Analytical Modeling of Base Transit Time in SiGe ‐ HBTs Considering Recombination Effects Under Intermediate Injection Levels

Effect of dosing time on the total intestinal transit time of non-disintegrating systems

The current gain of a silicon bipolar transistor has been quantitatively modelled by the Early effect, the conductivity modulation effects in the base and in emitter, the effective base widening effect and the emitter current crowding effect at 77 and 300K involved in the carrier recombination currents in the emitter-base space charge region and in the base. On this basis, the transit times, the total transit time from the emitter to collector and the cutoff frequency are modelled as functions of the collector current at 77 and 300K. The results obtained are in agreement with the experimental data. Besides this, the influence of the maximum base doping concentration on the maximum current gain and the maximum cutoff frequency has been also analysed. The main results show that the current gain is mainly determined by the conductivity modulation effect and the emitter current crowding effect at high injection level at 77K, but at 300K it is mainly determined by the effective base widening effect. The cutoff frequency is mainly determined by the minority-carrier base transit time at 300K, and at 77K the minority-carrier emitter transit time may be dominant for the large bandgap narrowing effect in emitter. The bandgap narrowing effect is the main reason for the degradation of the cutoff frequency with lowering temperature, instead of the low-temperature trapping effect by the compensated impurities with the shallow energy levels.

Colonic transit time in long-term dialysis patients

Gastrointestinal transit times in young and old cats

Transit times through the whole colon and its segments were measured in 10 healthy children and 14 children suffering constipation secondary to myelomeningocele. The subjects ingested radio-opaque markers on three successive days, and on the fourth a plain abdominal roentgenogram was taken using fast film. In the healthy children, total colonic transit time (mean +/- SD) was 37.8 +/- 6.2 h, with segmental times of 10.8 +/- 3.5 h for the right colon, 12.2 +/- 2.7 h for the left, and 14.7 +/- 2.1 h for the rectosigmoid; upper normal limits of 17.8 h for the right colon, 17.6 h for the left, 19.1 h for the rectosigmoid, and 50.2 h for the total colonic transit time were established. In the constipated children, the total transit time was 59.9 +/- 5.4 h, with segmental times of 15.9 +/- 2.3 h for the right colon, 18.9 +/- 2.3 h for the left, and 25.0 +/- 2.6 h for the rectosigmoid. The technique described is simple, is easy to use in clinical practice, and involves a lower radiation dose than other methods. It may prove useful for measurement of colonic transit time in suitable patients.

SummaryTransit times through the whole colon and its segments were measured in 10 healthy children and 14 children suffering constipation secondary to myelomeningocele. The subjects ingested radio‐opaque markers on three successive days, and on the fourth a plain abdominal roentgenogram was taken using fast film. In the healthy children, total colonic transit time (mean ± SD) was 37.8 ± 6.2 h, with segmental times of 10.8 ± 3.5 h for the right colon, 12.2 ± 2.7 h for the left, and 14.7 ± 2.1 h for the rectosigmoid; upper normal limits of 17.8 h for the right colon, 17.6 h for the left, 19.1 h for the rectosigmoid, and 50.2 h for the total colonic transit time were established. In the constipated children, the total transit time was 59.9 ± 5.4 h, with segmental times of 15.9 ± 2.3 h for the right colon, 18.9 ± 2.3 h for the left, and 25.0 ± 2.6 h for the rectosigmoid. The technique described is simple, is easy to use in clinical practice, and involves a lower radiation dose than other methods. It may prove useful for measurement of colonic transit time in suitable patients.

This study aimed to evaluate the variation associated with repeated measurement of gastrointestinal (GI) transit times and the effect of oral ranitidine on GI transit times in healthy dogs using a wireless motility capsule (WMC) system. Eight privately owned healthy adult dogs were enrolled, and one developed diarrhea and was removed from the study. For the first 3 repetitions, each dog was fed a standard meal followed by oral administration of a WMC. For the 4th repetition, each dog was given ranitidine hydrochloride (75 mg PO every 12 hours) prior to and during assessment of GI transit times. Mean between-subject coefficients of variation for gastric emptying time (GET), small and large bowel transit time (SLBTT), and total transit time (TTT) were 26.9%, 32.3%, and 19.6%, respectively. Mean within-subject coefficients of variation for GET, SLBTT, and TTT were 9.3%, 19.6%, and 15.9%, respectively. Median GET, SLBTT, and TTT without ranitidine were 719, 1,636, and 2,735 minutes, respectively. Median GET, SLBTT, and TTT with ranitidine were 757, 1,227, and 2,083 minutes, respectively. No significant differences in GI transit times were found between any of the 4 repetitions. Under these experimental conditions, no significant effects of oral ranitidine on GI transit times were observed.

