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Hybrid multilevel converters using bidirectional thyristors and IGBTs have gained significant interest in recent times, as they possess important features of both voltage-source and line-commutated converter technologies. This article presents a classification of hybrid multilevel converters for HVdc applications. The methodologies to derive, evaluate, and select these converter topologies are proposed as well. The hybrid converters are classified from the power device to the system configuration based on the analogy of the voltage-source converter and the current-source converter. Derivation methods of hybrid cell, cluster, arm, phase, and converter, based on the topology tree presented in this article, are applied to derive both existing and new hybrid converters. Comparisons show that hybrid converters have functionality similar to either the modular multilevel converter or the line-commutated converter, depending on the ratio between thyristor and active switch IGBT counts employed. Several hybrid-station configurations are discussed in order to suggest the most suitable converter topology for each configuration. The presented analysis can provide a point of reference and a useful framework for the future developments of hybrid multilevel converters for HVdc applications.

This article studies a new hybrid converter that utilizes thyristors and full-bridge (FB) arms for achieving high-power capability with reduced semiconductor power rating compared to the FB modular multilevel converter. The study covers the theoretical analysis of the energy balancing, the dimensioning principles, the maximum power capability, and the limitations imposed by the discontinuous operation of the converter. Based on the analysis of these aspects, the theoretical analysis is concluded by identifying the operational constraints that need to be fulfilled for maximizing the power capability of the converter. It is concluded that the maximum power capability can be achieved for a certain range of modulation indices and is limited by both the commutation time of the thyristors and the power angle. Moreover, the P – Q capability of the hybrid converter is presented and discussed. Finally, simulation and experimental results that confirm the theoretical analysis and the feasibility of the studied converter are presented and discussed.

Despite the volume of publications dedicated to unraveling the biological characteristics and clinical manifestations of SARS-CoV-2, available data on pregnant patients are limited. In the current review of literature, we present an overview on the developmental course, complications, and adverse effects of COVID-19 on pregnancy. A comprehensive review of the literature was performed in PubMed/Medline, Embase, and Cochrane Central databases up to June 2021. This article collectively presents what has been so far reported on the identified critical aspects, namely complications during pregnancy, delivery challenges, neonatal health care, potential routes of viral transmission, including vertical transmission or breastfeeding, along with the risks involved in the vaccination strategy during pregnancy. Despite the fact that we are still largely navigating uncharted territory, the observed publication explosion in the field is unprecedented. The overwhelming need for data is undoubtable, and this serves as the driver for the plethora of publications witnessed. Nonetheless, the quality of data sourced is variable. In the midst of the frenzy for reporting on SARS-CoV-2 data, monitoring this informational overload is where we should head to next, considering that poor quality research may in fact hamper our attempts to prevail against this unparalleled pandemic outbreak.

The presence of empty zona pellucida (EZP) in oocytes following oocyte retrieval (OR) during an in vitro fertilization (IVF) cycle presents a major clinical and laboratory challenge in assisted reproduction. It has been attributed to several factors such as the ovarian stimulation protocol employed, the damaging of the follicles during oocyte retrieval (OR) mainly through the high aspiration pressure, during the denudation technique, and the degeneration of oolemma within the zona pellucida (ZP) through apoptosis. The role of ZP is pivotal from the early stages of follicular development up to the preimplantation embryo development and embryo hatching. Polymorphisms or alterations on the genes that encode ZP proteins may contribute to EZP. We present a critical review of the published literature hitherto on EZP and available options when encountered with the phenomenon of EZP. Concerning the former, we found that there is rare data on this phenomenon that merits documentation. The latter includes technical, genetic, and pathophysiological perspectives, along with specific treatment options. In conclusion, we identify the lack of a definitive management proposal for couples presenting with this phenomenon, we underline the need for an algorithm, and indicate the questions raised that point towards our goal for a strategy when addressing a previous finding of EZP.

