The Variation of “Surface” Pressure in a Nanocrystal as a Function of Temperature

The Mie-Lennard-Jones potential of interatomic interaction is used to derive an expression for “surface” pressure in a nanocrystal with free surface. The nanocrystal has the form of a parallelepiped with a square base. The number of atoms N may vary from eight to ∞. It is found that a certain “inversion temperature” T _i exists for any substance, where the temperature dependences of surface pressure for different sizes of nanocrystal intersect. When the crystal disperses in the T < T _i region, the “surface” pressure increases, and in the T > T _i region decreases, with decreasing size of nanocrystal: P _sf(N) ～ N ^?1/3. The greater the deviation of the nanocrystal shape from cubic, the stronger the dependence P _sf(N). It is demonstrated that, at some temperatures (T < T ₀), the “surface” pressure compresses the nanocrystal, and at other temperatures-stretches this nanocrystal, as its size decreases. The more clearly the quantum effects are defined in the crystal, the lower the value of the “temperature of zero surface pressure” T ₀, which depends on the nanocrystal size and shape.     

Rate constant of <Emphasis Type="Italic">VT</Emphasis>/<Emphasis Type="Italic">VV</Emphasis> energy exchange in the collision of di- and polyatomic molecules within the SFO model

The numerical-analytical investigation of the shock forced oscillator (SFO) model is complete. Approaches for calculating the probabilities of quantum transitions from the initial to some final state with VV energy exchange of diatomic molecules and VV and VT energy exchange of polyatomic molecules are considered. Formulas for calculating the probabilities of the \({W_{{i_1},{i_2} \to {f_1},{f_2}}}\) transition for VV energy exchange in collision of molecules AB and CD within the harmonic approximation are represented (SFHO model). It is shown that the probabilities of a quantum transition in VV and VT energy exchange of polyatomic molecules can be calculated in terms of the quantum transition probability for VT energy exchange of diatomic molecules on the assumption of “frozen” quantum transitions of polyatomic molecules. The problem of determining the dissociation rate constant is considered by the example of a nitrogen molecule (N₂) in the N₂–N₂ system for the “improved” Lennard-Jones potential in VV energy exchange. The calculated dissociation rate constant is compared with the experimental data obtained for a shock tube.     

The Effect of Charge Transport Mechanisms on the Efficiency of Al<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Ga<Subscript>1 – <Emphasis Type="Italic">x</Emphasis></Subscript>As/GaAs Photodiodes

Photovoltaic characteristics of heterostructure Al_xGa_{1 – x}As/GaAs p–i–n photodiodes fabricated by molecular-beam epitaxy have been studied. Efficiencies of 50% were reached in conversion of monochromatic light in the photovoltaic mode at power density of up to 200 W/cm² at a wavelength λ = 830 nm. A relationship was demonstrated between the “saturation currents” for the diffusion-related charge-transport mechanism (Shockley) in p–i–n photodiodes, calculated from dark current–voltage characteristics, and the experimental values of efficiency. As the “saturation current” of the diffusion-related charge-transport mechanism increases by an order of magnitude, a relative decrease in the efficiency from the maximum value by more than 10% is observed under excitation by constant or pulsed monochromatic light.     

International graduate training,digital inequality and professional network structure: An ego-centric social network analysis of knowledge producers at the “Global South”

Based on a face-to-face survey of 312 scientists from government research institutes and state universities in two Philippine locations — Los Baños, Laguna and Muñoz, Nueva Ecija — we examine how graduate training and digital factors shape the professional network of scientists at the “Global South.” Results suggest that scientists prefer face-to-face interaction; there is no compelling evidence that digitally-mediated interaction will replace meaningful face-to-face interaction. What is evident is that among none face-to-face modes of communication a reordering maybe in progress.The effect of digital factors — expressed through advance hardware-software-user interaction skills — lies on network features pertaining to size, proportion of male and of core-based alters, and locational diversity. International graduate training and ascribed factors (gender and number of children) also configure the professional network of scientists — actors traditionally viewed as the epitome of rationality and objectivity. We argue that these factors influence knowledge production through a system of patronage and a culture that celebrates patrifocality. We forward the hypothesis that knowledge production at the “Global South” closely fits Callon’s [1995] extended translation model of science.     

Inelastic collisions of molecules within the SFO model

An inelastic collision of diatomic molecule AB with structureless particle M (VT energy exchange) is considered within the SFO/SFHO model. An approach for determining the energy efficiency of excitation of molecular vibrational levels, energy-loss matrix, and total energy loss in a head-on collision with molecules/atoms is proposed. Nitrogen molecules N₂ are chosen as AB and M. An interaction in the AB–M system is described using the “improved” Lennard-Jones potential.     

