Peeling from a patterned thin elastic film

Inspired by the observation that many naturally occurring adhesives arise as textured thin films, we consider the displacement controlled peeling of a flexible plate from an incision-patterned thin adhesive elastic layer. We find that crack initiation from an incision on the film occurs at a load much higher than that required to propagate it on a smooth adhesive surface; multiple incisions thus cause the crack to propagate intermittently. Microscopically, this mode of crack initiation and propagation in geometrically confined thin adhesive films is related to the nucleation of cavitation bubbles behind the incision which must grow and coalesce before a viable crack propagates. Our theoretical analysis allows us to rationalize these experimental observations qualitatively and quantitatively and suggests a simple design criterion for increasing the interfacial fracture toughness of adhesive films.Comment: 8 pages, To appear in Proceedings of Royal Society London, Ser.

Critical properties and stability of stationary solutions in multi-transonic pseudo-Schwarzschild accretion

For inviscid, rotational accretion flows, both isothermal and polytropic, a simple dynamical systems analysis of the critical points has given a very accurate mathematical scheme to understand the nature of these points, for {\em any} pseudo-potential by which the flow may be driven on to a Schwarzschild black hole. This allows for a complete classification of the critical points for a wide range of flow parameters, and shows that the only possible critical points for this kind of flow are saddle points and centre-type points. A restrictive upper bound on the angular momentum of critical solutions has been established. A time-dependent perturbative study reveals that the form of the perturbation equation, for both isothermal and polytropic flows, is invariant under the choice of any particular pseudo-potential. Under generically true outer boundary conditions, the inviscid flow has been shown to be stable under an adiabatic and radially propagating perturbtion. The perturbation equation has also served the dual purpose of enabling an understanding of the acoustic geometry for inviscid and rotational flows

Sharing the Risks of Bankruptcy: \u3ci\u3eTimbers\u3c/i\u3e, \u3ci\u3eAhlers\u3c/i\u3e, and Beyond

Bankruptcy policy appears to be in disarray. Recent decisions by the United States Supreme Court have only served to reinforce the uncertainties that mar the bankruptcy process. In United Savings Association of Texas v. Timbers of Inwood Forest Associates, Ltd., the Court held that an undersecured creditor was not entitled to interest on its collateral as compensation for the opportunity costs of delay caused by the bankruptcy process. Timbers thus supports the argument that secured creditors should be forced to share the burdens of bankruptcy with other claimants. Conversely, in Norwest Bank Worthington v. Ahlers, the Court held that the proposed contribution of future labor on the family farm could not trump the absolute priority rule that bars a debtor\u27s retention of an equity interest over the objections of senior creditors. Thus, Ahlers rejects the claim that secured creditors should be forced to share the burdens of bankruptcy through a liberalized contribution rule. Can these decisions be reconciled? And what light do they shed on the future of bankruptcy sharing? There are a number of ways to rationalize the results in Timbers and Ahlers through careful statutory and doctrinal analyses. The fact that this article does not address them does not belittle the value of careful allegiance to the Bankruptcy Code and prior case law in seeking to predict the future of bankruptcy law. Nevertheless, few would doubt that the Court could have written carefully reasoned opinions justifying the opposite result in each case. Thus, it seems probable that unacknowledged and unexpressed policy considerations may have influenced the Court. This article examines precisely what those policy goals are and what they imply for the future of federal bankruptcy. Part I of the article analyzes the traditional objectives of the bankruptcy process in terms of the techniques of contemporary legal analysis. This exercise is principally one of translation, the time-honored task of pouring old wine into new bottles. By attempting to recharacterize old truths in contemporary terms, I mean to clarify what those truths really mean. Thereafter, Part II sketches a theory that rationalizes the apparently conflicting objectives of bankruptcy law. The theory suggests that the Court\u27s decisions in Timbers and Ahlers are, in fact, entirely consistent and complementary. This approach thus provides a convenient benchmark for assessing how the burdens of bankruptcy ought best to be shared between various claimants of different classes

