Publications by authors named "Alexandre Ivanov"

10 Publications

  • Page 1 of 1

Topological magnon insulators in two-dimensional van der Waals ferromagnets CrSiTe and CrGeTe: Toward intrinsic gap-tunability.

Sci Adv 2021 Sep 10;7(37):eabi7532. Epub 2021 Sep 10.

Jülich Centre for Neutron Science JCNS and Peter Grünberg Institut PGI, JARA-FIT, Forschungszentrum Jülich, D-52425 Jülich, Germany.

[Figure: see text].
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http://dx.doi.org/10.1126/sciadv.abi7532DOI Listing
September 2021

Polarized neutron scattering studies of magnetic excitations in iron-selenide superconductor LiFeODFeSe (41 K).

J Phys Condens Matter 2021 Sep 1;33(45). Epub 2021 Sep 1.

State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, People's Republic of China.

We report polarized neutron scattering measurements of the low energy spin fluctuations of the iron-selenide superconductor LiFeODFeSe below and above its superconducting transition temperature= 41 K. Our experiments confirmed that the resonance mode near 21 meV is magnetic. Moreover, the spin excitations are essentially isotropic in spin space at 5 ⩽⩽ 29 meV in the superconducting and normal states. Our results suggest that the resonance mode in iron-based superconductors becomes isotropic when the influence of spin-orbit coupling and magnetic/nematic order is minimized, similar to those observed in cuprate superconductors.
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http://dx.doi.org/10.1088/1361-648X/ac1d16DOI Listing
September 2021

Noninvasive mechanical ventilation in the COVID-19 era: Proposal for a continuous positive airway pressure closed-loop circuit minimizing air contamination, oxygen consumption, and noise.

Artif Organs 2021 Jul 26;45(7):754-761. Epub 2021 Jan 26.

PoliToBIOMed Lab, Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Turin, Italy.

Noninvasive continuous positive airway pressure (NIV-CPAP) is effective in patients with hypoxemic respiratory failure. Building evidence during the COVID-19 emergency reported that around 50% of patients in Italy treated with NIV-CPAP avoided the need for invasive mechanical ventilation. Standard NIV-CPAP systems operate at high gas flow rates responsible for noise generation and inadequate humidification. Furthermore, open-configuration systems require a high concentration of oxygen to deliver the desired FiO . Concerns outlined the risk for aerosolization in the ambient air and the possible pressure drop in hospital supply pipes. A new NIV-CPAP system is proposed that includes automatic control of patient respiratory parameters. The system operates as a closed-loop breathing circuit that can be assembled, combining a sleep apnea machine with existing commercially available components. Analytical simulation of a breathing patient and simulation with a healthy volunteer at different FiO were performed. Inspired and expired oxygen fraction and inspired and expired carbon dioxide pressure were recorded at different CPAP levels with different oxygen delivery. Among the main findings, we report (a) a significant (up to 30-fold) reduction in oxygen feeding compared to standard open high flow NIV-CPAP systems, to assure the same FiO levels, and (b) a negligible production of the noise generated in ventilatory systems, and consequent minimization of patients' discomfort. The proposed NIV-CPAP circuit, reshaped in closed-loop configuration with the blower outside of the circuit, has the advantages of minimizing aerosol generation, environmental contamination, oxygen consumption, and noise to the patient. The system is easily adaptable and can be implemented using standard CPAP components.
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http://dx.doi.org/10.1111/aor.13888DOI Listing
July 2021

Quality of life and nasal splints after primary cleft lip and nose repair: Prospective assessment of information and tolerance.

J Craniomaxillofac Surg 2018 Oct 9;46(10):1783-1789. Epub 2018 Aug 9.

Assistance Publique - Hôpitaux de Paris, Service de chirurgie maxillofaciale et plastique, Hôpital Necker - Enfants Malades, Université Paris Descartes, Université Sorbonne Paris Cité, (Head: Pr. Arnaud Picard, MD PhD), Paris, France. Electronic address:

Splints are commonly used after primary cleft surgery in order to secure the position of the nasal cartilages. Although the importance of splints is more and more stressed in the literature, many questions remain unanswered relative to the psychological impact of this device on children and families. Two questionnaires, Information and Tolerance, were used in order to measure the quality of life (QoL) associated with the use of nasal splints after primary cleft surgery. Information assessed the understanding of the parents the day before the procedure. Tolerance assessed their experience 3 months after splint placement. We prospectively included 41 consecutive patients from a Paris cleft center, 21 consecutive patients from a Russian center (Moscow) and 10 consecutive patients form a another French center (Nantes). In Paris and Nantes, an initial fixed splint was placed during the procedure until day 10, and then replaced by a removable splint for a period of 4 months. In the Moscow group, removable splints were used primarily for a total period of 4 months. Three types of removable splints were considered: commercial anatomical self-retentive splints (Nose-Fit™, Moscow, Russian Federation), in-house anatomical self-retentive splints and commercial Talmant-type splints requiring taping (Sebbin, Boissy-l'Aillerie, France). The data was analyzed as Likert scales and internal consistency was assessed using the Cronbach coefficient. Age at surgery, uni- or bilateral cleft, type of splint, number of splint changes and complications were tested against the scores of the questionnaires using multivariate models. We did not find correlations between the factors assessed by the multivariate analysis and the splint type. Information and Tolerance scores were high and showed satisfactory QoL associated with the use of splints. The internal consistency of the combination of the two forms was good. While the effects of splints on nasal morphology still need to be confirmed based on a controlled prospective study, we show here that this device is well tolerated by families and is not associated with specific complications.
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http://dx.doi.org/10.1016/j.jcms.2018.07.022DOI Listing
October 2018

Diffuse scattering in metallic tin polymorphs.

J Phys Condens Matter 2014 Mar 3;26(11):115401. Epub 2014 Mar 3.

European Synchrotron Radiation Facility, BP 220 F-38043 Grenoble Cedex 9, France.

The lattice dynamics of the metallic tin β and γ polymorphs has been studied by a combination of diffuse scattering, inelastic x-ray scattering and density functional perturbation theory. The non-symmorphic space group of the β-tin structure results in unusual asymmetry of thermal diffuse scattering. Strong resemblance of the diffuse scattering intensity distribution in β and γ-tin were observed, reflecting the structural relationship between the two phases and revealing the qualitative similarity of the underlying electronic potential. The strong influence of the electron subsystem on inter-ionic interactions creates anomalies in the phonon dispersion relations. All observed features are described in great detail by the density functional perturbation theory for both β- and γ-tin at arbitrary momentum transfers. The combined approach delivers thus a complete picture of the lattice dynamics in harmonic description.
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http://dx.doi.org/10.1088/0953-8984/26/11/115401DOI Listing
March 2014

Choline intake, plasma riboflavin, and the phosphatidylethanolamine N-methyltransferase G5465A genotype predict plasma homocysteine in folate-deplete Mexican-American men with the methylenetetrahydrofolate reductase 677TT genotype.

J Nutr 2009 Apr 11;139(4):727-33. Epub 2009 Feb 11.

Division of Nutritional Sciences and Genomics, Cornell University, Ithaca, NY 14853, USA.

We previously showed that provision of the folate recommended dietary allowance and either 300, 550, 1100, or 2200 mg/d choline for 12 wk resulted in diminished folate status and a tripling of plasma total homocysteine (tHcy) in men with the methylenetetrahydrofolate reductase (MTHFR) 677TT genotype. However, the substantial variation in tHcy within the 677TT genotype at wk 12 implied that several factors were interacting with this genotype to affect homocysteine. As an extension of this work, the present study sought to identify the main predictors of wk-12 plasma tHcy, alone and together with the MTHFR C677T genotype (29 TT, 31 CC), using linear regression analysis. A basic model explaining 82.5% of the variation (i.e. adjusted R(2) = 0.825) was constructed. However, the effects of the variables within this model were dependent upon the MTHFR C677T genotype (P for interaction < or = 0.021). Within the 677TT genotype, serum folate (P = 0.005) and plasma riboflavin (P = 0.002) were strong negative predictors (inversely related) explaining 12 and 15%, respectively, of the variation in tHcy, whereas choline intake (P = 0.003) and serum creatinine (P < 0.001) were strong positive predictors, explaining 19 and 25% of the variation. None of these variables, except creatinine (P = 0.021), correlated with tHcy within the 677CC genotype. Of the 8 additional polymorphisms tested, none appeared to influence tHcy. However, when creatinine was not in the model, the phosphatidylethanolamine N-methyltransferase 5465G-->A variant predicted lower tHcy (P < 0.001); an effect confined to the MTHFR 677TT genotype. Thus, in folate-deplete men, several factors with roles in 1-carbon metabolism interact with the MTHFR C677T genotype to affect plasma tHcy.
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http://dx.doi.org/10.3945/jn.108.100222DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2714377PMC
April 2009

Genetic variants in phosphatidylethanolamine N-methyltransferase and methylenetetrahydrofolate dehydrogenase influence biomarkers of choline metabolism when folate intake is restricted.

J Am Diet Assoc 2009 Feb;109(2):313-8

Beverly Hospital, Montebello, CA, USA.

