Residual strain investigation of a polycrystalline quartzite rock sample using time-of-flight neutron diffraction

In this work, we studied the residual micro lattice strain of an onyx sample, which is a micro- to the cryptocrystalline variety of the mineral quartz SiO$_2$. That the investigation has been carried out using in-situ stress experiments with the time-of-flight neutron diffraction method. The aim of the study is to investigate residual lattice strains and pressure directions in the sample using time-of-flight neutron diffraction, which is a powerful tool for the study of the residual strain behavior in bulk materials, like geological rock samples containing large grains. The residual strain was detected in different sample directions turning the sample in steps of 30° by 180° around the cylindrical z-axis. These experiments have been performed at the time-of-flight neutron strain diffractometer EPSILON, situated on the pulsed neutron source IBR-2M of the Joint Institute for Nuclear Research in Dubna, Russia. The results of this study will provide insights into the compressional and tensional residual strain of the crystallographic lattice planes, and will have implications for our understanding of the tectonic history of this region. These different strains are arranged in the sample by a sinusoidal distribution in radial directions

Size-dependent electronic-transport mechanism and sign reversal of magnetoresistance in Nd0.5Sr0.5CoO3

A detailed investigation of electronic-transport properties of Nd0.5Sr0.5CoO3 has been carried out as a function of grain size ranging from micrometer order down to an average size of 28 nm. Interestingly, we observe a size induced metal-insulator transition in the lowest grain size sample while the bulk-like sample is metallic in the whole measured temperature regime. An analysis of the temperature dependent resistivity in the metallic regime reveals that the electron-electron interaction is the dominating mechanism while other processes like electron-magnon and electron-phonon scatterings are also likely to be present. The fascinating observation of enhanced low temperature upturn and minimum in resistivity on reduction of grain size is found due to electron-electron interaction (quantum interference effect). This effect is attributed to enhanced disorder on reduction of grain size. Interestingly, we observed a cross over from positive to negative magnetoresistance in the low temperature regime as the grain size is reduced. This observed sign reversal is attributed to enhanced phase separation on decreasing the grain size of the cobaltite

Сорбционное концентрирование следовых количеств хлорамфеникола на поверхности силикагеля, модифицированного октадецильнимы группами

