Ultrathin organic solvent nanofiltration membrane with polydopamine-HKUST-1 interlayer for organic solvent separation

Polydopamine (PDA) and metal-organic skeleton HKUST-1 were co-deposited on the base membrane of hexamethylenediamine (HDA)-crosslinked polyetherimide (PEI) ultrafiltration membrane as the interlayer, and high-throughput organic solvent nanofiltration membrane (OSN) was prepared by interfacial polymerization and solvent activation reaction. The polyamide (PA) layer surface roughness from 28.4 nm in PA/PEI to 78.3 nm in PA/PDA-HKUST-10.6/PEI membrane, reduced the thickness of the separation layer from 79 to 14 nm, and significantly improved the hydrophilic, thermal and mechanical properties. The flux of the PA/PDA-HKUST-10.6/PEI membrane in a 0.1 g/L Congo Red (CR) ethanol solution at 0.6 MPa test pressure reached 21.8 L/(m2·hr) and the rejection of CR was 92.8%. Solvent adsorption test, N, N-dimethylformamide (DMF) immersion experiment, and long-term operation test in ethanol showed that the membranes had high solvent tolerance. The solvent flux test demonstrated that, under the test pressure of 0.6 MPa, the flux of different solvents ranked as follows: methanol (56.9 L/(m2·hr)) > DMF (39.6 L/(m2·hr)) > ethanol (31.2 L/(m2·hr)) > IPA (4.5 L/(m2·hr)) > N-hexane (1.9 L/(m2·hr)). The ability of the membranes to retain dyes in IPA/water dyes solution was also evaluated. The flux of the membrane was 30.4 L/(m2·hr) and the rejection of CR was 91.6% when the IPA concentration reached 50%. This OSN membrane-making strategy is economical, environment-friendly and efficient, and has a great application prospect in organic solvent separation systems.

An Immune-Related Gene Prognostic Prediction Risk Model for Neoadjuvant Chemoradiotherapy in Rectal Cancer Using Artificial Intelligence

PURPOSE/OBJECTIVE(S)

To develop and validate an immune-related gene prognostic model (IRGPM) that can predict disease-free survival (DFS) in patients with locally advanced rectal cancer (LARC) who received neoadjuvant chemoradiotherapy and to clarify the immune characteristics of patients with different prognostic risks.

MATERIALS/METHODS

In this study, we obtained transcriptomic and clinical data from the Gene Expression Omnibus (GEO) database and rectal cancer database of West China Hospital. Genes in the RNA immune-oncology panel were extracted. Elastic net was used to identify the immune-related genes that significantly affected the DFS of patients. A prognostic risk model (IRGPM) for rectal cancer was constructed with the random forest method. The prognostic risk score was calculated by the model, and the patients were divided into high- and low-risk groups according to the median risk score. Immune characteristics were analyzed and compared between the high- and low-risk groups.

RESULTS

A total of 407 LARC samples were used in this study. A 20-gene signature was identified by elastic net and was found to be significantly correlated with DFS. The IRGPM was constructed on the basis of the 20 immune-related genes. Kaplan‒Meier survival analysis showed poorer 5-year DFS in the high-risk group than in the low-risk group, and the receiver operating characteristic (ROC) curve suggested good model prediction (areas under the curve (AUCs) of 0.87, 0.94, 0.95 at 1, 3, and 5 years, respectively). The model was validated in the GSE190826 cohort (AUCs of 0.79, 0.64, and 0.63 at 1, 3, and 5 years, respectively) and the cohort from our institution (AUCs of 0.64, 0.66, and 0. 64 at 1, 3, and 5 years, respectively). The differentially expressed genes between the high- and low-risk groups were enriched in cytokine‒cytokine receptor interactions. The patients in the low-risk group had higher immune scores than the patients in the high-risk group. Subsequently, we found that activated B cells, activated CD8 T cells, central memory CD8 T cells, macrophages, T follicular helper cells and type 2 helper cells were more abundant in the low-risk group. Moreover, we compared the expression of immune checkpoints and found that the low-risk group had a higher PDCD1 expression level.

CONCLUSION

The IRGPM, which was constructed based on the random forest and elastic net methods, is a promising method to distinguish DFS in LARC patients treated with a standard strategy. The low-risk group identified by IRGPM was characterized by the activation of adaptive immunity in tumor microenvironment.

