Laser spectroscopy of muonic deuterium Pohl, Randolf; Nez, François; Fernandes, Luis M. P. ...
Science (American Association for the Advancement of Science),
08/2016, Letnik:
353, Številka:
6300
Journal Article
Recenzirano
Odprti dostop
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 rd = 2.12562(78) fm, which is 2.7 times more accurate but 7.5σ smaller than the CODATA-2010 value rd = 2.1424(21) fm. The μd value is also 3.5σ smaller than the rd value from electronic deuterium spectroscopy. The smaller rd, when combined with the electronic isotope shift, yields a "small" proton radius rp, similar to the one from muonic hydrogen, amplifying the proton radius puzzle.
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.
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 $2{\mathrm{S}}_{1/2}^{\mathrm{F}=0}-2{\mathrm{P}}_{3/2}^{\mathrm{F}=1}$ transition frequency in μp to be 54611.16(1.05) gigahertz (numbers in parentheses indicate one standard deviation of uncertainty) and reevaluated the $2{\mathrm{S}}_{1/2}^{\mathrm{F}=1}-2{\mathrm{P}}_{3/2}^{\mathrm{F}=1}$ 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.
Purpose
To assess the effect of letrozole, an aromatase inhibitor (AI), in patients with resistant prolactinoma that presented an increase in serum prolactin (PRL) levels during testosterone ...replacement therapy (TRT).
Methods
A retrospective cohort study in a single tertiary care center. From March 2012 to July 2023, 53 male patients over 18 years with prolactinoma were followed in our Neuroendocrine Unit. Of those, 90.6% presented macroadenomas, 41% of them were resistant to cabergoline and 25% presented persistent hypogonadism to whom TRT was indicated. Among them, five presented a significant increase in PRL levels and AI was initiated. All five patients had resistant prolactinomas. One of them was excluded due to tumor aggressiveness and concomitant use of temozolomide during AI therapy.
Results
Four patients were included in the analysis, with a mean age of 28.5 (± 7.5) years, median prolactin of 1060 (600 to 6700) ng/mL and median of the largest tumor diameter of 3.6 (1.5 to 5) cm at the time of prolactinoma diagnosis. On TRT, all presented an increase in serum PRL levels (231 to 396%), with a subsequent decrease (61 to 93%) after adding AI. During AI treatment for a median time of 60.5 (21 to 120) months, tumor shrinkage was observed in two cases (-8 and -3 mm in the maximum diameter) and tumor stability in the other two. No major side effects occurred and AI was well tolerated.
Conclusion
AI might be an option for men with resistant prolactinoma who have an increase in PRL levels on TRT. Nevertheless, prospective randomized clinical trials are needed to ensure efficacy and security for this approach.
DESIGN: Cross-sectional visit to a subsample of a population-based birth cohort. SAMPLE: A total of 1076 adolescents aged 14-16 y; 51% males. MEASUREMENTS: Weight, height, subscapular and triceps ...skinfolds were used for assessing overweight and obesity in adolescence, using WHO-recommended criteria. Anthropometric status in early life was measured through birthweight and through weight and length/height at average ages of 20 and 43 months. RESULTS: All analyses were adjusted for socioeconomic and maternal confounding factors. Birthweight and attained size (Z-scores of weight-for-age, height-for-age and weight-for-height) at 20 and 43 months were associated linearly and positively with overweight and obesity in adolescence. Four in each five obese adolescents were not overweight in childhood. Rapid weight gain, both between birth and 20 months, and between 20 and 43 months, was also associated with adolescent overweight and with obesity. Rapid height gain between 20 and 43 months was associated with overweight only. Most associations were stronger for boys. CONCLUSIONS: Birth size, attained size in childhood and particularly growth velocity in early life were associated with increased prevalence of obesity and overweight in Brazilian adolescents. On the other hand, the vast majority of overweight or obese adolescents were not overweight children. Early interventions are undoubtedly important, but population-based strategies aimed at improving diets and physical activity appear to have greater long-term potential than measures targeted at overweight children.
