40,430 research outputs found
Probing chiral interactions between L- and D-arginine-based polymers and sodium deoxycholate solutions
No full textNowadays the spontaneous self-organization of a polymer into an ordered structure is a soughtafter property of many smart materials, whose applications might range from catalysis [1] to drugdelivery [2]. However, literature regarding the role played by these specific conformations in chiral recognition remains scarce. In this context, polyamidoamino acids (PAACs) are an emerging class of stimuli-responsive bioinspired synthetic polymers able to self-assemble into pH depend conformations [3,4]. PAACs are an off-spring of polyamidoamines (PAAs), a family of polymers obtained by the Michael-type polyaddition of prim-monoamines or sec-diamines with bisacrylamides. The reaction occurs in aqueous solution at pH = 8–9 and at room temperature. By using α-amino acids as monomers, PAACs are obtained.
The first example of PAAC was named ARGO7, obtained by the stepwise polyaddition in water of L- or D-arginine to N,N’-methylenebisacrylamide. Results indicated Mn 8500, PDI 1.4 and Rh of 1.2 nm [3]. Molecular dynamics (MD) and circular dichroism (CD) showed ARGO7 folded into a rigid structure, reminiscent of the hairpin conformation, solely driven by the polymer main chain. Due to its ability to self-assemble in solution forming chiral structures, L- and D-ARGO7 may selectively interact with biological components.
To assess chiral recognition, sodium deoxycholate (NaDC), one of the components of bile salts, was chosen as a chiral model surface. In aqueous solution, NaDC showed three different pH dependent behaviour: homogeneous solution (pH>8), gel phase (pH 7-8) and aggregation/flocculation (pH<6.5). Notwithstanding the ability of NaDC to self-assemble into different conformations at each pH interval, signs of chiral recognition were found in NaDC gel phase only. Conformational modifications were probed by circular dichroism spectroscopy: both D- and L-ARGO7 changed shape and magnitude of the CD pattern, whereas D,L-ARGO7 did not modify the CD spectra of NaDC. After 8 days, NaDC compact structure loosened, ended up being fluid and the CD pattern were completely modified due to NaDC and D- or L-ARGO7 interactions. Incoming diffusion NMR and SANS studies will probably highlight the mechanisms and dynamics of the chiral interactions in these polyelectrolyte-micelle systems.
[1] Luo, R.; Zhu, M.; Shen, X.; Li, S. J. Catal. 2015, 331, 49. [2] Quiñones, J. P.; Peniche, H.; Peniche, C. Polymers. 2018, 10, 3, 235. [3] Manfredi, A.; Mauro, N.; Terenzi, A.; Alongi, J.; Lazzari, F.; Ganazzoli, F.; Raffaini, G.; Ranucci, E.; Ferruti, P. ACS Macro Lett. 2017, 6, 987. [4] Lazzari, F.; Manfredi, A.; Alongi, J.; Mendichi, R.; Ganazzoli, F.; Raffaini, G.; Ferruti, P.; Ranucci, E. Polymers 2018, 10, 1261
Chiral recognition in D-, L-arginine derived polyamidoamino acids and sodium deoxycholate solutions
No full textNowadays the spontaneous self-organization of a polymer into an ordered structure is a sought-after property of many smart materials, whose applications might range from catalysis1 to drug-delivery2. However, literature regarding the role played by these specific conformations in chiral recognition remains scarce. In this context, polyamidoamino acids (PAACs) are an emerging class of stimuli-responsive bioinspired synthetic polymers able to self-assemble into pH depend conformations.3,4 Arginine based PAACs, named ARGO7, were obtained in water at pH 8-9 from the stepwise polyaddition of L- or D-arginine to N,N’methylenebisacrylamide. Results indicated Mn 8500, PDI 1.4 and Rh of 1.2 nm.3 Molecular dynamics (MD) and circular dichroism (CD) showed ARGO7 folded into a rigid structure, reminiscent of the hairpin conformation, solely driven by the polymer main chain. Due to its ability to self-assemble in solution forming chiral structures, L- and D-ARGO7 may selectively interact with biological components. To assess chiral recognition, sodium deoxycholate (NaDC), one of the components of bile salts, was chosen as a chiral model surface. In aqueous solution, NaDC showed three different pH dependent behaviour: homogeneous solution (pH>8), gel phase (pH 7-8) and aggregation/flocculation (pH<6.5). Notwithstanding the ability of NaDC to self-assemble into different conformations at each pH interval, signs of chiral recognition were found in NaDC gel phase only. Conformational modifications were probed by circular dichroism spectroscopy: both D- and L-ARGO7 changed shape and magnitude of the CD pattern, whereas D,LARGO7 did not modify the CD spectra of NaDC. After 8 days, NaDC compact structure loosened, ended up being fluid and the CD pattern were completely modified due to NaDC and D- or L-ARGO7 interactions. Incoming SANS studies will probably highlight the mechanisms and dynamics of the chiral interactions in these polyelectrolyte-micelle systems.
