Plasticization, antiplasticization, and molecular packing in amorphous carbohydrate-glycerol matrices

The molecular packing of amorphous maltodextrin-glycerol matrices is systematically explored by combining positron annihilation lifetime spectroscopy (PALS) with thermodynamic measurements and dilatometry. Maltodextrin-glycerol matrices are equilibrated at a range of water activities between 0 and 0.54 at T = 25 °C to analyze the effect of both water and glycerol on the average molecular hole size and the specific volume of the matrices. In the glassy state, glycerol results in a systematic reduction of the average molecular hole size. In contrast, water interacts with the carbohydrate matrix in a complex way. Thermodynamic clustering theory shows that, at very low water contents the water molecules are well dispersed and are closely associated with the carbohydrate chains. In this regime water acts as an antiplasticizer, whereby it reduces the size of the molecular holes. Conversely, at higher water contents, while still in the glassy state, water acts as a plasticizer by increasing the average hole volume of the carbohydrate matrices. This plasticization-dominated mechanism is likely to be due to the interplay between the ability of water to form hydrogen bonds with the hydroxyl residues on the carbohydrate chains and its mobility, which is significantly decoupled from the bulk mobility of the matrix. Our findings are of key importance for the understanding of the effect of glycerol on the biostabilization performance of these carbohydrate matrices, as it provides a first insight on how molecular packing can relate to the dynamics in such matrices.     

Electron and hole transfer from DNA base radicals to oxidized products of guanine in DNA

An investigation of electron and hole transfer to oxidized guanine bases in DNA is reported. Guanine in DNA was preferentially oxidized by Br(2)(*-) at 298 K to 8-oxo-7,8-dihydro-guanine (8-oxo-G) and higher oxidation products. HPLC-EC analysis of irradiated DNA shows that the formation of 8-oxo-G could not be increased above the ratio of one 8-oxo-G to 127 +/- 6 bp regardless of dose. 8-oxo-G can be produced only at low levels because it is further oxidized to other species. These oxidation products of guanine have been extensively investigated and identified by others. Our electron spin resonance studies suggest that at 77 K 8-oxo-G is a trap for radiation-produced holes, but certain further oxidation products of 8-oxo-G (G(ox)) are found to be efficient electron traps. Gamma irradiation of oxidized DNA samples in frozen (D(2)O) aqueous ices and glassy 7 M LiBr solutions resulted in radicals formed by electron attachment to the G(ox) sites that were monitored by electron spin resonance spectroscopy (ESR) at 77 K. These ESR spectra suggest that those oxidation products of 8-oxo-G containing alpha-diketo groups account for the electron traps (G(ox)) in oxidized DNA with oxaluric acid a likely major trap. Electron transfer from DNA anion radicals to G(ox) was followed by monitoring of their ESR signals with time at 77 K. Using typical values for the tunneling constant beta estimates of the relative amount of G(ox) to base pairs were obtained. Radicals formed by UV photolysis of oxidized DNA in 8 M NaClO(4) glassy aqueous solutions were also investigated. The 8-oxo-G cation accounts for less than 10% of all the radicals observed after either gamma irradiation of oxidized DNA in frozen (D(2)O) aqueous solution or UV photolysis of oxidized DNA in 8 M NaClO(4) glassy aqueous solutions. We estimate hole transfer distances of about 7 +/- 1 bp at 1 min from G(*+) to 8-oxo-G.     

Fluorescence hole-burning and site-selective studies of LHCII

We report the observation of two types of changes in fluorescence spectra of LHCII at 4.2 K following intense illumination of the sample with a spectrally narrow laser beam at wavelengths between 678 and 686 nm. Nonspecific changes (burning-wavelength independent) are characterized by two relatively broad bands: a positive one at ∼ 678.7 nm and a negative one at ∼ 680.8 nm. These changes reveal a ∼1.3-nm blue shift of the distribution of final emitters in LHCII, from 680.3 nm to ∼ 679.0 nm independent of the excitation wavelength. Specific fluorescence changes (burning-wavelength dependent) are characterized by a sharp hole exactly at the burning wavelength, and positive changes directly to the shorter-and longer-wavelength side of the narrow hole. The negative changes are interpreted as zero-phonon holes, while the positive features are assigned to non-photochemical products. In the low-burning intensity experiment, in addition to the zero-phonon holes, we observed also the holes to the longer wavelength of the zero-phonon hole, which were assigned to a sum of phonon and pseudo-phonon side bands. The shapes of these extra holes are identical to the shapes of the holes revealed in the fluorescence line narrowing experiment. On the basis of the low-burning intensity experiment we estimated the upper limit of the electron-phonon coupling strength for LHCII, characterized by a Huang-Rhys factor of 1.5.     

