First-Principle Description of Correlation Effects in Layered Materials

We present a first-principles description of anisotropic materials characterized by having both weak (dispersion-like) and strong covalent bonds, based on the Adiabatic--Connection Fluctuation--Dissipation Theorem within Density Functional Theory. For hexagonal boron nitride the in-plane and out of plane bonding as well as vibrational dynamics are well described both at equilibrium and when the layers are pulled apart. Also bonding in covalent and ionic solids is described. The formalism allows to ping-down the deficiencies of common exchange-correlation functionals and provides insight towards the inclusion of dispersion interactions into the correlation functional.Comment: Accepted for publication in Physical Review Letter

Cupid:commitments in relational algebra

We propose Cupid, a language for specifying commitments that supports their information-centric aspects, and offers crucial benefits. One, Cupid is first-order, enabling a systematic treatment of commitment instances. Two, Cupid supports features needed for real-world scenarios such as deadlines, nested commitments, and complex event expressions for capturing the lifecycle of commitment instances. Three, Cupid maps to relational database queries and thus provides a set-based semantics for retrieving commitment instances in states such as being violated, discharged, and so on. We prove that Cupid queries are safe. Four, to aid commitment modelers, we propose the notion of well-identified commitments, and finitely violable and finitely expirable commitments. We give syntactic restrictions for obtaining such commitments

Generalized commitment alignment

The interoperability of interacting components means that their expectations of each other remain in agreement. A commitment captures what one agent (its creditor) may expect from another agent (its debtor). Chopra and Singh (C&S) motivate commitment alignment as a meaning-based form of interoperation and show how to ensure alignment among agents despite asynchrony. Although C&S’s approach demonstrates the key strengths of relying on commitment semantics, it suffers from key shortcomings, which limit its applicability in practice. One, C&S do not model commitments properly, causing unacceptable interference between commitments in different transactions. Two, they require that the communication infrastructure guarantee first-in first-out (FIFO) delivery of messages for every agent-agent channel. Three, C&S guarantee alignment only in quiescent states (where no messages are in transit); however, such states may never obtain in enactments of real systems. Our approach retains and enhances C&S’s key strengths and avoids their shortcomings by providing a declarative semantics-based generalized treatment of alignment. Specifically, we (1) motivate a declarative notion of alignment relevant system states termed completeness; (2) prove that it coincides with alignment; and (3) provide the computations by which a system of agents provably progresses toward alignment assuming eventual delivery of messages

Cell Cycle of Normal and Psoriatic Epidermis In Vitro

Studies of growth kinetics of normal and psoriatic epidermal cells in vitro indicate that there is no significant difference in the rate of proliferation under these conditions. The data may also be compatible with the hypothesis that both kinds of cells replicate at similar rates in vivo and that earlier conclusions regarding the markedly shortened cell cycle in psoriasis were based on insufficient data regarding the size of the proliferative pool in normal steady state epidermis

Retrospective analysis of indications of primary caesarean sections done at a tertiary care hospital

Background: Caesarean section rates have globally risen above the levels that can be considered medically necessary. The aim of the study is to analyze the rate and indications of caesarean sections for primigravidae in the period 2016 to 2018 at a tertiary care hospital in Delhi.Methods: It is a retrospective observational study conducted in the Department of Obstetrics and Gynaecology at PGIMER and Dr RML Hospital, New Delhi. A total of 552 caesarean deliveries in primigravidae were studied.Results: The total deliveries during the study period were 3346 and the total caesarean section rate observed was 30.66%. The caesarean section rate among primigravidae was 29.1%. The rate of caesarean section in primigravidae rose from 22.7% in 2016 to 39.3% in 2018 with 17% increase. Majority of them belonged to the age group 20-30 years (79.34%) and 2.53% were elderly primigravidae. Out of the total number of primigravidae caesarean deliveries, 67.2% were performed in emergency and 32.7% were performed electively. Among the emergency caesarean sections performed, 64% of patients had induced labor and 22% had spontaneous labor. The most common indication of caesarean section was fetal distress (19.77%) followed by arrest of labor (17.87%) and malpresentations (8.9%). The short-term caesarean morbidity rate was 25.4% including one mortality. Wound infection was the most common complication.Conclusions: Various reasons like changing maternal risk profile increased IVF pregnancies, scientific advances, personal choice and medico legal considerations have been cited for increased caesarean rate. Following evidence-based labor protocols, judicious use of cardiotocography, proper patient selection for labor induction and patient education will contribute in reduction of caesarean sections and related complications

Broad boron sheets and boron nanotubes: An ab initio study of structural, electronic, and mechanical properties

Based on a numerical ab initio study, we discuss a structure model for a broad boron sheet, which is the analog of a single graphite sheet, and the precursor of boron nanotubes. The sheet has linear chains of sp hybridized sigma bonds lying only along its armchair direction, a high stiffness, and anisotropic bonds properties. The puckering of the sheet is explained as a mechanism to stabilize the sp sigma bonds. The anisotropic bond properties of the boron sheet lead to a two-dimensional reference lattice structure, which is rectangular rather than triangular. As a consequence the chiral angles of related boron nanotubes range from 0 to 90 degrees. Given the electronic properties of the boron sheets, we demonstrate that all of the related boron nanotubes are metallic, irrespective of their radius and chiral angle, and we also postulate the existence of helical currents in ideal chiral nanotubes. Furthermore, we show that the strain energy of boron nanotubes will depend on their radii, as well as on their chiral angles. This is a rather unique property among nanotubular systems, and it could be the basis of a different type of structure control within nanotechnology.Comment: 16 pages, 17 figures, 2 tables, Versions: v1=preview, v2=first final, v3=minor corrections, v4=document slightly reworke