Shrinkage Events Research Articles

Stable GDP-tubulin islands rescue dynamic microtubules.

Microtubules are dynamic polymers that interconvert between phases of growth and shrinkage, yet they provide structural stability to cells. Growth involves hydrolysis of GTP-tubulin to GDP-tubulin, which releases energy that is stored within the microtubule lattice and destabilizes it; a GTP cap at microtubule ends is thought to prevent GDP subunits from rapidly dissociating and causing catastrophe. Here, using in vitro reconstitution assays, we show that GDP-tubulin, usually considered inactive, can itself assemble into microtubules, preferentially at the minus end, and promote persistent growth. GDP-tubulin-assembled microtubules are highly stable, displaying no detectable spontaneous shrinkage. Strikingly, islands of GDP-tubulin within dynamic microtubules stop shrinkage events and promote rescues. Microtubules thus possess an intrinsic capacity for stability, independent of accessory proteins. This finding provides novel mechanisms to explain microtubule dynamics.

Genome-wide identification of exon extension/shrinkage events induced by splice-site-creating mutations

ABSTRACT Mutations that affect phenotypes have been identified primarily as those that directly alter amino acid sequences or disrupt splice sites. However, some mutations not located in functionally important sites can also affect phenotypes, such as splice-site-creating mutations (SCMs). To investigate how frequent exon extension/shrinkage events induced by SCMs occur in normal individuals, we used personal genome sequencing data and transcriptome data of the corresponding individuals and identified 371 exon extension/shrinkage events in normal individuals. This number was about three times higher than the number of pseudo-exon activation events identified in the previous study. The average numbers of exon extension and exon shrinkage events in each sample were 3.3 and 11.2, respectively. We also evaluated the impact of exon extension/shrinkage events on the resulting transcripts and their protein products and found that 40.2% of the identified events may have possible functional impacts by either generating premature termination codons in transcripts or affecting protein domains. Our results indicated that a certain fraction of SCMs identified in this study can be pathogenic mutations by creating novel splice sites.

Changes in the new particle formation and shrinkage events of the atmospheric ions during the COVID-19 lockdown

Impacts of environmental changes at Pune, India during the lockdown period imposed due to the Covid-19 pandemic, on the characteristics of the atmospheric ions and the new particle formation (i.e. the formation of molecular clusters and their subsequent growth to larger sizes) and shrinkage events have been investigated. The increase in the small and big cluster ion concentrations and the decrease in intermediate ion concentrations observed during the lockdown period have been associated with the decrease in the aerosols and precursor gases, respectively. During the NPF events, the nucleation mode particles of both polarities grow in size. However, during the unique shrinkage events observed here, particles increase in concentration but do not grow in size during the morning-to-noon period and shrink in the noon-to-evening period during the lockdown period. Simultaneously, the concentration of particles of >25 nm decrease i during the morning hours and increase during the afternoon hours .On the shrinkage event days, solar irradiance is higher and relative humidity is lower throughout the day than on the NPF/no-event days. Occurrence of shrinkage events has been proposed to be associated with the change in saturation vapour pressure of different chemical species with temperature/solar irradiance.

Single-Cell Time-Lapse Observation Reveals Cell Shrinkage upon Cell Death in Batch Culture of Saccharomyces cerevisiae.

ABSTRACTSaccharomyces cerevisiae is a model organism for aging and longevity studies. In a clonal population of S. cerevisiae, the timing of cell death in the stationary phase is not synchronized, indicating that heterogeneity exists in survival at a single-cell level. Heterogeneity also exists in the cell size, and its correlation with the death rate has been discussed in past studies. However, the direct cause of the heterogeneity in survival remains unknown. In this report, we revisited this question and asked whether the death rate has any correlation with cell size. Past studies did not exclude a possibility that cells change their size upon or after death. If such a change exists, the size dependence of cell death could be misinterpreted. Therefore, we analyzed the correlation between the death rate and cell size before death by time-lapse imaging. It turned out that the size dependence of the death rate varied from one strain to another, suggesting that general principles between cell size and death do not exist. Instead, cells shrink upon cell death, resulting in the accumulation of small dead cells. The degree of cell shrinkage was proportional to the cell size, and the ratio was constant in two strains, which is between 25 and 28%, suggesting the presence of general principles and mechanisms behind the shrinkage event upon cell death. Further investigation of the cause and mechanism of the shrinkage will help us to understand the process of cell death and the origin of the heterogeneity in survival.

