Reliability Evaluation of Board-Level Flip-Chip Package under Coupled Mechanical Compression and Thermal Cycling Test Conditions.

Flip Chip Ball Grid Array (FCBGA) packages, together with many other heterogeneous integration packages, are widely used in high I/O (Input/Output) density and high-performance computing applications. The thermal dissipation efficiency of such packages is often improved through the use of an external heat sink. However, the heat sink increases the solder joint inelastic strain energy density, and thus reduces the board-level thermal cycling test reliability. The present study constructs a three-dimensional (3D) numerical model to investigate the solder joint reliability of a lidless on-board FCBGA package with heat sink effects under thermal cycling testing, in accordance with JEDEC standard test condition G (a thermal range of -40 to 125 °C and a dwell/ramp time of 15/15 min). The validity of the numerical model is confirmed by comparing the predicted warpage of the FCBGA package with the experimental measurements obtained using a shadow moiré system. The effects of the heat sink and loading distance on the solder joint reliability performance are then examined. It is shown that the addition of the heat sink and a longer loading distance increase the solder ball creep strain energy density (CSED) and degrade the package reliability performance accordingly.

Extension neural network and its applications.

In this paper, a novel extension neural network (ENN) is proposed. This new neural network is a combination of extension theory and neural network. It uses an extension distance (ED) to measure the similarity between data and cluster center. The learning speed of the proposed ENN is shown to be faster than the traditional neural networks and other fuzzy classification methods. Moreover, the new scheme has been proved to have high accuracy and less memory consumption. Experimental results from two different examples verify the effectiveness and applicability of the proposed work.

Real and illusory contour processing in area V1 of the primate: a cortical balancing act.

It is known that neurons in area V2 (the second visual area) can signal the orientation of illusory contours in the primate. Whether area V1 (primary visual cortex) can signal illusory contour orientation is more controversial. While some electrophysiology studies have ruled out illusory signaling in V1, other reports suggest that V1 shows some illusory-specific response. Here, using optical imaging and single unit electrophysiology, we report that primate V1 does show an orientation-specific response to the 'abutting line grating' illusory contour. However, this response does not signal an illusory contour in the conventional sense. Rather, we find that illusory contour stimulation leads to an activation map that, after appropriate subtraction of real line signal, is inversely related to the real orientation map. The illusory contour orientation is thus negatively signaled or de-emphasized in V1. This 'activation reversal' is robust, is not due merely to presence of line ends, is not dependent on inducer orientation, and is not due to precise position of line end stimulation of V1 cells. These data suggest a resolution for previous apparently contradictory experimental findings. We propose that the de-emphasis of illusory contour orientation in V1 may be an important signal of contour identity and may, together with illusory signal from V2, provide a unique signature for illusory contour representation.

Building surfaces from borders in Areas 17 and 18 of the cat.

Several brightness illusions indicate that borders can dramatically affect the perception of adjoining surfaces. In the Craik-O'Brien-Cornsweet illusion, in particular, two equiluminant surfaces can appear different in brightness due to the contrast border between them. Although the psychophysical nature of this phenomenon has been well characterized, the neural circuitry underlying this effect is unexplored. Here, we have asked whether there are cells in visual cortex which respond to edge-induced illusory brightness percepts such as the Cornsweet. Using optical imaging and single unit recordings methods, we have studied responses of the primary (Area 17) and second (Area 18) visual cortical areas of the anesthetized cat to both real luminance change and Cornsweet brightness change. We find that there are indeed cells whose responses are modulated in phase with the modulation of the Cornsweet stimulus. These cells are present in both Area 17 and Area 18, but are more prevalent in Area 18. These responses are generally weak and are found even when receptive fields are distant from the contrast border. Consistent with perception, cells which respond to the Cornsweet border are modulated in antiphase to the Narrow Real (another border-induced illusory brightness stimulus). Remarkably, we also find evidence of edge-induced responses to illusory brightness change using intrinsic signal optical imaging. Both real luminance change and edge-induced brightness change produces a greater imaged response in Area 18 than in Area 17. Thus, in the absence of direct luminance stimulation, cells in visual cortex can respond to modulation of distant border contrasts. We suggest that the perception of surface brightness was encoded in the early visual cortical pathway by both surface luminance contrast signals in Area 17 (Rossi, A. F., Rittenhouse, C. D., & Paradiso, M. A. (1996). The representation of brightness in primary visual cortex. Science, 273, 1104-7) and border-induced contrast signals that predominate in Area 18.

Is total knee replacement more painful than total hip replacement?

