The development of an integrated modelling system to support decisions on organic farms

This paper was presented at the UK Organic Research 2002 Conference of the Colloquium of Organic Researchers (COR). An Integrated Decision Support System (IDSS) is developed which synthesises current understanding of organic farming by means of a multiple objective framework incorporating GIS, biophysical models and socio-economic models of the farming goals. The IDSS uses a multitiered concept of a farming system as a collection of micro-enterprises at the field level, with individual resource endowments, objectives and activities. Farm-level decision drivers trickle down to affect the micro-level field enterprise selection. Biophysical models describe typical forage, cereal, root and legume output and a user-friendly interfaces permits easy access and output display via a GIS. A prototype of the IDSS framework, being developed as a part of the SAC organic research programme is presented

The percutaneous absorption of ionisable compounds

The effects of ionisation on transdermal drug delivery using excised human epidermis (HS) and silastic rubber (SR) as model permeation barriers were investigated in vitro using Franz-type absorption cells. Suspensions and solutions of salicylic acid (SA), the model ionogenic permeant, were used as donors and the variables studied were vehicle pH and trans-membrane pH-gradients. For solutions, the pH effect was related to the level of ionisation of the drug and the degree of saturation of the solution. With suspensions, the observed permeation rate was unaffected by pH. The penetration profiles through HS and SR were similar, although the overall flux through HS was about 70% of that observed through SR. Pretreatment of the membranes with various enhancer regimens, including oleic acid, Azone and N, N-dimethylamides in propylene glycol (PG) and isopropyl myristate (IPM) promoted the penetration of SA. SR was not a suitable model for enhancer pretreatment using IPM as a vehicle as the membrane was significantly disrupted by this vehicle. The results from comparable experiments with and without a trans-membrane pH-gradient did not have a significant effect upon flux or flux enhancement after pretreatment with the above enhancers. A theoretical model for the extraction coefficients of weak acids was derived using the partition coefficients of the ionised and unionised species, pH and pKa. This model was shown to account for the variation in overall partition of salicylic acid dependent upon pH and pKa. This model was shown to account for the variation in overall partition of salicylic acid dependent upon pH and pKa. The distribution of this solute between aqueous and oily phases, with and without added enhancer, was measured as a function of pH. The extraction coefficients determined were consistent with the model and showed that the behaviour of the system can be explained without referral to ion-pair mechanisms. Phosphonoacetate is an effective antiviral agent. However, as it is charged at physiological pH, its permeation across cell membranes is limited. To assess the improvement of the transport properties of this molecule, mono-, di- and tri-ester prodrugs were examined. These were assessed for stability and subsequent breakdown with respect to pH by HPLC. In vitro percutaneous absorption was observed using the triester, but not the ionic mono- or di-esters. The triester absorption could be potentiated using a range of enhancers with oleic acid being the most effective. Cyclodextrins (CD) have a role as absorption enhancers for peptide compounds across nasal epithelium. One potential mode of action is that CDs include these compounds, protect them from enzymic attack and thereby increase their residence time in the nasal epithelium. This study investigated the potential of CDs to protect ester prodrugs from enzymatic breakdown and prevent production of poorly transportable ionic species. Using a range of CD to ester molar ratios (10:1 to 2500:1) a small, but measurable, protection for the model esters (parabens) against esterase attack was observed. Possible mechanisms for this phenomenon are that CDs include the ester, making it unavailable for hydrolysis, the CDs may also affect the esterase in some way preventing access for the ester into the active site

The Effects of the Food Stamp Program on Energy Balance and Obesity

The Effects of the Food Stamp Program on Energy Balance and ObesityFood Stamp Program (FSP), Supplemental Nutrition Assistance Program (SNAP), obesity, body mass index (BMI), nutrition assistance, Food Consumption/Nutrition/Food Safety, Q18, H53, I12, I18, I38,

Quantifying Obesity in Economic Research: How Misleading is the Body Mass Index?

