Electrospinning is a technique used to produce micron to submicron diameter polymeric fibers. The surface of electrospun fibers is important when considering end-use applications. For example, the ability to introduce porous surface features of a known size is required if nanoparticles need to be deposited on the surface of the fiber or if drug molecules are to be incorporated for controlled release. Surface features, or pores, became evident when electrospinning in an atmosphere with more than 30% relative humidity. Increasing humidity causes an increase in the number, diameter, shape, and distribution of the pores. Increasing the molecular weight of the polystyrene (PS) results in larger, less uniform shaped pores. This work includes an investigation of how humidity and molecular weight affect the surface of electrospun PS fibers. The results of varying the humidity and molecular weight on the surface of electrospun PS fibers were studied using optical microscopy, field emission scanning electron micros...

Controlling Surface Morphology of Electrospun Polystyrene Fibers: Effect of Humidity and Molecular Weight in the Electrospinning Process

In-service structural health monitoring (SHM) of engineering structures has assumed a significant role in assessing their safety and integrity. Fibre Bragg grating (FBG) sensors have emerged as a reliable, in situ, non-destructive tool for monitoring, diagnostics and control in civil structures. The versatility of FBG sensors represents a key advantage over other technologies in the structural sensing field. In this article, the recent research and development activities in structural health monitoring using FBG sensors have been critically reviewed, highlighting the areas where further work is needed. A few packaging schemes for FBG strain sensors are also discussed. Finally a few limitations and market barriers associated with the use of these sensors have been addressed.

Fibre Bragg gratings in structural health monitoring—Present status and applications

Recent applications of fiber optic sensors to health monitoring in civil engineering

This paper reports a simple spin-coating technique for rapidly fabricating three types of technologically important materials--colloidal crystal, macroporous polymer, and polymeric nanocomposite, each with high crystalline qualities and wafer-scale sizes. Dispersion of monodisperse silica colloids in triacrylate monomers is spin-coated onto a variety of substrates. Shear-induced ordering and subsequent polymerization lead to the formation of three-dimensionally (3D) ordered colloidal crystals trapped inside a polymer matrix. The thickness of as-synthesized colloidal crystal-polymer nanocomposite is highly uniform and can be controlled simply by changing the spin speed and time. Selective removal of the polymer matrix and silica spheres lead to the formation of large-area colloidal crystals and macroporous polymers, respectively. The wafer-scale process is compatible with standard semiconductor microfabrication, as multiple micrometer-sized patterns can be created simultaneously for potential device applications. Normal-incidence transmission spectra in the visible and near-infrared regions show distinct peaks due to Bragg diffraction from 3D ordered structures. The spin-coating process opens a new route to the fundamental studies of shear-induced crystallization, melting and relaxation.

Large-scale fabrication of wafer-size colloidal crystals, macroporous polymers and nanocomposites by spin-coating.

The restless, resurgent Campi Flegrei nested caldera (Italy): constraints on its evolution and configuration

Magmatic carbon dioxide (CO2) degassing has been documented before the 31 March 2000 eruption of Usu volcano, Hokkaido, Japan. Six months before the eruption, an increase in CO2 flux was detected on the summit caldera, from 120 (September 1998) to 340 metric tons per day (September 1999), followed by a sudden decrease to 39 metric tons per day in June 2000, 3 months after the eruption. The change in CO2 flux and seismic observations suggests that before the eruption, advective processes controlled gas migration toward the surface. The decrease in flux after the eruption at the summit caldera could be due to a rapid release of CO2 during the eruption from ascending dacitic dikes spreading away from the magma chamber beneath the caldera.

https://science.sciencemag.org/content/sci/292/5514/83.full.pdf

Carbon Dioxide Degassing by Advective Flow from Usu Volcano, Japan

On the possible use of optical fiber Bragg gratings as strain sensors for geodynamical monitoring

Ground deformations in collapsed caldera structures

Ground deformations related to unrest episodes in calderas are generally interpreted, like in other volcanic environments, in terms of increased pressure within a magma chamber embedded in a continuous, elastic medium, In this framework, the depth of the pressure source is inferred from the size of the deformed area. This scheme works quite well for individual volcanoes (for instance Hawaiian shields) where a good correspondence between inflation events and eruptive episodes has been observed. Ground deformation in calderas, however, show unusual features that are difficult to interpret within such a scheme, because considerable positive deformation (in the order of several meters) and microfracturing (i.e. intense seismicity) may occur without eruptions, altough the estimated depth for the magma source is sometime very shallow (less than 1–2 km). It has been recently suggested that the contact zones at the border of collapsed calderas, could act as stress-strain discontinuity zones and thus bias modeling results obtained for continuous elastic media. We use both observations and theoretical modeling based on 3-D finite element techniques to show that ground deformations in collapsed calderas are strongly influenced by the caldera structure, giving a new perspective in related geological and geophysical observations in such areas.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/97GL01600

The effect of collapse structures on ground deformations in calderas

Unrest at large calderas rarely ends in eruption, encouraging vulnerable communities to perceive emergency warnings of volcanic activity as false alarms A classic example is the Campi Flegrei caldera in southern Italy, where three episodes of major uplift since 1950 have raised its central district by about 3 m without an eruption Individual episodes have conventionally been treated as independent events, so that only data from an ongoing episode are considered pertinent to evaluating eruptive potential An implicit assumption is that the crust relaxes accumulated stress after each episode Here we apply a new model of elastic-brittle failure to test the alternative view that successive episodes promote a long-term accumulation of stress in the crust The results provide the first quantitative evidence that Campi Flegrei is evolving towards conditions more favourable to eruption and identify field tests for predictions on how the caldera will behave during future unrest

/pdf/progressive-approach-to-eruption-at-campi-flegrei-caldera-in-4zk00gu9i8.pdf

Giuseppe De Natale

Papers

Carbon Dioxide Degassing by Advective Flow from Usu Volcano, Japan

On the possible use of optical fiber Bragg gratings as strain sensors for geodynamical monitoring

Ground deformations in collapsed caldera structures

The effect of collapse structures on ground deformations in calderas

Progressive approach to eruption at Campi Flegrei caldera in southern Italy.