Selective generalized travelling salesman problem

ABSTRACT

This paper introduces the Selective Generalized Traveling Salesman Problem (SGTSP). In SGTSP, the goal is to determine the maximum profitable tour within the given threshold of the tour’s duration, which consists of a subset of clusters and a subset of nodes in each cluster visited on the tour. This problem is a combination of cluster and node selection and determining the shortest path between the selected nodes. We propose eight mixed integer programming (MIP) formulations for SGTSP. All of the given MIP formulations are completely new, which is one of the major novelties of the study. The performance of the proposed formulations is evaluated on a set of test instances by conducting 4608 experimental runs. Overall, 4138 out of 4608 (~90%) test instances were solved optimally by using all formulations.     

Preconcentration and determination of trace metals by flow injection micelle-mediated extraction using flame atomic absorption spectrometry

Micelle-mediated extraction/preconcentration is incorporated on-line into a flow injection system used to determine low levels of Cd(II), Co(II), Cu(II), Mn(II), Ni(II), Pb(II) and Zn(II) present in various samples. The analyte is complexed with HBDAP (N,N′-bis(2-hydroxy-5-bromo-benzyl)1,2-diaminopropane). Under optimal conditions, a solution of 30% (m/v) NaCl and a sample solution containing 2.5 mL of 1% (m/v) sodium dodecyl sulfate (SDS), 0.5 mL of 1.8 × 10⁻³ M HBDAP and 2.5 mL of pH 8.5 borate buffer solution in 25 mL were pumped through the cotton filled mini-column; onto which the surfactant-rich phase containing the complex is collected. A solution of 0.5 M HNO₃ in 50% acetone is used as the eluent. The limits of detection are (ng mL⁻¹) Cd = 0.39, Cu = 3.2, Co = 7.5, Mn = 3.0, Ni = 3.4, Pb = 17.9 and Zn = 0.89 if the sample is allowed to flow for 30 s, but improved for extended preconcentration periods. Analysis of liquid and solid reference materials showed good agreement with the certified values. Complex formation constants between HBDAP and these metal ions were also determined potentiometrically.     

Determination of Electrochemical Interaction between 2‐(1H‐benzimidazol‐2‐yl) Phenol and DNA Sequences

A benzimidazole derivate, 2‐(1H‐benzimidazol‐2‐yl) phenol (2‐Bip) and its interaction mechanism with sequence specific DNA was examined with Differential Pulse Voltammetry (DPV). We, for the first time, investigated the effect of 2‐Bip on sequence specific DNA with electrochemical methods by evaluating both guanine and 2‐Bip oxidation signal changes. In the study, probe sequences were immobilized to the surface of the electrodes and then hybridization was achieved by sending the complementary target onto the probe modified electrodes. Following the hybridization, 2‐Bip solution was interacted with probe and hybrid sequences to see the effect of 2‐Bip on different DNA sequences. The binding constant (K), toxicity (S%) and thermodynamic parameters, i. e., Gibbs free energy (ΔG°) of 2‐Bip‐DNA complexes were evaluated. K was calculated as 5×10⁵ and the change in the ΔG° was found as ?32.50 kJ mol^?1, which are consistent well with the literature. Furthermore, S% showed that 2‐Bip is moderately toxic to single stranded DNA (ssDNA) and toxic to double stranded DNA (dsDNA). From our experimental data, we made four conclusions (i) 2‐Bip affects both ssDNA and dsDNA, (ii) 2‐Bip interaction mode with DNA could be non‐covalent interactions, (iii) 2‐Bip could be used as new DNA hybridization indicator due to its distinct effects on ssDNA and dsDNA, (iv) 2‐Bip could be used as a drug molecule for its DNA effect.     