BACKGROUND: During its use in pain management the patient-controlled analgesia (PCA) devices are capable of registering the course of treatment at patient request, the condition of drug delivery and total amount of drug being given. The patients could determine the need of medication to their own satisfaction while forced treatment by the bias of the health care personnel is avoided and the safety of patients is further warranted. In pain relief with this device, the number of requests for analgesia and the dose of analgesic used can be easily measured. Therefore, it is more objective to compare the pain intensity among different types of operation when PCA device is used. Using PCA morphine consumption as a parameter, we attempted to elucidate the difference of intensity of pain associated with total hip and total knee replacements by comparing their morphine requirement. METHODS: In this prospective cohort study, 50 patients who underwent either total hip replacement (THR, n = 24) or total knee replacement (TKR, n = 26) were enrolled. After recovery from general anesthesia when the patients first complained intense pain in the recovery room, morphine was given intravenously in titration with a calculated loading dose in 30 min to achieve an acceptable analgesia (VAS < or = 3) followed by morphine PCA at 1 mg bolus with a lockout interval of 6 min. The patients were then followed for 48 h. During and at the end of the course the data relevant to pain score, total dose, demand, delivery, and adverse effects were recorded for assessment. RESULTS: With the use of PCA, the pain scores were similar in both surgical groups in the 48 h observation. Total consumption of morphine in THR was 13.2 +/- 8.1 mg as against 19.7 +/- 5.7 mg in TKR in postoperative day 1 and 25.2 +/- 12.7 mg as against 34.1 +/- 13.9 mg in postoperative day 2 (P < 0.05, t-test). Demand/delivery ratio was not statistically significant between the 2 groups at 24 and 48 h (t-test). Minor adverse effects were seen in both groups but the differences were not significant. CONCLUSIONS: Using PCA morphine consumption as parameter, we can distinguish the magnitude of pain intensity between 2 major orthopedic surgeries. The deeper and more extensive operation would in total hip replacement does not mean that it is a more painful procedure than total knee replacement. Several speculations are proposed.

Intraoperative loading attenuates nausea and vomiting of tramadol patient-controlled analgesia.

PURPOSE: To evaluate the adverse effect profile of tramadol by patient-controlled analgesia (PCA) with administration of the loading dose either intraoperatively or postoperatively. METHODS: Sixty adult patients scheduled for elective abdominal surgery were enrolled into this prospective, randomized, double blind study. The patients were anesthetized in a similar manner. At the beginning of wound closure, the patients were randomly allocated to receive 5 mg x kg(-1) tramadol (Group 1) or normal saline (Group 2). In the post-anesthesia care unit (PACU), when patients in either group complained of pain, 30 mg x ml(-1) tramadol i.v. were given every three minutes until visual analogue scale (VAS) 3, followed by tramadol PCA with bolus dose of 30 mg and five minute lockout interval. Pain control and adverse effect assessments were done in the PACU and every six hours for 48 hr post drug by an independent observer. RESULTS: The loading dose was 290 +/- 45 mg in Group 1 and 315 +/- 148 mg in Group 2. In PACU, more nausea/vomiting both in terms of incidence (13/30, 43% vs 2/30, 6.6%, P < 0.05) and severity (nausea/vomiting score 2.5 +/- 2.0 vs 0.2 +/- 0.6, P < 0.05) was observed in patients with postoperative loading than in those with intraoperative loading of tramadol. CONCLUSION: Administering the loading dose of tramadol during surgery decreases the nausea/vomiting associated with high dose of tramadol and improves the quality of tramadol PCA in the relief of postoperative pain.

Optical imaging of functional domains in the cortex of the awake and behaving monkey.

As demonstrated by anatomical and physiological studies, the cerebral cortex consists of groups of cortical modules, each comprising populations of neurons with similar functional properties. This functional modularity exists in both sensory and association neocortices. However, the role of such cortical modules in perceptual and cognitive behavior is unknown. To aid in the examination of this issue we have applied the high spatial resolution optical imaging methodology to the study of awake, behaving animals. In this paper, we report the optical imaging of orientation domains and blob structures, approximately 100-200 micrometer in size, in visual cortex of the awake and behaving monkey. By overcoming the spatial limitations of other existing imaging methods, optical imaging will permit the study of a wide variety of cortical functions at the columnar level, including motor and cognitive functions traditionally studied with positron-emission tomography or functional MRI techniques.

A role for the cadherin family of cell adhesion molecules in hippocampal long-term potentiation.

The cadherins are a family of cell-cell adhesion molecules that mediate Ca2+-dependent homophilic interactions between cells and transduce signals by interacting with cytoplasmic proteins. In the hippocampus, immunostaining combined with confocal microscopy revealed that both neural- (N-) and epithelial- (E-) cadherin are present at synaptic sites, implying a role in synaptic function. Pretreatment of hippocampal slices with antibodies (Abs) raised against the extracellular domain of either N-cad or E-cad had no effect on basal synaptic properties but significantly reduced long-term potentiation (LTP). Infusion of antagonistic peptides containing the His-Ala-Val (HAV) consensus sequence for cadherin dimerization also attenuated LTP induction without affecting previously established LTP. Because the intense synaptic stimulation associated with LTP induction might transiently deplete extracellular Ca2+ and hence potentially destabilize cadherin-cadherin interactions, we examined whether slices could be protected from inhibition by N-cad Abs or HAV peptides by raising the extracellular Ca2+ concentration. Indeed, we found that high extracellular Ca2+ prevented the block of LTP by these agents. Taken together, these results indicate that cadherins are involved in synaptic plasticity, and the stability of cadherin-cadherin bonds may be regulated by synaptic stimulation.

The effect of low dose propofol for prevention of nausea and vomiting during spinal anesthesia for cesarean section.

In order to investigate the possible antiemetic property of propofol at subhypnotic dosage, fifty patients scheduled for elective cesarean section under spinal anesthesia were accepted into the study. Patients were randomly given intravenous propofol 10 mg (group I) or 1 ml intralipid (group II) after delivery of the infant. Overall incidence of nausea (24% in group I and 40% in group II) and vomiting (16% in group I and 20% in group II) were not statistically different in the two groups. However, onset time to the appearance of nausea and vomiting were longer in group I (14 +/- 5.8 min vs 5.4 +/- 3.6 min). In conclusion, low dose propofol (10 mg) administered during spinal anesthesia for cesarean section failed to reduce the incidence of emesis.