Replaced with revised version of paper 07/19/10.Obesity, percent body fat (PBF), body mass index (BMI), economic costs, measurement error, Health Economics and Policy, Research and Development/Tech Change/Emerging Technologies, C52, I10,

The Effects of the Food Stamp Program on Energy Balance and Obesity

The Food Stamp Program (FSP) administered by the U.S. Department of Agriculture (USDA) is the cornerstone of the U.S. federal income and food safety net policy. The FSP has subsidized the food budget for millions of American households for over forty years, spending more than $60 billion per year in recent times. Prior research has demonstrated that women who participate in the FSP are more likely to be overweight or obese than eligible non-participants. This finding raises the concern that the additional income provided by FSP benefits induces participants to eat significantly more calories and gain weight, contributing to the U.S. obesity epidemic. Previous studies of the FSP have yielded mixed results. In this study we develop new conceptual and empirical models linking FSP participation, calorie consumption, physical activity, and weight gain, while controlling for genetic variation, weight history, and other physiological characteristics of individuals. The models enable us to test whether participants gained more weight, ate more calories, or engaged less in physical activity; or if previously omitted variables and individual health characteristics explain the higher prevalence of obesity among female FSP participants. We find a positive relationship between FSP participation and weight gain for a small subset of women. We do not find convincing evidence for the hypothesis that FSP participation causes obesity by increasing caloric consumption, decreasing physical activity, or some combination of the two. Our findings suggest that a positive association between FSP and weight exists, but we find no evidence of a direct causal link from one to the other. The association between weight and FSP likely results from confounding factors that make individuals more likely both to gain weight and to participate in the FSP.Food Stamp Program (FSP), Supplemental Nutrition Assistance Program (SNAP), obesity, body mass index (BMI), nutrition assistance, Agricultural and Food Policy, Food Consumption/Nutrition/Food Safety, Food Security and Poverty, Health Economics and Policy, Q18, H53, I12, I18, I38,

Group Leaders’ Perceptions of Interventions with Grandparent Caregivers: Content and Process

Nineteen (Mage = 45, SD = 12.8) professionally trained group leaders were surveyed regarding their experiences in leading a 10-week program with one of three RCT conditions (cognitive behavior training, parenting skills training, information only support). While a high percentage indicated that the intervention led by them was beneficial, leaders nevertheless felt that some participants benefited more so than others. Perceived program benefits were seen as being linked to regular attendance and the completion of weekly homework. The major benefits to participants were gaining personal insight, receiving and providing support to others, successfully applying learned skills and knowledge to everyday life, and feeling empowered and hopeful about the future. Peer leaders were viewed positively as was the provision of food and childcare. Group leaders faced numerous practical challenging in conducting group interventions: ensuring regular attendance, keeping participants focused and on track, and dealing with participants who dominated discussion. These unprecedented findings not only allow us insight into the dynamics of leading group interventions with grandmother caregivers, but they may also have implications as influences on the measured efficacy of such programs

Fowler-Nordheim-like local injection of photoelectrons from a silicon tip

Tunneling between a photo-excited p-type silicon tip and a gold surface is studied as a function of tip bias, tip/sample distance and light intensity. In order to extend the range of application of future spin injection experiments, the measurements are carried out under nitrogen gas at room temperature. It is found that while tunneling of valence band electrons is described by a standard process between the semiconductor valence band and the metal, the tunneling of photoelectrons obeys a Fowler-Nordheim-like process directly from the conduction band. In the latter case, the bias dependence of the photocurrent as a function of distance is in agreement with theoretical predictions which include image charge effects. Quantitative analysis of the bias dependence of the dark and photocurrent spectra gives reasonable values for the distance, and for the tip and metal work functions. For small distances image charge effects induce a vanishing of the barrier and the bias dependence of the photocurrent is exponential. In common with many works on field emission, fluctuations in the tunneling currents are observed. These are mainly attributed to changes in the prefactor for the tunneling photocurrent, which we suggest is caused by an electric-field-induced modification of the thickness of the natural oxide layer covering the tip apex.Comment: 12 pages, 11 figures. Submitted to Phys. Rev.

