Abrupt Frequency Research Articles

Analysis of the SARS-CoV-2nsp12 P323L/A529V mutations: coeffect in the transiently peaking lineage C.36.3 on protein structure and response to treatment in Egyptian records.

SARS-CoV-2nsp12, the RNA-dependent RNA-polymerase plays a crucial role in virus replication. Monitoring the effect of its emerging mutants on viral replication and response to antiviral drugs is important. Nsp12 of two Egyptian isolates circulating in 2020 and 2021 were sequenced. Both isolates included P323L, one included the A529V. Tracking A529V mutant frequency, it relates to the transience peaked C.36.3 variant and its parent C.36, both peaked worldwide on February-August 2021, enlisted as high transmissible variants under investigation (VUI) on May 2021. Both Mutants were reported to originate from Egypt and showed an abrupt low frequency upon screening, we analyzed all 1104nsp12 Egyptian sequences. A529V mutation was in 36 records with an abrupt low frequency on June 2021. As its possible reappearance might obligate actions for a candidate VUI, we analyzed the predicted co-effect of P323L and A529V mutations on protein stability and dynamics through protein structure simulations. Three available structures for drug-nsp12 interaction were used representing remdesivir, suramin and favipiravir drugs. Remdesivir and suramin showed an increase in structure stability and considerable change in flexibility while favipiravir showed an extreme interaction. Results predict a favored efficiency of the drugs except for favipiravir in case of the reported mutations.

Optimal Estimation of Under-Frequency Load Shedding Scheme Parameters by Considering Virtual Inertia Injection

Under-frequency load shedding (UFLS) schemes are the latest safety measures applied for safeguarding the integrity of the grid against abrupt frequency imbalances. The overall inertia of electrical power systems is expected to decrease with an increased penetration of renewable energy as well as elements connected through power electronic interfaces. However, voltage source converter-based high voltage direct current (VSC-HVDC) links can provide virtual inertia through a control loop that allows for a reaction to occur at certain frequency fluctuations. This paper evaluates a UFLS scheme that considers the injection of virtual inertia through a VSC-HVDC link. A genetic algorithm (GA) is used to determine the location of the UFLS relays, the activation threshold of each stage, the delay time and the percentage of load shedding at each stage. It was found that the virtual inertia causes the nadir to delay and sometimes reach a greater depth. Furthermore, the implemented GA approximates the frequency response to the limits set with the constraints, reducing the load shedding but achieving a steeper nadir and a lower steady-state frequency level than traditional UFLS. The simulations were performed using the IEEE 39-bus test system.

Frequency and Outcome of Pregnant Females Presenting With Thrombocytopenia at a Tertiary Care Hospital.

Platelet-related problems are more frequently discovered in women during pregnancy because screening is carried out as part of the initial clinic examination using automated blood counts. This study was done to find out the frequency and outcomes of pregnant females presenting with thrombocytopenia at a tertiary care hospital. This cross-sectional study was conducted at the Department of Obstetrics and Gynecology, Jinnah Hospital, Lahore, Pakistan, from April 2023 to September 2023. This study involved 280 pregnant women presenting in the third trimester. Blood examination was acquired, and a platelet count less than 150x109/L was labeled as thrombocytopenia. Outcome variables were frequency of thrombocytopenia, while post-delivery, frequency of placental abruption, preterm delivery, stillbirth, need for blood transfusion, and poor Apgar score were noted and compared among women with and without thrombocytopenia. In a total of 280 pregnant females, the mean age and gestational age at the time of presentation were 29.34±4.38 years and 31.30±2.87 weeks, respectively. The mean BMI of the females was 27.97±4.72 kg/m2. Thrombocytopenia was noted in 34 females (12.1%). Placental abruption, preterm delivery, need for blood transfusion, stillbirth, and poor Apgar score were observed in 1.4%, 4.3%, 8.2%, 1.1%, and 2.1% cases, respectively. Placental abruption (11.8% vs. 0.0%; p<0.001), preterm delivery (29.4% vs. 0.8%; p<0.001), need of blood transfusion (35.3% vs. 4.5%; p<0.001), stillbirth (8.8% vs. 0.0%; p<0.001), and poor Apgar score (17.6% vs. 0.0%; p<0.001) were all significantly higher among pregnant women with thrombocytopenia as compared to those with a normal platelet count. The frequency of thrombocytopenia was 12.1% among pregnant females. The frequency of placental abruption, preterm delivery, need for blood transfusion, stillbirth, and poor Apgar score were all significantly higher among pregnant women with thrombocytopenia as compared to those with a normal plateletcount, irrespective of the patient's age, parity, and BMI.

