Month: January 2017

How forensic science can unlock the mysteries of human evolution

By Patrick Randolph-Quinney, University of Central Lancashire; Anthony Sinclair, University of Liverpool; Emma Nelson, University of Liverpool, and Jason Hall, University of Liverpool.

People are fascinated by the use of forensic science to solve crimes. Any science can be forensic when used in the criminal and civil justice system – biology, genetics and chemistry have been applied in this way. Now something rather special is happening: the scientific skill sets developed while investigating crime scenes, homicides and mass fatalities are being put to use outside the courtroom. Forensic anthropology is one field where this is happening.

Loosely defined, forensic anthropology is the analysis of human remains for the purpose of establishing identity in both living and dead individuals. In the case of the dead this often focuses on analyses of the skeleton. But any and all parts of the physical body can be analysed. The forensic anthropologist is an expert at assessing biological sex, age at death, living height and ancestral affinity from the skeleton.

Our newest research has extended forensic science’s reach from the present into prehistory. In the study, published in the Journal of Archaeological Science, we applied common forensic anthropology techniques to investigate the biological sex of artists who lived long before the invention of the written word.

We specifically focused on those who produced a type of art known as a hand stencil. We applied forensic biometrics to produce statistically robust results which, we hope, will offset some of the problems archaeological researchers have encountered in dealing with this ancient art form.

Sexing rock art

Ancient hand stencils were made by blowing, spitting or stippling pigment onto a hand while it was held against a rock surface. This left a negative impression on the rock in the shape of the hand.

Experimental production of a hand stencil. Jason Hall, University of Liverpool

These stencils are frequently found alongside pictorial cave art created during a period known as the Upper Palaeolithic, which started roughly 40 000 years ago.

Archaeologists have long been interested in such art. The presence of a human hand creates a direct, physical connection with an artist who lived millennia ago. Archaeologists have often focused on who made the art – not the individual’s identity, but whether the artist was male or female.

Until now, researchers have focused on studying hand size and finger length to address the artist’s sex. The size and shape of the hand is influenced by biological sex as sex hormones determine the relative length of fingers during development, known as 2D:4D ratios.

But many ratio-based studies applied to rock art have generally been difficult to replicate. They’ve often produced conflicting results. The problem with focusing on hand size and finger length is that two differently shaped hands can have identical linear dimensions and ratios.

To overcome this we adopted an approach based on forensic biometric principles. This promises to be both more statistically robust and more open to replication between researchers in different parts of the world.

The study used a branch of statistics called Geometric Morphometric Methods. The underpinnings of this discipline date back to the early 20th century. More recently computing and digital technology have allowed scientists to capture objects in 2D and 3D before extracting shape and size differences within a common spatial framework.

In our study we used experimentally produced stencils from 132 volunteers. The stencils were digitised and 19 anatomical landmarks were applied to each image. These correspond to features on the fingers and palms which are the same between individuals, as depicted in figure 2. This produced a matrix of x-y coordinates of each hand, which represented the shape of each hand as the equivalent of a map reference system.

Figure 2. Geometric morphometric landmarks applied to an experimentally produced hand stencil. This shows the 19 geometric landmarks applied to a hand. Emma Nelson, University of Liverpool

We used a technique called Procrustes superimposition to move and translate each hand outline into the same spatial framework and scale them against each other. This made the difference between individuals and sexes objectively apparent.

Procrustes also allowed us to treat shape and size as discrete entities, analysing them either independently or together. Then we applied discriminant statistics to investigate which component of hand form could best be used to assess whether an outline was from a male or a female. After discrimination we were able to predict the sex of the hand in 83% of cases using a size proxy, but with over 90% accuracy when size and shape of the hand were combined.

An analysis called Partial Least Squares was used to treat the hand as discrete anatomical units; that is, palm and fingers independently. Rather surprisingly the shape of the palm was a much better indicator of the sex of the hand than the fingers. This goes counter to received wisdom.

This would allow us to predict sex in hand stencils which have missing digits – a common issue in Palaeolithic rock art – where whole or part fingers are often missing or obscured.

Palaeo-forensics

This study adds to the body of research that has already used forensic science to understand prehistory. Beyond rock art, forensic anthropology is helping to develop the emergent field of palaeo-forensics: the application of forensic analyses into the deep past.

