The information-theoretic capacity of discrete-time queues

The information-theoretic capacity of continuous-time queues was analyzed recently by Anantharam and Verdu (see ibid. vol.42, p.4-18, 1996). Along similar lines, we analyze the information-theoretic capacity of two models of discrete-time queues. The first model has single packet arrivals and departures in a time slot and independent packet service times, and is the discrete-time analog of the continuous-time model analyzed by Anantharam and Verdu. We show that in this model, the geometric service time distribution plays a role analogous to that of the exponential distribution in continuous-time queues, in that, among all queues in this model with a given mean service time, the queue with geometric service time distribution has the least capacity. The second model allows multiple arrivals in each slot, and the queue is modeled as serving an independent random number of packets in each slot. We obtain upper and lower bounds on the capacity of queues with an arbitrary service distribution within this model, and show that the bounds coincide in the case of the queue that serves a geometrically distributed number of packets in each slot. We also discuss the extremal nature of the geometric service distribution within this model     

Adiabatic couplers: design rules and optimization

Explicit analytic design rules are derived for both 3 dB and full adiabatic couplers. The design rules are in excellent agreement with numerical calculations using the beam propagation method (BPM). It is shown that the length scaling for 3 dB couplers compared to full couplers makes the former more difficult to design. The design for each case is optimized to obtain the upper limit of performance and a comparison is carried out between two different design geometries for both 3 dB and full adiabatic couplers     

The effects of observational feedback on treatment integrity in school-based behavioral consultation.

Evaluated the effects of performance feedback on levels of treatment integrity in school-based behavioral consultation. Three teachers employed in a residential treatment community were responsible for treatment implementation. Treatment integrity was defined as the percentage of 2-min intervals during which contingent teacher reinforcement for student on-task behavior was directly observed. Teacher and child behavior were monitored across baseline, traditional consultation, and consultation with performance feedback conditions in a multiple baseline design. Following a Problem Identification Interview and Problem Analysis Interview (J. R. Bergan, 1977), mean levels of treatment integrity for the 3 teachers ranged from 9% to 37%. The addition of a performance feedback package increased treatment integrity for all 3 teachers to levels ranging from 60% to 83%. The findings contribute to a growing literature supporting the need for direct assessment of treatment integrity in school-based consultation research and practice. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Penetrating ocular injuries: an epidemiologic and retrospective study

Penetrating injuries of the eye are an important cause of unilateral visual loss. We studied a series of 82 cases of penetrating injuries treated here from 1987 through 1993. The injuries were caused by sharp objects in 66% and blunt trauma in 6%. The prognosis after a penetrating injury is greatly influenced by the nature of the injury and the extent of the initial drainage. Among factors associated with an unfavorable visual outcome were diminished preoperative visual acuity and scleral wounds with dense vitreous hemorrhage.     

Procedural memory stimulation in Alzheimer''s disease: impact of a training programme

The operative results of 23 patients with a specific or unspecific spondylodiscitis were documented over 2 years after the focus of the inflammation had been eradicated, bone chip had been interposed and a CDH instrumentation had been performed by an anterior approach only. These outcomes were compared with the results of 32 patients in whom the focus had been removed and the defect had been filled with bone graft from an anterior approach, followed by stabilisation with CD instrumentation through an additional dorsal approach. In the cases where CDH instrumentation was applied, the range of fusion averaged 1.3 segments. This was clearly less extensive than in dorsoventral stabilisation, in which on average 3.5 segments were fused. In 47 of 55 cases mobilisation was achieved without orthesis. Eight months after the operations bony fusion could be observed radiologically in all patients. The mean preoperative kyphotic angle of the affected segments was 14.4 degrees, compared to 4 degrees after the operation. The mean loss of reposition was measured to be about 2.7 degrees in both groups. Average operation time and blood loss were about 50% higher in the patients treated dorsoventrally. We conclude that even in the case of florid spondylodiscitis, a short-range anterior fusion of the affected spinal segment may be performed by use of a stable-angle implant without an increased risk of infection-related loosening.     

IsK and KvLQT1: mutation in either of the two subunits of the slow component of the delayed rectifier potassium channel can cause Jervell and Lange-Nielsen syndrome

The Jervell and Lange-Nielsen syndrome (JLNS) comprises profound congenital sensorineural deafness associated with syncopal episodes. These are caused by ventricular arrhythmias secondary to abnormal repolarisation, manifested by a prolonged QT interval on the electrocardiogram. Recently, in families with JLNS, Neyroud et al. reported homozygosity for a single mutation in KVLQT1 , a gene which has previously been shown to be mutated in families with dominantly inherited isolated long QT syndrome [Neyroud et al . (1997) Nature Genet ., 15, 186-189]. We have analysed a group of families with JLNS and shown that the majority are consistent with mutation at this locus: five families of differing ethnic backgrounds were homozygous by descent for markers close to the KVLQT1 gene and a further three families from the same geographical region were shown to be homozygous for a common haplotype and to have the same homozygous mutation of the KVLQT1 gene. However, analysis of a single small consanguineous family excluded linkage to the KVLQT1 gene, establishing genetic heterogeneity in JLNS. The affected children in this family were homozygous by descent for markers on chromosome 21, in a region containing the gene IsK . This codes for a transmembrane protein known to associate with KVLQT1 to form the slow component of the delayed rectifier potassium channel. Sequencing of the affected boys showed a homozygous mutation, demonstrating that mutation in the IsK gene may be a rare cause of JLNS and that an indistinguishable phenotype can arise from mutations in either of the two interacting molecules.     

Microfabricated Lamb wave device based on PZT sol-gel thin film formechanical transport of solid particles and liquids

The fabrication using silicon micromachining and characterization of an acoustic Lamb wave actuator is presented. The intended use of the device is for mass transport and sensor applications. The device consists of dual interdigitated transducers patterned on a thin-film composite membrane of silicon nitride, platinum, and a sol-gel-derived piezoelectric ceramic (PZT) thin film. The acoustic properties of the device are presented along with preliminary applications to mechanical transport and liquid delivery systems. Improved acoustic signals and improved mass transport are achieved with PZT over present Lamb wave devices utilizing ZnO or AlN as the piezoelectric transducer     

Influence of structure on the antioxidant activity of indolinic nitroxide radicals

An in vitro study was carried out to verify whether the chain length of a substituent on an indolinic nitroxide could influence its antioxidant activity in different biological environments subjected to oxidative stress. Three distinct indolinic nitroxides were synthesized and compared with vitamin E and Trolox (a hydrophilic analogue of vitamin E), where the only difference between the nitroxides was the length of the hydrocarbon chain in the 2-position of indole, namely 2 (C2), 10 (C10), and 18 (C18) carbons. All the nitroxides were effective in preventing oxidation of bovine serum albumin, but to different extents, with the longer chain derivatives being more efficient. However, the C2 compound was the most efficient in preventing lipid peroxidation in microsomal membranes. The C2 and C18 compounds, Trolox, and vitamin E protected microsomal protein oxidation to the same extent at the highest concentration used (13 microM). The nitroxide with a C10 chain was less effective in this system. The influence of these compounds on the enzymatic activity of two mitochondrial proteins subjected to oxidative stress was also studied by means of oxygraph measurements. Mitochondrial rotenone-sensitive NADH oxidase and succinate oxidase responded differently to BuOOH-induced radical chemistry, and the compounds under study also protected the activity of the two enzymes but to different extents. The results clearly demonstrate that indolinic nitroxides are very efficient antioxidants, protecting both lipids and proteins from peroxidation. The indole structure influences the antioxidant efficacy in biological systems.