Overwintering and regrowth of Sonchus arvensis roots in Finland as affected by fragmentation and burial in three different soil types

In this study the effect of root fragmentation, burial depth and soil type on overwintering and regrowth of Sonchus arvensis L. (perennial sow-thistle) was studied

Response of Sonchus arvensis to mechanical and cultural weed control

In order to study the biology and physical control of Sonchus arvensis, a 3-year field experiment was established in 2001 at Vihti, southern Finland

Sonchus arvensis - a challenge for organic farming

Perennial sow-thistle (Sonchus arvensis L.) represents an increasing problem in Finland. Options for mechanical and cultural control of S. arvensis were studied in a 3 year field experiment on clay soil under organic production

Weed problems in various tillage systems in the Nordic countries

There is an increasing use of various forms of reduced tillage or no-tillage in the Nordic countries. This will favour the growth of grass weed species and perennial species. Perennial creeping weeds like Elymus repens, Cirsium arvense, and Sonchus arvensis are important in all Nordic countries. Stationary weeds such as Taraxacum spp., Artemisia vulgaris and volunteer grassland species increase in areas with reduced tillage and especially no-tillage systems. Winter annual and biennial species such as Matricaria perforata, Poa annua, Alopecurus geniculatus and Stellaria media are frequently occuring weeds in reduced tillage systems in all countries, while Alopecurus myosuroides and Apera spica-venti are problems in Denmark and Southern parts of Sweden and Finland

Quantitative climate reconstructions based on fossil pollen : novel approaches to calibration, validation, and spatial data analysis

Palaeoclimatic reconstructions from fossil proxies have provided important insights into the natural variability of climate in the late Quaternary. However, major challenges remain in ensuring the robustness of these reconstructions. Multiple factors may introduce variability and biases into the palaeoclimatic estimates. For example, quantitative reconstructions use diverse modern calibration data-sets, and a wide variety of numerical calibration methods. While the choice of calibration data-set and calibration method may significantly influence the reconstructions, the comparison and analysis of these data-sets and methods have received relatively little attention. Further challenges are presented by the validation of the prepared reconstructions and the identification of climatic variables which can be robustly reconstructed from a given proxy. In this work, summer temperature reconstructions are prepared based on late-Quaternary pollen sequences from northern Finland and northern Russia, covering the Holocene and the early part of the last glacial period (Marine Isotope Stages 5d c). The major aim of this work is to validate these reconstructions and to identify sources of bias in them. Reconstructions are prepared using a number of different calibration methods and calibration sets, to analyse the between-reconstruction variability introduced by the choice of calibration method and calibration set. In addition, novel regression tree methods are used to test the ecological significance of different climatic factors, with the aim of identifying parameters which could feasibly be reconstructed. In the results, it is found that the choice of calibration method, calibration data-set, and fossil pollen sequence can all significantly affect the reconstruction. The problems in choosing calibration data are especially acute in pre-Holocene reconstructions, as it is difficult to find representative calibration data for reconstructions from non-analogue palaeoclimates which become increasingly common in the more distant past. First-order trends in the reconstructed palaeoclimates are found to be relatively robust. However, the degree of between-reconstruction variability stresses the importance of independent validation, and suggests that ensemble reconstructions using different methods and proxies should be increasingly relied on. The analysis of climatic response in northern European modern pollen samples by regression trees suggests secondary climatic determinants such as winter temperature and continentality to have major ecological influence, in addition to summer temperature which has been the most commonly reconstructed variable in palaeoclimatic studies. This suggests the potential to reconstruct the secondary parameters from fossil pollen. However, validating the robustness of secondary-parameter reconstructions remains a major challenge for future studies.Väitöstutkimuksessa selvitettiin Pohjois-Euroopan ilmaston kehitystä viimeisten noin sadantuhannen vuoden aikana. Tutkimus perustuu Euroopan puoleisen Pohjois-Venäjän tundra-alueelta ja Pohjois-Suomesta kerättyihin kasvifossiiliaineistoihin. Tutkimus edustaa paleoklimatologiaa eli tutkimusalaa, joka pyrkii selvittämään ilmastossa erittäin pitkillä aikaväleillä, tuhansien ja miljoonien vuosien aikana tapahtuneita muutoksia. Tutkimuksessa tehtiin niin sanottuja rekonstruktioita Pohjois-Euroopan ilmastosta ja kasvillisuudesta fossiiliaineistojen perusteella: tuhansien vuosien takaisten ilmastojen ja kasvillisuuden piirteitä arvioitiin tutkimalla eri-ikäisissä maaperän kerrostumissa säilyneitä fossiileita. Tässä tutkimuksessa erityishuomion kohteena olivat fossiiliset siitepölyhiukkaset. Fossiilisten siitepölyjen lajisuhteiden perusteella arvioitiin muinaisten ilmastovaiheiden lämpötiloja käyttämällä erilaisia tilastollisia menetelmiä. Yksi väitöstutkimuksen keskeisistä tuloksista koskee Euroopan puoleisen Pohjois-Venäjän tundra-alueen herkkyyttä ilmaston lämpenemiselle. Tutkimuksessa selvitettiin kasvillisuuden ja lämpötilan muutoksia tällä alueella noin 5000 vuotta sitten, nykyistä selvästi lämpimämmän ilmastovaiheen aikana. Tulosten perusteella lämpötila oli 5000 vuotta sitten noin 2,5 °C nykyistä korkeammalla. Samalla havumetsän pohjoisraja oli n. 150 km pohjoisempana, kaukana nykyisellä tundra-alueella. Myös ikiroudan määrä alueella oli tuolloin huomattavasti nykyistä pienempi. Nämä suuret ympäristömuutokset osoittavat Euraasian pohjoisen tundra-alueen olevan erittäin herkkä ilmaston muutoksille. Pohjoisen Euraasian on ennustettu lämpenevän tämän vuosisadan aikana useilla asteilla, mikä saattaa tämän tutkimuksen tulosten perusteella aiheuttaa suuria muutoksia alueen kasvillisuudessa ja ikiroudassa. Tutkimuksessa analysoitiin lisäksi erilaisia tilastollisia menetelmiä, joita käytetään paleoklimatologiassa ilmastoarvioiden tekemiseen fossiilien perusteella. Tulosten mukaan eri tilastolliset menetelmät näyttävät tuottavan jossain määrin erilaisia ilmastoarvioita. Muinaisten ilmastojen rekonstruktiot olivat kuitenkin pääpiirteiltään samanlaisia riippumatta siitä, mitä tilastollista menetelmää käytettiin. Tämä viittaa siihen, että ilmastojen keskeisimpiä piirteitä voidaan luotettavasti arvioida fossiiliaineistojen perusteella

