bluuebunny/crossref_metadata_2025 huggingface dataset:
Vitamin D insufficiency and mild cognitive impairment: cross‐sectional association
Authors: Annweiler C. , Fantino B. , Schott A. M. , Krolak‐Salmon P. , Allali G. , Beauchet O.
Published: February 2012

Background:  Low serum 25‐hydroxyvitamin D (25OHD) concentrations have been associated with dementia. The association with mild cognitive impairment (MCI) has not yet been explored. Our aim was to examine the association between vitamin D status and MCI status amongst older community‐dwellers with subjective memory complaint.

Methods:  Ninety‐five non‐demented Caucasian community‐dwellers with subjective memory complaint (mean, 71.1 ± 6.4 years; 54.7% women) included in the Gait and Alzheimer Interaction Tracking (GAIT) study were categorized into two groups according to Winblad et al. consensus criteria [i.e., subjects with MCI or cognitively healthy individuals (CHI)]. Serum 25OHD concentration was divided into quartiles, the fourth quartile corresponding to the highest 25OHD concentration. The cross‐sectional associations between 25OHD concentrations and MCI were modeled using logistic regressions. Age, gender, body mass index, number of comorbidities, education level, Mini‐Mental State Examination score, Frontal Assessment Battery score, Geriatric Depression Scale score, creatinine clearance, and season tested were considered as potential confounders.

Results:  Compared to CHI, patients with MCI (n = 43; mean, 71.4 ± 5.6 years; 34.9% women) had lower mean serum 25OHD concentrations (P = 0.006) and belonged more often to the lower quartiles compared to the highest quartile (P = 0.03). Increased serum 25OHD concentration was associated with a lower risk of MCI [adjusted odds ratio (OR) = 0.96, P = 0.002]. Accordingly, lower quartiles of 25OHD were positively associated with MCI whilst using the highest quartile as reference (adjusted OR = 25.46, P = 0.002 for the first quartile; adjusted OR = 6.89, P = 0.03 for the second quartile; and adjusted OR = 10.29, P = 0.02 for the third quartile).

Conclusions:  Low 25OHD concentrations were associated with MCI status in older non‐demented community‐dwellers with subjective memory complaint.
Activation of phospholipase‐Cγ and protein kinase C signal pathways helps the survival of spinal motoneurons injured by root avulsion
Authors: Zhao Xiu‐Chun , Wang Lin‐Lin , Wang Ya‐Qiong , Song Fa‐Huan , Li Ying‐Qin , Fu Rao , Zheng Wen‐Hua , Wu Wutian , Zhou Li‐Hua
Published: February 2012

J. Neurochem. (2012) 121, 362–372.

The signaling transduction processes involved in avulsion‐induced motoneuron (MN) death have not been elucidated. Using the brachial plexus root avulsion rat model, we showed that avulsion‐activated phosphorylation of phospholipase‐Cγ (PLCγ) and protein kinase C (PKC) occurred in injured spinal MNs within 72 h of injury. Moreover, some MNs positive for PLCγ and PKC are also positive for avulsion‐induced neuronal nitric oxide synthase (nNOS). Inhibition of PLCγ/PKC signal pathway, either with PLCγ inhibitor, 1‐[6‐((17β‐3‐methoxyestra‐1,3,5(10)‐trien‐17‐yl) amino)hexyl]‐1H‐pyrrole‐2,5‐dione, or with PLCγ siRNA augmented avulsion‐induced MN death. 1‐[6‐((17β‐3‐Methoxyestra‐1,3,5(10)‐trien‐17‐yl) amino)hexyl]‐1H‐pyrrole‐2,5‐dione also inhibited PKC phosphorylation and exacerbated avulsion‐induced reductions in the nNOS protein level in injured spinal segments. Moreover, activation of PLCγ/PKC signal pathway with PKC activator, phorbol‐12‐myristate‐13‐acetate, decreased avulsion‐induced MN death. The temporal profile of PLCγ/PKC signaling appears to be crucial for the survival of spinal MNs after root avulsion. Our data suggest that PLCγ mediates, while PKC and nNOS are associated with, the avulsion‐induced MN death in brachial plexus root avulsion.
Hypertonic saline: a change of practice
Authors: Williams Elizabeth , von Fintel Nichola
Published: February 2012

Background: This practice development review describes how the introduction of hypertonic saline in the treatment of raised intracranial pressure was brought about in one critical care unit. It considers the need for staff education and patient safety as an integral part of the change process.

Aim: The aim was to review making a practice change, using Lewin's three step change model and describes possible pitfalls in the process and ways of overcoming or avoiding them.

Methods: The inclusion criterion for critiqued literature was: Worldwide, English language studies from the last 26 years. Exclusion was articles from non‐academically recognized sources. The search was limited to primary and empirical sources.

Discussion: This article uses Lewin's change model to describe driving and restraining forces, highlighting potential problems and suggesting ways in which they can be overcome when implementing a change in practice. Critical to the success of any change is the importance of evaluation, and suitable methods of evaluating the change are also suggested.

