Explainable artificial intelligence (xAI) in neuromarketing/consumer neuroscience: an fMRI study on brand perception.

Introduction: The research in consumer neuroscience has identified computational methods, particularly artificial intelligence (AI) and machine learning, as a significant frontier for advancement. Previously, we utilized functional magnetic resonance imaging (fMRI) and artificial neural networks (ANNs) to model brain processes related to brand preferences in a paradigm exempted from motor actions. In the current study, we revisit this data, introducing recent advancements in explainable artificial intelligence (xAI) to gain insights into this domain. By integrating fMRI data analysis, machine learning, and xAI, our study aims to search for functional brain networks that support brand perception and, ultimately, search for brain networks that disentangle between preferred and indifferent brands, focusing on the early processing stages. Methods: We applied independent component analysis (ICA) to overcome the expected fMRI data's high dimensionality, which raises hurdles in AI applications. We extracted pertinent features from the returned ICs. An ANN is then trained on this data, followed by pruning and retraining processes. We then apply explanation techniques, based on path-weights and Shapley values, to make the network more transparent, explainable, and interpretable, and to obtain insights into the underlying brain processes. Results: The fully connected ANN model obtained an accuracy of 54.6%, which dropped to 50.4% after pruning. However, the retraining process allowed it to surpass the fully connected network, achieving an accuracy of 55.9%. The path-weights and Shapley-based analysis concludes that, regarding brand perception, the expected initial participation of the primary visual system is followed. Other brain areas participate in early processing and discriminate between preferred and indifferent brands, such as the cuneal and the lateral occipital cortices. Discussion: The most important finding is that a split between processing brands|preferred from brands|indifferent may occur during early processing stages, still in the visual system. However, we found no evidence of a "decision pipeline" that would yield if a brand is preferred or indifferent. The results suggest the existence of a "tagging"-like process in parallel flows in the extrastriate. Network training dynamics aggregate specific processes within the hidden nodes by analyzing the model's hidden layer. This yielded that some nodes contribute to both global brand appraisal and specific brand category classification, shedding light on the neural substrates of decision-making in response to brand stimuli.

Burnout, resilience, and subjective well-being among Portuguese lecturers' during the COVID-19 pandemic.

Background: Lecturers face a large wide of occupational stressors. If the prolonged stress and the symptomatology associated with the working conditions to which lecturers were exposed were already a concern before the pandemic, the pandemic may have exacerbated this psychosocial vulnerability. Burnout is a psychological syndrome that develops in response to chronic work stress. This study aims to describe burnout amongst lecturers working in Portugal and to analyse potential determinants of burnout during the COVID-19 pandemic. Methods: A cross-sectional study was performed using an online questionnaire distributed via social networks. The survey collected sociodemographic and sleep patterns data in addition to applying the Copenhagen Burnout Inventory (personal, work- and student-related burnout), the Resilience Scale, the Depression Anxiety and Stress Scales, and the Satisfaction with Life Scale. Results: The sample included 331 lecturers from 35 different colleges and faculties. Three significant models explained personal (R2 = 54%), work- (R2 = 47%) and student- (R2 = 19%) related burnout. Lower levels of resilience and higher levels of depression and stress were significantly associated with personal and work-related burnout. Changes in sleep patterns were additionally associated with both personal and work-related burnout. Conclusion: Higher education institutions must recognize the impact of the work environment and organizational culture on faculty mental health and take proactive measures to improve this environment. These institutions can implement support strategies such as educational technology training, professional development programmes, emotional support resources, and workload flexibility. Implementing measures to enhance lecturers' resilience and overall life satisfaction could potentially help mitigate burnout and improve the well-being of educators, ultimately contributing to the overall quality of education.

Intensity Ratio of Kß/Kα in Selected Elements from Mg to Cu, and the Chemical Effects of Cr Kα1,2 Diagram Lines and Cr Kß/Kα Intensity Ratio in Cr Compounds.

Kα,ß X-ray lines from photon excitation were measured in selected elements from Mg to Cu using a high-resolution double-crystal X-ray spectrometer with a proportional counter, and the Kß/Kα intensity ratio for each element was obtained, after correcting for self-absorption, detection efficiency, and crystal reflectance. This intensity ratio increases rapidly from Mg to Ca but, in the 3d elements region, the increase becomes slower. This is related to the intensity of the Kß line involving valence electrons. The slow increase of this ratio in the 3d elements region is thought to be due to the correlation between 3d and 4s electrons. Moreover, the chemical shifts, FWHM, asymmetry indices, and Kß/Kα intensity ratios of the Cr compounds, due to different valences, were also investigated using the same double-crystal X-ray spectrometer. The chemical effects were clearly observed, and the Kß/Kα intensity ratio was found to be compound-dependent for Cr.

