bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of the Effect of Non-Uniform Membrane Properties on Performance of Mini/Microchannel Energy Recovery Ventilator Devices
Authors: Armatis Paul D. , Fronk Brian M.
Published: August 2018

Membrane based energy recovery ventilators (ERV) can be used to recover sensible and latent energy from exhaust-to-supply air in building applications. These typically consist of parallel layers of membrane separating the air streams, across which heat and moisture are exchanged. Reducing equipment cost and size remain a key challenge for continued commercialization and adoption of these devices. As membrane effectiveness improves, the air-side heat resistance can begin to dominate transport. To mitigate this, minichannel flow passages (DH < 2 mm) can be used to reduce convective heat and mass transfer. Channels can be formed through direct manipulation of membrane (e.g., pleating, corrugating, etc.), or through the use of spacer or other insert. The use of multiple parallel channels can result in large spatial variations in driving temperature and humidity ratio differences in a single layer membrane, impacting overall transport. Furthermore, the local membrane mass transfer resistance is typically a function of the surface temperature and relative humidity and not a constant value throughout the device. Accurate design models are required to appropriately size ERV equipment and maximize performance for a given equipment volume. Thus, the goal of this study is to use simulation tools to understand how the use of parallel mini- and microchannels and non-uniform membrane properties effect the performance of a membrane ERV in a building application. A two dimensional coupled heat and mass transfer resistance network model is developed. The model is compared against existing data from more detailed CFD analysis, and used to parametrically investigate effects different inlet conditions on device performance.
A Loop Thermosyphon With Hydrophobic Spots Evaporator Surface
Authors: He Hongbin , Shen Biao , Hidaka Sumitomo , Takahashi Koji , Takata Yasuyuki
Published: August 2018

Heat transfer characteristic of a closed two-phase thermosyphon with enhanced boiling surface is studied and compared with that of a copper mirror surface. Two-phase cooling improves heat transfer coefficient (HTC) a lot compared to single-phase liquid cooling. The evaporator surfaces, coated with a pattern of hydrophobic circle spots (non-electroplating Ni-PTFE, 0.5∼2 mm in diameter and 1.5–3 mm in pitch) on Cu substrates, achieve very high heat transfer coefficient and lower the incipience temperature overshoot using water as the working fluid. Sub-atmospheric boiling on the hydrophobic spot-coated surface shows a much better heat transfer performance. Tests with heat loads (30 W to 260 W) reveals the coated surfaces enhance nucleate boiling performance by increasing the bubbles nucleation sites density. Hydrophobic circle spots coated surface with diameter 1 mm, pitch 1.5 mm achieves the maximal heat transfer enhancement with the minimum boiling thermal resistance as low as 0.03 K/W. The comparison of three evaporator surfaces with same spot parameters but different coating materials is carried out experimentally. Ni-PTFE coated surface with immersion method performs the optimal performance of the thermosyphon.
Mixing Time Scale Measurement With Fast Exothermic Reactions Using Microchannel Reaction Calorimetry
Authors: Reichmann Felix , Jirmann Yannick , Kockmann Norbert
Published: August 2018

Continuous reaction calorimetry in microreactors is a powerful technology for the investigation of fast and exothermic reactions regarding thermokinetic data. A Seebeck element based reaction calorimeter has been designed, manufactured, and its performance has been shown in previous works using neutralization reaction in a microreactor made from PVDF-foils [1]. The Seebeck elements allow for spatial and temporal resolution of heat flux profiles across the reactor. Therefore, hot spots and regions of main reaction progress are detected. Finally, heat of reaction has been determined in good agreement with literature data [1].

However, more information can be retrieved related to chemical transformations using the continuously operated reaction calorimeter. In this work, mixing time scale is determined for instantaneous and exothermic reactions. Volumetric flow rate is varied and the region of main reaction progress is shifted within the microreactor. The reaction occurs near the reactor outlet for low flow rates. Here, mixing is dominated by diffusion. However, the reaction and hot spot are shifted towards the reactor inlet for high flow rates as convective mixing regime is reached and secondary flow profile with Dean vortices develop due to curvature of the reaction channel. Finally, mixing time scales can be derived from the location of heat flux peaks. Results display a decrease in mixing time at increased flow rates. Additionally, passive micromixers can be evaluated regarding their efficiency and comparison can be drawn.

Moreover, pumps can be characterized and evaluated regarding low-pulsation dosing using the Seebeck element based reaction calorimeter.
Droplet Deformation and Breakup due to Shear Flow and Electric Field in a Confined Geometry
Authors: Singh Rattandeep , Bahga Supreet Singh , Gupta Amit
Published: August 2018

In this work, the behavior of a spherical droplet suspended in a confined shear flow and subjected to an external electric field has been investigated. The continuous and dispersed fluids are treated as leaky dielectrics. The subsequent flow has been computed numerically using a low spurious current, multi-component lattice Boltzmann method coupled with a leaky dielectric model. The numerical model has been validated by analyzing droplet deformation due to shear flow and electric field separately. The results obtained are shown to be in good agreement with earlier published analytical solutions. Droplet elongation predicted by our simulations rises with increase in the electric field strength. Beyond a threshold value of electric field, breakup of droplet into smaller droplets is observed. Droplet breakup in case of fluids with equal viscosity is observed at low electric field strength as compared to low viscosity ratio drops.
Controlling the Wetting State With Bio-Mimetic Hierarchical Conical Microstructures
Authors: Park Il Woong , Fernandino Maria , Dorao Carlos Alberto
Published: August 2018

