bluuebunny/crossref_metadata_2025 huggingface dataset:
Interleukin-6 Is an Afferent Signal to the Hypothalamo-Pituitary-Adrenal Axis during Local Inflammation in Mice
Authors: Turnbull Andrew V. , Prehar Sukhpal , Kennedy Adam R. , Little Roderick A. , Hopkins Stephen J.
Published: April 2003

The cytokines IL-1 and IL-6 are able to induce prostaglandin (PG)-dependent activation of the hypothalamo-pituitary-adrenal axis (HPAA) and are thought to play key roles in immune-neuroendocrine interactions during inflammation. The present study shows that inflammation induced by im injection of turpentine (TPS) in the hind limb of mice causes an increase in the plasma concentration of IL-6, but not that of IL-1α or IL-1β, together with a prolonged (>18-h) activation of the HPAA. IL-6 plays a causal role in the TPS-induced elevation in HPAA activity, because the sustained (8–18 h) increases in 1) plasma corticosterone, 2) plasma ACTH, and 3) induction of c-Fos in the hypothalamic paraventricular nucleus are all markedly blunted in IL-6-deficient (IL-6−/−) mice. Peripheral administration of a neutralizing IL-6 antiserum inhibited the plasma corticosterone response of normal (C57BL/6) mice to hind limb inflammation to an extent similar to that seen in IL-6−/− mice, suggesting that the IL-6 responsible for the increased HPAA activity is produced, or acts, on the blood side of the blood-brain barrier. We also show that IL-6 in the circulation is induced almost exclusively at the local inflammatory site, where IL-1β is produced. Induction of IL-6 and activation of the HPAA are dependent upon prior activation of an IL-1 type I receptor, as both are inhibited in type I IL-1 receptor-deficient mice. Furthermore, hind limb inflammation induced cyclooxygenase-2 protein expression around the cerebrovasculature of normal (IL-6+/+), but not IL-6−/−, mice. Based on these data, we propose that IL-6 is produced at the local inflammatory site under the control of IL-1β and is the circulating afferent signal that is in part responsible for elevated HPAA activity, possibly acting via eicosanoid production within the cerebrovasculature.
The more electric aircraft—assessing the benefits
Authors: Jones R I
Published: April 2003

The concept of the more electric aircraft (MEA), where electrical power is used for at least some of the on-board functions at present powered by hydraulics and pneumatics, has many claimed benefits and is far from new. However, almost all larger aircraft retain hydraulics and pneumatics.

Over recent years there has been a great deal of interest in the MEA concept, with developments in relevant technologies and their adoption in other areas of engineering. In support of UK efforts on this and related concepts, the College of Aeronautics has been performing studies since the mid 1980s to assess the benefits of changes. This paper describes the background to these studies and the relationships between them as well as some of their findings, concluding that it is important that such assessment work should be continued in the future.
Theoretical Study on the Structures and Absorption Properties of Yellow Azomethine Dyes
Authors: Ichijima Seiji , Fukunaga Hiroo , Kobayashi Hidetoshi , Ishihara Makoto , Koga Nobuaki
Published: April 2003

To examine the relationship between the structural features and the visible absorption spectra of yellow α-acylacetanilide azomethine dyes, we carried out measurements of the visible absorption spectra, X-ray crystal structure analyses, and density functional theory calculations for 2-benzoyl-2-[N-(4-diethylamino-2-methylphenyl)imino]-2′-chloroacetanilide (BA) and 2-[N-(4-diethylamino-2-methylphenyl)imino]-2-pivaloyl-2′-chloroacetanilide (PA). BA shows a visible absorption spectrum, which has a relatively high molar extinction coefficient and an unwanted absorption curve in the green region, while PA shows a visible absorption spectrum, which has a relatively low molar extinction coefficient and a sharp cut absorption curve in the green region. BA and PA have a common structural feature that the p-aminophenyl fragment is coplanar with the azomethine-carbamoyl (–N=C–CONH–) fragment, resulting in a chromophore, but is perpendicular to the acyl fragment. The stable structures are dominated by the effect of π-conjugation in the chromophore moiety and a repulsive interaction between the p-aminophenyl fragment and the acyl fragment. The potential energy curve for the rotation of the p-aminophenyl fragment shows two minima, and suggests that in BA two conformations coexist in equilibrium, while PA takes only single conformation in equilibrium. The difference in the absorption spectra of BA and PA is mainly attributed to the number of conformers coexisting in equilibrium.
Syntheses and Magnetic Properties of Ruthenium(II,III) Pivalate Dimers Axially Coordinated by Nitronyl Nitroxide Radicals [Ru2(O2CCMe3)4(L)2]BF4 and [{Ru2(O2CCMe3)4(L)2}{Ru2(O2CCMe3)4(H2O)2}]n(BF4)2n, L = 2,4,4,5,5-Pentamethyl-4,5-dihydro-1H-imidazol-1-oxyl-3-N-oxide and 2-Ethyl-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxyl-3-N-oxide
Authors: Sayama Yasuyoshi , Handa Makoto , Mikuriya Masahiro , Hiromitsu Ichiro , Kasuga Kuninobu
Published: April 2003