Hemorrhagic Versus Ischemic Risk in Patients with Atrial Fibrillation on Hemodialysis

Abstract Background Hemodialysis (HD) patients with atrial fibrillation (AF) have a particularly high risk of stroke and bleeding, but no high-quality evidence-based recommendations exist to properly manage these patients. Objectives We aim to evaluate the ischemic versus the hemorrhagic risk in a HD population with AF. Methods We selected incident patients that started hemodialysis between 2011 and 2015. All patients that had AF before HD, or developed AF during the follow-up, were included. Both CHA2DS2 -VASC and HAS-BLED scores were calculated at the time of beginning of HD or AF diagnosis and correlated with the outcomes using a logistic regression model. The outcomes were hemorrhagic events, ischemic events and death related to any of these events. A p-value < 0.05 was set as statistically significant. Results Forty-six patients were included. Most of them had had AF before they started hemodialysis. Twenty-two patients were on oral anticoagulation (OAC). There was no significant difference between the incidence of ischemic and hemorrhagic events, regardless of the use of OAC. Previous stroke, transient ischemic attack, and thromboembolic event significantly increased the risk of an ischemic event (OR 6.78, p=0.028). Conclusions In this population, we did not observe any difference between the incidence of ischemic and hemorrhagic events, which was also true in patients with OAC. Therefore, the benefit of OAC in such patients remains questionable. However, patients with previous stroke, transient ischemic attack, or thromboembolic event seem to have a higher risk of new ischemic events and might benefit from anticoagulation.

Robust, maintainable, emergency invasive mechanical ventilator. / Ventilador mecânico invasivo de emergência resistente e de fácil manutenção.

OBJECTIVE: To develop a simple, robust, safe and efficient invasive mechanical ventilator that can be used in remote areas of the world or war zones where the practical utility of more sophisticated equipment is limited by considerations of maintainability, availability of parts, transportation and/or cost. METHODS: The device implements the pressure-controlled continuous mandatory ventilation mode, complemented by a simple assist-control mode. Continuous positive airway pressure is also possible. The consumption of compressed gases is minimized by avoiding a continuous flow of oxygen or air. Respiratory rates and inspiration/expiration time ratios are electronically determined, and an apnea/power loss alarm is provided. RESULTS: The pressure profiles were measured for a range of conditions and found to be adjustable within a ± 2.5cmH2O error margin and stable well within this range over a 41-hour period. Respiratory cycle timing parameters were precise within a few percentage points over the same period. The device was tested for durability for an equivalent period of four months. Chemical and biological tests failed to identify any contamination of the gas by volatile organic compounds or microorganisms. A ventilation test on a large animal, in comparison with a well established ventilator, showed that the animal could be adequately ventilated over a period of 60 minutes, without any noticeable negative aftereffects during the subsequent 24-hour period. CONCLUSION: This ventilator design may be viable, after further animal tests and formal approval by the competent authorities, for clinical application in the abovementioned atypical circumstances.

OBJETIVO: Desenvolver um ventilador mecânico invasivo simples, resistente, seguro e eficiente que possa ser utilizado em áreas remotas do mundo ou zonas de guerra, em que a utilidade prática de equipamentos mais sofisticados é limitada por questões de manutenção, disponibilidade de peças, transporte e/ou custo. MÉTODOS: O dispositivo implementa o modo de ventilação mandatória contínua com pressão controlada, complementado por um simples modo assisto-controlado. Pode-se também utilizar a pressão positiva contínua nas vias aéreas. Ao se evitar o fluxo contínuo de oxigênio ou ar, minimiza-se o consumo de gases comprimidos. As taxas respiratórias e as relações de tempo de inspiração e expiração são determinadas eletronicamente. Além disso, conta com um alarme de apneia/falta de energia. RESULTADOS: Os perfis de pressão foram medidos para uma série de condições, sendo considerados ajustáveis dentro de uma margem de erro de ± 2,5cmH2O, e foram considerados bem estáveis dentro dessa variação durante um período de 41 horas. Os parâmetros de tempo do ciclo respiratório foram precisos dentro de alguns pontos percentuais durante o mesmo período. O dispositivo foi testado quanto à durabilidade por um período equivalente a 4 meses. Os testes químicos e biológicos não conseguiram identificar qualquer contaminação do gás por compostos orgânicos voláteis ou micro-organismos. Em comparação com um ventilador bem estabelecido, o teste de ventilação em um animal de grande porte mostrou que este poderia ser ventilado adequadamente durante um período de 60 minutos, sem quaisquer efeitos negativos perceptíveis durante o período subsequente de 24 horas. CONCLUSÃO: Este projeto de ventilador pode ser viável após novos testes em animais e aprovação formal pelas autoridades competentes, para aplicação clínica nas circunstâncias atípicas anteriormente mencionadas.

