Robust upward dispersion of the neutron spin resonance in the heavy fermion superconductor Ce1-xYbxCoIn5.

The neutron spin resonance is a collective magnetic excitation that appears in the unconventional copper oxide, iron pnictide and heavy fermion superconductors. Although the resonance is commonly associated with a spin-exciton due to the d(s±)-wave symmetry of the superconducting order parameter, it has also been proposed to be a magnon-like excitation appearing in the superconducting state. Here we use inelastic neutron scattering to demonstrate that the resonance in the heavy fermion superconductor Ce1-xYbxCoIn5 with x=0, 0.05 and 0.3 has a ring-like upward dispersion that is robust against Yb-doping. By comparing our experimental data with a random phase approximation calculation using the electronic structure and the momentum dependence of the -wave superconducting gap determined from scanning tunnelling microscopy (STM) for CeCoIn5, we conclude that the robust upward-dispersing resonance mode in Ce1-xYbxCoIn5 is inconsistent with the downward dispersion predicted within the spin-exciton scenario.

The anaesthetist's SonoSite Probe - Successful adjunct to complex intradural spinal surgery or poor man's intraoperative ultrasound?

The use of expensive, sophisticated, intraoperative ultrasound systems is established in cranial neurosurgery and less so in the realms of intradural spine. For units yet to acquire such costly devices, we demonstrate our experience of the readily available, anaesthetist's SonoSite™ probe in intradural spinal surgery.

Weak hybridization and isolated localized magnetic moments in the compounds CeT2Cd20 (T = Ni, Pd).

We report the physical properties of single crystals of the compounds CeT2Cd20 (T = Ni, Pd) that were grown in a molten Cd flux. Large separations of ∼6.7-6.8 Šbetween Ce ions favor the localized magnetic moments that are observed in measurements of the magnetization. The strength of the Ruderman-Kittel-Kasuya-Yosida magnetic exchange interaction between the localized moments is severely limited by the large Ce-Ce separations and by weak hybridization between localized Ce 4 f and itinerant electron states. Measurements of electrical resistivity performed down to 0.138 K were unable to observe evidence for the emergence of magnetic order; however, magnetically-ordered ground states with very low transition temperatures are still expected in these compounds despite the isolated nature of the localized magnetic moments. Such a fragile magnetic order could be highly susceptible to tuning via applied pressure, but evidence for the emergence of magnetic order has not been observed so far in our measurements up to 2.5 GPa.

Nodal to nodeless superconducting energy-gap structure change concomitant with fermi-surface reconstruction in the heavy-fermion compound CeCoIn(5).

The London penetration depth λ(T) was measured in single crystals of Ce_{1-x}R_{x}CoIn_{5}, R=La, Nd, and Yb down to T_{min}≈50 mK (T_{c}/T_{min}∼50) using a tunnel-diode resonator. In the cleanest samples Δλ(T) is best described by the power law Δλ(T)∝T^{n}, with n∼1, consistent with the existence of line nodes in the superconducting gap. Substitutions of Ce with La, Nd, and Yb lead to similar monotonic suppressions of T_{c}; however, the effects on Δλ(T) differ. While La and Nd substitution leads to an increase in the exponent n and saturation at n∼2, as expected for a dirty nodal superconductor, Yb substitution leads to n>3, suggesting a change from nodal to nodeless superconductivity. This superconducting gap structure change happens in the same doping range where changes of the Fermi-surface topology were reported, implying that the nodal structure and Fermi-surface topology are closely linked.

Crossover between Fermi liquid and non-Fermi liquid behavior in the non-centrosymmetric compound Yb2Ni12P7.

A crossover from a non-Fermi liquid to a Fermi liquid phase in Yb2Ni12P7 is observed by analyzing electrical resistivity ρ(T), magnetic susceptibility χ(T), specific heat C(T), and thermoelectric power S(T) measurements. The electronic contribution to specific heat, Ce(T), behaves as Ce(T)/T∼-ln(T) for 5 K4 K. A crossover between Fermi-liquid and non-Fermi liquid behavior suggests that Yb2Ni12P7 is in close proximity to a quantum critical point, in agreement with results from recent measurements of this compound under applied pressure.

Persistent non-metallic behavior in Sr2IrO4 and Sr3Ir2O7 at high pressures.

Iridium-based 5d transition-metal oxides are attractive candidates for the study of correlated electronic states due to the interplay of enhanced crystal-field, Coulomb and spin-orbit interaction energies. At ambient pressure, these conditions promote a novel Jeff = 1/2 Mott-insulating state, characterized by a gap of the order of ~0.1 eV. We present high-pressure electrical resistivity measurements of single crystals of Sr2IrO4 and Sr3Ir2O7. While no indications of a pressure-induced metallic state up to 55 GPa were found in Sr2IrO4, a strong decrease of the gap energy and of the resistance of Sr3Ir2O7 between ambient pressure and 104 GPa confirm that this compound is in the proximity of a metal-insulator transition.