High throughput exploration of the oxidation landscape in high entropy alloys

High entropy alloys (HEAs) have gained interest for structural applications in extreme environments. With a potentially vast chemical and phase space, there are significant opportunities to discover superior performing alloys. Crucial for most high-temperature applications is understanding and mitigating the oxidation behavior of these chemically complex alloys. Most experimental and computational HEA studies have focused on a limited set of compositions and only a fraction of these compositions have been characterized for oxidation. We present a high-throughput framework that utilizes density-functional theory (DFT) in concert with a combined machine-learning model and grand-canonical linear programming for assessing phase stability, phase-fraction, chemical activity and high-temperature survivability of arbitrary HEAs. This framework considers temperature dependent contributions to the Gibbs energy of the competing phases arising from short-range order and vibrational entropy. We demonstrate the effectiveness of the framework by assessing the thermodynamic stability, oxidation behavior, chemical activity, and phase decomposition of body-centered cubic Mo-W-Ta-Ti-Zr refractory HEAs. A total of 51 compositions were analyzed and ranked in order of their survivability based on the Pareto-front analysis. Oxidation was performed at 1373 K on four samples in air showing the difference in oxidation behavior determined experimentally through scale thickness and their mass changes. The insights on oxidation behavior presented in this work will enable the fast assessment of technologically useful HEAs needed for future structural application in extreme conditions.

Geometry-dependent band shift and dielectric modification of nanoporous Si nanowires

In order to obtain a detailed understanding of the modulation of electronic properties in nanoporous Si (np-Si) nanowires with containing ordered, nanometer-sized cylindrical pores, we propose a theoretical method to clarify the band shift and associated with the dielectric modification determined by the geometrical parameters, including nanowire diameter, pore size, pore spacing and porosity, in terms of size-dependent surface energy and atomic-bond-relaxation correlation mechanism. Our results reveal that the self-equilibrium strain induced by the atoms located at inner and outer surfaces with high ratio of under-coordinated atoms as well as elastic interaction among pores in np-Si nanowires play the dominant role in the bandgap shift and dielectric depression. The tunable electronic properties of np-Si nanowires with negative curvature make them attractive for nanoelectronic and optoelectronic devices.

Size-dependent optical absorption modulation of Si/Ge and Ge/Si core/shell nanowires with different cross-sectional geometries

We present an atomic-level and quantitative study of the absorption properties in Si/Ge and Ge/Si core/shell nanowires (CSNWs) along [110] direction with different cross-sectional geometries using the atomic bond relaxation method. We find that the strain existing in self-equilibrium state of CSNWs and associated with elastic energy originating from interface mismatch and surface relaxation affect the band shift and absorption properties. Compared to the CSNWs with tetragonal, hexagonal and circular shapes, the triangular CSNWs have the largest band gap shift at a fixed strain and the smallest absorption coefficient at a determinate incident light wavelength. The tunable absorption property, realized by controlling the size and geometry structure, could be helpful for nanoelectronic applications.

Anomalous interface adhesion of graphene membranes

In order to understand the anomalous interface adhesion properties between graphene membranes and their substrates, we have developed a theoretical method to calibrate the interface adhesion energy of monolayer and multilayer graphene on substrates based on the bond relaxation consideration. Four kinds of interfaces, including graphene/SiO₂, graphene/Cu, graphene/Cu/Ni and Cu/graphene/Ni, were taken into account. It was found that the membrane thickness and the interface confinement condition determine the adhesion energy. The relationship between the critical interface separation and the graphene thickness showed that the interface separation in the self-equilibrium state drops with decreasing membrane thickness. The size-dependent Young's modulus of graphene membrane and the interfacial condition were responsible for the novel interface adhesion energy. The proposed theory was expected to be applied to the design of graphene-based devices.

Reversible nanodiamond-carbon onion phase transformations

Because of their considerable science and technical interest, nanodiamonds (3-5 nm) are often used as a model to study the phase transformation between graphite and diamond. Here we demonstrated that a reversible nanodiamond-carbon onion phase transformation can become true when laser irradiates colloidal suspensions of nanodiamonds at the ambient temperature and pressure. Nanodiamonds are first transformed to carbon onions driven by the laser-induced high temperature in which an intermediary bucky diamond phase is observed. Sequentially, carbon onions are transformed back to nanodiamonds driven by the laser-induced high temperature and high pressure from carbon onions as nanoscaled temperature and pressure cell upon the laser irradiation process in liquid. Similarly, the same bucky diamond phase serving as an intermediate phase is found during the carbon onion-to-nanodiamond transition. To have a clear insight into the unique phase transformation the thermodynamic approaches on the nanoscale were proposed to elucidate the reversible phase transformation of nanodiamond-to-carbon onion-to-nanodiamond via an intermediary bucky diamond phase upon the laser irradiation in liquid. This reversible transition reveals a series of phase transformations between diamond and carbon allotropes, such as carbon onion and bucky diamond, having a general insight into the basic physics involved in these phase transformations. These results give a clue to the root of meteoritic nanodiamonds that are commonly found in primitive meteorites but their origin is puzzling and offers one suitable approach for breaking controllable pathways between diamond and carbon allotropes.

