Open Bags Research Articles

Eksplorasi Mikroflora Alami Cairan Nepenthes mirabilis (Lour) Druce di Kawasan Hutan Penelitian dan Pendidikan Biologi Universitas Andalas

Indonesia is a country that is rich in flora and fauna diversity, one of the unique flora in Indonesia is Nepenthes. This bag serves to trap insects or other small animals, the Biology Education and Research Forest (HPPB) is located in the Andalas Limau Manis University campus area which is classified as lowland tropical rain forest which is the habitat of Nepenthes, in the Biology Education and Research Forest (HPPB) this type of pitcher plant, namely Nepenthes mirabilis. Nepenthes mirabilis is a plant that is able to digest insects trapped in pockets at the ends of its leaf tendrils, so it is classified as a carnivorous plant. Microorganisms play an important role in breaking down organic materials into inorganic ones available to plants. Types of bacteria and bacterial populations greatly determine the decomposition process of animals that have been trapped in the bag as a source of nutrients for Nepenthes plants. This study aims to explore the natural microflora of Nepenthes mirabilis fluids, determine the proportional presence of potential bacteria, and determine the in vitro potential of chitinolytic bacteria from Nepenthes mirabilis fluids. This study used a survey method which was analyzed descriptively. The results showed that Nepenthes mirabilis fluid contained the presence of Fermentative, Amylolytic, Proteolytic, Chitinolytic and Lipolitical bacteria. Nepenthes mirabilis liquid in open bags contained chitinolytic bacteria, the highest presence of chitinolytic bacteria was found in MBB samples (20,104 cfu/ml) and MBA samples (18,104 cfu/ml). .28), fermentative (2.33 and 2.00), amylolytic (1.42 and 1.28), proteolytic (2.00 and 2.00), lipolytic (1.75 and 1.28).

Comparative study on oyster mushroom grown on composited substrate: The effect on yield, growing period and fruiting body size

Cultivation of the oyster mushroom on horse manure and wheat straw compost without nutrient supplementation was investigated. The growing, yield and fruiting body size effects on open trays and substrate bags were determined. Incubation and fruiting period on trays and inoculated bags were compared. The bagged compost yielded higher mushroom growth rate and yield than the tray compost. The fruiting bodies of the mushroom on trays were smaller, pile and thinner as compared to the mushrooms on the bags, which were bigger, fresh and strong. However, it was found that when oyster mushroom are grown on trays, the yield decrease, there is less moisture in the tray and substrate is exposed to heat, the pin head dries as they develop and those that succeed to grown further will grow as thin with a little head due to lack of oxygen. Comparing compost in bags with compost substrate in trays, bags yielded about 20% more mushrooms than trays under the same cultivation conditions. Conversely, the incubation period of compost in bags took longer, as compared to the incubation of compost in trays. Trays gave their first flash 10% earlier than the bags.

Quality determinates of rice price in open bag markets in Sub-Saharan Africa

PurposeWeaknesses in the grades and standards system in low-income countries across Sub-Saharan Africa undermine the transparency of agricultural markets. In the Democratic Republic of the Congo (DRC), Ghana and Mozambique rice is predominately sold in open bags and if rice price does not reflect its quality, then inefficiencies may lead to consumer welfare losses. Importantly, it is possible that impoverished communities are priced out of the market due to inflated and inefficient prices. The objective of this study is to examine determinates of rice price by estimating the impact of selected rice quality attributes on rice prices in Democratic Republic of the Congo, Ghana and Mozambique.Design/methodology/approachWe collected 363 rice samples from open air markets in Bukavu (DRC), Nampula (Mozambique) and across Ghana in 2019. Each rice sample was analyzed in a food science lab for the quality attributes: percentage of chalk and brokens, chalk impact, length and length-to-width ratio. We used multiple regression analysis to estimate if and to what extent quality attributes were the drivers of price.FindingsFindings suggest that there are irregularities in the Ghanaian market for broken rice and that regardless of quality, imported rice is priced higher than domestic rice. In the DRC and Mozambique, our results indicate price is driven by length and length-to-width ratio in the former and length-to-width ratio in the latter.Research limitations/implicationsRice samples were purchased from market vendors and thus consumer preferences for attributes were not revealed.Originality/valueThese results provide valuable insight to policymakers regarding the need for proper labeling and regulation of open bag rice sales in an effort to increase consumer welfare and improve food security.

