726 research outputs found

    Effective action of a five-dimensional domain wall

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    We calculate the four-dimensional low-energy effective action for the perturbations of a two-scalar domain wall model in five dimensions. Comparison of the effective action to the Nambu-Goto action reveals the presence of an additional coupling between the light scalar field and the massless translation mode (branon excitation), which can be written in terms of the curvature scalar of the induced metric. We comment on the impact of this interaction to branon physics.Comment: 24 page

    Neurohormonal consequences of diuretics in different cardiovascular syndromes

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    Diuretics have long been used to lower blood pressure in hypertensive patients or to control body fluid and electrolyte homeostasis in diseases such as congestive heart failure, chronic renal failure or cirrhosis. The initial response to diuretics is negative sodium and fluid balance. The diuretic-induced loss of salt and water activates several hormonal systems such as vasopressin, the renin-angiotensin-aldosterone system or the sympathetic nervous system which tend to compensate for the changes in sodium and water balance. This neurohormonal response may have important clinical implications. Thus, the activation of the renin-angiotensin-aldosterone cascade appears to be partially responsible for the flat dose-blood pressure response curve of thiazides in hypertensive patients. It may also be responsible for the difference between responders and non-responders to diuretic therapy and for the development of side-effects such as hypokalaemia, metabolic alkalosis or hyponatraemia. There are several ways to prevent the undesirable consequences of the neurohormonal responses to diuretics. The first is to use low doses of these agents. It is also possible to combine them with agents that block the activity of the renin-angiotensin-aldosterone system such as ACE inhibitors or in combination with drugs that reduce aldosterone secretion such as calcium antagonists. The development of drugs able to enhance urinary sodium excretion and to reduce simultaneously the activity of the renin-angiotensin-aldosterone system may offer a new interesting alternative. This might perhaps be achieved in the future with the administration of neutral endopeptidase inhibitors which interfere with the enzymatic degradation of atrial natriuretic peptid

    Dynamics of the infinitely-thin kink

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    We consider the dynamics of the domain-wall kink soliton, in particular we study the zero mode of translation. In the infinitely-thin kink limit, we show that the zero mode is almost completely frozen out, the only remnant being a dynamically constrained four-dimensional mode of a single but arbitrary frequency. In relation to this result, we show that the usual mode expansion for dealing with zero modes -- implicit collective coordinates -- is not in fact a completely general expansion, and that one must use instead a traditional generalised Fourier analysis.Comment: 13 pages; v2: added references, to appear in Phys Lett

    One-loop fermionic corrections to the instanton transition in two dimensional chiral Higgs model

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    The one-loop fermionic contribution to the probability of an instanton transition with fermion number violation is calculated in the chiral Abelian Higgs model in 1+1 dimensions, where the fermions have a Yukawa coupling to the scalar field. The dependence of the determinant on fermionic, scalar and vector mass is determined. We show in detail how to renormalize the fermionic determinant in partial wave analysis, which is convenient for computations.Comment: 36 pages, 5 figure

    Can an odd number of fermions be created due to chiral anomaly?

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    We describe a possibility of creation of an odd number of fractionally charged fermions in 1+1 dimensional Abelian Higgs model. We point out that for 1+1 dimensions this process does not violate any symmetries of the theory, nor makes it mathematically inconsistent. We construct the proper definition of the fermionic determinant in this model and underline its non-trivial features that are of importance for realistic 3+1 dimensional models with fermion number violation.Comment: 12 pages revtex, 2 figure

    Orbital Metastasis from an Occult Breast Carcinoma (T0, N1, M1)

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    The authors report a case of an orbital metastasis from an occult breast carcinoma. A 66-year-old woman presented with a growing left orbital tumour. Orbital CT scan was consistent with lymphoma. However, ocular pathology revealed small neoplastic cells showing an 'indian file pattern' suggestive of metastatic carcinoma and immunohistochemistry was positive for CK7, CK CAM5.2 and oestrogen receptor. A systemic evaluation was then performed with mammogram, breast ultrasound and MRI considered normal. An exhaustive systemic evaluation revealed multiple bone lesions, a right axillary lymph node lesion, which presented the same pattern on pathology and immunohistochemistry, with no evidence of a primary tumour. A diagnosis of a metastatic lobular carcinoma of the breast (T0, N1, M1) was made and the patient was started on chemotherapy and adjuvant hormonal therapy.info:eu-repo/semantics/publishedVersio

    Minimally invasive repair of pectus excavatum using the Nuss technique in children and adolescents: Indications, outcomes, and limitations

