Two-year field study on the emission of N2O from coarse and middle-textured Belgian soils with different land use

In the following study N₂O emissions from 3 different grasslands and from 3 different arable lands, representing major agriculture areas with different soil textures and normal agricultural practices in Belgium, have been monitored for 1 to 2 years. One undisturbed soil under deciduous forest was also included in the study. Nitrous oxide emission was measured directly in the field from vented closed chambers through photo-acoustic infrared detection. Annual N₂O emissions from the arable lands ranged from 0.3 to 1.5 kg N ha⁻¹ y⁻¹ and represent 0.3 to 1.0% of the fertilizer N applied. Annual N₂O emissions from the intensively managed grasslands and an arable land sown with grass were significantly larger than those from the cropped arable lands. Emissions ranged from 14 to 32 kg N ha⁻¹ y⁻¹, representing fertilizer N losses between 3 and 11%. At the forest soil a net N₂O uptake of 1.3 kg N₂O-N ha⁻¹ was recorded over a 2-year period. It seems that the N₂O-N loss per unit of fertilizer N applied is larger for intensively managed and heavily fertilized (up to 500 kg N ha⁻¹) grasslands than for arable lands and is substantially larger than the 1.25% figure used for the global emission inventory. Comparison of the annual emission fluxes from the different soils also indicated that land use rather than soil properties influenced the N₂O emission. Our results also show once again the importance of year-round measurements for a correct estimate of N₂O losses from agricultural soils: 7 to 76% of the total annual N₂O was emitted during the winter period (October–February). Disregarding the emission during the off-season period can lead to serious underestimation of the actual annual N₂O flux. This revised version was published online in August 2006 with corrections to the Cover Date.     

Redesigning the active site of Geotrichum candidum lipase

Attempts to engineer enzymes with unique catalytic propertieshave largely focused on altering the existing specificitiesby reshaping the substrate binding pockets. Few experimentshave aimed at modifying the configuration of the residues essentialfor catalysis. The difference in the topological location ofthe triad acids of Geotrichum candidum lipase (GCL) and thecatalytic domain of human pancreatic lipase (HPL), despite greatsimilarities in their topologies and 3-D structures, suggestthat these are related enzymes whose catalytic triads have beenrearranged in the course of evolution (Schrag et aL, 1992).In this study we prepared a double mutant GCL in which the catalytictriad acid is shifted to the position equivalent to the locationof the triad acid of HPL. The double mutant maintains 10% ofthe wild type activity against triglycerides and the fluorogenicester 4-methylumbelliferyl-oleate. The only significant differencesbetween the 3-D structures of the double mutant and wild typeGCL are at the mutated sites. Even the water structure in theregion of the triad is unchanged. The hydrogen bonding patternof the catalytic triad of the double mutant is very similarto that of pancreatic lipase. The acid of the double mutantis stabilized by only two hydrogen bonds, whereas three hydrogenbonds are observed in the wild type enzyme. These results stronglysupport the hypothesis that the pancreatic Upases are evolutionaryswitchpoints between the two observed arrangements of the catalytictriads supported by the /ß hydrolase fold and suggestthat this fold provides a stable protein core for engineeringenzymes with unique catalytic properties.     

Long-Term Follow-up of HPV Infection Using Urine and Cervical Quantitative HPV DNA Testing

The link between infection with high-risk human papillomavirus (hrHPV) and cervical cancer has been clearly demonstrated. Virological end-points showing the absence of persistent HPV infection are now accepted as a way of monitoring the impact of prophylactic vaccination programs and therapeutic vaccine trials. This study investigated the use of urine samples, which can be collected by self-sampling at home, instead of cervical samples for follow-up of an HPV intervention trial. Eighteen initially HPV DNA-positive women participating in an HPV therapeutic vaccine trial were monitored during a three-year follow-up period. A total of 172 urine samples and 85 cervical samples were collected. We obtained a paired urine sample for each of the 85 cervical samples by recovering urine samples from six monthly gynaecological examinations. We performed a small pilot study in which the participating women used a urine collection device at home and returned their urine sample to the laboratory by mail. All samples were analyzed using quantitative real-time HPV DNA PCR. A good association (κ value of 0.65) was found between the presence of HPV DNA in urine and a subsequent cervical sample. Comparisons of the number of HPV DNA copies in urine and paired cervical samples revealed a significant Spearman rho of 0.676. This correlation was superior in women with severe lesions. The HPV DNA results of the small pilot study based on self-collected urine samples at home are consistent with previous and subsequent urine and/or cervical results. We demonstrated that urine sampling may be a valid alternative to cervical samples for the follow-up of HPV intervention trials or programs. The potential clinical value of urine viral load monitoring should be further investigated.     