The objective of the study was to evaluate the psychological effect of an intervention of 8 stress-management sessions in women undergoing in vitro fertilization (IVF). Moreover, the overall IVF success was assessed against the fluctuation of the participants' stress levels. A total of 144 women participated in the study with 74 of them in the intervention group and 70 women in the control group. Demographics and medical history of all participants were recorded. The intervention group only underwent 8 weekly stress management sessions. During the 1st and 8th week of the study, both groups completed the Depression, Anxiety, Stress Scale 21 (DASS-21), the Perceived Stress Scale 14 (PSS-14) and the Fertility Problem Inventory (FPI). Following the intervention, the outcome of the IVF cycles, as defined by clinical pregnancy rates, were recorded. Our results indicated that total stress in the intervention group declined significantly (p

Introduction: We aimed to investigate the incidence of hypertension and to identify potential risk factors in healthy, non-diabetic recently postmenopausal Greek women with normal renal function.Pa...

Infertility patients are willing to travel abroad to receive the medical treatment of choice. A 2010 study reported that approximately 25,000 couples travel abroad annually seeking infertility treatment. The purpose of this review is to analyze the criteria and risks related to cross-border reproductive care (CBRC) from the perspective of the patients and explore the issues raised regarding the country of origin and the destination country. A computerized search was performed in PubMed employing respective keywords. The total number of published articles provided by our PubMed search was 1905. Criteria for selecting the destination country include: the economic status, legislation, quality of care and anonymity. Despite the fact that CBRC is becoming a familiar concept, it raises concerns for the practitioner and issues of a social and bioethical nature. Most of them stem from the fact that health care acquires a commercialization aspect. Medical tourism entails several risks, such as misconceptions regarding the destination country, and legal issues arising from differences in the judiciary systems. Larger studies evaluating all aspects of CBRC are imperative. Quality assurance, a consensus and a common platform of practice, along with a system of international governance based on human rights, are a necessity for CBRC patients.

This systematic review aimed to investigate the inconsistency of research data concerning the contribution of systematic psychosocial interventions to infertility treatments. More specifically, the objective of this review was to investigate the cause of the contradictions in the results of contemporary research with respect to the role of systematic psychosocial interventions in the success of fertility treatments. The suspected cause of these contradictions is the heterogeneity of the relevant clinical studies with respect to their methodology. Thus, the specific aim of the current review was to evaluate the degree of heterogeneity of certain parameters in the design of the relevant clinical studies during the last decade, including sample heterogeneity, assisted reproductive technology methods, types of psychosocial interventions and methods of recording and analyzing psychometric data. This investigation may be considered imperative considering that despite the great number of relevant clinical studies and their meta-analyses, there are still no conclusive results concerning the potential of improving fertility through psychosocial support. Search for relevant studies was performed employing the PubMed and Google Scholar databases based on specific criteria. According to these criteria the selected publications have been meta-analyses of clinical studies on humans, evaluating the effect of psychosocial interventions on the success of assisted reproductive treatments during the last decade. The studies may have included all the different infertility etiologies, as well as all types of assisted reproductive treatments. The extensive search based on the specific inclusion/exclusion criteria resulted in reporting results from 6 studies in total. The clinical studies included have reported on various types of interventions for psychosocial support such as individual, couples' or group therapies performed either in facilities offering mental health services or in the form of home-based self-treatment. Moreover, these studies investigated various techniques of stress management ranging from counseling to specialized methods such as biofeedback and diaphragmatic breathing or alternative techniques such as yoga and meditation. Our results suggest that clinical studies designed specifically to evaluate the effect of systematic interventions on the efficacy of fertility treatments are limited. Moreover, their degree of heterogeneity is highly significant with respect to included participants, treatment protocols, psychosocial support techniques as well as methods for the documentation and statistical analysis of psychometric data. Consequently, the conduction of well-design clinical studies based on strict criteria aiming to investigate specific infertility causes, similar fertility treatment protocols or particular types of psychosocial interventions is necessary in order to reach definitive conclusions.

The COVID-19 pandemic has fueled numerous debates in the field of assisted reproductive technology (ART) as the effect of SARS-CoV-2 on pregnancy and infancy is still considered uncharted territory. Various theses and recommendations on what optimal practice is have emerged, as evidenced by surveys, webinars, and recent publications. ART specialists are faced with dilemmas in light of the lack of concrete scientific evidence required to pave the way towards future safe practice. Meanwhile, infertile couples were similarly left in limbo unable to exercise their reproductive autonomy unlike fertile couples-where achieving a pregnancy via natural conception is a matter of decision. ART treatment being classified as non-essential has only recently re-started, facing new challenges while enabling pregnancy at a time of uncertainty. This article highlights matters of bioethical nature to be considered in the ART world at the time of COVID-19 while presenting an all-inclusive critique of the current status. When pursuing pregnancy through IVF treatment during the pandemic, distancing and caution have the lead role in an effort to defend the health of the intended parents and future children. To promote patient autonomy along with our ethical, moral, and legal duty towards our patients, emphasis should be given on ascertaining shared decision-making, and ensuring that an appropriate all-inclusive informed consent is signed prior to initiating any IVF treatment.