(1) Luo, R.; Zhu, M.; Shen, X.; Li, S. J. Catal. 2015, 331, 49. (2) Quiñones, J. P.; Peniche, H.; Peniche, C. Polymers. 2018, 10, 3, 235. (3) Manfredi, A.; Mauro, N.; Terenzi, A.; Alongi, J.; Lazzari, F.; Ganazzoli, F.; Raffaini, G.; Ranucci, E.; Ferruti, P. ACS Macro Lett. 2017, 6, 987. (4) Lazzari, F.; Manfredi, A.; Alongi, J.; Mendichi, R.; Ganazzoli, F.; Raffaini, G.; Ferruti, P.; Ranucci, E. Polymers 2018, 10, 1261
Optimum filters for detector charge measurements in presence of 1/f noise
No full textThe optimum shape of the weighting function for detector charge measurements, in the presence of series 1/f noise superimposed on parallel and series white noises, is investigated. The corresponding theoretical limits in charge resolution for finite or infinite processing times have been calculated, and compared with the values obtained using traditional cusplike weighting functions optimum for white noises onl
Low-noise electronics in elementary particle physics
No full textThe noise requirements for the front-end electronics fixed by several detecting and tracking devices and by different kinds of calorimeters are reviewed. Practical design suggestions to meet these requirements are presented
On the feasibility of front-end electronics for microstrip vertex detectors under the operating conditions of large hadron colliders
No full text
How to create public value through integrated cultural systems?
No full textThe topic of performance measurement (Bovaird, 2003; Holzer and Yang, 2004; Borgonovi, 2008; Bianchi, Williams, 2013) of public value (Benington, 2009: 5,6; Benington and Moore, 2011) for the welfare of citizens is not merely, today, a subject of interest amongst academics of public management. More increasingly, it has become a heated matter for public managers and their organizations’ practitioners since they are daily confronted with problem of delivering efficiently and effectively public actions, policies, goods and services under the rubric of the 21st century’s paradigm in the Public Management literature, that is Community Governance (Manfredi, 2009, 2013). This perspective, which unfolds through a series of networks and relationships has sparked off the development of innovative public and private models aimed at integrating all community’s views and interests in a systemic view. Community Governance, therefore, entails a method of governing that pursues, as its primarily aim, sustainable development for communities and territories, and it is supported by coherent processes of community planning and programming by adopting a multidisciplinary, strategic and systemic approach (Totikidis, 2005). This paper focuses on the topic of Public Value (PV) in the realm of Community Governance and in Integrated Cultural Systems in particular, with the aim to fill the gap in the literature of Public Management and Governance and to provide practitioners with good tools for measuring Public Value. It is argued, infact, that there is a major opportunity for governments to achieve effective and efficient results in improving their communities by allowing citizens to use performance measurement (Bovaird 2003, Holzer and Yang, 2004; Borgonovi 2008; Bianchi, Wiliams, 2013) to generate actions towards better public services (Bianchi, 2009, 2012, 2014; Bianchi, Rivenbark, 2014). In other words, the model of Community Governance, observes the linkages between citizens, governments and measuring performance as configured in a triangle (Foley, Martin, 2000). The literature will also cover the issue of the territorial dimension named the Metropolitan Area (Bryson J.M. 2011) that, by its natural and original configuration as a public policy, is “per se” conceived as a form of public value that is generated or destroyed (Esposito, Ricci, 2015). Within the territorial configuration of Metropolitan Areas, policies towards the creation of integrated systems, such as culture systems in this circumstance, will be also explored in order to understand how can create public value through Integrated Cultural Systems and if Performance Measurement represents a tool that is useful to visualize tangible and intangible Public Values or if it is, rather, a “myth” as argued by some authoritative scholars (Modell, 2004)
On the correct choise of transformer ratio in low noise preamplifiers for large detector capacitances.
No full textRealization and characterization of optical frequency standards
No full textDuring the Ph.D. Course I worked on the realization and the characterization of an ytterbium optical frequency standard. Since year 2000, it is possible using optical frequency comb to directly and reliably scale a frequency measurement in the optical domain to a measurement in the microwave domain. This possibility allows the realization of high accuracy and high stability optical frequency standards, whose atomic quality factors are several orders of magnitude higher than the best microwave ones. Among others, the alkaline earth atoms are very promising and, once trapped in an optical lattice, are capable of a short term stability approaching 10−15 at 1 s. A ytterbium optical clock is currently being developed in the laboratories of the Optics Division of Istituto Nazionale di Ricerca Metrologica (INRIM) The experiment aims to cool and trap ytterbium atoms in a two stage magneto-optical trap (MOT) (at 399 nm and 556 nm) and to probe them in an optical lattice with a ultrastable laser at 578 nm. This thesis presents the realization of the required laser sources, the stabilization of the clock laser, the development of the cooling and trapping stages and the design of a new experimental setup. The blue and green radiations for the two-stage MOT at 399 nm and 556 nm are obtained by second harmonic generation in non-linear crystals. The yellow clock laser at 578 nm is generated by sum of frequency in non-linear crystal. The clock laser is stabilized with the Pound-Drever-Hall technique on a high-finesse Fabry-Pérot cavity. The temperature stabilization of the cavity is implemented with a novel Active Disturbance Rejection Control scheme. The frequency noise of the laser is characterized with a stability 3 × 10−15 at 1 s. Atoms are trapped in the blue magneto-optical trap at 399 nm and transferred in the green trap at 556 nm. A new experimental setup is designed, studying the vacuum chamber, the MOT coils and the atomic source. I have been guest researcher at National Institute of Standards and Technology (NIST) for six months in 2011. I will describe development of NIST ytterbium optical clocks during my visi
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