Relevance to clinical practice: Critical care and neurosurgical nurses need to be aware of the potentially serious side effects, actions and correct methods of administration of hypertonic saline to ensure its safe use and ensure patient safety. Effects and side effects of hypertonic saline are described, highlighting the need for care in introducing such agents into a clinical area. The methodology used was an electronic search. The change in practice relates to the introduction of hypertonic saline, but could be adapted for any change in clinical nursing practice.
An audit of independent nurse prescribing in a critical care outreach team
Authors: Wilson Mark , Gerber Karin , Mahoney Sean , Odell Mandy
Published: February 2012

Background: In 2006, legislative changes enabled independent prescribers to prescribe any licensed medication within their field of expertise. This has transformed nurse prescribing and opened up more opportunities for nurses to develop their practice in acute care settings. The need for further evaluation in this developing area of advanced practice was highlighted in the British Association of Critical Care Nurses (BACCN) position statement published in 2009.

Aims: The aims of this audit were to describe the prescribing practices of nurses working in a critical care outreach (CCO) team by exploring: which medications were prescribed; the number of prescribing decisions being made and if prescribing practice changed during the out of hours period. The findings can be used to inform practice, develop CCO services, provide a basis for further research, and contribute to the debate in this developing area of CCO practice.

Methods: The prescribing practices of two independent non‐medical prescribers in a CCO team were audited from January to April 2011.

Results: The findings showed that; there were a wide range of medications prescribed, that prescribing decisions increased over time and that the majority of prescriptions were written out of hours.

Conclusions: This preliminary audit has shown that prescribing in a CCO setting which covers a wide patient population is manageable. By evaluating drug prescribing patterns, a ‘critical care outreach formulary’ can be developed to guide individuals and the team in their continuing professional and service development. The CCO teams ability to prescribe could have the potential to improve the patients' experience and outcome, and positively affect the efficiency of service delivery; however, an increase in CCO referrals can have an impact on the CCO service resource. Further evaluation and study are needed to explore this developing area of critical care delivery.
Therapeutic Apheresis for Renal Disorders
Authors: Sanchez Amber P. , Ward David M.
Published: February 2012

This review summarizes the clinical evidence and practical details for the use of plasmapheresis and other apheresis modalities for each indication in nephrology. Updated information on the molecular biology and immunology of each renal disease is discussed in relation to the rationale for apheresis therapy and its place amid other available treatments. Autoantibody‐mediated diseases, such as anti‐GBM (anti‐glomerular basement membrane) glomerulonephritis (GN), ANCA (antineutrophil cytoplasmic antibody)‐related GN and the antibody‐mediated type of TTP (thrombotic thrombocytopenic purpura), and alloantibody‐mediated diseases such as kidney transplant sensitization and humoral rejection, can be treated by various plasmapheresis methods. These include standard plasmapheresis with a replacement volume, or plasmapheresis with online plasma purification using adsorption columns or secondary filtration. However, it should be noted that the pathogenic molecules implicated in FSGS (focal segmental glomerulosclerosis), myeloma cast nephropathy, and perhaps other diseases are too small to be removed by most online purification methods. A great majority of controlled trials and series on which evidence‐based treatment recommendations are made were performed using centrifugal plasmapheresis; it is presumed that membrane‐separation plasmapheresis is equally efficacious. For some rarer diseases, such as MPGN (membranoproliferative GN) type 2 with factor H abnormalities or C3Nef (C3 nephritic factor) autoantibodies, there are only a few case reports, but enough scientific understanding to warrant a trial of plasmapheresis in severe cases. Photopheresis, which is effective for cell‐mediated rejection in heart and lung transplantation, has not yet found a place in the routine treatment of kidney transplant rejection.
Alcohol Outlet Density and Intimate Partner Violence‐Related Emergency Department Visits
Authors: Cunradi Carol B. , Mair Christina , Ponicki William , Remer Lillian
Published: February 2012

Background:  Previous research has identified risk factors for intimate partner violence (IPV) severity, injury, and emergency department (ED) visits. These risk factors have been shown at both the individual level (heavy drinking and other substance use on the part of 1 or both partners) and the neighborhood level (residence in an area characterized by poverty and social disadvantage). Alcohol outlet density has been linked with assaultive violence in community settings, but has not been analyzed in relation to IPV‐related ED visits. This study examined the effects of outlet densities on IPV‐related ED visits throughout California between July 2005 and December 2008.

Methods:  Half‐yearly counts of ED visits related to IPV (E‐code 967.3) were computed for each zip code from patient‐level public data sets. Alcohol outlet density measures, calculated separately for bars, off‐premise outlets, and restaurants, were derived from California Alcohol Beverage Control records. Census‐based neighborhood demographic characteristics previously shown to be related to health disparities and IPV (percent black, percent Hispanic, percentage below 150% of poverty line, percent unemployed) were included in models. This study used Bayesian space–time models that allow longitudinal analysis at the zip code level despite frequent boundary redefinitions. These spatial misalignment models control for spatial variation in geographic unit definitions over time and account for spatial autocorrelation using conditional autoregressive (CAR) priors. The model incorporated data from between 1,686 (2005) and 1,693 (2008) zip codes across California for 7 half‐year time periods from 2005 through 2008 (n = 11,836).

