bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of the Characteristics of the Fuel Injection Pump of a Diesel Engine Fuelled with Viscous Vegetable Oil-Diesel Oil Blends
Authors: Bannikov M G , Tyrlovoy S I , Vasilev I P , Chattha J A
Published: June 2006

The potential of vegetable oils as an alternative to diesel fuel has already been proved. Nevertheless, the high viscosity of vegetable oils poses some problems concerning their use in unmodified vehicle diesels. In particular, distortion of the speed characteristics of a distributor fuel injection pump with a maximum-minimum speed mechanical governor when using sunflower oil-diesel oil blends has been observed. A diesel engine fuelled by a viscous blend could not develop its rated power. After fuel delivery was increased to retain the rated power, the engine was overfuelled at lower speeds and the smoke limit was exceeded. In the present paper, measures required to retain the characteristics of an injection pump fuelled by viscous blends are described. This can be done by readjusting the pump governor and changing the hydraulic characteristics of the fuel delivery system.
The Biomechanical Effect of Vertebroplasty on the Adjacent Vertebral Body: A Finite Element Study
Authors: Wilcox R K
Published: June 2006

The increased use of vertebroplasty for the treatment of osteoporotic vertebral compression fractures has led to concerns that the technique may increase the risk of fracture in the adjacent vertebrae. The aim of this study was to simulate the biomechanical effects of vertebroplasty using an osteoporotic two-vertebrae finite element model. Following a simulated compression fracture, the model was augmented with one of three volumes of PMMA-based cement or left untreated. Upon reloading, an increase in segment stiffness was found with increasing volumes of cement. However, in all the treated models there was an increase in endplate deflection into the adjacent vertebra causing plastic failure of the surrounding trabecular bone. More damage was caused in the adjacent vertebra of the treated models than in the untreated model. The model results suggest that clinicians should be wary of using standard vertebroplasty cements to treat compression fractures in patients with highly osteoporotic bone.
Compliant Layer Acetabular Cups: Friction Testing of a Range of Materials and Designs for a New Generation of Prosthesis that Mimics the Natural Joint
Authors: Scholes S C , Burgess I C , Marsden H R , Unsworth A , Jones E , Smith N
Published: June 2006

Total joint replacements (TJRs) have a limited lifetime, but the introduction of components that exhibit good lubricating properties with low friction and low wear could extend the life of TJRs. A novel acetabular cup design using polyurethane (PU) as a compliant layer (to mimic the natural joint) has been developed. This study describes a series of friction tests that have been used to select the most appropriate material, optimize the design parameters, and fine-tune the manufacturing processes of these joints. To determine accurately the mode of lubrication under which these joints operate, a synthetic lubricant was used in all these tests. Friction tests were carried out to assess the lubrication of four PU bearing materials. Corethane 80A was the preferred material and was subjected to subsequent testing. Friction tests conducted on acetabular cups, manufactured using Corethane 80A articulating against standard, commercially available femoral heads, demonstrated friction factors approaching those for full-fluid-film lubrication with only approximately 1 per cent asperity contact. As the joint produces these low friction factors within less than half a walking cycle after prolonged periods of loading, start-up friction was not considered to be a critical factor. Cups performed well across the full range of femoral head sizes, but a number of samples manufactured with reduced radial clearances performed with higher than expected friction. This was caused by the femoral head being gripped around the equator by the low clearance cup. To avoid this, the cup design was modified by increasing the flare at the rim. In addition to this the radial clearance was increased. As the material is incompressible, a radial clearance of 0.08 mm was too small for a cup diameter of 32 mm. A clearance of between 0.10 and 0.25 mm produced a performance approaching full-fluid-film lubrication. This series of tests acted as a step towards the optimization of the design of these joints, which has now led to an in vivo ovine model.
The Clinical Repair of Teeth Using Direct Filling Materials: Engineering Considerations
Authors: Nicholson J W , Czarnecka B
Published: June 2006

This paper reviews the way in which teeth damaged by caries may be repaired clinically. The mechanical effects of caries are described, as are the materials available to repair the damage caused by this disease. Studies are reported which have shown that caries reduces the compressive strength of the tooth to less than 50 per cent of its original value and that, by use of appropriate materials and placement techniques, this can be restored to some 80 per cent of this value. However, very few studies have been carried out which view tooth repair from an engineering perspective. Instead, emphasis is placed on determining clinical durability of repairs. This is related to repair strength but brings in other factors, such as the oral hygiene of the patient. Despite this complication, durability studies show that modern restorative materials perform well under clinical conditions, from which it may be concluded that the repair process allows a structure to be fabricated that is essentially sound from an engineering view-point, even if inferior to the original tooth structure provided by nature.
Numerical Predictions of the Thermal Behaviour and Resultant Effects of Grouting Cements While Setting Prosthetic Components in Bone
Authors: Quarini G L , Learmonth I D , Gheduzzi S
Published: June 2006

Acrylic cements are commonly used to attach prosthetic components in joint replacement surgery. The cements set in short periods of time by a complex polymerization of initially liquid monomer compounds into solid structures with accompanying significant heat release. Two main problems arise from this form of fixation: the first is the potential damage caused by the temperature excursion, and the second is incomplete reaction leaving active monomer compounds, which can potentially be slowly released into the patient. This paper presents a numerical model predicting the temperature-time history in an idealized prosthetic-cement-bone system. Using polymerization kinetics equations from the literature, the degree of polymerization is predicted, which is found to be very dependent on the thermal history of the setting process. Using medical literature, predictions for the degree of thermal bone necrosis are also made. The model is used to identify the critical parameters controlling thermal and unreacted monomer distributions.
A New Approach to C2 Continuous Piecewise Bicubic Representation of the Articular Surfaces of Diarthrodial Joints
Authors: Jafari A , Farahmand F , Meghdari A , Golestanha A S
Published: June 2006

