Leakage gate current in a heterostructure field effect transistor

A theoretical formulation for the leakage gate current in a heterostructure insulated-gate field effect transistor (HIGFET) is presented. Three important components of the leakage gate current, namely 2-D tunneling, 3-D tunneling and thermionic emission current, are considered. The conduction band edge profile of the HIGFET is obtained by a self consistent solution to the Poisson and Schroedinger equations. The transmission coefficient for 2-D and 3-D tunneling currents is obtained by solving the Schroedinger equation; The leakage gate currents are obtained as a function of the gate voltage for the AlI-nAs/GaInAs and AlGaAs/GaAs based HIGFET structures. For the AlInAs/GaInAs system, the calculated leakage currents are within a factor of 10 of the experimental values for most of the voltage range of study. This is more accurate than the results obtained in earlier literature, where the currents are off by more than a factor of 100 for most of the voltage range. For the AlGaAs/GaAs system, the qualitative behaviour of the results are good, however, the calculated currents are off by about a factor of 1000 for most gate voltages. The reasons for this discrepancy are discussed

Synthesis and analysis of carbon nanowalls and their raman spectroscopy

Growth of Carbon Nanowalls has been carried out by Radio Frequency Chemical Vapor Deposition (RF-PECVD) on various substrates. Hydrogen was used as an active gas for the growth where as Ethanol bubbled with Argon was used as carbon source for formation of Carbon Nanowalls (CNW). The growth was then confinned by Raman Spectroscopy and Scanning Electron Microscope (SEM) images. Also the need of using catalyst in CNW has been analyzed. The intensities of D and G bands obtained from Raman spectrum have been related to the length of Graphene walls, to study the CNW\u27s length on different substrates. The growth was carried on three substrates; Silicon wafer, Silicon wafer coated with Nickel Formate Dihydrate (NFD) as a catalyst.and Pure Nickel foil. It has been found that the catalyst does not play much important role in the growth of Carbon Nanowalls. Also it has been determined that Graphene sheets are the basic building blocks for nanowalls and the Graphene walls obtained in our experiment comprise only of one to two Graphene sheets. The morphologies of the growth of Carbon Nanowalls have been studied on the three substrates using SEM images. The growth of CNW in case of Silicon substrate and Silicon substrate having catalyst was found to be only in that direction and places, where the gases were passing these substrates. But in case of Nickel foil CNWs were found over the whole substrate that might be resulting because of Nickel itself acting as an active catalyst for the whole surface

