Influence of Polyols on the Stability and Kinetic Parameters of Invertase from Candida utilis: Correlation with the Conformational Stability and Activity

Invertase (β-d-fructofuranoside fructohydrolase-E.C. 3.2.1.26) is a sucrose hydrolyzing enzyme found in microbial, plant and animal sources. Invertase from Candida utilis is a dimeric glycoprotein composed of two identical monomer subunits with an apparent molecular mass of 150 kDa. We investigated the mechanism of stabilization of invertase with polyols (glycerol, xylitol, and sorbitol). Activity, thermodynamic and kinetic measurements of invertase were performed as a function of polyol concentration and showed that polyols act as very effective stabilizing agents. The result from the solvent-invertase interaction shows preferential exclusion of the polyols from the protein domain leading to preferential hydration of protein. Apparent thermal denaturation temperature of the protein (T _m ) rose from 75 °C to a maximum of 85 °C in 30% glycerol. The stabilization has been attributed to the preferential hydration of the enzyme.     

Influence of Oil Type on Characteristics of β-Sitosterol and Stearic Acid Based Oleogel

Oleogels were prepared from extra virgin olive oil, corn oil, sunflower oil, and flaxseed oil with a mixture of β-sitosterol and stearic acid (Sit1:SA4, w/w) at concentrations of 15 and 20 g/100 g oil. The prepared oleogels were characterized by different methods to study the influence of oil type on the oleogel properties. The oil type influenced the colour and appearance of the oleogel. The flaxseed oil based oleogel showed lower oil loss and higher firmness than those of other oils based oleogels. The increase of gelator mixture from 15 to 20 g/100 g oil reduced the oil loss and improved the firmness of oleogel samples. The microscopy and small-angle x-ray scattering analyses showed different microstructures and crystallographic reflections for oleogels prepared from different oil types. Also, the oil type and concentration of gelator mixture influenced the melting and crystallization enthalpies of oleogel. Furthermore, different oils based oleogels showed varying values of viscosity, storage modulus (G’), and loss modulus (G”). Therefore, it can be concluded that the oil type and concentration of gelator influence the functional properties of oleogel and the flaxseed oil resulted in oleogel with good properties compared with other oils used in the study.     

Influence of Critical Parameters of Nanosuspension Formulation on the Permeability of a Poorly Soluble Drug through the Skin—A Case Study

In transdermal drug delivery systems, it is always a challenge to achieve stable and prolonged high permeation rates across the skin since the concentrations of the drug dissolved in the matrix have to be high in order to maintain zero order release kinetics. Several attempts have been reported to improve the permeability of poorly soluble drug compounds using supersaturated systems. However, due to thermodynamic challenges, there was a high tendency for the drug to nucleate immediately after formulating or even during storage. The present study focuses on the efficiency of nanoparticles and influence of different concentrations of solubilizer such as vitamin E TPGS (d-a-tocopheryl polyethylene glycol 1000 succinate) to improve the permeation rate through the skin. Effects of several formulation factors were studied on the nanosuspension systems using ibuprofen as a model drug. The overall permeation enhancement process through the skin was influenced mostly by the solubilizer and also by the size of nanoparticles. The gel formulation developed with vitamin E TPGS + HPMC nanosuspension, consequently represent a promising approach aiming to improve the permeability performance of a poorly water soluble drug candidate.KEY WORDS: dermal drug delivery, human skin, nanosuspension, permeation rate, porcine skin, vitamin E TPGS     

Do Biological and Bedsite Characteristics Influence Survival of Neonatal White-Tailed Deer?

