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Listeria monocytogenes (L. monocytogenes) is a ubiquitous foodborne pathogens responsible for listeriosis, which is associated with high morbidity and mortality. Development of simple and fast methods for L. monocytogenes detection is of great needed. In this study, we present a simple method for L. monocytogenes detection combined aptamers decorated magnetic beads for selective capture and gold nanoparticles (AuNPs) mediated signal amplication. A NH2 labeled aptamer specific to L. monocytogenes was decorated on magnetic beads for selective capture and isolation of L. monocytogenes from food sample. AuNPs was functionalized with sulfhydryl modified primers specific to hly gene of L. monocytogenes in acidic environments. The AuNP@primers could catalyze TMB-H2O2 to TMB2+ and generate a significant blue color, this reaction was found to be enhanced by DNA. AuNP@primers was used as a signal indicator for the presence of L. monocytogenes DNA by enhancing the catalytic reaction of TMB-H2O2. The colour change was observed by naked eye and the optical density of TMB2 + was analyzed to quantify the result. The developed assay was highly specific and the limit of detection was 101 CFU/mL of L. monocytogenes. For the detection of L. monocytogenes in spiked food samples, the recoveries were ranging from 73.63 to 84.21% with the coefficient of variation less than 2.41% in meat, and ranged from 94.13 to 100.71% with the coefficient of variation less than 2.82% in milk, respectively. Therefore, the developed colorimetric assay is suitable for food sample testing, the detection takes less than 1.5 h, which enables on-site screening. This study offers a promising approach for rapid, sensitive and accurate detection of L. monocytogenes in food. [ABSTRACT FROM AUTHOR]

The environment friendly Cu2ZnSnSe4 (CZTSe) quantum dot-sensitized solar cells (QDSSCs) has become one of the most promising photovoltaic technologies due to its earth-abundant component and excellent photoelectric properties. However, the power conversion efficiency (PCE) is far behind other high-efficiency chalcogenide sensitizer systems and the main obstacle can be attributed to the inappropriate conduction band position relative to the TiO2 films. Herein, we developed a partial substitution approach to transform CZTSe QDs to Cu2Zn(SnxGe1−x)Se4 (CZTGSe) QDs to resolve the CBM mismatch problem in QDSSCs. The CZTGSe QDs with narrow size distribution were synthesized via one-step method and Ge/(Ge+Sn) ratios were prepared. It is found that the introduction of Ge upshifts the CBM and broadens the band gap of CZTGSe QDs. Benefiting from the enhanced driving force of photoelectron injection and depressed charge recombination at TiO2/QDs/electrolyte interface, the short-circuit current (Jsc) and open-circuit voltage (Voc) of Ge-substituted QDSSCs are synchronously improved and the PCE of the 30% Ge content device finally is increased from 3.83 to 4.42%. This Ge-assisted band engineering approach solves the main obstacle for the further development of panchromatic CZTGSe QDSSCs. [ABSTRACT FROM AUTHOR]

Foodborne pathogens Listeria monocytogenes, Salmonella Typhimurium and Escherichia coli O157:H7 continue to be leading causes of foodborne illness. Herein, we describe a sensitive and reliable lateral flow immunoassay for the simultaneous detection of these three bacteria via multiplex PCR and test strip by using gold nanoparticles (AuNPs) as label. Biotin, FITC and digoxin were used as tags for Listeria monocytogenes, Salmonella Typhimurium and Escherichia coli O157:H7, respectively. AuNPs were conjugated with thiolated probes and detected by multiplex lateral flow strip with three test lines corresponding to the three bacteria. The proposed method exhibited excellent specificity (no cross-reactivity with other tested foodborne bacteria were observed), good precision with the coefficient of variation less than 8.73%, and satisfactory recoveries (82.34–98.34%). The limits of detection were from 0.3 × 101 to 3.5 × 102 CFU mL−1 for the three bacteria in chicken breast sample, without culture enrichment, revealing the feasible and reliable of this method. The developed process, including sample preparation, PCR amplification, AuNPs conjugation and test strip detection, can be completed within 4 h. In light of the high level of targets specificity and sensitivity, this method provides a novel application potential for the simultaneous detection of foodborne pathogenic microorganisms. [ABSTRACT FROM AUTHOR]

