Engineering properties of vertical cutoff walls consisting of reactive magnesia-activated slag and bentonite: workability, strength and hydraulic conductivity

Soil–cement–bentonite (SCB) vertical cutoff walls are commonly used to control the flow of contaminated groundwater at polluted sites. However, conventional backfill consisting of ordinary portland cement (OPC) is associated with a relatively high CO2 footprint. Potential chemical interactions between OPC and bentonite could also undermine the long-term durability of SCB materials. This paper proposes an innovative backfill material for cutoff walls that is composed of MgO-activated ground granulated blast furnace slag (GGBS), bentonite, and soil. The OPC–soil, OPC–bentonite–soil, and OPC–GGBS–bentonite–soil backfill materials are also tested for comparison purposes. The workability of fresh backfills and unconfined compressive strength of aged backfills are investigated. The hydraulic conductivities of aged backfills permeated with tap water, Na2SO4, and Pb–Zn solutions are assessed. The unconfined compressive strength and hydraulic conductivity of the proposed backfill permeated with tap water are in the range of 230–520 kPa and 1.1×10−10  to  6.3×10−10  m/s after 90 days of curing, respectively, depending on the mix composition. The hydraulic conductivity of the proposed MgO–GGBS–bentonite–soil backfill permeated with sodium sulfate (Na2SO4) or lead–zinc (Pb–Zn) solution is well below the commonly used limit, while the OPC–bentonite–soil backfill shows a significant loss in impermeability. Environmental and economic analyses indicate that, compared with conventional backfill made from OPC–bentonite–soil mixtures, the proposed backfill reduces CO2 emissions by approximately 84.7%–85.1% and costs by 15.3%–16.9%. The environmental and economic advantages will promote the use of MgO-activated GGBS–bentonite mixtures in cutoff walls and lead to their increased application in land remediation projects

Knockout of Pannexin-1 Induces Hearing Loss

Mutations of gap junction connexin genes induce a high incidence of nonsyndromic hearing loss. Pannexin genes also encode gap junctional proteins in vertebrates. Recent studies demonstrated that Pannexin-1 (Panx1) deficiency in mice and mutation in humans are also associated with hearing loss. So far, several Panx1 knockout (KO) mouse lines were established. In general, these Panx1 KO mouse lines demonstrate consistent phenotypes in most aspects, including hearing loss. However, a recent study reported that a Panx1 KO mouse line, which was created by Genentech Inc., had no hearing loss as measured by the auditory brainstem response (ABR) threshold at low-frequency range (\u3c 24 kHz). Here, we used multiple auditory function tests and re-examined hearing function in the Genentech Panx1 (Gen-Panx1) KO mouse. We found that ABR thresholds in the Gen-Panx1 KO mouse were significantly increased, in particular, in the high-frequency region. Moreover, consistent with the increase in ABR threshold, distortion product otoacoustic emission (DPOAE) and cochlear microphonics (CM), which reflect active cochlear amplification and auditory receptor current, respectively, were significantly reduced. These data demonstrated that the Gen-Panx1 KO mouse has hearing loss and further confirmed that Panx1 deficiency can cause deafness