3,437 research outputs found
Balanced metrics on Cartan and Cartan-Hartogs domains
This paper consists of two results dealing with balanced metrics (in S.
Donaldson terminology) on nonconpact complex manifolds. In the first one we
describe all balanced metrics on Cartan domains. In the second one we show that
the only Cartan-Hartogs domain which admits a balanced metric is the complex
hyperbolic space. By combining these results with those obtained in [13]
(Kaehler-Einstein submanifolds of the infinite dimensional projective space, to
appear in Mathematische Annalen) we also provide the first example of complete,
Kaehler-Einstein and projectively induced metric g such that is not
balanced for all .Comment: 11 page
Balanced metrics on homogeneous vector bundles
Let be a holomorphic vector bundle over a compact Kaehler
manifold and let be its
decomposition into irreducible factors. Suppose that each admits a
-balanced metric in Donaldson-Wang terminology. In this paper we prove
that admits a unique -balanced metric if and only if
for all , where denotes
the rank of and . We apply our result to the case
of homogeneous vector bundles over a rational homogeneous variety
and we show the existence and rigidity of balanced Kaehler embedding from into Grassmannians.Comment: 5 page
On the tectonic evolution of the Tyrrhenian basin: new data from detrital zircons sampled in the Sardinia-Corsica Block and in the Calabria-Peloritain Arc
Berezin quantization of homogeneous bounded domains
We prove that a homogeneous bounded domain admits a Berezin quantization
New insights into the early evolution of horizontal spiral trace fossils and the age of the Brioverian series (Ediacaran-Cambrian) in Brittany, NW France
In northwestern France, the Brioverian series is a thick siliciclastic succession deposited during the Cadomian cycle (c. 750-540 Ma). In the uppermost Brioverian beds, previous studies unravelled an assemblage dominated by simple horizontal trace fossils associated with microbially stabilized surfaces. Here, we report Spirodesmos trace fossils - one-way, irregular and regular horizontal spirals - from Crozon (Finistère, Brittany), Montfort-sur-Meu and St-Gonlay (Ille-et-Vilaine, Brittany). After reviewing the literature on horizontal spiral trace fossils, an Ediacaran-Fortunian Spirodesmos pool is identified from marginal-marine to shelf settings, while an Ordovician-Recent trend formed in the deep-marine realm. These results suggest that an onshore-offshore migration in Spirodesmos took place during Ediacaran-Fortunian to Ordovician time, similar to what happened in graphoglyptids. In addition, the age of the uppermost Brioverian beds (Ediacaran or early Cambrian) is still a pending question. Here, we report two new U-Pb detrital zircon datings from sandstone samples in St-Gonlay, giving maximum deposition ages of 551 ± 7 Ma and 540 ± 5 Ma. Although these results do not discard an Ediacaran age for the uppermost Brioverian beds, a Fortunian age is envisioned because the new dating corroborates previous dating from Brittany, Mayenne and Normandy. However, the intervals of error of the radiometric dating, and the dominance of non-penetrative trace fossils associated with matgrounds (an ecology more typical of the Ediacaran Period), do not allow definitive conclusions on the age of the uppermost Brioverian beds
An Adaptive Cognitive Sensor Node for ECG Monitoring in the Internet of Medical Things
The Internet of Medical Things (IoMT) paradigm is becoming mainstream in multiple clinical trials and healthcare procedures. Cardiovascular diseases monitoring, usually involving electrocardiogram (ECG) traces analysis, is one of the most promising and high-impact applications. Nevertheless, to fully exploit the potential of IoMT in this domain, some steps forward are needed. First, the edge-computing paradigm must be added to the picture. A certain level of near-sensor processing has to be enabled, to improve the scalability, portability, reliability and responsiveness of the IoMT nodes. Second, novel, increasingly accurate data analysis algorithms, such as those based on artificial intelligence and Deep Learning, must be exploited. To reach these objectives, designers, and programmers of IoMT nodes, have to face challenging optimization tasks, in order to execute fairly complex computing tasks on low-power wearable and portable processing systems, with tight power and battery lifetime budgets. In this work, we explore the implementation of a cognitive data analysis algorithm, based on a convolutional neural network trained to classify ECG waveforms, on a resource-constrained microcontroller-based computing platform. To minimize power consumption, we add an adaptivity layer that dynamically manages the hardware and software configuration of the device to adapt it at runtime to the required operating mode. Our experimental results show that adapting the node setup to the workload at runtime can save up to 50% power consumption. Our optimized and quantized neural network reaches an accuracy value higher than 97% for arrhythmia disorders detection on MIT-BIH Arrhythmia dataset
