Superconductivity versus quantum criticality: what can we learn from heavy fermions?

Two quantum critical point (QCP) scenarios are being discussed for different classes of antiferromagnetic (AF) heavy-fermion (HF) systems. In the itinerant one, where AF order is of the spin-density wave (SDW) type, the heavy 'composite' charge carriers keep their integrity at the QCP. The second one implies a breakdown of the Kondo effect and a disintegration of the composite fermions at the AF QCP. We discuss two isostructural compounds as exemplary materials for these two different scenarios: CeCu(2)Si(2) exhibits a three-dimensional (3D) SDW QCP and superconductivity, presumably mediated by SDW fluctuations, as strongly suggested by recent inelastic neutron scattering experiments. In Y bRh(2)Si(2), the AF QCP is found to coincide with a Kondo-destroying one. However, in the latter compound these two QCPs can be detached by varying the average unit-cell volume, e.g. through the application of chemical pressure, as realized by partial substitution of either Ir or Co for Rh. A comparison of CeCu(2)Si(2) and Y bRh(2)Si(2) indicates that the apparent differences in quantum critical behaviour go along with disparate behaviour concerning the (non-) existence of superconductivity (SC). No sign of SC could be detected in Y bRh(2)Si(2) down to mK temperatures. A potential correlation between the specific nature of the QCP and the occurrence of SC, however, requires detailed studies on further quantum critical HF superconductors, e.g. on β-Y bAlB(4), UBe(13), CeCoIn(5) and CeRhIn(5).

[Upper abdominal pain with recurrent cholangitis and pyelonephritis]

A 38-year-old man presented with pain in the right upper abdomen combined with elevated C-reactive protein (5.37 mg/dl) and creatinine levels (2.0 mg/dl). The medical history revealed recurrent abdominal pain. Duplex sonography showed large intrahepatic cystic structures, partially combined with a ribbon-shaped flow signal inside, as well as multiple cysts in the kidneys. The following MRI identified these findings as dilatated bile ducts surrounding the portal vein branches. This is known as the central dot sign. Overall, this special constellation is indicative of Caroli's disease, a rare congenital cystic dilatation of the intrahepatic bile ducts. The imaging results substantiated the diagnosis, especially in combination with cystic renal disease and recurrent cholangitis. Depending on the grade of liver involvement the treatment is partial hepatectomy or, as in our case transplantation, which also eliminates the risk of associated cholangiocarcinoma.

Mutation frequency of NS5A in patients vertically infected with HCV genotype 1 predicts sustained virological response to peginterferon alfa-2b and ribavirin combination therapy

Viral genome analyses performed in adult HCV-patients yielded very inconsistent results and are not transferable to children who are often infected vertically during a state of high immune tolerance. We analysed the mutational frequency in the PKR-binding domain (PKR-BD) of NS5A and PePHD of E2 protein pre- and post-treatment with peginterferon-alfa-2b and ribavirin in children chronically infected with HCV genotype 1. Amino acid sequences of NS5A (2 209-2 274) and E2 (618-681) were determined in serum samples using standard PCR procedures. Concerning the PKR-BD a significant higher number of mutations was observed in vertically compared to horizontally infected patients (2.14 vs 1.24, P-value = 0.03). This difference was exclusively based on the increased number of mutations in responders vs non-responders in vertically infected patients (2.95 vs 1.33; P-value = 0.02). While all patients with at least four mutations (n = 3) did respond to therapy, no other predictive parameters could be identified. In the PePHD no differences could be observed between either of these groups. These findings support the idea that viral properties, mode and therewith time of infection in terms of immune tolerance are equally important factors for predicting SVR in children. However given the low number of cases further studies are required to confirm this hypothesis.

Necromenic life style of Histiostoma polypori (Acari: Histiostomatidae)

Histiostoma polypori (Histiostomatidae, Astigmata) is associated with the earwig Forficula auricularia, which has an interesting brood behavior: the adult earwig female cares for her eggs and stays with the N2 and N3 nymphs in the nest. Deutonymphs of H. polypori only leave the female earwig to develop on dead earwig N2 and N3 nymphs. The newly molted deutonymphs attach to live earwig N3 nymphs. The earwig's cleaning behavior displaces the deutonymphs to the exuvial suture, around the area between cephalon and prothorax. From there, deutonymphs switch from one earwig stage to the following, always occupying that region. Histiostoma polypori obviously has a necromenic life style, that is, it ascends a carrier organism and develops on the carrier's cadavers. Necromeny within the Histiostomatidae presumably derived at least twice convergently from phoretic transport.

