On the formation of radiation fogs under heavily polluted conditions

International audienceWe have studied the effect of gaseous pollutants on fog droplet growth in heavily polluted air using a model that describes time-dependent sulfate production in the liquid phase and thermodynamical equilibrium between the droplets and the gas phase. Our research indicates that the oxidation of SO2 to sulfate has a significant effect on fog droplet growth especially when hygroscopic trace gases, for example HNO3 and NH3 are present. The increased sulfate production by dissolution of hygroscopic gases results from increased pH (caused by absorption of ammonia) and from the increased size of the fog/smog droplets. Our results indicate that unactivated fogs may become optically very thick when the droplet concentrations are on the order of several thousand per cubic centimeter of air

Parameterization of the nitric acid effect on CCN activation

International audienceIn this paper we present a parameterization of the nitric acid effect on cloud droplet formation. The new parameterization is intended to be used in large scale models in order to obtain regional and global estimates of the effect of nitric acid on cloud drop concentrations and the radiative balance. The parameterization is based on numerical air parcel model simulations and can be applied for unimodal and bimodal lognormal aerosol particle size distributions in a large variety of different conditions. In addition to the aerosol particle distribution and gas-phase HNO3 concentration, the parameterization requires temperature, total pressure, updraft velocity, and the number concentration of cloud droplets formed at zero nitric acid concentration, as input parameters. The parametrization is also suitable for describing the effect of hydrochloric acid on the cloud drop concentrations, and in practice, the HNO3 and HCl concentrations can be summed up to yield the total effect. The comparison between the parameterization and the results from numerical air parcel model simulations show good consistency

Dependency of the impacts of geoengineering on the stratospheric sulfur injection strategy - Part 1: Intercomparison of modal and sectional aerosol modules

Injecting sulfur dioxide into the stratosphere with the intent to create an artificial reflective aerosol layer is one of the most studied options for solar radiation management. Previous modelling studies have shown that stratospheric sulfur injections have the potential to compensate for the greenhouse-gas-induced warming at the global scale. However, there is significant diversity in the modelled radiative forcing from stratospheric aerosols depending on the model and on which strategy is used to inject sulfur into the stratosphere. Until now, it has not been clear how the evolution of the aerosols and their resulting radiative forcing depends on the aerosol microphysical scheme used - that is, if aerosols are represented by a modal or sectional distribution. Here, we have studied different spatio-temporal injection strategies with different injection magnitudes using the aerosolclimate model ECHAM-HAMMOZ with two aerosol microphysical modules: the sectional module SALSA (Sectional Aerosol module for Large Scale Applications) and the modal module M7. We found significant differences in the model responses depending on the aerosol microphysical module used. In a case where SO2 was injected continuously in the equatorial stratosphere, simulations with SALSA produced an 88 %-154% higher all-sky net radiative forcing than simulations with M7 for injection rates from 1 to 100 Tg(S) yr(-1). These large differences are identified to be caused by two main factors. First, the competition between nucleation and condensation: while injected sulfur tends to produce new particles at the expense of gaseous sulfuric acid condensing on pre-existing particles in the SALSA module, most of the gaseous sulfuric acid partitions to particles via condensation at the expense of new particle formation in the M7 module. Thus, the effective radii of stratospheric aerosols were 10 %-52% larger in M7 than in SALSA, depending on the injection rate and strategy. Second, the treatment of the modal size distribution in M7 limits the growth of the accumulation mode which results in a local minimum in the aerosol number size distribution between the accumulation and coarse modes. This local minimum is in the size range where the scattering of solar radiation is most efficient. We also found that different spatial-temporal injection strategies have a significant impact on the magnitude and zonal distribution of radiative forcing. Based on simulations with various injection rates using SALSA, the most efficient studied injection strategy produced a 33 %-42% radiative forcing compared with the least efficient strategy, whereas simulations with M7 showed an even larger difference of 48 %-116 %. Differences in zonal mean radiative forcing were even larger than that. We also show that a consequent stratospheric heating and its impact on the quasi-biennial oscillation depend on both the injection strategy and the aerosol microphysical model. Overall, these results highlight the crucial impact of aerosol microphysics on the physical properties of stratospheric aerosol which, in turn, causes significant uncertainties in estimating the climate impacts of stratospheric sulfur injections

