Solidification mechanism of highly undercooled metal alloys

Experiments were conducted on metal droplet undercooling, using Sn-25wt%Pb and Ni-34wt%Sn alloys. To achieve the high degree of undercooling, emulsification treatments were employed. Results show the fraction of supersaturated primary phase is a function of the amount of undercooling, as is the fineness of the structures. The solidification behavior of the tin-lead droplets during recalescence was analyzed using three different hypotheses; (1) solid forming throughout recalescence is of the maximum thermodynamically stable composition; (2) partitionless solidification below the T sub o temperature, and solid forming thereafter is of the maximum thermodynamically stable composition; and (3) partitionless solidification below the T sub o temperature with solid forming thereafter that is of the maximum thermodynamically metastable composition that is possible. The T sub o temperature is calculated from the equal molar free energies of the liquid solid using the regular solution approximation

Nonalbuminuric Renal Impairment in Type 2 Diabetic Patients and in the General Population (National Evaluation of the Frequency of Renal Impairment cO-existing with NIDDM [NEFRON] 11)

OBJECTIVE Most diabetic patients with impaired renal function have a urinary albumin excretion rate in the normal range. In these patients, the etiology of renal impairment is unclear, and it is also unclear whether this nonalbumunuric renal impairment is unique to diabetes. RESEARCH DESIGN AND METHODS In this study, we examined the frequency and predictors of nonalbumunuric renal impairment (estimated glomerular filtration rate [eGFR] <60 ml/min per 1.73 m(2)) in a nationally representative cohort of 3,893 patients with type 2 diabetes and compared our findings with rates observed in the general population from the Australian Diabetes, Obesity and Lifestyle Study (AusDiab) survey (n = 11,247). RESULTS Of the 23.1% of individuals with type 2 diabetes who had eGFR <60 ml/min per 1.73 m(2) (95% CI 21.8-24.5%), more than half (55%) had a urinary albumin excretion rate that was persistently in the normal range. This rate of renal impairment was predictably higher than that observed in the general population (adjusted odds ratio 1.3, 95% CI 1.1-1.5, P < 0.01) but was solely due to chronic kidney disease associated with albuminuria. In contrast, renal impairment in the absence of albuminuria was less common in those with diabetes than in the general population, independent of sex, ethnicity, and duration of diabetes (0.6, 0.5-0.7, P < 0.001). CONCLUSIONS Nonalbuminuric renal impairment is not more common in those with diabetes. However, its impact may be more significant. New studies are required to address the pathogenesis, prevention, and treatment of nonalbuminuric renal disease

The effect of sewage on uptake of inorganic nitrogen and carbon by natural populations of marine phytoplankton

The short-term effect of sewage effluent on nitrogen and carbon productivity of natural marine phytoplankton obtained near two California outfalls has been studied. Uptake of ammonium was shown to be inhibited at much lower effluent concentrations than was carbon uptake. Since the populations studied were shown to exhibit Michaelis-Menten kinetics for ammonium uptake, a precise measurement of inhibition could be obtained. The results have immediate application since the phytoplankton populations of the area studied have been shown previously to be nitrogen limited

Seasonal and Vertical Distribution, Food Web Dynamics and Contaminant Biomagnification of Cercopagis pengoi in Lake Ontario

During the early growth season of 1999 to 2001, Cercopagis abundance in offshore waters of Lake Ontario remained low (less than 30 individuals/m3). From late July, its abundance increased rapidly until it peaked during August. After first appearing in 1998, maximum offshore abundance in Lake Ontario decreased each year since 1999 (1999:1759/m3; 2000: 679/m3; 2001: 355/m3). Cercopagis appears not to migrate below the thermocline and is restricted to the epilimnion. A comparison of pre- and post-invasion average abundance of Daphnia retrocurva, Bosmina longirostris and Diacyclops thomasi suggests that Cercopagis is having a major effect on zooplankton composition and abundance in Lake Ontario. Abundance of all three species has decreased significantly in the offshore waters since the invasion of Cercopagis. Preliminary results also suggest that insertion of Cercopagis pengoi into the Lake Ontario food web will not elevate levels of hydrophobic organic compounds in salmonids through biomagnification

Invasion risk of active and diapausing invertebrates from residual ballast in ships entering Chesapeake Bay

