bluuebunny/crossref_metadata_2025 huggingface dataset:
PSEs and the Mix of Measures to Support Farm Incomes
Authors: Hertel Thomas W.
Published: April 2007

SUMMARY AND CONCLUSIONS

In summary, the mix of support provided to agriculture does matter when PSEs are to be cut. Across‐the‐board reductions in individual components of PSEs will have different implications for output, exports, land values and employment in different countries. These differences can be systematically related to the type of instruments used to support agriculture. For example, cutting subsidies on an input such as fertilizer can result in greater long‐run reductions in output, exports and employment in agriculture than would cuts in output subsidies (of equal magnitude). These differences may make it attractive for countries engaging in partial liberalization to change the mix of subsidies, even as they reduce their aggregate PSE. In so doing, they may be able to lessen, or even eliminate, some of the deleterious effects of reduced farm support. For example, the United States could maintain the demand for farm labour, while cutting its aggregate PSE in half, by shifting the mix of farm support towards selected input subsidies. By contrast, there appears to be little incentive for substituting export subsidies for output subsidies under the ‘pure’ PSE approach proposed by Professor Tangermann et al. This is because such a switch would have to be accompanied by further reductions in budgetary outlays in order to avoid exceeding the PSE target agreed in negotiations.
BOOK REVIEWS
Authors: Barve A. G.
Published: April 2007

Dynamics and Conflict in Regional Structura1 Change—Essay in Honor of Walter Isard Volume 2

Practical Methods of Regional Science and Empirical Applications—Selected Papers of Walter Isard, Volume 2

Department of Economics Loughborough University

Export Promotion Strategies—Theory and Evidence from Developing Countries

Commonwealth Secretariat Export Market Development Division

Human Development Report 1990 for the United Nations Development Programme (UNDP) (New York and Oxford:

University of Nottingham

The World Bank and the Environment—First Annual Report Fiscal 1990, The World Bank (New York: The World Bank, 1990

London Environmental Economics Centre University College London

The European Communities' Single Market: The Challenge of 1992 for Sub‐Saharan Africa

Loughborough University
Book Reviews
Authors: Falvey Rod , Parkinson J R
Published: April 2007

Quantitative Methods, for Trade‐Barrier Analysis by SAM LAIRD and ALEXANDER YEATS. London: Macmillan 1990.

The NEW. Global Economy and the Developing Countries: Essays in International Economics and development by G. K. HELLEINER. Alder‐shot: Edward Elgar. 1990.

Pacific. Basin Developing Countries: Prospects for. the Future by MARCUS NOLAND. Washington: Institute for International Economics, 1990.

Prospects, for. the Business Sector. in Developing Countries. THE WORLD BANK. Washington (available in Britain from Microinfo Ltd, PO Box 3, Omega Park, Alton, Hampshire, GU34 2PG): International Finance Corporation. 1989.
The ‘New’ Theory of Optimum Currency Areas
Authors: Tavlas George S.
Published: April 2007

Highbrow opinion is like a hunted hare; if you stand long enough it will come back to the place it started from.

Dennis Robertson
Offshore Production and the Base of Import Taxation
Authors: Lloyd P.J.
Published: April 2007

The Scheme is designed to encourage the maximum use of Australian made fabrics which are cut or knitted to shape in Australia (Textiles, Clothing and Footwear Development Authority, 1993, p. 4).

When an Australian firm sets up production in South East Asia, it often attracts criticism because it means losing jobs to low‐cost labour in the region. However, our study shows that such criticism is not wholly justified. For many firms, offshore production is critical to establishing a long‐term position as an insider in the market and therefore is critical to exports from an Australian base.

Different methods have been used to determine origin, but none has proved totally unsatisfactory, and none is likely to do so.
Some Lessons From ‘Developing’ Countries' Trade Policy Reviews in the GATT Framework: An Enforcement Perspective
Authors: Qureshi Asif H.
Published: April 2007

It is one thing to draw up regulations for international trade, and yet another to apply them; but it is also a completely different thing to explain them fairly in a report for the contracting parties….1
THE IRREDUCIBLE ROLE OF DERIVED MARGINAL UTILITY IN DYNAMIC STOCHASTIC PROGRAMMING
Authors: Samuelson Paul A.
Published: April 2007

Abstract. Using the important case of multi‐period investing between a safe asset with a low mean return and an equity basket with a higher total return but a riskier one, this analysis demonstrates that the relevant stochastic programming involves irreducibly recursive variational relations. The “direct” Lagrange‐Chow procedure is related to the derivatives of the Bellman “indirect”’algorithms and shown to require essentially the same computations save only for standard integrations or taking of first derivatives. To demonstrate that the comparison is unchanged when a vector of control variables must be optimized in a many‐period stochastic scenario, the problem is solved for a rentier to both decide how much to save in each period and how much to put of each period's investment into risky securities.
CHINA'S RURAL INDUSTRY AND MONOPSONY: AN EXPLORATION
Authors: Dong Xiao‐Yuan , Putterman Louis
Published: April 2007

Abstract.Despite spectacular output growth and significant employment creation, recent findings suggest that China's TVEs are “under‐employing”’labour relative to the competitive benchmark. The paper reconfirms these findings on a new data set, discusses the possibility that it is caused by enterprises confronting upward‐sloping labour supply curves, and performs a preliminary test for this by regressing the estimated marginal product‐wage gaps for our enterprise sample on variables proxying for labour scarcity, labour market infrastructure, and pressure to maximize profits. The results are broadly supportive of the hypothesis.
THE ENRICHMENT OF A SECTOR (INDIVIDUAL, REGION OR COUNTRY) BENEFITS OTHERS: THE THIRD WELFARE THEOREM?
Authors: Ng Yew‐Kwang
Published: April 2007