Carbohydrate polymers in amorphous states: an integrated thermodynamic and nanostructural investigation

The effect of water on the structure and physical properties of amorphous polysaccharide matrices is investigated by combining a thermodynamic approach including pressure- and temperature-dependent dilatometry with a nanoscale analysis of the size of intermolecular voids using positron annihilation lifetime spectroscopy. Amorphous polysaccharides are of interest because of a number of unusual properties which are likely to be related to the extensive hydrogen bonding between the carbohydrate chains. Uptake of water by the carbohydrate matrices leads to a strong increase in the size of the holes between the polymer chains in both the glassy and rubbery states while at the same time leading to an increase in matrix free volume. Thermodynamic clustering theory indicates that, in low-moisture carbohydrate matrices, water molecules are closely associated with the carbohydrate chains. Based on these observations, we propose a novel model of plasticization of carbohydrate polymers by water in which the water dynamically disrupts chains the hydrogen bonding between the carbohydrates, leading to an expansion of the matrix originating at the nanolevel and increasing the number of degrees of freedom of the carbohydrate chains. Consequently, even in the glassy state, the uptake of water leads to increased rates of matrix relaxation and mobility of small permeants. In contrast, low-molecular weight sugars plasticize the carbohydrate matrix without appreciably changing the structure and density of the rubbery state, and their role as plasticizer is most likely related to a reduction of the number of molecular entanglements. The improved molecular packing in glassy matrices containing low molecular weight sugars leads to a higher matrix density, explaining, despite the lower glass transition temperature, the reduced mobility of small permeants in such matrices.     

A Manipulated Extraordinary Optical Transmission Filter Composed with Subwavelength Hole Complex Arrays

We present a new style extraordinary optical transmission (EOT) nano optical filter combined by two kinds of subwavelength holes array on a gold film. In the design, a square array of non-penetrating holes (hollow holes) inlays into another square array of penetrating holes ordered by a central arrange mode. We numerically calculated the transmission spectra of the patterned gold films by finite-difference time-domain (FDTD) method. Results show that the transmission of the filter can be manipulated by changing the depth of non-penetrating holes. The (1, 1) peak can be enhanced when the incident light normally illuminates one side of the filter with the hollow holes, yet the (1, 1) peak can be suppressed when the light illuminates the other side without hollow holes. It also depicts that the hollow hole array results in energy level splitting of (1, 0) mode propagating on the surface of the filter. What’s more, the splitting can be eliminated by modulating the depth of the hollow holes. Our study further reveals the role of suface plasmon effect in the EOT.     

粉煤灰基质-草坪砖栽培环境对坪草生长的影响

为了解决停车场、甬路、渠坝与草坪争地的矛盾,增加城市绿地面积,在已研究粉煤灰草坪基质最佳混合比例的基础上,进一步探讨草坪砖作为草坪栽培环境(砖孔内填人粉煤灰混合基质,简称砖孔环境)的肥力效应与生物效应。为了对比分析,特此设置了土孔环境(在土壤中挖取与草坪砖形状和容积相同的孔并填入粉煤灰混合基质)与土灰环境(在粉煤灰混合基质中按照草坪砖孔模式划出同样大小的圈)种植黑麦草作为对照。研究结果表明：坪草N、K、Na、Cu、Zn等含量以砖孔环境最高,土灰环境和土孔环境较低,差异显著,说明砖孔环境能为植物生长提供较多的养分元素;砖孔环境中的坪草含有的Fe、Cu、Zn浓度远高于坪草最佳需求量,今后不再需要补充铁肥、铜肥和锌肥。试验还表明砖孔环境的蒸散率最小,基质含水量最大,基质势最高,持续供水能力强,抗旱效果十分明显。砖孔环境与土孔环境中的草坪草屑累积量差异不显著,但均比土灰环境中的高,且差异显著。夏季高温期砖孔环境中的草坪质量显著高于土孔环境和土灰环境中的草坪质量。     

