Network externalities in a dynamic monopoly

We reconsider the role of network externalities in a dynamic spatial monopoly where the firm must invest in order to accumulate capacity, while consumers may have either linear or quadratic preferences. We (1) characterise saddle point equilibria, (2) prove that the extent of market coverage is increasing in the network effect and (3) unlike the existing static literature on the same problem, the monopolist may not make introductory price offers. Then, we briefly deal with the socially optimal solution, showing that, in general, a planner would serve more consumers than a profit-seeking monopolist.      

A chemoselective deprotection of trimethylsilyl acetylenes catalyzed by silver salts

Trimethylsilyl acetylenes can be selectively deprotected in the presence of a catalytic amount of silver salts. AgNO₃ and AgOTf proved to be the most effective catalyst in a mixture of methanol, water and dichloromethane. Other functional groups, and especially silyl ethers, are not affected in these conditions.     

C-Metallated reformatsky intermediates. Structure and reactivity.

¹³C-NMR analysis of the Reformatsky intermediates from t-b$\text{u}$tyl-α-bromo acetate, t-b$\text{u}$tyl-α-bromo isobutyrate and t-b$\text{u}$tyl-α-bromo pr$\text{o}$pionate have evidenced C-metallated species. Their ability to act as n$\text{u}$cleophilic reagents under mild conditions and their selectivity towards h$\text{a}$logen-and oxygen containing electrophiles is reported.     

Contribution à l'étude du comportement de la catéchine en milieu alcalin

Contribution to the study of the behaviour of catechin in alkaline medium When catechin ( 1 ) is warmed with aqueous alkali it first undergoes rapid epimerisation. After some time a novel bridged carbocyclic enol, catechinic acid ( 3 ) separates out and may be isolated in excellent yield. Eventually catechinic acid isomerises to 2-(3′,4′-dihydroxyphenyl)-3,9-epoxy-6-oxo-bicyclo[3,3,1]-non-7-en-8,9-diol ( 4 ) via an open chain anion ( 5 ) which is also involved in the epimerisation of catechin. Assignments of structure are given and the equilibria observed are discussed.     

Microwave assisted digestion of atmospheric aerosol samples followed by inductively coupled plasma mass spectrometry determination of trace elements

A microwave digestion method in a closed vessel was developed for the determination of trace metals in atmospheric aerosols using inductively coupled plasma mass spectrometry (ICP-MS). A recovery study for the elements V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Cd, Sb, and Pb was conducted using multi-elemental standard solutions, NIST 1633b Trace Elements in Coal Fly Ash, and NIST 1648 Urban Particulate Matter. A simple digestion method using only HNO3/H2O2 gave good recoveries (90%-108%) for all elements except Cr in SRM 1648, but yielded low recoveries for SRM 1633b. A more robust method using HNO3/H2O2/HF/H3BO3 yielded higher recoveries (82%-103%) for the lighter elements (V-Zn) in SRM 1633b, and improved the Cr recovery in SRM 1648, but decreased the Se recovery in both SRMs. A comparative analysis of aerosol samples obtained at a remote mountain location Nathiagali, Pakistan (2.5 km above mean sea level), and Mayville, New York, downwind from the highly industrialized Midwestern United States, was carried out using Instrumental Neutron Activation Analysis (INAA) for the elements Cr, Mn, Fe, Co, Zn, As, Se, and Sb. The simple digestion method yielded excellent agreement for Cr, Fe, Zn, As, Se, and Sb, with slopes of the ICP-MS vs. INAA regressions of 0.90-1.00 and R2 values of 0.96-1.00. The regressions for Mn and Co had slopes of 0.82 and 0.84 with R2 values of 0.83 and 0.82, respectively. Addition of HF/H3BO3 did not improve the correlation for any of the elements and degraded the precision somewhat. The technique provides sensitivity and accuracy for trace elements in relatively small aerosol samples used in atmospheric chemistry studies related to SO2 oxidation in cloud droplets. The ability to determine concentrations of a very large number of elements from a single analysis will permit source apportionment of various trace pollutants and hence strategies to control the sources of air pollution. This is particularly important as the health effects of particulate matter are increasingly recognized.     

1,3-Dipolar cycloadditions of azomethine ylides with dipolarophiles. II. Synthesis of pyrrolizidines

Substituted pyrrolizidines have been synthesized by 1,3-dipolar cycloaddition of various dipolarophiles with the azomethine ylide generated by treatment of proline with benzaldehyde in dimethylsulfoxide. The regio- and stereochemical outcome of the reaction as well as the stability of the isomers obtained are discussed.     