For instance, we have been able to understand fatal falls in Australopithecus sediba from Malapa and primitive mortuary practices in the species Homo naledi from Rising Star Cave, both in South Africa.

All of this shows the synergy that arises when the palaeo, archaeological and forensic sciences are brought together to advance humans’ understanding of the past.

The ConversationPatrick Randolph-Quinney, Senior Lecturer in Biological and Forensic Anthropology, University of Central Lancashire; Anthony Sinclair, Professor of Archaeological Theory and Method, University of Liverpool; Emma Nelson, Lecturer in Clinical Communication, University of Liverpool, and Jason Hall, Chief Archaeology Technician, University of Liverpool

This article was originally published on The Conversation. Read the original article.

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Dengue virus antibodies may worsen a Zika infection

By Sharon Isern, Florida Gulf Coast University.

The World Health Organization declared in November that Zika was no longer a public health emergency of international concern.

That doesn’t mean concern over Zika is over, but now that a link between Zika and microcephaly has been established, it is viewed as a long-term problem, which requires constant attention.

While researchers have concluded that Zika infection can cause microcephaly and other birth defects such as eye damage in newborns, there are still many unanswered questions about the virus.

Earlier Zika outbreaks in Africa and Asia were gradual, continuous and associated with mild clinical outcomes, but the Zika outbreaks in the Pacific in 2013 and 2014 and the Americas in 2015 and 2016 have been explosive. They have been associated with severe disease, including birth defects in newborns and Guillain-Barre, a condition that can cause temporary paralysis in adults. Scientists are trying to figure out why.

I study flaviviruses, which include Zika and dengue, at Florida Gulf Coast University. Like other flavivirus researchers, I am turning to dengue to better understand Zika. Dengue, a close relative of Zika, is regularly found in places like Brazil, and is spread by the same mosquitoes, Aedes aegypti.

My colleagues and I wanted to find out whether having immunity to dengue from an earlier infection could make a Zika infection worse.

Aedes aegypti mosquitoes can transmit both Zika and dengue viruses.
AP Photo/Felipe Dana, File

A brief history of Zika

Zika was first isolated in Uganda in 1947. For decades Zika infections in humans were sporadic. Perhaps cases of Zika went underreported, since its symptoms were similar to other fever-causing diseases and most cases are asymptomatic.

By the 1980s, Zika had spread beyond Africa and had become endemic, or habitually present, in Asia. Many individuals living in these regions may be immune to the virus.

The first reported Zika outbreak outside of Africa and Asia occurred in the Pacific, in Micronesia, in 2007. To our knowledge there were no associations with microcephaly or Guillain-Barre reported at the time.

Zika transmission in the Pacific wasn’t reported again until 2013, when French Polynesia experienced an explosive outbreak. In 2014 further outbreaks were reported in New Caledonia, Easter Island and the Cook Islands. When French Polynesia experienced another outbreak in 2014, there were reports of Zika being transmitted to babies, most likely in utero, and complications associated with Guillian-Barre in adults.

Map showing countries affected by the Zika virus. Reuters

By early 2015 the virus had spread to the Americas, and the first confirmed case of locally acquired Zika in the region was confirmed in May 2015 by Brazil’s National Reference Laboratory. The Pan American Health Organization reports that Zika virus transmission had occurred in over 48 countries or territories in the Americas, with 177,614 confirmed cases of locally acquired Zika in the region, over half a million suspected cases, and 2,525 confirmed congenital syndrome associated cases with Zika infections as of Dec. 29.

Why did Zika start to cause explosive outbreaks? And why did it start to cause more health problems?

Dengue a common connector

A few factors might explain. For instance, perhaps the difference may lie in the age of the person exposed to Zika.

If children are infected before they reach puberty, they become immune and cannot pass Zika along to their children. And in parts of the world where Zika is endemic, people are more likely to have been exposed and become immune while young.

The scenario we’ve seen in the Americas is different. Since Zika had not been reported in the region prior to 2015, people, including women of child-bearing age, had never been exposed to the virus. However, this doesn’t explain why certain people develop severe disease, whereas others do not.

