Atom interferometry with Bose-Einstein condensates in a double-well potential

A trapped-atom interferometer was demonstrated using gaseous Bose-Einstein condensates coherently split by deforming an optical single-well potential into a double-well potential. The relative phase between the two condensates was determined from the spatial phase of the matter wave interference pattern formed upon releasing the condensates from the separated potential wells. Coherent phase evolution was observed for condensates held separated by 13 $\mu$m for up to 5 ms and was controlled by applying ac Stark shift potentials to either of the two separated condensates.Comment: 4 pages, 4 figure

Distillation of Bose-Einstein condensates in a double-well potential

Bose-Einstein condensates of sodium atoms, prepared in an optical dipole trap, were distilled into a second empty dipole trap adjacent to the first one. The distillation was driven by thermal atoms spilling over the potential barrier separating the two wells and then forming a new condensate. This process serves as a model system for metastability in condensates, provides a test for quantum kinetic theories of condensate formation, and also represents a novel technique for creating or replenishing condensates in new locations

Convergence of Wnt signalling on the HNF4a-driven transcription in controlling liver zonation

BACKGROUND & AIMS: In each hepatocyte, the specific repertoire of gene expression is influenced by its exact location along the portocentrovenular axis of the hepatic lobule and provides a reason for the liver functions compartmentalization defined "metabolic zonation." So far, few molecular players controlling genetic programs of periportal (PP) and perivenular (PV) hepatocytes have been identified; the elucidation of zonation mechanisms remains a challenge for experimental hepatology. Recently, a key role in induction and maintenance of the hepatocyte heterogeneity has been ascribed to Wnt/beta-catenin pathway. We sought to clarify how this wide-ranging stimulus integrates with hepatocyte specificity. METHODS: Reverse transcriptase polymerase chain reaction (RT-PCR) allowed the transcriptional profiling of hepatocytes derived from in vitro differentiation of liver stem cells. The GSK3beta inhibitor 6-bromoindirubin-3'-oxime (BIO) was used for beta-catenin stabilization. Co-immunoprecipitations were used to study biochemical protein interactions while ChIP assays allowed the in vivo inspection of PV and PP genes regulatory regions. RESULTS: We found that spontaneous differentiation of liver stem cells gives rise to PP hepatocytes that, after Wnt pathway activation, switch into PV hepatocytes. Next, we showed that the Wnt downstream player LEF1 interacts with the liver-enriched transcriptional factor HNF4alpha. Finally, we unveiled that the BIO induced activation of PV genes correlates with LEF1 binding to both its own and HNF4alpha consensus, and the repression of PP genes correlates with HNF4alpha displacement from its own consensus. CONCLUSION: Our data show a direct and hitherto unknown convergence of the canonical Wnt signaling on the HNF4alpha-driven transcription providing evidences of a mechanism controlling liver zonated gene expression

Aesthetic and Mechanical Suitability of a Clear Synthetic Resin as a Unconventional Binder for Road Pavements

Current environmental awareness interests several aspects of civil engineering, including road construction. Indeed, new challenges related to environmental pollution and landscape preservation must be faced. In this sense, clear road pavement surfaces represent an effective technology aimed at guaranteeing environmental-friendly aesthetic pavements. The use of clear synthetic resin as a binder involves several benefits for the mitigation of in-service reached temperatures and the heat distribution within pavements (with appreciable effects on pavement mechanical performance too). The present paper illustrates an experimental study aimed at analysing the chromatic and mechanical properties of a clear synthetic resin and thus its suitability as a binder for road pavement mixes. Chromatic characteristics were assessed through digital image analysis at different aging conditions. A dynamic shear rheometer was used to evaluate the linear viscoelastic properties as well as fatigue and rutting potential of the binder in a wide range of temperatures and frequencies. A conventional 35/50 penetration grade bitumen was also investigated for comparison purposes. The clear resin exhibited limited changes in colour (darkening effects), mainly in the case of short-term aging. On the other hand, a low temperature-dependency of such a binder was observed up to 58\ub0C. Slightly increased aptitude to rutting at the higher temperatures was detected, even if it is worth noting that clear in-service mixtures would achieve lower temperatures than traditional "black" materials at a given environmental condition (air temperature, solar radiation, etc.). The resin also exhibited a softer behaviour, along with an enhanced fatigue resistance. Overall, the studied innovative binder showed promising results in view of its effective use in road paving

Steel slag as valuable aggregate in eco\u2013friendly mixtures for asphalt pavements

