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Polymer-grafted surfaces and channels are increasingly used for the design of responsive materials and sensors due to robust performance and ease of use. Various strategies for the control of the nanoscale morphologies of such materials and devices are being tested. Entropic repulsion between the polymer chains in a grafted brush of sufficient density causes the chains to extend in the direction perpendicular to the grafting surface in comparison to the position of unattached polymers. When nanoparticles having attractive interactions with the polymers are introduced into the solvent, these nanoparticles tend to infiltrate into the brush and reduce its extension. Under certain conditions, a sharp reduction in brush height extension can occur over a narrow range of nanoparticle concentrations in solution. We describe a way of controlling transport through polymer-functionalized nanochannels with nanoparticle additives, relying on the physics of nanoparticles and polymer brushes under confinement, and we suggest a blueprint for the creation of a tunable nanovalve. The nanovalve is modeled as a cylinder with a polymer brush grafted on its inside surface. Brush properties such as the chain length and the grafting density are chosen so that the brush chains extend into the center of the cylinder in the absence of nanoparticles, occluding the flux of analyte molecules through the pore. When nanoparticles that are attracted to the polymers are introduced into solution, they infiltrate into the brush and partially collapse it against the cylindrical grafting surface, opening space in the center of the cylinder through which analyte molecules can flow. The operation of such a nanovalve is analyzed via self-consistent field theory calculations in the strong-stretching approximation. Self-consistent field analysis is supported by Langevin dynamics simulations of the underlying coarse-grained model of the polymer-nanoparticle system.

The liver and spleen are major biological barriers to translating nanomedicines because they sequester the majority of administered nanomaterials and prevent delivery to diseased tissue. Here we examined the blood clearance mechanism of administered hard nanomaterials in relation to blood flow dynamics, organ microarchitecture and cellular phenotype. We found that nanomaterial velocity reduces 1,000-fold as they enter and traverse the liver, leading to 7.5 times more nanomaterial interaction with hepatic cells relative to peripheral cells. In the liver, Kupffer cells (84.8 ± 6.4%), hepatic B cells (81.5 ± 9.3%) and liver sinusoidal endothelial cells (64.6 ± 13.7%) interacted with administered PEGylated quantum dots, but splenic macrophages took up less material (25.4 ± 10.1%) due to differences in phenotype. The uptake patterns were similar for two other nanomaterial types and five different surface chemistries. Potential new strategies to overcome off-target nanomaterial accumulation may involve manipulating intra-organ flow dynamics and modulating the cellular phenotype to alter hepatic cell interactions.

Despite the proliferation in coastal development world-wide little is known of the biological and ecological effects of man-made submerged habitats in coastal reefal environments. Such habitats, when able to move, offer unique environmental conditions, mainly in terms of hydro- dynamic aspects. The current study tested whether floating habitats would develop unique commu- nities in comparison to identical fixed ones, due to differences in current regime between the 2 types of habitat. We found significant differences in the hydrodynamic features associated with habitats of different motion capabilities, predominantly in mass-transfer rate, current velocity and shear stress. Floating installations had greater flow velocities and shear stress compared to fixed ones. We suggest that these hydrodynamic features determine the nature of the benthic communities on floating and fixed habitats, as the former revealed greater biomass and less chlorophyll content compared to the latter, while coral settlement was greater on the fixed installations, particularly near the seabed. The motion of floating artificial habitats increased the mass-transfer rate, as reflected by higher current velocities, and elevated the shear stress felt on their surfaces. These conditions encourage massive settlement of benthic macroinvertebrates and determine the community structure of floating artificial habitats in reefal environments.

The wave resistance, side force, and yawing moment acting on a hovercraft moving on the free surface of a heavy fluid is studied. The hovercraft is represented by a distributed excess pressure. Various types of pressure and bounding contours are considered. The sensitivity of the results to numerous uncertainties in the problem's physical parameters is investigated. It is found that constant pressure over a rectangular region moving with an angle of drift results in peculiar side force values. Several robust mathematical models of a moving hovercraft are proposed and analyzed.

