J. Segar

Institute of Mathematical Sciences · Faculty of Physics

It is known that there are two inequivalent $\mathbb{Z}_2^2$-graded $osp(1|2)$ Lie superalgebras. Their affine extensions are investigated and it is shown that one of them admits two central elements, one is non-graded and the other is $(1,1)$-graded. The affine $\mathbb{Z}_2^2$-$osp(1|2)$ algebras are used by the Sugawara construction to study pos...

The quantum coherence of a multipartite system is investigated when some of the parties are moving with uniform acceleration and the analysis is carried out using the single-mode approximation. Due to acceleration the quantum coherence is divided into two parts as accessible and inaccessible coherence. First we investigate tripartite systems, consi...

The quantum coherence of a multipartite system is investigated when some of the parties are moving with constant acceleration. Due to relativistic motion the quantum coherence is divided into two parts as accessible and inaccessible coherence. First we investigate tripartite systems, considering both GHZ and W-states. We find that the quantum coher...

The quantum coherence of the two-site XYZ model with Dzyaloshinsky–Moriya (DM) interactions in an external inhomogenous magnetic field is studied. The DM interaction, the magnetic field and the measurement basis can be along different directions, and we examine the quantum coherence at finite temperature. With respect to the spin–spin interaction p...

The quantum coherence of the two-site XYZ model with Dzyaloshinsky-Moriya (DM) interactions in an external inhomogenous magnetic field is studied. The DM interaction, the magnetic field and the measurement basis can be along different directions, and we examine the quantum coherence at finite temperature. With respect to the spin-spin interaction p...

We introduce a class of novel ℤ2 × ℤ2-graded color superalgebras of infinite dimension. It is done by realizing each member of the class in the universal enveloping algebra of a Lie superalgebra which is a module extension of the Virasoro algebra. Then the complete classification of central extensions of the ℤ2 × ℤ2-graded color superalgebras is pr...

In recent years there has been a great deal of focus on a globe-spanning quantum network, including linked satellites for applications ranging from quantum key distribution to distributed sensors and clocks. In many of these schemes, relativistic transformations may have deleterious effects on the purity of the distributed entangled pairs. In this...

The time evolution of the distribution and shareability of quantum coherence of a tripartite system in a non-Markovian environment is examined. The total coherence can be decomposed into various contributions, ranging from local, global bipartite and global tripartite, which characterize the type of state. We identify coherence revivals for non-Mar...

We introduce a class of novel $\mathbb{Z}_2 \times \mathbb{Z}_2$-graded color superalgebras of infinite dimension. It is done by realizing each member of the class in the universal enveloping algebra of a Lie superalgebra which is a module extension of the Virasoro algebra. Then the complete classification of central extensions of the $\mathbb{Z}_2...

We introduce two classes of novel color superalgebras of Z2×Z2 grading. This is done by realizing members of each class within the universal enveloping algebra of the N=1 supersymmetric extension of the conformal Galilei algebra. This allows us to upgrade any representation of the super conformal Galilei algebras to a representation of the Z2×Z2 gr...

We introduce two classes of novel color superalgebras of $ \mathbb{Z}_2 \times \mathbb{Z}_2 $ grading. This is done by realizing members of each in the universal enveloping algebra of the ${\cal N}=1$ supersymmetric extension of the conformal Galilei algebra. This allows us to upgrade any representation of the super conformal Galilei algebras to a...

The time evolution of the distribution and shareability of quantum coherence of a tripartite system in a non-Markovian environment is examined. The total coherence can be decomposed into various contributions, ranging from local, global bipartite and global tripartite, which characterize the type of state. We identify coherence revivals for non-Mar...

We generalize the real and chiral N=2 super Schrödinger algebras to Z2×Z2-graded Lie superalgebras. This is done by D-module presentation, and as a consequence, the D-module presentations of Z2×Z2-graded superalgebras are identical to the ones of super Schrödinger algebras. We then generalize the calculus over the Grassmann number to Z2×Z2 setting....

We study quantum coherence in a spin chain with both symmetric exchange and antisymmetric Dzyaloshinsky-Moriya couplings. Quantum coherence is quantified using the recently introduced quantum Jensen-Shannon divergence, which has the property that it is easily calculable and has several desirable mathematical properties. We calculate exactly the coh...

