A Microwave Josephson Refrigerator

We present a microwave quantum refrigeration principle based on the Josephson effect. When a superconducting quantum interference device (SQUID) is pierced by a time-dependent magnetic flux, it induces changes in the macroscopic quantum phase and an effective finite bias voltage appears across the SQUID. This voltage can be used to actively cool well below the lattice temperature one of the superconducting electrodes forming the interferometer. The achievable cooling performance combined with the simplicity and scalability intrinsic to the structure pave the way to a number of applications in quantum technology.Comment: 6 pages, 3 figure

Parasitic effects in SQUID-based radiation comb generators

We study several parasitic effects on the implementation of a Josephson radiation comb generator (JRCG) based on a dc superconducting quantum interference device (SQUID) driven by an external magnetic field. This system can be used as a radiation generator similarly to what is done in optics and metrology, and allows one to generate up to several hundreds of harmonics of the driving frequency. First we take into account how assuming a finite loop geometrical inductance and junction capacitance in each SQUID may alter the operation of this device. Then, we estimate the effect of imperfections in the fabrication of an array of SQUIDs, which is an unavoidable source of errors in practical situations. We show that the role of the junction capacitance is in general negligible, whereas the geometrical inductance has a beneficial effect on the performance of the device. The errors on the areas and junction resistance asymmetries may deteriorate the performance, but their effect can be limited up to a large extent with a suitable choice of fabrication parameters.Comment: 9 pages, 9 figure

Harbour sites as a support to the reconstruction of networks and influences: the case of the Mistras Lagoon (Sardinia, Italy)

Ancient harbours and anchorages are valuable contexts to investigate the different material culture that could reach a region, and to reconstruct ancient commerce and connections between different areas. Moreover, as they usually present waterlogged and anoxic sedimentation conditions, organic materials are preserved in addition to ceramics and other inorganic objects, giving more elements to the archaeological reconstruction. This is the case of the Mistras lagoon in Central-West Sardinia. The lagoon has been identified as the harbour of the city of Tharros, active during the Punic period, from the 7th to the 3rd century BC. It is characterised by an interior sandy barrier, recognised as a palaeobeach; here the University of Cagliari held two archaeological excavations during the years 2014 and 2015, revealing a natural stratigraphy rich in archaeological materials, typical of a waterlogged site. The analysis of the carpological remains, seeds, and fruits, recovered by sampling 29 different stratigraphic units, reveals the presence of a great number of cultivated species. Some of the species identified were possibly introduced during that period to the island, together with agricultural practices and technologies that improved local cultivations. Concerning the xylological remains found in the excavations, some fragments of manufactured wood provide important information about objects of common use, while other fragments are attributable to remains of ships.Gli antichi porti e approdi sono siti di grande valore per ricostruire le antiche rotte commerciali e più in generale le connessioni tra diverse regioni. Inoltre, grazie alla frequente presenza di condizioni di sedimentazione anossiche, essi possono restituire non solo ceramiche e altri materiali inorganici, ma anche elementi organici, raramente preservati sui siti terrestri, che forniscono elementi aggiuntivi alla ricostruzione archeologica e paleoambientale. È questo il caso della laguna di Mistras, nella Sardegna centro-occidentale. La laguna è stata identificata come porto della città di Tharros in età punica, tra il VII e il III sec. a.C. Essa è caratterizzata nella parte interna da una cuspide sabbiosa, riconosciuta come una paleospiaggia; in quest’area, durante gli anni 2014 e 2015, l’Università degli Studi di Cagliari ha condotto due campagne di scavo archeologico che hanno consentito di indagare una stratigrafia di formazione naturale ricchissima di materiali archeologici, tipica di un sito impregnato d’acqua. L’analisi dei reperti carpologici, semi e frutti recuperati grazie al campionamento sistematico dei sedimenti, sta rivelando la presenza di un gran numero di resti di specie coltivate. Alcune di queste furono probabilmente introdotte nell’Isola durante il periodo in questione, altre sono già attestate durante i periodi precedenti e continuano ad essere sfruttate con nuovo impulso. Per quanto riguarda i resti xilologici rinvenuti negli scavi, alcuni frammenti di legno lavorato forniscono importanti informazioni su oggetti di uso comune, mentre altri sono attribuibili a resti di imbarcazion