Abruptio placenta and pregnancy outcome at Al-Sadka teaching hospital, Aden, Yemen

Background: Placental abruption is a serious obstetric complication with many potential adverse outcomes for both mother and fetus. The aim of this study was to determine the clinical characteristics, risk factors, and maternal and perinatal consequences of placental abruption among pregnant women, at Al-Sadka Teaching Hospital. Methods: This was a prospective descriptive study including women with placental abruption, who delivered at Al-Sadka University Hospital, Aden, Yemen, during the period from August 01, 2015, to September 31, 2016. Statistical analysis of the data was performed with (statistics is a statistical software version 24). Results: The frequency of placental abruption in this study was 0.84%. The majority of women with placental abruption were in the 20–25 age group (34.3%), multiparous (51.4%), had no antenatal care (ANC) (51.4%). and illiterate (37.1%). The most common clinical presentation was vaginal bleeding (82.9%), followed by tetanic uterine contractions (68.6%). The most common risk factors associated with placental abruption were pre-eclampsia (34.5%) and premature rupture of membrane (21.8%). Most of our patients (77.1%) had a vaginal delivery, while the rest had a cesarean section delivery. The most common maternal complications were postpartum hemorrhage (100%) and hemorrhagic shock (27.5%). Perinatal death was more commonly associated with pre-eclampsia (55.0%), severe placental abruption (95%), and preterm birth (70%). On the other hand, perinatal death was reported in 28.6% of our patients (n=20). A higher percentage of fetuses born by cesarean section died (56.3%), while 79.6% of vaginal deliveries involved live fetuses. Conclusion: The frequency of placental abruption was 0.84%. Women with abruptio placenta had a higher likelihood of being illiterate, between 20 and 25-year-old, multipara, and receiving inadequate ANC. Accordingly, we recommend raising women’s awareness of the importance of ANC through the media (television and radio) and creating policies to encourage high-quality routine prenatal care for all pregnant women by policymakers, particularly the Ministry of Public Health.

Frequency of Preterm Placental Abruption and its Contributing Factors

Objectives: The objectives of this study were to determine the frequency of preterm placental abruption in patients presenting with heavy bleeding in a tertiary care hospital and to determine the frequency of contributing factors towards preterm placental abruption. Methodology: This was a descriptive case series conducted at Department of Obstetrics &amp; Gynecology at Allama Iqbal Memorial Teaching Hospital, Sialkot. This study involved 260 women aged between 20-40 years who presented with heavy vaginal bleeding between 32-37 weeks of gestation. Preterm placental abruption was noted and contributing factors namely Dai handling, chronic hypertension, premature rupture of membranes, grand multi parity, and maternal age more than 35 years were looked for. A written informed consent was taken from each patient. Results: The age of the patients ranged from 20 years to 40 years with a mean of 29.78±6.07 years. The gestational age of the patients ranged from 32 weeks to 37 weeks with a mean of 34.40±1.68 weeks. BMI of the patients ranged from 21.1 Kg/m2 to 35.8 Kg/m2 with a mean of 28.03±4.15 Kg/m2. Preterm placental abruption was noted in 12 (4.6%) patients. There was no significant difference in the frequency of placental abruption across gestational age (p=0.913) and BMI (p=0.958) of the patient. Among the contributing factors Dai handling was noted in 58.3% patients with preterm placental abruption followed by maternal age &gt; 35 years (33.3%) and premature rupture of membranes and grand multiparity which were observed in 25.0% patients each. Chronic hypertension was recorded in 16.7% patients. There was no significant difference in the frequency of these contributing factors across gestational age and BMI of the patient. Conclusion: The frequency of preterm placental abruption was found to be 4.6% with Dai handling (58.3%) and maternal age more than 35 years (33.3%) as the frequent contributing factors. Keywords: Preterm Placental Abruption, Contributing Factors, Dai Handling

