Observation of Griffiths phase in antiferromagnetic La(0.32)Eu(0.68)MnO3

We report the Griffiths phase (GP) scenario for isovalent doping in antiferromagnetic La(0.32)Eu(0.68)MnO(3). Rietveld refinement of structural data displays strong crystal structural distortion. The dc and ac magnetic studies nicely demonstrate unambiguous aspects of robust GP. The presence of ferromagnetically correlated spin clusters is found above the transition temperature, T(N). The disorder-driven phase inhomogeneity is correlated to strong structural distortion, giving rise to the GP. This is an unique example in manganite where double exchange interaction does not play any role for the observed phenomenon.

Insulin entry into muscle involves a saturable process in the vascular endothelium

AIMS/HYPOTHESIS

Insulin's rate of entry into skeletal muscle appears to be the rate-limiting step for muscle insulin action and is slowed by insulin resistance. Despite its obvious importance, uncertainty remains as to whether the transport of insulin from plasma to muscle interstitium is a passive diffusional process or a saturable transport process regulated by the insulin receptor.

METHODS

To address this, here we directly measured the rate of (125)I-labelled insulin uptake by rat hindlimb muscle and examined how that is affected by adding unlabelled insulin at high concentrations. We used mono-iodinated [(125)I]Tyr(A14)-labelled insulin and short (5 min) exposure times, combined with trichloroacetic acid precipitation, to trace intact bioactive insulin.

RESULTS

Compared with saline, high concentrations of unlabelled insulin delivered either continuously (insulin clamp) or as a single bolus, significantly raised plasma (125)I-labelled insulin, slowed the movement of (125)I-labelled insulin from plasma into liver, spleen and heart (p < 0.05, for each) but increased kidney (125)I-labelled insulin uptake. High concentrations of unlabelled insulin delivered either continuously (insulin clamp), or as a single bolus, significantly decreased skeletal muscle (125)I-labelled insulin clearance (p < 0.01 for each). Increasing muscle perfusion by electrical stimulation did not prevent the inhibitory effect of unlabelled insulin on muscle (125)I-labelled insulin clearance.

CONCLUSIONS/INTERPRETATION

These results indicate that insulin's trans-endothelial movement within muscle is a saturable process, which is likely to involve the insulin receptor. Current findings, together with other recent reports, suggest that trans-endothelial insulin transport may be an important site at which muscle insulin action is modulated in clinical and pathological settings.

Visual grading of motion induced image degradation in high resolution peripheral computed tomography: impact of image quality on measures of bone density and micro-architecture

Motion artifacts are a common finding during high-resolution peripheral quantitative computed tomography (HR-pQCT) image acquisitions. To date it is not clear (i) when to repeat an acquisition, (ii) when to exclude a motion-degraded dataset post hoc, and (iii) how motion induced artifacts impact measures of trabecular and cortical parameters. In this study we present inter- and intra-observer reproducibility of a qualitative image quality grading score and report the prevalence of repeat acquisitions in our population. Finally the errors in bone density and micro-architectural parameters estimated from repeat acquisitions with and without motion degradation are presented. The relationship between these errors and the image quality grade is evaluated for each parameter. Repeat acquisitions performed due to operator-observed motion in the reconstructed image occurred for 22.7% of the exams (29.7% radius, 15.7% tibia). Of this subset, 88 exams with repeat acquisitions had at least one acquisition graded 1 (best quality). In this subset, the percent differences in bone density and micro-architecture measures tended to increase as the relative image quality decreased. Micro-architectural parameters were more sensitive to motion compared to geometric and densitometric parameters. These results provide estimates of the error in bone quality measures due to motion artifacts and provide an initial framework for developing standardized quality control criteria for cross-sectional and longitudinal HR-pQCT studies.

Tuning A-site ionic size in R(0.5)Ca(0.5)MnO3 (R = Pr, Nd and Sm): robust modulation in dc and ac transport behavior

Structural investigations on Pr(0.5)Ca(0.5)MnO(3), Nd(0.5)Ca(0.5)MnO(3) and Sm(0.5)Ca(0.5)MnO(3) display a systematic tuning in orthorhombic distortion which appears due to a change in A-site ionic size. Comprehensive investigations on dc conduction using various models indicate strong correlation with structural changes. Careful analysis of the ac conductivity mechanism as a function of frequency and temperature brings out a pronounced effect of structural modifications on the polaron conduction mechanism. Contrary to typical manifestations, dc conductivity and relaxation of charge carriers reveal non-Arrhenius behavior. This work provides a detailed and systematic addition to the phase diagram of electronic transport in the rare-earth manganite system doped with a divalent alkali atom.

