Terahertz spectroscopic evidence of electron correlations in SrVO3epitaxial thin films.

Electron correlation in transition metal oxides (TMOs) is an intriguing topic in condensed matter physics, revealing a wide variety of exotic physical properties. Investigating low-energy carrier dynamics by terahertz (THz) spectroscopy is an efficient route to obtain the essential insights into electron correlation. In the present study, THz-time-domain spectroscopy is employed to probe electron correlation in SrVO3epitaxial thin films. The low energy carrier dynamics of SrVO3in the range of 0.2-6.0 meV shows a typical metallic behavior as overserved in dc transport measurements. The obtained temperature-dependent optical parameters provide evidence of mass renormalization in the low energy regime and carrier momentum relaxation happens via the electron-electron scattering mechanism. Overall, the frequency and temperature-dependent optical parameters indicate the Fermi liquid ground state in a Mott-Hubbard type correlated metal SrVO3thin film. Our results provide significant insight on low energy carrier dynamics in the correlated electron system, particularly perovskite-basedd1TMOs.

A randomized, controlled trial of comparison of a continuous femoral nerve block (CFNB) and continuous epidural infusion (CEI) using 0.2% ropivacaine for postoperative analgesia and knee rehabilitation after total knee arthroplasty (TKA).

BACKGROUND AND AIMS: Postoperative pain relief following total knee arthroplasty (TKA) is a major concern as it will help to achieve an effective functional outcome. The present study was conducted to compare continuous femoral nerve block (CFNB) and continuous epidural infusion (CEI) techniques using ropivacaine. MATERIAL AND METHODS: Forty patients were randomly allocated into group F and group E to receive 0.2% ropivacaine through femoral catheter or epidural catheter respectively. An infusion was started @6 ml/h post-operatively when VAS was ≥4. The dose was titrated to keep VAS <4 (with minimum rate 2 ml/h and maximum rate 10 ml/h). If VAS ≥4 occurred despite maximum rate of infusion, a rescue analgesic was given. Primary objectives were to compare visual analogue score (VAS), rehabilitation indices, and rescue analgesic requirement. Secondary objectives were to assess patient and surgeon's satisfaction score, motor blockade, and complications if any. RESULTS: The mean VAS score, rehabilitation goals, rescue analgesic requirement, and patient's and surgeon's mean satisfaction scores were comparable in both the groups. Motor blockade was not seen and though the number of side effects were more in group E, they did not achieve statistical or clinical significance. CONCLUSION: CFNB can be used as an alternative, effective postoperative analgesic technique for TKA.

A Room-Temperature Ferroelectric Ferromagnet in a 1D Tetrahedral Chain Network.

Ferroelectricity occurs in crystals with broken spatial inversion symmetry. In conventional perovskite oxides, concerted ionic displacements within a 3D network of transition-metal-oxygen polyhedra (MOx ) manifest spontaneous polarization. Meanwhile, some 2D networks of MOx foster geometric ferroelectricity with magnetism, owing to the distortion of the polyhedra. Because of the fundamentally different mechanism of ferroelectricity in a 2D network, one can further challenge an uncharted mechanism of ferroelectricity in a 1D channel of MOx and estimate its feasibility. Here, ferroelectricity and coupled ferromagnetism in a 1D FeO4 tetrahedral chain network of a brownmillerite SrFeO2.5 epitaxial thin film are presented. The result provides a new paradigm for designing low-dimensional MOx networks, which is expected to benefit the realization of macroscopic ferro-ordering materials including ferroelectric ferromagnets.

Directing Oxygen Vacancy Channels in SrFeO2.5 Epitaxial Thin Films.

Transition-metal oxides (TMOs) with brownmillerite (BM) structures possess one-dimensional oxygen vacancy channels (OVCs), which play a key role in realizing high ionic conduction at low temperatures. The controllability of the vacancy channel orientation, thus, possesses a great potential for practical applications and would provide a better visualization of the diffusion pathways of ions in TMOs. In this study, the orientations of the OVCs in BM-SrFeO2.5 are stabilized along two crystallographic directions of the epitaxial thin films. The distinctively orientated phases are found to be highly stable and exhibit a considerable difference in their electronic structures and optical properties, which could be understood in terms of orbital anisotropy. The control of the OVC orientation further leads to modifications in the hydrogenation of the BM-SrFeO2.5 thin films. The results demonstrate a strong correlation between crystallographic orientations, electronic structures, and ionic motion in the BM structure.

