This paper examines how productivity changes and price changes have contributed to short-run profit change in the railroad industry. Using an unbalanced panel of US Class I railroads for the period ...1996–2003, a short-run profit change decomposition model is used to attribute intertemporal profit change to its causal factors. We find that productivity improvements and an increased scale of production contributed to increases in profit, and that variation in operating efficiency had a mixed impact on profit. We also find that relative changes in rail rates and variable input prices exerted downward pressure on profit.
Abstract
We investigated the direct and indirect influence of tides on net ecosystem exchange (NEE) of carbon dioxide (CO
2
) in a temperate brackish tidal marsh. NEE displayed a tidally driven ...pattern with obvious characteristics at the multiday scale, with greater net CO
2
uptake during spring tides than neap tides. Based on the relative mutual information between NEE and biophysical variables, this was driven by a combination of higher water table depth (WTD), cooler air temperature, and lower vapor pressure deficit (VPD) during spring tides relative to neap tides, as the fortnightly tidal cycle not only influenced water levels but also strongly modulated water and air temperature and VPD. Tides also influenced NEE at shorter timescales, with a reduction in nighttime fluxes during growing season spring tides when the higher of the two semidiurnal tides caused inundation at the site. WTD significantly influenced ecosystem respiration (
R
eco
), with lower
R
eco
during spring tides than neap tides. While WTD did not appear to affect ecosystem photosynthesis (gross ecosystem production, GPP) directly, the impact of tides on temperature and VPD influenced GPP, with higher daily light‐use efficiency and photosynthetic activity during spring tides than neap tides when temperature and VPD were lower. The strong direct and indirect influence of tides on NEE across the diel and multiday timescales has important implications for modeling NEE in tidal wetlands and can help inform the timing and frequency of chamber measurements as annual or seasonal net CO
2
uptake may be underestimated if measurements are only taken during nonflooded periods.
Key Points
CO
2
fluxes fluctuated notably with the biweekly spring‐neap tide cycle, with greater net CO
2
uptake during spring tides
Water levels significantly influenced measurements of ecosystem respiration with lower respiration when water levels were higher
Water levels had little effect on GPP, instead higher photosynthesis during spring tides was caused by lower temperature and VPD
The American Pain Society (APS) set out to revise and expand its 1995 Quality Improvement Guidelines for the Treatment of Acute Pain and Cancer Pain and to facilitate improvements in the quality of ...pain management in all care settings.
Eleven multidisciplinary members of the APS with expertise in quality improvement or measurement participated in the update. Five experts from organizations that focus on health care quality reviewed the final recommendations. MEDLINE and Cumulative Index to Nursing and Allied Health Literature databases were searched (1994-2004) to identify articles on pain quality measurement and quality improvement published after the development of the 1995 guidelines. The APS task force revised and expanded recommendations on the basis of the systematic review of published studies. The more than 3000 members of the APS were invited to provide input, and the 5 experts provided additional comments. The task force synthesized reviewers' comments into the final set of recommendations.
The recommendations specify that all care settings formulate structured, multilevel systems approaches (sensitive to the type of pain, population served, and setting of care) that ensure prompt recognition and treatment of pain, involvement of patients and families in the pain management plan, improved treatment patterns, regular reassessment and adjustment of the pain management plan as needed, and measurement of processes and outcomes of pain management.
Efforts to improve the quality of pain management must move beyond assessment and communication of pain to implementation and evaluation of improvements in pain treatment that are timely, safe, evidence based, and multimodal.
To examine the flow dynamics in a fatal aneurysm of the basilar artery in humans.
We made transparent elastic replicas of the vertebrobasilar arteries of an elderly patient who died of a ruptured ...aneurysm in the basilar artery. Using non-Newtonian fluid, physiological pulsatile flow volumes and profiles, and isobaric dyes and particles, we observed and recorded the slipstreams as they entered the aneurysm while changing relative flow in the vertebral arteries. Finally, we placed clips on the aneurysm, leaving residuals (or dog-ears), and observed the slipstreams.
