Measurement and modeling of multiple substrate oxidation by methanotrophs at 20 °C

Earlier experiments have shown that when Methylosinus trichosporium OB3b was grown at 30 °C, greater growth and degradation of chlorinated ethenes was observed under particulate methane monooxygenase (pMMO)-expressing conditions than sMMO-expressing conditions. The effect of temperature on the growth and ability of methanotrophs to degrade chlorinated ethenes, however, has not been examined, particularly temperatures more representative of groundwater systems. Thus, experiments were performed at 20 °C to examine the effect of mixtures of trichloroethylene, trans -dichloroethylene and vinyl chloride in the presence of methane on the growth and ability of Methylosinus trichosporium OB3b cells to degrade these pollutants. Although the maximal rates of chlorinated ethane degradation were greater by M. trichosporium OB3b expressing sMMO as compared with the same cell expressing pMMO, the growth and ability of sMMO-expressing cells to degrade these cosubstrates was substantially inhibited in their presence as compared with the same cell expressing pMMO. The Δ model developed earlier was found to be useful for predicting the effect of chlorinated ethenes on the growth and ability of M. trichosporium OB3b to degrade these compounds at a growth temperature of 20 °C. Finally, it was also discovered that at 20 °C, cells expressing pMMO exhibited faster turnover of methane than sMMO-expressing cells, unlike that found earlier at 30 °C, suggesting that temperature may exert selective pressure on methanotrophic communities to express sMMO or pMMO.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75464/1/j.1574-6968.2008.01314.x.pd

Comparative effectiveness of hand scaling by undergraduate dental students following a two-week pre-clinical training course

BACKGROUND The Bologna reform resulted in a drastic restructuring of pre-clinical training courses at the University of Zurich. The aim of this study was to assess student pre-clinical scaling/root planning skills after just 8.5 hours of manual training. MATERIAL AND METHODS Three consecutive classes of dental students (n = 41; n = 34; n = 48) were tasked with removing lacquer concrement from the maxillary left canine on a typodont using Gracey and universal (Deppeler M23A) curettes. At baseline (prior to instruction), a timed five-minute session of scaling/root planning was undertaken. The second scaling/root planning session was held immediately following training. Eight experienced dental hygienists and eight lay people served as positive and negative controls, using the same instruments and time limit, respectively. Instrumented teeth were collected, scanned and planimetrically analysed for the percentage of tooth surface cleaned. Statistical analyses were performed to assess the dental students' improvement after the training (Wilcoxon signed-rank test) and to compare it to that of laypeople and dental hygienists (Kruskal-Wallis rank sum test followed by Conover's post hoc test). RESULTS At baseline, the dental students' mean scaling scores of the cleaned surfaces were not significantly different than those of laypeople (29.8%, 31.0%, 42% vs 27.9%). However, after 8.5 hours of manual training, the students' ability to clean the maxillary tooth improved significantly and they achieved mean removal values of 61.7%, 79.5% and 76% compared to the 67.4% (P < .001) of the experienced dental hygienists (Tables Tables  and ). There were no statistically significant differences between the scores achieved by students after training and those achieved by experienced dental hygienists. CONCLUSION A shortened pre-clinical training time was sufficient for students to acquire the basic scaling/root planning skills needed in preparation for clinical training. Further research is needed to identify ways to help students consistently reach highest skill levels

Bone defect development in experimental canine peri-implantitis models: a systematic review

