The Self-Assembly Mechanism of Alkanethiols on Au(111)

The self-assembly mechanism of alkanethiol monolayers on the (111) surface of gold was discovered with the use of an ultrahigh-vacuum scanning tunneling microscope. Monolayer formation follows a two-step process that begins with condensation of low-density crystalline islands, characterized by surface-aligned molecular axes, from a lower density lattice-gas phase. At saturation coverage of this phase, the monolayer undergoes a phase transition to a denser phase by realignment of the molecular axes with the surface normal. These studies reveal the important role of molecule-substrate and molecule-molecule interactions in the self-assembly of these technologically important material systems.     

Origin of repopulating cells after localized bone marrow depletion

The restoration of marrow in a mechanically depleted segment of rabbit femur is locally determined and apparently initiated by cells normally resident in bone. This conclusion follows from results of two types of radiation experiments: local x-irradiation of the femur shaft immediately before depopulation and x-irradiation of the total body with exception of the femur diaphysis which was depopulated either just before or after irradiation. In contrast to the rapid initiation of marrow restoration in an unirradiated femur, there was little regeneration during the first 3 weeks in an irradiated femur. Recovery of the shielded depopulated femur in the rabbit that otherwise received total-body irradiation was similar to that in the unirradiated animal. Hence, it would appear that the seeding of circulating hemic stem cells is not essential to repopulation and that cells with hematopoietic potential are present in osseous tissue.     

Dwarf mistletoe-host interactions in mixed-conifer forests in the sierra nevada

ABSTRACT We determined the spatial pattern of dwarf mistletoe (Arceuthobium spp.) associated with two different conifer hosts, white fir (Abies concolor) and Jeffrey pine (Pinus jeffreyi), in forests around the Lake Tahoe Basin and at the Teakettle Experimental Forest, both located in the Sierra Nevada. We also examined a number of host variables and bark beetle incidence to determine how these factors might be involved in the Arceuthobium-conifer interaction. There was no significant relationship between dwarf mistletoe-infected trees and associated bark beetles. We found the highest incidence of dwarf mistletoe on Jeffrey pine in Lake Tahoe (87%), followed by dwarf mistletoe on white fir in Lake Tahoe (30%), with the lowest incidence on white fir at Teakettle (27%). Dwarf mistletoe incidence on white fir in our Lake Tahoe grid was not correlated to density but the dwarf mistletoe rating (DMR) was positively correlated to host size. At the Teakettle Forest, dwarf mistletoe incidence on white fir was not correlated with host density but the DMR was correlated with host size. Dwarf mistletoe incidence and DMR on Jeffrey pine were correlated with host density. Individuals, of both conifer species, in all diameter size classes were susceptible to dwarf mistletoe, with the lowest infection rate in the seedling-10-cm-diameter class. Arceuthobium on white fir in Lake Tahoe showed spatial dependence to a range of 20 m. However, Arceuthobium on Jeffrey pine in Lake Tahoe and on white fir at Teakettle showed no clear pattern of spatial structuring. The degree of infection and stand history appear to be important in the spatial dynamics of Arceuthobium spp.     

Synchronous climate changes in antarctica and the north atlantic

Central Greenland ice cores provide evidence of abrupt changes in climate over the past 100,000 years. Many of these changes have also been identified in sedimentary and geochemical signatures in deep-sea sediment cores from the North Atlantic, confirming the link between millennial-scale climate variability and ocean thermohaline circulation. It is shown here that two of the most prominent North Atlantic events-the rapid warming that marks the end of the last glacial period and the Bolling/Allerod-Younger Dryas oscillation-are also recorded in an ice core from Taylor Dome, in the western Ross Sea sector of Antarctica. This result contrasts with evidence from ice cores in other regions of Antarctica, which show an asynchronous response between the Northern and Southern Hemispheres.     

Pododermatitis in captive-reared black stilts (Himantopus novaezelandiae)

A potential cause of pododermatitis ("bumblefoot") was investigated in captive-reared juvenile black stilts at the Department of Conservation "Kaki Recovery Program" at Twizel, New Zealand. To address the importance of substrate, the development of clinical signs in individuals was compared among aviaries that contained rubber matting and/or salt footbaths, and controls. No effect of either experimental manipulation of the environment was apparent on pododermatitis development. With the substrate appearing not to be an initiating factor, and a previous study that indicated that the birds' diet fulfills the nutritional requirements for rearing black stilts in captivity, results of this study suggest that insufficient space for exercise may instead be the cause.     

