Computer Systems Based on Silicon Photonic Interconnects

We present a computing microsystem that uniquely leverages the bandwidth, density, and latency advantages of silicon photonic interconnect to enable highly compact supercomputer-scale systems. We describe and justify single-node and multinode systems interconnected with wavelength-routed optical links, quantify their benefits vis-a-vis electrically connected systems, analyze the constituent optical component and system requirements, and provide an overview of the critical technologies needed to fulfill this system vision. This vision calls for more than a hundredfold reduction in energy to communicate an optical bit of information. We explore the power dissipation of a photonic link, suggest a roadmap to lower the energy-per-bit of silicon photonic interconnects, and identify the challenges that will be faced by device and circuit designers towards this goal.     

A study of electrical characteristic changes in MOSFET by electron beam irradiation

Mechanisms for electrical characteristic changes in MOSFET caused by electron beam irradiation were studied using a SEM-based nano-probing system. A shift in V_th occurs when a hole is trapped in a defect (oxygen vacancy) in the gate dielectric layer. Holes are generated when the plasmon is excited by electron beam irradiation. Further, an electric field is created by the positive charge-up resulting from electron beam irradiation of the ILD, causing an increase in leakage between gate and drain leading to an increase in I_off. This study shows that advanced devices can be measured using a SEM-based nano-probing system without inducing electrical characteristic changes by optimizing the measurement conditions such as acceleration voltage, electron beam current, image magnification, ILD thickness, and electron beam irradiation time.     

Implications of sensor location in steam reformer temperature control

Hydrogen can be produced via steam reformation of many feedstocks. External heat sources provide the thermal energy required by the endothermic steam reformation reactions. Temperature control of the steam reformation reactor is critical to reactor performance and catalyst life. Closed-loop control systems are typically used to modulate the heat input rate based on a comparison between a set point temperature and a temperature measurement. The location of the temperature sensor relative to the heat input location is a choice made during reactor design that can have significant impact on reactor temperature control.     

New tunable thieno[3,4-b]pyrazine-based materials

The effect of electron-donating and electron-withdrawing side chains on the electronic properties of thieno[3,4-b]pyrazines and their corresponding homopolymers have been investigated. Contrary to common trends in polythiophene materials, the addition of electron-donating groups results in higher HOMO–LUMO energies in the monomers and higher E_g values in the resulting polymers. The use of electron-withdrawing groups, however, provides reduced HOMO–LUMO energies and lower E_g values. The application of electron-withdrawing functionalized thieno[3,4-b]pyrazines appears to be a promising new approach for the production of low E_g materials.     

Vibrational spectroscopy and periodic DFT studies of LaMg2PdH7: A material with two types of hydride

The need for a safe, reliable and cheap method for hydrogen transportation has prompted an intense effort in the synthesis of novel hydrides. To direct the search for better materials, it is essential to understand the bonding present in these systems. A newly synthesized material is LaMg₂PdH₇ which is best formulated as {La³⁺}{Mg²⁺}₂{[PdH₄]⁴⁻}{H⁻}₃. Thus hydrogen is formally present both as a free hydride ion and also as a covalently bound ligand. The combination of inelastic neutron scattering (INS), infrared and Raman spectroscopies and periodic density functional theory (DFT) has been used to characterise the material. We find that the material is less ionic than Ba₂[PdH₄], which also contains [PdH₄]⁴⁻. The charges carried by both the coordinating and free hydrides are similar which hints at a degree of covalency in the interactions between the interstitial hydrides and the lanthanum and magnesium ions.     

Tolerance of a standard intact protein formula versus a partially hydrolyzed formula in healthy, term infants

Background  

Parents who perceive common infant behaviors as formula intolerance-related often switch formulas without consulting a health professional. Up to one-half of formula-fed infants experience a formula change during the first six months of life.     