Enhancement of superconductivity near the pressure-induced semiconductor-metal transition in the BiS2-based superconductors LnO0.5F0.5BiS2 (Ln = La, Ce, Pr, Nd).

Measurements of electrical resistivity were performed between 3 and 300 K at various pressures up to 2.8 GPa on the BiS2-based superconductors LnO0.5F0.5BiS2 (Ln=Pr, Nd). At lower pressures, PrO0.5F0.5BiS2 and NdO0.5F0.5BiS2 exhibit superconductivity with critical temperatures Tc of 3.5 and 3.9 K, respectively. As pressure is increased, both compounds undergo a transition at a pressure Pt from a low Tc superconducting phase to a high Tc superconducting phase in which Tc reaches maximum values of 7.6 and 6.4 K for PrO0.5F0.5BiS2 and NdO0.5F0.5BiS2, respectively. The pressure-induced transition is characterized by a rapid increase in Tc within a small range in pressure of ∼0.3 GPa for both compounds. In the normal state of PrO0.5F0.5BiS2, the transition pressure Pt correlates with the pressure where the suppression of semiconducting behaviour saturates. In the normal state of NdO0.5F0.5BiS2, Pt is coincident with a semiconductor-metal transition. This behaviour is similar to the results recently reported for the LnO0.5F0.5BiS2 (Ln=La, Ce) compounds. We observe that Pt and the size of the jump in Tc between the two superconducting phases both scale with the lanthanide element in LnO0.5F0.5BiS2 (Ln=La, Ce, Pr, Nd).

Giant Nernst effect and bipolarity in the quasi-one-dimensional metal Li0.9Mo6O17.

The Nernst coefficient for the quasi-one-dimensional metal, Li{0.9}Mo{6}O{17}, is found to be among the largest known for metals (ν≃500 µV/KT at T∼20 K), and is enhanced in a broad range of temperature by orders of magnitude over the value expected from Boltzmann theory for carrier diffusion. A comparatively small Seebeck coefficient implies that Li{0.9}Mo{6}O{17} is bipolar with large, partial Seebeck coefficients of opposite sign. A very large thermomagnetic figure of merit, ZT∼0.5, is found at high field in the range T≈35-50 K.

Observation of a martensitic structural distortion in V, Nb, and Ta.

Thermal-expansion measurements of the Group 5 elements V, Nb, and Ta reveal a structural distortion below 300 K. Data for single-crystalline Nb and Ta display anisotropic thermal expansion, martensitic in character, that is inconsistent with cubic crystal structures at low temperature. Published results on V show similar behavior. Interstitial impurities suppress the transition.

Anterior cervical foramenotomy for cervical radiculopathy.

Anterior cervical discectomy (ACD) is standard practice for cervical radiculopathy. Irrespective of the precise method used, it involves more or less complete disc removal with resultant anatomical and biomechanical derangements, and frequently the insertion of a bone or prosthetic graft. Anterior cervical foramenotomy is an alternative procedure that allows effective anterior decompression of the nerve root and lateral spinal cord, whilst conserving the native disc, preserving normal anatomy and movement, and protecting against later degeneration at adjacent spaces as far as possible. The aim of the study was to determine the safety and efficacy of anterior cervical foramenotomy in the treatment of cervical radiculopathy and took the form of a prospective study of 21 cases under the care of a single surgeon. All patients had a single level or two level anterior cervical foramenotomy. All had pre- and postoperative visual analogue scores for arm and neck pain, arm strength, sensation and overall use. A comparison between patients' perceptions and surgeon's observations was also made. Patients were followed up for between 10 and 36 months. Sixty-eight per cent completed full pre- and postoperative assessments. Twenty-eight per cent of the responders had complete arm pain resolution. There were statistically significant reductions in arm and neck pain, and overall disability. The surgeon's impression of improvement paralleled that of the patients. There was one complication with discitis. Anterior cervical foramenotomy is a safe and effective treatment for cervical radiculopathy caused by posterolateral cervical disc prolapse or uncovertebral osteophyte, and might also reduce adjacent segment degeneration.

Dimensional crossover in the purple bronze Li0.9Mo6O17.

Thermal expansion of Li0.9Mo6O17 is a-axis dominated which reduces the separation of the conducting chains at low temperature enhancing the interchain coupling. This destabilizes the Luttinger-liquid fixed point leading to an electronic charge- (or spin-) density wave dominated by Coulomb repulsion, as predicted by theories for Luttinger liquids.