Synthetic aperture radar (SAR) images of ships and their wakes frequently exhibit long dark and bright streaks. Some of them can be attributed to the Kelvin wavewake and others to the turbulent and bright narrow V-wake. The wakes contain information about the ship. The present work deals with estimates of the ship beam and its velocity by processing SAR images of the Kelvin and turbulent wakes. It is assumed that the ship moves along a straight path with constant speed. For the detection of the linear features of the ship wake, the fast discrete Radon transform is employed. Once the turbulent wake is detected, the ship beam is estimated by a novel method that exploits the expansion of the turbulent wake aft a ship. A semiempirical relation between the ship beam and the width of its turbulent wake is derived and analyzed. An algorithm for estimating the width of the turbulent wake in SAR images and the ship beam is developed. The spectrum of ship-generated waves along the Kelvin cusp-lines is discussed. Processing of the lines, pertaining to the Kelvin wake bounds, and analysis of the spectral peaks enables to estimate the ship speed. Numerical examples of processing of airborne SAR images are provided.

We predict the thermodynamic and structural behavior of solutions of long cross-linked filaments. We find that at the mean field level, the entropy of self-assembled junctions induces an effective attraction between the filaments that can result in a phase separation into a connected network, in equilibrium with a dilute phase. A connected network can also be formed in a non-thermodynamic transition upon increase of the chain, or cross link density, or with decreasing temperature. For rigid rods, at low temperatures, we predict a transition from an isotropic network, to anisotropic bundles of rods tightly bound by cross links, that is triggered by the interplay between the configurational entropy of the cross-link distribution among the rods, and the rotational and translational entropy of the rods., Comment: typos and graphics corrected; 6 pages 1 figure

Self-assembly in soft-matter systems often results in the formation of locally cylindrical or chain-like structures. We review the theory of these systems whose large-scale structure and properties depend on whether the chains are finite, with end-caps or join to form junctions that result in networks. Physical examples discussed here include physical gels, wormlike micelles, dipolar fluids and microemulsions. In all these cases, the competition between end-caps and junctions results in an entropic phase separation into junction-rich and junction-poor phases, as recently observed by electron microscopy and seen in computer simulations. A simple model that accounts for these phenomena is reviewed. Extensions of these ideas can be applied to treat network formation and phase separation in a system of telechelic (hydrophobically tipped, hydrophilic) polymers and oil-in-water microemulsions, as observed in recent experiments.

We investigate the short time and short scale dynamics of membrane phases. The dynamics of the two point displacement correlator of the membrane is shown to be dominated by the transverse mean-square displacement of a tagged membrane point and to vary with time t as ∼t2/3. As a result, the structure factor of oriented lamellar phases at nearly perpendicular orientations (mean membrane normal parallel to the wavevector k → ) decays as a stretched exponential S( k → ,t)∼ e −( Γ k z t) 2/3 with Γkz∼(T/κ)1/2(T/η)kz3. For isotropic systems, angular averaging retains the stretched exponential decay, S(k,t)∼e−(Γkt)α, but with α>2/3 and no longer universal. We also find Γk∼kz with z

The immediate impulsive flow of an incompressible fluid due to a concentrated flux through an otherwise impermeable boundary is investigated analytically in three dimensions. The flow is inviscid and irrotational, and obeys the equipotential condition at the free surface, which is initially horizontal. Various elementary bottom geometries are analyzed: rectangular basins, sloping beaches, semi-cylindrical and hemispherical basins. Special attention is paid to the case of impulsive free-surface flows generated on a uniform sloping beach. A general integral solution is presented and compared against a series solution found for a discrete set of angles. The results are relevant for the modeling of tsunami generation due to rapid bottom deflections.

