Basics of Genetics

In trying to solve the puzzling results he found in his experiment, Mendel developed a hypothesis that explains what genes do on chromosomes when they are transmitted, even though he had no idea what genes or chromosomes were. We can divide Mendel’s hypothesis into four related ideas. First, Mendel argued that the different versions of what he called “heritable factors” must be responsible for producing the different traits. A “heritable factor” was responsible for the purple flower, and a different one was responsible for white flowers. What Mendel called heritable factors are what we now call genes. The different versions of the genes are what we call alleles. For example, the gene responsible for flower color in peas has two alleles, one for purple flowers and the other for white flowers.

Mendel’s second idea was to conclude that each individual had not one but two different particles for each character. In other words, each individual has two alleles for each gene. Mendel made this conclusion knowing nothing about chromosomes, but microbiologists confirmed this by showing that each offspring has two copies of every gene.

Mendel’s third suggestion was that one allele of the two that an individual possesses might actually be dominant over the other one. In other words, one allele is expressed even if the other allele is present. We say that one allele would be dominant, and the one that is not expressed we call recessive.

Let’s go back to Mendel’s experiment to clarify this. He started with true breeding lines of purple and white flowers. He argued that these true breeding lines, that produce only one or the other flower color, must always have two of the same kind of allele. The purple flower plant has two purple alleles and the white plant has two white alleles.

The offspring of this cross must receive one allele from each parent, and thus have one purple allele from one parent and one allele from the other parent. Because all of the offspring in the F1 generation had purple flowers, Mendel argued that the purple form must be dominant over the recessive white form.

Mendel’s forth idea was that when a parent produces gametes in preparation for sexual reproduction; each gamete only gets one of the two alleles that that parent possesses for a particular gene. If we are talking about flower color, if a parent possesses two of the same kind of allele, when it produces gametes, all of the gametes would have only that kind of allele. For example, purple plants from Mendel’s parental generation would only make gametes that have purple flower alleles. The same would be true of the parental white plants.

Here’s the kicker. When we have individuals that have two different kinds of alleles, for example individuals in the F1 generation, can produce two kinds of alleles. They have both a purple allele and a white allele, so they can produce gametes that have either purple or white alleles. In fact, they do so in a 50:50 ratio. It is equally likely that their gametes would have one or the other allele.

The original parental plants Mendel started had two alleles for the same color. We call individuals that posses two of the same kind of allele “homozygous”. The parental plants were homozygous. By contrast, when an individual possesses two different kinds of alleles for the same gene, we say that it is heterozygous. Individuals in the F1 generation were heterozygous.

We give some labels to the alleles. We’re going to give the purple flower allele the capital letter P, and the white flower allele the lowercase p. Giving the uppercase and the lowercase versions of the same letter is one common way that geneticists designate different alleles for a gene.

Because the original in Mendel’s cross were homozygous, they could produce only one kind of gamete. We’ve already said why their offspring should have all purple flowers. If the purple allele is dominant to the white allele, the F1 offspring all have one big P and one little p. Because they all have a big P, which is dominant, they’ll all be purple, regardless of the fact that they have the little p too.

Now I want to introduce two new terms: phenotype and genotype. An organism’s phenotype refers to what it looks like. It refers to the traits that organism expresses. For example, we would say of a purple plant that it has the purple phenotype. The genotype of an organism represents its genetic makeup. The genetic makeup of an organism clearly would have something to do with the traits that the organism expresses. It is important to keep in mind, though, that a given phenotype might be produced by different genotypes.

Let’s go back to our pea plants. Because the purple allele is dominant over the white allele, there are two possible genotypes that could give rise to the purple flower phenotype. Individuals having two big P alleles clearly would have the purple phenotype. So would individuals having one P and one p allele. Both the PP and the Pp genotypes yield the purple flower phenotype. That’s because the purple allele is dominant over the white allele.

On the other hand, the only way we could get the white flower phenotype is if we have a genotype that has both p alleles. This helps us explain the surprising findings from Mendel’s first cross. The white flower phenotype had disappeared completely in the F1 generation, but not the white allele, which was hidden in the heterozygous genotypes of those individuals.

Let’s look at what Mendel found when he crossed these heterozygous F1 individuals together. He found that the offspring in the F2 generation produced both purple and white phenotypes in the ratio 3:1. To understand that 3:1 ratio, let’s consider again the kinds of gametes and the proportions of gametes that those F1 individuals could produce. Because these individuals were all heterozygous, they could produce two kinds of gametes, either a purple allele or a white one. Indeed, each individual would produce equal numbers of both types of gametes.

This makes an intuitive sense. This is very like flipping coins. We’ve got two possibilities; we could come up with a heads or a tails. The key question to ask is what proportion of individuals in the F2 generation would have the possible genotypes that could be formed by joining the gametes that the F1 individuals produced.

An easy way to think about this is to use a convention that we call a Punnett square. Along the top of the square we have one column that has big P on top of it and one column that has little p. Along the side, we have one big P and one little p.

The point of making this grid is that it helps us think about how these different gametes can combine to form genotypes in the offspring. If you fill out the grid by connecting the two alleles possible for each cell, you’ll see that you’ll get three different genotypes. We have PP, Pp and pp individuals. What you also see is that both PP and Pp have the dominant allele, which is the represented in the phenotype. Looking at this you’ll expect to see three purple individuals for every one individual.

With this we can explain why Mendel found a 3:1 ratio in his experiment in the F2 generation. Mendel’s brilliant insight was to put all of this together without knowing anything about genes or the physical basis of chromosomes.

We now refer to this key idea of the existence of two different alleles in each individual as “Mendel’s Law of Segregation”. This law is significant for a number of reasons. First, it completely refuted the blending hypothesis and demonstrated that heritable factors must be particulate. Second, what Mendel did was to provide a framework for looking at more complicated patterns of how traits are transmitted between parents and offspring, which allow us a more complete understanding of the genetic basis of inheritance.

1 Comment:

Amazing Flower said...

wow it's such a good lesson you share thanks and love from Singapore Florist :)

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What’s in the small print?

Online shopping is big business with millions of transactions taking place every day worldwide, but do we know exactly what we’re signing ourselves up to? Dr Joasia Luzak investigates the provision of information and what it means to be transparent.

Every online trader operating within the European Union is required to provide consumers with ‘clear’ and ‘transparent’ information about the transaction to ensure the customer is aware of the contractual agreement taking place. This is a duty of the trader and is in place to protect not only the customer, but to also ensure traders are complying with the law. Despite this legal requirement, there are currently no agreed standards or guidelines in place to define what transparent information looks or sounds like. This grey area leaves the topic of transparency open to interpretation and potentially abuse, leaving traders and consumers alike at risk.

Funded by the Open Research Area (ORA), Dr. Joasia Luzak, Associate Professor of Law at Exeter University is the principal investigator of a new three-year international study aimed at addressing this issue. With a multi-disciplinary, multi-national team behind her, Dr. Luzak leads on this exciting project undertaking comparative and empirical legal research in order to develop clear guidelines that will better protect all those involved.

Having grown up with her mother working as a Polish language teacher, Dr. Luzak has always been aware of how people can play with language to manipulate it’s meaning and subsequently people’s understanding of it. That’s why this project not only focuses on what’s being said, but how what’s being said is provided. The aim is to develop guidelines that will also offer recommendations on font type, font size, colour, layout and the general user journey as each of these factors contribute to whether or not the information is understood, or read at all.

Dr. Luzak explained, “I’ve always been interested in the provision of information. I read a lot and I read fast, but even knowing the consequences, as a consumer I rarely read the provisions provided. Some academics argue we should lose all this information because it doesn’t do anything. However, if there is a problem, being able to go back to the contract and seeing what you agreed to is paramount.” The project, which has been running since September 2016 has already delivered some interesting results that indicate there are ways to ensure more people will read and understand the information being provided.

The project team works from both Germany and the Netherlands. The team in Germany, led by Professor Alexander Wulf (SRH Hochschule Berlin) has completed a literature review that looked at what is considered effective provision of information across a multitude of disciplines including communications, neurosciences and psychology. There appears to me a huge amount of information on provisions, but very little when it comes to the transparency of providing them. This section of the project has already generated some interesting insights for which a paper is being drafted.

To fully understand what is meant by transparent information, it is important to also review current perceptions. To do this, an interview questionnaire has been devised to determine the current understanding of what is required to be legally compliant in this area. This will be used to question consumer authorities, consumer organisations, employees of the Ministry of Justice and traders associations across England, Germany, Poland and potentially the Netherlands to gain Pan-European insight. Dr. Luzak is also working with the help of a post-graduate student who will be using this questionnaire to conduct interviews in Croatia. As a relatively new member of the EU and having a less developed knowledge of consumer law, this is set to add an interesting element to the project. In context to Brexit negotiations, the project is unlikely to be affected given that the aim is to create guidance where nothing currently exists. The second part of the empirical research will devise a consumer survey to examine their perception of transparency.


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Sunday, June 10, 2012

letter to the editor

A couple of months ago, I found this article on "Christian Worldview" by Albert Mohler and wanted to share my email response to him.

Never Having to Say You’re Dead? The New Interest in Reincarnation

One of Dr. DeBell’s patients told of finding relief from grief over her mother’s death by discovering that in previous lives she had been an Italian merchant who sold textiles along the Amalfi Coast, a herbalist in Africa, and a freed slave in New Orleans.
Lisa Miller has a point when she suggests that the growing acceptance of reincarnation is tied to a loss of Christian knowledge and conviction among Americans. Nevertheless, it seems very likely that this new acceptance of reincarnation is more a matter of therapeutic fads and cultural fashions than as huge theological shift. The shift is more likely a loss of Christian conviction in the face of secularization — not a comprehensive embrace of Eastern worldviews.

