The Use Of Amido- And Imido-Functionalized Alpha Hydroxy Acids In The Creation Of Biodegradable Polyesters: An Exploration Of Va

The purpose of this thesis was to synthesize biodegradable polyesters from a wide array of functionalized ¿-hydroxy acids. The initial strategy was to use amido-functionalized ¿-hydroxy acids and 2-bromopropanoyl bromide to form amido-functionalized cyclic diesters. Then, the resulting cyclic diesters would be used in ring opening polymerization to create biodegradable polyesters. However, the spontaneous rapid degradation of the secondary amido-functionalized cyclic diester structure, as seen with 2-benzamido-hydroxyacetic acid, limited ring formation to tertiary amido-functionalized ¿-hydroxy acids. Also, the hydrophilic nature of most ¿-hydroxy acids allowed water into the crystal structure of the ¿-hydroxy acid. Then, when the ¿-hydroxy acid was used in ring forming reactions, the associated water deactivated reactive reagents and limited cyclic diester synthesis. These issues led to the synthesis of hydrophobic and tertiary amido- and imido-functionalized ¿-hydroxy acids, 2-phthalimido-2-hydroxyacetic acid and 2-(1-oxoisoindolin-2-yl) hydroxyacetic acid. The new ¿-hydroxy acids were used in two new polymerization techniques, melt polycondensation and solution polymerization, instead of ring open polymerization. Melt polycondensation and solution polymerization had shown previous success in forming oligomers of amido-functionalized ¿-hydroxy acids. Melt polycondensation was conducted by heating the monomer past its melting temperature under reduced pressure. The uncatalyzed melt polycondensation of 2-(1-oxoisoindolin-2-yl) hydroxyacetic acid created polyesters (¿ 960 g/mol). The scandium(III) trifluoromethanesulfonate enhanced melt polycondensation polymerization created slightly larger oligomers (¿ 1340 g/mol). However, 2-phthalimido-2-hydroxyacetic acid was not compatible with melt polycondensation because thermal degradation occurred. Thus, solution polymerization was conducted via Steglich esterification. Only oligomeric functionalized polyesters were formed (¿ 1060 g/mol). Future work should focus on optimization of the catalyst and the reaction conditions to obtain higher molecular weight polyesters. Also, 2-(1-oxoisoindolin-2-yl) hydroxyacetic acid should be utilized in the cyclic diester synthesis technique.

Periodontal and peri-implant wound healing following laser therapy

Laser irradiation has numerous favorable characteristics, such as ablation or vaporization, hemostasis, biostimulation (photobiomodulation) and microbial inhibition and destruction, which induce various beneficial therapeutic effects and biological responses. Therefore, the use of lasers is considered effective and suitable for treating a variety of inflammatory and infectious oral conditions. The CO2 , neodymium-doped yttrium-aluminium-garnet (Nd:YAG) and diode lasers have mainly been used for periodontal soft-tissue management. With development of the erbium-doped yttrium-aluminium-garnet (Er:YAG) and erbium, chromium-doped yttrium-scandium-gallium-garnet (Er,Cr:YSGG) lasers, which can be applied not only on soft tissues but also on dental hard tissues, the application of lasers dramatically expanded from periodontal soft-tissue management to hard-tissue treatment. Currently, various periodontal tissues (such as gingiva, tooth roots and bone tissue), as well as titanium implant surfaces, can be treated with lasers, and a variety of dental laser systems are being employed for the management of periodontal and peri-implant diseases. In periodontics, mechanical therapy has conventionally been the mainstream of treatment; however, complete bacterial eradication and/or optimal wound healing may not be necessarily achieved with conventional mechanical therapy alone. Consequently, in addition to chemotherapy consisting of antibiotics and anti-inflammatory agents, phototherapy using lasers and light-emitting diodes has been gradually integrated with mechanical therapy to enhance subsequent wound healing by achieving thorough debridement, decontamination and tissue stimulation. With increasing evidence of benefits, therapies with low- and high-level lasers play an important role in wound healing/tissue regeneration in the treatment of periodontal and peri-implant diseases. This article discusses the outcomes of laser therapy in soft-tissue management, periodontal nonsurgical and surgical treatment, osseous surgery and peri-implant treatment, focusing on postoperative wound healing of periodontal and peri-implant tissues, based on scientific evidence from currently available basic and clinical studies, as well as on case reports.

History of Atmospheric Lead Deposition Since 12,370 14C yr BP from a Peat Bog, Jura Mountains, Switzerland

A continuous record of atmospheric lead since 12,370 carbon-14 years before the present (14C yr BP) is preserved in a Swiss peat bog. Enhanced fluxes caused by climate changes reached their maxima 10,590 14C yr BP (Younger Dryas) and 823014C yr BP. Soil erosion caused by forest clearing and agricultural tillage increased lead deposition after 532014C yr BP. Increasing lead/scandium and decreasing lead-206/lead-207 beginning 3000 14C yr BP indicate the beginning of lead pollution from mining and smelting, and anthropogenic sources have dominated lead emissions ever since. The greatest lead flux (15.7 milligrams per square meter per year in A.D. 1979) was 1570 times the natural, background value (0.01 milligram per square meter per year from 8030 to 5320 14C yr BP).

