Movie recommender systems: Concepts, methods, challenges, and future directions

Movie recommender systems are meant to give suggestions to the users based on the features they love the most. A highly performing movie recommendation will suggest movies that match the similarities with the highest degree of performance. This study conducts a systematic literature review on movie recommender systems. It highlights the filtering criteria in the recommender systems, algorithms implemented in movie recommender systems, the performance measurement criteria, the challenges in implementation, and recommendations for future research. Some of the most popular machine learning algorithms used in movie recommender systems such as K-means clustering, principal component analysis, and self-organizing maps with principal component analysis are discussed in detail. Special emphasis is given to research works performed using metaheuristic-based recommendation systems. The research aims to bring to light the advances made in developing the movie recommender systems, and what needs to be performed to reduce the current challenges in implementing the feasible solutions. The article will be helpful to researchers in the broad area of recommender systems as well as practicing data scientists involved in the implementation of such systems.Web of Science2213art. no. 490

Potential COVID -19 Therapeutics in Clinical Trials – A Brief Review

The severe acute respiratory syndrome coronavirus 2 (SARS – CoV2), the causative viral pathogen of the COVID-19 pandemic belongs to the family of Coronaviruses which are positive single stranded RNA viruses. The scientific fraternity has developed and developing various types of vaccines for prevention against COVID-19, such as inactivated virus vaccines, mRNA vaccines, replicating vector protein subunit vaccines, etc., Out of which ten vaccines namely Novovax, Covovax (protein subunit vaccines), Pfizer BNT16b2, Moderna mRNA 1273 (mRNA vaccines), Johnson & Johnson Ad26, Cov2.S, Astrazeneca AZD1222, Covishield (non-replicating viral vector vaccines), Covaxin, Sinopharm BBIBP-CorV, CoronoVac (inactivated vaccines) have been approved for clinical use by WHO. There is an urgent need for SARS-CoV2 specific therapeutics for the treatment of COVID-19 as there is the emergence of various variants such as Alpha, Beta, Gamma, Delta, Omicron, etc. The emergence of variants that possesses immune evading property and spike protein mutation have increased infectivity and more pathogenicity which impelled the need to develop various therapeutics for the treatment of COVID-19. This review compiles the information about potential antiviral candidates in preclinical trials intended for the treatment of COVID-19. The clinical development of such antivirals will be very crucial for the treatment of COVID-19 and also to curb the spread as the present scenario depends on the development of effective prophylactic vaccines

EpCAM aptamer mediated cancer cell specific delivery of EpCAM siRNA using polymeric nanocomplex

BACKGROUND: Epithelial cell adhesion molecule (EpCAM) is overexpressed in solid tumors and regarded as a putative cancer stem cell marker. Here, we report that employing EpCAM aptamer (EpApt) and EpCAM siRNA (SiEp) dual approach, for the targeted delivery of siRNA to EpCAM positive cancer cells, efficiently inhibits cancer cell proliferation. RESULTS: Targeted delivery of siRNA using polyethyleneimine is one of the efficient methods for gene delivery, and thus, we developed a novel aptamer-PEI-siRNA nanocomplex for EpCAM targeting. PEI nanocomplex synthesized with EpCAM aptamer (EpApt) and EpCAM siRNA (SiEp) showed 198 nm diameter sized particles by dynamic light scattering, spherical shaped particles, of 151 ± 11 nm size by TEM. The surface charge of the nanoparticles was -30.0 mV using zeta potential measurements. Gel retardation assay confirmed the PEI-EpApt-SiEp nanoparticles formation. The difference in size observed by DLS and TEM could be due to coating of aptamer and siRNA on PEI nanocore. Flow cytometry analysis revealed that PEI-EpApt-SiEp has superior binding to cancer cells compared to EpApt or scramble aptamer (ScrApt) or PEI-ScrApt-SiEp. PEI-EpApt-SiEp downregulated EpCAM and inhibited selectively the cell proliferation of MCF-7 and WERI-Rb1 cells. CONCLUSIONS: The PEI nanocomplex fabricated with EpApt and siEp was able to target EpCAM tumor cells, deliver the siRNA and silence the target gene. This nanocomplex exhibited decreased cell proliferation than the scrambled aptamer loaded nanocomplex in the EpCAM expressing cancer cells and may have potential for EpCAM targeting in vivo