On the Interpretation of Near-Critical Gas–Liquid Heat Capacities by L. V. Woodcock,Int. J. Thermophys. (2017) 38, 139: Comments

It is shown that: (1) the expressions for the isochoric (C_V) and isobaric (C_P) heat capacities of liquid and gas, coexisting in phase equilibrium, the heat capacities at saturation of liquid and gas (C_σ) and the heat capacity C_λ used in the article “On the Interpretation of Near-Critical Gas–Liquid Heat Capacities, L. V. Woodcock, Int. J. Thermophys. (2017) 38, 139” are incorrect; (2) the conclusions of the article based on the comparison of the incorrect C_V, C_P and C_λ with experimental data are also incorrect; (3) the lever rule cannot be used to define C_V and C_P in the two-phase coexistence region; (4) a correct expression for the isochoric heat capacity describes well the experimental data; (5) there is no misinterpretation of near-critical gas–liquid heat capacity measurements in the two-phase coexistence region; (6) there are no proofs in the article that: (a) the divergence of C_V is apparent; (b) it has not been established experimentally that the thermodynamic properties of fluids satisfy scaling laws with universal critical exponents asymptotically close to a single critical point of the vapor–liquid phase transition; and (c) there is no singular critical point on Gibbs density surface. We obtained the relations connecting the isochoric heat capacity in the two-phase region with thermodynamic properties at saturation of homogeneous liquid and gas which can be used to verify the equation of state.     

Surface-enhanced Raman scattering nanosensors for <Emphasis Type="Italic">in vivo</Emphasis> detection of nucleic acid targets in a large animal model

Although nanotechnology has led to important advances in in vitro diagnostics, the development of nanosensors for in vivo detection remains very challenging. Here, we demonstrated the proof-of-principle of in vivo detection of nucleic acid targets using a promising type of surface-enhanced Raman scattering (SERS) nanosensor implanted in the skin of a large animal model (pig). The in vivo nanosensor used in this study involves the “inverse molecular sentinel” detection scheme using plasmonics-active nanostars, which have tunable absorption bands in the near infrared region of the “tissue optical window”, rendering them efficient as an optical sensing platform for in vivo optical detection. Ex vivo measurements were also performed using human skin grafts to demonstrate the detection of SERS nanosensors through tissue. In this study, a new core–shell nanorattle probe with Raman reporters trapped between the core and shell was utilized as an internal standard system for self-calibration. These results illustrate the usefulness and translational potential of the SERS nanosensor for in vivo biosensing.

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The “<Emphasis Type="Italic">Daphnia</Emphasis>” Lynx Mark I Suborbital Flight Experiment: Hardware Qualification at the Drop Tower Bremen

The Drop Tower Bremen, a ground-based facility enabling research under real microgravity conditions, is an excellent platform for testing new types of experimental hardware to ensure full performance when deployed in costly and rare flight opportunities such as suborbital flights. Here we describe the “Daphnia” experiment which will fly on XCOR Aerospace Lynx Mark I and our experience from the hardware tests with the catapult system at the drop tower. The aim of the “Daphnia” experiment is to obtain data on the biological performance of daphnids and predator-prey interactions in microgravity, which are important for the development of aquatic bioregenerative life support systems (BLSS). The experiment consists of two subunits: The first unit is dedicated to predator-prey interactions, where behavioural analysis should reveal if microgravity interfere with prey (Daphnia) detection or feeding and therefore may interrupt the trophic cascade. The functioning of such an artificial food web is indispensable for a long-lasting BLSS suitable for long-duration manned space missions or Earth-based explorations to extreme habitats. The second unit is designed to investigate the impact of microgravity on gene expression and the cytoskeleton in Daphnia. Next to data collection, the real microgravity conditions at the drop tower have helped to identify the weak points of the “Daphnia” experimental hardware and lead to further improvement. Hence, the drop tower is ideal for testing new experimental hardware which is indispensable before the implementation in suborbital flights.     

How much is a quantum controller controlled by the controlled system?

We consider unitary transformations on a bipartite system A × B. To what extent entails the ability to transmit information from A to B the ability to transfer information in the converse direction? We prove a dimension-dependent lower bound on the classical channel capacity C(A ← B) in terms of the capacity C(A → B) for the case that the bipartite unitary operation consists of controlled local unitaries on B conditioned on basis states on A. If the local operations are given by the regular representation of a finite group G we have C(A → B) = log |G| and C(A ← B) = log N where N is the sum over the degrees of all inequivalent representations. Hence the information deficit C(A → B) ? C(A ← B) between the forward and the backward capacity depends on the “non-abelianness” of the control group. For regular representations, the ratio between backward and forward capacities cannot be smaller than 1/2. The symmetric group S _n reaches this bound asymptotically. However, for the general case (without group structure) all bounds must depend on the dimensions since it is known that the ratio can tend to zero. Our results can be interpreted as statements on the strength of the inevitable backaction of a quantum system on its controller.     