Dengue virus is endemic many parts of Asia, Africa and the Americas, infecting up to 100 million people globally each year. And the areas of the Pacific and the Americas that experienced explosive Zika outbreaks have two things in common: they had not been exposed to Zika before and dengue is endemic. And dengue may provide a clue to why Zika has caused severe disease in these new outbreaks.

Could a prior dengue infection make Zika worse?

When a person is infected with a particular virus for the first time, the immune system springs into action, producing antibodies to destroy it. The next time a person encounters that virus, the body produces those antibodies again to fight back, preventing illness. This is called immunity.

There are four different kinds of dengue virus, called serotypes. Antibodies produced during infection with one dengue serotype confer lifelong immunity against only that particular serotype. If a person is infected with another serotype later on, the antibodies from the earlier infection will bind to the new virus type, but can’t prevent it from infecting cells.

Instead, the bound antibodies can transport the viruses to immune cells that are normally not infected by dengue. In other words, if a person is infected with one serotype of dengue and then gets infected with another serotype, the antibodies from the previous infection then make the new serotype infect cells that it otherwise wouldn’t. Then the virus can reproduce to very high numbers in these cells, leading to severe disease. This process is called antibody-dependent enhancement, or ADE.

Zika virus is closely related to dengue and has been shown to undergo ADE in response to other flavivirus antibodies. Zika virus antibodies in turn have been shown to have a similar effect on related viruses. And other researchers have shown that preexisting immunity to Zika can enhance dengue virus disease severity in animals.

A digitally colorized electron microscope from the CDC shows the Zika virus, in red. Cynthia Goldsmith/CDC via AP

My lab studied the African strain of the Zika virus in 2015 before the connection with microcephaly was known.

Our results, posted in April to bioRxiv, a preprint server for biology, showed that antibodies from a prior dengue virus infection greatly enhanced Zika virus production in cell culture. Other groups have since independently verified our work. And, as we found in a more recent study, the same results hold true with a strain of Zika isolated in Puerto Rico by the CDC.

Our findings suggest that preexisting dengue virus antibodies may enhance Zika virus infection in patients, potentially making the infection more severe.

However, this correlation needs to be confirmed in the clinic. We do not know how many people infected with Zika in the outbreaks in the Pacific and in the Americas had prior dengue infections. But since the virus is endemic in those areas, it is possible that some people may have been infected with dengue before they were infected with Zika.

Zika’s spread may become limited

Like dengue and other mosquito-borne viruses, Zika spread is seasonal, and outbreaks occur when mosquitoes are abundant. As the United States heads into winter and South America heads into summer, what can we expect with regard to Zika and dengue and disease severity?

As more and more people acquire immunity to Zika, its spread will be limited to those who have never been exposed. Given enough time, new infections will be limited to the young. As long as infections occur prior to child-bearing years, microcephaly in newborns should not be a concern.

If these studies hold true in the clinic, cocirculation of Zika and dengue could increase the severity of both viruses. Vaccines to protect against Zika, and dengue for that matter, would need to be designed carefully so that vaccination with one does not enhance a natural infection with the other virus.

Public health emergency or not, there is still much to be learned about Zika virus and its associated consequences.

The ConversationSharon Isern, Professor of Biological Sciences, Florida Gulf Coast University

This article was originally published on The Conversation. Read the original article.

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Why you can’t fry eggs (or testicles) with a cellphone

By Timothy J. Jorgensen, Georgetown University.

A minor craze in men’s underwear fashions these days seems to be briefs that shield the genitals from cellphone radiation. The sales claim is that these products protect the testicles from the harmful effects of the radio waves emitted by cellphones, and therefore help maintain a robust sperm count and high fertility. These undergarments may shield the testicles from radiation, but do male cellphone users really risk infertility?

The notion that electromagnetic radiation in the radio frequency range can cause male sterility, either temporary or permanent, has been around for a long time. As I describe in my book “Strange Glow: The Story of Radiation,” during World War II some enlisted men would consistently and inexplicably volunteer for radar duty just prior to their scheduled leave days. It turned out that a rumor had been circulating that exposure to radio waves from the radar equipment produced temporary sterility, which the soldiers saw as an employment benefit.

