Liquid cooling of non-uniform heat flux of chip circuit by submicrochannels

Sumbmicrochannels have been placed on the hotspots in a non-uniform heat generated chip circuit to increase the liquid/solid interaction area and then to enhance the heat dissipation. Main microchannels width is 185µm, which is twice the width of the submicrochannels and also includes the wall thickness of 35µm, and wall height is 500µm. The chip dimension is 10mm×10mm and the hotspot is 4mm×10m. Different positions of the hotspot have been investigated e.g. upstream, middle and downstream. Uniform heat flux is 100W/cm2 while for the hot spot is 150 W/cm2. Single channel simulation reveals that the downstream hotspot gives a lower temperature of the chip circuit surface; however the upstream hotspot has more uniform temperature distribution. A special design of manifold was adopted to ensure an equal mass distribution through the microchannels

Dimension- and shape-dependent thermal transport in nano-patterned thin films investigated by scanning thermal microscopy

Scanning thermal microscopy (SThM) is a technique which is often used for the measurement of the thermal conductivity of materials at the nanometre scale. The impact of nano-scale feature size and shape on apparent thermal conductivity, as measured using SThM, has been investigated. To achieve this, our recently developed topography-free samples with 200 and 400 nm wide gold wires (50 nm thick) of length of 400–2500 nm were fabricated and their thermal resistance measured and analysed. This data was used in the development and validation of a rigorous but simple heat transfer model that describes a nanoscopic contact to an object with finite shape and size. This model, in combination with a recently proposed thermal resistance network, was then used to calculate the SThM probe signal obtained by measuring these features. These calculated values closely matched the experimental results obtained from the topography-free sample. By using the model to analyse the dimensional dependence of thermal resistance, we demonstrate that feature size and shape has a significant impact on measured thermal properties that can result in a misinterpretation of material thermal conductivity. In the case of a gold nanowire embedded within a silicon nitride matrix it is found that the apparent thermal conductivity of the wire appears to be depressed by a factor of twenty from the true value. These results clearly demonstrate the importance of knowing both probe-sample thermal interactions and feature dimensions as well as shape when using SThM to quantify material thermal properties. Finally, the new model is used to identify the heat flux sensitivity, as well as the effective contact size of the conventional SThM system used in this study

Thermocouple heating impact on the temperature measurement of small volume of water in a cooling system

Experimental and numerical analyses have been performed to investigate the heating impact of using a thermocouple for the temperature measurement of a small volume of cold water (∼24 mm3), due to thermal conduction through the wires. Two sizes of K-type thermocouple, 80 µm and 315 µm, were used to measure the temperature of cold water inside a small, thermally regulated chamber within a Centeo TG40 cooling system. The results show that thermal conduction from the ambient environment into the cold water produces a heating effect. This effect decreases for greater submersion depth of the thermocouple junction and is eliminated when the thermocouple junction is close to the copper bottom of the chamber. The inclusion of an insert into the chamber increases the thermal resistance between the copper block and the water, raising the heating effect of the thermocouple. The cooling effect of the copper block on the water is diminished when the air gap between copper block and plastic insert is increased, consequently raising the temperature inside the small well. Moreover, increasing the water height inside the large well has a negligible effect on the temperature of the small well

Self-efficacy for eating a healthy diet can moderate the impact of stress on diet quality

Introduction. Family child care home (FCCH) providers are individuals who care for children in their own home. This group has been identified as at-risk for high stress and poor sleep quality, contributing to poor health behaviors. High self-efficacy for the diet may moderate the relationship between these risk factors and diet quality. Little research has examined how these factors may relate to one another when describing the health of FCCH providers.Methods. We utilized baseline data on FCCH providers from the cluster-randomized control trial Keys to a Healthy Family Child Care Home. We estimated correlations between self-reported perceived stress, sleep quality, diet self-efficacy and diet quality. A linear regression including interaction terms was run to assess how diet self-efficacy may moderate the relationships between perceived stress and sleep quality, respectively, and diet quality. Results. Perceived stress and sleep quality were not significantly correlated with diet quality in this population. However, diet self-efficacy was identified as a moderator of the association between perceived stress and diet quality. With high diet self-efficacy, increasing perceived stress was associated with improved diet quality.Conclusion. Improving self-efficacy may be one critical strategy for improving the health of a population at-risk for poor behaviors. As FCCH providers care for many children and model behaviors, improving their diet quality may positively impact the children in their care.Bachelor of Science in Public Healt