Dear Mr. Mohler,

I just found your article online about reincarnation and wanted to share my viewpoint as a Cultural Christian who believes without doubt that our souls take on human form time and time again.  Of course the first thing I wanted to do was poke holes in your argument, specifically the following quote from the good book:

The Bible is an awesome resource.  One from which a person of any religious persuasion can learn and grow.  But it's also a book that has been, can be and will be translated and interpreted for all time.  As many will agree, the book is alive.  The idea of reincarnation does not compete with this quote from The Bible.  A man does die once - well, in most cases.  Sometimes a man can die, be resuscitated then die again later.  But, yes, we agree that an individual man usually dies once.  And, yes, after that comes judgment.  The soul reviews the life of its individual, along with Jesus or other Masters and, according to the research done by folks like Raymond A. Moody, experiences the joys and pains inflicted upon others during that lifetime.  There is no "do-over".  That personality existed once in your steadfast chronology and the soul grew exponentially by the lessons learned in that lifetime.

The second idea I'd like to refute is that this is an American's need to stay connected to material wealth.  In fact, I have spend years working on disconnecting myself emotionally from material things, as Buddhists teachings have advised.  In addition, I can safely assume that when my soul does return to earth, I will not be "me" again.  I will not live in my house again.  I will not drive my car again.  I could be a man in Africa, I could be a nun in Switzerland, I could be a humpback whale for all I know.  So the argument that westerners are frantically reaching in attempt to hold onto possessions is simply invalid.

My faith is not a "fad".  I believe, as well as BILLIONS of others around the world, that while the man lives once, energy is forever.  Like trees and flowers that bloom and die, capturing energy for a short time then releasing it back to the universe only to capture it again...  so does the human body.  No energy can be created or destroyed; therefore the soul exists eternally.  Before AND after death.  Just think:  If God can launch my soul into a little baby's body once and pluck it out of a wrinkly old body once, then who's to say that God doesn't have the power to do that a hundred times?  A thousand times?  Our earthly lives are a drop in the ocean.  Why would God waste all of that heavenly energy when He/She/We can recycle it over and over?  Doesn't it make good efficient sense to reincarnate souls?  Do you really think that when you die you will spend eternity sitting on a cloud and playing the harp?  What or where was your soul before you were born?  These are the big questions that I asked myself and why reincarnation was the only idea that made sense to me.

Another incorrect assessment is that folks always regress to lifetimes when they were somebody special or important.  I have regressed through meditation many times and visited many past life times.  I have seen myself as a poor Chinese woman in the times before Christ - no one special.  I have seen myself as a little girl living in the country - no one special.  I have seen myself as a civil rights activist - passionate, but seemingly un-special.  I've seen myself as a nomad in Nepal - completely alone in life.  But I have had experiences when special people have been revealed to me, too.  The Universe released these lives to me when the time is right.  *Note:  I don't see what's so special about being a caveman who was eaten, or about being a caveman at all.

I respect the Christian faith and those who believe so passionately that they are living their "one sacred life".  I believe with equal passion that God created man in harmony with the Universe, as a reflection of nature, with a soul that cycles just like everything else on Earth.  And I love Jesus.  He is awesome.  We can all learn from his messages of love and compassion.  I can't limit his teachings to a single book, though.  I prefer to keep my eyes and ears open to the messages that God's great universe delivers in the here and now - and not limit myself to the messages provided to us through lens of founders of Christianity.  Those men had clear agendas.  I, as a seeker, do not.

Vanessa Gobes

p.s.  Dr. Weiss has a terrific saying regarding the experience of channeling past life memories:  "When you hear hoofbeats, don't look for zebras."

Peace, love and gratitude to my readers.  Feel free to post comments here.  Love to hear all of your ideas and viewpoints.  Oh, and please share the blog with friends if you like.

1 comment:

  1. p.s. even the title "new interest" makes me wrinkle my nose. how is a philosophy that's older than christianity "new"?


Rewrite Lebanon’s unfair tax laws

Make the rich pay more to benefit all

Lebanon's tax system is unfair and unproductive

As part of Executive’s ‘10 Ways to Save Lebanon’ issue, we asked leading experts from a range of fields to put the case for one major policy for the country. In this article, economist Jad Chaaban makes the case for rewriting the country’s tax laws.

Building on broad shoulders

Jad Chaaban

Jad Chaaban is an associate professor of economics at the American University of Beirut and the lead author of the UNDP’s Arab Human Development Report 2015

  1. E said:

    You compare the tax regime to European countries. However, in European countries, the taxes are much higher than in Lebanon, but in return the people get access to free/low cost schooling, medical care, unemployment & retirement benefits, etc etc
    Would you think by increasing the taxes, the Government should not offer these things? if so, what would be the impact on the budget?

  2. Kermit said:

    Reforming the Taxation module, is a good place to start a discussion on public revenue. Citizens expecting a return on their taxable income in the form government services is a good place to start a discussion on government public spending and civic responsibilities.

    Talk is good. But every time someone in Lebanon starts coming up with ideas on how to ‘modernise’ the establishment or using a ‘western’ setup as a blueprint evades the base of all civic development.

    In the West, there are several taxation modules and several civil modules. Some are flawed, some are not; but their existence is based on a singular service that makes them all function. The same singular service that in Lebanon keeps on being ignored and perhaps has contributed over the many years why so much public reform has failed.

    I am talking about the Postcode system and I certainly do not just mean having letters delivered to a particular address.

    In the West, everything from income to electoral registrars to asset ownership to government planning and development to statistics etc .. are all linked to fixed addresses – a code – a post code.

    Until every dwelling in Lebanon has a fixed (government-issued) house number and every area has a fixed (government-issued) post code, only then can you start establishing and enforcing direct taxes as well as providing public services to postal areas. No reform plan will ever work without proper planning, no planning can be conducted without public statistics, every civilised statistics module is based on variables between areas/postcodes and every public service that we receive here is linked to the Full Name and Address.


Anglican bishop urges Church of England to support the freedom to marry

This week, Anglican Bishop Alan Wilson, who has served as the Bishop of Buckingham in the Diocese of Oxford for the Church of England since 2003, recorded a video as part of Out 4 Marriage, a British campaign that encourages prominent individuals to express their support for the freedom to marry. In the video, Wilson explains that the Church of England has typically been ahead of the curve on opposing discrimination against gay and lesbian people, but that on the issue of marriage, the Church is far behind.
Bishop Wilson, who is a married father of five, explains that respecting marriages between same-sex couples may actually enrich the institution of marriage, not diminish it as so many conservative religious people in England have claimed. Wilson explains:
In over thirty-three years of ordained ministry, it's been an amazing joy to help people celebrate their marriages - not a piece of paper, but a way of life. Marriage enriches society and strengthens community. It makes God's love visible in a broken world - it's good news for everyone. I don't think the Church has anything to fear from formally recognizing love like that for what it is.
In the United Kingdom, same-sex couples may currently enter into "civil partnerships," which provide some, but not all, of the protections that marriage provides. In the past few months, many high-profile British figures, including current Prime Minister David Cameron and former Prime Minister Tony Blair, have wholeheartedly advocated for a law to establish the freedom to marry in the country.
Bishop Wilson joined those British voices with his passionate and moving video. The video is an example of how many people of faith are guided by their religion to support - rather than reject - the freedom to marry. Bishop Wilson supports love and wants people to foster that love for themselves and their families. He says:
Love is the fulfilling of the law - God is love, and those who live in love live in God, and God lives in them. That's why I'm out for marriage.
To read more about how communities of faith draw on their religion to strenghten their support for marriage for same-sex couples, check out these great resources. And click here to find out more about the freedom to marry abroad


the Rational Radical

No Ipod Needed!  Listen on your computer.

Bogus "Class Warfare" Charge

Republicans are once again using verbal sleight-of-hand against the Democrats, and so far seem to be getting away with it.

When Democrats criticize the Bush tax cut plan, Republicans charge that the Democrats are using "class warfare" arguments, or even that they're actually fomenting class warfare.

Pointing out the economic injustice of the Bush tax plan isn't conducting class warfare. The Bush tax plan itself is class warfare.

A plan enabling the richest 10% or so of the population to aggrandize unto themselves even more of the nation's wealth than the 71% they already own, at the expense of the middle and working class -- that is class warfare with blood and guts, real life consequences.

It's like when Southerners accused Martin Luther King, Jr. of causing racial conflict when he marched against segregation. King's exposing and protesting against racial injustice was not the cause of racial conflict, the racial conflict was caused by the oppression of the African-American population.

Likewise, any class warfare that exists is caused by the Republican assault on the financial integrity of the poor and working class -- NOT by those who expose it.

Update:  Here's a mainstream columnist finally picking up this concept.

2004 Update:  Here's Bob Herbert on the latest example of greed at the top.

the Rational Radical: Bogus "Class Warfare" Charges

Latest Updates on my BLOG!!

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System Working State S0

System power state S0, the system working state, has the following characteristics:

Power consumption
Maximum. However, the power state of individual devices can change dynamically as power conservation takes place on a per-device basis. Unused devices can be powered down and powered up as needed.

Software resumption
Not applicable.

Hardware latency

System hardware context
All context is retained.


