Parametric X-Ray detection in UA9 experiment

Parametric X-Ray radiation (PXR) is a phenomenon due to the interaction of charged particles inside a crystal well ordered lattice. The passage of the particles inside the potential field into the crystal causes small deflections which result in radiation emissions. By this way the emission is diffracted by the crystal planes. In this work the results of the last five years of activity on PXR detection during UA9 experiment are reported. The beam provided in H8 area, protons or Pb ions, is channeled inside different crystals and PXR emission is detected

Polycapillary based μXRF station for 3D colour tomography

The “Rainbow X-Ray” (RXR) experimental station at XLab Frascati of the Frascati’s National Laboratories (LNF) INFN is a dedicated station for X-ray fluorescence studies based on the use of polycapillary lenses in a confocal geometry. The flexible RXR layout allows investigating specimens of the dimensions ranging from several millimeters up to half meter and weighting up to several tens of kilograms. Compared to similar existing XRF stations, apart of the possibility for investigating large samples, the main advantage of this equipment is the detection system with two spectrometers optimized to work separately at high and at low X-ray energie

Mechanisms Responsible for omega-Pore Currents in Ca-v Calcium Channel Voltage-Sensing Domains

Mutations of positively charged amino acids in the S4 transmembrane segment of a voltage-gated ion channel form ion-conducting pathways through the voltage-sensing domain, named ω-current. Here, we used structure modeling and MD simulations to predict pathogenic ω-currents in CaV1.1 and CaV1.3 Ca2+ channels bearing several S4 charge mutations. Our modeling predicts that mutations of CaV1.1-R1 (R528H/G, R897S) or CaV1.1-R2 (R900S, R1239H) linked to hypokalemic periodic paralysis type 1 and of CaV1.3-R3 (R990H) identified in aldosterone-producing adenomas conducts ω-currents in resting state, but not during voltage-sensing domain activation. The mechanism responsible for the ω-current and its amplitude depend on the number of charges in S4, the position of the mutated S4 charge and countercharges, and the nature of the replacing amino acid. Functional characterization validates the modeling prediction showing that CaV1.3-R990H channels conduct ω-currents at hyperpolarizing potentials, but not upon membrane depolarization compared with wild-type channels

Mixed cation halide perovskite under environmental and physical stress

Despite the ideal performance demonstrated by mixed perovskite materials when used as active layers in photovoltaic devices, the factor which still hampers their use in real life remains the poor stability of their physico-chemical and functional properties when submitted to prolonged permanence in atmosphere, exposure to light and/or to moderately high temperature. We used high resolution photoelectron spectroscopy to compare the chemical state of triple cation, double halide Cs-x(FA(0.83)MA(0.17))(()Pb-1-(x))(I0.83Br0.17)(3) perovskite thin films being freshly deposited or kept for one month in the dark or in the light in environmental conditions. Important deviations from the nominal composition were found in the samples aged in the dark, which, however, did not show evident signs of oxidation and basically preserved their own electronic structures. Ageing in the light determined a dramatic material deterioration with heavily perturbed chemical composition also due to reactions of the perovskite components with surface contaminants, promoted by the exposure to visible radiation. We also investigated the implications that 2D MXene flakes, recently identified as effective perovskite additive to improve solar cell efficiency, might have on the labile resilience of the material to external agents. Our results exclude any deleterious MXene influence on the perovskite stability and, actually, might evidence a mild stabilizing effect for the fresh samples, which, if doped, exhibited a lower deviation from the expected stoichiometry with respect to the undoped sample. The evolution of the undoped perovskites under thermal stress was studied by heating the samples in UHV while monitoring in real time, simultaneously, the behaviour of four representative material elements. Moreover, we could reveal the occurrence of fast changes induced in the fresh material by the photon beam as well as the enhanced decomposition triggered by the concurrent X-ray irradiation and thermal heating

Nanoscale FasL Organization on DNA Origami to Decipher Apoptosis Signal Activation in Cells

Cell signaling is initiated by characteristic protein patterns in the plasma membrane, but tools to decipher their molecular organization and activation are hitherto lacking. Among the well-known signaling pattern is the death inducing signaling complex with a predicted hexagonal receptor architecture. To probe this architecture, DNA origami-based nanoagents with nanometer precise arrangements of the death receptor ligand FasL are introduced and presented to cells. Mimicking different receptor geometries, these nanoagents act as signaling platforms inducing fastest time-to-death kinetics for hexagonal FasL arrangements with 10 nm inter-molecular spacing. Compared to naturally occurring soluble FasL, this trigger is faster and 100x more efficient. Nanoagents with different spacing, lower FasL number or higher coupling flexibility impede signaling. The results present DNA origami as versatile signaling scaffolds exhibiting unprecedented control over molecular number and geometry. They define molecular benchmarks in apoptosis signal initiation and constitute a new strategy to drive particular cell responses

The SHERPA experiment

The SHERPA project aim is to develop an efficient technique for extracting a positron beam from one of the accelerator rings composing the DAΦNE accelerator complex at the Frascati National Laboratory of INFN, setting up a new beam line delivering positron spills of O(ms) length, excellent beam energy spread and emittance. The main idea is to use coherent processes in bent crystals to slowly kick out positrons from the ring, a cheaper and less complex alternative. This non-resonant technique, already successfully used and still developed mainly in hadron accelerators, will provide a continuous multi-turn extraction of a high quality beam. In this manuscript an overview of the whole experiment will be given, describing in particular the crystal extraction principle, the accelerator optics studies, the crystal prototype and its characterization. A first estimation of the crystal extraction performance at DAΦNE is also reported

Crystal slow extraction of positrons from the Frascati da φ NE collider

The slow high-efficiency extraction from a ring positron accelerator (SHERPA) project's aim is to develop an efficient technique to extract a positron beam from one of the accelerator rings composing the DAφNE complex at the Frascati National Laboratory of INFN, setting up a new beam line able to deliver positron spills of O(ms) length, excellent beam energy spread and emittance. The most common approach to slowly extract from a ring is to increase betatron oscillations approaching the third order tune resonance to gradually eject particles from the circulating beam. SHERPA proposes a paradigm change for lepton machines using coherent processes in bent crystals to kick out positrons from the ring, a cheaper and less complex alternative. A description of this innovative nonresonant extraction technique is reported in this manuscript, including its performance preliminary estimation