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We use aerosol synthesis to fabricate ordered metal-silica nanocomposites consisting of alternating layers of pure silica and silica nanoparticles decorated with silver nanodots. These multilayer structures preserve the narrow plasmon resonance of the nanodots even for high optical densities and allow second-harmonic generation due to spontaneous symmetry breaking arising from the interfaces between silica and nanoparticle layers. Our concept opens up perspectives for complex structures for advanced optical applications.
Surface-enhanced Raman spectroscopy (SERS) has attracted a lot of attention in molecular sensing because of the remarkable ability of plasmonic metal nanostructures to enhance the weak Raman scattering process. On the other hand, coherent vibrational spectroscopy triggered by impulsive excitation using ultrafast laser pulses provides complete information about the temporal evolution of molecular vibrations, allowing dynamical processes in molecular systems to be followed in "real time". Here, we combine these two concepts and demonstrate surface-enhanced impulsive vibrational spectroscopy. The vibrational modes of the ground and excited states of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), spin-coated on a substrate covered with monodisperse silver nanoparticles, are impulsively excited with a sub-10 fs pump pulse and characterized with a delayed broad-band probe pulse. The maximum enhancement in the spectrally and temporally resolved vibrational signatures averaged over the whole sample is about 4.6, while the real-time information about the instantaneous vibrational amplitude together with the initial vibrational phase is preserved. The phase is essential to determine the vibrational contributions from the ground and excited states.
We perform a detailed characterisation of the second-order nonlinear optical response of nanocomposites consisting of alternating layers of silver-decorated silica glass nanoparticles and pure silica glass. The samples are fabricated using aerosol techniques and electron-beam dielectric coating, resulting in a bulk-like material with symmetry-breaking induced by the porosity of the alternating layers. The second-order nonlinear response increases with the number of layers. Further, by determining the components of the second-order susceptibility tensor of the samples, we show that the structural properties of the samples are well maintained as the sample thickness is increased. Our results form an important baseline for any further optimization of these types of structures, which can be fabricated using very straightforward methods.
Navigation and location-based applications, including business such as transport, tourism, and mining, in Arctic areas face a variety of specific challenges. In fact, these challenges concern not only the Arctic Circle but certain other areas as well, such as the Gulf of Bothnia. This report provides a review on these challenges which concern a variety of technologies ranging from satellite navigation to telecommunications and mapping. In order to find out end-users' views on the significance of Arctic challenges, an online survey was conducted. The 77 respondents representing all Arctic countries, the majority being from Finland, highlighted the challenges in telecommunications as well as accuracy concerns for emerging applications dealing with precise navigation. This report provides a review of possible technologies for addressing the Arctic challenges, based on which a road map for solving them is developed. The road map also uses the results of expert working groups from the Challenges in Arctic Navigation workshop arranged in April 2018 in Olos, Muonio, Finland. This report was produced within the ARKKI project. It was funded by the Finnish Ministry of Foreign Affairs under the Baltic Sea, Barents and Arctic cooperation programme, and implemented by the Finnish Geospatial Research Institute in collaboration with the Finnish Ministry of Transport and Communications.
Virallisten lajikekokeiden tarkoituksena on kasvilajikkeiden viljelyarvon arviointi. Viljoilla lajikkeiden taudinkestävyyden merkitys viljelyarvon osana on koko ajan kasvanut. Tiedot lajikkeiden taudinkestävyydestä perustuvat useimpien tautien osalta virallisten lajikekokeiden kenttäkokeista 1995-2002 tehtyihin tautihavaintoihin. Seuraavien tautien esiintyminen on havainnoitu lajikekokeista: Syysrukiin härmä, rukiinruskearuoste, rengaslaikku ja lumihome; kevätrukiin härmä ja rukiinruskearuoste; ruisvehnän lehti- ja tähkälaikku, keltaruoste, rengaslaikku ja lumihome; syysvehnän härmä, lehti ja tähkälaikku, keltaruoste ja lumihome; kevätvehnän härmä, lehti- ja tähkälaikku, keltaruoste; ohran härmä, verkkolaikku, rengaslaikku sekä kauran lehtilaikku. Lajikekokeista taudit on arvosteltu asteikolla 0-100, jossa nolla merkitsee täysin tervettä kasvustoa ja 100 täysin taudin saastuttamaa tai kuollutta kasvustoa. Vehnän haisunoen ja kauranavonoen arkuus on tutkittu saastutuskokeilla. Haisunokitulokset ovat vuosilta 1991-2002 ja kauranavonokitulokset vuosilta 1994-1996 ja 1998-2002. Saastutuskokeista on laskettu terveiden ja infektoituneiden kasviyksiköiden määrät. Tautitulokset on analysoitu käyttäen lineaarisia sekamalleja. Tuloksena saadut lajikekohtaiset tautikeskiarvot ovat keskenään vertailukelpoisia lajikkeiden koejaksojen erilaisuudesta huolimatta. Tuloksissa ensimmäisenä on esitetty mittarilajikkeet, sitten muut lajikkeet taudinkestävyyden mukaisessa järjestyksessä.
