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A case study in low-power system-level design is presented. We detail the design of a low-power embedded system, a touchscreen interface device for a personal computer. This device is designed to operate on excess power provided by unused RS232 communication lines. We focus on the design and measurement procedures used to reduce the power requirements of this system to less than 50 mW. Additionally, we highlight opportunities to use system-level design and analysis tools for low-power design and the obstacles that prevented using such tools in this design.

We designed TigerSwitch, a digital private branch exchange (PBX) implemented on an IBM PC-compatible platform, as an experiment in embedded system design. A telephone switching system is an interesting example of embedded system co-design because it combines a rich functionality with deadlines ranging from seconds to tenths of a millisecond. This paper uses design decisions from TigerSwitch to illustrate the difficulties faced in the partitioning and allocation of a system specification into an architecture: the critical performance paths may not be obvious from the initial specification, and it is often difficult to obtain the performance data required to allocate functions in the architecture.

Many commercial and academic disciplines need digital video libraries. Such libraries must provide the user with the opportunity to manipulate the material non-linearly. This paper discusses digital video libraries and various non-linear services these libraries will provide. The architectural components of such libraries are discussed and a model of user access is developed. Results from caching experiments utilizing that model are reported for several usage patterns and four cache organizations.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Embedded computer systems are characterized by the presence of one or more processors running application specific software. A large number of these systems must satisfy performance constraints in addition to cost constraints. Because embedded systems are constructed from large, complex components — CPUs and ASICs — we need new techniques to analyze the performance of these components as well as their compositions. Since the performance analysis of ASICs is considered to be a well studied problem, the main challenges in performance analysis of embedded system are in the area of software performance analysis and analysis of concurrent components. Here the research can be broadly classified into two areas. Program analysis methods consider the behavior of a single process on a given processor and attempt to determine bounds on the execution time of the process. This task is made complicated for modern CPUs by the presence of relatively non-deterministic features such as caches and instruction pipelines which make the execution time of one instruction depend on both the recent and distant history of the executed instruction trace. System analysis methods study the performance of a network of machines—either CPUs or ASICs—which execute a set of processes. Even if we know the execution time of each process in isolation, we must consider conflicts in allocation of processes to processing elements and the scheduling of events on the processing elements and communication channels.

Video is a challenging material for digital libraries because it contains large amounts of data which must be processed quickly and because video programming has not been as conveniently structured for algorithmic processing as text. Since moving images are used as scholarly material in a number of disciplines, digital libraries must be able to support cataloging, browsing, and navigating through video collections. We have shown that computationally tractable algorithms can be used to solve some of the important problems in digital video libraries. While much further work needs to be done, we believe that signal and image processing algorithms will help us solve other important problems in video libraries.

This paper deals with the distribution of functionality among the functional units of a superscalar processor. Starting with configurations including identical functional units capable of executing any instruction, we have assessed the effect provoked by replacing these complex units with specialized units to execute memory access and branch instructions. Our experiments show that the maximum speedup ratios obtained by configurations equipped with eight complex units can also be achieved by machines with the same number of simpler units.

1. A variety of neuroendocrine approaches has been used to characterize cellular mechanisms governing luteinizing hormone-releasing hormone (LHRH) pulse generation. We review recent in vivo microdialysis, in vitro superfusion, and in situ hybridization experiments in which we tested the hypothesis that the amplitude and frequency of LHRH pulses are subject to independent regulation via distinct and identifiable cellular pathways. 2. Augmentation of LHRH pulse amplitude is proposed as a central feature of preovulatory LHRH surges. Three mechanisms are described which may contribute to this increase in LHRH pulse amplitude: (a) increased LHRH gene expression, (b) augmentation of facilitatory neurotransmission, and (c) increased responsiveness of LHRH neurons to afferent synaptic signals. Neuropeptide Y (NPY) is examined as a prototypical afferent transmitter regulating the generation of LHRH surges through the latter two mechanisms. 3. Retardation of LHRH pulse generator frequency is postulated to mediate negative feedback actions of gonadal hormones. Evidence supporting this hypothesis is reviewed, including results of in vivo monitoring experiments in which LHRH pulse frequency, but not amplitude, is shown to be increased following castration. A role for noradrenergic neurons as intervening targets of gonadal hormone negative feedback actions is discussed. 4. Future directions for study of the LHRH pulse generator are suggested.

Publisher Summary This chapter presents a single-source compendium of techniques for both the sampling and administration of hormone pulses in unanesthetized, freely moving rodents. Pulsatility is now recognized as a nearly ubiquitous functional feature of mammalian neuroendocrine systems. Sampling parameters need to be chosen a priori based on published or preliminary data on pulsatility patterns in the particular experimental subject. Careful consideration is given to the technical limits of sampling intensity, sample recovery, and assay sensitivity. For each hormone and particular sampling regimen, it is recommended that preliminary experiments be conducted in which pulse characteristics are compared among sampling time windows. Based on these observations, an empirical determination can be made as to the length of time that sampling can be conducted without the appearance of artifactual alterations in pulsatility. A suitable compromise must be reached, therefore, between the need for resolution of pulses through collection over shorter intervals and the requirement for sufficient detectability through collection over longer intervals.

