Biomedical subjects

C Roland

Publications and source records attributed to C Roland.

At least 19 recordsLinked to original sources

PubMed2001

Event-by-event fluctuations of the Kaon-to-Pion ratio in central Pb+Pb collisions at 158 GeV per nucleon.

We present the first measurement of fluctuations from event to event in the production of strange particles in collisions of heavy nuclei. The ratio of charged kaons to charged pions is determined for individual central Pb+Pb collisions. After accounting for the fluctuations due to detector resolution and finite number statistics we derive an upper limit on genuine nonstatistical fluctuations, which could be related to a first- or second-order QCD phase transition. Such fluctuations are shown to be very small.

Journal Article↗

PubMed2000

Charged-particle multiplicity near midrapidity in central Au+Au collisions at sqrt[SNN]=56 and 130 GeV.

We present the first measurement of pseudorapidity densities of primary charged particles near midrapidity in Au+Au collisions at sqrt[s(NN)] = 56 and 130 GeV. For the most central collisions, we find the charged-particle pseudorapidity density to be dN/deta|(|eta|<1) = 408+/-12(stat)+/-30(syst) at 56 GeV and 555+/-12(stat)+/-35(syst) at 130 GeV, values that are higher than any previously observed in nuclear collisions. Compared to proton-antiproton collisions, our data show an increase in the pseudorapidity density per participant by more than 40% at the higher energy.

Journal Article↗

PubMed2000

An intervention study on screening for breast cancer among single african-american women aged 65 and older.

PURPOSE: Older single African-American women are the population that is least likely to use screening procedures because of cognition-related, income-related, social-support-related and medical care-related barriers. This study aims to evaluate a breast screening intervention program developed according to socioeconomic, cultural, psychological and behavioral characteristics of older single African-American women.METHODS: Ten public housing complexes were randomly assigned to either intervention or control group. African-American women aged 65 and over were recruited into the study if they were widowed, divorced, separated or never-married in the preceding year, and did not have a history of breast cancer (n = 325). Delivered by lay health educators, the intervention program targeted increasing knowledge on breast health and breast screening, reducing emotional or psychological problems, and increasing support from the significant others of study women. Breast screening-related cognition and behavior were measured at pre-intervention and post-intervention.RESULTS: Comparisons of the pre-intervention and post-intervention measurements showed that while the proportion of women who had a clinical breast examination or mammogram in the preceding year was decreased at the post-intervention in the control group, it was increased in the intervention group. However, the differences did not reach a significant level. No consistent patterns could be found in changes of variables in knowledge, attitudes and beliefs. These results remained similar when potential confounding factors were adjusted using mixed model regression analyses.CONCLUSIONS: These results did not suggest significant effects of an intervention program which used lay health educators to promote breast cancer screening in older single African-American women.

Journal Article↗

PubMed2000

Depression-related variables and breast self-examination in single older african-american women.

PURPOSE: Depression-related symptoms, such as despair and loneliness, may prevent women from using preventive screening for diseases. This study aimed to assess if depression-related variables affect the likelihood of implementation of breast self-examination (BSE) in single African-American women aged 65 and older.METHODS: Subjects for this study included 325 African-American women, aged 65 and older, who were widowed, divorced, separated, or never-married, and lived in ten public housing tenements in Nashville, Tennessee. In-person interviews were conducted to collect information on breast screening behavior, knowledge and attitudes, social networks and activities, medical care use and depression. Depression variables included 19 factors, such as feeling guilty, feeling sad or blue, and feeling worthless.RESULTS: Using logistic regression with adjustment for potential confounders, we found that, compared with women who did not perform BSE, those who performed BSE were less likely to have felt guilty in the preceding year (p < 0.05, odds ratio (OR) = 0.3, confidence interval (CI) = 0.13-0.71). However, the other depression-related variables were not associated with BSE. For example, women who performed BSE and those who did not perform BSE reported feeling sad or blue in equal frequencies (OR = 0.93, CI 0.49-1.7).CONCLUSIONS: In general, this study suggests that there is no overall association between depression-related symptoms and breast self-examination in single African-American women aged 65 and older.

Journal Article↗

PubMed2000

Trophic egg laying in the spider, Amaurobius ferox: mother-offspring interactions and functional value.

Offspring of the spider Amaurobius ferox (Araneae, Amaurobiidae) were provided with trophic eggs of their mother the day after their emergence from the egg sac. This precisely timed egg laying followed after a series of mother-offspring interactions involving specific behaviors. Experiments showed that the trophic egg laying of the mother (providing she is in the appropriate reproductive condition) necessitated not only their presence, but also the stimulating behavior of the spiderlings. By stimulating their mother the spiderlings actually inhibited the normal maturation of the second generation of maternal eggs and prompted the release. Comparing to the trophic egg-deprived clutches, the clutches provided with the trophic eggs developed with higher body mass, earlier moulting and matriphagy. More offspring survived at the matriphagy with the mother normally provisioning the first clutch with trophic eggs rather than with the mother that did not produced the trophic eggs for her first clutch but for her second clutch. By turning her potential second generation into food, the mother increases her reproductive success.

Journal Article↗

PubMed2000

Dynamic conductance of carbon nanotubes

The dynamic conductance of carbon nanotubes was investigated using the nonequilibrium Green's function formalism within the context of a tight-binding model. Specifically, we have studied the ac response of tubes of different helicities, both with and without defects, and an electronic heterojunction. Because of the induced displacement currents, the dynamic conductance of the nanotubes differs significantly from the dc conductance displaying both capacitive and inductive responses. The important role of photon-assisted transport through nanotubes is revealed and its implications for experiments discussed.

