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.

Growing substrates for aromatic plant species in green roofs and water runoff quality: pilot experiments in a Mediterranean climate.

Green roof technology has evolved in recent years as a potential solution to promote vegetation in urban areas. Green roof studies for Mediterranean climates, where extended drought periods in summer contrast with cold and rainy periods in winter, are still scarce. The present research study assesses the use of substrates with different compositions for the growth of six aromatic plant species - Lavandula dentata, Pelargonium odoratissimum, Helichrysum italicum, Satureja montana, Thymus caespititius and T. pseudolanuginosus, during a 2-year period, and the monitoring of water runoff quality. Growing substrates encompassed expanded clay and granulated cork, in combination with organic matter and crushed eggshell. These combinations were adequate for the establishment of all aromatic plants, allowing their propagation in the extensive system located on the 5th storey. The substrate composed of 70% expanded clay and 30% organic matter was the most suitable, and crushed eggshell incorporation improved the initial plant establishment. Water runoff quality parameters - turbidity, pH, conductivity, NH4+, NO3-, PO43- and chemical oxygen demand - showed that it could be reused for non-potable uses in buildings. The present study shows that selected aromatic plant species could be successfully used in green roofs in a Mediterranean climate.

The size of the proton.

The proton is the primary building block of the visible Universe, but many of its properties-such as its charge radius and its anomalous magnetic moment-are not well understood. The root-mean-square charge radius, r(p), has been determined with an accuracy of 2 per cent (at best) by electron-proton scattering experiments. The present most accurate value of r(p) (with an uncertainty of 1 per cent) is given by the CODATA compilation of physical constants. This value is based mainly on precision spectroscopy of atomic hydrogen and calculations of bound-state quantum electrodynamics (QED; refs 8, 9). The accuracy of r(p) as deduced from electron-proton scattering limits the testing of bound-state QED in atomic hydrogen as well as the determination of the Rydberg constant (currently the most accurately measured fundamental physical constant). An attractive means to improve the accuracy in the measurement of r(p) is provided by muonic hydrogen (a proton orbited by a negative muon); its much smaller Bohr radius compared to ordinary atomic hydrogen causes enhancement of effects related to the finite size of the proton. In particular, the Lamb shift (the energy difference between the 2S(1/2) and 2P(1/2) states) is affected by as much as 2 per cent. Here we use pulsed laser spectroscopy to measure a muonic Lamb shift of 49,881.88(76) GHz. On the basis of present calculations of fine and hyperfine splittings and QED terms, we find r(p) = 0.84184(67) fm, which differs by 5.0 standard deviations from the CODATA value of 0.8768(69) fm. Our result implies that either the Rydberg constant has to be shifted by -110 kHz/c (4.9 standard deviations), or the calculations of the QED effects in atomic hydrogen or muonic hydrogen atoms are insufficient.

Contributions to the design of rainwater harvesting systems in buildings with green roofs in a Mediterranean climate.

Green roofs (GRs) are becoming a trend in urban areas, favouring thermal performance of buildings, promoting removal of atmospheric pollutants, and acting as possible water collection spots. Rainwater harvesting systems in buildings can also contribute to the management of stormwater runoff reducing flood peaks. These technologies should be enhanced in Mediterranean countries where water scarcity is increasing and the occurrence of extreme events is becoming very significant, as a result of climate change. An extensive pilot GR with three aromatic plant species, Satureja montana, Thymus caespititius and Thymus pseudolanuginosus, designed to study several parameters affecting rainwater runoff, has been in operation for 12 months. Physico-chemical analyses of roof water runoff (turbidity, pH, conductivity, NH4(+), NO3(-), PO4(3-), chemical oxygen demand) have shown that water was of sufficient quality for non-potable uses in buildings, such as toilet flushing. An innovative approach allowed for the development of an expression to predict a 'monthly runoff coefficient' of the GR system. This parameter is essential when planning and designing GRs combined with rainwater harvesting systems in a Mediterranean climate. This study is a contribution to improving the basis for the design of rainwater harvesting systems in buildings with extensive GRs under a Mediterranean climate.

Modelling growth of, and removal of Zn and Hg by a wild microalgal consortium.