The reaction of [Ru2II,III(O2CCMe3)4]BF4 with nitronyl nitroxide radicals (2,4,4,5,5-pentamethyl-4,5-dihydro-1H-imidazol-1-oxyl-3-N-oxide (nitme) and 2-ethyl-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxyl-3-N-oxide (nitet)) in CH2Cl2/hexane gave dimer and chain complexes [Ru2(O2CCMe3)4(L)2]BF4 and [{Ru2(O2CCMe3)4(L)2}{Ru2(O2CCMe3)4(H2O)2}]n(BF4)2n (L = nitme and nitet). The latter complexes have a chain structure formed by hydrogen bonds between the axial radical ligands and the water molecules. It was shown that the antiferromagnetic interaction between the coordinated radicals through the Ru–Ru bond as well as the ferromagnetic interaction between the radical and the Ru(II,III) dimeric core are operative for all of the complexes. Both of the magnetic interactions were concluded to result from their axial Ru–Oax–N bond angles being close to 120°. The hydrogen bonds were not found to be magnetically important in the chain complexes.
Chemical Modification of Lacquer Tree Paint Using Primary Amines
Authors: Watanabe Osamu , Nagai Katsutoshi
Published: April 2003

An investigation was undertaken on a chemical modification of urushi paint using a small amount of primary amines as additives by taking advantage of their reactivity with urushiol, one of the main components of urushi liquid, at room temperature. The first modification method is related to an accelerated curing reaction of urushi paint, as a result of an enhanced formation of reversed micelles of urushiol. With this method, a large reduction in the curing time and curing at low humidity were achieved, and the light resistance of the cured film was also improved, as evaluated by an accelerated exposure test. The second modification method is based on the functionality of a compound linked to urushiol. Primary amine, having a water-repellent property, was synthesized, added to urushi liquid, and then cured. The resulting film demonstrated a good water-repellent property, and maintained this property even against degradation under accelerated exposure. These primary amines as additives undergo neither bleeding nor elution from urushi film, because they combine with urushiol. In addition, because these methods are based on a homogeneous mixing of additives and urushi liquid, they have advantages that neither large-scale plants nor equipment investment is required for their production.
Nucleophilic Reactions of 5-tert-Butyl-2-methoxy-3H-azepine with Alkoxides and Alkyllithium Reagents
Authors: Kubota Yasuhiro , Satake Kyosuke , Ikui Ryusuke , Okamoto Hideki , Kimura Masaru
Published: April 2003

The reaction of 5-tert-butyl-2-methoxy-3H-azepine (2a) with sodium alkoxides gave 2-alkoxy-3H-azepine derivatives 3–6 by nucleophilic transetherification. The treatment of 2a with tert-butyllithium also yielded 2,5-di-tert-butyl-3H-azepine (7); however, the reaction of 2a and methyllithium gave the expected 5-tert-butyl-2-methyl-3H-azepine (8) along with unexpected 5-tert-butyl-2,2-dimethyl-2,3-dihydro-1H-azepine (9), but also 5,5′-di(tert-butyl)-2,2′-methylenedi(3H-azepine) (11), the structure of which was found to be tautomerized 5-tert-butyl-2-(5-tert-butyl-2,3-dihydro-1H-azepin-2-ylidenemethyl)-3H-azepine (12). The energy profile for the observed tautomerization is discussed based on ab initio DFT calculations and kinetic measurements.
Stereoselective Crossed Aldol Reaction via Boron Enolates Generated from α-Iodo Ketones and 9-Borabicyclo[3.3.1]nonane
Authors: Mukaiyama Teruaki , Takuwa Tomofumi , Yamane Keiko , Imachi Shouhei
Published: April 2003

Boron enolates were in situ-generated reductively by treating various α-iodo ketones such as 2-iodo-1-phenylpropan-1-one, 2-iodo-1-(4-methoxyphenyl)propan-1-one, 2-iodopentan-3-one, 2-iodo-2-methyl-1-phenylpropan-1-one, 3,4-dihydro-2-iodo-1(2H)-naphthalenone, 2-iodo-1-phenylethan-1-one and 1-iodo-4-phenylbutan-2-one with 9-borabicyclo[3.3.1]nonane (9-BBN). Aldols were produced in good yields with good to high diastereoselectivities by subsequent reaction of boron enolates thus formed with various aldehydes. Several boron enolates derived from α-iodo ketones and pinacolatoborane were successfully isolated by distillation, though the yields were rather moderate.
Static and Dynamic Stereochemistry of O-Substituted N-9-Triptycylhydroxylamines
Authors: Yamamoto Gaku , Agawa Chiharu , Minoura Mao
Published: April 2003

The static and dynamic stereochemistry of N-9-triptycylhydroxylamine derivatives (TpNHOR) with O-benzyl (3), O-ethyl (4), and O-phenyl (5) groups were studied. X-ray crystallographic analysis revealed that these compounds reside in a chiral conformation, with the Tp–N–O–R dihedral angle of 140–160°. Dynamic NMR studies of 3 and 4 show the presence of two separate stereomutation processes: chirality reversal (enantiomer interconversion) and rotation of the Tp–N bond with retaining the chirality, the latter having a lower energy barrier. Compound 5 gave solely information on the Tp–N rotation because of the lack of a probe for chirality reversal.
Transplantation of both kidneys from one donor rat
Authors: Grau Veronika , Steiniger Birte
Published: April 2003

