Infrared spectroscopy of acetic acid and formic acid aerosols: pure and compound acid/ice particles

Acetic acid aerosol particles, formic acid aerosol particles and mixed acid/ice particles were generated in a collisional cooling cell at a temperature of 78 K and investigated using in situ rapid scan Fourier transform infrared spectroscopy. The infrared spectra reveal that the internal structure of the particles critically depends on the particle formation conditions and, especially for the mixed particles, on the composition. The acetic acid particles are likely to have only a partially crystalline structure whereas the formic acid particles are likely to have an overall crystalline structure. The existence of acid in the mixed acid/ice particles prevents the ice from crystallization even at low acid concentrations (less than 10%). Mid-infrared refractive index data were derived from the different particle spectra, which can be helpful for remote sensing of such systems.     

Molecular recognition of oxoanions based on guanidinium receptors

Guanidinium is a versatile functional group with unique properties. In biological systems, hydrogen-bonding and electrostatic interactions involving the arginine side chains of proteins are critical to stabilise complexes between proteins and nucleic acids, carbohydrates or other proteins. Leading examples of artificial receptors for carboxylates, phosphates and other oxoanions, such as sulfate or nitrate are highlighted in this tutorial review, addressed to readers interested in biology, chemistry and supramolecular chemistry.     

Novel use of glow discharge optical emission spectroscopy (GDOES) to study corrosion of AA2024‐T3 in the presence and absence of inhibitors – part 3: investigating the effects of various proportions of inhibitor in the coating matrix or in nanocontainers

Elemental depth profiling by glow discharge optical emission spectroscopy has been used to characterize the corrosion products on AA2024‐T3. In previous work, the aluminium, oxygen and copper depth profiles were shown to provide information regarding surface roughening, the thickness of corroded layers and extent of copper de‐alloying/relocation. Nitrogen, sulfur, phosphorus and chromium depth profiles were examined in the hope of detecting inhibitor species within the corroded/altered layers after 5 h of exposure to a corrosive solution. In the present work, the study is extended to longer exposure time. The work presents a further study of the leaching of benzotriazole from the coating matrix or from nanocontainers during various times of exposure to a corrosive environment. Copyright © 2016 John Wiley & Sons, Ltd.     

The Nehari problem for nonexponentially stable systems

The Nehari problem and its suboptimal extension are solved under the assumption that the system (A, B, C) has bounded controllability and observability maps, an L₂-impulse response and a transfer matrix that is bounded and holomorphic on the right half-plane. Exponential stability of the semigroup is not assumed and the Hankel operator is not compact. The new contribution is an explicit parameterization of all solutions given in terms of the system parametersA, B, C.     

The Nehari problem for the Pritchard-Salamon class of infinite-dimensional linear systems: a direct approach

A complete solution is obtained to the Nehari problem for symbols which have a realization as an exponentially stable Pritchard-Salamon system (A, B, C). This allows for the possibility thatB andC be unbounded and have infinite rank. The approach is to solve an equivalentJ-spectral factorization problem for this particular realization.     

The synthesis of 1-haloalkyl-1,3,4,5-tetrahydro-2-benzoxepins

Short, efficient routes to several 7,8-dimethoxy-1-haloalkyl-1,3,4,5-tetrahydro-2-benzoxepins were developed. These benzoxepins were prepared by the Lewis acid catalyzed condensation of the acetals of chloropropionaldehyde or bromoacetaldehyde with 3-(3,4-dimethoxyphenyl)-1-propanol. This condensation was facilitated by methyl substitution on the propanol. In an alternate route, ethyl 3-(3,4-dimethoxyphenyl)propanoate was acylated with 3-chloropropionyl chloride. The adduct was reduced with lithium aluminum hydride. The resultant 3-[2-(3-chloro-1-hydroxypropyl)-4,5-dimethoxyphenyl]propanol was dehydrated to the corresponding tetrahydrobenzoxepin. By these two general routes, 7,8-dimethoxy-1,3,4,5-tetrahydro-2-benzoxepins were produced which were substituted by hydrogen or methyl at benzoxepin C-4 and chloroethyl or bromomethyl at benzoxepin C-1.     

The preparation and stereochemistry of 1-chloroethyl-4-methyl-6,7-dimethoxyisochroman

The boron trifluoride catalyzed reaction of 2-methyl-2-(3,4-dimethoxypbenyl)ethanol and chloropropionaldehyde diethyl acetal yields a mixture of cis and trans 1-ehloroethyl-4-methyl-6,7-dimethoxyisochroman. The structure of the trans compound was established by X-ray analysis. The trans compound equilibrates to a mixture of the cis and trans when exposed to boron trifluoride catalyst.     

A CDMA Dual-Band Zero-IF Receiver With Integrated LNAs and VCOs in an Advanced SiGe BiCMOS Process

This paper describes one of the first dual PCS- and CEL-band CDMA receivers that includes LNAs and VCOs on a single die. The PCS-band LNA achieves a noise figure (NF) of 1.5dB and IP3 of +7.5 dBm at 16-dB gain. The PCS demodulating mixer achieves an NF of 5 dB, IP3 of +5 dBm and uncalibrated IP2 of +60 dBm. The PCS VCO is capable of -134 dBc/Hz phase noise at 3.9 GHz and 1.25-MHz offset. A copper BiCMOS process was chosen for both performance and cost benefits, compared with lower geometry CMOS     

The mechanism of Raf activation through dimerization

Raf, a threonine/serine kinase in the Raf/MEK/ERK pathway, regulates cell proliferation. Raf''s full activation requires dimerization. Aberrant activation through dimerization is an important therapeutic target. Despite its clinical importance, fundamental questions, such as how the side-to-side dimerization promotes the OFF-to-ON transition of Raf''s kinase domain and how the fully activated ON-state kinase domain is stabilized in the dimer for Raf signaling, remain unanswered. Herein, we decipher an atomic-level mechanism of Raf activation through dimerization, clarifying this enigma. The mechanism reveals that the replacement of intramolecular π–π stacking by intermolecular π–π stacking at the dimer interface releases the structural constraint of the αC-helix, promoting the OFF-to-ON transition. During the transition, the inhibitory hydrophobic interactions were disrupted, making the phosphorylation sites in A-loop approach the HRD motif for cis-autophosphorylation. Once fully activated, the ON-state kinase domain can be stabilized by a newly identified functional N-terminal basic (NtB) motif in the dimer for Raf signaling. This work provides atomic level insight into critical steps in Raf activation and outlines a new venue for drug discovery against Raf dimerization.

We decipher an atomic-level mechanism of Raf activation through dimerization, revealing that the disruption of intramolecular π–π stacking at the dimer interface promotes the OFF-to-ON transition.