Ferroelectric : CNTs structures fabrication for advanced functional nano devices

Doutoramento em Ciência e Engenharia de MateriaisThis work is about the combination of functional ferroelectric oxides with Multiwall Carbon Nanotubes for microelectronic applications, as for example potential 3 Dimensional (3D) Non Volatile Ferroelectric Random Access Memories (NVFeRAM). Miniaturized electronics are ubiquitous now. The drive to downsize electronics has been spurred by needs of more performance into smaller packages at lower costs. But the trend of electronics miniaturization challenges board assembly materials, processes, and reliability. Semiconductor device and integrated circuit technology, coupled with its associated electronic packaging, forms the backbone of high-performance miniaturized electronic systems. However, as size decreases and functionalization increases in the modern electronics further size reduction is getting difficult; below a size limit the signal reliability and device performance deteriorate. Hence miniaturization of siliconbased electronics has limitations. On this background the Road Map for Semiconductor Industry (ITRS) suggests since 2011 alternative technologies, designated as More than Moore; being one of them based on carbon (carbon nanotubes (CNTs) and graphene) [1]. CNTs with their unique performance and three dimensionality at the nano-scale have been regarded as promising elements for miniaturized electronics [2]. CNTs are tubular in geometry and possess a unique set of properties, including ballistic electron transportation and a huge current caring capacity, which make them of great interest for future microelectronics [2]. Indeed CNTs might have a key role in the miniaturization of Non Volatile Ferroelectric Random Access Memories (NVFeRAM). Moving from a traditional two dimensional (2D) design (as is the case of thin films) to a 3D structure (based on a tridimensional arrangement of unidimensional structures) will result in the high reliability and sensing of the signals due to the large contribution from the bottom electrode. One way to achieve this 3D design is by using CNTs. Ferroelectrics (FE) are spontaneously polarized and can have high dielectric constants and interesting pyroelectric, piezoelectric, and electrooptic properties, being a key application of FE electronic memories. However, combining CNTs with FE functional oxides is challenging. It starts with materials compatibility, since crystallization temperature of FE and oxidation temperature of CNTs may overlap. In this case low temperature processing of FE is fundamental. Within this context in this work a systematic study on the fabrication of CNTs - FE structures using low cost low temperature methods was carried out. The FE under study are comprised of lead zirconate titanate (Pb1-xZrxTiO3, PZT), barium titanate (BaTiO3, BT) and bismuth ferrite (BiFeO3, BFO). The various aspects related to the fabrication, such as effect on thermal stability of MWCNTs, FE phase formation in presence of MWCNTs and interfaces between the CNTs/FE are addressed in this work. The ferroelectric response locally measured by Piezoresponse Force Microscopy (PFM) clearly evidenced that even at low processing temperatures FE on CNTs retain its ferroelectric nature. The work started by verifying the thermal decomposition behavior under different conditions of the multiwall CNTs (MWCNTs) used in this work. It was verified that purified MWCNTs are stable up to 420 ºC in air, as no weight loss occurs under non isothermal conditions, but morphology changes were observed for isothermal conditions at 400 ºC by Raman spectroscopy and Transmission Electron Microscopy (TEM). In oxygen-rich atmosphere MWCNTs started to oxidized at 200 ºC. However in argon-rich one and under a high heating rate MWCNTs remain stable up to 1300 ºC with a minimum sublimation. The activation energy for the decomposition of MWCNTs in air was calculated to lie between 80 and 108 kJ/mol. These results are relevant for the fabrication of MWCNTs – FE structures. Indeed we demonstrate that PZT can be deposited by sol gel at low temperatures on MWCNTs. And particularly interesting we prove that MWCNTs decrease the temperature and time for formation of PZT by ~100 ºC commensurate with a decrease in activation energy from 68±15 kJ/mol to 27±2 kJ/mol. As a consequence, monophasic PZT was obtained at 575 ºC for MWCNTs - PZT whereas for pure PZT traces of pyrochlore were still present at 650 ºC, where PZT phase formed due to homogeneous nucleation. The piezoelectric nature of MWCNTs - PZT synthesised at 500 ºC for 1 h was proved by PFM. In the continuation of this work we developed a low cost methodology of coating MWCNTs using a hybrid sol-gel / hydrothermal method. In this case the FE used as a proof of