Results:  Density of bars was positively associated with IPV‐related ED visits. Density of off‐premise outlets was negatively associated with IPV‐related ED visits; this association was weaker and smaller than the bar association. There was no association between density of restaurants and IPV‐related ED visits.

Conclusions:  Further research is needed to understand the mechanisms by which environmental factors, such as alcohol outlet density, affect IPV behaviors resulting in ED visits.
The significance of multiplex PCR/heteroduplex analysis‐based TCR‐γ gene rearrangement combined with laser‐capture microdissection in the diagnosis of early mycosis fungoides
Authors: Yang Hanjun , Xu Chen , Tang Yuan , Wan Chuan , Liu Weiping , Wang Lin
Published: February 2012

Background: The diagnosis of early mycosis fungoides (MF) is a big challenge to dermatologists and dermatopathologists because it lacks specific clinicopathologic features.

Methods: Fifty‐two paraffin‐embedded skin samples from 50 patients, including 31 with suspected MF, 10 with typical MF and 9 with benign inflammatory dermatosis (BID), were obtained from our archives. DNA was extracted both by traditional phenol‐chloroform method and by the laser‐capture microdissection (LCM)‐proteinase K approach. The TVG/TJG, V2–5/V8–12/JGT1 and BIOMED‐2‐TCR‐γ primers were used to assess TCR‐γ monoclonal rearrangement as measured by polymerase chain reaction (PCR).

Results: In the suspected MF group, clonal TCR‐γ gene rearrangements were detected in 11/31 cases (35.5%) by phenol‐chloroform DNA extraction and in 25/31 cases (80.7%) by LCM‐proteinase K extraction (p < 0.05). While T‐cell clonality was detected in 8/10 cases (80%) by the phenol‐chloroform method and 10/10 cases (100%) by LCM (p > 0.05) in the typical MF group, no TCR‐γ monoclonal rearrangement was detected in the BID group.

Conclusions: The strategy of multiple PCR/heteroduplex analysis for TCR‐γ gene rearrangement combined with LCM increases the detection rate of clonal TCR‐γ gene rearrangement in early MF cases and could provide strong evidence to confirm the diagnosis of early MF.

Yang H, Xu C, Tang Y, Wan C, Liu W, Wang L. The significance of multiplex PCR/heteroduplex analysis‐based TCR‐γ gene rearrangement combined with laser‐capture microdissection in the diagnosis of early mycosis fungoides.
Gaps in continuity of medication management during the transition from hospital to residential care: An observational study (MedGap Study)
Authors: Elliott Rohan A , Tran Tim , Taylor Simone E , Harvey Penelope A , Belfrage Mary K , Jennings Rhonda J , Marriott Jennifer L
Published: February 2012

Aim:  To assess continuity of medication management during transition from hospital to residential care facilities (RCFs).

Method:  Telephone interviews with RCF staff were performed 24 hours after patient transfer to determine the proportion of patients with: missed or significantly delayed doses; RCF medication chart not written/updated in time for the first dose; suitably packed medications not available for the first dose; and RCF medication chart written/updated by a locum doctor. Retrospective audit was used to identify discharge summary discrepancies.

Results:  Seventy‐five doses for 37/202 (18.3%) patients were missed or significantly delayed in the 24 hours after discharge. One hundred and twenty‐five (61.9%) patients did not have their medication chart written/updated and 77 (38.1%) did not have suitably packed medications available for the first dose. Locum doctors wrote RCF medication charts for 66 (32.7%) patients. One hundred and ninety‐seven of 392 (50.3%) changes to regularly scheduled medications were communicated.

Conclusions:  Strategies are needed to address gaps in the continuity of medication management.
‘Intelligent’ ribozyme whose activity is altered in response to K+ as a result of quadruplex formation
Authors: Nagata Takashi , Sakurai Yu , Hara Yukari , Mashima Tsukasa , Kodaki Tsutomu , Katahira Masato
Published: February 2012

The structure of r(GGAGGAGGAGGA) (R12) changes from a single‐stranded form to a compact quadruplex one in response to K+. In a hammerhead ribozyme, two portions of the catalytic core are linked with the stem and are located in close proximity in order to exert activity. In this study, the stem was replaced by R12 (or R11, which lacks the terminal A residue) with or without linker residues. One of the newly constructed ribozymes exhibited enhanced activity in response to K+, and we suggest that quadruplex formation restored the active catalytic core. Other ribozymes exhibited repressed activity in response to K+, suggesting that formation of the active core was prevented. Thus, we have succeeded in developing ‘intelligent’ ribozymes whose activity is either repressed or enhanced in response to K+. This switching capability may have therapeutic applications because of the differences between intra‐ and extracellular K+ concentrations.
Human rights, citizenship and dementia care nursing
Authors: Kelly Fiona , Innes Anthea
Published: February 2012

Background.  Human rights and citizenship are concepts widely used in health and social care literature. However, they are applied less frequently and less rigorously in dementia care. This paper briefly presents these concepts before exploring how they have been applied to dementia care policy and practice. We highlight areas of dementia care where human rights can be violated and citizenship can be denied. We suggest reasons why people with dementia can be denied their human and civil rights and discuss how such concepts provide a way to address cultural and practice change in dementia care.