3D Magnetic Holes in Collisionless Plasmas

Recent multispacecraft observations in the Earth’s magnetosphere have revealed an abundance of magnetic holes—localized magnetic field depressions. These magnetic holes are characterized by the plasma pressure enhancement and strongly localized currents flowing around the hole boundaries. There are several numerical and analytical models describing 2D configurations of magnetic holes, but the 3D distribution of magnetic fields and electric currents is studied poorly. Such a 3D magnetic field configuration is important for accurate investigation of charged particle dynamics within magnetic holes. Moreover, the 3D distribution of currents can be used for distant probing of magnetic holes in the magnetosphere. In this study, a 3D magnetic hole model using the single-fluid approximation and a spatial scale hierarchy with the distinct separation of gradients is developed. It is shown that such 3D holes can be obtained as a generalization of 1D models with the plasma pressure distribution adopted from the kinetic approach. The proposed model contains two magnetic field components and field-aligned currents. The magnetic field line configuration resembles the magnetic trap where hot charged particles bounce between mirror points. However, the approximation of isotropic pressure results in a constant plasma pressure along magnetic field lines, and the proposed magnetic hole model does not confine plasma along the field direction.     

Preliminary analysis of drinking from seawater sources by free-ranging rhesus macaques (Macaca mulatta)

Rhesus macaques on Key Lois Island were observed drinking seawater that flowed into four holes they had excavated in the sand. Data were gathered to determine the salinity (TDS) and pH levels of the water and which animals were using the holes. Average TDS level (4,506.8 ± 1,750.8), but not pH (8.1 ± .30) level, of water from the holes differed from the surrounding seawater (TDS = 29,000, pH = 8.0). There were significant variations in TDS and pH levels of water between holes. A total of 249 drinking and 11 digging bouts were observed. Adult females drank and dug most often (46.9% of total bouts). Of the 260 total drinking and digging bouts, 76.1% (N = 198) were concentrated at one hole. This hole had the lowest average TDS level (3,714.2 ± 1,504.4) and one of the highest average pH levels (8.1 ± .29). Age/sex class differences in drinking bout frequencies may have been due to differential social status. We suggest that the holes were excavated to overcome a temporary shortage of provisioned water. © 1993 Wiley-Liss, Inc.     

Energy selection is not correlated in the Qx and Qy bands of a Mg-porphyrin embedded in a protein

The Qx-Qy splitting observed in the fluorescence excitation spectra of Mg-mesoporphyrin-IX substituted horseradish peroxidase (MgMP-HRP) and of its complex with naphthohydroxamic acid (NHA) was studied by spectral hole burning techniques. The width of a hole directly burnt in the Qy band and that of a satellite hole indirectly produced in Qy as a result of hole burning in Qx was compared. We also studied the dependence of the satellite hole in the Qy band on the burning frequency used in the Qx band. Both the directly and indirectly burnt holes were very broad in the (higher energy) Qy band. The width of the satellite hole in the Qy band was equal to the entire width of the inhomogeneously broadened band, independently from the position of hole burning in Qx. This is indicative of a clear lack of correlation between the electronic transition energies of the Qx and Qy bands. A photoproduct was produced by laser irradiation of the MgMP-HRP/NHA complex and was identified as a species with lowered Q-splitting. Conversion of the photoproduct could be achieved by thermal activation measured in temperature-cycling experiments, with a characteristic temperature of 25 K. We attribute the phototransformation to a conformational change of MgMP.     