Microorganisms isolated from sites contaminated with heavy metals usually possess a higher removal capacity than strains from regular cultures. Heavy metal-containing soil samples from an industrial dumpsite in Northern Portugal were accordingly collected; following enrichment under metal stress, a consortium of wild microalgae was obtained. Their ability to grow in the presence of, and their capacity to recover heavy metals was comprehensively studied; the datasets thus generated were fitted to by a combined model of biomass growth and metal uptake, derived from first principles. After exposure to 15 and 25 mg/L Zn(2+) for 6 days, the microalgal consortium reached similar, or higher cell density than the control; however, under 50 and 65 mg/L Zn(2+), 71% to 84% inhibition was observed. Growth in the presence of Hg(2+) was significantly inhibited, even at a concentration as low as 25 µg/L, and 90% inhibition was observed above 100 µg/L. The maximum amount of Zn(2+) removed was 21.3 mg/L, upon exposure to 25 mg/L for 6 day, whereas the maximum removal of Hg(2+) was 335 µg/L, upon 6 day in the presence of 350 µg/L. The aforementioned mechanistic model was built upon Monod assumptions (including heavy metal inhibition), coupled with Leudeking-Piret relationships between the rates of biomass growth and metal removal. The overall fits were good under all experimental conditions tested, thus conveying a useful tool for rational optimisation of microalga-mediated bioremediation.

Characterization of Desmodesmus pleiomorphus isolated from a heavy metal-contaminated site: biosorption of zinc.

Microalgae have been proven efficient biological vectors for heavy metal uptake. In order to further study their biosorption potential, a strain of Desmodesmus pleiomorphus (L) was isolated from a strongly contaminated industrial site in Portugal. Under different initial Zn(2+) concentrations, metal removal by that strain reached a maximum of 360 mg Zn/g biomass after 7 days, at 30 mg Zn/l, after an initial rapid phase of uptake. Comparative studies were carried out using a strain of the same microalgal species that is commercially available (ACOI 561): when exposed to 30 mg Zn/l, it could remove only 81.8 mg Zn/g biomass. Biosorption experiments using inactivated biomass of the isolated strain reached a maximum Zn(2+) uptake of 103.7 mg/g. Metal removal at various initial pH values was studied as well; higher removal was obtained at pH 5.0. The microalga strain L, isolated from the contaminated site, exhibited a much higher removal capacity than the commercial strain, and the living biomass yielded higher levels of metal removal than its inactivated form.

Laser spectroscopy of muonic deuterium.

The deuteron is the simplest compound nucleus, composed of one proton and one neutron. Deuteron properties such as the root-mean-square charge radius rd and the polarizability serve as important benchmarks for understanding the nuclear forces and structure. Muonic deuterium µd is the exotic atom formed by a deuteron and a negative muon µ(-). We measured three 2S-2P transitions in µd and obtain r(d) = 2.12562(78) fm, which is 2.7 times more accurate but 7.5σ smaller than the CODATA-2010 value r(d) = 2.1424(21) fm. The µd value is also 3.5σ smaller than the r(d) value from electronic deuterium spectroscopy. The smaller r(d), when combined with the electronic isotope shift, yields a "small" proton radius r(p), similar to the one from muonic hydrogen, amplifying the proton radius puzzle.

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.

Proton structure from the measurement of 2S-2P transition frequencies of muonic hydrogen.

Accurate knowledge of the charge and Zemach radii of the proton is essential, not only for understanding its structure but also as input for tests of bound-state quantum electrodynamics and its predictions for the energy levels of hydrogen. These radii may be extracted from the laser spectroscopy of muonic hydrogen (µp, that is, a proton orbited by a muon). We measured the 2S(1/2)(F=0)-2P(3/2)(F=1) transition frequency in µp to be 54611.16(1.05) gigahertz (numbers in parentheses indicate one standard deviation of uncertainty) and reevaluated the 2S(1/2)(F=1)-2P(3/2)(F=2) transition frequency, yielding 49881.35(65) gigahertz. From the measurements, we determined the Zemach radius, r(Z) = 1.082(37) femtometers, and the magnetic radius, r(M) = 0.87(6) femtometer, of the proton. We also extracted the charge radius, r(E) = 0.84087(39) femtometer, with an order of magnitude more precision than the 2010-CODATA value and at 7σ variance with respect to it, thus reinforcing the proton radius puzzle.

