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For test scores to be used to appropriately inform decision-making, and for the associated academic practice opportunities afforded during testing to benefit students, it is critical that students put forth sufficient effort and engagement during testing sessions. Existing research highlights that a substantial proportion of students may disengage during large-scale testing, and that this can be due to anxiety, difficulties sustaining attention, and/or low motivation. These reasons may vary by individual student and by the magnitude of test stakes attached to test scores. The universal design aspect of "multiple means of engagement" is described as a framework to inform the development and application of test engagement strategies for improving student test engagement. Various associated strategies that could be applied to improve student test engagement are described and situated as part of a multi-tiered approach. In addition, considerations for promoting student test engagement in the future by embedding targeted features within test program design are highlighted.

Since their first demonstration in 2001 [Gol'tsman et al., Appl. Phys. Lett. 79, 705–707 (2001)], superconducting-nanowire single-photon detectors (SNSPDs) have witnessed two decades of great developments. SNSPDs are the detector of choice in most modern quantum optics experiments and are slowly finding their way into other photon-starved fields of optics. Until now, however, in nearly all experiments, SNSPDs were used as "binary" detectors, meaning that they could only distinguish between 0 and > = 1 photons, and photon number information was lost. Recent research has demonstrated proof-of-principle photon-number resolution (PNR) SNSPDs counting 2–5 photons. The photon-number-resolving capability is highly demanded in various quantum-optics experiments, including Hong–Ou–Mandel interference, photonic quantum computing, quantum communication, and non-Gaussian quantum state preparation. In particular, PNR detectors at the wavelength range of 850–950 nm are of great interest due to the availability of high-quality semiconductor quantum dots (QDs) [Heindel et al., Adv. Opt. Photonics 15, 613–738 (2023)] and high-performance cesium-based quantum memories [Ma et al., J. Opt. 19, 043001 (2017)]. In this paper, we demonstrate NbTiN-based SNSPDs with >94% system detection efficiency, sub-11 ps timing jitter for one photon, and sub-7 ps for 2 photons. More importantly, our detectors resolve up to 7 photons using conventional cryogenic electric readout circuitry. Through theoretical analysis, we show that the PNR performance of demonstrated detectors can be further improved by enhancing the signal-to-noise ratio and bandwidth of our readout circuitry. Our results are promising for the future of optical quantum computing and quantum communication. [ABSTRACT FROM AUTHOR]

Single photon detectors are indispensable tools in optics, from fundamental measurements to quantum information processing. The ability of superconducting nanowire single photon detectors (SNSPDs) to detect single photons with unprecedented efficiency, short dead time, and high time resolution over a large frequency range enabled major advances in quantum optics. However, combining near-unity system detection efficiency (SDE) with high timing performance remains an outstanding challenge. In this work, we fabricated novel SNSPDs on membranes with 99.5 − 2.07 + 0.5 % SDE at 1350 nm with 32 ps timing jitter (using a room-temperature amplifier), and other detectors in the same batch showed 94%–98% SDE at 1260–1625 nm with 15–26 ps timing jitter (using cryogenic amplifiers). The SiO2/Au membrane enables broadband absorption in small SNSPDs, offering high detection efficiency in combination with high timing performance. With low-noise cryogenic amplifiers operated in the same cryostat, our efficient detectors reach a timing jitter in the range of 15–26 ps. We discuss the prime challenges in optical design, device fabrication, and accurate and reliable detection efficiency measurements to achieve high performance single photon detection. As a result, the fast developing fields of quantum information science, quantum metrology, infrared imaging, and quantum networks will greatly benefit from this far-reaching quantum detection technology. [ABSTRACT FROM AUTHOR]

Superconducting Nanowire Single Photon Detectors (SNSPDs) based on Nb0.15Re0.85 disordered nanowires are developed. The devices have a meander structure of wires 50 – 100 nm wide and cover a circular detection area with a diameter of about 10–16 μm. The main figures of merit of the detectors are extracted from a flood illumination process at 2.8 K, featuring a saturated internal efficiency up to λ = 1301 nm, recovery times between about 8 and 19 ns, and a jitter of about 35 ps. These results confirm that Nb0.15Re0.85 is a promising candidate for the realization of fast SNSPDs, as recently suggested. [ABSTRACT FROM AUTHOR]

