bluuebunny/crossref_metadata_2025 huggingface dataset:
Dissecting the proteome dynamics of the early heat stress response leading to plant survival or death in Arabidopsis
Authors: Echevarría‐Zomeño Sira , Fernández‐Calvino Lourdes , Castro‐Sanz Ana B. , López Juan Antonio , Vázquez Jesús , Castellano M. Mar
Published: November 2015

In many plant species, an exposure to a sublethal temperature triggers an adaptative response called acclimation. This response involves an extensive molecular reprogramming that allows the plant to further survive to an otherwise lethal increase of temperature. A related response is also launched under an abrupt and lethal heat stress that, in this case, is unable to successfully promote thermotolerance and therefore ends up in plant death. Although these molecular programmes are expected to have common players, the overlapping degree and the specific regulators of each process are currently unknown.

We have carried out a high‐throughput comparative proteomics analysis during acclimation and during the early stages of the plant response to a severe heat stress that lead Arabidopsis seedlings either to survival or death. This analysis dissects these responses, unravels the common players and identifies the specific proteins associated with these different fates. Thermotolerance assays of mutants in genes with an uncharacterized role in heat stress demonstrate the relevance of this study to uncover both positive and negative heat regulators and pinpoint a pivotal role of JR1 and BAG6 in heat tolerance.
Pharmacological induction of skin pigmentation unveils the neuroendocrine circuit regulated by light
Authors: Bertolesi Gabriel E. , Vazhappilly Sherene T. , Hehr Carrie L. , McFarlane Sarah
Published: November 2015

Light‐regulated skin colour change is an important physiological process in invertebrates and lower vertebrates, and includes daily circadian variation and camouflage (i.e. background adaptation). The photoactivation of melanopsin‐expressing retinal ganglion cells (mRGCs) in the eye initiates an uncharacterized neuroendocrine circuit that regulates melanin dispersion/aggregation through the secretion of alpha‐melanocyte‐stimulating hormone (α‐MSH). We developed experimental models of normal or enucleated Xenopus embryos, as well as in situ cultures of skin of isolated dorsal head and tails, to analyse pharmacological induction of skin pigmentation and α‐MSH synthesis. Both processes are triggered by a melanopsin inhibitor, AA92593, as well as chloride channel modulators. The AA9253 effect is eye‐dependent, while functional data in vivo point to GABAA receptors expressed on pituitary melanotrope cells as the chloride channel blocker target. Based on the pharmacological data, we suggest a neuroendocrine circuit linking mRGCs with α‐MSH secretion, which is used normally during background adaptation.
FK506 regulates pigmentation by maturing the melanosome and facilitating their transfer to keratinocytes
Authors: Jung Hyejung , Chung Heesung , Chang Sung Eun , Kang Duk‐Hee , Oh Eok‐Soo
Published: November 2015

Despite the clinical ability of topical tacrolimus (FK506) to effectively promote repigmentation in vitiligo, the underlying mechanism through which FK506 regulates melanogenesis was previously unclear. We found that FK506 treatment increased the melanin contents (especially that of eumelanin) in both melanocytes and melanoma cells. This treatment did not affect the transcription levels of tyrosinase, suggesting that FK506 increases melanin synthesis by regulating cellular levels of tyrosinase. Interestingly, FK506 promoted melanosome maturation by increasing melanosomal pH (a marker of melanosome maturation), thereby enhancing the stability of melanosome‐localized tyrosinase. In addition, FK506 enhanced UVB‐mediated melanosome secretion, the uptake of melanosomes by HaCaT cells, and the transfer of melanosomes to keratinocytes co‐cultured with melanocytes. Together, these findings suggest that FK506 contributes to melanin synthesis by regulating the maturation of melanosomes and their transfer to keratinocytes. This offers a novel regulatory mechanism through which FK506 and UVB can have a combined effect on melanogenesis.
Moral Testimony Pessimism and the Uncertain Value of Authenticity
Authors: Mogensen Andreas L.
Published: November 2015

Many philosophers believe that there exist distinctive obstacles to relying on moral testimony. In this paper, I criticize previous attempts to identify these obstacles and offer a new theory. I argue that the problems associated with moral deference can't be explained in terms of the value of moral understanding, nor in terms of aretaic considerations related to subjective integration. Instead, our uneasiness with moral testimony is best explained by our attachment to an ideal of authenticity that places special demands on our moral beliefs.
Responsibility and Judgment
Authors: Strabbing Jada Twedt
Published: November 2015