We have developed a technique for harvesting and transplanting two kidneys from one donor rat. Our method involves end-to-end anastomosis of the renal artery and the renal vein. Because of the short distance between the caudal vena cava and the right kidney, renal transplantation is not feasible on the right side of the recipient. The right donor kidney was therefore transplanted to the left side. Graft morphology was assessed on paraffin sections. We observed no differences between conventionally transplanted kidneys ( n = 116) and right kidneys transplanted according to the method described ( n = 40). In conclusion, our technique is simple, saves time and reduces the number of donor rats.
Inventory Management of Remanufacturable Products
Authors: Toktay L. Beril , Wein Lawrence M. , Zenios Stefanos A.
Published: April 2003

We address the procurement of new components for recyclable products in the context of Kodak's single-use camera. The objective is to find an ordering policy that minimizes the total expected procurement, inventory holding, and lost sales cost. Distinguishing characteristics of the system are the uncertainty and unobservability associated with return flows of used cameras. We model the system as a closed queueing network, develop a heuristic procedure for adaptive estimation and control, and illustrate our methods with disguised data from Kodak. Using this framework, we investigate the effects of various system characteristics such as informational structure, procurement delay, demand rate, and length of the product's life cycle.
How the Incumbent Can Win: Managing Technological Transitions in the Semiconductor Industry
Authors: Iansiti Marco
Published: April 2003

The paper reports on an empirical study of the management of technological transitions. It focuses on project-level mechanisms for the generation of knowledge through experimentation and for its accumulation through individual experience. It proposes a model that links these mechanisms to effectiveness in the management of revolutionary and evolutionary development approaches. This argument is tested with data describing projects conducted by all major competitors in the semiconductor industry. Each project was aimed at a technological transition, defined as the introduction of a major new generation of process technology. The analysis shows substantial differences among competitors in the approach taken (i.e., evolutionary vs. revolutionary) and results achieved. Additionally, it shows that individual organizations can migrate, over time, from evolution to revolution and vice versa. The analysis further indicates that accumulating experience and generating knowledge through experimentation are significantly associated with project performance. While product performance improvement through revolution is associated with research experience and with parallel experimentation capacity, improvement through evolution is associated with project experience and minimum experimental iteration time.
Improving Manufacturing Performance Through Process Change and Knowledge Creation
Authors: Carrillo Janice E. , Gaimon Cheryl
Published: April 2003

A model is introduced to guide a profit maximizing firm in its quest to enhance performance through process change. The key benefit sought from process change is a long term increase in effective capacity. However, realizing success from process change is not trivial. First, while process change may increase effective capacity in the long run, the disruptions during implementation typically reduce short term capacity. Second, competitive forces such as decreasing revenue streams and shrinking product life cycles complicate the implementation of process change. Third, while knowledge may enhance the ultimate benefits derived from process change, the correct timing and means of knowledge creation are difficult to discern. Lastly, a variety of trade-offs must be evaluated when selecting the particular process change to pursue. For example, choices range from hardware and software replacements to modification of manufacturing procedures.

The model introduced here explicitly considers both the short term loss due to disruption and the long term gain in effective capacity associated with the process change. In addition, investments in the accumulation of knowledge are investigated for their potential to enhance process change effectiveness. Knowledge is generated from investment in preparation and training (learning-before-doing) and as a by-product of process change (learning-by-doing). Analysis of the model provides managerial recommendations for several key decisions relating to process change implementation including: (i) the selection of an appropriate process change alternative, (ii) the rate and timing for investment in process change, and (iii) the rate and timing for investment in preparation and training. New results are reported reflecting the important relationship between process change and knowledge. For example, we show that under certain conditions, a firm should optimally delay investment in process change until sufficient accumulation of knowledge is achieved. More generally, we identify conditions whereby investment in process change occurs at an increasing rate over time. This result is particularly important since it demonstrates a limitation of the existing literature where process change always occurs at a decreasing rate.
Frictionless Commerce? A Comparison of Internet and Conventional Retailers
Authors: Brynjolfsson Erik , Smith Michael D.
Published: April 2003

There have been many claims that the Internet represents a new nearly “frictionless market.” Our research empirically analyzes the characteristics of the Internet as a channel for two categories of homogeneous products—books and CDs. Using a data set of over 8,500 price observations collected over a period of 15 months, we compare pricing behavior at 41 Internet and conventional retail outlets.

We find that prices on the Internet are 9–16% lower than prices in conventional outlets, depending on whether taxes, shipping, and shopping costs are included in the price. Additionally, we find that Internet retailers' price adjustments over time are up to 100 times smaller than conventional retailers' price adjustments—presumably reflecting lower menu costs in Internet channels. We also find that levels of price dispersion depend importantly on the measures employed. When we compare the prices posted by different Internet retailers we find substantial dispersion. Internet retailer prices differ by an average of 33% for books and 25% for CDs. However, when we weight these prices by proxies for market share, we find dispersion is lower in Internet channels than in conventional channels, reflecting the dominance of certain heavily branded retailers.

