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We present results from an off-lattice Monte Carlo simulation of DNA-mediated colloidal assembly. In this simulation, the aggregation-fragmentation of a binary mixture of DNA-coated colloidal particles is studied through a simplified model of base-pair hybridization. Bonding between monomers is modeled as a simple temperature-sensitive A/B-type interaction, where type A and B monomers can bond to only the opposite type (no A/A or B/B attachments are allowed). The actual chemistry of base-pair hybridization is not included in the model. The morphological structures of the clusters formed as well as the kinetics of growth are analyzed in our 2D simulations. The fractal dimension and kinetic growth exponents for clusters formed near the DNA "melting" temperature agree with those seen previously for 2D diffusion-limited cluster aggregation (DLCA) models. The clusters appear more compact, exhibiting signs of local order at intermediate temperature values. At higher temperatures, the formation of large clusters is not favorable under the action of temperature-dependent fragmentation, and the system eventually reaches a steady state as a collection of small aggregates. The temperature profile for this dissolution of the colloidal assembly is sharp, indicating that the selective hybridization process provides a highly sensitive measurement tool. At high temperatures, we analyze the steady-state behavior of the average cluster size in terms of an aggregation-fragmentation model.

We present results from extensive Monte Carlo simulations of flexible and semiflexible excluded-volume polymer chains confined to impenetrable spherical surfaces. Our results are compared with the ...

The composition of sandstones often provides key evidence about the tectonic, weathering and transport processes operating on the surface at the time of deposition. Petrologic and geochemical analyses of little-metamorphosed middle^late Archean sandstones from the Eastern Indian Craton show that the sedimentary rocks were derived from dominantly 3.3-Ga-old amphibolites of the Older Metamorphic Group (OMG) and tonalites of the Older Metamorphic Tonalite Gneisses (OMTG), the two oldest lithologic units of this craton. Chondrite-normalized rare earth element (REE) patterns of the sandstones show a light REE-enriched signature with (La/Sm)N varying from 5.2 to 6.7 with no Eu anomaly, while the heavy REEs display flat patterns with (Gd/Lu)N values of 0.9^1.6. Primitive mantle-normalized incompatible and compatible trace element plots of these sandstones demonstrate an overall similarity with global Proterozoic^Archean sandstones, including strong Nb^Ta negative anomalies. In an fSm=Nd vs. ONd(0) diagram, the sandstones plot precisely between the regional amphibolites and tonalites. We infer from the REE abundances and the fSm=Nd vs. ONd(0) plot that the sandstones represent a bimodal mechanical mixture of OMG and OMTG. The low Ce/Pb ratios of these rocks of 1^4 indicate a variably Pb-enriched Archean crust and that the Ce/Pb ratio acquired the continental crustal signature, distinctly different from those of the bulk silicate earth and mantle values at least as early as mid-Archean. Strong Nb^Ta depletion relative to the primitive mantle suggests the sandstones were derived from subduction-related magmatic arc sources. This latter suggestion is strongly supported by the low Nb/Ta and high Zr/Sm ratios of these sandstones, identical to Archean tonalite^trondhjemites that require, based on recent trace-element partitioning results, their protoliths to have formed by subduction melting of lowmagnesium amphibolites or metamorphosed hydrous basalts [1,2]. The average Nd model ages of the sandstones are greater than the Sm^Nd crystallization ages of the OMG and OMTG at V3.3 Ga. The geochemical data presented here can be collectively interpreted to suggest the presence of subduction^accretion processes operational in the midArchean Eastern Indian Craton. Because the OMG and OMTG, the source rocks of the sandstones, formed in a subduction-related arc setting, the basement rocks upon which this arc was constructed must have been older. This observation and the depleted mantle Nd model ages (TDM) of the sandstones, ranging from 3.6 to 4.0 Ga, strongly indicate the presence of continental crust in this Eastern Indian craton older than 3.3 Ga and possibly as old as

In this study, differential display technology was used to compare gene expression in cultured fibroblasts from patients with major depression, melancholic subtype vs nonmelancholic depressives and normal volunteer controls. Genes differentially expressed in depressives and normals included an overexpressed 269 bp sequence tag showing approximately 95% identity with the Homo sapiens long pentraxin 3 (PTX3) gene sequence in the 3' noncoding region. The 269 bp complimentary DNA probe hybridized with the 1.9 kb PTX3 mRNA. The densitometric analysis of slot blots showed that the mean steady-state mRNA level of PTX3 was 3.5-fold higher in the melancholic group as compared to that in normal controls and in nonmelancholic depressives (n=8, all groups). Incubation experiments were then conducted: confluent fibroblasts from melancholics and normal volunteers were incubated with isoproterenol 1 microM, dexamethasone (DEX) 500 nM, and interleukin 1beta (IL-1beta) 50 ng/ml, for 0, 0.5, 1, 4, and 24 h. mRNA was isolated and quantitated using Northern blot analysis. Isoproterenol produced no significant change in PTX3 expression; DEX produced a significant increase at 4 and 24 h; IL-1beta induced an increase in both the groups that peaked at 4 h, declining to near basal levels at 24 h. There were no differences between melancholics or controls in mean change or maximum response with either DEX or IL-1beta. The results are consistent with the reported effects of IL-1beta on PTX3 expression in mouse brain. The results are of potential importance because PTX3 is a member of the long pentraxin subfamily of acute-phase proteins, which is inducible by IL-1beta, and may play roles in neuroimmunity and neuroprotection.