Ventilador mecânico invasivo de emergência resistente e de fácil manutenção / Robust, maintainable, emergency invasive mechanical ventilator

RESUMO Objetivo: Desenvolver um ventilador mecânico invasivo simples, resistente, seguro e eficiente que possa ser utilizado em áreas remotas do mundo ou zonas de guerra, em que a utilidade prática de equipamentos mais sofisticados é limitada por questões de manutenção, disponibilidade de peças, transporte e/ou custo. Métodos: O dispositivo implementa o modo de ventilação mandatória contínua com pressão controlada, complementado por um simples modo assisto-controlado. Pode-se também utilizar a pressão positiva contínua nas vias aéreas. Ao se evitar o fluxo contínuo de oxigênio ou ar, minimiza-se o consumo de gases comprimidos. As taxas respiratórias e as relações de tempo de inspiração e expiração são determinadas eletronicamente. Além disso, conta com um alarme de apneia/falta de energia. Resultados: Os perfis de pressão foram medidos para uma série de condições, sendo considerados ajustáveis dentro de uma margem de erro de ± 2,5cmH2O, e foram considerados bem estáveis dentro dessa variação durante um período de 41 horas. Os parâmetros de tempo do ciclo respiratório foram precisos dentro de alguns pontos percentuais durante o mesmo período. O dispositivo foi testado quanto à durabilidade por um período equivalente a 4 meses. Os testes químicos e biológicos não conseguiram identificar qualquer contaminação do gás por compostos orgânicos voláteis ou micro-organismos. Em comparação com um ventilador bem estabelecido, o teste de ventilação em um animal de grande porte mostrou que este poderia ser ventilado adequadamente durante um período de 60 minutos, sem quaisquer efeitos negativos perceptíveis durante o período subsequente de 24 horas. Conclusão: Este projeto de ventilador pode ser viável após novos testes em animais e aprovação formal pelas autoridades competentes, para aplicação clínica nas circunstâncias atípicas anteriormente mencionadas.

ABSTRACT Objective: To develop a simple, robust, safe and efficient invasive mechanical ventilator that can be used in remote areas of the world or war zones where the practical utility of more sophisticated equipment is limited by considerations of maintainability, availability of parts, transportation and/or cost. Methods: The device implements the pressure-controlled continuous mandatory ventilation mode, complemented by a simple assist-control mode. Continuous positive airway pressure is also possible. The consumption of compressed gases is minimized by avoiding a continuous flow of oxygen or air. Respiratory rates and inspiration/expiration time ratios are electronically determined, and an apnea/power loss alarm is provided. Results: The pressure profiles were measured for a range of conditions and found to be adjustable within a ± 2.5cmH2O error margin and stable well within this range over a 41-hour period. Respiratory cycle timing parameters were precise within a few percentage points over the same period. The device was tested for durability for an equivalent period of four months. Chemical and biological tests failed to identify any contamination of the gas by volatile organic compounds or microorganisms. A ventilation test on a large animal, in comparison with a well established ventilator, showed that the animal could be adequately ventilated over a period of 60 minutes, without any noticeable negative aftereffects during the subsequent 24-hour period. Conclusion: This ventilator design may be viable, after further animal tests and formal approval by the competent authorities, for clinical application in the abovementioned atypical circumstances.

Analysis of human tissues using Energy Dispersive X Ray Fluorescence - Dark matrix determination for the application to cancer research.

