Electric-Field Tuning of Spin-Dependent Exciton-Exciton Interactions in Coupled Quantum Wells

We have shown experimentally that an electric field decreases the energy separation between the two components of a dense spin-polarized exciton gas in a coupled double quantum well, from a maximum splitting of $\sim 4$ meV to zero, at a field of $\sim$35 kV/cm. This decrease, due to the field-induced deformation of the exciton wavefunction, is explained by an existing calculation of the change in the spin-dependent exciton-exciton interaction with the electron-hole separation. However, a new theory that considers the modification of screening with that separation is needed to account for the observed dependence on excitation power of the individual energies of the two exciton components.Comment: 5 pages, 4 eps figures, RevTeX, Physical Review Letters (in press

Polarization Control of the Non-linear Emission on Semiconductor Microcavities

The degree of circular polarization ($\wp$) of the non-linear emission in semiconductor microcavities is controlled by changing the exciton-cavity detuning. The polariton relaxation towards \textbf{K} $\sim 0$ cavity-like states is governed by final-state stimulated scattering. The helicity of the emission is selected due to the lifting of the degeneracy of the $\pm 1$ spin levels at \textbf{K} $\sim 0$. At short times after a pulsed excitation $\wp$ reaches very large values, either positive or negative, as a result of stimulated scattering to the spin level of lowest energy ($+1/-1$ spin for positive/negative detuning).Comment: 8 pages, 3 eps figures, RevTeX, Physical Review Letters (accepted

Coupling dynamics and linear polarization phenomena in codirectional polariton waveguide couplers

In this work, the previous studies investigating the potential of integrated devices using polariton waveguides that form codirectional couplers is extended. For suitable coupler parameters, a transfer of condensates between the arms of the coupler occurs leading to the observation of previously predicted Josephson-like oscillations. The ability to tune the periodicity of these oscillations opens the way to the design of polaritonic circuits in which the directionality of the signal towards the output terminals can be controlled, for a fixed separation between the arms, varying the coupling length. The response of the devices to linearly polarized excitation is also investigated, delving into the dynamics of linear polarization at the output terminals of long couplers, providing valuable insights into their potential applications, including polariton switches and logic gates with efficient operation. The results are supported by numerical simulations based on the generalized Gross–Pitaevskii equation describing the dynamics of coherent polaritons in spatially non-uniform systems, reproducing the polariton distribution on the output terminals and an oscillatory dependence of the corresponding emission as a function of the polarization azimuth. How the coupling and the controllable polarization degree of freedom in polariton couplers opens avenues for innovative optical architectures and functionalities is shown herePID2020-113445GB-I0

Spin degree of freedom in two dimensional exciton condensates

We present a theoretical analysis of a spin-dependent multicomponent condensate in two dimensions. The case of a condensate of resonantly photoexcited excitons having two different spin orientations is studied in detail. The energy and the chemical potentials of this system depend strongly on the spin polarization . When electrons and holes are located in two different planes, the condensate can be either totally spin polarized or spin unpolarized, a property that is measurable. The phase diagram in terms of the total density and electron-hole separation is discussed.Comment: 4 pages, 3 figures, Accepted for publication in Physical Review Letter

Spin relaxation in low-dimensional systems

We review some of the newest findings on the spin dynamics of carriers and excitons in GaAs/GaAlAs quantum wells. In intrinsic wells, where the optical properties are dominated by excitonic effects, we show that exciton-exciton interaction produces a breaking of the spin degeneracy in two-dimensional semiconductors. In doped wells, the two spin components of an optically created two-dimensional electron gas are well described by Fermi-Dirac distributions with a common temperature but different chemical potentials. The rate of the spin depolarization of the electron gas is found to be independent of the mean electron kinetic energy but accelerated by thermal spreading of the carriers.Comment: 1 PDF file, 13 eps figures, Proceedings of the 1998 International Workshop on Nanophysics and Electronics (NPE-98)- Lecce (Italy

Gluten-Free Autochthonous Foodstuff (South America and Other Countries)

