Formal verification of storm topologies through D-VerT

Data-intensive applications (DIAs) based on so-called Big Data technologies are nowadays a common solution adopted by IT companies to face their growing computational needs. The need for highly reliable applications able to handle huge amounts of data and the availability of infrastructures for distributed computing rapidly led industries to develop frame-works for streaming and big-data processing, like Apache Storm and Spark. The definition of methodologies and principles for good software design is, therefore, fundamental to support the development of DIAs. This paper presents an approach for non-functional analysis of DIAs through D- VerT, a tool for the architectural assessment of Storm applications. The verification is based on a translation of Storm topologies into the CLTLoc metric temporal logic. It allows the designer of a Storm application to check for the existence of components that cannot process their workload in a timely manner, typically due to an incorrect design of the topology

Multi-scale theoretical approach to X-ray absorption spectra in disordered systems: an application to the study of Zn(II) in water

We develop a multi-scale theoretical approach aimed at calculating from first principles X-ray absorption spectra of liquid solutions and disordered systems. We test the method by considering the paradigmatic case of Zn(II) in water which, besides being relevant in itself, is also of interest for biology. With the help of classical molecular dynamics simulations we start by producing bunches of configurations differing for the Zn(II)-water coordination mode. Different coordination modes are obtained by making use of the so-called dummy atoms method. From the collected molecular dynamics trajectories, snapshots of a more manageable subsystem encompassing the metal site and two solvation layers are cut out. Density functional theory is used to optimize and relax these reduced system configurations employing a uniform dielectric to mimic the surrounding bulk liquid water. On the resulting structures, fully quantum mechanical X-ray absorption spectra calculations are performed by including core-hole effects and core-level shifts. The proposed approach does not rely on any guessing or fitting of the force field or of the atomic positions of the system. The comparison of the theoretically computed spectrum with the experimental Zn K-edge XANES data unambiguously demonstrates that among the different a priori possible geometries, Zn(II) in water lives in an octahedral coordination mode.Comment: 8 pages, 3 figure

Cortico-Cortical Connectivity between Right Parietal and Bilateral Primary Motor Cortices during Imagined and Observed Actions: A Combined TMS/tDCS Study

Previous transcranial magnetic stimulation (TMS) studies showed functional connections between the parietal cortex (PC) and the primary motor cortex (M1) during tasks of different reaching-to-grasp movements. Here, we tested whether the same network is involved in cognitive processes such as imagined or observed actions. Single pulse TMS of the right and left M1 during rest and during a motor imagery and an action observation task (i.e., an index–thumb pinch grip in both cases) was used to measure corticospinal excitability changes before and after conditioning of the right PC by 10 min of cathodal, anodal, or sham transcranial direct current stimulation (tDCS). Corticospinal excitability was indexed by the size of motor-evoked potentials (MEPs) from the contralateral first dorsal interosseous (FDI; target) and abductor digiti minimi muscle (control) muscles. Results showed selective ipsilateral effects on the M1 excitability, exclusively for motor imagery processes: anodal tDCS enhanced the MEPs’ size from the FDI muscle, whereas cathodal tDCS decreased it. Only cathodal tDCS impacted corticospinal facilitation induced by action observation. Sham stimulation was always uneffective. These results suggest that motor imagery, differently from action observation, is sustained by a strictly ipsilateral parieto-motor cortex circuits. Results might have implication for neuromodulatory rehabilitative purposes

Biomechanics in crutch assisted walking

Crutch-assisted walking is very common among patients with a temporary or permanent impairment affecting lower limb biomechanics. Correct crutches’ handling is the way to avoid undesired side effects in lower limbs recovery or, in chronic users, upper limbs joints diseases. Active exoskeletons for spinal cord injured patients are commonly crutch assisted. In such cases, in which upper limbs must be preserved, specific training in crutch use is mandatory. A walking test setup was prepared to monitor healthy volunteers during crunch use as a first step. Measurements were performed by using both a motion capture system and instrumented crutches measuring load distribution. In this paper, we present preliminary tests results based on different subjects - having a variety of anthropometrical characteristics - during walking with parallel or alternate crutches, the so-called three and two-points strategies. Tests results present inter and intra subject variabilities and, as a first goal, influencing factors affecting crutch loads have been identified. In the future we aim to address crutch use errors that could lead to delayed recovery or upper limbs suffering in patients, giving valuable information to physicians and therapists to improve user’s training

3C-SiC nanowires and layers grown on Si: attractive material for biosensor applications

