On string topology of classifying spaces

Peer reviewed

Enhanced Volatile Organic Compounds emissions and organic aerosol mass increase the oligomer content of atmospheric aerosols

Secondary organic aerosol (SOA) accounts for a dominant fraction of the submicron atmospheric particle mass, but knowledge of the formation, composition and climate effects of SOA is incomplete and limits our understanding of overall aerosol effects in the atmosphere. Organic oligomers were discovered as dominant components in SOA over a decade ago in laboratory experiments and have since been proposed to play a dominant role in many aerosol processes. However, it remains unclear whether oligomers are relevant under ambient atmospheric conditions because they are often not clearly observed in field samples. Here we resolve this long-standing discrepancy by showing that elevated SOA mass is one of the key drivers of oligomer formation in the ambient atmosphere and laboratory experiments. We show for the first time that a specific organic compound class in aerosols, oligomers, is strongly correlated with cloud condensation nuclei (CCN) activities of SOA particles. These findings might have important implications for future climate scenarios where increased temperatures cause higher biogenic volatile organic compound (VOC) emissions, which in turn lead to higher SOA mass formation and significant changes in SOA composition. Such processes would need to be considered in climate models for a realistic representation of future aerosol-climate-biosphere feedbacks.

EUSAAR size distribution analysis database

Two years of harmonized aerosol number size distribution data from 24 European field monitoring sites have been analysed. The results give a comprehensive overview of the European near surface aerosol particle number concentrations and number size distributions between 30 and 500 nm of dry particle diameter. Spatial and temporal distribution of aerosols in the particle sizes most important for climate applications are presented. We also analyse the annual, weekly and diurnal cycles of the aerosol number concentrations, provide log-normal fitting parameters for median number size distributions, and give guidance notes for data users. Emphasis is placed on the usability of results within the aerosol modelling community. We also show that the aerosol number concentrations of Aitken and accumulation mode particles (with 100 nm dry diameter as a cut-off between modes) are related, although there is significant variation in the ratios of the modal number concentrations. Different aerosol and station types are distinguished from this data and this methodology has potential for further categorization of stations aerosol number size distribution types. The European submicron aerosol was divided into characteristic types: Central European aerosol, characterized by single mode median size distributions, unimodal number concentration histograms and low variability in CCN-sized aerosol number concentrations; Nordic aerosol with low number concentrations, although showing pronounced seasonal variation of especially Aitken mode particles; Mountain sites (altitude over 1000 m a.s.l.) with a strong seasonal cycle in aerosol number concentrations, high variability, and very low median number concentrations. Southern and Western European regions had fewer stations, which decreases the regional coverage of these results. Aerosol number concentrations over the Britain and Ireland had very high variance and there are indications of mixed air masses from several source regions; the Mediterranean aerosol exhibit high seasonality, and a strong accumulation mode in the summer. The greatest concentrations were observed at the Ispra station in Northern Italy with high accumulation mode number concentrations in the winter. The aerosol number concentrations at the Arctic station Zeppelin in Ny-Ålesund in Svalbard have also a strong seasonal cycle, with greater concentrations of accumulation mode particles in winter, and dominating summer Aitken mode indicating more recently formed particles. Observed particles did not show any statistically significant regional work-week or weekday related variation in number concentrations studied. Analysis products are made for open-access to the research community, available in a freely accessible internet site. The results give to the modelling community a reliable, easy-to-use and freely available comparison dataset of aerosol size distributions.

