As a clinical geneticist, Paul James is accustomed to discussing some of the most delicate issues with his patients. But in early 2010, he found himself having a particularly awkward conversation about sex.
A 46-year-old pregnant woman had visited his clinic at the Royal Melbourne Hospital in Australia to hear the results of an amniocentesis test to screen her baby's chromosomes for abnormalities. The baby was fine — but follow-up tests had revealed something astonishing about the mother. Her body was built of cells from two individuals, probably from twin embryos that had merged in her own mother's womb. And there was more. One set of cells carried two X chromosomes, the complement that typically makes a person female; the other had an X and a Y. Halfway through her fifth decade and pregnant with her third child, the woman learned for the first time that a large part of her body was chromosomally male1. “That's kind of science-fiction material for someone who just came in for an amniocentesis,” says James.
Sex can be much more complicated than it at first seems. According to the simple scenario, the presence or absence of a Y chromosome is what counts: with it, you are male, and without it, you are female. But doctors have long known that some people straddle the boundary — their sex chromosomes say one thing, but their gonads (ovaries or testes) or sexual anatomy say another. Parents of children with these kinds of conditions — known as intersex conditions, or differences or disorders of sex development (DSDs) — often face difficult decisions about whether to bring up their child as a boy or a girl. Some researchers now say that as many as 1 person in 100 has some form of DSD2.
When genetics is taken into consideration, the boundary between the sexes becomes even blurrier. Scientists have identified many of the genes involved in the main forms of DSD, and have uncovered variations in these genes that have subtle effects on a person's anatomical or physiological sex. What's more, new technologies in DNA sequencing and cell biology are revealing that almost everyone is, to varying degrees, a patchwork of genetically distinct cells, some with a sex that might not match that of the rest of their body. Some studies even suggest that the sex of each cell drives its behaviour, through a complicated network of molecular interactions. “I think there's much greater diversity within male or female, and there is certainly an area of overlap where some people can't easily define themselves within the binary structure,” says John Achermann, who studies sex development and endocrinology at University College London's Institute of Child Health.
These discoveries do not sit well in a world in which sex is still defined in binary terms. Few legal systems allow for any ambiguity in biological sex, and a person's legal rights and social status can be heavily influenced by whether their birth certificate says male or female.
“The main problem with a strong dichotomy is that there are intermediate cases that push the limits and ask us to figure out exactly where the dividing line is between males and females,” says Arthur Arnold at the University of California, Los Angeles, who studies biological sex differences. “And that's often a very difficult problem, because sex can be defined a number of ways.”
That the two sexes are physically different is obvious, but at the start of life, it is not. Five weeks into development, a human embryo has the potential to form both male and female anatomy. Next to the developing kidneys, two bulges known as the gonadal ridges emerge alongside two pairs of ducts, one of which can form the uterus and Fallopian tubes, and the other the male internal genital plumbing: the epididymes, vas deferentia and seminal vesicles. At six weeks, the gonad switches on the developmental pathway to become an ovary or a testis. If a testis develops, it secretes testosterone, which supports the development of the male ducts. It also makes other hormones that force the presumptive uterus and Fallopian tubes to shrink away. If the gonad becomes an ovary, it makes oestrogen, and the lack of testosterone causes the male plumbing to wither. The sex hormones also dictate the development of the external genitalia, and they come into play once more at puberty, triggering the development of secondary sexual characteristics such as breasts or facial hair.
Researchers from FOM, the University of Amsterdam, the Delft University of Technology and the University of the Algarve have discovered that when light hits germanium nanocrystals, the crystals produce 'bonus electrons'. These additional electrons could increase the yield of solar cells and improve ...
(Phys.org) —The universe may have existed forever, according to a new model that applies quantum correction terms to complement Einstein's theory of general relativity. The model may also account for dark matter and dark energy, resolving multiple problems at once.
Decades of data security research have brought us highly reliable, standardized tools for common tasks such as digital signatures and encryption. But hackers are constantly working to crack data security innovations. Current credit/debit card technologies put personal money at risk because they’re vulnerable to fraud.
Physical security – which deals with anti-counterfeiting and the authentication of actual objects – is part of the problem too. The good guys and bad guys are locked in a never-ending arms race: one side develops objects and structures that are difficult to copy; the other side tries to copy them, and often succeeds.
But we think our new invention has the potential to leave the hackers behind. This innovative security measure uses the quantum properties of light to achieve fraud-proof authentication of objects.
The arms race is fought in secret; revealing your technology helps the enemy. Consequently, nobody knows how secure a technology really is. Remarkably, a recent development called Physical Unclonable Functions (PUFs) has made it possible to be completely open. A PUF is a piece of material that can be probed in many ways and that produces a complex response that depends very precisely on the challenge and the PUF’s internal structure.
The best known examples are Optical PUFs. The PUF is a piece of material – such as white paint with millions of nanoparticles – that will strongly scatter any light beamed at it. The light bounces around inside the paint, creating a unique pattern that can be used for authentication. Optical PUFs could be used on any object, but would be especially useful on credit/debit cards.
In 2012, researchers at Twente University realized they discovered something very important. The magic ingredient is a Spatial Light Modulator (SLM), a programmable device that re-shapes the speckle pattern. In their experiments, they programmed an SLM such that the correct response from an Optical PUF gets concentrated and passes through a pinhole, where a photon detector notices the presence of the photon. An incorrect response, however, is transformed to a random speckle pattern that does not pass through the pinhole. The method was dubbed Quantum-Secure Authentication (QSA).
QSA does not require any secrets, so no money has to be spent on protecting them. QSA can be implemented with relatively simple technology that is already available. The PUF can be as simple as a layer of paint. It turns out that the challenge does not have to be a single photon; a weak laser pulse suffices, as long as the number of photons in the pulse is small enough. Laser diodes, as found in CD players, are widely available and cheap. SLMs are already present in modern projectors. A sensitive photodiode or image sensor can serve as the photon detector. With all these advantages, QSA has the potential to massively improve the security of cards and other physical credentials.
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