Tensor characteristics of forward Brillouin sensors in bare and coated fibers

Forward Brillouin scattering fiber sensors can detect and analyze media outside the cladding of standard fibers, where guided light does not reach. Nearly all such sensors reported to-date have relied on the radially symmetric guided acoustic modes of the fiber. Wave motion in these modes is strictly dilatational. However, forward Brillouin scattering also takes place through torsional–radial guided acoustic modes of the fiber. Torsional–radial modes exhibit more complex tensor characteristics, and they consist of both dilatational and shear wave contributions. In this work, we show that forward Brillouin sensing through torsional–radial acoustic modes is qualitatively different from processes based on the radial ones. While dilatational wave components may dissipate toward liquids outside the fiber cladding, shear waves do not. Consequently, the effect of outside liquids varies among torsional–radial modes. Those modes that are dominated by their dilatational components undergo faster decay rates, whereas other modes with large shear contributions decay at much slower rates in the same liquid. The difference in decay rates may reach a factor of seven. Experimental observations are well supported by the analysis. The differences among modes are also found with liquid outside specific coating layers. Large changes in decay rates are observed when a phase transition between solid and liquid occurs outside the cladding boundary. The monitoring of multiple mode categories provides more complete assessment of outside media and enhances the capabilities of forward Brillouin scattering fiber sensors

A New Israeli <i>Tobamovirus</i> Isolate Infects Tomato Plants Harboring <i>Tm-2²</i> Resistance Genes

<div><p>An outbreak of a new disease infecting tomatoes occurred in October-November 2014 at the Ohad village in Southern Israel. Symptomatic plants showed a mosaic pattern on leaves accompanied occasionally by narrowing of leaves and yellow spotted fruit. The disease spread mechanically and rapidly reminiscent of tobamovirus infection. Epidemiological studies showed the spread of the disease in various growing areas, in the South and towards the Southeast and Northern parts of the country within a year. Transmission electron microscope (TEM) analysis showed a single rod-like form characteristic to the <i>Tobamovirus</i> genus. We confirmed Koch’s postulates for the disease followed by partial host range determination and revealed that tomato cultivars certified to harbor the <i>Tm-2</i>^<i>2</i> resistance gene are susceptible to the new viral disease. We further characterized the viral source of the disease using a range of antisera for serological detection and analyzed various virus genera and families for cross-reactivity with the virus. In addition, next generation sequencing of total small RNA was performed on two cultivars grown in two different locations. In samples collected from commercial cultivars across Israel, we found a single virus that caused the disease. The complete genome sequence of the new Israeli tobamovirus showed high sequence identity to the Jordanian isolate of tomato brown rugose fruit virus.</p></div

Risk factors for functional decline among survivors of Gram-negative bloodstream infection: A prospective cohort study

To identify risk factors for functional decline after hospitalization for Gram-negative bacteremia