4,725 research outputs found
Rate of Spread of Introduced Rhodophytes Kappaphycus alvarezii, Kappaphycus striatum, and Gracilaria salicornia and Their Current Distribution in Kane'ohe Bay, O'ahu Hawai'i
Spread of the introduced macroalgae Kappaphycus alvarezii
(Doty), Kappaphycus striatum Schmitz, and Graci/aria salicornia C. Ag. was
measured on reefs in Kane'ohe Bay, O'ahu, Hawai'i. The red algae Kappaphycus
alvarezii and Gracilaria salicornia were introduced to specific sites in
Kane'ohe Bay in the 1970s. Since that time their distributions have increased,
and the algae have spread through the bay. To assess the current extent of these
algae in the bay and determine their rate of spread, we performed surveys with
a manta towboard. In addition, abundance of these species was determined by
detailed reef transects in the central bay in three habitats: barrier reef, patch
reef, and fringing reef. All three species have become well established. These
algae were found in all areas of Kane'ohe Bay. Distributions are not uniform
within the central bay. Abundance of Kappaphycus spp. was highest on patch
reefs in shallow water. Gracilaria salicornia was most abundant on the fringing
reef. Kappaphycus alvarezii and K. striatum have spread 6km from their points
of introduction in 1974, an average rate of spread of approximately 250 m yet.
Gracilaria salicornia has spread over 5 km since its introduction in 1978, an
average rate of spread of approximately 280 m yr -1. High abundance of these
introduced species appears to be associated with moderate water motion
Submillimeter satellite radiometer first semiannual engineering progress report
Development of 560 GHz fourth harmonic mixer and 140 GHz third harmonic generator for use in radiomete
Nonlinear models of the bump cepheid HV 905 and the distance modulus to the large magellanic cloud
Nonlinear pulsation models have been used to simulate the light curve of the LMC bump Cepheid HV 905. In order to reproduce the light curve accurately, tight constraints on the input parameters M, L, and T-eff are required. The results, combined with accurate existing V and I photometry, yield an LMC distance modulus of 18.51 +/- 0.05, and they show that the luminosity of HV 905 is much higher than expected from the mass-luminosity relation of stellar evolution theory. If we assume that the pulsation models are accurate, this suggests that there is a larger amount of convective core overshoot during the main-sequence evolution of stars with M similar to 5 M. than is usually assumed
Why does the Engel method work? Food demand, economies of size and household survey methods
Estimates of household size economies are needed for the analysis of poverty and inequality. This paper shows that Engel estimates of size economies are large when household expenditures are obtained by respondent recall but small when expenditures are obtained by daily recording in diaries. Expenditure estimates from recall surveys appear to have measurement errors correlated with household size. As well as demonstrating the fragility of Engel estimates of size economies, these results help resolve a puzzle raised by Deaton and Paxson (1998) about differences between rich and poor countries in the effect of household size on food demand
Sparse random matrices: the eigenvalue spectrum revisited
We revisit the derivation of the density of states of sparse random matrices.
We derive a recursion relation that allows one to compute the spectrum of the
matrix of incidence for finite trees that determines completely the low
concentration limit. Using the iterative scheme introduced by Biroli and
Monasson [J. Phys. A 32, L255 (1999)] we find an approximate expression for the
density of states expected to hold exactly in the opposite limit of large but
finite concentration. The combination of the two methods yields a very simple
simple geometric interpretation of the tails of the spectrum. We test the
analytic results with numerical simulations and we suggest an indirect
numerical method to explore the tails of the spectrum.Comment: 18 pages, 7 figures. Accepted version, minor corrections, references
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Phenotypes of the ovarian follicular basal lamina predict developmental competence of oocytes
BACKGROUND: The ovarian follicular basal lamina underlies the epithelial membrana granulosa and maintains the avascular intra-follicular compartment. Additional layers of basal lamina occur in a number of pathologies, including pili annulati and diabetes. We previously found additional layers of follicular basal lamina in a significant percentage of healthy bovine follicles. We wished to determine if this phenomenon existed in humans, and if it was related to oocyte function in the bovine. METHODS: AND RESULTS: We examined follicles from human ovaries (n = 18) by electron microscopy and found that many follicles had additional layers of basal lamina. Oocytes (n = 222) from bovine follicles with normal or unusual basal laminas were isolated and their ability to undergo in vitro maturation, fertilization and culture to blastocyst was compared. Healthy bovine follicles with a single layer of basal lamina had oocytes with significantly (P < 0.01) greater developmental competence than healthy follicles with additional layers of follicular basal lamina (65 versus 28). CONCLUSIONS: These findings provide direct evidence that the phenotype of the follicular basal lamina is related to oocyte competence
Norm-dependent Random Matrix Ensembles in External Field and Supersymmetry
The class of norm-dependent Random Matrix Ensembles is studied in the
presence of an external field. The probability density in those ensembles
depends on the trace of the squared random matrices, but is otherwise
arbitrary. An exact mapping to superspace is performed. A transformation
formula is derived which gives the probability density in superspace as a
single integral over the probability density in ordinary space. This is done
for orthogonal, unitary and symplectic symmetry. In the case of unitary
symmetry, some explicit results for the correlation functions are derived.Comment: 19 page
A coarse grained model of granular compaction and relaxation
We introduce a theoretical model for the compaction of granular materials by discrete vibrations which is expected to hold when the intensity of vibration is low. The dynamical unit is taken to be clusters of granules that belong to the same collective structure. We rigourously construct the model from first principles and show that numerical solutions compare favourably with a range of experimental results. This includes the logarithmic relaxation towards a statistical steady state, the effect of varying the intensity of vibration resulting in a so-called `annealing' curve, and the power spectrum of density fluctuations in the steady state itself. A mean-field version of the model is introduced which shares many features with the exact model and is open to quantitative analysi
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