bluuebunny/crossref_metadata_2025 huggingface dataset:
STM Imaging of Proteins on Semiconducting Substrates
Authors: Skorupska Katarzyna , Smith Dr James , Campbell Dr Sheelagh A. , Jungblut Helmut , Lewerenz Hans, Joachim J.
Published: February 2007

The enzyme reverse transcriptase (RT) of the human immunodeficiency virus (HIV) is imaged by scanning tunnelling microscopy (STM). RTs are selected due to their highly specific structure and their biochemical and medical relevance. The enzymes are deposited on layered semiconducting MoTe2. Structural defects on the substrate surface are suggested to attach the biomolecules due to electrostatic forces. The STM images clearly show the structure of the protein in excellent agreement with structural predictions from small angle neutron scattering and X-ray diffraction measurements. The high resolution imaging process is discussed with regard to the STM metal tip / protein / semiconductor junction energetics. Resonant electron tunnelling is ascribed to an overlap of semiconductor conduction band and extended LUMO states of the enzyme. Within the biomolecule, electron transfer is suggested to occur via Poole-Frenkel mechanism in combination with electron release due to solvation shell fluctuations.
Some Milestones in the 50-year History of Electrochemical Oxygen Sensor Development
Authors: Nei Lembit
Published: February 2007

Fifty years have passed since Leland C. Clark proposed the concept of membrane-covered oxygen sensor. The system consists of a two electrode cell with a thin oxygen-permeable membrane separating the electrodes and the electrolyte solution from the analysed media. Oxygen diffuses through the membrane and is reduced at the indicator electrode. This results in current that is proportional to the oxygen concentration in the sample. The Clark Oxygen Sensor has found wide application in medicine, environmental and industrial monitoring. In 1962 Clark and Lyons described the first biosensor. A Clark oxygen sensor was combined with glucose oxidase to detect glucose levels. In spite of the commercial popularity the output currents of Clark-type oxygen sensors are unstable and oxygen analysers need frequent pre-calibration. In 1963 a different oxygen sensor was reported by Mackereth. This design found wide application in water monitoring in the former Soviet Union.
Use of SUNRAY-3D Code for Prediction of Stability in a High Gain TWT
Authors: Kumar Vikas , Srivastava Vishnu , Vohra Anil
Published: February 2007

The stability of a High Gain Helix TWT has been analyzed using the SUNRAY-3D code employing large signal modeling. The performance of one section fixed length TWT has been evaluated for the fixed beam voltage, drive power, no circuit loss and no mismatch at the terminations by varying the beam current under different passes through the tube. The output power has also been evaluated for the different drive levels and the beam currents. Study has also been done at the pi-point to evaluate the effect of beam current and the pass number on output power for zero drive power. Same studies have been done on the 3.90GHz as in case of pi-point frequency. The instability conditions in the TWT have been predicted on the basis of simulated results.
Increasing Cycle Life of Nickel Hydroxide Electrodes at High Currents
Authors: Snook Graeme A. , Duffy Noel W. , Pandolfo Anthony G.
Published: February 2007

The effect of high current (>10C) cycling on the capacity of nickel hydroxide was investigated in aqueous KOH with the objective of increasing cycle life at high currents. Capacity loss at high voltages has been attributed to excess oxygen evolution which occurs when charging is conducted at high rates without voltage limits. Cyclic voltammetry of nickel hydroxide microparticles, attached to glassy carbon electrodes, enabled the separation of the oxidation process from oxygen evolution. With large pasted electrodes, due to their large uncompensated resistance (Ru), these processes are poorly resolved. An alternate method for the discrimination of oxygen evolution has been developed using Scanning Electrochemical Microscopy (SECM) to map the evolution of oxygen against potential. With no control of upper voltage, poor cycle-life was confirmed at 15C (40% capacity loss in 50 cycles). By contrast, voltage control based on SECM studies (Vmax = 1.45V) allowed thousands of cycles with little capacity loss.
Estimation of Ion Pairs Formation Constants of Lithium Salts in 1,2-dimethoxyethane and 1,4-dioxane Mixtures.
Authors: Siekierski Maciej S. , Kalita Michal , Plewa Anna , Sołgała Agnieszka
Published: February 2007

In this paper the 19F NMR spectroscopy and conductivity measurements by means of impedance spectroscopy together with Fuoss-Krauss formalism calculations are used as two independent methods to determine the ion pair formation constants for lithium tetrafluoroborate and lithium trifluoromethylsulfonate solutions in mixtures of 1,2-dimethoxyethane and 1,4-dioxane. These liquid systems have very similar coordinating properties (donor and acceptor numbers) as liquid poly(ethylene glycol) dimethyl ether and solid poly(ethylene oxide) and can be tailored to have identical dielectric constants. Thus, they can be used as a model system for discussion of the role of the chain length in cation and anion coordination and conduction mechanism in polymeric electrolytes. Similar experiments were performed for theoretically unassociated tetraalkylamonium salts with identical anions. The results are compared with literature data for liquid poly(ethylene glycol) dimethyl ether and solid poly(ethylene oxide) in the field of ion-ion and ion-solvent interactions.
Ionic Liquid-Incorporated Gel Polymer Electrolytes for Ultracapacitors
Authors: Lu Wen , Henry Kent , Turchi Craig , Pellegrino John
Published: February 2007

