Rotational bands in the proton emitter (141)Ho

Rotational bands feeding the ground state and the isomeric state in the proton emitter (141)Ho were observed using the recoil-decay tagging method. This constitutes direct evidence that (141)Ho is deformed. A quadrupole deformation of beta(2) = 0.25(4) was deduced for the ground state from the extracted dynamic moment of inertia. Based on observed band crossings and signature splittings the 7/2(-)[523] and 1/2(+)[411] configurations were proposed for the ground state and the isomeric state, respectively. Comparison with particle-rotor calculations for beta(2) = 0.25 indicates, however, that (141)Ho may have significant hexadecapole deformation and could be triaxial in the 7/2(-)[523] ground state.     

Identification of excited states in the T(z) = 1 nucleus (110)Xe: evidence for enhanced collectivity near the N=Z=50 double shell closure

Gamma-ray transitions have been identified for the first time in the extremely neutron-deficient (N=Z+2) nucleus (110)Xe, and the energies of the three lowest excited states in the ground-state band have been deduced. The results establish a breaking of the normal trend of increasing first excited 2(+) and 4(+) level energies as a function of the decreasing neutron number as the N=50 major shell gap is approached for the neutron-deficient Xe isotopes. This unusual feature is suggested to be an effect of enhanced collectivity, possibly arising from isoscalar n-p interactions becoming increasingly important close to the N=Z line.     

Self-interaction and strong correlation in DFTB

The density functional based tight-binding (DFTB) method can benefit substantially from a number of developments in density functional theory (DFT) while also providing a simple analytical proving ground for new extensions. This contribution begins by demonstrating the variational nature of charge-self-consistent DFTB (SCC-DFTB), proving the presence of a defined ground-state in this class of methods. Because the ground state of the SCC-DFTB method itself can be qualitatively incorrect for some systems, suitable forms of the recent LDA+U functionals for SCC-DFTB are also presented. This leads to both a new semilocal self-interaction correction scheme and a new physical argument for the choice of parameters in the LDA+U method. The locality of these corrections can only partly repair the HOMO-LUMO gap and chemical potential discontinuity, hence a novel method for introducing this further physics into the method is also presented, leading to exact derivative discontinuities in this theory at low computational cost. The prototypical system NiO is used as an illustration for these developments.     

Selective bond breaking in beta-D-ribose by gas-phase electron attachment around 8 eV

Electron attachment experiments are carried out on the beta-d-ribose molecule in the gas phase for the energy region around 8 eV, and clear fragmentation products are observed for different mass values. A computational analysis of the relevant dynamics is also carried out for the beta-d-ribose in both the furanosic and pyranosic form as gaseous targets around that energy range. The quantum scattering attributes obtained from the calculations reveal in both systems the presence of transient negative ions (TNIs). An analysis of the spatial features of the excess resonant electron, together with the computation and characterization of the target molecular normal modes, suggests possible break-up pathways of the initial, metastable molecular species.     

High strength modified nanofibrillated cellulose-polyvinyl alcohol films

In this study surface-modified nanofibrillated cellulose (NFC) was used at low levels (0.5 to1.5 wt%) as a reinforcement in a polyvinyl alcohol (PVA) matrix. The modified-NFC–PVA composite films prepared using the solution casting technique showed improved mechanical performance. Birch pulp cellulose was initially modified by allylation using a solvent-free, dry modification method followed by subsequent epoxidation of the allyl groups and finally grinding the pulp to yield epoxy-NFC. In order to obtain optimal mechanical performance, epoxy-NFC with different degrees of substitution was evaluated in the reinforcement of PVA. The addition of 1 wt% epoxy-NFC (degree of substitution, DS 0.07) enhanced the modulus, strength, and strain of pure PVA film by 307, 139 and 23 %, respectively, thus producing the best performing film. The results demonstrate the favourable effect of chemically functionalized NFC on the mechanical properties of polyvinyl alcohol compared to unmodified NFC as reinforcement. In order to improve industrial and economic feasibility, the manufacture of the composite was also done in situ by grinding cellulose directly in PVA to produce the new biocomposite in a one-step process.     