The economic enrichment of a sector may make other sectors as a whole better or worse off. However, for the benchmark case of proportionate enrichment, other sectors tend to gain. This result is shown using offer curves, supply and demand analysis, Cobb‐Douglas utility functions, and a more general case. Allowing the enriching sector to be monopolistic does not affect the result. Semi‐economic enrichment through migration and population growth also makes others better off. Most enrichments also tend to be equalizing in their effects on others.
TAXATION AND ECONOMIC GROWTH IN NEW ZEALAND
Authors: Scully Gerald W.
Published: April 2007

Since the Second World War and until recent reforms, New Zealand has suffered from a low rate of economic growth and a high level of taxation. This paper models the relationship between taxation and economic growth and estimates the “optimal”or “growth‐maximizing” tax rate. It is found to be about half of the actual tax rate. The marginal cost of taxation in New Zealand is S2.64 for each extra dollar of taxes collected.
PRODUCTIVITY GROWTH IN APEC COUNTRIES
Authors: Chambers Robert G. , Fāure Rolf , Grosskopf Shawna
Published: April 2007

Abstract. This paper introduces a new technique for measuring productivity growth and applies it to a sample of APEC countries. The technique is based on a version of Luenberger's shortage function which generalizes Shephard's input and output distance functions.
IN SEARCH OF THE BEST BUNDLE: HILL‐CLIMBING CONSUMERS AND THE MICRODYNAMICS OF CONSUMER CHOICE
Authors: KUHN PETER
Published: April 2007

Abstract. The paper considers the consequences of hill‐climbing consumer behavior in the presence of nonconvex utility, and considers the optimal reactions of nonmyopic firms and governments to such behavior. Both firms and governments have an incentive to induce consumers to start consuming goods subject to nonconvexities by offering introductory price discounts. Monopolists appear to offer smaller introductory discounts than is optimal; competitive markets may never be able to supply such goods at all.
INTERNATIONAL TRADE AND REGIONAL DEVELOPMENT
Authors: Hazari Bharat R. , Sgro Pasquale M.
Published: April 2007

The paper considers a two‐region model of trade based on the authors’earlier (HS) model, in which two nontraded goods, one urban and one rural, were introduced into the Harris‐Todaro model. The HS framework captures the duality of the labour market, and it is argued that the HS model is suited to the purpose of regional analysis where the urban and rural agents may be in conflict as their welfare (income) may not respond in an identical manner to exogenous shocks and policy changes. The paper examines the implications of a change in capital and the terms of trade on outputs and regional incomes. It is established that in response to a terms‐of‐trade shock the prices of urban and rural nontraded goods could move in opposite directions, so structural change could also be in opposite directions. The same could also be true of welfare in the two regions.
Effect of peroxisome proliferator‐activated receptor‐α agonist (bezafibrate) on gastric secretion and gastric cytoprotection in rats
Authors: Pathak Rahul , Asad Mohammed , Jagannath Hrishikeshavan H. , Prasad Satya
Published: April 2007

The effect of peroxisome proliferator‐activated receptor‐α (PPAR‐α) on gastric secretion and gastric cytoprotection was evaluated using five different models of gastric ulcers: acetic acid‐induced chronic gastric ulcers, pylorus ligation, ethanol‐induced, indomethacin‐induced and ischemia–reperfusion‐induced gastric ulcers. Bezafibrate, a PPAR‐α agonist was administered at two different doses of 10 and 100 mg/kg body weight intraperitoneanally. Both doses of bezafibrate showed significant antiulcer effect in ethanol‐induced, indomethacin‐induced and pylorus ligation‐induced gastric ulcers. Bezafibrate increased healing of ulcer in acetic acid‐induced chronic gastric ulcer model. Both doses were also effective in preventing gastric lesions induced by ischemia–reperfusion. It was concluded that PPAR‐α activation increases healing of gastric ulcers and also prevents development of gastric ulcers in rats.
Effect of leptin on peroxidation and antioxidant defense in ethanol‐supplemented Mus musculus heart
Authors: Balasubramaniyan V. , Nalini N.
Published: April 2007

The aim of the study was to evaluate the effect of exogenous mouse leptin on ethanol‐induced cardiac toxicity in mice. Administering ethanol (6.32 g/kg body weight p.o.) to 4‐week‐old healthy mice for 45 days resulted in significantly elevated plasma levels of leptin, lactate dehydrogenase (LDH), cardiac lipid hydroperoxides (LOOH) and thiobarbituric acid reactive substances (TBARS) and significantly decreased cardiac superoxide dismutase, catalase, vitamin C, vitamin E, reduced glutathione and glutathione‐dependent enzyme levels (glutathione peroxidase and glutathione S‐transferase). Subsequent to the experimental induction of toxicity (i.e., after the initial period of 30 days) exogenous leptin was administered (230 μg/kg body weight i.p.) every alternate day for 15 days along with the daily dose of ethanol. Leptin administration to ethanol‐treated mice significantly elevated the levels of plasma leptin, LDH and cardiac LOOH, TBARS, whereas the activity of antioxidant enzymes and the concentrations of vitamins C and E were further decreased significantly. These findings were consistent with our histological observations, confirming that leptin enhances cardiac toxicity in ethanol‐supplemented mice.
Optimal Electrogram Voltage Recording Technique for Detecting the Acute Ablative Tissue Injury in the Human Right Atrium
Authors: LIN YENN‐JIANG , TAI CHING‐TAI , LO LI‐WEI , UDYAVAR AMEYA R. , CHANG SHIH‐LIN , WONGCHAROEN WANWARANG , TUAN TA‐CHUAN , HU YU‐FENG , CHIANG SHUO‐JU , CHEN YI‐JEN , CHEN SHIH‐ANN
Published: April 2007

