483 research outputs found
Photon indistinguishability measurements under pulsed and continuous excitation
The indistinguishability of successively generated photons from a single quantum emitter is most commonly measured using two-photon interference at a beam splitter. Whilst for sources excited in the pulsed regime the measured bunching of photons reflects the full wavepacket indistinguishability of the emitted photons, for continuous wave (cw) excitation the inevitable dependence on detector timing resolution and driving strength obscures the underlying photon interference process. Here we derive a method to extract the photon indistinguishability from cw measurements by considering the relevant correlation functions. The equivalence of both methods is experimentally verified through comparison of cw and pulsed excitation of an archetypal source of photons, a single molecule
Loop Quantum Gravity a la Aharonov-Bohm
The state space of Loop Quantum Gravity admits a decomposition into
orthogonal subspaces associated to diffeomorphism equivalence classes of
spin-network graphs. In this paper I investigate the possibility of obtaining
this state space from the quantization of a topological field theory with many
degrees of freedom. The starting point is a 3-manifold with a network of
defect-lines. A locally-flat connection on this manifold can have non-trivial
holonomy around non-contractible loops. This is in fact the mathematical origin
of the Aharonov-Bohm effect. I quantize this theory using standard field
theoretical methods. The functional integral defining the scalar product is
shown to reduce to a finite dimensional integral over moduli space. A
non-trivial measure given by the Faddeev-Popov determinant is derived. I argue
that the scalar product obtained coincides with the one used in Loop Quantum
Gravity. I provide an explicit derivation in the case of a single defect-line,
corresponding to a single loop in Loop Quantum Gravity. Moreover, I discuss the
relation with spin-networks as used in the context of spin foam models.Comment: 19 pages, 1 figure; v2: corrected typos, section 4 expanded
Intraspecific Variation in Pinus Pinaster PSII Photochemical Efficiency in Response to Winter Stress and Freezing Temperatures
As part of a program to select maritime pine (Pinus pinaster Ait.) genotypes for resistance to low winter temperatures, we examined variation in photosystem II activity by chlorophyll fluorescence. Populations and families within populations from contrasting climates were tested during two consecutive winters through two progeny trials, one located at a continental and xeric site and one at a mesic site with Atlantic influence. We also obtained the LT50, or the temperature that causes 50% damage, by controlled freezing and the subsequent analysis of chlorophyll fluorescence in needles and stems that were collected from populations at the continental trial site
Observation of an Exotic Baryon with S=+1 in Photoproduction from the Proton
The reaction was studied at Jefferson Lab using a
tagged photon beam with an energy range of 3-5.47 GeV. A narrow baryon state
with strangeness S=+1 and mass MeV/c was observed in the
invariant mass spectrum. The peak's width is consistent with the CLAS
resolution (FWHM=26 MeV/c), and its statistical significance is 7.8
1.0 ~. A baryon with positive strangeness has exotic structure and
cannot be described in the framework of the naive constituent quark model. The
mass of the observed state is consistent with the mass predicted by a chiral
soliton model for the baryon. In addition, the invariant mass
distribution was analyzed in the reaction with high
statistics in search of doubly-charged exotic baryon states. No resonance
structures were found in this spectrum.Comment: 5 pages, 5 figures, add reference
Exclusive Photoproduction of the Cascade (Xi) Hyperons
We report on the first measurement of exclusive Xi-(1321) hyperon
photoproduction in gamma p --> K+ K+ Xi- for 3.2 < E(gamma) < 3.9 GeV. The
final state is identified by the missing mass in p(gamma,K+ K+)X measured with
the CLAS detector at Jefferson Laboratory. We have detected a significant
number of the ground-state Xi-(1321)1/2+, and have estimated the total cross
section for its production. We have also observed the first excited state
Xi-(1530)3/2+. Photoproduction provides a copious source of Xi's. We discuss
the possibilities of a search for the recently proposed Xi5-- and Xi5+
pentaquarks.Comment: submitted to Phys. Rev.
Transcriptome, Methylome and Genomic Variations Analysis of Ectopic Thyroid Glands
Congenital hypothyroidism from thyroid dysgenesis (CHTD) is predominantly a sporadic disease characterized by defects in the differentiation, migration or growth of thyroid tissue. Of these defects, incomplete migration resulting in ectopic thyroid tissue is the most common (up to 80%). Germinal mutations in the thyroid-related transcription factors NKX2.1, FOXE1, PAX-8, and NKX2.5 have been identified in only 3% of patients with sporadic CHTD. Moreover, a survey of monozygotic twins yielded a discordance rate of 92%, suggesting that somatic events, genetic or epigenetic, probably play an important role in the etiology of CHTD.Journal ArticleResearch Support, Non-U.S. Gov'tValidation StudiesSCOPUS: ar.jinfo:eu-repo/semantics/publishe
Impact of Lack of Breast Feeding during Neonatal Age on the Development of Clinical Signs of Pneumonia and Hypoxemia in Young Infants with Diarrhea