Coyotes recently expanded into the eastern U.S. and potentially have caused localized white-tailed deer population declines. Research has focused on quantifying coyote predation on neonates, but little research has addressed the potential influence of bedsite characteristics on survival. In 2011 and 2012, we radiocollared 65 neonates, monitored them intensively for 16 weeks, and assigned mortality causes. We used Program MARK to estimate survival to 16 weeks and included biological covariates (i.e., sex, sibling status [whether or not it had a sibling], birth weight, and Julian date of birth). Survival to 16 weeks was 0.141 (95% CI = 0.075-0.249) and the top model included only sibling status, which indicated survival was lower for neonates that had a sibling. Predation was the leading cause of mortality (35 of 55; 64%) and coyotes were responsible for the majority of depredations (30 of 35; 86%). Additionally, we relocated neonates for the first 10 days of life and measured distance to firebreak, visual obstruction, and plant diversity at bedsites. Survival of predation to 10 days (0.726; 95% CI = 0.586-0.833) was weakly associated with plant diversity at bedsites but not related to visual obstruction. Our results indicate that neonate survival was low and coyote predation was an important source of mortality, which corroborates several recent studies from the region. Additionally, we detected only weak support for bedsite cover as a covariate to neonate survival, which indicates that mitigating effects of coyote predation on neonates may be more complicated than simply managing for increased hiding cover.     

Influence of Guar Gum on the In Vitro Starch Digestibility—Rheological and Microstructural Characteristics

The present study investigates the effect of guar gum on the digestibility of a waxy maize starch in vitro under simulated gastric and intestinal conditions. A detailed rheology and confocal scanning laser microscopy of the digesta were performed in order to study the possible mechanisms of interactions involved during in vitro hydrolysis of starch. No starch hydrolysis was observed under simulated gastric conditions, whereas more than 90% hydrolysis was observed at the end of digestion under simulated intestinal conditions. In the presence of guar gum, the starch hydrolysis was reduced by nearly 25% during the first 10 min and by 15% at the end of in vitro intestinal digestion. The rheological behavior of the digesta was significantly affected in the presence of the gum. The viscosity of digesta decreased during intestinal digestion; however, the extent of decrease was quite low in the presence of guar gum. The consistency index increased and flow behavior index of digesta decreased in the presence of gum after 1 min of intestinal digestion. All the samples (digested or undigested) displayed a pseudoplastic behavior as their apparent viscosity (η _a) decreased with an increase in shear rate. A negative correlation between the starch hydrolysis (%) and storage modulus for the starch sample without gum and a positive correlation for the starch sample with gum were found. Large granule remnants observed through confocal micrographs have shown that the solubilization of starch granule remnants during in vitro digestion is significantly reduced in the presence of gum.     

Development and Evaluation of α-Asarone Transdermal Patches Based on Hot-Melt Pressure-Sensitive Adhesives

A hot-melt, pressure-sensitive adhesive (HMPSA) based on styrene–isoprene–styrene was prepared, and its compatibility with various transdermal penetration enhancers was investigated. The effect of penetration enhancers on the adhesion properties of HMPSA was also studied. A drug-in-adhesive patch was formulated using α-asarone as a model drug, and penetration enhancers were screened by an in vitro transdermal study across excised pig skin. The pharmacokinetics in rabbits was also studied. The results show that HMPSA was miscible with most penetration enhancers (azone, menthol, isopropyl myristate, 1-methyl-pyrrolidinone, N,N-dimethylformamide, oleic acid), apart from propylene glycol. Penetration enhancers had a plasticizer-like effect that decreased the peel strength and shear strength of HMPSA. A combination of 1% oleic acid and 4% menthol had the highest in vitro penetration rate and was selected for patch preparation. The patch formulation was optimized by replacing some of the plasticizer by penetration enhancers to achieve good adhesion and effective transdermal flux. The final patch showed a high efficiency, with a relative bioavailability of 1,494%. This suggests that HMPSA may be a promising material for drug-delivery patches.     

Influence of a Thiophosphate Linkage on the Duplex Stability - Does Sp Configuration Always Lead to Higher Stability Than Rp?

