Implications of physical layer overhead on the design ofmultiaccess protocols

The authors examine the implications of physical layer overhead on the design of multiaccess protocols under a demand-assignment framework, comparing full-slot contention with mini-slot contention. Even if the physical layer overhead is substantial relative to the packet size, we show that after `paying the price' of transmitting the physical layer overhead it is still better, from a delay-throughput perspective, to only transmit a short request rather than a full packet during a contention period     

The sum of the parts does not equal the whole: Evidence from bihemispheric processing.

Examined in 5 experiments whether bihemispheric processing can be predicted from the processing observed when information is directed initially to just 1 hemisphere. Ss decided if laterally presented words rhymed with a previously presented central target. Trials varied in the degree to which the information displayed was redundant. On some trials, the same word appeared twice; in others, different words appeared, but they both led to the same decision; and finally, on some trials, different words appeared, each of which also led to a different decision. The patterns found for unilateral and bilateral trials were distinct. Furthermore, the pattern observed on bilateral trials could not be predicted from that found on unilateral trials, suggesting that interhemispheric interaction cannot be surmised from observing a hemisphere processing information in relative isolation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Probabilistic analysis of continuum damage mechanics of brittle materials

Uncertainty of material properties in solution of engineering problems is often a fundamental question. Statistical methods give a powerful tool for analysis of uncertainty. Monte Carlo simulations together with Gumbel distribution are used as a possible way to study influence of data dispersion on assessment of damage of brittle materials.     

An overview of lightwave packet networks

The unique systems opportunities offered by, and the unique systems constraints imposed by, lightwave technology as it applies to the field of distributed packet networks are examined. Single-channel and star topology approaches are first considered. Terabit-capacity lightwave networks are discussed, covering both wavelength-division and time-division multiplexing. Multichannel multihop lightwave networks are then considered, and a particular implementation, the ShuffleNet, is described, and its performance, as well as some simple addressing and routing schemes, is discussed     

Using a packet switch for circuit-switched traffic: a queueingsystem with periodic input traffic

Consideration is given to the effects of time-multiplexed stream traffic on the performance of a store-and-forward packet switch. Substantially reducing the amount of buffering in the switch results in only a small probability that an existing circuit will be disrupted during the length of its connection. For example, with a circuit-switched frame of length 1000 and 100% loading, reducing the buffer size from 999 packets to 83 results in only a 10^-6 circuit-disruption probability     

Severe lumbar lordosis after dorsal rhizotomy

The purpose of this study is to compare the safety, efficacy, and potential benefits of vaginal radical hysterectomy (VRH) versus abdominal radical hysterectomy (ARH) in the treatment of early-stage cervical cancer. We reviewed the charts of our first 52 patients with cervical cancer. We reviewed the charts of our first 52 patients with cervical cancer who underwent a laparoscopic pelvic lymphadenectomy (LPL), followed either by a VRH (Schauta) in 25 cases or ARH in 27 cases. For the 52 patients, the mean lymph nodes count obtained by LPL was 27 (range 8-59), and the only complication was an external iliac vein trauma requiring laparotomy. Both VRH and ARH groups were comparable in terms of age, weight, parity, stage, histology, and tumor volume. The mean blood loss was 400 cc for VRH vs 450 cc for ARH, operating time was 270 min vs 280 min, blood transfusion in 5 vs 4 women, and postoperative stay was 7 days for both groups. The only intraoperative complication in addition to the vein trauma was a cystotomy which occurred in 2 VRH patients. Febrile morbidity was noted in 4 VRH patients vs 9 ARH patients. There were one preperitoneal abscess and one hematoma in the VRH group vs 4 wound infections and 1 hematoma after ARH. Ileus occurred in 1 VRH vs 4 ARH patients. The current mean follow-up time is 27 months (8-52) and there has been one recurrence so far in the ARH group. Even though this is a retrospective study, our data indicate that VRH and ARH are comparable, except for the absence of an abdominal scar and less febrile morbidity with the vaginal approach. However, in our opinion, the main advantage in learning the Schauta operation is that the experience gained allows one to offer radical trachelectomy to selected young patients who wish to preserve their fertility.     

