Ferromagnetism of 2D Solid 3He Investigated by SQUID NMR

Pulsed NMR measurements have been performed on ³He films adsorbed on an exfoliated graphite sample of area 2 m². The spectrometer is constructed using a DC SQUID with additional positive feedback, operating in flux locked loop mode with a bandwidth of 3.4 MHz. The input circuit, is a superconducting flux transformer, and so is intrinsically broadband. This spectrometer can therefore operate from typical frequencies used in conventional NMR down to otherwise inaccessible low kHz frequencies. With this system studies at the “ferromagnetic anomaly” have been undertaken at frequencies from 2 kHz to 100 kHz (0.06 to 3.09 mT), with the static magnetic field oriented normal to the nominal direction of the graphite platelets. At 50 and 100 kHz, measurements of the susceptibility are fit by high temperature series expansions between 100 mK and 5 mK, to determine an exchange constant J=1.86 mK. Below 1.3 mK the dipolar frequency shift increases linearly with temperature down to 0.3 mK, extrapolating to 10 kHz, close to our calculated value of 9.6 kHz, for fully polarised spins with an assumed lattice spacing of 0.392 nm for the second layer solid. Below 1.5 mK, a significant field dependence to the magnetisation and dipolar frequency shift appears at fields comparable to the characteristic dipolar field, below which the equilibrium alignment of the magnetization is field dependent. Assuming the frequency shift, in applied fields of 1.54 and 3.09 mT, to be proportional to the sample polarisation we find that it is not possible to fit the observed temperature dependence by 2D ferromagnetic spin-wave theory, with a consistent set of parameters for both fields. The theory is applied in the range 0.15>T/J>0.5, takes into account the Zeeman gap and finite system size, and includes the k=0 spin wave term. At present, the data provide no unambiguous evidence for a finite ordering temperature induced by the anisotropic dipolar interaction.     

Bythotrephes longimanus in shallow,nearshore waters: Interactions with Leptodora kindtii, impacts on zooplankton,and implications for secondary dispersal from southern Green Bay,Lake Michigan

The spiny water flea Bythotrephes longimanus is a predatory cladoceran that invaded Green Bay, Lake Michigan by 1988 and has been shown to negatively affect zooplankton prey. Bythotrephes is thought to occur where a deep-water daytime refuge from fish predation is available. Information from shallow, nearshore environments is relatively sparse, yet risk of secondary dispersal from these areas to inland waters is high. The production of desiccation-tolerant resting eggs, coupled with recreational boating activities, can facilitate spread inland. We determined Bythotrephes population demographics and dynamics at two sites in southern Green Bay during 2015 and 2016 to examine interactions with zooplankton and timing of resting egg production. Estimates of prey consumption rates by Bythotrephes were compared to those for a native predatory zooplankter, Leptodora kindtii, and against productivity estimates for potential crustacean prey. Bythotrephes population dynamics were similar at both sites in each year, with biomass peaks in September 2015 and July 2016. Earliest resting egg production occurred by 8 July 2015 and 17 June 2016; resting eggs occurred until at least October each year, when sampling ceased. Consumption by Bythotrephes generally exceeded that by Leptodora. Zooplankton productivity rates were lower than consumption rates on all dates in 2015 but approximated or exceeded consumption rates in 2016. Bythotrephes has become a major predator in the Green Bay lower food web, changing energy transfer through this major Great Lakes ecosystem. Its success has increased potential dispersal to inland lakes, especially from shallow, nearshore habitats such as occur in southern Green Bay.     

A Path to Providing User-Centered Subject Guides

The experience at the University of Akron illustrates a transitional path from static websites to dynamic, user-centered Web design. Starting with Web-based subject resource guides that were difficult to maintain and navigate, University Libraries migrated to a content management system that solved existing maintenance issues and created the opportunity for interactive resource lists. Subsequent usability testing found that users needed librarian-designed subject guides to understand and access resources. Consequently, University Libraries redesigned its website functionality. In the course of this article, it is shown that ease of maintenance and ease of use need not be mutually exclusive.     

Long-term patterns in Lake Champlain's zooplankton: 1992–2010

We examined patterns in Lake Champlain zooplankton abundance from 1992 to 2010 using summer data from five study sites. Rotifer abundance (#/m³) for many common taxa such as Polyarthra, Kellicottia, and Keratella declined lakewide in the mid-1990s which coincided with the invasion of zebra mussels (Dreissena polymorpha) into Lake Champlain. The only rotifer to increase in density following zebra mussel invasion was Conochilus which is a colonial species. Long-term shifts in copepod and cladoceran community composition can be attributed to the arrival of another invasive species in 2004–2005, the alewife (Alosa pseudoharengus). Our results support previous findings that alewife predation can impact larger bodied zooplankton within temperate lake systems. Following alewife invasion into Lake Champlain, body length of Leptodiaptomus and Daphnia retrocurva decreased to a size at or below known alewife feeding preferences. In addition, smaller bodied copepods (primarily Diacyclops thomasi) have increased in abundance since alewife invasion while juvenile copepods have declined. Our results suggest that post-alewife zooplankton patterns are most likely due to alewife size-selective feeding strategies. Observed long-term changes in zooplankton community structure have potential implications for the lake's food web dynamics, particularly recent declines in large bodied zooplankton which may release smaller plankton from top-down control.     

