Mid-infrared passively switched pulsed dual wavelength Ho3+ -doped fluoride fiber laser at 3 μm and 2 μm

Cascade transitions of rare earth ions involved in infrared host fiber provide the potential to generate dual or multiple wavelength lasing at mid-infrared region. In addition, the fast development of saturable absorber (SA) towards the long wavelengths motivates the realization of passively switched mid-infrared pulsed lasers. In this work, by combing the above two techniques, a new phenomenon of passively Q-switched ~3 μm and gain-switched ~2 μm pulses in a shared cavity was demonstrated with a Ho3+-doped fluoride fiber and a specifically designed semiconductor saturable absorber (SESAM) as the SA. The repetition rate of ~2 μm pulses can be tuned between half and same as that of ~3 μm pulses by changing the pump power. The proposed method here will add new capabilities and more flexibility for generating mid-infrared multiple wavelength pulses simultaneously that has important potential applications for laser surgery, material processing, laser radar, and free-space communications, and other areas

Catalytic upgrading of refinery cracked products by trans-hydrogenation: a review

The production of high premium fuel is an issue of priority to every refinery. The trans-hydrogenation process is devised to convert two low valued refinery cracked products to premium products; the conversion processes involve the combination of dehydrogenation and hydrogenation reaction as a single step process. The paper reviews the recent literature on the use of catalysts to convert low value refinery products (i.e. alkanes and alkynes or alkadienes) to alkenes (olefins) by trans-hydrogenation. Catalysts based on VOx, CrOx and Pt all supported on alumina have been used for the process. However, further studies are still required to ascertain the actual reaction mechanism, mitigating carbon deposition and catalyst deactivation, and the role of different catalysts to optimize the reaction desired products

Investigation of MoOx/Al2O3 under Cyclic Operation for Oxidative and Non-Oxidative Dehydrogenation of Propane

A MoOx/Al2O3 catalyst was synthesised and tested for oxidative (ODP) and non-oxidative (DP) dehydrogenation of propane in a reaction cycle of ODP followed by DP and a second ODP run. Characterisation results show that the fresh catalyst contains highly dispersed Mo oxide species in the +6 oxidation state with tetrahedral coordination as [MoVIO4]2− moieties. In situ X-ray Absorption Spectroscopy (XAS) shows that [MoVIO4]2− is present during the first ODP run of the reaction cycle and is reduced to MoIVO2 in the following DP run. The reduced species are partly re-oxidised in the subsequent second ODP run of the reaction cycle. The partly re-oxidised species exhibit oxidation and coordination states that are lower than 6 but higher than 4 and are referred to as MoxOy. These species significantly improved propene formation (relatively 27% higher) in the second ODP run at similar propane conversion activity. Accordingly, the initial tetrahedral [MoVIO4]2− present during the first ODP run of the reaction cycle is active for propane conversion; however, it is unselective for propene. The reduced MoIVO2 species are relatively less active and selective for DP. It is suggested that the MoxOy species generated by the reaction cycle are active and selective for ODP. The vibrational spectroscopic data indicate that the retained surface species are amorphous carbon deposits with a higher proportion of aromatic/olefinic like species

Osteoblastoma of the rib with CT and MR imaging: a case report and literature review

Osteoblastoma is a rare bone tumor which is mostly found in the vertebral column and long bone. We describe a 59-year-old woman with osteoblastoma in the right fifth posterior segment of the rib, whose presenting symptoms were right back pain for two years and awakened at night. Chest computer tomography (CT) and thoracic spine magnetic resonance (MR) imaging findings included an expansile lesion of the right fifth rib and an ossified matrix. Surgical resection of the lesion confirmed a benign osteoblastoma. 12 months follow-up revealed disappearance of right back pain. Rib osteoblastoma in plain film has been described previously; however, to our knowledge this is the only case report emphasized in CT and MR imaging

Kinetic study of the selective hydrogenation of styrene over a Pd egg-shell composite catalyst

This is a study on the kinetics of the liquid-phase hydrogenation of styrene to ethylbenzene over a catalyst of palladium supported on an inorganic–organic composite. This support has a better mechanical resistance than other commercial supports, e.g. alumina, and yields catalysts with egg-shell structure and a very thin active Pd layer. Catalytic tests were carried out in a batch reactor by varying temperature, total pressure and styrene initial concentration between 353–393 K, 10–30 bar, and 0.26–0.60 mol L−1. Kinetic models were developed on the assumptions of dissociative hydrogen chemisorption and non-negligible adsorption of hydrogen and styrene. Final chemical reaction expressions useful for reactor design were obtained. The models that best fitted the experimental data were those ones that considered the surface reaction as the limiting step. In this sense, a two-step Horiuti–Polanyi working mechanism with half hydrogenation intermediates gave the best fit of the experimental data. The heats of adsorption of styrene and ethylbenzene were also estimated.The authors are gratefully indebted to CONICET, ANPCyT and Universidad Nacional del Litoral for financially sponsoring this research work

Assessment of protein allergenicity on the basis of immune reactivity: animal models.

