The impact of Group Intelligence software on enquiry-based learning

Despite the increasing use of groupware technologies in education, there is little evidence of their impact, especially within an enquiry-based learning (EBL) context. In this paper, we examine the use of a commercial standard Group Intelligence software called GroupSystems®ThinkTank. To date, ThinkTank has been adopted mainly in the USA and supports teams in generating ideas, categorising, prioritising, voting and multi-criteria decision-making and automatically generates a report at the end of each session. The software was used by students carrying out an EBL project, set by employers, for a full academic year. The criteria for assessing the impact of ThinkTank on student learning were those of creativity, participation, productivity, engagement and understanding. Data was collected throughout the year using a combination of interviews and questionnaires, and written feedback from employers. The overall findings show an increase in levels of productivity and creativity, evidence of a deeper understanding of their work but some variation in attitudes towards participation in the early stages of the project

Type I superconductivity in the Dirac semimetal PdTe2

The superconductor PdTe$_2$ was recently classified as a Type II Dirac semimetal, and advocated to be an improved platform for topological superconductivity. Here we report magnetic and transport measurements conducted to determine the nature of the superconducting phase. Surprisingly, we find that PdTe$_2$ is a Type I superconductor with $T_c = 1.64$ K and a critical field $\mu_0 H_c (0) = 13.6$ mT. Our crystals also exhibit the intermediate state as demonstrated by the differential paramagnetic effect. For $H > H_c$ we observe superconductivity of the surface sheath. This calls for a close examination of superconductivity in PdTe$_2$ in view of the presence of topological surface states.Comment: 5 page

The Role of Freshwater Mussels in River Bed Dynamics and Sediment Flux

Freshwater mussels have been found capable of improving water quality in river environments by filtering particles from the water column and depositing them on the river bed as pseudofaecal pellets. Growing recognition of the ecosystem services that freshwater mussels provide in river habitats has led to their inclusion in several river restoration projects. The focus of many of these projects in Europe has been on the freshwater pearl mussel, Margaritifera margaritifera with attempts to repopulate rivers with this critically endangered species. However, the very specific habitat requirements of M. margaritifera mean that many European rivers are not suitable environments for this species. In comparison to M. margaritifera, very little conservation effort has been directed at some of our more common, yet declining freshwater mussel species, and little is known about how these species influence river sediments and habitat conditions. Some of the more common European freshwater mussel species, such as Anodonta anatina and A. cygnea are capable of living in a much broader range of habitat conditions compared with M. margaritifera, meaning they could potentially be of benefit in river remediation projects not suitable for M. margaritifera. To improve understanding of how Anodonta species may influence river environments through bioturbation, filtration, and biodeposition, their influence on river sediment characteristics, sediment dynamics, and habitat conditions was investigated in two lowland English rivers and a laboratory-based flume environment. Anodonta anatina and A. cygnea from Markeaton Brook, Derbyshire and the River Sence, Leicestershire were translocated from mussel-dense reaches to locations within each river where mussels were absent. In both rivers, quadrats where mussels had been removed were compared with control quadrats where mussels were present, whilst quadrats at the sites where mussels had been introduced were compared with control quadrats where mussels were absent. At sites in both rivers where mussels had been removed from the river bed, significant decreases in hyporheic oxygen saturation were found in all quadrats, compared with the control quadrats that contained mussels. Half of all quadrats where mussels had been introduced to river sites showed significantly increased hyporheic oxygen saturation, with the remaining quadrats showing non-significant increases compared with the control quadrats without mussels. Grain-size distribution patterns of sediment cores taken from the stream bed indicated that the introduction of mussels to the River Sence increased the textural heterogeneity of the river bed sediment, whereas removal of mussels reduced textural heterogeneity of the river bed sediment. No significant differences in river bed textural heterogeneity were found in Markeaton Brook. Mean percentages of organic matter, inorganic carbon, and fine-grained sediment were not significantly affected by the presence of mussels in the majority of quadrats. Significant reductions in water turbidity were found in Markeaton Brook, where mussels were introduced, but no significant differences in turbidity were found in the River Sence. Significantly higher BMWP scores were found where mussels were present in the River Sence but differences in Markeaton Brook were non-significant. The variation in results between the river sites suggest that the extent to which freshwater mussels influence river bed conditions and water quality may be mussel density-dependent and site-specific. A recirculating flume-based study using fifty A. anatina investigated the impact of this species on substrate characteristics, hydrological conditions, and particle flux of a polymodal substrate. River seston was added to the flume at weekly intervals to provide food for the mussels, and water and substrate conditions were monitored for the eight-week duration of the study. A control experiment was also set up with mussels absent from the flume. It was found that the presence of A. anatina led to reduced near-bed, 0.6 depth and 0.4 depth velocities, and reduced suspended and dissolved solids in the water column. Anodonta anatina reduced the entrainment of fine and organic material but increased the entrainment of sand and gravel compared with the control study. Although water velocities were reduced with mussels in the flume, calculations based on the grain-sizes entrained into the flume’s sediment trap indicated that critical boundary shear stresses were significantly increased with mussels in the flume. Additionally, sediment grain-size distribution patterns and topographical measurements of the substrate surface indicated that the mussels increased the heterogeneity of the substrate. The results of the research described in this thesis indicate that bioturbation, filtration and biodeposition by Anodonta species may positively influence hyporheic oxygen saturation levels, water quality and habitat heterogeneity in river environments. Increased mixing and mobilisation of river bed sediment, and the transferral of material from the water column to the substrate by mussels implies they constitute a critical element in the sediment and nutrient dynamics of fluvial systems

