Cage Wall Research Articles

The feeding mechanisms ofLynceus(Crustacea: Branchiopoda: Laevicaudata), with special reference toL. simiaefaciesHarding

Although generally assumed to be filter feeders, branchiopod crustaceans of the laevicaudatan genus Lynceus O.F. Muller, 1776 possess no filters and do not collect food by filtration. Investigated species of these bivalved, multi-limbed animals have basically benthic habits and collect particulate food, mostly detritus, by scraping or sweeping it from surfaces with suitably armed trunk limbs. L. simiaefacies Harding, 1941, known only from a desert pool in Yemen, has trunk limbs that are armed with particularly robust scrapers and much of the complexity of these limbs and their armature is related to the collection and manipulation of detrital food by mechanical means. Material collected by scrapers borne distally on the more anterior limbs – although the anteriormost is very lightly armed – is swept posteriorly and dorsally, assisted by the armature of the more proximal endites, towards the posterior end of a deep food groove, whence it is passed anteriorly by the substantial gnathobases of the trunk limbs. The necessary movements of the trunk limbs are facilitated by a system of intrinsic muscles that enable individual endites to be moved independently – a remarkable specialized feature of a phyllopodial appendage. Before it enters the food groove, collected material is at all times confined to a narrow median chamber, or cage, between the two sets of opposed trunk limbs that extends over most of the anterior limbs – which are the largest. Each cage wall serves as a screen, covering the limbs of its side and is made up of long setose screening setae that superficially resemble coarse filter setae, and arise from the more proximal endites of most of the anterior trunk limbs. The screens prevent collected material from entering the inter-limb spaces into which water flows during each cycle of trunk limb movements, where its presence would be disastrous. They do not interfere with the spines of the proximal endites that can protrude between them. The screens do not extend to the extreme posterior end of the trunk limb series where a complex and dense array of specialized spines of the short posterior trunk limbs completes the task of sweeping food material into the food groove. Material is passed anteriorly along the food groove by the trunk limb gnathobases and the small but robustly armed maxillules to the mandibles. Although constructed on the basic, boat-like, branchiopod plan, in contrast to those of most particle-feeding branchiopods whose mandibles have a broad masticatory surface, those of Lynceus have a masticatory surface that is narrow and elongate in the antero-posterior plane. Interestingly, while the number of ‘teeth’ into which this surface is elaborated is few in most species of the genus, inviting comparison with a similar attribute in the Notostraca, L. simiaefacies has more numerous, smaller teeth. Although following the branchiopod plan, the mandibular musculature appears to have its own distinctive features but remains to be investigated in properly fixed material. At its distal extremity the oesophagus is differentiated into a small but complex gizzard, of which there appears to be no parallel in any other branchiopod order. This is described for the first time. Although provided with natatory antennae, species of Lynceus also employ their trunk limbs as organs of propulsion. In L. gracilicornis (Packard, 1871) the carapace valves can gape to more than 90°, which allows the trunk limbs to make a contribution to propulsion in a manner akin to that of the Anostraca. In this respect the Laevicaudata appears to stand in contrast to the Spinicaudata, in most species of which the trunk limbs contribute little or nothing to locomotion. More information is needed on representatives of both orders, which have received little study as living animals. Brief comments are made on the systematic position of the Laevicaudata, about which much remains to be resolved. © 2009 The Natural History Museum. Journal compilation © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 155, 513–541.

Clathrate hydrates with hydrogen-bonding guests

Clathrate hydrates (CHs) are inclusion compounds in which "tetrahedrally" bonded H(2)O forms a crystalline host lattice composed of a periodic array of cages. The structure is stabilized by guest particles which occupy the cages and interact with cage walls via van der Waals interactions. A host of atoms or small molecules can act as guests; here the focus is on guests that are capable of strong to intermediate H-bonding to water (small ethers, H(2)S, etc.) but nevertheless "choose" this hydrate crystal form in which H-bonding is absent from the equilibrium crystal structure. These CHs can form by exposure of ice to guest molecules at temperatures as low as 100-150 K, at the (low) guest saturation pressure. This is in contrast to the "normal" CHs whose formation typically requires temperatures well above 200 K and at least moderate pressures. The experimental part of this study addresses formation kinetics of CHs with H-bonding guests, as well as transformation kinetics between different CH forms, studied by CH infrared spectroscopy. The accompanying computational study suggests that the unique properties of this family of CHs are due to exceptional richness of the host lattice in point defects, caused by defect stabilization by H-bonding of water to the guests.

