Detection of Porphyrins in Hair Using Capillary Liquid Chromatography-Mass Spectrometry

Unlike humans, some animals have evolved a physiological ability to deposit porphyrins, which are pigments produced during heme synthesis in cells, in the skin and associated integument such as hair. Given the inert nature and easiness of collection of hair, animals that present porphyrin-based pigmentation constitute unique models for porphyrin analysis in biological samples. Here we present the development of a simple, rapid, and efficient analytical method for four natural porphyrins (uroporphyrin I, coproporphyrin I, coproporphyrin III and protoporphyrin IX) in the Southern flying squirrel Glaucomys volans, a mammal with hair that fluoresces and that we suspected has porphyrin-based pigmentation. The method is based on capillary liquid chromatography-mass spectrometry (CLC-MS), after an extraction procedure with formic acid and acetonitrile. The resulting limits of detection (LOD) and quantification (LOQ) were 0.006–0.199 and 0.021–0.665 µg mL⁻¹, respectively. This approach enabled us to quantify porphyrins in flying squirrel hairs at concentrations of 3.6–353.2 µg g⁻¹ with 86.4–98.6% extraction yields. This method provides higher simplicity, precision, selectivity, and sensitivity than other methods used to date, presenting the potential to become the standard technique for porphyrin analysis.     

Game based capacity allocation for utility computing environments

Utility computing has the potential to greatly increase the efficiency of IT operations by sharing resources across multiple users. This sharing, however, introduces complex problems with regards to pricing and allocating these resources in a way that is fair, easy to implement, and economically efficient. In this paper, we study a queue-based model that attempts to address these issues. Each client/user has a continuous flow of jobs that need to be processed. The service rate each receives, however, is proportional to a bid it submits to the system operator. Assuming that user costs are some function of their average backlogs plus their bid amounts, we use this allocation mechanism to construct an economic game. Much previous research has shown that these types of allocation games have desirable properties if the cost functions are well-defined and convex over the space of possible outcomes. Because of its queueing interface, however, our model induces functions that do not satisfy the latter, commonly assumed properties. In spite of these complications, we show that the game still has a unique equilibrium and that the system will converge to this point if users iteratively make ??best response?? updates to their bids. Finally, we explore the ??price of anarchy?? in our model, proving a bound on efficiency losses as a function of several fundamental system parameters. Thus, our scheme results in equilibria with a number of highly desirably properties.     

Space communications scheduler: A rule-based approach to adaptive deadline scheduling

Job scheduling is a deceptively complex subfield of computer science. The highly combinatorial nature of the problem, which is NP-complete in nearly all cases, requires a scheduling program to intelligently traverse an immense search tree to create the best possible schedule in a minimal amount of time. In addition, the program must continually make adjustments to the initial schedule when faced with last-minute user requests, cancellations, unexpected device failures, etc. A good scheduler must be quick, flexible, and efficient, even at the expense of generating slightly less-than-optimal schedules.

The Space Communications Scheduler (SCS) is an intelligent rule-based scheduling system developed at GE's Advanced Technology Laboratories. SCS is an adaptive deadline scheduler, which allocates modular communications resources to meet an ordered set of user-specified job requests on board the NASA Space Station. SCS uses pattern-matching techniques to detect potential conflicts within a schedule, then resolves these conflicts through algorithmic and heuristic means. As a result, the system generates and maintains high-density schedules without relying heavily on backtracking or blind search techniques. SCS was designed to allocate communication devices on board the Space Station, but its general-purpose scheduling strategy is suitable for many common real-world applications.     

抽象工具排解系统设计复杂性

复杂性是相对的.如果您无法在特定环境内描绘问题的特性并了解问题,那么复杂性就会使您无法解决问题.同时,复杂性为你提供制造出与众不同产品的机会.     

Biocatalytic Nanoscale Coatings Through Biomimetic Layer‐by‐Layer Mineralization

Recent insight into the molecular mechanisms of biological mineral formation (biomineralization) has enabled biomimetic approaches for the synthesis of functional organic‐inorganic hybrid materials under mild reaction conditions. Here we describe a novel method for enzyme immobilization in thin (nanoscale) conformal mineral coatings using biomimetic layer‐by‐layer (LbL) mineralization. The method utilizes a multifunctional molecule comprised of a naturally‐occurring peptide, protamine (PA), covalently bound to the redox enzyme Glucose oxidase (GOx). PA mimics the mineralizing properties of biomolecules involved in silica biomineralization in diatoms, and its covalent attachment to GOx does not interfere with the catalytic activity. Highly efficient and stable incorporation of this modified enzyme (GOx‐PA) into nanoscale layers (～5–7 nm thickness) of Ti‐O and Si‐O is accomplished during protamine‐enabled LbL mineralization on silica spheres. Depending on the layer location of the enzyme and the type of mineral (silica or titania) within which the enzyme is incorporated, the resulting multilayer biocatalytic hybrid materials exhibit between 20–100% of the activity of the free enzyme in solution. Analyses of kinetic properties (V_max, K_M) of the immobilized enzyme, coupled with characterization of physical properties of the mineral‐bearing layers (thickness, porosity, pore size distribution), indicates that the catalytic activities of the synthesized hybrid nanoscale coatings are largely determined by substrate diffusion rather than enzyme functionality. The GOx‐PA immobilized in these nanoscale layers is substantially stabilized against heat‐induced denaturation and largely protected from proteolytic attack. The method for enzyme immobilization described here enables, for the first time, the high yield immobilization and stabilization of enzymes within continuous, conformal, and nanoscale coatings through biomimetic LbL mineralization. This approach will likely be applicable to a wide variety of surfaces and functional biomolecules. The ability to synthesize thin (nanoscale) conformal enzyme‐loaded layers is of interest for numerous applications, including enzyme‐based biofuel cells and biosensors.     

Cons and pros: prison education through the eyes of the prison educated*

ABSTRACT

While much has been written within academic journals about prisoners, rarely is there anything written by prisoners. In this essay, we, a group of prisoners who are earning or have earned college degrees while incarcerated in Texas, address the purpose, merits, and pitfalls of prison education and reform. Written as a response to the essays appearing in this special issue, we discuss our experiences of being othered as inmates, the impact of societal bias against us, our perspectives on prison education, and our own ideas for reforming prisons and making them more humane.     

The location of hydrogen in the kinetics of oxidation of ferrous alloys by superheated steam

The rate of emission of hydrogen from the metal surface and from the oxide surface has been determined during the oxidation of ferrous alloys at 501°C. The kinetics were in accordance with the assumption of a parabolic rate law, and the rate constants were in agreement with those calculated from the thickness of the oxide layer at the end of the reaction. The proportion of hydrogen emitted from the metal to that from the oxide surface showed a dependence on the partial pressure of steam for the 9%Cr-1%Mo alloy at 501°C. The ratio was dependent on the alloy composition, and also on temperature, as shown by results for the 9%Cr-1%Mo alloy at 450 and 552°C. For this alloy, the activation energy and rate constants are consistent with a rate-determining step dependent on cation diffusion. The oxide film is almost impermeable to hydrogen gas. A possible oxidation mechanism is suggested.     

交错操作模数转换器,实现更高的采样率

设计人员经常试图组合多个模数转换器（ADC),以尽量提高有效采样率。尽管快闪转换器(仍然是最快的ADC体系结构)在高速制造工艺诞生之前就已经问世了,但工艺技术的种种限制使早期的快闪转换器速度局限于10～20Msps(Megosamples per second)的范围内。现在,我们拥有了一些允许以千兆赫兹速率采样的工艺速度和体系结构。