A Novel Molecule: 1-(2,6 Dichlorobenzyl)-4-(2-(2-4-hydroxybenzylidene)hydrazinyl)pyridinium Chloride and its Interaction with DNA

Herein, a novel pyridine derivative, 1-(2,6 dichlorobenzyl)-4-(2-(2-4-hydroxybenzylidene)hydrazinyl)-pyridinium chloride (DHPC), was synthesized as a candidate drug molecule. Interaction of DHPC with DNA was used to explore its effect on DNA via Differential Pulse Voltammetry, Cyclic Voltammetry, and Electrochemical Impedance Spectroscopy. We demonstrated that oxidation signal of guanine bases of DNA decreased significantly while that of DHPC increased after its interaction with one another. Our candidate drug molecule exhibits LOD and LOQ, e.g., 1.5 μg/mL and 4.9 μg/mL, respectively. Toxicity effect value for DHPC (S%) was calculated as %31, demonstrating the candidate drug molecule's toxic effect on DNA.     

Synthesis and Antinociceptive Effect of Some Thiazole-Piperazine Derivatives: Involvement of Opioidergic System in the Activity

In this study, we aimed to design and synthesize novel molecules carrying both the thiazole and piperazine rings in their structures and to investigate their antinociceptive activity. Targeted compounds were obtained by reacting thiosemicarbazide derivative and appropriate 2-bromoacetophenone in ethanol. The structures of the obtained compounds were determined using data from various spectroscopic methods (IR, ¹H-NMR, ¹³C-NMR, and LCMSMS). Experimental data from in vivo tests showed that test compounds 3a–3c, 3f, and 3g (50 mg/kg) significantly prolonged reaction times of animals in tail-clip and hot-plate tests compared to the controls, indicating that these compounds possess centrally mediated antinociceptive activities. Furthermore, these compounds reduced the number of writhing behaviors in the acetic acid-induced writhing tests, showing that the compounds also possess peripheral antinociceptive activity. In the mechanistic studies, naloxone pre-treatments abolished the antinociceptive activities of compounds 3a–3c, 3f, and 3g, indicating that opioidergic mechanisms were involved in their antinociceptive effects. Molecular docking studies demonstrating significant interactions between the active compounds and µ- and δ-opioid receptor proteins supported the pharmacological findings. This study is the first showing that molecules designed to bear thiazole and piperazine moieties together on their structure exert centrally and peripherally mediated antinociceptive effects by activating the opioid system.     

Effects of solvent casted poly (lactic acid)/poly(ethylene glycol)/paraben derivative triazine films on antibacterial performance and cytotoxicity

A series of poly(lactic acid) (PLA) films that including fully paraben substituted triazine derivatives having anti-bacterial properties have been prepared by utilizing the solvent-casting method. PLA as biodegradable polymer, poly(ethylene glycol) (PEG) as a plasticizing agent and s-triazine molecules (TA01, TA02, TA03, TA04, and TA05) behaving as an anti-bacterial component have been utilized in the experiments. The influence of TA compounds on the antibacterial performance of PLA/PEG films was investigated for the first time against Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) bacteria via the contact active method. TA01-03-05 incorporated PLA/PEG films gave the best results against E.coli bacteria and log10 reductions of these films were 0.78, 0.64, and 0.65 respectively. The effect of TA compounds on the cell viability was investigated against cancer and non-cancerous cell lines using an MTS assay. The results showed that TA compounds had a positive effect on cell growth in non-cancerous cells, while they had a negative effect on cell growth in cancer cells. Furthermore, the addition of TA considerably increased the decomposition temperatures from 349° to 361° and char yield from 0.65 for PLA/PEG film to 2.3 for PLA/PEG/TA05. All of the films had good transparency and low opacity which was 7.2 for pure PLA used for control and the maximum opacity value was 11.2 observed for PLA/PEG/01. TA03 and TA04 caused a decrement of water vapor permission when compared to PLA/PEG films from 1439 to 749 and 664. It was also observed that pure PLA/PEG film lost weight rapidly over time during degradation tests. On the other hand, weight loss wasn't observed in PLA/PEG/TA films. This study focused on demonstrating the use of our new, flexible PLA/PEG derivatives in food and medical packaging.     