Metal uptake by microalgae: underlying mechanisms and practical applications.

Metal contamination of a few aquatic, atmospheric, and soil ecosystems has increased ever since the industrial revolution, owing to discharge of such elements via the effluents of some industrial facilities. Their presence to excessive levels in the environment will eventually lead to serious health problems in higher animals owing to accumulation throughout the food web. Current physicochemical methods available for recovery of metal pollutants (e.g., chemical precipitation, oxidation/reduction, or physical ion exchange) are either expensive or inefficient when they are present at very low concentrations. Consequently, removal of toxic metals by microorganisms has emerged as a potentially more economical alternative. Microalgae (in terms of both living and nonliving biomass) are an example of microorganisms suitable to recover metals and able to attain noteworthy percent removals. Their relatively high metal-binding capacities arise from the intrinsic composition of their cell walls, which contain negatively charged functional groups. Consequently, microalgal cells are particularly efficient in uptake of those contaminants when at low levels. Self-defense mechanisms developed by microalgal cells to survive in metal-containing media and environmental factors that affect their removal (e.g., pH, temperature, and biomass concentration) are reviewed here in a comprehensive way and further discussed in attempts to rationalize this form of remediation vis-a-vis with conventional nonbiological alternatives.

Aspectos histológicos e morfométricos dos testículos de gatos domésticos (Felis catus) / Histological and morphometric evaluation of the testes of cats (Felis catus)

Nesta pesquisa foram obtidos dados histológicos e morfométricos comparativos sobre os testículos de gatos, pós-orquiectomia, divididos em dois grupos: Grupo 1, gatos com até 1 ano de idade e Grupo 2, animais acima de 1 ano. Verificou-se que: (1) aos 4 meses de idade os túbulos seminíferos apresentaram-se pouco desenvolvidos e com ausência de luz, epitélio seminífero baixo, células de Sertoli indiferenciadas e tecido intersticial escasso; (2) aos 5 meses os túbulos seminíferos começaram a se diferenciar com aumento do diâmetro e luz tubulares e as demais estruturas permaneceram semelhantes à observação anterior; (3) aos 6-7 meses ocorreu o início da espermatogênese e espermiogênese; as células de Leydig apareceram maiores, poliédricas com citoplasma vacuolizado e núcleo claro, e tecido intersticial esparso com poucos vasos sangüíneos; (4) os animais com 1 ano de idade apresentaram morfologia testicular igual à do animal adulto, com túbulos seminíferos de maior diâmetro, epitélio germinativo alto e luz tubular pequena, as células de Leydig aparecendo poliédricas, com dimensões variadas, citoplasma vacuolizado, núcleo claro e nucléolo evidente, e espaço intertubular seminífero variado com vasos sanguíneos, predominantemente evidentes; (5) no Grupo 1 o diâmetro médio dos túbulos seminíferos foi de 160,58µm e no Grupo 2 foi de 185,94µm, sendo os valores médios significantes entre si; (6) a altura média do epitélio seminífero foi de 49,51µm para o Grupo 1 e de 63,29µm para o Grupo 2, estaticamente significantes; (7) os maiores valores mensurados foram obtidos para os gatos do Grupo 2, por serem gatos adultos e portanto com os órgãos reprodutores funcionais.

