Search

The case of a man whose periapical infection progressed to cervical necrotizing fasciitis is discussed. The patient underwent surgical debridement procedures and had an intensive stay at the hospital. The condition. Dentists should suspect this condition if their conventional therapy for maxillofacial cellulitis or abscess fails.

Mandated Environmental Protection Agency biofuel qualifications focused on greenhouse gas ( GHG) emissions and fossil fuel use are limited in perspective and have the potential to encourage burden shifting. When a broader host of environmental impacts are examined, environmental trade-offs often exist when biofuels are compared to gasoline. Multivariate analysis methods examining a wide variety of weighting value systems and methodology assumptions were used to determine process design options with the lowest overall environmental impact. A multivariate environmental analysis was applied to the dilute acid pre-treatment process followed by enzymatic hydrolysis and the fermentation process for converting loblolly pine, eucalyptus, natural hardwood, switchgrass, and sweet sorghum biomass to ethanol. The influence of co-product treatment method choices, inclusion of direct land-use change, and electrical grid assumptions were examined using 16 different weighting methods to create a single score result. Biofuel system rankings based on GHG emissions following the Renewable Fuel Standards 2 ( RFS2) methods were very sensitive to the co-product treatment method, inclusion of land-use change emissions, and energy grid assumptions. The multivariate analysis ranking was heavily influenced by other environmental impacts resulting from the production of process chemicals used in ethanol conversion. Weighting methods examined had no influence on the environmental preference ranking of the biofuel scenarios. Additionally, the biofuel ranking based on the RFS2 methodology was different than the ranking following the multivariate approach examining additional impacts. These findings demonstrate a robust approach to biofuel life cycle assessment ( LCA) scenario analysis and suggest that the limited scope of the RFS2 environmental analysis could result in burden shifting. © 2015 Society of Chemical Industry and John Wiley & Sons, Ltd [ABSTRACT FROM AUTHOR]

The financial and environmental performance of the National Renewable Energy Lab's (NREL) thermochemical and biochemical biofuel conversion processes are examined herein with pine, eucalyptus, unmanaged hardwood, switchgrass, and sweet sorghum. The environmental impacts of the process scenarios were determined by quantifying greenhouse gas (GHG) emissions and TRACI impacts. Integrated financial and environmental performance metrics were introduced and used to examine the biofuel production scenarios. The thermochemical and biochemical conversion processes produced the highest financial performance and lowest environmental impacts when paired with pine and sweet sorghum, respectively. The high ash content of switchgrass and high lignin content of loblolly pine lowered conversion yields, resulting in the highest environmental impacts and lowest financial performance for the thermochemical and biochemical conversion processes, respectively. Biofuel produced using the thermochemical conversion process resulted in lower TRACI single score impacts and somewhat lower GHG emissions per megajoule (MJ) of fuel than using the biochemical conversion pathway. The cost of carbon mitigation resulting from biofuel production and corresponding government subsidies was determined to be higher than the expected market carbon price. In some scenarios, the cost of carbon mitigation was several times higher than the market carbon price, indicating that there may be other more cost-effective methods of reducing carbon emissions. [ABSTRACT FROM AUTHOR]

Dilute sulfuric acid pre-treatment followed by enzymatic hydrolysis and fermentation is a technology widely studied as a potential pathway for conversion of lignocellulosic biomass to ethanol. Six feedstocks were evaluated in process and financial simulations. The woody feedstocks include natural hardwood, Eucalyptus, and loblolly pine while the non-woody feedstocks include corn stover, switchgrass, and sweet sorghum. Based on experimental and literature data, ethanol yields for the non-woody biomasses range from 315 to 328 liters per bone dry metric ton (L/BDt). Sweet sorghum that is pressed and washed to remove soluble sugars prior to dilute acid processing can have an ethanol yield of approximately 470 L/BDt. Natural hardwood and Eucalyptus produce ethanol yields of 336 and 309 L/BDt, respectively. When processing 700 000 bone dry metric tons per year, the non-woody biomasses have lower minimum ethanol revenues to achieve a 12% internal rate of return (MER@12%) than the woody biomasses. The non-wood MER@12% ranged from $0.70 to $080/liter while the MER@12% for natural hardwood and Eucalyptus was $0.84-$0.85/liter. The impact of feedstock composition variability on the net present value at 12% (NPV@12%) discount was estimated for corn stover, switchgrass, and loblolly pine. One standard deviation in the sample carbohydrate content for corn stover, switchgrass, and loblolly pine will impact the NPV@12% by approximately $40 M, $72 M, and $24 M, respectively. If recent historical cost and revenue variability continues for the life of the project the most attractive feedstock is squeezed sweet sorghum where the probability of achieving at least a 12% internal rate of return is 64%. [ABSTRACT FROM AUTHOR]

