Role of bound pairs in the optical properties of highly excited semiconductors: a self consistent ladder approximation approach

Presence of bound pairs (excitons) in a low-temperature electron-hole plasma is accounted for by including correlation between fermions at the ladder level. Using a simplified one-dimensional model with on-site Coulomb interaction, we calculate the one-particle self-energies, chemical potential, and optical response. The results are compared to those obtained in the Born approximation, which does not account for bound pairs. In the self-consistent ladder approximation the self-energy and spectral function show a characteristic correlation peak at the exciton energy for low temperature and density. In this regime the Born approximation overestimates the chemical potential. Provided the appropriate vertex correction in the interaction with the photon is included, both ladder and Born approximations reproduce the excitonic and free pair optical absorption at low density, and the disappearance of the exciton absorption peak at larger density. However, lineshapes and energy shifts with density of the absorption and photoluminescence peaks are drastically different. In particular, the photoluminescence emission peak is much more stable in the ladder approximation. At low temperature and density a sizeable optical gain is produced in both approximations just below the excitonic peak, however this gain shows unphysical features in the Born approximation. We conclude that at low density and temperature it is fundamental to take into account the existence of bound pairs in the electron-hole plasma for the calculation of its optical and thermodynamic properties. Other approximations that fail to do so are intrinsically unphysical in this regime, and for example are not suitable to address the problem of excitonic lasing.Comment: 14 pages, 12 figure

Requerimientos de energía de cincel y subsolador en suelos de la Región Semiárida Pampeana

Los suelos agrícolas de la Región Semiárida Pampeana presentan, por lo general, capas subsuperficiales endurecidas, con distintos grados de densificación, produciendo efectos negativos en el rendimiento de los cultivos. El control de estas capas con labranza vertical profunda, tiene efectos diferentes sobre el suelo y distintos requerimientos de energía del tractor, según el diseño de herramienta que se utilice. En el presente trabajo se estudiaron un arado de cinceles y un subsolador a dos velocidades de trabajo, en Haplustoles énticos de la Facultad de Agronomía de la Universidad Nacional de La Pampa. Se realizaron determinaciones de esfuerzos de tracción, patinamiento, humedad del suelo, velocidad de trabajo y consumo de combustible. Los datos obtenidos fueron analizados por medio del test de Tukey con una significancia del 5%. Entre los dos diseños utilizados no se encontraron diferencias significativas en la roturación del suelo, excepto entre los 20-25 cm de profundidad, donde se observó mejores efectos con el subsolador. No hubo diferencias significativas en el esfuerzo de tracción al aumentar la velocidad de trabajo de ambos diseños. Se registraron esfuerzos de tracción y requerimientos de potencia, significativamente mayores para el cincel que para el sub solador.Director: lng. Agr. Ulises R. Hernández. Cátedra de Maquinaria Agrícola.

A retrospective analysis of pegylated liposomal doxorubicin in ovarian cancer: Do we still need it?

Background: Ovarian cancer (OC) is the sixth most common cancer in women. Currently, carboplatin/ paclitaxel bevacizumab is the cornerstone of front-line treatment. Conversely, the therapeutic options for recurrent or progressive disease are not well defined. For platinum-sensitive patients the best therapeutic approach is still a re-challenge with a platinum-based regimen. Pegylated liposomal doxorubicin (PLD), is considered one of the most active therapeutic options for recurrent or progressive OC. In this retrospective mono-institutional analysis, we evaluated the impact of PLD on the outcome of OC patients. Patients and methods: We performed the retrospective study on a cohort of 108 patients with histologically confirmed serous papillary OC, followed at our Institution between 2001 and 2011. 80 patients were in stage III/IV and 55 of them received a second-line treatment. Thirty patients were treated with PLD. Both groups (PLD-treated versus PLD-untreated) underwent a median of 3 treatment lines and were prognostically balanced. The median follow-up was 60 months. Survival endpoints, toxicity and correlations between patients' baseline characteristics and treatment efficacy were evaluated. Results: Patients who had undergone PLD treatment (PLD group) showed a median overall survival (OS) of 45 months as compared to 65 months of patients not treated with PLD (PLD-free group) (HR 2.50 [0.95-6.67; p = 0.06]). Moreover, the median progression-free survival was 6 months in the PLD group versus 10 months in the PLD-free group (HR 1.75 [0.94-3.34; p = 0.07]). The overall objective response rate in II line treatment was 43% (13% in PLD group versus 57% in PLD-free group). Furthermore, we investigated survival endpoints in platinum-refractory patients who received PLD at least once during the course of disease. No OS advantage was achieved by PLD administration when compared to other therapeutic options (30 versus 32 months; HR 1.16 [0.31-4.34; p = 0.81]). No difference in term of toxicity was observed among different groups. Conclusions: No evidence of superiority if PLD was compared to alternative agents was found in this analysis, particularly in the platinum-refractory setting. Our findings indicate a modest therapeutic activity of PLD in OC. Analysis of cost/benefit of PLD in OC is eagerly awaited

The route to solve the interplay between inflammation, angiogenesis and anti-cancer immune response

Even though the crucial role played by inflammation in cancer development and progression was first hypothesized by Rudolf Virchow at the beginning of the nineteenth century, only recently inflammation has been recognized as a hallmark of cance

LncRNA NEAT1 in Paraspeckles: A Structural Scaffold for Cellular DNA Damage Response Systems?