Abstract

ABSTRACT: In order to design an oligodeoxynucleoside phosphorothioate as an antisense molecule, it is important to establish the structure of the S-oligo with a strong affinity to the target RNA. In these molecules, internucleotide thiophosphate linkages produce diastereomers, the number of which increases in proportion to 2ⁿ (n: number of thiophosphate). To estimate the effect of this linkage on the duplex stability by UV melting curves, oligodeoxynucleotides having a single thiophosphate (referred to Soligo), dGCNsN'CG (s: thiophosphate, N, N′ = A or T), were prepared and their diastereomers isolated by HPLC. As demonstrated previously, the melting temperatures (Tm) for the Sp isomers were higher than those of the Rp when DNA was a target. On the other hand, it was found that for RNA as a target, the Rp isomers of dGCTsTCG and dGCAsTCG had higher stability than the Sp, and that the difference in the Tm values between the diastereomers was smaller than when DNA was a target. With dGCsTsACG, which has two thiophosphates, it was also found that the Tm values decreased with an increase in the number of thiophosphate linkages, and that the difference in Tm between the diastereomers was smaller when RNA was a target. Consequently, in practical clinical applications where RNA is a target, the influence of thiophosphate chirality on the duplex structure is almost negligible and Rp/Sp separation of an S-oligo may be of no major concern.     

Biobanking of Fresh-Frozen Human Adenocarcinomatous and Normal Colon Tissues: Which Parameters Influence RNA Quality?

Medical research projects become increasingly dependent on biobanked tissue of high quality because the reliability of gene expression is affected by the quality of extracted RNA. Hence, the present study aimed to determine if clinical, surgical, histological, and molecular parameters influence RNA quality of normal and tumoral frozen colonic tissues. RNA Quality Index (RQI) was evaluated on 241 adenocarcinomas and 115 matched normal frozen colon tissues collected between October 2006 and December 2012. RQI results were compared to patients’ age and sex, tumor site, kind of surgery, anastomosis failure, adenocarcinoma type and grade, tumor cell percentage, necrosis extent, HIF-1α and cleaved caspase-3 immunohistochemistry, and BRAF, KRAS and microsatellites status. The RQI was significantly higher in colon cancer tissue than in matched normal tissue. RQI from left-sided colonic cancers was significantly higher than RQI from right-sided cancers. The RNA quality was not affected by ischemia and storage duration. According to histological control, 7.9% of the samples were unsatisfactory because of inadequate sampling. Biobanked tumoral tissues with RQI ≥5 had lower malignant cells to stromal cells ratio than samples with RQI <5 (p <0.05). Cellularity, necrosis extent and mucinous component did not influence RQI results. Cleaved caspase-3 and HIF-1α immunolabelling were not correlated to RQI. BRAF, KRAS and microsatellites molecular status did not influence RNA quality. Multivariate analysis revealed that the tumor location, the surgical approach (laparoscopy versus open colectomy) and the occurrence of anastomotic leakage were the only parameters influencing significantly RQI results of tumor samples. We failed to identify parameter influencing RQI of normal colon samples. These data suggest that RNA quality of colonic adenocarcinoma biospecimens is determined by clinical and surgical parameters. More attention should be paid during the biobanking procedure of right-sided colon cancer or laparoscopic colectomy specimen. Histological quality control remains essential to control sampling accuracy.     

Influence of Protein – Micelle Ratios and Cysteine Residues on the Kinetic Stability and Unfolding Rates of Human Mitochondrial VDAC-2

Delineating the kinetic and thermodynamic factors which contribute to the stability of transmembrane β-barrels is critical to gain an in-depth understanding of membrane protein behavior. Human mitochondrial voltage-dependent anion channel isoform 2 (hVDAC-2), one of the key anti-apoptotic eukaryotic β-barrel proteins, is of paramount importance, owing to its indispensable role in cell survival. We demonstrate here that the stability of hVDAC-2 bears a strong kinetic contribution that is dependent on the absolute micellar concentration used for barrel folding. The refolding efficiency and ensuing stability is sensitive to the lipid-to-protein (LPR) ratio, and displays a non-linear relationship, with both low and high micellar amounts being detrimental to hVDAC-2 structure. Unfolding and aggregation process are sequential events and show strong temperature dependence. We demonstrate that an optimal lipid-to-protein ratio of 2600∶1 – 13000∶1 offers the highest protection against thermal denaturation. Activation energies derived only for lower LPRs are ∼17 kcal mol⁻¹ for full-length hVDAC-2 and ∼23 kcal mol⁻¹ for the Cys-less mutant, suggesting that the nine cysteine residues of hVDAC-2 impart additional malleability to the barrel scaffold. Our studies reveal that cysteine residues play a key role in the kinetic stability of the protein, determine barrel rigidity and thereby give rise to strong micellar association of hVDAC-2. Non-linearity of the Arrhenius plot at high LPRs coupled with observation of protein aggregation upon thermal denaturation indicates that contributions from both kinetic and thermodynamic components stabilize the 19-stranded β-barrel. Lipid-protein interaction and the linked kinetic contribution to free energy of the folded protein are together expected to play a key role in hVDAC-2 recycling and the functional switch at the onset of apoptosis.     

