Emergence of Classicality in Stern–Gerlach Experiment via Self-Gravity

Emergence of classicality from quantum mechanics, a hotly debated topic, has had no satisfactory resolution so far. Various approaches including decoherence and gravitational interactions have been suggested. In the present work, the Schrödinger–Newton model is used to study the role of semi-classical self-gravity in the evolution of massive spin-1/2 particles in a Stern-Gerlach experiment. For small mass, evolution of the initial wavepacket in a spin superposition shows a splitting in the magnetic field gradient into two trajectories as in the standard Stern–Gerlach experiment. For larger mass, the deviations from the central path are less than in the standard Stern–Gerlach case, while for high enough mass, the wavepacket does not split, and instead follows the classical trajectory for a magnetic moment in inhomogeneous magnetic field. This indicates the emergence of classicality due to self-gravitational interaction when the mass is increased. In contrast, decoherence which is a strong contender for emergence of classicality, leads to a mixed state of two trajectories corresponding to the spin-up and spin-down states, and not the classically expected path. The classically expected path of the particle probably cannot be explained even in the many-worlds interpretation of quantum mechanics. Stern–Gerlach experiments in the macroscopic domain are needed to settle this question.     

ssDNA binding reveals the atomic structure of graphene

We used AFM to investigate the interaction of polyelectrolytes such as ssDNA and dsDNA molecules with graphene as a substrate. Graphene is an appropriate substrate due to its planarity, relatively large surfaces that are detectable via an optical microscope, and straightforward identification of the number of layers. We observe that in the absence of the screening ions deposited ssDNA will bind only to the graphene and not to the SiO(2) substrate, confirming that the binding energy is mainly due to the π-π stacking interaction. Furthermore, deposited ssDNA will map the graphene underlying structure. We also quantify the π-π stacking interaction by correlating the amount of deposited DNA with the graphene layer thickness. Our findings agree with reported electrostatic force microscopy (EFM) measurements. Finally, we inspected the suitability of using a graphene as a substrate for DNA origami-based nanostructures.     

Characterization of [peptide+(Ag)n]+ complexes using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Silver ion complexes of peptides [M + (Ag)_n]⁺, M = angiotensin I or substance P where n = 1–8 and 17–23 for angiotensin I and n = 1–5 for substance P, are identified and characterized using matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS). The Ag⁺ coordination number exceeds the number of available amino acid residues in angiotensin I whereas the number of observed complexes in substance P is less than the number of amino acid residues in it. The larger coordination number of angiotensin I with Ag⁺ indicates the simultaneous binding of several Ag⁺ ions to the amino acid residue present in it. The lower number of observed complexes in substance P suggests the binding of two or more residues to one Ag⁺ ion. The presence of trifluoroacetic acid in the peptide samples reduces the Ag⁺ coordination ability in both the peptides which indicates that the basic residues in it are already protonated and do not participate in the Ag⁺‐binding process. The Ag⁺ ion also forms a complex with the α‐cyano‐4‐hydroxycinnamic acid (CHCA) matrix and is observed in the MALDI mass spectra and the formation of [CHCA + Ag]⁺, [CHCA + AgNO₃]⁺ and [(CHCA)₂ + Ag]⁺ ions is due to the high binding affinity of Ag⁺ to the CN group of CHCA. Copyright © 2010 John Wiley & Sons, Ltd.     

Stability of nonthermodynamic equilibrium cation distribution frozen during pulsed laser deposition of Co-ferrite thin films

Co-ferrite thin films were prepared by pulsed laser deposition technique at room temperature, and magnetization was studied as a function of annealing temperature (T _A ) and annealing time. One set of films was quenched immediately after annealing while the other set was furnace cooled. Spontaneous magnetization value, 4π M _S , of the quenched films was observed to be higher than the furnace cooled films in all the cases. Magnetization increases monotonically up to T _A =650°C and then became nearly constant with the increase in T _A . Magnetization values even higher than the Co-ferrite bulk value of 5300 G was observed in the quenched films annealed at and above 650°C. In the case of furnace cooled films, magnetization decreased with the increase in annealing time, while it remained nearly constant in quenched films. Coercivity values of the quenched films were always found to be lower than those of the furnace cooled films. The observed magnetic properties in the films were attributed to the cation distribution and the grain sizes.     