concept was BT. BT is a well-known lead free perovskite used in many microelectronic applications. However, synthesis by solid state reaction is typically performed around 1100 to 1300 ºC what jeopardizes the combination with MWCNTs. We also illustrate the ineffectiveness of conventional hydrothermal synthesis in this process due the formation of carbonates, namely BaCO3. The grown MWCNTs - BT structures are ferroelectric and exhibit an electromechanical response (15 pm/V). These results have broad implications since this strategy can also be extended to other compounds of materials with high crystallization temperatures. In addition the coverage of MWCNTs with FE can be optimized, in this case with non covalent functionalization of the tubes, namely with sodium dodecyl sulfate (SDS). MWCNTs were used as templates to grow, in this case single phase multiferroic BFO nanorods. This work shows that the use of nitric solvent results in severe damages of the MWCNTs layers that results in the early oxidation of the tubes during the annealing treatment. It was also observed that the use of nitric solvent results in the partial filling of MWCNTs with BFO due to the low surface tension (<119 mN/m) of the nitric solution. The opening of the caps and filling of the tubes occurs simultaneously during the refluxing step. Furthermore we verified that MWCNTs have a critical role in the fabrication of monophasic BFO; i.e. the oxidation of CNTs during the annealing process causes an oxygen deficient atmosphere that restrains the formation of Bi2O3 and monophasic BFO can be obtained. The morphology of the obtained BFO nano structures indicates that MWCNTs act as template to grow 1D structure of BFO. Magnetic measurements on these BFO nanostructures revealed a week ferromagnetic hysteresis loop with a coercive field of 956 Oe at 5 K. We also exploited the possible use of vertically-aligned multiwall carbon nanotubes (VA-MWCNTs) as bottom electrodes for microelectronics, for example for memory applications. As a proof of concept BiFeO3 (BFO) films were in-situ deposited on the surface of VA-MWCNTs by RF (Radio Frequency) magnetron sputtering. For in situ deposition temperature of 400 ºC and deposition time up to 2 h, BFO films cover the VA-MWCNTs and no damage occurs either in the film or MWCNTs. In spite of the macroscopic lossy polarization behaviour, the ferroelectric nature, domain structure and switching of these conformal BFO films was verified by PFM. A week ferromagnetic ordering loop was proved for BFO films on VA-MWCNTs having a coercive field of 700 Oe. Our systematic work is a significant step forward in the development of 3D memory cells; it clearly demonstrates that CNTs can be combined with FE oxides and can be used, for example, as the next 3D generation of FERAMs, not excluding however other different applications in microelectronics.Este trabalho é sobre a combinação de óxidos ferroelétricos funcionais com nanotubos de carbono (CNTs) para aplicações na microeletrónica, como por exemplo em potenciais memórias ferroelétricas não voláteis (Non Volatile Ferroelectric Random Access Memories (NV-FeRAM)) de estrutura tridimensional (3D). A eletrónica miniaturizada é nos dias de hoje omnipresente. A necessidade de reduzir o tamanho dos componentes eletrónicos tem sido estimulada por necessidades de maior desempenho em dispositivos de menores dimensões e a custos cada vez mais baixos. Mas esta tendência de miniaturização da eletrónica desafia consideravelmente os processos de fabrico, os materiais a serem utilizados nas montagens das placas e a fiabilidade, entre outros aspetos. Dispositivos semicondutores e tecnologia de circuitos integrados, juntamente com a embalagem eletrónica associada, constituem a espinha dorsal dos sistemas eletrónicos miniaturizados de alto desempenho. No entanto, à medida que o tamanho diminui e a funcionalização aumenta, a redução das dimensões destes dipositivos é cada vez mais difícil; é bem conhecido que abaixo de um tamanho limite o desempenho do dispositivo deteriora-se. Assim, a miniaturização da eletrónica à base de silício tem limitações. É precisamente neste contexto que desde 2011 o Road Map for Semiconductor Industry (ITRS) sugere tecnologias alternativas às atualmente em uso, designadas por Mais de Moore (More than Moore); sendo uma delas com base em carbono (CNTs e grafeno) [1]. Os CNTs com o seu desempenho único e tridimensionalidade à escala nanométrica, foram considerados como elementos muito promissores para a eletrónica miniaturizada [2]. Nanotubos de carbono possuem uma geometria tubular e um conjunto único de propriedades, incluindo o transporte balístico de eletrões e uma capacidade enorme de transportar a corrente elétrica, o que os tornou de grande interesse para o futuro da microeletrónica [2]. Na