Prisutnost bakterija u zraku nastambi za svinje i neposrednom okolišu

This paper describes a bacteriological analysis of air samples taken from swine housing facilities and the immediate environment. The air volume of the samples was pre-programmed by a standard air sampler (MAS-100, Merck) and was directly impacted onto the bacteriologic agar surface (Petri dishes, standard diameter of 90 mm). The bacterial contamination in forty-eight samples was 2.59x105 CFU/m3 (ranging from 8.46x104 to 5.30x105 CFU/m3). Potentially pathogenic bacterial agents predominated in all samples (100%), while primarily pathogenic bacteria were isolated in a minor proportion of samples (33%–66%). Airborne bacterial contamination in samples (N=16) obtained from emptied facilities ranged from 1.8x103 CFU/m3 (that is, after coarse mechanical washing) to 0.8x102 CFU/m3 (upon completion of disinfection). Control measurements at different locations and distance from the farm (N=32) pointed to the presence of non-pathogenic airborne bacteria, ranging from 1.55x102 to 3.70x102 CFU/m3. The results of this preliminary study showed that the emission of potentially pathogenic bacteria from animal housing facilities to the immediate farm environment via aerosol was very low.Pored kontrole emisija štetnih plinova, vlage i čestica prašine u nastambama za životinje, važna je i detekcija ukupne bakterijske kontaminacije zraka. Od posebnog su značenja i moguće emisije u okoliš, osobito potencijalno ili primarno patogenih bakterija. U raspravi su prikazani rezultati prvih istraživanja bakterijske kontaminacije zraka u nastambama, kao i u neposrednom okolišu provedenih na jednoj farmi svinja. Programirani volumen zraka standardnim je skupljačem zraka (MAS-100-Merck) direktno naslojen na površine bakterioloških podloga (Petrijeve ploče promjera 90 mm). U pretraženih 48 uzoraka u nastambama ustanovljena je prosječna bakterijska kontaminacija zraka za farmu od 2,595 CFU/m3 (od 8,464 do 5,305). U svim su uzorcima dominantno bili prisutni Streptococcus spp., Micrococcus spp., Escherichia coli, Staphylococcus aureus i Streptococcus suis. U manjem broju uzoraka izdvojeni su potencijalno patogeni uzročnici Pasteurella multocida (66%), Actinobacillus suis (50%), hemolitični sojevi E. coli (41%) te Pasteurella haemolytica, Bordetella bronchiseptica i Actinobacillus pleuropneumoniae (33%). Mjerenjima u praznim objektima, prije useljenja životinja (16 uzoraka), ustanovljena je srednja kontaminacija zraka od 9,01 do 0,41 CFU/m3 s bakterijskim uzročnicima Streptococcus spp., Staphylococcus spp. i E. coli. Kontrolna mjerenja izvan objekata (32 uzorka) upozorila su na prosječnu kontaminaciju zraka od 0,261 CFU/m3 (od 0,151 do 0,371) i uz zastupljenost apatogenih uzročnika Bacillus subtilis, Bacillus cereus, E. coli, Streptococcus spp., Micrococcus spp. i Staphylococcus spp. Rezultati pokazuju da su neznatne emisije potencijalno patogenih bakterijskih uzročnika putem aerosola iz nastambi za svinje u neposredni okoliš. Unatoč sve sofisticiranijim uređajima za monitoring, ni danas još, u okviru programa animalne higijene, nisu određene granične vrijednosti za bakteriološku kontaminaciju zraka kao što je to slučaj s emisijom štetnih plinova NH3 i CO2

Depairing critical currents and self-magnetic field effects in submicron YBa2Cu3O7-delta microbridges and bicrystal junctions

We report on depairing critical currents in submicron YBa 2 Cu 3 O 7-δ microbridges. A small-angle bicrystal grain boundary junction is used as a tool to study the entrance of vortices induced by a transport current and their influence on the I-V curves. The interplay between the depairing and the vortex motion determines a crossover in the temperature dependence of the critical current. The high entrance field of vortices in very narrow superconducting channels creates the possibility of carrying a critical current close to the depairing limit determined by the S-S ′ -S nature of the small-angle grain boundary junction. \ua9 2004 American Institute of Physics

Surface potential variations in epitaxial graphene devices investigated by Electrostatic Force Spectroscopy

Electrostatic Force Spectroscopy and Scanning Kelvin Probe Microscopy techniques are used to study the performance of side-gated Hall devices made of epitaxial graphene on 4H-SiC(0001). Electrostatic Force Spectroscopy is a novel method which allows quantitative surface potential measurements with high spatial resolution. Using these techniques, we calibrate work function of the metal coated tip and define the work functions for single and double-layer graphene. We also show that the use of moderate strength electrical fields in the side-gate geometry does not notably change the performance of the device

Fabrication of graphene quantum hall resistance standard in a cryogen-Table-Top system

We have demonstrated quantum Hall resistance measurements with metrological accuracy in a relatively easy to use and compact cryogen-free system operating at a temperature of around 3.8 K and magnetic field below 5 T. This advance in technology is due to the unique properties of epitaxial graphene on silicon carbide (SiC) which lifts the stringent requirements for quantum hall effect seen in conventional semiconductors. This paper presents the processes involved in fabrication and characterization of metrologically viable epitaxial graphene samples

Direct Identification of Dilute Surface Spins on Al2 O3: Origin of Flux Noise in Quantum Circuits

An on-chip electron spin resonance technique is applied to reveal the nature and origin of surface spins on Al2O3. We measure a spin density of 2.2 71017 spins/m2, attributed to physisorbed atomic hydrogen and S=1/2 electron spin states on the surface. This is direct evidence for the nature of spins responsible for flux noise in quantum circuits, which has been an issue of interest for several decades. Our findings open up a new approach to the identification and controlled reduction of paramagnetic sources of noise and decoherence in superconducting quantum devices

Phase coherence and energy relaxation in epitaxial graphene under microwave radiation

We have performed low-temperature magnetotransport measurements on monolayer epitaxial graphene under microwave radiation and extracted the radiation-induced effective temperatures, energy relaxation, and the dephasing times. We established that the response of the graphene sample is entirely bolometric at least up to 170 GHz. Dynamic dephasing, i.e., the time-reversal symmetry breaking effect of the ac electromagnetic field rather than mediated by heating, may become significant in the terahertz frequency range and in samples with longer phase coherence time

The EMRP project GraphOhm- Towards quantum resistance metrology based on graphene

A new joint research project (JRP) integrating metrology institutes and universities from nine countries is aimed at realization of a new generation of standards for quantum resistance metrology. The project exploits graphene\u27s properties to simplify operation of standards without compromising the unprecedented precision delivered by semiconductor quantum Hall devices. Higher operating temperatures (above 4.2 K, and up to 8 K) and together with lower magnetic fields (below 5 T, and potentially down to 2 T) will lead to a significantly improved and cost-saving dissemination of intrinsically referenced resistance standards to all end-users relying on electrical measurements

Towards a cryogen-free table-top primary resistance standard

We demonstrate quantum Hall resistance measurements with metrological accuracy in a small cryogen-free system operating at a temperature of around 3.8 K and magnetic fields below 5 T. We use this system to investigate the optimisation of graphene/SiC devices for maximum breakdown current. In addition we report the first characterisation of a cryogen-free cryogenic current comparator which enables entirely cryogen-free primary resistance metrology