Vaginal delivery at term with previous one cesarean section: is it safe?

Background: Post cesarean pregnancies are high risk pregnancy and main concern is uterine scar rupture with increasing maternal and perinatal risks, for vaginal birth after cesarean delivery (VBAC). Objective of this study is to know neonatal and maternal outcome at term who attempt vaginal delivery with previous one cesarean section presenting in active stage of labor.Methods: A total of 277 pregnant women with single live fetus at term, cephalic presentation with previous one cesarean section, underwent a trial of labor and outcome of successful and failed vaginal birth were noted.Results: Trial of labor was successful in 52.3% and failed in 47.7% (p=0.269). VBAC was successful where the previous cesarean section indications were fetal distress (79% versus 21%, p=0.000), pregnancy induced hypertension (77.3% versus 22.7%, p=0.000) and fetal growth restriction (81.8% versus 18.2%, p=0.000), when compared with failed trial of labor who required emergency cesarean section in pre-labor rupture of the membranes (8.3% versus 91.7%, p=0.000) and dystocia (3.3% versus 96.7%, p=0.000). VBAC was successful at gestational age of 37 0/7-38 6/7 weeks (p=0.000). In the failed VBAC women who required emergency cesarean section there was significant early neonatal death (p=0.025). Scar dehiscence and hospital stay with or without complications were more in the failed VBAC group.Conclusions: Early neonatal death and duration of hospital stay were significantly more in the failed VBAC, who were posted for emergency cesarean delivery. Scar dehiscence occurred in the failed VBAC group. Women presenting at 37 0/7 to 38 6/7 weeks of gestation with cephalic presentation in active stage of labor who had previous cesarean section done for fetal distress, pregnancy induced hypertension and fetal growth restriction with inter pregnancy interval of > 24 months can be planned and counselled for VBAC trial of labor

Differences in Electronic Structure of Global Warming Molecules Lead to Different Molecular Properties. Reply to Wallington et al.

No abstract availabl

Initiating Molecular Growth in the Interstellar Medium via Dimeric Complexes of Observed Ions and Molecules

A feasible initiation step for particle growth in the interstellar medium (ISM) is simulated by means of ab quantum chemistry methods. The systems studied are dimer ions formed by pairing nitrogen containing small molecules known to exist in the ISM with ions of unsaturated hydrocarbons or vice versa. Complexation energies, structures of ensuing complexes and electronic excitation spectra of the encounter complexes are estimated using various quantum chemistry methods. Moller-Plesset perturbation theory (MP2, Z-averaged perturbation theory (ZAP2), coupled cluster singles and doubles with perturbative triples corrections (CCSD(T)), and density functional theory (DFT) methods (B3LYP) were employed along with the correlation consistent cc-pVTZ and aug-cc-pVTZ basis sets. Two types of complexes are predicted. One type of complex has electrostatic binding with moderate (7-20 kcal per mol) binding energies, that are nonetheless significantly stronger than typical van der Waals interactions between molecules of this size. The other type of complex develops strong covalent bonds between the fragments. Cyclic isomers of the nitrogen containing complexes are produced very easily by ion-molecule reactions. Some of these complexes show intense ultraviolet visible spectra for electronic transitions with large oscillator strengths at the B3LYP, omegaB97, and equations of motion coupled cluster (EOM-CCSD) levels. The open shell nitrogen containing carbonaceous complexes especially exhibit a large oscillator strength electronic transition in the visible region of the electromagnetic spectrum

Planned versus emergency cesarean delivery with previous one cesarean section: a prospective observational study

Background: Women presents with previous history of cesarean section (CS) is a ‘high risk pregnancy’ and requires regular antenatal check-ups. Planned CS at term done for perinatal interest. Post cesarean pregnancy admitted through emergency required direct CS, for those not fit for vaginal birth as per different guidelines. Main objective of this study is to know neonatal and maternal outcome at term for planned versus emergency CS with previous one CS.Methods: Planned or emergency CS were done in 1003 pregnant women at term with previous one CS and outcome of both neonatal and maternal were noted. Emergency CS done in failed VBAC women were excluded from the study.Results: Planned CS before onset of labor were done in 22.93% and emergency CS in 77.07% in the present study. A significant number of women has undergone planned CS in cephalo-pelvic disproportion (45.21%), contracted pelvis (24.34%) and fetal growth restriction (6.95%) where P=0.000. Scar tenderness (20.18%), fetal distress (16.04%) and cephalo-pelvic disproportion (15.52%) were major indications for emergency CS. Maternal complications in the emergency CS group were pyrexia (P=0.000) and blood transfusion, required in 1.81% (P=0.000). There were two maternal death and hysterectomy required in 0.38% in the emergency CS compared to 1.30% in the planned CS (P=0.274). Neonatal complications were significant(P=0.018) in the emergency CS group. Common complications were jaundice (2.84% versus 1.73%, P=0.489), sepsis (0.25% versus 0.86%, P=0.487) and early neonatal death (2.97% versus 0.86%, P=0.119) in emergency CS compared to planned CS.Conclusions: Neonatal morbidity and mortality were significant in the emergency CS, compared to planned CS. Pyrexia and blood transfusion were significant maternal morbidity in the emergency CS group

Association Mechanisms of Unsaturated C2 Hydrocarbons with Their Cations: Acetylene and Ethylene