We conclude that while there is lower friction in many dimensions of Internet competition, branding, awareness, and trust remain important sources of heterogeneity among Internet retailers.
Scheduling Resource-Constrained Projects Competitively at Modest Memory Requirements
Authors: Sprecher Arno
Published: April 2003

We consider the resource-constrained project scheduling problem. The purpose of this paper is to direct the focus to a branch-and-bound concept that can, by simple adaptations, operate on a wide range of problem settings. The general approach can, e.g., deal with multimode problems, resource availability varying with time, and a wide range of objectives. Even the simple assembly line balancing problem of type-1 can be competitively approached with some modifications. Although the algorithm is the most general and simple one currently available for resource-constrained project scheduling, the computational performance can compete with the best approaches available for the single-mode problem. The algorithm uses far less memory than the state-of-the-art procedure, i.e., 256 KB versus 24 MB, for solving the standard benchmark set with projects consisting of 32 activities within comparable time. If both approaches are allowed to make limited use of memory, i.e., 256 KB, then more than 97% of the benchmark instances can be solved within fractions of the time required by the current state-of-the-art procedure. The truncated version of our algorithm achieves at 256 KB approximately the results of the truncated version of the state-of-the-art approach at 24 MB. Since in general the memory requirements exponentially grow with the number of activities the project consists of, memory will become a critical resource, and the strategy to access previously stored information will gain fundamental importance when solving larger projects.
Information, Contracting, and Quality Costs
Authors: Baiman Stanley , Fischer Paul E. , Rajan Madhav V.
Published: April 2003

This article analyzes the relation between product quality, the cost of quality, and the information that can be contracted upon. We consider a setting where a risk neutral supplier sells an intermediate product to a risk neutral buyer. The supplier incurs prevention costs to reduce the probability of selling a defective product, and the buyer incurs appraisal costs to identify defects. Both decisions are subject to moral hazard. We show that the first-best outcome can be obtained if either: (i) the supplier's prevention decision is contractible; or (ii) the buyer's appraisal decision and either internal failure (i.e., the product's failing the buyer's appraisal test) or external failure (i.e., the product's failing after being sold by the buyer) are contractible events; or (iii) both internal and external failure are contractible events. We then focus on the second-best setting where actions and failures are not contractible and study the effect of making the buyer's appraisal result contractible. Relative to first-best, if a buyer's return decision is contractible (but not his appraisal result), the supplier incurs lower prevention costs, the buyer incurs higher appraisal costs, expected internal failure costs are higher, and the total cost of quality is higher. The expected costs of external failure, however, may actually be lower relative to first-best. We then show that installing an information system that makes the appraisal result contractible reduces the inefficiency associated with the seller's prevention activity, increases the inefficiency associated with the buyer's quality appraisal activity, and unambiguously improves product quality.
Assessing Dependence: Some Experimental Results
Authors: Clemen Robert T. , Fischer Gregory W. , Winkler Robert L.
Published: April 2003

Constructing decision- and risk-analysis probability models often requires measures of dependence among variables. Although data are sometimes available to estimate such measures, in many applications they must be obtained by means of subjective judgment by experts. We discuss two experimental studies that compare the accuracy of six different methods for assessing dependence. Our results lead to several conclusions: First, simply asking experts to report a correlation is a reasonable approach. Direct estimation is more accurate than the other methods studied, is not prone to mathematically inconsistent responses (as are some other measures), and is judged to be less difficult than alternate methods. In addition, directly assessed correlations showed less variability than the correlations derived from other assessment methods. Our results also show that experience with the variables can improve performance somewhat, as can training in a given assessment method. Finally, if a judge uses several different assessment methods, an average of the resulting estimates can also lead to better performance.
Analytical Valuation of American-Style Asian Options
Authors: Hansen Asbjørn T. , Jørgensen Peter Løchte
Published: April 2003

This article derives the first analytical pricing formulas for American-style Asian options of the so-called floating strike type. Geometric as well as arithmetic averaging is considered. The setup is a standard Black-Scholes framework where the price of the underlying security evolves according to a geometric Brownian motion. A decomposition result that splits up the value of the floating strike American option into the price of an otherwise equivalent European option and an early exercise premium is first presented. This decomposition result is then manipulated further for the two separate types of averaging. With geometric averaging we derive an exact pricing formula, whereas with arithmetic averaging we develop an analytical approximation formula that proves to be very precise. Numerical examples are provided.
Superlinear Convergence of an Interior-Point Method Despite Dependent Constraints
Authors: Ralph Daniel , Wright Stephen J.
Published: April 2003

We show that an interior-point method for monotone variational inequalities exhibits superlinear convergence provided that all the standard assumptions hold except for the well-known assumption that the Jacobian of the active constraints has full rank at the solution. We show that superlinear convergence occurs even when the constant-rank condition on the Jacobian assumed in an earlier work does not hold.
Index Policies and a Novel Performance Space Structure for a Class of Generalised Branching Bandit Problems
Authors: Crosbie J. H. , Glazebrook K. D.
Published: April 2003