I focus on the type of responsibility that an agent has for actions that express his practical identity, making it appropriate to evaluate him on the basis of those actions. This kind of responsibility is often called attributability. In this paper, I argue for a novel view of attributability—the Judgment Responsiveness View (JRV). According to the JRV, an agent is attributability responsible for an action A if and only if A results from either 1) his responding to his judgments about the (normative) reasons that he has in favor of doing A by doing A or 2) his failing to exercise his capacity to respond to his judgments about the (normative) reasons that he has against doing A by not doing A. The JRV diverges from other views of attributability for actions in two significant respects. First, it is not reasonably thought of as a “deep self view.” According to deep self views, attributable actions are actions that express deep features of the agent, such as his fundamental values, cares, or commitments. As I show, thinking in terms of the deep self is too narrow for attributability. Second, unlike other views, the JRV claims—via condition 2)—that we can be attributionally responsible for actions that result from failing to exercise the attributability‐relevant capacity to avoid them. My argument for the JRV thus shows that attributability is a broader and richer conception of responsibility than has been previously thought.
Safety of IV amikacin in the treatment of pulmonary non‐tuberculous mycobacterial disease
Authors: Ellender Claire M. , Law Dayna B. , Thomson Rachel M. , Eather Geoffrey W.
Published: November 2015

Background and objective

Pulmonary non‐tuberculous mycobacterial (NTM) disease has a high mortality rate and often requires treatment with intravenous amikacin. We report on safety data in patients treated with intravenous amikacin for pulmonary.

Methods

A retrospective observational study (2002–2012) was performed including 45 patients that met American Thoracic Society criteria for pulmonary NTM disease and were treated with intravenous amikacin at three hospitals in Brisbane, Australia. The aim was to define the rates of common adverse effects, the patient and regimen factors associated with these adverse effects and describe the rates of treatment success and associated factors.

Results

Forty‐five patients (34 women; median age 63 years) were treated for Mycobacterium intracellulare (25), Mycobacterium abscessus (13), Mycobacterium avium (6) and Mycobacterium fortuitum (1) using multi‐drug therapy that included IV amikacin. Transient ototoxicity was seen in eight (18%) but long‐term ototoxicity was seen in only three (7%). There were no cases of nephrotoxicity and no long‐term vestibulotoxicity. Sustained culture conversion at 6 months was only found in 17 (38%), however, the majority (34 patients, 76%) had a clinical response to treatment determined by an improvement in symptoms.

Conclusion

Carefully selected and closely monitored patients with pulmonary NTM can be treated using IV amikacin safely with low rates of toxicity. No pretreatment patient or regimen factors were predictive of toxicity or treatment success in this small cohort. Lower treatment success rates were found than previous trials suggest there is a difficult balance in this patient group between treatment success and toxicities.
Inference for Multiple Change Points in Time Series via Likelihood Ratio Scan Statistics
Authors: Yau Chun Yip , Zhao Zifeng
Published: November 2015

We propose a likelihood ratio scan method for estimating multiple change points in piecewise stationary processes. Using scan statistics reduces the computationally infeasible global multiple-change-point estimation problem to a number of single-change-point detection problems in various local windows. The computation can be efficiently performed with order O{npt log (n)}. Consistency for the estimated numbers and locations of the change points are established. Moreover, a procedure is developed for constructing confidence intervals for each of the change points. Simulation experiments and real data analysis are conducted to illustrate the efficiency of the likelihood ratio scan method.
Acute and delayed peripheral and central neuromuscular alterations induced by a short and intense downhill trail run
Authors: Giandolini M. , Horvais N. , Rossi J. , Millet G. Y. , Morin J.‐B. , Samozino P.
Published: November 2015

Downhill sections are highly strenuous likely contributing to the development of neuromuscular fatigue in trail running. Our purpose was to investigate the consequences of an intense downhill trail run (DTR) on peripheral and central neuromuscular fatigue at knee extensors (KE) and plantar flexors (PF). Twenty‐three runners performed a 6.5‐km DTR (1264‐m altitude drop) as fast as possible. The electromyographic activity of vastus lateralis (VL) and gastrocnemius lateralis (GL) was continuously recorded. Neuromuscular functions were assessed Pre‐, Post‐, and 2‐day Post‐DTR (Post2d). Maximal voluntary torques decreased Post (∼ −19% for KE, ∼ −25% for PF) and Post2d (∼ −9% for KE, ∼ −10% for PF). Both central and peripheral dysfunctions were observed. Decreased KE and PF voluntary activation (VA), evoked forces, VL M‐wave amplitude, and KE low‐frequency fatigue were observed at Post. Changes in VL M‐wave amplitude were negatively correlated to VL activity during DTR. Changes in PF twitch force and VA were negatively correlated to GL activity during DTR. The acute KE VA deficit was about a third of that reported after ultramarathons, although peripheral alterations were similar. The prolonged force loss seems to be mainly associated to VA deficit likely induced by the delayed inflammatory response to DTR‐induced ultrastructural muscle damage.
The Copenhagen Muscle Research Centre (CMRC) 1994–2004
Authors: Joyner M. , Kjaer M. , Larsen P. O.
Published: November 2015

