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Search Results: 1 - 10 of 222949 matches for " Lisa C. Davenport "
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Aid to a Declining Matriarch in the Giant Otter (Pteronura brasiliensis)
Lisa C. Davenport
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0011385
Abstract: Scientists are increasingly revealing the commonalities between the intellectual, emotional and moral capacities of animals and humans. Providing assistance to elderly and ailing family members is a human trait rarely documented for wild animals, other than anecdotal accounts. Here I report observations of multiple forms of assistance to the declining matriarch of a habituated group of giant otters (Pteronura brasiliensis) in Manu National Park, Peru. The otter group had been observed annually for several years and all members were known individually. In 2007, the breeding female of the group failed to reproduce and appeared to be in physical decline. She begged from other family members 43 times over 41 contact hours and received food 11 times. Comparisons with 2004–2006 demonstrate that the family's behavior in 2007 constitutes a role-reversal, in which the majority of assistance and prey transfers accrued from young-to-old rather than from old-to-young. As in human societies, both non-adaptive and adaptive hypotheses could explain the family members' aid to their declining matriarch. I suggest that giant otter families may benefit from the knowledge and experience of an elderly matriarch and “grandparent helper,” consistent with the “Grandmother Hypothesis” of adaptive menopause in women.
East with the Night: Longitudinal Migration of the Orinoco Goose (Neochen jubata) between Manú National Park, Peru and the Llanos de Moxos, Bolivia
Lisa C. Davenport, Inés Nole Bazán, Nancy Carlos Erazo
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0046886
Abstract: We report on the intra-Amazonian migration of a pair of Orinoco Geese (Neochen jubata) from Manú National Park, Peru. The species is Critically Endangered in Peru, so a major aim of the study was to aid conservation planning by learning the wet season location of the country's last known breeding population. We captured a breeding pair on October 27, 2010, and fitted the birds with Microwave Telemetry, Inc. GPS/Argos satellite PTT's. The pair migrated ~655 km from Manú National Park to the Llanos de Moxos, Bolivia (Dept. of Bení) in a predominantly longitudinal migration, reaching their final destination on December 23, 2010. Major movements (>5 km per time period) were almost exclusively at night and were undertaken with and without moonlight. Foraging areas used at stopovers in the Llanos de Moxos were remarkably limited, suggesting the importance of grazing lawns maintained by the geese and other herbivores, possibly including cattle. Orinoco Geese are resident in the Llanos de Moxos year-round, so the Manú geese represent a partial migration from the Bení region. We hypothesize that cavity nest limitation explains the partial migration of Orinoco Geese from the Llanos de Moxos.
Preliminary Findings from a New Study of the Congo Clawless Otter (Aonyx congicus) on the Dji Dji River, Ivindo National Park, Gabon (or “Where Have all the Otters Gone?”)
Lisa C. Davenport,Hélène Jacques,Marie-Louise Yedi
IUCN Otter Specialist Group Bulletin , 2011,
Abstract: The Congo Clawless Otter (Aonyx congicus), is a little-known otter species that inhabits central African rivers and swamps. We report on the results of 3 field expeditions into the Dji Dji River, (Ivindo National Park, Gabon) of varying length (3 days to 6 weeks) to collect preliminary observations on this species, the sympatric spot-necked otter (Lutra maculicollis), and the fish community of the Dji Dji River. We also surveyed local people (primarily artisanal fishermen) in the Makokou area of Ivindo National Park about their knowledge of otter species and human/wildlife conflicts in the area. Sightings of otters in 2010 indicated both otter species to be common on the Dji Dji River. Fish sampling in 2011 indicated high abundance but low diversity of fishes in this blackwater river. Feeding observations of a solitary animal on the Dji Dji and a family of 3 on the Ivindo River indicate a high dependence on large earthworms (Annelidae) captured near the river’s edge. With a severe drought in 2011 affecting the Dji Dji River level, we found fewer otters compared to 2010 observations and no families with young. We speculate on the possibility of seasonal downstream movements, which could affect conservation of the species in the region.