Oxygen ion conduction in 12CaO·7Al 2O 3: O 2− conduction mechanism and possibility of O − fast conduction

12CaO·7Al 2O 3 (C12A7) with a unique nano-porous structure and free O 2− ions entrapped in sub-nanometer-sized cages is a fast oxygen-ion-conducting material. These free O 2– may be replaced by various oxygen-related species, OH −, O 2− and O −, by tuning the atmosphere during the heat treatment. We examined the conduction mechanism for stoichiometric C12A7 (C12A7:O 2−), in which O 2− ions exist as counter anions in sub-nanometer-sized cages, by Raman measurement of C12A7:O 2− annealed in a dry 18O 2 atmosphere. It was revealed that the primary ion conducting species is an O 2− ion which diffuses via exchange with O 2− in the cage wall. An experimental result on the sample containing O − ions implied that O − is more mobile than O 2− in C12A7. Ab initio calculations on the diffusion paths of O 2− and O − ions in C12A7 supported the above experimental results.

Modelling of Atlantic salmon (Salmo salar L.) behaviour in sea-cages: A Lagrangian approach

We constructed a Lagrangian (individual-based) model of the behaviour of Atlantic salmon in sea-cages. The behaviour of individual fish was affected by a set of environmental factors and the other individuals in the population. The model was based on behavioural parameters derived from literature and comparisons between model performance and published quantitative data sets. Simulations demonstrated that the model was able to predict the circular schooling patterns familiar to caged Atlantic salmon based on social interactions among the individuals and a motivation to keep a certain distance to the cage wall. The model accurately predicted the vertical distribution patterns of salmon over 24 h within a sea-cage when verified against three detailed observational data sets from autumn, implying that the model closely replicated behavioural responses toward the combined effects of temperature and light. Deviations seen in the comparisons were possibly due to unmodelled features in the feeding response. Potential uses of the model include: 1) increasing understanding of how environmental factors affect fish behaviour; 2) coupling with measurements in a model-based estimator structure to accurately estimate biomasses within sea-cages; and 3) predicting the welfare status of fish in sea-cages under specific environmental conditions.

Effects of field cage colour and supplementary shade on environmental conditions and mating behaviour of Queensland fruit flies, Bactrocera tryoni

AbstractThe mating performance field cage test is a required periodic quality‐control assessment for factory‐reared fruit flies used for the sterile insect technique. The FAO/IAEA/USDA guidelines for assessing fly quality state that if during tests a large proportion of flies call and mate on cage walls, away from host trees, then environmental conditions within the cage need to be adjusted and tests repeated. Here we test effects of cage design, specifically mesh colour (green, white) and addition of supplementary shade, on the mating behaviour of Queensland fruit fly (Q‐fly), Bactrocera tryoni Froggatt (Diptera: Tephritidae). Observations were made over a 4‐h period at dusk when these flies mate. Changes in environmental conditions in each cage over the dusk period varied with cage design. We recorded the highest proportion of matings taking place on trees as opposed to cage walls (>90%) in the unshaded white cage, the shaded white and un‐shaded green cages being intermediate (ca. 70%), and the shaded green cage had the least (ca. 40%). The effects of field cage colour and supplementary shade on mating behaviour are discussed. We recommend that Q‐fly field cage tests should be conducted in cages with a light coloured mesh, and that supplementary shading should only be applied if there is a need to adjust temperature and light within the cage.

