3,222 research outputs found

    Global symplectic coordinates on gradient Kaehler-Ricci solitons

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    A classical result of D. McDuff asserts that a simply-connected complete Kaehler manifold (M,g,ω)(M,g,\omega) with non positive sectional curvature admits global symplectic coordinates through a symplectomorphism Ψ:M→R2n\Psi: M\rightarrow R^{2n} (where nn is the complex dimension of MM), satisfying the following property (proved by E. Ciriza): the image Ψ(T)\Psi (T) of any complex totally geodesic submanifold T⊂MT\subset M through the point pp such that Ψ(p)=0\Psi(p)=0, is a complex linear subspace of Cn≃R2nC^n \simeq R^{2n}. The aim of this paper is to exhibit, for all positive integers nn, examples of nn-dimensional complete Kaehler manifolds with non-negative sectional curvature globally symplectomorphic to R2nR^{2n} through a symplectomorphism satisfying Ciriza's property.Comment: 8 page

    The bisymplectomorphism group of a bounded symmetric domain

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    An Hermitian bounded symmetric domain in a complex vector space, given in its circled realization, is endowed with two natural symplectic forms: the flat form and the hyperbolic form. In a similar way, the ambient vector space is also endowed with two natural symplectic forms: the Fubini-Study form and the flat form. It has been shown in arXiv:math.DG/0603141 that there exists a diffeomorphism from the domain to the ambient vector space which puts in correspondence the above pair of forms. This phenomenon is called symplectic duality for Hermitian non compact symmetric spaces. In this article, we first give a different and simpler proof of this fact. Then, in order to measure the non uniqueness of this symplectic duality map, we determine the group of bisymplectomorphisms of a bounded symmetric domain, that is, the group of diffeomorphisms which preserve simultaneously the hyperbolic and the flat symplectic form. This group is the direct product of the compact Lie group of linear automorphisms with an infinite-dimensional Abelian group. This result appears as a kind of Schwarz lemma.Comment: 19 pages. Version 2: minor correction

    New insights into the early evolution of horizontal spiral trace fossils and the age of the Brioverian series (Ediacaran-Cambrian) in Brittany, NW France

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    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

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    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

    Elliptical body fossils from the Fortunian (Early Cambrian) of Normandy (NW France)

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    Body fossils have been discovered in the Fortunian deposits of the Rozel Cape, in Normandy (NW France). The material consists of about 80 specimens preserved on a shale surface, recently observed at the base of a cliff at the Cap Rozel, in the Cotentin region. The fossils, centimetric in size, have an elliptical outline, with a peripheral bulge, generally without other conspicuous ornamentation, but showing sometimes concentric or radial lines possibly of taphonomic origins. In addition, these body fossils are preserved parallel to the bedding plane, locally rich in horizontal trace fossils (e.g. Archaeonassa Fenton & Fenton, 1937, Helminthoidichnites Fitch, 1850, Helminthopsis Heer, 1877) and also complex treptichinids burrows (e.g. Treptichnus pedum (Seilacher, 1955)) sometimes associated with microbial mats. The sedimentological characteristics of these deposits (ripple marks, syneresis cracks) correspond to a shallow marine shelf environment, with a variable hydrodynamism in the intertidal zone, low for surfaces showing elliptic fossils and syneresis cracks, higher for surfaces with ripple marks. These new discoveries unravel the potential of the Fortunian strata from Normandy and provide new information about the early Cambrian biocenoses

    The Role of Bacillithiol in Gram-Positive Firmicutes

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    Significance: Since the discovery and structural characterization of bacillithiol (BSH), the biochemical functions of BSH-biosynthesis enzymes (BshA/B/C) and BSH-dependent detoxification enzymes (FosB, Bst, GlxA/B) have been explored in Bacillus and Staphylococcus species. It was shown that BSH plays an important role in detoxification of reactive oxygen and electrophilic species, alkylating agents, toxins, and antibiotics. Recent Advances: More recently, new functions of BSH were discovered in metal homeostasis (Zn buffering, Fe-sulfur cluster, and copper homeostasis) and virulence control in Staphylococcus aureus. Unexpectedly, strains of the S. aureus NCTC8325 lineage were identified as natural BSH-deficient mutants. Modern mass spectrometry-based approaches have revealed the global reach of protein S-bacillithiolation in Firmicutes as an important regulatory redox modification under hypochlorite stress. S-bacillithiolation of OhrR, MetE, and glyceraldehyde-3-phosphate dehydrogenase (Gap) functions, analogous to S-glutathionylation, as both a redox-regulatory device and in thiol protection under oxidative stress. Critical Issues: Although the functions of the bacilliredoxin (Brx) pathways in the reversal of S-bacillithiolations have been recently addressed, significantly more work is needed to establish the complete Brx reduction pathway, including the major enzyme(s), for reduction of oxidized BSH (BSSB) and the targets of Brx action in vivo. Future Directions: Despite the large number of identified S-bacillithiolated proteins, the physiological relevance of this redox modification was shown for only selected targets and should be a subject of future studies. In addition, many more BSH-dependent detoxification enzymes are evident from previous studies, although their roles and biochemical mechanisms require further study. This review of BSH research also pin-points these missing gaps for future research. Antioxid. Redox Signal. 28, 445–462

    Mr.Wolf: An Energy-Precision Scalable Parallel Ultra Low Power SoC for IoT Edge Processing

