omenti

burning teslas and sandwiches with a bang

Eating lunch and catching up on email, I came across a question on the significance of the recent Tesla fires.  It isn't something I'm comfortable commenting on as anything I might say would be speculation as I don't know the specifics.  That said a fair amount of energy is stored in a large battery - up to 80 kilowatt-hours in the largest model - and one should treat stored energy with respect.  

 

It got me thinking about the energy in my sandwich and comparing it to the battery.  As it happens my sandwich, two slices of homemade rugbrød with my own cashew butter and some store-bought jam - has about twice the energy density of dynamite - nearly 11 vs about 5 megajoules per kilogram.¹  My sandwich packs nearly twice the energy of a stick of dynamite and 131 would hold the same amount of energy as the Tesla.

 

We tend to be careful around explosives like dynamite but don't worry about shrapnel from accidential sandwich detonations.  The difference is dynamite can convert its stored energy to another form quickly enough to impart damaging forces to nearby objects.  Power is the amount of energy released per unit time.  Exploding dynamite produces a lot of power, a digesting and metabolizing sandwich doesn't.

 

Lithium ion automotive batteries have an energy density of about 0.7 MJ/kg.² Much worse than dynamite, a sandwich and especially gasoline.    In the case of dynamite and sandwiches energy is stored in molecular bonds and is released when a chemical reaction takes place.  As it happens hydrocarbons are a dandy material for storing chemical energy.  Their energy density is fairly high, they are relatively easy to handle and natural has built up an enormous supply of them in the form of fossil fuels.³  An interesting feature of hydrocarbons is their creation and disassembly are a form of rechargeable chemical battery.  A process light photosynthesis captures energy and rearranges water and carbon dioxide to form a hydrocarbon and oxygen.  This is stored until a bit of energy is added to cause the hydrocarbon and oxygen to reform giving off water, carbon dioxide and the energy used to initially run photosynthesis.  Terribly nifty.  Sadly we have yet to make our own "good enough" version of photosynthesis although some progress is being made.

 

There are other ways to store energy - if you've ever dropped anything on your toe, gravitaty storage is painfully familiar.   Water allowed to follow downhill releases potential energy converting it to kinetic energy in the process.  We spin turbines and create electricity with this.  Normally the storage part of the cycle is run by the Sun.  Water evaporates, rain falls at high elevations and we don't have to work to move the water uphill.  But sometimes we do.  You can pump water up to a reservoir and release it at a more opportune time to smooth out energy production and demand cycles.  The fact that electricity costs vary throughout the day can make this an attractive financial arrangement - assuming you have the right geography to build artificial lakes in the hills.  The energy density is very low - a 100 meter head of water packs about 0.001 MJ/kg - but it is cheap as utility scale storage goes. 

 

IHere is some grounding if power and energy aren't things you think about every day.  I don't have the time to make a proper table, but for rough comparisons a few common energy densities are (all in megajoules per kilogram and a few common hydrocarbons highlighted⁴

83,000,000 U-235

123 hydrogen 

53.6 natural gas

46 gasoline 

43 E10 gasohol

42.8 turbine A

38  fats

33 E85 gasohol

32 coal - anthracite

24 coal -bituminous

17 carbohydrates and proteins

16 dry wood

15 dry cow dung (I've measured this)

14 coal - lignite

5 dynamite

3 gun powder

0.7 Li-Ion battery (rechargeable)

0.5 compressed air at 300 atmospheres

0.335 latent heat of fusion of water

0.3 NiMH  battery

0.17 lead acid battery

0.02 super capacitor

0.001 water at 100 meters

 

Natural gas and hydrogen may look attractive, but they are normally in gaseous form.  To make them practical for applications like transportation you need to compress or liquify them and that often renders their application impractical.  Also energy densities have nothing to do with the conversion efficiency.  That is a function of how the energy is extracted and must answer to physics.   The gasoline engine in your car running in its sweet spot manages to move about 20% of the energy from the fuel to the wheels while an electric car can get over 75%. 

