Wednesday, December 19, 2018

The relation between life changes, stress, and illness

I have often wondered about my personal experience and the anecdotal evidence that when you get stressed you seem more likely to get a cold or the flu. I finally found some research literature on the subject.
A helpful review is
Modern Approaches to Conceptualizing and Measuring Human Life Stress
Scott M. Monroe

A seminal paper from 50 years ago
The social readjustment rating scale 
TH Holmes, RH Rahe

The authors developed a quiz to estimate how your recent life circumstances and changes may be producing different levels of stress. They then correlated the stressful life circumstances to recent illness of the subjects.

It is worth occasionally doing the quiz. Here is one version.
Aside: One interesting aspect is that positive changes can create stress (e.g. starting a new job, getting married, having a baby, ...).

However, as discussed in detail by Monroe in his review all of this is more complicated than we might like. Measures of stress are subjective, subtle, personal, and hard to agree upon. For example, do you define the level of stress largely in terms of the environment or in terms of the response of the individual to the environment?
This is hardly surprising given that the subject is at the interface of medicine, psychology, and sociology.

Saturday, December 15, 2018

Metastability and first-order phase transitions

One of the simplest examples of a first-order phase transition is occurs in a ferromagnet at a temperature below the critical temperature and in an external magnetic field. The transition occurs when the field is varied so that it changes sign.

This can be described in terms of the following Landau free energy where H is the external field and r is negative.
One observes hysteresis as for non-zero H there is a metastable state.
The order parameter phi versus H is shown below

The boundaries of the region of metastability are defined by the field Hc given by
The above description is taken from a review article by Kurt Binder.
I have never seen this in a textbook.
Have you?
Any clear detailed presentations of this topic would be appreciated.

Monday, December 3, 2018

What should everyone know about science?

In a time when misunderstandings of science anti-science views are rising around the world, it is important that scientists do a better job of communicating to the broader public what science actually is, what it can do, and what it cannot do.

An interesting and important question is what it is that people should know and understand. There is a multitude of views on this (which is not necessarily a completely bad thing).

I only learned last week that in 1994, Phil Anderson had tackled this issue in a short article he wrote for The Daily Telegraph, a London-based newspaper. An interesting paper about Anderson's article just appeared. It nicely places the article in a broader context and gives a more recent perspective on the issues he raised.

Four Facts Everyone Ought to Know about Science:
The Two-Culture Concerns of Philip W. Anderson
Andrew Zhang and Andrew Zangwill

The four ``facts'' that Anderson chose were (as paraphrased by Zhang and Zangwill):

1. Science is not democratic.
2. Computers will not replace scientists.
3. Statistical methods are misused and often misunderstood.
4. Good science has aesthetic qualities.

This is a fascinating choice. 

One thing I learned was about Anderson's argument that Bayesian methods should have been used to rule out the significance of "discoveries" such as the 10 keV neutrino and the fifth force. In 1992 he wrote a Physics Today column on the subject.