The conservation and sustainable use of biodiversity for agriculture and nutrition have been extensively pointed out as crucial elements for food security and nutrition. Likewise, the relevance of learning from traditional foods and applying indigenous knowledge for the development and production of innovative gluten-free foods has been referred. South and Central America have supplied a great quantity of plant foods for the sustenance of the humankind. Latin-America is by this time one of the World largest net food exporting area. However, its complete potential to expand agricultural production for regional consumption and global export has not yet been achieved. The region has a large number of skilled farmers that have preserved and transmitted their knowledge through generations. Feeding a rapidly growing global population without expanding farming into environmentally susceptible areas and reducing the productive ability of the land already cultivated is a challenge that presents an elevated complexity level. In a framework of a strong need for diet diversification, populations with special nutritional requirements, such as celiac patients, should be benefited with the offer of more balanced, rich and safe diet components. The possibility of learning to a great extent from traditional foods and spread on local and territorial knowledge for the development and production of innovative gluten-free foods appears as a promising alternative. This chapter collects information about several plant species from the American continent that are more extensively used for the production of gluten-free foods (e. g. maize, potato, cassava, sweet potato, quinoa, amaranth, some legume grains) as well as other species that could potentially be developed with the same purpose, such as the Andean root and tuber crops: achira, ahipa, arracacha, maca, mashua, mauka, oca, ulluco, and yacon.Centro de Investigación y Desarrollo en Criotecnología de AlimentosLaboratorio de Investigación en Productos Agroindustriale

Human exceptional longevity: transcriptome from centenarians is distinct from septuagenarians and reveals a role of Bcl‐xL in successful aging

Centenarians not only enjoy an extraordinary aging, but also show a compression of morbidity. Using functional transcriptomic analysis of peripheral blood mononuclear cells (PMBC) we identified 1721 mRNAs differentially expressed by centenarians when compared with septuagenarians and young people. Sub‐network analysis led us to identify Bcl ‐ xL as an important gene up‐regulated in centenarians. It is involved in the control of apoptosis, cellular damage protection and also in modulation of immune response, all associated to healthy aging. Indeed, centenarians display lower plasma cytochrome C levels, higher mitochondrial membrane potential and also less cellular damage accumulation than septuagenarians. Leukocyte chemotaxis and NK cell activity are significantly impaired in septuagenarians compared with young people whereas centenarians maintain them. To further ascertain the functional role of Bcl‐ xL in cellular aging, we found that lymphocytes from septuagenarians transduced with Bcl‐xL display a reduction in senescent‐related markers. Finally, to demonstrate the role of BcL‐xL in longevity at the organism level, C. elegans bearing a gain of function mutation in the BcL‐xL ortholog ced‐9, showed a significant increase in mean and maximal life span. These results show that mRNA expression in centenarians is unique and reveals that BcL‐ xL plays an important role in exceptional aging

Pharmacological and genetic increases in liver NADPH levels ameliorate NASH progression in female mice