Gait analysis and muscle strength in children with surgically treated clubfeet

Twenty-three children who had unilateral surgery for idiopathic clubfeet underwent gait analysis and isokinetic muscle-strength testing at an average of 10 years after surgical release. Ankle sagittal-plane kinematics were disturbed in 20 clubfeet. Fifteen children had an internal foot-progression angle. Genu valgum and knee hyperextension were common. Plantarflexion power was decreased by 23% on the side of surgery (p = 0.00005). Quadriceps weakness (defined as a decrease in strength >10% of the nonoperated-on limb's strength) was seen in nine of 22 operated-on limbs and hamstring weakness in eight of 22. Gastrocsoleus weakness exceeded 10% in 16 of 21 clubfeet. Average weakness of the gastrocsoleus was 27% (p < 0.05). Ten-year analysis of children treated with clubfoot releases revealed disturbances in ankle motion and strength. Loss of plantarflexion power and gastrocsoleus strength can be predicted by Achilles tendon lengthening. Knee kinematic abnormalities and weakness also were seen. These abnormalities produce functional difficulties in gait and may lead to degenerative changes later.     

Input Versus Output Queueing on a Space-Division Packet Switch

Two simple models of queueing on anN times Nspace-division packet switch are examined. The switch operates synchronously with fixed-length packets; during each time slot, packets may arrive on any inputs addressed to any outputs. Because packet arrivals to the switch are unscheduled, more than one packet may arrive for the same output during the same time slot, making queueing unavoidable. Mean queue lengths are always greater for queueing on inputs than for queueing on outputs, and the output queues saturate only as the utilization approaches unity. Input queues, on the other hand, saturate at a utilization that depends onN, but is approximately(2 -sqrt{2}) = 0.586whenNis large. If output trunk utilization is the primary consideration, it is possible to slightly increase utilization of the output trunks-upto(1 - e^{-1}) = 0.632asN rightarrow infty-by dropping interfering packets at the end of each time slot, rather than storing them in the input queues. This improvement is possible, however, only when the utilization of the input trunks exceeds a second critical threshold-approximatelyln (1 +sqrt{2}) = 0.881for largeN.     

A role of parameters in RF PA CVD technology of a-C:N:H layers

Results concerning influence of radio-frequency plasma-assisted chemical vapor deposition (RF PA CVD; 13.56 MHz) processing parameters on a-C:N:H layer deposition are presented in this work. The following parameters have been taken into consideration: substrate temperature, plasma RF generator power, composition of reactive gas mixture, gas pressure and time of deposition. A special interest has been focused on the deposition rate as well as on the structure and chemical composition of layers. The layer thicknesses have been measured and deposition rates evaluated. Structure analysis has been performed with application of FT-IR spectroscopy. The obtained results may serve as a basis in the design of the technology of a-C:N:H layers for various applications.     

Inhibition of Streptococcus mutans binding to hydroxylapatite using partially digested whey protein concentrate and individual whey proteins

The effect of a bovine whey protein concentrate partially digested with lipase to release free fatty acids (WPD) on growth and viability of Streptococcus mutans, and its adherence to hydroxylapatite (HA) in phosphate-buffered saline were examined. The effects of other whey mixtures and individual whey proteins, β-lactoglobulin (BLG), lactoferrin (LF), caseinoglycomacropeptide (CGMP) and α-lactalbumin were also investigated. Bacterial viability was assessed by incubation with whey protein and measuring colony-forming units. S. mutans binding was quantified using Syto-13 nucleic-acid binding dye and Alamar Blue, which measures cellular metabolic activity. WPD was bactericidal, and inhibited S. mutans growth and adhesion to HA. Other wheys inhibited S. mutans adhesion, particularly acid whey, as well as the parent compound for WPD, Carbelac 80, and a whey protein isolate. BLG, CGMP and LF inhibited S. mutans adhesion. A mixture containing 56% BLG and 20% CGMP was as effective an inhibitor of bacterial adhesion as WPD.