Utilization of algal assays to assess the effects of municipal,industrial, and agricultural wastewater effluents upon phytoplankton production in the Snake River system

The most characteristic water quality problem of the Snake River Basin is the excessive aquatic growth and thick blooms of algae. The cause of these aquatic growths is related to the high concentrations of basic nutrients — nitrogen and phosphorus — in the Snake system. Industrial wastes, natural phosphate levels, irrigation return flows, municipal wastes, and the decay of aquatic biota all contribute to the nutrient balance which stimulates aquatic growths. Algal assays were conducted on waters of eighteen Snake River and tributary sites to: (1) determine if algal growth was consistent with results predicted from review of chemical analysis for orthophosphorus and total soluble inorganic N; (2) determine if algal yields were limited by P, N, or some other nutrient essential to algal growth; and (3) predict the effects of N or P additions on algal productivity.     

High-elevation landforms limit the movement of invasive small mammal species

Landscape Ecology - Large-scale programs for eradication of pest mammals are confronted with the challenge of managing reinvasion. Exploiting high-elevation landscape features that naturally limit...     

Shadow Europe: Alternative European Financial Geographies

ABSTRACT This paper sets out to trace some major points of convergence between an emerging literature on the political geographies of corruption¹ and current attempts to develop a renewed research agenda in the geographies of global finance—in this case in a specifically European context. In particular, we offer some preliminary observations on the need to elaborate an alternative geography of Europe's financial architecture that could incorporate the role of flows of illegal and informal finance as major driving forces behind the way in which that architecture currently constitutes itself. This is an inherently complex task due to the intrinsically hidden nature of these flows and the difficulties involved in their accurate measurement; nevertheless, they are too important to be ignored, as is too frequently the case at present. In the paper we offer some necessarily preliminary, and deliberately provocative, reflections on how to take forward such a re‐conceptualisation. Ultimately, our analysis revolves around the identification of an uneasy tension between the demand for deregulated financial markets and the increasing integration of those markets, and the international momentum towards finding ways of dealing with the (apparently) ever‐increasing problems of corruption, money laundering, and the financing of terrorism through new forms of financial regulation and control.     

Effects of age and season on the type and occurrence of sperm abnormalities in Nubian bucks

Effects of age and season on type and occurrence of sperm abnormalities were examined in semen samples collected from 3 groups of Nubian bucks at ages of 4 to 9 months, 10 to 21 months, and 39 to 50 months. The average total percentage of sperm abnormalities at the onset of puberty (141 +/- 4 days) was 64.6 +/- 14.8% (head, 19.5 +/- 13.6%; middle piece, 17.2 +/- 9.3%; and proximal protoplasmic droplets, 14.6 +/- 10.5%), but this improved rapidly and was reduced to 12.5 +/- 7.5% by 8 months of age (head, 1.9 +/- 4.5%; middle piece, 4.6 +/- 2.8%). Further increase in age, at least up to 4 years, did not reveal a significant effect (P less than 0.05) on the type or percentage of total abnormalities. Similar to age, a comparison of data among seasons did not reveal a significant effect on the type or occurrence of sperm abnormalities in 10- to 21-month-old or 39- to 50-month-old bucks. Seemingly, Nubian bucks started producing good quality semen at 8 months of age, and season did not influence sperm abnormalities.     

Oxygen reservoirs in the early solar nebula inferred from an allende CAI

Ultraviolet laser microprobe analyses of a calcium-aluminum-rich inclusion (CAI) from the Allende meteorite suggest that a line with a slope of exactly 1.00 on a plot of delta17O against delta18O represents the primitive oxygen isotope reservoir of the early solar nebula. Most meteorites are enriched in 17O and 18O relative to this line, and their oxygen isotope ratios can be explained by mass fractionation or isotope exchange initiating from the primitive reservoir. These data establish a link between the oxygen isotopic composition of the abundant ordinary chondrites and the primitive 16O-rich component of CAIs.