A 360 Degree View Of Selecting A Lubricant For My New Low GWP Refrigerant

The advent of environmentally friendly refrigerants and the global drive for higher efficiency is bringing change to our industry. A review of current HFC refrigerants and their lubricant choices over a range of evaporator temperatures will be summarized and compared to the numerous low GWP refrigerant replacements and associated lubricant considerations. The paper details a methodology for matching a refrigerant and a lubricant over a variety of low GWP refrigerant options. The current challenges in meeting miscibility, solubility, discharge temperature and working viscosity targets will be discussed and options presented. As the industry develops and implements both interim, lower GWP alternatives and long-term low or ultra-low GWP refrigerant options, in some cases the door has opened for development of new or optimized lubricant chemistries which are both compatible with the new refrigerants and also maintain or improve equipment performance and reliability. For example, CPI recognizes that the solubility characteristics of the low GWP refrigerants in many cases are different than the incumbent HFC refrigerants. CPI has investigated the solubility characteristics of new refrigerants and has developed innovative lubricant formulations to control solubility to minimize the need for equipment hardware or operating changes. While low GWP refrigerants are environmentally friendly with a shorter atmospheric life, in some cases either the refrigerants or the equipment operating conditions will bring about system chemistry concerns that didn’t exist with the stable HFC refrigerants such as R-134a. CPI will discuss methods to monitor for lubricant and refrigerant stability in a refrigeration system, and options to mitigate chemical stability concerns. The information shared in this presentation will provide a 360-degree view of the important aspects of matching a refrigerant to a lubricant for successful and reliable equipment operation

Integrals of Motion for Critical Dense Polymers and Symplectic Fermions

We consider critical dense polymers ${\cal L}(1,2)$. We obtain for this model the eigenvalues of the local integrals of motion of the underlying Conformal Field Theory by means of Thermodynamic Bethe Ansatz. We give a detailed description of the relation between this model and Symplectic Fermions including the indecomposable structure of the transfer matrix. Integrals of motion are defined directly on the lattice in terms of the Temperley Lieb Algebra and their eigenvalues are obtained and expressed as an infinite sum of the eigenvalues of the continuum integrals of motion. An elegant decomposition of the transfer matrix in terms of a finite number of lattice integrals of motion is obtained thus providing a reason for their introduction.Comment: 53 pages, version accepted for publishing on JSTA

The Baxter Q Operator of Critical Dense Polymers

We consider critical dense polymers ${\cal L}_{1,2}$, corresponding to a logarithmic conformal field theory with central charge $c=-2$. An elegant decomposition of the Baxter $Q$ operator is obtained in terms of a finite number of lattice integrals of motion. All local, non local and dual non local involutive charges are introduced directly on the lattice and their continuum limit is found to agree with the expressions predicted by conformal field theory. A highly non trivial operator $\Psi(\nu)$ is introduced on the lattice taking values in the Temperley Lieb Algebra. This $\Psi$ function provides a lattice discretization of the analogous function introduced by Bazhanov, Lukyanov and Zamolodchikov. It is also observed how the eigenvalues of the $Q$ operator reproduce the well known spectral determinant for the harmonic oscillator in the continuum scaling limit.Comment: improved version, accepted for publishing on JSTA

Risky choices in strategic environments: An experimental investigation of a real options game

Managers frequently make decisions under conditions of fundamental uncertainty due the stochastic nature of the outcomes and competitive rivalry. In this study, we experimentally test a theoretical model under fundamental uncertainty and competitive rivalry by designing a sequential interaction game between two players. The first mover can decide either to choose a sure outcome that assigns a risky outcome to the second mover or to pass the decision to the second mover. If the second player gets the chance to decide, she can choose between a sure outcome, conditioned by the assignment of a risky payoff to the first mover, or the sharing of the risky outcome with the first mover. We then introduce the following experimental treatments: (i) relegating second-mover participants to a purely passive role and substituting them with a random device (absence of strategic uncertainty - that is, when the source of uncertainty is a human subject); (ii) providing information about the behaviour of second-mover counterparts; and (iii) completely removing the second-mover participant.We find that decision makers are sensitive to the presence or absence of strategic uncertainty; indeed, in the presence of strategic uncertainty, first movers more often diverge from the behaviour predicted by the model. Given our experimental results, the theoretical model needs to be revisited. The standard model of monetary payoff-maximizing agents should be substituted by one of decision makers who maximize a utility function which includes the psychological cost induced by strategic uncertainty. (C) 2019 Published by Elsevier B.V

