Emergence of ferroelectricity at the morphotropic phase boundary of ultrathin BiFeO3_3

We demonstrate the robustness of polarization in ultrathin compressive strained BiFeO$_3$ single layers and heterostructures during epitaxial thin-film growth. Using in-situ optical second harmonic generation (ISHG), we explore the emergence of ferroelectric phases at the strain-driven morphotropic phase boundary in the ultrathin regime. We find that the epitaxial films grow in the ferroelectric tetragonal (T-) phase without exhibition of a critical thickness. The robustness of this high-temperature T-phase against depolarizing-field effects is further demonstrated during the growth of capacitor-like (metal|ferroelectric|metal) heterostructures. Using temperature-dependent ISHG post-deposition, we identify the thickness-dependent onset of the monoclinic distortion in the T-matrix and trace the signature of the subsequent emergence of the strain-relaxed rhombohedral-like monoclinic phase. Our results show that strain-driven T-phase stabilization in BiFeO$_3$ yields a prominent candidate material for realizing ultrathin ferroelectric devices.Comment: 5 pages, 3 figure

Evolution of microbial communities and nutrient removal performances in aerobic granular sludge sequencing batch reactor during change of substrate

• Aerobic granular sludge (AGS) is a promising alternative wastewater treatment to the conventional activated sludge system. As AGS has enhanced settling abilities and provides different redox conditions across the granules at the same time, the processes based on AGS allow substantial space, energy and chemical products savings. A few wastewater treatment plants (mainly hybrid or pilot plants) are already using AGS. Nevertheless the performances of lab-scale reactors fed with simple synthetic wastewater are usually different from those of plants treating real wastewater where nutrient removal performances are more versatile and granules have a fluffy structure. Moreover, if the microbial community structures from AGS reactor fed with simple synthetic substrate have been extensively studied, it is less the case of the biomass from AGS reactors fed with more complex substrates or real wastewater. Material and Methods • In order to make a step toward the comprehension of AGS used to treat municipal wastewater, this experiment was designed to study the impact of polymeric organic compounds on nutrient removal performances and microbial communities. These properties were monitored on a lab scale AGS sequencing batch reactor during a progressive substrate transition from volatile fatty acids (VFAs), to a more complex substrate mixture containing VFAs, glucose and amino acids, and finally to a synthetic wastewater containing VFAs, starch and oligo-peptides. Results and Conclusions • With the lowered VFA concentrations, phosphorus (P)-removal performances were impaired. At the same time, amino acids fermentation significantly increased the ammonium concentration, thus extending the time required for total nitrification. The composition of the artificial wastewater was further adapted in order to recover efficient P- and nitrogen (N)-removal. Molecular analyses will show how the changes in substrate composition have influenced the AGS bacterial community structure that has kept its high settling ability and the granule size distribution throughout the first substrate transition

Evolution of microbial communities in aerobic granular sludge during changes in wastewater composition

Aerobic granular sludge (AGS) is an emerging technology offering an alternative wastewater treatment with a reduced footprint compared to conventional activated sludge systems. Basic understanding of AGS has mainly been obtained in lab-scale reactors fed with simple synthetic wastewaters. Yet, the properties and performances of AGS cultivated in these model systems are different from those obtained in reactors treating real wastewater. The composition of the synthetic wastewater of an AGS reactor was progressively changed from a simple wastewater containing mainly volatile fatty acids to a complex monomeric wastewater containing amino acids and glucose (1), from complex monomeric wastewater to a complex polymeric wastewater containing starch and peptone (2), and from complex monomeric back to simple wastewater (3). The microbial community of the sludge, its performances and properties were monitored. During transition (1), a clear shift from the dominant class of β-Proteobacteria to Actinobacteria was first observed, followed by a second phase where the two classes were present in high abundance. During transition (2), a slight increase of members of the Saccharibacteria phylum and the class of Sphingobacteria was noticed. After transition (3) the microbial community was similar to the initial one. The nutrient removal performances and granulation remained stable with the monomeric wastewaters. However, denitrification and granulation were impaired with the addition of polymeric compounds (2). As conclusion, changes in the influent wastewater composition led to reversible changes in the microbial communities of AGS while denitrification performances and granulation were affected by the presence of polymeric compounds in the influent wastewate

Phage-dependent variability of Candidatus ‘Accumulibacter phosphatis’ populations in aerobic granular sludge