Stabilisasi merupakan proses memperbaiki struktur tanah menjadi lebih kuat dan lebih stabil dengan penambahan beberapa bahan stabilisasi seperti seperti cangkang kelapa sawit.. Penelitian ini bertujuan untuk mengetahui bahwa dengan penambahan cangkang kelapa sawit pada tanah lempung dapat meningkatkan daya dukung tanah lempung. Pengujian tanah yang dilakukan yaitu pengambilan contoh tanah terganggu, yang kemudian dilanjutkan dengan pengujian laboratorium sifat-sifat fisik tanah, kepadatan, CBR, dan swelling. Standar pengujian terhadap tanah ini juga mengacu kepada standar ASTM serta pengujian dengan beragam variasi pencampuran cangkang kelapa sawit (30%, 60%, 80%) dari berat kering tanah) tanpa pengeraman Penelitian ini memberikan indikasi bahwa metode yang telah dilakukan dengan penambahan cangkang kelapa sawit dapat meningkatkan daya dukung tanah lempung. Hasil penelitian mendapatkan hasil maksimum pada penambahan 30%, dengan nilai CBR 20,12. Kata Kunci : Cangkang Kelapa Sawit, Pemadatan, CBR

Nuclear Pore Complex (NPC) is a biological “nano-machine” that controls the macromolecular transport between the cell nucleus and the cytoplasm. It is a remarkable device that combines selectivity with robustness and speed. Unlike many other biological nano-channels, it functions without direct input of metabolic energy and without transitions of the gate from a 'closed' to an 'open' state during transport. The key aspect of transport is the interaction of the cargo-carrying transport factors with the unfolded, natively unstructured proteins that partially occlude the channel of the NPC and its nuclear and cytoplasmic exits.Mechanistic understanding of the transport through the Nuclear Pore Complex, and in particular its selectivity, is still lacking. Conformational transitions of the unfolded proteins of the NPC, induced by the transport factors, have been hypothesized to underlie the transport mechanism and its selectivity. These conformational changes are hard to access in vivo; they have been investigated in vitro, generating apparently contradictory results.We have investigated the biophysical underpinning of these conformational changes, using computational modeling based on the ideas the ideas of the polymer physics. We show that the differences in the experimentally observed behaviors can be explained by rather general physical factors, such as the attraction strength between the transport factors and the unfolded chains, protein density and the transport factor size. We also show how these general behaviors can be modulated by molecule-specific details, such as the aminoacid sequence and the relative arrangement in space of the charged and hydrophobic residues. Finally, we extend the model into a realistic NPC geometry. These results provide new insights into the fundamental principles of transport through the NPC and the control of the behavior of natively unfolded proteins in general.

Surface waves generated by a moving ship in water of finite depth are affected by the rheological properties of the movable bottom. The aim of this work is to evaluate the wave resistance exerted on a hovercraft modeled as a two-dimensional pressure distribution moving on the free surface of water with nonrigid bottom. Analysis of three-dimensional flows in two-fluid layers of finite depths is performed by assuming an inviscid upper layer (water) and a viscous lower layer (nonrigid bottom). Numerical calculations show that the maximum wave resistance occurs in the vicinity of the critical Froude number F=1. This maximum value decreases as the muddy bottom becomes less rigid.

Synthetic aperture radar (SAR) ship wake images in light wind and calm sea conditions frequently appear in the form of a bright V with a half-angle of 2 to 3 deg. Sophisticated and conflicting explanations of this phenomenon, based on the Bragg scattering mechanism, have been proposed. There is a belief that the narrow V-wake is not a part of the Kelvin wake. An alternative approach, which is not generally accepted, suggests that short divergent Kelvin waves may contribute to the V-wake imaging although these waves are mixed with unsteady surface waves generated by the ship-induced turbulence. Ship-generated divergent waves contaminated by surfactants and their radar backscattering cross section are studied. The hull of the ship is represented by a single layer of hydrodynamic singularities. The Green function of a point source moving below a free surface covered by surfactants is derived. A closed-form asymptotic solution for the far ship wave wake is obtained. It is used to calculate analytically the corresponding radar backscattering cross section. The radiative, viscous, and surfactant-induced decay of the V-wake brightness along the V-arms is discussed. The theoretical results are compared against available experimental data.

