Characterization of a Gas Oil Fraction and Its Hydrotreated Products

In this work we explore the chemistry of a gas oil fraction in the mid-boiling range (433-483°C) and its products after hydrotreating at 375, 385, and 400°C. Each sample was fractionated by high performance liquid chromatography (HPLC) based on the elution times for saturate, mono-, di-, and poly-aromatic standards. The HPLC saturate fraction is practically free of aromatic components. The nominal mono- and di-aromatics fractions differ in that the former has a higher molecular weight and H/C ratio cbut lower aromaticity and heteroatom content. The H/C atomic ratios, aromaticities, and average structural parameters of the HPLC poly-aromatic subfractions are virtually the same. Regardless of their structural resemblances they differ substantially in their HPLC elution behavior. This can be attributed to the differences in their oxygen and, especially, nitrogen contents. Hydrogenation produced a significantly greater amount of saturate material having a higher H/C ratio than the original feed. A large part of this increase must result from dealkylation, saturation, or opening of aromatic molecules. This mechanism also produced nominally mono-aromatic compounds from the poly-aromatic species originally present. The effect of hydrogenation on heteroatoms was mixed. While the overall amount of nitrogen was reduced, its concentration in the poly-aromatic fractions actually increased. Overall, oxygen concentration in the product was not much affected by hydrogenation, except that its distribution became skewed towards the more easily eluted HPLC front-fractions. Both thiophenic and sulphide sulphur were significantly reduced in all of the separated fractions.     

凝胶中罗丹明6G的荧光性质

用溶胶—凝胶法将不同浓度的罗丹明6G(Rhodamine 6G,R6G)染料掺入硅凝胶块和涂层薄膜中,用倍频 YAG 激光(0.53μm)做激发光源研究其荧光性质。对凝胶块、凝胶薄膜和乙醇溶液中 R6G 的荧光光谱进行了比较,研究了温度和 R6G 浓度对荧光性质的影响。实验结果表明,当R6G/SiO_2摩尔比高达 10~(-4)时,凝胶薄膜中的 R6G 分子仍不发生聚集现象;在475K 以下,积分荧光强度随温度的变化表现出很好的重现性;当温度高于600K 时,荧光消失,表明染料 R6G 已完全分解。     

Clinical and microbiological effects of minocycline-loaded microcapsules in adult periodontitis

Clinical and microbiological effects of subgingival delivery of 10% minocycline-loaded (MC), bioabsorbable microcapsules were examined in 15 adult periodontitis patients. Patients received oral hygiene instruction 2 weeks prior to the study. At baseline (day 0) all teeth received supragingival scaling (SC); 2 quadrants received no further treatment and 1 quadrant received subgingival scaling and root planning (SRP). In the fourth quadrant, the tooth with the deepest probing sites (at least 1 site > or = 5 mm) was treated with minocycline microcapsules. The sites were evaluated at baseline and weeks 1, 2, 4, and 6. Clinical indices included bleeding on probing (BOP), probing depths (PD), and attachment loss (AL). Microbiological evaluations included percent morphotypes by phase-contrast microscopy; cultivable anaerobic, aerobic, and black-pigmented Bacteroides (BPB); and percent Porphyromonas gingivalis, Prevotella intermedia, Eikenella corrodens, and Actinomyces viscosus by indirect immunofluorescence. In the SC + MC group, BOP, PD, and AL were significantly reduced from baseline for weeks 1 to 6. BOP in the SC + MC group was significantly reduced compared to the SRP group from weeks 2 to 6. In the SC + MC group the percent of spirochetes and motile rods decreased and the percent of cocci increased after 1 week. The increased cocci and decreased motile rods were statistically greater at weeks 4 and 6 in the SC + MC group compared to the SRP group. This study demonstrates that local subgingival delivery of 10% minocycline-loaded microcapsules as an adjunct to scaling results in reduction in the percent sites bleeding on probing greater than scaling and root planning alone and induces a microbial response more favorable for periodontal health than scaling and root planing.     