Проблематика. Хлорамфенікол (ХЛ) – антибіотик широкого спектра дії, використовується у різних галузях ветеринарії і може накопичуватись у продуктах харчування тваринного походження. Тому гранично допустиму концентрацію ХЛ у продуктах харчування істотно обмежено в країнах ЄС та США. Часто сучасні методи аналізу не дають змоги визначати слідові кількості препарату із різних матриць без попереднього концентрування. Метод рідинно-рідинної екстракції (РРЕ) може супроводжуватись втратою цільового компонента. Тому доцільно використовувати твердофазову екстракцію аналіту задля підвищення чутливості визначення інструментальними методами та забезпечення стабільності вилучення ХЛ. Мета дослідження. Розробка методики сорбційного концентрування ХЛ із проб меду з його подальшим детектуванням за допомогою імуноферментного методу. Методика реалізації. Використовували набір реагентів для визначення ХЛ імуноферментним методом “Хлорамфенікол ІФА” виробництва ТОВ “ХЕМА”. Для розробки методики твердофазового екстрагування ХЛ із проб меду використано картриджі, заповнені силікагелем (SiO2-C18) з прищепленими октадецильними групами виробництва фірми “Agilent”. Апробацію методики проводили на зразках меду, що були попередньо досліджені на наявність ХЛ за стандартною процедурою РРЕ аналіту. Результати дослідження. Досліджено можливість проведення сорбційного концентрування ХЛ на поверхні силікагелю із прищепленими октадецильними групами. Встановлено оптимальні умови вилучення аналіту на поверхні сорбенту та досліджено умови дерсорбування ХЛ з поверхні силікагелю. Методику тведофазового екстрагування ХЛ із матриць меду випробувано на контрольних матеріалах – зразках меду з відомою концентрацією ХЛ, придбаних ТОВ “ХЕМА” для проведення референсних досліджень. Висновки. Для вилучення ХЛ із матриць меду доцільно використовувати метод твердофазової екстракції. Запропонований нами метод пробопідготовки дає змогу скоротити час пробопідготовки зразків меду та є перспективним для розробки методу одночасного концентрування антибіотиків різних груп для імуноферментного дослідження.Background. Chloramphenicol (CAP) is a broad spectrum antibiotic. It’s widely used in various fields of veterinary and can be accumulated in food of animal origin. A minimum required performance limit (MRPL) for CAP in food is significantly restricted in the EU and the USA. Most modern methods make it difficult to determine the trace amounts of the drug from various matrices without concentration. The method of liquid-liquid extraction (LLE) may be accompanied by loss of trust component. It is therefore advisable to use solid phase analyte extraction to increase the determination sensitivity by instrumental methods and CL withdrawal stability. Objective. Development of the solid phase extraction method of chloramphenicol from honey, followed by enzyme linked immunoassay. Methods. Quantitative determination of chloramphenicol was determined using enzyme linked assay (ELISA) test-kit for determination of chloramphenicol in foods, provided by LLC “XEMA”. Solid phase extraction of chloramphenicol from honey samples was studied on silica gel surface modified with octadecyl groups (SiO2-C18), “Agilent”. This method of solid phase extraction was carried out on samples of honey, that previously checked by ELISA using LLE for sample preparation. Results. Our results showed the possibility of solid phase extraction of CAP on the surface of the silica gel with oktadecyl groups. The optimal conditions for extraction the analyte on the surface of sorbent were found and the eluation condition for CAP was studied. We tested the method of solid phase extraction of CAP from honey matrics on control materials — honey samples with known concentrations of CAP, that were bought by LLC “XEMA”. Conclusions. Solid phase extraction of CAP could be used for CAP extraction form honey. The proposed method of sample preparation reduces the time of preparation for honey samples. This method is perspective for developing the method of simultaneous concentration of antibiotics from different groups followed by ELISA determination.Проблематика. Хлорамфеникол (ХЛ) – антибиотик широкого спектра действия, используется в различных отраслях ветеринарии и может накапливаться в продуктах питания животного происхождения. Поэтому предельно допустимая концентрация ХЛ в продуктах питания существенно ограничена в странах ЕС и США. Часто современные методы анализа не позволяют определять следовые количества препарата из различных матриц без предварительного концентрирования. Метод жидкостно-жидкостной экстракции (ЖЖЭ) может сопровождаться потерей целевого компонента. Поэтому целесообразно использовать твердофазовую экстракцию аналита для повышения чувствительности определения инструментальными методами и обеспечения стабильности извлечения ХЛ. Цель исследования. Разработка методики сорбционного концентрирования ХЛ из проб меда с его последующим детектированием с помощью иммуноферментного метода. Методика реализации. Использовали набор реагентов для определения ХЛ иммуноферментным методом “Хлорамфеникол ИФА” производства ООО “ХЕМА”. Для разработки методики твердофазового экстрагирования ХЛ из проб меда использовали картриджи, заполненные силикагелем (SiO2-C18) с привитыми октадецильнимы группами производства фирмы “Agilent”. Апробацию методики проводили на образцах меда, которые были предварительно исследованы на наличие ХЛ по стандартной процедуре ЖЖЭ аналита. Результаты исследования. Исследована возможность проведения сорбционного концентрирования ХЛ на поверхности силикагеля с привитыми октадецильнимы группами. Установлены оптимальные условия извлечения аналита на поверхности сорбента и исследованы условия десорбции ХЛ с поверхности силикагеля. Методика твердофазового экстрагирования ХЛ из матриц меда проверена на контрольных материалах – образцах меда с известной концентрацией ХЛ, приобретенных ООО “ХЕМА” для проведения референсных исследований. Выводы. Для извлечения ХЛ из матриц меда целесообразно использовать метод твердофазовой экстракции. Предложенный нами метод пробоподготовки позволяет сократить время пробоподготовки образцов меда и является перспективным для разработки метода одновременного концентрирования антибиотиков различных групп для иммуноферментного исследования

Dzyaloshinskii-Moriya interaction and spin re-orientation transition in the frustrated kagome lattice antiferromagnet

Magnetization, specific heat, and neutron scattering measurements were performed to study a magnetic transition in jarosite, a spin-5/2 kagome lattice antiferromagnet. When a magnetic field is applied perpendicular to the kagome plane, magnetizations in the ordered state show a sudden increase at a critical field H_c, indicative of the transition from antiferromagnetic to ferromagnetic states. This sudden increase arises as the spins on alternate kagome planes rotate 180 degrees to ferromagnetically align the canted moments along the field direction. The canted moment on a single kagome plane is a result of the Dzyaloshinskii-Moriya interaction. For H < H_c, the weak ferromagnetic interlayer coupling forces the spins to align in such an arrangement that the canted components on any two adjacent layers are equal and opposite, yielding a zero net magnetic moment. For H > H_c, the Zeeman energy overcomes the interlayer coupling causing the spins on the alternate layers to rotate, aligning the canted moments along the field direction. Neutron scattering measurements provide the first direct evidence of this 180-degree spin rotation at the transition.Comment: 13 pages, 15 figure

