On the performance of microlysimeters to measure non-rainfall water input in a hyper-arid environment with focus on fog contribution

The measurement of non-rainfall atmospheric water input (NRWI) in arid environments requires instruments that are capable to detect even smallest amounts of total daily water input of less than 0.1 mm. Microlysimeters yield robust and high precision data of such low NRWI. We provide a technical description of a self-constructed microlysimeter and demonstrate its excellent performance regarding the analysis of NRWI in the Central Namib Desert. Three stations of the FogNet measurement network have been equipped with microlysimeters in order to measure fog deposition. NRWI and evaporation for days/nights without fog shows a persistent diurnal course. Deviations from this baseline define the amount of fog deposition, intensity and duration of a fog events. A more detailed analysis of a five-day period reveals the complex nature and variation between individual fog events with respect to the different patterns of fog deposition and fog precipitation and the contribution of adsorption, dew and fog to NRWI. The relation between fog precipitation and fog deposition is not straightforward and a simple parameterization of the processes that quantifies the amount of the water sampled by fog collectors and its connection to NRWI is still lacking

The PRE-Derived NMR Model of the 38.8-kDa Tri-Domain IsdH Protein from Staphylococcus aureus Suggests That It Adaptively Recognizes Human Hemoglobin

Staphylococcus aureus is a medically important bacterial pathogen that, during infections, acquires iron from human hemoglobin (Hb). It uses two closely related iron-regulated surface determinant (Isd) proteins to capture and extract the oxidized form of heme (hemin) from Hb, IsdH and IsdB. Both receptors rapidly extract hemin using a conserved tri-domain unit consisting of two NEAT (near iron transporter) domains connected by a helical linker domain. To gain insight into the mechanism of extraction, we used NMR to investigate the structure and dynamics of the 38.8-kDa tri-domain IsdH protein (IsdHN2N3, A326–D660 with a Y642A mutation that prevents hemin binding). The structure was modeled using long-range paramagnetic relaxation enhancement (PRE) distance restraints, dihedral angle, small-angle X-ray scattering, residual dipolar coupling and inter-domain NOE nuclear Overhauser effect data. The receptor adopts an extended conformation wherein the linker and N3 domains pack against each other via a hydrophobic interface. In contrast, the N2 domain contacts the linker domain via a hydrophilic interface and, based on NMR relaxation data, undergoes inter-domain motions enabling it to reorient with respect to the body of the protein. Ensemble calculations were used to estimate the range of N2 domain positions compatible with the PRE data. A comparison of the Hb-free and Hb-bound forms reveals that Hb binding alters the positioning of the N2 domain. We propose that binding occurs through a combination of conformational selection and induced-fit mechanisms that may promote hemin release from Hb by altering the position of its F helix

Broadband velocity modulation spectroscopy of HfF^+: towards a measurement of the electron electric dipole moment

Precision spectroscopy of trapped HfF^+ will be used in a search for the permanent electric dipole moment of the electron (eEDM). While this dipole moment has yet to be observed, various extensions to the standard model of particle physics (such as supersymmetry) predict values that are close to the current limit. We present extensive survey spectroscopy of 19 bands covering nearly 5000 cm^(-1) using both frequency-comb and single-frequency laser velocity-modulation spectroscopy. We obtain high-precision rovibrational constants for eight electronic states including those that will be necessary for state preparation and readout in an actual eEDM experiment.Comment: 13 pages, 7 figures, 3 table

Effects of TLR Agonists on the Hypoxia-Regulated Transcription Factor HIF-1α and Dendritic Cell Maturation under Normoxic Conditions

Dendritic cells (DC) are professional antigen presenting cells that represent an important link between innate and adaptive immunity. Danger signals such as toll-like receptor (TLR) agonists induce maturation of DC leading to a T-cell mediated adaptive immune response. In this study, we show that exogenous as well as endogenous inflammatory stimuli for TLR4 and TLR2 induce the expression of HIF-1α in human monocyte-derived DC under normoxic conditions. On the functional level, inhibition of HIF-1α using chetomin (CTM), YC-1 and digoxin lead to no consistent effect on MoDC maturation, or cytokine secretion despite having the common effect of blocking HIF-1α stabilization or activity through different mechanisms. Stabilization of HIF-1α protein by hypoxia or CoCl2 did not result in maturation of human DC. In addition, we could show that TLR stimulation resulted in an increase of HIF-1α controlled VEGF secretion. These results show that stimulation of human MoDC with exogenous as well as endogenous TLR agonists induces the expression of HIF-1α in a time-dependent manner. Hypoxia alone does not induce maturation of DC, but is able to augment maturation after TLR ligation. Current evidence suggests that different target genes may be affected by HIF-1α under normoxic conditions with physiological roles that differ from those induced by hypoxia