BACKGROUND: X ray Fluorescence has been essayed as a suitable technique for the elemental quantification of trace element in human tissues, namely comparison of normal and cancerous tissue. However, accurate results depend on a robust quantification approach, namely correct evaluation of the samples' dark matrix. METHODS: In order to determine the most suitable dark matrix composition for the quantification of such samples using the Fundamental Parameter approach, we have measured several Certified Reference Materials and essayed different dark matrix compositions to achieve the most accurate results. The resulting dark matrix was then applied to normal and tumor ovarian and prostate tissue samples, and the obtained results were compared with the ones obtained with a comparative method using external standard calibration curves. RESULTS: Using a dark matrix composed of 10 % - H, 22 % - C, 3 % - N and 60 % - O yielded the best compromise in accuracy for the light and heavy elements. For the reduced sample size and conditions of this study, for both organs, the concentrations of transition metals decrease in tumor tissues, while the concentration of lighter elements, P and Cl, increases. On the other hand, there are elements that showed different behavior between the two types of tissue, namely Zn and S, that increase in prostate tumor tissue and decrease in ovarian tissue. CONCLUSION: An increase in precision was one of the improvements found with the newly developed method, as the FP-approach contemplates matrix effects and the influence of other elements in the analytes' quantification. Additionally, the determined dark matrix can be employed in any tissue analysis application by means of EDXRF.

Impact of COVID-19 on Medicine Lecturers' Mental Health and Emergency Remote Teaching Challenges.

COVID-19 has presented a novel pedagogical challenge in dealing with the sudden shift from classic instruction to emergency remote teaching (ERT). It had an impact on the well-being and mental health of lecturers, increasing burnout risk. A cross-sectional, quantitative, qualitative and analytical online study was conducted to collect participants' sociodemographic data, responses to ERT open-ended questions and mental health assessments using relevant instruments (CBI for burnout, Resilience Scale, DASS for depression, anxiety and stress, SWLS for satisfaction with life). High personal burnout levels were found in 41.2% of participants, high work-related burnout in 37.3% and high student-related burnout in 15.7%. Satisfaction with life, sleep routine changes and stress were determinants for personal burnout; stress and resilience for work-related burnout; satisfaction of life and sleep routine changes for students-related burnout. Opportunities for pedagogical innovation were pointed out as the main advantages to ERT, while the main negative impacts were on practical lessons and social interaction. Students and lecturers' safety and adequate institutional support might be insured, considering their expectations and needs, promoting mental health. Combining the advantages of online and traditional methods in a so-called "blended learning" approach, with close collaboration and communication between all those involved, appears to achieve better results.

Measuring the α-particle charge radius with muonic helium-4 ions.

The energy levels of hydrogen-like atomic systems can be calculated with great precision. Starting from their quantum mechanical solution, they have been refined over the years to include the electron spin, the relativistic and quantum field effects, and tiny energy shifts related to the complex structure of the nucleus. These energy shifts caused by the nuclear structure are vastly magnified in hydrogen-like systems formed by a negative muon and a nucleus, so spectroscopy of these muonic ions can be used to investigate the nuclear structure with high precision. Here we present the measurement of two 2S-2P transitions in the muonic helium-4 ion that yields a precise determination of the root-mean-square charge radius of the α particle of 1.67824(83) femtometres. This determination from atomic spectroscopy is in excellent agreement with the value from electron scattering1, but a factor of 4.8 more precise, providing a benchmark for few-nucleon theories, lattice quantum chromodynamics and electron scattering. This agreement also constrains several beyond-standard-model theories proposed to explain the proton-radius puzzle2-5, in line with recent determinations of the proton charge radius6-9, and establishes spectroscopy of light muonic atoms and ions as a precise tool for studies of nuclear properties.

A rare complication of a hemodialysis tunneled catheter: Case report of a superior vena cava and right atrium candida endocarditis.

Infections remain an important cause of death among hemodialysis patients. This population have a higher risk of candidemia. Candida endocarditis it´s a rare but frequently fatal complication of candidemia. A 64 year-old female presented with a purulent discharge at the insertion site of a hemodialysis tunneled cuff catheter. A catheter related bloodstream infection was suspected, cultures were obtained and wide-spectrum antibiotic therapy was administered. A multi sensitive Candida albicans was isolated. Transesophageal echocardiography showed a large vegetation located in the superior vena cava, in probable relation with a previous catheter. The first approach was antifungal treatment. Due to non-response, she did a surgical removal of the vegetation. Culture of the vegetation showed the same as the blood cultures. After one year she has no signs of relapse. To improve the prognosis of this high mortality condition a high index of suspicion is necessary for early diagnosis and timely intervention.