Despite recent striking advances in assisted reproductive technology (ART), poor ovarian response (POR) diagnosis and treatment is still considered challenging. Poor responders constitute a heterogeneous cohort with the common denominator of under-responding to controlled ovarian stimulation. Inevitably, respective success rates are significantly compromised. As POR pathophysiology entails the elusive factor of compromised ovarian function, both diagnosis and management fuel an ongoing heated debate depicted in the literature. From the criteria employed for diagnosis to the plethora of strategies and adjuvant therapies proposed, the conundrum of POR still puzzles the practitioner. What is more, novel treatment approaches from stem cell therapy and platelet-rich plasma intra-ovarian infusion to mitochondrial replacement therapy have emerged, albeit not claiming clinical routine status yet. The complex and time sensitive nature of this subgroup of infertile patients indicates the demand for a consensus on a horizontally accepted definition, diagnosis and subsequent effective treating strategy. This critical review analyzes the standing criteria employed in order to diagnose and aptly categorize POR patients, while it proceeds to critically evaluate current and novel strategies regarding their management. Discrepancies in diagnosis and respective implications are discussed, while the existing diversity in management options highlights the need for individualized management.

Background and Objectives: The evaluative strength of available bibliometric tools in the field of clinical embryology has never been examined in the literature. The aim is to bring insight regarding the identity of clinical embryology research, introducing concerns when solely relying on the methodology of bibliometric analysis. Methods: An all-inclusive analysis of the most bibliometrically highlighted scientific contributions regarding the cornerstones of clinical embryology was performed employing the Scopus, Web of Science (WoS) and PubMed databases, between 1978&ndash, 2018. An analysis of the number of publications, respective citations and h-index, g-index, along with m-quotient is presented. The top 30 contributing authors for each distinctive area of research are listed. An attempt at visualizing the yearly published articles, clusters, and collaborations of authors, along with the geographic origin of publications, is also presented. Results: Combining all searches and keywords yielded 54,522 results. In the Scopus database, employing the keyword &ldquo, In Vitro Fertilization&rdquo, yielded 41,292 results. The publications of the top five authors in each research field were analytically presented and compared to the total number of publications for each respective field. The research field of Preimplantation Genetic Diagnosis/Screening/Testing was allocated the highest percentage of publications produced by the top five authors. Regarding journal bibliometrics, based on the year 2017 metrics, there are only 29 journals according to WoS that refer to &ldquo, Reproductive Biology&rdquo, ranking it 187th among 235 disciplines. The USA produced the highest number of publications (12,537). Conclusion: Results indicate an explosion of interest published in the literature regarding the field of clinical embryology. Further analysis on collaborations and the trends involved should be of added value as productivity between countries varies significantly. This may guide researchers, in vitro fertilization professionals, and prospective authors during literature search, while proving useful regarding manuscript design and concurring on keywords and abstract content.

Aim of the study was to examine the accuracy of embryo transfer based on the previous measurement of cervical length and total uterine length. The study has taken place in an academic-assisted reproduction clinic. 248 patients with infertility requiring IVF/ICSI treatment have been included. All patients underwent IVF/ICSI cycles with antagonist protocol and were treated with controlled ovarian stimulation using recombinant FSH (100–400 IU/day). On the day of oocyte retrieval, all patients were given vaginally natural micronized progesterone in a dose of 200 mg/tds. All patients had transvaginal ultrasound measurement of cervical length and endometrial cavity length prior to embryo transfer and measurement of embryo distance (intrauterine air bubbles) from fundal surface of uterine cavity and internal cervical os immediately after embryo transfer. Embryo transfer was performed on days 2–3. Primary outcome was to estimate the accuracy of embryo transfer based on the measurement of the embryo distance from middle of uterine cavity after embryo transfer and secondary outcome was to assess the effect of embryo distance from uterine fundus and internal cervical os to clinical pregnancy rate. The clinical pregnancy rate was 42.7%. The mean embryo distance from the middle of endometrial cavity was 0.48 ± 0.02 cm, the mean embryo distance from the uterine fundus was 0.88 ± 0.32 cm, and from the internal cervical os was 1.67 ± 0.45 cm. Multiple regression analysis showed that the embryo distance from middle of cavity was related to endometrial cavity length and to the embryo distance from the fundus and it was not related to Cx length, total uterine length, embryo distance from internal Cx os, and embryo transfer length. Embryo transfer with the previous measurement of total uterine length and estimation of embryo transfer length can be performed with very good accuracy by a single operator.

