Copper Assisted Inverted Pyramids Texturization of Monocrystalline Silicon in a Nitrogen Bubbling Bath for Highly Efficient Light Trapping

Silicon - Inverted pyramid (IP) texturization on silicon wafers has recently attracted attention for the structure’s light trapping ability and low specific surface area. The later property...     

Prophylactic ureteral catheterization in gynecologic surgery

OBJECTIVES: To examine the frequency of ureteral catheter usage, its efficacy in preventing injury, and related complications, because the preoperative routine placement of ureteral catheters as a prophylactic measure to prevent ureteral injury is controversial. METHODS: All major gynecologic operations performed between January 1992 and December 1994 were identified. All gynecologic procedures that were preceded by ureteral catheter placement were also identified. A data base maintained by the Department of Quality Management allowed identification of all urinary tract complications and ureteral injuries. Four categories of surgery were analyzed: exploratory laparotomy with catheters, exploratory laparotomy without catheters, operative laparoscopy with catheters, and operative laparoscopy without catheters. The medical records of all patients with urinary tract complications were reviewed. RESULTS: Bilateral prophylactic ureteral catheterization was performed in 469 (15.3%) of 3071 patients. A ureteral injury occurred in 4 (0.13%) of 3071 patients. All four ureteral injuries (0.17%) occurred among 2338 patients who underwent exploratory laparotomy. None of the 733 patients who underwent operative laparoscopy suffered ureteral injury. The incidence of ureteral injury in patients who had ureteral catheters placed before exploratory laparotomy was 2 (0.62%) of 322. Two (0.10%) of 2016 patients who did not have prophylactic ureteral catheters suffered a ureteral injury. There was no statistically significant difference in the incidence of ureteral injury between patients who did and patients who did not undergo ureteral catheterization (P=0.094). CONCLUSIONS: The use of prophylactic ureteral catheters did not affect the rate of ureteral injury in our patients. The very low incidence of ureteral injury among our patients is attributed mainly to meticulous surgical technique.     

Soot generation of diesel fuels with substantial amounts of oxygen-bearing compounds added

Two-colour pyrometry, thermodynamic analysis, and exhaust emissions analysis have been used to improve understanding of the formation of soot during combustion in a high speed direct-injection automotive diesel engine. Three fuel blends were used: a Base Fuel commercially available in Northern Europe; a blend of the Base Fuel (70%) and esterified rape-seed oil (RME) (30%) and a blend of the Base Fuel (90%) and an ether compound (diglyme) (10%). While the Base Fuel contained no oxygen, both the other two fuels contained equal amounts of oxygen of 3% by mass. The principal results show significant differences in soot generation during combustion between the two oxygenated fuel blends, despite both having the same amount of oxygen.     

Electronic structure of LiSi

Silicon is of special interest in lithium-ion batteries (LIBs) since it has large theoretical specific capacity or volumetric capacity. The crystal structure, charge distribution and density of states of LiSi as the Li-poorest side compound at the start of Li intercalation mechanism for Si anode in LIBs has been studied by using density functional theory (DFT) calculations. The triangular pyramids are formed by four Li atoms in LiSi. Compared to the charge density of crystalline Si, the SiSi covalent bonds in LiSi become weak due to Li intercalation. On the other hand, the electrons around the Li atoms in LiSi increase compared to those in metallic Li. The Li atoms in LiSi have negative charge of 0.83–0.84. These electrons, which are transferred from p electrons in the Si atoms, are mainly made of p electrons of the Li atoms. When considering the lithium intercalation reaction from crystalline Si to LiSi, the average intercalation voltage is about 0.4 V.     

Discovering Error Classes from Discrepancies in Novice Behaviors Via Multistrategy Conceptual Clustering

The automatic discovery of classes of errors that represent misconceptions and other knowledge errors underlying discrepancies in novice behavior is not a trivial task. A novel approach to this problem is described, in which relationships among behavioral discrepancies are analyzed and inductively generalized via an unsupervised, incremental, relational multistrategy conceptual clustering method that takes into account similarities as well as causalities in the data. Performance results on the classification of discrepancy sets and discovery of error classes from discrepancies of buggy PROLOG programs demonstrate the potential of the approach.     

Analysis of Acoustic Emissions from a Steel Bridge Hanger

A steel bridge hanger with three fatigue cracks was monitored for acoustic emission (AE) using combined source location, strain gauge monitoring, and waveform analysis. AE activities from all three cracks were clearly identified and classified as crack growth or noise signals using location, strain magnitude, position on strain cycle, and uniqueness of waveforms as the primary criteria. A vast majority of AE from the cracks was found to be due to crack face rubbing and the crushing of corrosion products between the crack faces while limited crack growth emissions were detected. Results from laboratory tests on A588 compact tension specimens under variable-amplitude tension-tension fatigue loading were used to aid in interpreting AE data from the hanger. Crack growth AEs from these tests were detected only on overload cycles mostly above 92% of the maximum load while AE due to crack face rubbing occurred throughout the load cycle.     

