Binary orbits as the driver of γ-ray emission and mass ejection in classical novae

Classical novae are the most common astrophysical thermonuclear explosions, occurring on the surfaces of white dwarf stars accreting gas from companions in binary star systems. Novae typically expel �10,000 solar masses of material at velocities exceeding 1,000 km/s. However, the mechanism of mass ejection in novae is poorly understood, and could be dominated by the impulsive flash of the thermonuclear runaway, prolonged optically thick winds, or binary interaction with the nova envelope. Classical novae are now routinely detected in GeV gamma-rays, suggesting that relativistic particles are accelerated by strong shocks in nova ejecta. Here we present high-resolution imaging of the gamma-ray-emitting nova V959 Mon at radio wavelengths, showing that its ejecta were shaped by binary motion: some gas was expelled rapidly along the poles as a wind from the white dwarf, while denser material drifted out along the equatorial plane, propelled by orbital motion. At the interface between the equatorial and polar regions, we observe synchrotron emission indicative of shocks and relativistic particle acceleration, thereby pinpointing the location of gamma-ray production. Binary shaping of the nova ejecta and associated internal shocks are expected to be widespread among novae, explaining why many novae are gamma-ray emitters

Friends with Benefits: Social Coupons as a Strategy to Enhance Customers’ Social Empowerment

Businesses often seek to leverage customers’ social networks to acquire new customers and stimulate word-of-mouth recommendations. While customers make brand recommendations for various reasons (e.g., incentives, reputation enhancement), they are also motivated by a desire for social empowerment—to feel an impact on others. In several multi-method studies, we show that facilitating sharing of social coupons (i.e., coupon sets that include one for self-use and one to be shared) is a unique marketing strategy that facilitates social empowerment. Firms benefit from social coupons because customers who share spend more and report greater purchase intentions than those who do not. Furthermore, we demonstrate that social coupons are most effective when the sharer’s brand relationship is new versus established. For customers with an established relationship, sharing with a receiver who also has an established relationship maximizes potential impact. Together, these studies connect social empowerment to relationship marketing and provide guidance to managers targeting social coupons

The functional brain networks that underlie Early Stone Age tool manufacture

After 800,000 years of making simple Oldowan tools, early humans began manufacturing Acheulian handaxes around 1.75 million years ago. This advance is hypothesized to reflect an evolutionary change in hominin cognition and language abilities. We used a neuroarchaeology approach to investigate this hypothesis, recording brain activity using functional near-infrared spectroscopy as modern human participants learned to make Oldowan and Acheulian stone tools in either a verbal or nonverbal training context. Here we show that Acheulian tool production requires the integration of visual, auditory and sensorimotor information in the middle and superior temporal cortex, the guidance of visual working memory representations in the ventral precentral gyrus, and higher-order action planning via the supplementary motor area, activating a brain network that is also involved in modern piano playing. The right analogue to Broca’s area—which has linked tool manufacture and language in prior work1,2—was only engaged during verbal training. Acheulian toolmaking, therefore, may have more evolutionary ties to playing Mozart than quoting Shakespeare

A comparison of microhardness of indirect composite restorative materials Estudo comparativo da microdureza de materiais resinosos indiretos

The purpose of this study was to compare the microhardness of four indirect composite resins. Forty cylindrical samples were prepared according to the manufacturer’s recommendations using a Teflon mold. Ten specimens were produced from each tested material, constituting four groups (n=10) as follows: G1 - Artglass; G2 - Sinfony; G3 - Solidex; G4 - Targis. Microhardness was determined by the Vickers indentation technique with a load of 300g for 10 seconds. Four indentations were made on each sample, determining the mean microhardness values for each specimen. Descriptive statistics data for the experimental conditions were: G1 - Artglass (mean ±&#61472;standard deviation: 55.26 ± 1.15HVN; median: 52.6); G2 - Sinfony (31.22 ± 0.65HVN; 31.30); G3 - Solidex (52.25 ± 1.55HVN; 52.60); G4 - Targis (72.14 ± 2.82HVN; 73.30). An exploratory data analysis was performed to determine the most appropriate statistical test through: (I) Levene's for homogeneity of variances; (II) ANOVA on ranks (Kruskal-Wallis); (III) Dunn's multiple comparison test (0.05). Targis presented the highest microhardness values while Sinfony presented the lowest. Artglass and Solidex were found as intermediate materials. These results indicate that distinct mechanical properties may be observed at specific materials. The composition of each material as well as variations on polymerization methods are possibly responsibles for the difference found in microhardness. Therefore, indirect composite resin materials that guarantee both good esthetics and adequate mechanical properties may be considered as substitutes of natural teeth.<br>O objetivo deste estudo foi comparar a microdureza de 4 resinas compostas indiretas. Quarenta amostras cilíndricas foram obtidas com o auxílio de uma matriz de teflon, seguindo-se as recomendações dos fabricantes. Foram obtidas 10 amostras para cada material testado, contituindo-se 4 grupos (n=10) como se segue: G1-Artglass; G2-Sinfony; G3-Solidex; G4-Targis. A microdureza foi determinada pela técnica da indentação Vickers com uma carga de 300g por 10 segundos. Quatro indentações foram realizadas em cada amostra, obtendo-se um valor médio. Os dados da análise estatística descritiva para cada condição experimental foram: G1-Artglass (média ± desvio padrão:55,26 ± 1,15HVN; mediana: 52,6); G2- Sinfony (31,22 ± 0,65HVN; 31,30); G3- Solidex (52,25 ± 1,55HVN; 52,60); G4- Targis (72,14 ± 2,82HVN; 73,30). Uma análise exploratória dos dados foi realizada para determinar o teste estatístico mais apropriado: (I) Teste de Levene para variâncias homogêneas; (II) Teste de ANOVA (Kruskal-Wallis); (III) Teste de comparação múltipla de Dunn. O Targis apresentou os maiores valores de microdureza, enquanto que o Sinfony apresentou os menores valores. O Artglass e o Solidex se comportaram como materiais intermediários. Estes resultados indicaram que propriedades mecânicas distintas podem ser observadas nos materiais. A composição de cada material, bem como as variações nos métodos de polimerização são possivelmente responsáveis pelas diferenças observadas na microdureza. Portanto, materiais resinosos indiretos que garantam estética e propriedades mecânicas satisfatórias podem ser considerados como substitutos dos dentes naturais

PRECISE MEASUREMENT OF THE TAU LIFETIME*

We have measured the r lifetime with the Mark II Vertex Detector at PEP. We find rr = (3.20 f 0.41 f.35) x lo-l3 set, which agrees well with e- p- r universality