Background: The optimal recording technique of the electrogram voltage for detecting abnormal atrial tissue remains unclear. The aim of this study was to compare the impact of various recording techniques on the electrogram voltage after the delivery of ablation therapy in the human right atrium (RA).

Material and Methods: Noncontact mapping was performed in 27 patients with typical atrial flutter (mean age = 63 ± 16, males = 20). Noncontact unipolar and bipolar electrograms were obtained before and after cavotricuspid isthmus (CTI) linear ablation. All unipolar electrograms were acquired with both wide‐band filtering (0.5–300 Hz) and narrow‐band filtering (32–300 Hz). The unipolar voltage measurements included both the peak‐to‐peak voltage and peak‐negative voltage (PNV) for both filter settings.

Results: A comparison of the electrogram voltage along the ablation line before and after the ablation demonstrated a greater reduction in the unipolar PNV with wide‐band filtering (70 ± 24%) than in any of the other recording modalities (P = 0.03). It was the most sensitive and specific recording technique to predict conduction block (cut‐off Value 0.35 mV; sensitivity = 94.4% and specificity = 80%). A comparison of the electrogram voltage between the ablated atrial myocardium and nearby nonablated myocardium showed that the unipolar PNV with the wide‐band filtering remained the most sensitive method to detect the acute ablative tissue injury, whereas the peak‐to‐peak bipolar voltage was the most specific method.

Conclusion: The noncontact unipolar electrogram using the PNV with wide‐band filter settings (0.5–300 Hz) provided the most sensitive recording technique for detecting acute ablative tissue injury.
Rapid Ablation for Atrial Flutter by Targeting Maximum Voltage—Factors Associated with Short Ablation Times
Authors: SUBBIAH RAJESH N. , GULA LORNE J. , KRAHN ANDREW D. , POSAN EMOKE , YEE RAYMOND , KLEIN GEORGE J. , SKANES ALLAN C.
Published: April 2007

Background: The maximum voltage‐guided (MVG) approach to ablation for atrial flutter targets high‐amplitude signals along the cavotricuspid isthmus (CTI). It is based on the observation that the isthmus is often composed of bundles of conducting tissue and the hypothesis that these bundles manifest as high‐amplitude electrograms, providing targets for selective ablation. We aim to identify patient and procedural factors that correlate with rapid isthmus ablation.

Methods: All patients undergoing CTI ablation at our center from January 2005 to May 2006 were included. Patients were divided into outcome groups relative to the median value for total ablation time. The two groups were compared according to patient and procedural variables, using multivariate regression methods.

Results: Seventy‐six patients were assessed with mean age 60.2 ± 10.6 years; 63 (82.9%) were male. Mean ablation time to bidirectional block across the CTI was 6.85 ± 5.87 min (range 0.68–28.7); median 4.77 min. Seventy‐six percent of patients required less than 5 min total ablation time until bidirectional block was achieved. Variables independently associated with a short ablation time were the presence of sinus rhythm at start of ablation (P = 0.0050, odds ratio (OR) 8.03), high mean temperature among all ablations (P = 0.019, OR 17.81), and low variability of mean power among all ablations (P = 0.0048, OR 19.26).

Conclusions: Using the MVG approach to atrial flutter ablation, shorter total ablation times are observed among patients in sinus rhythm at the onset of ablation, with higher mean temperature among ablation lesions, and less variability of power between ablations.
Adverse Interaction Between a Left Ventricular Assist Device and an Implantable Cardioverter Defibrillator
Authors: MATTHEWS JENNIFER COWGER , BETLEY DAPHNE , MORADY FRED , PELOSI FRANK
Published: April 2007

An increasing number of patients have a coexisting implantable cardioverter defibrillator (ICD) and left ventricular assist device (LVAD) to treat ventricular arrhythmias and refractory heart failure, respectively. To date, there have been no published reports of negative interactions between these devices that have impacted appropriate ICD or LVAD function. In this case report, we describe a patient with an LVAD‐ICD interaction that necessitated replacement of the implantable defibrillator.
Heavy silicone oil versus standard silicone oil as vitreous tamponade in inferior PVR (HSO Study): design issues and implications
Authors: Joussen Antonia M. , Kirchhof Bernd , Schrage Norbert , Ocklenburg Christina , Hilgers Ralf‐Dieter ,   on behalf of the HSO Study Group
Published: April 2007

Purpose:  Proliferative vitreoretinopathy (PVR) is the most important reason for blindness following retinal detachment. Presently, vitreous tamponades such as gas or silicone oil cannot contact the lower part of the retina. A heavier‐than‐water tamponade displaces the inflammatory and PVR‐stimulating environment from the inferior area of the retina. The Heavy Silicone Oil versus Standard Silicone Oil Study (HSO Study) is designed to answer the question of whether a heavier‐than‐water tamponade improves the prognosis of eyes with PVR of the lower retina.

