Noncommutative gauge theory using covariant star product defined between Lie-valued differential forms

We develop an internal gauge theory using a covariant star product. The space-time is a symplectic manifold endowed only with torsion but no curvature. It is shown that, in order to assure the restrictions imposed by the associativity property of the star product, the torsion of the space-time has to be covariant constant. An illustrative example is given and it is concluded that in this case the conditions necessary to define a covariant star product on a symplectic manifold completely determine its connection.Comment: AMS-LaTeX 19 pages. v2: corrections in language and equations (typos), expanded sections 3-5, added references. v3: minor presentational and grammatical corrections, completed, corrected and reordered some references

Magnetic nanocomposites at microwave frequencies

Most conventional magnetic materials used in the electronic devices are ferrites, which are composed of micrometer-size grains. But ferrites have small saturation magnetization, therefore the performance at GHz frequencies is rather poor. That is why functionalized nanocomposites comprising magnetic nanoparticles (e.g. Fe, Co) with dimensions ranging from a few nm to 100 nm, and embedded in dielectric matrices (e.g. silicon oxide, aluminium oxide) have a significant potential for the electronics industry. When the size of the nanoparticles is smaller than the critical size for multidomain formation, these nanocomposites can be regarded as an ensemble of particles in single-domain states and the losses (due for example to eddy currents) are expected to be relatively small. Here we review the theory of magnetism in such materials, and we present a novel measurement method used for the characterization of the electromagnetic properties of composites with nanomagnetic insertions. We also present a few experimental results obtained on composites consisting of iron nanoparticles in a dielectric matrix.Comment: 20 pages, 10 figures, 5 table

Decomposition of coarse woody debris in a long-term litter manipulation experiment: A focus on nutrient availability

The majority of above-ground carbon in tropical forests is stored in wood, which is returned to the atmosphere during decomposition of coarse woody debris. However, the factors controlling wood decomposition have not been experimentally manipulated over time scales comparable to the length of this process.We hypothesized that wood decomposition is limited by nutrient availability and tested this hypothesis in a long-term litter addition and removal experiment in a lowland tropical forest in Panama. Specifically, we quantified decomposition using a 15-year chronosequence of decaying boles, and measured respiration rates and nutrient limitation of wood decomposer communities.The long-term probability that a dead tree completely decomposed was decreased in plots where litter was removed, but did not differ between litter addition and control treatments. Similarly, respiration rates of wood decomposer communities were greater in control treatments relative to litter removal plots; litter addition treatments did not differ from either of the other treatments. Respiration rates increased in response to nutrient addition (nitrogen, phosphorus, and potassium) in the litter removal and addition treatments, but not in the controls.Established decreases in concentrations of soil nutrients in litter removal plots and increased respiration rates in response to nutrient addition suggest that reduced rates of wood decomposition after litter removal were caused by decreased nutrient availability. The effects of litter manipulations differed directionally from a previous short-term decomposition study in the same plots, and reduced rates of bole decomposition in litter removal plots did not emerge until after more than 6 years of decomposition. These differences suggest that litter-mediated effects on nutrient dynamics have complex interactions with decomposition over time

Graphene Optomechanics Realized at Microwave Frequencies

Cavity optomechanics has served as a platform for studying the interaction between light and micromechanical motion via radiation pressure. Here we observe such phenomena with a graphene mechanical resonator coupled to an electromagnetic mode. We measure thermal motion and backaction cooling in a bilayer graphene resonator coupled to a microwave on-chip cavity. We detect the lowest flexural mode at 24 MHz down to 60 mK, corresponding to 50±6 mechanical quanta, which represents a phonon occupation that is nearly 3 orders of magnitude lower than that which has been recorded to date with graphene resonators.Peer reviewe

SOURCES OF HEALTHCARE WORKERS' COVID-19 INFECTIONS AND RELATED SAFETY GUIDELINES

Objectives: To evaluate the effectiveness of safety guidelines in the workplace, the authors analyzed the work-related exposure to SARS-CoV-2 and the source of COVID-19 infections among healthcare workers (HCWs), together with the use of personal protective equipment (PPE). Material and Methods: A cross-sectional prospective study was conducted in tertiary hospitals in the Uusimaa region, Finland, with 1072 volunteers being enrolled in the study from among the HCWs at the Helsinki University Hospital. Overall, 866 (80.8%) HCWs (including 588 nurses, 170 doctors, and 108 laboratory and medical imaging nurses) completed the questionnaire by July 15, 2020, with 52% of the participants taking care of COVID-19 patients. The participants answered a structured questionnaire regarding their use of PPE, the ability to follow safety guidelines, exposure to COVID-19, and the source of potential COVID-19 infections. The participants with COVID-19 symptoms were tested with the SARS-CoV-2 real-time polymerase chain reaction method. All infected participants were contacted, and their answers were confirmed regarding COVID-19 exposure. Results: In total, 41 (4.7%) participants tested positive for SARS-CoV-2, with 22 (53.6%) of infections being confirmed or likely occupational, and 12 (29.3%) originating from colleagues. In 14 cases (63.6%), occupational infections occurred while using a surgical mask, and all infections originating from patients occurred while using a surgical mask or no mask at all. No occupational infections were found while using an FFP2/3 respirator and following aerosol precautions. The combined odds ratio for working at an intensive care unit, an emergency department, or a ward was 3.4 (95% CI: 1.2-9.2, p = 0.016). Conclusions: A high infection rate was found among HCWs despite safety guidelines. Based on these findings, the authors recommend the use of FFP2/3 respirators in all patient contacts with confirmed or suspected COVID-19, along with the use of universal masking, also in personnel rooms.Peer reviewe

