Search

Nylon-6–clay hybrid (NCH) is a molecular composite of Nylon-6 and uniformly dispersed silicate monolayers of montmorillonite. In this study, orientation of montmorillonite and Nylon-6 crystallites in the NCH film was measured by x-ray diffraction and transmission electron micrography (TEM), which revealed that, the silicate layers and the Nylon-6 crystallites (γ-form) have planar orientation, independent of montmorillonite content. Based on the crystal structure model proposed by Bradbury et al., it seems that hydrogen bonded sheet plane {020} or zigzag plane of molecular backbone {110} is parallel to the film surface. In contrast, crystallites in pure Nylon-6 film are randomly oriented. The degree of orientation of Nylon-6 crystallites increases with content of montmorillonite. © 1994 John Wiley & Sons, Inc.

Dynamics of amorphous cis‐1,4‐polybutadiene was studied by incoherent inelastic and quasielastic neutron scattering below 10 meV in a wide temperature range covering the glass transition temperature Tg. The spectra at low temperatures below Tg show a broad excitation peak at about 2–3 meV, which is the so‐called low‐energy excitation and believed to be an origin of anomalous thermal properties of amorphous materials at low temperatures. It was found that the temperature dependence of the low‐energy excitation intensity can be normalized by the Bose factor at temperatures low enough below Tg. With increasing temperature, a very fast motion appears in the energy range below ∼4 meV at around the Vogel–Fulcher temperature T0, which is ∼50 K below Tg. This fast motion is often interpreted as the β process predicted by the mode coupling theory. In this paper, both the low‐energy excitation and the fast motion were analyzed in terms of a common microscopic picture, i.e., an asymmetric double well potential. The ...

We constructed a crystal analyzer type inelastic scattering neutron spectrometer LAM-D at the KENS spallation thermal neutron source in the National Laboratory for High Energy Physics (KEK), Tsukuba, Japan. This spectrometer can cover the energy transfer range up to 300 meV with a resolution ΔϵE1 of less than 6%. The basic principle of LAM-D is the same as the quasi-elastic scattering spectrometers LAM-40 and LAM-80 at KENS so that the combination of the three spectrometers is a very powerful tool for studies of molecular motions in condensed matters in the energy range of 1 μeV to 300 meV.

Local dynamics of cis-1, 4-polybutadiene near the glass transition temperature Tg (=170K) has been investigated by quasielastic neutron scattering in the energy range of 0.01 meV to 10meV. It was found that two models of motions appear near the Tg in the energy range of ca. 1 meV and 10 ∽ 30 μeV. The fast mode arises ca. 50 K below Tg which corresponds to the so-called Vogel temperature T0. On the other hand, the slow mode appears just above Tg. The natures of the two modes are discussed from viewpoints of glass transition.

We have recently developed a high resolution quasielastic neutron scattering spectrometer LAM-80ET by applying mica crystals as analyzers and achieved a resolution of Δ e =1.3 µeV using the 002 reflection. Single chain dynamics of polyethylene has been investigated below and above the melting temperature T m (=135°C) to show the feasibility of the mica 002 reflection as the analyzer. It was found that elastic scattering intensity from polyethylene decreases very steeply around the T m . Quasielastic broadening in the spectrum at Q =0.082 A -1 is observed only above 210°C, which is 75°C higher than the T m . From the analysis of the spectra by a curve-fitting method, the width of the quasielastic component was evaluated to be 1.8 µeV at 250°C and the activation energy of the width to be 34 kJ/mol.

A new finding is reported concerning some structural change in the amorphous state of the polymer which occurs during the so-called induction period before the start of crystallization. Annealing of poly(ethylene terephthalate) (PET) at 115°C, or 40°C above the glass transition temperature, Tg, has been investigated by small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) techniques. At a very early stage of the induction period the SAXS intensity starts to increase in the range of Q = 0.02–0.04 A −1 , where Q is the length of the scattering vector (Q = 4π sin θ/λ), and continues to increase until the beginning of crystallization. Corresponding to the initation of crystallization, another strong peak, caused by the usual long-period structure, appears in the vicinity of Q = 0.05 A −1 . It is confirmed from the WAXS measurements that no local ordering takes place during the induction period. To clarify the crystallization process, distance distribution analysis is also carried out.