Aims and objectives.  To demonstrate how these concepts can be used to challenge and improve dementia care nursing.

Conclusions.  This paper contributes to emerging discussion about dementia care nursing by challenging conventional ways of understanding dementia and the care practices that result. Taking a rights‐based approach allows nurses to examine inequity in services and address poor practice.

Implications for practice.  Looking at dementia through the lenses of citizenship and human rights provides a way to broaden the scope of contemporary dementia care nursing, to enable nurses to challenge inequity and to develop and improve the direct nursing care offered to people with dementia.
Effect of plastic occlusive clips used as an alternative to mulesing on breech conformation, body weight and survival of Merino lambs
Authors: Evans IB , Lawton PW , Sergeant E , Lloyd JB
Published: February 2012

Objective  To determine the effect of applying plastic clips to the breech and tail of lambs on the perineal and tail bare areas, breech wrinkle, dag (faecal) accumulation, urine stain, body weight and survival of lambs, compared with unclipped, unmulesed lambs and mulesed lambs.

Method  The study was conducted on five commercial wool‐growing farms in southern Australia. On each study site lambs (2–12‐weeks‐old) were divided into three groups: (1) unclipped, unmulesed control (tail dock only); (2) treated with clips; and (3) treated with the mules operation. Evaluations of effects, including visual scoring, bare area measurements and body weight, were performed before treatment and on or approximately days 30, 60, 90 and 180 after treatment. On each occasion, lambs were recorded as either present or absent to allow estimates of survival.

Results  The clip treatment increased the size of the perineal and tail bare areas compared with the unclipped, unmulesed control lambs (P < 0.05), although the increases were less than in mulesed lambs (P < 0.05). The clips reduced breech wrinkle, dag and urine stain to levels partway between those recorded in the unclipped, unmulesed controls and the mulesed lambs (P < 0.05). Clipped lambs weighed more than mulesed lambs after treatment (days 30–90 P < 0.001; day 180 P < 0.01) and had higher cumulative percentage survival to 90 days after treatment (P = 0.03).

Conclusions  The clips successfully modified the breech region of lambs, although the changes were less than with mulesing. The clips did not reduce the body weight of lambs, compared with the unclipped, unmulesed control lambs, and improved 90‐day cumulative percentage survival compared with mulesed lambs.
The response of correlated traits following cessation of fishery‐induced selection
Authors: Salinas Santiago , Perez Kestrel O. , Duffy Tara A. , Sabatino Stephen J. , Hice Lyndie A. , Munch Stephan B. , Conover David O.
Published: February 2012

The application of evolutionary principles to the management of fisheries has gained considerable attention recently. Harvesting of fish may apply directional or disruptive selection to key life‐history traits, and evidence for fishery‐induced evolution is growing. The traits that are directly selected upon are often correlated (genetically or phenotypically) with a suite of interrelated physiological, behavioral, and morphological characters. A question that has received comparatively little attention is whether or not, after cessation of fishery‐induced selection, these correlated traits revert back to previous states. Here, we empirically examine this question. In experiments with the Atlantic silverside, Menidia menidia, we applied size‐selective culling for five generations and then maintained the lines a further five generations under random harvesting. We found that some traits do return to preharvesting levels (e.g., larval viability), some partially recover (e.g., egg volume, size‐at‐hatch), and others show no sign of change (e.g., food consumption rate, vertebral number). Such correlations among characters could, in theory, greatly accelerate or decelerate the recovery of fish populations. These results may explain why some fish stocks fail to recover after fishing pressure is relaxed.
Pollinator nesting guilds respond differently to urban habitat fragmentation in an oak‐savannah ecosystem
Authors: NEAME LISA A. , GRISWOLD TERRY , ELLE ELIZABETH
Published: February 2012

Abstract.  1. Habitat fragmentation is thought to threaten biodiversity, but the response of pollinators to fragmentation is still poorly understood, and research seldom includes pollinator nesting requirements.

2. We investigated pollinator community composition in a highly fragmented oak‐savannah ecosystem in south‐western British Columbia, Canada. We sampled pollinators in 19 fragments ranging from 0.3 to 31 ha and surrounded by a variety of land‐use types, including forest, low‐density suburban, and urban neighbourhoods. Pan‐trapping and netting surveys captured 4464 bees, flies, and wasps in 138 species and 48 genera.

3. Contrary to expectations, overall species richness did not increase with fragment size. However, ground‐nester abundance (not diversity) and cavity‐nester diversity (not abundance) were higher in larger fragments, as expected. Floral richness and abundance did not foster pollinator diversity for either guild. Brood parasite responses were complex: host availability (ground‐nesting bees) was generally important, richness and abundance increased in fragments with high surrounding road density, and abundance also increased in fragments with other habitat fragments nearby.

4. Responses of different nesting guilds to fragmentation may be related to their use of the landscape surrounding habitat fragments. Some common cavity nesters can nest in fences and gardens, but urban land use may be less hospitable for ground nesters. Brood parasites apparently respond both to host availability and landscape characteristics associated with movement among fragments.

