Proposing new variables for the identification of strategic groups in franchising

The identification of strategic groups in the Spanish franchising area is the main aim of this study. The authors have added some new strategic variables (not used before) to the study and have classified franchisors between sectors and distribution strategy. The results reveal the existence of four perfectly differentiated strategic groups (types of franchisors). One of the major implications of this study is that the variables that build a strategic group vary depending on the respective sector the network operates in and its distribution strategy. This fact indicates that including sector and distribution strategy is absolutely necessary to achieve good classifications of franchisor type

A model for transition of 5 '-nuclease domain of DNA polymerase I from inert to active modes

Bacteria contain DNA polymerase I (PolI), a single polypeptide chain consisting of similar to 930 residues, possessing DNA-dependent DNA polymerase, 3'-5' proofreading and 5'-3' exonuclease (also known as flap endonuclease) activities. PolI is particularly important in the processing of Okazaki fragments generated during lagging strand replication and must ultimately produce a double-stranded substrate with a nick suitable for DNA ligase to seal. PolI's activities must be highly coordinated both temporally and spatially otherwise uncontrolled 5'-nuclease activity could attack a nick and produce extended gaps leading to potentially lethal double-strand breaks. To investigate the mechanism of how PolI efficiently produces these nicks, we present theoretical studies on the dynamics of two possible scenarios or models. In one the flap DNA substrate can transit from the polymerase active site to the 5'-nuclease active site, with the relative position of the two active sites being kept fixed; while the other is that the 5'-nuclease domain can transit from the inactive mode, with the 5'-nuclease active site distant from the cleavage site on the DNA substrate, to the active mode, where the active site and substrate cleavage site are juxtaposed. The theoretical results based on the former scenario are inconsistent with the available experimental data that indicated that the majority of 5'-nucleolytic processing events are carried out by the same PolI molecule that has just extended the upstream primer terminus. By contrast, the theoretical results on the latter model, which is constructed based on available structural studies, are consistent with the experimental data. We thus conclude that the latter model rather than the former one is reasonable to describe the cooperation of the PolI's polymerase and 5'-3' exonuclease activities. Moreover, predicted results for the latter model are presented

The Effects of Various Concentrations of FGF-2 on the Proliferation and Neuronal Yield of Murine Embryonic Neural Precursor Cells In Vitro

Embryonic neural precursors (ENPs), also termed neural stem cells or "neurospheres," are an attractive potential source of tissue for neural transplantation, because of their capacity to expand in number in vitro while retaining the ability to develop into the major phenotypes of the CNS. ENPs are isolated from the developing brain and proliferate in the presence of mitogens such as FGF-2 and EGF. Subsequent withdrawal of these mitogens and exposure to a suitable substrate results in differentiation into the major cell types of the CNS. As well as its role in precursor cell expansion, FGF-2 also plays a key role in the division of astrocytes, and in neuronal differentiation. Thus, it is important to establish the optimal concentrations of this factor for expansion and differentiation of neuronal phenotypes. Here we explore the effect of FGF-2 concentrations ranging from 1 to 20 ng/ml on the expansion and differentiation capacity of ENPs isolated from the cortex and striatum of E14 mice. ENP expansion was seen under all conditions, but was greatest at 10 and 20 ng/ml and least at 1 ng/ml. The numbers of neurons (as a proportion of total cell number) differentiating from these ENP populations appeared to be greatest at 1 ng/ml. However, once adjustments were made for the amount of expansion at each dose, final neuronal yield was maximum at the highest concentration of FGF-2 used (20 ng/ml)

The Effects of Various Concentrations of FGF-2 on the Proliferation and Neuronal Yield of Murine Embryonic Neural Precursor Cells In Vitro

Embryonic neural precursors (ENPs), also termed neural stem cells or "neurospheres," are an attractive potential source of tissue for neural transplantation, because of their capacity to expand in number in vitro while retaining the ability to develop into the major phenotypes of the CNS. ENPs are isolated from the developing brain and proliferate in the presence of mitogens such as FGF-2 and EGF. Subsequent withdrawal of these mitogens and exposure to a suitable substrate results in differentiation into the major cell types of the CNS. As well as its role in precursor cell expansion, FGF-2 also plays a key role in the division of astrocytes, and in neuronal differentiation. Thus, it is important to establish the optimal concentrations of this factor for expansion and differentiation of neuronal phenotypes. Here we explore the effect of FGF-2 concentrations ranging from 1 to 20 ng/ml on the expansion and differentiation capacity of ENPs isolated from the cortex and striatum of E14 mice. ENP expansion was seen under all conditions, but was greatest at 10 and 20 ng/ml and least at 1 ng/ml. The numbers of neurons (as a proportion of total cell number) differentiating from these ENP populations appeared to be greatest at 1 ng/ml. However, once adjustments were made for the amount of expansion at each dose, final neuronal yield was maximum at the highest concentration of FGF-2 used (20 ng/ml)

