A simple mix design method for structural lightweight aggregate concrete

Current design methods for structural lightweight aggregate concrete (SLWAC) are usually only valid for a limited range of concrete compositions that have previously been subjected to trial tests. The SLWAC mix design is more complex than that of normal weight concrete as more parameters need to be determined. Taking this into account, a simplified design method is proposed for SLWAC made with natural sand. The major advantages of the proposed method are that it is easy to apply and it can be generalized to any type of lightweight aggregate (LWA). For this, three additional design parameters are needed: the strength of LWA in concrete; the limit strength; the SLWAC potential strength. At most, two experimental mixtures are needed to determine these parameters. A biphasic model to estimate the strength of SLWAC is evaluated and high correlations are obtained. The good performance of the suggested method is demonstrated by examples of practical application and by the comparison with experimental results reported by the authors and other investigators.     

Research and partnership in studies of sugarcane using molecular markers: a scientometric approach

In this study, we applied scientometric methods and performed a science mapping analysis to investigate and describe the application of molecular markers in genetic studies for sugarcane. We analyzed 344 papers retrieved from Web of Science Thomson Reuters database, considering the time frame from 1974 to 2017, allowing the analysis of the produced scientific knowledge, temporal trends and research partnership in the subject. To our knowledge, a scientometric evaluation of the use of molecular markers for genetic studies in sugarcane has not yet been reported. Our main finding shows that dominant markers are more commonly used than co-dominant markers, and that when co-dominant markers are applied, most of the retrieved information is underexploited, due to lack of knowledge for the use of dosage information. Our results also show that despite the development of high-throughput sequencing technologies, for sugarcane only 13.33% of the studies reported the use of more than 1000 markers. We also found connectivity among researchers and institutions publishing worldwide, but only few authors represented a bridge between different research groups. Thus, the international research partnership is still low. Our findings show dominance in country publication. Six countries (India, Brazil, USA, Australia, China, and France) were responsible for 80% of the published papers and received most citations. We suggest special reinforcement in building international partnership, since collaborations occur mostly within countries. International collaboration can improve research performance and eventually lead to a better exploitation and more development of knowledge for sugarcane.

     

Using common weights and efficiency invariance principles for resource allocation and target setting

Data envelopment analysis (DEA) has proven to be a useful technique for evaluating the relative performance of comparable and homogeneous decision-making units (DMUs). In recent years, DEA-based resource allocation and target setting approaches have gained more and more attention from both practitioners and academic researchers. In this paper, we propose a new mechanism to simultaneously adopt the principles of common weights and efficiency invariance in allocating multiple resources and setting multiple targets among DMUs. To obtain the final plan, we minimise the deviation between the possible plan based on common weights and another feasible plan emphasising efficiency invariance. If the minimum deviation equals zero, one optimal plan will be determined. In general situations, however, the proposed approach will present two plans that have a non-zero deviation. One is generated using a common set of weights for all DMUs in such a way that the change of efficiencies is minimised, while the other is generated by strictly keeping efficiency scores unchanged yet having similar or even identical weights on input–output measures for each DMU to the utmost extent. The efficacy and usefulness of the proposed approach are demonstrated using a numerical example from previous literature and an empirical application to an urban bus company in China.     

High-pressure gas phase femtosecond laser ionization mass spectrometry

We describe a novel ion source for analytical mass spectrometry based on femtosecond laser ionization at pressures at and above atmospheric and characterize its performance when coupled to a tandem quadrupole/time-of-flight mass spectrometer. We assess source saturation limits, ionization and sampling efficiencies, the effective ionization volume, and limits of detection. We demonstrate 100% efficient ionization for a set of organic compounds and show that the degree of ion fragmentation over a range of laser powers is favorable compared to electron impact ionization, especially in that a substantial parent ion signal is always observed. We show how collisional cooling plays a role in controlling fragmentation at high pressures and address how ion-molecule chemistry can be controlled or exploited. High-pressure femtosecond laser ionization will allow "universal" and efficient ionization, presenting a research direction that will broaden the options for gas phase analysis beyond the capabilities of electron impact ionization.     

