Tuesday, January 22, 2019

Post-colonial science

Today there are many threats to science playing an appropriate role in education, public policy, and general public discourse. Some include anti-vaccination campaigns, climate change denial, young earth creationism, "health" products, ...
In the Western world issues such as these rightly get considerable attention. However, in the Majority World there is an issue that does considerable harm and is growing significantly. The basic claims are along the following lines. Modern science did not first arise in Europe but was already present in ancient cultures, often in religious texts. Post-colonial nations need to be proud of this heritage and this "science" should be an integral part of science education. Nations need to embrace their own methods and epistemologies consistent with their culture.

I recently become aware of just how prevalent these views are and the powerful political forces promoting them. You can get some of the flavour from this recent newspaper article and watching some of this video.

A relevant book is
Lost Discoveries: The Ancient Roots of Modern Science—from the Babylonians to the Maya
(Aside: The author, Dick Teresi wrote The God Particle with Leon Lederman.)
This book is authoritatively quoted in a recent book by a prominent South Asian political leader.
A helpful and critical review of Teresi's book is in Science. Basically, it is bad history. There is no doubt that various ancient civilisations did develop some pre-cursors of various aspects of modern mathematics, science, and technology. However, they were never comparable in scope, coherence, conceptual framework, and longevity to what happened in the "scientific revolution" in Europe. A very detailed debunk of some specific claims was given by Meera Nanda, and unfortunately received a vicious response.

So what is the source of the problem here?
I think several very distinct entities get conflated: colonialism, Western civilisation, science, technology, the greed and duplicity of some multinational corporations, and modernism.
A particularly tragic example of this conflation was arguably instrumental in the AIDS-HIV denialism of the South African government from 1999-2008. It was probably responsible for the death of hundreds of thousands of people.

Colonialism was a brutal system which ruthlessly exploited, humiliated, raped, and murdered millions of people across the globe. (See for example). Countless nations today labour under that horrific legacy. No doubt the colonising powers had a patronising view of the "natives", claiming they were bringing them the great achievements of Western civilisation such as science and modernism, and they ruthlessly used technology to maximise their exploitative agenda.
The subtle interplay between scientific, colonial, and theological ideas is described by Sarah Irving in
Natural Science and the Origins of the British Empire.

However, one can decry European colonialism but affirm good things about Western civilisation such as science.
One can decry how technology [based on science] is used to harm people but still affirm science.
Modernism is a particular world view or philosophical framework that claims scientific foundations. One can embrace science without embracing modernism.

I consider postcolonialism an understandable struggle for post-colonial nations to find an identity and direction in the era of globalisation. Somehow these nations need to honor the good parts of their own culture and history [including an accurate assessment of their scientific achievements], accept some good achievements of the West [science, democracy, rule of law, individual freedoms] without uncritically accepting dubious aspects of the West [consumerism, neoliberalism, narcissism, arrogance, ....].

Friday, January 18, 2019

First-order transitions and critical points in spin-crossover compounds

An interesting feature of spin-crossover compounds is that the transition from low-spin to high-spin with increasing temperature is usually a first-order phase transition. This is associated with hysteresis and the temperature range of the hysteresis varies significantly between compounds.
If there was no interaction between the transition metal ions the transition would be a smooth crossover. This is nicely illustrated in a figure taken from the paper below.

Abrupt versus Gradual Spin-Crossover in FeII(phen)2(NCS)2 and FeIII(dedtc)3 Compared by X-ray Absorption and Emission Spectroscopy and Quantum-Chemical Calculations 
Stefan Mebs, Beatrice Braun, Ramona Kositzki, Christian Limberg, and Michael Haumann

For the first compound, the transition is abrupt [much earlier work found a narrow hysteresis region of about 0.15 K]. For the second compound, the transition is a crossover.

The authors fit their data to an empirical equation that has a parameter n, describing the "interactions". You have to read the Supplementary Material to find the details. This equation cannot describe hysteresis.

