The Moisture Regain of Acetylated Silk Fibroin

Abstract

Moisture regain measurements have been made at 25° C. and 79.3% relative humidity on non-acetylated and acetylated fibroin.The equilibrium moisture content of acetylated fibroin is slightly lower than that of non-acetylated fibroin and varies with the degree of acetylation.In the case of fibres acetylated by the action of acetic anhydride it is shown that the decrease in moisture content is not attributable to the action of liberated acetic acid.

Primordial Black Holes from the QCD Axion

“…We show in this Letter that there can be a fourth small contribution to the axion DM abundance in the form of heavy, 10 4−7 M , PBHs. Interestingly, this provides a concrete realization of the proposed role of massive PBHs in the early Universe [10] in the context of QCD axion DM. Moreover, our scenario is not subject to some of the strong constraints arising from CMB µ-distortions, which plague PBH formation mechanisms from gaussian inflationary fluctuations (see [10]).…”

“…Although there are constraints on the abundance of PBHs for almost all viable masses (see e.g. [8]), a small relic abundance of heavy (M 10 5 M ) PBHs may play an important role in the generation of cosmological structures and alleviate shortcomings of the CDM scenario on sub-galactic scales [9,10]. Furthermore, such PBHs could shed light on the origin of the super-massive BHs in the centers of most galaxies, some of which were already in place at very early times [11,12].…”

“…Observations require f 10 −5 for PBHs with M ∼ 10 6 M [8] (see also [10,48]). This constraint is easily satisfied in our scenario.…”

“…However, under reasonable assumptions, depending on the temperature behavior of the bias term, PBHs with masses in the range M ∼ 10 4 − 10 7 M and representative fraction f 10 −6 can be created. Interestingly, such heavy PBHs can play an important role as seeds for the formation of cosmological structure, alleviating several problems of the CDM scenario on sub-galactic scales, and providing an avenue to explain the origin of the supermassive BHs [9,10].…”