We discuss the structure and the interaction of telechelic brushes. We show that the association of functionalized chain ends is capable of giving rise to attractive interactions between telechelic brush-covered surfaces, in contrast to conventional repulsion. Our predictions for the interaction free energy are in agreement with experimental data.

Sinar matahari yang sangat melimpah di Nusa Tenggara Timur (NTT), memiliki dampakyang dirasakan di perairan NTT adalah suhu dan temperatur udara pada siang hari mencapai34 derajat celsius, suhu panas sangat dirasakan terutama di Kupang, pada siang hari tepatpukul 12.00 WITA, temperatur udara di sebagian besar wilayah NTT seperti Kupang dansekitarnya mencapai 34 derajat Celsius. Kondisi tersebut berbeda dengan hari-hari biasanya dimana temperatur minimum NTT 32-33 derajat Celsius, kondisi alam ini (suhu naik hingga 34-35 derajat celsius) terjadi karena matahari berada di titik kulminasi atau tepat di atas KotaKupang.Kondisi suhu panas yang dirasakan di Kupang selama ini dapat dimanfaatkan sebagaipembangkit tenaga listrik, hal ini telah dibuktikan oleh Pemerintah Kota (Pemko) Kupang NusaTenggara Timur (NTT) yaitu dengan memanfaatkan solar cell untuk lampu jalan yang terbuktimampu menghemat pembayaran tagihan listrik untuk lampu jalan sebesar Rp.1 miliar per bulan.Penghematan ini diperoleh setelah dipasang 541 unit lampu jalan di Kupang denganmenggunakan panel surya dari jenis lampu LED (laigth emmiting diode) dengan daya 23-35watt .(detikfinance, 14/6/2011).Kendaraan Motor Listrik yang dijalankan dengan tenaga listrik DC (direct current)menggunakan accu (baterai) sebagai sumbernya yang diperoleh dari hasil pengisian melaluilistrik AC (alternating current) yang telah disearahkan dan atau dari panel surya (Solar Cell)atau tenaga matahari. Panel surya merupakan komponen yang sangat penting karena dapatmengubah sinar matahari menjadi energi listrik yang kemudian disimpan di dalam baterai.Selanjutnya digunakan untuk menggerakkan motor DC yang terhubung dengan sistem penggerakroda berupa kombinasi geer, sistem penggerak ini akan memberikan daya gerak yangmenggerakkan kendaraan solar cel ini yang bergantung pada beberapa hal seperti kecepatanmotor, putaran penggerak, berat kendaraan dan lain-lain.Tujuan jangka panjangnya adalah : 1) Untuk menyediakan kendaraan yang tidakmemerlukan bahan bakar minyak dan bersih dari polusi karena menggunakan listrik DC dantenaga matahari melimpah di NTT terutama untuk kendaraan yang dapat diantar-pulaukanmengingat NTT terdiri dari pulau-pulau kecil dan besar dan tidak semua pulau memiliki pangkalanbahan bakar minyak; 2) Aplikasi penggunaan panel solar cell dapat dikembangkan lagi sepertiuntuk pengairan pada lahan yang kesulitan air dimusim kemarau yaitu dengan membuat pompaair bertenaga matahari dan kemanfaatan lainya.Tujuan Khusus :Berdasarkan fenomena di atas, maka tujuan khusus dari penelitian ini adalah : 1) Untuk membuatmodel Kendaraan Motor Listrik (kendaraan) dengan tenaga solar cell; 2) Untuk merancangpenggunaan solar cell sebagai sumber daya untuk Kendaraan Motor Listrik DC; 3) Untukmengevaluasi penggunaan motor dan sistim geer yang sesuai dan aman. Untuk mencapai tujuan penelitian, dilakukan penelitian secara bertahap selama 2 (dua)tahun dengan rincian sebagai berikut :Tahun I : Perancangan Kendaraan Motor Listrik (Kendaraan) dengan tenaga listrik DC(direct current) dan sistem transmisi geer mekanik. Penelitian Tahun I terdiri dari dua tahap,yaitu Tahap (1) Perancangan dan pembuatan rangka Kendaraan Motor Listrik dengan penggerakmekanik dan motor listrik DC. Dan Tahap (2) Uji kelayakan jalan (jarak tempuh) dan kecepatanserta kemampuan motor DC Pada Penelitian Tahap I Dengan sistem pengaturan kecepatan.Tahun II : Perancangan Kendaraan Motor Listrik (Kendaraan) dengan tenaga listrik DC(direct current) dari Solar Cell dan penyesuaian sistem transmisi geer mekanik. PenelitianTahun II juga terdiri dari dua tahap, yaitu Tahap (1) Perancangan dan pemasangan Solar Cellrangka Kendaraan Motor Listrik dengan penggerak mekanik yang disesuaikan dengan sistemtransmisi geer mekanik terhadap motor listrik DC yang digunakan. Dan Tahap (2) Uji kelayakanjalan (jarak tempuh) dan kecepatan serta kemampuan motor DC dengan sumber Solar CellPada Penelitian Tahap I Dengan menggunakan sistem pengaturan kecepatan