Comparative Study of the Assemblies and the Resulting Plasmon Fields of Langmuir−Blodgett Assembled Monolayers of Silver Nanocubes and Gold Nanocages

Silver nanocubes (72 nm) and gold nanocages (75 nm) were assembled by varying the average interstitial particle distances by the Langmuir−Blodgett technique. The shape of the surface pressure−area isotherms for the two types of nanoparticles are discussed in terms of the degree of surface capping of each nanoparticle which depends on the surface quality. Monolayer films formed at different surface pressures were transferred by the vertical dipping method to silicon and glass substrates where their optical spectra and SEM images were examined. A red-shift of the strong plasmon peak maximum was observed as the average particle distance was decreased. From the SEM images, the morphology as well as the percent area of the substrate surface covered at different pressures was determined. A linear relationship was observed between the percent of covered area and the plasmon peak maximum, the slope of which reflects the average plasmon field felt by the nanoparticles. The increase in the average field with increasing percent covered area is a result of the decrease in the average nanoparticle separation and/or the increase in the number of nanoparticles in each cluster in the distribution formed. The strength of the plasmon field resulting from gold cages is found to be much higher than that from the silver cubes and increases as the gold wall thickness decreases. These results are discussed in terms of the coupling between the two separate fields of the cage wall surfaces.

An Organic Spin Cage

A mixture of the verdazyl radical 1 and a Pd(II) complex was shown to quantitatively self-assemble to the M6L4 spin cage 2 in water. Various neutral molecules could be enclathrated by the large cavity of 2. Enclathration of small-molecule organic radicals led to energy transfer between the verdazyl radicals comprising the cage walls and the guest radical.

Essential role of the chaperonin folding compartment in vivo

The GroEL/GroES chaperonin system of Escherichia coli forms a nano-cage allowing single protein molecules to fold in isolation. However, as the chaperonin can also mediate folding independently of substrate encapsulation, it remained unclear whether the folding cage is essential in vivo. To address this question, we replaced wild-type GroEL with mutants of GroEL having either a reduced cage volume or altered charge properties of the cage wall. A stepwise reduction in cage size resulted in a gradual loss of cell viability, although the mutants bound non-native protein efficiently. Strikingly, a mild reduction in cage size increased the yield and the apparent rate of green fluorescent protein folding, consistent with the view that an effect of steric confinement can accelerate folding. As shown in vitro, the observed acceleration of folding was dependent on protein encapsulation by GroES but independent of GroES cycling regulated by the GroEL ATPase. Altering the net-negative charge of the GroEL cage wall also strongly affected chaperonin function. Based on these findings, the GroEL/GroES compartment is essential for protein folding in vivo.

Translation and reorientation of CD4 molecules in nanoscale cages of zeolites as studied by deuteron spin-lattice relaxation

Deuteron spin-lattice relaxation was applied to study translational and rotational mobility of CD(4) molecules trapped in the cages of zeolites. Tetrahedral methane molecules are treated as quantum rotators. Relaxation rates related to the intraquadrupole interaction are derived for the T and A+E symmetry species in the presence of large tunneling splittings, consistently with the assumption that A and E species molecules relax at the same rate. An exchange model is presented, which describes the effect on relaxation of CD(4) jumping between two positions characterized by different potentials. While staying at either position bonded to an atom or ion at the cage wall, the molecule has some freedom to move in the vicinity. This causes a time-dependent external electric field gradient, which contributes to the deuteron relaxation rate via the electric quadrupole interaction. Spin conversion transitions couple the relaxation of magnetizations M(T) and M(AE), which is taken into account by reapplying the presented model under somewhat different conditions. Such a two-step procedure leads to successful fits with the experimental results obtained in the range of temperatures roughly 20-200 K for zeolites HY, NaA, and NaMordenite. At higher temperatures CD(4) molecules fly freely across zeolite cages and relaxation changes accordingly, while incoherent tunneling dominates for immobile molecules below 20 K.

