Asynchronous techniques for system-on-chip design

SoC design will require asynchronous techniques as the large parameter variations across the chip will make it impossible to control delays in clock networks and other global signals efficiently. Initially, SoCs will be globally asynchronous and locally synchronous (GALS). But the complexity of the numerous asynchronous/synchronous interfaces required in a GALS will eventually lead to entirely asynchronous solutions. This paper introduces the main design principles, methods, and building blocks for asynchronous VLSI systems, with an emphasis on communication and synchronization. Asynchronous circuits with the only delay assumption of isochronic forks are called quasi-delay-insensitive (QDI). QDI is used in the paper as the basis for asynchronous logic. The paper discusses asynchronous handshake protocols for communication and the notion of validity/neutrality tests, and completion tree. Basic building blocks for sequencing, storage, function evaluation, and buses are described, and two alternative methods for the implementation of an arbitrary computation are explained. Issues of arbitration, and synchronization play an important role in complex distributed systems and especially in GALS. The two main asynchronous/synchronous interfaces needed in GALS-one based on synchronizer, the other on stoppable clock-are described and analyzed

ET^2: A Metric For Time and Energy Efficiency of Computation

We investigate an efficiency metric for VLSI computation that includes energy, E, and time, t, in the form E t^2. We apply the metric to CMOS circuits operating outside velocity saturation when energy and delay can be exchanged by adjusting the supply voltage; we prove that under these assumptions, optimal Et^2 implies optimal energy and delay. We give experimental and simulation evidences of the range and limits of the assumptions. We derive several results about sequential, parallel, and pipelined computations optimized for E t^2, including a result about the optimal length of a pipeline. We discuss transistor sizing for optimal Et^2 and show that, for fixed, nonzero execution rates, the optimum is achieved when the sum of the transistor-gate capacitances is twice the sum of the parasitic capacitances-not for minimum transistor sizes. We derive an approximation for E t^n (for arbitrary n) of an optimally sized system that can be computed without actually sizing the transistors; we show that this approximation is accurate. We prove that when multiple, adjustable supply voltages are allowed, the optimal Et^2 for the sequential composition of components is achieved when the supply voltages are adjusted so that the components consume equal power. Finally, we give rules for computing the Et^2 of the sequential and parallel compositions of systems, when the Et^2 of the components are known

Long-term adherence to healthy dietary guidelines and chronic inflammation in the prospective Whitehall II study

Background Inflammation plays an important role in the cause of cardiovascular diseases and may contribute to the association linking an unhealthy diet to chronic age-related diseases. However, to date the long-term associations between diet and inflammation have been poorly described. Our aim was to assess the extent to which adherence to a healthy diet and dietary improvements over a 6-year exposure period prevented subsequent chronic inflammation over a 5-year follow-up in a large British population of men and women. Methods Data were drawn from 4600 adults (mean ± standard deviation, age 49.6 ± 6.1 years, 28% were women) from the prospective Whitehall cohort II study. Adherence to a healthy diet was measured using Alternative Healthy Eating Index (AHEI) scores in 1991-1993 (50.7 ± 11.9 points) and 1997-1999 (51.6 ± 12.4 points). Chronic inflammation, defined as average levels of serum interleukin-6 from 2 measures 5 years apart, was assessed in 1997-1999 and 2002-2004. Results After adjustment for sociodemographic factors, health behaviors, and health status, participants who maintained a high AHEI score (ie, a healthy diet, n = 1736, 37.7%) and those who improved this score over time (n = 681, 14.8%) showed significantly lower mean levels of interleukin-6 (1.84 pg/mL, 95% confidence interval [CI], 1.71-1.98 and 1.84 pg/mL, 95% CI, 1.70-1.99, respectively) than those who had a low AHEI score (n = 1594, 34.6%) over the 6-year exposure period (2.01 pg/mL, 95% CI, 1.87-2.17). Conclusions These data suggest that maintaining and improving adherence to healthy dietary recommendations may reduce the risk of long-term inflammation.</p

DISCUS - The Deep Interior Scanning CubeSat mission to a rubble pile near-Earth asteroid

We have performed an initial stage conceptual design study for the Deep Interior Scanning CubeSat (DISCUS), a tandem 6U CubeSat carrying a bistatic radar as main payload. DISCUS will be operated either as an independent mission or accompanying a larger one. It is designed to determine the internal macroporosity of a 260-600 m diameter Near Earth Asteroid (NEA) from a few kilometers distance. The main goal will be to achieve a global penetration with a low-frequency signal as well as to analyze the scattering strength for various different penetration depths and measurement positions. Moreover, the measurements will be inverted through a computed radar tomography (CRT) approach. The scientific data provided by DISCUS would bring more knowledge of the internal configuration of rubble pile asteroids and their collisional evolution in the Solar System. It would also advance the design of future asteroid deflection concepts. We aim at a single-unit (1U) radar design equipped with a half-wavelength dipole antenna. The radar will utilize a stepped-frequency modulation technique the baseline of which was developed for ESA's technology projects GINGER and PIRA. The radar measurements will be used for CRT and shape reconstruction. The CubeSat will also be equipped with an optical camera system and laser altimeter to sup- port navigation and shape reconstruction. We provide the details of the measurement methods to be applied along with the requirements derived of the known characteristics of rubble pile asteroids.Comment: Submitted to Advances in Space Researc

Speed and Energy Performance of an Asynchronous MIPS R3000 Microprocessor

This paper presents the speed and energy figures for an asynchronous implementation of a MIPS R3000 microprocessor. The design is almost entirely QDI and introduces a new fine-grained pipeline. The performance figures show that this design is four times as efficient as equivalent clocked designs and that its cycle time in FO4 units compares to that of high-performance dynamic pipelines

