To send content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about sending content to .
To send content items to your Kindle, first ensure email@example.com
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about sending to your Kindle.
Note you can select to send to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Thermoacoustic devices represent a significant future opportunity in the fields of energy generation and refrigeration. A key component of this type of device is the regenerator, where the conversion between acoustic energy and thermal energy takes place. This conversion occurs due to an externally imposed temperature gradient on the walls of the regenerator channels. Hence, this paper concerns the physics of sound waves in the proximity of such walls. It establishes a new analytical framework which clarifies the disturbance energy conservation in thermoacoustic devices. In this framework, a thermoacoustic production term is proposed to quantify the generation or consumption of disturbance energy originating from the temperature gradient. An extended disturbance energy flux term is identified to account for wave growth or decay through the regenerator. The disturbance energy balance relation states that the disturbance energy flux equals the thermoacoustic production less the viscous and thermal dissipation resulting from gradients of fluctuating velocity and temperature. The analytical framework is implemented in an axisymmetric cylindrical domain; the two-dimensional nature of this work helps to uncover that the wave always decays in the region close to the wall. A dimensional analysis is conducted to identify the controlling parameters, namely the Womersley, Helmholtz and Prandtl numbers. A parametric study of the Womersley and Helmholtz numbers is conducted to showcase the new analytical methodology; the results make it possible to optimize the geometry, wave properties and working conditions of a thermoacoustic device according to the preference of its efficiency, loss and output.
The aim of this study is to investigate the impact of anatomical changes in prostate cancer patients on the target coverage when using 6 MV beams-VMAT therapy and to propose strategies that allow us to evaluate the dose or correct it by normalization without having to perform a new simulation.
Methods and materials:
Ten patients of high-risk prostate cancer were chosen for the study. All test plans were delivered using the same isocenter and monitor units as the original plan and compared against the original unedited plan. The expansion and contraction of body contours due to size changes was mimicked by increasing and decreasing the body contour with depths of −2, −1·5, …, 1·5, 2 cm, in the anterior, and both lateral directions of the patient. A total of 90 plans were evaluated, 9 for each patient. Dose-volume histogram statistics were extracted from each plan and normalized to prescription dose.
Weight changes resulted in considerable dose modifications to the target and critical structures. Plans were found to be varied with 2·9% ± 0·3% per cm SSD change for VMAT treatment with a correlation index close to one. Therefore, doses variations were linear to the changes of depth. Gamma index evaluation was performed for the 10 renormalized plans. All of them passed criteria of 3%/3 mm in at least 98.2% of points. Eight of them passed criteria in 99% points. Gamma index 4%/4 mm passed 100% points in all patients for the chosen region of interest.
The dosimetry estimation presented in this study shows important data for the radiation oncology staff to justify whether a CT rescan is necessary or not when a patient experiences weight changes during treatment. Based on the results of our study, discrepancies between real dose and planned dose were >5% for 1·7 cm of difference in external contour in the anterior and both lateral directions of the patient.
We report on structural, magnetic, optical, and dielectric properties of rare earth (Er and Yb)-doped ZnO nanoparticles with Na-co-doping for charge compensation by sol-gel process. The effect of doping concentration on the structural and dielectric properties of ZnO has been studied under magnetic field and UV excitation. The magnetodielectric and photodielectric effects at room temperature of doped ZnO are discussed in the light of magnetic and optical properties of Er3+ and Yb3+ ions.
The work focuses on the analysis of electrochemical corrosion in synthetic salt medium of the TiC/Ni-20Cr composite through the polarization curve technique at four exposure times (0, 6, 12 and 24 h). The composite was prepared by liquid infiltration of the liquid alloy into a porous body of TiC. It was found a continuous and homogeneous distribution of the reinforcing material in the interconnected matrix, having a residual porosity of 6.49 vol.%. According to the electrochemical results, in both samples the highest corrosion rate (CR) was obtained at 12 h exposure due to the rupture of the film of the corrosion products, allowing the interaction of chloride ions with the metal surface. The CR of the composite was slightly higher than that of the alloy at all exposure times, so that the presence of the reinforcing particles and the residual porosity reduce the corrosion resistance of the matrix in the composite. The mechanism of corrosion observed in the alloy and the composite was by pitting, however, the composite also presents crevice corrosion by a differential aeration cell mechanism formed between the metal matrix and the ceramic reinforcement, affected by the residual porosity as confirmed by electron microscopy examination.
