Analytical Study of Low-Field Diffusive Transport in Highly Asymmetric Bilayer Graphene Nanoribbon

We present a simplified theory of carrier backscattering coefficient in a twofold degenerate asymmetric bilayer graphene nanoribbon (BGN) under the application of a low static electric field. We show that for a highly asymmetric BGN(Delta = gamma), the density of states in the lower subband increases more that of the upper, in which Delta and gamma are the gap and the interlayer coupling constant, respectively. We also demonstrate that under the acoustic phonon scattering regime, the formation of two distinct sets of energy subbands signatures a quantized transmission coefficient as a function of ribbon width and provides an extremely low carrier reflection coefficient for a better Landauer conductance even at room temperature. The well-known result for the ballistic condition has been obtained as a special case of the present analysis under certain limiting conditions which forms an indirect validation of our theoretical formalism.

Two-channel Kondo physics in odd impurity chains

We study odd-membered chains of spin-1/2 impurities, with each end connected to its own metallic lead. For antiferromagnetic exchange coupling, universal two-channel Kondo (2CK) physics is shown to arise at low energies. Two overscreening mechanisms are found to occur depending on coupling strength, with distinct signatures in physical properties. For strong interimpurity coupling, a residual chain spin-1/2 moment experiences a renormalized effective coupling to the leads, while in the weak-coupling regime, Kondo coupling is mediated via incipient single-channel Kondo singlet formation. We also investigate models in which the leads are tunnel-coupled to the impurity chain, permitting variable dot filling under applied gate voltages. Effective low-energy models for each regime of filling are derived, and for even fillings where the chain ground state is a spin singlet, an orbital 2CK effect is found to be operative. Provided mirror symmetry is preserved, 2CK physics is shown to be wholly robust to variable dot filling; in particular, the single-particle spectrum at the Fermi level, and hence the low-temperature zero-bias conductance, is always pinned to half-unitarity. We derive a Friedel-Luttinger sum rule and from it show that, in contrast to a Fermi liquid, the Luttinger integral is nonzero and determined solely by the ``excess'' dot charge as controlled by gate voltage. The relevance of the work to real quantum dot devices, where interlead charge-transfer processes fatal to 2CK physics are present, is also discussed. Physical arguments and numerical renormalization-group techniques are used to obtain a detailed understanding of these problems.

How does DNA break during chromosomal translocations?

Chromosomal translocations are one of the most common types of genetic rearrangements and are molecular signatures for many types of cancers. They are considered as primary causes for cancers, especially lymphoma and leukemia. Although many translocations have been reported in the last four decades, the mechanism by which chromosomes break during a translocation remains largely unknown. In this review, we summarize recent advances made in understanding the molecular mechanism of chromosomal translocations.

Interacting magnetic sublattices and ferrimagnetism in Sr-doped DyMnO3

We present the magnetic properties of polycrystalline Dy1−xSrxMnO3 (0.1 ≤ x ≤ 0.4) with an orthorhombic (o) crystal structure. The parent compound, o-DyMnO3, undergoes an incommensurate antiferromagnetic ordering of the Mn spins at 39 K, followed by a spiral order at 18 K. A further antiferromagnetic transition at 5 K marks an ordering of the Dy-sublattice. Doping of divalent Sr ions results in diverse magnetization phenomena. The zero-field cooled (ZFC) and field cooled (FC) magnetization curves display the presence of strongly interacting magnetic sublattices. For x = 0.1 and 0.2, a bifurcation between the ZFC and FC magnetization sets in at around 30 and 32 K, respectively. The ZFC magnetization peaks at about 5 K, indicating antiferromagnetic Dy-couplings similar to the case of o-DyMnO3. For x = 0.3, clear signatures of ferrimagnetism and strong anisotropy are found, including negative magnetization. The compound with x = 0.4 behaves as a spin glass, similar to Dy0.5Sr0.5MnO3.

Higgs Working Group Summary Report

Report of the Higgs working group for the Workshop "Physics at TeV Colliders", Les Houches, France 8-18 June 1999. It contains 6 separate sections: 1. Measuring Higgs boson couplings at the LHC. 2. Higgs boson production at hadron colliders at NLO. 3. Signatures of Heavy Charged Higgs Bosons at the LHC. 4. Light stop effects and Higgs boson searches at the LHC. 5. Double Higgs production at TeV Colliders in the MSSM. 6. Programs and Tools for Higgs Bosons.

TeV scale implications of non commutative space time in laboratory frame with polarized beams

We analyze e(+)e(-) -> gamma gamma, e(-)gamma -> e(-)gamma and gamma gamma -> e(+)e(-) processes within the Seiberg-Witten expanded noncommutative scenario using polarized beams. With unpolarized beams the leading order effects of non commutativity starts from second order in non commutative(NC) parameter i.e. O(Theta(2)), while with polarized beams these corrections appear at first order (O(Theta')) in cross section. The corrections in Compton case can probe the magnetic component(Theta(B)) while in Pair production and Pair annihilation probe the electric component((Theta) over right arrow (E)) of NC parameter. We include the effects of earth rotation in our analysis. This study is done by investigating the effects of non commutativity on different time averaged cross section observables. The results which also depends on the position of the collider, can provide clear and distinct signatures of the model testable at the International Linear Collider(ILC).

