Infrared catastrophe in two-quasiparticle collision integral

Relaxation of a non-equilibrium state in a disordered metal with a spin-dependent electron energy distribution is considered. The collision integral due to the electron-electron interaction is computed within the approximation of a two-quasiparticle scattering. We show that the spin-flip scattering processes with a small energy transfer may lead to the divergence of the collision integral for a quasi one-dimensional wire. This divergence is present only for a spin-dependent electron energy distribution which corresponds to the total electron spin magnetization M=0 and only for non-zero interaction in the triplet channel. In this case a non-perturbative treatment of the electron-electron interaction is needed to provide an effective infrared cut-off.Comment: 6 pages, 3 figure

Enhancement of Tc in the Superconductor-Insulator Phase Transition on Scale-Free Networks

A road map to understand the relation between the onset of the superconducting state with the particular optimum heterogeneity in granular superconductors is to study a Random Tranverse Ising Model on complex networks with a scale-free degree distribution regularized by and exponential cutoff p(k) \propto k^{-\gamma}\exp[-k/\xi]. In this paper we characterize in detail the phase diagram of this model and its critical indices both on annealed and quenched networks. To uncover the phase diagram of the model we use the tools of heterogeneous mean-field calculations for the annealed networks and the most advanced techniques of quantum cavity methods for the quenched networks. The phase diagram of the dynamical process depends on the temperature T, the coupling constant J and on the value of the branching ratio / where k is the degree of the nodes in the network. For fixed value of the coupling the critical temperature increases linearly with the branching ration which diverges with the increasing cutoff value \xi or value of the \gamma exponent \gamma< 3. This result suggests that the fractal disorder of the superconducting material can be responsible for an enhancement of the superconducting critical temperature. At low temperature and low couplings T<<1 and J<<1, instead, we observe a different behavior for annealed and quenched networks. In the annealed networks there is no phase transition at zero temperature while on quenched network we observe a Griffith phase dominated by extremely rare events and a phase transition at zero temperature. The Griffiths critical region, nevertheless, is decreasing in size with increasing value of the cutoff \xi of the degree distribution for values of the \gamma exponents \gamma< 3.Comment: (17 pages, 3 figures

Magnetically frustrated synthetic end member Mn2(PO4)OH in the triplite-triploidite family

The manganese end member of triplite-triploidite series of compounds, Mn2(PO4)OH, is synthesized by a hydrothermal method. Its crystal structure is refined in the space group P21/c with a = 12.411(1) Å, b = 13.323(1) Å, c = 10.014(1) Å, β = 108.16(1), V = 1573.3 Å3, Z = 8, and R = 0.0375. Evidenced in measurements of magnetization M and specific heat Cp, Mn2(PO4)OH reaches a long range antiferromagnetic order at TN = 4.6 K. As opposed to both triplite Mn2(PO4)F and triploidite-type Co2(PO4)F, the title compound is magnetically frustrated being characterized by the ratio of Curie-Weiss temperature Θ to Néel temperature TN of about 20. The large value of frustration strength Θ/TN stems from the twisted saw tooth chain geometry of corner sharing triangles of Mn polyhedra, which may be isolated within tubular fragments of a triploidite crystal structure. © 2017 The Royal Society of Chemistry.We thank E. V. Guseva for the X-ray spectral analysis of the sample and N. V. Zubkova for her help in the X-ray experiment. This work was supported by the Ministry of Education and Science of the Russian Federation in the framework of Increase Competitiveness Program of NUST "MISiS" project K2-2016-066 and by RFBR projects 15-05-06742, 16-02-00021 and 17-02-00211. The work was supported by Act 211 Government of the Russian Federation, contracts 02.A03.21.0004, 02.A03.21.0006 and 02.A03.21.0011

Laser therapy in ROP: a literature review and our experience

Introduction: Retinopathy of prematurity (ROP) is a serious, vision threatening disease and among the leading causes of irreversible loss of vision. It affects prematurely born children, predominantly prior to the 32nd GW or with a body weight at birth below 1500 g. The highest risk for the development of ROP includes the time period of two weeks before to two weeks after the supposed due date. Materials and Methods: We included 10 prematurely born children with ROP requiring therapy. All of the children were screened by indirect ophthalmoscopy and the condition was documented by RetCam imaging. The treatment was conducted by the application of 810 nm diode laser. Results: Nine out of the 10 children were born before 32 GW and were with a body weight at birth below 1500 g. The disease was bilateral in 9 of the children. Laser therapy was applied to all 10 children and 18 eyes. Discussion and Conclusion: The active ophthalmological screening of all children born before 32 GW and with a body weight at birth below 1500 g, including all new-born children at risk, and the application of early laser treatment are the basis for the prevention of the development of irreversible visual loss