Admittance spectroscopy of charge traps of FET based on nanotubes
Investigation of electrical properties of FET based on polymer wrapped nanotubes, namely charge carrier transport and trap appear mechanisms. Model of carrier transport in the device was performed. Local traps states activation energies were obtained
Relaxation processes in thiophene-based random copolymers
The relaxation dynamics of soluble polyalkylthiophenes obtained by the random copolymerisation of 3,4-dibutylthiophene and 3-butylthiophene monomers is investigated. In these systems, the effective conjugation length, the optical gap and the non-radiative decay rate are controlled by varying the content of disubstituted monomers, the steric hindrance of which induces a twisting angle between thiophene rings. Several indications are reported in favour of spectral diffusion of the photoexcitations. Migration processes mainly occur within a few tens of picoseconds
Fundamentals of tin iodide perovskites:A promising route to highly efficient, lead-free solar cells
Hybrid tin-iodide perovskites are investigated as potential lead-free replacement of the lead-iodide perovskites; however, the intrinsic operational limit of these systems has not been described in detail, so far. In this work we combine advanced ab initio calculations with XRD and absorption measurements to lay out the fundamentals of formamidinium (FASnI3) and methylammonium (MASnI3) tin iodide perovskites, in comparison with the lead-halide MAPbI3 prototype. Our theoretical analysis reveals that the tin-based materials display an intrinsic photoconversion efficiency on a par with the lead perovskites, and even superior in the thick-layer limit, where the theoretical PCE reaches 30.5% for lead-halides, and 32.3% for tin-halides under AM1.5G illumination; this is the result of two competing factors: a smaller absorption cross section at the onset for stannates, and their smaller band gap of 1.36 eV, thus very close to the ideal Shockley-Queisser limit. We found the rate of photoluminescence emission extremely sensitive to the absorption spectral weight at the band extrema, resulting in B-factor as different as 7.6 × 10-9 s-1 cm3 for MASnI3 and 0.4 × 10-10 s-1 cm3 for FASnI3. The additional impact of Urbach energy and hole doping, giving rise to large Burstein-Moss effect, is described in detail. This journal i
Challenges and opportunities of light-emitting diode (Led) as key to modulate antioxidant compounds in plants. a review
Plant antioxidants are important compounds involved in plant defense, signaling, growth, and development. The quantity and quality of such compounds is genetically driven; nonetheless, light is one of the factors that strongly influence their synthesis and accumulation in plant tissues. Indeed, light quality affects the fitness of the plant, modulating its antioxidative profile, a key element to counteract the biotic and abiotic stresses. With this regard, light-emitting diodes (LEDs) are emerging as a powerful technology which allows the selection of specific wavelengths and intensities, and therefore the targeted accumulation of plant antioxidant compounds. Despite the unique advantages of such technology, LED application in the horticultural field is still at its early days and several aspects still need to be investigated. This review focused on the most recent outcomes of LED application to modulate the antioxidant compounds of plants, with particular regard to vitamin C, phenols, chlorophyll, carotenoids, and glucosinolates. Additionally, future challenges and opportunities in the use of LED technology in the growth and postharvest storage of fruits and vegetables were also addressed to give a comprehensive overview of the future applications and trends of research
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