Achieving a high apparent contact angle with a low contact angle hysteresis represent a major enabling step in applications by the self-cleaning property. In this work, bio-mimetic inspired structures complemented with silanization coating are presented for developing surfaces with a high apparent contact angle with a low contact angle hysteresis. The structures are based on hierarchical conical structures with the different geometric parameter. It was observed that the fabricated surface has high apparent contact angle and low contact angle hysteresis. For that, bio-mimetic texturing of surface and silanization coating can be applied. In this study, hierarchical conical structures were fabricated. The shape of the structures has been inspired from the surface from nature. Moreover, the effect of the silanization coating on the surfaces which has different geometric parameter has been identified.
A Simplified Model for Species Transport in Very Large Scale Microfluidic Networks
Authors: Taher Ahmed , Jones Ben , Peumans Peter , Lagae Liesbet
Published: August 2018

A novel modeling technique for fluid flow and species transport in very large scale microfluidic networks is developed with applications to massively parallelized microreactors. Very large scale integration (VLSI) of microfluidic circuits presents an attractive solution for many biological testing applications such as gene expression, DNA sequencing and drug screening, which require massive parallelization of reactions to increase throughput and decrease time-to-result. However, the design and modeling of VLSI microfluidics remains challenging with conventional 2D or 3D computational fluid dynamic (CFD) techniques due to the large computational resources required. Using simplified models is crucial to reduce simulation time on existing computational resources. Many microfluidic networks can be solved using resistance based networks similar to electrical circuits; however, simplified models for species transport (diffusion plus advection) in microfluidic networks has received much less attention.

Here, we introduce a simplified model based on resistance network based modeling for flow dynamics and couple it with a one-dimensional discretization of the advection-diffusion transport equation. The developed model was validated against CFD simulations using ANSYS Fluent for a flow network consisting of a 4 by 4 array of microreactors. It showed good agreement with 2D CFD simulations with less than 6% error in total pressure drop across the network for channels with a length to width ratio of 10. The error was only 3% for a channel length to width ratio of 20. The developed model was then used to optimize the design of a 100-microreactors network used for high purity cyclical loading of reagents. The reactor configuration with a minimum cycle time for reagent loading and unloading and minimum operating pressure were evaluated with the code. In theory, the simulation can be scaled to much larger reactor arrays after further optimizations of the code and utilizing parallel processing.
Heat Transfer Enhancement in Compact Phase Change Microchannel Heat Exchangers for High Flux Laser Diodes
Authors: Hoke Jensen , Bandhauer Todd , Kotovsky Jack , Hamilton Julie , Fontejon Paul
Published: August 2018

Liquid-vapor phase change heat transfer in microchannels offers a number of significant advantages for thermal management of high heat flux laser diodes, including reduced flow rates and near constant temperature heat rejection. Modern laser diode bars can produce waste heat loads >1 kW cm−2, and prior studies show that microchannel flow boiling heat transfer at these heat fluxes is possible in very compact heat exchanger geometries. This paper describes further performance improvements through area enhancement of microchannels using a pyramid etching scheme that increases heat transfer area by ∼40% over straight walled channels, which works to promote heat spreading and suppress dry-out phenomenon when exposed to high heat fluxes. The device is constructed from a reactive ion etched silicon wafer bonded to borosilicate to allow flow visualization. The silicon layer is etched to contain an inlet and outlet manifold and a plurality of 40μm wide, 200μm deep, 2mm long channels separated by 40μm wide fins. 15μm wide 150μm long restrictions are placed at the inlet of each channel to promote uniform flow rate in each channel as well as flow stability in each channel. In the area enhanced parts either a 3μm or 6μm sawtooth pattern was etched vertically into the walls, which were also scalloped along the flow path with the a 3μm periodicity. The experimental results showed that the 6μm area-enhanced device increased the average maximum heat flux at the heater to 1.26 kW cm2 using R134a, which compares favorably to a maximum of 0.95 kw cm2 dissipated by the plain walled test section. The 3μm area enhanced test sections, which dissipated a maximum of 1.02 kW cm2 showed only a modest increase in performance over the plain walled test sections. Both area enhancement schemes delayed the onset of critical heat flux to higher heat inputs.
Thermal Performance of Micro-Jet Impingement Device With Parallel Flow, Jet-Adjacent Fluid Removal
Authors: Bandhauer Todd M. , Hobby David R. , Jacobsen Chris , Sherrer Dave
Published: August 2018

In a variety of electronic systems, cooling of various components imposes a significant challenge. A major aspect that inhibits the performance of many cooling solutions is the thermal resistance between the chip package and the cooling structure. Due to its low thermal conductivity, the thermal interface material (TIM) layer imposes a significant thermal resistance on the chip to cooling fluid thermal path. Advanced cooling methods that bypass the TIM have shown great potential in research and some specialty applications, yet have not been adopted widely by industry due to challenges associated with practical implementation and economic constraints. One advanced cooling method that can bypass the TIM is jet impingement. The impingement cooling device investigated in the current study is external to the integrated circuit (IC) package and could be easily retrofitted onto any existing microchip, similar to a standard heatsink. Jet impingement cooling has proven effective in previous studies. However, it has been shown that jet-to-jet interference severely degrades thermal performance of an impinging jet array. The present research addresses this challenge by utilizing a flow path geometry that allows for withdrawal of the impinging fluid immediately adjacent to each jet in the array.

