Hidden magnetic fields of young suns Kochukhov, O.; Hackman, T.; Lehtinen, J. J. ...
Astronomy & astrophysics,
03/2020, Letnik:
635
Journal Article
Recenzirano
Odprti dostop
Global magnetic fields of active solar-like stars are, nowadays, routinely detected with spectropolarimetric measurements and are mapped with Zeeman Doppler imaging (ZDI). However, due to the ...cancellation of opposite field polarities, polarimetry only captures a tiny fraction of the magnetic flux and cannot assess the overall stellar surface magnetic field if it is dominated by a small-scale component. The analysis of Zeeman broadening in high-resolution intensity spectra can reveal these hidden complex magnetic fields. Historically, there were very few attempts to obtain such measurements for G dwarf stars due to the difficulty of disentangling the Zeeman effect from other broadening mechanisms affecting spectral lines. Here, we developed a new magnetic field diagnostic method based on relative Zeeman intensification of optical atomic lines with different magnetic sensitivity. By using this technique, we obtained 78 field strength measurements for 15 Sun-like stars, including some of the best-studied young solar twins. We find that the average magnetic field strength
B
f
drops from 1.3−2.0 kG in stars younger than about 120 Myr to 0.2−0.8 kG in older stars. The mean field strength shows a clear correlation with the Rossby number and with the coronal and chromospheric emission indicators. Our results suggest that magnetic regions have roughly the same local field strength
B
≈ 3.2 kG in all stars, with the filling factor
f
of these regions systematically increasing with stellar activity. In comparing our results with the spectropolarimetric analyses of global magnetic fields in the same stars, we find that ZDI recovers about 1% of the total magnetic field energy in the most active stars. This figure drops to just 0.01% for the least active targets.
Viral respiratory tract infection (RTI) is the most frequent cause of infectious illnesses including the common cold. Pharmacological solutions for treating or preventing viral RTIs are so far ...limited and thus several self-care products are available in the market. Some dietary supplements such as probiotics have been shown to modulate immune system function and their role in reducing the risk and the course of RTIs has been investigated extensively within the past decade. However, the mechanism of action and the efficacy of probiotics against viral RTIs remains unclear. We searched PubMed, Google Scholar, and Web of Knowledge for pre-clinical and clinical studies investigating the effect of probiotics on respiratory virus infections, immune response, and the course of upper and lower respiratory tract illness. The literature summarized in this narrative review points out that specific probiotic strains seem effective in pre-clinical models, through stimulating the immune system and inhibiting viral replication. Clinical studies indicate variable efficacy on upper respiratory illnesses and lack proof of diagnosed viral infections. However, meta-analyses of clinical studies indicate that probiotics could be beneficial in upper respiratory illnesses without specific etiology. Further studies aiming at discovering the mechanisms of action of probiotics and clinical efficacy are warranted.
Toward Direct Measurement of Atmospheric Nucleation Kulmala, Markku; Riipinen, Ilona; Sipilä, Mikko ...
Science (American Association for the Advancement of Science),
10/2007, Letnik:
318, Številka:
5847
Journal Article
Recenzirano
Atmospheric aerosol formation is known to occur almost all over the world, and the importance of these particles to climate and air quality has been recognized. Although almost all of the processes ...driving aerosol formation take place below a particle diameter of 3 nanometers, observations cover only larger particles. We introduce an instrumental setup to measure atmospheric concentrations of both neutral and charged nanometer-sized clusters. By applying the instruments in the field, we come to three important conclusions: (i) A pool of numerous neutral clusters in the sub-3 nanometer size range is continuously present; (ii) the processes initiating atmospheric aerosol formation start from particle sizes of ~1.5 nanometers; and (iii) neutral nucleation dominates over the ion-induced mechanism, at least in boreal forest conditions.
Among athletes, nutrition plays a key role, supporting training, performance, and post-exercise recovery. Research has primarily focused on the effects of diet in support of an athletic physique; ...however, the role played by intestinal microbiota has been much neglected. Emerging evidence has shown an association between the intestinal microbiota composition and physical activity, suggesting that modifications in the gut microbiota composition may contribute to physical performance of the host. Probiotics represent a potential means for beneficially influencing the gut microbiota composition/function but can also impact the overall health of the host. In this review, we provide an overview of the existing studies that have examined the reciprocal interactions between physical activity and gut microbiota. We further evaluate the clinical evidence that supports the effects of probiotics on physical performance, post-exercise recovery, and cognitive outcomes among athletes. In addition, we discuss the mechanisms of action through which probiotics affect exercise outcomes. In summary, beneficial microbes, including probiotics, may promote health in athletes and enhance physical performance and exercise capacity. Furthermore, high-quality clinical studies, with adequate power, remain necessary to uncover the roles that are played by gut microbiota populations and probiotics in physical performance and the modes of action behind their potential benefits.
