The spectrum of the hydrogen atom has played a central part in fundamental physics over the past 200 years. Historical examples of its importance include the wavelength measurements of absorption ...lines in the solar spectrum by Fraunhofer, the identification of transition lines by Balmer, Lyman and others, the empirical description of allowed wavelengths by Rydberg, the quantum model of Bohr, the capability of quantum electrodynamics to precisely predict transition frequencies, and modern measurements of the 1S-2S transition by Hänsch to a precision of a few parts in 10
. Recent technological advances have allowed us to focus on antihydrogen-the antimatter equivalent of hydrogen. The Standard Model predicts that there should have been equal amounts of matter and antimatter in the primordial Universe after the Big Bang, but today's Universe is observed to consist almost entirely of ordinary matter. This motivates the study of antimatter, to see if there is a small asymmetry in the laws of physics that govern the two types of matter. In particular, the CPT (charge conjugation, parity reversal and time reversal) theorem, a cornerstone of the Standard Model, requires that hydrogen and antihydrogen have the same spectrum. Here we report the observation of the 1S-2S transition in magnetically trapped atoms of antihydrogen. We determine that the frequency of the transition, which is driven by two photons from a laser at 243 nanometres, is consistent with that expected for hydrogen in the same environment. This laser excitation of a quantum state of an atom of antimatter represents the most precise measurement performed on an anti-atom. Our result is consistent with CPT invariance at a relative precision of about 2 × 10
.
The observation of hyperfine structure in atomic hydrogen by Rabi and co-workers and the measurement of the zero-field ground-state splitting at the level of seven parts in 10
are important ...achievements of mid-twentieth-century physics. The work that led to these achievements also provided the first evidence for the anomalous magnetic moment of the electron, inspired Schwinger's relativistic theory of quantum electrodynamics and gave rise to the hydrogen maser, which is a critical component of modern navigation, geo-positioning and very-long-baseline interferometry systems. Research at the Antiproton Decelerator at CERN by the ALPHA collaboration extends these enquiries into the antimatter sector. Recently, tools have been developed that enable studies of the hyperfine structure of antihydrogen-the antimatter counterpart of hydrogen. The goal of such studies is to search for any differences that might exist between this archetypal pair of atoms, and thereby to test the fundamental principles on which quantum field theory is constructed. Magnetic trapping of antihydrogen atoms provides a means of studying them by combining electromagnetic interaction with detection techniques that are unique to antimatter. Here we report the results of a microwave spectroscopy experiment in which we probe the response of antihydrogen over a controlled range of frequencies. The data reveal clear and distinct signatures of two allowed transitions, from which we obtain a direct, magnetic-field-independent measurement of the hyperfine splitting. From a set of trials involving 194 detected atoms, we determine a splitting of 1,420.4 ± 0.5 megahertz, consistent with expectations for atomic hydrogen at the level of four parts in 10
. This observation of the detailed behaviour of a quantum transition in an atom of antihydrogen exemplifies tests of fundamental symmetries such as charge-parity-time in antimatter, and the techniques developed here will enable more-precise such tests.
Resumen Introducción El glioblastoma es el tumor cerebral más frecuente. A pesar de los avances en su tratamiento, el pronóstico sigue siendo pobre, con una supervivencia media en torno a los 14 ...meses. Los costes directos, aquellos asociados al diagnóstico y el tratamiento de la enfermedad, han sido descritos ampliamente. Los costes indirectos, aquellos derivados de la pérdida de productividad debido a la enfermedad, han sido descritos en escasas ocasiones. Material y método Realizamos un estudio retrospectivo, incluyendo a los pacientes diagnosticados entre el 1 de enero del 2010 y el 31 de diciembre del 2013 de glioblastoma en el Hospital Universitario Donostia. Recogimos datos demográficos, relativos al tratamiento ofertado y la supervivencia. Calculamos los costes indirectos a través del método del capital humano, obteniendo datos de sujetos comparables según sexo y edad, y de mortalidad de la población general a través del Instituto Nacional de Estadística. Los salarios pasados fueron actualizados a euros de 2015 según la tasa de inflación interanual y los salarios futuros fueron descontados en un 3,5% anual en forma de interés compuesto. Resultados Revisamos a 99 pacientes, 46 mujeres (edad media 63,53 años) y 53 hombres (edad media 59,94 años). En 29 pacientes se realizó una biopsia y en los 70 restantes se realizó una cirugía resectiva. La supervivencia global media fue de 18,092 meses. Los costes indirectos totales fueron de 11.080.762 € (2015). El coste indirecto medio por paciente fue de 111.926 € (2015). Discusión A pesar de que el glioblastoma es un tipo relativamente poco frecuente de tumor, que supone el 4% de todos los tipos de cáncer, su mal pronóstico y sus posibles secuelas generan una mortalidad y morbilidad desproporcionadamente altas. Esto se traduce en unos costes indirectos muy elevados. El clínico debe ser consciente del impacto del glioblastoma en la sociedad y los costes indirectos deben ser tenidos en cuenta en los estudios de coste-efectividad para conocer las consecuencias globales de esta enfermedad.