In this study, a jet impingement cooling solution for high-performance ICs was developed and tested. The cooling device was fabricated using modern advanced manufacturing techniques and consisted of an array of micro-scale impinging jets. A second array of fluid return paths was overlain across the jet array to allow for direct fluid extraction in the immediate vicinity of each jet, and fluid return passages were oriented in parallel to the impinging jets. The following key geometric parameters were utilized in the device: jet diameter (D = 300μm), distance from jet to impinging surface (H/D = 2.5), spacing between jets (S/D = 8), spacing between fluid returns (Sr/D = 8), diameter of fluid returns (Dr/D = 5). The device was mounted to a 2cm × 2cm uniformly heated surface which produced up to 165W and the resulting fluid-to-surface temperature difference was measured at a variety of flow rates. For this study, the device was tested using single-phase water. Jet Reynolds number ranged from 300–1500 and an average heat transfer coefficient of 13,100 W m−2 K−1 was achieved at a Reynolds number of only Red = 305.
Investigation of In-Air Droplet Generation in Confined PDMS Microchannels Operating in the Jetting Regime
Authors: Tirandazi Pooyan , Healy John , Arroyo Julian D. , Hidrovo Carlos H.
Published: August 2018

Liquid-in-air generation of monodisperse, microscale droplets is an alternative to conventional liquid-in-liquid methods. Previous work has validated the use of a highly inertial gaseous continuous phase in the production of monodisperse droplets in the dripping regime using planar, flow-focusing, PDMS microchannels. The jetting flow regime, characteristic of small droplet size and high generation rates, is studied here in novel microfluidic geometries. The region associated with the jetting regime is characterized using the liquid Weber number (Wel) and the gas Reynolds number (Reg). We explore the effects of microchannel confinement on the development and subsequent breakup of the liquid jet as well as the physical interactions between the jet and continuous gaseous flow. Droplet breakup in the jetting regime is also studied numerically and the influence of different geometrical parameters is investigated. Numerical simulations of the jetting regime include axisymmetric cases where the jet diameter and length are studied. This work represents a vital investigation into the physics of droplet breakup in the jetting regime subject to a confined gaseous co-flow. By understanding the effects that different flow and geometry conditions have on the generation of droplets, the use of this system can be optimized for specific high-demand applications in the aerospace, material, and biological industries.
Numerical Investigation of Heat Transfer in the Wake of a Single Highly Confined Bubble in a Horizontal Minichannel
Authors: Willard John R. , Hollingsworth D. Keith
Published: August 2018

Confined bubbly flows in millimeter-scale channels produce significant heat transfer enhancement when compared to single-phase flows. Experimental studies support the hypothesis that the enhancement is driven by a convective phenomenon in the liquid phase as opposed to sourcing from microlayer evaporation or active nucleation. A numerical investigation of flow structure and heat transfer produced by a single bubble moving through a millimeter-scale channel was performed in order to document the details of this convective mechanism. The simulation includes thermal boundary conditions emulating those of the experiments, and phase change was omitted in order to focus only on the convective mechanism. The channel is horizontal with a uniform-heat-generation upper wall and an adiabatic lower surface. A Lagrangian framework was adopted such that the computational domain surrounds the bubble and moves at the nominal bubble speed. The liquid around the bubble moves as a low-Reynolds-number unsteady laminar flow. The volume-of-fluid method was used to track the liquid/gas interface.

This paper reviews the central results of this simulation regarding wake heat transfer. It then compares the findings regarding Nusselt number enhancement to a reduced-order model on a two-dimensional domain in the wake of the bubble. The model solves the advective-diffusion equation assuming a velocity field consistent with fully developed channel flow in the absence of the bubble. The response of the uniform-heat-generation upper wall is included. The model assumes a temperature profile directly behind the bubble which represents a well-mixed region produced by the passage of the bubble.

