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PubMed2006

Identification of PM sources by principal component analysis (PCA) coupled with wind direction data.

The effectiveness of combining principal component analysis (PCA) with multi-linear regression (MLRA) and wind direction data was demonstrated in this study. PM data from three grain-size fractions from a highly industrialised area in Northern Spain were analysed. Seven independent PM sources were identified by PCA: steel (Pb, Zn, Cd, Mn) and pigment (Cr, Mo, Ni) manufacture, road dust (Fe, Ba, Cd), traffic exhaust (P, OC + EC), regional-scale transport (, , V), crustal contributions (Al2O3, Sr, K) and sea spray (Na, Cl). The spatial distribution of the sources was obtained by coupling PCA with wind direction data, which helped identify regional drainage flows as the main source of crustal material. The same analysis showed that the contribution of motorway traffic to PM10 levels is 4-5 microg m-3 higher than that of local traffic. The coupling of PCA-MLRA with wind direction data proved thus to be useful in extracting further information on source contributions and locations. Correct identification and characterisation of PM sources is essential for the design and application of effective abatement strategies.

Air Pollutants↗

PubMedDate not supplied

Postoperative analgesia and recovery course after major colorectal surgery in elderly patients: a randomized comparison between intrathecal morphine and intravenous PCA morphine.

BACKGROUND AND OBJECTIVES: Intrathecal morphine is a widely used method for postoperative pain relief after major abdominal surgery. The aim of this randomized, double-blinded study was to compare intrathecal morphine and intravenous PCA morphine for postoperative analgesia and recovery course after major colorectal surgery in elderly patients. METHODS: After written informed consent, patients >70 years of age were prospectively and randomly assigned to receive either preoperative intrathecal morphine (0.3 mg) and postoperative patient-controlled (PCA) intravenous morphine (IT morphine) or PCA alone (group control). Results are presented as mean +/- SD (95% confidence interval). RESULTS: Twenty-six patients successfully completed the study in each group. In the IT morphine group, rate of awakening was delayed. Pain intensity and daily intravenous morphine consumption were significantly reduced 1 and 2 days after surgery in the IT morphine group (P < .01). Mental function (assessed by Mini Mental State and Digit Symbol Substitution Test) was similar in both groups. Episodes of postoperative delirium/confusion occurred similarly in both groups. Time to ileus resolution and time to ambulation without assistance did not differ between the 2 groups. The duration of hospitalization was 8.4 +/- 1.7 (7-11) days and 7.9 +/- 2.0 (6-9.9) days for control and IT morphine, respectively (nonstatistical difference). Patients in the IT morphine group had longer time to awakening from anesthesia and experienced more sedation. CONCLUSIONS: Intrathecal morphine, as compared with intravenous PCA morphine alone, improves immediate postoperative pain and reduces parenteral morphine consumption but does not improve postoperative recovery in elderly patients after major colorectal surgery.

Aged↗

PubMed1981

A simple electrostatic model can explain the effect of pH upon the force-pCa relation of skinned frog skeletal muscle fibers.

The relative force-pCa relation of skinned frog skeletal muscle fibers is shifted along the pCa axis by changes in pH. This shift has been interpreted as arising from competition between H+ and Ca2+ for a binding site on troponin. Unfortunately, binding studies have been unable to confirm such competition. Alternatively, however, the data fit a model where H+ influences the degree of dissociation of ionizable groups on the surface of the thin filaments, thus altering the electrostatic potential surrounding the filaments. Alterations in the potential will, in turn, change the concentration of Ca2+ near the troponin binding sites in accordance with the Boltzmann relation. A simple model, based upon the Gouy-Chapman relation between surface potential and charge density, provides a quantitative explanation for the shift of the relative force-pCa curve with pH, given a reasonable estimate of the surface charge density on the thin filament. A best fit is obtained when the ionizable groups giving rise to the potential have a log proton ionization constant (pKa) of 6.1, similar to that for the imidazole group on histidine, and when the density of these groups is near that estimated from amino acid analysis of thin filament proteins and from filament geometry. In preliminary experiments, reaction of skinned frog fibers with diethylpyrocarbonate (DEP) at pH 6 shifted the force-pCa curve toward lower Ca2+. This would be expected in the model since DEP at pH 6 is reported to specifically react with histidine imidazole groups and to irreversibly decrease their pKa, which would increase the net negative charge of the filaments.