Electrolytes are an important component in determining the performance and cycle life of ultracapacitors. Good electrolytes should have high conductivity, large electrochemical windows, excellent thermal and chemical stability, and negligible electrolyte depletion. Ionic liquids are ideal electrolytes to satisfy these requirements. In the present work, we developed easy-to-use methods to incorporate ionic liquids into a polymer matrix to synthesize gel polymer electrolytes. The obtained solid-state ionic liquid- incorporated gel polymer electrolytes (ILGPEs) are mechanically strong, electrochemically and thermally stable, and highly conductive. We have used these electrolytes to fabricate solid-state ultracapacitors. Large cell voltage, high performance, and long cycle life have been realized for these ultracapacitors.
Electroreduction of O2 on Cytochrome c Oxidase Modified Electrode for Biofuel Cell
Authors: Su Leon , Kelly James , Hawkridge Fred M.
Published: February 2007

Bovine cytochrome c oxidase is immobilized in a gold substrate- supported lipid bilayer membrane to investigate reduction of oxygen using flow through detection technique. The results shown that system temperature, pH and component of solution affect the electroreductive rate of oxygen. In each case the reduction rate of oxygen is controlled by electron transfer. The oxidase modified electrode can be used for the direct electroreduction of oxygen to water in a biofuel cell.
Arsenic Removal from Underground Water by Electrocoagulation with Zinc, Brass and Iron
Authors: Montero Cecilia , Maldonado Araceli , Solorza-Feria Omar
Published: February 2007

The purification of water using metal electrodes by electrocoagulation (EC) is widely used in different spheres of science and industry. The comparative characteristics of the electro-oxidation under galvanostatic conditions of zinc (Zn), brass (Cu-Zn) and iron (Fe) anodes for arsenic (As) removal from underground water by the EC process were determined at a current density of 1.5 mA cm-2. A solution containing different concentrations of As(V) (from 70 to 130 µg L-1) was used. The results of the electrochemical characterization show that Zn exhibited the lower anodic overpotential, followed by Fe, and Cu-Zn. The performance of the removal of As was relatively efficient, with the followed tendency: Fe (> 93%) similar or equal to Zn (> 93%) > Cu-Zn (> 73%).
A Demonstration of Electrodeposited Nanocomposites using a Rotating Cylinder Hull Cell
Authors: Podlaha Elizabeth J. , Lozano-Morales Alonso
Published: February 2007

The Rotating Cylinder Hull Cell was used to demonstrate the electrodeposition of nanocomposites. A two-part lecture and demonstration unit is presented here that attempts to motivate students through the development of new materials right in the classroom. Current distribution concepts are introduced as a way to survey electrodeposition conditions for alloy and metal matrix composite materials. NiCu-alumina and ceria composites were successfully fabricated. Particles altered the deposition rate of both Cu and Ni affecting the deposit composition.
Perovskite-Based Catalysts for Direct Ethanol Fuel Cells
Authors: Lan Aidong , Mukasyan Alexander
Published: February 2007

A new catalyst development strategy, featuring an energy efficient and rapid synthesis technique so-called solution combustion (SC), and an high throughput electro-catalysts screening system (NuVant), is proposed. Under this strategy, a library of conductive perovskites were synthesized and tested as anode electrodes in the Direct Ethanol Fuel Cell conditions. It was found that a variety of Ru-based perovskites showed considerable electro-catalytic activity for ethanol oxidation. Further, it was demonstrated that the composite perovskite-platinum catalysts with low noble metal loading prepared directly by SC method exhibit comparable performance with standard Pt-Ru alloy.
Development of Semi-Empirical Cell Voltage Model for Direct Methanol Fuel Cell
Authors: Choi Ji Eun , Bae Young Chan , Kim Dong Lae
Published: February 2007

A new semi-empirical model is established to describe the cell voltage of a direct methanol fuel cell (DMFC) as a function of current density. The proposed model focuses on very unfavorable conditions for the cell operation, i.e. low methanol solution concentrations and relatively low cell temperatures. A newly developed semi-empirical equation, includes the methanol crossover effect that plays a major role in determining the cell voltage of DMFC. The model equation is validated experimental data over a wide range of a methanol concentration and temperature.
Multiblock Hydrophilic-Hydrophobic Proton Exchange Membranes for Direct Methanol Based Fuel Cell
Authors: McGrath James E. , Roy Abhishek , Lee Hae-Seung , Yu Xiang , Badami Anand , Li Yanxiang , Wang Hang
Published: February 2007

The integral part of the fuel cell is the proton exchange membrane. Two series of novel ion containing multiblock copolymers were synthesized with varying IECs and block lengths. The hydrophilic block was composed of 100% disulfonated poly(arylene ether sulfone)s for both of the two multiblocks. The hydrophobic unit for one of the multiblocks is composed of highly fluorinated poly(arylene ether) blocks and for the other is naphtalene dianhydride based poly imide blocks. All the multiblock copolymers showed high proton conductivity under fully hydrated conditions. In comparison to Nafion 117, the multiblock copolymers showed significantly lower methanol permeability and satisfactory DMFC performance. Thus by synthesizing multiblock copolymers, it is possible to have both higher proton conductivity and lower methanol permeability at the same time.
Development of Methanol Permeation Control Layer
Authors: Kobayashi Toru
Published: February 2007

Methanol crossover (MCO) is controllable by regulating mass transfer. By forming a methanol permeation control layer that We have developed on the gas diffusion layer base material of the anode side, I have succeeded in reducing MCO. Furthermore, durability has also been improved by minimizing flooding.
Effects of a nucleoside reverse transcriptase inhibitor, stavudine, on glucose disposal and mitochondrial function in muscle of healthy adults
Authors: Fleischman Amy , Johnsen Stine , Systrom David M. , Hrovat Mirko , Farrar Christian T. , Frontera Walter , Fitch Kathleen , Thomas Bijoy J. , Torriani Martin , Côté Hélène C. F. , Grinspoon Steven K.
Published: February 2007