Examining COVID-19-triggered changes in spatial connectivity patterns in the European air transport network up to June 2021

The integrity of international supply chain operations heavily relies on air transport services to facilitate the movement of goods and enable human interactions between its stakeholders. With the outbreak of COVID-19 in Europe around March 2020, air transport networks have been subject to profound alterations. Although the link between variations in air transport service levels and changes in user costs for network-wide travel has been analysed extensively, few studies have examined the extent to which severe network shrinkage events lead to a reduction in network connectivity, which is therefore difficult to predict. This paper investigates how the COVID-19 pandemic has structurally altered the European air transport network in 2020/21 and how these changes have deteriorated users' ease when utilising network-wide air transport services. To do this, the paper estimates the change in average quickest path length at the airport level during different stages of this period. Results indicate there is strong heterogeneity in airports' susceptibility to pandemic-induced network changes, with both regional variations and variations in the airline type serving individual airports. Furthermore, topological features of individual airports are found to determine airport susceptibility. The findings are discussed in terms of their implications for locational decisions in supply chain designs.

The multiscale nature of leaf growth fields

A growing leaf is a prototypical active solid, as its active units, the cells, locally deform during the out-of-equilibrium process of growth. During this local growth, leaves increase their area by orders of magnitude, yet maintain a proper shape, usually flat. How this is achieved in the lack of a central control, is unknown. Here we measure the in-plane growth tensor of Tobacco leaves and study the statistics of growth-rate, isotropy and directionality. We show that growth strongly fluctuates in time and position, and include multiple shrinkage events. We identify the characteristic scales of the fluctuations. We show that the area-growth distribution is broad and non-Gaussian, and use multiscale statistical methods to show how growth homogenizes at larger/longer scales. In contrast, we show that growth isotropy does not homogenize in time. Mechanical analysis shows that with such growth statistics, a leaf can stay flat only if the fluctuations are regulated/correlated.

Genetic diversity of the free-living population of Przewalski's horses in the Chernobyl Exclusion Zone

The present study is aimed at evaluating the genetic diversity, genetic status and the extent of hybridization with the domestic horse for the Przhevalski’s horse (Equus ferus przewalskii Poliakov 1881) population free-ranging in the territory of the Chernobyl Exclusion Zone (CEZ) in Belarus and Ukraine. The sample size included 12 individuals (10 sampled in the Belarusian part of the CEZ and 2 from the Ukrainian part of the CEZ). Ten microsatellites recommended by the International Society for Animal Genetics (ISAG) for horse genetic status and pedigree determination were used as markers in this study. The fragment analysis data obtained utilising this microsatellite panel determined that two individuals from Belarus possess no allelic variants typical for Przhevalski’s horse. Most of the other individuals presented diagnostically valuable allelic variants. Demographic history analysis for the population did not indicate any drastic population shrinkage events in the population’s recent history. The studied population is characterised by heterogeneous population structure with signs of inbreeding (0.21 %), intermediate level of genetic diversity (He = 0.63) and allelic richness (5.15), possesses 16 unique alleles among 2 microsatellite loci and valuable alleles for loci HMS3 and HMS7 (46.4 and 67.9 % specific alleles for Przhevalski’s horse, respectively). Genetic structure evaluation for the population was performed via Bayesian population structure analysis and factorial correspondence analysis (FCA), which indicated the presence of intrapopulation genetic subdivision. Taking into account the obtained indicators of genetic diversity, we may conclude on the relatively favourable status of Przewalski’s horse in the exclusion zone with good potential for the long-term existence of the species population in the wild. In order to minimise inbreeding effects and the risk of a decline in genetic diversity in the population of Przewalski’s horse of the exclusion zone, as well as to increase the value of this free-living group to preserve the gene pool of the species as a whole, it is necessary to provide detailed genetic monitoring of the livestock’s state, as well as develop a regional population management plan, including measures aimed to minimise the possibility of further hybridisation of wild horses with domestic ones.

