Recent comments in /f/askscience

Norklander t1_j9biiaf wrote

Skin to skin contact, including oral sex can transfer HPV virus. In some cultures/counties the definition of a virgin means no vaginal/penile penetrative sex, therefore it’s important in the context of cervical cancer not to equate absence of the above with zero risk of cervical cancer.

For example in Turkey when the Erdogan government rolled out HPV primary testing for cervical cancer screening (in 2014) the message got hijacked by right wing religious parties saying the infection was only sexually transmitted (mainly in the SE Turkey region), and that an HPV positive result meant the person had an STI. Result was uptake was low and cervical pre-cancers were missed as women were scared and men scared of being stigmatised or accused as a result.

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kdeff t1_j9bh9rs wrote

When a metal is molten and cooling, it's atoms start forming bonds and binding together to form the lattice structure. But this cooling process happens simultaneously all over the structure. So all over, new lattices are forming in all different directions! The places where these differently-oriented lattices meet are called "grains boundaries" and they are the weakest points in the metals, where failure eventually happens.

But there are a few examples of perfect crystal lattices through a metal structure - the most well known (the only one I know of) is in Jet Engines. Jet turbines undergo so much stress yet need to be so reliable that they have developed manufacturing processes to make a whole turbine blade be a single crystal lattice. How they do it is a pretty closely held trade secret. But the advantages are huge:

  • NO plastic deformation - since there are no dislocations/imperfections
  • ~10x the material strength compared to the same metal cast normally

There are probably more but this isn't really my field of expertise, maybe someone else can add more..

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