This week's fun papers

Anders Sandberg (
08 Jan 1999 16:53:09 +0100

This time, a mixed bouquet of phramacology, psychoepidemology, EEG, computer graphics, anthrocomology and a few twigs of particle physics:

	Sneaking neuroprotectants through the blood-brain barrier
	Social class in childhood affecting health in adulthood
	Brain-wave recognition of sentences
	Modelling of plant ecosystems
	A virtual-reality interface for a scanning tunneling microscope
	Is the strong anthropic principle too weak?
	Decay of protons and neutrons induced by acceleration

Neuroprotection with noninvasive neurotrophin delivery to the brain Dafang Wu and William M. Pardridge Proceedings of the National Academy of Sciences USA, Vol 96 254-259 January 1999

Neutrotrophic factors are known to have neuroptrotective properties, and might be candidates both for treating ischemia and dementias (as well as nerve damage). Unfortunately they have to be injected intraventricularly to have any effect, since they do not cross the blood brain barrier. Wu and Pardridge manage to sneak BDNF into the brain anyway, by polyglycosylating the protein so that it isn't absorbed by the peripheral tissues, linking it with another protein so that it is actively transported through the barrier and adding biotin which seems to enhance the process. They tested this on rats, and the treatment (given intravenously for two weeks after ischemic damage to the brain) managed to keep the number of neurons in the CA1 region near normal. Very nice, and the possibility of "smuggling" other drugs into the brain is promising.

Social class in childhood and general health in adulthood: questionnaire study of contribution of psychological attributes Hans Bosma, H Dike van de Mheen and Johan P Mackenbach, British Medical Journal 2 January 1999, 318 18--22

A tricky but interesting subject: how does social class affect attitudes and health? The article suggests that childhood social class affects health more than adult social class. Adverse personality profiles such as external locus of control, neuroticism, parochialism, lack of future orientation and negative coping styles are more common for people who grew up with a low childhood social class, and they might make people more susceptible to illness; this seems to account for half of the association low social class and bad health. These results seems to suggest that the memes you acquire as young might actually have health effects later in life. Yet another reason to spread dynamical optimism, and especially among the young.

Brain-wave recognition of sentences
P. Suppes, B. Han and Z. L. Lu
Proc Natl Acad Sci U S A, 95:26 15861--6 Dec 22

It seems that it is possible to at least partially detect the brainwave patterns of words and sentences a subject hears. The authors measured the electrical and magnetic brain waves from two subjects hearing 12 test sentences (of the type Subject-verb-object; "Bill loves Susan", "Mary sees John", ...) a number of times, and then used averaging to create prototypes that were in turn fourier transformed, filtered and inverse transformed into filters. Recognition rates varied a lot, but the average recognition was around 40-50% (the best was 86.7%). Electrode location, the use of bipolar electrodes and various transforms of the data improved recognition. They tried to paste together the EEG of individual words, in order to see if one word has a standardized EEG representation or if it changes depending on its position in the sentence; it turned out that recognition was still possible. Overall, this paper shows some interesting possibilities for us interested in EEG-interface, but it is clear that a practical interface might be rather tricky.

Realistic modeling and rendering of plant ecosystems Oliver Deussen, Pat Hanrahan, Bernd Lintermann, Radomír Měch, Matt Pharr, Przemyslaw Prusinkiewicz
SIGGRAPH '98. Proceedings of the conference on Computer Graphics, pages 275-286

A lovely paper about how to model a realistic plant ecosystem. They start with setting up a terrain model, both interactively and with pseudorandom features. Then they calculate the amount of water in the soil in different regions, since this affects what plants will grow. Then they "seed" different species (again, partially interactive, partially random) and let them grow according to a competition model (self-thinning: if two plants get too close together, the weaker will die and vanish; since the strength of plants depends on the environment the model naturally makes plants grow at the "right" places). Then the plants themselves are modelled as L-systems, and some simplifications in order to keep the specification files manageable (without them the specification files would be several hundred gigabytes!). The results are wonderfully realistic.

Transhuman relevance? I don't know, but it is a lovely paper and beautiful graphics. Well worth remembering when we as uploads want to take on gardening :-)

The nanomanipulator: a virtual-reality interface for a scanning tunneling microscope
Russell M. Taylor, Warren Robinett, Vernon L. Chi, Frederick P., J r. Brooks, William V. Wright, R. Stanley Williams, Erik J. Snyder SIGGRAPH '93. Proceedings of the 20th annual conference on Computer graphics, pages 127-134

A head-mounted display and force-feedback manipulator arm connected to a STM - nice! The user can view the surface and move around on it, feel it and modify it. Maybe not really useful yet other than interactive exploration, but it definitely sounds like a tool that will be used when nanotech gets truly underway.

Is the Strong Anthropic Principle Too Weak? A.Feoli, S.Rampone
to appear in Il Nuovo Cimento B

Something for the discussions about the Great Filter, I suppose; I'm personally not that fond of this realm. The authors revisit Carter's formula for the expected time between the emergence of intelligent life and the end of the biosphere (either interpreted as "we're very unlikely and the biosphere will soon vanish!" if you assume many unlikely steps in our ontogenesis, or "we're surprisingly likely!" if you start from the estimated lifetime of the biosphere). They show that if the steps are not independent but chained the formula gives an overestimate of the time. In addition, if you assume a large universe with many planets where life can develop, the number of improbable steps in our evolution is balancee large number of planets producing a longer time between the emergence of intelligence and the end of its biosphere, and this grows with the number of terrestrial planets in the Universe. In the end they propose a stronger form of the Strong Anthropic Principle, the Mediocrity Anthropic Principle: "The Universe (and hence both the fundamental parameters on which it depends, and the amount of places where the evolitoon can take place9 must be such as to admit the creation of observers on some stage, and to assure them a not trivial living time". Well, we have the WAP, SAP, FAP and now the MAP.

Decay of protons and neutrons induced by acceleration George E.A. Matsas, Daniel A.T. Vanzella

Apparently accelerations can help induce proton decay in the standard model; the authors calculate that for accelerations around 11MeV (I'm not sure how they convert energy into acceleration) the proton lifetime becomes roughly equal to the neutron lifetime. Maybe useful for matter conversion.

Anders Sandberg                                      Towards Ascension!                  
GCS/M/S/O d++ -p+ c++++ !l u+ e++ m++ s+/+ n--- h+/* f+ g+ w++ t+ r+ !y