Time domain identification and ranking of noise sources in a pneumatic nail gun

This paper investigates the noise sources in a pneumatic nail gun. The study combines two complementary experimental approaches. The first uses simultaneous data observation, with sound, acceleration and air pressure signals simultaneously recorded in conjunction with a nail gun motion high speed video. This strategy allows the identification of the physical processes involved in the operation of the machine at different time instants, as well as the associated noise generation mechanisms. However, since multiple noise sources radiate at the same time, this observation technique is not sufficient for noise source identification and ranking. Thus, a second approach introduces a selective wrapping procedure, and the strategy assures a reliable classification of the noise sources. The investigation considers the following noise origins: the air exhaust, the machine body and the workpiece/worktable.     

Solidified floating organic drop microextraction–electrothermal atomic absorption spectrometry for ultra trace determination of antimony species in tea, basil and water samples

Solidified floating organic drop microextraction was applied as a separation/preconcentration step prior to the electrothermal atomic absorption spectrometric (ETAAS) determination of ultra trace of antimony species. The method was based on the formation of an extractable complex between Sb(III) and ammonium pyrrolidinedithiocarbamate at pH ~ 5, while Sb(V) was remained in the aqueous phase. The antimony extracted into 1-undecanol was determined by ETAAS. Total antimony was determined after the reduction of Sb(V) to Sb(III) with potassium iodide and ascorbic acid. The amount of Sb(V) was determined from the difference of concentration of total antimony and Sb(III). Under the optimum conditions an enhancement factor of 437.5 and a detection limit of 5.0 ng L^?1for the preconcentration of 25 mL of sample was achieved. The relative standard deviation at 300 ng L^?1 of antimony was found to be 3.5 % (n = 6). The proposed method was successfully applied to the determination of antimony in tea, basil and natural water samples.     

On Proximal Relations in Transformation Semigroups Arising from Generalized Shifts

For a finite discrete topological space $X$ with at least two elements, a nonempty set $\Gamma$, and a map $\varphi:\Gamma \to \Gamma$, $\sigma_{\varphi}:X^{\Gamma} \to X^{\Gamma}$with $\sigma_{\varphi}((x_{\alpha})_{\alpha \in \Gamma})=(x_{\varphi(\alpha)})_{\alpha \in \Gamma}$ (for $(x_{\alpha})_{\alpha \in \Gamma} \in X^{\Gamma}$) is a generalized shift. In this text for $\mathcal{S} = \{\sigma_{\varphi}:\varphi \in \Gamma^{\Gamma}\}$ and $\mathcal{H}=\{\sigma_{\varphi}:\Gamma \xrightarrow{\varphi} \Gamma$ is bijective$\}$ we study proximal relations of transformation semigroups $(\mathcal{S}, X^{\Gamma})$ and $(\mathcal{H}, X^{\Gamma})$. Regarding proximal relation we prove: $$P(\mathcal{S}, X^{\Gamma}) = \{((x_{\alpha})_{\alpha \in \Gamma},(y_{\alpha})_{\alpha \in \Gamma}) \in X^{\Gamma} \times X^{\Gamma} : \exists \beta \in \Gamma (x_{\beta} = y_{\beta})\}$$and $P(\mathcal{H}, X^{\Gamma} ) \subseteq \{((x_{\alpha})_{\alpha \in \Gamma},(y_{\alpha})_{\alpha \in \Gamma}) \in X^{\Gamma} \times X^{\Gamma} : \{\beta \in \Gamma : x_{\beta} = y_{\beta}\}$ is infinite$\}$ $\cup\{($ $x,x) : x \in \mathcal{X}\}$. Moreover, for infinite $\Gamma$, both transformation semigroups $(\mathcal{S}, X^{\Gamma})$ and $(\mathcal{H}, X^{\Gamma})$ are regionally proximal, i.e., $Q(\mathcal{S}, X^{\Gamma}) = Q(\mathcal{H}, X^{\Gamma} ) = X^{\Gamma} \times X^{\Gamma}$, also for sydetically proximal relation we have $L(\mathcal{H}, X^{\Gamma}) = \{((x_{\alpha})_{\alpha \in \Gamma},(y_{\alpha})_{\alpha \in \Gamma}) \in X^{\Gamma} \times X^{\Gamma} : \{\gamma ∈ \Gamma :$ $x_{\gamma} \neq y_{\gamma}\}$ is finite$\}$.     