Physical mechanism of surface roughening of the radial Ge-core/Si-shell nanowire heterostructure and thermodynamic prediction of surface stability of the InAs-core/GaAs-shell nanowire structure

As a promising and typical semiconductor heterostructure at the nanoscale, the radial Ge/Si NW heterostructure, that is, the Ge-core/Si-shell NW structure, has been widely investigated and used in various nanodevices such as solar cells, lasers, and sensors because of the strong changes in the band structure and increased charge carrier mobility. Therefore, to attain high quality radial semiconductor NW heterostructures, controllable and stable epitaxial growth of core-shell NW structures has become a major challenge for both experimental and theoretical evaluation. Surface roughening is usually undesirable for the epitaxial growth of high quality radial semiconductor NW heterostructures, because it would destroy the core-shell NW structures. For example, the surface of the Ge-core/Si-shell NWs always exhibits a periodic modulation with island-like morphologies, that is, surface roughening, during epitaxial growth. Therefore, the physical understanding of the surface roughening behavior during the epitaxial growth of core-shell NW structures is essential and urgent for theoretical design and experimentally controlling the growth of high quality radial semiconductor NW heterostructures. Here, we proposed a quantitative thermodynamic theory to address the physical process of epitaxial growth of core-shell NW structures and surface roughening. We showed that the transformation from the Frank-van der Merwe mode to the Stranski-Krastanow mode during the epitaxial growth of radial semiconductor NW heterostructures is the physical origin of surface roughening. We deduced the thermodynamic criterion for the formation of the surface roughening and the phase diagram of growth and showed that the radius of the NWs and the thickness of the shell layer can not only determine the formation of the surface roughening in a core-shell NW structure, but also control the periodicity and amplitude of the surface roughness. The agreement between the theoretical results and the experimental data of the Ge-core/Si-shell NW structure implied that the established approach could be applicable to the understanding and design of various semiconductor core-shell NW structures. Consequentially, we used the established theoretical model to study the epitaxial growth of the InAs-core/GaAs-shell NW structure and predict the surface roughening formation, as well as the periodicity and amplitude of the surface roughness, which provided useful information to theoretically design and experimentally control the epitaxial growth of the radial InAs-core/GaAs-shell NW structure.

ZnO hollow quantum dot: a promising deep-UV light emitter

We establish an analytic model to illustrate the energy bandgap of ZnO hollow quantum dots (HQDs) with negative curvature surface from the perspective of nanothermodynamics. It was found that the bandgap of ZnO HQDs shows a pronounced blue-shift as comparable to those of bulk counterpart and free nanocrystals. Furthermore, the photoelectric properties of ZnO HQDs can be effectively modulated by three independent dimensions, including the outer surface, the inner surface and the shell thickness. Strikingly, the emission wavelength of ZnO HQDs can be extended into the deep-ultraviolet (DUV) region, which suggests this kind of nanostructure could be expected to be applicable for the new-generation, compact, and environmentally friendly alternative DUV light emitter.

Twist2 contributes to breast cancer progression by promoting an epithelial-mesenchymal transition and cancer stem-like cell self-renewal

The epithelial to mesenchymal transition (EMT) is a highly conserved cellular programme that has an important role in normal embryogenesis and in cancer invasion and metastasis. We report here that Twist2, a tissue-specific basic helix-loop-helix transcription factor, is overexpressed in human breast cancers and lymph node metastases. In mammary epithelial cells and breast cancer cells, ectopic overexpression of Twist2 results in morphological transformation, downregulation of epithelial markers and upregulation of mesenchymal markers. Moreover, Twist2 enhances the cell migration and colony-forming abilities of mammary epithelial cells and breast cancer cells in vitro and promotes tumour growth in vivo. Ectopic expression of Twist2 in mammary epithelial cells and breast cancer cells increases the size and number of their CD44(high)/CD24(low) stem-like cell sub-populations, promotes the expression of stem cell markers and enhances the self-renewal capabilities of stem-like cells. In addition, exogenous expression of Twist2 leads to constitutive activation of STAT3 (signal transducer and activator of transcription 3) and downregulation of E-cadherin. Thus, the overexpression of Twist2 may contribute to breast cancer progression by activating the EMT programme and enhancing the self-renewal of cancer stem-like cells.

