Increase of an introduced bird competitor in old-growth forest associated with restoration

Many successful invasions involve long initial periods in which the invader exists at low densities followed by sudden population increases. The reasons for such time-lags remain poorly understood. Here we document a sudden increase in density of the introduced Japanese white-eye (Zosterops japonicus) in a restoration area contiguous with old-growth forest at Hakalau Forest National Wildlife Refuge on the Island of Hawaii. The refuge, with very high density of native birds, existed in a pocket of low whiteeye density that persisted for at least 20 years since the late 1970s. The refuge began an extensive native trees restoration project in 1989 within a 1314 ha abandoned pasture above old-growth forest. This area was soon colonized by white-eyes and their population grew exponentially once the trees had grown tall enough to develop a canopy. This increase was in turn followed by significantly more white-eyes in the open and closed forests adjacent to the restoration area. Competition between white-eyes and native species was documented on study sites within these forests. Density data indicate that competition was more widespread, with loss of tens of thousands of native birds in the 5371 ha area surveyed. Our results are consistent with the view that ecological barriers may delay the population increase of invaders and that human-derived activities may help invaders cross these barriers by creating new ecological opportunities. Control of white-eye numbers may be essential for recovery of native species

Viscoplasticity: A thermodynamic formulation

A thermodynamic foundation using the concept of internal state variables is given for a general theory of viscoplasticity, as it applies to initially isotropic materials. Three fundamental internal state variables are admitted. They are: a tensor valued back stress for kinematic effects, and the scalar valued drag and yield strengths for isotropic effects. All three are considered to phenomenologically evolve according to competitive processes between strain hardening, strain induced dynamic recovery, and time induced static recovery. Within this phenomenological framework, a thermodynamically admissible set of evolution equations is put forth. This theory allows each of the three fundamental internal variables to be composed as a sum of independently evolving constituents

A Large k Asymptotics of Witten's Invariant of Seifert Manifolds

We calculate a large $k$ asymptotic expansion of the exact surgery formula for Witten's $SU(2)$ invariant of Seifert manifolds. The contributions of all flat connections are identified. An agreement with the 1-loop formula is checked. A contribution of the irreducible connections appears to contain only a finite number of terms in the asymptotic series. A 2-loop correction to the contribution of the trivial connection is found to be proportional to Casson's invariant.Comment: 51 pages (Some changes are made to the Discussion section. A surgery formula for perturbative corrections to the contribution of the trivial connection is suggested.

Annual Survey of Virginia Law: Corporate and Business Law

Corporate and business law has undergone a variety of changes in the past two years. This article summarizes the developments that occurred in this area of the law from June 1996, through June 1998. In 1997, the Virginia General Assembly amended numerous provisions of the Virginia Code. The amendments became effective January 1, 1998. Virginia state courts and the federal courts have issued opinions which have impacted the law in this area. Part II examines the abundant legislative changes made to title 13.1 of the Virginia Code and the recent judicial decisions affecting corporations. Most of the changes discussed were made by the 1997 Session of the Virginia General Assembly. The 1998 Session made very few notable changes to the Virginia Code. Part M discusses the recent legislative and judicial developments affecting limited liability companies. And finally, Part IV reviews the recent legislative developments affecting partnerships, but does not address the amendments to the Virginia Uniform Partnership Act which were made by the General Assembly in its 1996 Session

Characterization of the Bioluminescent Symbionts from Ceratioids Collected in the Gulf of Mexico

