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PubMed2001

Optimization with extremal dynamics.

We explore a new general-purpose heuristic for finding high-quality solutions to hard discrete optimization problems. The method, called extremal optimization, is inspired by self-organized criticality, a concept introduced to describe emergent complexity in physical systems. Extremal optimization successively updates extremely undesirable variables of a single suboptimal solution, assigning them new, random values. Large fluctuations ensue, efficiently exploring many local optima. We use extremal optimization to elucidate the phase transition in the 3-coloring problem, and we provide independent confirmation of previously reported extrapolations for the ground-state energy of +/-J spin glasses in d = 3 and 4.

Journal Article↗
PubMed1993

Cell cycle progression in human cells following re-oxygenation after extreme hypoxia: consequences concerning initiation of DNA synthesis.

The initiation of DNA synthesis and further cell cycle progression in cells during and following exposure to extremely hypoxic conditions in either G1 or G2 + M has been studied in human NHIK 3025 cells. Populations of cells, synchronized by mitotic selection, were rendered extremely hypoxic (< 4 p.p.m. O2) for up to 24 h. Cell cycle progression was studied from flow cytometric DNA recordings. No accumulation of DNA was found to take place during extreme hypoxia. Cells initially in G1 at the onset of treatment did not enter S during up to 24 h exposure to extreme hypoxia, but started DNA synthesis in a highly synchronous manner within 1.5 to 2.25 h after reoxygenation. The duration of S phase was only slightly affected (increased by approximately 10%) by the hypoxic treatment. This suggests that the DNA synthesizing machinery either remains intact during hypoxia or is rapidly restored after reoxygenation. Cells initially in G2 at the onset of hypoxia were able to complete mitosis, but further cell cycle progression was blocked in the subsequent G1. Following reoxygenation, these cells progressed into S phase, but the initiation of DNA synthesis was delayed for a period corresponding to at least the duration of normal G1 and did not appear in a synchronous manner. In fact, cell cycle variability was found to be increased rather than decreased as a result of exposure to hypoxia starting in G2. We interpret these findings as an indication that important steps in the preparation for initiation of DNA synthesis take place before mitosis. Furthermore, the change in cell cycle duration induced by hypoxia commencing in G1 is of a nature other than that induced by hypoxia commencing in other parts of the cell cycle.

Cell Cycle↗
PubMed2006

Retrospective comparative examination of the long term effects of venous access devices on upper extremity limb measurement in children with haemophilia: pilot observations from a single haemophilia treatment centre.

BACKGROUND: Venous access devices (VADs) have been used in some individuals with haemophilia to facilitate infusions of factor concentrates. Studies have reported complications of infection and thrombosis with VADs but there have been no studies looking at the potential effect that VADs may have on growth of the upper extremities in children with haemophilia. We hypothesize that there could be potential growth discrepancies in upper extremities in children with VADs related to changes in blood flow to the extremity caused by the VADs. METHODS: This study was a cohort descriptive comparative study to determine if VAD use correlated to discrepancies in upper extremity limb measurement data. A multivariate analysis compared limb measurements with VAD use, bleeding, clotting, infections, surgeries, chest wall collateral patterns and magnetic resonance venogram results. RESULTS: A total of 59 children with haemophilia participated (36 subjects with VADs, 23 subjects without). Overall, in subjects with VADs the non-VAD side was found to be shorter and measured less in girth than the VAD side. These differences did not reach statistical significance except bicep/tricep girth in the 11-15 age group. There was no correlation found between duration of VAD placement and subject age vs. length and girth measurements. When comparing subjects with VADs to those without VADs, no differences in measurements were seen. Differences in girth were measured between dominant hand and non-dominant hand in all subjects indicating that the dominant hand arm was larger. Reproducibility of this data may be hampered by limitations of sample size, subject homogeneity and variability in bleeding history between subject groups.

Adolescent↗
PubMed1993

Significance of pre-existent conditions in basal cell carcinoma on the lower extremities.

BACKGROUND: Basal cell carcinoma (BCC) rarely appears on the lower extremities; over 85% appear on the head and neck. CASE REPORTS: Five patients had BCC on the lower extremity. Histologically, this was of the superficial type. One patient developed a lesion of actinic keratosis. RESULTS: The presence of pre-existent cutaneous changes of BCC arising on the lower extremities was studied. Among 40 tumors reported in Japan, 10 cases (25%) had pre-existent cutaneous changes. This value is significantly higher than those of BCC over the whole body in both Japanese and Caucasian. CONCLUSIONS: Pre-existent cutaneous changes, thus, are thought to be a possible etiologic factor in the pathogenesis of BCC on the lower extremities.

