The Dilute Fermi Gas via Bogoliubov Theory

We study the ground state properties of interacting Fermi gases in the dilute regime, in three dimensions. We compute the ground state energy of the system, for positive interaction potentials. We recover a well-known expression for the ground state energy at second order in the particle density, which depends on the interaction potential only via its scattering length. The first proof of this result has been given by Lieb, Seiringer and Solovej (Phys Rev A 71:053605, 2005). In this paper, we give a new derivation of this formula, using a different method; it is inspired by Bogoliubov theory, and it makes use of the almost-bosonic nature of the low-energy excitations of the systems. With respect to previous work, our result applies to a more regular class of interaction potentials, but it comes with improved error estimates on the ground state energy asymptotics in the density

Molecular dynamics simulations show how the FMRP Ile304Asn mutation destabilizes the KH2 domain structure and affects its function

Mutations or deletions of FMRP, involved in the regulation of mRNA metabolism in brain, lead to the Fragile X syndrome (FXS), the most frequent form of inherited intellectual disability. A severe manifestation of the disease has been associated with the Ile304Asn mutation, located on the KH2 domain of the protein. Several hypotheses have been proposed to explain the possible molecular mechanism responsible for the drastic effect of this mutation in humans. Here, we performed a molecular dynamics simulation and show that the Ile304Asn mutation destabilizes the hydrophobic core producing a partial unfolding of two α-helices and a displacement of a third one. The affected regions show increased residue flexibility and motion. Molecular docking analysis revealed strongly reduced binding to a model single-stranded nucleic acid in agreement with known data that the two partially unfolded helices form the RNA-binding surface. The third helix, which we show here to be also affected, is involved in the PAK1 protein interaction. These two functional binding sites on the KH2 domain do not overlap spatially, and therefore, they can simultaneously bind their targets. Since the Ile304Asn mutation affects both binding sites, this may justify the severe clinical manifestation observed in the patient in which both mRNA metabolism activity and cytoskeleton remodeling would be affected

Esculetin provides neuroprotection against mutant huntingtin-induced toxicity in huntington’s disease models

Huntington’s disease (HD) is a neurodegenerative disorder caused by an abnormal CAG trinucleotide repeat expansion within exon 1 of the huntingtin (HTT) gene. This mutation leads to the production of mutant HTT (mHTT) protein which triggers neuronal death through several mechanisms. Here, we investigated the neuroprotective effects of esculetin (ESC), a bioactive phenolic compound, in an inducible PC12 model and a transgenic Drosophila melanogaster model of HD, both of which express mHTT fragments. ESC partially inhibited the progression of mHTT aggregation and reduced neuronal death through its ability to counteract the oxidative stress and mitochondria impairment elicited by mHTT in the PC12 model. The ability of ESC to counteract neuronal death was also confirmed in the transgenic Drosophila model. Although ESC did not modify the lifespan of the transgenic Drosophila, it still seemed to have a positive impact on the HD phenotype of this model. Based on our findings, ESC may be further studied as a potential neuroprotective agent in a rodent transgenic model of HD

Role of IGF1 and IGF1/VEGF on Human Mesenchymal Stromal Cells in Bone Healing: Two Sources and Two Fates.

In the repair of skeletal defects one of the major obstacles still remains an efficient vascularization of engineered scaffolds. We have examined the ability of insulin growth factor-1, alone or in association with vascular endothelial growth factor, to modulate the osteoblastic or endothelial commitment of periosteum-derived progenitor cells (PDPCs) and skin-derived multipotent stromal cells (S-MSCs). A selected gene panel for endothelial and osteoblastic differentiation as well as genes that can affect MAPK and PI3K/AKT signaling pathways were investigated. Moreover, gene expression profile of Sox2, Oct4, and Nanog transcription factors was assessed. Our results showed that under growth factor stimulation PDPCs are induced toward an osteoblastic differentiation, while S-MSCs seem to move along an endothelial phenotype. This different commitment seems to be linked to a diverse MAPK or PI3K/AKT signaling pathway activation. The analysis of genes for stemness evidenced that at least in PDPCs multipotency and differentiation could coexist. These results open interesting perspective for the development of innovative bone tissue engineering approaches based on a good network of angiogenesis and osteogenesis processes