Based on the force-deflection equation for a beam subjected to lateral point loads, a C2 continuous piecewise bicubic mathematical representation was proposed to model complicated geometrical surfaces, e.g. the articular surfaces of human joints. The method was then extended so that it could be used for mathematical modelling of incomplete nets of data points, as well as smoothing of noisy and/or filtering of erroneous data points. Mathematical techniques were also developed to calculate the required unknown parameters explicitly, with no need to solve the system of equations simultaneously. The performance of the proposed method was evaluated on a number of surface modelling problems, including two known analytical surfaces and the human femoral and patellar articular surfaces. The results indicate that the proposed method is precise, flexible, and easy to apply and has several advantages over the conventional smoothing methods, i.e. the B-spline approach.
Increased Total Knee Arthroplasty Ultra-High Molecular Weight Polyethylene Wear Using a Clinically Relevant Hyaluronic Acid Simulator Lubricant
Authors: DesJardins J , Aurora A , Tanner S L , Pace T B , Acampora K B , LaBerge M
Published: June 2006

In this study, osteoarthritic and periprosthetic synovial fluid samples were rheologically and biochemically compared to develop a hyaluronic acid (HA) supplemented bovine serum (BS) lubricant that mimicked the properties of human joint synovial fluid. The effect of this BS + HA lubricant (50 per cent bovine calf serum + 1.5 g/l HA) on the wear rate of ultra-high molecular weight polyethylene (UHMWPE) during a total knee replacement wear test was then investigated. In conjunction with biochemical similarities, the rheological analysis showed that the BS + HA lubricant viscosity was not statistically different to aspirated total knee arthroplasty (TKA) revision joint fluid viscosity over a range of physiologic shear rates. Gravimetric results at 5 million wear testing cycles showed that the BS + HA lubricant produced an average of 6.88 times more UHMWPE wear than 50 per cent bovine serum lubricant alone. The BS + HA lubricated CoCr femoral component surfaces revealed pitting and surface roughening that was not observed using standard bovine serum only lubricants, but that was similar to the metallic surface corrosion observed on in vivo CoCr femoral component retrievals. These findings support the hypothesis that the addition of HA to simulator lubricant is capable of producing CoCr femoral component surface damage similar to that observed in vivo.
Comparison of Kinematics Between Thoracolumbar T11-T12 and T12-L1 Functional Spinal Units
Authors: Qiu Tian-Xia , Teo Ee-Chon , Zhang Qing-Hang
Published: June 2006

The purpose of this study was to compare the kinematics in terms of the locations and loci of instantaneous axes of rotation (IARs) at levels T11-T12 and T12-L1 of thoracolumbar junction (TLJ). The IAR is one of the kinematics characteristics of a functional spinal unit (FSU) in a plane under load. There is little information about loci of IARs in the TLJ. Validated finite element (FE) models of T11-T12 and T12-L1 FSUs were used to determine the locations and loci of IARs in three anatomical planes. In the sagittal plane, the locations and loci of the IARs were located below the intervertebral disc for T11-T12, and situated in the intervertebral disc for T12-L1. In the frontal plane, they were all located around the mid-sagittal plane for T11-T12 and T12-L1. In the transverse plane, they fell in the medio-anterior region of the movable vertebra T11 for T11-T12, and located near the cortical shell of the upper vertebra T12 for T12-L1. These findings may offer an insight to better understanding the kinematics of the human thoracolumbar spine and provide clinically relevant information for the evaluation of spinal stability and functionality of implant devices.
An Alternative Fuel for Spark Ignition Engines
Authors: Hull A , Golubkov I , Kronberg B , Marandzheva T , van Stam J
Published: June 2006

Alternative fuels have been developed for standard spark ignition engines. The fuels, which contain generic bio-components, maintain all the advantages of ethanol, i.e. the ability to increase considerably the octane number of gasoline and to reduce the amount of harmful pollutants in the exhaust emissions of engines operating on such blends. In contrast with ethanol the new fuel components do not increase the vapour pressure of gasoline-ethanol blends, have a better tolerance to water, and do not increase the fuel consumption. The bio-component-based fuels also compare favourably with mineral-sourced octane boosters such as methyl tert-butyl ether. Additionally reformulation of the base gasoline becomes unnecessary.
Computationally Inexpensive Methods of Ion Current Signal Manipulation for Predicting the Characteristics of Engine In-Cylinder Pressure
Authors: Gazis A , Panousakis D , Chen R , Chen W-H
Published: June 2006

Recent research on the use of ion current has focused on matching the characteristics of the in-cylinder pressure, thus avoiding the use of a pressure transducer. This paper explores techniques of calculating these pressure characteristics through the use of simple and computationally inexpensive artificial neural networks. Two neural networks are presented to deduce the in-cylinder pressure from ion current measurements, where one is used to predict the characteristics directly and the other is used to calculate the in-cylinder pressure curve. Experimental results show that both networks give satisfactory results for different purposes. Some engineering implementation issues and the further improvement of the developed techniques are discussed.
Probability of Flooding a Compartment (the pi Factor) - A Critique and a Proposal
Authors: Pawlowski M
Published: June 2006