Response of the Mogan and Eymir lakes (Ankara, Central Anatolia) to global warming: Extreme events in the last 100 years

Mogan and Eymir lakes are shallow wetlands which are potentially susceptible to global warming. Previous geological studies demonstrated several complete desiccation and shrinkage events in Lake Mogan since the 1800s. Archival records show at least three desiccation events in 1910, 1934 and 1938, and many severe shrinkages later. Here, the significance of climatic and anthropogenic drivers is still a subject of curiosity. The back-analysis of the hydrological data during the regulator intervention indicates that Lake Mogan would have dried out in 1974, and would have shrunk considerably in the years 2007/2008 and 2017/2018 if human intervention was not involved. Our lake budget analysis shows that, assuming no human intervention and stream recharge, the water level of both lakes would have dropped below the threshold level in less than a week by natural downstream discharge, and the remaining volume of the lakes would evaporate in less than two years. This fact indicates the benefits of regulators for the protection of the lakes. The meteorological and lake budget data suggest that the underlying climatic threat over the studied lakes is high frequency (sub-decadal) rainfall scarcity coupled with long-term (several decades) insolation increase but not slow, steady deterioration of the climatic parameters.

MAP6 is an intraluminal protein that induces neuronal microtubules to coil.

Neuronal activities depend heavily on microtubules, which shape neuronal processes and transport myriad molecules within them. Although constantly remodeled through growth and shrinkage events, neuronal microtubules must be sufficiently stable to maintain nervous system wiring. This stability is somehow maintained by various microtubule-associated proteins (MAPs), but little is known about how these proteins work. Here, we show that MAP6, previously known to confer cold stability to microtubules, promotes growth. More unexpectedly, MAP6 localizes in the lumen of microtubules, induces the microtubules to coil into a left-handed helix, and forms apertures in the lattice, likely to relieve mechanical stress. These features have not been seen in microtubules before and could play roles in maintaining axonal width or providing flexibility in the face of compressive forces during development.

Comparative Analysis of the Mitochondrial Genomes of Nicotiana tabacum: Hints Toward the Key Factors Closely Related to the Cytoplasmic Male Sterility Mechanism.

BackgroundCytoplasmic male sterility (CMS) is a complex phenomenon of plant sterility that can produce non-functional pollen. It is caused by mutation, rearrangement or recombination in the mitochondrial genome. So far, the systematic structural characteristics of the changes in the mitochondrial genome from the maintainer lines to the CMS lines have not been reported in tobacco.ResultsThe mitochondrial genomes of the flower buds from both CMS lines and maintainer lines of two Nicotiana tabacum cultivars (YY85, sYY85, ZY90, and sZY90) were sequenced using the PacBio and Illumina Hiseq technology, and several findings were produced by comparative analysis based on the de novo sequencing. (1) The genomes of the CMS lines were larger, and the different areas were mostly non-coding regions. (2) A large number of rearrangement regions were detected in the CMS lines, with many translocation regions. (3) Thirteen gene clusters were shared by the four mitochondrial genomes, among which two of the gene clusters, nad2-sdh3 and nad6-rps4, were far from each other in the CMS lines. (4) Thirty-three protein-coding genes were conserved in four mitochondrial genomes. However, nad3 was detected one additional copy in the maintainer lines, and sequence differences were revealed in the four candidate genes (atp6, cox2, nad2, and sdh3). Importantly, the evolutionary tree based on the four genes could be used to distinguish the CMS lines and the maintainer lines well for the sequenced mitochondrial genomes of the tobacco. (5) Sixteen CMS-specific open reading frames (ORFs) were found, three of which (orf91, orf115b, and orf100) were previously reported. (6) The differences in intensity of the protein–protein (PPI) interaction in ATP6 were further verified using the yeast two-hybrid analysis.ConclusionAlthough the majority of the sequences, genes and gene clusters were shared by the mitochondrial genomes of the maintainer and the CMS lines in tobacco, extensive structural variations identified with comprehensive analysis based on the mitochondrial genomes, including rearrangement, gene order, the mitochondrial genome expansion and shrinkage events, might be related to CMS. Additionally, the candidate protein-coding genes and CMS-specific ORFs were closely associated with the CMS mechanism. Verification experiments of one of the candidate genes were performed, and the validity of our research results was supported.

