bluuebunny/crossref_metadata_2025 huggingface dataset:
High Frequency Deep Brain Stimulation in the Hippocampus Modifies Seizure Characteristics in Kindled Rats
Authors: Wyckhuys Tine , De Smedt Tim , Claeys Pieter , Raedt Robrecht , Waterschoot Liesbeth , Vonck Kristl , Broecke Caroline Van den , Mabilde Cyriel , Leybaert Luc , Wadman Wytse , Boon Paul
Published: March 2007

Summary:  Purpose: This experimental animal study evaluates the effect of high frequency deep brain stimulation (HFS DBS) on seizures in the Alternate Day Rapid Kindling model for temporal lobe epilepsy (TLE). The target for HFS is the hippocampus, as this structure is often presumed to be the seizure focus in human TLE.

Methods: Rats (n = 12) were fully kindled in the hippocampus according to the Alternate Day Rapid Kindling protocol. Characteristics of the evoked afterdischarges (AD) were determined in the baseline period using AD threshold, AD latency, and AD duration as parameters. Rats were divided into a treated group (n = 7) that received 130 Hz HFS for 1 week, and a control group (n = 5) that did not receive HFS. Rats were retested in the following week. After 1 additional week of rest, the HFS group was continuously stimulated again for 1 week, during which AD evoked by kindling stimuli were characterized again.

Results: HFS had a direct effect on evoked AD: during HFS, it increased AD threshold to 203 ± 13% of controls (p < 0.01) and increased AD latency to 191 ± 19% (p < 0.05). It decreased AD duration to 71 ± 9% (p < 0.05) of controls. The effect outlasted the HFS stimulation as in the week following HFS similar differences, but smaller in size, could still be established.

Conclusion: Continuous HFS (130 Hz) in the hippocampus of epileptic rats modulates the characteristics of evoked AD in a way that reflects a reduction in excitability of the target region.
Small Human Hepatocytes in Rotary Culture for Treatment of Alcohol Addicts? A Pilot Study
Authors: Pavlic Marion , Libiseller Kathrin , Hermann Martin , Hengster Paul , Margreiter Raimund , Wurm Martin
Published: March 2007

Background: Current approaches to support alcohol addict and/or benzodiazepine‐treated patients with liver failure include culturing human cells to take over basic metabolic functions for a certain time.

Methods: Small human hepatocytes (SH) were grown in a rotary cell culture system, and their potential to metabolize alcohol and the benzodiazepines oxazepam and diazepam was evaluated. Control experiments were performed with SV40‐immortalized HEP cells and cell respective drug‐free media.

Results: Our results show that SH in rotary culture are able to metabolize ethanol in reasonable amounts compared with evaporation controls (p<0.01). Moreover, SH are also able to metabolize oxazepam and diazepam which proves their ability to perform conjugation and the presence of functional cytochrome P450 enzymes. Basic metabolic activities such as glucose consumption, albumin and urea production are not significantly influenced by the drugs used, which is a precondition for clinical use of these cells. Significantly increased lactate dehydrogenase release indicates enhanced cell death in cultures of SH incubated with either ethanol (p<0.05) or diazepam (p<0.005), but stable viability at or above 90% suggests that cell proliferation is able to keep up with drug‐induced cell death.

Conclusion: Our preliminary study provides evidence that SH are basically suited to support alcohol‐abusing and/or benzodiazepine‐treated patients undergoing liver failure.
Ethanol‐Associated Cues Produce General Pavlovian‐Instrumental Transfer
Authors: Corbit Laura H. , Janak Patricia H.
Published: March 2007

Background: Conditioned stimuli are thought to play an important role in maintaining ethanol use and inducing relapse. Therefore, understanding the mechanisms through which such stimuli trigger ethanol seeking is of interest in the study and treatment of alcoholism.

Methods: This series of experiments examined the impact of ethanol‐associated cues on ethanol‐seeking behavior using a Pavlovian‐instrumental transfer design. Rats received Pavlovian training in which an auditory stimulus predicted ethanol (10%) delivery. In a separate instrumental training phase, animals were trained to press a lever for ethanol. In the test phase, the impact of the stimulus on instrumental performance was assessed in extinction by presenting the stimulus while animals were free to perform the lever‐press response. Experiment 2 assessed the selectivity of the transfer effect; rats received training with 2 auditory stimuli which predicted either ethanol or sucrose (2%) delivery and were trained to perform 2 instrumental responses, one earning ethanol and the other earning sucrose. Finally, Experiment 3 examined the selectivity of PIT using 2 natural rewards (sucrose and polycose).

Results: The results from Experiment 1 show that ethanol supports excitatory conditioning and that ethanol‐associated cues facilitate instrumental performance for ethanol. When the selectivity of the transfer effect was examined in Experiment 2, the ethanol‐paired stimulus was found to have a general excitatory effect on reward‐seeking behavior, affecting both ethanol‐directed and sucrose‐directed responding equally. In contrast, the sucrose‐paired stimulus had a selective effect, elevating sucrose‐directed responding only. Experiment 3 confirms that selective transfer is observed when 2 natural rewards are used to reinforce responding.

