Intermittent Type Research Articles

Intermittent type fluctuation of target fragments produced in 16O-AgBr interactions at 4.5 AGeV/c**Supported by National Natural Science Foundation of China (10675077, 10475054), Shanxi Provincial Natural Science Foundation (2007011005) and Shanxi Provincial Science Foundation for Youths (20051002)

A study of intermittency of target associated fragments produced in the interactions of 16OAgBr at 4.5 AGeV/c with nuclear emulsion using the method of factorial moments, Fq, has been performed. The dependence of the moments on the number of bins M is found to follow a power law behavior for the experimental data in terms of new scaled variable χ(z) suggested by Bialas and Gazdzicki. The anomalous dimensions, dq, increase linearly with the order of moments, q. This observation indicates the association of multifractility with production mechanism of target associated fragments.

Do intermittent and ephemeral Mediterranean rivers belong to the same river type?

The benthic macroinvertebrate communities and ecological quality of eleven temporary rivers (seven intermittent and four ephemeral) in Dadia National Park, north-eastern Greece, were examined with respect to the degree of flow temporality. Sampling took place during the high flow season at both ephemeral and intermittent sites and during the low flow season only at the intermittent ones, which receded to pools. Despite the remarkable seasonal variation in both the hydrology and ecology of the intermittent rivers, the various metrics and indices as well as the multivariate analyses confirmed the clear distinction between the two river types (ephemeral and intermittent). Existing European quality indices do not sufficiently differentiate between ephemeral and intermittent river types, and thus cannot reliably discriminate the degree of natural variability from human induced stressors in temporary rivers.

Glucose Monitoring in Acute Care: Technologies on the Horizon

Current glucose monitoring technology appears inadequate for the management of diabetic surgical and in critically ill patients requiring intensive insulin therapy. Subcutaneous sensors measure interstitial fluid glucose, and this technology has not yet been shown to provide the timely and accurate measurements necessary for intravenous insulin administration in surgical and critical care patients on intensive insulin therapy. Technologies under development that may be more suitable for surgical and intensive care unit patients are the automated intermittent type glucose monitors and central catheter glucose monitors. Improved accuracy, patient safety, incorporation of control algorithms, and alleviation of added nursing labor are important factors for consideration with future acute care glucose monitors. Hospital costs for these monitors are difficult to estimate but may be relatively low if their use can be related to better patient outcome, reduced labor costs, and increased job satisfaction for the nursing staff.

COMPLEX INTERMITTENCY IN SWITCHING CONVERTERS

Intermittent instability is commonly observed in switching power supplies during the design and development phase. It manifests as symmetrical period-doubling bifurcation in the time domain with long intermittent periods. Such intermittent operation is considered undesirable in practice and is usually avoided by appropriate adjustments of circuit parameters. This paper explores the mechanism and conditions for the emergence of intermittency in a common voltage-mode controlled buck converter. It is found that interference at frequencies near the switching frequency or its rational multiples will induce intermittent operation. The strengths and frequencies of the interfering signals determine the type and period of intermittency. The problem is analyzed by transforming the conventional parameter-bifurcation analysis to a time-bifurcation analysis. Analytical results are verified by simulations and experimental measurements.