Our object of study is a new class of controlled stochastic systems called generalised branching bandits which include discounted branching bandits and generalised bandit problems as special cases. These models allow us to study queueing scheduling and project scheduling problems in which the reward earned from processing a particular job is influenced by other job types present in the system. Our mode of analysis is the achievable region approach. What is novel here is that the full system may be partitioned into two subsystems, each of which satisfies its own set of conservation laws and has its own highly structured performance space. An optimal policy for the full system is constructed from two sets of Gittins indices derived from the conservation laws governing the two subsystems.
Partially Symmetric Values
Authors: Haimanko Ori
Published: April 2003

We consider spaces of differentiable nonatomic and mixed vector measure games, pNA and pM, with finitely or countably many types of players. Type-symmetric values on these spaces of games are investigated (all Aumann and Shapley conditions except symmetry are assumed, the latter being replaced by a weaker assumption of covariance under automorphisms of the space of players that preserve each type). We show that if the types are uncountable, then type-symmetric values are random path values. In particular, the symmetric values on pM are characterized as mixtures of values defined in Hart (1973).
Asymptotic Strong Duality for Bounded Integer Programming: A Logarithmic-Exponential Dual Formulation
Authors: Sun Xiaoling , Li Duan
Published: April 2003

A logarithmic-exponential dual formulation is proposed in this paper for bounded integer programming problems. This new dual formulation possesses an asymptotic strong duality property and guarantees the identification of an optimal solution of the primal problem. These prominent features are achieved by exploring a novel nonlinear Lagrangian function, deriving an asymptotic zero duality gap, investigating the unimodality of the associated dual function and ensuring the primal feasibility of optimal solutions in the dual formulation. One other feature of the logarithmicexponential dual formulation is that no actual dual search is needed when parameters are set above certain threshold-values.
The Stochastic Economic Lot Scheduling Problem: Heavy Traffic Analysis of Dynamic Cyclic Policies
Authors: Markowitz David M. , Reiman Martin I. , Wein Lawrence M.
Published: April 2003

We consider two queueing control problems that are stochastic versions of the economic lot scheduling problem: A single server processes N customer classes, and completed units enter a finished goods inventory that services exogenous customer demand. Unsatisfied demand is backordered, and each class has its own general service time distribution, renewal demand process, and holding and backordering cost rates. In the first problem, a setup cost is incurred when the server switches class, and the setup cost is replaced by a setup time in the second problem. In both problems we employ a long-run average cost criterion and restrict ourselves to a class of dynamic cyclic policies, where idle periods and lot sizes are state-dependent, but the N classes must be served in a fixed sequence. Motivated by existing heavy traffic limit theorems, we make a time scale decomposition assumption that allows us to approximate these scheduling problems by diffusion control problems. Our analysis of the approximating setup cost problem yields a closed-form dynamic lot-sizing policy and a computational procedure for an idling threshold. We derive structural results and an algorithmic procedure for the setup time problem. A computational study compares the proposed policy and several alternative policies to the numerically computed optimal policy.
Shape – A Stochastic Hybrid Approximation Procedure for Two-Stage Stochastic Programs
Authors: Cheung Raymond K.-M. , Powell Warren B.
Published: April 2003

We consider the problem of approximating the expected recourse function for two-stage stochastic programs. Our problem is motivated by applications that have special structure, such as an underlying network that allows reasonable approximations to the expected recourse function to be developed. In this paper, we show how these approximations can be improved by combining them with sample gradient information from the true recourse function. For the case of strictly convex nonlinear approximations, we prove convergence for this hybrid approximation. The method is attractive for practical reasons because it retains the structure of the approximation.
Scheduling with Inserted Idle Time: Problem Taxonomy and Literature Review
Authors: Kanet John J. , Sridharan V.
Published: April 2003

In the context of production scheduling, inserted idle time (IIT) occurs whenever a resource is deliberately kept idle in the face of waiting jobs. IIT schedules are particularly relevant in multimachine industrial situations where earliness costs and/or dynamically arriving jobs with due dates come into play. We provide a taxonomy of environments in which IIT scheduling is relevant, review the extant literature on IIT scheduling, and identify areas of opportunity for future research.
The Uncapacitated Facility Location Problem with Client Matching
Authors: Gourdin Éric , Labbé Martine , Laporte Gilbert
Published: April 2003

The Uncapacitated Facility Location Problem with Client Matching (LCM) is an extension of the Uncapacitated Facility Location Problem (UFLP), where two clients allocated to a facility can be matched. As in the UFLP, facilities can be opened at any of m predefined locations with given fixed costs, and n clients have to be allocated to the open facilities. In classical location models, the allocation cost is the distance between a client and an open facility. In the LCM, the allocation cost is either the cost of a return trip between the facility and the client, or the length of a tour containing the facility and two clients. The similarities of the LCM with the classical UFLP and the matching problem are exploited to derive valid inequalities, optimality cuts, and polyhedral results. A greedy heuristic and a branch-and-cut algorithm are developed, and several separation procedures are described. Computational experiments confirm the efficiency of the proposed approach.
Dynamic Scheduling in a Make-to-Stock System: A Partial Characterization of Optimal Policies
Authors: De Vericourt Francis , Karaesmen Fikri , Dallery Yves
Published: April 2003

