[en] Small angle scattering (SAS) is the collective name given to the techniques of small angle neutron (SANS) and X-ray (SAXS) scattering. They offer the possibility to analyze particles without disturbing their natural environment. In each of these techniques radiation is elastically scattered by a sample and the resulting scattering pattern is analyzed to provide information about the size, shape and orientation of some component of the sample. Accordingly, a large number of methods and experimental patterns have been developed to ease the investigation of condensed matter by use of these techniques. Some of them are the discussed in this paper

[en] Small-angle neutron scattering (SANS) measurements on 0.3M sodium dodecyl sulfate (SDS) micellar solutions have been performed in the presence of n-alcohols, from ethanol to decanol at different alcohol concentrations, 2–10 wt%. The ellipsoid micellar structure which occurred in the 0.3M SDS in aqueous solution with the size range of 30–50 Å has different behavior at various hydrocarbon chain length and concentration of alcohols. At low concentration and short chain-length of alcohols, such as ethanol, propanol, and butanol, the size of micelles reduced and had a spherical-like structure. The opposite effect occurred as medium to long chain alcohols, such as hexanol, octanol and decanol was added into the 0.3M SDS micellar solutions. The micelles structure changed to be more elongated in major axis and then crossed the critical phase transition from micellar solution into liquid crystal phase as lamellar structure emerged by further addition of alcohols. The inter-lamellar distances were also depending on the hydrocarbon chain length and concentration of alcohols. In the meantime, the persistent micellar structures occurred in addition of medium chain of n-alcohol, pentanol at all concentrations

[en] Antiferromagnets produce no stray field, and therefore, a tip electrode made of antiferromagnetic material has been considered to be the most suitable choice to measure such as magnetoresistance (MR) through single isolated magnetic nanoparticles, molecules, and ultrathin films. Spin polarizations (P) of antiferromagnetic 3-nm, 6-nm, and annealed 3-nm Mn films grown on W tips with a bcc(110) apex as well as bulk-NiMn tips were obtained at 300 K by measuring MR in ultrahigh vacuum by means of spin-polarized scanning tunneling microscopy using a layerwise antiferromagnetically stacking bct-Mn(001) film electrode. The Mn-coated tips with coverages of 3 and 6 nm exhibited P values of 1 ± 1% and 3 ± 2%, respectively, which tips likely contain α- or strained Mn. With a thermal assist, the crystalline quality and the magnetic stability of the film could increase. The annealed tip exhibited P = 9 ± 2%. The bulk-NiMn tips exhibit spin polarizations of 0 or 6 ± 2% probably depending on the chemical species (Mn or Ni) present at the apex of the tip. Fe-coated W tips were used to estimate the bct-Mn(001) film spin polarization

[en] The structure of the SPRY domain of the human RNA helicase DDX1 was determined at 2.0 Å resolution. The SPRY domain provides a putative protein–protein interaction platform within DDX1 that differs from other SPRY domains in its structure and conserved regions. The human RNA helicase DDX1 in the DEAD-box family plays an important role in RNA processing and has been associated with HIV-1 replication and tumour progression. Whereas previously described DEAD-box proteins have a structurally conserved core, DDX1 shows a unique structural feature: a large SPRY-domain insertion in its RecA-like consensus fold. SPRY domains are known to function as protein–protein interaction platforms. Here, the crystal structure of the SPRY domain of human DDX1 (hDSPRY) is reported at 2.0 Å resolution. The structure reveals two layers of concave, antiparallel β-sheets that stack onto each other and a third β-sheet beneath the β-sandwich. A comparison with SPRY-domain structures from other eukaryotic proteins showed that the general β-sandwich fold is conserved; however, differences were detected in the loop regions, which were identified in other SPRY domains to be essential for interaction with cognate partners. In contrast, in hDSPRY these loop regions are not strictly conserved across species. Interestingly, though, a conserved patch of positive surface charge is found that may replace the connecting loops as a protein–protein interaction surface. The data presented here comprise the first structural information on DDX1 and provide insights into the unique domain architecture of this DEAD-box protein. By providing the structure of a putative interaction domain of DDX1, this work will serve as a basis for further studies of the interaction network within the hetero-oligomeric complexes of DDX1 and of its recruitment to the HIV-1 Rev protein as a viral replication factor