PURPOSE To provide a systematic overview of preclinical research regarding bone defect formation around different implant surfaces after ligature-induced peri-implantitis models in dogs. Two focused questions were formulated: 'How much bone loss can be expected after a certain time of ligature induced peri-implantitis?' and 'Do different implant types, dog breeds and study protocols differ in their extent of bone loss?' MATERIALS AND METHODS A systematic literature search was conducted on four databases (MEDLINE, Web of Science, EMBASE and Scopus). Observations, which consisted of bone defects measured directly after ligature removal in canine models, were included and analysed. Two approaches were used to analyse the relatively heterogeneous studies that fulfilled the inclusion criteria. First, separate simple linear regressions were calculated for each study and implant surface, for which observations were available across multiple time points. Second, a linear mixed model was specified for the observations at 12 weeks after ligature initiation, and assessing the potential influencing factors on defect depth was explored using lasso regularisation. RESULTS Thirty-six studies with a total of 1082 implants were included after. Bone loss was determined at different time points, either with clinical measurements radiographically or histologically. Different implant groups [e.g. turned, sand-blasted-acid-etched (SLA), titanium-plasma-sprayed (TPS) and other rough surfaces] were assessed and described in the studies. A mean incremental defect depth increase of 0.08 mm (SD: -0.01-0.28 mm) per week was observed. After 12 weeks, the defect depths ranged between 0.7 and 5 mm. Based on the current data set, implant surface could not be statistically identified as an essential factor in defect depth after 12 weeks of ligature-induced peri-implantitis. CONCLUSION Expectable defect depth after a specific time of ligature-induced peri-implantitis can vary robustly. It is currently impossible to delineate apparent differences in bone loss around different implant surfaces

Five-Year Survival of Short Single-Tooth Implants (6 mm): A Randomized Controlled Clinical Trial

The aim of the present study was to evaluate whether 6-mm dental implants in the posterior segments of either jaw perform equally well in terms of clinical and radiographic outcomes when compared with 10-mm implants after 5 y of loading. Patients with single-tooth gaps in the posterior area who were scheduled for implant therapy were randomly assigned to a group receiving either a 6- or 10-mm implant. After a healing period of 10 wk, implants were loaded with a screw-retained single crown and followed up at yearly intervals. Of 96 patients, 86 could be recalled after 5 y. The implant survival rates amounted to 91% (95% confidence interval: 0.836 to 0.998) for the 6-mm group and 100% for the 10-mm group ( P = 0.036). Median crown-to-implant (C/I) ratios were 1.75 (interquartile range [IQR], 1.50 to 1.90) for the 6-mm group and 1.04 (IQR, 0.95 to 1.15) for the 10-mm group, whereas the median marginal bone levels measured -0.29 mm (IQR, -0.92 to 0.23) for the 6-mm group and -0.15 mm (IQR: -0.93 - 0.41) for the 10-mm group after 5 y. The C/I ratio turned out to be statistically significant ( P < 0.001), whereas marginal bone levels showed no significant difference between the groups. The 6-mm implants exhibited significantly lower survival rates than the 10-mm implants over 5 y, whereas there was no difference between upper and lower jaws in terms of survival ( P = 0.58). Lost implants did not show any sign of marginal bone loss or peri-implant infection previous to loss of osseointegration. High C/I ratio and implant length had no significant effect on marginal bone level changes or technical and biological complications (German Clinical Trials Registry: DRKS00006290)

Towards a Medically Approved Technology for Large-Scale Stem Cell Banks: Tools and Method

The importance, of the development of stem cell cryobanking has increased recently with an augmentation of stem cell research and its therapeutic applications. The development of therapies is, among other things, limited by high sensitivity of stem cells to freezingthawing procedures. Thus, new approaches are needed for preservation and related evaluation methods, as well as new technologies for long term storage of large numbers of stem cells. Here we present selected recent improvements of stem cell cryopreservation, e.g. for freezing of adherent human embryonic stem cells using gel-like matrices. We report the application and performance of novel microsystem-based cryosubstrates and devices and describe new evaluation methods and the results of a thermal stress cycle study.В настоящее время возросла важность развития криобанков стволовых клеток в связи с их расширенным изучением и терапевтическим применением. Однако, наряду с другими факторами, вышеуказанная терапия ограничена высокой чувствительностью стволовых клеток к процедурам замораживания-оттаивания. Необходимы как новые подходы к криоконсервированию и связанным с ним методам оценки, так и новые технологии для долгосрочного хранения большого количества стволовых клеток. В настоящей работе мы представляем некоторые улучшенные методы криоконсервирования стволовых клеток, например замораживание эмбриональных стволовых клеток человека с использованием гелеобразного матрикса. Мы представляем результаты применения разработанных на базе микросистемной техники новых криосубстратов и устройств, а также описываем новые методы оценки и результаты изучения циклов температурного стресса.Наразі зросла важливість розвитку кріобанків стовбурових клітин у зв’язку з їх розширеним вивченням і терапевтичним застосуванням. Але водночас з іншими факторами вищезгадана терапія обмежена високою чутливістю стовбурових клітин до процедур заморожування-відтавання. Необхідні як нові підходи до кріоконсервування та повязаних з ним методам оцінки, так і нові технології для довгострокового зберігання великої кількості стовбурових клітин. В цій роботі ми представляємо деякі покращені методи кріоконсервування стовбурових клітин, наприклад заморожування ембріональних стовбурових клітин людини з використанням гелеподібного матриксу. Ми представляємо результати застосування розроблених на базі мікросистемної техніки нових кріосубстратів та приладів, а також описуємо нові методи оцінки і результати вивчення циклів температурного стресу