We consider the bialgebras defined by the invertible R-matrices that are not deformation of identity. We study their relations, duals, representations, baxterisation and the corresponding quantum planes.

We study the geometric aspects of two exotic bialgebras S03 and S14 introduced in math.QA/0206053. These bialgebras are obtained by the Faddeev-Reshetikhin-Takhtajan RTT prescription with non-triangular R-matrices which are denoted $R_{03}$ and $R_{14}$ in the classification of Hietarinta, and they are not deformations of either GL(2) or GL(1/1). We give the spectral decomposition which involves two, resp., three, projectors. These projectors are then used to provide the Baxterisation procedure with one, resp., two, parameters. Further, the projectors are used to construct the noncommutative planes together with the corresponding differentials following the Wess-Zumino prescription. In all these constructions there appear non-standard features which are noted. Such features show the importance of systematic study of all bialgebras of four generators., 14 pages, LaTeX2e, using packages: cite, amsfonts, amsmath, subeqn; v2: small improvements, coincides with journal version

We report the observation of a novel phase of soot in an acetylene/air laminar diffusion flame. As was measured by a small-angle light scattering apparatus, the phase consists of about 10-μm superaggregates with a fractal dimension of D ≃ 2.6. This phase coexists with submicrometer D ≃ 1.8 soot fractal aggregates typical for most flames. Both percolation and shear-induced restructuring are considered as possible mechanisms of formation for those superaggregates.

Tidal point bars located 30–50 km inland from the present-day east coast of India have been extensively studied under varying seasonal conditions. The surface of these bars, when exposed during low tide, is sculptured by various physical sedimentary structures such as linguid ripples, interference ripples of different patterns, asymmetric ripples of cuspate and lunate forms, ladder-back ripples, double-crested ripples and wrinkle marks. The associated biogenic structures are tracks and trails of gastropods, hermit crabs, gobiid fish, birds and various surface designs made by bubbler crabs with their feeding pellets. Study of relief peels from 500 box cores taken from point bars developed in two tidal estuaries of contrasting character shows that horizontal lamination, small ripple lamination, flaser bedding, wavy and lenticular bedding, herringbone cross-stratification, mud/silt couplets, bubble sand in silt, etc. are the common features in these deposits. Flaser bedding and herringbone cross-stratification are more common in this transitional facies than in the open-sea tidal flats of this tropical coast. Similarly, biogenic structures related to the burrowing activity of polychaetes (e.g.Lumbrineris sp.,Nereis sp.) and bubbler crabs (Scopimera sp. andIlyoplax sp.) are the most common features found in the estuarine sediments. Although many features registered in the open-sea tidal flats of the region, such as resting and grazing trails of starfish, ghost crab burrows or agglutinated tubes ofDiapatra sp., are not found in the point bar facies, most of the physical and biogenic structures present in this facies bear a strong resemblance to those found in the open-sea tidal flat environment. This finding advises caution regarding the use of such structures for identifying near-coastal tidal flat environments in the rock record.

We numerically study morphology of thin diblock copolymer films as a function of the relative size or the “composition” f of the shorter block of the copolymer chains. We probe various values of f, spanning the whole bulk phase diagram of asymmetric diblock copolymers. Finite size of the film and wetting properties of the substrate modify the film morphology by shifting the effective value of the composition f in the film. A dramatic change in film morphology takes place for a small change in external parameters if one chooses the composition f to be at the borderline between two different bulk phases.

Using a contraction procedure developed earlier, we construct, in the first part of the present paper, the Jordanian quantum Hopf algebra h(sl(3)) which has a remarkably simple coalgebraic structure and contains the Jordanian algebra h(sl(2)), obtained by Ohn, as a Hopf subalgebra. A nonlinear map between the quantum h(sl(3)) and the classical (sl(3)) algebras is then established; and the universal h-matrix of the h(sl(3)) algebra is given. In the second part, we give the higher dimensional Jordanian algebras h(sl(N)) for all N. The universal h-matrix of the h(sl(N)) algebra is also given.