We report on photo-induced magnetic effect and infrared (IR) spectroscopic behavior of colossal magnetorestive manganite La0.7Sr0.3MnO3 (LSMO) with rare earth co-doping (Er3+ and Yb3) at room temperature. X-ray diffraction shows that a structural phase transformation from rhombohedral to hexagonal with increasing Er and Yb concentrations. Photo-induced magnetoresistance showed that Er3+ and Yb+3 ions have significant influence on the magnetic and electrical ordering of LSMO under the influence of UV light. The optical excitation also shows an enhancement in the magnetotransport properties of LSMO.
Cyberbullying has aroused scientific interest given the impact it has on the lives of young people. The present study proposes to analyze the relationship between self-concept (Self-Description Questionnaire I), academic goals (Achievement Goals Tendencies Questionnaire), and the participation of the roles of victim, bully and bystander in cyberbullying (Cyberbullying. Screening for peer bullying and cyberbullying), by gender and grade. The sample was composed of 548 students (49.8% girls) in 5th and 6th grade of Primary Education (Mage = 10.95, SD = 0.7). Logistic regression analyses showed the explicative role of social self-concept and learning goals in the three roles, highlighting the academic self-concept and achievement goals in the victims, as well as the high social reinforcement goals in bullies and bystanders. This relation varied slightly according to gender and grade, being the motivational orientation towards school achievement a protector of victimization in girls and 6th grade students. The findings are discussed, pointing out their involvement in the development of preventive cyberbullying programs in preadolescence.
The work presents an electrochemical study of the corrosion behaviour of two TiC/Cu-Ni metal matrix composites with a content of 10 and 20 wt.% Ni immersed in synthetic seawater. The composites were synthesized by a capillary infiltration technique, obtaining dense materials TiC/Cu-10Ni and TiC/Cu-20 Ni with a residual porosity of 1.8 and 1.7%, respectively. The corrosion rate (CR) was evaluated from the techniques of polarization curves (PC), linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS). Electrochemical measurements were carried out under static conditions, ambient temperature and atmospheric pressure at 24 hours exposure in the electrolytic medium. The corrosion rate is affected by the Ni content in the matrix, with less corrosion in the composite with a higher Ni content. The higher content of Ni in the Cu-Ni alloy provides higher passivation and stability to the corrosion products film that are absorbed on the composite surface. Microscopic examination (SEM) showed a characteristic morphology of a corrosion mechanism of the localized type (pits and crevices) generated by a differential aeration, where the TiC/Cu-10Ni composite showed greater degradation.
To estimate the dietary share of ultra-processed foods and to determine its association with the overall nutritional quality of diets in Brazil.
A representative sample of 32 898 Brazilians aged ≥10 years was studied. Food intake data were collected. We calculated the average dietary content of individual nutrients and compared them across quintiles of energy share of ultra-processed foods. Then we identified nutrient-based dietary patterns, and evaluated the association between quintiles of dietary share of ultra-processed foods and the patterns’ scores.