Second-generation octarellins: two new de novo ({beta}/{alpha})8 polypeptides designed for investigating the influence of {beta}-residue packing on the {alpha}/{beta}-barrel structure stability

The sequence of octarellin I, the first de novo (ß/)₈polypeptide, was revised according to several criteria, amongothers the symmetry of the sequence, ß-residue volumeand hydrophobicity, and charge distribution. These considerationsand the overall conclusions drawn from the first design ledto two new sequences, corresponding to octarellins II and III.Octarellin II retains perfect 8-fold symmetry. Octarellin IIIhas the same sequence as octarellin II, except for the ß-strandswhich exhibit a 4-fold symmetry. The two proteins were producedin Escherichia coli. Infrared and CD spectral analyses of octarellinsII and III reveal a high secondary structure content. Non-denaturinggel electrophoresis, molecular sieve chromatography and analyticalultracentrifugation suggest that both of these second-generationartificial polypeptides exist as a mixture of a monomer anda dimer form. Octarellins II and III are at least 10 times moresoluble than octarellin I. Ureainduced unfolding followed byfluorescence emission suggests that the tryptophan residues,designed to be buried in the (ß/)₈, are indeed packedin the hydrophobic core of both proteins. However, octarellinIII displays a higher stability towards urea denaturation, indicatingthat introducing 4-fold symmetry into the ß-barrelmight be important for stability of the overall folding.     

Cumulative energy demand for small molecule and polymer photovoltaics

Organic photovoltaics (OPVs) are expected to be a low cost, environmentally friendly energy solution with advantageous properties such as flexibility and light weight that enable their use in new applications. Considerable progress in power conversion efficiencies has brought OPV technology closer to commercialization. However, little consideration has been given to potential environmental impact associated with their production. Although environmental life cycle studies of OPV exist, their scope is narrow or too reliant on outdated technologies. Some of the most significant recent improvements are the result of new semiconductors materials, which have not yet been assessed from a life cycle perspective. Therefore, this study calculates life cycle embodied energy for 15 new materials encompassing a variety of donor, acceptor, and interface compounds showing the most promise in organic electronics. With the use of new inventory data, life cycle energy impact associated with production of both single junction and multi‐junction architectures has been calculated including bulk heterojunction polymer, planar small molecule, and planar‐mixed small molecule devices. The cumulative energy demand (CED) required to fabricate small molecule and polymer photovoltaics were found to be similar from 2.9 to 5.7 MJ/Wp. This CED is on average of 50% less than for conventional inorganic photovoltaics, motivating the continued development of both technologies. The use of fullerenes was shown to have a dramatic impact on polymer solar cells, comprising 18–30% of the CED, despite only being present in small quantities. Increases in device efficiency are shown to marginally reduce CED for both small molecule and polymer designs. Copyright © 2012 John Wiley & Sons, Ltd.     

Photonics based on carbon nanotubes

Among direct-bandgap semiconducting nanomaterials, single-walled carbon nanotubes (SWCNT) exhibit strong quasi-one-dimensional excitonic optical properties, which confer them a great potential for their integration in future photonics devices as an alternative solution to conventional inorganic semiconductors. In this paper, we will highlight SWCNT optical properties for passive as well as active applications in future optical networking. For passive applications, we directly compare the efficiency and power consumption of saturable absorbers (SAs) based on SWCNT with SA based on conventional multiple quantum wells. For active applications, exceptional photoluminescence properties of SWCNT, such as excellent light-emission stabilities with temperature and excitation power, hold these nanometer-scale materials as prime candidates for future active photonics devices with superior performances.     

