The effect of dopants SiO2, GeO2, and SnO2, on the microstructure and magnetic properties of Mn-Zn ferrites

Ferrite have found a variety of uses in electronic and communication engineering. Mn-Zn ferrites (Mn1-XZnxFe2O4 ) are widely used as filter core materials over a range of frequencies varying from several hundred Hz to several MHz. There are many other applications such as in television receivers as deflection yokes and E.H.T. cores etc. The development of a ferrite suitable for a particular application is an interesting scientific problem and technological challenge. The properties of ferrites are determined by a number of intrinsic properties and their interaction with the ceramic microstructure. Impurities, present in or added to the raw materials used for processing ferrites, play an important role in determining the properties of the ferrites. The cost of ferrites is very much related to the purity level of the raw materials used. It is, therefore, both scientifically and economically important that the behaviour of ferrites is studied with additions of controlled amounts of impurities commonly present in the raw materials cheaply available. Silica (Si0 2) is commonly found in the raw materials and is also, to some extent, contributed by atmospheric dust. In order to determine the tolerance of SiO2 as an impurity in the raw materials and during processing, a systematic study has been carried out to investigate the effect of SiO2 addition in the raw materials. The effect of controlled additions of oxides of germanium and tin to the raw materials has also been studied since Si, Ge and Sn are all elements of the IV group in the periodic table. The studies have been presented in five chapters. Chapter I gives the background essential for the present study. This chapter deals with the important properties of ferrites. The properties of ferrites can be classified in two categories. Firstly intrinsic properties i.e. those properties which are decided by the basic composition of the ferrite. Secondly extrinsic properties i.e. those properties which depend upon the microstructure and processing parameters. The literature presently available with special reference to impurities and their effect on the magnetic properties has also been discussed. The effect of impurities on the magnetic properties of ferrites depends upon whether they go in solid solution with the ferrite or stay insoluble. The nature of the three impurities - SiO2 , GeO2 and SnO2 in the ferrite has been studied in chapter II by employing scanning electron microscopy, X-ray and Auger microprobe and X-ray diffraction (lattice parameter measurement) techniques. Both. Si0 2 and Ge20 have been found to have a limited solubility in the ferrite and tend to segregate at the grain boundaries, Si02 has been found to form a compound at the grain boundaries. Si-rich inclusions have also been detected in the grains at larger concentrations of Si02 (1.28 mol%) . Ge-enrichment (ii) at the grain boundaries has been observed with the help of Auger electron spectroscopy. No detectable segregation of Sn0 2 , was observed with the help of XMA even for as high a concentration as 5.70 mol%. This may be due to a high solid solubility of Sn0 2 in the ferrite. Ferrite lattice has been found to expand on additions of Sn0 2 up to a level of 5.70 mol%, the highest concentration studied. The third chapter deals with the effect of these impurities -- SiO2 , GeO2 and SnO2 doped in various amounts on the microstructure of the Mn-Zn ferrite. It has been discussed that the impurities present could affect the microstructure in a number of ways. Impurities present in solid solution could give rise to an impurity drag effect which impedes boundary motion. The insoluble impurities would disturb the course of normal grain growth during sintering more drastically. It has been discussed that small concentrations of the insoluble impurity such that the impurity remains as a dispersed phase result in abnormal or discontinuous grain growth. At higher concentrations, the impurity phase would exist as plates or films on the grain boundaries altering the kinetics for growth. Microstructure studies of SiO2 and GeO2 doped Mn-Zn ferrites show that these impurities lower the sintering temperature thereby enhancing the rate of grain growth. Both of these impurities give rise to discontinuous grain growth. Giant grains with almost entire porosity being intragranular are formed at a SiO2 content of 0.08 mol% and at a Ge0 2 content of 1.28 mol%. From these observations, (iii) it is inferred that up to these levels they exist as dispersed phase therefore giving rise to discontinuous grain growth. At a level higher than 0.64 mol% SiO2 and 3.82 mol% GeO2 somewhat regular grain structure reappears through with much higher intragranular porosity as compared to undoped ferrite. It is discussed that at these levels, the impurities are present as second phase film around the grains suppressing the abnormal grain control. regular grain structure reappears though with