Left ventricular function assessment by free-breathing magnetic resonance sequence with multiple excitations

OBJECTIVE: To evaluate the efficacy of free-breathing magnetic resonance sequence with three excitations in the determination of ventricular volumes and masses in individuals without breathholding. MATERIALS AND METHODS: Left ventricular volumes and masses determined in 32 healthy volunteers through two cine magnetic resonance imaging sequences were compared: the first sequence, traditionally utilized and considered as a standard, performed under apnea, with a single excitation, and the second one, with free-breathing and three excitations. Three observers at different levels of experience evaluated the agreement and reproducibility. Intraclass correlation coefficient, paired t-test, Bland-Altman plots and sign test were utilized for statistical analysis. RESULTS: According to the two most experienced observers, intraclass correlation coefficients were > 0.913, the paired t-test demonstrated P values > 0.05, Bland-Altman plots had differences randomly distributed around zero and the sign test descriptive levels were > 0.05. CONCLUSION: The sequence evaluated presents an excellent agreement and reproducibility as compared with the standard sequence, and can be utilized in patients with respiratory limitations.OBJETIVO: Avaliar a eficácia da sequência de ressonância magnética com três excitações, para obtenção de volumes e massas ventriculares, em indivíduos com respiração livre, sem apneia. MATERIAIS E MÉTODOS: Em 32 voluntários sadios, foram comparados os volumes e massas do ventrículo esquerdo, obtidos por meio de duas sequências de ressonância magnética em modo cine. A primeira, tradicionalmente utilizada e considerada padrão, em apneia e com excitação única, e a segunda, em respiração livre e com três excitações. Três leitores, com diferentes níveis de experiência, testaram a concordância e a reprodutibilidade. Para a análise estatística foram utilizados o coeficiente de correlação intraclasse, o teste t-pareado, os gráficos de Bland-Altman e o teste do sinal. RESULTADOS: Para os dois observadores mais experientes, os coeficientes de correlação intraclasse foram superiores a 0,913, assim como os níveis descritivos do teste t-pareado acima de 0,05, os gráficos de Bland-Altman com as diferenças distribuídas aleatoriamente em torno do zero e o teste do sinal com seu nível descritivo superior a 0,05. CONCLUSÃO: A sequência testada apresenta ótima concordância e reprodutibilidade em relação à sequência padrão, podendo ser aplicada em indivíduos com limitações respiratórias.Universidade Federal de São Paulo (UNIFESP) Escola Paulista de MedicinaColégio Brasileiro de Radiologia e Diagnóstico por ImagemUNIFESP, EPMSciEL

Hunting Dark Matter Lines in the Infrared Background with the James Webb Space Telescope

Dark matter particles with a mass around 1 eV can decay into near-infrared photons. Utilising available public blank sky observations from the NIRSpec IFU on the James Webb Space Telescope (JWST), we search for a narrow emission line due to decaying dark matter and derive leading constraints in the mass range 0.8-3 eV on the decay rate to photons, and more specifically, on the axion-photon coupling for the case of axion-like particles. We exclude $\tau < 6.7\cdot 10^{26}$ s at $m_{\rm DM} \simeq 0.9$ eV and, in the case of axions, $g_{a \gamma \gamma} > 9.4 \cdot 10^{-12}$ GeV$^{-1}$ for $m_a = 2.15$ eV. Our results do not rely on dedicated observations, rather we use blank sky observations intended for sky subtraction, and thus our reach may be automatically strengthened as JWST continues to observe.Comment: 12 pages, 2 figure

Hunting Dark Matter Lines in the Infrared Background with the James Webb Space Telescope

Dark matter particles with a mass around 1 eV can decay into near-infrared photons. Utilizing available public blank sky observations from the NIRSpec IFU on the James Webb Space Telescope (JWST), we search for a narrow emission line due to decaying dark matter and derive leading constraints in the mass range 0.8–3 eV on the decay rate to photons, and more specifically, on the axion-photon coupling for the case of axionlike particles. We exclude $1.3×10^{−11}  GeV^{−1}$ for $_≃2.2  eV$. Our results do not rely on dedicated observations, rather we use blank sky observations intended for sky subtraction, and thus our reach may be automatically strengthened as JWST continues to observe

Searching for Synchrotron Emission from the Geminga TeV Halo using the Planck Satellite

Pulsars convert a significant fraction of their total spin-down power into very high-energy electrons, leading to the formation of TeV halos. It is not yet known, however, whether these sources also efficiently accelerate electrons at lower energies and, if so, how those particles propagate through the surrounding environment. If pulsars produce $\sim 50-300 \, {\rm GeV}$ electrons, these particles would produce a spatially extended halo of synchrotron emission in the frequency range measured by Planck. Such emission could be used to constrain the low-energy diffusion coefficient in the regions surrounding these pulsars, as well as the spectrum and intensity of the electrons that are accelerated in this energy range. In this study, we attempt to use Planck data to constrain the nature of the Geminga pulsar's TeV halo. We find no conclusive evidence of this emission in Planck's frequency range, however, and calculate that the synchrotron flux from Geminga should be well below the total flux measured by Planck, even for models with favorable diffusion parameters or soft injection spectra. At this time, these measurements are not capable of significantly constraining the values of these parameters.Comment: 11 pages, 3 figure

Reviving MeV-GeV indirect detection with inelastic dark matter

Thermal relic dark matter below0 $∼10  GeV$ is excluded by cosmic microwave background data if its annihilation to visible particles is unsuppressed near the epoch of recombination. Usual model-building measures to avoid this bound involve kinematically suppressing the annihilation rate in the low-velocity limit, thereby yielding dim prospects for indirect detection signatures at late times. In this work, we investigate a class of cosmologically viable sub-GeV thermal relics with late-time annihilation rates that are detectable with existing and proposed telescopes across a wide range of parameter space. We study a representative model of inelastic dark matter featuring a stable state $_1$ and a slightly heavier excited state $_2$ whose abundance is thermally depleted before recombination. Since the kinetic energy of dark matter in the Milky Way is much larger than it is during recombination, $_1⁢_1→_2⁢_2$ upscattering can efficiently regenerate a cosmologically long-lived Galactic population of $_2$, whose subsequent coannihilations with $_1$ give rise to observable gamma-rays in the $∼1  MeV−100  MeV$ energy range. We find that proposed MeV gamma-ray telescopes, such as e-ASTROGAM, AMEGO, and MAST, would be sensitive to much of the thermal relic parameter space in this class of models and thereby enable both discovery and model discrimination in the event of a signal at accelerator or direct detection experiments