Polariton Analysis of a Four-Level Atom Strongly Coupled to a Cavity Mode

We present a complete analytical solution for a single four-level atom strongly coupled to a cavity field mode and driven by external coherent laser fields. The four-level atomic system consists of a three-level subsystem in an EIT configuration, plus an additional atomic level; this system has been predicted to exhibit a photon blockade effect. The solution is presented in terms of polaritons. An effective Hamiltonian obtained by this procedure is analyzed from the viewpoint of an effective two-level system, and the dynamic Stark splitting of dressed states is discussed. The fluorescence spectrum of light exiting the cavity mode is analyzed and relevant transitions identified.Comment: 12 pages, 9 figure

Determinants of infant and young child feeding practices in Nepal : secondary data analysis of demographic and health survey 2006

Background: Childhood undernutrition and mortality\ud are high in Nepal, and therefore interventions on infant\ud and young child feeding practices deserve high priority.\ud Objective. To estimate infant and young child feeding\ud indicators and the determinants of selected feeding\ud practices.\ud \ud Methods: The sample consisted of 1,906 children aged\ud 0 to 23 months from the Demographic and Health Survey\ud 2006. Selected indicators were examined against a set of\ud variables using univariate and multivariate analyses.\ud Results. Breastfeeding was initiated within the first\ud hour after birth in 35.4% of children, 99.5% were ever\ud breastfed, 98.1% were currently breastfed, and 3.5%\ud were bottle-fed. The rate of exclusive breastfeeding\ud among infants under 6 months of age was 53.1%, and\ud the rate of timely complementary feeding among those 6\ud to 9 months of age was 74.7%. Mothers who made antenatal\ud clinic visits were at a higher risk for no exclusive\ud breastfeeding than those who made no visits. Mothers\ud who lived in the mountains were more likely to initiate\ud breastfeeding within 1 hour after birth and to introduce\ud complementary feeding at 6 to 9 months of age, but less\ud likely to exclusively breastfeed. Cesarean deliveries were\ud associated with delay in timely initiation of breastfeeding.\ud Higher rates of complementary feeding at 6 to 9 months\ud were also associated with mothers with better education\ud and those above 35 years of age. Risk factors for\ud bottle-feeding included living in urban areas and births\ud attended by trained health personnel.\ud \ud Conclusions: Most breastfeeding indicators in Nepal\ud are below the expected levels to achieve a substantial\ud reduction in child mortality. Breastfeeding promotion\ud strategies should specifically target mothers who have\ud more contact with the health care delivery system, while\ud programs targeting the entire community should be\ud continued

Asymmetrical tidal tails of open star clusters: stars crossing their cluster's prah challenge Newtonian gravitation

International audienceAfter their birth a significant fraction of all stars pass through the tidal threshold (prah) of their cluster of origin into the classical tidal tails. The asymmetry between the number of stars in the leading and trailing tails tests gravitational theory. All five open clusters with tail data (Hyades, Praesepe, Coma Berenices, COIN-Gaia 13, NGC 752) have visibly more stars within dcl = 50 pc of their centre in their leading than their trailing tail. Using the Jerabkova-compact-convergent-point (CCP) method, the extended tails have been mapped out for four nearby 600-2000 Myr old open clusters to dcl>50 pc. These are on near-circular Galactocentric orbits, a formula for estimating the orbital eccentricity of an open cluster being derived. Applying the Phantom of Ramses code to this problem, in Newtonian gravitation the tails are near-symmetrical. In Milgromian dynamics (MOND) the asymmetry reaches the observed values for 50 < dcl/pc < 200, being maximal near peri-galacticon, and can slightly invert near apo-galacticon, and the Küpper epicyclic overdensities are asymmetrically spaced. Clusters on circular orbits develop orbital eccentricity due to the asymmetrical spill-out, therewith spinning up opposite to their orbital angular momentum. This positive dynamical feedback suggests Milgromian open clusters to demise rapidly as their orbital eccentricity keeps increasing. Future work is necessary to better delineate the tidal tails around open clusters of different ages and to develop a Milgromian direct n-body code

Adequate surgical margins for dermatofibrosarcoma protuberans – A multi-centre analysis

Background: Dermatofibrosarcoma protuberans (DFSP) is a locally aggressive tumour. Adequate margins have a positive impact on recurrence rates. The aim of this study is to assess how adequate margins are achieved and secondly which additional treatment modalities might be necessary to achieve adequate margins. Material & methods: Patients with DFSP treated between 1991 and 2016 at three tertiary centres were included. Patient- and tumour characteristics were obtained from a prospectively held database and patient files. Results: A total of 279 patients with a median age of 39 (Interquartile range [IQ], 31–50) years and a median follow-up of 50 (IQ, 18–96) months were included. When DFSP was preoperatively confirmed by biopsy and resected with an oncological operation in a tertiary centre, in 86% was had clear pathological margins after one excision. Wider resection margins were significantly correlated with more reconstructions (p = 0.002). A substantial discrepancy between the primary surgical macroscopic and the pathological margins was found with a median difference of 22 (range, 10–46) mm (Fig. 1). There was no significant influence of the width of the pathological clear margins (if > 1 mm) and the recurrence rate (p = 0.710). Conclusion: The wider the resection margins, the more likely it is to obtain clear pathological margins, but the more likely patients will need any form of reconstruction after resection. The aim of the primary excision should be wide surgical resection, where the width of the margin should be balanced against the need for reconstructions and surgical morbidity

Gain-assisted superluminal light propagation through a Bose-Einstein condensate cavity system

The propagation of a probe laser field in a cavity optomechanical system with a Bose-Einstein condensate is studied. The transmission properties of the system are investigated and it is shown that the group velocity of the probe pulse field can be controlled by Rabi frequency of the pump laser field. The effect of the decay rate of the cavity photons on the group velocity is studied and it is demonstrated that for small values of the decay rates, the light propagation switches from subluminal to superluminal just by changing the Rabi frequency of the pump field. Then, the gain-assisted superluminal light propagation due to the cross-Kerr nonlinearity is established in cavity optomechanical system with a Bose-Einstein condensate. Such behavior can not appear in the pump-probe two-level atomic systems in the normal phase. We also find that the amplification is achieved without inversion in the population of the quantum energy levels