Incision rates

The Sierra Nevada provide an example of the perils of relating erosion rates to relief. They are thought to have persisted since 60-80 Ma with high (1.5 km) relief over long wavelengths ( 50 km), but erosion rates over these timescales are estimated to have been only 0.03-0.08 mm/yr (House et al. 1997, 2001 Clark et al. 2005). Incision rates may have been higher ( 0.2 mm/yr) in the Pliocene (Stock et al. 2004), possibly aided by convective instability at depth (e.g., Ducea and Saleeby 1996), but this is still slow relative to erosion rates in many other tectonically active and inactive regions, and similar to some with much lower relief (e.g., Heffern et al. 2007). 

The elevation of the cave in relation to local base-level may also serve to constrain the age of the cave. The morphology of the cave makes it reasonable to believe that it formed at or above local base-level. The lowest portions of the cave are presently at about 53 ft. (16 m) above the Little Juniata River. As an end-member calculation, let us assume that the cave formed at base-level and had a negligible gradient toward the surface stream. Furthermore, let us assume an incision rate of 0.05 m/ka (Sasowsky et al., 1995). Under such conditions the river could have cut this distance below the cave in 320 ka, yielding a similar age for the cave. Because we do not know the actual gradient that was present when the cave formed, this number should be considered a maximum possible value. 

Sasowsky, I.D., White, W.B., and Schmidt, V.A., 1995, Determination of stream incision rate in the Appalachian plateaus by using cave-sediment magnetostratigraphy (Seology, v. 23, p. 415-418. 

Despite the universal use of sutures for wound closure, there is a need to utilize adhesives instead, because of their ease of use and the reduced risk of infection. Alkyl cyanoacrylate adhesives have been studied extensively for this use, and a significant amount of research has been performed to evaluate their interaction with living tissue [40,41 J. They have been approved for external use only, because of concerns with the fact that the polymers do not readily biodegrade and can cause inflammation around the area to which it was applied. However, these concerns are reduced for -butyl cyanoacrylate, as compared to the ethyl cyanoacrylate. There is even some evidence that their use as liquid sutures actually reduces the rate of infection around the healing wound or surgical incision [42J. 

Studies have found that administration of the antimicrobial should begin as close to the first incision as possible. This is important for antibiotics with short half-lives so that therapeutic concentrations are maintained during the operation and reduce the need for redosing. Beginning the infusion after the first incision is of little value in preventing SSL Stone and associates found that administration of the antimicrobial after the first incision had SSI rates similar to patients who did not receive prophylaxis.20... 

Use of prophylactic antibiotics during head and neck surgery depends on the procedure type. Clean procedures, such as parotidectomy or a simple tooth extraction, are associated with low rates of SSI. Head and neck procedures involving an incision through a mucosal layer carry a high risk of SSI. 

A very incisive set of experiments on Pd(lll) (16a) and Pt(lll) (16b) done in Gerhard Ertl s lab, show that the Eley-Rideal pathway makes no measurable contribution to the C0 production rate for many low pressure conditions. In these experiments, a steady-state CO pressure was established, the 0 pressure was modulated and the phase-lag of the modulated CO2 product signal was measured. The slope of In (tamj)), where 4> is the phase lag, as a function of T- can be interpreted in terms of an activation energy difference (Er - E ) between reaction and desorption. The result for Pt(lll) is -10.8 kcal mole- as shown in Figure 12 (16b). For an Eley-Rideal pathway in which a gas phase CO molecule makes a direct or impact attack on an oxygen adatom, E[Pg.51]

Isotope-exchange reactions can provide incisive information about the mechanisms by which hydrogenases catalyse their reactions. The ratios of products formed, and in the rates of reaction with different isotopes, can be measured. Different hydrogenases show significantly different proportions of and H HO produced in reactions (3) and (4), and this effect has been used to identify the different types of hydrogenases in whole cells, without the need for purification (Berber et al. 1987). 

The most incisive studies of the problem at the molecular level are those from the Felsenfeld laboratory (see, for example. Refs. [75,76]). They have shown that at least under some circumstances, a polymerase can step around a nucleo-some, displacing it in cis, but not causing dissociation. It is not yet clear, however, if this mechanism is physiologically relevant and/or whether it is the only mechanism. There exist results in apparent conflict with this model (i.e.. Ref. [77]). That the in vivo process is certainly more complex than the in vitro models used to date is further indicated by the discovery of elongation factors that markedly increase transcriptional rates and suppress pausing (see, for example, Conaway and Conaway [78]). Thus, the question as to how transcription elongation occurs in a chromatin template remains at least partially unresolved. For a further discussion, see Jackson, this volume, p. 467. 

Continuous infusion-(to provide attenuation of response to intubation and incision) 50-75 mcg/kg 0.5-3 mcg/kg/min. Average infusion rate 1-1.5 mcg/kg/min dependent on duration of procedure... 

Smart fibers can make smart sutures—threads used by surgeons to sew up incisions—such as suture that ties itself when heated And Sensatex Incorporated makes a smart shirt that automatically monitors the wearer s vital signs. Special sensors and conducting fibers embedded in the shirt measure heart rate, respiration, and body temperature, and a tiny controller relays this information by transmitter to a medical station. 

The simplest phenol, shown in Figure 12.13, is called phenol. In 1867, Joseph Lister (1827-1912) discovered the antiseptic value of phenol, which, when applied to surgical instruments and incisions, greatly increased surgery survival rates. Phenol was the first purposefully used antibacterial solution, or... 

Placebos are effective for a variety of conditions. Patients with angina pectoris (insufficient blood flow to the heart) responded to placebo surgery in which surgeons made only an incision in the chest. And in a study of the drug propranolol that is used after heart attacks to prevent further damage, investigators noticed that patients who took placebo pills regularly had a lower death rate than patients who took placebos sporadically. Therefore, the placebo effect is not unique to psychiatric illness. 

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