University of Crete

About: University of Crete is a education organization based out in Rethymno, Greece. It is known for research contribution in the topics: Population & Galaxy. The organization has 8681 authors who have published 21684 publications receiving 709078 citations. The organization is also known as: Panepistimio Kritis.

Repulsive Casimir force in chiral metamaterials.

Abstract: We demonstrate theoretically that one can obtain repulsive Casimir forces and stable nanolevitations by using chiral metamaterials. By extending the Lifshitz theory to treat chiral metamaterials, we find that a repulsive force and a minimum of the interaction energy possibly exist for strong chirality, under realistic frequency dependencies and correct limiting values (for zero and infinite frequencies) of the permittivity, permeability, and chiral coefficients.

Insight on the Formation of Chitosan Nanoparticles through Ionotropic Gelation with Tripolyphosphate

Abstract: This work reports details pertaining to the formation of chitosan nanoparticles that we prepare by the ionic gelation method. The molecular interactions of the ionic cross-linking of chitosan with tripolyphosphate have been investigated and elucidated by means of all-electron density functional theory. Solvent effects have been taken into account using implicit models. We have identified primary-interaction ionic cross-linking configurations that we define as H-link, T-link, and M-link, and we have quantified the corresponding interaction energies. H-links, which display high interaction energies and are also spatially broadly accessible, are the most probable cross-linking configurations. At close range, proton transfer has been identified, with maximum interaction energies ranging from 12.3 up to 68.3 kcal/mol depending on the protonation of the tripolyphosphate polyanion and the relative coordination of chitosan with tripolyphosphate. On the basis of our results for the linking types (interaction energ...

Editorial: Nicotine and SARS-CoV-2: COVID-19 may be a disease of the nicotinic cholinergic system.

Abstract: As of 20 April, almost 1.7 million people globally have been diagnosed with Corona Virus Disease 2019 (COVID-19), a pandemic that has evolved from the emergence of a new coronavirus strain, acute respiratory syndrome coronavirus 2 (SARS-CoV-2), in China. More than 170,000 deaths have been reported, while there are certainly many more cases of milder disease that have not been diagnosed and officially confirmed due to limited testing capacity in most countries. The pandemic is a global emergency due to the rapid transmission of the disease and the potential to overwhelm the healthcare systems, and is expected to have considerable economic and health impacts. Contributing factors and their possible role in the relatively high infection, death rates between countries and origin have recently been studied [1,2]. This new outbreak has been additionally evaluated for current knowledge on coronaviruses based on a short history to epidemiology, pathogenesis, clinical manifestation of the disease, as well as treatment and prevention strategies [3]. The search for potential protective and therapeutic antiviral strategies is of particular and urgent concern [4]. While in most cases, especially in young people without any comorbidities, the disease is expected to be relatively mild, there is a substantial proportion of patients who develop complications and need intensive care-unit support and mechanical ventilation. In one case series of 1099 patients in China [5], 6.1 % of cases suffered from the primary composite end-point of admission to an intensive care unit, use of mechanical ventilation, or death. Patients with severe disease typically present with dyspnea and hypoxemia shortly after disease initiation, and may quickly progress to respiratory failure, acute respiratory distress syndrome (ARDS) and multi-organ failure [6]. Predictors of adverse outcomes include elevated levels of inflammatory markers and pro-inflammatory cytokines. A study of 150 COVID-19 cases reported that elevated levels of C-reactive protein (CRP), ferritin and IL-6 were associated with death [7]. IL-6, an important pro-inflammatory cytokine, was elevated in fatal cases of COVID-19 in another study of 191 patients [8]. Another study of 452 patients reported that those with severe disease showed lymphocytopenia, neutrophilia, low levels of monocytes, eosinophils and basophils, and elevated levels of infection-related biomarkers and inflammatory cytokines [9]. Pathological examination of a case in China revealed bilateral diffuse alveolar damage, desquamation of pneumocytes, hyaline membrane formation and interstitial mononuclear inflammatory infiltrates [10]. Flow cytometry of peripheral blood revealed reduced levels of CD4+ and CD8 + T cells, which however were hyper-activated, and elevated concentration of pro-inflammatory CCR6+ Th17 in CD4 + T cells. Such findings are hallmarks of ARDS and resemble features observed in SARS and Middle Eastern Respiratory Syndrome [11,12]. Systemic vasculitis was also observed [10]. Therefore, it seems that immune dysregulation may be implicated in the pathophysiology of severe COVID-19.

Widespread Recombination in Published Animal mtDNA Sequences

Abstract: Mitochondrial DNA (mtDNA) recombination has been observed in several animal species, but there are doubts as to whether it is common or only occurs under special circumstances. Animal mtDNA sequences retrieved from public databases were unambiguously aligned and rigorously tested for evidence of recombination. At least 30 recombination events were detected among 186 alignments examined. Recombinant sequences were found in invertebrates and vertebrates, including primates. It appears that mtDNA recombination may occur regularly in the animal cell but rarely produces new haplotypes because of homoplasmy. Common animal mtDNA recombination would necessitate a reexamination of phylogenetic and biohistorical inference based on the assumption of clonal mtDNA transmission. Recombination may also have an important role in producing and purging mtDNA mutations and thus in mtDNA-based diseases and senescence.

Impacts of atmospheric nutrient deposition on marine productivity: Roles of nitrogen, phosphorus, and iron

Abstract: Nutrients are supplied to the mixed layer of the open ocean by either atmospheric deposition or mixing from deeper waters, and these nutrients drive nitrogen and carbon fixation. To evaluate the importance of atmospheric deposition, we estimate marine nitrogen and carbon fixation from present-day simulations of atmospheric deposition of nitrogen, phosphorus, and iron. These are compared with observed rates of marine nitrogen and carbon fixation. We find that Fe deposition is more important than P deposition in supporting N fixation. Estimated rates of atmospherically supported carbon fixation are considerably lower than rates of marine carbon fixation derived from remote sensing, indicating the subsidiary role atmospheric deposition plays in total C uptake by the oceans. Nonetheless, in high-nutrient, low-chlorophyll areas, the contribution of atmospheric deposition of Fe to the surface ocean could account for about 50% of C fixation. In marine areas typically thought to be N limited, potential C fixation supported by atmospheric deposition of N is only ~1%-2% of observed rates. Although these systems are N-limited, the amount of N supplied from below appears to be much larger than that deposited from above. Atmospheric deposition of Fe has the potential to augment atmospherically supported rates of C fixation in N-limited areas. In these areas, atmospheric Fe relieves the Fe limitation of diazotrophic organisms, thus contributing to the rate of N fixation. The most important uncertainties in understanding the relative importance of different atmospheric nutrients are poorly understood speciation and solubility of Fe as well as the N:Fe ratio of diazotrophic organisms.