Conclusions: These data provide further evidence that ethanol‐associated cues can drive ethanol‐seeking behaviors. Because ethanol‐associated cues also enhanced seeking behavior for a nonalcohol reward, these results additionally suggest that the modulation of reward‐directed behaviors by cues associated with ethanol versus natural rewards may rely on different behavioral and neural mechanisms.
A Pilot Double‐Blind Treatment Trial of Memantine for Alcohol Dependence
Authors: Evans Suzette M. , Levin Frances R. , Brooks Daniel J. , Garawi Fatima
Published: March 2007

Background: There is growing evidence that N‐methyl‐d‐aspartate (NMDA) receptor antagonists may have potential for the treatment of alcohol disorders. Memantine is a selective noncompetitive NMDA receptor antagonist that has been shown to decrease alcohol craving in moderate drinkers. This 16‐week double‐blind outpatient pilot clinical trial determined if memantine was more effective than placebo at reducing alcohol use in actively drinking alcohol‐dependent patients.

Methods: Forty‐four treatment‐seeking alcohol‐dependent individuals were enrolled, with 34 patients stratified to either the memantine group (n=19; maximum dose of 40 mg/d) or the placebo (PBO; n=15) group. The primary outcome measures were related to alcohol use (average drinks per day, average drinks per drinking day, percentage of heavy drinking days, and percentage of days abstinent) based on the timeline follow‐back (TLFB). Secondary outcome measures included the Obsessive Compulsive Drinking Scale, Clinical Global Impression ratings, and γ‐glutamyltransferase (GGT), a biomarker of recent alcohol use. To enhance retention, patients received voucher incentives for clinic attendance.

Results: Of those randomized, approximately 80% (27) completed the entire 16‐week trial. Longitudinal analysis of drinks per day and drinks per drinking day showed a significant reduction in alcohol use, but no difference between the 2 groups. Further, the percentage of heavy drinking days indicated that both groups showed a significant decrease in drinking behavior, but there was significant treatment effect in favor of the PBO group. Similarly, for the percentage of days abstinent, the PBO group achieved a significantly greater percentage of days abstinent at a faster rate than the memantine group. Lastly, the memantine group reported a greater number of side effects compared with the PBO group, such that 26% of patients had their drug dose decreased or discontinued due to memantine‐related side effects.

Conclusions: The results of this double‐blind placebo‐controlled pilot trial do not support the use of memantine for the treatment of actively drinking alcohol‐dependent patients. However, voucher incentives did facilitate retention.
Ideology and Voter Preferences as Determinants of Financial Globalization
Authors: Quinn Dennis P. , Toyoda A. Maria
Published: March 2007

We propose that the global spread of ideas affects international economic openness policies, and that to omit ideology as an explanatory variable for economic globalization is to risk omitted variable bias. Using voting data, we create measures of global ideology regarding economic openness and propose that changes in both global and domestic ideology influence how open or closed to international finance an economy is. We also test other influences on liberalization, including proposed state‐centered diffusion mechanisms. Using PCSTS and system‐GMM models, we estimate the determinants of change in international capital account regulation for 82 countries, 1955 to 1999. We thereby examine diffusion of both liberalizations (1950s and 1990s) and closures (1960s and 1970s). Changes in both global and domestic ideology robustly influence liberalization and closure. The capital account policies of neighboring countries (positively) and of the leading economies (negatively) also influenced a country's capital account liberalization.
Sanctions, Signals, and Militarized Conflict
Authors: Lektzian David J. , Sprecher Christopher M.
Published: March 2007

Economic sanctions are frequently used as a tool of foreign policy, described by some as falling between diplomacy and military force. An important question regarding the use of sanctions is whether they can function as an alternative to military force by demonstrating the sender's resolve and making military force unnecessary, or if their use tends to result in an increased probability that military force will be used. Based on a theory of sanctions as costly signals, the authors develop and test hypotheses regarding the relationship between sanctions and military force. The results show that after a sanction occurs, there is a significantly increased probability of a use of military force. Democracies, because of their propensity to tie their hands with audience costs, while at the same time facing domestic pressure to devise sanctions to be costless to the sender, are highly likely to be involved in a militarized dispute after using sanctions.
Ocular findings in Norwegian patients with ataxia‐telangiectasia: a 5 year prospective cohort study
Authors: Riise Ruth , Ygge Jan , Lindman Carl , Stray‐Pedersen Asbjørg , Bek Toke , Rødningen Olaug Kristin , Heiberg Arvid
Published: March 2007

Purpose:  To describe the outcome of ophthalmologic examination of 10 Norwegian children with ataxia‐telangiectasia (AT) followed through 5 years.

Methods:  Ten Norwegian patients with AT aged 2–22 years (three females, seven males) were examined. The diagnosis was confirmed clinically as well as with molecular genetic studies. Conventional ophthalmologic examination was performed and supplemented by photographs of the conjunctiva, video recordings and registration of eye motility in five consecutive years. Additionally conjunctival biopsies were performed at the end of the follow‐up period.

Results:  General ataxia was usually detected when the child started to walk. All children over the age of 4 years had abnormal saccade movements, a form of ocular motor apraxia. Conjunctival telangiectasias were mostly visible at 4–5 years, primarily within the palpebral fissure. Immunohistochemical examination of conjunctival biopsies showed an increased number of cross‐sections of blood vessels and neurons surrounded by glial tissue. There was a tendency to slightly earlier onset of conjunctival telangiectasias in the patients homozygous for a founder mutation compared with the other patients.