Highlights on the Binding of Cobalta-Bis-(Dicarbollide) with Glucose Units

Metalla-bis-dicarbollides, such as the cobalta-bis-dicarbollide (COSAN) anion [Co(C₂B₉H₁₁)₂]⁻, have attracted much attention in biology but a deep understanding of their interactions with cell components is still missing. For this purpose, we studied the interactions of COSAN with the glucose moiety, which is ubiquitous at biological interfaces. Octyl-glucopyranoside surfactant (C8G1) was chosen as a model as it self-assembles in water and creates a hydrated glucose-covered interface. At low COSAN content and below the critical micellar concentration (CMC) of C8G1, COSAN binds to C8G1 monomers through the hydrophobic effect. Above the CMC of C8G1, COSAN adsorbs onto C8G1 micelles through the superchaotropic effect. At high COSAN concentrations, COSAN disrupts C8G1 micelles and the assemblies become similar to COSAN micelles but with a small amount of solubilized C8G1. Therefore, COSAN binds in a versatile way to C8G1 through either the hydrophobic or superchaotropic effect depending on their relative concentrations.     

Zinc (0)-Mediated Formation of Carbon-Carbon Bond from γ-Bromo Crotonate

The coupling reaction of allylic halides with diffferent organometallic reagents has been widely utilized for synthetic purpose.¹ Unfortunately, with the exception of primary halides which give mostly α attack and of hindered substrates which prefer γ attack, the lack of regioselectivity is a great handicap for the generalization of the method.     

Quiet-time solar-wind ionic composition

Summary The ISEE-B EGD solar-wind plasma experiment often observes heavy ions in the solar wind. Selecting two periods of quiet solar wind with no particles observed backstreaming from the Earth’s bow-shock, we show that different ion species follow similar trends in terms of changes in the bulk speed and changes in the particle number density. In particular, quiet-solar-wind ionic abundances in these two cases are (relative to H⁺)⁴He²⁺=(1”5)·10⁻²,³He²⁺=1.5·10⁻⁴, 0⁺⁶=(3”15)·10⁻⁴, O⁺⁷=3·10⁻⁴, Si=1·10⁻⁴, Fe=0.5·10⁻⁴. We show that, if⁴He²⁺ abundance increases, the same occurs for the Si, O⁺⁷ and O⁺⁶ abundances. Finally the O⁺⁶ density fluctuations seem to be anticorrelated with⁴He²⁺ density fluctuations.

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Riassunto L’esperimento sul plasma del vento solare dell’EGD ISEE-B spesso osserva ioni pesanti nel vento solare. Scegliendo due periodi di vento solare quieto in cui non si osservano particelle che rifluiscono dall’onda d’urto della Terra, si mostra che differenti specie di ioni hanno andamenti simili delle variazioni della velocità complessiva e dei cambiamenti nella densità numerica delle particelle. In particolare le abbondanze ioniche nei periodi di vento solare quieto sono in questi due casi (relativamente all’H⁺)⁴He²⁺=(1”5)·10⁻²,³He²⁺=1.5·10⁻⁴, O⁺⁶=(3”15)·10⁻⁴, O⁺⁷=3·10⁻⁴, Si=1·10⁻⁴, Fe=0.5·10⁻⁴. Si mostra che, se l’abbondanza dell’⁴He²⁺ cresce, lo stesso avviene dalle abbondanze di Si, O⁺⁷ e O⁺⁶. Infine, le fluttuazioni della densità dell’O⁺⁶ sembrano essere anticorrelate a quelle dell’⁴He²⁺.

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Резюме При проведении плазменного эксперимента ISEE-B EGD часто обнаруживают тяжелые ионы в солнечном ветре. Отбирая два периода спокойного солнечного ветра, мы показываем, что различные ионные компоненты подчиняются аналогичным тенденциям в изменениях объемной скорости и в изменениях плотности числа частиц. При особенно спокойном солнечном ветре ионные концентрации в указанных двух случаях составляют (по отношению к H⁺)⁴He²⁺=(1”5)·10⁻²,³He²⁺=1.5·10⁻⁴, O⁺⁶=(3”15)·10⁻⁴, O⁺⁷=3·10⁻⁴, Si=1·10⁻⁴, Fe=0.5·10⁻⁴. Мы показываем, что если распространенность⁴He²⁺ увеличивается, то имеет место увеличение распространенностей Si, O⁺⁷ и O⁺⁶. Флуктуации плотности O⁺⁶, по-видимому, антикоррелируют с флуктуациями плотности⁴He²⁺.

     

Directionality of dog vocalizations

The directionality patterns of sound emission in domestic dogs were measured in an anechoic environment using a microphone array. Mainly long-distance signals from four dogs were investigated. The radiation pattern of the signals differed clearly from an omnidirectional one with average differences in sound-pressure level between the frontal and rear position of 3-7 dB depending from the individual. Frequency dependence of directionality was shown for the range from 250 to 3200 Hz. The results indicate that when studying acoustic communication in mammals, more attention should be paid to the directionality pattern of sound emission.