Pseudostrabismus, masking manifest strabismus

Въведение: Често диагнозата страбизъм е "изписана на лицето", особено при голям ъгъл на отклонение.Въпреки това диагностичната дилема с риск от хипердиагностика е налице, особено при деца с епикантус, телекантус, положителен или отрицателен ъгъл капа. Обратно, в някои случаи без козметичен вид на кривогледство, се установява дълбоко разстройство на бинокулярното зрение (анормална ретинена кореспонденция, амблиопия, централен скотом, редуцирана стерео острота) - микрострабизъм.Псевдострабизмът може да съществува едновременно с истински страбизъм, като козметично го неутрализира, преувеличава или дори създава илюзия за кривене в обратна посока.Цел: Да покажем интересни случаи с псевдострабизъм, съществуващ едновременно с истински страбизъм.Материал и методи: Представени са два клинични случаи на деца с регресирала форма на ретинопатия на недоносените (РН, ROP) и положителен ъгъл капа в резултат от ектопия на макулата. Използвани са офталмологични и артоптични методи.Резултати: В единия случай псевдоекзотропията козметично компенсира напълно съществуващата истинска есотропия, a в другия случай при наличие на голям ъгъл есотропия, козметичният вид е на екзотропия.Заключение: Децентрацията на корнео-фовеоларният рефлекс по Хиршберг не доказва страбизъм, нито измерва ъгъла на кривене. Диагнозата за истинска хетеротропия или хетерофория се поставя след cover/uncover тест. Така може да се натъкнем на съществени разлики между видимото и истинско кривене. Правилната диагностика е важна за правилното ортоптично и хирургична лечение на страбизма.Introduction: The diagnosis strabismus is often "written on the face", especially in cases with large angle of deviation. Nevertheless, the diagnostic dilemma with a risk of hyperdiagnosis is present, especially in children with epicanthus, telecanthus, positive or negative kappa angle. Conversely, in some cases without a cosmetic appearance of squinting, there is a severe impairment of binocular vision (abnormal retinal correspondence, amblyopia, central scotoma, reduced stereo vision) - microstrabismus. Pseudostrabismus may coexist with real strabismus, cosmetically neutralizing it, exaggerating it or even creating an illusion of squinting in the opposite direction.Objective: To report interesting cases with pseudostrabismus, coexisting with real manifest strabismus.Material and Methods: We present two clinical cases of children with cicatricial retinopathy of prematurity (ROP) and positive angle kappa, resulting from ectopia of the macula. We use ophthalmic and ortoptic methods.Results: In one case the existing real esotropia is fully cosmetically compensated by pseudoexotropia. The other case has cosmetic appearance of exotropia, while a large angle of esotropic deviation is present on cover/uncover test.Conclusion: Decentration of the corneo-foveal reflex (Hirshberg) does not diagnose strabismus, nor it measures the angle of deviation. Diagnosis for real heterotropia or heterophoria is done only after cover/uncover test. Thus, we may encounter significant differences between visible and real squinting. Correct diagnosis of strabismus is important for the right ortoptic and surgical treatment

Helical vortex phase in the non-centrosymmetric CePt_3Si

We consider the role of magnetic fields on the broken inversion superconductor CePt_3Si. We show that upper critical field for a field along the c-axis exhibits a much weaker paramagnetic effect than for a field applied perpendicular to the c-axis. The in-plane paramagnetic effect is strongly reduced by the appearance of helical structure in the order parameter. We find that to get good agreement between theory and recent experimental measurements of H_{c2}, this helical structure is required. We propose a Josephson junction experiment that can be used to detect this helical order. In particular, we predict that Josephson current will exhibit a magnetic interference pattern for a magnetic field applied perpendicular to the junction normal. We also discuss unusual magnetic effects associated with the helical order.Comment: 5 pages, 2 figures, Accepted as Phys Rev. Lette