Objective To assess the long-term outcomes of tension-free vaginal tape obturator (inside-out) (TVTO) with or without anterior colporrhaphy. Methods The present prospective follow-up observational study included patients attending the 2nd Department of Obstetrics and Gynecology, Aretaieio Hospital, University of Athens, Greece, between April 3 and December 20, 2017, for follow-up care after treatment for urodynamic stress urinary incontinence (USUI) with or without cystocele. Patients without cystocele had been treated with TVTO only; those with cystocele underwent TVTO with anterior colporrhaphy. The primary outcome was the objective cure rate assessed by the cough stress test during filling cystometry. Results Follow-up data were available for 70 patients who underwent TVTO only and 38 who underwent TVTO and anterior colporrhaphy. The mean follow-up period was 13 years. Objective cure was achieved for 57 (81%) patients in the TVTO-only group and 32 (84%) patients in the TVTO and anterior colporrhaphy group. Regarding cystocele management, objective cure was recorded for 35 (92%) patients. Conclusion At 13-year follow-up, anterior colporrhaphy demonstrated a cure rate of 92% in the management of cystocele, and 84% in the management of cystocele and USUI when combined with TVTO. TVTO alone for the management of USUI had an objective cure rate of 81%.

Assisted reproductive technology has evolved tremendously since the emergence of in vitro fertilization (IVF). In the course of the recent decade, there have been significant efforts in order to minimize multiple gestations, while improving percentages of singleton pregnancies and offering individualized services in IVF, in line with the trend of personalized medicine. Patients as well as clinicians and the entire IVF team benefit majorly from 'knowing what to expect' from an IVF cycle. Hereby, the question that has emerged is to what extent prognosis could facilitate toward the achievement of the above goal. In the current review, we present prediction models based on patients' characteristics and IVF data, as well as models based on embryo morphology and biomarkers during culture shaping a complication free and cost-effective personalized treatment. The starting point for the implementation of prediction models was initiated by the aspiration of moving toward optimal practice. Thus, prediction models could serve as useful tools that could safely set the expectations involved during this journey guiding and making IVF treatment more effective. The aim and scope of this review is to thoroughly present the evolution and contribution of prediction models toward an efficient IVF treatment.IVF: In vitro fertilization; ART: assisted reproduction techniques; BMI: body mass index; OHSS: ovarian hyperstimulation syndrome; eSET: elective single embryo transfer; ESHRE: European Society of Human Reproduction and Embryology; mtDNA: mitochondrial DNA; nDNA: nuclear DNA; ICSI: intracytoplasmic sperm injection; MBR: multiple birth rates; LBR: live birth rates; SART: Society for Assisted Reproductive Technology Clinic Outcome Reporting System; AFC: antral follicle count; GnRH: gonadotrophin releasing hormone; FSH: follicle stimulating hormone; LH: luteinizing hormone; AMH: anti-Müllerian hormone; DHEA: dehydroepiandrosterone; PCOS: polycystic ovarian syndrome; NPCOS: non-polycystic ovarian syndrome; CE: cost-effectiveness; CC: clomiphene citrate; ORT: ovarian reserve test; EU: embryo-uterus; DET: double embryo transfer; CES: Cumulative Embryo Score; GES: Graduated Embryo Score; CSS: Combined Scoring System; MSEQ: Mean Score of Embryo Quality; IMC: integrated morphology cleavage; EFNB2: ephrin-B2; CAMK1D: calcium/calmodulin-dependent protein kinase 1D; GSTA4: glutathione S-transferase alpha 4; GSR: glutathione reductase; PGR: progesterone receptor; AMHR2: anti-Müllerian hormone receptor 2; LIF: leukemia inhibitory factor; sHLA-G: soluble human leukocyte antigen G.