Following Jesus is ALL about Freedom

Since my last blog post, several of you have asked me to expand on what the difference between being a "Christian" and "following Jesus"? Like I said, some may see this as semantics but there are several crucial differences. First and foremost, it starts with correctly understanding the implications of the atonement. Mainstream evangelical theology... Continue Reading →

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Oracle PL/SQL Associative Arrays Example

I used this example in a presentation the other day, so I figured I’d post it up for anyone who is interested. This uses features that are new to Oracle 11g (such as Indexing by a VARCHAR2 key). Sample Code showing use of Associative Arrays declare — create an associative array data type type account_map [...]

Inserting multiple rows in one SQL statement

Comparison of Auto Incrementing Primary Key feature in several SQL Dialects

The Problem The whole point in using SQL to interact with a database is for developers to be able to use the same basic language to interact with any database. The intentions were good but, as it turns out, even something as universally desired as having a primary key that automatically increments itself is not [...]


Tuesday, February 9, 2016

Private sector mourns death of former PM Koirala

The private sector has expressed grief at the demise of former Prime Minister and Nepali Congress (NC) president Sushil Koirala. Koirala, 77, passed away today morning at his residence. The private sector was stunned by Koirala's sudden demise, they said.
Issuing separate statements, the Federation of Nepalese Chambers of Commerce and Industry (FNCCI), Confederation of Nepalese Industries (CNI), Nepal Chamber of Commerce (NCC) and Non-Resident Nepali Association (NRNA) described Koirala's passing away as 'a great loss' to the nation.
According to the president of FNCCI Pashupati Muraraka, the country has suffered an unbearable loss. "Koirala had a significant contribution to the democratic movement with commendable leadership," he said, adding that the private sector will always appreciate his contribution of leading the country through the transition and promulgation of a new Constitution. It was Sushil Koirala, who drivered the promulgation of a new Constitution through the Constituent Assembly, despite a huge pressure from in and out of the country.
The FNCCI also claimed that Koirala was always concerned for the economic development of Nepal. "Now the implementation of the new Constitution and lead the country towards a prosperous future rests on the political parties," the umbrella organisation of the private sector said, adding that Koirala had played a legendary role in the democratic movement and especially in institutionalising democratic republic in the country. “During meetings with the private sector, Koirala used to encourage the private sector to make investments and attract foreign investment as well."
The biggest achievement of Koirala's political career was the promulgation of the Constitution on September 20, 2015. In his capacity as the Prime Minister, Koirala played a crucial role in generating political consensus for the statute’s endorsement despite various pressures.
Under his leadership, the Nepali Congree (NC) re-emerged as the largest party with the highest number of votes. Koirala led the government from February 2014, after the election to the second Constituent Assembly (CA). He was elected as the NC party president in September 2010.
Koirala, when was the premier, used to say that Nepal would embark on a economic development journey and the government’s focus would shift towards economic development once the Constitution was promulgated.
According to CNI, the country lost an honest and simple person with a clean character. "Koirala was a strong supporter of independence, democratic values and liberal economy," it further said, adding that Koirala’s death has not just created a void on the political front but also on the economic front.
The chamber has also lauded Koirala’s role in uniting the political parties for the promulgation of the new Constitution. "The people’s hopes of seeing a new constitution through the Constituent Assembly was fulfilled during his tenure,” according to president of chamber Rajesh Kazi Shrestha.
The supporter of open market and free economy, Koirala firmly believed open market and free economy play a crucial role for country's development and prosperity.
According to the chamber, Koirala always played an inspirational role for the country’s private sector. "Koirala believed that the sustainable development of the country was possible only through an open market, liberal economy and private sector," the NCC said, adding that he always believed the nation will prosper with private sector-led economic growth.
Though, he did not have much knowledge about economics, and was not aware of how it exactly functioned, he was keen on attracting domestic and foreign investments for employment generation and economic development of the country. He also used to say that the country’s resources have to be used properly so that prosperity could be shared.
Going against the tide, he also made some bold decisions like signing power trade deal with India during his 20-month reign from February 2014 to October 2015. Likewise, the signing of two agreements on development of 900MW Upper Karnali and 900MW Arun-3 hydroelectric projects worth over $2 billion was also possible under Koirala's premiership.
Koirala’s government also revived talks on construction of 5,600MW Pancheshwar Multipurpose Project after a hiatus of almost two decades; allowed at least three foreign companies to establish cement plants worth tens of billions of rupees; and lured billions of rupees of investment in the hotel sector. Koirala, however, did not sign any agreement that was against the national interest, despite pressures from within and outside his party.
During his tenure as Prime Minister Nepal's received a record Rs 270.60 billion foreign aid commitments in fiscal year 2014-15. Koirala also supported the process of revising or framing around three dozen policies and Acts to attract foreign investment and protect the interest of investors.
The Koirala government was also hailed by the international community as it was quick in responding the devastating earthquake of April 25 and mobilised the National Planning Commission -- chaired by him -- to conduct Post Disaster Needs Assessment (PDNA). An International Conference on Nepal's Reconstruction (ICNR) on the basis of PDNA helped Nepal receive funding commitment of $4.1 billion for reconstruction and rehabilitation works from the international community.
The international community, including Non-Resident Nepali Association (NRNA) has also mourned the sudden demise of Koirala.
NRNA president Shesh Ghale, in a statement, said that Koirala’s death had stunned the association. "We have lost our parent, who always remained helpful and guided the NRNA in its movement," he is quoted in the statement. "Koirala’s demise has caused an irreparable loss to the nation."

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How do animals become extinct? | Education

How do animals become extinct? We believe that an animal species is endangered when its distribution is drastically reduced, threatening the survival of the species

We believe that an animal species is endangered when its distribution is drastically reduced, threatening the survival of the species. Before the advent of human extinction is the result of natural selection as happened with the dinosaurs. Studying fossil remains, we conclude that one species becomes extinct every thousand years, but since the early 20th century, expanding and developing technology that takes away more and more space for nature, and the rate of extinction has risen to a disturbing kind of year. |
addition to the naturally destroy habitat, man is the principle of the natural balance of hunting - often illicit - and bringing the same kind of environment that have proved to be enemies. addition Man damages natural habitats, destroying the forest to get to the wood, drawing on the unreasonable way the bowels of the Earth, to come to the mining, industrial effluents polluting the water, using over-protective agents for field crops, etc.
protective equipment and Water pollution can lead to the extinction of certain animal species. Take as an example of peregrine falcons who was on the brink of extinction. Its usual prey are the ducks that were fed fish and algae from areas contaminated with DDT. This is an insecticide, taložeći in tissue ducks, falcons raised in the process of changing the transfer of calcium in the egg. In some cases, calcium in the shells were so small that shot before the young are developed. In others, however, the calcium level was so high that young people have not managed to break the egg shell and to go outside.
Animals that are exposed to danger because of man to die out, the turtle - which are hunted for their shells -, elephants - the tusks -, crocodiles - the skin -, wolves and big cats - for fur - , whales - the oil -. predicted the extinction of many species in the near future. Among the most vulnerable are: Javanese rhinoceros, Mauritius kestrel and Chinese alligator. are made lists of endangered animals, which are called Red Book. Among the most vulnerable groups of the big cats and birds prey.
animals and plants contribute to maintaining the ecological balance necessary for the survival of humankind. There are laws to protect animals in the wild and institutions - such as national parks - and the facilities under the supervision of a man - such as zoos - which protect certain animals from extinction. Today zoos are often meant for a certain type of guarantee that they will be able to save from the nature of which is less suitable to their survival. Sometimes the protection of some kind of very complex problem, as in the case of a bear that lives only if every individual has the available 25-50 km2 of forest. This means that for the survival of many groups bear need large expanses of forest.

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Presentation on theme: "FLUIDS AND ELECTROLYTES"— Presentation transcript:

2 Terms to KNOW Total Body Water (TBW) Intracellular fluid Extracellular fluid Intravascular fluid Interstitial fluid Solvent

3 Electrolyte Dissociate ion cation Anion Buffer Isotonic

4 Hypotonic Osmotic gradient Diffusion Osmosis Active transport Facilitated diffusion Osmolality

5 Osmolarity Osmotic pressure pH

6 PaO2 PaCO2 HCO3- Acidosis Alkalosis Metabolic Acidosis Respiratory Acidosis Respiratory Alkalosis

7 WATER Most abundant substance in the body Aprox. 60% of TBW 70 kg adult (154 lbs) TBW aprox. 42L (11 gallons) Water distribution

8 Various compartments all separated by a cell membrane
Intracellular fluid (ICF) Fluid inside body cells Largest compartment Contains 75% of TBW

9 Extracellular Fluid (ECF)
All of the fluid found outside the body’s cells Contains the 25% of TBW Two divisions intravascular fluid interstitial fluid

10 Intravascular Fluid Outside the cells, within the circulatory system Pretty much the same as blood plasma Interstitial Fluid Outside the cell membranes but outside the circulatory system

11 Examples of Interstitial Fluid
Synovial fluid Aqueous humor of the eye Secretions Water is a universal solvent Solvent dissolves other substances yeilding a solution

12 ELECTROLYTES when placed in water dissociates into electrically charged particles or IONS Cation Positively charged ion Anion Negatively charged ion Cations in our body

13 Sodium Na+ Common in extracellular fluid Regulates the distribution of water WATER FOLLOWS SALT Transmission of nervous impulses

14 Potassium K+ Prevelent in extracellular fluid Transmission of electrical impulses Calcium Ca++ Muscle contraction Nervous impulse transmission

15 Magnesium Mg++ Several biochemical processes enzymes require magnesium to function ATP, DNA and RNA also need Magnesium

16 Anions in our body Chloride Cl- Balances cations Renal function Closely associated with sodium

17 Bicarbonate HCO3- Primary buffer Phosphate HPO4- Energy stores Buffer primarily in the intracellular space

18 OSMOSIS AND DIFFUSION Cells have semipermeable membranes When the concentration of fluid is equal on both sides of the membrane this is ISOTONIC When the concentration of fluid is less on one side of the membrane this is HYPOTONIC

19 When the concentration of fluid is greater on one side of the membrane this is HYPERTONIC
The difference in concentration is the OSMOTIC GRADIENT There is a shift to maintain homeostasis or a state of equilibrium

20 Molecules will normally move to an area of higher concentration to that of lower concentration which is DIFFUSION Diffusion does not require E Water, which moves faster than electrolytes moves across the membrane to dilute the higher concentration of electrolytes

21 Osmosis The movement of any solvent across the membrane Active Transport {requires E} Movement against the osmotic gradient less concentrated to more concentrated area i.e.