Non-alcoholic steatohepatitis (NASH) is one of the fastest growing liver diseases worldwide, and oxidative stress is one of NASH main key drivers. Nicotinamide adenine dinucleotide phosphate (NADPH) is the ultimate donor of reductive power to a number of antioxidant defences. Here, we explored the potential of increasing NADPH levels to prevent NASH progression. We used nicotinamide riboside (NR) supplementation or a G6PD-tg mouse line harbouring an additional copy of the human G6PD gene. In a NASH mouse model induced by feeding mice a methionine-choline deficient (MCD) diet for three weeks, both tools increased the hepatic levels of NADPH and ameliorated the NASH phenotype induced by the MCD intervention, but only in female mice. Boosting NADPH levels in females increased the liver expression of the antioxidant genes Gsta3, Sod1 and Txnrd1 in NR-treated mice, or of Gsr for G6PD-tg mice. Both strategies significantly reduced hepatic lipid peroxidation. NR-treated female mice showed a reduction of steatosis accompanied by a drop of the hepatic triglyceride levels, that was not observed in G6PD-tg mice. NR-treated mice tended to reduce their lobular inflammation, showed a reduction of the NK cell population and diminished transcription of the damage marker Lcn2. G6PD-tg female mice exhibited a reduction of their lobular inflammation and hepatocyte ballooning induced by the MCD diet, that was related to a reduction of the monocyte-derived macrophage population and the Tnfa, Ccl2 and Lcn2 gene expression. As conclusion, boosting hepatic NADPH levels attenuated the oxidative lipid damage and the exhausted antioxidant gene expression specifically in female mice in two different models of NASH, preventing the progression of the inflammatory process and hepatic injury.This project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No - 832741. (Acronym Food-PPP-NAFLD). I.R-R was recipient and funded by the Marie Skłodowska-Curie grant. AP-F was a recipient of a predoctoral fellowship from the Spanish association against cancer - AECC (PRDMA18011PAST). JLL-A was funded by the Spanish Ministry of Science and Innovation (MICINN) (PTA2017‐14689‐I). PJF-M was funded by a Ramon y Cajal Award from the Spanish Ministry of Science, Innovation and Universities (MICINN) (RYC-2017-22335 financed by the MCIN/AEI/10.13039/501100011033 and by the ESF Investing in your future). Work at the laboratory of PJF-M was funded by the AECC (SIRTBIO- LABAE18008FERN) and the RETOS Program projects from the MICINN (SAF2017-85766-R and PID2020-114077RB-I00/AEI/10.13039/501100011033). E.G.-D. was a recipient of a predoctoral grant financed by the Spanish Ministry (FPU18/05350). A. M. V. is funded by Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERdem).Peer reviewe

The Effectiveness of Glutathione Redox Status as a Possible Tumor Marker in Colorectal Cancer

[EN] The role of oxidative stress (OS) in cancer is a matter of great interest due to the implication of reactive oxygen species (ROS) and their oxidation products in the initiation of tumorigenesis, its progression, and metastatic dissemination. Great efforts have been made to identify the mechanisms of ROS-induced carcinogenesis; however, the validation of OS byproducts as potential tumor markers (TMs) remains to be established. This interventional study included a total of 80 colorectal cancer (CRC) patients and 60 controls. By measuring reduced glutathione (GSH), its oxidized form (GSSG), and the glutathione redox state in terms of the GSSG/GSH ratio in the serum of CRC patients, we identified significant changes as compared to healthy subjects. These findings are compatible with the effectiveness of glutathione as a TM. The thiol redox state showed a significant increase towards oxidation in the CRC group and correlated significantly with both the tumor state and the clinical evolution. The sensitivity and specificity of serum glutathione levels are far above those of the classical TMs CEA and CA19.9. We conclude that the GSSG/GSH ratio is a simple assay which could be validated as a novel clinical TM for the diagnosis and monitoring of CRC.This work was partially supported by grants GST, UGP-19-037 FISABIO, Universitat Politecnica de Valencia-the Hospital Universitario Doctor Peset POLISABIO collaboration program (UPV-FISABIO) NanOdGSens-2, the Spanish Government project RTI2018-100910-B-C41 (MCUI/AEI/FEDER, UE), the Generalitat Valenciana project PROMETEO/2018/024 and PI18/00932 by Instituto de Salud Carlos III and co-funded by the European Regional Development Fund (ERDF "A way to build Europe"). C.B. is a recipient of a Miguel Servet contract (CP19/00077) from the Instituto de Salud Carlos III.Acevedo-León, D.; Monzó-Beltrán, L.; Gómez-Abril, SÁ.; Estañ-Capel, N.; Camarasa-Lillo, N.; Pérez-Ebri, ML.; Escandón-Álvarez, J.... (2021). The Effectiveness of Glutathione Redox Status as a Possible Tumor Marker in Colorectal Cancer. International Journal of Molecular Sciences. 22(12):1-15. https://doi.org/10.3390/ijms22126183115221