872 research outputs found
Classifying previously undefined days from eleven years of aerosol-particle-size distribution data from the SMEAR II station, Hyytiälä, Finland
Peer reviewe
A Model System for Dimensional Competition in Nanostructures: A Quantum Wire on a Surface
The retarded Green’s function (E−H + iε)−1is given for a dimensionally hybrid Hamiltonian which interpolates between one and two dimensions. This is used as a model for dimensional competition in propagation effects in the presence of one-dimensional subsystems on a surface. The presence of a quantum wire generates additional exponential terms in the Green’s function. The result shows how the location of the one-dimensional subsystem affects propagation of particles
WNT signalling in prostate cancer
Genome sequencing and gene expression analyses of prostate tumours have highlighted the potential importance of genetic and epigenetic changes observed in WNT signalling pathway components in prostate tumours-particularly in the development of castration-resistant prostate cancer. WNT signalling is also important in the prostate tumour microenvironment, in which WNT proteins secreted by the tumour stroma promote resistance to therapy, and in prostate cancer stem or progenitor cells, in which WNT-β-catenin signals promote self-renewal or expansion. Preclinical studies have demonstrated the potential of inhibitors that target WNT receptor complexes at the cell membrane or that block the interaction of β-catenin with lymphoid enhancer-binding factor 1 and the androgen receptor, in preventing prostate cancer progression. Some WNT signalling inhibitors are in phase I trials, but they have yet to be tested in patients with prostate cancer
Vertical profiles of sub-3nm particles over the boreal forest
This work presents airborne observations of sub-3 nm particles in the lower troposphere and investigates new particle formation (NPF) within an evolving boundary layer (BL). We studied particle concentrations together with supporting gas and meteorological data inside the planetary BL over a boreal forest site in Hyytiala, southern Finland. The analysed data were collected during three flight measurement campaigns: May-June 2015, August 2015 and April-May 2017, including 27 morning and 26 afternoon vertical profiles. As a platform for the instrumentation, we used a Cessna 172 aircraft. The analysed flight data were collected horizontally within a 30 km distance from SMEAR II in Hyytiala and vertically from 100 m above ground level up to 2700 m. The number concentration of 1.5-3 nm particles was observed to be, on average, the highest near the forest canopy top and to decrease with increasing altitude during the mornings of NPF event days. This indicates that the precursor vapours emitted by the forest play a key role in NPF in Hyytiala. During daytime, newly formed particles were observed to grow in size and the particle population became more homogenous within the well-mixed BL in the afternoon. During undefined days with respect to NPF, we also detected an increase in concentration of 1.5-3 nm particles in the morning but not their growth in size, which indicates an interrupted NPF process during these undefined days. Vertical mixing was typically stronger during the NPF event days than during the undefined or non-event days. The results shed light on the connection between boundary layer dynamics and NPF.Peer reviewe
Hematological and physiological changes induced by short-term exposure to copper in the freshwater fish, Prochilodus scrofa
Refined classification and characterization of atmospheric new-particle formation events using air ions
Atmospheric new-particle formation (NPF) is a worldwide-observed phenomenon that affects the human health and the global climate.
With a growing network of global atmospheric measurement stations, efforts
towards investigating NPF have increased. In this study, we present an
automated method to classify days into four categories including NPF events,
non-events and two classes in between, which then ensures reproducibility
and minimizes the hours spent on manual classification. We applied our
automated method to 10 years of data collected at the SMEAR II measurement
station in Hyytiälä, southern Finland using a Neutral cluster and Air Ion
Spectrometer (NAIS). In contrast to the traditionally applied classification
methods, which categorize days into events and non-events and ambiguous days as
undefined days, our method is able to classify the undefined days as it
accesses the initial steps of NPF at sub-3 nm sizes. Our results show that, on
∼24 % of the days in Hyytiälä, a regional NPF event
occurred and was characterized by nice weather and favourable conditions
such as a clear sky and low condensation sink. Another class found in
Hyytiälä is the transported event class, which seems to be NPF
carried horizontally or vertically to our measurement location and it
occurred on 17 % of the total studied days. Additionally, we found that an
ion burst, wherein the ions apparently fail to grow to larger sizes, occurred
on 18 % of the days in Hyytiälä. The transported events and ion
bursts were characterized by less favourable ambient conditions than regional
NPF events and thus experienced interrupted particle formation or growth.
Non-events occurred on 41 % of the days and were characterized by
complete cloud cover and high relative humidity. Moreover, for regional
NPF events occurring at the measurement site, the method identifies the start
time, peak time and end time, which helps us focus on variables within an
exact time window to better understand NPF at a process level. Our automated
method can be modified to work in other measurement locations where NPF is
observed.</p
Development of a concept and basis for the DEMO diagnostic and control system
An initial concept for the plasma diagnostic and control (D&C) system has been developed as part of European studies towards the development of a demonstration tokamak fusion reactor (DEMO). The main objective is to develop a feasible, integrated concept design of the DEMO D&C system that can provide reliable plasma control and high performance (electricity output) over extended periods of operation. While the fusion power is maximized when operating near to the operational limits of the tokamak, the reliability of operation typically improves when choosing parameters significantly distant from these limits. In addition to these conflicting requirements, the D&C development has to cope with strong adverse effects acting on all in vessel components on DEMO (harsh neutron environment, particle fluxes, temperatures, electromagnetic forces, etc.). Moreover, space allocation and plasma access are constrained by the needs for first wall integrity and optimization of tritium breeding. Taking into account these boundary conditions, the main DEMO plasma control issues have been formulated, and a list of diagnostic systems and channels needed for plasma control has been developed, which were selected for their robustness and the required coverage of control issues. For a validation and refinement of this concept, simulation tools are being refined and applied for equilibrium, kinetic and mode control studies
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