Virallisten lajikekokeiden tarkoituksena on kasvilajikkeiden viljelyarvon arviointi. Viljoilla lajikkeiden taudinkestävyyden merkitys viljelyarvon osana on koko ajan kasvanut. Tiedot lajikkeiden taudinkestävyydestä perustuvat useimpien tautien osalta virallisten lajikekokeiden kenttäkokeista 1996-2003 tehtyihin tautihavaintoihin. Seuraavien tautien esiintyminen on havainnoitu lajikekokeista: Syysrukiin härmä, rukiinruskearuoste, rengaslaikku ja lumihome; ruisvehnän lehti- ja tähkälaikku, keltaruoste, rengaslaikku ja lumihome; syysvehnän härmä, lehti ja tähkälaikku, keltaruoste ja lumi home; kevätvehnän härmä, lehti- ja tähkälaikku, keltaruoste; ohran härmä, verkkolaikku, rengaslaikku sekä kauran lehtilaikku. Lajikekokeista taudit on arvosteltu asteikolla 0 - 100, jossa nolla merkitsee täysin tervettä kasvustoa ja 100 täysin taudin tartuttamaa tai kuollutta kasvustoa. Vehnän haisunoen, kauranavonoen sekä ohranviirutaudin arkuus on tutkittu infektointikokeilla. Haisunoen tulokset ovat vuosilta 1996-2003 ja kauranavonoen tulokset vuosilta 1996-1996 ja 1998-2003. Ohranviirutaudin tulokset ovat vuosilta 1999-2002. Kokeista on laskettu terveiden ja infektoituneiden kasviyksiköiden määrät. Tautitulokset on analysoitu käyttäen lineaarisia sekamalleja. Tuloksena saadut lajikekohtaiset tautikeskiarvot ovat keskenään vertailukelpoisia lajikkeiden koejaksojen erilaisuudesta huolimatta. Tuloksissa ensimmäisenä on esitetty mittarilajikkeet, sitten muut lajikkeet taudinkestävyyden mukaisessa järjestyksessä.
Virallisten lajikekokeiden perusteella arvioidaan uusien kasvilajikkeiden viljelyarvo. Viljoilla taudinkestävyyden merkitys osana viljelyarvoa on koko ajan lisääntynyt. Kasvitautien esiintymistä on havainnoitu viljojen virallisista lajikekokeista vuodesta 1991 lähtien. Tässä julkaisussa esitetään tulokset tärkeimpien havainnoitujen kasvitautien esiintymisestä syysruis-, ruisvehnä-, syysvehnä-, kevätvehnä-, ohra- ja kauralajikkeissa vuosina 1991-2001.
Background: Gastrointestinal (GI) symptoms are common in end-stage kidney disease. Mounting evidence indicates that the intestine plays an important role in the pathogenesis of IgA nephropathy (IgAN). However, no studies have addressed the obvious question; do IgAN patients suffer from GI symptoms? Methods: Presence of GI symptoms and health-related quality of life were evaluated using the validated Gastrointestinal Symptom Rating Scale (GSRS) and Psychological General Well-Being (PGWB) questionnaires in 104 patients with kidney biopsy-verified IgAN and in 147 healthy controls. A person was regarded to experience ‘increased GI symptoms’ if the GSRS score exceeded plus 1 standard deviation of the mean of the corresponding score in the healthy controls. Results: According to the GSRS total score, the IgAN patients had more GI symptoms than the healthy controls (2.0 vs. 1.7, p < 0.001). Female IgAN patients had higher GSRS total score than male patients (2.2 vs. 1.7, p = 0.001). More IgAN patients with preserved kidney function (eGFR > 60ml/min/1.73m2) suffered from increased symptoms of diarrhoea (76 vs. 25%, p = 0.028), constipation (81 vs. 19%, p = 0.046) and reflux (85 vs. 15%, p = 0.004) than did IgAN patients with reduced kidney function (eGFR < 60ml/min/1.73m2). Conclusions: IgAN patients and especially female IgAN patients experienced more GI symptoms than healthy controls. More prevalent GI symptoms were already observed before kidney function was clearly reduced. Systematic enquiry of GI symptoms might increase the standard of care among IgAN patients. Moreover, GI symptoms may provide clues for future studies that examine the pathophysiology of IgAN.
