bluuebunny/crossref_metadata_2025 huggingface dataset:
Mineral Content and Sensory Characteristics of Gordal Green Table Olives Fermented in Chloride Salt Mixtures
Authors: María Moreno‐Baquero José , Bautista‐Gallego Joaquín , Garrido‐Fernández Antonio , López‐López Antonio
Published: February 2012

Abstract:  This work studies the effects of the initial brine concentrations of NaCl, KCl, and CaCl2 on the mineral content and gustatory and kinaesthetic sensations of fermented green table olives, using a simplex centroid mixture design augmented with interior points. The sodium in the flesh was linearly related to the mixture concentrations while potassium and calcium were linked by quadratic and special cubic models respectively. Acidity, saltiness, hardness, fibrousness, and crunchiness were expressed as linear funtions of the NaCl, KCl, and CaCl2 initial brine contents but bitterness required quadratic equations. The models can be used to produce table olives with specific mineral contents in the flesh and to predict their corresponding sensory characteristics.

Practical Application:  The study provides the industry with models to estimate the Na, K, and Ca mineral contents in the flesh of fermented Gordal green table olives as well as their sensory characteristics as a function of the NaCl, KCl, and CaCl2 initial compositions in the brining solution. Therefore, the paper provides tools which are able to support the production of commercial presentations which not only satisfy consumer demand for low Na, but are also K and Ca fortified table olive presentations with specific sensory profiles.
Identification and Quantification of Flavor Attributes present in Chicken, Lamb, Pork, Beef, and Turkey
Authors: Maughan Curtis , Martini Silvana
Published: February 2012

Abstract:  The objectives of this study were to use a meat flavor lexicon to identify and quantify flavor differences among different types of meats such as beef, chicken, lamb, pork, and turkey, and to identify and quantify specific flavor attributes associated with “beef flavor” notes. A trained descriptive panel with 11 participants used a previously developed meat lexicon composed of 18 terms to evaluate the flavor of beef, chicken, pork, turkey, and lamb samples. Results show that beef and lamb samples can be described by flavor attributes such as barny, bitter, gamey, grassy, livery, metallic, and roast beef. Inversely related to these samples were pork and turkey and those attributes that were closely related to them, namely brothy, fatty, salty, sweet, and umami. Chicken was not strongly related to the other types of meats or the attributes used. The descriptive panel also evaluated samples of ground beef mixed with chicken to identify and quantify flavor attributes associated with a “beef flavor.” Meat patties for this portion consisted of ground beef mixed with ground chicken in varying amounts: 0%, 25%, 50%, 75%, and 100% beef, with the remainder made up of chicken. Beef and beef‐rich patties (75% beef) were more closely related to flavor attributes such as astringent, bloody, fatty, gamey, metallic, livery, oxidized, grassy, and roast beef, while chicken was more closely associated with brothy, juicy, sour, sweet, and umami. This research provides information regarding the specific flavor attributes that differentiate chicken and beef products and provides the first set of descriptors that can be associated with “beefy” notes.

Potential Application:  The use of a standardized flavor lexicon will allow meat producers to identify specific flavors present in their products. The impact is to identify and quantify negative and positive flavors in the product with the ultimate goal of optimizing processing or cooking conditions and improve the quality of meat products.
Impact of Sea Level Rise on Groundwater Salinity in a Coastal Community of South Florida1
Authors: Guha Hillol , Panday Sorab
Published: February 2012

Guha, Hillol and Sorab Panday, 2012. Impact of Sea Level Rise on Groundwater Salinity in a Coastal Community of South Florida. Journal of the American Water Resources Association (JAWRA) 48(3): 510‐529. DOI: 10.1111/j.1752‐1688.2011.00630.x

Abstract:  Freshwater resources of coastal communities in the United States and world over are threatened by the rate of sea level rise. According to recent estimates by various governmental agencies and climate researchers, the global sea level rise is likely to be between 0.6 and 2.1 m by the year 2100. South Florida is a coastal community and much of its coastline is subject to sea level rise and potential impacts to wetlands and the water resources of the area. To understand what the impact of sea level rise would cause to the groundwater level and salinity intrusion, an integrated groundwater and surface water model was developed for North Miami‐Dade and Broward Counties of South Florida. The model was calibrated against daily groundwater heads, base flows in canals, and chloride concentrations for a period of one year and six months. Three separate sensitivity analyses were conducted by increasing the sea level by 0.6, 0.9, and 1.22 m. Results of the simulations shows increase of groundwater heads in some areas from 4 to 15%; whereas the average relative chloride concentrations increased significantly by 100‐600% in some wells. The increase in groundwater elevations and chloride concentrations varies from location of the wells and its proximity to the coast. The model results indicate that even a 0.6 m increase in sea level (which is the conservative estimate) is likely to impair the vital freshwater resources in many parts of South Florida.
Musculoskeletal CPD revision: Cases from the New Zealand bone and soft tissue tumour registry
Authors: Weerakkody Yuranga Dilan , Dray Michael , Pinto Clinton , Rosenfeldt Michael , Flint Michael
Published: February 2012

The following case report was selected from the New Zealand Bone and Soft Tissue Tumour Registry to highlight some key concepts and findings in musculoskeletal imaging with radiological‐pathological correlation. The presentation follows a question and answer format followed by clinical information, selected images, diagnosis, discussion and teaching points.
Negative coronary CT angiography for chest pain assessment predicts low event rate in 5 years
Authors: Chong Fei Y , Soon Kean , Brown Fraser , Bell Kevin , Lim Yean L
Published: February 2012

Introduction: Coronary CT angiography (CTA) is becoming a popular investigation for chest pain. A negative coronary CTA is known to have a good negative predictive value for major adverse cardiovascular events in short term. The data on the long‐term outcomes of negative coronary CTA are lacking. We aim to investigate the long‐term prognostic value of negative coronary CTA in the evaluation of chest pain.