To graft or not to graft: rationalizing choice in anterior cervical discectomy.

Anterior cervical discectomy has been performed for almost 50 years. Initially, bone grafts were used routinely, but soon their necessity was questioned. It remains disputed to this day. The aim was to establish whether there are grounds for basing choice of technique on individual patient data. The cervical spine radiographs of 148 patients who had undergone grafted or ungrafted anterior cervical discectomy were reviewed and changes in geometry at the operated level were measured. These data were then examined for any correlation between preoperative geometry, choice of operative technique and adverse clinical outcome. Disturbances to spinal geometry after ungrafted discectomy are minimal at disc heights below 4 mm. At and above 4 mm significant settlement and angulation occur. Complications in our series were fewer where small disc spaces were left ungrafted and larger ones grafted. Disc spaces below 4 mm should not be grafted, but spaces of 4 mm or more should.

Computed tomography diagnosis of tracheobronchopathia osteochondroplastica.

Tracheobronchopathia osteochondroplastica (TO) is a rare benign disease characterized by the presence of osseous and cartilaginous submucosal nodules projecting into the tracheobronchial tree. Most cases are asymptomatic and discovered incidentally at post-mortem. We identified a case of TO on thoracic spiral CT and confirmed the diagnosis of bronchoscopy. This article reviews the imaging characteristics of TO, and shows the 3-D virtual bronchoscopic and multiplanar reconstruction appearances of TO.

Corpus callosum changes following shunting for hydrocephalus: case report and review of the literature.

Diffuse callosal signal changes can rarely occur following successful shunting for obstructive hydrocephalus. We report on a patient who underwent ventriculoperitoneal shunting for aqueductal stenosis and required two revisions for neurological deterioration and presumed shunt malfunction. Extensive changes involving the corpus callosum, periventricular white matter and optic chiasm were noted after the first, and were prominent after second shunt revision. Thus, post-shunting callosal changes may be associated with more extensive white matter disease, and may not imply wide pressure fluctuations. However, they need not prompt further intervention.

Idiopathic anterior spinal cord hernia: under-recognized cause of thoracic myelopathy.

Until recently, idiopathic anterior spinal cord herniation was thought to be vanishingly rare. It is an increasingly recognized, readily treatable, condition causing progressive thoracic myelopathy. We have operated on five cases and know of two other patients locally who are as yet undecided on surgery. We are aware of several other unpublished cases in the UK. The syndrome presents typically in middle age with a history of stepwise slowly progressive mid-thoracic anterior hemicord dysfunction characterized by hemianalgesia below the affected segment followed by asymmetric lower limb hypertonia, with initial sparing of posterior column sensation, that progresses through paraparesis to complete paraplegia. The radiological findings, although subtle, are equally typical and surgical repair is easily effected. With increasing clinical and radiological awareness, we believe the apparent incidence of this condition will increase. Idiopathic anterior spinal cord hernia is more common than currently appreciated, and should be positively considered and excluded in every case of progressive thoracic cord dysfunction.

Low dietary protein is associated with an increase in food intake and a decrease in the in vitro release of radiolabeled glutamate and GABA from the lateral hypothalamus.

Moderately low-protein diets lead to a rapid increase in food intake and body fat. The increase in feeding is associated with a decrease in the concentration of serum urea nitrogen, suggesting that the low-protein-induced increase in food intake may be related to the decreased metabolism of nitrogen from amino acids. We hypothesized that low dietary protein would be associated with a decrease in the synaptic release of two nitrogen-containing neurotransmitters, GABA and glutamate, whose nitrogen can be derived from amino acids. In this study, we examined the effects of a low-protein diet (10% casein) in Sprague-Dawley rats on the in vitro release of 3H-GABA and 14C-glutamate from the lateral and medial hypothalamus. The low-protein diet increased food intake by about 25% after one day. After four days, the in vitro release of radiolabeled GABA and glutamate was assessed. The calcium-dependent, potassium-stimulated release of radiolabeled GABA and glutamate from the lateral hypothalamus was decreased in rats fed the low-protein diet. The magnitude of neurotransmitter release from the lateral hypothalamus inversely correlated with food intake. No dietary differences in the release of neurotransmitters from the medial hypothalamus were observed. These results support the contention that alterations in nitrogen metabolism are associated with low-protein-induced feeding.

A subdural haematoma following 'reverse' bungee jumping.

Bungee jumping has been exploited commercially for 13 years and proprietors claim a good safety record. However, published case reports document a wide variety of possible injuries. To this list, we add a report of a subdural haematoma sustained during a variant of the sport, the 'reverse' bungee jump.