Plant diversity and functional trait composition during mire development

During succession, plant species composition undergoes changes that may have implications for ecosystem functions. Here we aimed to study changes in plant species diversity, functional diversity and functional traits associated with mire development. We sampled vegetation from 22 mires on the eastern shore of the Gulf of Bothnia (west coast of Finland) that together represent seven different time steps along a mire chronosequence resulting from post-glacial rebound. This chronosequence spans a time period of almost 2500 years. Information about 15 traits of vascular plants and 17 traits of mosses was collected, mainly from two different databases. In addition to species richness and Shannon diversity index, we measured functional diversity and community weighted means of functional traits. We found that plant species diversity increased from the early succession stages towards the fen-bog transition. The latter stage also has the most diverse surface structure, consisting of pools and hummocks. Functional diversity increased linearly with species richness, suggesting a lack of functional redundancy during mire succession. On the other hand, Rao's quadratic entropy, another index of functional diversity, remained rather constant throughout the succession. The changes in functional traits indicate a trade-off between acquisitive and conservative strategies. The functional redundancy, i.e. the lack of overlap between similarly functioning species, may indicate that the resistance to environmental disturbances such as drainage or climate change does not change during mire succession. However, the trait trade-off towards conservative strategy, together with the developing microtopography of hummocks and hollows with strongly differing vegetation composition, could increase resistance during mire succession.Peer reviewe

Environment simulator for studying automatic crop farming

Agricultural machines capable of utilizing variable rate application technology are tackling spatial variability in agricultural fields.  Agricultural field robots are the next step in technology, robots which are capable of utilizing sensor and actuating technologies without human contact and operate only areas of interest.  However, agricultural field robots are still under research.  Robots are just one part of the next generation of crop farming having more advanced tools to do the work which currently requires humans.  The next generation of crop farming, in the vision of the authors, is based on automation, which incorporates stationary and moving sensors systems, robots, model based decision making, automated operation planning which adapts to spatial variability according to the measurements as well as to weather conditions.  This article presents a top-down approach of automated crop farming using simulation, trying to cover all the component parts on a fully automated farm.  In the article, the developed simulation platform is presented as well as sample simulation results.  The environment simulator is based on crop growth models, weed growth models, soil models, spatial variation generation and weather statistics.  Models for the environment were found in literature and were tailored and tuned to fit the simulation purposes, to form a collection of models.  The collection of models was evaluated by using sensitivity analysis.  Furthermore, a full scale scenario was simulated over one season, incorporating 9000 spatial cells in five fields of a farm.   Keywords: robots, crop growth models, soil water models, decision making, operation plannin

Antidepressant use and work-related injuries

Background. Adverse effects of antidepressants are most common at the beginning of the treatment, but possible also later. We examined the association between antidepressant use and work-related injuries taking into account the duration of antidepressant use. Method. Antidepressant use and work-related injuries between 2000 and 2011 were measured among 66 238 employees (mean age 43.8 years, 80% female) using linkage to national records (the Finnish Public Sector study). We analysed data using time-dependent modelling with individuals as their own controls (self-controlled case-series design). Results. In 2238 individuals who had used antidepressants and had a work-related injury during a mean follow-up of 7.8 years, no increase in the risk of injury was observed in the beginning of antidepressant treatment. However, an increased injury risk was seen after 3 months of treatment (rate ratio, compared with no recent antidepressant use, 1.27, 95% confidence interval 1.10-1.48). This was also the case among those who had used only selective serotonin re-uptake inhibitors (n = 714; rate ratio 1.41, 95% confidence interval 1.08-1.83). Conclusions. Antidepressant use was not associated with an increased risk of work-related injury at the beginning of treatment. Post-hoc analyses of antidepressant trials are needed to determine whether long-term use of antidepressants increases the risk of work-related injury.Peer reviewe

Are you what you eat? A highly transient and prey‐influenced gut microbiome in the grey house spider Badumna longinqua

Stable core microbial communities have been described in numerous animal species and are commonly associated with fitness benefits for their hosts. Recent research, however, highlights examples of species whose microbiota are transient and environmentally derived. Here, we test the effect of diet on gut microbial community assembly in the spider Badumna longinqua. Using 16S rRNA gene amplicon sequencing combined with quantitative PCR, we analyzed diversity and abundance of the spider's gut microbes, and simultaneously characterized its prey communities using nuclear rRNA markers. We found a clear correlation between community similarity of the spider's insect prey and gut microbial DNA, suggesting that microbiome assembly is primarily diet-driven. This assumption is supported by a feeding experiment, in which two types of prey-crickets and fruit flies-both substantially altered microbial diversity and community similarity between spiders, but did so in different ways. After cricket consumption, numerous cricket-derived microbes appeared in the spider's gut, resulting in a rapid homogenization of microbial communities among spiders. In contrast, few prey-associated bacteria were detected after consumption of fruit flies; instead, the microbial community was remodelled by environmentally sourced microbes, or abundance shifts of rare taxa in the spider's gut. The reshaping of the microbiota by both prey taxa mimicked a stable core microbiome in the spiders for several weeks post feeding. Our results suggest that the spider's gut microbiome undergoes pronounced temporal fluctuations, that its assembly is dictated by the consumed prey, and that different prey taxa may remodel the microbiota in drastically different ways.journal articl