Methods: This was a retrospective observational study involving 259 cases of coronary CTA on our registry from July 2004 to November 2006. All coronary CTA were performed with GE 16‐slice CT and then GE 64‐slice CT scanner in late 2006. A negative coronary CTA was defined as no single coronary segment with stenosis ≥50% based on American Heart Association 16‐segment model. The end point of the study was defined as a composite of major cardiovascular events such as myocardial infarction, myocardial death or revascularisation.

Results: Seventy cases of 259 on the registry were diagnosed as negative studies. Mean follow‐up period was 4.64 ± 0.6 years (range from 3.4 to 5.7 years). Of these negative studies, only one patient suffered from the end point during the follow‐up. Thus, the negative predictive value of a negative coronary CTA for a long‐term major cardiovascular event was 0.986 (95% confidence interval: 0.92–0.99).

Conclusions: A negative coronary CTA in patients with a low or intermediate pretest probability for significant coronary artery disease predicts a low rate of major cardiovascular events within a 5‐year period.
Radiotherapy in the management of high‐grade gliomas diagnosed in Western Australia: A patterns of care study
Authors: Jackson Melanie , Bydder Sean , Maujean Eric , Taylor Mandy , Nowak Anna
Published: February 2012

Purpose: Radiotherapy (RT) plays an integral role in the management of high‐grade glioma (HGG). However, there is little information on the patterns of care in unselected Australian patients with HGG.

Patient and Methods: This prospective cohort study collected information on patients with a diagnosis of HGG managed in Western Australia over a 25‐month period from 2006 to 2008. RT treatment and survival data were analysed.

Results: 86% of Western Australian patients with HGG were treated at the study site over this period. Of these, 80% were reviewed by a radiation oncologist with RT recommended in 88% of cases. One hundred eighty‐seven patients proceeded to have RT, with most receiving 60 Gy in 30 fractions with limited field external beam radiotherapy (LFRT). Median survival from diagnosis was 13.6 months for all patients and 15.4 months for those planned for treatment with 60 Gy in 30 fractions. The median time from surgery to the start of RT was 41 days. Longer waiting times were not predictors of poor survival. Failure to receive all planned treatment (13% of patients) predicted for poor survival (hazard ratio 0.38).

Conclusion: Dose and fractionation practices show concordance with published data and guidelines. Survival is also consistent with clinical trial data for patients planned for aggressive therapy. Nevertheless, a substantial number of patients are not suited to aggressive therapy or fail to complete planned therapy, and these patients have poor outcomes. Treatment delays did not affect survival outcomes but are confounded by earlier treatment of those unsuited to LFRT.
A systematic review of radiation dose associated with different generations of multidetector CT coronary angiography
Authors: Sabarudin Akmal , Sun Zhonghua , Ng Kwan‐Hoong
Published: February 2012

The purpose of this paper is to perform a systematic review on radiation dose reduction in coronary computed tomography (CT) angiography that is done using different generations of multidetector CT (MDCT) scanners ranging from four‐slice to 320‐slice CTs, and have different dose‐saving techniques. The method followed was to search for references on coronary CT angiography (CTA) that had been published in English between 1998 and February 2011. The effective radiation dose reported in each study based on different generations of MDCT scanners was analysed and compared between the types of scanners, gender, exposure factors and scanning protocols. Sixty‐six studies were eligible for inclusion in this analysis. The mean effective dose (ED) for MDCT angiography with retrospective electrocardiogram (ECG) gating without use of any dose‐saving protocol was 6.0 ± 2.8, 10.4 ± 4.90 and 11.8 ± 5.9 mSv for four‐slice, 16‐slice and 64‐slice CTs, respectively. More dose‐saving strategies were applied in recent CT generations including prospective ECG‐gating protocols, application of lower tube voltage and tube current modulation to achieve a noteworthy dose reduction. Prospective ECG‐gating protocol was increasingly used in 64, 125, 256 and 320 slices with corresponding ED of 4.1 ± 1.7, 3.6 ± 0.4, 3.0 ± 1.9 and 7.6 ± 1.6 mSv, respectively. Lower tube voltage and tube current modulation were widely applied in 64‐slice CT and resulted in significant dose reduction (P < 0.05). This analysis has shown that dose‐saving strategies can substantially reduce the radiation dose in CT coronary angiography. The fact that more and more clinicians are opting for dose‐saving strategies in CT coronary angiography indicates an increased awareness of risks associated with high radiation doses among them.
Australian & New Zealand Faculty of Radiation Oncology Genito‐Urinary Group: 2011 consensus guidelines for curative radiotherapy for urothelial carcinoma of the bladder
Authors: Hindson Benjamin R , Turner Sandra L , Millar Jeremy L , Foroudi Farshad , Gogna N Kumar , Skala Marketa , Kneebone Andrew , Christie David RH , Lehman Margot , Wiltshire Kirsty L , Tai Keen‐Hun ,   on behalf of the RANZCR Faculty of Radiation Oncology Genito‐Urinary Group (FROGG)
Published: February 2012