Effect of Packaging on the Stability of Stored Dry Silver Cyprinid (Rastrineobola argentea)

Dried silver cyprinid (Rastrineobola argentea) has the potential to provide an affordable and accessible food-based strategy to fight malnutrition among Ugandans and enrich diets of the vulnerable persons. However, there is inadequate information on changes in the nutritional content and safety of stored dry silver cyprinid along the local handling chain. This study evaluated the effect of conventionally used packaging on microbial safety and nutrient quality of dry silver cyprinid during storage. Freshly dried silver cyprinid was obtained from stores at four landing sites on Lake Victoria and stored in open and closed gunny bags for 8 weeks. Samples were collected at 0, 1, 2, 4, 6 and 8 weeks of storage and assessed for nutritional and microbial quality. The type of packaging used (open or closed gunny bags) had no significant effect on most nutrient content and microbial safety parameters (p >0.05) except iron content, aflatoxin content, and TVBN content. Open gunny bags had higher aflatoxin content, greater iron degradation and greater variation in TVBN as compared to closed gunny bags throughout the storage duration. The observed difference in some of the quality parameters can be attributed to increased permeability to oxygen and moisture in open gunny bags as compared to closed gunny bags.

Evaluation of quality, phenolic and carotenoid composition of fresh-cut purple Polignano carrots stored in modified atmosphere

Purple Polignano carrot is a traditional Italian landrace cultivated in Apulia region rich in antioxidants and with a high nutritional value. On the other hand, these carrots showed a high perishability. The postharvest behaviour of fresh-cut purple Polignano carrots stored in open bags (AIR) or passive modified atmosphere (pMA) was studied, analysing the main qualitative parameters and the polyphenols and carotenoids profile. The storage in pMA allowed to preserve visual quality and respiration rate better than the storage in AIR. Polyphenols (hydroxycinnamic acids, their derivatives and anthocyanins) increased during storage of about 249 % in samples stored in pMA and of about 306 % in those stored in AIR at 4 °C during the first 4 days of storage, respect to fresh carrots. Instead, carotenoids mean content in carrots just after harvest (6.28 ± 0.48 mg kg-1 fw) did not change significantly during storage at 4 °C (both in AIR or pMA). According to our results, pMA resulted a valid solution to cold store fresh-cut purple Polignano carrots until two weeks, preserving quality and nutritional value.

Recovery of decomposition rates and decomposer invertebrates during rain forest restoration on disused pasture

AbstractConverting forest to pasture can alter the roles of biota in ecosystem functioning, while vegetation restoration should arguably assist functional recovery. Since tests of this are scarce, this study quantifies both litter decomposition rates and their association with decomposer invertebrates, across 25 sites representing different phases of deforestation and subsequent reforestation of rain forest. Open and closed (to exclude macro‐invertebrates) mesh bags containing forest leaves were exposed in the field for up to eight months, and invertebrates were extracted from separate collections of ground surface litter. Sites spanned five vegetation categories (five sites in each): reference states of both old‐growth forest and grazed pasture; unassisted woody regrowth aged 20–50 years on former pasture; and assisted regeneration aged 1–3 and 5–10 years after interventions were applied to similar regrowth. Decomposition rates in open bags were about 50% slower in pasture than old‐growth forest, and abundances of macro‐ and meso‐decomposer invertebrates were 95% and 77% lower, respectively. However, in all restoration site‐types, decomposition rates had recovered to 83% of old‐growth values, and abundances of invertebrate decomposers were similar in old‐growth forest. Decomposer community composition at a broad taxonomic level differed strongly between pasture and all other vegetation types. Exclusion of macro‐invertebrates decreased decomposition rates by only about 3.1%, but decomposition rates in open bags were significantly correlated (across sites) with abundances of both macro‐ and meso‐decomposers, most strongly so for meso‐decomposers. Drawing useful generalizations across studies is impeded by differing methodologies and because few include both agricultural and forest reference sites.