Surrogacy is an assisted reproduction-based approach in which the intended parents assign the gestation and birth to another woman called the surrogate mother. The drivers of surrogacy refer largely to infertility, medical conditions, same-sex couples’ parenting, and cases of diversity regarding sexual identity and orientation. Surrogacy consists of a valid option for a variety of conditions or circumstances ranging from medical to social reasons. However, surrogacy may be associated with risks during the preimplantation, prenatal, and neonatal period. It became obvious during the exhaustive literature research that data on surrogacy and its association with factors specific to the IVF practice and the options available were not fully represented. Could it be that surrogacy management adds another level of complexity to the process from the ovarian stimulation, the subsequent IVF cycle, and the techniques employed within the IVF and the Genetic Laboratory to the fetal, perinatal, and neonatal period? This work emphasizes the risks associated with surrogacy with respect to the preimplantation embryo, the fetus, and the infant. Moreover, it further calls for larger studies reporting on surrogacy and comparing the surrogate management to that of the routine IVF patient in order to avoid suboptimal management of a surrogate cycle. This is of particular importance in light of the fact that the surrogate cycle may include not only the surrogate but also the egg donor, sperm donor, and the commissioning couple or single person.

The objective of this study is to assess if the difference of repeated measurements of estradiol and progesterone during luteal phase predict the outcome of intrauterine insemination.Prospective study.Reproductive clinic.126 patients with infertility.Patients underwent controlled ovarian stimulation with recombinant FSH (50-150 IU/d). The day of IUI patients were given p.o natural micronized progesterone in a dose of 100 mg/tds.The area under the receiver characteristic operating curve (ROC curve) in predicting clinical pregnancy for % change of estradiol level on days 6 and 10 was 0.892 with 95% CI: 0.82-0.94. A cutoff value of change -29.5% had a sensitivity of 85.7 with a specificity of 90.2. The corresponding ROC curve for % change of progesterone level was 0.839 with 95% CI: 0.76-0.90. A cutoff value of change -33% had a sensitivity of 85 with a specificity of 75.The % change of estradiol and progesterone between days 6 and 10 has a predictive ability of pregnancy after IUI with COS of 89.2% and 83.4%, respectively. The addition of % of progesterone to % change of estradiol does not improve the predictive ability of % estradiol and should not be used.

Objective To describe two clinical cases concerning patients at risk of developing severe ovarian hyperstimulation syndrome (OHSS) during in vitro fertilization (IVF) stimulation. Design Description of clinical management and outcomes of patients using an IVF antagonist rescue protocol to prevent OHSS. Setting Reproductive medicine unit, University Hospital. Materials and methods Two infertile patients undergoing controlled ovarian stimulation (COS) for IVF/intracytoplasmic sperm injection (ICSI) presenting with high risk of OHSS. IVF/ICSI patients following COS under short protocol and high risk of OHSS were managed by withdrawing the agonist and replacing it with an antagonist and triggering ovulation with an agonist bolus. Main outcome measures included incidence of OHSS, oocytes retrieved, and pregnancy rates. Results None of the two patients developed OHSS. None of the patients had metaphase II retrieved oocytes at oocyte retrieval. Conclusions Use of COS with short protocol in an IVF/ICSI cycle carries a risk of severe OHSS. Rescuing the cycle by withdrawing the agonist and replacing it with an antagonist and triggering ovulation with an agonist bolus is not always effective and should not be used if short time interval between agonist replacement with antagonist and ovulation triggering is available.

This paper investigates the impact of the thyristor commutation time on the peak currents and the active-power capability of the hybrid alternate-common-arm converter (HACC). This converter employs director thyristors for the alternate connection of a common arm in parallel to the main arms. The parallel connection enables current sharing among the arms, which allows the HACC to transfer higher output power without increasing the peak arm current. It is shown that the active-power capability of the HACC is doubled for a certain current-sharing factor, which, however, is altered by the thyristor commutation time. Therefore, the impact of the commutation time on the active-power capability of the HACC is investigated theoretically. Finally, this analysis is verified by simulation results.