Research and application concerning the use of environmentally friendly materials and technologies in road pavements have reached high relevance mainly due to the increasing public consciousness addressed to environmental protection and preservation. In this sense, the possible use of steel slags for construction applications (including road pavements) has a strategic importance to convert a waste into a valuable resource, taking also into account that ferrous slag may have a lower potential to negatively impact the environment. The environmental sustainability of asphalt mixtures prepared with steel slags can be further enhanced adopting the so-called Warm Mix Asphalt (WMA) technology. In fact, WMA is an asphalt concrete modified with additives that can be produced and applied at lower temperatures than the traditional Hot Mix Asphalt (HMA), thus reducing energy consumption, gas and fume emissions. Given this background, the paper illustrates a part of a wide research study aimed at verifying the utilization feasibility of steel slags in warm asphalt concretes. In particular, midrange and high-service temperature properties as well as water susceptibility of warm mixtures containing steel slags were assessed in the laboratory. The warm modification was performed using a chemical tensoactive additive, whereas slags were taken from a metallurgical plant equipped with an electric arc furnace (EAF). A WMA prepared with only natural aggregates was also studied for comparison purpose. The performance characterization was carried out through both static and cyclic laboratory tests. The results mainly showed that asphalt mixtures prepared combining chemical warm technology and EAF steel slag aggregates demonstrate promising field applicability

Experimental study aimed at highlighting warnings for proper design, construction and control of geocomposite-reinforced asphalt pavements

The proper use of interlayers in asphalt pavements can be an effective and economic option to enhance their service life. However, the presence of a foreign element at the interface should be properly taken into account during design, construction and control of reinforced pavements. Given this background, the present laboratory study investigated stiffness and interface bonding properties of reinforced asphalt systems in order to achieve fundamental information for a correct design as well as proper construction and control of reinforced pavements. To accomplish this objective, different composite reinforcements (grids/fabrics embedded in bituminous membranes) were studied as interlayers of double-layered systems prepared with both traditional and polymer-modified asphalt concretes. Dynamic flexural tests and static interface shear tests were carried out. Unreinforced reference systems was also studied for comparison purposes. Results confirmed the abovementioned warnings that will allow delineating some preliminary guidelines related to the use of reinforcements in pavements

The Rotation of Sub-Populations in omega Centauri

We present the first result of the Ital-FLAMES survey of red giant branch (RGB) stars in omega Cen. Radial velocities with a precision of ~0.5 km/s are presented for 650 members of omega Cen observed with FLAMES-Giraffe at the Very Large Telescope. We found that stars belonging to the metal -poor (RGB-MP), metal-intemediate (RGB-MInt) and metal-rich (RGB-a) sub -populations of Omega Cen are all compatible with having the same rotational pattern. Our results appear to contradict past findings by Norris et al., who could not detect any rotational signature for metal -rich stars. The slightly higher precision of the present measurements and the much larger sample size, especially for the metal-richer stars, appear as the most likely explanation for this discrepancy. The result presented here weakens the body of evidence in favour of a merger event in the past history of omega Cen.Comment: 5 pages, 3 fiures, electronic table can be obtained from E. Pancino. Accepted for publication in ApJ Letter

Optical Weak Link between Two Spatially Separate Bose-Einstein Condensates

Two spatially separate Bose-Einstein condensates were prepared in an optical double-well potential. A bidirectional coupling between the two condensates was established by two pairs of Bragg beams which continuously outcoupled atoms in opposite directions. The atomic currents induced by the optical coupling depend on the relative phase of the two condensates and on an additional controllable coupling phase. This was observed through symmetric and antisymmetric correlations between the two outcoupled atom fluxes. A Josephson optical coupling of two condensates in a ring geometry is proposed. The continuous outcoupling method was used to monitor slow relative motions of two elongated condensates and characterize the trapping potential.Comment: 4 pages, 5 figure

2d frustrated Ising model with four phases

In this paper we consider a 2d random Ising system on a square lattice with nearest neighbour interactions. The disorder is short range correlated and asymmetry between the vertical and the horizontal direction is admitted. More precisely, the vertical bonds are supposed to be non random while the horizontal bonds alternate: one row of all non random horizontal bonds is followed by one row where they are independent dichotomic random variables. We solve the model using an approximate approach that replace the quenched average with an annealed average under the constraint that the number of frustrated plaquettes is keep fixed and equals that of the true system. The surprising fact is that for some choices of the parameters of the model there are three second order phase transitions separating four different phases: antiferromagnetic, glassy-like, ferromagnetic and paramagnetic.Comment: 17 pages, Plain TeX, uses Harvmac.tex, 4 ps figures, submitted to Physical Review