Proton configurations in the hydrogen bonds of KH2PO4 as seen by resonant x-ray diffraction

KH2PO4 (KDP) belongs to the class of hydrogen-bonded ferroelectrics, whose paraelectric to ferroelectric phase transition is driven by the ordering of the protons in the hydrogen bonds. We demonstrate that forbidden reflections of KDP, when measured at an x-ray absorption edge, are highly sensitive to the asymmetry of proton configurations. The change of average symmetry caused by the "freezing" of the protons during the phase transition is clearly evidenced. In the paraelectric phase, we identify in the resonant spectra of the forbidden reflections a contribution related to the transient proton configurations in the hydrogen bonds, which violates the high average symmetry of the sites of the resonant atoms. The analysis of the temperature dependence reveals a change of relative probabilities of the different proton configurations. They follow the Arrhenius law, and the activation energies of polar and Slater configurations are 18.6 and 7.3 meV, respectively

An X-ray study of the Dzyaloshinskii-Moriya interaction in the weak ferromagnet FeBO3

International audienceWe report on the axis, magnitude and direction of the Dzyaloshinskii-Moriya (DM) interaction in the weak ferromagnet FeBO3. The latter relies on the determination of the phase of the magnetic x-ray scattering amplitude. We outline a new technique based on interference with forbidden quadrupole resonant scattering to obtain this phase information

Phase transition of KDP observed by Resonant X-ray Diffraction at forbidden reflections

International audienceWe report observations of space-group-forbidden Bragg reflections in Potassium (KH2PO4), at the potassium K edge. We find clear evidence for a transition from one class of space-group-forbidden reflections, where scattering is ruled out by the electric dipole approximation, to a second class, in the ferroelectric phase, where scattering can proceed due to resonant anisotropy within the dipole approximation. The change of symmetry is clearly evidenced by the sudden change of intensity and energy spectrum of the forbidden reflections

Teeth sizes in their correlation with parameters of dentofacial arches and maxillofacial area based on native cranial preparations examination

The work offers a view on the results obtained from a radiological and morphometric study of native preparations obtained from 43 passported skulls with physiological occlusion and normodontia of permanent teeth under neutral position of the jaws and a neutral type of gnathic facial skull. It was found that in patients with physiological occlusion of permanent teeth, skulls with neutral type of gnathic facial part of the cranium as well as neutral jaw relationships proved to be predominant, while the major parameters of the dentofacial arches are determined through mesial-distal diameters of the teeth

Dzyaloshinskii--Moriya interaction: How to measure its sign in weak ferromagnetics?

Three experimental techniques sensitive to the sign of the Dzyaloshinskii--Moriya interaction are discussed: neutron diffraction, Moessbauer gamma-ray diffraction, and resonant x-ray scattering. Classical examples of hematite (alpha-Fe2O3) and MnCO3 crystals are considered in detailComment: 5 pages, 1 figure; to be published in JETP Letter

Comment on "X-ray resonant scattering studies of orbital and charge ordering in Pr1-xCaxMnO3"

In a recent published paper [Phys. Rev. B 64, 195133 (2001)], Zimmermann et al. present a systematic x-ray scattering study of charge and orbital ordering phenomena in the Pr1-xCaxMnO3 series with x= 0.25, 0.4 and 0.5. They propose that for Ca concentrations x=0.4 and 0.5, the appearance of (0, k+1/2, 0) reflections are originated by the orbital ordering of the eg electrons in the a-b plane while the (0, 2k+1, 0) reflections are due to the charge ordering among the Mn3+ and Mn4+ ions. Moreover, for small Ca concentrations (x<0.3), the orbital ordering is only considered and it occurs at (0, k, 0) reflections. A rigorous analysis of all these resonance reflections will show the inadequacy of the charge-orbital model proposed to explain the experimental results. In addition, this charge-orbital model is highly inconsistent with the electronic balance. On the contrary, these reflections can be easily understood as arising from the anisotropy of charge distribution induced by the presence of local distortions, i.e. due to a structural phase transition.Comment: 10 pages, 2 figures.To be published Phys. Rev.

Interplay of inequivalent atomic positions in resonant x-ray diffraction of Fe3BO6

'Forbidden' Bragg reflections of iron orthoborate Fe3BO6 were studied theoretically and experimentally in the vicinity of the iron K edge. Their energy spectra are explained as resulting from the interference of x-rays scattered from two inequivalent crystallographic sites occupied by iron ions. This particular structure property gives rise to complex azimuthal dependences of the reflection intensities in the pre-edge region as they result from the interplay of site specific dipole-quadrupole and quadrupole-quadrupole resonant scattering. Also evidenced is an isotropic character of the absorption spectrum. Self-absorption correction to the diffraction data, as well as possible contributions of thermal vibrations and magnetic order, are discussed. Particular care is given to extracting clean spectra from the data, and it is demonstrated that excellent results can be obtained even from measurements that appear corrupted by several effects such as poor crystal quality and multiple scattering.Comment: 12 page

