Spin polarization versus lifetime effects at point contacts between superconducting niobium and normal metals

Point-contact Andreev reflection spectroscopy is used to measure the spin polarization of metals but analysis of the spectra has encountered a number of serious challenges, one of which is the difficulty to distinguish the effects of spin polarization from those of the finite lifetime of Cooper pairs. We have recently confirmed the polarization-lifetime ambiguity for Nb-Co and Nb-Cu contacts and suggested to use Fermi surface mismatch, the normal reflection due to the difference of Fermi wave vectors of the two electrodes, to solve this dilemma. Here we present further experiments on contacts between superconducting Nb and the ferromagnets Fe and Ni as well as the noble metals Ag and Pt that support our previous results. Our data indicate that the Nb - normal metal interfaces have a transparency of up to about 80 per cent and a small, if not negligible, spin polarization.Comment: 7 pages, 2 figures, submitted to Proceedings of the 26th Conference on Low Temperature Physic

Shear induced grain boundary motion for lamellar phases in the weakly nonlinear regime

We study the effect of an externally imposed oscillatory shear on the motion of a grain boundary that separates differently oriented domains of the lamellar phase of a diblock copolymer. A direct numerical solution of the Swift-Hohenberg equation in shear flow is used for the case of a transverse/parallel grain boundary in the limits of weak nonlinearity and low shear frequency. We focus on the region of parameters in which both transverse and parallel lamellae are linearly stable. Shearing leads to excess free energy in the transverse region relative to the parallel region, which is in turn dissipated by net motion of the boundary toward the transverse region. The observed boundary motion is a combination of rigid advection by the flow and order parameter diffusion. The latter includes break up and reconnection of lamellae, as well as a weak Eckhaus instability in the boundary region for sufficiently large strain amplitude that leads to slow wavenumber readjustment. The net average velocity is seen to increase with frequency and strain amplitude, and can be obtained by a multiple scale expansion of the governing equations

Ruthenium(III) complexes entrapped in liposomes with enhanced cytotoxic and anti-metastatic properties

Metal-based anticancer drugs are pivotal in the fight against cancer pathologies. Since 1978 cis-platin was licensed for medical treatment of a wide number of tumor pathologies(1). However its chemiotherapic use is strongly limited by many and severe side effects and acquired tumor resistance. Since these limitations could be overcome by other metal complexes, in the last thirty years ruthenium compounds have been tested showing a remarkable antitumoral and antimetastatic activity associated with a lower toxicity. A hexacoordinate Ru(III) complex (NAMI-A) is currently undergoing advanced clinical evaluation (2). All data indicate that NAMI-A acts as a pro-drug, but the integrity of ruthenium complexes is essential to store the cytotoxic activity. In this scenario the condition of administration of ruthenium drugs are crucial to exploit their anticancer activity (3). In the last years innovative strategies have been produced to vehicle ruthenium ions in tumor cells like aggregates. This study aims to incorporate the ruthenium complexes in the inner aqueous compartment of liposomes and to test biological properties of two NAMI-A like pyridine derivatives. Specifically, we have investigated the pyridine derivatives of the sodium-compensated analogue of NAMI-A, Na[trans-RuCl4(pyridine)(DMSO)] (NAMI-Pyr) and Na[trans-RuCl4(Pytri)(DMSO)] (NAMI-Pytri). In thelatter complex the pyridine ligand is functionalized with a sugar moiety so as to increase biocompatibility and the ability to cross the cell membrane. The stability of the complexes was studied and compared in solution at different pH following UV-VIS spectra. Lipid formulations based on Egg PC were prepared adding Cholesterol, DSPE-PEG2000 joining molar ratio 57/38 /5% w/w respectively in MeOH/CHCl3 (50/50 v/v) mixture and hydrated with 0.9% w/w of NaCl. This composition was selected to reproduce analog supramolecular aggregates in clinical use to vehicle doxorubicin (Doxil). Ruthenium complexes were loaded into liposomes using the passive equilibration loading method. Full drug containing liposomes were structurally characterized by dynamic light scattering (DLS) measurements. Data indicate the formation of stable aggregates with size and shape in the right range for in vivo applications. The amount of encapsulated ruthenium complexes was quantified by means of ICP-AES. Stability and drug release properties of ruthenium containing liposomes were confirmed in buffer. The growth inhibitory effects of both liposomal and free complexes drug were tested on prostate cancer cells (PC3). Preliminary results show high cytotoxic effect of ruthenium complexes delivered by supramolecular aggregates with respect to free complexes drug

Physicochemical properties of mixed micellar aggregates containing CCK peptides and Gd complexes designed as tumor specific contrast agents in MRI

New amphiphilic molecules containing a bioactive peptide or a claw moiety have been prepared in order to obtain mixed micelles as target-specific contrast agents in magnetic resonance imaging. The first molecule, C18H37CONH(AdOO)2-G-CCK8 (C18CCK8), contains a C18 hydrophobic moiety bound to the C-terminal cholecystokinin octapeptide amide (CCK 26-33 or CCK8). The second amphiphilic compound, C18H37CONHLys(DTPAGlu)CONH2 (C18DTPAGlu) or its gadolinium complex, (C18DTPAGlu- (Gd)), contains the same C18 hydrophobic moiety bound, through a lysine residue, to the DTPAGlu chelating agent. The mixed aggregates as well as the pure C18DTPAGlu aggregate, in the presence and absence of Gd, have been fully characterized by surface tension measurements, FT-PGSE-NMR, fluorescence quenching, and small-angle neutron scattering measurements. The structural characterization of the mixed aggregates C18DTPAGlu(Gd)-C18CCK8 indicates a spherical arrangement of the micelles with an external shell of 21 Å and an inner core of 20 Å. Both the DTPAGlu(Gd) complexes and the CCK8 peptides point toward the external surface. The measured values for relaxivity in saline medium at 20 MHz proton Larmor frequency and 25 °C are 18.7 mM-1 s-1. These values show a large enhancement in comparison with the isolated DTPAGlu(Gd) complex

