The Power of Rankings: Quantifying the Effect of Rankings on Online Consumer Search and Purchase Decisions

Online search intermediaries, such as Amazon or Expedia, use rankings (ordered lists) to present third party sellers’ products to consumers. These rankings decrease consumer search costs and increase the probability of a match with a seller, ultimately increasing consumer welfare. Constructing relevant rankings requires understanding their causal effect on consumer choices. However, this is challenging since rankings are endogenous: highly ranked products are also the most relevant ones for consumers. In this dissertation, I use the first data set with experimental variation in the ranking from a field experiment at Expedia to identify the causal effect of rankings. Using this data set, I make three contributions. First, I show that rankings affect what consumers search, but conditional on search, do not affect purchases. I also exploit a feature of the data set (opaque offers), to show that rankings lower search costs, instead of affecting consumer expectations or utility. Second, I quantify the effect of rankings using a sequential search model and find an average position effect of $2.64, lower than previous estimates in the literature obtained without experimental varia- tion. Finally, I show that a utility-based ranking built on this model’s estimates leads to an almost twofold increase in consumer welfare, while also increasing transactions and revenue for the search intermediary

CYBERBULLYING – VIOLENŢA ÎN ERA DIGITALĂ

Lucrarea de faţă reprezintă un prim demers de conştientizare cu privire la o dimensiune a violenţei manifestate în special în rândul copiilor şi tinerilor – cyberbullying, violenţa în spaţiul virtual. În contextul erei digitale, al societăţii contemporane care se defineşte şi redefineşte continuu în acord cu evoluţia tehnologiei, într-o lume care se construieşte, se destramă şi se reconstruieşte permanent din spatele monitoarelor, în şcoala nativilor digitali care se formează cu pre­dilecţie prin apel la oceanul de informaţii oferite prin acces la Internet, agresivitatea capătă proporţii nebănuite cu efecte devastatoare. Primul pas în soluţionarea problemei constă în recunoaşterea sa, în definirea corectă a tuturor faţetelor sale, în identificarea factorilor declanşatori.CYBERBULLYING – VIOLENCE IN THE DIGITAL ERAThis paper represents a first approach for raising the awareness regarding a dimension of violence manifested especially among children and youngsters – cyberbullying, violence in virtual environment. In the context of the digital era, of the contemporary society that defines and redefines itself constantly according to the technological evolution, in a world that builds itself, crumbles and rebuilds itself from behind the monitors, in a school of the digital natives that develop themselves especially by using the ocean of information offered through the Internet, the aggressiveness gets enormous proportions with devastating effects. The first step in solving the problem is to admit its existence, to define correctly all its aspects, to identify the triggers.</p

An unusual presentation of atrioventricular nodal reentrant tachycardia

Introduction: Atrioventricular nodal reentrant tachycardia (AVNRT) is the most frequent supraventricular tachycardia, commonly manifesting as autolimited paroxysmal episodes of rapid regular palpitations that exceed 150 beats per minute (bpm), dizziness and pounding neck sensation. Case presentation: We present a case of a male patient, 70 years old, with ischemic heart disease and slow-fast AVNRT treated with radiofrequency catheter ablation (RFCA) in March 2019, with regular 6-months follow-ups. He was readmitted in our department in November 2020 for rest dyspnea and incessant fluttering sensation in the neck, without palpitations. The event electrocardiogram (ECG) was initially interpreted by general cardiologist as accelerated junctional rhythm, 75 bpm. Due to the persistence of symptoms and ECG findings, a differential diagnosis between reentry and focal automaticity was imposed. The response to vagal maneuvers and Holter ECG monitoring characteristics provided valuable information. We suspected recurrent slow ventricular rate typical AVNRT, which was confirmed by electrophysiological study and we successfully performed the RFCA of the slow intranodal pathway. Conclusion: AV nodal reentry tachycardia may have an unusual presentation, occurring in elder male patients with structural heart disease. Antiarrhythmic drugs can promote reentry in this kind of patients. In cases of slow ventricular rate, vagal maneuvers and Holter ECG monitoring can help with the differential diagnosis. The arrhythmia can be successfully treated with RFCA with special caution regarding the risk of AV block

News Posting by Strategic Users in a Social Network

Abstract. We argue that users in social networks are strategic in how they post and propagate information. We propose two models — greedy and courteous — and study information propagation both analytically and through simulations. For a suitable random graph model of a social network, we prove that news propagation follows a threshold phenomenon, hence, “high-quality ” information provably spreads throughout the network assuming users are “greedy”. Starting from a sample of the Twitter graph, we show through simulations that the threshold phenomenon is exhibited by both the greedy and courteous user models.