Hypoxemia is a grave sequel of pneumonia, and an important predictor of a fatal outcome. Pneumonia in the neonatal period is often associated with lack of breast feeding. However, there is no published report on the impact of the cessation of breast feeding in the neonatal period on the development of pneumonia and hypoxemia. The purpose of our study was to assess the impact of non-breast feeding or stopping breast feeding during the neonatal period (henceforth to be referred to as non-breast fed) on clinical features of pneumonia and hypoxemia in 0-6-month-old infants with diarrhea admitted to an urban hospital in Bangladesh.We prospectively enrolled all infants (nβ=β107) aged 0 to 6 months who were admitted to the Special Care Ward (SCW) of the Dhaka Hospital of the International Centre for Diarrhoeal Disease Research Bangladesh (ICDDR,B) with diarrhea and pneumonia from September 2007 through December 2007.We compared the clinical features of pneumonia and hypoxemia of breast fed infants (nβ=β34) with those who were non-breast fed (nβ=β73).The median (inter-quartile range) duration of hypoxemia (hours) in non-breast-feds was longer than breast-fed infants [0.0 (0.0, 12.0) vs. 12.0 (0.0, 21.75); pβ=β0.021]. After adjusting for potential confounders such as inability to drink, fever, head nodding, cyanosis, grunting respiration, and lower chest wall in drawing, the non-breast-fed infants with pneumonia along with diarrhea had a higher probability of cough (OR 9.09; CI 1.34-61.71; pβ=β0.024), hypoxemia (OR 3.32; CI 1.23-8.93; pβ=β0.017), and severe undernutrition (OR 3.42; CI 1.29-9.12; pβ=β0.014).Non-breast feeding or cessation of breast feeding during the neonatal period may substantially increase the incidence of severe malnutrition, incidence of cough, and both the incidence and duration of hypoxemia in young infants presenting with pneumonia and diarrhea. The findings emphasize the paramount importance of the continuation of breast feeding in the neonatal period and early infancy
The course of mental health after miscarriage and induced abortion: a longitudinal, five-year follow-up study
BACKGROUND: Miscarriage and induced abortion are life events that can potentially cause mental distress. The objective of this study was to determine whether there are differences in the patterns of normalization of mental health scores after these two pregnancy termination events. METHODS: Forty women who experienced miscarriages and 80 women who underwent abortions at the main hospital of Buskerud County in Norway were interviewed. All subjects completed the following questionnaires 10 days (T1), six months (T2), two years (T3) and five years (T4) after the pregnancy termination: Impact of Event Scale (IES), Quality of Life, Hospital Anxiety and Depression Scale (HADS), and another addressing their feelings about the pregnancy termination. Differential changes in mean scores were determined by analysis of covariance (ANCOVA) and inter-group differences were assessed by ordinary least squares methods. RESULTS: Women who had experienced a miscarriage had more mental distress at 10 days and six months after the pregnancy termination than women who had undergone an abortion. However, women who had had a miscarriage exhibited significantly quicker improvement on IES scores for avoidance, grief, loss, guilt and anger throughout the observation period. Women who experienced induced abortion had significantly greater IES scores for avoidance and for the feelings of guilt, shame and relief than the miscarriage group at two and five years after the pregnancy termination (IES avoidance means: 3.2 vs 9.3 at T3, respectively, p < 0.001; 1.5 vs 8.3 at T4, respectively, p < 0.001). Compared with the general population, women who had undergone induced abortion had significantly higher HADS anxiety scores at all four interviews (p < 0.01 to p < 0.001), while women who had had a miscarriage had significantly higher anxiety scores only at T1 (p < 0.01). CONCLUSION: The course of psychological responses to miscarriage and abortion differed during the five-year period after the event. Women who had undergone an abortion exhibited higher scores during the follow-up period for some outcomes. The difference in the courses of responses may partly result from the different characteristics of the two pregnancy termination events
Salivary biomarkers of HPA axis and autonomic activity in adults with intellectual disability with and without stereotyped and self-injurious behavior disorders
Salivary levels of biomarkers for the hypothalamicβpituitaryβadrenal axis (HPA; cortisol) and sympatho-adreno-medullary system (SAM; Ξ±-amylase) were measured in 51 adults (57% male) with neurodevelopmental disorders associated with intellectual disability (i.e., mental retardation) and chronic self-injurious behavior (SIB) and compared with matched controls without SIB. Cortisol levels differed significantly (pβ<β0.01) between the SIB and control group (SIBβ>βcontrol). Within-group analyses showed significant differences (pβ<β0.05) in levels of salivary Ξ±-amylase between individuals with SIB and those with SIB meeting criteria for stereotyped movement disorder (SMD; SIBβ+βSMDβ>βSIB). Salivary Ξ±-amylase was significantly correlated with frequency of stereotypy among the SIB group (rβ=β0.36, pβ<β0.05). These preliminary findings warrant further exploration into the role of the SAM system in the pathophysiology of SIB and related repetitive behaviors among individuals with neurodevelopmental disorders associated with intellectual disability
Multiple Wnt/Γ-Catenin Responsive Enhancers Align with the MYC Promoter through Long-Range Chromatin Loops
Inappropriate activation of c-Myc (MYC) gene expression by the Wnt/Γ-catenin signaling pathway is required for colorectal carcinogenesis. The elevated MYC levels in colon cancer cells are attributed in part to Γ-catenin/TCF4 transcription complexes that are assembled at proximal Wnt/Γ-catenin responsive enhancers (WREs). Recent studies suggest that additional WREs that control MYC expression reside far upstream of the MYC transcription start site. Here, I report the characterization of five novel WREs that localize to a region over 400 kb upstream from MYC. These WREs harbor nucleosomes with post-translational histone modifications that demarcate enhancer and gene promoter regions. Using quantitative chromatin conformation capture, I show that the distal WREs are aligned with the MYC promoter through large chromatin loops. The chromatin loops are not restricted to colon cancer cells, but are also found in kidney epithelial and lung fibroblast cell lines that lack de-regulated Wnt signaling and nuclear Γ-catenin/TCF4 complexes. While each chromatin loop is detected in quiescent cells, the positioning of three of the five distal enhancers with the MYC promoter is induced by serum mitogens. These findings suggest that the architecture of the MYC promoter is comprised of distal elements that are juxtaposed through large chromatin loops and that Γ-catenin/TCF4 complexes utilize this conformation to activate MYC expression in colon cancer cells
- β¦