A brief spiritual beliefs inventory for use in quality of life research in life-threatening illness

This paper reports on the initial efforts to validate a brief self-report inventory, the Systems of Belief Inventory(SBI-15R), for use in quality of life (QOL) and psychosocial research studying adjustment to illness. The SBI-15R was designed to measure religious and spiritual beliefs and practices, and the social support derived from a community sharing those beliefs. The authors proposed this scale to address the need for greater exploration of spiritual and religious beliefs in QOL, stress and coping research. Phase I: Item generation. The research team identified four domains comprised of 35 items that make up spiritual and religious beliefs and practices. The instrument was piloted in a structured interview format on 12 hospitalized patients with varying sites of cancer. Phase II: Formation of SBI-54. After these initial efforts, the research team increased the number of items to 54 and adopted a self-report format. To assess patients reactions to the questionnaire, the new version was piloted on 50 outpatients with malignant melanoma. Phase III: Initial validation. To begin establishing validation, 301 healthy individuals with no history of cancer or serious illness in the prior year were asked to complete the SBI-54 and several other instruments. A principal components analysis with varimax rotation of the SBI-54 identified two factors, in contrast to the four which were hypothesized, one measuring spiritual beliefs and practices, the other measuring social support related to the respondent's religious community. Phase IV: Item reduction of the SBI-54. A shortened version of the SBI-54 with 15 items, five from the items identifying factor I and ten from those identifying factor II, was developed to lessen patient burden. The new SBI-15 correlated highly with the SBI-54, and demonstrated convergent, divergent, and discriminant validity. Revision of SBI-15. The investigators rephrased one statement in order to broaden the applicability of the SBI-15 to patients other than those with a diagnosis of cancer, and to healthy individuals. DISCUSSION. The SBI-15R met tests of internal consistency, test-retest reliability, and convergent, divergent, and discriminant validity in both physically healthy and physically ill individuals. The SBI-15R may have value in measuring religious and spiritual beliefs as a potentially mediating variable in coping with life-threatening illness, and in the measurement of QOL.     

First-principles calculations of the dissolution and coalescence properties of Pt nanoparticle ORR catalysts: The effect of nanoparticle shape

The degradation of Pt nanoparticles (NPs) in fuel cell cathodes leads to the loss of the precious metal catalyst. While the effect of NP size on Pt dissolution has been studied extensively, the influence of NP shape is largely unexplored. Because of the recent development of experimental methods to control the shape of metal NPs, rational guidelines/insights on the shape effects on NP stability are imperative. In this study, first-principles calculations based on density functional theory were conducted to determine the stability of 1–2 nm Pt NPs against Pt dissolution and coalescence with respect to NP shape. Toward dissolution, the stability of the Pt NPs increases in the following order: Hexagonal close-packed < icosahedral < cuboctahedral < truncated octahedral. This trend is attributed to the synergy of the oxygen adsorption strength and the local coordination of the Pt atoms. With respect to coalescence, the size of a NP is related to its propensity to coalesce or detach/migrate to form larger particles. The stability of the Pt NPs was found to increase in the following order: Hexagonal close-packed < truncated octahedral < cuboctahedral < icosahedral, and was correlated with the cohesive energies of the particles. By combining the characteristic stabilities of the shapes, new “metal-interfaced” Pt-based coreshell architectures were proposed that should be more stable than pure Pt nanoparticles with respect to both dissolution and coalescence.

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High loading denitrification by biological activated carbon process

High loading denitrification was studied using granular activated carbon (Calgon Filtrasorb 400, size: 0.8–1.4 mm) column with injecting carbon source (sucrose) only once a day. Under the condition of EBCT (empty bed contact time) = 80 min, C:N RATIO = 1.88, once per day injection mode of organic supply was able to sustain an average denitrification efficiency of 84 to 89% even with influent NO₃---N concentration of 80 mgl⁻¹. With an influent NO₃---N of 20 mgl⁻¹ and C:N ratio of 1.88, however, reduction of EBCT to 20 min resulted in very poor denitrification. In the latter case, 46% of the added carbon was lost in the effluent immediately after the injection. Short EBCT critically affected the process mainly due to insufficient adsorption rate. Microbial denitrification capability and fermentation might also limit the process. Extended organic injection is a possible option to improve the process efficiency. Occurrence of the sulfate reduction was limited in early phase of the cycle.     

Cluster-based predictive modeling to improve pedagogic reasoning

This paper discusses a predictive modeling framework actualized in a learning agent that uses logged tutorial interactions to discover predictive characteristics of students. The agent automatically forms cluster models that are described in terms of student–system interaction attributes, i.e., in terms of the student’s knowledge state and behaviour and system’s tutoring actions. The agent utilizes the knowledge of its various clusters together with a weighting scheme to learn predictive models of high-level student information, specifically, the time it will take the student to respond to a problem and whether the response is correct, that can be utilized to support individualized adaptation. We investigated utilizing the Self-Organizing Map and AutoClass as clustering algorithms and the naïve Bayesian classifier and single layer neural network as weighting algorithms. Empirical results show that by utilizing cluster knowledge the agent’s predictions are acceptably strong for response time and accurate at the average for response correctness. Further investigation is needed to validate the scalability of the framework given other datasets and possibly migrate to other approaches that can obtain more meaningful cluster models, detect richer attribute relations, and provide better approximations to further improve prediction of response behaviour for a more informed pedagogical decision-making by the system.