Triplet spin resonance of the Haldane compound with interchain coupling

Spin resonance absorption of the triplet excitations is studied experimentally in the Haldane magnet PbNi2V2O8. The spectrum has features of spin S=1 resonance in a crystal field, with all three components, corresponding to transitions between spin sublevels, being observable. The resonance field is temperature dependent, indicating the renormalization of excitation spectrum in interaction between the triplets. Magnetic resonance frequencies and critical fields of the magnetization curve are consistent with a boson version of the macroscopic field theory [Affleck 1992, Farutin & Marchenko 2007], implying the field induced ordering at the critical field, while contradict the previously used approach of noninteracting spin chains.Comment: 7 pages, 9 figure

Magnetic excitations in dipolar pyrochlore antiferromagnet Gd2_2Sn2_2O7_7

The spin dynamics in the geometrically frustrated pyrochlore antiferromagnet $\rm Gd_2Sn_2O_7$ is studied by means of the electron spin resonance. In the ordered phase ($T_N = 1$ K), we have detected three gapped resonance modes. Their values agree well with the developed spin-wave theory which takes into account the Heisenberg nearest-neighbor exchange, the single-ion anisotropy and the long-range dipolar interactions. The theory also predicts a fourth lowest-frequency gap, which lies beyond the experimental range of frequencies, but determines the exponential decrease of the specific heat at low temperature.Comment: 8 pages, 5 figure

Magnetic excitations in dipolar pyrochlore antiferromagnet Gd2_2Sn2_2O7_7

The spin dynamics in the geometrically frustrated pyrochlore antiferromagnet $\rm Gd_2Sn_2O_7$ is studied by means of the electron spin resonance. In the ordered phase ($T_N = 1$ K), we have detected three gapped resonance modes. Their values agree well with the developed spin-wave theory which takes into account the Heisenberg nearest-neighbor exchange, the single-ion anisotropy and the long-range dipolar interactions. The theory also predicts a fourth lowest-frequency gap, which lies beyond the experimental range of frequencies, but determines the exponential decrease of the specific heat at low temperature.Comment: 8 pages, 5 figure

Magnetic phase diagram of the frustrated S=1/2 chain magnet LiCu_2O_2

We present the results of the magnetization and dielectric constant measurements on untwinned single crystal samples of the frustrated S=1/2 chain cuprate LiCu_2O_2. Novel magnetic phase transitions were observed. A spin flop transition of the spiral spin plane was observed for the field orientations H||a,b. The second magnetic transition was observed at H~15 T for all three principal field directions. This high field magnetic phase is discussed as a collinear spin-modulated phase which is expected for an S=1/2 nearest-neighbor ferromagnetic and next-nearest-neighbor antiferromagnetic chain system

КЛЮЧОВІ ФУНКЦІОНАЛЬНІ ЗМІНИ У КЛІТИНАХ БРИЖОВИХ ЛІМФАТИЧНИХ ВУЗЛІВ НАЩАДКІВ ЩУРІВ З ЕКСПЕРИМЕНТАЛЬНИМ ГЕСТАЦІЙНИМ ДІАБЕТОМ

Gestational diabetes (GD) is an important metabolic disorder that can affect the morphogenesis of the immune system. The aim of the study – to find out the peculiarities of mesenteric lymph nodes cells functional state in the posterity of rats with experimental gestational diabetes (EGD). Materials and Methods. Studies were performed on 80 posterity of Wistar rats with EGD at 1 and 6 months of age. For the induction of EGD streptozotocin (SIGMA Chemical, USA) was administered intraperitoneally at a dose of 45 mg/kg. For identification of TLR2, TLR4, NOD2, RIGI, T-bet, Nlrp3, RORγt and Foxp3 in histological sections of lymph nodes immunofluorescence method was used. To study the mRNA expression of Aire, Deaf1, Foxp3, IL10, Ctla4, Cxcr4, Ccr7, Madcam1, S1pr1 genes, a real-time reverse transcription polymerase chain reaction method was used. Results. The complex of key pathophysiological and functional changes in cells of mesenteric lymph nodes (MLN) in the posterity of rats with EGD was established: changes in the expression of lymphocyte recycling regulators and homemaking; impaired formation of peripheral immunological tolerance; activation of patterns of recognition receptors of the innate immune system on MLN lymphocytes; changes in the distribution of effector T cells in MLN. Conclusions. Prenatal hyperglycemia leads to increased proinflammatory signaling and activation of innate immune system components more clearly at 1 month of life.Гестаційний діабет (ГД) є важливим порушенням обміну речовин, що може впливати на морфогенез органів імунної системи. Мета дослідження – з’ясувати особливості змін функціонального стану клітин брижових лімфатичних вузлів у нащадків щурів з експериментальним гестаційним діабетом (ЕГД). Матеріали і методи. Дослідження проведено на 80 нащадках щурів лінії Wistar з ЕГД віком 1 і 6 місяців. Для індукції ЕГД вводили внутрішньочеревно стрептозотоцин (SIGMA Chemical, США) у дозі 45 мг/кг. Для ідентифікації TLR2, TLR4, NOD2, RIGI, T-bet, Nlrp3, RORγt і Foxp3 у гістологічних зрізах лімфатичних вузлів застосовували імунофлюоресцентний метод. Для дослідження експресії мРНК генів Aire, Deaf1, Foxp3, IL10, Ctla4, Cxcr4, Ccr7, Madcam1, S1pr1 використовували метод полімеразної ланцюгової реакції зі зворотною транскрипцією в режимі реального часу. Результати. Встановлено комплекс ключових патофізіологічних і функціональних змін у клітинах брижових лімфатичних вузлів (БЛВ) у нащадків щурів з ЕГД: зміни експресії регуляторів рециркуляції і хоумінгу лімфоцитів; порушення формування периферичної імунологічної толерантності; активація патернрозпізнавальних рецепторів уродженої імунної системи на лімфоцитах БЛВ; зміни розподілу ефекторних Т-клітин в БЛВ. Висновки. Пренатальна гіперглікемія призводить до посилення прозапальної сигналізації та активації компонентів уродженої імунної системи більш виразно на 1 місяці життя

