Narrow End Research Articles

Prescribing the behavior of Weil–Petersson geodesics in the moduli space of Riemann surfaces

We study Weil–Petersson (WP) geodesics with narrow end invariant and develop techniques to control length-functions and twist parameters along them and prescribe their itinerary in the moduli space of Riemann surfaces. This class of geodesics is rich enough to provide for examples of closed WP geodesics in the thin part of the moduli space, as well as divergent WP geodesic rays with minimal filling ending lamination. Some ingredients of independent interest are the following: A strength version of Wolpert's Geodesic Limit Theorem proved in Sec. 4. The stability of hierarchy resolution paths between narrow pairs of partial markings or laminations in the pants graph proved in Sec. 5. A kind of symbolic coding for laminations in terms of subsurface coefficients presented in Sec. 7.

Testing quantised inertia on the emdrive

It has been shown that truncated cone-shaped cavities with microwaves resonating within them move slightly towards their narrow ends (the emdrive). Standard physics has no explanation for this and an error has not yet been found. It is shown here that this effect can be predicted by assuming that the inertial mass of the photons in the cavity is caused by Unruh radiation, whose wavelengths must fit exactly within the cavity, using a theory already applied successfully to astrophysical anomalies such as galaxy rotation where the Unruh waves have to fit within the Hubble scale. In the emdrive this means that more Unruh waves are allowed at the wide end, leading to a greater inertial mass for the photons there, and to conserve momentum the cavity must move towards its narrow end, as observed. The model predicts thrusts of 3.8, 149, 7.3, 0.23, 0.57, 0.11, 0.64 and 0.02 mN compared with the observed thrusts of 16, 147, 9, 0.09, 0.05, 0.06, 0.03 and 0.02 mN and predicts that if the axial length is equal to the diameter of the small end of the cavity, the thrust should be reversed.

Curvature Concentrations on the HIV-1 Capsid

Abstract It is known that the retrovirus capsids possess a fullerene-like structure. These caged polyhedral arrangements are built entirely from hexagons and exactly 12 pentagons according to the Euler theorem. Viral capsids are composed of capsid proteins, which create the hexagon and pentagon shapes by groups of six (hexamer) and five (pentamer) proteins. Different distributions of these 12 pentamers result in icosahedral, tubular, or conical shaped capsids. These pentamer clusters introduce declination and hence curvature on the capsids. This paper provides explicit and quantitative characterization of curvature on virus capsids. The concept of curvature concentration is also introduced. For the HIV (5,7)-cone, it is shown that the curvature concentration at the narrow end is about at least four times higher than that at the broad end. Our modeling results about curvature concentrations on HIV-1 capsids echo the results in the literature that the pentamers are in the regions with the highest stress, although the connection between the two approaches (curvature concentration and stress) is to be explored. This also leads to a conjecture that “HIV-1 capsid narrow end may close last during maturation but open first during entry into a host cell".

Biomechanical properties of five different currently used implants for open-wedge high tibial osteotomy.