Guyana, “Land of Waters,” Moves to Harness Hydro Potential

ABSTRACT

Heavy metal concentrations (cadmium, chromium, lead, zinc) in 46 cistern water supply systems from single-family dwellings on St. Maarten, Netherlands Antilles were considerably below US drinking water limits in most cases. Release of zinc, lead, and cadmium in the distribution system, which is not related to the corrosiveness of the cistern water, caused lead and cadmium to exceed the US Public Health Service standard for 3 (6.5%) and 1 (2.2%) of the cisterns, respectively.

The following recommendations are suggested for protecting the roof catchment drinking water supply against heavy metal contamination:

? engineer the withdrawal of cistern water to exclude the metal-laden sediment

? identify appropriate paints to be used for cistern collection systems

? install substituted materials, protective coatings, and replacement of corroded metal parts in the distribution system

? discourage the usage of metal containers (e.g., oil) for prolonged water storage

? expand cistern water quality analyses to include lead

? exercise plumbosolvency control by treating the cistern water before distribution.

These recommendations, based on the case study, also apply to other areas of the world where cisterns of similar construction are used or are being planned.     

Families created through surrogacy: Mother–child relationships and children's psychological adjustment at age 7.

Each year, an increasing number of children are born through surrogacy and thus lack a genetic and/or gestational link with their mother. This study examined the impact of surrogacy on mother–child relationships and children's psychological adjustment. Assessments of maternal positivity, maternal negativity, mother–child interaction, and child adjustment were administered to 32 surrogacy, 32 egg donation, and 54 natural conception families with a 7-year-old child. No differences were found for maternal negativity, maternal positivity, or child adjustment, although the surrogacy and egg donation families showed less positive mother–child interaction than the natural conception families. The findings suggest that both surrogacy and egg donation families function well in the early school years. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Correction to Guillot et al. (2010).

Reports an error in Effects of alcohol on tests of executive functioning in men and women: A dose response examination by Casey R. Guillot, Jennifer R. Fanning, Joshua S. Bullock, Michael S. McCloskey and Mitchell E. Berman (Experimental and Clinical Psychopharmacology, 2010[Oct], Vol 18[5], 409-417). This article contained errors in the text. These errors are explained and corrected in the correction. (The following abstract of the original article appeared in record 2010-21046-003.) Alcohol has been shown to affect performance on tasks associated with executive functioning. However, studies in this area have generally been limited to a single dose or gender or have used small sample sizes. The purpose of this study was to provide a more nuanced and systematic examination of alcohol's effects on commonly used tests of executive functioning at multiple dosages in both men and women. Research volunteers (91 women and 94 men) were randomly assigned to one of four drink conditions (alcohol doses associated with target blood alcohol concentrations of .000%, .050%, .075%, and .100%). Participants then completed three tasks comprising two domains of executive functioning: two set shifting tasks, the Trail Making Test and a computerized version of the Wisconsin Card Sorting Task, and a response inhibition task, the GoStop Impulsivity Paradigm. Impaired performance on set shifting tasks was found at the .100% and .075% dosages, but alcohol intoxication did not impair performance on the GoStop. No gender effects emerged. Thus, alcohol negatively affects set shifting at moderately high levels of intoxication in both men and women, likely attributable to alcohol's interference with prefrontal cortex function. Although it is well established that alcohol negatively affects response inhibition as measured by auditory stop-signal tasks, alcohol does not appear to exert a negative effect on response inhibition as measured by the GoStop, a visual stop-signal task. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Nanogel surface coatings for improved single-molecule imaging substrates

Surfaces that resist protein adsorption are important for many bioanalytical applications. Bovine serum albumin (BSA) coatings and multi-arm poly(ethylene glycol) (PEG) coatings display low levels of non-specific protein adsorption and have enabled highly quantitative single-molecule (SM) protein studies. Recently, a method was developed for coating a glass with PEG–BSA nanogels, a promising hybrid of these two low-background coatings. We characterized the nanogel coating to determine its suitability for SM protein experiments. SM adsorption counting revealed that nanogel-coated surfaces exhibit lower protein adsorption than covalently coupled BSA surfaces and monolayers of multi-arm PEG, so this surface displays one of the lowest degrees of protein adsorption yet observed. Additionally, the nanogel coating was resistant to DNA adsorption, underscoring the utility of the coating across a variety of SM experiments. The nanogel coating was found to be compatible with surfactants, whereas the BSA coating was not. Finally, applying the coating to a real-world study, we found that single ligand molecules could be tethered to this surface and detected with high sensitivity and specificity by a digital immunoassay. These results suggest that PEG–BSA nanogel coatings will be highly useful for the SM analysis of proteins.