Drag force in a string model dual to large-N QCD

We compute the drag force exerted on a quark and a di-quark systems in a background dual to large-N QCD at finite temperature. We find that appears a drag force in the former setup with flow of energy proportional to the mass of the quark while in the latter there is no dragging as in other studies. We also review the screening length.Comment: 15 pages, typos removed, error corrected, refs adde

No-Drag String Configurations for Steadily Moving Quark-Antiquark Pairs in a Thermal Bath

We investigate the behavior of stationary string configurations on a five-dimensional AdS black hole background which correspond to quark-antiquark pairs steadily moving in an N=4 super Yang-Mills thermal bath. There are many branches of solutions, depending on the quark velocity and separation as well as on whether Euclidean or Lorentzian configurations are examined.Comment: references added; statements corrected; eliminated computation of jet quenching parameter from Wilson loop of [Liu, Rajagopal, Wiedemann, hep-th/0605178] using Euclidean string configurations since those authors advocate [hep-th/0607062, footnote 14] the use of spacelike Lorentzian string configurations instea

The Energy of a Moving Quark-Antiquark Pair in an N=4 SYM Plasma

We make use of the AdS/CFT correspondence to determine the energy of an external quark-antiquark pair that moves through strongly-coupled thermal N=4 super-Yang-Mills plasma, both in the rest frame of the plasma and in the rest frame of the pair. It is found that the pair feels no drag force, has an energy that reproduces the expected 1/L (or gamma/L) behavior at small quark-antiquark separations, and becomes unbound beyond a certain screening length whose velocity-dependence we determine. We discuss the relation between the high-velocity limit of our results and the lightlike Wilson loop proposed recently as a definition of the jet-quenching parameter.Comment: LaTeX 2e, 27 pages, 8 eps figures; v2: added computation of the pair energy in the plasma rest frame, clarified the comparison with hep-ph/0607062, corrected typos, added reference

Drag force in SYM plasma with B field from AdS/CFT

We investigate drag force in a thermal plasma of N=4 super Yang-Mills theory via both fundamental and Dirichlet strings under the influence of non-zero NSNS $B$-field background. In the description of AdS/CFT correspondence the endpoint of these strings correspondes to an external monopole or quark moving with a constant electromagnetic field. We demonstrate how the configuration of string tail as well as the drag force obtains corrections in this background.Comment: 13 pages, 2 figures, more discussion and reference adde

Energy Loss of Gluons, Baryons and k-Quarks in an N=4 SYM Plasma

We consider different types of external color sources that move through a strongly-coupled thermal N=4 super-Yang-Mills plasma, and calculate, via the AdS/CFT correspondence, the dissipative force (or equivalently, the rate of energy loss) they experience. A bound state of k quarks in the totally antisymmetric representation is found to feel a force with a nontrivial k-dependence. Our result for k=1 (or k=N-1) agrees at large N with the one obtained recently by Herzog et al. and Gubser, but contains in addition an infinite series of 1/N corrections. The baryon (k=N) is seen to experience no drag. Finally, a heavy gluon is found to be subject to a force which at large N is twice as large as the one experienced by a heavy quark, in accordance with gauge theory expectations.Comment: Latex 2e, 24 pages, 1 eps figure; v2: slightly amplified discussion on the relation between the drag force and the tension of a spatial Wilson loop; v3: minor changes, version to appear in JHE

Spacelike strings and jet quenching from a Wilson loop

We investigate stationary string solutions with spacelike worldsheet in a five-dimensional AdS black hole background, and find that there are many branches of such solutions. Using a non-perturbative definition of the jet quenching parameter proposed by Liu et. al., hep-ph/0605178, we take the lightlike limit of these solutions to evaluate the jet quenching parameter in an N=4 super Yang-Mills thermal bath. We show that this proposed definition gives zero jet quenching parameter, independent of how the lightlike limit is taken. In particular, the minimum-action solution giving the dominant contribution to the Wilson loop has a leading behavior that is linear, rather than quadratic, in the quark separation.Comment: 38 pages, 6 figures, statements correcte

Compound heterozygous variants in NBAS as a cause of atypical osteogenesis imperfecta

