Effect of chloride on the chemical conversion of nitrate to nitrous oxide for δ15N analysis

We investigate the influence of chloride concentration on the performance of the chemical reduction method for measurement of the nitrogen isotopic ratio (δ15N) in NO3− in natural waters (McIlvin and Altabet, 2005). In this method, NO3− is first reduced to NO2− using activated cadmium metal, with further reduction to N2O using sodium azide in an acetic acid buffer. N2O is introduced into an isotope ratio mass spectrometer (IRMS) for isotopic measurement. Previously, it was recognized that the presence of halides was necessary for the speed and efficiency of the second step but not thought to be important for the first step. Whereas quantitative Cd reduction of NO3− to NO2− had been noted for seawater samples, here we report, for freshwater and low‐salinity (S 99%) reduction of NO3− to NO2− as well as stable δ15N values that closely matched expected values for standards (within 0.3‰ of standard value). The positive effect of NaCl is likely due to a decrease in free Cd2+ produced over the course of the reaction due to formation of CdCl2

3. Wochenbericht M80/2

M80/2, Mindelo – Dakar ; Wochenbericht #3 7.12.2009 bis 13.12.2009 [Meteor

2. Wochenbericht M80/2

M80/2, Mindelo – Dakar ; Wochenbericht #2 30.11.2009 bis 6.12.2009 [Meteor

4. Wochenbericht M80/2

M80/2, Mindelo – Dakar ; Wochenbericht #4 14.12.2009 bis 20.12.2009 [Meteor

Managing Global Training Utilizing Distance Learning Technologies and Techniques: The United States Army Readiness Training

Distance learning (e-learning) is expanding at a very rapid pace as organizations throughout the world search for economical, responsive, and effective means to train workers to meet the challenges of the information age workplace. The Army Distance Learning Program (TADLP) model is discussed in the context of the global e-learning environment. Both e-learning infrastructure and management issues are identified, with emphasis on: (1) developing policy, (2) measuring performance, (3) managing resources, (4) maintaining standards, and (5) satisfying users. The TADLP program is challenging to manage effectively, and difficult to accurately assess program outcomes. The TADLP program is shown to have a well-executed infrastructure plan, quality management of both facilities and services by contractor-supplied staff, and well-designed classrooms. However, the program suffers from limited courseware, creating a bottleneck for full program utilization. A discussion follows relating the Army program to public and private e-learning programs and expectations.

Optimizing Land Use and Water Supply Planning: A Path to Sustainability?

The rise of the environmental movement and the growing public embrace of ecological values roughly coincided with the end of the dambuilding era. By the 1970s, most of the good sites for dams had already been taken, and those that remained, such as California’s North Coast rivers, were increasingly valued as natural and recreational resources that should be permanently protected. At the same time, California’s population continued to swell, from under 20 million in 1970 to nearly 38 million today. How did these trends affect water supply development in California? Among other impacts, the average time a major water supply project took from conception to construction more than doubled. Before the enactment of the major environmental statutes of the 1970s, project planning was far simpler, because the adverse impacts could largely be overlooked. With the advent of environmental impact reports and public involvement, planning water projects became much more complex and time-consuming. Moreover, the projects that succeeded in getting built added progressively smaller increments of storage to the state’s supply, with the hurdles of increasing complexity and expense. As water supply development began to slow down, the prospects for serious rationing became more real

Neuroethology of spatial cognition

A key challenge for animals is recognising locations and navigating between them. These capacities are varied: we can remember where our car is parked at the mall, rats are able to remember where their nest location is while foraging for food morsels, and bats are able to fly directly to a favourite fruit tree 20 kilometers from their home cave.  These spatial abilities, both commonplace or remarkable, raises fundamental questions. First, how do animals find their way? Second, how does the brain represent the outside world? In this primer, we will attempt to answer both questions from the perspective of rodent cognition and neuroscience