The permanently rotating wind turbines: a new strategy for reliable power system frequency support under low and no wind conditions

The problem of frequency stability becomes more concerning as the presence of converter-interfaced units increases and conventional generators are suppressed. A decrease in total system inertia, inherently delivered by synchronous generators, results in abrupt frequency changes and jeopardizes power system stability. Therefore, securing sufficient flexible resources with frequency support capability is necessary. The rotational masses of wind turbines (WTs) are a significant and economical source of flexibility in power systems. However, the available kinetic energy (KE) of the WTs’ rotational masses depends on wind conditions and can only be exploited when the wind speed is sufficient for their rotation. When the wind speed is low, the WT is stopped and cannot support the frequency recovery. In this paper, a new concept of WT operation is proposed, which enables the permanent rotation of the WT under low and no wind conditions, making them reliable flexible resources that can continuously provide frequency support. Due to its widespread presence, the doubly-fed induction generator (DFIG) type of machine was considered. The variable-speed WT’s converter management allows rotational speed control, fast power injection, and release of the turbine’s stored KE even when no wind energy is available. The estimated accessible KE in the WT justifies the proposed concept, and the energy consumption due to motoring operation under low and no wind conditions is shown to be acceptable. A case study is performed for the South Banat region in Serbia to demonstrate the presented management concept. Additionally, a dynamic simulation was implemented to illustrate the permanent operation strategy’s impact on frequency stability in a low-inertia system under low and no wind conditions. Besides virtual inertia continuous capability, the proposed concept provides reduced wear of the WT mechanical components due to a lower number of on/off events.

Pregnancy outcomes in women with anorexia nervosa: a population-based study and analysis of a matched cohort

Research questionWhat implications does anorexia nervosa have on pregnancy outcomes in a US population? DesignA retrospective, population-based study using data from the Healthcare Cost and Utilization Project—Nationwide Inpatient Sample. A dataset of all deliveries between 2004 and 2014 inclusively was created. The population was divided into women with anorexia nervosa (n = 214) and women without anorexia nervosa (n = 9,096,574), and a cohort matched 1:4 with anorexia nervosa for age, race, medical insurance type and income quartile. Delivery and neonatal outcomes were compared between the two matched groups and with the control group of deliveries. A multivariable logistic regression analysis, controlling for statistically significant baseline characteristics, explored associations between anorexia nervosa and delivery, and neonatal outcomes. ResultsCompared with the entire group, women diagnosed with anorexia nervosa were more likely to be white, smokers, of higher income or diagnosed with another psychiatric disorder. In the unmatched comparison, women with anorexia nervosa had a higher frequency of preterm delivery (adjusted odds ratio [aOR] 2.98 CI 1.86 to 4.76, P < 0.001), placental abruption (aOR 3.41 CI 1.38 to 8.40, P = 0.008) and small for gestational age (SGA) neonates (aOR 5.32 CI 3.12 to 9.09, P < 0.001). In the matched comparison, preterm delivery (aOR 5.31, CI 3.02 to 9.32, P < 0.001) and SGA neonates were significantly higher in the anorexia nervosa group (aOR 4.69 CI 2.6 to 8.41, P < 0.001), providing results similar to the unmatched comparison. ConclusionHealthcare providers, specifically fertility specialists, should be aware of the magnitude of adverse outcomes related to pregnancy in women with anorexia nervosa.

Maternal complications in women presenting with first trimester threatened miscarriage.