Kidney Transplant From Elderly Donors: A Center Experience.

BACKGROUND: Renal transplantation is the treatment of choice in end-stage renal disease. With the aging of the population and better medical care available, the number of high-risk patients in terms of age and comorbidities on transplant waiting lists is increasing. Due to severe organ shortage, the use of expanded criteria and elderly donors is also increasing. We will review the outcomes of graft function and survival from a series of transplants from elderly deceased donors and compare the characteristics of the organs from donors older and younger than 70 years. METHODS: We collected data from our transplant unit from 1993 until May 2019 and considered 2 groups of donors: donors A (aged ≥70 years) and donors B (aged <70 years). RESULTS: The donors A group had more comorbidities with consequently higher Kidney Donor Profile Index scores than the donors B group, although there was no statistical difference regarding pre-donation serum creatinine level. Among transplant recipients, we also considered 2 groups, according to the age of the organ received: recipients A and recipients B. No difference was found between groups regarding the number of HLA mismatches, incidence of delayed graft function, number of hospitalizations, or incidence of acute rejection. Recipients' age, cold ischemia time, and graft function 1 year after transplant were worse in the recipients A group. CONCLUSIONS: Although kidney graft function was worse in recipients from elderly donors, this difference had no clinical relevance, showing a possible benefit in patient survival compared with permanence in dialysis, so this type of transplant could be considered for older recipients.

Probing deep tissues with laser-induced thermotherapy using near-infrared light.

Optically tunable gold nanoparticles have been widely used in research with near-infrared light as a means to enhance laser-induced thermal therapy since it capitalizes on nanoparticles' plasmonic heating properties. There have been several studies published on numerical models replicating this therapy in such conditions. However, there are several limitations on some of the models which can render the model unfaithful to therapy simulations. In this paper, two techniques of simulating laser-induced thermal therapy with a high-absorbing localized region of interest inside a phantom are compared. To validate these models, we conducted an experiment of an agar-agar phantom with an inclusion reproducing it with both models. The phantom was optically characterized by absorption and total attenuation. The first model is based on the macroperspective solution of the radiative transfer equation given by the diffusion equation, which is then coupled with the Pennes bioheat equation to obtain the temperature. The second is a Monte Carlo model that considers a stochastic solution of the same equation and is also considered as input to the Pennes bioheat transfer equation which is then computed. The Monte Carlo is in good agreement with the experimental data having an average percentage difference of 4.5% and a correlation factor of 0.98, while the diffusion method comparison with experimental data is 61% and 0.95 respectively. The optical characterization of the phantom and its inclusion were also validated indirectly since the Monte Carlo, which used those parameters, was also validated. While knowing the temperature in all points inside a body during photothermal therapy is important, one has to be mindful of the model which fits the conditions and properties. There are several reasons to justify the discrepancy of the diffusion method: low-scattering conditions, absorption, and reduced scattering are comparable. The error bars that are normally associated when characterizing an optical phantom can justify also a part of that uncertainty. For low-size tumors in depth, one may have to increase the light dosage in photothermal therapies to have a more effective treatment.

Determination of Nickel and Manganese Contaminants in Pharmaceutical Iron Supplements Using Energy Dispersive X-ray Fluorescence.

In this study, we investigate the capability of energy dispersive X-ray fluorescence (EDXF) spectrometry in a triaxial geometry apparatus as a fast and nondestructive determination method of both dominant and contaminant elements in pharmaceutical iron supplements. The following iron supplements brands with their respective active ingredients were analyzed: Neutrofer fólico (iron gylcinate), Anemifer (iron(II) sulfate monohydrate), Noripurum (iron(III)-hydroxide polymaltose complex), Sulferbel (iron(II) sulfate monohydrate), and Combiron Fólico (carbonyl iron). Although we observe a good agreement between the iron content obtained by the present method and that indicated in the supplement's prescribed dose, we observe contamination by manganese and nickel of up to 180 µg and 36 µg, respectively. These contents correspond to 7.2% and 14.4% of the permitted daily exposure of manganese and nickel, respectively, for an average adult individual as determined by the European Medicine Agency (EMEA). The method was successfully validated against the concentrations of several certified reference materials of biological light matrices with similar concentrations of contaminants. Moreover, we also validated our method by comparing the concentrations with those obtained with the inductively coupled plasma-atomic emission technique.