Curative radiotherapy, with or without concurrent chemotherapy, is recognized as a standard treatment option for muscle‐invasive bladder cancer. It is commonly used for two distinct groups of patients: either for those medically unfit for surgery, or as part of a ‘bladder preserving’ management plan incorporating the possibility of salvage cystectomy. However, in both situations, the approach to radiotherapy varies widely around the world. The Australian and New Zealand Faculty of Radiation Oncology Genito‐Urinary Group recognised a need to develop consistent, evidence‐based guidelines for patient selection and radiotherapy technique in the delivery of curative radiotherapy. Following a workshop convened in May 2009, a working party collated opinions and conducted a wide literature appraisal linking each recommendation with the best available evidence. This process was subject to ongoing re‐presentation to the Faculty of Radiation Oncology Genito‐Urinary Group members prior to final endorsement. These Guidelines include patient selection, radiation target delineation, dose and fractionation schedules, normal tissue constraints and investigational techniques. Particular emphasis is given to the rationale for the target volumes described. These Guidelines provide a consensus‐based framework for the delivery of curative radiotherapy for muscle‐invasive bladder cancer. Widespread input from radiation oncologists treating bladder cancer ensures that these techniques are feasible in practice. We recommend these Guidelines be adopted widely in order to encourage a uniformly high standard of radiotherapy in this setting, and to allow for better comparison of outcomes.
Spectrum of imaging in Budd Chiari syndrome
Authors: Patil Pritam , Deshmukh Hemant , Popat Bhavesh , Rathod Krantikumar
Published: February 2012

Budd Chiari syndrome is an uncommon heterogeneous group of disorders which occur due to obstruction at any level from the hepatic venules to the junction of inferior vena cava and right atrium of heart which has significant morbidity and mortality. An early diagnosis of the disease is required for appropriate treatment. Due to the diffuse nature of the disease, normal biopsy findings do not exclude the disease. Proper clinical history and imaging are essential for definitive diagnosis. In this pictorial essay, we discuss the imaging spectrum of Budd Chiari syndrome.
Short‐term progression of wet AMD and correlation with 1‐year treatment results
Authors: Munk Marion , Kiss Christopher , Sulzbacher Florian , Eisenkölbl Stefan , Sacu Stefan , Kalcher Klaudius , Jampol Lee , Schmidt‐Erfurth Ursula
Published: February 2012

Purpose:  Quantification of short‐term progression of active neovascular age‐related macular degeneration and correlation with 1‐year outcome.

Methods:  Sixty‐five patients with newly diagnosed treatment‐naive active subfoveal choroidal neovascularization (CNV), who had participated in clinical trials testing anti‐vascular endothelial growth factor therapy, were retrospectively assessed. Early Treatment Diabetic Retinopathy Study best‐corrected visual acuity (BCVA), Spectral Domain Optical Coherence Tomography (SD‐OCT) and fluorescein angiography (FA) were performed twice during the pretreatment period. Changes in BCVA, central retinal thickness (CRT), average macular thickness (AMT) and leakage area were documented within this pretreatment period for all patients and for lesion type I (occult CNV, n = 42) and type II (classic CNV, n = 23). Three‐month and 1‐year BCVA were then correlated with the pretreatment period.

Results:  The pretreatment period was 19 ± 3 days (range: 2–108). Neither type I nor type II lesions showed a significant BCVA decrease or CRT/AMT increase during this period. On FA, mean leakage area increased significantly during the pretreatment period: in the pooled group from 5.50 ± 0.62 (screening) to 7.60 ± 0.86 mm2 (baseline) (p < 0.0001), in type II from 4.65 ± 0.90 to 7.83 ± 1.62 mm2 (p < 0.01) and in type I from 6.08 ± 0.85 to 7.45 ± 0.96 mm2 (p < 0.0001). The mean increase in leakage area per day was 0.046 ± 0.02 mm2, p = 0.034. Type II showed a daily growth of 0.09 ± 0.08 mm2 (p < 0.042) and type I 0.045 ± 0.008 mm2 per day (p < 0.0001). However, neither leakage area increase nor pretreatment period was correlated with 3‐month or 1‐year BCVA outcome.

Conclusions:  SD‐OCT and BCVA testing did not reveal deterioration during the pretreatment period. However, the leakage area progressed rapidly. Despite the rapid increasing leakage area, the 19‐day waiting period was not associated with a poorer visual outcome at 3 months and 1 year.
Efficacy of Dose Escalation of Tamsulosin for the Treatment of Lower Urinary Tract Symptoms
Authors: KIM Jin Wook , OH Mi Mi , YEO Jeong Kyun , BAE Jae Hyun , JOO Kwan Joong , CHOI Jong Bo , PARK Hong Seok , KIM Hyung Jee , MOON Du Geon , LEE Jeong Gu
Published: February 2012

Objectives: The aim of this study was to compare the efficacy of low (0.2 mg) and intermediate (0.4 mg) dose tamsulosin in treating lower urinary tract symptoms (LUTS).