One and Two Hydrogen Molecules in the Large Cage of the Structure II Clathrate Hydrate: Quantum Translation−Rotation Dynamics Close to the Cage Wall

We have performed a rigorous theoretical study of the quantum translation-rotation (T-R) dynamics of one and two H2 and D2 molecules confined inside the large hexakaidecahedral (5(12)6(4)) cage of the sII clathrate hydrate. For a single encapsulated H2 and D2 molecule, accurate quantum five-dimensional calculations of the T-R energy levels and wave functions are performed that include explicitly, as fully coupled, all three translational and the two rotational degrees of freedom of the hydrogen molecule, while the cage is taken to be rigid. In addition, the ground-state properties, energetics, and spatial distribution of one and two p-H2 and o-D2 molecules in the large cage are calculated rigorously using the diffusion Monte Carlo method. These calculations reveal that the low-energy T-R dynamics of hydrogen molecules in the large cage are qualitatively different from that inside the small cage, studied by us recently. This is caused by the following: (i) The large cage has a cavity whose diameter is about twice that of the small cage for the hydrogen molecule. (ii) In the small cage, the potential energy surface (PES) for H2 is essentially flat in the central region, while in the large cage the PES has a prominent maximum at the cage center, whose height exceeds the T-R zero-point energy of H2/D2. As a result, the guest molecule is excluded from the central part of the large cage, its wave function localized around the off-center global minimum. Peculiar quantum dynamics of the hydrogen molecule squeezed between the central maximum and the cage wall manifests in the excited T-R states whose energies and wave functions differ greatly from those for the small cage. Moreover, they are sensitive to the variations in the hydrogen-bonding topology, which modulate the corrugation of the cage wall.

Zeolite A imidazolate frameworks

Faujasite (FAU) and zeolite A (LTA) are technologically important porous zeolites (aluminosilicates) because of their extensive use in petroleum cracking and water softening. Introducing organic units and transition metals into the backbone of these types of zeolite allows us to expand their pore structures, enhance their functionality and access new applications. The invention of metal-organic frameworks and zeolitic imidazolate frameworks (ZIFs) has provided materials based on simple zeolite structures where only one type of cage is present. However, so far, no metal-organic analogues based on FAU or LTA topologies exist owing to the difficulty imposed by the presence of two types of large cage (super- and beta-cages for FAU, alpha- and beta-cages for LTA). Here, we have identified a strategy to produce an LTA imidazolate framework in which both the link geometry and link-link interactions play a decisive structure-directing role. We describe the synthesis and crystal structures of three porous ZIFs that are expanded analogues of zeolite A; their cage walls are functionalized, and their metal ions can be changed without changing the underlying LTA topology. Hydrogen, methane, carbon dioxide and argon gas adsorption isotherms are reported and the selectivity of this material for carbon dioxide over methane is demonstrated.

Patterns of chest wall kinematics during volitional pursed-lip breathing in COPD at rest

Analysis of chest wall kinematics can contribute to identifying the reasons why some patients benefit from pursed-lip breathing (PLB). We evaluated the displacement of the chest wall and its compartments, the rib cage and abdomen, by optoelectronic plethysmography (OEP), during supervised PLB maneuver in 30 patients with mild to severe chronic obstructive pulmonary disease (COPD). OEP showed two different patterns. A first pattern characterized the 19 most severely obstructed and hyperinflated patients in whom PLB decreased end-expiratory volumes of the chest wall and abdomen, and increased end-inspiratory volumes of the chest wall and rib cage. Deflation of the abdomen and inflation of the rib cage contributed to increasing tidal volume of the chest wall. The second pattern characterized 11 patients in whom, compared to the former group, PLB resulted in the following: (i) increased end-expiratory volume of the rib cage and chest wall, (ii) greater increase in end-inspiratory volume of the rib cage and abdomen, and (iii) lower tidal volume of the chest wall. In the patients as a whole changes in end-expiratory chest wall volume were related to change in Borg score (r(2)=0.5, p<0.00002). OEP helps identifying the reason why patients with COPD may benefit from PLB at rest.

Chest Wall Motion During Speech Production in Patients With Advanced Ankylosing Spondylitis

To test the hypothesis that ankylosing spondylitis (AS) alters the pattern of chest wall motion during speech production. The pattern of chest wall motion during speech was measured with respiratory inductive plethysmography in 6 participants with advanced AS (5 men, 1 woman, age 45+/-8 years, Schober test 1.45+/-1.5 cm, Bath Ankylosing Spondylitis Functional Index [BASFI] score 6+/-1.7) and 6 healthy volunteers, matched for age and gender. Measurements were made with participants in the upright seated and upright standing body position. During reading in the seated and standing body positions, the rib cage wall volume displacements were smaller and abdominal wall volume displacements were larger in participants with AS than in healthy controls. There were no differences in the overall lung volume displacements recorded during the expiratory limb of reading in either body position. In the participants with AS, the rib cage remained near the end-expiratory level in both the seated and standing body position, differing from that for the control group. In individuals with advanced AS, the abdomen is the primary contributor to volume displacement. In the absence of speech impairment in participants with AS, the data show the capacity of the abdomen to compensate for the decreased compliance of the rib cage.