Effect of pH and Glucose on the Stability of α-lactalbumin

The objective of this study is to understand the influence of pH and effect of cosolvent (glucose) on the stabilization of bovine α-lactalbumin by using ultrasonic techniques. Values of density, ultrasonic velocity and viscosity were measured for bovine α-lactalbumin (5 mg/ml) dissolved in phosphate buffer (pH 2, 5, 7, 9 and 12) solutions mixed with and without the cosolvent at 30 °C. These measurements were used to calculate few thermo-acoustical parameters such as adiabatic compressibility, intermolecular free length, acoustic impedance, relaxation time, relative association constant, the partial apparent specific volume and the partial apparent specific adiabatic compressibility for the said systems. The obtained results revealed a strong comparison between the effects of acidic and alkaline pH values on protein denaturation, i.e., the acidic pH are instantaneous and are of less magnitude whereas alkaline pH are slower but sharper. Further the present study supports the fact that the presence of glucose stabilizes α-lactalbumin against denaturation due to pH variation, which may be due to the strengthening of non-covalent interactions and the steric exclusion effect.     

Encapsulation of β-carotene in Nanoemulsion-Based Delivery Systems Formed by Spontaneous Emulsification: Influence of Lipid Composition on Stability and Bioaccessibility

Nanoemulsion-based delivery systems are finding increasing use in food, pharmaceutical, agrochemical, and personal care applications due to their ability to increase the stability and/or activity of lipophilic functional components. In this study, a low-energy homogenization method (spontaneous emulsification) was used to encapsulate β-carotene in nanoemulsions. The main objective was to optimize lipid phase composition to form stable nanoemulsions that would effectively enhance β-carotene bioavailability. Lipid phase composition was varied by mixing long chain triglycerides (LCT) with medium chain triglycerides (MCT) or flavor oil (orange oil). LCT was added to promote bioaccessibility, whereas MCT or orange oil was added to facilitate nanoemulsion formation. Our hypothesis was that an optimum level of LCT is required to form stable nanoemulsions with good bioaccessibility characteristics. Stable nanoemulsions could be formed at LCT-to-orange oil ratios of 1:1 (d ₃₂ = 109 nm) and at LCT-to-MCT ratios of 1:2 (d ₃₂ = 145 nm). Thus, higher LCT loading capacities and smaller droplet sizes could be obtained using orange oil. The influence of oil composition on the potential gastrointestinal fate of the nanoemulsions was studied using a simulated gastrointestinal tract (GIT) consisting of mouth, stomach, and small intestine phases. The transformation and bioaccessibility of β-carotene in the GIT was highly dependent on lipid phase composition. In particular, β-carotene bioaccessibility increased with increasing LCT level due to greater solubilization in mixed micelles. These results are useful for optimizing the design of nanoemulsion-based delivery systems for encapsulation and release of lipophilic nutraceuticals and pharmaceuticals.     

Influence of ε-caprolactam on growth and physiology of environmental bacteria

ε-Caprolactam was found to have an effect on ecologically important soil bacteria. It inhibited the growth of several Bacillus sp. and Rhizobium sp. but cells of Arthrobacter sp. were able to grow in the presence of caprolactam. Sphingomonas sp. lost its inherent capacity to produce extracellular polymer (EPS) if grown in medium containing caprolactam. In the case of raw domestic sewage, the diversity of native bacteria was diminished in presence of caprolactam. Polluted sea water yielded predominantly one type of caprolactam-degrading bacteria of the genus Achromobacter. These cells efficiently utilized up to 10 g caprolactam/L as the sole source of carbon and nitrogen in synthetic medium even in the presence of 20 g NaCl/L. Compared to cells of Arthrobacter sp., cells of Achromobacter sp. accumulated high amount of 6-aminocaproic acid due to degradation of caprolactam. When using caprolactam as sole source of carbon and nitrogen, Achromobacter cells showed unique physiological ability to produce EPS upon prolonged incubation in solid medium and in broth with low phosphate (C:N:P ratio 100:20:0.05). Hydrolyzed cell-free EPS had glucose as its major component though the only substrate provided in the medium for growth was caprolactam.     