Decreasing trend in the incidence of serious pneumonias in Finnish children with juvenile idiopathic arthritis

OBJECTIVES: Children with juvenile idiopathic arthritis (JIA) may be predisposed to serious pneumonia due to modern disease-modifying anti-rheumatic treatment. In this nationwide retrospective study with clinical data, we describe the pneumonia episodes among children with JIA. METHODS: Patients under 18 years of age with JIA and pneumonia during 1998-2014 were identified in the National Hospital Discharge Register in Finland. Each individual patient record was reviewed, and detailed data on patients with JIA and pneumonia were retrieved, recorded, and analyzed. If the patient was hospitalized or received intravenous antibiotics, the pneumonia was considered serious. RESULTS: There were 157 episodes of pneumonia among 140 children with JIA; 111 episodes (71%) were serious (80% in 1998-2006 and 66% in 2007-2014). The mean age of the patients was 9 years. Forty-eight percent had active JIA and 46% had comorbidities. Disease-modifying anti-rheumatic drugs (DMARD) were used at the time of 135 episodes (86%): methotrexate (MTX) by 62% and biologic DMARDs (bDMARD) by 30%. There was no significant difference in the use of bDMARDs, MTX and glucocorticoids between the patient groups with serious and non-serious pneumonia episodes. During six of the episodes, intensive care was needed. Two patients (1.3%) died, the remaining ones recovered fully. CONCLUSIONS: Although the incidence of pneumonia and the use of immunosuppressive treatment among children with JIA increased from 1998 to 2014, the proportion of serious pneumonias in these patients decreased. There was no significant difference in the use of anti-rheumatic medication between patients with serious and non-serious pneumonia.Key Points• The incidence of serious pneumonias decreased from 1998 to 2014 among children with juvenile idiopathic arthritis (JIA).• There was no significant difference in the use of the disease-modifying anti-rheumatic medication between JIA patients with serious and non-serious pneumonias.• Active JIA, comorbidities, and combination medication were associated with nearly half of the pneumonias.Peer reviewe

Enhanced dielectrophoresis of nanocolloids by dimer formation

We investigate the dielectrophoretic motion of charge-neutral, polarizable nanocolloids through molecular dynamics simulations. Comparison to analytical results derived for continuum systems shows that the discrete charge distributions on the nanocolloids have a significant impact on their coupling to the external field. Aggregation of nanocolloids leads to enhanced dielectrophoretic transport, provided that increase in the dipole moment upon aggregation can overcome the related increase in friction. The dimer orientation and the exact structure of the nanocolloid charge distribution are shown to be important in the enhanced transport

Shilla growth guidance compared with magnetically controlled growing rods in the treatment of neuromuscular and syndromic early-onset scoliosis

Peer reviewe