The size of the proton dos Santos, Joaquim M. F; Fernandes, Luis M. P; Liu, Yi-Wei ...
Nature (London),
07/2010, Letnik:
466, Številka:
7303
Journal Article
Recenzirano
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, rp, has been determined with an accuracy of 2 per cent (at best) by electron–proton scattering experiments. The present most accurate value of rp (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 rp 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 rp 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 2S1/2 and 2P1/2 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 rp = 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.
Penguins are the only extant family of flightless diving birds. They currently comprise at least 18 species, distributed from polar to tropical environments in the Southern Hemisphere. The history of ...their diversification and adaptation to these diverse environments remains controversial. We used 22 new genomes from 18 penguin species to reconstruct the order, timing, and location of their diversification, to track changes in their thermal niches through time, and to test for associated adaptation across the genome. Our results indicate that the penguin crown-group originated during the Miocene in New Zealand and Australia, not in Antarctica as previously thought, and that Aptenodytes is the sister group to all other extant penguin species. We show that lineage diversification in penguins was largely driven by changing climatic conditions and by the opening of the Drake Passage and associated intensification of the Antarctic Circumpolar Current (ACC). Penguin species have introgressed throughout much of their evolutionary history, following the direction of the ACC, which might have promoted dispersal and admixture. Changes in thermal niches were accompanied by adaptations in genes that govern thermoregulation and oxygen metabolism. Estimates of ancestral effective population sizes (Nₑ) confirm that penguins are sensitive to climate shifts, as represented by three different demographic trajectories in deeper time, themost common (in 11 of 18 penguin species) being an increased Nₑ between 40 and 70 kya, followed by a precipitous decline during the Last Glacial Maximum. The latter effect is most likely a consequence of the overall decline in marine productivity following the last glaciation.
Several miRNAs are known to control myogenesis in vertebrates. Some of them are specifically expressed in muscle while others have a broader tissue expression but are still involved in establishing ...the muscle phenotype. In teleosts, water temperature markedly affects embryonic development and larval growth. It has been previously shown that higher embryonic temperatures promoted faster development and increased size of Senegalese sole (Solea senegalensis) larvae relatively to a lower temperature. The role of miRNAs in thermal-plasticity of growth is hitherto unknown. Hence, we have used high-throughput SOLiD sequencing to determine potential changes in the miRNA transcriptome in Senegalese sole embryos that were incubated at 15°C or 21°C until hatching and then reared at a common temperature of 21°C.
We have identified 320 conserved miRNAs in Senegalese sole, of which 48 had not been previously described in teleosts. mir-17a-5p, mir-26a, mir-130c, mir-206-3p, mir-181a-5p, mir-181a-3p and mir-199a-5p expression levels were further validated by RT- qPCR. The majority of miRNAs were dynamically expressed during early development, with peaks of expression at pre-metamorphosis or metamorphosis. Also, a higher incubation temperature (21°C) was associated with expression of some miRNAs positively related with growth (e.g., miR-17a, miR-181-5p and miR-206) during segmentation and at hatching. Target prediction revealed that these miRNAs may regulate myogenesis through MAPK and mTOR pathways. Expression of miRNAs involved in lipid metabolism and energy production (e.g., miR-122) also differed between temperatures. A miRNA that can potentially target calpain (miR-181-3p), and therefore negatively regulate myogenesis, was preferentially expressed during segmentation at 15°C compared to 21°C.
Temperature has a strong influence on expression of miRNAs during embryonic and larval development in fish. Higher expression levels of miR-17a, miR-181-5p and miR-206-3p and down-regulation of miR-181a-3p at 21°C may promote myogenesis and are in agreement with previous studies in Senegalese sole, which reported enhanced growth at higher embryonic temperatures compared to 15°C. Moreover, miRNAs involved in lipid metabolism and energy production may also contribute to increased larval growth at 21°C compared to 15°C. Taken together, our data indicate that miRNAs may play a role in temperature-induced phenotypic plasticity of growth in teleosts.