We study quantum coherence in a spin chain with both symmetric exchange and antisymmetric Dzyaloshinsky-Moriya couplings. Quantum coherence is quantified using the recently introduced quantum Jensen-Shannon divergence, which has the property that it is easily calculable and has several desirable mathematical properties. We calculate exactly the coh...

We generalize the real and chiral $ {\cal N} =2 $ super Schr\"odinger algebras to ${\mathbb Z}_2 \times {\mathbb Z}_2$-graded Lie superalgebras. This is done by $D$-module presentation and as a consequence, the $D$-module presentations of ${\mathbb Z}_2 \times {\mathbb Z}_2$-graded superalgebras are identical to the ones of super Schr\"odinger alge...

In recent years there has been a great deal of focus on a globe-spanning quantum network, including linked satellites for applications ranging from quantum key distribution to distributed sensors and clocks. In many of these schemes, relativistic transformations may have deleterious effects on the purity of the distributed entangled pairs. This bec...

Quantum coherence is investigated using a new measure with metric properties and entropic nature and decomposed into local and intrinsic contributions. The trade-off relation between these contributions as well as their distribution properties are studied for simple tripartite systems and the more complex spin chain model. We find that the coherenc...

In this work we construct a infinite dimensional $\ell$-super Galilean conformal algebra, which is a generalization of the $\ell=1$ algebra found in the literature. We give a classification of central extensions, the vector field representation, the coadjoint representation and the operator product expansion of the infinite dimensional $\ell$-super...

The distribution of coherence in multipartite systems is examined. We use a new coherence measure with entropic nature and metric properties, based on the quantum Jensen-Shannon divergence. The metric property allows for the coherence to be decomposed into various contributions, which arise from local and intrinsic coherences. We find that there ar...

Conformal Galilei algebra is a class of non-semisimple Lie algebras. Each member of the class is labelled by two parameters d (positive integer) and l (positive integer or positive half-integer). We investigate the lowest weight representations of the conformal Galilei algebra for d = 1 and any integer l. We start with the Verma modules and then ex...

A two parameter generalization of Boltzmann-Gibbs-Shannon entropy based on natural logarithm is introduced. The generalization of the Shannon-Kinchinn axioms corresponding to the two parameter entropy is proposed and verified. We present the relative entropy, Jensen-Shannon divergence measure and check their properties. The Fisher information measu...

The conformal Galilei algebra (CGA) is a non-semisimple Lie algebra labelled by two parameters $ d $ and $ \ell. $ The aim of the present work is to investigate the lowest weight representations of CGA with $ d = 1 $ for any integer value of $ \ell. $ First we focus on the reducibility of the Verma modules. We give a formula for the Kac determinant...

The ℓ-conformai Galilei algebra, denoted by gℓ(d), is a particular non-semisimple Lie algebra specified by a positive integer d and a spin value ℓ. The algebra gℓ(d) admits central extensions. We study lowest weight representations, in particular Verma modules, of gℓ(d) with the central extensions for d = 1,2. We give a classification of irreducibl...

l-Conformal Galilei algebra, denoted by g{l}{d}, is a non-semisimple Lie algebra specified by a pair of parameters (d,l). The algebra is regarded as a nonrelativistic analogue of the conformal algebra. We derive hierarchies of partial differential equations which have invariance of the group generated by g{l}{d} with central extension as kinematica...

A unified framework to describe the adiabatic class of ensembles in the generalized statistical mechanics based on Schwammle-Tsallis two parameter (q, q') entropy is proposed. The generalized form of the equipartition theorem, virial theorem and the adiabatic theorem are derived. Each member of the class of ensembles is illustrated using the classi...

We consider multibaryon configurations in a SU(2) quark soliton model based on chiral invariant quark-meson couplings. We compute the energy of interaction between two nucleons by considering configurations which correspond to two B=1 solitons separated by a fixed distance. The gross features of the inter-nucleon potential are reproduced. We also f...

We introduce and investigate a one-parameter family of quantum spaces invariant under the left (right) co-action of the group-like element of the Jordanian function algebra Funh(SL(2)). These spaces may be regarded as Jordanian quantization of the two-dimensional spheres.