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¹ The sandwich weighed about 200 grams and had about 525 nutritional calories of stored energy in it.  A good stick of dynamite has an energy density of about 5 megajoules per kilogram.  Converting calories to joules (calories and joules are both units of energy - we could have used BTUs, electron volts, ergs or more obscure forms, but joules are convenient), the sandwich's energy density is about 11 MJ/kg.

A single stick of dynamite stores about 1 MJ .. my sandwich is about 2.2...  One reason why dynamite is so low is that it packs its own oxidizer for it can burn - er explode - so quickly.

 ² There is a range depending on battery chemistry, operating conditions and so on.  Battery energy densities are usually expressed in terms of kilowatt-hours/kilogram. 190 kWh/kg is close to 0.7 MJ/kg and sort of the high end for current electric cars.

³ A quick primer.  In hydrocarbons energy is released by combining them with oxygen and somehow igniting the mixture.  Chemical bonds rearrange and carbon dioxide and water are formed with energy being given off.  A nice way to think of it is to consider a very simple hydrocarbon - methane - with its single carbon atom bonded to four hydrogen atoms.  Combine it with two oxygen molecules and you get

CH₄ + 2O₂ -> CO₂ + 2H₂O + energy

It takes energy to break each of the four C-H bonds - you need to start the reaction.  Breaking the two O=O bonds takes additional energy.  A fair amount so a hydrocarbon like methane is reasonably stable even in an oxygen rich atmosphere.  Now you have some components wandering around and a couple of C=O bonds are formed liberating a lot of energy.  Also four O-H bonds form giving off even more energy.  

The energy released by the reaction is greater than what was required to get it going.  There is enough extra energy to keep the reaction going splitting up other methane and oxygen molecules.  

⁴ These are mostly average values.  For some (batteries, supercaps etc) there are a better values, but these are industrial average numbers .. just use for rough comparisons

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Recipe Corner

If you are cooking for Thanksgiving you probably already have a good idea of what you're making, so rather than the recipe corner I'll offer a link to an old post that speaks about the rate of energy transfer - power.  Our foods are hydrocarbon based and we're impressive compared to our household electrical needs when it comes to power.  Consider that it is no big thing to eat my 525 calorie sandwich in five minutes (we can often consume food at rates two or three times higher) - that's over 7,300 watts!  To put things in perspective a 15 amp circuit breaker blows at 1800 watts and the self cleaning mode on my over is 5,300 watts.  Check out the post for the power involved in fueling your car.

To impress and possibly appall your visitors estimate how many calories someone eats in some amount of time.  Now  multiply by a conversion factor (4187 watts/calorie) and divide by time:      

calories * 4,187/time in seconds == watts.

example: 2,500 calories in 2 hours is (2500*4187)/(2*3600) or about 1,454 watts.  enough to light 14 one hundred watt lightbulbs over the period... I've convinced some people do well over 2,500 calories.

 

getting mooned

Last night I stood in the chilly air watching the Eastern horizon waiting to watch a rocket launch from Wallops Island.  The sky was mostly clear, but the moon was almost full and bright enough that I wondered if I would see very much.  

 

My mind wandered to a lunch in the late 70s.  I was just back from watching a total solar eclipse and had newly developed prints to prove it.  Ray Davis was a regular at our lunch table and I thought he'd appreciate it more than most - after all - he had forced a massive rethinking of the physics deep within the Sun and possibly even deeper.¹ As he shuffled through the deck of images he said "isn't it wonderful that we can detect the Moon and deduce what it is..."

 

I've thought about that over the years.  Our senses only detect a tiny bit of our universe -  our separation from much of Nature is enormous.  We're so much larger than the microscopic and so much smaller than the astronomical.  Our perception of time removes us from the fast and slow.   The range of our senses is incomplete - vision and hearing are primary senses, but occupy a small portion of what exists.  Evolution has provided our brain with filters that give us an imperfect view of what we can sense.

