689 research outputs found
Comparative Analysis of Super-Kamiokande and SNO Solar-Neutrino Data and the Photospheric Magnetic Field
We analyze Super-Kamiokande, SNO, and photospheric magnetic-field data for
the common time interval, namely the SNO D2O phase. Concerning rotational
modulation, the magnetic-field power spectrum shows the strongest peaks at the
second and sixth harmonics of the solar synodic rotation frequency [3 nu(rot)
and 7 nu(rot)]. The restricted Super-Kamiokande dataset shows strong modulation
at the second harmonic. The SNO D2O dataset shows weak modulation at that
frequency, but strong modulation in the sixth-harmonic frequency band. We
estimate the significance level of the correspondence of the Super-Kamiokande
second-harmonic peak with the corresponding magnetic-field peak to be 0.0004,
and the significance level of the correspondence of the SNO D2O sixth-harmonic
peak with the corresponding magnetic-field peak to be 0.009. By estimating the
amplitude of the modulation of the solar neutrino flux at the second harmonic
from the restricted Super-Kamiokande dataset, we find that the weak power at
that frequency in the SNO D2O power spectrum is not particularly surprising.
Concerning 9.43 yr-1, we find no peak at this frequency in the power spectrum
formed from the restricted Super-Kamiokande dataset, so it is no surprise that
this peak does not show up in the SNO D2O dataset, either.Comment: 32 pages, 8 tables, 16 figure
Chemical composition of barks from Quercus faginea trees and characterization of their lipophilic and polar extracts
The bark from Quercus faginea mature trees from two sites was chemically characterized for the first time. The barks showed the
following composition: ash 14.6%, total extractives 13.2%, suberin 2.9% and lignin 28.2%. The polysaccharides were composed
mainly of glucose and xylose (50.3% and 35.1% of all monosaccharides respectively) with 4.8% of uronic acids. The suberin
composition was: ω-hydroxyacids 46.3% of total compounds, ɑ,ω-alkanoic diacids 22.3%, alkanoic acids 5.9%, alkanols 6.7% and
aromatics 6.9% (ferulic acid 4.0%). Polar extracts (ethanol-water) had a high phenolic content of 630.3 mg of gallic acid equivalents
(GAE)/g of extract, condensed tannins 220.7 mg of catechin equivalents (CE)/g extract, and flavonoids 207.7 mg CE/g of extract.
The antioxidant activity was very high corresponding to 1567 mg Trolox equivalents/g of extract, and an IC50 of 2.63 μg extract/ml.
The lipophilic extracts were constituted mainly by glycerol and its derivatives (12.3% of all compounds), alkanoic acids (27.8%),
sterols (11.5%) and triterpenes (17.8%). In view of an integrated valorization, Quercus faginea barks are interesting sources of
polar compounds including phenols and polyphenols with possible interesting bioactivities, while the sterols and triterpenes
contained in the lipophilic extracts are also valuable bioactive compounds or chemical intermediates for specific high-value market
niches, such as cosmetics, pharmaceuticals and biomedicineinfo:eu-repo/semantics/publishedVersio
Quercus rotundifolia bark as a source of polar extracts: structural and chemical characterization
Quercus rotundifolia bark was studied regarding anatomical, chemical, and antioxidant
properties from trees in two sites in southern Portugal and are here reported for the first time. The
general structure and anatomy of Q. rotundifolia bark showed a rhytidome with sequential undulated
and anastomosed periderms with a small proportion of cork, while the phloem included broad rays
with strong cell sclerification, groups of sclereids with embed large prismatic crystals, and abundant
druses in parenchyma cells. The mean chemical composition was 15.5% ash, 1.6% dichloromethane
extractives, 6.4% ethanol and 9.3% water extractives, 3.0% suberin, 30.5% total lignin, and 33.8%
carbohydrates. Carbohydrates included mainly glucose (50.7% of total monomers) and xylose
(23.8%), with uronic (3.0%) and acetic acids (1.0%). Suberin was mainly composed of !-hydroxyacids
(48.0% of all compounds) and ,!-diacids (19.5%). The main compounds found in the lipophilic
extracts were triterpenes (43.6%–56.2% of all compounds) and alkanoic acids (32.7%–41.7%). Phenolic
content was high especially in the ethanol extracts, ranging from 219.5–572.9 mg GAE/g extract and
comprising 162.5–247.5 CE/g extract of flavonoids and 41.2–294.1 CE/g extract of condensed tannins.
