12,327 research outputs found
The Final Frontier of pH and the Undiscovered Country Beyond
Full text linkThe comparison of volumes of cells and subcellular structures with the pH values reported for them leads to a conflict with
the definition of the pH scale. The pH scale is based on the ionic product of water, Kw = [H+]6[OH2].We used Kw [in a
reversed way] to calculate the number of undissociated H2O molecules required by this equilibrium constant to yield at
least one of its daughter ions, H+ or OH2 at a given pH. In this way we obtained a formula that relates pH to the minimal
volume VpH required to provide a physical meaning to Kw, VpH~10DpH{pKw=2D|
10pKw=2
NA
(where NA is Avogadro’s number).
For example, at pH 7 (neutral at 25uC) VpH = 16.6 aL. Any deviation from neutral pH results in a larger VpH value. Our results indicate that many subcellular structures, including coated vesicles and lysosomes, are too small to contain free H+ ions at equilibrium, thus the definition of pH based on Kw is no longer valid. Larger subcellular structures, such as mitochondria, apparently contain only a few free H+ ions. These results indicate that pH fails to describe intracellular conditions, and that water appears to be dissociated too weakly to provide free H+ ions as a general source for biochemical reactions. Consequences of this finding are discussed
An intracellular pH gradient in the anammox bacterium Kuenenia stuttgartiensis as evaluated by (31)P NMR
Full text linkThe cytoplasm of anaerobic ammonium oxidizing (anammox) bacteria consists of three compartments separated by membranes. It has been suggested that a proton motive force may be generated over the membrane of the innermost compartment, the “anammoxosome”. 31P nuclear magnetic resonance (NMR) spectroscopy was employed to investigate intracellular pH differences in the anammox bacterium Kuenenia stuttgartiensis. With in vivo NMR, spectra were recorded of active, highly concentrated suspensions of K. stuttgartiensis in a wide-bore NMR tube. At different external pH values, two stable and distinct phosphate peaks were apparent in the recorded spectra. These peaks were equivalent with pH values of 7.3 and 6.3 and suggested the presence of a proton motive force over an intracytoplasmic membrane in K.stuttgartiensis. This study provides for the second time—after discovery of acidocalcisome-like compartments in Agrobacterium tumefaciens—evidence for an intracytoplasmic pH gradient in a chemotrophic prokaryotic cell.BiotechnologyApplied Science
Dehydroepiandrosterone (DHEA) supplementation improves in vitro fertilization outcomes of poor ovarian responders, especially in women with low serum concentration of DHEA-S: a retrospective cohort study
Full text linkBackground: Dehydroepiandrosterone (DHEA) is now widely used as an adjuvant for in vitro fertilization (IVF)
cycles in poor ovarian responders (PORs). Several studies showed that DHEA supplementation could improve IVF
outcomes of PORs. However, most of the PORs do not respond to DHEA clinically. Therefore, the aim of this study
is to confirm the beneficial effects of DHEA on IVF outcomes of PORs and to investigate which subgroups of PORs
can best benefit from DHEA supplementation.
Methods: This retrospective cohort study was performed between January 2015 and December 2017. A total of
151 PORs who fulfilled the Bologna criteria and underwent IVF cycles with the gonadotropin-releasing hormone
antagonist protocol were identified. The study group (n = 67) received 90 mg of DHEA daily for an average of
3 months before the IVF cycles. The control group (n = 84) underwent the IVF cycles without DHEA pretreatment.
The basic and cycle characteristics and IVF outcomes between the two groups were compared using independent
t-tests, Chi-Square tests and binary logistic regression.
Results: The study and control groups did not show significant differences in terms of basic characteristics. The study
group demonstrated a significantly greater number of retrieved oocytes, metaphase II oocytes, fertilized oocytes, day 3
embryos and top-quality embryos at day 3 and a higher clinical pregnancy rate, ongoing pregnancy rate and live birth
rate than those measures in the control group. The multivariate analysis revealed that DHEA supplementation was
positively associated with clinical pregnancy rate (OR = 4.93, 95% CI 1.68–14.43, p = 0.004). Additionally, in the study
group, the multivariate analysis showed that serum dehydroepiandrosterone-sulfate (DHEA-S) levels < 180 μg/dl were
significantly associated with a rate of retrieved oocytes > 3 (OR = 5.92, 95% CI 1.48–23.26, p = 0.012).
Conclusions: DHEA supplementation improves IVF outcomes of PORs. In PORs with DHEA pretreatment, women with
lower DHEA-S level may have greater possibility of attaining more than 3 oocytes
Pregnancy-induced hypertension is an independent risk factor for meconium aspiration syndrome: A retrospective population based cohort study
Full text linkObjective: Meconium aspiration syndrome (MAS), possibly resulting from fetal hypoxia, is a respiratory
distress disorder in the infant. Pregnancy-induced hypertension (PIH) can cause placental dysfunction
and lead to fetal hypoxia, which may induce the development of MAS. Therefore, the aim of this study
was to determine the association between PIH and MAS and to identify the predictive risk factors.
Materials and methods: This was a retrospective cohort study. We selected patients with newly diagnosed
PIH and a matched cohort group from the Taiwan National Health Insurance Research Database
(NHIRD), from January 1, 2000 till December 31, 2013. For each patient in the PIH cohort, 4 subjects
without PIH, matched for age and year of delivery, were randomly selected as the comparison cohort. The
incidence of meconium aspiration syndrome was assessed in both groups.
