The terminal speed of single drops or bubbles in an infinite medium

This paper synthesises previous studies of the terminal speed of single drops or bubbles to provide a universal calculational procedure.     

Recent Developments in Lanchester Theory

This paper reports the Operational Research Conference on Recent Developments in Lanchester Theory held in Munich in July 1967 under the auspices of the NATO Science Committee.     

Synthetic strategies to chiral organosulfur donors related to bis(ethylenedithio)tetrathiafulvalene

Syntheses of enantiopure organosulfur donors by three different strategies requiring only four-six steps are reported. The key step involves either double substitution of an enantiopure cyclic sulfate ester by a dithiolate, attachment of a chiral diol as a ketal, or completely diastereoselective cycloaddition of 1,3-dithiole-2,4,5-trithione to an enantiopure alkene.     

Thermal Boundary Resistance Between GaN and Substrate in AlGaN/GaN Electronic Devices

The influence of a thermal boundary resistance (TBR) on temperature distribution in ungated AlGaN/GaN field-effect devices was investigated using 3-D micro-Raman thermography. The temperature distribution in operating AlGaN/GaN devices on SiC, sapphire, and Si substrates was used to determine values for the TBR by comparing experimental results to finite-difference thermal simulations. While the measured TBR of about 3.3 x 10^-8 W^-1 ldr m² ldr K for devices on SiC and Si substrates has a sizeable effect on the self-heating in devices, the TBR of up to 1.2 x 10^-8 W^-1 ldr m² ldr K plays an insignificant role in devices on sapphire substrates due to the low thermal conductivity of the substrate. The determined effective TBR was found to increase with temperature at the GaN/SiC interface from 3.3 x 10^-8 W^-1 ldr m² ldr K at 150degC to 6.5 x 3.3 x 10^-8 W^-1 ldr m² ldr K at 275degC, respectively. The contribution of a low-thermal-conductivity GaN layer at the GaN/substrate interface toward the effective TBR in devices and its temperature dependence are also discussed.     

Attractive interactions between functional groups in crowded molecules: The solid state structures of diethyl 2-cyano(2′-nitrophenyl)methyltartronate and diethyl (2′-,6′-dinitrophenyl)methyltartronate

The molecular structures of two substituted diethyl tartronates show a variety of interactions between functional groups. Oxygen atoms interact with the electron deficient carbon and nitrogen atoms of nitrile and nitro groups which in response show small distortions from their normal geometries. Short O ··· H contacts between benzyl hydrogen atoms and ortho nitro groups indicate some weak hydrogen bonding effects. Crystal data: C₁₅H₁₆N₂O₇, Mr = 336.3, a = 7.668(2), b = 7.961(3), c = 15.244(3) Å, = 86.78(1), = 81.56(1), = 61.92(1)°, triclinic, P1¯, Z = 2; C₁₄H₁₆N₂O₉, Mr = 356.3, a = 7.786(2), b = 10.324(2), c = 11.155(4) Å, = 71.43(2), = 77.21(2), = 76.40(3)°, triclinic, P1¯ and Z = 2.     

Intramolecular interactions in ethyl bis-(2,4-dinitrophenyl)acetate

The crystal structure of ethyl bis(2,4-dinitrophenyl)acetate, determined by room temperature X-ray diffraction, shows that this crowded molecule contains two short intramolecular interactions between nitro oxygen atoms and electron deficient carbon atoms. One mimics an early stage of the nucleophilic addition to a carbonyl group (O...C, 2.730 Å), and the other mimics an early stage of a Michael reaction (O...C, 2.854 Å). Crystal data: C₁₆H₁₂N₄O₁₀, M _r = 420.29, a = 10.079(1), b = 11.139(1), c = 16.162(1) Å, = 91.319(7)°, monoclinic, P2₁/c, Z = 4.