Influence of Peroxide Impurities in Povidone on the Stability of Selected β-Blockers with the Help of HPLC

A present study was conducted to investigate compatibility of β-blocker drugs( like atenolol, labetalol hydrochloride, bisoprolol fumarate, metoprolol succinate, carvedilol and propranolol hydrochloride) with the pharmaceutical excipient povidone. To check the influence of peroxide impurity present in povidone on the stability of β-blockers, a binary mixture technique has been adopted. The binary mixtures (1:1) of β-blockers with povidone excipient were stored for the duration of 6 months at accelerated conditions (40°C and 75% RH) and analyzed with the technique of high-performance liquid chromatography (HPLC). On analysis, HPLC results shows that, the percentage of total impurity for atenolol—2.15%, bisoprolol fumarate—3.55%, carvedilol—2.19%, and labetalol hydrochloride—1.89%, with respect to povidone. To verify the interaction of H₂O₂ present in povidone as an impurity, oxidative degradation of selected active pharmaceutical ingredients were performed and degradation profile were compared with that of degradation impurities generated in drug-excipient mixture at accelerated conditions. The relative retention time (RRT) of impurities generated in accelerated stability study samples resembles the RRT of degradation products generated by oxidative degradation of pure drugs. Thus, it confirms that degradation of β-blockers with povidone was mediated by organic peroxides present as an impurity in povidone.     

Characteristics and effects of specific peptides on heat-induced aggregation of β-lactoglobulin

A bovine β-lactoglobulin hydrolysate, obtained by the hydrolysis by the Glu specific enzyme Bacillus licheniformis protease (BLP), was fractionated at pH 7.0 into a soluble and an insoluble fraction and characterized by LC-MS. From the 26 peptides identified in the soluble fraction, five peptides (A[f97-112] = [f115-128], AB[f1-45], AB[f135-157], AB[f135-158], and AB[f138-162]) bound to β-lactoglobulin at room temperature. After heating of β-lactoglobulin in the presence of peptides, eight peptides were identified in the pellet formed, three of them belonging to the previously mentioned peptides. Principle component analysis revealed that the binding at room temperature (to β-lactoglobulin) was related to the total hydrophobicity and the total charge of the peptides. The binding to the unfolded protein could not be attributed to distinct properties of the peptides. The presence of the peptides caused a 50% decrease in denaturation enthalpy (from 148 ± 3 kJ/mol for the protein alone to 74 ± 2 kJ/mol in the presence of peptides), while no change in secondary structure or denaturation temperature was observed. At temperatures <85 °C, the addition of peptides resulted in a 30-40% increase of precipitated β-lactoglobulin. At pH < 6, no differences in the amount of aggregated β-lactoglobulin were observed, which indicates the lack of binding of peptides to β-lactoglobulin at those pH values as was also observed by SELDI-TOF-MS. Although only a few peptides were found to participate in aggregation, suggesting specificity, principal component analysis was unable to identify specific properties responsible for this.     

Enhanced Solubility and Dissolution Rate of Lacidipine Nanosuspension: Formulation Via Antisolvent Sonoprecipitation Technique and Optimization Using Box–Behnken Design

