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Bridge in Genoa (Italy)

Dear Reader,

I strongly suspect that some of you will be aware that a bridge in Italy has fallen down resulting in a considerable loss of human life. Now some of you might be wondering what caused it to happen.

At this time I do not know for sure exactly what caused the bridge to fall down, there are reports that a lightning bolt hit the bridge shortly before the bridge came crashing down. The bridge was a suspension bridge (cable stayed bridge) which had reinforced concrete elements which go from the tops of the towers to the part of the bridge which the people / cars travel over.

Now years ago in the senior common room at Reading it was explained to me that there are two types of suspension bridge. There is the true suspension bridge where a long cable which has a shape similar to a washing line exists between two towers. From this cable a series of vertical elements are connected. At the bottom end of the vertical elements are connected to the road way on which the people, cars etc travel over. The other design is a cable stayed bridge in which straight elements which are under tension go from the tower to the road.

For the suspension bridge it is impossible to change the main cable (the one with the washing line shape) but for the cable stayed bridge it is possible to replace a cable.

One big problem is tension, now it is important to understand that concrete is very weak in tension but strong in compression. This is why reinforced concrete is so good a material. The strength of a concrete object can be sometimes increased further by stressing the structure by putting the concrete under additional compression. This can be done by having a hole going through the concrete, the concrete is poured and allowed to set. Afterwards a steel rope in the hole is then put under tension, this then subjects the concrete to compression. One way of doing this would be to have a long bolt passing through the hole with large washers on both ends. By putting a nut on this bolt and tightening it up then the bolt will be under tension and the concrete under compression.

post stressed concrete

Another method would be to use prestressing where the rebar is put under tension before the concrete is poured. It is important to note that when carbon steel is placed in concrete made from ordinary portland cement (OPC) that the pore water in the cement is slightly alkaline. This is good for the steel, under these conditions the steel does not corrode quickly. The steel is in a chemical environment in which the corrosion is very slow.

Corrosion or rusting of rebar is a very big problem, the volume occupied by the rust is greater than that of the steel rebar. As a result if rusting occurs then not only does the rebar lose its strength but also it tends to cause concrete to spall off from the structure. This expansion from within tends to make more holes in it.

However there are two main problems, if the concrete becomes contaminated with chloride salts from sea spray or deicing salts used on the road then the rebar can start to corrode more quickly. Also if as a result of cracking carbon dioxide from the air can enter the concrete then the pore water will become less alkaline. The steel will then be exposed to a new chemical environment in which it will corrode more quickly. All concretes will slowly be carbonated by the air, but in the ideal world only the very outer layer will be carbonated.

If the concrete becomes cracked due to vandalism, a changing mechanical load or even due to corrosion then the rate of carbonation tends to increase. This is due to the fact that the air has greater access to the inner part of the concrete object.

The last main thing which we should be aware of is that some corrosion modes such as stress corrosion cracking are worse when the object is placed under tension such as in the cable of the suspension or cable stayed bridge.

What I think that one of the things the investigators should be doing is to check the chemistry of the concrete used in the reinforced concrete cables used to connect the towers to the deck of the bridge. There are two simple chemical tests which can be used.

The first one is to drill a hole into the concrete and apply a solution of phenolphthalein to the surface. This is an acid/base indicator. When it is acidic it is colourless but when it is alkaline it is intense pink. What you then do is to measure how far the colourless reagion extends into the concrete object. This will give an indication of how bad the carbonation effect was at the point where the hole was drilled. As the bridge has fallen down this test can be used without having to worry so much about plugging up the holes made in the test if you were to examine the fallen lumps of concrete.

Another simple test is to grind up a sample of concrete, then to make this into a paste with a known amount of water. If this paste is then examined by either ion chromatography or a chloride test strip (based on the reaction of silver nitrate with sodium chloride to form insoluble silver chloride) then it is possible to determine how much chloride contamination was present in the concrete.

It would be interesting to know if the people responsible for the bridge were using these tests and some other corrosion tests before the bridge fell down. Now I think that the wreckage from the bridge should be subject to these tests and some other tests to try to work out what has happened. I will try to write more about the bridge and steel corrosion when I get the chance.