Noncommutative (super) spaces relating to the coherent states for quantum (super) groups are investigated. Introducing a new definition of coherent states, it is shown that for some examples the use of such coherent states provide a complex description of homogeneous spaces of quantum groups. We give a concise summary of our study on the cases of q...

The heart undergoes marked changes in energy substrate availability, utilization, and metabolic activity during the transition from the fetal to postnatal environment. Availability of these substrates to the newborn is dependent on adequate gas exchange in the lungs, coronary blood flow, and, after a period of time, enteral or parenteral intake of...

Representations of the quantum superalgebra U_q[osp(1/2)] and their relations to the basic hypergeometric functions are investigated. We first establish Clebsch-Gordan decomposition for the superalgebra U_q[osp(1/2)] in which the representations having no classical counterparts are incorporated. Formulae for these Clebsch-Gordan coefficients are de...

We obtain a closed form expression of the universal T-matrix encapsulating the duality between the quantum superalgebra Uq[osp(1/2)] and the corresponding supergroup OSpq(1/2). The classical q→1 limit of this universal T-matrix yields the group element of the undeformed OSpq(1/2) supergroup. The finite dimensional representations of the quantum sup...

We obtain a closed form expression of the universal T-matrix encapsulating the duality of the quantum superalgebra U_q[osp(1/2)] and the corresponding supergroup OSp_q(1/2). The classical q-->1 limit of this universal T-matrix yields the group element of the undeformed OSp(1/2) supergroup. The finite dimensional representations of the quantum super...

Starting with a given generalized boson algebra U_ (h(1)) known as the bosonized version of the quantum super-Hopf U_q[osp(1/2)] algebra, we employ the Hopf duality arguments to provide the dually conjugate function algebra Fun_ (H(1)). Both the Hopf algebras being finitely generated, we produce a closed form expression of the universal T matrix th...

In 17 fetal sheep aged 129 days, the effects of large-dose infusions of cortisol (72.1 mg/day for 2-3 days) on proliferation, binucleation, and hypertrophy of cardiac myocytes, cardiac expression of angiotensinogen, angiotensin receptor subtypes 1 and 2, Glut-1, glucocorticoid and mineralocorticoid receptors, proteins of the MAPK pathways and calci...

Background: The postnatal heart responds to biomechanical stress by myocyte hypertrophy, whereas the fetal heart may additionally undergo hyperplasia. Before 100 d gestational age (GA), nearly 100% of fetal sheep cardiomyocytes are mitotically active, which decreases to about 20% near term. The mitogen-activated protein kinases (MAPKs) and Akt are...

BACKGROUND: Exposure of the ovine fetus to glucocorticoids early in gestation programs postnatal elevation of blood pressure and enhanced coronary artery reactivity to second messenger-dependent vasoconstrictors. It is unknown whether the coronary alterations are a direct consequence of the corticosteroid exposure or related to the hypertension tha...

Background: Fetal programming of adult diseases, including coronary artery disease, may be a consequence of fetal exposure to increased levels of maternally derived glucocorticoids. In an established ovine model, early gestation glucocorticoid exposure alters postnatal coronary artery vascular reactivity. This programming effect may be related to m...

Background: Infants born to mothers with gestational diabetes are known to have organomegally and asymmetric septal hypertrophy. The purpose of this study is to evaluate the myocardial response in the offspring of severely diabetic rats and characterize the mitogen-activated protein kinase (MAPK) signaling pathways that may mediate these responses.

A quantum deformation of the Lie superalgebra osp(2/1) from the classical r-matrix including an odd generator is presented with its full Hopf algebraic structure. A class of deformation maps and the corresponding twisting elements, the interrelation between these twists, and the tensor operators are considered for the deformed osp(2/1) algebra. It...

We previously demonstrated in fetal sheep that blockade of ANG II type 1 (AT(1)) receptors did not attenuate an increase in right ventricle (RV) mass resulting from partial occlusion of the pulmonary artery (PA). We have now determined the effects of AT(2)-receptor blockade (PD-123319, 10 mg. kg(-1). day(-1) continuous iv) on the response of the fe...