Lacidipine (LCDP) is a highly lipophilic calcium channel blocker of poor aqueous solubility leading to poor oral absorption. This study aims to prepare and optimize LCDP nanosuspensions using antisolvent sonoprecipitation technique to enhance the solubility and dissolution of LCDP. A three-factor, three-level Box–Behnken design was employed to optimize the formulation variables to obtain LCDP nanosuspension of small and uniform particle size. Formulation variables were as follows: stabilizer to drug ratio (A), sodium deoxycholate percentage (B), and sonication time (C). LCDP nanosuspensions were assessed for particle size, zeta potential, and polydispersity index. The formula with the highest desirability (0.969) was chosen as the optimized formula. The values of the formulation variables (A, B, and C) in the optimized nanosuspension were 1.5, 100%, and 8 min, respectively. Optimal LCDP nanosuspension had particle size (PS) of 273.21 nm, zeta potential (ZP) of ?32.68 mV and polydispersity index (PDI) of 0.098. LCDP nanosuspension was characterized using x-ray powder diffraction, differential scanning calorimetry, and transmission electron microscopy. LCDP nanosuspension showed saturation solubility 70 times that of raw LCDP in addition to significantly enhanced dissolution rate due to particle size reduction and decreased crystallinity. These results suggest that the optimized LCDP nanosuspension could be promising to improve oral absorption of LCDP.     

The Influence of Plant Diversity and Functional Composition on Ecosystem Stability of Four StipaCommunities in the Inner Mongolia Plateau

The main purpose of this study was to examine the effects of plant species diversity and functional composition (the identity of the plant functional groups) on ecosystem stability of Stipa communities in the Inner Mongolia Plateau. The research work was based on a 12-year study (from 1984 to 1995) of species abundance, diversity, and primary productivity of four Stipa communities, i.e. S. baicalensis Roshev., S. grandis P. Smirn., S. krylovii Roshev., and S. klemenzii Roshev. respectively. The Shnnon-Wiener index was used as a measurement of plant diversity, while functional composition was used to differentiate the functional groups that were included in the communities. The plant species of four Stipa communities were classified into functional groups based on the differences in life forms and ecological groups, which influence their performance in resource requirements, seasonality of growth, tolerance to water stress, and life history. Plant species were classified into five functional groups based on their differences in life form, shrubs and half shrubs, perennial bunch grasses, perennial rhizome grasses, forbs, annuals and biennials. Based on their differences in water requirement these species were classified into four functional groups: xerads, intermediate xerads, intermediate mesophytes, and mesophytes. The results showed: 1) Plant species diversity stabilized ecosystem processes. Shannon-Wiener index were 2.4014, 2.1720, 1.6248, 0.3543 from S. baicalensis community to S. grandis, S. krylovii and S. klemenzii community, respectively. The dynamics of the aboveground net primary productivity (ANPP) for a 12-year's period showed a reverse pattern, the coefficients of variation of the four communities were 21.94%, 20.63%, 29.21% and 39.72% respectively. 2) The life form functional group component of diversity was a greater determinant of the ecosystem processes than the species component of diversity. The effects of perennial bunch grasses, perennial rhizome grasses and forbs on community stability were highly significant. 3) The ecological group component of diversity was also a great determinant of the ecosystem processes. The effects of xerads, intermediate xerads, and mesophytes on community stability were also very strong.     

Influence of edge on predator–prey distribution and abundance

I investigated the effect of spatial configuration on distribution and abundance of invertebrate trophic groups by counting soil arthropods under boxes (21 × 9.5 cm) arranged in six different patterns that varied in the amount of edge (137–305 cm). I predicted fewer individuals from the consumer trophic group (Collembola) in box groups with greater amount of edge. This prediction was based on the assumption that predators (mites, ants, spiders, centipedes) select edge during foraging and thereby reduce abundance of the less mobile consumer group under box patterns with greater edge. Consumer abundance (Collembola) was not correlated with amount of edge. Among the predator groups, mite, ant and centipede abundance related to the amount of edge of box groups. However, in contrast to predictions, abundance of these predators was negatively correlated with amount of edge in box patterns. All Collembola predators, with the exception of ants, were less clumped in distribution than Collembola. The results are inconsistent with the view that predators used box edges to predate the less mobile consumer trophic group. Alternative explanations for the spatial patterns other than predator–prey relations include (1) a negative relationship between edge and moisture, (2) a positive relationship between edge and detritus decomposition (i.e. mycelium as food for the consumer group), and (3) a negative relationship between edge and the interstices between adjacent boxes. Landscape patterns likely affect microclimate, food, and predator–prey relations and, therefore, future experimental designs need to control these factors individually to distinguish among alternative hypotheses.     