Heuristics and biases in decisions to stay with or renege from sequential waits

Consumer wait situations such as being put on hold during a telephone call require the consumer to make continuous decisions on whether to stay on line and receive service or terminate the current wait and reinitiate a new wait. The key question that is addressed in my dissertation is how do consumers decide how long to wait and when to renege? I expect that going into a wait situation consumers are likely to hold optimistic priors about wait completions. Further, as the wait progresses, rational instincts to stay during the wait are increasingly likely to be affected by various psychological factors such as emotional cost of the wait, uncertainty about the wait, perceptions about likely length of future wait and the extent to which prior wait expectations are violated. The net effect is that I expect consumers to abandon waits when they perceive the utility of the current wait net of the psychological factors as less than that associated with starting a new wait. I study renege decisions in contexts where it is never optimal to renege and in contexts where it is optimal to renege within a small window of time and show that consumer decisions to renege are far from optimal and are likely driven by psychological factors. Further, I show how moderators such as activity within a wait, often used as time management strategies by marketers, are likely to affect decisions to stay or renege

Verformung und bruchmechanische Eigenschaften von Si-C-N-Precursorkeramiken

This thesis deals with the investigation of the deformation and fracture mechanical properties of precursor-derived (PDC) Si-C-N ceramics. The materials were synthesized from a liquid poly(ureamethylvinyl)silazane precursor. In order to access the intrinsic mechanical behavior of the materials, fully dense defect-free PDC specimens devoid of process induced extrinsic features were fabricated using a special casting and crosslinking process and controlled thermolysis procedures. The investigations were performed on a range of Si-C-N-(H) PDC with progressively varying material structures from hydrogenated amorphous to phase-separated nanocrystalline microstructures, from which the influence of material structure on the mechanical behavior was analyzed. The crack-tip fracture toughness (KI0) of the materials were evaluated using the novel crack opening displacement (COD) method. The estimated KI0 values ranged from 0.6 to 1.2 MPa m1/2. The variation in KI0 was well correlated with the structural evolution in the materials, effected by the progressive stripping of the one-fold coordinated hydrogen in the amorphous materials leading to increased network connectivity, and the nucleation and growth of turbostratic graphite (TG) and nanocrystalline SiC in the phase-separated materials. The net change in the resistance to fracture in these materials was effected by the change in the average fracture surface energy and crack deflection toughening. Crack deflection observed even in the amorphous materials revealed the presence of structural and compositional inhomogeneities. To further understand the cause and effect of crack deflection in terms of crack tip damage mechanisms, roughness analysis of fracture surfaces was carried out using the fractal approach. The analysis revealed self-affine scaling up to a correlation length of around 50 nm and a self-affine roughness exponent (ζ) of 0.8 ± 0.1 in all the materials, the latter in agreement with the universal roughness exponent conjectured in literature. However, no correlation was observed between the observed roughness exponents and the fracture toughness of the corresponding materials. Examination of the crack opening near the crack tip by high resolution AFM imaging revealed no persistent damage cavities along the crack, concluding that the fracture in the investigated Si-C-N ceramics proceeded in a brittle manner in the resolvable length scales, at crack velocities employed in the present experiments. The deformation behavior of the present Si-C-N ceramics under contact loading conditions was investigated using spherical as well as sharp (Vickers and Berkovich) indentation experiments. The elastic moduli and nanoindentation hardness evaluated from the analysis of the nanoindentation load-displacement curves correlated well with the evolution of material resistance to elastic and plastic deformation, commensurate with the structural and microstructural evolution in the materials. Analysis of the elastic and plastic deformation work quantities derived from the load-unload cycle in the Berkovich nanoindentation enabled the discrimination of the different plastic deformation characteristics of the amorphous and phase segregated materials. The equi-proportional variation of elastic and plastic deformation in the amorphous Si-C-N materials identical to vitreous silica indicated the anomalous character of plastic deformation in these materials that induced appreciable strain hardening under progressive densification. This was manifested in the load-dependant increase in hardness. The contrasting variation of plastic deformation work in the phase-separated materials indicated the emergence of an additional plastic deformation mechanism in these materials, that proceeded by a shear deformation promoted by the TG-phase. The anomalous densification behavior in amorphous Si-C-N materials also led to a load dependence of the strain rate sensitivity (m), also observed in vitreous silica, and controlled the evolution