Nerve gas cult leader hanged

Dear Reader,

It has come to my attention that the leader (Shoko Asahara) of the horrible nerve gas cult in Japan (Aum Shinrikyo) has been hung in Japan. I first heard of this cult before the nerve gas attack which made it famous for all the wrong reasons (infamous). Some of the tales which were leaking out from this cult were perfectly horrifying, one author in a book on religious cults described some of the deeds of the cult as being like something from a Edgar Alan Poe story. But he did comment that it would be unlikely that Poe would have been able to imagine some of the atrocities which involve modern technology.

The Japanese have a death penalty for murder, I checked and a Law academic (Prof Norio Takahashi) wrote some time ago

In the “serial shooting murder case (Nagayama Incident) (Showa 58-7-8 Police Procedure 37-6 609 pages), the supreme court ruled that the death penalty may be imposed inevitably in consideration of the degree of criminal liability and balance of justice based on a nine-point set of criteria which includes;

  1. degree of viciousness of the crime,
  2. motive of the crime,
  3. how the crime was committed-especially the manner in which the victim was killed,
  4. outcome of the crime especially the number of murdered victims,
  5. sentiments of the victim’s bereaved family members,
  6. impact of the crime on society,
  7. defendant’s age,
  8. defendant’s previous criminal record,
  9. degree of remorse shown by the defendant.

Now if we look at Shoko Asahara we can point out that

  1. The murder weapon causes the victims to suffer greatly before death, this also touches point three.
  2. The motivation for the crime was an attempt to overthrow the state and inhibit the actions of the police.
  3. The crime does involve wanton cruelty.
  4. The attack caused multiple deaths (13) and causes injuries to many other people (1000s)
  5. I have no idea what the different families think about the death sentence, but Minoru Kariya whose father died in another of the cults crimes (the smaller scale nerve gas attack) supported the death sentence.
  6. The crime was intended to have a serious impact on society and the first nerve gas attack was an attempt to inhibit the legal system (it targeted judges involved in a case regarding the cult)
  7. The defendant was an adult at the time of the crime.
  8. The defendant has a criminal record at the time the crime was committed
  9. I am unable to be sure, but from what I have heard the defendant has shown little or no remorse.

So according to the nine points, using the criteria used by the legal system in Japan it appears that Shoko Asahara is a candidate for the death penalty. I have to ask however what is the point of the death penalty ? In a perverse way the “ultimate punishment” renders the criminal incapable of any further punishment. So if we wanted to impose a truely ultimate punishment then the hanging will defeat our attempts to punish the criminal. I will comment shortly on the chemistry of this case.

Nickel extraction where the reaction occurs at the interface

Dear Reader,

Recently I considered the idea of a reaction in which a BTBP reacts with a nickel cation in the aqueous phase before the nickel BTBP complex is extracted. Now let us consider a system where the chemcial reactions only occur at the interface.

We need to consider the amount of the extraction agent at the interface, I will assume for a moment that the concentration of the extractant in the bulk of the organic phase is proportional to the amount of extractant in a given area of the interface. In some real life systems this is not true.

If in a given area two BTBP molecules are present then if a nickel atom is present at the interface then they will have a given probability of being able to extract the nickel during one second. The probability that a nickel atom will be present will be proportional to the concentration of the nickel in the bulk of the aqueous phase. Thus we will have a third order reaction for the extraction of the nickel.

2BTBP(org) + Ni2+(aq) [Ni(BTBP)2]2+(org)

When this reaction exists in isolation we can write

-d[Ni2+aq]/dt = kex[BTBP]2[Ni2+aq]

We then have the backwards reaction (first order reaction) which is

[Ni(BTBP)2]2+(org) → 2BTBP(org) + Ni2+(aq)

When this exists in isolation we can write

d[Ni2+aq]/dt = kstrip[[Ni(BTBP)2]2

We can combine these two kinetics equations when the system reaches equilibrium

Kstrip[Ni(BTBP)2] = kex[BTBP]2[Ni2+aq]

Rearrange to

[Ni(BTBP)2] / [Ni2+aq] = kex[BTBP]2/ Kstrip

Then simplify to

DNi = kex[BTBP]2/ Kstrip

If we were to do some kinetics experiments in a Lewis cell, then it would be possible from both extraction experiments and stripping experiments to calculate the equilibrium distribution ratio.