Adult↗
PubMed1991

Protein stability and molecular adaptation to extreme conditions.

Proteins, due to the delicate balance of stabilizing and destabilizing interactions, are only marginally stable. Adaptation to extreme environments tends to shift the 'mesophilic' characteristics of proteins to the respective extremes of temperature, hydrostatic pressure, pH and salinity, such that, under the mutual physiological conditions, the molecular properties are similar regarding overall topology, flexibility and solvation. Enhanced intrinsic stability requires only minute local structural changes so that general strategies of stabilization cannot be established. Apart from mutative changes of amino-acid sequences, extrinsic factors (or cellular components) may be involved in 'extremophilic adaptation'. The molecular basis of acidophilic, alkalophilic and barophilic adaptation is still obscure. Mechanisms of enhanced thermal stability involve improved packing density, as well as specific local interactions. In halophiles, water and salt binding of the intrinsically stable protein inventory is accomplished by favoring acidic over basic amino acid residues and decreased hydrophobicity. General limits of viability are: (a) the susceptibility of the covalent structure of the polypeptide chain toward hydrolysis or hydrothermal degradation; (b) the competition of extreme solvent parameters with the weak electrostatic and hydrophobic interactions involved in protein stabilization; (c) perturbations of the folding and assembly of proteins; and (d) 'dislocation' of biochemical pathways due to effects of extreme conditions on the intricate network of metabolic reactions.

Amino Acid Sequence↗
PubMed2005

Physician counselling practices and decision-making for extremely preterm infants in the Pacific Rim.

OBJECTIVES: This study was undertaken to evaluate physician counselling practices and resuscitation decisions for extremely preterm infants in countries of the Pacific Rim. We sought to determine the degree to which physician beliefs, parents' opinion and medical resources influence decision-making for infants at the margin of viability. METHODS: A survey was administered to neonatologists and paediatricians who attend deliveries of preterm infants in Australia, Hong Kong, Japan, Malaysia, Taiwan and Singapore. Questions were asked regarding physician counselling practices, decision-making for extremely preterm infants and demographic information. RESULTS: Physicians counsel parents antenatally with increasing frequency as gestational age increases. Most physicians discuss infant mortality and morbidity with parents prior to delivery. Physicians less frequently discuss the option of no resuscitation of an extremely preterm infant, withdrawal of support at a later time, or financial costs to parents. Severe congenital malformations, perception of a poor future quality of life, parental wishes and a high probability of death for the infant are influential in limiting resuscitation in very preterm infants for a majority of physicians. Less influential factors are parent socioeconomic status, language barriers, financial costs for the family, allocation of national resources, moral or religious considerations, or fear of litigation. Physician thresholds for resuscitation of infants ranged between 22 and 25 weeks gestation and between 400 and 700 g birthweight. CONCLUSIONS: We report physician beliefs and practices regarding resuscitation and the counselling of parents of extremely preterm infants in Pacific Rim countries. While we find variation among countries, physician practices appear to be determined by ethical decision-making and medical factors rather than social or economic factors in each country.

Adult↗
PubMed1993

Ethnic differences in the incidence of lower extremity amputation secondary to diabetes mellitus.

Patients of Asian ethnic origin with diabetes mellitus living in the United Kingdom (UK) have been shown to have a higher prevalence of coronary heart disease and renal disease. Little is known about the incidence of lower extremity amputation in this racial group. The incidence of lower extremity amputation was estimated for patients of Asian ethnic origin and White Caucasians with diabetes mellitus in the county of Leicestershire from 1980 to 1985. The age and sex-adjusted incidence rate of lower extremity amputation for the estimated population of patients with diabetes mellitus in patients of Asian ethnic origin was 3.4 (95% CI, 1.1-10.7) cases per 10,000 patients year-1, compared to 14.2 (12.6-15.9) in White Caucasians. Similarly, a lower incidence rate of lower extremity amputation was recorded in patients of Asian ethnic origin without diabetes mellitus (0.4 (0.2-0.6) vs 1.5 (1.4 to 1.6) cases per 10,000 persons year-1). These findings contrast markedly with the high rates of coronary heart disease and renal disease previously reported in patients of Asian ethnic origin residing in the UK.