Mitochondrial dysfunction may contribute to the development of insulin resistance and type 2 diabetes. Nucleoside reverse transcriptase inhibitors (NRTIs), specifically stavudine, are known to alter mitochondrial function in human immunodeficiency virus (HIV)-infected individuals, but the effects of stavudine on glucose disposal and mitochondrial function in muscle have not been prospectively evaluated. In this study, we investigated short-term stavudine administration among healthy control subjects to determine effects on insulin sensitivity. A secondary aim was to determine the effects of stavudine on mitochondrial DNA (mtDNA) and function. Sixteen participants without personal or family history of diabetes were enrolled. Subjects were randomized to receive stavudine, 30–40 mg, twice a day, or placebo for 1 mo. Insulin sensitivity determined by glucose infusion rate during the hyperinsulinemic euglycemic clamp was significantly reduced after 1-mo exposure in the stavudine-treated subjects compared with placebo (−0.8 ± 0.5 vs. +0.7 ± 0.3 mg·kg−1·min−1, P = 0.04, stavudine vs. placebo). In addition, muscle biopsy specimens in the stavudine-treated group showed significant reduction in mtDNA/nuclear DNA (−52%, P = 0.005), with no change in placebo-treated subjects (+8%, P = 0.9).31P magnetic resonance spectroscopy (MRS) studies of mitochondrial function correlated with insulin sensitivity measures ( r2= 0.5, P = 0.008). These findings demonstrate that stavudine administration has potent effects on insulin sensitivity among healthy subjects. Further studies are necessary to determine whether changes in mtDNA resulting from stavudine contribute to effects on insulin sensitivity.
Possible role of carbonic anhydrase in rat pancreatic islets: enzymatic, secretory, metabolic, ionic, and electrical aspects
Authors: Sener Abdullah , Jijakli Hassan , Asl Saleh Zahedi , Courtois Philippe , Yates Allen P. , Meuris Sylvain , Best Leonard C. , Malaisse Willy J.
Published: February 2007

The presence of carbonic anhydrase (type V) was recently documented in rat and mouse pancreatic islet β-cells by immunostaining and Western blotting. In the present study, the activity of carbonic anhydrase was measured in rat islet homogenates and shown to be about four times lower than in rat parotid cells. The pattern for the inhibitory action of acetazolamide on carbonic anhydrase activity also differed in islet and parotid cell homogenates, suggesting the presence of different isoenzymes. NaN3inhibited carbonic anhydrase activity in islet homogenates and both d-[U-14C]glucose oxidation and glucose-stimulated insulin secretion. Acetazolamide (0.3–10.0 mM) also decreased glucose-induced insulin output but failed to affect adversely d-[U-14C]glucose oxidation, although it inhibited the conversion of d-[5-3H]glucose to [3H]OH and that of d-[U-14C]glucose to acidic metabolites. Hydrochlorothiazide (3.0–10.0 mM), which also caused a concentration-related inhibition of the secretory response, like acetazolamide (5.0–10.0 mM), decreased H14CO3−production from d-[U-14C]glucose (16.7 mM). Acetazolamide (5.0 mM) did not affect the activity of volume-sensitive anion channels in β-cells but lowered intracellular pH and adversely affected both the bioelectrical response to d-glucose and its effect on the cytosolic concentration of Ca2+in these cells. The lowering of cellular pH by acetazolamide, which could well be due to inhibition of carbonic anhydrase, might in turn account for inhibition of glycolysis. The perturbation of stimulus-secretion coupling in the β-cells exposed to acetazolamide may thus involve impaired circulation in the pyruvate-malate shuttle, altered mitochondrial Ca2+accumulation, and perturbation of Cl−fluxes, resulting in both decreased bioelectrical activity and insulin release.
Flux profile and modularity analysis of time-dependent metabolic changes of de novo adipocyte formation
Authors: Si Yaguang , Yoon Jeongah , Lee Kyongbum
Published: February 2007

White adipose tissue (WAT) mass is the main determinant of obesity and associated health risks. WAT expansion results from increases in white adipocyte cell number and size, which in turn reflect a series of shifts in the cellular metabolic state. To quantitatively profile the metabolic alterations occurring during de novo adipocyte formation, metabolic flux analysis (MFA) was used in conjunction with a novel modularity analysis algorithm on differentiating 3T3-L1 preadipocytes. Use of a type I collagen gel as an effective long-term culture substrate was also assessed. The calculated flux distributions predicted the sequential activation of several intracellular cross-compartmental pathways, including lipogenesis, the pentose phosphate pathway, and the malate cycle, in good agreement with earlier isotopic tracer experiments and gene profiling studies. Partition of the adipocyte metabolic network into highly interacting reaction subgroups suggested a functional reorganization of the major pathways consistent with the lipid-loading phenotype of the adipocyte. Flux and modularity analysis results together point to the flux distribution around pyruvate as a key indicator of adipocyte lipid accumulation.
Dysregulation of muscle lipid metabolism in rats selectively bred for low aerobic running capacity
Authors: Spargo Fiona J. , McGee Sean L. , Dzamko Nick , Watt Matthew J. , Kemp Bruce E. , Britton Steven L. , Koch Lauren G. , Hargreaves Mark , Hawley John A.
Published: February 2007