Animals↗

PubMed2005

An improved PCA method with application to boiler leak detection.

Principal component analysis (PCA) is a popular fault detection technique. It has been widely used in process industries, especially in the chemical industry. In industrial applications, achieving a sensitive system capable of detecting incipient faults, which maintains the false alarm rate to a minimum, is a crucial issue. Although a lot of research has been focused on these issues for PCA-based fault detection and diagnosis methods, sensitivity of the fault detection scheme versus false alarm rate continues to be an important issue. In this paper, an improved PCA method is proposed to address this problem. In this method, a new data preprocessing scheme and a new fault detection scheme designed for Hotelling's T2 as well as the squared prediction error are developed. A dynamic PCA model is also developed for boiler leak detection. This new method is applied to boiler water/steam leak detection with real data from Syncrude Canada's utility plant in Fort McMurray, Canada. Our results demonstrate that the proposed method can effectively reduce false alarm rate, provide effective and correct leak alarms, and give early warning to operators.

Algorithms↗

PubMed1999

A novel local PCA-based method for detecting activation signals in fMRI.

A novel local principal component analysis (LPCA) technique is presented for activation signal detection in functional magnetic resonance imaging (fMRI) without explicit knowledge about the shape of the model activation signal. Unlike the traditional PCA methods, our LPCA algorithm is based on a measure of separation between two clusters formed by the signal segments in active periods and inactive periods, which is computed in an eigen-subspace. In addition, we only applied PCA to the temporal sequence of each individual voxel instead of applying PCA to the fMRI data set. In our algorithm, we first applied a linear regression procedure to alleviate the baseline drift artifact. Then, the baseline-corrected temporal signals were partitioned into active and inactive segments according to the paradigm used for the fMRI data acquisition. Principal components were computed from all these segments for each voxel by PCA. By projecting the segments of each voxel onto a linear subspace formed by the corresponding most dominant principal components, two separate clusters were formed from active and inactive segments. An activation measure was defined based on the degree of separation between these two clusters in the projection space. We show experimental results on the activation signal detection from various sets of fMRI data with different types of stimulation by using the proposed LPCA algorithm and the standard t-test method for comparison. Our experiments indicate that the LPCA algorithm in general provides substantial signal-to-noise ratio improvement over the t-test method.

Algorithms↗

PubMed1995

Cemented collarless (Exeter-CPT) versus cementless collarless (PCA) femoral components. A 2- to 14-year follow-up evaluation.

The purpose of this study was to compare the intermediate results of total hp arthroplasty with a cemented, collarless, femoral prosthesis design (Exeter, Howmedica, Middlesex, UK and CPT, Zimmer, Warsaw, IN) with those of a cementless, collarless, porous-coated femoral component (PCA, Howmedica). A total of 151 hips in 128 patients were reviewed. In the cemented group, 85 Exeter-CPT prostheses were used in 71 patients with an average follow-up period of 6.5 years. In the uncemented group, 66 PCA prostheses were placed in 57 patients with an average follow-up period of 7 years. Harrington hip scores improved from 50.1 to 80.7 for the PCA group and from 49.5 to 87.3 for the Exeter-CPT group. The patient satisfaction rates were 89 and 96%, respectively. Sixty-eight patients with Exeter or CPT prostheses had excellent function and no significant thigh pain after 2 years. One Exeter stem was revised 10 years after the primary surgery because of aseptic osteolysis due to cement defect. Two Exeter sockets were revised because of aseptic loosening. In the PCA group, the incidence of thigh pain that persisted beyond 2 years was 39.4%, and there were high incidences of distal cortical hypertrophy (66.6%) and bead loosening (45.5%). Sixteen hips were revised for aseptic stem loosening of the socket. The cementless ingrowth stems failed earlier (around 5 years), whereas the cemented stems continued to perform well past 14 years. In this study, the cemented, collarless, tapered, femoral prosthesis gave results superior to those of the uncemented collarless, porous-coated anatomic design at an average follow-up period of 7 years (range, 2-14 years).