This paper compares two hybrid topologies that combine the line-commutated converter (LCC) with cascaded full-bridge (FB) converters. The latter are utilized for compensating the reactive power and filtering the current harmonics of the LCC. The method that was developed for dimensioning these hybrid topologies is presented in detail. This method is utilized for calculating the arm voltage and current waveforms, which are used to estimate other important quantities, such as conduction losses and energy variations. Finally, the studied converters are compared in terms of voltage/current ratings, semiconductor requirements, conduction losses, and energy variations.

Background: How do stress related phenomena during labor differ between vaginal delivery (VD) and elective cesarean section (CS), remains of heightened interest. The purpose of this study is to investigate discrepancies regarding the stress response during VD and CS. Methods: Cortisol, interleukin 6 (IL-6), growth hormone (GH) and insulin-like growth factor 1 (IGF-1) levels from parturients&rsquo, peripheral blood were evaluated on three time-points, namely during the first stage of labor (TP1), two hours post labor (TP2) and 48 h post labor (TP3). Levels were also evaluated from the umbilical cord blood. A total of 50 women were enrolled in this prospective cohort study, with 24 and 26 subjected to CS and VD, respectively. Results: No statistically significant differences were observed between the two groups at TP1. Only GH levels presented the same pattern during the three time-points among both groups. In the umbilical cord blood, the CS group presented statistically significant higher IGF-1 and GH levels. In the umbilical cord blood, IGF-1 and GH levels were positively correlated, while GH and cortisol levels were negatively correlated. Conclusion: CS is a less stressful procedure than VD and is further associated with less intense inflammation, albeit with a longer inflammatory response period. Labor physiology during CS differs considerably regarding respective observations during VD. This merits extensive investigation in order to decipher these data for optimal clinical practice and guidelines.

To assess if the amount of postoperative postvoid residual of urine that is within the normal range (less than 100 mls) could predict the outcome of TVTO (Tension -free vaginal tape obturator) procedure.Second Department of Obstetrics and Gynecology, Aretaieio Hospital, University of Athens, Greece. Patients that had been submitted to TVTO procedure between 2013 and 2017 were reviewed and outcome was assessed.The follow up assessment included cough stress test, the Patient Satisfaction Questionnaire (PSQ), the Urinary Distress Inventory-6 (UDI-6) and the Patient Global Impression of Improvement (PGI-I) questionnaire.The mean follow-up was 3.7 years (+1.35 years). Forty eight patients (40.3%) had only a TVTO procedure. Forty three patients (36.1%) had a TVTO procedure combined with anterior colporrhaphy. Twenty eight patients (23.6%) underwent a TVTO procedure and anterior colporrhaphy and posterior colpoperineorrhaphy. According to cough stress test 88% patients (105/119) were cured having a negative cough stress test. Using logistic regression analysis it was found that patient's age (p = 0.78), postoperative postvoid residual of urine ( = 0.24) or day of catheter removal (p = 0.22) had no statistically significant correlation with the medium term outcome of TVTO procedure. Also, regression analysis shows that patients' Body Mass Index (BMI) has negative correlation to the postoperative outcome.PVR 50 mls appears to be related with successful medium term outcome after TVTO procedure. Also, patients' (BMI) has negative correlation to the postoperative outcome.

Future meshed high-voltage direct current grids require modular multilevel converters with extended functionality. One of the most interesting new submodule topologies is the semi-full-bridge because it enables efficient handling of DC-side short circuits while having reduced power losses compared to an implementation with full-bridge submodules. However, the semi-full-bridge submodule requires the parallel connection of capacitors during normal operation which can cause a high redistribution current in case the voltages of the two submodule capacitors are not equal. The maximum voltage difference and resulting redistribution current have been studied analytically, by means of simulations and in a full-scale standalone submodule laboratory setup. The most critical parameter is the capacitance mismatch between the two capacitors. The experimental results from the full-scale prototype show that the redistribution current peaks at 500A if the voltage difference is 10V before paralleling and increases to 2500A if the difference is 40V. However, neglecting very unlikely cases, the maximum voltage difference predicted by simulations is not higher than 20-30V for the considered case. Among other measures, a balancing controller is proposed which reduces the voltage difference safely if a certain maximum value is surpassed. The operating principle of the controller is described in detail and verified experimentally on a down-scaled submodule within a modular multilevel converter prototype. It can be concluded that excessively high redistribution currents can be prevented. Consequently, they are no obstacle for using the semi-full-bridge submodule in future HVDC converters. QC 20190107