Apparent gelation rates t−1gel, defined as the reciprocal of the gelation time, are measured for poly(vinyl alcohol) solutions as functions of polymer concentration, Cp, and quenching temperature, TQ. Here the measurements are limited to the case of homogeneous gelation where TQ is below 0°C. The critical gelation concentration, C∗ t = ∞ , extrapolated to t−1gel = 0 is independent of TQ, and is identical to the polymer chain overlap concentration, C∗ Rg . In order to represent the degree of polymer chain overlap a reduced concentration, o = (C p - C∗ Rg ) C∗ Rg , is introduced. An experimental relation, t−1gel = A(TQ) o2, is obtained where A(TQ) is the temperature factor. The o dependence of the equation can be explained using the chain overlap concept for gelation and random bond percolation theory, and the temperature factor A(TQ) is analysed by the crystal nucleation theory.

Crystallization processes of poly(ethylene terephthalate) (PET) when annealed at 80°C, or 5°C above the glass transition temperature, Tg, have been investigated by a small-angle X-ray scattering (SAXS) technique. At a very early stage of annealing, a scattering maximum appears at around Q = 0.04 A −1 , where Q is the length of the scattering vector (Q = 4π sin θ/λ). During the so-called induction period of crystallization, this maximum intensity increases with annealing time and the maximum position shifts towards the low Q side. These results confirm the previously reported new finding that the long-range ordered structure is formed in the induction period before crystallization. These ordering processes can be divided into two stages: an early and a late stage. The scattering behaviour in the early stage is in accordance with the prediction of Cahn's linearized theory for spinodal decomposition. The scattering profiles in the late stage can be described in terms of Furukawa's scaling theory for the cluster growth regime. From these experimental results, we conclude that the growth process of the density fluctuation occurs in the induction period and this process is very similar to the spinodal decomposition type of phase separation process. It is considered that after this dense domain grows to a certain size, crystallization begins.

Direct reprogramming of somatic cells to a pluripotent state, substantiated only three years prior, is one of the most rapidly developing areas of stem cell research. The generation of patient-derived pluripotent cells applicable to disease modelling, drug screening, toxicology tests and, ultimately, autologous cell-based therapies, has the potential to revolutionize medicine. Since 2006, when Takahashi and Yamanaka first reported the generation of induced pluripotent stem cells from murine fibroblasts via retroviral transduction of a defined set of transcription factors, various new methods have been developed to refine and improve reprogramming technology. This review focusses on these evolving strategies to generate genetically unmodified or reprogramming factor-free iPSCs.

Reprogramming of somatic cells to pluripotency, thereby creating induced pluripotent stem (iPS) cells, promises to transform regenerative medicine. Most instances of direct reprogramming have been achieved by forced expression of defined factors using multiple viral vectors(1-7). However, such iPS cells contain a large number of viral vector integrations(1,8), any one of which could cause unpredictable genetic dysfunction. Whereas c-Myc is dispensable for reprogramming(9,10), complete elimination of the other exogenous factors is also desired because ectopic expression of either Oct4 (also known as Pou5f1) or Klf4 can induce dysplasia(11,12). Two transient transfection-reprogramming methods have been published to address this issue(13,14). However, the efficiency of both approaches is extremely low, and neither has been applied successfully to human cells so far. Here we show that non-viral transfection of a single multiprotein expression vector, which comprises the coding sequences of c-Myc, Klf4, Oct4 and Sox2 linked with 2A peptides, can reprogram both mouse and human fibroblasts. Moreover, the transgene can be removed once reprogramming has been achieved. iPS cells produced with this nonviral vector show robust expression of pluripotency markers, indicating a reprogrammed state confirmed functionally by in vitro differentiation assays and formation of adult chimaeric mice. When the single-vector reprogramming system was combined with a piggyBac transposon(15,16), we succeeded in establishing reprogrammed human cell lines from embryonic fibroblasts with robust expression of pluripotency markers. This system minimizes genome modification in iPS cells and enables complete elimination of exogenous reprogramming factors, efficiently providing iPS cells that are applicable to regenerative medicine, drug screening and the establishment of disease models.