Aged↗

PubMed1978

Effects of PCA and DMAE on the namatode Caenorhabditis briggsae.

Concentration of 6.8 mM DMAE did not retard age pigment accumulation in Caenorhabditis briggsae. However, when the nematodes were exposed to 6.8 mM PCA + 6.8 mM DMAE combined, the accumulation of age pigment was significantly retarded. A combination of 3.4 mM DMAE + 3.4 mM PCA had no effect on age pigment. It is concluded from this study that PCA and DMAE act in concert to produce the observed effect on age pigment. In respect to this parameter neither molecule was effective alone. The results indicate that the effect of centrophenoxine on age pigment might be enhanced by retarding the hydrolysis of centrophenoxine. The accumulation of electron dense aggregates, thought to be aggregates of cross-linked molecules, was reduced by 6.8 PCA + 6.8 DMAE. It is suggested that centrophenoxine be tested for its ability to remove random, unwanted cross-linkages in higher animals.

Animals↗

PubMed1998

Patient-controlled interscalene analgesia with ropivacaine after major shoulder surgery: PCIA vs PCA.

We have compared the efficacy of patient-controlled interscalene analgesia (PCIA) using ropivacaine with patient-controlled analgesia (PCA) using nicomorphine in 60 patients (n = 30 in each group), in a prospective, randomized study. In both groups, all patients received interscalene block with 0.75% ropivacaine before induction of anaesthesia. Six hours after interscalene block, patients in group PCIA received continuous infusion of 0.2% ropivacaine at a rate of 5 ml h-1 with a bolus dose of 3 or 4 ml and a lockout time of 20 min; patients in group PCA received continuous infusion of nicomorphine 0.5 mg h-1 and a bolus dose of 2 or 3 mg with a lockout time of 20 min. Control of pain was significantly better from 12 to 48 h after operation (except at 42 h) in group PCIA. Nausea and pruritus occurred significantly more frequently in group PCA. Patient satisfaction was greater in group PCIA. We conclude that the use of 0.2% ropivacaine using PCIA was an efficient way of managing pain after major shoulder surgery and compared favourably with PCA nicomorphine in terms of pain relief, side effects and patient satisfaction.

Adolescent↗

PubMed2001

Prophylactic ondansetron does not improve patient satisfaction in women using PCA after Caesarean section.

Eighty-one consenting women undergoing elective Caesarean section under spinal anaesthesia were randomly divided into two groups. In Group O patients, ondansetron 4 mg was given intravenously at the end of the surgery and 8 mg added to the morphine solution in the PCA syringe. Patients in Group P received only morphine via PCA syringe. Analgesia and nausea were measured until PCA was discontinued 24 h after the operation. Women in the two groups were similar with respect to age, duration of use of the PCA, amount of morphine used, previous history of PONV, and incidence of motion sickness and morning sickness during the current pregnancy. The number of women who complained of nausea and those needing rescue antiemetic medication was significantly less in Group O. However, there was no statistically significant difference between the two groups in the patient's perception of the control of nausea and their overall satisfaction. It was noted that PONV was more frequent among women who had significant morning sickness during early pregnancy and ondansetron was beneficial in reducing PONV in these women. Although the ondansetron reduced the incidence of PONV and the need for further antiemetic medication, this did not affect patient's satisfaction regarding their postoperative care.

Analgesia, Patient-Controlled↗

PubMed1992

Effects of a nighttime opioid infusion with PCA therapy on patient comfort and analgesic requirements after abdominal hysterectomy.

