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SrFe12O19 coatings, intended as electromagnetic wave absorbers, were produced by atmospheric plasma spraying (APS) using two different kindsof feedstock powders: spray-dried agglomerates of micrometric SrFe12O19 particles (type-A) or spray-dried agglomerates of raw materials (SrCO3,Fe2O3), reactively sintered at 1100 ◦C (type-B).During spraying, type-A agglomerates either remain unmelted, producing porous coating regions where crystalline hexaferrite is retained, orare disrupted into smaller granules which melt completely, resulting in dense coating regions with no crystalline hexaferrite.The sintered type-B agglomerates possess higher cohesive strength and do not fall apart: the finer ones melt completely, whereas, in the largerones, the outer region melts and infiltrates the porous unmelted core which retains crystalline hexaferrite. Dense coatings can therefore be obtainedwhile preserving high amounts of crystalline hexaferrite even inside the dense areas. Such coatings show magnetic properties that are promisingfor electromagnetic wave absorption applications

Diffusive Josephson junctions made out of multiwalled carbon nanotubes

We have investigated electrical transport in diffusive multiwalled carbon nanotubes (MWNT) contacted using superconducting leads made of Ti/Al/Ti sandwich structure. We measure proximity-induced supercurrents up to Icm = 1.3 nA and find tunability by the gate voltage due to variation of the Thouless energy via the diffusion constant that is controlled by scattering in the MWNT. The modeling of these results by long, diffusive SNS junctions, supplemented with phase diffusion effects is discussed: the agreement between theory and experiments is tested especially on the basis of the temperature dependence of the Josephson coupling energy. In order to prove conclusively that the diffusive model works for MWNT proximity junctions, we propose an improved measurement scheme that is based on the kinetic inductance of superconducting junctions.Peer reviewe

Single-electron transistor made of two crossing multiwalled carbon nanotubes and its noise properties

A three-terminal nanotube device was fabricated from two multiwalled nanotubes by pushing one on top of the other using an atomic-force microscope. The lower nanotube, with gold contacts at both ends, acted as the central island of a single-electron transistor while the upper one functioned as a gate electrode. Coulomb blockade oscillations were observed on the nanotube at sub-Kelvin temperatures. The voltage noise of the nanotube single-electron transistor (SET) was gain dependent as in conventional SETs. The charge sensitivity at 10 Hz was 6×10 exp −4  e/√Hz.Peer reviewe

Stark effect and generalized Bloch-Siegert shift in a strongly driven two-level system

A superconducting qubit was driven in an ultrastrong fashion by an oscillatory microwave field, which was created by coupling via the nonlinear Josephson energy. The observed Stark shifts of the `atomic' levels are so pronounced that corrections even beyond the lowest-order Bloch-Siegert shift are needed to properly explain the measurements. The quasienergies of the dressed two-level system were probed by resonant absorption via a cavity, and the results are in agreement with a calculation based on the Floquet approach.Comment: 4+ page

Multiwalled carbon nanotubes as ultrasensitive electrometers

We show that it is possible to construct low-noise single-electron transistors (SETs) using free-standing multiwalled carbon nanotubes. The 1/fα -noise of our devices, 6×10 exp −6 e/√Hz at 45 Hz, is close in the performance to the best metallic SETs of today.Peer reviewe

Surface spin waves in 3He-A, a probe for vortex phenomena in narrow gaps

We report measurements on a new collective spin-wave mode trapped by the textural boundary layers of 3 He-A within a stack of thin Mylar plates. The surface mode was seen as a new peak in the cw NMR spectrum measured at H0=284 Oe. Rotation of the sample, with Ω orthogonal to the gaps, increased the spectral weight of the surface mode, indicating an increase in the textural boundary layers caused by a counterflow-induced transition. This phenomenon was used to study vortex creation and persistent currents.Peer reviewe

Increased brain histamine H(3 )receptor expression during hibernation in golden-mantled ground squirrels

BACKGROUND: Hibernation is a state of extremely reduced physiological functions and a deep depression of CNS activity. We have previously shown that the histamine levels increase in the brain during hibernation, as does the ratio between histamine and its first metabolite, suggesting increased histamine turnover during this state. The inhibitory histamine H(3 )receptor has both auto- and heteroreceptor function, rendering it the most likely histamine receptor to be involved in regulating the activity of histamine as well as other neurotransmitters during hibernation. In view of accumulating evidence that there is a global depression of transcription and translation during hibernation, of all but a few proteins that are important for this physiological condition, we reasoned that an increase in histamine H(3 )receptor expression would clearly indicate an important hibernation-related function for the receptor. RESULTS: In this study we show, using in situ hybridization, that histamine H(3 )receptor mRNA increases in the cortex, caudate nucleus and putamen during hibernation, an increase that is accompanied by elevated receptor binding in the cerebral cortex, globus pallidus and substantia nigra. These results indicate that there is a hibernation-related increase in H(3 )receptor expression in cortical neurons and in striatopallidal and striatonigral GABAergic neurons. GTP-γ-S binding autoradiography shows that the H(3 )receptors in the globus pallidus and substantia nigra can be stimulated by histamine throughout the hibernation cycle, suggesting that they are functionally active during hibernation. CONCLUSIONS: These results show that the histamine H(3 )receptor gene is one of the few with a transcript that increases during hibernation, indicating an important role for the receptor in regulating this state. Moreover, the receptor is functionally active in the basal ganglia, suggesting a function for it in regulating e.g. dopaminergic transmission during hibernation

Manipulation of Ag nanoparticles utilizing noncontact atomic force microscopy

We have developed a scheme to manipulate metallic aerosol particles on silicon dioxide substrates using an atomic force microscope. The method utilizes the noncontact mode both for locating and moving nanoparticles of size 10–100 nm. The main advantage of our technique is the possibility of “seeing” the moving particle in real time. Our method avoids well sticking problems that typically hamper the manipulation in the contact mode.Peer reviewe

Noise of a single electron transistor on a Si3N4 membrane

We have investigated the influence of electron-beam writing on the creation of charge trapping centers which cause 1/f noise in single electron transistors (SET). Two Al/AlOx/Al devices were compared: one where the SET is on a {100} silicon wafer covered by a 120-nm-thick layer of Si3N4, and another one in which the Si was etched away from below the nitride membrane before patterning the SET. The background charge noise was found to be 1×10 exp −3 e/√Hz at 10 Hz in both devices, independent of the substrate thickness.Peer reviewe

Shot noise in lithographically patterned graphene nanoribbons

We have investigated shot noise and conductance of multiterminal graphene nanoribbon devices at temperatures down to 50 mK. Away from the charge neutrality point, we find a Fano factor F≈0.4, nearly independent of the charge density. Our shot noise results are consistent with theoretical models for disordered graphene ribbons with a dimensionless scattering strength K0 ≈ 10 corresponding to rather strong disorder. Close to charge neutrality, an increase in F up to ∼0.7 is found, which indicates the presence of a dominant Coulomb gap possibly due to a single quantum dot in the transport gap.Peer reviewe