Dynamical Boson Stars

The idea of stable, localized bundles of energy has strong appeal as a model for particles. In the 1950s John Wheeler envisioned such bundles as smooth configurations of electromagnetic energy that he called {\em geons}, but none were found. Instead, particle-like solutions were found in the late 1960s with the addition of a scalar field, and these were given the name {\em boson stars}. Since then, boson stars find use in a wide variety of models as sources of dark matter, as black hole mimickers, in simple models of binary systems, and as a tool in finding black holes in higher dimensions with only a single killing vector. We discuss important varieties of boson stars, their dynamic properties, and some of their uses, concentrating on recent efforts.Comment: 79 pages, 25 figures, invited review for Living Reviews in Relativity; major revision in 201

Constant light enhances synchrony among circadian clock cells and promotes behavioral rhythms in VPAC(2)-signaling deficient mice

Individual neurons in the suprachiasmatic nuclei (SCN) contain an intracellular molecular clock and use intercellular signaling to synchronize their timekeeping activities so that the SCN can coordinate brain physiology and behavior. The neuropeptide vasoactive intestinal polypeptide (VIP) and its VPAC2 receptor form a key component of intercellular signaling systems in the SCN and critically control cellular coupling. Targeted mutations in either the intracellular clock or intercellular neuropeptide signaling mechanisms, such as VIP-VPAC2 signaling, can lead to desynchronization of SCN neuronal clocks and loss of behavioral rhythms. An important goal in chronobiology is to develop interventions to correct deficiencies in circadian timekeeping. Here we show that extended exposure to constant light promotes synchrony among SCN clock cells and the expression of ~24 h rhythms in behavior in mice in which intercellular signaling is disrupted through loss of VIP-VPAC2 signaling. This study highlights the importance of SCN synchrony for the expression of rhythms in behavior and reveals how non-invasive manipulations in the external environment can be used to overcome neurochemical communication deficits in this important brain system

Calcium signals can freely cross the nuclear envelope in hippocampal neurons: somatic calcium increases generate nuclear calcium transients

<p>Abstract</p> <p>Background</p> <p>In hippocampal neurons, nuclear calcium signaling is important for learning- and neuronal survival-associated gene expression. However, it is unknown whether calcium signals generated by neuronal activity at the cell membrane and propagated to the soma can unrestrictedly cross the nuclear envelope to invade the nucleus. The nuclear envelope, which allows ion transit via the nuclear pore complex, may represent a barrier for calcium and has been suggested to insulate the nucleus from activity-induced cytoplasmic calcium transients in some cell types.</p> <p>Results</p> <p>Using laser-assisted uncaging of caged calcium compounds in defined sub-cellular domains, we show here that the nuclear compartment border does not represent a barrier for calcium signals in hippocampal neurons. Although passive diffusion of molecules between the cytosol and the nucleoplasm may be modulated through changes in conformational state of the nuclear pore complex, we found no evidence for a gating mechanism for calcium movement across the nuclear border.</p> <p>Conclusion</p> <p>Thus, the nuclear envelope does not spatially restrict calcium transients to the somatic cytosol but allows calcium signals to freely enter the cell nucleus to trigger genomic events.</p

Myocardial tagging by Cardiovascular Magnetic Resonance: evolution of techniques--pulse sequences, analysis algorithms, and applications