Results: Among the 23.3 million individuals registered in the NHIRD, 29,013 patients with PIH and
116,052 matched controls were identified. Patients who experienced PIH had a higher incidence of MAS
than did those without PIH. According to a multivariate analysis, PIH (odds ratio [OR] 1⁄4 1.70, 95% confidence
interval [CI] 1⁄4 1.49e1.93, p < 0.0001) was independently associated with increased risk of MAS.
Additionally, age 30 years (OR 1⁄4 1.26, 95% CI 1⁄4 1.12e1.42, p 1⁄4 0.0001), nulliparity (OR 1⁄4 1.13, 95%
CI 1⁄4 1.01e1.27, p 1⁄4 0.0367) and patients with diabetes mellitus (OR 1⁄4 3.09, 95% CI 1⁄4 1.35e7.09,
p 1⁄4 0.0078) were also independent risk factors of MAS.
Conclusion: Patients with PIH obtained higher subsequent risk for the development of MAS than those
without PIH. Besides, age 30 years, nulliparity and patients with diabetes mellitus are the independent risk factors of developing MAS
Concept and development of an autonomous wearable micro-fluidic platform for real time pH sweat analysis
Full text linkIn this work the development of an autonomous, robust and wearable micro-fluidic platform capable of performing on-line analysis of pH in sweat is discussed. Through the means of an optical detection system based on a surface mount light emitting diode (SMD LED) and a light photo sensor as a detector, a wearable system was achieved in which real-time monitoring of sweat pH was performed during 55 minutes of cycling activity. We have shown how through systems engineering, integrating miniaturised electrical components, and by improving the micro-fluidic chip characteristics, the wearability, reliability and performance of the micro-fluidic platform was significantly improved
Exploring the effect of the pH on the corrosion of multilayer nickel-chromium coatings
No full textThe impact of the pH on the corrosion of microporous nickel-chromium coatings has been explored at localised scale by Scanning Electrochemical Microscopy and validated by potentiodynamic polarisation measurements. Results not only reveal the correlation between both techniques but also enables to identify the different corrosion rate after increasing the electrolyte aggressiveness varying the pH. However, independently of the pH, a similar corrosion mechanism was determined: the cross-section micrographs (by Field Emission-Scanning Electron Microscope) have revealed an isotropic growth of the actives sites at early-stage corrosion as well as the attack of different nickel layers during the corrosion propagation.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Team Yaiza Gonzalez Garci
Il dibattito italiano su principi e clausole generale e l'ideale della certezza del diritto
No full textThis essay provides a critical assessment of the current Italian debate on general clauses and principles as set forth in a recent book edited by Giovanni D’Amico. The Author focuses on the role that legal certainty has played so far in this discussion and suggests that its impact on real life decisions and the functioning of the legal system has been greatly undervalued. The essay’s central argument attempts to demonstrate that, in the interpretation of general clauses and their translation into specific rules, the objective of legal certainty should be pursued and can ultimately be achieved
Dynamics of Network Formation Processes in the Co-Author Model
Full text linkThis article studies the dynamics in the formation processes of a mutual consent network in game theory setting: the Co-Author Model. In this article, a limited observation is applied and analytical results are derived. Then, 2 parameters are varied: the number of individuals in the network and the initial probability of the links in the network in its initial state. A simulation result shows a finding that is consistent with an analytical result for a state of equilibrium while it also shows different possible equilibria.Dynamics, Network, Game Theory, Model,Simulation, Equilibrium, Complexity
Analysis of load shedding strategies for battery management in PV-based rural off-grids
No full textAccepted Author ManuscriptOld - EWI-ESE-DC&S DC systems & Storag
Feasibility Exploration of Blood Flow Estimation by Contrast-Assisted Nakagami Imaging
No full text[[abstract]]©2008 Elsevier - The microbubble contrast agent destruction/replenishnient technique has been widely applied to ultrasound-based blood flow estimation. The rate of increase of the time-intensity curve (TIC) due to microbubbles flowing into the region of interest as measured from B-mode images closely reflects the flow velocity. In this study, we monitored microbubble replenishment by a proposed new approach called the time-Nakagami-parameter curve (TNC) obtained from Nakagami-parameter images for quantifying the flow velocity. The feasibility of using the TNC to estimate the flow was evaluated in computer simulations of the TIC and TNC for flow velocities from 10 to 30 cm/s under an ultrasound frequency of 5 MHz. The clutter effects on the TIC and TNC were explored in a more realistic situation by carrying out phantom measurements of 25 MHz. The rates of increase of the TIC and TNC were expressed by the rate constants beta(1) and beta(N) of a monoexponential model, respectively. The average beta(1) increased from 38 to 110 s(-1) as the flow velocity increased front 10 to 30 cm/s (r = 0.98), and the average beta(N) increased from approximately 40 to 120 s(-1) for the same increase in flow velocity (r = 0.98). The p-value between the results of beta(1) and beta(N) as a function of flow velocity was 0.77. These results represent that beta(N) quantifies the flow velocity similarly to the conventional beta(1). In particular, both the simulation and experimental results revealed that the TNC method conditionally tolerates the presence of nonperfused areas (e.g., surrounding tissues or vessel walls) in the region of interest without requiring application of an additional wall filter to cancel the influences of clutter echoes on the flow estimation. These findings suggest that the TNC-based technique may be a potential method as a complementary tool for the conventional TIC technique to improve the estimation of blood flow.[[department]]生醫工程與環境科學
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