Nonotechnology is becoming an interesting field of research for biomolecular and medical diagnostics. The repeated screening is of crucial importance in the diagnosis of cancer and malignant tumours, since the pathologies at the early stages can be treated with the highest success probability. Many innovative approaches are emerging for the overcoming of this challenge, such as nanostructured surfaces for the enhancement of proteomic analysis, nanowires (NW) as biologically gated transistor, transductor for molecular binding events into real-time electrical signals and cantilevers for mechanical-based detection of biomolecules The interface of a biological system with tailored made detectors at the molecular scale opens the possibility to develop a entirely new class of devices and personal monitoring systems. The materials selected for these nanostructures must be biocompatible to ensure they are nontoxic and non-invasive for the organism, and must be capable to work in a very harsh environment. Silicon carbide (SiC) is mechanically robust, chemically inert, non toxic and biocompatible, so is a good material for biomedical purpose and for biosensor and bioelectronic applications. Several medical tools already uses SiC as bio-compatible coating, such as biomedical needles used in open heart surgery monitoring or temperature sensors based on bulk SiC. Nanosensors for ultrasensitive detection of proteins down to individual virus particles are also realised. Covalent bonding between specific molecules and stable interfaces are required for the realisation of biosensors based on molecular recognition, and since it was also demonstrated that SiC surfaces can be functionalized in order to react to specific biomolecules, this material is an optimal candidate for these kind of medical applications. Here we report a study on properties b-SiC-NWs and SiC layers deposited on silicon. Nanowires has been prepared with carbon oxide and nickel as catalytic element in nitrogen or argon atmosphere at the temperature between 1050 to 1100?C. Nanowires has been characterised by X-ray diffraction (XRD), by Scanning Electron Microscopy (SEM), Cathodoluminescence (CL) and by means Transmission Electron Microscopy (TEM). XRD patterns confirmed the characteristic peaks at 2q =35.6? (111), 41.4? (200), 59.9? (220), 75.5? (222) indexed as b-SiC. The room temperature CL spectrum revealed a broad peak centred at about 2.34 eV, related to the indirect band gap transition in b-SiC, and an intense blue band at about 2.68 eV. TEM images showed the crystalline core, having a <111> growth axis, sheathed by amorphous oxide. Typical SiC planar defects were present mainly on (111) planes, either stacking faults or rotational twins. Selected area electron diffraction from single NWs indicated the main phase as b-SiC. The SiC thin films were deposited on 2?? 001 Si wafers by means of VPE technique in a home made reactor with induction heating. A growth procedure at atmospheric pressure involving several steps (thermal etching, carburisation, epitaxial growth) was implemented. The precursor of choice were dilute SiH4 and C3H8 while H2 was used as carrier gas. The layers have been characterised by XRD, SEM, AFM. X-Ray diffraction evidences SiC(001) film is well oriented whit respect to the substrate having a narrow peak. SEM and AFM observations indicate a smooth film with good morphology

TEM and SEM-CL studies of SiC Nanowires

3C-SiC and 3C-SiC/SiO2 core-shell nanowires (NWs) grown on silicon substrates by three different processes, based on the use of i) carbon monoxide, ii) silane with propane and iii) carbon tetrachloride precursors, are analysed by structural and optical techniques. Spectroscopic cathodoluminescence studies show a luminescence enhancement in core-shell structures, ascribed to an effective role of the shell as both carrier injecting barrier and passivation layer. In NWs grown using CCl4 precursor, a peculiar luminescence with dominant red component at about 2 eV has been detected and ascribed to point defects related to an unintentional oxygen incorporation.vedi abstract ingles

Surface Functionalization of 3C-SiC Nanowires

One dimensional nanostrucures have potential applications in nanoscale electronic, optoelectronic or sensing devices. Core-shell nanowire (NW) structures of SiO2/&#946;-SiC and SiC-NWs are interesting for fundamental studies and technological applications: 3C-SiC is particularly appealing because of its good physical, chemical properties and biocompatibility, offering opportunities for nano-scale devices operating in biological environment. Moreover, functionalized 3C-SiC nanowires have the potential to act as highly sensitive detector elements in bio-chemical field. Here, we report on the preliminary results of the functionalization of 3C-SiC nanowires with an optically active, thiophene-based, &#960;-conjugated oligomer (PyT4). Oligothiophenes are semiconducting and fluorescent materials, widely used in organic electronics and biodiagnostic. SiC/SiO2 core/shell NWs grown by a Chemical Vapour Deposition (CVD) process on n-type Si (001) substrates, using carbon monoxide (CO) as the carbon source and nickel nitrate as the catalyst. The synthesis, performed at temperatures between 1050-1100?C. 3C-SiC NWs were grown in a home-made Vapor Phase Epitaxy (VPE) reactor using propane and silane as precursors (both diluted 3% in hydrogen) and a few nm of Ni as catalyst, deposited on Si(100) substrate using e-beam system. The nickel-deposited substrate is preheated at 1100?C for 5 minutes before introducing reagents for the grow time of 10 minutes. SiC/SiO2 core/shell NWs were then reacted with the triethoxysilane terminated with PyT4 to yield the hybrid NWs. The covalent grafting of the fluorophores was confirmed by fluorescence microscopy. The nanowires were further characterised by X-ray diffraction, Scanning Electron Microscopy, Cathodoluminescence and Transmission Electron Microscopy

Growth and characterization of 3C-SiC grown using CBr4 as a precursor

The growth of silicon carbide on silicon is being studied for many diverse applications and so the search for precursors that could be used to grow with improved or novel physical, structural and morphological properties is a relevant issue in this field. Here we present a study of the use of CBr4 as a precursor in the deposition of 3C-SiC in a cold walled MOVPE reactor. The growth has been studied in a range of temperatures between 1100 and 1250 ?C, on differently oriented substrates. Additionally, the effect of the C:Si ratio in the gas phase was examined by the addition of propane to the reaction mixture. At lower temperatures faceted crystals grew as islands on the substrate; faceting and 2D planar growth was obtained if higher growth temperatures were applied and at higher C:Si ratios. Atomic force and scanning microscopies revealed interesting growth habits of the island type crystals. Transmission electron microscopy in cross-section confirms that these islands are 3C-SiC and have a high crystal perfection. The crystal habit has been characterised and will be presented. Carbon tetrabromide has revealed itself to be a useful precursor for the growth of SiC and, with a judicious control of the growth conditions could be applied to the growth of thin films and nanocrystals

Efficient Scalable Verification of LTL Specifications

Linear Temporal Logic (LTL) has been used in computer science for decades to formally specify programs, systems, desired properties, and relevant behaviors. This paper presents a novel, efficient technique for verifying LTL specifications in a fully automated way. Our technique belongs to the category of Bounded Satisfiability Checking approaches, where LTL formulae are encoded as formulae of another decidable logic that can be solved through modern satisfiability solvers. The target logic in our approach is Bit-Vector Logic. We present our novel encoding, show its correctness, and experimentally compare it against existing encodings implemented in well-known formal verification tools