Second review on serious reactor accidents

Dear Reader,

I have published an update on serious accident chemistry, partly to my horror and also partly to my amazement I understood recently that the work of critically discussing the topic seems to have no end. Keep in mind that critical does not mean carping, critical is to use rational reasoning consider something and then to make a judgement of it.

If you want carping then I have to disappoint you, you will need to look elsewhere. Some years ago as a joke I discussed with some PhD students at Chalmers the idea of the “Journal of Offensive Chemistry” where every paper, referee report, submission and editorial document has to be as rude and obnoxious as possible. We had visions of hateful, spite ridden and nasty comments. Thankfully this journal has never come to exist (well not yet). I imagine it would be rather hard work for the editor of this horrible journal to keep on coming up with new ways to be offensive about papers, I imagine that there would be a limit to the number of times each insult could be used.

I freely admit that some people will not be happy that I have chosen to write about the topic again. I am sure that there are some elements on both the pro and antinuclear side who have made up their minds on some issues before considering the evidence. I suspect that these people may not like having their bubble poked or even burst. I have during the review pointed out some issues in the work of some other writers on the subject.

Some authors on the subject who have strayed have been willing to engage in a reasonable and honest discussion with me, I tend to be more forgiving of these people. But there are some who persist in getting some things wrong even after it has been pointed out to them. As an academic I hold the view that part of my mission in life is to make the world a better place. Part of my work is to spread knowledge / skills / understanding and to confront nonsense and falsehood wherever it might be.

Now these days with the amount of nonsense which exists in the world it seems we have a lot of nonsense, false information and other things to take care of. Now one rather interesting person is Helen Caldicott who is an Australian who was shocked after reading “On the Beach”. Now for a moment I wonder what would have happened if she had read Mary Shelley’s Frankenstein. Both “On the Beach” and Frankenstein are clearly gross distortions and exaggerations of some things which exist in real life.

In Frankenstein, it suggests that electricity can create a monster, should we now be concerned about the use of AEDs to treat heart attacks ? Equally if you watch “Wishmaster” you might be very concerned about making any wish, that is if you think it is a documentary rather than a work of pure fiction. My worry is that novels and feature films are not good education when it comes to driving cars, dating, resolving conficts or science.

Now the thing I do not like about “On the Beach” is the way in which it exagerates fallout, it ignores for example the fact that radioactivity decays away with time. Also the further you get away from the blast site the less of some of the worst of the medium lived high energy photon emitters (such as Zr-95) will be deposited on the ground by fallout. The zirconium-95 from a ground burst tends to be deposited near the blast site in coarser particles while the finer particles are lofted high into the atmosphere. These particles injected into the upper atmosphere tend to take a long time to fall to earth again. During this time they have plenty of time for radioactive decay to occur.

Now lets look for a moment at what Helen writes she wroteShute had loudly protested that the film was a “bastardization” of his work because of its American cast and what he saw as the soft-peddling of the horrors of radiation sickness, which include nausea, vomiting, fever, skin and hair loss, massive ulcers, blisters, burns, emaciation, destruction of the soft tissues, bone marrow depletion, and ultimately inflammation of the membrane around the heart, leading to a slow, agonizing death.”

I am not going to discuss the acting skills of american actors vs non american actors, that would be a mighty silly thing to waste my time on. Now I am also not going to claim that radiation is a big barrel of laughs, to be blunt with you if I did then I would be very stupid. Now Helen wrote about “Radiation Sickness”, the problem is that there is no such disease in my view. There are a series of syndromes which can be caused by radiation. The “Acute Radiation Syndrome” is the closest thing to what the general public think is “radiation sickness”. I would have thought that a medical doctor she would have known better than to use such loose and poor terminology. Now it is interesting that she comments that “inflammation of the membrane around the heart,” (Pericarditis) is the ultimate ending of this condition. I find her choice of language to be rather emotive, but I will let that slide.

I considered the question of “is cardiac issues common in people who have had an acute whole body dose ?“. Now the thing is that I will admit that it is possible to induce cardiac damage in humans with radiation, but the dose required is high. I have checked the ICRP opinion regarding early and late non carcinogenic effects in healthy tissue (ICRP 118), this is a document mainly about the side effects of radiotherapy for cancer. This document does indicate that the α/β value is 2.5 for pericarditis.