In the classification of Hietarinta, three triangular $4\times 4$ $R$-matrices lead, via the FRT formalism, to matrix bialgebras which are not deformations of the trivial one. In this paper, we find the bialgebras which are in duality with these three exotic matrix bialgebras. We note that the $L-T$ duality of FRT is not sufficient for the construction of the bialgebras in duality. We find also the quantum planes corresponding to these bialgebras both by the Wess-Zumino R-matrix method and by Manin's method., Comment: 25 pages, LaTeX2e, using packages: cite, amsfonts, amsmath, subeqn

We numerically study morphology of symmetric diblock copolymer films with a thickness smaller than the bulk equilibrium period. These films are cast on either flat or corrugated substrates. Our results show that the formation of uniformly sized lateral domains that appear randomly on a flat surface can be controlled by using topographically patterned substrates. This is in excellent agreement with recent experimental studies. Control of lateral pattern fails if (i) the distance between the steps of the substrate is smaller than the bulk lamellar wavelength, or (ii) the lateral size of the corrugation is larger than the bulk lamellar wavelength.

For thin block copolymer (BCP) films on a homogeneous substrate, a fast domain growth exponent has recently been observed in experiments. This growth exponent is larger than what one would expect from theoretical considerations of two-dimensional coarsening of small molecular liquid mixtures in the viscous regime. Thus it is not clear whether the growth kinetics is truly different for block copolymer films, or if the observed anomalous exponent is a result of a possible dimensional crossover from two to three dimensions. To address part of this question, we have carried out numerical simulations of ordering and domain growth in a two-dimensional system of BCP melts. The model calculations reported here explicitly include viscous, hydrodynamic flow and provide a scaling description of the growth of domains in a quenched BCP system. Our results indicate that the growth kinetics of BCP melts in two dimensions belong to the same dynamical universality class of small molecular liquid mixtures in the viscosity dominated regime.

We study phase separation of quenched polymer solutions under an external shear flow by using a stochastic molecular dynamics method. We observe the formation of a stringlike pattern of polymer domains normal to the direction of the shear flow. The characteristic size of the layered domains has a power law relation with the shear rate. Shear-induced rheological behavior of the mixture is also examined in terms of the excess viscosity. We find that the maximum excess viscosity scales as the shear rate, and that the numerical value of the power-law exponent agrees well with theoretical scaling predictions.

A number of recent experiments have allowed direct study of diblock copolymer morphology on patterned surfaces. Here we examine, by computer simulation, the morphology of a diblock thin film in contact with a substrate having large stripes. The diblock aligns parallel to the surface but is frustrated at the point where two stripes join. We show here that at the joint one of the phases is continuous while the other is discontinuous. In the region of the join the lamellae form a kink with a length scale of the same size as the lamellar period. Within the kink the ordering is suppressed.

We investigated the effects of androgen and taxol on the androgen-responsive LNCaP and androgen-independent DU145 prostate cancer cell lines. Cells were treated for 48 and 72 h with 0.05-1 nM of the synthetic androgen R1881 and with 100 nM taxol. Treatment of LNCaP cells with 0.05 nM R1881 led to increased cell proliferation, whereas treatment with 1 nM R1881 resulted in inhibited cell division, DNA cycle arrest, and altered centrosome organization. After treatment with 1 nM R1881, chromatin became clustered, nuclear envelopes convoluted, and mitochondria accumulated around the nucleus. Immunofluorescence microscopy with antibodies to centrosomes showed altered centrosome structure. Although centrosomes were closely associated with the nucleus in untreated cells, they dispersed into the cytoplasm after treatment with 1 nM R1881. Microtubules were only faintly detected in 1 nM R1881-treated LNCaP cells. The effects of taxol included microtubule bundling and altered mitochondria morphology, but not DNA organization. As expected, the androgen-independent prostate cancer cell line DU145 was not affected by R1881. Treatment with taxol resulted in bundling of microtubules in both cell lines. Additional taxol effects were seen in DU145 cells with micronucleation of DNA, an indication of apoptosis. Simultaneous treatment with R1881 and taxol had no additional effects on LNCaP or DU145 cells. These results suggest that LNCaP and DU145 prostate cancer cells show differences not only in androgen responsiveness but in sensitivity to taxol as well. Copyright 2000 Wiley-Liss, Inc.

Results from molecular dynamics simulations of phase separation in a quenched polymer solution are presented for both two- and three-dimensional systems. Simulations clearly demonstrate the existence of a networklike pattern formation at an early to intermediate time regime for sufficiently dense polymer solutions. This network structure, however, relaxes at late times as the minimization of the interface energy wins over the elastic stress of the network. A crossover of domain growth exponent from a smaller value at intermediate times to the Lifshitz–Slyozov value of 1/3 at late times is seen in three-dimensional (3D) simulations of network breakup. Our results for the late-time growth exponent and dynamical scaling of the structure factors strongly indicate that the late-time growth kinetics of quenched polymer solutions belong to the same universality class of small molecular mixtures.