Corrigendum: A cooperative microRNA-tumor suppressor gene network in acute T-cell lymphoblastic leukemia (T-ALL)

This study measures the impact of changing economic conditions in OECD countries on tourist arrivals to countries/destinations in Latin America and the Caribbean. A model of utility maximization across labor, consumption of goods and services at home, and consumption of tourism services across monopolistically competitive destinations abroad is presented. The model yields estimable equations arrivals as a function of OECD economic conditions and the elasticity of substitution across tourist destinations. Estimates suggest median tourism arrivals decline by at least three to five percent in response to a one percent increase in OECD unemployment, even after controlling for declines in OECD consumption and output gaps. Arrivals to individual destination are driven by differing exposure to OECD country groups sharing similar business cycle characteristics. Estimates of the elasticity of substitution suggest that tourism demand is highly price sensitive, and that a variety of costs to delivering tourism services drive market share losses in uncompetitive destinations. One recent cost change, the 2009 easing of restrictions on U.S. travel to Cuba, supported a small (countercyclical) boost to Cuba’s arrivals of U.S. non-family travel, as well as a pre-existing surge in family travel (of Cuban origin). Despite the US becoming Cuba’s second highest arrival source, Cuban policymakers have significant scope for lowering the relatively high costs of family travel from the United States.

Introduction: Paediatric early warning tools (PEWT) were developed to identify clinical deterioration in acutely ill patients. Deviations from defined physiological parameters are used to initiate medical review and intervention. PEWT was incorporated into observation charts at a UK tertiary referral hospital and an outreach response team was trialled providing immediate high dependency care. Aims: An audit was undertaken to determine the effectiveness of the outreach team combined with PEWT and assess the impact on patient outcome. Method: A nurse-led outreach team was trialled for 3 months during 2009. Patient observation charts were reviewed for all inpatients over one week. Data was collected to determine: number of patient triggers, actions taken and patient outcome (133 patient observation charts reviewed). Data collection was repeated once the trial had finished (n=167). Results: 28% (n=37) of patients triggered when team available ((133 charts); mean age 6.3 years (SD=5.5)) which was comparable to the period without the team 28% (47/167, p=0.1); 5.8 years (SD=5.6)) when triggered. Help was requested on 12 (32%) occasions compared with 8 (17%, p< 0.05) with and without teams respectively. No arrest calls occurred during the period with the team; 2 occurred during the period without. A reduction in critical incident reporting was observed during team availability. Conclusions: Decreased emergency team calls and critical incidents were observed by introduction of an outreach team and PEWT. The outreach team received a positive response from all staff, providing immediate high dependency care. Use of the PEWT allowed earlier review and prompt medical intervention.

We have analyzed the mechanisms by which several known regulators of the LHRH release process may exert their effects. For each, we have attempted to determine how and where the regulatory input is manifest and, according to our working premise, we have attempted to identify factors which specifically regulate the LHRH pulse generator. Of the five regulatory factors examined, we have identified two inputs whose primary locus of action is on the pulse-generating mechanism--one endocrine (gonadal negative feedback), and one synaptic (alpha 1-adrenergic inputs) (see Fig. 29). Other factors which regulate LHRH and LH release appear to do so in different ways. The endogenous opioid peptides, for example, primarily regulate LHRH pulse amplitude (Karahalios and Levine, 1988), a finding that is consistent with the idea that these peptides exert direct postsynaptic or presynaptic inhibition (Drouva et al., 1981). Gonadal steroids exert positive feedback actions which also result in an increase in the amplitude of LHRH release, and this action may be exerted through a combination of cellular mechanisms which culminate in the production of a unique, punctuated set of synaptic signals. Gonadal hormones and neurohormones such as NPY also exert complementary actions at the level of the pituitary gland, by modifying the responsiveness of the pituitary to the stimulatory actions of LHRH. The LHRH neurosecretory system thus appears to be regulated at many levels, and by a variety of neural and endocrine factors. We have found examples of (1) neural regulation of the pulse generator, (2) hormonal regulation of the pulse generator, (3) hormonal regulation of a neural circuit which produces a unique, punctuated synaptic signal, (4) hormonal regulation of pituitary responsiveness to LHRH, and (5) neuropeptidergic regulation of pituitary responsiveness to LHRH. While an attempt has been made to place some of these regulatory inputs into a physiological context, it is certainly recognized that the physiological significance of these mechanisms remains to be clarified. We also stress that these represent only a small subset of the neural and endocrine factors which regulate the secretion or actions of LHRH. A more comprehensive list would also include CRF, GABA, serotonin, and a variety of other important regulators. Through a combination of design and chance, however, we have been able to identify at least one major example of each type of regulatory mechanism.

Obesity is associated with insulin resistance in metabolic tissues such as adipose, liver, and muscle, but it is unclear whether non-classical target tissues, such as those of the reproductive axis, are also insulin resistant. To determine if the reproductive axis maintains insulin sensitivity in obesity in vivo, murine models of diet-induced obesity with and without intact insulin signaling in pituitary gonadotrophs were created. Diet-induced obese wild type female mice (WT DIO) were infertile and experienced a robust increase in luteinizing hormone (LH) after gonadotropin releasing hormone (GnRH) or insulin stimulation. By contrast, both lean and obese mice with a pituitary-specific knockout of the insulin receptor (PitIRKO) exhibited reproductive competency, indicating that insulin signaling in the pituitary is required for the reproductive impairment seen in diet-induced obesity and that the gonadotroph maintains insulin sensitivity in a setting of peripheral insulin resistance.