Cluster size dependence of high-order harmonic generation

We investigate high-order harmonic generation (HHG) from noble gas clusters in a supersonic gas jet. To identify the contribution of harmonic generation from clusters versus that from gas monomers, we measure the high-order harmonic output over a broad range of the total atomic number density in the jet (from 3*10^16 cm^{-3} to 3x10^18 cm{-3}) at two different reservoir temperatures (303 K and 363 K). For the firrst time in the evaluation of the harmonic yield in such measurements, the variation of the liquid mass fraction, g, versus pressure and temperature is taken into consideration, which we determine, reliably and consistently, to be below 20% within our range of experimental parameters. By comparing the measured harmonic yield from a thin jet with the calculated corresponding yield from monomers alone, we find an increased emission of the harmonics when the average cluster size is less than 3000. Using g, under the assumption that the emission from monomers and clusters add up coherently, we calculate the ratio of the average single-atom response of an atom within a cluster to that of a monomer and find an enhancement of around 10 for very small average cluster size (~200). We do not find any dependence of the cut-off frequency on the composition of the cluster jet. This implies that HHG in clusters is based on electrons that return to their parent ions and not to neighbouring ions in the cluster. To fully employ the enhanced average single-atom response found for small average cluster sizes (~200), the nozzle producing the cluster jet must provide a large liquid mass fraction at these small cluster sizes for increasing the harmonic yield. Moreover, cluster jets may allow for quasi-phase matching, as the higher mass of clusters allows for a higher density contrast in spatially structuring the nonlinear medium.Comment: 16 pages, 6 figure

Field assessment of guar gum stabilized microscale zerovalent iron particles for in-situ remediation of 1,1,1-trichloroethane

A pilot injection test with guar gum stabilized microscale zerovalent iron (mZVI) particles was performed at test site V (Belgium) where different chlorinated aliphatic hydrocarbons (CAHs) were present as pollutants in the subsurface. One hundred kilograms of 56 μm-diameter mZVI (~ 70 g/L) was suspended in 1.5 m3 of guar gum (~ 7 g/L) solution and injected into the test area. In order to deliver the guar gum stabilized mZVI slurry, one direct push bottom-up injection (Geoprobe) was performed with injections at 5 depths between 10.5 and 8.5 m bgs. The direct push technique was preferred above others (e.g. injection at low flow rate via screened wells) because of the limited hydraulic conductivity of the aquifer, and to the large size of the mZVI particles. A final heterogeneous distribution of the mZVI in the porous medium was observed explicable by preferential flow paths created during the high pressure injection. The maximum observed delivery distance was 2.5 m. A significant decrease in 1,1,1-TCA concentrations was observed in close vicinity of spots where the highest concentration of mZVI was observed. Carbon stable isotope analysis (CSIA) yielded information on the success of the abiotic degradation of 1,1,1-TCA and indicated a heterogeneous spatio-temporal pattern of degradation. Finally, the obtained results show that mZVI slurries stabilized by guar gum can be prepared at pilot scale and directly injected into low permeable aquifers, indicating a significant removal of 1,1,1-TCA

Development of a Multiphoton Fluorescence Lifetime Imaging Microscopy (FLIM) system using a Streak Camera

We report the development and detailed calibration of a multiphoton fluorescence lifetime imaging system (FLIM) using a streak camera. The present system is versatile with high spatial (0.2 micron) and temporal (50 psec) resolution and allows rapid data acquisition and reliable and reproducible lifetime determinations. The system was calibrated with standard fluorescent dyes and the lifetime values obtained were in very good agreement with values reported in literature for these dyes. We also demonstrate the applicability of the system to FLIM studies in cellular specimens including stained pollen grains and fibroblast cells expressing green fluorescent protein. The lifetime values obtained matched well with those reported earlier by other groups for these same specimens. Potential applications of the present system include the measurement of intracellular physiology and Fluorescence Resonance Energy Transfer (FRET) imaging which are discussed in the context of live cell imaging

On the determinants of local government debt: Does one size fit all?

This paper analyzes the factors that directly influence levels of debt in Spanish local governments. Specifically, the main objective is to find out the extent to which indebtedness is originated by controllable factors that public managers can influence, or whether it hinges on other variables beyond managers’ control. The importance of this issue has intensified since the start of the crisis in 2007, due to the abrupt decline of revenues and, simultaneously, to the stagnation (or even increase) in the levels of costs facing these institutions face. Results can be explored from multiple perspectives, given that the set of explanatory factors is also multiple. However, the most interesting result relates to the varying effect of each covariate depending on each municipality’s specific debt level, which suggests that economic policy recommendations should not be homogeneous across local governments

Examining the human infectious reservoir for Plasmodium falciparum malaria in areas of differing transmission intensity.