Biliary atresia
Sinha C,Davenport Mark
Journal of Indian Association of Pediatric Surgeons , 2008,
Abstract: Biliary atresia (BA) is a cholangiodestructive disease affecting biliary tract, which ultimately leads to cirrhosis, liver failure and death if not treated. The incidence is higher in Asian countries than in Europe. Up to 10% of cases have other congenital anomalies, such as polysplenia, asplenia, situs inversus, absence of inferior vena cava and pre-duodenal portal vein, for which we have coined the term Biliary Atresia Splenic Malformation (BASM) syndrome. For these infants the aetiology lies within the first trimester of gestation. For others affected with BA, aetiology is more obscure and perinatal destruction of fully-formed ducts perhaps by the action of hepatotropic viruses has been suggested. Whatever the cause, the lumen of the extrahepatic duct is obliterated at a variable level and this forms the basis for the commonest classification (Types I, II, III). All patients with BA present with varying degree of conjugated jaundice, pale non-pigmented stools and dark urine. Key diagnostic tests include ultrasonography, biochemical liver function tests, viral serology, and (in our centre) a percutaneous liver biopsy. In some centres, duodenal intubation and measurement of intralumenal bile is the norm. Currently BA is being managed in two stages. The first stage involves the Kasai operation, which essentially excises all extrahepatic biliary remnants leaving a transected portal plate, followed by biliary reconstruction using a Roux loop onto that plate as a portoenterostomy. If bile flow is not restored by Kasai procedure or life-threatening complications of cirrhosis ensue then consideration should be given to liver transplantation as a second stage. The outcome following the Kasai operation can be assessed in two ways: clearance of jaundice to normal values and the proportion who survive with their native liver. Clearance of jaundice (< 2 mg/dL or < 34 μmol/L) after Kasai has been reported to be around 60%, whereas five years survival with native liver ranges from 40% to 65%.
Ferromagnetic--nematic order and strongly correlated phases of fermions in optical flux lattices
Simon C. Davenport,Nigel R. Cooper
Physics , 2015, DOI: 10.1103/PhysRevA.92.023608
Abstract: We study a model of a 2D ultracold atomic gas subject to an "optical flux lattice": a laser configuration where Raman-dressed atoms experience a strong artificial magnetic field. This leads to a bandstructure of narrow energy bands with non-zero Chern numbers. We consider the case of two-level (spin-$1/2$) fermionic atoms in this lattice, interacting via a repulsive $s$-wave contact interaction. Atoms restricted to the lowest band are described by an effective model of spinless fermions with interactions that couple states in a momentum-dependent manner across the Brillouin zone; a consequence of the Raman dressing of the two spin states. We present the results of detailed exact diagonalization studies of the many-body states for a range of filling factors, $\nu$. First, we present evidence for the existence of a phase with coupled ferromagnetic--nematic ordering, which was previously suggested by a mean-field analysis. Second, we present evidence indicating the presence of a Laughlin-like fractional quantum Hall state occurring at filling factor $\nu = 1/3$. Finally, we observe a charge density wave state at $\nu=1/2$, which we are able to cleanly distinguish from the Laughlin-like state by its translational symmetry breaking and relatively small participation ratio.
Spinful Composite Fermions in a Negative Effective Field
Simon C. Davenport,Steven H. Simon
Physics , 2012, DOI: 10.1103/PhysRevB.85.245303
Abstract: In this paper we study fractional quantum Hall composite fermion wavefunctions at filling fractions \nu = 2/3, 3/5, and 4/7. At each of these filling fractions, there are several possible wavefunctions with different spin polarizations, depending on how many spin-up or spin-down composite fermion Landau levels are occupied. We calculate the energy of the possible composite fermion wavefunctions and we predict transitions between ground states of different spin polarizations as the ratio of Zeeman energy to Coulomb energy is varied. Previously, several experiments have observed such transitions between states of differing spin polarization and we make direct comparison of our predictions to these experiments. For more detailed comparison between theory and experiment, we also include finite-thickness effects in our calculations. We find reasonable qualitative agreement between the experiments and composite fermion theory. Finally, we consider composite fermion states at filling factors \nu = 2+2/3, 2+3/5, and 2+4/7. The latter two cases we predict to be spin polarized even at zero Zeeman energy.
Multi-Particle Pseudopotentials for Multi-Component Quantum Hall Systems
Simon C. Davenport,Steven H. Simon
Physics , 2011, DOI: 10.1103/PhysRevB.85.075430
Abstract: The Haldane pseudopotential construction has been an extremely powerful concept in quantum Hall physics --- it not only gives a minimal description of the space of Hamiltonians but also suggests special model Hamiltonians (those where certain pseudopotential are set to zero) that may have exactly solvable ground states with interesting properties. The purpose of this paper is to generalize the pseudopotential construction to situations where interactions are N-body and where the particles may have internal degrees of freedom such as spin or valley index. Assuming a rotationally invariant Hamiltonian, the essence of the problem is to obtain a full basis of wavefunctions for N particles with fixed relative angular momentum L. This basis decomposes into representations of SU(n) with n the number of internal degrees of freedom. We give special attention to the case where the internal degree of freedom has n=2 states, which encompasses the important cases of spin-1/2 particles and quantum Hall bilayers. We also discuss in some detail the cases of spin-1 particles (n=3) and graphene (n=4, including two spin and two valley degrees of freedom).
