Complex magnetic structure and magnetocapacitance response in a non-oxide NiF2 system.

We report here on the complex magnetic structure and magnetocapacitance in NiF2, a non-oxide multifunctional system. It undergoes an anti-ferromagnetic transition near 68.5 K, superimposed with canted Ni spin driven weak ferromagnetic ordering, followed by a metastable ferromagnetic phase at or below 10 K. Our density functional calculations account for the complex magnetic structure of NiF2 deduced from the temperature and the field dependent measurements. Near room temperature, NiF2 exhibits a relatively large dielectric response reaching >103 with a low dielectric loss of <0.5 at frequencies >20 Hz. This is attributed to the intrinsic grain contribution in contrast to the grain boundary contribution in most of the known dielectric materials. The response time is 10 µs or more at 280 K. The activation energy for such temperature dependent relaxation is ~500 meV and is the main source for grain contribution. Further, a large negative magneto capacitance >90% is noticed in 1 T magnetic field. We propose that our findings provide a new non-oxide multifunctional NiF2, useful for dielectric applications.

Intra-Vial Heterogeneity in Physical Form of Mannitol in Colyophilized Binary Systems.

PURPOSE: To study spatial heterogeneity in phase composition when mannitol is co-lyophilized with non-crystallizing lyoprotectant, such as sucrose or trehalose. To study the influence of formulation composition and processing conditions on the extent of mannitol hemihydrate (MHH) formation in the final lyophile. METHODS: We used synchrotron X-ray diffractometry (XRD) to spatially map and thereby comprehensively characterize mannitol phase composition in unperturbed lyophiles. Low temperature thermal analysis and XRD was used to study phase behavior of frozen systems. RESULT: When colyophilized with sucrose, trehalose or lysozyme as a second solute, mannitol crystallized partially as MHH (mannitol hemihydrate). The MHH content, based on the intensity of characteristic MHH peak (d-spacing 4.92 Å), was highest in the middle region of lyophile. This heterogeneity, studied in detail in presence of sucrose, occurred irrespective of cosolute content. Annealing the frozen solution at -30°C for 2 h essentially eliminated the heterogeneity, accompanied by an overall increase in MHH content. From differential scanning calorimetry it was evident that annealing caused mannitol crystallization while XRD revealed the crystallizing phase to be MHH. CONCLUSION: The intra-vial heterogeneity and total MHH content in the final lyophile is a complex interplay of formulation composition and processing conditions. Graphical Abstract Figure depicting spatial heterogeneity in mannitol hemihydrate content, when mannitol is lyophilized with a cosolute, such as sucrose, trealose or lysozyme.

Annealing effect reversal by water sorption-desorption and heating above the glass transition temperature-comparison of properties.

Our objective is to compare the physical properties of materials obtained from two different methods of annealing reversal, that is, water sorption-desorption (WSD) and heating above glass transition temperature (HAT). Trehalose was annealed by storing at 100 °C for 120 h. The annealing effect was reversed either by WSD or HAT, and the resulting materials were characterized by differential scanning calorimetry (DSC), water sorption studies, and positron annihilation spectroscopy (PAS). While the products obtained by the two methods of annealing reversal appeared to be identical by conventional characterization methods, they exhibited pronounced differences in their water sorption behavior. Positron annihilation spectroscopy (PAS), by measuring the fractional free volume changes in the processed samples, provided a mechanistic explanation for the differences in the observed behavior.

Magnetic order in hybrid frustrated magnets Gd(2-x)Tb(x)Ti2O7 (x = 0.2 and 0.5).

We report on the specific heat, magnetization and ac susceptibility measurements of single crystals of hybrid frustrated magnets Gd(1.8)Tb(0.2)Ti(2)O(7) and Gd(1.5)Tb(0.5)Ti(2)O(7). The analysis of experimental data revealed that, although partial replacing of the Gd(3+) ions by the Tb(3+) ions in the Gd(2)Ti(2)O(7) host lattice slightly enhances antiferromagnetic coupling, as inferred from the evolution of the paramagnetic Curie-Weiss temperature, the ordering temperature gradually decreases. Paramagnetic correlations introduced by the Tb(3+) ions cause this perturbation, altering the effective further neighbor interactions and destabilizing the ground state in Gd(2)Ti(2)O(7). In addition, the low-energy states of Gd(2-x)Tb(x)Ti(2)O(7) are suggested to possess a nature different from those in parent members Tb(2)Ti(2)O(7) and Gd(2)Ti(2)O(7). Finally, the frequency-dependent magnetic susceptibility behavior in Gd(1.5)Tb(0.5)Ti(2)O(7) is consistent with the formation of a spin-glass-like state indicating a pronounced slowing down of the dynamical response of the studied hybrid magnets.

