Browsing by Subject "volume"
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Item Analysis of Antarctic Sea Ice Thickness: A Newly Created Database for 2000-2009(2012-10-19) Morgan, Benjamin PatrickObservations of Antarctic sea ice thickness are sporadic in space and time, hindering knowledge of its variability. A proxy based on stage of development data from the National Ice Center (NIC) weekly operational charts is used to create a high-resolution time series of sea ice concentration, thickness and volume for 2000-2009. Record-length mean thickness and volume of Antarctic sea ice are 66.7 cm and 7.7 x10^3 km^3. The mean growth and decay seasons in the Southern Ocean and in the Ross sector are 210 days and 155 days, but at least at least one week shorter (growth) and longer (decay) in the Amundsen/Bellingshausen sector. Over 90% of the Antarctic continental shelf is covered with sea ice for 3-5 months, and for 2 to 4 months longer periods in the Amundsen/Bellingshausen and Ross sectors. Yearly mean sea ice area (extent) in the Southern Ocean increased at a rate of 0.71 x 10^6 km^2/decade (0.70 x 10^6 km^2/decade), equivalent to a 7.7 %/decade (6.3 %/decade) rise. A comparable trend of 9.1 %/decade (8.5 %/decade) is estimated in the Ross sector, at 0.21 x 10^6 km2/decade (0.23 x 10^6 km2/decade). The opposite trend is found in the Amundsen/Bellingshausen sector: a -0.15 x 10^6 km^2/decade (-0.17 x 10^6 km^2/decade) decline, or -14.6 %/decade (-13.4 %/decade). The estimated annual increase of Antarctic sea ice thickness is 22.6 cm/decade (49.2 %/decade) and of volume is 3.78 x 10^3 km^3/decade (68.3 %/decade). The Ross sector showed similar trends for thickness, at 23.8 cm/decade (47.0 %/decade), and volume, at 1.11 x 10^3 km^3/decade (75.8 %/decade). Thickness has increased in the Amundsen/Bellingshausen sector, 20.7 cm/decade (44.8 %/decade), but with a less pronounced volume rise of 0.17 x10^3 km^3/decade (26.0 %/decade). Monthly sea ice thickness anomalies show a weak response to the El Nino Southern Oscillation (ENSO) index. A strong positive response is observed in 2008 when a negative a negative ENSO index compounded to a positive Southern Annular Mode (SAM) index. Therefore the estimated increase of sea ice thickness in the Southern Ocean could be attributed to the prevailing atmospheric conditions with a positive SAM phase over the past decade.Item Influence of Salinous Solutions in the Pressure and Volume Modulations of the Intracranial Cavity(2012-10-19) Ceballos, MarianaFollowing a head concussion the intracranial pressure increases due to the impact, which cannot be adequately relieved because of the stiffness of the skull. Popular strategies aimed at decompressing the head consist in the administration of osmotic agents and skull removal. The mechanical properties of bone can be affected by the administration of different solutions. If the malleability of skull is influenced by the osmotic agents that are administered to the patient then the pressure and volume in the intracranial cavity can also be modified following the treatment. In this thesis research, we hypothesize that administered osmotic agents can influence the mechanical properties of the skull, which can also impact the volume the cavity can hold and subsequently the pressure in the head. This premise was tested by modifying existing mathematical models compiled through two general MATLAB codes that allow the computation of a non-symbolic differential-algebraic initial value problem. Three main features were changed in comparison to current models: the skull's influence on the pressure and volume modulation was tested (inputs were obtained from skull tested under different solutions); pulsatile flow was accounted for on the creation and movement of cerebrospinal fluid; and the input on the mechanical behavior of the cranial vessels was accounted for through previously published continuum-mechanics vessel-behavior models. To complete the model, materials and mechanical properties were obtained through laboratory experiments as well as data collection from existing literature. From our bone test we were able to conclude that there are different factors that affect the mechanical properties of bone in various degrees. There is a mild statistical correlation (p-value 0.05) between the mechanical properties of bone obtained from different regions of the skull samples (2-14mm) and the DPBS and hDPBS solutions. Additionally there is a strong statistical difference (p-value 0.05) between the mechanical properties obtained from cross head speed (0.02, 0.002, and 0.004 (mm/s)) and solution variation (DI, DPBS and hDPBS). Finally, we were able to see that there seems to be a correlation between the mechanical properties of bone, the solution treatments and hypertension; although more test need to be developed to affirm this premise since our results are preliminary.Item Structural and functional characterization of a lymphatic system using computational and experimental approaches(2009-05-15) Madabushi Venugopal, ArunThe lymphatic system returns interstitial fluid back to the blood circulation. They have a network of vessels with numerous lymphangions, the segment of lymphatic vessel between two unidirectional valves. The valves aid in transporting lymph against a pressure gradient, in addition to the lymphangion pump which exhibit cyclical variations in diameter. Like blood vessels, baseline lymphatic tone is regulated with changes in transmural pressure; however, the transient response of lymphatic diastolic diameter following changes in transmural pressure has not been studied. The lymphangion pump is often described using cardiac analogies. However, since an active system empties into another active system in a lymphatic vessel, the analogy cannot characterize the principles governing optimal lymphatic vessel function. Furthermore, to optimize lymph flow there is also a need to characterize the lymphatic network structure. To characterize the transient diameter response of lymphatic segment, we used post-nodal bovine mesenteric lymphangions in an isobaric preparation and measured the diameter response to a step change in pressure. An immediate active reduction in enddiastolic diameter with each incremental increase in pressure was observed. To identify the principles governing optimal lymphatic vessel function, we applied the result obtained from optimizing the interaction of the heart-arterial system to measured lymphangion pressure-volume relationships. We assumed that the slope of end systolic pressure-volume relationship (Emax) is equal to the slope of end-diastolic relationship (Emin) above a cutoff pressure and Emax>Emin below the cutoff pressure. Unlike the heart, we found that stroke work is not optimized when Emax = Emin. However, there is a region where lymph flow is insensitive to changes in transmural pressure. To characterize the lymphatic network structure, we used an approximation of time-varying elastance model. We found there is an optimal length for the lymphangion when it produces maximal flow. To develop a fractal network model, we determined the ratio of radius and ratio of length of lymphangion at a confluence. Using conservation of mass and certain simplifying assumptions, we showed that the ratio of radius, as well as ratio of length of upstream lymphangion, to the downstream lymphangion at confluences is 1.26.