Lengthening Of Period Research Articles

3'-Phosphoadenosine 5'-Phosphate Accumulation Delays the Circadian System.

The circadian system optimizes cellular responses to stress, but the signaling pathways that convey the metabolic consequences of stress into this molecular timekeeping mechanism remain unclear. Redox regulation of the SAL1 phosphatase during abiotic stress initiates a signaling pathway from chloroplast to nucleus by regulating the accumulation of a metabolite, 3'-phosphoadenosine 5'-phosphate (PAP). Consequently, PAP accumulates in response to redox stress and inhibits the activity of exoribonucleases (XRNs) in the nucleus and cytosol. We demonstrated that osmotic stress induces a lengthening of circadian period and that genetically inducing the SAL1-PAP-XRN pathway in plants lacking either SAL1 or XRNs similarly delays the circadian system. Exogenous application of PAP was also sufficient to extend circadian period. Thus, SAL1-PAP-XRN signaling likely regulates circadian rhythms in response to redox stress. Our findings exemplify how two central processes in plants, molecular timekeeping and responses to abiotic stress, can be interlinked to regulate gene expression.

Effect of repetitive transcranial magnetic stimulation on action myoclonus: A pilot study in patients with EPM1

ObjectiveThe objective of this study was to explore the short-term effects of repetitive transcranial magnetic stimulation (rTMS) on action myoclonus. MethodsNine patients with Unverricht–Lundborg (EPM1) progressive myoclonus epilepsy type underwent two series of 500 stimuli at 0.3Hz through round coil twice a day for five consecutive days. Clinical and neurophysiological examinations were performed two hours before starting the first rTMS session and two hours after the end of the last rTMS session. ResultsEight patients completed the protocol; one discontinued because of a transient increase in spontaneous jerks. The unified myoclonus rating scale indicated a 25% reduction in posttreatment myoclonus with action score associated with an increase in the cortical motor threshold and lengthening of the cortical silent period (CSP). The decrease in the myoclonus with action scores correlated with the prolongation of CSP. ConclusionsRepetitive transcranial magnetic stimulation can be safely used in patients with EPM1, improves action myoclonus, and partially restores deficient cortical inhibition.

Reakcja ozimych odmian lnianki siewnej (Camelina sativa (L.) Crantz) na zróżnicowany termin siewu

In the seasons 2012/2013 - 2014/2015 an experiment was conducted in the fields of the Experimental Station Variety Examination in Przeclaw. The evaluated factors were as follows: (A) - sowing time (early, optimal, delayed) and (B) – Polish winter varieties of false flax (Maczuga, Luna, Przybrodzka). The study showed that early sowing time contributed to the lengthening of the vegetation period of plants, especially in relation to delayed sowing date. During the winter, the plant losses amounted on average to 11.3 pcs.∙m-2. The highest plant density before harvest was recorded in the plots of the optimal sowing date. The early sowing time contributed to the increase in the value of SPAD (Soil Plant Analysis Development) and the number of silicles per plant as well as seed yield. Sowing the seeds in the optimal time was increased lodging while delayed caused an increase in the MTA (Mean Tip Angle) and LAI (Leaf Area Index) index and plant height as well as the number of seeds per silicle. The thousand seeds weight was 0.85 g and was not significantly modified by experimental factors. The varieties were differed in most of the studied traits, including yield seeds. The results of the research carried out indicate that in the area of the research, the best time sowing the seeds of winter false flax is the first decade of September.

Variability of ultraplankton composition and distribution in an oligotrophic coastal ecosystem of the NW Mediterranean Sea derived from a two-year survey at the single cell level.

