Power-law running of the effective gluon mass

The dynamically generated effective gluon mass is known to depend non-trivially on the momentum, decreasing sufficiently fast in the deep ultraviolet, in order for the renormalizability of QCD to be preserved. General arguments based on the analogy with the constituent quark masses, as well as explicit calculations using the operator-product expansion, suggest that the gluon mass falls off as the inverse square of the momentum, relating it to the gauge-invariant gluon condensate of dimension four. In this article we demonstrate that the power-law running of the effective gluon mass is indeed dynamically realized at the level of the non-perturbative Schwinger-Dyson equation. We study a gauge-invariant non-linear integral equation involving the gluon self-energy, and establish the conditions necessary for the existence of infrared finite solutions, described in terms of a momentum-dependent gluon mass. Assuming a simplified form for the gluon propagator, we derive a secondary integral equation that controls the running of the mass in the deep ultraviolet. Depending on the values chosen for certain parameters entering into the Ansatz for the fully-dressed three-gluon vertex, this latter equation yields either logarithmic solutions, familiar from previous linear studies, or a new type of solutions, displaying power-law running. In addition, it furnishes a non-trivial integral constraint, which restricts significantly (but does not determine fully) the running of the mass in the intermediate and infrared regimes. The numerical analysis presented is in complete agreement with the analytic results obtained, showing clearly the appearance of the two types of momentum-dependence, well-separated in the relevant space of parameters. Open issues and future directions are briefly discussed.Comment: 37 pages, 5 figure

A dynamical gluon mass solution in a coupled system of the Schwinger-Dyson equations

We study numerically the Schwinger-Dyson equations for the coupled system of gluon and ghost propagators in the Landau gauge and in the case of pure gauge QCD. We show that a dynamical mass for the gluon propagator arises as a solution while the ghost propagator develops an enhanced behavior in the infrared regime of QCD. Simple analytical expressions are proposed for the propagators, and the mass dependency on the $\Lambda_{QCD}$ scale and its perturbative scaling are studied. We discuss the implications of our results for the infrared behavior of the coupling constant, which, according to fits for the propagators infrared behavior, seems to indicate that $\alpha_s (q^2) \to 0$ as $q^2 \to 0$.Comment: 17 pages, 7 figures - Revised version to be consistent with erratum to appear in JHE

A surface-patterned chip as a strong source of ultracold atoms for quantum technologies

Laser-cooled atoms are central to modern precision measurements. They are also increasingly important as an enabling technology for experimental cavity quantum electrodynamics, quantum information processing and matter–wave interferometry. Although significant progress has been made in miniaturizing atomic metrological devices, these are limited in accuracy by their use of hot atomic ensembles and buffer gases. Advances have also been made in producing portable apparatus that benefits from the advantages of atoms in the microkelvin regime. However, simplifying atomic cooling and loading using microfabrication technology has proved difficult. In this Letter we address this problem, realizing an atom chip that enables the integration of laser cooling and trapping into a compact apparatus. Our source delivers ten thousand times more atoms than previous magneto-optical traps with microfabricated optics and, for the first time, can reach sub-Doppler temperatures. Moreover, the same chip design offers a simple way to form stable optical lattices. These features, combined with simplicity of fabrication and ease of operation, make these new traps a key advance in the development of cold-atom technology for high-accuracy, portable measurement devices

Chemotherapy with BCNU in recurrent glioma: Analysis of clinical outcome and side effects in chemotherapy-naïve patients

Background: To date, standardized strategies for the treatment of recurrent glioma are lacking. Chemotherapy with the alkylating agent BCNU (1,3-bis (2-chloroethyl)-1-nitroso-urea) is a therapeutic option even though its efficacy and safety, particularly the risk of pulmonary fibrosis, remains controversial. To address these issues, we performed a retrospective analysis on clinical outcome and side effects of BCNU-based chemotherapy in recurrent glioma. Methods: Survival data of 34 mostly chemotherapy-naïve glioblastoma patients treated with BCNU at 1st relapse were compared to 29 untreated control patients, employing a multiple Cox regression model which considered known prognostic factors including MGMT promoter hypermethylation. Additionally, medical records of 163 patients treated with BCNU for recurrent glioma WHO grade II to IV were retrospectively evaluated for BCNU-related side effects classified according to the National Cancer Institute Common Toxicity Criteria for Adverse Events (CTCAE) version 2.0. Results: In recurrent glioblastoma, multiple regression survival analysis revealed a significant benefit of BCNU-based chemotherapy on survival after relapse (p = 0.02; HR = 0.48; 95 % CI = 0.26–0.89) independent of known clinical and molecular prognostic factors. Exploratory analyses suggested that survival benefit was most pronounced in MGMT-hypermethylated, BCNU-treated patients. Moreover, BCNU was well tolerated by 46 % of the 163 patients analyzed for side effects; otherwise, predominantly mild side effects occurred (CTCAE I/II; 45 %). Severe side effects CTCAE III/IV were observed in 9 % of patients including severe hematotoxicity, thromboembolism, intracranial hemorrhage and injection site reaction requiring surgical intervention. One patient presented with a clinically apparent pulmonary fibrosis CTCAE IV requiring temporary mechanical ventilation. Conclusion: In this study, BCNU was rarely associated with severe side effects, particularly pulmonary toxicity, and, in case of recurrent glioblastoma, even conferred a favorable outcome. Therefore BCNU appears to be an appropriate alternative to other nitrosoureas although the efficacy against newer drugs needs further evaluation

The Generation R Study: design and cohort update 2010

The Generation R Study is a population-based prospective cohort study from fetal life until young adulthood. The study is designed to identify early environmental and genetic causes of normal and abnormal growth, development and health during fetal life, childhood and adulthood. The study focuses on four primary areas of research: (1) growth and physical development; (2) behavioural and cognitive development; (3) diseases in childhood; and (4) health and healthcare for pregnant women and children. In total, 9,778 mothers with a delivery date from April 2002 until January 2006 were enrolled in the study. General follow-up rates until the age of 4 years exceed 75%. Data collection in mothers, fathers and preschool children included questionnaires, detailed physical and ultrasound examinations, behavioural observations, and biological samples. A genome wide association screen is available in the participating children. Regular detailed hands on assessment are performed from the age of 5 years onwards. Eventually, results forthcoming from the Generation R Study have to contribute to the development of strategies for optimizing health and healthcare for pregnant women and children