Although a diet that is rich in fiber is widely recommended for preventing and treating constipation, the efficacy of fiber supplements have not been tested sufficiently in children. Our aim with this pilot study was to evaluate if fiber supplementation is beneficial for the treatment of children with idiopathic chronic constipation. Using a parallel, randomized, double-blind, controlled trial, we conducted an interventional study to evaluate the efficacy of a supplement of cocoa husk rich in dietary fiber on intestinal transit time and other indices of constipation in children with constipation. After screening, the patients were randomly allocated to receive, for a period of 4 weeks, either a cocoa husk supplement or placebo plus standardized toilet training procedures. Before and after 4 weeks of treatment, we (1) performed anthropometry, a physical examination, and routine laboratory measurements, (2) determined total and segmental colonic transit time, (3) evaluated bowel movement habits and stool consistency using a diary, and (4) received a subjective evaluation from the parents regarding the efficacy of the treatment. The main variable for verifying the efficacy of the treatment was the total colonic transit time. Fifty-six chronically constipated children were randomly assigned into the study, but only 48 children completed it. These children, who were aged between 3 and 10 years, had a diagnosis of chronic idiopathic constipation. With respect to total, partial colon, and rectum transit time, there seemed to be a trend, although statistically nonsignificant, toward faster transit times in the cocoa husk group than in the placebo group. When we analyzed the evolution of the intestinal transit time throughout the study of children whose total basal intestinal transit time was > 50th percentile, significant differences were observed between the groups. The total transit time decreased by 45.4 +/- 38.4 hours in the cocoa husk group and by 8.7 +/- 28.9 hours in the placebo group (-38.1 hours). In the case of the right colon, changes in transit time also were significant between groups. Mean changes tended toward faster transit times in the left colon and the rectum, although the differences were not statistically significant. The children who received cocoa husk supplements tended to increase the number of bowel movements by more than that of the children of the placebo group. We also observed a reduction in the percentage of patients who reported hard stools (hard scybalous or pebble-like stools), although this reduction was significantly greater in the cocoa husk group. At the end of the intervention, 41.7% and 75.0% of the patients who received cocoa husk supplementation or placebo, respectively, reported having hard stools. Moreover, a significantly higher number of children (or their parents) reported a subjective improvement in stool consistency. No significant adverse effects were reported during the study. This study confirms the beneficial effect of a supplement of cocoa husk that is rich in dietary fiber on chronic idiopathic constipation in children. These benefits seem to be more evident in pediatric constipated patients with slow colonic transit time.

Small intestinal ileus affects up to half of all horses undergoing small intestinal surgery, leading to prolonged gastrointestinal (GI) transit time which can be life-threatening. Various prokinetic medications have been associated with varying side effects, questionable efficacy, and increased cost. Gum chewing as a form of sham feeding is used as a safe, effective, well-tolerated, and inexpensive way to ameliorate ileus following GI surgery in humans. Bit chewing for horses, an analogous activity, has been shown to significantly decrease GI total transit time (TTT); however, a direct effect of bit chewing on gastric emptying time (GET), small intestinal transit time (SITT), and total orocecal transit time (OCTT) has not been investigated. Our objective was to determine whether bit chewing increased small intestinal motility and decreased GE, SITT, and OCTT in clinically normal horses. Gastrointestinal motility was compared in horses that were bit chewing compared to control conditions (no bit chewing) in a prospective crossover design study using acetaminophen as a marker for GET and video endoscopy (ALICAM) capsules to determine GET, SITT, and OCTT. Bit chewing was well tolerated by all horses with no side effects noted. Bit chewing led to a shorter GET, SITT, and significantly shorter OCTT when compared to the control group (P = 0.015). Median times for bit chewing conditions were as follows: GE 2.86 hr, SITT 3.65 hr, and OCTT 6.15 hr whereas the median times for control conditions were as follows: GE: 5 hr, SITT 4.4 hr, and OCTT 9.92 hr. In summary, bit chewing proves to be a potential tool to hasten the motility of the oral GIT. It is safe, inexpensive, and potentially effective prokinetic treatment to horses suffering from postoperative ileus and further investigation is warranted.

Background and study aim Video capsule endoscopy (VCE) is limited by reliance on bowel motility for propulsion, and lack of physical activity has been proposed as a cause of incomplete studies. Our aim was to prospectively investigate the association between physical activity and VCE bowel transit.Patients and methods Ambulatory outpatients receiving VCE were eligible for the study. A pedometer was attached at the time of VCE ingestion and step count was recorded at the end of the procedure. VCE completion was assessed by logistic regression models, which included step count (500 steps as one unit). Total transit time was analyzed by Cox proportional hazards models. The hazard ratios (HR) with 95 % confidence interval (CI) indicated the “hazard” of completion, such that HRs > 1 indicated a reduced transit time.Results A total of 100 patients were included. VCE was completed in 93 patients (93 %). The median step count was 2782 steps. Step count was not significantly associated with VCE completion (odds ratio 1.45, 95 %CI 0.84, 2.49). Pedometer step count was significantly associated with shorter total, gastric, and small-bowel transit times (HR 1.09, 95 %CI 1.03, 1.16; HR 1.05, 95 %CI 1.00, 1.11; HR 1.07, 95 %CI 1.01, 1.14, respectively). Higher body mass index (BMI) was significantly associated with VCE completion (HR 1.87, 95 %CI 1.18, 2.97) and shorter bowel transit times (HR 1.05, 95 %CI 1.02, 1.08).Conclusions Increased physical activity during outpatient VCE was associated with shorter bowel transit times but not with study completion. In addition, BMI was a previously unreported clinical characteristic associated with VCE completion and should be included as a variable of interest in future studies.