Visualizing Intracellular Organelle and Cytoskeletal Interactions at Nanoscale Resolution on Millisecond Timescales

In eukaryotic cells, organelles and the cytoskeleton undergo highly dynamic yet organized interactions capable of orchestrating complex cellular functions. Visualizing these interactions requires noninvasive, long-duration imaging of the intracellular environment at high spatiotemporal resolution and low background. To achieve these normally opposing goals, we developed grazing incidence structured illumination microscopy (GI-SIM) that is capable of imaging dynamic events near the basal cell cortex at 97-nm resolution and 266 frames/s over thousands of time points. We employed multi-color GI-SIM to characterize the fast dynamic interactions of diverse organelles and the cytoskeleton, shedding new light on the complex behaviors of these structures. Precise measurements of microtubule growth or shrinkage events helped distinguish among models of microtubule dynamic instability. Analysis of endoplasmic reticulum (ER) interactions with other organelles or microtubules uncovered new ER remodeling mechanisms, such as hitchhiking of the ER on motile organelles. Finally, ER-mitochondria contact sites were found to promote both mitochondrial fission and fusion.

Sources and physicochemical characteristics of submicron aerosols during three intensive campaigns in Granada (Spain)

Aerosol particles in the submicron range and their physicochemical characteristics were investigated for the first time in Granada, southeastern Iberian Peninsula, during three intensive campaigns. The physical and chemical characteristics were analysed during two spring campaigns and one autumn campaign. New particle formation (NPF) events were found to be more frequent in spring than in autumn. The mean duration, growth rates and maximum diameters had ranges of 5.3–13.2 h, 2.4–4.0 nm h−1 and 35–47 nm, respectively. In addition, one shrinkage event occurred and had a duration of 2.2 h and a shrinkage rate of −2.5 nm h−1. During a period of atmospheric stagnation conditions under the influence of mountain breezes, three consecutive NPF events occurred. The high frequency of the NPF events was attributed to higher temperature and radiation levels and lower relative humidity than during a previous day with similar stagnant conditions but no nucleation occurrence. According to correlation analysis, mineral components correlated with particle number in the Aitken mode, while metals and secondary inorganic aerosols correlated with particle number in the finer and larger fractions, respectively. Pollutants such as CO, NO2, NO and black carbon showed moderate and high correlations with particle number in the submicron fraction. To assess the impact of the particle number contribution according to sources, a new approach was introduced using black carbon concentrations, resulting in four major contributors: urban background, traffic, NPF and biomass burning. The proposed approach was validated by means of different models based on the aerosol spectral dependencies and chemical compositions that classify aerosol populations. Both the models and the proposed approach identified biomass burning and fossil fuel particles during the same periods, and the results showed good agreement. The proposed approach can guide future studies attempting to account for submicron particle contributions in other urban environments.

Late-Holocene fossil evidence and the interpretation of the vegetation in NW Iberia: management issues in the light of palaeoecological findings

The management of the forests of Pinus sylvestris L. in north-western Iberia has been subjected to intense debate as the tree has been long considered an alien species while it has been widely used as a major species in forest restoration throughout the last 50 years. In the light of new palaeoecological data, we identify here a new late-Holocene population of P. sylvestris outside of the currently known Holocene range, also representing the westernmost continental Holocene subfossil record of this tree. Macro- and megafossil data from Montes de Leon (northwest Spain) occur in an area where oral testimonies of peasants suggested the occurrence of historical pine forests. The relevance of this finding and the reviewed regional palaeoecological data is crucial for both management and conservation actions. Here, we primarily discuss the implications of the naturalness of pinewoods within the Natura 2000 network and analyse the linkages between abrupt landscape changes involving pinewood shrinkage and historical events, such as Roman occupation and mediaeval livestock development. As a result, a new role for pinewoods in the management of protected areas is proposed.

