bluuebunny/crossref_metadata_2025 huggingface dataset:
Ablative stabilization of Rayleigh-Taylor instabilities resulting from a laser-driven radiative shock
Authors: Huntington C. M. , Shimony A. , Trantham M. , Kuranz C. C. , Shvarts D. , Di Stefano C. A. , Doss F. W. , Drake R. P. , Flippo K. A. , Kalantar D. H. , Klein S. R. , Kline J. L. , MacLaren S. A. , Malamud G. , Miles A. R. , Prisbrey S. T. , Raman K. S. , Remington B. A. , Robey H. F. , Wan W. C. , Park H.-S.
Published: May 2018

The Rayleigh-Taylor (RT) instability is a common occurrence in nature, notably in astrophysical systems like supernovae, where it serves to mix the dense layers of the interior of an exploding star with the low-density stellar wind surrounding it, and in inertial confinement fusion experiments, where it mixes cooler materials with the central hot spot in an imploding capsule and stifles the desired nuclear reactions. In both of these examples, the radiative flux generated by strong shocks in the system may play a role in partially stabilizing RT instabilities. Here, we present experiments performed on the National Ignition Facility, designed to isolate and study the role of radiation and heat conduction from a shock front in the stabilization of hydrodynamic instabilities. By varying the laser power delivered to a shock-tube target with an embedded, unstable interface, the radiative fluxes generated at the shock front could be controlled. We observe decreased RT growth when the shock significantly heats the medium around it, in contrast to a system where the shock did not produce significant heating. Both systems are modeled with a modified set of buoyancy-drag equations accounting for ablative stabilization, and the experimental results are consistent with ablative stabilization when the shock is radiative. This result has important implications for our understanding of astrophysical radiative shocks and supernova radiative hydrodynamics [Kuranz et al., Nature Communications 9(1), 1564 (2018)].
Nanoprobe diffusion in entangled polymer solutions: Linear vs. unconcatenated ring chains
Authors: Nahali Negar , Rosa Angelo
Published: May 2018

We employ large-scale molecular dynamics computer simulations to study the problem of nanoprobe diffusion in entangled solutions of linear polymers and unknotted and unconcatenated circular (ring) polymers. By tuning both the diameter of the nanoprobe and the density of the solution, we show that nanoprobes of diameter smaller than the entanglement distance (tube diameter) of the solution display the same (Rouse-like) behavior in solutions of both polymer architectures. Instead, nanoprobes with larger diameters appear to diffuse markedly faster in solutions of rings than in solutions of linear chains. Finally, by analysing the distribution functions of spatial displacements, we find that nanoprobe motion in rings’ solutions shows both Gaussian and ergodic behaviors, in all regimes considered, while, in solutions of linear chains, nanoprobes exceeding the size of the tube diameter show a transition to non-Gaussian and non-ergodic motion. Our results emphasize the role of chain architecture in the motion of nanoprobes dispersed in polymer solutions.
Enhancement in magnetocaloric properties of ErCrO3 via A-site Gd substitution
Authors: Shi Jianhang , Yin Shiqi , Seehra Mohindar S. , Jain Menka
Published: May 2018

Rare earth chromites (RCrO3) continue to be of considerable interest due to their intriguing physical properties such as spin-reorientation, multiferroicity, and magnetocaloric effect. In this paper, we compare the structural, magnetic, and magnetocaloric properties of bulk ErCrO3 with those of bulk Er0.33Gd0.67CrO3, the latter obtained by Gd substitution at the A-site (Er-site) and report substantial enhancement in the magnetocaloric response by Gd substitution. The samples prepared by the citrate route were structurally characterized at room temperature using x-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy. The XRD measurements refined by Rietveld analysis indicate that both samples crystallized in the orthorhombically distorted perovskite structure with Pbnm space group. Magnetic measurements on both samples were carried out between 5 K and 300 K in magnetic fields up to 7 T and show that TNCr (where Cr3+ orders) for Er0.33Gd0.67CrO3 is enhanced to 155 K vs. 133 K for ErCrO3 with analogous changes in the other magnetic parameters. Isothermal magnetization M vs. H data at different temperatures were used to determine changes in the magnetic entropy (−ΔS) and relative cooling power (RCP) for the two samples showing considerable improvement with Gd substitution in bulk ErCrO3. The maximum value of −ΔS for Er0.33Gd0.67CrO3 is 27.6 J kg−1 K−1 at 5 K and 7 T with a RCP of 531.1 J kg−1, in comparison to maximum −ΔS = 10.7 J kg−1 K−1 at 15 K with an RCP of 416.4 J kg−1 for ErCrO3 at 7 T.
Deciphering the relative contribution of vascular inflammation and blood rheology in metastatic spreading
Authors: Mollica Hilaria , Coclite Alessandro , Miali Marco E. , Pereira Rui C. , Paleari Laura , Manneschi Chiara , DeCensi Andrea , Decuzzi Paolo
Published: May 2018

