EPR measurement of Cu2+-fe2+ exchange in FeSif6 · 6H20 at 4.2 K

Six inequivalent Cu2+ EPR spectra were observed at 4.2 K in single crystals of FeSiF 6 • 6H20. The estimated parametersgz ---2.38 and 8=40°, where 8 is the angle between the ionicz axis and the c axis, differ from those measured in crystals of similar structure. Thes~ differences have been explained in terms of an isotropic Cu2+ -Fe2+ exchange Hamiltonian JS1 • S2, with J = + (0.030 ± 0.003) em - 1 ' which gives a contribution gex = - 5.05 J sin2 e, where e is the angle between the external magnetic field and the z axis. Perpendicular to the c axis, an independent estimate of + 0.034 em -I for J was made from the low-field displacement of a satellite spectru

EPR study of the Jahn-Teller effect of Cu2+ in ZnTiF6·6H20

The 34-GHz EPR spectrum of Cu2+ in ZnTiF6·6H20 shows a Jahn-Teller effect with a transition from a single-line spectrum at high temperatures to a multiline anisotropic spectrum. The transition temperature on cooling varied with Cu concentration from 172 K for a sample containing 0.2 at.% Cu to roughly 90 K for a 46-at. % Cu sample. For dilute samples, the single-line spectrum was isotropic at 300 K with g =2.223±0.005, but showed axial symmetry about the trigonal axis at 180 K with gj1 =2.226±0.005 and g~ =2.223±0.005. At 4.2 K, a "static" Jahn-Teller effect was observed with six axially symmetric Cu2+ spectra, each with g 11 =2.470±0.005, g1 =2.100±0.005, I A 11 I ~ I 06 X 10- 4 em -I, and I A 1 I ~30 X 10- 4 em - I. The z axis of these spectra was found to lie along the fourfold axes of two cubes with a common [Ill] axis, rotated by 40"±2" with respect to each other about this axis. Analysis of the 4.2-K data leads to the values q~O. 50 for the Ham reduction factor and K~O. 26 for the Fenni contact parameter, with A uA 1 < 0. An activation energy of about 100 cm-1 was deduced from the gradual increase of the anisotropy of the spectrum on cooling in the low-temperature region

Могут ли поражения, вызванные актиническим кератозом, стать загадкой для дерматологов? Результаты открытого перспективного исследования

Different face skin diseases (basal cell carcinoma, actinic keratosis, rosacea, solar elastosis, etc.) could clinically manifest itself as erythematic patches, pimples or plagues. It is very hard to make the clinical exclusion in some cases of these diseases since their characters can partially overlap or certain lesion can mimic another one especially in the cases of skin areas affected with sun. Therefore, the histopathological analysis remains the “golden standard” of the dermatological diagnosis at skin diseases. Our study has shown that certified dermatologists detect actinic keratosis (AK) of face/head skin of I/II levels very well. Verdicts of dermatologists and pathomorfologists are congruent on account of diagnosis in 90,7% cases. Diseases clinically excluded as AK revealed as malignant neoplasms (basal cell carcinoma) in less than 1% of case lesions.Различные кожные заболевания на лице (базально-клеточная карцинома, актинический кератоз, розацеа, солнечный эластоз и т. д.) могут клинически проявляться как эритематозные пятна, папулы или бляшки. Иногда клинический диагноз таких поражений кожи поставить очень сложно, поскольку их признаки могут частично совпадать или же одно заболевание может мимикрировать под другое, особенно в случае поражения участков, подвергающихся солнечному воздействию. По этой причине гистопатологический анализ остается золотым стандартом диагностики при кожных заболеваниях. Наше исследование показало, что сертифицированные дерматологи очень хорошо диагностируют актинический кератоз (АК) I/II степени на коже лица/головы. В 90,7% случаев мнения дерматолога и врача-патоморфолога относительно диагноза совпадают, и менее чем в 1% случаев поражения, диагностированные как АК, оказались злокачественными новообразованиями (базально-клеточная карцинома)