Electric‐field dependence of interband transitions in In_(0.53)Ga_(0.47)As/In_(0.52)Al_(0.48)As single quantum wells by room‐temperature electrotransmittance

Room‐temperature electrotransmittance has been used in order to investigate the interband excitonic transitions in a 250‐Å‐thick In_(0.53)Ga_(0.47)As/In_(0.52)Al_(0.48)As single‐quantum‐well system as a function of an externally applied electric field. Parity forbidden transitions, involving conduction‐band states with quantum numbers up to n=5, which become more pronounced at high electric fields were observed. The ground‐state and the forbidden transitions showed a significant red shift due to the quantum confined Stark effect. A comparison with previously reported results on thinner InGaAs/InAlAs quantum wells indicated that the wide‐well sample exhibits the largest shift, as expected from theory. Despite the appreciable Stark shift, the rather large, field‐induced linewidth broadening and the relatively low electric field at which the ground‐state exciton is ionized poses limitations on using this wide‐quantum‐well system for electro‐optic applications

Muon spin rotation study of the topological superconductor SrxBi2Se3

We report transverse-field (TF) muon spin rotation experiments on single crystals of the topological superconductor Sr$_x$Bi$_2$Se$_3$ with nominal concentrations $x=0.15$ and $0.18$ ($T_c \sim 3$ K). The TF spectra ($B= 10$ mT), measured after cooling to below $T_c$ in field, did not show any additional damping of the muon precession signal due to the flux line lattice within the experimental uncertainty. This puts a lower bound on the magnetic penetration depth $\lambda \geq 2.3 ~\mu$m. However, when we induce disorder in the vortex lattice by changing the magnetic field below $T_c$ a sizeable damping rate is obtained for $T \rightarrow 0$. The data provide microscopic evidence for a superconducting volume fraction of $\sim 70~ \%$ in the $x=0.18$ crystal and thus bulk superconductivity.Comment: 6 pages, includes 4 figure

Superconductivity under pressure in the Dirac semimetal PdTe2

The Dirac semimetal PdTe$_2$ was recently reported to be a type-I superconductor ($T_c =$1.64 K, $\mu_0 H_c (0) = 13.6$ mT) with unusual superconductivity of the surface sheath. We here report a high-pressure study, $p \leq 2.5$ GPa, of the superconducting phase diagram extracted from ac-susceptibility and transport measurements on single crystalline samples. $T_c (p)$ shows a pronounced non-monotonous variation with a maximum $T_c =$1.91 K around 0.91 GPa, followed by a gradual decrease to 1.27 K at 2.5 GPa. The critical field of bulk superconductivity in the limit $T \rightarrow 0$, $H_c(0,p)$, follows a similar trend and consequently the $H_c(T,p)$-curves under pressure collapse on a single curve: $H_c(T,p)=H_c(0,p)[1-(T/T_c(p))^2]$. Surface superconductivity is robust under pressure as demonstrated by the large superconducting screening signal that persists for applied dc-fields $H_a > H_c$. Surprisingly, for $p \geq 1.41$ GPa the superconducting transition temperature at the surface $T_c^S$ is larger than $T_c$ of the bulk. Therefore surface superconductivity may possibly have a non-trivial nature and is connected to the topological surface states detected by ARPES. We compare the measured pressure variation of $T_c$ with recent results from band structure calculations and discuss the importance of a Van Hove singularity.Comment: manuscript 9 pages with 8 figures + supplemental material 3 pages with 6 figure

Limits of flexural wave absorption by open lossy resonators: reflection and transmission problems

The limits of flexural wave absorption by open lossy resonators are analytically and numerically reported in this work for both the reflection and transmission problems. An experimental validation for the reflection problem is presented. The reflection and transmission of flexural waves in 1D resonant thin beams are analyzed by means of the transfer matrix method. The hypotheses, on which the analytical model relies, are validated by experimental results. The open lossy resonator, consisting of a finite length beam thinner than the main beam, presents both energy leakage due to the aperture of the resonators to the main beam and inherent losses due to the viscoelastic damping. Wave absorption is found to be limited by the balance between the energy leakage and the inherent losses of the open lossy resonator. The perfect compensation of these two elements is known as the critical coupling condition and can be easily tuned by the geometry of the resonator. On the one hand, the scattering in the reflection problem is represented by the reflection coefficient. A single symmetry of the resonance is used to obtain the critical coupling condition. Therefore the perfect absorption can be obtained in this case. On the other hand, the transmission problem is represented by two eigenvalues of the scattering matrix, representing the symmetric and anti-symmetric parts of the full scattering problem. In the geometry analyzed in this work, only one kind of symmetry can be critically coupled, and therefore, the maximal absorption in the transmission problem is limited to 0.5. The results shown in this work pave the way to the design of resonators for efficient flexural wave absorption