Comparison of the effect of different medicaments on surface reproduction of two commercially available Polyvinyl Siloxane impression materials: an Invitro Study

Objective:To determine the effect of different retraction cord medicaments on surface detail reproduction of polyvinyl siloxane impression materials and compare this effect on any two brands of commercially available polyvinyl siloxane impression materials. Material and methods: Four stainless steel dies were made according to ADA specification no.19. Three dies were treated with aluminium chloride (5%), ferric sulphate (13.3%) and epinephrine (0.1%) while the fourth one was left untreated to serve as control. Two impression materials (Dentsply and 3M ESPE) were used. Results: All the three medicaments adversely affected the surface detail reproduction of both the brands of the polyvinyl siloxane impression materials. These effects were statistically significant as compared to untreated control. The impressions of 3M ESPE brand have shown better surface detail reproduction as compared to Dentsply impression material. Conclusion: Surface detail reproduction of the polyvinyl siloxane impression materials is adversely affected by the retraction cord medicaments. The presence of moisture or any traces of the medicaments should be removed from the tooth surface to provide a dry field for the correct reproduction of the surface detail of these material

Maternal and perinatal outcome in eclampsia at a tertiary care center

Background: Preeclampsia is the occurrence of hypertension in combination with proteinuria, developing after 20 weeks gestation in a previously normotensive non-proteinuric patient. The objective of this study was to study the prevalance of eclampsia at PGIMS, Rohtak. To study the clinical profile, maternal and perinatal outcome in eclamptic patients.Methods: This is a retrospective study and case records of all eclampsia cases were analysed from the study period of January 2018 to December 2018.Results: There were 113 cases of eclampsia out of 11,661 deliveries and prevalence of eclampsia was calculated to be 0.96%. Majority of the patients were not registered 95.57%. 58% of patients were Primigravidas. 56% of the patient in the age group of 21-25 years. Antepartum, intrapartum and postpartum eclampsia were 71%, 1.7% and 27% respectively. Caesarean section was the preferred mode of delivery and was performed in 57% cases. ICU admission was required in 25% and remaining cases were managed in general/eclampsia ward. All patients received MgSO4 by Zuspan regimen. 12% patient developed HELLP syndrome and pulmonary oedema developed in 6% patient. There were a total of 3.5% maternal deaths during the study period. Total percentage of perinatal deaths due to eclampsia was 23%.Conclusions: Eclampsia continues to be one of the prime etiological factors for maternal and perinatal morbidity and mortality. This is due to lack of proper antenatal care, low socioeconomic condition and lack of education. Regular antenatal checkup, early recognition and proper management are vital to tackle this challenge. MgSo4 is the anticonvulsant of choice and Zuspan regimen of MgSO4 is effective in the management of eclampsia

Maternal and neonatal outcome in pregnancy with previous lower segment caesarean section undergoing trial of scar

Background: Women with previous LSCS often have to make a decision about mode of delivery of their second baby. As the rate of caesarean section is continuously increasing, vaginal birth after caesarean section (VBAC) is a good strategy to decrease caesarean rate. The present study was planned to assess the fetomaternal outcome in pregnancies with previous lower segment caesarean section undergoing trial of scar and to identify the factors, which can influence the outcome of trial of scar.Methods: This was a prospective observational study on 100 patients at a tertiary care institute. Pregnant women with previous LSCS were selected randomly for the study on the basis of the inclusion and exclusion criteria. Each labor monitored closely using a partogram. Decision for repeat emergency caesarean was taken by consultant. All women included in the study were followed through delivery and till discharge.Results: Out of 100 pregnant women 49 % cases had successful VBAC, 50% had emergency caesarean and one patient had laparotomy for rupture uterus. In women, who also had a prior vaginal delivery, 72% delivered vaginally, as compared to 40% of the women who did not undergo prior vaginal delivery (p value=0.003). Women who were in spontaneous labor, 59.21% delivered vaginally, whereas women who were induced, 16.6% delivered vaginally. The rate of perinatal complication was more in the patients who required an emergency CS after a failed trial. Conclusions: Our findings may encourage obstetricians to encourage VBAC in the properly screened ANC patients and decrease the rate of recommending caesarean section