We have carried out a systematic investigation of the kinetics of domain growth of a model binary mixture in contact with a fractal network similar to the fumed silica network used in recent experiments with polymer blends. This network has selective affinity for one component of the blend. We study the morphology of the growing domains and the wetting layer, the growth exponent, and dynamical scaling behavior for a critical composition of the mixture. We find that the characteristic size of domains grows as t1/3 for deep quenches, as long as the average domain size is small compared to the average “pore” radius of the unoccupied region. This suggests that the kinetics of domain growth at intermediate times is not appreciably perturbed by the presence of the network. For off-critical compositions, we study domain growth in two different situations where either the majority or the minority component of the blend wets the network. When the majority component wets the network, a network-induced nucleation is...

Calcium loss and muscle atrophy are two of the main metabolic changes experienced by astronauts and crew members during exposure to microgravity in space. Calcium and cytoskeletal events were investigated within sea urchin embryos which were cultured in space under both microgravity and 1 g conditions. Embryos were fixed at time-points ranging from 3 h to 8 days after fertilization. Investigative emphasis was placed upon: (1) sperm-induced calcium-dependent exocytosis and cortical granule secretion, (2) membrane fusion of cortical granule and plasma membranes; (3) microfilament polymerization and microvilli elongation; and (5) embryonic development into morula, blastula, gastrula, and pluteus stages. For embryos cultured under microgravity conditions, the processes of cortical granule discharge, fusion of cortical granule membranes with the plasma membrane, elongation of microvilli and elevation of the fertilization coat were reduced in comparison with embryos cultured at 1 g in space and under normal conditions on Earth. Also, 4% of all cells undergoing division in microgravity showed abnormalities in the centrosome-centriole complex. These abnormalities were not observed within the 1 g flight and ground control specimens, indicating that significant alterations in sea urchin development processes occur under microgravity conditions.

A general construction is given for a class of invertible maps between the classical $U(sl(2))$ and the Jordanian $U_{h}(sl(2))$ algebras. Different maps are directly useful in different contexts. Similarity trasformations connecting them, in so far as they can be explicitly constructed, enable us to translate results obtained in terms of one to the other cases. Here the role of the maps is studied in the context of construction of twist operators between the cocommutative and noncocommutative coproducts of the $U(sl(2))$ and $U_{h}(sl(2))$ algebras respectively. It is shown that a particular map called the `minimal twist map' implements the simplest twist given directly by the factorized form of the ${\cal R}_{h}$-matrix of Ballesteros-Herranz. For other maps the twist has an additional factor obtainable in terms of the similarity transformation relating the map in question to the minimal one. The series in powers of $h$ for the operator performing this transformation may be obtained up to some desired order, relatively easily. An explicit example is given for one particularly interesting case. Similarly the classical and the Jordanian antipode maps may be interrelated by a similarity transformation. For the `minimal twist map' the transforming operator is determined in a closed form., LaTeX, 13 pages

It is found experimentally that the coexistence region of a vapor-liquid system or a binary mixture is substantially narrowed when the fluid is confined in an aerogel with a high degree of porosity (e.g., of the order of 95 to 99%). A Hamiltonian model for this system has recently been introduced [1]. We have performed Monte-Carlo simulations for this model to obtain the phase diagram for the model. We use a periodic fractal structure constructed by diffusion-limited cluster-cluster aggregation (DLCA) method to simulate a realistic gel environment. The phase diagram obtained is qualitatively similar to that observed experimentally. We also have observed some metastable branches in the phase diagram which have not been seen in experiments yet. These branches, however, might be important in the context of recent theoretical predictions and other simulations.

We present results from a numerical study of a coarse-grained model of diblock copolymer (BCP) thin films cast on a chemically patterned surface. The patterned surface contains chemical inhomogeneities with a repeat spacing length scale comparable to the linear size of the BCP molecules. We find that the orientation of the lamellae in the thin film and the overlap of the film morphology with the preassigned surface pattern is strongly influenced by the commensurability between the bulk unconstrained lamellar size λ * , and the linear size of the surface inhomogeneities w. PACS Numbers: 64.60.Cn, 61.41. +e, 64.60.My, 64.75. +g.

We present results from a molecular dynamics simulation of the dewetting process of microscopically thin polymer films cast on a solid surface. The chain length and time scales accessed in the present simulation would correspond to early stages of the dewetting process before hydrodynamic interactions become important. Even though the surface in contact with the film is purely repulsive, we find that there is a “nucleation time” for dry patches to appear due to the competition between the interfacial energy and the surface energy contributions. Kinetics of growth of dry patches during the early stages of the dewetting process is controlled by surface diffusion of polymers.