The impact of lignin-derived inhibition on enzymatic hydrolysis is investigated by using lignins isolated from untreated woods and pretreated wood pulps. A new method, biomass reconstruction, for which isolated lignins are precipitated onto bleached pulps to mimic lignocellulosic biomass, is introduced, for the first time, to decouple the lignin distribution issue from lignin chemistry. Isolated lignins are physically mixed and reconstructed with bleached pulps. Lignins obtained from pretreated woods adsorb two to six times more cellulase than lignins obtained from untreated woods. The higher adsorption of enzymes on lignin correlates with decreased carbohydrate conversion in enzymatic hydrolysis. In addition, the reconstructed softwood substrate has a lower carbohydrate conversion than the reconstructed hardwood substrate. The degree of condensation of lignin increases significantly after pretreatment, especially with softwood lignins. In this study, the degree of condensation of lignin (0.02 to 0.64) and total OH groups in lignin (1.7 to 1.1) have a critical impact on cellulase adsorption (9 to 70 %) and enzymatic hydrolysis (83.2 to 58.2 %); this may provide insights into the more recalcitrant nature of softwood substrates. [ABSTRACT FROM AUTHOR]

The production of six regionally important cellulosic biomass feedstocks, including pine, eucalyptus, unmanaged hardwoods, forest residues, switchgrass, and sweet sorghum, was analyzed using consistent life cycle methodologies and system boundaries to identify feedstocks with the lowest cost and environmental impacts. Supply chain analysis was performed for each feedstock, calculating costs and supply requirements for the production of 453,592 dry tonnes of biomass per year. Cradle-togate environmental impacts from these modeled supply systems were quantified for nine mid-point indicators using SimaPro 7.2 LCA software. Conversion of grassland to managed forest for bioenergy resulted in large reductions in GHG emissions due to carbon uptake associated with direct land use change. By contrast, converting forests to cropland resulted in large increases in GHG emissions. Production of forest-based feedstocks for biofuels resulted in lower delivered cost, lower greenhouse gas (GHG) emissions, and lower overall environmental impacts than the agricultural feedstocks studied. Forest residues had the lowest environmental impact and delivered cost per dry tonne. Using forest-based biomass feedstocks instead of agricultural feedstocks would result in lower cradle-to-gate environmental impacts and delivered biomass costs for biofuel production in the southern U.S. [ABSTRACT FROM AUTHOR]

Inthis study a forest biorefinery concept based on larch woodwas technically and economically evaluated. Two slightly differentcases of a larch-based biorefinery were compared to conventional kraftpulping. The wood chips of Larix sibirica(Lebed.) were pre-extracted (PE) and washed with water prior topulping, in order to generate an additional sugar side-stream. Thesugars were hydrolyzed into monosugars, which were then fermentedby Bacillus coagulansinto lactic acid.The lactic acid needs to be purified before sold to the market. Bypulping the pre-extracted wood chips with anthraquinone (AQ) and polysulfide(PS), the pulp yield loss was reduced. The pulp was then bleached(O-D0-Ep-D1-P). The products of this larch biorefinery are bleachedsoftwood pulp and lactic acid. Three process cases were simulated:conventional kraft pulping, PE-PSAQ with 0.5% PS, and PE-PSAQ with2% PS, in terms of mass and energy balances. Considering the availabilityof larch resources, this kind of a biorefinery could suitably be locatedin Siberia, Russia. Market prices were collected, and based on thesimulation results, cash flows were determined. Sensitivity analysiswas carried out, and investment costs were estimated. Based on thesimulation with the addition of a lactic acid production line to anexisting pulp mill, the payback time for the investment costs wouldbe about 16 months. [ABSTRACT FROM AUTHOR]