The military wanted to know whether there was any substance to the sterility rumor. So they asked Hermann Muller – a geneticist who won the Nobel Prize for showing that x-rays could cause sterility and genetic mutations – to evaluate the effects of radio waves in the same fruit fly experimental model he had used to show that x-rays impaired reproduction.

Muller could find no dose of radio waves that produced either sterility or genetic mutations, and concluded that radio waves did not present the same threat to fertility that x-rays did. Radio waves were different. But why? Aren’t both x-rays and radio waves electromagnetic radiation?

The electromagnetic spectrum, tiny wavelengths on the left, longer wavelengths on the right.
Inductiveload, CC BY-SA

Yes, they are – but they differ in one key factor: They have very different wavelengths. All electromagnetic radiation travels through space as invisible waves of energy. And it’s the specific wavelength of the radiation that determines all of its effects, both physical and biological. The shorter wavelengths carry higher amounts of energy than the longer wavelengths.

X-rays are able to damage cells and tissues precisely because their wavelengths are extremely short – one-millionth the width of a human hair – and thus are highly energetic and very harmful to cells. Radio waves, in contrast, carry little energy because their wavelengths are very long – about the length of a football field. Such long-wavelength radiations have really low energies – too low to damage cells. And it’s this big difference between the wavelengths of x-rays and radio waves that the infertility theorists fail to recognize.

X-rays, and other high-energy waves, produce sterility by killing off the testicular cells that make sperm – the “spermatogonia.” And x-ray doses must be extremely high to kill enough cells to produce sterility. Still, even when the doses are high, the sterility effect is usually temporary because the surviving spermatogonia are able to spawn replacements for their dead comrades, and sperm counts typically return to their normal levels within a few months.

So, if high doses of highly energetic x-rays are needed to kill enough cells to produce sterility, how can low doses of radio waves with energies too low to kill cells do it? Good question.

Don’t fall for the phone-cooking-egg hoax.

At this point you may be thinking that you’ve seen videos of cellphones cooking eggs. And you’ve even experienced your cellphone getting pretty warm when it’s used heavily. But this doesn’t show that cellphones put out a lot of radiation energy. The cooked egg video is a prank, and the phone gets hot because of the heat generated by the chemical reactions going on within the battery, not from radio waves.

Still you protest: What about those sporadic reports claiming that cellphones suppress sperm counts? For the moment, that’s all they are – sporadic reports, unconfirmed by other investigators. You can find all kinds of random assertions about the effects of radiation on health, both good and bad, most of which imply that there is some type of validated scientific evidence to support the claim. Why not believe all of them?

If we’ve learned anything over the years about scientific evidence, it’s that isolated findings from individual labs, reporting limited experimental data, do not a strong case make. Most of the very limited “scientific” reports of infertility caused by cellphones, often cited by anti-cellphone activists, come from outside the radiation biology community, and are published in lower-tier journals of questionable quality. Few, if any, of these reports make any attempt at actually measuring the radiation doses received from the cellphones (probably because they lack either the expertise or the equipment required to do it).

Human sperm, unconcerned by what’s in your pocket.
Doc. RNDr. Josef Reischig, CSc., CC BY-SA

And none actually measure fertility rates – the health endpoint of concern – but rather measure sperm counts and other sperm quality parameters and then infer that there will be an impact on fertility. In fact, sperm counts can vary widely between normally fertile individuals and even within the same individual from day to day. For example, men who frequently ejaculate have lower sperm counts, as you might expect, because they are regularly jettisoning sperm. (Men who ejaculate daily can have sperm counts 50 percent lower than men who don’t.) Perhaps the allegedly lower sperm counts of cellphone users just means that they are having more sex!

But seriously, the point is this: There are so many things that can affect sperm counts in big ways that minor fluctuations in sperm counts have no practical impact on whether a man will produce babies, even if it were true that cellphones can modestly suppress sperm counts.

It is clear that these infertility claims are not the consensus of the mainstream scientific community – a community that demands more rigorous evidence. There are many excellent laboratories around the world that study radiation effects, and it isn’t difficult to study infertility in fruit flies, mice and even people. (It’s fairly easy to find men willing to donate sperm samples.) If the sterility story were true, there would be a chorus of well-respected laboratories from around the world singing the cellphone infertility song, not just a few.

