Showing papers by "University College Dublin published in 2008"

The CMS experiment at the CERN LHC

Abstract: The Compact Muon Solenoid (CMS) detector is described. The detector operates at the Large Hadron Collider (LHC) at CERN. It was conceived to study proton-proton (and lead-lead) collisions at a centre-of-mass energy of 14 TeV (5.5 TeV nucleon-nucleon) and at luminosities up to 10(34)cm(-2)s(-1) (10(27)cm(-2)s(-1)). At the core of the CMS detector sits a high-magnetic-field and large-bore superconducting solenoid surrounding an all-silicon pixel and strip tracker, a lead-tungstate scintillating-crystals electromagnetic calorimeter, and a brass-scintillator sampling hadron calorimeter. The iron yoke of the flux-return is instrumented with four stations of muon detectors covering most of the 4 pi solid angle. Forward sampling calorimeters extend the pseudo-rapidity coverage to high values (vertical bar eta vertical bar <= 5) assuring very good hermeticity. The overall dimensions of the CMS detector are a length of 21.6 m, a diameter of 14.6 m and a total weight of 12500 t.

Amyloid-beta protein dimers isolated directly from Alzheimer's brains impair synaptic plasticity and memory.

Abstract: Alzheimer's disease constitutes a rising threat to public health. Despite extensive research in cellular and animal models, identifying the pathogenic agent present in the human brain and showing that it confers key features of Alzheimer's disease has not been achieved. We extracted soluble amyloid-beta protein (Abeta) oligomers directly from the cerebral cortex of subjects with Alzheimer's disease. The oligomers potently inhibited long-term potentiation (LTP), enhanced long-term depression (LTD) and reduced dendritic spine density in normal rodent hippocampus. Soluble Abeta from Alzheimer's disease brain also disrupted the memory of a learned behavior in normal rats. These various effects were specifically attributable to Abeta dimers. Mechanistically, metabotropic glutamate receptors were required for the LTD enhancement, and N-methyl D-aspartate receptors were required for the spine loss. Co-administering antibodies to the Abeta N-terminus prevented the LTP and LTD deficits, whereas antibodies to the midregion or C-terminus were less effective. Insoluble amyloid plaque cores from Alzheimer's disease cortex did not impair LTP unless they were first solubilized to release Abeta dimers, suggesting that plaque cores are largely inactive but sequester Abeta dimers that are synaptotoxic. We conclude that soluble Abeta oligomers extracted from Alzheimer's disease brains potently impair synapse structure and function and that dimers are the smallest synaptotoxic species.

Nanoparticle size and surface properties determine the protein corona with possible implications for biological impacts

Abstract: Nanoparticles in a biological fluid (plasma, or otherwise) associate with a range of biopolymers, especially proteins, organized into the "protein corona" that is associated with the nanoparticle and continuously exchanging with the proteins in the environment. Methodologies to determine the corona and to understand its dependence on nanomaterial properties are likely to become important in bionanoscience. Here, we study the long-lived ("hard") protein corona formed from human plasma for a range of nanoparticles that differ in surface properties and size. Six different polystyrene nanoparticles were studied: three different surface chemistries (plain PS, carboxyl-modified, and amine-modified) and two sizes of each (50 and 100 nm), enabling us to perform systematic studies of the effect of surface properties and size on the detailed protein coronas. Proteins in the corona that are conserved and unique across the nanoparticle types were identified and classified according to the protein functional properties. Remarkably, both size and surface properties were found to play a very significant role in determining the nanoparticle coronas on the different particles of identical materials. We comment on the future need for scientific understanding, characterization, and possibly some additional emphasis on standards for the surfaces of nanoparticles.

The LHCb detector at the LHC

Abstract: The LHCb experiment is dedicated to precision measurements of CP violation and rare decays of B hadrons at the Large Hadron Collider (LHC) at CERN (Geneva). The initial configuration and expected performance of the detector and associated systems, as established by test beam measurements and simulation studies, is described.