We consider the problem of dynamically allocating production capacity between two products to minimize the average inventory and backorder costs per unit time in a make-to-stock single machine system. Using sample path comparisons and dynamic programming, we give a characterization of the optimal hedging point policy for a certain region of the state space. The characterization is simple enough to lead to easily implementable heuristics and provides a formal justification of some of the earlier heuristics proposed.
Multistage Inventory Management with Expediting
Authors: Lawson David G. , Porteus Evan L.
Published: April 2003

After reformulating Clark and Scarf's (1960) classical serial multi-echelon model so that the lead time between adjacent echelons is one week (period), the option to expedite between each resulting echelon is added. Thus, each week requires a decision to be made at each echelon on how many units to expedite in from the next upstream echelon (to be received immediately) and how many to regular order (to be received in one week), with the remainder detained (left as is). The model can be interpreted as addressing dynamic lead time management, in which the (remaining) effective lead time for each ordered unit can be dynamically reduced by expediting and/or extended. Use of Clark and Scarf's (1960) idea of echelon stocks reduces a complex, multidimensional stocking problem to the analysis of a series of one-dimensional subproblems. What are called top-down base stock policies, which are readily amenable to managerial interpretation, are shown to be optimal. Myopic policies are shown to be optimal in the stationary, in1nite horizon case. The results are illustrated numerically.
Exact Algorithm for Minimising the Number of Setups in the One-Dimensional Cutting Stock Problem
Authors: Vanderbeck François
Published: April 2003

The cutting stock problem is that of finding a cutting of stock material to meet demands for small pieces of prescribed dimensions while minimising the amount of waste. Because changing over from one cutting pattern to another involves significant setups, an auxiliary problem is to minimise the number of different patterns that are used. The pattern minimisation problem is significantly more complex, but it is of great practical importance. In this paper, we propose an integer programming formulation for the problem that involves an exponential number of binary variables and associated columns, each of which corresponds to selecting a fixed number of copies of a specific cutting pattern. The integer program is solved using a column generation approach where the subproblem is a nonlinear integer program that can be decomposed into multiple bounded integer knapsack problems. At each node of the branch-and-bound tree, the linear programming relaxation of our formulation is made tighter by adding super-additive inequalities. Branching rules are presented that yield a balanced tree. Incumbent solutions are obtained using a rounding heuristic. The resulting branch-and-price-and-cut procedure is used to produce optimal or approximately optimal solutions for a set of real-life problems.
Jazz Improvisation and Organizing: Once More from the Top
Authors: Zack Michael H.
Published: April 2003

This is a response to the special issue of Organization Science on Jazz Improvisation and Organizing (Vol. 9, No. 5, 1998). It is a call to unpack the jazz metaphor by extending the notion of jazz, and thereby the value of the metaphor, beyond the limited definition described in the issue. In that issue, jazz was described as a process of improvising within a highly constrained structure and set of rules. Other genres of jazz, however, have gone beyond those constraints. Jazz improvisation has occurred within forms, with forms, and beyond forms. Perhaps organizational improvisation may as well.
Dynamics and Dilemmas of Women Leading Women
Authors: Bartunek Jean M. , Walsh Kate , Lacey Catherine A.
Published: April 2003

Through examination of transcripts of the first five leadership succession discussions that occurred in a work group designed to empower teachers we explored dynamics and dilemmas associated with women leading a women's group based on feminist principles. We addressed three research questions: How is leadership, as reflected in leadership succession processes, experienced in such a group? What dynamics are associated with leadership succession in this type of group? What are outcomes of the process for members?

Results indicated that the experience of leadership shifted considerably during the first six years of the group, with reflective images of leadership moving from the mythical to the pragmatic, from the powerful to the less powerful. Dynamics evolved in ways that were partially consistent and partially inconsistent with organizational life-cycle literature.

The group experienced ambivalence and tension surrounding the type of authority given to designated leaders. Members dealt with discomfort by shifting the focus of the group coordinator's attention to external relations and by rotating internal leadership responsibilities. This approach resolved tensions associated with authority and increased members' senses of their own power, even as it decreased the range of initiative-taking that was implicitly allowable within the group.

