Underfill material selection for flip chip technology

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1998.Includes bibliographical references (leaf 34).Six underfill materials were examined for the selection of an appropriate underfill material for Digital Equipment Corporation's flip chip development project. Several tests were performed to determine the material properties, process properties, and the reliability of each underfill material. A material with a fast flow rate, uniform and void free flow pattern, fast curing schedule, good thermal and mechanical properties, and good reliability results is needed to satisfy the requirements for this project. Materials F and E exhibited all the above requirements and were concluded as the two best underfill materials for the flip chip process. Important material properties which contributed to the desired results of these materials include a filler particle content of about 65%, a weight loss percentage during cure of less than 1%, and a Tg of 140°C.by Diana C. Chiang.S.M

Counseling in China: Implications for Counselor Education Preparation and Distance Learning Instruction

Counselor educators are preparing an increased number of international students to become counselors via online and distance education programs. There are also increasing mental health needs within schools and communities and limited counseling programs in the People’s Republic of China. The focus on educating and training Chinese and international students in Western counseling theories and practices is potentially limiting and fails to address the cultural differences among Chinese individuals. We discuss the implications for counselor education preparation through distance education and offer counselor educators culturally appropriate strategies and suggestions to best prepare students

Challenges of Recruiting a Vulnerable Population in a Grounded Theory Study

Recruitment is a crucial and fundamental part of research and one that poses various degrees of difficulty. This is particularly so when the area of research is one that is either highly sensitive, or that involves participants who are deemed to be particularly vulnerable. This article explores the inherent tensions in matters of participant recruitment among meeting the demands of institutional ethics committees, satisfying the concerns of clinicians in the field and the need to maintain methodological rigor. A postgraduate research student’s experience of these tensions underpins the discussion. The article concludes with an outline of the student’s strategies and resolution of these issues.postprin

MobileTL: On-device Transfer Learning with Inverted Residual Blocks

Transfer learning on edge is challenging due to on-device limited resources. Existing work addresses this issue by training a subset of parameters or adding model patches. Developed with inference in mind, Inverted Residual Blocks (IRBs) split a convolutional layer into depthwise and pointwise convolutions, leading to more stacking layers, e.g., convolution, normalization, and activation layers. Though they are efficient for inference, IRBs require that additional activation maps are stored in memory for training weights for convolution layers and scales for normalization layers. As a result, their high memory cost prohibits training IRBs on resource-limited edge devices, and making them unsuitable in the context of transfer learning. To address this issue, we present MobileTL, a memory and computationally efficient on-device transfer learning method for models built with IRBs. MobileTL trains the shifts for internal normalization layers to avoid storing activation maps for the backward pass. Also, MobileTL approximates the backward computation of the activation layer (e.g., Hard-Swish and ReLU6) as a signed function which enables storing a binary mask instead of activation maps for the backward pass. MobileTL fine-tunes a few top blocks (close to output) rather than propagating the gradient through the whole network to reduce the computation cost. Our method reduces memory usage by 46% and 53% for MobileNetV2 and V3 IRBs, respectively. For MobileNetV3, we observe a 36% reduction in floating-point operations (FLOPs) when fine-tuning 5 blocks, while only incurring a 0.6% accuracy reduction on CIFAR10. Extensive experiments on multiple datasets demonstrate that our method is Pareto-optimal (best accuracy under given hardware constraints) compared to prior work in transfer learning for edge devices

MaxEVA: Maximizing the Efficiency of Matrix Multiplication on Versal AI Engine

The increasing computational and memory requirements of Deep Learning (DL) workloads has led to outstanding innovations in hardware architectures. An archetype of such architectures is the novel Versal AI Engine (AIE) by AMD/Xilinx. The AIE comprises multiple programmable processors optimized for vector-based algorithms. An AIE array consisting of 400 processor cores, operating at 1.25 GHz is able to deliver a peak throughput of 8 TFLOPs for 32-bit floating-point (fp32), and 128 TOPs for 8-bit integer (int8) precision. In this work, we propose MaxEVA: a novel framework to efficiently map Matrix Multiplication (MatMul) workloads on Versal AIE devices. Our framework maximizes the performance and energy efficiency of MatMul applications by efficiently exploiting features of the AIE architecture and resolving performance bottlenecks from multiple angles. When demonstrating on the VC1902 device of the VCK190 board, MaxEVA accomplishes up to 5.44 TFLOPs and 77.01 TOPs throughput for fp32 and int8 precisions, respectively. In terms of energy efficiency, MaxEVA attains up to 124.16 GFLOPs/W for fp32, and 1.16 TOPs/W for int8. Our proposed method substantially outperforms the state-of-the-art approach by exhibiting up to 2.19x throughput gain and 20.4% higher energy efficiency. The MaxEVA framework provides notable insights to fill the knowledge gap in effectively designing MatMul-based DL workloads on the new Versal AIE devices.Comment: Accepted as full paper at FPT 202

Ultrasound Molecular Imaging of VEGFR-2 in Clear-Cell Renal Cell Carcinoma Tracks Disease Response to Antiangiogenic and Notch-Inhibition Therapy

Metastatic clear-cell renal cell carcinoma (ccRCC) affects thousands of patients worldwide each year. Antiangiogenic therapy has been shown to have beneficial effects initially, but resistance is eventually developed. Therefore, it is important to accurately track the response of cancer to different therapeutics in order to appropriately adjust the therapy to maximize efficacy. Change in tumor volume is the current gold standard for determining efficacy of treatment. However, functional variations can occur much earlier than measurable volume changes. Contrast-enhanced ultrasound (CEUS) is an important tool for assessing tumor progression and response to therapy, since it can monitor functional changes in the physiology. In this study, we demonstrate how ultrasound molecular imaging (USMI) can accurately track the evolution of the disease and molecular response to treatment

Estimating survival in patients with gastrointestinal cancers and brain metastases: An update of the graded prognostic assessment for gastrointestinal cancers (GI-GPA).