Geochemistry of bulk samples and various minerals of sediment core CRP-1 from the Ross Sea, Antarctica

Thirty-nine medium and fine grained sandstones from between 19,26 and 147,23 mbsf in the Cape Roberts-l core (CRP-1) were analysed for 10 major and 16 trace elements. Using whole-lock compositions, 9 samples were selected for analyses of mineral and glass grains by energy dispersive electron microscope. Laser-Ablation Mass-Spectrometry was used to determine rare earth elements and 14 additional trace elements in glass shards, pyroxenes and feldspars in order to examine their contribution to the bulk rock chemistry. Geochemical data reveal the major contribution played by the Granite Harbour Intrusives to the whole rock composition, even if a significant input is supplied by McMurdo volcanics and Ferrar dolerite pyroxenes McMurdo volcanics were studied in detail; they appeal to derive from a variety of litologies, and a dominant role of wind transpoitation from exposures of volcanic rocks may be inferred from the contemporary occurrence of different compositions at all depths. Only at 116.55 mbsf was a thin layer of tephra found, linked to an explosive eruption McMurdo volcanic rocks exhibit larger abundances at depths above 62 mbsf, in correspondence with the onset of volcanic activity in the McMurdo Sound area. From 62 mbsf to the bottom of the core, McMurdo volcanics are less abundant and probably issued from some centres in the McMurdo Sound region. However, available data do not allow the exclusion of wind transport from some eruptive centres active in north Victoria Land at the beginning of the Miocene Epoch.

Petrology and geochemistry at DSDP Site 89-462

The 16 samples of Deep Sea Drilling Project (DSDP) Leg 89 basalts that we analyzed for whole rock major and trace elements and for mineralogic compositions are identical to some of the basalts recovered during Leg 61. Leg 89 samples are mostly olivine-plagioclase-clinopyroxene sparsely phyric basalts and exhibit a wide variety of textures. These basalts have lower TiO2 at a given Mg/(Mg+Fe2+)*100 than MORB (midocean ridge basalt). We recognize three major chemical types of basalts in the Nauru Basin. We believe that different degrees of partial melting, modified by fractional crystallization and possibly by magma mixing at shallow depths, can explain the chemical differences among the three groups. This petrogenetic model is consistent with the observed downhole chemical-chronostratigraphic relations of the samples. New 87Sr/86Sr and U3Nd/144Nd analyses of basalt samples from DSDP Site 462 indicate that the Nauru Basin igneous complex is within the Sr-Nd isotopic range of ocean island basalt. Thus the Nauru Basin igneous complex resembles MORB in many aspects of its chemistry, morphology, and secondary alteration patterns (Larson, Schlanger, et al., 1981), but not in its isotopic characteristics. If it were not for the unambiguous evidence that the Nauru Basin complex was erupted off-ridge, the complex could easily be interpreted as normal oceanic layer 2. For this reason, we speculate that the Nauru Basin igneous complex was produced in an oceanic riftlike environment when multiple, fast-propagating rifts were formed during the fast seafloor spreading episode in the Cretaceous.

Major and trace element concentrations of sediments from the IODP Exp302 sites

We analyzed a suite of sediment samples recovered in the central Arctic Ocean for major, trace, and rare earth elements in order to assess changes in terrigenous source material throughout the Cenozoic. The terrigenous component consists of two end-members. Input from a shale-like composition dominates bulk sediments, especially those deposited during the Paleocene and since the Miocene, and may represent sediment supply from the eastern Laptev Sea. Therefore, even though the environment and transport mechanisms may have varied from ice free to ice dominated, sequences of the early Paleogene and later Neogene appear to have been influenced by a single major terrigenous source. This suggests similar transport capabilities and trajectories for both ocean and drift currents through significant parts of the Cenozoic. Influence from a more mafic source appears to be more important through the early Eocene to the middle Miocene and most likely represents material from the western Laptev Sea or Kara Sea. Thus, Eocene major changes in surface water productivity appear broadly synchronous with those in terrigenous provenance. A combination of regional sea level variations, local shelf processes, and transport mechanisms are among the more probable causes for the observed source changes. Although the assignment of sources using chemistry presently is constrained by a lack of data from certain regions (e.g., eastern Siberian Sea) our results generally agree with inferences based on mineralogy or radiogenic isotopes and shed further light on long-term reconstructions of the central Arctic Ocean.

Chemistry of minerals from amphibole-chlorite veins of ODP Site 209-1270

We examined small-scale shear zones in drillcore samples of abyssal peridotites from the Mid-Atlantic Ridge. These shear zones are associated with veins consisting of chlorite + actinolite/tremolite assemblages, with accessory phases zircon and apatite, and they are interpreted as altered plagiogranite melt impregnations, which originate from hydrous partial melting of gabbroic intrusion in an oceanic detachment fault. Ti-in-zircon thermometry yields temperatures around 820°C for the crystallization of the evolved melt. Reaction path modeling indicates that the alteration assemblage includes serpentine of the adjacent altered peridotites. Based on the model results, we propose that formation of chlorite occurred at higher temperatures than serpentinization, thus leading to strain localization around former plagiogranites during alteration. The detachment fault represents a major pathway for fluids through the oceanic crust, as evidenced by extremely low d18O of altered plagiogranite veins (+3.0-4.2 per mil) and adjacent serpentinites (+ 2.6-3.7 per mil). The uniform oxygen isotope data indicate that fluid flow in the detachment fault system affected veins and adjacent host serpentinites likewise.