5. Consideration of nesting requirements of pollinators provided some insight into their response to habitat loss in our analysis and should be considered in future studies of fragmentation impacts on pollinator biodiversity.
Effect of Aging on Tensile Properties and Microstructures of Eutectic Sn-Pb Solder With Small Amounts of Au and Pd for Aerospace Application
Authors: Kikuchi Ryou , Shohji Ikuo , Saitoh Yuta , Nemoto Norio , Nakagawa Tsuyoshi , Ebihara Nobuaki , Iwase Fusao
Published: February 2012

In the joint with eutectic Sn-Pb solder and a lead-free Ni/Pd/Au electrode, degradation of mechanical properties of the solder due to dissolution of Au and Pd into the solder would be anxious. In this study, the effect of aging was investigated on tensile properties and microstructures of the eutectic Sn-Pb solder with small amounts of Au and Pd added. In as-cast solders with both Au and Pd added, the tensile strength increases with increasing contents of Au and Pd. A similar tendency was observed after aging at 100°C for 1000 h. The effect of aging on elongation was relatively small and elongation degraded when brittle (Pd,Au)Sn4 phases formed in the solder. In solders with Au ranging from 1 to 5 mass%, regardless of aging conditions investigated, the tensile strength is stable at approximately 50 MPa and 45 MPa before and after aging, respectively. The effect of aging on improvement of elongation was negligible and elongation degraded when rod shaped AuSn4 formed in the solder. On the basis of the result of microstructural observation, it was clarified that the strengthening by dispersion of (Pd,Au)Sn4 phases is superior to softening by microstructure coarsening upon aging when the contents of Au and Pd are 2 mass% and 1 mass% or above, respectively.
From Chip to Cooling Tower Data Center Modeling: Chip Leakage Power and its Impact on Cooling Infrastructure Energy Efficiency
Authors: Breen Thomas J. , Walsh Ed J. , Punch Jeff , Shah Amip J. , Bash Cullen E. , Kumari Niru , Cader Tahir
Published: February 2012

The power consumption of the chip package is known to vary with operating temperature, independently of the workload processing power. This variation is commonly known as chip leakage power, typically accounting for ∼10% of total chip power consumption. The influence of operating temperature on leakage power consumption is a major concern for the IT industry for design optimization where IT system power densities are steadily increasing and leakage power expected to account for up to ∼50% of chip power in the near future associated with the reducing package size. Much attention has been placed on developing models of the chip leakage power as a function of package temperature, ranging from simple linear models to complex super-linear models. This knowledge is crucial for IT system designers to improve chip level energy efficiency and minimize heat dissipation. However, this work has been focused on the component level with little thought given to the impact of chip leakage power on entire data center efficiency. Studies on data center power consumption quote IT system heat dissipation as a constant value without accounting for the variance of chip power with operating temperature due to leakage power. Previous modeling techniques have also omitted this temperature dependent relationship. In this paper we discuss the need for chip leakage power to be included in the analysis of holistic data center performance. A chip leakage power model is defined and its implementation into an existing multi-scale data center energy model is discussed. Parametric studies are conducted over a range of system and environment operating conditions to evaluate the impact of varying degrees of chip leakage power. Possible strategies for mitigating the impact of leakage power are also illustrated in this study. This work illustrates that when including chip leakage power in the data center model, a compromise exists between increasing operating temperatures to improve cooling infrastructure efficiency and the increase in heat load at higher operating temperatures due to leakage power.
Multi-Physics of Nanoscale Thin Films and Interfaces
Authors: Haque M. A.
Published: February 2012

We present the design and fabrication of a microchip capable of performing mechanical (tensile, fracture, fatigue), electrical (conductivity and band gap) and thermal (conductivity and specific heat) characterization of materials and interfaces. The chip can study thin films and wires of any material that can be deposited on a substrate or study thin coupons if the specimen is in bulk form. The 3 mm × 3 mm size of the chip results in the unique capability of in-situ testing in analytical chambers such as the transmission electron microscope. The basic concept is to ’see’ the micro-mechanisms while ‘measuring’ the deformation and transport properties of materials and interfaces. The advantage of such simultaneous acquisition of quantitative and qualitative data is the accurate and quick physics-based modeling of materials behavior. We present preliminary studies on multi-physics, or the coupling among mechanical thermal and electrical domains in materials will be presented. These results are particularly important when the specimen dimension becomes comparable to the mean free paths of electron and phonons.
Critical Heat Flux During Submerged Jet Impingement Boiling of Saturated Water at Sub-Atmospheric Conditions
Authors: Cardenas Ruander , Narayanan Vinod
Published: February 2012

Experimental data for critical heat flux (CHF) during submerged jet impingement boiling of saturated water at sub-atmospheric conditions is presented. Experiments are performed at three sub-atmospheric pressures of 0.176 bar, 0.276 bar, and 0.477 bar with corresponding fluid saturation temperatures of about 57.3 °C, 67.2 °C, and 80.2 °C. Jet exit Reynolds numbers ranging from 0 to 14,000 are considered for two different heater surface finishes at a fixed nozzle to surface spacing of six nozzle diameters. CHF correlations from literature on jet impingement boiling are compared against the experimental data and found to poorly predict CHF under the conditions considered. A CHF correlation that captures the entire experimental data set within an average error of ±3 percent and a maximum error of ±13 percent is developed to serve as a predictive tool for the range of conditions examined.
Effect of Crystallographic Quality of Grain Boundaries on Both Mechanical and Electrical Properties of Electroplated Copper Thin Film Interconnections
Authors: Murata Naokazu , Saito Naoki , Tamakawa Kinji , Suzuki Ken , Miura Hideo
Published: February 2012