Ultraplankton [heterotrophic prokaryotes and ultraphytoplankton (<10 μm)] were monitored weekly over two years (2009 & 2010) in a coastal area of the NW Mediterranean Sea. Six clusters were differentiated by flow cytometry on the basis of their optical properties, two heterotrophic prokaryote (HP) subgroups labelled LNA and HNA (low and high nucleic acid content respectively), Prochlorococcus, Synechococcus, autotrophic picoeukaryotes and nanoeukaryotes. HP represented an important component of the microbial assemblage over the survey with relatively small abundance variation through seasons. The carbon biomass ratio HP/ultraphytoplankton averaged 0.45, however this ratio exceeded 1 during spring. Ultraphytoplankton biomass made about 50% of the total autotrophic carbon estimates but this contribution increased up to 97% and 67% during the 2009 and 2010 spring periods respectively. Within ultraphytoplankton, nanoeukaryote represent the most important ultraphytoplankton group in terms of autotrophic carbon biomass (up to 70%). Picoeukaryote maximum abundance occurred in winter. Synechococcus was the most abundant population (maximum 1.2 x 10 5 cells cm-3) particularly in spring where it represented up to 54% of ultraphytoplankton carbon biomass. The warmer winter-spring temperatures and the lengthening of the stratification period created a favorable situation for the earlier appearance of Synechococcus and its persistence throughout summer, paralleling Prochlorococcus development. Prochlorococcus was dominant over summer and autumn with concentrations up to 1.0 × 10 5 cells cm-3. While the abundance of Synechococcus throughout survey was of the same order as that reported in western Mediterranean Sea, Prochlorococcus was more abundant and similar to the more typical oligotrophic and warm waters. The abundance variation of the ultraplankton components through the survey was relatable to variations in the hydrological and nutrient conditions.

Multi-criteria approach in solar urban water supply systems

An innovative method for sizing solar photovoltaic (PV) pumping systems in urban water supply systems (UWSSs) is presented. The methodology is based on various critical period approaches (the critical period method). A multi-criteria analysis was carried out to evaluate the effects of the critical period duration on the system characteristics. It was found that the critical period length is a design variable that significantly affects the economic, environmental and social aspects of the solution, with a lengthening of the critical period resulting in improvement of the overall sustainability of the solution. The results obtained indicate that a solar PV system is a promising solution to the energy sustainability of UWSSs. This form of energy supply does not emit greenhouse gases and furthermore the ‘social cost’ of carbon dioxide estimates decrease. The concept of a stand-alone PV energy system is a particularly promising sustainable energy solution.

STUDY OF NATURAL BORRELIA CONTAMINATION OF IXODES TICKS IN CHERNIVTSI REGION FOR THE YEARS 2015-2016

Our study indicates that the number of applications affected about tick I. ricinus bites has increased in 2016 year compared to 2015 year. An important test to assess the need of preventive treatment of Lyme disease (LD) is the identification Borrelia in ticks, which have bitten into people. It was established increasing the risk of LD due to ticks bites on indicators of the odds ratio of 4,8 (95 % CI 1,45-15,82) in 2015 to 8,3 (95 % CI 4,46-15,29) in 2016 year and 7,5 (95 % CI 4,37-12,84) for 2015-2016 years. Our research showed that the most part of the Chernivtsi region is endemic for LD. There is a lengthening of the activity period of ticks I. ricinus from March to November, which may be related to climate changes and gradual adaptation of ticks I. ricinus to more severe environmental conditions

Non-small cell lung cancer clinical trials requiring biopsies with biomarker-specific results for enrollment provide unique challenges.

Clinical trials in lung cancer increasingly require patients to provide fresh tumor tissue as a prerequisite to enrollment. The effects of this requirement on enrollment rates, enrollment durations, and patient selection have not been fully elucidated. The authors retrospectively reviewed data generated by patients who consented to 1 or more interventional lung cancer clinical trials at the University of California-Los Angeles Jonsson Comprehensive Cancer Center between January 2013 and December 2014. Trials were considered to require a biopsy when enrollment was conditional on the procurement of tissue without intervening therapy between procurement and enrollment. In total, 311 patients underwent 368 screening incidents for 1 or more of 19 trials. Trials that required a new biopsy had a longer median screening duration (34 vs 14 days) than trials that did not require a biopsy (P < .001). Trials that required a biopsy had a greater screen failure rate (49.1% vs 26.5%; P < .001), which was largely driven by patients who did not undergo the required biopsy or lacked the required biomarker. Worsening performance status led to the majority of screen failures (56.5%) among biomarker-eligible patients. Although the scientific benefits of obtaining a new biopsy and requiring specific results for trial enrollment are clear, these requirements lead to a lengthening of the screening period, which, in some patients, is associated with clinical decline before enrollment. Implications for the interpretation of data from studies of this design should be explored. Cancer 2017;123:4800-7. © 2017 American Cancer Society.