Experimental and theoretical approaches to the study of TMI-zeolite (TM = Fe, Co, Cu)

Transition metal ions in zeolites TMI-zeolite (TM = Fe, Co, Cu) attract great attention due to their potentialities as catalysts. In the recent years, the high efficiency of TMI-zeolites for the selective catalytic reduction (SCR) of contaminated flue gases has been demonstrated. It has been shown that the structure of the framework, the nature and location of extraframework cation species play a fundamental role in the process. Experimental results based on spectroscopies, as well as on reactivity studies have led to valuable insights about the structure of cationic sites as well as about the active species involved during the catalytic reactions. However, it is not sufficient to obtain all this information. This review reporting density functional theory (DFT) calculations shows that a molecular approach is very useful and has become an indispensable tool for the determination of the geometries, the electronic structures, the spectroscopic properties and the reactivity of TMI-zeolites.     

Influence of oxygen on phase transformations in a Ti-48 At. pct Al alloy

The composition and structure of Ti-48 at. pct Al alloys with various oxygen contents, quenched from a homogeneous α state, have been studied by means of one-dimensional atom-probe (1DAP) and transmission electron microscopy (TEM) analysis. Two regimes are observed. The change from one regime to the other depends on the global oxygen content. If the oxygen content is lower than 1.2 at. pct, the α→γ _m massive transformation is involved during the quench. The alloys, hence, exhibit massive γ _m-structure regions and regions having a two-phase (α ₂+γ) ultrafine lamellar structure. Very thin α ₂ plates, saturated with oxygen, are observed in γ _m regions. The precipitation of these α ₂ plates is promoted by excess oxygen in the γ _m structure. Within ultra-fine lamellar-structure regions, oxygen is concentrated in α ₂ lamellae (not saturated with oxygen) and is found to be responsible for the high volume fraction of α ₂ phase. When the oxygen content is larger than 1.2 at. pct, the massive transformation is suppressed and the ultrafine lamellar structure is only observed in quenched samples. Analysis of the α → α ₂ chemical ordering in the classical lamellar structure, formed within the (α+γ) dual-phase field, shows that high oxygen contents favor the chemical-ordering reaction of α phase at high temperatures (e.g., 1423 and 1523 K). It has, hence, been inferred that, above 1.2 at. pct O, the α → γ _m massive transformation is suppressed and replaced by the α → α ₂+y transformation paths. This article is based on a presentation made in the symposium entitled “Fundamentals of Structural Intermetallics,” presented at the 2002 TMS Annual Meeting, February 21–27, 2002, in Seattle, Washington, under the auspices of the ASM and TMS Joint Committee on Mechanical Behavior of Materials.     

Worker flexibility and its perceived contribution to performance: The moderating role of task characteristics

This study examined the relationship between worker flexibility in team‐based work and its perceived contribution to efficiency, work quality, and innovation, and the moderating role of task autonomy, skill utilization, and task monotony. Four‐hundred ninety‐four employees from 113 teams in 15 organizations completed and returned questionnaires. Skill utilization proved to be positively related to perceived contribution of flexibility to efficiency, work quality, and innovation. Furthermore, skill utilization strengthened the positive relationships between worker flexibility and its perceived contribution to efficiency and work quality and weakened the negative relationship between worker flexibility and its perceived impact on innovation. Task monotony was negatively related to the perceived quality benefits of being flexible. In addition, it weakened the positive relationship between worker flexibility and its perceived contribution to both efficiency and quality and strengthened the negative relationship with the perceived impact of flexibility on innovation. Task autonomy was positively related to the perceived contribution of flexibility to innovation and weakened the negative relationship between worker flexibility and the perceived innovation benefits of being flexible. The authors conclude that skill utilization and lack of monotony are important issues in relation to worker flexibility on all performance objectives that were considered, whereas task autonomy seems especially relevant when innovation is a key issue. © 2007 Wiley Periodicals, Inc. Hum Factors Man 17: 117–135, 2007.