INFORMATION SYSTEMS OUTSOURCING: A MIXED INTEGER PROGRAMMING ANALYSIS

In the recent past, the trend toward outsourcing has become a major information systems phenomenon. Outsourcing is the subcontracting of various information systems subfunctions such as managing of data centers, operations, hardware support software maintenance, and even application software by user-firms to either incumbent vendors or outside vendors. Outsourcing is therefore emerging as a key approach for managing infonnation systems functions. In this research, we investigate the outsourcing bidding process pertinent to the selection of one subcontractor by a userfirm. We analyze bidding situations where the bidders have different levels of expertise and cost structures. The theoretical foundations for this research lie iii the theory of mechanism design (Myerson 1983), as well as the theory of imperfect information (Philips 1988) and incentive design (Ledyard 1989; McAfee 1986). We build a mixed integer programming model to represent what happens in an outsourcing bidding context involving a user-firm, an incumbent firm, and a challenger firm and explore the implications. The analysis is conducted over two different time horizons called the ex ante and the ex post periods. Two mixed-integer programming models are presented for two time horizons (in developing the model, we follow Kreps 1990). To reflect the different levels of expertise and cost structures of bidders, a discrete probability distribution is assigned to each bidder to approximate a bidder\u27 s true cost. A bidder\u27s true cost is private information, but its probability distribution is assumed to be common knowledge. An incumbent firm is assumed to have cost advantages over other bidders as a result of being familiar with the information needs of the user-firm. Therefore, the incumbent firm is assigned a cost probability distribution that is skewed toward low cost. The competing bidder\u27s cost structure is skewed toward high cost. The objective function of each model is formulated so as to minimize the expected cost subject to participation, and truthtelling constraints. Participation constraints indicate that each bidder participates only if a positive profit is given by the user-firm. Truth-telling constmints denote that each bidder prefers telling the truth to misrepresentation. The preliminary results of the models suggest that a policy of awarding incentives and levying penalties needs to be followed by the user firm. The results show that in order to induce the bidders to behave truthfully, some penalties would have to be levied and incentives would have to be provided. For example, if both the incumbent bidder and the challenger bid the same. the challenger is awarded the bid. If the incumbent firm is found to be inflating quotes, a penalty would have to be levied against the incumbent in the sense that the contract would be awarded to the challenger. Finally, in order to reward the bidder who quotes the true costs, subsides would have to be awarded. Thus, the models provide theoretical justification and guidelines for bidding behavior practices in the real world. Interestingly, both the ex-ante and ex-post models based on Krep\u27s assumptions show identical results. Implications of this finding need to be further explored in future research

Finding the optimum activation energy in DNA breathing dynamics: A Simulated Annealing approach

We demonstrate how the stochastic global optimization scheme of Simulated Annealing can be used to evaluate optimum parameters in the problem of DNA breathing dynamics. The breathing dynamics is followed in accordance with the stochastic Gillespie scheme with the denaturation zones in double stranded DNA studied as a single molecule time series. Simulated Annealing is used to find the optimum value of the activation energy for which the equilibrium bubble size distribution matches with a given value. It is demonstrated that the method overcomes even large noise in the input surrogate data.Comment: 9 pages, 4 figures, iop article package include

Magnetoelectric Effect and Spontaneous Polarization in HoFe3_3(BO3_3)4_4 and Ho0.5_{0.5}Nd0.5_{0.5}Fe3_3(BO3_3)4_4