The significant wake heat transfer enhancement and its decay with distance from the bubble documented by the simulation were captured by the reduced-order model. However, the channel surface temperature recovered in a much shorter distance in the simulation compared to the reduced-order model. This difference is attributed to the omission of transverse conduction within the heated surface in the two-dimensional model. Beyond approximately one bubble diameter into the bubble wake, the complex flow structures are replaced by the momentum field of the precursor channel flow. However, the properties and thickness of the heated upper channel wall govern the heat transfer for many bubble diameters behind the bubble.
A Volume of Fluid Based Model for the Simulation of Bubble Growth Over a Heated Surface
Authors: Perez-Raya Isaac , Kandlikar Satish G.
Published: August 2018

Nucleate boiling simulations uncover the dynamic and thermal behavior near the bubble-edge for different fluids and operating conditions. This information is essential to optimize boiling systems and to propose more effective heat and mass transport mechanisms. Some of the main challenges simulating boiling are preserve interface sharpness, compute mass transfer, and include interface effects. The present work analyzes the role of mass transfer estimation, sharp interface model, and surface tension computation on interface deformations in the simulation of bubble growth over a heated surface. The simulation accounts for the saturation temperature of the bubble-edge and computes mass transfer with interfacial temperature gradients. Volume-of-fluid tracks the interface and defines interfacial gradients. Results provide evidence of a stable and more realistic simulation that declares mass transfer only on mixture cells and that defines a sharp interface. In addition, results show that surface tension effects play a primary role on interface deformations. Numerical results reveal the formation of a thin thermal film near the bubble edge and liquid moving away from the interface due to vapor expansion.
Experimental Investigations on Thermal Performance of PCM Based Heat Sink for Passive Cooling of Electronic Components
Authors: Kothari Rohit , Mahalkar Pawan , Sahu Santosh K. , Kundalwal Shailesh I.
Published: August 2018

In the present experimental study, an attempt has been made to study the efficient thermal management system based on phase change material for cooling of portable electronic devices. Paraffin wax is used as PCM to keep the temperature of electronic devices below critical temperature by absorbing thermal energy released by electronic components. PCM is filled inside the heat sink made of aluminum. Four different configuration of heat sink such as unfinned heat sink filled with pure PCM, two finned heat sink filled with pure PCM, unfinned heat sink filled with MF-PCM composite and two finned heat sink filled with MF-PCM composite are used in the present investigation to enhance the operating time of heat sink to reach critical set point temperature. Unfinned heat sink filled with and without PCM is used for baseline comparison. Effect of volume fraction of PCM, effect of heat flux and enhancement in operating time are reported in this study. Enhancement ratios are obtained for various heat sink configurations. The comparison of thermal performance of different configuration shows that higher enhancement ratio and effective thermal control is obtained with two finned metal foam heat sink.
Physics of Transition to Annular Flow in Microchannel Flow Boiling Process
Authors: Matin Meisam , Fazeli Abdy , Moghaddam Saeed
Published: August 2018

Transition to annular flow regime in microchannels is arguably one of the most complex phenomena in the flow boiling process. The instability of the vapor-liquid interface in this interstitial regime presents an intricate situation in which the interface pattern rapidly changes with the mass flow rate and surface heat flux. Although a few past studies have reported observing this regime, thermohydraulics of the process and flow and boundary conditions under which this transition occurs have remained largely unknown. The main obstacle in deciphering the physics of this process is lack of measurement tools to characterize hydrodynamics and thermal characteristics of this flow regime at microscales. The present study benefits from implementation of a novel test device that enables measuring the liquid film thickness and its rapid variations with micrometer and microseconds spatial and temporal resolutions. It is determined that each flow regime has a unique surface temperature signature that enables its clear distinction without need for high-speed visualization. Based on the dynamics of the flow, we identified that the transitional region is comprised of two regimes coalescing bubbles (CB) and semi-annular flow conditions. The difference between these two flow regimes emanates from motion of liquid film beneath the bubble.
Synthesis of Polydimethylsiloxane Microspheres Using Microfluidics for Treatment of Toluene in Wastewater
Authors: Lian Zheng , Ren Yong , He Jun , Chen George Z. , Koh Kai Seng
Published: August 2018

Monodispersed polydimethylsiloxane (PDMS) microspheres are fabricated by a needle-based versatile microfluidic device with flow-focusing geometry. Microdroplets with various diameters are generated by tuning the flow rate of the dispersed and continuous phase, using single emulsion as the template. The collected PDMS microdroplets are then thermally cured to form solid microspheres. We employ an optical microscope to observe the particles and capture photos. The figures are processed by ImageJ which measures the diameter of each particle. The coefficients of variation (CV) of particles are found to be less than 1.5% for all sizes, indicating that a high monodispersity has been achieved. Thereafter, we adopt the PDMS microspheres to a simulated industrial wastewater that contains organic pollutant such as toluene, for removing purposes. Since the solubility parameters of PDMS and toluene are close, toluene molecules can be extracted from its solvent into PDMS. The absorption efficiency provided by PDMS microspheres on organic pollutant such as toluene has been tested by utilizing a Headspace-Gas Chromatography (GC-HS). We then compare the obtained peak signals of toluene before and after treatment to verify the treatment effect. The needle-based microfluidic device is advantageous in its facile assembly and low cost, displaying a great potential for industrial applications.
Evaluation of Heat Transfer Performance of a Spiral Microfluidic Heatsink and Heat Exchanger Device
Authors: Virik Niven Singh , Marshall Samuel D. , Arayanarakool Rerngchai , See Hian Hian , Wang Heng , Lee Poh Seng , Yu Peter Chen Chao
Published: August 2018

Developments in micro-technology have seen vast improvements in the design and the thermal performance of heat sinks and heat exchangers, particularly in the case of spiral microfluidic devices which deals with the flow of liquids inside curved micrometer-sized channels. The current research deals with a specially designed curved microfluidic channel used to employ the fluid mixing characteristics of Dean vortices and thus transfer heat more efficiently. This curved microfluidic channel is deployed as a spiral channel to create an effective heat sink and a heat exchanger.