much higher intragranular porosity as compared to undoped ferrite, It is discussed that at these levels, the impurities are present as second phase film around the grains suppressing the abnormal grain growth. Sn02 additions are not found to affect the microstructure even up to a level of 5.70 mol%. These results are in agreement with the findings in the first chapter that SnO2 goes in solid solution with the ferrite. In chapter IV, the effect of these impurities on the magnetic property - initial permeability, u1, and resistivity of the Mn-Zn ferrite has been studied. It is known that an increase in density increases the saturation magnetization, Ms, and hence the initial permeability. It has also been discussed that in samples containing intragranular porosity, an increase in pore to pore distance, D, increases the span P\u27 of domain walls and hence the ui. In the case of SiO2 as dopant, it ha s been observed that ui increases up to a Si0 2 concentration of 0.04 mol%. This is in confirmity with the increase in the product Mg.D P in this range. At a Si0 2 concentration of 0.08 mol%, even though Ms increases, /ui decreases on account of a decrease in Dp \u27because here the microstructure shows large intra--_ granular porosity. Beyond a silica concentration of C.32 mol%, although the product Ms Dp does not decrease, the ui is found to decrease because of the formation of a nonmagnetic layer at the grain boundaries and precipitation inside the grains. In the case of Ge0 2, similar effects are observed though the peak in ui occurs at a content of 0.64 mol%. Sn0 2 additions are not found to affect ui appresiably. A study of the temperature variation of ,u i shows\u27 that in the case of SnO2, there is a shift in the secondary maximum. peak (SMP) indicating a solubility of SnO2 in the ferrite. Such an observation is not appreciable in Si0 2 and GeO2 . Thei-T curves further show a flatness at higher impurity concentrations in all the three cases presumably due to wall discontinuities at the grain boundaries. A study of disaccommodation with various concentrations of these impurities shows that the disaccommodation decreases with impurity concentrations, the maximum change being in SnO2. The results have been discussed in terms of the solubility of Sn4+ ions and their tendency to localize Fe 2+ ions, Variations in the resistivity with temperature for the three impurities indicate that the predominant conduction mechanism is the electron hopping from Fe 3+ to Fe 2+ and that Sn4+ - Fe 2+ pairs dissociate at higher temperatures. Chapter V deals with the effect of these impurities on the core losses of the Mn-Zn ferrite. The core losses have been studied at a flux density of 0.2 wb/m 2 (2000 gauss) and up to a frequency of 15.75 KHz. At 15.75 KHz, the core losses decrease up to a silica content of 0.04 moi corresponding to an increase in. yu i . At higher silica contents the core losses are always higher going through a peak at 0.08 mol%. The peak becomes more predominant (v) as frequency increases. Similar effects have been observed in the case of Ge02 additions though the peak in the core losses occurs at 1.28 mol%. This peak is also found to be more predominant at higher frequencies. Sn02 additions are n ot found to affect the core losses appreciably. The hysteresis loops under similar conditions have also been studied. The measurements of loop areas suggest that the core losses measured are essentially the hysteresis losses. Core losses/frequency therefore represent the loop area. At low impurity concentrations (up to 0.04 mol% Si02 and 0.64 mol% Ge0 2 ), core losses decrease mainly due to a decrease in H e which has been found to follow the relationship Ho :.DP \u27 S . At a Si0 2 concentration of 0.08 mol% and a Ge02 concentration of 1,28 mol%, an increase in loop area with frequency is observed. These very samples also exhibit giant grains with large trapped porosity. These effects have been attributed to the relaxation of amplitude permeability at high field strengths. At higher field strengths, closure domains are formed at intragranular pores enabling the domain walls to become detached from the pores. This process is a comparatively slow process and therefore the amplitude permeability is subjected to a strong relaxation even at frequencies of 10 to 50 KHz, At further higher Si0 2 and Ge0 0 contents the core losses/frequency are always high but are independent of frequency. The coercive force, H o is found to be much higher than that given by the relationship Here Dp0 5. It is discussed (vi) that this increase in Nc has been brought in by the presence of inclusions inside the grains. The Ares ence of the grain boundary phase around the grains is also responsible for increasing the losses since it gives rise to wall discontinuities resulting in the demagnetizing effects. This phase also puts the grains under stress while cooling further deteriorating the core losses. Finally, the major conclusions drawn from the entire study are listed under the \u27CONCLUSIONS\u27

