% (0.01-0.75)]. The predictive model curve obtained for SRL response showed an AUC of 0.82 CI (0.71-0.94). ConclusionsThe most frequent phenotype in newly diagnosed acromegaly in the elderly includes small adenomas and moderately high IGF-1 levels. GH at diagnosis <= 6 ng/ml and female gender, but not age per se, were associated with a greater chance of response to SRL

Natural history and surgical outcomes of Rathke’s cleft cysts: a Spanish multicenter study

Rathke’s cleft cysts (RCC) are a common type of lesion found in the sellar or suprasellar area. They are usually monitored clinically, but in some cases, surgery may be required. However, their natural progression is not yet well understood, and the outcomes of surgery are uncertain. The objective of this study is to evaluate the natural history of Rathke’s cleft cysts in patients who are clinically monitored without treatment, and to determine the outcomes of surgery and the incidence of recurrences over time.Design and patientsNational multicentric study of patients diagnosed of Rathke’s cleft cyst (RCC- Spain) from 2000 onwards and followed in 15 tertiary centers of Spain. A total of 177 patients diagnosed of RCC followed for 67.3 months (6–215) and 88 patients who underwent surgery, (81 patients underwent immediate surgery after diagnosis and 7 later for subsequent growth) followed for 68.8 months (3–235).ResultsThe cyst size remained stable or decreased in 73.5% (133) of the patients. Only 44 patients (24.3%) experienced a cyst increase and 9 of them (5.1%) experienced an increase greater than 3 mm. In most of the patients who underwent surgery headaches and visual alterations improved, recurrence was observed in 8 (9.1%) after a median time of 96 months, and no predictors of recurrence were discovered.ConclusionsRathke’s cleft cysts without initial compressive symptoms have a low probability of growth, so conservative management is recommended. Patients who undergo transsphenoidal surgery experience rapid clinical improvement, and recurrences are infrequent. However, they can occur after a long period of time, although no predictors of recurrence have been identified

Why Are Outcomes Different for Registry Patients Enrolled Prospectively and Retrospectively? Insights from the Global Anticoagulant Registry in the FIELD-Atrial Fibrillation (GARFIELD-AF).

Background: Retrospective and prospective observational studies are designed to reflect real-world evidence on clinical practice, but can yield conflicting results. The GARFIELD-AF Registry includes both methods of enrolment and allows analysis of differences in patient characteristics and outcomes that may result. Methods and Results: Patients with atrial fibrillation (AF) and ≥1 risk factor for stroke at diagnosis of AF were recruited either retrospectively (n = 5069) or prospectively (n = 5501) from 19 countries and then followed prospectively. The retrospectively enrolled cohort comprised patients with established AF (for a least 6, and up to 24 months before enrolment), who were identified retrospectively (and baseline and partial follow-up data were collected from the emedical records) and then followed prospectively between 0-18 months (such that the total time of follow-up was 24 months; data collection Dec-2009 and Oct-2010). In the prospectively enrolled cohort, patients with newly diagnosed AF (≤6 weeks after diagnosis) were recruited between Mar-2010 and Oct-2011 and were followed for 24 months after enrolment. Differences between the cohorts were observed in clinical characteristics, including type of AF, stroke prevention strategies, and event rates. More patients in the retrospectively identified cohort received vitamin K antagonists (62.1% vs. 53.2%) and fewer received non-vitamin K oral anticoagulants (1.8% vs . 4.2%). All-cause mortality rates per 100 person-years during the prospective follow-up (starting the first study visit up to 1 year) were significantly lower in the retrospective than prospectively identified cohort (3.04 [95% CI 2.51 to 3.67] vs . 4.05 [95% CI 3.53 to 4.63]; p = 0.016). Conclusions: Interpretations of data from registries that aim to evaluate the characteristics and outcomes of patients with AF must take account of differences in registry design and the impact of recall bias and survivorship bias that is incurred with retrospective enrolment. Clinical Trial Registration: - URL: http://www.clinicaltrials.gov . Unique identifier for GARFIELD-AF (NCT01090362)