Aerosol techniques were used to synthesize spherical and monodisperse silver nanoparticles for plasmonic materials. The particles were generated with an evaporation–condensation technique followed by size selection and sintering with a differential mobility analyzer and a tube furnace, respectively. Finally, the nanoparticles were collected on a glass substrate with an electrostatic precipitator. The particle size distributions were measured with a scanning mobility particle sizer and verified with a transmission electron microscope. A spectrophotometer was used to measure the optical extinction spectra of the prepared samples, which contained particles with diameters of approximately 50, 90 and 130 nm. By controlling the particle size, the dipolar peak of the localized surface plasmon resonance was tuned between wavelengths of 398 and 448 nm. In addition, quadrupolar resonances were observed at shorter wavelengths as predicted by the simplified theoretical model used to characterize the measured spectra.
Healthcare associated infections (HAIs) are known as one of the major problems of the modern healthcare system, which result in additional cost and mortality. It has also been shown that pathogenic bacteria are mostly transferred via surfaces in healthcare settings. Therefore, antibacterial surfaces, which include fabrics and textiles, can be used in a healthcare environment to reduce the transfer of pathogenic bacteria, hence reducing HAIs. Silver nanoparticles have been shown to have broad spectrum antibacterial properties, and therefore they have been incorporated into fabrics to provide antibacterial functionality. Liquid flame spray (LFS) nanoparticle synthesis allows nanoparticles to be produced and deposited on surfaces at speeds up to and beyond 300 m/min. Herein, LFS is used to deposit silver nanoparticles onto two fabrics that are commonly used in the hospital environment with the aim of producing antibacterial fabrics. A thin plasma coating on top of the fabrics after silver deposition is used to improve nanoparticle adhesion. Fabrics coated with silver nanoparticles demonstrated antibacterial properties against Escherichia coli. Nanoparticle imaging and surface chemical characterization are performed using scanning electron microscopy and X-ray photoelectron spectroscopy. The highlights of this research are as follows: • high-speed synthesis and deposition of silver nanoparticles on fabrics; • plasma coating onto fabrics with silver nanoparticles; • antibacterial fabrics for potential use in healthcare environments.
Bacterial infections, especially by antimicrobial resistant (AMR) bacteria, are an increasing problem worldwide. AMR is especially a problem with health care-associated infections due to bacteria in hospital environments being easily transferred from patient to patient and from patient to environment, and thus, solutions to prevent bacterial transmission are needed. Hand washing is an effective tool for preventing bacterial infections, but other approaches such as nanoparticle-coated surfaces are also needed. In the current study, direct and indirect liquid flame spray (LFS) method was used to produce silver nanoparticle-coated surfaces. The antimicrobial properties of these nanoparticle surfaces were evaluated with the “touch test” method against Escherichia coli and Staphylococcus aureus. It was shown in this study that in glass samples one silver nanoparticle-coating cycle can inhibit E. coli growth, whereas at least two coating cycles were needed to inhibit S. aureus growth. Silver nanoparticle-coated polyethylene (PE) and PE terephthalate samples did not inhibit bacterial growth as effectively as glass samples: three nanoparticle-coating cycles were needed to inhibit E. coli growth, and more than 30 coating cycles were needed until S. aureus growth was inhibited. To conclude, with the LFS method, it is possible to produce nanostructured large-area antibacterial surfaces which show antibacterial effect against clinically relevant pathogens. Results indicate that the use of silver nanoparticle surfaces in hospital environments could prevent health care-associated infections in vivo.