The novel micro heat exchanger is built by integrating two or more of the specially designed microfluidic heat sink layers. For the ease of fabricating the microchannels, these devices are polymer-based. In this paper, the thermal performance of the spiral microfluidic devices is analyzed numerically and experimentally using a range of flow rates where Thermal Performance Factor is used to find a balanced point between heat transfer and pressure drop. The spiral heat exchange device proves to be an effective thermal transport system with the introduction of curved channels in the devices where the presence of Dean vortices in the system is observed, especially at lower flow rates. It can be observed that by increasing the number of layers, the thermal performance is greatly improved. This is due to the higher surface area with increasing number of layers, as well as a parallel flow structure through the layers.

These results serve as a design parameter for developing microchannel-based heat transfer devices that can achieve high efficiency of heat and mass transfer. Further heat sink and heat exchanger design improvements are discussed.
Estimating the thermochemical properties of trimethylaluminum for thin-film processing applications
Authors: Adomaitis Raymond A.
Published: August 2018

The published thermochemical property data for vapor- and liquid-phase trimethylaluminum (TMA) monomer and dimer species are reviewed in this letter. A regression scheme is developed to estimate the missing data to produce a complete set of Gibbs-free energy of formation values over temperature ranges relevant to predicting the vapor pressure and degree of TMA dimerization within thin-film deposition gas delivery and reactor systems.
A simulated annealing approach to the student-project allocation problem
Authors: Chown Abigail H. , Cook Christopher J. , Wilding Nigel B.
Published: August 2018

We describe a solution to the student-project allocation problem using simulated annealing. The problem involves assigning students to projects, where each student has ranked a fixed number of projects in order of preference. Each project is offered by a specific supervisor (or supervisors), and the goal is to find an optimal matching of students to projects taking into account the students' preferences, the constraint that only one student can be assigned to a given project, and the constraint that supervisors have a maximum workload. We show that when applied to a real dataset from a university physics department, simulated annealing allows the rapid determination of high quality solutions to this allocation problem. The quality of the solution is quantified by a satisfaction metric derived from empirical student survey data. Our approach provides high quality allocations in a matter of minutes that are as good as those found previously by the course organizer using a laborious trial-and-error approach. We investigate how the quality of the allocation is affected by the ratio of the number of projects offered to the number of students and the number of projects ranked by each student. We briefly discuss how our approach can be generalized to include other types of constraints and discuss its potential applicability to wider allocation problems.
Lagrangian vs Hamiltonian: The best approach to relativistic orbits
Authors: Price Richard H. , Thorne Kip S.
Published: August 2018

In introductory general relativity courses, free particle trajectories, such as astronomical orbits, are generally developed via a Lagrangian and variational calculus, so that physical examples can precede the mathematics of tensor calculus. The use of a Hamiltonian is viewed as more advanced and typically comes later if at all. We suggest here that this might not be the optimal order in a first course in general relativity, especially if orbits are to be solved with numerical methods. We discuss some of the issues that arise in both the Lagrangian and Hamiltonian approaches.
Ancient DNA reveals tryst between extinct human species
Authors: Vogel Gretchen
Published: August 2018

Woman had a Neanderthal mother and a Denisovan father.
Sticky glaciers slowed tempo of ice ages
Authors: Voosen Paul
Published: August 2018

Seafloor cores suggest thickening ice sheets triggered near-collapse of Atlantic currents
An intrinsic S/G
2
checkpoint enforced by ATR
Authors: Saldivar Joshua C. , Hamperl Stephan , Bocek Michael J. , Chung Mingyu , Bass Thomas E. , Cisneros-Soberanis Fernanda , Samejima Kumiko , Xie Linfeng , Paulson James R. , Earnshaw William C. , Cortez David , Meyer Tobias , Cimprich Karlene A.
Published: August 2018

An additional cell cycle checkpoint

Cell division is controlled by checkpoints that regulate the temporal order of the cell cycle phases, including the G
1
/S, G
2
/M, and metaphase/anaphase transitions. Yet there are no known control mechanisms for a fourth fundamental transition—the S/G
2
transition. Saldivar
et al.
report a switchlike control mechanism that regulates the S/G
2
transition. The checkpoint kinase ATR senses ongoing DNA replication in S phase and represses the mitotic transcriptional network, ensuring that DNA replication in S phase is completed before mitosis.

