1,038 research outputs found
Effects of Diffusion on Photocurrent Generation in Single-Walled Carbon Nanotube Films
We have studied photocurrent generation in large carbon nanotube (CNT) films
using electrodes with different spacings. We observe that the photocurrent
depends strongly on the position of illumination, with maximum observed
response occurring upon illumination at the electrode edges. The rate of change
of the response decays exponentially, with the fastest response occurring for
samples with the smallest electrode spacing. We show that the time response is
due to charge carrier diffusion in low-mobility CNT films
Current and Shot Noise Measurements in a Carbon Nanotube-Based Spin Diode
Low-temperature measurements of asymmetric carbon nanotube (CNT) quantum dots
are reported. The CNTs are end-contacted with one ferromagnetic and one
normal-metal electrode. The measurements show a spin-dependent rectification of
the current caused by the asymmetry of the device. This rectification occurs
for gate voltages for which the normal-metal lead is resonant with a level of
the quantum dot. At the gate voltages at which the current is at the maximum
current, a significant decrease in the current shot noise is observed
Electric Field Effect in Ultrathin Films near the Superconductor-Insulator Transition
The effect of an electric field on the conductance of ultrathin films of
metals deposited on substrates coated with a thin layer of amorphous Ge was
investigated. A contribution to the conductance modulation symmetric with
respect to the polarity of the applied electric field was found in regimes in
which there was no sign of glassy behavior. For films with thicknesses that put
them on the insulating side of the superconductor-insulator transition, the
conductance increased with electric field, whereas for films that were becoming
superconducting it decreased. Application of magnetic fields to the latter,
which reduce the transition temperature and ultimately quench
superconductivity, changed the sign of the reponse of the conductance to
electric field back to that found for insulators. We propose that this
symmetric response to capacitive charging is a consequence of changes in the
conductance of the a-Ge layer, and is not a fundamental property of the physics
of the superconductor-insulator transition as previously suggested.Comment: 4 pages text, 4 figure
Carbonized Jute Sorbent for Oil Cleanup
Over 90 million tons of textile waste is produced every year. A large share of waste comes from the goods made of cellulose fibers. Recently, special attention has been directed towards the use of textile cellulose waste for clean-up of oil spills. The major problem relies on their relatively small oil capacity and complex separation of individual cellulose fibers from the treated spills. In an attempt to overcome this drawback, a non-woven sorbent based on recycled jute fibers obtained from the carpet industry was manufactured. Improvement of porosity and hydrophobicity/oleophilicity of the sorbent was achieved by carbonization process in an inert atmosphere. FESEM analysis revealed the fiber reduction of almost 40% induced by fiber degradation while EDX analysis confirmed the increase in the carbon content by 75% after carbonization. Oil capacity in water medium, buoyancy, oil retention and reusability of non-carbonized and carbonized sorbents were evaluated by testing four different oils (crude oil, diesel oil, two motor oils). After carbonization process, the oil sorption capacity was doubled in comparison with noncarbonized sorbent independent of oil viscosity. Carbonized sorbent not only remained afloat after 24 h of staying in water, but it sorbed a negligible amount of water unlike non-carbonized sorbent. in addition to good buoyancy, oil retention on carbonized sorbents ranged from 64-80% after 30 min of draining. Larger uptake was achieved with oils of higher viscosity, but their retention was worse. Oil sorption capacity after 5 repeated sorption/desorption trials was significantly larger in the case of carbonized sorbent since it retained 80-88% of its initial oil sorption capacity depending on tested oil
Neuropsychological constraints to human data production on a global scale
Which are the factors underlying human information production on a global
level? In order to gain an insight into this question we study a corpus of
252-633 Million publicly available data files on the Internet corresponding to
an overall storage volume of 284-675 Terabytes. Analyzing the file size
distribution for several distinct data types we find indications that the
neuropsychological capacity of the human brain to process and record
information may constitute the dominant limiting factor for the overall growth
of globally stored information, with real-world economic constraints having
only a negligible influence. This supposition draws support from the
observation that the files size distributions follow a power law for data
without a time component, like images, and a log-normal distribution for
multimedia files, for which time is a defining qualia.Comment: to be published in: European Physical Journal
A contribution to the data on tench (Tinca tinca L., Cyprinidae, pisces) distribution in Serbia
The studies on the ichthyofauna of Serbia that have been conducted so far indicate the sporadic tench (Tinca tinca L.) presence in typical habitats. The hydroenvironmental conditions necessary for the survival of this fish species are highly variable and, generally, are more favourable in the northern part of the country (the Vojvodina Province). Although the tench presence has been registered at over 30 sites, there is a tendency of a decrease in population abundance. This is due to the reduction of the surface area of the macrophyte-covered flood zones induced by the damming and regulation of rivers, high water level fluctuations, and water amount reduction in the majority of watercourses, a massive increase in the number of allochthonous phytofagous species, reservoir sediment deposition, water quality deterioration and other factors. The tench conservation status in Serbia is officially designated as Low Risk - Least Concern. It may be transferred to a higher category if the tendency towards deterioration of survival conditions for the species should continue
Classical stability and quantum instability of black-hole Cauchy horizons
For a certain region of the parameter space , the Cauchy
horizon of a (charged) black hole residing in de Sitter space is classically
stable to gravitational perturbations. This implies that, when left to its own
devices, classical theory is unable to retain full predictive power: the
evolution of physical fields beyond the Cauchy horizon is not uniquely
determined by the initial conditions. In this paper we argue that the Cauchy
horizon of a Reissner-Nordstr\"om-de Sitter black hole must always be unstable
quantum mechanically.Comment: 4 pages; uses ReVTeX; figure available upon request to
[email protected]
Wind towers - design of flange ring connection
Today, wind power is second largest available renewable resource of energy, with 870 TW (terawatts). Large wind farms, with hundreds of wind towers are big opportunity for steel production industry. Designers and manufacturers of wind towers pay special attention on every single detail, always looking for some new solutions, trying to reduce price of wind towers. Some of the most interesting design and manufacturing details are connections used to assemble sections of tubular steel towers supporting wind turbins. There is traditional and actually more used flange ring connection and on the
other side, as a new proposal which is used more and more, friction connection. In this paper theoretic basis of design of flange ring connection of wind towers is give
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