Showing papers on "Latency (engineering) published in 1990"

The Switch between Latency and Replication of Epstein-Barr Virus

Abstract: Latency is characteristic behavior of many viruses that persist in their hosts. During latency an intact viral genome resides in the cell, but most viral genes are silent. Diverse inducing stimuli, by which the environment interacts with the host cell, trigger the latent viral genome into replication. Experiments are described that led to the identification of a crucial Epstein-Barr virus (EBV) gene, called ZEBRA, which acts as a switch between latency and replication of this herpes virus. During latency of EBV, ZEBRA expression is repressed. Inducing stimuli cause synthesis of ZEBRA which, in turn, activates expression of several individual EBV early genes. The ZEBRA polypeptide is a site-specific DNA binding protein that is likely to function as a transcriptional transactivator. The recognition that a single viral product may control the latency-to-replication switch offers promise of a detailed understanding of a central process in virology.

Long Latency Auditory Event-Related Potentials from Children with Auditory Processing Disorders

Abstract: The purpose of this study was to evaluate auditory event-related potentials, and related long latency components, in children with auditory processing disorders, and to compare these results with a normal group matched for age, intelligence, and gender. Results showed a significant latency increase for the N1, P2, and P3 components in the processing disordered group. Furthermore, the interpeak latency interval P2-P3 was significantly longer in the clinical group. In terms of amplitude measures, only P3 amplitude differed significantly between groups. These results suggest that the long latency potentials may be useful in the assessment of children with processing disorders.

Latency analysis in occupational epidemiology.

Abstract: Allowance for prolonged disease induction and latency times is an important consideration in occupational epidemiology studies of cancer and other delayed effects of exposure. Two useful approaches for assessing prolonged induction and latency periods are (1) exposure lagging and (2) considering exposures only within moving time windows. The exposure weighting scheme proposed by Jahr2 to assess exposure burdens is another method that accounts for induction and latency, although not explicitly. These three approaches, which are shown to be special cases of exposure weighting, are illustrated with an analysis of lung cancer mortality among a cohort of workers from an asbestos textile plant.

Latency and throughput tradeoffs in self-timed speed-independent pipelines and rings

Abstract: Asynchronous pipelines control the flow of tokens through a sequence of logical stages based on the status of local completion detectors. As in a synchronously clocked circuit, the design of self-timed pipelines can trade off between achieving low latency and high throughput. However, there are more degrees of freedom because of the variances in specific latch and function block styles, and the possibility of varying both the number of latches between function blocks and their connections to the completion detectors. This report demonstrates the utility of a graph-based methodology for analyzing the timing dependencies and uses it to make comparisons of different configurations. It is shown that the extremes for high throughput and low latency differ significantly, the placement of the completion detectors influences timing as much as adding an additional latch, and the choice as to whether precharged or static logic is best is dependent on the cost in complexity of the completion detectors.

Variable latency method and apparatus for floating-point coprocessor

Abstract: A programmable latency (a programmable number of clock cycles) needed for an operation completion. The required latency for a pipe is determined from a formula including the system clock cycle time which the unit will be specified to operate under. The latency is preprogrammed by setting the count of a timer accordingly to provide at least the minimum number of clock cycles necessary to cover the time required to do the computation. Separate timers are independently set for arithmetic logic unit (ALU) operations, multiply operations, logical operations and divide and square root operations.

Ring latency timer

Abstract: A ring latency timer provides a station attached to a token ring network with the capability of obtaining an accurate latency measurement of the ring to which it is attached. An internal hardware register, which may be read via the processor control bus interface, contains the latest ring latency measurement. A latency interrupt bit, when cleared, enables the latency measurement function. A subsequent interrupt which causes the latency interrupt bit to be set by the chip signals the completion of the latency measurement and the function is once again disabled. The latency register holds the latency information until the interrupt bit is cleared by the processor.

Speed-accuracy tradeoff during response preparation.

Abstract: The speed-accuracy operating curve was investigated in a movement precuing two- or four-choice reaction time task. Four levels of response preferences were manipulated with subject instructions and postresponse information: (a) accuracy, (b) reaction time latency, (c) accuracy and reaction time latency, and (d) no preference. Eighty subjects completed 480 discrete keypressing responses with the index and middle fingers of both hands. The mixed design mean reaction time analysis indicated faster performances for the reaction time latency and the accuracy and reaction time latency groups than the no preference group. Additionally, the percent correct analysis revealed two significant interactions: (a) Trial Block x Precue x Response Preference, and (b) Delay x Precue x Hand Position. Overall, the present findings provide partial support for the speed-accuracy operating curve predictions. Caution is advised when drawing chronometric inferences based only on reaction time data or when response accura...

Circuit simulation system with wake-up latency

Abstract: An event-driven logic simulator provides for future evaluation events. Evaluation latencies are assigned to respective inputs of components based on component type. At least some of these latencies are positive and finite. When a signal status event specifies a change at an input associated with a positive latency, the function for the component is not evaluated at the present time. Instead, the evaluation is postponed to a future time equal to the present time plus the assigned latency. The evaluation is thus latent until the scheduled time becomes present. When multiple evaluation events are indicated for a common component output, a queue manager resolves the conflicts by discarding all but one of the evaluation events for that output. This approach minimizes redundant and superfluous evaluations during circuit simulation.