Topotactic Metal-Insulator Transition in Epitaxial SrFeOx Thin Films.

Topotactic phase transformation enables structural transition without losing the crystalline symmetry of the parental phase and provides an effective platform for elucidating the redox reaction and oxygen diffusion within transition metal oxides. In addition, it enables tuning of the emergent physical properties of complex oxides, through strong interaction between the lattice and electronic degrees of freedom. In this communication, the electronic structure evolution of SrFeOx epitaxial thin films is identified in real-time, during the progress of reversible topotactic phase transformation. Using real-time optical spectroscopy, the phase transition between the two structurally distinct phases (i.e., brownmillerite and perovskite) is quantitatively monitored, and a pressure-temperature phase diagram of the topotactic transformation is constructed for the first time. The transformation at relatively low temperatures is attributed to a markedly small difference in Gibbs free energy compared to the known similar class of materials to date. This study highlights the phase stability and reversibility of SrFeOx thin films, which is highly relevant for energy and environmental applications exploiting the redox reactions.

A Clinical Study to Examine the Effect of Complete Denture on Head Posture/Craniovertical Angle.

INTRODUCTION: Edentulous patients show some significant changes in ridge relationship caused by resorption of alveolar ridge. The changes are characterized by an upward rotation of mandible, increase in mandibular prognathism that ultimately results in change of natural head posture. AIM: This clinical study was planned to know the effect of complete denture on head posture in different age groups of Indian completely edentulous population, after placement of complete denture at various time intervals. MATERIALS AND METHODS: The sample consisted of completely edentulous patients without previous experience of the dentures. They were divided into 2 age groups: Group A (45-60) and Group B (61-75). During placement of complete denture craniovertical angle was measured with the help of custom made ruler protector device. Readings were taken before denture placement, immediately after denture placement, 30 minutes, 24 hours and 30 days after dentures placement. RESULTS: The results of this study indicated that in most of the patients (90%) despite their age, change in head posture (extension) occurred immediately after the denture placement. Thereafter reading remains same for measurement at 30 minutes and 24 hours of denture placement. However after 30 days, observation revealed that all the patients showed reduced craniovertical angle (flexion). Even though the values of craniovertical angle remain higher than its baseline in both groups, significant changes were noticed only in Group A. CONCLUSION: Findings revealed that head posture was significantly altered by the placement of dentures in completely edentulous patients. Within the time interval of 30 minutes and 24 hours extension of head posture remained constant with slight variation. Although after 30 days, changes remained significant for group 'A', but no significant changes were observed in the subjects of group 'B'.

Universal electronic structure of polar oxide hetero-interfaces.

The electronic properties of NdGaO3/SrTiO3, LaGaO3/SrTiO3, and LaAlO3/SrTiO3 interfaces, all showing an insulator-to-metal transition as a function of the overlayer-thickness, are addressed in a comparative study based on x-ray absorption, x-ray photoemission and resonant photoemission spectroscopy. The nature of the charge carriers, their concentration and spatial distribution as well as the interface band alignments and the overall interface band diagrams are studied and quantitatively evaluated. The behavior of the three analyzed heterostructures is found to be remarkably similar. The valence band edge of all the three overlayers aligns to that of bulk SrTiO3. The near-interface SrTiO3 layer is affected, at increasing overlayer thickness, by the building-up of a confining potential. This potential bends both the valence and the conduction band downwards. The latter one crossing the Fermi energy in the proximity of the interface and determines the formation of an interfacial band offset growing as a function of thickness. Quite remarkably, but in agreement with previous reports for LaAlO3/SrTiO3, no electric field is detected inside any of the polar overlayers. The essential phenomenology emerging from our findings is discussed on the base of different alternative scenarios regarding the origin of interface carriers and their interaction with an intense photon beam.

Photoresponse dynamics in amorphous-LaAlO3/SrTiO3 interfaces.