A microRNA DNA methylation signature for human cancer metastasis

Abstract: MicroRNAs (miRNAs) are small, noncoding RNAs that can contribute to cancer development and progression by acting as oncogenes or tumor suppressor genes. Recent studies have also linked different sets of miRNAs to metastasis through either the promotion or suppression of this malignant process. Interestingly, epigenetic silencing of miRNAs with tumor suppressor features by CpG island hypermethylation is also emerging as a common hallmark of human tumors. Thus, we wondered whether there was a miRNA hypermethylation profile characteristic of human metastasis. We used a pharmacological and genomic approach to reveal this aberrant epigenetic silencing program by treating lymph node metastatic cancer cells with a DNA demethylating agent followed by hybridization to an expression microarray. Among the miRNAs that were reactivated upon drug treatment, miR-148a, miR-34b/c, and miR-9 were found to undergo specific hypermethylation-associated silencing in cancer cells compared with normal tissues. The reintroduction of miR-148a and miR-34b/c in cancer cells with epigenetic inactivation inhibited their motility, reduced tumor growth, and inhibited metastasis formation in xenograft models, with an associated down-regulation of the miRNA oncogenic target genes, such as C-MYC, E2F3, CDK6, and TGIF2. Most important, the involvement of miR-148a, miR-34b/c, and miR-9 hypermethylation in metastasis formation was also suggested in human primary malignancies (n = 207) because it was significantly associated with the appearance of lymph node metastasis. Our findings indicate that DNA methylation-associated silencing of tumor suppressor miRNAs contributes to the development of human cancer metastasis.

European Society of Hypertension guidelines for blood pressure monitoring at home: a summary report of the Second International Consensus Conference on Home Blood Pressure Monitoring.

Abstract: This document summarizes the available evidence and provides recommendations on the use of home blood pressure monitoring in clinical practice and in research. It updates the previous recommendations on the same topic issued in year 2000. The main topics addressed include the methodology of home blood pressure monitoring, its diagnostic and therapeutic thresholds, its clinical applications in hypertension, with specific reference to special populations, and its applications in research. The final section deals with the problems related to the implementation of these recommendations in clinical practice.

State of the art: using natriuretic peptide levels in clinical practice.

Abstract: Natriuretic peptide (NP) levels (B-type natriuretic peptide (BNP) and N-terminal proBNP) are now widely used in clinical practice and cardiovascular research throughout the world and have been incorporated into most national and international cardiovascular guidelines for heart failure. The role of NP levels in state-of-the-art clinical practice is evolving rapidly. This paper reviews and highlights ten key messages to clinicians: 1) NP levels are quantitative plasma biomarkers of heart failure (HF). 2) NP levels are accurate in the diagnosis of HF. 3) NP levels may help risk stratify emergency department (ED) patients with regard to the need for hospital admission or direct ED discharge. 4) NP levels help improve patient management and reduce total treatment costs in patients with acute dyspnoea. 5) NP levels at the time of admission are powerful predictors of outcome in predicting death and re-hospitalisation in HF patients. 6) NP levels at discharge aid in risk stratification of the HF patient. 7) NP-guided therapy may improve morbidity and/or mortality in chronic HF. 8) The combination of NP levels together with symptoms, signs and weight gain assists in the assessment of clinical decompensation in HF. 9) NP levels can accelerate accurate diagnosis of heart failure presenting in primary care. 10) NP levels may be helpful to screen for asymptomatic left ventricular dysfunction in high-risk patients.

Prevalence of Unsuspected Pancreatic Cysts on MDCT

Abstract: OBJECTIVE. Current generation MDCT technology facilitates identification of small, nonenhancing lesions in the pancreas. The objective of this study was to determine the prevalence of findings of unsuspected pancreatic cysts on 16-MDCT in a population of adult outpatients imaged for disease unrelated to the pancreas.MATERIALS AND METHODS. Contrast-enhanced MDCT scans of the abdomen were reviewed from 2,832 consecutive examinations to identify pancreatic cysts. Patients with a history of pancreatic lesions or predisposing factors for pancreatic disease or who were referred for pancreatic CT were excluded.RESULTS. A total of 73 patients had pancreatic cysts, representing a prevalence of 2.6 per 100 patients (95% CI, 2.0–3.2). Cysts ranged in size from 2 to 38 mm (mean, 8.9 mm) and were solitary in 85% of cases. Analysis of demographic information showed a strong correlation between pancreatic cysts and age, with no cysts identified among patients under 40 years and a prevalence of 8.7 per 100 (95% CI, 4.6–1...