An RP-HPLC determination of 5-hydroxymethylfurfural in honey The case of strawberry tree honey

The use of the RP-HPLC official method of the International Honey Commission (IHC) for the determination of 5-hydroxymethylfurfural (HMF) in strawberry tree honey (Arbutus unedo, a typical Sardinian honey) has brought to light a specific and heavy chromatographic interference that prevents accurate quantification. The interference has been identified as homogentisic acid (HA), i.e. the marker of the botanical origin of the honey. For this reason, an alternative RP-HPLC method is proposed. The bias-free method allows a complete separation of HMF from HA to the baseline level and is faster and more precise than the RP-HPLC official method: the detection and quantification limits are 1.9 and 4.0 mg kg⁻¹, respectively, whereas the repeatability is ca. 2% in the HMF concentration range of 5-140 mg kg⁻¹.     

Integration of self-assembled three-dimensional photonic crystals onto structured silicon wafers

We report on the fabrication of high-quality opaline photonic crystals from large silica spheres (diameter of 890 nm), self-assembled in hydrophilic trenches of silicon wafers by using a novel technique coined a combination of "lifting and stirring". The achievements reported here comprise a spatial selectivity of opal crystallization without special treatment of the wafer surface, a filling of the trenches up to the top, leading to a spatially uniform film thickness, particularly an absence of cracks within the size of the trenches, and finally a good 3D order of the opal lattice even in trenches with a complex confined geometry, verified using optical measurements. The opal lattice was found to match the pattern precisely in width as well as depth, providing an important step toward applications of opals in integrated optics.     

Theoretical modeling of the valence UV spectra of 1,2,3-triazine and uracil in solution

Assessment of the perturbed matrix method (PMM) ability in reproducing valence UV absorption spectra is carried out on two model systems: 1,2,3-triazine in methanol solution and uracil in water solution. Results show that even using the simplest definition of the quantum center, i.e. the portion of the system explicitly treated quantum mechanically, PMM provides rather good results. This paper further confirms the possibility of using PMM as a theoretical-computational tool, complementary to other methodologies, for addressing the electronic properties in molecular systems of high complexity.     

Copper(II) complexes of terminally protected pentapeptides containing three histidyl residues in alternating positions, Ac-His-Xaa-His-Yaa-His-NH2

Copper(II) complexes of the pentapeptides Ac-HisAlaHisValHis-NH2, Ac-HisValHisAlaHis-NH2, Ac-HisProHisAlaHis-NH2, Ac-HisAlaHisProHis-NH2, Ac-HisGlyHisValHis-NH2 and Ac-HisValHisGlyHis-NH2 have been studied by potentiometric, UV-Vis, CD and EPR spectroscopic methods. It has been found that the pentapeptides are efficient ligands for the complexation with copper(II) and exhibit an outstanding versatility in the co-ordination geometry of complexes. The presence of three histidyl residues provides a high possibility for the formation of macrochelates via the exclusive binding of imidazole-N donor atoms. The macrochelation suppresses, but cannot preclude the deprotonation and metal ion co-ordination of amide functions and the species [CuH(-2)L] and [Cu2H(-4)L] predominate at physiological pH in equimolar solutions and in the presence of excess metal ions, respectively. It is also clear from the data that both C-terminal and internal histidyl residues can work as the anchoring sites for metal binding and subsequent amide deprotonation resulting in the formation of co-ordination isomers and dinuclear species in equimolar solutions and in the presence of excess metal ions, respectively. In more alkaline solutions (pH approximately 10) a third amide function can be deprotonated and co-ordinated in the species [CuH(-3)L]- with (N-,N-,N-,N(im)) co-ordination. The dinuclear species [Cu2H(-5)L]- and [Cu2H(-6)L](2-) containing hydroxide ions and/or imidazolato bridges are formed at high pH in the presence of excess of metal ions. The insertion of one proline into the sequence preceding histidyl residues hinders the deprotonation of amide functions at that site and the formation of only mononuclear complexes was observed with these peptides.