Polyimide-Derived Supramolecular Systems Containing Various Amounts of Azochromophore for Optical Storage Uses

The progress of digital technologies demands more speed and larger storage capacity. Optical storage systems have the advantage of being cheap, fast and capacious. This article explores the potential use of polyimide-based films as a recording medium for optical storage devices. The materials were designed through a host–guest approach that involves a cyano-containing polyimide precursor and an azochromophore combined in the following ratios: 1:0.25, 1:0.5, 1:0.75 and 1:1. After thermal treatment up to 200 °C, polyimide systems were formed with supramolecular structures constructed via hydrogen bonding as shown by molecular modeling and FTIR at around 3350 cm−1. The aspects arising from the variation of the azo-dye content in the polyimide samples and their impact on the vitrification temperature, colorimetric features, refractive index, band gap, non-linear optical susceptibility and birefringence were investigated for the first time. The thermal analysis indicated a slight decrease in the vitrification temperature from 190.84 °C for the sample without azo dye to 163.91 °C for the film containing the highest leading of azo dye. The morphology images revealed the occurrence of periodic structures in azo-derived materials exposed to a UV laser, which is accentuated by the addition of more azo dye molecules. Optical tests allowed observation of the increase in the dominant wavelength, refractivity and optical conductivity of the samples, produced by the incorporation of azochromophore and laser irradiation. The photo-generated birefringence increased from 0.014 (sample with 1:0.25) to 0.036 (sample with 1:1), which in combination with the created regular topography pattern, is essential for the use of these materials as recording media in optical storage applications

Glomerular Endothelial Cell-Derived miR-200c Impairs Glomerular Homeostasis by Targeting Podocyte VEGF-A

Deciphering the pathophysiological mechanisms of primary podocytopathies that can lead to end-stage renal disease and increased mortality is an unmet need. Studying how microRNAs (miRs) interfere with various signaling pathways enables identification of pathomechanisms, novel biomarkers and potential therapeutic options. We investigated the expression of miR-200c in urine from patients with different renal diseases as a potential candidate involved in podocytopathies. The role of miR-200c for the glomerulus and its potential targets were studied in cultured human podocytes, human glomerular endothelial cells and in the zebrafish model. miR-200c was upregulated in urine from patients with minimal change disease, membranous glomerulonephritis and focal segmental glomerulosclerosis and also in transforming growth factor beta (TGF-β) stressed glomerular endothelial cells, but not in podocytes. In zebrafish, miR-200c overexpression caused proteinuria, edema, podocyte foot process effacement and glomerular endotheliosis. Although zinc finger E-Box binding homeobox 1/2 (ZEB1/2), important in epithelial to mesenchymal transition (EMT), are prominent targets of miR-200c, their downregulation did not explain our zebrafish phenotype. We detected decreased vegfaa/bb in zebrafish overexpressing miR-200c and could further prove that miR-200c decreased VEGF-A expression and secretion in cultured human podocytes. We hypothesize that miR-200c is released from glomerular endothelial cells during cell stress and acts in a paracrine, autocrine, as well as context-dependent manner in the glomerulus. MiR-200c can cause glomerular damage most likely due to the reduction of podocyte VEGF-A. In contrast, miR-200c might also influence ZEB expression and therefore EMT, which might be important in other conditions. Therefore, we propose that miR-200c-mediated effects in the glomerulus are context-sensitive

Obtaining and Characterizing Composite Biomaterials of Animal Resources with Potential Applications in Regenerative Medicine

Raw materials, such as collagen and chitosan, obtained from by-products from the food industry (beef hides and crustacean exoskeletons), can be used to obtain collagen–chitosan composite biomaterials, with potential applications in regenerative medicine. Functionalization of these composite biomaterials is a possibility, thus, resulting in a molecule with potential applications in regenerative medicine, namely clotrimazole (a molecule with antibacterial, antifungal, and antitumor activity), at a mass ratio (collagen–chitosan–clotrimazole) of 1:1:0.1. This functionalized composite biomaterial has great potential for application in regenerative medicine, due to the following properties: (1) it is porous, and the pores formed are interconnected, due to the use of a mass ratio between collagen and chitosan of 1:1; (2) the size of the formed pores is between 500–50 μm; (3) between collagen and chitosan, hydrogen bonds are formed, which ensure the unity of composite biomaterial; (4) the functionalized bio-composite exhibits in vitro antimicrobial activity for Candida albicans, Staphylococcus aureus, and Staphylococcus aureus MRSA; for the latter microorganism, the antimicrobial activity is equivalent to that of the antibiotic Minocycline; (5) the proliferation tests performed on a standardized line of normal human cells with simple or composite materials obtained by lyophilization do not show cytotoxicity in the concentration range studied (10–500) μg/mL

The Involvement of Photobiology in Contemporary Dentistry—A Narrative Review

Light is an emerging treatment approach that is being used to treat many diseases and conditions such as pain, inflammation, and wound healing. The light used in dental therapy generally lies in visible and invisible spectral regions. Despite many positive results in the treatment of different conditions, this therapy still faces some skepticism, which has prevented its widespread adoption in clinics. The main reason for this skepticism is the lack of comprehensive information about the molecular, cellular, and tissular mechanisms of action, which underpin the positive effects of phototherapy. However, there is currently promising evidence in support of the use of light therapy across a spectrum of oral hard and soft tissues, as well as in a variety of important dental subspecialties, such as endodontics, periodontics, orthodontics, and maxillofacial surgery. The merging of diagnostic and therapeutic light procedures is also seen as a promising area for future expansion. In the next decade, several light technologies are foreseen as becoming integral parts of modern dentistry practice