Near Shannon limit performance of low density parity check codes

The authors report the empirical performance of Gallager's low density parity check codes on Gaussian channels. They show that performance substantially better than that of standard convolutional and concatenated codes can be achieved; indeed the performance is almost as close to the Shannon limit as that of turbo codes     

Clinical trial of a new lightwand device (Trachlight) to intubate the trachea

BACKGROUND: Transillumination of the soft tissue of the neck using a lighted stylet (lightwand) is an effective and safe intubating technique. A newly designed lightwand (Trachlight) incorporates modifications to improve the brightness of the light source as well as flexibility. The goal of this study was to determine the effectiveness and safety of this device in intubating the trachea of elective surgical patients. METHODS: Healthy surgical patients were studied. Patients with known or potential problems with intubation were excluded. During general anesthesia, the tracheas were intubated randomly using either the Trachlight or the laryngoscope. Failure to intubate was defined as lack of successful intubation after three attempts. The duration of each attempt was recorded as the time from insertion of the device into the oropharynx to the time of its removal. The total time to intubation (TTI), an overall measure of the ease of intubation, was defined as the sum of the durations of all (as many as three) intubation attempts. Complications, such as mucosal bleeding, lacerations, dental injury, and sore throat, were recorded. RESULTS: Nine hundred fifty patients (479 in the Trachlight group and 471 in the laryngoscope group) were studied. There was a 1% failure rate with the Trachlight, and 92% of intubations were successful on the first attempt, compared with a 3% failure rate and an 89% success rate on the first attempt with the laryngoscope (P not significant). All failures were followed by successful intubation using the alternate device. The TTI was significantly less with the Trachlight compared with the laryngoscope (15.7 +/- 10.8 vs. 19.6 +/- 23.7 s). For laryngoscopic intubation, the TTI was longer for patients with limited mandibular protrusion and mentohyoid distance, with a larger circumference of the neck, and with a high classification according to Mallampatti et al. However, there was no relation between the TTI and any of the airway parameters for Trachlight. There were significantly fewer traumatic events in the Trachlight group than in the laryngoscope group (10 vs. 37). More patients complained of sore throat in the laryngoscope group than in the Trachlight group (25.3% vs. 17.1%). CONCLUSIONS: In contrast to laryngoscopy, the ease of intubation using the Trachlight does not appear to be influenced by anatomic variations of the upper airway. Intubation occasionally failed with the Trachlight but in all cases was resolved with direct laryngoscopy. The failures of direct laryngoscopy were resolved with Trachlight. Thus the combined technique was 100% successful in intubating the tracheas of all patients.     

Infrared study of salt free and salt treated cellulose pyrolysis under nitrogen atmosphere

The pyrolysis under nitrogen of salt free and salt treated cellulose was studied by infrared spectroscopy. The results confirm the unzipping mechanism suggested by DTA and TGA studies, and show this mechanism to apply to the untreated and salt treated samples. The results also show the unzipping to stop at the stage of char formation. The onset of this stage was found to occur after the volatilization of only 45–50% of the initial sample of the borax treated cellulose, compared with 65–70% of the KCl treated cellulose and 80–85% of the untreated cellulose.     

Treatment of acute bronchitis in adults without underlying lung disease

OBJECTIVE: To determine whether antibiotic and bronchodilator treatment of acute bronchitis in patients without lung disease is efficacious. DESIGN: A MEDLINE search of the literature from 1966 to 1995 was done, using "Bronchitis" as the key word. Papers addressing acute bronchitis in adults were used as well as several citations emphasizing pediatric infections. A manual search of papers addressing the microorganisms causing acute bronchitis was also done. Data were extracted manually from relevant publications. SETTING: All published reports were reviewed. Papers dealing with exacerbations of chronic bronchitis were excluded in this review. RESULTS: Although acute bronchitis has multiple causes, the large majority of cases are of viral etiology. Mycoplasma pneumoniae, Chlamydia pneumoniae, and Bordetella pertussis are the only bacteria identified as contributing to the cause of acute bronchitis in otherwise healthy adults. Nine double-blind, placebo-controlled trials were reviewed. Four studies showed no advantage for doxycycline and one study showed no advantage for erythromycin. One study using erythromycin and one study using trimethoprim and sulfamethoxazole showed that these antibiotics were slightly better than placebo. Two other studies showed an impressive superiority for liquid or inhaled albuterol when compared with erythromycin. CONCLUSIONS: Most studies showed no significant difference between drug and placebo, and the two studies that did showed only small clinical differences. Albuterol had an impressive advantage over erythromycin. Antibiotics should not be used in the treatment of acute bronchitis in healthy persons unless convincing evidence of a bacterial infection is present.     

Estimating the Removal of Anthropogenic Organic Chemicals from Raw Drinking Water by Coagulation Flocculation

A mathematical model was developed to estimate the efficacy of coagulation–flocculation treatment for removing neutral hydrophobic organic chemicals from raw drinking water. The model assumed that the only significant removal mechanism was the destabilization and settling of organic matter containing sorbed anthropogenic organic compounds. The model was validated with standard jar tests using compounds with a range of hydrophobicities (log?Kow = 1.89?to?5.48), including contaminant candidate list chemicals, pesticides, pharmaceuticals, and endocrine disrupting chemicals. Final concentrations of test compounds after coagulation and flocculation were in good agreement with model estimations for synthetic waters composed of Aldrich (Milwaukee, WI) humic acid solutions. The final compound concentrations in coagulated natural waters from two drinking water reservoirs were about 80% lower than those estimated with the model. Overestimations of treated water concentrations by the model were attributed to an increase in sorption by natural organic matter when coiled in aluminum hydroxide flocs, compared to sorption to dispersed natural organic matter in untreated water.     

Traffic accidents—a modern epidemic

Accidental trauma in general and traffic accidents in particular are discussed briefly within the framework of the host, agent, environment complex of conventional epidemiology. The rise of accidents is contrasted to the fall in infectious disease over the years, and then some of the basic characteristics of traffic accidents are reviewed. It is suggested that programmes which aim at behavioural modification are unlikely to produce startling improvements in the short run. Similarly the economic restrictions on environmental changes would seem to inhibit radical benefits from being achieved in the immediate future. The possibilities of injury reduction rather than crash avoidance are then discussed, and improvements in this area are suggested as having the greatest effect within the next few years. The emerging science of accident research is mentioned as an appropriate and distinctive field of study which should be encouraged.     

Chemometrics, econometrics, psychometrics—How best to handle hedonics?

Sensory scientists may choose models from multiple disciplines for analyzing the relationship of consumer hedonics to the physical, chemical and perceptual characteristics of sensory objects. Two characteristics of sensory hedonics, satiety and differential variation, severely constrain the ability of models that cannot process these characteristics to successfully model this relationship. Overestimation of models with an excessive number of parameters is also shown to be a serious problem.     

DASHER--an efficient writing system for brain-computer interfaces?

DASHER is a human-computer interface for entering text using continuous or discrete gestures. Through its use of an internal language model, DASHER efficiently converts bits received from the user into text, and has been shown to be a competitive alternative to existing text-entry methods in situations where an ordinary keyboard cannot be used. We propose that DASHER would be well-matched to the low bit-rate, noisy output obtained from brain-computer interfaces (BCIs), and discuss the issues surrounding the use of DASHER with BCI systems.     

Near Shannon limit performance of low density parity check codes

The authors report the empirical performance of Gallager's low density parity check codes on Gaussian channels. It is shown that performance substantially better than that of standard convolutional and concatenated codes can be achieved, indeed the performance is almost as close to the Shannon limit as that of Turbo codes