We study self-assembly of surfactants in two dimensions using off-lattice Monte Carlo moves. Here the Monte Carlo moves consist of slithering snake reptation motion of the surfactant chains and kink-jump of the individual monomers. Unlike many previous studies an important feature of our model is that the solution degrees of freedom are kept implicit in the model by appropriate choice of the phenomenological interaction parameters for the surfactants. This enables us to investigate rather large systems with less number of parameters. The method is powerful enough to study multimicellar systems with regular and inverted micelles for both neutral and ionic surfactants. As a function of several parameters of the model, we study self-assembly of neutral surfactants into micelles of various forms and sizes and compute appropriate cluster-size distributions. Ionic surfactants exhibit, apart from micellization, additional intermicellar ordering. We further study the role of host particles to mimic recent experim...

We present results from a numerical study of a coarse-grained model of di-block copolymer (BCP) thin films confined between two hard walls. One of these walls is neutral to the components of the BCP melt and the other one contains chemical inhomogeneities with a repeat spacing length scale comparable to the linear size of the BCP molecules. We find that the morphology of the BCP thin film is strongly influenced by the commensurability between the bulk unconstrained lamellar size λ*, and the linear size of the surface inhomogeneities w. When w≈λ*/2, the ordered morphology of the diblock copolymers has a strong overlap with the pre-assigned substrate chemical pattern throughout the film. However, for w≈λ*, the overlap strongly depends on the distance from the substrate surface. Close to the substrate surface, the overlap of the morphology with the pre-assigned chemical pattern is large but the pattern becomes out-of-phase at a distance of approximately λ*/2 from the substrate. For w≈3λ*/4, the morphology of...

Starting from a coarse-grained model, which includes hydrodynamic interactions, we numerically study kinetics of phase separation in a two-dimensional model of a polymer blend. In the absence of hydrodynamics, domains grow according to the Lifshitz–Slyozov power law without any evidence of pinning, regardless of the relative concentration of the blend components. In the presence of hydrodynamics, our results suggest that critical and off-critical mixtures are characterized by different growth laws. For the critical composition of the blend, hydrodynamic effects are found to be important during the entire growth process and this leads to a larger growth exponent. On the other hand, for off-critical blends, hydrodynamic effects are important only for blends with volume fraction not far away from the critical value. Even in these cases, domains show a faster growth only at intermediate times under the influence of hydrodynamics; subsequently the growth exponent crosses over to a Lifshitz–Slyozov value at late times. This gives strong support to the argument that the apparent pinning of domain growth observed in experiments on off-critical polymer blends may be due to this crossover phenomenon.

A class of transformations of Rq-matrices is introduced such that the q→1 limit gives explicit nonstandard Rh-matrices. The transformation matrix is singular as q→1. For the transformed matrix, the singularities, however, cancel yielding a well-defined construction. Our method can be implemented systematically on Rq-matrices of all dimensions and not only for q-deformed sl(2) algebra but also for algebras of higher dimensions. Explicit constructions are presented starting with [Formula: see text] and [Formula: see text], while choosing Rq for (fund. rep.) ⊗ (arbitrary irresp.). The treatment for the general case of [Formula: see text] algebras is indicated. Our method yields nonstandard deformations along with a nonlinear map of the h-Borel subalgebra on the corresponding classical Borel subalgebra. For [Formula: see text] this map is extended to the whole algebra and compared with the other proposed by us previously. The usual classical coproduct on [Formula: see text] and the non-cocommutative coproduct structure on [Formula: see text] are related via Drinfeld twist operators, determined up to O(h2) for both of these nonlinear maps.

The dynamics of phase separation of a quenched polymer solution is studied using a stochastic molecular dynamics simulation. At early times, the elastic nature of the polymer chains generates a networklike domain morphology for sufficiently dense polymer solutions. However, at late times, this network structure breaks up into disconnected polymer-rich domains to minimize the interfacial energy. Our simulations explain why different experiments carried out to different time regimes seem to produce contradictory results, and strongly indicate that the true late-time growth kinetics of quenched polymer solutions belong to the same universality class of small molecular mixtures.

The objective of the present study was to determine the neurobehavioral effects of the putative endogenous cannabinoid ligand, anandamide, and its influence on cannabinoid (CB1) receptor gene expression. The effect of acute administration of anandamide to C57BL/6, DBA/2, and ICR mice were evaluated in motor function and emotionality tests. The C57BL/6 and ICR mouse strains were more sensitive than the DBA/2 strain to the depression of locomotor activity and stereotyped behavior caused by anandamide. Although anandamide produced catalepsy in all three strains, anandamide induced ataxia in the minus-maze test only in the C57BL/6 animals and only at the lowest dose used. In the plus-maze test system, anandamide produced a mild aversive response, and by the third day of treatment the mouse strains developed an intense aversion to the open arms of the plus-maze. Northern analysis data using the recently cloned mouse cannabinoid receptor cDNA as a probe indicated that there was abundant expression of CB1 gene in the whole brain of the ICR mouse than in the brains of the C57BL/6 and DBA/2 strains with or without pretreatment with anandamide. The anandamide induced neurobehavioral profile does not seem to correspond to the CB1 gene expression in the mouse strains. It is, therefore, unlikely that the CB1 receptor mediates all the cannabinomimetic effects of anandamide in the brain.

