13 research outputs found
The Evolution from Design to Verification of the Antenna System and Mechanisms in the AcubeSAT mission
AcubeSAT is an open-source CubeSat mission aiming to explore the effects of
microgravity and radiation on eukaryotic cells using a compact microfluidic LoC
platform. It is developed by SpaceDot, a volunteer, interdisciplinary student
team at the Aristotle University of Thessaloniki and supported by the "Fly Your
Satellite! 3" program of the ESA Education Office. The scientific data of the
mission is comprised of microscope images captured through the on-board
integrated camera setup. As the total size of the payload data is expected to
be close to 2GB over 12 months, a fast and efficient downlink fulfilling the
restrictive power, cost and complexity budgets is required. Currently, there is
no open-source communications system design which fully supports these specific
constraints, so we opted to develop our own solutions. The antenna system
underwent multiple iterations as the design matured, a process highly aided by
the feedback received from the ESA experts. The final communications system
configuration consists of an S-band microstrip antenna operating at 2.4GHz and
a UHF deployable antenna, for the payload data and TM&TC respectively, both
in-house designed. In this paper, we will present AcubeSAT's antenna system
iterations that span over 3 years, as well as the rationale and analysis
results behind each. The development decisions will be highlighted throughout
the paper in an effort to aid in the future development of such a low-cost
CubeSat mission communications system.Comment: 74th International Astronautical Congres
Toxic effects multi-walled carbon nanotubes on bivalves: comparison between of functionalized and non-functionalized nanoparticles
Despite of the large array of available carbon nanotube (CNT) configurations that allow different industrial and scientific applications of these nanoparticles, their impacts on aquatic organisms, especially on invertebrate species, are still limited. To our knowledge, no information is available on how surface chemistry alteration (functionalization) of CNTs may impact the toxicity of these NPs to bivalve species after a chronic exposure. For this reason, the impacts induced by chronic exposure (28 days) to unfunctionalized MWCNTs (Nf-MWCNTs) in comparison with functionalized MWCNTs (f-MWCNTs), were evaluated in R. philippinarum, by measuring alterations induced in clams' oxidative status, neurotoxicity and metabolic capacity. The results obtained revealed that exposure to both MWCNT materials altered energy-related responses, with higher metabolic capacity and lower glycogen, protein and lipid concentrations in clams exposed to these CNTs. Moreover, R. philippinarum exposed to Nf-MWCNTs and f-MWCNTs showed oxidative stress expressed in higher lipid peroxidation and lower ratio between reduced and oxidized glutathione, despite the activation of defense mechanisms (superoxide-dismutase, glutathione peroxidase and glutathione S-transferases) in exposed clams. Additionally, neurotoxicity was observed by inhibition of Cholinesterases activity in organisms exposed to both MWCNTs.publishe
The influence of salinity on the effects of Multi-walled carbon nanotubes on polychaetes
Salinity shifts in estuarine and coastal areas are becoming a topic of concern and are one of the main factors influencing nanoparticles behaviour in the environment. For this reason, the impacts of multiwalled carbon nanotubes (MWCNTs) under different seawater salinity conditions were evaluated on the common ragworm Hediste diversicolor, a polychaete species widely used as bioindicator of estuarine environmental quality. An innovative method to assess the presence of MWCNT aggregates in the sediments was used for the first time. Biomarkers approach was used to evaluate the metabolic capacity, oxidative status and neurotoxicity of polychaetes after long-term exposure. The results revealed an alteration of energy-related responses in contaminated polychaetes under both salinity conditions, resulting in an increase of metabolism and expenditure of their energy reserves (lower glycogen and protein contents). Moreover, a concentration-dependent toxicity (higher lipid peroxidation, lower ratio between reduced and oxidized glutathione and activation of antioxidant defences and biotransformation mechanisms) was observed in H. diversicolor, especially when exposed to low salinity. Additionally, neurotoxicity was observed by inhibition of Cholinesterases activity in organisms exposed to MWCNTs at both salinities.publishe
Gastric mucosa epithelial cell kinetics are differentiated by anatomic site and Helicobacter pylori infection
Changes in epithelial cell turnover related to Helicobacter pylori
infection may contribute to gastric cancer development. The response of
different anatomic sites of the gastric mucosa to H. pylori is not
known. We studied apoptosis and cell proliferation at the grater and
lesser curvature of the antrum and corpus, the fundus, and the cardia
from 9 H. pylori gastritis patients and 11 H. pylori-negative controls
with normal histology. Proliferation was highest at the major curve of
the antrum and lowest at the fundus, and apoptosis was highest at the
cardia and lowest at the major curve of the antrum in both H. pylori
gastritis and normal mucosa. Proliferation was significantly higher at
all anatomic sites, while apoptosis was significantly lower only at the
major and lesser curve of the corpus in H. pylori gastritis compared
with normal controls. Our data suggest that gastric mucosa epithelial
cell kinetics is differentiated by the anatomic site and H. pylori
infection