In order to investigate low‐energy excitations below 10 meV, inelastic neutron‐scattering measurements have been carried out on various organic amorphous polymers at 10 and 50 K and three inorganic glasses at 150 and 295 K. It was found that a broad excitation peak is observed for all amorphous materials in the ω range of 1.5–4.0 meV irrespective of different chemical structures. On the other hand, highly crystalline polyethylene with a degree of crystallinity 0.96 shows no such broad peak, indicating that the low‐energy excitation is characteristic of amorphous materials. We have employed an asymmetric double‐well potential as a common origin for the low‐energy excitation in amorphous materials and analyzed the results of amorphous polyisobutylene to confirm validity of this model and alternatively to determine parameters of the potential. Analysis of the temperature dependence of the inelastic‐scattering intensity of the low‐energy excitation leads to a concept of phonon‐assisted tunneling in the asymmetric double‐well potential.

Local motions are investigated in the time range 10 −13 to 10 −10 s. Two modes are found in this time range. The faster and slower modes are assigned to damped vibrational motion and local conformational transition, respectively. The latter is analyzed in terms of a jump diffusion model with the damped vibrational motions on the jump sites. The observed conformational transition rate is compared with the Kramers' rate theory, and the spatial scales of the motions are discussed based on the molecular structure of cis-1,4-polybutadiene

We report the quasielastic neutron scattering results on an amorphous polyimide below the glass transition temperature Tg (=523 K). The so-called fast process in picosecond order has been observed far below Tg. We also performed dynamic-mechanical measurements at 10 Hz to find that the β-relaxation temperature is close to the onset temperature of the fast process although the difference in the frequencies in both the measurements are more than ∼1010 Hz.

Neutron spin echo measurements were performed on polymeric micelles consisting of deuterated polystyrene (d-PS)-polyisoprene (PI) diblock copolymers in dilute and concentrated solutions. The scattering length density of the core of the micelles matched to the solvent so that dynamics of polymer chains in the corona were measured. The observed intermediate scattering functions in the dilute solution were analyzed by the theory for tethered chains proposed by de Gennes. In the concentrated solutions, motional slowing down was observed, which may be caused not only by increase of the viscosity but also by decrease of the osmotic compressibility.

Low energy excitations in crystalline and amorphous solids of Tri- O -methyl-β-cyclodextrin (TMCD) were studied by neutron scattering and calorimetric techniques. Amorphous solids of TMCD were prepared by two different ways: mechanical milling and liquid-quenching amorphization. Both the amorphous solids showed a boson peak at around 2 meV and there was no significant difference between them. It was noted that crystalline TMCD also showed a boson peak. This anomalous boson peak in the crystalline state was confirmed by low temperature heat capacity measurements.

Mbd3 is a core component of the NuRD (Nucleosome Remodeling and Histone Deacetylation) co-repressor complex, and NuRD-mediated silencing has been implicated in cell fate decisions in a number of contexts. Mbd3-deficient embryonic stem (ES) cells made by gene targeting are viable but fail to form a stable NuRD complex, are severely compromised in the ability to differentiate,and show LIF-independent self-renewal. Mbd3 is known to be essential for postimplantation embryogenesis in mice, but the function of Mbd3 in vivo has not previously been addressed. Here we show that the inner cell mass (ICM) of Mbd3-deficient blastocysts fails to develop into mature epiblast after implantation. Unlike Mbd3-null ES cells, Mbd3-deficient ICMs grown ex vivo fail to expand their Oct4-positive, pluripotent cell population despite producing robust endoderm outgrowths. Additionally, we identify a set of genes showing stage-specific expression in ICM cells during preimplantation development, and show that Mbd3 is required for proper gene expression patterns in pre- and peri-implantation embryos and in ES cells. These results demonstrate the importance of Mbd3/NuRD for the development of pluripotent cells in vivo and for their ex vivo progression into embryonic stem cells, and highlight the differences between ES cells and the ICM cells from which they are derived.

The electrostatic persistence lengths bc of NaPSS polyions have been measured as a function of ionic strength I in the solutions using a small-angle neuron scattering (SANS) technique combined with a zero average contrast (ZAC) method. This ZAC method provides the optical theta condition distinguishing the intermolecular scattering functions S2(q), and thereby the scattering functions of a single chain S1(q) free from the intermolecular interferences were obtained. The resulting bc values which were derived by the analysis of S1(q) are proportional to I−12. This work confirms and extends an earlier SANS study where the contrast-match was used.

