A Supercooled Spin Liquid State in the Frustrated Pyrochlore Dy2Ti2O7

A "supercooled" liquid develops when a fluid does not crystallize upon cooling below its ordering temperature. Instead, the microscopic relaxation times diverge so rapidly that, upon further cooling, equilibration eventually becomes impossible and glass formation occurs. Classic supercooled liquids exhibit specific identifiers including microscopic relaxation times diverging on a Vogel-Tammann-Fulcher (VTF) trajectory, a Havriliak-Negami (HN) form for the dielectric function, and a general Kohlrausch-Williams-Watts (KWW) form for time-domain relaxation. Recently, the pyrochlore Dy2Ti2O7 has become of interest because its frustrated magnetic interactions may, in theory, lead to highly exotic magnetic fluids. However, its true magnetic state at low temperatures has proven very difficult to identify unambiguously. Here we introduce high-precision, boundary-free magnetization transport techniques based upon toroidal geometries and gain a fundamentally new understanding of the time- and frequency-dependent magnetization dynamics of Dy2Ti2O7. We demonstrate a virtually universal HN form for the magnetic susceptibility, a general KWW form for the real-time magnetic relaxation, and a divergence of the microscopic magnetic relaxation rates with precisely the VTF trajectory. Low temperature Dy2Ti2O7 therefore exhibits the characteristics of a supercooled magnetic liquid; the consequent implication is that this translationally invariant lattice of strongly correlated spins is evolving towards an unprecedented magnetic glass state, perhaps due to many-body localization of spin.Comment: Version 2 updates: added legend for data in Figures 4A and 4B; corrected equation reference in caption for Figure 4

Extended Spectrum Beta-Lactamase Carriage State among Elderly Nursing Home Residents in Beirut

Introduction. ESBL-producing Enterobacteriaceae can cause severe infections, but they are also isolated from the stool of asymptomatic subjects. Faecal carriage of such organism is poorly understood. Methods. First phase of the study was cross-sectional with prevalence and epidemiology of ESBL faecal carriage in two nursing homes in Beirut: 57 residents in the first (NH1) and 151 residents in the second (NH2). In second phase, faecal swabs from cohort of NH1 residents were examined for carriage at six-week intervals over three-month period. Residents’ charts were reviewed to assess carriage risk factors. Results. Over 3 consecutive samplings at NH1, 81% of residents were at least one-time carriers with 50% at the first round, 60.4% at the second, and 74.5% at the last one. At NH2, 68.2% of residents were carriers. Constipation (in NH1) and antibiotic intake (in NH2) were significantly associated with higher ESBL faecal carriage while the length of stay at the nursing home (in NH2) was associated with less carriage. Conclusion. Faecal carriage of ESBL-producing Enterobacteriaceae is high among nursing home patients in Beirut. The rate of carriage changes rapidly and significantly over time either with multiple factors playing a possible role like outbreak spreading, antibiotic, and health care system exposure

Statistical mechanics of budget-constrained auctions

Finding the optimal assignment in budget-constrained auctions is a combinatorial optimization problem with many important applications, a notable example being the sale of advertisement space by search engines (in this context the problem is often referred to as the off-line AdWords problem). Based on the cavity method of statistical mechanics, we introduce a message passing algorithm that is capable of solving efficiently random instances of the problem extracted from a natural distribution, and we derive from its properties the phase diagram of the problem. As the control parameter (average value of the budgets) is varied, we find two phase transitions delimiting a region in which long-range correlations arise.Comment: Minor revisio

The impact of teamwork on an organization’s performance: a cooperative game’s approach

In this article we study the impact of teamwork on the organizations’ performance, considering a cooperative game’s framework. To promote the teamwork culture, performance indexes are considered individually and collectively, respectively, and by comparing the scores that every employee earns individually and collectively, their differences become obvious. In this approach, a cooperative games’ model is used in order to improve the organization’s performance. The proposed model, in addition to evaluating the organization and employee's activities, can implement all payments, including the overtime pay, reward, etc., fairly and along with increasing performance and satisfaction. The cooperative approach creates effective communications between employees and authorities and enhances their motivation for teamwork. Moreover, results can be used for decisions related to employees (such as promotion, transition, firing, and detachment), analysis of training requirements, employees’ development, and research and plan valuation. Our findings show that the collaborative coefficient is a key factor in increasing productivity and improving the efficiency of an organization in the long run. The collaborative coefficient is a new concept in teamwork that has rarely been considered in scientific research.info:eu-repo/semantics/publishedVersio

Global Ultrasound Elastography Using Convolutional Neural Network

Displacement estimation is very important in ultrasound elastography and failing to estimate displacement correctly results in failure in generating strain images. As conventional ultrasound elastography techniques suffer from decorrelation noise, they are prone to fail in estimating displacement between echo signals obtained during tissue distortions. This study proposes a novel elastography technique which addresses the decorrelation in estimating displacement field. We call our method GLUENet (GLobal Ultrasound Elastography Network) which uses deep Convolutional Neural Network (CNN) to get a coarse time-delay estimation between two ultrasound images. This displacement is later used for formulating a nonlinear cost function which incorporates similarity of RF data intensity and prior information of estimated displacement. By optimizing this cost function, we calculate the finer displacement by exploiting all the information of all the samples of RF data simultaneously. The Contrast to Noise Ratio (CNR) and Signal to Noise Ratio (SNR) of the strain images from our technique is very much close to that of strain images from GLUE. While most elastography algorithms are sensitive to parameter tuning, our robust algorithm is substantially less sensitive to parameter tuning.Comment: 4 pages, 4 figures; added acknowledgment section, submission type late

