Ingestive behaviour and physiology of the medicinal leech

Ingestion lasts 25 min in Hirudo medicinalis and is characterized by pharyngeal peristalsis which fills the crop. This peristalsis has an initial rate of 2.4 Hz which decays smoothly to 1.2 Hz at termination of ingestion. During ingestion, the leech body wall undergoes peristalsis which appears to aid in filling the crop diverticula. Body peristalsis begins at a rate of 10 min^(-1) and decreases linearly to 2 min^(-1) at termination. The body also undergoes dorsoventral flexions when blood flow is occluded. Blood meal size increases slightly with leech size: 8.4 g for 1-g leeches and 9.7 g for 2-g leeches. However, relative meal size decreases markedly with increasing animal size; from 8.15 times body mass for 1-g to 4.80 times for 2-g leeches. When intact leeches were exposed to micromolar concentrations of serotonin, there was an increase in the rate of pharyngeal peristalsis and the size of the blood meals. Leeches excrete the plasma from their ingested blood meals. Excretion is activated during ingestion, which increases feeding efficiency by increasing the proportion of blood cells in the ingestate. Excretion continues for 4–6 days following ingestion, removing all the remaining plasma from the ingestate. Leech ingestion comprises stereotyped muscular movements, secretion of saliva and excretion of plasma. A strikingly similar feeding physiology is seen in the blood-sucking insect Rhodnius, and we suggest that efficient sanguivory may require the convergent evolution of similar ingestive mechanisms

Coherent electronic transfer in quantum dot systems using adiabatic passage

We describe a scheme for using an all-electrical, rapid, adiabatic population transfer between two spatially separated dots in a triple-quantum dot system. The electron spends no time in the middle dot and does not change its energy during the transfer process. Although a coherent population transfer method, this scheme may well prove useful in incoherent electronic computation (for example quantum-dot cellular automata) where it may provide a coherent advantage to an otherwise incoherent device. It can also be thought of as a limiting case of type II quantum computing, where sufficient coherence exists for a single gate operation, but not for the preservation of superpositions after the operation. We extend our analysis to the case of many intervening dots and address the issue of transporting quantum information through a multi-dot system.Comment: Replaced with (approximately) the published versio

Reallocating resources to focused factories: a case study in chemotherapy

This study investigates the expected service performance associated with a proposal to reallocate resources from a centralized chemotherapy department to a breast cancer focused factory. Using a slotted queueing model we show that a decrease in performance is expected and calculate the amount of additional resources required to offset these losses. The model relies solely on typical outpatient scheduling system data, making the methodology easy to replicate in other outpatient clinic settings. Finally, the paper highlights important factors to consider when assigning capacity to focused factories. These considerations are generally relevant to other resource allocation decisions

Quantum dynamics, dissipation, and asymmetry effects in quantum dot arrays

We study the role of dissipation and structural defects on the time evolution of quantum dot arrays with mobile charges under external driving fields. These structures, proposed as quantum dot cellular automata, exhibit interesting quantum dynamics which we describe in terms of equations of motion for the density matrix. Using an open system approach, we study the role of asymmetries and the microscopic electron-phonon interaction on the general dynamical behavior of the charge distribution (polarization) of such systems. We find that the system response to the driving field is improved at low temperatures (and/or weak phonon coupling), before deteriorating as temperature and asymmetry increase. In addition to the study of the time evolution of polarization, we explore the linear entropy of the system in order to gain further insights into the competition between coherent evolution and dissipative processes.Comment: 11pages,9 figures(eps), submitted to PR

Reallocating resources to focused factories: a case study in chemotherapy

This study investigates the expected service performance associated with a proposal to reallocate resources from a centralized chemotherapy department to a breast cancer focused factory. Using a slotted queueing model we show that a decrease in performance is expected and calculate the amount of additional resources required to offset these losses. The model relies solely on typical outpatient scheduling system data, making the methodology easy to replicate in other outpatient clinic settings. Finally, the paper highlights important factors to consider when assigning capacity to focused factories. These considerations are generally relevant to other resource allocation decisions

An exact approach for relating recovering surgical patient workload to the master surgical schedule

No other department influences the workload of a hospital more than the Department of Surgery and in particular, the activities in the operating room. These activities are governed by the master surgical schedule (MSS), which states which patient types receive surgery on which day. In this paper we describe an analytical approach to project the workload for downstream departments based on this MSS. Specifically the ward occupancy distributions, patient admission/discharge distributions, and the distributions for ongoing interventions/treatments is computed. Recovering after surgery requires the support of multiple departments, such as nursing, physiotherapy, rehabilitation and long term care. With our model, managers from these departments can determine their workload by aggregating tasks associated with recovering surgical patients. The model, which supported the development of a new MSS at the Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital, provides the foundation for a decision support tool to relate downstream hospital departments to the operating room