Eukaryotic translation initiation factor 3 (eIF3), which plays an essential role in initiation of protein synthesis, was purified from rabbit reticulocyte lysates using an assay that specifically measures its ability to stimulate the binding of Met-tRNAf (as a Met-tRNAf·eIF2·GTP ternary complex) to 40 S ribosomal subunits. Purified eIF3 consisted of six major polypeptides of molecular masses 110, 67, 42, 40, 36, and 35 kDa but lacked the 170-kDa polypeptide reported to be a constituent of other eIF3 preparations. Characterization of purified eIF3 lacking the 170-kDa polypeptide showed that the eIF3-mediated 40 S initiation complex formed in the presence of AUG codon efficiently joined 60 S ribosomal subunits in an eIF5-dependent reaction to form a functional 80 S initiation complex. eIF3, which was originally bound to the 40 S initiation complex, was released from the 40 S subunit during the subunit joining reaction. Additionally, chicken antibodies raised against rabbit reticulocyte eIF3 were used to immunochemically characterize eIF3 subunits and to isolate a 3.1-kilobase pair human cDNA that encodes the p110 subunit of mammalian eIF3. The derived amino acid sequence (calculated M r 95,214) shows that the p110 subunit is the mammalian homologue ofSaccharomyces cerevisiae protein Prt1p, a subunit of yeast eIF3.

Results are presented from a series of lattice Monte Carlo simulations of the adsorption and desorption of polymer chains from semidilute solution onto a solid/liquid interface, where either the chains or the adsorbing surface contain chemical impurities. We compare these results with our previous results for chemically pure systems with regard to the growth, equilibrium structure, and dynamics of the adsorbed layers. Generally, the presence of impurities causes a reduction in the total adsorbance, but does not gravely affect the de Gennes-type self-similar grid found for the pure system. In one case, however, the impurities are found to increase the total adsorbance. We find some correspondence between the static chain characteristics for cases of impurities within the chains and impurities within the surface. There are, however, visible differences between the dynamics of the two cases, particularly in their growth and exchange kinetics. Dramatic changes in behavior are shown to arise when the chain impurities impede the “reeling in” motion of the chains onto the surface, altering the chains’ relaxations. We compare our results with previous theoretical predictions for cases of random copolymer adsorption, and adsorption onto heterogeneous surfaces.

By solving a set of recursion relations for the matrix elements of the [Formula: see text] generators, the finite dimensional highest weight representations of the algebra were obtained as factor representations. Taking a nonlinear combination of the generators of the two copies of the [Formula: see text] algebra, we obtained [Formula: see text] algebra. The latter, on contraction, yields [Formula: see text] algebra. A nonlinear map of [Formula: see text] algebra on its classical analog e(3) was obtained. The inverse mapping was found to be singular. It signifies a physically interesting situation, where in the momentum basis, a restricted domain of the eigenvalues of the classical operators is mapped on the whole real domain of the eigenvalues of the deformed operators.

We present results from a numerical study of surface-directed spinodal decomposition in a binary fluid mixture, for critical and various off-critical concentrations. We explicitly add a long-range surface interaction term to the bulk free-energy functional leading to preferential attraction of one of the components of the fluid mixture to a solid surface. We also consider hydrodynamic interactions in these model calculations. Results of the wetting layer thickness and the domain size as a function of time and the scaling behavior of the density profile perpendicular to the surface are presented in the fluid inertia controlled regime.

We propose a new structure ${\cal U}^{r}_{\displaystyle{q}}(sl(2)) $. This is realized by multiplying $\delta$ ($q=e^{\delta}$, $\delta\in \CC$) by $\theta$, where $\theta$ is a real nilpotent -paragrassmannian- variable of order $r$ ($\theta^{r+1}=0$) that we call the order of deformation, the limit $r\rightarrow \infty$ giving back the standard ${\cal U}_{\displaystyle {q}}(sl(2))$. In particular we show that, for $r=1$, there exists a new ${\cal R}$-matrix associated with $sl(2)$. We also proof that the restriction of the values of the parameters of deformation give nonlinear algebras as particular cases.