Rotator cuff tendinopathy has a multifactorial origin. Rejecting the mechanistic theory has also led to abandoning operative treatment at initial presentation in the first line. Physiotherapy ...exercise programmes are the accepted first line treatment. The aim of this study was to assess the long-term additional benefits of subacromial decompression in the treatment of rotator cuff tendinopathy.
This randomised controlled trial of 140 patients (52 men, 88 women, mean age 47.1 years; 18 to 60) with rotator cuff tendinopathy extended previous work up to a maximum of 13 years. The patients were randomised into two treatment groups: arthroscopic acromioplasty and a supervised exercise treatment and a similar supervised exercise treatment alone. Self-reported pain on a visual analogue scale (VAS) was the primary outcome measure. Secondary measures were disability, working ability, pain at night, Shoulder Disability Questionnaire score and the number of painful days during the three months preceding the final assessment.
A total of 90 patients (64%) returned questionnaires at a mean 12 years after randomisation. On an intention-to-treat basis, both treatment groups reached statistically significant improvement compared with the initial VAS for pain, but there was no significant difference between groups. The same was true in the secondary outcome measures. Due to group changes, the results were also analysed per protocol: operated or not. No significant differences between the groups were found.
The natural history of rotator cuff tendinopathy probably plays a significant role in the results in the long-term. Even though the patients who underwent operative treatment had a stronger belief in recovery, which is likely to be surgical and the effect of placebo, the exercise group obtained similar results. In the future, an optimum exercise regime should be searched for, as the most clinically and cost-effective conservative treatment for rotator cuff tendinopathy. Cite this article:
2017;99-B:799-805.
Aims. The goal of this work is to study the magnetic fields of six young solar-analogue stars both individually, and collectively, to search for possible magnetic field trends with age. If such ...trends are found, they can be used to understand magnetism in the context of stellar evolution of solar-like stars and to understand the past of the Sun and the solar system. This is also important for the atmospheric evolution of the inner planets, Earth in particular. Methods. We used Stokes IV data from two different spectropolarimeters, NARVAL and HARPSpol. The least-squares deconvolution multi-line technique was used to increase the signal-to-noise ratio of the data. We then applied a modern Zeeman-Doppler imaging code in order to reconstruct the magnetic topology of all stars and the brightness distribution of one of our studied stars. Results. Our results show a significant decrease in the magnetic field strength and energy as the stellar age increases from 100 Myr to 250 Myr, while there is no significant age dependence of the mean magnetic field strength for stars with ages 250−650 Myr. The spread in the mean field strength between different stars is comparable to the scatter between different observations of individual stars. The meridional field component is weaker than the radial and azimuthal field components in 15 of the 16 magnetic maps. It turns out that 89−97% of the magnetic field energy is contained in l = 1 − 3. There is also no clear trend with age and distribution of field energy into poloidal/toroidal and axisymmetric/non-axisymmetric components within the sample. The two oldest stars in this study show an octupole component that is twice as strong as the quadrupole component. This is only seen in 1 of the 13 maps of the younger stars. One star, χ1 Ori, displays two field polarity switches during almost 5 yr of observations suggesting a magnetic cycle length of 2, 6, or 8 yr.
•The impact of probiotics on gut-brain-axis signaling is species- and strain-specific.•Chronic restraint is a suitable model for detecting efficacy of candidate probiotics.•Lpc-37, LP12407 and ...LP12418 improved stress-related deficits in learning and memory.•Lpc-37, LP12407 and LP12418 improved stress-related symptoms of anxiety and depression.•Large-scale pre-clinical screening is essential to discover strain-specific efficacy.
Changes in the gut microbiota have been implicated in mood and cognition. In rodents, supplementation with certain bacteria have been shown to alleviate adverse effects of stress on gut microbiota composition and behaviour, but little is known of how the performance of different strains compare to each other. We took a systematic approach to test the efficacy of twelve candidate probiotic strains from ten species/sub-species of Bifidobacterium and Lactobacillus on behaviours and neuroendocrine responses of chronically stressed mice.
The strains were tested in four screening experiments with non-stressed and chronically stressed vehicle groups. The three most efficacious strains were re-tested to validate the results. Mice were administered a daily oral gavage containing either 1 × 109 colony forming units (CFU) of selected candidate probiotic or saline solution for one week prior to and for three weeks during daily chronic restraint stress. Behavioural tests including the elevated plus maze, open field, novel object recognition, and forced swim test were applied during week five. Corticosterone and adrenocorticotropic hormone (ACTH) were analysed to measure the neuroendocrine response to stress. Plasma and tissue samples were collected for biomarker analyses.
Of the twelve candidate probiotics, Lactobacillus paracasei Lpc-37, Lactobacillus plantarum LP12407, Lactobacillus plantarum LP12418 and Lactobacillus plantarum LP12151 prevented stress-associated anxiety and depression-related behaviours from developing compared with chronically stressed vehicle mice. In addition, Lpc-37 improved cognition.
This systematic screening indicates species- and strain-dependent effects on behavioural outcomes related to stress and further suggests that strains differ from each other in their effects on potential mechanistic outcomes.
PDF
