scholarly journals Polonnaruwa Stones Revisited – Evidence for Non-Terrestrial Life

2021 ◽  
Vol 6 (2) ◽  
Author(s):  
Milton Wainwright ◽  
◽  
N. Chandra Wickramasinghe ◽  
◽  
Keyword(s):  
Sri Lanka ◽  
Space Exploration ◽  
Low Density ◽  
Terrestrial Life ◽  
Biological Entities ◽  
Highly Porous

Recent discoveries of highly porous low-density carbonaceous asteroids such as 101955 Bennu and Ryugu have motivated a re-examination of the Polonnaruwa stones which fell in central Sri Lanka on 27 December 2012 following a fireball sighting. Previous discoveries of biological entities including fossilized extinct microorganisms (acritarchs) have tended to be discounted as contaminants for the reason that the stones did not fit into a known meteorite category. In view of the new data from space exploration we re-examine samples of the Polonnaruwa stones and confirm earlier evidence for the existence of diatom frustules and other complex biology.

scholarly journals Productionof poly(L-CO-D,L LacticAcid) porous fibers by electrospinning

2021 ◽  
Vol 3 (2) ◽  
Author(s):  
Nayara Maysa da Silva Carvalho ◽  
Bárbara E. Ciocca ◽  
Rubens Maciel Filho ◽  
Marcele Fonseca Passos ◽  
Maria Regina Wolf Maciel ◽  
...  
Keyword(s):  
Pore Formation ◽  
Scientific Community ◽  
Low Dielectric Constant ◽  
Porous Scaffolds ◽  
Low Density ◽  
Fiber Morphology ◽  
Low Dielectric ◽  
Mean Diameter ◽  
Porous Fibers ◽  
Highly Porous

The production of porous scaffolds has been widely investigated by the scientific community due to its suitability for tissue engineering. Among techniques that allow the fabrication of porous materials, electrospinning is appealing for being robust and versatile. This research investigated the pore formation in poly (L-co-D,L lactic acid) fibers obtained by conventional electrospinning and the influence of chloroform as a single solvent on fiber morphology. Random and highly porous fibers with a mean diameter of 2.373 ± 0.564 µm were collected. Chloroform affects the fiber morphology, mainly for its fast evaporation and low density of charges. The solvent on the surface evaporates quickly, and the low stretch of the jet does not help the polymer to reorganize over the length of the fiber, forming pores. In conclusion, the low dielectric constant and boiling point of chloroform induce pores formation along the PLDLA fibers.  

Highly porous PEM fuel cell cathodes based on low density carbon aerogels as Pt-support: Experimental study of the mass-transport losses

2009 ◽  
Vol 190 (2) ◽  
pp. 423-434 ◽  
Author(s):  
Julien Marie ◽  
Regis Chenitz ◽  
Marian Chatenet ◽  
Sandrine Berthon-Fabry ◽  
Nathalie Cornet ◽  
...  
Keyword(s):  
Experimental Study ◽  
Fuel Cell ◽  
Mass Transport ◽  
Pem Fuel Cell ◽  
Carbon Aerogels ◽  
Low Density ◽  
Transport Losses ◽  
Fuel Cell Cathodes ◽  
Cell Cathodes ◽  
Highly Porous

Erosion protective coatings for low density, highly porous carbon/carbon composites

Carbon ◽  
2009 ◽  
Vol 47 (6) ◽  
pp. 1511-1519 ◽  
Author(s):  
F. Smeacetto ◽  
M. Salvo ◽  
M. Ferraris ◽  
V. Casalegno ◽  
G. Canavese ◽  
...  
Keyword(s):  
Porous Carbon ◽  
Protective Coatings ◽  
Carbon Composites ◽  
Low Density ◽  
Highly Porous

