In this work, a procedure to obtain an accurate value of the critical speed of a cracked shaft is presented. The method is based on the transversal displacements of the cracked section when the shaft ...is rotating at submultiples of the critical speed. The SERR (Strain Energy Ralease Rate) theory and the CCL (Crack Closure Line) approach are used to analyse the proposed methodology for considering the behaviour of the crack. In order to obtain the best information and to define the procedure, the orbits and the frequency spectra at different subcritical rotational speed intervals are analyzed by means of the Fast Fourier Transform. The comparison of the maximum values of the FFT peaks within the intervals allows the subcritical speed to be determined, along with the value of the critical speed. When verified, the proposed procedure is applied to shafts with the same geometry and material and with cracks of increasing depth. The results show that the critical speed diminishes with the severity of the crack, as expected. A comparison is made between the critical speed obtained using the vertical and the horizontal displacements, finding no remarkable differences, meaning that in practical applications only one sensor for one of the displacements (in the vertical or horizontal direction) is needed to determine the critical speed. This is one of the main contributions of the paper, as it means that the orbits of the shaft are not needed. Finally, after this study we can conclude that the best results are achieved when the critical speed is obtained using data displacement in only one direction within the intervals around 12 or 13 of the critical speed.
Bicarbonate plays a fundamental role in the cell pH status in all organisms. In autotrophs, HCO₃
may further contribute to carbon concentration mechanisms (CCM). This is especially relevant in the ...CO₂-poor habitats of cyanobacteria, aquatic microalgae, and macrophytes. Photosynthesis of terrestrial plants can also benefit from CCM as evidenced by the evolution of C₄ and Crassulacean Acid Metabolism (CAM). The presence of HCO₃
in all organisms leads to more questions regarding the mechanisms of uptake and membrane transport in these different biological systems. This review aims to provide an overview of the transport and metabolic processes related to HCO₃
in microalgae, macroalgae, seagrasses, and terrestrial plants. HCO₃
transport in cyanobacteria and human cells is much better documented and is included for comparison. We further comment on the metabolic roles of HCO₃
in plants by focusing on the diversity and functions of carbonic anhydrases and PEP carboxylases as well as on the signaling role of CO₂/HCO₃
in stomatal guard cells. Plant responses to excess soil HCO₃
is briefly addressed. In conclusion, there are still considerable gaps in our knowledge of HCO₃
uptake and transport in plants that hamper the development of breeding strategies for both more efficient CCM and better HCO₃
tolerance in crop plants.
Background
Critical care survivors often experience symptoms of anxiety, depression, or post‐traumatic stress disorder (PTSD).
Aims
To determine the prevalence and severity of psychological symptoms ...during the first 6 months after discharge from the intensive care unit (ICU) and to evaluate its association with patients who are difficult to sedate during admission.
Design
Descriptive, prospective analysis of psychological symptoms in survivors from medicosurgical ICU over a 2‐year period.
Methods
All ICU survivors who required mechanical ventilation (MV) for more than 24 hours were followed for 6 months after their ICU discharge. ICU outcome and complications as well as the presence of psychological symptoms, 1 to 3 to 6 months after discharge were prospectively evaluated through phone interviews comparing the incidence and intensity of patients who were difficult to sedate during their ICU stay with those who were not. Descriptive analysis and multivariate logistic regression were performed.
Results
Data were obtained for 195 patients, of whom 30% experienced difficult sedation (DS). Difficult‐to‐sedate patients were younger (P = .001), less critically ill (APACHE II score P = .002), and more likely to engage in harmful use of alcohol (P = .001) and psychoactive/psychotropic drug abuse. They also spent longer times on MV and in the ICU (P = .001). Anxiety incidence at 1 to 3 to 6 months post‐discharge was significantly higher in DS patients than in those who were not (87.7% vs 45.4%, 75.5% vs 29.0%, and 70.8% vs 23.7%; P < .01), respectively. Depression incidence was also significantly higher in the DS group (82.4% vs 43.1%, 66% vs 33.9%, and 60.4% vs 27.2%; P = .001) at 1 to 3 to 6 months, respectively. A higher percentage of patients in the DS group reported symptoms of PTSD at 1 month (28.1% vs 11.5%) (P = .007) when compared with non‐DS group.