Conclusion:  The diagnosis of AT can be supported at preschool age by the onset of ocular motor apraxia and conjunctival telangiectasias. The findings become more prominent with age. The conjunctival telangiectasias seem to appear slightly earlier in the patients who are homozygous for a Norwegian founder mutation than in the rest of the patients.
Hypoalbuminemia is Also a Marker of Fluid Excess Determined by Bioelectrical Impedance Parameters in Dialysis Patients
Authors: Cigarran Secundino , Barril Guillermina , Cirugeda Antonio , Bernis Carmen , Aguilera Abelardo , Sanz Paloma , Herraez Isabel , Alegre Laura , Selgas Rafael
Published: March 2007

Abstract:  Hypoalbuminemia may be secondary to volume expansion conditions and an independent risk factor for cardiovascular disease. Bioelectrical impedance analysis (BIA) is an accurate, non‐invasive method to measure body composition, especially the water compartments in humans. The aim of this cross‐sectional study is to evaluate the relationship between serum albumin concentration (SA) and hydration state measured by whole BIA. The study investigated 108 non‐selected patients (73 on hemodialysis, 35 on peritoneal dialysis) with a mean age of 61.4 ± 15.6 years, 42.7% of whom were female. The patients were allotted to groups according to their SA: Group 1, ≤3.5 g/dL; Group 2, 3.6–4.0 g/dL; and Group 3, >4.0 g/dL. The BIA parameters used included: total body water, intracellular water (ICW), extracellular water (ECW), phase angle (PA), body cell mass (BCM), ICW/ECW ratio and ICW/ECW ratio patients/controls (fluid index). Seventy‐five healthy volunteers formed the control group. A strong positive correlation was found between the PA and fluid index (r 2 = 0.993, P < 0.001), as well as between the PA and SA (r = 0.386, P < 0.001), and the ICW/ECW ratio and SA (r = 0.227, P < 0.001). The ECW was negatively correlated with SA (r = −0.330, P < 0.001). Every 0.1 g/dL decrease in SA was associated with a 0.33 L increase in ECW. Group 1 patients had lower reactance (P = 0.006), PA (P < 0.001), BCM (P = 0.012), fluid index (P < 0.001) and ICW/ECW ratio (P = 0.015), and an increased ECW (NS) than groups 2 and 3. We conclude that hypoalbuminemia is also a marker of fluid excess. The SA is associated to the fluid index and the PA allows assessment of the dry weight and its variations in an individualized manner in dialysis patients.
A Case Report of the Therapeutic Effect of Cryofiltration in a Patient With Glucocorticoid‐Resistant Ulcerative Colitis
Authors: Ohkawara Tatsuya , Saito Masao , Nakagawa Souichi , Ohizumi Hiroko , Tamaki Toru , Yonekawa Motoki , Takeda Hiroshi , Asaka Masahiro , Nishihira Jun , Kawamura Akio
Published: March 2007

Abstract:  Ulcerative colitis (UC) is characterized by chronic inflammation of the colon and its cause and pathogenesis have not been fully clarified. Although UC is treated with various drugs, including 5‐amino‐salycilate and glucocorticoids, some patients are resistant to them. It was recently reported that apheresis, such as leukocytapheresis and granulocytapheresis, improves intestinal inflammation in refractory cases of UC. On the other hand, cryofiltration, in which plasma apheresis is used to remove immunoglobulin and immune complexes, has been used for the treatment of autoimmune diseases. We herein report a case of glucocorticoid‐resistant UC successfully treated with cryofiltration. Interestingly, the level of interleukin‐10 (IL‐10) in the patient's serum was markedly increased after eight sessions of cryofiltration. This suggests that cryofiltration suppresses intestinal inflammation, in part via up‐regulation of IL‐10.
Effects of Lowering Dialysate Calcium Concentration on Mineral Metabolism and Parathyroid Hormone Secretion: A Multicentric Study
Authors: Lezaic Visnja , Pejanovic Svetlana , Kostic Sveta , Pljesa Stevo , Dimkovic Nada , Komadina Ljiljana , Jovanovic Dragan , Marinkovic Jelena , Djukanovic Ljubica
Published: March 2007

Abstract:  This prospective study was conducted with the aim of examining the efficacy of lowering dialysate calcium (dCa) in order to: (i) stimulate bone turnover in hemodialysis patients with biochemical signs of adynamic bone disease (ABD) (hypercalcemia, normal alkaline phosphatase and intact parathyroid hormone (iPTH) <150 pg/mL); and (ii) diminish hypercalcemia in patients with secondary hyperparathyroidism (sHPT) (hypercalcemia, high alkaline phosphatase and iPTH > 400 pg/mL), thus permitting the use of calcium‐containing phosphorus binders and vitamin D metabolites. Patients were divided into: an ABD–treated group (24 patients), a sHPT–treated group (18 patients), an ABD–control group (12 patients) and a sHPT–control group (11 patients). For the ABD‐ and sHPT–treated patients, hemodialysis was conducted with dCa 1.5 mmol/L for three months and then with dCa 1.25 mmol/L for an additional three months, while in the control groups hemodialysis was conducted with dCa 1.75 mmol/L during the entire study. Reduction of dCa in patients with ABD caused a slight but insignificant decrease of Ca, but a significant and permanent increase of bone‐specific alkaline phosphatase and intact parathyroid hormone level serum levels. Reduction of dCa in patients with sHPT slightly but insignificantly decreased Ca and intact parathyroid hormone level values. Nevertheless, this enabled the calcium‐based phosphate binder dose to be raised and vitamin D3 metabolites to be introduced. Logistic regression analysis indicated that milder bone disease (both ABD and sHPT) was associated with more the favorable effect of dCa reduction. Thus, low dCa stimulated parathyroid glands and increased bone turnover in ABD patients, and enabled better control of mineral metabolism in sHPT patients.
A Case Report of the Effect of Acetate‐Free Biofiltration on Arrhythmia in a Hemodialysis Patient
Authors: Shiohira Shunji , Kikuchi Kan , Yoshida Takumi , Tsukada Misao , Nitta Kosaku , Akiba Takashi
Published: March 2007