As substrate for evaluation of metabolic diseases, we developed novel rat models that contrast for endurance exercise capacity. Through two-way artificial selection, we created rodent phenotypes of intrinsically low-capacity runners (LCR) and high-capacity runners (HCR) that also differed markedly for cardiovascular and metabolic disease risk factors. Here, we determined skeletal muscle proteins with putative roles in lipid and carbohydrate metabolism to better understand the mechanisms underlying differences in whole body substrate handling between phenotypes. Animals ( generation 16) differed for endurance running capacity by 295%. LCR animals had higher resting plasma glucose (6.58 ± 0.45 vs. 6.09 ± 0.45 mmol/l), insulin (0.48 ± 0.03 vs. 0.32 ± 0.02 ng/ml), nonesterified fatty acid (0.57 ± 0.14 v 0.35 ± 0.05 mM), and triglyceride (TG; 0.47 ± 0.11 vs. 0.25 ± 0.08 mmol/l) concentrations (all P < 0.05). Muscle TG (72.3 ± 14.7 vs. 38.9 ± 6.2 mmol/kg dry muscle wt; P < 0.05) and diacylglycerol (96 ± 28 vs. 42 ± 8 pmol/mg dry muscle wt; P < 0.05) contents were elevated in LCR vs. HCR rats. Accompanying the greater lipid accretion in LCR was increased fatty acid translocase/CD36 content (1,014 ± 80 vs. 781 ± 70 arbitrary units; P < 0.05) and reduced TG lipase activity (0.158 ± 0.0125 vs. 0.274 ± 0.018 mmol·min−1·kg dry muscle wt−1; P < 0.05). Muscle glycogen, GLUT4 protein, and basal phosphorylation states of AMP-activated protein kinase-α1, AMP-activated protein kinase-α2, and acetyl-CoA carboxylase were similar in LCR and HCR. In conclusion, rats with low intrinsic aerobic capacity demonstrate abnormalities in lipid-handling capacity. These disruptions may, in part, be responsible for the increased risk of metabolic disorders observed in this phenotype.
Downmodulation of mitochondrial F0F1ATP synthase by diazoxide in cardiac myoblasts: a dual effect of the drug
Authors: Comelli Marina , Metelli Giuliana , Mavelli Irene
Published: February 2007

Similar to ischemic preconditioning, diazoxide was documented to elicit beneficial bioenergetic consequences linked to cardioprotection. Inhibition of ATPase activity of mitochondrial F0F1ATP synthase may have a role in such effect and may involve the natural inhibitor protein IF1. We recently documented, using purified enzyme and isolated mitochondrial membranes from beef heart, that diazoxide interacts with the F1sector of F0F1ATP synthase by promoting IF1binding and reversibly inhibiting ATP hydrolysis. Here we investigated the effects of diazoxide on the enzyme in cultured myoblasts. Specifically, embryonic heart-derived H9c2 cells were exposed to diazoxide and mitochondrial ATPase was assayed in conditions maintaining steady-state IF1binding (basal ATPase activity) or detaching bound IF1at alkaline pH. Mitochondrial transmembrane potential and uncoupling were also investigated, as well as ATP synthesis flux and ATP content. Diazoxide at a cardioprotective concentration (40 μM cell-associated concentration) transiently downmodulated basal ATPase activity, concomitant with mild mitochondria uncoupling and depolarization, without affecting ATP synthesis and ATP content. Alkaline stripping of IF1from F0F1ATP synthase was less in diazoxide-treated than in untreated cells. Pretreatment with glibenclamide prevented, together with mitochondria depolarization, inhibition of ATPase activity under basal but not under IF1-stripping conditions, indicating that diazoxide alters alkaline IF1release. Diazoxide inhibition of ATPase activity in IF1-stripping conditions was observed even when mitochondrial transmembrane potential was reduced by FCCP. The results suggest that diazoxide in a model of normoxic intact cells directly promotes binding of inhibitor protein IF1to F0F1ATP synthase and enhances IF1binding indirectly by mildly uncoupling and depolarizing mitochondria.
Facilitating Sensory Responses in Developing Mouse Somatosensory Barrel Cortex
Authors: Borgdorff Aren J. , Poulet James F. A. , Petersen Carl C. H.
Published: February 2007

The sensory responses in the barrel cortex of mice aged postnatal day (P)7–P12 evoked by a single whisker deflection are smaller in amplitude and spread over a smaller area than those measured in P13–P21 mice. However, repetitive 10-Hz stimulation or paired pulse whisker stimulation in P7–P12 mice evoked facilitating sensory responses, contrasting with the depressing sensory responses observed in P13–P21 mice. This facilitation occurred during an interval ranging 300–1,000 ms after the first stimulus and was measured using whole cell recordings, voltage-sensitive dye imaging, and calcium-sensitive dye imaging. The facilitated responses were not only larger in amplitude but also propagated over a larger cortical area. The facilitation could be blocked by local application of pharmacological agents reducing cortical excitability. Local cortical microstimulation could substitute for the first whisker stimulus to produce a facilitated sensory response. The enhanced sensory responses evoked by repetitive sensory stimuli in P7–P12 mice may contribute to the activity-dependent specification of the developing cortical circuits. In addition, the facilitating sensory responses allow long integration times for sensory processing compatible with the slow behavior of mice during early postnatal development.
Circadian profiling of the transcriptome in NIH/3T3 fibroblasts: comparison with rhythmic gene expression in SCN2.2 cells and the rat SCN
Authors: Menger Gus J. , Allen Gregg C. , Neuendorff Nichole , Nahm Sang-Soep , Thomas Terry L. , Cassone Vincent M. , Earnest David J.
Published: February 2007