 

Despite all of these shortcomings we also have a powerful tool - our brain.  We are naturally curious and have figured out good ways to ask questions.  Part of this process has involved making instruments that augment our senses.

 

It looked like a big tank buried about two miles underground in an abandoned South Dakota mine, but it was the world's first serious neutrino telescope made to detect neutrinos coming from the Sun.  Neutrinos are nearly ephemeral particles that interact very weakly with matter.  If one encounters a chunk of lead a light-year thick it only has about a fifty-fifty chance of interacting along the way.  But neutrinos are very common - when four protons fuse to become a helium nucleus in the Sun's core two neutrinos are produced in the process.²   Point your palm towards the Sun - an average sized palm will have about seven trillion neutrinos pass through it every second.  It also turns out that if fusion in the Sun's core  suddenly stopped,  it would take thousands of years to notice it visually as light takes many thousands of years to make the journey from the core to the surface. Neutrinos fly out directly, so we'd notice it in about 500 seconds (the time it takes a neutrino to travel from the solar core to the Earth).

 

Since Ray's solar telescope neutrino detectors have grown and improved.  The newest and best is the IceCube facility at the South Pole.  It is designed to look for neutrino bursts from extremely energetic events - exploding stars and beyond.  The biggest problem with neutrino detection is beating down the noise from other sources.  A good way to do this is a thick shield - IceCube uses a lot of ice.  it is relatively easy to sink holes in the ice and then drop strings of detectors down the holes.  The result is a cube shaped array that is mostly embedded in one and a half to two kilometers of ice.  The detectors sense the passage of muons  - particles created from an interaction between a  type of neutrino and the ice.³

 

So what does this have to do with the moon?  Hang on ..  I'm getting there ...

 

Part of the practice of building a particle detector is calibrating it (this is true of any detectors - a point I fear is lost in some early attempt of the Internet of Things).  Muon and neutrino tracks are reconstructed by examining the time and position signals are produced in the cube.  There is also a huge amount of noise that needs to be rejected.  It would be really nice to have a strong muon source at a known location in the sky to use as a baseline.  Unfortunately there isn't one, but there is a very good anti-source called the Moon.

 

The largest source of muons at the Earth's surface are cosmic rays.  They strike atoms in the atmosphere and create muons in the process.  A muon view of the sky would show a mostly constant glow as cosmic rays come in straight lines from all directions.   The Moon is a cosmic ray shield, so if you could only see muons there would be something of a hole where the Moon lurks. 

 

That's exactly what the IceCube guys did - a map of the muon shadow of the Moon.

 

There are other neat ways to detect the Moon outside the visual.  Here is one done with gamma rays.  Processes in the Sun aren't energetic enough to produce a large flux of gamma rays, but cosmic rays (which are really high energy charged particles rather than electromagnetic radiation) can produce them when they strike a surface - the Moon for example.  The Moon is much brighter than the Sun in the gamma ray portion of the spectrum and shows up rather nicely.

 

Oh - the launch was lovely...

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¹ I wrote a bit about this in an earlier post.  Through extremely difficult and careful experimentation and observation of the Sun he had determined either some fundamental particle physics or our understanding of the nuclear physics in stars was incomplete or possibly wrong.  It turned out the problem was with particle physics.

² The actual process is a bit too involved to note here, but basically two protons are converted to two neutrons and two neutrinos.  

³ There are three basic types of neutrinos.  It turns out muon neutrinos are the most practical to detect.  Also the detectors detect light from the rapidly moving muons.  As they move through the very clear ice they give of Cherenkov radiation.  Lots of beautiful physics going on:-)  A proposal to build a similar cube in water was made in the late 70s - the Deep Underwater Muon and Neutrino detector.  It was to live in deep water off Hawaii.  It turned out to be impractical.