Prospective evaluation of causes of infertility at a tertiary care hospital

Background: Infertility is defined as the failure to achieve a clinical pregnancy after 12 months or more of regular unprotected sexual intercourse. Worldwide, its prevalence is approximately 8-12%. There are numerous factors such as anatomical, physiological, genetic, environmental and acquired factors that cause infertility. The aim of the present study was to determine the causes and clinical pattern of infertility in infertile couples in North West India.Methods: It was a hospital based observational study carried out on 211 infertile couples in reproductive age group attending infertility clinic of Sardar Patel Medical College and associated PBM Hospital, Bikaner, Rajasthan between September 2016-February 2017. Collection of data was performed by means of a specifically designed questionnaire, which apart from the demographic data also included questions concerning the causes of infertility. Cases of infertility diagnosed after detailed history, clinical examinations and laboratory tests were included.Results: Out of 211 infertile couples, female factor was predominant in 60.18%, male factor in 15.16%, unexplained in 15.16% while a combination of both factors was seen in 9.47% cases in our study. 33.17% women had ovulatory dysfunction diagnosed by menstrual history and ultrasonography. Tubal block was observed in 9.47% infertile women. 6.63% women had hypothyroidism and 1.89% infertile women were diagnosed to have endometriosis. Husband semen analysis was also done to assess male factor. Nearly 5.21% of their male partners suffered from oligospermia, 4.73% had azoospermia and oligoasthenospermia was observed in 3.79% male partners.Conclusions: Predominant cause of infertility can be reported in male or female partner or both so, either partner should be counselled and investigated properly. Our study reports a predominance of female factors as a cause of female infertility but male factors also accounted for a significant number of cases

Three-dimensional isofield micromechanics model for effective electrothermoelastic properties of piezoelectric composites

A fully coupled three-dimensional micromechanics model based on the isofield method is developed for the effective electrothermoelastic properties of piezoelectric fiber-reinforced composite (PFRC) materials with poling and an electric field applied normal to the fiber direction. In the isofield method, the strain and electric field components parallel to the plane connecting two phases are assumed to be uniform across both phases, and likewise for the stress and electric displacement components normal to the connecting plane. The model employs the isofield assumptions for two possible connectivities, which are then combined so as to yield transverse isotropy of the effective properties when both constituents are transversely isotropic. The assumption of uniform electric field across two phases made by some existing theories can be achieved as a special case of the present formulation when the dielectric constants of the fiber and matrix phases are equal. The effects of the fiber volume fraction and dielectric ratio on the effective properties are studied for two PFRC systems, PZT-7A/epoxy and PZT-5H/epoxy. The results are compared with those available in the literature based on uniform electric field assumptions. It is found that the dielectric ratio has a very significant effect on the electromechanical and electrothermal coupling constants of PFRCs

Maternal and perinatal outcome of placenta previa in a tertiary care centre: an observational study

