Seasonal dynamics of soil microbial growth, respiration, biomass, and carbon use efficiency in temperate soils

Soil microbial growth, respiration, and carbon (C) use efficiency (CUE) are essential parameters to understand, describe and model the soil carbon cycle. While seasonal dynamics of microbial respiration are well studied, little is known about how microbial growth and CUE change over the course of a year, especially outside the plant growing season. In this study, we measured soil microbial respiration, gross growth via 18O incorporation into DNA, and biomass in an agricultural field and a deciduous forest 16 times over the course of two years. We sampled soils to a depth of 5 cm from plots at which harvest residues or leaf litter remained on the plot or was removed. We observed strong seasonal variations of microbial respiration, growth, and biomass. All these microbial parameters were significantly higher at the forest site, which contained 4.3 % organic C compared to the agricultural site with 0.9 % organic C. CUE also varied strongly (0.1 to 0.7) but was overall significantly higher at the agricultural site compared to the forest site. We found that microbial respiration and to a lesser extent microbial growth followed the seasonal dynamics of soil temperature. Microbial growth was further affected by the presence of plants in the agricultural system or foliage in the forest. At low temperatures in winter, both microbial respiration and gross growth showed the lowest rates, whereas CUE (calculated from both respiration and growth) showed amongst the highest values determined during the two years, due to the higher temperature sensitivity of microbial respiration. Microbial biomass C strongly increased in winter. Surprisingly, this winter peak was not connected to high microbial growth or an increase in DNA content. This suggests that microorganisms accumulated C and N, potentially in the form of osmo- or cryoprotectants or increased in cell size but did not divide. This microbial winter bloom and following decline, where C is released from microbial biomass and freely available, might constitute a highly dynamic time in the annual C cycle in temperate soil systems. Highly variable CUE, which was observed in our study, and the fact that CUE is calculated from independently controlled microbial respiration and microbial growth, ask for great caution when CUE is used to describe soil microbial physiology, soil C dynamics or C sequestration. Instead, microbial respiration, microbial growth, and microbial biomass C should be investigated individually in combination to better understand the soil C cycle

Reading tea leaves worldwide: decoupled drivers of initial litter decomposition mass‐loss rate and stabilization

The breakdown of plant material fuels soil functioning and biodiversity. Currently, process understanding of global decomposition patterns and the drivers of such patterns are hampered by the lack of coherent large‐scale datasets. We buried 36,000 individual litterbags (tea bags) worldwide and found an overall negative correlation between initial mass‐loss rates and stabilization factors of plant‐derived carbon, using the Tea Bag Index (TBI). The stabilization factor quantifies the degree to which easy‐to‐degrade components accumulate during early‐stage decomposition (e.g. by environmental limitations). However, agriculture and an interaction between moisture and temperature led to a decoupling between initial mass‐loss rates and stabilization, notably in colder locations. Using TBI improved mass‐loss estimates of natural litter compared to models that ignored stabilization. Ignoring the transformation of dead plant material to more recalcitrant substances during early‐stage decomposition, and the environmental control of this transformation, could overestimate carbon losses during early decomposition in carbon cycle models

Recombination of Injected and Photogenerated Charge Carriers in Photovoltaic Blends and Devices