[en] The critical properties of perovskite manganite La_0.65Eu_0.05Sr_0.3Mn_1−xCr_xO₃ (x=0.10 and x=0.15) around the paramagnetic–ferromagnetic phase transition are investigated through various techniques such as the modified Arrott plot, Kouvel–Fisher method, and critical isotherm analysis. The experimental results have revealed that the samples exhibited the second-order magnetic phase transition and the critical exponents of β and γ for La_0.65Eu_0.05Sr_0.3Mn_1−xCr_xO₃ (x=0.10) are consistent with the prediction of the mean field model. Furthermore, the estimated critical exponents of La_0.65Eu_0.05Sr_0.3Mn_1−xCr_xO₃ (x=0.15) are close to those found out by the 3D-Heisenberg model. The magnetization–field–temperature M–H–T behaviors of all compounds at below and above T_C were properly renormalized following the scaling of state equation M(H,ε)=|ε|^βf_±(H/|ε|^β+γ), where ε=(T−T_C)/T_C, f₊ for T>T_C and f₋ for T< T_C. This confirms that the obtained values of the critical exponent as well as T_C are reasonably accurate and unambiguous. - Highlights: • The paramagnetic to ferromagnetic phase transition of La_0.65Eu_0.05Sr_0.3Mn_1−xCr_xO₃ (x=0.10 and x=0.15) is found to be of second-order. • Critical exponents fit with both models 3D-Heisenberg and mean field. • Widom scaling relation and the universal scaling hypothesis confirm the critical exponent value. • La_0.65Eu_0.05Sr_0.3Mn_1−xCr_xO₃ belongs to the mean field class with long-range interaction for x=0.10 and 3D Heisenberg ferromagnets with short-range interaction for x=0.15

[en] In this paper, the effect of dimension on dispersion and absorption properties in an AlGaAs/GaAs quantum well (QW) nanostructure is investigated. We use the conduction-band Hamiltonian to calculate the envelope functions and the eigenenergies. The Schrödinger equation is solved numerically using homemade codes. Then we employ the density matrix formalism to evaluate the behavior of optical susceptibly. The impact of the width of the well and the barrier on the linear optical susceptibility behavior is explored. This investigation can be used for the optimal design of quantum well nanostructures to achieve electromagnetically induced transparency, which is much more practical than atomic structures because of their flexible design and the controllable quantum coherence effects

[en] A new synthesis method of Ba₂CrO₄ is developed and its magnetic properties are investigated by magnetic susceptibility, magnetization curve, and specific heat measurements. The compound shows a conventional antiferromagnetic transition at T_N=3.5 K although magnetic properties due to honeycomb lattice is seen in Sr₂CrO₄. The g-value of Cr⁴⁺ ions in Ba₂CrO₄ is estimated to be g=1.94, which agrees well with the g-values of Cr⁴⁺ ions in other compounds

[en] In this communication, we have investigated the substrate effect on the growth of MoO₃ nanostructured thin films prepared by plasma assisted sublimation process (PASP). Three different substrates viz. ITO glass, Ni/Si [100], and Ni/glass are used in deposition process. The surface analysis endorsed that Ni/Si and Ni/glass substrates are most favorable for the uniform growth of vertically aligned MoO₃ nanoplates (NP_s) and nanoflakes (NF_s) of well controlled features with very high aspect ratio (height/thickness) >30, whereas nanostructure formed on ITO/glass substrate is improper (in terms of features and alignment). The X-ray diffractograms divulge that MoO₃ films deposited on all substrates exhibit pure orthorhombic phase with preferential crystallographic orientation along [110] direction particularly in case of Ni/Si and Ni/glass substrates. Atomic force microscopic analysis reveals that the average substrates roughness enhanced in presence of pre-deposited layer and monitor the growth of nanostructures. High resolution transmission electron microscopic analysis with selected area diffraction pattern confirmed that both the MoO₃ NP_s and NF_s are single crystalline in nature. The Raman and IR spectrum of all films further endorse the presence of single orthorhombic phase in accordance with the XRD results and also confirm the effect of nanosize on the vibrational properties

[en] Local pseudo-potential formalism under the virtual crystal approximation including the effective disorder potential was applied to study the electronic and optical properties of the quaternary Ga_xIn_1−xAs_yP_1−y alloy lattice matched to GaAs, InP and ZnSe substrates. Results are presented for the energy gaps, ionicity, polarity, refractive index, high frequency and static dielectric constants of the considered alloy. The dependence of these properties on temperature and hydrostatic pressure for each matched substrate has been also studied. Comparison between the calculated energy band gaps and the available experimental and published data showed good agreement

[en] Mesoporous silica substrate consists of uniformly distributed, unconnected cylindrical or spherical pores. Since the diameters of the pores are less than the wavelength, near-field radiative heat transfer across a cylindrical or spherical pore was simulated by employing the fluctuation dissipation theorem and Green function. Such factors as the diameter of the pore, and the temperature of the material were analyzed. It turned out that when the diameter is greater than 1 nm and less than 50 nm, the radiative heat flux at the mesoscale is 2–6 orders higher than the value at the macroscale, and decreases exponentially with the pore radius increasing for both cylindrical and spherical pore. The thermal conductivity of the mesoporous silica was modified with consideration of near-field radiation. It was concluded that the combined thermal conductivities of mesoporous silica which considering near-field radiation can agree with the experimental results more properly than non-considering near-field radiation. The smaller the pore diameter, the more significant the near-field radiation effect. The combined thermal conductivities of mesoporous silica decrease gradually with the pore diameter increasing, while increase smoothly with the temperature increasing