Nickel binding sites in histone proteins

Nickel compounds are well known as human carcinogens, though the molecular events that are responsible for this are not well understood. It has been proposed that a crucial element in the mechanism of carcinogenesis is the binding of Ni(II) ions within the cell nucleus. It is known that DNA polymer binds Ni(II) only weakly, leaving the proteins of the cell nucleus as the likely Ni(II) targets. Being histone proteins the most abundant among them, they can be considered the primary sites for nickel binding. Here we describe the interactions of nickel with histone H4, core tetramer (H3-H4)2 and several peptide fragments which have been selected as the candidates for specific binding sites in the histone octamer. The results allowed us to propose several mechanisms of nickel induced damage resulting from metal coordination, including structural changes of histone proteins, as well as nucleobase oxidation and sequence-specific histone hydrolysis. The aim of the present work is to provide a comprehensive overview of literature dealing with nickel coordination to histone proteins and its link with nickel involvement in toxicity and carcinogenicity

0-π\pi phase-controllable thermalthermal Josephson junction

Two superconductors coupled by a weak link support an equilibrium Josephson electrical current which depends on the phase difference $\varphi$ between the superconducting condensates [1]. Yet, when a temperature gradient is imposed across the junction, the Josephson effect manifests itself through a coherent component of the heat current that flows oppositely to the thermal gradient for $\varphi <\pi/2$ [2-4]. The direction of both the Josephson charge and heat currents can be inverted by adding a $\pi$ shift to $\varphi$. In the static electrical case, this effect was obtained in a few systems, e.g. via a ferromagnetic coupling [5,6] or a non-equilibrium distribution in the weak link [7]. These structures opened new possibilities for superconducting quantum logic [6,8] and ultralow power superconducting computers [9]. Here, we report the first experimental realization of a thermal Josephson junction whose phase bias can be controlled from $0$ to $\pi$. This is obtained thanks to a superconducting quantum interferometer that allows to fully control the direction of the coherent energy transfer through the junction [10]. This possibility, joined to the completely superconducting nature of our system, provides temperature modulations with unprecedented amplitude of $\sim$ 100 mK and transfer coefficients exceeding 1 K per flux quantum at 25 mK. Then, this quantum structure represents a fundamental step towards the realization of caloritronic logic components, such as thermal transistors, switches and memory devices [10,11]. These elements, combined with heat interferometers [3,4,12] and diodes [13,14], would complete the thermal conversion of the most important phase-coherent electronic devices and benefit cryogenic microcircuits requiring energy management, such as quantum computing architectures and radiation sensors.Comment: 10 pages, 9 color figure

Archeobotanica dell'Adriatico in età romana: stato dell'arte

EnThe shores of the Adriatic Sea since Prehistory have been a crossroads of cultural, human and commercial exchanges between West and East and in all this the Roman civilization could not have failed to exploit this internal "canal" that united the shores of the Italian and Balkan peninsula. The Adriatic Sea is also unique from an environmental and climatic point of view, with marine and wind currents coming from Africa and the Balkans meeting and colliding, resulting in rather intense meteorological cycles. All this was decisive in the history of the Adriatic and its coasts, during the Roman period; how much natural environmental conditions have influenced anthropic ones and vice versa; through a review of paleoenvironmental and archaeobotanical studies we will try to define the impact that Romanization had on the territories and environments along the two western and eastern shores of the Adriatic.ItLe sponde del Mare Adriatico sin dalla preistoria sono state un crocevia di scambi culturali, umani e commerciali tra occidente e oriente e in tutto ciò la civiltà romana non avrebbe potuto non sfruttare questo "canale" interno che univa le coste della penisola italiana a quelle della penisola balcanica. Il mare Adriatico rappresenta anche un unicum dal punto di vista ambientale e climatico: le correnti marine ed eoliche provenienti dall'Africa e dai Balcani che si incontrano e si scontrano, determinano cicli meteorologici piuttosto intensi. Tutto questo è stato determinante nella storia dell'Adriatico e dei suoi litorali, durante il periodo romano, infatti le condizioni ambientali naturali hanno condizionato quelle antropiche e viceversa. Attraverso una review degli studi paleoambientali e archeobotanici si cercherà di definire l'impatto che la romanizzazione ha avuto sui territori e gli ambienti lungo le due sponde occidentali e orientali dell'Adriatico

Homocysteine and risk of age-related macular degeneration: a systematic review and meta-analysis