Surface alloying at the nanoscale: Mo on Au nanocrystalline films

Aiming at the physical and chemical mechanisms of surface alloying at the nanometer scale in immiscible binary metallic systems, we have studied the Mo growth mode upon depositing Mo on the surface of Au nanocrystalline films via molecular beam epitaxy. Mo-Au surface alloying was observed when Mo was deposited on Au nanocrystalline films at a high temperature. A relevant thermodynamic and kinetic model was established to address the surface alloying at the nanoscale. The size-dependent interface energy between the Mo particles and the Au nanocrystalline films, as the thermodynamic driving force, is attributed to be the reason behind the physical and chemical mechanisms of the Mo-Au surface alloying on Au nanocrystalline films.

Surface energy of nanowires

An analytical model is developed for calculation of the surface energy of a nanowire based on thermodynamics and continuum medium mechanics. The core-shell structure and the outer surface skin of the nanowire are considered for the one-dimensional nanostructure and contributions from chemical and structural effects to the surface energy are discussed. It is found that the surface energy of nanowires decreases with the diameter reduction, which induces the melting temperature depression of nanowires. Theoretical results are in agreement with the results of experiments and simulations.

Roughing titanium quantum wire on patterned monohydride diamond (001) surface

The authors have performed the roughing of titanium (Ti) quantum wires forming on a hydrogen-terminated diamond (001)-2x1 surface patterned with an ordered bare strip array and demonstrated that well-ordered Ti quantum wires are achieved only if the growth conditions (temperature and flux) have optimal values via kinetic Monte Carlo simulations. Considering that a scanning tunneling microscope is capable of selectively desorbing H from diamond (001)-2x1-H surface, they proposed a viable and easy approach to fabricate "ideal quantum wires" on the patterned hydrogen-terminated diamond (001) surface. The physical origin of the Ti quantum wire formation was pursued.

Solid solubility limit in alloying nanoparticles

In order to gain a better thermodynamic understanding of the phase diagram of alloying nanoparticles, we establish a size-dependent solid solubility model of binary metallic systems to elucidate the anomalous solid solubility in nanometre-sized alloying particles. It is found that a diameter of 20 nm seems a threshold value of the size of alloying nanoparticles for the unusual solid solubility, i.e. the solubility is greatly promoted with decreasing grain size when the size of alloying nanoparticles is less than 20 nm. Taking the Pb-Sn system as an example, we show that the theoretical predictions are consistent with experimental data.

Comparative study of air-core and coaxial Bragg fibers: single-mode transmission and dispersion characteristics

Using an asymptotic formalism we developed in an earlier paper, we compare the dispersion properties of the air-core Bragg fiber with those of the coaxial Bragg fiber. In particular we are interested in the way the inner core of the coaxial fiber influence the dispersion relation. It is shown that, given appropriate structural parameters, large single-mode frequency windows with a zero-dispersion point can be achieved for the TM mode in coaxial fibers. We provide an intuitive interpretation based on perturbation analysis and the results of our asymptotic calculations are confirmed by Finite Difference Time Domain (FDTD) simulations.

Evidence for cleft closure in actomyosin upon ADP release

Structural insights into the interaction of smooth muscle myosin with actin have been provided by computer-based fitting of crystal structures into three-dimensional reconstructions obtained by electron cryomicroscopy, and by mapping of structural and dynamic changes in the actomyosin complex. The actomyosin structures determined in the presence and absence of MgADP differ significantly from each other, and from all crystallographic structures of unbound myosin. Coupled to a complex movement ( approximately 34 A) of the light chain binding domain upon MgADP release, we observed a approximately 9 degrees rotation of the myosin motor domain relative to the actin filament, and a closure of the cleft that divides the actin binding region of the myosin head. Cleft closure is achieved by a movement of the upper 50 kDa region, while parts of the lower 50 kDa region are stabilized through strong interactions with actin. This model supports a mechanism in which binding of MgATP at the active site opens the cleft and disrupts the interface, thereby releasing myosin from actin.