22 The inside of a myocardium cell must be negatively charged
The inside of a myocardium cell must be negatively charged. Sodium being positively charged diffuses passively into the cell. Sodium ions are pumped out of the cell while potassium is pumped into the cell More sodium than potassium is moved achieving equillibrium

23 Facilitated diffusion
Requires the assistance of a helper protein to move into the cell An example is Glucose

24 Osmolality The concentration of solute per Kg The movement of water and solutes across the cell membrane maintains a state of equilibrium of osmolality Osmolarity The concentration of solute per L of water

25 Sodium maintains osmolality in the extracellular space
Potassium maintains omolality in the intracellular space

27 Acid-Base Balance The regulation of H+ in the body H+ Is acidic A deviation has an adverse affects on all biochemical functions of the body pH Potential of Hydrogen

28 Through metabolism and other biochemical processes, H+ is constantly produced
Normal pH is 7.35 to 7.45 <7.35 = Acidosis >7.45 = Alkalosis THREE FORMS OF REGULATION

29 Bicarbonate Buffer System
The fastest The players [in equilibrium with H+ ] Bicarbonate {HCO3-} Carbonic Acid {H2CO3-} Either H+ will combine with bicarbonate ion to produce carbonic acid or

30 Carbonic acid will dissociate into bicarbonate ion and hydrogen ion
Erythrocytes contain have an enzyme called carbonic anhydrase which converts carbonic acid into CO2 and H2O and this occurs very rapidly Most buffering occurs in the erythrocytes

31 Respiration | two other mechanisms
Kidney function| of regulation Respiration An increase blows off CO2 thus decreases H+ thus decreases pH Kidneys Modifies the concentration of HCO3- in the blood

32 So what is the significance of all this?
Increased elimination of HCO3- lowers pH Decreased elimination of HCO3- raises pH The kidneys achieve acid-base balance by removing or retaining certain chemicals So what is the significance of all this?

33 The bottom line is to determine:
If a patient is in a state of acidosis If a patient is in a state of alkalosis If the disturbance is respiratory in nature If the disturbance is metabolic in nature In order to make this determination we must know the norms

34 pH 7.35 to 7.45 PaCO2 35 to 45 mm Hg HCO3- 22 to 26 mEq/L 75 to 100 mm Hg

35 The first determination is if the patient is in a state of acidosis or alkalosis
Next is to determine if the disturbance is respiratory or metabolic in nature

36 Assess the PaCO2 level If respiratory the PaCO2 should rise as the pH falls {acidosis} conversely the PaCO2 should fall as the pH rises SO……. If the pH and PaCO2 are moving in opposite directions then the disturbance is respiratory

37 To determine if the disturbance is metabolic in nature the HCO3- is considered
As pH increases, so should the HCO3- The opposite is true Thus If the pH and HCO3- is moving in the same direction then the disturbance is metabolic in nature

38 Ph PaCO2 HCO3- 22-26 Fall Rise Normal 7.35-7.45 35-45 Respiratory
Acidosis Fall Rise Normal Alkalosis Metabolic

39 Ph 7.22 PaCO2 55 HCO3- 25 Respiratory Acidosis Alkalosis Metabolic

40 Ph 7.22 PaCO2 55 HCO3- 25 decreased increased normal Respiratory
Acidosis decreased increased normal Alkalosis Metabolic

41 pH 7.50 PaCO2 42 HCO3- 33 Respiratory Acidosis Alkalosis Metabolic

42 pH 7.50 PaCO2 42 HCO3- 33 increased normal Respiratory Acidosis
Alkalosis Metabolic increased normal

43 partially compensated fully compensated
COMPENSATION Remember with the buffering systems the body attempts to regulate hence a state of compensation uncompensated partially compensated fully compensated

44 In a state of uncompensated or partially compensated the ph is still abnormal
In full compensation the pH is normal but other values may not be

45 Partial Compensation Assess the pH this step is unchanged Assess the PaCO2 remember the pH and PaCO2 should be moving opposite If however they are moving in the same direction would indicate a metabolic disturbance

46 If as an example the PaCO2 was decreasing it would mean the body was blowing off CO2 in order to return pH to normal limits. Meaning the respiratory system is acting as a buffer system As evidenced that this is actually metabolic in nature then plugging in the PaCO2 moving in the same direction………

47 The determination then would be a metabolic disturbance with partial respiratory compensation
Assess the HCO3- which moves in the same direction as the pH If they move in the opposite direction, the disturbance would actually be respiratory in nature with the kidneys acting as the buffer system by retaining HCO3- .

49 Ph PaCO2 HCO3- 22-26 Rise Fall 7.35-7.45 35-45 Normal but <7.40
Fully Compensated Ph PaCO2 35-45 HCO3- 22-26 Respiratory Acidosis Normal but <7.40 Rise Alkalosis Normal but >7.40 Fall Metabolic

50 Ph PaCO2 HCO3- 22-26 Fall Rise 7.35-7.45 35-45 Respiratory Acidosis
Partially Compensated Ph PaCO2 35-45 HCO3- 22-26 Respiratory Acidosis Fall Rise Alkalosis Metabolic

51 The only difference between fully compensated and partially compensated is whether the pH has returned to within the normal range

52 RESPIRATORY ACIDOSIS Causes [hypoventilation] Head injury Narcotics Sedatives Spinal cord injury Neuromuscular disease

53 Atelectasis Pneumonia Pneumothorax Pulmonary edema Bronchial obstruction Pulmonary embolus Pain Chest wall injury or deformity Abdominal distension

54 Signs and symptoms of respiratory acidosis
Dyspnea Respiratory distress Headache Restlessness Confusion Drowsiness unresponsiveness

55 Tachycardia Dysrhythmias

56 Respiratory Alkalosis
Causes [hyperventilation] Anxiety Fear Pain Fever Sepsis pregnancy

57 Signs and Symptoms Light-headedness Numbness/tingling Confusion Inability to concentrate Blurred vision

58 Dysrythmias Palpitations Dry mouth Diaphoresis Spasms of arms and legs

59 Metabolic Acidosis Causes Renal failure DKA Anaerobic metabolism Starvation Salicylate intoxication

60 Signs and Symptoms Headache Confusion Restlessness into lethargy Kusmal respirations Warm flushed skin Nausea and vomiting

61 Metabolic Alkalosis Causes Antacids Overuse of bicarbonate Lactate as used in dialysis Protracted vomiting Gastric suction High levels of aldosterone

62 Signs and symptoms Dizziness Lethargy Disorientation Seizure Coma Weakness Muscle twitching Muscle cramps Tetany

63 Nausea and vomiting Respiratory depression

64 Tetany Involuntary contraction of muscles Proracted Prolonged Aldosterone a hormone that increases the reabsorption of sodium ions and water and the release of potassium ions

65 Atelectasis the lack of gas exchange within alveoli, due to alveolar collapse or fluid

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New Zealand quake scientists discover surprise: Hot water

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This Oct. 3, 2014 photo shows the drilling site of an earthquake fault near Franz Josef Glazier on the South Island in New Zealand.

This Oct. 3, 2014 photo shows the drilling site of an earthquake fault near Franz Josef Glazier on the South Island in New Zealand. (Photo: John Townend/Victoria University via AP)

WELLINGTON, New Zealand (AP) — When researchers in New Zealand drilled deep into an earthquake fault, they stumbled upon a discovery they say could provide a significant new energy source for the South Pacific nation.

The scientists found the water in the Alpine Fault was much hotter than expected, and could potentially be harnessed to generate electricity or provide direct heating in industries like dairy farming.

The finding was surprising because geothermal energy is usually associated with volcanic activity, but there are no volcanoes where the scientists drilled. Because the Alpine Fault stretches for hundreds of kilometers (miles) like a spine along the country's South Island, the energy source could be enormous.

Led by Victoria University of Wellington professor Rupert Sutherland, the study was published Thursday in the journal Nature.

Sutherland said the intention of the study near the popular tourist destination of Franz Josef Glacier was to collect rock cores and install monitoring equipment rather than gauge water temperatures, but researchers are excited about their unexpected findings.

"Economically, it could be very significant for New Zealand," Sutherland told The Associated Press in an interview. "It's a totally new paradigm."

In their study, the scientists say they believe two actions are creating the hot water.

First, they say, previous earthquakes have moved hot rocks up from deep within the Earth into the mountains along the fault line.

Second, the shaking has broken up the rocks, allowing rain water and snow melt to quickly percolate through the hot interior of the mountains, which concentrates the heat beneath the valleys.