Double‐Barrel Coronary Sinus

A 78-year-old woman with severe nonischemic cardiomyopathy (EF 25%), congestive heart failure (persistent NYHA class III symptoms), left bundle branch block, and intermittent Mobitz Type II second-degree heart block with a previously implanted dual-chamber pacemaker was referred for upgrade to a biventricular defibrillator system. After the coronary sinus was selectively engaged, a balloon-occluding catheter was placed in the mid-portion of the vessel and an angiogram was performed in orthogonal views. Initial images showed retrograde opacification of the main coronary sinus, great cardiac, and anterior interventricular veins, but there appeared to be a complete absence of posterolateral branches from the left ventricular free wall. After manipulation of the catheter, contrast injection closer to the ostium identified a faint shadow of a second coronary sinus lumen. An ostial injection confirmed an anomalous “double-barrel” coronary sinus, with the second vessel running parallel to the main coronary sinus and terminating into two posterolateral branches (see Fig. 1), one of which was successfully used for left ventricular lead placement. Right anterior oblique view taken after catheter manipulation and contrast reinjection from the coronary sinus ostium. An anomalous “double-barrel” coronary sinus was revealed, with the second vessel running parallel to the main coronary sinus. Off this second lumen, two posterolateral branches were clearly visualized, one of which is seen with a guide wire in place. A left ventricular lead was then successfully placed. Comprehensive understanding of coronary venous anatomy and its anomalies is becoming increasingly important as more biventricular devices are being placed. Catheter manipulation and reinjection of contrast may be needed multiple times to ensure accurate visualization of the coronary venous system. Our case demonstrates that posterolateral venous branches may arise selectively from one “barrel” of a “double-barrel” coronary sinus. This anomaly of the coronary sinus should be considered when there is apparent angiographic lack of posterolateral branches.

Cervical Musculoskeletal Impairment in Frequent Intermittent Headache. Part 2: Subjects With Concurrent Headache Types

A pattern of musculoskeletal impairment inclusive of upper cervical joint dysfunction, combined with restricted cervical motion and impairment in muscle function, has been shown to differentiate cervicogenic headache from migraine and tension-type headache when reported as single headaches. It was questioned whether this pattern of cervical musculoskeletal impairment could discriminate a cervicogenic headache as one type of headache in more complex situations when persons report two or more headaches. Subjects with two or more concurrent frequent intermittent headache types (n = 108) and 57 non-headache control subjects were assessed using a set of physical measures for the cervical musculoskeletal system. Discriminant and cluster analyses revealed that 36 subjects had the pattern of musculoskeletal impairment consistent with cervicogenic headache. Isolated features of physical impairment, e.g. range of movement (cervical extension), were not helpful in differentiating cervicogenic headache. There were no differences in measures of cervical musculoskeletal impairment undertaken in this study between control subjects and those classified with non-cervicogenic headaches.

Intermittencies on tori: A way to characterize them

Since the three types of intermittency have been theoretically described, many experimental observations of such regimes have been reported. Chaotic behaviors occurring after torus breakdowns and quasi-periodic regimes are also very often observed. It is not so surprising that intermittencies on tori were never reported as soon as it is understood that these common characteristic of intermittencies should be investigated in a Poincaré section of a Poincaré section, that is, in a set which is not possible to define. A specific approach is therefore required to identify them as shown in the paper with two examples of type-I intermittency on tori solution to two different systems.

The evaluation of new classification of Allergic Rhinitis in patients referred to a clinic in the city of Shiraz.

Allergic rhinitis is the most common cause of allergic diseases. The recent guidelines of Allergic Rhinitis and its Impact on Asthma (ARIA) group, classified it to intermittent (less than 4 days per week and for less than 4 weeks) and persistent (more than 4 days per week or lasting more than 4 weeks regardless of the number of days per week). The present study evaluates the patients with ARIA classification. The patients referred to Motahhari Clinic (Shiraz, Iran) were evaluated. Age, sex, seasonal or perennial, intermittent or persistent type, duration, sneezer or blocker, diurnal change and presence of allergic conjunctivitis were recorded. The patients who had one or more symptoms of; impairment of sleep, daily activity or work in school or troublesome symptoms had moderate to severe disease and those who did not have these problems have mild disease. The information of 96 patients (46 male and 50 female) were analysed (mean age+/-SD: 24.45+/-10.37 years). The mean duration of disease was 4.26+/-4.12 years, was more in female (P<0.05). Seasonal allergic rhinitis was present in 49 (52%) patients; 30 male, 19 female (P=0.007), perennial in 15 (16%), 1 male, 14 female and mixed type in 29 (30%); 11 male, 18 female. Mild intermittent rhinitis was diagnosed in only 2 (2%) patients, 1 male and 1 female, mild persistent rhinitis in 23 (24%); male 11, female 12; moderate/severe intermittent rhinitis in 4 (4%); 3 male, 1 female; and moderate/severe persistent rhinitis in 56 (58%); 22 male, 34 female (P<0.05). Fifty-seven percent were more sneezer and 36% were more blocker type, sneezers suffered more in days and others more at nights. Others were both sneezer and blocker. Sixty percent had allergic conjunctivitis too, 76% of them were moderate/severe persistent, and 85% were in seasonal or mixed groups. Eleven patients (12%), in persistent group, had history of asthma. Family history of allergic rhinitis and asthma was found in 53% and in 25% of patients, respectively. According to new guidelines for classification of allergic rhinitis, most of the patients are moderate to severe types. The classification of allergic rhinitis to seasonal and perennial disease is not proportional to intermittent and persistent types of classification. .

