A Review of the Development and Performance of the ARPANET Routing Algorithm

This paper presents a comprehensive review of the ARPANET routing algorithm, from its original implementation to our plans for future modifications. We hope that by collecting this information, and by providing considerable details, we can provide others with a useful reference document concerning some of the practical problems of network algorithm design. Much of the discussion below assumes a basic familiarity with the principles of packet switching, the ARPANET implementation, and some of the relevant terminology, information which can be found, for example, in [4]. Sections 1 and 2 give a brief summary of basic routing concepts and of the original routing algorithm, respectively. The following two sections describe in detail subsequent modifications and the actual implementation currently in use. Section 5 then discusses some problems that have developed over the past few years, as network usage has grown considerably. The final sections outline some explanations for these problems and some mechanisms for improving performance. We are in the process of implementing these and other changes to the routing algorithm.     

Adhesive secretions of live mussels observed in situ by attenuated total reflection-infrared spectroscopy

The chemical species involved in the adhesion of blue mussels (Mytilus galloprovincialis) and greenshell mussels (Perna canaliculus) to surfaces has been investigated using in situ attenuated total reflection infrared (ATR-IR) spectroscopy. Mussel spat ranging in size from 0.5 to 25 mm were placed in a flow cell containing a ZnSe multiple internal reflection prism and supplied with temperature-controlled seawater. Distinctively different absorption spectra were obtained when the mussels were predominantly moving across the surface or forming permanent bonds. With limited movement, the absorption spectrum was characteristic of protein with peaks near 1647 cm-1 (amide I), 1543 cm-1 (amide II), and 1235 cm-1 (amide III). When the mussels were observed to be moving across the surface of the ATR-IR crystal there was a strong broad absorption maximum around 1200-900 cm-1 (carbohydrate polymers), presumably due to the secretion of a weakly acidic mucopolysaccharide. Distinct differences in the spectra obtained from the adhesive secretions of blue or greenshell mussels were not observed. The data presented is the first reported use of IR spectroscopy to obtain in situ, real-time, chemical data on the interactions between invertebrates and substrates immersed in sea water.     

Fast VLSI algorithms for division and square root

Real time digital signal processing demands high performance implementations of division and square root. This can only be achieved by the design of fast and efficient arithmetic algorithms which address practical VLSI architectural design issues. In this paper, new algorithms for division and square root are described. The new schemes are based on pre-scaling the operands and modifying the classical SRT method such that the result digits and the remainders are computed concurrently and the computations in adjacent rows are overlapped. Consequently, their performance exceeds that of the SRT methods. The hardware cost for higher radices is considerably more than that of the SRT methods but for many applications, this is not prohibitive. A system of equations is presented which enables both an analysis of the method for any radix and the parameters of implementations to be easily determined. This is illustrated for the case of radix 2 and radix 4. In addition, a highly regular array architecture combining the division and square root method is described.     

The growth of crystals of erbium hydride

Crystals of the rare-earth hydride ErH₂ have been produced with face areas greater than a square millimetre and corresponding volumes exceeding those of earlier crystals by orders of magnitude. The hydride, which was produced in bulk polycrystalline form by hydriding erbium metal at 950° C, has been examined by optical and X-ray techniques. For material of composition ErH₂ and ErH_1.8 the size of the grains and their degree of strain appears to depend more on oxygen contamination during formation and on the subsequent cooling procedure, than on the size of erbium metal crystals in the starting material.     

Do patient‐reported measures of symptoms and health status predict mortality in hemodialysis? An assessment of POS‐S Renal and EQ‐5D

Introduction Experience with the use of patient‐reported outcome measures such as EQ‐5D and the symptom module of the Palliative care Outcome Scale—Renal Version (POS‐S Renal) as mortality prediction tools in hemodialysis is limited. Methods A prospective survival study of people receiving hemodialysis (N = 362). The EQ‐5D and the POS‐S Renal were used to assess symptom burden and self‐rated health (with a self‐rated component). Participants were followed from instrument completion to death or study end. Competing risks survival analysis was used to evaluate associations with time to death, with renal transplant as a competing risk. Findings 32% (N = 116) of participants died over a median (25th–75th centile) of 2.6 (1.41–3.38) years. Factors most notably associated with mortality adjusted hazard ratio (95%CI) included: lower EQ VAS score 2.7 (1.4, 5.2) P = 0.004 (lowest tertile), higher POS‐S Renal score 2.4 (1.3, 4.3) P = 0.004 (highest tertile), and lower EQ‐5D score 2.6 (1.3, 5.3) P = 0.01 (lowest tertile) as well as the presence of: “problems with mobility?” 2 (1.1, 3.3) P = 0.01, or “problems with usual activities?” 2.1 (1.4, 3.3), P < 0.001. After age adjustment area under the receiver operating curves (AUC) (95%CI) for mortality were: 0.71 (0.62, 0.79) for EQ VAS score, 0.71 (0.63, 0.80) for POS‐S Renal‐S Renal score, and 0.76 (0.68, 0.84) for EQ‐5D score. AUC 95%CI was highest for our fourth model at 0.79 (0.72, 0.86) comprised of individual elements from both instruments and established risk factors. Discussion EQ VAS scores and predictive models based on combinations of elements from the POS‐S Renal and EQ‐5D instruments may aid in mortality discrimination and possibly in the delivery of supportive care services.     