Since pain during the early postoperative period can disrupt a patient's normal sleep pattern, we investigated the influence of a nighttime "basal" infusion of morphine on patient comfort, ability to sleep at night, restfulness, and analgesic requirements following elective abdominal hysterectomy. One hundred fifty-six adult women were randomly assigned to receive either patient-controlled analgesia (PCA) alone or PCA supplemented with a nighttime infusion of morphine 1.0 mg.h-1. The infusion was started in the postanesthesia care unit and continued until the morning after surgery. Subsequently, the infusion was used only during the nighttime hours (10 PM-8 AM). Patients in both treatment groups were able to self-administer supplemental bolus doses of morphine, 2 mg intravenously, as needed during the 72-h study period. The use of a nighttime morphine infusion did not significantly improve the patient's ability to sleep or to rest comfortably at night. Only 8% and 7% of patients in the control and infusion groups, respectively, found it inconvenient to self-administer bolus doses at night. In addition, the number of patient demands and supplemental bolus doses, opioid usage, and recovery parameters were similar in the two treatment groups. The use of a basal infusion resulted in six programming errors, and three patients required discontinuation of the infusion because of hemoglobin oxygen desaturation (i.e., SpO2 less than 85% for greater than 5 min). We concluded that the routine use of a continuous nighttime opioid infusion in combination with a standard PCA regimen failed to improve the management of postoperative pain, sleep patterns, or recovery profiles compared to PCA alone after abdominal hysterectomy.

Adult↗

PubMedDate not supplied

The effect of structured preoperative teaching on patients' use of patient-controlled analgesia (PCA) and their management of pain.

This study examined the effect of structured preoperative teaching on patients' understanding of patient-controlled analgesia (PCA) and their management of pain. The experimental group received a written pamphlet and structured preoperative teaching on the use of PCA to manage their pain. The control group received the usual preoperative preparation normally provided by the physician. Both groups were later asked to complete a posttest to determine how well they understood the use of PCA and how well they managed their pain. There was no statistically significant evidence that the experimental group's knowledge of PCA was different from that of the control group. However, there was significant evidence that the experimental group managed their pain better.

Adult↗

PubMed2000

Nonlinear PCA: characterizing interactions between modes of brain activity.

This paper presents a nonlinear principal component analysis (PCA) that identifies underlying sources causing the expression of spatial modes or patterns of activity in neuroimaging time-series. The critical aspect of this technique is that, in relation to conventional PCA, the sources can interact to produce (second-order) spatial modes that represent the modulation of one (first-order) spatial mode by another. This nonlinear PCA uses a simple neural network architecture that embodies a specific form for the nonlinear mixing of sources that cause observed data. This form is motivated by a second-order approximation to any general nonlinear mixing and emphasizes interactions among pairs of sources. By introducing these nonlinearities principal components obtain with a unique rotation and scaling that does not depend on the biologically implausible constraints adopted by conventional PCA. The technique is illustrated by application to functional (positron emission tomography and functional magnetic resonance imaging) imaging data where the ensuing first- and second-order modes can be interpreted in terms of distributed brain systems. The interactions among sources render the expression of any one mode context-sensitive, where that context is established by the expression of other modes. The examples considered include interactions between cognitive states and time (i.e. adaptation or plasticity in PET data) and among functionally specialized brain systems (using a fMRI study of colour and motion processing).

Acoustic Stimulation↗

PubMed1978

Quantitation of passive cutaneous anaphylaxis (PCA) by using radiolabelled antigen.

The major problem of detecting reaginic antibody by passive cutaneous anaphylaxis (PCA) is the quantitation of the dye reaction. Radiolabelled antigen was used in an attempt to quantitate the PCA reaction (Radio-PCA). Antisera containing reaginic antibody against human serum albumin (HSA) were produced in rabbits. These antisera were injected into normal rabbit skin in different dilutions. Twenty-four hours later HSA was injected intravenously either with Evans Blue or as 125-I-HSA. Radioactivity found in antibody-containing skin was significantly higher than in control specimens containing saline or normal rabbit serum, as low as antiserum dilutions of 1:1,000. Compared with the Evans Blue technique Radio-PCA was able to distinguish quantitatively between different antiserum dilutions at a higher level of statistical significance.

