An HDS is composed of a combination of continuous and non-ordered discrete dimensions. This combination presents new challenges in data organization and search ordering. In this paper, we present an algorithm for k -NN searches using a multidimensional index structure in hybrid data spaces.
We examine the concept of search stages and use the properties of an HDS to derive a new search heuristic that greatly reduces the number of disk accesses in the initial stage of searching. Further, we present a performance model for our algorithm that estimates the cost of performing such searches. Our experimental results demonstrate the effectiveness of our… algorithm and the accuracy of our performance estimation model.
Highlights • Developed algorithm for searching multi-dimensional hybrid data spaces. • Introduced the method of improving search performance by examining search stages. • Suggested new search heuristic to improve initial stage of searching by 33%. • Derived theoretical model accurately predicts the performance of algorithm.
The peasantry cannot be seen outside the totality of the social formation in which it is found. The peasantry, further, occupies a critical position in the transition to capitalism, a process which involves an equally transitory class of the peasantry called the middle peasantry. In Kenya, the emergence of this class, and its confusion with a peasant bourgeoisie, has been problematic.
As other sections of the peasantry have been impoverished, such categories as large scale/small scale production have not helped in clarifying issues. Instead, statistics have been used blindly to prove that better incomes are trickling down to the peasant producers… in the countryside, hence a healthy capitalist development with income re-distribution.
This essay argues that no such thing is taking place: there is a differentiation of the peasantry due to capitalist development in agriculture with the majority of the peasantry being reduced to owners of patches of land every day.
In particular, she examines the class privilege that attends both queer theory’s and university’s deployment of travel metaphors. In both cases, the language of travel is the potentially empowering language of intellectual agility and social mobility.
Importantly, though, both queer theorists’ and university administrators’ employment of travel metaphors often serves to reaffirm cultural hegemony, specifically to sustain rather than to examine and combat social oppression.
This sad irony is particularly apparent when one compares university representations of commuter and residential students. Thus, the… question that faces universities is how to keep queer studies critically queer so that universities can recognize and address the various forms or models of social mobility that are present on their campuses, commuter as well as residential.
It has been suggested by studies in animals and humans that substance P (SP) and its receptor neurokinin 1 (NK1R) play an important role in the pathology of depression. The pharmacological blockade or genetic deletion of the NK1 receptor, or the substance P coding gene tac1 led to a decreased emotionality and a reduction of depression-related behaviours in different animal models.
In order to characterize molecular changes associated with reduced SP-NK1 signalling in animal models of depression, we assessed the regulation of the CRH system. First, tac1(-/-) animals and tac1(+/+) controls were subjected to bulbectomy, which induces physiological and behavioural changes that are relevant to depression. We demonstrate that tac1(-/-) animals, in contrast to tac1(+/+) controls, do not show… anhedonia in the saccharine preference test after bulbectomy. Next, we studied expression levels of CRH, the receptors CRHR1 and CRHR2, and the binding protein CRHBP in the cortex and paraventricular nucleus using real-time RT-PCR.
Our results show a strong induction of CRH, CRHBP and CRHR1 expression in the cortex of tac1(-/-), but not in tac1(+/+) animals. In the PVN, bulbectomized tac1(-/-) mice showed an elevated expression of CRHR1 and CRHR2. These results show that substance P/NKA is involved in modulating CRH signalling in an animal model of depression.
This paper gives a survey of the Mars Express orbit design, as it evolved from before launch to arrival at Mars. The orbit selection for Mars Express has major scientific impacts, as the orbit is elliptical, with continuous changes of the latitude and local hour of the pericentre. A first target orbit was defined in 1999 by combining scientific and engineering constraints.
As a very favourable launch date was achieved and the launcher injection error was ‘better than nominal’ (the error removed part of the planned re-targeting), propellant reserves turned out to be available after launch. Part of this was used to improve the target orbit. The plane turn manoeuvre was increased to start with the pericentre near the equator rather… than at 20°S latitude, with the objective of increasing the early observation phase with good day-side viewing conditions.
A few weeks after launch, an anomaly in the spacecraft power system was detected, with a loss of up to 40% in terms of available power. This led to a series of studies on back-up orbits, to the extreme of Sun-synchronous eclipse free orbits. Luckily the problem could be solved at the spacecraft engineering level and the orbit with the best science return could be reached in early February 2004.
Previous studies suggest that membrane lipids may regulate proteolytic processing of the amyloid precursor protein (APP) to generate amyloid-beta peptide (Abeta). In the present study, we have assessed the capacity for a series of structurally related synthetic ceramide analogues to modulate APP processing in vitro.