The extracts revealed very good antioxidant properties with IC50 values of 4.4 g ethanol extract/mL
and 4.7 g water extract/mL. Similar anatomical, chemical, and antioxidant characteristics were
found in the bark from both sites. The high phenolic content and excellent antioxidant characteristics
of polar extracts showed holm oak barks to be a promising natural source of antioxidants with
possible use in industry and pharmaceutical/medical areasinfo:eu-repo/semantics/publishedVersio
Structure and application of antifreeze proteins from Antarctic bacteria
Indexación: Web of Science; Scopus.Background: Antifreeze proteins (AFPs) production is a survival strategy of psychrophiles in ice. These proteins have potential in frozen food industry avoiding the damage in the structure of animal or vegetal foods. Moreover, there is not much information regarding the interaction of Antarctic bacterial AFPs with ice, and new determinations are needed to understand the behaviour of these proteins at the water/ice interface. Results: Different Antarctic places were screened for antifreeze activity and microorganisms were selected for the presence of thermal hysteresis in their crude extracts. Isolates GU1.7.1, GU3.1.1, and AFP5.1 showed higher thermal hysteresis and were characterized using a polyphasic approach. Studies using cucumber and zucchini samples showed cellular protection when samples were treated with partially purified AFPs or a commercial AFP as was determined using toluidine blue O and neutral red staining. Additionally, genome analysis of these isolates revealed the presence of genes that encode for putative AFPs. Deduced amino acids sequences from GU3.1.1 (gu3A and gu3B) and AFP5.1 (afp5A) showed high similarity to reported AFPs which crystal structures are solved, allowing then generating homology models. Modelled proteins showed a triangular prism form similar to β-helix AFPs with a linear distribution of threonine residues at one side of the prism that could correspond to the putative ice binding side. The statistically best models were used to build a protein-water system. Molecular dynamics simulations were then performed to compare the antifreezing behaviour of these AFPs at the ice/water interface. Docking and molecular dynamics simulations revealed that gu3B could have the most efficient antifreezing behavior, but gu3A could have a higher affinity for ice. Conclusions: AFPs from Antarctic microorganisms GU1.7.1, GU3.1.1 and AFP5.1 protect cellular structures of frozen food showing a potential for frozen food industry. Modeled proteins possess a β-helix structure, and molecular docking analysis revealed the AFP gu3B could be the most efficient AFPs in order to avoid the formation of ice crystals, even when gu3A has a higher affinity for ice. By determining the interaction of AFPs at the ice/water interface, it will be possible to understand the process of adaptation of psychrophilic bacteria to Antarctic ice.https://microbialcellfactories.biomedcentral.com/articles/10.1186/s12934-017-0737-
Role of association in chiral catalysis: from asymmetric synthesis to spin selectivity
"This is the peer reviewed version of the following article: Ageeva, Aleksandra A., Ekaterina A. Khramtsova, Ilya M. Magin, Peter A. Purtov, Miguel A. Miranda, and Tatyana V. Leshina. 2018. Role of Association in Chiral Catalysis: From Asymmetric Synthesis to Spin Selectivity. Chemistry A European Journal 24 (70). Wiley: 18587 600. doi:10.1002/chem.201801625, which has been published in final form at https://doi.org/10.1002/chem.201801625. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving."[EN] The origin of biomolecules in the pre-biological period is still a matter of debate, as is the unclarified nature of the differences in enantiomer properties, especially for the medically important activity of chiral drugs. With regards to the first issue, significant progress was made in the last decade of the 20th century through experimental confirmation of Frank's popular theory on chiral catalysis in spontaneous asymmetric synthesis. Soai examined the chiral catalysis of the alkylation of achiral aldehydes by achiral reagents. Attempts to model this process demonstrated the key role of chiral compounds associates as templates for chiral synthesis. However, the elementary mechanism of alkylation and the role of free radicals in this process are still incompletely understood. Meanwhile, the influence of external magnetic fields on chiral enrichment in the radical path of alkylation has been predicted. In addition, the role of chiral dyad association in another radical process, electron transfer (ET), has been recently demonstrated by the following methods: chemically induced dynamic nuclear polarisation (CIDNP), NMR spectroscopy, XRD and photochemistry. The CIDNP analysis of ET in two dyads has revealed a phenomenon first observed for chiral systems, spin selectivity, which results in the difference between the CIDNP enhancement coefficients of dyad diastereomers. These dyads are linked systems consisting of the widespread drug (S)-naproxen (NPX) or its R analogue and electron donors, namely, (S)-tryptophan and (S)-N-methylpyrrolidine. Because NPX is one of the most striking examples of the difference in the therapeutic properties of enantiomers, the appearance of spin selectivity in dyads with (S)- and (R)-NPX and S donors can shed light on the chemical nature of these differences. This review is devoted to discussing the chemical nature of spin selectivity and the role of chiral associates in the chiral catalysis of an elementary radical reaction: ET in chiral dyads.The work was supported by the Russian Science Foundation (18-13-00047).Ageeva, A.; Khramtsova, E.; Magin, I.; Purtov, P.; Miranda Alonso, MÁ.; Leshina, T. (2018). Role of association in chiral catalysis: from asymmetric synthesis to spin selectivity. Chemistry - A European Journal. 24(70):18587-18600. https://doi.org/10.1002/chem.201801625S18587186002470Avalos, M., Babiano, R., Cintas, P., Jiménez, J. L., Palacios, J. C., & Barron, L. D. (1998). Absolute Asymmetric Synthesis under Physical Fields: Facts and Fictions. Chemical Reviews, 98(7), 2391-2404. doi:10.1021/cr970096oLin, G.-Q., Zhang, J.-G., & Cheng, J.-F. (2011). Overview of Chirality and Chiral Drugs. Chiral Drugs, 3-28. doi:10.1002/9781118075647.ch1Liu, Y., & Gu, X.-H. (2011). Pharmacology of Chiral Drugs. Chiral Drugs, 323-345. doi:10.1002/9781118075647.ch8Frank, F. C. (1953). On spontaneous asymmetric synthesis. Biochimica et Biophysica Acta, 11, 459-463. doi:10.1016/0006-3002(53)90082-1Soai, K., Kawasaki, T., & Matsumoto, A. (2014). Asymmetric Autocatalysis of Pyrimidyl Alkanol and Its Application to the Study on the Origin of Homochirality. Accounts of Chemical Research, 47(12), 3643-3654. doi:10.1021/ar5003208Soai, K., Kawasaki, T., & Matsumoto, A. (2014). The Origins of Homochirality Examined by Using Asymmetric Autocatalysis. The Chemical Record, 14(1), 70-83. doi:10.1002/tcr.201300028Soai, K., Matsumoto, A., & Kawasaki, T. (2017). Asymmetric Autocatalysis and the Origins of Homochirality of Organic Compounds. An Overview. Advances in Asymmetric Autocatalysis and Related Topics, 1-30. doi:10.1016/b978-0-12-812824-4.00001-0Matsumoto, A., Kawasaki, T., & Soai, K. (2017). Structural Study of Asymmetric Autocatalysis by X-Ray Crystallography. Advances in Asymmetric Autocatalysis and Related Topics, 183-202. doi:10.1016/b978-0-12-812824-4.00010-1Schiaffino, L., & Ercolani, G. (2010). Mechanism of the Asymmetric Autocatalytic Soai Reaction Studied by Density Functional Theory. Chemistry - A European Journal, 16(10), 3147-3156. doi:10.1002/chem.200902543Buono, F. G., & Blackmond, D. G. (2003). Kinetic Evidence for a Tetrameric Transition State in the Asymmetric Autocatalytic Alkylation of Pyrimidyl Aldehydes†. Journal of the American Chemical Society, 125(30), 8978-8979. doi:10.1021/ja034705nGridnev, I. D., & Vorobiev, A. K. (2012). Quantification of Sophisticated Equilibria in the Reaction Pool and Amplifying Catalytic Cycle of the Soai Reaction. ACS Catalysis, 2(10), 2137-2149. doi:10.1021/cs300497hGridnev, I. D., Serafimov, J. M., & Brown, J. M. (2004). Solution Structure and Reagent Binding of the Zinc Alkoxide Catalyst in the Soai Asymmetric Autocatalytic Reaction. Angewandte Chemie International Edition, 43(37), 4884-4887. doi:10.1002/anie.200353572Gridnev, I. D., Serafimov, J. M., & Brown, J. M. (2004). Solution Structure and Reagent Binding of the Zinc Alkoxide Catalyst in the Soai Asymmetric Autocatalytic Reaction. Angewandte Chemie, 116(37), 4992-4995. doi:10.1002/ange.200353572Noble-Terán, M. E., Cruz, J.