The paper presents a critical review of recent developments in the pi factor, accomplished within an EU-funded research project, ‘Harder’. Certain omissions and weaknesses have been identified in the derivation of this factor, made without reference to the available knowledge on multi-dimensional random quantities in non-rectangular domains. Its correct formulation in the form of regulation is proposed in Appendix 2, based on triangular conditional distributions of damage length and damage penetration. Other distributions prove to have a negligible effect on the pi factor.
Modelling the Torsional Interaction of Wire and Polyester Fibre Ropes Used for Offshore Moorings
Authors: Bradon J , Ridge I , Chaplin R
Published: June 2006

Oil rig mooring lines have traditionally consisted of chain and wire rope. As production has moved into deeper water it has proved advantageous to incorporate sections of fibre rope into the mooring lines. However, this has highlighted torsional interaction problems that can occur when ropes of different types are joined together.

This paper describes a method by which the torsional properties of ropes can be modelled and can then be used to calculate the rotation and torque for two ropes connected in series. The method uses numerical representations of the torsional characteristics of both the ropes, and equates the torque generated in each rope under load to determine the rotation at the connection point. Data from rope torsional characterization tests have been analysed to derive constants used in the numerical model. Constants are presented for: a six-strand wire rope; a torque-balanced fibre rope; and a fibre rope that has been designed to be torque-matched to stranded wire rope. The calculation method has been verified by comparing predicted rotations with measured test values. Worked examples are given for a six-strand wire rope connected, firstly, to a torque-balanced fibre rope that offers little rotational restraint, and, secondly, to a fibre rope whose torsional properties are matched to that of the wire rope.
Hexagonal Liquid-crystalline Nanoparticles in Aqueous Mixtures of Glyceryl Monooleyl Ether and Pluronic F127
Authors: Barauskas Justas , Johnsson Markus , Nylander Tommy , Tiberg Fredrik
Published: June 2006

A liquid-crystalline nanoparticles with internal reversed hexagonal structure has been prepared by use of a single lipid system. The obtained particles are essentially monocrystalline nanoporous hexagonal prisms with the size of about 200 nm.
(Z)-1,2,3,4-Tetraboryl-2-butene: A Reagent for Stereoselective One-pot Triple Aldehyde Addition
Authors: Shimizu Masaki , Shimono Katsuhiro , Hiyama Tamejiro
Published: June 2006

(Z)-1,2,3,4-Tetraboryl-2-butene reacted with three molecules of 2,3-dialkylidene-1,5-alkanediol as a single stereoisomer. Preparation and triple addition of the butene can be effected in a single operation.
Iron–Sulfur Carbonyl Compounds with Unique Terminal Thioether Ligation Modeling for the Active Site of [Fe]-only Hydrogenases
Authors: Hu Ming-Qiang , Ma Cheng-Bing , Zhang Xiao-Feng , Chen Feng , Chen Chang-Neng , Liu Qiu-Tian
Published: June 2006

Model compounds of the H-cluster of the [Fe]-only hydrogenase, Fe2{μ-S(CH2)3S}(CO)5S(CH2CH3)2, Fe2{μ-S(CH2)3S}(CO)5{S(CH2CH3)C6H5}·0.5THF, and Fe2{μ-S(CH2)3S}(CO)5{S(CH2CH3)CH2CH2Cl} have been synthesized and characterized by X-ray diffraction, spectroscopy, and electrochemistry. Organic thioethers were introduced by simple method as terminal S-ligation to simulate the cystine-S linkage between the 2Fe unit and cuboidal [4Fe4S] moiety.
Efficient Thermal Conversion of Poly(pyridinediylbutadiynylene)s to Nitrogen-containing Microporous Carbon
Authors: Kijima Masashi , Oda Takayuki , Yamazaki Takahisa , Tazaki Yasunori , Nakamura Junji
Published: June 2006

Poly(pyridinediylbutadiynylene)s, a conjugated polymer alternatively consisted of the pyridine and butadiyne units, were synthesized by oxidative polycondensation of diethynylpyridine with the Hay catalyst. They converted to microporous carbons in high yields with a high efficiency of fixation of nitrogen by heating up from room temperature to 900 °C under flowing of argon.
End-to-end Assemblies of Gold Nanorods Adsorbed on a Glass Substrate Modified with Polyanion Polymers
Authors: Honda Kanako , Niidome Yasuro , Nakashima Naotoshi , Kawazumi Hirofumi , Yamada Sunao
Published: June 2006

Phosphatidylcholine-passivated gold nanorods (NRs) adsorbed on polyanion-modified glass substrates. The NRs on glass substrates formed end-to-end assemblies showing red-shifted and broaden longitudinal surface plasmon (SP) bands. Addition of aminohexanethiol (AHT) induced dumping of SP bands but increased the density of NRs on glass surfaces. Thiol groups of AHT were effective to change the properties of NR assemblies on glass surfaces.
In Situ Localization of P-glycoprotein (ABCB1) in Human and Rat Brain
Authors: Bendayan Reina , Ronaldson Patrick T. , Gingras Diane , Bendayan Moise
Published: June 2006