 

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Recipe Corner

 

This one was inspired by Yotam Ottolenghi's wonderful Jerusalem cookbook.  The trick to a cookbook is to find a bit of inspiration and then improvise.  It will find its way to a Thanksgiving table.

 

Figs and Sweet Potatoes 

 

Ingredients

 

° 2 large sweet potatoes (about 1 kg or 2.2 lb total) washed

° 5 tbl olive oil

° 3 tbl balsamic vinegar

° 1.5 tbl white cane sugar

° 12 scallions cut in half lengthwise and then cut into inch long segments

° 1 red chili thinly sliced

° 6 ripe figs cut into quarters

° a finishing sea salt (I love Maldon) and fresh ground black pepper

° something to sprinkle over the top ... I used toasted crushed pecans, if you are into  cheese I think crumbled soft goat cheese should work well.

 

Technique

 

° preheat oven to 475°F

° halve the sweet potatoes lengthwise and cut into 3 or 4  long wedges  (I usually peel them, but not here - the skin is tasty when roasted).  Mix with the olive oil, about 2 tsp salt and some pepper

° spread the sweet potatoes out on a baking sheet with the skin side down.  Bake for about a half hour or until soft.  cool

° make a balsamic reduction by putting the vinegar and sugar in a small saucepan.  Bring to a boil, cut the heat and let it simmer until the mixture thickens.  Remove the pan from the heat - you don't want it to get too viscous (less than honey for me).

° arrange the potatoes on a plate

° heat 2 tbl olive oil in a saucepan over a medium heat and add the scallions and chili slices.  Cook for about 5 minutes stiring frequently - don't let the chili burn.  Spoon over the potatoes. Drizzle the reduction over everything - if it is too thin add a few drops of water.  Sprinkle the pecans or goat cheese over the top and serve.

 

 

a tale of early tails

I had come on a most unusual quest.  One that was both nearby and far away and happened to link my work to threads that led back six decades.

 

Sheldon, the high priest, was used to the unusual and led led the way through the maze of crates filled with movie projectors from the 20s, washing machines and vacuum cleaners from the teens, any number of telephone prototypes, a rack from an ESS4 digital switch, the prototype for the traveling wave tube to be used in the Telstar satellite, the first videophone from the late 1920s...  all tempting objects worthy of study.  We weaved through the stacks of lab books - a written testament to the process that was Bell Laboratories - or perhaps I should say the Bell Telephone Laboratories.  I was reminded of the last scene from Raiders of the Lost Arc every time I was in the temple.

 

We were in a large  otherwise unremarkable steel frame building in Warren, New Jersey.  AT&T's storage facility - where the artifacts of Bell Labs were stored.  Sheldon knew it like the back of his hand.  Much of the history was there - except for the crown jewels.  The core patents and notebooks for the fundamental inventions - telephone and transistor for example - were stored in safes we were told.

 

I was after a disk from Harvey Fletcher's early recordings.  We were putting together a demo for a very important potential customer and it seemed reasonable to impress him with a bit of our tradition.  Fletcher was a physicist who had did pioneering work in high quality recording, multichannel recording and even psychoacoustics.  In the early 30s he arranged to record the Philadelphia Symphony Orchestra with Leopold Stokowski conducting.  The technology was home brew and the recordings were remarkable for the day - two and more channels at up to 15kHz.  

 

There they were - the master disks - about one hundred of them.  They were far too important for me to borrow one, but I was compelled to look at many of them and the lab books describing the sessions.  I was able to borrow a test disk of less historical importance.  These were large stereo platters recorded and played with two arms - the concept of a stereo grove came a few months afterwards.  I also was able to find submasters of the important recordings that were made in the 1950s and borrowed one.

 

Harvey would have been proud. We were showing off a a way to compress music by simply throwing out what the mind ignores as it creates music.   It was uncleverly called Advanced Audio Coding.  I set the compression software at a 11:1 ratio discarding 10 parts of the signal for every 11 it encountered.¹  The trick, of course, is to pick the right parts to save.  A call to his executive secretary revealed our potential customer liked the Beetles and Bob Dylan so tracks were compressed from our personal CDs.