Abstract:  This case report concerns a hemodialysis patient with arrhythmia. A 71‐year‐old man had undergone hemodiafiltration (HDF) for 17 years for the treatment of chronic glomerulonephritis. Because of repeated heart failure and chronic atrial fibrillation, he could not continue receiving standard hemodialysis, which is hemodialysis using bicarbonate dialysate including a small amount of acetate. Neither elevating the sodium concentration of the dialysate nor changing the HDF modality was effective. Acetate‐free biofiltration (AFB) was initiated and this treatment dramatically ameliorated the patient's intradialytic acute hypotension and arrhythmia. The patient's quality of life subsequently improved and his scores on the Short‐form 36 questionnaire (a measure of quality of life) increased. AFB is an HDF technique based on the continuous postdilution infusion of a sterile isotonic bicarbonate solution. Previous studies have reported that acetate induces chemical cytokines and vasodilator substances. AFB may be effective for preventing acute hypotension and arrhythmia during dialysis and may improve quality of life, including mental status.
Evaluation of Markers to Estimate Volume Status in Hemodialysis Patients: Atrial Natriuretic Peptide, Inferior Vena Cava Diameter, Blood Volume Changes and Filtration Coefficients of Microvasculature
Authors: Yashiro Masatomo , Kamata Tadashi , Yamadori Noriko , Tomita Mayumi , Muso Eri
Published: March 2007

Abstract:  Relationships among five markers of volume status—cardio–thoracic ratio (CTR), atrial natriuretic peptide (ANP), inferior vena cava diameter at quiet expiration (IVCe), blood volume change (▵BV/TUF) during ultrafiltration and filtration coefficients of microvasculature (Lpst)—were investigated. Fifty stable hemodialysis patients were enrolled. The CTR was measured before hemodialysis (HD), and ultrasonic measurement of IVCe and sample collection for ANP were performed shortly after HD. Lpst and ▵BV/TUF were calculated using a CRIT‐LINE monitor. Overhydrated patients determined by each marker (OVERctr, OVERivc, OVERanp, OVERlp and OVERbv) were compared. The agreement of volume status determined by each marker was assessed by κ value, and the sensitivity and specificity of each marker to distinguish overhydrated patients were analyzed by a receiver‐operating characteristic (ROC) curve. IVCe, ANP, ▵BV/TUF and Lpst, significantly correlated with each other. The correlation coefficients of Lpst with IVCe, ANP and ▵BV/TUF were higher than the others. The κ value between ANP and Lpst was the highest. OVERanp was the highest, then OVERlp, OVERivc and OVERbv, in this order. The OVERlp and OVERivc patients were completely included in OVERanp. All patients, except one OVERbv patient, were included in OVERlp. The relatively high distinguishing ability of Lpst was demonstrated by ROC analysis. These results suggest that the determination of overhydration solely by ANP was an overestimation and by ▵BV/TUF was an underestimation. The relatively high correlation coefficients of Lpst with other markers, as well as its distinguishing ability, suggest that Lpst fluctuates in close relation to other markers.
Three Secondary Reference Materials for Lithium Isotope Measurements: Li7‐N, Li6‐N and LiCl‐N Solutions
Authors: Carignan Jean , Vigier Nathalie , Millot Romain
Published: March 2007

The CRPG (Nancy, France) has prepared secondary reference materials for Li isotope measurements by mixing 7Li or 6Li spikes and either L‐SVEC or IRMM‐016 certified reference materials to produce solutions having a known Li concentration and isotopic composition. The Li7‐N and Li6‐N solution samples (1.5 mol l−1 HNO3) have nominal δ7Li isotopic compositions of 30.1‰ and ‐9.7‰ respectively relative to L‐SVEC and concentrations of 100 mg l−1. Repeated measurement of these samples using the QUAD‐ICP‐MS at the CRPG yielded δ7Li of 30.4 ± 1.1‰ (n = 13) and ‐8.9 ± 0.9‰ (n = 9) at the 2s level of confidence. An additional LiCl‐N solution was measured and yielded a delta value of 9.5 ± 0.6‰ (n = 3). Identical results were obtained at the BRGM (Orléans, France) from determinations performed with a Neptune MC‐ICP‐MS (30.2 ± 0.3‰, n = 89 for the Li7‐N, ‐8.0 ± 0.3‰, n = 38 for the Li6‐N and 10.1 ± 0.2‰, n = 46 for LiCl‐N at the 2s level of confidence). The deviation of measured composition relative to the nominal value for the Li6‐N solution might be explained by either contamination during preparation or an error during sample weighing. These secondary reference materials, previously passed through ion exchange resin or directly analysed, may be used for checking the accuracy of Li isotopic measurements over a range of almost 40‰ and will be available to the scientific community upon request to J. Carignan or N. Vigier, CRPG.
Predicting the Optical Performance of the Space Interferometry Mission Using a Modeling, Testing, and Validation Methodology
Authors: Basdogan Ipek , Elias Laila Mireille , Dekens Frank , Sievers Lisa
Published: March 2007