Transport of several xenobiotics including pharmacological agents into or out of the central nervous system (CNS) involves the expression of ATP-dependent, membrane-bound efflux transport proteins such as P-glycoprotein (P-gp) at the blood-brain barrier (BBB). Previous studies have documented gene and protein expression of P-gp in brain microvessel endothelial cells. However, the exact localization of P-gp, particularly at the abluminal side of the BBB, remains controversial. In the present study we examined the cellular/subcellular distribution of P-gp in situ in rat and human brain tissues using immunogold cytochemistry at the electron microscope level. P-gp localizes to both the luminal and abluminal membranes of capillary endothelial cells as well as to adjacent pericytes and astrocytes. Subcellulary, P-gp is distributed along the nuclear envelope, in caveolae, cytoplasmic vesicles, Golgi complex, and rough endoplasmic reticulum (RER). These results provide evidence for the expression of P-gp in human and rodent brain capillary along their plasma membranes as well as at sites of protein synthesis, glycosylation, and membrane trafficking. In addition, its presence at the luminal and abluminal poles of the BBB, including pericytes and astrocyte plasma membranes, suggests that this glycoprotein may regulate drug transport processes in the entire CNS BBB at both the cellular and subcellular level.
Epithelial Trafficking of Sonic Hedgehog by Megalin
Authors: Morales Carlos R. , Zeng Jibin , Alfy Mohamed El , Barth Jeremy L. , Chintalapudi Mastan Rao , McCarthy Robert A. , Incardona John P. , Argraves W. Scott
Published: June 2006

We present here evidence of in vivo epithelial endocytosis and trafficking of non-lipid-modified Sonic hedgehog (ShhN) when infused into rat efferent ducts via microinjection. Initially, exogenous ShhN is detected in endocytic vesicles and early endosomes located near the apical plasma membrane of non-ciliated cells. Within 30-60 min following infusion, ShhN can be detected in lysosomes and at basolateral regions of non-ciliated cells. Basolaterally, ShhN was observed along the extracellular surfaces of interdigitated plasma membranes of adjacent cells and in the extracellular compartment underlying the efferent duct epithelium. Uptake and subcellular trafficking of infused ShhN by non-ciliated cells could be blocked by either anti-megalin IgG or the megalin antagonist, RAP. Ciliated cells, which do not express megalin, displayed little if any apical internalization of ShhN even though they were found to express Patched-1. However, ShhN was found in coated pits of lateral plasma membranes of ciliated cells as well as in underlying endocytic vesicles. We conclude that megalin-mediated endocytosis of ShhN can occur in megalin-expressing epithelia in vivo, and that the internalized ShhN can be targeted to the lysosome or transcytosed in the plane of the epithelium or across the epithelium. These findings highlight the multiple mechanisms by which megalin may influence Shh morphogen gradients in vivo.
Expression of Prostasin and Protease Nexin-1 in Rhesus Monkey (Macaca mulatta) Endometrium and Placenta During Early Pregnancy
Authors: Lin Hai-Yan , Zhang Heng , Yang Qing , Wang Hong-Xing , Wang Hong-Mei , Chai Karl X. , Chen Li-Mei , Zhu Cheng
Published: June 2006

Serine proteases have been documented to play key roles in uterine matrix turnover and trophoblastic invasion during implantation. Roles of prostasin serine protease in these processes, however, are currently unclear. The present study was first conducted to investigate the colocalization of prostasin and its cognate serpin, protease nexin-1 (PN-1), in rhesus monkey endometrium and placenta on days 12, 18, and 26 of pregnancy by using in situ hybridization (ISH) and immunohistochemistry. With ISH, expression of prostasin mRNA was intensely localized in the glandular epithelium on days 12 and 18 and in the placental villi, trophoblastic column, trophoblastic shell, and fetal-maternal border on days 18 and 26. With the progress of pregnancy, expression level in the glandular epithelium was significantly decreased, and the accumulation in the placental compartments was further increased. In addition, the stroma and arterioles exhibited modest levels of prostasin signals. However, expression level of PN-1 in these compartments on adjacent sections in the three stages of early pregnancy was weak or below the level of detection. Prostasin protein expression in the endometrium was found to be consistent with the distribution patterns revealed in the ISH experiments. It may be suggested from these results that prostasin is involved in endometrial epithelial morphology establishment, tissue remodeling, and trophoblastic invasion during early pregnancy. The cognate serpin PN-1 was not coordinately expressed along with prostasin, creating a tissue environment favorable for proteolytic activities of prostasin during early pregnancy events.
Multidisciplinary Surgical Approach to a Surviving Infant With Sirenomelia
Authors: Messineo Antonio , Innocenti Marco , Gelli Riccardo , Pancani Simone , Lo Piccolo Roberto , Martin Alessandra
Published: June 2006

Sirenomelia is an extremely complex and rare malformation with different degrees of lower-extremities fusion associated with gastrointestinal, musculoskeletal, vascular, cardiopulmonary, and central nervous system malformations. In the English literature, there are only 5 reports of infants surviving with this condition. In our case, a 2540-g female infant was born with normal vital signs, no facial dysmorphism, and a complete soft tissue fusion of the lower limbs, from perineum to ankles. Radiologic examinations revealed an intestinal atresia and a single pelvic kidney, with a unique ureter, 2 femurs, 2 tibias, 2 fibulas, and 2 feet (simpus dipus). At 7 months of age, a multidisciplinary surgical team achieved complete separation of the lower limbs, with independent vascular and nerve supplies. At the time of this writing, the infant was 28 months old and had a regular growth curve. Many future reconstructive surgeries have been planned to achieve an acceptable quality of life for this infant.
Fluorescence Lifetimes Study of α‐Tocopherol and Biological Prenylquinols in Organic Solvents and Model Membranes
Authors: Kruk Jerzy , Myśliwa‐Kurdziel Beata , Jemiola‐Rzemińska Malgorzata , Strzalka Kazimierz
Published: June 2006