Influence of proline and β-turn mimetics on the cyclization of penta- and hexapeptides

Summary Proline and Pro-derived peptidomimetics, such as meoxPro-Oic (4-methoxy-proline-octahydro indolic acid), and DBF (2-aminoethyl-6-dibenzofuran propionic acid) were introduced into thymopentin-derived penta-[SP5-] and hexa-[SP6-] peptides and penta-, hexa- and hepta-alanine. Surprisingly, we found that cyclomonomer formation in the investigated penta- and hexapeptides was drastically hindered by the presence of proline regardless of position.     

Nitrogen Transport and Retention in an Arid Land Watershed: Influence of Storm Characteristics on Terrestrial–aquatic Linkages

Arid ecosystems experience prolonged dry periods, as well as storms that vary in size, intensity and frequency. As a result, nitrogen (N) retention and export patterns may be a function of individual storm characteristics. Our objective was to determine how seasonal patterns in rainfall as well as individual storm characteristics influence N transport and retention on terrestrial hill slopes in a Sonoran Desert watershed. Regression models indicated that variation in runoff ammonium (NH₄⁺) was best explained by antecedent conditions (cumulative seasonal rainfall, days since last storm) while variation in runoff nitrate (NO₃⁻) was best explained by single storm characteristics, primarily rain NO₃⁻. Increases in runoff NO₃⁻ along overland surface flowpaths were balanced by decreases in NH₄⁺ during summer, with no change in dissolved inorganic nitrogen (DIN) concentration; a pattern consistent with nitrification. Nitrate increases along flowpaths were not as strong during winter storms. Results indicate that NH₄⁺ is transported from hillslopes to other parts of the catchment, including streams, and that nitrification occurs along surface flowpaths, particularly during summer storms. These findings suggest that the extent to which a receiving patch is supplied with NH₄⁺ or NO₃⁻ depends on the distance runoff has traveled (flowpath length) and the length of the antecedent dry period. The extent and configuration of fluvial reconnection amongst patches in the landscape following long drought periods likely determines the fate of available N, whether N is processed and retained in the terrestrial or in the aquatic component of the watershed, and the mechanisms involved. The nature of this fluvial reconnection is driven by the size, intensity and sequence of storms in space and time.     

Influence of Flexibility and Variability of Working Hours on Health and Well‐Being

Flexible working hours can have several meanings and can be arranged in a number of ways to suit the worker and/or employer. Two aspects of “flexible” arrangement of working hours were considered: one more subjected to company control and decision (variability) and one more connected to individual discretion and autonomy (flexibility). The aim of the study was to analyze these two dimensions in relation to health and well‐being, taking into consideration the interaction with some relevant background variables related to demographics plus working and social conditions. The dataset of the Third European Survey on working conditions, conducted in 2000 and involving 21,505 workers, was used. Nineteen health disorders and four psycho‐social conditions were tested by means of multiple logistic regression analysis, in which mutually adjusted odds ratios were calculated for age, gender, marital status, number of children, occupation, mode of employment, shift work, night work, time pressure, mental and physical workload, job satisfaction, and participation in work organization. The flexibility and variability of working hours appeared inversely related to health and psycho‐social well‐being: the most favorable effects were associated with higher flexibility and lower variability. The analysis of the interactions with the twelve intervening variables showed that physical work, age, and flexibility are the three most important factors affecting health and well‐being. Flexibility resulted as the most important factor to influence work satisfaction; the second to affect family and social commitment and the ability to do the same job when 60 years old, as well as trauma, overall fatigue, irritability, and headache; and the third to influence heart disease, stomachache, anxiety, injury, and the feeling that health being at risk because of work. Variability was the third most important factor influencing family and social commitments. Moreover, shift and night work confirmed to have a significant influence on sleep, digestive and cardiovascular troubles, as well and health and safety at work. Time pressure also showed a relevant influence, both on individual stress and social life. Therefore, suitable arrangements of flexible working time, aimed at supporting workers' coping strategies, appear to have a clear beneficial effect on worker health and well‐being, with positive consequences also at the company and social level, as evidenced by the higher “feeling to be able to work until 60 years of age”.