Persistent photoinduced magnetization in the coexisting spin-glass and ferromagnetic phases of Pr₀.₉Ca₀.₁MnO₃ thin film

The persistent photoinduced magnetization (PPM) in the low bandwidth material Pr(1-x)Ca(x)MnO₃ at the low hole doping level of x = 0.1 is reported. Upon zero-field cooling under photoexcitation, significant improvement of the ferromagnetic (FM) ordering was observed in the low temperature spin-glass phase. However, upon field cooling, the FM ordering was found to be suppressed due to weakening of the double-exchange interaction. High kinetic energy x-ray photoelectron spectroscopy measurements indicated a slight increase in the Mn³⁺ peak under photoexcitation which clarifies the weakening of the FM interaction. The fast relaxation of the PPM is discussed in view of localization of spin polarons in sites of magnetic disorders and the results are compared with previous reports of PPM in intermediate bandwidth Pr₀.₉Ca₀.₁MnO₃ samples.

Design and gamma scintigraphic evaluation of colon specific pectin-EC pellets of secnidazole prepared by powder layering technology

The aim of the present study was to prepare a colon targeted pellet formulation of secnidazole and to evaluate the formulation in vitro and in vivo by a gamma scintigraphy method. Pectin/ethyl cellulose in different ratios and in different coating labels with plasticizer was used to prepare secnidazole pellets by a powder layering technique. The formulations were tagged with 99mTC-DTPA, a tracer in gamma scintigraphy to evaluate its transit behavior in rabbits. Morphology and compatibility were studied using Scanning Electron Microscopy, IR spectroscopy and Differential Scanning Calorimetry were used for the characterization of prepared pellets. The in-vitro study suggested that pectin (59%) esterification and ethyl cellulose 45cps at 20% coating label led to an optimum bacterial enzyme dependent released behavior. The optimized formulation was subjected to an in-vivo transit study. Scintigraphy images clearly indicated that the formulation can delay the drug release prior to the colon. The average time of gastric emptying and colon arrival was 57 min and 6.08 h, respectively. The coated pellets prepared by powder layering technology successfully released drug in the colon indicating that site specificity has been achieved with pectin 59% esterification and ethyl cellulose 45 cps at 1:2 ratio with 20% coating label.

Optimization of Pr(0.9)Ca(0.1)MnO(3) thin films and observation of coexisting spin-glass and ferromagnetic phases at low temperature

Optimization of thin films of small bandwidth manganite, Pr(1-x)Ca(x)MnO3 (for x = 0.1), and their magnetic properties are investigated. Using different pulsed laser deposition (PLD) conditions, several films were deposited from the stoichiometric target material on SrTiO3 (001) substrate and their thorough structural and magnetic characterizations were carried out using x-ray diffraction, atomic force microscopy, x-ray photoelectron spectroscopy (XPS), SQUID magnetometry and ac susceptibility measurements. A systematic investigation shows that irrespective of the growth temperature (between 550 and 750 °C), all the as-deposited films have twin boundaries and magnetic double phases. Post-annealing in partial or full oxygen pressure removes the extra phase and the twin boundaries. Zero-field-cooled magnetization data show an antiferromagnetic to paramagnetic transition at around 100 K whereas the field-cooled magnetization data exhibit a paramagnetic to ferromagnetic transition close to 120 K. However, depending on the oxygen treatments, the saturation magnetization and Curie temperature of the films change significantly. Redistribution of oxygen vacancies due to annealing treatments leading to a change in ratio of Mn3+ and Mn4+ in the films is observed from XPS measurements. Low temperature (below 100 K) dc magnetization of these films shows metamagnetic transition, high coercivity and irreversibility magnetizations, indicating the presence of a spin-glass phase at low temperature. The frequency dependent shift in spin-glass freezing temperature from ac susceptibility measurement confirms the coexistence of spin-glass and ferromagnetic phases in these samples at low temperature.