Conhecimento dos enfermeiros sobre evento adverso e os desafios para a sua notificação / Nurses' knowledge about adverse events and the challenges of reporting these events / Conocimiento de los enfermeros acerca del evento adverso y los desafíos para sua notificación

Estudo descritivo transversal com abordagem quanti-qualitativa, que objetivou investigar o conhecimento e percepção dos enfermeiros sobre os eventos adversos, sua notificação e os fatores que limitam a sua realização. A coleta de dados foi realizada entre novembro e dezembro de 2015 em um hospital público da região centro sul de Sergipe. A amostra foi composta por 28 enfermeiros, que responderam a um formulário semiestruturado analisado com estatística descritiva e análise de conteúdo. Dentre os participantes, 16 (57%) demonstraram conhecimento deficiente sobre evento adverso, entretanto 27 (96%) dos envolvidos no estudo tem percepção da importância da notificação, porém existe subnotificação devido a fatores como o medo de punições. Conclui-se que devem ser realizadas ações educativas a fim de esclarecer o que são eventos adversos e medidas que incentivem a notificação (AU).

A descriptive cross-sectional study with quantitative and qualitative approach that aimed to investigate the nurses' knowledge and perception of adverse effects, reporting of such events and factors that may limit reporting. Data collection was performed between November and December 2015 in a public hospital of the Center-South region of the state of Sergipe. The sample was composed of 28 nurses who completed a semi-structured form analyzed through descriptive statistics and content analysis. Among the participants, 16 (57%) were 16 (57%) showed little knowledge on adverse events, and, 27 (96%) respondents perceived the importance of reporting. However, these events are underreported due to fear of punishment, among other factors. It is concluded that educational actions and measures aimed to clarify these health professionals on adverse events and encourage reporting are needed (AU).

Estudio descriptivo transversal de abordaje cuantitiva cualitativa, cuya finalidad fue investigar el conocimiento y percepción de los enfermeros acerca de eventos adversos, su notificación y los factores que limitan su realizacióno. Los datos fueron obtenidos entre noviembre y diciembre de 2015 en un hospital público de la región centro sur de Sergipe. La muestra fue compuesta por 28 enfermeros, que contestaron a un formulario semiestructurado analizado con estadística descriptiva y análisis de contenido. Entre los participantes, 16 (57%) demostraron conocimiento deficiente acerca de evento adverso, sin embargo 27 (96%) de las personas abarcadas en el estudio tienen percepción de la importancia de la notificación, pero hay subnotificación a causa de factores como el miedo de puniciones. Se concluye que se deben realizar acciones educativas para aclarar lo que son eventos adversos y medidas que incentiven la notificacióN (AU).

Improved x-ray detection and particle identification with avalanche photodiodes.

Avalanche photodiodes are commonly used as detectors for low energy x-rays. In this work, we report on a fitting technique used to account for different detector responses resulting from photoabsorption in the various avalanche photodiode layers. The use of this technique results in an improvement of the energy resolution at 8.2 keV by up to a factor of 2 and corrects the timing information by up to 25 ns to account for space dependent electron drift time. In addition, this waveform analysis is used for particle identification, e.g., to distinguish between x-rays and MeV electrons in our experiment.

Monte Carlo simulation of laser beams interaction with the human eye using Geant4.

BACKGROUND: Due to the unique characteristics of the eye, ophthalmologic diagnostic techniques often rely on the photons interaction with the retina to infer its internal structure. Although these techniques are widely used, the interpretation of the generated images is not always fully understood, as in scanning laser ophthalmoscopy dark field imaging. This limits the exploitation of its full potential as a diagnostic tool for deep abnormalities in the retina, as in the situation of drusen. METHODS: With the aim of better understanding the retinal diagnostic images, we have carried out computer simulations of incident laser beams interacting with different structures of the human eye, including a retina with and without drusen. We have used the Geant4 simulation toolkit, applying the optical package of the electromagnetic (EM) physics working group, to simulate the physical processes of reflection, refraction, absorption, and scattering of low energy photons (2 eV) in biological tissues. For each simulation it was used a single beam of orange light, with a Gaussian profile, that travels through all optical elements of the eye. The reflected beam characteristics were analyzed by virtual detectors in different locations, which collected information about the number and position of photons. The geometry and optical properties of all components of the eye were considered according to the published data. RESULTS: Simulation results put in evidence that the presence of drusen influences the profile of the reflected beams. It changes the mean free path of the photons, modifying its reflection pattern, which depends on the area illuminated by the incident beam. This result is also visible when the reflected beam is analyzed outside of the eye, when the profile has no longer a symmetrical Gaussian distribution. These results will support the retinal diagnostic images that will be obtained in a near future with a new developed ophthalmic apparatus. CONCLUSIONS: The shape analysis of the reflected beams in retinal laser scanning techniques could increase its potential as a diagnostic examination tool for the deeper structures of the retina.