Thermal. Acoustical and Structural Properties of Silica Aerogels

1986 ◽  
Vol 73 ◽  
Author(s):  
J. Fricke ◽  
G. Reichenauer
Keyword(s):  
Optical Properties ◽  
Structural Properties ◽  
Silica Aerogels ◽  
Low Density ◽  
Density Structure ◽  
Secondary Particles ◽  
Window Systems ◽  
Fractal Properties ◽  
Primary Particles ◽  
Highly Porous

ABSTRACTSilica aerogels either in monolithic or in granular form provide excellent thermal insulation and thus may be used as superinsulating spacer in all kinds of window systems. Highly porous aerogels also are exciting acoustic materials with sound velocities in the order of 100 m/s and acoustic impedances between 104 and 105 kg/(m2·s). Silica aerogels produced from TMOS seem to consist of massive primary particles (ø ≅ 1 nm, ρ ≅ 2000 kg/m3) which form secondary particles (ø ≅ 5 to 6 nm, ρ ≅800 kg/in 3) displaying fractal properties (D≅ 2). The further buildup creates the highly porous low-density structure which is responsible for the special thermal, acoustical and optical properties of aerogels. Above about 100 nm, transparent aerogels should be homogeneous.

Partially Hydrolyzed Alkoxysilanes as Precursors for Silica Aerogels

1988 ◽  
Vol 121 ◽  
Author(s):  
T. M. Tillotson ◽  
L. W. Hrubesh ◽  
I. M. Thomas
Keyword(s):  
Sol Gel ◽  
Silica Aerogels ◽  
Low Density ◽  
Density Range ◽  
Moist Air ◽  
Wide Range ◽  
Sol Gel Process ◽  
Hydrolysis Of ◽  
Highly Porous ◽  
Controlled Hydrolysis

ABSTRACTThe classical sol-gel process for synthesizing SiO2 aerogels involves the hydrolysis/condensation of tetraethyoxysilane (TEOS) and/or teramethyoxysilane (TMOS) to produce a gel which can then be super-critically extracted to a low density, highly porous aerogel glass. Controlled hydrolysis of TEOS and TMOS leads to partially hydrolyzed compounds that can be subsequently water processed to form silica aerogels in the density range from .020 to .500 gms/cc. The partially hydrolyzed compounds are stable when sealed from moist air and can be stored for future use.We discuss the controlled conditions used to obtain these compounds and present data that characterize their structure. We detail the procedures for preparing the wide range of aerogel densities. We also report on their use as an adhesive.

scholarly journals Setting the scene: what did we know before Rosetta?

2017 ◽  
Vol 375 (2097) ◽  
pp. 20160247 ◽  
Author(s):  
K. J. Meech
Keyword(s):  
Space Exploration ◽  
Thermal Inertia ◽  
Formation Processes ◽  
Solar System Formation ◽  
Small Bodies ◽  
Porous Bodies ◽  
Rosetta Mission ◽  
Interstellar Material ◽  
Modern Era ◽  
Highly Porous

This paper provides an overview of our state of knowledge about comets prior to the Rosetta mission encounter. Starting with the historical perspective, this paper discusses the development of comet science up to the modern era of space exploration. The extent to which comets are tracers of solar system formation processes or preserve pristine interstellar material has been investigated for over four decades. There is increasing evidence that in contrast with the distinct dynamical comet reservoirs we see today, comet formation regions strongly overlapped in the protoplanetary disc and there was significant migration of material in the disc during the epoch of comet formation. Comet nuclei are now known to be very low-density highly porous bodies, with very low thermal inertia, and have a range of sizes which exhibit a deficiency of very small bodies. The low thermal inertia suggests that comets may preserve pristine materials close to the surface, and that this might be accessible to sample return missions. This article is part of the themed issue ‘Cometary science after Rosetta’.

scholarly journals Mechanical Properties of Ultralow Density Graphene Oxide/Polydimethylsiloxane Foams