Science
, this issue p.
806
Comment on “Tracking the global footprint of fisheries”
Authors: Amoroso R. O. , Parma A. M. , Pitcher C. R. , McConnaughey R. A. , Jennings S.
Published: August 2018

Kroodsma
et al
. (Reports, 23 February 2018, p. 904) mapped the global footprint of fisheries. Their estimates of footprint and resulting contrasts between the scale of fishing and agriculture are an artifact of the spatial scale of analysis. Reanalyses of their global (all vessels) and regional (trawling) data at higher resolution reduced footprint estimates by factors of >10 and >5, respectively.
Genomic and epidemiological monitoring of yellow fever virus transmission potential
Authors: Faria N. R. , Kraemer M. U. G. , Hill S. C. , Goes de Jesus J. , Aguiar R. S. , Iani F. C. M. , Xavier J. , Quick J. , du Plessis L. , Dellicour S. , Thézé J. , Carvalho R. D. O. , Baele G. , Wu C.-H. , Silveira P. P. , Arruda M. B. , Pereira M. A. , Pereira G. C. , Lourenço J. , Obolski U. , Abade L. , Vasylyeva T. I. , Giovanetti M. , Yi D. , Weiss D. J. , Wint G. R. W. , Shearer F. M. , Funk S. , Nikolay B. , Fonseca V. , Adelino T. E. R. , Oliveira M. A. A. , Silva M. V. F. , Sacchetto L. , Figueiredo P. O. , Rezende I. M. , Mello E. M. , Said R. F. C. , Santos D. A. , Ferraz M. L. , Brito M. G. , Santana L. F. , Menezes M. T. , Brindeiro R. M. , Tanuri A. , dos Santos F. C. P. , Cunha M. S. , Nogueira J. S. , Rocco I. M. , da Costa A. C. , Komninakis S. C. V. , Azevedo V. , Chieppe A. O. , Araujo E. S. M. , Mendonça M. C. L. , dos Santos C. C. , dos Santos C. D. , Mares-Guia A. M. , Nogueira R. M. R. , Sequeira P. C. , Abreu R. G. , Garcia M. H. O. , Abreu A. L. , Okumoto O. , Kroon E. G. , de Albuquerque C. F. C. , Lewandowski K. , Pullan S. T. , Carroll M. , de Oliveira T. , Sabino E. C. , Souza R. P. , Suchard M. A. , Lemey P. , Trindade G. S. , Drumond B. P. , Filippis A. M. B. , Loman N. J. , Cauchemez S. , Alcantara L. C. J. , Pybus O. G.
Published: August 2018

Arbovirus risk in Brazil

Despite the existence of an effective vaccine for yellow fever, there are still almost 80,000 fatalities from this infection each year. Since 2016, there has been a resurgence of cases in Africa and South America—and this at a time when the vaccine is in short supply. The worry is that yellow fever will spread from the forests to the cities, because its vector,
Aedes
spp. mosquitoes, are globally ubiquitous. Faria
et al.
integrate genomic, epidemiological, and case distribution data from Brazil to estimate patterns of geographic spread, the risks of virus exposure, and the contributions of rural versus urban transmission (see the Perspective by Barrett). Currently, the yellow fever epidemic in Brazil seems to be driven by infections acquired while visiting forested areas and indicates spillover from susceptible wild primates.

Science
, this issue p.
894
; see also p.
847
Putting sleep myths to bed
Sleepyhead: The Neuroscience of a Good Night's Rest
Henry Nicholls
Basic Books, 2018. 368 pp.
Nodding Off: The Science of Sleep from Cradle to Grave
Alice Gregory
Bloomsbury Sigma, 2018. 304 pp.
Authors: Woolfson Adrian
Published: August 2018

From groggy teenagers to fatal insomnia, two tomes tackle the science of slumber
How titanium dioxide cleans itself
Authors: Park Jeong Young
Published: August 2018

Adsorption of hydrophobic molecules explains titanium dioxide self-cleaning properties
Simplified Aztreonam Dosing in Patients with End-Stage Renal Disease: Results of a Monte Carlo Simulation
Authors: Gross Alan E. , Xu Hongmei , Zhou Diansong , Al-Huniti Nidal
Published: August 2018

The manufacturer-recommended aztreonam dosing for patients with creatinine clearance values of <10 ml/min/1.73 m
2
is complex. It is not known whether simpler posthemodialysis dosing administered once daily or thrice weekly can reliably achieve pharmacodynamic goals.
Developing a tool to measure the reciprocal benefits that accrue to health professionals involved in global health
Authors: Wigle Jannah Margaret , Akseer Nadia , Carbone Sarah , Barac Raluca , Barwick Melanie , Zlotkin Stanley
Published: August 2018

Research to date on global health collaborations has typically focused on documenting improvements in the health outcomes of low/middle-income countries. Recent discourse has characterised these collaborations with the notion of ‘reciprocal value’, namely, that the benefits go beyond strengthening local health systems and that both partners have something to learn and gain from the relationship. We explored a method for assessing this reciprocal value by developing a robust framework for measuring changes in individual competencies resulting from participation in global health work. The validated survey and evidence-based framework were developed from a comprehensive review of the literature on global health competencies and reciprocal value. Statistical analysis including factor analysis, evaluation of internal consistency of domains and measurement of floor and ceiling effects were conducted to explore global health competencies among diverse health professionals at a tertiary paediatric health facility in Toronto, Canada. Factor analysis identified eight unique domains of competencies for health professionals and their institutions resulting from participation in global health work. Seven domains related to individual-level competencies and one emphasised institutional capacity strengthening. The resulting Global Health Competency Model and validated survey represent useful approaches to measuring the reciprocal value of global health work among diverse health professionals and settings. Insights gained through application of the model and survey may challenge the dominant belief that capacity strengthening for this work primarily benefits the recipient individuals and institutions in low/middle-income settings.
Can honesty survive in a corrupt parliament?
Authors: Crokidakis Nuno , Sá Martins Jorge S.
Published: August 2018