Sutherland said they found the water in the fault reached 100 degrees Celsius (212 Fahrenheit) at a depth of 630 meters (2,100 feet). Water typically gets progressively hotter with depth, but under normal conditions it doesn't reach that temperature until about 3 kilometers (2 miles) underground.

One hundred Celsius is boiling point on the Earth's surface, although water doesn't boil underground because it remains under pressure, much like the liquid inside a pressure cooker.

The Alpine Fault is among the most active faults in the world. It typically creates large earthquakes about once every 300 years, and scientists figure there is about a one-third chance it will rupture again in the next few decades. The resulting quake could devastate some New Zealand towns, although the fault is not located near any large cities.

Sutherland said the discovery of the hot water doesn't have any bearing on predicting when the next quake might hit.

He said before any commercial ventures begin, scientists will need to determine the extent of the hot water, what purposes it could be used for, how easy it is to extract, and whether it can be done safely. He said he didn't think removing water from the fault would risk triggering a quake but scientists would need to study that question as well.

New Zealand already generates about 15 percent of its electricity from geothermal sources, most of it from the Taupo volcanic zone in the central North Island. Sutherland said the declining coal mining industry in the South Island could provide needed expertise, engineering and infrastructure for any new geothermal ventures on the Alpine Fault.

He said the hot water could potentially be used by the dairy industry as a heating source to dry milk. Milk powder is one of the nation's largest exports.

Dave Craw, a professor at New Zealand's University of Otago who was not involved in the study, said that in a global context, the high temperatures found in the fault are very unusual.

"The famous San Andreas Fault of California was drilled in a similar way to this New Zealand borehole, and the temperatures and thermal gradient encountered there were much lower than the Alpine Fault," Craw wrote in an email. "The Alpine Fault is a spectacular thermal anomaly for an area without active volcanic activity."

Bill Ellsworth, a professor at Stanford University who helped review safety aspects of the study but who was not involved in the research, said that because elevated fluid pressures weaken faults, the study's findings also have important implications for understanding the workings of quakes on similar faults around the world.

© Samoa Observer 2016

Developed by Samoa Observer in Apia


Saturday, April 23, 2011

Malcolm X: A Life of Reinvention

Article first published as Book Review: Malcolm X: A Life of Reinvention by Manning Marable on Blogcritics.

'Abdu'l-Baha (1844-1921), Head of the Baha'i Faith from 1892-1921 wrote, "Truthfulness is the foundation of all the virtues of the world of humanity. Without truthfulness, progress and success in all of the worlds of God are impossible for a soul. When this holy attribute is established in man, all the divine qualities will also become realized." (Abdu'l-Baha, Tablets of Abdu'l-Baha v2, p. 459)

This "holy attribute" is as essential to the process of understanding historical figures as it is to the development of the personal soul. James. W. Loewen argued this point eloquently in his "Lies My Teacher Told Me". Loewen critiques the tendency toward "heroification" of historical figures. He describes "heroification" as "a degenerative process (much like calcification) that makes people over into heroes. Through this process, our educational media turn flesh-and-blood individuals into pious, perfect creatures without conflicts, pain, credibility, or 'human interest" (pg. 11).

The late Manning Marable's "Malcolm X: A Life of Reinvention" provides a sterling example of a commitment to truth-telling about his subject. The book "makes it plain" as brother Malcolm would say. Marable acts as a kind of freedom fighter, in this case fighting to free Malcolm the man from Malcolm the myth. This includes myths propagated by Malcolm himself in his celebrated "Autobiography". For example, Marable argues that the "Autobiography" greatly exaggerates Malcolm's criminal history in order to emphasize the regenerative power attributed to the teachings of Nation of Islam leader Elijah Muhammad.

Marable takes the reader on a journey from the Garveyism of Malcolm's parents to the moment of Malcolm's murder with the concept of "reinvention" as an organizing theme. From Malcolm Little to Malcolm X, from Minister Malcolm to civil rights martyr, what emerges is the story of a man figuring out who he is and who he wants to become. Marable does a masterful job of describing the familial, social, cultural and politic contexts that influenced Malcolm's numerous reinventions as he worked and reworked his sense of self and public image. Malcolm's existential struggle is so palpable that the very pages of this book appear to perspire.

Among the most implacable of these enemies proves ironically to be the Nation of Islam itself. Marable's description of Malcolm's troubled relationship with the Nation's leadership and his eventual split reads like a political thriller. A deepening atmosphere of dread wafts from the pages as the war of words escalates into outright violence and climaxes in a hail of bullets at the Audubon Ballroom.

Once the book reaches the point of Malcolm's assassination, Marable approaches the topic with a near "CSI-style" attention to reconstructing the events of that fateful day. He raises a variety of disturbing questions related to who really killed Malcolm X and the investigation that followed (or didn't).

However one ultimately answers those questions, at the end of the book I was left with a different one: "What if Malcolm had lived?" I can only imagine the wisdom and insight he might have brought to bear on some of the most challenging questions of the day. What would he say about American involvement in Afghanistan, Iraq and now Libya? What role might he being playing in relations between the West and the Muslim World? What would he think about the so-called "Arab Spring"? What example might he provide of living as a Muslim in America? Thanks to his killers we will never know.


A long and winding track takes you out of the village of Casalini for almost 3 km before you reach the hushed, olive-flanked Perugian valley where La Rosa Canina lies. Sandro Belardinelli and his wife made their home here in 1989, setting aside part of two 15thC cottages as guest quarters.
  The dog-rose, from which the farm takes its name, is just one of the profusion of flowers which give the banks of the front garden their perennial colour. Behind the house, the menagerie of animals and the wire-fenced vegetable garden breathe real country living into what might have been just another converted farmhouse.
  Inside, the guest rooms are reasonably proportioned and furnished with a hotch-potch of furniture, old and not so old. The wooden mangers in the downstairs dining room are a reminder that it was once a cattle stall. The dinner menu, based upon traditional cucina umbra, varies according to season, but Swiss-born Signora Belardinelli places emphasis on the quality of her food - all vegetables are home produce, as is the olive oil, much of the meat, and the jam on the breakfast table.


Disaster could strike at any time. Sure, you’ve got peanut butter and jelly on hand, but what if you lost power for three days, a few weeks or even a year?

Are you equipped to handle severe weather and long-term power outages? How about a dirty-bomb or biological attack?

Answer the five questions below to find out how prepared you are really are.

How did you do? Share your result in the comments section below.


Article | Open

A novel, optical, on-line bacteria sensor for monitoring drinking water quality

  • Scientific Reports volume 6, Article number: 23935 (2016)
  • doi:10.1038/srep23935
  • Download Citation

Today, microbial drinking water quality is monitored through either time-consuming laboratory methods or indirect on-line measurements. Results are thus either delayed or insufficient to support proactive action. A novel, optical, on-line bacteria sensor with a 10-minute time resolution has been developed. The sensor is based on 3D image recognition, and the obtained pictures are analyzed with algorithms considering 59 quantified image parameters. The sensor counts individual suspended particles and classifies them as either bacteria or abiotic particles. The technology is capable of distinguishing and quantifying bacteria and particles in pure and mixed suspensions, and the quantification correlates with total bacterial counts. Several field applications have demonstrated that the technology can monitor changes in the concentration of bacteria, and is thus well suited for rapid detection of critical conditions such as pollution events in drinking water.

One of the major challenges in ensuring safe drinking water is the difference between the time it takes to produce, distribute, and consume the water, and the time it takes to investigate whether it is safe to drink1 it. In drinking water some of the major health risks are constituted by microorganisms2,3,4,5 either coming from the water source, entering storage or distribution systems unintendedly or growing in the water. Unfortunately, by the time routine microbial analysis reveals a possible bacterial pollution, the investigated water has often already been distributed and consumed.

Water utilities are required to verify the water quality on a regular basis, applying standard methods at predetermined sampling frequencies. These methods are typically growth-based, laborious and time-consuming, giving answers one to three days later6 and merely providing point information without insight into temporal development. Further, application of heterotrophic plate count methods only reveal a fraction of the total population present in drinking water as they do not include viable, but non-culturable bacteria7,8,9.

Automating existing technology for on-line detection of bacteria10,11, e.g. flow cytometry12,13, or indirect indicators of bacterial activity, such as ATP14, have been given much attention over the past years. A great deal of effort has also been put into the development of sensors that sense bacteria by direct contact with the sensor surface15,16,17. Unfortunately, these solutions are either complicated to operate, require addition of chemicals, daily or weekly maintenance, or are too expensive to be deployed throughout distribution networks. The contact type sensors further encompass the probability of a bacterium actually touching the sensor surface. Considering the relatively low concentration of bacteria in drinking water, this probability may be very low.

Since many parameters in drinking water systems may vary significantly, spatially and timely, it is likely that routine monitoring with lab sampling will fail to catch short-term pollutions18. Consequently, major utilities often increase the number of analyses beyond the requirements and supplement their data with on-line measurements of turbidity, conductivity, etc.19,20,21 Since such parameters respond to more than just bacterial content, they are likely to show false positives as well as false negatives in terms of microbiological pollution detection.

Conclusively, the delay and limitations associated with current growth-based methods and the missing specificity of current on-line methods make it practically impossible to proactively react on contamination events in today’s drinking water distribution systems. What seems to be missing in this technology gap is a compromise between the two extremes: A sensor that may have a longer response time than the indirect sensors (pH, conductivity, etc.) and may be far less specific than the laboratory-based methods, but instead provides valuable information on the dynamics of bacteria concentrations in general. For such a sensor to be applicable in remote locations, e.g. throughout a drinking water distribution network, it should need as little maintenance as possible, should not require chemical supplies, and should not create hazardous waste.