T Peak–T End Interval Alteration as Parameter of Successful Fibrinolysis in Patients with ST Segment Elevation Acute Myocardial Infarction

Background: In STEMI patients, the duration of action potential dispersion occurs between normal and ischemic tissue due to the lengthening of the refractory period, causing transmural dispersion of repolarization, which could be detected with Tp-Te interval prolongation on the electrocardiogram (ECG). Benefits of fibrinolytic therapy in patients with STEMI has been demonstrated, with reduced mortality significantly and improve coronary patency in order to increase myocardial perfusion. The goal of this study was to determine Tp-Te interval alteration in STEMI patients before and after the fibrinolytic therapy between successful fibrinolysis compared to failed fibrinolysis. Method: Cross-sectional study was conducted to collect ECG from medical records at Dr. Sardjito General Hospital in January–September 2016. STEMI patients with onset less than 12hours whom reperfused with fibrinolytic therapy were registered. Tp-Te interval was measured before, soon after (0 minute), and 30 minutes after fibrinolysis with successful and failed results. The unpaired t-test analysis was used to compare Tp-Te interval alteration after fibrinolysis. Then, ΔTp-Te cut-off value was determined to find sensitivity and specificity based on ROC. Result: Among 84 patients enrolled in this study, 46 patients with successful fibrinolysis and 38patients with failed fibrinolysis. Both of groups had Tp-Te interval prolongation before fibrinolysis, with mean value of 120.30 ± 13.02 ms in successful fibrinolysis group and 118.57 ± 15.24 ms in failed fibrinolysis group. In successful fibrinolysis group, Tp-Te interval reduced significantly with ΔTp-Te value of 17.55 ± 13.35 ms on 0 minute and 20.85 ± 15.62 ms on 30 minutes after fibrinolysis, while in failed fibrinolysis group there was not a decrease of Tp-Te interval with ΔTp-Te value of -0.77 ± 11.00 ms on 0 minute (p &lt;0.001) and -1.53 ± 14.35 ms on 30 minutes after fibrinolysis (p &lt;0.001). Cut-off value ΔTp-Te 20 ms had sensitivity 52.2% and specificity 94.7% based on ROC, with strong discriminator value of AUC (0.888). Conclusion: There was a greater reduction of Tp-Te interval in STEMI patients with successful fibrinolysis compared to failed fibrinolysis, so it may be used as a alternative parameter of successful fibrinolysisKeywords: STEMI; Tp-Te interval; fibrinolysis

Delta progradation in Greenland driven by increasing glacial mass loss.

Climate changes are pronounced in Arctic regions and increase the vulnerability of the Arctic coastal zone. For example, increases in melting of the Greenland Ice Sheet and reductions in sea ice and permafrost distribution are likely to alter coastal morphodynamics. The deltas of Greenland are largely unaffected by human activity, but increased freshwater runoff and sediment fluxes may increase the size of the deltas, whereas increased wave activity in ice-free periods could reduce their size, with the net impact being unclear until now. Here we show that southwestern Greenland deltas were largely stable from the 1940s to 1980s, but prograded (that is, sediment deposition extended the delta into the sea) in a warming Arctic from the 1980s to 2010s. Our results are based on the areal changes of 121 deltas since the 1940s, assessed using newly discovered aerial photographs and remotely sensed imagery. We find that delta progradation was driven by high freshwater runoff from the Greenland Ice Sheet coinciding with periods of open water. Progradation was controlled by the local initial environmental conditions (that is, accumulated air temperatures above 0 °C per year, freshwater runoff and sea ice in the 1980s) rather than by local changes in these conditions from the 1980s to 2010s at each delta. This is in contrast to a dominantly eroding trend of Arctic sedimentary coasts along the coastal plains of Alaska, Siberia and western Canada, and to the spatially variable patterns of erosion and accretion along the large deltas of the main rivers in the Arctic. Our results improve the understanding of Arctic coastal evolution in a changing climate, and reveal the impacts on coastal areas of increasing ice mass loss and the associated freshwater runoff and lengthening of open-water periods.