Management of jugular bulb injury during drilling of the internal auditory canal (ICA) for vestibular schwannoma surgery

The retrosigmoid approach for vestibular schwannoma surgery has remained the standard approach by most neurosurgeons. Drilling the posterior wall of the internal auditory meatus (IAM) is an essential step in removing the intrameatal tumor. During IAM drilling, three anatomical structures can be encountered, including the posterior semicircular canal, vestibular aqueduct, and jugular bulb. Any of these can be injured during drilling, especially if the jugular bulb lies above the inferior edge of the IAM. Although IAM drilling is performed in most vestibular schwannoma surgeries, information on how to manage complications such as jugular bulb injury is lacking. Here we use an intraoperative video to demonstrate how to manage the inadvertent injury to the jugular bulb in order to avoid massive blood loss. We present a case of a 39-year-old woman with hearing loss, diagnosed with a cerebellopontine angle mass extending into the IAM. Surgery was required due to tumor progression. We used the retrosigmoid approach to access the tumor. During IAM drilling, the jugular bulb was injured. A thin layer of bone wax was applied under continuous suction. The margins of the wax were then gently compressed with a dissector; great care was taken to avoid pushing the wax into the jugular bulb. Excess bone wax was removed (video 1). A small diamond drill (2 mm) was used for further drilling. Our instructional video shows the surgical approach, microsurgical anatomy, and technical aspects of managing massive bleeding from jugular bulb injury. It should therefore be helpful for young neurosurgeons.Non peer reviewe

Bypass Surgery for Complex Internal Carotid Artery Aneurysms : 39 Consecutive Patients

OBJECTIVE: Bypass surgery is a special technique used to treat complex internal carotid artery (ICA) aneurysms. The aim of this retrospective study is to provide a comprehensive description of treatment and outcome of complex ICA aneurysms at different ICA segments (cavernous, supraclinoid, ICA bifurcation) treated with bypass procedures. METHODS: We identified 39 consecutive patients with 41 complex ICA aneurysms that were treated with 44 bypass procedures between 1998 and 2016. We divided the aneurysms into 3 anatomic subgroups to review our treatment strategy. All the imaging studies and medical records were reviewed for relevant information. RESULTS: The aneurysm occlusion (n = 34, 83%) or flow modification (n = 5, 12%) was achieved in 39 aneurysms (95%). The long-term bypass patency rate was 68% (n = 30). Minor postoperative ischemia or hemorrhage was commonly seen (n = 20, 51%), but large-scale strokes were rare (n = 1, 3%). Preoperative dysfunction of extraocular muscles (cranial nerves III, IV, and VI) showed low-to-moderate improvement rates (20%-50%). Preoperative vision disturbance (cranial nerve II) improved seldom (22%). At the latest follow-up (mean; 51 months) 29 patients (74%) were independent (modified Rankin Scale CONCLUSIONS: Bypass surgery for complex ICA aneurysms is a feasible treatment method with an acceptable risk profile. Patients should be informed of the uncertainty related to improvement of pretreatment cranial nerve dysfunctions.Peer reviewe

Polyethylene terephthalate (PET) recycling via steam gasification – The effect of operating conditions on gas and tar composition

Polyethylene terephthalate (PET) is widely used in textile fiber, film, and bottles. Although PET bottle recycling has made great progress, other PET waste is still not recycled. Gasification could be an option for recycling or recovering energy and chemicals from PET waste. However, single stream PET steam gasification in fluidized bed is seldom investigated. In this paper, individual PET gasification experiments were then conducted in a lab-scale bubbling fluidized bed to investigate how gasifying agents, temperature, residence time and steam/fuel ratio affect the product composition. The results showed that, in steam gasification, steam was the main source of H , but increasing the steam to fuel ratio cannot increase the H yield remarkably. Temperature was an essential parameter. Increasing temperature from 750 to 800 \ub0C improved the yields of H (+87.7%), the dominant gas product CO (+40.3%), and biphenyl (+123%) notably. In contrast to other common thermoplastics, high concentrations of CO and biphenyl are the prominent characteristics of PET steam gasification. In addition, plastic steam gasification optimizations for syngas applications were discussed

The Joint Effect of Sleep Duration and Disturbed Sleep on Cause-Specific Mortality: Results from the Whitehall II Cohort Study

Background: Both sleep duration and sleep quality are related to future health, but their combined effects on mortality are unsettled. We aimed to examine the individual and joint effects of sleep duration and sleep disturbances on cause-specific mortality in a large prospective cohort study. Methods: We included 9,098 men and women free of pre-existing disease from the Whitehall II study, UK. Sleep measures were self-reported at baseline (1985-1988). Participants were followed until 2010 in a nationwide death register for total and cause-specific (cardiovascular disease, cancer and other) mortality. Results: There were 804 deaths over a mean 22 year follow-up period. In men, short sleep (≤6 hrs/night) and disturbed sleep were not independently associated with CVD mortality, but there was an indication of higher risk among men who experienced both (HR = 1.57; 95% CI: 0.96-2.58). In women, short sleep and disturbed sleep were independently associated with CVD mortality, and women with both short and disturbed sleep experienced a much higher risk of CVD mortality (3.19; 1.52-6.72) compared to those who slept 7-8 hours with no sleep disturbances; equivalent to approximately 90 additional deaths per 100,000 person years. Sleep was not associated with death due to cancer or other causes. Conclusion: Both short sleep and disturbed sleep are independent risk factors for CVD mortality in women and future studies on sleep may benefit from assessing disturbed sleep in addition to sleep duration in order to capture health-relevant features of inadequate sleep. © 2014 Rod et al