This paper presents the modeling, testing, and validation methodologies developed to predict the optical performance of the Space Interferometry Mission (SIM) at the Jet Propulsion Laboratory (JPL). The modeling methodology combines structural, optical, and control system design within a common state space framework and incorporates reaction wheel assembly (RWA) disturbances to evaluate the end-to-end performance of the system requirements. The validation methodology uses the Micro-Precision Interferometer (MPI) testbed, which is a ground-based, representative hardware model of SIM. In this study, the integrated model of the MPI testbed was used to calculate the transfer functions from RWA input to optical performance output. The model-predicted transfer functions were compared with the MPI testbed measurements, and the accuracy of the integrated model was quantified using a metric that was based on output power of the transfer functions. The RWA disturbances were then propagated through the modeled and measured transfer functions to predict the optical performance of the MPI testbed. This method is called the “decoupled disturbance analysis” and relies on the “blocked” RWA disturbances, measured with the RWA hardmounted to a rigid surface. These predictions were compared with the actual (measured) optical performance of MPI, measured with the RWA mounted to MPI, to evaluate the accuracy of the decoupled disturbance analysis method. The results show that this method is not an accurate representation of the coupled boundary conditions that occurs when the RWA is mounted to the flexible MPI structure. In order to correct for the blocked RWA disturbance boundary conditions, the “coupled disturbance analysis” method was developed. This method uses “force filters” that depend on estimates of the interface accelerances of the RWA and the MPI structure to effectively transform the blocked RWA disturbance measurements into their corresponding “coupled” disturbances (the disturbances that would occur at the coupled RWA-MPI interface). Compared to the decoupled method, the coupled method more accurately predicts the system’s performance. Additionally, the RWA cross-spectral density terms were found to be influential in matching the performance predictions to the measured optical performance of MPI.
Mode Interactions and Sound Power Transmission Loss of Expansion Chambers
Authors: Lau C. K. , Tang S. K.
Published: March 2007

The mode interactions and the sound transmission loss across the expansion chambers with and without tapered sections are studied by the finite element method in the present investigation. Results from chambers with symmetrical inlet and outlet suggest lower sound power transmission loss at frequencies below that of the first symmetrical transverse chamber mode when the tapered section angle is reduced. Weak sound power transmission loss is also observed for this chamber type at frequency higher than that of the first symmetrical duct mode. Numerous high and low sound power transmission loss regions are observed between these two eigenfrequencies. Higher plane wave power transmission loss can be found at smaller tapered section angle only if one of the chamber endings is not tapered. Such chamber bears important industrial application.
Vibration of Nonhomogeneous Orthotropic Elliptic and Circular Plates With Variable Thickness
Authors: Chakraverty S. , Jindal Ragini , Agarwal V. K.
Published: March 2007

In this paper, study of nonhomogeneity as well as variable thickness in elliptic and circular orthotropic plates is undertaken. Nonhomogeneity of plate material is assumed to be a quadratic variation of Young’s modulii and density whereas shear modulus, is considered to vary linearly along both the axes. The quadratic thickness variation in orthotropic nonhomogeneous plates is also considered. Effect of variation of these parameters on vibrational characteristics are analyzed for various boundary conditions at the edges. Results are obtained using boundary characteristic orthogonal polynomials generated by using Gram-Schmidt orthogonalization procedure in Rayleigh-Ritz method.
An Adaptive Time–Frequency Representation and its Fast Implementation
Authors: Liu Bao , Riemenschneider Sherman , Shen Zuowei
Published: March 2007

This paper presents a fast adaptive time–frequency analysis method for dealing with the signals consisting of stationary components and transients, which are encountered very often in practice. It is developed based on the short-time Fourier transform but the window bandwidth varies along frequency adaptively. The method therefore behaves more like an adaptive continuous wavelet transform. We use B-splines as the window functions, which have near optimal time–frequency localization, and derive a fast algorithm for adaptive time–frequency representation. The method is applied to the analysis of vibration signals collected from rotating machines with incipient localized defects. The results show that it performs obviously better than the short-time Fourier transform, continuous wavelet transform, and several other most studied time–frequency analysis techniques for the given task.
Convection Heat Transfer in Microchannels With High Speed Gas Flow
Authors: Turner Stephen E. , Asako Yutaka , Faghri Mohammad
Published: March 2007