Both mechanical and electronic properties of electroplated copper films used for interconnections were investigated experimentally considering the change of their micro texture caused by heat treatment. The fracture strain of the film annealed at 400°C increased from about 3% to 15% and their yield stress decreased from about 270 MPa to 90 MPa. In addition, it was found that two different fatigue fracture modes appeared in the film. One was a typical ductile fracture mode and the other was brittle one. When the brittle fracture occurred, a crack propagated along weak or porous grain boundaries which were formed during electroplating. The brittle fracture mode disappeared after the annealing at 300°C. These results clearly indicated that the mechanical properties of electroplated copper thin films vary drastically depending on their micro texture. The electrical reliability of the electroplated copper yjin film interconnections was also investigated. The interconnections used for electromigration tests were made using by a damascene process. An abrupt fracture mode due to local fusion appeared in the as-electroplated interconnections. Since the fracture rate increased almost linearly with the square of the applied current density, this fracture mode was dominated by local Joule heating. It seemed that the local current concentration occurred around the porous grain boundaries. The life of the interconnections was improved drastically after the annealing at 400°C. This was because of the increase of the average grain size and the improvement of the quality of grain boundaries in the annealed interconnections. However, the stress-induced migration occurred in the interconnections annealed at 400°C. This was because of the high tensile residual stress caused by the constraint of the densification of the films during annealing by the surrounding oxide film. Therefore, it is very important to control the crystallographic quality of electroplated copper films for improving the reliability of thin film interconnections. The quality of the grain boundaries can be evaluated by applying an EBSD (Electron Back Scatter Diffraction) analysis. New two experimentally determined parameters are proposed for evaluating the quality of grain boundaries quantitatively. It was confirmed that the crystallographic quality of grain boundaries can be evaluated quantitatively by using the two parameters, and it is possible to estimate both the strength and reliability of the interconnections.
Development of a Hybrid PCM-Air Heat Sink
Authors: Kozak Y. , Abramzon B. , Ziskind G.
Published: February 2012

The present study deals with the transient thermal management of electro-optical equipment using the phase-change materials (PCMs). These materials can absorb large amounts of heat without significant rise of their temperature during the melting process. This effect is attractive for using in the passive thermal management of portable electro-optical systems, particularly those where the device is intended to operate in the periodic regime, or where the relatively short stages of high power dissipation are followed by long stand-by periods without a considerable power release. In the present work, a so-called hybrid heat sink is developed. The heat sink is made of aluminum. The heat is dissipated on the heat sink base, and then is transferred by thermal conduction to the PCM and to a standard forced-convection air heat sink cooled by an attached fan. The whole system may be initially at some constant temperature which is below the PCM melting temperature. Then, power dissipation on the heat sink base is turned on. As heat propagates within the heat sink, some part of it is absorbed by the PCM causing a delay in the temperature growth at the heat sink base. Alternatively, the steady-state conditions may be such that the base temperature is below the PCM melting temperature, meaning that all the heat generated on the heat sink base is transferred to the cooling air. Then, the fan is turned off reducing the heat transfer to the ambient air, and the heat is absorbed into the PCM resulting in its melting. In both cases, the time that it will take the heat sink base to approach some specified maximum allowed temperature is expected to be longer than that without the PCM.
Band Gap Properties of Piezoelectric/Viscous Liquid Phononic Crystals
Authors: Wang Yi-Ze , Inaba Kazuaki , Li Feng-Ming , Kishimoto Kikuo
Published: February 2012

The viscous effects on the band gap characteristics of the piezoelectric/viscous liquid phononic crystals are studied. The expressions of the generalized eigenvalue equation for the cylindrical phononic crystals are derived. Numerical calculations are performed to discuss the band gap characteristics with different filling ratios and viscous damping parameters. Form the results, it can be observed that the out-of-plane mode will appear, which caused by the viscous effects. Both of the real and imaginary parts of frequencies will increase with the filling fraction becoming larger. The maximum of the normalized band gap width is achieved by f = 0.5. Furthermore, the band gap edges become higher with the viscous damping parameter increasing, especially for higher band gaps.
A Study on the Thermal Deformation and the Mechanical Properties due to Curing Process of the Encapsulation Resin
Authors: Sato Hiroyuki , Yu Qiang , Sone Ryusuke
Published: February 2012

Since the flexural rigidity of thin semiconductor package becomes much lower than normal components, the warpage of the component becomes a much more important issue to evaluate the reliability. In this study the author propose a new practical method to measure the real time curing deformation and the elastic modulus of the resin during the whole curing process. The thermal deformation of the resin under curing was measured by using the optical digital image correlation method. Next, to examine the mechanical properties of the resin, the liquid resin was poured into an aluminum frame with thin sole, and the bending rigid of the aluminum frame was measured by the three points bending test every minutes at the curing temperature of the resin. Based upon the experimented result, the warpage of a package caused of curing shrinkage was simulated.
Development of Highly Reliable BGA and Flip-Chip Structures by Using Cu-Cored Solder Ball
Authors: Tanie Hisashi , Chiwata Nobuhiko , Wakano Motoki , Fujiyoshi Masaru , Fujiwara Shinichi
Published: February 2012