Methods: Patients were treated with low‐dose tamsulosin for an initial run‐in period of 12 weeks, then divided into two groups based on their clinical improvement. Patients were measured for objective parameters of peak flow rate and postvoid residual urine volume, as well as subjective symptom scores and perceived patient benefit of treatment. The items were then integrated as the LUTS Outcome Score to determine dose increase or maintenance. Overall outcome was determined at 36 weeks.

Results: One hundred and seventy‐four patients were enrolled and started on 0.2 mg tamsulosin treatment. One hundred and fifty‐five patients completed the 36‐week study. Sixty patients required dose increase to 0.4 mg at the 12th week. Baseline characteristics showed that a patient who would benefit from 0.4 mg dosage had higher age, daytime frequency, and lower peak urine flow rate. Patients receiving both 0.2 and 0.04 mg both showed improved clinical outcome measures. Higher improvement was found in voiding component symptom scores and urine flow rate improvement in patients receiving an increased dose.

Conclusion: Both low‐ and intermediate‐dose tamsulosin are effective treatment regimens. Increasing from low to intermediate dose should follow assessment of both objective and subjective improvements.
Lung Cancer Risk in Workers in the Meat and Poultry Industries – A Review
Authors: Johnson E. S. , Choi K.‐M.
Published: February 2012

Laboratory and in vivo studies in primates, and serological evidence in humans, indicate that food animal oncogenic viruses show potential for causing cancer in humans. However, until fairly recently, supporting analytic epidemiologic studies have been lacking and have concentrated on lung cancer. We conducted an extensive Medline search and reviewed 60 studies investigating lung cancer risk in highly exposed workers in the meat and poultry industries. The overwhelming majority of studies of different designs (including all the cohort mortality and cancer incidence studies) indicate at least a 30% excess risk of lung cancer in meat and poultry plant workers, even after controlling for smoking. Evidence points to food animal oncogenic microorganisms as one of the main causes. This has important public health implications because the general population is also widely exposed. Studies carried out thus far have not had sufficient statistical power to investigate other potentially carcinogenic exposures within the industries. Thus, large studies that can adequately control for occupational and non‐occupational confounding factors are needed, so that the possible role of food animal oncogenic viruses in the occurrence of human lung cancer can be clearly defined.
Fibrinous pericarditis and cardiac tamponade in a 3‐week‐old pony foal
Authors: Alcott C. J. , Howard J. , Wong D. , Haynes J.
Published: February 2012

A 3‐week‐old Pony of the Americas foal presented with a history of respiratory distress presumed to result fromActinobacillus equulipleuropneumonia and septic arthritis. Failure of transfer of passive colostral immunity was suspected, but not confirmed, based on a history of the foal being separated from its dam shortly after parturition. Transient improvement was noted following thoracocentesis and removal of approximately 600 ml of pleural fluid but progressive clinical signs of congestive heart failure developed. Fibrinous pericarditis with evidence of cardiac tamponade was subsequently diagnosed via thoracic ultrasonography. Early clinical signs of cardiogenic shock were identified and fibrinopurulent exudate removed through a catheter placed with ultrasound guidance into the pericardium. The foal experienced cardiorespiratory arrest during the procedure and died despite resuscitative efforts.Post mortemexamination identified extensive hypertrophy of the pericardium, septic arthritis, mild pleural effusion and focal bronchopneumonia. This report details the clinical evaluation, haematology, treatment andpost mortempathology of a foal withActinobacillus equuliassociated fibrinous pericarditis, as well as a brief review of cardiac tamponade.
Exploring stakeholder perspectives on medication review services for older residents in retirement villages
Authors: Lee Cik Yi , George Johnso , Elliott Rohan A , Stewart Ka
Published: February 2012

Objective

To explore stakeholder perspectives on a government-subsidised Home Medicines Review (HMR) service and factors affecting the uptake of HMRs for older residents of retirement villages in Australia.

Methods

Thirty-two in-depth interviews and four focus groups were undertaken with a purposive sample of 32 residents of retirement villages, 10 pharmacists, nine general practitioners (GPs) and a general practice nurse. Data were transcribed verbatim and analysed using the framework approach.

Key findings

Three major themes were identified: participants' perceptions of the HMR service, barriers to the uptake of HMRs and strategies for increasing the uptake of HMR. Residents had positive, negative or mixed perceptions, whereas health professionals were generally positive about the benefits of the service. Barriers to the uptake of HMRs were related to GPs, pharmacists, patients and the healthcare system. A strategy recommended by multiple stakeholders for increasing the uptake of HMRs was to use a multi-faceted intervention targeting residents and their health professionals.