Skull base surgery (SBS) is considered the standard of care in treating benign and malignant lesions of the cranial base. SBS is a multidisciplinary team approach used to treat these complex lesions that may have intracranial extension. SBS can be broken down into 3 steps. Transfacial access is performed, followed by resection with sound oncologic principles, and then reconstruction of the cranial base and facial structures. Functional and esthetic concerns must be addressed by the surgeons. Oral and maxillofacial surgeons frequently perform elective facial osteotomies and treat victims of cranial base trauma. These same principles can be applied to SBS as a part of the skull base team. [Copyright &y& Elsevier]

Calcium phosphate cements have many desirable properties for bone tissue engineering, including osteoconductivity, resorbability, and amenability to rapid prototyping-based methods for scaffold fabrication. In this study, we show that dicalcium phosphate dihydrate (DCPD) cements, which are highly resorbable but also inherently weak and brittle, can be reinforced with poly(propylene fumarate) (PPF) to produce strong composites with mechanical properties suitable for bone tissue engineering. Characterization of DCPD-PPF composites revealed significant improvements in mechanical properties for cements with a 1.0 powder to liquid ratio. Compared with nonreinforced controls, flexural strength improved from 1.80 ± 0.19 MPa to 16.14 ± 1.70 MPa, flexural modulus increased from 1073.01 ± 158.40 MPa to 1303.91 ± 110.41 MPa, maximum displacement during testing increased from 0.11 ± 0.04 mm to 0.51 ± 0.09 mm, and work of fracture improved from 2.74 ± 0.78 J/m2 to 249.21 ± 81.64 J/m2. To demonstrate the utility of our approach for scaffold fabrication, 3D macroporous scaffolds were prepared with rapid prototyping technology. Compressive testing revealed that PPF reinforcement increased scaffold strength from 0.31 ± 0.06 MPa to 7.48 ± 0.77 MPa. Finally, 3D PPF-DCPD scaffolds were implanted into calvarial defects in rabbits for 6 weeks. Although the addition of mesenchymal stem cells to the scaffolds did not significantly improve the extent of regeneration, numerous bone nodules with active osteoblasts were observed within the scaffold pores, especially in the peripheral regions. Overall, the results of this study suggest that PPF-DCPD composites may be promising scaffold materials for bone tissue engineering. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2012. [ABSTRACT FROM AUTHOR]

Biomass pretreatment by autohydrolysis uses hot-water to extract soluble components from wood prior to converting the woody residuals into paper, wood products, or fuel, etc. Mixed hardwood chips were autohydrolyzed in hot-water at 150, 160, 170, and 180 ºC, for 1 and 2 h. The tradeoff between fermentable sugar yield and caloric value of the residual solids was studied for a process that will be referred to as "value prior to combustion". The extracted liquid was treated with dilute sulfuric acid to break down sugar oligomers into fermentable monomers. Material balances were performed around autohydrolysis to evaluate the role of temperature and residence time on sugar production and residual solid heating value. The composition (sugars and byproducts) of the extracted liquid was determined. As the autohydrolysis temperature increased, the material balance became less precise, presumably due to more volatile byproducts being formed that were not quantified. More hemicelluloses were extracted from the wood by the hot water extraction process under higher temperature and longer residence time, but a greater degree of sugar degradation was also observed. After hot-water extraction the heating value of the solid residues was higher than the original wood. The total energy content of the residual solid after extraction ranged from 74 to 95% of the original energy content of the feed. [ABSTRACT FROM AUTHOR]