Absolute measurement of the relativistic magnetic dipole transition energy in heliumlike argon.

The 1s2s (3)S(1)→1s(2) (1)S(0) relativistic magnetic dipole transition in heliumlike argon, emitted by the plasma of an electron-cyclotron resonance ion source, has been measured using a double-flat crystal x-ray spectrometer. Such a spectrometer, used for the first time on a highly charged ion transition, provides absolute (reference-free) measurements in the x-ray domain. We find a transition energy of 3104.1605(77) eV (2.5 ppm accuracy). This value is the most accurate, reference-free measurement done for such a transition and is in good agreement with recent QED predictions.

Lead in liver and kidney of exposed rats: aging accumulation study.

The concentration of lead in liver and kidneys of Wistar rats, fed with lead since fetal period in relation to their age and to a control group, was determined. A group of rats was exposed to lead acetate (n=30) in drinking water and the other group was exposed to normal water (n=20). Samples were collected from rats aging between 1 and 11 months and were analyzed by Energy Dispersive X-ray Fluorescence (EDXRF) without any chemical preparation. The EDXRF results were assessed by the PIXE (Proton Induced X-ray Emission) technique. The formaldehyde used to preserve the samples was also analyzed by ETAAS (Electro-Thermal Atomic Absorption Spectrometry) in order to verify if there was any loss of lead from the samples to the formaldehyde. We found that the loss was not significant (<2%). Concerning the mean values of the lead concentration measured in the contaminated soft tissues, in liver they range from 6 to 22µgg(-1), and in kidneys from 44 to 79µgg(-1). The control rats show, in general, values below the EDXRF detection limit (2µgg(-1)). The ratio kidney/liver ranges from 2 to 10 and is strongly positively correlated with the age of the animals. A Spearman correlation matrix to investigate the correlation between elemental concentrations and the dependence of these concentrations with age showed that there is a strong positive correlation with age for lead in the liver but not in the kidney. The correlation matrix showed also that the concentration of lead in these two soft tissues is not correlated. The lead accumulation in liver is made by different plateaus that strongly decrease with age. It was verified the existence of two levels of accumulation in kidney, not very highlighted, which might be indicative of a maximum accumulation level for lead in kidney.

Study of lead accumulation in bones of Wistar rats by X-ray fluorescence analysis: aging effect.

The accumulation of lead in several bones of Wistar rats with time was determined and compared for the different types of bones. Two groups were studied: a control group (n = 20), not exposed to lead and a contaminated group (n = 30), exposed to lead from birth, first indirectly through mother's milk, and then directly through a diet containing lead acetate in drinking water (0.2%). Rats age ranged from 1 to 11 months, with approximately 1 month intervals and each of the collections had 3 contaminated rats and 2 control rats. Iliac, femur, tibia-fibula and skull have been analysed by Energy Dispersive X-ray Fluorescence Technique (EDXRF). Samples of formaldehyde used to preserve the bone tissues were also analysed by Electrothermal Atomic Absorption (ETAAS), showing that there was no significant loss of lead from the tissue to the preservative. The bones mean lead concentration of exposed rats range from 100 to 300 µg g(-1) while control rats never exceeded 10 µg g(-1). Mean bone lead concentrations were compared and the concentrations were higher in iliac, femur and tibia-fibula and after that skull. However, of all the concentrations in the different collections, only those in the skull were statistically significantly different (p < 0.05) from the other types of bones. Analysis of a radar chart also allowed us to say that these differences tend to diminish with age. The Spearman correlation test applied to mean lead concentrations showed strong and very strong positive correlations between all different types of bones. This test also showed that mean lead concentrations in bones are negatively correlated with the age of the animals. This correlation is strong in iliac and femur and very strong in tibia-fibula and skull. It was also shown that the decrease of lead accumulation with age is made by three plateaus of accumulation, which coincide, in all analysed bones, between 2nd-3rd and 9th-10th months.