[Low fever of unknown reason in patients undergoing autologous stem cell transplantation after hematopoietic reconstitution: a clinical analysis of 13 cases]

OBJECTIVE

To investigate the reason of low fever in patients undergoing autologous stem cell transplantation after hematopoietic reconstitution.

METHODS

The reasons for low fever in 13 patients undergoing autologous stem cell transplantation after hematopoietic reconstitution were comprehensively analyzed.

RESULTS

After analysis of clinical features, laboratory tests, imaging and microbiological data, no reason was found for the low fever. There was no effect on the fever with anti-microbial therapy. However the low fever was controlled by low dose prednisone 5-10 mg/d or dexamethasone 2-4 mg.

CONCLUSION

The reason for the low fever is not clear; it is probably nonspecific low fever induced by high-dose radiotherapy or high-dose chemotherapy.

[Three dimensional finite element analysis on the mandibular complete overdenture supported by nature roots or implants]

OBJECTIVE

To investigate the stress distribution around the bone tissue of overdenture supported by teeth roots or implants in the process of mastication which may assist to improve the design of the dentures.

METHODS

By means of CT scan, CAD and a three distribution finite element methods to study the stress distribution of the supporting tissue of overdenture supported by roots or implants when various attachment retentive apparatus and various bite forces were applied.

RESULTS

No matter overdenture supported by roots or implants the stress distribution on bone tissue are difference between the bar and stud attachments, However these difference were minor compared with the difference caused by the direction of force. The stress value of cortical bone around the roots or implants with twenty degree oblique force is 2.2-3 times higher than that with vertical force. Overdenture supported by implants produced 2.5-4 times higher stress in the cortical bone around than that of overdenture supported by roots when various superstructures or various loads were applied.

CONCLUSION

It must consider to reduce the stress peaks and provent bone resorption by increasing the number of implants and using the force-breaking design of implant super-strcture when the overdenture were supported with implants only.

[The three-dimensional analysis of mandibular overdenture supported by implants]

In recent decade, the treatment in which two or four implants are placed in an edentulous patient to support an overdenture has been more effective and safe, and the retention and stability of overdenture have been improved by the use of attachments fabricated on implant abutments. This study aimed to investigate the supporting tissue stress distributions of implant-overdenture with a 3-D finite element model built by CT scan and CAD technology when various attachments and loads were used respectively. The results demonstrated that the establishment of the three-dimensional finite element model with CT scan and CAD technique had saved time and effort, and it did not damage the experiment model. The tissue structure was quite distinct in imaging. In terms of the stress distribution of bone tissue in the overdenture supported by implant, there was a difference between bar attachment and stud attachment. However, such a difference was minor as compared with the difference caused by the bite force direction. The stress value of cortical bone around abutment with 20 degree oblique force was 2.2-3 times that with vertical force. Therefore, to reduce high stress peaks, attention must be paid to the direction of the bite force, as this variable is much more important than the design of superstructure.

[A study of the relationship between electromyographic activity of the masticatory muscles and the variations of the occlusal vertical dimension for edentulous subjects]

The study was performed in fifteen edentulous subjects with the EMG activity were recorded at the varying occlusal vertical dimension maintaining constant bite force value of 4kg.The results showed that maintaining constant bite force the amplitudes of EMG activity of the anterior temporal and masseter muscles are decreased with increasing the occlusal vertical dimension and correlation relation between them,that there is a stable region about 1.0mm for the anterior temporal muscle and about 1.5mm for the masseter muscle during the changes in electrical activity.It is represent that there is a physiological region of the occlusal vertical dimension for edentulous patient.

A minimal motor domain from chicken skeletal muscle myosin

The myosin head (S1) consists of a wide, globular region that contains the actin- and nucleotide-binding sites and an alpha-helical, extended region that is stabilized by the presence of two classes of light chains. The essential light chain abuts the globular domain, whereas the regulatory light chain lies near the head-rod junction of myosin. Removal of the essential light chain by a mild denaturant exposes the underlying heavy chain to proteolysis by chymotrypsin. The cleaved fragment, or "motor domain" (MD), migrates as a single band on SDS-polyacrylamide gel electrophoresis, with a slightly greater mobility than S1 prepared by papain or chymotrypsin. Three-dimensional image analysis of actin filaments decorated with MD reveals a structure similar to S1, but shorter by an amount consistent with the absence of a light chain-binding domain. The actin-activated MgATPase activity of MD is similar to that of S1 in Vmax and Km. But the ability of MD to move actin filaments in a motility assay is considerably reduced relative to S1. We conclude that the globular, active site region of the myosin head is a stable, independently folded domain with intrinsic motor activity, but the coupling efficiency between ATP hydrolysis and movement declines markedly as the light chain binding region is truncated.

