Why should geological criteria used on Earth not be valid also for Mars? Evidence of possible microbialites and algae in extinct Martian lakes

AbstractDuring the Noachian period, 4.1-3.7 Gys ago, the Martian environment was moderately similar to the one on present Earth. Liquid water was widespread in a neutral environment, volcanic activity and heat flow more vigorous, and atmospheric pressure and temperature were higher than today. These conditions may have favoured the spread of life on the surface of Mars. The recognition that different planets and moons share rocky material cast in space by meteoroid impact entails that life creation is not necessary for each single planetary body, but could travel through the Solar system on board of rock fragments. Studies conducted on the past forms of Martian life have already highlighted possible positive matches with microbialite-like structures, referable to the geo-environmental conditions in the Noachian and Hesperian. However, by necessity, these studies are on predominantly micro and meso-scopic scale structures and doubts arise as to their attribution to the biogenic world. We suggest that in the identification of Martian life, we are currently in a position similar to the one of Kalkowsky who in 1908, based solely on morphological and sedimentological arguments, hypothesized the (now accepted) view of the biotic origin of stromatolites. Our analysis of thousands of images from Spirit, Opportunity and Curiosity has provided a selection of images of ring-shaped, domal and coniform macrostructures that resemble terrestrial microbialites such as the ring-shaped stromatolites of Lake Thetis, and stacked cones reminiscent of the group of terrestrialConophyton. Notably, the latter were detected by Curiosity in the mudstone known as 'Sheepbed', the same outcrop where past organic molecules have been detected and where the occurrence of microbial-induced sedimentary structures (MISS) and of many more microbialitic micro, meso and macrostructures has already been hypothesized. Some of the structures discussed in this work are so complex that alternative biological hypotheses can be formulated as possible algae. Alternate, non-abiotic explanations are examined but we find difficult to explain some of such structures in the context of normal sedimentary processes, both syngenetic or epigenetic

Flexible virtual machine networking using netmap passthrough

The rising interest in Network Function Virtualization (NFV) requires Virtual Machines (VMs) to operate with diversified networking workloads, from traditional, bulk TCP transfers to novel ones featuring extremely high packet rates. In response, researchers have explored and proposed new solutions for high performance VM networking, including optimizations to virtual network adapters (such as VirtIO) to support high speed bulk traffic, and alternative frameworks for userspace networking and physical or virtual passthrough. To date, we are still missing a comprehensive solution that supports such extreme workloads across multiple operating systems and hypervisors, while at the same time addressing other requirements such as ease of configuration, operating system independence, scalability and isolation. In this paper we present ptnet, an approach to network I/O virtualization that provides high performance for both traditional TCP/IP and high packet rate applications. ptnet leverages the features of the netmap framework (including virtualization and passthrough support), and defines a simple yet performant network device model that can be easily supported in different operating systems and hypervisors. We prove the effectiveness of our approach by comparing ptnet's performance with one of the state of the art I/O virtualization solutions, namely VirtIO on Linux and QEμKVM. ptnet is available under a BSD license as part of the netmap distributions on github

Very high speed link emulation with TLEM

In this work we discuss the limitations of link emulators based on conventional network stacks, and present our alternative architecture called TLEM, which is designed to address current high speed links and be open to future speed improvements. TLEM is structured as a pipeline of stages, implemented with separate threads and with limited interactions with each other, so that high performance can be achieved. Our emulator can handle bidirectional traffic at speeds of over 18 Mpps (64 byte packets) and 40 Gbit/s (1500 byte packets) per direction even with large emulation delays. Even higher performance can be achieved with shorter delays, as the workload fits better into the L3 cache of the system. TLEM is distributed as BSD-licensed opensource as part of the netmap distributions, and runs on any system that supports netmap (this includes FreeBSD, Linux and now even Windows)

A Study of I/O Performance of Virtual Machines

In this study, we investigate some counterintuitive but frequent performance issues that arise when doing high-speed networking (or I/O in general) with Virtual Machines (VMs). VMs use one or more single-producer/single-consumer systems to exchange I/O data (e.g. network packets) with their hypervisor. We show that when the producer and the consumer process packets at different rates, the high cost required for synchronization (interrupts and ‘kicks’) may reduce throughput of the system well below the slowest of the two parties; moreover, accelerating the faster party may cause the throughput to decrease. Our work provides a model for throughput, efficiency and latency of producer/consumer systems when notifications or sleeping are used as a synchronization mechanism; identifies different operating regimes depending on the operating parameters; validates the accuracy of our model against a VirtIO-based prototype, taking into account most of the details of real-world deployments; provides practical and robust strategies to maximize throughput and minimize energy while keeping the latency under control, without depending on precise timing measurements nor unreasonable assumptions on the system’s behavior. The study is particularly interesting for Network Function Virtualization deployments, where high-rate producer/consumer systems in virtualized environments are the core components