Effect of electron-phonon interaction and temperature dependence of resistivity in some heavy fermion systems

Here we have considered the electron-phonon interaction in the Periodic Anderson Model (PAM) to describe the temperature dependence of resistivity in some heavy fermion (HF) systems. Since the resistivity is related to the imaginary part of the electron self energy, the expression of the same is evaluated from electron Green function by the double time temperature dependant Green function technique of the Zubarev type. In order to understand the effect of electron-phonon interaction in these systems, we couple the phonons to both the f-electrons as well as to the electrons of the hybridization band of both conduction and f-electrons. The influence of various model parameters, namely, the position of 4f level E ₀, the electron-phonon coupling strengths f ₁(q) and f ₂(q), the effecting coupling strength g = N(0)γ ₀²/ω ₀ have been studied on the temperature dependence of resistivity in HF systems. The numerical analysis is performed for q = 0 and for finite temperature in the static limit. The analysis of the results gives satisfactorily in comparison to the experimental observations.     

Distance distributions of short polypeptides recovered by fluorescence resonance energy transfer in the 10 A domain

Fluorescence resonance energy transfer (FRET) between tryptophan (Trp) as donor and 2,3-diazabicyclo[2.2.2]oct-2-ene (Dbo) as acceptor was studied by steady-state and time-resolved fluorescence spectroscopy. The unique feature of this FRET pair is its exceptionally short F?rster radius (10 A), which allows one to recover distance distributions in very short structureless peptides. The technique was applied to Trp-(GlySer)n-Dbo-NH2 peptides with n = 0-10, for which the average probe/quencher distance ranged between 8.7 and 13.7 A experimentally (in propylene glycol, analysis according to wormlike chain model) and 8.6-10.2 A theoretically (for n = 0-6, GROMOS96 molecular dynamics simulations). The larger FRET efficiency in steady-state compared to time-resolved fluorescence experiments was attributed to a static quenching component, suggesting that a small but significant part (ca. 10%) of the conformations are already in van der Waals contact when excitation occurs.     

Food chain model with optimal harvesting in fuzzy environment

A multispecies harvesting model with mutual interactions is formulated based on Lotka–Voltera model with three competing species which are affected not only by harvesting but also by the presence of prey, predator and the third species, which is super predator. In order to understand the dynamics of the system, it is assumed that the super predator follows the logistic growth. Further, there is demand for all the above three species in the market and hence harvesting of all species is performed. We derive the condition for global stability of the system using a suitable Lyapunov function. The possibility of existence of bioeconomic equilibrium is discussed. The optimal harvest policy is studied and the solution is derived under imprecise inflation in fuzzy environment using Pontryagin’s maximal principle. Finally some numerical examples are discussed to illustrate the model.     

Assessment of the natural radioactivity using two techniques for the measurement of radionuclide concentration in building materials used in Japan

The specific activities of ²³⁸U, ²³²Th, and ⁴⁰K in selected building materials used in Japan were measured using a high-purity germanium detector. The uranium and thorium concentrations were determined from same samples using inductively coupled plasma mass spectrometry. There was a good agreement between the measurement of uranium and thorium with both methods (R ² = 0.94, and 0.97, respectively). Based on the specific activities, we have estimated some hazard indexes such as radium equivalent activities (Ra _eq), external hazard index (H _ex), internal hazard index (H _in), annual gonadal equivalent dose (AGED), internal alpha dose, mass exhalation rate and emanation coefficient of radon.     

Model pharmaceutical co-crystallization: Guest-directed assembly of caffeine and aromatic tri-hydroxy and dicarboxylic acids into different heteromolecular hydrogen bonding networks in solid state

Three model pharmaceutical caffeine-containing co-crystals of 1,3,5-trihydroxybenzene (phloroglucinol), isophthalic acid and 5-hydroxyisophthalic acid were synthesized and characterized via single-crystal X-ray diffraction. The three crystalline forms reported are an anhydrous co-crystal and other two are co-crystal hydrates. Also their binding properties were studied by UV-vis analysis. In each of these structures, an organised intermolecular hydrogen bonding motif was observed. A comparison of hydrogen bonding motifs in the crystal sheets was presented.