Evaluation of gastrointestinal transit times and pH in healthy cats using a continuous pH monitoring system

Objectives The aim of this study was to characterize gastrointestinal (GI) transit times and pH in healthy cats. Methods GI transit times and pH were measured in six healthy, colony-housed, purpose-bred spayed female cats using a continuous, non-invasive pH monitoring system in a sequential order design. For the first period (‘pre-feeding’), food was withheld for 20 h, followed by oral administration of a pH capsule. Five hours post-capsule administration, cats were meal-fed by offering them their daily allowance of food for 1 h. For the second period (‘post-feeding’), food was withheld for 24 h and cats were fed for 1 h, after which a pH capsule was orally administered. Studies in both periods were repeated three times. GI transit times and pH were compared between the two periods. Results The median transit times for the pre- and post-feeding periods, respectively, were: gastric –94 mins (range 1–4101) and 1068 mins (range 484–5521); intestinal –1350 mins (range 929–2961) and 1534 mins (range 442–2538); and GI –1732 mins (range 1105–5451) and 2795 mins (range 926–6563). The median GI pH values for the first and second periods, respectively, were: esophageal –7.0 (range 3.5–7.8) and 4.5 (range 2.9–6.4); gastric –2.7 (range 1.7–6.2) and 2.0 (range 1.1–3.3); intestinal –8.2 (range 7.6–8.7) and 7.8 (range 6.7–8.5); first-hour small intestinal –8.2 (range 7.4–8.7) and 8.3 (range 7.9–8.6); and last-hour large intestinal –8.5 (range 7.0–8.9) and 7.8 (range 6.3–8.7). Gastric ( P <0.0020) and intestinal pH ( P <0.0059) were significantly increased in the pre-feeding period compared with the post-feeding period. Conclusions and relevance Gastric and intestinal pH differed significantly when the capsule was administered 5 h prior to feeding compared with 1 h after feeding. Transit times for both periods showed high degrees of intra- and inter-individual variability.

A Study on the Influence of the Chemical Nature of Fillers on Rheological and Fatigue Behavior of Bitumen Emulsion Mastic

Cold Bitumen Emulsion (CBE) mixture technologies have been recently developed to lower pavement construction temperatures to reduce environmental costs and control gas emissions. Due to its poor early mechanical strength, active fillers (i.e., cement) have been used to obtain high early stiffness in order to have the potential for timely construction of the next layer. There is, however, a lack of understanding about the impact of active fillers on the viscoelastic behavior and fatigue damage resistance of CBE mastics. This study, therefore, aims to identify the influence of active fillers on the rheological properties and the resulting fatigue behavior of CBE mastic, supported by chemical analysis for the filler-bitumen emulsion. For this aim, bitumen emulsion was mixed separately with seven fillers/blended fillers to prepare the CBE mastics. Various experiments, including continuous pH monitoring tests (chemical reactivity of filler-bitumen emulsion), Strain Sweep (SS) tests, Temperature-Frequency Sweep (TFS) tests, Time Sweep (TS) tests, and Linear Amplitude Sweep (LAS) tests were conducted on the CBE binder and the prepared mastics. Results show that the rheological performance and the fatigue damage resistance depend not only on the filler inclusions but also on filler type and chemistry. On this basis, the rise in complex shear modulus and the decrease in the viscous component is associated with a significant enhancement in fatigue performance for specific fillers.

A Study on The Influence of Chemical Nature of Fillers on Rheological and Fatigue Behaviour of Bitumen Emulsion Mastic

Recently Cold Bitumen Emulsion (CBE) mixture technologies have been developed to lower the pavement construction temperatures to reduce the environmental costs and control the gas emissions. Due to its poor early mechanical strength, active fillers (i.e. cement) have been used to obtain high early stiffness in order to have the potential for timely construction of the next layer. There is, however, a lack of understanding about the impact of active fillers nature on viscoelastic behaviour and fatigue damage resistance of CBE mastics. This study, therefore, aims to identify the influence of active fillers on the rheological properties and the resulted fatigue behaviour of CBE mastic, supported by chemical analysis for the filler-bitumen emulsion. For this aim, bitumen emulsion was mixed separately with seven fillers/blended fillers to prepare the CBE mastics. Various experiments include continuous pH monitoring tests (chemical reactivity of filler-bitumen emulsion), Strain sweep (SS) tests, Temperature-Frequency Sweep (TFS) tests, Time Sweep (TS) tests, and Linear Amplitude Sweep (LAS) tests were conducted on the CBE binder and the prepared mastics. Results show that the rheological performance and the fatigue damage resistance is not only dependent on the filler inclusions, but it significantly relies on filler type and chemistry. Based on that, the raise in complex shear modulus and the decrease in viscous components were associated with a significant enhancement in fatigue performance for specific filler.

Towards a continuous culture (Rusitec) model of rumen acidosis: effects of buffer concentration, non-protein nitrogen and concentrate level on pH and feed degradation

Rumen acidosis is a problem in many production systems where readily fermentable concentrates are fed. Although acidosis is more common as a subclinical condition that can impair fibre digestion, numerous factors can precipitate the clinical disorder. The objective of the present study was to begin development of a model of acidosis using a rumen simulation technique (Rusitec) and continuous pH monitoring for subsequent evaluation of contributing factors. In the present report the effect of reduced buffer concentration, non-protein nitrogen (NPN) addition and method of NPN provision on pH and feed dry matter disappearance were examined.