Adult↗
PubMed2006

Genetic and environmental influences on extreme personality dispositions in adolescent female twins.

BACKGROUND: The objective was to determine whether the pattern of environmental and genetic influences on deviant personality scores differs from that observed for the normative range of personality, comparing results in adolescent and adult female twins. METHODS: A sample of 2,796 female adolescent twins ascertained from birth records provided Junior Eysenck Personality Questionnaire data. The average age of the sample was 17.0 years (S.D. 2.3). Genetic analyses of continuous and extreme personality scores were conducted. Results were compared for 3,178 adult female twins. RESULTS: Genetic analysis of continuous traits in adolescent female twins were similar to findings in adult female twins, with genetic influences accounting for between 37% and 44% of the variance in Extraversion (Ex), Neuroticism (N), and Social Non-Conformity (SNC), with significant evidence of shared environmental influences (19%) found only for SNC in the adult female twins. Analyses of extreme personality characteristics, defined categorically, in the adolescent data and replicated in the adult female data, yielded estimates for high N and high SNC that deviated substantially (p < .05) from those obtained in the continuous trait analyses, and provided suggestive evidence that shared family environment may play a more important role in determining personality deviance than has been previously found when personality is viewed continuously. However, multiple-threshold models that assumed the same genetic and environmental determinants of both normative range variation and extreme scores gave acceptable fits for each personality dimension. CONCLUSIONS: The hypothesis of differences in genetic or environmental factors responsible for N and SNC among female twins with scores in the extreme versus normative ranges was partially supported, but not for Ex.

Adolescent↗
PubMed1996

Assessment of upper-extremity function in children with spastic diplegia before and after selective dorsal rhizotomy.

The upper-extremity function of 26 children (mean age 6.0 years) with spastic diplegia was assessed prior to and one year following selective dorsal rhizotomy (SDR). No significant change was found in upper extremity range of motion, muscle tone, or strength (MMT). A significant increase was noted in grasp strength bilaterally which could not be explained simply on the basis of maturation. Manipulation patterns were noted to improve significantly one year after SDR; however, this was proposed to be a maturation rather than intervention effect. Standardized test results revealed no significant improvement in functional hand use when the scores of children with spastic diplegia were compared with age-matched norms, to control for the effect of maturation. The significant improvement found in ability to toilet, dress and undress independently was most likely due to the effect of SDR on lower-extremity muscle tone. Further investigation with a matched control group would provide a conclusive result regarding the effect of SDR on upper extremity function and assist in understanding the maturation of hand function in children with spastic diplegia.

Activities of Daily Living↗
PubMed2005

A methodological study of computerized venous strain-gauge plethysmography of the upper extremities.

This study was performed to assess the efficiency of computerized strain-gauge plethysmography for evaluation of venous volume (VV) and outflow capacity of the upper extremities and to receive reference values. For this purpose, we investigated 34 healthy controls; 16 males and 18 females with a mean age of 45 years (range 31-58 years). These results were compared with those obtained in 32 patients with earlier spontaneous deep venous thrombosis (DVT) in the upper extremities. In the control group, there was no difference between right and left arm and none of the variables were influenced by age and gender. Venous volume and rate of venous emptying (VE) were significantly lower in arms with earlier DVT than in those without (VV: DVT arms 3.7+/-0.96 ml 100ml-1 and controls 4.6+/-0.81 ml 100 ml-1; VE: DVT arms 79+/-24 ml 100 ml-1 min-1 and controls 110+/-21 ml 100 ml-1 min-1). Repeated measurements had a coefficient of variation of approximately 10% in both groups. We found the device easy to handle and the results demonstrates that this is a useful method to study venous function in upper extremities. This implicates that computerized strain-gauge plethysmography is an efficient method both for clinical diagnostic routine and research studies of circulatory changes in acute and chronic DVT in the upper extremity.

Adult↗
PubMed1993

Cool laser optics treatment of large telangiectasia of the lower extremities.

