Observation of Fano-Resonances in Single-Wall Carbon Nanotubes

We have explored the low-temperature linear and non-linear electrical conductance $G$ of metallic carbon nanotubes (CNTs), which were grown by the chemical-vapor deposition method. The high transparency of the contacts allows to study these two-terminal devices in the high conductance regime. We observe the expected four-fold shell pattern together with Kondo physics at intermediate transparency {G\alt 2e^2/h} and a transition to the open regime in which the maximum conductance is doubled and bound by $G_{max}=4e^2/h$. In the high-$G$ regime, at the transition from a quantum dot to a weak link, the CNT levels are strongly broadened. Nonetheless, sharp resonances appear superimposed on the background which varies slowly with gate voltage. The resonances are identified by their lineshape as Fano resonances. The origin of Fano resonances is discussed along the modelling.Comment: pdf including figures, see: http://www.unibas.ch/phys-meso/Research/Papers/2004/Fano-CVD-SWNT.pd

Theoretical studies of spin-dependent electrical transport through carbon nanotbes

Spin-dependent coherent quantum transport through carbon nanotubes (CNT) is studied theoretically within a tight-binding model and the Green's function partitioning technique. End-contacted metal/nanotube/metal systems are modelled and next studied in the magnetic context, i.e. either with ferromagnetic electrodes or at external magnetic fields. The former case shows that quite a substantial giant magnetoresistance (GMR) effect occurs ($\pm 20$) for disorder-free CNTs. Anderson-disorder averaged GMR, in turn, is positive and reduced down to several percent in the vicinity of the charge neutrality point. At parallel magnetic fields, characteristic Aharonov-Bohm-type oscillations are revealed with pronounced features due to a combined effect of: length-to-perimeter ratio, unintentional electrode-induced doping, Zeeman splitting, and energy-level broadening. In particular, a CNT is predicted to lose its ability to serve as a magneto-electrical switch when its length and perimeter become comparable. In case of perpendicular geometry, there are conductance oscillations approaching asymptotically the upper theoretical limit to the conductance, $4 e^2/h$. Moreover in the ballistic transport regime, initially the conductance increases only slightly with the magnetic field or remains nearly constant because spin up- and spin down-contributions to the total magnetoresistance partially compensate each other.Comment: 15 pages, 6 figures (to apppear in Semicond. Sci. Technol.

Magnetophoresis of Flexible DNA-based Dumbbell Structures

Controlled movement and manipulation of magnetic micro and nanostructures using magnetic forces can give rise to important applications in biomedecine, diagnostics and immunology. We report controlled magnetophoresis and stretching, in aqueous solution, of a DNA-based dumbbell structure containing magnetic and diamagnetic microspheres. The velocity and stretching of the dumbbell were experimentally measured and correlated with a theoretical model based on the forces acting on individual magnetic beads or the entire dumbbell structures. The results show that precise and predictable manipulation of dumbbell structures is achievable and can potentially be applied to immunomagnetic cell separators.Comment: 4 pages, 3 figures, preprint, to be published in AP

Pore geometry of ceramic device: The key factor of drug release kinetics

Release kinetics of tigecycline, a potential antibiotic in treatment of osteomyelitis, from calcium hydroxyapatite (CHA), as one of the most important ceramic materials in bone tissue engineering, was investigated in this study. Tigecycline, in solid state, was mixed with CHA powder and the obtained mixture was compressed into tablets using two different pressures. These tablets were immersed in a phosphate-buffered saline solution and tigecycline release was measured by a UV-VIS spectrophotometer. The total release time was 5 or 28 days, depending on the pressure applied during compression. It was shown that there is a close relationship between pore sizes and drug release rate. The drug release kinetics was interpreted on the base of pore sizes and pore size distribution. [Projekat Ministarstva nauke Republike Srbije, br. 172026

Evolution and dynamics of the vertical temperature profile in an oligotrophic lake

In this study, the fine-scale responses of a stratified oligotrophic karstic lake (Kozjak Lake, Plitvice Lakes, Croatia; the lake fetch is 2.3 km, and the maximum depth is 46 m) to atmospheric forcing on the lake surface are investigated. Lake temperatures measured at a resolution of 2 min at 15 depths ranging from 0.2 to 43 m, which were observed during the 6 July–5 November 2018 period, were analyzed. The results show thermocline deepening from 10 m at the beginning of the observation period to 16 m at the end of the observation period, where the latter depth corresponds to approximately one-third of the lake depth. The pycnocline followed the same pattern, except that the deepening occurred throughout the entire period approximately 1 m above the thermocline. On average, thermocline deepening was 3–4 cm d$^{-1}$, while the maximum deepening (12.5 cm d$^{-1}$) coincided with the occurrence of internal seiches. Furthermore, the results indicate three different types of forcings on the lake surface; two of these forcings have diurnal periodicity – (1) continuous heat fluxes and (2) occasional periodic stronger winds – whereas forcing (3) corresponds to occasional nonperiodic stronger winds with steady along-basin directions. Continuous heat fluxes (1) produced forced diurnal oscillations in the lake temperature within the first 5 m of the lake throughout the entire observation period. Noncontinuous periodic stronger winds (2) resulted in occasional forced diurnal oscillations in the lake temperatures at depths from approximately 7 to 20 m. Occasional strong and steady along-basin winds (3) triggered both baroclinic internal seiches with a principal period of 8.0 h and barotropic surface seiches with a principal period of 9 min. Lake currents produced by the surface seiches under realistic-topography conditions generated baroclinic oscillations of the thermocline region (at depths from 9 to 17 m) with periods corresponding to the period of surface seiches (≈ 9 min), which, to the best of our knowledge, has not been reported in previous lake studies