Impact of pasireotide on postoperative pancreatic fistulas following distal resections

Purpose Postoperative pancreatic fistula (POPF), a difficult complication after surgery, can cause peripancreatic fluid collection and infections in the operative area. In addition, pancreatic fluid is corrosive and can lead to postoperative bleeding. Clinically significant grade B and C fistulas (CR-POPF) increase postoperative morbidity, resulting in a prolonged hospital stay. Delaying adjuvant therapy due to fistula formation in cancer patients can affect their prognosis. In this study, we aimed to determine if pasireotide affects fistula formation, and the severity of other complications in patients following pancreatic distal resections. Data and methods Between 2000 and 2016, 258 distal pancreatectomies were performed at Helsinki University Hospital and were included in our analysis. Pasireotide was administered to patients undergoing distal resections between July 2014 and December 2016. Patients received 900-mu g pasireotide administered twice daily perioperatively. Other patients who received octreotide treatment were analyzed separately. Complications such as fistulas (POPF), delayed gastric emptying (DGE), postpancreatectomy hemorrhage (PPH), reoperations, and mortality were recorded and analyzed 90 days postoperatively. Results Overall, 47 (18%) patients received pasireotide and 31 (12%) octreotide, while 180 patients (70%) who received neither constituted the control group. There were 40 (16%) clinically relevant grade B and C POPFs: seven (15%) in the pasireotide group, three (10%) in the octreotide group, and 30 (17%) in the control group (p = 0.739). Severe complications categorized as Clavien-Dindo grade III or IV were recorded in 64 (25%) patients: 17 (27%) in the pasireotide group, 4 (6%) in the octreotide group, and 43 (67%) in the control group (p = 0.059). We found no 90-day mortality. Conclusions In this study, pasireotide did not reduce clinically relevant POPFs or severe complications following pancreatic distal resection.Peer reviewe

Technical note: Analytical formulae for the critical supersaturations and droplet diameters of CCN containing insoluble material

International audienceIn this paper, we consider the cloud drop activation of aerosol particles consisting of water soluble material and an insoluble core. Based on the Köhler theory, we derive analytical equations for the critical diameters and supersaturations of such particles. We demonstrate the use of the equations by comparing the critical supersaturations of particles composed of ammonium sulfate and insoluble substances with those of model organic particles with varying molecular sizes

On the hygroscopic growth of ammoniated sulfate particles of non-stoichiometric composition

International audienceThe hygroscopic growth of ammoniated sulfate particles was studied by measurements and model calculations for particles with varying ammonium-to-sulfate ratio. In the measurements, the ammonium-to-sulfate ratio was adjusted by using mixtures of ammonium sulfate and ammonium bisulfate in generating the solid particles. The hygroscopic growth was measured using a tandem differential mobility analyzer. The measurements were simulated using a thermodynamical equilibrium model. The calculations indicated that the solid phases in particle with ammonium-to-sulfate ratio between 1.5?2, were ammonium sulfate and letovicite. Both in the calculations and in the experiments the hygroscopic growth was initiated at relative humidities less than the theoretical deliquescence relative humidity of these particles. This indicates that the particles were multi-phase particles including solids and liquids. The equilibrium model yielded a satisfactory prediction of the hygroscopic growth of particles generated from a solution with 1:1 mass ratio between dissolved ammonium sulfate and ammonium bisulfate. However, for particles with 3:1 and 10:1 mass ratios, the model predictions overestimated the growth at relative humidities between about 60% and the point of complete deliquescence (close to 80% RH). In contrast, a model, in which letovicite was allowed to dissolve only after complete dissolution of ammonium sulfate, reproduced the observations well. This indicates that the dry particles had a letovicite core surrounded by an ammonium sulfate shell