Melittin-Induced Permeabilization, Re-sealing, and Re-permeabilization of E. coli Membranes

The permeabilization of model lipid bilayers by cationic peptides has been studied extensively over decades, with the bee-sting toxin melittin perhaps serving as the canonical example. However, the relevance of these studies to the permeabilization of real bacterial membranes by antimicrobial peptides remains uncertain. Here, we employ single-cell fluorescence microscopy in a detailed study of the interactions of melittin with the outer membrane (OM) and the cytoplasmic membrane (CM) of live Escherichia coli. Using periplasmic green fluorescent protein (GFP) as a probe, we find that melittin at twice the minimum inhibitory concentration first induces abrupt cell shrinkage and permeabilization of the OM to GFP. Within ∼4 s of OM permeabilization, the CM invaginates to form inward facing “periplasmic bubbles.” Seconds later the bubbles begin to leak periplasmic GFP into the cytoplasm. Permeabilization is localized, consistent with possible formation of toroidal pores. Within ∼20 s, first the OM and then the CM re-seals to GFP. Some 2–20 min later, both CM and OM are re-permeabilized to GFP. We invoke a mechanism based on curvature stress concepts derived from model bilayer studies. The permeabilization and re-sealing events involve sequential, time-dependent build-up of melittin density within the outer and inner leaflets of each bilayer. We also propose a mechanical explanation for the early cell shrinkage event induced by melittin and a variety of other cationic peptides. As peptides gain access to the periplasm, they bind to the anionic peptido-crosslinks of the lipopolysaccharide layer, increasing its longitudinal elastic modulus. The cell wall shrinks because it can withstand the same turgor pressure with smaller overall extension. Shrinkage in turn induces invagination of the CM, preserving its surface area. We conclude by comparing the behavior of different peptides.

The structural basis of cooking loss in beef: Variations with temperature and ageing

Meat loses fluid during cooking, resulting in textural changes and loss in cook yield. To understand the structural basis of cooking losses, this work used 10 bovine semitendinosus muscles and two ageing periods (1 vs 14days) to examine micro- and macro-level dimensional changes in muscle during heating. Muscle blocks, muscle fibre fragments and myofibrils all showed similar maximum shrinkage in cross sectional area (20–24%) but maximum length shrinkage was less in myofibrils (15%) than muscle blocks and fibre fragments (25%). Dimensional changes were dominated by shrinkage in individual muscle fibres and myofibrils, indicating that connective tissue does not play a major role. Transverse shrinkage predominantly occurred over 50–65°C whereas the longitudinal shrinkage predominantly occurred over 70–75°C; we attribute these two separate shrinkage events to denaturation of myosin and actin respectively. Higher cook losses in samples aged for 14days versus 1day suggests that desmin, nebulin and titin denaturation are not major drivers of fluid expulsion as these proteins are degraded during ageing. We postulate that proteolysis during ageing produces protein fragments which are more easily lost from the structure during cooking, along with water.

OC-006: Concomitant treatment (CRT or cetuximab/RT) with or without induction TPF in Locally Advanced head and neck