Conclusions
Critical care survivors who are difficult to sedate during their ICU stay are more likely to present psychological sequelae. Early identification of at‐risk patients is necessary to implement appropriate preventive strategies.
Relevance to clinical practice
Patients who are difficult to sedate in the ICU may develop psychological disorders upon discharge, which may negatively affect their recovery. The prevention of DS and the early detection of psychological disorders are essential to minimize its subsequent impact.
NHX-type antiporters in the tonoplast have been reported to increase the salt tolerance of various plants species, and are thought to mediate the compartmentation of Na⁺ in vacuoles. However, all ...isoforms characterized so far catalyze both Na⁺/H⁺ and K⁺/H⁺ exchange. Here, we show that AtNHX1 has a critical involvement in the subcellular partitioning of K⁺, which in turn affects plant K⁺ nutrition and Na⁺ tolerance. Transgenic tomato plants overexpressing AtNHX1 had larger K⁺ vacuolar pools in all growth conditions tested, but no consistent enhancement of Na⁺ accumulation was observed under salt stress. Plants overexpressing AtNHX1 have a greater capacity to retain intracellular K⁺ and to withstand salt-shock. Under K⁺-limiting conditions, greater K⁺ compartmentation in the vacuole occurred at the expense of the cytosolic K⁺ pool, which was lower in transgenic plants. This caused the early activation of the high-affinity K⁺ uptake system, enhanced K⁺ uptake by roots, and increased the K⁺ content in plant tissues and the xylem sap of transformed plants. Our results strongly suggest that NHX proteins are likely candidates for the H⁺-linked K⁺ transport that is thought to facilitate active K⁺ uptake at the tonoplast, and the partitioning of K⁺ between vacuole and cytosol.
In this study, two closed-form solutions for determining the first two natural frequencies of the flapwise bending vibration of a cracked Euler–Bernoulli beam at low rotational speed have been ...developed. To solve the governing differential equations of motion, the Frobenius method of solution in power series has been used. The crack has been modeled using two undamaged parts of the beam connected by a rotational spring. From the previous results, two novel polynomial expressions have been developed to obtain the first two natural frequencies as a function of angular velocity, slenderness ratio, cube radius and crack characteristics (depth and location). These expressions have been formulated using multiple regression techniques. To the knowledge of the authors, there is no similar expressions in the literature, which calculate, in a simple way, the first two natural frequencies based on beam features and crack parameters, without the need to know or solve the differential equations of motion governing the beam. In summary, the derived natural frequency expressions provide an extremely simple, practical, and accurate instrument for studying the dynamic behavior of rotating cracked Euler–Bernoulli beams at low angular speed, especially useful, in the future, to establish small-scale wind turbines’ maintenance planes.
Plant cell growth and stress signaling require Ca²⁺ influx through plasma membrane transport proteins that are regulated by reactive oxygen species. In root cell growth, adaptation to salinity ...stress, and stomatal closure, such proteins operate downstream of the plasma membrane NADPH oxidases that produce extracellular Superoxide anion, a reactive oxygen species that is readily converted to extracellular hydrogen peroxide and hydroxyl radicals, OH˙ In root cells, extracellular OH˙ activates a plasma membrane Ca²⁺ -permeable conductance that permits Ca²⁺ influx. In Arabidopsis thaliana, distribution of this conductance resembles that of annexin1 (ANN1). Annexins are membrane binding proteins that can form Ca²⁺ -permeable conductances in vitro. Here, the Arabidopsis loss-of-function mutant for annexin1 (Atann1) was found to lack the root hair and epidermal OH˙-activated Ca²⁺ -and K⁺ -permeable conductance. This manifests in both impaired root cell growth and ability to elevate root cell cytosolic free Ca²⁺ in response to OH˙. An OH˙-activated Ca²⁺ conductance is reconstituted by recombinant ANN1 in planar lipid bilayers. ANN1 therefore presents as a novel Ca²⁺-permeable transporter providing a molecular link between reactive oxygen species and cytosolic Ca²⁺ in plants.