Class-Sparing Regimens for Initial Treatment of HIV-1 Infection

Abstract: Background The use of either efavirenz or lopinavir–ritonavir plus two nucleoside reverse-transcriptase inhibitors (NRTIs) is recommended for initial therapy for patients with human immunodeficiency virus type 1 (HIV-1) infection, but which of the two regimens has greater efficacy is not known. The alternative regimen of lopinavir– ritonavir plus efavirenz may prevent toxic effects associated with NRTIs. Methods In an open-label study, we compared three regimens for initial therapy: efavirenz plus two NRTIs (efavirenz group), lopinavir–ritonavir plus two NRTIs (lopinavir–ritonavir group), and lopinavir–ritonavir plus efavirenz (NRTI-sparing group). We randomly assigned 757 patients with a median CD4 count of 191 cells per cubic millimeter and a median HIV-1 RNA level of 4.8 log 10 copies per milliliter to the three groups. Results At a median follow-up of 112 weeks, the time to virologic failure was longer in the efavirenz group than in the lopinavir–ritonavir group (P = 0.006) but was not significantly different in the NRTI-sparing group from the time in either of the other two groups. At week 96, the proportion of patients with fewer than 50 copies of plasma HIV-1 RNA per milliliter was 89% in the efavirenz group, 77% in the lopinavir–ritonavir group, and 83% in the NRTI-sparing group (P = 0.003 for the comparison between the efavirenz group and the lopinavir–ritonavir group). The groups did not differ significantly in the time to discontinuation because of toxic effects. At virologic failure, antiretroviral resistance mutations were more frequent in the NRTIsparing group than in the other two groups. Conclusions Virologic failure was less likely in the efavirenz group than in the lopinavir–ritonavir group. The virologic efficacy of the NRTI-sparing regimen was similar to that of the efavirenz regimen but was more likely to be associated with drug resistance. (ClinicalTrials.gov number, NCT00050895.)

Effective Analysis of Reaction Time Data.

Abstract: Most analyses of reaction time (RT) data are conducted by using the statistical techniques with which psychologists are most familiar, such as analysis of variance on the sample mean. Unfortunately, these methods are usually inappropriate for RT data, because they have little power to detect genuine differences in RT between conditions. In addition, some statistical approaches can, under certain circumstances, result in findings that are artifacts of the analysis method itself. A corpus of research has shown more effective analytical methods, such as analyzing the whole RT distribution, although this research has had limited influence. The present article will summarize these ad’ances in methods for analyzing RT data.

Discretionary Disclosure Strategies in Corporate Narratives: Incremental Information or Impression Management?

Abstract: Prior research assumes that discretionary disclosures either (a) contribute to useful decision making by overcoming information asymmetries between managers and firm outsiders (informational perspective); or (b) constitute opportunistic behavior whereby managers exploit information asymmetries between them and firm outsiders through engaging in biased reporting, i.e. impression management (opportunistic perspective). We consider possible theoretical underpinnings of the two competing positions. We discuss different theories explaining managers' motives to engage in impression management or to provide incremental information. We identify various theories, in particular from behavioral finance and from psychology that explain why investors might be susceptible to managerial impression management. We examine the discretionary disclosure strategies applied by managers in corporate narratives, classifying them into seven categories. This enables a better understanding of the wide range of techniques applied by managers to manage impressions/enhance disclosure quality. We bring together both capital markets and behavioral research on whether discretionary narrative disclosure strategies influence decision making and whether, therefore, they are effective. Finally, we suggest future research opportunities. We propose alternative theories from the accounting, management, and social psychology literature to suggest additional impression management motivations and strategies not previously considered in a financial reporting context. We take different theories and prior research in behavioral finance and psychology to put forward new avenues for studying the effect of discretionary narrative disclosures on users, and to explain why users might be influenced by managerial impression management.

The determinants of export performance: A review of the research in the literature between 1998 and 2005

Abstract: Considerable attention has been paid to the determinants of export performance. However, despite this research effort in identifying and examining the influence of such determinants, the literature is characterized by fragmentation and diversity, hindering theory development and practical advancement in the field. This paper attempts to review and synthesize the knowledge on the subject. As a result, this study reviews and evaluates 52 articles published between 1998 and 2005 to assess the determinants of export performance. The assessment reveals that: (a) more studies have been conducted outside the USA; (b) the majority of the studies focus on manufacturing firms, with relatively few studies examining the service sector; (c) the majority of the export studies continue to focus on small to medium-sized firms; (d) there is a continuous increase in the sample size; (e) despite the problems that may arise from the use of single informants, it seems that none of the studies reviewed here collected data from more than one informant in the firm; (f) an increasing number of studies have been using the export venture as the unit of analysis; (g) the level of statistical sophistication has improved; (h) the use of control and moderating variables in export performance studies has increased; (i) more studies have started to include the external environment in their models, including domestic market characteristics; and (j) market orientation as a key determinant of export performance emerges in this review. Finally, conclusions are drawn, along with some suggestions for further research.