Living cells are constantly exchanging momentum with their surroundings. So far, there is no consensus regarding how cells respond to such external stimuli, although it reveals much about their ...internal structures, motility as well as the emergence of disorders. Here, we report that twelve cell lines, ranging from healthy fibroblasts to cancer cells, hold a ubiquitous double power-law viscoelastic relaxation compatible with the fractional Kelvin-Voigt viscoelastic model. Atomic Force Microscopy measurements in time domain were employed to determine the mechanical parameters, namely, the fast and slow relaxation exponents, the crossover timescale between power law regimes, and the cell stiffness. These cell-dependent quantities show strong correlation with their collective migration and invasiveness properties. Beyond that, the crossover timescale sets the fastest timescale for cells to perform their biological functions.
Aims
Brazil ranks high in the number of coronavirus disease 19 (COVID‐19) cases and the COVID‐19 mortality rate. In this context, autopsies are important to confirm the disease, determine associated ...conditions, and study the pathophysiology of this novel disease. The aim of this study was to assess the systemic involvement of COVID‐19. In order to follow biosafety recommendations, we used ultrasound‐guided minimally invasive autopsy (MIA‐US), and we present the results of 10 initial autopsies.
Methods and results
We used MIA‐US for tissue sampling of the lungs, liver, heart, kidneys, spleen, brain, skin, skeletal muscle and testis for histology, and reverse transcription polymerase chain reaction to detect severe acute respiratory syndrome coronavirus 2 RNA. All patients showed exudative/proliferative diffuse alveolar damage. There were intense pleomorphic cytopathic effects on the respiratory epithelium, including airway and alveolar cells. Fibrinous thrombi in alveolar arterioles were present in eight patients, and all patients showed a high density of alveolar megakaryocytes. Small thrombi were less frequently observed in the glomeruli, spleen, heart, dermis, testis, and liver sinusoids. The main systemic findings were associated with comorbidities, age, and sepsis, in addition to possible tissue damage due to the viral infection, such as myositis, dermatitis, myocarditis, and orchitis.
Conclusions
MIA‐US is safe and effective for the study of severe COVID‐19. Our findings show that COVID‐19 is a systemic disease causing major events in the lungs and with involvement of various organs and tissues. Pulmonary changes result from severe epithelial injury and microthrombotic vascular phenomena. These findings indicate that both epithelial and vascular injury should be addressed in therapeutic approaches.
Wide band gap niobium oxides are particularly important for electronic device applications. Two types of NbO powders were sintered between 300 and 1100 °C. The structural characterization of the ...pellets, performed by X-ray diffraction measurements and Raman spectroscopy, revealed the appearance of the NbO and T-, B-, and H-Nb2O5 polymorphs, depending on the sintering temperature. The optical characterization was complemented with absorption measurements and photoluminescence, where it was possible to identify a bandgap of 3.5 eV. A strong dependence of luminescence on the sintering temperature and therefore of the niobium oxide crystalline phases nature was observed. The influence of the morphological and structural characteristics on the dielectrical properties, at room temperature and in the low frequency range (<100 MHz), was studied. The sample with the H-Nb2O5 polymorph presents higher dielectric constant (∼55) than the samples with T- and B-Nb2O5 (∼25).
We have analyzed solar-like oscillations in ~1700 stars observed by the Kepler Mission, spanning from the main sequence to the red clump. Using evolutionary models, we test asteroseismic scaling ...relations for the frequency of maximum power ( Delta *nmax), the large frequency separation ( Delta *D Delta *n), and oscillation amplitudes. We show that the difference of the Delta *D Delta *n- Delta *nmax relation for unevolved and evolved stars can be explained by different distributions in effective temperature and stellar mass, in agreement with what is expected from scaling relations. For oscillation amplitudes, we show that neither (L/M) s scaling nor the revised scaling relation by Kjeldsen & Bedding is accurate for red-giant stars, and demonstrate that a revised scaling relation with a separate luminosity-mass dependence can be used to calculate amplitudes from the main sequence to red giants to a precision of ~25%. The residuals show an offset particularly for unevolved stars, suggesting that an additional physical dependency is necessary to fully reproduce the observed amplitudes. We investigate correlations between amplitudes and stellar activity, and find evidence that the effect of amplitude suppression is most pronounced for subgiant stars. Finally, we test the location of the cool edge of the instability strip in the Hertzsprung-Russell diagram using solar-like oscillations and find the detections in the hottest stars compatible with a domain of hybrid stochastically excited and opacity driven pulsation.
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