A detailed understanding of the human infectious reservoir is essential for improving malaria transmission-reducing interventions. Here we report a multi-regional assessment of population-wide malaria transmission potential based on 1209 mosquito feeding assays in endemic areas of Burkina Faso and Kenya. Across both sites, we identified 39 infectious individuals. In high endemicity settings, infectious individuals were identifiable by research-grade microscopy (92.6%; 25/27), whilst one of three infectious individuals in the lowest endemicity setting was detected by molecular techniques alone. The percentages of infected mosquitoes in the different surveys ranged from 0.05 (4/7716) to 1.6% (121/7749), and correlate positively with transmission intensity. We also estimated exposure to malaria vectors through genetic matching of blood from 1094 wild-caught bloodfed mosquitoes with that of humans resident in the same houses. Although adults transmitted fewer parasites to mosquitoes than children, they received more mosquito bites, thus balancing their contribution to the infectious reservoir

Calmodulin Interaction with hEAG1 Visualized by FRET Microscopy

BACKGROUND: Ca(2+)-mediated regulation of ion channels provides a link between intracellular signaling pathways and membrane electrical activity. Intracellular Ca(2+) inhibits the voltage-gated potassium channel EAG1 through the direct binding of calmodulin (CaM). Three CaM binding sites (BD-C1: 674-683, BD-C2: 711-721, BD-N: 151-165) have been identified in a peptide screen and were proposed to mediate binding. The participation of the three sites in CaM binding to the native channel, however, remains unclear. METHODOLOGY/PRINCIPAL FINDINGS: Here we studied the binding of Ca(2+)/CaM to the EAG channel by visualizing the interaction between YFP-labeled CaM and Cerulean-labeled hEAG1 in mammalian cells by FRET. The results of our cellular approach substantiate that two CaM binding sites are predominantly involved; the high-affinity 1-8-14 based CaM binding domain in the N-terminus and the second C-terminal binding domain BD-C2. Mutations at these sites completely abolished CaM binding to hEAG1. CONCLUSIONS/SIGNIFICANCE: We demonstrated that the BD-N and BD-C2 binding domains are sufficient for CaM binding to the native channel, and, therefore, that BD-C1 is unable to bind CaM independently

Successful learning: balancing self-regulation with instructional planning

Many recent studies have stressed the importance of teacher candidates’ (TCs) self-regulated learning (SRL) skills for successful learning. Because of the promising consequences of SRL for academic performance, teacher educators (TEs) are encouraged to increase TCs’ SRL opportunities in educational programs. Because of the difficulty and complexity for TEs to successfully guide TCs towards SRL, the present study contributes to the discussion how to best facilitate TEs in finding a balance between student- and teacher-control. For this purpose, a conceptual model is presented. The model draws upon literature related to the perspective of the learner, the teacher and the learning task. Besides the context of teacher education, the model is beneficial for higher education as well as teaching and teacher professionalization. It will help instructors provide a more balanced approach between teacherand student-controlled learning, and support students develop essential SRL skills

Characteristics of general practice care: What do senior citizens value? A qualitative study

<p>Abstract</p> <p>Background</p> <p>In view of the increasing number of senior citizens in our society who are likely to consult their GP with age-related health problems, it is important to identify and understand the preferences of this group in relation to the non-medical attributes of GP care. The aim of this study is to improve our understanding about preferences of this group of patients in relation to non-medical attributes of primary health care. This may help to develop strategies to improve the quality of care that senior citizens receive from their GP.</p> <p>Methods</p> <p>Semi-structured interviews (N = 13) with senior citizens (65-91 years) in a judgement sample were recorded and transcribed verbatim. The analysis was conducted according to qualitative research methodology and the frame work method.</p> <p>Results</p> <p>Continuity of care providers, i.e. GP and practice nurses, GPs' expertise, trust, free choice of GP and a kind open attitude were highly valued. Accessibility by phone did not meet the expectations of the interviewees. The interviewees had difficulties with the GP out-of-office hours services. Spontaneous home visits were appreciated by some, but rejected by others. They preferred to receive verbal information rather than collecting information from leaflets. Distance to the practice and continuity of caregiver seemed to conflict for respondents.</p> <p>Conclusions</p> <p>Preferences change in the process of ageing and growing health problems. GPs and their co-workers should be also aware of the changing needs of the elderly regarding non-medical attributes of GP care. Meeting their needs regarding non-medical attributes of primary health care is important to improve the quality of care.</p

Sensitive Detection of p65 Homodimers Using Red-Shifted and Fluorescent Protein-Based FRET Couples

BACKGROUND: Fluorescence Resonance Energy Transfer (FRET) between the green fluorescent protein (GFP) variants CFP and YFP is widely used for the detection of protein-protein interactions. Nowadays, several monomeric red-shifted fluorescent proteins are available that potentially improve the efficiency of FRET. METHODOLOGY/PRINCIPAL FINDINGS: To allow side-by-side comparison of several fluorescent protein combinations for detection of FRET, yellow or orange fluorescent proteins were directly fused to red fluorescent proteins. FRET from yellow fluorescent proteins to red fluorescent proteins was detected by both FLIM and donor dequenching upon acceptor photobleaching, showing that mCherry and mStrawberry were more efficient acceptors than mRFP1. Circular permutated yellow fluorescent protein variants revealed that in the tandem constructs the orientation of the transition dipole moment influences the FRET efficiency. In addition, it was demonstrated that the orange fluorescent proteins mKO and mOrange are both suitable as donor for FRET studies. The most favorable orange-red FRET pair was mKO-mCherry, which was used to detect homodimerization of the NF-kappaB subunit p65 in single living cells, with a threefold higher lifetime contrast and a twofold higher FRET efficiency than for CFP-YFP. CONCLUSIONS/SIGNIFICANCE: The observed high FRET efficiency of red-shifted couples is in accordance with increased Förster radii of up to 64 A, being significantly higher than the Förster radius of the commonly used CFP-YFP pair. Thus, red-shifted FRET pairs are preferable for detecting protein-protein interactions by donor-based FRET methods in single living cells