We investigate effects of short range interactions on the addition spectra of quantum dots using a disordered Hubbard model. A correlation function S(q) is defined on the inverse compressibility versus filling data, and computed numerically for small lattices. Two regimes of interaction strength are identified: the even/odd fluctuations regime typical of Fermi liquid ground states, and a regime of structureless S(q) at strong interactions. We propose to understand the latter regime in terms of magnetically correlated localized spins. PACS: 73.20.DxCoulomb interactions and disorder in electronic systems have posed a major challenge to condensed matter physics for quite some time.Quantum dots with discrete electronic spectra offer a new avenue to this problem. A direct probe to the ground state energy is given by Coulomb blockade peaks in the conductance as the gate voltage is varied [1][2][3][4]. Theory of spectral fluctuations of non interacting electrons has made much progress during the last decade due to the advent of semiclassical approximations, random matrix theory and the non linear sigma model approach [1,5]. However since Coulomb interactions are essential for the "Coulomb blockade" effect, one may wonder as to the validity of non interacting approximations to quantum dots in general. In particular: Is the ground state qualitatively similar or different than a Fock state of the lowest single electron orbitals?To gain insight into this question, we consider a system of interacting electrons on a finite tight binding lattice with onsite disorder. The inverse compressibility at consecutive fillings iswhere E(N ) is the ground state energy of a dot with N electrons. (We assume weakly coupled leads such that N is well defined within the area of the dot.) By varying a gate potential ϕ, the dot's energy is modified to E ϕ N = E(N ) − eϕN . Conductance peaks through the leads are observed at E ϕ (N ) = E ϕ (N + 1), i.e. at potentials eϕ N = E(N + 1) − E(N ). Thus differences between the peak potentials ϕ N yield direct measurements of ∆(N ) which can be defined as e 2 times the discrete inverse capacitance of the dot.We shall model the single electron part of the dot's Hamiltonian by a site-disordered tight binding model
Although its incidence is declining with the widespread use of intrapartum antibiotics, early-onset sepsis (EOS) continues to be associated with high morbidity and mortality. Maternal, infant, and peripartum risk factors, as well as infant's laboratory tests, have been used to try and identify asymptomatic newborns at risk. In this study, we reevaluate the management of newborns at risk for EOS by comparing our outcomes using two different approaches. Comparison of clinical data and outcomes of newborns at risk for EOS between two study periods, in which we have used two different protocols for their evaluation and management. Although outcomes were not different, adoption of the criteria suggested in the 2012 American Academy of Pediatrics guidelines in the second era resulted in increased utilization of diagnostic laboratory tests and increased use of empiric antibiotic treatments with less yield in a population with a low incidence of EOS (< 0.3/1,000 live births), such as ours. In asymptomatic newborns at risk for EOS, careful assessment of a set of maternal, infant, and peripartum risk factors and their severity combined with careful clinical observation, judicious use of laboratory evaluations, and empiric antibiotic treatment only in selected cases seem to be appropriate.
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