This analysis of leadership succession in a women's group with an empowerment agenda offers a salient case for the study of dilemmas likely to be present in many change efforts. Its results suggest that attempting to resolve contradictions and tensions is less helpful than acknowledging them and working within them.
Organizational Routines as a Source of Continuous Change
Authors: Feldman Martha S.
Published: April 2003

In this paper I claim that organizational routines have a great potential for change even though they are often perceived, even defined, as unchanging. I present descriptions of routines that change as participants respond to outcomes of previous iterations of a routine. Based on the changes in these routines I propose a performative model of organizational routines. This model suggests that there is an internal dynamic to routines that can promote continuous change. The internal dynamic is based on the inclusion of routine participants as agents. When we do not separate the people who are doing the routines from the routine, we can see routines as a richer phenomenon. Change occurs as a result of participants' reflections on and reactions to various outcomes of previous iterations of the routine. This perspective introduces agency into the notion of routine. Agency is important for understanding the role of organizational routines in learning and in processes of institutionalization.
How to measure reproductive success?
Authors: Strassmann Beverly I. , Gillespie Brenda
Published: April 2003

To date there have been few empirical comparisons between alternative methods for measuring reproductive success (RS). We consider the pros and cons of alternative measures of RS to provide guidance for the design of field studies in human behavioral ecology. We compare cross‐sectional measures that count offspring alive at the time of the interview and retrospective measures that require data on offspring age at death or censoring. We consider analyses that include adult women (yielding age‐specific estimates of RS) as well as analyses restricted to postreproductive women (yielding data on lifetime RS). These methods are applied to reproductive data for the Dogon of Mali, West Africa. Am. J. Hum. Biol. 15:361–369, 2003. © 2003 Wiley‐Liss, Inc.
Grandmothers and the evolution of human longevity
Authors: Hawkes Kristen
Published: April 2003

Great apes, our closest living relatives, live longer and mature later than most other mammals and modern humans are even later‐maturing and potentially longer‐lived. Evolutionary life‐history theory seeks to explain cross‐species differences in these variables and the covariation between them. That provides the foundation for a hypothesis that a novel role for grandmothers underlies the shift from an ape‐like ancestral pattern to one more like our own in the first widely successful members of genus Homo. This hypothesis links four distinctive features of human life histories: 1) our potential longevity, 2) our late maturity, 3) our midlife menopause, and 4) our early weaning with next offspring produced before the previous infant can feed itself. I discuss the problem, then, using modern humans and chimpanzees to represent, respectively, genus Homo and australopithecines, I focus on two corollaries of this grandmother hypothesis: 1) that ancestral age‐specific fertility declines persisted in our genus, while 2) senescence in other aspects of physiological performance slowed down. The data are scanty but they illustrate similarities in age‐specific fertility decline and differences in somatic durability that are consistent with the hypothesis that increased longevity in our genus is a legacy of the “reproductive” role of ancestral grandmothers. Am. J. Hum. Biol. 15:380–400, 2003. © 2003 Wiley‐Liss, Inc.
Water and ion flow across cellulosic membranes
Authors: Reid C. E. , Breton E. J.
Published: April 2003

The primary objective of this investigation has been to explain why cellulose acetate behaves as a semipermeable membrane in saline water. To explain this phenomenon, two different mechanisms for the transfer to water and ions through cellulose acetate membranes were formulated. Those ions and molecules that cannot enter into hydrogen bonding with the membrane are transferred by hole‐type diffusion. The rate of diffusion appears to be governed by a water‐cellulose acetate structure. The reaction between water and the cellulose polymers to form bound water regions is favored by compressing the membrane. As pressure is applied on the membrane, more bound water is produced, which causes the rate of hole‐type diffusion to decrease. On the other hand, those ions and molecules that can associate with the membrane and are transported through it by alignment‐type diffusion. The formation of the water‐cellulose acetate structure does not appreciably diminish the diffusion rate of water through the membrane. Cellulose acetate begins to behave as an effective semipermeable membrane in saline water when it is compressed sufficiently to retard greatly the diffusion of NaCl. Several types of experiments were conducted to support these hypotheses. The most important evidence was obtained from resistance experiments. The electrical resistances of specific ions was measured across cellulose acetate at various pressures by using permselective membranes to prevent migration of the ion of opposite charge. It was observed that the rate of diffusion of those ions that cannot combine with the membrane actually does decrease as the membrane is compressed. The rate of diffusion of H3O+, which can enter into hydrogen bonding with cellulose acetate, is much higher and is not appreciably reduced as the membrane is compressed. These resistance‐pressure relationships are correlated with the semipermeability of the cellulose acetate.
Time, temperature, and linear viscoelasticity
Authors: Haugh Eugene F.
Published: April 2003

Linear viscoelastic bodies satisfy the Boltzmann superposition principle which permits the calculation of the effect of arbitrary stress or strain history in terms of creep or stress relaxation parameters, respectively. In such calculations, the temperature is not considered as an independent variable; rather, the temperature must be constant, and the stress relaxation and creep parameters used are for the given temperature. By assuming the validity of the time‐temperature superposition principle, it is shown how an arbitrary thermal history may be included. By employing spring‐dashpot model methods, Boltzmann's principle is generalized, leading to the concepts of equivalent stress σ(t) and equivalent time w(t), the latter concept having also been introduced for creep and stress relaxation by Hopkins. These quantities are defined by

where t = time, p = density, T = temperature, and a[T(t), T(0)] is the time‐temperature shift factor between temperatures T(0) and T(t). In terms of the equivalent stress and equivalent time, Boltzmann's principle for shear remains the same as for the isothermal case with stress relaxation or creep parameters at the initial temperature, T(0). In the case of tensile experiments, the observed strain must be corrected for thermal expansion.
The dynamic mechanical properties of hypalon‐20 synthetic rubber at small strains
Authors: Kurath S. F. , Passaglia E. , Pariser R.
Published: April 2003