During the past 20 years, aerobic granular sludge (AGS) has been extensively studied with the aim to develop an attractive alternative to conventional activated sludge for wastewater treatment. The phosphate-accumulating organism (PAO) Candidatus ‘Accumulibacter phosphatis’ is often found with significant abundance in AGS as well as in other enhanced biological phosporus removal (EPBR) systems. Although they have never been isolated in pure culture, members of this bacterial genus appear to be genetically and physiologically more diversified than initially expected. Impaired EBPR performances observed in lab- and full-scale reactors have often been correlated to a decrease in Accumulibacter populations. This phenomenon has mainly been linked to the presence of bacterial competitors such as glycogen-accumulating organisms (GAO), and bacteriophages have only rarely been suspected to be responsible for this depletion (1). In the present study, the metagenome of 46 individual granules from a lab-scale AGS sequencing batch reactor was sequenced. The results showed a surprisingly variable relative abundance of Accumulibacter populations amongst the different granules that could only be partially explained by the “phenotype” of these granules. A co-occurrence analysis revealed a strong negative correlation between the number of Accumulibacter sequencing reads with the relative abundance of two bacteriophages, namely EBPR podovirus 1 (EPV1) and EBPR podovirus 3 (EPV3), that have been previously detected in a lab-scale EBPR reactor (2). These results suggest that these phages are the major reason for the variability of Accumulibacter relative abundance in the sampled granules which raises the question whether the Accumulibacter populations in the different granules have different sensitivities towards these phages. (1) Barr et al., 2010, Fems Microbiology Ecology, 631-642 (2) Skennerton et al., 2011, Plos On

Effects of a physical activity programme to prevent physical performance decline in onco-geriatric patients: a randomized multicentre trial

Background Older adults with cancer experience negative long-term functional effects of both cancer and treatments. Exercise may minimize their age-related and cancer-related functional decline. Methods We conducted a multicentre open-label 12 month randomized clinical trial with two parallel arms including participants aged >= 70 years with lymphoma or carcinoma requiring curative treatment. The study started at the beginning of any phase of cancer treatment (surgery, chemotherapy, or radiotherapy). The usual care group (UCG) received the current national recommendations in physical activity (a guideline without specific counselling). The intervention group (IG) received 1 year phoned physical activity advice individually adapted to physical assessment (twice a month during the first 6 months and then monthly). The primary outcome was the proportion of subjects with a 1 year decreased short physical performance battery (SPPB) score of 1 point or more. Physical, cognitive, and clinical secondary outcomes were also investigated. Results We allocated 301 participants (age 76.7 +/- 5.0, female 60.6%) to each group. At baseline, the median SPPB was 10/12 in both groups. Breast was the most frequent tumour site (35.7%). After 1 year, 14.0% of participants in the UCG and 18.7% in the IG had a decrease in SPPB score of 1 point or more (P = 0.772). At 2 years, there was no difference in SPPB, gait speed, International Physical Activity Questionnaire score, and verbal fluency. Subgroup analyses after 2 years showed a decline in SPPB for 29.8% of UCG and 5.0% of IG breast cancer participants (P = 0.006), in 21.7% of UCG and 6.2% of IG female participants (P = 0.019), and in 24.5% of UCG and 11.1% of IG normal nutritional status participants (P = 0.009). Falls, hospitalization, institutionalization, and death rates were similar in both groups. Conclusions Personalized phoned physical activity advice had not reduced functional decline at 1 year but provided preliminary evidence that may prevent physical performance decline at 2 years in older adults with breast cancer.This work was funded by the National Hospital Program of Clinical Research (Programme Hospitalier de Recherche Clinique 2010) and sponsored by the University Hospital of Bordeaux (CHU Bordeaux). Haritz Arrieta was supported by a fellowship from University of the Basque Country (UPV/EHU)

Polyphosphate - a key biopolymer in aerobic granular sludge technology

Polyphosphate is the key biopolymer in wastewater treatment (WWT) processes applying enhanced biological phosphorus removal (EBPR) by polyphosphate-accumulating organisms (PAO). Alternating anaerobic (no oxygen and no nitrate) and aerobic phases is used to promote a net phosphorus removal from the wastewater as PAO are capable to take up and store phosphate as intracellular polyphosphate during the aerobic growth phase. In the anaerobic phase, PAO replenish their carbon and energy source in form of polyhydroxyalkanoates (PHA) from volatile fatty acids (VFA) present or formed in the wastewater. The energy and reducing equivalents needed to form PHA come from glycogen and polyphosphate, the polymers that are replenished during the aerobic phase. A few PAO have been already identified, among which Candidatus Accumulibacter phosphatis is a major player in WWT microbial communities enriched with VFA. However, depending on the carbon source the microbial community can strongly fluctuate and other PAO might play a major role in phosphorus removal. We are studying the dynamics of microbial communities in lab-scale aerobic granular sludge sequencing batch reactors subjected to changes of carbon source going from simple VFA to a mixture of VFA, glucose and amino acids. Both metagenomic approaches targeting polyphosphate kinase (ppk) genes and functional analysis of PAO using fluorescence techniques staining the polyphosphate polymer allow us to investigate the key metabolic genes in the synthesis of polyphosphate and expand the knowledge on the diversity of PAO in such engineered systems