In this paper, we present a rapid, chemical-free method for on-line monitoring of non-specific bacteria in water with a 10-minute time resolution, based on 3D scanning by a moving digital microscope. We aim to prove the sensor concept, demonstrating its applicability to distinguish between microbial and abiotic particles, and detect variations so fast that it enables proactive actions to potential pollution events, thus providing a new tool for risk management in drinking water applications. The ability of the method to quantify particles, measure their size and eccentricity, and classify them as either bacteria or abiotic particles, has been proved through laboratory tests. The applicability and robustness of the method in on-line monitoring have been demonstrated through field tests. Various drinking water systems have been monitored by the method revealing both stable base lines and responses to various events.

Measuring principle

The developed sensor consists of: 1) an optical flow-cell holding the water sample during analysis, 2) a dark field imaging setup with a light-emitting diode (LED) light source, a magnification lens, and a complementary metal-oxide semiconductor (CMOS)-based camera arrangement (Fig. 1A), and 3) an image analysis system to identify and classify individual particles.

Figure 1: The various steps in determining the concentration of bacteria and abiotic particles.
Figure 1

(A) Schematic of flow cell, light source, lens, and camera. (B) Image stack of a particle coming into focus and out again as the tilted image plane moves across it. (C) Extraction of parameters from recorded image stacks and comparison to library data. (D) Classification of particles in “Bacteria” and “Abiotic particles”.

The water sample is led through the flow-cell by the pressure of the water source or by a peristaltic inlet pump. Initiating each measurement, the water sample is sealed inside the flow cell, designed to minimize internal circulation and thus fix the particles spatially. The sample is stagnant in the flow-cell while scanned along the length of the flow-cell by the tilted imaging setup, causing the acquired images to span a fixed volume of 6 μl (Fig. 1A). After sampling and image acquisition, the cell is flushed for one minute by the source water, preparing it for the next sample.

The camera is only moved a small fraction of the image length (2.3%) between individual images, causing each particle to be recorded on up to 40 images. Due to the tilting of the acquisition setup, each particle may be out of focus on the first images, in focus on the middle images, and out of focus again on the later images22 (Fig. 1B). Besides information about the particle in focus, information about the diffraction of light by the particular particle is also recorded, allowing for classification of each particle into specific particle classes, i.e. bacteria and abiotic particles.

Our newly developed software divides the images into segments containing individual particles, which are subsequently gathered in image stacks of 10 to 40 images. From each image stack, 59 optical parameters related to the nature of the original particle is extracted. Some spatial parameters are linked to a thresholded image of the particle in focus, e.g. area, length, perimeter, eccentricity, convexity, and binary moments. Other parameters are linked to the grayscale image, e.g. contrast, light-scattering properties, absorption, moments, granularity, and features extracted from Fourier-transformed image spaces23. The size feature, dividing the identified particles into 20 size bins ranging from <0.62 μm to >9.5 μm, can be used as an additional indicator of deviations from the normal baseline of particle size distribution in the particular water matrix.

The results, such as concentrations of bacteria and abiotic particles, particle eccentricities or sizes, are transferred wirelessly to a data server that handles and distributes the data to the users. At server level, further algorithms can be applied to set off alarms based on e.g. levels of bacteria or certain patterns in the development of the bacteria concentration.

Particle classification

To distinguish between different types of particles, e.g. bacteria versus abiotic particles, a software library was established from scanning suspensions of known particles from each group i.e. bacteria and abiotic particles. The library included morphologically different bacterial shapes, such as rods, curved rods and cocci, as well as various abiotic particles relevant to drinking water, e.g. humic acid, clay, and iron oxides. Each suspension scan included 59 measured parameter values to characterize the specific particle types.

Neural networks were used to establish a boundary between bacteria and abiotic particles in the 59-dimensional space spanned by these parameters. The result was an algorithm capable of distinguishing between bacteria and abiotic particles based on image acquisition (Fig. 1C). Illustrating the 59-dimensional space is not graphically possible, which is why the graph in Fig. 1C is a mere projection onto two dimensions.

By comparing each particle recorded in an unknown sample with the library, the individual particles may be classified as either a “bacteria” or an “abiotic particle” (Fig. 1D).

Handling fouling of the optical windows

The background of scattered light in the recorded image is measured as an indication of fouling on the wetted surfaces of the flow cell. Biotic or abiotic fouling on the flow-cell window diffracts the light and increases the background level of the recorded dark-field image. By monitoring this level and setting limits for flow-cell exchange based on these levels, the influence of fouling on the measured concentrations is confined to an acceptable and negligible level. The sensor tracks the fouling level of the flow-cell with the same time resolution as the particle measurements. When the flow-cell needs to be replaced, the sensor alerts the user.

If for example an air bubble or a significant spot of fouling should affect a small fraction of the analyzed volume, the sensor rejects this volume as bad volume and corrects the analyzed volume accordingly.

Proof of concept

The concept of detecting, measuring, and classifying particles was evaluated for: 1) accuracy of classification measure in pure and mixed suspensions, 2) accuracy of size measure, 3) linearity of concentration measure.

To evaluate the ability of the sensor to classify particles correctly, we used the sensor to analyze a series of monotype suspensions of known abiotic particles and bacteria, including pure cultures of known bacteria, unknown bacteria isolated from drinking water and abiotic particles. The classification accuracy (Fig. 2) was determined as the percentage of identified particles assigned to the correct class, e.g. the percentage of abiotic particles (96 ± 2%, s.d.) reported for a suspension of lepidocrocite or the percentage of bacteria (88 ± 2%, s.d.) reported for a suspension of Vibrio natriegens. For monotype suspensions, the classification accuracy was 90 ± 7% (s.d.).

Figure 2: Ability of the sensor to distinguish between bacteria and abiotic particles in suspensions shown as the fraction classified as bacteria.
Figure 2

The suspension included model particles in pure suspensions (orange: bacteria, blue: abiotic particles) and mixtures of bacteria and abiotic particles (grey). Mixed suspensions would ideally be reported as 30 and 70% bacteria if they were classified 100% correctly. Error bars represent standard deviations.

Mixed suspensions of Lactococcus lactis and humic acid and mixed suspensions of E. coli and lepidocrocite were prepared in ratios of 30/70 and 70/30. When analyzed by the sensor, the ratio between classified bacteria and abiotic particles was 19/81 and 57/43 in the ‘L. lactis and humic acid’ suspension and 27/73 and 60/40 in the ‘E. coli and lepidocrocite’ suspension (Fig. 2). For mixed-type suspensions, the average classification accuracy was 78 ± 14% (s.d.).

To address the linearity of the sensor signal, a dilution series covering three decades of suspensions of 1) lepidocrocite particles (Fig. 3A) and 2) E. coli (Fig. 3B) were analyzed by the sensor. The analysis revealed linear regression coefficients of determination (R2) of 0.9796 and 0.9971, respectably. For comparison, linear regression between dilution factors of the E. coli suspension and total bacterial counts by DAPI staining gave an R2 of 0.9889.

Figure 3: Linearity of the sensor signal and size measures.
Figure 3

(A) Linearity of the sensor signal for abiotic particles in tenfold dilutions of lepidocrocite. (B) Linearity of the sensor signal for bacteria in tenfold dilutions of E. coli as well as total bacterial counts. (C) Accuracy of particle size measured by the sensor, standard diameter refers to certified sizes of standard particles used. Inserts indicate the measured size distribution (by number of particles) with indication of the actual size (vertical orange lines). For peaks split between two size bins, both bin sizes are plotted.

To further investigate the correlation between sensor response and total counts, the growth of bacteria in tap water with different nutrient additions was followed by both methods (Fig. 4). The results showed stagnant bacterial numbers for tap water with no addition and with 0.02 mg/l yeast extract. When 0.2 and 2 mg/l yeast extract was added, the results showed increasing bacterial numbers with a maximum after 2–7 days (0.2 mg/l) and 2 days (2 mg/l) followed by a decrease in the number of bacteria. The sensor response was similar to the concentrations obtained by DAPI staining (R2 0.9727).

Figure 4: Development of total bacterial counts in drinking water with added yeast extract as reported by the sensor and measured through DAPI staining.
Figure 4

Error bars represent standard deviations.

The size feature of the algorithm, dividing the identified particles into 20 size bins ranging from <0.62 μm to >9.5 μm, was verified by analyzing suspensions of certified monodisperse polystyrene beads of 0.771, 0.99, 1.53, and 3.004 μm in diameter. These were chosen to represent bacteria sizes expected to occur in drinking water. Particle sizes reported by the sensor decreased in the correct size bin, approximately within 5% of the correct diameter, or in the adjacent bin up to 10% off the correct value (Fig. 3C). The sensor reported silica beads of 0.69 μm in diameter in the size bin of 0–0.62 μm. Larger particles with a relatively high density may be expected to precipitate during the image acquisition, and the concentration of such particles may thus be underestimated by the sensor.

Based on the relatively small volume measured inside the flow cell, the theoretical detection limit (a single particle detected) is 1.6 × 102 particles/ml, which is also the theoretical resolution provided the entire flow-cell volume is included in the measurement. Sampling from a water source with such a low concentration of particles would be associated with a high degree of uncertainty due to sample inhomogeneity. The sensor is designed to operate in drinking water, which seldom contains less than a few thousand particles/bacteria per ml, according to our field test experiences. Depending on the nature of the particles and how much background scattering they cause, the upper limit has proved to be around 1–5 × 106 particles/ml. Above this concentration, small particles are not detected due to the high background scattering, and the sensor thus underestimates the concentrations.