Fiber reinforced composites are widely used in the production of parts for load bearing structures. It is generally recognized that composites can be affected both by monotonic and cyclic loading. ...For assembly purposes, drilling is needed, but holes can act as stress concentration notches, leading to damage propagation and failure. In this work, a batch of carbon/epoxy plates is drilled by different drill geometries, while thrust force is monitored and the hole's surrounding region is inspected. Based on radiographic images, the area and other features of the damaged region are computed for damage assessment. Finally, the specimens are subjected to Bearing Fatigue tests. Cyclic loading causes ovality of the holes and the loss of nearly 10% of the bearing net strength. These results can help to establish an association between the damaged region and the material's fatigue resistance, as larger damage extension and deformation by cyclic stress contribute to the loss of load carrying capacity of parts.
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 scattering
, 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 puzzle
, in line with recent determinations of the proton charge radius
, and establishes spectroscopy of light muonic atoms and ions as a precise tool for studies of nuclear properties.
Enhanced production of high quality and healthy fry is a key target for a successful and competitive expansion of the aquaculture industry. Although large quantities of fish larvae are produced, ...survival rates are often low or highly variable and growth potential is in most cases not fully exploited, indicating significant gaps in our knowledge concerning optimal nutritional and culture conditions. Understanding the mechanisms that control early development and muscle growth are critical for the identification of time windows in development that introduce growth variation, and improve the viability and quality of juveniles. This literature review of the current state of knowledge aims to provide a framework for a better understanding of fish skeletal muscle ontogeny, and its impact on larval and juvenile quality as broadly defined. It focuses on fundamental biological knowledge relevant to larval phenotype and quality and, in particular, on the factors affecting the development of skeletal muscle. It also discusses the available methodologies to assess growth and larvae/juvenile quality, identifies gaps in knowledge and suggests future research directions. The focus is primarily on the major farmed non‐salmonid fish species in Europe that include gilthead sea bream, European sea bass, turbot, Atlantic cod, Senegalese sole and Atlantic halibut.
Skeletal muscle growth and flesh quality were evaluated in Senegalese sole fed plant protein (PP) diets. A control fish meal-based diet (FM) was compared with three isonitrogenous (54%) and ...isolipidic (9%) diets with increasing levels of PP blends (50% PP50, 75% PP75 and 100% PP100). By the end of the experiment sole fed PP50 and PP75 had a body length similar to the CTR (25cm), but fish fed PP100 were significantly smaller (23cm). Total FM replacement (PP100) resulted in significantly smaller muscle cross sectional area mainly due to a decrease in the muscle fibre size as the total number of fibres did not vary significantly among treatments. The dietary incorporation of PP significantly reduced the expression of several key genes involved in myogenesis and muscle growth (mrf4, fgf6, myhc and mylc2). Fillet texture was affected by the total substitution of FM. Fish fed PP100 diet had a significantly higher modulus of elasticity (lower flesh stiffness) compared with the other groups. Muscle fibre size was moderately related (r=0.573) to the modulus of elasticity and positively correlated with the expression of lysyl oxidase (r=0.495). Muscle cellularity changes were not associated with the expression of texture-related genes (capn2, ctsb, ctsd), since no significant differences were observed among diets. The present results point towards a modulation of the expression of several muscle growth related genes by increasing levels of PP sources that alter muscle cellularity and textural properties of Senegalese sole when total FM is replaced by PP.
The biological basis through which sustainable and practical plant protein diets (PP) affect flesh texture determinants is extremely scarce so the present results will be valuable to the aquafeed industry, fish producers and final consumers. This study clearly shows that PP diets reduced expression of several key genes involved in myogenesis and muscle growth and can hence affect fish growth potential at long term. This study identifies useful markers that correlated well with muscle cellularity and muscle growth and can be further used to select the most appropriate diets for a fish species.