Development of effervescence-assisted switchable polarity solvent homogeneous liquid-phase microextraction for the determination of permethrin and deltamethrin in water samples prior to gas chromatography–flame ionization detection

An effervescent tablet-assisted switchable polarity solvent–based homogeneous liquid-phase microextraction combined with gas chromatography with flame ionization detection has been conducted for the separation, preconcentration, and detection of permethrin and deltamethrin in the river water specimens. Triethylamine (TEA) was utilized as the switchable polarity solvent in this method. The switching process was carried out by the dissolution of an effervescent tablet including an effervescency agent (sodium carbonate) and a proton donor agent (citric acid). Changing the pH of the specimen solution enhanced the conversion of TEA into protonated triethylamine carbonate through the tablet that generated carbon dioxide bubbles in situ. Finally, the addition of sodium hydroxide changed the ionization state of TEA and separated the two phases. Influential factors in the extraction were investigated. According to optimal situations, the limit of detection and the limit of quantification were 0.16 and 0.5 μg L⁻¹ for permethrin and 0.03 and 0.1 μg L⁻¹ for deltamethrin, respectively. The preconcentration factor was 194 in river water samples and inter- and intra-day precision (relative standard deviation %; n = 5) was <5%. The extraction recovery was obtained in the range of 93.0%–97% for permethrin and deltamethrin in water samples.     

Approximation Algorithms for Min–Max Tree Partition

We consider the problem of partitioning the node set of a graph intopequal sized subsets. The objective is to minimize the maximum length, over these subsets, of a minimum spanning tree. We show that no polynomial algorithm with bounded error ratio can be given for the problem unless P = NP. We present anO(n²) time algorithm for the problem, wherenis the number of nodes in the graph. Assuming that the edge lengths satisfy the triangle inequality, its error ratio is at most 2p − 1. We also present an improved algorithm that obtains as an input a positive integerx. It runs inO(2^{(p + x)p}n²) time, and its error ratio is at most (2 − x/(x + p − 1))p.     

Nonlinear dynamic modeling of pneumatic nailing devices

This paper develops a mathematical modeling procedure for pneumatic nailing devices. The representation integrates all the operation phases composing the nailing process. The model accounts for the dynamics of the chamber pressures, the moving parts, the nonlinear interactions and impacts between the fixed and moving components, and includes the nail gun body and workpiece. All the system parameters integrated into the proposed model were established from experimental measurements. This model also integrates a nonlinear empirical formulation to predict the nail penetration resistance force. The final representation is validated through a comparison of the predicted piston motion and air pressures to experimental measurements made on a specific nail gun. The average of the percent error established at important time positions is lower than 7%.     

Small molecule correctors of F508del-CFTR discovered by structure-based virtual screening

Folding correctors of F508del-CFTR were discovered by in silico structure-based screening utilizing homology models of CFTR. The intracellular segment of CFTR was modeled and three cavities were identified at inter-domain interfaces: (1) Interface between the two Nucleotide Binding Domains (NBDs); (2) Interface between NBD1 and Intracellular Loop (ICL) 4, in the region of the F508 deletion; (3) multi-domain interface between NBD1:2:ICL1:2:4. We hypothesized that compounds binding at these interfaces may improve the stability of the protein, potentially affecting the folding yield or surface stability. In silico structure-based screening was performed at the putative binding-sites and a total of 496 candidate compounds from all three sites were tested in functional assays. A total of 15 compounds, representing diverse chemotypes, were identified as F508del folding correctors. This corresponds to a 3% hit rate, ~tenfold higher than hit rates obtained in corresponding high-throughput screening campaigns. The same binding sites also yielded potentiators and, most notably, compounds with a dual corrector-potentiator activity (dual-acting). Compounds harboring both activity types may prove to be better leads for the development of CF therapeutics than either pure correctors or pure potentiators. To the best of our knowledge this is the first report of structure-based discovery of CFTR modulators.