verdade, os CNTs podem ter um papel fundamental na miniaturização das memórias ferroelétricas não voláteis (NV-FeRAM). A mudança de uma construção tradicional bidimensional (2D) (ou seja, a duas dimensões, como são os filmes finos) para uma construção tridimensional 3D, com base num arranjo tridimensional de estruturas unidimensionais (1D), como são as estruturas nanotubulares, resultará num desempenho melhorado com deteção de sinal elétrico optimizada, devido à grande contribuição do elétrodo inferior. Uma maneira de conseguir esta configuração 3D é usando nanotubos de carbono. Os materiais ferroelétricos (FE) são polarizados espontaneamente e possuem constantes dielétricas altas e as suas propriedades piroelétricas, piezoelétricas e eletroópticas tornam-nos materiais funcionais importantes na eletrónica, sendo uma das suas aplicações chave em memórias eletrónicas. No entanto, combinar os nanotubos de carbono com óxidos FE funcionais é um desafio. Começa logo com a compatibilidade entre os materiais e o seu processamento, já que as temperaturas de cristalização do FE e as temperaturas de oxidação dos CNTs se sobrepõem. Neste caso, o processamento a baixa temperatura dos óxidos FE é absolutamente fundamental. Dentro deste contexto, neste trabalho foi realizado um estudo sistemático sobre a fabricação e caracterização estruturas combinadas de CNTs – FE, usando métodos de baixa temperatura e de baixo custo. Os FE em estudo foram compostos de titanato zirconato de chumbo (Pb1-xZrxTiO3, PZT), titanato de bário (BaTiO3, BT) e ferrite de bismuto (BiFeO3, BFO). Os diversos aspetos relacionados com a síntese e fabricação, como efeito sobre a estabilidade térmica dos nanotubos de carbono multiparede (multiwall CNTs, MWCNTs), formação da fase FE na presença de MWCNTs e interfaces entre CNTs / FE foram abordados neste trabalho. A resposta ferroelétrica medida localmente através de microscopia de ponta de prova piezoelétrica (Piezoresponse Force Microscopy (PFM)), evidenciou claramente que, mesmo para baixas temperaturas de processamento óxidos FE sobre CNTs mantém a sua natureza ferroelétrica. O trabalho começou pela identificação do comportamento de decomposição térmica em diferentes condições dos nanotubos utilizados neste trabalho. Verificou-se que os MWCNTs purificados são estáveis até 420 ºC no ar, já que não ocorre perda de peso sob condições não isotérmicas, mas foram observadas, por espectroscopia Raman e microscopia eletrónica de transmissão (TEM), alterações na morfologia dos tubos para condições isotérmicas a 400 ºC. Em atmosfera rica em oxigénio os MWCNTs começam a oxidar-se a 200 ºC. No entanto, em atmosfera rica em árgon e sob uma taxa de aquecimento elevada os MWCNTs permanecem estáveis até 1300 ºC com uma sublimação mínima. A energia de ativação para a decomposição destes MWCNTs em ar foi calculada situar-se entre 80 e 108 kJ / mol. Estes resultados são relevantes para a fabricação de estruturas MWCNTs - FE. De facto, demonstramos que o PZT pode ser depositado por sol-gel a baixas temperaturas sobre MWCNTs. E, particularmente interessante foi provar que a presença de MWCNTs diminui a temperatura e tempo para a formação de PZT, em cerca de ~ 100 ºC comensuráveis com uma diminuição na energia de ativação de 68 ± 15 kJ / mol a 27 ± 2 kJ / mol. Como consequência, foi obtido PZT monofásico a 575 ºC para as estruturas MWCNTs – PZT, enquanto que para PZT (na ausência de MWCNTs) a presença da fase de pirocloro era ainda notória a 650 ºC e onde a fase de PZT foi formada por nucleação homogénea. A natureza piezoelétrica das estruturas de MWCNTs - PZT sintetizadas a 500 ºC por 1 h foi provada por PFM. Na continuação deste trabalho foi desenvolvida uma metodologia de baixo custo para revestimento de MWCNTs usando uma combinação entre o processamento sol – gel e o processamento hidrotermal. Neste caso o FE usado como prova de conceito foi o BT. BT é uma perovesquita sem chumbo bem conhecida e utilizada em muitas aplicações microeletrónicas. No entanto, a síntese por reação no estado sólido é normalmente realizada entre 1100 - 1300 ºC o que coloca seriamente em risco a combinação com MWCNTs. Neste âmbito, também se ilustrou claramente a ineficácia da síntese hidrotérmica convencional, devido à formação de carbonatos, nomeadamente BaCO3. As estruturas MWCNTs - BT aqui preparadas são ferroelétricas e exibem resposta electromecânica (15 pm / V). Considera-se que estes resultados têm impacto elevado, uma vez que esta estratégia também pode ser estendida a outros compostos de materiais com elevadas temperaturas de cristalização. Além disso, foi também verificado no decurso deste trabalho que a cobertura de MWCNTs com FE pode ser optimizada, neste caso com funcionalização não covalente dos tubos, ou seja, por exemplo com sodium dodecyl sulfate (SDS)