BACKGROUND: Lower extremity telangiectases have been traditionally treated using sclerotherapy. However, because of significant side effects from sclerotherapy, laser treatments have been investigated. Results from laser treatments have been generally unsatisfactory. OBJECTIVE: This study was based on the premise that simultaneous cooling and lasing would permit more effective treatment. METHODS: Thirty lower extremity telangiectases on 13 patients were treated by a technique of simultaneous cooling and lasing. Argon (488/514 nm) and argon dye (577 nm, 585 nm) laser light were delivered through a new cooling device to telangiectatic vessels of approximately 1-mm diameter on the thigh and leg. Pulsed and continuous beam treatments were utilized at high levels of irradiance. RESULTS: Sixty-seven percent of treated sites were improved; half of these were completely or nearly completely cleared. There were no complications. In only 2 of 30 (7%) treated sites were there persistent pigmentary changes. CONCLUSION: These results compare favorably with other methods for treatment of lower extremity telangiectases. Successful treatment of large lower extremity telangiectases by simultaneous cooling and lasing with minimal side effects suggests a reduction of thermal injury to nonvascular tissue while allowing destruction of ectatic vasculature.

Adult↗
PubMed1999

Extremely acute phenytoin-induced peripheral neuropathy.

PURPOSE: Peripheral neuropathy is a rare adverse effect associated with phenytoin (PHT), and it usually occurs after the prolonged use of PHT. Acute PHT-induced peripheral neuropathy is extremely rare. METHODS: An 18-year-old girl was admitted for the control of epilepsy. Just a few hours after the administration of PHT, she complained of distal lower-extremity paresthesia in a stocking distribution and motor weakness: the Achilles tendon reflex was absent. RESULTS: Electrophysiological studies revealed slightly reduced sensory-conduction velocity and mild prolongation of distal latency in the lower extremities. After the discontinuation of PHT, these symptoms disappeared gradually, and sensory-conduction velocity and distal latency became normal. CONCLUSIONS: Although it has been reported that peripheral neuropathy occurred after treatment with PHT for a week, there has been no report of a patient such as ours, who developed peripheral neuropathy just a few hours after the initial administration of PHT. The underlying mechanism remains unknown; however, we should pay attention to such extremely acute peripheral neuropathy when using PHT.

Acute Disease↗
PubMed2000

Stepping performance during obstacle clearance in women: age differences and the association with lower extremity strength in older women.

OBJECTIVE: To compare stepping performance during obstacle clearance in younger and older women, and to examine the relationship between lower extremity strength and stepping performance during obstacle clearance in older women. DESIGN: Correlational study. SETTING: A small community. PARTICIPANTS: Twenty-four older women (mean age = 74.4), and 16 younger women (mean age = 20.7). The older participants lived independently in the community and were able to walk unaided. MEASUREMENTS: Lower extremity muscle strength, measures of stepping performance including reaction time, movement time, extent of obstacle clearance, time to clear obstacle, among others. MAIN RESULTS: The older women were far slower in stepping than the younger women. Toe trajectories differed between older and younger women during the initial portion of the step. The younger women tended to lift the toe straight up, whereas the older women tended to move the toe backward, away from the obstacle, passing farther from the obstacle when the toe cleared the obstacle height. There was little, if any, association between relative lower extremity strength and stepping performance during obstacle clearance in older women. CONCLUSIONS: Dramatic differences in the speed of volitional stepping performance were found between younger and older women. Among the older women, lower extremity strength was not related to volitional stepping performance.

Adult↗
PubMed2002

Microbial survival of space vacuum and extreme ultraviolet irradiation: strain isolation and analysis during a rocket flight.

We have recovered new isolates from hot springs, in Yellowstone National Park and the Kamchatka Peninsula, after gamma-irradiation and exposure to high vacuum (10(-6) Pa) of the water and sediment samples. The resistance to desiccation and ionizing radiation of one of the isolates, Bacillus sp. strain PS3D, was compared to that of the mesophilic bacterium, Deinococcus radiodurans, a species well known for its extraordinary resistance to desiccation and high doses of ionizing radiation. Survival of these two microorganisms was determined in real and simulated space conditions, including exposure to extreme UV radiation (10-100 nm) during a rocket flight. We found that up to 15 days of desiccation alone had little effect on the viability of either bacterium. In contrast, exposure to space vacuum ( approximately 10(-6) Pa) decreased cell survival by two and four orders of magnitude for Bacillus sp. strain PS3D and D. radiodurans, respectively. Simultaneous exposure to space vacuum and extreme UV radiation further decreased the survival of both organisms, compared to unirradiated controls. This is the first report on the isolated effect of extreme UV at 30 nm on cell survival. Extreme UV can only be transmitted through high vacuum, therefore its penetration into the cells may only be superficial, suggesting that in contrast to near UV, membrane proteins rather than DNA were damaged by the radiation.