 

When he listened to our player this, recorded on April 29, 1932, is what greeted him.

 

Download Wagner - Die Walküre - Ride of the Valkyries (aac file .. most players will handle it)²

 

Amazing fidelity for its day, the kit was too impractical for widespread use.

 

I'm often stuck by how early developments take place in many technologies and how many paths are tried.  

 

The late 20s and early 30s were an interesting time if you were interesting in video and audio.  In the period of about two years several television systems were developed including color television and a videophone. There were a few dozen television schemes by the late 20s. Hobbyists in the US were buying kits and watching FCC sanctioned transmissions from about 30 stations scattered around the country.  It seemed like a natural extension of the telephone and had been predicted forty years before - people saw the telegraph, telephone and Edison's moving pictures and assumed a technical mashup was possible.  

 

A sketch of a possible future technology can be fairly clear.  Less apparent is how we get there and completely unknown are the societal implications.

 

Using smartphones as an example Horace Dediu has a piece on the diffusion of a technology great Asymco blog.  Such discussions are important in the understanding technologies and markets, but they ignore a very complex set of pathways on the left side of the curve - before the technologies became marketable.  The point where, at any given time, it looks like several candidates might emerge and it is possible none of them will survive in their then current form.  Many of us knew in the 90s we'd be carrying small computers with some sort of radio and possibly a digital camera.  Some of us would include a GPS in the device.  None of us had any clear ideas of a final winning form or who would do it or what the societal impact would be.  There were guesses, but betting on them at that stage is dangerous.

 

Our society needs a set of pioneers working at the leading edge.  Most of the paths won't go anywhere, but they can influence others and have remarkably important impacts.  Digital photography came out of an afternoon's realization of some of the implications of a certain type of semiconductor memory - at a time when the type of memory that would take hold in computers was still up in the air.  Unfortunately the lead times for these early forms of applied research are so long that few companies can invest in them - companies today are rewarded for having very lean R&D budgets and by really focusing on very near term - usually under five years - development.   AT&T and IBM did when they were monopolies and others were allowed to do so with rich contracts from the government as part of the Cold War.  Now Universities carry much of the load - they are important, but not sufficient. 

 

Tales of the tails --  fantastic areas when anything seems simultaneously possible and impractical.

 

There are too many ways to go and I'm about out of time.  It would be fun to write about television, computer memory, cars, heavens - so much...  So clear in retrospect, so difficult in the period.

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¹ This is a common compression ratio that fools most people - 128 kilobits per second - down from the 1411 kbps of a compact disc.  The AAC codec is used for iTunes.  Tests have shown even excellent ears have problems statistically distinguishing CD from compressed AAC at 160 kbps.  Apple uses 256 kbps.  Of course you can get into the imperfect sound on a compact disc, but a significant learning I've had over the years is that, for most people, it doesn't matter.

² I assume no responsibility for triggering  Mel Blanc, Arthur Bryan and Chuck Jones flashbacks.

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Recipe Corner

 

This one was very good - it has a nice buttery mouthfeel from the avocado and should be very healthy. I don't know where it came from - it was in my notes for a long time and I modified it.

 

Mashed Sweet Potatoes with Avocado

 

Ingredients

 

° 1 large sweet potato

° 2 heads of garlic (less if you like - I used two medium sized heads)

° 1 tsp olive oil

° 1 medium avocado

° 1/3 cup slice yellow onion

° juice from 1/2 lemon

° sea salt and freshly ground pepper (to taste)

° an herb like parsley to garnish

 

Technique

 

° oven to 400°F

° clean and dry the sweet potato poke holes in it and nuke in your microwave for about 3 to 4 minutes (depending on how strong your microwave is)

° lop off the top half inch or so off a head of garlic so the individual cloves are exposed

°  put the topless garlic head on foil and drizzle with olive oil.  Seal the foil

° put the sweet potato and foiled garlic on a pan and roast for 20 minutes until cooked - leave the garlic in

° after 30 minutes total cooking time take the garlic out.  It should be soft and wonderful smelling.  Let it cool and squeeze out the cloves

° mash the garlic and sweet potatoes and season with salt and pepper

° peel the avocado and mash with lemon juice.  Combine with the mashed sweet potato/garlic mix and serve topped with onions and the herb.