In this work, we study a simple model of social contagion that aims to represent the dynamics of social influences among politicians in an artificial corrupt parliament. We consider an agent-based model with three distinct types of artificial individuals (deputies), namely honest deputies, corrupt deputies and inflexible corrupt deputies. These last agents are committed to corruption, and they never change their state. The other two classes of agents are susceptible deputies, that can change state due to social pressure of other agents. We analyze the dynamic and stationary properties of the model as functions of the frozen density of inflexible corrupt individuals and two other parameters related to the strength of the social influences. We show that the honest individuals can disappear in the steady state, and such disappearance is related to an active-absorbing nonequilibrium phase transition that appears to be in the directed percolation universality class. We also determine the conditions leading to the survival of honesty in the long-time evolution of the system, and the regions of parameters for which the honest deputies can be the either the majority or the minority in the artificial parliament.
Surfaces of ℙ3 containing one conic and one line
Authors: Araújo André L. Meireles , Maia José Alberto , Xavier Fernando
Published: August 2018

We know from a result due to Noether–Lefschetz that a very general surface of degree at least 4 in [Formula: see text] contains only curves which are complete intersections with other surfaces. The main goal of this paper is to construct an explicit and smooth compactification of a parameter space for surfaces in [Formula: see text] of degree [Formula: see text] for all sufficiently large [Formula: see text], containing one conic and one line. The construction also applies to surfaces in [Formula: see text] containing one plane curve and one line. As an application, we compute the degree of the locus of surfaces of degree [Formula: see text] containing one conic and one line.
Distinct ground state features and the decay chains of Z = 121 superheavy nuclei
Authors: Saxena G. , Singh U. K. , Kumawat M. , Kaushik M. , Jain S. K. , Aggarwal Mamta
Published: August 2018

A fully systematic study of even and odd isotopes [Formula: see text] of [Formula: see text] superheavy nuclei is presented in theoretical frameworks of Relativistic mean-field plus state dependent BCS approach and macroscopic–microscopic approach with triaxially deformed Nilsson-Strutinsky prescription. The ground state properties namely shell correction, binding energy, two- and one-proton and neutron separation energy, shape, deformation, density profile and the radius are estimated that show strong evidences for magicity in [Formula: see text], 228. Central depletion in the charge density due to large repulsive Coulomb field indicating bubble like structure is reported. A comprehensive analysis for the possible decay modes specifically [Formula: see text]-decay and spontaneous fission (SF) is presented and the probable [Formula: see text]-decay chains are evaluated. Results are compared with Finite Range Droplet Model (FRDM) calculations and the available experimental data which show excellent agreement.
An academic's observations from a sabbatical at Google
Authors: Barker Adam
Published: August 2018

How experiences gained in industry can improve academic research and teaching.
Peer assessment of CS doctoral programs shows strong correlation with faculty citations
Authors: Vucetic Slobodan , Chanda Ashis Kumar , Zhang Shanshan , Bai Tian , Maiti Aniruddha
Published: August 2018

Strong correlation indicates notable research productivity of individual faculty members in turn boosts the standing of their programs.
Performance and Thermal Tradeoffs for Energy-Efficient Monolithic 3D Network-on-Chip
Authors: Lee Dongjin , Das Sourav , Doppa Janardhan Rao , Pande Partha Pratim , Chakrabarty Krishnendu
Published: August 2018

Three-dimensional (3D) integration enables the design of high-performance and energy-efficient network on chip (NoC) architectures as communication backbones for manycore chips. To exploit the benefits of the vertical dimension of 3D integration, through-silicon-via (TSV) has been predominantly used in state-of-the-art manycore chip design. However, for TSV-based systems, high power density and the resultant thermal hotspot remain major concerns from the perspectives of chip functionality and overall reliability. The power consumption and thermal profiles of 3D NoCs can be improved by incorporating a Voltage-Frequency-Island (VFI)-based power management strategy. However, due to inherent thermal constraints of a TSV-based 3D system, we are unable to fully exploit the benefits offered by the power management methodology. In this context, emergence of monolithic 3D (M3D) integration has opened up new possibility of designing ultra-low-power and high-performance circuits and systems. The smaller dimensions of the inter-layer dielectric (ILD) and monolithic inter-tier vias (MIVs) offer high-density integration, flexibility of partitioning logic blocks across multiple tiers, and significant reduction of total wire-length. In this work, we present the first-ever study of the performance-thermal tradeoffs for energy efficient monolithic 3D manycore chips. In particular, we present a comparative performance evaluation of M3D NoCs with respect to their conventional TSV-based counterparts. We demonstrate that the proposed M3D-based NoC architecture incorporating VFI-based power management achieves a maximum of 29.4% lower energy-delay-product (EDP) compared to the TSV-based designs for a large set of benchmarks. We also demonstrate that the M3D-based NoC shows up to 29.1% lower maximum temperature than the TSV-based counterpart for these benchmarks.
Toward Effective Reliability Requirement Assurance for Automotive Functional Safety
Authors: Xie Guoqi , Li Zhetao , Yuan Na , Li Renfa , Li Keqin
Published: August 2018

