Using a nonparametric technique to measure the cost efficiency of postal delivery branches

A multiple-input and multiple-output model for measuring the cost efficiency of postal delivery branches is proposed. We analyze the complete postal network of the Serbian post delivery offices, which includes 1,194 post office branches. To compare the branches that operate under the same or similar conditions, the branches are grouped into 18 clusters by implementing the appropriate clustering algorithm. This enables a three-level analysis: branches–clusters–network. The cost efficiency of the branches is measured using data envelopment analysis. The efficiency of a particular cluster is calculated as an average cost efficiency score of the branches that belong to this cluster, and finally, the efficiency of the postal delivery network is assessed. The distribution of cost efficiency scores per clusters takes values from 15 to 92 %. At the level of the total network, the cost efficiency is 40 %, which indicates that there are possibilities for improvement. To obtain more specific guidelines, that is, the decomposition of cost efficiency into pure technical efficiency, the scale efficiency and allocative efficiency were assessed for each cluster and for the total delivery network. This research is beneficial to policy makers defining the scope of universal service obligation and to company managers who want to optimize the postal network. For example, the results of this study indicate that, at a minimum, 794 delivery branches could improve their efficiency by resource reallocation.     

Fixed Points of Sequence of Ćirić Generalized Contractions of Perov Type

Perov used the concept of vector valued metric space and obtained a Banach type fixed point theorem on such a complete generalized metric space. In this article, we study fixed point results for the new extensions of sequence of ?iri? generalized contractions on cone metric space, and we give some generalized versions of the fixed point theorem of Perov. The theory is illustrated with some examples. It is worth mentioning that the main result in this paper could not be derived from ?iri?’s result by the scalarization method, and hence indeed improves many recent results in cone metric spaces.     

Phenolic compounds in field horsetail (Equisetum arvense L.) as natural antioxidants

In this paper, the study of antioxidant activity and phenolic composition of three different extracts (EtOAc, n-BuOH and H(2)O) of field horsetail (Equisetum arvense L.) is presented. The antioxidant activity has been evaluated measuring the total reducing power (expressed by Ascorbate Equivalent Antioxidant Capacity - AEAC), inhibition of lipid peroxidation, and free radical scavenging capacity (RSC) towards 2,2-diphenyl-1-picrylhydrazyl (DPPH radical) and nitric oxide (NO), respectively. In addition, the total flavonoid content (TFC) and phenolic constituents of each extract have been determined. The results obtained show that the highest RSC regarding both DPPH and NO radicals is expressed by EtOAc extract (EC(50)=2.37 microg/mL and EC(50)=90.07 microg/mL, respectively), and the lowest by H(2)O extract (EC(50)=37.2 microg/mL and EC(50)>333.33 microg/mL, respectively). n-BuOH extract showed the highest total reducing power (AEAC=13.40 microg/mL). Differences in the phenolic composition of examined extracts are found comparing the HPLC chemical profiles. Although, isoquercitrin is the main flavonoid in both EtOAc and n-BuOH extracts, a considerable amount of di-E-caffeoyl-meso-tartaric acid was presented in the n-BuOH extract. In H(2)O extract high content of phenolic acids and low percentage of flavonoids were detected.     

Feasibility study for cell electroporation detection and separation by means of dielectrophoresis

Electroporation is a phenomenon during which exposure of a cell to high voltage electric pulses results in a significant increase in its membrane permeability. Aside from the fact that after the electroporation the cell membrane becomes more permeable, the cells' geometrical and electrical properties change considerably. These changes enable use of the force on dielectric particles exposed to non-uniform electric field (dielectrophoresis) for separation of non-electroporated and electroporated cells. This paper reports the results of an attempt to separate non-electroporated and electroporated cells by means of dielectrophoresis. In several experiments we managed to separate the non-electroporated and electroporated cells suspended in a medium with conductivity 0.174 S/m by exposing them to a non-uniform electric field at a frequency of 2 MHz. The behaviour of electroporated cells exposed to dielectrophoresis raises the presumption that in addition to conductivity, considerable changes in membrane permittivity occur after the electroporation.     

Disappearing Polymorphs Revisited

Nearly twenty years ago, Dunitz and Bernstein described a selection of intriguing cases of polymorphs that disappear. The inability to obtain a crystal form that has previously been prepared is indeed a frustrating and potentially serious problem for solid‐state scientists. This Review discusses recent occurrences and examples of disappearing polymorphs (as well as the emergence of elusive crystal forms) to demonstrate the enduring relevance of this troublesome, but always captivating, phenomenon in solid‐state research. A number of these instances have been central issues in patent litigations. This Review, therefore, also highlights the complex relationship between crystal chemistry and the law.     

Molecular above-threshold ionization with a circularly polarized laser field

Molecular above-threshold ionization by a circularly polarized laser field is investigated. Our theoretical approach is based on the modified molecular strong-field approximation. Various gauge-dependent versions of this approximation are considered and homonuclear and heteronuclear molecular species characterized by different symmetries are used as targets. As in the case of a linearly polarized field, the imprint of the molecular multicenter structure can be observed in the above-threshold ionization spectra. It manifests itself as minima in the rate of the ionized electrons as a function of their energy. The locations of these minima are strongly influenced by the symmetry of the corresponding highest occupied molecular orbital as well as the internuclear separation. Analyzing the interference structures of the electron spectra one can obtain information about the molecular symmetry.     

Two new zincophosphates, (H3NCH2CH2NH3)2[Zn(μ-PO4)2] and (NH4)[(H3N)Zn{(μ-PO4)Zn}3]: Crystal structures and relationships to similar open framework zinco- and aluminophospates

Two new zincophosphates, bis(ethylenediammonim) catena-bis(μ-phosphato)zincate, (H₃NCH₂CH₂NH₃)₂[Zn(μ-PO₄)₂] (1), and ammonium ammine-tris(μ-phosphato)tetrazincate, (NH₄)[(H₃N)Zn{(μ-PO₄)Zn}₃] (2), were synthesized under hydrothermal conditions and their crystal structures were determined by single-crystal X-ray diffraction analysis. The crystal structure of 1 consists of infinite macroanionic ZnP₂O₈⁴⁻ chains, running along the [0 0 1] direction, and diprotonated ethylenediammonium cations, H₂en²⁺. The crystal structure of 2 is built up from ZnO₄, Zn(NH₃)O₃ and PO₄ vertex-sharing tetrahedra connected to form an open 3D framework. The ammonium groups, NH₄⁺, are located in the channels formed by 8M-rings extending along [1 0 0]. In order to study vibrational behavior of H₂en²⁺ and NH₄⁺ cations, NH₃ molecules in 1 and 2, single-crystal Raman spectra were obtained. Structural, chemical and topological similarities to the other open framework zinco- and aluminophosphates incorporating different guest species are discussed.