Teriparatide in bisphosphonate-resistant osteoporosis: microarchitectural changes and clinical results after 6 and 18 months

A number of osteoporotic patients under bisphosphonate treatment present persistent fragility fractures and bone loss despite good compliance. The objective of this 18-month prospective study was to investigate the effect of teriparatide [rhPTH(1-34)] in 25 female osteoporotics who were inadequate responders to oral bisphosphonates and to correlate microarchitectural changes in three consecutive iliac crest biopsies measured by micro-computed tomography (μCT) with bone mineral density (BMD) and bone serum markers. Scanned biopsies at baseline (M0), 6 months (M6), and 18 months (M18) demonstrated early significant (P < 0.01) increases in bone volume per tissue volume (+34%) and trabecular number (+14%) at M6 with only moderate changes in most μCT structural parameters between M6 and M18. μCT-measured bone tissue density was significantly decreased at M18, expressing an overall lower degree of tissue mineralization characteristic for new bone formation despite unchanged trabecular thickness due to increased intratrabecular tunneling at M18. μCT results were consistent with serum bone turnover markers, reaching maximal levels of bone alkaline phosphatase and serum β-crosslaps at M6, with subsequent decline until M18. BMD assessed by DXA demonstrated persistent increases at the lumbar spine until M12, whereas no significant change was observed at the hip. Type (alendronate/risedronate) and duration (3.5 ± 4 years) of prior bisphosphonate treatment did not influence outcome on μCT, BMD, or bone marker results. The overall results indicate a positive ceiling effect of teriparatide on bone microarchitecture and bone markers after 6 and 12 months for lumbar spine BMD, with no additional gain until M18 in bisphosphonate nonresponders.

Mineral composition is altered by osteoblast expression of an engineered G(s)-coupled receptor

Activation of the G(s) G protein-coupled receptor Rs1 in osteoblasts increases bone mineral density by 5- to 15-fold in mice and recapitulates histologic aspects of fibrous dysplasia of the bone. However, the effects of constitutive G(s) signaling on bone tissue quality are not known. The goal of this study was to determine bone tissue quality in mice resulting from osteoblast-specific constitutive G(s) activation, by the complementary techniques of FTIR spectroscopy and synchrotron radiation micro-computed tomography (SRμCT). Col1(2.3)-tTA/TetO-Rs1 double transgenic (DT) mice, which showed osteoblast-specific constitutive G(s) signaling activity by the Rs1 receptor, were created. Femora and calvariae of DT and wild-type (WT) mice (6 and 15 weeks old) were analyzed by FTIR spectroscopy. WT and DT femora (3 and 9 weeks old) were imaged by SRμCT. Mineral-to-matrix ratio was 25% lower (P = 0.010), carbonate-to-phosphate ratio was 20% higher (P = 0.025), crystallinity was 4% lower (P = 0.004), and cross-link ratio was 11% lower (P = 0.025) in 6-week DT bone. Differences persisted in 15-week animals. Quantitative SRμCT analysis revealed substantial differences in mean values and heterogeneity of tissue mineral density (TMD). TMD values were 1,156 ± 100 and 711 ± 251 mg/cm(3) (mean ± SD) in WT and DT femoral diaphyses, respectively, at 3 weeks. Similar differences were found in 9-week animals. These results demonstrate that continuous G(s) activation in murine osteoblasts leads to deposition of immature bone tissue with reduced mineralization. Our findings suggest that bone tissue quality may be an important contributor to increased fracture risk in fibrous dysplasia patients.

Broken chain effect in doped SrCuO2

We report the effect of magnetic (Ni) and nonmagnetic (Zn, Ga) doping on the overall magnetic behaviour of the spin chain compound SrCuO(2). The doping causes systematic reduction in the intrachain exchange interaction, and the influence is found to be almost independent of the dopant. The low temperature Curie tail in the temperature dependence of susceptibility also increases with the doping concentration, which is an indication of the enhanced chain breaking effect with doping. The doping also gives rise to nonlinearity in the isothermal magnetization behaviour, which can be accounted for by the effect of free/quasi-free spin in the doped sample. Our analysis indicates that doped Ni(2+) ions remain in a low spin state (S = 0) and behave almost similar to the nonmagnetic counterpart as far as the doping effects are concerned.

Quality of life and functional outcomes in the management of early glottic carcinoma: a systematic review of studies comparing radiotherapy and transoral laser microsurgery

BACKGROUND

Early glottic carcinoma can be managed by radiotherapy and transoral laser microsurgery with similar control and survival rates. The functional and quality of life outcomes of these interventions are therefore important to guide management.