We have found that for biological prenyllipids, such as plastoquinol‐9, α‐tocopherol quinol, and α‐tocopherol, the shortest fluorescence lifetimes were found in aprotic solvents (hexane, ethyl acetate) whereas the longest lifetimes were those of ubiquinonol‐10 in these solvents. For all the investigated prenyllipids, fluorescence lifetime in alcohols increased along with an increase in solvent viscosity. In a concentrated hexane solution, the lifetimes of prenylquinols considerably decreased. This contrasts with methanol solutions, which is probably due to the self‐association of these compounds in aprotic solvents. We have also found a correlation of the Stokes shift of prenyllipids fluorescence with the orientation polarizability of the solvents. Based on data obtained in organic solvents, measurements of the fluorescence lifetimes of prenyllipids in liposomes allowed an estimation of the relative distance of their fluorescent rings from the liposome membrane surface, and was found to be the shortest for α‐tocopherol quinol in egg yolk phosphatidyl‐choline liposomes, and increased in the following order: α‐tocopherol in dipalmitoyl phosphatidylcholine liposomes < α‐tocopherol < plastoquinol‐9 < ubiquinol‐10 in egg‐yolk phosphatidylcholine liposomes.
Reasons and Reasoning for Leaving College among the Academic Elite: Case Study Findings and Implications
Authors: Hermanowicz Joseph C.
Published: June 2006

Attrition from any institution, especially in large numbers, may generate concern among that institution's officials. But high attrition from a selective institution is especially unexpected: students and schools invest significant resources to ensure an appropriate match. This study examines the reasons and reasoning behind students' decisions to leave college, based on a case study of attrition at a major selective American university. The analysis is based on in-depth interviews in order to uncover the qualitative details about how attrition occurs, and the ways in which it is experienced, in the lives of students. The results of this study indicate that intervention may most profitably lie in the reasoning, rather than the reasons alone, that underlie students decisions to leave. Students' reasons and reasoning turn out to have generic properties, which can likely inform retention policy at many other types of institutions.
Balancing Work and Academics in College: Why Do Students Working 10 to 19 Hours per Week Excel?
Authors: Dundes Lauren , Marx Jeff
Published: June 2006

Given that 74% of undergraduates work an average of 25.5 hours per week while going to school, we know surprisingly little about how off-campus employment affects undergraduates and to what extent its impact varies by the number of hours worked. Our survey of undergraduates at a small liberal arts college found that the academic performance of students who worked off-campus was comparable to nonworkers. Notably, the academic performance (greater hours studied and higher grades) of students who worked 10–19 hours per week was superior to all other students, working and non-working. We suggest that the increase in performance is due to an optimal work-college balance that establishes structure and discipline not achieved by working too few or too many hours. Yet students must balance the benefits of organization and efficiency with increased stress and reduced time for socializing (noted among students working 10+ hours per week off-campus).
Factors Influencing the Educational Success of Minority Pre-Service Educators
Authors: Clark Mary Ann , Brooks Michael , Lee Sang Min , Daley Lauren Pasquarella , Crawford Yashica , Maxis Sophie
Published: June 2006

A mixed methods study surveying minority pre-service educators to examine the factors deemed to be important in their educational success was conducted. Forty-three scholarship studies in a College of Education provided quantitative and qualitative data on their perceptions of factors that contributed to their journey to success in college and/or graduate school. Quantitative group results indicated that a strong sense of perseverance and determination, a belief in one's abilities, influence of family members, scholarships/fellowships, spirituality, and hope ranked highest among a number of factors rated. Qualitative data offered insight and detail about the significance of these factors upon educational success for these minority students.
International Student Persistence: Integration or Cultural Integrity?
Authors: Andrade Maureen S.
Published: June 2006

As diverse student populations expand in colleges and universities in the United States, attention must be given to preserving students' cultural integrity. Dominant theories of student persistence contend that integration, not cultural preservation is necessary to student success. This qualitative study examines the experiences of one group of diverse students who had low retention and graduation rates. International students in their senior year at a private, religiously-affiliated university were interviewed to determine if they had integrated into the mainstream campus culture to be successful. Three areas of change were identified: those that most students make when transitioning to college, those required by the religious environment of the institution, and those related to students' home cultures. The study demonstrates that one group of diverse students, international students, saw integration as positive. They did not view their integration as assimilation and felt that they had preserved their cultural integrity.
The Importance of Creating a “Sense of Community”
Authors: Harris Breck A.
Published: June 2006

This article presents the results of a research project conducted with 39 adult students enrolled in a management degree completion program. The research indicates that creation of a sense of community among students in a “closed” cohort setting is a significant factor in helping adults reach their goal of getting a college degree. The data suggest that degree completion programs using a closed-cohort format, which are successful in creating perceptions of a genuine sense of community among adult students, may increase student retention rates.
Identification of a Novel Member of the Carboxylesterase Family That Hydrolyzes Triacylglycerol
Authors: Okazaki Hiroaki , Igarashi Masaki , Nishi Makiko , Tajima Makiko , Sekiya Motohiro , Okazaki Sachiko , Yahagi Naoya , Ohashi Ken , Tsukamoto Kazuhisa , Amemiya-Kudo Michiyo , Matsuzaka Takashi , Shimano Hitoshi , Yamada Nobuhiro , Aoki Junken , Morikawa Rei , Takanezawa Yasukazu , Arai Hiroyuki , Nagai Ryozo , Kadowaki Takashi , Osuga Jun-ichi , Ishibashi Shun
Published: June 2006