We challenged the two hypotheses: first, that defecation can be suppressed for an extended time, and second, if so, that this has an effect on upper colonic motility. Thus we studied 12 male volunteers with conditions of identical nutrition and patterns of physical activity over a two-week period, where one week with normal defecation and one week with voluntary prolonged suppression of defecation followed each other in randomized order. Frequencies of defecation, stool weights, total and segmental colonic transit times (using radiopaque markers) were compared. Frequency of defecations and stool weights were lower during suppressed defecation [8.9 +/- 0.66 vs 3.7 +/- 0.41 (mean +/- SE) bowel movements per week, P = 0.003, and 1.30 +/- 0.09 vs 0.98 +/- 0.13 kg/week, P = 0.01]. Total transit times were increased from 28.8 +/- 4.4 to 53.1 +/- 4.3 hr, P = 0.004. Segmental transit times were increased in the rectosigmoid (from 8.83 +/- 3.6 to 32.1 +/- 5.6 hr, P = 0.04) and right hemicolon (from 14.5 +/- 0.9 hr to 19.7 +/- 1.5 hr, P = 0.02) by suppression of defecation. We conclude that defecation habits may induce changes in colonic function such as those seen in constipation and that functional anorectal outlet obstruction may, probably by reflex mediation, affect the right colon.

The pathophysiology underlying chronic constipation in older people is poorly understood. Our objective was to determine if functional bowel disease (particularly constipation) in this population is associated with risk factors (age, immobility, low dietary fiber intake, and medication use) or directly with slow colonic transit. A previously validated questionnaire was administered to a random sample of older residents (age range 65-104 years, n = 1609) of Olmsted County, MN. A random subset who met standard diagnostic criteria for functional constipation (n = 52) or irritable bowel syndrome (IBS) (n = 55) and a group without gastrointestinal symptoms (n = 93) were selected for further study. Each subject underwent structured interview and physical examination. Total caloric and fiber intake were assessed by dietitian interview, a food frequency questionnaire, and a food diary. Physical activity was assessed using a previously validated instrument. Medication use was determined by self-report, physician interview, and review of medical records. Total and segmental colonic transit was assessed radiographically using radioopaque markers. Total colonic transit times were prolonged in subjects with functional constipation (median 50.4 hours) but not in subjects with IBS (median 34.2 hours) or in healthy controls (median 28.8 hours); however, only rectosigmoid transit was delayed significantly. Age, gender, physical activity, and dietary fiber intake were not associated with total transit times, nor could they discriminate among the three patient groups. Laxative use was associated with prolonged total transit times independent of patient group. Older subjects can be classified by abdominal pain and bowel symptoms, which reflect colonic transit times. Older subjects with constipation symptoms generally have prolonged rectosigmoid transit. Other potential risk factors do not distinguish symptom subgroups, nor are they associated with altered colonic transit although older people who use laxatives regularly have prolonged colonic transit.

Negligible Effects of Erythromycin On Image Quality and Transit Time of Endoscopic Capsule: A Two-Center Study

To compare the effect of oral erythromycin vs no preparation with prokinetics on the transit time and the image quality of capsule endoscopy (CE) in evaluating small bowel (SB) pathology. We conducted a retrospective, blinded (to the type of preparation) review of 100 CE studies, 50 with no preparation with prokinetics from one medical center (Group A) and 50 from another center with administration of a single dose of 200 mg oral erythromycin 1 h prior to CE (Group B). Gastric, SB and total transit times were calculated, the presence of bile in the duodenum was scored, as was cleanliness within the proximal, middle and distal intestine. The erythromycin group had a slightly shorter gastric transit time (21 min vs 28 min, with no statistical significance). SB transit time was similar for both groups (all P > 0.05). Total transit time was almost identical in both groups. The rate of incomplete examination was 16% for Group A and 10% for Group B (P = 0.37). Bile and cleanliness scores in different parts of the intestine were similar for the two groups (P > 0.05). Preparation for capsule endoscopy with erythromycin does not affect SB or total transit time. It tends to reduce gastric transit time, but it does not increase the cecum-reaching rate. Erythromycin does not adversely affect image quality. We consider the routine use of oral erythromycin preparation as being unjustified, although it might be considered in patients with known prolonged gastric emptying time.

Effect of Erythromycin On Transit Time in Video Capsule Endoscopy: A Randomized Prospective Placebo Controlled Trial