Solubilization of 1-hexanol in aqueous solutions of sodium dodecyl sulfate at pressures up to 140 MPa: partial molar volumes, compressibilities, and partition coefficients.

Partial molar volumes and partial molar compressibilities of aqueous solutions of sodium dodecyl sulfate (SDS) and 1-hexanol at pressure up to 140 MPa have been determined. For aqueous SDS solutions the partial molar compressibility increases with pressure below the cmc and decreases with pressure above the cmc. The partial molar compressibility of aqueous 1-hexanol increases with pressure. The increased partial molar compressibility reflects that the structure of water is gradually broken down by increased pressure. Thus, the negative effect of electrostriction around the charged parts of SDS decreases as do the effects of hydrophobic hydration around the CH2 groups. In the micellar state the compressibility of the aggregate is the main factor, becoming less compressible as pressure increases. The cmc of SDS, as determined by speed of sound measurements, increases with pressure and goes through a shallow maximum at about 110 MPa. When 1-hexanol is added to SDS solutions, it will be partitioned between the aqueous and micellar (pseudo) phases. The partition coefficient has been determined from partial molar compressibilites, and it appears to decrease with pressure, reach a minimum around 80 MPa, and then increase, though the change with pressure is small.

Microbial hydrogen consumption leads to a significant pH increase under high-saline-conditions: implications for hydrogen storage in salt caverns.

Salt caverns have been successfully used for natural gas storage globally since the 1940s and are now under consideration for hydrogen (H2) storage, which is needed in large quantities to decarbonize the economy to finally reach a net zero by 2050. Salt caverns are not sterile and H2 is a ubiquitous electron donor for microorganisms. This could entail that the injected H2 will be microbially consumed, leading to a volumetric loss and potential production of toxic H2S. However, the extent and rates of this microbial H2 consumption under high-saline cavern conditions are not yet understood. To investigate microbial consumption rates, we cultured the halophilic sulphate-reducing bacteria Desulfohalobium retbaense and the halophilic methanogen Methanocalculus halotolerans under different H2 partial pressures. Both strains consumed H2, but consumption rates slowed down significantly over time. The activity loss correlated with a significant pH increase (up to pH 9) in the media due to intense proton- and bicarbonate consumption. In the case of sulphate reduction, this pH increase led to dissolution of all produced H2S in the liquid phase. We compared these observations to a brine retrieved from a salt cavern located in Northern Germany, which was then incubated with 100% H2 over several months. We again observed a H2 loss (up to 12%) with a concurrent increase in pH of up to 8.5 especially when additional nutrients were added to the brine. Our results clearly show that sulphate-reducing microbes present in salt caverns consume H2, which will be accompanied by a significant pH increase, resulting in reduced activity over time. This potentially self-limiting process of pH increase during sulphate-reduction will be advantageous for H2 storage in low-buffering environments like salt caverns.

[Use of the B-Lynch suture technique in postpartum hemorrhage]. / Bruk av B-Lynch-sutur ved blødning etter fødsel.

BACKGROUND: Serious postpartum haemorrhage occurs in approximately 1.4% of all deliveries in Norway and may result in hysterectomy. Stepwise devascularisation and hysterectomy are technically difficult and time consuming. A simple suture technique, B-Lynch suture, has recently been introduced, by which atonic postpartum haemorrhage may be controlled and hysterectomy avoided. MATERIAL, METHODS AND RESULTS: We have used the B-Lynch technique in five patients with serious postpartum uterine atonia and haemorrhage. In all patients serious bleeding and hysterectomy were avoided. Three of the patients are described in detail, one with failed induction of labour resulting in Caesarean section, one with placenta previa, and one with prolonged normal vaginal delivery. INTERPRETATION: If performed early, the B-Lynch suture technique is less mutilating to the woman; it may prevent excessive blood loss and is probably beneficial for the patient's future fertility. It is easy to perform in Caesarean sections and can be adopted in vaginal deliveries.