Journal Article↗

PubMed2000

Carbon nanotube based magnetic tunnel junctions

Spin-coherent quantum transport in carbon nanotube magnetic tunnel junctions is investigated theoretically. A spin-valve effect is found for metallic, armchair tubes, with a magnetoconductance ratio ranging up to 20%. Because of the finite length of the nanotube junctions, transport is dominated by resonant transmission. The magnetic tunnel junctions are found to have distinctly different transport behavior depending on whether or not the length of the tubes is commensurate with a 3N+1 rule, with N the number of basic carbon repeat units along the nanotube length.

Journal Article↗

PubMed1998

Remifentanil versus propofol as adjuncts to regional anesthesia. Remifentanil 3010 Study Group.

STUDY OBJECTIVE: To compare the safety and efficacy of remifentanil and propofol as adjuncts to regional anesthesia in patients undergoing orthopedic or urogenital surgery. DESIGN: Prospective, randomized study. SETTING: Multicenter university hospitals. PATIENTS: 107 ASA physical status I, II, and III adult patients who underwent orthopedic or urogenital surgery with axillary, ankle, or spinal block. INTERVENTIONS: Patients were randomized to receive either an infusion of remifentanil 0.2 microg/kg/min or propofol 100 microg/kg/min 5 minutes before nerve block placement. The infusions were decreased by 50% on block completion, increased by 50% for patient discomfort, and decreased by 50% for hypoventilation (< 8 breaths/min) or hemodynamic instability. MEASUREMENTS AND MAIN RESULTS: Pain, discomfort, anxiety, and sedation were assessed by both patient and investigator. Vital signs and adverse events were recorded. Fewer patients in the remifentanil group experienced pain during block placement (6%), and were oversedated (7%) than patients in the propofol group (23% and 26%, respectively; p < 0.05). Hypoventilation during and after block placement (21% and 25%, respectively) and nausea and vomiting during and after block placement (60% and 21%, respectively) were more common in the remifentanil group than in the propofol group (0% and 3%; 17% and 6%, respectively; p < 0.05). The incidence of hypoventilation in remifentanil-treated patients was higher in patients over 65 years of age (p < 0.05), but was transient, resolving within minutes of discontinuing the infusion. CONCLUSIONS: At the doses studied, remifentanil was more effective than propofol in minimizing pain without producing excessive sedation. Remifentanil was associated with more transient respiratory depression and short-term nausea. Our findings indicate that the initial remifentanil rate should be 0.1 microg/kg/min (50% lower than the study's initial rate) and should be further decreased an additional 50% in the elderly to minimize adverse effects.

Adult↗

PubMed1997

Comparison of remifentanil and fentanyl in patients undergoing craniotomy for supratentorial space-occupying lesions.

BACKGROUND: Remifentanil hydrochloride is an ultra-short-acting, esterase-metabolized mu-opioid receptor agonist. This study compared the use of remifentanil or fentanyl during elective supratentorial craniotomy for space-occupying lesions. METHODS: Sixty-three adults gave written informed consent for this prospective, randomized, double-blind, multiple-center trial. Anesthesia was induced with thiopental, pancuronium, nitrous oxide/oxygen, and fentanyl (n = 32; 2 micrograms.kg.-1. min-1) or remifentanil (n = 31; 1 mu.kg-1.min-1). After tracheal intubation, infusion rates were reduced to 0.03 microgram.kg-1.min-1 (fentanyl) or 0.2 microgram.kg-1.min-1 (remifentanil) and then adjusted to maintain anesthesia and stable hemodynamics. Isoflurane was given only after specified infusion rate increases had occurred. At the time of the first burr hole, intracranial pressure was measured in a subset of patients. At bone flap replacement either saline (fentanyl group) or remifentanil (approximately 0.2 microgram.kg-1.min-1) were infused until dressing completion. Hemodynamics and time to recovery were monitored for 60 min. Analgesic requirements and nausea and vomiting were observed for 24 h. Neurological examinations were performed before operation and on postoperative days 1 and 7. RESULTS: Induction hemodynamics were similar. Systolic blood pressure was greater in the patients receiving fentanyl after tracheal intubation (fentanyl = 127 +/- 18 mmHg; remifentanil = 113 +/- 18 mmHg; P = 0.004). Intracranial pressure (fentanyl = 14 +/- 13 mmHg; remifentanil = 13 +/- 10 mmHg) and cerebral perfusion pressure (fentanyl = 76 +/- 19 mmHg; remifentanil = 78 +/- 14 mmHg) were similar. Isoflurane use was greater in the patients who received fentanyl. Median time to tracheal extubation was similar (fentanyl = 4 min: range = -1 to 40 min; remifentanil = 5 min: range = 1 to 15 min). Seven patients receiving fentanyl and none receiving remifentanil required naloxone. Postoperative systolic blood pressure was greater (fentanyl = 134 +/- 16 mmHg; remifentanil = 147 +/- 15 mmHg; P = 0.001) and analgesics were required earlier in patients receiving remifentanil. Incidences of nausea and vomiting were similar. CONCLUSIONS: Remifentanil appears to be a reasonable alternative to fentanyl during elective supratentorial craniotomy.

Adult↗

PubMed1996