Influence of the Structure on Magnetic Properties of Calcium-Phosphate Systems Doped with Iron and Vanadium Ions

The aim of this study was to prepare and characterize the glasses made of x(Fe$_{2}$O$_{3}$∙V$_{2}$O$_{5}$)∙(100 − x)[P$_{2}$O$_{5}$∙CaO] with x ranging of 0–50%. The contribution of Fe$_{2}$O$_{3}$ and V$_{2}$O$_{5}$ amount on the structure of P$_{2}$O$_{5}$·CaO matrix was investigated. The vitreous materials were characterized by XRD (X-ray diffraction analysis), EPR (Electron Paramagnetic Resonance) spectroscopy, and magnetic susceptibility measurements. A hyperfine structure typical for isolated V4+ ions was noticed to all spectra containing low amount of V$_{2}$O$_{5}$. The XRD spectra show the amorphous nature of samples, apart x = 50%. An overlap of the EPR spectrum of a broad line without the hyperfine structure characteristic of clustered ions was observed with increasing V2O5 content. The results of magnetic susceptibility measurements explain the antiferromagnetic or ferromagnetic interactions expressed between the iron and vanadium ions in the investigated glass

Neutron powder diffraction study of NaMn2_2O4_4 and Li0.92_{0.92}Mn2_2O4_4: New insights on spin-charge-orbital ordering

The high-pressure synthesized quasi-one-dimensional compounds NaMn$_2$O$_4$ and Li$_{0.92}$Mn$_2$O$_4$ are both antiferromagnetic insulators, and here their atomic and magnetic structures were investigated using neutron powder diffraction. The present crystal structural analyses of NaMn2O4 reveal that Mn3+/Mn4+ charge-ordering state exist even at low temperature (down to 1.5 K). It is evident from one of the Mn sites shows a strongly distorted Mn3+ octahedra due to the Jahn-Teller effect. Above TN = 39 K, a two-dimensional short-range correlation is observed, as indicated by an asymmetric diffuse scattering. Below TN, two antiferromagnetic transitions are observed (i) a commensurate long-range Mn3+ spin ordering below 39 K, and (ii) an incommensurate Mn4+ spin ordering below 10 K. The commensurate magnetic structure (kC = 0.5, -0.5, 0.5) follows the magnetic anisotropy of the local easy axes of Mn3+, while the incommensurate one shows a spin-density-wave order with kIC = (0,0,0.216). For Li$_{0.92}$Mn$_2$O$_4$, on the other hand, absence of a long-range spin ordered state down to 1.5 K is confirmed.Comment: 11 pages, 8 figure

Negative magnetization of Li2Ni2Mo3O12 having a spin system composed of distorted honeycomb lattices and linear chains

We study themagnetism of a spin-1 substance Li2Ni2Mo3O12. The spin system consists of distorted honeycomb lattices and linear chains of Ni2+ spins. Li+ ions enter about 25% and 50% of the honeycomb and chain Ni sites, respectively, creating disorder in both spin subsystems. A magnetic phase transition occurs at Tc = 8.0 K in the zero magnetic field. In low magnetic fields, the magnetization increases rapidly below Tc, decreases below 7 K, and finally becomes negative at low temperatures. We determine the magnetic structure using neutron powder diffraction results. The honeycomb lattices and linear chains show antiferromagnetic and ferromagnetic long-range order, respectively. We investigate static and dynamic magnetic properties using the local probe technique of muon spin relaxation. We discuss the origin of the negative magnetization

Electromechanical and magnetic properties of BiFeO3-LaFeO3-CaTiO3 ceramics near the rhombohedral-orthorhombic phase boundary

BiFeO3-LaFeO3-CaTiO3 ceramics have been studied by X-ray diffraction, magnetization measurements, and piezoresponse force microscopy (PFM). The compositional ranges of the polar, antipolar, and non-polar phases have been estimated. PFM measurements testify gradual decrease of piezoelectric response in Bi(0.85-x)La(0.15)CaxFe(1-x)Ti(x)O(3) system with Ca/Ti content increase, except a narrow concentration region near polar-antipolar phase boundary where piezoelectric signal shows maximum value. It is found that increase of dopant concentration leads to apparent decrease of the off-center Bi-O displacement and, consequently, causes a reduction of piezoelectric response. It is concluded that notable remanent magnetization in polar and non-polar structural phases is a result of the Dzyaloshinsky-Moria interaction. (C) 2013 AIP Publishing LL