The mean per capita daily dietary energy intake was 7933 kJ (1896 kcal), with 58·1 % from unprocessed or minimally processed foods, 10·9 % from processed culinary ingredients, 10·6 % from processed foods and 20·4 % from ultra-processed foods. Consumption of ultra-processed foods was directly associated with high consumption of free sugars and total, saturated and trans fats, and with low consumption of protein, dietary fibre, and most of the assessed vitamins and minerals. Four nutrient-based dietary patterns were identified. ‘Healthy pattern 1’ carried more protein and micronutrients, and less free sugars. ‘Healthy pattern 2’ carried more vitamins. ‘Healthy pattern 3’ carried more dietary fibre and minerals and less free sugars. ‘Unhealthy pattern’ carried more total, saturated and trans fats, and less dietary fibre. The dietary share of ultra-processed foods was inversely associated with ‘healthy pattern 1’ (−0·16; 95 % CI −0·17, −0·15) and ‘healthy pattern 3’ (−0·18; 95 % CI −0·19, −0·17), and directly associated with ‘unhealthy pattern’ (0·17; 95 % CI 0·15, 0·18).
Dietary share of ultra-processed foods determines the overall nutritional quality of diets in Brazil.
To assess the consumption of ultra-processed foods and analyse its association with the content of added sugars in the Chilean diet.
Cross-sectional study of national dietary data obtained through 24 h recalls and classified into food groups according to the extent and purpose of food processing (NOVA classification).
A probabilistic sample of 4920 individuals (aged 2 years or above) studied in 2010 by a national dietary survey (Encuesta Nacional de Consumo Alimentario).
Ultra-processed foods represented 28·6 (se 0·5) % of total energy intake and 58·6 (se 0·9) % of added sugars intake. The mean percentage of energy from added sugars increased from 7·7 (se 0·3) to 19·7 (se 0·5) % across quintiles of the dietary share of ultra-processed foods. After adjusting for several potential sociodemographic confounders, a 5 percentage point increase in the dietary share of ultra-processed foods determined a 1 percentage point increase in the dietary content of added sugars. Individuals in the highest quintile were three times more likely (OR=2·9; 95 % CI 2·4, 3·4) to exceed the 10 % upper limit for added sugars recommended by the WHO compared with those in the lowest quintile, after adjusting for sociodemographic variables. This association was strongest among individuals aged 2–19 years (OR=3·9; 95 % CI 2·7, 5·9).
In Chile, ultra-processed foods are important contributors to total energy intake and to the consumption of added sugars. Actions aimed at limiting consumption of ultra-processed foods are being implemented as effective ways to achieve WHO dietary recommendations to limit added sugars and processed foods, especially for children and adolescents.
Both maternal Fe deficiency (ID) and being overweight or obese (Ow/Ob, BMI≥25 kg/m2) may negatively affect offspring brain development. However, the two risk factors correlate and their independent effects on infant neurodevelopment are unclear. PREOBE is a prospective observational study that included 331 pregnant Spanish women, of whom 166 had pre-gestational Ow/Ob. Fe status was analysed at 34 weeks and at delivery, and babies were assessed using Bayley III scales of neurodevelopment at 18 months. In confounder-adjusted analyses, maternal ID at 34 weeks was associated with lower composite motor scores at 18 months (mean 113·3 (sd 9·9) v. 117·1 (sd 9·2), P=0·039). Further, the offspring of mothers with ID at delivery had lower cognitive scores (114·0 (sd 9·7) v. 121·5 (sd 10·9), P=0·039) and lower receptive, expressive and composite (99·5 (sd 8·6) v. 107·6 (sd 8·3), P=0·004) language scores. The negative associations between maternal ID at delivery and Bayley scores remained even when adjusting for maternal Ow/Ob and gestational diabetes. Similarly, maternal Ow/Ob correlated with lower gross motor scores in the offspring (12·3 (sd 2·0) v. 13·0 (sd 2·1), P=0·037), a correlation that remained when adjusting for maternal ID. In conclusion, maternal ID and pre-gestational Ow/Ob are both negatively associated with Bayley scores at 18 months, but independently and on different subscales. These results should be taken into account when considering Fe supplementation for pregnant women.