PC-based gamma knife radiosurgery dose calculation

The PC-based dose-calculation system designed for gamma knife radiosurgery introduced in this article delivers desired accuracy and is equipped with a friendly graphical user interface to allow foolproof operations. With the ongoing advancement in PC technology, the performance/cost ratio is expected to continue to rise to render more incentive in developing a PC-based dose-calculation system.     

An availability calculation for k-out-of-N redundant system with common-cause failures and replacement

This paper presents a k-out-of-N:G three-state unit redundant system availability model including common-caue failures. The steady-state probability and system availability equations are developed. Further, the frequency of encountering a state and the average duration of residence in a state are also derived.     

Theory of optical-waveguide distributed feedback lasers: A Green's functions approach

The total scattered electric field of a periodic dielectric optical waveguide is derived in terms of the Green's functions of the unperturbed structure. A condition for self-excitation that takes into account the coupling between radiation and guided modes is obtained in a very general manner and, therefore, is valid for arbitrary periods of the grating structure. Results show that the effect of the coupling between the oscillating guided field and radiation modes is to change the dependence of the threshold gain on the amplitude of the periodic perturbation: increasing the depth of the grating beyond an optimum value causes an increase in threshold due to larger coupling to radiation modes.     

Screw horsepower dependence on screw speed and size—theory and experiment

Within a normal operating range of extruders, it has been well established that the output increases nearly proportionally to the screw speed but the screw horsepower increases more than proportionally to the screw speed, making the screw HP difficult to predict. It has been also known in scale-up of extruders that the output may be predicted with reasonable accuracy but the screw HP is difficult to predict. No sound theoretical or empirical method predicting screw HP in a scale-up calculation has been offered heretofore. Since a screw performs solid conveying, melting and pumping (or metering) functions simultaneously, any theoretical analysis of screw HP has to consider all three extrusion theories; solid conveying theory, melting theory and pumping theory. In this paper, semi-theoretical equations for predicting screw HP as a function of screw speed and size are developed. Experiments are conducted to test the utility of these equations and the implications of the experimental results on extrusion theories are discussed.     

Mild combined immunodeficiency in identical twins

Fourteen adult cats were exercised on a motor-driven treadmill 5 days each week for 6 weeks to determine the effect of exercise conditioning on the intrinsic contractile state of the myocardium. The exercise program was sufficient to produce a cardiovascular training effect manifested by slower exercising heart rates and resting heart rates after atropine by the end of the 6th week. The mechanical function of the isolated right ventricular papillary muscle from exercised cats was compared with that of 17 sedentary adult cats. There were no significant differences between exercised and control cats in in heart weight-body weight ratios, resting and active lenght - tension relations, maximal rate of isometric force development at the peak of the length-tension curve (Lmax), time to peak force at Lmax, maximal force development with paired stimulation and norepinephrine, or force-velocity relations. These results indicate that the intrinsic state of feline myocardium is unaffected by exercise conditioning.     

Long-term results in the treatment of femoral-shaft fractures in young children by immediate spica immobilization

Manual traction reduction without anesthesia and immediate immobilization in a spica cast were used to treat eighty-five children ranging in age from birth to ten years old who had closed femoral-shaft fractures and no associated injuries. Up to two centimeters of overriding, 30 degrees of anterior angulation, and 15 degrees of medial angulation were accepted. Any angulation in excess of these amounts, or lateral or posterior angulation, was corrected by wedging the cast at the fracture site. Further telescoping of the fracture fragments in the case was attributed to the child pressing the foot against the bottom of the cast and was prevented by removing the sole of the cast. Of the seventy-five children examined two to eighteen years after fracture, none had any residual skeletal deformity or joint stiffness. The length discrepancies of the fractured limbs ranged from 1.7 centimeters of shortening to 0.9 centimeter of overgrowth.