Ozone Gas Antifungal Effect on Extruded Dog Food Contaminated with Aspergillus flavus

ABSTRACTDecontamination of Aspergillus flavus spores in inoculated extruded food (Standard and Super-Premium types), through ozone (O3) gas, was investigated at different concentrations (40 and 60 µmol/mol) and times (30, 60, and 120 min) of exposure. The gas antifungal efficiency, humidity, and lipid stability were evaluated before and after treatments. O3 reduced A. flavus spores of the extruded food, on both types (p < 0.05). The highest reduction (98.3%) was observed for both food types, when gas was applied for 120 min, regardless of the O3 concentration. Regarding humidity and peroxide index, there was no difference, either prior to or after the gas application for all treatments conditions. O3 gas can be an efficient method for fungi spores’ contamination control during commercialization of extruded food in open bags exposed to the environment.

Influence of 1-MCP and modified atmosphere packaging in the quality and preservation of fresh basil

A study was conducted to assess the individual and combined effect of 1-methylcyclopropene (1-MCP) and modified atmospheres packaging (MAP) in preserving basil (Ocimum basilicum L.) leaves. Fresh samples were stored at 11°C and 85% RH, by packing them in sealed LDPE bags and in open macro-perforated LDPE bags with and without previous exposition to 1-MCP. Preliminary evaluations were performed to define a suitable 1-MCP dose in solution and exposure time being these, 0.3cm3m−3 and 24h, respectively, and to preconfigure the MAP system with satisfactory gas levels, obtaining steady concentrations inside the packaging of ca. 10.5% of O2 and 4.2% of CO2. The combined treatment of MAP and 1-MCP increased the storage life of the basil leaves up to 18days, compared to 9days in the control samples (stored at 11°C in open bags without 1-MCP exposure), delaying changes in the evaluated quality properties.

Prevalence of diarrhoea and risk factors among children under five years old in Mbour, Senegal: a cross-sectional study

BackgroundDiarrhoeal diseases remain an important cause of mortality and morbidity among children, particularly in low- and middle-income countries. In Senegal, diarrhoea is responsible for 15% of all deaths in children under the age of five and is the third leading cause of childhood deaths. For targeted planning and implementation of prevention strategies, a context-specific understanding of the determinants of diarrhoeal diseases is needed. The aim of this study was to identify risk factors of diarrhoeal diseases in children under the age of five in Mbour, Senegal.MethodsBetween February and March 2014, a cross-sectional survey was conducted in four zones of Mbour to estimate the burden of diarrhoeal diseases (i.e. diarrhoea episodes in the 2 weeks preceding the survey) and associated risk factors. The zones covered urban central, peri-central, north peripheral and south peripheral areas. Overall, 596 households were surveyed by a questionnaire, yielding information on sociodemographic, environmental and hygiene behavioural factors. Univariable and multivariable logistic regression analyses were used to identify risk factors associated with the occurrence of diarrhoea.ResultsThe reported prevalence of diarrhoea among children under the age of five during the 2 weeks preceding the survey was 26%. Without adjustment, the highest diarrhoea prevalence rates were observed in the peri-central (44.8%) and urban central zones (36.3%). Multivariable regression revealed significant associations between diarrhoeal diseases and unemployment of mothers (adjusted odds ratio [aOR] = 1.62, 95% confidence interval [CI]: 1.18–2.23), use of open bags for storing household waste (aOR = 1.75, 95% CI: 1.00–3.02), evacuation of household waste in public streets (aOR = 2.07, 95% CI: 1.20–3.55), no treatment of stored drinking water (aOR = 1.69, 95% CI: 1.11–2.56) and use of shared toilets (aOR = 1.69, 95% CI: 1.11–2.56).ConclusionWe found a high prevalence of diarrhoea in children under the age of five in Mbour, with the highest prevalence occurring in the central and peri-central areas. These findings underscore the need for public health interventions to alleviate the burden of diarrhoea among vulnerable groups. Promotion of solid waste disposal and reduction of wastewater exposure should be implemented without delay.