Orthodontic-Prosthodontic Rehabilitation: a Case Report

A 25 year-old female came to the Department of Prosthodontics, complaining of problems with masticatory function, described as pain in both temporomandibular joints during mastication and dissatified with esthetics in the upper jaw. After a thorough clinical escaminations, diagnostic casts and X-ray analysis it was determined that the patent had oligodontium of 10 teeth (14, 15, 17, 18, 24, 25, 28, 38, 44, 48), discoloration of incisors caused by hypomaturated enamel (amelogenesis imperfecta), disproportion of the front teeth (in completely defined microdontia), Angle class II/1 (deep overbite) and compression of the front teeth. The case history showed that the problems were of a congenital nature apart from the frontal compression, caused by inadequate orthodontic therapy at a younger age. Despite numerous congenital abnormalities, the patient had no systemic disorders. In consultation with an orthodontist, the patient commenced orthodontic therapy with a fixed orthodontic appliance in the upper jaw for placing the teeth in the right position for fabrication of a semicircular bridge. After 6 months of orthodontic therapy, a fixed prosthodontic appliance 600321 123006 (upper jaw) was made of metal ceramic. The aim of the therapy was to replace missing teeth, protect existing teeth with hypomaturated enamel and readjust occlusal height. With the new intermaxillary relations and teeth contour esthetic and functional concordance was achieved. After therapy the patient had no pain in the temporomandibular joints

Orthodontic-Prosthodontic Rehabilitation: a Case Report

A 25 year-old female came to the Department of Prosthodontics, complaining of problems with masticatory function, described as pain in both temporomandibular joints during mastication and dissatified with esthetics in the upper jaw. After a thorough clinical escaminations, diagnostic casts and X-ray analysis it was determined that the patent had oligodontium of 10 teeth (14, 15, 17, 18, 24, 25, 28, 38, 44, 48), discoloration of incisors caused by hypomaturated enamel (amelogenesis imperfecta), disproportion of the front teeth (in completely defined microdontia), Angle class II/1 (deep overbite) and compression of the front teeth. The case history showed that the problems were of a congenital nature apart from the frontal compression, caused by inadequate orthodontic therapy at a younger age. Despite numerous congenital abnormalities, the patient had no systemic disorders. In consultation with an orthodontist, the patient commenced orthodontic therapy with a fixed orthodontic appliance in the upper jaw for placing the teeth in the right position for fabrication of a semicircular bridge. After 6 months of orthodontic therapy, a fixed prosthodontic appliance 600321 123006 (upper jaw) was made of metal ceramic. The aim of the therapy was to replace missing teeth, protect existing teeth with hypomaturated enamel and readjust occlusal height. With the new intermaxillary relations and teeth contour esthetic and functional concordance was achieved. After therapy the patient had no pain in the temporomandibular joints

Adrb2 gene polymorphisms and salbutamol responsiveness in Serbian children with asthma

Inhaled beta 2 adrenergic receptor (beta 2-AR) agonists are the mainstay of asthma therapy. The beta 2-AR protein is encoded by the ADRB2 gene and variants within this gene can have significant consequences for modulating the response to asthma therapy. This cross-sectional study performed at the University Children's Hospital in Belgrade, included 54 children with asthma. The subjects were genotyped for ADRB2 +46A gt G (Arg16Gly, rs1042713) and +79C gt G (G1n27G1u, rs1042714) polymorphisms and the association with asthma severity and response to inhaled salbutamol was examined. In Serbian asthmatic children, allele +46A was detected with a frequency of 41.7% and allele +79G was detected with a frequency of 23.1%. Allele +460 was found to be associated with a better response to inhaled salbutamol (p lt 0.05) and with mild form of asthma (p lt 0.05). Polymorphism ADRB2 +46A gt G may be a determinant of asthma severity and response to salbutamol in children with asthma. We did not find any association of +79C gt G polymorphisms with the asthma severity and bronchodilator response to inhaled salbutamol. The results of this study can be potentially useful for personalization of asthma treatment