Objective: To determine the frequency of miscarriage, hypertensive disorder of pregnancy, placental abruption and preterm birth in women with first trimester threatened miscarriage. Study Design: Cross-sectional study. Setting: Department of Obstetric &amp; Gynaecology, Sir Syed Hospital and Pakistan Naval Ship Shifa Hospital (Karachi). Period: April, 2021 to March, 2022. Material &amp; Methods: Ninety two women 18-40 year old, diagnosed as threatened miscarriage at ≤ 13 weeks based on history, examination and ultrasound were included in the study after informed consent and followed till delivery. Women with genital infection, other form of miscarriage and multiple pregnancy were excluded. Data recorded from hospital documents. Maternal age, parity and Gestational age assessed. Miscarriage, hypertensive disorder of pregnancy, placental abruption, preterm birth and PPROM expressed as frequency and percentages. Logistic regression analysis performed. Chi square test (x2) used and P-value ≤ 0.05 taken as significant. Results: Mean age of women was 29.21±3.49 years. Mean parity was 2.65±1.15. Mean Gestational age at presentation was 7.96±1.78 weeks. 11.11%. (10/90) cases had miscarriage. 88.88% (80/90) women continued their pregnancy. 42.5% (34/80) had hypertensive disorder of pregnancy. 20% had pregnancy induced hypertension and 22.5% had pre-eclampsia. Preterm birth was seen in 26.3% (21/80). Frequency of PPROM and placental abruption was 6.3% (5/80) each. Women of 21-25 yr age were more at risk of hypertensive disorder of pregnancy than other age groups. There was no significant affect of maternal age and parity on preterm birth and placental abruption. Frequency of Preterm birth was 38.4% in women with hypertensive disorder, more than 2 times higher than non-hypertensives (17.4%) and found significant (P-value=0.043). Conclusion: Hypertensive disorder of pregnancy was the most common maternal complication observed in women who had threatened miscarriage in first trimester. Preterm birth had significant association with hypertensive disorder of pregnancy.

Frequency of Placental Abruption in Preterm Premature Rupture of Membranes (PPROM)

Placental abruption is the premature separation of normally placed placenta. Its incidence is 1% worldwide in all pregnancies and 7% in Pakistan. Objective: To determine frequency of placental abruption in preterm premature rupture of membranes. Methods: This study was conducted in Department of obstetrics and gynecology DHQ Hospital Topi Swabi from 1st March 2021 to 31st October 2022. Total of 276 patients were recruited. Routine clinical examination was done for the confirmation of preterm PROM. All the patients were followed till delivery and placental abruption was diagnosed. All the mentioned information obtained were noted on a pre designed proforma. Results: Mean age was 33 ±2.17 years. Primi para and multi para were 40% and 60% respectively. Forty-two % patients were primi gravida, 58% patients were multi gravida. 33% mothers had gestational period of age range from 28-32 weeks while 67% patients had POG range 33-37 weeks. More over the frequency of placental abruption in preterm premature rupture of membranes was 5%. Conclusions: On the basis of results, it was concluded that active expectant management strategy and strict follow up minimizes the risk of occurrence of perinatal asphyxia, and neonatal morbidity and mortality

Frequency of Abruption and Associated Factors among Cases of APH

Objective: To make a rough estimate of the frequency of abruption, its likely risk factors and its various complications, among the cases of APH in hospitalized patients. Design: Prospective descriptive study Setting: Obstetrical inpatients Department of Bakhtawar Hospital, Multan. Duration of study: 1 year (1/6/20 – 31/5/21) Subjects and Methods: Patients with objective evidence of placental abruption, were initially recruited and managed accordingly. Those cases in which abruption was a likely cause, were selected for the study purpose and other cases of APH were dropped from the study. Results: Frequency of abruption was 2.3% of all obstetrical admissions and about 32.7% (1/3 rd) of all cases of APH. The most likely risk factors identified were grand multiparity (46.1%), pregnancy induced hypertension (38.4%), advanced maternal age (43.5%) and previous history of abruption (12.8%). Majority (82%) of the patients belonged to lower socioeconomic class, with no proper antenatal care throughout pregnancy. In this class, increased obstetrical complications were due to anemia, trend of grand multiparity and too late approach to health care professional. Conclusion: The study addresses the frequency of abruption placenta, which is one of the serious obstetrical emergencies and timely aggressive management can reduce its complications. All professionals who care for women during pregnancy and child birth must be aware of it and have a clear plan in mind for its prompt diagnosis and management. Keyword: Frequency of abruption, APH, abruption placenta.