Barriers and Facilitators of Parent Engagement with Health Promotion in Child Care: A Mixed-Methods Evaluation

BACKGROUND: Early care and education providers cite lack of parent engagement as a central barrier to promoting healthy behaviors among young children. However, little research exists about factors influencing parent engagement with promoting healthy eating and activity behaviors in the this setting. AIMS: This study aimed to address this gap by examining low and high parent engagement with the Healthy Me, Healthy We campaign to identify barriers and facilitators of parent engagement with the intervention. METHOD: This comparative case study used an explanatory sequential mixed-methods approach. We created center-level parent engagement scores using process evaluation data from the effectiveness trial of Healthy Me, Healthy We. Recruitment focused on centers with the five lowest and five highest scores. Twenty-eight adults (7 directors, 9 teachers, 12 parents) from seven centers (3 low engagement, 4 high engagement) completed semistructured interviews and the Family and Provider/Teacher Relationship Quality measure. Analytic approaches included descriptive statistical analyses for surveys and a framework-informed thematic analysis for interviews. RESULTS: Prominent contrasts between low- and high-engagement groups involved center culture for parent engagement and health promotion, practices for fostering networks and communication within centers, and communication between centers and parents. Personal attributes of providers (e.g., attitudes) also differentially influenced practices for engaging parents. DISCUSSION AND CONCLUSION: Organizational characteristics and individual practices can facilitate or impede parent engagement with health promotion efforts. Assessing organizational context, gaining input from all stakeholders, and conducting capacity-building interventions may be critical for laying the foundation for positive relationships that support parent engagement in implementation of health promotion programs and beyond

Predicting arrhythmias in primary prevention heart failure patients: picking up the fragments

Identifying patients with high-risk heart failure (HF) who would benefit from an implantable cardioverter-defibrillator (ICD) remains controversial. A potential marker for arrhythmic sudden death is fragmented QRS (fQRS). fQRS is the notching and slurring of the QRS complex in a 12-lead ECG and it indicates abnormal ventricular depolarisation and myocardial scarring and fibrosis. However, before fQRS complex can be included into selection criteria for ICD therapy, more complete reporting is required on their association with malignant arrhythmias, left ventricular remodelling and myocardial scarring/fibrosis in patients with HF. The molecular basis of the fQRS-arrhythmia-fibrosis connection in HF also needs to be explored. It is not widely appreciated that changes in the QRS complex and phases 0 and 1 of the ventricular action potential occur before contraction and predetermine Ca2+ release during contraction and later Ca2+ sparks. It is currently not known whether the different zig-zag patterns of the QRS are associated with aberrant Ca2+ cycling and arrhythmogenic sparks in patients with HF

Quantification of atomic force microscopy tip and sample thermal contact

A thermal conduction measurement device was fabricated, consisting of a silicon dioxide membrane with integrated thermal sensors (Pt resistance heater/thermometer and Pt–Au thermocouples) using MEMS technology. Heat transfer between the heated device and a number of unused atomic force microscope and scanning thermal microscope probes was measured. Changes in thermal conduction related to changes in the tip shape resulting from initial contact were observed. The sensors were fabricated by electron beam lithography and lift-off followed by local subtractive processing of a Pt–Au multilayer to form Pt heater–resistance thermometer elements and Pt–Au thermocouples. Thermal isolation from the silicon substrate was provided by dry release of the supporting 50 nm thick SiO2 membrane using an isotropic SF6 inductively coupled plasma etch. The high thermal isolation of the sample combined with the sensitivity of the temperature sensors used allowed the detection of thermal conduction between the tip and the sample with high precision. The measured temperature range of the Pt resistor was 293–643 K. The measured thermal resistance of the membrane was 3 × 105 K/W in air and 1.44 × 106 K/W in vacuum. The tip contact resistance was measured with a noise level of 0.3g0 T at room temperature, where g0 is the thermal resistance quantum

Topography-free sample for thermal spatial response measurement of scanning thermal microscopy