The compounds tested are established glucosylceramide synthase (GS) inhibitors based on the d -1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP) structure. PDMP and related compounds PPMP and EtDO-P4 inhibited Abeta secretion from Chinese hamster ovary cells expressing human APP (CHO-APP) with approximate IC 50 values of 15, 5, and 1μM, respectively. A trend for reduced secretion of the APP alpha-secretase product, sAPPalpha, was also observed in… PDMP-treated cells but not in PPMP- or ETDO-P4-treated cells, whereas levels of the cellular beta-secretase product APP C-terminal fragment, CTFbeta, were increased by both PDMP and PPMP but unaltered with EtDO-P4 treatment.
Our data also revealed that EtDO-P4 inhibits endogenous Abeta production by human neurons. In conclusion, this study provides novel information regarding the regulation of APP processing by synthetic ceramide analogues and reveals that the most potent of these compounds is EtDO-P4.
A map that shows the necessary condition for avoiding the generation of low-frequency stick-slip of a creep groan is introduced. The map is obtained as a result of comprehensive investigation employing a novel caliper-slider experimental model.
According to the map, creep groan generation is controlled by two dimensionless parameters, designated as stiffness ratio, Sr, and low-frequency stick-slip index, Ls. Stiffness ratio, Sr, is the ratio of structure stiffness to the stiffness at contact interface and Ls is an index formed by various parameters such as normal force, sliding velocity, and difference between static and kinetic coefficients of friction.
On the experimental model, creep groan generation can be avoided if one or both of the following conditions is fulfilled: (a) stiffness… 400). It is expected that the map can be used as a useful guideline for avoiding the generation of similar phenomenon on a real brake system. [PUBLICATION ABSTRACT]
The 395-residue proteolytic fragment E3, which comprises the two most C-terminal LG modules of the mouse laminin alpha1 chain, was previously shown to contain major binding sites for heparin, alpha-dystroglycan and sulfatides. The same fragment (alpha1LG4-5) and its individual alpha1LG4 and alpha1LG5 modules have now been obtained by recombinant production in mammalian cells.
These fragments were apparently folded into a native form, as shown by circular dichroism, electron microscopy and immunological assays. Fragment alpha1LG4-5 bound about five- to tenfold better to heparin, alpha-dystroglycan and sulfatides than E3. These binding activities could be exclusively localized to the alpha1LG4 module. Side-chain modifications and proteolysis demonstrated that Lys and Arg residues in the… C-terminal region of alpha1LG4 are essential for heparin binding. This was confirmed by 14 single to triple point mutations, which identified three non-contiguous basic regions (positions 2766-2770, 2791-2793, 2819-2820) as contributing to both heparin and sulfatide binding. Two of these regions were also recognized by monoclonal antibodies which have previously been shown to inhibit heparin binding.
The same three regions and a few additional basic residues also make major contributions to the binding of the cellular receptor alpha-dystroglycan, indicating a larger binding epitope. The data are also consistent with previous findings that heparin competes for alpha-dystroglycan binding.
Shared buffer switches consist of a memory pool completely shared among output ports of a switch. Shared buffer switches achieve low packet loss performance as buffer space is allocated in a flexible manner. However, this type of buffered switches suffers from high packet losses when the input traffic is imbalanced and bursty. Heavily loaded output ports dominate the usage of shared memory and lightly loaded ports cannot have access to these buffers.
To regulate the lengths of very active queues and avoid performance degradations, threshold‐based dynamic buffer management policy, decay function threshold, is proposed in this paper. Decay function threshold is a per‐queue threshold scheme that uses a tailored threshold for each output port queue. This scheme… suggests that buffer space occupied by an output port decays as the queue size of this port increases and/or empty buffer space decreases.
Results have shown that decay function threshold policy is as good as well‐known dynamic thresholds scheme, and more robust when multicast traffic is used. The main advantage of using this policy is that besides best‐effort traffic it provides support to quality of service (QoS) traffic by using an integrated buffer management and scheduling framework. Copyright © 2006 John Wiley & Sons, Ltd.
We consider the inverse problem in classification systems described as follows. Given a set of prototype cases representing a set of categories, a similarity function, and a new case classified in some category, we find the cost-minimizing changes to the attribute values such that the case is reclassified as a member of a (different) preferred category. The problem is “inverse” because the usual mapping is from a case to its unknown category.
The increased application of classification systems in business suggests that this inverse problem can be of significant benefit to decision makers as a form of sensitivity analysis. Analytic approaches to this inverse problem are difficult to formulate as the constraints are either not available or difficult to determine. To investigate this inverse… problem, we develop several genetic algorithms and study their performance as problem difficulty increases.
We develop a real genetic algorithm with feasibility control, a traditional binary genetic algorithm, and a steepest ascent hill climbing algorithm. In a series of simulation experiments, we compare the performance of these algorithms to the optimal solution as the problem difficulty increases (more attributes and classes). In addition, we analyze certain algorithm effects (level of feasibility control, operator design, and fitness function) to determine the best approach. Our results indicate the viability of the real genetic algorithm and the importance of feasibility control as the problem difficulty increases.