Pregnancy outcome in maternal Crigler-Najjar syndrome type II: a case report and systematic review of the literature

OBJECTIVE

To report a case of maternal Crigler-Najjar syndrome (CNS) type II in pregnancy, systematically review the literature for similar case reports, and to evaluate whether pregnancy is safe in patients with the disease. Data sources included the PubMed and up to date databases.

RESULTS

A 37-year-old mother with CNS type II was treated with phenobarbital during her pregnancy and her bilirubin levels were monitored. Her newborn had mild direct hyperbilirubinemia, did not require any treatment and his postnatal follow-up showed normal growth and development as well as normal hearing.

CONCLUSION

CNS type II is rare, and only a few pregnancies with this condition have been reported. Maternal treatment with phenobarbital lowers the unconjugated bilirubin and avoids fetal and newborn sequelae.

Bilateral obstetric brachial plexus paralysis: a case report

BACKGROUND

Whereas cases of unilateral obstetric brachial plexus paralysis have been sufficiently described and discussed in the literature cases of bilateral obstetric brachial plexus paralysis are extremely rare and so far have not been mentioned and discussed satisfactorily.

PATIENTS

We present a case of bilateral obstetric brachial plexus paralysis in an 8-months-old white boy. We performed a neurotisation of the Nervus suprascapularis with the Nervus accessorius and an Oberlin procedure on both sides in two operative steps.

RESULTS

In an early follow-up 6 months after the second operation and intensive physiotherapy the little patient was able to crawl with the active help of both arms.

CONCLUSIONS

Bilateral obstetric brachial plexus paralysis is a very rare incidence in infants. An interdisciplinary approach including paediatrics, plastic surgeons, neurosurgeons, neurologists, radiologists and physiotherapists is essential for the success of treatment strategies in such cases.

Phase transitions and rare-earth magnetism in hexagonal and orthorhombic DyMnO(3) single crystals

The floating-zone method with different growth ambiences has been used to selectively obtain hexagonal or orthorhombic DyMnO(3) single crystals. The crystals were characterized by x-ray powder diffraction of ground specimens and a structure refinement as well as electron diffraction. We report magnetic susceptibility, magnetization and specific heat studies of this multiferroic compound in both the hexagonal and the orthorhombic structure. The hexagonal DyMnO(3) shows magnetic ordering of Mn(3+) (S = 2) spins on a triangular Mn lattice at T(N)(Mn) = 57 K characterized by a cusp in the specific heat. This transition is not apparent in the magnetic susceptibility due to the frustration on the Mn triangular lattice and the dominating paramagnetic susceptibility of the Dy(3+) (S = 9/2) spins. At T(N)(Dy) = 3 K, a partial antiferromagnetic order of Dy moments has been observed. In comparison, the magnetic data for orthorhombic DyMnO(3) display three transitions. The data broadly agree with results from earlier neutron diffraction experiments, which allows for the following assignment: a transition from an incommensurate antiferromagnetic ordering of Mn(3+) spins at T(N)(Mn) = 39 K, a lock-in transition at T(lock-in) = 16 K and a second antiferromagnetic transition at T(N)(Dy) = 5 K due to the ordering of Dy moments. Both the hexagonal and the orthorhombic crystals show magnetic anisotropy and complex magnetic properties due to 4f-4f and 4f-3d couplings.

Investigations on the spin-glass state in Dy(0.5)Sr(0.5)MnO(3) single crystals through structural, magnetic and thermal properties

Single crystals of Dy(0.5)Sr(0.5)MnO(3) are grown using the optical floating zone technique, and their structural, magnetic, transport and thermal properties have been investigated. Magnetization measurements under field-cooled and zero-field-cooled conditions display irreversibility below 35 K. The magnetization does not saturate up to fields of 5 T in the temperature range 5-350 K. AC susceptibility shows a cusp around 32 K that shifts to higher temperature with increasing frequency. This frequency dependence of the peak temperature follows a critical slowing down with exponent zν = 3.6. Electrical resistivity shows insulating behavior, and the application of magnetic fields up to 10 T does not change this qualitative behavior. However, a marked negative magnetoresistance is observed in the paramagnetic phase reaching 80% at 70 K and 10 T. The observed resistivity behavior does not obey an activated type of conduction. These features are characteristic of spin-glass behavior in this half-doped insulating manganite. It is argued that the spin-glass-like state originates from the A-site disorder, which in turn results from the random distribution of cations with different ionic radii. Specific-heat measurements reveal a sizable linear contribution at low temperature that may be associated with the glassy magnetic ordering and a Schottky-like anomaly in a wide temperature range between 8 and 40 K. The distribution of Schottky levels is explained by the inhomogeneity of the molecular field in the spin-glass state that leads to variable splitting of the Kramers ground-state doublets in Dy(3+).