Organiska, eller plast, solceller har möjligheten att kunna tillverkas billigt på böjbara plastfilmer. Med tanke på dessa egenskaper kan organiska solceller användas i specialiserade tillämpningar såsom på kläder och väskor etc. Verkningsgraden för organiska solceller har stadigt ökat under de senaste åren och börjar nu närma sig verkningsgraden för kiselsolceller. En stor nackdel med organiska solceller är deras stabilitet. För att kunna tillverka solceller med högre verkningsgrad och stabilitet behövs en grundlig förståelse av de fysikaliska processer som pågår i organiska material som används i solceller. En viktig förlustprocess i solceller är rekombination av laddningsbärare. I denna process försvinner laddningsbärarna t.ex. genom att kollidera med andra laddningar. Det är viktigt att kunna klargöra hur många laddningsbärare som försvinner genom rekombination och vilken typ av rekombination som dominerar i organiska material. I denna avhandling har två olika mätmetoder utnyttjats för att klargöra rekombinationen i organiska material och solceller. I detta arbete visas hur man använder dessa mätmetoder för att erhålla rekombinationen i material med en känd typ av rekombination och används sedan för att visa vilken sort av rekombination dominerar i flera andra organiska material och solceller. Resultaten i denna avhandling är av nytta i framtiden för att kunna klargöra rekombinationen i organiska material som ger information om hur man kan designa nya material för att göra effektivare organiska solceller. ------------------------------------ Orgaaniset, tai muoviset, auringonkennot voidaan valmistella halvasti joustavalla muovikalvoilla. Ottaen huomioon nämä ominaisuudet, orgaanisia auringonkennoja voidaan käyttää erikoistuneissa sovelluksissa, kuten vaatteissa tai laukkuissa jne. Orgaanisten auringonkennojen tehokkuusaste on kasvanut tasaisesti viime vuosina ja alkaa nyt lähestyä pii-auringonkennojen tehokkuutta. Orgaanisten aurinkokennojen suuri haitta on niiden vakaus. Jotta aurinkokennoja tuotettaisiin suuremmalla tehokkuudella ja vakaudella, tarvitaan aurinkokennoissa käytettävien orgaanisten materiaalien perusteellista ymmärrystä. Tärkeä häviöprosessi auringonkennoissa on varauksien rekombinaatio. Tässä prosessissa varaukset katoavat esim. törmäämällä muihin varauksiin. On tärkeä pystyä selvittämään, kuinka monta varauksia menetetään rekombinaatiolla ja minkä tyyppinen rekombinaation hallitsee orgaanisissa materiaaleissa. Tässä väitöskirjassa on käytetty kahta erilaista mittausmenetelmää rekombinaation selvittämiseksi orgaanisissa materiaaleissa ja aurinkokennoissa. Tämä työ näyttää, kuinka näitä mittausmenetelmiä käytetään rekombinaation selventämisessä materiaaleissa, joilla on tunnettua rekombinaatiotyyppiä ja jota käytetään sitten osoittamaan millainen rekombinaatio hallitsee muissa orgaanisissa materiaaleissa ja aurinkokennoissa. Tämän väitöskirjan tulokset ovat hyödyllisiä tulevaisuudessa selkeyttämään rekombinaatiota orgaanisissa materiaaleissa, jotka tarjoavat tietoa uusien materiaalien suunnittelusta tehostamaan orgaanisien aurinkokennojen tehokkuus

Generation of Photoexcitations and Trap-Assisted Recombination in TQ1:PC71BM Blends

The generation and recombination of long-lived photoexcitations is clarified in TQ1 films and TQ1:PC71BM 1:1 and 1:3, by weight, blends using photoinduced absorption measurements. At 80 K triplets are formed in TQ1 films, while both triplets and polarons are formed in the 1:1 and 1:3 blends. We suggest that the triplet state acts as a loss mechanism for generation of free charges in these blends and suggest an energy diagram for the photoexcitations in the blends. We estimate the triplet polaron annihilation (gamma(TPA)) constant to be 1.12 x 10(-14) and 3.10 x 10(-13) cm(3) s(-1) for the TQ1:PC71BM 1:1 and 1:3 blends, respectively. At 300 K triplets are mainly formed in the TQ1 films, while only polarons are present in the TQ1:PC71BM blends. Using frequency measurements we show that the TQ1:PC71BM 1:1 blend shows nondispersive kinetics (zeta = 1), while the 1:3 blend exhibits dispersive kinetics (zeta = 0.87). Using intensity-dependent measurements, we show that trap-assisted recombination is the dominating recombination mechanism for polarons in TQ1:PC71BM blends. Assuming an exponential trap-density we show that the characteristic energy E-ch, the mean trap-depth, is E-ch = 38.7 +/- 2 meV in 1:1 blends and slightly deeper in 1:3 blends, E-ch = 48.4 +/- 2 meV. The trap density is shown to be higher in the 1:1 compared to the 1:3 blends