Herein, a novel core-shell material Fe3O4@MIL-100(Fe) was synthesized for developing a novel LFIA by a two-step solvothermal method with good magnetic properties and high specific surface area. It was used as both magnetic separation and label agents in LFIA for the detection of Listeria monocytogenes. The enrichment of target bacteria can be achieved quickly and easily by direct adsorption of Fe3O4@MIL-100(Fe) on the bacteria and by the action of an applied magnetic field. It was beneficial in separation and concentration of target bacteria from food samples. The Fe3O4@MIL-100(Fe)-bacterial was then detected by the anti-Listeria monocytogenes antibody on the T line under the capillary action of the LFIA strip, resulting in the formation of a visible orange band. Under the optimal conditions, there was a good linear relationship between the intensity of the T line and the quantity of Listeria monocytogenes in the range of 105-108 CFU mL− 1, with a visual detection limit of 3.3 × 106 CFU mL− 1. The strip showed strong specificity for L. monocytogenes, and the detection could be finished in 45 min, without the needing of pre-treatment. Thus, the proposed Fe3O4@MIL-100(Fe)-based strip was simple prepared, label-free, low cost, rapid and convenience. [ABSTRACT FROM AUTHOR]

Clustering, a traditional machine learning method, plays a significant role in data analysis. Most clustering algorithms depend on a predetermined exact number of clusters, whereas, in practice, clusters are usually unpredictable. Although the Elbow method is one of the most commonly used methods to discriminate the optimal cluster number, the discriminant of the number of clusters depends on the manual identification of the elbow points on the visualization curve. Thus, experienced analysts cannot clearly identify the elbow point from the plotted curve when the plotted curve is fairly smooth. To solve this problem, a new elbow point discriminant method is proposed to yield a statistical metric that estimates an optimal cluster number when clustering on a dataset. First, the average degree of distortion obtained by the Elbow method is normalized to the range of 0 to 10. Second, the normalized results are used to calculate the cosine of intersection angles between elbow points. Third, this calculated cosine of intersection angles and the arccosine theorem are used to compute the intersection angles between elbow points. Finally, the index of the above-computed minimal intersection angles between elbow points is used as the estimated potential optimal cluster number. The experimental results based on simulated datasets and a well-known public dataset (Iris Dataset) demonstrated that the estimated optimal cluster number obtained by our newly proposed method is better than the widely used Silhouette method. [ABSTRACT FROM AUTHOR]

In-memory big data computing, widely used in hot areas such as deep learning and artificial intelligence, can meet the demands of ultra-low latency service and real-time data analysis. However, existing in-memory computing frameworks usually use memory in an aggressive way. Memory space is quickly exhausted and leads to great performance degradation or even task failure. On the other hand, the increasing volumes of raw data and intermediate data introduce huge memory demands, which further deteriorate the short of memory. To release the pressure on memory, those in-memory frameworks provide various storage schemes options for caching data, which determines where and how data is cached. But their storage scheme selection mechanisms are simple and insufficient, always manually set by users. Besides, those coarse-grained data storage mechanisms cannot satisfy memory access patterns of each computing unit which works on only part of the data. In this paper, we proposed a novel task-aware fine-grained storage scheme auto-selection mechanism. It automatically determines the storage scheme for caching each data block, which is the smallest unit during computing. The caching decision is made by considering the future tasks, real-time resource utilization, and storage costs, including block creation costs, I/O costs, and serialization costs under each storage scenario. The experiments show that our proposed mechanism, compared with the default storage setting, can offer great performance improvement, especially in memory-constrained circumstances it can be as much as 78%. [ABSTRACT FROM AUTHOR]