Fabrication of composite thick films of BaLa4Ti4O15 and Ba4Nd9.33Ti18O54 by electrophoretic deposition

Mestrado em Ciência e Engenharia de MateriaisAs comunicações sem fios experimentaram um crescimento excepcional nas últimas décadas e que se prevê que continue nos próximos anos (Capítulo 1, Referêcia 3) Com este crescimento há uma procura crescente de dispositivos de menores dimensões e mais versáteis, do que os actualmente existentes, que permitam maiores níveis de integração, possibilidade de operação a altas frequências e produção a custos reduzidos. Actualmente existe também a necessidade de desenvolver materiais com permitividade dieléctrica relativa (εr) entre 40 - 80, baixas perdas dieléctricas e coeficiente de temperatura da frequência de ressonância (tf) próximo de zero. Actividades de investigação e desenvolvimento para explorar a utilização de tecnologias de fabrico de filmes finos e espessos para substituir os materiais cerâmicos em uso corrente, estão actualmente em curso. Neste contexto, foi explorada no presente trabalho a fabricação de filmes espessos por deposição electroforética (EPD) do composto BaLa4Ti4O15 (BLT), cuja selecção se relaciona com as óptimas propriedades que apresenta para aplicação às frequências das microondas. Foi igualmente tentada a preparação de filmes espessos compósitos de BaLa4Ti4O15 (BLT) - Ba4Nd9.33Ti18O54 (BNT) para preenchimento do intervalo existente em termos de materiais com permitividades dieléctricas 40-80. A escolha da deposição electroforética de entre os vários processos de fabricação de filmes espessos prende-se com as características únicas desta técnica, nomedamente, elevada flexibilidade e simplicidade para aplicação a vários materiais e combinação de materiais, possibilidade de aplicação a uma gama variada de formas e estruturas tridimensionais complexas, densas e porosas e a capacidade de ser utilizada à escala industrial a baixos custos. Neste trabalho foi seguida uma aproximação sistemática para a fabricação dos filmes espessos compósitos pr EPD. Primeiramente procedeu-se à síntese de pós monofásicos de BLT e BNT pelo processo convencional de reacção no estado sólido e a sua pureza foi confirmada por análises de Difracção de Raios X. O tamanho e distribuição de tamanho e a morfologia dos pós de BLT e BNT foram caracterizados por recurso a técnicas de determinação de tamanho de partícula e microscopia electrónica de varrimento. De seguida foram preparadas suspensões dos pós de BNT e BLT em diferentes meios suspensores, como água, etanol e trietanolamina. Ao mesmo tempo, foi estudada a estabilidade das suspensões por análises de tamanho de partícula e medidas de transmitância de luz UV. As suspensões com estabilidade optimizada foram utilizadas para deposição de filmes espessos, em meio básico e meio ácido e foram estudadas as variáveis de processamento, como espessura, massa do depósito, corrente eléctrica em função do tempo e voltagem. Foi também discutido o efeito do passo de prensagem isostática, após deposição, na morfologia e densidade dos filmes e também na sua resposta dieléctrica. Filmes de BLT de 10 mm de espessura depositados sobre folhas de platina e sinterizados a 1600ºC/1h exibem εr = 58, TCεr +30ppm/ºC e perda dieléctrica de 0.002 a 1 MHz. Como termo de comparação foram preparados cerâmicos de BLT. Foi feita a caracterização estrutural, microestrutural e dieléctrica de filmes e cerâmicos de BLT, sinterizados entre 1400ºC e 1600ºC. Filmes espessos compósitos de BNT/BLT e BLT/BNT foram preparados com sucesso por EPD. Através da combinação de camadas de BLT e BNT foram preparados filmes espessos compósitos de 30 μm com εr ~71, TCεr ~-16ppm/ºC e perda dieléctrica de a 1 MHz. Estes resultados