Bacillus↗
PubMed1976

Blood flow and venous distensibility in the upper and lower extremities of newborn infants.

The electrocapacitance plethysmograph was utilized to measure peripheral blood flow and venous distensibility in 17 newborn infants and 20 adults. Measurements were made in the upper and lower extremities in each subject under identical environmental conditions. Blood flow in the forearm and calf were found to be significantly higher in infants than adults. In infants there were no significant differences in the blood flow between the upper and lower extremities. In contrast, in the adults, the blood flow was significantly higher in the upper than in the lower extremities. Similarly, venous distensibility was observed to be higher in infants than in adults. While no significant differences were observed in the venous distensibility between the upper and lower extremities in infants, the venous distensibility was found to be higher in the forearm than in the leg in adults.

Adult↗
PubMedDate not supplied

Determining extreme parameter correlation in ground water models.

In ground water flow system models with hydraulic-head observations but without significant imposed or observed flows, extreme parameter correlation generally exists. As a result, hydraulic conductivity and recharge parameters cannot be uniquely estimated. In complicated problems, such correlation can go undetected even by experienced modelers. Extreme parameter correlation can be detected using parameter correlation coefficients, but their utility depends on the presence of sufficient, but not excessive, numerical imprecision of the sensitivities, such as round-off error. This work investigates the information that can be obtained from parameter correlation coefficients in the presence of different levels of numerical imprecision, and compares it to the information provided by an alternative method called the singular value decomposition (SVD). Results suggest that (1) calculated correlation coefficients with absolute values that round to 1.00 were good indicators of extreme parameter correlation, but smaller values were not necessarily good indicators of lack of correlation and resulting unique parameter estimates; (2) the SVD may be more difficult to interpret than parameter correlation coefficients, but it required sensitivities that were one to two significant digits less accurate than those that required using parameter correlation coefficients; and (3) both the SVD and parameter correlation coefficients identified extremely correlated parameters better when the parameters were more equally sensitive. When the statistical measures fail, parameter correlation can be identified only by the tedious process of executing regression using different sets of starting values, or, in some circumstances, through graphs of the objective function.

Models, Theoretical↗
PubMed2003

[A case of septicemia type Vibrio vulnificus infection with necrotizing fasciitis rescued by lower extremity amputation].

We report a case of septicemia type Vibrio vulnificus infection. The patient was a 74-year-old man who had liver cirrhosis and hepatocelluler carcinoma. He felt a pain in the right femoral lesion after eating raw shellfish (Japanese "Umitake") two days ago. He was admitted to our emergency center due to his shock status and thrombocytopenia two days after the onset. We diagnosed necrotizing fasciitis due to Vibrio vulnificus infection, his life was saved by emergency amputation of the right lower extremity. The culture of the blood and vesicle fluid showed Vibrio vulnificus. There are some reports that the debridement was effective to necrotizing fasciitis due to Vibrio vulnificus infection, but these reports are all about single upper extremity lesion. As far as we know, this is the second report of lower extremity necrotiaong fasciitis due to septicemia type Vibrio vulnificus infection rescued by extremity amputation in Japan. The mortality of septicemia type Vibrio vulnificus infection with necrotizing fasciitis is very high, this is quite a valuable report in making a decision for therapy of septicemia type Vibrio vulnificus infection.

Aged↗
PubMed1994

Astronomy and the Extreme Ultraviolet Explorer satellite.

The extreme ultraviolet wave band (100 to 912 angstroms) was thought until recently to be useless to astronomy, primarily because the opacity of the interstellar medium would prevent observations at these wavelengths. However, the interstellar medium has been found to be markedly inhomogeneous in both density and ionization state and the sun is fortunately located in a region of low extreme ultraviolet opacity. The Extreme Ultraviolet Explorer, launched in June 1992, has surveyed the sky in this wave band and has detected a wide variety of astronomical sources at considerable distances, including some extragalactic objects. Studies in the extreme ultraviolet band have already begun to increase our understanding of the contents of the universe.

Astronomy↗