Two novel nonlinear optical (NLO) chromophores JC-T-TCF and JC-F-TCF utilizing tetramethyljulolidine-based coumarin and tricyanofuran(TCF) as the electron donor and acceptor, respectively, were designed and synthesized. The two chromophores were linked with different π conjugated electron bridge (thiophene group and furan group), which provide the opportunity to study the structure–property relationship of coumarin-based chromophores. Both the novel obtained chromophores exhibited reasonable stability and solvatochromic effect. The theoretical calculation results indicated that both chromophores possess microscopic hyperpolarizability (β) in excess of 320 × 10−30esu, and the chromophore JC-T-TCF utilizing thiophene group as the electron bridge exhibited obviously larger β value (456.8 × 10−30esu). The larger β value, combination with the larger µ value, endowed JC-T-TCF with larger electro-optic activity of 70 pm V−1 at the wavelength of 1310 nm in the guest–host films of chromophores doped into PMMA, which provide the potential application opportunity in the field of optical waveguide devices. [ABSTRACT FROM AUTHOR]

Since service level agreement (SLA) is essentially used to maintain reliable quality of service between cloud providers and clients in cloud environment, there has been a growing effort in reducing power consumption while complying with the SLA by maximizing physical machine (PM)-level utilization and load balancing techniques in infrastructure as a service. However, with the recent introduction of container as a service by cloud providers, containers are increasingly popular and will become the major deployment model in the cloud environment and specifically in platform as a service. Therefore, reducing power consumption while complying with the SLA at virtual machine (VM)-level becomes essential. In this context, we exploit a container consolidation scheme with usage prediction to achieve the above objectives. To obtain a reliable characterization of overutilized and underutilized PMs, our scheme jointly exploits the current and predicted CPU utilization based on local history of the considered PMs in the process of the container consolidation. We demonstrate our solution through simulations on real workloads. The experimental results show that the container consolidation scheme with usage prediction reduces the power consumption, number of container migrations, and average number of active VMs while complying with the SLA. [ABSTRACT FROM AUTHOR]

Two principally novel chromophores A, B based on fluorene electron donor were synthesized and explored by 1H NMR, 13C NMR, and MS spectra. The delocalized energy levels have been estimated by UV–Vis absorption spectra. The principal innovation consists in modification by addition of amino group. The titled materials have demonstrated a high solubility in common organic solvents, good compatibility with polymers. The maximally achieved electro-optic efficiency of the poled film possessing 25 wt% of A doped in PMMA (25 wt% A/PMMA) achieved a value of 18 pm/V at wavelength 1310 nm, and 25 wt% B/PMMA possessed an electrooptical coefficient equal to 43 pm/V. This one open a perspective of their direct application in optoelectronic telecommunication devices for laser light modulation. [ABSTRACT FROM AUTHOR]

Organic nonlinear optical materials have been widely explored because of their advantages in the design of materials with large electro-optic coefficients used in the fabrication of novel optoelectronic and telecommunication devices. However, the huge dipole-dipole interactions between organic nonlinear optical chromophores have limited further improvements in the electro-optic coefficients and long-term material stability. Here, a novel polymer based on poly(aryl ether ketone) was designed and prepared to enhance the electro-optic coefficients and achieve higher long-term stability. This novel poly(aryl ether ketone) has a relatively high glass transition temperature and offers active functional groups for the attachment of organic nonlinear optical chromophores. After attachment of nonlinear optical chromophores the materials showed higher chromophore loading density, less inter-molecular interaction, and suitable solubility. This resulted in better film-forming ability, higher electro-optics coefficients and better long-term stability. Quantum chemical simulations of the second order hyperpolarizabilities and ground sate dipole moments were done to understand the origin of the effects. [ABSTRACT FROM AUTHOR]

