# Econstudentlog

## Stuff

File under: Stuff you probably didn’t know about that actually matters a great deal.

“Generation of electricity using coal started at the end of the 19th century. The first power stations had an efficiency of around 1%, and needed 12.3 kg of coal for the generation of 1 kWh. […] With increasing experience, in combination with research and development, these low efficiency levels improved rapidly. Increased technical experience with coal processing and combustion technology enabled a steady increase in the steam parameters ‘pressure’ and ‘temperature’, resulting in higher efficiency. In the years 1910, efficiency had already increased to 5%, reaching 20% by 1920. In the fifty’s, power plants achieved 30% efficiency, but the average efficiency of all operating power plants was still a modest 17%. […] continuous development resulted around the mid 80’s in an average efficiency of 38% for all power stations, and best values of 43%. In the second half of the nineties, a Danish power plant set a world record at 47%. […] The average efficiency of all coal power stations in the world is around 31%. […] In the next 10 years [the paper is from 2005, US], efficiencies up to 55% can be expected.” […]

Often, the question is asked why the ‘other 45%’ cannot be converted into electricity. This relates to the laws of physics: the absolute maximum efficiency is the so-called ‘Carnot efficiency‘. For a turbine operating with gasses of 600°C, it is 67%. Then we need to take into account the exergy content of steam (around 94%). Also combustion has an efficiency less than 100% (around 95%). The transfer of combustion heat to steam in the boiler is for example 96% efficient. Losses due to friction can be around 5% (efficiency 95%). The efficiency of a generator is about 98% on average . . . .
To obtain the combined efficiency, one needs to multiply the efficiency of each process. Taking the above mentioned components, one obtains 0.67 x 0.94 x 0.95 x 0.96 x 0.95 x 0.98 = 0.535 or 53.5%.
This does not yet take into account the efficiency of all components. The power station’s own power use for motors to grind coal, pumps, ventilators, . . . further reduces efficiency. In practice, net efficiency will be around 40 and 45%. Continuous load changes, i.e. following the load, and start-up/shutdown procedures further lower efficiency. The increasing variability of the load, through increased use of intermittent sources such as wind, will lead to increased swings in the load of the power station, reducing efficiency.”

“Allostatic load (AL) has been proposed as a new conceptualization of cumulative biological burden exacted on the body through attempts to adapt to life’s demands. Using a multisystem summary measure of AL, we evaluated its capacity to predict four categories of health outcomes, 7 years after a baseline survey of 1,189 men and women age 70–79. Higher baseline AL scores were associated with significantly increased risk for 7-year mortality as well as declines in cognitive and physical functioning and were marginally associated with incident cardiovascular disease events, independent of standard socio-demographic characteristics and baseline health status. The summary AL measure was based on 10 parameters of biological functioning, four of which are primary mediators in the cascade from perceived challenges to downstream health outcomes. Six of the components are secondary mediators reflecting primarily components of the metabolic syndrome (syndrome X). AL was a better predictor of mortality and decline in physical functioning than either the syndrome X or primary mediator components alone. The findings support the concept of AL as a measure of cumulative biological burden.

In elderly populations, comorbidity in the form of multiple co-occurring chronic conditions is the norm rather than the exception. For example, in the U.S. 61% of women and 47% of men age 70–79 report two or more chronic conditions. These figures rise to 70% of women and 53% of men age 80–89 with 2+ chronic conditions (1). No single form of comorbidity occurs with high frequency, but rather a multiplicity of diverse combinations are observed (e.g., osteoarthritis and diabetes, colon cancer, coronary heart disease, depression, and hypertension). This diversity underscores the need for an early warning system of biomarkers that can signal early signs of dysregulation across multiple physiological systems.

One response to this challenge was the introduction of the concept of allostatic load (AL) (24) as a measure of the cumulative physiological burden exacted on the body through attempts to adapt to life’s demands. The ability to successfully adapt to challenges has been referred to by Sterling and Eyer (5) as allostasis. This notion emphasizes the physiological imperative that, to survive, “an organism must vary parameters of its internal milieu and match them appropriately to environmental demands” (5). When the adaptive responses to challenge lie chronically outside of normal operating ranges, wear and tear on regulatory systems occurs and AL accumulates.”

They conclude that: “The analyses completed to date suggest that the concept of AL offers considerable insight into the cumulative risks to health from biological dysregulation across multiple regulatory systems.” I haven’t come across the concept before but I’ll try to keep it in mind. There’s a lot of stuff on this.

“a few years ago, I learned that it’s actually pretty common to survive a plane crash. Like most people, I’d assumed that the safety in flying came from how seldom accidents happened. Once you were in a crash situation, though, I figured you were probably screwed. But that’s not the case.

