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Observations with the Herschel satellite have revealed that the backbone of molecular clouds is a compex network of connecting and interacting filaments \citep[e.g.][]{2010A&A...518L.102A,2010A&A...518L.100M,2011A&A...529L...6A,2012A&A...540L..11S}. The dynamics of this web of dense molecular gas not only determines the evolution and stability of molecular clouds, but also regulates their condensation into stars. Molecular cloud cores and single low-mass stars are almost always found in filaments, often aligned like pearls on a string \citep{2002ApJ...578..914H,2008ApJ...672..410L,2010A&A...518L.102A}. This can be interpreted as a result of the gravitational instability of a supercritical filamentary section \citep{1997ApJ...480..681I,2011A&A...533A..34H}. Where filaments intersect, more massive hubs form \citep{2009ApJ...700.1609M,2013ApJ...764..140M} that later on could become the progenitors of star clusters.  \citet{2010ApJ...724..687L} \citep[see also e.g.][]{2007ApJ...666..982E} demonstrated that the fraction of gas in the dense molecular web is of order 10 percent of the total molecular mass. Interestingly, the mass fraction of protostars to dense ($n > 10^4$ cm$^{-3}$)  molecular gas is also a constant of the same order.This means that where there are more stars, there is even more dense gas available.  \citet{2013ApJ...773...48B} showed that this requires new filamentary segments to continuously form from the diffuse intra-filament medium on a gravitational collapse timescale. Classically, gas filaments have been treated as cylinders of gas in hydrostatic equilibrium \citep{1964ApJ...140.1529O,2012A&A...542A..77F,2013A&A...558A..27R}. It is not clear, however, how such quiescent structures could form in the turbulent environment of a molecular cloud \citep[e.g.][]{2010A&A...520A..17K,2013ApJ...769..115H}. In addition, millimeter line studies indicate that filaments have intrinsic, super-thermal linewidths \citep{2013A&A...553A.119A}.