This weeks papers

Anders Sandberg (
11 Dec 1998 19:36:25 +0100

	Intelligent Paper
	Memory effects of estrogen in rats, women and transsexuals
	Architectural Considerations for Self-Replicating Manufacturing Systems
	Information, evolution and "error-friendliness
	Energy cost of information transmission
	The maximum speed of dynamical evolution


Intelligent Paper
Marc Dymetman and Max Copperman, in Electronic Publishing, Electronic Publishing, Artistic Imaging and Digital Typography (proceedings from the 7th international condference on electronic publishing), St. Malo, France, March/April 1998, Springer Lecture Notes in Computer Science 1376, Roger D. Hersch, Jacques Andre and Heather Brown (eds.) pages 392-406

A neat idea for "smart paper" without the need for advanced technology. Each physical page has an unique identity number and is covered with an invisible pattern encoding the id and the location on the page (using Xerox DataGlyphs 400 bytes of data per square inch can be written using a 300dpi printer). On top of this a visible page is printed. By pointing a pen-shaped camera to a place on the page, the pen can determine which page it is, and where it is pointed. This information is sent to a server, which looks up the web page or online service linked to the page id (for example an interactive encyclopedia, an online map or advertisements) and displays it on a suitable screen (for example the one linked to the pen, or one in the vicinity). The authors propose several interesting applications, and the idea seems at least practically feasible.

Estrogen and memory

Hormones and Behavior 34 had a lot of articles of Estrogen effects on memory. Yummy for neuromodulation hackers like me!

Posttraining estrogen and memory modulation M. G. Packard, Horm Behav 34:2, 126-39 oct 1998

A review of the effect of injections of estradiol after a training event in rats, and how this interacts with acetylcholine in memory modulation. Ovariectomized (lacking ovaries) rats that got estradiol had better retention of a water maze than rats that got placebo, if the injection was done immediately after the training but not two hours later. It turns out that acetylcholine antagonists counteract this effect, which suggests ACh interacts with estradiol in enhancing memory. Good news for ovariectomized rats.

Effects of estrogen replacement therapy on PET cerebral blood flow and neuropsychological performance
S. M. Resnick, P. M. Maki, S. Golski, M. A. Kraut, A. B. Zonderman Horm Behav 34:2, 171-82 oct 1998

There are also reports that estrogen might protect against age-related memory loss or Alzheimer's Disease. In this study, linked to the Baltimore Longitudinal Study of Aging, they did PET scans and assessments of people 55 years old or older. They tested verbal and visual delayed recognition memory, and compared women receiving estrogen with untreated women of the same age. There were no obvious anatomical differences, but in memory processing there were significant differences in regional blood flow in brain areas likely related to memory, and the treated women did better on the memory tests. Good news for older women.

Estrogen and memory in a transsexual population C. Miles, R. Green, G. Sanders and M. Hines Horm Behav, 34:2 199-208 oct 1998

What about estrogen effects in men? For obvious reasons nobody has tried it, but here is a study that exploits one rare window of opportunity: male->female transsexuals awaiting gender reassignment surgery and receiving hormone treatment. Treated persons scored higher on paired associate learning than an untreated transsexual control group, but not on digit span tests (working memory) or other cognitive tasks. It seems that estrogen has the same verbal memory enhancing effects in men as in women. Good news for transsexual men.


Architectural Considerations for Self-Replicating Manufacturing Systems J. Storrs Hall, 6th Foresight Conference on Molecular Nanotechnology

A discussion about how to use self-replicating nanotech in an efficient manner; it turns out that it is not optimal to have a replicator replicate too many or too few generations when nanofacturing a macroscopic object (the optimum seems to be to divert them when their mass equals 69% of the size of the task to be done). In the same manner there might be an optimal complexity: very complex replicators replicate slower than a manufacturing system of simpler units. There is also a discussion of the bootstrapping process from a single seed to a nanofacturing system; you start with a complex replicator that builds successive generations of devices, each generation with more kinds but simpler units.

Philosophy of information and evolution

Information, evolution and "error-friendliness" Ernst Ulrich von Weizäcker, Christine von Weizäcker, Biological Cybernetics 79 501-506 1998

Information is a rather confused concept in modern science; the Shannon information is for example sometimes equated with entropy, sometimes to negentropy, the entropy with a negated sign; the results are often that systems we view as having much or little information according to theory has the opposite (white noise is very energy rich, in classical information theory). What the authors suggest as a better model for speaking about information based on two components, novelty and confirmation. Novelty represents the surprise we get from a message, and is quite close to the Shannon idea. Confirmation is more abstract, and represents the stabilizing factors that give the message a meaning: the channel it is transmitted through, the code, the knowledge of the receiver (this is what Shannon took for granted). If novelty or confirmation is zero, the information is zero. They then go on to apply this to discuss information in biology, evolution and human action. The problem is to create error-friendliness: errors produce novelty, and we need confirmation to make use of it. The article is rather philosophical and a bit rambling, but good food for thought.

Physics of Information

Energy cost of information transmission
Lev B. Levitin, Physica D 120 (1998) 162-167

There is a minimum energy required to transmit a unit of information over a noisy channel equal to kT. This is the latest response in a series of papers about the energy costs of communication, apparently contradicting Landauer's claim that information transmission doesn't have to be dissipative. What really happens is that if you ignore noise you set the temperature to zero, and then there is no real cost. But otherwise, you have to dissipate some energy.

The maximum speed of dynamical evolution Norman Margolus and Lev B. Levitin Physica D 120 (1998) 188-195

A discussion of how quickly an isolated system can pass through distinct states; they derive a bound 2E/h of the rate based on E-E0, the systems average energy minus the ground state energy. This shows that 1J of energy cannot increase a computer's processing rate by more than 3*10^33 operations per second.

Bad news for jupiter brain designers :-)

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