title: Non-linear time domain model of electropermeabilization: Effect of extracellular conductivity and applied electric field parameters

authors: Talele, Sadhana

subjects: electroporation

abstract: This paper describes simulation results obtained from a previously reported numerical model for a single cell exposed to an arbitrary waveform electric field pulse. This paper concentrates on how the efficiency of electroporation related applications can be significantly improved by appropriately adjusting the parameters of applied electric field and conductivity of the external medium, σe. Emphasis is given here on the normalization of the degree of electroporation for a range of cell radii.
The simulated results indicate that it may be difficult for cells of substantially different sizes to be close to uniformly electroporated if surrounded by media with a conductivity higher than around 5*10⁻³ S/m for 100 kHz bipolar pulses, or 0.2 S/m for 1 MHz bipolar pulses. To achieve as normalized as possible electroporation for the radii/size variation required in any particular application, using a lower σe would be preferable. There is, however, a limit to how low the external conductivity can be made, as the applied electric field amplitude must stay within practical limits. Considering 3*10¹³ pores/m² as a nominal pore density N for approximately optimum electroporation, σe could be as low as 0.08 S/m for a 7.5 µm cell radius with a peak electric field of 1.2*10⁵V/m (depending on the pulse shape and frequency). For a 15 µm cell radius, σe could be as low as 0.05 S/m (depending on the pulse shape and frequency). It is seen that the relative difference of N between the two cell sizes investigated is consistently lower for a bipolar sine wave electric field compared to a bipolar square wave electric field, even though the square wave electric field peak amplitude is always lower for an equivalent N.

text: Non-linear time domain model of electropermeabilization: Effect of extracellular conductivity and applied electric field parameters This paper describes simulation results obtained from a previously reported numerical model for a single cell exposed to an arbitrary waveform electric field pulse. This paper concentrates on how the efficiency of electroporation related applications can be significantly improved by appropriately adjusting the parameters of applied electric field and conductivity of the external medium, σe. Emphasis is given here on the normalization of the degree of electroporation for a range of cell radii.
The simulated results indicate that it may be difficult for cells of substantially different sizes to be close to uniformly electroporated if surrounded by media with a conductivity higher than around 5*10⁻³ S/m for 100 kHz bipolar pulses, or 0.2 S/m for 1 MHz bipolar pulses. To achieve as normalized as possible electroporation for the radii/size variation required in any particular application, using a lower σe would be preferable. There is, however, a limit to how low the external conductivity can be made, as the applied electric field amplitude must stay within practical limits. Considering 3*10¹³ pores/m² as a nominal pore density N for approximately optimum electroporation, σe could be as low as 0.08 S/m for a 7.5 µm cell radius with a peak electric field of 1.2*10⁵V/m (depending on the pulse shape and frequency). For a 15 µm cell radius, σe could be as low as 0.05 S/m (depending on the pulse shape and frequency). It is seen that the relative difference of N between the two cell sizes investigated is consistently lower for a bipolar sine wave electric field compared to a bipolar square wave electric field, even though the square wave electric field peak amplitude is always lower for an equivalent N.

year: 2008

title: The influences of sonic sensory awareness through the production and consumption of screened nature documentaries

authors: Delmotte, Isabelle A.

abstract: Multiple commercial and technological factors influence the soundscapes experienced by audiences of nature documentaries. As a genre, nature documentary is a consensual term for fauna and wildlife screened programmes whose storylines need very specific audio and visual data content. Often what audiences hear in these documentaries echoes what they see. However, this illusion of perceptual unity between sight and sound can be exposed by examining the asynchronous production of moving images and sounds. The paper provides a discussion of the ways in which the commercial production practices of nature documentaries reveal aspects of sonic environments in relation to human modes of perception. As well, it examines the production constraints generated by technologies that enhance sonic perception and alter engagements of sound-makers and audiences. This account examines the phenomenological practices of listening to sonic nature and the audiovisual assemblage integral to screened representations of nature. Audience experiences of nature documentaries highlight the perception of a hyper-real environment that might ultimately obscure the sonic landscapes found in nature.

text: The influences of sonic sensory awareness through the production and consumption of screened nature documentaries Multiple commercial and technological factors influence the soundscapes experienced by audiences of nature documentaries. As a genre, nature documentary is a consensual term for fauna and wildlife screened programmes whose storylines need very specific audio and visual data content. Often what audiences hear in these documentaries echoes what they see. However, this illusion of perceptual unity between sight and sound can be exposed by examining the asynchronous production of moving images and sounds. The paper provides a discussion of the ways in which the commercial production practices of nature documentaries reveal aspects of sonic environments in relation to human modes of perception. As well, it examines the production constraints generated by technologies that enhance sonic perception and alter engagements of sound-makers and audiences. This account examines the phenomenological practices of listening to sonic nature and the audiovisual assemblage integral to screened representations of nature. Audience experiences of nature documentaries highlight the perception of a hyper-real environment that might ultimately obscure the sonic landscapes found in nature.

year: 2017

title: An ashy septingentenarian: the Kaharoa tephra turns 700 (with notes on its volcanological, archaeological, and historical importance)

authors: Lowe, David J.

abstract: Most of us are aware of the basaltic Tarawera eruption on 10th June 1886: the high toll on life (~120 people), landscape devastation, and loss of the Pink and White Terraces. But this was not the first time that Mt Tarawera produced an eruption of importance both to volcanology and human history. This edition of the GSNZ Newsletter marks the 700th anniversary of the Kaharoa eruption – its septingentenary to be precise – which occurred at Mt Tarawera in the winter of 1314 AD (± 12 years) (Hogg et al. 2003) (Fig. 1). The importance of the Kaharoa eruption is at least threefold. (1) It is the most recent rhyolite eruption in New Zealand, and the largest New Zealand eruption volumetrically of the last millennium. (2) The Kaharoa tephra is an important marker horizon in late Holocene stratigraphy and geoarchaeology (Lowe et al. 1998, 2000), and in particular helps to constrain the timing of settlement of early Polynesians in North Island (Newnham et al. 1998; Hogg et al. 2003; Lowe 2011). (3) There is a link between the soils that developed on the Kaharoa tephra, the animal ‘wasting’ disease known as ‘bush sickness’, and the birth of a government soil survey group as an independent organisation (Tonkin 2012).

text: An ashy septingentenarian: the Kaharoa tephra turns 700 (with notes on its volcanological, archaeological, and historical importance) Most of us are aware of the basaltic Tarawera eruption on 10th June 1886: the high toll on life (~120 people), landscape devastation, and loss of the Pink and White Terraces. But this was not the first time that Mt Tarawera produced an eruption of importance both to volcanology and human history. This edition of the GSNZ Newsletter marks the 700th anniversary of the Kaharoa eruption – its septingentenary to be precise – which occurred at Mt Tarawera in the winter of 1314 AD (± 12 years) (Hogg et al. 2003) (Fig. 1). The importance of the Kaharoa eruption is at least threefold. (1) It is the most recent rhyolite eruption in New Zealand, and the largest New Zealand eruption volumetrically of the last millennium. (2) The Kaharoa tephra is an important marker horizon in late Holocene stratigraphy and geoarchaeology (Lowe et al. 1998, 2000), and in particular helps to constrain the timing of settlement of early Polynesians in North Island (Newnham et al. 1998; Hogg et al. 2003; Lowe 2011). (3) There is a link between the soils that developed on the Kaharoa tephra, the animal ‘wasting’ disease known as ‘bush sickness’, and the birth of a government soil survey group as an independent organisation (Tonkin 2012).

year: 2014