In this paper, we have developed composites with Poly-methyl methacrylate (PMMA) as the matrix material, while transition metal dichalcogenides (TMDCs), MoS2 and WS2 and graphite served as the filler materials. The PMMA was chosen as the matrix material due to its low-cost, wide availability, as well as its promising mechanical and optical properties for enabling opto-electro-mechanical sensing devices. The amount of filler material used ranged from 100 mg/ml up to 400 mg/ml. With the aid of designed fixtures we related the electrical properties of the PMMA-based composite sensors to the degree of strain or deformation. Additionally, a nanoindenter was used to measure the modulus of elasticity, with values as low as 2 GPa and as high as 20 GPa for the graphite composites, and hardness values which ranged from 0.1 GPa to ∼ 1.6 GPa.
Bacteriocins are natural compounds used as food biopreservatives instead of chemical preservatives. Bifidobacterium animalis subsp. lactis (Bifid. lactis) was shown to produce a bacteriocin-like inhibitory substance (BLIS) able to inhibit the growth of Listeria monocytogenes selected as an indicator microorganism. To enhance this production by the strain Bifid. lactis BL 04, skim milk (SM) was used as a fermentation medium either in the presence or in the absence of yeast extract, Tween 80 or inulin as stimulating additives, and the results in terms of bacterial growth and BLIS production were compared with those obtained in a traditional high cost complex medium such as Man, Rogosa and Sharpe (MRS). To this purpose, all the cultivations were carried out in flasks at 200 rpm under anaerobic conditions ensured by a nitrogen flowrate of 1·0 L/min for 48 h, and BLIS production was quantified by means of a modified agar diffusion assay at low values of both temperature and concentration of List. monocytogenes. Although all these ingredients were shown to exert positive influence on BLIS production in both media, yeast extract and SM were by far the best ingredient and the best medium, respectively, allowing for a BLIS production at the late exponential phase of 2000 AU/ml.
Spherical and conical nanoindentation experiments were performed for the same polymer specimens to compare Young's moduli measured from the elastic loading and unloading curves, and bending experiments. Finite-element simulation was employed to ensure pure elastic deformation during spherical nanoindentation. The moduli measured from the elastic loading curves using Hertz's contact law are very close to the bending moduli, because both measurements were conducted under the same elastic deformation. However, the moduli measured from the elastic unloading curves are up to 60% higher than the bending moduli owing to plastic deformation close to the sharp conical indenter tip.
The objective of the study was to design and evaluate a pilot programme aimed at promoting the active ageing of older adults at the Mexican Institute of Social Security. The study was conducted in three stages: (a) design; (b) implementation; and (c) before–after evaluation through analysis of changes in functional status, occupational functioning and health-related quality of life. To overcome the limitations of the study design, we evaluated the effect of 80 per cent adherence to the programme on the outcome variables using the generalised linear regression models (GLM). Two hundred and thirty-nine older adults agreed to participate, of whom 65 per cent completed the programme. Most were women; the average age was 77 years. Adherence to the programme was higher than 75 per cent for the group who completed active ageing services and less than 60 per cent for the drop-out group. Overall, 46 per cent of older adults reached an adherence level of 80 per cent or higher. Adherence was significantly associated with improved quality of life total score (coefficient 2.7, p<0.0001) and occupational functioning total score (coefficient 2.2, p<0.0001). Participation of older adults in an active ageing programme may improve their health-related quality of life and occupational functioning. It is necessary to identify the potential barriers and to implement strategies to improve the recruitment and retention rates during the intervention.
Individuals affected by Muscle Dysmorphia (MD; body image disorder based on the sub estimation of muscle size), practice weightlifting in order to alleviate their muscular dissatisfaction. Although physical activity is associated with increased physical self-perception, we assume that this was not reproduced in full in people with MD. The study sample consisted of 734 weightlifters and bodybuilders, 562 men and 172 women, who completed the Escala de Satisfacción Muscular, the Physical Self-Concept Questionnaire, and from whom measures of body fat and Fat -Free Mass Index (FFMI) were obtained. The results showed that people suffering from MD symptoms, overall, have poorer physical self-concept perceptions (F = 18.46 - 34.77, p < .01).