This paper deals with a comparative histologic and morphometric study of the testes of domestic cats distributed into two groups: Group 1, cats until 1 year of age, and Group 2, cats over 1 year. It was found that: (1) at 4 months of age the seminiferous tubules were poorly developed, appeared as seminiferous cords without lumen, lined by a low epithelium, and showed undifferentiated Sertoli cells and scarce interstitial tissue; (2) at 5 months the seminiferous tubules began to differentiate with increase in tubular diameter and lumen, the other tubular structures remaining similar to those previous referred; (3) at 6 and 7 months of age spermatocytogenesis began to appear, Leydig cells were large, polyhedral in shape, with vacuolated cytoplasm and clear nuclei, resting on a sparse interstitial tissue with few blood vessels; (4) 1-year-old cats showed testicular histological features of an adult animal, had seminiferous tubules of large diameter and high seminiferous epithelium with small lumen, and Leydig cells of different sizes, with polyhedral shape, vacuolated cytoplasm, clear nuclei and evident nucleoli resting in a sparse interstitial tissue with some blood vessels; (5) in Group 1 the average diameter of the seminiferous tubules was 160.58µm, and 185.94µm in Group 2; (6) the height of the seminiferous epithelium was 49.51µm for Group 1 and 63.29µm for Group 2; (7) the largest measures of the analyzed parameters were found in animals of Group 2, with functional reproductive organs.

Aspectos histológicos e morfométricos dos testículos de gatos domésticos (Felis catus) / Histological and morphometric evaluation of the testes of cats (Felis catus)

Nesta pesquisa foram obtidos dados histológicos e morfométricos comparativos sobre os testículos de gatos, pós-orquiectomia, divididos em dois grupos: Grupo 1, gatos com até 1 ano de idade e Grupo 2, animais acima de 1 ano. Verificou-se que: (1) aos 4 meses de idade os túbulos seminíferos apresentaram-se pouco desenvolvidos e com ausência de luz, epitélio seminífero baixo, células de Sertoli indiferenciadas e tecido intersticial escasso; (2) aos 5 meses os túbulos seminíferos começaram a se diferenciar com aumento do diâmetro e luz tubulares e as demais estruturas permaneceram semelhantes à observação anterior; (3) aos 6-7 meses ocorreu o início da espermatogênese e espermiogênese; as células de Leydig apareceram maiores, poliédricas com citoplasma vacuolizado e núcleo claro, e tecido intersticial esparso com poucos vasos sangüíneos; (4) os animais com 1 ano de idade apresentaram morfologia testicular igual à do animal adulto, com túbulos seminíferos de maior diâmetro, epitélio germinativo alto e luz tubular pequena, as células de Leydig aparecendo poliédricas, com dimensões variadas, citoplasma vacuolizado, núcleo claro e nucléolo evidente, e espaço intertubular seminífero variado com vasos sanguíneos, predominantemente evidentes; (5) no Grupo 1 o diâmetro médio dos túbulos seminíferos foi de 160,58µm e no Grupo 2 foi de 185,94µm, sendo os valores médios significantes entre si; (6) a altura média do epitélio seminífero foi de 49,51µm para o Grupo 1 e de 63,29µm para o Grupo 2, estaticamente significantes; (7) os maiores valores mensurados foram obtidos para os gatos do Grupo 2, por serem gatos adultos e portanto com os órgãos reprodutores funcionais.(AU)

This paper deals with a comparative histologic and morphometric study of the testes of domestic cats distributed into two groups: Group 1, cats until 1 year of age, and Group 2, cats over 1 year. It was found that: (1) at 4 months of age the seminiferous tubules were poorly developed, appeared as seminiferous cords without lumen, lined by a low epithelium, and showed undifferentiated Sertoli cells and scarce interstitial tissue; (2) at 5 months the seminiferous tubules began to differentiate with increase in tubular diameter and lumen, the other tubular structures remaining similar to those previous referred; (3) at 6 and 7 months of age spermatocytogenesis began to appear, Leydig cells were large, polyhedral in shape, with vacuolated cytoplasm and clear nuclei, resting on a sparse interstitial tissue with few blood vessels; (4) 1-year-old cats showed testicular histological features of an adult animal, had seminiferous tubules of large diameter and high seminiferous epithelium with small lumen, and Leydig cells of different sizes, with polyhedral shape, vacuolated cytoplasm, clear nuclei and evident nucleoli resting in a sparse interstitial tissue with some blood vessels; (5) in Group 1 the average diameter of the seminiferous tubules was 160.58µm, and 185.94µm in Group 2; (6) the height of the seminiferous epithelium was 49.51µm for Group 1 and 63.29µm for Group 2; (7) the largest measures of the analyzed parameters were found in animals of Group 2, with functional reproductive organs.(AU)