This paper presents an experimental investigation of convective heat transfer for laminar gas flow through a microchannel. A test stand was set up to impose thermal boundary conditions of constant temperature gradient along the microchannel length. Additionally, thin film temperature sensors were developed and used to directly measure the microchannel surface temperature. Heat transfer experiments were conducted with laminar nitrogen gas flow, in which the outlet Ma was between 0.10 and 0.42. The experimental measurements of inlet and outlet gas temperature and the microchannel wall temperature were used to validate a two-dimensional numerical model for gaseous flow in microchannel. The model was then used to determine local values of Ma, Re, and Nu. The numerical results show that after the entrance region, Nu approaches 8.23, the fully developed value of Nu for incompressible flow for constant wall heat flux if Nu is defined based on (Tw−Tref) and plotted as a function of the new dimensionless axial length, X*=(x∕2H)(Ma2)∕(RePr).
Performance of Phase Change Materials in a Horizontal Annulus of a Double-Pipe Heat Exchanger in a Water-Circulating Loop
Authors: Balikowski J. R. , Mollendorf J. C.
Published: March 2007

Phase change materials (PCMs) are used in applications where temperature regulation is important because they absorb and release a large amount of energy at a fixed temperature. In the experimental part of this investigation, PCM was placed in the annular region of a double-pipe heat exchanger with water circulated in the inside pipe. Experiments were performed in which the PCM would absorb (charge) and then release (discharge) energy at various temperatures and water flows. Two materials, Climsel 28 (C28) by Climator and microencapsulated Thermasorb 83 (TY83) by Outlast Technologies, were each tested in smooth and spined annuli to observe which configuration facilitated heat transfer. The latent heats and thermal conductivities of C28 and TY83 are 126kJ∕kg and 186kJ∕kg and 0.6W∕m∕°C and 0.15W∕m∕°C, respectively. The experimental data were analyzed to verify which PCM transferred more heat. The effect of different water flow rates on the heat transfer rate was also examined. In the theoretical part of this investigation, heat transfer theory was applied to C28 in the smooth-piped heat exchanger in order to better understand the phase change process. The presence of spined fins in the phase change material accelerated charging and discharging due to increased fin contact with the outer layers of the PCM. The spined heat exchanger charged and discharged in 180min and 120min, respectively, whereas the temperature in the smooth heat exchanger remained below the fully charged/fully discharged asymptote by about 3°C and thus failed to fully charge or fully discharge. Also, higher water flows increased heat transfer between the PCM and water. TY83 in the spined heat exchanger transferred more heat and did it faster than C28 in the spined heat exchanger. The heat transfer rate from the water to TY83 while charging was 25% greater during the transient period than in C28. While discharging, the heat transfer from TY83 to the water was about 20% greater than in C28. There was generally good agreement (±1.5°C) between theory and experimental data of C28 in the smooth-piped heat exchanger in terms of the trends of the temperature responses. The differences are expected to be a result of approximations in boundary conditions and uncertainties in how the temperature variation of the specific heat is formulated.
A New Approach to Numerical Simulation of Small Sized Plate Heat Exchangers With Chevron Plates
Authors: Jain Sanjeev , Joshi Aniruddha , Bansal P. K.
Published: March 2007

A numerical and experimental study of heat transfer and fluid flow in a single pass counter flow plate heat exchanger with chevron plates has been presented in this paper. CFD analysis of small sized plate heat exchanger was carried out by taking the complete geometry of the heat transfer surface and more realistic hydrodynamic and thermal boundary conditions. A cold channel with two chevron plates and two halves of hot channels on either side having flat periodic boundaries was selected as the computational domain. The numerical model was validated with data from experiments and empirical correlations from literature. Heat transfer and pressure drop data were obtained experimentally with water as the working fluid, in the Reynolds number range 400–1300 and the Prandtl number range 4.4–6.3.
The Effects of Film Thickness, Light Polarization, and Light Intensity on the Light Transmission Characteristics of Thermochromic Liquid Crystals
Authors: Roth Timothy B. , Anderson Ann M.
Published: March 2007

Thermochromic liquid crystal materials change their crystalline structure and optical properties with temperature, making them useful in temperature measurement applications. This paper presents the results of a study to develop a temperature measurement system that uses light transmission through thermochromic liquid crystals instead of light reflection. We painted Hallcrest R25C10W sprayable liquid crystals on a clear surface and placed it in a spectrophotometer. The amount of light transmitted at monochromatic wavelengths from 400nm to 700nm was measured for temperatures from 25°C to 55°C under conditions of nonpolarized, linearly polarized, and cross-polarized light, for three light intensity levels, and three liquid crystal layer thicknesses. As the temperature was increased the amount of light transmitted through the liquid crystal layer increased. When the liquid crystals are in their active range the transmission spectra exhibit an s-curve shape and the percent of light transmitted through the liquid crystals at a fixed temperature increases with increasing wavelength. We detected significant changes in the transmission spectra for temperatures from 27°C to 48°C, whereas when used with reflected light the thermochromic liquid crystals are useful over a significantly smaller range. As the thickness of the thermochromic liquid crystal layer increases or as the incoming light intensity decreases, the amount of light transmitted through the liquid crystals decreases. We also investigated the effects of temperature overheat on the transmission spectra and found that heating the thermochromic liquid crystals above their active range increases the amount of light transmission. However, when the liquid crystals are cooled below their active range they return to their original state. We have analyzed the spectrophotometer data in a number of ways including: (a) total amount of light transmitted, (b) amount of red, green, and blue light transmitted; and (c) spectral curve shape characteristics (peak transmission, inflection wavelength and wavelength for peak transmission) all as a function of temperature. A linear relationship exists between temperature and all of these variables which we believe can be exploited for the development of a charge coupled light camera based light transmission system for temperature measurement.
Analysis of Solid–Liquid Phase Change Under Pulsed Heating
Authors: Krishnan Shankar , Murthy Jayathi Y. , Garimella Suresh V.
Published: March 2007