O-179 Pregnancy outcomes in women with anorexia nervosa: a North American population-based study

Abstract Study question What implications does anorexia nervosa (AN) have on pregnancy outcomes in a North American population (NAP)? Summary answer Anorexia nervosa is associated with substantial increased risk of 500% in SGA, 270% in preterm delivery and 335% in placental abruption in a NAP. What is known already While considered by many a contraindication to fertility treatment, many women with AN do conceive with the help of reproductive medicine and spontaneously. This could be either because of lack of proper screening for anorexia nervosa (as studies show), or this being a lifelong disease. Many fertility specialists are faced with the dilemma of treating women who are undernourished, or if by refusing to do so, possibly preventing these patients the joy of parenthood. Most data regarding the consequences of AN on pregnancy complications, comes from Northern Europe and data from North America is lacking. Study design, size, duration A retrospective population-based study utilizing data from the Healthcare Cost and Utilization Project—Nationwide Inpatient Sample (HCUP-NIS), was performed. A dataset of all deliveries between 2004 and 2014 inclusively, was created. Within this group, all deliveries to women who had a diagnosis of AN during pregnancy were identified as part of the study group (n = 214), and the remaining deliveries comprised the reference group (n = 9,096,574). Participants/materials, setting, methods Descriptive analyses were performed to compare the demographic features among both groups, Chi-squared test or Fisher’s exact test were used when appropriate. Multivariate logistic regression analysis was performed to calculate unadjusted and adjusted odds ratios (aORs) and corresponding 95% confidence intervals (CI). According to Tri-Council Policy statement(2018), IRB approval was not required, given data was anonymous and publicly available. Main results and the role of chance Women diagnosed with AN were more likely to be white, of higher income, to be smokers, have thyroid disease or diagnosed with another psychiatric disorder (p &amp;lt; 0.05 all). No difference was found in the rates of hypertensive diseases of pregnancy, gestational diabetes mellitus, incidence of placenta previa, need for cesarean section, postpartum hemorrhage or chorioamnionitis(P&amp;gt;.05, all). Women with AN had a higher frequency of preterm delivery (aOR 2.70 CI 1.69-4.3, p &amp;lt; 0.001) and placental abruption (aOR 3.35 CI 1.36-8.26, p = 0.009). The incidence of small for gestational age neonates was shockingly higher in the AN group (aOR 5.00 CI 2.93-8.53, p &amp;lt; 0.001). Limitations, reasons for caution The limitations of our study are its retrospective nature and the fact that it relies on an administrative database. The severity of AN could not be assessed, nor could compliance with treatment. Wider implications of the findings Women with AN often conceive through ovulation induction. Fertility specialist should be aware of the magnitude of adverse outcomes related to pregnancy in women with AN, with a 500% increase in SGA 500% compared to a control population, and likely contributing to the increase in preterm delivery. Trial registration number not applicable

Changes in the spatiotemporal patterns of dry/wet abrupt alternation frequency, duration, and severity in Mainland China, 1980–2019

Changes in extreme events have received increasing attention in the context of climate change. Extreme changes in wet and dry events due to changes in meteorological elements, such as the spatial and temporal redistribution of precipitation and temperature increases, are extreme weather events that have attracted much attention in recent years. In contrast, there is a relative lack of research on extreme compound events that focuses on a transition between wet and dry spells in adjacent months. This paper provides maps of the frequency, duration, and severity of national-scale dry wet abrupt alternation (DWAA) events for 1980–1999 and 2000–2019, aiming to obtain information regarding events in the hotspot areas of DWAA in China during the past four decades in order to analyze their change patterns. This paper performs station-based standardized precipitation evapotranspiration index (SPEI) calculations to characterize local wet and dry spells based on meteorological observations provided by the China Meteorological Administration (CMA) since 1980 with regional analyses based on seven geographic divisions of China. Our finding explicitly discloses the “more-less-more” DWAA variation pattern from North to South China. Additionally, the changes in frequency, duration, and severity in the different regions are revealed. The frequency, duration, and severity of DW increased from 5.08 to 6.74, 17.71 to 24.62, and 12.51 to 17.01, respectively, an increase of 32.53%, 39.04% and 36.01%, while the corresponding WD only increased by 9.45%, 15.22% and 13.51%. In addition, events with a higher severity of DWAA are prone to appear in most regions due to the increasing interval between heavy rainfall and the increase in precipitation under global warming.

