139 research outputs found
BRAMS: The Belgian RAdio Meteor Stations
In the last months, the Belgian Institute for Space Aeronomy has been developing a Belgian network for observing radio meteors using forward scattering technique. This network is called BRAMS for Belgian RAdio Meteor Stations. Two beacons emitting a circularly polarized pure sine wave toward the zenith act as the transmitters at frequencies of 49.97 and 49.99 MHz. The first one located in Dourbes (Southern Belgium) emits a constant power of 150 Watts while the one located in Ieper (Western Belgium) emits a constant power of 50 Watts. The receiving network consists of about 20 stations hosted mainly by radio amateurs. Two stations have crossed-Yagi antennas measuring horizontal and vertical polarizations of the waves reflected off meteor trails. This will enable a detailed analysis of the meteor power profiles from which physical parameters of the meteoroids can be obtained. An interferometer consisting of 5 Yagi-antennas will be installed at the site of Humain in order to determine the angular detection of one reflection point, allowing us to determine meteoroid trajectories. We describe this new meteor observing facility and present the goals we expect to achieve with the network
Laboratory measurements of the performances of the Sweeping Langmuir Probe instrument aboard the PICASSO CubeSat
The Sweeping Langmuir Probe (SLP) is one of the
instruments on board the triple-unit CubeSat PICASSO, an ESA in-orbit
demonstrator launched in September 2020, which is flying at about 540âkm
altitude. SLP comprises four small cylindrical probes mounted at the tip of the
solar panels. It aims to perform in situ measurements of the plasma
parameters (electron density and temperature together with ion density) and
of the spacecraft potential in the ionosphere. Before the launch, the
instrument, accommodated on an electrically representative PICASSO mock-up,
was tested in a plasma chamber. It is shown that the traditional
orbital-motion-limited collection theory used for cylindrical Langmuir
probes cannot be applied directly for the interpretation of the measurements
because of the limited dimensions of the probes with respect to the Debye
length in the ionosphere. Nevertheless, this method can be adapted to take
into account the short length of the probes. To reduce the data downlink
while keeping the most important information in the current-voltage
characteristics, SLP includes an on-board adaptive sweeping capability. This
functionality has been validated in both the plasma chamber and in space, and
it is demonstrated that with a reduced number of data points the electron
retardation and electron saturation regions can be well resolved. Finally,
the effect of the contamination of the probe surface, which can be a serious
issue in Langmuir probe data analysis, has been investigated. If not
accounted for properly, this effect could lead to substantial errors in the
estimation of the electron temperature.</p
Humanized Mouse Model of Ovarian Cancer Recapitulates Patient Solid Tumor Progression, Ascites Formation, and Metastasis
Ovarian cancer is the most common cause of death from gynecological cancer. Understanding the biology of this disease, particularly how tumor-associated lymphocytes and fibroblasts contribute to the progression and metastasis of the tumor, has been impeded by the lack of a suitable tumor xenograft model. We report a simple and reproducible system in which the tumor and tumor stroma are successfully engrafted into NOD-scid IL2RÎłnull (NSG) mice. This is achieved by injecting tumor cell aggregates derived from fresh ovarian tumor biopsy tissues (including tumor cells, and tumor-associated lymphocytes and fibroblasts) i.p. into NSG mice. Tumor progression in these mice closely parallels many of the events that are observed in ovarian cancer patients. Tumors establish in the omentum, ovaries, liver, spleen, uterus, and pancreas. Tumor growth is initially very slow and progressive within the peritoneal cavity with an ultimate development of tumor ascites, spontaneous metastasis to the lung, increasing serum and ascites levels of CA125, and the retention of tumor-associated human fibroblasts and lymphocytes that remain functional and responsive to cytokines for prolonged periods. With this model one will be able to determine how fibroblasts and lymphocytes within the tumor microenvironment may contribute to tumor growth and metastasis, and will make it possible to evaluate the efficacy of therapies that are designed to target these cells in the tumor stroma
Non-Functional Parathyroid Carcinoma: A Review of the Literature and Report of a Case Requiring Extensive Surgery
Parathyroid carcinoma is a rare malignancy, and only accounts for 0.5â2% of cases of primary hyperparathyroidism. Less than 10% of parathyroid carcinomas are non-functional, and as such, they have been rarely reported in the literature. Importantly, margin status at resection is related to prognosis, and only a handful of case reports of non-functional carcinoma note this important parameter. Here we report the first case of non-functional parathyroid carcinoma with negative margins, and review the literature on this rare entity. Whether functional or non-functional, parathyroid carcinoma can often be difficult to differentiate from benign parathyroid adenoma. While diagnosis has been based on clinical and histological criteria, recent data concerning the molecular underpinnings of parathyroid carcinoma may allow for improved accuracy in distinguishing benign and malignant parathyroid tumors
Restricted growth of Schwann cells lacking Cajal bands slows conduction in myelinated nerves
Nerve impulses are propagated at nodes of Ranvier in the
myelinated nerves of vertebrates. Internodal distances have
been proposed to affect the velocity of nerve impulse conduction;
however, direct evidence is lacking, and the cellular mechanisms
that might regulate the length of the myelinated segments
are unknown. Ramon y Cajal described longitudinal and transverse
bands of cytoplasm or trabeculae in internodal Schwann
cells and suggested that they had a nutritive function. Here we
show that internodal growth in wild-type nerves is precisely
matched to nerve extension, but disruption of the cytoplasmic
bands in Periaxin-null mice impairs Schwann cell elongation during nerve growth. By contrast, myelination proceeds normally.