Methods:  The HSO Study is a multicentre, randomized, prospective controlled clinical trial comparing two endotamponades within a two‐arm parallel group design. Patients with inferiorly and posteriorly located PVR are randomized to either heavy silicone oil or standard silicone oil as a tamponading agent. Three hundred and fifty consecutive patients are recruited per group. After intraoperative re‐attachment, patients are randomized to either standard silicone oil (1000 cSt or 5000 cSt) or Densiron® as a tamponading agent. The main endpoint criteria are complete retinal attachment at 12 months and change of visual acuity (VA) 12 months postoperatively compared with the preoperative VA. Secondary endpoints include complete retinal attachment before endotamponade removal, quality of life analysis and the number of retina affecting re‐operation within 1 year of follow‐up.

Results:  The design and early recruitment phase of the study are described.

Conclusions:  The results of this study will uncover whether or not heavy silicone oil improves the prognosis of eyes with PVR.
Enhanced optical coherence patterns of diabetic macular oedema and their correlation with the pathophysiology
Authors: Soliman Wael , Sander Birgit , Jørgensen Thomas Martini
Published: April 2007

Purpose:  To describe different patterns of diabetic macular oedema (DMO) using a computerized alignment and averaging of sequences in optical coherence tomography (OCT) B‐scans and to show the correlation of these patterns with the pathophysiology of the condition.

Methods:  We carried out a prospective, uncontrolled study, including 46 human subjects with untreated DMO. Enhanced OCT images were produced. We correlated different OCT patterns of DMO with ETDRS visual acuity and with the thickness of the central 1‐mm of the macula. We also correlated these patterns with theories of the pathophysiology of DMO.

Results:  Enhanced OCT images enabled us to examine how different layers of the macula were affected. The external limiting membrane (ELM) was clearly seen in all stages, including advanced stages. The sequence of DMO events in different macular layers can be divided into five patterns. Morphologically, DMO starts at the outer nuclear layer/Henle's layer. As the oedema progresses, cysts are seen in the fovea and the DMO spreads further into the inner nuclear layer. The ELM seems to act as a barrier for proteins and plays an important role in the development of DMO.

Conclusions:  Enhanced OCT revealed new details of DMO pathophysiology. The different morphological patterns of DMO seen in enhanced OCT may represent different levels of severity of the disease.
Pertussis toxin modulation of sodium channels in the central neurons of cyhalothrin‐resistant and cyhalothrin‐susceptible cotton bollworm,Helicoverpa armigera
Authors: ZHAO QIANG , KONG DE‐LING , HE BING‐JUN , LIU YAN‐QIANG , FAN XIAN‐LIN , LIU AN‐XI
Published: April 2007

Pertussis toxin (PTX) inhibits the activation of the α‐subunit of the inhibitory heterotrimeric G‐proteins (Gαi./o) and modulates voltage‐gated sodium channels, which may be one of the primary targets of pyrethroids. To investigate the potential mechanisms of agricultural pests resistance to pyrethroid insecticides, we examined the modulations by PTX on sodium channels in the central neurons of the 3rd—4th instar larvae of cyhalothrin‐resistant (Cy‐R) and cyhalothrin‐susceptible (Cy‐S)Helicoverpa armigeraby the whole‐cell patch‐clamp technique. The isolated neurons were cultured for 12—16 h in an improved L15 insect culture medium with or without PTX (400 ng/mL). The results showed that both the Cy‐R and Cy‐S sodium channels exhibited fast kinetics and tetrodotoxin (TTX) sensitivity. The Cy‐R sodium channels exhibited not only altered gating properties, including a 8.88‐mV right shift in voltage‐dependent activation (V0.5act) and a 6.54‐mV right shift in voltage‐dependent inactivation (V0.5inact), but also a reduced peak in sodium channel density (Idensity) (55.2% of that in Cy‐S neurons). Cy‐R sodium channels also showed low excitability, as evidenced by right shift of activation potential (Vacti) by 5—10 mV and peak potential (Vpeak) by 20 mV. PTX exerted significant effects on Cy‐S sodium channels, reducing sodium channel density by 70.04%, right shiftingV0.5actby 14.41 mV andV0.5inactby 9. 38 mV. It did not cause any significant changes of the parameters mentioned above in the Cy‐R sodium channels. The activation time (Tpeak) from latency to peak at peak voltage and the fast inactivation time constant (τinact) in both Cy‐S and Cy‐R neurons were not affected. The results suggest that cotton bollworm resistant to pyrethroid insecticides involves not only mutations and allosteric alterations of voltage‐gated sodium channels, but also might implicate perturbation of PTX‐sensitive Gαi./o‐coupled signaling transduction pathways.
Comparison of fatty acid composition in total lipid of diapause and non‐diapause larvae of Cydia pomonella (Lepidoptera: Tortricidae)
Authors: KHANI ABBAS , MOHARRAMIPOUR SAEID , BARZEGAR MOHSEN , NADERI‐MANESH HOSSEIN
Published: April 2007