Vascular adhesion of circulating tumor cells (CTCs) is a key step in cancer spreading. If inflammation is recognized to favor the formation of vascular “metastatic niches,” little is known about the contribution of blood rheology to CTC deposition. Herein, a microfluidic chip, covered by a confluent monolayer of endothelial cells, is used for analyzing the adhesion and rolling of colorectal (HCT-15) and breast (MDA-MB-231) cancer cells under different biophysical conditions. These include the analysis of cell transport in a physiological solution and whole blood over a healthy and a TNF-α inflamed endothelium with a flow rate of 50 and 100 nl/min. Upon stimulation of the endothelial monolayer with TNF-α (25 ng/ml), CTC adhesion increases from 2 to 4 times whilst cell rolling velocity only slightly reduces. Notably, whole blood also enhances cancer cell deposition from 2 to 3 times, but only on the unstimulated vasculature. For all tested conditions, no statistically significant difference is observed between the two cancer cell types. Finally, a computational model for CTC transport demonstrates that a rigid cell approximation reasonably predicts rolling velocities while cell deformability is needed to model adhesion. These results would suggest that, within microvascular networks, blood rheology and inflammation contribute similarly to CTC deposition, thereby facilitating the formation of metastatic niches along the entire network, including the healthy endothelium. In microfluidic-based assays, neglecting blood rheology would significantly underestimate the metastatic potential of cancer cells.
Light-induced negative differential resistance in gate-controlled graphene-silicon photodiode
Authors: Liu Wei , Guo Hongwei , Li Wei , Wan Xia , Bodepudi Srikrishna Chanakya , Shehzad Khurram , Xu Yang
Published: May 2018

In this letter, we investigated light-induced negative differential resistance (L-NDR) effects in a hybrid photodiode formed by a graphene-silicon (GS) junction and a neighboring graphene-oxide-Si (GOS) capacitor. We observed two distinct L-NDR effects originating from the gate-dependent surface recombination and the potential-well-induced confinement of photo-carriers in the GOS region. We verified this by studying the gate-controlled GS diode, which can distinguish the photocurrent from the GS region with that from the GOS region (gate). A large peak-to-valley ratio of up to 12.1 has been obtained for the L-NDR due to gate-dependent surface recombination. Such strong L-NDR effect provides an opportunity to further engineer the optoelectronic properties of GS junctions along with exploring its potential applications in photodetectors, photo-memories, and position sensitive devices.
Direct emission of chirality controllable femtosecond LG01 vortex beam
Authors: Wang S. , Zhang S. , Yang H. , Xie J. , Jiang S. , Feng G. , Zhou S.
Published: May 2018

Direct emission of a chirality controllable ultrafast LG01 mode vortex optical beam from a conventional z-type cavity design SESAM (SEmiconductor Saturable Absorber Mirror) mode locked LD pumped Yb:Phosphate laser has been demonstrated. A clean 360 fs vortex beam of ∼45.7 mW output power has been achieved. A radial shear interferometer has been built to determine the phase singularity and the wavefront helicity of the ultrafast output laser. Theoretically, it is found that the LG01 vortex beam is obtained via the combination effect of diagonal HG10 mode generation by off-axis pumping and the controllable Gouy phase difference between HG10 and HG01 modes in the sagittal and tangential planes. The chirality of the LG01 mode can be manipulated by the pump position to the original point of the laser cavity optical axis.
40-Tesla pulsed-field cryomagnet for single crystal neutron diffraction
Authors: Duc F. , Tonon X. , Billette J. , Rollet B. , Knafo W. , Bourdarot F. , Béard J. , Mantegazza F. , Longuet B. , Lorenzo J. E. , Lelièvre-Berna E. , Frings P. , Regnault L.-P.
Published: May 2018

We present the first long-duration and high duty cycle 40-T pulsed-field cryomagnet addressed to single crystal neutron diffraction experiments at temperatures down to 2 K. The magnet produces a horizontal field in a bi-conical geometry, ±15° and ±30° upstream and downstream of the sample, respectively. Using a 1.15 MJ mobile generator, magnetic field pulses of 100 ms length are generated in the magnet, with a rise time of 23 ms and a repetition rate of 6-7 pulses per hour at 40 T. The setup was validated for neutron diffraction on the CEA-CRG three-axis spectrometer IN22 at the Institut Laue Langevin.
Phase field study of surface-induced melting and solidification from a nanovoid: Effect of dimensionless width of void surface and void size
Authors: Basak Anup , Levitas Valery I.
Published: May 2018

The size effect and the effects of a finite-width surface on barrierless transformations between the solid (S), surface melt (SM), and melt (M) from a spherical nanovoid are studied using a phase field approach. Melting (SM → M and S → M) from the nanovoid occurs at temperatures which are significantly greater than the solid-melt equilibrium temperature θe but well below the critical temperature for solid instability. The relationships between the SM and M temperatures and the ratio of the void surface width and width of the solid-melt interface, Δ¯, are found for the nanovoids of different sizes. Below a critical ratio Δ¯*, the melting occurs via SM and the melting temperature slightly reduces with an increase in Δ¯. Both S → SM and SM → M transformations have a jump-like character (excluding the case with the sharp void surface), causing small temperature hysteresis. However, the solid melts without SM for Δ¯>Δ¯*, and the melting temperature significantly increases with increasing Δ¯. The results for a nanovoid are compared with the melting/solidification of a nanoparticle, for which the melting temperatures, in contrast, are much lower than θe. A linear dependency of the melting temperatures with the inverse of the void radius is shown. The present study shows an unexplored way to control the melting from nanovoids by controlling the void size and the width and energy of the surface.
Resonant excitation cross-sections of erbium in freestanding GaN bulk crystals
Authors: Sun Z. Y. , Yan Y. Q. , Zhao W. P. , Li J. , Lin J. Y. , Jiang H. X.
Published: May 2018