Influence of lipid content and packaging methods on the quality of dried capelin (Mallotus villosus) during storage.

Capelin annual catch exceeds half a million tons in Iceland, with only a small quantity (<20%) of female with roe used for human food. There is a potential to use dried male capelin as a new product for human consumption, but its lipid content varies considerably (4-20% body weight). Earlier studies were more concentrated on the influence of drying conditions than the influence of storage conditions on the quality of dried fish, as dried fish are usually considered to be stable and safe during storage. Three batches of dried male capelin differing in lipid content were packaged and studied during 5months storage at 22±2°C to establish appropriate lipid content at harvesting and product packaging method. Lipid composition, lipid hydrolysis and oxidation, sensory attributes and microbial activity were evaluated. Batches differed in composition and stability, with low lipid capelin constituting higher proportion of polyunsaturated fatty acids (22% lipid) than high lipid (18% lipid) capelin. Lipid oxidation was influenced by lipid content and packaging method, as accelerated oxidation occurred in high lipid and open packed capelin. Lipid hydrolysis was less influenced by packaging and was greater in low lipid capelin. High lipid capelin in open bags scored the highest for rancid odor. All batches were micro-biologically stable with colony-forming unit counts increasing less than log 1 (log 5-6) during 5months storage.

Impact of opening hermetic storage bags on grain quality, fungal growth and aflatoxin accumulation

Purdue Improved Crop Storage (PICS) bags are used by farmers in Sub-Saharan Africa for pest management of stored grains and products, including maize. These bags hermetically seal the products, preventing exchange with external moisture and gases. Biological respiration within the bags create an environment that is unsuitable for insect development and fungal growth. This study was conducted to determine the impact of routine opening of the storage bags for maize consumption on fungal growth and aflatoxin contamination. Maize with moisture contents (MC) high enough to support fungal growth (15%, 16%, 18% and 20%) was stored in PICS bags, which were opened weekly and exposed to humid conditions (85% RH) for 30 min over a period of 8 weeks and 24 weeks. Monitors indicated that oxygen defused into the open bags but did not reach equilibrium with the bottom layers of grain during the 30-min exposure period. Fungal colony forming units obtained from the grain surface increased 3-fold (at 15% MC) to 10,000-fold (at 20% MC) after 8 weeks. At both 8 weeks and 24 weeks, aflatoxin was detected in at least one bag at each grain moisture, suggesting that aflatoxin contamination spread from a planted source of A. flavus-colonized grain to non-inoculated grain. The results indicate that repeatedly breaking the hermetic seal of the PICS bags will increase fungal growth and the risk of aflatoxin contamination, especially in maize stored at high moisture content. This work also further demonstrates that maize should be properly dried prior to storage in PICS bags.

Merits of partial shielding in dumping sediment spoils

The commonly adopted method of dumping dredge spoil at sea using split-hull barges leads to considerable sediment loss to the water column and a subsequent dispersion of fine material that can pose a risk to sensitive “downstream” habitats such as coral reefs. Containing sediment loads using stitched closed geotextile bags is practiced for minimizing loss of contaminated sediment, but is expensive in terms of operational efficiency. Following promising observations from initial laboratory trials, the plunging of partially shielded sediment loads, released on open sea, was studied. The partial shielding was achieved with rigid, open containers as well as flexible, open bags. The loss of sediment from these modes of shielding was measured, and it was observed that even limited and unstitched shielding can be effective in debilitating the entrainment of water into the descending load. In particular, long-sleeved flexible bags practically self-eliminated the exposure of the load and thus losses.