This paper presents an impressionistic summary of the formation, activities, accomplishments, and impact of the Copenhagen Muscle Research Centre (CMRC) from 1994 to 2004. The history of the CMRC is viewed in the context of the goals of the original program, the tradition of excellence in exercise physiology in Copenhagen since the time of August Krogh, and the structure of the center. The key role of Professor Bengt Saltin as a visionary, flexible, and inclusive leader is highlighted.
Muscle glycogen and cell function – Location, location, location
Authors: Ørtenblad N. , Nielsen J.
Published: November 2015

The importance of glycogen, as a fuel during exercise, is a fundamental concept in exercise physiology. The use of electron microscopy has revealed that glycogen is not evenly distributed in skeletal muscle fibers, but rather localized in distinct pools. In this review, we present the available evidence regarding the subcellular localization of glycogen in skeletal muscle and discuss this from the perspective of skeletal muscle fiber function. The distribution of glycogen in the defined pools within the skeletal muscle varies depending on exercise intensity, fiber phenotype, training status, and immobilization. Furthermore, these defined pools may serve specific functions in the cell. Specifically, reduced levels of these pools of glycogen are associated with reduced SR Ca2+ release, muscle relaxation rate, and membrane excitability. Collectively, the available literature strongly demonstrates that the subcellular localization of glycogen has to be considered to fully understand the role of glycogen metabolism and signaling in skeletal muscle function. Here, we propose that the effect of low muscle glycogen on excitation‐contraction coupling may serve as a built‐in mechanism, which links the energetic state of the muscle fiber to energy utilization.
The elite cross‐country skier provides unique insights into human exercise physiology
Authors: Holmberg H.‐C.
Published: November 2015

Successful cross‐country skiing, one of the most demanding of endurance sports, involves considerable physiological challenges posed by the combined upper‐ and lower‐body effort of varying intensity and duration, on hilly terrain, often at moderate altitude and in a cold environment. Over the years, this unique sport has helped physiologists gain novel insights into the limits of human performance and regulatory capacity. There is a long‐standing tradition of researchers in this field working together with coaches and athletes to improve training routines, monitor progress, and refine skiing techniques. This review summarizes research on elite cross‐country skiers, with special emphasis on the studies initiated by Professor Bengt Saltin. He often employed exercise as a means to learn more about the human body, successfully engaging elite endurance athletes to improve our understanding of the demands, characteristics, and specific effects associated with different types of exercise.
Performance in sports – With specific emphasis on the effect of intensified training
Authors: Bangsbo J.
Published: November 2015

Performance in most sports is determined by the athlete's technical, tactical, physiological and psychological/social characteristics. In the present article, the physical aspect will be evaluated with a focus on what limits performance, and how training can be conducted to improve performance. Specifically how intensified training, i.e., increasing the amount of aerobic high‐intensity and speed endurance training, affects physiological adaptations and performance of trained subjects. Periods of speed endurance training do improve performance in events lasting 30 s–4 min, and when combined with aerobic high‐intensity sessions, also performance during longer events. Athletes in team sports involving intense exercise actions and endurance aspects, such as soccer and basketball, can also benefit from intensified training. Speed endurance training does reduce energy expenditure and increase expression of muscle Na+, K+ pump α subunits, which may preserve muscle cell excitability and delay fatigue development during intense exercise. When various types of training are conducted in the same period (concurrent training), as done in a number of sports, one type of training may blunt the effect of other types of training. It is not, however, clear how various training modalities are affecting each other, and this issue should be addressed in future studies.
Exercise, muscle, and CHO metabolism
Authors: Hargreaves M.
Published: November 2015

Carbohydrates (CHO) are a key source of energy for contracting skeletal muscle during strenuous exercise and fatigue during such exercise often coincides with CHO depletion. Our current understanding of the importance of CHO for exercise metabolism has its foundations in classic studies in the early 20th century by Scandinavian physiologists and Bengt Saltin contributed significantly to that tradition. This brief review summarizes our contemporary understanding of key aspects of muscle glycogen and glucose metabolism during exercise, through the lens of seminal studies by Bengt Saltin.
Regulation of cardiac output in hypoxia
Authors: Siebenmann Christoph , Lundby Carsten
Published: November 2015

This brief review addresses the regulation of cardiac output (Q) at rest and during submaximal exercise in acute and chronic hypoxia. To preserve systemic O2 delivery in acute hypoxia Q is increased by an acceleration of heart rate, whereas stroke volume (SV) remains unchanged. Tachycardia is governed by activation of carotid and aortic chemoreceptors and a concomitant reduction in arterial baroreflex activation, all balancing sympathovagal activity toward sympathetic dominance. As hypoxia extends over several days a combination of different adaptive processes restores arterial O2 content to or beyond sea level values and hence Q normalizes. The latter however occurs as a consequence of a decrease in SV whereas tachycardia persists. The diminished SV reflects a lower left ventricular end‐diastolic volume which is primarily related to hypoxia‐generated reduction in plasma volume. Hypoxic pulmonary vasoconstriction may contribute by increasing right ventricular afterload and thus decreasing its ejection fraction. In summary, the Q response to hypoxia is the result of a complex interplay between several physiological mechanisms. Future studies are encouraged to establish the individual contributions of the different components from an integrative perspective.
Serum protein concentration and protein fractions in clinically healthy Lacaune and Sarda sheep using agarose gel electrophoresis
Authors: Miglio Arianna , Antognoni Maria Teresa , Maresca Carmen , Moncada Claudia , Riondato Fulvio , Scoccia Eleonora , Mangili Vittorio
Published: November 2015

Background

Serum protein electrophoresis (SPE) provides useful information in ruminants, but reference intervals (RI) are different from other species. There have been no reports of SPE RI for dairy sheep using agarose gel electrophoresis (AGE).