ABSTRACT: We examined the invasion risk posed by active invertebrates and their diapausing stages (e.g. resting eggs, quiescent adults) carried in residual sediment and water of non-ballasted ships to Chesapeake Bay. Many taxa were recorded that are not native to Chesapeake Bay, supporting the contention that residual ballast represents an invasion vector of some risk to marine systems. Composition and propagule supply differed relative to that in ships entering the Laurentian Great Lakes (e.g. marine taxa dominated in Chesapeake Bay ships), indicating that risk varies geographically. Average abundances of active invertebrates in residual sediment (1002.1 ind. kg–1) and water (2.7 ind. l–1), and diapausing eggs in sediments (779.4 eggs kg–1), were typically low relative to those in ships entering the Great Lakes (1322.5 ind. kg–1, 10.9 ind. l–1 and 3650.0 eggs kg–1, respectively). However, due to high variability among ships, differences were not statistically significant. The major cause of composition and abundance differences is dissimilar trade routes between each system, with vessels entering Chesapeake Bay primarily originating from marine rather than freshwater ports, and because diapausing stages are less commonly found among marine invertebrates. Low propagule supplies, predominant intra-continental ship movements, and salinity disparity between the upper (20 to 28‰) and lower (3 to 8‰) regions of Chesapeake Bay (where ballast water is loaded and offloaded) may greatly reduce invasion risk and be a contributing factor to the bay’s low invasion rate: invasion risk from non-ballasted ships here may be low relative to hull fouling or ballast water discharge. Other marine coastal areas may be at greater risk from this vector

On the context-dependent scaling of consumer feeding rates

The stability of consumer-resource systems can depend on the form of feeding interactions (i.e. functional responses). Size-based models predict interactions - and thus stability - based on consumer-resource size ratios. However, little is known about how interaction contexts (e.g. simple or complex habitats) might alter scaling relationships. Addressing this, we experimentally measured interactions between a large size range of aquatic predators (4-6400 mg over 1347 feeding trials) and an invasive prey that transitions among habitats: from the water column (3D interactions) to simple and complex benthic substrates (2D interactions). Simple and complex substrates mediated successive reductions in capture rates - particularly around the unimodal optimum - and promoted prey population stability in model simulations. Many real consumer-resource systems transition between 2D and 3D interactions, and along complexity gradients. Thus, Context-Dependent Scaling (CDS) of feeding interactions could represent an unrecognised aspect of food webs, and quantifying the extent of CDS might enhance predictive ecology. © 2016 John Wiley & Sons Ltd/CNRS

Aging in a Two-Dimensional Ising Model with Dipolar Interactions

Aging in a two-dimensional Ising spin model with both ferromagnetic exchange and antiferromagnetic dipolar interactions is established and investigated via Monte Carlo simulations. The behaviour of the autocorrelation function $C(t,t_w)$ is analyzed for different values of the temperature, the waiting time $t_w$ and the quotient $\delta=J_0/J_d$, $J_0$ and $J_d$ being the strength of exchange and dipolar interactions respectively. Different behaviours are encountered for $C(t,t_w)$ at low temperatures as $\delta$ is varied. Our results show that, depending on the value of $\delta$, the dynamics of this non-disordered model is consistent either with a slow domain dynamics characteristic of ferromagnets or with an activated scenario, like that proposed for spin glasses.Comment: 4 pages, RevTex, 5 postscript figures; acknowledgment added and some grammatical corrections in caption

Bayesian Centroid Estimation for Motif Discovery

Biological sequences may contain patterns that are signal important biomolecular functions; a classical example is regulation of gene expression by transcription factors that bind to specific patterns in genomic promoter regions. In motif discovery we are given a set of sequences that share a common motif and aim to identify not only the motif composition, but also the binding sites in each sequence of the set. We present a Bayesian model that is an extended version of the model adopted by the Gibbs motif sampler, and propose a new centroid estimator that arises from a refined and meaningful loss function for binding site inference. We discuss the main advantages of centroid estimation for motif discovery, including computational convenience, and how its principled derivation offers further insights about the posterior distribution of binding site configurations. We also illustrate, using simulated and real datasets, that the centroid estimator can differ from the maximum a posteriori estimator.Comment: 24 pages, 9 figure

In situ hatching of invertebrate diapausing eggs from ships’ ballast sediment

Ships that enter the Great Lakes laden with cargo carry only residual ballast water and sediment in ballast tanks. These ships are designated ‘no ballast on board’ (NOBOB) and constitute > 90% of inbound traffic. We conducted in situ experiments using emergence traps to assess the viability and the introduction potential of invertebrate diapausing stages present in ships’ ballast sediment. All trials commenced while vessels operated on the lower lakes (Erie, Ontario) and were completed 6–11 days later at ports on the upper lakes (Michigan, Lake Superior). Eight trials were conducted on four ships using five different ballast sediments. Hatching was observed on every ship, although not from all sediments on all ships. Overall hatch rates were very low (0.5 individuals per 500 g sediment), typically involving activation of < 0.05% of total eggs present. Five species of rotifers and copepod nauplii were hatched from ballast sediments, although only one or two species typically hatched from any one sediment. Results of this study indicate that hatching of diapausing eggs contained in ballast sediment of NOBOB ships poses a relatively low risk of invasion to the Great Lakes. However, as reproduction may occur in tanks, and non-indigenous species may be involved in numerous introduction events, the risk posed by this vector is small but potentially important. While dormancy is a characteristic enabling enhanced survival during transportation in ballast tanks, it becomes a hindrance for introduction.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72804/1/j.1366-9516.2005.00150.x.pd