Erbium doped GaN (Er:GaN) is a promising candidate as a new gain medium for high energy lasers. The excitation and emission mechanisms as well as the transition cross sections of the pump and laser wavelength are of paramount importance for understanding the performance of lasers and amplifiers made of Er:GaN materials. We report here the results of direct measurements of resonantly excited photoluminescence emission, photoluminescence excitation, and optical absorption spectroscopy in the 1.5 μm “retina-safe” spectral region performed on freestanding Er:GaN bulk crystals synthesized by hydride vapor phase epitaxy. The results established that 1514 nm and 1538 nm are the most appropriate resonant pump wavelengths for achieving gain and lasing, which differs from Er in YAG and glass hosts. The absorption coefficients (α) and absorption cross-sections (σexc) of Er in GaN in the 1.5 μm window have been directly measured, providing σexc = 1.4 × 10−20 cm2 and 2.7 × 10−20 cm2 for 1514 nm and 1538 nm pump wavelengths, respectively. These values are considerably higher than those of Er ions in glass and YAG hosts.
Drift dust acoustic soliton in the presence of field-aligned sheared flow and nonextensivity effects
Authors: Shah AttaUllah , Mushtaq A. , Farooq M. , Khan Aurangzeb , Aman-ur-Rehman
Published: May 2018

Low frequency electrostatic dust drift acoustic (DDA) waves are studied in an inhomogeneous dust magnetoplasma comprised of dust components of opposite polarity, Boltzmannian ions, and nonextensive distributed electrons. The magnetic-field-aligned dust sheared flow drives the electrostatic drift waves in the presence of ions and electrons. The sheared flow decreases or increases the frequency of the DDA wave, mostly depending on its polarity. The conditions of instability for this mode, with nonextensivity and dust streaming effects, are discussed. The nonlinear dynamics is then investigated for the DDA wave by deriving the Koeteweg-deVries (KdV) nonlinear equation. The KdV equation yields an electrostatic structure in the form of a DDA soliton. The relevancy of the work to laboratory four component dusty plasmas is illustrated.
Diel leaf growth of rapeseed at critically low temperature under winter field conditions
Authors: Nagelmüller S. , Yates S. , Walter A.
Published: May 2018

Growth and development of winter crops is strongly limited by low temperature during winter. Monitoring the temporal dynamics and thermal limits of leaf growth in that period can give important insights into the growth physiology at low temperature, crop management and future breeding traits for winter crops. In this study, we focussed on winter rapeseed as a model, dicotyledonous winter crop to study leaf growth under natural winter field conditions. Leaf growth was measured using a high-resolution marker based image sequence analysis method and the results were evaluated in the context of environmental conditions. Leaves stopped growing at a base temperature of 0°C. Above ~4°C, leaves grew with a diel (24 h) growth rhythm, which is typically known for dicots at thermally non-limiting growth conditions. Relative leaf growth rates at temperatures above this 4°C threshold were higher at night and showed a pronounced depression during the day, which we could describe by a model based on the environmental factors vapour pressure deficit (VPD), temperature and light with VPD exerting the strongest negative effect on leaf growth. We conclude that leaf growth of the selected model species at low temperatures shows a transition between pronounced environmental regulation and a superposition of environmental and internal, possibly circadian-clock-dependent regulation.
Evaluation of salt-tolerant germplasm and screening of the salt-tolerance traits of sweet sorghum in the germination stage
Authors: Ding Tonglou , Yang Zhen , Wei Xiaocen , Yuan Fang , Yin Shanshan , Wang Baoshan
Published: May 2018

Soil salinity is one of the major abiotic stresses that reduces agricultural productivity and affects large terrestrial areas around the world. Germination is the starting point of the growth and development process of all crops, and it is severely affected by salt stress. Sweet sorghum (Sorghum bicolor (L.) Moench.) is one of the most promising crops that has a relatively high salt tolerance and biomass. However, few studies have evaluated the salt tolerance or screened the reliable evaluation traits of sweet sorghum. In this study, the membership function value of five traits was used as a comprehensive index for the evaluation and selection of salt tolerance in 300 sweet sorghum germplasms. After salt tolerance evaluation, 23 highly salt-tolerant, 38 salt-tolerant, 195 moderately salt-tolerant, 38 salt-sensitive and 6 highly salt-sensitive germplasms during the germination stage were screened. Moreover, the germination index under the 200 mM NaCl treatment showed the highest correlation with salt tolerance during the germination stage. This information can be used for effectively evaluating sweet sorghum during the germination stage. These results are important for the evaluation of the salt tolerance of sweet sorghum germplasms during the germination stage.
Non-Abelian Lefschetz hyperplane theorems
Authors: Litt Daniel
Published: May 2018

LetXXbe a smooth projective variety over the complex numbers, and letD⊂XD\subset Xbe an ample divisor. For which spacesYYis the restriction mapr:Hom(X,Y)→Hom(D,Y)\begin{equation*}r: \mathrm {Hom}(X, Y)\to \mathrm {Hom}(D, Y) \end{equation*}an isomorphism?

Using positive characteristic methods, we give a fairly exhaustive answer to this question. An example application of our techniques is: ifdim⁡(X)≥3\dim (X)\geq 3,YYis smooth,ΩY1\Omega ^1_Yis nef, anddim⁡(Y)>dim⁡(D),\dim (Y)> \dim (D),the restriction maprris an isomorphism. TakingYYto be the classifying space of a finite groupBGBG, the moduli space of pointed curvesMg,n\mathscr {M}_{g,n}, the moduli space of principally polarized Abelian varietiesAg\mathscr {A}_g, certain period domains, and various other moduli spaces, one obtains many new and classical Lefschetz hyperplane theorems.
Does Index Insurance Crowd In or Crowd Out Informal Risk Sharing? Evidence from Rural Ethiopia
Authors: Takahashi Kazushi , Barrett Christopher B. , Ikegami Munenobu
Published: May 2018

We study how the introduction of a formal index insurance product affects informal risk‐sharing among pastoralists in southern Ethiopia. Using detailed social networks data, randomized incentives to purchase the insurance product, and hypothetical informal transfer data that mirror the existing customary arrangements, we find respondents’ own formal insurance uptake has no significant effect on their willingness to share risk through customary institutions. We also find weak evidence that a randomly matched peer's insurance uptake positively influences respondents’ willingness to make informal transfers to that match. Overall, our results imply that in this context index insurance does not crowd out informal risk‐sharing mediated by social networks.
Phenylephrine Infusion: Driving a Wedge in Our Practice of Left Uterine Displacement?
Authors: Farber M.K. , Bateman B.T.
Published: May 2018