Principally novel crosslinking nonlinear optical and optoelectronics system based on Diels-Alder reaction was designed. The copolymer of methyl methacrylate and anthracen-9-ylmethyl methacrylate (PMMA-AMA) was used as a host polymer; chromophore ETO was used as guest chromophore; chromophore ETO and N,N-(methylenediphenyl)bismaleimide were used as crosslinker. The thermodynamic property of crosslinking system studied by differential scanning calorimeter (DSC) showed us that the glass transition temperature was about 65 °C and the crosslinking temperature was varied between 80 and 120 °C The crosslinking reactive speed and effectiveness were studied by ultraviolet absorption and infrared absorption spectroscopy with spectral resoluiotn 1 cm. These results have indicated that the cross linking process could be finished at 110 °C for 20 min. Surprisingly, such EO polymer showed us a large EO coefficient of about 96.3 pm/V at wavelength 1 µm and excellent long term stability about 85% with respect to its initial value and can be kept after 250 h of heating at 80 °C. [ABSTRACT FROM AUTHOR]

Due to the simple preparation technology and appropriate crosslinking process, polyurethane was selected as the host polymer for the preparation of organic electro-optics (EO) materials. The synthesis and crosslinking process of polyurethane demanded the nonlinear optical (NLO) chromophore possessing strong stability in acid environment. Fortunately, after the introduction of azo group in the electronic bridge, the stability of this kind of chromophores in acidic environment was improved greatly. Polyurethane EO polymers and EO films based on this kind of chromophore were prepared successfully. The crosslinking process was monitored by infrared spectroscopy clearly. The crosslinking process has direct relationship with the molecular weight of the crosslinkers. Crosslinker of triethanolamine with small molecular weight showed low crosslinking temperature (80 °C) and short crosslinking time (20 min). The crosslinking temperature and time was improved to 140 °C and 60 min based on Poly(bisphenol A glycidyl ether aniline) (BPAN) crosslinker with large molecular weight. More importantly, this kind of EO polymers showed us large second order nonlinear optical coefficients (76.1 pm/V) and good long term stability (130 °C). [ABSTRACT FROM AUTHOR]

Two principally novel organic nonlinear optical chromophores (1 and 2) with flexible ( n-hexyl group) or rigid isolated (benzyl group) group are designed and successfully synthesized. The prepared chromophores were characterized by MS, H-NMR and UV-Vis spectra. Their thermal stability was studied by thermal gravimetric analyzer and differential scanning calorimetry. Poled films of the chromophores doped in amorphous polycarbonate afford the maximum electro-optic tensor coefficient (r) equal to 39 pm/V, 63 pm/V for chromophore 1 and chromophore 2, respectively at the wavelength 1,064 nm. The reason of so large differences between these two chromophores' linear electrooptics coefficients were explained within a framework of performed quantum chemical calculations and it is crucially dependent on distances between the chromophore molecules and the polymer chains. [ABSTRACT FROM AUTHOR]

Binary polymer blends that can form hydrogen-bond networks were prepared and used to fabricate the guest-host organic electro-optic (EO) materials. The hydrogen-bonds network in the solid films of novel guest-host organic EO materials was verified by FT-IR spectra. After corona poling, two kinds of EO films revealed the maximum EO coefficient value ( r) of 19.5 and 30 pm/V at the wavelength of 1310 nm. The EO activity and the order parameter of the chromophores in the poled films both indicated that the hydrogen-bond network has little impact on the motion of the chromophores while poling. These new EO films exhibited better temporal stability after 250 h at 55 and 85 °C compared with the conventional guest-host systems that have the similar or higher Ts. Moreover, the results also indicated that polymer blends as the host of EO materials can change the dielectric strength of the materials, which directly influence the poling efficiency. [ABSTRACT FROM AUTHOR]

Three chromophores with tricyanofuran and tricyanopyrroline electron acceptors were synthesized and doped in high glass transition temperature ( T) polymer poly( N-(4-acetoxylphenyl)maleimide-co-styrene, NAPMI-co-ST). The electro-optic (EO), optical, and thermal properties of the doped poly(NAPMI-co-ST) were characterized and discussed. After being corona poled under 12 kV, this high T polymer material showed excellent EO activity and thermal stability. The highest EO coefficient ( r) reached 48.2 pm V (1,310 nm) and could remain 90 % of the original value for 100 h at 85 °C. The EO coefficient was relatively higher compared with other high T EO polymers. The thermal stability was also very good and the manufacture process was convenient and applicable for device fabrication. [ABSTRACT FROM AUTHOR]