BackgroundAs several new tibial osteotomy plates recently appeared on the market, the aim of the present study was to compare mechanical static and fatigue strength of three newly designed plates with gold standard plates for the treatment of medial knee joint osteoarthritis.MethodsSixteen fourth-generation tibial bone composites underwent a medial open-wedge high tibial osteotomy (HTO) according to standard techniques, using five TomoFix standard plates, five PEEKPower plates and six iBalance implants. Static compression load to failure and load-controlled cyclic fatigue failure tests were performed. Forces, horizontal and vertical displacements were measured; rotational permanent plastic deformations, maximal displacement ranges in the hysteresis loops of the cyclic loading responses and dynamic stiffness were determined.ResultsStatic compression load to failure tests revealed that all plates showed sufficient stability up to 2400 N without any signs of opposite cortex fracture, which occurred above this load in all constructs at different load levels. During the fatigue failure tests, screw breakage in the iBalance group and opposite cortex fractures in all constructs occurred only under physiological loading conditions (<2400 N). The highest fatigue strength in terms of maximal load and number of cycles performed prior to failure was observed for the ContourLock group followed by the iBalance implants, the TomoFix standard (std) and small stature (sm) plates. The PEEKPower group showed the lowest fatigue strength.ConclusionsAll plates showed sufficient stability under static loading. Compared to the TomoFix and the PEEKPower plates, the ContourLock plate and iBalance implant showed a higher mechanical fatigue strength during cyclic fatigue testing. These data suggest that both mechanical static and fatigue strength increase with a wider proximal T-shaped plate design together with diverging proximal screws as used in the ContourLock plate or a closed-wedge construction as in the iBalance design. Mechanical strength of the bone-implant constructs decreases with a narrow T-shaped proximal end design and converging proximal screws (TomoFix) or a short vertical plate design (PEEKPower Plate). Whenever high mechanical strength is required, a ContourLock or iBalance plate should be selected.

More ties than we thought

We extend the existing enumeration of neck tie-knots to include tie-knots with a textured front, tied with the narrow end of a tie. These tie-knots have gained popularity in recent years, based on reconstructions of a costume detail from The Matrix Reloaded, and are explicitly ruled out in the enumeration by Fink and Mao (2000). We show that the relaxed tie-knot description language that comprehensively describes these extended tie-knot classes is context free. It has a regular sub-language that covers all the knots that originally inspired the work. From the full language, we enumerate 266682 distinct tie-knots that seem tie-able with a normal neck-tie. Out of these 266682, we also enumerate 24882 tie-knots that belong to the regular sub-language.

The Ovary of Tubifex tubifex (Clitellata, Naididae, Tubificinae) Is Composed of One, Huge Germ-Line Cyst that Is Enriched with Cytoskeletal Components.

Recent studies on the ovary organization and oogenesis in Tubificinae have revealed that their ovaries are small polarized structures that are composed of germ cells in subsequent stages of oogenesis that are associated with somatic cells. In syncytial cysts, as a rule, each germ cell is connected to the central cytoplasmic mass, the cytophore, via only one stable intercellular bridge (ring canal). In this paper we present detailed data about the composition of germ-line cysts in Tubifex tubifex with special emphasis on the occurrence and distribution of the cytoskeletal elements. Using fixed material and live cell imaging techniques, we found that the entire ovary of T. tubifex is composed of only one, huge multicellular germ-line cyst, which may contain up to 2,600 cells. Its architecture is broadly similar to the cysts that are found in other clitellate annelids, i.e. a common, anuclear cytoplasmic mass in the center of the cyst and germ cells that are connected to it via intercellular bridges. The cytophore in the T. tubifex cyst extends along the long axis of the ovary in the form of elongated and branched cytoplasmic strands. Rhodamine-coupled phalloidin staining revealed that the prominent strands of actin filaments occur inside the cytophore. Similar to the cytophore, F-actin strands are branched and they are especially well developed in the middle and outermost parts of the ovary. Microfilaments are also present in the ring canals that connect the germ cells with the cytophore in the narrow end of the ovary. Using TubulinTracker, we found that the microtubules form a prominent network of loosely and evenly distributed tubules inside the cytophore as well as in every germ cell. The well-developed cytoskeletal elements in T. tubifex ovary seem to ensure the integrity of such a huge germ-line cyst of complex (germ cells - ring canals - cytophore) organization. A comparison between the cysts that are described here and other well-known female germ-line cysts is also made.