The thermodynamic, magnetic, dielectric, and magnetoelectric properties of HoFe$_3$(BO$_3$)$_4$ and Ho$_{0.5}$Nd$_{0.5}$Fe$_3$(BO$_3$)$_4$ are investigated. Both compounds show a second order Ne\'{e}l transition above 30 K and a first order spin reorientation transition below 10 K. HoFe$_3$(BO$_3$)$_4$ develops a spontaneous electrical polarization below the Ne\'{e}l temperature (T$_N$) which is diminished in external magnetic fields. No magnetoelectric effect could be observed in HoFe$_3$(BO$_3$)$_4$. In contrast, the solid solution Ho$_{0.5}$Nd$_{0.5}$Fe$_3$(BO$_3$)$_4$ exhibits both, a spontaneous polarization below T$_N$ and a magnetoelectric effect at higher fields that extends to high temperatures. The superposition of spontaneous polarization, induced by the internal magnetic field in the ordered state, and the magnetoelectric polarizations due to the external field results in a complex behavior of the total polarization measured as a function of temperature and field.Comment: 12 pages, 15 figure

A Two Stage Investigation of the Determinants of Information Systems Outsourcing

Outsourcing has recently emerged as akey method of managing Information Systems especially since the report about Eastman Kodak and IBM\u27s outsourcing partnership in 1989 (Loh and Venkatraman, 1992a, 1992b). The importance of outsourcing is partially illustrated by the fact that there are myriad conflicting arguments both for and against outsourcing (Chaudhury et al, 1989, 1995; Gantz, 1990; Lacity and Hirschheim, 1993; Nam et al, 1995a, 1995b). Most outsourcing studies have focused on the investigation of the determinants of the decision to outsource by clients. Transaction cost economics (TCE) theory has recently been used in the study of the determinants of outsourcing (Lacity and Hirschheim, 1993; Nam et al, 1995a, 1995b). The theory of transaction cost economics (TCE) was originally formulated to address the make versus buy choice (Anderson and Coughlan, 1987; Erramilli and Rao, 1993) In TCE, Williamson (1989, 1987, 1981, 1979) proposed that firms should insource when they expect opportunistic behavior by the vendors. In particular when clients are locked-in with vendors, vendors\u27 opportunistic behavior will significantly impair the clients\u27 interests. This statement implies that attributes of existing relationships such as opportunism affect the firms\u27 subsequent make-or-buy decision with the incumbent vendors. However, most prior empirical research on TCE has treated each sourcing decision as an independent event (Masten, 1984; Walker and Walker, 1987, 1984) thereby disregarding the prior relationships that affect the subsequent sourcing decisions. Therefore, any outsourcing study must explicitly incorporate the role of prior ties in its analytical framework (Gulati, 1995). In the outsourcing context, it has been reported that very often clients continue their relationships with vendors. Also, many firms have to decide whether they should continue the outsourcing relationships with the vendors or not. Factors that affect continuation of the relationships are different from factors that affect the initial outsourcing behavior because client firms have locked-in relationships with vendors. According to Seabright et al (1992), and Levinthal et al (1988), prior relationships need to be investigated in order to study the subsequent relationships between clients and vendors. This study willfocus on i) the determinants of the outsourcing decisions and ii) the tendency to persist in the locked-in outsourcing relationship. We investigate the factors that determine outsourcing decisions in two stages. In the first stage, both insourcing and outsourcing firms are studied to investigate the determinants of make-or-buy decision. In the second stage, only outsourcing firms are considered in order to study the intention to continue with the relationship. Two dimensions are proposed in order to conceptualize the diverse types of outsourcing between clients and vendors (Nam et al, 1994a, 1994b). The first dimension is the extent of substitution by IS vendors and the second dimension is the strategic impact of IS applications. There are two types of strategic impact of IS applications: differentiation and cost reduction. The first dimension is proposed from the IS vendors\u27 point of view while the second dimension is proposed from the client firms\u27 point of view. Based on these two dimensions, four types of outsourcing relationships are proposed. These four types are support, reliance, alignment, and alliance. The support cell has a low extent of substitution and low strategic impact. This cell corresponds to the traditional IS vendors service. Vendorsare usually restricted to non-core IS activities and the size of contract is small. The reliance cell has a high extent of substitution and low strategic impact. The IBM and Kodak outsourcing example corresponds to this cell. In recent years, the trend ofoutsourcing has moved from the support cell to the reliance cell. The alignment cell has a low extent of substitution and high strategic impact. Examples in this cell are mostly IS consulting types of services. Even though vendors are not significantly involved with client firms\u27 IS operations, IS vendors significantly influence clients\u27 IS operations. The alliance cell has a high extent of substitution and high strategic impact. Outside vendors not only substitute in-house IS operations but also contribute to clients\u27 competitive advantages through provision of important IS functional activities. In the first stage, hypotheses are developed based on transaction and non-transaction cost factors with respect to the two proposed outsourcing dimensions. Threetransaction cost factors are studied as determinants of the two dimensions: asset specificity, uncertainty, potential number of vendors. Four non-transaction cost factors are also investigated. These four non-TCE factors are IT competency, IS influence, heterogeneity of information systems, and decision analysis effort. Multiple regressions are used to test hypotheses in the first stage. In the second stage, hypotheses are proposed based on prior relationships between clients and vendors in order to studythe determinants of the intention to continue with the outsourcing relationships. Prior relationships are represented by the four types of outsourcing relationships based on two dimensions of outsourcing, vendors performance in terms of client satisfaction, vendors\u27 opportunistic behavior and the length of prior relationships. Logistic regression is employed to test hypotheses in the second stage. Questionnaires were developed based on interviews with IS manager and pretested. Following a pretest, 800 questionnaires were sent to senior IS managers in the U.S. A follow-up letter was mailed to those who had not responded after about three weeks. In total 154 usable questionnaires were received representing a response rate of 19.25%. Out of 154, 93 respondedas outsourcing firms and 61 responded as insourcing firms

