Radiochemical separation and determination of europium by Ge(Li) detector in biological tissues

A simple neutron activation method has been developed for the determination of europium in biological tissues and applied in the analysis of marine organism samples with ±9% precision at the nanogram level. The method is based on the separation, by ion-exchange, of the rare earth group from dry or ashed irradiated tissues and subsequent determination of^152mEu, by γ-spectrometry using a lithium drifted germanium detector.^152mEu, separated almost completely from other than rare earth elements, with better than 98% chemical yield, is counted on the 121.8 keV photopeak which then is practically free from any other γ-ray energy interfering in this counting.     

Synthesis of polycyclic pyrazoles through formation of the first fused heterocyclic o-quinodimethane intermediate

1-Benzoyl-4,6-dibromo-3-methyl-1,4,5,6-tetrahydrocyclopenta[c]pyrazole (2) was used as a precursor for o-quinodimethane 3, which was trapped by in situ reactions with dienophiles to give bridged pyrazole derivatives.     

A flow-through microfluidic chip for continuous dielectrophoretic separation of viable and non-viable human T-cells

Effective methods for rapid sorting of cells according to their viability are critical in T cells based therapies to prevent any risk to patients. In this context, we present a novel microfluidic device that continuously separates viable and non-viable T-cells according to their dielectric properties. A dielectrophoresis (DEP) force is generated by an array of castellated microelectrodes embedded into a microfluidic channel with a single inlet and two outlets; cells subjected to positive DEP forces are drawn toward the electrodes array and leave from the top outlet, those subjected to negative DEP forces are repelled away from the electrodes and leave from the bottom outlet. Computational fluid dynamics is used to predict the device separation efficacy, according to the applied alternative current (AC) frequency, at which the cells move from/to a negative/positive DEP region and the ionic strength of the suspension medium. The model is used to support the design of the operational conditions, confirming a separation efficiency, in terms of purity, of 96% under an applied AC frequency of 1.5 × 10⁶ Hz and a flow rate of 20 μl/h. This work represents the first example of effective continuous sorting of viable and non-viable human T-cells in a single-inlet microfluidic chip, paving the way for lab-on-a-chip applications at the point of need.     

Dynamical disorder of spin-induced Jahn-Teller orbitals with the insulator-metal transition in cobaltites

Using elastic and inelastic neutron scattering, we investigated the evolution of the local atomic structure and lattice dynamics of La(1-x)SrxCoO3 (x=0-0.5) as it crosses over with x from an insulator to a ferromagnetic metal (FMM). Our pair density function analysis indicates that, in the paramagnetic insulating phase for all x, spin activation of Co3+ ions induces local static Jahn-Teller (JT) distortions. The size of the JT lattice increases almost linearly with x. However, in the FMM phase, static JT distortions are absent for x< or =30%. This coincides with narrowing of variant Planck's constant over 2 pi omega=22 and 24 meV modes in the phonon spectrum which we argue is due to localized dynamical JT fluctuations. For x>30%, static JT distortions reappear along with broadening of the phonon modes because of weakened charge-lattice interactions.     

In search for mixed transition metal/lanthanide single-molecule magnets: Synthetic routes to NiII/TbIII and NiII/DyIII clusters featuring a 2-pyridyl oximate ligand

Employing the mononuclear complex [Ni{(py)C(Me)NO}₂{(py)C(Me)NOH}] (1) as ‘ligand’ [(py)C(Me)NOH = methyl 2-pyridyl ketone oxime], the use of the ‘metal complexes as ligands’ approach has led to the synthesis of the mixed Ni^II/Ln^III complexes [NiTb{(py)C(Me)NO}₂(NO₃)₃{(py)C(Me)NOH}] (2), [Ni₂Ln₂{(py)C(Me)NO}₆(NO₃)₄] (Ln = Dy, 3; Ln = Tb, 4) and [Ni₂Tb{(py)C(Me)NO}₆](NO₃) (5). The structures of 2, 3, and 5, and the magnetic properties of 2 and 5 are briefly discussed.     

Possible link of a structurally driven spin flip transition and the insulator-metal transition in the perovskite La(1-x)Ba(x)CoO3

The nature of the magnetic ground state near the insulator-metal transition (IMT) in La(1-x)Ba(x)CoO3 was investigated via neutron scattering. Below the critical concentration, x(c)～0.22, a commensurate antiferromagnetic (AFM) phase appears initially. Upon approaching x(c), the AFM component weakens and a ferromagnetic (FM) ordered phase sets in while in the rhombohedral lattice. At x(c), a spin flip to a new FM structure occurs at the same time as the crystal symmetry transforms to orthorhombic (Pnma). The Pnma phase may be the driving force for the IMT.     

DNA reorientation on Au nanoparticles: label-free detection of hybridization by surface enhanced Raman spectroscopy

DNA sequences attached to Au nanoparticles via thiol linkers stand up from the surface, giving preferential enhancement of the adenine ring breathing SERS band. Non-specific binding via the nucleobases reorients the DNA, reducing this effect. This change in intensity on reorientation was utilised for label-free detection of hybridization of a molecular beacon.     

Study of the trace element content in human cataractous lenses by instrumental neutron activation analysis

Cataract is a very common disease of the eye lens known since ancient times. Different mechanisms are responsible for the biogenesis of cataract but most scientists agree with the theory that cataract formation can be attributed to metabolism disorders in the lens. Instrumental neutron activation analysis has been applied in this work for the determination of the following trace elements: antimony, cobalt, iron, rubidium, selenium and zinc in human lenses with mature cataract. The results are statistically treated and correlated with age and sex of patients. Based on these findings, the concentration of elements studied does not have any correlation with the age and/or sex of the patients, i.e. when the lens becomes totally opaque.