Conclusions

Multiple barriers to the uptake of HMRs and multiple strategies for increasing the uptake of HMRs were identified. These findings could inform the design of interventions to improve uptake of HMRs by residents and health professionals, in turn leading to better medicine use and safety.
Internal Heat Transfer Coefficient Determination in a Packed Bed From the Transient Response Due to Solid Phase Induction Heating
Authors: Geb David , Zhou Feng , Catton Ivan
Published: February 2012

Nonintrusive measurements of the internal heat transfer coefficient in the core of a randomly packed bed of uniform spherical particles are made. Under steady, fully-developed flow the spherical particles are subjected to a step-change in volumetric heat generation rate via induction heating. The fluid temperature response is measured. The internal heat transfer coefficient is determined by comparing the results of a numerical simulation based on volume averaging theory (VAT) with the experimental results. The only information needed is the basic material and geometric properties, the flow rate, and the fluid temperature response data. The computational procedure alleviates the need for solid and fluid phase temperature measurements within the porous medium. The internal heat transfer coefficient is determined in the core of a packed bed, and expressed in terms of the Nusselt number, over a Reynolds number range of 20 to 500. The Nusselt number and Reynolds number are based on the VAT scale hydraulic diameter, dh=4ɛ/S. The results compare favorably to those of other researchers and are seen to be independent of particle diameter. The success of this method, in determining the internal heat transfer coefficient in the core of a randomly packed bed of uniform spheres, suggests that it can be used to determine the internal heat transfer coefficient in other porous media.
A Numerical Study of Concurrent Flame Propagation Over Methanol Pool Surface
Authors: Mansoor Ali Seik , Raghavan Vasudevan , Velusamy K. , Tiwari Shaligram
Published: February 2012

Concurrent flame spread over methanol pool surface under atmospheric conditions and normal gravity has been numerically investigated using a transient, two-phase, reacting flow model. The average flame spread velocities for different concurrent air velocities predicted using the model are quite close to the experimental data available in the literature. As the air velocity is increased, the fuel consumption rate increases and aids in faster flame spread process. The flame initially anchors around the leading edge of the pool and the flame tip spreads over the pool surface. The rate of propagation of flame tip along the surface is seen to be steady without fluctuations. The flame spread velocity is found to be nonuniform as the flame spreads along the pool surface. The flame spread velocity is seen to be higher initially. It then decreases up to a point when the flame has propagated to around 40% to 50% of the pool length. At this position, a secondary flame anchoring point is observed, which propagates toward the trailing edge of the pool. As a result, there is an increasing trend observed in the flame spread velocity. As the air velocity is increased, the initial flame anchoring point moves downstream of the leading edge of the fuel pool. The variations of interface quantities depend on the initial flame anchoring location and the attainment of thermodynamic equilibrium between the liquid- and gas-phases.
Scaling Weld or Melt Pool Shape Affected by Thermocapillary Convection With High Prandtl Numbers
Authors: Wei P. S. , Lin C. L. , Liu H. J. , DebRoy T.
Published: February 2012

The molten pool shape and thermocapillary convection during melting or welding of metals or alloys are self-consistently predicted from scale analysis. Determination of the molten pool shape and transport variables is crucial due to their close relationship with the strength and properties of the fusion zone. In this work, surface tension coefficient is considered to be negative, indicating an outward surface flow, whereas high Prandtl number represents a reduced thickness of the thermal boundary layer compared to that of the momentum boundary layer. Since the Marangoni number is usually very high, the domain of scaling is divided into hot, intermediate and cold corner regions, boundary layers along the solid–liquid interface and ahead of the melting front. The results show that the width and depth of the pool, peak and secondary surface velocities, and maximum temperatures in the hot and cold corner regions can be explicitly and separately determined as functions of working variables, or Marangoni, Prandtl, Peclet, Stefan, and beam power numbers. The scaled results agree with numerical results and available experimental data.
Design of Simulated Server Racks for Data Center Research
Authors: Smith James F. , Abdelmaksoud Waleed A. , Erden Hamza S. , Dannenhoffer John F. , Dang Thong Q. , Khalifa H. Ezzat , Schmidt Roger R. , Iyengar Madhusudan
Published: February 2012

Conducting experiments on real high-density computer servers can be an expensive and risky task due to the risks associated with unintended inlet temperatures that exceed the server’s red-line temperature limit. Presented herein is the development of the simulated chassis that mimic real computer servers. Briefly, twelve high-power simulated chassis were designed and built to accurately simulate the actual operating conditions of a real computer chassis in a data center. Each simulated chassis is designed to have approximately 300 Pa pressure drop at a flow rate of 600 cfm to represent a real IBM server chassis. Additionally, the simulated chassis are designed to match the thermal mass of a real server. Eight of the simulated chassis were designed to have constant speed fans and variable heating power while the remaining four chassis were designed to have variable speed fans and variable heating power. Further discussions about the design phase of the simulated chassis are the substantial part of this paper. Underlining the challenges and safety issues with high-power chassis, guidelines for designing and constructing a chassis that simulates the real environment of a typical data center are presented.
Optimized Thermoelectric Module-Heat Sink Assemblies for Precision Temperature Control
Authors: Zhang Rui , Brooks David A. , Hodes Marc , van Lieshout Matthew , Manno Vincent P.
Published: February 2012

