Testing inflation: a bootstrap approach

We note that the essential idea of inflation, that the Universe underwent a brief period of accelerated expansion followed by a long period of decelerated expansion, can be encapsulated in a "closure condition" which relates the amount of accelerated expansion during inflation to the amount of decelerated expansion afterward. We present a protocol for systematically testing the validity of this condition observationally.     

Mesogenic dipyrrins-building blocks for the fabrication of fluorescent and metal-containing materials

A new class of mesogenic dipyrrins is reported and their use in the fabrication of fluorescent and metal-containing self assembling materials is demonstrated.     

'Pincer' pyridine dicarbene complexes of nickel and their derivatives. Unusual ring opening of a coordinated imidazol-2-ylidene

The reaction of NiBr2(DME), DME = 1,2-dimethoxyethane, with the pincer pyridine dicarbene ligands (C-N-C) ( 2) and (C-NMe-C) ( 2Me), (C-N-C = 2,6-bis-[(DiPP)imidazol-2-ylidene]pyridine, C-NMe-C = 2,6-bis-[(DiPP)imidazol-2-ylidene]-3,5-dimethylpyridine, DiPP = 2,6-diisopropylphenyl) gave the square planar complexes [Ni(C-N(Me)-C)Br]Br, 3.( Br)- and 3Me.( Br)- respectively. Transmetallation from [(C-NMe-C)2Ag2](Ag6I8), 6Me.( Ag6 I8)2- to NiBr2(DME) gave [Ni(C-NMe-C)Br](AgI2), 3Me.( AgI2)-. Reaction of 3.( Br)- with KPF6 resulted only in exchange of the ionic bromide, however the reaction of 3.( Br)- with AgBF4 in MeCN or AgOTf in THF resulted in the exchange of both coordinated and ionic bromides, giving rise to the square planar 4.( BF4)-2 and octahedral 5, respectively. In contrast, the reaction of 3Me.( AgI2)-, with excess AgOTf resulted in an unusual reverse transmetallation leading to 6Me.( OTf)-. The substitution of tmeda in Ni(CH3)2(tmeda), tmeda = N,N,N,N-tetramethylethylenediamine, by 2 produced the complex 7, in which ring opening of the heterocyclic imidazole ring of one of the NHC functional groups has taken place.     

Velocity and attenuation of ultrasonic waves in n-GaAs at low temperatures

Measurements of velocity and attenuation of ultrasonic waves in n-type GaAs have been made between 4.2 and 240 K. They are interpreted in terms of available theory dealing with sound propagation in piezoelectric semiconductors. We find the piezoelectric constant $\text{e}{}_{14}\text{=}\text{0.16 C}\text{m}{}^2$.     

Sparsely substituted chlorins as core constructs in chlorophyll analogue chemistry. III. Spectral and structural properties

The availability of stable chlorins bearing few or no substituents has enabled a variety of fundamental studies. The studies described herein report absorption spectra of diverse chlorins, comparative NMR features of chlorins bearing 0-3 meso-aryl substituents, and X-ray structures of the fully unsubstituted chlorin and the oxochlorin.     

The effects of collision energy, vibrational mode, and vibrational angular momentum on energy transfer and dissociation in NO2+-rare gas collisions: an experimental and trajectory study

A combined experimental and trajectory study of vibrationally state-selected NO2+ collisions with Ne, Ar, Kr, and Xe is presented. Ne, Ar, and Kr are similar in that only dissociation to the excited singlet oxygen channel is observed; however, the appearance energies vary by approximately 4 eV between the three rare gases, and the variation is nonmonotonic in rare gas mass. Xe behaves quite differently, allowing efficient access to the ground triplet state dissociation channel. For all four rare gases there are strong effects of NO2+ vibrational excitation that extend over the entire collision energy range, implying that vibration influences the efficiency of collision to internal energy conversion. Bending excitation is more efficient than stretching; however, bending angular momentum partially counters the enhancement. Direct dynamics trajectories for NO2+ + Kr reproduce both the collision energy and vibrational state effects observed experimentally and reveal that intracomplex charge transfer is critical for the efficient energy transfer needed to drive dissociation. The strong vibrational effects can be rationalized in terms of bending, and to a lesser extent, stretching distortion enhancing transition to the Kr+ -NO2 charge state.     

X-ray Crystal Structure of (CNSSS)2(M)2 (M = AsF6 −, SbF6 −, Sb2F11 −)

The crystal structures of (CNSSS)₂(AsF₆)₂, (CNSSS)₂(SbF6)₂, and two phases of (CNSSS)₂(Sb₂F₁₁)₂ have been determined. The AsF₆ ^?, SbF₆ ^?, and α-Sb₂F₁₁ ^? salts crystallize as reddish-brown plates whereas the β-Sb₂F₁₁ ^? salt crystallizes as green rods. The dication ^ß+SSSNCCNSSS^+ß (1²⁺) is the same in all four structures and consists of two 7π rings linked by a sp²-sp² C-C bond (1.462 Å in 1 (AsF₆)₂). The packing in the four structures is similar with stacks of dications along the a-axis and alternating sheets of dications and anions lying in the bc-plane. The differences in the dication-dication contacts is reflected in the variable temperature magnetic data.     

A dicoordinate palladium(0) complex with an unusual intramolecular eta(1)-arene coordination

The reaction of (tmeda)PdMe2 with dcpBiph gives (dcpBiph)2Pd in high yield. The solid-state structure of (dcpBiph)2Pd reveals a bent P-Pd-P framework and an unusual eta1-arene interaction between the palladium and the distal ring of one of the biphenyl substituents. In solution, an additional conformer exists which does not show a pi-interaction with a biphenyl ring. The low-coordinate complex, (dcpBiph)2Pd, undergoes C-X oxidative addition reactions with PhX (X = I, Br, Cl). A minor product resulting from metalation of the biphenyl ring is also observed.