A Cu-cored solder joint is a micro-joint structure in which a Cu sphere is encased in solder. It results in a more accurate height and has low thermal and electrical resistance. In a previous paper, we examined the thermal fatigue life of a Cu-cored solder ball grid array (BGA) joint through actual measurements and crack propagation analysis. As a result, we found that the thermal fatigue life of a Cu-cored solder BGA joint is about twice as long as that of a conventional joint. In this paper, we describe the impact strength of a Cu-cored solder BGA joint determined by conducting an impact bending test. This test is a technique to measure the impact strength of a micro-solder joint. This method was developed by Yaguchi et al., and they confirmed that it is an easier and more accurate method of measuring impact strength than the board level drop test. First, we simulated the impact bending test by finite element analysis (FEA) and calculated solder strains of both Cu-cored solder joints and conventional joints. The results indicated that the maximum solder strain of a Cu-cored solder joint during the impact bending test was slightly smaller than that of a conventional joint. The solder volume of the Cu-cored solder joint was also smaller than that of a conventional joint. On the other hand, joint stiffness of the Cu-cored solder joint was larger than in a conventional joint. The former increases the solder strain of the Cu-cored solder joint, and the latter decreases it. By balancing these phenomena, it is possible to obtain a maximum solder strain in the Cu-cored solder joint that is slightly smaller than in a conventional joint. Based on these phenomena, the impact strength of the Cu-cored solder joint is predicted to be the same as or higher than that of a conventional joint. Therefore, we measured the impact strengths of a Cu-cored solder joint and a conventional joint using the impact bending test. As a result, we confirmed that the impact strength of the Cu-cored solder joint was the same as or higher than that of a conventional joint. Accordingly, a Cu-cored solder BGA joint is a micro-joint structure that makes it possible to improve thermal fatigue life without decreasing impact strength. Moreover, we investigated whether the use of Cu-cored solder in a flip-chip (FC) joint improved its reliability. As a result, we found that the stress of an insulating layer on a Si die surface was reduced by using a Cu-cored solder FC joint. This is because bending deformation of the Cu land occurs, and the difference in thermal deformation between the Si chip and the Cu land becomes small. Accordingly, the Cu-cored solder FC joint is a suitable structure for improving reliability of a low-strength insulating layer.
Impedance-Based Void Fraction Measurement and Flow Regime Identification in Microchannel Flows
Authors: Paranjape Sidharth , Ritchey Susan N. , Garimella Suresh V.
Published: February 2012

Electrical impedance of a two-phase mixture is a function of void fraction and phase distribution. The difference in the electrical conductance and permittivity of the two phases can be exploited to measure electrical impedance for obtaining void fraction and flow regime characteristics. An electrical impedance meter is constructed for the measurement of void fraction in microchannel two-phase flow. The experiments are conducted in air-water two-phase flow under adiabatic conditions. A transparent acrylic test section of hydraulic diameter 780 micrometer is used in the experimental investigation. The impedance void meter is calibrated against the void fraction measured using analysis of images obtained with a high-speed camera. Based on these measurements, a methodology utilizing the statistical characteristics of the void fraction signals is employed for identification of microchannel flow regimes.
A Rack-Level Cooling Redundancy Metric for Data Center Applications
Authors: VanGilder James W. , Healey Christopher M.
Published: February 2012

Redundancy is an important measure of an operation’s ability to withstand planned or unplanned system failures. While this concept is commonly used in power systems, redundancy can be extended to data center cooling systems, as well. We propose a rack-based redundancy metric for cooling performance that is similar in nomenclature to metrics for power systems, but also captures the local nature of data center cooling. This paper will explain how to compute this metric for general data center layouts and show how cooling redundancy can influence design choices when used in combination with typical measures of cooling coverage: inlet temperature and Capture Index.
Optimizing System-on-Film (SOF) Design Using Finite Element Analysis
Authors: Venkatadri Vikram , Downey Mark , Xue Xiaojie , Sengupta Dipak , Santos Daryl , Havens Ross , Srihari Krishnaswami
Published: February 2012

System-On-Film (SOF) module is a complex integration of a fine pitch high density die and surface mounted discrete devices on a polyimide (PI) film laminate. The die is connected to the film using a thermo-compression flip-chip bonding (TCB) process which is capable of providing a very high density interconnect at less than 50um pitch. Several design and bonding parameters have to be controlled in order to achieve a reliable bond between the Au bumps on the die and the Sn plated Cu traces on the PI film. In the current work, the TCB process is studied using Finite Element Analysis (FEA) to optimize the design parameters and assure proper process margins. The resultant forces acting on the bump-to-trace interfaces are quantified across the different potential geometrical combinations. Baseline simulations showed higher stresses on specific bump locations and stress gradients acting on the bumps along the different sides of the die. These observations were correlated to both the failures and near failures on the actual test vehicles. Further simulations were then utilized to optimize and navigate design tradeoffs at both the die and flexible substrate design levels for a more robust design solution. Construction analysis performed on parts built using optimized design parameters showed significant improvements and correlated well with the simulation results.
Experimental and Numerical Study on Uniaxial-Stress Effects of N-Type Metal-Oxide-Semiconductor Field Effect Transistors
Authors: Koganemaru Masaaki , Yoshida Keisuke , Tada Naohiro , Ikeda Toru , Miyazaki Noriyuki , Tomokage Hajime
Published: February 2012