Ovary ultrastructure and oogenesis in Propappus volki Michaelsen, 1916 (Annelida: Clitellata)

The paired ovaries of Propappus volki are small, conically shaped structures with a narrow end that is connected to the intersegmental septum, while the wide end extends into the coelom. Ultrastructural studies showed that the ovaries are composed of interconnected germ cells that form syncytia and accompanying somatic cells. Each germ cell in a cyst is connected with the central, anuclear cytoplasmic core, the cytophore, via one cytoplasmic bridge. The somatic cells form both a thin ligament that joins the gonad with the septum and also surround the germ cells, thus, forming a thin ovary envelope. The somatic cells that are in immediate contact with growing oocytes, i.e., follicular cells, are more voluminous than other somatic cells. There is a clear gradient in the development of germ cells along the long ovary axis. As a consequence, three zones can be distinguished. In zone I all of the germ cells are in the prophase I of meiosis, while zone II contains undifferentiated germ cells with a similar morphology. In zone III there are two morphologically distinct categories of germ cells – the more numerous but smaller germ cells that are regarded here as nurse cells and several growing oocytes. The growing oocytes gradually accumulate cytoplasm and yolk material and protrude from the ovary into the segment cavity. The late vitellogenic oocytes, which are filled with yolk spheres, lose contact with the gonad and float within the coelom.The comparison of the results that were obtained with the ovary structure and oogenesis in other Clitellata shows that: (1) the pattern of germ-line cyst organization in P. volki and other Clitellata is the same; (2) the course of oogenesis in P. volki is similar to other oligochaetous clitellates and (3) the ovary organization in P. volki is broadly similar to that which has been described in tubificins, brachiobdellids and lumbriculids but which differs significantly from that found in Enchytraeus albidus.

Experimental investigation on the friction and sealing characteristics of narrow end-face seal ring with spiral grooves for wet clutch

Purpose – The purpose of this paper is to investigate the friction and sealing characteristics of narrow end face seal ring with spiral grooves for wet clutch by experiment. Design/methodology/approach – The shallow spiral grooves are machined in the end face of narrow seal ring by laser, and all of other parameters of specimens are the same with the actual production. The investigation of friction and sealing characteristics are carried out by comparing the experiment results of end face seal ring with spiral grooves with the conventional seal ring without spiral grooves through friction coefficient test, volume leakage rate test and pv value test. Findings – Comparing with conventional seal ring without spiral grooves, seal ring with spiral grooves experiences boundary lubrication, mixed lubrication and fluid film lubrication with the increase of rotation speed, whereas the conventional seal ring only experiences mixed lubrication. Besides this, the volume leakage rate is slightly larger, but the pv value is much larger than that of conventional seal ring. Originality/value – Effect of spiral grooves on the friction and sealing characteristics of narrow end face seal ring for wet clutch is investigated. The improved lubrication performance can be achieved by shallow spiral grooves even if the distance of radius difference used to machine grooves is very small.

A histological evaluation of development and axis formation in freshwater fish ectoparasite Argulus bengalensis Ramakrishna, 1951 (Crustacea: Branchiura).

The present investigation was carried out to underscore the developmental events of a crustacean ectoparasite of fish, Argulus bengalensis. Serial histological sections of the embryo were made at lateral, sagittal and longitudinal planes to explain its cleavage, gastrulation and axis specification. The centrolecithal egg of A. bengalensis underwent meroblastic superficial cleavage. The cleavage initiated at the future dorsal side of the egg within 5 h to 5 h and 30 min of incubation. Consequently, a small mass of energids appeared superficially at the future dorsal side within 6 h. Later, energids were found at the future ventral and lateral sides. A syncytial blastoderm was formed around the centrally placed yolk material which was transformed into a cellular blastoderm within 30 h of incubation. In the blastoderm, two cell masses were formed at the dorsal and ventral part which initially extended towards each other and later spread out though future anterior-posterior direction. The pressure exerted by the cell flow displaced the entire yolk material at the future postero-ventral side. At the time of egg laying, a prototype of the embryonic axes is determined. The substratum side of the egg formed the dorsal part, whilst the side facing water turned to the ventral part. The broader end of the egg formed the anterior side and the narrow end formed the posterior side of the embryo. The anterior-posterior axis formation was initiated within 72 to 96 h of incubation when the blastodermal cells displaced the yolk material at the future posterior end. Within 120 h of incubation, the germ layers of the embryo were determined. The study reveals that the cleavage pattern of A. bengalensis shows close similarities with that of the Malacostraca amongst the crustaceans and dipteran and hymenopteran amongst the insects.