(Anesthesiology. 2017;127(2):212–214)

Reported in up to 95% of healthy women, maternal hypotension is very common after spinal anesthesia during cesarean delivery when no prophylactic therapy is used. Both mechanical prophylaxis (tilting or wedging) and pharmacologic prophylaxis are recommended to prevent hypotension following a neuraxial anesthetic. Left uterine displacement, using either a pelvic wedge or lateral table adjustment, is widely used during cesarean delivery under spinal anesthesia to prevent hypotension related to aortocaval compression.
Aortocaval Compression Syndrome: Time to Revisit Certain Dogmas
Authors: Lee A.J. , Landau R.
Published: May 2018

(Anesth Analg. 2017;125(6):1975–1985)

A fundamental principle in the management of pregnant women has been the avoidance of the supine position in late pregnancy to prevent aortocaval compression (ACC) by the gravid uterus. However, this principle is based on studies designed over 70 years ago. In this review, the authors addressed the body of literature that has accumulated since the 1920s regarding ACC by the gravid uterus and proposed a critical reappraisal of common beliefs.
The CAPS Study: Incidence, Management and Outcomes of Cardiac Arrest in Pregnancy in the UK: A Prospective, Descriptive Study
Authors: Beckett V.A. , Knight M. , Sharpe P.
Published: May 2018

(BJOG. 2017;124(9):1374–1381)

It is estimated that cardiac arrest in pregnancy occurs in about 1 in 30,000 pregnancies, and it is crucial that rapid delivery for maternal benefit occur in these cases. Performing a perimortem cesarean section (PMCS) within 5 minutes of cardiac arrest minimizes the risk of maternal neurological damage from cerebral anoxia and emptying the uterus in maternal cardiac arrest can result in rapid improvement, with a return to spontaneous circulation and a chance of neonatal survival. However, there is a lack of prospective data to evaluate the timing of this intervention in practice and in relation to outcomes. The present study used the United Kingdom Obstetric Surveillance System (UKOSS) to identify cases of cardiac arrest and details of associated PMCS in the United Kingdom from July 1, 2011 and June 30, 2014 in order to estimate the incidence of maternal cardiac arrest, describe the management of cardiac arrest during pregnancy, and report fetal outcome data.
Estimating the Hospital Delivery Costs Associated With Severe Maternal Morbidity in New York City, 2008-2012.
Authors: Howland R.E. , Angley M. , Won S.H. , Wilcox W. , Searing H. , Tsao T.Y.
Published: May 2018

(Obstet Gynecol. 2018;131(2):242–252)

Rates of maternal morbidity and mortality have been increasing in the United States over the past decade. However, there is minimal information regarding the economic burden associated with these events, which include blood transfusion, hysterectomy, disseminated intravascular coagulation, adult respiratory distress syndrome, and acute renal failure. In the present study, to evaluate the cost-effectiveness of current interventions, the authors quantified the average and total hospital costs associated with severe maternal morbidity over a 5-year period within the 5 boroughs of New York City.
Short-term Costs of Preeclampsia to the United States Health Care System
Authors: Stevens W. , Shih T. , Incerti D. , Ton T.G.N. , Lee H.C. , Peneva D. , Macones G.A. , Sibai B.M. , Jena A.B.
Published: May 2018

(Am J Obstet Gynecol. 2017;217(3):237–248.e16)

The prevalence of preeclampsia has risen over the past 30 years, in part due to increasing maternal age and the increasing rate of obesity in the United States. Preeclampsia is associated with maternal and neonatal morbidity, mortality and many adverse outcomes. This study aimed to explore the extent of the annual health and cost burden of preeclampsia in the United States in 2012.
Informed Consent and Refusal in Obstetrics: A Practical Ethical Guide
Authors: Kotaska A.
Published: May 2018

(Birth. 2017;44(3):195–199)

When women refuse their provider’s advice, it can cause ethical tension and compromise care. Caregivers may believe they are legally or ethically liable when women decline recommended treatment. This article examined the ethical and legal basis of informed consent in order to build trust between patients and providers and minimize risk in these situations.
Pregnancy Outcomes After Liver Transplantation in Finland
Authors: Mattila M. , Kemppainen H. , Isoniemi H. , Polo-Kantola P.
Published: May 2018

(Acta Obstet Gynecol Scand. 2017;96(9):1106–1111)

There are limited data on pregnancy following liver transplant (LT). Immunosuppression is needed for the rest of a patient’s life after LT. Immunosuppressive drugs can include cyclosporine, tacrolimus, azathioprine, and mycophenolate mofetil; these can be problematic during pregnancy due to potential hypertensive and nephrotoxic effects. Pregnancy after LT is possible, but there is an increased risk of complications such as fetal growth restriction, preterm birth, and preeclampsia. This study reported on pregnancy outcomes in women in Finland who had undergone LT.
Contribution of Maternal Age and Pregnancy Checkbox on Maternal Mortality Ratios in the United States, 1978-2012
Authors: Davis N.L. , Hoyert D.L. , Goodman D.A. , Hirai A.H. , Callaghan W.M.
Published: May 2018

(Am J Obstet Gynecol. 2017;217(3):352.e1–352.e7)

