Damping of long-wavelength collective excitations in quasi-onedimensional Fermi liquids

The imaginary part of the exchange-correlation kernel in the longitudinal current-current response function of a quasi-onedimensional Fermi liquid is evaluated by an approximate decoupling in the equation of motion for the current density, which accounts for processes of excitation of two particle-hole pairs. The two-pair spectrum determines the intrinsic damping rate of long-wavelength collective density fluctuations, which is calculated and contrasted with a result previously obtained for a clean Luttinger liquid.Comment: 9 pages, no figures, Physica B in pres

Revisiting the outcome of adult wild-type Htt inactivation in the context of HTT-lowering strategies for Huntington's disease.

Huntingtin-lowering strategies are central to therapeutic approaches for Huntington's disease. Recent studies reported the induction of age- and cell type-specific phenotypes by conditional huntingtin knockout, but these experimental conditions did not precisely mimic huntingtin-lowering or gene-editing conditions in terms of the cells targeted and brain distribution, and no transcriptional profiles were provided. Here, we used the adeno-associated delivery system commonly used in CNS gene therapy programmes and the self-inactivating KamiCas9 gene-editing system to investigate the long-term consequences of wild-type mouse huntingtin inactivation in adult neurons and, thus, the feasibility and safety of huntingtin inactivation in these cells. Behavioural and neuropathological analyses and single-nuclei RNA sequencing indicated that huntingtin editing in 77% of striatal neurons and 16% of cortical projecting neurons in adult mice induced no behavioural deficits or cellular toxicity. Single-nuclei RNA sequencing in 11.5-month-old animals showed that huntingtin inactivation did not alter striatal-cell profiles or proportions. Few differentially expressed genes were identified and Augur analysis confirmed an extremely limited response to huntingtin inactivation in all cell types. Our results therefore indicate that wild-type huntingtin inactivation in adult striatal and projection neurons is well tolerated in the long term

Resonant Raman scattering by collective modes of the one-dimensional electron gas

We show that the low-energy peak in the polarized resonant Raman spectra of quantum wires, which is commonly associated with ``single particle excitations'', can be interpreted as signature of intra-band collective spin excitations. A broad maximum in the resonant depolarized spectra is predicted to exist above the frequency of the spin density excitation, due to simultaneous but independent propagation of spin- and charge-density modes.Comment: 4 pages, accepted for publication in Phys. Rev. Let

Enhanced suppresion of localization in a continuous Random-Dimer Model

We consider a one-dimensional continuous (Kronig-Penney) extension of the (tight-binding) Random Dimer model of Dunlap et al. [Phys. Rev. Lett. 65, 88 (1990)]. We predict that the continuous model has infinitely many resonances (zeroes of the reflection coefficient) giving rise to extended states instead of the one resonance arising in the discrete version. We present exact, transfer-matrix numerical calculations supporting, both realizationwise and on the average, the conclusion that the model has a very large number of extended states.Comment: 10 pages, 3 Figures available on request, REVTeX 3.0, MA/UC3M/1/9

Catálogo de los Halictini Halictus Latreille, 1804 y Lasioglossum Curtis, 1833 (Hymenoptera, Apoidea, Halictidae) de la Península Ibérica y de las islas Canarias

The current work is a catalogue of the Halictini genera Halictus Latreille, 1804 and Lasioglossum Curtis, 1833 in the Iberian Peninsula and the Canary Islands. It includes the taxa, their synonymies, discussion, when necessary, and their geographic distribution as well (Tables 1, 2, 3 y 4). Some recent records of several species have been included too. The results (Table 1) indicate that this fauna is composed of 143 species and 161 subspecies: 126 appear in the Iberian Peninsula and 17 in the Canary Islands, where 6 of them and 17 subspecies are endemic, out of a total of 29 subespecies; 9 of the Canary species are present in both territories.En este catálogo se presenta un inventario actualizado de las especies de Halictini de los géneros Halictus Latreille, 1804 y Lasioglossum Curtis, 1833 de la Península Ibérica y de las Islas Canarias. Contiene 143 especies y 161 subespecies: 126 de las especies se conocen en la fauna ibérica y 17 en las Islas Canarias y, de estas, 6 especies y 17 subespecies son endémicas, de un total de 29 subespecies presentes en las islas; 9 de las especies canarias, son comunes a ambos territorios. De todos los taxones, además de la correspondiente discusión, si procede, se incluye su lista sinonímica y su distribución geográfica (Tablas 1, 2, 3 y 4). En algunas especies, se han incluido registros recientes que pueden resultar de interés

The effect of strontium incorporation into sol-gel biomaterials on their protein adsorption and cell interactions