Transverse relaxation dispersion of the p7 membrane channel from hepatitis C virus reveals conformational breathing.

The p7 membrane protein encoded by hepatitis C virus (HCV) assembles into a homo-hexamer that selectively conducts cations. An earlier solution NMR structure of the hexameric complex revealed a funnel-like architecture and suggests that a ring of conserved asparagines near the narrow end of the funnel are important for cation interaction. NMR based drug-binding experiments also suggest that rimantadine can allosterically inhibit ion conduction via a molecular wedge mechanism. These results suggest the presence of dilation and contraction of the funnel tip that are important for channel activity and that the action of the drug is attenuating this motion. Here, we determined the conformational dynamics and solvent accessibility of the p7 channel. The proton exchange measurements show that the cavity-lining residues are largely water accessible, consistent with the overall funnel shape of the channel. Our relaxation dispersion data show that residues Val7 and Leu8 near the asparagine ring are subject to large chemical exchange, suggesting significant intrinsic channel breathing at the tip of the funnel. Moreover, the hinge regions connecting the narrow and wide regions of the funnel show strong relaxation dispersion and these regions are the binding sites for rimantadine. Presence of rimantadine decreases the conformational dynamics near the asparagine ring and the hinge area. Our data provide direct observation of μs-ms dynamics of the p7 channel and support the molecular wedge mechanism of rimantadine inhibition of the HCV p7 channel.

Primary wave transmission in the hexagonally packed, damped granular crystal with a spatially varying cross section

Present study concerns the dynamics of a primary pulse propagating through the uncompressed, 2D hexagonally packed granular crystal with spatially varying cross-section and given to onsite perturbation. In this study, the system under consideration is referred to as a fundamental model. We demonstrate that application of the uniform, soliton like loading on the narrow end of granular crystal leads to the formation of a spatially localized, traveling, primary pulse. At the first stage of propagation, the shape of a spatial distribution of a primary pulse is nearly straight, consequently preserving the main features of incoming pulse (i.e. preserving the waveform and the local speed of Nesterenko soliton). However, as it propagates, the shape of a spatial distribution slowly deviates from a straight line. Primary pulse becomes distributed along the curve after sufficient number of layers, rather than follows a straight line. In current work we primarily focus on the first stage of propagation of the primary pulse. We show that a spatial evolution of the strongly localized primary pulse can be efficiently described by a reduced order model comprising the perturbed, purely nonlinear (Hertz interaction law) chain of effective particles with the linearly increasing masses and stiffness coefficients. Using the recently developed analytical procedure of nonlinear maps and a subsequent homogenization, we derive a closed form, analytical approximation depicting the evolution of the traveling primary pulse. It is worthwhile noting that the devised analytical approximation accounts for the presence of an onsite perturbation (e.g. dissipation) imposed on the full model. Results of the numerical simulations of the reduced order model as well as these of the analytical approximation are found to be in a spectacular agreement with the results of numerical simulations obtained for the full 2D model.

Effect of EDM parameters on hole quality characteristics in deep hole drilling of Inconel 718 superalloy

This paper presents the effect of electrical discharge machining parameters on the hole quality characteristics during small hole deep drilling of Inconel 718 superalloy. Through holes of 62 mm depth and diameters ranging from 3.055 to 3.316 mm are drilled. The hole quality are characterised by surface roughness value (Ra), depth averaged radial overcut (DAROC) and hole profile. The experimental results show that process parameters such as peak current and pulse on–time are significant parameters on Ra and the parameter pulse on–time is significant on DAROC. Analysis of hole profiles show three distinct segments along the depth of hole: wide mouth at the top; barrel shaped at the midway; narrow end at the bottom. Further, surface topography of EDM drilled surfaces are studied at different depths along the hole using SEM and are reported here. [Received 9 September 2013; Revised 30 July 2014; Accepted 2 October 2014]