 

 

 

carpetland and west africa

Carpetland..

 

The other day I drove by Verizon's headquarters in Basking Ridge, NJ.  Before AT&T was sold to SBC, it was the palatial AT&T headquarters complex.  Several of us spent time there working with upper management in the business units as well as a few above that level.  In theory we were helping them understand the Internet and what it might mean, but we saw how that turned out.

 

One of the members of my human computer interface department was an anthropologist. I was a bit puzzled by the Basking Ridge dress standard, so she offered a bit of fashion guidance to sort out the power structure.  AT&T had 15 management salary grades and eight effective levels.  Dress standards were enforced by a common convention.  If someone was wearing a fitted Brooks Brothers suit you knew he (and it was almost always a he) was a E band executive or perhaps someone aspiring to that level.  It would be presumptuous for a D band to dress that well.  The BU chiefs and top corporate people were usually dressed a level above that - it was my introduction to noticing bespoke tailoring.  

 

Bonnie, our anthropologiest, noted all of this was "tribal".  The high level people were physically separate.  These were the people who used the helicopters and corporate jets.   Their lair was carpetland - the carpeting was so thick it was borderline difficult to walk across.

 

Subject matter experts from the Labs could get away with more casual clothing. Directors usually wore suits, but not particularly impressive cuts.  Department heads and below could be very casual and many of us dressed that way to differentiate ourselves.¹  

 

Over time I've come to see fashion as expression a person makes about themselves.  It can be personal, creative and even artistic, but it also is an interaction with the culture we are embedded in.  As culture is dynamic, fashion can be ephemeral.  As a personal statement it can be timeless.

 

Fashion has traditionally been created by designers, selected by buyers and promoted through advertising.  My Danish friend Jheri notes how boring most American fashion is.  Many of us, particularly the young, feel a necessity to be part of a current trend and are very susceptible to advertising and store displays.  We want to be individuals, but there seems to be a need to be part of a group.

 

Fast fashion is a direction the low end of the industry is taking.   Mostly a change to distribution that relies on very cheap third world labor and a hyped up promotion channel.  Clothing is no longer designed to be durable, but rather close to the moment.  It tends to follow a very uniform pattern.  It is still boring, but the clock cycle has been increased.

 

Signs of change are emerging.  Designers often relied on the muse of the street, but now street fashion is being communicated to everyone directly through blogs, Pinterest and a few other social mechanisms.  The quality of design varies, but the number of people participating is growing and it is having an impact on design.  Importantly a curious artifact of American copyright law is that most fashion is immune ..  we may have to think of a world where high end designers collaborate with people from the street.  

 

Johanna Blakley's (she is with the Norman Lear Center) TEDx talk is worth watching

 

Jheri and I have spent some time investigating possible trajectories for made to measure clothing - she has an interesting guest post here.  The bottom line is, at least for women, most off the shelf clothing has fit issues.  This can be addressed with money and/or technology and changes in technology combined with new distribution mechanisms may be very disruptive to a rather enormous industry.  Things get even more interesting when you consider customization and shared intellectual property from the street.  

 

When you are studying something this complex it helps to look into something similar but different...  I like to say that studying the weather on Jupiter and Saturn is a great way to gain insights into the Earth's weather.

 

Last Summer I because aware of some amazing looking wax print fabric displayed in the Fashion Institute of Technology's collection.  These are associated with West Africa with the best examples being from one of the more important companies in the area - Vlisco.  