of indentation size effect (ISE). The magnitude and direction of ISE was determined by the relative dominance of the two concurrent effects, namely strain hardening and indentation creep deformation. The evolution of strain rate sensitivity in the range of investigated materials showed good agreement with the cluster model, which relates the increase in the number density of isolated regions in the microstructure to a corresponding increase in m. The non-densifying shear mode of plastic deformation in phase-separated materials led to a decrease in the strain hardening capability, increase in m and increased vulnerability to ISE.In der vorliegenden Dissertation wird die Untersuchung der Verformung und der bruchmechanischen Eigenschaften von Si-C-N-Precursorkeramiken (precursor-derived ceramics, PDC) beschrieben. Die Hauptziele der vorliegenden Arbeit waren (i) die intrinsischen mechanischen Eigenschaften der Si-C-N-Precursorkeramiken zu bestimmen und (ii) die me¬chanischen Eigenschaften dann mit der Struktur der Materialien, die bei der mehrstufigen Phasenbildung während der Precursor-zu-Keramik Umwandlung entsteht, zu korrelieren. Mit dieser Ziele wurden völlig dichte defektfreie keramische Proben mit Strukturen, vom organisch amorphen bis zum anorganisch nano-kristallinen Zustand durch thermische Vernetzung und temperaturkontrollierte Thermolyse eines flüssigen Poly(ureamethylvinyl)silazan-Precursorpolymers hergestellt. Strukturelle Veränderungen der amorphen Probenmaterialien wurden durch die fortschreitende Entfernung des Wasserstoffs im Verlauf der Thermolyse und die damit einhergehende kontinuierliche Zunahme der Strukturver¬dichtung festgestellt. Die Be¬seitigung des Wasserstoffs führte bei 1200°C zu einer Phasenausscheidung durch Überführung des überschüssigen freien Kohlenstoffs in eine turbostrati¬sche Graphitphase (TG-Phase) und bei 1300°C zur Keimbildung von nano-kri¬stallinem SiC (n-SiC). Für die bruchmechanische Charakterisierung diente als Bewertungskriterium die Bruchzähigkeit an der Rissspitze („crack-tip toughness“, kritischer Spannungsin¬tensitätsfaktor an der Rissspitze, KI0), wozu eine neu entwickelte Rissöffnungspro¬fil-Methode (crack-opening displacement, COD) eingesetzt wurde. In Abhängigkeit vom Umwandlungs¬grad der Materialien wurden KI0-Werte von 0.6 bis 1,2 MPam1/2 ermittelt. Die Zunahme des Bruchwiderstandes der amorphen Materialien kann auf die zu¬nehmende Vernetzung durch die kontinuierliche Entfernung des Wasserstoffs zu¬rückgeführt werden. Durch die daraus resultierende Erhöhung des Vernetzungsgrades wurde auch die nanoskalige Rissablenkung in amorphen Materialien erhöht. Andererseits steuerten die Pfade mit niedrigerer Oberflächenenergie im Gefüge, die auf die Separierung der TG-Phase zurückzuführen sind, die Mikromechanik der Riss¬ausbreitung in phasengetrennten Materialien. Die Netto-Änderung des Bruchwiderstandes in diesen Materialien erfolgte sowohl durch die Änderung der durchschnittlichen Bruch¬oberflächenenergie als auch durch eine Zunahme der Rissablenkung. Die Rauhigkeit der Bruchoberflächen wurde mit der fraktalen Annäherung analysiert. Die Fraktal¬analyse ergab eine Korrelationslänge (ξ) von ca. 50 nm und einen Rauhigkeitsexponent (ζ) von 0.8 ± 0.1 in allen Materialien. Dieser Wert stimmt mit dem Universalrauhigkeitsexponent, der, nach Bouchaud et al. bei 0.8 liegt, überein. Es wurde jedoch keine Wechselwirkung zwischen den ermittelten Rauhigkeitsexponenten und der Bruchzähigkeit der entsprechenden Materialien festgestellt. Die Prüfung der Rissöffnung in der Nähe der Rissspitze ließ keine Beschädigungs¬kavitäten entlang des Bruches erkennen. Daraus ist zu schließen, dass der Bruch in den untersuchten Si-C-N-Keramiken soweit mit den gegebenen Abbil¬dungstechniken erkennbar als reiner Sprödbruch verlief. Das elastische und plastische Verformungsverhalten der untersuchten Si-C-N-Keramiken unter Kontaktbelastungsbedingungen wurde durch Eindruckexperimente untersucht. Die Elas¬tizitätsmodule und Härte, die sich aus der Nanoindentation-Last-Eindrucktiefe Kurven ergaben, stimmten mit dem Materialwiderstand gegen die elastische und plastische Verformung der jeweiligen Materialien überein. Die equiproportionale Änderung der Eindrucksarbeit der elastischen und plasti¬schen Verformung in amorphen Materialien zeigte den anomalen Charakter der plastischen Verformung, die bei der Materialverdichtung stattfand. Der Materialverdichtung führte in den amorphen Materialien zu einer Kaltverfesti¬gung. Die Größe der Kaltverfestigung sowohl von der angewandten Belastung als auch von der Belastungsrate abhängt. Die entgegen¬gesetzte Entwicklung der Verformungsarbeit in den phasengetrennten Materia¬lien zeigte das Auftreten einer zusätzlichen Form von plastischer Verformung, die durch die Scherverformung der TG-Phase gefördert wurde. Die Kapazität der phasen¬getrennten Materialien für die Verfestigung war niedriger als bei den amorphen Materialien. Die beiden Modi der plastischen Verformung beein¬flussten auch die Lastabhängigkeit der Härte (indentation size effect, ISE). Das Ausmaß der ISE scheint durch die relative Dominanz von Eindruck-Kriechverformung und Fähigkeit zur Kaltverfestigung bestimmt zu werden. Die Änderung der Dehnraten¬empfindlichkeit der untersuchten Si-C-N-Materialien stimmte mit dem sogenannten „cluster model“ des Materialflusses überein. Der entgegengesetzte Einfluss der Belastung auf die Dehnratenempfindlichkeit der amorphen und phasengetrennten Materialien verdeutlicht wiederum deres unterschiedlich wirksamen Verformungsmechanismen