são de particular relevância visto que combinam a possibilidade de preparar filmes espessos com propriedades desenhadas para aplicações a frequências elevadas e das microondas com a capacidade de diminuir o tamanho do dispositivo. Embora preliminares estes resultados abrem novas oportunidades tecnológicas, que deverão ser mais exploradas ABSTRACT: Wireless communications have experienced an exceptional growth in the last decades and similar growth is expected for next coming years, according to the ABI analysis [Chapter 1, Reference 3]. With this growth there is an increase demand for the production of devices of smaller dimensions and more flexible than the current in use ones, with increased integration, possibility of operation at high frequencies and produced with reduced costs. There is also a present demand to develop materials with relative permittivity (εr) between 40 - 80, low loss and near zero temperature coefficient of resonant frequency (tf). Research activities to exploit thin and thick film technologies to replace the bulk ceramics are currently underway. Within this context, in this work, the fabrication of thick films by electrophoretic deposition of the tertiary compound BaLa4Ti4O15 (BLT) was exploited, because of the optimal properties for microwave applications of BLT. Simultaneously, the preparation of BaLa4Ti4O15 (BLT) - Ba4Nd9.33Ti18O54 (BNT) composite thick films was attempted to fill the permittivity gap of 40-80 as describe above. The choice of electrophoretic deposition (EPD) technique over other thick film processing techniques is obvious because of its unique features, such as the high flexibility and simplicity for application with various materials and combinations of materials, and on a wide range of shapes and 3D complex and porous structures, and its ability to be scaled-up to the fabrication of large product volumes and sizes at low costs. A systematic approach was used to fabricate the composite thick films. Firstly, BLT and BNT powders were prepared by solid state reaction synthesis and the phase purity of the powders was confirmed by XRD. The size and morphology of the powders were assessed by particle size analysis and scanning electron microscopy. BNT and BLT suspensions were prepared in different suspension media such as water, ethanol and acetone. The pH of the suspension was varied by dilute nitric acid and triethanolamine. Concomitantly the stability of the suspensions was characterised by particle size analysis and UV transmittance measurements. Stable suspensions were used for the deposition of particles in acidic and basic conditions, and the processing parameters such as thickness, deposit weight, current as a function of time and voltage were studied. The effect of iso static pressing and film thickness on the properties and morphology was also discussed. 10 mm thick BLT films on platinum foils and sintered at 1600ºC/1h exhibit εr = 58, TCεr +30ppm/ºC and loss tangent 0.002 at 1 MHz. As a comparison tool, BLT ceramics were prepared as well. Films and ceramics were sintered between 1400ºC to 1600ºC and their morphology and dielectric response assessed. BNT/BLT and BLT/BNT composite thick films were successfully prepared by electrophoretic deposition. By the combination of BLT and BNT layers a 30 μm composite thick film with εr ~71, TCεr ~-16ppm/ºC and loss tangent of 0.002 at 1 MHz were prepared. These results are of particular relevance since they combine the possibility to prepare thick films with tailored properties for high frequency and microwave properties with the aptitude to decrease the device size. Although preliminary these results open further technological opportunities, that should be more explore

