5,289 research outputs found
Excitation spectrum of bosons in a finite one-dimensional circular waveguide via the Bethe ansatz
The exactly solvable Lieb-Liniger model of interacting bosons in
one-dimension has attracted renewed interest as current experiments with
ultra-cold atoms begin to probe this regime. Here we numerically solve the
equations arising from the Bethe ansatz solution for the exact many-body wave
function in a finite-size system of up to twenty particles for attractive
interactions. We discuss the novel features of the solutions, and how they
deviate from the well-known string solutions [H. B. Thacker, Rev. Mod. Phys.\
\textbf{53}, 253 (1981)] at finite densities. We present excited state string
solutions in the limit of strong interactions and discuss their physical
interpretation, as well as the characteristics of the quantum phase transition
that occurs as a function of interaction strength in the mean-field limit.
Finally we compare our results to those of exact diagonalization of the
many-body Hamiltonian in a truncated basis. We also present excited state
solutions and the excitation spectrum for the repulsive 1D Bose gas on a ring.Comment: 13 pages, 12 figure
α-Tocopherols modify the membrane dipole potential leading to modulation of ligand binding by P-glycoprotein
Journal ArticleThis is the author accepted manuscript. The final version is available from ASBMB via the DOI in this record.α-Tocopherol (vitamin E) has attracted considerable attention as a potential protective or palliative agent. In vitro, its free radical-scavenging antioxidant action has been widely demonstrated. In vivo, however, vitamin E treatment exhibits negligible benefits against oxidative stress. α-Tocopherol influences lipid ordering within biological membranes and its derivatives have been suggested to inhibit the multi-drug efflux pump, P-glycoprotein (P-gp). This study employs the fluorescent membrane probe, 1-(3-sulfonatopropyl)-4-[β[2-(di-n-octylamino)-6-naphthyl]vinyl] pyridinium betaine, to investigate whether these effects are connected via influences on the membrane dipole potential (MDP), an intrinsic property of biological membranes previously demonstrated to modulate P-gp activity. α-Tocopherol and its non-free radical-scavenging succinate analog induced similar decreases in the MDP of phosphatidylcholine vesicles. α-Tocopherol succinate also reduced the MDP of T-lymphocytes, subsequently decreasing the binding affinity of saquinavir for P-gp. Additionally, α-tocopherol succinate demonstrated a preference for cholesterol-treated (membrane microdomain enriched) cells over membrane cholesterol-depleted cells. Microdomain disruption via cholesterol depletion decreased saquinavir's affinity for P-gp, potentially implicating these structures in the influence of α-tocopherol succinate on P-gp. This study provides evidence of a microdomain dipole potential-dependent mechanism by which α-tocopherol analogs influence P-gp activity. These findings have implications for the use of α-tocopherol derivatives for drug delivery across biological barriers
One Loop Predictions of the Finely Tuned SSM
We study the finely tuned SSM, recently proposed by Arkani-Hamed and
Dimopoulos, at the one loop level. The runnings of the four gaugino Yukawa
couplings, the mu term, the gaugino masses, and the Higgs quartic coupling are
computed. The Higgs mass is found to be 130 - 170 GeV for M_s > 10^6 GeV. If
the Yukawa coupling constants are measured at the 1% level, this can determine
the SUSY breaking scale to within an order of magnitude. Measuring the
relationships between the couplings to this accuracy provides a striking signal
for this model.Comment: 5 pages, 4 figures; v2: Minor corrections to anomalous dimensions and
beta functions. Numerical results are not significantly affected. v3: Minor
changes to figures and references, as published in PR
Lensing Properties of Lightlike Current Carrying Cosmic Strings
The lensing properties of superconducting cosmic strings endowed with a time
dependent pulse of lightlike current are investigated. The metric outside the
core of the string belongs to the --wave class, with a deficit angle. We
study the field theoretic bosonic Witten model coupled to gravity, and we show
that the full metric (both outside and inside the core) is a Taub-Kerr-Shild
generalization of that for the static string with no current. It is shown that
the double image due to the deficit angle evolves in an unambiguous way as a
pulse of lightlike current passes between the source and the observer.
Observational consequences of this signature of the existence of cosmic strings
are briefly discussed.Comment: 21 pages, LaTeX-REVTeX, 7 figures available upon request, preprint #
DAMTP-R94/1
Orotracheal intubation in infants performed with a stylet versus without a stylet
Background:
Neonatal endotracheal intubation is a common and potentially life-saving intervention. It is a mandatory skill for neonatal trainees, but one that is difficult to master and maintain. Intubation opportunities for trainees are decreasing and success rates are subsequently falling. Use of a stylet may aid intubation and improve success. However, the potential for associated harm must be considered.
Objectives
To compare the benefits and harms of neonatal orotracheal intubation with a stylet versus neonatal orotracheal intubation without a stylet.
Search methods:
We searched the Cochrane Central Register of Controlled Trials (CENTRAL) in the Cochrane Library; MEDLINE; Embase; the Cumulative Index to Nursing and Allied Health Literature (CINAHL), and previous reviews. We also searched cross-references, contacted expert informants, handsearched journals, and looked at conference proceedings. We searched clinical trials registries for current and recently completed trials. We conducted our most recent search in April 2017.
Selection criteria
All randomised, quasi–randomised, and cluster-randomised controlled trials comparing use versus non-use of a stylet in neonatal orotracheal intubation.
