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Vegetables
Published in Christopher Cumo, Ancestral Diets and Nutrition, 2020
The foregoing does not exclude plants from the archeological record. Several factors affect persistence. First, by desiccating plants, aridity increases chances of preservation. Southwestern Asia, Egypt, and North Africa supply such an environment, which may explain the antiquity of evidence for the regions’ early invention or adoption of agriculture. Second, not all plant parts are equally susceptible to decay. For example, microbes cannot break down silica (silicon dioxide or SiO2), which is common in plants wherever soils contain it. Plant structures with silica—like grain kernels’ tough outer coat (the husk, hull, or chaff)—are known as phytoliths and may constitute the sole evidence for plant consumption in remote times. Third, cooking without enough oxygen prevents complete combustion. The remaining carbon persists through a process known as carbonization. Fourth, freezing temperatures retard decomposition. Fifth, waterlogging prevents aerobic but not anaerobic degradation. Sixth, where present, calcium (Ca2+) cations and phosphate (PO43-) anions may replace plant cells, a process known as mineralization. Calcium phosphate compounds endure longer than plants’ organic molecules.
Principles of the Laser and Applications
Published in Sujoy K. Guba, Bioengineering in Reproductive Medicine, 2020
Some quantitative aspects of energy are important in surgery. A beam power level of 40 W with a spot diameter of 0.5 mm gives an energy density of about 20 kW/cm2. In use the spot is moved over the tissue and the actual biological effect then depends on the beam movement rate. For incision of skin, fat, or fascia, power densities range from 60 to 200 kW/cm2. These high power densities are achieved by having a small spot diameter such as 125 μ. To remove adhesions a power density of 0.8 to 4 kW/cm2 is adequate. Interestingly after operating on a serosal surface “relasing” with a power density of 300 to 600 W/cm2 reduces the formation of postoperative adhesions. When using for coagulation the power density required is not more than 150 W/cm2. If tissue carbonization occurs heat transfer to the underlying tissue is markedly reduced. At times it is necessary to wipe off the carbon film with a wet sponge. The film of water then left behind attenuates the beam and therefore it is desirable to wipe off the moisture film with a dry sponge.
Personal Protective Equipment (PPE): Practical and Theoretical Considerations
Published in Brian J. Lukey, James A. Romano, Salem Harry, Chemical Warfare Agents, 2019
Additionally, because of the creation of oxides (carbon monoxide) formed in this reactive process, there is also an increase in the diameter and volume of pre-existing pores. The temperature (usually between 800 and 1100°C) and the time of treatment are both important elements in determining the size, volume, and distribution of the ensuing pores. The temperatures required for physical activation are higher than those required for carbonization, and this high temperature precipitates another chemical reaction, in which the carbon monoxide and steam react to produce carbon dioxide and hydrogen. This reaction is catalyzed by the surface of the AC; consequently, the content of carbon dioxide and free hydrogen gas (H2) is increased, and carbon monoxide (CO) and steam (H2O) content are decreased. This reversible reaction is as follows (Leimkuehler, 2010; Shabanzadeh, 2012):
Factors related to the absorption rate of benign thyroid nodules after image-guided microwave ablation: a 3-year follow-up
Published in International Journal of Hyperthermia, 2022
Li-Hong Liu, Bei-Bei Yang, Ying Liu, Jin-Ling Wang, Dan-Dan Wang, Hong-Yu Ding, Shu-Rong Wang
Our study identified energy delivered per ml as a factor related to nodule VRR. The underlying mechanism for this relationship might arise from the process of MWA. If the unit volume energy is too much, the central temperature of the tissue will be too high, often exceeding 150 °C [43,44], which will carbonize the ablated tissue. It is difficult for the body to absorb this carbonization. The fixed electrode technique or high output power was applied to block blood flow in the most richly vascular portions of the nodule. After ablation, we found that the absorption of some nodules with blocked peripheral blood flow was slow. We speculated that blockage of peripheral blood flow was a factor affecting nodule absorption. After ablation, the ablation area enters a period of damage repair, and the necrotic tissue in the ablation area is constantly engulfed and removed by macrophages and other inflammatory response cells [45]. Blocking blood flow around the ablation nodules may break the absorptive balance of necrotic tissue.
Tissue shrinkage in microwave thermal ablation: comparison of three commercial devices
Published in International Journal of Hyperthermia, 2018
Laura Farina, Yitzhak Nissenbaum, Marta Cavagnaro, S. Nahum Goldberg
We note that when carbonisation is present no device dependence is noted for the shrinkage in the coagulated-but-not-carbonised tissue (Figure 5). Yet, in absence of carbonisation, the shrinkage in this coagulated-but-not-carbonised tissue zone shows a different behaviour due to the different used devices (Figure 6). In the samples treated with the HS system, carbonisation is present and the obtained shrinkage decreases from a maximum value corresponding to the carbonisation margin to a minimum value at the necrosis edge. In the samples treated with the CV device without inducing carbonisation, i.e. for ablation times up to 5 min, constant shrinkage in the tissue close to the antenna is found (about 25%), although this is lower than the maximum observed in HS (35%). Nonetheless, farther from the CV antenna, decreasing amounts of shrinkage converging on the HS trend were observed; so that, very close values are obtained for the two devices considering the whole thermally ablated area. The lack of carbonisation during the first minutes of heating (below 5 min) is likely linked to the different cooling system implemented in the CV applicators that allows the cooling liquid to reach the antenna tip, thus preventing the early overheating of the tissue close to the antenna axis and its carbonisation. It follows that different technologies can influence the appearance of carbonisation, and consequently the profile of the induced tissue shrinkage. In particular, it can be evidenced that the performance of the cooling system plays a dominant role.
Temperature control and intermittent time-set protocol optimization for minimizing tissue carbonization in microwave ablation
Published in International Journal of Hyperthermia, 2022
Xiaofei Jin, Yu Feng, Roujun Zhu, Lu Qian, Yamin Yang, Qindong Yu, Zhihan Zou, Weitao Li, Yangyang Liu, Zhiyu Qian
During MWA process, direct energy deposition in the confined range of action will lead to excessively high central temperature in tissues around the microwave antenna. The carbonization in the ablated lesion could easily occur, where highly desiccated charring tissues usually appear. The tissue after MWA can be divided into carbonization zone (black part), coagulation zone (light yellow in color), transition zone (red hyperemic band) and normal zone [10,11]. Previous studies have shown that in the MWA of some organs such as the spleen [12], the crushing and avulsion of charring tissues in the course of needle withdrawal can cause bleeding. The carbonization phenomenon may also induce both regional and systemic inflammatory response and other unwanted side effects [13–19].