 However, there is an elegant analytical theory going back to a paper by Wajnflasz and Pick from 1971. This is nicely summarised in the first section of a paper by Kamel Boukheddaden, Isidor Shteto, Benoit Hôo, and François Varret.
The system can be described by the Ising model

where the Ising spin denotes the high- and low-spin states. Delta is the energy difference between them and ln g the entropy difference.
The mean-field Hamiltonian for q nearest neighbours is

There are two independent dimensionless variables, d and r. Solving for the fraction of high-spin states (HS) versus temperature gives the graphs below for different values of d.
The vertical arrows show the hysteresis region for a specific value of d=2. 
As d increases the hysteresis region gets smaller. Above the critical value of d=r/2, the crossover temperature T0=Delta/ln g is larger than the mean-field critical temperature Tc= qJ, and the transition is no longer first-order but a crossover.
Using DFT-based quantum chemistry the authors calculate the change in vibrational frequencies and the associated entropy change for the SCO transition in a single molecule. The values for compound 1 and 2 are 0.68  and 0.21 meV/K respectively. The spin entropy changes are 0.21and 0.22 meV/K respectively. The total entropy changes are thus 0.89 and 0.43 meV/K respectively. The values of Delta are 175 and 125 meV, respectively. The corresponding crossover temperatures are 210 and 360 K, compared to the experimental values of 176 and 285 K.

If we assume that J is roughly the same for both compounds then the fact that the entropy change is half as big for compound 2, means r is twice as big. This naturally explains why the second compound has a smooth crossover, compared to the first, which is very close to the critical point.

Tuesday, January 15, 2019

Thinking skills for scientists (and engineers)

I keep coming back to the basic claim that the key ingredient of education is learning to think in particular ways. [n.b. In science, I am not at all playing up theory over experiment. You have to learn to think about what experiment to do and how to think about your results.].

In the past year, several people brought to my attention that MIT recently reviewed their engineering curricula. It is interesting that a key element is to teach students 11 ways of thinking. The list is worth reading and contemplating.

I have two minor comments. Although I affirm this as an admirable goal. I think the list is incredibly ambitious (even for MIT students) both in scope and content. But, maybe that is a good thing.
What do you think?

One of the 11 ways is Systems Thinking
Predicting emergence of the whole by examining inter-related entities in context, in the face of complexity and ambiguity, for homogeneous systems and systems that integrate multiple technologies.
Again, I love it. But, some would even argue you cannot predict emergence...

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.

Monday, November 26, 2018

A case for (and against) multi-dimensional measures

I am a vocal critic of the use of metrics to evaluate individuals, single scientific papers, journals, sub-fields, institutions, ....
However, my problem is really one of abuse. I don't think metrics are totally meaningless or useless. Rather, it is the mindless use of metrics, with a disregard for their limitations, that is a problem.

This post is not about metrics, jobs, and funding. I have probably already written too many posts on that. Rather, I want to give two examples where I have found some multi-dimensional metrics helpful, when considering issues relating to public policy and development, particularly in the Majority World.

The case is that of the HDI (Human Development Index). Prior to its introduction people tended to use GDP (Gross Domestic Product) as a measure of how a country was performing and where it ranked in the world. In contrast, the HDI is a composite metric, factoring in income per capita, life expectancy, and education. The map below gives a sense of how the HDI varies around the world.

There is a lot one can learn from just the map.  Sub-saharan Africa is the worst as a region. Even though India now has a middle class of several hundred million people, it is still comparable to some African countries.

Whenever I need to know something about a country, I look at the HDI. The fact that Australia often ranks in the top 3 tells me what a privileged environment I live in. Unfortunately, too many Australians really don't know or appreciate this.

I recently met a medical doctor from Niger [which I knew nothing about it]. He told me that Niger is ranked 182 out of 182 countries! This quickly gave me a sense of some of the challenges he faces.

Obviously, like any metric it has limitations. For example, some people prefer the IHDI (Inequality-adjusted HDI). The USA ranks 25th on the HDI.

The second example of a multi-dimensional metric concerns broader issues than human development, that is "human flourishing". This often means quite different things to different people. Last year there was a nice paper in PNAS that argues why this is important for both public policy, but also research in medicine and social sciences.

On the promotion of human flourishing 
Tyler J. VanderWeele

The abstract gives an excellent summary.
Many empirical studies throughout the social and biomedical sciences focus only on very narrow outcomes such as income, or a single specific disease state, or a measure of positive effect. Human well-being or flourishing, however, consists in a much broader range of states and outcomes, certainly including mental and physical health, but also encompassing happiness and life satisfaction, meaning and purpose, character and virtue, and close social relationships. The empirical literature from longitudinal, experimental, and quasi-experimental studies is reviewed in an attempt to identify major determinants of human flourishing, broadly conceived. Measures of human flourishing are proposed. Discussion is given to the implications of a broader conception of human flourishing, and of the research reviewed, for policy, and for future research in the biomedical and social sciences.
Broadly, when trying to describe and understand complex systems one should search for some measures of the properties of the system. Given the systems are complex one may need several measures. These will never be complete or perfect. But, provided one uses them with the appropriate caution this is a good thing.