Objective

The purpose of the study was to evaluate the serum concentration of total protein (TP) and protein fractions determined by AGE in mid‐lactating dairy ewes, to establish RI, and to assess potential differences between Lacaune (L) and Sarda (S) sheep breeds.

Methods

Blood samples were collected from healthy, mid‐lactating ewes. SPE was assessed using a semi‐automated AGE system. Reference intervals (90% confidence intervals) for TP and each protein fraction were determined using the nonparametric method for combined data, and the robust method for data from the single breeds. Data from S and L sheep were compared using the Mann–Whitney U test.

Results

The 172 sheep included 116 L and 56 S ewes, 2–6 years old. There were significant differences between S and L breeds, and RI were calculated for TP, albumin, α1‐globulin, α2‐globulin, β1‐globulin, β2‐globulin, γ1‐globulin, and γ2‐globulin concentrations, and for the Albumin/Globulin ratio. Group S showed higher concentrations of TP, α2‐, β1‐, β2‐, and γ1‐globulins, whereas L was higher for albumin and γ2‐globulin concentrations, and A/G ratio (P < .05).

Conclusions

The resolution with AGE was excellent, allowing standardization of 7 protein fractions, detection of differences between S and L ewes, and determination of RI for French (Lacaune) and Italian (Sarda) dairy sheep.
Effects of one's sex and sex hormones on sympathetic responses to chemoreflex activation
Authors: Usselman Charlotte W. , Steinback Craig D. , Shoemaker J. Kevin
Published: November 2015

New Findings

What is the topic of this review?

This review summarizes sex‐dependent differences in the sympathetic responses to chemoreflex activation, with a focus on the role of circulating sex hormones on the sympathetic outcomes.

What advances does it highlight?

The importance of circulating sex hormones for the regulation of sympathetic nerve activity in humans has only recently begun to be elucidated, and few studies have examined this effect during chemoreflex regulation. We review recent studies indicating that changes in circulating sex hormones are associated with alterations to chemoreflex‐driven increases in sympathetic activity and highlight those areas which require further study.

Sex‐dependent differences in baseline sympathetic nerve activity are established, but little information exists on the influence of sex on sympathetic activation during chemoreflex stimulation. In this article, we review the evidence for the effect of sex on chemoreflex‐driven increases in sympathetic nerve activity. We also review recent studies which indicate that changes in circulating sex hormones, as initiated by the menstrual cycle and hormonal contraceptive use, elicit notable changes in the muscle sympathetic activation during chemoreflex stimulation.
Reliability Analysis of Aging in Joint Microstructures for Sn-Ag-Cu Solder Joints During Thermal Cycling
Authors: Shen Chaobo , Hai Zhou , Zhao Cong , Zhang Jiawei , Bozack M. J. , Suhling J. C. , Evans John L.
Published: November 2015

This study illustrates test results and comparative literature data on the influence of isothermal aging and thermal cycling associated with Sn-1.0Ag-0.5Cu (SAC105) and Sn-3.0Ag-0.5Cu (SAC305) ball grid array (BGA) solder joints on three board finishes (ImAg, ENIG, ENEPIG). The resulting degradation shows that the characteristic lifetimes for both SAC105 and SAC305 decrease in the order ENIG > ENEPIG > ImAg. SAC305, with a higher relative fraction of Ag3Sn IMC within the solder, performs better than SAC105. SEM and EDX analysis shows continuous growth of Cu-Sn intermetallic compounds (IMC) on SAC/ImAg systems and Cu-Ni-Sn IMC on SAC/ENIG/ENEPIG systems at board side solder joints, which eventually cause fatigue failures.
Design Guideline to Improve Thermal Management of 3D Package Using Cu-to-Cu Direct Bonding
Authors: Park Ah-Young , Park S. B.
Published: November 2015