A novel fabrication technique is described for the production of multimaterial, lithographically defined, topography-free samples for use in experiments to investigate the nature of contrast in scanning probe microscopy (SPM). The approach uses a flat sacrificial substrate as the base for fabrication, which is deleted in the final step. This leaves an exposed, flat surface with patterns of materials contrast defined during the lithography stages. In the example application presented, these are designed to challenge the detection ability of a scanning thermal microscopy (SThM) probe, although many other applications can be envisioned. There are many instances in SPM where images can exhibit topographically induced artifacts. In SThM, these can result in a change of the thermal signal which can easily be misinterpreted as changes in the sample thermal conductivity or temperature. The elimination of these artifacts through postprocessing requires a knowledge of how the probe responds thermal features of differing sizes. The complete sample fabrication process, followed by successful topographic/thermal scanning is demonstrated, showing sub-1.5 nm topography with a clear artifact-free thermal signal from sub-100 nm gold wires. The thermal spatial resolution is determined for the sample materials and probe used in this study to be in the range of 35–75 nm

7.5% NaCl resuscitation leads to abnormal clot fibrinolysis after severe hemorrhagic shock and its correction with 7.5% NaCl adenosine, lidocaine, and Mg2+

Background: Hyperfibrinolysis is a common complication of hemorrhagic shock. Our aim was to examine the effect of small-volume 7.5% NaCl adenosine, lidocaine, and Mg2+ (ALM) on fibrinolysis in the rat model of hemorrhagic shock. Methods: Rats were anesthetized and randomly assigned to one of four groups: (1) baseline, (2) shock, (3) 7.5% NaCl controls, and (4) 7.5% NaCl ALM. Animals were bled for 20 min (42% blood loss) and left in shock for 60 min before resuscitation with 0.3 ml intravenous bolus 7.5% NaCl ± ALM. Rats were sacrificed at 5, 10, 15, 30, and 60 min for rotation thromboelastometry and 15 and 60 min for ELISA analyses. Results: After hemorrhagic shock, 7.5% NaCl failed to resuscitate and exacerbated coagulopathy and fibrinolysis. At 15 and 60 min, the activation as extrinsically-activated test using tissue factor (EXTEM) with aprotinin to inhibit fibrinolysis (APTEM) test showed little or no correction of fibrinolysis, indicating a plasmin-independent fibrinolysis. Clots also had ~ 60% lower fibrinogen (fibrin-based EXTEM activated test with platelet inhibitor cytochalasin D A10) and 36%–50% reduced fibrinogen-to-platelet ratio (11%–14% vs. 22% baseline). In contrast, 7.5% NaCl ALM resuscitated mean arterial pressure and attenuated hyperfibrinolysis and coagulopathy by 15 min. Correction was associated with lower plasma tissue factor, higher plasminogen activator inhibitor-1, and lower D-dimers (5% of controls at 60 min). Platelet selectin fell to undetectable levels in ALM animals, which may imply improved endothelial and platelet function during resuscitation. Conclusions: Small-volume 7.5% NaCl resuscitation exacerbated coagulopathy and fibrinolysis that was not corrected by APTEM test. Fibrinolysis appears to be associated with altered fibrin structure during early clot formation and elongation. In contrast, 7.5% NaCl ALM rapidly corrected both coagulopathy and hyperfibrinolysis

Numerical investigation of nanofluid deposition in a microchannel cooling system

Nanofluid-microchannels (NF-MCs) have emerged as an important topic for thermal management of electronic devices. However, deposition of nanoparticles is a tricky problem, and this paper conducts a numerical study to identify the best working conditions to prevent deposition of nanofluids in a microchannel cooling system. According to the findings, large nanoparticles, high velocity, low inlet temperature, high nanoparticle density, low nanofluid density, and high base fluid viscosity are the best working conditions for improving nanofluid stability. However, heat transfer rates and pressure drop must also be taken into account. The nanoparticle deposition rate and average heat transfer coefficient only increase by 2.71% and 0.92% respectively as the heat flux increases from 20 kW/m2 to 100 kW/m2, but the pressure drop decreases by 10.57%. Therefore, changing the heat flux is not the best option. Moreover, the inlet temperature has only a minor effect on the heat transfer coefficient, so it is crucial to balance the pressure drop and nanoparticle deposition when designing systems