A small satellite mission devoted to mid-low latitude earth observation

This paper aims at assessing the feasibility of a small mission devoted to observe the mid-low latitude regions. The satellite will be equipped with three optical sensors: a medium-high spatial resolution VIS-NIR multi-spectral sensor, allowing the surface monitoring and land-use and land-cover studies; a medium spatial-resolution 3-bands thermal (MIR-TIR) sensor allowing the surface temperature (LST, SST) estimate and hot-spots (fires, volcanic eruption, etc.) detection; a panchromatic VIS-NIR camera for night-time observation able to reveal artificial and natural lights. The selected orbit, called multi-sun-synchronous (MSS), represents an innovation with respect to the classical sun-synchronous orbit much suitable for observing tropical regions, allowing an enhanced revisit frequency. Further, such an orbit allows the observation of the same region of the Earth at different local-time. In this way, the diurnal cycle of surface temperatures can be reconstructed with a 2-hours local-time step. An analysis of the capability of the selected ground stations to acquire the data gathered by the remote sensing sensors has been carried out. Orbital perturbations have been taken into account and an estimate of the propellant required for ground track control has been performed in order to verify its compatibility with a small mission requirements

OTFS vs. OFDM in the Presence of Sparsity: A Fair Comparison

Many recent works in the literature declare that Orthogonal Time-Frequency-Space (OTFS) modulation is a promising candidate technology for high mobility communication scenarios. However, a truly fair comparison with its direct concurrent and widely used Orthogonal Frequency-Division Multiplexing (OFDM) modulation has not yet been provided. In this paper, we present such a fair comparison between the two digital modulation formats in terms of achievable communication rate. In this context, we explicitly address the problem of channel estimation by considering, for each modulation, a pilot scheme and the associated channel estimation algorithm specifically adapted to sparse channels in the Doppler-delay domain, targeting the optimization of the pilot overhead to maximize the overall achievable rate. In our achievable rate analysis we consider also the presence of a guard interval or cyclic prefix. The results are supported by numerical simulations, for different time-frequency selective channels including multiple scattering components and under non-perfect channel state information resulting from the considered pilot schemes. This work does not claim to establish in a fully definitive way which is the best modulation format, since such choice depends on many other features which are outside the scope of this work (e.g., legacy, intellectual property, ease and know-how for implementation, and many other criteria). Nevertheless, we provide the foundations to properly compare multi-carrier communication systems in terms of their information theoretic achievable rate potential, within meaningful and sensible assumptions on the channel models and on the receiver complexity (both in terms of channel estimation and in terms of soft-output symbol detection)

Recent advances on the mechanisms regulating cholangiocyte proliferation and the significance of the neuroendocrine regulation of cholangiocyte pathophysiology

Cholangiocytes are epithelial cells lining the biliary epithelium. Cholangiocytes play several key roles in the modification of ductal bile and are also the target cells in chronic cholestatic liver diseases (i.e., cholangiopathies) such as PSC, PBC, polycystic liver disease (PCLD) and cholangiocarcinoma (CCA). During these pathologies, cholangiocytes (which in normal condition are in a quiescent state) begin to proliferate acquiring phenotypes of neuroendocrine cells, and start secreting different cytokines, growth factors, neuropeptides, and hormones to modulate cholangiocytes proliferation and interaction with the surrounding environment, trying to reestablish the balance between proliferation/loss of cholangiocytes for the maintenance of biliary homeostasis. The purpose of this review is to summarize the recent findings on the mechanisms regulating cholangiocyte proliferation and the significance of the neuroendocrine regulation of cholangiocyte pathophysiology. To clarify the mechanisms of action of these factors we will provide new potential strategies for the management of chronic liver diseases

Microcorrosion Casts in the Microcirculation of Skeletal Muscle

The authors review the contribution of microcorrosion cast studies towards clarifying the structure of skeletal muscle microcirculation. Former studies performed on naturally contracted muscles show the presence of a primary and a secondary arterial network and a capillary network. At the level of the capillary network pericyte imprints are present. Muscles characterized by different types of metabolism show different features of the capillary pattern. Other authors have affirmed that the extended muscle is characterized by long and straight capillaries, while the contracted one features clusters of vessels all around a muscle fiber. The authors have made the present observations in order to determine how the capillary pattern of muscles with different metabolism is modified by extension and shortening of the muscle belly. The capillary pattern observed appears very similar to that observed in former studies. The differences between the oxidative and the glycolytic muscle are evident in every condition of the muscle belly. These data confirm the theory that there is a permanent endogenous difference in microcirculation between oxidative and glycolytic muscle, determined by muscle fiber metabolism

A novel ultrafast-low-dose computed tomography protocol allows concomitant coronary artery evaluation and lung cancer screening