 

I had no idea what a wax print was so it was time to investigate.  It turns out the Dutchman Pieter Fentener van Vlissingen sorted out how to product Indonesian batik fabric in the mid 1800s.  Batik is a cloth that is patterned with a dye resistant wax technique and it had a reputation for beauty and price at the time. Batik, modifying the technique for something much like a printing press, figured out he could manufacture it in Holland and export it to Indonesia at a profit.  Unfortunately the quality wasn't up to snuff and Vlissingen found himself with a ship full of surplus cloth and more coming from his factory.² He tried selling it in West Africa and it took hold.  Over the years it became popular, improving in quality adopting traditional African patterns.  Over time the catalog of patterns became huge.  They were the story of the people and, with revolution and independence, Vlisco wax print fabrics had become a central part of West and Central African culture.

 

Now it gets very interesting.  

 

West African women treasure Vlicso fabric.  Good clothing for the rich and emerging middle class is frequently made with using it. Labor is inexpensive and often has high quality - higher quality than most Western pieces.  Even small villages have a woman or two doing tailoring work.  Everything is made to measure.  Vlisco doesn't make finished pieces - they sponsor fashion shows and regularly put out pattens, but this is promotion. A woman buys the fabric, finds a tailor and uses an existing pattern, an of her's or the tailor's, or some combination.  The pieces fit perfectly and have the style the owner wants telling her story.³  

 

We may find ourselves going down a similar path, but there is an important cultural issue.  It turns out most people in West Africa identify with a tribe.  The identification has a big impact on their lives and one does not have to signal through clothing what they belong to.  It gives a great deal of freedom compared to what we see in the West.  A woman can show much more creativity that what is our social norm.  I'm wondering if the growing importance of street fashion and its global nature (a good deal of The Sartorialist blog is external to NYC) with trigger a greater degree of expression in the West as made to measure and its customization  - a mass customization becomes possible.

 

Culture - from the tribally reinforced conformity of carpetland to the freedom of West Africa - perhaps there are lessons that help us puzzle out some of the emerging threads in this story.

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¹ I used to take my slide rule for quick calculations.  These were back of the envelope estimates used in sessions that investigated ideas quickly.  My director told me to stop bringing it as it was intimidating the executives.

² There are several variations to the story - this is the most frequently quoted.  The companies production was in Holland for about a hundred years and then some shifted to Africa.  The finest cloth was, and is still, produced in Holland and is highly prized.  About ten years ago a British company bought Vlisco and is currently expanding.

³ I note that Western conventions are rapidly mixing with the culture and poorly fitting and cheap clothing from South Asia is becoming much more common among young women.  Some of this is tailored, but the quality is often the effort isn't justified.  Africa may be drifting to where were are now.  Their terrible transportation infrastructure is acting as a moderator.

 

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 Recipe Corner

 

This is not authentic, but is in the spirit of a Cameroonian peanut and sweet potato soup.  As with all soups the measurements aren't terribly important, but be sure to do the seasoning to your own taste.  

 

Cameroon Inspired Sweet Potato and Peanut Soup

 

Ingredients

 

° 2/3 cup of roasted peanuts (not dry roasted)

° 2 tsp oil

° 2 large onion chopped (about 2 cups?)

° about 800g vegetable broth (most in west africa would use a chicken broth) 

° 2 large sweet potatoes cut in inchish cubes (maybe 6 cups total)

° 1 tbl cumin

° 1/2 tsp ground black pepper

° salt to taste (not much if your peanuts were salty)

° 2 large cans (mine were about a pound) cans of garbanzo beans drained 

 

Technique

 

° process peanuts in a food processor for a few minutes until smooth

° heat the oil over medium-high heat and sauté the onions until lightly browned.  

° add all other ingredients and bring to a boil

° reduce heat and simmer uncovered for about 30 minutes until the sweet potato is tender.