Angiotensin II (ANG II) contracts umbilical arteries and has been hypothesized to regulate fetal blood pressure primarily by altering umbilical vascular resistance. To determine whether systemic arteries in term fetal sheep are sensitive to ANG II, isometric contraction of endothelium-intact isolated fetal renal, mesenteric, and umbilical arteries...

The mechanisms by which antenatal glucocorticoids facilitate postnatal circulatory function in preterm infants are uncertain but may be related to augmented angiotensinergic functions. To test the hypothesis that the effects of glucocorticoids on postnatal cardiovascular and sympathetic activity are mediated via the renin-angiotensin system, we stu...

In fetal sheep, severe hypotension causes heart rate (HR) slowing. Studies during development have also shown that a reflex bradycardia and hypotension can be elicited after chemostimulation with veratridine and is dependent on the age of the animal. In adults, a vagally mediated depressor reflex characterized by bradycardia, hypotension, and withd...

Activation of the malate/aspartate and alpha -glycerophosphate shuttles (the NADH shuttles) has been identified in glycolytically active newborn myocardium. The goal of this study was to determine if the NADH shuttles and their regulatory genes are activated in hypertrophied myocardium as substrate utilization shifts away from fatty acids and towar...

Previous work in our laboratory has demonstrated impairment of cardiopulmonary reflex control of renal sympathetic nerve activity (RSNA) during the newborn period. The present study was designed to test the hypothesis that this delayed maturation is secondary to incomplete central integration of vagal afferent input. Term fetal (135-140 days; n = 6...

Physiological responses at birth include increases in heart rate (HR), blood pressure, sympathetic nerve activity, and circulating vasoactive peptides. The factors mediating these responses are not known. To test the hypothesis that afferent input from peripheral mechanoreceptors (arterial and cardiopulmonary baroreceptors) and chemoreceptors contr...

A general construction is given for a class of invertible maps between the classical U(sl(2)) and the Jordanian Uh(sl(2)) algebras. Here the role of the maps is studied in the context of construction of twist operators relating the cocommutative and non-cocommutative coproducts of the U(sl(2)) and Uh(sl(2)) algebras respectively. It is shown that a...

To investigate developmental changes in autonomic cardiovascular reflexes in preterm infants, we used autoregressive power spectral analysis to analyze the effect of upright tilting on heart rate variability in preterm infants. Twenty-eight infants were studied in a longitudinal fashion beginning at 28-32 weeks postconceptional age (postnatal age 1...

Previous studies have shown that the expression of cardiac angiotensin II (ANG II) type 1 (AT1) and type 2 (AT2) receptors are developmentally regulated, although factors modulating these receptors have not been well investigated. The present study was designed 1) to characterize the ontogeny of cardiac AT1 and AT2 gene expression during the last t...

The effect of inhaled nitric oxide (iNO) on bleeding time and platelet aggregation was studied in nine newborn infants with resolving pulmonary hypertension. Infants treated with iNO at 40 ppm for 30 minutes had bleeding times that were nearly twofold longer than those obtained 24 hours after iNO was discontinued. iNO had no effect on in vitro plat...

Renal sympathetic nerve activity (RSNA) increases rapidly after delivery of term fetal sheep and parallels the rise in heart rate (HR) and arterial pressure. To examine the RSNA response at birth in immature lambs, experiments were performed in chronically instrumented preterm fetal sheep (118- to 125-day gestation, term 145 days) before and after...

We examined the hypothesis that endogenous angiotensin II and angiotensin type 1 (AT1) receptors participate in the development of fetal right ventricular hypertrophy by studying the effects of AT1 receptor blockade on cardiac growth in fetal sheep subjected to constrictive banding of the pulmonary artery (PA). Seven pairs of twin fetuses were stud...

The autonomic nervous system is intimately involved in regulating cardiovascular function. Sensing mechanisms dispersed throughout the circulation, including arterial baroreceptors, low pressure receptors, and chemosensitive receptors, continually evoke reflexes designed to maintain cardiovascular homeostasis. Although there is a growing body of kn...

The present study was designed to test the hypothesis that endogenous angiotensin II (ANG II) influences baroreflex control of heart rate (HR) and renal sympathetic nerve activity (RSNA) early in life and to determine whether these actions are mediated by angiotensin AT1 or AT2 receptors. To test this hypothesis, we studied the effects of systemic...