Farmers around the world are concerned about the effects of human-induced salinity on crop yield and quality. Therefore, researchers are actively testing wild relatives of cultivated plants to identify candidates to improve crop performance under salt stress. A study was conducted to understand the effects of salt stress (Sodium chloride, NaCl) on cultivated tomato species (Solanum lycopersicum var. cerasiforme L.) and a wild tomato relative (Solanum chilense Dun.) from the Northern part of Chile. Plants were cultivated hydroponically under controlled environmental conditions for 112 days with nutrient solution containing 0 mM (3 dS m−1), 40 mM (6 dS m−1) and 80-mM (9 dS m−1) NaCl. Salt stress reduced the shoot biomass in S. lycopersicum but not in S. chilense. Both species were able to maintain the leaf water content; however, the cultivated S. lycopersicum showed osmotic adjustment, while S. chilense did not. Salt stress reduced the total fruit yield in S. lycopersicum based on a decrease in the mean fruit weight, but it had no impact on the number of fruits per plant. In contrast, salt stress had no significant impact on the fruit yield in S. chilense. Salt stress increased the total soluble solids content in S. lycopersicum and the titratable acidity in S. chilense. It was concluded that S. chilense displays a contrasting behaviour in response to prolonged exposure to moderate salinity compared with S. lycopersicum, and that this related species could be an interesting plant for breeding purposes.
A novel biopolymer derived from diallyl sucrose (A2S) and dithiotreitol (DTT) was prepared by means of Thiol-Ene Photopolymerization. A2S was prepared by alkylating the sucrose with allyl bromide, using water as solvent. After purification by column chromatography, a fraction (F2A2S) with 94% diallyl sucrose (A2S), 4 % of triallyl sucrose (A3S) and 2 % of monoallyl sucrose (A1S) was obtained. This fraction was subsequently photopolymerized with Dithiothreitol (DTT) which is a difunctional thiol. Kinetics of photopolymerization were determined by means of Real-Time Infrared spectroscopy. It was found that the photocurable formulation with DTT and F2A2S, polymerized rapidly in the presence and absence of a photoinitiator, at low intensities of UV light. After bulk polymerization, a flexible material with high elastic modulus and a Tg of 30 °C was obtained. Besides, the polymer displayed moderate water absorbance properties as a result of the presence of multiple hydroxyl groups. This property was pH dependent with maximum absorbance at pH=14. The polymer degraded rapidly under acidic conditions
Out-of-hospital cardiac arrest is one of the leading causes of death in Mexico, but many survival and prognostic factors are unknown. The aim of this study was to assess out-of-hospital cardiac arrest in a Mexican city.
This was a prospective, cohort study that evaluated the records of the major ambulance services in the city of Queretaro, Mexico. Means, standard deviation, and percentages for the categorical variables were obtained. Logistic regression was performed to determine the effects between interventions, times, and return of spontaneous circulation (ROSC).
For an 11-month period, 148 out-of-hospital cardiac arrest cases were recorded. The mean age of the victims was 54 ±22.6 years and 90 (65.3%) were males. Forty-nine cases were related to cardiac disease, 46 to other disease, 27 to trauma, 18 to terminal illnesses, and three to drowning. Twelve (8.6%) patients had a pulse upon hospital arrival, but none survived to discharge. No victims were defibrillated prior to ambulance arrival. The collapse-assessment interval was 22.5 ±19:1 minutes, the mean value for the ambulance response times was 13:6 ±10:4 minutes. Basic emergency medical technicians applied chest compressions to 40 victims (27.2%), controlled the airway in 32 (21.8%), and defibrillated seven (4.8%). Chest compressions and airway control showed an OR of 8 and 12 respectively for ROSC.
The poor survival rate in this study emphasizes the need to improve efforts in provider training and public education. Authorities must promote actions to enhance prehospital emergency services capabilities, shorten response times, and provide community education to increase the chances of survival for out-of-hospital cardiac arrest victims in Mexico.