Use of Dynamic Computed Tomography to Evaluate Pre- and Postoperative Aortic Changes in AAA Patients Undergoing Endovascular Aneurysm Repair

To utilize dynamic computed tomographic angiography (CTA) on pre- and postoperative endovascular aneurysm repair (EVAR) patients to characterize cardiac-induced aortic motion within the aneurysm neck, an essential EVAR sealing zone. Electrocardiographically-gated CTA datasets were acquired utilizing a 64-slice Philips Brilliance CT scanner on 15 consecutive pre- and postoperative AAA patients. Axial pulsatility measurements were taken at 2 clinically relevant levels within the aneurysm neck: 2 cm above the highest renal artery and 1 cm below the lowest renal artery. Changes in aortic area and diameter were determined. Significant aortic pulsatility exists within the aneurysm neck during the cardiac cycle. Preoperative aortic area increased significantly, with a maximum increase of up to 12.5%. The presence of an endograft did not affect aortic pulsatility (p=NS). Postoperative area also changed significantly during a heart cycle, with a maximum increase of up to 14.5%. Diameter measurements demonstrated an identical pattern, with significant pre- and postoperative intracardiac pulsatility within and above the aneurysm neck (p<0.05). An increase in maximum diameter change up to 15% was evident. Patients undergoing EVAR experience aortic diameter changes within and above the aneurysm neck. The presence of an endograft does not abrogate this response to intracardiac pressure changes. Static CT imaging may not adequately identify patients with large aortic pulsatility, potentially resulting in endograft undersizing, stent-graft migration, intermittent type I endoleaks, and poor patient outcomes. The current standard regime of 10% to 15% oversizing based on static CT may be inadequate for some patients.

Crisis-induced intermittency in non-linear economic cycles

A new type of economic intermittency is found in non-linear business cycles. Following a merging crisis, a complex economic system has the ability to retain memory of its weakly chaotic dynamics prior to crisis. The resulting time series exhibits episodic regime switching between periods of weakly and strongly chaotic fluctuations of economic variables. The characteristic intermittency time, useful for forecasting the average duration of contractionary phases and the turning point to the expansionary phase of business cycles, is computed from the simulated time series.

Effective Speed and Agility Conditioning Methodology for Random Intermittent Dynamic Type Sports

Different coaching methods are often used to improve performance. This study compared the effectiveness of 2 methodologies for speed and agility conditioning for random, intermittent, and dynamic activity sports (e.g., soccer, tennis, hockey, basketball, rugby, and netball) and the necessity for specialized coaching equipment. Two groups were delivered either a programmed method (PC) or a random method (RC) of conditioning with a third group receiving no conditioning (NC). PC participants used the speed, agility, quickness (SAQ) conditioning method, and RC participants played supervised small-sided soccer games. PC was also subdivided into 2 groups where participants either used specialized SAQ equipment or no equipment. A total of 46 (25 males and 21 females) untrained participants received (mean +/- SD) 12.2 +/- 2.1 hours of physical conditioning over 6 weeks between a battery of speed and agility parameter field tests. Two-way analysis of variance results indicated that both conditioning groups showed a significant decrease in body mass and body mass index, although PC achieved significantly greater improvements on acceleration, deceleration, leg power, dynamic balance, and the overall summation of % increases when compared to RC and NC (p < 0.05). PC in the form of SAQ exercises appears to be a superior method for improving speed and agility parameters; however, this study found that specialized SAQ equipment was not a requirement to observe significant improvements. Further research is required to establish whether these benefits transfer to sport-specific tasks as well as to the underlying mechanisms resulting in improved performance.