Fog in the Namib - Occurrence Dynamics Properties

This thesis is a treatise on fog in the Central Namib. In this hyper-arid area, fog represents the primary water source as rain is rare and rivers only flow underground. Fog occurs regularly at night with a distinct seasonality inland compared to the coast. At the coast, radiation, advection and inversion fog have been reported whereas inland additionally "high fog", that is cloud interception, occurs. This cloud interception fog is likely the most frequent fog type despite contrasting findings in the recent literature. The cloud interception itself is the consequence of the inland movement of a quasi-permanent stratus deck off the Namibian coast that is the result of the interaction of warm air with the cold Benguela current that leads to saturation and the large-scale subsidence that limits the vertical extent. Notably, previous studies identified spatial variation even in the inland fog zone, that is the interception zone of the stratus. The water input from the fog, so-called fog precipitation, can vary by hundreds of millimetres per year between sites, but also by years, highlighting the immense complexity of this phenomenon. The fog climatology based on eleven stations of a distributed measurement network shows that the amount of fog precipitation is linked partially to elevation but also to the wind regime, where faster winds during a longer time tend to result in more fog precipitation. Notably, too strong winds seem to reduce the amount as well, potentially due to the flow regime around fog collectors. An intensive observation period within the frame of the Namib fog life cycle analysis project further revealed the connection of the stratus within the fog zone and the vertical extent. Both findings confirm earlier schematics and reiterate that wind direction during fog is from a northerly sector not only on the ground but also higher up. Vertical temperature and humidity profile conducted within the period further constrain the extent of the stratus to between 200 m and 350 m above ground. The interception of the cloud base and subsequent appearance of fog is also consistent with the cloud base registered at the coast. Non-rainfall water input measurements by microlysimeters during and after the intensive observation period showcase the challenging nature of measurements of fog water input. Whereas fog precipitation with fog collectors is the usual way, non-rainfall water input is far lower and no connection between the two amounts could be found. This may be partially due to the sampling mechanism (vertical deposition in microlysimeters vs. horizontal impact on fog collectors) but has far-reaching consequences. Fog collectors then indicate the wetness of fog and the potential of fog harvesting as a water source but do not indicate the amount of water the ecosystem receives out of fog. Ultimately, even the microlysimeters can only estimate this amount because many desert organisms in the Namib have adjusted to the regular fog with their behaviour and complex adaptations that enhance fog water collection. Furthermore, a cloud droplet probe that sampled fog over the course of more than 1.5 years yielded insight into the patterns of fog in the Central Namib. Within the fog zone and probably as a result of intersection with different layers of the stratus, distinct distributions of fog droplets (∼2 to 50 μm) do exist. Larger droplets are pronouncedly absent at the site with higher fog precipitation. This contradiction indicates that mainly duration and wind speed may be controlling factors of fog precipitation rather than liquid water content. Collection efficiencies of the fog collectors did not express a clear connection for the site with the broad droplet size distribution and were generally below 10 %. Ultimately, the combination of different measurement approaches demonstrates how complex the study of fog is: Firstly, where fog is officially defined as when visibility is below 1000 m, the reality is that significant deposition occurs mainly during very dense fog with a visibility below 200 m, at least in the Central Namib. In such dense fogs, up to 7.5 mm fog precipitation per event may occur, with one event during peak season roughly every second to third day. In total, up to ∼ 180 mm per year are collected compared to on average below 50 mm annually from rain. Secondly, depending on the measurement approach and the fog type, different amounts of water input are recorded, where each approach is as important as the next because each represents another physical process taking place. As expected, the research presented herein poses new questions from the performance of the devices, to the spatial and temporal variation within the fog zone to the general inter-event variation as each fog event differs slightly from the next

Droplet size distribution, liquid water content and water input of the seasonally variable, nocturnal fog in the Central Namib Desert

In the arid Central Namib desert, rainfall is rare, but fog frequently occurs at night and exhibits a seasonal pattern. We deployed an eddycovariance setup at two different inland locations, namely Gobabeb and Vogelfederberg. The setup consisted of a cloud droplet probe and at times of up to two sonic anemometer-thermometers. It was deployed for 1.5 years, collecting data during more than 150 fog events at either one of the sites. We characterize the different fog regimes at the two stations with co-located measurements of visibility, fog collector mesh precipitation by fog collectors, and non-rainfall water input by microlysimeters for selected periods. At similar levels of visibility, fog collector mesh precipitation at Vogelfederberg is generally higher, likely due to its higher elevation and exposed location. Fog events appear front-like with a decrease of visibility and an increase of droplet numbers above 10 μm and the associated liquid water content. Fog events regularly lasted 6 h, with the first two to three hours exhibiting higher liquid water content. The droplet distribution, especially droplets above 20 μm, and thus liquid water content varied in numbers between the locations. Liquid water content correlates with fog collector mesh precipitation at Gobabeb, where the droplet distribution spans the whole resolved spectrum. While liquid water flux was bi-directional, the net sum was still a net gain for the surface. We found only a low correlation between liquid water flux and non-rainfall water input, which demonstrates that the liquid water flux can only partially connect the measured input in the fog collectors and the microlysimeters despite similar values. We therefore presume that drizzle, that is droplets out of the CDP sampling range, may play a role in the Central Namib fog, especially when fog is intermittent as fog deposition in microlysimeters continues when no droplets of the respective size range are present near the ground. Furthermore, the contrast of higher fog collector mesh precipitation at Vogelfederberg compared to Gobabeb despite lower liquid water content is potentially a result of the more numerous small droplets as a consequence of the interception with the upper parts of the stratus

Low molecular weight dextran sulfate as complement inhibitor and cytoprotectant in solid organ and islet transplantation

Complement is an essential part of the innate immune system and plays a crucial role in organ and islet transplantation. Its activation, triggered for example by ischemia/reperfusion (I/R), significantly influences graft survival, and blocking of complement by inhibitors has been shown to attenuate I/R injury. Another player of innate immunity are the dendritic cells (DC), which form an important link between innate and adaptive immunity. DC are relevant in the induction of an immune response as well as in the maintenance of tolerance. Modulation or inhibition of both components, complement and DC, may be crucial to improve the clinical outcome of solid organ as well as islet transplantation. Low molecular weight dextran sulfate (DXS), a well-known complement inhibitor, has been shown to prevent complement-mediated damage of the donor graft endothelium and is thus acting as an endothelial protectant. In this review we will discuss the evidence for this cytoprotective effect of DXS and also highlight recent data which show that DXS inhibits the maturation of human DC. Taken together the available data suggest that DXS may be a useful reagent to prevent the activation of innate immunity, both in solid organ and islet transplantation