Seasonal changes in the fatty acid composition of the total lipid extracted from the whole body of Cydia pomonella L. larvae were determined by gas chromatography. The six most abundant fatty acids in both non‐diapause and diapause larvae of codling moth were oleic (35%–39%), palmitic (23%–33%), linoleic (16%–30%), palmitoleic (5%–10%), stearic (1.5%–3.0%) and linolenic acids (1.0%–2.5%). This represents a typical complement of Lepidopteran fatty acids. The fatty acid composition of total lipid of C. pomonella larvae was related to diapause. In similarity to most other reports, the proportion of unsaturated fatty acids increased in diapause initiation state. The total lipid of diapause larvae contained more linoleic acid (25.8%vs. 16.1%) and less palmitic acid (24.7%vs. 33.4%), than that of non‐diapause larvae. The weight percentage of linoleic acid (C18:2) increased from 16% to 26% from early‐August through early‐September during transition to diapause, while palmitic acid (C16:0) decreased from 33% to 25% at the same time. These changes resulted in an increase in the ratio of unsaturated to saturated fatty acids (UFA/SFA) from 1.72 in non‐diapause larvae to 2.63 in diapause larvae.
Insecticidal efficacy of three vegetable oils as post‐harvest grain protectants of stored wheat against Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae)
Authors: NIKPAY AMIN
Published: April 2007

The lesser grain borer, Rhyzopertha dominica is a major insect pests of stored grain in the tropics. Vegetable oils (chamomile, sweet almond and coconut) at 2.5, 3.5, 5.0, 7.0 and 10.0 mL/kg were tested against Rhyzopertha dominica (F.) in wheat grain. All bioassays were conducted at 30°C and 65%± 2% RH. Treatments with vegetable oils at high dose (10.0 mL/kg) achieved over 95% control within 24 h of exposure to freshly treated grain. There was little difference between the three oils in their effect. Persistence of oils in grains was tested at short‐term storage intervals (48, 72 and 96 h) and intermediate‐term intervals (10, 20 and 30 days) after treatments. The activity of all products decreased with storage period. Seed viability was reduced by the high dose rate (10.0 mL/kg) of oil treatments. The potential use of vegetable oils as supplementary or alternative grain protectants against insect damage in traditional grain storage in developing countries is discussed.
Impact of greenhouse whitefly management on strawberry fruit quality
Authors: BI JIAN‐LONG , TUAN SHU‐JEN , TOSCANO NICK C.
Published: April 2007

The greenhouse whitefly, Trialeurodes vaporariorum (Westwood), is an important pest of strawberries in California, USA. The adults and nymphs feed on phloem sap of leaves to remove the photo‐assimilates. The objective of this study is to test the impact of whitefly management with insecticides on strawberry fruit quality. Applications of imidacloprid, thiamethoxam, buprofezin and pyriproxyfen decreased the mean adult white‐fly numbers by 2.80‐, 2.17‐, 1.69‐ and 1.39‐fold, respectively, compared to the untreated control. Similarly, the mean numbers of first and second instar whiteflies were reduced 4.36‐, 2.20‐, 1.90‐ and 2.02‐fold, respectively, while the mean numbers of third and fourth instars were reduced 5.48‐, 2.28‐, 2.71‐ and 1.43‐fold, respectively, in plants treated with imidacloprid, thiamethoxam, buprofezin and pyriproxyfen. The mean soluble solids content in imidacloprid, thiamethoxam, buprofezin and pyriproxyfen treatments was 1.04‐, 1.06‐, 1.03‐ and 1.04‐fold greater, respectively, than that in the control. The whitefly reduction enhanced the mean fruit titratable acidity by 4%‐6%. Mean glucose levels in imidacloprid and thiamethoxam treatments were significantly higher than in other treatments. However, the whitefly management did not affect the mean fructose levels. Imidacloprid, thiamethoxam and pyriproxyfen treatments boosted the ascorbic acid levels by up to 4%. The impact of whitefly management on strawberry fruit nutrition and antioxidant capacity is discussed.
Trap catches of the sweetpotato whitefly (Homoptera: Aleyrodidae) in the Imperial Valley, California, from 1996 to 2002
Authors: CHU CHANG‐CHI , BARNES EDWARD , NATWICK ERIC T. , CHEN TIAN‐YE , RITTER DAVID , HENNEBERRY THOMAS J.
Published: April 2007

An outbreak of the sweetpotato whitefly, Bemisia tabaci (Gennadius), biotype B occurred in the Imperial Valley, California in 1991. The insects destroyed melon crops and seriously damaged other vegetables, ornamentals and row crops. As a result of the need for sampling technology, we developed a whitefly trap (named the CC trap) that could be left in the field for extended time periods. We used the traps to monitor populations of B. tabaci adults during year‐round samplings from 1996 to 2002 to study variations in the weekly trap catches of the insect. The greatest number of B. tabaci adults was recorded in 1996, followed by a continuing annual decrease in trap catches each year through 2002. The overall decline of B. tabaci is attributed in part to the adoption of an integrated pest management (IPM) program initiated in 1992 and reduced melon hectares from 1996 to 2002. Other factors may also have contributed to the population reductions. Seasonally, B. tabaci trap catches decreased during the late summer and fall concurrent with decreasing minimum temperatures that are suggested to be a significant factor affecting seasonal activity and reproduction.
Lubrication and Wear of Artificial Knee Joint Materials in a Rolling∕Sliding Tribotester
Authors: Kennedy Francis E. , Van Citters Douglas W. , Wongseedakaew Khanittha , Mongkolwongrojn Mongkol
Published: April 2007