To screen for output signals that may distinguish the pacemaker in the mammalian suprachiasmatic nucleus (SCN) from peripheral-type oscillators in which the canonical clockworks are similarly regulated in a circadian manner, the rhythmic behavior of the transcriptome in forskolin-stimulated NIH/3T3 fibroblasts was analyzed and compared relative to SCN2.2 cells in vitro and the rat SCN. Similar to the circadian profiling of the SCN2.2 and rat SCN transcriptomes, NIH/3T3 fibroblasts exhibited circadian fluctuations in the expression of the core clock genes, Per2, Cry1, and Bmal1, and 323 functionally diverse transcripts, many of which regulate cellular communication. Overlap in rhythmic transcripts among NIH/3T3 fibroblasts, SCN2.2 cells, and the rat SCN was limited to these clock genes and four other genes that mediate fatty acid and lipid metabolism or function as nuclear factors. Compared with NIH/3T3 cells, circadian gene expression in SCN oscillators was more prevalent among genes mediating glucose metabolism and neurotransmission. Coupled with evidence for the rhythmic regulation of the inducible isoform of nitric oxide synthase ( iNos) in SCN2.2 cells and the rat SCN but not in fibroblasts, studies examining the effects of a NOS inhibitor on metabolic rhythms in cocultures containing SCN2.2 cells and untreated NIH/3T3 cells suggest that the gaseous neurotransmitter nitric oxide may play a key role in SCN pacemaker function. This comparative analysis of circadian gene expression in SCN and non-SCN cells may have important implications in the selective analysis of circadian signals involved in the coupling of SCN oscillators and regulation of rhythmicity in downstream cells.
An X-Ray Microtomography Study on the Mineral Concentration of Carious Dentine Removed during Cavity Preparation in Deciduous Molars
Authors: Willmott N.S. , Wong F.S.L , Davis G.R.
Published: February 2007

Dentists use a number of criteria in order to assess when a cavity is caries free, amongst which hardness is probably the most widely used. However, the judgement is subjective. X-ray microtomography (XMT) is a non-destructive microscopic technique that allows in vitro specimens to be scanned, manipulated and then rescanned. In this study, a high-definition XMT scanner was used to determine the mineral distribution of carious dentine in 10 deciduous molars, and the extent of dentine removed by an experienced clinician was investigated. For each tooth, after an initial XMT scan, caries was removed using a steel bur in a slow hand-piece. The tooth was then repositioned and rescanned. Mineral concentrations were calculated from the linear attenuation coefficients assuming the mineral phase to be hydroxyapatite and the organic phase to be collagen. The volume of dentine tissues removed was calculated by subtracting data of the second scan from the first. The results showed that the mean modal mineral concentration for the 10 teeth was 1.42 g · cm–3 for sound dentine. Because of uncertainty about collagen concentration in carious dentine, the mean modal mineral concentration for the carious dentine had a range of 0.37–0.5 g · cm–3. It was found that the subjective criteria used by the operator could lead to inconsistency of cavity preparation. The cavities could be overprepared by 8.5–44.3% in volume. However, the overpreparation was not uniform throughout the cavity: residual demineralised dentine could still be detected in the postoperative scan in isolated regions.
Laser Fluorescence Measurements Compared to Electrical Resistance of Residual Dentine in Excavated Cavities in vivo
Authors: Krause F. , Braun A. , Eberhard J. , Jepsen S.
Published: February 2007

It has been suggested that laser fluorescence close to the dental pulp shows higher values than more distant measurements. The aim of this study was to assess fluorescence on the cavity floor and to correlate these measurements with electrical resistance as a measure of residual dentine thickness. Thirty carious lesions were excavated with a bur. The endpoint of caries removal was determined by visual, tactile and auditory means. Fluorescence was measured with the Diagnodent device and with the fluorescence feedback system of a therapeutic Er:YAG laser. Electrical resistance of the residual dentine (Prepometer units, PU) was measured with a proprietary device. Significant differences were observed between the fluorescence systems (p < 0.05). For Diagnodent, a decrease of electrical resistance of the residual dentine resulted in an increase of the fluorescence values of 2.99 units/PU (95% CI = 2.00–3.97) and an increase of 0.30 units/PU (95% CI = 0.19–0.40) for the fluorescence feedback system. For zero electrical resistance, a predicted maximum value of 51.5 units (95% CI = 41.3–61.7) was calculated for the Diagnodent and 5.1 units (95% CI = 4.1–6.2) for the feedback system. The study indicates that using the suggested detection cut-off with the Diagnodent device may be not suited to assess the endpoint of caries removal close to the dental pulp. Employing the Key Laser III, values up to 6 units might be caused solely by close proximity to the pulp, which should be considered when caries removal by laser is controlled by laser fluorescence feedback.
Effect of Titanium Tetrafluoride and Sodium Fluoride on Erosion Progression in Enamel and Dentine in vitro
Authors: Schlueter N. , Ganss C. , Mueller U. , Klimek J.
Published: February 2007