The Potential Management of a Ground-Nesting, Solitary Bee:Anthophora abrupta(Hymenoptera: Apidae)

Abstract In Apr 2010, Anthophora abrupta (Say) (Hymenoptera: Apidae) was discovered nesting in open bags of colloidal clay in Gainesville, Florida, USA, in an open-air shed. Label data from A. abrupta specimens in the Hymenoptera holdings of the Florida State Collection of Arthropods indicated that no specimen had been collected previously from Alachua County and that the most recent Floridian specimen was collected in 1987. This suggests that A. abrupta may be locally rare and possibly in decline or threatened regionally. Many of the plants that A. abrupta is reported to visit are listed as threatened or endangered in 1 or more states. In an effort to study the potential management and conservation of this species, the original nest aggregation was split in 2012 and 2013, and the splits were moved to new nest sites to see if they would establish at the new sites. Both mother and daughter nest aggregations were monitored in Spring of 2012–2014. Herein, a brief review of A. abrupta natural history, an acco...

House dust and storage mite contamination of dry dog food stored in open bags and sealed boxes in 10 domestic households

Dry pet food is a potential source of exposure to house dust and storage mite allergens in canine atopic dermatitis. This study evaluated contamination of house dust and dry dog food stored in paper bags, sealable plastic bags and sealable plastic boxes in 10 households for 90 days using Acarex(®) tests for guanine, a Der p 1 ELISA and mite flotation. Acarex(®) tests were negative in all the food samples but positive in all the house dust samples. The Der p 1 levels and mite numbers significantly increased in food from paper bags (P = 0.0073 and P = 0.02, respectively), but not plastic bags or boxes. Mite numbers and Der p 1 levels were 10-1000 times higher in house dust than the corresponding food samples (P < 0.0001). There were significant correlations between Der p 1 in house dust and food from the paper (P < 0.0001) and plastic bags (P = 0.003), and mite numbers in house dust and food from the paper bags (P = 0.0007). Bedding and carpets were significantly associated with Der p 1 levels in house dust (P = 0.015 and P = 0.01, respectively), and food from the paper (both P = 0.02) and plastic bags (P = 0.03 and P = 0.04, respectively). Mites were identified in six of 10 paper bag, three of 10 plastic bag, one of 10 plastic box and nine of 10 house dust samples. These comprised Dermatophagoides (54%), Tyrophagus (10%; all from food) and unidentified mites (36%). Storage of food in sealable plastic boxes largely prevented contamination for 3 months. Exposure to mites and mite proteins in all the stored food, however, appeared to be trivial compared with house dust.

Stability of pigments and oil in pistachio kernels during storage

SummaryThis work tested the stability of pigments (chlorophyll [chl] a and chlorophyll [chl] b, and lutein] and oil in pistachio kernels stored up to 14 months at three different temperatures: 10, 25 and 37 °C. The samples were hermetically packaged using two films (nylon and ethylene vinyl alcohol) with and without oxygen scavengers. For each temperature, reference samples were packaged in open bags. For both the oil and pigments, no differences were observed during storage, irrespective of packaging or oxygen scavengers. After 14 months, the oil showed very few changes: a slight increase in acidity and peroxide value (PV) irrespective of storage temperature; the spectrophotometric indices K232 and K268 remained the same. As for pigment stability, the lowest concentrations were observed at 37 °C with a degradation of about 62% for chl a, 44% for chl b and 57.5% for lutein. At 10 and 25 °C, the samples showed slight differences, the pigments degradations were about 46% for chl a, 33% for chl b and 37% for lutein. The degradation rate constants for the three pigments fitted a pseudo‐zero‐order kinetic in which Ea was 11.7 kJ mol−1, 12.1 kJ mol−1 and 18.2 kJ mol−1 for chl a, chl b and lutein respectively.