Examining Vegetation Change and Associated Spatial Patterns in Wuyishan National Park at Different Protection Levels

Examining the characteristics of vegetation change and associated spatial patterns under different protection levels can provide a scientific basis for national park protection and management. Based on the dense time-series Landsat enhanced vegetation index (EVI) data between 1986 and 2020, we utilized the Wild Binary Segmentation (WBS) approach to detect spatial and temporal characteristics of abrupt, gradual, and total changes in Wuyishan National Park. The differences in vegetation change in three protection-level areas (strictly protected [Prots], generally protected [Prot], and non-protected [NP]) were examined, and the contributions to their spatial patterns were evaluated through Geodetector. The results showed the following: (1) The highest percentage of area without abrupt change was in Prots (39.89%), and the lowest percentage was in NP (17.44%). The percentage of abrupt change frequency (larger than three times) increased from 4.40% to 9.10% and 12.49% with the decreases in protection. The significance test showed that the difference in changed frequencies was not significant among these regions, but the interannual variation of abrupt change in Prots was significantly different from other areas. (2) The vegetation coverage of the Wuyishan National Park generally improved. The total EVI change (TEVI) showed that the positive percentage of Prots and Prot was 90.43% and 91.71%, respectively, slightly higher than that of NP (88.44%). However, the mean greenness change of NP was higher than that of Prots and Prot. (3) The park’s EVI spatial pattern in 1986 was the strongest factor determining the EVI spatial pattern in 2020; the explanatory power reduced as the protection level decreased. The explanation power (q value) of abrupt vegetation change was lower and increased as the protection level decreased. The interaction detection showed that EVI1986 and TEVI had the strongest explanatory powers, but the explanatory ability gradually weakened from 0.713 to 0.672 to 0.581 in Prots, Prot, and NP, respectively. This study provided a systematic analysis of vegetation changes and their impacts on spatial patterns.

The significance of clinical symptoms of subchorionic hematomas, “bleeding first”, to stratify the high-risk subgroup of very early preterm delivery

ObjectiveTo investigate the factors that stratify high-risk cases among subchorionic hematomas (SCHs) patients with persistent vaginal bleeding in early pregnancy. Materials and methodsA total of 56 patients who required hospitalization for SCH with vaginal bleeding in early pregnancy were classified into two groups: 1) no hematoma by ultrasonography when vaginal bleeding occurred, and then hematoma was observed by ultrasonography “bleeding to hematoma (BH group, n = 15)” and 2) no vaginal bleeding when hematoma was observed by routine ultrasonography, and then vaginal bleeding occurred later “hematoma to bleeding (HB group, n = 41)”. Retrospective cohort study was performed and maternal and neonatal outcomes were evaluated. ResultsThe duration of SCHs and/or vaginal bleeding was significantly longer in the BH group than in the HB group (mean: 60.8 days [BH group] vs. 33.3 days [HB group], p = 0.015). BH group patients delivered earlier than HB group patients significantly (mean: 27.3 weeks [BH group] vs. 35.6 weeks [HB group], p = 0.0028). The frequency of chronic abruption and oligohydramnios sequence (CAOS) was significantly higher in the BH group than in the HB group (3/15; 20.0% [BH group] vs. 0/41; 0.0% [HB group], p = 0.016). The frequency of sever fetal distress (Apgar score <4 points) was significantly higher in the BH group than in the HB group (4/15; 26.7% [BH group] vs. 0/41; 0.0% [HB group], p = 0.0037). The levels of factor XIII were relatively lower in the BH group than in the HB group (mean: 54.8% (n = 4) [BH group] vs. 76.1% (n = 7) [HB group], p = 0.077). ConclusionThe order of the symptoms, bleeding first, is an important feature that reflects the subsequent prolonged duration of SCHs/vaginal bleeding, resulting in very early preterm delivery. Continuous hemorrhage consumes coagulation factor XIII, which further worsen the hemostasis.