Two novel soluble polyarylates with different nonlinear optical chromophores as the side chains were prepared and characterized by UV-visible spectra, nuclear magnetic resonance, and infrared spectroscopy. The titled polymers show us good thermal stability; the thermal decomposition temperature values were 201 and 253 °C, respectively, for polymer sPAR-CTCF and sPAR-CTCP. The glass transition temperatures were 139 and 122 °C for sPAR-CTCF and sPAR-CTCP, respectively. Chromophore FTC-wl was doped in these polymers as a guest chromophore to form binary chromophore electro-optic (EO) system. And super large EO coefficients (124 pm/V) were found from FTC-wl-doped sPAR-CTCP binary chromophore system at high chromophore loading density. [ABSTRACT FROM AUTHOR]

This article reports a synthesis a new class of nonlinear optical (NLO) polymer, containing 3-methyl-4-cyano-5-dicyanomethylidene-2-oxo-3-pyrroline (TCP) acceptor. TCP chromophore was synthesized and characterized by Uv-Vis absorption, H NMR, and mass-spectrometry. The titled polymer shows high thermal stability and large optical nonlinearity. A high glass transition temperature of 125°C was determined by DSC measurement, and measured electrooptical (EO) at wavelength 1.31 mm was equal to 37.4 pm/V. The order parameter of these films evaluated by absorption was equal to about 24%. [ABSTRACT FROM AUTHOR]

A tricyanopyrroline chromophore with methacrylate reactive group was synthesized to fabricate the side chain (polymer 1) and crosslinkable (polymer 2) EO (electro optic) polymers with enhanced electrooptical tensor coefficients. These type of polymers have demonstrated the large EO coefficients with values of 29 pm/V and 25 pm/V at wavelength 1,310 nm, respectively. Compared with polymer 1, t polymer 2 had demonstrated a better stability of polar structure. The thermal stability of polar structure was improved for about 100 °C. The temperatures of poling and crosslinking processes were compatible in polymer 2, which allowed obtaining the EO films with improved features. The experimental results have been interpreted with the aid of quantum-chemical calculations. [ABSTRACT FROM AUTHOR]

Three novel nonlinear optical polyarylate polymers were prepared containing one main-chain polymer (mPAR-chr1) and two side-chain polymers (sPAR-chr1, sPAR-chr2) with different kinds of chromophores. The obtained polymers were characterized and evaluated by UV-Vis, H NMR, DSC and TGA. All the polymers exhibited excellent thermal stability, film forming ability and good electro-optic (EO) activity. The relationship between EO coefficients ( r) and the chromophore concentration of the three polymers had been also characterized and discussed. There were no obvious differences found in EO activity between main-chain and side-chain polyarylates with the same chromophore (chr1). Due to the stronger electron-withdrawing tricyanopyrroline acceptor and the steric effect of the large dendritic groups of chromophore 2 (chr2), polymer sPAR-chr2 showed the largest EO cofficients (64 pm V) in these new polymers. [ABSTRACT FROM AUTHOR]

series of nonlinear optical chromophores with the strong electron-withdrawing tricyanopyrroline (TCP) acceptor and rigid-flexible dendron was synthesized and their thermal and optical properties were investigated. Modification of the TCP chromophore with rigid-flexible dendron groups provides reduction of dipole-dipole interactions and thus great improvement of the macroscopic electro-optic (EO) response of the polymeric materials obtained by incorporating these derivatives as a guest in a high Tg amorphous polycarbonate (APC). The best result was obtained with chromophore Lj-Dr1, with three rigid-flexible dendrons, which shows the largest EO activity (39 pm V at 1,310 nm). Furthermore, all chromophores in this study possess good processability and exhibit high thermal decomposition temperatures (highest T = 300 °C). [ABSTRACT FROM AUTHOR]