OBJECTIVE OF REVIEW

To compare the different treatment modalities for early glottic carcinoma with respect to quality of life, post-treatment voice character and swallowing outcomes.

TYPE OF REVIEW

A systematic review of the literature with defined search strategy.

SEARCH STRATEGY

Searches of EBM databases, and literature databases using key words: glotti*, laryn*, neoplasm, radiotherapy and laser surgery from 1970 to November 2009. Articles were screened for relevance using pre-determined inclusion and exclusion criteria.

EVALUATION METHOD

Articles reviewed by authors and data compiled in tables for analysis.

RESULTS

No randomised controlled trials were identified. There were 15 studies reporting vocal outcomes, and perception of voice disability was measured in eight studies; numbers were low in all the papers. Cumulatively, results for 880 patients were included, 448 had trans-oral laser microsurgery and 442 had radiotherapy. For vocal outcomes, 12 studies found no significant difference between radiotherapy and laser surgery, three reported superior outcomes for radiotherapy, whereas for the perception of voice disability, five reported no difference between treatment groups, while the remaining three reported conflicting results. Nine studies reported quality of life outcomes; seven of these reported no difference between the treatment groups in overall scores although some report differences in subsets of questions.

CONCLUSIONS

The evidence base to date demonstrates comparable vocal and quality of life outcomes for radiotherapy and transoral laser surgery for early glottic carcinoma. There is a need for consensus on which measures of vocal quality and life satisfaction to be used in research trials to allow comparison between studies.

Structural and magnetic properties of spontaneously phase-separated Eu0.5Sm0.5MnO3

We have studied structural and magnetic properties of Eu(0.5)Sm(0.5)MnO(3). The system shows strong orthorhombic distortion. The static Jahn-Teller effect modifies the low temperature magnetic properties, creating a complicated anisotropic magnetic ground state. A low temperature magnetic phase separation has also been realized that builds magnetic interfaces exhibiting strong exchange bias. Careful analysis of the magnetic behaviour indicates the origin of the exchange bias to be a phase separation between an A-type antiferromagnetic phase and a low temperature highly anisotropic phase originating from another ordering at the rare-earth sublattice.

Exchange bias effect in alloys and compounds

The phenomenology of exchange bias effects observed in structurally single-phase alloys and compounds but composed of a variety of coexisting magnetic phases such as ferromagnetic, antiferromagnetic, ferrimagnetic, spin-glass, cluster-glass and disordered magnetic states are reviewed. The investigations on exchange bias effects are discussed in diverse types of alloys and compounds where qualitative and quantitative aspects of magnetism are focused based on macroscopic experimental tools such as magnetization and magnetoresistance measurements. Here, we focus on improvement of fundamental issues of the exchange bias effects rather than on their technological importance.

Removal of olefinic fat chemical shift artifact in diffusion MRI

Diffusion-weighted (DW) MRI has emerged as a key tool for assessing the microstructure of tissues in healthy and diseased states. Because of its rapid acquisition speed and insensitivity to motion, single-shot echo-planar imaging is the most common DW imaging technique. However, the presence of fat signal can severely affect DW-echo planar imaging acquisitions because of the chemical shift artifact. Fat suppression is usually achieved through some form of chemical shift-based fat saturation. Such methods effectively suppress the signal originating from aliphatic fat protons, but fail to suppress the signal from olefinic protons. Olefinic fat signal may result in significant distortions in the DW images, which bias the subsequently estimated diffusion parameters. This article introduces a method for removing olefinic fat signal from DW images, based on an echo time-shifted acquisition. The method is developed and analyzed specifically in the context of single-shot DW-echo-planar imaging, where image phase is generally unreliable. The proposed method is tested with phantom and in vivo datasets, and compared with a standard acquisition to demonstrate its performance.

The effects of acute loading on T1rho and T2 relaxation times of tibiofemoral articular cartilage

OBJECTIVE

To evaluate the effect of acute loading on healthy and osteoarthritic knee cartilage T(1ρ) and T(2) relaxation times.