Purpose/Objective: Patients with recurrent and/or metastatic (R/M) head and neck squamous cell carcinoma (HNSCC) who progress after first-line platinum-based therapy have a dismal prognosis and limited efficacious treatment options. Afatinib, an irreversible ErbB family blocker, showed anti-tumour activity in a phase II trial in this setting (Seiwert et al. Ann Oncol 2014). LUX-Head & Neck 1, a global, openlabel, randomised phase III trial, evaluated second-line afatinib vs methotrexate (MTX) in patients with R/M HNSCC who progressed on/after platinum-based therapy (NCT01345682). Materials and Methods: Patients were randomised 2:1 to 40 mg/day oral afatinib (n=322) or 40 mg/m/week intravenous MTX (n=161), stratified by Eastern Cooperative Oncology Group performance status (0/1) and prior use of anti-EGFR antibody therapy (Yes/No) in the R/M setting. The primary endpoint was progression-free survival (PFS) by independent central review; overall survival (OS) was the key secondary endpoint. Other endpoints included objective response rate (ORR), patient-reported outcomes (PROs), tumour shrinkage, and adverse events (AEs). Disease control rate (DCR) was also assessed. Results: Patient baseline characteristics were well balanced between treatment groups (Table). Afatinib significantly improved the primary endpoint of PFS vs MTX by independent central review (median 2.6 vs 1.7 months; HR=0.80 [95% CI 0.65–0.98; p=0.03]; Figure); similar results were observed by investigator assessment. A trend towards improved PFS with afatinib was observed in a subgroup of patients aged ≥65 years (HR=0.68 [95% CI 0.45–1.03]). OS was not significantly improved with afatinib vs MTX (median 6.8 vs 6.0 months; HR=0.96 [0.77–1.19]). DCR was higher with afatinib vs MTX (49.1% vs 38.5%; p=0.04); ORR was 10.2% vs 5.6%, respectively (p=0.10). Tumour shrinkage was observed in 34.8% of afatinib-treated patients vs 22.4% of MTX-treated patients. Afatinib significantly delayed deterioration of global health status, pain and swallowing (all p≤0.03); significantly less pain over time was observed in afatinib-treated patients (p=0.03). Median duration of treatment was 83 days (range, 2–546) with afatinib and 43 days (range, 1–442) with MTX. The most frequent grade 3/4 treatment-related AEs were rash/acne (9.7%) and diarrhoea (9.4%) with afatinib, and stomatitis (8.1%) and neutropenia (6.9%) with MTX. Fewer treatment-related AEs led to dose reductions (32.2% vs 41.9%), drug discontinuations (7.2% vs 16.3%) or fatal outcome (2 [0.6%] vs 5 [3.1%]) in afatinib-treated patients. Conclusions: In this phase III trial in patients with R/M HNSCC after failure of platinum-based therapy, second-line afatinib significantly improved the primary endpoint of PFS vs MTX, with a manageable safety profile. A significant delay in deterioration of PROs and less pain over time was also observed with afatinib compared to MTX. OC-006 Concomitant treatment (CRT or cetuximab/RT) with or without induction TPF in Locally Advanced head and neck Cancer M.G. Ghi, A. Paccagnella, D. Ferrari, P. Foa, M. Cossu Rocca, E. Verri, F. Morelli, G. Azzarello, C. D'Ambrosio, C. Casanova, M. Guaraldi, E. Massa, C. Rossetto, A. Bonetti, S. Siena, A. Frattegiani, H. Koussis, G. Pieri, A. Gava, I. Floriani, For the GSTTC Italian Study Group Ospedale SS Giovanni e Paolo, Medical Oncology, Venezia, Italy San Paolo Hospital, Medical Oncology Unit, Milano, Italy Medical Oncology Unit of Urogenital and Head and Neck Tumors, European Institute of Oncology, Milano, Italy IRCCS Casa Sollievo della Sofferenza, Medical Oncology, San Giovanni Rotondo, Italy Azienda ULSS 13, Internal Medical Sciences, Mirano, Italy University Hospital, Oncology, Modena, Italy Azienda USL, Medical Oncology, Ravenna, Italy Policlinico Sant'Orsola-Malpighi, Medical Oncology, Bologna, Italy Azienda Ospedaliero Universitaria, Internal Medical Science, Cagliari, Italy University Hospital, Oncology, Udine, Italy Mater Salutis Hospital-AULSS 21 della Regione Veneto, Legnago, Italy Niguarda Ca' Granda Hospital, Milano, Italy Azienda Ospedaliera, Raditation Therapy, Perugia, Italy Istituto Oncologico Veneto IRCCS, Padova, Italy Ospedali Riuniti di Trieste, Oncology, Trieste, Italy Ospedale Ca Foncello, Radiation Therapy Department, Treviso, Italy Laboratorio Trials Clinici, Istituto di Ricerche Farmacologiche Mario Negri, Milano, Italy

Shrinkage of Newly Formed Particles in an Urban Environment

New particle formation (NPF) significantly influences the number concentrations and size distributions of an atmospheric aerosol and is often followed by the rapid growth of the newly formed particles. Recently a reversal process leading to particle shrinkage was reported and was found to occur under specific atmospheric conditions, which are unfavourable for the growth of nucleated particles. In this study we present an analysis of particle shrinkage events following prior NPF at an urban background station in Prague, Czech Republic. The study is based on two-year measurements of particle number size distributions using Scanning Mobility Particle Size (SMPS). A total of 22 shrinkage events were identified and the vast majority of the events was observed in the spring and summer seasons. The determined shrinkage rates span the range from -2.5 to -12.5nm/h. During the most intensive events, the grown particles shrank back to the smallest measurable size of 10nm. The particle shrinkage was attributed to the evaporation of previously condensed volatile and semi-volatile species from the particulate phase to the gas phase. When analysing the dependence on meteorological conditions, the particle shrinkage was found to occur under peak global radiance intensity, which was gradually decreasing, or under a sharp drop of global radiance intensity. The shrinkage events were also related to high ambient temperature and low relative humidity. The occurrence of atmospheric mixing was found to promote particle shrinkage very effectively, because the decrease of vapour concentration due to changing atmospheric conditions is more rapid than the decrease of vapour concentration caused by lower photochemical activity due to a drop in solar radiation intensity.