The effects of diuretic therapy on body water compartments were studied in preterm infants with chronic lung disease. Gestational age of the infants ranged from 24 to 28 weeks, while the median postnatal age at the time of study was 40 days. Infants were randomized to receive furosemide (1.0 mg/kg/day) alone (n = 5) or combined with metolazone (0.2...

The present study was designed to test the hypothesis that the influence of circulating vasopressin (AVP) on the arterial baroreflex control of renal sympathetic nerve activity (RSNA) and heart rate (HR) changes during development. To test this hypothesis, we studied arterial baroreflex-mediated control of HR and RSNA in the presence of increasing...

Nonlinear effective Lagrangian models with a chiral symmetry have been used to describe strong interactions at low energy, for a long time. The Skyrme model and the chiral quark-meson model are two such models, which have soliton solutions which can be identified with the baryons. We describe the various kinds of soliton states in these nonlinear m...

We present a comparative study of the dynamical behaviour of topological systems of recent interest, namely the non-Abelian Chern-Simons Higgs system and the Yang-Mills Chern-Simons Higgs system. By reducing the full field theories to temporal differential systems using the assumption of spatially homogeneous fields , we study the Lyapunov exponent...

In this paper, we study the chiral soliton models for baryons, from the viewpoint of classical nonlinear dynamical systems. In particular, we discuss (i) the Skyrme model, an effective Lagrangian model with purely mesonic degrees of freedom based on chiral symmetry, whose topological soliton solutions are identified with baryons, as well as (ii) a...

Autonomic adjustments to severe hypotension are more complex than a generalized sympathoadrenal discharge. Activation of unmyelinated vagal afferent fibers during severe hypotension evokes reflex bradycardia and sympathoinhibition in adults. This reflex, known as the Bezold-Jarisch reflex(BJR), can be elicited by stimulation of either chemo or mech...

The present studies were designed to assess the contribution of onset of respiration, separation from the placenta, and a decrease in environmental temperature on the increase in renal sympathetic nerve activity (RSNA) that occurs at birth. In the first series of experiments, heart rate (HR), mean arterial blood pressure (MABP), and RSNA were recor...

Previous studies have shown that angiotensin II subtype 2 (AT2) receptors appear early during renal embryonic development. Factors involved in the regulation of AT2 receptors during renal development, however, have not been investigated. The present study was designed 1) to characterize the ontogeny of renal AT2 gene expression during the last half...

Components of the renin-angiotensin system have been found in a variety of tissues during fetal and postnatal life and appear to be developmentally regulated. We postulated that hormonal changes associated with parturition participate in the regulation of renin, angiotensinogen (Ao) and angiotensin type 1 receptor (AT1) gene expression. Cortisol, w...

The present study was designed to characterize the maturation of cardiopulmonary reflex control of renal sympathetic nerve activity (RSNA) independent of influences from the arterial baroreflex. Studies were conducted in conscious newborn lambs (3- to 7-days-old) (n = 16) and older lambs (6- to 8-wk-old) (n = 18). All animals underwent either sinoa...

We find the baryon number two solution of a SU(2) quark soliton model based on chiral invariant quark-meson couplings. The solution is classically stable and has an axial symmetry associated with it. The energy distribution corresponding to the soliton is toroidal in nature. The results closely parallel the Skyrme-model calculations. The symmetries...

Factors regulating the expression of the angiotensin II subtype 1 (AT1) receptor during fetal life have not been investigated previously. The present study was designed 1) to characterize the ontogeny of AT1 receptor gene expression in the kidney of fetal and newborn sheep and 2) to determine the influence of both glucocorticoids and renal nerves i...

The purposes of this study were to characterize the changes in renal sympathetic nerve activity (RSNA) and baroreflex function at birth in conscious sheep. One hour after delivery by cesarean section, RSNA increased by 239 +/- 24% compared with fetuses. The upper and lower plateau values of the baroreflex function curves for RSNA, expressed as the...

Recent studies demonstrated that renal denervation had no effect on the natriuretic response to volume expansion (VE) in fetal sheep, suggesting that the sensitivity of the cardiopulmonary reflex in response to VE is impaired in the fetus. To test this hypothesis, we investigated the renal sympathetic nerve activity (RSNA) and heart rate (HR) respo...