Sulfosuccinate and Sulfocarballylate Surfactants As Charge Control Additives in Nonpolar Solvents

A series of eight sodium sulfonic acid surfactants with differently branched tails (four double-chain sulfosuccinates and four triple-chain sulfocarballylates) were studied as charging agents for sterically stabilized poly­(methyl methacrylate) (PMMA) latexes in dodecane. Tail branching was found to have no significant effect on the electrophoretic mobility of the latexes, but the number of tails was found to influence the electrophoretic mobility. Triple-chain, sulfocarballylate surfactants were found to be more effective. Several possible origins of this observation were explored by comparing sodium dioctylsulfosuccinate (AOT1) and sodium trioctylsulfocarballylate (TC1) using identical approaches: the inverse micelle size, the propensity for ion dissociation, the electrical conductivity, the electrokinetic or ζ potential, and contrast-variation small-angle neutron scattering. The most likely origin of the increased ability of TC1 to charge PMMA latexes is a larger number of inverse micelles. These experiments demonstrate a small molecular variation that can be made to influence the ability of surfactants to charge particles in nonpolar solvents, and modifying molecular structure is a promising approach to developing more effective charging agents

Fixed-dose combination orally disintegrating tablets to treat cardiovascular disease:formulation, in vitro characterization and physiologically based pharmacokinetic modelling to assess bioavailability

Cardiovascular disease (CVD) is the leading cause of death among men and women worldwide. In CVD, hypertension and dyslipidemia commonly coexist and are managed through coadministration of amlodipine and atorvastatin, respectively. The case for fixed-dose combination (FDC) oral dosage forms and orally disintegrating tablet (ODT) technology to enhance outcomes and compliance is strong. This work follows the development and characterization of single and FDC ODTs containing amlodipine and atorvastatin, followed by bioequivalence comparison between these single and FDC formulations, using in vitro dissolution and Caco-2 apparent permeability (Papp) and in silico physiologically based pharmacokinetic modeling approaches. ODTs containing amlodipine (5 mg) and atorvastatin (10 mg) either alone or in combination rapidly disintegrated (<30 s) while displaying a radial crushing strength in excess of 100 N and friability ≤1%. In vitro dissolution test was performed in fasted and fed-state simulated intestinal fluid (FeSSIF) and analyzed using high-performance liquid chromatography. Dissolution profiles for single and FDC ODTs were compared using US FDA recommended difference (f1) and similarity (f2) factor testing for bioequivalence. In all cases, there was no difference in active pharmaceutical ingredient dissolution between single or FDC ODTs, with the exception of amlodipine in FeSSIF. Pharmacokinetic clinical trial simulations were conducted using Simcyp (Version 14), incorporating Papp and dissolution data. Simulated clinical trials in healthy volunteers showed no difference in bioavailability based on pharmacokinetic parameters between single and combination doses with either active pharmaceutical ingredient. An increase in Cmax and AUC for atorvastatin in fed subjects was attributed to extended transit along the gut lumen and reduced atorvastatin metabolism due to lower CYP3A4 expression at more distal small intestine absorption sites. The results demonstrated bioequivalence of an FDC ODT for amlodipine and atorvastatin, while highlighting several limitations of f1 and f2 bioequivalence testing and strengths of mechanistic pharmacokinetic modeling for oral drug absorption

Decreasing Cerebral Oxygen Consumption During Upright Tilt in Vasovagal Syncope

We measured changes in transcranial Doppler ultrasound (TCD) and near infrared spectroscopy (NIRS) during 70 degrees upright tilt in patients with recurrent vasovagal syncope (VVS, N = 20), postural tachycardia syndrome (POTS, N = 20), and healthy controls (N = 12) aged 15-27 years old. VVS was included if they fainted during testing within 5-15 min of upright tilt. We combined TCD and NIRS to obtain estimates of percent change in the cerebral metabolic rate of oxygen consumption (CMRO2), cerebral blood flow velocity (CBFv), and oxygen extraction fraction (OEF). Over the course of 10 min of upright tilt, CBFv decreased from a baseline of 70 +/- 5 to 63 +/- 5 cm/sec in controls and 74 +/- 3 to 64 +/- 3 cm/sec in POTS while decreasing from 74 +/- 4 to 44 +/- 3 cm/sec in VVS CMRO2 was unchanged in POTS and controls during tilt while OEF increased by 19 +/- 3% and 15 +/- 3%, respectively. CMRO2 decreased by 31 +/- 3% in VVS during tilt while OEF only increased by 7 +/- 3%. Oxyhemoglobin decreased by 1.1 +/- 1.3 mumol/kg brain tissue in controls, by 1.1 +/- 1.3 mumol/kg in POTS, and 11.1 +/- 1.3 mumol/kg in VVS CBFv and CMRO2 fell steadily in VVS during upright tilt. The deficit in CMRO2 in VVS results from inadequate OEF in the face of greatly reduced CBF