Predictors of placental abruption during expectant management of premature preterm rupture of membranes

ObjectiveTo predict the risk factors of placental abruption during expectant management of preterm rupture of membranes.BackgroundA frequency of abruption of 4.0%–6.8% has been reported in patients with preterm premature rupture of membranes (PPROM). Antepartum vaginal bleeding occurs during the period of expectant management, the associated risk of developing placental abruption is high. It may be possible to approximate the risk for placental abruption based on these simple prepregnancy risk factors.Patients and methodsAn observational study was conducted on 100 pregnant women. The patients were randomly selected from those attending labor ward at Menoufia University Hospital and Shebin EL-Kom Teaching Hospital. All women included in this study are with PPROM, divided into group I that included 79 without placental abruption and group II included 21 with placental abruption. Full analysis of detailed history and examination and primarily samples are taken during the study period from January 2019 to December 2020.ResultsThere were statistically significant differences among patients with placental abruption than those without placental abruption regarding antepartum or intrapartum fetal distress requiring urgent cesarean section and gestational age. The majority of patients with placental abruption had gestational age more than 32 weeks (P < 0.05). Most of the patients with placental abruption had latency to its occurrence more than 48 h since the time of admission with PPROM with a percentage of 85.71%.ConclusionPlacental abruption is a complex disease. Although several risk factors are known, the etiopathogenesis is not fully understood and its occurrence often remained unpredictable or unpreventable. Placental abruption was absent in 79% of our patients.

A Fully Informative Phasor Measurement Unit for Distribution Networks With Harmonic Distortion

We introduce a fully informative distribution network phasor measurement unit (FI-DPMU), that is capable of performing a simultaneous estimation of phasor dynamics and harmonic components. This is in contrast with current state-of-the-art devices, that only provide information about the fundamental component of voltages/currents—by discriminating or filtering-out their harmonic content. The FI-DPMU hence represents a significant economical solution, since it bypasses the need to deploy power quality analyzers to retrieve full information about the network. To validate the accuracy of the FI-DPMU, we performed a hardware-in-the-loop implementation to emulate a distribution network that is subject to abrupt frequency variations and high harmonic distortion. The tests demonstrate that the FI-DPMU satisfies the standards of distribution network phasor measurement units (DPMUs), providing a real-time fast Fourier transform (FFT) as additional feature. Experimental results show a comparison between FI-DPMU measurement data with the information provided by a commercial DPMU.

Partial stability criterion for a heterogeneous power grid with hub structures

One of the priority tasks in studying power grids is to find the conditions of their stable operation. The fundamental requirement is synchronizing all the elements (generators and consumers) of a power grid. However, various disturbances can destroy the synchronization. Moreover, desynchronization occurring in a small part of the grid can lead to severe large-scale power outages (or blackouts) due to numerous cascading failures. Here we consider the model of a heterogeneous power grid with hub structures (subgrids), taking into account arbitrary lengths and impedances of grid’s transmission lines and also their arbitrary amount. Using the auxiliary comparison systems approach, we analyze the dynamics of a hub subgrid. Based on the findings, we develop a novel criterion of partial stability of power grids featuring hub structures. The criterion makes it possible to identify the regions of safe operation of individual hub subgrid elements. First, the criterion allows obtaining parameters’ values that guarantee existence and local stability of either synchronous or quasi-synchronous modes in individual hub subgrid elements, i.e. steady-state stability. Second, the criterion allows obtaining the safe values of abrupt frequency and phase disturbances that eventually vanish, i.e. imply transient stability with respect to state disturbance. Third, the criterion permits determining the safe ranges of parameters’ disturbances that do not lead to catastrophic desynchronizing effects, i.e. imply transient stability with respect to parameters’ disturbance. Also, we discover typical dependences of the safe regions on the parameters of transmission lines. We demonstrate the applicability of the criterion on two test power grids with arbitrary distributions of powers as well as effective lengths and impedances of transmission lines. The results may help optimize stability and contribute to developing new real-time control schemes for smart grids that can automatically recover from failures.