The sensor was investigated in various drinking water systems, primarily Danish and French. In a Danish non-chlorinated distribution system, one sensor was installed at a waterworks and one at a downstream reservoir (Fig. 5). A 9-km-long pipeline connected the waterworks and the reservoir. The water had an average transport time of 32 hours with an average flow velocity of 0.08 m/sec. The abiotic particle concentration was substantially lower in the reservoir water than in the waterworks effluent, probably due to sedimentation during the transport as a result of the very low flow velocity. The bacteria concentration did not change accordingly, and the sensor thus clearly detected different behavior of abiotic particles and bacteria.

Figure 5: Dynamics of the concentration of bacteria and abiotic particles at two locations in a large Danish drinking water distribution system measured by the sensor.
Figure 5

At the waterworks outlet, the concentration of abiotic particles was approximately three times higher than the bacteria concentration. At the downstream reservoir, the concentration of bacteria and abiotic particles were similar and significantly lower as compared to the waterworks. The substantial variations at the reservoir were caused by the flow direction, with highest concentrations in the water coming from the reservoir.

The pipe was used as inlet to as well as outlet from the reservoir. The sensor recorded alternating water qualities reflecting whether the water came from the pipeline or the reservoir. The turbidity and the measured concentration of the abiotic particles showed similar behavior (R2 0.92). The measurement of the bacteria (Fig. 6) differed clearly from these patterns (R2 0.78) and turbidity were thus less able to detect the changes in the bacteria concentration.

Figure 6: Turbidity, bacteria, and abiotic particles measured at the inlet/outlet of a Danish clean water reservoir.
Figure 6

Note the distinct difference between the water entering (around 5 × 103 cells/ml) and leaving (2–4 × 104 cells/ml) the reservoir.

The sensor was also installed at a Danish cattle slaughterhouse, where the water quality did not meet guideline values (based on routine analyses of plate count numbers). A notice to boil the water prior to consumption had been issued. A sensor was installed to monitor the water inlet to the slaughterhouse by sampling every ten minutes for 11 weeks. The sampling revealed a daily peak in the concentration of both bacteria and abiotic particles (Fig. 7A). Overlaying individual days of data showed the peak to occur in the morning between 5:30 and 7:30 in the morning (Fig. 7B). During the peak, the sensor detected an increase in the bacteria concentration from 1–4 × 104 to 2–5 × 105 cells/ml and an increase in the concentration of abiotic particles from 3–5 × 104 to 3–8 × 105 particles/ml.

Figure 7: Water quality monitoring at a Danish cattle slaughterhouse.
Figure 7

(A) Part of the 11 weeks monitoring campaign showing bacteria peaks occurring daily. (B) Overlaying daily bacteria curves for normal workdays show a daily peak occurring in the early morning. One day also showed a gradually increasing bacterial concentration. (C) Applying the developed bacteria sensor, total bacteria counts, and plate counts. Peaks for plate counts at 22 °C and total counts co-occurred with the peaks measured by the sensor. However, plate counts at 37 °C showed peaks that did not correlate with other parameters.

During a sampling campaign around the estimated time of the peak, grab samples of the water was collected before each sensor measurement and analyzed for total counts and plate counts at 22 and 37 °C. The bacteria and abiotic particles recorded by the sensor correlated well with the water quality analyses at the time of the peak (Fig. 7C). From DAPI staining of non-homogenized samples, it was noted that part of the bacteria within the samples were clustered together in groups or pieces of biofilm, which could explain why the total numbers in the homogenized sample used for total counts were 3–4 times higher than the numbers quantified by the sensor.

It was discovered that the reason why the microbial water quality guidelines were exceeded was a combination of stagnant water in an inappropriate piping layout upstream from the sensor location and the onset of the morning cleaning. The lack of flow during the night prevented the sensor from picking up the slow increase in bacteria concentration that was expected to have occurred upstream.

The development of the presented sensor focused on the recognition of particles based on shape and pattern of light diffraction. From a size distribution point of view, emphasis was put into classifying particles in the range of 500 nm to a few micrometers according to the size of most bacteria24. The library used to build the classification algorithm was thus dominated by particles in this size range. From field test data, we have experienced that particles above 5 μm are scarce, and particles above 10 μm hardly occur within the sample volume. Particle size distribution in Danish drinking water measured by Coulter Counter (data not shown) typically showed that less than 0.1% of the particles were larger than 5 μm. Thus, the influence of particle sedimentation can be ignored for the majority of particles.

In most optical imaging systems, a spatial resolution limit is reached around 1 μm. The imaging system presented uses a 505 nm light source and a lens with a numerical aperture of 0.2. The Abbe diffraction limit for such a system is 1.26 μm25, which is well above the bacteria sizes characterized. Due to the added information about how the particles behave over time and in and out of focus, it is possible to characterize objects below the resolution limit of the imaging system. Particles larger than 3.0 μm were not investigated. However, the accuracy is expected to be at least as good as for the smaller sizes, due to the higher number of pixels covered.

Fouling of the flow-cell is unavoidable, as it is the case with all optical sensor windows. Since the flow-cell is easy to replace, the fouling of the optical window can essentially be kept at a very low level where it does not influence the measurements. In drinking water, the time between flow-cell changes may be several months, whereas in water with a higher fouling potential, the service intervals may be significantly shorter.

The optical on-line bacteria sensor revealed bacteria concentrations which correlated well with total bacterial counts. Such correlation was expected as similar requirements apply for a cell to be identified by both methods; it has to be intact, but not necessarily alive and active. Dead and inactive bacteria are detected by both methods if they are intact. Once the cell is ruptured by e.g. treatment with ozone, DNA will leak out of the cell, and it will no longer be detected by DAPI staining. Cell debris will most likely not be classified as “bacteria”, but instead as “abiotic particles” by the sensor. The classification shift for a decaying cell has not been fully investigated yet. The immediate and long-term effect of various disinfectants on the detection of bacteria is thus not clearly understood. However, it is obvious that the effect of UV treatment and biostatic treatment with low residual chlorine concentrations, which does not change the morphology of the cells significantly, will not be immediately visible by this technique, as it will include both active and inactive cells. We have observed that total bacterial counts by DAPI staining yields a higher number compared to the sensor, depending on the degree of aggregation among the bacteria. The main reason is that the microscope operator counting stained fluorescent cells is able to distinguish individual aggregated cells, whereas the sensor detects such cells as a single particle.

There were no simple correlations between the sensor bacteria counts and plate counts. Because the plate count method only reveals a fraction of the current population, and since this fraction may vary concurrently with the change in the population, e.g. during a pollution event, a simple correlation was not expected. Similar observations have been reported for total bacterial counts26.

By the ability of closely monitor trends in the total number of bacteria and other particles in drinking water with a frequency of 10 minutes, we have demonstrated that it is possible to detect slow or sudden changes that may influence the water quality, and further determine if such changes are primarily of biotic or abiotic nature. Information on the particle size distribution, which is also provided by the sensor, may serve as further indicators of pollution27,28. Such pollution indications may be used to trigger auto-sampling at opportune moments followed by detailed analyses of the event. In such cases, the combination of sampling at the right time and analyzing for relevant parameters using fast molecular microbiological methods29 may prove to be a powerful tool for source tracking as well as for obtaining specific information on the pollution event.

Flow cytometry has lately been demonstrated to be applicable for online measurements12,13. Flow cytometry has a measurement range (1 × 103–1 × 106 cells/ml) similar to the operating range presented in this paper (1.6 × 102–1–5 × 106 cells/ml) and an error of less than 5%. The method requires chemical staining solutions and may thus be limited to locations where these can be stored and exchanged regularly. Chemical reactants are also required for the online measurements of ATP14 as an indirect indicator of bacteria presence. Turbidity, as implemented in many drinking water distribution systems, may give a good indication of abiotic particles, but it is unlikely to correlate with total bacterial counts30.

The optical sensor has proven to be stable for several months during field-testing in waterworks environments. The most critical parameter determining the integrity of the measured concentrations and classification has been fouling of the optical flow cell. In Danish non-chlorinated drinking water, flow-cells were replaced after approximately two months, whereas in the French, chlorinated drinking water flow-cells lasted around four months.

We have presented a novel optical sensor with a 10-minute resolution, capable of counting particles in water and classifying them as either bacteria or abiotic particles with a certainty of 90 ± 7% for monotype suspensions and 78 ± 14% for mixed-type suspensions. The results from the sensor correlated with total bacterial counts by DAPI staining and epi-fluorescence microscopy and responded linearly to serial dilutions. The sensor operates within a range of 1.6 × 102–1–5 × 106 particles/ml, the lower theoretical level corresponding to the detection of a single particle, and reports correct particle sizes in the range of 0.77–3 μm. Smaller particles or bacteria may not be detected or classified correctly.

During field tests, the sensor has been stable for up to four months without maintenance. In non-chlorinated waters, maintenance in terms of flow-cell changes are required at intervals of around two months. In other waters with high fouling potentials, higher maintenance frequencies are required. In a field test, the sensor was able to pinpoint the time of a daily reoccurring bacterial peak event, allowing for targeted sampling and detailed verification of the cause.

Analyses throughout a drinking water distribution system demonstrated that the optical sensor can monitor the different dynamics of bacteria and abiotic particle levels in drinking water and may serve as an early warning for drinking water pollution. Used as such, the sensor enables proactive responses to pollution events such as change of treatment scheme or redirection of water flows to avoid polluted water to reach consumers.