Spin-singlet Gaffnian wave function for fractional quantum Hall systems
Simon C. Davenport,Eddy Ardonne,Nicolas Regnault,Steven H. Simon
Physics , 2012, DOI: 10.1103/PhysRevB.87.045310
Abstract: We characterize in detail a wave function conceivable in fractional quantum Hall systems where a spin or equivalent degree of freedom is present. This wave function combines the properties of two previously proposed quantum Hall wave functions, namely the non-Abelian spin-singlet state and the nonunitary Gaffnian wave function. This is a spin-singlet generalization of the spin-polarized Gaffnian, which we call the "spin-singlet Gaffnian" (SSG). In this paper we present evidence demonstrating that the SSG corresponds to the ground state of a certain local Hamiltonian, which we explicitly construct, and, further, we provide a relatively simple analytic expression for the unique ground-state wave functions, which we define as the zero energy eigenstates of that local Hamiltonian. In addition, we have determined a certain nonunitary, rational conformal field theory which provides an underlying description of the SSG and we thus conclude that the SSG is ungapped in the thermodynamic limit. In order to verify our construction, we implement two recently proposed techniques for the analysis of fractional quantum Hall trial states: The "spin dressed squeezing algorithm", and the "generalized Pauli principle".
Critical role of the circadian clock in memory formation: lessons from Aplysia
Lisa C. Lyons
Frontiers in Molecular Neuroscience , 2011, DOI: 10.3389/fnmol.2011.00052
Abstract: Unraveling the complexities of learning and the formation of memory requires identification of the cellular and molecular processes through which neural plasticity arises as well as recognition of the conditions or factors through which those processes are modulated. With its relatively simple nervous system, the marine mollusk Aplysia californica has proven an outstanding model system for studies of memory formation and identification of the molecular mechanisms underlying learned behaviors, including classical and operant associative learning paradigms and non-associative behaviors. In vivo behavioral studies in Aplysia have significantly furthered our understanding of how the endogenous circadian clock modulates memory formation. Sensitization of the tail-siphon withdrawal reflex represents a defensive non-associative learned behavior for which the circadian clock strongly modulates intermediate and long-term memory formation. Likewise, Aplysia exhibit circadian rhythms in long-term memory, but not short-term memory, for an operant associative learning paradigm. This review focuses on circadian modulation of intermediate and long-term memory and the putative mechanisms through which this modulation occurs. Additionally, potential functions and the adaptive advantages of time of day pressure on memory formation are considered. The influence of the circadian clock on learning and memory crosses distant phylogeny highlighting the evolutionary importance of the circadian clock on metabolic, physiological, and behavioral processes. Thus, studies in a simple invertebrate model system have and will continue to provide critical mechanistic insights to complementary processes in higher organisms.
Group cohomology construction of the cohomology of moduli spaces of flat connections on 2-manifolds
Lisa C. Jeffrey
Physics , 1994,
Abstract: We use group cohomology and the de Rham complex on simplicial manifolds to give explicit differential forms representing generators of the cohomology rings of moduli spaces of representations of fundamental groups of 2-manifolds. These generators are constructed using the de Rham representatives for the cohomology of classifying spaces $BK$ where $K$ is a compact Lie group; such representatives (universal characteristic classes) were found by Bott and Shulman. Thus our representatives for the generators of the cohomology of moduli spaces are given explicitly in terms of the Maurer-Cartan form. This work solves a problem posed by Weinstein, who gave a corresponding construction (following Karshon and Goldman) of the symplectic forms on these moduli spaces. We also give a corresponding construction of equivariant differential forms on the extended moduli space $X$, which is a finite dimensional symplectic space equipped with a Hamiltonian action of $K$ for which the symplectic reduced space is the moduli space of representations of the 2-manifold fundamental group in $K$. (This paper is in press in Duke Math. J. The substance of the text is unaltered; inor changes and corrections have been made to the file to correspond to the version that will be published.)
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