82 research outputs found
Spectral features of a many-body localized system weakly coupled to a heat bath
We study many-body-localized (MBL) systems that are weakly coupled to
thermalizing environments, focusing on the spectral functions of local
operators. We argue that these spectral functions carry signatures of
localization even away from the limit of perfectly isolated systems. We find
that, in the limit of vanishing coupling to a bath, MBL systems come in two
varieties, with either discrete or continuous local spectra. Both varieties of
MBL systems exhibit a "soft gap" at zero frequency in the spatially-averaged
spectral functions of local operators, which serves as a diagnostic for
localization. We estimate the degree to which coupling to a bath broadens these
spectral features, and find that characteristics of incipient localization
survive as long as the system-bath coupling is much weaker than the
characteristic energy scales of the system. Since perfect isolation is
impossible, we expect the ideas discussed in this paper to be relevant for all
experiments on many-body localization.Comment: Expanded discussion of multiple lengthscales and of properties as a
quantum memor
Understanding the Initial Stages of Reversible Mg Deposition and Stripping in Inorganic Non-Aqueous Electrolytes
Multi-valent (MV) battery architectures based on pairing a Mg metal anode
with a high-voltage ( 3 V) intercalation cathode offer a realistic design
pathway toward significantly surpassing the energy storage performance of
traditional Li-ion based batteries, but there are currently only few
electrolyte systems that support reversible Mg deposition. Using both static
first-principles calculations and molecular dynamics, we perform
a comprehensive adsorption study of several salt and solvent species at the
interface of Mg metal with an electrolyte of Mg and Cl dissolved in
liquid tetrahydrofuran (THF). Our findings not only provide a picture of the
stable species at the interface, but also explain how this system can support
reversible Mg deposition and as such we provide insights in how to design other
electrolytes for Mg plating and stripping. The active depositing species are
identified to be (MgCl) monomers coordinated by THF, which exhibit
preferential adsorption on Mg compared to possible passivating species (such as
THF solvent or neutral MgCl complexes). Upon deposition, the energy to
desolvate these adsorbed complexes and facilitate charge-transfer is shown to
be small ( 61 46.2 kJ mol to remove 3 THF from the strongest
adsorbing complex), and the stable orientations of the adsorbed but desolvated
(MgCl) complexes appear favorable for charge-transfer. Finally,
observations of Mg-Cl dissociation at the Mg surface at very low THF
coordinations (0 and 1) suggest that deleterious Cl incorporation in the anode
may occur upon plating. In the stripping process, this is beneficial by further
facilitating the Mg removal reaction
Foundations of Group Key Management – Framework, Security Model and a Generic Construction
Group Key Establishment is fundamental for a variety of security mechanisms in group applications. It allows n > 1 principals to agree upon a common secret key. This can further be classified into Group Key Exchange (or Group Key Agreement), where all the principals participate in the construction of the key, and Group Key Transport (or Group Key Distribution), where the key is chosen by a singe principal and is then securely communicated to the others. Both these techniques can be analyzed in the context of either static or dynamic groups. Dynamic Group Key Establishment is better known as Group Key Management (GKM), as it involves not only the initital key establishment, but also efficient key management when group members join or leave the group. Dynamic Group Key Exchange is also known as decentralized or distributed GKM, while Dynamic Group Key Transport is known as centralized GKM. While there has been a lot of recent work in formal security models for Dynamic Group Key Exchange, little, if any, attention has been directed towards building a concrete framework and formal security model for centralized GKM. Many such schemes that have been proposed so far have been broken, as they cite ambiguous arguments and lack formal proofs. In this paper, we take a first step towards addressing this problem by providing firm foundations for centralized Group Key Management. We provide a generalized framework for centralized GKM along with a formal security model and strong definitions for the security properties that dynamic groups demand. We also show a generic construction of a centralized GKM scheme from any given multi-receiver ID-based Key Encapsulation Mechanism (mID-KEM). By doing so, we unify two concepts that are significantly different in terms of what they achieve. Our construction is simple and efficient. We prove that the resulting GKM inherits the security of the underlying mID-KEM up to CCA security. We also illustrate our general conversion using the mID-KEM proposed in 2007 by Delerablée
Macro Flora & Fauna of the Gulf of Mannar a checklist
The Gulf of Mannar (GoM) located along the south eastern tip of India falls in the Indo-Pacific realm
and is one of the richest regions in the world from a marine biodiversity perspective. The region has a
distinctive socio-economic and cultural profile shaped by its geography. It has an ancient maritime history
and was famous for the production of pearls, an important item in trade with the Roman Empire as early as
the first century AD. Rameshwaram along the GoM with its links to the legend Ramayana is an important
pilgrim centre. The region has been and continues to be famous for its production of Indian sacred chanks.