We used molecular dynamics and the empirical potential for carbon LCBOPII to simulate the nucleation/growth process of carbon clusters both in vacuum and under pressure. In vacuum, our results show that the growth process is homogeneous and yields mainly sp2 structures such as fullerenes. We used an argon gas and Lennard–Jones potentials to mimic the high pressures and temperatures reached during the detonation of carbon-rich explosives. We found that these extreme thermodynamic conditions do not affect substantially the topologies of the clusters formed in the process. However, our estimation of the growth rates under pressure are in much better agreement with the values estimated experimentally than our vacuum simulations. The formation of sp3 carbon was negligible both in vacuum and under pressure which suggests that larger simulation times and cluster sizes are needed to allow the nucleation of nanodiamonds. [ABSTRACT FROM AUTHOR]

Using a crossed molecular-beam technique, electron transfer is studied in collisions of fast potassium atoms with benzene and fluorobenzene molecules. The negative fragment ions formed in the collision region are extracted by a pulsed voltage, and their masses and energy release distributions analyzed by a time-of-flight (TOF) method. The dominant fragment from C6H5F is F-. The phenyl ring fragments CH- and C2H- are also observed but with lower intensities. In the case of C6H6 the dominant anionic specie is C2H-. The kinetic-energy release distributions of the various fragments are derived from the width and shapes of the TOF peaks in the spectrum. [ABSTRACT FROM AUTHOR]

The lattice Monte Carlo (MC) model for binary crystal growth is considered to induce a freedom of choice in the transition probabilities, as the thermodynamic properties of the system does not ensure an agreement between MC simulations and the thermodynamic constraints. The analysis confirms that the kinetics have an extremely strong effect on the segregation of such models and hence also enables a straightforward determination of the optimal set of transition probabilities.

Analyzes the scattering of CF[sup +] and CF[sup +][sub 2] ions from a perfluoropolyether on the basis of the conservation laws of energy and momentum. Conservation of momentum and energy; Energy partitioning; Treatment of ion-surface collisions as binary collisions between the primary ions and a representative group of the perfluoropolyether molecule.

Ionic species obtained by electron impact on (OCS)n clusters produced by expansion of OCS mixed with argon at two different (OCS/argon) concentrations are studied as a function of stagnation pressure and electron energy. Ionization efficiency curves of homogeneous cluster ions (OCS)+n, homogeneous sulfur cluster ions S+m and inhomogeneous ions (OCS)nS+m are analyzed. Several reactions paths, ending in S+m, have been identified. The strong correlation between reaction path and cluster size is discussed. Finally, by minimization of the potential function created by dipole–dipole, dipole–quadrupole, and quadrupole–quadrupole interactions between OCS molecules, we propose the geometrical configurations of neutral (OCS)n (n=2–5) clusters. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

In this paper we report on complementary measurements on ion-pair formation in collisions between K atoms and CH3NO2 molecules. The experiments were performed in a c.m. energy range from 20 up to 300 eV. Double differential cross sections were obtained by measuring the K+ ion yield as a function of the scatter angle and as a function of the post-collision laboratory energy. On the other hand, relative total partial cross sections for the formation of CH3NO-2, NO-2, and O- were measured in the same energy range. The experimental results lead to the conclusion that in this energy range electron transfer takes place to three ionic states of CH3NO-2, a dominantly repulsive 2A1 state and two 2B1 states with relatively deep potential wells. [ABSTRACT FROM AUTHOR]

Using translational spectroscopy we have studied the d 1Πg and C 3 Πg Rydberg states of O2 . The dissociation of the vibrational levels v=0–2 to all energetically accessible dissociation limits has been followed. The dissociation pathways directly reflect the predissociation mechanisms involved. For the d 1 Πg Rydberg state competition between predissociation by a 3 Πg valence state, due to singlet–triplet mixing, and by a 1 Πg valence state has been observed. Using the Fermi golden rule the observed vibrationally dependent competition is reproduced, corroborating the positions of the lower 1 Πg and 3 Πg valence state curves and yielding various coupling strengths. [ABSTRACT FROM AUTHOR]

Predissociation of the higher vibrational states (v=4–8) of the d 1Πg Rydberg state is investigated experimentally using translational spectroscopy. These states predissociate to the O(1D)+O(1D) dissociation limit. Individual rotational levels of the v=4 state are observed for the first time, and the energies and rotational constants for both 16O2 and 18O2 isotopes are established. The observed predissociation behavior and natural linewidths are explained by invoking both Rydberg–valence and valence–valence interactions. The nearly diabatic nature of the 1 1Πg and 2 1Πg valence states is deduced from these observations. One of the‘‘diabatic’’ valence states is ‘‘bound,’’ and its perturbations on the v=1 to 3 of the Rydberg state explain observations reported from resonance enhanced multiphoton ionization experiments. [ABSTRACT FROM AUTHOR]