On VLSI interconnect optimization and linear ordering problem

Some well-known VLSI interconnect optimizations problems for timing, power and cross-coupling noise immunity share a property that enables mapping them into a specialized Linear Ordering Problem (LOP). Unlike the general LOP problem which is NP-complete, this paper proves that the specialized one has a closed-form solution. Let f(x,y):?²→? be symmetric, non-negative, defined for x≥0 and y≥0, and let f(x,y) be twice differentiable, satisfying ? ² f(x,y)/?x?y<0. Let π be a permutation of {1,…,n}. The specialized LOP comprises n objects, each associated with a real value parameter r _i , 1≤i≤n, and a cost f(r _i ,r _j ) associated to any two objects if |π(i)?π(j)|=1,1≤i,j≤n, and f(r _i ,r _j )=0 otherwise. We show that the permutation π which minimizes \(\sum_{i= 1}^{n - 1} f( r_{\pi^{ - 1}( i )},r_{\pi^{ - 1}( i + 1 )} )\), called “symmetric hill”, is determined upfront by the relations between the parameter values r _i .     

Average current per vacuum-arc cathode spot and spot velocity in a magnetic field on a CuCr50/50 nanocomposite

It has been shown that such cathode spot characteristics as the average current per spot and its dependence on tangential magnetic-field induction B _t and the spot velocity and its dependence on B _t for two CuCr50/50 specimens with very different structures (nanocomposite and “solid-state sintered” composite) almost coincide if the surface of contacts has been totally remelted before measurements with the use of moderate arc currents in the process of conditioning.     

Proposed the ANOVA Method for Analysis of Proficiency Test Result

Analysis of variance “ANOVA”, as a trustful statistical method most commonly applied to the results of the experiment to determine the percent contribution of each factor, is used in this paper in comparison with Z-score statistical method. Z-score, Zeta score, and En number are the most credible statistical methods used in proficiency testing evaluation. In this paper four different PT examples were demonstrated, both ANOVA as well as Z-score were used for the analysis of the testing. The first example showed a consistency of the results between both of them, however in the other three examples dissimilarity happened between the two results. While Z-score gave the participant laboratory a satisfactory result, ANOVA gave the same laboratory unsatisfactory result. Final results showed the advantage and reliability of ANOVA analysis over Z-score analysis.     

Investigation of the breakage parameters of gypsum as dependent on interstitial filling in a laboratory ball mill

Gypsum is an industrial material used in many applications such as building and chemical industry, fertilizer manufacture, medicine and dentistry. In these industries, there is need for finely ground gypsum. Energy consumption is very high in grinding processes. Therefore, the effects on breakage kinetics of powder filling and ball filling were investigated on gypsum samples taken from the Denizli-Honaz region (Turkey), for batch grinding conditions based on a kinetic model. For this purpose, firstly, eight different mono-size fractions between 1.7 and 0.106 mm formed by a \({\surd 2}\) sieve series were obtained. Then, S _i and B _i,j equations were determined from the size distributions at different grinding times, and the model parameters (S _i , a _T , α, γ and \({\phi_{j}}\)) were compared for four different proportions of powder filling (5, 7.5, 10 and 15%), and three different proportions of ball filling (25, 35 and 45%). Finally, model parameters are discussed for each test. From the result of tests, obtained of the effect of ball filling and powder filling on the grinding, it was found our results differed from those of other investigators.     

High-Efficiency AlGaAs/GaAs Photovoltaic Converters with Edge Input of Laser Light

High-efficiency photovoltaic converters (PVCs) have been developed and fabricated by liquidphase epitaxy in the AlGaAs–GaAs system with laser light (λ = 850 nm) introduced through the edge surface in parallel to the plane of the p–n junction of the device structure. To raise the efficiency of light “capture” by the p–n junction, an Al_xGa_1–xAs waveguide layer is formed, in which the content of aluminum gradually varies from x = 0.55 to 0.15 so that the refractive index gradient is created in this layer and light beams are diverted toward the p–n junction. When a PVC (having no antireflection coating) is exposed to 0.1- to 0.2-W laser light, an efficiency of 41.5% is obtained. Depositing an antireflection coating on the edge surface of a PVC raises its efficiency to 55%.     