There is still no agreement on total plasma homocysteine (tHcy) role in age-related macular degeneration (AMD), the leading cause of new blindness in industrialized countries. We performed a systematic review and meta-analysis of the published data on the correlation between tHcy and AMD. MEDLINE/PubMed and ISI Web of Sciences searches were performed according to MOOSE guidelines. Case-control studies were eligible for inclusion. Participants and controls were AMD patients and subjects without AMD. The main outcome measure was wet AMD. Homocysteine level was the main exposure variable. Data were pooled using a random-effects model. Twelve case-control studies were identified: 10 assessed wet AMD, four dry AMD, one early AMD, one late AMD, and one any AMD. As for wet AMD, there was a total of 453 cases and 514 controls. Mean tHcy was on average 1.1 μmol/l (95% confidence interval [CI] = 0.96-1.25) greater in wet AMD cases, but there was evidence of extreme between-study heterogeneity (p &lt; 0.001, I2 = 91.8%). In a model homogenous for age, including six wet AMD studies (214 cases, 274 controls), mean tHcy was on average 0.58 μmol/l (95% CI = 0.35-0.73) greater in the case group, a not statistically significant result (p = 0.144) associated with moderate heterogeneity (I2 = 39.2%). Our meta-analysis indicates that there is some weak evidence that increased tHcy might be associated with wet AMD; however, this result should be interpreted cautiously, because of a marked between-study heterogeneity and the possible effect of publication bias. Future studies, preferably of cohort design, are necessary before any firm conclusions on the putative role of increased tHcy on AMD can be drawn

Interaction of divalent cations with protein PARK9

Metals have been shown to play a role in the genesis and development of many neurodegenerative diseases. Park9 encoded protein can protect cells from manganese poisoning, an environmental risk factor for a Parkinson’s disease- like syndrome. Park9 belongs to a family of ATP-ases involved in metal coordination and transportation; familial mutations of this gene may result in early development of PD. We tested two peptide sequences from Park9, -P1D2E3K4H5E6L7- (1) and -F1C2G3D4G5A6N7D8C9G10- (2), for Mn(II), Zn(II) and Cu(II) binding. These fragments are located from 1165 to 1171 and from 1184 to 1193 residues in Park9 sequence, and are highly conserved in a number of organisms, from yeasts to humans. Experiments have been carried out at different pH values and ligand/metal molar ratios with both potentiometric and spectroscopic (NMR, UV-vis) techniques, showing that the three metals are able to effectively bind the examined peptides. Mn(II) and Zn(II) coordination with peptide (1) involves imidazol of His5 and carboxyl γ-O of Asp2, Glu3 and Glu6 residues, in a distorted octahedral geometry, possibly involving bidentate interaction of carboxyl groups; four donor atoms participate in Zn(II) binding, resulting in a tetracoordinated geometry. Mn(II) and Zn(II) coordination involves the two cysteines in peptide (2); Mn(II) accepts additional ligand bonds from D4 and D8 to complete the coordination sphere, together with some water molecules. Details of Cu(II) coordination are under study

An online reinforcement learning approach for HVAC control

Heating, Ventilation and Air Conditioning (HVAC) optimization for energy consumption reduction is becoming ever more a topic of the utmost environmental and energetic concerns. The two most employed methodologies for optimizing HVAC systems are Model Predictive Control (MPC) and Reinforcement Learning (RL). This paper compares three different RL approaches to HVAC optimization: one based on a black-box system identification model trained on historical data, one based on a white-box model of a building and one online method based on an imitation learning pretraining phase on historical data. The three approaches are compared with a literature baseline and an EnergyPlus baseline. Results show that the overall best method in terms of energy consumption reduction (65% decrease) and thermal comfort increase (25% increase) is the approach based on the white-box model. However, the proposed methodology, based on online and imitation learning, demonstrates remarkable efficiency, achieving comparable improvements in energy consumption after just a few months of online training, while maintaining thermal comfort at around the same level as the baseline. These results prove a direct online RL approach, which avoid the use of costly simulations, can provide a reliable and inexpensive solution to the problem of HVAC optimization

Electrically Tunable Superconductivity Through Surface Orbital Polarization

We investigate the physical mechanisms for achieving an electrical control of conventional spin-singlet superconductivity in thin films by focusing on the role of surface orbital polarization. Assuming a multi-orbital description of the metallic state, due to screening effects the electric field acts by modifying the strength of the surface potential and, in turn, yields non-trivial orbital-Rashba couplings. The resulting orbital polarization at the surface and in its close proximity is shown to have a dramatic impact on superconductivity. We demonstrate that, by varying the strength of the electric field, the superconducting phase can be either suppressed, i.e. turned into normal metal, or undergo a $0-\pi$ transition with the $\pi$ phase being marked by non-trivial sign change of the superconducting order parameter between different bands. These findings unveil a rich scenario to design heterostructures with superconducting orbitronics effects.Comment: version ad published; 14 pages, 15 panels of figure