Department of Physics, Kansas State University, Manhattan, Kansas 66506-2601~Received 24 August 1995; revised manuscript received 21 November 1995!Diffusion and magnetic relaxation are studied in computer-generated model two-dimensional porous mediawhose three-dimensional analogs resemble commercially prepared Vycors and aerogels. When diffusion ratesare compared for two different samples, one with average pore diameter much shorter than the other but withthe same porosity, a crossover is observed where the asymptotic long-time diffusion rateD(t) for the smallerpore becomes larger than the bigger one. However, this crossover disappears for relatively larger pores of fixedporosity. Physically, this crossover is a characteristic of changed surface morphology where for a fixed poros-ity, pore diameters could be made bigger but at the cost of separating the pores from each other by thin butmore ordered walls, linked to each other with very narrow necks. This results in a net decrease in the long-timediffusion constant. We have also been able to relate this crossover to the absence of dynamical scaling for thestructures. Adding a surface relaxation term at the pore walls increases the effective diffusion rate at earlytimes. We compare our simulation results for the model systems, wherever possible, with some of the generalresults for porous media obtained analytically.I. INTRODUCTION

The Gay-Berne model for liquid crystals in the presence of a substrate surface is studied using the hybrid Monte Carlo method. A simple non-mean-field substrate-molecule potential is proposed to describe the effects of rubbed polymer-coated substrates on the liquid crystals. Effects of the substrate surface on the bulk alignment of the liquid crystals are studied. It is found that the bulk pretilt angle is controlled by the surface through the orientation of the adsorbed liquid crystal monolayer. This is consistent with the results of recent experimental studies. \textcopyright{} 1996 The American Physical Society.

We present results from an extensive lattice Monte Carlo study of the adsorption and desorption of homopolymer chains from semidilute solution onto a solid/liquid interface. We have studied in detail the growth, equilibrium structure and dynamics, and rinsing of layers of homopolymers adsorbed from solution. For solution concentrations at or near the overlap threshold we directly verify the self‐similar structure of the adsorbed layer first predicted by de Gennes. This scaling result is confirmed without our having to make any assumptions or inferences as required in experiments. By following the flight of the individual chains, we obtain a detailed description of their structure and dynamics, including direct proof that the adsorbed chains form two broad categories: a tightly bound category with a long characteristic time of exchange with the solution, and a loosely bound category with a very short characteristic time of exchange. We study the differing conformations of these two subpopulations, as well ...

A microscopic lattice model for nematic liquid crystals in the presence of random fields is studied by Monte Carlo simulations. The order parameter autocorrelation function shows a standard dynamical scaling for weak random fields, and an activated dynamical scaling for strong random fields. These results are consistent with recent experiments. Evidence is also found that local correlations in the orientation of the liquid crystals along the pore surface should be taken into account for some details of the scaling functions observed in recent experiments.

In spite of apparent improvement in outcome in locally advanced breast cancer, the prognosis remains dismal in many patients. The aim of this study was to define prognostic subgroups within this heterogeneous entity. The prospective follow-up study was carried out for a period of three and half years involving patients attending the radiotherapy department of Burdwan Medical College and Hospital. Forty-five patients with clinical stages IIIA and IIIB breast cancer were treated with neoadjuvant chemotherapy followed by mastectomy, radiotherapy and completion of chemotherapy with an objective to assess the 2 years disease free and overall survival and to find out the correlates of prognosis. On follow-up disease-free survival and overall survival at 2 years were noted to be 60% and 80% respectively. Patients with age more than 45 years, earlier stage, less than 4 positive axillary nodes, tumour size less than 8 cm, oestrogen receptor positive and Her-2-neu negative status and lesser number of chemotherapy cycles required before surgery had better outcome though not statistically significant. Thus it can be concluded that the above mentioned prognostic variables are strong predictors of treatment outcome in locally advanced breast cancer though further studies with larger sample size are required to establish their statistical significance.

The differential sensitivity following the administration of delta 9-THC to 3 mouse strains, C57BL/6, DBA/2 and ICR mice, indicated that some of the neurobehavioral changes may be attributable to genetic differences. The objective of this study was to determine the extent to which the cannabinoid (CB1) receptor is involved in the observed behavioral changes following delta 9-THC administration. This objective was addressed by experiments using: (1) DNA-PCR and reverse PCR; (2) systemic administration of delta 9-THC, and; (3) intracerebral microinjection of delta 9-THC. The site specificity of action of delta 9-THC in the brain was determined using stereotaxic surgical approaches. The intracerebral microinjection of delta 9-THC into the nucleus accumbens was found to induce catalepsy, while injection of delta 9-THC into the central nucleus of amygdala resulted in the production of an anxiogenic-like response. Although the DNA-PCR data indicated that the CB1 gene appeared to be identical and intronless in all 3 mouse strains, the reverse PCR data showed two additional distinct CB1 mRNAs in the C57BL/6 mouse which also differed in pain sensitivity and rectal temperature changes following the administration of delta 9-THC. It is suggested that the diverse neurobehavioral alterations induced by delta 9-THC may not be mediated solely by the CB1 receptors in the brain and that the CB1 genes may not be uniform in the mouse strains.

We report results from Monte Carlo simulations of the orientational ordering of the two-dimensional Lebwohl-Lasher model for nematic liquid crystals confined inside a model porous medium of Vycor-like tortuous geometry. We find that the magnitude of the order parameter and the susceptibility are strongly suppressed in the presence of the porous medium. The system breaks into many nematic domains with a random distribution of nematic directors. This feature is similar to the ``nematic-glass'' behavior that is seen in experiments. We find that the relaxation of the order parameter autocorrelation function satisfies an activated dynamical scaling, which is in agreement with recent simulations of random-field models and some recent experiments.

