Dynamics and interactions of active rotors

We consider a simple model of an internally driven self-rotating object; a rotor, confined to two dimensions by a thin film of low Reynolds number fluid. We undertake a detailed study of the hydrodynamic interactions between a pair of rotors and find that their effect on the resulting dynamics is a combination of fast and slow motions. We analyse the slow dynamics using an averaging procedure to take account of the fast degrees of freedom. Analytical results are compared with numerical simulations. Hydrodynamic interactions mean that while isolated rotors do not translate, bringing together a pair of rotors leads to motion of their centres. Two rotors spinning in the same sense rotate with an approximately constant angular velocity around each other, while two rotors of opposite sense, both translate with the same constant velocity, which depends on the separation of the pair. As a result a pair of counter-rotating rotors are a promising model for controlled self-propulsion.Comment: 6 pages, 6 figure

Violation and persistence of the K-quantum number in warm rotating nuclei

The validity of the K-quantum number in rapidly rotating warm nuclei is investigated as a function of thermal excitation energy U and angular momentum I, for the rare-earth nucleus 163Er. The quantal eigenstates are described with a shell model which combines a cranked Nilsson mean-field and a residual two-body interaction, together with a term which takes into account the angular momentum carried by the K-quantum number in an approximate way. K-mixing is produced by the interplay of the Coriolis interaction and the residual interaction; it is weak in the region of the discrete rotational bands (U \lesim 1MeV), but it gradually increases until the limit of complete violation of the K-quantum number is approached around U \sim 2 - 2.5 MeV. The calculated matrix elements between bands having different K-quantum numbers decrease exponentially as a function of $\Delta K$, in qualitative agreement with recent data.Comment: 29 pages, 7 figure

Conductance quantization in etched Si/SiGe quantum point contacts

We fabricated strongly confined Schottky-gated quantum point contacts by etching Si/SiGe heterostructures and observed intriguing conductance quantization in units of approximately 1e2/h. Non-linear conductance measurements were performed depleting the quantum point contacts at fixed mode-energy separation. We report evidences of the formation of a half 1e2/h plateau, supporting the speculation that adiabatic transmission occurs through 1D modes with complete removal of valley and spin degeneracies.Comment: to appear in Physical Review

Vibrio parahaemolyticus-specific Halobacteriovorax From Seawater of a Mussel Harvesting Area in the Adriatic Sea: Abundance, Diversity, Efficiency and Relationship With the Prey Natural Level

This research aimed to study the abundance and molecular diversity of Vibrio parahaemolyticus-specific Halobacteriovorax strains isolated from seawater of the Adriatic Sea and the relationship between predator and prey abundances. Moreover, predator efficiency of the Halobacteriovorax isolates toward V. parahaemolyticus and Vibrio cholerae non-O1/O139 strains was tested. V. parahaemolyticus NCTC 10885 was used as primary host for the isolation of Halobacteriovorax from seawater by the plaque assay. Molecular identification was performed by PCR detection of a fragment of the 16S rRNA gene of the Halobacteriovoraceae family members. Moreover, 700 bp PCR products were sequenced and compared between them and to clones described for other sampling sites. Vibrio counts were performed on TCBS agar from 100 ml of filtered water samples and presumptive colonies were confirmed by standard methods. Predatory efficiency of Halobacteriovorax isolates was tested by monitoring abilities of 3-day enrichments to form clear lytic halos on a lawn of Vibrio preys, by the plaque assay. Out of 12 seawater samples monthly collected from June 2017 to May 2018, 10 were positive for V. parahaemolyticus specific Halobacteriovorax with counts ranging from 4 to 1.4 × 103 PFU per 7.5 ml. No significant relationship was found between Halobacteriovorax and Vibrio abundances. The 16SrRNA sequences of our Halobacteriovorax strains, one for each positive sample, were divided into three lineages. Within the lineages, some sequences had 100% similarity. Sequence similarity between lineages was always <94.5% suggesting that they may therefore well belong to three different species. All Halobacteriovorax isolates had the ability to prey all tested Vibrio strains. Additional research is necessary to assess whether stable strains of Halobacteriovorax are present in the Adriatic Sea and to understand the mechanisms by which Halobacteriovorax may modulate the abundance of V. parahaemolyticus and other vibrios in a complex marine ecosystem

Exposure to active and passive smoking during pregnancy and severe small for gestational age at term

Objective. The objective of this study was to assess the relationship between active smoking as well as environmental tobacco smoke (ETS) exposure and severe small for gestational age (SGA) at term in a sample of pregnant Italian women. Methods. A case-control study was conducted in nine cities in Italy between October 1999 and September 2000. Cases of severe SGA were singleton, live born, at term children with a birth weight5th percentile for gestational age. Controls (10:1 to cases) were enrolled from among singleton at term births that occurred in the same hospitals one or two days after delivery of the case, with a birth weight10th percentile for gestational age. A total of 84 cases of severe SGA and 858 controls were analyzed. A self-administered questionnaire was used to assess active smoking and ETS exposure, as well as potential confounders. Results. Multivariate logistic regression analysis showed a relationship between active smoking during pregnancy and severe SGA (adjusted odds ratio (OR) 2.10, 95% confidence interval (CI) 1.13-3.68). ETS exposure was associated with severe SGA (adjusted OR 2.51, 95% CI 1.59-3.95) with a dose-response relationship to the number of smokers in the home