DESIGN

Twenty subjects with radiographic evidence of osteoarthritis (OA) and 10 age-matched controls were enrolled. Magnetic resonance imaging (MRI) acquisition, including T(1ρ) and T(2) map sequences were performed unloaded and loaded at 50% body mass. Cartilage masks were segmented semi-automatically on registered high-resolution spoiled gradient-echo (SPGR) images for each compartment (medial and lateral). Cartilage lesions were identified using a modified Whole Organ Magnetic Resonance Imaging Score (WORMS) score. Statistical differences were explored using separate two-way (group×loading condition) Analysis of Variance (ANOVA) using age as a covariate to evaluate the effects of loading on T(1ρ) and T(2) relaxation times.

RESULTS

A significant decrease in T(1ρ) (44.5±3.8 vs 40.2±4.8ms for unloaded and loaded, respectively; P<0.001) and T(2) (31.8±3.8 vs 30.5±4.8ms for unloaded and loaded, respectively; P<0.001) relaxation times was observed in the medial compartment with loading while no differences were observed in the lateral compartment. This behavior occurred independent of WORMS score. Cartilage compartments with small focal lesions experienced greater T(1ρ) change scores with loading when compared to cartilage without lesions or cartilage with larger defects (P=0.05).

CONCLUSIONS

Acute loading resulted in a significant decrease in T(1ρ) and T(2) relaxation times of the medial compartment, with greater change scores observed in cartilage regions with small focal lesions. These data suggest that changes of T(1ρ) values with loading may be related to cartilage biomechanical properties (i.e., tissue elasticity) and may be a valuable tool for the scientist and clinician at identifying early cartilage disease.

Cartilage and meniscus assessment using T1rho and T2 measurements in healthy subjects and patients with osteoarthritis

OBJECTIVE

The purpose of this study was to evaluate meniscal degeneration in healthy subjects and subjects with osteoarthritis (OA) using T(1ρ) and T(2) measurements and to examine the interrelationship between cartilage and meniscus abnormalities.

METHODS

Quantitative assessment of cartilage and meniscus was performed using 3T Magnetic Resonance Imaging (MRI) with a T(1ρ) and T(2) mapping technique in 19 controls and 44 OA patients. A sagittal T(2)-weighted fast spin echo (FSE) fat-saturated image was acquired for cartilage and meniscal Whole-Organ Magnetic Resonance Imaging Score (WORMS) assessment. Western Ontario and McMasters Universities Arthritis Index (WOMAC) scores were obtained to assess clinical symptoms.

RESULTS

The posterior horn of the medial meniscus (PHMED) had the highest incidence of degeneration. Stratifying subjects on the basis of PHMED grade revealed that the T(1ρ) and the T(2) measurements of the PHMED and the medial tibial (MT) cartilage were higher in subjects having a meniscal tear (meniscal grade 2-4) compared to subjects with a meniscal grade of 0 or 1 (P<0.05). While not statistically significant, there was a trend for T(1ρ) and T(2) being higher in PHMED grade 1 compared to grade 0 (P=0.094, P=0.073 respectively). WOMAC scores had a stronger correlation with meniscus relaxation measures than cartilage measures.

CONCLUSIONS

Magnetic Resonance (MR) T(1ρ) and T(2) measurements provide a non-invasive means of detecting and quantifying the severity of meniscal degeneration. Meniscal damage has been implicated in OA progression and is correlated with cartilage degeneration. Early detection of meniscal damage represented by elevations in meniscal relaxation measures may identify subjects at increased risk for OA.

A comparison of Thiel and formalin embalmed cadavers for thyroid surgery training

BACKGROUND

The European Working Time Directive has increased the need for surgical skills training which does not involve patients. Recent changes in the anatomy legislation now make it possible to perform surgical procedures on human cadavers. Standard formalin embalming, however does not provide a very realistic model and alternative approaches, such as Thiel soft-fix embalmed cadavers, should be explored and evaluated.

METHODS

Two formalin and 3 Thiel embalmed cadavers were used at a senior trainee and consultant course in thyroid surgery. The 12 participants (8 trainees and 4 consultants) were asked to score 15 aspects, such as quality of different tissues, for each type of cadaver. Some of these aspects were specific to thyroid surgery, however many are equally applicable to other specialties.

RESULTS

All participants rated the Thiel embalmed cadavers better or equal for all aspects. Of the 180 pairs of scores 33 were excluded, 10 were equal for formalin and Thiel, while in the remaining 137 Thiel scored better. The preference was particularly pronounced in aspects that require flexibility of tissues such as flap raising.

CONCLUSIONS

Thiel embalmed cadavers provide a more realistic model for training of thyroid surgical skills; this is expected to be similar for many other types of surgery.