Seasonal dynamics of soil microbial growth, respiration, biomass, and carbon use efficiency in temperate soils

Soil microbial growth, respiration, and carbon (C) use efficiency (CUE) are essential parameters to understand, describe and model the soil carbon cycle. While seasonal dynamics of microbial respiration are well studied, little is known about how microbial growth and CUE change over the course of a year, especially outside the plant growing season. In this study, we measured soil microbial respiration, gross growth via 18O incorporation into DNA, and biomass in an agricultural field and a deciduous forest 16 times over the course of two years. We sampled soils to a depth of 5 cm from plots at which harvest residues or leaf litter remained on the plot or was removed. We observed strong seasonal variations of microbial respiration, growth, and biomass. All these microbial parameters were significantly higher at the forest site, which contained 4.3 % organic C compared to the agricultural site with 0.9 % organic C. CUE also varied strongly (0.1 to 0.7) but was overall significantly higher at the agricultural site compared to the forest site. We found that microbial respiration and to a lesser extent microbial growth followed the seasonal dynamics of soil temperature. Microbial growth was further affected by the presence of plants in the agricultural system or foliage in the forest. At low temperatures in winter, both microbial respiration and gross growth showed the lowest rates, whereas CUE (calculated from both respiration and growth) showed amongst the highest values determined during the two years, due to the higher temperature sensitivity of microbial respiration. Microbial biomass C strongly increased in winter. Surprisingly, this winter peak was not connected to high microbial growth or an increase in DNA content. This suggests that microorganisms accumulated C and N, potentially in the form of osmo- or cryoprotectants or increased in cell size but did not divide. This microbial winter bloom and following decline, where C is released from microbial biomass and freely available, might constitute a highly dynamic time in the annual C cycle in temperate soil systems. Highly variable CUE, which was observed in our study, and the fact that CUE is calculated from independently controlled microbial respiration and microbial growth, ask for great caution when CUE is used to describe soil microbial physiology, soil C dynamics or C sequestration. Instead, microbial respiration, microbial growth, and microbial biomass C should be investigated individually in combination to better understand the soil C cycle

Combinatorial molecule screening identifies a novel diterpene and the BET inhibitor CPI-203 as differentiation inducers of primary acute myeloid leukemia cells

Combination treatment has proven effective for patients with acute promyelocytic leukemia, exemplifying the importance of therapy targeting multiple components of oncogenic regulation for a successful outcome. However, recent studies have shown that the mutational complexity of acute myeloid leukemia (AML) precludes the translation of molecular targeting into clinical success. Here as a complement to genetic profiling, we used unbiased, combinatorial in vitro drug screening to identify pathways that drive AML and to develop personalized combinatorial treatments. First, we screened 513 natural compounds on primary AML cells and identified a novel diterpene (H4) that preferentially induced differentiation of FLT3 wild-type AMLs, while FLT3-ITD/mutations conferred resistance. The responding samples to H4, displayed increased expression of myeloid markers, a clear decrease in the nuclear-cytoplasmic ratio and the potential of re-activation of the monocytic transcriptional program reducing leukemia propagation in vivo. By combinatorial screening using H4 and molecules with defined targets, we demonstrated that H4 induces differentiation by the activation of protein kinase C (PKC) signaling pathway, and in line with this, activates PKC phosphorylation and translocation of PKC to the cell membrane. Furthermore, the combinatorial screening identified a bromo- and extra-terminal domain (BET) inhibitor that could further improve H4-dependent leukemic differentiation in FLT3 wild-type monocytic AML. Taken together, this illustrates the value of an unbiased and multiplex screening platform for developing combinatorial therapeutic approaches for AML