Solid/liquid phase change occurring in a rectangular container with and without metal foams subjected to periodic pulsed heating is investigated. Natural convection in the melt is considered. Volume-averaged mass and momentum equations are employed, with the Brinkman–Forchheimer extension to Darcy’s law used to model the porous resistance. A local thermal nonequilibrium model, assuming equilibrium melting at the pore scale, is employed for energy transport through the metal foams and the interstitial phase change material (PCM). Separate volume-averaged energy equations for the foam and the PCM are written and are closed using a heat transfer coefficient. The enthalpy method is employed to account for phase change. The governing equations for the PCM without foam are derived from the porous medium equations. The governing equations are solved implicitly using a finite volume method on a fixed grid. The coupled effect of pulse width and natural convection in the melt is found to have a profound effect on the overall melting behavior. The influence of pulse width, Stefan number, and Rayleigh number on the temporal evolution of the melt front location and the melting rate for both the cases with and without metal foams is investigated.
Analysis of Heat Transfer Inside Flexible Thin-Film Channels With Nonuniform Height Distributions
Authors: Khaled A.-R. A.
Published: March 2007

Heat transfer inside flexible thin-film channels having nonuniform height distributions is analyzed in this work. The terminology “flexible thin film channel” is referred to a thin-film channel having two plates separated by soft elastic seals. The fluidic volume enclosed between the plates can expand due to any increase in the fluid pressure. This expansion which is determined from the height (distance between the plates) distribution is related to the pressure drop and the seals stiffness by applications of force or moment balance laws on the mobile plate. The seals stiffness parameter (S), Peclet number (Pe), dimensionless inlet height (Hi), and the aspect ratio (ε) are found to be the controlling parameters. It is found that flexible thin-film channels with flexible plates produce additional cooling over the cooling effect for those having inflexible plates. The heated plate temperature when plates are flexible is lower than that for the other case by more than 14.8% when Peε<1.0 and Hi=3.0 Moreover, the cooling effect of flexible thin-film channels is found to increase relative to rigid thin-film channels as the S and Peε decrease. Finally, it is recommended to treat flexible thin-film channels as rigid ones when SA>3.45 (inflexible plates case) or SB>10 (flexible plates case).
Reliability-Based Design Optimization of Robotic System Dynamic Performance
Authors: Bowling Alan P. , Renaud John E. , Newkirk Jeremy T. , Patel Neal M. , Agarwal Harish
Published: March 2007

In this investigation a robotic system’s dynamic performance is optimized for high reliability under uncertainty. The dynamic capability equations (DCE) allow designers to predict the dynamic performance of a robotic system for a particular configuration and reference point on the end effector (i.e., point design). Here the DCE are used in conjunction with a reliability-based design optimization (RBDO) strategy in order to obtain designs with robust dynamic performance with respect to the end-effector reference point. In this work a unilevel performance measure approach is used to perform RBDO. This is important for the reliable design of robotic systems in which a solution to the DCE is required for each constraint call. The method is illustrated on a robot design problem.
Temporal Frequency of Subthreshold Oscillations Scales with Entorhinal Grid Cell Field Spacing
Authors: Giocomo Lisa M. , Zilli Eric A. , Fransén Erik , Hasselmo Michael E.
Published: March 2007

Grid cells in layer II of rat entorhinal cortex fire to spatial locations in a repeating hexagonal grid, with smaller spacing between grid fields for neurons inmore dorsal anatomical locations. Data from in vitro whole-cell patch recordings showed differences in frequency of subthreshold membrane potential oscillations in entorhinal neurons that correspond to different positions along the dorsal-to-ventral axis, supporting a model of physiological mechanisms for grid cell responses.
Chlamydia trachomatis
Load at Matched Anatomic Sites: Implications for Screening Strategies
Authors: Michel Claude-Edouard C. , Sonnex Christopher , Carne Christopher A. , White John A. , Magbanua Jose Paolo V. , Nadala Elpidio Cesar B. , Lee Helen H.
Published: March 2007

Urethral and endocervical swabs and self-collected vaginal swabs (SCVSs) and urine specimens are all used as samples for diagnosis of urogenital infection with
Chlamydia trachomatis
. We have now determined chlamydial organism load in matched specimens from different anatomic sites and examined its relation to clinical signs and symptoms in men and women. Organism load was measured with assays based on the ligase chain reaction or real-time PCR analysis. The mean organism loads in 58 infected men were 1,200 and 821 elementary bodies (EBs) per 100 μl of sample for first-void urine (FVU) and urethral swabs, respectively (
P
> 0.05). Organism load in FVU samples or urethral swabs was positively associated with symptoms (
P
< 0.01) and clinical signs (
P
< 0.01) in men. The mean organism loads in 73 infected women were 2,231, 773, 162, and 47 EBs/100 μl for endocervical swabs, SCVSs, urethral swabs, and FVU samples, respectively (
P
< 0.001 for each comparison). Only the presence of multiple symptoms or clinical signs was associated with organism load in women. These results show that FVU is a suitable noninvasive sample type for men, given the fact that its chlamydial load did not differ significantly from that of urethral swabs. Given their higher organism load compared with FVU, SCVSs are the preferred noninvasive sample type for women.
Dissection of Double-Stranded RNA Binding Protein B2 from Betanodavirus
Authors: Fenner Beau J. , Goh Winnie , Kwang Jimmy
Published: March 2007