The role of the facial nerve latency test in the prognosis of Bell's Palsy

Abstract: Eighty patients with idiopathic facial nerve palsy were evaluated by the facial nerve latency test. Depending on the latency time, the patients were classified into the following four groups: group A patients had normal latency times (3.25 msec); group B patients had slightly extended latency times (4 to 7 msec) and a mean of 5.6 msec; group C patients had extended latency times (10 to 14 msec) and a mean of 10.2 msec; and group D patients displayed complete disappearance of evoked compound muscle action potential (no responses). Under the same therapeutic regimen, it was determined that, when the latency time was normal or close to normal, the functional recovery of the nerve was complete or almost complete, and the recovery time was short. When the latency time was extended or there was no response, the functional recovery of the nerve was either incomplete or absent.

Measurement and analysis of workload effects on fault latency in real-time systems

Abstract: The authors demonstrate the need to address fault latency in highly reliable real-time control computer systems. It is noted that the effectiveness of all known recovery mechanisms is greatly reduced in the presence of multiple latent faults. The presence of multiple latent faults increases the possibility of multiple errors, which could result in coverage failure. The authors present experimental evidence indicating that the duration of fault latency is dependent on workload. A synthetic work generator is used to vary the workload, and a hardware fault injector is applied to inject transient faults of varying durations. This method makes it possible to derive the distribution of fault latency duration. Experimental results obtained from the fault-tolerant multiprocessor at the NASA Airlab are presented and discussed. >

P 300 latency of the auditory evoked potential in dementia.

Abstract: A two-tone discrimination paradigm was employed to elicit the P 300 component of the event related brain potential from 10 demented patients. P 300 latency was found not to be prolonged in the dementia group compared to age normative predictions derived from a patient control group. This finding contrasts with a number of studies of demented patients that generally found P 300 latency to exceed normative data. It was concluded that the results of normal latency in dementia is obviously due to the control of medication and the exclusion of patients who were unable to perform the required counting task.

The Effect of pH Adjustment of 0.5% Bupivacaine on the Latency of Epidural Anesthesia

Abstract: &NA; pH adjustment of lidocaine and 2‐chloroprocaine has been reported to decrease the latency of epidural anesthesia (EA). The effect of alkalinization of bupivacaine on onset of surgical anesthesia has not been adequately studied to date. To determine what effect raising the pH of 0.5% bupivacaine has on the latency of EA in patients undergoing lower extremity surgery, we performed a randomized, double‐blind study. Forty patients were randomly divided into two groups. Group I patients received 15 ml of a local anesthetic (LA) solution containing 0.5% bupivacaine and 0.15 mEq of NaHCO3. Group II patients received 15 ml of a standard solution of 0.5% bupivacaine. Both solutions contained freshly added epinephrine (1:200,000). After injection of LA via Tuohy needle, sensory testing was conducted using a safety pin. The pH of the LA used for Group I was 6.96 ± 0.01 and for Group II was 5.33 ± 0.11. No statistically significant difference was found between the anesthetic parameters tested in each group. On this basis, we find no advantage of pH adjustment of 0.5% bupivacaine for EA.

Epstein-Barr virus latency and activation in vivo.

Abstract: Epstein-Barr virus (EBV) infects most human beings in childhood or adolescence. Lifelong latency is established after primary infection.

Sensitivity of the spread of HIV-infection to the latency period of contagiousness and the continuously increasing infectivity of HIV carriers

Abstract: Simulation models are used to study the importance of the latency period of contagiousness and the slowly developing infectivity of HIV carriers. The results show that the latency period could be more influential than previously assumed. A longer latency period leads to a surprisingly long delay in the spread of HIV

Microcomputer measurement and analysis of newborn sucking

Abstract: An on-line Basic computer program with on-line monitor prompts and read-out collects, stores, and digitizes pressure and latency of sucking responses for later analyses. The program and analog equipment are described, and approximate costs are noted.

Real-time performance improvements for distributed databases on a wide area network

Abstract: An effort to improve the performance of distributed processing applications on very-high-speed wide area networks is described The primary limiting factor in this case appears to be latency, the innate propagation delay connected with sending signals over a long distance A method to mask the effects of latency by continuously sending large amounts of status information over an endless loop connecting the various nodes in the distributed system is proposed Particular attention is given to the case of unbalanced transaction arrival patterns Simulation results are presented >

New Latency Bounds for Atomic Broadcast (EXTENDED ABSTRACT)

Abstract: This paper provides new tighter bounds on the time required to reach agreement in a distributed system as a function of the failure model.

Throughput-latency tradeoffs in concurrent communication and DSP systems

Abstract: The actual throughput, latency, and cost-effectiveness of feedback systems, concurrent recursive systems, and generalized concurrent systems are analyzed, and an overall design methodology is proposed. The differences between the throughput speedup, the iteration bound speedup, and the intrinsic throughput-latency tradeoffs in concurrent design are discussed. It is shown that the iteration bound can be relaxed at the expense of latency and that a concurrent system can achieve the relaxed iteration bound only if the recursion hardware is not pipelined and sufficient concurrency (sometimes higher than the improvement in the iteration bound) is available. >

Optical Switched-Star Networks for Computer-System Interconnection

Abstract: This paper describes three designs for switched-star networks for computer-system interconnection based on an optical crossbar switch and an electronic controller. These switch designs demonstrate tradeoffs between hardware cost, bandwidth, and latency.