This paper reviews the authors' investigation into polymer crystallization, especially involving a spinodal decomposition (SD) type phase separation due to the orientation fluctuation of stiff segments prior to crystal nucleation. Evidences for SD obtained from small-angle X-ray and neutron scattering (SAXS and SANS), depolarized light scattering (DPLS), Fourier-transform infrared spectroscopy (FT-IR) are discussed in detail in the case of the glass crystallization of poly(ethylene terephthalate) (PET) just above Tg. SD-like optical micrographs are also shown as a function of crystallization temperature for the melt crystallization of PET; their characteristic wavelengths A, which are of the order of μm above 120 °C, follow a van Aartsen equation derived from the Cahn-Hilliard theory for SD. By fitting the equation to the observed characteristic wavelengths the spinodal temperature T s was determined to be T s = 213 ± 5 °C for the PET melt, above which the SD pattern suddenly changed to the usual spherulite pattern. On the basis of a theory by Olmsted et al. [4], the general mechanisms of polymer crystallization are also discussed; the crystallization from the metastable melt causes the nucleation and growth (N&G) of dense (nematic) domains while that from the unstable melt causes SD into the dense (nematic) and less dense (isotropic) domains. Furthermore, the secondary phase separation of the SD-type phase separation into smectic and amorphous domains subsequently occurs inside the nematic domain for both these cases.

Sperm–oocyte fusion is one of the most impressive events in sexual reproduction, and the elucidation of its molecular mechanism has fascinated researchers for a long time. Because of the limitation of materials and difficulties in analyzing membrane protein–protein interactions, many attempts have failed to reach this goal. Recent studies involving gene targeting have clearly demonstrated the various molecules that are involved in sperm–oocyte binding and fusion. Sperm ADAMs (family of proteins with a disintegrin and metalloprotease domain), including fertilin α, fertilin β and cyritestin, have been investigated and found to be important for binding rather than for fusion and painstaking studies have raised suspicions that their putative receptors, oocyte integrins, are necessary for the sperm–oocyte interaction. Recently, several studies have focused the spotlight on CD9 and glycosylphosphatidylinositol (GPI)-anchored proteins on oocytes, and epididymal protein DE on sperm, as candidate molecules involved in sperm–oocyte fusion. Lack of, or interference with the function of, these proteins can disrupt the sperm–oocyte fusion without changing the binding. In this review we highlight the candidate molecules involved in the sperm–oocyte interaction suggested from the recent progress in this research field.

A converging collimator with NiC/Ti supermirrors has been mounted on the high-resolution neutron spectrometer LAM-80ET (Δ ɛ ∼ 1.2 μeV) installed at the pulsed cold-neutron source in the National Laboratory for High Energy Physics (KEK), Tsukuba, Japan. The design and the performance of the collimator are described.

The change of chain conformation during the induction period of crystallization of poly(ethylene terephthalate) (PET) has been studied by means of a deuterium-labelling technique with small-angle neutron scattering. The scattering function of a single chain was analyzed based on the worm-like chain model. The stiffness of PET chains increased in the early stage of the induction period. According to the isotropic-nematic transition theory proposed by Doi et al., this increase of the chain stiffness induces the parallel ordering of polymer segments due to the excluded-volume effect. This orientational ordering may play an important role in the growth process of the density fluctuations observed in the induction period of crystallization.

The local dynamics of amorphous polystyrene have been investigated by incoherent inelastic and quasielastic neutron scattering in a temperature range of 20 to 300 K, below the glass transition temperature T g ( = 373 K). The elasticscattering intensity shows an anomalous decrease at temperatures above 200 K. Corresponding to the anomalous decrease, the shape of the dynamic scattering law S ( Q,ω ) changes from inelastic-like to quasielastic-like, suggesting the onset of a fast relaxation process. On the basis of the results from hydrogenated polystyrene and polystyrene with a deuterated phenyl ring, the fast relaxation process occurring far below T g has been assigned to motion of the phenyl side chains.