A Decade after Invasion: Evaluating the Continuing Effects of Rusty Crayfish on a Michigan River

In 2004, we revisited a Michigan stream invaded by rusty crayfish ( Orconectes rusticus) to determine if this species continued to expand its downstream range and negatively impact the stream food web. Compared to a 1992 study, we predicted that rusty crayfish would increase in density and downstream distribution from a small lake, resulting in further reduction of in-stream resources such as organic matter, benthic invertebrates, and periphyton. To determine current crayfish distributions and impacts, we conducted a longitudinal survey of crayfish abundance, ran a 28-d leaf breakdown experiment, and sampled benthic substrates. Leaf packs of sugar maple ( Acer saccharum) leaves were placed at three sites with differing crayfish densities (high, intermediate, and none). Breakdown rates were compared across the three sites and for two treatments (closed leaf bags excluding crayfish and open bags allowing crayfish access). Benthic invertebrates were sampled from leaf bags and invertebrates and periphyton were sampled from cobbles. In contrast to 1992, we found that the maximum downstream distance of rusty crayfish declined from 4 km to less than 3 km downstream from the lake. Leaves in open bags decayed significantly faster (k = 0.143) than did leaves in closed bags at all sites (k = 0.079) (p = 0.0005). The site lacking crayfish had significantly higher densities of invertebrates compared to both high and intermediate crayfish density sites (p = 0.005). Although we found that rusty crayfish reduced standing stocks of leaves and invertebrates, we did not detect measurable changes in periphyton biomass. Therefore, rusty crayfish have not dispersed further downstream since 1992, but where present, these omnivores significantly reduce resource availability via the consumption of leaf material and benthic invertebrates.

Keeping Quality of Desalted Cod Fillets in Consumer Packs

ABSTRACTTo meet modern consumer demands, it is important to be able to offer “ready‐to‐use” desalted cod in consumer packs with sufficient keeping quality at chill temperatures. The aim of this work was to investigate the effect of potassium sorbate, citric acid, and modified atmosphere packaging (MAP) in varying combinations on the keeping quality of desalted cod fillets in consumer packs. After desalting, cod fillets were packed in trays and stored at 1.0 ± 0.2 °C for up to 33 d. The fillets were packed in open bags, in modified atmosphere (MA) (CO2/N2/O2:75/ 20/5) only, or in MS following a potassium sorbate and/or a citric acid treatment. The rate of microbial growth was by far fastest in fillets in open bags. MAP alone decreased the growth rate considerably and still further decrease was obtained in MAP fillets treated with citric acid and/or sorbate solutions. The concurrent effect of these treatments was distinct. Quantitative descriptive analysis (QDA) was used to assess cooked samples. During the 1st d of storage, the samples were described by sweet and butter odor, salt taste, clammy and rubberlike texture, which became less evident with increasing storage time, but differed by groups and the least in samples treated with sorbate and citric acid/sorbate solutions. Sensory spoilage attributes and total volatile bases (TVB‐N)/trimethylamine (TMA) measurements correlated well with microbial counts. Use of MAP increased the shelf life from 6 to 10 d to 18 to 24 d, MAP and citric acid to 24 to 28 d, while the addition of sorbate to MAP fillets extended the shelf life to at least 33 d.