Looking at all the commercial airline accidents between 1983 and 2000, the National Transportation Safety Board found that 95.7% of the people involved survived. Even when they narrowed down to look at only the worst accidents, the overall survival rate was 76.6%. Yes, some plane crashes kill everyone on board. But those aren’t the norm. So you’re even safer than you think. Not only are crashes incredibly rare, you’re more likely to survive a crash than not. In fact, out of 568 accidents during those 17 years, only 71 resulted in any fatalities at all.”

iv. Now that we’re talking about planes: What does an airplane actually cost? Here’s one article on the subject:

“As for actual prices, airlines occasionally let numbers slip, either because of disclosure requirements or loose tongues.

Southwest Airlines Co., LUV +0.11% for example, recently published numbers related to its new order for Boeing 737 Max jetliners in a government filing. Mr. Liebowitz of Wells Fargo crunched the data and estimated an actual base price of roughly \$35 million per plane, or a discount of around 64%. He noted that Southwest is one of Boeing’s best customers and that early buyers of new models get preferential pricing. A Southwest spokeswoman declined to comment.

Air India, in seeking funding last year for seven Boeing 787 Dreamliners it expects to receive this year, cited an average “net cost” of about \$110 million per plane. The current list price is roughly \$194 million, suggesting a 43% discount. Air India didn’t respond to a request for comment for this article.

In March 2011, Russian flag carrier Aeroflot mentioned in a securities filing that it would pay at most \$1.16 billion for eight Boeing 777s…”

100+ million dollars for a plane. I had not seen that one coming. File under: Questions people don’t seem to be asking, which I think is sort of weird. Now that we’re at it, what about trains? Here’s a Danish article about our new IC4-trains.  A conservative estimate is at \$1,09 billion (6,4 billion kroner) for 83 trains, which is ~\$13,2 million/train (or rather per trainset (US terminology) or ~77 million Danish kroner. That’s much cheaper than the big airplanes, but it sure is a lot of money. What about busses? I’ve often thought about this one, perhaps because it’s a mode of transportation I use far more frequently than the others. Here’s one bit of information about the situation in the US, which is surely different from the Danish one but not that different:

“Diesel buses are the most common type of bus in the United States, and they cost around \$300,000 per vehicle, although a recent purchase by the Chicago Transit Authority found them paying almost \$600,000 per diesel bus. Buses powered by natural gas are becoming more popular, and they cost about \$30,000 more per bus than diesels do. Los Angeles Metro recently spent \$400,000 per standard size bus and \$670,000 per 45 foot bus that run on natural gas.

Hybrid buses, which combine a gasoline or diesel engine with an electric motor much like a Toyota Prius, are much more expensive than either natural gas or diesel buses. Typically, they cost around \$500,000 per bus with Greensboro, NC’s transit system spending \$714,000 per vehicle.”

So of course you can’t actually compare these things this way because of the different way costs are calculated, but let’s just for fun assume you can: When you use the average price of a standard US diesel bus and compare it to the price of the recently bought Danish trains, the conclusion is that you could buy 44 busses for the price of one train. And you could buy 367 busses for the price of one of the Dreamliners.

v. A new blog you might like: Collectively Unconscious. A sort of ‘The Onion’ type science-blog.

vi. I was considering including this stuff in a wikipedia-post, but I thought I’d include it here instead because what’s interesting is not the articles themselves but rather their differences: Try to compare this english language article, about a flame tank designed in the United States, with this article about the same tank but written in Russian. I thought ‘this is weird’ – anybody have a good explanation for this state of affairs?

vii. The Emergence and Representation of Knowledge about Social and Nonsocial Hierarchies. I haven’t found an ungated version of the paper, but here’s the summary:

“Primates are remarkably adept at ranking each other within social hierarchies, a capacity that is critical to successful group living. Surprisingly little, however, is understood about the neurobiology underlying this quintessential aspect of primate cognition. In our experiment, participants first acquired knowledge about a social and a nonsocial hierarchy and then used this information to guide investment decisions. We found that neural activity in the amygdala tracked the development of knowledge about a social, but not a nonsocial, hierarchy. Further, structural variations in amygdala gray matter volume accounted for interindividual differences in social transitivity performance. Finally, the amygdala expressed a neural signal selectively coding for social rank, whose robustness predicted the influence of rank on participants’ investment decisions. In contrast, we observed that the linear structure of both social and nonsocial hierarchies was represented at a neural level in the hippocampus. Our study implicates the amygdala in the emergence and representation of knowledge about social hierarchies and distinguishes the domain-general contribution of the hippocampus.”

viii.

I’ve only actually watched the first 15 minutes (and I’m not sure I’ll watch the rest), but I assume some of you will find this interesting.