The aneurysm originated laterally from the greater curvature of a tortuous basilar artery, measured 19 x 11 x 12 mm, and had a Murphy's teat at the apex, the rupture site. The neck measured 10 x 4 mm, about the diameter of the basilar artery. Slipstreams joined at the confluence of the vertebral arteries, formed helical flow patterns, and entered the aneurysm violently, striking the apex. They then passed proximally around the sac walls, then centrally, and finally reentered the basilar artery to pass distally. Altering the relative flows in the vertebral arteries could modify and prevent slipstream flow into the aneurysm. When a dog-ear was created by incorrect placement of an aneurysm clip, slipstreams entered only dog-ears that lay distal to the clip. Correctly placed clips excluded the aneurysm from the circulation, but did not return the flow dynamics to normal.
High-velocity slipstreams strike aneurysms at their rupture site and have an impact on distal but not proximal dog-ears. Modifying relative flow may prevent aneurysmal filling. Further, a knowledge of flow dynamics may allow us to predict which aneurysms are at risk of enlarging and rupturing, and may help guide proper therapy.
Hookworm infection is one of the most important parasitic infections of humans, possibly outranked only by malaria as a cause of misery and suffering. An estimated 1.2 billion people are infected ...with hookworm in areas of rural poverty in the tropics and subtropics. Epidemiological data collected in China, Southeast Asia and Brazil indicate that, unlike other soil-transmitted helminth infections, the highest hookworm burdens typically occur in adult populations, including the elderly. Emerging data on the host cellular immune responses of chronically infected populations suggest that hookworms induce a state of host anergy and immune hyporesponsiveness. These features account for the high rates of hookworm reinfection following treatment with anthelminthic drugs and therefore, the failure of anthelminthics to control hookworm. Despite the inability of the human host to develop naturally acquired immune responses to hookworm, there is evidence for the feasibility of developing a vaccine based on the successes of immunising laboratory animals with either attenuated larval vaccines or antigens extracted from the alimentary canal of adult blood-feeding stages. The major antigens associated with each of these larval and adult hookworm vaccines have been cloned and expressed in prokaryotic and eukaryotic systems. However, only eukaryotic expression systems (e.g., yeast, baculovirus, and insect cells) produce recombinant proteins that immunologically resemble the corresponding native antigens. A challenge for vaccinologists is to formulate selected eukaryotic antigens with appropriate adjuvants in order to elicit high antibody titres. In some cases, antigen-specific IgE responses are required to mediate protection. Another challenge will be to produce anti-hookworm vaccine antigens at high yield low cost suitable for immunising large impoverished populations living in the developing nations of the tropics.
Aims: This study examined the long‐term effects of nitrous oxide anaesthesia on serum levels of cobalamin and folate, red cell folate levels and haematological parameters, and neurological status in ...elderly Omani patients.
Methods: Sixty‐nine consecutive patients undergoing ophthalmic surgery were randomly and double‐blind assigned to nitrous oxide or propofol anaesthesia. They met the following entry criteria: age 55 years or above, no major organ failure, no clinical signs or symptoms of cobalamin or folate deficiency, mean cell volume (MCV) ≤ 96 fl, haematocrit (Hct) higher than 0·3 and no cobalamin and/or folate substitution therapy during the preceding months. Serum levels of cobalamin and folate, red cell folate levels, and haematological parameters were measured prior to anaesthesia and 3–5 weeks later. At that time, the patients also underwent thorough neurological examination.
Results: Data of 51 patients were complete and considered for analysis. In both nitrous oxide and propofol group, the range of exposure time was comparable (±1 h). In the nitrous oxide group, a slight but significant decrease in haemoglobin, Hct, and red blood cell count (RBC) (P < 0·001) was observed, whereas there was a mild increase in mean cell haemoglobin (MCH) and mean cell volume (P < 0·05). In addition, there was a significant decrease in serum folate levels (P < 0·05). Hct and RBC decreased slightly in the propofol group (P < 0·05), whereas there was a small increase in MCH. There was no difference between the two anaesthetics with regard to serum cobalamin and red cell folate levels, but there was a significant decrease in serum folate levels in the nitrous oxide group compared to those in the propofol group. Three patients with pre‐existing low red cell folate levels, who were randomized to nitrous oxide anaesthesia, developed clinical symptoms of folate deficiency.
Conclusions: This study showed that short‐term (40–80 min) nitrous oxide anaesthesia did not affect cobalamin levels but reduced serum folate levels in this elderly population. Although this reduction was clinically irrelevant, some patients with pre‐existing asymptomatic folate deficiency developed nitrous oxide‐induced folate deficiency.