Molecular mechanisms underlying lipolysis, as defined by mobilization of fatty acids from adipose tissue, are not fully understood. A database search for enzymes with α/β hydrolase folds, the GXSXG motif for serine esterase and the His-Gly dipeptide motif, has provided a previously unannotated gene that is induced during 3T3-L1 adipocytic differentiation. Because of its remarkable structural resemblance to triacylglycerol hydrolase (TGH) with 70.4% identity, we have tentatively designated this enzyme as TGH-2 and the original TGH as TGH-1. TGH-2 is also similar to TGH-1 in terms of tissue distribution, subcellular localization, substrate specificity, and regulation. Both enzymes are predominantly expressed in liver, adipose tissue, and kidney. In adipocytes, they are localized in microsome and fatcake. Both enzymes hydrolyzed p-nitophenyl butyrate, triolein, and monoolein but not diolein, cholesteryl oleate, or phospholipids; hydrolysis of short-chain fatty acid ester was 30,000-fold more efficient than that of long-chain fatty acid triacylglycerol. Fasting increased the expression of both genes in white adipose tissue, whereas refeeding suppressed their expression. RNA silencing of TGH-2 reduced isoproterenol-stimulated glycerol release by 10% in 3T3-L1 adipocytes, while its overexpression increased the glycerol release by 20%. Thus, TGH-2 may make a contribution to adipocyte lipolysis during period of increased energy demand.
Serum- and Glucocorticoid-Inducible Kinase 1 Mediates Salt Sensitivity of Glucose Tolerance
Authors: Boini Krishna M. , Hennige Anita M. , Huang Dan Yang , Friedrich Björn , Palmada Monica , Boehmer Christoph , Grahammer Florian , Artunc Ferruh , Ullrich Susanne , Avram Diana , Osswald Hartmut , Wulff Peer , Kuhl Dietmar , Vallon Volker , Häring Hans-Ulrich , Lang Florian
Published: June 2006

Excess salt intake decreases peripheral glucose uptake, thus impairing glucose tolerance. Stimulation of cellular glucose uptake involves phosphatidylinositide-3-kinase (PI-3K)–dependent activation of protein kinase B/Akt. A further kinase downstream of PI-3K is serum- and glucocorticoid-inducible kinase (SGK)1, which is upregulated by mineralocorticoids and, thus, downregulated by salt intake. To explore the role of SGK1 in salt-dependent glucose uptake, SGK1 knockout mice (sgk1−/−) and their wild-type littermates (sgk1+/+) were allowed free access to either tap water (control) or 1% saline (high salt). According to Western blotting, high salt decreased and deoxycorticosterone acetate (DOCA; 35 mg/kg body wt) increased SGK1 protein abundance in skeletal muscle and fat tissue of sgk1+/+ mice. Intraperitoneal injection of glucose (3 g/kg body wt) into sgk1+/+ mice transiently increased plasma glucose concentration approaching significantly higher values ([glucose]p,max) in high salt (281 ± 39 mg/dl) than in control (164 ± 23 mg/dl) animals. DOCA did not significantly modify [glucose]p,max in control sgk1+/+ mice but significantly decreased [glucose]p,max in high-salt sgk1+/+ mice, an effect reversed by spironolactone (50 mg/kg body wt). [Glucose]p,max was in sgk1−/− mice insensitive to high salt and significantly higher than in control sgk1+/+ mice. Uptake of 2-deoxy-d-[1,2-3H]glucose into skeletal muscle and fat tissue was significantly smaller in sgk1−/− mice than in sgk1+/+ mice and decreased by high salt in sgk1+/+ mice. Transfection of HEK-293 cells with active S422DSGK1, but not inactive K127NSGK, stimulated phloretin-sensitive glucose uptake. In conclusion, high salt decreases SGK1-dependent cellular glucose uptake. SGK1 thus participates in the link between salt intake and glucose tolerance.
Interventional Strategies to Prevent β-Cell Apoptosis in Islet Transplantation
Authors: Emamaullee Juliet A. , Shapiro A.M. James
Published: June 2006

A substantial proportion of the transplanted islet mass fails to engraft due to death by apoptosis, and a number of strategies have been explored to inhibit β-cell loss. Inhibition of extrinsic signals of apoptosis (i.e., cFLIP or A20) have been explored in experimental islet transplantation but have only shown limited impact. Similarly, strategies targeted at intrinsic signal inhibition (i.e., BCL-2) have not yet provided substantial improvement in islet engraftment. Recently, investigation of downstream apoptosis inhibitors that block the final common pathway (i.e., X-linked inhibitor of apoptosis protein [XIAP]) have demonstrated promise in both human and rodent models of engraftment. In addition, XIAP has enhanced long-term murine islet allograft survival. The complexities of both intrinsic and extrinsic apoptotic pathway inhibition are discussed in depth.
Evaluation of the Effect of Gain on the Meal Response of an Automated Closed-Loop Insulin Delivery System
Authors: Panteleon Antonios E. , Loutseiko Mikhail , Steil Garry M. , Rebrin Kerstin
Published: June 2006