Differential diagnosis of suspected multiple sclerosis: a consensus approach

Abstract: Background and objectivesDiagnosis of multiple sclerosis (MS) requires exclusion of diseases that could better explain the clinical and paraclinical findings A systematic process for exclusion of alternative diagnoses has not been defined An International Panel of MS experts developed consensus perspectives on MS differential diagnosisMethodsUsing available literature and consensus, we developed guidelines for MS differential diagnosis, focusing on exclusion of potential MS mimics, diagnosis of common initial isolated clinical syndromes, and differentiating between MS and non-MS idiopathic inflammatory demyelinating diseasesResultsWe present recommendations for 1) clinical and paraclinical red flags suggesting alternative diagnoses to MS; 2) more precise definition of “clinically isolated syndromes” (CIS), often the first presentations of MS or its alternatives; 3) algorithms for diagnosis of three common CISs related to MS in the optic nerves, brainstem, and spinal cord; and 4) a classification schem

Cyclostationary Signatures in Practical Cognitive Radio Applications

Abstract: We define a cyclostationary signature as a feature which may be intentionally embedded in a digital communications signal, detected through cyclostationary analysis and used as a unique identifier. The purpose of this paper is to demonstrate how cyclostationary signatures can be exploited to overcome a number of the challenges associated with network coordination in emerging cognitive radio applications and spectrum sharing regimes. In particular we show their uses for signal detection, network identification and rendezvous and discuss these in the context of dynamic spectrum access. We present a theoretical discussion followed by application-oriented examples of the cyclostationary signatures used in practical cognitive radio and dynamic spectrum usage scenarios. We focus on orthogonal frequency division multiplexing (OFDM) based systems and present an analysis of a transceiver implementation employing these techniques developed on a cognitive radio test platform.

National Academy of Clinical Biochemistry Laboratory Medicine Practice Guidelines for Use of Tumor Markers in Testicular, Prostate, Colorectal, Breast, and Ovarian Cancers

Abstract: Background: Updated National Academy of Clinical Biochemistry (NACB) Laboratory Medicine Practice Guidelines for the use of tumor markers in the clinic have been developed. Methods: Published reports relevant to use of tumor markers for 5 cancer sites—testicular, prostate, colorectal, breast, and ovarian—were critically reviewed. Results: For testicular cancer, α-fetoprotein, human chorionic gonadotropin, and lactate dehydrogenase are recommended for diagnosis/case finding, staging, prognosis determination, recurrence detection, and therapy monitoring. α-Fetoprotein is also recommended for differential diagnosis of nonseminomatous and seminomatous germ cell tumors. Prostate-specific antigen (PSA) is not recommended for prostate cancer screening, but may be used for detecting disease recurrence and monitoring therapy. Free PSA measurement data are useful for distinguishing malignant from benign prostatic disease when total PSA is <10 μg/L. In colorectal cancer, carcinoembryonic antigen is recommended (with some caveats) for prognosis determination, postoperative surveillance, and therapy monitoring in advanced disease. Fecal occult blood testing may be used for screening asymptomatic adults 50 years or older. For breast cancer, estrogen and progesterone receptors are mandatory for predicting response to hormone therapy, human epidermal growth factor receptor-2 measurement is mandatory for predicting response to trastuzumab, and urokinase plasminogen activator/plasminogen activator inhibitor 1 may be used for determining prognosis in lymph node–negative patients. CA15-3/BR27–29 or carcinoembryonic antigen may be used for therapy monitoring in advanced disease. CA125 is recommended (with transvaginal ultrasound) for early detection of ovarian cancer in women at high risk for this disease. CA125 is also recommended for differential diagnosis of suspicious pelvic masses in postmenopausal women, as well as for detection of recurrence, monitoring of therapy, and determination of prognosis in women with ovarian cancer. Conclusions: Implementation of these recommendations should encourage optimal use of tumor markers.

Citizenship and Immigration: Multiculturalism, Assimilation, and Challenges to the Nation-State

Abstract: Citizenship encompasses legal status, rights, participation, and belonging. Traditionally anchored in a particular geographic and political community, citizenship evokes notions of national identity, sovereignty, and state control, but these relationships are challenged by the scope and diversity of international migration. This review considers normative and empirical debates over citizenship and bridges an informal divide between European and North American literatures. We focus on citizenship within nation-states by discussing ethnic versus civic citizenship, multiculturalism, and assimilation. Going beyond nation-state boundaries, we also look at transnational, postnational, and dual citizenships. Throughout, we identify methodological and theoretical challenges in this field, noting the need for a more dynamic and comprehensive understanding of the inter-relationships between the dimensions of citizenship and immigration.