On the use of EMI for the assessment of dental implant stability

The achievement and the maintenance of dental implant stability are prerequisites for the long-term success of the osseointegration process. Since implant stability occurs at different stages, it is clinically required to monitor an implant over time, i.e. between the surgery and the placement of the artificial tooth. In this framework, non-invasive tests able to assess the degree of osseointegration are necessary. In this paper, the electromechanical impedance (EMI) method is proposed to monitor the stability of dental implants. A 3D finite element model of a piezoceramic transducer (PZT) bonded to a dental implant placed into the bone was created, considering the presence of a bone- implant interface subjected to Young’s modulus change. The numerical model was validated experimentally by testing bovine bone samples. The EMI response of a PZT, bonded to the abutment screwed to implants inserted to the bone, was measured. To simulate the osseointegration process a pulp canal sealer was used to secure the implant to the bone. It was found that the PZT’s admittance is sensitive to the stiffness variation of the bone-implant interface. The results are promising because they show the potential of EMI method to (i) evaluate the material properties around dental implant, and (ii) promote a novel non-invasive monitoring of dental implant surgical procedure

Possible organosedimentary structures on Mars

This study, using the Microscopic Imager (MI) of NASA Rover Exploration Mission’s (REM) ‘Opportunity’, aims to explain the origin of laminated sediments lying at Meridiani Planum of Mars, and of the strange spherules, known as blueberries, about which several hypotheses have been formulated. To this purpose, images of the sedimentary textures of layers and fragments captured by REM have been analysed; sediments that NASA has already established as ‘pertinent to water presence’. Our study shows that such laminated sediments and the spherules they contain could be organosedimentary structures, probably produced by microorganisms. The laminated structures are characterized by a sequence of a thin pair of layers, which have the features of skeletal/agglutinated laminae and whose basic constituents are made by a partition of septa and vacuoles radially arranged around a central one. The growth of these supposed organosedimentary masses is based on the ‘built flexibility’ of such a basal element; it may be a coalescing microfossil formed by progressive film accretion (calcimicrobe), in a variety of geometrical gross forms, such as a repeated couplet sequence oflaminae or domal mass and large composite polycentric spherule, both in elevation. The acquired structural and textural data seem to be consistent with the existence of life on Mars and could explain an origin of sediments at Meridiani Planum similar to that of terrestrial stromatolites. The Martian deposits, probably produced by cyanobacterial activity, and the embedded blueberries could represent a recurrent and multiform product of colonies with sheath forms, resembling in shape those of the fossil genus Archaeosphaeroides (stromatolites of Fig Tree, South Africa)

Satellite differential SAR interferometry for the evaluation of effects of hydrogeological disasters: definition of a scale for damage evaluation

In this paper we present the results of monitoring soil movements over an about 10 km 2 area around the border be- tween the Calabria and Basilicata regions in Italy. Monitoring has been performed using the satellite differential SAR interferometry measurements integrated with GPS measurements. In particular, we used ERS data acquired at time interval of several months (about two acquisitions per year), and after particularly strong pluvial events. Terrain dis- placement spatial and temporal analysis has been performed by employing the original method described in Berardi- no et al. (2002, 2003). Obtained results allow us to characterise unstable areas, and can be used within projects aimed at territory classification and characterisation, and at performing damage evaluation. Accordingly, this technique has been included in the framework of a proposed UE project (WEDELOP project) aimed at developing an integrated methodology to devise a damage scale for hydrogeological disasters. This scale is of great interest in many fields; in particular, definition of a damage scale would be highly desirable from the viewpoint of insurance companies

Cognitive Health of Nonagenarians in Southern Italy: A Descriptive Analysis from a Cross-Sectional, Home-Based Pilot Study of Exceptional Longevity (Cilento Initiative on Aging Outcomes Or CIAO).

Background: Nonagenarians and centenarians (NCs) are an extremely fragile population, particularly in regard to their physical and cognitive function. The aim of this study was to define the neurocognitive profiles among 29 NCs and their 49 younger cohabitants aged 50-75 years from The Cilento Initiative on Aging Outcomes (CIAO) Pilot study in the South of Italy that had provided initial hypotheses regarding positive psychological traits related to exceptional longevity. Methods: During the home visits, lifestyle information with specific questionnaires, functional autonomy and the neuropsychological Mini Mental Scale Examination (MMSE), and the Alzheimer's Disease Assessment Scale-Cognitive (ADAS-Cog) scale were obtained by qualified study personnel. The total blood oxidative capacity was also determined by testing the reactive derivative of oxygen metabolites (d-ROM) and by the Biological Antioxidant Potential (BAP). In all individuals, the APOE genotype determination was also performed. Results: All the subjects in both groups showed high adherence to the Mediterranean Diet. None of the NCs had severe cognitive impairment, and a very low incidence of dementia was found. The data obtained on the Activities ed Instrumental Activities of Daily Living (ADL-IADL) scale showed that the majority of NCs (16/29) were autonomous in daily life activities. The comparative assessment of NCs and cohabitants showed no significant differences in the laboratory assessment of oxidative stress and APOE genotype. Conclusion: In the Cilento Region of Southern Italy, NCs seemed to have good cognitive status when compared to younger cohabitants aging 50-65 years without significant differences in oxidative stress markers or APOE genotype. These results might be related to optimal adherence to the Mediterranean diet, although other lifestyle factors and positive personality traits may also contribute to their healthy aging. Further studies on a larger population should be performed to confirm the results of this pilot study