Least-action principle and path-integral for classical mechanics

In this paper we show how the equations of motion of a superfield, which makes its appearance in a path-integral approach to classical mechanics, can be derived without the need of the least-action principleComment: to appear IN PHYS.REV.D (Brief Report

Fractional momentum correlations in multiple production of W bosons and of b-anti_b pairs in high energy pp collisions

Multiple parton collisions will represent a rather common feature in pp collisions at the LHC, where regimes with very large momentum transfer may be studied and events rare in lower energy accelerators might occur with a significant rate. A reason of interest in large p_t regimes is that, differently from low p_t, evolution will induce correlations in x in the multiparton structure functions. We have estimated the cross section of multiple production of W bosons with equal sign, where the correlations in x induced by evolution are particularly relevant, and the cross section of b-bar_b b-bar_b production, where the effects of evolution are much smaller. Our result is that, in the case of multiple production of W bosons, the terms with correlations may represent a correction of the order of 40% of the cross sections, for pp collisions at 1 TeV c.m. energy, and a correction of the order of 20% at 14 TeV. In the case of b-bar_b pairs the correction terms are of the order of 10-15% at 1 TeV and of the order of 5% at 14 TeV.Comment: Submitted to Phys. Rev.

High-speed and high-resolution 2D and 3D elemental imaging of corroded ancient glass by laser ablation-ICP-MS

In this work, laser ablation-inductively coupled plasma-mass spectrometry was used to investigate for the first time glass weathering mechanisms using high-resolution 2D and 3D elemental maps of altered layers of ancient glass. Roman archaeological glass shards, displaying several corrosion indicators, were studied using multiple raster-scanning ablation with high depth and lateral resolution. The concentration gradients of different elements were captured (in their variations from the surface to the bulk of pristine glass) by multiple ablations on degraded regions of interest to observe the dissolution of the glass network due to the hydration and leaching processes that occur during its alteration. The results indicated an enrichment of silicon and a depletion of alkaline/alkaline earth element concentration in the first few microns of depth under the surface area suggesting that a de-alkalinisation phenomenon occurs on the glass surface when ancient items have been buried under soil for extended timeframes. The layer-by-layer elemental distribution revealed also how the composition of the archaeological glass changes from the bulk to the surface, shedding light on the leaching behaviour of glass constituents during the alteration process

Consolidation and coating treatments for glass in the cultural heritage field: A review

Consolidation and coating treatments are two types of interventions that form part of the active con- servation actions developed for historical and archaeological glass over the years. While thermoplastic and thermosetting resins are widely adopted by conservators worldwide, issues related to the toxicity and the material compatibility of these products remains unsolved. To address these issues, effort s have been made to develop new formulations that can functionally replace or exhibit performance advantages with respect to these canonical polymeric materials. In this review, we discuss the main classes of ma- terials applied thus far for protection and consolidation aims in the cultural heritage glass field, starting from the beginning of the 19th century and continuing until present days. We also assess the potential of hybrid organic-inorganic materials and full inorganic materials as alternative solutions to the limita- tions of organic materials in application. Finally, we provide our perspectives on future directions for the development of consolidation products that meet the specific requirements of the cultural heritage field

Are the school prevention programmes - aimed at de-normalizing smoking among youths - beneficial in the long term? An example from the Smoke Free Class Competition in Italy

Tobacco smoking by young people is of great concern because it usually leads to regular smoking, nicotine addiction and quitting difficulties. Young people "hooked" by tobacco maintain the profits of the tobacco industry by replacing smokers who quit or die. If new generations could be tobacco-free, as supported by tobacco endgame strategies, the tobacco epidemic could end within decades. Smoking prevention programmes for teens are offered by schools with the aim to prevent or delay smoking onset. Among these, the Smoke Free Class Competition (SFC) was widely implemented in Europe. Its effectiveness yielded conflicting results, but it was only evaluated at short/medium term (6 - 18 months). The aim of this study is to evaluate its effectiveness after a longer follow-up (3 to 5 years) in order to allow enough time for the maturing of the students and the internalization of the experience and its contents. Fifteen classes were randomly sampled from two Italian high schools of Bologna province that regularly offered the SFC to first year students; 382 students (174 participating in the SFC and 208 controls) were retrospectively followed-up and provided their "smoking histories". At the end of their last year of school (after 5 years from the SFC), the percentage of students who stated that they were regular smokers was lower among the SFC students than in controls: 13.5% vs 32.9% (p=0.03). From the students' "smoking histories", statistically significant protective ORs were observed for SFC students at the end of 1st and 5th year: 0.42 (95% CI 0.19-0.93) and 0.32 (95% CI 0.11-0.91) respectively. Absence of smokers in the family was also a strongly statistically significant factor associated with being a non-smoker student. These results suggest that SFC may have a positive impact on lowering the prevalence of smoking in the long term (5 years)

Compositional changes by SIMS and XPS analyses on fresh and aged Roman-like glass