Novel Thiosemicarbazone Derivatives: In Vitro and In Silico Evaluation as Potential MAO-B Inhibitors

MAO-B inhibitors are frequently used in the treatment of neurodegenerative diseases such as Parkinson’s and Alzheimer’s. Due to the limited number of compounds available in this field, there is a need to develop new compounds. In the recent works, it was shown that various thiosemicarbazone derivatives show hMAO inhibitory activity in the range of micromolar concentration. It is thought that benzofuran and benzothiophene structures may mimic structures such as indane and indanone, which are frequently found in the structures of such inhibitors. Based on this view, new benzofuran/benzothiophene and thiosemicarbazone hybrid compounds were synthesized, characterized and screened for their hMAO-A and hMAO-B inhibitory activity by an in vitro fluorometric method. The compounds including methoxyethyl substituent (2b and 2h) were found to be the most effective agents in the series against MAO-B enzyme with the IC₅₀ value of 0.042 ± 0.002 µM and 0.056 ± 0.002 µM, respectively. The mechanism of hMAO-B inhibition of compounds 2b and 2h was investigated by Lineweaver–Burk graphics. Compounds 2b and 2h were reversible and non-competitive inhibitors with similar inhibition features as the substrates. The K_i values of compounds 2b and 2h were calculated as 0.035 µM and 0.046 µM, respectively, with the help of secondary plots. The docking study of compound 2b and 2h revealed that there is a strong interaction between the active sites of hMAO-B and analyzed compound.     

Electrochemical Aptasensors for Biological and Chemical Analyte Detection

Aptamers are short length, single-stranded DNA or RNA affinity molecules which interact with any desired targets such as biomarkers, cells, biological molecules, drugs or chemicals with high sensitivity. They have been extensively employed for medical applications due to having more advantages than the antibodies such as easier preparation and modification, higher stability, lower batch-to-batch variability and cost. Moreover, aptamers can be easily integrated efficiently with sensors, biosensors, actuators and other devices. In this review article, different applications of aptamers for biological and chemical molecules detection within the scope of electrochemical methods were presented with recent studies. In addition, the present status and future perspectives for highly-effective aptasensors for specific and selective analyte detection were discussed. As in stated throughout the review, combining of extraordinary properties of aptamers with the electrochemical-based biosensors could have improved the sensitivity of the assay and reduced limit of detection.     

Enhanced catalytic activity of lipase encapsulated in PCL nanofibers

Use of biocatalysis for industrial synthetic chemistry is on the verge of significant growth. Enzyme immobilization as an effective strategy for improving the enzyme activity has emerged from developments especially in nanoscience and nanotechnology. Here, lipase from Burkholderia cepacia (LBC), as an example of the luxuriant enzymes, was successfully encapsulated in polycaprolactone (PCL) nanofibers, proven by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Evaluated in both organic and aqueous medium, the activation factor of the encapsulated enzymes in the hydrolysis reaction was generally higher than that in the transesterification reaction. Enhanced catalytic activities were found when 5-20 w/w % of LBC was loaded. The effect of different solvents pretreatment on the activity of immobilized LBC was also investigated. The highest activation factor was found up to 14 for the sample containing acetone-treated LBC/PCL (10 w/w %). The encapsulated lipase reserved 50% of its original activity after the 10th run in the transesterification reaction in hexane medium. The mechanism of activation of lipase catalytic ability based on active PCL nanofiberous matrix is proposed.     

Uniqueness of uniform decompositions in exact categories

Two uniqueness theorems on uniform decompositions due to Krause, Diracca and Facchini are extended from abelian categories to weakly idempotent complete exact categories. We give applications to (quasi-)abelian categories, finitely accessible additive categories and exactly definable additive categories.