Protein aggregation in the brain: the molecular basis for Alzheimer's and Parkinson's diseases.

Abstract: Developing effective treatments for neurodegenerative diseases is one of the greatest medical challenges of the 21st century. Although many of these clinical entities have been recognized for more than a hundred years, it is only during the past twenty years that the molecular events that precipitate disease have begun to be understood. Protein aggregation is a common feature of many neurodegenerative diseases, and it is assumed that the aggregation process plays a central role in pathogenesis. In this process, one molecule (monomer) of a soluble protein interacts with other monomers of the same protein to form dimers, oligomers, and polymers. Conformation changes in three-dimensional structure of the protein, especially the formation of β-strands, often accompany the process. Eventually, as the size of the aggregates increases, they may precipitate as insoluble amyloid fibrils, in which the structure is stabilized by the β-strands interacting within a β-sheet. In this review, we discuss this theme as it relates to the two most common neurodegenerative conditions—Alzheimer’s and Parkinson’s diseases.

Cronobacter gen. nov., a new genus to accommodate the biogroups of Enterobacter sakazakii, and proposal of Cronobacter sakazakii gen. nov., comb. nov., Cronobacter malonaticus sp. nov., Cronobacter turicensis sp. nov., Cronobacter muytjensii sp. nov., Cronobacter dublinensis sp. nov., Cronobacter genomospecies 1, and of three subspecies, Cronobacter dublinensis subsp. dublinensis subsp. nov., Cronobacter dublinensis subsp. lausannensis subsp. nov. and Cronobacter dublinensis subsp. lactaridi subsp. nov.

Abstract: [Enterobacter] sakazakii is an opportunistic pathogen that can cause infections in neonates. This study further clarifies the taxonomy of isolates described as [E.] sakazakii and completes the formal description of the proposed reclassification of these organisms as novel species and subspecies within a proposed novel genus, Cronobacter gen. nov. [E.] sakazakii was first defined in 1980, however recent polyphasic taxonomic analysis has determined that this group of organisms consists of several genomospecies. In this study, the phenotypic descriptions of the proposed novel species are expanded using Biotype 100 and Biolog Phenotype MicroArray data. Further DNA–DNA hybridization experiments showed that malonate-positive strains within the [E.] sakazakii genomospecies represent a distinct species, not a subspecies. DNA–DNA hybridizations also determined that phenotypically different strains within the proposed species, Cronobacter dublinensis sp. nov., belong to the same species and can be considered as novel subspecies. Based on these analyses, the following alternative classifications are proposed: Cronobacter sakazakii gen. nov., comb. nov. [type strain ATCC 29544T (=NCTC 11467T)]; Cronobacter malonaticus sp. nov. [type strain CDC 1058-77T (=LMG 23826T=DSM 18702T)]; Cronobacter turicensis sp. nov. [type strain z3032T (=LMG 23827T=DSM 18703T)]; Cronobacter muytjensii sp. nov. [type strain ATCC 51329T (=CIP 103581T)]; Cronobacter dublinensis sp. nov. [type strain DES187T (=LMG 23823T=DSM 18705T)]; Cronobacter dublinensis subsp. dublinensis subsp. nov. [type strain DES187T (=LMG 23823T=DSM 18705T)]; Cronobacter dublinensis subsp. lausannensis subsp. nov. [type strain E515T (=LMG 23824=DSM 18706T)], and Cronobacter dublinensis subsp. lactaridi subsp. nov. [type strain E464T (=LMG 23825T=DSM 18707T)].

Inhibition of amyloid beta protein fibrillation by polymeric nanoparticles.

Abstract: Copolymeric NiPAM:BAM nanoparticles of varying hydrophobicity were found to retard fibrillation of the Alzheimer’s disease-associated amyloid β protein (Aβ). We found that these nanoparticles affect mainly the nucleation step of Aβ fibrillation. The elongation step is largely unaffected by the particles, and once the Aβ is nucleated, the fibrillation process occurs with the same rate as in the absence of nanoparticles. The extension of the lag phase for fibrillation of Aβ is strongly dependent on both the amount and surface character of the nanoparticles. Surface plasmon resonance studies show that Aβ binds to the nanoparticles and provide rate and equilibrium constants for the interaction. Numerical analysis of the kinetic data for fibrillation suggests that binding of monomeric Aβ and prefibrillar oligomers to the nanoparticles prevents fibrillation. Moreover, we find that fibrillation of Aβ initiated in the absence of nanoparticles can be reversed by addition of nanoparticles up to a particular time po...