Valtatien 13 parantaminen välillä Lappeenranta–Nuijamaa : Hanke-esite

Valtatien 13 osuus Lappeenrannasta Nuijamaalle kuuluu Euroopan komission päättämään Suomen kattavaan liikenneverkkoon TEN-T. Tieosuus on maan toiseksi tärkein kansainvälisen liikenteen yhteys kuljetuksille ja henkilöliikenteelle. Valtatie 13 kulkee maan poikki länsirannikolta Kokkolasta Lappeenrantaan ja siitä edelleen Nuijamaan rajanylityspaikan kautta Venäjän puolelle Viipuriin. Valtatie 13 palvelee osaltaan myös paikallista liikkumista Nuijamaan kylätaajaman ja Lappeenrannan välillä. Erityisesti Mustolan alueelle ja myös osittain Nuijamaan raja-aseman läheisyyteen suunnitellut ja jo osittain toteutuneet maankäytön kaupalliset palvelut lisäävät voimakkaasti kasvaessaan myös seudullista liikennettä suunnitteluosuudella. Nuijamaan raja-asema on ollut Suomen itärajan toiseksi vilkkain tieliikenteen rajanylityspaikka. Rajanylityspaikan kautta kulki vuonna 2015 noin miljoona ajoneuvoa ja 2,4 miljoonaa matkustajaa. Venäjän ja Suomen valtioiden välisen liikenteen kasvu on ollut voimakkainta Kaakkois-Suomessa ja sille on edelleen perusteltuja kasvuodotuksia, vaikka viime aikoina liikenne on merkittävästi vähentynyt. Myös tavaraliikenteellä on potentiaalia lisääntyä viimeaikaisesta. Suunnittelualueeseen kuuluu valtatien 13 (16,6 km) lisäksi valtatien 6 länsipuolinen valtatien 13 jatke Karjalantie (mt 3821) (1,2 km). Yleissuunnitelmassa on selvitetty valtatien 13 puutteet ja ongelmat, palvelutasotavoitteet, valtatien 13 ja muiden väylien periaateratkaisut tilantarpeineen, suhde ympäröivään maankäyttöön, vaikutukset sekä mahdollisuudet vaiheittain toteuttamiseksi. Päätavoitteena on ollut selvittää valtatien 13 ja muiden väylien kehittämisen periaatteet niin, että palvelutasopuutteet saadaan poistettua ja valtatie 13 vastaa sille asetettuja vaatimuksia liikenteen sujuvuuden ja turvallisuuden kannalta. Osana suunnitelmaa on esitetty toimenpiteet meluhaittojen torjumiseksi ja ympäristövaikutusten lieventämiseksi. Valtatie 13 parannetaan nykyisellä paikallaan korkealuokkaiseksi nelikaistaiseksi valtatieksi tarvittavine tie-, katu- ja liittymäjärjestelyineen. Vastakkaiset ajosuunnat on erotettu toisistaan rakenteellisesti ja kaikki valtatien liittymät ovat eritasoliittymiä.

The Virtual International Stroke Trials Archive

Background and Purpose - Stroke has global importance and it causes an increasing amount of human suffering and economic burden, but its management is far from optimal. The unsuccessful outcome of several research programs highlights the need for reliable data on which to plan future clinical trials. The Virtual International Stroke Trials Archive aims to aid the planning of clinical trials by collating and providing access to a rich resource of patient data to perform exploratory analyses. Methods - Data were contributed by the principal investigators of numerous trials from the past 16 years. These data have been centrally collated and are available for anonymized analysis and hypothesis testing. Results - ”Currently, the Virtual International Stroke Trials Archive contains 21 trials. There are data on 15 000 patients with both ischemic and hemorrhagic stroke. Ages range between 18 and 103 years, with a mean age of 6912 years. Outcome measures include the Barthel Index, Scandinavian Stroke Scale, National Institutes of Health Stroke Scale, Orgogozo Scale, and modified Rankin Scale. Medical history and onset-to-treatment time are readily available, and computed tomography lesion data are available for selected trials. Conclusions - This resource has the potential to influence clinical trial design and implementation through data analyses that inform planning. (Stroke. 2007;38:1905-1910.)