Limitations in Predicting the Space Radiation Health Risk for Exploration Astronauts

Despite years of research, understanding of the space radiation environment and the risk it poses to long-duration astronauts remains limited. There is a disparity between research results and observed empirical effects seen in human astronaut crews, likely due to the numerous factors that limit terrestrial simulation of the complex space environment and extrapolation of human clinical consequences from varied animal models. Given the intended future of human spaceflight, with efforts now to rapidly expand capabilities for human missions to the moon and Mars, there is a pressing need to improve upon the understanding of the space radiation risk, predict likely clinical outcomes of interplanetary radiation exposure, and develop appropriate and effective mitigation strategies for future missions. To achieve this goal, the space radiation and aerospace community must recognize the historical limitations of radiation research and how such limitations could be addressed in future research endeavors. We have sought to highlight the numerous factors that limit understanding of the risk of space radiation for human crews and to identify ways in which these limitations could be addressed for improved understanding and appropriate risk posture regarding future human spaceflight.Comment: Accepted for publication by Nature Microgravity (2018

Jahn-Teller EPA spectra of Cu2 + in MgSif6.6H20

The 34 GHz EPR spectrum ofCu2+ in MgSiF6-6H20 showed a "static" Jahn-Teller effect at 4.2 K with two inequivalent Jahn- Teller sites per unit cell. The six axially symmetric sets of Cu2+ lines had their z axes parallel to the three tetragonal axes of two cubes, which were rotated by approximately 40" with respect to each other about a common (Ill) axis, which is the crystal c axis. The measured spin-Hamiltonian parameters at 4.2 K for each set of lines were g11 = 2.47 ± 0.01, g1 = 2.10 ± 0.01 , and lA 11 1 = (110 ± 3)X 10- 4 em- •. There was a gradual decrease in the anisotropy of the spectrum on warming the crystal, with a single, nearly isotropic line being observed above 220 K. At 270 K the spectrum had axial symmetry about the c axis with Kn = 2.23 ± 0.01 and g~ = 2.25 ± 0.01 . The temperature evolution of the spectrum was interpreted in terms of a Boltzmann distribution over inequivalent distorted Jahn-Teller configurations, with one potential well lowered by an amount L1:::::: I 05 em- 1 below the other two