Induced-charge electrokinetics in a conducting nanochannel with broken geometric symmetry: Towards a flexible control of ionic transport

In the literature, conventional electrokinetics is widely used as a principle of operating nanofluidic devices. Different from the conventional electrokinetics involving nonpolarizable solid surfaces with fixed surface charge, induced-charge electrokinetic (ICEK) phenomena deal with polarizable surfaces with the ability of surface charge modulation through electric polarization under external electric fields. Because of several advantages, ICEK phenomena have drawn a great deal of attention in microfluidic community. Herein, we propose the first effort of extending the ICEK phenomena from microfluidics to nanofluidics. In particular, we report a numerical model for the ICEK phenomena in a tapered nanochannel with conducting (ideally polarizable) walls. It is shown that due to the broken geometric symmetry of the nanochannel, induced-charge electroosmotic flow inside the nanochannel exhibits a flow rectification such that electrolyte solution always flows from the narrow end of the nanochannel to the wide end for either a forward electric bias (electric field from the narrow to wide ends) or a reverse electric bias (electric field from the wide to narrow ends). In addition, we demonstrate that the ion selectivity of such tapered conducting nanochannel can be actively tuned to be cation-selective with a forward bias and anion-selective with a reverse bias. Promisingly, conducting nanochannels with broken geometric symmetry could be potentially used for constructing nanofluidic pumps with the unidirectional pumping capacity and ion selectors with the tuneable ionic selection.

Paradigm Shift in the Mechanism of HIV-1 Core Biogenesis

The proteolytic cleavage of the poly-protein HIV-1 Gag, which is assembled on the surface of plasma membranes of infected cells, drives the conversion of the virus from the initial immature, non-infectious form to the functionally distinct mature, infectious form. Gag cleavage results in a series of structural changes, ultimately leading to the formation of a mature core. Current models for assembly of the mature core suggest that the cleaved HIV capsid protein (CA) nucleates in a concentration-dependent manner, and polymerizes forming the conical core in a diffusion-controlled process. These models also postulate that the core begins to grow at its narrow end, and stops growing once it reaches the membrane at the opposite end. Thus, the size of the virus itself is expected to be the primary factor that determines core size. Our findings challenge this view.Cryo-electron microscopic analyses show that along with infectious viruses, viral isolates also comprise large membranous structures that contain multiple, freely-floating mature cores. Numerous instances of membrane-attached assembly intermediates with partially formed “core-rolls” that are at different stages of conversion from a planar Gag lattice to the mature core are also observed. These results indicate that the mechanism of core formation involves a non-diffusional, cooperative transition triggered by cleavage of the immature Gag lattice, resulting in its rolling away from the plasma membrane to form sheets that wrap around the viral RNA. Unlike the present models, our mechanism predicts that the generation of infectious HIV-1 will be severely affected by incomplete cleavage CA from the Gag matrix (MA), and that even a small percentage of uncleaved MA-CA would prevent the core from rolling away. This prediction explains previous experimental results; only 4% of cleavage-resistant MA-CA is sufficient to cause a 50% reduction of infectivity.

