Preconditioning of low-frequency repetitive transcranial magnetic stimulation with transcranial direct current stimulation: evidence for homeostatic plasticity in the human motor cortex

Recent experimental work in animals has emphasized the importance of homeostatic plasticity as a means of stabilizing the properties of neuronal circuits. Here, we report a phenomenon that indicates a homeostatic pattern of cortical plasticity in healthy human subjects. The experiments combined two techniques that can produce long-term effects on the excitability of corticospinal output neurons: transcranial direct current stimulation (TDCS) and repetitive transcranial magnetic stimulation (rTMS) of the left primary motor cortex. "Facilitatory preconditioning" with anodal TDCS caused a subsequent period of 1 Hz rTMS to reduce corticospinal excitability to below baseline levels for >20 min. Conversely, "inhibitory preconditioning" with cathodal TDCS resulted in 1 Hz rTMS increasing corticospinal excitability for at least 20 min. No changes in excitability occurred when 1 Hz rTMS was preceded by sham TDCS. Thus, changing the initial state of the motor cortex by a period of DC polarization reversed the conditioning effects of 1 Hz rTMS. These preconditioning effects of TDCS suggest the existence of a homeostatic mechanism in the human motor cortex that stabilizes corticospinal excitability within a physiologically useful range

Radiation zeros and scalar particles beyond the standard model

Standard radiation zeros arise from the factorization properties of tree-level amplitudes involving a massless photon and can occur when all charged particles in the initial and final state have the same sign. We investigate how several different processes involving new scalar particles beyond the standard model may exhibit radiation zeros and how this structure might be exploited to probe their electromagnetic structure. We focus on (i) unnoticed aspects of angular zeros in the process e- + e- --> Delta-- + gamma for doubly charged Higgs boson (or any bilepton) production and (ii) the process gamma + e- --> q + S/V for scalar (S) or vector (V) leptoquarks (LQs). We also discuss how factorized amplitudes and radiation zeros may appear in the gauge boson fusion production of non-conjugate leptoquark pairs via gamma + W --> S_i + S_j* in high energy ee reactions and how the zeros affect the production cross-sections for various types of scalar leptoquarks.Comment: 18 pages (LaTeX) plus 5 postscript figure

Higgsless Electroweak Symmetry Breaking in Warped Backgrounds: Constraints and Signatures

We examine the phenomenology of a warped 5-dimensional model based on SU(2)$_L \times$ SU(2)$_R \times$ U(1)$_{B-L}$ model which implements electroweak symmetry breaking through boundary conditions, without the presence of a Higgs boson. We use precision electroweak data to constrain the general parameter space of this model. Our analysis includes independent $L$ and $R$ gauge couplings, radiatively induced UV boundary gauge kinetic terms, and all higher order corrections from the curvature of the 5-d space. We show that this setup can be brought into good agreement with the precision electroweak data for typical values of the parameters. However, we find that the entire range of model parameters leads to violation of perturbative unitarity in gauge boson scattering and hence this model is not a reliable perturbative framework. Assuming that unitarity can be restored in a modified version of this scenario, we consider the collider signatures. It is found that new spin-1 states will be observed at the LHC and measurement of their properties would identify this model. However, the spin-2 graviton Kaluza-Klein resonances, which are a hallmark of the Randall-Sundrum model, are too weakly coupled to be detected.Comment: More detailed analysis, added references, 43 pages, 15 figures, LaTe

Birefringence of interferential mirrors at normal incidence Experimental and computational study

In this paper we present a review of the existing data on interferential mirror birefringence. We also report new measurements of two sets of mirrors that confirm that mirror phase retardation per reflection decreases when mirror reflectivity increases. We finally developed a computational code to calculate the expected phase retardation per reflection as a function of the total number of layers constituting the mirror. Different cases have been studied and we have compared computational results with the trend of the experimental data. Our study indicates that the origin of the mirror intrinsic birefringence can be ascribed to the reflecting layers close to the substrate.Comment: To be published in Applied Physics