Glioblastoma is the most common primary brain tumour. Despite advances in treatment, its prognosis remains dismal, with a mean survival time of about 14 months. Many articles have addressed direct ...costs, those associated with the diagnosis and treatment of the disease. Indirect costs, those associated with loss of productivity due to the disease, have seldom been described.
We conducted a retrospective study in patients diagnosed with glioblastoma at Hospital Universitario Donostia between January 1, 2010 and December 31, 2013. We collected demographics, data regarding the treatment received, and survival times. We calculated the indirect costs with the human capital approach, adjusting the mean salaries of comparable individuals by sex and age and obtaining mortality data for the general population from the Spanish National Statistics Institute. Past salaries were updated to 2015 euros according to the annual inflation rate and we applied a discount of 3.5% compounded yearly to future salaries.
We reviewed the records of 99 patients: 46 women (mean age 63.53) and 53 men (mean age 59.94); 29 patients underwent a biopsy and the remaining 70 underwent excisional surgery. Mean survival was 18.092 months for the whole series. The total indirect cost for the series was €11 080 762 (2015). Mean indirect cost per patient was €111 926 (2015).
Although glioblastoma is a relatively uncommon type of tumour, accounting for only 4% of all cancers, its poor prognosis and potential sequelae generate disproportionately large morbidity and mortality rates which translate to high indirect costs. Clinicians should be aware of the societal impact of glioblastoma and indirect costs should be taken into account when cost effectiveness studies are performed to better illustrate the overall consequences of this disease.
Glioblastoma is the most common primary brain tumour. Despite advances in treatment, its prognosis remains dismal, with a mean survival time of about 14 months. Many articles have addressed direct ...costs, those associated with the diagnosis and treatment of the disease. Indirect costs, those associated with loss of productivity due to the disease, have seldom been described.
We conducted a retrospective study in patients diagnosed with glioblastoma at Hospital Universitario Donostia between January 1, 2010 and December 31, 2013. We collected demographics, data regarding the treatment received, and survival times. We calculated the indirect costs with the human capital approach, adjusting the mean salaries of comparable individuals by sex and age and obtaining mortality data for the general population from the Spanish National Statistics Institute. Past salaries were updated to 2015 euros according to the annual inflation rate and we applied a discount of 3.5% compounded yearly to future salaries.
We reviewed the records of 99 patients: 46 women (mean age 63.53) and 53 men (mean age 59.94); 29 patients underwent a biopsy and the remaining 70 underwent excisional surgery. Mean survival was 18.092 months for the whole series. The total indirect cost for the series was €11080762 (2015). Mean indirect cost per patient was €111926 (2015).
Although glioblastoma is a relatively uncommon type of tumour, accounting for only 4% of all cancers, its poor prognosis and potential sequelae generate disproportionately large morbidity and mortality rates which translate to high indirect costs. Clinicians should be aware of the societal impact of glioblastoma and indirect costs should be taken into account when cost effectiveness studies are performed to better illustrate the overall consequences of this disease.
El glioblastoma es el tumor cerebral más frecuente. A pesar de los avances en su tratamiento, el pronóstico sigue siendo pobre, con una supervivencia media en torno a los 14 meses. Los costes directos, aquellos asociados al diagnóstico y el tratamiento de la enfermedad, han sido descritos ampliamente. Los costes indirectos, aquellos derivados de la pérdida de productividad debido a la enfermedad, han sido descritos en escasas ocasiones.
Realizamos un estudio retrospectivo, incluyendo a los pacientes diagnosticados entre el 1 de enero del 2010 y el 31 de diciembre del 2013 de glioblastoma en el Hospital Universitario Donostia. Recogimos datos demográficos, relativos al tratamiento ofertado y la supervivencia. Calculamos los costes indirectos a través del método del capital humano, obteniendo datos de sujetos comparables según sexo y edad, y de mortalidad de la población general a través del Instituto Nacional de Estadística. Los salarios pasados fueron actualizados a euros de 2015 según la tasa de inflación interanual y los salarios futuros fueron descontados en un 3,5% anual en forma de interés compuesto.
Revisamos a 99 pacientes, 46 mujeres (edad media 63,53 años) y 53 hombres (edad media 59,94 años). En 29 pacientes se realizó una biopsia y en los 70 restantes se realizó una cirugía resectiva. La supervivencia global media fue de 18,092 meses. Los costes indirectos totales fueron de 11.080.762 € (2015). El coste indirecto medio por paciente fue de 111.926 € (2015).
A pesar de que el glioblastoma es un tipo relativamente poco frecuente de tumor, que supone el 4% de todos los tipos de cáncer, su mal pronóstico y sus posibles secuelas generan una mortalidad y morbilidad desproporcionadamente altas. Esto se traduce en unos costes indirectos muy elevados. El clínico debe ser consciente del impacto del glioblastoma en la sociedad y los costes indirectos deben ser tenidos en cuenta en los estudios de coste-efectividad para conocer las consecuencias globales de esta enfermedad.