Choline is a required nutrient with roles in liver and brain function, lipid metabolism, and fetal development. Recent data suggest that choline requirements may be altered by polymorphisms in the phosphatidylethanolamine N-methyltransferase (PEMT) gene (ie, 5465G-->A; rs7946 and -744G-->C; rs12325817) and in the methylenetetrahydrofolate dehydrogenase (MTHFD1) gene (ie, 1958G-->A; rs2236225). This controlled feeding study, conducted in 2000-2001, examined the effects of the PEMT and MTHFD1 genetic variants on biomarkers of choline metabolism in premenopausal Mexican-American women (N=43) after a 7-week period of folate restriction (135 microg as dietary folate equivalents) and after a 7-week period of folate treatment (400 and 800 microg dietary folate equivalents/day combined). Throughout the 14-week study choline intake remained constant at 349 mg/day. The genotype frequencies of the women were 3GG, 19GA, and 21AA for PEMT G5465A; 9GG, 17GC and 17CC for PEMT G-744C; and 9GG, 21GA and 13AA for MTHFD1 G1958A. During folate restriction, homocysteine was adversely influenced by PEMT 5465AA (P=0.001 relative to the G allele) and by MTHFD1 1958AA (P=0.085 relative to 1958GG); whereas the decline in phosphatidylcholine was attenuated by PEMT -744CC (P=0.017 relative to -744GG). During folate treatment, no effects of the genotypes on the response of the measured variables were detected. These data suggest that polymorphisms in genes relevant to choline metabolism modulate parameters of choline status when folate intake is restricted. Additional studies with larger samples sizes are needed to examine the relationship between these genetic variants and varied choline intake in populations with increased demands for choline (eg, pregnant women).
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http://dx.doi.org/10.1016/j.jada.2008.10.046DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2655101PMC
February 2009

Folate intake at RDA levels is inadequate for Mexican American men with the methylenetetrahydrofolate reductase 677TT genotype.

J Nutr 2008 Jan;138(1):67-72

Human Nutrition and Food Science Department, Cal Poly Pomona University, Pomona, CA 91768, USA.

Since the establishment of the 1998 folate recommended dietary allowance (RDA), the methylenetetrahydrofolate reductase (MTHFR) 677C-->T variant has emerged as a strong modifier of folate status. This controlled feeding study investigated the adequacy of the RDA, 400 microg/d as dietary folate equivalents (DFE), for Mexican American men with the MTHFR 677CC or TT genotype. Because of the interdependency between folate and choline, the influence of choline intake on folate status was also assessed. Mexican American men (n = 60; 18-55 y) with the MTHFR 677CC (n = 31) or TT (n = 29) genotype consumed 438 microg DFE/d and total choline intakes of 300, 550 (choline adequate intake), 1100, or 2200 mg/d for 12 wk. Folate status response was assessed via serum folate (SF), RBC folate, plasma total homocysteine (tHcy), and urinary folate. SF decreased (P < 0.001) 66% to 7.9 +/- 0.7 nmol/L (means +/- SEM) in men with the 677TT genotype and 62% to 11.3 +/- 0.9 nmol/L in the 677CC genotype. Plasma tHcy increased (P < 0.0001) 170% to 31 +/- 3 micromol/L in men with the 677TT genotype and 18% to 11.6 +/- 0.3 micromol/L in the 677CC genotype. At the end of the study, 34% (677TT) and 16% (677CC) had SF concentrations <6.8 nmol/L and 79% (677TT) and 7% (677CC) had tHcy concentrations >14 micromol/L. Choline intake did not influence the response of the measured variables. These data showed that the folate RDA is not adequate for men of Mexican descent, particularly for those with the MTHFR 677TT genotype, and demonstrated a lack of influence of choline intake on the folate status variables measured in this study.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2646848PMC
http://dx.doi.org/10.1093/jn/138.1.67DOI Listing
January 2008

Diffuse neutron scattering in relaxor ferroelectric PbMg1/3Nb2/3O3.

Phys Chem Chem Phys 2005 Jun;7(11):2340-5

Ioffe Physico-Technical Institute, 26, Politekhnicheskaya, 194021 St.-Petersburg, Russia.

High-energy resolution neutron spin-echo spectroscopy has been used to measure the intrinsic width of diffuse scattering discovered earlier in relaxor ferroelectric crystals. The anisotropic and transverse components of the scattering have been observed in different Brillouin zones. Both components are found to be elastic and have been measured within an experimental accuracy of 1 microeV. The possible physical origin of the static-like behavior is discussed for each diffuse scattering contribution.
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http://dx.doi.org/10.1039/b416454gDOI Listing
June 2005
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