Perspecta 20, Perspecta 21

In preparation of the JAE Jubilee issue many invitations were made to respond to the paragraph printed below. Because of a highly condensed schedule in the production of this special issue, the cut-off date for receipt of articles had to be moved up and several individuals, whose invited responses were in the final stages of preparation or even in transit to JAE, could not be included in that issue. This is regrettable; however, during the upcoming year we will be printing those articles and again invite our readership to respond and discuss those issues put forward in the Jubilee statement.—Ed.     

Low temperature cure of epoxy thermosets attaining high Tg using a uniform microwave field

It is demonstrated for the first time that an epoxy thermoset resin can be cured at temperatures well below its T_g∞. This study compared the use of a uniform variable frequency microwave (VFM) field to standard oven curing at temperatures above and below T_g∞. Using T_g, tan δ, modulus, and FTIR measurements, it is shown that the reaction of BFDGE with MDA to attain a product with T_g∞ of 133 °C is achieved by VFM at temperatures from 100 to 140 °C; in contrast, the thermal cure normally requires 170 °C to attain the same T_g∞ and the same extent of cure. By following the pregel cure reaction with ¹³C‐NMR spectroscopy, it was determined that the lower cure temperatures of VFM cure predominately lead to chain extension and smaller amounts of crosslinking compared to the thermal cure. To explain these results, it is suggested that, after gelation, with VFM cure there is higher mobility from dipole rotations that continues the cure to completion without vitrification. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44222.     

Sustaining humans in space

One goal of NASA's Ames Research Center is to extend the presence of humans in space. Biomedical research, human performance, and life-support systems form the core of the Ames program. Major questions highlight how the effects of microgravity on living systems are modified by exercise, artificial gravity, autogenic feedback training, and nutrition. Bioengineering and life science studies include humans, animals, and plants. Ames investigators collaborate extensively with outside university and commercial scientists, both within the United States and internationally.     

IT专业人员如何充分发挥5G的全部潜力

GSMA(全球移动通信系统协会)研究数据显示,2020年我国建设5G基站63.1万个,占全球总数的87％.可以说,消费者对5G的接受程度最终转化成了实际的推动力,而该技术的优势也日益明显.在中国,5G技术是支撑经济社会数字化、网络化、智能化转型的关键新型基础设施.5G技术在领跑新基建的过程中,不仅在助力疫情防控、复工复...     

Droplet evaporation: Effects of transients and variable properties

A numerical study of the effects of transients and variable properties on single droplet evaporation into an infinite stagnant gas is presented. Sample calculations are reported for octane droplets, initially at 300°K with R_o = 0·1, 0·5, 2·5 × 10^?4m, evaporating into air at temperatures and pressures in the ranges 600–2000°K and 1–10 atm, respectively. It is found that initial size R_o is eliminated from the problem on scaling time with respect to R²₀ and that the evaporative process becomes quasi-steady with ($\text{R}\text{R}{}_0\text{)}{}^2\text{= (}\text{R1}{}_0\text{R}{}_0\text{)}{}^2\text{?}\text{βt}\text{R}{}^2{}_0$, as suggested by experiment. Comparisons of solutions using various reference property schemes with those for variable properties show that best agreement obtains using a simple $\text{1}\text{3}$ rule wherein properties are evaluated at $\text{T}{}_{\mathrm{r}}\text{= T}{}_{\mathrm{s}}\text{+}\text{(T}{}_{\mathrm{e}}\text{?T}{}_{\mathrm{s}}\text{)}\text{3}$ and $\text{m}{}_{\mathrm{1,r}}\text{= m}{}_{\mathrm{1,s}}\text{+}\text{(m}{}_{\mathrm{1,e}}\text{? m}{}_{\mathrm{1,s}}\text{)}\text{3}$. The effects of temporal storage of mass species, energy, etc. and radial pressure variations in the vapor phase prove to be negligible, the early transient behavior being solely due to sensible heat effects within the droplet and related variations in vapor-side driving forces.     