Our aim was to investigate the effect of TiF4 solutions on mineral loss on enamel and dentine in vitro. Samples were fluoridated 1 × 5 min per day with 1.64% w/v TiF4 or 2.2% w/v NaF solutions, each with a pH of 1.2, and then subjected to a cyclic de- and remineralization procedure for 5 days. Demineralization was performed for 6 × 10 min per day with citric acid (pH 2.3). In controls no fluoridation was performed. Mineral content was determined by longitudinal microradiography. Enamel mineral loss was markedly reduced by both fluoride solutions, but TiF4 was significantly more effective than NaF: cumulative mineral loss on day 3 was 61.7 ± 15.0 µm in the NaF and 34.2 ± 13.1 µm in the TiF4 group (p ≤ 0.001) compared with 121.0 ± 27.0 µm in the control group. Dentine mineral loss ceased after both TiF4 and NaF applications (cumulative mineral loss on day 5 in controls: 61.0 ± 17.0 µm, in the TiF4 group: 15.4 ± 13.4 µm and in the NaF group: 21.8 ± 11.8 µm). Both TiF4 and NaF application reduced mineral loss both on enamel and dentine, which could open new possibilities for a symptomatic therapy of erosions.
Correlation of Postural Blood Pressure Test and Head-Up Tilt Table Test in Patients with Vasovagal Syncope
Authors: Aydin Muhammet Ali , Mortensen Kai , Meinertz Thomas , Schuchert Andreas , Willems Stephan , Ventura Rodolfo
Published: February 2007

Background: Vasovagal syncope is triggered by complex cerebral and cardiovascular reflex mechanisms leading to general vasodilatation and bradycardia resulting in cerebral hypoperfusion. Methods: We prospectively studied the correlation of postural blood pressure test (PBT) and head-up tilt table test (TT) in patients with recurrent vasovagal syncope. Sixty-eight patients (37 male, 52.4 ± 18.6 years) were included in the trial. They were asked to participate in a PBT and a TT. Independent samples t-test, ANOVA and Fisher’s exact test were used for statistical analysis. p values <0.05 were considered statistically significant. Results: Thirty patients (44%) showed a positive TT and thirty-four patients (50%) had a positive PBT. PBT did not show any correlation with TT, although pathophysiological mechanisms in vasovagal syncope and orthostatic hypotension are supposed to be similar. Furthermore neither TT nor PBT nor their combination had any predictive value for the patient’s risk of syncope recurrence. Conclusions: TT and PBT are not correlated with each other. Both investigations cannot predict the patient’s risk of syncope recurrence.
Lipoprotein(a) and LDL Particle Size Are Related to the Severity of Coronary Artery Disease
Authors: Moon Jae-Youn , Kwon Hyuck Moon , Kwon Sung Woo , Yoon Se-Jung , Kim Jung-Sun , Lee Sung-Ju , Park Jong Kwan , Rhee Ji-Hyuck , Yoon Young Won , Hong Bum-Kee , Rim Se-Joong , Kim Hyun Seung
Published: February 2007

Background: The pathophysiological role and metabolic pathway of Lp(a) have not been clearly defined. An association between Lp(a) and oxidative low-density lipoprotein (LDL) were recently reported. And small dense LDL (sd-LDL) were associated with circulating malondialdehyde-modified LDL. We investigated the relationships between serum Lp(a) level and LDL particle size in coronary artery disease (CAD) patients. Further, we investigated the relationships of sd-LDL and Lp(a) with the extent and severity of CAD. Methods: A total of 490 patients (mean: 60.5 ± 11.5 years old) who underwent coronary angiography to evaluate chest pain were investigated. Patients were classified into two groups, a CAD group (n = 256), who had significant stenosis observed by coronary angiogram, and a control group (n = 234), who had normal, or minimal coronary arteries. CAD severity was measured by Gensini scores. The distribution of the LDL subfraction was analyzed using a Quantimetrix Lipoprint LDL System. Results: The serum Lp(a) concentration was correlated with the fraction of sd-LDL (r = 0.193, p < 0.001) and mean LDL size (r = 0.160, p = 0.003). The Lp(a) level and mean LDL particle size were significantly correlated with a high Gensini score. LDL particle size in the CAD group was smaller than in the control group (26.74 ± 0.64 vs. 26.43 ± 0.93 nm, p < 0.001). The Gensini score was significantly higher in small LDL with high Lp(a) level groups. Conclusion: The positive correlation of the level of Lp(a) and sd-LDL fraction were demonstrated. The mechanism of this association is not clearly defined; we can suggest that it may stem from the individual atherogenic condition that linked to increased oxidative stress. Both increased Lp(a) and sd-LDL fraction were correlated with the severity of CAD.
Long-Term Effects of Atrial Synchronous Ventricular Pacing on Systolic and Diastolic Ventricular Function in Patients with Normal Left Ventricular Ejection Fraction
Authors: Chiladakis John A. , Koutsogiannis Nikolaos , Kalogeropoulos Andreas , Alexopoulos Dimitrios
Published: February 2007

Background: Atrial synchronous right ventricular pacing (VP) may compromise ventricular function in patients undergoing pacemaker implantation for atrioventricular block. We assessed the usefulness of tissue Doppler imaging (TDI) and color M-mode echocardiography in evaluating patients with VP, and examined the long-term effects of VP on ventricular function by echocardiographic indices and B-type natriuretic peptide (BNP) measurements. Methods: We studied 60 clinically stable elderly dual-chamber pacemaker recipients (mean age: 74 ± 9 years) who had normal left ventricular (LV) systolic function and on the long term the same cardiac rhythm, either intrinsic normal ventricular activation (IA) (n = 20), or VP (n = 40). Results: Paced patients, compared to patients with IA, had decreased stroke volume (p < 0.05) and a more depressed relaxation pattern, as indicated by decreased peak early mitral velocity (E)/peak atrial contraction velocity ratio and tissue Doppler imaging (TDI)-early transmitral diastolic velocity (Ea) measures (p < 0.05). Both groups presented similar BNP levels and LV filling pressures, as assessed by E/Ea and E/early diastolic transmitral flow propagation velocity. In VP patients, age (β = 0.31), Ea (β = –0.28) and E/Ea (β = 0.32) emerged as independent predictors of BNP levels. Conclusions: VP is associated with reduced LV systolic function and signs of impaired relaxation. Elevated BNP levels in elderly VP patients with normal ejection fraction may be predicted by TDI signs of LV diastolic dysfunction.
Prolonged Postpartum Urinary Retention: The Importance of Asking the Right Questions at the Right Time
Authors: Humburg Joerg , Holzgreve Wolfgang , Hoesli Irene
Published: February 2007

