Confined chiral polymer nematics: ordering and spontaneous condensation

We investigate condensation of a long confined chiral nematic polymer inside a spherical enclosure, mimicking condensation of DNA inside a viral capsid. The Landau-de Gennes nematic free energy {\sl Ansatz} appropriate for nematic polymers allows us to study the condensation process in detail with different boundary conditions at the enclosing wall that simulate repulsive and attractive polymer-surface interactions. Increasing the chirality, we observe a transformation of the toroidal condensate into a closed surface with an increasing genus, akin to the ordered domain formation observed in cryo-microscopy of bacteriophages

Tensorial conservation law for nematic polymers

We derive the "conservation law" for nematic polymers in tensorial form valid for quadrupolar orientational order in contradistinction to the conservation law in the case of polar orientational order. Due to microscopic differences in the coupling between the orientational field deformations and the density variations for polar and quadrupolar order, we find that respective order parameters satisfy fundamentally distinct constraints. Being necessarily scalar in its form, the tensorial conservation law is obtained straightforwardly from the gradients of the polymer nematic tensor field and connects the spatial variation of this tensor field with density variations. We analyze the differences between the polar and the tensorial forms of the conservation law, present some explicit orientational fields that satisfy this new constraint and discuss the role of singular "hairpins", which do not affect local quadrupolar order of polymer nematics, but nevertheless influence its gradients.Comment: 10 pages, 6 figure

Težka akutna zastrupitev z bakrovim sulfatom - prikaz primera

As copper sulphate pentahydrate (CSP) is a common compound used in agriculture and industry, chronic occupational exposures to CSP are well known, but acute poisoning is rare in the Western world. This case report describes acute poisoning of a 33-year-old woman who attempted suicide by ingesting an unknown amount of CSP. On admission to the hospital, she had symptoms and signs of severe hemorrhagic gastroenteritis, dehydration, renal dysfunction and methaemoglobinaemia with normal serum copper level. Therapy included early gastric lavage, fluid replacement, vasoactive drugs, furosemide, antiemetic drugs, ranitidine, and antidotes methylene blue and 2,3-dimercaptopropane-1-sulphonate (DMPS). However, the patient developed severe intravascular haemolysis, acute severe hepatic and renal failure, as well as adrenal insufficiency. After prolonged, but successful hospital treatment, including haemodialysis and IV hydrocortisone, the patient was discharged with signs of mild renal and liver impairment. Our conclusion is that in severe cases of copper poisoning early supportive measures are essential. In addition, antidotes such as methylene blue for methaemoglobinaemia and chelating agent such as DMPS improve morbidity and survival of severely poisoned victims.Bakrov sulfat pentahidrat (BSP) se pogosto uporablja v kmetijstvu in industriji, zato so kronične poklicne zastrupitve dobro poznane, akutne zastrupitve pa so v razvitem svetu redke. Opisujemo primer akutne zastrupitve zaradi poskusa samomora pri 33-letni ženski zaradi zaužitja neznane količine BSP. Ob sprejemu so bili prisotni simptomi in znaki težkega hemoragičnega gastroenteritisa, izsušitve, razvijajoče se ledvične odpovedi in methemoglobinemije z normalno vrednostjo bakra v serumu. Takoj smo sprali želodec in začeli iv. dajati tekočine, kateholamine, furosemid, antiemetik, ranitidin in antidota metilensko modrilo in 2,3- dimerkaptopropan-1-sulfonat (DMPS). Kljub zgodnjim ukrepom se je razvila težka znotrajžilna hemoliza, težka akutna jetrna in ledvična odpoved ter odpoved nadledvičnice. Po dolgem, vendar uspešnem zdravljenju, vključno z zdravljenjem s hemodializo in iv. steroidi, je bila bolnica odpuščena z znaki blage ledvične in jetrne okvare. Zaključujemo, da je pri težkih zastrupitvah z bakrom zgodnje simptomatsko zdravljenje prvi najpomembnejši ukrep. Uporaba antidotov, kot je metilensko modrilo pri methemoglobinemiji, in ionskih izmenjevalcev, kot je DMPS, pa dodatno zmanjša obolevnost in izboljša preživetje težko zastrupljenih

Magneto-optic dynamics in a ferromagnetic nematic liquid crystal

We investigate dynamic magneto-optic effects in a ferromagnetic nematic liquid crystal experimentally and theoretically. Experimentally we measure the magnetization and the phase difference of the transmitted light when an external magnetic field is applied. As a model we study the coupled dynamics of the magnetization, M, and the director field, n, associated with the liquid crystalline orientational order. We demonstrate that the experimentally studied macroscopic dynamic behavior reveals the importance of a dynamic cross-coupling between M and n. The experimental data are used to extract the value of the dissipative cross-coupling coefficient. We also make concrete predictions about how reversible cross-coupling terms between the magnetization and the director could be detected experimentally by measurements of the transmitted light intensity as well as by analyzing the azimuthal angle of the magnetization and the director out of the plane spanned by the anchoring axis and the external magnetic field. We derive the eigenmodes of the coupled system and study their relaxation rates. We show that in the usual experimental set-up used for measuring the relaxation rates of the splay-bend or twist-bend eigenmodes of a nematic liquid crystal one expects for a ferromagnetic nematic liquid crystal a mixture of at least two eigenmodes.Comment: 20 pages, 23 figures, 42 reference