Phase separation of symmetric diblock copolymers end-grafted to a wall is studied using a Monte Carlo simulation. The nearest-neighbor repulsion between the two types of monomers is quenched from X = 0 to X = 1 for chains of length N = 100 at near-melt densities. We present evidence that the two monomer species vertically segregate to form a three-layer structure that is uniform in the grafting plane. This is qualitatively different from a binary mixture of grafted homopolymers, which laterally segregates to form a structure with concentration modulated in the grafting plane at a scale of the side-to-side fluctuation distance.

We carry out extensive off-lattice computer simulations of bimodal polymer brushes and discuss the effects of different grafting geometry and solvent quality on the structure of such mixed polymer brushes. For a flat grafting surface and good solvents, the short and long chains segregate vertically and the long chains stretch more in the coexisting region. The situation is different for polymers grafted onto a flat surface and in contact with poor solvents where vertical segregation between the long and the short chains is found to be much weaker. Also, as the function of short chains increases in the layer, both the short and the long chains stretch less. This is different from the good solvent case where the stretching of the short chains increases as the short chain fraction increases. For a spherical grafting surface and in good solvents, the stretching of the two type of chains is similar in the inner layer. In a poor solvent, the situation is similar to a flat grafting surface with poor solvents and both types of chains are equally stretched over the entire region of the layer.

Phase separation of a binary Lennard-Jones fluid confined in a variety of two-dimensional pores is studied using molecular dynamics simluations. We consider a simple strip pore, an uneven single pore, and a junction made out of two pores. We have studied dynamics of phase separation for both critical and off-critical composition of the binary fluid. We find the existence of long-lived metastable states in the presence of asymmetries both in the geometry and the composition of the fluid. The results are compared with theoretical predictions and with experimental observations.

An apparatus was designed and assembled to measure scattered light in the range of 180°±6° where enhanced backscattering, the cause of a glory, occurs. The apparatus was calibrated and tested using Fraunhofer circular aperture diffraction, angle of incidence correction, and a diffuse reflector. Theory indicates that backscattering is strongly dependent on particle size, refractive index, and shape. Experimental measurements from polystyrene latex spheres of two sizes and water droplets showed good agreement with Mie theory, but also indicated the extreme sensitivity of the backscattering to particle parameters. The results presented should have use in the fields of particle scattering, particle metrology, and LIDAR.

Microphase separation of symmetric diblock copolymers between two rigid walls is simulated by a coarse‐grained model to study the geometry of the microdomains without presupposing their basic shape. The geometry is found to be dependent on the wall separation and the domains can be either aligned horizontally or vertically. The horizontal geometry is induced by wetting at the walls and lamellas parallel to them develop quickly after a quench from the one‐phase region. The vertical geometry involves domains oriented perpendicular to the walls and develops much more slowly. For identical walls, some segregation of the wetting phase to the walls is observed for the vertical geometry. This segregation does not significantly change the structure. If the vertical phase develops between walls that attract opposite phases, however, a linear concentration profile develops. In some cases the structure of this vertical phase is found to be quite different from simple, perpendicularly oriented lamellas.

We review some recent numerical studies of the Cahn-Hilliard model in two dimensions, for phase separation with different values of the minority area fraction φ. We find that dynamical scaling is satisfied at sufficiently late times for the pair correlation function, the structure factor and the droplet distribution function. We study how the shape of these scaling functions change with the area fractions and compare these results with available theoretical predictions. The time dependence of the characteristics length is consistent with an asymptotic growth law exponent 1 3 for all area fractions.

Results from extensive Brownian dynamics simulations are presented for nucleation in a system of colloidal particles interacting via a short-range attractive potential. Our analysis shows that, even though the system is not in equilibrium, structures of small size clusters compare well with the theoretically predicted and experimentally observed ground state structures for short-range colloidal systems. In addition, the distribution of the symmetric structures in nucleation is comparable to the distribution seen in equilibrium. We also investigate how the shape and structure of fluctuating clusters in the prenucleation regime affect the formation of a stable nucleating cluster.

Stimulated by experiments, we have carried out detailed simulations of aggregation in the presence of shear in a model colloidal system with a short-range attractive potential. For weak shear rates, we find that the shear enhanced the aggregation and that the long-time state of the system is independent of the shear history. For strong shear rates, precipitous fragmentation occurred after the shear was turned on and, after an induction period, the aggregation quickly rebounded in a stochastic manner similar to classical nucleation phenomena. However, the long-time state of the system is, once again, independent of the shear history. Thus, for both weak and strong shear cases, the shear rate acts as a state variable of the aggregating system. Shear rates employed in the simulations can be attained in laboratory experiments, as confirmed by computing the dimensionless Peclet numbers.