The Dorsal Medial Habenula Minimally Impacts Circadian Regulation of Locomotor Activity and Sleep.

In nocturnal rodents, voluntary wheel-running activity (WRA) represents a self-reinforcing behavior. We have previously demonstrated that WRA is markedly reduced in mice with a region-specific deletion of the transcription factor Pou4f1 (Brn3a), which leads to an ablation of the dorsal medial habenula (dMHb). The decrease in WRA in these dMHb-lesioned (dMHbCKO) mice suggests that the dMHb constitutes a critical center for conveying reinforcement by exercise. However, WRA also represents a prominent output of the circadian system, and the possibility remains that the dMHb is a source of input to the master circadian pacemaker located in the suprachiasmatic nucleus (SCN) of the hypothalamus. To test this hypothesis, we assessed the integrity of the circadian system in dMHbCKO mice. Here we show that the developmental lesion of the dMHb reduces WRA under both a light-dark cycle and constant darkness, increases the circadian period of WRA, but has no effect on the circadian amplitude or period of home cage activity or the daily amplitude of sleep stages, suggesting that the lengthening of period is a result of the decreased WRA in the mutant mice. Polysomnographic sleep recordings show that dMHbCKO mice have an overall unaltered daily amplitude of sleep stages but have fragmented sleep and an overall increase in total rapid eye movement (REM) sleep. Photoresponsiveness is intact in dMHbCKO mice, but compared with control animals, they reentrain faster to a 6-h abrupt phase delay protocol. Circadian changes in WRA of dMHbCKO mice do not appear to emerge within the central pacemaker, as circadian expression of the clock genes Per1 and Per2 within the SCN is normal. We do find some evidence for fragmented sleep and an overall increase in total REM sleep, supporting a model in which the dMHb is part of the neural circuitry encoding motivation and involved in the manifestation of some of the symptoms of depression.

Immunohistochemical Study of the Expression of Vascular Endothelial Growth Factor Receptor-2 (KDR/Flk-1) during Myocardial Infarction.

Immunohistochemical study showed that vascular endothelial growth factor receptor-2 (KDR/Flk-1) is expressed in the cytoplasm of viable cardiomyocytes, mononuclear cells of the granulation tissue, and smooth muscle cells of intramural arteries at all terms of postinfarction reparative regeneration. Cardiomyocytes were highly heterogeneous by the intensity of staining. This feature was typical of cardiomyocytes in the ischemic area (no staining), as well as within various muscle bundles and one muscle bundle. KDR/Flk-1 expression was revealed in mononuclear cells of the necrotic area (macrophages and fibroblast cells). The distribution of KDR/Flk-1 remained practically unchanged with lengthening of the postinfarction period (more than 7 days). The increase in the heterogeneity of cardiomyocyte staining under these conditions illustrates variations in the intensity of cytoprotective processes during ischemia. KDR/Flk-1 expression in smooth muscle cells of intramural arteries was shown to increase in a later period of observations.

A point mutation in the ion conduction pore of AMPA receptor GRIA3 causes dramatically perturbed sleep patterns as well as intellectual disability.