The United States has seen a rise in the maternal mortality ratio (MMR) in the past decade, one of only 8 countries to do so. Three possible reasons for this include: an increasing maternal age and therefore increase in higher-risk pregnancies, changes in age-specific MMRs, and the inclusion of a checkbox about recent pregnancy status on death certificates. This checkbox was introduced in 2003 but was not adopted by all states, and was adopted by different states at different times, with various wording. This study aimed to assess whether the change in MMR was caused by a change in the general population or by shifts in maternal age distribution, while also assessing whether some of the increase in MMR could be attributed to the adoption of the pregnancy checkbox.
Urgency of Caesarean Section, Grading, Alarm Chain and Intrauterine Resuscitation: A Survey of Scandinavian Practice
Authors: Wildgaard K. , Ismaiel M. , Hetmann F.
Published: May 2018

(Acta Anaesthesiol Scand. 2018;62(2):167–176)

In urgent cesarean sections (CS), time to delivery is essential for maternal and fetal outcomes. Therefore, a 4-point classification system (Lucas classification) to recognize the urgency of CS is often used to streamline communication. However, nationwide guidelines for urgent CS vary across Scandinavia, and data regarding intrauterine resuscitation, organizational factors, and auditable decision-to-delivery intervals (DDI) have not been investigated in Scandinavian countries. The authors of the present study surveyed Scandinavian anesthesiologists practicing obstetric anesthesia, to establish a consensus on current clinical practice guidelines for emergency CS.
Outcomes of a Coaching-based WHO Safe Childbirth Checklist Program in India
Authors: Semrau K.E.A. , Hirschhorn L.R. , Marx Delaney M. , Singh V.P. , Saurastri R. , Sharma N. , Tuller D.E. , Firestone R. , Lipsitz S. , Dhingra-Kumar N. , Kodkany B.S. , Kumar V. , Gawande A.A.
Published: May 2018

(N Engl J Med. 2017;377(24):2313–2324)

The Safe Childbirth Checklist, created by the World Health Organization, is a practical tool encompassing a bundle of 28 essential birth practices. In the present study, the authors performed a large cluster-randomized trial of the BetterBirth program, which involves a coaching-based implementation of this checklist, to determine whether or not facility-based birth adherence to this checklist improved evidence-based care. The authors hypothesized that, if implemented at the cluster level, the intervention would reduce the composite outcome of stillbirth, early neonatal death, maternal death, or maternal severe complications during postpartum days 0 to 7.
Trends in Operative Vaginal Delivery, 2005-2013: A Population-based Study
Authors: Merriam A.A. , Ananth C.V. , Wright J.D. , Siddiq Z. , D’Alton M.E. , Friedman A.M.
Published: May 2018

(BJOG. 2017;124(9):1365–1372)

Operative vaginal delivery, using forceps or vacuum extraction during the second stage of labor, is an important labor management option. Indications for the use of an operative vaginal delivery include situations where it is beneficial to shorten the second stage of labor, such as a concerning fetal heart rate tracing, certain maternal medical conditions, and maternal exhaustion. The use of operative vaginal delivery in the United States, particularly forceps deliveries, has declined recently. As a result, concerns have been raised that obstetric residents currently being trained may not develop adequate skills to perform operative vaginal deliveries in their practices. In this retrospective population-based study of US births from 2005 to 2013, researchers evaluated the use of forceps and vacuum devices in live-born, nonanomalous singleton births from ≥36 to <42 weeks gestation.
Establishing Obstetric Anesthesiology Practice Guidelines in the Republic of Armenia: A Global Health Collaboration
Authors: Yuill G. , Amroyan A. , Millar S. , Vardapetyan E. , Habib A.S. , Owen M.D.
Published: May 2018

(Anesthesiology. 2017;127(2):220–226)

Clinical practice guidelines are developed using current literature and/or expert opinion in a specific field for the purpose of enhancing quality, safety and patient satisfaction. Guidelines in high-income countries may differ from those of low-to-middle income countries as there may be differences in provider training and availability, infrastructure and resources. In low-to-middle income countries, guidelines are best developed by local practitioners. This report was based on the process of developing national obstetric anesthesia practice guidelines in the Republic of Armenia as the result of a global partnership.
Preeclampsia: Novel Insights From Global RNA Profiling of Trophoblast Subpopulations
Authors: Gormley M. , Ona K. , Kapidzic M. , Garrido-Gomez T. , Zdravkovic T. , Fisher S.J.
Published: May 2018

(Am J Obstet Gynecol. 2017;217(2):200.e1–200.e17)

Preeclampsia is associated with defects in deep placentation, a characteristic shared with other obstetric syndromes like preterm labor, intrauterine growth restriction, late spontaneous abortion, preterm premature rupture of membranes, and placental abruption. This study used a laser microdissection approach to placentas from severe (and early onset) preeclampsia (sPE) pregnancies to allow for the transcriptional profiling of specific trophoblast subpopulations, including invasive cytotrophoblasts (iCTBs), syncytiotrophoblasts (STBs), and endovascular cytotrophoblasts. Researchers theorized that new insights into the role of these cells in preeclampsia pathogenesis would be revealed using transcriptomic analyses of the trophoblast subpopulations.
Maternal Salvage With Extracorporeal Life Support: Lessons Learned in a Single Center
Authors: Biderman P. , Carmi U. , Setton E. , Fainblut M. , Bachar O. , Einav S.
Published: May 2018

(Anesth Analg. 2017;125(4):1275–1280)

Extracorporeal life support (ECLS) has been used in severe cases of maternal H1N1 infection, cardiogenic shock, massive pulmonary embolism, and peripartum hemorrhage. However, although the Society for Obstetric Anesthesia and Perinatology (SOAP) suggested ECLS as an appropriate therapy for maternal salvage, the American Heart Association did not endorse the SOAP recommendation at that time due to the lack of cohort data on maternal outcome. Currently, cohort data are available. The authors of the present study contributed to this data and described a consecutive cohort of 11 women placed on ECLS for salvage due to maternal death/near-demise during pregnancy and the peripartum period.
Recovery From Ropivacaine-induced or Levobupivacaine-induced Cardiac Arrest in Rats: Comparison of Lipid Emulsion Effects
Authors: Yoshimoto M. , Horiguchi T. , Kimura T. , Nishikawa T.
Published: May 2018