BACKGROUND:Cardiac computed tomography (CT) is often performed in patients who are at high risk for lung cancer in whom screening is currently recommended. We tested diagnostic ability and radiation exposure of a novel ultra-low-dose CT protocol that allows concomitant coronary artery evaluation and lung screening. METHODS: We studied 30 current or former heavy smoker subjects with suspected or known coronary artery disease who underwent CT assessment of both coronary arteries and thoracic area (Revolution CT, General Electric). A new ultrafast-low-dose single protocol was used for ECG-gated helical acquisition of the heart and the whole chest. A single IV iodine bolus (70-90 ml) was used. All patients with CT evidence of coronary stenosis underwent also invasive coronary angiography. RESULTS: All the coronary segments were assessable in 28/30 (93%) patients. Only 8 coronary segments were not assessable in 2 patients due to motion artefacts (assessability: 98%; 477/485 segments). In the assessable segments, 20/21 significant stenoses (> 70% reduction of vessel diameter) were correctly diagnosed. Pulmonary nodules were detected in 5 patients, thus requiring to schedule follow-up surveillance CT thorax. Effective dose was 1.3 ± 0.9 mSv (range: 0.8-3.2 mSv). Noteworthy, no contrast or radiation dose increment was required with the new protocol as compared to conventional coronary CT protocol. CONCLUSIONS:The novel ultrafast-low-dose CT protocol allows lung cancer screening at time of coronary artery evaluation. The new approach might enhance the cost-effectiveness of coronary CT in heavy smokers with suspected or known coronary artery disease

Common features between neoplastic and preneoplastic lesions of the biliary tract and the pancreas

The bile duct system and pancreas show many similarities due to their anatomical proximity and common embryological origin. Consequently, preneoplastic and neoplastic lesions of the bile duct and pancreas share analogies in terms of molecular, histological and pathophysiological features. Intraepithelial neoplasms are reported in biliary tract, as biliary intraepithelial neoplasm (BilIN), and in pancreas, as pancreatic intraepithelial neoplasm (PanIN). Both can evolve to invasive carcinomas, respectively cholangiocarcinoma (CCA) and pancreatic ductal adenocarcinoma (PDAC). Intraductal papillary neoplasms arise in biliary tract and pancreas. Intraductal papillary neoplasm of the biliary tract (IPNB) share common histologic and phenotypic features such as pancreatobiliary, gastric, intestinal and oncocytic types, and biological behavior with the pancreatic counterpart, the intraductal papillary mucinous neoplasm of the pancreas (IPMN). All these neoplastic lesions exhibit similar immunohistochemical phenotypes, suggesting a common carcinogenic process. Indeed, CCA and PDAC display similar clinic-pathological features as growth pattern, poor response to conventional chemotherapy and radiotherapy and, as a consequence, an unfavorable prognosis. The objective of this review is to discuss similarities and differences between the neoplastic lesions of the pancreas and biliary tract with potential implications on a common origin from similar stem/progenitor cells

Relation between the spectral properties of wall turbulence and the scaling of the Darcy-Weisbach friction factor

Empirical formulas describing the Darcy-Weisbach friction factor remain indispensable for applications in sciences and engineering dealing with turbulent flows. Despite their practical significance, these formulas have remained without theoretical interpretation for many decades. To close this knowledge gap, much research has been devoted to the development of the so-called "spectral link"introduced in the early 2000s. Such a theory is entirely based on elegant phenomenological arguments that make no contact with equations describing turbulent wall flows. The spectral link spawned alternative approaches, now labeled "cospectral budget"(or CSB) models, that describe how turbulent eddies contribute to wall stresses. The CSB overcomes some of the shortcomings of the phenomenological approach and is here employed to provide a thorough clarification of the link between spectral properties of velocity fluctuations and the scaling of friction factors in turbulent pipe flows in the hydraulically smooth and fully rough regimes

A Three-Dimensional Study of the Morphology and Topography of Pericytes in the Microvascular Bed of Skeletal Muscle

Digested tissue specimens and corrosion casts of rat soleus and tibialis anterior muscles were employed for this Scanning Electron Microscopy (SEM) study. The shape, morphology, and position of pericytes were compared to corresponding imprints on the cast surfaces. Pericytes, observed in digested tissue specimens, showed a typical morphological pattern: a central body with two primary processes that run along the capillary in opposite directions. From these primary processes, secondary ones arise and often encircle the vessel almost completely. On the surface of corrosion casts, roundish imprints were found in the microvascular tree at the same level where digested tissue specimens showed the presence of pericyte bodies. Along and around the cast surface, shallow grooves reproduced the course of the primary and secondary processes. The peculiar tridimensional arrangement of pericytes at the level of capillary bifurcations underlines their role in red cell flow regulation. However, if the mechanical linkage of the pericytes to the endothelium and their contractability is taken into account, additional roles of these perivascular cells may be hypothesized