Age-related response of male melon fliesDacus cucurbitae (Diptera: Tephritidae) to cue-lure

Laboratory-reared and wild adults of the melon fly,Dacus cucurbitae Coquillett, were tested for response to cue-lure at various ages. Virgin laboratory (4, 6, 8, 10, 12, and 14 days old) and wild (10, 12, 14, 16, 18, 20, and 22 days old) flies were released into outdoor field cages and trapped from 0800 until 1600 hr. Response of males to cue-lure increased with age and corresponded with sexual maturity for each strain. Females of both strains were relatively nonresponsive to cue-lure. Failure to eradicate in past male annihilation programs againstD. cucurbitae may be explained in part by the fact that only older males, which may have already mated with gravid females, respond to cue-lure.     

Modulation of phosphatidylcholine biosynthesis by peroxisome proliferating fatty acid analogues

The modulation of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) biosynthesis by sulfur-substituted fatty acid analogues has been investigated in rats. We have compared the effects of two non-β-oxidizable fatty acid analogues, 3-thiadicarboxylic acid and tetradecylthioacetic acid, which induce proliferation of peroxisomes, with those of the analogue tetradecylthiopropionic acid, which is a weak peroxisome proliferator. Repeated administration of 3-thiadicarboxylic acid for seven days resulted in increased hepatic concentrations of both PC and PE, but the PC/PE ratio was decreased. PC synthesis was increased, as evidenced by increased incorporation of [³H]choline into PC and an increased activity of cytidinetriphosphate (CTP): phosphocholine cytidylyltransferase. This was accompanied by a reduction in the pool sizes of choline and phosphocholine. TheS-adenosylmethione/S-adenosylhomocysteine ratio (AdoMet/AdoHcy) was marginally affected, indicating no increase in the rate of methylation of PE to PC. Administration of tetradecylthioacetic acid also resulted in increased hepatic phospholipid levels, increased AdoMet/AdoHcy ratios and in slightly elevated activity of CTP:phosphocholine cytidylyltransferase. The most striking effect observed after tetradecylthiopropionic acid treatment was the development of fatty liver. The activity of CTP:phosphocholine cytidylyltransferase and the incorporation of [³H]choline into PC was reduced compared to 3-thiadicarboxylic acid treatment. Although the rate of methylation of PE seemed to be increased at an elevated AdoMet/AdoHcy ratio, this resulted in only minor changes in the hepatic PC and PE levels, and the PC/PE ratio remained unchanged. Furthermore, the hepatic levels of choline and phosphocholine were reduced in these rats. The activities of the two enzymes competing for choline in the liver, choline kinase and choline dehydrogenase were changed in opposite directions, with the activity of choline kinase increasing approximately 1.5-fold. In addition, it was found that the level of homocysteine was elevated in the liver of tetradecylthiopropionic acid-treated rats. The possibility is discussed that this reflects a reduced flux of choline through the oxidative pathway in the liver. In tetradecylthiopropionic acid-treated rats, there seemed to be a coordinated regulation of the two pathways for PC biosynthesis, with an increase in the methylation of PE to PC and a reduced synthesisvia the CDPcholine pathway. The increase in PC observed in rats treated with 3-thiadicarboxylic acid and tetradecylthioacetic acid suggests that increased PC synthesis is linked to peroxisome proliferation.     

Effects of α-Terthienyl on the midgut detoxification enzymes of the European corn borer,Ostrinia nubilalis

The biochemical basis for the tolerance of the European corn borer,Ostrinia nubilalis, to the phototoxin-terthienyl was investigated by measuring the midgut polysubstrate monooxygenases and glutathioneS-transferase activities.-Terthienyl administered in the diet to the corn borers increased the level of cytochromeb ₅, NADH-cytochromec reductase,O-demethylase, and glutathioneS-transferase activities. The induced detoxification enzyme activities should enable the corn borer to metabolize-terthienyl more efficiently and therefore render the corn borer highly tolerant to-terthienyl.