A continuous closed-loop insulin delivery system using subcutaneous insulin delivery was evaluated in eight diabetic canines. Continuous glucose profiles were obtained by extrapolation of blood glucose measurements. Insulin delivery rate was calculated, using a model of β-cell insulin secretion, and delivered with a Medtronic MiniMed subcutaneous infusion pump. The model acts like a classic proportional-integral-derivative controller, delivering insulin in proportion to glucose above target, history of past glucose values, and glucose rate of change. For each dog, a proportional gain was set relative to the open-loop total daily dose (TDD) of insulin. Additional gains based on 0.5 × TDD and 1.5 × TDD were also evaluated (gain dose response). Control was initiated 4 h before the meal with a target of 6.7 mmol/l. At the time of the meal, glucose was similar for all three gains (6.0 ± 0.3, 5.2 ± 0.3, and 4.9 ± 0.5 mmol/l for 0.5 × TDD, TDD, and 1.5 × TDD, respectively; P > 0.05) with near-target values restored at the end of experiments (8.2 ± 0.9, 6.0 ± 0.6, and 6.0 ± 0.5, respectively). The peak postprandial glucose level decreased significantly with increasing gain (12.1 ± 0.6, 9.6 ± 1.0, and 8.5 ± 0.6 mmol/l, respectively; P < 0.05). The data demonstrate that closed-loop insulin delivery using the subcutaneous site can provide stable glycemic control within a range of gain.
Aldose Reductase–Deficient Mice Are Protected From Delayed Motor Nerve Conduction Velocity, Increased c-Jun NH2-Terminal Kinase Activation, Depletion of Reduced Glutathione, Increased Superoxide Accumulation, and DNA Damage
Authors: Ho Eric C.M. , Lam Karen S.L. , Chen Yuk Shan , Yip Johnny C.W. , Arvindakshan Meena , Yamagishi Shin-Ichiro , Yagihashi Soroku , Oates Peter J. , Ellery Craig A. , Chung Stephen S.M. , Chung Sookja K.
Published: June 2006

The exaggerated flux through polyol pathway during diabetes is thought to be a major cause of lesions in the peripheral nerves. Here, we used aldose reductase (AR)-deficient (AR−/−) and AR inhibitor (ARI)-treated mice to further understand the in vivo role of polyol pathway in the pathogenesis of diabetic neuropathy. Under normal conditions, there were no obvious differences in the innervation patterns between wild-type AR (AR+/+) and AR−/− mice. Under short-term diabetic conditions, AR−/− mice were protected from the reduction of motor and sensory nerve conduction velocities observed in diabetic AR+/+ mice. Sorbitol levels in the sciatic nerves of diabetic AR+/+ mice were increased significantly, whereas sorbitol levels in the diabetic AR−/− mice were significantly lower than those in diabetic AR+/+ mice. In addition, signs of oxidative stress, such as increased activation of c-Jun NH2-terminal kinase (JNK), depletion of reduced glutathione, increase of superoxide formation, and DNA damage, observed in the sciatic nerves of diabetic AR+/+ mice were not observed in the diabetic AR−/− mice, indicating that the diabetic AR−/− mice were protected from oxidative stress in the sciatic nerve. The diabetic AR−/− mice also excreted less 8-hydroxy-2′-deoxyguanosine in urine than diabetic AR+/+ mice. The structural abnormalities observed in the sural nerve of diabetic AR+/+ mice were less severe in the diabetic AR−/− mice, although it was only mildly protected by AR deficiency under short-term diabetic conditions. Signs of oxidative stress and functional and structural abnormalities were also inhibited by the ARI fidarestat in diabetic AR+/+ nerves, similar to those in diabetic AR−/− mice. Taken together, increased polyol pathway flux through AR is a major contributing factor in the early signs of diabetic neuropathy, possibly through depletion of glutathione, increased superoxide accumulation, increased JNK activation, and DNA damage.
Common Variants of the Endothelial Nitric Oxide Synthase Gene and the Risk of Coronary Heart Disease Among U.S. Diabetic Men
Authors: Zhang Cuilin , Lopez-Ridaura Ruy , Hunter David J. , Rifai Nader , Hu Frank B.
Published: June 2006

Endothelial nitric oxide synthase (eNOS) gene represents a promising candidate gene for coronary heart disease (CHD) because of its impact on eNOS activity. We systematically examined the associations of eight variants of the eNOS gene (two potentially functional variants [−786T>C and Glu298Asp] and six tagging single nucleotide polymorphisms) with CHD risk in a large cohort of diabetic patients. Among 861 diabetic men (>97% Caucasian) from the Health Professionals Follow-Up Study, 220 developed CHD, and 641 men without cardiovascular disease were used as control subjects. Genotype distributions of −786T>C and Glu298Asp polymorphisms were not significantly different between case and control subjects. CHD risk was significantly higher among men with the variant allele at the rs1541861 locus (intron 8 A/C) than men without it (adjusted odds ratio 1.5 [95% confidence interval 1.1–2.1]). Moreover, among control subjects, plasma soluble vascular cell adhesion molecule concentrations were significantly higher among carriers of this allele (P 0.019) and carriers of the variant allele of the −786T>C (P 0.010), or the Glu298Asp polymorphism (P 0.002), compared with noncarriers. In conclusion, our data suggested that −786T>C, Glu298Asp, and an intron 8 polymorphism of the eNOS gene are potentially involved in the atherogenic pathway among U.S. diabetic men.
The Role of Ca2+ Influx for Insulin-Mediated Glucose Uptake in Skeletal Muscle
Authors: Lanner Johanna T. , Katz Abram , Tavi Pasi , Sandström Marie E. , Zhang Shi-Jin , Wretman Charlott , James Stephen , Fauconnier Jérémy , Lännergren Jan , Bruton Joseph D. , Westerblad Håkan
Published: June 2006