Global fire emissions buffered by the production of pyrogenic carbon

Landscape fires burn 3–5 million km2 of the Earth’s surface annually. They emit 2.2 Pg of carbon per year to the atmosphere, but also convert a significant fraction of the burned vegetation biomass into pyrogenic carbon. Pyrogenic carbon can be stored in terrestrial and marine pools for centuries to millennia and therefore its production can be considered a mechanism for long-term carbon sequestration. Pyrogenic carbon stocks and dynamics are not considered in global carbon cycle models, which leads to systematic errors in carbon accounting. Here we present a comprehensive dataset of pyrogenic carbon production factors from field and experimental fires and merge this with the Global Fire Emissions Database to quantify the global pyrogenic carbon production flux. We found that 256 (uncertainty range: 196–340) Tg of biomass carbon was converted annually into pyrogenic carbon between 1997 and 2016. Our central estimate equates to 12% of the annual carbon emitted globally by landscape fires, which indicates that their emissions are buffered by pyrogenic carbon production. We further estimate that cumulative pyrogenic carbon production is 60 Pg since 1750, or 33–40% of the global biomass carbon lost through land use change in this period. Our results demonstrate that pyrogenic carbon production by landscape fires could be a significant, but overlooked, sink for atmospheric CO2

Biochar: pyrogenic carbon for agricultural use: a critical review.

O biocarvão (biomassa carbonizada para uso agrícola) tem sido usado como condicionador do solo em todo o mundo, e essa tecnologia é de especial interesse para o Brasil, uma vez que tanto a ?inspiração?, que veio das Terras Pretas de Índios da Amazônia, como o fato de o Brasil ser o maior produtor mundial de carvão vegetal, com a geração de importante quantidade de resíduos na forma de finos de carvão e diversas biomassas residuais, principalmente da agroindústria, como bagaço de cana, resíduos das indústrias de madeira, papel e celulose, biocombustíveis, lodo de esgoto etc. Na última década, diversos estudos com biocarvão têm sido realizados e atualmente uma vasta literatura e excelentes revisões estão disponíveis. Objetivou-se aqui não fazer uma revisão bibliográfica exaustiva, mas sim uma revisão crítica para apontar alguns destaques na pesquisa sobre biochar. Para isso, foram selecionados alguns temaschave considerados críticos e relevantes e fez-se um ?condensado? da literatura pertinente, mais para orientar as pesquisas e tendências do que um mero olhar para o passad

Phase stability of the earth-abundant tin sulfides SnS, SnS2, and Sn2S3

The various phases of tin sulfide have been studied as semiconductors since the 1960s and are now being investigated as potential earth-abundant photovoltaic and photocatalytic materials. Of particular note is the recent isolation of zincblende SnS in particles and thin-films. Herein, first-principles calculations are employed to better understand this novel geometry and its place within the tin sulfide multiphasic system. We report the enthalpies of formation for the known phases of SnS, SnS2, and Sn2S3, with good agreement between theory and experiment for the ground-state structures of each. While theoretical X-ray diffraction patterns do agree with the assignment of the zincblende phase demonstrated in the literature, the structure is not stable close to the lattice parameters observed experimentally, exhibiting an unfeasibly large pressure and a formation enthalpy much higher than any other phase. Ab initio molecular dynamics simulations reveal spontaneous degradation to an amorphous phase much lower in energy, as Sn(II) is inherently unstable in a regular tetrahedral environment. We conclude that the known rocksalt phase of SnS has been mis-assigned as zincblende in the recent literature