Biomimetics of Campaniform Sensilla: Measuring Strain from the Deformation of Holes

We present a bio-inspired strategy for designing embedded strain sensors in space structures. In insects, the campaniform sensillum is a hole extending through the cuticle arranged such that its shape changes in response to loads. The shape change is rotated through 90 by the suspension of a bell-shaped cap whose deflection is detected by a cell beneath the cuticle. It can be sensitive to displacements of the order of 1 nm. The essential morphology, a hole formed in a plate of fibrous composite material, was modelled by Skordos et al. who showed that global deformation of the plate (which can be flat, curved or a tube) induces higher local deformation of the hole due to its locally higher compliance. Further developments reported here show that this approach can be applied to groups of holes relative to their orientation.The morphology of the sensillum in insects suggests that greater sensitivity can be achieved by arranging several holes in a regular pattern; that if the hole is oval it can be "aimed" to sense specific strain directions; and that either by controlling the shape of the hole or its relationship with other holes it can have a tuned response to dynamic strains.We investigate space applications in which novel bio-inspired strain sensors could successfully be used.     

Biomimetics of Campaniform Sensilla： Measuring Strain from the Deformation of Holes

We present a bio-inspired strategy for designing embedded strain sensors in space structures. In insects, the campaniform sensillum is a hole extending through the cuticle arranged such that its shape changes in response to loads. The shape change is rotated through 90° by the suspension of a bell-shaped cap whose deflection is detected by a cell beneath the cuticle. It can be sensitive to displacements of the order of 1 nm. The essential morphology, a hole formed in a plate of fibrous composite mate- rial, was modelled by Skordos et al. who showed that global deformation of the plate （which can be flat, curved or a tube） induces higher local deformation of the hole due to its locally higher compliance. Further developments reported here show that this approach can be applied to groups of holes relative to their orientation. , The morphology of the sensillum in insects suggests that greater sensitivity can be achieved by arranging several holes in a regular pattern; that if the hole is oval it can be ＂aimed＂ to sense specific strain directions; and that either by controlling the shape of the hole or its relationship with other holes it can have a tuned response to dynamic strains. We investigate space applications in which novel bio-inspired strain sensors could successfully be used.     

The abundance,distribution and structural characteristics of tree‐holes in Nothofagus forest,New Zealand

Tree‐holes provide an important microhabitat that is used for feeding, roosting and breeding by numerous species around the world. Yet despite their ecological importance for many of New Zealand's endangered species, few studies have investigated the abundance or distribution of tree‐holes in native forests. We used complementary ground and climbed tree surveys to determine the abundance, distribution and characteristics of tree‐holes in undisturbed Nothofagus forest in the Lewis Pass, New Zealand. We found that hole‐bearing trees were surprisingly abundant compared with many other studies, including Australian Eucalyptus species and American beech. In fact, we estimated as many as 3906 tree‐holes per hectare, of which 963 holes per hectare were potentially large enough to provide roost sites for hole‐nesting bats in New Zealand, while only eight holes per hectare were potentially suitable for specialist hole‐nesting birds. This was of great interest as primary cavity‐excavating animals are absent from New Zealand forests, compared with North America and Australia. Moreover, tree‐hole formation in New Zealand is likely to be dominated by abiotic processes, such as branch breakage from windstorms and snow damage. As has been found in many other studies, tree‐holes were not uniformly distributed throughout the forest. Tree‐holes were significantly more abundant on the least abundant tree species, Nothofagus fusca, than on either N. menziesii or N. solandri. In addition to tree species, tree size was also an important factor influencing the structural characteristics of tree‐holes and their abundance in this forest. Moreover, these trends were not fully evident without climbed tree surveys. Our results revealed that ground‐based surveys consistently underestimated the number of tree‐holes present on Nothofagus trees, and illustrate the importance of using climbed inspections where possible in tree‐hole surveys. We compare our results with other studies overseas and discuss how these are linked to the biotic and abiotic processes involved in tree‐hole formation. We consider the potential implications of our findings for New Zealand's hole‐dwelling fauna and how stand dynamics and past and future forest management practices will influence the structural characteristics of tree‐holes and their abundance in remnant forest throughout New Zealand.     