In order to clarify the structure formation processes in the induction period of polymer crystallization the annealing time dependence of depolarized light-scattering ~DPLS! intensities has been investigated as a function of crystallization temperature for poly~ethylene terephthalate!, poly~ethylene naphthalate!, syndiotactic polystyrene, and isotactic polystyrene. It is found that the induction period may be separated into three stages: the first stage where the DPLS intensity hardly changes with time, the second stage where the intensity increases exponentially, and the third stage where it levels off. Considering that the DPLS provides information about the degree of parallel orientation of rigid polymer segments, the first stage whose time length depends on the annealing temperature may be assigned to a process where the polymer chains begin to partially assume a rigid conformation, generally a helical structure being almost the same as the structure in the corresponding crystal. This process is limited to a time when the average length of the rigid segments attains a critical value given by a Shimada, Doi, and Okano theory @J. Chem. Phys. 88, 7181 ~1988!# above which spinodal decomposition ~SD! is caused. The second and third stages correspond to the early and late stages of SD, respectively, which was confirmed by small-angle x-ray scattering measurements. The apparent activation energies obtained from the temperature dependence of the DPLS intensities for the three stages were 35‐ 40, 25‐50, and 180‐ 400 kJ/mol, respectively, for all the polymers. The large apparent activation energies for the late stage of SD is discussed within a framework of Binder and Stauffer’s theory @Phys. Rev. Lett. 33, 1006 ~1974!#.

We carried out incoherent and coherent inelastic neutron scattering on glassy poly(methyl methacrylate) in a wide scattering vector range up to 4.9 ${\mathrm{\AA{}}}^{\mathrm{\ensuremath{-}}1}$ with a high-energy resolution of 0.16 meV to investigate low-energy modes: the so-called boson peak and the picosecond-scale process. First, we studied the basic features of the two modes in the incoherent measurements and found that they are similar to those reported for many glass-forming materials. In the coherent scattering measurements, focusing on the Q dependence of the inelastic scattering intensity, we found that the boson peak and picosecond-scale process modes do not move in phase at a length scale of \ensuremath{\sim}7 \AA{}, while the motional coherency is preserved between neighboring side chains in a polymer. These observations suggest that the boson peak and picosecond-scale process are localized modes on two monomers within a polymer chain. The intrachain localization becomes more pronounced with increasing the excitation energy.

CD9, a member of the tetraspan family of proteins, is highly expressed on macrophages. Although a clear function for the molecule has yet to be described, we have found that the anti-CD9 mAb activates mouse macrophages. The rat anti-CD9 mAb, KMC8.8, but not the F(ab')(2), induced tyrosine phosphorylation of proteins including syk and cbl and induced cell aggregation in the mouse macrophage cell line, J774, suggesting that co-cross-linking of CD9 and Fc gamma R was required for the signal. Co-cross-linking of CD9-Fc gamma R with KMC8.8 on macrophages from three different FcR-deficient mice, FcR gamma-chain(-/-), Fc gamma RIIB(-/-), and Fc gamma RIII(-/-), revealed that Fc gamma RIII is specific and crucial for syk phosphorylation. Although both KMC8.8 and the anti-Fc gamma RIIB/III mAb, 2.4G2, evoked similar phosphorylation patterns, only KMC8.8 induced cell aggregation. Additionally, KMC8.8 treatment led to reduce levels of TNF-alpha production and p42/44 extracellular signal-related kinase phosphorylation relative to 2.4G2 stimulation. Immunofluorescence staining showed that co-cross-linking of CD9-Fc gamma R with KMC8.8 induced filopodium extension before cell aggregation, which was followed by simultaneous colocalization of CD9, Fc gamma RIIB/III, Mac-1, ICAM-1, and F-actin at the cell-cell adhesion site. Moreover, KMC8.8 treatment of Fc gamma R-deficient macrophages revealed that the colocalization of CD9, Fc gamma RIII, Mac-1, and F-actin requires co-cross-linking of CD9-Fc gamma RIII, whereas co-cross-linking of CD9-Fc gamma RIIB induced the colocalization of only CD9 and Fc gamma RIIB. Our results demonstrate that co-cross-linking of CD9 and Fc gamma Rs activates macrophages; therefore, CD9 may collaborate with FcRs functioning in infection and inflammation on macrophages.

This review covers the recent progress of studies on dynamics in the glassy states and near the glass transition of amorphous polymers as revealed by inelastic and quasielastic neutron scattering, covering four topics: (i) low energy excitation (boson peak) in the glassy states; (ii) fast process in picosecond order; (iii) E-process related to conformational transitions; (iv) dynamical heterogeneity as revealed by non-Gaussian parameter.

The sol-gel-glass transition of atactic polystyrene in carbon disulfide over a wide temperature range from 170 to 300 K has been investigated by neutron quasielastic scattering methods. A drastic narrowing of the quasielastic peaks was observed for the present system as the temperature is lowered and the narrowing completes at the glass transition. Two types of local motion were observed in the sol-gel transition.