Dynamics of spatial Fourier modes in turbulence

We report an experimental investigation of the statistical time dynamic of spatial Fourier modes in a fully developped turbulent jet flow. Measurements rely on an original acoustic scattering technique, allowing the direct and continuous probing in a time of spatial Fourier modes of the turbulent vorticity field at well defined spatial wavevectors. From the recordings of the amplitude of the spatial Fourier modes corresponding to different wavevectors in the inertial range, we compute the time correlation functions of the modal amplitude. The modal vorticity dynamics exhibits two well separated time scales: a short one which is scale dependant and related to the well known sweeping effect (random advection), and a much longer one, of order the integral time scale, which is not scale dependent. By computing the cross-correlation of the amplitude of two different wavevectors, we evidence a clear statistical dependance between scales, whatever their separation, at variance with the original Kolmogorov 41 theory. We ascribe our experimental results to a manifestation of a new type of statistical intermittency. We call this new statistical feature a large scale time intermittency effect, in contrast with the usual small scale spatial intermittency reported in Eulerian velocity measurements. We propose to attribute this time intermittency, to the fluctuations in time of the injected energy at large scale, in the spirit of the objection formulated by Landau against the K41 theory.

Prediction of pressure drop in multiphase horizontal pipe flow

Empirical correlations were tested against reliable two phase pipe flow data for the prediction of pressure drop. Correlations are recommended for the prediction with stratified and annular type flows. When these correlations were adapted to three phase gas–water–oil pipe flow in general they predicted for intermittent slug type flows. Momentum balance models could not be successfully adapted to the prediction of pipe three phase pressure drop.

Dynamic Cine-CT Angiography for the Evaluation of the Thoracic Aorta; Insight in Dynamic Changes with Implications for Thoracic Endograft Treatment

Thoracic aneurysm preoperative imaging is performed using static techniques without consideration of normal aortic dynamics. Improved understanding of the native aortic environment into which thoracic endografts are placed may aid in device selection. It is unclear what comprises normal thoracic aortic pulsatility. We studied these phenomena dynamically using ECG-gated 64-slice CTA. Maximum diameter and area change per cardiac cycle was measured at surgically relevant anatomic thoracic landmarks in ten patients; 1.0 cm proximal and distal to the subclavian artery, 3.0 cm distal to the subclavian artery, and 3.0 cm proximal to the celiac trunk. Data was acquired using a novel ECG-gated dynamic 64-slice CT scanner during a single breath hold with a standard radiation dose and contrast load. Eight gated data sets, covering the cardiac cycle were reconstructed, perpendicular to the central lumen. There is impressive change in both maximum diameter and area in the thoracic aorta during the cardiac cycle. Mean maximum diameter changes of greater than 10% are observed in the typical sealing zones of commercially available endografts corresponding to diameter increases of up to 5mm. Aortic area increases by over 5% per cardiac cycle. ECG-gated dynamic CTA with standard radiation dose is feasible on a 64-slice scanner and provides insight into (patho) physiology of thoracic aortic conformational changes. Clinicians typically oversize thoracic endografts by 10%. With aortic pulsatility resulting in diameter changes of up to 17.8%, the potential exists for endograft undersizing, graft migration, intermittent type I endoleak, and poor patient outcome. Furthermore, aortic pulsatility is not evenly distributed, and non-circular stentgraft designs should be considered in the future since aortic distension in the aneurysm neck is not evenly distributed.