The mass spectrum of thermally evaporated glycerol is measured as a function of temperature by photoionization mass spectrometry (PIMS) at two wavelengths, the Ar i (11.8 eV) and Kr i (10.6 eV) resonance lines. Also the PIMS of glycerol molecules sputtered from the liquid at 267 K is measured. By comparison with the vapor phase measurements, the internal temperature of the sputtered molecules is determined as 190±40 K. Then the assumed ejection by a ‘‘thermal spike’’ must be followed by an expansion which cools the sputtered molecules to an internal temperature which is even lower than the temperature of the liquid. Applying an analytical deconvolution, the breakdown curve of the glycerol molecules is calculated. Comparison between the Ar i and Kr i vapor phase data shows that only 0.3 eV of the excess energy of the argon photon is converted into internal energy. [ABSTRACT FROM AUTHOR]

Presents a study that investigated the negative ion formation at a barium surface exposed to an intense positive-hydrogen ion beam. Formation of negative ions; Experimental setup; Results.

Presents a study which examined the formation of negative hydrogen ions on a coadsorbed layer of cesium and hydrogen on a tungsten (110) surface. Details of the negative ion formation process; Adsorption of hydrogen on a tungsten (110) surface; Experimental arrangement; Results.

Presents information on a study that examined the negative hydrogen ion formation process on a cesiated tungsten surface by scattering a proton beam from a surface. Theoretical background; Experimental arrangement; Results and discussion on the study.

Presents a study which examined charge and energy transfer in collisions of cesium ions with a cesiated W(110) surface. Method of the study; Results and discussion; Conclusion.

Presents information on a study which examined the production of sputtered flux for a metallic barium converter and a cesiated tungsten converter. Methods; Results; Discussion.

The paper presents a system for measuring photon statistics and photon timing in the few-photon regime down to the single-photon level. The measurement system is based on superconducting nanowire single photon detectors and a time-to-digital converter implemented into a programmable device. The combination of these devices gives high performance to the system in terms of resolution and adaptability to the actual experimental conditions. As a case of application, we present the measurement of photon statistics for coherent light states. In this measurement, we make use of 8th order single photon correlations to reconstruct with high fidelity the statistics of a coherent state with average photon number up to 4. The processing is performed by means of a tapped-delay-line time-to-digital converter architecture that also hosts an asynchronous-correlated-digital-counter implemented in a field programmable gate array device and specifically designed for performance optimization in multichannel usage. [ABSTRACT FROM AUTHOR]

We present an approach to the melting of graphene based on nucleation theory for a first order phase transition from the two-dimensional (2D) solid to the 3D liquid via an intermediate quasi-2D liquid. The applicability of nucleation theory, supported by the results of systematic atomistic Monte Carlo simulations, provides an intrinsic definition of the melting temperature of graphene, Tm, and allows us to determine it. We find Tm ∼ 4510 K, about 250 K higher than that of graphite using the same interatomic interaction model. The found melting temperature is shown to be in good agreement with the asymptotic results of melting simulations for finite disks and ribbons of graphene. Our results strongly suggest that graphene is the most refractory of all known materials. [ABSTRACT FROM AUTHOR]

In this work, we revisit the problem of predicting the surface segregation trends in binary transition metal alloys from the knowledge of the basic features of the pure component d-band electronic structure within tight- binding approximation. In contrast to previous trend studies, the present one includes, within the fourth-moment approximation (FMA) of the tight-binding scheme, both the difference in the average band energies (diagonal disorder) and the difference in the band widths (off-diagonal disorder) of the two components. We show that treating on the same footing these two effects is essential for a correct prediction of surface segregation. The presented study, giving a natural link between the electronic structure and mixing/segregation properties, is particularly interesting and useful in the context of the possibility of building efficient new energy models based on FMA for use in large (time) scale atomistic simulations. [ABSTRACT FROM AUTHOR]

Accurate prediction of the ordering behavior of transition metal alloys from the electronic structure is a challenging task, opening the way to build materials with unique properties in a controlled way. To this goal, we provide an accurate model based on the fourth-moment approximation of the tight-binding approach, which exhaustively gives ordering trends as a function of d-band filling, within maps where both the d-band positions and widths are used as parameters. [ABSTRACT FROM AUTHOR]