Histomorphometric and histologic evaluation of titanium–zirconium (<Emphasis Type="Italic">a</Emphasis>TiZr) implants with anodized surfaces

The choice of implant surface has a significant influence on osseointegration. Modification of TiZr surface by anodization is reported to have the potential to modulate the osteoblast cell behaviour favouring more rapid bone formation. The aim of this study is to investigate the effect of anodizing the surface of TiZr discs with respect to osseointegration after four weeks implantation in sheep femurs. Titanium (Ti) and TiZr discs were anodized in an electrolyte containing dl-α-glycerophosphate and calcium acetate at 300 V. The surface characteristics were analyzed by scanning electron microscopy, electron dispersive spectroscopy, atomic force microscopy and goniometry. Forty implant discs with thickness of 1.5 and 10 mm diameter (10 of each-titanium, titanium–zirconium, anodized titanium and anodized titanium–zirconium) were placed in the femoral condyles of 10 sheep. Histomorphometric and histologic analysis were performed 4 weeks after implantation. The anodized implants displayed hydrophilic, porous, nano-to-micrometer scale roughened surfaces. Energy dispersive spectroscopy analysis revealed calcium and phosphorous incorporation into the surface of both titanium and titanium–zirconium after anodization. Histologically there was new bone apposition on all implanted discs, slightly more pronounced on anodised discs. The percentage bone-to-implant contact measurements of anodized implants were higher than machined/unmodified implants but there was no significant difference between the two groups with anodized surfaces (P > 0.05, n = 10). The present histomorphometric and histological findings confirm that surface modification of titanium–zirconium by anodization is similar to anodised titanium enhances early osseointegration compared to machined implant surfaces.     

Facilitating the care of terminally Ill children

Life-threatening illness is fortunately rare in children. Some children, however, will need palliative care for symptom control; psychological support may be needed by the child and the child's family; and families may require help with decisions about life-prolonging treatment. Providing consistent high-quality care for a relatively uncommon problem is difficult. Adult palliative care services, liaison with pediatricians can help provide this care.     

Laboratory scale Clean-In-Place (CIP) studies on the effectiveness of different caustic and acid wash steps on the removal of dairy biofilms

Seven strains of Bacillus cereus isolated from the environment and from patients with diarrheic symptoms were examined from two angles: their spore surface properties, and their ability to adhere to stainless steel and to resist a cleaning in place (CIP) procedure. Our results revealed significant differences in their morphology (size of exosporium, length and number of appendages), hydrophobic character and surface protein composition. Most of these proteins originated in the vegetative cell and were tightly bound to the external surface of the exosporium such as EA1 or alanine racemase. Spore adhesion properties also varied from strain to strain. The ability to adhere was higher when spores were surrounded by long appendages, while the largest spores displayed the least resistance to cleaning. These observations suggest that food processing line contamination might be due to a given type of strain with specific surface properties (long appendages and small exosporium), which would represent an increased threat under the milder processing conditions required by consumers (minimally heat-treated foods for example) and by legal requirements (to limit effluents caused by hygiene procedures). Elsewhere, no clear relationship of the strain characteristics to the clinical vs. foodborne strains could be established.     

Evidence that childhood acute lymphoblastic leukemia is associated with an infectious agent linked to hygiene conditions

OBJECTIVES: The incidence of acute lymphoblastic leukemia (ALL) in children has shown temporal and geographic variation during the 20th century, with higher rates in developed nations appearing in the first half of the century, but with persisting low rates in developing nations. We sought to assess the relation of childhood ALL with hygiene conditions, an aspect of socioeconomic development affecting rates of exposure to infectious agents. METHODS: Infection patterns for hepatitis A virus (HAV), an agent with a fecal-oral route of transmission, were used to indicate hygiene conditions in different populations, with emphasis on instructive United States and Japanese data. A catalytic model was fit to these data, estimating the HAV force of infection and age-specific seroprevalence rates over time. These analyses were used to assess the temporal relationship of changes in HAV infection rates to changes in childhood leukemia mortality and incidence rates. RESULTS: We observed an inverse relationship between HAV infection prevalence and rates of childhood leukemia. Further, decreases in the HAV force of infection in the United States and Japan appear to have preceded increases in childhood leukemia rates. We describe a model based on a putative leukemia-inducing agent with a change in infection rate over time correlated with that of HAV that describes well the temporal trends in childhood leukemia rates for White children in the US and for Japanese children. CONCLUSION: The data suggest that improved public hygiene conditions, as measured by decreased prevalence of HAV infection, are associated with higher childhood ALL incidence rates. The model that we present supports the plausibility of the hypothesis that decreased childhood exposure to a leukemia-inducing agent associated with hygiene conditions leads to higher rates of ALL in children by increasing the frequency of in utero transmission caused by primary infection during pregnancy (or by increasing the number of individuals infected in early infancy because of lack of protective maternal antibodies).