The capacity of wild-type and mutant Schwann cells to
elongate is cell-autonomous, indicating that passive stretching
can account for the lengthening of the internode during limb
growth. As predicted on theoretical grounds, decreased internodal
distances strikingly decrease conduction velocities and so
affect motor function.We propose that microtubule-based transport
in the longitudinal bands of Cajal permits internodal
Schwann cells to lengthen in response to axonal growth, thus
ensuring rapid nerve impulse transmission
The Comet Interceptor Mission
Here we describe the novel, multi-point Comet Interceptor mission. It is dedicated to the exploration of a little-processed long-period comet, possibly entering the inner Solar System for the first time, or to encounter an interstellar object originating at another star. The objectives of the mission are to address the following questions: What are the surface composition, shape, morphology, and structure of the target object? What is the composition of the gas and dust in the coma, its connection to the nucleus, and the nature of its interaction with the solar wind? The mission was proposed to the European Space Agency in 2018, and formally adopted by the agency in June 2022, for launch in 2029 together with the Ariel mission. Comet Interceptor will take advantage of the opportunity presented by ESAâs F-Class call for fast, flexible, low-cost missions to which it was proposed. The call required a launch to a halo orbit around the Sun-Earth L2 point. The mission can take advantage of this placement to wait for the discovery of a suitable comet reachable with its minimum ÎV capability of 600 msâ1. Comet Interceptor will be unique in encountering and studying, at a nominal closest approach distance of 1000 km, a comet that represents a near-pristine sample of material from the formation of the Solar System. It will also add a capability that no previous cometary mission has had, which is to deploy two sub-probes â B1, provided by the Japanese space agency, JAXA, and B2 â that will follow different trajectories through the coma. While the main probe passes at a nominal 1000 km distance, probes B1 and B2 will follow different chords through the coma at distances of 850 km and 400 km, respectively. The result will be unique, simultaneous, spatially resolved information of the 3-dimensional properties of the target comet and its interaction with the space environment. We present the missionâs science background leading to these objectives, as well as an overview of the scientific instruments, mission design, and schedule
Poly-SiGe-based MEMS Xylophone Bar Magnetometer
peer reviewedThis paper presents the design, fabrication and preliminary characterization of highly sensitive MEMS-based Xylophone Bar Magnetometers (XBMs) realized in imecâs poly-SiGe MEMS technology. Key for our Lorentz force driven capacitively sensed resonant sensor are the combination of reasonably high Q-factor and conductivity of imecâs poly-SiGe, our optimized multiphysics sensor design targeting the maximization of the Q-factor in a wide temperature range as well as our proprietary monolithic above-CMOS integration and packaging schemes. Prototypes 3-axis devices were fabricated and characterized. We present optical vibrometer and electrical S-parameter measurements of XBMs performed in vacuum with a reference magnet at increasing sensor separation. The optical oscillation amplitude is well correlated with the magnetic field amplitude. The electrical 2-port measurements, 1st port as Lorentz force actuator and 2nd port as capacitive sensor, also reproduces the designed magnetic field dependence. This opens the way towards the on-chip integration of small footprint
extremely sensitive magnetometers
Influence of multiphysics couplings on the performance of a MEMS magnetometer
In this paper, several physical phenomena that are usually not taken into account in MEMS simulations are considered for the simulation of a MEMS xylophone bar magnetometer. These phenomena are the temperature dependency of the material properties, the strong coupling between various fields of physics (thermal, electric and mechanical) and the stress produced by the change of temperature inside the structure. It is shown that the temperature dependency of the material properties has a relatively small influence whereas the pre-stress has a significant one. Because of the pre-stressed state, the deformation of the bar at the fundamental frequency is not a typical first mode vibration but it exhibits additional waves between the linkages, where the bar is stressed, which significantly decrease the amplitude of the deflection
- âŠ