Background Osteogenesis imperfecta (OI), the commonest inherited bone fragility disorder, affects 1 in 15,000 live births resulting in frequent fractures and reduced mobility, with significant impact on quality of life. Early diagnosis is important, as therapeutic advances can lead to improved clinical outcome and patient benefit. Report Whole exome sequencing in patients with OI identified, in two patients with a multi-system phenotype, compound heterozygous variants in NBAS (neuroblastoma amplified sequence). Patient 1: NBAS c.5741G > A p.(Arg1914His); c.3010C > T p.(Arg1004*) in a 10-year old boy with significant short stature, bone fragility requiring treatment with bisphosphonates, developmental delay and immunodeficiency. Patient 2: NBAS c.5741G > A p.(Arg1914His); c.2032C > T p.(Gln678*) in a 5-year old boy with similar presenting features, bone fragility, mild developmental delay, abnormal liver function tests and immunodeficiency. Discussion Homozygous missense NBAS variants cause SOPH syndrome (short stature; optic atrophy; Pelger-Huet anomaly), the same missense variant was found in our patients on one allele and a nonsense variant in the other allele. Recent literature suggests a multi-system phenotype. In this study, patient fibroblasts have shown reduced collagen expression, compared to control cells and RNAseq studies, in bone cells show that NBAS is expressed in osteoblasts and osteocytes of rodents and primates. These findings provide proof-of-concept that NBAS mutations have mechanistic effects in bone, and that NBAS variants are a novel cause of bone fragility, which is distinguishable from ‘Classical’ OI. Conclusions Here we report on variants in NBAS, as a cause of bone fragility in humans, and expand the phenotypic spectrum associated with NBAS. We explore the mechanism underlying NBAS and the striking skeletal phenotype in our patients

Silencing Nociceptor Neurons Reduces Allergic Airway Inflammation

Lung nociceptors initiate cough and bronchoconstriction. To elucidate if these fibers also contribute to allergic airway inflammation, we stimulated lung nociceptors with capsaicin and observed increased neuropeptide release and immune cell infiltration. In contrast, ablating Nav1.8(+) sensory neurons or silencing them with QX-314, a charged sodium channel inhibitor that enters via large-pore ion channels to specifically block nociceptors, substantially reduced ovalbumin- or house-dust-mite-induced airway inflammation and bronchial hyperresponsiveness. We also discovered that IL-5, a cytokine produced by activated immune cells, acts directly on nociceptors to induce the release of vasoactive intestinal peptide (VIP). VIP then stimulates CD4(+) and resident innate lymphoid type 2 cells, creating an inflammatory signaling loop that promotes allergic inflammation. Our results indicate that nociceptors amplify pathological adaptive immune responses and that silencing these neurons with QX-314 interrupts this neuro-immune interplay, revealing a potential new therapeutic strategy for asthma

The Concise Guide to PHARMACOLOGY 2023/24: Ion channels.

The Concise Guide to PHARMACOLOGY 2023/24 is the sixth in this series of biennial publications. The Concise Guide provides concise overviews, mostly in tabular format, of the key properties of approximately 1800 drug targets, and over 6000 interactions with about 3900 ligands. There is an emphasis on selective pharmacology (where available), plus links to the open access knowledgebase source of drug targets and their ligands (https://www.guidetopharmacology.org/), which provides more detailed views of target and ligand properties. Although the Concise Guide constitutes almost 500 pages, the material presented is substantially reduced compared to information and links presented on the website. It provides a permanent, citable, point-in-time record that will survive database updates. The full contents of this section can be found at http://onlinelibrary.wiley.com/doi/10.1111/bph.16178. Ion channels are one of the six major pharmacological targets into which the Guide is divided, with the others being: G protein-coupled receptors, nuclear hormone receptors, catalytic receptors, enzymes and transporters. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. The landscape format of the Concise Guide is designed to facilitate comparison of related targets from material contemporary to mid-2023, and supersedes data presented in the 2021/22, 2019/20, 2017/18, 2015/16 and 2013/14 Concise Guides and previous Guides to Receptors and Channels. It is produced in close conjunction with the Nomenclature and Standards Committee of the International Union of Basic and Clinical Pharmacology (NC-IUPHAR), therefore, providing official IUPHAR classification and nomenclature for human drug targets, where appropriate