New frontiers in bariatric surgery laparoscopic adjustable silicone gastric banding (LASGB)

LASGB is a minimally invasive procedure indicated for the treatment of morbid obesity. Since January 1996, six patients have successfully undergone the laparoscopic procedure. Preoperative BMI was 42 ± 3.1; range 39-46. Mean operative time was 260 ± 110, range was 160-360. Mean hospital stay was 3 ± 1 days

Novel Sugar-incorporated N-heterocyclic Carbene (NHC) Gold(I) Complexes as Potential Anticancer Agents

New metal complexes containing anticancer drugs are one of the major interests in bioinorganic or bioorganometallic medicinal chemistry. The development of novel metallodrugs is shifting to the use of non platinum central atoms coordinating different organic ligands in order to overcome the drawbacks (e.g. resistance, side effects) of the platinum antitumor agents. [1]. Gold(I) complexes show a very promising antiproliferative effects, but they are remarkable oxidizing properties. In order to reduce this character, in the last years, several studies have been reported based on gold(I) N-heterocyclic carbenes (NHCs) in vitro and in a few cases also in vivo [2]. Within this frame we have designed new gold(I) complexes based on sugar incorporated N-heterocyclic carbene. The presence of the sugar moiety allows to tune the lipophilicity behavior of the complexes. The complexes have been synthesized according to the scheme reported below. After the preparation of the NHC ligand, in the first step the corresponding Ag-complex (1AgBr) was prepared from Ag2O, to act as starting materials for transmetalation. The reaction of 1AgBr with gold(I) precursor, THTAuCl (THT = tetrahydrothiophene), in dichloromethane at room temperature overnight afford to gold complex. The compound was identified by NMR and RX. Starting from 1Cl, the cationic gold derivatives were prepared adding phosphorous and sulphur based neutral ligands, in the presence of silver tetrafluoroborate, as a chloride abstractor. The ligands have been selected in order to modulate electronic and hydrophilic complexes properties. The compounds will be investigated in screening on human cell line

Defect Dynamics for Spiral Chaos in Rayleigh-Benard Convection

A theory of the novel spiral chaos state recently observed in Rayleigh-Benard convection is proposed in terms of the importance of invasive defects i.e defects that through their intrinsic dynamics expand to take over the system. The motion of the spiral defects is shown to be dominated by wave vector frustration, rather than a rotational motion driven by a vertical vorticity field. This leads to a continuum of spiral frequencies, and a spiral may rotate in either sense depending on the wave vector of its local environment. Results of extensive numerical work on equations modelling the convection system provide some confirmation of these ideas.Comment: Revtex (15 pages) with 4 encoded Postscript figures appende

Penta-Hepta Defect Motion in Hexagonal Patterns

Structure and dynamics of penta-hepta defects in hexagonal patterns is studied in the framework of coupled amplitude equations for underlying plane waves. Analytical solution for phase field of moving PHD is found in the far field, which generalizes the static solution due to Pismen and Nepomnyashchy (1993). The mobility tensor of PHD is calculated using combined analytical and numerical approach. The results for the velocity of PHD climbing in slightly non-optimal hexagonal patterns are compared with numerical simulations of amplitude equations. Interaction of penta-hepta defects in optimal hexagonal patterns is also considered.Comment: 4 pages, Postscript (submitted to PRL

The possible role of physical activity in the modulation of gut microbiota in chronic kidney disease and its impact on cardiovascular risk: a narrative review

Chronic degenerative non-communicable diseases (CDNCDs), in particular chronic kidney disease, induce gut microbiota (GM) dysbiosis, which, in turn, worsens the progression of CDNCDs and patients' quality of life. We analyzed literature studies to discuss the possible positive and beneficial impact of physical activity on GM composition and CV risk in CKD patients. Regular physical activity seems to be able to positively modulate the GM, reducing the systemic inflammation and consequently the production of uremic gut-derived toxins, which are directly correlated with the increase of cardiovascular risk. In particular, the accumulation of indoxyl sulphate (IS) seems to be able to induce vascular calcifications, vascular stiffness and cardiac calcifications, while p-Cresyl sulphate (p-CS) seems to be able to exert a cardiotoxic action through metabolic pathways, capable of inducing oxidative stress. In addition, trimethylamine N-oxide (TMAO) can alter lipid metabolism, inducing the production of foam cells and causing an accelerated atherosclerosis process. In this context, a regular physical activity program seems to represent an adjuvant non-pharmacological approach to the clinical management of CKD patients

Grain boundary motion in layered phases

We study the motion of a grain boundary that separates two sets of mutually perpendicular rolls in Rayleigh-B\'enard convection above onset. The problem is treated either analytically from the corresponding amplitude equations, or numerically by solving the Swift-Hohenberg equation. We find that if the rolls are curved by a slow transversal modulation, a net translation of the boundary follows. We show analytically that although this motion is a nonlinear effect, it occurs in a time scale much shorter than that of the linear relaxation of the curved rolls. The total distance traveled by the boundary scales as $\epsilon^{-1/2}$, where $\epsilon$ is the reduced Rayleigh number. We obtain analytical expressions for the relaxation rate of the modulation and for the time dependent traveling velocity of the boundary, and especially their dependence on wavenumber. The results agree well with direct numerical solutions of the Swift-Hohenberg equation. We finally discuss the implications of our results on the coarsening rate of an ensemble of differently oriented domains in which grain boundary motion through curved rolls is the dominant coarsening mechanism.Comment: 16 pages, 5 figure