Background: Placenta previa is an important cause of maternal and fetal morbidity and mortality and is on forefront in deadly triad for maternal mortality followed by eclampsia and sepsis in India. To determine the incidence, maternal and perinatal outcomes among women with placenta previa.Methods: This is a prospective observational study carried out at in the Department of Obstetrics and Gynaecology of a tertiary care hospital of Northern India for a period of six months between Feb 2018 to July 2018.Results: Total number of patients delivered during this period was 6840 and out of which 35 patients were diagnosed with placenta previa, so the incidence is 0.51%. Incidence of placenta previa was the highest in the maternal age group 20-30 years i.e. 71.42%. Placenta previa was noticed in 17.14% of the women with previous cesarean section. Caesarean hysterectomy was performed in 2.85%, 11.42% of the women had postpartum haemorrhage. Perinatal morbidity was studied as the percentage of babies requiring resuscitation and NICU admission which was 25.71 %. There was 19.99 % perinatal mortality.Conclusions: Placenta previa is a major cause of maternal and perinatal morbidity and mortality which could be prevented by early registration, regular antenatal care, early detection of high-risk cases, and early referral to higher centre with good NICU services and blood bank facility

EFFECT OF COCONUT WATER SUPPLEMENTATION ON BLOOD PRESSURE OF PRIMARY HYPERTENSIVE SUBJECTS.

Objective: To investigate the effect of Tender Coconut Water (TCW) on the blood pressure (BP) of Primary hypertensive subjects. Materials and methods: 70 subjects were chosen at random for the 6-week intervention program. Forty subjects were selected as the experimental group and given 300ml per day for six weeks, while the control group was instructed to adhere to the same regimen. Both groups underwent an initial, two mid-intervention (every 15 days), and a final (post-intervention) blood pressure measurement. The obtained data was analyzed statistically. Results: The average systolic blood pressure of the experimental and control groups decreased from 145.8 mm Hg and 141 mm Hg, respectively, to 135.3 mm Hg and 140 mm Hg, respectively. The average diastolic blood pressure of the experimental and control groups decreased from 93.7 and 90.9 mmHg to 86.9 and 89.7 mmHg, respectively. Conclusion: Regardless of the aetiology of hypertension, TCW has a beneficial effect on blood pressure. TCW contains a high concentration of potassium, which induces vasodilation and enhances endothelial function. Recommendation: A complete medical and family history is recommended and should include values of blood pressure, risk factors, overall cardiovascular risk assessment, signs and symptoms of coexistent/hypertension illness, and symptoms of secondary hypertension

SYNTHESIS AND CHARACTERIZATION OF STARCH MALONATE: DEVELOPMENT OF FAST DISSOLVING TABLETS OF ACECLOFENAC BY 23 FACTORIAL DESIGNS

Objective: The aim of the research work is to develop a new superdisintegrant (starch malonate) which can help in enhancing the solubility and drug dissolution of poorly soluble drugs. Hence, starch malonate (new superdisintegrant) was prepared and has been evaluated for its superdisintegrant property by incorporating it into fast dissolving tablets of Aceclofenac. Methods: Superdisintegrant was developed by using esterification reaction. Prepared starch malonate was then subjected for different characterization tests (solubility, pH, melting point, swelling index, FTIR, DSC studies. 23 factorial design method was used to formulate fast dissolving tablets of aceclofenac employing starch malonate. Two known superdisintegrants croscarmellose sodium and crospovidone have been used along with starch malonate in combinations to develop fast dissolving tablets. Prepared tablets were then subjected to different tests for tablets like hardness, friability, disintegration time, dissolution studies. A stability study was performed to determine the stability of the formulation. Design expert study was conducted to know the interaction between different superdisintegrants and to select best optimized formulation in among all formulations. Results: Starch malonate prepared was found to be fine, free flowing slightly crystalline powder, insoluble in aqueous and organic solvents. Tablets of all formulations were of excellent quality concerning drug content (100±5%), hardness (3.8-4.2 kg/cm2), and friability (less than 0.15%). In all formulations, formulation F2 found to be optimized formulation with least disintegration time 38 S, less wetting time 17±0.08 s and enhanced percent dissolved rate in 5 min i.e., 99.84% as compared to other formulations. Conclusion: From this it was concluded that starch malonate can be used as a novel superdisintegrant to enhance the drug dissolution of poorly soluble drugs. Optimized formulation F2 showed enhanced drug dissolution at 5% concentration as compared to other formulation and showed least disintegration time and enhanced drug dissolution as compared to other formulations and pure drug