Because of the public concern surrounding the issue of the safety of genetically modified organisms, it is critical to have appropriate methodologies to aid investigators in identifying potential hazards associated with consumption of foods produced with these materials. A recent panel of experts convened by the Food and Agriculture Organization and World Health Organization suggested there is scientific evidence that using data from animal studies will contribute important information regarding the allergenicity of foods derived from biotechnology. This view has given further impetus to the development of suitable animal models for allergenicity assessment. This article is a review of what has been achieved and what still has to be accomplished regarding several different animal models. Progress made in the design and evaluation of models in the rat, the mouse, the dog and in swine is reviewed and discussed

Novel concepts in virally induced asthma

Viruses are the predominant infectious cause of asthma exacerbations in the developed world. In addition, recent evidence strongly suggests that viral infections may also have a causal role in the development of childhood asthma. In this article, we will briefly describe the general perception of how the link between infections and asthma has changed over the last century, and then focus on very recent developments that have provided new insights into the contribution of viruses to asthma pathogenesis. Highlighted areas include the contribution of severe early life viral infections to asthma inception, genetic determinants of severe viral infections in infancy, the differences in innate and adaptive immune system cytokine responses to viral infection between asthmatic and nonasthmatic subjects, and a potential vaccine strategy to prevent severe early life virally-induced illness

The genome sequence of <i>Trypanosoma brucei gambiense</i>, causative agent of chronic Human African Trypanosomiasis

&lt;p&gt;&lt;b&gt;Background:&lt;/b&gt; &lt;i&gt;Trypanosoma brucei gambiense&lt;/i&gt; is the causative agent of chronic Human African Trypanosomiasis or sleeping sickness, a disease endemic across often poor and rural areas of Western and Central Africa. We have previously published the genome sequence of a &lt;i&gt;T. b. brucei&lt;/i&gt; isolate, and have now employed a comparative genomics approach to understand the scale of genomic variation between &lt;i&gt;T. b. gambiense&lt;/i&gt; and the reference genome. We sought to identify features that were uniquely associated with &lt;i&gt;T. b. gambiense&lt;/i&gt; and its ability to infect humans.&lt;/p&gt; &lt;p&gt;&lt;b&gt;Methods and findings:&lt;/b&gt; An improved high-quality draft genome sequence for the group 1 &lt;i&gt;T. b. gambiense&lt;/i&gt; DAL 972 isolate was produced using a whole-genome shotgun strategy. Comparison with &lt;i&gt;T. b. brucei&lt;/i&gt; showed that sequence identity averages 99.2% in coding regions, and gene order is largely collinear. However, variation associated with segmental duplications and tandem gene arrays suggests some reduction of functional repertoire in &lt;i&gt;T. b. gambiense&lt;/i&gt; DAL 972. A comparison of the variant surface glycoproteins (VSG) in &lt;i&gt;T. b. brucei&lt;/i&gt; with all &lt;i&gt;T. b. gambiense&lt;/i&gt; sequence reads showed that the essential structural repertoire of VSG domains is conserved across &lt;i&gt;T. brucei&lt;/i&gt;.&lt;/p&gt; &lt;p&gt;&lt;b&gt;Conclusions:&lt;/b&gt; This study provides the first estimate of intraspecific genomic variation within &lt;i&gt;T. brucei&lt;/i&gt;, and so has important consequences for future population genomics studies. We have shown that the &lt;i&gt;T. b. gambiense&lt;/i&gt; genome corresponds closely with the reference, which should therefore be an effective scaffold for any &lt;i&gt;T. brucei&lt;/i&gt; genome sequence data. As VSG repertoire is also well conserved, it may be feasible to describe the total diversity of variant antigens. While we describe several as yet uncharacterized gene families with predicted cell surface roles that were expanded in number in &lt;i&gt;T. b. brucei&lt;/i&gt;, no &lt;i&gt;T. b. gambiense&lt;/i&gt;-specific gene was identified outside of the subtelomeres that could explain the ability to infect humans.&lt;/p&gt

The predictability of the extratropical stratosphere on monthly time-scales and its impact on the skill of tropospheric forecasts

This is the final version of the article. Available from Wiley via the DOI in this record.Extreme variability of the winter- and spring-time stratospheric polar vortex has been shown to affect extratropical tropospheric weather. Therefore, reducing stratospheric forecast error may be one way to improve the skill of tropospheric weather forecasts. In this review, the basis for this idea is examined. A range of studies of different stratospheric extreme vortex events shows that they can be skilfully forecasted beyond 5 days and into the sub-seasonal range (0–30 days) in some cases. Separate studies show that typical errors in forecasting a stratospheric extreme vortex event can alter tropospheric forecast skill by 5–7% in the extratropics on sub-seasonal time-scales. Thus understanding what limits stratospheric predictability is of significant interest to operational forecasting centres. Both limitations in forecasting tropospheric planetary waves and stratospheric model biases have been shown to be important in this context.This work is supported by the Natural Environmental Research Council (NERC) funded project Stratospheric Network for the Assessment of Predictability (SNAP) (Grant H5147600) and partially supported by the SPARC. ACP and RGH acknowledge funding through the EU ARISE project (Grant 284387) (EU-FP7). We also acknowledge Steven Pawson and Lawrence Coy from NASA for providing Figure 1. We wish to thank Lorenzo Polvani from Columbia University for providing Figure 4 and Amy Butler from NOAA for her contribution to Figure 5. We thank Adrian Simmons of ECMWF for his insightful review and two anonymous reviewers for their comments and suggestions that improved the quality of the manuscript