The influence of nitric acid on the cloud processing of aerosol particles

International audienceIn this paper we present simulations of the effect of nitric acid (HNO3) on cloud processing of aerosol particles. Sulfuric acid (H2SO4) production and incloud coagulation are both affected by condensed nitric acid as nitric acid increases the number of cloud droplets, which will lead to smaller mean size and higher total surface area of droplets. As a result of increased cloud droplet number concentration (CDNC), the incloud coagulation rate is enhanced by a factor of 1?1.3, so that the number of interstitial particles reduces faster. In addition, sulfuric acid production occurs in smaller particles and so the cloud processed aerosol size distribution is dependent on the HNO3 concentration. This affects both radiative properties of aerosol particles and the formation of cloud droplets during a sequence of cloud formation-evaporation events. It is shown that although the condensation of HNO3 increases the number of cloud droplets during the single updraft, it is possible that presence of HNO3 can actually decrease the cloud droplet number concentration after several cloud cycles when also H2SO4 production is taken into account

Serum MMP-8 and TIMP-1 as prognostic biomarkers in gastric cancer

Despite gastric cancer being rare nowadays in Western countries, it remains one of the leading causes of cancer death worldwide. The course of the disease varies, so the individual gastric cancer patient’s prognosis is difficult to determine. The need for new biomarkers is crucial. The aim of this study was to evaluate the prognostic value of serum matrix metalloproteinase-8, serum tissue inhibitor of metalloproteinase-1, and tissue matrix metalloproteinase-8 in patients with gastric cancer. Preoperative serum samples from 233 patients with gastric cancer were retrospectively analyzed. Serum levels of matrix metalloproteinase-8 were analyzed with immunofluorometric assay, and tissue inhibitor of metalloproteinase-1 levels were determined by enzyme-linked immunosorbent assay. We also determined the tissue expression of matrix metalloproteinase-8 in 276 gastric cancer samples by immunohistochemistry. Survival data and death causes came from patient records, the Population Register Center of Finland, and Statistics Finland. Patients with a low (131 ng/mL) serum matrix metalloproteinase-8 level had a considerably unfavorable prognosis (p = 0.002). Those patients with a high (≥170 ng/mL) serum tissue inhibitor of metalloproteinase-1 level also had a poor prognosis (p <0.001), and the latter remained significant in multivariable analysis (hazard ratio = 1.85; 95% confidence interval: 1.26–2.72; p = 0.002). The molar ratio of serum matrix metalloproteinase-8 and tissue inhibitor of metalloproteinase-1 levels with low (0.30) molar ratios predicted a worse prognosis (p = 0.020). Tissue matrix metalloproteinase-8 did not influence prognosis. These results suggest that serum matrix metalloproteinase-8, tissue inhibitor of metalloproteinase-1, and the ratio of matrix metalloproteinase-8/ tissue inhibitor of metalloproteinase-1 may prove useful biomarkers for prediction of prognosis in patients with gastric cancer. © The Author(s) 2018.Peer reviewe

Diagnosis, natural course and treatment outcomes of groove pancreatitis

Background: Groove pancreatitis (GP) is a rare form of chronic pancreatitis with limited data on its diagnostics and treatment outcomes. The aim of this study was to assess its diagnostics, natural course, and treatment options. Methods: The study is a retrospective population-based study from Southern Finland, including all patients with suspected GP between January 2005 and December 2015. Two certified gastrointestinal radiologists re-reviewed the imaging studies. The radiological re-review, clinical judgment, and final histopathology confirmed the GP diagnoses. Results: Out of 67 patients with possible GP, 39 patients were considered to have high radiological certainty of GP. Out of these 39, five patients had cancer instead. Thirty-three patients with confirmed GP formed the final study cohort. Patients with GP were mostly middle-aged (median 55 years) men. All had at least moderate alcohol consumption. No intervention was needed in 14 patients. In five-year follow-up all conservatively treated patients became asymptomatic, while 10 out of 16 patients undergoing at least one intervention were asymptomatic at five years. Conclusion: The radiological diagnosis of GP is difficult, and a low threshold for cancer suspicion should be kept. Symptoms of GP decrease with time and suggest conservative treatment as the first-line option.Peer reviewe