Purpose: Clinical studies have revealed that the most important predictor of successful bypass grafting is the origin and quality of the bypass conduit. Attempts at intraoperative evaluation of the ...hemodynamic properties of the conduit, including assessment of blood flow (Q), pressure gradients (ΔP), and resistance (R), have not been useful. This is because each of these parameters measures the characteristics of the graft plus the outflow bed. To date, no specific measurement of the resistive properties of the conduit only is available. The purpose of this investigation was to evaluate longitudinal impedance (Z
L) as a measure of conduit-specific resistance and to evaluate its potential in predicting the outcome of infrainguinal vascular reconstructions.
Methods: Z
L was measured during surgery in 73 infrainguinal autologous vein reconstructions performed in 68 patients in two separate institutions over a 21-month period. Vein graft ultrasonic transit time Q and ΔP (from proximal to distal anastomosis) were measured at baseline and after maximal peripheral vasodilatation with an intraarterial injection of papaverine 30 mg. Waveforms were recorded for 10 seconds at 200 Hz using a digital acquisition system. R was calculated as proximal mean pressure divided by mean blood flow (Q̄). After Fourier transformation, Z
L was calculated as ΔP/Q at each harmonic and total Z
L (∫Z
L) was defined as the integral of moduli from 0 to 4 Hz.
Results: All hemodynamic variables were significantly affected by papaverine vasodilatation (ΔP̄, 3.9 ± 0.5 vs 6.3 ± 0.8 mm Hg; Q, 78.2 ± 7.0 vs 126 ± 11 ml/min; R, 134 ± 17 vs 72.7 ± 6.2 × 10
3 dyne · sec · cm
−5;
p < 0.0001), except ∫Z
L, which remained constant (31.1 ± 2.8 vs 30.8 ± 2.8 × 10
3 dyne · cm
−5;
p = NS). After follow-up of 1 week to 17 months (median, 5 months), the 1-year primary, primary-assisted, and secondary patency rates were 72% ± 7%, 77% ± 6%, and 81% ± 6%, respectively. Using Cox analysis, primary patency was significantly associated with decreased ∫Z
L (
p = 0.0001), but not with baseline or papaverine-stimulated ΔP̄, Q̄, ΔP̄/Q̄, or R. ∫Z
L > 47 × 10
3 dyne · cm
−5 predicted primary failure with 90% positive and negative predictive value.
Conclusions: Intraoperative measurement of ∫Z
L in infrainguinal vein grafts is independent of outflow conditions (that is, does not change with papaverine), and hence describes the resistive properties of the conduit only. In addition, these preliminary data suggest that ∫Z
L is predictive of short-term primary patency. ∫Z
L is the first available hemodynamic measurement that is conduit-specific and may therefore be a better predictor of graft patency than currently available methods.
Psychosocial factors, particularly depression and lack of social support, are important predictors of morbidity and mortality in patients with coronary heart disease. This article describes the ...design and methods of the Enhancing Recovery in Coronary Heart Disease Patients (ENRICHD) study, a multicenter, randomized clinical trial involving 3000 patients enrolled after acute myocardial infarction. ENRICHD aims to investigate the effects of a psychosocial intervention that targets depression and/or low social support on survival and reinfarction among adult men and women who are at high risk for recurrent cardiac events because of psychosocial factors (depressive or social isolation). Design features include the use of an individually tailored yet standardized intervention, rigorous clinical trial methods, and enrollment of a large number of women and minorities. (Am Heart J 2000;139:1-9.)
Depression and low social support are risk factors for medical morbidity and mortality after acute MI. The ENRICHD study is a multicenter, randomized, controlled clinical trial of a ...cognitive-behavioral treatment for depression and low social support in post-MI patients. A total of 2481 patients were recruited (26% with low social support, 39% with depression, and 34% with low social support and depression). Our objective is to describe the rationale, design, and delivery of the ENRICHD intervention.
Key features of the intervention include the integration of cognitive-behavioral and social learning approaches to the treatment of depression and a diverse set of problems that can contribute to low social support; rapid initiation of treatment after MI; a combination of individual and group modalities; adjunctive pharmacotherapy for severe or intractable depression; training, certification, and supervision of therapists; and quality assurance procedures.
The trial's psychosocial and medical outcomes will be presented in future reports.
The ENRICHD protocol targets two complex psychosocial risk factors with a multifaceted intervention, which is delivered in an individualized manner to accommodate a demographically, medically, and psychiatrically diverse patient population. Additional research will be needed to identify optimal matches between patient characteristics and specific components of the intervention.
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