This paper describes the influence of lubrication on wear during testing of materials for artificial knee joints in a rolling∕sliding tribotester built to simulate contact conditions in a total knee replacement. The test configuration consists of parallel cylinders (pucks) of ultrahigh molecular weight polyethylene (UHMWPE) and polished cobalt-chrome alloy in oscillatory rolling∕sliding contact in a bath of dilute (25%) bovine serum. Wear tests of three different UHMWPE materials were run under constant load at 40% sliding for 1.5 million oscillation cycles at 1.5cycles∕s. Wear of the UHMWPE was determined by measuring the profile of the cylindrical contact surface of the puck before and after each test. Profile measurements were repeated after at least 53days to eliminate the contribution from creep. Differences between initial and final profiles were attributed to wear of the UHMWPE. It was found that the largest wear depth in the lubricated tests occurred near the ends of the oscillatory contact area, while dry (unlubricated) tests of the same materials showed a peak wear depth near the center of the contact area. In the lubricated tests, the worn depth was lowest for the most heavily irradiated material. Analysis of the elastohydrodynamic lubrication in the rolling∕sliding contact was carried out assuming a line-contact situation with smooth cylindrical surfaces. The time-dependent modified Reynolds equation and the elasticity equation with initial conditions were solved numerically using a multigrid technique with full approximation scheme, and using a Newton Raphson method to solve the highly nonlinear system of equations. The thickness of the lubricating film of bovine serum was determined for points along the length of the wear track. It was found that the smallest film thickness (hmin) occurs very close to the location in the oscillating contact where the greatest wear occurs, owing to the very low entraining velocity near the ends of the oscillation cycle. The coefficient (K) for wear of the UHMWPE was found to be relatively constant over the central section of the oscillatory motion, but increased to a higher value where hmin decreased to near zero. Thus, the important influence of lubrication on wear of artificial knee bearings was demonstrated.
Experimental and Theoretical Investigation of Bouncing Vibrations of a Flying Head Slider in the Near-Contact Region
Authors: Ono Kyosuke , Yamane Masami
Published: April 2007

We experimentally and theoretically investigated in detail bouncing vibrations of a flying head slider in the near-contact region between the head and disk surface. By changing the Z-height in the experiment, we evaluated the effect of the pitch static angle on the ambient pressure at which unstable bouncing vibration starts and stops. We found that the touch-down and take-off pressure hysteresis decreased as the pitch static angle increased even though the flying height at the trailing edge decreased slightly. From detailed measurement of the slider dynamics at the threshold of the bouncing vibration, we found that the trailing edge of the slider was first attracted to the disk. As the pitch static angle decreased, the magnitude of the first drop of the trailing edge increased and the bouncing vibration amplitude increased more rapidly. We also measured the mode of the bouncing vibration by using two laser Doppler vibrometers simultaneously. By using an improved two-degree-of-freedom slider model, in which the small micro-waviness and the shearing force of the lubricant were taken into account, we could analyze the touch-down/take-off hysteresis, mode, and destabilization process of the bouncing vibration similar to the experimental results. We also theoretically found that either self-excited bouncing vibration with lower pitch frequency or forced vibration with higher pitch frequency was generated, depending on the magnitudes of the micro-waviness and the disturbance.
Evaluation of Stresses Around Inclusions in Hertzian Contacts Using the Discrete Element Method
Authors: Raje Nihar , Sadeghi Farshid , Rateick Richard G. , Hoeprich Michael R.
Published: April 2007

Inclusions are the primary sites for subsurface fatigue crack initiation in bearing contacts. To understand the mechanisms of subsurface crack nucleation under contact loading, a detailed description of the stress field around these inclusions is necessary. This paper presents a new approach to computing stresses in an inhomogeneous medium where inclusions are treated as inhomogeneities in a homogeneous material matrix. The approach is based on the Discrete Element (DE) Method in which the material continuum is replaced by a set of rigid discrete interacting elements. The elements are connected to each other along their sides through springs and dampers to form the macro-continuum and undergo relative displacements in accordance with Newton’s laws of motion under the action of external loading. The spring properties are derived in terms of the overall elastic properties of the continuum. The relative motion between elements gives rise to contact forces due to stretching or compression of the inter-element springs. These forces are evaluated at each time-step and the corresponding equations of motion are solved for each element. Stresses are calculated from the inter-element joint forces. A Hertzian line contact case, with and without the presence of subsurface inclusions, is analyzed using the DE model. The DE model was used to determine stresses for an inclusion-free medium that compares well with that obtained from the continuum elasticity models. Parametric studies are then carried out to investigate the effects of size, location, orientation, and elastic properties of inclusions on the subsurface stress field. Both inclusions that are stiffer and/or softer than the base material are seen to give rise to stress concentrations. For inclusions that are stiffer than the base material (semi-infinite domain), the stress concentration effect increases with their elastic modulus. The stress concentration effect of a softer inclusion is higher than that of a stiffer inclusion. Inclusions that are oriented perpendicular to the surface give rise to much higher von Mises stresses than the ones that are oriented parallel to the surface. There is little change in the maximum von Mises stress for inclusions that are located deep within the surface.
Elucidation of the Corrosion Mechanism of Vegetable-Oil-Based Lubricants
Authors: Jayadas N. H. , Nair K. Prabhakaran
Published: April 2007