The discovery of genetic variants influencing sleep patterns can shed light on the physiological processes underlying sleep. As part of a large clinical sequencing project, WGS500, we sequenced a family in which the two male children had severe developmental delay and a dramatically disturbed sleep-wake cycle, with very long wake and sleep durations, reaching up to 106-h awake and 48-h asleep. The most likely causal variant identified was a novel missense variant in the X-linked GRIA3 gene, which has been implicated in intellectual disability. GRIA3 encodes GluA3, a subunit of AMPA-type ionotropic glutamate receptors (AMPARs). The mutation (A653T) falls within the highly conserved transmembrane domain of the ion channel gate, immediately adjacent to the analogous residue in the Grid2 (glutamate receptor) gene, which is mutated in the mouse neurobehavioral mutant, Lurcher. In vitro, the GRIA3(A653T) mutation stabilizes the channel in a closed conformation, in contrast to Lurcher. We introduced the orthologous mutation into a mouse strain by CRISPR-Cas9 mutagenesis and found that hemizygous mutants displayed significant differences in the structure of their activity and sleep compared to wild-type littermates. Typically, mice are polyphasic, exhibiting multiple sleep bouts of sleep several minutes long within a 24-h period. The Gria3A653T mouse showed significantly fewer brief bouts of activity and sleep than the wild-types. Furthermore, Gria3A653T mice showed enhanced period lengthening under constant light compared to wild-type mice, suggesting an increased sensitivity to light. Our results suggest a role for GluA3 channel activity in the regulation of sleep behavior in both mice and humans.

Bio-Gasification Under Partially Aerated Conditions

Anaerobic digestion (AD) under mild aerobic loading is investigated. Aeration can apparently have both positive and negative impacts on biogas generation. This study aims to recognize and describe these different aeration effects on AD. Seven series of batch experiments (BT 1- 7) were conducted under varying feed and oxygenation conditions at 35 oC. Oxygen was introduced as headspace air in four of the batch experiments and as pure oxygen in two series. Effects of extensive initial aeration of inoculum were investigated in one batch series. The methane yield of the reactors fed with starch (1.09 g COD/LReactor) was positively influenced by oxygenation in the load range up to 38 % O2 (as % of feed COD). A negative influence of oxygen was observed at the next experimental level of 79 % O2. For the glucose fed reactors under similar operating conditions, the oxygen impact was near linearly negative in the tested range of 0 - 49 % O2. These results demonstrate that digestion of soluble substrates like glucose is not enhanced by O2, while substrates requiring hydrolysis are. Thus, limited aeration can enhance biogas production from non-soluble substrates under batch conditions. According to the experiment where the effects of extensive initial aeration was investigated, lengthening of the aeration period increasingly slowed down the gas generation rate but eventually resulted in the same methane yield. The lag period before gas generation started was three times longer for the aerated inoculum reactors than un-aerated. These observations suggest that oxygen induced inhibition of the biomass activity is mostly reversible. Reduced biogas production rates with initial aeration extent suggest some permanent damage to the anaerobes. Extensively aerated inoculums generated less methane compared to the un-aerated inoculum, probably due to the loss of some biogas potential initially present in the inoculum. Oxygen assisted degradation of some recalcitrant organic matter, including biomass cells themselves, present in the inoculum is also detected in an unfed inoculum test series.

Anatomical and Behavioral Investigation of C1ql3 in the Mouse Suprachiasmatic Nucleus.

Many biochemical, physiological, and behavioral processes such as glucose metabolism, body temperature, and sleep-wake cycles show regular daily rhythms. These circadian rhythms are adjusted to the environmental light-dark cycle by a central pacemaker located in the suprachiasmatic nucleus (SCN) in order for the processes to occur at appropriate times of day. Here, we investigated the expression and function of a synaptic organizing protein, C1QL3, in the SCN. We found that C1ql3 is robustly expressed in the SCN. C1ql3 knockout mice have a reduced density of excitatory synapses in the SCN. In addition, these mice exhibited less consolidated activity to the active portions of the day and period lengthening following a 15-minute phase-delaying light pulse. These data identify C1QL3 as a signaling molecule that is highly expressed in SCN neurons, where it contributes to the formation and/or maintenance of glutamatergic synapses and plays a role in circadian behaviors, which may include circadian aftereffects.