Land Surface Temperature with Land Cover Dynamics:Multi-Resolution, Spatio-Temporal Data Analysis of Greater Bangalore

Bangalore is experiencing unprecedented urbanisation in recent times due to concentrated developmental activities with impetus on IT (Information Technology) and BT (Biotechnology) sectors. The concentrated developmental activities has resulted in the increase in population and consequent pressure on infrastructure, natural resources, ultimately giving rise to a plethora of serious challenges such as urban flooding, climate change, etc. One of the perceived impact at local levels is the increase in sensible heat flux from the land surface to the atmosphere, which is also referred as heat island effect. In this communication, we report the changes in land surface temperature (LST) with respect to land cover changes during 1973 to 2007. A novel technique combining the information from sub-pixel class proportions with information from classified image (using signatures of the respective classes collected from the ground) has been used to achieve more reliable classification. The analysis showed positive correlation with the increase in paved surfaces and LST. 466% increase in paved surfaces (buildings, roads, etc.) has lead to the increase in LST by about 2 ºC during the last 2 decades, confirming urban heat island phenomenon. LSTs’ were relatively lower (~ 4 to 7 ºC) at land uses such as vegetation (parks/forests) and water bodies which act as heat sinks.

Discrimination of Nuclear Grade Steel Samples Subjected to Different Heat Treatment Procedures Based on Acoustic Emission (AE) Data Profiling at Crack Initiation

The present work is an attempt to study crack initiation in nuclear grade, 9Cr-1Mo ferritic steel using AE as an online NDE tool. Laboratory experiments were conducted on 5 heat treated Compact Tension (CT) specimens made out of nuclear grade 9Cr-1Mo ferritic steel by subjecting them to cyclic tensile load. The CT Specimens were of 12.5 mm thickness. The Acoustic emission test system was setup to acquire the data continuously during the test by mounting AE sensor on one of the surfaces of the specimen. This was done to characterize AE data pertaining to crack initiation and then discriminate the samples in terms of their heat treatment processes based on AE data. The AE signatures at crack initiation could conclusively bring to fore the heat treatment distinction on a sample to sample basis in a qualitative sense.Thus, the results obtained through these investigations establish a step forward in utilizing AE technique as an on-line measurement tool for accurate detection and understanding of crack initiation and its profile in 9Cr-1Mo nuclear grade steel subjected to different processes of heat treatment.

Tracing the source of bottled water using stable isotope techniques

The Indian Summer Monsoon (ISM) precipitation recharges ground water aquifers in a large portion of the Indian subcontinent. Monsoonal precipitation over the Indian region brings moisture from the Arabian Sea and the Bay of Bengal (BoB). A large difference in the salinity of these two reservoirs, owing to the large amount of freshwater discharge from the continental rivers in the case of the BoB and dominating evaporation processes over the Arabian Sea region, allows us to distinguish the isotopic signatures in water originating in these two water bodies. Most bottled water manufacturers exploit the natural resources of groundwater, replenished by the monsoonal precipitation, for bottling purposes. The work presented here relates the isotopic ratios of bottled water to latitude, moisture source and seasonality in precipitation isotope ratios. We investigated the impact of the above factors on the isotopic composition of bottled water. The result shows a strong relationship between isotope ratios in precipitation (obtained from the GNIP data base)/bottled water with latitude. The approach can be used to predict the latitude at which the bottled water was manufactured. The paper provides two alternative approaches to address the site prediction. The limitations of this approach in identifying source locations and the uncertainty in latitude estimations are discussed. Furthermore, the method provided here can also be used as an important forensic tool for exploring the source location of bottled water from other regions. Copyright (C) 2011 John Wiley & Sons, Ltd.

When should fig fruit produce volatiles? Pattern in a ripening process

Ripe fruit need to signal their presence to attract dispersal agents. Plants may employ visual and/or olfactory sensory channels to signal the presence of ripe fruit. Visual signals of ripe fruit have been extensively investigated. However, the volatile signatures of ripe fruit that use olfactorily-oriented dispersers have been scarcely investigated. Moreover, as in flowers, where floral scents are produced at times when pollinators are active (diurnal versus nocturnal), whether plants can modulate the olfactory signal to produce fruit odours when dispersers are active in the diel cycle is completely unknown. We investigated day night differences in fruit odours in two species of figs, Ficus racemosa and Ficus benghalensis. The volatile bouquet of fruit of F.racemosa that are largely dispersed by bats and other mammals was dominated by fatty acid derivatives such as esters. In this species in which the ripe fig phase is very short, and where the figs drop off soon after ripening, there were no differences between day and night in fruit volatile signature. The volatile bouquet of fruit of F. benghalensis that has a long ripening period, however, and that remain attached to the tree for extended periods when ripe, showed an increase in fatty acid derivatives such as esters and of benzenoids such as benzaldehyde at night when they are dispersed by bats, and an elevation of sesquiterpenes during the day when they are dispersed by birds. For the first time we provide data that suggest that the volatile signal produced by fruit can show did l differences based on the activity period of the dispersal agent. (C) 2011 Elsevier Masson SAS. All rights reserved.