УЗЕЛКИ ДОИЛЬЩИЦ. СЛОЖНОСТИ В ИДЕНТИФИКАЦИИ ИНФЕКЦИЙ ДОМАШНИХ ЖИВОТНЫХ И УГРОЗА ПАЦИЕНТАМ С ОСЛАБЛЕННЫМ ИММУНИТЕТОМ

Milker’s nodules, also called paravaccinia, is a DNA virus transmitted from infected cows to humans. It results from contact with cattle, cattle byproducts, or fomites. Classified as an occupational disorder, those at risk of exposure include farmers, butchers, and agricultural tourists. The viral infection begins 5—15 days after inoculation as an erythematous-purple, round nodule with a clear depressed center, and a surrounding erythematous ring. While familiar to those in farming communities, the presence of the nodule may be concerning to others, particularly the immunosuppressed. Milker’s nodules are selflimited in immunocompetent individuals and heal without scarring within 8 weeks. Another member of the Parapoxvirus genus, the orf virus, is also transmitted from animals to humans by direct-contact. While complications are rare, hematopoietic stem cell transplant recipients are at risk of graft-versus-host disease, as the parapoxvirus may trigger these complications in immunocompromised individuals. In addition, paravaccinia may serve as the antigen source for the development of erythema multiforme. The unique structure and replication process of viruses in the Poxvirus family, while includes the Parapoxvirus genus, have been a focus for treatment of infections and cancer. Manipulation of these viruses has demonstrated promising therapeutic possibilities as vectors for vaccines and oncologic therapy.Узелки доильщиц, также известные как паравакциния, являются заболеванием, вызываемым ДНК-содержащим вирусом, который передается от зараженных коров к человеку. Передача происходит при контакте с крупным рогатым скотом, его субпродуктами или выделениями животных. Рассматриваемые узелки классифицируются как профессиональное заболевание, риску которого подвержены фермеры, мясники и агротуристы. Вирусное заражение начинается через 5—15 дней после инокуляции в виде фиолетового эритематозного круглого узелка с четким вдавлением в центре и окружающим его эритематозным кольцом. Кроме того, в фермерских сообществах появление узелков может затронуть и людей с ослабленным иммунитетом. Узелки самостоятельно разрешаются у лиц без ослабленного иммунитета и заживают без образования рубцов в течение 8 недель. Другой представитель рода Парапоксвирусы — контагиозная эктима, также передается от животных к человеку при непосредственном контакте. Осложнения встречаются достаточно редко, однако при трансплантации гемопоэтических стволовых клеток реципиент подвергается риску возникновения реакции «трансплантат против хозяина», а парапоксвирус может вызывать осложнения у лиц с ослабленным иммунитетом. Кроме того, паравакциния может стать источником антигена для развития многоформной эритемы. Уникальная структура и процесс репликации вирусов семейства Поксвирус, также включающего род Парапоксвирусы, активно исследуется при лечении различных инфекций и рака. Работа с данными вирусами открыла перспективные терапевтические возможности для направленных вакцин и лечения онкологических заболеваний

Single-ion and exchange anisotropy effects and multiferroic behavior in high-symmetry tetramer single molecule magnets

We study single-ion and exchange anisotropy effects in equal-spin $s_1$ tetramer single molecule magnets exhibiting $T_d$, $D_{4h}$, $D_{2d}$, $C_{4h}$, $C_{4v}$, or $S_4$ ionic point group symmetry. We first write the group-invariant quadratic single-ion and symmetric anisotropic exchange Hamiltonians in the appropriate local coordinates. We then rewrite these local Hamiltonians in the molecular or laboratory representation, along with the Dzyaloshinskii-Moriay (DM) and isotropic Heisenberg, biquadratic, and three-center quartic Hamiltonians. Using our exact, compact forms for the single-ion spin matrix elements, we evaluate the eigenstate energies analytically to first order in the microscopic anisotropy interactions, corresponding to the strong exchange limit, and provide tables of simple formulas for the energies of the lowest four eigenstate manifolds of ferromagnetic (FM) and anitiferromagnetic (AFM) tetramers with arbitrary $s_1$. For AFM tetramers, we illustrate the first-order level-crossing inductions for $s_1=1/2,1,3/2$, and obtain a preliminary estimate of the microscopic parameters in a Ni$_4$ from a fit to magnetization data. Accurate analytic expressions for the thermodynamics, electron paramagnetic resonance absorption and inelastic neutron scattering cross-section are given, allowing for a determination of three of the microscopic anisotropy interactions from the second excited state manifold of FM tetramers. We also predict that tetramers with symmetries $S_4$ and $D_{2d}$ should exhibit both DM interactions and multiferroic states, and illustrate our predictions for $s_1=1/2, 1$.Comment: 30 pages, 14 figures, submitted to Phys. Rev.

Observation of the cubic-field splitting of an excited S = 2 manifold in a cubic copper tetramer

EPR measurements on single crystals of Cu40Cl6(triphenylphosphine oxide)4 at liquid helium temperatures in the frequency ranges 14-17 and 34-35 GHz were fitted to a simple cubicS= 2 spin Hamiltonian with g = 2.10 ± 0.01 and a zero-field splitting of(0.53 ± 0.01) em - 1 • From the decrease in intensity of the S = 2 spectrum on cooling below 4.2 K and the absence of an S = 1 spectrum, the S = 2 manifold was deduced to lie ( 14 ± 1) em- 1 above a nonmagnetic ground state. The EPR results are used as a test of the various theories developed to explain the magnetic susceptibility of copper tetramer