Application of the fourth moment approximation (FMA) to the local density of states within a tight binding description to build a reactive, interatomic interaction potential for use in large scale molecular simulations, is a logical and significant step forward to improve the second moment approximation, standing at the basis of several, widely used (semi-)empirical interatomic interaction models. In this paper we present a sufficiently detailed description of the FMA and its technical implications, containing the essential elements for an efficient implementation in a simulation code. Using a recent, existing FMA-based model for C-Ni systems, we investigated the size dependence of the diffusion of a liquid Ni cluster on a graphene sheet and find a power law dependence of the diffusion constant on the cluster size (number of cluster atoms) with an exponent very close to -2/3, equal to a previously found exponent for the relatively fast diffusion of solid clusters on a substrate with incommensurate lattice matching. The cluster diffusion exponent gives rise to a specific contribution to the cluster growth law, which is due to cluster coalescence. This is confirmed by a simulation for Ni cluster growth on graphene, which shows that cluster coalescence dominates the initial stage of growth, overruling Oswald ripening. [ABSTRACT FROM AUTHOR]

We review recent developments in the modelling of the phase diagram and the kinetics of crystallization of carbon. In particular, we show that a particular class of bond-order potentials (the so-called LCBOP models) account well for many of the known structural and thermodynamic properties of carbon at high pressures and temperatures. We discuss the LCBOP models in some detail. In addition, we briefly review the 'history' of experimental and theoretical studies of the phase behaviour of carbon. Using a well-tested version of the LCBOP model (viz. LCBOPI+) we address some of the more controversial hypotheses concerning the phase behaviour of carbon, in particular: the suggestion that liquid carbon can exist in two phases separated by a first-order phase transition and the conjecture that diamonds could have formed by homogeneous nucleation in Uranus and Neptune. [ABSTRACT FROM AUTHOR]

The stability of two-dimensional (2D) layers and membranes is the subject of a long-standing theoretical debate. According to the so-called Mermin–Wagner theorem, long-wavelength fluctuations destroy the long-range order of 2D crystals. Similarly, 2D membranes embedded in a 3D space have a tendency to be crumpled. These fluctuations can, however, be suppressed by anharmonic coupling between bending and stretching modes meaning that a 2D membrane can exist but will exhibit strong height fluctuations. The discovery of graphene, the first truly 2D crystal, and the recent experimental observation of ripples in suspended graphene make these issues especially important. Besides the academic interest, understanding the mechanisms of the stability of graphene is crucial for understanding electronic transport in this material that is attracting so much interest owing to its unusual Dirac spectrum and electronic properties. We address the nature of these height fluctuations by means of atomistic Monte Carlo simulations based on a very accurate many-body interatomic potential for carbon. We find that ripples spontaneously appear owing to thermal fluctuations with a size distribution peaked around 80 Å which is compatible with experimental findings (50–100 Å). This unexpected result might be due to the multiplicity of chemical bonding in carbon. [ABSTRACT FROM AUTHOR]

The 3-D distribution of atrial and ventricular isomyosins is analysed in tubular chicken hearts (stage 12+ to 17 (H/H)) using antibodies specific for adult chicken atrial and ventricular myosin heavy chains, respectively. At stage 12+ (H/H) all myocytes express the atrial isomyosin; furthermore, all myocytes except those originally situated in the dorsolateral wall of the sinu-atrium coexpress the ventricular isomyosin as well. Moreover, it appears that recently incorporated myocardial cells at both ends of the heart tube start with a coexpression of both isomyosins. From stage 14 (H/H) onwards a regional loss of expression of one of either isomyosins is observed in the atrial and ventricular compartment. In this way the single isomyosin expression types that are characteristic for the adult working myocardium of the atria and ventricles arise. So, the isomyosin expression patterns are, unexpectedly, hardly useful to discriminate the different heart parts of the tubular heart. The ventricle, defined by its adult type of isomyosin expression, is even not detectable before stage 14 (H/H). Interestingly, interconnected coexpression areas, which may be precursor conductive tissues, are still present at stage 17 (H/H) in the outflow tract, the ventricular trabeculae, the atrio-ventricular transitional zone and in the sinuatrium. The pattern of isomyosin coexpression was found to correlate with a peristaltoid contraction and a slow conduction velocity, whereas single expression areas correlate with a synchronous contraction and a relatively fast conduction velocity. The possible implications of the changing isomyosin pattern for the differentiation of the tubular myocardium, in particular in relation to the development of the conductive tissues, will be discussed. [ABSTRACT FROM AUTHOR]