Guglielmo Marconi, inventor of the radio. Smithsonian Institution

The fact is, the current data suggesting that cellphones cause infertility are too weak to challenge the dogma of over 100 years of commercial experience with radio waves. Radio waves are not unique to cellphones. They have been used for telecommunication ever since Marconi first demonstrated in 1901 that they could carry messages across the entire Atlantic Ocean. Early radio workers received massive doses of radio waves, yet there is no indication they had any problems with their fertility. If they didn’t experience fertility problems with their high doses, how can the relatively low doses from cellphones have such an effect? Hard to understand.

Nevertheless, people can spend their money as they please and wear any underwear they want. But if you are still concerned about radio waves affecting your fertility, why not just carry your cellphone in your shirt pocket rather than your pants, and let your testicles be?

The ConversationTimothy J. Jorgensen, Director of the Health Physics and Radiation Protection Graduate Program and Associate Professor of Radiation Medicine, Georgetown University

This article was originally published on The Conversation. Read the original article.

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Static electricity’s tiny sparks

By Sebastian Deffner, University of Maryland, Baltimore County.

Static electricity is a ubiquitous part of everyday life. It’s all around us, sometimes funny and obvious, as when it makes your hair stand on end, sometimes hidden and useful, as when harnessed by the electronics in your cellphone. The dry winter months are high season for an annoying downside of static electricity – electric discharges like tiny lightning zaps whenever you touch door knobs or warm blankets fresh from the clothes dryer.

Static electricity is one of the oldest scientific phenomena people observed and described. Greek philosopher Thales of Miletus made the first account; in his sixth century B.C. writings, he noted that if amber was rubbed hard enough, small dust particles will start sticking to it. Three hundred years later, Theophrastus followed up on Thales’ experiments by rubbing various kinds of stone and also observed the “power of attraction.” But neither of these natural philosophers found a satisfactory explanation for what they saw.

It took almost 2,000 more years before the English word “electricity” was first coined, based on the Latin “electricus,” meaning “like amber.” Some of the most famous experiments were conducted by Benjamin Franklin in his quest to understand the underlying mechanism of electricity – which is one of the reasons why his face smiles from the US$100 bill. People quickly recognized electricity’s potential usefulness.

The amazing flying boy relies on static electricity to wow the crowd. Frontispiece of Novi profectus in historia electricitatis, post obitum auctoris, by Christian August Hausen (1746)

Of course, in the 18th century people mostly made use of static electricity in magic tricks and other performances. For instance, Stephen Gray‘s “flying boy experiment” became a popular public demonstration: He’d use a Leyden jar to charge up the youth, suspended from silk cords, and then show how he could turn book pages via static electricity, or lift small objects just using the static attraction.

Building on Franklin’s insights – including his realization that electric charge comes in positive and negative flavors, and that total charge is always conserved – we nowadays understand at the atomic level what causes the electrostatic attraction, why it can cause mini lightning bolts and how to harness what can be a nuisance for use in various modern technologies.

What are these tiny sparks?

Static electricity comes down to the interactive force between electrical charges. At the atomic scale, negative charges are carried by tiny elementary particles called electrons. Most electrons are neatly packed inside the bulk of matter, whether it be a hard and lifeless stone or the soft, living tissue of your body. However, many electrons also sit right on the surface of any material. Each different material holds on to these surface electrons with its own different characteristic strength. If two materials rub against each other, electrons can be ripped out of the “weaker” material and find themselves on the material with stronger binding force.

This transfer of electrons – what we know as a spark of static electricity – happens all the time. Infamous examples are children sliding down a playground slide, feet shuffling along a carpet or someone removing wool gloves in order to shake hands.

But we notice its effect more frequently in the dry months of winter, when the air has very low humidity. Dry air is an electrical insulator, whereas moist air acts as a conductor. This is what happens: In dry air, electrons get trapped on the surface with the stronger binding force. Unlike when the air is moist, they can’t find their way to flow back to the surface where they came from, and they can’t make the distribution of charges uniform again.