Pilot Study of Dynamic Cine CT Angiography for the Evaluation of Abdominal Aortic Aneurysms: Implications for Endograft Treatment

To utilize 40-slice electrocardiographically (ECG)-gated cine computed tomographic angiography (CTA) to characterize normal aortic motion during the cardiac cycle at relevant anatomical landmarks in preoperative abdominal aortic aneurysm (AAA) patients. In 10 consecutive preoperative AAA patients (10 men; mean age 78.8 years, range 69-86), an ECG-gated CTA dataset was acquired on a 40-slice CT scanner using a standard radiation dose. CTA quality was graded and scan time was measured. Pulsatility measurements at multiple relevant anatomical levels were performed in the axial plane. Changes in aortic circumference were determined for both the aortic wall and the luminal diameter. All 10 CT scans were of good quality. All patients could be scanned in 14 to 33 seconds (mean 21). At each anatomical level measured, there was a 2.2- to 3.4-mm increase in the aortic wall circumference per cardiac cycle. A similar increase was observed in luminal circumference, with a 2.4- to 3.6-mm increase per cycle. This study introduces the concept of dynamic cine CTA imaging of aortic motion, providing insight into the pathophysiology of abdominal aortic and iliac pulsations. Patients with AAAs selected for EVAR demonstrate changes in aortic circumference with each cardiac cycle that may have consequences for endograft sizing and future design. The potential for graft migration, intermittent type I endoleak, and poor patient outcome following EVAR can be anticipated. Complex aortic dynamics deserve increased scrutiny in an effort to prevent potential complications.

Conversion of intermittent exotropia types subsequent to part-time occlusion therapy and its sustainability

To evaluate the effects of part-time occlusion therapy on types of intermittent exotropia and sustainability of converted types. Forty-four and 26 children with basic-type and convergence-insufficiency-type intermittent exotropia, respectively, were evaluated in this study. Upon initial examination, we obtained both distant and near deviating angles using prism cover tests, after correcting for refractive errors. We conducted occlusion of the nondeviating eye for 3 months at 3 h/day and assessed the changes in types of intermittent exotropia. We also observed the changes of deviating angles and sustainability of types after 3 months of cessation of part-time occlusion in patients who did not undergo surgery. Preocclusion deviating angles (mean +/- SD) were determined to be 27.1+/-7.46 prism diopters (PD) on distant measurements and 30.6+/-7.92 PD on near measurements. After 3 months of occlusion, the deviating angles were 25.9+/-9.10 PD on distant measurements and 21.4+/-11.00 PD on near measurements, corresponding to a significant reduction (p=0.005 and p<0.001, respectively). Fourteen patients (32%) suffering from basic type of intermittent exotropia converted to the pseudodivergence excess type. In patients suffering from the basic type who exhibited no changes in type, 9 patients (20%) exhibited reductions on both near and distant angle measurements. Among the convergence insufficiency type of patients, 18 (69%) converted to basic type and 2 patients (7%) converted to the pseudodivergence excess type. In the 15 patients who did not undergo surgery, the converted types were maintained in 6 patients, though the other 9 patients showed regression to the prepatching types after cessation of patching for 3 months. Part-time occlusion therapy resulted in the conversion of the basic and convergence insufficiency types to pseudodivergence excess and basic types in more than half of the intermittent exotropes. Future studies on correlation between type conversion and surgical outcome would be necessary.

Effect of concentric or eccentric weight training on the expression of heat shock proteins in m. biceps brachii of very well trained males

Increased HSP expression in response to acute exercise is well documented in animal studies, and there is growing evidence that similar responses occur in man. In general, many human exercise studies have investigated the HSP response to low force continuous activity, while the knowledge about the HSP response to high force intermittent type of activity, like weight training, is so far sparse. In addition, most studies have used untrained subjects, and a common observation is that acute low force continuous activity in untrained individuals increases the HSP expression in these individuals. The main scope of this study was to investigate the HSP response in very well trained males subjected to longitudinal high intensity exercise, and if this response was dependent on exercise modality [i.e. eccentric (ECC) or concentric (CON) contractions]. Very well trained males performed progressive strength training consisting of either high force ECC or high force CON elbow flexions 2-3 times a week for 12 weeks. Compared with pre-exercise levels, HSP72 expression decreased by 46.1% (P<0.05) after CON contractions. GRP75 expression was unchanged after ECC or CON contractions, while ubiquitin expression decreased by 19.9% (P<0.02) after ECC contractions. These findings imply that chronic, intensive exercise may attenuate the HSP response in well-trained males.