The ion-molecule association mechanism of acetylene and ethylene with their cations is investigated by ab initio quantum chemical methods to understand the structures, association energies, and the vibrational and electronic spectra of the products. Stable puckered cyclic isomers are found as the result of first forming less stable linear and bridge isomers. The puckered cyclic complexes are calculated to be strongly bound, by 87, 35 and 56 kcal/mol for acetylene-acetylene cation, ethylene-ethylene cation and acetylene-ethylene cation, respectively. These stable complexes may be intermediates that participate in further association reactions. There are no association barriers, and no significant inter-conversion barriers, so the initial linear and bridge encounter complexes are unlikely to be observable. However, the energy gap between the bridged and cyclic puckered isomers greatly differs from complex to complex: it is 44 kcal/mol in C4H4 +, but only 6 kcal/mol in C4H8 +. The accurate CCSD(T) calculations summarized above are also compared against less computationally expensive MP2 and density functional theory (DFT) calculations for structures, relative energies, and vibrational spectra. Calculated vibrational spectra are compared against available experiments for cyclobutadiene cation. Electronic spectra are also calculated using time-dependent DFT

Identifying the Molecular Origin of Global Warming

We have investigated the physical characteristics of greenhouse gases (GHGs) to assess which properties are most important in determining the efficiency of a GHG. Chlorofluorcarbons (CFCs), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), nitrogen fluorides, and various other known atmospheric trace molecules have been included in this study. Compounds containing the halogens F or Cl have in common very polar X-F or X-Cl bonds, particularly the X-F bonds. It is shown that as more F atoms bond to the same central atom, the bond dipoles become larger as a result of the central atom becoming more positive. This leads to a linear increase in the total or integrated XF bond dipole derivatives for the molecule, which leads to a non-linear (quadratic) increase in infrared (IR) intensity. Moreover, virtually all of the X-F bond stretches occur in the atmospheric IR window as opposed to X-H stretches, which do not occur in the atmospheric window. It is concluded that molecules possessing several F atoms will always have a large radiative forcing parameter in the calculation of their global warming potential. Some of the implications for global warming and climate change are discussed

A Group Increment Scheme for Infrared Absorption Intensities of Greenhouse Gases

A molecule's absorption in the atmospheric infrared (IR) window (IRW) is an indicator of its efficiency as a greenhouse gas. A model for estimating the absorption of a fluorinated molecule within the IRW was developed to assess its radiative impact. This model will be useful in comparing different hydrofluorocarbons and hydrofluoroethers contribution to global warming. The absorption of radiation by greenhouse gases, in particular hydrofluoroethers and hydrofluorocarbons, was investigated using ab initio quantum mechanical methods. Least squares regression techniques were used to create a model based on this data. The placement and number of fluorines in the molecule were found to affect the absorption in the IR window and were incorporated into the model. Several group increment models are discussed. An additive model based on one-carbon groups is found to work satisfactorily in predicting the ab initio calculated vibrational intensities

Energy and Spectroscopic Characterization of the Isomers of C4H3-, C6H3-, and C6H5-

Organic and inorganic molecules, neutral and ions have been observed in the interstellar medium. A few anions of organic molecules have also been observed recently. The Cassini spacecraft in the upper atmosphere of Titan has observed anions of large organic molecules. In this project we have studied the physical and spectroscopic properties of C4H3-, C6H3-, and C6H5-. We have optimized the geometrical structures of all low-lying isomers of the anions, calculated rotational, and harmonic vibrational frequencies of the anions mentioned above using the B3LYP density functional along with the augmented correlation consistent polar valence triple zeta (aug-cc-pVTZ) basis set. We have found many low-lying isomers on the potential energy surface of these anions

Climate Metrics for C1–C4 Hydrofluorocarbons (HFCs)

This article looks at hydrofluorocarbons (HFCs) which are potent greenhouse gases that are potential substitutes for ozone depleting substances. The Kigali amendment lists 17 HFCs that are currently in commercial use to be regulated under the Montreal Protocol. Future commercial applications may explore the use of other HFCs, most of which currently lack an evaluation of their climate metrics. In this work, atmospheric lifetimes, radiative efficiencies (REs), global warming potentials (GWPs), and global temperature change potentials (GTPs) for all saturated HFCs with fewer than 5 carbon atoms are estimated to help guide future usage and policy decisions

PDRs4All III: JWST's NIR spectroscopic view of the Orion Bar

(Abridged) We investigate the impact of radiative feedback from massive stars on their natal cloud and focus on the transition from the HII region to the atomic PDR (crossing the ionisation front (IF)), and the subsequent transition to the molecular PDR (crossing the dissociation front (DF)). We use high-resolution near-IR integral field spectroscopic data from NIRSpec on JWST to observe the Orion Bar PDR as part of the PDRs4All JWST Early Release Science Program. The NIRSpec data reveal a forest of lines including, but not limited to, HeI, HI, and CI recombination lines, ionic lines, OI and NI fluorescence lines, Aromatic Infrared Bands (AIBs including aromatic CH, aliphatic CH, and their CD counterparts), CO2 ice, pure rotational and ro-vibrational lines from H2, and ro-vibrational lines HD, CO, and CH+, most of them detected for the first time towards a PDR. Their spatial distribution resolves the H and He ionisation structure in the Huygens region, gives insight into the geometry of the Bar, and confirms the large-scale stratification of PDRs. We observe numerous smaller scale structures whose typical size decreases with distance from Ori C and IR lines from CI, if solely arising from radiative recombination and cascade, reveal very high gas temperatures consistent with the hot irradiated surface of small-scale dense clumps deep inside the PDR. The H2 lines reveal multiple, prominent filaments which exhibit different characteristics. This leaves the impression of a "terraced" transition from the predominantly atomic surface region to the CO-rich molecular zone deeper in. This study showcases the discovery space created by JWST to further our understanding of the impact radiation from young stars has on their natal molecular cloud and proto-planetary disk, which touches on star- and planet formation as well as galaxy evolution.Comment: 52 pages, 30 figures, submitted to A&