Automotive functional safety requirement includes response time and reliability requirements learning from the functional safety standard ISO 26262. These two requirements must be simultaneously satisfied to assure automotive functional safety requirement. However, increasing reliability increases the response time intuitively. This study proposes a method to find the solution with the minimum response time while assuring reliability requirement. Pre-assigning reliability values to unassigned tasks by transferring the reliability requirement of the function to each task is a useful reliability requirement assurance approach proposed in recent years. However, the pre-assigned reliability values in state-of-the-art studies have unbalanced distribution of the reliability of all tasks, thereby resulting in a limited reduction in response time. This study presents the geometric mean-based non-fault-tolerant reliability pre-assignment (GMNRP) and geometric mean-based fault-tolerant reliability pre-assignment (GMFRP) approaches, in which geometric mean-based reliability values are pre-assigned to unassigned tasks. Geometric mean can make the pre-assigned reliability values of unassigned tasks to the central tendency, such that it can distribute the reliability requirements in a more balanced way. Experimental results show that GMNRP and GMFRP can effectively reduce the response time compared with their individual state-of-the-art counterparts.
AI holds the better hand
Authors: Monroe Don
Published: August 2018

Exploiting the techniques of game theory to come up with the superior poker hand.
Navigating with accelerating technology change
Authors: Denning Peter J.
Published: August 2018

Mathematical tools such as S-curves locate inflection points in technology-accelerated social spaces; where we move next depends on our navigational skills.
How to avoid an AI interaction singularity
Authors: Lukowicz Paul , Slusallek Philipp
Published: August 2018

Envisioning, designing, and implementing the user interface require a comprehensive understanding of interaction technologies. In this forum we scout trends and discuss new technologies with the potential to influence interaction design.
--- Albrecht Schmidt, Editor
Acute ultraviolet radiation exposure attenuates nitric oxide-mediated vasodilation in the cutaneous microvasculature of healthy humans
Authors: Wolf S. Tony , Stanhewicz Anna E. , Jablonski Nina G. , Kenney W. Larry
Published: August 2018

5-Methyltetrahydrofolate (5-MTHF) is important for nitric oxide (NO)-mediated cutaneous microvascular vasodilation. Ultraviolet B (UVB) radiation may deplete 5-MTHF, either directly or via production of reactive oxygen species (ROS), decreasing NO-mediated vasodilation. We hypothesized that 1) acute UVB exposure would attenuate NO-dependent cutaneous vasodilation, 2) local perfusion of 5-MTHF or ascorbate (ASC) (antioxidant) would augment NO-dependent vasodilation after UVB, and 3) darker skin pigmentation would be UVB-protective. Intradermal microdialysis fibers ( n = 3) placed in each forearm of 22 healthy young adults (23 ± 1 yr; 8M/14F) locally delivered lactated Ringer’s (control), 5 mM 5-MTHF, or 10 mM ASC. One arm was UVB-exposed (300 mJ/cm2), and the other served as a nonexposed control (CON). Following UVB exposure, a standardized local heating (42°C) protocol induced cutaneous vasodilation. After attaining a plateau blood flow, 15 mM NG-nitro-l-arginine methyl ester (nitric oxide synthase inhibiter) was infused at all sites to quantify the NO contribution. Red cell flux was measured at each site by laser-Doppler flowmetry (LDF), and cutaneous vascular conductance (CVC = LDF/mean arterial pressure) was expressed as a percentage of maximum (28 mM sodium nitroprusside + 43°C). UVB attenuated NO-mediated vasodilation compared with CON (23.1 ± 3.6 vs. 33.9 ± 3.4%; P = 0.001). Delivery of 5-MTHF or ASC improved NO-mediated vasodilation versus lactated Ringer’s in the UVB-exposed arm (MTHF: 30.1 ± 4.8% vs. 23.1 ± 3.8%; P = 0.03; ASC: 30.9 ± 4.3% vs. 23.1 ± 3.8%; P = 0.02). Neither treatment affected the response in the nonexposed arm ( P ≥ 0.09). Skin pigmentation (melanin index) was not predictive of the UVB response ( P ≥ 0.34). These data suggest that acute UVB exposure attenuates NO-mediated vasodilation via direct and/or ROS-induced reductions in 5-MTHF, independent of skin pigmentation.

NEW & NOTEWORTHY Endothelial-derived nitric oxide (NO) contributes to normal healthy function of the human cutaneous microvasculature. Bioavailability of 5-methyltetrahydrofolate (5-MTHF) is important for the production of NO. Ultraviolet (UV) radiation exposure, specifically UVB, may deplete cutaneous 5-MTHF, thereby reducing NO-mediated microvascular function. Our findings suggest that acute UVB exposure attenuates NO-mediated vasodilation of the cutaneous microvasculature via degradation of 5-MTHF. These findings advance our understanding of the potential negative health impacts of acute UV exposure.