Competitive interactions and the availability of sleeping sites for a diurnal coral reef fish

A field study was made to test whether the population size of a diurnal reef fish, the wrasse Thalassoma bifasciatum (Bloch), was limited by inter- or intraspecific competition for sleeping shelter. T. bifasciatum is often attacked at dusk by two small territorial damselfishes, Eupomacentrus dorsopunicans (Poey) and E. planifrons (Cuvier). Although these three species sleep in the same general habitats, there are qualitative differences in the types of holes they use and how they use them. Wrasse holes are usually in these damselfishes' territories, but damselfish attacks do not prevent wrasses entering holes. Wrasses infrequently defend their holes intraspecifically. They regularly change their holes, with little intra- or interspecific aggressive interaction. When its hole is removed, a wrasse is late in retiring but finds a hole near its old one with little aggressive interaction, and does not have a higher mortality rate. Empty wrasse holes are rarely refilled, and then only by conspecifics. Wrasses added to reefs find unoccupied holes and do not usurp other fishes' holes. Damselfish defend their eggs and food against the wrasse, but not their sleeping shelter, nor living space per se. Sleeping sites are not limiting the wrasse, but are present in a surplus. Intraspecific hole defense by a wrasse prevents a delay in its retiring that would increase the risk of crepuscular predation on it.     

Characteristics and utilization of old Black Woodpecker Dryocopus martius holes by hole-nesting species

Old nest holes made by the Black Woodpecker Dryocopus martius were examined in two study areas in Sweden. We found a large variation in nest hole characteristics and that the height in the tree and depth of the hole were important factors in the choice of nest hole by secondary hole nesters. A large proportion of old nest holes remained unoccupied. Many holes were probably of poor quality due to shallow depth, low height or narrow entrance. Nest holes in the vicinity of farmland (<200 m from the field-forest edge) were more often occupied than nest holes deeper into the forest. This was because Jackdaws Corvus monedula , the numerically dominant species, only used nest holes near farmland. Jackdaws usually used the best nest holes, while other subordinate species had to use inferior holes near fields or nest holes in areas with less competition, deeper in the forest. Besides birds, some mammals and bees were found using old Black Woodpecker holes.     

Nest-site re-use: Marsh Tit Poecile palustris decisions in a primeval forest

Capsule Re-use is infrequent although birds reproduce equally well in re-used and new holes.

Aims To describe frequency of hole re-use by Marsh Tits in primeval forest with superabundant holes; to examine how depredation, disturbance, ectoparasites or the low quality of previously used holes influenced birds' decision to switch holes; to assess whether Marsh Tits benefited from re-using holes.

Methods Birds were observed living in undisturbed conditions in a strictly protected part of the Bia?owie?a National Park (Poland) during 13 breeding seasons, hole attributes were measured, and observations made of nest fate and bird survival.

Results Marsh Tits re-occupied 35.5% of available holes used the previous year (n = 214). The holes were most often re-used when both birds survived (42%) or when the surviving female was paired to a new male (35%). Holes were re-used less often after brood failure than after successful breeding (13% versus 39%). Other possible factors (ectoparasite infestation, inferior hole quality or a bird being caught at hole) had no effect on the re-occupation frequency. Birds in the retained and new holes bred at the same time, laid the same number of eggs, and had almost identical nesting success (78% versus 76%).

Conclusion Superabundant holes in the primeval forest allow Marsh Tits to change holes frequently. Similar outcomes of breeding in the re-used and new holes indicate that choices made by the birds are largely neutral, i.e. there is no strong selection pressure for or against hole re-use.     

The cloning of two Arabidopsis genes belonging to a phosphate transporter family

Two genes, APT1 and APT2 , with DNA sequences that exhibit significant sequence identity to yeast and fungal H⁺/orthophosphate co-transporters, have been isolated from Arabidopsis thaliana . These genes are genetically linked and map to chromosome 5 between markers g4028 and m435. The genes encode almost identical 524 amino acid polypeptides and are predicted to contain 12 membrane-spanning domains. Both APT1 and APT2 are predominantly expressed in A. thaliana root tissues. The level of expression of both genes in roots is regulated by the phosphorus status of the plant, being considerably enhanced when the plants were deprived of an external phosphate supply. The APT1 and APT2 polypeptides are likely to be associated with the membrane transport of phosphate within A. thaliana roots.     

Undermining game fences: who is digging holes in Kalahari sands?