BackgroundPatients with gastrointestinal cancers and brain metastases (BM) represent a unique and heterogeneous population. Our group previously published the Diagnosis-Specific Graded Prognostic Assessment (DS-GPA) for patients with GI cancers (GI-GPA) (1985-2007, n = 209). The purpose of this study is to update the GI-GPA based on a larger contemporary database.MethodsAn IRB-approved consortium database analysis was performed using a multi-institutional (18), multi-national (3) cohort of 792 patients with gastrointestinal (GI) cancers, with newly-diagnosed BM diagnosed between 1/1/2006 and 12/31/2017. Survival was measured from date of first treatment for BM. Multiple Cox regression was used to select and weight prognostic factors in proportion to their hazard ratios. These factors were incorporated into the updated GI-GPA.ResultsMedian survival (MS) varied widely by primary site and other prognostic factors. Four significant factors (KPS, age, extracranial metastases and number of BM) were used to formulate the updated GI-GPA. Overall MS for this cohort remains poor; 8 months. MS by GPA was 3, 7, 11 and 17 months for GPA 0-1, 1.5-2, 2.5-3.0 and 3.5-4.0, respectively. >30% present in the worst prognostic group (GI-GPA of ≤1.0).ConclusionsBrain metastases are not uncommon in GI cancer patients and MS varies widely among them. This updated GI-GPA index improves our ability to estimate survival for these patients and will be useful for therapy selection, end-of-life decision-making and stratification for future clinical trials. A user-friendly, free, on-line app to calculate the GPA score and estimate survival for an individual patient is available at brainmetgpa.com

Double-Stranded RNA Attenuates the Barrier Function of Human Pulmonary Artery Endothelial Cells

Circulating RNA may result from excessive cell damage or acute viral infection and can interact with vascular endothelial cells. Despite the obvious clinical implications associated with the presence of circulating RNA, its pathological effects on endothelial cells and the governing molecular mechanisms are still not fully elucidated. We analyzed the effects of double stranded RNA on primary human pulmonary artery endothelial cells (hPAECs). The effect of natural and synthetic double-stranded RNA (dsRNA) on hPAECs was investigated using trans-endothelial electric resistance, molecule trafficking, calcium (Ca2+) homeostasis, gene expression and proliferation studies. Furthermore, the morphology and mechanical changes of the cells caused by synthetic dsRNA was followed by in-situ atomic force microscopy, by vascular-endothelial cadherin and F-actin staining. Our results indicated that exposure of hPAECs to synthetic dsRNA led to functional deficits. This was reflected by morphological and mechanical changes and an increase in the permeability of the endothelial monolayer. hPAECs treated with synthetic dsRNA accumulated in the G1 phase of the cell cycle. Additionally, the proliferation rate of the cells in the presence of synthetic dsRNA was significantly decreased. Furthermore, we found that natural and synthetic dsRNA modulated Ca2+ signaling in hPAECs by inhibiting the sarco-endoplasmic Ca2+-ATPase (SERCA) which is involved in the regulation of the intracellular Ca2+ homeostasis and thus cell growth. Even upon synthetic dsRNA stimulation silencing of SERCA3 preserved the endothelial monolayer integrity. Our data identify novel mechanisms by which dsRNA can disrupt endothelial barrier function and these may be relevant in inflammatory processes

The controlled delivery of hydrogen sulfide for the preservation of heart tissue

Gemstone Team Organ Storage and HibernationThere are over 100,000 patients on organ transplant waiting lists, creating a significant need to expand the donor pool. The heart is the most difficult organ to preserve ex vivo, with a short viable storage time of 4-6 hours, because damage to mitochondria during preservation can impair the heart's contractile function. By extending the viability time, the geographical range of donors can be extended. Hydrogen sulfide (H2S) has been shown to reduce metabolism, increase preservation times, and enhance graft viability. We have developed gelatin microspheres under 10 microns able to slowly release H2S and investigated different crosslinking concentrations to understand the time release profiles. These microspheres were then used to maintain H2S levels in cardiomyocyte cell cultures without decreasing cell viability. Histological samples from 20 cold-stored rat hearts in various experimental treatments show H2S-releasing microspheres offer protection against preservation injury comparable to the current clinical standard, University of Wisconsin solution

Ultrasound Measurement of Vascular Density to Evaluate Response to Anti-angiogenic Therapy in Renal Cell Carcinoma

Background: Functional and molecular changes often precede gross anatomical changes, so early assessment of a tumor's functional and molecular response to therapy can help reduce a patient's exposure to the side effects of ineffective chemotherapeutics or other treatment strategies. Objective: Our intent was to test the hypothesis that an ultrasound microvascular imaging approach might provide indications of response to therapy prior to assessment of tumor size. Methods: Mice bearing clear-cell renal cell carcinoma xenograft tumors were treated with antiangiogenic and Notch inhibition therapies. An ultrasound measurement of microvascular density was used to serially track the tumor response to therapy. Results: Data indicated that ultrasound-derived microvascular density can indicate response to therapy a week prior to changes in tumor volume and is strongly correlated with physiological characteristics of the tumors as measured by histology (ρ = 0.75). Furthermore, data demonstrated that ultrasound measurements of vascular density can determine response to therapy and classify between-treatment groups with high sensitivity and specificity. Conclusion/Significance: Results suggests that future applications utilizing ultrasound imaging to monitor tumor response to therapy may be able to provide earlier insight into tumor behavior from metrics of microvascular density rather than anatomical tumor size measurements