Three-dimensional (3D) packaging technology is directly related to the increasing I/O number as stacking chips. This technology has the potential to produce integrated circuits with a much better combination of cost, functionality, performance and power consumption. However, stacked chips raise several thermal issues that need to be addressed and eliminated. In this study, a quantitative study of the conventional solder-based interconnection is conducted based on many different cases of thermal loading, using finite element analysis (FEA). This preliminary study clearly shows limitation of the solder-based interconnection in the thermal management perspective. Underfill for microbμmp acts as a barrier of heat transfer in the conventional 3D stacked chip packages. Therefore, as an alternative, Cu-to-Cu direct bonding (CuDB), which has a better thermal conductivity, is proposed. Its parametric study is performed under the same/different loading conditions and dimensions. This study helps to highlight the thermal behavior of 3D packages consisting of various interconnections. Finally, based on the results, we can propose qualitative design guidelines of 3D packaging depending on various environment and conditions.
Experimental and Analytical Study of Micro-Serrations on Surgical Blades
Authors: Giovannini Marco , Moser Newell , Ehmann Kornel
Published: November 2015

This paper reports on a study and application of laser ablation for machining of micro-serrations on surgical blades. The proposed concept is inspired by nature and mimics a mosquito’s maxilla, which is characterized by a number of serrations along its edge in order to painlessly penetrate human skin and tissue. The focus of this study is to investigate the maxilla’s penetration mechanisms and its application to commercial surgical blades. The fundamental objective is to understand the friction and cutting behavior between a serrated hard surface and soft materials, as well as to identify serration patterns that would minimize the cutting force and the friction of the blade during tissue cutting. Micro-serrations characterized by different patterns and sizes ranging from 200 μm to 400 μm were designed and manufactured on surgical blades. As supported by finite element methods (FEM), a reduction of 20∼30% in the force during blade cutting has been achieved, which encourages further studies and their applications to biomedical devices.
Computational Study of Behavior of Gas Absorption in Data Center Equipment and its Effects on the Rate of Corrosion/Contamination
Authors: Bagul Tejeshkumar , Pujara Kanan , Shah Jimil , Awe Oluwaseun , Agonafer Dereje
Published: November 2015

The reliability of the data center equipment is being compromised as the American Society of Heating, Refrigeration and Air Conditioning Engineers recommendable psychometric limits are stretched outside the recommendable zones. When the ambient conditions are conducive enough the humidity and the gaseous contaminants present in the data centers react with the elements of Printed Circuit Boards (PCB) at various temperatures. The products of the reaction may lead to short circuit or extra resistance to the passage of current. This poses an increased threat to the reliability of the PCB. Contamination has become a serious problem in the developing nations like China and India where new data centers are rapidly coming up. The heavy industrialization and vehicular activities are the major source of the contamination. The losses due the corrosion of PCB by contaminants depends on various factors like concentration of gases, amount of humidity present, time of the day, location of the data center, filtration technique used for the air-conditioning system, etc. An actual study of effects of contaminants in data centers across the world would be a tedious task. Computational study saves the time as well as cost for this study. This research study gives deeper insights of the reaction mechanism. A computational study of the reaction of copper foils (representing the PCB) placed in a Paddle Wheel Test setup would be carried out. A Paddle Wheel Test setup gives us the flexibility to test various gases, that could pose a threat to data center equipment, without disturbing the actually data center servers. A reaction of hydrogen sulfide and sulfur dioxide on copper in the presence of humidity will be carried out in this study.
Novel Dynamic Numerical Microchannel Evaporator Model to Investigate Parallel Channel Instabilities
Authors: Saenen Tom , Thome John R.
Published: November 2015

A novel fully dynamic model of a microchannel evaporator is presented. The aim of the model is to study the highly dynamic parallel channel instabilities that occur in these evaporators in more detail. The numerical solver for the model is custom-built and the majority of the paper is focused on detailing the various aspects of this solver. The one-dimensional homogeneous two-phase flow conservation equations are solved to simulate the flow. The full three-dimensional conduction domain of the evaporator is also dynamically resolved. This allows for the correct simulation of the complex hydraulic and thermal interactions between the microchannels that give rise to the parallel channel instabilities. The model uses state-of-the-art correlations to calculate the frictional pressure losses and heat transfer in the microchannels. In addition, a model for inlet restrictions is also included to simulate the stabilizing effect of these components. In the final part of the paper, initial validation results of the model are presented, in which stability results of the model are compared to existing experimental data from literature. Finally, some representative dynamic results are also given to demonstrate some of the unique capabilities of the model.
A Study on the Thermo-Fluid Simulation Model Using Porous Media in the Power Conversion System
Authors: Han Chang-Woo , Moon You-Lim , Jeong Seung-Boong , Han Jong-Hee
Published: November 2015

When converting an electric power by an insulated-gate bipolar transistor (IGBT) module, the problem which is the heat generation in the IGBT module should be prudently considered in the design process. As an engineer reviews the cooling performance of power semi-conductor devices only at the component level, it is difficult to predict the reduction of airflow rates in the heat sink when power semi-conductor devices including the heat sink are integrated into the power conversion system. As the porous media model is adopted in the IGBT stack of the PCS, the problem that the meshes are heavily concentrated in the IGBT module including the heat sink, air, and IGBT/diode chips can be evaded and the airflow rate which is reflected in the effect of flow resistance by all interior structures including the IGBT module is calculated. For the outdoor type PCS, the hotspot temperature on the heat sink of the simulation and experiment is 99.3 and 101.6 Celsius, respectively. The proposed numerical simulation model considerably accurately predicts the hotspot temperature on the heat sink and can earn benefits in terms of efforts of mesh generation and computation time.
Compact Thermal Modeling Methodology for Active and Thermal Bumps in 3D Microelectronic Packages
Authors: Choudhury Arnab , Kothari Shrenik , Mahanta Nayandeep , Dhavaleswarapu Hemanth , Chang Je-Young
Published: November 2015