It has unique ecosystems mainly consisting of coral reefs, sea grass beds, salt marshes and mangroves
which constitute important habitats for many species of commercially important finfishes and shellfishes.
The GoM was established as a Biosphere Reserve (the first marine biosphere reserve in south and south
east Asia) by 1989 by the Indian Government and the state of Tamil Nadu. A biosphere reserve is an area
that is indented to secure the fundamental diversity of life in a region while continuing to advocate in
economic growth. The overall objective of this Marine Biosphere Reserve is to conserve the Gulf of Mannar's
globally significant assemblage of coastal and marine biodiversity and to integrate biodiversity
conservation into coastal zone management plans. Thus, the GoM in addition to being a national priority
also assumes global significance
Apocyclops cmfri sp. nov. (Cyclopoda : Cyclopoida : Cyclopidae), a new copepod species from Arabian Sea off Karwar, Karnataka, India
A new species of Apocyclops Lindberg (Cyclopoda: Cyclopoida: Cyclopidae) is described based on specimens collected from marine waters of Karwar, Karnataka, India. At present, there are 11 valid and accepted species excluding one extinct species (fossil) in this genus which are widely distributed in fresh and brackishwater areas in the tropics and subtropics. Five valid species of Apocyclops are reported from the Asian region, including two species from India. The new species is closer to the previously reported Indian species, A. royi (Lindberg) and A. dengizicus dengizicus (Lepeshkin). Apocyclops cmfri sp. nov. differs from these in the size of caudal rami, in the characteristic shape of disto-medial part of coxa and basis of first to fourth pleopods (P1-P4) and in the presence of a single broad spinous expansion with a pointed tip in between exopod and endopod in basis of P1 to P4. Only one terminal spine is present in the second segment of endopod of P1. In P2 to P4, both exopod and endopod terminate in a spine and a seta of almost equal size. Maxillule highly dentate and maxilla basis form a large dentate claw with inner serration. All these characters form distinct identification features of the new species in comparison with the 12 accepted species under the genus. A key to all the species of the genus including the newly described species is proposed here. Molecular identification of the new species was carried out by mitochondrial cytochrome c oxidase 1 (CO1) gene sequencing and the sequence was submitted to NCBI, GenBank. Genetic differentiation and divergence between A. cmfri sp. nov. and species belonging to other closely related genera; Thermocyclops, Mesocyclops and Eucyclops were compared using CO1 gene sequences. The new species belonging to Apocyclops showed significant divergence from Apocyclops borneoensis with K2P value of 10.2% and from species under the genera Mesocyclops, Thermocyclops and Eucyclops with K2P values of 26.6, 27.5and
34.9% respectively
Mitochondrial signatures for identification of grouper species from Indian waters
Groupers are important commercial fish in many parts of the world. Accurate identification is
critical for effective conservation assessment and fisheries management. Genetic barcodes provide
a simple and reproducible method for the identification of species even in the absence of
taxonomic expertise. The generation of reference barcodes from properly identified specimens is
an important first step in this direction. Here, 36 species belonging to the subfamily Epinephelinae
(Family: Serranidae) were collected from landings on the west coast of India and Port Blair,
Andaman, and partial nucleotide sequence data of the mitochondrial cytochrome C oxidase
subunit I (COI) gene was generated. Barcodes for 13 species were developed from Indian waters for
the first time. Analysis using the COI gene produced phylogenetic trees in concurrence with other
multi-gene studies. Epinephelus fasciatus and E. areolatus were found to be a species complex, as
hypothesized in other studies. The DNA barcodes developed in the study can be used for
identifying species within Epinehelinae, where taxonomic ambiguity still exists
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