Control of Sexually Transmitted Infections, Reproductive Tract Infections, and HIV/AIDS in India: Current Status and the Way Forward

Sexually transmitted infections (STIs) and reproductive tract infections (RTIs) form an important public health problem with a huge burden of disease and an adverse impact on reproductive health of people worldwide. Caused by a variety of infectious agents and manifesting as different clinical syndromes, STIs/RTIs remain highly prevalent in India too, reportedly up to 6% in general population (and maybe higher in reality due to secrecy maintained by many people around such diseases) and much more in certain vulnerable population groups. The situation has worsened further with the epidemic of human immunodeficiency virus (HIV) infection and resultant acquired immunodeficiency syndrome (AIDS). Similarities of unique host risk behaviors and socio-demographic factors associated with STIs, RTIs and HIV/AIDS call for an integrated approach for their control with multipronged intervention strategies. The National AIDS Control Programme, the National RTI/STI Control Programme, the National Strategy for Elimination of Parent-to-Child Transmission of Syphilis, the National Blood Policy, and other related health programs and policies have set out clear objectives and guiding principles for phased programmatic interventions, with focus on checking the spread of these infections through health education, behavior change, targeted interventions, early diagnosis, and prompt treatment. Freely available and easily accessible services for comprehensive care, support, and treatment of patients with these infections will help reduce the disease burden and improve their reproductive health as well as overall well-being. Increased decentralization of public health services; strengthening institutional capacities; setting up of designated STI/RTI clinics, antiretroviral treatment (ART) clinics and integrated counseling and testing centers; availability of rapid test kits, color-coded drug kits for syndromic treatment and ART treatment; promotion of condoms; integrated counseling and testing; partner notification; involvement of non-governmental organizations; community mobilization; universal precautions and augmentation of voluntary blood donation; robust surveillance; evidence-based planning, and effective program implementation are major components for control of these infections. The present systematic review discusses the current situation, the key programmatic measures, and the way forward for control of STIs/RTIs and HIV/AIDS in India

Broad ligament pregnancy a diagnostic dilemma: a case report

Broad ligament pregnancy is one of the rarest forms of ectopic pregnancy with high risk of maternal mortality. Although ultrasonography is usually helpful in making the diagnosis but it is mostly established during laparotomy. 34 year old G2P1 with previous caesarean section reported at 8th month of pregnancy with inability to perceive foetal movements. Ultrasonography confirmed intrauterine fetal demise. Patient was taken for caesarean section after failed induction. Intraoperative diagnosis of broad ligament pregnancy was made and broad ligament along with fetus, sac, fallopian tube and ovary was excised. Post-operative period was uneventful

Approximate information state based convergence analysis of recurrent Q-learning

In spite of the large literature on reinforcement learning (RL) algorithms for partially observable Markov decision processes (POMDPs), a complete theoretical understanding is still lacking. In a partially observable setting, the history of data available to the agent increases over time so most practical algorithms either truncate the history to a finite window or compress it using a recurrent neural network leading to an agent state that is non-Markovian. In this paper, it is shown that in spite of the lack of the Markov property, recurrent Q-learning (RQL) converges in the tabular setting. Moreover, it is shown that the quality of the converged limit depends on the quality of the representation which is quantified in terms of what is known as an approximate information state (AIS). Based on this characterization of the approximation error, a variant of RQL with AIS losses is presented. This variant performs better than a strong baseline for RQL that does not use AIS losses. It is demonstrated that there is a strong correlation between the performance of RQL over time and the loss associated with the AIS representation.Comment: 25 pages, 6 figure

Management of non-tubal ectopic pregnancies: rural tertiary care centre experience

Non-tubal ectopic pregnancies are rare but potentially life-threatening conditions. Nearly 95% of ectopic pregnancies are implanted in the various segments of fallopian tube. The remaining 5% implant in non-tubal sites like ovary, cervix, rudimentary horn, cesarean scar, abdominal and even heterotopic. Seven patients with non-tubal ectopic pregnancy at rural tertiary institute at Dr. RPGMC Tanda, from February 2020 to January 2021 were included in the study. Demographic details, symptoms, beta human chorionic gonadotrophin (β-hCG) levels, ultrasound findings, management and treatment outcomes were presented. Medical treatment and surgical procedure, alone or combined, resulted in effective treatment in women with early diagnosis of non-tubal ectopic pregnancy and two patients had live birth (heterotopic and abdominal pregnancy). In our study, we report two cases of ovarian pregnancy, one case of rudimentary horn successfully managed surgically, one case of LSCS scar pregnancy managed medically with methotrexate followed by suction and evacuation, one case of cervical pregnancy managed by D&amp;C, one case of heterotopic pregnancy managed surgically and abdominal pregnancy managed surgically. In this paper we report a single centre experience in the management of non-tubal ectopic pregnancy Early diagnosis of ectopic pregnancy especially non tubal ectopic, requires a high index of suspicion and availability of point of care, transvaginal USG. Accurate diagnosis and timely intervention will help reduce maternal morbidity, mortality and preserve future fertility