Combustion and emissions characteristics of a compression-ignition engine using ammonia-DME mixtures

In this study operating characteristics of a compression-ignition engine using mixtures of ammonia and dimethyl ether (DME) are investigated. Ammonia can be regarded as a carbon-free fuel that can help mitigate greenhouse gas emissions. Ammonia is one of the world\u27s most synthesized chemicals and its infrastructure is well established. Recent technological advances also show that ammonia can be produced from renewable resources, making it an attractive energy carrier. In the present study, a high-pressure mixing system is developed to blending liquid ammonia with DME that serves to initiate combustion. The engine uses a modified injection system without fuel return to prevent fuel mixture from vaporizing in the return line. Results using different mixture quantities of ammonia and DME show that ammonia causes longer ignition delays and limits the engine load conditions due to its high autoignition temperature and low flame speed. The inclusion of ammonia in the fuel mixture also decreases combustion temperature, resulting in higher CO and HC emissions. NOx emissions increase due to the formation of fuel NOx when ammonia is used. However, improvements for the same operating conditions were made by increasing the injection pressure using 40%NH3-60%DME. Exhaust ammonia emissions is on the order of hundreds of ppm under the conditions tested. Soot emissions are extremely low for all cases. Double injection schemes using 20%NH3-80%DME are also employed and found not to extend engine performance. Its effects on the exhaust emissions vary with operating conditions

Long range population prospects of Finland in the European context

The population of Finland is projected along eleven different scenarios assuming widely diverging alternative trends in fertility, mortality and migration up to the year 2100. The definitions of these scenarios follow those of a recent study (Lutz, 1991) on Europe and North America. They range from constant rates to assuming replacement fertility versus a Total Fertility Rate (TFR) of 1.1, mortality stagnation versus a strong increase in life expectancy, and no immigration versus 30,000 migrants per year. The results show that no matter what scenario is chosen, the next 30 years will bring an enormous increase of the population over age 65. The proportion in working age will be relatively stable up to the year 2010 and then strongly decline under all conditions, which is a consequence of the Finnish baby boom of the late 1940s. Projected total population sizes in 2050 will range from 3.5 million in the fertility decline scenario to 6.6 million in the high immigration scenario

Acute insult of ammonia leads to calcium-dependent glutamate release from cultured astrocytes, an effect of pH

Hyperammonemia is a key factor in the pathogenesis of hepatic encephalopathy (HE) as well as other metabolic encephalopathies, such as those associated with inherited disorders of urea cycle enzymes and in Reye's syndrome. Acute HE results in increased brain ammonia (up to 5 mM), astrocytic swelling, and altered glutamatergic function. In the present study, using fluorescence imaging techniques, acute exposure (10 min) of ammonia (NH4+/NH3) to cultured astrocytes resulted in a concentration-dependent, transient increase in [Ca2+]i. This calcium transient was due to release from intracellular calcium stores, since the response was thapsigargin-sensitive and was still observed in calcium-free buffer. Using an enzyme-linked fluorescence assay, glutamate release was measured indirectly via the production of NADH (a naturally fluorescent product when excited with UV light). NH4+/NH3 (5 mM) stimulated a calcium-dependent glutamate release from cultured astrocytes, which was inhibited after preincubation with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester but unaffected after preincubation with glutamate transport inhibitors dihydrokainate and DL-threo-beta-benzyloxyaspartate. NH4+/NH3 (5 mM) also induced a transient intracellular alkaline shift. To investigate whether the effects of NH4+/NH3 were mediated by an increase in pH(i), we applied trimethylamine (TMA+/TMA) as another weak base. TMA+/TMA (5 mM) induced a similar transient increase in both pH(i) and [Ca2+]i (mobilization from intracellular calcium stores) and resulted in calcium-dependent release of glutamate. These results indicate that an acute exposure to ammonia, resulting in cytosolic alkalinization, leads to calcium-dependent glutamate release from astrocytes. A deregulation of glutamate release from astrocytes by ammonia could contribute to glutamate dysfunction consistently observed in acute HE

Answer Set Programming for Qualitative Spatio-Temporal Reasoning: Methods and Experiments

We study the translation of reasoning problems involving qualitative spatio-temporal calculi into answer set programming (ASP). We present various alternative transformations and provide a qualitative comparison among them. An implementation of these transformations is provided by a tool that transforms problem instances specified in the language of the Generic Qualitative Reasoner (GQR) into ASP problems. Finally, we report on an experimental analysis of solving consistency problems for Allen\u27s Interval Algebra and the Region Connection Calculus with eight base relations (RCC-8)