COMPARISON ON THE DIFFERENCE IN SOIL SEED BANK BETWEEN GRAZED AND ENCLOSED GRASSLANDS IN HORQIN SANDY LAND

Background and Aims In Horqin sandy land, vegetation degradation usually occurs in improper management regimes under fragile conditions, e.g. clearing and grazing. However, few information is available about the effects of grazing and enclosing on the structure and performance of soil seed banks in the semi-arid desert environment. Therefore, a field experiment was conducted in grazed and enclosed grasslands to examine the structure and performance of soil seed banks. Methods In late March 2003, three parallel 200-m line transects (20 m apart) were established in two experimental sites, grazed and enclosed grasslands. For each transect, 20 sampling points were set up at 10-m intervals, and a soil sample of 5 cm in depth and 20 cm × 20 cm in dimension was collected from each sampling point. All soil samples were transported to the laboratory in open plastic bags and chopped and sieved (mess width is 0.2 mm) soon. The sieved soil samples were placed in plastic germination pots (33 cm in diameter and 12 cm in depth) and spread evenly to form an approximately 1 cm thick layer in individual pots. Pots were placed in an unheated greenhouse for seed germination. Pots were watered daily with a very fine nozzle in the afternoon. Emergent seedlings were identified to species and carefully removed from the pots. Seed germination and seedling identification were carried out continuely in the following three months. However, some unidentifiable seedlings remained longer in the pots until they were identified. The density of the existing seed bank was expressed as the number of viable seeds per square meter. At each site, the frequency of species in the soil seed bank was determined in terms of the 60 sampling points or the 60 quadrats. Key Results The study was conducted in grazed and enclosed grasslands to examine the relationship between density and composition of soil seed bank and vegetation in Horqin sandy land, Inner Mongolia. The results showed that there were 22 and 30 plant species in seed banks in the grazed and enclosed grasslands, respectively. In the grazed and enclosed grasslands, the seed bank density were 20 657±3 342 and 16 149±1 900 viable seeds·m -2 , respectively, with annual herbaceous plants dominating in both sites (occupied 99% and 98%, respectively) Shannon-Wiener index and richness of the grazed grassland were 0.836 3 and 4.954 9, respectively, which were distinctly lower than those in the enclosed grassland (0.968 2 and 7.226 0), suggesting negative impacts of grazing on seed bank diversity. Seed bank density strongly related to the standing vegetation density in both grazed and enclosed grasslands (p0.001), indicating the standing vegetation density increased with the increase of seed bank density. Differences in seed bank density accounted for 78% and 58% of the variance of standing vegetation density in grazed and enclosed communities, respectively. Conclusions Our results showed that adoption of enclosure management practice significantly increased density and species diversity of the seed bank, compared with the grazed grassland. Therefore, reseeding, enclosure and other management steps should be used to speed up the restoration process of the degraded grassland.

Quantum particles inside Gaussian bags in (1+1) general relativity

The quantum modes of massive scalar particles inside open bags generated by Gaussian conformaly flat (1+1) metrics are investigated. Using computational methods, it is shown that the energy spectrum is mixed having a finite discrete part and a continuous one. A specific behavior of the discrete levels to the limit of separation between these parts is pointed out.

Leaf litter breakdown in Patagonian streams: native versus exotic trees and the effect of invertebrate size

1. Nothofagus native forest in the Southern Andes is being progressively substituted by forestation with rapid growth of the exotic trees, mainly species of Pinaceae. The effect on stream processing dynamics is explored through in situ experiments. 2. The effects of leaf litter quality and macroinvertebrate size on in situ litter breakdown were analysed. Experiments were run in litter bags which allowed access of macroinvertebrate fauna in streams running through a dense forest of the deciduous Nothofagus pumilio. 3. In Experiment 1, the decay rates of N. pumilio leaves and Pinus ponderosa needles were measured during an autumn-winter period. N. pumilio decayed twice as fast as P. ponderosa (P<0.01). Shredders fed only on N. pumilio leaves. The total abundance of macroinvertebrates colonizing both treatments was similar; however, the biomass was higher in the N. pumilio treatment. Large shredders were only found colonizing N. pumilio leaves. Since no decay due to shredders was observed in P. ponderosa, the presence of macroinvertebrates in these litter bags was related to refuge and feeding on FPOM-biofilm resources. 4. In Experiment 2, N. pumilio leaf litter was exposed in order to allow (open bags) or restrict (closed bags) access of invertebrates. The invertebrate assemblage in open bags showed the similar pattern observed for N. pumilio in the first experiment. Gathering-collectors were generally smaller and dominant in number while shredder biomass was higher in open bags as a result of high individual biomass. N. pumilio decayed faster when the whole size spectrum of macroinvertebrates colonized the bags (P<0.01). However, feeding signs of small shredders were observed in closed bags, therefore their role on leaf litter breakdown in Andean streams should not be neglected. 5. The combined results of both experiments lead to the conclusion that the whole litter processing mechanism would be affected as a consequence of the substitution of native forest by exotic pine forestation. Copyright © 2002 John Wiley & Sons, Ltd.