Apomyoglobin as a molecular recognition surface: expression, reconstitution and crystallization of recombinant porcine myoglobin in Escherichia coli

Recombinant porcine myoglobin has been produced in Escherichiacoli using the cII fusion expression system of Nagai and Th?gersen[Nature, 309, 810–812 (1984)]. After processing and reconstitutionwith haem, the protein is gel-electrophoretically and spectrophotometricallyindistinguishable from native pig myoglobin. Large crystalsof both native and recombinant porcine myoglobin were grownfrom 50 mM sodium phosphate, pH 7.1, 80% ammonium sulphate.The crystals belong to space group C2 (a = 156.9 ?, b = 42.0?, c = 92.2 ?, ß = 127.9?) and diffract to a nominal2.5 ? resolution. We plan to explore apomyoglobin as a bindingsurface in studies combining site-directed mutagenesis and X-rayanalysis. These experiments will be extended by studying thebinding of haem analogues to the mutant apoproteins.     

Comparison of interwell connectivity predictions using percolation, geometrical, and Monte Carlo models

Reservoir connectivity is often an important consideration for reservoir management. For example, connectivity controls waterflood sweep efficiency and it affects decisions concerning well placement and spacing. The uncertainty of sandbody distributions, however, can make interwell connectivity prediction extremely difficult. Percolation models are a useful tool to simulate sandbody connectivity behavior to estimate interwell connectivity.This study applies a percolation method to estimate interwell connectivity. Using results derived by Andrade, King, and others for fluid travel time between locations in a percolation model, we develop a method to estimate interwell connectivity. Four parameters are needed to use this approach: the net-to-gross ratio p_sand, the typical sandbody size, reservoir length and well spacing. To evaluate this new percolation method, the results are compared to results from geometrical models, Monte Carlo, and reservoir simulation.These methods were applied to estimate interwell connectivity for three non-communicating stratigraphic intervals in Monument Butte oil field, Utah. The results suggest that the percolation method can estimate the probability of interwell connectivity reliably for thin intervals for any values of p_sand, well spacing, and reservoir length. The geometrical model also performs well, but can only be applied in fields where the well spacing is less than one-half of the sandbody size.The proposed method requires that the reservoir interval for evaluation be sufficiently thin so that 2D percolation results can be applied. For thick intervals or heterogeneous sandbody distributions, the percolation method developed here is not suitable because it assumes thin layers. Future percolation research will be needed to adapt this new method to 3D cases.     

Representational momentum is not (totally) impervious to error feedback.

The influence of feedback on representational momentum for the final location of a moving target was examined in 3 experiments. The presence of binary feedback (correct, error) during practise trials or during larger blocks of experimental trials did not reduce representational momentum, nor did the presence of more informative feedback specifying the direction of error (error—in front of, error—behind) during larger blocks of experimental trials reduce representational momentum. Effects on representational momentum of whether feedback was consistently provided were inconsistent. Even though feedback did not reduce representational momentum per se, feedback did influence the probability of a same response for different probe positions. Implications of the data for R. A. Finke and J. J. Freyd's (1985; J. J. Freyd, 1987) claim that representational momentum is impervious to error feedback, and possible roles of perceptual learning in representational momentum, are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A Plan for the Development of Fusion Energy

This is the final report of a panel set up by the U.S. Department of Energy (DOE) Fusion Energy Sciences Advisory Committee (FESAC) in response to a charge letter dated September 10, 2002 from Dr. Ray Orbach, Director of the DOE's Office of Science. In that letter, Dr. Orbach asked FESAC to develop a plan with the end goal of the start of operation of a demonstration power plant in approximately 35 years. This report, submitted March 5, 2003, presents such a plan, leading to commercial application of fusion energy by mid-century. The plan is derived from the necessary features of a demonstration fusion power plant and from the time scale defined by President Bush. It identifies critical milestones, key decision points, needed major facilities and required budgets. The report also responds to a request from DOE to FESAC to describe what new or upgraded fusion facilities will best serve our purposes over a time frame of the next twenty years.     

Factors associated with suicide attempts among patients with schizophrenia

This study explored the association between psychosocial variables and symptoms among patients with schizophrenia-spectrum disorders who have attempted suicide and those who have not attempted suicide. Of 336 patients with a DSM-III-R diagnosis of schizophrenia or schizoaffective disorder who were consecutively evaluated at a university-affiliated clinical research center, 98, or 29.2 percent, reported one or more suicide attempts. Compared with patients who had not attempted suicide, patients who had made an attempt had a greater number of lifetime depressive episodes, an earlier age of onset of their illness, and an earlier age at first hospitalization.