Cardiovascular magnetic resonance (CMR) tagging has been established as an essential technique for measuring regional myocardial function. It allows quantification of local intramyocardial motion measures, e.g. strain and strain rate. The invention of CMR tagging came in the late eighties, where the technique allowed for the first time for visualizing transmural myocardial movement without having to implant physical markers. This new idea opened the door for a series of developments and improvements that continue up to the present time. Different tagging techniques are currently available that are more extensive, improved, and sophisticated than they were twenty years ago. Each of these techniques has different versions for improved resolution, signal-to-noise ratio (SNR), scan time, anatomical coverage, three-dimensional capability, and image quality. The tagging techniques covered in this article can be broadly divided into two main categories: 1) Basic techniques, which include magnetization saturation, spatial modulation of magnetization (SPAMM), delay alternating with nutations for tailored excitation (DANTE), and complementary SPAMM (CSPAMM); and 2) Advanced techniques, which include harmonic phase (HARP), displacement encoding with stimulated echoes (DENSE), and strain encoding (SENC). Although most of these techniques were developed by separate groups and evolved from different backgrounds, they are in fact closely related to each other, and they can be interpreted from more than one perspective. Some of these techniques even followed parallel paths of developments, as illustrated in the article. As each technique has its own advantages, some efforts have been made to combine different techniques together for improved image quality or composite information acquisition. In this review, different developments in pulse sequences and related image processing techniques are described along with the necessities that led to their invention, which makes this article easy to read and the covered techniques easy to follow. Major studies that applied CMR tagging for studying myocardial mechanics are also summarized. Finally, the current article includes a plethora of ideas and techniques with over 300 references that motivate the reader to think about the future of CMR tagging

Lawson criterion for ignition exceeded in an inertial fusion experiment

For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin "burn propagation" into surrounding cold fuel, enabling the possibility of high energy gain. While "scientific breakeven" (i.e., unity target gain) has not yet been achieved (here target gain is 0.72, 1.37 MJ of fusion for 1.92 MJ of laser energy), this Letter reports the first controlled fusion experiment, using laser indirect drive, on the National Ignition Facility to produce capsule gain (here 5.8) and reach ignition by nine different formulations of the Lawson criterion

The influence of sour taste and cold temperature in pharyngeal transit duration in patients with stroke

CONTEXT: The effect of sour taste and food temperature variations in dysphagic patients has not been entirely clarified. OBJECTIVE: To determine the effect of sour and cold food in the pharyngeal transit times of patients with stroke. METHODS: Patients participating in this study were 30 right-handed adults, 16 of which were male and 14 were female, aged 41 to 88 (average age 62.3 years) with ictus varying from 1 to 30 days (median of 6 days). To analyze the pharyngeal transit time a videofluoroscopy swallow test was performed. Each patient was observed during swallow of a 5 mL paste bolus given by spoon, totaling four different stimuli (natural, cold, sour and cold sour), one at a time, room temperature (22ºC) and cold (8ºC) were used. Later, the tests were analyzed using specific software to measure bolus transit time during the pharyngeal phase. RESULTS: The results showed that the pharyngeal transit time was significantly shorter during swallow of cold sour bolus when compared with other stimuli. Conclusion - Sour taste stimuli associated to cold temperature cause significant change in swallowing patterns, by shortening the pharyngeal transit time, which may lead to positive effects in patients with oropharyngeal dysphagia.CONTEXTO: O efeito do sabor azedo e as variações da temperatura dos alimentos em indivíduos disfágicos, ainda não foi totalmente esclarecidos. OBJETIVO: Verificar o efeito do sabor azedo e da temperatura fria no tempo de trânsito faríngeo da deglutição em indivíduos após acidente vascular encefálico hemisférico isquêmico. MÉTODOS: Participaram deste estudo 30 indivíduos adultos, sendo 16 do gênero masculino e 14 do feminino, destros, com faixa etária variando de 41 a 88 anos (média de 62,3 anos) e ictus que variou de 1 a 30 dias (mediana de 6 dias). Para analisar o tempo de trânsito faríngeo da deglutição foi realizado o exame de videofluoroscopia da deglutição. Cada indivíduo foi observado durante a deglutição de bolo na consistência pastosa, oferecido em colher, com 5 mL cada, sendo ao todo quatro estímulos diferentes, um por vez. Posteriormente os exames foram analisados com auxílio de um software específico para medição do tempo de deslocamento do bolo pela fase faríngea. RESULTADOS: Os resultados mostraram que o tempo de trânsito faríngeo da deglutição foi significantemente menor durante a deglutição de bolo azedo gelado quando comparado aos outros estímulos. CONCLUSÃO: Constatou-se que estímulos com sabor azedo associado à temperatura fria provocam significativa mudança na dinâmica da deglutição, diminuindo o tempo de trânsito faríngeo, podendo assim proporcionar efeitos positivos em indivíduos com disfagia orofaríngea