Accurate estimation of the thermal conductivity of logic-memory and memory-memory interfaces, between stacked die in 3D microelectronic packages, is key to effective design and early estimates of performance and reliability. Typically, interconnect layers contain hundreds to a few thousands of bumps. Hence lumped/compact modeling of this interfacial layer is essential to reduce computational time and complexity. The typical approach to this lumped modeling is to estimate the effective conductivity of the layer by assuming the bumps and underfill regions can be modelled as parallel thermal resistances (referred to as the volumetric method). This work demonstrates that the volumetric method can significantly underpredict 3D stack thermal resistance and junction temperatures. An alternative method-referred to as the single bump method-of estimation of the thermal conductivity of interconnect layers in 3D stacked-die packages is presented. Studies demonstrate that the proposed single bump method captures the heat transfer in these interfaces accurately. Validation of the single bump modeling is presented by comparing the single bump and volumetric methods with fully discretized models. This comparison also demonstrates that the prevalent volumetric method overestimates the effective thermal conductivity of the interface, while the single bump approach results in more accurate assessment of 3D stack resistance.
The Prediction of the Thermal Conductivity of Gallium Arsenide: A Molecular Dynamics Study
Authors: Saiz Fernan , Amon Cristina H.
Published: November 2015

Gallium arsenide is the second most used semiconductor material with applications in light-emitting diodes, field-effect transistors, and integrated circuits. Thus, understanding and controlling the thermal conductivity of gallium arsenide is crucial to design devices for such applications. The goal of this study is to predict the thermal conductivity of gallium arsenide as a function of temperature and vacancy concentration. Thermal conductivities are predicted using an equilibrium molecular dynamics method based on the Green-Kubo formalism with temperatures between 300 K and 900 K and vacancy concentrations up to 0.5%. Our results show that the thermal conductivities of the vacancy-free system predicted by our model are in good agreement with experimental values around the Debye temperature. In addition, our model predicts that conductivities significantly decrease with increasing vacancy concentration. At 300 K conductivities drop by 39.5% with a 0.1% defect content and 74.4% with 0.5% respect to that of the pure system. The power spectra of thermal conductivities and heat current autocorrelation functions indicate that phonon scattering produced near the vacancies reduces the contribution of the acoustic frequencies. The density of states quantifies the decrease of acoustic and optic frequencies by increasing the vacancy concentration.
Reliability Implications of Thermo-Mechanically and Electrically Induced Interfacial Sliding of Through-Silicon Vias in 3D Packages
Authors: Meinshausen Lutz , Liu Ming , Lee Tae-Kyu , Dutta Indranath , Li Li
Published: November 2015

In conjunction with micro bumps, Through-Silicon-Vias (TSVs) are used for die stacking, leading to reduced footprints and a higher performance due to shorter communication bus-length. However the large difference between the thermal expansion of silicon and copper and an increased temperature of the die stack due to Joule heating lead to shear stress at the interface between TSV and substrate. Temperature activated interfacial diffusion in combination with the shear stress leads to diffusional interfacial sliding, resulting in TSV pro- or intrusion. In addition, electromigration (EM) at the interface leads to TSV motion.

Against this background the protrusion/intrusion of Cu TSVs (ø 10 μm, length 100 μm) during fast and slow rate thermal cycling (TC) and during EM experiments was investigated.

Parallel to the experimental investigation a finite element analysis (FEA) was performed to study the micro-mechanical responses of Cu-filled TSV during thermal cycling. For this purpose interfacial sliding was incorporated into the FE model by diffusional creep mechanism. The FE model captures the main features being observed in experiments such as stress hysteresis and intrusion/protrusion of the TSV relative to Si substrate.
Fracture Mechanisms in Sn-Ag-Cu Solder Micro-Bumps for 3D Microelectronic Packages
Authors: Talebanpour Babak , Dutta Indranath
Published: November 2015