P2X7 receptor-sensitivity of astrocytes and neurons in the substantia gelatinosa of organotypic spinal cord slices of the mouse depends on the length of the culture period

The whole-cell patch-clamp technique was used to record current responses to AMPA, N-methyl-d-aspartate (NMDA), muscimol and dibenzoyl-ATP (Bz-ATP) in superficial (reactive/gliotic) substantia gelatinosa (SG) astrocytes and neurons of spinal cord slices kept for different periods of time in organotypic culture. Currents induced by AMPA, NMDA and muscimol confirmed the existence of their specific receptors in 2-week-old neurons; astrocytes cultured for the same period of time responded to AMPA and muscimol, but not to NMDA. AMPA had a larger effect on 2-week-old astrocytes than on the 1-week-old ones, in spite of a similar sensitivity of the age-matched neurons to this amino acid. The effect of the prototypic P2X7 receptor agonist Bz-ATP on superficial astrocytes and neurons depended on the drug concentration applied and increased in parallel with the lengthening of the culture period. The amplitudes of Bz-ATP currents of deep (resting) astrocytes were age-independent. Neurons located in deep layers exhibited after 1week of culturing much larger Bz-ATP currents than the superficial ones of the same age. In conclusion, whereas resting astrocytes had culture period-independent P2X7 receptor-sensitivity, reactive/gliotic astrocytes exhibited P2X7 receptor-sensitivity increasing in parallel with the prolongation of the time spent in culture. The results with Bz-ATP agree with the facilitation of AMPA-induced currents in reactive astrocytes during development, and with the hypothesis that extracellular ATP is an ontogenetically early transmitter/signaling molecule in the CNS.

Influence of scaling of different types of ground motions on analysis of code-compliant four-story reinforced concrete buildings isolated with elastomeric bearings

Understanding the effects of selection and scaling of ground motions on the response of base-isolated buildings is important because these structures are routinely designed using nonlinear response history analysis (RHA). Previous studies lack a comprehensive evaluation of the influence of choices made in the selection of type of ground motions and the method of scaling on a range of response indicators of code-compliant base-isolated reinforced concrete (RC) buildings. Therefore, in this study four-story base-isolated RC buildings with a range of isolation system properties are designed in accordance with the provisions of ASCE 7-10 and large sets of near-fault pulse-like and far-fault non-pulse-like ground motions are considered. The effects of scaling (weighted scaling versus spectral matching) on the mean values as well as dispersions of various response indicators are systematically evaluated. Uncertainties in isolator properties are accounted for by conducting bounding analysis. Three-dimensional finite element models are developed considering nonlinearity of the isolation system as well as that of the superstructure and RHAs are conducted using risk-targeted maximum considered earthquake (MCER)-level ground motions. It is found that the type of ground motion and scaling method have more pronounced effects on superstructure response indicators compared with those on isolation system displacement demands. For the base-isolated buildings considered in this study, inter-story drift ratios and column curvature ductilities are affected significantly due to the choices made in the selection and scaling of ground motions while superstructure base shear forces and roof accelerations are less severely affected. Lengthening of the fundamental period was found to be more efficient than increasing effective damping in the isolation system in order to not only reduce superstructure demands but also to reduce the variability of the superstructure response to selection and scaling of ground motions.

The plant leaf movement analyzer (PALMA): a simple tool for the analysis of periodic cotyledon and leaf movement in Arabidopsis thaliana

BackgroundThe analysis of circadian leaf movement rhythms is a simple yet effective method to study effects of treatments or gene mutations on the circadian clock of plants. Currently, leaf movements are analysed using time lapse photography and subsequent bioinformatics analyses of leaf movements. Programs that are used for this purpose either are able to perform one function (i.e. leaf tip detection or rhythm analysis) or their function is limited to specific computational environments. We developed a leaf movement analysis tool—PALMA—that works in command line and combines image extraction with rhythm analysis using Fast Fourier transformation and non-linear least squares fitting.ResultsWe validated PALMA in both simulated time series and in experiments using the known short period mutant sensitivity to red light reduced 1 (srr1-1). We compared PALMA with two established leaf movement analysis tools and found it to perform equally well. Finally, we tested the effect of reduced iron conditions on the leaf movement rhythms of wild type plants. Here, we found that PALMA successfully detected period lengthening under reduced iron conditions.ConclusionsPALMA correctly estimated the period of both simulated and real-life leaf movement experiments. As a platform-independent console-program that unites both functions needed for the analysis of circadian leaf movements it is a valid alternative to existing leaf movement analysis tools.