A CMOS Energy Harvesting Interface Circuit With Cycle-to-Cycle Frequency-to-Amplitude Conversion MPPT for Centimeter-Scale Wind Turbine

An energy harvesting (EH) system is proposed to extract energy from a centimeter-scale electromagnetic (EM) micro wind turbine. To improve the end-to-end efficiency, an autonomous and self-biased active rectifier is employed. A hysteresis-controlled boost converter is designed with self-zero-current-switching calibrations, which achieves a peak DC-DC efficiency of 93.3% with a maximum efficiency improvement of 12.7%. In addition, a novel frequency-to-amplitude conversion (FAC) maximum power point tracking (MPPT) method is proposed for a cycle-to-cycle MPPT. In measurements, the proposed FAC MPPT requires no more than three cycles to locate the maximum power point (MPP) in abrupt frequency changes, with an 80% tracking accuracy in the first turbine cycle. In wind-field testing, the EH system starts to track the MPP one cycle after start-up at 2.0 V. In the steady-state, the EH system maintains its cycle-to-cycle MPP under different wind conditions. In wind-field testing for wind speeds from 1.0 to 5.0 m/s, the peak MPPT accuracy is 99.27%, with an MPPT efficiency of 99.85%. The extracted power is from 0.1 to 8 mW with a peak end-to-end efficiency of 88.2%. Compared to a full-bridge rectifier, a 630% energy extraction gain is measured at a low wind speed of 1.2 m/s. To the best of the authors' knowledge, this is the first IC prototype for a cm-scale EM wind turbine EH to achieve a cycle-to-cycle MPPT with the highest reported MPPT efficiency.

A cogeneration scheme with biogas and improvement of frequency stability using inertia based control in AC microgrid

Abstract Currently, penetration of the renewable energy sources (RES) like solar photovoltaic (PV) panels, wind turbine-based plants is increasing in the conventional power grid to combat pollution, global warming, and to enhance energy sustainability. Fast power electronic converters are necessary to extract power from these sources which do not have any inertia. When more renewable sources are connected to the power grid, it reduces the effective system inertia which results in unacceptable grid frequency changes for any transient. This leads to frequent tripping, cascading fault, and instability of the overall system which can create large-scale blackouts. This work is related to the generation of physical inertia through the biogas plant and emulates inertia from the dc-link capacitor to control the rate of change of frequency (RoCoF) under abrupt load change. The stored energy in a biogas plant and dc-link capacitor in an AC microgrid (MG) can support momentary power requirement which improves the transient performance of grid frequency under unavailability of PV power. A storage system can help to compensate for abrupt frequency change during transient but due to its higher cost and relatively lesser lifetime, these systems can’t be relied upon in the long run. The proposed scheme of cogeneration and frequency control can provide better performance which is simulated in MATLAB 2013 (b). The control system is implemented in hardware using NI-cRiO 9082 in 500 W AC MG which shows 53.57% improvement in RoCoF which complies with the requirement of IEEE/IEC 60255-118-1.

A High-Q Resonant Inductive Link Transmit Driver With Adaptive-Predictive Phase-Continuous Tuning and Deviation Frequency Calibration for Enhanced FSK/PSK Modulation and Power Transfer

Inductively coupled power transfer systems often use high- $Q$ antenna circuits to reduce losses and increase transmission range. However, the narrow bandwidth due to the high $Q$ -factor conventionally constrains the modulation rate on the carrier, creating a tradeoff between power transfer efficiency and data rate. In this article, we show how instantaneous tuning of the antenna can permit frequency and phase modulation data rates beyond the $Q$ -factor limitations, provided that the drive and antenna resonance frequencies are kept the same at all times. It is also necessary to ensure that the modulation symbol boundaries are precisely aligned with the tracking of the resonance tuning to ensure phase continuity and optimum power transfer. With instantaneous tuning, phase modulation can be implemented by defined numbers of cycles at an offset frequency, provided the offset is precisely controlled. We describe how the required instantaneous resonance tuning can be achieved using a switched fractional capacitor technique and present a system architecture that can follow abrupt frequency changes due to the modulation while tracking changes to the resonant condition due to environmental detuning effects at each modulation frequency. An integrated mixed-signal driver/modulator/tuner demonstrator system is presented, operating from 10 kHz–2 MHz using a 0.18- $\mu$ m 1.8–50-V CMOS/laterally-diffused metal-oxide semiconductor (LDMOS) process. The system maintains phase continuity in the antenna current throughout frequency shift keying (FSK) and phase-shift keying (PSK) modulation and employs self-calibration of the PSK modulation frequencies to achieve precise angles of phase rotation for QPSK. The antenna tuning, modulation, and frequency calibration are verified with experimental results.