A high-throughput LC-MS/MS method suitable for population biomonitoring measures five serum folate vitamers and one oxidation product

Small specimen volume and high sample throughput are key features needed for routine methods used for population biomonitoring. We modified our routine eight-probe solid phase extraction (SPE) LC-MS/MS method for the measurement of five folate vitamers [5-methyltetrahydrofolate (5-methylTHF), folic acid (FA), plus three minor forms: THF, 5-formylTHF, 5,10-methenylTHF] and one oxidation product of 5-methylTHF (MeFox) to require less serum volume (150 μL instead of 275 μL) by using 96-well SPE plates with 50 mg instead of 100 mg phenyl sorbent and to provide faster throughput by using a 96-probe SPE system. Total imprecision (10 days, two replicates/day) for three serum quality control pools was 2.8–3.6 % for 5-methylTHF (19.5–51.1 nmol/L), 6.6–8.7 % for FA (0.72–11.4 nmol/L), and ≤11.4 % for the minor folate forms (<1–5 nmol/L). The mean (±SE) recoveries of folates spiked into serum (3 days, four levels, two replicates/level) were: 5-methylTHF, 99.4?±?3.6 %; FA, 100?±?1.8 %; minor folates, 91.7–108 %. SPE extraction efficiencies were ≥85 %, except for THF (78 %). Limits of detection were ≤0.3 nmol/L. The new method correlated well with our routine method [n?=?150, r?=?0.99 for 5-methylTHF, FA, and total folate (tFOL, sum of folate forms)] and produced slightly higher tFOL (5.6 %) and 5-methylTHF (7.3 %) concentrations, likely due to the faster 96-probe SPE process (1 vs. 5 h), resulting in improved SPE efficiency and recovery compared to the eight-probe SPE method. With this improved LC-MS/MS method, 96 samples can be processed in ～2 h, and all relevant folate forms can be accurately measured using a small serum volume.

A review of recent advances in chemiluminescence detection using nano-colloidal manganese(IV)

The application of ‘soluble’ (colloidal) manganese(IV) for chemiluminescence detection is reviewed, focussing on papers published since the last comprehensive review of the subject in 2008. Advances in this reagent system include: the on-line formation of manganese(IV); new insight into the light-producing pathway and selectivity of the reagent; its application to assess total antioxidants in plant derived samples and oxidative stress in biological fluids and tissues; and the replacement of the formaldehyde enhancer with ethanol.     

Selective capillary coating materials for in-tube solid-phase microextraction coupled to liquid chromatography to determine drugs and biomarkers in biological samples: A review

In-tube solid-phase microextraction (in-tube SPME) coupled with high performance liquid chromatography (HPLC) or liquid chromatography coupled to mass spectrometry (LC-MS) successfully determines drugs or biomarkers in biological samples by direct sample injection or by simple sample treatment. This technique uses a capillary column as extraction device. Several capillaries (wall-coated open tubular, sorbent-packed, porous monolithic rods, or fiber-packed) with unique phases have been developed and evaluated, aiming to improve the efficiency and selectivity of the in-tube SPME-LC technique. This review describes new developments and applications occurred in recent years, and discusses future trends with emphasis on new extraction devices and current technology used for the synthesis of selective sorbents for bioanalysis, such as (i) polypyrrole, (ii) restricted-access materials, (iii) immunosorbents, (iv) molecular imprinting polymers, (v) monolithic polymers, and (vi) bi-functional materials.     

C-Triazolyl β-d-furanosides as LpxC inhibitors: stereoselective synthesis and biological evaluation

C-Triazolyl β-d-furanosides 10a–f were synthesized in a stereocontrolled way, starting from d-mannose. In the key steps of the synthesis a diastereoselective reduction of hemiketal 14 and a Cu(I) catalyzed [3+2]-cycloaddition of central building block 18 with various azides were performed. The synthesized hydroxamic acids were tested for their inhibitory activity against LpxC, a Zn²⁺-dependent deacetylase playing an important role in the biosynthesis of lipid A and therefore representing an interesting target for the development of novel antibiotics against Gram-negative bacteria. The C-triazolyl glycosides 10a–f did not exhibit antibiotic activity. However, the described synthesis is a versatile way to access C-triazolyl β-d-furanosides bearing all of their substituents at the same side of the tetrahydrofuran ring.     