In this study, the effects of uniaxial stress on n-type metal-oxide-semiconductor field effect transistors are investigated by experiments and numerical simulations. In the numerical evaluation, mechanical stress simulation and drift-diffusion device simulation are conducted to consider the impact of stress distribution in the device. The device simulation incorporates an electron mobility model by considering the effects of stress on the following: 1) change in relative population, 2) momentum relaxation time and 3) effective mass of electrons in conduction-band valleys. The variations in the dc characteristics (i.e., drain current and transconductance) of n-type metal-oxide-semiconductor field effect transistors with a gate length of 12μm are evaluated under (nominal) uniaxial stress applied to the device parallel (0°), 45° and perpendicular (90°) to the current flow direction. The results of device simulation are in good qualitative agreement with the experimental results; the device simulation including the present electron mobility model can determine the uniaxial-load-direction dependence of the stress sensitivity of the change in transconductance.
Squeeze Flow Models for Thermal Interface Materials Contained Between Parallel Plates and Plates With Posts
Authors: Khalsa Simranjit , Subbarayan Ganesh
Published: February 2012

In this paper, motivated by a need to develop heat spreaders with post-containing (or nested channeled) configurations, we develop analytical models for the Squeeze Flow behavior of particle-filled Thermal Interface Materials (TIMs) between parallel plates and those with posts. The fluids are modeled as either Newtonian, or as Bingham fluids. The pressure distribution is analytically described for axisymmetric and non-axisymmetric configurations of fluids squeezed between parallel plates as well as for non-planar configurations with a cylindrical post at the center of one of the two circular plates. The developed analytical solutions to Newtonian behavior of the fluids are validated using squeeze flow models created in a commercial finite element code (COMSOL). The analysis for non-planar geometries is verified that as the post height is reduced to zero, the developed solution reduces to that of the parallel plate configuration. The influence of the height of the post on the force is systematically analyzed from which it is observed that the force required to compress the fluid increases with the post height. With increased post height, the force solution deviates by a greater amount from the parallel plate solution. The Bond-Line Thickness (BLT) of Newtonian and Bingham fluids contained within circular plates is determined. It is shown that materials with greater yield strength produce higher BLTs. The effect of backpressure is also shown to increase the BLT. Lastly, it is shown that as particles are added into the fluid, the effective viscosity increases and as a result a greater force is required to squeeze the fluid material.
Assessment of Thermal Performance of Electronic Enclosures With Rectangular Fins: A Passive Thermal Solution
Authors: Tamayol A. , McGregor F. , Demian E. , Trandafir E. , Bowler P. , Rada P. , Bahrami M.
Published: February 2012

Passive heat transfer from enclosures with rectangular fins is studied both experimentally and theoretically. Several sample enclosures with various lengths are prepared and tested. To calibrate the thermal measurements and the analyses, enclosures without fins (“bare” enclosures) are also prepared and tested. Surface temperature distribution is determined for various enclosure lengths and heat generation rates. Existing relationships for natural convection and radiation heat transfer are used to calculate the heat transfer rate of the tested samples. The theoretical results successfully predict the trends observed in the experimental data. It is observed that the contribution of the radiation heat transfer is on the order of 50% of the total heat transfer for the tested enclosures. As such, a new correlation is reported for calculating optimum fin spacing in uniformly finned surfaces, with rectangular straight fins, that takes into account both natural convection and radiation.
The Most Cost-Effective Integrator (TSV Interposer) for 3D IC Integration System-in-Package (SiP)
Authors: Lau John H.
Published: February 2012

The significant roles of Cu-filled TSV passive interposers for 3D IC integration are investigated in this study. Emphasis is placed on the roles they play as: (1) substrates; (2) carriers; (3) thermal management tools; and (4) reliability buffers. It is shown that the Cu-filled TSV passive interposers are the most cost-effective integrator for 3D IC integration system-in-package (SiP).
TSV Interposers With Embedded Microchannels for 3D IC and LED Integration
Authors: Lau John , Chien Heng-Chieh , Tain Ray
Published: February 2012

A low-cost (with bare chips), high cooling ability and very low pressure drop 3D IC integration system-in-package (SiP) is designed and described. This system consists of a silicon interposer with through-silicon vias (TSV) and embedded fluidic microchannels, which carries all the Moore’s law chips and optical devices on its top and bottom surfaces. TSVs in the Moore’s law chips are optional but should be avoided. This novel structural design offers potential solutions for high-power, high-performance, high pin-count, ultra fine-pitch, small real-estate, and low-cost 3D IC SiP applications.