Solder micro-bumps, which serve as interconnects between stacked dies in 3D electronic packages, are typically very thin (25μm or less) and contain a high proportion of intermetallic compounds (IMCs). This makes micro-bumps brittle, and prone to fracture, particularly under drop conditions. In this paper, the fracture mechanics and mechanisms of SAC305 solder micro-bumps attached to Cu metallizations are studied as functions of the proportion of IMC in the joint. The effects of IMC content, IMC composition (i.e., the relative amounts of Cu3Sn and Cu6Sn5), strain rate, and mode mixity on both fracture toughness and fracture mechanism were investigated. The fracture mechanisms were studied via quantitative fractography. It was found that fracture toughness decreases dramatically (∼80%) with increase in IMC content (from ∼22% to 100%IMC). In all samples, the majority of the fracture surface comprised IMC/Sn interface failure, which constitutes the predominant fracture mechanism. With increasing aging, the proportion of ductile fracture of Sn decreases, fracture through Cu6Sn5 cleavage increases, and more Cu3Sn/Cu6Sn5 interface failure is observed. In general, bulk fracture properties of Cu3Sn plays little role in the fracture process. Thin joints also frequently display an alternating crack path between the two solder-substrate interfaces with the crack transitioning from one interface to the other, through the intervening Sn. Such crack transition between two surfaces increases with increase in IMC content, as long as there is intervening Sn, and may be utilized to improve the fracture toughness of thin joints. Finally, joint fracture toughness decreased with increase in both strain rate and mode mixity.
A Basic Study on Creep-Fatigue Damages Interaction for Sn-3.0Ag-0.5Cu as Lead Free Solder Material
Authors: Oriyama Hirokazu , Kawakami Takashi , Kinoshita Takahiro
Published: November 2015

Sn-Ag-Cu solder materials have been widely used for the mount process of electronics devices or semiconductor packages on print circuit board (PCB). The solder joints are sometimes opened under thermal cyclic loads as low cycle fatigue phenomenon. The fatigue life of solder joint has been investigated by many researchers with experimental and numerical methods. Generally, the induced thermal stress in solder joints should be relaxed as soon and creep damage is considered to be ignored in order to estimate lives of joints. However, it is probable that long term stress is applied to solder joints by the elastic follow-up phenomenon which are depending on the stiffness ratio between solder joints and the electronics device, because the elastic strain in PCB or the electronics device shifts to creep strain in solder joints gradually during a long time. Then the creep damage of solder joint should be counted for the mechanical design of mounted PCBs. And it is known that the interaction between creep damage and fatigue damage significantly shorten the life. In this study, it was discussed whether the interaction between fatigue damage and creep damage has to be considered or not for the mechanical design of the lead free solder joint with basic creep-fatigue tests at an elevated temperature.
Warpage Hysteresis Estimation of an Electronic Package During a Thermal Cycle
Authors: Ikeda Toru , Ozaki Akiko , Hatao Takuya , Miyazaki Noriyuki
Published: November 2015

The mechanical reliability of electronic packages is one of the critical problems in the reliability of electronic products in general. Estimating the warpage of an electronic package is useful for increasing its mechanical reliability. The warpage of an electronic package often shows a hysteresis curve during a thermal cycle. However, this hysteresis is difficult to simulate. We measured the master curves of the relaxation modulus using a Dynamic Mechanical Analyzer (DMA) before and after the first heating. Measured equilibrium elastic modulus after heating was two times higher than before heating. Curing rate of the resin before heating was already more than 99%. Change of elastic modulus in the range over 99% curing rate was much stronger than expected according to the conventional theory of rheology. We then analyzed the warpage of the specimen considering the change in the master curve of the relaxation modulus of the underfill resin. The hysteresis of the warpage of the bonded specimen was successfully predicted using the proposed method. In this study, we extended this method to a package on package (PoP). The PoP package also showed temperature hysteresis of the warpage. We considered the same viscoelastic material properties for the underfill resin. We also took the multi layered print circuit board and the viscoelastic material properties of solder resist into account. Simulated thermal hysteresis of the warpage of a PoP successfully corresponded with the measured warpage.
Effect of Relative Humidity, Temperature and Gaseous and Particulate Contaminations on Information Technology Equipment Reliability
Authors: Singh Prabjit , Klein Levente , Agonafer Dereje , Shah Jimil M. , Pujara Kanan D.
Published: November 2015

The energy used by information technology (IT) equipment and the supporting data center equipment keeps rising as data center proliferation continues unabated. In order to contain the rising computing costs, data center administrators are resorting to cost cutting measures such as not tightly controlling the temperature and humidity levels and in many cases installing air side economizers with the associated risk of introducing particulate and gaseous contaminations into their data centers. The ASHRAE TC9.9 subcommittee, on Mission Critical Facilities, Data Centers, Technology Spaces, and Electronic Equipment, has accommodated the data center administrators by allowing short period excursions outside the recommended temperature-humidity range, into allowable classes A1-A3. Under worst case conditions, the ASHRAE A3 envelope allows electronic equipment to operate at temperature and humidity as high as 24°C and 85% relative humidity for short, but undefined periods of time. This paper addresses the IT equipment reliability issues arising from operation in high humidity and high temperature conditions, with particular attention paid to the question of whether it is possible to determine the all-encompassing x-factors that can capture the effects of temperature and relative humidity on equipment reliability. The role of particulate and gaseous contamination and the aggravating effects of high temperature and high relative humidity will be presented and discussed. A method to determine the temperature and humidity x-factors, based on testing in experimental data centers located in polluted geographies, will be proposed.
A Cost-Effective Modeling Approach for Simulating Phase Change and Flow Boiling in Microchannels
Authors: Pan Zhenhai , Weibel Justin A. , Garimella Suresh V.
Published: November 2015