The management of dental practices in the post-covid 19 era: An economic and operational perspective

Background: In order to protect dental teams and their patients during the COVID-19 pandemic, dentists have had to adopt several measures (operating and post-operating procedures) which may increase the total treatment time and costs relating to individual protective measures. This paper will propose a thorough analysis of operating dentistry procedures, comparing the economic performance of the activity in a dental surgery before and after the adoption of these protective measures, which are required to contain the risk of SARS-COV-2 infections. Methods: The economic analysis is articulated in three approaches. Firstly, it assesses a reduction in markup by maintaining current charges (A); alternatively, it suggests revised charges to adopt in order to maintain unvaried levels of markup (B). And the third Approach (C) examines available dental treatments, highlighting how to profitably combine treatment volumes to reduce markup loss or a restricted increase in dental charges. Results: Maintaining dental charges could cause a loss in markup, even rising to 200% (A); attempting to maintain unvaried levels of markup will result in an increase in dental charges, even at 100% (B); and varying the volumes of the single dental treatments on offer (increasing those which current research indicates as the most profitable) could mitigate the economic impact of the measures to prevent the transmission of SARS-COV-2 (C). Conclusions: The authors of this paper provide managerial insights which can assist the dentist-entrepreneur to become aware of the boundaries of the economic consequences of governmental measures in containing the virus infection

On the Integrable Structure of the Ising Model

Starting from the lattice $A_3$ realization of the Ising model defined on a strip with integrable boundary conditions, the exact spectrum (including excited states) of all the local integrals of motion is derived in the continuum limit by means of TBA techniques. It is also possible to follow the massive flow of this spectrum between the UV $c=1/2$ conformal fixed point and the massive IR theory. The UV expression of the eigenstates of such integrals of motion in terms of Virasoro modes is found to have only rational coefficients and their fermionic representation turns out to be simply related to the quantum numbers describing the spectrum.Comment: 18 pages, no figure

Removal torque of zirconia abutment screws under dry and wet conditions

The aim of this study was to verify whether screw abutment lubrication can generate higher preload values compared to non-lubricated screws, a titanium abutment was screwed onto an implant analog and scanned with the Procera System to generate 20 zirconia abutments. MKIII Brånemark implants were clamped to a precision torque device, and the abutments were distributed in dry and wet groups with 10 specimens each. In the wet groups, the inner threads of the implants were filled with artificial saliva. All abutments were fastened with a Torqtite screw under 32 Ncm. Ten detorque measurements were performed per group pushing the reverse button of the Torque controller soon after screw tightening with values registered. The mean detorque values were calculated and compared by a Student's t test (?=0.05). The wet condition presented significantly higher mean detorque than the dry condition (31.5 ± 1.2 versus 27.5 ± 1.5 Ncm, respectively; p=0.0000024). In conclusion, there was always a loss in the initial torque values when the removal torque was measured under both conditions. The wet condition presented higher mean torque than the dry condition. Better preload values were established in the wet group, suggesting that the abutment screw must be lubricated in saliva to avoid further loosening.A fim de verificar se a lubrificação do parafuso do pilar pode gerar valores maiores de pré-carga do que nos parafusos não lubrificados, um pilar de titânio foi parafusado no análogo do implante e escaneado pelo Sistema Procera para gerar 20 pilares de zircônia. Depois, os implantes MKIII Brånemark foram presos num dispositivo de torque. Os pilares foram distribuídos em grupos seco e úmido com 10 amostras cada. No grupo úmido, as roscas internas dos implantes foram preenchidas com saliva artificial. Então, todos os pilares foram apertados com parafuso Torqtite a 32 Ncm. Dez medidas de destorque foram realizadas por grupo apertando-se o botão reverso do Torque Controller logo depois do parafusamento, e os valores foram registrados. As medias de destorque foram calculadas e comparadas pelo teste t de Student (?=0,05). Os valores médios obtidos nas condições seca e úmida foram 27,5 ± 1,5 Ncm e 31,7 ± 1,2 Ncm, respectivamente. Diferenças estatisticamente significantes foram observadas (p=0,0000024). Observou-se sempre existir uma perda do torque inicial quando o torque de remoção é mensurado em ambas as condições. A condição úmida demonstrou um valor médio maior de torque do que a condição seca. Valores melhores de pré-carga podem ser estabelecidos no grupo úmido, sugerindo que o parafuso do pilar deve ser lubrificado em saliva para evitar seu afrouxamento