VO2 Phase Change Electrodes in Li-ion Batteries

Use of electrode materials that show phase change behavior and hence drastic changes in electrochemical activity during operation, have not been explored for Li-ion batteries. Here we demonstrate the vanadium oxide (VO2) cathode that undergoes metal-insulator transition due to first-order structural phase transition at accessible temperature of 68{\deg}C for battery operation. Using a suitable electrolyte operable across the phase transition range and compatible with vanadium oxide cathodes, we studied the effect of electrode structure change on lithium insertion followed by the electrochemical characteristics above and below the phase transition temperature. The high-temperature VO2 phase shows significantly improved capacitance, enhanced current rate capabilities, improved electrical conductivity and lithium-ion diffusivity compared to the insulating low temperature phase. This opens up new avenues for electrode designs, allowing manipulation of electrochemical reactions around phase transition temperatures, and in particular enhancing electrochemical properties at elevated temperatures contrary to existing classes of battery chemistries that lead to performance deterioration at elevated temperatures.Comment: 21 pages, 4 figure

Nanostructured Silicon–Carbon 3D Electrode Architectures for High-Performance Lithium-Ion Batteries

Silicon is an attractive anode material for lithium-ion batteries. However, silicon anodes have the issue of volume change, which causes pulverization and subsequently rapid capacity fade. Herein, we report organic binder and conducting diluent-free silicon–carbon 3D electrodes as anodes for lithium-ion batteries, where we replace the conventional copper (Cu) foil current collector with highly conductive carbon fibers (CFs) of 5–10 μm in diameter. We demonstrate here the petroleum pitch (P-pitch) which adequately coat between the CFs and Si-nanoparticles (NPs) between 700 and 1000 °C under argon atmosphere and forms uniform continuous layer of 6–14 nm thick coating along the exterior surfaces of Si-NPs and 3D CFs. The electrodes fabricate at 1000 °C deliver capacities in excess of 2000 mA h g–1 at C/10 and about 1000 mA h g–1 at 5 C rate for 250 cycles in half-cell configuration. Synergistic effect of carbon coating and 3D CF electrode architecture at 1000 °C improve the efficiency of the Si–C composite during long cycling. Full cells using Si–carbon composite electrode and Li1.2Ni0.15Mn0.55Co0.1O2-based cathode show high open-circuit voltage of >4 V and energy density of >500 W h kg–1. Replacement of organic binder and copper current collector by high-temperature binder P-pitch and CFs further enhances energy density per unit area of the electrode. It is believed that the study will open a new realm of possibility for the development of Li-ion cell having almost double the energy density of currently available Li-ion batteries that is suitable for electric vehicles

Site-Specific Sodiation Mechanisms of Selenium in Microporous Carbon Host

We combined advanced TEM (HRTEM, HAADF, EELS) with solid-state (SS)MAS NMR and electroanalytical techniques (GITT, etc.) to understand the site-specific sodiation of selenium (Se) encapsulated in a nanoporous carbon host. The architecture employed is representative of a wide number of electrochemically stable and rate-capable Se-based sodium metal battery (SMB) cathodes. SSNMR demonstrates that during the first sodiation, the Se chains are progressively cut to form an amorphous mixture of polyselenides of varying lengths, with no evidence for discrete phase transitions during sodiation. It also shows that Se nearest the carbon pore surface is sodiated first, leading to the formation of a core–shell compositional profile. HRTEM indicates that the vast majority of the pore-confined Se is amorphous, with the only localized presence of nanocrystalline equilibrium Na2Se2 (hcp) and Na2Se (fcc). A nanoscale fracture of terminally sodiated Na–Se is observed by HAADF, with SSNMR, indicating a physical separation of some Se from the carbon host after the first cycle. GITT reveals a 3-fold increase in Na+ diffusivity at cycle 2, which may be explained by the creation of extra interfaces. These combined findings highlight the complex phenomenology of electrochemical phase transformations in nanoconfined materials, which may profoundly differ from their “free” counterparts

