Efficient energy based modeling and experimental validation of liquid filling in planar micro-fluidic components and networks

This paper presents a model that describes how liquid flow fills micro-fluidic components and networks. As an alternative to computational fluid dynamic (CFD) simulations, we use a constrained energy minimization approach. This approach is based on two assumptions that hold in many micro-fluidic devices: (i) The length scales are small, and we consider slow filling rates, hence fluid momentum and viscous terms are small compared to surface tension forces, consequently the liquid/gas interfaces can be viewed as a succession of quasi-steady equilibrium configurations. (ii) Any equilibrium configuration corresponds to a surface tension energy minima which is constrained by the device shape and the volume of liquid in the device. The model is developed for planar micro-fluidic devices, is based on a fundamental physical principle, and shows accurate agreement with experimental data. It takes us only a few minutes to evaluate the model for a planar component of any shape using the Surface Evolver software, and this is significantly less then the computer run time required for CFD simulations. Moreover, once a library of component models has been created (which takes less than an hour of computer time) it then takes only seconds to simulate different network architectures with thousands of components. This fast "reconfigure the network and simulate in seconds" capability is essential for the design of truly complex networks that will enable the next generation of passive, micro-fluidic, lab-on-a-chip systems.

Identification and quantitation of 11-nor-delta9-tetrahydrocannabivarin-9-carboxylic acid, a major metabolite of delta9-tetrahydrocannabivarin

After incubation of delta9-tetrahydrocannabivarin with human hepatocytes, a major metabolic product was detected by gas chromatography-mass spectrometry that showed identical retention time and mass spectrum to the synthetic 11-nor-delta9-tetrahydrocannabivarin-9-carboxylic acid (11-nor-delta9-THCV-9-COOH). Analysis of human urine specimens from marijuana users and plasma samples from Marinol users showed that 11-nor-delta9-THCV-9-COOH was only present in urine specimens of marijuana users. These results supported the conclusion that identification of 11-nor-delta9-THCV-9-COOH in a donor's urine specimen indicates the use or ingestion of cannabis-related product(s) and would not explain the sole use of Marinol.

An empirical study of nursing in patients undergoing two different procedures for abdominal aortic aneurysm repair

Specialized vascular nursing has to meet the challenge presented through progress and modern developments in vascular surgery. Endovascular techniques are becoming more widespread and are now available for diseases that previously have required extensive surgery. A comparative study was carried out in two groups of patients with infrarenal abdominal aortic aneurysms (N = 50), either by means of the traditional open surgical approach or by the new endovascular stented graft technology. Four problems were compared in both groups of patients: (1) length of hospital stay, (2) dependency on nursing, (3) patients mobility after surgery, and (4) analgesic requirements. Data were obtained from a designated data sheet. Analysis of the data obtained helped us in our service to optimize the nursing process for patients undergoing major aortic surgery for open, as well as endovascular, procedures, especially regarding the nursing anamnesis and nursing diagnosis.

Marijuana-positive urine test results from consumption of hemp seeds in food products

Commercially available snack bars and other foodstuffs prepared from pressed hemp seeds were ingested by volunteers. Urine specimens were collected for 24 h after ingestion of the foodstuffs containing hemp seeds and tested for marijuana using an EMIT immunoassay and gas chromatography-mass spectrometry (GC-MS). Specimens from individuals who ate one hemp seed bar demonstrated little marijuana immunoreactivity, and only one specimen screened positive at a 20-ng/mL cutoff. Specimens from individuals who ate two hemp seed bars showed increased immunoreactivity, and five specimens screened positive at a 20-ng/mL cutoff. A single specimen yielded a quantitative GC-MS value (0.6 ng/mL), but it failed to meet reporting criteria. Several specimens from individuals who ate three cookies made from hemp seed flour and butter screened positive at both 50- and 20-ng/mL cutoffs. Two specimens produced quantitative GC-MS values (0.7 and 3.1 ng/mL), but they failed to meet reporting criteria. Several specimens also tested positive with an FDA-approved on-site marijuana-screening device. Hemp seeds similar to those used in the foodstuffs did not demonstrate the presence of marijuana when tested by GC-MS. In this study, ingestion of hemp seed food products resulted in urine specimens that screened positive for marijuana. No specimens gave a GC-MS quantitative value above the limit of detection for marijuana.