Robust precision temperature control of photonics components is achieved by mounting them on thermoelectric modules (TEMs) which are in turn mounted on heat sinks. However, the power consumption of TEMs is high because high currents are driven through Bi2Te3-based semiconducting materials with high electrical resistivity and finite thermal conductivity. This problem is exacerbated when the ambient temperature surrounding a TEM varies in the usual configuration where the air-cooled heat sink a TEM is mounted to is of specified thermal resistance. Indeed, heat sinks of negligible and relatively high thermal resistances minimize TEM power consumption for sufficiently high and low ambient temperatures, respectively. Optimized TEM-heat sink assemblies reduce the severity of this problem. In the problem considered, total footprint of thermoelectric material in a TEM, thermoelectric material properties, heat load, component operating temperature, relevant component-side thermal resistances and ambient temperature range are prescribed. Provided is an algorithm to compute the unique combination of the height of the pellets in a TEM and the thermal resistance of the heat sink attached to it which minimizes the maximum power consumption of the TEM over the specified ambient temperature range. This optimization maximizes the fraction of the power budget in an optoelectronics circuit pack available for other uses. Implementation of the algorithm is demonstrated through an example for a typical set of conditions.
The Effects of Variations in Manufacturing on PCB Thermal Properties
Authors: Maddox John F. , Knight Roy W. , Bhavnani Sushil H.
Published: February 2012

The thermal performance of an electronic device is heavily dependent on the properties of the printed circuit board (PCB) to which it is attached. However, even small variations in the process used to fabricate a PCB can have drastic effects on its thermal properties. Therefore, it is necessary to experimentally verify that each stage in the manufacturing process is producing the desired result. Steady state thermal resistance measurements, taken with a comparative cut bar apparatus based on ASTM D 5470-06, were used to compare PCBs manufactured from the same design by different vendors and the effects of vias filled with epoxy versus unfilled vias on the thermal resistance of a PCB. It was found that the thermal resistance of the PCBs varied by as much as 30% between vendors and that the PCBs with epoxy filled vias had a higher thermal resistance than those with unfilled vias, possibly due to the order in which the manufacturing steps were taken.
Development of Micro/Nano Engineered Wick-Based Passive Heat Spreaders for Thermal Management of High Power Electronic Devices
Authors: Altman David H. , Wasniewski Joseph R. , North Mark T. , Kim Sungwon S. , Fisher Timothy S.
Published: February 2012

Spreading of high-flux electronics heat is a critical part of any packaging design. This need is particularly profound in advanced devices where the dissipated heat fluxes have been driven well over 100W/cm2. To address this challenge, researchers at Raytheon, Thermacore and Purdue are engaged in the development and characterization of a low resistance, coefficient of thermal expansion (CTE)-matched multi-chip vapor chamber heat spreader, which utilizes capillary driven two-phase heat transport. The vapor chamber technology under development overcomes the limitations of state-of-the-art approaches by combining scaled-down sintered Cu powder and nanostructured materials in the vapor chamber wick to achieve low thermal resistance. Cu-coated vertically aligned carbon nanotubes is the nanostructure of choice in this development. Unique design and construction techniques are employed to achieve CTE-matching with a variety of device and packaging materials in a low-profile form-factor. This paper describes the materials, design, construction and characterization of these vapor chambers. Results from experiments conducted using a unique high-heat flux capable 1DSS test facility are presented, exploring the effects of various microscopic wick configurations, CNT-functionalizations and fluid charges on thermal performance. The impacts of evaporator wick patterning, CNT evaporator functionalization and CNT condenser functionalization on performance are assessed and compared to monolithic Cu wick configurations. Thermal performance is explained as a function of applied heat flux and temperature through the identification of dominant component thermal resistances and heat transfer mechanisms. Finally, thermal performance results are compared to an equivalent solid conductor heat spreader, demonstrating a >40% reduction in thermal resistance. These results indicate great promise for the use of such novel vapor chamber technology in thickness-constrained high heat flux device packaging applications.
An Overview of the Power 775 Supercomputer Water Cooling System
Authors: Ellsworth Michael J. , Goth Gary F. , Zoodsma Randy J. , Arvelo Amilcar , Campbell Levi A. , Anderl William J.
Published: February 2012

Back in 2008 IBM reintroduced water cooling technology into its high performance computing platform, the Power 575 Supercomputing node/system. Water cooled cold plates were used to cool the processor modules which represented about half of the total system (rack) heat load. An air-to-liquid heat exchanger was also mounted in the rear door of the rack to remove a significant fraction of the other half of the rack heat load; the heat load to air. The next generation of this platform, the Power 775 Supercomputing node/system, is a monumental leap forward in computing performance and energy efficiency. The compute node and system were designed from the start with water cooling in mind. The result, a system with greater than 96% of it’s heat load conducted directly to water; a system that, together with a rear door heat exchanger, removes 100% of it’s heat load to water with no requirement for room air conditioning. In addition to the processor, memory, power conversion, and I/O electronics conduct their heat to water. Included within the framework of the system is a disk storage unit (disc enclosure) containing an interboard air-to-water heat exchanger. This paper will overview the water cooling system featuring the water conditioning unit and rack manifolds. Advances in technology over this system’s predecessor will be highlighted. An overview of the cooling assemblies within the server drawer (i.e. central electronics complex,) the disc enclosure, and the centralized (Bulk) power conversion system will also be given. Further, techniques to enhance performance and energy efficiency will also be described.
Single-Phase Liquid Cooling of a Quad-Core Processor
Authors: Chauhan Anjali , Sammakia Bahgat , Afram Furat F. , Ghose Kanad , Refai-Ahmed Gamal , Agonafer Dereje
Published: February 2012