Oxide‐Based Solid‐State Batteries: A Perspective on Composite Cathode Architecture

The garnet-type phase Li$_7$La$_3$Zr$_2$O$_{12}$ (LLZO) attracts significant attention as an oxide solid electrolyte to enable safe and robust solid-state batteries (SSBs) with potentially high energy density. However, while significant progress has been made in demonstrating compatibility with Li metal, integrating LLZO into composite cathodes remains a challenge. The current perspective focuses on the critical issues that need to be addressed to achieve the ultimate goal of an all-solid-state LLZO-based battery that delivers safety, durability, and pack-level performance characteristics that are unobtainable with state-of-the-art Li-ion batteries. This perspective complements existing reviews of solid/solid interfaces with more emphasis on understanding numerous homo- and heteroionic interfaces in a pure oxide-based SSB and the various phenomena that accompany the evolution of the chemical, electrochemical, structural, morphological, and mechanical properties of those interfaces during processing and operation. Finally, the insights gained from a comprehensive literature survey of LLZO–cathode interfaces are used to guide efforts for the development of LLZO-based SSBs

Multifunctional Utilization of Pitch‐Coated Carbon Fibers in Lithium‐Based Rechargeable Batteries

This work reports carbon fibers as an electrode material and current collector for dual-carbon and lithium-ion batteries. Fully graphitic and semigraphitic carbon fibers undergo anion intercalation beyond 4.5 V versus Li/Li+. Symmetric dual-carbon full cells using a pitch-coated fully graphitic carbon fiber mat as both cathode and anode delivers an energy-density of 276 and 322 Wh kg−1 at 342 W kg−1 power density in the voltage range of 3.0–5.0 and 3.0–5.2 V, respectively. On the other hand, nongraphitic carbon fibers do not exhibit anion intercalation up to 5.2 V and can be used as a current collector. They also possess a larger number of Li+ storage sites in their randomly oriented microstructure when used as an anode. A lithium-ion full cell with double carbon-coated C-LiFePO4 loaded on nongraphitic carbon fiber as a cathode and pitch-coated nongraphitic carbon fiber as an anode exhibits 202.6 and 75.2 Wh kg−1 energy density at power densities of 46.75 W kg−1 and 11.7 kW kg−1, respectively in 2.0–3.5 V range. This pitch-coated carbon fiber-based battery configuration eliminates the need for metal foils and costly fluorinated binders, lowers overall weight of the cell, and is capable of sustaining mechanical stress and thermal shock

Artificial Solid Electrolyte Interphase To Address the Electrochemical Degradation of Silicon Electrodes

Electrochemical degradation on silicon (Si) anodes prevents them from being successfully used in lithium (Li)-ion battery full cells. Unlike the case of graphite anodes, the natural solid electrolyte interphase (SEI) films generated from carbonate electrolytes do not self-passivate on Si, causing continuous electrolyte decomposition and loss of Li ions. In this work, we aim at solving the issue of electrochemical degradation by fabricating artificial SEI films using a solid electrolyte material, lithium phosphorus oxynitride (Lipon), which conducts Li ions and blocks electrons. For Si anodes coated with Lipon of 50 nm or thicker, a significant effect is observed in suppressing electrolyte decomposition, while Lipon of thinner than 40 nm has a limited effect. Ionic and electronic conductivity measurements reveal that the artificial SEI is effective when it is a pure ionic conductor, but electrolyte decomposition is only partially suppressed when the artificial SEI is a mixed electronic–ionic conductor. The critical thickness for this transition in conducting behavior is found to be 40–50 nm. This work provides guidance for designing artificial SEI films for high-capacity Li-ion battery electrodes using solid electrolyte materials