Magnetic Field resulting from non-linear electrical transport in single crystals of charge-ordered Pr0.63_{0.63} Ca0.37_{0.37} MnO3_{3}}

In this letter we report that the current induced destabilization of the charge ordered (CO) state in a rare-earth manganite gives rise to regions with ferromagnetic correlation. We did this experiment by measurement of the I-V curves in single crystal of the CO system Pr$_{0.63}$Ca$_{0.37}$MnO$_{3}$ and simultanously measuring the magnetization of the current carrying conductor using a high T$_c$ SQUID working at T = 77K. We have found that the current induced destabilization of the CO state leads to a regime of negative differential resistance which leads to a small enhancement of the magnetization of the sample, indicating ferromagnetically aligned moments.Comment: 4 pages LateX, 4 eps figure

Prevalence of various β-lactamase (ESBL, AmpC and MBL) producing multidrug resistant clinical isolates of Acinetobacter spp. in a tertiary care hospital.

Background: Extensive use of β- lactam group of antibiotics to treat the gram negative bacterial infections the antibiotic resistance are increasing and Acinetobacter species are budding as multidrug resistant (MDR) gram negative bacteria showing various β-lactamases mediated resistance. Materials and Methods: The presence of β-lactamases in the multi drug resistant clinical isolates of Acinetobacter species were screened by β-lactamase assay method. The presence of ESBL was detected by phenotypic confirmatory test recommended by Clinical and Laboratory Standards Institute (CLSI), AmpC was detected by CX/BA inhibitor method and carbapenem (IMP or MER)/EDTA combined disc method and Modified Hodge tests were performed to detect MBL mediated resistance mechanism. Results: We found high level of beta lactamase mediated resistance mechanism as part of multidrug resistance. Among 180 MDR isolates, 147 isolates were shown positive for beta lactamase assay method and these 147 isolates were further subjected to confirm presence of beta lactamase such as AmpC 105 (71.42%) followed by ESBL 84 (57.14%), MBL 43 (29.25%). Co-existence of ESBL and MBL also identified in 13 (8.84%) isolates. Conclusion: β-lactamase mediated resistance mechanisms are accounting very high in the multidrug resistant isolates of Acinetobacter species. Therefore early detection is necessary to screen and confirm beta lactamase mediated resistant strains to avoid treatment failure and prevent the spread of MDR