Splitting algorithm for DMT optimal cooperative MAC protocols in wireless mesh networks

A cooperative protocol for wireless mesh networks is proposed in this paper. The protocol implements both on-demand relaying and a selection of the best relay terminal so only one terminal is relaying the source message when cooperation is needed. Two additional features are also proposed. The best relay is selected with a splitting algorithm. This approach allows fast relay selection within less than three time-slots, on average. Moreover, a pre-selection of relay candidates is performed prior to the splitting algorithm. Only terminals that are able to improve the direct path are pre-selected. So efficient cooperation is now guaranteed. We prove that this approach is optimal in terms of diversity-multiplexing trade-off. The protocol has been designed in the context of Nakagami-m fading channels. Simulation results show that the performance of the splitting algorithm does not depend on channel statistics.     

Bandwidth allocation in cooperative wireless networks: Buffer load analysis and fairness evaluation

In modern cooperative wireless networks, the resource allocation is an issue of major significance. The cooperation of source and relay nodes in wireless networks towards improved performance and robustness requires the application of an efficient bandwidth sharing policy. Moreover, user requirements for multimedia content over wireless links necessitate the support of advanced Quality of Service (QoS) features. In this paper, a novel bandwidth allocation technique for cooperative wireless networks is proposed, which is able to satisfy the increased QoS requirements of network users taking into account both traffic priority and packet buffer load. The performance of the proposed scheme is examined by analyzing the impact of buffer load on bandwidth allocation. Moreover, fairness performance in resource sharing is also studied. The results obtained for the cooperative network scenario employed, are validated by simulations. Evidently, the improved performance achieved by the proposed technique indicates that it can be employed for efficient traffic differentiation. The flexible design architecture of the proposed technique indicates its capability to be integrated into Medium Access Control (MAC) protocols for cooperative wireless networks.     

The effect of Laplacian filter in adaptive unsharp masking for infrared image enhancement

Image processing, in particular image enhancement techniques have been the focal point of considerable research activity in the last decade. With the aid of an existing image enhancement technique, adaptive unsharp masking (AUM), we propose a novel kernel to be used in AUM filtering in order to enhance discontinuities which occur on the edges of targets of interest in infrared (IR) images. The proposed method uses an adaptive filter approach where an objective function is minimized by using descent algorithms. The output IR image has better sharpness and contrast adjustment for the detection of targets in terms of objective quality metrics. Hence, the proposed method ensures that the edges of the targets in IR images are sharper and that the quality of contrast adjustment has its optimum level in terms of peak signal-to-noise ratios.     

The economics of social computing: Some preliminary findings on healthcare organizations

Large-scale organizations have used social computing platforms for various purposes. This research focuses on how hospitals utilize these platforms to attract potential customers (which represents the “extensivity” of a social computing platform) and generate interests in specific topics (which represents the “intensivity” of a platform). Specifically, we examine the effects of size of a hospital (or “size”) and the time that the social computing platform has been in existence (or “time”) on extensivity and intensivity. Our findings show that time is a significant variable on both dimensions; whereas size affects intensivity under certain conditions. We discuss the implications of these findings, and set the stage for future research.     

Network robustness and irreversibility of information diffusion in Complex networks

Complex networks are characterized based on a newly proposed parameter, “degree of diffusion α”. It defines the ratio of information adopters to non-adopters within a diffusion process over consecutive penetration depths. Furthermore, the perfectness of a social network is evaluated by exploring different variations of α such as the reverse diffusion (α_reverse) and the random-kill-diffusion (RKD) processes. The analysis of α_reverse and RKD processes shows information diffusion irreversibility in small-world and scale-free but not in random networks. It also shows that random networks are more stable toward attacks, resulting a complete information diffusion process over the entire network. Finally, a real Complex network example, represented as a “virtual friendship network” was analyzed and found to share properties of both random and small-world networks. Therefore, it is characterized to be somewhere between random and small-world network models or in other words, it is a randomized small-world network model.     

Wide band gain flattening Yb-doped fiber amplifier

The gain flattening of Yb³⁺-doped fiber amplifier of 1053 nm band has been realized in experiment using three cascade 1 × 2 fused tapered fiber coupler. The gain flattening band is about 20 nm with less than 1 dB power fluctuation around 1053 nm, which is agree with our numerical stimulation results very well.