Laser cooling of antihydrogen atoms Baker, C J; Bertsche, W; Capra, A ...
Nature (London),
04/2021, Letnik:
592, Številka:
7852
Journal Article
Recenzirano
Odprti dostop
The photon-the quantum excitation of the electromagnetic field-is massless but carries momentum. A photon can therefore exert a force on an object upon collision
. Slowing the translational motion of ...atoms and ions by application of such a force
, known as laser cooling, was first demonstrated 40 years ago
. It revolutionized atomic physics over the following decades
, and it is now a workhorse in many fields, including studies on quantum degenerate gases, quantum information, atomic clocks and tests of fundamental physics. However, this technique has not yet been applied to antimatter. Here we demonstrate laser cooling of antihydrogen
, the antimatter atom consisting of an antiproton and a positron. By exciting the 1S-2P transition in antihydrogen with pulsed, narrow-linewidth, Lyman-α laser radiation
, we Doppler-cool a sample of magnetically trapped antihydrogen. Although we apply laser cooling in only one dimension, the trap couples the longitudinal and transverse motions of the anti-atoms, leading to cooling in all three dimensions. We observe a reduction in the median transverse energy by more than an order of magnitude-with a substantial fraction of the anti-atoms attaining submicroelectronvolt transverse kinetic energies. We also report the observation of the laser-driven 1S-2S transition in samples of laser-cooled antihydrogen atoms. The observed spectral line is approximately four times narrower than that obtained without laser cooling. The demonstration of laser cooling and its immediate application has far-reaching implications for antimatter studies. A more localized, denser and colder sample of antihydrogen will drastically improve spectroscopic
and gravitational
studies of antihydrogen in ongoing experiments. Furthermore, the demonstrated ability to manipulate the motion of antimatter atoms by laser light will potentially provide ground-breaking opportunities for future experiments, such as anti-atomic fountains, anti-atom interferometry and the creation of antimatter molecules.
Antihydrogen, a positron bound to an antiproton, is the simplest anti-atom. Its structure and properties are expected to mirror those of the hydrogen atom. Prospects for precision comparisons of the ...two, as tests of fundamental symmetries, are driving a vibrant programme of research. In this regard, a limiting factor in most experiments is the availability of large numbers of cold ground state antihydrogen atoms. Here, we describe how an improved synthesis process results in a maximum rate of 10.5 ± 0.6 atoms trapped and detected per cycle, corresponding to more than an order of magnitude improvement over previous work. Additionally, we demonstrate how detailed control of electron, positron and antiproton plasmas enables repeated formation and trapping of antihydrogen atoms, with the simultaneous retention of atoms produced in previous cycles. We report a record of 54 detected annihilation events from a single release of the trapped anti-atoms accumulated from five consecutive cycles.Antihydrogen studies are important in testing the fundamental principles of physics but producing antihydrogen in large amounts is challenging. Here the authors demonstrate an efficient and high-precision method for trapping and stacking antihydrogen by using controlled plasma.
Antimatter continues to intrigue physicists because of its apparent absence in the observable Universe. Current theory requires that matter and antimatter appeared in equal quantities after the Big ...Bang, but the Standard Model of particle physics offers no quantitative explanation for the apparent disappearance of half the Universe. It has recently become possible to study trapped atoms of antihydrogen to search for possible, as yet unobserved, differences in the physical behaviour of matter and antimatter. Here we consider the charge neutrality of the antihydrogen atom. By applying stochastic acceleration to trapped antihydrogen atoms, we determine an experimental bound on the antihydrogen charge, Qe, of |Q| < 0.71 parts per billion (one standard deviation), in which e is the elementary charge. This bound is a factor of 20 less than that determined from the best previous measurement of the antihydrogen charge. The electrical charge of atoms and molecules of normal matter is known to be no greater than about 10(-21)e for a diverse range of species including H2, He and SF6. Charge-parity-time symmetry and quantum anomaly cancellation demand that the charge of antihydrogen be similarly small. Thus, our measurement constitutes an improved limit and a test of fundamental aspects of the Standard Model. If we assume charge superposition and use the best measured value of the antiproton charge, then we can place a new limit on the positron charge anomaly (the relative difference between the positron and elementary charge) of about one part per billion (one standard deviation), a 25-fold reduction compared to the current best measurement.
The Escherichia coli melR gene encodes MelR protein which is a member of the AraC/XylS family of bacterial transcription activators. The function of MelR was investigated by making a targeted ...deletion in the melR gene of the Escherichia coli chromosome. MelR is a transcription activator essential for melibiose-dependent expression of the melAB operon which is needed for bacterial growth with melibiose as a carbon source. To investigate the interactions of MelR at the melAB promoter, both full length MelR and a shortened derivative, MelR173, containing the C-terminal DNA-binding domain, were purified as fusions to glutathione-S-transferase. Circular permutation studies show that both full-length MelR and MelR173 induce an apparent bend upon binding to target sites at the melAB promoter. Bound full-length MelR, but not MelR173, can oligomerise to form larger complexes that are likely to be involved in transcription activation.
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