[EN] It is known strontium can both inhibit the osteoclast formation and stimulate the osteoblast maturation, so biomaterials containing this element can favour bone structure stabilisation. The addition of Sr to biomaterials could affect their interactions with proteins and cells. Here, a silica-hybrid sol-gel network doped with different amounts of SrCl2 and applied as coatings on titanium discs was examined. in vitro analysis was performed to determine the potential effect of Sr in the coatings, showing enhanced gene expression of osteogenic markers (alkaline phosphatase and transforming growth factor-beta) in MC3T3-E1 incubated with Sr-doped biomaterials. The examination of inflammatory markers (tumour necrosis factor-alpha and interleukin 10) in RAW 264.7 macrophages revealed an anti-inflammatory potential of these materials. Proteins adsorbed onto the coatings incubated with human serum (3 h at 37 degrees C) were also analysed; mass spectrometry was used to characterise the proteins adhering to materials with different Sr content. Adding Sr to the coatings increased their affinity to APOE and VTNC proteins (associated with anti-inflammatory and osteogenic functions). Moreover, the proteins involved in coagulation processes, such as prothrombin, were more abundant on the coatings containing Sr than on the base sol-gel surfaces. Correlations between gene expression and proteomic results were also examined.This work was supported by MINECO (MAT2017-86043-R); Universitat Jaume I (grant numbers Predoc/2014/25, UJI-B2017-37); Basque Government (grant numbers IT611-13, Predoc/2016/1/0141), and University of the Basque Country (UFI11/56). Authors would like to thank Antonio Coso and Jaime Franco (GMI-Ilerimplant) for their inestimable contribution to this study, and Raquel Oliver, Jose Ortega (UJI), and Iraide Escobes (CIC bioGUNE) for their valuable technical assistance.Romero-Gavilán, F.; Araújo-Gomes, N.; García-Arnáez, I.; Martínez-Ramos, C.; Elortza, F.; Azkargorta, M.; Iloro, I.... (2019). The effect of strontium incorporation into sol-gel biomaterials on their protein adsorption and cell interactions. Colloids and Surfaces B Biointerfaces. 174:9-16. https://doi.org/10.1016/j.colsurfb.2018.10.075S91617

Control mechanisms of primary productivity revealed by Calcareous Nannoplankton from marine isotope stages 12 to 9 at the Shackleton Site (IODP Site U1385)

Nowadays, primary productivity variations at the SW Iberian Margin (IbM) are primarily controlled by wind-driven upwelling. Thus, major changes in atmospheric circulation and wind regimes between the Marine Isotope Stages (MIS) 12 and 9 could have driven substantial changes in phytoplankton productivity which remains poorly understood. We present a high-resolution calcareous nannofossil record from the Shackleton Site Integrated Ocean Discovery Program Site U1385 that allow the assessment of primary productivity and changing surface conditions on orbital and suborbital timescales over the SW IbM. These records are directly compared and integrated with terrestrial – Mediterranean forest pollen – and marine – benthic and planktic oxygen stable isotopes (δ18O), alkenone concentration [C37], Uk´37-Sea Surface Temperature and % C37:4 – proxy records from Site U1385. Our results indicate intra-interglacial increase in primary productivity together with intensification of the Azores anticyclonic high-pressure cell beyond the summer that suggests a two-phase upwelling behavior during the full interglacial MIS 11c (420–397ka), potentially drived by atmospheric NAO-like variability. Primary productivity is largely enhanced during the inception of glacial MIS 10 and the early MIS 10 (392–356ka), linked to intensified upwelling and associated processes during a period of strengthened atmospheric circulation. In agreement with the conditions observed during Heinrich events of the last glacial cycle, primary productivity reductions during abrupt cold episodes, including the Heinrich-type (Ht) events 4 to 1 (436, 392, 384 and 339ka) and the Terminations V and IV, seems to be the result of halocline formation induced by meltwater arrival, reducing the regional upward nutrient transferenceFPU17/03349, PTDC/CTA-GEO/29897/2017, UIDB/04326/2020, UIDB/04326/2020, CEECIND/02208/2017info:eu-repo/semantics/publishedVersio

Exact-exchange density-functional theory for quasi-two-dimensional electron gases

A simple exact-exchange density-functional method for a quasi-two-dimensional electron gas with variable density is presented. An analytical expression for the exact-exchange potential with only one occupied subband is provided, without approximations. When more subbands are occupied the exact-exchange potential is obtained numerically. The theory shows that, in contradiction with LDA, the exact-exchange potential exhibits discontinuities and the system suffers a zero-temperature first-order transition each time a subband is occupied. Results suggesting that the translational symmetry might be spontaneously broken at zero temperature are presented. An extension of the theory to finite temperatures allows to describe a drop in the intersubband spacing in good quantitative agreement with recent experiments.Comment: 14 pages, 3 figure

Tratamiento con octreotide (SMS 201-995) en un caso de tumor carcinoide intestinal

Over the past few years the usefulness of some somatostatin's analogues in the treatment of intestinal tract endocrine tumors has been demonstrated. Notwithstanding, the results obtained are variable. The case of a carcinoid tumor with a hepatic metastasis is presented and its clinical as well as its biochemical and its morphological results are evaluated after treatment with octreotide over a seven months period. It is important to highlight the great clinical improvement obtained at the beginning of treatment. Treatment was not effective in the control of tumor progression. After the injection of such a drug, a decrease in serotonin and 5-hydroxy-indoleacetic acid serum levels was observed as well as a reduction in the urinary metabolite. It is concluded that octreotide is very useful for the symptomatic treatment of carcinoid syndrome

Far-infrared absorption in parallel quantum wires with weak tunneling

We study collective and single-particle intersubband excitations in a system of quantum wires coupled via weak tunneling. For an isolated wire with parabolic confinement, the Kohn's theorem guarantees that the absorption spectrum represents a single sharp peak centered at the frequency given by the bare confining potential. We show that the effect of weak tunneling between two parabolic quantum wires is twofold: (i) additional peaks corresponding to single-particle excitations appear in the absorption spectrum, and (ii) the main absorption peak acquires a depolarization shift. We also show that the interplay between tunneling and weak perpendicular magnetic field drastically enhances the dispersion of single-particle excitations. The latter leads to a strong damping of the intersubband plasmon for magnetic fields exceeding a critical value.Comment: 18 pages + 6 postcript figure