Betanodaviruses are small RNA viruses that infect teleost fish and pose a considerable threat to marine aquaculture production. These viruses possess a small protein, termed B2, which binds to and protects double-stranded RNA. This prevents cleavage of virus-derived double-stranded RNAs (dsRNAs) by Dicer and subsequent production of small interfering RNA (siRNA), which would otherwise induce an RNA-silencing response against the virus. In this work, we have performed charged-to-alanine scanning mutagenesis of the B2 protein in order to identify residues required for dsRNA binding and protection. While the majority of the 19 mutated B2 residues were required for maximal dsRNA binding and protection in vitro, residues R53 and R60 were essential for both activities. Subsequent experiments in fish cells confirmed these findings by showing that mutations in these residues abolished accumulation of both the RNA1 and RNA2 components of the viral genome, in addition to preventing any significant induction of the host interferon gene,
Mx
. Moreover, an obvious positive correlation was found between dsRNA binding and protection in vitro and RNA1, RNA2, and
Mx
accumulation in fish cells, further validating the importance of the selected amino acid residues. The same trend was also demonstrated using an RNA silencing system in HeLa cells, with residues R53 and R60 being essential for suppression of RNA silencing. Importantly, we found that siRNA-mediated knockdown of Dicer dramatically enhanced the accumulation of a B2 mutant. In addition, we found that B2 is able to induce apoptosis in fish cells but that this was not the result of dsRNA binding.
Elevated Expression Levels of Inhibitory Receptor Programmed Death 1 on Simian Immunodeficiency Virus-Specific CD8 T Cells during Chronic Infection but Not after Vaccination
Authors: Velu Vijayakumar , Kannanganat Sunil , Ibegbu Chris , Chennareddi Lakshmi , Villinger Francois , Freeman Gordon J. , Ahmed Rafi , Amara Rama Rao
Published: March 2007

Here, we study the temporal expression of the inhibitory receptor programmed death 1 (PD-1) on simian immunodeficiency virus (SIV) Gag-specific T cells following pathogenic SIV infection or following vaccination with a DNA/modified vaccinia virus Ankara (DNA/MVA) vaccine and simian/human immunodeficiency virus (SHIV) challenge in macaques. Following infection, the majority (>95%) of Gag-specific CD8 T cells expressed PD-1, and the level of PD-1 expression per cell increased over time. The level of PD-1 expression in lymph nodes and rectal mucosal tissue, the major sites of virus replication, was higher compared to blood. In vitro blockade of PD-1 resulted in enhanced proliferation of SIV-specific CD8 as well as CD4 T cells. In contrast, following vaccination, the majority of peak effector Gag-specific CD8 T cells expressed low levels of PD-1, and these levels decreased further as the cells differentiated into memory cells. In addition, following SHIV challenge of these vaccinated macaques, the level of PD-1 expression on Gag-specific CD8 T cells correlated positively with plasma viremia. These results demonstrate that SIV-specific CD8 T cells express PD-1 after exposure to antigen but downregulate expression under conditions of antigen clearance and enhance expression under conditions of antigen persistence. They also demonstrate that the level of PD-1 expression per cell rather than the presence or absence of expression plays an important role in regulating CD8 T-cell dysfunction in pathogenic SIV infection. In addition, they demonstrate that similar to HIV infection, the PD-1:PD-1 ligand inhibitory pathway is operational in pathogenic SIV infection, and the macaque/SIV model would be ideal to test the safety and therapeutic benefit of blocking this pathway in vivo.
Cytomegalovirus Infection in Gambian Infants Leads to Profound CD8 T-Cell Differentiation
Authors: Miles David J. C. , van der Sande Marianne , Jeffries David , Kaye Steve , Ismaili Jamila , Ojuola Olubukola , Sanneh Mariama , Touray Ebrima S. , Waight Pauline , Rowland-Jones Sarah , Whittle Hilton , Marchant Arnaud
Published: March 2007

Cytomegalovirus (CMV) infection is endemic in Gambian infants, with 62% infected by 3 months and 85% by 12 months of age. We studied the CD8 T-cell responses of infants to CMV following primary infection. CMV-specific CD8 T cells, identified with tetramers, showed a fully differentiated phenotype (CD28−CD62L−CD95+perforin+granzyme A+Bcl-2low). Strikingly, the overall CD8 T-cell population developed a similar phenotype following CMV infection, which persisted for at least 12 months. In contrast, primary infection was accompanied by up-regulation of markers of activation (CD45R0 and HLA-D) on both CMV-specific cells and the overall CD8 T-cell population and division (Ki-67) of specific cells, but neither pattern persisted. At 12 months of age, the CD8 T-cell population of CMV-infected infants was more differentiated than that of uninfected infants. Although the subpopulation of CMV-specific cells remained constant, the CMV peptide-specific gamma interferon response was lower in younger infants and increased with age. As the CD8 T-cell phenotype induced by CMV is indicative of immune dysfunction in the elderly, the existence of a similar phenotype in large numbers of Gambian infants raises the question of whether CMV induces a similarly deleterious effect.