Endometriosis-related infertility describes a case of deteriorated fecundity when endometriosis is diagnosed. Numerous mechanisms have been proposed in an effort to delineate the multifaceted pathophysiology that induces impairment of reproductive dynamics in patients with endometriosis. In this critical analysis, authors present the plethora of molecular events that are entailed and elaborate on how they potentially impair the oocyte’s and embryo’s competence in patients with endometriosis. Reactive oxygen species, dysregulation of the immune system and cellular architectural disruption constitute the crucial mechanisms that detrimentally affect oocyte and embryo developmental potential. The molecular level impairment of the reproductive tissue is discussed, since differentiation, proliferation and apoptosis constitute focal regulatory cellular functions that appear severely compromised in cases of endometriosis. Mapping the precise molecular mechanisms entailed in endometriosis-related infertility may help delineate the complex nature of the disorder and bring us a step closer to a more personalized approach in understanding, diagnosing and managing endometriosis-related infertility.

Oocyte freezing for ‘social reasons’ refers to women of reproductive age who are aiming to prolong, protect and secure their fertility. The term emerged to describe application of the highly promising technique, namely vitrification on oocytes retrieved through controlled ovarian stimulation (COS) from women intending to preserve their fertility for social reasons. These women opt to cryopreserve their oocytes at a point in their life when they need to postpone childbearing on the grounds of so called ‘social’ reasons. These reasons may include a highly driven career, absence of an adequate partner, financial instability, or personal reasons that make them feel unprepared for motherhood. This is a sensitive and multifaceted issue that entails medical, bioethical and socio-psychological components. The latest trend and the apparent increase noted on oocyte freezing for ‘social reasons’ has prompted our team of fertility specialists, embryologists, obstetricians, gynecologists and psychologists to proceed with a thorough, critical and all-inclusive comprehensive analysis. The wide range of findings of this analysis involve concerns of embryology and epigenetics that shape decisions made in the IVF laboratory, issues regarding obstetric and perinatal concerns on the pregnancy concluding from these oocytes and the respective delivery management and neonatal data, to the social and bioethical impact of this trend’s application. This literature review refers to matters rising from the moment the ‘idea’ of this option is ‘birthed’ in a woman’s thoughts, to proceeding and executing it clinically, up until the point of the pediatric follow up of the children born. We aim to shed light to the controversial issue of oocyte freezing, while objectively exhibit all aspects regarding this complex matter, as well as to respectfully approach how could the prospect of our future expectations be shaped from the impact of its application.

Mathematics rules the world of science. Innovative technologies based on mathematics have paved the way for implementation of novel strategies in assisted reproduction. Ascertaining efficient embryo selection in order to secure optimal pregnancy rates remains the focus of the in vitro fertilization scientific community and the strongest driver behind innovative approaches. This scoping review aims to describe and analyze complex models based on mathematics for embryo selection, devices, and software most widely employed in the IVF laboratory and algorithms in the service of the cutting-edge technology of artificial intelligence. Despite their promising nature, the practicing embryologist is the one ultimately responsible for the success of the IVF laboratory and thus the one to approve embracing pioneering technologies in routine practice. Applied mathematics and computational biology have already provided significant insight into the selection of the most competent preimplantation embryo. This review describes the leap of evolution from basic mathematics to bioinformatics and investigates the possibility that computational applications may be the means to foretell a promising future for the IVF clinical practice.

Vitamin D, a soluble steroid hormone synthesized in the skin after sun exposure, plays a crucial role in calcium metabolism and is also involved in cardiovascular pathophysiology. The aim of this review is to summarize the available evidence (a) on the association between endogenous vitamin D status and cardiovascular disease, and (b) on the effect of vitamin D supplementation on cardiovascular outcomes. Most studies have shown an inverse association between vitamin D levels and cardiovascular outcomes. Randomized controlled trials, however, do not consistently support a beneficial effect of vitamin D administration on cardiovascular health. Population characteristics, comorbid conditions such as diabetes, the overall population prevalence of cardiovascular disease, vitamin D status and the regimen of vitamin D supplementation may account for the conflicting results.