The present study was designed to examine the effect of direct intrarenal infusion of the alpha 1-adrenoceptor agonist, phenylephrine, on urinary flow rate (UFR) and on renal Na and Cl excretion in conscious and chronically instrumented fetal (128-133 days gestation, term 145 days), newborn (6-12 days), and adult sheep. Five different renal concent...

Significant fluctuation in heart rate (HR) and arterial pressure occur during fetal life. However, the mechanisms regulating this normal variability are not completely understood. To test the hypothesis that the normal variability in fetal HR and blood pressure are produced by intrinsic fluctuations in sympathetic outflow, we recorded HR, mean arte...

Angiotensin II (ANG II) has been shown in adults to modulate baroreflex responses in heart rate (HR) and sympathetic outflow. To test the hypothesis that high circulating levels of ANG II in the newborn period contribute to the resetting of the arterial baroreflex observed postnatally, we studied baroreflex-mediated changes in HR and renal sympathe...

The present review summarizes recent studies describing the role of renal sympathetic innervation in the regulation of renal function during development. The afferent renal innervation appears early during fetal life and probably precedes the development of efferent renal nerves. There is suggestive evidence that renal nerves are required for the p...

Endotracheal suctioning of intubated infants produces profound changes in cardiovascular and cerebral hemodynamics, but the mechanisms regulating these changes are not fully understood. To determine the role of the autonomic nervous system in regulating these physiologic changes, we investigated the effects of endotracheal suctioning on heart rate...

We examined whether prostanoids contribute to the impaired cardiac function and decrease in regional blood flow induced by increasing mean airway pressure. Using microspheres, we measured cardiac output and major organ blood flow and assayed prostaglandin E2, 6-ketoprostaglandin F1 alpha, and thromboxane B2 in blood at mean airway pressures of 5-25...

We consider aSU(3) quark soliton model based on chiral invariant quark-meson coupling. We find soliton solutions with nonzero strangeness andB=1 in the model with nontrivial kaonic fields, for values of the coupling constant greater than the phenomenologically acceptable number. Hence they do not correspond to known strange baryons.

The purpose of this study was to characterize the developmental changes in baroreflex function during fetal and postnatal life in sheep. Resting mean arterial blood pressure increased significantly from 55 +/- 2 mmHg in fetuses to 86 +/- 3 mmHg in newborn lambs and to 105 +/- 4 mmHg in 4- to 6-wk-old lambs. The sensitivity (gain) of the renal sympa...

The present study was designed to characterize the developmental changes in the renal responses to dopamine DA1-receptor activation in chronically instrumented preterm (109-115 days) and near-term (130-140 days, full term 145 days) fetal sheep. Cumulative doses of the selective DA1-agonist fenoldopam increased mean arterial blood pressure (MABP) in...

A decreased response to the loop diuretic furosemide develops within a few doses in young infants. We tested the hypothesis that the use of the thiazide-like diuretic metolazone, in combination with furosemide, would inhibit water and electrolyte reabsorption and overcome pharmacologic tolerance to furosemide alone. Infants with bronchopulmonary dy...

In addition to regulating developmental changes in body fluid content, the newborn kidney must maintain a positive sodium balance to ensure adequate body growth. Mechanisms by which the developing organism perceives changes in volume and the manner in which the kidney responds to these changes have been reviewed. Perception of changes in ECF volume...

The present review focuses on the ontogeny of mechanisms involved in renal sodium excretion during renal maturation. The effect of birth on renal excretion of sodium and the role played by the different tubular segments in the regulation of sodium excretion during maturation are discussed. The influence of circulating catecholamines and renal sympa...

The role of renal nerves in regulating changes in plasma renin activity (PRA) and renal renin gene expression was studied in intact (n = 6) and denervated (n = 6) fetal sheep before birth and during the first 24 h after delivery. Renal denervation completely blunted the rise in PRA observed 24 h after delivery in newborn lambs; in lambs with intact...

The transition from fetal to newborn life is associated with significant endocrine changes. Some of these changes may be triggered by the effects of spontaneous respiration, increased oxygenation and removal of the placental circulation at bir