Bucket brigades

The days of fighting fires by bucket brigade are long gone. Professional firefighters are here to stay, a... 

A Bucket Brigade of Molecules Carries Electrons from the TCA Cycle to 02 The Sequence of Electron Carriers Was Deduced from Kinetic Measurements Redox Potentials Give a Measure of Oxidizing and Reducing Strengths... 

A Bucket Brigade of Molecules Carries Electrons from the TCA Cycle to 02... 

Denny Larson, coordinator of the National Refinery Reform Campaign and Anne Rolfes, director of the Louisiana Bucket Brigade, personal communication, June 7, 2003,... 

Based on the wealth of both in vivo and in vitro biochemical experiments described in Section II, A, a diffusion-driven or bucket brigade mechanism of metal ion transfer between MXCXXC-motifs on the copper chaperone proteins and their target domains was predicted (Pufahl et al.. 

Fig. 1 Natural absorptive mechanism. The body absorbs peptides and proteins into the bloodstream by a natural process known as transcytosis which occurs deep in the lung. Transcytosis is the process by which large molecules move across an impermeable cell membrane without creating holes in the cells and destroying the barrier. It is performed by tiny membrane bubbles, or transcytotic vesicles, which form invaginations of the cell membrane on one side of the cell and dissolve back into the membrane on the other side of the cell. The result is that small volumes of alveolar fluid, including dissolved proteins, are carried by a bucket brigade from one side of a cell to the other.

Proton transfer is closely linked to the structure of the reaction-center protein. Since protons are present in the external aqueous medium, the (reduced) quinone molecules are buried inside the interior ofthe reaction-center protein, therefore protonation would seem to require some kind of channel for the passage of water molecules. However, at least until recently (see below), there was no evidence for the presence of channels large enough to accommodate water molecules. An alternative mechanism might involve a chain of ionizable amino acids which extends from the surface of the protein to the interior where the reduced quinone is located, forming a pathway along which protons may be transported. Such a mechanism has been likened to a bucket brigade or relay station and shown to exist in such proteins as bacteriorhodopsin, ATP synthase and cytochrome oxidase. 

This problem illustrates the concept of the rate-limiting step. In the familiar example of a bucket brigade, in which a water bucket passes sequentially from one person to his neighbor until it finally reaches the reservoir that is to be filled, the overall rate of transfer of water cannot be greater than the rate of the slowest step. Here the activation step (7) becomes the slowest step when [A] is low and the reaction step (3)... 

Bartholdi, J.J., and Eisenstein, D.D. Bucket Brigade Assembly Lines. Georgia Tech College of Engineering, H. Milton Stewart School of Industrial and Systems Engineering, http //www.bucketbrigades.com, downloaded 2006. 

In a bucket brigade, the product is moved forward from start to finish by a collection of workers working in sequence. As the last worker finishes a product, he walks back and takes over the partially finished product from his predecessor, who walks back and takes over from his predecessor, and so on. The workers continue to move product forward. 

Some of the benefits to a bucket brigade system are the following ... 

The role of the supervisor is decreased substantially because bucket brigades make the line self-balancing. 

The ability of bucket brigades to adjust themselves, without the need for supervisory or software intervention and associated delays, enables the lines to become agile and flexible. 

Details of a game to illustrate the impact of bucket brigades are provided in [6]. 

One implementation of bucket brigades reported in [6] was at the national distribution center of Revco in Knoxville, TN. Prior to bucket brigades, Revco faced productivity issues because of its reliance on temporary labor and on overtime during peak periods. Revco used a zonepicking system in which the pick line was partitioned into areas based on the assumption of identical workers but, given their employee experience mix, the actual pick rates of its workers could vary by a factor of three. The result was that the allocations of work were always unequal and the pick lanes were imbalanced the slowest pickers were frustrated at falling behind and the fastest pickers were underutilized. 

The report described in [6] claims that the idea of bucket brigades was explained to the workers in about fifteen minutes one morning. When implemented at Revco s warehouse, bucket brigades reduced work-in-process inventory, which relieved congestion on the conveyor. The reduced congestion and more effective task allocation increased pick rates and accuracy. 

Under the new system, supervisors could monitor the relative progress of different lanes and adjust allocation of workers to keep the lanes coordinated (to reduce sorting downstream). Bucket brigades simplified the shifting of workers from a fast lane to a slow one because there is no need to redefine zones. The research measured a 34% increase in pick rates at Revco when they shifted to a bucket-brigade-based task allocation. 

Weekly average pick rates were measured by Revco over most of a year (normalized to Revcos work standard 1.0). Prior to the introduction of bucket brigades, Revco was picking at about 95% of their own work standard. After bucket brigades, this rose to 134% of their work standard. (p. 3)... 

The apphcation of bucket brigades at Revco su ests that even after the warehouse location and layout are defined, there continue to be opportunities to improve performance by adjusting task allocation across workers to become more flexible and demand driven. 

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