The pathophysiology of postpartum urinary retention (PUR) is still unclear. The prevalence rate varies with the definition used and the literature discusses various risk factors. Bladder catheterization is the treatment of choice, but the best way to do it is not ascertained. Long-term sequelae seem to be rare. There are no widely accepted preventive measures. Our 2 cases illustrate that it is important to prevent PUR not only by avoiding the known risk factors, but also by additionally asking for signs of voiding dysfunction postpartum.
ACP1 and Th Class of Immunological Disease: Evidence of Interaction with Gender
Authors: Gloria-Bottini F. , Bottini N. , Renzetti G. , Bottini E.
Published: February 2007

Background: Data collected by our group in the past years indicate a relationship between ACP1 genetic polymorphism and susceptibility/resistance to immunological diseases. Recent observations suggest that through modulation of ZAP-70 activity, the enzyme may influence T cell activation. In view of the current interest in gender differences in autoimmune diseases we reviewed our data to enlighten possible effects of gender on the relationship between ACP1 and class of immunological disease. Methods: We studied three samples of subjects with allergic disorders of a total of 299 subjects, 71 subjects with Crohn’s disease and 188 children with type 1 diabetes. Three-way contingency tables were analyzed by a log linear model and two-way contingency tables by χ2 test. Results: There is an association between ACP1 and allergy (Th2 class) that depends on gender: the presence of the ACP1*A allele seems to make females more susceptible to allergic manifestations as compared to males. ACP1 is also associated with Crohn’s disease and type 1 diabetes: the relationship between this class (Th1) of immunological diseases and ACP1 depends on gender. The presence of *A allele seems to make females less susceptible to this class of diseases as compared to males. Conclusions: The ACP1*A allele which is associated with low ACP1 activity appears responsible for a complex relationship involving gender, ACP1 and Th1/Th2 orientation. Low ACP1 activity influencing ZAP-70 activity and in turn T cell activation seems to have opposite effects on Th1/Th2 orientation depending on gender.
Reproducibility of Renal Function Measurements in Adult Men with Diabetic Nephropathy: Research and Clinical Implications
Authors: Agarwal Rajiv
Published: February 2007

Background/Aim: Measurement of the renal function is critical to follow progression of kidney disease. Short-term and long-term variabilities in these measurements have significant impacts on clinical decision making and clinical trials. The goal of this study was to describe the variability in these measurements and to calculate minimum sample size estimates over varying time frames for clinical trials. Methods: We studied 44 elderly men with diabetic nephropathy who participated in a clinical trial. Glomerular filtration rate and renal plasma flow were measured by continuous infusion technique with five urine collection periods on two occasions 4 months apart. Protein and creatinine excretion rates were measured in the same specimens. In addition, two consecutive 24-hour specimens every month for 4 months were collected to analyze urine protein, creatinine, urea nitrogen, and electrolytes. A hierarchical random effects model was used to analyze the reproducibility from hour to hour, from day to day, and from month to month. Results: A total of 824 urine specimens were analyzed, of which 412 constituted specimens collected in the short term and 412 were 24-hour urine collections. Hour-to-hour variation accounted for 45% for urinary clearance of iothalamate, but for only 0.5% of the variability in plasma clearance of iothalamate. Day-to-day variability in 24-hour urinary excretion rates for creatinine was 46% and for protein 10%. Month-to-month variability in 24-hour excretion rates for creatinine was 11% and for protein 19%. The urine protein/creatinine ratio had a day-to-day variability of 2% and a month-to-month variability of 19%. Sample size requirements can be reduced by correcting for urine creatinine for some but not all urinary analytes. Conclusions: In nephrotic men with diabetic nephropathy, the coefficient of variation in the month-to-month protein excretion rate is 36%. Approximately 28 patients in each arm of two groups are needed to detect a difference in protein excretion rate of 28% (1 g/day in this study). The coefficient of variation in plasma iothalamate clearance over 4 months is 16%. To detect a 10% change in glomerular filtration rate between two groups, 44 patients per group are needed. To be deemed statistically significant, a change in daily protein excretion rate of at least 72% over month(s) is needed in individual patients.
Computed-Tomography-Directed Stereotaxis for Movement Disorder with Postoperative Magnetic Resonance Imaging Confirmation
Authors: Lehman R.M. , Hill R.P.
Published: February 2007

Movement disorders may respond dramatically to properly placed lesions in thalamic and subthalamic areas. Proper location of lesions may be verified post-operatively by magnetic resonance imaging (MRl). Herein is reported a case of stereo-tactically placed bilateral lesions under computed tomography control using the Leksell apparatus, with successful clinical outcome, and the verification of lesion placement by subsequent MRI images.
Age-Dependent Changes of Short-Latency Somatosensory Evoked Potentials in Healthy Adults
Authors: Adler G. , Nacimiento A.C.
Published: February 2007