The involvement of Ca2+ in insulin-mediated glucose uptake is uncertain. We measured Ca2+ influx (as Mn2+ quenching or Ba2+ influx) and 2-deoxyglucose (2-DG) uptake in single muscle fibers isolated from limbs of adult mice; 2-DG uptake was also measured in isolated whole muscles. Exposure to insulin increased the Ca2+ influx in single muscle cells. Ca2+ influx in the presence of insulin was decreased by 2-aminoethoxydiphenyl borate (2-APB) and increased by the membrane-permeable diacylglycerol analog 1-oleyl-2-acetyl-sn-glycerol (OAG), agents frequently used to block and activate, respectively, nonselective cation channels. Maneuvers that decreased Ca2+ influx in the presence of insulin also decreased 2-DG uptake, whereas increased Ca2+ influx was associated with increased insulin-mediated glucose uptake in isolated single cells and whole muscles from both normal and insulin-resistant obese ob/ob mice. 2-APB and OAG affected neither basal nor hypoxia- or contraction-mediated 2-DG uptake. 2-APB did not inhibit the insulin-mediated activation of protein kinase B or extracellular signal–related kinase 1/2 in whole muscles. In conclusion, alterations in Ca2+ influx specifically modulate insulin-mediated glucose uptake in both normal and insulin-resistant skeletal muscle. Moreover, the present results indicate that Ca2+ acts late in the insulin signaling pathway, for instance, in the GLUT4 translocation to the plasma membrane.
Single Nucleotide Polymorphisms of PPARD in Combination With the Gly482Ser Substitution of PGC-1A and the Pro12Ala Substitution of PPARG2 Predict the Conversion From Impaired Glucose Tolerance to Type 2 Diabetes
Authors: Andrulionytė Laura , Peltola Paula , Chiasson Jean-Louis , Laakso Markku ,   for the STOP-NIDDM Study Group
Published: June 2006

Peroxisome proliferator–activated receptor (PPAR)-δ regulates fatty acid oxidation and improves insulin sensitivity. We screened six single nucleotide polymorphisms (SNPs) of the PPAR-δ gene (PPARD) for an association with the conversion from impaired glucose tolerance (IGT) to type 2 diabetes in 769 subjects participating in the STOP-NIDDM trial. A 2.7-fold increase in the risk of diabetes was observed in female carriers of the C allele of rs6902123 (95% CI 1.44–5.30; adjusted P = 0.002). In the placebo group, subjects possessing both the 482Ser allele of the PPAR-γ coactivator-1α gene (PGC-1A) and the rare allele of two SNPs of PPARD (rs6902123 and rs3734254) had up to 2.5-fold increased risk for diabetes. Furthermore, women carrying the C allele of rs6902123 of PPARD and the Pro12Pro genotype of the PPAR-γ2 gene (PPARG2) had a 3.9-fold (95% CI 1.79–8.63; P = 0.001)-higher risk for diabetes than women with protective genotypes. Expression levels of PPAR-δ in subcutaneous adipose tissue of 87 offspring of Finnish patients with type 2 diabetes did not differ among the genotype groups of SNPs of PPARD. We conclude that SNPs in PPARD modify the conversion from IGT to type 2 diabetes, particularly in combination with the SNPs of PGC-1A and PPARG2.
Cystic Fibrosis Transmembrane Conductance Regulator Deficiency Exacerbates Islet Cell Dysfunction After β-Cell Injury
Authors: Stalvey Michael S. , Muller Christian , Schatz Desmond A. , Wasserfall Clive H. , Campbell-Thompson Martha L. , Theriaque Douglas W. , Flotte Terence R. , Atkinson Mark A.
Published: June 2006

The cause of cystic fibrosis–related diabetes (CFRD) remains unknown, but cystic fibrosis transmembrane conductance regulator (CFTR) mutations contribute directly to multiple aspects of the cystic fibrosis phenotype. We hypothesized that susceptibility to islet dysfunction in cystic fibrosis is determined by the lack of functional CFTR. To address this, glycemia was assessed in CFTR null (CFTR−/−), C57BL/6J, and FVB/NJ mice after streptozotocin (STZ)-induced β-cell injury. Fasting blood glucose levels were similar among age-matched non–STZ-administered animals, but they were significantly higher in CFTR−/− mice 4 weeks after STZ administration (288.4 ± 97.4, 168.4 ± 35.9, and 188.0 ± 42.3 mg/dl for CFTR−/−, C57BL/6J, and FVB/NJ, respectively; P < 0.05). After intraperitoneal glucose administration, elevated blood glucose levels were also observed in STZ-administered CFTR−/− mice. STZ reduced islets among all strains; however, only CFTR−/− mice demonstrated a negative correlation between islet number and fasting blood glucose (P = 0.02). To determine whether a second alteration associated with cystic fibrosis (i.e., airway inflammation) could impact glucose control, animals were challenged with Aspergillus fumigatus. The A. fumigatus–sensitized CFTR−/− mice demonstrated similar fasting and stimulated glucose responses in comparison to nonsensitized animals. These studies suggest metabolic derangements in CFRD originate from an islet dysfunction inherent to the CFTR−/− state.