Quasi-realistic heterotic-string models with vanishing one-loop cosmological constant and perturbatively broken supersymmetry?

Quasi-realistic string models in the free fermionic formulation typically contain an anomalous U(1), which gives rise to a Fayet-Iliopoulos D-term that breaks supersymmetry at the one--loop level in string perturbation theory. Supersymmetry is traditionally restored by imposing F- and D-flatness on the vacuum. By employing the standard analysis of flat directions we present a quasi--realistic three generation string model in which stringent F- and D-flat solution do not appear to exist to all orders in the superpotential. We speculate that this result is indicative of the non-existence of supersymmetric flat F- and D-solutions in this model. We provide some arguments in support of this scenario and discuss its potential implications. Bose-Fermi degeneracy of the string spectrum implies that the one--loop partition function and hence the one-loop cosmological constant vanishes in the model. If our assertion is correct, this model may represent the first known example with vanishing cosmological constant and perturbatively broken supersymmetry. We discuss the distinctive properties of the internal free fermion boundary conditions that may correspond to a large set of models that share these properties. The geometrical moduli in this class of models are fixed due to asymmetric boundary conditions, whereas absence of supersymmetric flat directions would imply that the supersymmetric moduli are fixed as well and the dilaton may be fixed by hidden sector nonperturbative effects.Comment: 37 pages, LaTeX. Added discussion on stringent flat directions. PRD published versio

Synthesis and in vitro cytotoxicity of glycans-capped silver nanoparticles

Silver nanostructures were successfully synthesized through a simple and "green" method using saccharides as reducing and caping agent. Transmission electron microscopy (TEM) and UV-Vis absorption were used to certify the quality of the silver nanoparticles obtained: firstly, size and dispersion. In this work Silver NanoParticles (AgNPs) cytotoxicity related to saccharides capping (Glucose and (GlucoseSucrose) was explored in human epithelia cervix carcinoma cells (HeLa). The cells were incubated with increasing AgNPs number/cell and HeLa cells viability was monitored for a period of 48 h compared with the positive and negative controls. We observed that the toxicity increases with incubation time and with AgNPs number/cell. In particular, the different cytotoxic degree of the AgNPs, i.e. AgNP-G are more toxic than AgNP-GS, suggest that the cytotoxic effects are largely depended on the capping agent. The highest concentration of AgNP-G number/cell is able to induce extensive cell death of HeLa cells soon after 1hr of incubation; conversely the lowest concentration of AgNP-GS number/cell, surprisingly, is able to induce cell proliferation

Organic or junk food? Microplastic contamination in Antarctic krill and salps

Microplastics (MP) have been reported in Southern Ocean (SO), where they are likely to encounter Antarctic zooplankton and enter pelagic food webs. Here we assess the presence of MP within Antarctic krill (Euphausia superba) and salps (Salpa thompsoni) and quantify their abundance and type by micro-Fourier transform infrared microscopy. MP were found in both species, with fibres being more abundant than fragments (krill: 56.25% and salps: 22.32% of the total MP). Polymer identification indicated MP originated from both local and distant sources. Our findings prove how in situ MP ingestion from these organisms is a real and ongoing process in the SO. MP amount was higher in krill (2.13 ± 0.26 MP ind−1) than salps (1.38 ± 0.42 MP ind−1), while MP size extracted from krill (130 ± 30 µm) was significantly lower than MP size from salps (330 ± 50 µm). We suggest that differences between abundance and size of MP ingested by these two species may be related to their food strategies, their ability to fragment MP as well as different human pressures within the collection areas of the study region. First comparative field-based evidence of MP in both krill and salps, two emblematic zooplankton species of the SO marine ecosystems, underlines that Antarctic marine ecosystems may be particularly sensitive to plastic pollution

The Ocean Plastic Incubator Chamber (OPIC) system to monitor in situ plastic degradation at sea

Marine plastic pollution is a global and pervasive environmental issue. Knowledge on plastic degradation in natural settings is still very limited due to current technological limitations, hampering our understanding of plastic fate (including its breakdown into micro- and nanoplastics) and of its risk for marine ecosystems. Here we present the proof of concept of the Ocean Plastic Incubator Chamber (OPIC), a novel equipment to follow plastic degradation in situ at sea over time. OPIC consists of a frame containing a motorised rotating stage with transparent tubes sub-assemblies where reference plastic materials are incubated and exposed to natural weathering conditions for defined time multi-years period. OPIC has been designed, tested and adapted for deployment with mooring line platforms in the open ocean with potential future application in remote environments at different depths (from shallow waters to deep sea environments). This incubator will allow us to measure different markers of plastic aging in situ in the ocean for the first time, providing new insights into the multiple and locally driven dynamics regulating plastic transformations and fate at sea

Image Based Robust Target Classification For Passive ISAR

This paper presents an automatic and robust, image feature-based target extraction, and classification method for multistatic passive inverse synthetic aperture radar range/cross-range images. The method can be used as a standalone solution or for augmenting classical signal processing approaches. By extracting textural, directional, and edge information as low-level features, a fused saliency map is calculated for the images and used for target detection. The proposed method uses the contour and the size of the detected targets for classification, is lightweight, fast, and easy to extend. The performance of the approach is compared with machine learning methods and extensively evaluated on real target images

High ordered biomineralization induced by carbon nanoparticles in the sea urchin Paracentrotus lividus

A surprising and unexpected biomineralization process was observed during toxicological assessment of carbon nanoparticles on Paracentrotus lividus (sea urchin) pluteus larvae. The larvae activate a process of defense against external material, by incorporating the nanoparticles into microstructures of aragonite similarly to pearl oysters. Aiming at a better understanding of this phenomenon, the larvae were exposed to increasing concentrations of carbon nanoparticles and the biomineralization products were analyzed by electron microscopy, x-ray diffraction and Raman spectroscopy. In order to evaluate the possible influence of Sp-CyP-1 expression on this biomineralization process by larvae, analyses of gene expression (Sp-CyP-1) and calcein labeling were performed. Overall, we report experimental evidence about the capability of carbon nanoparticles to induce an increment of Sp-CyP-1 expression with the consequent activation of a biomineralization process leading to the production of a new pearl-like biomaterial never previously observed in sea urchins

Proof-of-Concept Study on the Use of Tangerine-Derived Nanovesicles as siRNA Delivery Vehicles toward Colorectal Cancer Cell Line SW480

In the last years, the field of nanomedicine and drug delivery has grown exponentially, providing new platforms to carry therapeutic agents into the target sites. Extracellular vesicles (EVs) are ready-to-use, biocompatible, and non-toxic nanoparticles that are revolutionizing the field of drug delivery. EVs are involved in cell-cell communication and mediate many physiological and pathological processes by transferring their bioactive cargo to target cells. Recently, nanovesicles from plants (PDNVs) are raising the interest of the scientific community due to their high yield and biocompatibility. This study aims to evaluate whether PDNVs may be used as drug delivery systems. We isolated and characterized nanovesicles from tangerine juice (TNVs) that were comparable to mammalian EVs in size and morphology. TNVs carry the traditional EV marker HSP70 and, as demonstrated by metabolomic analysis, contain flavonoids, organic acids, and limonoids. TNVs were loaded with DDHD1-siRNA through electroporation, obtaining a loading efficiency of 13%. We found that the DDHD1-siRNA complex TNVs were able to deliver DDHD1-siRNA to human colorectal cancer cells, inhibiting the target expression by about 60%. This study represents a proof of concept for the use of PDNVs as vehicles of RNA interference (RNAi) toward mammalian cells