This study reports important analytical evidence of an unusual non-uniform element distribution in the superficial layers of glass matrices (from few nm up to 1 µm). The unforeseen observation was made on silica-soda-lime glass mock-ups before and after their artificial ageing, using secondary ion mass spectrometry (SIMS) and X-ray photoelectron spectroscopy (XPS) surface analysis techniques. The analyses showed a marked non-homogeneous element distribution at the glass surface. The results indicated a very low concentration of Na at the surface up to a depth of around 500 nm below the surface, where its concentration increases reaching a plateau. In addition, the profile distribution of H in the first 200 nm of the pristine glass surface indicated a diffusion of hydrogen from the surrounding environment to the glass network. Additional modifications during the glass ageing process related to external factors (such as temperature and humidity) were also identified in relation to sodium atoms, with atoms on the glass surface showing a different chemical state from those in the bulk. This study confirms that glass composition as well as glass alteration are non-homogeneous locally supporting the importance of studying glass surface as region of interaction with surrounding environment

In Situ-Generated Oxide in Sn-Doped Nickel Phosphide Enables Ultrafast Oxygen Evolution

Water splitting is considered one of the most promising approaches to power the globe without the risk of environmental pollution. The oxygen evolution reaction (OER) is even more challenging because the generation of only one oxygen molecule involves the transfer of four e- and removal of four H+ ions from water. Thus, developing highly efficient catalysts to meet industrial requirements remains a focus of attention. Herein, the prominent role of Sn in accelerating the electron transfer kinetics of Ni5P4 nanosheets in OER is reported. The post catalytic survey elucidates that the electrochemically induced Ni-Sn oxides at the vicinity of phosphides are responsible for the observed catalytic activity, delivering current densities of 10, 30, and 100 mA cm-2 at overpotentials of only 173 ± 5.2, 200 ±7.4, and 310 ± 5.5 mV, respectively. The density functional theory calculation also supports the experimental findings from the basis of the difference observed in density of states at the Fermi level in the presence/absence of Sn. This work underscores the role of Sn in OER and opens a promising avenue toward practical implementation of hydrogen production through water splitting and other catalytic reactions

b \bar b b\bar b production in proton-nucleus collisions at the LHC

A sizable rate of events, with several pairs of $b$-quarks produced contemporarily by multiple parton interactions, may be expected at very high energies as a consequence of the large parton luminosities. The production rates are further enhanced in hadron-nucleus reactions, which may represent a convenient tool to study the phenomenon. We compare the different contributions to $b{\bar b}b{\bar b}$ production, due to single and double parton scatterings, in collisions of protons with nuclei at the CERN-LHC.Comment: 13 pages, 4 figure

From EMC- and Cronin-effects to signals of quark-gluon plasma

The EMC- and Cronin-effects are explained by a unitarized evolution equation, where the shadowing and antishadowing corrections are dynamically produced by gluon fusions. For this sake, an alternative form of the GLR-MQ-ZRS equation is derived. The resulting integrated and unintegrated gluon distributions in proton and nuclei are used to analyze the contributions of the initial parton distributions to the nuclear suppression factor in heavy ion collisions. A simulation of the fractional energy loss is extracted from the RHIC and LHC data, where the contributions of the nuclear shadowing and antishadowing effects are considered. We find a rapid crossover from week energy loss to strong energy loss at a universal critical energy of gluon jet $E_c\sim 10 GeV$.Comment: 35 pages, 13 figures, to be published in Int. J. Mod. Phys.

¿“Nos enfrentamos y nos abrazamos”? Un nuevo recorrido por los usos oficiales del pasado durante el bicentenario de la Revolución de Mayo

El presente trabajo analiza, en primer lugar, los modos en que la historia argentina se tradujo, durante los festejos oficiales del bicentenario de la Revolución de Mayo, en artefactos culturales y festivos dirigidos a atraer un público vasto, prestando especial atención a los usos del pasado allí exhibidos. En segundo lugar, pone en relación dichas operaciones con las variaciones ocurridas en el nivel de las prácticas políticas gubernamentales tras la crisis política de 2008. En última instancia, se plantea que el gobierno de Cristina Fernández de Kirchner se inclinó, al momento de proyectar el festejo patrio en cuestión, por una lógica discursiva liberal–centrada, especialmente, en el consenso inclusivo y la aceptación de las diferencias–con el fin de matizar la partición del espacio socio-político, exhibir una nación reconciliada, interpelar a la sociedad argentina en su conjunto y, de ese modo, contribuir a la reconstrucción de su hegemonía política.Firstly, this paper analyzes how Argentinian history was translated, during the national celebrations of the May Revolution bicentennial, into cultural and festive devices aimed at attracting a massive audience, paying special attention to the uses of the past displayed. Secondly, it illustrates the relations between these operations and the variations of government policy that occurred after the 2008 political crisis. Ultimately, it claims that the Cristina Fernández de Kirchner administration adopted, when it came to planning this national holiday, a liberal discursive logic – mainly characterized by inclusive consensus and pluralism – in order to ease the division of the social and political space, display a reconciled nation, address the entire Argentinean society and, thereby, contribute to the reconstruction of Kirchnerist hegemony.Fil: Amorebieta y Vera, María Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones en Humanidades y Ciencias Sociales. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación. Instituto de Investigaciones en Humanidades y Ciencias Sociales; Argentin