57 THE EFFECT OF VITRIFICATION FOR SHEEP EMBRYO VIABILITY

This work evaluated different methods for sheep embryo cryopreservation by vitrification (V) and super-cooling ultra-rapid vitrification (SCURV). The vitrification method was applied according to the method described by Vajta et al. Both treatments used a vitrification solution (VS) containing 20% ethylene glycol, 20% dimethylsulfoxide (Me2SO), 0.5 mol L–1 sucrose in Dulbecco's phosphate buffered saline (DPBS) with 10% BSA. The super-cooled LN facilitates heat transmission between LN and the cryosolution interface, and this is efficient for bovine semen and blastocyst cryoconservation (Arav et al. 2002). By surgical flushing 25 super-stimulated ewes, 109 transferable morulae were harvested; 35 morulae were transferred fresh to synchronized recipients (control) and the others were cryopreserved by V (n = 36) or SCURV (n = 38), respectively, thawed or warmed, and transferred to recipients. Embryos were vitrified using the HSV Kit. They were first incubated in 50% VS for 2 min and then transferred for 30 s into 100% VS. Each embryo was loaded by HSV Kit, which was immediately submerged into and stored in LN. Warming was done by placing the narrow end of the straw into DPBS + 0.25 M sucrose for 5 min. Embryos were then transferred into DPBS + 0.125 M sucrose for 3 min and finally to DPBS until transfer. The SCURV morulae were then exposed to 50 and 100% VS at 37°C for 2 min and 30 s, respectively. Embryos after saturation in VS were transferred on a surface of a nylon loop (volume 20 μL, diameter 0.5 mm) and using negative pressure of LN in the chamber for freezing with the VIT-Master. Thawing vitrified embryos was accomplished by placing the vitrified embryos in solutions of sucrose 0.25 M and 0.125 M with expositions 2 and 3 min accordingly. After thawing embryos, only good-quality embryos were transferred. Statistical analyses were performed with Student's t-test. The lambing rate following transfer of fresh, frozen-thawed vitrification and SCURV methods were 18, 12, 14 lambs accordingly. No statistical difference was found for the percentage of does lambing following transfer thawed after vitrification (33.4 ± 5.2a%) and SCURV methods (36.8 ± 6.3b%). The survival rate following transfer of fresh embryos (51.4 ± 4.8c) was higher and in line with previous findings using VS. Differences were statistically significant (ac,bc P &lt; 0.05). Importantly, our data suggest that the HSV Kit can be used to produce viable morulae for implantation as the SCURV, and to as vitrification method. Although further work on the developmental competence of embryos cryopreserved with the SCURV method are needed, these data suggest that with SCURV a faster freeze rate and lower level of cryoprotectants is able to minimize ice crystal formation and should be further evaluated as a routine mechanism for cryopreserving sheep embryos.

Pentameric viral ion channels: from structure to function

Pentameric viral ion channels: from structure to function Wahyu Surya, Yan Li, Jaume Torres School of Biological Sciences, Nanyang Technological University, Singapore Abstract: A family of small polypeptides in many virus types associate to form oligomers and have channel activity. These proteins have been referred to as viroporins or virochannels and are increasingly recognized as important virulence factors and potential drug targets. In this review, we focus on two of the viroporins that have been studied in more detail from a structural and functional point of view. One is the 76-residue envelope (E) protein found in coronaviruses (CoVs) that causes the severe acute respiratory syndrome (SARS). The other is the 65-residue small hydrophobic (SH) protein found in a paramyxovirus, the respiratory syncytial virus (RSV). RSV SH and SARS-CoV E proteins are short polypeptides with a single transmembrane domain. In both cases, the presence of the viroporin has a protective effect on cells, preventing early apoptosis, but it leads to increased virulence in infected animal models. Both viroporins form homopentameric oligomers that show channel activity with no or low selectivity. The role of channel activity is still unclear, but associations have been made to facilitation of the egress of the virus by modification of the secretory pathway, and contributions to inflammation. SARS-CoV E protein has a cytoplasmically oriented C-terminus and a lumenal N-terminus, whereas the opposite orientation is found in RSV SH protein. Despite this opposite topology, nuclear magnetic resonance (NMR)-based structural models of these two channels show a similar champagne flute shape, with the wider opening facing the cytoplasmic side. Good channel inhibitors are lacking, but those found seem to have a preference for the narrow end of the channel. Availability of good inhibitors will help reveal the specific role of these channels in the life cycle of these viruses. Keywords: respiratory syncytial virus, severe acute respiratory syndrome, small hydrophobic protein, envelope protein, channel structure