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    AbstractBackgroundPectus excavatum (PE) is a common congenital deformity. The Nuss technique for minimally invasive repair of PE involves thoracoscopy-assisted insertion of a bar or plate behind the deformity to displace the sternum anteriorly. Our objective here was to clarify the indications and limitations of the Nuss technique based on a review of 70 patients.Materials and methodsA retrospective review of children managed at two centres identified 70 patients who had completed their growth and had their plate removed. Mean age was 13.8 years (range, 6–19 years). The reason for surgery was cosmetic disfigurement in 66 (95%) patients. The original Nuss technique was used in 63 patients, whereas 7 patients required an additional sub-xiphoid approach. Time to implant removal ranged from 8 months to 3 years.ResultsThe cosmetic outcome was considered satisfactory by the patients in 64 (91%) cases and by the surgeon in 60 (85.7%) cases. Major complications requiring further surgery occurred in 6 (8.5%) patients and consisted of haemothorax (n=2), chest wall sepsis (n=2, including 1 after implant removal), allergy (n=1), and implant displacement (n=1). Early or delayed minor complications occurred in 46 (65%) patients and resolved either spontaneously or after non-surgical therapy.DiscussionThe minimal scarring and reliably good outcomes support the widespread use of the Nuss technique in children and adolescents. Our complication rates (minor, 65%; and major, 8.5%) are consistent with previous publications. In our opinion, contra-indications to thoracoscopic PE correction consist of a history of cardio-thoracic surgery and the finding by computed tomography of a sternum-to-spine distance of less than 5cm or of sternum rotation greater than 35°. In these situations, we recommend a sub- and retro-xiphoid approach to guide implant insertion or a classic sterno-chondroplasty procedure.Level of evidenceLevel IV, retrospective descriptive cohort study

    Towards flavour diffusion coefficient and electrical conductivity without ultraviolet contamination

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    By subtracting from a recent lattice measurement of the thermal vector-current correlator the known 5-loop vacuum contribution, we demonstrate that the remainder is small and shows no visible short-distance divergence. It can therefore in principle be subjected to model-independent analytic continuation. Testing a particular implementation, we obtain estimates for the flavour-diffusion coefficient (2 pi T D \gsim 0.8) and electrical conductivity which are significantly smaller than previous results. Although systematic errors remain beyond control at present, some aspects of our approach could be of a wider applicability.Comment: 7 pages. v2: clarifications added, published versio

    O-28: Molecular basis for the insurmountable AT-1 receptor antagonism of telmisartan

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    In vitro studies have shown that telmisartan is an insurmountable angiotensin II AT-1 receptor antagonist. In this study we have investigated the molecular basis of this insurmountable antagonism. The association and dissociation kinetics of telmisartan to angiotensin AT-1 receptors were measured using an in vitro radio-receptor binding assay. These radioligand binding studies were conducted either directly on rat vascular (aorta) smooth muscle cells (RVSMC) expressing solely the AT-1 receptor or on membrane preparation obtained from the same cells. The specific binding of3H-telmisartan to the surface of living RVSMC or membranes was saturable. From these data, a Kd value of 1.7 nM was estimated. Scatchard analysis of the3H-telmisartan binding on RVSMC indicated the existence of a single class of binding sites. The affinity of telmisartan for AT-1 receptor is only poorly affected by the presence of proteins (0.4% of rat plasma proteins) in the binding buffer, indicating that no great competition between telmisartan binding to its specific AT-1 receptor and to non-specific proteins binding sites occurs. In association experiments, the specific binding of3H-telmisartan increases quickly and reaches equilibrium within less than 1 hour, with an association rate constant calculated to be 0.006 min-1nM-1. Telmisartan dissociates very slowly from the AT-1 receptor, either in RVSMC membrane preparation or in living cells with a dissociation rate constant of ca. 0.01 min-1 resulting in a dissociation half-life (t1/2) of about 60 min, which is comparable to the previously published data for candesartan in bovine adrenal cortical membranes and almost 5 times slower than that of 125I-angiotensin II binding (t1/2=12 min). In contrast to candesartan that has been shown to re-associate with the AT-1 receptor, telmisartan does not appear to re-associate. Indeed, when the dissociation of labeled-telmisartan from AT-1 receptors was induced by washing the cells with cold-binding buffer, followed by addition of fresh binding buffer containing either cold telmisartan, Ang II or losartan, or nothing, no difference were observed in the dissociation rate constants measured with telmisartan whatever the composition of the binding buffer after removal of labeled-telmisartan. In conclusion, these results suggest that the insurmountable antagonism of telmisartan is due mainly to its very slow dissociation from angiotensin AT-1 receptor
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