Nuclear paraspeckle assembly transcript 1 (NEAT1) is a long non-coding RNA (lncRNA) reported to be frequently deregulated in various types of cancers and neurodegenerative processes. NEAT1 is an indispensable structural component of paraspeckles (PSs), which are dynamic and membraneless nuclear bodies that affect different cellular functions, including stress response. Furthermore, increasing evidence supports the crucial role of NEAT1 and essential structural proteins of PSs (PSPs) in the regulation of the DNA damage repair (DDR) system. This review aims to provide an overview of the current knowledge on the involvement of NEAT1 and PSPs in DDR, which might strengthen the rationale underlying future NEAT1-based therapeutic options in tumor and neurodegenerative diseases

Effect of different pre-slaughter procedures on behavioural and blood parameters in pigs.

The effect of different pre-slaughter procedures on behavioural and blood parameters were evaluated on 120 pigs reared in one farm and delivered in groups of 40 subjects to three slaughterouses. Due to the different attitude of the personnel involved, differences in handling were evident at loading and at unloading where the difficulties to srive the pigs incresed the behaviuoral events. Blood analysis parameter showed that different resting time did not reduce the physical stress exoerienced by the pigs, which seems related "per se" to loading, transport and unloading and not to the different handling applied in each slaughter plant

Enhancement of cytosine arabinoside-induced apoptosis in human myeloblastic leukemia cells by NFkB/Rel- specific decoy oligodeoxynucleotides

The activity of NF-kB/Rel nuclear factors is known to inhibit apoptosis in various cell types. We investigated whether the subtraction of NF-kB/Rel activity influenced the response of 11 AML (M1, M2 and M4) patients’ cells to AraC. To this end we used a phosphorothioate double-stranded decoy oligodeoxynucleotide (ODN) carrying the NF-kB/Rel- consensus sequence. Cell incubation with this ODN, but not its mutated (scrambled) form used as a control, resulted in abating the NF-kB/Rel nuclear levels in these cells, as verified by electrophoretic mobility shift assay (EMSA) of cells’ nuclear extracts. We incubated the leukemic cells with AraC (32 or 1 mM), in either the absence or presence of the decoy or the scrambled ODN, and analyzed cell apoptosis. The spontaneous cell apoptosis detectable in the absence of AraC (,25%) was not modulated by the oligonucleotide presence in cell cultures. On the other hand, in 10 of the 11 samples tested, the decoy kB, but not the scrambled ODN significantly (P ,0.01 in a Student’s t test) enhanced cell apoptotic response to AraC. Such an effect was particularly remarkable at low AraC doses (1 mM). These findings indicate that NF-kB/Rel activity influences response to AraC in human primary myeloblastic cells, and suggests that the inhibition of NF-kB/Rel factors can improve the effect of chemotherapy in AM

Targeting of multiple myeloma-related angiogenesis by miR-199a-5p mimics: in vitro and in vivo anti-tumor activity

Multiple myeloma (MM) cells induce relevant angiogenic effects within the human bone marrow milieu (huBMM) by the aberrant expression of angiogenic factors. Hypoxia triggers angiogenic events within the huBMM and the transcription factor hypoxia-inducible factor-1α (HIF-1α) is over-expressed by MM cells. Since synthetic miR-199a-5p mimics negatively regulates HIF-1α, we here investigated a miRNA-based therapeutic strategy against hypoxic MM cells. We indeed found that enforced expression of miR-199a-5p led to down-modulated expression of HIF-1α as well as of other pro-angiogenic factors such as VEGF-A, IL-8, and FGFb in hypoxic MM cells in vitro. Moreover, miR-199a-5p negatively affected MM cells migration, while it increased the adhesion of MM cells to bone marrow stromal cells (BMSCs) in hypoxic conditions. Furthermore, transfection of MM cells with miR-199a-5p significantly impaired also endothelial cells migration and down-regulated the expression of endothelial adhesion molecules such as VCAM-1 and ICAM-1. Finally, we identified a hypoxia\AKT/miR-199a-5p loop as a potential molecular mechanism responsible of miR-199a-5p down-regulation in hypoxic MM cells. Taken together our results indicate that miR-199a-5p has an important role for the pathogenesis of MM and support the hypothesis that targeting angiogenesis via a miRNA/HIF-1α pathway may represent a novel potential therapeutical approach for this still lethal diseas