In this paper, the corrosion properties of vegetable oils as base oil for industrial lubricants are evaluated by the copper strip corrosion test (ASTM D130) and rust prevention test (ASTM D665). An analysis of possible organic reaction mechanisms leading to corrosion of metals in the absence and presence of oxygen and moisture is presented, when vegetable oils are used as base oils. Corrosion properties of vegetable oil fatty acids, evolved as degradation products, are analyzed using quantum chemical calculations. The popular quantum chemical software SPARTAN 04 (Wavefunction Inc. USA) was used for the studies employing the semi-empirical PM3 method. The calculations were performed in line with similar reported studies used to analyze the corrosion inhibition properties of many nitrogen and sulfur-containing anti-corrosion additives. The corrosion inhibition properties of ZDDP (zinc dialkyldithiophosphate) were compared to other additives using PM3 semi-empirical calculations. Moisture content in vegetable oils is found to be the leading cause of corrosion in vegetable-oil-based lubricants. Control of moisture content and use of additives like ZDDP can be effective in controlling corrosion.
Rotordynamics of Small Turbochargers Supported on Floating Ring Bearings—Highlights in Bearing Analysis and Experimental Validation
Authors: San Andres Luis , Rivadeneira Juan Carlos , Gjika Kostandin , Groves Christopher , LaRue Gerry
Published: April 2007

Turbochargers (TCs) improve performance in internal combustion engines. Due to low production costs, TC assemblies are supported on floating ring bearings (FRBs). TCs show subsynchronous motions of significant amplitudes over a wide speed range. However, the subsynchronous whirl motions generally reach a limit cycle enabling continuous operation. The paper advances progress on the validation against measurements of linear and nonlinear rotordynamic models for predicting shaft motions of automotive TCs. A comprehensive thermohydrodynamic model predicts the floating ring speeds, inner and outer film temperatures and lubricant viscosity changes, clearances thermal growth, operating eccentricities for the floating ring and journal, and linearized force coefficients. A nonlinear rotordynamics program integrates the FRB lubrication model for prediction of system time responses under actual operating conditions. Measurements of shaft motion in a TC unit driven by pressurized air demonstrate typical oil-whirl induced instabilities and, due to poor lubricant conditions, locking of the floating rings at high shaft speeds. Nonlinear predictions are in good agreement with the measured total amplitude and subsynchronous frequencies when implementing the measured ring speeds into the computational model. The computational tools aid to accelerate TC prototype development and product troubleshooting.
Numerical Calculations of Pressure Distribution in the Bearing Clearance of Circular Aerostatic Thrust Bearings With a Single Air Supply Inlet
Authors: Yoshimoto Shigeka , Yamamoto Makoto , Toda Kazuyuki
Published: April 2007

This paper describes the pressure distribution in the bearing clearance of circular aerostatic thrust bearings with a single air supply inlet. For high air supply pressure, large bearing clearance, and a relatively small bearing outer radius, it was believed that shock waves are caused and that a complex fluid flow structure is formed in the bearing clearance. Accordingly, analytical models based on the occurrence of shock wave in the bearing clearance have been proposed. Recently, very small aerostatic bearings have been used in various machine devices where the pressure distribution near the air inlets has a large influence on the bearing characteristics due to a short distance between air inlets and the bearing edge. In order to predict various bearing characteristics accurately for these kinds of bearings, a proper analytical model has to be established. However, it is very difficult to obtain the detailed information about the flow structure from flow visualization because of a very thin bearing clearance. Therefore, we calculated the flow field using computational fluid dynamics, which can solve the Navier-Stokes equations directly. It was found that the airflow just after entering the bearing clearance becomes turbulent in a region where relatively rapid pressure recovery occurs and that no shock wave is generated at the boundary between subsonic and supersonic flow. In addition, the numerical results presented show good agreement with experimental data.
Linear Stability Analysis of a Tilting-Pad Journal Bearing System
Authors: Qiao Guang , Wang Liping , Zheng Tiesheng
Published: April 2007

This paper describes a mathematical model to study the linear stability of a tilting-pad journal bearing system. By employing the Newton-Raphson method and the pad assembly technique, the full dynamic coefficients involving the shaft degrees of freedom as well as the pad degrees of freedom are determined. Based on these dynamic coefficients, the perturbation equations including self-excited motion of the rotor and rotational motion of the pads are derived. The complex eigenvalues of the equations are computed and the pad critical mass identified by eigenvalues can be used to determine the stability zone of the system. The results show that some factors, such as the preload coefficient, the pivot position, and the rotor speed, significantly affect the stability of tilting-pad journal bearing system. Correctly adjusting those parameter values can enhance the stability of the system. Furthermore, various stability charts for the system can be plotted.
Modeling of the Rolling and Sliding Contact Between Two Asperities
Authors: Boucly Vincent , Nélias Daniel , Green Itzhak
Published: April 2007

A semi-analytical method for the tridimensional elastic-plastic contact between two hemispherical asperities is proposed. The first part of the paper describes the algorithm used to deal with the normal contact, which can be either load-driven or displacement-driven (dd). Both formulations use the conjugate gradient method and the discrete convolution and fast Fourier transform (DC-FFT) technique. A validation of the code is made in the case of the displacement-driven formulation for an elastic-plastic body in contact with a rigid punch, simulating a nano-indentation test. Another new feature is the treatment of the contact between two elastic-plastic bodies. The model is first validated through comparison with the finite element method. The contact pressure distribution, the hydrostatic pressure and the equivalent plastic strain state below the contacting surfaces are also found to be strongly modified in comparison to the case of an elastic-plastic body in contact with a purely elastic body. The way to consider rolling and sliding motion of the contacting bodies consists of solving the elastic-plastic contact at each time step while upgrading the geometries as well as the hardening state along the moving directions. The derivations concerning the interference calculation at each step of the sliding process are then shown, and an application to the tugging between two spherical asperities in simple sliding (dd formulation) is made. The way to project the forces in the global reference is outlined, considering the macro-projection due to the angle between the plane of contact and the sliding direction, and the micro-projection due to the pile-up induced by the permanent deformation of the bodies due to their relative motion. Finally, a load ratio is introduced and results are presented in terms of forces, displacements, and energy loss in the contact.
Rotordynamic Force Coefficients for a New Damper Seal Design
Authors: Ertas Bugra H. , Vance John M.
Published: April 2007

