Standard Model thermodynamics across the electroweak crossover

Even though the Standard Model with a Higgs mass mH = 125GeV possesses no bulk phase transition, its thermodynamics still experiences a "soft point" at temperatures around T = 160GeV, with a deviation from ideal gas thermodynamics. Such a deviation may have an effect on precision computations of weakly interacting dark matter relic abundances if their mass is in the few TeV range, or on leptogenesis scenarios operating in this temperature range. By making use of results from lattice simulations based on a dimensionally reduced effective field theory, we estimate the relevant thermodynamic functions across the crossover. The results are tabulated in a numerical form permitting for their insertion as a background equation of state into cosmological particle production/decoupling codes. We find that Higgs dynamics induces a non-trivial "structure" visible e.g. in the heat capacity, but that in general the largest radiative corrections originate from QCD effects, reducing the energy density by a couple of percent from the free value even at T > 160GeV.

Synthesis and Thermodynamic and Biophysical Properties of Tricyclo-DNA

The DNA analogue tricyclo-DNA, built from conformationally rigid nucleoside analogues that were linked via tertiary phosphodiester functions, can efficiently be synthesized from the corresponding phosphoramidites by conventional solid-phase cyanoethyl phosphoramidite chemistry. 5'-End phosphorylated tricyclo-DNA sequences are chemically stable in aqueous, pH-neutral media at temperatures from 0 to 90 C. Tricyclo-DNA sequences resist enzymatic hydrolysis by the 3'-exonuclease snake venom phosphodiesterase. Homobasic adenine- and thymine-containing tricyclo-DNA octa- and nonamers are extraordinarily stable A-T base-pairing systems, not only in their own series but also with complementary DNA and RNA. Base mismatch formation is strongly destabilized. As in bicyclo-DNA, the tricyclo-DNA purine sequences preferentially accept a complementary strand on the Hoogsteen face of the base. A thermodynamic analysis reveals entropic benefits in the case of hetero-backbone duplex formation (tricyclo-DNA/DNA duplexes) and both an enthalpic and entropic benefit for duplex formation in the pure tricyclo-DNA series compared to natural DNA. Stability of tricyclo-DNA duplex formation depends more strongly on monovalent salt concentration compared to natural DNA. Homopyrimidine DNA sequences containing tricyclothymidine residues form triplexes with complementary double-stranded DNA. Triple-helix stability depends on the sequence composition and can be higher when compared to that of natural DNA. The use of one tricyclothymidine residue in the center of the self-complementary dodecamer duplex (d(CGCGAAT t CGCG), t = tricyclothymidine) strongly stabilizes its monomolecular hairpin loop structure relative to that of the corresponding pure DNA dodecamer ( T m = +20 C), indicating (tetra)loop-stabilizing properties of this rigid nucleoside analogue.