Recognition and Management of the Difficult Airway
John C Watkinson, Raymond W Clarke, Louise Jayne Clark, Adam J Donne, R James A England, Hisham M Mehanna, Gerald William McGarry, Sean Carrie in Basic Sciences Endocrine Surgery Rhinology, 2018
Mechanism: The most common mistake made about jet ventilation is in its mechanism of action. It does not work by the Venturi effect; it works by friction. There are actually six postulated mechanisms as to how it might function: Convective or Bulk flow.Laminar flow in the small airways.Pendelluft.Cardiogenic mixing.Molecular Diffusion.Taylor type dispersion.
Diffusion Magnetic Resonance Imaging for Cancer Treatment Response Assessment
Martin G. Pomper, Juri G. Gelovani, Benjamin Tsui, Kathleen Gabrielson, Richard Wahl, S. Sam Gambhir, Jeff Bulte, Raymond Gibson, William C. Eckelman in Molecular Imaging in Oncology, 2008
Technical reviews of the topic of in vivo diffusion-weighted MR imaging have been published recently (8,9). In brief, molecular diffusion refers to the thermally driven, random translational motion of molecules in tissue, which is also called Brownian motion. MRI can be applied for quantification of water diffusion values spatially in vivo. Magnetic gradients are applied to the tissue region, which provide for “encoding” the initial locations of constituent water molecules within the tissue. For water molecules that experienced displacement from the initial location over short period of time, during the decoding process, these molecules will have a detectable loss of signal through spin de-phasing. The more mobile the water molecule is, the larger the net loss of signal will be relative to the corresponding immobile water molecules. Water signal loss is measured at several diffusion gradient values, which allows for determination of molecular mobility to be quantified in heterogeneous tissues such as tumors. Due to the fact that water is also located within different intra- and extracellular compartments, which are separated by semipermeable membranes, the measured diffusion values are reported as an apparent diffusion coefficient (ADC) (6,9).
Modelling and analysis of skin pigmentation
Ahmad Fadzil Mohamad Hani, Dileep Kumar in Optical Imaging for Biomedical and Clinical Applications, 2017
Diffusion is because of the deflection of light through impacts with molecules, particles or group of particles lessening the energy of the incident light at the same time. The diffusion procedure may be grouped into three: molecular diffusion, particle diffusion and surface/reflective–refractive diffusion [58–60]. Molecular scattering (Rayleigh scattering) happens when the wavelength of the light is larger than the size of the molecules/particles. Particle scattering (Mie scattering), meanwhile, happens when the wavelength of the incident light is comparable to the size of the molecules or particles. For some practical intent, the error in utilizing Rayleigh, rather than Mie theory, to small particles is less than 1% when the radius of the particle is smaller or equal to 0.03λ [59]. Moreover, reflective–refractive or geometrical optics diffusion happens when the size of the particles is much larger than the wavelength of incident light. This category of diffusion happens for a large portion of the internal diffusion in organic tissues, such as on human skin. It is fundamentally brought about by the arrangement of tissues, and the refractive differences, connected with the air-cell wall interfaces with respect to cells whose dimensions are quite larger compared to the wavelength of light. Due to its dependency on refractive differences, the variations across the spectrum are directly associated with the wavelength dependency of the refractive indices of the materials.
Updated insight into the characterization of nano-emulsions
Published in Expert Opinion on Drug Delivery, 2023
Xinyue Wang, Halina Anton, Thierry Vandamme, Nicolas Anton
Besides its common use for chemical characterization, in recent years, NMR was also used in NE characterization. This method reveals information on the arrangement of surfactants and co-surfactant on the oil-water interface by the modification of their chemical shift. Xie et al. chose 1H and 13C NMR as the major approach to identify the functional groups on the droplet’s interface, through following the variation of the peak intensity and comparing formulations with different interfacial composition [92]. Another NMR-based technology, so-called pulsed field gradient NMR (PFG-NMR), can be used to determine the particle size and size distribution for single and double emulsions [20]. This technique analyzes the reduction of the molecular diffusion, when they are confined in the discrete phase – i.e. emulsion droplets – in comparison to those located in the interfacial region. Analyzing when the diffusion becomes restricted provides an estimation of the droplet size. Beyond the information in size, PFG-NMR allows the fine characterization of assembled states and structures, level of sedimentation, or creaming of emulsions [93]. Figure 10 illustrates the size determination of the droplet suspension by PFG-NMR, showing that this technique is less affected by light scattering and permits to track the diffusion properties of individual components in turbid and concentrated samples, by measuring their characteristic spectra (inherently chemically selective).
Hydroxypropyl chitosan nail lacquer of ciclopirox-PLGA nanocapsules for augmented in vitro nail plate absorption and onychomycosis treatment
Published in Drug Delivery, 2022
Eman Yahya Gaballah, Thanaa Mohammed Borg, Elham Abdelmonem Mohamed
In vitro release profiles of CIX from the optimized NCs (F3) and its HPCH nail lacquer in phosphate buffers of pHs 5.8 and 7.4 in comparison with the free drug in both solution and dispersion forms are illustrated in Figure 4(A and B, respectively). At both media, a rapid release during the first 4 hours was followed by a sustained release till 24 h. Similar results were reported for PLGA-NCs (Maribel et al., 2019). The initial fast release could be attributed to the desorption of the drug on NCs surface. The sustained release phase may be owing to the drug encapsulated in the oil core that was protected by PLGA coat as indicated by TEM examination (Flores et al., 2017). Therapeutic drug concentrations can be attained due to the rapid drug release, while the sustained drug release could maintain these concentrations (Mohamed et al., 2018). As well, the drug gradual release may lead to the reduction in the application frequency enhancing the patient compliance. In vitro release of CIX from both formulations during the rapid and sustained release phases can be explained by first order model (Table 2(A and B)). Fickian diffusion mechanism (n < 0.45) in which the release is assumed to occur by the molecular diffusion of the drug due to a chemical potential gradient, was found to describe the drug release during the two phases from F3 and its lacquer at the two media (Singhvi & Singh, 2011).
Antibiotics adsorption from aqueous solutions using carbon nanotubes: a systematic review
Published in Toxin Reviews, 2020
Seyyed Alireza Mousavi, Hosna Janjani
Pollutant and adsorbent behavior varies by temperature. In a study, it has been showed low-temperature affected hydrophobic compounds more than hydrophilic compounds (Nam et al. 2014). In Ncibi et al study, increasing temperature from 15 to 45 °C has increased the adsorption capacity for MWCNTs (from 170 to 342 mg, respectively), while, an increase in adsorption was registered between 15 and 35 °C, for SWCNTs and DWCNTs and adsorption has decreased at higher temperatures (45 °C). This decreases has been related to decreasing the viscosity of the solution containing the nanotubes. But to range of 35 °C adsorption increases has been due to deagglomeration of nanotubes that helps to create of new adsorption sites. Increasing temperature will decrease the viscosity of solution and also can enhance the rate of molecular diffusion. So at higher temperatures due to much more dissociation, and broken down of pore structure, adsorption will decrease (Ncibi et al. 2015).
Related Knowledge Centers
- Absolute Zero
- Self-Diffusion
- Molecule
- Chemical Potential
- Fick'S Laws of Diffusion
- Catalysis
- Cell Biology
- Amino Acid
- Semipermeable Membrane
- Osmosis