Evidence for a thermally reversing window in bulk Ge–Te–Si glasses revealed by alternating differential scanning calorimetry

Experiments on Ge15Te85− x Si x glasses (2 ≤ x ≤ 12) using alternating differential scanning calorimetry (ADSC) indicate that these glasses exhibit one glass transition and two crystallization reactions upon heating. The glass transition temperature has been found to increase almost linearly with silicon content, in the entire composition tie-line. The first crystallization temperature (T c1) exhibits an increase with silicon content for x < 5; T c1 remains almost a constant in the composition range 5 < x ≤ 10 and it increases comparatively more sharply with silicon content thereafter. The specific heat change (ΔC p) is found to decrease with an increase in silicon content, exhibiting a minimum at x = 5 (average coordination number, r = 2.4); a continuous increase is seen in ΔC p with silicon concentration above x = 5. The effects seen in the variation with composition of T c1 and ΔC p at x = 5, are the specific signatures of the mean-field stiffness threshold at r = 2.4. Furthermore, a broad trough is seen in the enthalpy change (ΔH NR), which is indicative of a thermally reversing window in Ge15Te85− x Si x glasses in the composition range 2 ≤ x ≤ 6 (2.34 ≤ r ≤ 2.42).

The interaction of halogen molecules with SWNTs and graphene

The interaction of halogen molecules of varying electron affinity, such as iodine monochloride (ICl), bromine (Br(2)), iodine monobromide (IBr) and iodine (I(2)) with single-walled carbon nanotubes (SWNTs) and graphene has been investigated in detail. Halogen doping of the two nanocarbons has been examined using Raman spectroscopy in conjunction with electronic absorption spectroscopy and extensive theoretical calculations. The halogen molecules, being electron withdrawing in nature, induce distinct changes in the electronic states of both the SWNTs and graphene, which manifests with a change in the spectroscopic signatures. Stiffening of the Raman G-bands of the nanocarbons upon treatment with the different halogen molecules and the emergence of new bands in the electronic absorption spectra, both point to the fact that the halogen molecules are involved in molecular charge-transfer with the nanocarbons. The experimental findings have been explained through density functional theory (DFT) calculations, which suggest that the extent of charge-transfer depends on the electron affinities of the different halogens, which determines the overall spectroscopic properties. The magnitude of the molecular charge-transfer between the halogens and the nanocarbons generally varies in the order ICl > Br(2) > IBr > I(2), which is consistent with the expected order of electron affinities.

Minimal unsatisfiable sets: Classification and bounds

Proving the unsatisfiability of propositional Boolean formulas has applications in a wide range of fields. Minimal Unsatisfiable Sets (MUS) are signatures of the property of unsatisfiability in formulas and our understanding of these signatures can be very helpful in answering various algorithmic and structural questions relating to unsatisfiability. In this paper, we explore some combinatorial properties of MUS and use them to devise a classification scheme for MUS. We also derive bounds on the sizes of MUS in Horn, 2-SAT and 3-SAT formulas.

Observation of pseudo-gap and Kondo behaviour in Al70Pd30−xMnx quasicrystals

We report here the electrical and magnetic properties of Al70Pd30−xMnx quasicrystals (x=9 and 11), from resistivity and point contact spectroscopy measurements. Electrical resistivity shows a resistivity maximum for both of these compositions. The positive TCR at lower temperature is attributed to spin–orbit scattering. For x=11, we observe an upturn in the resistivity below 20 K, which follows a lnT dependence indicating Kondo-like behaviour. In the point contact spectroscopy studies we observe two regimes showing a V2 dependence at low bias voltages (for V<10 meV) crossing over to the V0.5 dependence at higher voltages. This is attributed to the signature of a pseudo-gap in the density of states at zero bias. We suggest that this V2 dependence can also arise due to magnetic scattering effects, which are signatures of the Kondo-like behaviour.

Effect of AC&DC field on the dielectric response of (Pb,La)TiO3 thin films

Lanthanum doped lead titanate thin films are the potential candidates for the capacitors, actuators and pyroelectric sensor applications due to their excellent dielectric, and ferroelectric properties. Lanthanum doped lead titanate thin films are grown on platinum coated Si substrates by excimer laser ablation technique. A broad diffused phase transition with the maximum dielectric permittivity (ϵmax) shifting to higher temperatures with the increase of frequency, along with frequency dispersion below Tc, which are the signatures of the relaxor like characteristics were observed. The dielectric properties are investigated from −60°C to 200°C with an application of different dc fields. With increasing dc field, the dielectric constant is observed to reduce and phase transition temperature shifted to higher temperature. With the increased ac signal amplitude of the applied frequency, the magnitude of the dielectric constant is increasing and the frequency dispersion is observed in ferroelectric phase, whereas in paraelectric phase, there is no dispersion has been observed. The results are correlated with the existing theories.