A comparative analysis of perceived stigma among HIV-positive Ghanaian and African American males

The purpose of this paper was to address two questions: (i) Do Ghanaian and African American males with HIV/AIDS experience different types and degrees of stigma? and (ii) Is the impact of stigma associated with HIV/AIDS on the self different for Ghanaian and African American males? A quantitative method was used, and the four dimensions of stigma (social rejection, financial insecurity, internalised shame, and social interaction) were identified and measured using combination Likert-type questionnaires. Data regarding positive feelings of selfworth and self-deprecation, stress related to body image, and personal control were also collected in Ghana and the southeastern USA.The sample consisted of 55 men from Ghana and 55 men from the southeastern USA. Results indicate that values for the scales measuring stigma and self-perception were significantly higher for the Ghanaian sample than for the African American sample.Thus we conclude that the Ghanaian sample living with HIV/AIDS experienced a greater amount of negative self-perception and stigma-related strife than the African American sample.Keywords: stigma, HIV/AIDS, social rejection, financial insecurity, internalised shame, cultureRésuméLe but de cette communication est d'aborder deux questions, à savoir: (i) Est-ce que les hommes Ghanéens et Afro-Américains vivant avec le VIH/SIDA éprouvent de types et de degrés différents de stigmatisation? et (ii) Estce que l'impact de stigmatisation liée au VIH/SIDA sur le moi est différent chez les Ghanéens en comparaison aux Afro-Américains? Une méthode quantitative a été employée et les quatre dimensions de stigmatisation (le rejet social, l'insécurité financière, la honte intériorisée et l'interaction sociale) ont été identifiés et mesurés grâce à une combinaison des questionnaires Likert-type. Des données concernant des sentiments positifs de la valeur personnelle et d'auto-dénigrement, le stresse lié à l'image corporel et le contrôle de soi-même ont été recueilles au Ghana et au sud-est des États Unis. L'échantillon consistait de 55 hommes du Ghana et 55 hommes du sud-est des États Unis. Les chiffres des barèmes utilisées pour mesurer la stigmatisation et la perception de soi-même étaient sensiblement élevés pour l'échantillon ghanéen par rapport à l'échantillon afro-américain. L'échantillon ghanéen vivant avec le VIH/SIDA a davantage de perception négative de soi-même ainsi que la lutte liée à la stigmatisation par rapport à l'échantillon afro-américain.Mots clés: stigmatisation,VIH, SIDA, rejet social, insécurité financière, honte intériorisée, culture SAHARA J (Journal of Social Aspects of HIV/AIDS Research Alliance) Vol. 2(3) 2005: 344-35

Analyzing consumer-based brand equity on Facebook: The impact of brand gender

In recent years, Facebook and other social media have become key players in branding activities. However, empirical research is still needed about the way in which consumerbased brand equity is created on social media. The purpose of this paper is to study the relationship between masculine and feminine brand personality and brand equity, on Facebook, and to analyze the mediating role of consumer-brand engagement and brand love on this relationship. Data were collected using an online survey with 614 valid responses. The hypotheses were tested using structural equation modeling. Results support 7 of the 11 hypotheses with significant relationship between analyzed constructs. This study confirms the advantages of a clear gender positioning and extends prior research by suggesting that brands with a strong brand gender identity will encourage brand love. Results also highlight that brand love has a mediating role on the relationship between brand gender and overall brand equity.info:eu-repo/semantics/publishedVersio

System-level investigation of multi-MW direct-drive wind power PM vernier generators

Surface mounted permanent magnet Vernier (SPM-V) machines are known for their high torque density but relatively poor power factor compared to conventional SPM machines. The high torque density feature of the SPM-V machines is desirable for direct-drive offshore wind power applications as it leads to reduced generator size, mass and cost. However, their poor power factor can negatively affect the converter cost and efficiency. This paper compares the system-level performance, including generator active and structural components and converter, between the SPM-V and the conventional SPM generator systems. Four different power ratings, i.e. 0.5MW, 3MW, 5MW and 10MW, have been considered to study the trend of system-level performance with increasing power rating. The study shows that the SPM-V generators can be lighter and cheaper than their conventional SPM counterparts. However, after the consideration of converter cost and efficiency, the conventional SPM generator exhibited slightly better overall performance. Nonetheless, with the development of novel Vernier topologies and reduction in converter costs in the future due to emerging technologies, the Vernier generators can still be competitive for direct-drive offshore wind power applications

Silicon Powder-Based Wafers for Low-Cost Photovoltaics: Laser Treatments and Nanowire Etching

In this study, laser-treated polycrystalline Si (pc-Si) wafers, fabricated by wire sawing of hot-pressed ingots sintered from Si powder, have been investigated. As-cut wafers and those with high-quality thin Si layers deposited on top of them by e-beam have been subjected to laser irradiation to clarify typical trends of structural modifications caused by laser treatments. Moreover, possibility to use laser-treated Si powder-based substrates for fabrication of advanced Si structures has been analysed. It is established that (i) Si powder-based wafers with thicknesses 180 μm can be fully (from the front to back side) or partly (subsurface region) remelted by a diode laser and grain sizes in laser-treated regions can be increased; (ii) a high-quality top layer can be fabricated by crystallization of an additional a-Si layer deposited by e-beam evaporation on top of the pc-Si; and (iii) silicon nanowires can be formed by metal-assisted wet chemical etching (MAWCE) of polished Si powder-based wafers and as-cut wafers irradiated with medium laser power, while a surface texturing on the as-cut pc-Si wafers occur, and no nanowires can form in the region subject to a liquid phase crystallization (LPC) caused by high-power laser treatments