Animals↗

PubMed1993

Patient-controlled analgesia (PCA) leads to more postoperative pain relief, but also to more fatigue and less vigour.

This investigation evaluated patient-controlled analgesia (PCA) for subjective well-being and mood in the postoperative period in comparison with the intramuscular (im) administration of morphine given on demand. Patients scheduled for elective upper abdominal surgery were assigned at random to either PCA (n = 17) or im morphine (n = 14). The PCA group experienced significantly more pain relief and consumed more morphine than those who received im morphine. The PCA patients suffered from more fatigue and showed less vigour than the im group. Neither preoperative trait anxiety nor locus of control was associated with postoperative pain in either of the groups.

Adult↗

PubMed1995

Intrathecal morphine (ITM) for postoperative pain control in children: a comparison with nalbuphine patient controlled analgesia (PCA).

This is a retrospective study covering the ten-year period 1984-1993. Single shot spinal morphine (ITM) is compared with PCA nalbuphine for postoperative pain relief in children having abdominal or thoracic procedures. The records of 52 patients meeting selection criteria were examined. Nursing and physician notations were reviewed for hourly pain assessments, evidence of associated complications, respiratory depression, nausea and or vomiting, pruritus, and urinary retention. ITM provided significantly better pain relief (2.2 h in pain) during the first 24 h postoperatively than PCA nalbuphine (9.2 h in pain). With the exception of urinary retention which was significantly more frequent following ITM (58.6%) compared to PCA nalbuphine (8.7%), narcotic related complications were not different between the two groups. No difference in duration of hospital stay or ICU stay could be demonstrated. We conclude that ITM provides better pain relief, without more serious complications, than PCA nalbuphine. We recommend it as a safe, effective technique to treat postoperative pain in children following thoracic or upper abdominal procedures.

Abdomen↗

PubMed1982

The pCa-tension and force-velocity characteristics of skinned fibres isolated from fish fast and slow muscles.

1. Single fast fibres and small bundles of two to six slow fibres were dissected from the myotomal muscles of the cod, Gadus morhua, and the dogfish, Scyliorhinus canicula. Fibres were chemically skinned with the non-ionic detergent Brij 58.2. The isometric tension properties were investigated. Maximal isometric tensions (mean +/- S.E. of mean) were 18.65+/-1.18 (n = 11) and 8.34+/-0.98 (n = 13) N cm(-2) for cod fast and slow fibres, and 18.34+/-0.88 (n = 28) and 8.24+/-0.39 (n = 12) N cm(-2) for dogfish fast and slow fibres respectively. The values are comparable to those observed in mammalian and amphibian skinned fibres. The lower tensions generated by the slow fibres cannot be fully explained on the basis of their lower myofibrillar fractional volume.3. In common with previous studies, a steep sigmoid relationship between pCa and tension was observed. The threshold for tension generation was around pCa 7.2. Half-maximal pCas were 6.08 and 6.42 for cod fast and slow muscle, and 6.41 and 6.50 for dogfish fast and slow fibres respectively. Cod fibres were maximally activated at around pCa 5.18, and dogfish fibres at pCa 5.62.4. Contraction-induced residual tensions were observed in cod fast fibres after return to relaxing solution. This phenomenon is a feature common to many skinned fibre studies, but the mechanism behind it has yet to be resolved.5. The force-velocity characteristics of fast and slow fibres have been investigated (at 8 degrees C).6. Points below 0.6 P(0) on the P-V curves could be fitted to a linear form of the Hill equation. Extrapolated V(max)s were calculated as follows: cod fast fibre V(max) = 1.01 muscle length sec(-1) (Lsec(-1)) (a = 0.21 P(0); b = 0.21 Lsec(-1)). Slow fibre = 0.53 Lsec(-1) (a = 0.28P(0); b = 0.21 Lsec(-1)). Dogfish fast fibre V(max) = 2.34 Lsec(-1) (a = 0.06 P(0); b = 0.14 Lsec(-1)). Slow fibre = 0.67 Lsec(-1) (a = 0.19 P(0); b = 0.13 Lsec(-1)).7. Contraction velocity in cod slow fibres decreased continuously to produce markedly non-linear velocity transients, similar to those reported for amphibian slow fibres.8. The effect of altering Ca(2+) concentration on the shape of the isotonic velocity curve (at low loads) was studied in dogfish fast fibres (0.5-1 degrees C). Contraction velocity decreased continuously during shortening, at both maximal and half-maximal Ca(2+) concentration. The rate of decay of velocity with shortening was greater at low Ca(2+) concentration.