Bdellovibrio bacteriovorus to control Escherichia coli on meat matrices

Bdellovibrio bacteriovorus is a predator micro-organism towards other Gram-negative bacteria. We tested B. bacteriovorus to control Escherichia coli growth on chicken slices and canned beef. Moreover, we analysed B. bacteriovorus's lytic ability on eight toxigenic or multidrug-resistant E. coli strains. In chicken slices, the predator induced the highest prey reduction (4.3 log) respect to control at 6 h. In canned beef, the predator induced the highest prey reduction (2.1 log) respect to control at 6 h. Moreover, B. bacteriovorus showed lytic ability towards all tested E. coli strains. B. bacteriovorus could control E. coli and other pathogenic and spoilage bacteria in those meat-based foods that have a shelf life <10 days. It could integrate modified atmosphere packaging (MAP) to prolong the shelf life and improve the safety of pre-packed fresh meat, meat preparations and meat products. In future applications on meat-based foods, B. bacteriovorus could also minimise the use of additives

Overlapping redox zones control arsenic pollution in Pleistocene multi-layer aquifers, the Po Plain (Italy)

Understanding the factors that control As concentrations in groundwater is vital for supplying safe groundwater in regions with As-polluted aquifers. Despite much research, mainly addressing Holocene aquifers hosting young (12,000 yrs) groundwaters are not yet fully understood and so are assessed here through an evaluation of the redox properties of the system in a type locality, the Po Plain (Italy). Analyses of redox-sensitive species and major ions on 22 groundwater samples from the Pleistocene arsenic-affected aquifer in the Po Plain shows that groundwater concentrations of As are controlled by the simultaneous operation of several terminal electron accepters. Organic matter, present as peat, is abundant in the aquifer, allowing groundwater to reach a quasi-steady-state of highly reducing conditions close to thermodynamic equilibrium. In this system, simultaneous reduction of Fe-oxide and sulfate results in low concentrations of As (median 7 μg/L) whereas As reaches higher concentrations (median of 82 μg/L) during simultaneous methanogenesis and Fe-reduction. The position of well-screens is an additional controlling factor on groundwater As: short screens that overlap confining aquitards generate higher As concentrations than long screens placed away from them. A conceptual model for groundwater As, applicable worldwide in other Pleistocene aquifers with reducible Fe-oxides and abundant organic matter is proposed: As may have two concentration peaks, the first after prolonged Fe-oxide reduction and until sulfate reduction takes place, the second during simultaneous Fe-reduction and methanogenesis

Pygmy dipole resonance in Ce 140 via inelastic scattering of O 17

M. Krzysiek et al. ; 8 págs.; 7 figs. ; 2 tabs.The γ decay from the high-lying states of Ce140 excited via inelastic scattering of O17 at a bombarding energy of 340 MeV was measured using the high-resolution AGATA-demonstrator array in coincidence with scattered ions detected in two segmented ΔE-E silicon detectors. Angular distributions of scattered ions and emitted γ rays were measured, as well as their differential cross sections. The excitation of 1- states below the neutron separation energy is similar to the one obtained in reactions with the α isoscalar probe. The comparison between the experimental differential cross sections and the corresponding predictions using the distorted-wave Born approximation allowed us to extract the isoscalar component of identified 1- pygmy states. For this analysis the form factor obtained by folding microscopically calculated transition densities and optical potentials was used. ©2016 American Physical SocietyThis work has been partly supported by the stipend from Marian Smoluchowski Krakow Research Consortium ’Matter-Energy-Future’ as a Leading National Research Center (KNOW) and also by several grants: the Polish National Science Centre under Contracts No. 2015/17/B/ST2/01534, No. 2013/09/N/ST2/04093, No. 2013/08/M/ST2/00591, and No. 2011/03/B/ST2/01894; US-NSF Grants No. PHY-1204486 and No. PHY-1404343; Croatian Science Foundation under Project No. IP-2014-09-9159; the Spanish Ministerio de Economía y Competitividad under Contract No. FPA2014-57196-C5-4-P. Also, A. Gadea has been supported by MINECO, Spain, under Grant No. FPA2014-57196-C5; Generalitat Valenciana, Spain, under Grant No. PROMETEOII/2014/019; and the EU under the FEDER program. The research leading to these results has also received funding from the European Union Seventh Framework Programme FP7/2007-2013 under Grant Agreement No. 262010 - ENSAR.Peer Reviewe

Superconducting nanowire photon number resolving detector at telecom wavelength

The optical-to-electrical conversion, which is the basis of optical detectors, can be linear or nonlinear. When high sensitivities are needed single-photon detectors (SPDs) are used, which operate in a strongly nonlinear mode, their response being independent of the photon number. Nevertheless, photon-number resolving (PNR) detectors are needed, particularly in quantum optics, where n-photon states are routinely produced. In quantum communication, the PNR functionality is key to many protocols for establishing, swapping and measuring entanglement, and can be used to detect photon-number-splitting attacks. A linear detector with single-photon sensitivity can also be used for measuring a temporal waveform at extremely low light levels, e.g. in long-distance optical communications, fluorescence spectroscopy, optical time-domain reflectometry. We demonstrate here a PNR detector based on parallel superconducting nanowires and capable of counting up to 4 photons at telecommunication wavelengths, with ultralow dark count rate and high counting frequency