High temperature resistance of a very high volume fly ash cement paste

The physical and chemical changes taking place in a very high volume fly ash cement paste (FAN-4) following exposure to temperatures up to 1000°C are presented. Tests were repeated with commercially available CEM II/A-M Portland composite-cement (MS). FAN-4 pastes showed impressive residual strengths after heat exposure which increased dramatically when heated previously at 800 or 1000°C. This was in stark contrast to the MS paste, which showed a continual decrease in residual strength following heating and subsequent cooling. The increase in residual strength with FAN-4 paste coincided with a major shrinkage event, which was associated with sintering and the formation of the new mineral phases anorthite, gehlenite, wollastonite, diopside and albite. The MS cement formed generally non-hydraulic calcium silicate phases upon heating at ⩾800°C. The differences in phase formation were linked to different starting elemental compositions. The FAN-4 paste was considerably richer in Si, Al, Fe and alkalis but poorer in Ca. The elemental composition of the binder phase will be an important factor to take into account when determining the high-temperature performance of future cements and concretes, which are likely to contain significantly higher contents of supplementary cementitious materials than is presently the case.

Real-time attack of LL-37 on single Bacillus subtilis cells

Time-lapse fluorescence microscopy of single, growing Bacillus subtilis cells with 2–12s time resolution reveals the mechanisms of antimicrobial peptide (AMP) action on a Gram-positive species with unprecedented detail. For the human cathelicidin LL-37 attacking B. subtilis, the symptoms of antimicrobial stress differ dramatically depending on the bulk AMP concentration. At 2μM LL-37, the mean single-cell growth rate decreases, but membrane permeabilization does not occur. At 4μM LL-37, cells abruptly shrink in size at the same time that Sytox Green enters the cytoplasm and stains the nucleoids. We interpret the shrinkage event as loss of turgor pressure (and presumably the membrane potential) due to permeabilization of the membrane. Movies of Sytox Green staining at 0.5frame/s show that nucleoid staining is initially local, more consistent with pore formation than with global permeabilization models. In a novel “growth recovery” assay, cells are incubated with LL-37 for a variable period and then rinsed with fresh growth medium lacking LL-37. The growth rate attenuation observed at 2μM LL-37 is a recoverable symptom, while the abrupt cell shrinkage observed at 4μM LL-37 is not.

A novel mathematical procedure to interpret the stem radius variation in olive trees

Stem radius variations result from the fluctuation of environmental factors, mostly temperature trend and water availability, in turn affecting plant water balance, and plant growth. High-resolution analysis of stem radius variation provides insights into the temporal patterns in radial growth and water balance, and their relationship with environmental variables. To test the causal effects of temporal climate fluctuation on stem radius variation, a mathematical procedure was applied to normalize and synchronize radial fluctuations and environmental parameters, whose baseline is largely unexplored.Stem radius variations were continuously monitored during two consecutive years in four saplings field-grown olive tree cultivars (Canino, Cipressino, Leccino, Maurino) in an experimental farm in central Italy, between November 2004 and October 2006, using automatic high-resolution point dendrometers. A derivative analysis approach applied on point dendrometer records was conveniently used to describe stem radius variation and to distinguish the timing of transition from the dormant winter state to the active growth stage and till the slow expansion phase.Stem diameter patterns showed intense shrinkage events suddenly after air temperature drop below 0°C during winter. The onset of radial growth was delimited by the occurrence of rehydration (beginning of transpiration cycles) and increase of air temperature (end of cold cycles). The course of the growing season was described by patterns of air temperature, reference evapotranspiration, cumulative degree-days, vapour pressure deficit and soil moisture deficit, and correlated to patterns in stem radius cycles. Three phases of stem radius variation were evidenced through the seasonal course: induction signal, growth period, and slow expansion.This approach provides new and objective insights on shrinkage–swelling phenomena in Mediterranean environments, related to dehydration and hydration cycles, which are difficult to detect with empirical treatment of stem radius variation records. The ability to switch quickly between dormancy to growth would enable the olive tree to restart physiological processes and to cope with erratic climatic conditions of the Mediterranean region.