A static electric spark occurs when an object with a surplus of negative electrons comes close to another object with less negative charge – and the surplus of electrons is large enough to make the electrons “jump.” The electrons flow from where they’ve built up – like on you after walking across a wool rug – to the next thing you contact that doesn’t have an excess of electrons – such as a doorknob.

You’ll feel the electrons jump.
Muhammed Ibrahim, CC BY-ND

When electrons have nowhere to go, the charge builds up on surfaces – until it reaches a critical maximum and discharges in the form of a tiny lightning bolt. Give the electrons a place to go – such as your outstretched finger – and you will most certainly feel the zap.

The power of the mini sparks

Though sometimes annoying, the amount of charge in static electricity is typically quite little and rather innocent. The voltage can be about 100 times the voltage of typical power outlets. However, these huge voltages are nothing to worry about, since voltage is just a measure of the charge difference between objects. The “dangerous” quantity is current, which tells how many electrons are flowing. Since typically only a few electrons are transmitted in a static electric discharge, these zaps are pretty harmless.

Nevertheless, these little sparks can be fatal to sensitive electronics, such as the hardware components of a computer. Small currents carried by only few electrons can be enough to accidentally fry them. That’s why workers in electronic industries have to remain “grounded.” Being grounded just means maintaining a wired connection to the ground, which for the electrons looks like an empty highway “home.” Grounding yourself is easily done by touching a metal component or holding a key in your hand. Metals are very good conductors, and so electrons are quite happy to go there.

A more serious threat is an electric discharge in the vicinity of flammable gases. This is why it’s advisable to ground yourself before touching the pumps at gas stations; you don’t want a stray spark to combust any stray gasoline fumes. Or you can invest in the kind of anti-static wristband widely used by workers in the electronic industries to safely ground individuals before they work on very sensitive electronic components. They prevent static buildups using a conductive ribbon that coils around your wrist.

In settings where a few electrons can do big damage, workers wear anti-static wrist straps.
Wristband image via www.shutterstock.com.

In everyday life, the best method to reduce charge buildups is running a humidifier to raise the amount of moisture in the air. Also keeping your skin moist by applying moisturizer can make a big difference. Dryer sheets prevent charges from building up as your clothes tumble dry by spreading a small amount of fabric softener over the cloth. These positive particles balance out loose electrons, and the effective charge nullifies, meaning your clothes won’t emerge from the dryer clingy and stuck to one another. You can rub fabric softener on your carpets to prevent charge buildup too. Last but not least, wearing cotton clothes and leather-soled shoes are the better choice, rather than wool clothing and rubber-soled shoes, if you’ve really had it with static electricity.

Harnessing static electricity

Despite the nuisance and possible dangers of static electricity, it definitely has its benefits.

Many everyday applications of modern technology crucially rely on static electricity. For instance, Xerox machines and photocopiers use electric attraction to “glue” charged tone particles onto paper. Air fresheners not only make the room smell nice, but they really do eliminate bad odors by discharging static electricity onto dust particles, thus dissembling the bad smell.

Static electricity can attract and trap charged pollution particles before they’re emitted from factories.
Muhammed Ibrahim, CC BY-ND

Similarly, the smokestacks found in modern factories use charged plates to reduce pollution. As smoke particles move up the stack, they pick up negative charges from a metal grid. Once charged, they are attracted to plates on the other sides of the smokestack that are positively charged. Finally, the charged smoke particles are collected onto a tray from the collecting plates and can be disposed of.

Static electricity has also found its way into nanotechnology, where it is used, for instance, to pick up single atoms by laser beams. These atoms can then be manipulated for all kinds of purposes as in various computing applications. Another exciting application in nanotechnology is the control of nanoballoons, which through static electricity can be switched between an inflated and a collapsed state. These molecular machines could one day deliver medication to specific tissues within the body.

Static electricity has seen two and a half millennia since its discovery. Still it’s a curiosity, a nuisance – but it’s also proven to be important for our everyday lives.

This article was coauthored by Muhammed Ibrahim, a system engineer at an environmental software company. He is conducting collaborative research with Dr. Sebastian Deffner on reducing computational errors in quantum memories.

The ConversationSebastian Deffner, Assistant Professor of Physics, University of Maryland, Baltimore County

This article was originally published on The Conversation. Read the original article.

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