Blue Light- and Low Temperature-Regulated COR27 and COR28 Play Roles in the Arabidopsis Circadian Clock.

Light and temperature are two key environmental signals that profoundly affect plant growth and development, but underlying molecular mechanisms of how light and temperature signals affect the circadian clock are largely unknown. Here, we report that COR27 and COR28 are regulated not only by low temperatures but also by light signals. COR27 and COR28 are negative regulators of freezing tolerance but positive regulators of flowering, possibly representing a trade-off between freezing tolerance and flowering. Furthermore, loss-of-function mutations in COR27 and COR28 result in period lengthening of various circadian output rhythms and affect central clock gene expression. Also, the cor27 cor28 double mutation affects the pace of the circadian clock. Additionally, COR27 and COR28 are direct targets of CCA1, which represses their transcription via chromatin binding. Finally, we report that COR27 and COR28 bind to the chromatin of TOC1 and PRR5 to repress their transcription, suggesting that their effects on rhythms are in part due to their regulation of TOC1 and PRR5 These data demonstrate that blue light and low temperature-regulated COR27 and COR28 regulate the circadian clock as well as freezing tolerance and flowering time.

Dynamic behavior of buildings with non-uniform stiffness along their height assessed through coupled flexural and shear beams

A novel model for assessing building behavior has been developed by coupling a Bernoulli beam with a quartic stiffness variation and a shear beam with a parabolic stiffness variation, trends that are expected in buildings designed for earthquake actions. Then the partial differential equation of motion governing the behavior of the model has been solved, obtaining analytic expressions (Closed form solutions) for mode shapes in terms of Legendre functions. These closed form solutions were validated with finite element model analyses and effects of non-uniformity of stiffness were assessed in a generalized manner. It was found that period lengthening is mild for the first mode, but for higher modes can be far more noticeable if shear stiffness at beam top is <20 % of its base value. Mode shapes also change notoriously for reductions beyond the same limit, potentially inducing large floor acceleration demands at unexpected locations. Also it was found that drift demands can be noticeably enhanced even if shear stiffness at top is 75 % of the base value, in what would be considered uniform buildings. This model has several applications for assessing the response or large stocks of buildings, calibrate complex models, assess damage on building contents, establishing in short time damage scenarios for large cities, and could be helpful for education, as emphasis is brought back on fundamental concepts.

A numerical study of nonlinear infrasound propagation in a windy atmosphere.

Direct numerical simulations of the two-dimensional unsteady compressible Navier-Stokes equations are performed to study the acoustic field generated by an infrasonic source in a realistic atmosphere. Some of the main phenomena affecting the propagation of infrasonic waves at large distances from the source are investigated. The effects of thermal and wind-related refraction on the signals recorded at ground level are highlighted, with particular emphasis on the phase shift induced by the presence of caustics in the acoustic field. Nonlinear waveform steepening associated with harmonic generation, and period lengthening, both of which are typical of large source amplitudes, are illustrated, and the importance of thermoviscous absorption in the upper atmosphere is clearly demonstrated. The role of diffraction in the shadow zone, around caustics and at stratospheric altitudes is also pointed out. The Navier-Stokes equations are solved using high-order finite-differences and a Runge-Kutta time integration method both originally developed for aeroacoustic applications, along with an adaptive shock-capturing algorithm which allows high-intensity acoustic fields to be examined. An improvement to the shock detection procedure is also proposed in order to meet the specificities of nonlinear propagation at long range. The modeling as well as the numerical results are reported in detail and discussed.