Age-dependent changes of short-latency somatosensory evoked potentials following median nerve stimulation in humans were investigated in two groups of healthy adults aged 20–30 and 50–60 years. Normative values for both age groups are given. Compared to the younger group, in the older one P27 latency and N20–P27 interpeak latency were about 2 ms longer, and P27–N35 and P27–P45 interpeak latencies were significantly decreased. These findings suggest that N20 and P27 are generated by different structures and that the subsequent components do not depend on P27.
Reexamining the Claim of Public Authority Efficacy
Authors: Bourdeaux Carolyn
Published: February 2007

Public authorities, a form of special purpose government, have often been associated with an effective, if authoritarian, implementation of public policy objectives. In the late 1980s, a group of counties in New York State made a choice about whether or not to create a public authority to site and develop an incinerator or landfill. Although the practitioners who created the public authorities expected them to perform well in a contentious political setting, a survey of the state indicates that the public authorities actually completed very few projects. This finding holds even controlling for key task and environmental variables.
The hospitable city: social relations in commercial spaces
Authors: Bell David
Published: February 2007

Recent theoretical discussions of the ‘spaces of hospitality’ have remained largely abstract, and have also ignored the commercial hospitality industry. At the same time, commercial hospitality is becoming increasingly important for the branding and promoting of cities. This paper highlights the connection between urban regeneration, commercial food and drink spaces, and the idea of the ‘hospitable city’ as it is conceived in both theoretical writings and in accounts of urban regeneration. The paper highlights the work of hospitality in the commercial sector, but also argues that commercial hospitality should not be seen as merely calculative, instrumental, economic exchange.
The philosophy, nature and practice of forensic sediment analysis
Authors: Morgan Ruth M. , Bull Peter A.
Published: February 2007

The rapidly expanding field of forensic geoscience derives its roots from nineteenth- and early twentieth-century scientists who both influence and are influenced by literature and fictional writing. Forensic geoscience borrows much, but not all, of its precepts from geological and geomorphological analytical techniques. Fundamental differences exist between forensic geoscience and its sister disciplines, fundamental enough to make the unwary geoscientist succumb to philosophical and practical pitfalls which will not only endanger the outline of their report, but may well indeed provide false-negative or false-positive results leading to contrary or inaccurate conclusions. In the law, such outcomes have devastating and untenable consequences. Forensic geoscience requires techniques of exclusion rather than inclusion and an acknowledgement that analytical techniques may be diagnostic only in very specific situations. Whether analysis of the ubiquitous or the exotic component is chosen, acknowledgement of the need for samples to be representative is required. The presentation of false-positive results or the lack of identification of sample ‘mixing’ is prerequisite to the application of statistical tests which must be applied in the most careful manner. The realization of the limitations of the technique requires, wherever possible, conjunctive analysis by other truly independent techniques. While personal opinion derives from experience, there is no place for assumption. Research papers in forensic geoscience are not submitted to be speculative or challenging as may be the case in many fields of geomorphology and geology. There is no place for conjecture in forensic geoscience.
Has the climate become more variable or extreme? Progress 1992-2006
Authors: Nicholls Neville , Alexander Lisa
Published: February 2007

In 1990 and 1992 the Intergovernmental Panel on Climate Change (IPCC), in its first assessment of climate change and its supplement, did not consider whether extreme weather events had increased in frequency and/or intensity globally, because data were too sparse to make this a worthwhile exercise. In 1995 the IPCC, in its second assessment, did examine this question, but concluded that data and analyses of changes in extreme events were ‘not comprehensive’and thus the question could not be answered with any confidence. Since then, concerted multinational efforts have been undertaken to collate, quality control, and analyse data on weather and climate extremes. A comprehensive examination of the question of whether extreme events have changed in frequency or intensity is now more feasible than it was 15 years ago. The processes that have led to this position are described, along with current understanding of possible changes in some extreme weather and climate events.
Anti-plane Yoffe Moving Crack Problem in Isotropic Functionally Graded Materials
Authors: Xu Hong Min , Yao Xue Feng , Feng Xi Qiao , Yeh Hsien Yang
Published: February 2007

A finite length Yoffe crack with specified anti-plane shear displacements in an infinite strip made by isotropic functionally graded material (FGM) is studied. Based on exponential variation of the shear modulus and the mass density in FGM, both stress and displacement fields are derived by means of the Fourier-transform method and dual-integral equations. The relationships between the dynamic stress intensity factors, crack moving-velocity, graded parameter and crack length are analyzed. The solution can be reduced to the case of dynamic problems in isotropic homogeneous materials, and shows identical results as well.
Thermal Study of Enhanced Plastic Ball Grid Array Package with Flat Heat Spreader
Authors: Huang T. P. , Wu G. H.
Published: February 2007

Three-dimensional finite element simulations are performed to study the thermal performance of a thermally enhanced plastic ball grid array (EPBGA) package with a flat heat spreader adhered to the top surface of the package. Variables available for modification during simulation include heat spreader thickness, heat spreader conductivity and airflow. Specific study is made of the relative effects on thermal resistance of variation of heat spreader conductivity (from 0 to 350 W/m.K), heat spreader thickness (from 0 to 5.5 mm) and airflow speed (from 0 to 3 m/s). Improved thermal performance by use of a heat spreader is confirmed and dangerous package hot spots are minimized. Increasing the thermal conductivity of the heat spreader is found significant at levels up to around 100 W/m.K, but beyond this value the thermal performance improvement is negligible. Increasing heat spreader thickness is found to have a positive effect on thermal performance, but over the range (thickness >0.2 mm) the improvement is small. Increasing the airflow has a positive effect on thermal performance, but again the level of improvement decreases as the airflow increases.