Action Potentials↗

PubMed1982

Effects of sarcomere length on the force-pCa relation in fast- and slow-twitch skinned muscle fibres from the rat.

1. Steady-state force-pCa relations were determined for mechanically skinned fibres of fast- and slow-twitch rat skeletal muscle, extensor digitorum longus (e.d.l.) and soleus respectively, at varied sarcomere lengths and temperatures (3-35 degrees C).2. This relation was different for the two fibre types at all sarcomere lengths, with soleus fibres having lower Ca(2+) concentration threshold for activation and requiring a wider Ca(2+) concentration range to reach force saturation.3. An increase in sarcomere length within the range 2.2-3.6 mum reversibly shifted the steady-state force-pCa curves for both fast- and slow-twitch fibres toward lower Ca(2+) without affecting the steepness of the curves.4. The results are consistent with the idea that the sensitivity of the contractile apparatus to Ca(2+) is increased with increasing sarcomere length.5. The change in apparent Ca(2+) sensitivity (measured as the change in pCa corresponding to 50% Ca-activated force (DeltapCa(50))) was approximately proportional to the change in sarcomere length (DeltaSL) at all temperatures for both types of muscle fibre.6. The proportionality coefficient (DeltapCa(50)/DeltaSL) was higher for slow-twitch fibres than for fast-twitch fibres by a factor of 1.5-2.0 at all temperatures investigated.7. The force-pCa relation was less affected by changes in sarcomere length at lower (3-5 degrees C) than at higher temperatures (22-35 degrees C).8. The sarcomere length-maximum force relation obtained with skinned fibres for sarcomere lengths between 2.10 and 4.05 mum was similar for both fibre types at all temperatures despite large temperature dependent variations in maximum Ca-activated force response. Maximum force decreased linearly to zero between ca. 2.8 and 3.95 mum; remained high and essentially constant between ca. 2.40 and 2.80 mum, and decreased significantly below 2.40 mum.9. Myofilament-generated tension oscillations produced by partially activated soleus skinned fibres are highly length dependent, disappearing completely when sarcomere length is increased above 3.15 mum.

Animals↗

PubMed1985

Pharmacological characterization of mouse ear PCA.

Effects of some antiallergic agents on homologous passive cutaneous anaphylaxis (PCA) in mouse ear were investigated by means of assessing the amount of extravasated dye. Antihistamines (chlorpheniramine and diphenhydramine) and antiserotonins (methysergide and cyproheptadine) suppressed mouse ear PCA significantly. In contrast, an antagonist of slow reacting substance of anaphylaxis (SRS-A) (FPL 55712) and an inhibitor of SRS-A synthesis (AA-861) did not suppress the reaction. beta-Adrenergic stimulants (isoproterenol and salbutamol) and theophylline, which elevate cyclic AMP (cAMP) levels, also suppressed mouse ear PCA significantly. The antiallergic agents, N(3',4'-dimethoxycinnamoyl)anthranilic acid(N-5') and ketotifen suppressed mouse ear PCA significantly, but disodium cromoglycate (DSCG) failed to suppress the reaction.

Albuterol↗