Pressure-induced colossal piezoresistance effect and the collapse of the polaronic state in the bilayer manganite (La(0.4)Pr(0.6))(1.2)Sr(1.8)Mn2O7.

We have investigated the effect of hydrostatic pressure as a function of temperature on the resistivity of a single crystal of the bilayer manganite (La(0.4)Pr(0.6))(1.2)Sr(1.8)Mn(2)O(7). Whereas a strong insulating behaviour is observed at all temperatures at ambient pressure, a clear transition into a metallic-like behaviour is induced when the sample is subjected to a pressure (P) of ~1.0 GPa at T < 70 K. A huge negative piezoresistance ~10(6) in the low temperature region at moderate pressures is observed. When the pressure is increased further (5.5 GPa), the high temperature polaronic state disappears and a metallic behaviour is observed. The insulator to metal transition temperature exponentially increases with pressure and the distinct peak in the resistivity that is observed at 1.0 GPa almost vanishes for P > 7.0 GPa. A modification in the orbital occupation of the e(g) electron between 3d(x(2)-y(2)) and 3d(z(2)-r(2)) states, as proposed earlier, leading to a ferromagnetic double-exchange phenomenon, can qualitatively account for our data.

Electronic confinement and ordering instabilities in colossal magnetoresistive bilayer manganites.

We present angle-resolved photoemission studies of (La{1-z}Pr{z}){2-2x}Sr{1+2x}Mn{2}O{7} with x=0.4 and z=0.1, 0.2, and 0.4 along with density functional theory calculations and x-ray scattering data. Our results show that the bilayer splitting in the ferromagnetic metallic phase of these materials is small, if not completely absent. The charge carriers are therefore confined to a single MnO{2} layer, which in turn results in a strongly nested Fermi surface. In addition to this, the spectral function also displays clear signatures of an electronic ordering instability well below the Fermi level. The increase of the corresponding interaction strength with z and its magnitude of ∼400 meV make the coupling to a bare phonon highly unlikely. Instead we conclude that fluctuating order, involving electronic and lattice degrees of freedom, causes the observed renormalization of the spectral features.

Anomalous temperature dependence of phonons and photoluminescence bands in pyrochlore Er2Ti2O7: signatures of structural deformation at 130 K.

We report a Raman study of single crystal pyrochlore Er(2)Ti(2)O(7) as a function of temperature from 12 to 300 K. In addition to the phonons, various photoluminescence (PL) lines of Er(3+) in the visible range are also observed. Our Raman data show an anomalous red-shift of two phonons (one at ~200 cm(-1) and another at ~520 cm(-1)) upon cooling from room temperature which is attributed to phonon-phonon anharmonic interactions. However, the phonons at ~310, 330, and 690 cm(-1) initially show a blue-shift upon cooling from room temperature down to about 130 K, followed by a red-shift, indicating a structural deformation at ~130 K. The intensities of the PL bands associated with the transitions between the various levels of the ground state manifold ((4)I(15/2)) and the (2)H(11/2) as well as (4)S(3/2) excited state manifolds of Er(3+) show a change at ~130 K. Moreover, the temperature dependence of the peak position of the two PL bands shows a change in their slope (dω/dT) at ~130 K, thus further strengthening the proposal of a structural deformation. The temperature dependence of the peak positions of the PL bands has been analyzed using the theory of optical dephasing in crystals.

The zero-field glassy ground state and field-induced ferromagnetic transition in (La0.4Pr0.6)1.2Sr1.8Mn2O7.

We have investigated glassy magnetic freezing in(La0.4Pr0.6)1.2Sr1.8Mn2O7 single crystals together with the field-induced transition to a metastable ferromagnetic phase using ac magnetic susceptibility and heat capacity measurements. The magnetization measurements show evidence for the development of a zero-field glassy ground state below 45 K along with a hysteretic, field-induced change in susceptibility associated with the transition to the ferromagnetic phase above 5 T. The heat capacity develops a clear peak at higher temperatures with the application of large magnetic fields, consistent with the development of a ferromagnetic order, while at low temperatures the Sommerfeld coefficient is monotonically reduced by an applied field, suggesting suppression of spin fluctuations. The heat capacity shows hysteretic behaviour, accompanied by a sharp decrease at a critical field, when held at fixed temperature, which does not recover on reducing the field back to zero. These measurements suggest that the zero-field ground state for (La0.4Pr0.6)1.2Sr1.8Mn2O7 consists of frozen disordered spin clusters, which develop into a metastable ferromagnetic state in modest magnetic fields.

