Krametosan, a new trinorlignan from the roots of Krameria tomentosa

A new phenylcoumarone type trinorlignan, krametosan (1), along with the known norlignans, ratanhiaphenol I (2) and 2-(2'-hydroxy-4',6'-dimethoxyphenyl)-5-(E)-propenylbenzofuran (3), the lignan conocarpan (4) and dinorlignan decurrenal (5), were isolated from the CHCl3 extract of the roots of Krameria tomentosa. The structure of these compounds were elucidated by the spectroscopic methods.     

LIGHT PROMOTION OF SEED GERMINATION IN Datura ferox IS MEDIATED BY A HIGHLY STABLE POOL OF PHYTOCHROME

Abstract— The duration of the far-red light-absorbing form of phytochrome (Pfr) of the photoreceptor pool involved in the control of seed germination was investigated for Datura ferox seeds. These seeds require both Pfr and alternating temperatures (20/30°C) to germinate. After 24 h imbibition (25°C), the seeds received pretreatment-light pulses providing different phytochrome photoequilibria (Pfr/P), followed by a 24 h dark incubation (25°C), and test-light pulses providing different Pfr/P immediately prior to transfer to alternating temperatures. Germination increased with increasing Pfr/P provided by the test-light pulses, but was unaffected by the pretreatment-light pulses. This suggests that phytochrome synthesis, phytochrome degradation and phytochrome-mediated changes in response to phytochrome were negligible. In other experiments, red light-pretreatment pulses were followed by dark incubations (25°C) of different duration before transfer to alternating temperatures. The proportion of Pfr remaining after the 25°C incubation period was estimated by comparing germination rates with those of seeds that received test-light pulses of known calculated Pfr/P immediately prior to the start of the cycles of alternating temperatures. More than 80% of the Pfr established by a Pfr/P= 0.87 light pulse was present and active even after 48 h dark incubation at 25°C. Surprisingly, when a pretreatmentlight pulse providing a Pfr/P= 0.70 was given, the reduction in [Pfr] was significantly faster.
Germination of Datura ferox seeds is under the control of a highly stable (type II like) phytochrome pool. Apparently, this pool follows Pfr dark reversion to the red light-absorbing form, the times to reach half the original Pfr pool being > 96 h or <14 h after light pulses providing Pfr/P= 0.87 or 0.70, respectively.     

A very simple Al-gate technology for high performance LSI circuits

This paper deals with a very simple technology for fabrication of high performance n-channel Al-gate enhancement load digital integrated circuits. Using a nine-stage ring oscillator with triode load, an intrinsic time delay of 1·9 ns and a speed-power product of 1·45 pJ were measured. A two kbit ROM memory with 50 ns access time was designed and fabricated with this technology.     

Epitaxially grown Si resonant interband tunnel diodes exhibitinghigh current densities

This study presents the room-temperature operation of δ-doped Si resonant interband tunneling diodes which were fabricated by low-temperature molecular beam epitaxy. Post growth rapid thermal annealing of the samples was found to improve the current-voltage (I-V) characteristics. Optimal performance was observed for a 600°C 1 min anneal, yielding a peak-to-valley current ratio (PVCR) as high as 1.38 with a peak current density (J_p) as high as 1.42 kA/cm² for a device with a 4-nm intrinsic Si tunnel barrier. When the tunnel barrier was reduced to 2 nm, a PVCR of 1.41 with a J_p as high as 10.8 kA/cm² was observed. The devices withstood a series of burn-in measurements without noticeable degradation in either the J_p or PVCR. The structures presented are strain-free, and are compatible with a standard CMOS or HBT process     

Neutron spectroscopy and magnetic relaxation of the Mn6 nanomagnets

Inelastic neutron scattering has been used to determine the microscopic Hamiltonian describing two high-spin variants of the high-anisotropy Mn₆ nanomagnet. The energy spectrum of both systems is characterized by the presence of several excited total-spin multiplets partially overlapping the S = 12 ground multiplet. This implies that the relaxation processes of these molecules are different from those occurring in prototype giant-spin nanomagnets. In particular, we show that both the height of the energy barrier and resonant tunnelling processes are greatly influenced by low-lying excited total-spin multiplets.     

A new way for controlling a stand-alone DC/AC converter

The conventional feedback scheme used in a switched-mode power supply is not suited for use in a stand-alone DC/AC converter. A new feedback scheme is presented which uses the input voltage of the LC filter as a feedback signal, instead of the output voltage.     

A tabular method for finding 2-summable and mutually 2-summable pairs of minterms

The paper presents a table look-up method for testing threshold and isobaric functions by finding out the possible 2-summable and mutually 2-summable pairs of minterms respectively. The method provides ready visualization of such pairs with a much less computational labour than the methods suggested so far. It has been shown that there will be further reduction in computational labour if the test functions are made positive unate.     

Hydrogen storage inside a toroidal carbon nanostructure C120: Density functional theory computer simulation

Ab initio density functional calculations were performed for a toroidal carbon C₁₂₀ nanostructure. Hydrogen molecules, n = 1–15, were added inside the nanotorus and for each one of these systems a geometry optimization was obtained. The cohesive energy shows that these structures are energetically stable. For example, the binding energies are ?34.95 and ?36.19 Hartrees and the interatomic distances H? H are 0.753 and 0.772 Å for 1 and 14 molecules, respectively. Considering only molecular hydrogen, we have always seen so far weak physisorption into the C₁₂₀ nanotorus. There is no chemisorption until the number oh hydrogen molecules are increased to 14. In this case, four hydrogen atoms are chemisorbed. With 15 molecules, there are 10 hydrogen atoms chemisorbed just at the inner nanotorus surface forming 10 H? C bondings with bond length close to that in methane. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem 110:2495–2508, 2010