The objective of the following work was to determine frequency-dependent rotordynamic force coefficients for a new annular gas damper seal design. Both rotating and nonrotating experimental tests are presented for inlet pressures at 1000psig(69bar), a frequency excitation range of 20-300Hz, and rotor speeds up to 15,200rpm. Two different testing methods were used for determining coefficients: (1) dynamic pressure response method and (2) mechanical impedance method. The dynamic pressure method required the measurement of internal seal cavity pressure modulations in combination with the vibratory motion, whereas the mechanical impedance method used the measurement of external shaker forces, accelerations, and motion of the mechanical system. In addition to the new fully partitioned damper seal (FPDS) tests, the same experiments were conducted for a conventional pocket damper seal (PDS) design. Results of the frequency-dependent force coefficients and the internal seal dynamics for the two different gas damper seals are compared. The conclusions of the tests show that the FPDS design possesses significantly more positive direct damping and direct stiffness compared to the conventional PDS. The experiments also show the measurement of same-sign cross-coupled (cross-axis) stiffness coefficients for both seals, which indicate that the seals do not produce a destabilizing influence on rotor-bearing systems.
A Generalized Formulation for the Contact Between Elastic Spheres: Applicability to Both Wet and Dry Conditions
Authors: Zheng Jie , Streator Jeffrey L.
Published: April 2007

The interaction between two elastic spheres with an intervening liquid film of given volume is studied theoretically. Using an energy minimization approach, equilibrium contact configurations are determined through numerical computation. Several dimensionless groups are identified that govern the character of the solution. Curve fits are performed to reveal analytical relationships among the dimensionless groups. At extreme values of particular parameters, the curve fits are found to recover the analytical results of the well-known Hertzian and Johnson–Kendall–Roberts elastic (dry contact) models, as well as the force of a liquid bridge between rigid spheres. Qualitative agreement is found between the current model and some published experiments.
Parametric Studies on Static and Dynamic Performance of Air Foil Bearings with Different Top Foil Geometries and Bump Stiffness Distributions
Authors: Kim Daejong
Published: April 2007

Experimental and analytical studies on air foil bearings have been performed extensively over the past decades, and significant improvement in load capacity and rotor dynamics stability have been reported. Often, advanced air foil bearings are believed to have complicated bump foil structure to provide unique underlying support mechanism, which in turn make the bearing very stable and have high load capacity. However, all the analytical studies on air foil bearings so far assume a circular profile of top foil with uniform bump stiffness distribution because detailed information on bump stiffness distribution and overall bearing shape is not known to the public. This paper investigates load capacities and rotordynamic performances of two different types of air foil bearings, e.g., circular cylindrical bearings with single continuous top foil and noncircular preloaded bearings with three top foil pads. Within the two subcategories, stiffness variations along axial and circumferential directions were given to have a total of four types of air foil bearings with different overall bearing shapes and stiffness distributions. Overall static and dynamic performance of the four different types of air foil bearings are presented and compared via calculations of load capacities and dynamic force coefficients, modal stability analyses, and time domain orbit simulations. The major difference of load capacities comes from the overall bearing shape (circular continuous foil or preloaded three pad) rather than spatial variation of bump stiffness within the bump foils. Preloaded three-pad bearings have significantly reduced load capacity compared to the circular bearings because of small pad arc length. Rotordynamic performance is also much more sensitive to the overall bearing shape than spatial variation of bump stiffness and damping within the bump foils. The linear stability analyses predict modal natural frequencies very close to those from the orbit simulations. However, onset speeds of instability from these two approaches are quite different, manifesting the limitation of the linear stability analyses. The orbit simulations show the three-pad bearings have higher onset speeds of instability than circular bearing (47,000rpm versus 24,000rpm).
Entrainment and Inlet Suction: Two Mechanisms of Hydrodynamic Lubrication in Textured Bearings
Authors: Fowell M. , Olver A. V. , Gosman A. D. , Spikes H. A. , Pegg I.
Published: April 2007

A new mechanism of hydrodynamic lubrication termed “inlet suction,” applicable to low convergence, micropocketed bearings, has been identified. In this, sliding of one of the bearing surfaces generates a subambient pressure in pockets close to the bearing inlet. Because this pressure is less than the external atmospheric pressure, lubricant is “sucked” into the bearing through the inlet land. This is quite a different mechanism from classical entrainment due to shear. In the current paper flow, hydrodynamic load support and friction are calculated using analytical solutions for simple pocketed bearings having a wide range of convergence ratios, including parallel surfaces. It is found that for the parallel case, inlet suction provides the only mechanism of hydrodynamic load support, and that inlet suction continues to play a major role in load support and friction reduction up to quite high convergence ratios. This mechanism of lubrication is believed to be responsible for the enhanced lubricant film formation and reduced friction of textured bearings, previously reported by a number of authors.