DTN: an architectural retrospective

We review the rationale behind the current design of the Delay/Disruption Tolerant Networking (DTN) Architecture and highlight some remaining open issues. Its evolution, from a focus on deep space to a broader class of heterogeneous networks that may suffer disruptions, affected design decisions spanning naming and addressing, message formats, data encoding methods, routing, congestion management and security. Having now achieved relative stability with the design, additional experience is required in long-running operational environments in order to fine tune our understanding of DTN concepts and the types of capabilities that are worth the investment in implementation complexity. We expect key management, handling of congestion, multicasting capability, and routing to remain active areas of research and development, and that DTN may continue to be an active research endeavor for at least the next few years.     

厂商压缩库存以实现第三季业绩目标

半导体供应链参与者在实现9月业绩目标方面遇到了一些困难。由于季节性因素,9月业绩目标本来就不高。 对7月发布的营收预期进行更新的厂商表示,第三季度情况接近预期。但是,尽管总体来看厂商没有报告有任何意外低迷的情况,可是许多厂商都在第三季度即将结束时降低了营收预期。大多数厂商都向下收窄了营收目标区间。     

A mathematical model for interfacial charge transfer at the semiconductor–dye–electrolyte interface of a dye-sensitised solar cell

A mathematical model for the interfacial charge transfer within dye-sensitised solar cells (DSC) is presented for the semiconductor–dye–electrolyte interface. The model explicitly accounts for each reaction at the interface involving dye molecules, electrolyte species and adsorbed electrons associated with the conduction band surface states of the semiconductor. Additionally, the model accounts for photoelectron injection via singlet and triplet excited dye states. The governing equations can be used to describe the total current produced by the DSC under illuminated and non-illuminated conditions, at steady state. Regular perturbation methods are applied to the model equations to obtain closed form analytic approximations, resulting in approximate solutions that negate the need for numerical solution of the model system. All parameter values associated with the model are obtained from the literature and from experimental data. The presented numerical results and analytic approximations compare favourably to experimental data, capturing the interfacial characteristics of current versus voltage curves of the DSC.     

Understanding soluble arsenate removal kinetics by zerovalent iron media

Zerovalent iron filings have been proposed as a filter medium for removing arsenic compounds from potable water supplies. This research investigated the kinetics of arsenate removal from aqueous solutions by zerovalent iron media. Batch experiments were performed to determine the effect of the iron corrosion rate on the rate of As(V) removal. Tafel analyses were used to determine the effect of the As(V) concentration on the rate of iron corrosion in anaerobic solutions. As(V) removal in column reactors packed with iron filings was measured over a 1-year period of continuous operation. Comparison of As(V) removal by freely corroding and cathodically protected iron showed that rates of arsenate removal were dependent on the continuous generation of iron oxide adsorption sites. In addition to adsorption site availability, rates of arsenate removal were also limited by mass transfer associated with As(V) diffusion through iron corrosion products. Steady-state removal rates in the column reactor were up to 10 times faster between the inlet-end and the first sampling port than between the first sampling port and the effluent-end of the column. Faster removal near the influent-end of the column was due to a faster rate of iron oxidation in that region. The presence of 100 microg/L As(V) decreased the iron corrosion rate by up to a factor of 5 compared to a blank electrolyte solution. However, increasing the As(V) concentration from 100 to 20,000 microg/L resulted in no further decrease in the iron corrosion rate. The kinetics of arsenate removal ranged between zeroth- and first-order with respect to the aqueous As(V) concentration. The apparent reaction order was dependent on the availability of adsorption sites and on the aqueous As(V) concentration. X-ray absorption spectroscopy analyses showed the presence of iron metal, magnetite (Fe3O4), an Fe(III) oxide phase, and possibly an Fe(II,III) hydroxide phase in the reacted iron filings. These mixed valent oxide phases are not passivating and permit sustained iron corrosion and continuous generation of new sites for As(V) adsorption.     

Phosphorylation of beta-casein and alpha-lactalbumin by casein kinase from lactating bovine mammary gland

Two milk proteins, beta-casein and alpha-lactalbumin, were compared as substrates for casein kinase from bovine mammary gland. beta-Casein could be rephosphorylated after removal of its phosphate groups, whereas alpha-lactalbumin was an effective substrate after the protein had been reduced and carboxymethylated. The native proteins could not be phosphorylated. Magnesium2+, Ca2+, and Mn2+ stimulated phosphorylation of the modified proteins. Calcium2+ was the most effective cation for alpha-lactalbumin and Mn2+ for beta-casein. Michaelis constants were 144 microM for alpha-lactalbumin in the presence of Ca2+ and 142 microM for beta-casein in the presence of Mn2+; however, the maximum velocity for alpha-lactalbumin was three times that of beta-casein. After phosphorylation with [gamma-32P] ATP, partial hydrolysis showed that only serine residues were phosphorylated in both proteins. Chymotryptic peptides of phosphorylated alpha-lactalbumin and tryptic peptides of phosphorylated beta-casein were examined by HPLC and selected peptides were analyzed for amino acid content. Comparison of the analyses with sequence data showed that serine at position 47 in alpha-lactalbumin is the major site of phosphate incorporation. Dephosphorylated beta-casein was only partially rephosphorylated. However, the sites identified correspond to the phosphorylated residues in native beta-casein, namely, serine at position 35 and the cluster of four serines between residues 15 and 20.     

Assay of prolactin after freezing cow's milk

Concentrations of prolactin were similar in aliquots of the same milk sample stored for 2 days at 4 C or --23 C but averaged lower if prepared for assay at 30 C than if prepared at 40 or 50 C. Average deviations in prolactin between duplicate measurements relative to respective treatment averages were lowest generally when technique of mixing included vortexing for 5 s immediately prior to pipetting volumes of milk for assay. The average deviation of differences in prolactin among duplicate measurements relative to average concentrations of prolactin were about the same for colostrum, milk, and blood plasma (11, 17, and 14%) stored frozen. Prolactin can be measured reliably in frozen cow's milk provided samples are warmed to 40 C to 50 C and mixed thoroughly when prepared for assay.     

Increased synthesis of prostaglandin-E-like material by platelets from patients with diabetes mellitus

We studied the effects of ADP, epinephrine, collagen and arachidonic acid on platelet production of immunoreactive prostaglandin-E-like material and aggregation in 17 subjects with diabetes mellitus and 21 matched controls. Plateletrich plasma obtained from patients synthesized significantly (P less than 0.05) greater quantities of the prostaglandin-E-like material after exposure to 1 muM ADP, 1, 2 and 5 muM epinephrine and 1 microgram per milliliter of collagen than platelet-rich plasma obtained from controls. That obtained from the diabetic patients was significantly more sensitive (P less than 0.001) to the aggregating effects of the prostaglandin precursor, arachidonic acid, in vitro as compared to controls. Diabetic platelet-rich plasma metabolized arachidonic acid (0.5 mM) to immunoreactive prostaglandin-E-like material at a significantly greater rate (P less than 0.05) and extent (P less than 0.001) than that of controls. Thus, platelets obtained from diabetic patients possess increased activity of the prostaglandin synthetase system, and this characteristic may be related to the increased platelet aggregation associated with the disease.     

Cryotherapy of periocular squamous cell carcinoma in the horse

Squamous cell carcinoma around the eyes of 3 horses was treated with liquid nitrogen, using cryotherapy probes as the method of application. In 2 cases, there was complete regression of the tumor; in the 3rd case, remission and relief of discomfort were temporary.