High-fidelity simulation of flow boiling in microchannels remains a challenging problem, but the increasing interest in applications of microscale two-phase transport highlight its importance. In this paper, a volume of fluid (VOF)-based flow boiling model is proposed with computational expense-saving features that enable cost-effective simulation of two-phase flow and heat transfer in realistic geometries. The vapor and liquid phases are distinguished using a color function which represents the local volume fraction of the tracked phase. Mass conservation is satisfied by solving the transport equations for both phases with a finite-volume approach. In order to predict phase change at the liquid-vapor interface, evaporative heat and mass source terms are calculated using a novel, saturated-interface-volume phase change model that fixes the interface at the saturation temperature at each time step to achieve stability. Numerical oscillation of the evaporation source terms is thus eliminated and a non-iterative time advancement scheme can be adopted to reduce computational cost. The reference frame is set to move with the vapor slug to artificially increase the local velocity magnitude in the thin liquid film region in the relative frame, which reduces the influence of numerical errors resulting from calculation of the surface tension force, and thus suppresses the development of spurious currents. This allows use of non-uniform meshes that can efficiently resolve high-aspect-ratio geometries and flow features and significantly reduces the overall numerical expense. The proposed model is used to simulate the growth of a vapor bubble in a heated 2D axisymmetric microchannel. The bubble motion, bubble growth rate, liquid film thickness, and local heat transfer coefficient along the wall are compared against previous numerical studies.
Improvement of the Long-Term Reliability of Interconnection by Controlling the Crystallinity of Grain Boundaries
Authors: Nakanishi Takahiro , Suzuki Ken , Miura Hideo
Published: November 2015

Electroplated copper thin films have started to be employed as the interconnection material in TSV structures of 3D semiconductor modules because of its low electric resistivity and high thermal conductivity. However, electrical and mechanical properties of electroplated copper thin-films have been found to vary drastically depending on their microtexture. In particular, the crystallographic quality (crystallinity) of grain boundaries in the electroplated copper thin-films plays an important role on the variations of these properties and the long-term reliability of the interconnections. This is because grain boundaries are the area where the atomic alignment of mateerials is disordered and thus, various defects such as vacancies, dislocations, impurities, and strain easily concentrate around them. This disorder of the atomic alignment causes the increase in the electrical resistivity, diffusion constant along the grain boundaries, and the brittleness of the material. Therefore, it is very important to evaluate the characteristics of a grain boundary quantitatively in order to control and assure the properties of the electroplated copper thin films. In this study, a novel tensile test method that can measure the strength of a grain boundary has been developed by using a focused ion beam system. In order to investigate the effect of the crystallinity of grain boundaries on their strength, an electron back-scatter diffraction method (EBSD) was employed for the quantitative characterization of grain boundaries. It was confirmed that the strength of grain boundaries with low crystallinity was much lower than that with high crystallinity.
Microprocessor Silicon Die Temperature Prediction by Simplified Boundary Conditions
Authors: Nishi Koji , Hatakeyama Tomoyuki , Nakagawa Shinji , Ishizuka Masaru
Published: November 2015

The thermal network method has a long history with thermal design of electronic equipment. In particular, a one-dimensional thermal network is useful to know the temperature and heat transfer rate along each heat transfer path. It also saves computation time and/or computation resources to obtain target temperature. However, unlike three-dimensional thermal simulation with fine pitch grids and a three-dimensional thermal network with sufficient numbers of nodes, a traditional one-dimensional thermal network cannot predict the temperature of a microprocessor silicon die hot spot with sufficient accuracy in a three-dimensional domain analysis. Therefore, this paper introduces a one-dimensional thermal network with average temperature nodes. Thermal resistance values need to be obtained to calculate target temperature in a thermal network. For this purpose, thermal resistance calculation methodology with simplified boundary conditions, which calculates thermal resistance values from an analytical solution, is also introduced in this paper. The effectiveness of the methodology is explored with a simple model of the microprocessor system. The calculated result by the methodology is compared to a three-dimensional heat conduction simulation result. It is found that the introduced technique matches the three-dimensional heat conduction simulation result well.
The Contribution of the Bulk Modes on Electrical Conductivity in 3D Topological Insulators
Authors: Babac Gulru
Published: November 2015

Determination of transport coefficients in 3D topological insulators is one of the highlighted topics in the literature. The main difficulty of the calculation of transport coefficients comes from the contribution of bulk modes. In this work, electrical conductivity in 3D topologic insulators is considered under zero magnetic fields and it is written in a size dependent form. For this purpose, Weyl conjecture is used. The contribution of the bulk modes to electrical conductivity is analytically derived by depending on the material size, hybridization energy and degeneracy of the carriers.