An efficient method for isolating individual long-chain alkenones for compound-specific hydrogen isotope analysis

Hydrogen isotope ratios (2H/H or D/H) of long-chain unsaturated ketones (alkenones) preserved in lake and marine sediments hold great promise for paleoclimate studies. However, compound-specific hydrogen isotope analysis of individual alkenones has not been possible due to chromatographic coelution of alkenones with the same carbon chain length but different numbers of double bonds. Published studies have only reported the deltaD values of the mixture of coeluting alkenones. We developed an efficient procedure to isolate individual alkenones based on double-bond numbers using silica gel impregnated with silver nitrate. The chromatographic procedure is simple, inexpensive, and highly reproducible, offers 87-100% sample recovery, and allows for the first time hydrogen isotopic measurement on individual alkenones. deltaD values of specific di-, tri- and tetraunsaturated C37 alkenones produced by an Emiliania huxleyi culture, as well as those isolated from Greenland lake sediments, differ consecutively by 43-65 per thousand. These findings suggest that alkenones with different numbers of carbon-carbon double bonds express significantly different deltaD values and that coelution of different alkenones may lead to erroneous source water deltaD reconstructions. Our alkenone isolation approach opens a new avenue for paleoclimate reconstructions using hydrogen isotope ratios of individual alkenones.     

Digital Predistortion for 5G Small Cell: GPU Implementation and RF Measurements

In this paper, we present a high data rate implementation of a digital predistortion (DPD) algorithm on a modern mobile multicore CPU containing an on-chip GPU. The proposed implementation is capable of running in real-time, thanks to the execution of the predistortion stage inside the GPU, and the execution of the learning stage on a separate CPU core. This configuration, combined with the low complexity DPD design, allows for more than 400 Msamples/s sample rates. This is sufficient for satisfying 5G new radio (NR) base station radio transmission specifications in the sub-6 GHz bands, where signal bandwidths up to 100 MHz are specified. The linearization performance is validated with RF measurements on two base station power amplifiers at 3.7 GHz, showing that the 5G NR downlink emission requirements are satisfied.

     

Rapid quantification of clostridial epsilon toxin in complex food and biological matrixes by immunopurification and ultraperformance liquid chromatography-tandem mass spectrometry

Epsilon toxin (ETX) is one of the most lethal toxins produced by Clostridium species and is considered as a potential bioterrorist weapon. Here, we present a rapid mass spectrometry-based method for ETX quantification in complex matrixes. As a prerequisite, naturally occurring prototoxin and toxin species were first structurally characterized by top-down and bottom-up experiments, to identify the most pertinent peptides for quantification. Following selective ETX immunoextraction and trypsin digestion, two proteotypic peptides shared by all the toxin forms were separated by ultraperformance liquid chromatography (UPLC) and monitored by ESI-MS (electrospray ionization-mass spectrometry) operating in the multiple reaction monitoring mode (MRM) with collision-induced dissociation. Thorough protocol optimization, i.e., a 15 min immunocapture, a 2 h enzymatic digestion, and an UPLC-MS/MS detection, allowed the whole quantification process including the calibration curve to be performed in less than 4 h, without compromising assay robustness and sensitivity. The assay sensitivity in milk and serum was estimated at 5 ng·mL(-1) for ETX, making this approach complementary to enzyme linked immunosorbent assay (ELISA) techniques.     

Influence diagnostics in a general class of beta regression models

In this article, we consider the issue of assessing influence of observations in the general class of beta regression models introduced by Simas et al. (Comput. Stat. Data Anal. 54:348–366, 2010), which is very useful in situations in which the response is restricted to the standard unit interval (0,1). Our results generalize those in Espinheira et al. (Comput. Stat. Data Anal. 52:4417–4431, 2008a; J. Appl. Stat. 35:407–419, 2008b), which only apply to linear beta regression models. We define some residuals, and a Portmanteau test for serial correlation. Further, some influence methods, such as the global, local, and total local influence of an individual and generalized leverage, are discussed. Moreover, we also derive the normal curvatures of local influence under various perturbation schemes. Finally, simulation results and an application to real data show the usefulness of our results.     

Ab initio studies of pristine and oxidized Cu3Au(100) and (111) surfaces

We review the previous literature and our recent work on first-principles studies of Cu₃Au(100) and (111) surfaces, with focus on the segregation of atomic species to the surface at pristine conditions and in the presence of oxygen. In particular, the combined use of experimental and theoretical tools to achieve chemical identification at an atomic level of the surface species is emphasized and discussed.