Anglerfishes are easily one of the most popular deep-sea creatures due to their menacing appearance, extreme sexual dimorphism, parasitic mating approach, and eye catching bioluminescent lure. Unlike most bioluminescent fishes, which intrinsically generate light, female anglerfishes belonging to nine of the 11 families within the suborder Ceratioidei (deep-sea anglerfishes) have developed a symbiotic relationship with bioluminescent bacteria that are housed within the light organs. Previous molecular work had identified symbionts from two anglerfish species as novel and possibly unculturable taxa (Haygood et al., 1992), but nothing more has been revealed about the bioluminecent symbionts of ceratioids. As part of the Gulf of Mexico Research Initiative-funded DEEPEND project (Deependconsortium.org), the objective of this study is to characterize the escal microbiome of deep-sea anglerfishes and identify potential-symbiont taxa. A total of 36 anglerfish specimens were collected on DEEPEND cruises DP01 through DP04. These specimens consist of adult and larval individuals belonging to six of the families with the suborder Ceratioidei: Ceratiidae (n=22), Oneirodidae (n=7), Linophrynidae (n=3), Melanocetidae (n=2), Centrophrynidae (n=1), Melanocetidae (n=2), Gigantactinidae (n=1). DNA was extracted from esca, skin, fin, gill, gut, and caruncle tissues, as well as seawater. High-throughput sequencing of the 16S rRNA hypervariable V4 region was carried out using the Illumina MiSeq. Sequencing revealed five potential bioluminescent-symbiont taxa (OTU IDs: 9129, 9131, 160210, 523223, and 939811), which had the greatest relative abundance (25.2% - 98.7%) within 12 of 21 adult specimens. These taxa belong to the family Vibrionaceae and were found at greater than 10% relative abundance in the escal samples of adult anglerfishes belonging to the Ceratiidae and Melanocetidae families, but they were not found in high abundance in larval individuals of the same families. Sequencing of larval samples revealed five potential bioluminescent-symbiont taxa (OTU IDs: 136178, 176420, 523223, 837366, 939811) which were of greatest relative abundance (8.1%-67.1%) within nine of 13 specimens. Also members of the family Vibrionaceae, these taxa were found in high abundance in larval anglerfishes belonging to the Oneirodidae, Linophrynidae, Gigantactinidae, and Ceratiidae families. This study is the first to to examine the bioluminescent symbionts from seven different ceratioid families

Formation of Cosmic Dust Bunnies

Planetary formation is an efficient process now thought to take place on a relatively short astronomical time scale. Recent observations have shown that the dust surrounding a protostar emits more efficiently at longer wavelengths as the protoplanetary disk evolves, suggesting that the dust particles are coagulating into fluffy aggregates, "much as dust bunnies form under a bed." One poorly understood problem in this coagulation process is the manner in which micron-sized, charged grains form the fractal aggregate structures now thought to be the precursors of protoplanetary disk evolution. This study examines the characteristics of such fractal aggregates formed by the collision of spherical monomers and aggregates where the charge is distributed over the aggregate structure. The aggregates are free to rotate due to collisions and dipole-dipole electrostatic interactions. Comparisons are made for different precursor size distributions and like-charged, oppositelycharged, and neutral grains

On the thermodynamics of stress rate in the evolution of back stress in viscoplasticity

A thermodynamic foundation using the concept of internal state variables is presented for the kinematic description of a viscoplastic material. Three different evolution equations for the back stress are considered. The first is that of classical, nonlinear, kinematic hardening. The other two include a contribution that is linear in stress rate. Choosing an appropriate change in variables can remove this stress rate dependence. As a result, one of these two models is shown to be equivalent to the classical, kinematic hardening model; while the other is a new model, one which seems to have favorable characteristics for representing ratchetting behavior. All three models are thermodynamically admissible

Residue Formulas for the Large k Asymptotics of Witten's Invariants of Seifert Manifolds. The Case of SU(2)

We derive the large k asymptotics of the surgery formula for SU(2) Witten's invariants of general Seifert manifolds. The contributions of connected components of the moduli space of flat connections are identified. The contributions of irreducible connections are presented in a residue form. This form is similar to the one used by A. Szenes, L. Jeffrey and F. Kirwan. This similarity allows us to express the contributions of irreducible connections in terms of intersection numbers on their moduli spaces.Comment: 39 pages, no figures, LaTe

Witten's Invariants of Rational Homology Spheres at Prime Values of KK and Trivial Connection Contribution

We establish a relation between the coefficients of asymptotic expansion of trivial connection contribution to Witten's invariant of rational homology spheres and the invariants that T.~Ohtsuki extracted from Witten's invariant at prime values of $K$. We also rederive the properties of prime $K$ invariants discovered by H.~Murakami and T.~Ohtsuki. We do this by using the bounds on Taylor series expansion of the Jones polynomial of algebraically split links, studied in our previous paper. These bounds are enough to prove that Ohtsuki's invariants are of finite type. The relation between Ohtsuki's invariants and trivial connection contribution is verified explicitly for lens spaces and Seifert manifolds.Comment: 32 pages, no figures, LaTe