Multicore microprocessor chips have emerged as an industry standard in recent years and have enabled Moore’s Law to be sustained when one considers the collective performance achieved by multiple cores. The industry has favored floor plans that use identical or symmetric layouts of individual cores in a linear array or a two-dimensional (2D) array, oblivious to the non-uniform heat dissipation within each core. Such non-uniform heat dissipations have hot spots within each core that must be aggressively cooled to avoid temporary or permanent device failures that can result from high temperature gradients. This paper evaluates alternative core layouts and microchannel configurations of a single-phase liquid cooling system for multi-core chips. We first examine the use of different planar flow patterns in microchannels for a realistic quad-core processor with non-uniform energy dissipation within each core. The direction of the flows in the microchannels is varied to achieve minimum hot spot temperatures on the die. A symmetric layout of the four cores with minimum achievable hot spot temperature is then selected and subjected to impingement flow. We establish the thermal efficiency of the optimized core floor plan compared to the traditional floor plan in a quad-core design and show that impingement provides the most efficient cooling solution compared to microchannels with planar flows for the same pressure difference.
Energy Savings Through Hot and Cold Aisle Containment Configurations for Air Cooled Servers in Data Centers
Authors: Schmidt Roger , Vallury Aparna , Iyengar Madhusudan
Published: February 2012

The increased focus on green technologies and energy efficiency coupled with the insatiable desire of IT equipment customers for more performance has driven manufacturers to deploy energy efficient technologies in the data centers. This paper describes a technique to achieve significant energy savings by preventing the cold and hot air streams within the data center from mixing. More specifically, techniques will be described that will separate the cool supply air to the server racks and exhaust hot air that returns to the air conditioning units. This separation can be achieved by three types of containment systems — cold aisle containment, hot aisle containment, and server rack exhaust chimneys. The advantages and disadvantages of each technique will be outlined. To show the potential for energy efficiency improvements a case study in deploying a cold aisle containment solution for a 8944 ft2 data center will be presented. This study will show that 59% of the energy required for the computer room air conditioning (CRAC) units used in a traditional open type data center could be saved.
Solder Joint Reliability in Underfilled Flip Chip Package With a Consideration of Chip-Package-Interaction (CPI)
Authors: Kwak Jae B. , Yu Da , Nguyen Tung T. , Park Seungbae
Published: February 2012

Since the introduction of Cu/low-k as the interconnect material, the chip-package interaction (CPI) has become a critical reliability challenge for flip chip packages. Revision of underfill material must be considered, which may compromise the life of flipchip interconnect by releasing the stresses transferred to the silicon devices from the solder bumps, and thereby maintain the overall package reliability. Thus, it is important to understand the thermo-mechanical behavior of solder bumps. In this study, the solder bump reliability in flip chip package was investigated through an experimental technique and numerical analysis. For the experimental assessment, thermo-mechanical behavior of solder joints, especially the solder bumps located at the chip corners where most failures usually occur was investigated. Digital Image Correlation (DIC) technique with optical microscope was utilized to quantify the deformation behavior and strains of a solder bump of flip-chip package subjected to thermal loading from 25°C to 100°C. As a specimen preparation for DIC technique, a flip-chip specimen was cross-sectioned before a manual polishing process followed by wet etching method in order to generate natural speckle patterns with high enough contrast on the measuring surface. Finally, finite element analysis (FEA) was conducted by simulating the thermal loading applied in the experiments, and validated with experimental results. Then, using the FEA analysis, parametric study for underfill material properties were performed on the reliability of flip chip package, by varying the glass transition temperature (Tg), Young’s modulus (E), and coefficient of thermal expansion (CTE). Averaged plastic work of the corner solder bump and stress at the die side were obtained and used as damage indicators for solder bumps and low-k dielectrics layer, respectively. The results show that high Tg, and E of underfill are generally desirable to improve the reliability of solder interconnects in the flip chip package.
Role of Interface Thermal Boundary Resistance, Straining, and Morphology in Thermal Conductivity of a Set of Si-Ge Superlattices and Biomimetic Si-Ge Nanocomposites
Authors: Samvedi Vikas , Tomar Vikas
Published: February 2012