Parenteral Suspensions: Stability Enhancing Liquid Dosage Forms

Oral route is the most common preferred route. In market number of drugs are available with solubility problem. It is difficult to prefer oral conventional dosage form other drugs on this less solubility which result in loss bioavailability. Parenteral suspensions are dosage forms containing drugs having low solubility. Drugs in suspension form increase the solubility, stability of the drugs. Drugs in sulfonation form have large surfaces areas. Parenteral suspensions provides onset of action for prolonged line on compared to solution. Keywords: Stability, Parenteral suspensions, Syringebility, Dosage forms

Plant Growth-Promoting Bacteria (PGPB) for Sustainable Agriculture: Current Prospective and Future Challenges

Sustainable agriculture is a global imperative to meet the challenges of food security and environmental protection. Plant Growth-Promoting Bacteria (PGPB) have emerged as key players in sustainable agricultural practices due to their diverse roles in enhancing plant growth, nutrient uptake, stress tolerance, and disease resistance. This review explores the diverse facts about PGPB and their potential applications in sustainable agriculture. The review begins by elucidating the mechanisms underlying PGPB-plant interactions, including phytohormone production, nutrient solubilization, and biocontrol activities. This review delves into the intricate signalling networks involved in PGPB-induced systemic resistance. In addition, this review discusses the pivotal role of PGPBs in mitigating abiotic stresses such as drought, salinity, and heavy metal toxicity, highlighting their contributions to climate-resilient agriculture. The ecological implications of PGPB application in sustainable agriculture are discussed, emphasizing the need for responsible and environmentally friendly practices. Furthermore, the use of PGPB for sustainable agriculture holds great promise for addressing the challenges of food security and environmental sustainability. In addition, this review provides a comprehensive overview of the multiple roles, mechanisms of action, and potential applications of PGPB, while emphasizing the importance of responsible and environmentally sound approaches in realizing the full potential of PGPB for a resilient and sustainable agricultural future

Extended Kantorovich 3D solution and performance of 2D laminate theories for edge effects in smart piezolaminated structures

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A CORRELATIONAL ANALYSIS OF CARDIAC AUTONOMIC NEUROPATHY, ARTERIAL STIFFNESS, AND LIPID PROFILE IN DIABETIC PATIENTS

Objective: It is necessary to comprehend the mechanistic connections between cardiovascular risk factors. This is the foundation for the present investigation. Materials and Methods: In the cross-sectional and observational research, patients with T2DM aged 53 to 62 years and age- and gender-matched healthy control subjects were recruited (n = 30 each, eight women). After obtaining the participants' consent, anthropometric measurements, physiological parameters including resting heart rate, peripheral blood pressure (PBP), central blood pressure (CBP), augmentation index% (AIx%), brachial-ankle pulse wave velocity, and lead II ECG for analysis of heart rate variability parameters were obtained. In addition, the lipid profile and fasting blood glucose were evaluated. Results: In T2DM patients, peripheral systolic blood pressure was significantly higher (P = 0.05). Patients with T2DM demonstrated dyslipidemia. In T2DM patients, the atherogenic index of plasma (AIP) was also significantly higher. The AIP index was discovered to have a negative association with HF. Multiple regression analysis identifies serum TG, high-density lipoprotein cholesterol (HDL-C), and AIP index as independent predictors of T2DM vasculopathy. Conclusion: Atherogenic dyslipidaemia was observed in T2DM patients in conjunction with elevated serum levels of TG, VLDL-C, and decreased serum levels of HDL-C in the present study. In addition, the AIP index, a predictor of cardiovascular risk, was significantly greater in T2DM patients. In these patients, dyslipidaemia was discovered to be associated with dysregulation of the autonomic nervous system. Recommendation: Recommendations for the treatment of CAN include early optimization of blood glucose regulation to avoid or delay the development of CAN in people with T1DM