The ICRP document indicates that Emami et. al. (1991) found that for whole heart irradation that 40 Gy was required to cause 5 % of people to develop pericarditis within five years when the radiation was divided into 2 Gy fractions. A often in radiotherapy the treatment is divided into a series of doses (fractionation). Now if we assume the classic LQ model for cell survival.

S = exp -(αD + βD^2)

Then if we assume that α = 0.01, then for a 2 Gy dose we can calculate that S is equal to 0.88692. If we repeat this 2 Gy dose 20 times (with plenty of time for sublethal damage to be repaired) then we will get a S value of 0.090718

Now if we assume that the radiation is delivered at a low dose rate (where the beta term disappears) then to get a S value of (which is what we will have after 20 treatments) then the dose required can be calculated using

ln S = -αD

ln S / -α = D =  240 Gy.

Now I hold the view that 240 gray delivered over a month would be exceptionally hard for a person to tolerate for other reasons. I suspect that things like the digestive system would not be able to tolerate about 7.75 Gy per day. Also the blood forming organs would not do very well with this amount of radiation each day. I think that under this exposure senario it is unlikely that pericarditis would play a role.

If we consider a single short pulse of radiation then we can calculate a dose which would be the equilivent. This will be a little harder in terms of maths. Using my GCSE maths I will now attack the problem. We can use successive approximation to deal with the problem.

I have estimated that a single short duration dose of about 9.6 Gy is able to give a person a 5 % chance of the pericarditis within five years. Now I know from the literature that people who get doses of about 10 Gy do not typcially live more than about 1 month. So I think it would be very unlikely for a person to be able to get pericarditis from a one off whole body dose, the only time this radiation effect is likely to be seen is for medical paitents who typically get a very uneven irradation, these uneven irradations are very unlikely under nuclear warfare conditions. Unless the person getting the dose is a worker assembling a nuclear bomb who makes a horrible mistake and causes a criticality to occur during the assembly process.

Now I have to ask the question of why is Helen making these bold claims that simple GCSE maths show to be wrong, I hold the view that things like radiation are sufficently bad that we do not need Helen to invent new horrors.

Solvent extraction of nickel

Dear Reader,

I was thinking about solvent extraction recently, now solvent extraction a bit more than “shake A and B, and the nickel extracts”. Rather than merely shaking things and seeing that the metal goes from one layer to the other (and stopping there) it is important to understand that a lot of things can control the equilibrium position. I was recently thinking about nickel with BTBP.

I made the assumption in this model of the thermodynamics that the nickel reacts with the BTBP in the bulk of the aqueous phase and that no reaction occurs in the organic phase. I make a lot of use of Hess’s law.

Some years ago I was involved in a study of the solvent extraction chemistry of nickel with the BTBP reagents. Here are some equations which I have written which help explain things.

Extraction behavior of nickel(II) using some of the BTBP-class ligands, Ekberg, C., Dubois, I. Fermvik, A., Retegan, T., Skarnemark, G., Drew, M. G. B.,Foreman, M. R. S. and Hudson, M. J. SOLVENT EXTRACTION AND ION EXCHANGE, Volume: 25, Issue: 5, Pages: 603-617, DOI: 10.1080/07366290701512634, Published: SEP-OCT 2007

At low concentrations of C6-BTBP the following equation is true.

Log D = Log K + log [BTBP]

Where D is the distribution ratio, K is an extraction constant and [BTBP] is the concentration of the BTBP in the organic phase. But when the concentration of the BTBP is higher then this equation

Log D = Log K’ + 2.5 log [BTBP]

When it is even higher the best equation becomes

Log D = Log K”

This paper clearly in figure 4 shows that the nickel distribution ratio reaches a plateau when the BTBP concentration reaches a value of about 1 mmol for C6 BTBP.

What I want you to do is to consider a BTBP which distributes between the organic and the aqueous phase.