Nanoscale engineered materials with tailored thermal properties are desirable for applications such as highly efficient thermoelectric, microelectronic and optoelectronic devices. It has been shown earlier that by judiciously varying interface thermal boundary resistance (TBR) thermal conductivity in nanostructures could be controlled. Two types of nanostructures that have gained significant attention owing to the presence of TBR are superlattices and nanocomposites. A systematic comparison of thermal behavior of superlattices and nanocomposites considering their characteristic structural factors such as periodicity and period length for superlattices, and morphology for nanocomposites, under different extents of straining at a range of temperatures remains to be performed. In this presented work, such analyses are performed for a set of Si-Ge superlattices and Si-Ge biomimetic nanocomposites using non-equilibrium molecular dynamics (NEMD) simulations at three different temperatures (400 K, 600 K, and 800 K) and at strain levels varying between −10% and 10%. The analysis of interface TBR contradicts the usual notion that each interface contributes equally to the heat transfer resistance in a layered structure. The dependence of thermal conductivity of superlattice on the direction of heat flow gives it a characteristic somewhat similar to a thermal diode as found in this study. The comparison of thermal behavior of superlattices and nanocomposites indicate that the nanoscale morphology differences between the superlattices and the nanocomposites lead to a striking contrast in the phonon spectral density, interfacial thermal boundary resistance, and thermal conductivity. Both compressive and tensile strains are observed to be important factors in tailoring the thermal conductivity of the analyzed superlattices, whereas have very insignificant influence on the thermal conductivity of the analyzed nanocomposites.
First-principles study of field-emission from carbon nanotubes in the presence of methane
Authors: Kashefian Naieni Ali , Yaghoobi Parham , Nojeh Alireza
Published: February 2012

Carbon nanotubes are promising candidates for field-emitters. It has been shown that the presence of various gases can enhance or degrade the performance of nanotube emitters. Small hydrocarbons are of particular interest because of their ability to enhance the emission properties. The authors report a simulation study of field-emission from a carbon nanotube exposed to methane in various configurations with an emphasis on calculating the emission current. The Hartree–Fock theory combined with a Green’s functions approach was used for the simulations. It was observed that the change in the emission current strongly depends on the particular arrangement of the methane molecules on the nanotube.
Optical properties of AlN thin films grown by plasma enhanced atomic layer deposition
Authors: Alevli Mustafa , Ozgit Cagla , Donmez Inci , Biyikli Necmi
Published: February 2012

Crystalline aluminum nitride (AlN) films have been prepared by plasma enhanced atomic layer deposition within the temperature range of 100 and 500 °C. The AlN films were characterized by x-ray diffraction, spectroscopic ellipsometry, Fourier transform infrared spectroscopy, optical absorption, and photoluminescence. The authors establish a relationship between growth temperature and optical properties and in addition, the refractive indices of the AlN films were determined to be larger than 1.9 within the 300–1000 nm wavelength range. Infrared reflectance spectra confirmed the presence of E1(TO) and A1(LO) phonon modes at ∼660 cm−1 and 895 cm−1, respectively. Analysis of the absorption spectroscopy show an optical band edge between 5.78 and 5.84 eV and the absorption and photoluminescence emission properties of the AlN layers revealed defect centers in the range of 250 and 300 nm at room temperature.
Horizontal Lloyd mirror patterns from straight and curved nonlinear internal waves
Authors: McMahon K. G. , Reilly-Raska L. K. , Siegmann W. L. , Lynch James F. , Duda T. F.
Published: February 2012

Experimental observations and theoretical studies show that nonlinear internal waves occur widely in shallow water and cause acoustic propagation effects including ducting and mode coupling. Horizontal ducting results when acoustic modes travel between internal wave fronts that form waveguide boundaries. For small grazing angles between a mode trajectory and a front, an interference pattern may arise that is a horizontal Lloyd mirror pattern. An analytic description for this feature is provided along with comparisons between results from the formulated model predicting a horizontal Lloyd mirror pattern and an adiabatic mode parabolic equation. Different waveguide models are considered, including boxcar and jump sound speed profiles where change in sound speed is assumed 12 m/s. Modifications to the model are made to include multiple and moving fronts. The focus of this analysis is on different front locations relative to the source as well as on the number of fronts and their curvatures and speeds. Curvature influences mode incidence angles and thereby changes the interference patterns. For sources oriented so that the front appears concave, the areas with interference patterns shrink as curvature increases, while convexly oriented fronts cause patterns to expand.
Wave motion and dispersion phenomena: Veering, locking and strong coupling effects
Authors: Mace Brian R. , Manconi Elisabetta
Published: February 2012

The dispersion curves describe wave propagation in a structure, each branch representing a wave mode. As frequency varies the wavenumbers change and a number of dispersion phenomena may occur. This paper characterizes, analyzes, and quantifies these phenomena in general terms and illustrates them with examples. Two classes of phenomena occur. Weak coupling phenomena—veering and locking—arise when branches of the dispersion curves interact. These occur in the vicinity of the frequency at which, for undamped waveguides, the dispersion curves in the uncoupled waveguides would cross: if two dispersion curves (representing either propagating or evanescent waves) come close together as frequency increases then the curves either veer apart or lock together, forming a pair of attenuating oscillatory waves, which may later unlock into a pair of either propagating or evanescent waves. Which phenomenon occurs depends on the product of the gradients of the dispersion curves. The wave mode shapes which describe the deformation of the structure under the passage of a wave change rapidly around this critical frequency. These phenomena also occur in damped systems unless the levels of damping of the uncoupled waveguides are sufficiently different. Other phenomena can be attributed to strong coupling effects, where arbitrarily light stiffness or gyroscopic coupling changes the qualitative nature of the dispersion curves.