To assess the outcome of the tension-free vaginal tape (TVT) procedure in female patients with urodynamic stress urinary incontinence at 17 years follow-up. We carried out a prospective study at the 2nd Department of Obstetrics and Gynecology, Aretaieio Hospital, University of Athens, Greece. Patients who had undergone a TVT procedure 17 years ago. The follow-up assessment included gynecological examination, urinalysis, cough stress test in the lithotomy and/or upright position, filling and voiding cystometry, and uroflow. Also, all patients were required to complete the Patient Satisfaction Questionnaire (PSQ). Out of the 61 initial patients, 56 were available for follow-up. Objective cure rate was 83.9% (47/56) at 17 years follow-up. Subjective cure rate was 78.6% (44/56), subjective improvement was 8.9%, and failure rate was 12.5%. Frequency was present in 39.3% of patients, overactive bladder symptoms were present in 30.3% of patients and urge urinary incontinence was reported by 12.5% of patients. Difficulty emptying the bladder was reported by 10 patients (17.8%) and recurrent urinary tract infection was seen in 3.5% of patients. There was one case of TVT erosion to the vaginal mucosa, which was managed conservatively. The TVT procedure for the management of stress urinary incontinence in women maintains its efficacy in the long term, having an objective cure rate of 83.9% and a subjective cure rate of 78.6% at 17 years’ follow-up, with a very low complications rate.

Growth hormone (GH) and insulin-like growth factor 1 (IGF-1) have been proposed to play a pivotal role in male infertility due to their anabolic effects. The aim of this study was to investigate possible associations between seminal plasma levels of GH and IGF-1 and sperm parameters. Fifty men participated in this study. Semen analysis was performed, while cell-free seminal plasma was collected following sperm centrifugation. Seminal plasma concentrations of IGF-1 and GH were determined by enzyme-linked immunosorbent assay (ELISA). Due to the presence of asthenozoospermia in all participants who presented with abnormal sperm parameters, the participants were further subdivided into normal (group A), asthenozoospermic (group B) and asthenozoospermic plus at least one additional abnormal parameter (group C). A marginally nonsignificant statistical difference (p = 0.063) was revealed between the GH levels corresponding to the asthenozoospermic and the normal group with the latter presenting with higher GH levels. A statistically significant positive correlation (p < 0.05) was noted between levels of GH and IGF-1 in group C. The above relationship has also been observed in men with low sperm concentration, vitality, volume and abnormal morphology. These novel findings require further investigation in order for the biological significance of those associations to be clarified.

This paper presents the basic operating principles of a new hybrid converter that combines thyristors and full-bridge (FB) arms for achieving high active-power capability. This converter consists of a modular multilevel converter (MMC) equipped with additional common arms, which alternate between the upper and lower dc poles. This alternation is achieved by the thyristors that are utilized as director switches and allow the parallel connection of the common arms and the arms of the MMC. The main contributions of this paper are the analysis of the operating principles, the simulation verification of the functionality of the proposed converter, and the comparison of the latter with the full-bridge modular multilevel converter (FB-MMC). QC 20181210. QC 20191018

This paper presents a review of concepts for enabling the operation of a line-commutated converter (LCC) at leading power angles. These concepts rely on voltage or current injection at the ac or dc sides of the LCC, which can be achieved in different ways. We focus on the voltage and current injection by full-bridge (FB) arms, which can be connected either at the ac or dc sides of the LCC and can generate voltages that approximate ideal sinusoids. Hybrid configurations of an LCC connected at the ac side in series or in parallel with FB arms are presented. Moreover, a hybrid configuration of an LCC connected in parallel at the ac side and in series at the dc side with an FB modular multilevel converter (MMC) is outlined. The main contribution of this paper is an analysis and comparison of the mentioned hybrid configurations in terms of the capability to independently control the active (P) and reactive power (Q). QC 20170405

In this paper, the cascaded H-bridge (CHB) inverter is evaluated as a PV power conversion solution for large-scale PV power plants. The advantages and disadvantages of the CHB inverter for large-scale PV power plants are discussed. Comparison between the CHB and conventional central inverters is also presented in terms of efficiency and cost. For comprehensive assessment of the CHB inverter on the system level, a system-level evaluation is also performed in this paper. The levelized cost of electricity (LCOE) is used as the evaluation metric. LCOE of PV system with either the conventional central or CHB inverters is calculated for different geographic locations and PV module technologies. The comparative evaluation demonstrates the promising benefits in using the CHB inverter for large-scale PV power plants.