The survival of neural precursor cell grafts is influenced by in vitro expansion

Embryonic neural precursor cells (ENPs) provide a potential alternative for transplantation in neurodegenerative diseases, as they can be expanded in culture, avoiding many of the practical obstacles that limit the application of transplanting primary neurones. However, grafts of ENPs into animal models show variable survival and limited differentiation into neurones. The effect of expansion time on their ability to survive and differentiate may be an important factor in this and has not been examined directly. In these experiments, murine and human ENPs were expanded for short (4 weeks) and long (20 weeks) periods before transplantation into the adult rat striatum. Whereas grafts of both short- and long-term expanded human ENPs survived for 4 weeks following transplantation, by 20 weeks all long-term expanded grafts had disappeared. Murine ENPs behaved similarly: only grafts of short-term expanded ENPs survived at 12 weeks following transplantation. RT-PCR analysis of ENP cultures after 4 and 20 weeks of expansion demonstrated changes in expression of a number of different groups of genes. We conclude that long-term expansion of ENPs profoundly impairs their ability to survive long-term after transplantation into the adult brain. This has implications for the potential use of these cells for neural transplantation strategies

Translational Symmetries in the Linear-Chain Semiconductors K\u3csub\u3e4\u3c/sub\u3e[Pt\u3csub\u3e2\u3c/sub\u3e(P\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e5\u3c/sub\u3eH\u3csub\u3e2\u3c/sub\u3e)\u3csub\u3e4\u3c/sub\u3eX]•nH\u3csub\u3e2\u3c/sub\u3eO (X = Cl, Br, I)

The solid-state structures of the linear-chain semiconductors K4[Pt2(P2O5H2)4X]•nH2O (X = Cl, Br, I), abbreviated Pt2Cl, Pt2Br, and Pt2I, have been studied. The X-ray crystal structures of Pt2Cl at 300 and 22 K and of Pt2Br at 19 K are reported. These structures show that Pt2Cl is a composite of alternating units of Pt2 and Pt2Cl2 with (AABCCB)n translational symmetry. The X-ray structure of Pt2Br, on the other hand, shows equivalent Pt-Pt bonds and two slightly different Pt-Br bonds. Raman data confirm the composite Pt2/Pt2Cl2 structure for Pt2Cl and indicate that the Pt2Br species is comprised of dimeric units with nearly equal Pt-Pt bonds. The Pt2Br structure is viewed as involving a slight distortion from idealized (AAB)n toward (AABCCB)n translational symmetry. Structural studies of Pt2I were attempted; however, all crystals were twinned. Magnetic susceptibility, microwave conductivity, ESCA, and reflectance spectroscopy measurements are reported for Pt2Br; the material is a semiconductor, with a = 10-3Ω-1 cm-1 at 300 K, a bandgap of 0.08 eV, and a bandwidth greater than 0.05 eV. © 1988, American Chemical Society. All rights reserved

Comparative Evaluation of Public-Private Partnerships in Roadway Preservation

In a bid to reduce overall costs, manage risks, and attract private capital, highway agencies worldwide strive to increase private-sector participation in road infrastructure development, particularly at the developmental phases of construction and preservation. A common mechanism for private-sector participation is the concept of a public-private partnership (PPP). As agencies grapple with the decision about whether to adopt a specific PPP or the traditional contracting approach for a specific project, they lack a rational decision-support structure. In addressing this major gap in PPP-related literature, this paper presents a framework by which an agency may assess the performance (relative benefits) of different PPP contracting approaches for highway preservation. For the purposes of this paper, performance is expressed in relation to the likelihood and intensity of cost savings calculated with data from domestic (U.S.) and international projects. In addition, the influence of project and contract attributes (such as the expected project duration, work type, and project size) on PPP project performance is investigated. The framework can be used or duplicated by highway-related agencies and international organizations for identifying the superior contracting option for a given road preservation project on the basis of project characteristics and for quantifying the consequences of such choices for cost savings or other performance criteria