A Novel Staphylococcus aureus Biofilm Phenotype Mediated by the Fibronectin-Binding Proteins, FnBPA and FnBPB

Abstract: Device-associated infections involving biofilm remain a persistent clinical problem. We recently reported that four methicillin-resistant Staphylococcus aureus (MRSA) strains formed biofilm independently of the icaADBC-encoded exopolysaccharide. Here, we report that MRSA biofilm development was promoted under mildly acidic growth conditions triggered by the addition of glucose to the growth medium. Loss of sortase, which anchors LPXTG-containing proteins to peptidoglycan, reduced the MRSA biofilm phenotype. Furthermore introduction of mutations in fnbA and fnbB, which encode the LPXTG-anchored multifunctional fibrinogen and fibronectin-binding proteins, FnBPA and FnBPB, reduced biofilm formation by several MRSA strains. However, these mutations had no effect on biofilm formation by methicillin-sensitive S. aureus strains. FnBP-promoted biofilm occurred at the level of intercellular accumulation and not primary attachment. Mutation of fnbA or fnbB alone did not substantially affect biofilm, and expression of either gene alone from a complementing plasmid in fnbA fnbB mutants restored biofilm formation. FnBP-promoted biofilm was dependent on the integrity of SarA but not through effects on fnbA or fnbB transcription. Using plasmid constructs lacking regions of FnBPA to complement an fnbAB mutant revealed that the A domain alone and not the domain required for fibronectin binding could promote biofilm. Additionally, an A-domain N304A substitution that abolished fibrinogen binding did not affect biofilm. These data identify a novel S. aureus biofilm phenotype promoted by FnBPA and FnBPB which is apparently independent of the known ligand-binding activities of these multifunctional surface proteins.

Multifunctional Magnetic-fluorescent Nanocomposites for Biomedical Applications

Abstract: Nanotechnology is a fast-growing area, involving the fabrication and use of nano-sized materials and devices. Various nanocomposite materials play a number of important roles in modern science and technology. Magnetic and fluorescent inorganic nanoparticles are of particular importance due to their broad range of potential applications. It is expected that the combination of magnetic and fluorescent properties in one nanocomposite would enable the engineering of unique multifunctional nanoscale devices, which could be manipulated using external magnetic fields. The aim of this review is to present an overview of bimodal “two-in-one” magnetic-fluorescent nanocomposite materials which combine both magnetic and fluorescent properties in one entity, in particular those with potential applications in biotechnology and nanomedicine. There is a great necessity for the development of these multifunctional nanocomposites, but there are some difficulties and challenges to overcome in their fabrication such as quenching of the fluorescent entity by the magnetic core. Fluorescent-magnetic nanocomposites include a variety of materials including silica-based, dye-functionalised magnetic nanoparticles and quantum dots-magnetic nanoparticle composites. The classification and main synthesis strategies, along with approaches for the fabrication of fluorescent-magnetic nanocomposites, are considered. The current and potential biomedical uses, including biological imaging, cell tracking, magnetic bioseparation, nanomedicine and bio- and chemo-sensoring, of magnetic-fluorescent nanocomposites are also discussed.

Avoiding monotony: improving the diversity of recommendation lists

Abstract: The primary premise upon which top-N recommender systems operate is that similar users are likely to have similar tastes with regard to their product choices. For this reason, recommender algorithms depend deeply on similarity metrics to build the recommendation lists for end-users.However, it has been noted that the products offered on recommendation lists are often too similar to each other and attention has been paid towards the goal of improving diversity to avoid monotonous recommendations.Noting that the retrieval of a set of items matching a user query is a common problem across many applications of information retrieval, we model the competing goals of maximizing the diversity of the retrieved list while maintaining adequate similarity to the user query as a binary optimization problem. We explore a solution strategy to this optimization problem by relaxing it to a trust-region problem.This leads to a parameterized eigenvalue problem whose solution is finally quantized to the required binary solution. We apply this approach to the top-N prediction problem, evaluate the system performance on the Movielens dataset and compare it with a standard item-based top-N algorithm. A new evaluation metric ItemNovelty is proposed in this work. Improvements on both diversity and accuracy are obtained compared to the benchmark algorithm.