On periodic cohort solurions of a size-structured population model

We consider a size-structured population model with discontinuous reproduction and feedback through the environmental variable ``substrate''. The model admits solutions with finitely many cohorts and in that case the problem is described by a system of ODEs involving a bifurcation parameter $beta$. Existence of nontrivial periodic $n$-cohort solutions is investigated. Moreover, we discuss the question whether $n$ cohorts ($n ge 2$) with small size differences will tend to a periodic one-cohort solution as $t to infty$

A modified electromagnetism-like algorithm based on a pattern search method

The Electromagnetism-like (EM) algorithm, developed by Birbil and Fang [2] is a population-based stochastic global optimization algorithm that uses an attraction-repulsion mechanism to move sample points towards optimality. A typical EM algorithm for solving continuous bound constrained optimization problems performs a local search in order to gather information for a point, in the population. Here, we propose a new local search procedure based on the original pattern search method of Hooke and Jeeves, which is simple to implement and does not require any derivative information. The proposed method is applied to different test problems from the literature and compared with the original EM algorithm.(undefined

A hybrid multiagent approach for global trajectory optimization

In this paper we consider a global optimization method for space trajectory design problems. The method, which actually aims at finding not only the global minimizer but a whole set of low-lying local minimizers(corresponding to a set of different design options), is based on a domain decomposition technique where each subdomain is evaluated through a procedure based on the evolution of a population of agents. The method is applied to two space trajectory design problems and compared with existing deterministic and stochastic global optimization methods

The Effect of Rainfall on the Surface Layer during a Westerly Wind Burst in the Western Equatorial Pacific

Measurements of a fresh surface anomaly (fresh lens) produced by rainfall during a westerly wind burst have been analyzed. The measurements were made in December 1992 as part of the Coupled Ocean–Atmosphere Response Experiment in the western equatorial Pacific (2°S, 156°E). Measurements included radar estimates of rainfall, upper-ocean temperature (T), salinity (S), horizontal velocity, and microstructure. In situ observations of the fresh lens were made 5 to 7 hours after its formation. In the 5 hours after formation, the lens deepened to a depth of 40 m as indicated by its salinity anomaly. Salinity and temperature were highly correlated within the lens, consistent with its initial formation by cold rainfall. The T–S relation exhibited curvature, which can be explained by surface cooling and upper-ocean mixing subsequent to formation of the lens. The lens exhibited a horizontal velocity anomaly in the direction of wind, which extended down to a depth of 40 m. The horizontal velocity anomaly is consistent with momentum being trapped near the surface due to rain-induced stratification. Vertical velocity, estimated from the divergence of zonal velocity, showed downwelling at the leading edge of the lens and upwelling at the trailing edge. The magnitude of vertical velocity at a depth of 20 m is 20 m day⁻¹. Richardson numbers within the lens were low (0.25 to 0.5), suggesting that turbulent mixing was governed by critical-Ri instability. Wavenumber spectra of T and S in the upper 20 m exhibit a −5/3 range, which extends to wavenumbers below the range of local isotropy. Spectral levels were used to estimate turbulent dissipation rates of T and S, which were in turn used to estimate turbulent fluxes of heat and salt. Turbulent fluxes were also estimated from microstructure observations between depths of 10 and 60 m. Fluxes within the fresh lens were nearly uniform from 2 m to 35 m depth, then decreased to near zero at 45 m. The lifetime of fresh lenses during westerly wind bursts appears to be less than one day

Horizontal wave number spectra of temperature in the unstably stratified oceanic surface layer