'Honeycomb' tegmen: multiple tegmen defects associated with superior semicircular canal dehiscence.

OBJECTIVE: To report the coexistence of multiple tegmen defects, forming a 'honeycomb' pattern, together with dehiscence of the superior semicircular canal. CASE REPORTS: We describe three cases in which the above findings were noted, and we review the relevant literature. CONCLUSION: Superior semicircular canal dehiscence is defined as the absence of portions of bone over the canal along the floor of the middle fossa. Most published articles describe the defect as an isolated finding which is either unilateral or bilateral. Studies on temporal bones show either a defect over the superior semicircular canal or isolated defects over the tegmen. We describe three cases in which we found multiple tegmen defects, giving a characteristic honeycomb appearance, coexisting with dehiscence over the superior semicircular canal. This finding, which supports the theory of a developmental defect as the origin of the condition, has not previously been reported. A literature review is presented, with discussion of the aetiology and management of superior semicircular canal dehiscence.

Septotomy: a useful approach to the anterior maxillary sinus.

In endonasal surgery, approaching the anterior maxillary wall via the ipsilateral nostril is difficult. It is necessary to have good visual and instrument control when removing lesions such as inverted papilloma. We describe an approach through a temporary septotomy which provides good access from the contralateral nostril. The contralateral mucoperichondrial incision is anterior and the ipsilateral one posterior. The cartilage is hinged superiorly. There is minimal chance of perforation.

Vestibular schwannoma: role of conservative management.

OBJECTIVE: To assess the outcome of conservative management of vestibular schwannoma. STUDY DESIGN: Observational study. SETTING: Tertiary referral centre. PATIENTS: Four hundred and thirty-six patients with vestibular schwannoma (490 tumours), including 327 sporadic tumours and 163 tumours in 109 patients with neurofibromatosis type two. MAIN OUTCOME MEASURES: The relationship of tumour growth to tumour size at presentation, and to certain demographic features. RESULTS: The initial tumour size was significantly larger in the neurofibromatosis type two group (11 mm) than in the sporadic vestibular schwannoma group (5.1 mm). In both groups, 68 per cent of tumours did not grow during follow up (mean 3.6 years; range one to 14 years). The mean growth rate was 1.1 mm/year (range 0-15 mm/year) for sporadic tumours and 1.7 mm/year (range 0-18 mm/year) for neurofibromatosis type two tumours. The tumour growth rate correlated positively with tumour size in the sporadic tumour group, and correlated negatively with age in the neurofibromatosis type two group. CONCLUSION: Two-thirds of vestibular schwannomas did not grow. Radiological surveillance is an acceptable approach in carefully selected patients. Once a sporadic vestibular schwannoma reaches 2 cm in intracranial diameter, it is likely to continue growing. We do not recommend conservative management for sporadic tumours with an intracranial diameter of 1.5 cm or more. Vestibular schwannoma management is more complex in patients with neurofibromatosis type two.

Transtympanic gentamicin treatment using Silverstein MicroWick in Ménière's disease patients: long term outcome.

OBJECTIVE: To assess the long term outcome of gentamicin inner-ear perfusion using the Silverstein MicroWick in the treatment of Ménière's disease. STUDY DESIGN: Retrospective questionnaire survey of patients and review of medical records. SETTING: A district general hospital. PARTICIPANTS: All 15 patients who completed a minimum follow up of at least 24 months were included. MAIN OUTCOME MEASURES: Subjective symptoms, change in hearing thresholds and Glasgow benefit inventory scores. RESULTS: Based on the American Association of Otolaryngology-Head and Neck Surgery (1995) guidelines for reporting, 80 per cent of respondents obtained class A vertigo control and 20 per cent obtained class B control. Respondents' functional level improved from pre-operative levels of between three and six to post-operative levels of between one and three. Three respondents had pre-operative 'dead ears' and one developed the condition post-operatively. Hearing deteriorated further in three respondents, improved in two and remained unchanged in the rest. Respondents with class A control demonstrated improved quality of life, with a mean Glasgow benefit inventory total score of +34. CONCLUSION: Transtympanic gentamicin therapy via the Silverstein MicroWick results in good vertigo control. Patients should however be made fully aware of the risk of hearing deterioration.

Effect of pressure on lattice distortion, transport and magnetic properties of Pr-substituted La(1.2)Sr(1.8)Mn(2)O(7) bilayered manganite.