The dynamic mechanical properties at small strains have been determined for Hypalon‐20 synthetic rubber, a commerical elastomer, by means of an electromagnetic transducer which is a modification of one described by Marvin, Fitzgerald, and Ferry. The measurements cover frequencies from 25 to 2500 cycles/sec. at twelve temperatures ranging from −8.4 to 68.4°C. Values of the real portion of the shear modulus (G′) vary from 7 × 106 to 2.1 × 109 dynes/cm.2, and those of the imaginary portion (G″) from 2.1 × 106 to 9 × 108 dynes/cm.2. The method of reduced variables (i.e., temperature‐frequency superposition) is applicable and is used to extend G′ and G″ over the range 10−1 to 109 radians/sec. At 25°C., G″/G′ = 1.3 at its maximum at 105 radians/sec. The general function for the temperature dependence of mechanical properties proposed by Williams, Landel, and Ferry is valid up to 35°C. if one uses −24.5°C. for the glass transition temperature (Tg); dilatometrically Tg = −28 ± 1°C. The distribution function of relaxation times H(τ) has a pronounced maximum at about τ = 10−8 sec., decreases with a slope of about −0.57 (for log H versus log τ) to about τ = 10−3 sec., and is nearly flat from τ = 10−2 to 10 sec. H (τ) for Hypalon‐20 is similar to those for polyisobutylene and polyhexene‐1.
Molecular structure of high molecular weight acetal resins
Authors: Koch T. A. , Lindvig P. E.
Published: April 2003

Stable, high molecular weight polymers of formaldehyde have been studied to determine their molecular structure. The polymer chain was shown to be a polyoxymethylene by chemical analysis and infrared absorption spectra. Infrared techniques also revealed hydroxyl end groups which were replaced by acetate groups on esterification. The endgroups, which were also measured by chemical methods, were used to determine the number‐average molecular weight over the range 20,000 to 98,000. Values obtained by assuming two endgroups per molecule agreed with osmotic pressure results, thus showing this to be an essentially unbranched polymer. Two theoretically possible branch‐point structures were investigated by chemical methods; none could be detected, further indicating a linear polymer structure. Indirect evidence of narrow molecular weight distribution was obtained by comparing melt viscosity properties with those of other polymers of known wide and narrow distribution.
Dielectric studies on cellulose fibers
Authors: Ishida Yoichi , Yōshino Masatsugu , Takayanagi Motowo , Irie Fujio
Published: April 2003

A method for obtaining the intrinsic dielectric constant and loss factor of dry cellulose fiber along the fiber axis was developed, and the dielectric properties of viscose rayon, Bemberg (cuprammonium rayon), and cotton sliver were measured over the frequency range from 500 cycles/sec. to 3 Mcycles/sec. and the temperature range from −60 to + 20°C. by using the mutual inductance bridge. Only one dispersion could be observed in this temperature and frequency range. Cole‐Cole's circular are law could be satisfactorily applied to the data obtained, and the parameters of the are (ϵ0 – ϵ∞) and β for the three samples could be determined at each temperature. The value of (ϵ0 – ϵ∞), which is proportional to concentration of the dipoles contributing to the orientation, increased with rising temperature and reached a limiting value at about −20°C. The value of β relating to the width of the distribution of relaxation times also increased with rising temperature, showing a little rise in the degree of increase at temperatures above −20°C. On the other hand, the apparent activation energy for dipole orientation, as calculated from the temperature dependence of the dispersion frequency, reached a maximum around −20°C. All these facts suggest that some transition will take place in the neighborhood of −20°C. This temperature is not considered to be likely to be the glass transition temperature for dry cellulose, since −20°C. is too low for a primary transition in stiff molecules such as cellulose, and since the observed value of the apparent activation energy is too small to activate the segmental movement of the main chains. It might be possible to expect some secondary transition, probably of a thermodynamical nature, relating to the movement of local parts such as side chains, especially methylol groups on glucose residue, at about −20°C., though there is no other support for this expectation. Moreover, the effect of the fine structures on the dielectric properties is that the magnitude of (ϵ0 – ϵ∞) at each temperature decreases in the order, viscose rayon > Bemberg > cotton sliver, and this order parallels that of the accessibility of the three samples. This fact suggests that the dipoles in the amorphous region and on the surface of the crystallite provide the chief contribution to this dispersion.
Molecular weights of polymethyl methacrylate in rubber‐methyl methacrylate graft copolymers
Authors: Cooper W. , Vaughan G. , Madden R. W.
Published: April 2003

Molecular weight distributions of homopolymer and graft polymer obtained from the gamma and photoinitiated polymerization of methyl methacrylate with natural rubber latex have been determined. Broad distributions were found with peaks of low and high molecular weight polymer. The distributions were insufficiently defined to make definite assignments to the speeds of the reactions involved but were not inconsistent with the mechanism proposed in an earlier paper from kinetic considerations. Details are given of the column fractionation apparatus employed.