Ultrastructure of skeletal muscle fibers studied by a plunge quick freezing method: myofilament lengths

We have set up a system to rapidly freeze muscle fibers during contraction to investigate by electron microscopy the ultrastructure of active muscles. Glycerinated fiber bundles of rabbit psoas muscles were frozen in conditions of rigor, relaxation, isometric contraction, and active shortening. Freezing was carried out by plunging the bundles into liquid ethane. The frozen bundles were then freeze-substituted, plastic-embedded, and sectioned for electron microscopic observation. X-ray diffraction patterns of the embedded bundles and optical diffraction patterns of the micrographs resemble the x-ray diffraction patterns of unfixed muscles, showing the ability of the method to preserve the muscle ultrastructure. In the optical diffraction patterns layer lines up to 1/5.9 nm-1 were observed. Using this method we have investigated the myofilament lengths and concluded that there are no major changes in length in either the actin or the myosin filaments under any of the conditions explored.

[A comparative study of masticatory efficiency between partial denture wearers having one remaining tooth and complete denture wears]

Masticatory efficiency is one of the important indexes of judging masticatory function after dentures restored.The aim of this study was to measure and analyze masticatory efficiency of partial dentur wearers having one tooth left and complete denture wearers,by using a method of measuring msticatory crushed granules.The results showed that the crushed granules for partial denture wearers with one remaining tooth were smaller than that for complete ones.Therefore,partial dentures with a few remaining teeth were better than complete ones on effects.

Frequency analysis of electromyographic signals in mandibular elevators at maximum clench level

Power spectral analysis of electromyogram (ENG) was used to investigate the relationship between mean power frequency (MPF) and sustained contraction time. Surface EMG activity was recorded from masseter and anterior temporal muscles on both sides for seven healthy subjects while clenching at intercuspal position in maximum potential level of these muscles. A visual sense feedback of EMG potential was used to control clenching level. According to linear regression analysis, there was a negative correlation between MPF of EMG and sustained contraction time. The results indicate that the slope of MPF versus contraction time may be used for detecting muscular fatigue in the stomatognathic system.

A comparative study of mastication between complete denture wearers and dentate subjects

A computer system was used for simultaneously collecting and processing mandibular movements and the myoelectric activities of the masticatory muscles of 15 dentate subjects and 11 complete denture wearers. The displacement, velocity, cycle of mandibular movements, and the muscular mean potentials were indices in observing mastication. A good complete denture should perform with physiologic characteristics, and restore masticatory function and oral health. The kinetic energy from the velocities of lateral and vertical directions can serve for the chewing and comminution of food, but lateral comminution may affect denture retention. The mean myoelectrical potentials of the mandibular elevator muscles of complete denture wearers tend to increase at the opening phase; however, the potentials decrease at the closing phase.

Power spectral analysis of electromyographic signal of masticatory muscles at rest position and habitual clench

Thirteen normal subjects were selected for this investigation. At the vertical dimension of rest position and habitual clench, their myoelectric activities of the masseter, anterior and posterior temporal, and digastric muscles on the left and right sides were simultaneously sampled and processed by computer, and the mean power frequency (MPF) and the mean amplitude (MA) of the myoelectric signal were calculated. At rest position, the temporal muscles were major muscles and the MPF differences of various masticatory muscles were not significant. At habitual clench, with the increase in MA, the MPF of various muscles increased. The results show that MPF may have application in describing a central tendency of myoelectrical signal frequency distribution and in evaluating recruitment of motor units. MPF and MA are the quantitative indices reflecting masticatory muscle function.

Comparison of food particle distribution masticated by subjects wearing complete dentures and with natural teeth

The sizes of soya particles masticated by 12 complete denture wearers and 10 subjects with natural dentition were directly measured by means of a graphic digitizer and computer, following a varied number of chewing strokes. It was found that the chewed particle size frequency distributions of the two groups tended to a state of normal logarithm distribution. Compared with the dentate subjects, the mean, 20th, 50th and 80th percentile of the particle sizes chewed by complete denture wearers were increased, whilst the distribution shapes were nearly identical. The results suggest that there are no qualitative differences in the manner in which the two groups break up food. Selection and breakage functions of complete denture wearers are decreased, and this could be related to the denture conditions and the change of oral state in such individuals.