Measurement of the Charge Collection Efficiency after Heavy Non-Uniform Irradiation in BaBar Silicon Detectors

We have investigated the depletion voltage changes, the leakage current increase and the charge collection efficiency of a silicon microstrip detector identical to those used in the inner layers of the BaBar Silicon Vertex Tracker (SVT) after heavy non-uniform irradiation. A full SVT module with the front-end electronics connected has been irradiated with a 0.9 GeV electron beam up to a peak fluence of 3.5 x 10^14 e^-/cm^2, well beyond the level causing substrate type inversion. We irradiated one of the two sensors composing the module with a non-uniform profile with sigma=1.4 mm that simulates the conditions encountered in the BaBar experiment by the modules intersecting the horizontal machine plane. The position dependence of the charge collection properties and the depletion voltage have been investigated in detail using a 1060 nm LED and an innovative measuring technique based only on the digital output of the chip.Comment: 7 pages, 13 figures. Presented at the 2004 IEEE Nuclear Science Symposium, October 18-21, Rome, Italy. Accepted for publication by IEEE Transactions on Nuclear Scienc

What every doctor should know about drug safety in patients with chronic kidney disease

Drug safety is a very relevant issue when dealing with patients with chronic kidney disease (CKD) who need vascular access procedures and interventions. Drug dosage adjustments are needed for patients with acute or chronic kidney disease. In CKD patients, the estimated glomerular filtration rate is used to guide dose adjustments. Determining the influence of renal replacement therapies on drug dosage adjustment is also very important. Safety issues for the following drugs used for situations related to vascular access are reported: anticoagulants and antiplatelet agents, antibiotics, antimicrobials for catheter lock therapy, thrombolytics, local anesthetics, and painkillers. General principles of the interactions of drugs in CKD are also reported

Third-generation leptoquark decays and collider searches

Collider searches for first-, second-, and third-generation scalar (S) or vector (V) leptoquarks (LQs) focus on the quark-lepton decay modes S,V -> q l. For SU(2)-doublet and -triplet leptoquarks with a sufficiently large splitting between the components, decays involving real W-boson emission (such as S_2^{(+5/3)} -> S_2^{(+2/3)} W^{+} and others) become possible and can change the patterns of leptoquark decays. For third-generation leptoquarks, where these mass splittings might be large, such modes could dominate certain leptoquark decays as they are (if kinematically allowed) guaranteed to be of order g^2 where g is the electroweak coupling. We calculate the decay rates for all such processes involving SU(2)-doublet and triplet, scalar and vector leptoquarks. Standard limits on mass splittings from precision electroweak measurements imply that only such decays involving SU(2)-doublet scalar LQs are likely kinematically possible.Comment: 13 pages, LaTeX, 2 separate postscript figure

Granular cell tumor of the trachea as a rare cause of dyspnea in a young woman

Tracheal granular cell tumors are rare neurogenic neoplasms characterized by an indolent behavior. We report the case of a young woman affected by this tumor with non-specific clinical presentation. We performed a literature search in order to identify all the cases of tracheal granular cell tumor and to summarize the current state of knowledge about this rare disease

Warped Phenomenology of Higher-Derivative Gravity

We examine the phenomenological implications at colliders for the existence of higher-derivative gravity terms as extensions to the Randall-Sundrum model. Such terms are expected to arise on rather general grounds, e.g., from string theory. In 5-d, if we demand that the theory be unitary and ghost free, these new contributions to the bulk action are uniquely of the Gauss-Bonnet form. We demonstrate that the usual expectations for the production cross section and detailed properties of graviton Kaluza-Klein resonances and TeV-scale black holes can be substantially altered by existence of these additional contributions. It is shown that measurements at future colliders will be highly sensitive to the presence of such terms.Comment: 29 pages, 8 figure