-M., Micheau, J.-C., & Buhse, T. (2018). A Quantification of the Soai Reaction. ChemCatChem, 10(3), 642-648. doi:10.1002/cctc.201701554Girard, C., & Kagan, H. B. (1998). Nonlinear Effects in Asymmetric Synthesis and Stereoselective Reactions: Ten Years of Investigation. Angewandte Chemie International Edition, 37(21), 2922-2959. doi:10.1002/(sici)1521-3773(19981116)37:213.0.co;2-1Girard, C., & Kagan, H. B. (1998). Nichtlineare Effekte bei asymmetrischen Synthesen und stereoselektiven Reaktionen. Angewandte Chemie, 110(21), 3088-3127. doi:10.1002/(sici)1521-3757(19981102)110:213.0.co;2-aNoble-Terán, M. E., Buhse, T., Cruz, J.-M., Coudret, C., & Micheau, J.-C. (2016). Nonlinear Effects in Asymmetric Synthesis: A Practical Tool for the Discrimination between Monomer and Dimer Catalysis. ChemCatChem, 8(10), 1836-1845. doi:10.1002/cctc.201600216Blackmond, D. G. (2000). Kinetic Aspects of Nonlinear Effects in Asymmetric Catalysis. 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Spin Selectivity in Chiral Linked Systems. Chemistry - A European Journal, 24(15), 3882-3892. doi:10.1002/chem.201705863Khramtsova, E. A., Sosnovsky, D. V., Ageeva, A. A., Nuin, E., Marin, M. L., Purtov, P. A., … Leshina, T. V. (2016). Impact of chirality on the photoinduced charge transfer in linked systems containing naproxen enantiomers. Physical Chemistry Chemical Physics, 18(18), 12733-12741. doi:10.1039/c5cp07305gKhramtsova, E. A., Ageeva, A. A., Stepanov, A. A., Plyusnin, V. F., & Leshina, T. V. (2017). Photoinduced Electron Transfer in Dyads with (R)-/(S)-Naproxen and (S)-Tryptophan. Zeitschrift für Physikalische Chemie, 231(3). doi:10.1515/zpch-2016-0842Magin, I. M., Polyakov, N. E., Kruppa, A. I., Purtov, P. A., Leshina, T. V., Kiryutin, A. S., … Marin, M. L. (2016). Low field photo-CIDNP in the intramolecular electron transfer of naproxen–pyrrolidine dyads. Physical Chemistry Chemical Physics, 18(2), 901-907. doi:10.1039/c5cp04233jDuggan, K. C., Hermanson, D. 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The Structure of TGB Phases
We study the transition from the cholesteric phase to two TGB phases near
the upper critical twist : the Renn-Lubensky TGB phase, with layer
normal rotating in a plane perpendicular to the pitch axis, and the Bordeaux
TGB phase, with the layer normal rotating on a cone parallel to the pitch
axis. We calculate properties, including order-parameter profiles, of both
phases.Comment: 4 pages, 4 figures, Submitted to Physical Review E, Rapid
Communications, September 5, 2003; Revised manuscript (to the paper submitted
on March 18, 2003, cond-mat/0303365)that includes an important missing
reference and presents an improved analysis of a generalized mode
Evidence for Solar Neutrino Flux Variability and its Implications
Althogh KamLAND apparently rules out Resonant-Spin-Flavor-Precession (RSFP)
as an explanation of the solar neutrino deficit, the solar neutrino fluxes in
the Cl and Ga experiments appear to vary with solar rotation. Added to this
evidence, summarized here, a power spectrum analysis of the Super-Kamiokande
data reveals significant variation in the flux matching a dominant rotation
rate observed in the solar magnetic field in the same time period. Three
frequency peaks, all related to this rotation rate, can be explained
quantitatively. A Super-Kamiokande paper reported no time variation of the
flux, but showed the same peaks, there interpreted as statistically
insignificant, due to an inappropriate analysis. This modulation is small (7%)
in the Super-Kamiokande energy region (and below the sensitivity of the
Super-Kamiokande analysis) and is consistent with RSFP as a subdominant