Magnetocaloric effect in pyrochlore antiferromagnet Gd2Ti2O7

An adiabatic demagnetization process is studied in Gd2Ti2O7, a geometrically frustrated antiferromagnet on a pyrochlore lattice. In contrast to conventional paramagnetic salts, this compound can exhibit a temperature decrease by a factor of ten in the temperature range below the Curie-Weiss constant. The most efficient cooling is observed in the field interval between 120 and 60 kOe corresponding to a crossover between saturated and spin-liquid phases. This phenomenon indicates that a considerable part of the magnetic entropy survives in the strongly correlated state. According to the theoretical model, this entropy is associated with a macroscopic number of local modes remaining gapless till the saturation field. Monte Carlo simulations on a classical spin model demonstrate good agreement with the experiment. The cooling power of the process is experimentally estimated with a view to possible technical applications. The results for Gd2Ti2O7 are compared to those for Gd3Ga5O12, a well-known material for low temperature magnetic refrigeration.Comment: 6 pages, 4 figures, accepted versio

Quasi two-dimensional antiferromagnet on a triangular lattice RbFe(MoO4)2

RbFe(MoO4)2 is a rare example of a nearly two-dimensional Heisenberg antiferromagnet on a triangular lattice. Magnetic resonance spectra and magnetization curves reveal that the system has a layered spin structure with six magnetic sublattices. The sublattices within a layer are arranged in a triangular manner with the magnetization vectors 120 degree apart. The H-T phase diagram, containing at least five different magnetic phases is constructed. In zero field, RbFe(MoO4)2 undergoes a phase transition at T_N=3.8 K into a non-collinear triangular spin structure with all the spins confined in the basal plane. The application of an in-plane magnetic field induces a collinear spin state between the fields H_c1=47 kOe and H_c2=71 kOe and produces a magnetization plateau at one-third of the saturation moment. Both the ESR and the magnetization measurements also clearly indicate an additional first-order phase transition in a field of 35 kOe. The exact nature of this phase transition is uncertain.Comment: 9 pages incl 11 figure

Seven new species of Rhynchobombyx Aurivillius, 1909 from Congolian lowland forests (Lepidoptera: Lasiocampidae)

Seven new species of the Afrotropic Lasiocampidae genus Rhynchobombyx are described and illustrated: Rh. gavinfilippone Prozorov, Saldaitis & Müller sp. n., Rh. avadomenicarocchio Prozorov, Saldaitis & Müller sp. n., Rh. julianjameseaton Prozorov, Saldaitis & Müller sp. n., Rh. anthonychristophereaton Prozorov, Saldaitis & Müller sp. n., Rh. nicolasroberteaton Prozorov, Saldaitis & Müller sp. n., Rh. arijakefriend Prozorov, Saldaitis & Müller sp. n., Rh. madisonellafriend Prozorov, Saldaitis & Müller sp. n. All species originate from the poorly studied Congolian lowland forests ecoregion of Congo and Democratic Republic of the Congo. Lectotype and paralectotype of Rh. nasuta Aurivillius, 1909 are designated here, the species type locality is specified

Fracture toughness of Al2O3/ZrSiO4 coatings obtained by multi-chamber gas-dynamic accelerator

In the current work the research of fracture toughness of Al2O3/xZrSiO4 composite coatings have been realized using automatic system for microhardness analysis. Al2O3/xZrSiO4 (x = 0, 3, 25 wt. %) coatings were produced from a mixture of cheap raw materials (alumina and zircon ZrSiO4) on the surface of stainless steels by a new multi-chamber gas-dynamic accelerator. It has been experimentally established that adding of ZrSiO4 increases fracture toughness of alumina coating

Deposition and characterization of the titanium-based coating by a multi-chamber detonation sprayer

This work introduces some of the aspects of the deposition of titanium-based coating (80-120 μm thick) on aluminium samples using a multi-chamber detonation sprayer (MCDS). It was established that MCDS has provided the conditions for formation of a dense titanium-based coating with a porosity of less than 1.0%, microhardness 810±250 HV0.05 and a specific wear rate of 2.077·10-4 mm3(m·N)-