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    This paper presents Mr. Wolf, a parallel ultra-low power (PULP) system on chip (SoC) featuring a hierarchical architecture with a small (12 kgates) microcontroller (MCU) class RISC-V core augmented with an autonomous IO subsystem for efficient data transfer from a wide set of peripherals. The small core can offload compute-intensive kernels to an eight-core floating-point capable of processing engine available on demand. The proposed SoC, implemented in a 40-nm LP CMOS technology, features a 108-mu W fully retentive memory (512 kB). The IO subsystem is capable of transferring up to 1.6 Gbit/s from external devices to the memory in less than 2.5 mW. The eight-core compute cluster achieves a peak performance of 850 million of 32-bit integer multiply and accumulate per second (MMAC/s) and 500 million of 32-bit floating-point multiply and accumulate per second (MFMAC/s) -1 GFlop/s-with an energy efficiency up to 15 MMAC/s/mW and 9 MFMAC/s/mW. These building blocks are supported by aggressive on-chip power conversion and management, enabling energy-proportional heterogeneous computing for always-on IoT end nodes improving performance by several orders of magnitude with respect to traditional single-core MCUs within a power envelope of 153 mW. We demonstrated the capabilities of the proposed SoC on a wide set of near-sensor processing kernels showing that Mr. Wolf can deliver performance up to 16.4 GOp/s with energy efficiency up to 274 MOp/s/mW on real-life applications, paving the way for always-on data analytics on high-bandwidth sensors at the edge of the Internet of Things

    Videoconferencing and telementoring about dementia care: evaluation of a pilot model for sharing scarce old age psychiatry resources

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    While videoconferencing, telementoring, and peer support have been shown to enhance services in some instances, there has been no research investigating the use of these technologies in supporting professionals managing clients with dementia. The objective of this research was to evaluate expansion of an old age psychiatry consultation service and pilot test a model to improve medical supervision and clinical governance for staff within regional and remote areas using remote information technology. The design was a mixed methods (qualitative and quantitative) evaluation using before, mid-point and post-implementation semi-structured interviews and questionnaires to examine orientation, acceptance, and impact underpinned by theoretical approaches to evaluation. Education evaluations used a Likert style response template. Participants were 18 dementia service staff, including staff from linked services and old age psychiatrists. Qualitative interviews addressed the pilot implementation including: expectations, experiences, strategies for improving the pilot, and perceived impact on work practice and professional development opportunities. There was high satisfaction with the program. The case conference process contributed to perceived improved outcomes for clients, family, and staff. Clinicians perceived improvement in family carer and staff carer stress and their confidence in managing clients with behavioral and psychological symptoms of dementia (BPSD). Thematic analysis indicated that the pilot enhanced professional development, decreased travel time, and improved team cohesion. Given the increasing aging population in regional, rural, and remote areas, initiatives using videoconferencing and telementoring will help to develop a confident and skilled workforce. This pilot program was found to be acceptable and feasible. Potential benefits for clients and family carers should be examined in future resesarch

    The impaired development of sheep ICSI derived embryos is not related to centriole dysfunction

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    While intracytoplasmic sperm injection (ICSI) is an asset in human Assisted Reproduction Technologies (ART), its outcomes, in terms of blastocyst, is still unacceptably low in ruminants. The picture typically found in ICSI derived bovine and ovine embryos is an asymmetry between a high activation rate, marked by a pronuclear development, and a low first cleavage rate. Abnormal centriole function has been indicated as a possible factor which undermines embryonic development following ICSI, especially when Freeze Dried spermatozoa (FD) are used. In order to verify the hypothesis that centriole dysfunction might be responsible for low ICSI outcomes in sheep, we have investigated micro-tubular dynamics, markedly aster nucleation, in fertilized sheep zygotes by ICSI with frozen/thawed (FT) and FD spermatozoa; In Vitro Fertilized (IVF) sheep oocytes were used as control. The spermatozoa aster nucleation was assessed at different time points following ICSI and IVF by immune-detection of α-tubulin. Pronuclear stage, syngamy and embryo development were assessed. No difference was noticed in the timing of aster nucleation and microtubule elongation in ICSI-FT derived embryos with control IVF ones, while a delay was recorded in ICSI-FD ones. The proportion of 2-pronuclear stage zygotes was similar in ICSI-FT and ICSI-FD (47% and 53%, respectively), both much lower comparing the IVF ones (73%). Likewise, syngamy was observed in a minority of both ICSI groups (28.5% vs 12.5% in ICSI-FT/FD respectively) comparing to IVF controls (50%), with a high number of zygotes blocked at the 2-pronuclear stage (71.5% vs 87.5% respectively). While no significant differences were noticed in the cleavage rate between ICSI-FD, ICSI-FT and IVF groups (31%, 34% and 44%) respectively, development to blastocyst stage was markedly compromised in both ICSI groups, especially with FD spermatozoa (10% in ICIS-FD and 19% in ICSI-FT vs 33% in IVF (P < 0.005, ICSI-FD vs IVF and P < 0.05, IVF vs ICSI-FT, respectively). Hence, here we have demonstrated that the reduced cleavage, and the ensuing impaired development to blastocysts stage of ICSI derived sheep embryos is not related to centriole dysfunction, as suggested by other authors. The major recorded problem is the lack of syngamy in ICSI derived zygotes, an issue that should be addressed in further studies to improve ICSI procedure in sheep embryos
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