A procedure for determining 2,4-dichlorophenoxyacetic acid using immobilized molecular imprinted polymers and an amperometric biosensor

A combined procedure was suggested for determining dichlorophenoxyacetic acid using polyacrylamidebased polymers immobilized in a nitrocellulose matrix with molecular imprints and amperometric cholinesterase biosensors. The sorbability of 2,4-dichlorophenoxyacetic acid on the immobilized polymers and reference polymers was evaluated, and the quantitative characteristics of the sorption-desorption process were calculated. © 2010 Pleiades Publishing, Ltd

Аромафитобальнеотерапия в лечении и профилактике частых респираторных инфекций у детей с хроническими и инвалидизирующими болезнями

In children with chronic pathologies, co-occurring frequent respiratory infections of a prolonged course obstructs and reduce the effectiveness of rehabilitation measures, and adversely affect the adaptation reserves. Hydrotherapeutic factors are widely used for the prevention of colds in children from the first days of life. Addition to the water of medicinal and phytoaromatic preparations increases their efficiency. For patients with chronic pathology, when prescribing balneotherapeutic factors for treatment and prophylaxis of respiratory infections, it is important to take into account the potential risk of adverse effects on the symptoms of the underlying disease. Researches in patients with orthopedic, chronic gastroenterological diseases, spastic forms of cerebral palsy, with co-occurring frequent respiratory infections of a prolonged course in history revealed that addition of medicinal baths based on phytoaromatic preparation, containing eucalyptus oil, to the rehabilitation complex is an effective method of preventing and stopping initial symptoms of respiratory infections. It also contributes to the adaptation reserves of the organism, without adversely affecting the course of the underlying disease.У детей с хронической патологией сопутствующие частые респираторные инфекции с затяжным течением затрудняют проведение и снижают эффективность реабилитационных мероприятий, крайне неблагоприятно влияют на адаптационные резервы. Водолечебные факторы широко используются для профилактики простудных заболеваний у детей с первых дней жизни. Повышает их эффективность добавление в воду лекарственных и фитоароматических препаратов. Для пациентов с хронической патологией при назначении бальнеотерапевтических процедур с целью лечения и профилактики респираторных инфекций важно учитывать возможный риск неблагоприятного влияния на симптомы основного заболевания. Исследования, проведенные у пациентов с ортопедической, хронической патологией желудочно-кишечного тракта, спастическими формами детского церебрального паралича, с сопутствующими частыми затяжными острыми респираторными болезнями в анамнезе, выявили, что включение в реабилитационный комплекс лекарственных ванн на основе фитоароматического препарата, содержащего эвкалиптовое масло, является эффективным методом профилактики и купирования начальных симптомов респираторных инфекций, способствует повышению адаптационных резервов организма, не оказывая отрицательного влияния на течение основного заболевания

METHODS OF BIOMETRICAL DIAGNOSTICS IN TRANSVERSAL DIRECTION IN PATIENTS WITH MESOGNATHIC TYPE OF DENTAL ARCHES

Aim. A comparative analysis of the horizontal parameters of mesognathic dental arches by the method of Pont and Linder-Harth. Materials and methods. The materials of the research were the results of measurements of diagnostic gypsum models of dental rows of 117 people aged 18-25 with a complete set of permanent teeth, physiological occlusion, mesognathic type of dental arches and various types of dental system. Measurement and calculation of the parameters of the dental arches in the transversal direction were carried out using the methods of Pont and Linder-Harth. Gnathic variants (mesognathy, dolichognathy, brachygnathy) of dental arches (Dmitrienko S.V., 2015) were determined taking into account the dental index calculated as the ratio of the half sum of the width of the crowns of 14 teeth to the width of the dental arch between the second molars. The types of the dental system (normodontia, macrodontia, microdontia) were determined from the summation of the width of the crowns of the upper teeth. Results. Biometric diagnostics of 117 pairs of gypsum models of dentition made it possible to establish that the methods of Pont and Linder-Harth are acceptable for the study of mesognathic dental arches as an estimate of transverse dimensions. There was no significant difference between the calculated indices and actual sizes in patients with mesognathic dental arches and various types of dental system, both in the premolar region and in the molar region. The size of the teeth is of decisive importance for the evaluation of the width of the dental arches of the mesognathic type. Conclusion. Optimization of medical and diagnostic measures in the clinic of orthodontics and orthopedic dentistry in the management of adult patients with dental-jaw pathology provides for the improvement of anthropometric studies, as well as the advisability of reviewing the conventional diagnostic regimens when studying the shape and size of dental arches to predict positive long-term results. Mathematically derived dependences of dental types of dental arches from their transversal parameters are informative, diagnostically significant values that can be used to predict the shape and size of dental arches in the treatment of patients with dentoalveolar anomalies in order to achieve an optimal functional and aesthetic result. The use of the Pont and Linder-Harth method in the analysis of the mesognathic dental arches has no significant errors, and can be used at the stages of diagnosis of shape and size anomalies in the transverse direction