Complete field-induced spectral response of the spin-1/2 triangular-lattice antiferromagnet CsYbSe2.

Fifty years after Anderson's resonating valence-bond proposal, the spin-1/2 triangular-lattice Heisenberg antiferromagnet (TLHAF) remains the ultimate platform to explore highly entangled quantum spin states in proximity to magnetic order. Yb-based delafossites are ideal candidate TLHAF materials, which allow experimental access to the full range of applied in-plane magnetic fields. We perform a systematic neutron scattering study of CsYbSe2, first proving the Heisenberg character of the interactions and quantifying the second-neighbor coupling. We then measure the complex evolution of the excitation spectrum, finding extensive continuum features near the 120°-ordered state, throughout the 1/3-magnetization plateau and beyond this up to saturation. We perform cylinder matrix-product-state (MPS) calculations to obtain an unbiased numerical benchmark for the TLHAF and spectacular agreement with the experimental spectra. The measured and calculated longitudinal spectral functions reflect the role of multi-magnon bound and scattering states. These results provide valuable insight into unconventional field-induced spin excitations in frustrated quantum materials.

Understanding Reentrance in Frustrated Magnets: The Case of the Er_{2}Sn_{2}O_{7} Pyrochlore.

Reentrance, the return of a system from an ordered phase to a previously encountered less-ordered one as a controlled parameter is continuously varied, is a recurring theme found in disparate physical systems, yet its microscopic cause is often not investigated thoroughly. Here, through detailed characterization and theoretical modeling, we uncover the microscopic mechanism behind reentrance in the strongly frustrated pyrochlore antiferromagnet Er_{2}Sn_{2}O_{7}. We use single crystal heat capacity measurements to expose that Er_{2}Sn_{2}O_{7} exhibits multiple instances of reentrance in its magnetic field B vs temperature T phase diagram for magnetic fields along three cubic high symmetry directions. Through classical Monte Carlo simulations, mean field theory, and classical linear spin-wave expansions, we argue that the origins of the multiple occurrences of reentrance observed in Er_{2}Sn_{2}O_{7} are linked to soft modes. These soft modes arise from phase competition and enhance thermal fluctuations that entropically stabilize a specific ordered phase, resulting in an increased transition temperature for certain field values and thus the reentrant behavior. Our work represents a detailed examination into the mechanisms responsible for reentrance in a frustrated magnet and may serve as a template for the interpretation of reentrant phenomena in other physical systems.

Gestational age and birth weight centiles of singleton babies delivered normally following spontaneous labor, in Southern Sri Lanka

Aims: To estimate the gestational age and birth weight centiles of babies delivered normally, without any obstetric intervention, in women with uncomplicated singleton pregnancies establishing spontaneous onset of labour. Method: Consecutive women with uncomplicated singleton pregnancies, attending the Academic Obstetrics and Gynecology Unit of the Teaching Hospital Mahamodara Galle, Sri Lanka, with confirmed dates and establishing spontaneous onset of labor and delivering vaginally between gestational age of 34 - 41 weeks, without any obstetric intervention , during the period September 2013 to February 2014 were studied. The gestational age at spontaneous onset of labor and vaginal delivery and the birth weights of the babies were recorded. Results: There were 3294 consecutive deliveries during this period, and of them 1602 (48.6%) met the inclusion criteria. Median gestational age at delivery was 275 days (range 238-291 days, IQR 269 to 280 days) and the median birth weight was 3000 g (range1700g - 4350g; IQR 2750-3250g). The 10th, 50th and 90th birth weight centiles of the babies delivered at a gestational age of 275 days were approximately 2570g, 3050g and 3550g respectively. Conclusions: The median gestational age among women with uncomplicated singleton pregnancies who established spontaneous onset of labor and delivered vaginally, without any obstetric intervention, was approximately five days shorter than the traditionally accepted 280 days. At a gestational age of 275 days, the mean birth weight was approximately 3038g and the 50th centile of the birth weight of the babies delivered was approximately 3050g.

Analysis of high caesarean section rates: the second step after audits using the Ten Group Classification System

Objective: To identify possible methods of reducing high caesarean section rates in a tertiary care hospital. Methods: Analysis of birth weight of neonates, maternal age and indications for caesarean section in the groups identified by a modification of Robson's 10 Group Classification of caesarean section (TGCS), which contribute significantly to the high caesarean section rates in the University Obstetric Unit, Teaching Hospital Mahamodara, Galle Sri Lanka during 2010 - to 2014. Results: Among nulliparous women, at term, having a singleton fetus, with a vertex presentation (NTSV) who underwent a caesarian section 25.6% delivered neonates weighing between 2500g and 2999g. Among multiparous women, at term, with no previous caesarean section, having a singleton fetes with a vertex presentation (MTSV) who underwent a caesarian section, those delivering neonates weighing between 2500g and 2999g ranged from 25.6% to 34.6%. Indications for ante part caesarean section included fetal distress, sub fertility, increased maternal age and cephalon-pelvic disproportion in NTSV, and fetal distress, vaginal varices, and a bad obstetric history in MTSV. Among multiparous women with one previous caesarean section undergoing repeat caesarean section, 29.8% delivered neonates weighing between 2500g and 2999g. Women >35 years had a higher risk of caesarean section, irrespective of whether they were nulliparous or multiparous, and whether they had a previous caesarean section or not. Conclusions: A reduction in caesarean section rates in NTSV and MTSV, and women with one previous caesarean section, especially in those with foetuses weighing 2500g - 2999g, should be considered. Increased maternal age and subfertility per se should not be routine indications for antepartum caesarean section. Antepartum caesarean section for vaginal varices and cephalo-pelvic disproportion should be avoided. The diagnosis of fetal distress should be improved.