Spectroscopic Signatures of Halogens in Clathrate Hydrate Cages. 1. Bromine

We report the first UV-vis spectroscopic study of bromine molecules confined in clathrate hydrate cages. Bromine in its natural hydrate occupies 51262 and 51263 lattice cavities. Bromine also can be encapsulated into the larger 51264 cages of a type II hydrate formed mainly from tetrahydrofuran or dichloromethane and water. The visible spectra of the enclathrated halogen molecule retain the spectral envelope of the gas-phase spectra while shifting to the blue. In contrast, spectra of bromine in liquid water or amorphous ice are broadened and significantly more blue-shifted. The absorption bands shift by about 360 cm-1 for bromine in large 51264 cages of type II clathrate, by about 900 cm-1 for bromine in a combination of 51262 and 51263 cages of pure bromine hydrate, and by more than 1700 cm-1 for bromine in liquid water or amorphous ice. The dramatic shift and broadening in water and ice is due to the strong interaction of the water lone-pair orbitals with the halogen sigma* orbital. In the clathrate hydrates, the oxygen lone-pair orbitals are all involved in the hydrogen-bonded water lattice and are thus unavailable to interact with the halogen guest molecule. The blue shifts observed in the clathrate hydrate cages are related to the spatial constraints on the halogen excited states by the cage walls.

NMR relaxation in the double clathrate hydrate tetrahydrofuran/hydrogen sulfide

Nuclear magnetic proton relaxation times T 1 are reported for the double clathrate hydrate tetrahydrofuran/hydrogen sulfide in the temperature range 4–285 K at frequencies 60 and 300 MHz. The guest molecules contained alternatively light and heavy hydrogen isotopes. This permitted the molecular motion of both guests to be studied separately. Data analysis of tetrahydrofuran shows that between 15 and 120 K isotropic rotation with activation energy of 5 kJ/mol occurs. Data analysis of hydrogen sulfide points to strong interactions with the cage wall, less at lower than at higher temperature resulting in two different activation energies of 0.3 kJ/mol below and 3 kJ/mol above 26 K.

Cageversagen nach LWK3-Ersatz bei M. Hodgkin

We present a case report and the histological analysis of cage failure following vertebral body replacement in Hodgkin's disease. In a 35-year-old patient with a single metastasis of Hodgkin's disease replacement of the third lumbar vertebral body (Harms-titanium-mesh-cage, DePuy Acromed, completely filled with autogenous spongiosa from the iliac crest) was performed. 51 months postoperatively, the patient presented with acute back pain without trauma. The X-ray showed a collapse of the Harms-titanium-mesh-cage. The cage fragments had caused ventral dislocation of the main blood vessels and dura compression without neurological deficits. After the replacement of the failed Harms-cage (Synex, Synthes) histological analysis (light microscope, non-decalcified horizontal cuts, thickness of 150-200 microm, Giemsa und van Gieson staining) was done. The histology showed a remodelling of new bone in the area of the endplates without contact to the cage wall. In the region of the cage corpus, bony necrosis and connective tissue rich in cells was found. Bridging fusion in vertebral body replacement cages is not proven. As a result cage failure may occur. Therefore, in tumour patients with high live expectancy, Palacos filling of the cages should be discussed.