An important mechanism for thermal rectification in graded nanowires

In the quest for the origin of the different thermal rectifying behavior of two graded nanowires, we reveal the important role that standing waves play in the thermal transport properties of such graded structures. Evidence for the existence of standing waves is given from two angles, and one possible scenario of the origin of the standing wave is presented. The key point is that the formation of the standing wave, which greatly hinders the propagation of phonon waves, occurs only when the narrow end of the nanowire is at a higher temperature than the wide end, making the heat current flow preferably from the wide end to the narrow end.

Investigation of the inclusion behavior of ofloxacin with methyl-β-cyclodextrin

The inclusion complexation behavior of ofloxacin with methyl-β-cyclodextrin (Me-β-CD) was investigated by fluorescence spectroscopy, SEM, FT-IR, 1H and 2D NMR. The results suggested the formation of inclusion complexes with a stoichiometric ratio of 1:1 and the formation constant (K) of the complex was calculated. Me-β-CD was more suitable for inclusion of neutral ofloxacin molecule and the major inclusion interactions between the guest and Me-β-CD cavity are hydrophobic interactions. 1H NMR data indicated an insertion of this guest molecule into Me-β-CD at the narrower end. Generally, the low aqueous solubility of ofloxacin severely limited its efficacy. By forming inclusion complex with Me-β-CD, the water solubility of ofloxacin was significantly increased, which may increase the absorption of ofloxacin with the result of an improved pharmacological efficacy.

Hysteresis loop and scanning curves of argon adsorption in closed-end wedge pores.

The hysteresis loop and scanning curves for argon adsorbed in a wedge pore with one end closed are studied with grand canonical Monte Carlo simulation. We have found multiple hysteresis loops for pores with either the narrow end or the wider end closed. In pores with the narrow end closed, adsorption and desorption exhibits a two-stage sequence of rapid change, followed by a gradual change in adsorbate density. The pore can be divided into zones of commensurate packing and junctions of incommensurate packing. A striking feature is that the sequence of these two stages is opposite for the adsorption and desorption processes. This can be explained by cohesion in the adsorbate, in which a steep condensation process is associated with the zones and a steep evaporation process is associated with the junctions between them. For pores with the wider end closed, the processes of adsorption and desorption from various zones are correlated with each other. In pores with the narrow end closed, the scanning curves trace reversibly along the segment of the isotherm, where the isotherm shows gradual change, and when the scanning curve reaches a point between the gradual change segment and the sharp change segment, the scanning curve crosses from one boundary of the hysteresis loop to the corresponding point on the other boundary. This indicates that the condensation and evaporation states are not affected by scanning but that, in scanning across the hysteresis loop, the adsorbate passes through a sequence of metastable states as the distribution of density is rearranged, without any significant change in the overall density. In contrast, for pores with the wider end closed, both the descending curve from a partially filled pore and the ascending curve are identical to the desorption branch of the corresponding pore with its narrow end closed.

Alignment and Structural Evolution of Cylinder-Forming Diblock Copolymer Thin Films in Patterned Tapered-Width Nanochannels

Control over the orientation of cylindrical block copolymer microdomains and the position of dislocations using tapered nanochannels is herein demonstrated. Dislocations are introduced periodically as the channels become progressively wider. Our high-temperature atomic force microscopy (AFM) enables us to probe real-time and real-space dislocation movement directly. Upon annealing, dislocations are observed to move to their equilibrium positions, where the average free energy of the polymer chains reaches a minimum. Smaller confinement widths impose a powerful guiding field for templating domain alignment, as the deviations of the dislocations at the narrower end of the channel from their equilibrium positions are minimal. Finally, the fluctuations of dislocations across the wedge are studied under different temperatures, and the perpendicular diffusion coefficients and activation energy are determined. These experiments demonstrate the ability to control the placement of periodically located dislocations...