(Anesth Analg. 2017;125(5):1496–1502)

Levobupivacaine and ropivacaine are 2 pure left-handed enantiomers that have less potential for central nervous system and cardiovascular system toxicity than bupivacaine. However, the potential for systemic toxicity still exists; comparative studies have found that a larger dose of ropivacaine than levobupivacaine is required to produce cardiac collapse in animal models. Intravenous lipid emulsion is a potential rescue therapy. As comparisons of lipid emulsion therapy between levobupivacaine-induced and ropivacaine-induced cardiac arrest have not been reported, the authors of the present study evaluated the difference in efficacy of this rescue therapy to treat cardiac arrest induced by these local anesthetics in awake rats.
Pressure Waveforms to Assess Epidural Placement: Is there a Role on Delivery Suite?
Authors: McKendry R.A. , Muchatuta N.A.
Published: May 2018

(Anaesthesia. 2017;72:811–825)

Reliable and timely administration of epidural analgesia during labor is a major goal for both parturients and anesthesiologists. Although maternal anatomy sometimes contributes to epidural failures, the incorrect placement of the epidural catheter is the major contributor to failed epidural labor analgesia. The “loss of resistance” technique is the most common method used to identify the epidural space, but it lacks specificity as advancement through other tissues may also provide what is often referred to as a “false loss of resistance.” Ultrasound can aid with insertion of the needle during epidural placement by calculating an estimated distance to the epidural space and guiding the correct puncture site and needle angulation. Dural puncture epidural, where a dural perforation is created with a spinal needle placed through an epidural needle to ensure the correct positioning of the epidural needle-tip in the epidural space, has been shown in some studies to provide better analgesia. Epidural test doses are also used to ensure successful epidural placement in obstetrics, but the lack of real-time feedback limits the usefulness of this method. Although CT fluoroscopy is useful for the placement and confirmation of epidural catheter tip position, the equipment and radiation exposure considerations do not allow its use in obstetrics.
Immediate Postpartum Neurological Deficits in the Lower Extremity: A Prospective Observational Study
Authors: Richards A. , McLaren T. , Paech M.J. , Nathan E.A. , Beattie E. , McDonnell N.
Published: May 2018

(Int J Obstet Anesth. 2017;31:5–1)

Minor and transient neurological deficits following childbirth have been reported in the literature with an incidence between 1 in 100 and 1 in 500. Most are obstetric palsies involving the lumbar nerve roots and sacral plexus. While a retrospective study reported an association between neuraxial blocks and transient postpartum neurological deficits, a large prospective study did not find an association. Overall, data regarding transient neurological deficits associated with childbirth are limited. The aim of this prospective, observational study was to quantify postpartum neurological deficits as well as delineate the types of deficits that occur.
Predictive Factors of Maternal Hypothermia During Cesarean Delivery: A Prospective Cohort Study
Authors: Desgranges F.P. , Bapteste L. , Riffard C. , Pop M. , Cogniat B. , Gagey A.C. , Boucher P. , Bonnard C. , Paturel B. , Mullet C. , Chassard D. , Bouvet L.
Published: May 2018

(Can J Anaesth. 2017;64(9):919–927)

Active warming techniques can lessen the incidence of perioperative maternal hypothermia during cesarean delivery (CD), preventing adverse events like wound infection or intraoperative blood loss. Despite wide availability, however, these active warming devices are used in fewer than 20% of units performing CD. Several preoperative and/or intraoperative factors may contribute to maternal hypothermia. This study aims to identify those predictors in order to help prevent maternal hypothermia during CD.
Differential Roles of the Right and Left Toe Perfusion Index in Predicting the Incidence of Postspinal Hypotension During Cesarean Delivery
Authors: Xu Z. , Xu T. , Zhao P. , Ma R. , Zhang M. , Zheng J.
Published: May 2018

(Anesth Analg. 2017;125(5):1560–1566)

Severe postspinal hypotension, which occurs in 70% of parturients, increases the risk of maternal and fetal complications. However, noninvasive methods used to predict spinal hypotension currently do not reflect aortocaval compression by the gravid uterus. One predictive method is the measurement of perfusion index (PI) parameters, usually measured via the finger. However, the authors of the present study speculated that measurement of toe PI may have greater predictive accuracy than finger PI and be associated with the incidence of postspinal hypotension in parturients. This is due to the fact that an underlying difference between finger and toe PI in supine parturients is the effect of direct aortocaval compression of the right iliac vessels by the gravid uterus.
Optimal Point of Insertion and Needle Angle in Neuraxial Blockade Using a Midline Approach
Authors: Vogt M. , van Gerwen D.J. , Lubbers W. , van den Dobbelsteen J.J. , Hagenaars M.
Published: May 2018

(Reg Anesth Pain Med. 2017;42(5):600–608)

When using a midline approach to neuraxial blockade, as few attempts as possible should be made to ensure patient comfort and reduce the risk of complications. This approach can be difficult, however, due to both patient factors beyond the clinician’s control as well as equipment used, clinician experience, the positioning of the patient, and point of insertion. While there are suggested needle insertion points and angles, none are supported by clinical research. This study aimed to establish a scientific rationale for choosing the optimal insertion angle and insertion point for access to the subarachnoid space or the epidural space by using a computer algorithm to perform measurements in computed tomography (CT) scans in 52 patients at different spine levels.
The Association Between the Time From Oxytocin Cessation During Labor to Cesarean Delivery and Postpartum Blood Loss: A Retrospective Cohort Study
Authors: Tran G. , Kanczuk M. , Balki M.
Published: May 2018