Green liquor pretreatment, a technology presently used worldwide in hundreds of kraft pulp mills, is proposed in this work as a potential pretreatment pathway for the efficient conversion of lignocellulosic biomass into ethanol. Mixed southern hardwood, eucalyptus, and loblolly pine were evaluated through process simulations in two investment scenarios: a greenfield mill scenario and a repurposing scenario, using existing kraft pulp mill assets for cellulosic ethanol production. Several advantages come with this concept: i) proven technology (both process and equipment), ii) chemical and energy recovery in place, iii) existing fiber supply chain, and iv) experienced labor force around the mill. Ethanol yields through enzymatic hydrolysis of pretreated fibers were highest in natural mixed hardwood and eucalyptus (280-285 liters of ethanol per dry ton of biomass) and lowest in loblolly pine (273 liters per dry ton of biomass). Natural hardwood and eucalyptus in the repurposing scenario form the most profitable combinations with an IRR of about 19%, mainly due to low capital expenditure (CAPEX) (per liter of ethanol), low enzyme costs, and higher ethanol yield (compared to loblolly pine). Production cost (in the repurposing scenario) was estimated at $2.51 per gallon of ethanol (or $0.66 per liter), cash cost at $2.14 gallon-1 (or $0.57 per liter), and CAPEX at $3.15 gallon-1 (or $0.83 per liter). Repurposing existing closed mills creates a potential alternative to ramp up in the task of producing alternative lignocellulosic biofuels. [ABSTRACT FROM AUTHOR]

A paradigm shift in the training, practice, and study of office-based anesthesia is necessary for our specialty. Practice improvement plans are required to prevent low-probability-high-consequence anesthesia mishaps in our offices. A scarcity of statistical data exists regarding the true risk of office-based anesthesia in oral and maxillofacial surgery. Effective proactive risk management mandates accurate data to correctly outline the problem before solutions can be implemented. Only by learning from our mistakes, will we be able to reduce errors and improve patient safety: 'The only real mistake is the one from which we learn nothing'-John Powell. [ABSTRACT FROM AUTHOR]

Abstract: In theory, biosugar for conversion to bioproducts can be produced economically from a variety of biomass types in many different technological, co‐production, and biorefinery siting contexts. In this paper, process modeling and financial analysis were conducted for all permutations of biochemical conversion pathways, global biomass types, co‐product options, and biorefinery siting contexts for biosugar production. Minimum sugar revenue (MSR) required to achieve a 15% internal rate of return values for scenarios examined ranged from $150–$748 per tonne. The scenarios with the lowest MSRs were sugarcane in South America and Asia, assuming hot water cook and co‐location or repurpose siting contexts. Another financially optimized scenario is corn grain, also assuming hot water cook, co‐producing distiller’s dry grains and solubles (DDGS), in a repurpose siting context. Against a benchmark sugar price of $408 per metric tonne, an internal rate of return on investment of >15% can typically only be achieved via previously demonstrated conversion pathways using sugar cane and corn grain. Major cost drivers were feedstock cost per metric tonne of carbohydrate, sugar yield, capital investment per annual metric tonne of sugar produced, residue value, and siting context. Near‐term promising technologies include autohydrolysis and dilute acid pathways. Generally, scenarios are financially enhanced by co‐location or repurposing, reducing capital expenditure (CAPEX) by about 33% and 50%, respectively, with negligible impact on cash cost. Conversion process complexity drives capital investment, making some scenarios infeasible despite high sugar yields. Any of the five major cost drivers can impact the order of financial attraction of scenarios, with the outcome of the analysis typically not obvious in advance. © 2018 Society of Chemical Industry and John Wiley & Sons, Ltd [ABSTRACT FROM AUTHOR]

A growth factor known as Bone Morphogenic Protein has through recombinant technology been made available to dentists as a "bone-less" bone graft. This recombinant human bone morphogenic protein-2 is placed on an absorbable collagen sponge carrier and delivered to a site of bone deficiency. This material will induce new osteoblasts to form from mesenchymal stem cells in the surrounding recipient site. This eliminates the need for an autogenous bone graft and its inherent surgical morbidity. The new bone formed is of the same quality and quantity as that produced by autogenous grafting. Dentists should be familiar with alternative techniques of bone grafting in contemporary practice.

The practice of office-based oral and maxillofacial surgery is continuously expanding and involves the management of a diverse population in regards to the surgical procedures performed within the office and the age and medical health of the patients treated within the office. Comfort, cooperation, and hemodynamic stability are critical to satisfactorily accomplishing the surgical procedure. Various anesthetic techniques are used, including local anesthesia, anxiolysis, analgesia and sedation, and general anesthesia. The topic is vast and too extensive to be fully discussed in this article. The intent of this article is to provide a discussion of some fundamental concepts that can optimize anesthetic safety and care.