Data collection and analysis:
Two review authors independently assessed results of searches against predetermined criteria for inclusion, assessed risk of bias, and extracted data. We used the standard methods of the Cochrane Collaboration, as documented in the Cochrane Handbook for Systemic Reviews of Interventions, and of the Cochrane Neonatal Review Group.
Main results:
We included a single-centre non-blinded randomised controlled trial that reported a total of 302 intubation attempts in 232 infants. The median gestational age of enrolled infants was 29 weeks. Paediatric residents and fellows performed the intubations. We judged the study to be at low risk of bias overall. Investigators compared success rates of first-attempt intubation with and without use of a stylet and reported success rates as similar between stylet and no-stylet groups (57% and 53%) (P = 0.47). Success rates did not differ between groups in subgroup analyses by provider level of training and infant weight. Results showed no differences in secondary review outcomes, including duration of intubation, number of attempts, participant instability during the procedure, and local airway trauma. Only 25% of all intubations took less than 30 seconds to perform. Study authors did not report neonatal morbidity nor mortality. We considered the quality of evidence as low on GRADE analysis, given that we identified only one unblinded study.
Authors' conclusions:
Current available evidence suggests that use of a stylet during neonatal orotracheal intubation does not significantly improve the success rate among paediatric trainees. However, only one brand of stylet and one brand of endotracheal tube have been tested, and researchers performed all intubations on infants in a hospital setting. Therefore, our results cannot be generalised beyond these limitations
Presenting video recordings of newborn resuscitations in debriefings for teamwork training
Background: The Neonatal Resuscitation Program (NRP) and similar courses have been used to train clinicians. However, formal teamwork training was not included in these courses, and their effectiveness has been questioned. In adult resuscitation, debriefings using video recordings have improved outcomes, but recordings of neonatal resuscitation have been used primarily for research
32P-Postlabeling analysis of IQ, MelQx and PhIP adducts formed in vitro in DNA and polynucleotides and found in vivo in hepatic DNA from IQ-, MelQx- and PhIP-treated monkeys
The P-32-postlabeling method was used to examine the adducts in DNA, polynucleotides, and mononucleotides reacted in vitro with the N-hydroxy and N-acetoxy derivatives of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-3, 8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) or 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). Adduct profiles were compared to those found in vivo in liver of cynomolgus monkeys fed IQ, MeIQx or PhIP. The N-acetoxy derivatives of IQ, MeIQx and PhIP (generated in situ from the corresponding N-hydroxylamine in the presence of acetic anhydride) each formed three principal adducts in DNA. Adduct 1 of IQ, MeIQx and PhIP was chromatographically identical to the P-32-labeled bis(phosphate) derivative of N-(deoxyguanosin-8-yl)-IQ, N-(deoxyguanosin-8-yl)-MeIQx, and N-(deoxyguanosin-8-yl)-PhIP respectively, and this adduct comprised approximately 65% of total adduct levels found in DNA in vitro. The C8-guanine adduct and the two minor adducts were also found in poly(dG-dC).poly(dG-dC), suggesting that the two minor adducts of IQ, MeIQx and PhIP are also formed on the guanine base. The N-acetoxy derivatives of IQ, MeIQx, and to a much lesser extent PhIP, also formed adducts with adenine-containing polynucleotides including poly(dA), poly(dA).poly(dT) and poly(dA-dT).poly(dA-dT), but these adenine adducts were chromatographically different from those found in DNA. The three guanine adducts of N-acetoxy-IQ, -MeIQx and -PhIP found in vitro in DNA and in guanine-containing polynucleotides were also found in the liver of monkeys fed IQ, MeIQx or PhIP respectively, indicating that metabolic activation via N-hydroxylation and esterification occurred in vivo in monkeys. With each compound, the C8-guanine adduct was the predominant adduct found in vivo. The results indicate similarities among IQ, MeIQx and PhIP in the DNA adducts formed in vitro and in vivo and substantiate the use of the P-32-postlabeling method for comparative adduct studies
Discovery of a red backsplash galaxy candidate near M81
Understanding quenching mechanisms in low-mass galaxies is essential for
understanding galaxy evolution overall. In particular, isolated galaxies are
important tools to help disentangle the complex internal and external processes
that impact star formation. Comparisons between quenched field and satellite
galaxies in the low mass regime offer a substantial opportunity for discovery,
although very few quenched galaxies with masses below are known outside the virial radius, , of any host halo.
Importantly, simulations and observations suggest that an in-between population
of backsplash galaxies also exists that may complement interpretations of
environmental quenching. Backsplash galaxies -- like field galaxies -- reside
outside the virial radius of a host halo, but their star formation can be
deeply impacted by previous interactions with more massive systems. In this
paper, we report the discovery of a low-mass () quenched galaxy approximately in projection from the
M81 group. We use surface brightness fluctuations (SBF) to investigate the
possibility that the new galaxy, dubbed dw0910p7326 (nicknamed Blobby), is a
backsplash galaxy or a more distant field galaxy. The measured SBF distance of
Mpc indicates that Blobby likely
lies between outside the combined M81--M82 system.
Given its distance and quiescence, Blobby is a good candidate for a backsplash
galaxy and could provide hints about the formation and evolution of these
interesting objects.Comment: 15 pages, 8 figures, to be submitted to MNRAS, comments welcome
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