Low energy excitations in amorphous polystyrene have been studied at 10 K using inelastic neutron scattering in the ω range of 0.2–10 meV.

Structural studies have been performed on poly(vinyl alcohol)(PVA) gels formed in mixtures of dimethylsulfoxide and water at 23°C by means of small angle and wide angle neutron scattering techniques in a wide Q range of 0.003–10A-1.

Osteoclasts are thought to belong to a macrophage lineage. However, the nature of common precursors of osteoclasts and macrophages remains to be investigated. We have characterized the differentiation potential of mouse bone marrow macrophages into mature osteoclasts. Monocyte macrophage-colony-stimulating factor (M-CSF) stimulated the proliferation of bone marrow macrophages in a dose-dependent manner and these M-CSF-dependent bone marrow macrophage (MDBM) cells efficiently differentiated into the tartrate-resistant acid phosphatase (TRAP)-positive osteoclasts in the presence of soluble RANKL (sRANKL) and M-CSF in the in vitro culture. The macrophage-like cell line TMC16 was established from tsA58 (temperature-sensitive SV40 large T-antigen) transgenic mice in the same manner to the preparation of MDBM cells and also differentiated into mature osteoclasts. During this differentiation in vitro, the morphology of the cells changed from spindle to round and smaller (termed pOC) on day 2 and to multinuclear (termed multinucleated cells [MNCs]) on day 4. The surface expression of macrophage marker CD14 was down-regulated and that of CD43 was up-regulated on pOC, analyzed by flow cytometry. RNA analysis revealed that osteoclast marker genes such as calcitonin receptor (CTR), carbonic anhydrase II (CAII), cathepsin K (cath K), MMP9, and TRAP were strongly expressed in MNCs and weakly in pOC whereas MDBM cells did not express these genes. However, the osteopontin (OPN) gene was strongly expressed in MDBM cells and this expression became weakened after differentiation into pOC. The TMC16 cell line weakly expressed cath K, TRAP, and OPN, suggesting that the TMC16 cell line is immortalized at a stage slightly differentiated from MDBM cells. Furthermore, cell sorting analysis revealed that osteoclast early progenitors in bone marrow cells are preferentially present in the Mac-1- F4/80dull population, which differentiated into MDBM cells (the osteoclast progenitor) expressing Mac-1+ F4/80int, suggesting that M-CSF plays roles of a differentiation factor as well as a growth factor for osteoclast early progenitors. These results showed the transition of morphology, surface markers, and gene expression from the early to mature stage in osteoclast differentiation. We propose three differentiation stages in the osteoclast lineage: the pro-osteoclast (spindle-shaped macrophage cells), the pre-osteoclast (small round mononucleated TRAP-positive cells), and the mature osteoclast (multinucleated TRAP-positive cells) stage.

The cell-surface molecule Cd9, a member of the transmembrane-4 superfamily, interacts with the integrin family and other membrane proteins. and is postulated to participate in cell migration and adhesion. Expression of Cd9 enhances membrane fusion between muscle cells and promotes viral infection in some cells. Fertilization also involves membrane fusion, between gametes. In mammals, the sperm binds to microvilli on the egg surface, and sperm-egg membrane fusion first occurs around the equatorial region of the sperm head12. The fused membrane is then disrupted, and the sperm nucleus as well as the cytoplasm is incorporated into the egg. Cd9 is expressed on the plasma membrane of the mouse egg, and an anti-Cd9 monoclonal antibody inhibits sperm-egg surface interactions. We generated Cd9 mice and found that homozygous mutant females were infertile. Sperm-egg binding was normal, but sperm-egg fusion was almost entirely inhibited in eggs from Cd9 females. Intracellular Ca2 oscillations, which signal fertilization, were absent in almost all mutant eggs; in rare cases, a response occurred after a long time period. In normal animals, Cd9 molecules were expressed on the egg microvilli and became densely concentrated at the sperm attachment site. Thus, our results show that Cd9 is important in the gamete fusion process at fertilization.