This paper considers a circular buoyant elastic plate of homogeneous stiffness floating in shallow water. The edge of the plate is free of shear forces and bending moments. The plate deflection is excited by a monochromatic ambient surface wave. A closed form solution of the corresponding linearized problem is obtained. Numerical examples, illustrating the analytic results for various physical parameters of the problem are presented.

We consider a lamellar phase of bilayer membranes held between two parallel plates and subject to a steady shear. Accounting for the coupling with the shear flow of the short wavelength undulation modes that are responsible for the membrane excess area, we argue that the flow generates an effective force which acts to reduce the excess area. From the viewpoint of the macroscopic lamellar whose geometric dimensions are fixed, this force translates into an effective lateral pressure. At low shear rates $\dot \gamma$ this pressure is balanced by the elastic restoring forces of the lamellar. Above a critical shear rate $\dot \gamma _c \sim d^{ - 5/2} D^{ - 1/2}$ , where d is the interlayer distance and D is the gap spacing, the lamellar buckles into a harmonic shape modulation, and we predict its wavelength λc and amplitude U o. We show that our model is isomorphic to a dilative strain, which is known to induce a similar buckling (undulation) instability. Indeed, at threshold the wavelength is $\lambda _c \sim \sqrt {Dd}$ and is identical in both cases. Using a non-linear analysis, we discuss how the wavelength and amplitude vary with shear rate away from the threshold. For $\dot \gamma \gg \dot \gamma _c$ we find $\lambda _c \sim \dot \gamma ^{ - 1/3}$ and $U_o \sim \dot \gamma ^{2/3}$ . We then focus on the coupling of the buckling modulation itself with the flow, and obtain a criterion for the limit of its stability. Motivated by experiments of D. Roux and coworkers, we assume that at this limit of stability the lamellar breakups into “onion”-like, multilamellar, vesicles. The critical shear rate $\dot \gamma *$ for the formation of onions is predicted to scale as $\dot \gamma * \sim \dot \gamma _c \sim d^{ - 5/2} D^{ - 1/2}$ . The scaling with d is consistent with available experimental data.

The problem of obtaining quantitative data on spatial ocean wave spectra from the images of the ocean surface by either regular SAR or along-track interferometric SAR (INSAR) is studied. The dominant mechanism which allows imaging of ocean waves by SAR/INSAR is the so-called velocity bunching. This mechanism is essentially nonlinear. The theoretical analysis of SAR/INSAR imagery of the ocean surface due to velocity bunching is performed, and nonlinear solutions of the SAR/INSAR images of monochromatic waves and of the spectra of these images are obtained. Analytic expressions are presented which allow for the accurate simulation both SAR and INSAR images of waves with arbitrary lengths, heights and propagation directions. It is demonstrated that a monochromatic wave expands in the SAR/INSAR images into an infinite number of harmonics. In addition to the nonlinearity parameters of SAR which is related to the velocity bunching mechanism, it is shown that for complex INSAR, the degree of nonlinearity depends also on separation time between the two antennas. The results of the present study indicate that in addition to the prevailing practice to consider the phase component of the INSAR image, an analysis of the imaginary part of the complex INSAR map of the ocean surface may provide some supplementary information, beneficial, in particular, for rough sea.