(Can J Anaesth. 2017;64(8):820–827)

Despite the use of prophylactic agents like oxytocin, the rise in postpartum hemorrhage (PPH) between 2003 and 2010 has been attributed to postpartum uterine atony. Oxytocin reduces PPH by up to 60% when used during the third stage of labor. However, oxytocin is associated with an increased risk of PPH secondary to uterine atony when used for labor augmentation that results in prolonged infusions or high doses. Myometrial oxytocin receptors (OTRs) may be less responsive to oxytocin administered to prevent PPH because the OTRs have become desensitized when exposed to oxytocin during labor augmentation. It is unclear if OTRs can become resensitized after a cessation of oxytocin. This study aimed to assess the association between blood loss and the interval of time between discontinuing oxytocin and cesarean delivery (CD).
Maternal Super Obesity and Risk for Intensive Care Unit Admission in the MFMU Cesarean Registry
Authors: Smid M.C. , Dotters-Katz S.K. , Vaught A.J. , Vladutiu C.J. , Boggess K.A. , Stamilio D.M.
Published: May 2018

(Acta Obstet Gynecol Scand. 2017;96(8):976–983)

Obesity is considered a risk factor for intensive care unit (ICU) admission, ICU morbidity and ICU mortality in the nonpregnant population. The prevalence of maternal super obesity [body mass index (BMI) ≥50 kg/m2] is growing and is associated with increased risk of complications including cesarean section (CS), maternal morbidity, hypertensive disorders of pregnancy, gestational diabetes, and peripartum hemorrhage. This study aimed to assess the association between maternal super obesity and ICU admission in women who delivered by CS or vaginal birth after cesarean section (VBAC).
Novel Oxytocin Receptor Variants in Laboring Women Requiring High Doses of Oxytocin
Authors: Reinl E.L. , Goodwin Z.A. , Raghuraman N. , Lee G.Y. , Jo E.Y. , Gezahegn B.M. , Pillai M.K. , Cahill A.G. , de Guzman Strong C. , England S.K.
Published: May 2018

(Am J Obstet Gynecol. 2017;217(2):214.e1–214.e8)

In the United States, oxytocin is administered to nearly half of women who give birth to either augment or induce labor. However, the required dosage of oxytocin varies widely among women, with a therapeutic window between 1 mU/min and >40 mU/min. Variations in the oxytocin receptor gene may explain some women’s requirements for high or low doses of oxytocin. This study aimed to identify variants in the oxytocin receptor gene in women in labor who had high or low dosage requirements.
Assisted Reproductive Technology and Severe Postpartum Haemorrhage: A Case-control Study
Authors: Nyfløt L.T. , Sandven I. , Oldereid N.B. , Stray-Pedersen B. , Vangen S.
Published: May 2018

(BJOG. 2017;124:1198–1205)

Assisted reproductive technology (ART) is used in many countries as infertility occurs in ∼9% of the world population. In some European countries it has been reported that at least 3% of children were conceived via ART. Severe postpartum hemorrhage (PPH) is a leading cause of maternal morbidity and the association between PPH and pregnancies achieved by ART is unclear. The aim of this case-control study was to determine whether an association exists between ART and severe PPH as well as to determine whether any association was affected by other risk factors for severe PPH.
Does the Addition of Active Body Warming to In-line Intravenous Fluid Warming Prevent Maternal Hypothermia During Elective Caesarean Section? A Randomized Controlled Trial
Authors: Chebbout R. , Newton R.S. , Walters M. , Wrench I.J. , Woolnough M.
Published: May 2018

(Int J Obstet Anesth. 2017;31:37–44)

Inadvertent perioperative hypothermia (IPH), defined as a core temperature <36°C, is a common occurrence during elective cesarean section with rates as high as 50% reported. Despite IPH occurring so frequently, active body warming is not commonly used during cesarean section nor are there guidelines for its use in obstetric populations. In the United Kingdom only 16% of obstetric units routinely use active body warming. The goal of the current study was to determine if the use of active body warming, either forced air warming or conduction mattress warming, provided additional benefit during cesarean section when warming of intravenous fluids was also utilized.
Mode of First Delivery and Severe Maternal Complications in the Subsequent Pregnancy
Authors: Colmorn L.B. , Krebs L. , Klungsøyr K. , Jakobsson M. , Tapper A.M. , Gissler M. , Lindqvist P.G. , Källen K. , Gottvall K. , Bordahl P.E. , Bjarnadóttir R.I. , Langhoff-Roos J.
Published: May 2018

(Acta Obstet Gynecol Scand. 2017;96(9):1053–1062)

Cesarean delivery rates have been rising worldwide since the 1990s despite well-known long-term maternal risks, including complications in subsequent pregnancies. In Nordic countries, intended vaginal delivery is traditionally the recommended mode of delivery after cesarean. The safety of vaginal delivery after cesarean has been called into question. This study aimed to explore the risks of severe complications at delivery following a first elective or emergency cesarean delivery and the risk of complications by the intended delivery mode.
Cesarean Risk in Obese Women at Term: A Retrospective Cohort Analysis
Authors: Nugent R. , de Costa C. , Vangaveti V.
Published: May 2018

(Aust N Z J Obstet Gynaecol. 2017;57(4):440–445)