neutrino process in the convection zone. The data display effects that
correspond to solar-cycle changes in the magnetic field, typical of the
convection zone. This subdominant process requires new physics: a large
neutrino transition magnetic moment and a light sterile neutrino, since an
effect of this amplitude occurring in the convection zone cannot be achieved
with the three known neutrinos. It does, however, resolve current problems in
providing fits to all experimental estimates of the mean neutrino flux, and is
compatible with the extensive evidence for solar neutrino flux variability.Comment: 9 pages, 10 figures (5 in color); new figure, data added to another
figure, more clarification, especially on the origin of the effect and its
connection to sterile neutrinos; v3 is updated, especially using the results
of hep-ph/0402194; v4 is a further update, mainly of references, with a small
change to make the title more appropriate; v5 includes more clarification and
the result of now having hep-ph/0411148 and hep-ph/0501205 and so increases
the length; v6 has a small change in the title and some additional
information at the referee's request to correspond to the version to be
published in Astroparticle Physic
Human papillomavirus (HPV) contamination of gynaecological equipment.
OBJECTIVE: The gynaecological environment can become contaminated by human papillomavirus (HPV) from healthcare workers' hands and gloves. This study aimed to assess the presence of HPV on frequently used equipment in gynaecological practice.
METHODS: In this cross-sectional study, 179 samples were taken from fomites (glove box, lamp of a gynaecological chair, gel tubes for ultrasound, colposcope and speculum) in two university hospitals and in four gynaecological private practices. Samples were collected with phosphate-buffered saline-humidified polyester swabs according to a standardised pattern, and conducted twice per day for 2 days. The samples were analysed by a semiquantitative real-time PCR. Statistical analysis was performed using Pearson's χ(2) test and multivariate regression analysis.
RESULTS: Thirty-two (18%) HPV-positive samples were found. When centres were compared, there was a higher risk of HPV contamination in gynaecological private practices compared with hospitals (OR 2.69, 95% CI 1.06 to 6.86). Overall, there was no difference in the risk of contamination with respect to the time of day (OR 1.79, 95% CI 0.68 to 4.69). When objects were compared, the colposcope had the highest risk of contamination (OR 3.02, 95% CI 0.86 to 10.57).
CONCLUSIONS: Gynaecological equipment and surfaces are contaminated by HPV despite routine cleaning. While there is no evidence that contaminated surfaces carry infectious viruses, our results demonstrate the need for strategies to prevent HPV contamination. These strategies, based on health providers' education, should lead to well-established cleaning protocols, adapted to gynaecological rooms, aimed at eliminating HPV material
Chromosome-level reference genome of stinkwort, Dittrichia graveolens (L.) Greuter : A resource for studies on invasion, range expansion, and evolutionary adaptation under global change
This work was funded by the United States Department of Agriculture, National Institute of Food and Agriculture “Agriculture and Food Research Initiative Grant” [2020-67013-31856]. NL acknowledges support from the Swiss National Science Foundation [P2EZP3_178481] and Natural Environment Research Council [NE/W006553/1].Peer reviewedPublisher PD
Anderson localization of polaron states
Using the vanishing of the typical polaron tunneling rate as an indicator of
the breakdown of itinerancy, we study the localization of polaron states in a
generic model for a disordered polaronic material. We find that extremely small
disorder causes an Anderson localization of small polaron states. However, the
ratio between the critical disorder strength needed to localize all states in
the polaron band and the renormalized bandwidth is not necessarily smaller than
for a bare electron.Comment: 4 pages, 3 figure
- …