The dynamics of flexible polymeric fractals in solutions is discussed using a linearization self-consistent approximation. When hydrodynamic interaction is not screened (Zimm model) we find that the mean square displacement $〈\ensuremath{\Delta}{(t)}^{2}〉$ of a monomer is anomalously increasing with time, $〈\ensuremath{\Delta}(\mathcal{t}{)}^{2}〉D\ensuremath{\sim}{t}^{\ensuremath{\alpha}}$ with a universal exponent $\ensuremath{\alpha}=2/d$ in $d$ dimensions, independent of the fractal ${(d}_{f})$ and spectral dimensions. The viscoelastic modulus behaves as $G(\ensuremath{\omega})\ensuremath{\sim}(i\ensuremath{\omega}{)}^{u},$ with ${u=d}_{f}/d.$ When hydrodynamics is screened (Rouse model) we find $\ensuremath{\alpha}{=2/(2+d}_{f})$ and ${u=d}_{f}{/(2+d}_{f}).$ We conclude that measurements of $\ensuremath{\alpha}=2/d$ indicate unambiguously that the Zimm model is applicable and thus should be correlated with ${u=d}_{f}/d$ in rheology measurements.

Settlement of marine larvae on a substrate is a fundamental problem of marine life. The probability of settlement is one of the quantitative characteristic of the settlement process. The probability of larval contact with a substrate is the upper bound of the probability of settlement. This work addresses the problem of contact probability and contact rate of marine invertebrate larvae with an isolated protruding collector located in an unbounded sea current. There are two common approaches to the problem of contact probability. In one, a collector induces certain cues, which help a larvae find the collector. In such a case, the larva moves towards the collector deliberately, using its navigation and propulsion devices. In the second approach, a larva moves towards a collector as a passive small particle. In this case, the cause of contact of a larva with a collector is a mechanical collision of a small moving body with a large obstacle. We considered a larva which does not know the location of the collector, which does not use its navigation device yet uses its self-propulsion. We mimicked a larva by a tiny self-propelled underwater vehicle, moving in shear flow of a large obstacle. We illustrated our approach by studying contact of a larva of the Bryozoan Bugula neritina with a cylindrical collector. We observed the behavior of this larva in a laboratory flume, and according to the observations formulated a mathematical model of larval motion in shear flow. The trajectories of a large number of larvae, starting their motion far from a collector with random initial conditions are calculated numerically, and the probability of their contact with a collector is estimated. The results of Monte-Carlo simulations illustrate that larval self-propulsion may increase the probability of their contact with a collector by orders of magnitude compared to passive particles.

A mathematical model that allows simulations of the image of waves in ship wakes by either regular or interferometric airborne Synthetic Aperture Radar (SAR or INSAR) is described. The three-component velocity field induced at the ocean surface by a moving ship serves as the input to the model. The simulations take into account the effect of temporal variations of the wave field in the wake on the INSAR imaging by the velocity bunching mechanism. The model also accounts for the scanning distortion of the image. The developed algorithm allows study of the visibility of the ship wave wake by a regular SAR or by INSAR for arbitrary imaging parameters, as well as for different ship sizes and ship velocity vectors relative to the platform flight track. Various patterns of ship wake images obtained by numerical simulations are presented.

The problem of a hydrofoil moving near an interface of two fluids of different densities is analyzed. An iteration scheme is proposed which imposes the boundary conditions on the body surface and on the interface alternately. The numerical solution is obtained by using the linearized theory and a Glauert-type expansion for the vortex distribution. Results are provided for various cases with different densities and different speeds.

A ship cross section undergoes periodic oscillations in a finite water layer, overlaying a mud layer. The upper fluid is considered to be inviscid, and the mud is modeled as a Newtonian liquid. The section contour is replaced by a distribution of wave sources with unknown strength, satisfying a corresponding boundary integral equation. Its kernel is expressed through a newly derived Green function. The numerical solution of the integral equation allows evaluation of the added-mass and damping coefficients. Specific computations pertaining to Lewis forms show a drastic dependence of the added-mass and damping coefficients on the mud thickness and density.