Horizontal wave number spectra of temperature in the unstably stratified oceanic surface layer were determined from measurements on a bow boom at a depth of 2 m. Spectra were estimated in the wavelength band from 2 m to 2 km, normalized in accordance with Monin-Obukhov similarity theory, and averaged in groups with similar stability parameter and fractional mixed layer depth. The shapes of the wave number-weighted oceanic spectra agree qualitatively with observed and modeled atmospheric spectra, including the wavelength of the peaks and the variation of peak wave number with stability. However, the peak spectral levels disagree by as much as a factor of two and the variation of spectral level with stability is in the opposite sense for the oceanic and atmospheric spectra. The wave number of the peak in the near neutral oceanic spectrum is similar to the wave number of the peak in the longitudinal velocity spectrum observed in the atmospheric surface layer, which is consistent with temperature acting as a passive tracer in near neutral conditions. The wave number of the peak in the free convection oceanic spectrum is similar to the wave number of the peak in the spectrum of vertical velocity observed in the atmospheric surface layer during free convection, which reflects the dynamical role played by temperature in a freely convecting boundary layer. The difference between oceanic and modeled near-neutral spectral levels at a wavelength of 2 m suggests that dissipation could be enhanced (u p to a factor of three) by surface wave breaking

Estrogen inhibits GH signaling by suppressing GH-induced JAK2 phosphorylation, an effect mediated by SOCS-2

Oral estrogen administration attenuates the metabolic action of growth hormone (GH) in humans. To investigate the mechanism involved, we studied the effects of estrogen on GH signaling through Janus kinase (JAK)2 and the signal transducers and activators of transcription (STATs) in HEK293 cells stably expressing the GH receptor (293GHR), HuH7 (hepatoma) and T-47D (breast cancer) cells. 293GHR cells were transiently transfected with an estrogen receptor-α expression plasmid and luciferase reporters with binding elements for STAT3 and STAT5 or the β-casein promoter. GH stimulated the reporter activities by four- to sixfold. Cotreatment with 17β-estradiol (E2) resulted in a dose-dependent reduction in the response of all three reporters to GH to a maximum of 49-66% of control at 100 nM (P < 0.05). No reduction was seen when E2 was added 1-2 h after GH treatment. Similar inhibitory effects were observed in HuH7 and T-47D cells. E2 suppressed GH-induced JAK2 phosphorylation, an effect attenuated by actinomycin D, suggesting a requirement for gene expression. Next, we investigated the role of the suppressors of cytokine signaling (SOCS) in E2 inhibition. E2 increased the mRNA abundance of SOCS-2 but not SOCS-1 and SOCS-3 in HEK293 cells. The inhibitory effect of E2 was absent in cells lacking SOCS-2 but not in those lacking SOCS-1 and SOCS-3. In conclusion, estrogen inhibits GH signaling, an action mediated by SOCS-2. This paper provides evidence for regulatory interaction between a sex steroid and the GH/JAK/STAT pathway, in which SOCS-2 plays a central mechanistic role

Preliminary Cruise Report, W0408D and W0409A, R/V WECOMA, 30 August – 3 September and 7-9 September 2004 : GLOBEC NEP Long-Term Observations off Oregon

PURPOSE (W0408D): To determine physical, plankton and nutrient/chemical conditions over the continental margin for climate change studies in NE Pacific. In particular, to make CTD and CTD/ rosette and net tow stations along 3 lines (off Newport, Strawberry Hill and Heceta Head, OR.), and to make continuous observations of currents using ADCP and of surface-layer temperature, salinity and fluorescence by means of ship’s thru-flo system

Preliminary Cruise Report, W0002A, R/V WECOMA, 1-3 February 2000 : GLOBEC/ENSO Long-Term Observations off Oregon

PURPOSE: To determine physical, plankton and nutrient/chemical conditions over the continental margin for climate change studies in NE Pacific. In particular, to make CTD and CTD/rosette and net tow stations along one line off Newport, OR, and to make continuous observations of currents using ADCP and of surface-layer temperature, salinity and fluorescence by means of ship’s thru-flo system

Preliminary Cruise Report, W0007A, R/V WECOMA, 7-13 July 2000 : GLOBEC/ENSO Long-Term Observations off Oregon

PURPOSE: To determine physical, plankton and nutrient/chemical conditions over the continental margin for climate change studies in NE Pacific. In particular, to make CTD and CTD/rosette and net tow stations along 5 lines (off Newport, Heceta Head, Coos Bay, the Rogue River, OR. and Crescent City, CA., to make continuous bio-acoustic observations between the 50-500m. isobaths along the 5 lines, to deploy drifters at selected locations on the Newport line, and to make continuous observations of currents using ADCP and of surface-layer temperature, salinity and fluorescence by means of ship’s thru-flo system