Obesity in pregnancy is a growing issue and has been associated with increased risk of maternal and fetal complications such as gestational diabetes and hypertensive disorders of pregnancy. While increased fetal surveillance during such pregnancies has been recommended, there is little information concerning the induction of labor (IOL) in pregnant obese women. This retrospective study aimed to compare the impact of IOL and expectant management on neonatal and maternal outcomes, hypothesizing that term IOL was not associated with an increased risk of cesarean delivery.
Predictors of Success of External Cephalic Version and Cephalic Presentation at Birth Among 1253 Women With Noncephalic Presentation Using Logistic Regression and Classification Tree Analyses
Authors: Hutton E.K. , Simioni J.C. , Thabane L.
Published: May 2018

(Acta Obstet Gynecol Scand. 2017;96(8):1012–1020)

While external cephalic version (ECV) can reduce the likelihood of cesarean birth and noncephalic presentation, many women are not offered, or they decline ECV due to low reported success rates. Factors which predict successful ECV have been studied and identified, but further study of the outcomes for clinically relevant groupings of women are lacking. This study used classification and regression tree (CART) analyses to divide observations into subgroups based on the factor that best separates those with and without a certain outcome. This resulted in a flow chart that may be helpful to clinicians predicting factors of successful ECV.
Can 3-Dimensional Power Doppler Indices Improve the Prenatal Diagnosis of a Potentially Morbidly Adherent Placenta in Patients With Placenta Previa?
Authors: Haidar Z.A. , Papanna R. , Sibai B.M. , Tatevian N. , Viteri O.A. , Vowels P.C. , Blackwell S.C. , Moise K.J.
Published: May 2018

(Am J Obstet Gynecol. 2017;217(2):202.e1–202.e13)

The incidence of morbidly adherent placenta (MAP), a condition that can result in life-threatening hemorrhage and other maternal morbidities, has been on the rise. Traditionally, 2-dimensional (2D) ultrasound has been used to diagnose MAP and severe MAP (increta and percreta). This diagnosis is subjective as it relies on clinician interpretation of the ultrasound examination. This study aimed to evaluate the ability of a 3D power Doppler technique to diagnose MAP and severe MAP, as compared with gray-scale 2D ultrasound.
Intravenous Dexamethasone as an Adjunct to Improve Labor Analgesia: A Randomized, Double-blinded, Placebo Controlled Clinical Trial
Authors: Dube P. , Mitra S. , Singh J. , Saroam R. , Mehra R.
Published: May 2018

(J Clin Anesth. 2017;43:6–10)

It is well recognized that lumbar epidural analgesia using local anesthetic with or without an adjuvant is a consistently effective method of pain relief during labor. However, newer adjuvants, such as clonidine and neostigmine, are associated with adverse side effects and may be less suitable in pregnant women. A potential alternative is dexamethasone, a well-known anti-inflammatory drug. As there are limited studies regarding its intrapartum use, the authors of the present study evaluated the role of intravenous dexamethasone as an adjuvant to neuraxial analgesia for labor pain in a double-blind, prospective, randomized, placebo-controlled study.
Core Temperature Monitoring in Obstetric Spinal Anesthesia Using an Ingestible Telemetric Sensor
Authors: du Toit L. , van Dyk D. , Hofmeyr R. , Lombard C.J. , Dyer R.A.
Published: May 2018

(Anesth Analg. 2018;126(1):190–195)

Maternal core temperature is difficult to monitor during cesarean delivery (CD) under spinal anesthesia (SA). A drop in maternal core temperature <36.0°C during the perioperative period is associated with increased risks of postoperative morbidity. Current knowledge of the thermal insult associated with obstetric SA is limited to small randomized controlled trials. In the present study, the authors used continuous core temperature recording to generate high-resolution data on thermal insult and thermal recovery associated with CD under SA.
Preemptive Analgesia for Postoperative Hysterectomy Pain Control: Systematic Review and Clinical Practice Guidelines
Authors: Steinberg A.C. , Schimpf M.O. , White A.B. , Mathews C. , Ellington D.R. , Jeppson P. , Crisp C. , Aschkenazi S.O. , Mamik M.M. , Balk E.M. , Murphy M.
Published: May 2018

(Am J Obstet Gynecol. 2017;217(3):303–313)

Preemptive analgesia, which may include multimodal pain management, is administered before surgery and is believed to prevent central sensitization. This can include narcotic or non-narcotic medications and may be administered in many ways. This systematic review used current studies of women receiving preemptive medication for abdominal hysterectomy, with a primary outcome of pain control. The aim was to determine the best method of pain control while decreasing narcotic consumption and adverse events.
Epidural Blood Patch Treatment for Headache Caused by a Ruptured Tarlov Cyst
Authors: Qasem F. , McCallum C. , Armstrong P.
Published: May 2018

(Can J Anaesth. 2017;64(9):983–984)

There are limited data on the management of Tarlov cysts, which are cerebrospinal fluid–containing nerve root cysts located between the endoneurium and perineurium. Patients with Tarlov cysts may be asymptomatic.
Combined Spinal Epidural in a Parturient With Tinea Versicolor
Authors: Turakhia M.B. , Bauchat J.
Published: May 2018

(J Clin Anesth. 2017;43:63–64)

In this correspondence, the authors discussed the case of a 33-year-old parturient who presented for labor analgesia (combined spinal epidural technique) with a history of recurrent lumbar tinea versicolor, as well as a maculopapular rash from the cervical to the sacral area on physical examination. Tinea versicolor is a benign condition in which Malassezia globosa, a yeast found in normal flora, becomes pathogenic following exposure to heat and humidity in immunosuppressed individuals. Following informed consent, combined spinal epidural labor analgesia was administered with a 27-G Pencan spinal needle following sterile skin preparation and using a needle-through-needle technique. The epidural catheter remained in situ for 13 hours. The authors reported an uneventful delivery and postoperative course.