A ship has to move from a point A to a point B and has on its way to navigate through a narrow zigzag channel. Using a realistic model of a tanker ship, a method is proposed for computing feasible rudder command strategies for the navigation of the ship.

Polymer-nanoparticle composites are a promising new class of materials for creation of controllable nano-patterned surfaces and nanopores. We use coarse-grained molecular dynamics simulations augmented with analytical theory to study the structural transitions of surface grafted polymer layers (brushes) induced by infiltration of nanoparticles that are attracted to the polymers in the layer. We systematically compare two different polymer brush geometries: one where the polymer chains are grafted to a planar surface and the other where the chains are grafted to the inside of a cylindrical nanochannel. We perform a comprehensive study of the effects of the material parameters such as the polymer chain length, chain grafting density, nanoparticle size, strength of attraction between nanoparticles and polymer monomers, and, in the case of the cylindrically grafted brush, the radius of the cylinder. We find a very general behavioral motif for all geometries and parameter values: the height of the polymer brush is non-monotonic in the nanoparticle concentration in solution. As the nanoparticle concentration increases, the brush height first decreases and after passing through a minimum value begins to increase, resulting in the swelling of the nanoparticle infused brush. These morphological features may be useful for devising tunable “smart” nano-devices whose effective dimensions can be reversibly and precisely adjusted by changing the nanoparticle concentration in solution. The results of approximate Self-Consistent Field Theory (SCFT) calculations, applicable in the regime of strong brush stretching, are compared to the simulation results. The SCFT calculations are found to be qualitatively, even semi-quantitatively, accurate when applied within their intended regime of validity, and provide a useful and efficient tool for modeling such materials.

A stochastic control approach is used in a parametric study of ship maneuverability in a restricted channel of prescribed geometry. A realistic method, based on some empirical data, is used for the mathematical modelling of the ship motion in deep water.

Control of the morphologies of polymer films and layers by addition of nanosize particles is a novel technique for design of nanomaterials and is also at the core of some important biological processes. In order to facilitate the analysis of experimental data and enable predictive engineering of such systems, solid theoretical understanding is necessary. We study theoretically and computationally the behavior of plane-grafted polymer layers (brushes) in athermal solvent, decorated with small nanoparticle inclusions, using mean field theory and coarse-grained simulations. We show that the morphology of such layers is very sensitive to the interaction between the polymers and the nanoparticles and to the nanoparticle density. In particular, the mean field model shows that for a certain range of parameters, the nanoparticles induce a sharp transition in the layer height, accompanied by a sharp increase in the number of adsorbed nanoparticles. At other parameter values, the layer height depends smoothly on the nanoparticle concentration. Predictions of the theoretical model are verified by Langevin dynamics simulations. The results of the paper are in qualitative agreement with experiments on in vitro models of biological transport and suggest strategies for morphological control of nanocomposite materials.

A stochastic control approach is used in a feasibility study of ship maneuverability in the vicinity of an obstacle. The study uses a realistic dynamical model for the ship's motion in deep-water.

We present calculations of surface tension of absorbed polymer solutions at the liquid/air interface. Lateral changes in the area per monomer on the surface are induced by changing the surface pressure (lateral compression), while keeping the total surface excess fixed. Lateral compression of the adsorbed layer immersed in a good solvent results in an increase in the surface monomer concentration and surface pressure up to a critical area per monomer value where the compressibility of the system vanishes. Our mean-field model is not appropriate to describe more compressed states. Calculations are repeated in theta and bad solvent conditions, and yield similar behavior of the isotherms.

A linearized theory is presented for the dead-water phenomena. A two-layer fluid model of finite depth is assumed and the solutions for both the wave resistance, as well as the interface and free-surface disturbances, are obtained in terms of Green’s function. Numerical solutions are given for the case of a semi-submersible slender-body (prolate spheroid) moving steadily on the free-surface.