Telmisartan to prevent recurrent stroke and cardiovascular events

Background Prolonged lowering of blood pressure after a stroke reduces the risk of recurrent stroke. In addition, inhibition of the renin–angiotensin system in high-risk patients reduces the rate of subsequent cardiovascular events, including stroke. However, the effect of lowering of blood pressure with a renin–angiotensin system inhibitor soon after a stroke has not been clearly established. We evaluated the effects of therapy with an angiotensin-receptor blocker, telmisartan, initiated early after a stroke. Methods In a multicenter trial involving 20,332 patients who recently had an ischemic stroke, we randomly assigned 10,146 to receive telmisartan (80 mg daily) and 10,186 to receive placebo. The primary outcome was recurrent stroke. Secondary outcomes were major cardiovascular events (death from cardiovascular causes, recurrent stroke, myocardial infarction, or new or worsening heart failure) and new-onset diabetes. Results The median interval from stroke to randomization was 15 days. During a mean followup of 2.5 years, the mean blood pressure was 3.8/2.0 mm Hg lower in the telmisartan group than in the placebo group. A total of 880 patients (8.7%) in the telmisartan group and 934 patients (9.2%) in the placebo group had a subsequent stroke (hazard ratio in the telmisartan group, 0.95; 95% confidence interval [CI], 0.86 to 1.04; P = 0.23). Major cardiovascular events occurred in 1367 patients (13.5%) in the telmisartan group and 1463 patients (14.4%) in the placebo group (hazard ratio, 0.94; 95% CI, 0.87 to 1.01; P = 0.11). New-onset diabetes occurred in 1.7% of the telmisartan group and 2.1% of the placebo group (hazard ratio, 0.82; 95% CI, 0.65 to 1.04; P = 0.10). Conclusions Therapy with telmisartan initiated soon after an ischemic stroke and continued for 2.5 years did not significantly lower the rate of recurrent stroke, major cardiovascular events, or diabetes. (ClinicalTrials.gov number, NCT00153062.)

Aspirin and extended-release dipyridamole versus clopidogrel for recurrent stroke

Background Recurrent stroke is a frequent, disabling event after ischemic stroke. This study compared the efficacy and safety of two antiplatelet regimens — aspirin plus extendedrelease dipyridamole (ASA–ERDP) versus clopidogrel. Methods In this double-blind, 2-by-2 factorial trial, we randomly assigned patients to receive 25 mg of aspirin plus 200 mg of extended-release dipyridamole twice daily or to receive 75 mg of clopidogrel daily. The primary outcome was first recurrence of stroke. The secondary outcome was a composite of stroke, myocardial infarction, or death from vascular causes. Sequential statistical testing of noninferiority (margin of 1.075), followed by superiority testing, was planned. Results A total of 20,332 patients were followed for a mean of 2.5 years. Recurrent stroke occurred in 916 patients (9.0%) receiving ASA–ERDP and in 898 patients (8.8%) receiving clopidogrel (hazard ratio, 1.01; 95% confidence interval [CI], 0.92 to 1.11). The secondary outcome occurred in 1333 patients (13.1%) in each group (hazard ratio for ASA–ERDP, 0.99; 95% CI, 0.92 to 1.07). There were more major hemorrhagic events among ASA–ERDP recipients (419 [4.1%]) than among clopidogrel recipients (365 [3.6%]) (hazard ratio, 1.15; 95% CI, 1.00 to 1.32), including intracranial hemorrhage (hazard ratio, 1.42; 95% CI, 1.11 to 1.83). The net risk of recurrent stroke or major hemorrhagic event was similar in the two groups (1194 ASA–ERDP recipients [11.7%], vs. 1156 clopidogrel recipients [11.4%]; hazard ratio, 1.03; 95% CI, 0.95 to 1.11). Conclusions The trial did not meet the predefined criteria for noninferiority but showed similar rates of recurrent stroke with ASA–ERDP and with clopidogrel. There is no evidence that either of the two treatments was superior to the other in the prevention of recurrent stroke. (ClinicalTrials.gov number, NCT00153062.)