We report on measurements of the incoherent elastic neutron-scattering intensity ${I}_{\mathrm{el}}(Q)$ of polyethylenes with degrees of crystallinity 0.46 and 0.96 in a wide Q (length of scattering vector) range from 0.4 to 6.2 ${\mathrm{\AA{}}}^{\mathrm{\ensuremath{-}}1}$ to observe the deviation from the Gaussian behavior. The non-Gaussian behavior was observed in both the amorphous and the crystalline phases. The non-Gaussian behavior in the theoretically well-known crystalline phase can be understood more or less quantitatively in terms of the anisotropy of the mean-square displacement. The result implies that at least a part of the non-Gaussian behavior of the amorphous phase is due to the same source, while another part may be due to the dynamical heterogeneity inherent to the amorphous phase.

Time-resolved light scattering measurements during the gelation process of a poly(vinyl alcohol) (PVA) solution in a mixture of dimethyl sulfoxide and water (H2O) have shown that a spinodal decomposition (SD) type phase separation takes place in the early stage of gelation. In this case the kinetics of SD is valid only before macroscopic gelation occurs because the growth rate is slowed down by gelation. Such SD type phase separation makes the solution opaque as it proceeds, and hence the structural change can no longer be followed by light scattering. To investigate the structure of the opaque PVA gel as well, we have employed an ultra-small-angle neutron scattering technique using a Bonse-Hart camera. These observations reveal that even after the macroscopic gelation the structure due to the microphase separation on a spatial scale of severalmgr;m continues to grow against the elasticity. This may be because at first the gel structure is too soft to suppress the growth of the microphase separation, but within 24 h after the quenching the growth terminates. On the basis of the results, we will discuss a possible mechanism of the microphase separation after gelation.

Distinct deviation from the Gaussian approximation was found in the Q dependence of incoherent elastic neutron scattering intensity of a glass-forming polymer, poly(methyl methacrylate). This non-Gaussian behavior was interpreted in terms of a distribution of the mean square displacement, which is caused by the heterogeneity due to different local environments around molecules in the glassy state. In order to see the nature of the distribution, we have examined three distribution functions; Gaussian, log-Gaussian and bimodal distribution functions.

We have reexamined the free-volume concept presented by Cohen and Turnbull on the basis of two microscopic quantities: the excess mean-square displacementu(2)(f) and the total free volume V(PA,t), of poly- butadiene evaluated from the quasielastic neutron scattering and the positron annihilation lifetime spectroscopy (PALS) data, respectively. Comparing with the viscosity eta we found two relations, eta=eta(0) exp u( 2)(0)/u(2)(f) and eta=eta(0) exp V(*)(PA,0)/V(PA,t)=eta(0) exp V(*)(PA,0)/v(PA,f), where u(2)(0), V(*)(PA,0) and v(*)(PA,0) are the critical values for the mean-square displacement, the total PALS free volume, and the PALS free volume per molecule, respectively, and further v(*)(PA,0)=V(*)(PA,0)/N, N being the total number of molecules or segments. On the basis of these relations, we discuss the microscopic basis of the free-volume theory. The experimentally evaluated critical values u(2)(0) and v(*)(PA,0) are much larger than the average values ofu(2)(f) and v(PA,f) calculated from the distributions. This has been explained from the low probability of escaping motions from a molecular cage. The free volume per monomer and the free-volume fraction were calculated from the excess mean-square displacementu(2)(f). The former was compared with the free-volume hole obtained by PALS, suggesting that 22 monomers are required for one PALS free-volume hole. The free-volume fraction obtained from the excess mean-square displacement was found to be 6.4% at 250 K, which is in reasonable agreement with that evaluated from the rheological data (9.0%).

The kinetics during the induction period of polymer crystallization is studied by means of depolarized light scattering measurements. The spinodal decomposition during this period is shown to be caused by orientation fluctuations of polymer segments. Time evolution of these orientation fluctuations can be described by the spinodal decomposition kinetics in terms of transformation from the isotropic to nematic phase proposed by Doi et al.

Dynamics of amorphous polymers near glass transition temperature Tg has ben studied by quasielastic neutron scattering in the ω‐range of 0.02 to 10 meV. It was found that two modes of motion appear near Tg in the energy range of ca. 1 meV and 10–20 μeV. The faster and slower modes arise from 30–50 K below Tg and 10–20 K above Tg, respectively.

A new finding is reported that the long range ordered structure is formed in the induction period before the crystallization, when poly(ethylene terephthalate) (PET) is annealed just above the glass transition temperature. This ordering process can be interpreted in terms of the spinodal decomposition type phase separation phenomenon.