Application of nanoscale zero valent iron (NZVI) for groundwater remediation in Europe

Purpose: Nanoscale zero valent iron (NZVI) is emerging as a new option for the treatment of contaminated soil and groundwater targeting mainly chlorinated organic contaminants (e.g., solvents, pesticides) and inorganic anions or metals. The purpose of this article is to give a short overview of the practical experience with NZVI applications in Europe and to present a comparison to the situation in the USA. Furthermore, the reasons for the difference in technology use are discussed. Method: The results in this article are based on an extensive literature review and structured discussions in an expert workshop with experts from Europe and the USA. The evaluation of the experiences was based on a SWOT (strength, weakness, opportunity, threat) analysis. Result: There are significant differences in the extent and type of technology used between NZVI applications in Europe and the USA. In Europe, only three full-scale remediations with NZVI have been carried out so far, while NZVI is an established treatment method in the USA. Bimetallic particles and emulsified NZVI, which are extensively used in the USA, have not yet been applied in Europe. Economic constraints and the precautionary attitude in Europe raise questions regarding whether NZVI is a cost-effective method for aquifer remediation. Challenges to the commercialization of NZVI include mainly non-technical aspects such as the possibility of a public backlash, the fact that the technology is largely unknown to consultants, governments and site owners as well as the lack of long-term experiences. Conclusion: Despite these concerns, the results of the current field applications with respect to contaminant reduction are promising, and no major adverse impacts on the environment have been reported so far. It is thus expected that these trials will contribute to promoting the technology in Europ

Transport strategy for ischaemic stroke patients with large vessel occlusion

Introduction. There are today two models of transporting patients with acute ischaemic stroke because of large artery occlusion (AIS-LVO): mothership (MS) and drip-and-ship (DS). Our aim was to evaluate our ongoing transport strategy (OT), which is an MS/DS hybrid. In our OT, the patient is transported directly to the CT of the Primary Stroke Centre (PSC), where intravenous thrombolysis (IVT) is administered. The patient then continues without delay to a Comprehensive Stroke Centre (CSC) with the same medical rescue team (MRT). The distance between our centres is 73 km.Material and methods. We retrospectively analysed data of 100 consecutive AIS-LVO patients treated with mechanical thrombectomy (MT) between January 2017 and October 2019. OT, MS and DS groups were compared. 31 patients were transported as MS, 32 as DS, and 37 as OT.Results. DS had significantly longer time to groin puncture (185 min) compared to OT and MS (p < 0.0001). OT shortened time almost to MS level (OT 124 min, MS 110 min, p = 0.002. Time to IVT administration (from MRT departure) differed statistically significantly in favour of OT (OT 27 min, MS 63 min, p < 0.0001). Logistical change in PSC had a significant effect on decreasing the door-to-needle time (DNT) median from 37 min to 11 min (p < 0.0001). DNT reduction also occurred in patients with AIS and without an indication for MT.Conclusions. OT is highly effective, significantly reducing the time to IVT administration, and combining all the benefits, while eliminating all the disadvantages, of DS and MS. The OT concept gives all indicated patients a chance for MT to be performed, and does not overload the performing centre

Gender board diversity and its impact on firm performance in the Czech Republic

The purpose of this study is to examine the extent of gender inequality on boards of joint-stock companies and the relationship between gender diversity on board of directors and the return on assets in the Czech Republic. Using a panel data set of 204 Czech companies of various sizes over the years 2003 - 2011, we discovered that women are considerably underrepresented on corporate boards and that the gender board diversity has not significantly changed over the observed time period. The results of regression analysis showed a non-significant effect on return on assets for all our gender diversity measures, even after we accounted for endogeneity of the gender diversity variable in the form of fixed effects method and two-stage least squares estimator. Economic justification of potential legislation that should force the companies to appoint more women into board positions was therefore not found. Moreover, if companies account for underlying cost of implementing such measures, firm performance might be negatively affected in the short term.

Genderová diverzita ve statutárních orgánech firem a její vliv na výsledek firmy v České republice

Cílem této práce je zaměřit se na genderovou nerovnováhu ve strukturálních orgánech firem a na vliv který má genderová diverzita v představenstvu na rentabilitu aktiv těchto firem v České republice. Použitím panelové série dat, čítající 204 akciových společností různých velikostí během let 2003 až 2011, byla zjištěna značná nerovnováha poměru žen a mužů ve strukturálních orgánech firem a zanedbatelný pokrok v tomto směru v rámci sledovaného období. Výsledky regresní analýzy ukázaly statisticky nevýznamný vliv genderové diverzity na rentabilitu aktiv pro všechna použitá měřítka zastoupení žen ve strukturálních orgánech firem i přesto, že jsme vzali v potaz endogenitu hlavní proměnné použitím metody fixních efektů a 2SLS. Čistě ekonomické odůvodnění potenciálních změn, které by přinutily podniky začlenit více žen do strukturálních orgánů firem, tedy nalezeno nebylo. Pokud by byly navíc započítány výdaje související se zavedením takovýchto změn, tak by mohlo v krátkém období dojít i k rovnou negativnímu vlivu na finance firem. 1The purpose of this study is to examine the extent of gender inequality on boards of joint-stock companies and the relationship between gender diversity on board of directors and the return on assets in the Czech Republic. Using a panel data set of 204 Czech companies of various sizes over the years 2003 - 2011, we discovered that women are considerably underrepresented on corporate boards and that the gender board diversity has not significantly changed over the observed time period. The results of regression analysis showed a non-significant effect on return on assets for all our gender diversity measures, even after we accounted for endogeneity of the gender diversity variable in the form of fixed effects method and two-stage least squares estimator. Economic justification of potential legislation that should force the companies to appoint more women into board positions was therefore not found. Moreover, if companies account for underlying cost of implementing such measures, firm performance might be negatively affected in the short term. 1Institute of Economic StudiesInstitut ekonomických studiíFakulta sociálních vědFaculty of Social Science

Activation process of air stable nanoscale zero-valent iron particles

Nanoscale Zero Valent Iron (nZVI) represents a promising material for subsurface water remediation technology. However, dry, bare nZVI particles are highly reactive, being pyrophoric when they are in contact with air. The current trends of nZVI manufacturing lead to the surface passivation of dry nZVI particles with a thin oxide layer, which entails a decrease in their reactivity. In this work an activation procedure to recover the reactivity of air-stable nZVI particles is presented. The method consists of exposing nZVI to water for 36 h just before the reaction with the pollutants. To assess the increase in nZVI reactivity based on the activation procedure, three types of nZVI particles with different oxide shell thicknesses have been tested for Cr(VI) removal. The two types of air-stable nZVI particles with an oxide shell thickness of around 3.4 and 6.5 nm increased their reactivity by a factor of 4.7 and 3.4 after activation, respectively. However, the pyrophoric nZVI particles displayed no significant improvement in reactivity. The improvement in reactivity is related mainly to the degradation of the oxide shell, which enhances electron transfer and leads secondarily to an increase in the specific surface area of the nZVI after the activation process. In order to validate the activation process, additional tests with selected chlorinated compounds demonstrated an increase in the degradation rate by activated nZVI particles