•Senegalese sole can effectively use diets with PP sources up to 75% of fish meal replacement.•Total FM substitution by PP (PP100) decreased final body size and muscle cross sectional area (CSA).•Smaller CSA in fish fed PP100 was associated with smaller fibre size.•PP diets reduced expression of several key genes involved in myogenesis and muscle growth.•Decreased stiffness (higher modulus of elasticity) in PP100 fillets was partially related with cell size reduction.
Fertilised eggs of Senegalese sole were incubated at 15, 18 or 21°C, and after hatching all larvae were reared at 21°C until 30days post-hatch. By this point larvae from the 18 or 21°C temperature ...groups had 11 and 9% more muscle fibres than those from 15°C, respectively. Hyperplastic growth during metamorphosis was higher in larvae from 18°C. Embryonic temperature induced gene expression changes, albeit with a variable pattern throughout development. Myf5, myod2, myHC and fst mRNA levels were significantly higher at several stages prior to hatching in embryos incubated at 21°C, whereas hsp90AB and hsp70 transcripts were present at higher levels in the 15°C group. Myf5, myod1, myod2, pax7, myog, fst, igf-II, igf1r, hsp90AA and hsp90AB were expressed at higher levels during early development, particularly during somitogenesis. In contrast, mrf4, myHC, mylc2, igf-I, mstn1 and hsp70 were up-regulated at later stages of larval development, namely during and after metamorphosis. This study is the first example of thermal plasticity of myogenesis with prolonged effect in a flatfish.
► Low embryonic temperatures produced smaller sole larvae with less and smaller fibres. ► Several key myogenic genes were differentially expressed with temperature. ► Embryonic temperature had a prolonged effect on gene expression and growth in sole.
A FEM thermal model was implemented to predict the bulk and flash temperature of gears in general and polymer gears in particular.
Using the capabilities of a gear power loss model previously ...validated, a solution for the temperature rise and distribution along the tooth is suggested. The accuracy of the power loss model is decisive for the prediction of gear temperature field by FEM model.
The FEM model was validated with experimental results from the literature. The model allows to predict the bulk temperatures for oil jet, dip lubrication or non-lubricated conditions.
The FEM model allows an higher accuracy on the calculation of the load carrying capacity of polymer gears, whose mechanical properties are critically dependent on the bulk temperature.
•FEM thermal model to predict bulk and ash temperatures on gears.•Validation of the model with experiments from the literature.•Oil jet lubrication, dip lubrication and dry lubrication conditions were studied.•Insight about how to improve thermal behaviour on polymer gears.
Previous studies have indicated that antibody responses can be robustly induced after the vaccination in individuals previously infected by SARS-CoV-2. To evaluate anti-SARS-CoV-2 humoral responses ...in vaccinated individuals with or without a previous history of COVID-19, we compared levels of anti-SARS-CoV-2 antibodies in the sera from 21 vaccinees, including COVID-19-recovered or -naïve individuals in different times, before and after immunization with an inactivated COVID-19 vaccine. Anti-SARS-CoV-2-specific antibodies elicited after COVID-19 and/or immunization with an inactivated vaccine were measured by ELISA and Plaque Reduction Neutralizing assays. Antibody kinetics were consistently different between the two vaccine doses for naïve individuals, contrasting with the SARS-CoV-2-recovered subjects in which we observed no additional increase in antibody levels following the second dose. Sera from SARS-CoV2-naïve individuals had no detectable neutralizing activity against lineage B.1 SARS-CoV-2 or Gamma variant five months after the second vaccine dose. Contrarily, SARS-CoV-2-recovered subjects retained considerable neutralizing activity against both viruses. We conclude that a single inactivated SARS-CoV-2 vaccine dose may be sufficient to induce protective antibody responses in individuals with previous history of SARS-CoV-2 infection.
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