The effect of the flow-to-wall temperature ratio on strong condensation of gas

The method of direct statistical simulation is used to investigate the effect of the flow-to-wall temperature ratio T on the strong subsonic condensation of monatomic gas. It is demonstrated that the dependence of relative pressure at the boundary of the Knudsen layer on relative temperature at a fixed value of the Mach number M has a minimum. In so doing, the marked supercooling of condensing gas (T < 1) causes an abrupt increase in relative pressure. At the same time, for a “moderately cold” wall (1.5 < T < 10), the dependence of relative pressure on relative temperature at a fixed value of M is very weak. It is demonstrated that, in the case of supersonic condensation, the dependence of minimal possible relative pressure on T at a fixed value of M likewise has a minimum. The calculation results agree well with the results of calculations by the method of moments using the suggested approximation of the molecule distribution function.     

Simultaneous Action of Intra- and Interband Pair Channels in Multiband Superconductivity

Interband superconductivity channels with pairs formed from the same (a) and different bands (b) are compared in common action. A simple mean-field multiband model is inspected. There are three order parameters Δ _a , Δ _{a d} and \({\Delta }_{b} \left ({\Delta }_{b1}^{2}={\Delta }_{b2}^{2} \right )\). Complicated quasiparticle energies induced by interactions of strengths W _a and W _b follow. The calculated operator averages lead to a coupled nonlinear system for the gap-type parameters. Illustrative calculations of them vs temperature have been made. Overlapping dispersive bands intersected by the chemical potential have been used. A novel result is that at a fixed parameter set the system of basic equations has two independent solutions. The free energy is of a complicated structure under the action of both channels. There are stable and metastable states. The W _a and W _b channels compete in simultaneous functioning. The phenomenon of the effective logout of one of the channels can be traced. Starting by the temperature where Δ _i reached zero, the solutions induced by W _j behaving as W _i were zero and define T _{c i} . The pairs Δ _a and Δ _{a d} have the same vanishing temperature. The general results are very sensible to |W _b | inclusive to critial behaviour. Reduced |W _b | stimulates the formation of closed “bubbles” built up by Δ _a , Δ _b and Δ _{a d} belonging to parallel solutions. The corresponding metastable state vanishes when the bubble closes.     

Liquid etching of metallization layers on GaAs/Al <Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Ga<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript> as heterostructures with HNO<Subscript>3</Subscript> + HCl + glycerol mixture

A program package is developed for simplex-lattice-design processing of the data on etching of solid systems in multicomponent etchants. The procedure suggested is implemented in studying the processes of etching of metallization layers on GaAs/Al _x Ga_{1 ? x} As semiconductor heterostructures in an HNO₃: HCl: glycerol etching mixture. The etchant compositions are selected to implement controllable removal of Au layers at a rate of 8–10 Å s^?1, with such quality of the surface of the epitaxial structure that allows the subsequent procedures specified by planar technology and the microscopic structural studies of multilayer metallization. The results are applied to the analysis of the characteristics of contacts to the GaAs/Al _x Ga_{1 ? x} As heterostructures in developing photoelectric detectors and can be used in replacing the operation of “dry” etching with the operation of “wet” etching during the technological cycle of formation of GaAs-based device structures.     

A parameter-free index for identifying under-cited sleeping beauties in science

We developed a systematic methodology for identifying the under-cited (or not-so-highly cited) Sleeping Beauty (SB) publications and tried to figure out their key characteristics. Based on the identification framework of “beauty coefficient” (B) introduced by Ke et al. (Proc Natl Acad Sci USA 112:7426–7431, 2015), taking into account the whole citation history of the publications concerned, we substituted yearly citations in “beauty coefficient” with yearly cumulative percentage of citations, and eliminated the denominator in “beauty coefficient” since the curve of a given document’s cumulative citations is always monotonically increasing if only the document is cited. The value of the modified beauty coefficient is denoted as Bcp. We also redefined the awakening year, sleeping length and sleeping depth within the Bcp framework with the intention of avoiding arbitrary thresholds as much as possible. We tested the new index using the data of SB articles identified from Science and Nature. The results showed that Bcp is more sensitive in identifying the “lower level SBs”, which refers to the case when the total citations and the maximum annual citations of SBs are not so high in comparison with other typical SBs. Bcp works better than B in at least two aspects: (1) it “punishes” the situations when the SBs experienced early citations instead of continuous sleeping; (2) it allows for comparing the extent of delayed citation impact of publications in different fields with different citation patterns. We also figured out some key characteristics of such SB publications and pondered some policy implications about the associations of SB publications with transformative research, research front and research evaluation.