Kd(BTBP) = [BTBP]org/[BTBP]aq

Then if the BTBP is able to bind to the nickel we can write the following two equations

k1 = [NiBTBP]aq/[Ni]aq[BTBP]aq

β2 = [Ni(BTBP)2]aq/[Ni]aq[BTBP]2aq

And then we combined these equations we get

[Ni]aq / total aqueous nickel = 1 / (1 + k1[BTBP]aq + β2[BTBP]2aq)

[NiBTBP]aq / total aqueous nickel = k1[BTBP]aq / (1 + k1[BTBP]aq + β2[BTBP]2aq)

[Ni(BTBP)2]aq / total aqueous nickel = β2[BTBP]2aq / (1 + k1[BTBP]aq + β2[BTBP]2aq)

Now we are about to add the physical distribution of the three forms of nickel between the aqueous and organic layers, we will use equations like this

Kd(Ni) = [Ni]org/[Ni]aq

Kd(NiBTBP) = [NiBTBP]org/[NiBTBP]aq

Kd(Ni(BTBP)2) = [Ni(BTBP)2]org/[Ni(BTBP)2]aq

I want you to combine these equations to get to now give us (take a deep breath), and trust me this will be pleasureable !

DNi = (Kd(Ni) / (1 + k1[BTBP]aq + β2[BTBP]2aq) + (k1[BTBP]aq/Kd(NiBTBP) / (1 + k1[BTBP]aq + β2[BTBP]2aq)) + ( β2[BTBP]2aqKd(Ni(BTBP)2)/ (1 + k1[BTBP]aq + β2[BTBP]2aq))

Now we take another step to include the constant Kd(BTBP) we get an even bigger equation which is harder to write here on wordpress. But I imagine that you will have no problem with it.

Poisoned milk (snake attack)

Dear Reader,

I have noticed a rather odd and deeply sad case which has been reported from India (Uttar Pradesh state). It has been reported that a 35 year old woman was bitten in her sleep by a poisonous snake, after she woke up she breast fed her three year old daughter. Sadly both of them passed away before they could reach medical help.

I looked up the nature of the venom of a cobra and it is a protein (polypeptide) with several loops of amino acids. The protein crystallographic data base (PDB) has an entry for the King Cobra venom.

Some time ago while at Scandevium in Göteborg, I was talking to a snake expert. I asked a question which I had always woundered about “is a snake immune to its own venom ?”. The snake worker said “no, if a snake was to bite itself then it could poison itself”. The interesting thing is that if the snake injects other animals with its poison. The snake then eats the dead animals, so surely the snake needs to be immune to its own poison when it swallows it.

The problem is that swallowing is a different exposure route to an injection. I worry that something odd has happened in India. I would expect the woman to suffer from the ill effects of the snake bite. But as the venom is a protein I would expect that the digestive system of the child would degrade it and thus render it far less toxic. Also the human digestive system does not normally allow proteins to pass from the gut contents into the blookd. When a person’s digestive system does start to allow a protein to cross in this way is the basis of an allergy to a particular food such as chicken.

I will make some searches of the academic literature and I will attempt to contact some snake experts to ask them about this sad case.

SWR paint

The spoof SWAR-grease advert in the 2017 april edition of RadCom made me smile. Many years ago as a teenager there was a joke doing the rounds about a special paint which would improve the SWR of your aerial. The idea was that your painted your aerial with this magic substance. All very funny, but there is more to it than you might think. If an aerial were to be coated with a thick layer of something with a higher relative dielectric constant than air then the resonant frequency of the aerial will decrease. If we start by thinking of a monopole aerial with a ground plane.

monopole aerial

Then this will have a resonant frequency, but when we add the dielectric cladding (in magenta), then the resonant frequency of the monopole will decrease.

monopole aerial with dielectric cladding

Thus if a very thick layer of “SWR paint” was applied to any aerial then the aerial would be useable at lower frequencies. Some years ago in the 1970s some papers on the subject were written by J.R. James et. al., here they expressed themselves with Smith charts which are nice and easy to understand. Chung-Yu Ting in the 1960s wrote some excellent papers on the topic in which he expressed himself with what I would describe as “extreme algebra”. While some people might not like Smith charts, I suspect that like myself many people would prefer a Smith chart to a wall of algebra.

Also if the coating of the aerial was a substance which is a lossy dielectric then this would increase the resistive losses in the aerial. I would expect that the aerial would be more easy to match with an ATU as it would be more lossy. Also the aerial would appear to be more wideband as the losses would make the changes in impedance as the frequency changes to be less obvious. I know that a 50 ohm resistor makes a very “good” wideband aerial in terms of SWR bandwidth, just sadly the gain of this “aerial” is rather bad.

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