The time-resolved photoconductance of amorphous and crystalline LaAlO3/SrTiO3 interfaces, both hosting an interfacial 2-dimensional electron gas, is investigated under irradiation by variable-wavelengths, visible or ultraviolet photons. Unlike bare SrTiO3 single crystals, showing relatively small photoconductance effects, both kinds of interfaces exhibit an intense and highly persistent photoconductance with extraordinarily long characteristic times. The temporal behaviour of the extra photoinduced conductance persisting after light irradiation shows a complex dependence on interface type (whether amorphous or crystalline), sample history and irradiation wavelength. The experimental results indicate that different mechanisms of photoexcitation are responsible for the photoconductance of crystalline and amorphous LaAlO3/SrTiO3 interfaces under visible light. We propose that the response of crystalline samples is mainly due to the promotion of electrons from the valence bands of both SrTiO3 and LaAlO3. This second channel is less relevant in amorphous LaAlO3/SrTiO3, where the higher density of point defects plays instead a major role.

The road to radiation protection: a rocky path.

Radiation has intrigued us with its magnificent properties of imaging and healing. But this discovery, like many others, came with a heavy price. The pioneers of this form of energy themselves often succumbed to its devastating effects and hence, paved a way for future generations to be wary of it, while continuing to use it. This paper attempts to salute those masters who have helped make the radiation world a safer place to live and work in.

Stress distribution among periodontally compromised abutments: A comparative study using three-dimensional finite element analysis.

AIMS: The aim of the study was to evaluate the stress distribution patterns in teeth and supporting structures of fixed prosthesis and design modifications in a fixed prosthesis with either normal or reduced bone support of an additional abutment. Study was also undertaken to disprove Ante's law. MATERIALS AND METHODS: Main models and variations of main models (modification 1, 2, 3, 4, 5, 6, 7, 8) were subjected to 200 N at angulations of 90° and 15° on functional cusps. Results for each loading were obtained as stress distribution color images and numerical values were recorded. A three-dimensional finite element analysis study of variations of normal models was performed using two finite element softwares, namely PRO-Engineer wildfire version 1.0 manufacturer: Parametric technology corporation, Needham, MA 02494 U.S.A. RESULTS: When periodontal compromised abutment teeth was splinted with an additional abutment an increase of stress was observed in periodontally compromised abutments so an additional abutment is not required. Eventhough the pericemental area of compromised abutments with an additional abutment (canine) was more than the combined pericemental area of pontics to be replaced, stress generated was more on abutments. This disproves Ante's law. Hence, it may be a reference, but should not be the ultimate criterion in determining the number of multiple abutments. CONCLUSIONS: When periodontal compromised abutment teeth was splinted with an additional abutment an increase of stress was observed in periodontally compromised abutments so an additional abutment is not required. Even though the pericemental area of compromised abutments with an additional abutment (canine) was more than combined pericemental area of pontics to be replaced, stress generated was more on abutments. This disproves Ante's law. Hence, it may be a reference, but should not be the ultimate criterion in determining the number of multiple abutments.

Fasting plasma homocysteine levels are increased in young patients with acute myocardial infarction from Western India.

BACKGROUND: Fasting hyperhomocysteinemia is positively associated with atherothrombosis and acute myocardial infarction in several prospective and retrospective studies. In India folic acid deficiency is not uncommon, and subclinical folic acid deficiency is known to cause hyperhomocysteinemia without thrombocytopenia. OBJECTIVE: To observe the prevalence of plasma hyperhomocysteinemia in a cohort of patients with acute myocardial infarction after 2 weeks of oral folic acid therapy. MATERIAL AND METHODS: A cohort of 120 consecutive patients with acute myocardial infarction below the age of 40 years was tested for fasting hyperhomocysteinemia 8-10 weeks after AMI. Five hundred age and sex matched unrelated controls and 50 family controls were also studied for two mutations, MTHFR C677T and cystathionine Beta synthase (CBS) T833C mutations Parents of the AMI patients were also tested to see hyperhomocysteinemia in the family. The patients were given two weeks of oral folic acid therapy (folviteR - 5mg once daily) and fasting plasma homocysteine levels were measured again and the pattern of response was noted. Patients who responded partially or not responded at all to oral folic acid therapy received intramuscular injection of 1 mg of cyanoco-balamin ( NeurobionR,) and their level of plasma homocysteine were noted 1 week later. RESULTS: Sixty three out of 120 patients showed hyperhomocysteinemia compared to 9% of the age and sex matched controls. Fifty seven therapy percent of hyperhomocysteinemia patients responded completely to oral folvite. Subsequent vitamin B12 & B6 therapy normalized homocysteine levels in only 2/12 partial responders with less than 50 microg/l of plasma homocysteine levels, but none of the folate non responders and partial responders having plasma homocysteine levels above 50 microgm/l responded to the therapy. CONCLUSION: Hyperhomocysteinemia is common amongst young acute myocardial infarction patients from western India. The major cause of hyperhomocysteinemia in young myocardial infarction cases is folic acid deficiency. However a fair number of patients who did not respond to folic acid, also did not respond to vitamin B12 and B6 parenterally suggesting existence of defect in other pathways of homocysteine metabolism in a subset of our patients.