Background
The term “difficult sedation” (DS) refers to situations of therapeutic failure, tolerance, or deprivation of the sedatives administered.
Aims
To characterize the profile of patients who ...developed DS and to assess its impact on the duration of mechanical ventilation (MV) and intensive care unit length of stay (ICU‐LOS), as well as other complications related to their stay.
Design
A prospective descriptive analysis was conducted of the practices of analgesia/sedation in a medical‐surgical intensive care unit (ICU) over a 2‐year period.
Methods
All critically ill patients undergoing MV and sedation for more than 24 hours were prospectively followed until death or discharge. Demographic data, type, duration, complications of analgesia/sedation, and clinical outcome during ICU stay were recorded. Patients who developed DS were compared with those who were not difficult to sedate (not‐DS).
Results
A total of 327 patients were included, 24.1% of whom were difficult to sedate (DS). Patients in the DS group were younger (P = .001); less severely ill (P = .003); and were more likely to have a history of smoking (P = .045), alcohol (P < .001), and psychotropic use (P = .001) than the not‐DS group. Patients included in the DS group were sedated for longer periods (P < .001) and required higher doses of midazolam (P < .036), propofol (P = .023), and remifentanyl (P = .026) than those in the not‐DS group. Difficult‐to‐sedate patients were twice as likely to require more than one sedative simultaneously (P < .001), presented more periods of over‐sedation (P = .031)/under‐sedation (P = .024), and suffered more pain (P < .001) than patients in the not‐DS group. Patients in the DS group had prolonged MV times (P < .001), developed more pressure ulcers (P > .001) and ventilator‐associated pneumonias (P = .025), and were more likely to require tracheotomy (P = .001) than those in the not‐DS group.
Conclusion
DS develops in one of four critically ill patients and has a negative impact on their outcomes. Early identification of the clinical profile of this group and active prevention and treatment are essential strategies in order to minimize its impact.
Relevance to Clinical Practice
A quarter of mechanically ventilated patients may develop situations of DS, which negatively affects their outcome. Early detection and prevention of DS are essential to minimize its impact.
Spanish fir (Abies pinsapo Boiss.) is an endemic, endangered tree that has been scarcely investigated at the molecular level. In this work, the transcriptome of Spanish fir was assembled, providing a ...large catalog of expressed genes (22,769), within which a high proportion were full-length transcripts (12,545). This resource is valuable for functional genomics studies and genome annotation in this relict conifer species. Two intraspecific variations of A. pinsapo can be found within its largest population at the Sierra de las Nieves National Park: one with standard green needles and another with bluish-green needles. To elucidate the causes of both phenotypes, we studied different physiological and molecular markers and transcriptome profiles in the needles. “Green” trees showed higher electron transport efficiency and enhanced levels of chlorophyll, protein, and total nitrogen in the needles. In contrast, needles from “bluish” trees exhibited higher contents of carotenoids and cellulose. These results agreed with the differential transcriptomic profiles, suggesting an imbalance in the nitrogen status of “bluish” trees. Additionally, gene expression analyses suggested that these differences could be associated with different epigenomic profiles. Taken together, the reported data provide new transcriptome resources and a better understanding of the natural variation in this tree species, which can help improve guidelines for its conservation and the implementation of adaptive management strategies under climatic change.