The effectiveness of game fencing as a tool to promote coexistence between humans and wildlife is highly dependent on the maintenance of fences. It is vital to identify animal species, which dig holes under fences, and their digging behaviour to maintain game fences appropriately. We provide data on some of southern Africa's major hole‐digging animal species for a simple albeit effective method enabling stakeholders to categorize species that are digging holes underneath game fences in deep sand habitats by species‐specific knowledge on sizes and shapes of holes. Using Botswana's Khutse Game Reserve/Central Kalahari Game Reserve fence as an example, we highlight the temporal aspect in the process of hole digging and enlargement. We present a method to determine the pressure a fence experiences by a number of hole‐digging species. Furthermore, we provide data on the time frame of necessary maintenance actions, required to prevent large predators from transgressing this specific fence line. We were especially interested in the effectiveness of fences in excluding African lions from human‐dominated areas. The predators proved to be very difficult to fence in and extremely opportunistic. They mostly utilized holes that were initially excavated by other, even very small species.     

Dispersed central place foraging in Australian meat ants

Summary Australian meat ants often inhabit colonies with widely dispersed nest holes, and this study examines how resource is harvested and distributed in a colony ofIridomyrmex sanguineus Smith (Formicidae: Dolichoderinae). The three principal types of foragers (tenders, honeydew transporters, scavengers) exhibited nest hole fidelity, where harvested resource was consistently delivered to the same nest hole by each foraging individual. Australian meat ants thus use a harvesting system based on dispersed central place foraging. Evidence of frequent larval transport among nest holes, age polyethism developing in the direction of foraging, and the tendency for nest-associated workers to accept new nest holes more readily than foragers, suggests that workers develop fidelity to the particular nest hole in which they eclose. Coupled with larval transport, nest hole fidelity may allow a colony with widely dispersed nest holes to adjust its structure to more efficiently harvest a resource distributed unevenly in space or time.     

Effects of Seasonal Water Scarcity on the Ranging Behavior of Eulemur fulvus rufus

The climate of western Madagascar is characterized by a long (8–9 mo) dry season during which small rivers run dry, so that most animals are dependent on access to a few permanent water holes. We studied the effects of water scarcity at the end of the dry season on the ranging behavior of 4 groups of redfronted lemurs (Eulemur fulvus rufus) living at different distances from the Kirindy Riverbed in the Kirindy/CFPF forest northeast of Morondava. Using radio-collars, we located 2 resident groups with permanent home ranges near the river, and 2 non-resident groups and followed them for 60 days. We obtained a GPS reading every 30 min and later analyzed them with GIS ArcView to determine the size and location of each group's (core) home range. One group resided in direct proximity to the riverbed with several water holes and made regular short trips (mean 330 m) to drink. A second resident group had no direct access to water and made regular trips to the same water hole at a mean distance of 590 m from their home range. One non-resident group had a center of activity about 1300 m from the nearest water hole, to which they traveled on a non-daily basis. The other non-resident group established a temporary binuclear home range with one center of activity near the riverbed, about 2900 m away from the other center of activity. Thus, redfronted lemurs use different drinking and ranging tactics as a function of the distance of their core areas from the nearest water source.     

Plasmid-associated bacteriocin production by a strain of Carnobacterium piscicola from meat.

Carnobacterium piscicola LV17 isolated from vacuum-packed meat produces bacteriocin(s) that is active against closely related lactic acid bacteria, Enterococcus spp., and a strain of Listeria monocytogenes but not against gram-negative bacteria. The bacteriocin has a bactericidal mode of action, is heat resistant, and is stable over a wide range of pH but is inactivated by proteolytic enzymes. Sensitive and resistant cells were shown to adsorb the bacteriocin, but cell death depended on contact of the bacteriocin with the cell membrane. Bacteriocin production is detected early in the growth cycle of the organism in APT broth, but it is not produced in APT broth adjusted to pH 5.5. Bacteriocin production and resistance to the bacteriocin produced are associated with two plasmids of 40 and 49 megadaltons. The possibility that two bacteriocins are produced is indicated because the inhibitory substances of the mutant strains containing either the 40- or 49-megadalton plasmids have different antimicrobial spectra.