Combination of thrombophilia markers in acute myocardial infarction of the young.

BACKGROUND: The pathogenesis of arterial thrombotic disease involves multiple genetic and environmental factors related to atherosclerosis and thrombosis. But, there have been very few studies in India which have investigated some of the thrombophilia markers. AIM: To look for combined thrombophilia in MI patients. SETTINGS AND DESIGN: One hundred twenty patients of myocardial infarction (age below 40 yrs.) were recruited 8-10 weeks after stabilization. Hundred age and sex-matched healthy controls were also recruited in the present study. METHODS AND MATERIAL: Following thrombophilia markers were screened in these patients--plasma fibrinogen, protein C, protein S, antithrombin III, factor V Leiden, PT G20210A polymorphism, MTHFR C677T, homocysteine, fibrinogen b448 Arg/Lys polymorphism and CBS T833C mutation. STATISTICAL ANALYSIS: Statistical analysis was done using Statistical Package for Social Sciences (SPSS) version 10.0, SPSS Inc., Chicago, USA. RESULTS AND CONCLUSION: Elevated fibrinogen levels, homocysteine (p< 0.001 and homocysteine with odds ratio 6.26) and factor V Leiden (p=0.038) were independently associated with MI in our patients. A total of 37 patients (42.5%) had the presence of more than one thrombophilia markers in combination. Out of these, 10 had the presence of three markers in combination and 1 had five thrombophilia markers in combination. Only 2 controls had prothrombotic markers in combination. Combined prothrombotic risk factors were significant in cases in comparison to controls (p< 0.001). Further larger studies on a nationwide basis recruiting a large number of young MI patients should be done to substantiate these findings.

Frequency distribution of antigens in the human platelet antigen-1 system in the western Indian population.

BACKGROUND: Neonatal alloimmune thrombocytopenic purpura (NAITP) occurring because of fetomaternal incompatibility in the human platelet antigen-1 (HPA-1) system is increasingly being detected worldwide. Several studies have reported the frequency and distribution of HPA-1 alleles in different countries and ethnic populations. A paucity of data regarding the frequency of the antigens in the HPA-1 system in the Indian population prompted an undertaking of this study. The molecular method of genotyping the platelet antigens is preferred to serology. It will enable future prenatal diagnosis in mothers suspected to have NAITP so that they can be managed better. STUDY DESIGN AND METHODS: Five hundred six unrelated subjects were screened for the alleles in the HPA-1 system, of which 185 were healthy males and 321 were females. DNA was extracted from the peripheral blood WBCs of these subjects, followed by PCR amplification and agarose gel electrophoresis of the PCR-amplified products. RESULTS: Four hundred two out of 506 subjects (79.44%) were found to be homozygous for HPA-1a. Ninety-nine subjects (19.57%) were heterozygous HPA-1a/HPA-1b, and five subjects out of 506 (0.99%) were homozygous for HPA-1b. CONCLUSION: Homozygosity for HPA-1b exists in the Indian population at a frequency of 0.99 percent, whereas homozygosity for HPA-1a is present in approximately 79 percent of the population. Hence, 0.98 x 0.79 of the females (0.77%) in the reproductive age group are likely to be pregnant with an HPA-1a-positive fetus, leading to a setting in which NAITP might develop. The development of NAITP also depends on the HLA type of the mother; nevertheless, the number of pregnancies in which the fetus is at risk for NAITP in India is quite significant.