Heuristics and biases in decisions to stay with or renege from sequential waits

Consumer wait situations such as being put on hold during a telephone call require the consumer to make continuous decisions on whether to stay on line and receive service or terminate the current wait and reinitiate a new wait. The key question that is addressed in my dissertation is how do consumers decide how long to wait and when to renege? I expect that going into a wait situation consumers are likely to hold optimistic priors about wait completions. Further, as the wait progresses, rational instincts to stay during the wait are increasingly likely to be affected by various psychological factors such as emotional cost of the wait, uncertainty about the wait, perceptions about likely length of future wait and the extent to which prior wait expectations are violated. The net effect is that I expect consumers to abandon waits when they perceive the utility of the current wait net of the psychological factors as less than that associated with starting a new wait. I study renege decisions in contexts where it is never optimal to renege and in contexts where it is optimal to renege within a small window of time and show that consumer decisions to renege are far from optimal and are likely driven by psychological factors. Further, I show how moderators such as activity within a wait, often used as time management strategies by marketers, are likely to affect decisions to stay or renege

Characterisation of manganese dioxide for nonaqueous lithium cells

Physicochemical properties of chemically prepared MnO2 were studied In detail. Li-MnO2 cells were fabricated with the prepared manganese dloxide and the performance characteristics were studied. The best manganese dioxide for Li-MnO2 nonaqueous cell was identifie