MRS Advances ◽  
2018 ◽  
Vol 3 (1-2) ◽  
pp. 61-66
Author(s):  
Cristiano F. Woellner ◽  
Peter S. Owuor ◽  
Tong Li ◽  
Soumya Vinod ◽  
Sehmus Ozden ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Graphene Oxide ◽  
High Performance ◽  
Structural Model ◽  
Md Simulations ◽  
Synthetic Approach ◽  
Low Density ◽  
Thermal Stabilities ◽  
Freeze Dried ◽  
Highly Porous

ABSTRACTLow-density, highly porous graphene/graphene oxide (GO) based-foams have shown high performance in energy absorption applications, even under high compressive deformations. In general, foams are very effective as energy dissipative materials and have been widely used in many areas such as automotive, aerospace and biomedical industries. In the case of graphene-based foams, the good mechanical properties are mainly attributed to the intrinsic graphene and/or GO electronic and mechanical properties. Despite the attractive physical properties of graphene/GO based-foams, their structural and thermal stabilities are still a problem for some applications. For instance, they are easily degraded when placed in flowing solutions, either by the collapsing of their layers or just by structural disintegration into small pieces. Recently, a new and scalable synthetic approach to produce low-density 3D macroscopic GO structure interconnected with polydimethylsiloxane (PDMS) polymeric chains (pGO) was proposed. A controlled amount of PDMS is infused into the freeze-dried foam resulting into a very rigid structure with improved mechanical properties, such as tensile plasticity and toughness. The PDMS wets the graphene oxide sheets and acts like a glue bonding PDMS and GO sheets. In order to obtain further insights on mechanisms behind the enhanced mechanical pGO response we carried out fully atomistic molecular dynamics (MD) simulations. Based on MD results, we build up a structural model that can explain the experimentally observed mechanical behavior.

scholarly journals Low-Density Urbanism in Medieval Sri Lanka: Exploring the Hinterland of Polonnaruva

2021 ◽  
Vol 60 (2) ◽  
pp. 248-271
Author(s):  
Mark Manuel ◽  
Prishanta Gunawardhana ◽  
Harendralal Namalgamuwa ◽  
Robin Coningham ◽  
Christopher Davis ◽  
...  
Keyword(s):  
Sri Lanka ◽  
Low Density

Banana fiber/low-density polyethylene recycled composites for third world eco-friendly construction applications – Waste for life project Sri Lanka

2018 ◽  
Vol 37 (21) ◽  
pp. 1322-1331 ◽  
Author(s):  
Sean Bolduc ◽  
Kyungmin Jung ◽  
Pramathanath Venkata ◽  
Mascareneous Ashokcline ◽  
Randika Jayasinghe ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Sri Lanka ◽  
Agricultural Waste ◽  
Fiber Content ◽  
Low Density Polyethylene ◽  
Low Density ◽  
Scanning Calorimetry ◽  
Banana Fiber ◽  
Fourfold Increase ◽  
Banana Fibers

In the framework of the waste for life Sri Lanka project, low value industrial low-density polyethylene waste plastics and banana fibers made from agricultural waste are upcycled into affordable eco-friendly building products. This creates income for the local communities while mitigating waste disposal and reducing ecological problems. Within this context, a robust manufacturing method using compression molding was developed. Panels with varying fiber content were manufactured using unchopped and chopped fibers. Low-density polyethylene characterization using Fourier transform infrared spectroscopy and differential scanning calorimetry to compare plastic sources was conducted. To reduce cost, no fiber treatments or compatibilizers were used. An estimate of critical fiber length was found to be around 1.45 cm to 2.5 cm. A trend of increasing strength with fiber content (up to 40 wt.%) was achieved by using longer fibers than in the previous research. Handling and dispersion of the fibers were increased by chopping the fibers to 20 cm lengths, which led to an increase in tensile strength due to easier manufacturing. Cross-ply panels made with fibers chopped to a length of 20 cm were found to be strongest peaking at around 40 wt.% with a tensile strength of 32.8 MPa, a fourfold increase compared to a raw low-density polyethylene (0 wt.%) panel.

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