The stress hormone abscisic acid (ABA) induces expression of defence genes in many organs, modulates ion homeostasis and metabolism in guard cells, and inhibits germination and seedling growth. ...Concerning the latter effect, several mutants of Arabidopsis thaliana with improved capability for H⁺ efflux (wat1-1D, overexpression of AKT1 and ost2-1D) are less sensitive to inhibition by ABA than the wild type. This suggested that ABA could inhibit H⁺ efflux (H⁺-ATPase) and induce cytosolic acidification as a mechanism of growth inhibition. Measurements to test this hypothesis could not be done in germinating seeds and we used roots as the most convenient system. ABA inhibited the root plasma-membrane H⁺-ATPase measured in vitro (ATP hydrolysis by isolated vesicles) and in vivo (H⁺ efflux from seedling roots). This inhibition involved the core ABA signalling elements: PYR/PYL/RCAR ABA receptors, ABA-inhibited protein phosphatases (HAB1), and ABA-activated protein kinases (SnRK2.2 and SnRK2.3). Electrophysiological measurements in root epidermal cells indicated that ABA, acting through the PYR/PYL/RCAR receptors, induced membrane hyperpolarization (due to K⁺ efflux through the GORK channel) and cytosolic acidification. This acidification was not observed in the wat1-1D mutant. The mechanism of inhibition of the H⁺-ATPase by ABA and its effects on cytosolic pH and membrane potential in roots were different from those in guard cells. ABA did not affect the in vivo phosphorylation level of the known activating site (penultimate threonine) of H⁺-ATPase in roots, and SnRK2.2 phosphorylated in vitro the C-terminal regulatory domain of H⁺-ATPase while the guard-cell kinase SnRK2.6/OST1 did not.
The concentration of CO
2
in the atmosphere has increased over the past 200 years and is expected to continue rising in the next 50 years at a rate of 3 ppm·year
−1
. This increase has led to a ...decrease in seawater pH that has changed inorganic carbon chemical speciation, increasing the dissolved
HC
O
3
−
.
Posidonia oceanica
is a marine angiosperm that uses
HC
O
3
−
as an inorganic carbon source for photosynthesis. An important side effect of the direct uptake of
HC
O
3
−
is the diminution of cytosolic Cl
−
(Cl
−
c) in mesophyll leaf cells due to the efflux through anion channels and, probably, to intracellular compartmentalization. Since anion channels are also permeable to
N
O
3
−
we hypothesize that high
HC
O
3
−
, or even CO
2
, would also promote a decrease of cytosolic
N
O
3
−
(
N
O
3
−
c
). In this work we have used
N
O
3
−
- and Cl
−
-selective microelectrodes for the continuous monitoring of the cytosolic concentration of both anions in
P. oceanica
leaf cells. Under light conditions, mesophyll leaf cells showed a
N
O
3
−
c
of 5.7 ± 0.2 mM, which rose up to 7.2 ± 0.6 mM after 30 min in the dark. The enrichment of natural seawater (NSW) with 3 mM NaHCO
3
caused both a
N
O
3
−
c
decrease of 1 ± 0.04 mM and a
Cl
c
−
decrease of 3.5 ± 0.1 mM. The saturation of NSW with 1000 ppm CO
2
also produced a diminution of the
N
O
3
−
c
, but lower (0.4 ± 0.07 mM). These results indicate that the rise of dissolved inorganic carbon (
HC
O
3
−
or CO
2
) in NSW would have an effect on the cytosolic anion homeostasis mechanisms in
P. oceanica
leaf cells. In the presence of 0.1 mM ethoxyzolamide, the plasma membrane-permeable carbonic anhydrase inhibitor, the CO
2
-induced cytosolic
N
O
3
−
diminution was much lower (0.1 ± 0.08 mM), pointing to
HC
O
3
−
as the inorganic carbon species that causes the cytosolic
N
O
3
−
leak. The incubation of
P. oceanica
leaf pieces in 3 mM
HC
O
3
−
-enriched NSW triggered a short-term external
N
O
3
−
net concentration increase consistent with the
N
O
3
−
c
leak. As a consequence, the cytosolic
N
O
3
−
diminution induced in high inorganic carbon could result in both the decrease of metabolic N flux and the concomitant biomass N impoverishment in
P. oceanica
and, probably, in other aquatic plants.
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