Hydrogen adsorption and spill-over effects on H–Y and Pd-containing Y zeolites: An experimental and theoretical investigation

The adsorption of hydrogen on H–Y and Pd(0)–H–Y zeolites was investigated by IR (in the 300–20 K temperature range) and EXAFS spectroscopies and the energy barriers for diffusion of hydrogen in the internal voids of the faujasite structure evaluated by ab initio calculations. On H–Y, H 2 is adsorbed at 20 K inside the super-cages giving rise to 1:1 –OH⋯H 2 hydrogen bonded complexes with the Brønsted acid groups, as well as less specific interaction with the cage walls. Due to the high energy barrier for crossing the framework hexagonal apertures, H 2 cannot enter the sodalite-cages. On Pd(0) containing zeolites, characterized as far the dispersion of the metal is concerned by TEM, EXAFS and IR spectroscopy of adsorbed CO, hydrogen is adsorbed in atomic form to give a metal-hydride phase; subsequent spill-over effects allow confinement of hydrogen also in the small sodalite-cages, as demonstrated by H/D isotopic substitution experiments.

Rates and Mechanisms of Conversion of Ice Nanocrystals to Ether Clathrate Hydrates: Guest-Molecule Catalytic Effects at ∼120 K

A Fourier transform infrared investigation of the rates and energetics of conversion of ice nanocrystals within 3-D arrays to ether clathrate-hydrate (CH) particles at approximately 120 K is reported. After an induction period, apparently necessitated by relatively slow nucleation of the CH phase, the well-established shrinking-core model of particle-adsorbate reaction applies to these conversions in the presence of an abundance of adsorbed ether. This implies that the transport of the ether adsorbate through the product crust encasing a reacting particle core (a necessary aspect of a particle reaction mechanism) is the rate-controlling factor. Diffusion moves adsorbed reactant molecules to the reaction zone at the interface of the ice core with the product (CH) crust. The results indicate that ether hydrate formation rates near 120 K resemble rates for gas hydrates measured near 260 K, implying rates greater by many orders of magnitude for comparable temperatures. A surprising secondary enhancement of ether CH-formation rates by the simultaneous incorporation of simple small gas molecules (N2, CO2, CH4, CO, and N2O) has also been quantified in this study. The rapid CH formation at low temperatures is conjectured to derive from defect-facilitated transport of reactants to an interfacial reaction zone, with the defect populations enhanced through transient H bonding of guest-ether proton-acceptor groups with O-H groups of the hydrate cage walls.

Comparing the influence of framework type on H2 absorption in hypothetical and existing clathrasils: a grand canonical Monte Carlo study

The influence of the framework type, in particular the influence of the type of cage, on the hydrogen absorption capacity in a range of clathrasil structures (frameworks having Si6O6 as their largest ring aperture) is investigated by means of grand canonical Monte Carlo simulations. Our systematic analysis includes twelve existing clathrasils and for the first time we also calculate practical properties for seven energetically viable hypothetical clathrasil frameworks. Hydrogen absorption isotherms are calculated for every material at 78, 85, and 90 K for 0–12 bar, and at 273 and 573 K for 0–3000 bar. At all investigated conditions, cages with a small volume (<400 A3) give rise to high absorption energies due to the larger attractive contact area between the cage wall and hydrogen. Despite this higher absorption energy, the H2 loading on a weight basis is relatively low in these small cages, because of the high internal surface-to-volume ratio, leaving little void space for the H2 molecule. As a result, the existing and hypothetical structures with the largest cages, LTN and Dt3_819, exhibit the highest absorption capacities. All investigated hypothetical clathrasils show similar absorption behavior to the existing clathrasils, supporting other evidence that these currently hypothetical materials are likely to be synthesized.

Quantum chemical calculations of N@Cn endofullerenes (n ≤ 60)

The geometric parameters and energy characteristics of small endofullerenes N@Cn (n = 20, 24, 30, 32, 40, 50) and N@C60 in the quartet ground state were calculated by the B3LYP/6-31G* method. The N atom is located at the center of the carbon cage in all molecules except N@C30, where it is bound to the cage wall. Encapsulation of nitrogen atom has little effect on the fullerene cage geometry for n = 40, 50, and 60. No significant charge transfer from the N endo-atom to the cage was revealed for all the N@Cn endofullerenes studied. The calculated spin density on the nitrogen endo-atom increases as the size (n) of the carbon cage increases. The relative stabilities of Cn fullerenes and corresponding endofullerenes N@Cn are discussed.