Design of a Multi-Wavelength Fiber Laser Based on Tm:Er:Yb:Ho Co-Doped Germanate Glass

In this article, for the first time, an efficient multi-wavelength fiber laser based on a Tm:Er:Yb:Ho co-doped germanate glass, optically pumped at 980 nm wavelength and simultaneously emitting at 1550 nm, 1800 nm and 2050 nm wavelengths, is designed and optimized. An exhaustive model, taking into account the energy transfer phenomena between different rare earths, is developed. The device behavior is investigated by means of several parametric sweeps with respect to the input pump power, the fiber length, the dopant concentrations and the output mirrors reflectivities. Four optimal concentrations have been found by means of a home-made computer code based on particle swarm optimization (PSO) approach, allowing a global solution search. These concentrations allow levels of output powers very close to each other, equal to 20 mW $pm$ 0.1$$ at 1550 nm, 1800 nm and 2050 nm, respectively. These results predict the possibility of tailoring the dopant concentrations in order to construct broadband optical sources with similar emission powers at multiple wavelengths and broadband amplifiers

Photonics-based tunable 1-50 GHz RF transmitter on silicon chip

The paper presents an innovative tunable software-defined RF transmitter based on integrated photonics, able to work in 1-50GHz with very fast tuning. The system has been characterized and verified in a communication scenario

Design of an Efficient Pumping Scheme for Mid-IR Dy3+:Ga5Ge20Sb10S65 PCF Fiber Laser

This letter illustrates the design of a novel medium infrared (Mid-IR) laser based on a photonic crystal fiber made of dysprosium-doped chalcogenide glass, Dy3+:Ga5Ge20Sb10S65. In order to perform a realistic investigation, the simulation is performed by taking into account the spectroscopic parameters measured on the rare earth-doped glass sample. The simulated results show that an optical beam emission close to 4400-nm wavelength can be obtained by employing two pump beams at 2850 nm (pump #1) and 4092 nm (pump #2) wavelengths. The pump beams can be provided by commercial quantum cascade lasers. As example, for the pump powers of 50 mW (pump #1) and 1 W (pump #2), the input mirror reflectivity of 99%, the output mirror reflectivity of 30%, and the optical cavity length of 50 cm, a signal power close to 350 mW at the wavelength of 4384 nm can be generated. This result indicates that the designed source configuration is feasible for high beam quality Mid-IR light generation and it is efficient enough to find applications in optical free propagation links, optical remote sensing, and medicine

Dysprosium-doped chalcogenide Master Oscillator Power Amplifier (MOPA) for Mid-IR emission

The paper describes the design of a medium infrared fiber laser based on a dysprosium-doped chalcogenide glass Dy3+: Ga5Ge20Sb10S65. To obtain a high efficiency, the fiber laser is followed by an optical amplifier. The optimized optical source exploits a master oscillator power amplifier (MOPA) configuration. The MOPA pump and signal wavelengths are 1709 and 4384 nm, respectively. Spectroscopic parameters measured on preliminary samples of chalcogenide glasses are taken into account to fulfill realistic simulations. The MOPA emission is maximized by applying a particle swarm optimization approach. For the dysprosium concentration 6, ×, 1025 ions/m3 and the input pump power of 3 W, an output power of 637 mW can be obtained for optical fiber losses close to 1 dB m-1. The optimized MOPA configuration allows a laser efficiency larger than 21%. By considering the high beam quality provided by photonic crystal fibers, it is a good candidate for medium infrared light generation whose main applications include, but are not limited to, molecular spectroscopy and environmental monitoring

Prognostic impact of Ki-67 proliferative index in resectable pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive disease characterized by complex biological features and poor prognosis. A prognostic stratification of PDAC would help to improve patient management. The aim of this study was to analyse the expression of Ki-67 in relation to prognosis in a cohort of patients with PDAC who had surgical treatment