Acute changes in muscle activation and leg extension performance after different running exercises in elite long distance runners

This study investigated acute changes in muscle activation and muscular power performance after three different running exercises in elite long-distance runners. Twenty-two nationally and internationally ranked long-distance runners performed first an incremental treadmill running test until exhaustion (MR) and then 40 min continuous (TR) and intermittent (2 min run/2 min rest) (IR) running exercises at an intensity of 80 and 100% of the velocity associated with VO(2max), respectively. Muscle activation and muscular power performance tests (counter-movement jumps, CMJ, and a set of ten maximal half squats from the static starting position with an extra load of 35% of the subjects, one repetition maximum) were performed before and immediately after the runs. The average mechanical power (P) of the half squats was calculated and the root mean square electromyogram (EMGrms) from the vastus lateralis, vastus medialis, gastrocnemius and biceps femoris muscles was recorded simultaneously during the half squat performances. The results showed an acute exercise-induced increase in P (ANOVA time effect, P = 0.000) together with a reduction in EMGrms of the knee extensor muscles (ANOVA time effect, P = 0.000). However, mechanical P expressed as a relative change within the set decreased after MR. In TR the improvement in P correlated positively with the maximal running performance of the runners (P < 0.05), while in IR it correlated negatively (P < 0.05). Jumping performance was significantly enhanced after each run (P < 0.001, for all) and the improvement correlated negatively with the maximal sprinting speed and maximal jumping height of the runners (P < 0.01, for all). It is concluded that in elite long distance runners an intensive prolonged running exercise reduces the surface EMG of the knee extensor muscles, and may lead to a different coordination strategy in leg extension exercises performed into the vertical direction. After continuous type of running the power improvement correlates positively with maximal endurance running capacity, whereas after intermittent type of running it correlates negatively.

Intermittency and fine structure of velocity fluctuations arising in flow-pattern transitions in stirred tanks

The intermittent velocity fluctuations, induced by a change in the vertical location of the impeller, associated with the double- to single-loop transition in stirred vessels are thoroughly analyzed. It is shown that this type of flow-pattern instability is characterized by a multiscale and nested structure of the velocity fluctuations, in which intermittent bursts pertaining to the two regimes are intermingled in a seemingly “self-similar” way. A filtering procedure based on a Markovian approach grounded on the definition of a transfer probability matrix is proposed in order to deconvolute from the original time series the nested intermittent bursts corresponding to local single- and double-loop patterns. This technique permits to define and estimate macroscopic statistical properties, such as the average burst duration in one of the two-regimes, and the frequency that characterizes this type of flow pattern intermittency. A heuristic analysis of the dynamic origin of the flow-pattern transitions in terms of global bifurcations and attractor crisis is addressed.

Impact of riparian buffer guidelines on old growth in western boreal forests of Canada

Summary As timber harvest expands over a previously unharvested landbase, riparian buffers will make up an increasing proportion of old-growth forests. This study examined the impact of different criteria for the formulation of riparian buffers on the temporal supply of old-growth forests in western boreal Canada. Three common criteria were applied through computer simulation over an �∼� 313 000-ha timber merchantable landbase for a 200-year time horizon. Guideline criteria included: (1) broad prescriptive approach, i.e. few-sizes-fi t-all; (2) special management of fi sh-bearing streams; and (3) two-zone, partial harvest buffers. While the numerical results are specifi c to this study area, they suggested fi ve general results applicable to forest planning. (1) Regardless of the criteria for buffers, old growth accumulated over the fi rst 40 – 60 years thereafter it dropped to 2 – 4 per cent of the total landbase after 100 years. (2) Guidelines recognizing fi sh-bearing water bodies retained more old growth, particularly conifer, because of their application to higher elevation and more intermittent stream types. Few-sizes-fi t-all retained the most deciduous and mixed-wood old growth, i.e. low elevation forest types. Two-zone buffers exhibited less temporal variance but an overall lower amount of old growth. (3) Operational and fi eld interpretations of the few-sizes-fi t-all guidelines retained three times more riparian area and three to seven times more old growth than just the planning phase alone. (4) Old-growth mixed-wood forests virtually disappeared from both timber harvest and riparian landbases. (5) The primary location of old growth shifted from the harvest to the riparian landbase.