Materials and Methods

Laboratory sensor set-up

For laboratory verification, three sensors were modified by disabling automatic sample intake and rinsing. This allowed for manual preparation of the flow cell, manual flushing, and manual introduction of the individual samples.

Preparation of glassware and flow cell

All glassware were washed, autoclaved at 121 °C and 15 psi for 20 minutes, rinsed three times with filter sterilized (0.22 μm polyethersulfone (PES)) tap water, and finally rinsed once with 0.22 μm filtered 70% ethanol before left to dry.

The flow cells were cleaned prior to each sample injection by flushing for five minutes with tap water (approximately 3 bars of pressure) while submerged in an ultrasonic bath. The flow cells were then flushed with 20 ml filter sterilized (0.22 μm) tap water. Finally, the flow cells were flushed twice with the actual particle suspension using a glass pipette. The remaining suspension in the flow-cell was used for analysis.

Each measurement of suspended particles was repeated seven times for single particle type suspensions and three times for mixed suspensions, in between which the above cleaning procedure was applied.

Size distribution analysis

Size distributions of particle suspensions were analyzed on a Malvern Zetasizer Nano dynamic light scattering system. Size distributions of drinking water samples were analyzed using a Beckman Coulter Multisizer 4e Coulter Counter with appropriate apertures.

Microbiological analyses

The total number of bacteria were counted, and their morphology was examined after the sample was filtered onto a 0.22 μm black polycarbonate filter and stained by 4′,6-diamidino-2-phenylindole (DAPI) (Life Technologies D1306). After filtering an amount of sample, yielding 20–400 cells per 100 × 100 μm filter area, through the filter, 25 μl of 1 mg/ml DAPI was applied on top of the filter along with 1 ml of filter-sterilized (0.22 μm) tap water. After 15 min in the dark, the staining solution was sucked through the filter, which was then rinsed with filter-sterilized tap water (3 × 1 ml). Filters were mounted in immersion oil (Citifluor AF87) and examined by epi-fluorescence microscopy using a Zeiss Axio Imager 2 microscope. Plate counts at 22 and 37 °C was made according to ISO 6222:199931 on yeast extract agar.

Abiotic particle suspensions

10 g blue clay was taken from a freshly exposed surface of commercially available decoration clay and suspended in 1 l 0.2 μm filtered Milli-Q water. Size distribution analysis showed particle size clusters from 200 nm to 2 μm.

Ferroxyhyte and lepicocrocite were prepared according to Schwertmann and Cornell32 with the following precautions taken to avoid bacteria in the final suspensions: For ferroxyhyte, 300 ml 0.1M FeCl2·4H2O (Sigma Aldrich 44939) was filtered through a 0.22 μm PES filter and placed in a beaker. 5M NaOH (Merch 1.06498) was added dropwise while stirring until the pH reached 8. 40 ml 30% H2O2 (Merch 1.07209) was added rapidly, and the pH raised to 8 by adding 5M NaOH. The precipitate was centrifuged, washed and dried. Scanning electron microscopy showed mainly amorphous particles. For lepidocrocite, 11.93 g FeCl2·4H2O was dissolved in 300 ml Milli-Q water and filtered through a 0.22 μm PES filter. pH was adjusted to 6.7–6.9 with 1M NaOH and the solution aerated with 100 ml/min of air for 2–3 hours. The pH of the solution was constantly adjusted to remove protons produced by the oxidation process, adding approximately 120 ml NaOH. The precipitate was centrifuged, washed and dried. Scanning electron microscopy showed solid particles with sharp contours. Size distribution analysis showed a range from 200 nm to 10 μm with a maximum intensity at 600 nm.

10 g humic acid (Sigma Aldrich 53680) was dissolved in 1 liter 0.2 μm PES filtered 0.1 mM pyrophosphate, Na4P2O7 · 10H2O (Alfa Aesar A16195) (pH 9–10) based on Milli-Q water. The solution was placed on a magnetic stirrer for 24 hours and left to settle. The dissolved fraction was decanted and filtered through a 1.6 μm filter to remove remaining undissolved humic acid. The pH of the filtered solution was adjusted to below 6 with phosphorous acid (Prolab 20624.295), causing humic acid particles to precipitate. Size distribution analysis showed two major fractions around 150–400 nm and 6 μm.

All abiotic particle stock suspensions were preserved by 2% formaldehyde (AppliChem A0421), and checked for the presence of bacteria by DAPI staining and epi-fluorescence microscopy. Only few bacteria were detected in the blue clay stock. It was not possible to determine the number of cells by the DAPI staining method due to the low number compared to clay particles. It was estimated that bacteria constituted less than 0.1‰ of the total particles.

Bacteria suspensions

Pure cultures of freeze dried Lactococcus lactis subsp. lactis (DSM no 20481), Bacillus subtilis (DSM no. 618), Escherichia coli (DSM no. 5695), and Vibrio natriegens (DSM no. 759) were obtained from Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH. Cultures were revived according to the specifications given by DSMZ, grown in specific growth media. L. lactis was grown in 10 g peptone (Fluka 70172), 5 g yeast extract (Sigma Aldrich Y0500), 5 g glucose (Sigma G7528), and 5 g NaCl (Merck 1.06404) per liter. B. subtilis was grown in 5 g peptone and 3 g meat extract (Fluka 70164) per liter. E. coli was grown in 5 g peptone, 3 g meat extract, 800 mg NaCl, and 1.23 g MgSO4 (Fluka 00627) per liter. V. natriegens was grown in 5 g peptone, 3 g meat extract, and 15 g NaCl per liter. For solid growth media, 15 g/l agar (Merck 1.01614) was added (11 g/l for E. coli). All were incubated at 22 °C for 20 hours.

Unidentified bacteria were isolated from various Danish drinking water supplies by spreading and incubation on plate count agar (Merch 1.05463) plates at 22 °C for 20 hours and repeatedly transferring single colonies to new plates.

The purity of the monocultures was tested by DAPI staining and examination of morphology by epi-fluorescence microscopy. The size of individual cells ranged from 600 nm to 3 μm (longest axis), as determined by microscopy.

The cultures were stored at −80 °C in growth media with 30% (v/v) glycerol. Thawed cultures were incubated on appropriate plates (described above) for 20 hours, transferred to new plates, and incubated for an additional 20 hours. A single colony was transferred to 200 ml 0.22 μm filter-sterilized growth medium. The bacteria were allowed to grow for 20–40 hours depending on their growth rates and re-inoculated in 0.22 μm filtered media twice before they were used in measurements.

Mixed suspensions

Prior to each mixed suspension measurements, the individual suspensions were measured in triplicate by the sensor to determine their concentration and mixed accordingly to achieve the desired ratio between bacteria and abiotic particles.

Comparison between sensor response and total counts

A series of tap water aliquots were spiked with increasing concentrations of yeast extract (Sigma Aldrich Y0500): 0, 0.02, 0.2, and 2 mg/l. The bacteria concentration in the aliquots were measured by the bacteria sensor (3–6 repetitions) and by DAPI staining (20 randomly selected fields of view) at initiation and after 2, 7, and 11 days of incubation at room temperature.

Particle size standards

Polybead polystyrene microspheres (2.5% solids latex) were obtained from PolyScience Inc. Warrington, PA, USA in the sizes 3.004 μm (17134, lot no. 629888), 1.53 μm (17133, lot no. 613529), 0.99 μm (08226, lot no. 644236), and 0.771 μm (07309, lot no.623715). Uniform, non-porous silica microspheres (SS03N, lot no. 8933) with a diameter of 690 nm were obtained from Bangs Laboratories, Inc., Fishers, IN, USA. Prior to dilution, stock suspensions were sonicated for 1–10 minutes to break any aggregation.

Turbidity measurements

For comparison, a Hach Lange ULTRATURB sc turbidimeter was installed alongside a bacteria sensor at the inlet/outlet of a major closed drinking water reservoir in a large Danish non-chlorinated drinking water distribution system.

Field test at a slaughterhouse

Around the time of an expected daily peak in bacteria and particle concentrations, samples were taken for laboratory analyses at intervals corresponding to the resolution of the sensor (approximately ten minutes). Samples were taken during flushing of the flow-cell and thus corresponded to the subsequent sensor response.

Single analyses of plate counts and total counts by DAPI staining were performed. The standard deviation of 10 counts on each stained filter was approximately 20%. Samples were homogenized by repeatedly passing through a syringe needle to break cell clustering and biofilm prior to analysis. However, a few clustered cells could still be observed within the stained samples.

Additional Information

How to cite this article: Højris, B. et al. A novel, optical, on-line bacteria sensor for monitoring drinking water quality. Sci. Rep. 6, 23935; doi: 10.1038/srep23935 (2016).

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Author information

  1. GRUNDFOS Holding A/S, Poul Due Jensens Vej 7, DK-8850 Bjerringbro, Denmark

    • Bo Højris
    • , Christian Smith
    •  & Mathis Dahlqvist
  2. HOFOR A/S, Ørestads Boulevard 35, DK-2300 København S, Denmark

    • Sarah Christine Boesgaard Christensen
  3. Technical University of Denmark, Department of Environmental Engineering, Miljøvej, Building 115, 2800 Kgs. Lyngby, Denmark

    • Hans-Jørgen Albrechtsen

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B.H. and S.C.B.C. wrote the main manuscript text with contribution from C.S., M.D. and H.-J.A. B.H., C.S. and M.D. prepared the figures. All authors reviewed the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Bo Højris.