We have studied the effect of pressure on the anomalous lattice striction, both in the ab-plane and along the c-axis, of (La,Pr)(1.2)Sr(1.8)Mn(2)O(7) single crystals over the temperature region where the paramagnetic insulator to ferromagnetic metal transition takes place. We have examined the temperature dependence of the resistivity and the magnetization under applied pressure. The chemical pressure effect due to Pr-substitution at the La site suppresses the transition temperature of the parent crystal, while the application of external pressure on Pr-substituted crystals enhances the double exchange driven metallic state, resulting in a stable rise of T(c).

Steplike lattice deformation of single crystalline (La0.4Pr0.6)1.2Sr1.8Mn2O7 bilayered manganite.

We report a steplike lattice transformation of single crystalline (La0.4Pr0.6)1.2Sr1.8Mn2O7 bilayered manganite accompanied by both magnetization and magnetoresistive jumps, and examine the ultrasharp nature of the field-induced first-order transition from a paramagnetic insulator to a ferromagnetic metal phase accompanied by a huge decrease in resistance. Our findings support that the abrupt magnetostriction is closely related to an orbital frustration existing in the inhomogeneous paramagnetic insulating phase rather than a martensitic scenario between competing two phases.

Homeopathic Arnica montana for post-tonsillectomy analgesia: a randomised placebo control trial.

OBJECTIVE: To evaluate the efficacy of Homeopathic Arnica in reducing the morbidity following tonsillectomy. METHODS: Randomised double blind, placebo controlled trial at a tertiary referral centre. 190 patients over the age of 18 undergoing tonsillectomy were randomised into intervention and control groups receiving either Arnica 30c or identical placebo, 2 tablets 6 times in the first post-operative day and then 2 tablets twice a day for the next 7 days. The primary outcome measure was the change in pain scores (visual analogue scale) recorded by the patient on a questionnaire over 14 days post-operatively; Secondary outcome measures were: analgesia consumption, visits to the GP or hospital, antibiotic usage, the day on which their swallowing returned to normal and the day on which they returned to work. RESULTS: 111 (58.4%) completed questionnaires were available for analysis. The Arnica group had a significantly larger drop in pain score from day 1 to day 14 (28.3) compared to the placebo group (23.8) with p < 0.05. The two groups did not differ significantly on analgesic consumption or any of the other secondary outcome measures (number of post-operative visits to GP, use of antibiotics and secondary haemorrhage readmissions). CONCLUSION: The results of this trial suggest that Arnica montana given after tonsillectomy provides a small, but statistically significant, decrease in pain scores compared to placebo.

Pneumosinus dilatans: demonstrated by sinus expansion on serial sinus X-rays with discussion of possible aetiology.

A case of pneumosinus dilatans of the frontal sinus is presented. The findings on serial skull X-rays, performed on three occasions over a 10-year period, seem to support a developmental aetiology for this rare condition.

Metastatic carcinoma mimicking a facial nerve schwannoma: the role of computerized tomography in diagnosis.

Secondary deposits in the temporal bone are uncommon but well recognized. Such tumours may involve the facial nerve by direct extension of the destructive process into the fallopian canal. We present a rare case of metastasis from a breast carcinoma in the facial nerve itself, involving the nerve in the internal acoustic meatus with extension into the labyrinthine segment, the first genu and into the middle-ear segment. The rest of the temporal bone was not involved. The lesion resembled a facial schwannoma on a routine magnetic resonance (MR) image. The diagnosis was confirmed after a post-operative computed tomography (CT) scan showed another separate secondary deposit in the basisphenoid. Histology was consistent with secondary tumour from a breast carcinoma. The case highlights the importance of keeping a high degree of suspicion for metastatic tumours in patients with a previous history of malignancy and the usefulness of CT scan in the evaluation of such cases.

Field-induced ferromagnetic metallic state in the bilayer manganite (La0.4Pr0.6)1.2Sr1.8Mn2O7, probed by neutron scattering.

The bilayer manganite La1.2Sr1.8Mn2O7 exhibits a phase transition from a paramagnetic insulating (PI) to a ferromagnetic metallic (FM) state with a colossal magnetoresistance (CMR) effect. Upon 60% Pr substitution, magnetic order and PI to FM transition are suppressed. Application of a moderate magnetic field restores an FM state with a CMR effect. Neutron scattering by a single crystal of (La0.4Pr0.6)1.2Sr1.8Mn2O7, under a magnetic field of 5 T, has revealed a long-range and homogeneous ferromagnetic order. In the PI phase, under zero field, correlated lattice polarons have been detected. At 28 K, under 5 T, the spin wave dispersion curve determines an in-plane isotropic spin wave stiffness constant of 146 meV A(2). So the magnetic field not only generates a homogeneous ferromagnetic ground state, but also restores a magnetic coupling characteristic of FM CMR manganites.